ET 16-0003, Flood Hazard Reevaluation Report, Revision 1

Flood Hazard Reevaluation Report, Revision 1

ML16032A191
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Site:	Wolf Creek
Issue date:	10/21/2015
From:	Oskamp J Rizzo Associates
To:	Office of Nuclear Reactor Regulation, Westinghouse
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ET 16-0003 14-5262/13-5031
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SUBMITTED TO:

WESTINGHOUSE ELECTRIC COMPANY LLC Corporate Headquarters 500 Penn Center Boulevard, Pittsburgh, PA ]15235 USA Telephone: 412.856.9700 j Fax: 412.856.9749

WOLF CREEK NUCLEAR OPERATING CORPORATION FLOOD HAZARD REEVALUATION REPORT PROJECT NOS.: 14-5262/13-5031 REVISION 1 OCTOBER 21, 2015 RIZZO ASSOCIATES 500 PENN CENTER BOULEVARD BUILDIN'G 5, SUITE 100 PITTSBURGH, PENNSYLVANIA 15235 TELEPHONE: (412) 856-9700 TELEFAX: (412) 856-9749 WWW.RIZZOASSOC.COM Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 2 of 105 r<1K

APPROVALS Project Nos.: 14-5262/13-5031 Report Name: Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Date: October 21, 2015 Revision No.:

Approval by responsible manager signifies that the document is complete, all required reviews are complete, and the document is released for use.

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• ,**.*Jeffrey Associate, RIZZO Associates A.Oskamp, Engineering Originator: October 21, 2015 Jeffrey A. Oskamp, E.I.T. Date Engineering Associate Independent Associate, RIZZO Associates October 21, 2015 Verifier: Tom Edwards Date Engineering Associate

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/* //*Engineering Mark Schwartz, Supervisor, Independent RIZZO Associates October 21, 2015 Verifier:

Mark Schwartz, P.E. Date Technical Supervisor

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J Thomas H.Jackson, P.E., PhD, Technical L. 1{i r$./. Water Resources Engineering Supervisor, RIZZO Associates Inc. October 21. 2015 Reviewer:

Thomas Jackson, Ph.D., P.E. Date Technical Supervisor

• Jemie Dababneh, Managing Project Principal, RIZZO Associates Manager: October 21. 2015 Ahmed "Jemie" Dababneh, Ph.D., P.E. Date Senior Director and Project Manager

• /*]_[ Daniel J. Barton, Vice Principal in CV~~L President, RIZZO Associates Charge: October 21.,2015 Daniel J. Barton, Jr., P.E. Date Vice President Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 3 of 105

CHANGE MANAGEMENT RECORD Project Nos.: 14-5262/13-5031 Report Name: Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report REVISION NO. DATE [ DESCRIPTIONS OF CHANGES/AFFECTED PAGES 0 February10, 2014 N/A Updated the Local Intense Precipitation analysis to account for changes to the site configuration up to 1October 21, 2015 July 2015. Incorporated updates to the design basis since the issuance of the Revision 0 report.

________________ Substantive changes are marked with_'Rev_1'_bars.

4 I-4 I.

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TABLE OF CONTENTS PAGE LIST OF TABLES ................................................................................ 7 LIST OF FIGURES.................... ........................................................... 8

1.0 INTRODUCTION

...................................................................... 10 1.1 PURPOSE AND SCOPE ........................................................... 10 1.2 LOCATION OF THE SITE............................................................. 10 1.3 SITE BACKGROUND AND HISTORY.............................................1 1 2.0 FLOOD HAZARDS AT THE SITE................................................... 12 2.1 DETAILED SITE INFORMATION .................................................... 12 2.1 .1 Design Site Information ............................................. 12 2.1.2 Present-Day Site Information ....................................... 15 2.2 CURRENT DESIGN BASIS FLOOD ELEVATIONS .................................. 16 2.3 FLOOD-RELATED CHANGES TO THE LICENSING BASIS......................... 19 2.3.1 Description of Hydrological Changes and Flood Elevations............................................................. 19 2.3.2 Description of Flood Protection Changes (Including Mitigation) ............................................................ 19 2.4 CHANGES TO THE WATERSHED AND LOCAL AREA............................. 20 2.4.1 Description of Watershed and Local Area at the Time of License Issuance...................................................... 20 2.4.2 Description of Any Changes to the Watershed and Local Area since License Issuance......................................... 20 2.5 CURRENT LICENSING BASIS FLOOD PROTECTION .............................. 21 2.6 ADDITIONAL SITE DETAILS ........................................................ 22 2.6.1 Wolf Creek Lake Bathymetry....................................... 22 2.6.2 Recommendation 2.3 Walkdown Results .......................... 22 2.6.3 Site Visit .............................................................. 23 3.0 FLOOD HAZARD REEVALUATION ANALYSIS................................ 24 3.1

SUMMARY

OF RECOMMENDATION 2.1......................................... 24 3.2 SOFTWARE USED.................................................................... 24 3.3 FLOOD-CAUSING MECHANISMS ................................................... 25 3.3.1 Local Intense Precipitation .......................................... 26 Wolf Creek Nuclear Operating Corporation ,*

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TABLE OF CONTENTS (CONTINUED)

PAGE 3.3.2 Flooding in Rivers and Streams .................................... 30 3.3.3 Dam Breaches and Failures ......................................... 41 3.3.4 Storm Surge .......................................................... 45 3.3.5 Seiche ................................................................. 45 3.3.6 Tsunami............................................................... 46 3.3.7 Ice-Induced Flooding ................................................ 46 3.3.8 Flooding Resulting from Channel Migration or Diversion......48 4.0 COMPARISON OF CURRENT DESIGN BASIS AND REEVALUATED FLOOD HAZARDS .............................................. 49 4.1 COMPARISON OF FLOOD-CAUSING M/ECHANISMS .............................. 49 4.2 COMPARISON OF FLOOD EFFECTS ................................................ 49 4.3 SUPPORTING DOCUMENTATION ................................................... 54 4.3.1 Technical Justification of the Flood Hazard Analysis ............ 55 4.3.2 Technical Justification of the Walkdown Results................. 55

4.4 CONCLUSION

S........................................................................57 5.0 INTERIM EVALUATION AND ACTIONS......................................... 59 5.1 EVALUATION OF THE IMPACT OF THE REEVALUATED FLOOD LEVELS ON STRUCTURES, SYSTEMS, AND COMPONENTS................................ 59 5.2 ACTIONS TAKEN TO ADDRESS FLOOD HAZARDS NOT COMPLETELY BOUNDED BY THE CURRENT DESIGN BASIS HAZARD.......................... 59 6.0 ADDITIONAL ACTIONS............................................................. 61

7.0 REFERENCES

.......................................................................... 62 TABLES FIGURES APPENDIX A FLO-2D PRO SOFTWARE QUALIFICATIONS Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation ReportPae6o10 145262/135031/15 Rev. 1 (October 21, 2015) Pag 6of10

LIST OF TABLES TABLE NO. TITLE TABLE 2-1 LIST OF POWERBLOCK STRUCTURES AND THEIR ELEVATIONS TABLE 2-2 EXISTING WOLF CREEK DESIGN PARAMETERS TABLE 2-3 CURRENT DESIGN BASIS FLOOD ELEVATIONS DUE TO ALL FLOOD MECHANISMS TABLE 3-1 WATER LEVELS AND PONDING DEPTHS DUE TO LOCAL INTENSE PRECIPITATION TABLE 3-2 LOCAL INTENSE PRECIPITATION FLOODING AT DOORS TO SEISMIC CATEGORY I BUILDINGS TABLE 3-3 LOCAL INTENSE PRECIPITATION FLOODING AT OTHER DOORS, HATCHES, MANHOLES, AND VAULTS FOR SAFETY-RELATED SS Cs TABLE 3-4 WATERSHED SUBBASIN CHARACTERISTICS AND HEC-HMS MODELING RESULTS TABLE 3-5

SUMMARY

OF HEC-HMS AND HEC-RAS SIMULATION CASES TABLE 4-1 COMPARISON OF MODELING APPROACHES FOR CURRENT LICENSING BASIS AND FLOODING REEVALUATION TABLE 4-2 COMPARISON OF CURRENT LICENSING BASIS AND FLOODING REEVALUATION ANALYTICAL INPUTS TABLE 4-3 COMPARISON OF CURRENT LICENSING BASIS AND REEVALUATED FLOOD LEVELS TABLE 4-4 COMPARISON OF VARIOUS FLOODING PARAMETERS BETWEEN THE CURRENT LICENSING BASIS AND THE FLOOD REEVALUATION Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 7 of 105

LIST OF FIGURES FIGURE NO. TITLE FIGURE 1-1 GENERAL LOCATION OF THE SITE FIGURE 1-2 SITE AREA MAP FIGURE 2-1 DESIGN SITE LAYOUT FIGURE 2-2 PRESENT-DAY SITE LAYOUT AND TOPOGRAPHY FIGURE 2-3 LOCATIONS OF BUILDINGS IN THE POWERBLOCK AREA FIGURE 2-4 WOLF CREEK LAKE WATER DEPTHS FIGURE 3-1 THE HHA DIAGRAM FOR LOCAL INTENSE PRECIPITATION FLOODING ANALYSIS FIGURE 3-2 FLO-2D INUNDATION MAP DUE TO LOCAL INTENSE PRECIPITATION FIGURE 3-3 THE HHA DIAGRAM FOR THE ANALYSIS OF FLOODING IN RIVERS AND STREAMS FIGURE 3-4 WOLF CREEK WATERSHED MAP SHOWING SUBBASINS FIGURE 3-5 PMP HYETOGRAPH FOR THE WOLF CREEK WATERSHED FIGURE 3-6 HEC-HMS MODEL FOR THE WOLF CREEK WATERSHED FIGURE 3-7 FLOOD LEVEL TIME HISTORY OF WOLF CREEK LAKE FOR THE ANALYSIS OF FLOODING IN RIVERS AND STREAMS FIGURE 3-8 HEC-RAS MODEL FOR THE WOLF CREEK WATERSHED FIGURE 3-9 FETCH LOCATIONS OVER WOLF CREEK LAKE FIGURE 3-10 THE HHA DIAGRAM FOR COMBINED-EFFECTS FLOODING ANALYSIS FIGURE 3-11 FLOOD LEVEL TIME HISTORY OF WOLF CREEK LAKE FOR THE ANALYSIS OF COMBINED-EFFECTS FLOOD FIGURE 3-12 LOCATION OF DAMS NEAR THE SITE FIGURE 3-13 THE JLD-ISG-2013-01 DIAGRAM FOR DETERMINING LEVELS OF ANALYSIS FOR DAM BREAK EVALUATION FIGURE 3-14 THE JLD-ISG-2013-01 DIAGRAM FOR THE ANALYSIS OF DAM BREACHES AND FAILURES USING THE "VOLUME METHOD" Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report

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LIST OF FIGURES (CONTINUED)

FIGURE 3-1!5 INUNDATION AREA CALCULATED USING "VOLUME METHOD" FOR DAM FAILURE ANALYSIS ASSUMING FAILURE OF ALL UPSTREAM DAMS FIGURE 4-1 DURATION OF FLOODING FOR THE LIP FLOOD ANALYSIS I II '1 I II I I ' . I* ... .. ,ill .. ........ .......... p, Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Page 9 of 105 FI K~i I 145262/135031/15 Rev. 1 (October 21, 2015)

WOLF CREEK NUCLEAR OPERATING CORPORATION FLOOD HAZARD REEVALUATION REPORT

1.0 INTRODUCTION

1.1 PURPOSE AND SCOPE The United States Nuclear Regulatory Commission (NRC) issued a letter on March 12, 2012, pursuant to Title 10 of the Code of Federal Regulations (CFR), Section 50.54(f), related to the implementation of Recommendations 2.1, 2.3, and 9.3 from the Near-Term Task Force (NTTF),

a portion of which calls for performing flood hazard reevaluations at all Nuclear Power Plants (NPP) in the United States (NRC, 2012a). On behalf of Wolf Creek Nuclear Operating Corporation (WCNOC), this Flood Hazard Reevaluation Report (FHRR) for the Wolf Creek Generating Station (WCGS) site provides the information required to address NRC Recommendation 2.1 with due consideration to the most recent guidance and regulations.

Revision 1 of this FHRR includes updates to account for additional analyses that have been completed since the issuance of Revision 0. These updates primarily relate to the evaluation of Local Intense Precipitation (LIP). An additional LIP simulation was performed to account for Rev 1 updates to the site configuration and topography that have occurred since the issuance of the Revision 0 FI-RR, which represents site conditions as of February 2013. In addition to LIP updates, the discussion of the flood forces on the Essential Service Water System (ESWS) pumphouse has been modified to account for a design basis analysis that has been completed since the issuance of the Revision 0 FHIRR.

1.2 LOCATION OF THE SITE WCNOC operates the WCGS, which is located in Coffey County in eastern Kansas. The WCGS site is approximately 90 miles southwest of Kansas City, approximately 3.5 miles northeast of the city of Burlington, and approximately 3.5 miles east of the Neosho River and the main dam at John Redmond Reservoir (Figure 1-1 and Figure 1-2). The WCGS site is located adjacent to Wolf Creek Lake (Coffey County Lake). Wolf Creek flows south into Wolf Creek Lake, which in turn drains into the Neosho River (U.S. Geological Survey [USGS], 2012a; 2012b). Wolf Wolf Creek Nuclear Operating Corporation -

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Creek Lake was established for station cooling, and was created by constructing an earthen dam across Wolf Creek. The location of the earthen dam is approximately four miles upstream of Wolf Creek's confluence with the Neosho River (Figure 1-2).

1.3 SITE BACKGROUND AND HISTORY WCNOC is a joint venture of three owners: Kansas Gas and Electric Company, Kansas City Power & Light Company, and Kansas Electric Power Cooperative, Inc. The WCGS site has one reactor, which is a Westinghouse Pressurized Water Reactor (PWR). The site has been in operation since the issuance of the license on June 4, 1985. The operating license for the WCGS expires on March 11, 2045 (NRC, 2013a).

The Updated Safety Analysis Report (USAR) for the WCGS (WCNOC, 2015) was last revised Rev 1 in March 2015. In the USAR, two elevation datums are referenced; Mean Sea Level (MSL) (the National Geodetic Vertical Datum of 1929 (NGVD29)) and the Standardized Nuclear Unit Power Plant System (SNUPPS) datum. The SNUPPS datum is equivalent to the MSL elevation plus 900 feet (fi). At the WCGS site, MSL is equivalent to NGVD29. All elevations in this report are with reference to MSL, unless otherwise stated.

PIZ Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 11 of 105

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2.0 FLOOD HAZARDS AT THE SITE Section 2. 0 has been prepared in response to Request for Information Item l .a. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a) and documents results, as well as pertinent site information and detailed analyses related to the applicable flood hazards. Relevant Structures, Systems, and Components (SSCs) important to safety and the Ultimate Heat Sink (UHS) are included in the scope of this reevaluation, including pertinent data concerning these SSCs. While the UHS is discussed separately, it is a safety-related SSC.

2.1 DETAILED SITE INFORMATION Section 2.1 has been prepared in response to Request for Information Item 1.a.i. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes detailed site information, present-day site layout, and elevations of pertinent SSCs important to safety, site topography, as well as pertinent spatial and temporal data sets.

2.1.1 Design Site Information Design site information describes characteristics considered for the original licensing basis of the WCGS site. The original topography and design of site layout are shown in the USAR for the WCGS (WCNOC, 2015, Figures 1.2-43 and 2.4-1). Changes to the site layout and SSCs related Rev 1 to flooding protection were evaluated as part of the Wolf Creek Nuclear Operating Corporation Post Fukushima Flooding Walkdown Report (WCNOC, 2012). Figure 2-1 shows the design layout of the WCGS site.

The design locations of the safety-related structures, as well as other buildings and structures in the powerblock area are shown in Figure 2-1. A list of the primary safety- and non-safety-related structures at the WCGS site is provided in Table 2-1. A list of the existing design Rev 1 parameters found in the license document (WCNOC, 2015) is included in Table 2-2.

2.1.1.1 Site Topography and Drainage The WCGS site is located on a small peninsula on the northeastern side of Wolf Creek Lake (Figure 1-2). The lake is a reservoir that is retained behind an earthen dam, which was Wolf Creek Nuclear Operating Corporation r[*

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constructed across Wolf Creek in order to provide cooling water for WCGS. The headwater area of Wolf Creek lies north of WCGS and the lake. The watershed area upstream of the dam is approximately 27.4 square miles (mi 2) (WCNOC, 2015). The lake itself has a surface area ofRv1 approximately 5,090 acres (approximately 8.0 mi 2) and a water storage capacity of about 111,280 acre-ft when it is at its normal water surface elevation of 1,087 ft (WCNOC, 2015). Rev 1 Below the damn, Wolf Creek flows about four miles south-southwest to where it joins the Neosho River.

The Neosho River is a relatively large river; its watershed covers approximately 6,300 mi2 in Kansas. The Neosho River originates in east-central Kansas (Morris County) and flows southeast toward Humbolt, Kansas, and then southward into Oklahoma (Figure 1-1). It lies west and south of the Wolf Creek watershed. Flow in the Neosho River near the WCGS site is controlled by John Redmond Reservoir. Wolf Creek flows south-southwest and joins the Neosho River about four miles south of the Wolf Creek Dam and 7.1 miles downstream of the John Redmond Dam (Figure 1-2). Cottonwood Creek is a large tributary of the Neosho River and joins the river approximately six miles east of Emporia, Kansas, or approximately 14 miles northwest of the John Redmond Reservoir and Dam (WCNOC, 2015). Revi1 Long Creek flows from north to south and is located directly east and northeast of the Wolf Creek watershed (Figure 1-2). It too flows into the Neosho River. Altogether, the Long Creek watershed covers approximately 84 mi 2 . Low topographic ridges separate the Wolf Creek watershed from the Long Creek and Neosho River watersheds (USGS, 2012b). Rev 1 The WCGS site lies in the Osage Plains physiographic section of the Central Lowland Province (WCNOC, 2015). It is an area of low rolling hills with very gentle slopes. The WCGS site is Rev 1 positioned near the top of a low hill and has a grade elevation of 1,099.5 ft adjacent to buildings in the powerblock area. The floor elevation of safety-related buildings is 1,100 ft (WCNOC, Rev 1 2015). The powerblock area is flat. The ground surface slopes gently down to the Wolf Creek Lake on the western, southern, and eastern sides of the powerblock. This is an elevation drop of approximately 12.5 ft when the lake is at its normal operating level (1,087 ft; WCNOC, 2015). Rev 1 Within a five-mile radius of the site, elevations range from highs of approximately 1,215 ft on hilltops to the north and northeast of the site down to approximately 985 ft near the confluence of Wolf Creek and the Neosho River, southwest of the site (Figure 1-2).

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2.1.1.2 Description of Safety-Related Structures, Systems, and Components The locations of the safety-related structures, including the ESWS pumphouse, are shown in Figure 2-1. A list of the WCGS site safety-related structures is provided in Table 2-1.

2.1.1.3 Description of Wolf Creek Lake and the Ultimate Heat Sink Wolf Creek Lake was created by erecting an earthen dam across Wolf Creek just downstream of the WCGS site. Filling of the reservoir began in October 1980 and was complete in June 1982 (Kansas Biological Survey [KBS], 2010). The dam retaining Wolf Creek Lake is not a Seismic Category I dam and is not considered to be safety-related. A service spillway is located on the east abutment of the cooling lake dam and is an uncontrolled concrete ogee-crested spiliway with a crest elevation of 1,088 ft and a crest length of 100 ft. The auxiliary spillway is approximately 1,500 ft east of the service spillway and is an open cut spiliway with a crest elevation of 1,090.5 ft and a crest length of 500 ft (WCNOC, 2015). As stated in the USAR (WCNOC, 2015, Section IRev 1 2.4.1.1), the lake has a surface area of 5,090 acres and a capacity of 111,280 acre-ft of water at its normal operating level of 1,087 ft.

The impoundment was initially filled and has been subsequently maintained with makeup water pumped from the nearby Neosho River (KB S, 2010). Wolf Creek Lake was designed to provide adequate cooling water to the WCGS during a fifty-year drought. The water level in the lake is normally sustained by the Wolf Creek watershed upstream of the lake. However, during dry months, it is sometimes necessary to pump water to the lake from the Neosho River, just below the John Redmond Reservoir (KBS, 2010). During times of flooding, the service and auxiliary spillways provide controlled release of water to prevent overtopping of the Wolf Creek Lake Dam.

The description of the UHS in this section is in regards to the design basis of the UHS, as described in the USAR (WCNOC, 2015). Any changes to the UHS are considered present-day ]Rev 1 information and are discussed in Section 2.1.2.3. The UHS is located within Wolf Creek Lake, created by the construction of a submerged Seismic Category I dam. The UHS provides water to the ESWS. The intake channel bottom in the UHS is at an elevation of 1,065 ft and locally slopes down to an elevation of 1,064 ft at the ESWS pumphouse. The design water surface elevation of the UHS is 1,070 ft, which is five feet lower than the design minimum Wolf Creek Lake elevation. The maximum allowable sediment volume in the UHS is limited to 130 acre-ft Wolf Creek Nuclear Operating Corporation '

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to provide sufficient surface area and volume to safely shut down and maintain shutdown of the plant (WCNOC, 2015). j Rev 1 2.1.2 Present-Day Site Information Present-day site information describes changes to the WCGS site that have occurred since the original design of the site, which may have the potential to influence the reevaluation of hydrological and flooding hazards. Figure 2-2 shows the WCGS present-day site layout and topography.

2.1.2.1 Site Topography All flooding analyses described in this FHRR have been undertaken with consideration and implementation of current techniques, software, and methods used in present-day standard engineering practice to determine the flood hazard. Topographic data from an October 2012 survey of the plant area were used in the generation of all of the applicable reevaluated flooding models for the Revision 0 FHRR. Topography reflecting changes to site grading as of July 2015 Re1 (Figure 2-2) was incorporated for specific areas for the LIP analysis documented in this Revision 1 FHRR. These modifications include areas adjacent to the Control Building and the ESWS pumphouse.

2.1.2.2 Description of Safety-Related Structures, Systems, and Components Changes to the site layout and SSCs related to flooding protection were evaluated as part of the Wolf Creek Nuclear Operating CorporationPost Fukushzima Flooding Walkdown Report (WCNOC, 2012). Additional changes in site layout, such as the addition, removal, and relocation of structures, trailers, and sea vans, that have occurred since the walkdown are reflected in Figure 2-2 and have been included in the updated LIP analysis.

The design locations of the safety and non-safety-related structures in the powerblock area are shown in Figure 2-3.

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2.1.2.3 Description of the Ultimate Heat Sink The UHS is located within Wolf Creek Lake and is described in Section 2.1.1.3. No changes in the UHS since license issuance are noted in the USAR (WCNOC, 2015) or the Wolf Creek Rev 1 Nuclear Operating CorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012).

2.2 CURRENT DESIGN BASIS FLOOD ELEVATIONS Section 2.2 has been prepared in response to Request for Information Item 1.a.ii. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes the current design basis flood elevations for all flood-causing mechanisms.

The current design basis, as presented in the USAR (WCNOC, 2015), indicates that the site is Rev 1 not adversely affected by flooding. The WCGS site has a plant grade elevation of 1,099.5 ft, and a floor elevation of 1,100 ft. The maximum calculated water levels near the safety-related buildings due to the LIP event range from 1,099.52 ft to 1,099.92 ft (WCNOC, 2015). During Rev 1 the LIP event, it is conservatively assumed in the design basis that the site drainage system is not functional. The maximum water level due to the LIP is below the plant floor elevation of 1,100 ft (WCNOC, 2015). The LIP (1-hour [hr], 1 mi 2) rainfall of 19 inches (in) is part of the Rev 1 cumulative six-hour rainfall of 28.79 is used in the design basis. The LIP rainfall is determined using Hydrometeorological Report Number 52 (HMR No. 52) (WCNOC, 2015). Rev 1 To characterize the Probable Maximum Flood (PMF) for the Wolf Creek watershed and Wolf Creek Lake, a Probable Maximum Precipitation (PMP) distribution was developed and applied over the design watershed (of 27.4 mi2 ). The PMP was determined using HMR No. 33 (WCNOC, 2015). The cumulative 48-hr duration PMP is 32.80 in (WCNOC, 2015, Table Rev 1 2.4.12), with the peak occurring at approximately 34 hrs.

The Wolf Creek Lake dam has a service spillway and an auxiliary spillway. Both spillways have uncontrolled crests, which are sized to pass floods up to and including the PMIF (WCNOC,Re1 2015). The flood event simulated for the design basis includes the combined effects of a single PMP event preceded by a Standard Project Flood (SPF) event (which is 50 percent of the PMP),

and an overland sustained wind speed of 40 miles per hour (mph) (WCNOC, 2015, Section Rev 1 2.4.2.2). The peak flow rate in the design basis for the spillways is 22,845 cubic feet per second Wolf Creek Nuclear Operating Corporation **.

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(cfs) (WCNOC, 2015, Section 2.4.3.5). The maximum water surface elevation in Wolf Creek Rev 1 Lake (i.e., the pool elevation) due to the PMF event is 1,095 ft at the plant site, which assumes a starting pool elevation of 1,088 ft (corresponding to the crest elevation of the service spillway for the Wolf Creek Lake Dam). The coincident wave activity of the PMF resulted in a maximum run-up of 0.8 ft at the plant site shore. The resulting run-up elevation was 1,095.8 ft when added to the PMF pool elevation (WCNOC, 2015, Table 2.4-16). Rev 1 The maximum wave run-up elevation on the vertical wall of the intake structure of the ESWS is 1,100.2 ft. However, the intake structure for the ESWS is designed to withstand a high water elevation of 1,102.5 ft. As stated in the USAR, the only openings below elevation 1,102.5 ft are the pressure doors and the pump structure forebay opening. The pressure doors are located at elevation 1,100.0 ft. These doors are normally closed and under administrative control. The Rev 1 pump structure forebay normally contains water (WCNOC, 2015).

With regard to the PMF, backwater caused by the PMF in the Neosho River or Long Creek does not affect the site due to the topographic ridges between the site and the Long Creek and Neosho River valleys.

Failure of dams located in the Neosho River watershed upstream of the John Redmond Reservoir will not adversely affect any safety-related facilities at the WCGS site (WCNOC, 2015). In the Rev 1 most critical case, which postulates the domino-type failure of all four reservoirs (John Redmond, Marion, Cedar Point, and Council Grove) (Case b.3 of Section 2.4.4.1 of the USAR

[WCNOC, 2015]), the maximum flood stage of the Neosho River was estimated to be 1,044.55 ft Rev 1 at a distance of about five miles downstream from the John Redmond Dam (WCNOC, 2015). As stated in the USAR, the topographic ridge between the Neosho River and Wolf Creek valleys below John Redmond Dam will separate the postulated flood levels in the Neosho River valley from any facilities at the site, with the exception of the cooling lake main dam. The maximum water elevation on the downstream slope of the Wolf Creek Lake Dam, due to the postulated combined maximum flood-causing events in the Neosho and Cottonwood River basins, is conservatively established at elevation 1,049.6 ft. This flood stage is well below surface grades of any Seismic Category I facilities at the site and is about 50 ft below the plant grade elevation of 1,099.5 ft (WCNOC, 2015).Re1 Storm surge and seiche, tsunami, and ice-induced flooding were screened out as potential flooding events in the current design basis in the USAR (WCNOC, 2015). The following lists Rev 1 the sections in the USAR where these flood mechanisms were screened out:

Wolf Creek Nuclear Operating Corporation 1 "

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• Probable maximum storm surge and seiche flooding: Section 2.4.5

• Probable maximum tsunami flooding: Section 2.4.6

• Ice effects: Section 2.4.7 Frazil ice is screened out in the design basis. Frazil ice is prevented by diffusing warmed water in front of the ESWS track racks (WCNOC, 2015, Section 2.4.7.2). The design basis states that Rev 1 warming lines divert heat to ensure that frazil ice does not block the ESWS trash racks (WCNOC, 2015, Section 9.2.1.2.2). There are two trains (Trains A & B) in the ESWS; Revi1 therefore, the ESWS pumphouse has two redundant trains. Each train has its own independent warming system. There is a secondary system, a portable air bubbler system, which can also be placed at the ESWS pumphouse. In addition, there is a procedure for the ESWS pumphouse for the prevention of frazil ice formation.

The sources of the makeup water to the cooling lake are Wolf Creek and the Neosho River. In reference to channel diversion in the US AR, there is no indication that Wolf Creek or its tributaries would be diverted from its present course of flow into Wolf Creek Lake. Ice jams will also not cause diversion of flow because the jams do not prevent overbank flow. The ESWS intake is designed to prevent ice from jamming against it and cutting off inflow (WCNOC, 2015, Rev 1 Section 9.2.1.2.2.2).

As stated in the USAR, if the Wolf Creek flow was temporarily cut off, makeup water to the plant would still be available from the Joh~n Redmond Reservoir on the Neosho River. Due to the regional topographical conditions, it is unlikely that the upper Neosho River would be diverted from the John Redmond Reservoir due to ice jams or subsidence. Therefore, it is unlikely that the Neosho River inflows would be completely cut off and affect the makeup water available to the cooling lake (WCNOC, 2015). Rev 1 In addition, it is not expected that any potential morphological changes in Wolf Creek will affect any safety-related SSCs at the WCNOC site. As stated in the USAR, "there is no historic or topographic evidence indicating that flow in Wolf Creek can be diverted away from its present course. Local relief and the natural geomorphological condition preclude the likelihood of Wolf Creek and its tributaries discharging anywhere other than into the cooling lake" (WCNOC, 2015, Rev I Section 2.4.10).

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2.3 FLOOD-RELATED CHANGES TO THE LICENSING BASIS Section 2.3 has been prepared in response to Request for Information Item 1.a.iii of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes flood-related changes to the licensing basis and any flood protection changes (including mitigation) since license issuance.

2.3.1 Description of Hydrological Changes and Flood Elevations The design basis flood elevations for the flood-causing mechanisms that are applicable to WCGS are summarized in Table 2-3. The original design basis LIP analysis was based on HMR No. 33, using the procedures outlined in EM-i1110-2-1411 to obtain a 6-hr distribution; this resulted in a maximum flood elevation of 1,099.86 ft around the powerblock (WCNOC, 2013, Section 2.4.2.3.2). The design basis LIP analysis was updated based on HMR No. 52, using a 6-hr Rv distribution. Based on the updated analysis, the current design LIP flood level at safety-related buildings on the powerblock is now established at 1,099.92 ft, which is documented in Revision 28 of the USAR (WCNOC, 2015, Section 2.4.2.3.2).

2.3.2 Description of Flood Protection Changes (Including Mitigation)

The flood protection system and flood mitigation measures described in the USAR (WCNOC, Rev 1 2015) and documented in the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) are relevant to the flood hazard reevaluation analyses. Changes to the site layout and SSCs related to flooding protection were evaluated as part of the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012). Safety-related SSCs that are credited in the Current Licensing Basis (CLB) for protecting the plant from external flood hazards were identified, inspected, and evaluated to be adequate.

According to the walkdown report (WCNOC, 2012), "The walkdown visual inspection has verified that there is reasonable assurance the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The Wolf Creek external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard." No changes since license issuance and no comments regarding adverse site conditions affecting flooding protection were noted in the walkdown report (WCNOC, 2012). The LIP model developed for this[

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Revision 1 FHRR incorporates changes to site grading and layout through July 2015 (Figure 2-Re1 2), as well as the addition of safety-related vaults installed since the walkdown.

2.4 CHANGES TO THlE WATERSHED AND LOCAL AREA Section 2.4 has been prepared in response to Request for Information Item 1.a.iv of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes changes to the watershed and local area since license issuance. A description of the watershed at the time Of license issuance and pertinent changes to the watershed since license issuance are presented in the following sections.

2.4.1 Description of Watershed and Local Area at the Time of License Issuance The drainage area of the Wolf Creek watershed defined at the time of the license issuance was 27.4 mi 2 . There are no gages located on the Wolf Creek watershed; therefore, no streamfiow records are available. Additional information regarding the Wolf Creek watershed and adjacent watersheds are presented in Section 2.1.1.1.

2.4.2 Description of Any Changes to the Watershed and Local Area since License Issuance As previously discussed, changes to the site layout and SSCs related to flooding protection were evaluated as part of the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012). In addition, the flood reevaluation analysis determined that there were no significant changes to the watershed since the original design basis.

The walkdown visual inspection conducted during the walkdown verified that there is reasonable assurance that the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The WCGS external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard. The purpose of the Recommendation 2.3 walkdown was to verify the conformance with the CLB; the adequacy of the CLB is addressed as part of the Rev 1 Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Pg 0o 0 145262/135031/15 Rev. 1 (October 21, 2015) Page20 o 10

flood reevaluations, along with a focused LIP evaluation 1 per the forthcoming guidance (NRC, 2015a).

The original design site layout did not include a vehicle barrier system (VB S). However, a VBS has been added to the WCGS site. The VBS configuration as of February 2013 was used as the Rev 1 basis for the Revision 0 FHRR. Subsequent changes to the VBS configuration up to July 2015 are accounted for in an additional LIP simulation prepared for this Revision 1 FHIRR. In addition to modification of the VBS, any other changes to the site layout that have occurred since license issuance (through July 2015, Figure 2-2) are captured in the reevaluation analysis.

The slope for the Wolf Creek Lake shoreline reported for the design basis is 30:1 (horizontal to vertical) (WCNOC, 2015, Table 2.4-16). Based on the current topographic data used for the ]Rev 1 flood hazard reevaluation, the average shoreline slope is determined to be 46:1. The difference in slope is likely due to the method of computing an average slope for the shoreline, not due to significant change in the shoreline topography.

All flooding analyses described in this FHRR and described in Section 3.0 have been undertaken with consideration and implementation of current techniques, software, data, and methods used in present-day standard engineering practice to develop the flood hazard.

2.5 CURRENT LICENSING BASIS FLOOD PROTECTION Section 2.5 has been prepared in response to Request for Information Item 1.a.v. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes current licensing basis flood protection and pertinent flood mitigation features at the site.

The safety-related facilities are not affected by the PMF in the cooling lake or by the LIP at the plant site and no flood protection requirements are necessary (WCNOC, 2015). The Wolf Creek IRev 1 Nuclear Operating CorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) 1 At the time of issuance of this Revision 1 FHRR, the NRC is currently in the process of revising the guidance related to the performance of the integrated assessment described in the 50.54(f) letter (NRC, 2012a) and subsequent guidance (NRC, 2012c). Of significance, the NRC has stated (NRC, 2015b) that "Licensees with LIP hazards exceeding their current design-basis flood will not be required to complete a revised integrated assessment." The Rev 1 forthcoming guidance "...will discuss a graded approach to flooding evaluations and provide for more focused evaluations of local intense precipitation and available physical margin in lieu of proceeding to an integrated assessment" (NRC, 2015a).

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identified the credited flood protection and mitigation features that are considered in the WCGS CLB to protect against the ingress of water to safety-related SSCs. These include topography, structures, floors, walls, penetrations, vaults, the forebay, doors, sump pumps, and sump pump motors. The ESWS pumphouse has pressure doors that are located at elevation 1,100.0 ft. These pressure doors are flood protection doors and are normally closed and under administrative control (WCNOC, 2015). R ev 1 2.6 ADDITIONAL SITE DETAILS Section 2.6 has been prepared in response to Request for Information Item 1.a.vi. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes additional site details, as necessary, to assess the flood hazard (i.e., walkdown results, etc.).

2.6.1 Wolf Creek Lake Bathymetry During October and November 2009, the KBS performed a bathymetric Survey of Wolf Creek Lake. The survey (KBS, 2010) was carried out using an acoustic echo sounding apparatus linked to a global positioning system. Nearly 74,000 georeferenced depths were measured and used to create a digital bathymetric model of the reservoir (Figure 2-4). For a water surface elevation of 1,088.90 ft, the surface area and volume of the lake were 4,863 acres and 117,407 acre-fl, respectively (KBS, 2010). The maximum depth was 73.75 ft. As stated in the USAR (WCNOC, Revi1 2015, Section 2.4.1.1), the lake has a surface area of 5,090 acres and a capacity of 111,280 acre-ft of water at its normal operating level. In June 1998, Coffey County assumed responsibility for managing public use of the lake. The lake is open for public use seven days a week from sunrise to sunset, weather, and reservoir levels permitting (KBS, 2010).

2.6.2 Recommendation 2.3 Walkdown Results The Wolf Creek Nuclear Operating,CorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) gives results of the walkdown, including key findings and identified degraded, non-conforming, or unanalyzed conditions, and includes detailed descriptions of the actions taken or planned to address these conditions. The results of the walkdown observations were reviewed through site processes in accordance with Regulatory Issues Summary 2005-20, Revision 1 (WCNOC, 2012).

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Safety-related SSCs that are credited in the CLB for protecting the plant from external flood hazards were identified, inspected, and evaluated to be adequate. According to the report (WCNOC, 2012), "The walkdown visual inspection has verified that there is reasonable assurance the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The Wolf Creek external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard." The review of the walkdown concludes that the WCGS site '"flood protection features would be capable of performing their intended flood protection function if subjected to a design basis flooding hazard. No flooding walkdown observations were deemed to be a deficiency per Section 3.8 of Nuclear Energy Institute (NEI) 12-07" (WCNOC, 2012).

2.6.3 Site Visit In support of the Revision 0 FHRR and associated analyses, a site visit was conducted on March 18 and 19, 2013. An additional site visit was performed on September 3, 2014 in support of the Rev 1 updated analysis documented in this Revision 1 report. The areas visited included:

• The powerblock area and area immediately surrounding the powerblock

• The ESWS pumphouse

• The cooling water discharge structure

• The VBS

• Portions of Wolf Creek Lake

• Wolf Creek and its tributaries (north of Wolf Creek Lake)

Rev 1 Photographs of the site and surrounding area from both site visits were reviewed during the development of the flood hazard reevaluation analyses.

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3.0 FLOOD HAZARD REEVALUATION ANALYSIS Section 3.0 has been prepared in response to Request for Information Item 1.b. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a): Evaluation of the flood hazard for each flood-causing mechanism should be based on present-day methodologies and regulatory guidance. Provide an analysis of each flood-causing mechanism that may impact the site including local intense precipitation and on-site drainage, flooding in streams and rivers, dam breaches and failures, storm surge and seiche, tsunami, channel migration or diversion, and combined effects. Mechanisms that are not applicable at the site may be screened out; however, a justification should be provided. Provide a basis for inputs and assumptions, methodologies and models used including input and output files, and other pertinent data.

3.1

SUMMARY

OF RECOMMENDATION 2.1 To respond to Phase 1 of NRC Recommendation 2.1 (NRC, 2012a) and the 2012 Appropriations Act, the NRC requested that each licensee provide a reevaluation of all appropriate external flooding sources, including the effects from local intense precipitation on the site, PMF on streams and rivers, storm surges, seiches, tsunamis, and dam failures. A hazard evaluation should be performed for each reactor licensed under 10 CFR Part 50, including the spent fuel pool and the various modes of reactor operation. The reevaluation should apply present-day regulatory guidance and methodologies being used for Early Site Permit (ESP) and Combined Operating License (COL) reviews. The reevaluation should employ current techniques, software, and methods used in present-day standard engineering practice to develop the flood hazard.

3.2 SOFTWARE USED Software programs used in the flood hazard reevaluation included FLO-2D Pro versions 2 Rev I 13.02.04 and 14.03.07 (FLO-2D, 2014), the USACE HEC-HMS program version 3.5 (USACE, 2010Oa), the USACE HEC-RAS program version 4.1 (USACE, 2010Ob), USACE HMR52 program (USACE, 1987), ArcGIS 9.3 (ESRI, 2009), and ArcGIS 10.1 (ESRI, 2012).

2 FLO-2D Pro version 13.02.04 was used for LIP Cases 1 through 6, which were prepared for the FHRR Revision 0. Re1 LIP Case 7 was prepared for this Revision 1 FHRR using FLO-2D Pro version 14.03.07. The software release notes (FLO-2D, 2014) outline the changes between versions.

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The FLO-2D Pro software is a volume conservation model, which routes fluid flow in one-dimensional (1D) channel flow, two-dimensional (2D) overland flow, or an interaction between the two model components (FLO-2D, 2012). The FLO-2D Pro software is an "effective tool for delineating flood hazards or designing flood mitigation" (FLO-2D, 2012). The FLO-2D Basic model is the other model available from FLO-2D Software, Inc., and includes fewer features than the Pro model. The Basic model has been approved by the Federal Emergency Management Agency (FEMA) for use in Flood Insurance Studies (FIS). The Pro model, though not specifically approved by FEMA, includes all the features of the Basic model, along with some additional features (e.g., storm drain interface with surface water, parallel processing capabilities, and expanded capabilities for simulating sediment transport) (FLO-2D, 2012).

Additional qualifications of the FLO-2D Pro software are presented in Appendix A.

3.3 FLOOD-CAUSING MECHANISMS NRC NUREG/CR-7046 (NRC, 2011) recommends using a Hierarchical Hazard Assessment (HHA) method for evaluating the safety of SSCs. The HHA is a progressively refined, stepwise estimation of site-specific hazards that starts with the most conservative plausible assumptions consistent with available data. The HHA process proceeds as follows (NRC, 2011):

a. Select one flood-causing mechanism to be reanalyzed.

b. Develop a conservative estimate of the site-related parameters using simplifying assumptions for a flood-causing mechanism and perform the reevaluation.

c. Determine if the reevaluated flood hazard elevation (from step b) is higher than the original design flood elevation for the selected flood-causing mechanism. If not, use this flood elevation for this causal mechanism for comparison of reevaluation against the current design basis.

d. Determine if the site-related parameters can be further refined. If yes, perform reevaluation (repeat step c). If no, use this flood elevation for this causal mechanism for comparison of reevaluation against the current design basis.

e. Determine if all flood-causing mechanisms have been addressed. If yes, continue to the following. If no, select another flood-causing mechanism (step a).

For each flood-causing mechanism, compare the final flood elevations from the hazard reevaluation against the current design basis flood elevations. Using this comparison, determine whether the design basis flood bounds each reevaluated hazard.

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Each potential flood-causing mechanism has been evaluated using present-day methodologies and regulatory guidance. Details regarding the considerations and outcome of the analyses regarding each flood-causing mechanism are presented in the following sections.

3.3.1 Local Intense Precipitation Section 3.3.1.1 through Section 3.3.1.4 address the effects of LIP on the local area of the WCGS site. The HHJA diagram for LIP flooding is presented in Figure 3-1.

3.3.1.1 Local Intense Precipitation Rainfall NUREG/CR-7046 (NRC, 2011) states that "Local Intense Precipitation is a measure of the extreme precipitation at a given location." The LIP is "deemed equivalent to the 1 hr, 2.56-km 2 (1-mi 2 ) PMP at the location of the site" (NRC, 2011).

The design basis LIP analysis described in the USAR (WCNOC, 2015) uses the most up-to-date Hydrometeorological Report (HMR) applicable to the WCGS site, HMR No. 52 (National Weather Service ['NWS], 1982). For the purposes of the flood hazard reevaluation, a hyetograph was prepared from the rainfall depths obtained from HMR No. 52. The hyetograph has a Rev I duration of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, subdivided into five-minute intervals, with the most intense rainfall occurring in the first hour. The cumulative LIP rainfall depth for the 6-hr LIP is 28.79 inches, including 19 inches that falls in the first hour (i.e., the 1-hr, 1-mi 2 LIP).

3.3.1.2 Effects of Local Intense Precipitation In accordance with the guidance presented in NRC NUREG/CR-7046 (NRC, 2011), the considerations addressed in the analysis of flooding resulting from LIP were:

• Depth of Flooding

• Duration of Flooding

• Maximum Velocities

• Hydrodynamic and Hydrostatic Loads

• Sedimentation

• Debris Loading Wolf Creek Nuclear Operating Corporation ,*

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Each of these considerations was evaluated based on the results of a detailed two-dimensional (2D) flood routing model that was developed for the WCGS site. This model, FLO-2D Pro (FLO-2D, 2014), represented all the topographical and man-made features (i.e., buildings, tanks, and structures) that significantly affect runoff at the WCGS site. The FLO-2D model developed for the Revision 0 FHRR represented the WCGS site as of February 2013. An additional Rev 1 simulation (Case 7, below) was added for this Revision 1 FHRR to represent the WCGS site as of July 2015.

The output of the FLO-2D model includes water surface elevations, water depths, maximum water velocities, and the duration of flooding. FLO-2D also computes the hydrostatic and hydrodynamic forces that the floodwater could exert on obstacles (e.g., buildings) within flooded areas. These results from FLO-2D directly address the requirements of NRC NUREG/CR-7046 (NRC, 2011). The potential for sedimentation and debris loading is evaluated outside of FLO-2D, based on FLO-2D output of depths, maximum velocities, and flow directions.

The extent of the FLO-2D model is illustrated in Figure 3-2. The model boundaries were established away from the powerblock area and safety-related SSCs in order to prevent boundary conditions from affecting flood levels evaluated within the powerbiock area and to ensure the stability of the model. The FLO-2D domain covered an area of approximately one quarter of a square mile. The southern and western boundaries follow the surrounding roads (Figure 3-2).

These roads form drainage divides, making an appropriate place for a model boundary.

The eastern boundary of the model domain follows the edge of Wolf Creek Lake, including a narrow portion of the lake around the ESWS pumphouse and then extends north (to include areas that could contribute runoff into the FLO-2D domain). The northern boundary is placed to include areas that could contribute runoff toward the powerbiock area.

The following simulations were completed for the model area to investigate the effects of Rev 1 flooding from a LIP event. Six cases were developed for the Revision 0 FHRR as follows:

• Case 1 was the most conservative, a steady-state simulation with no infiltration losses and the VBS blocked (i.e., water is not allowed to flow through spaced between the VBS jersey barriers). This is in accordance with the HHA method outlined in NRC NUREG/CR-7046 (NRC, 2011).

Additionally, a relatively high Manning's roughness coefficient was used for this simulation. The grid cell size was 15 ft for this simulation.

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• Case 2 was built on the same FLO-2D grid as Case 1. However, the time-varying LIP distribution was applied. The VBS was partially unblocked in this case.

• Case 3 provided a sensitivity analysis for grid cell size by constructing a model with 20 ft grid cells that is otherwise equivalent to Case 2.

• Case 4 was similar to Case 2, but applied lower Manning's roughness coefficients (toward the middle of recommended ranges) than Case 1 through 3.

• Case 5 was similar to Case 4. However, rainfall infiltration was accounted for using the Curve Number Method.

• Case 6 was the same as Case 5, except that the Manning's roughness coefficients for Case 6 were assigned based on the lower end of recommended ranges.

An additional simulation (Case 7) was completed for this Revision 1 FHRR to represent the plant configuration and topography as of July 2015. Case 7 represents an update to the Case 6 model, applying the same Manning's roughness coefficients as Case 6, with updates to represent the July 201i5 plant configuration and topography. In addition to plant configuration updates, Rev 1 refinements were made to the characterization of building roofs and transformer curbs. The roof characterization refinements included crediting some of the retention storage on the powerblock building roofs. Flow through downspouts was not credited for Case 7, which is consistent with Cases 1 through 6.

In accordance with the HHA method (Figure 3-1), Case 1 was the most conservative case and the subsequent simulations were progressively refined. The results of the FLO-2D modeling show that the steady-state LIP distribution (Case 1) provided the most conservative estimate of flood levels. The other Revision 0 FHRR simulations provided comparable results with some variation. Case 6 was presented as the final simulation per the HHA methodology. Case 7 is an Rev 1 update of the Case 6 model and is presented as the final simulation for this Revision 1 FHRR.

The FLO-2D results for the Case 7 simulation are summarized in Table 3-1 for buildings and tanks on the powerblock. The corresponding inundation map for Case 7 is included in Figure 3-2, illustrating the peak flood depths across the FLO-2D model domain. The peak flood Rev 1 elevations for Case 7 ranged from 1,100.03 ft to 1,100.38 ft adjacent to Seismic Category I buildings. The highest simulated water level adjacent to a safety-related building was elevation 1,100.38 ft, adjacent to the Auxiliary and Reactor Buildings (Table 3-1).

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Potential pathways along which surface water runoff could reach safety-related SSCs include 40 different doors, vaults, and manholes. Table 3-2 and Table 3-3 present the potential pathways evaluated and the associated flood parameters for the Case 7 simulation. It is important to note that the ESW manholes (Table 3-3, Items 7 through 16) are designed to be watertight, which is Rev 1 discussed in the Wolf Creek Nuclear Operating CorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012).

In all simulations (Cases 1 through 7), floodwaters exceeded entrance elevations at several Rev I pathways leading to Seismic Category I structures. This flooding was higher than flood levels that are reported in the design basis, which states that water levels during a LIP event do not exceed an elevation of 1,099.92 ft near safety-related buildings (WCNOC, 2015, Section Rev 1 2.4.2.3.2). One site feature that significantly affects flood levels near safety-related SSCs is the old railroad track that approaches the east side of the Fuel Building. The railroad track slows runoff from the east side of the powerblock and causes higher water levels near safety-related SSCs.

Wolf Creek Lake is much larger than the area of interest for a LIP event. Consequently, the entire lake was not included in the same flood model used for the LIP analysis. The change in lake level due to a LIP event was evaluated with a hand calculation. It was determined that the Rev I water level in Wolf Creek Lake could increase by approximately 0.32 ft, which results in a water level of 1,088.32 if, based on an antecedent water level of 1,088.00 ft. A water level of 1,088.32 ft is significantly lower than the flood elevation predicted when simulating the flooding effects of PMP in the entire watershed (Section 3.3.2).

The results of the reevaluated flooding event due to LIP are compared against the CLB in Section 4.2.

3.3.1.3 Sedimentation and Debris Loading Coincident with Local Intense Precipitation Sedimentation and debris loading are screened out qualitatively as hazards during a LIP event in the powerblock area. This screening is based on the flow depths, flow velocities, and flow directions predicted in the FLO-2D model. Runoff depths and velocities are generally small (Table 3-2 and Table 3-3) and do not constitute a credible hazard for sedimentation or debris loading. Additionally, runoff is generally directed away from safety-related SSCs, precluding any impact on the SSCs from sedimentation or debris loading.

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3.3.1.4 Wind-Waves and Run-Up Coincident with Local Intense Precipitation Wave run-up is a process whereby waves can be generated by high wind velocities coincident with large storm events. The wind speed concurrent with the postulated wind-wave analysis is a two-year maximum sustained wind of 38.65 mph, calculated using procedures in the United States Army Corps of Engineers' (USAGE) Coastal Engineering Manual (GEM) (USAGE, 2008). Ponding depths in the powerblock area did not support the growth of wind-waves because ponding depths are relatively mild (approximately 1 to 2 ft; Figure 3-2). In addition, flow velocities were generally directed away from safety-related SSCs, preventing waves from reaching safety-related SS~s. Also, tall buildings within the powerbiock area block wind. As a result, the various buildings and structures (including the VBS) shorten potential fetch lengths.

The PMF causes higher water levels to occur in Wolf Greek Lake (Section 3.3.2.2) than for LIP flooding. Consequently, the effects of wind-waves during the LIP were bounded by the effects of wind-waves during the PMF. Based on these reasons, no further analysis of wind-waves during a LIP event was required. Run-up from wind-waves in Wolf Creek Lake resulting from the PMF in Wolf Creek watershed is evaluated in Section 3.3.2.2.3.

3.3.2 Flooding in Rivers and Streams River flooding at the WCGS site was evaluated with respect to the Wolf Creek watershed. The Wolf Creek watershed was identified in the USAR (WGNOG, 2015, Section 2.4.2.2) as the Rev 1 controlling watercourse for flood protection at the site. Therefore, it is included in the models for river flooding evaluation.

The WCGS lies in the Wolf Creek watershed, which is bordered by the Long Creek watershed to the east and the larger Neosho River watershed to the west and south (Figure 1-2). In the analysis of flooding potential by rivers, the Neosho River and Long Creek watersheds were first screened to estimate the PMF in those watersheds and to determine whether their respective river channels and valleys are capable of containing the maximum flow rates resulting from a PMF.

For this assessment, the total areas of the two watersheds were obtained. NRC Regulatory Guide (RG) 1.59 (NRG, 1977, Appendix B) was followed to estimate peak PMF discharges for those two watersheds, based on the locations of the watersheds and the watershed drainage areas. It was determined that representative watershed cross-sectional areas are capable of containing the PMF peak discharges in those two watersheds. Therefore, they were screened out as potential Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Pg 0o 0 145262/135031/15 Rev. 1 (October 21, 2015) Pae 0of10 J

sources of flooding risk to the WCGS by PMF, and were not included in the flooding analysis of the Wolf Creek watershed area described in Section 3.3.2.2.

NRC NUREG/CR-7046 (NRC, 2011) prescribes a methodology for determining the PMF based on the HHA method (Figure 3-3). As stated in NRC NUREG/CR-7046 (NRC, 2011), "The hierarchical hazard assessment [HHA] is a progressively refined, stepwise estimation of site-specific hazards that evaluates the safety of SSCs with the most conservative plausible assumptions consistent with available data." The HHA method starts with the most conservative simplifying assumptions that maximize the hazards for the probable maximum event. If the most conservative assumptions do not result in site inundation, no further flood hazard assessment is required. However, if the flood level of an assessed hazard may adversely affect any safety-related SSC, more refined hazard assessments are performed using site-specific data to demonstrate whether SSCs are adequately protected from the adverse effects of severe floods (NRC, 2011).

For the river flooding analysis, the Wolf Creek watershed was divided into five subbasins (Figure 3-4), which is consistent with the methods outlined in NRC NUREG/CR-7046 (NRC, 2011) for subbasin delineation and composite curve number evaluation. Subbasins 1 through 3 represented watersheds upstream of Wolf Creek Lake. Part of Subbasin 4 represented the land from which runoff reaches Wolf Creek Lake directly. Subbasin 5 represented the southern portion of the watershed that drains directly into Wolf creek downstream of the Wolf Creek Lake Dam. The delineated watershed ended at the confluence of Wolf Creek and the Neosho River.

Subbasin 5 was delineated to model potential backwater effects from the Neosho River.

The PMP for the Wolf Creek watershed was calculated using the USACE's HMR52 computer program (USACE, 1987), as described in Section 3.3.2.1.

A watershed hydrologic response model (HEC-HMS) was developed to compute runoff hydrographs and runoff volumes for each subbasin for the PMP event (Section. 3.3.2.2.1). A stream course model (HEC-RAS) was then used to compute flood levels at representative points within the Wolf Creek watershed using the runoff rates from the HEC-HMS model (Section 3.3.2.2.2).

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3.3.2.1 Probable Maximum Precipitation for Wolf Creek Watershed The PMP is "a deterministic estimate of the theoretical maximum depth of precipitation that can occur at a time of year over a specified area" as defined in NRC NUREG/CR-7046 (NRC, 2011).

The PMP is estimated to determine the Probable Maximum Storm (PMS) event that generates the maximum direct runoff (or peak discharge) from the Wolf Creek watershed.

The HMR52 program is used to compute the PMP. The 72-hr duration cumulative rainfall is computed to be 36.70 in (Figure 3-5), per the guidance of NRC NUREG/CR-7046 (NRC, 2011).

The maximum rainfall occurs at approximately 39 hrs after the beginning of the rainfall event.

3.3.2.2 Probable Maximum Flood for Wolf Creek Watershed The river flooding for Wolf Creek watershed was performed using two different software packages. The HEC-UMS modeling software was initially used to simulate a PMP storm in the Wolf Creek watershed and to calculate PMF flow rates emanating from each subbasin during the PMP event. Five cases were simulated and the results of each simulation are described in Section 3.3.2.2.1.

The HEC-RAS modeling software was used to evaluate water levels associated with the PMF in the Wolf Creek watershed. Ten simulations were performed to evaluate the effects of a PMP event on the flood depths, duration, and average flow velocities in the watershed and Wolf Creek Lake. Cases 1 through 5 were run as steady-state simulations. Case 6 was a more refined model, and represented a non-steady (i.e., transient) simulation of a PMP storm event and the resulting PMF in the watershed. The results of these simulations are presented and discussed in Section 3.3.2.2.2. The HEC-RAS Case 6 model results were considered to be the most refined modeling results of river flooding in this reevaluation per the HHA approach (NRC, 2011).

The Case 6 HEC-RAS model was also used to evaluate wind-wave run-up (Section 3.3.2.2.3) and to calculate hydrostatic forces on the ESWS pumphouse (Section 3.3.2.2.3). The effects of partially blocked spillways of the Wolf Creek Lake Dam by debris (Cases 7 through 9) and sedimentation in the lake (Case 10) are presented and discussed in Sections 3.3.2.2.4 and 3.3.2.2.5, Wolf Creek Nuclear Operating Corporation ,,

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3.3.2.2.1 Water Level Due to Probable Maximum Flood Using HEC-HMS Model To evaluate the PMF for the Wolf Creek watershed, HEC-HMS modeling software was used to perform the first level of modeling. The HEC-HMS model was set up using the five subbasins delineated for the watershed (Figure 3-4) and the PMP event (Figure 3-6). Physical characteristics of the five subbasins are listed in Table 3-4. Wolf Creek Lake was part of Subbasin 4. Subbasin 5 was included in the model to evaluate potential backwater effects that could occur downstream of Wolf Creek Lake. The HEC-HMS model was calibrated before running the PMF simulations.

Five different variations of the model input values and/or model conditions were utilized to create five different HEC-HMS cases, which are summarized in Table 3-5. The HEC-HMS model (Figure 3-6) was run for an eight-day period of time to capture the full effects of the PMF event on Wolf Creek Lake.

The cases for the HEC-'IMS model were based on the criteria documented in NRC NUREG/CR-7046 (NRC, 2011, Appendix B). Case 1 was the most unrefined case and the other cases are more refined. For Cases 3 through 5, the nonlinearity effect during the PMP event was taken into consideration by reducing the lag time by 33 percent and increasing the resulting peak discharge.

As stated in NRC NUREG/CR-7046 (NRC, 2011, Section 3.3.2), the recommended adjustments are "a 5-to-20-percent increase for the peak discharge and a 33-percent reduction in the lag time." Increasing the peak discharge by 20 percent resulted in a higher discharge than the discharge for Case 1 (the most conservative case). Therefore, a five percent increase in the peak discharge (i.e., the lower range suggested in NRC NUREG/CR-7046 [NRC, 2011]) was applied in Cases 3 through 5.

The maximum water level predicted in Wolf Creek Lake (1,095.3 ft) resulted from the Case 1 model run, as expected because Case 1 is a steady-state simulation. The results of Case 5 are considered to be the most refined of the HEC-HMS model runs. The hydrograph of the lake level for HEC-HMS Case 5 model run is presented in Figure 3-7. The Case 5 flow rates computed for each subbasin were used as input values for the HEC-RAS modeling, presented in Section 3.3.2.2.2.

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3.3.2.2.2 Water Level Due to Probable Maximum Flood Using HEC-RAS Model In order to refine the flood analysis, HEC-RAS version 4.1 (USACE, 2010~b) was used to simulate rainfall and runoff on Wolf Creek and Wolf Creek Lake. HEC-RAS can represent steady-state and unsteady-state conditions accurately, as necessary for this reevaluation. HEC-RAS is also used in NRC NUREG/CR-7046 (NRC, 2011) in examples similar to those encountered in the Wolf Creek watershed.

The purpose of the HEC-RAS model was to produce a more refined estimated of peak water level in Wolf Creek Lake during the PMF event and to evaluate the potential impact to flood levels in the lake if the spiliway of the Wolf Creek Lake Dam was partially blocked by debris.

The calibrated HEC-RAS model (Figure 3-8) included:

• A reach representing Wolf Creek upstream of Wolf Creek Lake (i.e., Upper Reach)

• Wolf Creek Lake

• Wolf Creek Lake Dam

• A reach representing Wolf Creek downstream of Wolf Creek Lake (i.e.,

Lower Reach)

Ten HEC-RAS simulations (Table 3-5) were performed to address the following NRC requirements:

• Flood levels

• Flood duration

• Flow velocities

• Debris loading and blockage of the flow

• Sedimentation HEC-RAS Cases 1 through 6 addressed the level, duration, and velocities of the PMF flood.

Cases 7 through 9 addressed debris loading and blockage of the spillways of the Wolf Creek Lake dam. Case 10 addressed sedimentation in Wolf Creek Lake.

A diagram of the HEC-RAS model and the channel cross-sections created within the model area is presented in Figure 3-8. Wolf Creek Lake was represented as a storage area and the Wolf Wolf Creek Nuclear Operating Corporation EN*.

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Creek Lake Dam was represented as an inline structure in the HEC-RAS model. The elevation-storage information for Wolf Creek Lake was obtained from the Bathymetric Survey of Wolf Creek Reservoir (Coffey County Lake), Coffey County, Kansas (KBS, 2010).

The boundary conditions used in the HEC-RAS model setup included inflows, storage area initial conditions, and upstream and downstream slopes. Initial lake levels were set at, or just above, the lowest spillway crest elevation. A normal flow condition was specified at the downstream ends of the model reaches. The stream slopes associated with this normal flow condition were set in the model using the topographic elevations along the last two downstream cross-sections.

A total of ten numerical simulations were conducted using the calibrated HEC-RAS model (Table 3-5). HEC-RAS Cases 1 through 5 used the peak flow rates from HEC-HMS Cases 1 through 5 as input values. These cases were run under steady-state conditions.

HEC-RAS Case 6 was run as an unsteady (i.e., transient) model, which is more realistic and more refined than the first five cases. The hydrograph of water level in the lake resulting from HEC-RAS Case 6 is presented in Figure 3-7. The peak water level in Wolf Creek Lake for Case 6 was 1,093.57 fi, which did not exceed the capacity of the spillways.

3.3.2.2.3 Wind-waves and Run-Up Coincident with Probable Maximum Flood Wave run-up associated with maximum flooding in the Wolf Creek Lake is evaluated and discussed in this subsection. Wave run-up is a process whereby waves can be generated by high wind velocities coincident with storm events. Wave run-up is evaluated using procedures outlined in the USACE's CEM (USACE, 2008) at the following locations:

• Wolf Creek Lake Dam

• Wolf Creek Lake shoreline (near the WCGS site)

• Intake structure of the ESWS pumphouse According to the USACE CEM (USACE, 2008), "Fetch is defined as a region in which the wind speed and direction are reasonably constant." The longest fetch was determined for critical locations along the Wolf Creek Lake Dam, the Wolf Creek Lake shoreline, and at the intake structure of the ESWS pumphouse. These locations and the fetch paths and fetch lengths used to calculate wave run-up are shown in Figure 3-9. These fetch lengths were used in the wave run-Wolf Creek Nuclear Operating Corporation -'

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up analysis. The Wolf Creek Lake Dam fetch was defined as the longest fetch that approaches the dam (Figure 3-9). For the Wolf Creek Lake shoreline, the fetch was defined at a critical location where the longest fetch approached nearest the WCGS site (Figure 3-9). For the intake structure of the ESWS pumphouse, Fetch 1 was chosen as the most feasible fetch.

To perform the wind-wave analysis, the two-year return period maximum sustained wind (MSW) speed was calculated, using procedures defined in the USACE CEM (USACE, 2008).

The two-year MSW speed was calculated to be 38.65 mph. Once the fetch and MSW were computed, the sustained overland wind speed (MSW) was converted to an overwater wind speed, because the wind is traveling over a body of water (i.e., Wolf Creek Lake). The overwater wind speed (46.38 mph) was calculated using procedures outlined in the USACE CEM (USACE, 2008).

The peak PMF water level in Wolf Creek Lake (1,093.54 ft) obtained from the HEC-RAS Case 6 model (the most refined case) was used as the antecedent water level (or stillwater level) for the wind-wave analysis. Equations from the USACE CEM (USACE, 2008, Figure 11-2-20) were used to calculate significant wave height and peak period.

There are two general categories of run-up equations:

1. Equations for run-up on structures (steeper slopes)

2. Equations for run-up on beaches (shallower slopes)

Consequently, the wave run-up equations utilized for the intake structure of the ESWS pumphouse and for the Wolf Creek Lake Dam and the shoreline of Wolf Creek Lake differed.

However, both run-up equations are for run-up levels exceeded by only two percent of the incident waves. The two-percent run-up (R2 %) equations were used because this is reconumended in the USACE CEM (USACE, 2008, Part II Chapter 4). Field measurements of run-up have shown that the two percent run-up equation in the USACE CEM conservatively overestimates run-up by a factor of two, but is roughly an upper envelope of the data scatter (USACE, 2008, p. II-4-18).

The equation recommended in the USACE CEM (USACE, 2008) for beaches was applied for computing the run-up level on the Wolf Creek Lake shoreline and the Wolf Creek Lake Dam, Wolf Creek Nuclear Operating Corporation "

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because the slopes where run-up occurs are relatively mild. The standard run-up equation for two percent run-up level beaches (USACE, 2008, Equation 1I-4-29) was used for this analysis.

The final computed wave run-up computed for the reevaluation were 7.01 fi, 0.83 fi, and 4.89 fi, resulting in elevations of 1,100.55 fi, 1,094.37 fi, and 1,098.43 ft for the Wolf Creek Lake Dam, Wolf Creek Lake shoreline, and the ESWS pumphouse, respectively. The final wave run-up level on the Wolf Creek Lake Dam exceeded the crest of the dam of 1,100 ft (WCNOC, 2015). Revi1 However, the dam is not a safety-related structure. In addition, the upstream slope of the Wolf Creek Lake Dam has riprap to protect against erosion from wind-wave activity (WCNOC, 2015). Rev I The maximum run-up level for the Wolf Creek Lake shoreline did not exceed the design basis flood elevation of 1,095 ft (WCNOC, 2015, Section 2.4.3.5). The maximum estimated run-up Rev 1 level for the intake structure of the ESWS pumphouse did not exceed the design basis flood elevation of 1,100.2 ft (WCNOC, 2015, Section 2.4.10). Therefore, the maximum anticipated Revi1 wave run-up elevations at the Wolf Creek Lake shoreline and the ESWS pumphouse did not adversely affect any SSCs at the WCGS site.

An evaluation of the effects of baffle dikes A and B and the breakwater (near the ESWS pumphouse) (Figure 3-9) on waves and wave run-up was also performed. Baffle dikes A and B did not affect the fetches or wave setup for the Wolf Creek Lake Dam, the Wolf Creek Lake shoreline, or the inlet structure of the ESWS pumphouse. Near the ESWS pumphouse, the lake depth was shallow and the breakwater located near the ESWS pumphouse would cause waves to break even though it is submerged due to the PMF water level (the antecedent water level). As determined from light detection and ranging (LiDAR) data, the top of the breakwater was approximately 1,092 ft. The antecedent lake water level was 1,093.54 ft. Therefore, any waves approaching the ESWS pumphouse and intake structure would break at the breakwater and reach the intake structure of the ESWS pumphouse with a smaller wave height than the wave height that approached the breakwater.

3.3.2.2.4 Effects of Spillway Blockage on the Maximum Wolf Creek Lake Level HEC-RAS Cases 7 through 9 considered varying levels of blockage of the spillways following the HHA approach (50 percent, 20 percent, and ten percent blockage of the service spillway, respectively, and ten percent of the auxiliary spiliway) to provide a sensitivity analysis on the percent blockage of the spillways (Table 3-5) per NRC JLD-ISG-2013-01 (NRC, 2013b).

Simulated peak water levels for Cases 7 and 8 exceeded the design basis elevation of 1,095.0 ft.

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However, Cases 7 and 8 were sensitivity cases and were not considered realistic due to the dimensions of the spillways (given in Section 2.1.1.3). Case 9 did not exceed the design basis elevation of 1,095.0 ft.

The unsteady flow case (Case 6, the most refined case) was used as the final case that was compared against the USAR because the design basis did not block the spillways and the case was considered the most realistic case due to the dimensions of the spiliways and the history of debris production in the watershed. The Case 6 peak water level of 1093.57 ft did not exceed the design basis elevation of 1,095.0 ft (WCNOC, 2015, Section 2.4.3.5). Rev 1 3.3.2.2.5 Effects of Sedimentation in Wolf Creek Lake A HEC-RAS model run (Case 10) was performed to evaluate what effect sedimentation in Wolf Creek Lake might have on the water level in the lake during a PMF event. HEC-RAS Case 6 was used as the basis for this analysis. In Case 10, the Wolf Creek Lake storage was adjusted to represent conditions after a sediment inflow volume of 1,080 acre-ft over 40 years. The predicted maximum water level in the lake was 1,093.54 ft, which was the same elevation as determined for Case 6.

3.3.2.2.6 Combined-Effects Flood Many flood-causing mechanisms can occur concurrently because they are not truly independent.

For example, floods from precipitation events may occur concurrently with an antecedent snowpack and wind-induced waves. The impact of a simultaneous occurrence of flood-causing mechanisms was defined by the American Nuclear Society (ANS), ANSI/ANS-2.8-1992 (ANS, 1992), and later defined as "combined effect flooding" in NRC NUTREG/CR-7046 (NRC, 2011).

Three alternative combinations of flood-causing events for precipitation floods are described in Section 9.2.1.1 of ANSI/ANS-2.8-1992 (ANS, 1992):

Alternative I

1. Mean monthly (base) flow

2. Median soil moisture Wolf Creek Nuclear Operating Corporation *1 Flood Hazard Reevaluation Report Pg 8o 0 145262/135031/15 Rev. 1 (October 21, 2015) Page38 o 10

3. Antecedent or subsequent rain: the lesser of (1) rainfall equal to 40 percent of PMP or (2) a 500-year rainfall

4. PMP

5. Two-year wind speed applied in the critical direction Alternative II

1. Mean monthly (base) flow

2. Probable maximum snowpack

3. Coincident 100-year snow season rain

4. Two-year wind speed applied in the critical direction Alternative III

1. Mean monthly (base) flow

2. 100-year snowpack

3. Coincident snow season PMP

4. Two-year wind speed applied in the critical direction Alternative I analysis represents a flood based on summer meteorological conditions (maximum PMP). Alternative II and III analyses are based on winter conditions. Due diligence requires a preliminary evaluation of the Probable Maximum Snow Accumulation (PMSA) and winter season PMP depths before Alternative II and III combined events can be screened out. The calculations to assess the impact of winter hydrometeorologic loadings show that the PMSA combined with a 100-year winter rainfall event (with total snowpack melting and no water losses, Alternative II) produced total runoff depths of 23.62 in to 26.94 in for Cottonwood Falls and Osage City, respectively. This amount was significantly less than the PMP rainfall depth (36.70 in) calculated in Section 3.3.2.1. The calculation of an April PMP falling on a 100-year snowpack (Alternative III) produced a total water depth of 34.7 in, which was also less than the PMP rainfall depth (36.70 in) calculated in Section 3.3.2.1. As a result, the conservative estimates of combined snowmelt-rainfall runoff in winter months (Alternatives II and III) were Wolf Creek Nuclear Operating Corporation *1*,

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• screened out. Alternative I was deemed the most conservative combined-effects alternative to evaluate.

3.3.2.2.6.1 Evaluation of Combined-Effects Flooding Using ANS Alternative I The HHA approach is followed for combined-effects flooding analysis, as shown in Figure 3-10.

Two antecedent rain conditions prior to the PMP were evaluated in the flood hazard reevaluation:

• A 72-hr rainfall event with a total depth of 40 percent of the PMP

• A 24-hr 500-year rainfall event The 40 percent PMP event was approximated by multiplying all PMP ordinates by a constant factor of 0.4. A 24-hr duration was used for the 500-year storm to be consistent with standard industry practice. The Soil Conservation Service (SCS) unit rainfall curves are typically set up for 24-hrs (Chow et al., 1988, p. 461). Following the procedures laid out in NRC NUREG/CR-7046 (NRC, 2011), the storm with the lesser impact on peak discharge was utilized for combined-effect modeling. After evaluating the two possible storm events, 24-hr 500-year rainfall event was utilized as the rainfall event preceding the PMP for combined-effect modeling.

The combination of 500-year rainfall and PMP were then used to create a new rainfall hyetograph for modeling.

The new storm hyetograph was used as input to the HEC-HMS Case 5 model. The Case 5 HEC-HMS model was run with the 500-year/PMP hyetograph combination to obtain the subbasin hydrographs for input to the HEC-RAS model.

The HEC-RAS Case 6 model (Section 3.3.2.2.2) was then used to model the unsteady (transient) streamfiow in the creek and water level in Wolf Creek Lake. The HEC-RAS combined-effects simulation yielded a maximum predicted water level in Wolf Creek Lake of 1,094.63 ft. This water level was higher than the predicted lake water level for the PMP alone, but was still less than the design basis flood elevation of 1,095 ft (WCNOC, 2015, Section 2.4.3.5). Rev 1 Wolf Creek Nuclear Operating Corporation I

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3.3.2.2.6.2 Wind-waves and Run-up Coincident with Combined-Effects Flood The combined-effects flood level included maximum wave run-up calculated at key locations.

The maximum wave run-up computed for the Wolf Creek Lake Dam, the shoreline at the WCGS, and the ESWS pumphouse were 7.01 fi, 0.83 fi, and 4.89 ft, respectively (Section 3°3.2.2.3). Thus, the combined-effects lake water levels of 1,101.64 fi, 1,095.46 fi, and 1,099.52 ft were computed for those three locations, respectively.

The maximum water surface elevation along the shoreline nearest to the powerblock, including the impact of wave action was 1,095.46 fi, providing a freeboard of 4.04 ft, with respect to the plant grade elevation of 1,099.5 ft (Figure 3-11), and was bounded by the design basis flood Rev 1 elevation including run-up of 1,095.8 ft (WCNOC, 2015, Table 2.4-16).

The maximum water surface elevation at the ESWS pumphouse, including the impact of wave action was calculated as 1,099.52 fi, providing a freeboard of 0.48 fi, with respect to the top of grade-level slab elevation of 1,100 ft and was bounded by the design basis flood elevation for the pumphouse of 1,100.2 ft (WCNOC, 2015, Section 2.4.10). Revi1 3.3.2.2.6.3 Effects of a Combined-Effects Flooding on Debris Loads If debris exists in Wolf Creek Lake, it was expected that the debris would be small (e.g., tree branches, etc.) and would not adversely affect the WCGS site because floodwaters do not rise to the plant grade elevation of 1,099.5 ft, and would not adversely affect the Wolf Creek Lake Dam due to the size of debris. It was expected that debris would not adversely affect the ESWS pumphouse because the intake structure is equipped with trash racks, which protect the ESWS pumphouse from debris (WCNOC, 2015, Section 2.4.7.2). Additionally, the baffle dikes and Rev 1 breakwater provide a defense for the ESWS pumphouse against debris that could be floating in Wolf Creek Lake due to a combined-effects flooding event. In addition, the flow of the floodwater would be southerly towards the main dam, not directed northeasterly around the WCGS site peninsula to the ESWS pumphouse.

3.3.3 Dam Breaches and Failures The potential flooding of the WCGS site due to breaches and failures of dams located upstream of the site was evaluated. Except for the Wolf Creek Lake Dam, no other dams were listed in the USACE National Inventory of Dams (NID) database (USACE, 201 3a) for the Wolf Creek Wolf Creek Nuclear Operating Corporation 1 .,

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watershed. A total of 322 dams were been identified in the Neosho River watershed upstream and downstream of the Wolf Creek watershed. These are shown in Figure 3-12.

The evaluation of dam failure was performed using a quantitative assessment that screened out flooding hazards due to a dam breach using the storage level, distance from the WCGS site, and head differential. The quantitative assessment utilized the Volume Method outlined in the NRC JLD-ISG-2013-01 guidance for dam failure analysis, "Guidance for Assessment of Flooding Hazards Due to Dam Failure" (NRC, 201 3b). This assessment includes the following steps:

1. Obtain a list of dams from the USACE NID (USACE, 2013a).

2. Identify which dams are "inconsequential" or downstream using watershed boundaries (USGS, 2013) and other sources of information (e.g., the Kansas Department of Agriculture [KDA]) (KDA, 2011).

3. Use the Volume Method to identify "noncritical" and "potentially critical" dams. The Volume Method outlined in Section 3 of NRC JLD-ISG-2013-01 (NRC, 2013b) is a simplified dam failure screening analysis.

The Volume Method (i.e., the "Screening" step presented in Figure 3-13) was used because it is the most conservative of the simplified methods listed in Section 3 of NRC JLD-ISG-2013-01 (NRC, 201 3b). Figure 3-14 provides a more detailed illustration of steps within the Volume Method. Other more refined methods are available should the Volume Method identify any "potentially critical" dams.

NRC JLD-ISG-2013-01 (NRC, 2013b) classifies dams as "inconsequential," "noncritical," or "potentially critical," as follows:

• "Inconsequential" dams: "Dams identified by Federal or State agencies as having minimal or no adverse failure consequences beyond the owner's property may be removed from further consideration in the Recommendation 2.1 reevaluation. Dams owned by licensees may not be removed. Other inconsequential dams may be removed with appropriate justification (e.g., if they can be easily shown to have minimal or no adverse downstream failure consequences)" (NRC, 2013b, p. 3-2).

• "Noncritical" dams are dams that have little impact on flooding at the NPP site using a simplified analysis (NRC, 2013b, p. 1-3) (e.g., flood elevations below plant grade).

• "Potentially critical" dams include all other upstream dams (NRC, 2013b, p.

1-3).

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The Volume Method analysis represented a condition with the total upstream reservoir storage volume simultaneously transferred to the WCGS site without attenuation. As part of the Volume Method, the volume of water required for antecedent flood conditions within a reach was first removed from the volume available for storing water from the upstream reservoirs. NRC JLD-ISG-2013-01 (NRC, 2013b) recommends using the antecedent 500-year return period flood flow (R.PFF).

The Volume Method was used to determine the potential for flooding above the WCGS plant grade elevation of 1,099.5 ft (WCNOC, 2015, Section 2.4.3.5). NRC JLD-ISG-2013-01 (NRC, ]Rev 1 201 3b) uses the term "plant grade" in reference to simplified modeling approaches to screen flooding that result from the failure of all dams in the watershed upstream of the site. For this application, flooding above plant grade would require that backwater from flooding on the Neosho River would overtop the Wolf Creek Lake Dam. For debris and sediments along the Neosho River to enter the Wolf Creek Lake, flood levels along the Neosho River would need to exceed the service spillway crest elevation (i.e., 1,088 ft) of the Wolf Creek Lake Dam.

The following steps were performed to evaluate the potential for flooding due to upstream dam failure at the WCGS site:

1. Topographic data were compiled and processed.

2. A list of dams within the Neosho River watershed was obtained. The NID database included a total of 322 dams (Figure 3-12), including 91 downstream dams within the watershed area. The remaining 231 upstream dams have a total volume of 1,633,036 acre -ft.

3. Downstream and "inconsequential" dams were screened out.

4. Antecedent flow conditions along the Neosho River were estimated using the FEMA-reported 500-year RPFF at the City of Burlington (FEMA, 1996). The FEMA Flood Insurance Study (FIS) for the City of Burlington (FEMA, 1996) reported a 500-year RPFF for the Neosho River between the City Dam (upstream Corporate City Limits) and the downstream Corporate City Limits of 290,000 cfs, and provides a 500-year Return Period Flood Elevations (RPFE) profile along the 2.1-mile reach with floodwater elevations ranging between 1,022.5 ft to 1,026.3 ft.

5. A steady-state HEC-RAS model was setup to represent the Neosho River from 334.4 to 343.3 river miles upstream of the Neosho River mouth.

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6. The HEC-RAS model was calibrated to the reported 100-year and 500-year RPFE (FEMA, 1996) using the associated 100- and 500-year RPFF as an upstream boundary condition.

7. The calibrated HEC-RAS model was run using the proper antecedent flow conditions to compute the associated flood levels and the remaining available storage volumes below plant grade.

8. "Noncritical" and "potentially critical" dams were identified. The available water storage volume near the WCGS site for upstream dams (i.e., reservoirs) was calculated using the Spatial Analyst extension and 3D Analyst extension within ArcGIS. If the available storage cannot accommodate the volume of water stored in the upstream dams, then "potentially critical" dams were identified.

9. Potential debris, sediment loading, and waves, were addressed as necessary.

The 500-year RPFE profile along the 2.1-mile reach with floodwater elevations ranged between 1,022.5 ft to 1,026.3 ft. Adding the volume of water stored in the 231 dams located in the upstream portion of the Neosho River watershed (i.e., 1,633,036 acre-fl) raised the floodwaters up to an elevation of 1,076.7 ft. The flood level of 1,076.7 ft in the Neosho River is less than the topographic ridge that separates the Neosho River from the Wolf Creek watershed. Therefore, floodwaters will not cross over to Wolf Creek Lake. However, floodwaters will flow up Wolf Creek from its confluence with the Neosho River. The dam break analysis shows the maximum backwater elevation to be 22.8 ft below the plant grade elevation and 11.8 ft below the Wolf Creek Lake Dam service spillway. Therefore, no "potentially critical" dams were identified, using the Volume Method (NRC, 2013b). All dams were either "inconsequential" or

noncritical.

The peak water level with failure of all upstream dams did not reach the Wolf Creek Lake Dam service spillway invert (i.e., 1,088 ft). The peak water level was 22.8 ft below plant grade (i.e.,

1,099.5 ft) (Figure 3-15"). As a result, no further consideration of debris or sediment at the WCGS site was required as part of the reevaluation analysis.

For a 40-mph wind over water, the run-up associated with maximum wave heights was less than one foot (WCNOC, 2015, Section 2.4.3.6.1). The maximum water level at the WCGS site with tRevi1 the failure of all upstream dams transferred without attenuation was below the Wolf creek Lake Dam service spillway invert (i.e., 1,088 ft), providing a "freeboard" of 22.8 ft below plant grade (i.e., 1,099.5 ft) and 11.3 ft below the service spillway invert. Therefore, the potential impacts of wind-wave activity coincident with dam failure were dismissed.

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3.3.4 Storm Surge The WCGS site is located more than 1,000 miles from the Pacific Ocean, approximately 935 miles inland from the Atlantic Coast, and approximately 600 miles inland from the Gulf of Mexico (USGS, 2013). The site is located adequately inland such that hurricanes and a Probable Maximum Hurricane (PMH) will not be a source of a potential flood hazard. Therefore, further consideration to storm surge flooding outlined in NRC NUREG/CR-7 134 and NRC JLD-JSG-2012-06 (NRC, 2012b; 2013c) was not applicable to the WCGS site.

Storm surge due to Probable Maximum Wind Storms (PMWS) and squall lines was also not applicable to the WCGS site, because the site is not located on the Great Lakes, as is discussed in ANSI/ANS-2.8 (ANS, 1992) and NRC JLD-ISG-2012-06 (NRC, 2013c). Therefore, according to NRC JLD-ISG-2012-06 guidance, determination of hydrostatic and hydrodynamic forces, debris, and water-borne projectiles, and effects of sediment erosion or deposition due to storm surge was not necessary because safety-related SSCs at the WCGS site were not affected from storm surge flood levels (NRC, 2013c).

3.3.5 Seiche A seiche is defined as "an oscillation of the water surface in an enclosed or semi-enclosed body of water initiated by an external cause" in NRC NURIEG/CR-7046 (NRC, 2011). To account for the potential of a seiche due to meteorological effects, the seiche periods for the length and width of Wolf Creek Lake were computed. In order to compute the seiche periods, the lake was assumed to be a rectangular basin with an averaged depth of the lake, which follows the methodologies outlined by Dean and Dalrymple (Dean and Dalrymple, 1991).

Using the Dean and Dairymple methodology for seiche periods for Wolf Creek Lake, the resulting seiche periods computed were 6.5 minutes for the lake's length and 38.7 minutes for the width of the lake. Seiching at these periods could only occur if an oscillatory force (jpressure or wind) excited lake oscillations at one of the seiche periods. The periods calculated for lake oscillation could not be continuously forced by changes in overall weather conditions because these conditions typically fluctuate at time scales of 1 hr or more (Peinke et al., 2004).

Therefore, seiches due to meteorological effects are dismissed as a source of flooding at the WCGS.

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Seiches can also occur due to seismic effects and landslides. The WCGS site is situated in an area of low seismic hazards according to the USGS (USGS, 2012c). The occurrence of landslides in the area adjacent to Wolf Creek Lake is not considered possible due to the low relief of topographic features in the vicinity of the WCGS site. Therefore, potential seismic events and landslide were not expected to cause seiches on Wolf Creek Lake and, therefore, cause flooding at the WCGS site. Additionally, according to NRC JLD-ISG-2012-06 guidance, determination of hydrostatic and hydrodynamic forces, debris and water-borne projectiles, and the effects of sediment erosion or deposition due to seiche were not necessary because safety-related S SCs at the WCGS site are not affected from seiche flood levels (NRC, 2013c).

3.3.6 Tsunami Following the guidance outlined in NRC NUREG/CR-6966 and NRC JLD-ISG-2012-06 (NRC, 2009; 2013c), a review was conducted of the National Oceanic and Atmospheric Administration's (NOAA) historic tsunami records that impacted the east coast of the United States and the Gulf of Mexico. The maximum historic water levels due to historic tsunami run-up recorded along the east cost of the United States and the Gulf of Mexico was 19.7 ft, which occurred at Daytona Beach, Florida, in 1992 (NOAA, 2013). Daytona Beach, Florida, is approximately 1,050 miles from the WCGS site (USGS, 2013), and the closest shoreline that could be subjected to tsunami flooding is approximately 600 miles away. NRC NUREG/CR-6966 indicates that if regional screening identifies that the site region is not subject to tsunamis, no further analysis for tsunami hazards is required (NRC, 2009). Additionally, according to NRC JLD-ISG-2012-06 guidance (NRC, 2013c), the determination of the hydrostatic and hydrodynamic forces, debris and water-borne projectiles, and the effects of sediment erosion and deposition were not considered because the safety-related SSCs of the WCGS site were not subject to tsunami flood levels (NRC, 2013c).

3.3.7 Ice-Induced Flooding Ice-induced flooding analysis for the WCGS site included an assessment of ice jams, frazil ice, and ice thickness. Review of the current Ice Jams Database (USACE, 2013b) indicated that only one ice jam has been recorded in the Neosho River Basin on February 1949, near the city of Council Grove, Kansas. Council Grove is approximately 50 miles northwest of the WCGS site, and upstream of the John Redmond Reservoir. Potential ice jams upstream of the John Redmond Reservoir would not adversely affect the WCGS site because any potential floodwaters occurring due to release from the ice jam would be mitigated or dissipated before entering, or within, the Wolf Creek Nuclear Operating Corporation rQ Flood Hazard Reevaluation Report Pg 6o 0 145262/135031/15 Rev. 1 (October 21, 2015) Pae 6 f 0

John Redmond Reservoir or one of the other flood control facilities on the Neosho River.

Additionally, the Neosho River is separated from the WCGS site by a topographic ridge (USGS, 2012b).

In the event of an ice jam occurring on the Neosho River, at the confluence of Wolf Creek, downstream of the John Redmond Reservoir (although there is no record of such an ice jam),

backwater effects would not affect the WCGS site as the confluence is over six miles from the WCGS site. Furthermore, no historical ice jams have been recorded in the Wolf Creek watershed (USACE, 2013b).

Frazil ice can only occur in supercooled turbulent waters (USACE, 2002). Supercooled water is water that is cooled below the freezing point without freezing. As presented in the USAR, frazil ice has the potential to form in Wolf Creek Lake when the water becomes supercooled, creating the potential to block the ESWS intake trash racks (WCNOC, 2015). Supercooling in Wolf Rev 1 Creek Lake requires a large heat loss associated with low air temperatures, clear water, and clear nights (WCNOC, 2015). Additionally, because the cooling heat transfer is at the surface of the Rev I water, strong winds are needed to mix supercooled water to a depth low enough to be drawn into the intake (WCNOC, 2015). Rev 1 In January 1996, the Train A ESWS intake trash racks became completely blocked by frazil ice (NRC, 1996). The frazil ice blockage was effectively cleared by sparging the trash racks with air (NRC, 1996). At the time of the blockage of the trash racks by frazil ice in January 1996, the ESWS warming flow was insufficient to prevent frazil ice from forming at the Train A trash racks (NRC, 1996). According to the current version of the USAR, WCGS has put in place a system to mitigate future potential frazil ice formation by diffusing warmed water in front of the ESWS intake trash racks (WCNOC, 2015). This technique of mixing warmed water with Rev 1 supercooled water is especially effective near water intakes, where the required quantity of warm water can be modest (USACE, 2002).

Ice thickness was estimated by an analysis of Freezing Degree Days (FDD), defined as the difference between 32 degrees Fahrenheit (0 F) and the average daily air temperature (USACE, 2004). The maximum estimated ice thickness on Wolf Creek Lake, based on the methodologies and equations in the Method to Estimate River Ice Thickness Based on MeteorologicalData report (USACE, 2004), was approximately 20.60 in (1.72 fi) using the data from the Emporia Municipal Airport weather station, and approximately 19.14 in using data from the John Redmond Lake weather station.

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The bottom of the intake channel to the ESWS pumphouse is at elevation 1,065 fi, which is 22 ft below the normal operating level (1,087 ft) of Wolf Creek Lake. Thus, the bottom of the conservatively estimated ice thickness of 20.60 in (1.72 fi) would still be approximately 20.28 ft above the bottom of the intake channel to the ESWS pumphouse. The reevaluation analysis and the design basis (WCNOC, 2015) screened out ice formation as a potential flood hazard. Rev 1 3.3.8 Flooding Resulting from Channel Migration or Diversion The rivers and creeks in the vicinity of the WCGS site are the Neosho River, Wolf Creek, and Long Creek. A qualitative assessment of the streams and rivers in the vicinity of the WCGS site, in conjunction with the information presented in the USAR (WCNOC, 2015), indicated that Rev 1 safety-related SSCs at the WCGS site would not be affected by diversion of flows from the Neosho River, Wolf Creek, or Long Creek.

This hazard reevaluation also indicated that any potential diversion of cooling water would not adversely affect safety-related SSCs at the WCGS site. The cooling water is provided by Wolf Creek Lake, and the intake channel is protected from potential ice blockage by diffusing warmed water in front of the ESWS intake trash racks (WCNOC, 2015). The UHS is contained by a Rev 1 submerged Seismic Category I dam in Wolf Creek Lake and is fully functional for safe shutdown of the WCGS site. The UHS will provide a sufficient volume of water to safely shut down and maintain shutdown of the WCGS site as long as the sediment volume in the UHS is limited to 130 acre-ft (WCNOC, 2015, Section 2.4.11.6). The sources of the makeup water to the cooling Revi1 lake are Wolf Creek and the Neosho River (WCNOC, 2015, Section 2.4.8.2). Significant morphological changes in the Neosho River are not expected to affect the water supply from the John Redmond Reservoir, and Wolf Creek was also not expected to diverge due to the topography in the area.

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4.0 COMPARISON OF CURRENT DESIGN BASIS AND REEVALUATED FLOOD HAZARDS Section 4. 0 has been prepared in response to Request for Information Item i .e. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a): Provide a comparison of current and reevaluated flood-causing mechanisms at the site. Provide an assessment of the current design basis flood elevation to the reevaluated flood elevation for each flood-causing mechanism. Include how the findings from Enclosure 4 of this letter (i.e.,

Recommendation 2.3 flooding walkdowns) support this determination. If the current design basis flood bounds the reevaluated hazard for all flood-causing mechanisms, include how this finding was determined.

4.1 COMPARISON OF FLOOD-CAUSING MECHANISMS Rev 1 The flood-causing mechanisms evaluated under the current design basis in the USAR include the.

effects of local intense precipitation, probable maximum flood on Wolf Creek Lake, including wave run-up at the site, seismically induced potential dam failure, probable maximum storm surge and seiche flooding, probable maximum tsunami flooding, ice flooding, and channel diversions (WCNOC, 2015). The flood hazard reevaluation includes the same evaluations of the Rev 1 flooding mechanisms as presented in the current design basis, including a combined-effects flood. Note that the USAR terminology differs from the terminology used in current NRC guidance, but the same mechanisms are evaluated. The flooding mechanisms, from both the USAR and the reevaluation, are listed in Table 4-1.

The conditions under which the flooding analyses were performed and the methods used to perform the analyses were slightly different between CLB analyses and the reevaluation analyses. The differences are highlighted in Table 4-1 through Table 4-4. Table 4-4 focuses on the additional parameters (i.e., flood duration, dynamic loads, debris loading, and sedimentation) that are required to be evaluated since the issuance of NRC Recommendation 2.1.

4.2 COMPARISON OF FLOOD EFFECTSReI The current design basis, as presented in the USAR (WCNOC, 2015), indicates that the site is Rev I not affected by flooding. The WCGS site has a grade elevation of 1,099.5 fi, and a floor elevation of 1,100 ft.

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Local Intense Precipitation The current design basis LIP analysis assumes that the site drainage system is not functional during the LIP event. The design basis LIP water level for the safety-related buildings is 1,099.92 ft (WCNOC, 201 5), which is below the plant floor elevation of 1,100 ft. Because the maximum design water level due to LIP is below the plant floor elevation, hydrostatic and hydrodynamic forces are not evaluated for safety-related SSCs. However, the design basis does include hydrostatic loads on safety-related structures for groundwater levels at plant grade (WCNOC, 2015). Rev I The reevaluated on-site LIP ponding levels range from 1,100.03 ft to 1,100.38 ft adjacent to safety-related SSCs (Table 3-1). These values exceed the design basis water levels.

Since the LIP rainfall depth and distribution used for the reevaluation are the same those used for the LIP event used for the current design basis, the design basis roof loading evaluation is considered to bound the roof loading for the reevaluated flood hazard.

Potential pathways along which surface water runoff could reach safety-related SSCs include 40 different doors, vaults, and manholes. Table 3-2 and Table 3-3 present the resulting flood elevations, duration of flood, and the dynamic and static loads for these pathways. The Revision 0 FHRR presented flooding results for Cases 5 and 6. Case 7 includes site updates and model Rev 1 refinements and is presented as the most refined simulation for this Revision 1 FHRR. For Case 7, the maximum flood depth outside of an entrance to a Seismic Category I building on the powerblock (Auxiliary Building pressure door) was approximately 1.01 ft. The associated duration of flooding above a depth of 0.5 ft at this location was 0.5 hrs, with a corresponding maximum velocity 3 of 1.2 ft/s, a maximum hydrostatic force of 32 lb/ft, and a maximum Rev 1 hydrodynamic force of 3 lb/ft. Figure 4-1 illustrates a timeline for flooding adjacent to powerblock building doors.

For other doors, hatches, manholes, and vaults associated with safety-related SSCs, the simulated maximum flood depth is 1.43 ft at ESWS manholes MHE5A and MHE5B. The associated Rev 1 duration of flooding above a depth of 0.5 ft is 10.0 hrs, with a corresponding maximum velocity SThe Auxiliary Building pressure door is located at the end of an alleyway between the Fuel Building and the Hot 1Rev 1 Machine shop. Consequently the dominant flow velocities are away from the Auxiliary Building pressure door.

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of 0.6 ft/s, a maximum hydrostatic force of 64 lb/fl, and a maximum hydrodynamic force of less Rev 1 than one pound per foot.

The potential for sedimentation and debris loading on safety-related SSCs due to the LIP was screened out qualitatively, as discussed in Section 3.3.1.3. Rev 1 Flooding~ in Rivers and Streams The normal operating level at the Wolf Creek Lake is 1,087 ft. Snyder's synthetic unit hydrograph was used for the design basis to determine that the peak flow rate for the spillways is 22,845 cfs (WCNOC, 2015, Section 2.4.3.5) for a sequential flood event with an antecedent Rev 1 standard project flood followed by a PMP, which is analogous to a combined-effects precipitation flood event. The maximum water surface elevation in Wolf Creek Lake (i.e., the pooi elevation) due to the design PMF event is 1,095 ft at the plant site, which occurs approximately 158 hrs after the start of the event (WCNOC, 2015, Figure 2.4-23). This would exert a lateral force of 42,713 lb/ft on the face of the pumphouse (reported as a depth-integrated Rev 1 force per linear foot along the pumphouse face to the bottom of the ESWS pumphouse at elevation 1,058.0 fi). The coincident wind-wave activity of the design PMF results in a maximum run-up of 0.8 ft at the plant site shore. The resulting design run-up elevation is 1,095.8 ft when added to the PMF pool elevation (Table 4-3). The design maximum wave run-up elevation on the vertical wall of the intake structure of the ESWS is 1,100.2 ft.

In the reevaluation, the simulated outflow from Wolf Creek Lake over the service spillway was 23,021 cfs. The maximum water level in the lake resulting from the PMF was 1,093.54 ft, which occurred approximately 47.5 hrs after the start of the event, and was less than the design value (1,095 ft). The shorter duration to the peak water level is not considered a controlling parameter since the reevaluated maximum water level was bounded by the design basis and no procedural actions are required by the site due to increases in lake level due to a PMF. The reevaluated lake levels including wind-generated wave run-up at the WCGS shoreline and the ESWS pumphouse were 1,094.37 ft and 1,098.43 ft, respectively (Table 4-3). The reanalyzed water levels, including wind-waves, were less than the design water levels (1,095.8 ft), which is less than the plant grade elevation (1,099.5 ft). Therefore, hydrodynamic and hydrostatic loads at the plant were not calculated for safety-related structures on the powerblock. However, hydrostatic loads at the ESWS pumphouse were calculated. The maximum static load for the peak simulated water levels was 39,408 lb/ft, which is less than the design basis hydrostatic loading of 42,713 lb/ft. Rev 1 Wolf Creek Nuclear Operating Corporation *1*

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This represents a depth-integrated force from the stiliwater level to the bottom of the ESWS Rev 1 pumphouse (elevation 1,058.0 fi).

The reevaluation analysis for the river hydraulic model included simulations representing potential debris build-up at the Wolf Creek Lake Dam auxiliary and service spillways. The potential impact of debris was simulated with ten percent blockage of the auxiliary spillway and 50, 20, and ten percent blockage of the service spillway. Peak water levels with 50 and 20 percent blockage of the service spillway exceeded the design basis PMF elevation of 1,095 ft.

However, simulated peak water levels for 50, 20, or ten percent blockage of the service spillway did not exceed the plant grade elevation of 1,099.5 ft. The 50 percent and 20 percent cases (Cases 7 and 8) were not considered realistic due to the dimensions of the spillways.

It was expected that debris caused by runoff associated with the PMF would not adversely impact the intake structure of the ESWS pumphouse. Additionally, the baffle dikes provide a defense for the ESWS pumphouse against debris that could be floating in Wolf Creek Lake due to the PMF. The source area for debris generation would essentially be limited to a small contributing area on the east side of the plant and it is expected that any debris generated by that area would be small in size (e.g., tree branches) and would not affect the ESWS pumphouse.

Furthermore, the intake structure is equipped with trash racks, which protect the ESWS pumphouse from loss of flow due to debris.

The reevaluation analysis also included a simulation representing sediment build-up within Wolf Creek Lake, which considered a loss in the capacity of Wolf Creek Lake due to sedimentation over a period of 40 years. This is equivalent to approximately 1,080 acre-ft of sediment. The peak water levels with lake sediments did not exceed the design basis PMF elevation of 1,095 ft.

Combined-Effects Flooding~

The design water level for combined-effects flooding is 1,095.80 ft and 1,100.20 ft for the WCGS shoreline and the ESWS pumphouse, respectively (Table 4-3), which occurs approximately 158 hrs after the start of the event (WCNOC, 2015, Figure 2.4-23). The ]Revi1 analogous values determined during the reevaluation were 1,095.46 ft and 1,099.52, respectively, which occurs approximately 68 hrs after the start of the event. The reevaluated flood levels are less than, and bounded by, the design water levels.

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The design loads on the roofs of safety-related structures are based on a 100-year snowpack with the probable maximum winter precipitation superimposed on it, which results in the maximum combined loading calculated as 153 pounds per square foot (psf) (WCNOC, 2015; Section Rev 1 2.4.2.3.3). Ground loads due to the all-winter snowfall were considered in the hazard revaluation using the event combinations of ANSI/ANS 2.8 (ANS, 1992) Alternatives II and III for the combined-effects flood. It was determined that the ground loading using the snow water equivalence method could reach was 169.4 psf, which is slightly higher than the design roof loading. However, the maximum reevaluated ground loading is due to an April event that only generated 4.3 in of snow (the remainder being due to coincident April rainfall) and is not considered to be equivalent to a roof load, because the total combined water and snow column would not be stored on the roofs. All other months (November through March) resulted in ground loadings that were less than the design roof loading. Therefore, it was determined that the design roof loadings bounded the reevaluated ground loadings.

Dam Breaches and Failures Failure of dams located above the John Redmond Reservoir will not adversely affect any safety-related facilities at the WCGS site (WCNOC, 2015). In the most critical case, which postulates Rev 1 the domino-type failure of the John Redmond, Marion, Cedar Point, and Council Grove Reservoirs, the maximum flood stage of the Neosho River was estimated to be 1,044.55 ft at a distance of about 5.0 miles downstream from the John Redmond Dam (WCNOC, 2015, Case b.3 Rev 1 of Section 2.4.4.1).

As stated in the USAR, the topographic ridge between the Neosho River and Wolf Creek valleys below John Redmond Dam will separate the postulated flood levels in the Neosho River valley from any facilities at the site, with the exception of the Wolf Creek Lake dam. The maximum water elevation on the downstream slope of the Wolf Creek Lake Dam, due to the postulated combined maximum flood-causing events in the Neosho and Cottonwood River basins, is conservatively established at elevation 1,049.6 ft. This flood stage is well below surface grades of any Seismic Category I facilities at the site and is about 50 ft below the plant grade elevation Rev 1 of 1,099.5 ft (WCNOC, 2015).

The reevaluated flood level resulting from the failure of all dams upstream of the John Redmond Reservoir was 1,076.70 ft, which is substantially greater than the design value due to the more conservative method used (i.e., the Volume Method per JLD-ISG-2013-01), but still far less than plant grade elevation (1,099.5 ft) and the service spillway elevation for the Wolf Creek Lake Wolf Creek Nuclear Operating Corporation *t-Flood Hazard Reevaluation Report Pg 3o 0 145262/135031I/15 Rev. 1 (October 21, 2015) Page53 o-10

Dam (1,088.00 fi). Therefore, dam failure was screened out for the reevaluation, as was done in the design basis.

Storm Surg~e and Seiche, Tsunami, and Ice-Induced Flooding~

Storm surge and seiche, tsunami, and ice-induced flooding were screened out as potential flooding events in the current design basis in the USAR (WCNOC, 2015). In the reevaluation, Rev 1 storm surge and seiche, tsunami, and ice-induced flooding were also screened out.

Channel Diversion Channel diversion is screened out as a potential flooding event in the design basis. In the design basis, there is no indication that Wolf Creek or its tributaries would be diverted from its present course of flowing into Wolf Creek Lake. In addition, supply of makeup water to the plant is available to be pumped from the Neosho River, if the supply from Wolf Creek is temporarily cutoff. In the reevaluation analysis, channel diversion was similarly screened out and it was determined that safety-related SSCs at the WCNOC site would not be affected by the diversion of flows from the Neosho River, Wolf Creek, and Long Creek.

4.3 SUPPORTING DOCUMENTATION Calculation briefs in support of the flood hazard reevaluation at the WCGS site have been prepared, on which the reevaluated flood levels are based. Additionally, the Wolf Creek Nuclear Operating CorporationPost FukushimaFlooding,Walkdown Report (WCNOC, 2012) provides further information regarding the design basis flood hazard levels, as well as flooding protection and mitigation features.

According to the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012), safety-related SSCs that are credited in the CLB for protecting the plant from external flood hazards were identified, inspected, and evaluated to be adequate. According to the report (WCNOC, 2012), "The walkdown visual inspection has verified that there is reasonable assurance the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The Wolf Creek external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard."

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4.3.1 Technical Justification of the Flood Hazard Analysis All flooding reevaluation analyses described in this report have been undertaken with consideration and implementation of current techniques, software, and methods used in present-day standard engineering practice to develop the flood hazard. The technical basis for the various scenarios modeled under the HHA approach and the key assumptions utilized in the determination of the reevaluated flooding levels for each flood-causing mechanism are discussed individually in Section 3.0.

4.3.2 Technical Justification of the Walkdown Results With respect to the implementation and conclusions of the flooding hazard reevaluation, results from the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) have been taken into consideration. According to the report (WCNOC, 2012), "The walkdown visual inspection has verified that there is reasonable assurance the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The Wolf Creek external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard."

Based on the reevaluated flood hazard results, the effects of flood levels that are not bounded by the CLB on the pertinent flood protection and mitigation features described in Section 2.6 and as identified in the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) are provided below.

Top ogranhy The walkdown evaluated the state of the 2012 site layout and topography against the design basis. The analysis presented in the Revision 0 FHRR accounted for the site layout and topography as documented by a 2012 aerial and ground survey. Updates to the site layout and topography through July 2015 are incorporated in this Revision 1 FHRR, as discussed in Rev 1 Sections 2.1.2.1 and 2.4.2. No credit was taken for underground drainage in either the analysis prepared for the Revision 0 FHRR or the analysis prepared for the Revision 1 FHRR. Table 3-1 through Table 3-3 indicate that peak ponding levels determined in the reevaluated LIP analysis result in potential propagation pathways to safe shutdown equipment. These flooding effects are Wolf Creek Nuclear Operating Corporation 1 Flood Hazaird Reevaluation Report Pg 5o 0 145262/135031/15 Rev. 1 (October 21, 2015) Pag 5 of10 N

mainly attributed to short duration ponding caused by the peak intensity of the rainfall and the Rev 1 mild slopes of the site grading.

Doors Credited pressure doors were evaluated during the flooding walkdown. The hazard reevaluation determined localized ponding exceeding the design plant floor elevation of 1,100 ft at doors that are potential pathways to safety-related systems and components in the following structures:

Auxiliary Building, Communication Corridor Building, Fuel Building, Hot Machine Shop, Turbine Building, Condensate Storage Tank Pipe House, and the Refueling Water Storage Tank Valve House.

Structures / Floors / Walls / Penetrations / Vaults The walkdown evaluated the state of credited flood protection boundaries related to the hydrostatic design basis of plant grade. The hazard reevaluation determined localized ponding exceeding the design basis at Seismic Category I structures, as indicated in Table 3-1.

Therefore, the hydrostatic design basis for Seismic Category I structures, which is based on the design groundwater level of plant grade (elevation 1,099.5 ft), inspected during the walkdown is not bounded for the following Seismic Category I structures: Auxiliary Building, Control Building, Diesel Generator Building, Fuel Building, Reactor Building, Refueling Water Storage Tank, ESWS manholes (MHE1A, MHE1B, MHE2A, MHE2B, MIIE3A, MHE3B, MHE4A, MHE4B, MHE5A, and MHE5), and the Emergency Fuel Oil Tank Access Vaults.

ESWS Pumphouse and Forebay The credited flood protection features associated with the ESWS pumphouse were evaluated during the flooding walkdown. The ESWS pumphouse forebay was considered restricted access during the flooding walkdowns, but was inspected by divers as an SSC scheduled in the preventative maintenance program meeting the frequency requirements of NRC Regulatory Guide 1.127. The results of the hazard reevaluation for flood elevation, including wave run-up, are bounded by the design basis. Therefore, the evaluations performed during the walkdown are still applicable to the ESWS pumphouse.

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Sumo Pumps & Motors Credited sump pumps and motors in Seismic Category I buildings were evaluated during the flooding walkdown due to the design basis of controlling groundwater inleakage. As discussed previously, the hazard reevaluation determined localized ponding exceeding the design plant floor elevation of 1,100 ft at potential pathways to safety-related systems and components. The sump pumps are credited to control groundwater inleakage, not the propagation of water into the Seismic Category I buildings due to external ponding because the design basis determined there was no ponding exceeding the plant floor elevation. The capacity of these pumps could be evaluated, if necessary, for handling water that enters the building due to ponding during the LIP event.

4.4 CONCLUSIoNs The flood hazard reevaluation for the river flooding event is bounded by the design basis. In addition, the reevaluated combined-effects analysis is also bounded by the design basis.

Hydrostatic loads were computed for the design basis of the ESWS pumphouse during river flooding and bound the reevaluated loadings. The reevaluation analysis of dam break, storm Rev 1 surge and seiche, tsunami, and ice flooding are screened out in the reevaluation and in the design basis.

The LIP modeling in support of the Revision 1 FHRR accounts for changes to the site layout and grading through July 2015. The results of the updated LIP modeling performed for this Revision Rev I 1 FHRR do not change the overall conclusions of the Revision 0 FIIRR.

The current design basis flood levels for LIP do not bound the reevaluated flood levels. The maximum reevaluated flood level for LIP was 1,100.38 ft, which is above the plant floor entrance elevation of 1,100 ft, whereas the maximum design flood level for LIP flooding is Rev 1 1,099.92 ft. Thus, the reevaluated. LIP flood levels are approximately 0.46 ft higher than the CLB values. The highest level of floodwater in the reevaluated LIP flooding analysis occurs in the small alleyway between the Fuel Building, the Auxiliary Building, and the Hot Machine Shop. Additional evaluation of flooding in this area may be performed as part of a focused LIP evaluation (NRC, 2015Sa).

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occur on the transient flows around buildings during a LIP event. Additionally, building settlement may lower the elevation of an entryway below the design value of 1,100 ft.

Therefore, a focused LIP evaluation (NRC, 201 5a) should consider any small differences Rev 1 between the stillwater levels and the plant floor elevation. This should be considered when evaluating the potential mitigation required for a LIP event.

Removing the unused rail tracks or modifying the grading of the site near safety-related structures may improve site drainage and could be considered during a focused LIP evaluation Rev 1 (NRC, 2015a).

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5.0 INTERIM EVALUATION AND ACTIONS Section 5. 0 has been prepared in response to Request for Information Item 1.d. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a): Provide an interim evaluation and actions taken or planned to address any higher flooding hazards relative to the design basis, prior to completion of an integrated assessment or focused LIP evaluation if/as Rev 1 required per the forthcoming guidance (NRC, 2015a).

5.1 EVALUATION OF THE IMPACT OF THE REEVALUATED FLOOD LEVELS ON STRUCTURES, SYSTEMS, AND COMPONENTS Except for flooding levels due to a LIP event, the flooding levels of all other potential flood-causing mechanisms, as presented in Section 3. 0, do not exceed the elevations of the exterior entrances of SSCs at the WCGS site. The design basis for the LIP event did not include hydrostatic and hydrodynamic loads because the maximum calculated water level near the Rev 1 safety-related buildings is 1,099.92 ft (WCNOC, 2015), which is below the plant floor elevation of 1,100 ft (WCNOC, 2015). However, the design basis did consider hydrostatic loads due to groundwater levels equivalent to plant grade.

For the reevaluation analysis, the most refined simulated conditions result in ponded water adjacent to Seismic Category I buildings with elevations above the plant floor elevation (1,100 ft) at several entrances. Additionally, water levels exceeded critical elevations at several manhole covers. The flood depths, associated durations, flow velocities, as well as hydrostatic and hydrodynamic forces that are computed in the reevaluation analysis are not bounded by the design basis LIP analysis. Water levels computed in the reevaluation indicate potential flow of water into Seismic Category I buildings. Debris loading and sedimentation during a LIP event were screened out in the reevaluation analysis.

5.2 ACTIONS TAKEN TO ADDRESS FLOOD HAZARDS NOT COMPLETELY BOUNDED BY THE CURRENT DESIGN BASIS HAZARD Request for Information Item 1.d. of NRC Recommendation 2.1 specifies that the flooding reevaluation contain an interim evaluation and actions taken or planned to address any higher flooding hazards relative to the design basis, if necessary (NRC, 2012a), prior to completion of Rev 1 an integrated assessment or focused LIP evaluation (NRC, 2015a).

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Based on the results of the site walkdowns and the indicated ponding levels during a LIP event (exceeding doorway entrance elevations and design hydrostatic loads), interim actions are necessary to preliminarily evaluate the need for mitigation (e.g., sand bags), while a focused LIP evaluation (NRC, 201 5a) is conducted to further evaluate the need for mitigation in the case of a Rev 1 LIP event.

The temporary mitigation measures for the interim action will consider parameters, such as the effect of small wind-waves (a few inches) that could occur on the transient flows around buildings during a LIP event and building settlement that may lower the elevation of an entryway below the design value of 1,100 ft. The focused LIP evaluation (NRC, 2015a) and interim measures to mitigate ponding during a LIP event will be tracked by Wolf Creek's corrective Rev I action program.

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6.0 ADDITIONAL ACTIONS Section 6.0 has been prepared in response to Request for Information Item i.e. of NRC Reconmmendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a): Provide additional actions beyond Request for Information item 1.d taken or planned to address flooding hazards, if any.

At this time, there are no additional actions beyond Request for Information Item 1.d. of NRC Recommendation 2.1 (Section 5.0) which have been taken or are planned to address flooding hazards at WCGS.

The plant response to the reevaluated LIP flood levels will be considered and evaluated in accordance with the forthcoming guidance (NRC, 2015a) from the NRC regarding closure of Rev 1 actions associated with Near-Term Task-Force Recommendation 2.1, Flooding.

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7.0 REFERENCES

1. American Nuclear Society (ANS), 1992, "Determining Design Basis Flooding at Power Reactor Sites," ANSI/ANS-2.8-1992, La Grange Park, Illinois.

2. Chow et al., 1988, Chow, Ven Te, David R. Maidment, and Larry Mays, "Applied Hydrology," McGraw-Hill Book Company, 1988.

3. Dean, R.G. and R.A. Dalrymple, 1991, "Water Wave Mechanics for Engineers and Scientists," World Scientific Publishing Co. Pte. Ltd., 1991.

4. Environmental Systems Research Institute (ESRI), 2009, ArcGIS ArcMap 9.3 Computer Program, 2009.

5. Environmental Systems Research Institute (ESRI), 2012, ArcGIS ArcMap 10.1 Computer program, 2012.

6. Environmental Systems Research Institute (ESRI), 201 3a, "US Topo Maps by National Geographic," Website: <http://goto.arcgisonline.com/maps/USATopoMaps>, Date Accessed: December 24, 2013.

7. Environmental Systems Research Institute (ESRI), 2013b, "World Street Map," Website:

<http ://goto.arcgisonline.com/maps/ World_StreetMap>, Date Accessed: December 24, 2013.

8. Environmental Systems Research Institute (ESRI), 2013 c, "ArcGIS Imagery," Website:

<http ://www. arcgis, com/home/item.html?id=a5 fef63 51 7cd4a099b43 7e5 5713 d3 d54>,

Date Accessed: October 18, 2013

9. Federal Emergency Management Agency (FEMA), 1996, "Flood Insurance Study, City of Burlington, Kansas, Coffey County, Community Number 200063," Revised:

September 20, 1996.

10. Federal Emergency Management Agency (FEMA), 2013, "Numerical Models Meeting the Minimum Requirement of National Flood Insurance Program," Website

<http ://www.fema.gov/national-flood-insurance-program-flood-hazard-mapping/numerical-models-meeting-minimum-requirement-0>, Date Accessed:

September 4, 2013.

11. FLO-2D Software, Inc. (FLO-2D), 2012, "FLO-2D Reference Manual," September 2012.

12. FLO-2D Software, Inc. (FLO-2D), 2014, "Revisions, Enhancements and Bug Fixes to the R[

FLO-2D Pro Model and Processor Programs Since October 1, 2012", March 2014. Rv Wolf Creek Nuclear Operating Corporation 1 .

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13. Kansas Biological Survey (KBS), 2010, "Bathymetric Survey of Wolf Creek Reservoir (Coffey County Lake), Coffey County, Kansas," Applied Science and Technology for Reservoir Assessment (ASTRA) Program, Report 2009-12 (December 2009), Revised January 2010.

14. Kansas Department of Agriculture (KDA), 2011, "Kansas Department of Agriculture Fact Sheet," Division of Water Resources, Water Structures Program, 2011.

15. National Oceanic and Atmospheric Administration (NOAA), 2013, National Geophysical Data Center, "Historical Tsunami Event Database," Website:

<http://www.ngdc.noaa.gov/hazard/ tsu_db.shtml>, Date Accessed: June 17, 2013.

16. National Weather Service (NWS), 1982, "Application of Probable Maximum Precipitation Estimates - United States East of the 1 0 5 th Meridian," Hvdrometeorological Report No. 52: August 1982.

17. Nuclear Regulatory Commission (NRC), 1 977, "Design Basis Floods for Nuclear Power Plants," Regulatory Guide 1.59, Revision 2, Washington, D.C., 1977.

18. Nuclear Regulatory Commission (NRC), 1996, "NRC Information Notice 96-3 6:

Degradation of Cooling Water Systems Due to Icing," Date of Publication: June 12, 1996, Website: <http ://www.nrc.gov/reading-rm/doc-collections/gen-commlinfo-notices/i1996/in9603 6.html>, Date Accessed: September 3, 2013.

19. Nuclear Regulatory Commission (NRC), 2009, "Tsunami Hazard Assessment at Nuclear Power Plant Sites in the United States of America," NUREG/CR-6966. PNNL-1 7397, NRC Job Code J3301, Washington, D.C., March 2009.

20. Nuclear Regulatory Commission (NRC), 2011, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America," NUREG/CR-7046, PNNL-20091, NRC Job Code N6575, Washington, D.C., November 2011.

21. Nuclear Regulatory Commission (NRC), 2012a, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," Washington, D.C., March 12, 2012.

22. Nuclear Regulatory Commission (NRC), 2012b, "The Estimation of Very-Low Probability Hurricane Storm Surges for Design and Licensing of Nuclear Power Plants in Coastal Areas," NUREG/CR-7 134, NRC Job Code N6676, Washington, D.C., October 2012.

23. Nuclear Regulatory Commission (NRC), 2012c, Guidance for Performing the Integrated Assessment for External Flooding," JLD-ISG-2012-05, NRC Interim Staff Guidance (ML12311A214), Washington, D.C., Revision 0, November 30, 2012.

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24. Nuclear Regulatory Commission (NRC), 2013a, "Wolf Creek Generating Station, Unit 1," Website: <http ://www.nrc.gov/info-finder/reactor/wc.html>, November 16, 2012.

Date accessed: August 9, 2013.

25. Nuclear Regulatory Commission (NRC), 2013b, "Guidance for Assessment of Flooding Hazards Due To Dam Failure," JLD-ISG-2013-01, NRC Interim Staff Guidance (ML13151A153), Washington, D.C., Revision 0, July 29, 2013.

26. Nuclear Regulatory Commission (NRC), 2013c, "Guidance for Performing a Tsunami, Surge, or Seiche Hazard Assessment," JLD-ISG-2012-06, NRC Interim Staff Guidance (ML12314A412), Washington, D.C., January 4, 2013.

27. Nuclear Regulatory Commission (NRC), 2015a, "Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for Beyond-Design-Basis External Events," Letter to Licensees (ML15174A257), September 1, 2015.

Rev 1

28. Nuclear Regulatory Commission (NRC), 2015b, "Closure Plan for the Reevaluation of Flooding Hazards for Operating Nuclear Power Plants," COMSECY- 15-0019 (ML15153A104), June 30, 2015.

29. Peinke et al., 2004, J. Peinke, S. Barth, F. Bottcher, D. Heinemann, and B. Lange, "Turbulence, a Challenging Problem for Wind Energy," Physica A, Volume 338 pp. 187-193, 2004.

30. United States Army Corps of Engineers (USACE), 1987, "11MR52 Probable Maximum Storm (Eastern United States) User's Manual," USACE, Davis, California, April 1987.

31. United States Army Corps of Engineers (USACE), 2002, "Engineering and Design, Ice Engineering," EM 1110-2-1612, Washington, D.C., October 30, 2002.

32. United States Army Corps of Engineers (USACE), 2004, "Ice Engineering, Method to Estimate River Thickness Based on Meteorological Data," ERDC/CRREL Technical Note 04-3, June 2004.

33. United States Army Corps of Engineers (UJSACE), 2008, "Coastal Engineering Manual,"

Engineer Manual 1110-2-1100, Washington, D.C., 2008.

34. United States Army Corps of Engineers (USACE), 2010a, "Hydrologic Engineering Center (HEC), HEC-HMS Version 3.5 Computer Program Build 1417, Release Date:

August 2010.

35. United States Army Corps of Engineers (USACE), 2010Ob, Hydrologic Engineering Center (HEC), HEC-RAS Version 4.1 Computer Program, Release Date: January 2010.

36. United States Army Corps of Engineers (USACE), 2013a, National Inventory of Dams, Website: <http://geo.usace.army.mil/pgis/tf?.p=397:1 :112429380233301>, Date Accessed: November 4, 2013.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Pg 4o 0 145262/135031/15 Rev. 1 (October 21, 2015) Page 6 of 10

37. United States Army Corps of Engineers (USACE), 2013b, "Ice Jams Database, Total Number of Events by River for the State of KS," Website:

<http ://rsgisias.crrel.usace.anmy.mil/apex/f?p=273 :39:748147269460901: :NO: :P3 9_STA ST:KS>, Date Accessed: June 19, 2013.

38. United States Geological Survey (USGS), 2012a, "The National Map US Topo New Strawn Quadrangle, Kansas-Coffey Co. 7.5-Minute Series," 2012.

39. United States Geological Survey (USGS), 2012b, "The National Map US Topo Burlington Quadrangle, Kansas-Coffey Co. 7.5-Minute Series," 2012.

40. United States Geological Survey (USGS), 2012c, "Earthquake Hazards Program," Date of Publication: November 1, 2012, Website:

<http://earthquake.usgs.gov/earthquakes/states/kansas/history.php>, Date Accessed:

June 19, 2013.

41. United States Geological Survey (USGS), 2013, "National Map Viewer and Download Platform," Website: <http://nationalmap.gov/viewer.html>, Date Accessed: June 27, 2013.

42. Wolf Creek Nuclear Operating Corporation (WCNOC), 2012, "Wolf Creek Nuclear Operating Corporation Post Fukushima Flooding Walkdown Report," Enclosure to ET 12-003 1, November 2012.

43. Wolf Creek Nuclear Operating Corporation (WCNOC), 2013, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 26, March 2013.

44. Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Rev I Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March 2015.

Wolf Creek Nuclear Operating Corporation *1[-

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TABLES Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report p 145262/135031/15 Rev. 1 (October 21, 2015) Page 66 of 105 kz1 l

TABLE 2-1: LIST OF POWERB3LOCK STRUCTURES AND THEIR ELEVATIONS STRUCTURE j T SAFETY-RLTD T I(t ELEVATION Auxiliary Building Yes 1,100.00 Communication Corridor No 1,100.00 Condensate Storage Tank, Pipe No/No 1,100.00 House Door Control Building Yes 1,100.00 Diesel Generator Building Yes 1,100.00 Emergency Fuel Oil Tanks and Ys1097 Access Vaults Ys1097 ESW Access Vaults (5) Yes 1,098.00 - 1,100.00 Rev I ESWS Manholes (10) Yes 1,097.00- 1,099.50 ESWS Pumphouse Pressure Doors Yes 1,100.00 Fuel Building Yes 1,100.00 Hot Machine Shop No 1,100.00 Radwaste Building No 1,100.00 Reactor Building, Tendon Gallery Yes!/No 1,100.27 Access Shaft Reactor Makeup Water Storage Tank, No/Yes 1,100.00 Valve House Door Refueling Water Storage Tank, Valve YsYs1100 House Door Turbine Building No 1,100.00 Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Page 67 of 105 F'E 145262/135031/15 Rev. 1 (October 21, 2015)

TABLE 2-2: EXISTING WOLF CREEK DESIGN PARAMETERS 1 Plant Grade Elevation DESIGN PARAMETER 1 VALUE 1,099.5 ft Top of Slab Elevation for Safety-Related Structures 1,100.0 ft Top of Wolf Creek Dam Elevation 1,100.0 ft Crest Elevation of Wolf Creek Dam Main Spiliway 1,088.0 ft Lowest Elevation of Exterior Entrances to any Safety- 1,097.0 ft Rev I Related Structure (ESWS manholes) _______________

Elevation of Service Water Intake Structure 2' 1,058.0 ft Top of UHS Baffle Dike 1,094.0 ft Top of Submerged UHS dam 1,070.0 ft Local Intense Precipitation 28.79 in (6-hr cumulative rainfall)

Probable Maximum Precipitation (for the watershed) 32.8 in (48-hr PMP)

Design Precipitation Rate for Roof Drainage 3 19 in (in one hr)

Maximum PMF Water Level at the Site, Including 1,095.8 ft Wave Run-up Maximum PMF Water Level at the ESWS 1102f Pumphouse, Including Wave Run-up 1102f Wind Speed for Wave Run-up 40 mph (overland)

LT-2 Notes:

1Maximum LIP flood levels for the powerbiock area are at or below 1,099.92 ft, which does not cause flooding Rev 1 into any safety-related SSCs. As a result, flood durations were not evaluated in the design basis.

2 h invert elevation of the sump of the ESWS pumphouse is 1,058.0 ft with a minimum design water surface elevation of 1,068.0 ft. The top of slab elevation of the operating deck of the ESWS facility is 1,100.0 ft. The pump discharge line leaving the pumphouse is at elevation 1,091.5 ft. The intake structure of the ESWS pumphouse is designed to withstand a water elevation of 1,102.5 ft.

3 h design basis reports maximum snow loads on roofs. The load of the 48-hr winter PMP is 103.0, 98.8, 111.3, and 127.9 lb/ft 2 for the months of December, January, February, and March, respectively (WCNOC, 2015, Rev 1 Section 2.4.2.3.3). Note also that rainfall in excess of 7.4 inches per hour would (by design) overflow the roof curb and the building walls to the site drainage system (WCNOC, 2015; Section 2.4.2.3).

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Rev 1 Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March 2015.

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F FJ

TABLE 2-3: CURRENT DESIGN BASIS FLOOD ELEVATIONS DUE TO ALL FLOOD MECHANISMS 1 FLOODING MECHANISM Local Intense Precipitation

]WATER LEVEL (ft) 1,099.92 2- Rev 1 Lake Flooding 1,095.00

• Combined-Effects Flooding1,9.0/,0.24 (WCGS ShorelineiESWS Pumphouse)1,9.0/,0.2 Dam Failure Flooding on the Neosho River 1,044.55 5 Storm Surge and Seiche Flooding N/A 6 Tsunami Flooding N/A 6 Ice Flooding N/A 6 Channel Diversion Flooding N/A 6 LT-3 Notes:

SConsistent with 10 CFR 54.3, the Current Design Basis (CDB) information (as defined in 10 CFR 50.2) is included within the Current Licensing Basis (CLB) documented in the USAR (WCNOC, 2015). The CLB and CDB flood levels are equivalent. Rev 1 2 The highest estimated water level resulting from a LIP event is 1,099.92 ft, calculated near the safety-related buildings in the powerblock area (WCNOC, 2015).

SThe maximum PMvF water level in Wolf Creek Lake is 1,095.00 ft. This stillwater level is assumed to be constant across the lake.

4 obnd-fet Flooding includes PMIF flooding preceded by a standard project flood event (50 percent of PMiP) and wave run-up. The water level of 1,095.80 ft includes the maximum wind-wave run-up at the WCGS shoreline. The maximum water level, including wave run-up, at the ESWS pumphouse is 1,100.20 ft (WCNOC, Rev 1 2015, Section 2.4.10).

5Awater level of 1,044.55 ft is reported for the confluence of the Wolf Creek with the Neosho River, based on an unsteady flow model simulating a domino-type failure of the John Redmond, Council Grove, Cedar Point, and Marion Dams with standard project floods (50 percent of PMP).

6 NA= Not Applicable.

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March Rev 1 2015.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report F

145262/135031/15 Rev. 1 (October 21, 2015) Page 69 of 105 U.

S.I

TABLE 3-1: WATER LEVELS AND PONDING DEPTHS DUE TO LOCAL INTENSE PRECIPITATION PEAK PONDING FODHIH BULIGSAFETY- WATER BULIGRELATED?9 ELEVATION ABOVE 1,100 FT (ft) (ft)

Auxiliary Building Yes 1,100.38 0.38 Communications Corridor No 1,100.25 0.25 Condensate Storage Tank No 1,100.37 0.37 Control Building Yes 1,100.35 0.35 Demineralized Water Storage Tank No 1,100.37 0.37 Diesel Generator Building Yes 1,100.03 0.03 Fuel Building Yes 1,100.35 0.35 Hot Machine Shop No 1,100.35 0.35 Rev 1 Radwaste Building No 1,099.91 Reactor Building Yes 1,100.38 0.38 Reactor Makeup Water Storage Tank No 1,099.90 Refueling Water Storage Tank Yes 1,100.12 0.12 Turbine Building No 1,100.47 0.47 LT-4 Wolf Flood creek HazardNuclear Operating Corporation Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 70 of 105 KI*

TABLE 3-2: LOCAL INTENSE PRECIPITATION FLOODING AT DOORS TO SEISMIC CATEGORY I BUILDINGS GROUND TIlRESDIOLD MAXIMUM FLOOD MAXIMUM DURATION2 MAXIMUM MAXIMUM 3 MAXIMUM 3 DOOR NUMBER'! ASSET NUMBER STRUCTURE DESCRIPTION ELEVATION ELEVATION ELEVATION DEPTII OF FLOOD VELOCITY HYDROSTATIC FORCE HYDRODYNAMIC FORCE (ft) fit) (ft) (ft) (hours) (ft/s) (Ib/ft) (Ib/ft) 1 1195/I1198 Auxiliary Building Door

________ ________ (Pressure Door/Alcove Door) 1,099.33 1,100.00 1,100.35 1.01 0.5 123 2 13011 Auxiliary Building Door1,9.0 110010996.2 OO1583

__________ _________ (Missile Door) 1,099.40 1,100.0 1,099.960.52_<0.5_1.5_8_

3 13012/13013 Auxiliary Building Door 19.4 10.010.306 . . 11

_________(Pressure Door/Alcove Door) 1,099.44 1,100.0 1,100.3_0.600.2_2._11_1 4 33031 ~Communication Corridor 33031______(Double Door/Hollow Core Door) 072 1,098.98 1,100.00 1,100.05 0.89 1.0 072 302 Communication Corridor 1093 ,0.01100 .907071 33042______(Roll Up Door) 1093 ,0.01100 .907071 6 33043 Communication Corridor 1093 ,0.01100 .509092

________(Hollow Core Door) 1,099_0_1,00.0 1,100.8_0.8_0.9_09_22_

7 32013/32018 Control Building ,096 110.0,1 .4036.01.8 4 3 (Pressure Door/Alcove Door)1,9.0 ,0.011004.300 8 52011 Diesel Generator Building 1,099.35 1,100.00 1,099.90 0.57 0.1 2.8 10 10

_____________________________ (Missile Door)_________________________

9 52031 Diesel Generator Building 1091 ,0.01099 .405161 (Missile Door) 1,09.7_,10.0_,09.9_0640._16_3_

Rev1 10 61011 Fuel Building1,9.7 110010981.010 (Hollow Core Door) 1090 1,0.0,9.8070.01.7 15 5 11 61021 Fuel Building1.82

________ ________ (Hollow Core Door) 1,099.36 1,100.00 1,099.56 0.50 0.11.82 12 61022 Fuel Building0.51

_________(Roll Up Door) 1,099.58 1,100.00 1,100.05 0.41 0.00.51 13 13342 Hot Machine Shop 1090 1,0.0,1.8091.62326 11 (Hollow Core Door)1,9.0 11001,018.10623 14 13321 Hot Machine Shop 1092 1,0.0,9.2061.40.9 12I (Hollow Core Door)1,9.9 110010992.604 15132 Hot Machine Shop 1,099.32 1,100.00 1,099.94 0.61 0.1 121 15 13322 ~~~(Roll Up Door) _______________

16 16402 43092 ~ Stair T-2 (Hollow Core Door) 1,099.35 1,100.00 1,100.09 0.70 0.5 101 101 17 4102 Stair T-3 17______43102_______ (Hollow Core Door) 1,099.35 1,100.00 1,100.10 0.72 0.5 1.0 16 1 LT-12 Notes:

SSome of these doors are to non-Seismic Category I buildings that have entrances to Seismic Category I buildings behind them. The ESWS sod pumphouse and miscellaneous yard buildings are not included in this table.

2 Flooding duration was computed based sos threshold depth of 0.5 ft.

3 Hydrostatie and hydrodynamie forces are reported in force per unit1width. Multiplying the reported forces by the width of a structure or wall provides the total force exerted on the wall. Hydrodynamie forces set in the direction of flow velocity. Consequently, the reported hydrodynamic forces should be interpreted as a conservative estimate. In eases where flow velocity is directed away from the building or tank (i.e., off the roof and sway fr'om the building or tank), the hydrodynamic force acting on the door is zero.

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TABLE 3-3: LOCAL INTENSE PRECIPITATION FLOODING AT OTHER DOORS, HATCHES, MANHOLES, AND VAULTS FOR SAFETY-RELATED SSCs GRONDTHESHLD MAIMM FOO MXIUM LOD URTIO MXIUM MAXIMUM MAXIMUM ITEM'l ASSET GRUDTRSOD MXMM3OD MXMMFOD DRTO AIU HYDROSTATIC 4 HYDRODYNAMIC 4 NUMBER STRUCTURE DESCRIPTION ELEVATION ELEVATION ELEVATION DEPTH OF FLOOD 3 VELOCITY .FORCE FORCE (ft) (ft) (ft) (ft) (hours) (flI second) (lb/ft) (lb/ft)

I 91011 Condensate Storage Tank Pipe HousetDoor 1,099.31 1,1I00.00 1,100.37 1.06 1.8 1.0 35 1 2 Z055 Emergency Fuel Oil Tanks and Access Vaults 1,099.51 1,099.75 1,099.78 0.31 0.0 0.5 3 <1 7 MHEIA ESWS Manhole 2 1,099.53 1,099.50 1,099.92 0.47 0.0 0.5 7 <1 8 MHEIB ESWS Manhole 2 1,099.57 1,099.50 1,099.93 0.35 0.0 0.5 4 <1 9 MHE2A ESWS Manhole'2 1,097.51 1,098.00 1,097.73 0.22 0.0 0.7 1 <1 2

10 MHE2B ESWS Manhole 1,097.80 1,098.00 1,097.78 0.13 0.0 0.3 <1 <1 i11 MI-E3A ESWS Manhole 2 1,097.03 1,097.00 1,097.51 0.19 0.0 0.4 1 <1 2

12 MHE3B ESWS Manhole 1,097.11 1,097.00 1,097.51 0.19 0.0 0.4 1 <1 13 MHE4A ESWS Manhole'2 1,096.79 1,097.00 1,097.73 0.83 1.4 2.2 22 9 14 MHE4B ESWS Manhole 1,096.89 1,097.00 1,097.73 0.83 1.4 2.2 22 9 15 MHE5A ESWS Manhole'2 1,097.23 1,097.75 1,098.29 1.43 10.0 0.6 64 <1 16 MHE5B ESWS Manhole 2 1,097.29 1,097.75 1,098.29 1.43 10.0 0.6 64 <1 17 KI051 ESWS Pumphouse Pressure Door A 1,099.34 1,100.00 1,099.49 0.11 0.0 0.8 <1 <1 18 KI041 ESWS Pamphouse Pressure Door B 1,099.54 1,100.00 1,099.79 0.17 0.0 0.4 <1 <1 21 N/A Reactor Building Tendon Gallery Access'Shaft 1,099.22 1,1I00.27 1,100.23 1.09 6.4 0.7 37 <I Rev I 22 91031 Reactor Makeup Water Storage Tank Valve House Door 1,099.34 1,1I00.00 1,099.86 0.53 <0.05 1.7 9 3 23 91021 Refueling Water Storage Tank Valve House Door 1,099.18 1,100.00 1,099.93 0.74 0.9 3.4 17 20 24 N/A ESW Vertical Loop Chase 1,099.58 1,100.50 1,100.29 0.94 1.1 0.8 28 <1 25 AVI IESW Access Vault 1,098.59 1,100.00 1,099.39 1.00 5.8 1.3 31 2 26 AV2 ESW Access Vault 1,096.62 1,098.00 1,097.34 0.65 1.1I 4.0 13 25 27 AV3 ESW Access Vault 1,098.87 1,099.50 1,099.55 0.44 0.0 1.2 6 1 28 AV4 ESW Access Vault 1,097.86 1,098.50 1,098.28 0.73 1.9 2.5 17 8 29 AV5 ESW Access Vault 1,098.09 1,098.50 1,099.19 0.44 0.0 1.2 6 1 LT-10 Notes:

SSeveral items have been abandoned in place due to the site projects. These items have been removed fr'om the table and new items have been added for Rev. 1 of the FHRR. Therefore, several item numbers in the above table are skipped in order for numbering to align with prior analyses.

' Items 7 through 16 (the ESWS Manholes) are designed to be watertight, as discussed in the Wolf Creek Nnclear OperatingCorporationPost FukushirnaFlooding Walkdow'n Report (WCNOC, 2012).

SFlooding duration was computed based on a threshold depth of 0.5 ft.

4Hydrostatic and hydrodynamic forces ure reported in force per unit width. Multiplying the reported forces by the width of a stracture or wall provides the total force exerted on the wall. Hydrodynamnic forces act in the direction of flow velocity. Consequently, the reported hydrodynamic forces should be interpreted as a conscrvative estimate. In cases where flow velocity is directed away from the building or tank (i.e., off the roof and away from the building or tank), the hydrodynatnic force acting on the door is zero

Reference:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2012, "Wolf Creek Nuclear Operating Corporation Post Fukushima Flooding Walkdown Report," Enclosure to ET 12-0031, November 2012.

Wolfrck Nuclear OperatingCoq~oaution Flood HacardRceavaluaion Rcportae72o t 145262/135031/I15 Res. i (Otoaber 21. 2015) Pg 2o 0

TABLE 3-4: WATERSHED SUBBASIN CHARACTERISTICS AND HEC-HMS MODELING RESULTS DANG ARA RUNOFF LA IE2 PRECIPITATION PEAK 4 DRBASINAG AmiEA LAGRTIM DEPTH 3 RUNOFF SU AI m) NUMBER I (Minutes) (in) (cfs)

SB1 7.035 92 47.30 36.70 50,817 SB2 2.470 90 31.05 36.70 21,131 SB3 1.934 85 44.77 36.70 14,246 SB4 16.250 92 23.08 36.70 151,880 SB5 3.450 82 85.97 36.70 17,932 LT-5 Notes:

SSCS Runoff Curve Number after calibration 2Lag time after calibration and reduction by 33 percent to account for nonlinearity effects in accordance with guidance in NRC N1UREG/CR-7046.

3Precipitation depth is for the 72-hr PMv~P.

" Runoff hydrograph ordinates from HEC-HMS output are increased by five percent for Case 5.

Reference:

Nuclear Regulatory Commission (NRC), 2011, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America," NUREG/CR-7046. PNNL-20091, NRC Job Code N6575, Washington, D.C., November 2011.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 73 of 105

TABLE 3-5:

SUMMARY

OF HIEC-HMS AND HEC-RAS SIMULATION CASES CASE 1RAINFALL ILOSSESICHANNELS RUNOFF TRANSFORMATION RUIG TRUH NONLINEARITY EFFECTS PERCENT SPILL WAY SEI NT IO 1Ys/o (YES/NO) (YES/NO) (YES/NO) (YES/NO) 1 BLOCKED (E/O

__________________HEC-HMS Modeling _______

1 No No No No 0 No 2 No Yes Yes No 03 ~ No 3 No Yes Yes Yes 0 No 4 Yes Yes Yes Yes 0 3*Y No 5 Yes Yes No Yes 03 No HEC-RAS Modeling 1 No No No No 0 No 2 No Yes Yes No 0 No 3 No Yes Yes Yes 0 No 4 Yes Yes Yes Yes 03No 5 Yes Yes No Yes 0 No 6 Yes Yes No Yes 0 No 7 Yes Yes No Yes 50/10 No 8 Yes Yes No Yes 2/04No 9 Yes Yes No Yes 1/04No 10 Yes Yes No Yes 0 Yes LT-6 Notes:

' Nonlinearity effects include a decrease in lag time by 33 percent, and an increase in peak discharge. A five percent increase in discharge is used for Case 5 results as input into the HEC-RAS model.

2 Routing through channels is not used in HEC-HMS Cases 1 and 5. However, channels are represented in the HEC-RAS simulations. HEC-HMS simulated discharge from subbasins is used in the HEC-RAS simulations to avoid the potential of double accounting for delays in flow through channels.

SThe spillways are assumed to be unobstructed.

4"The first number is the percent of the service spillway that is blocked. The second number is the percent of the auxiliary spiliway that is blocked.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Page 74 of 105 U, d 145262/135031/15 Rev. 1 (October 21, 2015)

TABLE 4-1: COMPARISON OF MODELING APPROACHES FOR 1CURRENT LICENSING BASIS AND FLOODING REEVALUATION ANALYSIS CONSIDERATION REEVALUATED HAZARDS CURRENT LICENSING BASIS Local Intense Precipitation Calculation based on HMVR No. 52 Calculation based on HMR No. 52 (LIP) values values LIP Flooding Characterization FLO-2D Model USACE HEC-RAS PMP for the Wolf Creek Calculation based on HMR No. 52 Calculation based on HMR No. 33 Watershed values values PMP Rainfall Hyetograph Time period of 72 hrs with 48 hrs with 1-hr increments 5-minute increments HEC-HMS was not used for the USAR analysis. The USACE Rainfall-Runoff Model USACE HEC-HMS developed 1-hr Snyder unit hydrographs for 3 subbasins scaled from the Neosho River watershed.

Transformation Method SCS Synthetic Unit Hydrograph SndrsUiHyogahMtd MethodSndrsUiHyrgahMto PMFlos, tanforatin, nd Include loss, transformation, and Include loss and transformation, PMrossutasfratogn routing through the channels and with routing through Wolf Creek ruigthrough Wolf Creek Lake and dam. Lake and dam River Hydraulic Model USACE HEC-RAS USACE Water Surface Profiles 2 The Tennessee Valley Authority The Mthodwasuse olue to Software was used to compute the determine the water surface Dam Break Flooding elvto nNoh ie tte water surface elevation at the Wolf elevtio onNeoho ive atthe Creek confluence with the Neosho Wolf Creek confluence. Rvr Combined Effects Flooding ANSRECR992 anthds ANS, 1976 method LT-8 Notes:

SDue to changes in regulatory requirements since the original design basis, some of the mechanisms considered and the methodologies used in the reevaluation analysis are different from the original design basis analysis. Therefore direct comparison is not practicable in all cases.

2 Stated in USAR Section 2.4.3.5 (WCNOC, 2015). Rev 1

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March Rev 1 2015.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Page 75 of 105 IF-145262/135031/15 Rev. 1 (October 21,2015)

TABLE 4-2: COMPARISON OF CURRENT LICENSING BASIS AND) FLOODING REEVALUATION ANALYTICAL INPUTS ANALYTICAL INPUT REVALUATED HAZARDS CURRENT LICENSING BASIS Local Intense Precipitation 19.0 in 19.0 in (1-hr, 1 mi2 value)

Probable Maximum PrcpttinfrWaese'36.70 in (72-hr PMP) 32.80 in (48-hr PMP)

Wolf Creek Lake Dam outflow: Wolf Creek Lake Dam outflow:

Input for River Hydraulics 23,813 cfs 22,845 cfs Model Wolf Creek Lake inflow: Wolf Creek Lake inflow:

215,128 cfs 82,089 cfs Spillway Elevations for Wolf Creek Lake Dam1,8.f!1,9.ft10.0t/,9.5t (Service /Auxiliary1,8.ft1005f1,80f/,9.5t Spillways)

Maximum Sustained Overland 10-minute, 2-year 38.65 mph 40.00 mph 2 Wind Speed Maximum Sustained Overwater 10-minute, 2-year 46.38 mph 1 Not computed Wind Speed _______________ ______________

LT-9 Notes:

' The maximum storm duration of HMR No. 33 (used in the design basis) is 48 hrs and the maximum storm duration of HMR No. 52 (used for the reevaluation analysis) is 72 hrs.

2 Wind speed used for wave height calculation.

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March Rev I 2015.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report FE 145262/135031/15 Rev. 1 (October 21, 2015) Page 76 of 105

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TABLE 4-3: COMPARISON OF CURRENT LICENSING BASIS AND REEVALUATED FLOOD LEVELS 1 REEVALUATED WATER CURRENT LICENSING BASIS FLOODING MECHANISM LEVEL WATER LEVEL (ft) (ft)

Flooding Due2 to Local Intense Precipitation 1,100.38 1,099.92 Rev 1 Lake Flooding Due to PMF 1,093.54 1,095.00 Wave Run-up Coincident with Stillwater level + Stillwater level +

PMF Wave Run-up Wave Run-up WCGS Shoreline 1,094.37 1,095.8 ESWS Pumphouse 1,098.43 1,100.2 1,076.70 ft on the Neosho River at confluence of Wolf 1,044.55 ft on the Neosho Creek based on River at confluence of Wolf Dam Failure Flooding Instantaneous Transport of Creek based on dynamic Reservoir Storage (Volume modeling Screening Method)

Storm Surge and Seiche Flooding Dismissed Dismissed Tsunami Flooding Dismissed Dismissed Ice Flooding Dismissed Dismissed Channel Diversion Flooding Dismissed Dismissed Combined-Effects Flooding3 500-yr rainfall + PMP + SPF + PMP + Wave Run-up Wave Run-up WCGS Shoreline 1,095.46 1,095.80 ESWS Pumphouse 4 1,099.52 1,100.20 LT-7 Notes:

Consistent with 10 CFR 54.3, the Current Design Basis (CDB) information (as defined in 10 CFR 50.2) is included within the Current Licensing Basis (CLB) documented in the USAR (WCNOC, 2015). The CLB and CDB flood Rev 1 levels are equivalent.

2 The values reported are the highest water levels adjacent to safety-related buildings on the powerbiock.

SPMP = Probable Maximum Precipitation, SPF = Standard Project Flood = 50 percent PMP.

4 h intake structure for the ESWS Pumphouse is designed to withstand a high water elevation of 1, 102.50 ft (WCNOC, 2015, Section 2.4.10). Revi1

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March Rev 1 2015.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 77 of 105 U,> Ii

TABLE 4-4: COMPARISON OF VARIOUS FLOODING PARAMETERS BETWEEN THE CURRENT LICENSING BASIS AND THE FLOOD REEVALUATION FLOOD CONDITION REEVALUATED FLOOD HZR fCURRENT LICENSING AI Local Intense Precipitation Flood Depth 1.43 ft 1 0.42 ft 2 Flood Duration 10.0 hrs i N/A 3 Maximum Flow Velocity 4.0 ft/s 4 N/A 3 Rev 1 Hydrostatic Loading 64 lb/ft 1 N/A 3 Hydrodynamic Loading 25 lb/ft 4 NA3 Debris Impact Loading Debris Screened Out 5 N/A 3 Flood Elevation with Sedimentation Sedimentation Screened Out 6 N/A 3 Probable Maximum Flood Flood Elevation 1,093.54 ft 7 1,095.0 ft 7 ,'

Flood Duration N/A 9 N/A 3 Maximum Flow Velocity N/A 9 N/A 3 Hydrostatic Loading 39,409 lb/ft 10 42,713 lb/ft"1 Hydrodynamic Loading N/A 12 N/A 3' 11 Flood Elevation with Debris/Spillway 1,094.37 ft 13 N/A 3 Blockage Flood Elevation with Sedimentation 1,093.54 ft 7 N/A 3, 14 Combined-Effects Flooding Flood Elevation 15 1,095.46/1,099.52 ft 1,095.8/1,100.2 ft Flood Duration N/A 9 N/A 3 Maximum Flow Velocity N/A 9 N/A 3 Hydrostatic Loading N/A 16 N/A 3' 16 Hydrodynamic Loading N/A 12 N/A 3, 16 LT- 11 Notes:

1 Simulated values at ESWS Manholes MHTE5A and MHE5B (Table 3-3, Items 15 and 16).

2 This flood depth results in a maximum water elevation of 1,099.92 ft, which does not flood any safety-related SSCs (WCNOC, 2015).

Rev 1 3These parameters are not included in the CLB.

4~Maximum simulated value at ESW Access Vault AV2 (Table 3-3, Item 33).

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report p-145262/135031/15 Rev. 1 (October 21, 2015) Page 78 of 105

TABLE 4-4: COMPARISON OF VARIOUS FLOODING PARAMETERS BETWEEN TILE CURRENT LICENSING BASIS AND THE FLOOD REEVALUATION (CONTINUED) 5 These forces are screened out due to simulated low velocities and flow directions away fr'om safety-related SSCs.

SThe potential for increased flooding due to sedimentation was screened out due to negligible sediment source area Rv1 and low velocities limiting scour.

7 The peak stage simulated for Wolf Creek Lake, not including the effects of wind-waves.

8 The CLB value is from the USAR (WCNOC, 2015, Table 2.4-16).

Rev 1 9 Safety-related SSCs are not flooded, so these flooding affects are not applicable.

• 0 Hydrostatic forces are computed for the ESWS pumphouse only. This force is a depth-integrated force for the ESWS pumphouse from the stillwater level down to the bottom of the ESWS pumphouse (elevation 1058.0 fi).

• 1Although no values are reported in the current version of the USAR (WCNOC, 2015), the Design Basis analysis for the pumphouse reports a hydrostatic force of 42,713 lb/fl, corresponding to a lake level of 1095.0 ft. The Design Rev 1 Basis analysis also screens out hydrodynamic loads due to the stagnant nature of Wolf Creek Lake.

12Hydrodynamic forces are not applicable to the ESWS pumphouse because adjacent water is stagnant (i.e., Wolf Creek Lake). Hydrodynamic forces due to wind-waves are not computed in the reevaluation because wind-wave run-up levels in the reevaluation are bounded by the CLB run-up levels (1100.2 ft; WCNOC, 2015, Section 2.4.10). Rev 1 13 This is the peak stage simulated for Wolf Creek Lake with ten percent of the auxiliary and service spillways blocked.

14 The maximum fill over a period of 40-years is provided in the USAR (WCNOC, 2015).

15 The two flood elevations correspond to the lake shoreline and the pumphouse, respectively. Flood elevations for both locations include wind-wave effects. Rev 1 16The intake structure of the ESWS pumphouse can withstand a water elevation of 1,102.5 ft (WCNOC, 2015, Section 2.4.10).

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit i, Revision 28, March Rev 1 2015.

Wolf Creek Nuclear Operating Corporation * ,*

Flood Hazard Reevaluation Report Pg 9o 0 145262/135031/1 5 Rev. 1 (October 21, 2015) Pag.7 of10

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Reference:

Image Source: ESRI 2013a. Environmental Systems Research Institute Flood Hazard Reevaluation Report (ESRI), "US Topo Maps by National Geographic".

Website: httpJ/goto.arcgisonline.comlmapslUSA.jUopo..Maps Date Accesed December24, 2013 R3' ENGINEERS Paul Associates, /Inc.

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1. AUXILIARY BUILDING

2. COMMUNICATION CORRIDOR FROM: GOOGLE EARTH, 2013.

3. CONDENSATE STORAGE TANK

4. CONTROL BUILDING SCALE

5. DIESEL GENERATOR BUILDING

6. EMERGENCY FUEL OIL TANKS 100 0 100 FEET

7. FUEL BUILDING

8. HOT MACHINE SHOP

9. RADWASTE BUILDING FIGURE 2-3

10. REACTOR BUILDING LOCATIONS OF BUILDINGS 1 1. REACTOR MAKE-UP WATER STORAGE TANK

12. REFUELING WATER STORAGE TANK IN THE POWERBLOCK AREA

13. TURBINE BUILDING PREPARED FOR WOLF CREEK FLOOD HAZARD REEVALUATION REPORT A REMOVED CALL-OUT FOR ESWS VALVE HOUSE [-IIN* Paul C. Rizzo Associates, Inc.

APPROVED BY: JAO DATE: 10/21/15 ENGINEERS / CONSULTANTS / CM REVISIONS Page 85 of 105

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2009-12 (REVISED JANUARY 2010).

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Reference:

Image Source: ESRI 2013a, Environmental Systems Research Institute (ESRI), "US Topo Maps by National Geographic".

• F'Paul C. Rizzo Associates, Inc.

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FLOOD HAZARD REEVALUATION REPORT THE TIME INCREMENT OF HYETOGRAPH IS FIVE MINUTES.

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FLOODING IN RIVERS AND STREAMS PREPARED FOR (A) RESULTS FROM HEC-HMS MODEL (CASE 5) (B) RESULTS FROM HEC-RAS MODEL (CASE 6)

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DATE ACCESSED: JUNE 27, 201.3. WOLF CREEK

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[Pageau C.9izoAsofite105c Page 97 of' 105

W-- Neosho Watershed Neosho Watershed Dams Lii WCGS - WOLF CREEK GENERATING STATION

REFERENCES:

1. IMAGE SOURCE: ESRI, 2013c, ENVIRONMENTAL SYSTEMS RESEARCH INSTITUTE (ESRI), "ARCGIS IMAGERY,"

WEBSITE: <http://www.orcgis.com/home/

item.html?id =a5fef635 17cd4aO99b437e557 13d3d54>,

DATE ACCESSED: OCTOBER 18, 2013.

2. HUC BASIN SOURCE: USGS, 2013.

UNITED STATES GEOLOGICAL SURVEY (USGS), "NATIONAL MAP VIEWER AND FIGURE 3-12 DOWNLOAD PLATFORM," WEBSITE:

<http://viewer.nationalmap.gov/viewer/>, LOCATION OF DAMS NEAR THE SITE DATE ACCESSED: JUNE 27, 2013.

PREPARED FOR

3. USACE, 201.3a, UNITED STATES ARMY CORPS OF ENGINEERS (USACE),

NATIONAL INVENTORY OF DAMS, WEBSITE: WOLF CREEK

< http//geo.usace.army.mil/pgis/

FLOOD HAZARD REEVALUATION REPORT f?p=397: 1 :112429380233301 :::::>,

DATE ACCESSED: NOVEMBER 4, 2013.

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1. NRC JLD-ISG-201 2 (NRC, 201 2C) USES THE PHRASE "SITE PREPARATION FOR FLOOD EVENTS" FOR CONDITIONS THAT, WHEN MET. INITIATE FLOOD PROCEDURES OR NOTIFICATION OF IMPENDING FLOOD. A MORE GENERAL TERM OF "INITIATION OF SITE FIGURE 4-1 PREPARATION PROCEDURES" IS USED HERE.

2. THE TIMING OF FLOOD DEPTHS AT EACH DOOR IS UNIQUE. THE TIMES INDICATED ARE DURATION OF FLOODING FOR INTENDED TO BE REPRESENTATIVE AND BOUNDING OF THE DURATION OF FLOODING.

THE LIP FLOOD ANALYSIS

3. 0.5 FT REPRESENTS THE DIFFERENCE BETWEEN THE GRADE ELEVATION (1,099.5 Fr)

AND THE FLOOR ELEVATION (1,100 FT) FOR BUILDINGS ON THE POWERBLOCK. PREPARED FOR WOLF CREEK FLOOD HAZARD REEVALUATION REPORT NUCLEAR REGULATORY COMMISSION (NRC), 2012C, "GUIDANCE FOR PERFORMING THE INTEGRATED ASSESSMENT FOR EXTERNAL FLOODING," JLD-ISG-2012-05, NRC INTERIM STAFF GUIDANCE (ML12311A214), WASHINGTON DC, REVISION 0, NOVEMBER 30, 2012.

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APPENDIX A FLO-2D PRO SOFTWARE QUALIFICATIONS Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 103 of 105

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FLO-2D PRO MODELING SOFTWARE QUALIFICATIONS The FLO-2D Pro computer program was developed by FLO-2D Software, Inc., Nutrioso, Arizona. FLO-2D Pro is a combined two-dimensional (2D) hydrologic and hydraulic model that is designed to simulate river overbank flows, as well as unconfined flows over complex topography and variable roughness, split channel flows, and urban flooding. FLO-2D is a FEMA-approved software (FLO-2D, 2012). FLO-2D Pro is a physical process model that routes rainfall-runoff and flood hydrographs over unconfined flow surfaces using the dynamic wave approximation to the momentum equation. The model has components to simulate riverine flow, including flow through culverts, street flow, buildings and obstructions, levees, sediment transport, spatially variable rainfall and infiltration and floodways.

Application of the model requires knowledge of the site, the watershed, and engineering judgment. This software has been used to simulate local intense precipitation, propagation of storm surge, seiches, and riverine flow through overland flow and channels to establish stillwater levels at various flood hazard reevaluation project sites.

The major design inputs to the FLO-2D Pro computer model are digital terrain model of the land surface, inflow hydrographs, and/or rainfall data, Manning's roughness coefficient, and soil hydrologic properties, such as the SCS curve number. The digital terrain model of the land surface is used in creating the elevation grid system over which flow is routed. The specific design inputs depend on the modeling purpose and the level of detail that is desired.

This FLO-2D Pro Overland Flow component simulates overland flow and computes flow depth, velocities, impact forces, static pressure, and specific energy for each grid. Predicted flow depth and velocity between grid elements represent average hydraulic flow conditions computed for a small time step. For unconfined overland flow, FLO-2D applies the equations of motion to compute the average flow velocity across a grid element (cell) boundary.

By using a 2D model, floodwater is routed in a natural manner without being "forced" to flow in predefined directions. This allows for a more accurate flood analysis than is possible with one-dimensional (iD) models. The FLO-2D Reference Manual (FLO-2D, 2012) describes the FLO-2D model as follows: "FLO-2D is a physical process model that routes rainfall-runoff and flood hydrographs over unconfined flow surfaces or in channels using the dynamic wave Wolf Creek Nuclear Operating Corporation F L>

Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 104 of 105 **_1

approximation to the momentum equation." Additionally, the FLO-2D Basic model is approved by FEMA for use in Flood Insurance Studies (FEMA, 2013; FLO-2D, 2012).

NRC JLD-ISG-2013-01 (NRC, 2013a) provides guidance for dam failure analysis. Within this guidance, the NRC comments about the advantages of 2D modeling methodologies. These comments, though directed towards dam failure modeling within the context of NRC JLD-ISG-2013-01 (NRC, 2013a), provide a perspective on 2D modeling that is relevant for a LIP analysis as well. Section 9.1.2 of NRC JLD-ISG-2013-01 (NRC, 2013a) states:

"In fact, flood flows through extremely flat and wide flood plains may not be modeled adequately as one-dimensional flow. Velocity of the flow across the floodplain may be just as large as that of flow down the channel. If this occurs, a two-dimensional flow model will better simulate the physical processes."

Section 9.2 of NRC JLD-ISG-2013-01 (NRC, 2013a) states:

"In general, as the flood plain widens, one-dimensional analysis becomes less reliable.

Accurate estimates of flood elevation in areas of changing topography and near large objects (i.e. buildings and other structures) in the flow field will typically require localized two-dimensional analysis, in areas of particular interest or sensitivity."

Section 9.2 of NRC JLD-ISG-2013-01 (NRC, 2013a) further gives the NRC staff position as:

"For estimating inundation at or near a NPP [Nuclear Power Plant] site, two-dimensional models are generally preferred by the NRC staff. However, use of one-dimensional models may be appropriate in some cases. Therefore, use of one-dimensional models will be accepted on a case-by-case basis, with appropriate justification."~

As a 2D model that simulates rainfall runoff, FLO-2D is sufficient for meeting the guidance presented in NRC NUREG/CR-7046 (NRC, 2011) for flooding analyses.

Wolf Creek Nuclear Operating Corporation *E*

Flood Hazard Reevaluation ReportPae]0of15*

145262/135031/15 Rev. 1 (October 21, 2015) Pag 10 of10

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SUBMITTED TO:

WESTINGHOUSE ELECTRIC COMPANY LLC Corporate Headquarters 500 Penn Center Boulevard, Pittsburgh, PA ]15235 USA Telephone: 412.856.9700 j Fax: 412.856.9749

WOLF CREEK NUCLEAR OPERATING CORPORATION FLOOD HAZARD REEVALUATION REPORT PROJECT NOS.: 14-5262/13-5031 REVISION 1 OCTOBER 21, 2015 RIZZO ASSOCIATES 500 PENN CENTER BOULEVARD BUILDIN'G 5, SUITE 100 PITTSBURGH, PENNSYLVANIA 15235 TELEPHONE: (412) 856-9700 TELEFAX: (412) 856-9749 WWW.RIZZOASSOC.COM Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 2 of 105 r<1K

APPROVALS Project Nos.: 14-5262/13-5031 Report Name: Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Date: October 21, 2015 Revision No.:

Approval by responsible manager signifies that the document is complete, all required reviews are complete, and the document is released for use.

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• ,**.*Jeffrey Associate, RIZZO Associates A.Oskamp, Engineering Originator: October 21, 2015 Jeffrey A. Oskamp, E.I.T. Date Engineering Associate Independent Associate, RIZZO Associates October 21, 2015 Verifier: Tom Edwards Date Engineering Associate

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/* //*Engineering Mark Schwartz, Supervisor, Independent RIZZO Associates October 21, 2015 Verifier:

Mark Schwartz, P.E. Date Technical Supervisor

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J Thomas H.Jackson, P.E., PhD, Technical L. 1{i r$./. Water Resources Engineering Supervisor, RIZZO Associates Inc. October 21. 2015 Reviewer:

Thomas Jackson, Ph.D., P.E. Date Technical Supervisor

• Jemie Dababneh, Managing Project Principal, RIZZO Associates Manager: October 21. 2015 Ahmed "Jemie" Dababneh, Ph.D., P.E. Date Senior Director and Project Manager

• /*]_[ Daniel J. Barton, Vice Principal in CV~~L President, RIZZO Associates Charge: October 21.,2015 Daniel J. Barton, Jr., P.E. Date Vice President Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 3 of 105

CHANGE MANAGEMENT RECORD Project Nos.: 14-5262/13-5031 Report Name: Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report REVISION NO. DATE [ DESCRIPTIONS OF CHANGES/AFFECTED PAGES 0 February10, 2014 N/A Updated the Local Intense Precipitation analysis to account for changes to the site configuration up to 1October 21, 2015 July 2015. Incorporated updates to the design basis since the issuance of the Revision 0 report.

________________ Substantive changes are marked with_'Rev_1'_bars.

4 I-4 I.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 4 of 105

TABLE OF CONTENTS PAGE LIST OF TABLES ................................................................................ 7 LIST OF FIGURES.................... ........................................................... 8

1.0 INTRODUCTION

...................................................................... 10 1.1 PURPOSE AND SCOPE ........................................................... 10 1.2 LOCATION OF THE SITE............................................................. 10 1.3 SITE BACKGROUND AND HISTORY.............................................1 1 2.0 FLOOD HAZARDS AT THE SITE................................................... 12 2.1 DETAILED SITE INFORMATION .................................................... 12 2.1 .1 Design Site Information ............................................. 12 2.1.2 Present-Day Site Information ....................................... 15 2.2 CURRENT DESIGN BASIS FLOOD ELEVATIONS .................................. 16 2.3 FLOOD-RELATED CHANGES TO THE LICENSING BASIS......................... 19 2.3.1 Description of Hydrological Changes and Flood Elevations............................................................. 19 2.3.2 Description of Flood Protection Changes (Including Mitigation) ............................................................ 19 2.4 CHANGES TO THE WATERSHED AND LOCAL AREA............................. 20 2.4.1 Description of Watershed and Local Area at the Time of License Issuance...................................................... 20 2.4.2 Description of Any Changes to the Watershed and Local Area since License Issuance......................................... 20 2.5 CURRENT LICENSING BASIS FLOOD PROTECTION .............................. 21 2.6 ADDITIONAL SITE DETAILS ........................................................ 22 2.6.1 Wolf Creek Lake Bathymetry....................................... 22 2.6.2 Recommendation 2.3 Walkdown Results .......................... 22 2.6.3 Site Visit .............................................................. 23 3.0 FLOOD HAZARD REEVALUATION ANALYSIS................................ 24 3.1

SUMMARY

OF RECOMMENDATION 2.1......................................... 24 3.2 SOFTWARE USED.................................................................... 24 3.3 FLOOD-CAUSING MECHANISMS ................................................... 25 3.3.1 Local Intense Precipitation .......................................... 26 Wolf Creek Nuclear Operating Corporation ,*

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TABLE OF CONTENTS (CONTINUED)

PAGE 3.3.2 Flooding in Rivers and Streams .................................... 30 3.3.3 Dam Breaches and Failures ......................................... 41 3.3.4 Storm Surge .......................................................... 45 3.3.5 Seiche ................................................................. 45 3.3.6 Tsunami............................................................... 46 3.3.7 Ice-Induced Flooding ................................................ 46 3.3.8 Flooding Resulting from Channel Migration or Diversion......48 4.0 COMPARISON OF CURRENT DESIGN BASIS AND REEVALUATED FLOOD HAZARDS .............................................. 49 4.1 COMPARISON OF FLOOD-CAUSING M/ECHANISMS .............................. 49 4.2 COMPARISON OF FLOOD EFFECTS ................................................ 49 4.3 SUPPORTING DOCUMENTATION ................................................... 54 4.3.1 Technical Justification of the Flood Hazard Analysis ............ 55 4.3.2 Technical Justification of the Walkdown Results................. 55

4.4 CONCLUSION

S........................................................................57 5.0 INTERIM EVALUATION AND ACTIONS......................................... 59 5.1 EVALUATION OF THE IMPACT OF THE REEVALUATED FLOOD LEVELS ON STRUCTURES, SYSTEMS, AND COMPONENTS................................ 59 5.2 ACTIONS TAKEN TO ADDRESS FLOOD HAZARDS NOT COMPLETELY BOUNDED BY THE CURRENT DESIGN BASIS HAZARD.......................... 59 6.0 ADDITIONAL ACTIONS............................................................. 61

7.0 REFERENCES

.......................................................................... 62 TABLES FIGURES APPENDIX A FLO-2D PRO SOFTWARE QUALIFICATIONS Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation ReportPae6o10 145262/135031/15 Rev. 1 (October 21, 2015) Pag 6of10

LIST OF TABLES TABLE NO. TITLE TABLE 2-1 LIST OF POWERBLOCK STRUCTURES AND THEIR ELEVATIONS TABLE 2-2 EXISTING WOLF CREEK DESIGN PARAMETERS TABLE 2-3 CURRENT DESIGN BASIS FLOOD ELEVATIONS DUE TO ALL FLOOD MECHANISMS TABLE 3-1 WATER LEVELS AND PONDING DEPTHS DUE TO LOCAL INTENSE PRECIPITATION TABLE 3-2 LOCAL INTENSE PRECIPITATION FLOODING AT DOORS TO SEISMIC CATEGORY I BUILDINGS TABLE 3-3 LOCAL INTENSE PRECIPITATION FLOODING AT OTHER DOORS, HATCHES, MANHOLES, AND VAULTS FOR SAFETY-RELATED SS Cs TABLE 3-4 WATERSHED SUBBASIN CHARACTERISTICS AND HEC-HMS MODELING RESULTS TABLE 3-5

SUMMARY

OF HEC-HMS AND HEC-RAS SIMULATION CASES TABLE 4-1 COMPARISON OF MODELING APPROACHES FOR CURRENT LICENSING BASIS AND FLOODING REEVALUATION TABLE 4-2 COMPARISON OF CURRENT LICENSING BASIS AND FLOODING REEVALUATION ANALYTICAL INPUTS TABLE 4-3 COMPARISON OF CURRENT LICENSING BASIS AND REEVALUATED FLOOD LEVELS TABLE 4-4 COMPARISON OF VARIOUS FLOODING PARAMETERS BETWEEN THE CURRENT LICENSING BASIS AND THE FLOOD REEVALUATION Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 7 of 105

LIST OF FIGURES FIGURE NO. TITLE FIGURE 1-1 GENERAL LOCATION OF THE SITE FIGURE 1-2 SITE AREA MAP FIGURE 2-1 DESIGN SITE LAYOUT FIGURE 2-2 PRESENT-DAY SITE LAYOUT AND TOPOGRAPHY FIGURE 2-3 LOCATIONS OF BUILDINGS IN THE POWERBLOCK AREA FIGURE 2-4 WOLF CREEK LAKE WATER DEPTHS FIGURE 3-1 THE HHA DIAGRAM FOR LOCAL INTENSE PRECIPITATION FLOODING ANALYSIS FIGURE 3-2 FLO-2D INUNDATION MAP DUE TO LOCAL INTENSE PRECIPITATION FIGURE 3-3 THE HHA DIAGRAM FOR THE ANALYSIS OF FLOODING IN RIVERS AND STREAMS FIGURE 3-4 WOLF CREEK WATERSHED MAP SHOWING SUBBASINS FIGURE 3-5 PMP HYETOGRAPH FOR THE WOLF CREEK WATERSHED FIGURE 3-6 HEC-HMS MODEL FOR THE WOLF CREEK WATERSHED FIGURE 3-7 FLOOD LEVEL TIME HISTORY OF WOLF CREEK LAKE FOR THE ANALYSIS OF FLOODING IN RIVERS AND STREAMS FIGURE 3-8 HEC-RAS MODEL FOR THE WOLF CREEK WATERSHED FIGURE 3-9 FETCH LOCATIONS OVER WOLF CREEK LAKE FIGURE 3-10 THE HHA DIAGRAM FOR COMBINED-EFFECTS FLOODING ANALYSIS FIGURE 3-11 FLOOD LEVEL TIME HISTORY OF WOLF CREEK LAKE FOR THE ANALYSIS OF COMBINED-EFFECTS FLOOD FIGURE 3-12 LOCATION OF DAMS NEAR THE SITE FIGURE 3-13 THE JLD-ISG-2013-01 DIAGRAM FOR DETERMINING LEVELS OF ANALYSIS FOR DAM BREAK EVALUATION FIGURE 3-14 THE JLD-ISG-2013-01 DIAGRAM FOR THE ANALYSIS OF DAM BREACHES AND FAILURES USING THE "VOLUME METHOD" Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report

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LIST OF FIGURES (CONTINUED)

FIGURE 3-1!5 INUNDATION AREA CALCULATED USING "VOLUME METHOD" FOR DAM FAILURE ANALYSIS ASSUMING FAILURE OF ALL UPSTREAM DAMS FIGURE 4-1 DURATION OF FLOODING FOR THE LIP FLOOD ANALYSIS I II '1 I II I I ' . I* ... .. ,ill .. ........ .......... p, Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Page 9 of 105 FI K~i I 145262/135031/15 Rev. 1 (October 21, 2015)

WOLF CREEK NUCLEAR OPERATING CORPORATION FLOOD HAZARD REEVALUATION REPORT

1.0 INTRODUCTION

1.1 PURPOSE AND SCOPE The United States Nuclear Regulatory Commission (NRC) issued a letter on March 12, 2012, pursuant to Title 10 of the Code of Federal Regulations (CFR), Section 50.54(f), related to the implementation of Recommendations 2.1, 2.3, and 9.3 from the Near-Term Task Force (NTTF),

a portion of which calls for performing flood hazard reevaluations at all Nuclear Power Plants (NPP) in the United States (NRC, 2012a). On behalf of Wolf Creek Nuclear Operating Corporation (WCNOC), this Flood Hazard Reevaluation Report (FHRR) for the Wolf Creek Generating Station (WCGS) site provides the information required to address NRC Recommendation 2.1 with due consideration to the most recent guidance and regulations.

Revision 1 of this FHRR includes updates to account for additional analyses that have been completed since the issuance of Revision 0. These updates primarily relate to the evaluation of Local Intense Precipitation (LIP). An additional LIP simulation was performed to account for Rev 1 updates to the site configuration and topography that have occurred since the issuance of the Revision 0 FI-RR, which represents site conditions as of February 2013. In addition to LIP updates, the discussion of the flood forces on the Essential Service Water System (ESWS) pumphouse has been modified to account for a design basis analysis that has been completed since the issuance of the Revision 0 FHIRR.

1.2 LOCATION OF THE SITE WCNOC operates the WCGS, which is located in Coffey County in eastern Kansas. The WCGS site is approximately 90 miles southwest of Kansas City, approximately 3.5 miles northeast of the city of Burlington, and approximately 3.5 miles east of the Neosho River and the main dam at John Redmond Reservoir (Figure 1-1 and Figure 1-2). The WCGS site is located adjacent to Wolf Creek Lake (Coffey County Lake). Wolf Creek flows south into Wolf Creek Lake, which in turn drains into the Neosho River (U.S. Geological Survey [USGS], 2012a; 2012b). Wolf Wolf Creek Nuclear Operating Corporation -

Flood Hazard Reevaluation Report Pg 0o 0 145262/135031/15 Rev. 1 (October 21, 2015) Pag 1 of10

Creek Lake was established for station cooling, and was created by constructing an earthen dam across Wolf Creek. The location of the earthen dam is approximately four miles upstream of Wolf Creek's confluence with the Neosho River (Figure 1-2).

1.3 SITE BACKGROUND AND HISTORY WCNOC is a joint venture of three owners: Kansas Gas and Electric Company, Kansas City Power & Light Company, and Kansas Electric Power Cooperative, Inc. The WCGS site has one reactor, which is a Westinghouse Pressurized Water Reactor (PWR). The site has been in operation since the issuance of the license on June 4, 1985. The operating license for the WCGS expires on March 11, 2045 (NRC, 2013a).

The Updated Safety Analysis Report (USAR) for the WCGS (WCNOC, 2015) was last revised Rev 1 in March 2015. In the USAR, two elevation datums are referenced; Mean Sea Level (MSL) (the National Geodetic Vertical Datum of 1929 (NGVD29)) and the Standardized Nuclear Unit Power Plant System (SNUPPS) datum. The SNUPPS datum is equivalent to the MSL elevation plus 900 feet (fi). At the WCGS site, MSL is equivalent to NGVD29. All elevations in this report are with reference to MSL, unless otherwise stated.

PIZ Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 11 of 105

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2.0 FLOOD HAZARDS AT THE SITE Section 2. 0 has been prepared in response to Request for Information Item l .a. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a) and documents results, as well as pertinent site information and detailed analyses related to the applicable flood hazards. Relevant Structures, Systems, and Components (SSCs) important to safety and the Ultimate Heat Sink (UHS) are included in the scope of this reevaluation, including pertinent data concerning these SSCs. While the UHS is discussed separately, it is a safety-related SSC.

2.1 DETAILED SITE INFORMATION Section 2.1 has been prepared in response to Request for Information Item 1.a.i. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes detailed site information, present-day site layout, and elevations of pertinent SSCs important to safety, site topography, as well as pertinent spatial and temporal data sets.

2.1.1 Design Site Information Design site information describes characteristics considered for the original licensing basis of the WCGS site. The original topography and design of site layout are shown in the USAR for the WCGS (WCNOC, 2015, Figures 1.2-43 and 2.4-1). Changes to the site layout and SSCs related Rev 1 to flooding protection were evaluated as part of the Wolf Creek Nuclear Operating Corporation Post Fukushima Flooding Walkdown Report (WCNOC, 2012). Figure 2-1 shows the design layout of the WCGS site.

The design locations of the safety-related structures, as well as other buildings and structures in the powerblock area are shown in Figure 2-1. A list of the primary safety- and non-safety-related structures at the WCGS site is provided in Table 2-1. A list of the existing design Rev 1 parameters found in the license document (WCNOC, 2015) is included in Table 2-2.

2.1.1.1 Site Topography and Drainage The WCGS site is located on a small peninsula on the northeastern side of Wolf Creek Lake (Figure 1-2). The lake is a reservoir that is retained behind an earthen dam, which was Wolf Creek Nuclear Operating Corporation r[*

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constructed across Wolf Creek in order to provide cooling water for WCGS. The headwater area of Wolf Creek lies north of WCGS and the lake. The watershed area upstream of the dam is approximately 27.4 square miles (mi 2) (WCNOC, 2015). The lake itself has a surface area ofRv1 approximately 5,090 acres (approximately 8.0 mi 2) and a water storage capacity of about 111,280 acre-ft when it is at its normal water surface elevation of 1,087 ft (WCNOC, 2015). Rev 1 Below the damn, Wolf Creek flows about four miles south-southwest to where it joins the Neosho River.

The Neosho River is a relatively large river; its watershed covers approximately 6,300 mi2 in Kansas. The Neosho River originates in east-central Kansas (Morris County) and flows southeast toward Humbolt, Kansas, and then southward into Oklahoma (Figure 1-1). It lies west and south of the Wolf Creek watershed. Flow in the Neosho River near the WCGS site is controlled by John Redmond Reservoir. Wolf Creek flows south-southwest and joins the Neosho River about four miles south of the Wolf Creek Dam and 7.1 miles downstream of the John Redmond Dam (Figure 1-2). Cottonwood Creek is a large tributary of the Neosho River and joins the river approximately six miles east of Emporia, Kansas, or approximately 14 miles northwest of the John Redmond Reservoir and Dam (WCNOC, 2015). Revi1 Long Creek flows from north to south and is located directly east and northeast of the Wolf Creek watershed (Figure 1-2). It too flows into the Neosho River. Altogether, the Long Creek watershed covers approximately 84 mi 2 . Low topographic ridges separate the Wolf Creek watershed from the Long Creek and Neosho River watersheds (USGS, 2012b). Rev 1 The WCGS site lies in the Osage Plains physiographic section of the Central Lowland Province (WCNOC, 2015). It is an area of low rolling hills with very gentle slopes. The WCGS site is Rev 1 positioned near the top of a low hill and has a grade elevation of 1,099.5 ft adjacent to buildings in the powerblock area. The floor elevation of safety-related buildings is 1,100 ft (WCNOC, Rev 1 2015). The powerblock area is flat. The ground surface slopes gently down to the Wolf Creek Lake on the western, southern, and eastern sides of the powerblock. This is an elevation drop of approximately 12.5 ft when the lake is at its normal operating level (1,087 ft; WCNOC, 2015). Rev 1 Within a five-mile radius of the site, elevations range from highs of approximately 1,215 ft on hilltops to the north and northeast of the site down to approximately 985 ft near the confluence of Wolf Creek and the Neosho River, southwest of the site (Figure 1-2).

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2.1.1.2 Description of Safety-Related Structures, Systems, and Components The locations of the safety-related structures, including the ESWS pumphouse, are shown in Figure 2-1. A list of the WCGS site safety-related structures is provided in Table 2-1.

2.1.1.3 Description of Wolf Creek Lake and the Ultimate Heat Sink Wolf Creek Lake was created by erecting an earthen dam across Wolf Creek just downstream of the WCGS site. Filling of the reservoir began in October 1980 and was complete in June 1982 (Kansas Biological Survey [KBS], 2010). The dam retaining Wolf Creek Lake is not a Seismic Category I dam and is not considered to be safety-related. A service spillway is located on the east abutment of the cooling lake dam and is an uncontrolled concrete ogee-crested spiliway with a crest elevation of 1,088 ft and a crest length of 100 ft. The auxiliary spillway is approximately 1,500 ft east of the service spillway and is an open cut spiliway with a crest elevation of 1,090.5 ft and a crest length of 500 ft (WCNOC, 2015). As stated in the USAR (WCNOC, 2015, Section IRev 1 2.4.1.1), the lake has a surface area of 5,090 acres and a capacity of 111,280 acre-ft of water at its normal operating level of 1,087 ft.

The impoundment was initially filled and has been subsequently maintained with makeup water pumped from the nearby Neosho River (KB S, 2010). Wolf Creek Lake was designed to provide adequate cooling water to the WCGS during a fifty-year drought. The water level in the lake is normally sustained by the Wolf Creek watershed upstream of the lake. However, during dry months, it is sometimes necessary to pump water to the lake from the Neosho River, just below the John Redmond Reservoir (KBS, 2010). During times of flooding, the service and auxiliary spillways provide controlled release of water to prevent overtopping of the Wolf Creek Lake Dam.

The description of the UHS in this section is in regards to the design basis of the UHS, as described in the USAR (WCNOC, 2015). Any changes to the UHS are considered present-day ]Rev 1 information and are discussed in Section 2.1.2.3. The UHS is located within Wolf Creek Lake, created by the construction of a submerged Seismic Category I dam. The UHS provides water to the ESWS. The intake channel bottom in the UHS is at an elevation of 1,065 ft and locally slopes down to an elevation of 1,064 ft at the ESWS pumphouse. The design water surface elevation of the UHS is 1,070 ft, which is five feet lower than the design minimum Wolf Creek Lake elevation. The maximum allowable sediment volume in the UHS is limited to 130 acre-ft Wolf Creek Nuclear Operating Corporation '

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to provide sufficient surface area and volume to safely shut down and maintain shutdown of the plant (WCNOC, 2015). j Rev 1 2.1.2 Present-Day Site Information Present-day site information describes changes to the WCGS site that have occurred since the original design of the site, which may have the potential to influence the reevaluation of hydrological and flooding hazards. Figure 2-2 shows the WCGS present-day site layout and topography.

2.1.2.1 Site Topography All flooding analyses described in this FHRR have been undertaken with consideration and implementation of current techniques, software, and methods used in present-day standard engineering practice to determine the flood hazard. Topographic data from an October 2012 survey of the plant area were used in the generation of all of the applicable reevaluated flooding models for the Revision 0 FHRR. Topography reflecting changes to site grading as of July 2015 Re1 (Figure 2-2) was incorporated for specific areas for the LIP analysis documented in this Revision 1 FHRR. These modifications include areas adjacent to the Control Building and the ESWS pumphouse.

2.1.2.2 Description of Safety-Related Structures, Systems, and Components Changes to the site layout and SSCs related to flooding protection were evaluated as part of the Wolf Creek Nuclear Operating CorporationPost Fukushzima Flooding Walkdown Report (WCNOC, 2012). Additional changes in site layout, such as the addition, removal, and relocation of structures, trailers, and sea vans, that have occurred since the walkdown are reflected in Figure 2-2 and have been included in the updated LIP analysis.

The design locations of the safety and non-safety-related structures in the powerblock area are shown in Figure 2-3.

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2.1.2.3 Description of the Ultimate Heat Sink The UHS is located within Wolf Creek Lake and is described in Section 2.1.1.3. No changes in the UHS since license issuance are noted in the USAR (WCNOC, 2015) or the Wolf Creek Rev 1 Nuclear Operating CorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012).

2.2 CURRENT DESIGN BASIS FLOOD ELEVATIONS Section 2.2 has been prepared in response to Request for Information Item 1.a.ii. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes the current design basis flood elevations for all flood-causing mechanisms.

The current design basis, as presented in the USAR (WCNOC, 2015), indicates that the site is Rev 1 not adversely affected by flooding. The WCGS site has a plant grade elevation of 1,099.5 ft, and a floor elevation of 1,100 ft. The maximum calculated water levels near the safety-related buildings due to the LIP event range from 1,099.52 ft to 1,099.92 ft (WCNOC, 2015). During Rev 1 the LIP event, it is conservatively assumed in the design basis that the site drainage system is not functional. The maximum water level due to the LIP is below the plant floor elevation of 1,100 ft (WCNOC, 2015). The LIP (1-hour [hr], 1 mi 2) rainfall of 19 inches (in) is part of the Rev 1 cumulative six-hour rainfall of 28.79 is used in the design basis. The LIP rainfall is determined using Hydrometeorological Report Number 52 (HMR No. 52) (WCNOC, 2015). Rev 1 To characterize the Probable Maximum Flood (PMF) for the Wolf Creek watershed and Wolf Creek Lake, a Probable Maximum Precipitation (PMP) distribution was developed and applied over the design watershed (of 27.4 mi2 ). The PMP was determined using HMR No. 33 (WCNOC, 2015). The cumulative 48-hr duration PMP is 32.80 in (WCNOC, 2015, Table Rev 1 2.4.12), with the peak occurring at approximately 34 hrs.

The Wolf Creek Lake dam has a service spillway and an auxiliary spillway. Both spillways have uncontrolled crests, which are sized to pass floods up to and including the PMIF (WCNOC,Re1 2015). The flood event simulated for the design basis includes the combined effects of a single PMP event preceded by a Standard Project Flood (SPF) event (which is 50 percent of the PMP),

and an overland sustained wind speed of 40 miles per hour (mph) (WCNOC, 2015, Section Rev 1 2.4.2.2). The peak flow rate in the design basis for the spillways is 22,845 cubic feet per second Wolf Creek Nuclear Operating Corporation **.

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(cfs) (WCNOC, 2015, Section 2.4.3.5). The maximum water surface elevation in Wolf Creek Rev 1 Lake (i.e., the pool elevation) due to the PMF event is 1,095 ft at the plant site, which assumes a starting pool elevation of 1,088 ft (corresponding to the crest elevation of the service spillway for the Wolf Creek Lake Dam). The coincident wave activity of the PMF resulted in a maximum run-up of 0.8 ft at the plant site shore. The resulting run-up elevation was 1,095.8 ft when added to the PMF pool elevation (WCNOC, 2015, Table 2.4-16). Rev 1 The maximum wave run-up elevation on the vertical wall of the intake structure of the ESWS is 1,100.2 ft. However, the intake structure for the ESWS is designed to withstand a high water elevation of 1,102.5 ft. As stated in the USAR, the only openings below elevation 1,102.5 ft are the pressure doors and the pump structure forebay opening. The pressure doors are located at elevation 1,100.0 ft. These doors are normally closed and under administrative control. The Rev 1 pump structure forebay normally contains water (WCNOC, 2015).

With regard to the PMF, backwater caused by the PMF in the Neosho River or Long Creek does not affect the site due to the topographic ridges between the site and the Long Creek and Neosho River valleys.

Failure of dams located in the Neosho River watershed upstream of the John Redmond Reservoir will not adversely affect any safety-related facilities at the WCGS site (WCNOC, 2015). In the Rev 1 most critical case, which postulates the domino-type failure of all four reservoirs (John Redmond, Marion, Cedar Point, and Council Grove) (Case b.3 of Section 2.4.4.1 of the USAR

[WCNOC, 2015]), the maximum flood stage of the Neosho River was estimated to be 1,044.55 ft Rev 1 at a distance of about five miles downstream from the John Redmond Dam (WCNOC, 2015). As stated in the USAR, the topographic ridge between the Neosho River and Wolf Creek valleys below John Redmond Dam will separate the postulated flood levels in the Neosho River valley from any facilities at the site, with the exception of the cooling lake main dam. The maximum water elevation on the downstream slope of the Wolf Creek Lake Dam, due to the postulated combined maximum flood-causing events in the Neosho and Cottonwood River basins, is conservatively established at elevation 1,049.6 ft. This flood stage is well below surface grades of any Seismic Category I facilities at the site and is about 50 ft below the plant grade elevation of 1,099.5 ft (WCNOC, 2015).Re1 Storm surge and seiche, tsunami, and ice-induced flooding were screened out as potential flooding events in the current design basis in the USAR (WCNOC, 2015). The following lists Rev 1 the sections in the USAR where these flood mechanisms were screened out:

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• Probable maximum storm surge and seiche flooding: Section 2.4.5

• Probable maximum tsunami flooding: Section 2.4.6

• Ice effects: Section 2.4.7 Frazil ice is screened out in the design basis. Frazil ice is prevented by diffusing warmed water in front of the ESWS track racks (WCNOC, 2015, Section 2.4.7.2). The design basis states that Rev 1 warming lines divert heat to ensure that frazil ice does not block the ESWS trash racks (WCNOC, 2015, Section 9.2.1.2.2). There are two trains (Trains A & B) in the ESWS; Revi1 therefore, the ESWS pumphouse has two redundant trains. Each train has its own independent warming system. There is a secondary system, a portable air bubbler system, which can also be placed at the ESWS pumphouse. In addition, there is a procedure for the ESWS pumphouse for the prevention of frazil ice formation.

The sources of the makeup water to the cooling lake are Wolf Creek and the Neosho River. In reference to channel diversion in the US AR, there is no indication that Wolf Creek or its tributaries would be diverted from its present course of flow into Wolf Creek Lake. Ice jams will also not cause diversion of flow because the jams do not prevent overbank flow. The ESWS intake is designed to prevent ice from jamming against it and cutting off inflow (WCNOC, 2015, Rev 1 Section 9.2.1.2.2.2).

As stated in the USAR, if the Wolf Creek flow was temporarily cut off, makeup water to the plant would still be available from the Joh~n Redmond Reservoir on the Neosho River. Due to the regional topographical conditions, it is unlikely that the upper Neosho River would be diverted from the John Redmond Reservoir due to ice jams or subsidence. Therefore, it is unlikely that the Neosho River inflows would be completely cut off and affect the makeup water available to the cooling lake (WCNOC, 2015). Rev 1 In addition, it is not expected that any potential morphological changes in Wolf Creek will affect any safety-related SSCs at the WCNOC site. As stated in the USAR, "there is no historic or topographic evidence indicating that flow in Wolf Creek can be diverted away from its present course. Local relief and the natural geomorphological condition preclude the likelihood of Wolf Creek and its tributaries discharging anywhere other than into the cooling lake" (WCNOC, 2015, Rev I Section 2.4.10).

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2.3 FLOOD-RELATED CHANGES TO THE LICENSING BASIS Section 2.3 has been prepared in response to Request for Information Item 1.a.iii of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes flood-related changes to the licensing basis and any flood protection changes (including mitigation) since license issuance.

2.3.1 Description of Hydrological Changes and Flood Elevations The design basis flood elevations for the flood-causing mechanisms that are applicable to WCGS are summarized in Table 2-3. The original design basis LIP analysis was based on HMR No. 33, using the procedures outlined in EM-i1110-2-1411 to obtain a 6-hr distribution; this resulted in a maximum flood elevation of 1,099.86 ft around the powerblock (WCNOC, 2013, Section 2.4.2.3.2). The design basis LIP analysis was updated based on HMR No. 52, using a 6-hr Rv distribution. Based on the updated analysis, the current design LIP flood level at safety-related buildings on the powerblock is now established at 1,099.92 ft, which is documented in Revision 28 of the USAR (WCNOC, 2015, Section 2.4.2.3.2).

2.3.2 Description of Flood Protection Changes (Including Mitigation)

The flood protection system and flood mitigation measures described in the USAR (WCNOC, Rev 1 2015) and documented in the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) are relevant to the flood hazard reevaluation analyses. Changes to the site layout and SSCs related to flooding protection were evaluated as part of the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012). Safety-related SSCs that are credited in the Current Licensing Basis (CLB) for protecting the plant from external flood hazards were identified, inspected, and evaluated to be adequate.

According to the walkdown report (WCNOC, 2012), "The walkdown visual inspection has verified that there is reasonable assurance the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The Wolf Creek external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard." No changes since license issuance and no comments regarding adverse site conditions affecting flooding protection were noted in the walkdown report (WCNOC, 2012). The LIP model developed for this[

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Revision 1 FHRR incorporates changes to site grading and layout through July 2015 (Figure 2-Re1 2), as well as the addition of safety-related vaults installed since the walkdown.

2.4 CHANGES TO THlE WATERSHED AND LOCAL AREA Section 2.4 has been prepared in response to Request for Information Item 1.a.iv of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes changes to the watershed and local area since license issuance. A description of the watershed at the time Of license issuance and pertinent changes to the watershed since license issuance are presented in the following sections.

2.4.1 Description of Watershed and Local Area at the Time of License Issuance The drainage area of the Wolf Creek watershed defined at the time of the license issuance was 27.4 mi 2 . There are no gages located on the Wolf Creek watershed; therefore, no streamfiow records are available. Additional information regarding the Wolf Creek watershed and adjacent watersheds are presented in Section 2.1.1.1.

2.4.2 Description of Any Changes to the Watershed and Local Area since License Issuance As previously discussed, changes to the site layout and SSCs related to flooding protection were evaluated as part of the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012). In addition, the flood reevaluation analysis determined that there were no significant changes to the watershed since the original design basis.

The walkdown visual inspection conducted during the walkdown verified that there is reasonable assurance that the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The WCGS external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard. The purpose of the Recommendation 2.3 walkdown was to verify the conformance with the CLB; the adequacy of the CLB is addressed as part of the Rev 1 Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Pg 0o 0 145262/135031/15 Rev. 1 (October 21, 2015) Page20 o 10

flood reevaluations, along with a focused LIP evaluation 1 per the forthcoming guidance (NRC, 2015a).

The original design site layout did not include a vehicle barrier system (VB S). However, a VBS has been added to the WCGS site. The VBS configuration as of February 2013 was used as the Rev 1 basis for the Revision 0 FHRR. Subsequent changes to the VBS configuration up to July 2015 are accounted for in an additional LIP simulation prepared for this Revision 1 FHIRR. In addition to modification of the VBS, any other changes to the site layout that have occurred since license issuance (through July 2015, Figure 2-2) are captured in the reevaluation analysis.

The slope for the Wolf Creek Lake shoreline reported for the design basis is 30:1 (horizontal to vertical) (WCNOC, 2015, Table 2.4-16). Based on the current topographic data used for the ]Rev 1 flood hazard reevaluation, the average shoreline slope is determined to be 46:1. The difference in slope is likely due to the method of computing an average slope for the shoreline, not due to significant change in the shoreline topography.

All flooding analyses described in this FHRR and described in Section 3.0 have been undertaken with consideration and implementation of current techniques, software, data, and methods used in present-day standard engineering practice to develop the flood hazard.

2.5 CURRENT LICENSING BASIS FLOOD PROTECTION Section 2.5 has been prepared in response to Request for Information Item 1.a.v. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes current licensing basis flood protection and pertinent flood mitigation features at the site.

The safety-related facilities are not affected by the PMF in the cooling lake or by the LIP at the plant site and no flood protection requirements are necessary (WCNOC, 2015). The Wolf Creek IRev 1 Nuclear Operating CorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) 1 At the time of issuance of this Revision 1 FHRR, the NRC is currently in the process of revising the guidance related to the performance of the integrated assessment described in the 50.54(f) letter (NRC, 2012a) and subsequent guidance (NRC, 2012c). Of significance, the NRC has stated (NRC, 2015b) that "Licensees with LIP hazards exceeding their current design-basis flood will not be required to complete a revised integrated assessment." The Rev 1 forthcoming guidance "...will discuss a graded approach to flooding evaluations and provide for more focused evaluations of local intense precipitation and available physical margin in lieu of proceeding to an integrated assessment" (NRC, 2015a).

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identified the credited flood protection and mitigation features that are considered in the WCGS CLB to protect against the ingress of water to safety-related SSCs. These include topography, structures, floors, walls, penetrations, vaults, the forebay, doors, sump pumps, and sump pump motors. The ESWS pumphouse has pressure doors that are located at elevation 1,100.0 ft. These pressure doors are flood protection doors and are normally closed and under administrative control (WCNOC, 2015). R ev 1 2.6 ADDITIONAL SITE DETAILS Section 2.6 has been prepared in response to Request for Information Item 1.a.vi. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a). Relevant site data to be considered includes additional site details, as necessary, to assess the flood hazard (i.e., walkdown results, etc.).

2.6.1 Wolf Creek Lake Bathymetry During October and November 2009, the KBS performed a bathymetric Survey of Wolf Creek Lake. The survey (KBS, 2010) was carried out using an acoustic echo sounding apparatus linked to a global positioning system. Nearly 74,000 georeferenced depths were measured and used to create a digital bathymetric model of the reservoir (Figure 2-4). For a water surface elevation of 1,088.90 ft, the surface area and volume of the lake were 4,863 acres and 117,407 acre-fl, respectively (KBS, 2010). The maximum depth was 73.75 ft. As stated in the USAR (WCNOC, Revi1 2015, Section 2.4.1.1), the lake has a surface area of 5,090 acres and a capacity of 111,280 acre-ft of water at its normal operating level. In June 1998, Coffey County assumed responsibility for managing public use of the lake. The lake is open for public use seven days a week from sunrise to sunset, weather, and reservoir levels permitting (KBS, 2010).

2.6.2 Recommendation 2.3 Walkdown Results The Wolf Creek Nuclear Operating,CorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) gives results of the walkdown, including key findings and identified degraded, non-conforming, or unanalyzed conditions, and includes detailed descriptions of the actions taken or planned to address these conditions. The results of the walkdown observations were reviewed through site processes in accordance with Regulatory Issues Summary 2005-20, Revision 1 (WCNOC, 2012).

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Safety-related SSCs that are credited in the CLB for protecting the plant from external flood hazards were identified, inspected, and evaluated to be adequate. According to the report (WCNOC, 2012), "The walkdown visual inspection has verified that there is reasonable assurance the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The Wolf Creek external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard." The review of the walkdown concludes that the WCGS site '"flood protection features would be capable of performing their intended flood protection function if subjected to a design basis flooding hazard. No flooding walkdown observations were deemed to be a deficiency per Section 3.8 of Nuclear Energy Institute (NEI) 12-07" (WCNOC, 2012).

2.6.3 Site Visit In support of the Revision 0 FHRR and associated analyses, a site visit was conducted on March 18 and 19, 2013. An additional site visit was performed on September 3, 2014 in support of the Rev 1 updated analysis documented in this Revision 1 report. The areas visited included:

• The powerblock area and area immediately surrounding the powerblock

• The ESWS pumphouse

• The cooling water discharge structure

• The VBS

• Portions of Wolf Creek Lake

• Wolf Creek and its tributaries (north of Wolf Creek Lake)

Rev 1 Photographs of the site and surrounding area from both site visits were reviewed during the development of the flood hazard reevaluation analyses.

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3.0 FLOOD HAZARD REEVALUATION ANALYSIS Section 3.0 has been prepared in response to Request for Information Item 1.b. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a): Evaluation of the flood hazard for each flood-causing mechanism should be based on present-day methodologies and regulatory guidance. Provide an analysis of each flood-causing mechanism that may impact the site including local intense precipitation and on-site drainage, flooding in streams and rivers, dam breaches and failures, storm surge and seiche, tsunami, channel migration or diversion, and combined effects. Mechanisms that are not applicable at the site may be screened out; however, a justification should be provided. Provide a basis for inputs and assumptions, methodologies and models used including input and output files, and other pertinent data.

3.1

SUMMARY

OF RECOMMENDATION 2.1 To respond to Phase 1 of NRC Recommendation 2.1 (NRC, 2012a) and the 2012 Appropriations Act, the NRC requested that each licensee provide a reevaluation of all appropriate external flooding sources, including the effects from local intense precipitation on the site, PMF on streams and rivers, storm surges, seiches, tsunamis, and dam failures. A hazard evaluation should be performed for each reactor licensed under 10 CFR Part 50, including the spent fuel pool and the various modes of reactor operation. The reevaluation should apply present-day regulatory guidance and methodologies being used for Early Site Permit (ESP) and Combined Operating License (COL) reviews. The reevaluation should employ current techniques, software, and methods used in present-day standard engineering practice to develop the flood hazard.

3.2 SOFTWARE USED Software programs used in the flood hazard reevaluation included FLO-2D Pro versions 2 Rev I 13.02.04 and 14.03.07 (FLO-2D, 2014), the USACE HEC-HMS program version 3.5 (USACE, 2010Oa), the USACE HEC-RAS program version 4.1 (USACE, 2010Ob), USACE HMR52 program (USACE, 1987), ArcGIS 9.3 (ESRI, 2009), and ArcGIS 10.1 (ESRI, 2012).

2 FLO-2D Pro version 13.02.04 was used for LIP Cases 1 through 6, which were prepared for the FHRR Revision 0. Re1 LIP Case 7 was prepared for this Revision 1 FHRR using FLO-2D Pro version 14.03.07. The software release notes (FLO-2D, 2014) outline the changes between versions.

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The FLO-2D Pro software is a volume conservation model, which routes fluid flow in one-dimensional (1D) channel flow, two-dimensional (2D) overland flow, or an interaction between the two model components (FLO-2D, 2012). The FLO-2D Pro software is an "effective tool for delineating flood hazards or designing flood mitigation" (FLO-2D, 2012). The FLO-2D Basic model is the other model available from FLO-2D Software, Inc., and includes fewer features than the Pro model. The Basic model has been approved by the Federal Emergency Management Agency (FEMA) for use in Flood Insurance Studies (FIS). The Pro model, though not specifically approved by FEMA, includes all the features of the Basic model, along with some additional features (e.g., storm drain interface with surface water, parallel processing capabilities, and expanded capabilities for simulating sediment transport) (FLO-2D, 2012).

Additional qualifications of the FLO-2D Pro software are presented in Appendix A.

3.3 FLOOD-CAUSING MECHANISMS NRC NUREG/CR-7046 (NRC, 2011) recommends using a Hierarchical Hazard Assessment (HHA) method for evaluating the safety of SSCs. The HHA is a progressively refined, stepwise estimation of site-specific hazards that starts with the most conservative plausible assumptions consistent with available data. The HHA process proceeds as follows (NRC, 2011):

a. Select one flood-causing mechanism to be reanalyzed.

b. Develop a conservative estimate of the site-related parameters using simplifying assumptions for a flood-causing mechanism and perform the reevaluation.

c. Determine if the reevaluated flood hazard elevation (from step b) is higher than the original design flood elevation for the selected flood-causing mechanism. If not, use this flood elevation for this causal mechanism for comparison of reevaluation against the current design basis.

d. Determine if the site-related parameters can be further refined. If yes, perform reevaluation (repeat step c). If no, use this flood elevation for this causal mechanism for comparison of reevaluation against the current design basis.

e. Determine if all flood-causing mechanisms have been addressed. If yes, continue to the following. If no, select another flood-causing mechanism (step a).

For each flood-causing mechanism, compare the final flood elevations from the hazard reevaluation against the current design basis flood elevations. Using this comparison, determine whether the design basis flood bounds each reevaluated hazard.

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Each potential flood-causing mechanism has been evaluated using present-day methodologies and regulatory guidance. Details regarding the considerations and outcome of the analyses regarding each flood-causing mechanism are presented in the following sections.

3.3.1 Local Intense Precipitation Section 3.3.1.1 through Section 3.3.1.4 address the effects of LIP on the local area of the WCGS site. The HHJA diagram for LIP flooding is presented in Figure 3-1.

3.3.1.1 Local Intense Precipitation Rainfall NUREG/CR-7046 (NRC, 2011) states that "Local Intense Precipitation is a measure of the extreme precipitation at a given location." The LIP is "deemed equivalent to the 1 hr, 2.56-km 2 (1-mi 2 ) PMP at the location of the site" (NRC, 2011).

The design basis LIP analysis described in the USAR (WCNOC, 2015) uses the most up-to-date Hydrometeorological Report (HMR) applicable to the WCGS site, HMR No. 52 (National Weather Service ['NWS], 1982). For the purposes of the flood hazard reevaluation, a hyetograph was prepared from the rainfall depths obtained from HMR No. 52. The hyetograph has a Rev I duration of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, subdivided into five-minute intervals, with the most intense rainfall occurring in the first hour. The cumulative LIP rainfall depth for the 6-hr LIP is 28.79 inches, including 19 inches that falls in the first hour (i.e., the 1-hr, 1-mi 2 LIP).

3.3.1.2 Effects of Local Intense Precipitation In accordance with the guidance presented in NRC NUREG/CR-7046 (NRC, 2011), the considerations addressed in the analysis of flooding resulting from LIP were:

• Depth of Flooding

• Duration of Flooding

• Maximum Velocities

• Hydrodynamic and Hydrostatic Loads

• Sedimentation

• Debris Loading Wolf Creek Nuclear Operating Corporation ,*

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Each of these considerations was evaluated based on the results of a detailed two-dimensional (2D) flood routing model that was developed for the WCGS site. This model, FLO-2D Pro (FLO-2D, 2014), represented all the topographical and man-made features (i.e., buildings, tanks, and structures) that significantly affect runoff at the WCGS site. The FLO-2D model developed for the Revision 0 FHRR represented the WCGS site as of February 2013. An additional Rev 1 simulation (Case 7, below) was added for this Revision 1 FHRR to represent the WCGS site as of July 2015.

The output of the FLO-2D model includes water surface elevations, water depths, maximum water velocities, and the duration of flooding. FLO-2D also computes the hydrostatic and hydrodynamic forces that the floodwater could exert on obstacles (e.g., buildings) within flooded areas. These results from FLO-2D directly address the requirements of NRC NUREG/CR-7046 (NRC, 2011). The potential for sedimentation and debris loading is evaluated outside of FLO-2D, based on FLO-2D output of depths, maximum velocities, and flow directions.

The extent of the FLO-2D model is illustrated in Figure 3-2. The model boundaries were established away from the powerblock area and safety-related SSCs in order to prevent boundary conditions from affecting flood levels evaluated within the powerbiock area and to ensure the stability of the model. The FLO-2D domain covered an area of approximately one quarter of a square mile. The southern and western boundaries follow the surrounding roads (Figure 3-2).

These roads form drainage divides, making an appropriate place for a model boundary.

The eastern boundary of the model domain follows the edge of Wolf Creek Lake, including a narrow portion of the lake around the ESWS pumphouse and then extends north (to include areas that could contribute runoff into the FLO-2D domain). The northern boundary is placed to include areas that could contribute runoff toward the powerbiock area.

The following simulations were completed for the model area to investigate the effects of Rev 1 flooding from a LIP event. Six cases were developed for the Revision 0 FHRR as follows:

• Case 1 was the most conservative, a steady-state simulation with no infiltration losses and the VBS blocked (i.e., water is not allowed to flow through spaced between the VBS jersey barriers). This is in accordance with the HHA method outlined in NRC NUREG/CR-7046 (NRC, 2011).

Additionally, a relatively high Manning's roughness coefficient was used for this simulation. The grid cell size was 15 ft for this simulation.

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• Case 2 was built on the same FLO-2D grid as Case 1. However, the time-varying LIP distribution was applied. The VBS was partially unblocked in this case.

• Case 3 provided a sensitivity analysis for grid cell size by constructing a model with 20 ft grid cells that is otherwise equivalent to Case 2.

• Case 4 was similar to Case 2, but applied lower Manning's roughness coefficients (toward the middle of recommended ranges) than Case 1 through 3.

• Case 5 was similar to Case 4. However, rainfall infiltration was accounted for using the Curve Number Method.

• Case 6 was the same as Case 5, except that the Manning's roughness coefficients for Case 6 were assigned based on the lower end of recommended ranges.

An additional simulation (Case 7) was completed for this Revision 1 FHRR to represent the plant configuration and topography as of July 2015. Case 7 represents an update to the Case 6 model, applying the same Manning's roughness coefficients as Case 6, with updates to represent the July 201i5 plant configuration and topography. In addition to plant configuration updates, Rev 1 refinements were made to the characterization of building roofs and transformer curbs. The roof characterization refinements included crediting some of the retention storage on the powerblock building roofs. Flow through downspouts was not credited for Case 7, which is consistent with Cases 1 through 6.

In accordance with the HHA method (Figure 3-1), Case 1 was the most conservative case and the subsequent simulations were progressively refined. The results of the FLO-2D modeling show that the steady-state LIP distribution (Case 1) provided the most conservative estimate of flood levels. The other Revision 0 FHRR simulations provided comparable results with some variation. Case 6 was presented as the final simulation per the HHA methodology. Case 7 is an Rev 1 update of the Case 6 model and is presented as the final simulation for this Revision 1 FHRR.

The FLO-2D results for the Case 7 simulation are summarized in Table 3-1 for buildings and tanks on the powerblock. The corresponding inundation map for Case 7 is included in Figure 3-2, illustrating the peak flood depths across the FLO-2D model domain. The peak flood Rev 1 elevations for Case 7 ranged from 1,100.03 ft to 1,100.38 ft adjacent to Seismic Category I buildings. The highest simulated water level adjacent to a safety-related building was elevation 1,100.38 ft, adjacent to the Auxiliary and Reactor Buildings (Table 3-1).

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Potential pathways along which surface water runoff could reach safety-related SSCs include 40 different doors, vaults, and manholes. Table 3-2 and Table 3-3 present the potential pathways evaluated and the associated flood parameters for the Case 7 simulation. It is important to note that the ESW manholes (Table 3-3, Items 7 through 16) are designed to be watertight, which is Rev 1 discussed in the Wolf Creek Nuclear Operating CorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012).

In all simulations (Cases 1 through 7), floodwaters exceeded entrance elevations at several Rev I pathways leading to Seismic Category I structures. This flooding was higher than flood levels that are reported in the design basis, which states that water levels during a LIP event do not exceed an elevation of 1,099.92 ft near safety-related buildings (WCNOC, 2015, Section Rev 1 2.4.2.3.2). One site feature that significantly affects flood levels near safety-related SSCs is the old railroad track that approaches the east side of the Fuel Building. The railroad track slows runoff from the east side of the powerblock and causes higher water levels near safety-related SSCs.

Wolf Creek Lake is much larger than the area of interest for a LIP event. Consequently, the entire lake was not included in the same flood model used for the LIP analysis. The change in lake level due to a LIP event was evaluated with a hand calculation. It was determined that the Rev I water level in Wolf Creek Lake could increase by approximately 0.32 ft, which results in a water level of 1,088.32 if, based on an antecedent water level of 1,088.00 ft. A water level of 1,088.32 ft is significantly lower than the flood elevation predicted when simulating the flooding effects of PMP in the entire watershed (Section 3.3.2).

The results of the reevaluated flooding event due to LIP are compared against the CLB in Section 4.2.

3.3.1.3 Sedimentation and Debris Loading Coincident with Local Intense Precipitation Sedimentation and debris loading are screened out qualitatively as hazards during a LIP event in the powerblock area. This screening is based on the flow depths, flow velocities, and flow directions predicted in the FLO-2D model. Runoff depths and velocities are generally small (Table 3-2 and Table 3-3) and do not constitute a credible hazard for sedimentation or debris loading. Additionally, runoff is generally directed away from safety-related SSCs, precluding any impact on the SSCs from sedimentation or debris loading.

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3.3.1.4 Wind-Waves and Run-Up Coincident with Local Intense Precipitation Wave run-up is a process whereby waves can be generated by high wind velocities coincident with large storm events. The wind speed concurrent with the postulated wind-wave analysis is a two-year maximum sustained wind of 38.65 mph, calculated using procedures in the United States Army Corps of Engineers' (USAGE) Coastal Engineering Manual (GEM) (USAGE, 2008). Ponding depths in the powerblock area did not support the growth of wind-waves because ponding depths are relatively mild (approximately 1 to 2 ft; Figure 3-2). In addition, flow velocities were generally directed away from safety-related SSCs, preventing waves from reaching safety-related SS~s. Also, tall buildings within the powerbiock area block wind. As a result, the various buildings and structures (including the VBS) shorten potential fetch lengths.

The PMF causes higher water levels to occur in Wolf Greek Lake (Section 3.3.2.2) than for LIP flooding. Consequently, the effects of wind-waves during the LIP were bounded by the effects of wind-waves during the PMF. Based on these reasons, no further analysis of wind-waves during a LIP event was required. Run-up from wind-waves in Wolf Creek Lake resulting from the PMF in Wolf Creek watershed is evaluated in Section 3.3.2.2.3.

3.3.2 Flooding in Rivers and Streams River flooding at the WCGS site was evaluated with respect to the Wolf Creek watershed. The Wolf Creek watershed was identified in the USAR (WGNOG, 2015, Section 2.4.2.2) as the Rev 1 controlling watercourse for flood protection at the site. Therefore, it is included in the models for river flooding evaluation.

The WCGS lies in the Wolf Creek watershed, which is bordered by the Long Creek watershed to the east and the larger Neosho River watershed to the west and south (Figure 1-2). In the analysis of flooding potential by rivers, the Neosho River and Long Creek watersheds were first screened to estimate the PMF in those watersheds and to determine whether their respective river channels and valleys are capable of containing the maximum flow rates resulting from a PMF.

For this assessment, the total areas of the two watersheds were obtained. NRC Regulatory Guide (RG) 1.59 (NRG, 1977, Appendix B) was followed to estimate peak PMF discharges for those two watersheds, based on the locations of the watersheds and the watershed drainage areas. It was determined that representative watershed cross-sectional areas are capable of containing the PMF peak discharges in those two watersheds. Therefore, they were screened out as potential Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Pg 0o 0 145262/135031/15 Rev. 1 (October 21, 2015) Pae 0of10 J

sources of flooding risk to the WCGS by PMF, and were not included in the flooding analysis of the Wolf Creek watershed area described in Section 3.3.2.2.

NRC NUREG/CR-7046 (NRC, 2011) prescribes a methodology for determining the PMF based on the HHA method (Figure 3-3). As stated in NRC NUREG/CR-7046 (NRC, 2011), "The hierarchical hazard assessment [HHA] is a progressively refined, stepwise estimation of site-specific hazards that evaluates the safety of SSCs with the most conservative plausible assumptions consistent with available data." The HHA method starts with the most conservative simplifying assumptions that maximize the hazards for the probable maximum event. If the most conservative assumptions do not result in site inundation, no further flood hazard assessment is required. However, if the flood level of an assessed hazard may adversely affect any safety-related SSC, more refined hazard assessments are performed using site-specific data to demonstrate whether SSCs are adequately protected from the adverse effects of severe floods (NRC, 2011).

For the river flooding analysis, the Wolf Creek watershed was divided into five subbasins (Figure 3-4), which is consistent with the methods outlined in NRC NUREG/CR-7046 (NRC, 2011) for subbasin delineation and composite curve number evaluation. Subbasins 1 through 3 represented watersheds upstream of Wolf Creek Lake. Part of Subbasin 4 represented the land from which runoff reaches Wolf Creek Lake directly. Subbasin 5 represented the southern portion of the watershed that drains directly into Wolf creek downstream of the Wolf Creek Lake Dam. The delineated watershed ended at the confluence of Wolf Creek and the Neosho River.

Subbasin 5 was delineated to model potential backwater effects from the Neosho River.

The PMP for the Wolf Creek watershed was calculated using the USACE's HMR52 computer program (USACE, 1987), as described in Section 3.3.2.1.

A watershed hydrologic response model (HEC-HMS) was developed to compute runoff hydrographs and runoff volumes for each subbasin for the PMP event (Section. 3.3.2.2.1). A stream course model (HEC-RAS) was then used to compute flood levels at representative points within the Wolf Creek watershed using the runoff rates from the HEC-HMS model (Section 3.3.2.2.2).

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3.3.2.1 Probable Maximum Precipitation for Wolf Creek Watershed The PMP is "a deterministic estimate of the theoretical maximum depth of precipitation that can occur at a time of year over a specified area" as defined in NRC NUREG/CR-7046 (NRC, 2011).

The PMP is estimated to determine the Probable Maximum Storm (PMS) event that generates the maximum direct runoff (or peak discharge) from the Wolf Creek watershed.

The HMR52 program is used to compute the PMP. The 72-hr duration cumulative rainfall is computed to be 36.70 in (Figure 3-5), per the guidance of NRC NUREG/CR-7046 (NRC, 2011).

The maximum rainfall occurs at approximately 39 hrs after the beginning of the rainfall event.

3.3.2.2 Probable Maximum Flood for Wolf Creek Watershed The river flooding for Wolf Creek watershed was performed using two different software packages. The HEC-UMS modeling software was initially used to simulate a PMP storm in the Wolf Creek watershed and to calculate PMF flow rates emanating from each subbasin during the PMP event. Five cases were simulated and the results of each simulation are described in Section 3.3.2.2.1.

The HEC-RAS modeling software was used to evaluate water levels associated with the PMF in the Wolf Creek watershed. Ten simulations were performed to evaluate the effects of a PMP event on the flood depths, duration, and average flow velocities in the watershed and Wolf Creek Lake. Cases 1 through 5 were run as steady-state simulations. Case 6 was a more refined model, and represented a non-steady (i.e., transient) simulation of a PMP storm event and the resulting PMF in the watershed. The results of these simulations are presented and discussed in Section 3.3.2.2.2. The HEC-RAS Case 6 model results were considered to be the most refined modeling results of river flooding in this reevaluation per the HHA approach (NRC, 2011).

The Case 6 HEC-RAS model was also used to evaluate wind-wave run-up (Section 3.3.2.2.3) and to calculate hydrostatic forces on the ESWS pumphouse (Section 3.3.2.2.3). The effects of partially blocked spillways of the Wolf Creek Lake Dam by debris (Cases 7 through 9) and sedimentation in the lake (Case 10) are presented and discussed in Sections 3.3.2.2.4 and 3.3.2.2.5, Wolf Creek Nuclear Operating Corporation ,,

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3.3.2.2.1 Water Level Due to Probable Maximum Flood Using HEC-HMS Model To evaluate the PMF for the Wolf Creek watershed, HEC-HMS modeling software was used to perform the first level of modeling. The HEC-HMS model was set up using the five subbasins delineated for the watershed (Figure 3-4) and the PMP event (Figure 3-6). Physical characteristics of the five subbasins are listed in Table 3-4. Wolf Creek Lake was part of Subbasin 4. Subbasin 5 was included in the model to evaluate potential backwater effects that could occur downstream of Wolf Creek Lake. The HEC-HMS model was calibrated before running the PMF simulations.

Five different variations of the model input values and/or model conditions were utilized to create five different HEC-HMS cases, which are summarized in Table 3-5. The HEC-HMS model (Figure 3-6) was run for an eight-day period of time to capture the full effects of the PMF event on Wolf Creek Lake.

The cases for the HEC-'IMS model were based on the criteria documented in NRC NUREG/CR-7046 (NRC, 2011, Appendix B). Case 1 was the most unrefined case and the other cases are more refined. For Cases 3 through 5, the nonlinearity effect during the PMP event was taken into consideration by reducing the lag time by 33 percent and increasing the resulting peak discharge.

As stated in NRC NUREG/CR-7046 (NRC, 2011, Section 3.3.2), the recommended adjustments are "a 5-to-20-percent increase for the peak discharge and a 33-percent reduction in the lag time." Increasing the peak discharge by 20 percent resulted in a higher discharge than the discharge for Case 1 (the most conservative case). Therefore, a five percent increase in the peak discharge (i.e., the lower range suggested in NRC NUREG/CR-7046 [NRC, 2011]) was applied in Cases 3 through 5.

The maximum water level predicted in Wolf Creek Lake (1,095.3 ft) resulted from the Case 1 model run, as expected because Case 1 is a steady-state simulation. The results of Case 5 are considered to be the most refined of the HEC-HMS model runs. The hydrograph of the lake level for HEC-HMS Case 5 model run is presented in Figure 3-7. The Case 5 flow rates computed for each subbasin were used as input values for the HEC-RAS modeling, presented in Section 3.3.2.2.2.

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3.3.2.2.2 Water Level Due to Probable Maximum Flood Using HEC-RAS Model In order to refine the flood analysis, HEC-RAS version 4.1 (USACE, 2010~b) was used to simulate rainfall and runoff on Wolf Creek and Wolf Creek Lake. HEC-RAS can represent steady-state and unsteady-state conditions accurately, as necessary for this reevaluation. HEC-RAS is also used in NRC NUREG/CR-7046 (NRC, 2011) in examples similar to those encountered in the Wolf Creek watershed.

The purpose of the HEC-RAS model was to produce a more refined estimated of peak water level in Wolf Creek Lake during the PMF event and to evaluate the potential impact to flood levels in the lake if the spiliway of the Wolf Creek Lake Dam was partially blocked by debris.

The calibrated HEC-RAS model (Figure 3-8) included:

• A reach representing Wolf Creek upstream of Wolf Creek Lake (i.e., Upper Reach)

• Wolf Creek Lake

• Wolf Creek Lake Dam

• A reach representing Wolf Creek downstream of Wolf Creek Lake (i.e.,

Lower Reach)

Ten HEC-RAS simulations (Table 3-5) were performed to address the following NRC requirements:

• Flood levels

• Flood duration

• Flow velocities

• Debris loading and blockage of the flow

• Sedimentation HEC-RAS Cases 1 through 6 addressed the level, duration, and velocities of the PMF flood.

Cases 7 through 9 addressed debris loading and blockage of the spillways of the Wolf Creek Lake dam. Case 10 addressed sedimentation in Wolf Creek Lake.

A diagram of the HEC-RAS model and the channel cross-sections created within the model area is presented in Figure 3-8. Wolf Creek Lake was represented as a storage area and the Wolf Wolf Creek Nuclear Operating Corporation EN*.

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Creek Lake Dam was represented as an inline structure in the HEC-RAS model. The elevation-storage information for Wolf Creek Lake was obtained from the Bathymetric Survey of Wolf Creek Reservoir (Coffey County Lake), Coffey County, Kansas (KBS, 2010).

The boundary conditions used in the HEC-RAS model setup included inflows, storage area initial conditions, and upstream and downstream slopes. Initial lake levels were set at, or just above, the lowest spillway crest elevation. A normal flow condition was specified at the downstream ends of the model reaches. The stream slopes associated with this normal flow condition were set in the model using the topographic elevations along the last two downstream cross-sections.

A total of ten numerical simulations were conducted using the calibrated HEC-RAS model (Table 3-5). HEC-RAS Cases 1 through 5 used the peak flow rates from HEC-HMS Cases 1 through 5 as input values. These cases were run under steady-state conditions.

HEC-RAS Case 6 was run as an unsteady (i.e., transient) model, which is more realistic and more refined than the first five cases. The hydrograph of water level in the lake resulting from HEC-RAS Case 6 is presented in Figure 3-7. The peak water level in Wolf Creek Lake for Case 6 was 1,093.57 fi, which did not exceed the capacity of the spillways.

3.3.2.2.3 Wind-waves and Run-Up Coincident with Probable Maximum Flood Wave run-up associated with maximum flooding in the Wolf Creek Lake is evaluated and discussed in this subsection. Wave run-up is a process whereby waves can be generated by high wind velocities coincident with storm events. Wave run-up is evaluated using procedures outlined in the USACE's CEM (USACE, 2008) at the following locations:

• Wolf Creek Lake Dam

• Wolf Creek Lake shoreline (near the WCGS site)

• Intake structure of the ESWS pumphouse According to the USACE CEM (USACE, 2008), "Fetch is defined as a region in which the wind speed and direction are reasonably constant." The longest fetch was determined for critical locations along the Wolf Creek Lake Dam, the Wolf Creek Lake shoreline, and at the intake structure of the ESWS pumphouse. These locations and the fetch paths and fetch lengths used to calculate wave run-up are shown in Figure 3-9. These fetch lengths were used in the wave run-Wolf Creek Nuclear Operating Corporation -'

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up analysis. The Wolf Creek Lake Dam fetch was defined as the longest fetch that approaches the dam (Figure 3-9). For the Wolf Creek Lake shoreline, the fetch was defined at a critical location where the longest fetch approached nearest the WCGS site (Figure 3-9). For the intake structure of the ESWS pumphouse, Fetch 1 was chosen as the most feasible fetch.

To perform the wind-wave analysis, the two-year return period maximum sustained wind (MSW) speed was calculated, using procedures defined in the USACE CEM (USACE, 2008).

The two-year MSW speed was calculated to be 38.65 mph. Once the fetch and MSW were computed, the sustained overland wind speed (MSW) was converted to an overwater wind speed, because the wind is traveling over a body of water (i.e., Wolf Creek Lake). The overwater wind speed (46.38 mph) was calculated using procedures outlined in the USACE CEM (USACE, 2008).

The peak PMF water level in Wolf Creek Lake (1,093.54 ft) obtained from the HEC-RAS Case 6 model (the most refined case) was used as the antecedent water level (or stillwater level) for the wind-wave analysis. Equations from the USACE CEM (USACE, 2008, Figure 11-2-20) were used to calculate significant wave height and peak period.

There are two general categories of run-up equations:

1. Equations for run-up on structures (steeper slopes)

2. Equations for run-up on beaches (shallower slopes)

Consequently, the wave run-up equations utilized for the intake structure of the ESWS pumphouse and for the Wolf Creek Lake Dam and the shoreline of Wolf Creek Lake differed.

However, both run-up equations are for run-up levels exceeded by only two percent of the incident waves. The two-percent run-up (R2 %) equations were used because this is reconumended in the USACE CEM (USACE, 2008, Part II Chapter 4). Field measurements of run-up have shown that the two percent run-up equation in the USACE CEM conservatively overestimates run-up by a factor of two, but is roughly an upper envelope of the data scatter (USACE, 2008, p. II-4-18).

The equation recommended in the USACE CEM (USACE, 2008) for beaches was applied for computing the run-up level on the Wolf Creek Lake shoreline and the Wolf Creek Lake Dam, Wolf Creek Nuclear Operating Corporation "

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because the slopes where run-up occurs are relatively mild. The standard run-up equation for two percent run-up level beaches (USACE, 2008, Equation 1I-4-29) was used for this analysis.

The final computed wave run-up computed for the reevaluation were 7.01 fi, 0.83 fi, and 4.89 fi, resulting in elevations of 1,100.55 fi, 1,094.37 fi, and 1,098.43 ft for the Wolf Creek Lake Dam, Wolf Creek Lake shoreline, and the ESWS pumphouse, respectively. The final wave run-up level on the Wolf Creek Lake Dam exceeded the crest of the dam of 1,100 ft (WCNOC, 2015). Revi1 However, the dam is not a safety-related structure. In addition, the upstream slope of the Wolf Creek Lake Dam has riprap to protect against erosion from wind-wave activity (WCNOC, 2015). Rev I The maximum run-up level for the Wolf Creek Lake shoreline did not exceed the design basis flood elevation of 1,095 ft (WCNOC, 2015, Section 2.4.3.5). The maximum estimated run-up Rev 1 level for the intake structure of the ESWS pumphouse did not exceed the design basis flood elevation of 1,100.2 ft (WCNOC, 2015, Section 2.4.10). Therefore, the maximum anticipated Revi1 wave run-up elevations at the Wolf Creek Lake shoreline and the ESWS pumphouse did not adversely affect any SSCs at the WCGS site.

An evaluation of the effects of baffle dikes A and B and the breakwater (near the ESWS pumphouse) (Figure 3-9) on waves and wave run-up was also performed. Baffle dikes A and B did not affect the fetches or wave setup for the Wolf Creek Lake Dam, the Wolf Creek Lake shoreline, or the inlet structure of the ESWS pumphouse. Near the ESWS pumphouse, the lake depth was shallow and the breakwater located near the ESWS pumphouse would cause waves to break even though it is submerged due to the PMF water level (the antecedent water level). As determined from light detection and ranging (LiDAR) data, the top of the breakwater was approximately 1,092 ft. The antecedent lake water level was 1,093.54 ft. Therefore, any waves approaching the ESWS pumphouse and intake structure would break at the breakwater and reach the intake structure of the ESWS pumphouse with a smaller wave height than the wave height that approached the breakwater.

3.3.2.2.4 Effects of Spillway Blockage on the Maximum Wolf Creek Lake Level HEC-RAS Cases 7 through 9 considered varying levels of blockage of the spillways following the HHA approach (50 percent, 20 percent, and ten percent blockage of the service spillway, respectively, and ten percent of the auxiliary spiliway) to provide a sensitivity analysis on the percent blockage of the spillways (Table 3-5) per NRC JLD-ISG-2013-01 (NRC, 2013b).

Simulated peak water levels for Cases 7 and 8 exceeded the design basis elevation of 1,095.0 ft.

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However, Cases 7 and 8 were sensitivity cases and were not considered realistic due to the dimensions of the spillways (given in Section 2.1.1.3). Case 9 did not exceed the design basis elevation of 1,095.0 ft.

The unsteady flow case (Case 6, the most refined case) was used as the final case that was compared against the USAR because the design basis did not block the spillways and the case was considered the most realistic case due to the dimensions of the spiliways and the history of debris production in the watershed. The Case 6 peak water level of 1093.57 ft did not exceed the design basis elevation of 1,095.0 ft (WCNOC, 2015, Section 2.4.3.5). Rev 1 3.3.2.2.5 Effects of Sedimentation in Wolf Creek Lake A HEC-RAS model run (Case 10) was performed to evaluate what effect sedimentation in Wolf Creek Lake might have on the water level in the lake during a PMF event. HEC-RAS Case 6 was used as the basis for this analysis. In Case 10, the Wolf Creek Lake storage was adjusted to represent conditions after a sediment inflow volume of 1,080 acre-ft over 40 years. The predicted maximum water level in the lake was 1,093.54 ft, which was the same elevation as determined for Case 6.

3.3.2.2.6 Combined-Effects Flood Many flood-causing mechanisms can occur concurrently because they are not truly independent.

For example, floods from precipitation events may occur concurrently with an antecedent snowpack and wind-induced waves. The impact of a simultaneous occurrence of flood-causing mechanisms was defined by the American Nuclear Society (ANS), ANSI/ANS-2.8-1992 (ANS, 1992), and later defined as "combined effect flooding" in NRC NUTREG/CR-7046 (NRC, 2011).

Three alternative combinations of flood-causing events for precipitation floods are described in Section 9.2.1.1 of ANSI/ANS-2.8-1992 (ANS, 1992):

Alternative I

1. Mean monthly (base) flow

2. Median soil moisture Wolf Creek Nuclear Operating Corporation *1 Flood Hazard Reevaluation Report Pg 8o 0 145262/135031/15 Rev. 1 (October 21, 2015) Page38 o 10

3. Antecedent or subsequent rain: the lesser of (1) rainfall equal to 40 percent of PMP or (2) a 500-year rainfall

4. PMP

5. Two-year wind speed applied in the critical direction Alternative II

1. Mean monthly (base) flow

2. Probable maximum snowpack

3. Coincident 100-year snow season rain

4. Two-year wind speed applied in the critical direction Alternative III

1. Mean monthly (base) flow

2. 100-year snowpack

3. Coincident snow season PMP

4. Two-year wind speed applied in the critical direction Alternative I analysis represents a flood based on summer meteorological conditions (maximum PMP). Alternative II and III analyses are based on winter conditions. Due diligence requires a preliminary evaluation of the Probable Maximum Snow Accumulation (PMSA) and winter season PMP depths before Alternative II and III combined events can be screened out. The calculations to assess the impact of winter hydrometeorologic loadings show that the PMSA combined with a 100-year winter rainfall event (with total snowpack melting and no water losses, Alternative II) produced total runoff depths of 23.62 in to 26.94 in for Cottonwood Falls and Osage City, respectively. This amount was significantly less than the PMP rainfall depth (36.70 in) calculated in Section 3.3.2.1. The calculation of an April PMP falling on a 100-year snowpack (Alternative III) produced a total water depth of 34.7 in, which was also less than the PMP rainfall depth (36.70 in) calculated in Section 3.3.2.1. As a result, the conservative estimates of combined snowmelt-rainfall runoff in winter months (Alternatives II and III) were Wolf Creek Nuclear Operating Corporation *1*,

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• screened out. Alternative I was deemed the most conservative combined-effects alternative to evaluate.

3.3.2.2.6.1 Evaluation of Combined-Effects Flooding Using ANS Alternative I The HHA approach is followed for combined-effects flooding analysis, as shown in Figure 3-10.

Two antecedent rain conditions prior to the PMP were evaluated in the flood hazard reevaluation:

• A 72-hr rainfall event with a total depth of 40 percent of the PMP

• A 24-hr 500-year rainfall event The 40 percent PMP event was approximated by multiplying all PMP ordinates by a constant factor of 0.4. A 24-hr duration was used for the 500-year storm to be consistent with standard industry practice. The Soil Conservation Service (SCS) unit rainfall curves are typically set up for 24-hrs (Chow et al., 1988, p. 461). Following the procedures laid out in NRC NUREG/CR-7046 (NRC, 2011), the storm with the lesser impact on peak discharge was utilized for combined-effect modeling. After evaluating the two possible storm events, 24-hr 500-year rainfall event was utilized as the rainfall event preceding the PMP for combined-effect modeling.

The combination of 500-year rainfall and PMP were then used to create a new rainfall hyetograph for modeling.

The new storm hyetograph was used as input to the HEC-HMS Case 5 model. The Case 5 HEC-HMS model was run with the 500-year/PMP hyetograph combination to obtain the subbasin hydrographs for input to the HEC-RAS model.

The HEC-RAS Case 6 model (Section 3.3.2.2.2) was then used to model the unsteady (transient) streamfiow in the creek and water level in Wolf Creek Lake. The HEC-RAS combined-effects simulation yielded a maximum predicted water level in Wolf Creek Lake of 1,094.63 ft. This water level was higher than the predicted lake water level for the PMP alone, but was still less than the design basis flood elevation of 1,095 ft (WCNOC, 2015, Section 2.4.3.5). Rev 1 Wolf Creek Nuclear Operating Corporation I

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3.3.2.2.6.2 Wind-waves and Run-up Coincident with Combined-Effects Flood The combined-effects flood level included maximum wave run-up calculated at key locations.

The maximum wave run-up computed for the Wolf Creek Lake Dam, the shoreline at the WCGS, and the ESWS pumphouse were 7.01 fi, 0.83 fi, and 4.89 ft, respectively (Section 3°3.2.2.3). Thus, the combined-effects lake water levels of 1,101.64 fi, 1,095.46 fi, and 1,099.52 ft were computed for those three locations, respectively.

The maximum water surface elevation along the shoreline nearest to the powerblock, including the impact of wave action was 1,095.46 fi, providing a freeboard of 4.04 ft, with respect to the plant grade elevation of 1,099.5 ft (Figure 3-11), and was bounded by the design basis flood Rev 1 elevation including run-up of 1,095.8 ft (WCNOC, 2015, Table 2.4-16).

The maximum water surface elevation at the ESWS pumphouse, including the impact of wave action was calculated as 1,099.52 fi, providing a freeboard of 0.48 fi, with respect to the top of grade-level slab elevation of 1,100 ft and was bounded by the design basis flood elevation for the pumphouse of 1,100.2 ft (WCNOC, 2015, Section 2.4.10). Revi1 3.3.2.2.6.3 Effects of a Combined-Effects Flooding on Debris Loads If debris exists in Wolf Creek Lake, it was expected that the debris would be small (e.g., tree branches, etc.) and would not adversely affect the WCGS site because floodwaters do not rise to the plant grade elevation of 1,099.5 ft, and would not adversely affect the Wolf Creek Lake Dam due to the size of debris. It was expected that debris would not adversely affect the ESWS pumphouse because the intake structure is equipped with trash racks, which protect the ESWS pumphouse from debris (WCNOC, 2015, Section 2.4.7.2). Additionally, the baffle dikes and Rev 1 breakwater provide a defense for the ESWS pumphouse against debris that could be floating in Wolf Creek Lake due to a combined-effects flooding event. In addition, the flow of the floodwater would be southerly towards the main dam, not directed northeasterly around the WCGS site peninsula to the ESWS pumphouse.

3.3.3 Dam Breaches and Failures The potential flooding of the WCGS site due to breaches and failures of dams located upstream of the site was evaluated. Except for the Wolf Creek Lake Dam, no other dams were listed in the USACE National Inventory of Dams (NID) database (USACE, 201 3a) for the Wolf Creek Wolf Creek Nuclear Operating Corporation 1 .,

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watershed. A total of 322 dams were been identified in the Neosho River watershed upstream and downstream of the Wolf Creek watershed. These are shown in Figure 3-12.

The evaluation of dam failure was performed using a quantitative assessment that screened out flooding hazards due to a dam breach using the storage level, distance from the WCGS site, and head differential. The quantitative assessment utilized the Volume Method outlined in the NRC JLD-ISG-2013-01 guidance for dam failure analysis, "Guidance for Assessment of Flooding Hazards Due to Dam Failure" (NRC, 201 3b). This assessment includes the following steps:

1. Obtain a list of dams from the USACE NID (USACE, 2013a).

2. Identify which dams are "inconsequential" or downstream using watershed boundaries (USGS, 2013) and other sources of information (e.g., the Kansas Department of Agriculture [KDA]) (KDA, 2011).

3. Use the Volume Method to identify "noncritical" and "potentially critical" dams. The Volume Method outlined in Section 3 of NRC JLD-ISG-2013-01 (NRC, 2013b) is a simplified dam failure screening analysis.

The Volume Method (i.e., the "Screening" step presented in Figure 3-13) was used because it is the most conservative of the simplified methods listed in Section 3 of NRC JLD-ISG-2013-01 (NRC, 201 3b). Figure 3-14 provides a more detailed illustration of steps within the Volume Method. Other more refined methods are available should the Volume Method identify any "potentially critical" dams.

NRC JLD-ISG-2013-01 (NRC, 2013b) classifies dams as "inconsequential," "noncritical," or "potentially critical," as follows:

• "Inconsequential" dams: "Dams identified by Federal or State agencies as having minimal or no adverse failure consequences beyond the owner's property may be removed from further consideration in the Recommendation 2.1 reevaluation. Dams owned by licensees may not be removed. Other inconsequential dams may be removed with appropriate justification (e.g., if they can be easily shown to have minimal or no adverse downstream failure consequences)" (NRC, 2013b, p. 3-2).

• "Noncritical" dams are dams that have little impact on flooding at the NPP site using a simplified analysis (NRC, 2013b, p. 1-3) (e.g., flood elevations below plant grade).

• "Potentially critical" dams include all other upstream dams (NRC, 2013b, p.

1-3).

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The Volume Method analysis represented a condition with the total upstream reservoir storage volume simultaneously transferred to the WCGS site without attenuation. As part of the Volume Method, the volume of water required for antecedent flood conditions within a reach was first removed from the volume available for storing water from the upstream reservoirs. NRC JLD-ISG-2013-01 (NRC, 2013b) recommends using the antecedent 500-year return period flood flow (R.PFF).

The Volume Method was used to determine the potential for flooding above the WCGS plant grade elevation of 1,099.5 ft (WCNOC, 2015, Section 2.4.3.5). NRC JLD-ISG-2013-01 (NRC, ]Rev 1 201 3b) uses the term "plant grade" in reference to simplified modeling approaches to screen flooding that result from the failure of all dams in the watershed upstream of the site. For this application, flooding above plant grade would require that backwater from flooding on the Neosho River would overtop the Wolf Creek Lake Dam. For debris and sediments along the Neosho River to enter the Wolf Creek Lake, flood levels along the Neosho River would need to exceed the service spillway crest elevation (i.e., 1,088 ft) of the Wolf Creek Lake Dam.

The following steps were performed to evaluate the potential for flooding due to upstream dam failure at the WCGS site:

1. Topographic data were compiled and processed.

2. A list of dams within the Neosho River watershed was obtained. The NID database included a total of 322 dams (Figure 3-12), including 91 downstream dams within the watershed area. The remaining 231 upstream dams have a total volume of 1,633,036 acre -ft.

3. Downstream and "inconsequential" dams were screened out.

4. Antecedent flow conditions along the Neosho River were estimated using the FEMA-reported 500-year RPFF at the City of Burlington (FEMA, 1996). The FEMA Flood Insurance Study (FIS) for the City of Burlington (FEMA, 1996) reported a 500-year RPFF for the Neosho River between the City Dam (upstream Corporate City Limits) and the downstream Corporate City Limits of 290,000 cfs, and provides a 500-year Return Period Flood Elevations (RPFE) profile along the 2.1-mile reach with floodwater elevations ranging between 1,022.5 ft to 1,026.3 ft.

5. A steady-state HEC-RAS model was setup to represent the Neosho River from 334.4 to 343.3 river miles upstream of the Neosho River mouth.

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6. The HEC-RAS model was calibrated to the reported 100-year and 500-year RPFE (FEMA, 1996) using the associated 100- and 500-year RPFF as an upstream boundary condition.

7. The calibrated HEC-RAS model was run using the proper antecedent flow conditions to compute the associated flood levels and the remaining available storage volumes below plant grade.

8. "Noncritical" and "potentially critical" dams were identified. The available water storage volume near the WCGS site for upstream dams (i.e., reservoirs) was calculated using the Spatial Analyst extension and 3D Analyst extension within ArcGIS. If the available storage cannot accommodate the volume of water stored in the upstream dams, then "potentially critical" dams were identified.

9. Potential debris, sediment loading, and waves, were addressed as necessary.

The 500-year RPFE profile along the 2.1-mile reach with floodwater elevations ranged between 1,022.5 ft to 1,026.3 ft. Adding the volume of water stored in the 231 dams located in the upstream portion of the Neosho River watershed (i.e., 1,633,036 acre-fl) raised the floodwaters up to an elevation of 1,076.7 ft. The flood level of 1,076.7 ft in the Neosho River is less than the topographic ridge that separates the Neosho River from the Wolf Creek watershed. Therefore, floodwaters will not cross over to Wolf Creek Lake. However, floodwaters will flow up Wolf Creek from its confluence with the Neosho River. The dam break analysis shows the maximum backwater elevation to be 22.8 ft below the plant grade elevation and 11.8 ft below the Wolf Creek Lake Dam service spillway. Therefore, no "potentially critical" dams were identified, using the Volume Method (NRC, 2013b). All dams were either "inconsequential" or

noncritical.

The peak water level with failure of all upstream dams did not reach the Wolf Creek Lake Dam service spillway invert (i.e., 1,088 ft). The peak water level was 22.8 ft below plant grade (i.e.,

1,099.5 ft) (Figure 3-15"). As a result, no further consideration of debris or sediment at the WCGS site was required as part of the reevaluation analysis.

For a 40-mph wind over water, the run-up associated with maximum wave heights was less than one foot (WCNOC, 2015, Section 2.4.3.6.1). The maximum water level at the WCGS site with tRevi1 the failure of all upstream dams transferred without attenuation was below the Wolf creek Lake Dam service spillway invert (i.e., 1,088 ft), providing a "freeboard" of 22.8 ft below plant grade (i.e., 1,099.5 ft) and 11.3 ft below the service spillway invert. Therefore, the potential impacts of wind-wave activity coincident with dam failure were dismissed.

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3.3.4 Storm Surge The WCGS site is located more than 1,000 miles from the Pacific Ocean, approximately 935 miles inland from the Atlantic Coast, and approximately 600 miles inland from the Gulf of Mexico (USGS, 2013). The site is located adequately inland such that hurricanes and a Probable Maximum Hurricane (PMH) will not be a source of a potential flood hazard. Therefore, further consideration to storm surge flooding outlined in NRC NUREG/CR-7 134 and NRC JLD-JSG-2012-06 (NRC, 2012b; 2013c) was not applicable to the WCGS site.

Storm surge due to Probable Maximum Wind Storms (PMWS) and squall lines was also not applicable to the WCGS site, because the site is not located on the Great Lakes, as is discussed in ANSI/ANS-2.8 (ANS, 1992) and NRC JLD-ISG-2012-06 (NRC, 2013c). Therefore, according to NRC JLD-ISG-2012-06 guidance, determination of hydrostatic and hydrodynamic forces, debris, and water-borne projectiles, and effects of sediment erosion or deposition due to storm surge was not necessary because safety-related SSCs at the WCGS site were not affected from storm surge flood levels (NRC, 2013c).

3.3.5 Seiche A seiche is defined as "an oscillation of the water surface in an enclosed or semi-enclosed body of water initiated by an external cause" in NRC NURIEG/CR-7046 (NRC, 2011). To account for the potential of a seiche due to meteorological effects, the seiche periods for the length and width of Wolf Creek Lake were computed. In order to compute the seiche periods, the lake was assumed to be a rectangular basin with an averaged depth of the lake, which follows the methodologies outlined by Dean and Dalrymple (Dean and Dalrymple, 1991).

Using the Dean and Dairymple methodology for seiche periods for Wolf Creek Lake, the resulting seiche periods computed were 6.5 minutes for the lake's length and 38.7 minutes for the width of the lake. Seiching at these periods could only occur if an oscillatory force (jpressure or wind) excited lake oscillations at one of the seiche periods. The periods calculated for lake oscillation could not be continuously forced by changes in overall weather conditions because these conditions typically fluctuate at time scales of 1 hr or more (Peinke et al., 2004).

Therefore, seiches due to meteorological effects are dismissed as a source of flooding at the WCGS.

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Seiches can also occur due to seismic effects and landslides. The WCGS site is situated in an area of low seismic hazards according to the USGS (USGS, 2012c). The occurrence of landslides in the area adjacent to Wolf Creek Lake is not considered possible due to the low relief of topographic features in the vicinity of the WCGS site. Therefore, potential seismic events and landslide were not expected to cause seiches on Wolf Creek Lake and, therefore, cause flooding at the WCGS site. Additionally, according to NRC JLD-ISG-2012-06 guidance, determination of hydrostatic and hydrodynamic forces, debris and water-borne projectiles, and the effects of sediment erosion or deposition due to seiche were not necessary because safety-related S SCs at the WCGS site are not affected from seiche flood levels (NRC, 2013c).

3.3.6 Tsunami Following the guidance outlined in NRC NUREG/CR-6966 and NRC JLD-ISG-2012-06 (NRC, 2009; 2013c), a review was conducted of the National Oceanic and Atmospheric Administration's (NOAA) historic tsunami records that impacted the east coast of the United States and the Gulf of Mexico. The maximum historic water levels due to historic tsunami run-up recorded along the east cost of the United States and the Gulf of Mexico was 19.7 ft, which occurred at Daytona Beach, Florida, in 1992 (NOAA, 2013). Daytona Beach, Florida, is approximately 1,050 miles from the WCGS site (USGS, 2013), and the closest shoreline that could be subjected to tsunami flooding is approximately 600 miles away. NRC NUREG/CR-6966 indicates that if regional screening identifies that the site region is not subject to tsunamis, no further analysis for tsunami hazards is required (NRC, 2009). Additionally, according to NRC JLD-ISG-2012-06 guidance (NRC, 2013c), the determination of the hydrostatic and hydrodynamic forces, debris and water-borne projectiles, and the effects of sediment erosion and deposition were not considered because the safety-related SSCs of the WCGS site were not subject to tsunami flood levels (NRC, 2013c).

3.3.7 Ice-Induced Flooding Ice-induced flooding analysis for the WCGS site included an assessment of ice jams, frazil ice, and ice thickness. Review of the current Ice Jams Database (USACE, 2013b) indicated that only one ice jam has been recorded in the Neosho River Basin on February 1949, near the city of Council Grove, Kansas. Council Grove is approximately 50 miles northwest of the WCGS site, and upstream of the John Redmond Reservoir. Potential ice jams upstream of the John Redmond Reservoir would not adversely affect the WCGS site because any potential floodwaters occurring due to release from the ice jam would be mitigated or dissipated before entering, or within, the Wolf Creek Nuclear Operating Corporation rQ Flood Hazard Reevaluation Report Pg 6o 0 145262/135031/15 Rev. 1 (October 21, 2015) Pae 6 f 0

John Redmond Reservoir or one of the other flood control facilities on the Neosho River.

Additionally, the Neosho River is separated from the WCGS site by a topographic ridge (USGS, 2012b).

In the event of an ice jam occurring on the Neosho River, at the confluence of Wolf Creek, downstream of the John Redmond Reservoir (although there is no record of such an ice jam),

backwater effects would not affect the WCGS site as the confluence is over six miles from the WCGS site. Furthermore, no historical ice jams have been recorded in the Wolf Creek watershed (USACE, 2013b).

Frazil ice can only occur in supercooled turbulent waters (USACE, 2002). Supercooled water is water that is cooled below the freezing point without freezing. As presented in the USAR, frazil ice has the potential to form in Wolf Creek Lake when the water becomes supercooled, creating the potential to block the ESWS intake trash racks (WCNOC, 2015). Supercooling in Wolf Rev 1 Creek Lake requires a large heat loss associated with low air temperatures, clear water, and clear nights (WCNOC, 2015). Additionally, because the cooling heat transfer is at the surface of the Rev I water, strong winds are needed to mix supercooled water to a depth low enough to be drawn into the intake (WCNOC, 2015). Rev 1 In January 1996, the Train A ESWS intake trash racks became completely blocked by frazil ice (NRC, 1996). The frazil ice blockage was effectively cleared by sparging the trash racks with air (NRC, 1996). At the time of the blockage of the trash racks by frazil ice in January 1996, the ESWS warming flow was insufficient to prevent frazil ice from forming at the Train A trash racks (NRC, 1996). According to the current version of the USAR, WCGS has put in place a system to mitigate future potential frazil ice formation by diffusing warmed water in front of the ESWS intake trash racks (WCNOC, 2015). This technique of mixing warmed water with Rev 1 supercooled water is especially effective near water intakes, where the required quantity of warm water can be modest (USACE, 2002).

Ice thickness was estimated by an analysis of Freezing Degree Days (FDD), defined as the difference between 32 degrees Fahrenheit (0 F) and the average daily air temperature (USACE, 2004). The maximum estimated ice thickness on Wolf Creek Lake, based on the methodologies and equations in the Method to Estimate River Ice Thickness Based on MeteorologicalData report (USACE, 2004), was approximately 20.60 in (1.72 fi) using the data from the Emporia Municipal Airport weather station, and approximately 19.14 in using data from the John Redmond Lake weather station.

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The bottom of the intake channel to the ESWS pumphouse is at elevation 1,065 fi, which is 22 ft below the normal operating level (1,087 ft) of Wolf Creek Lake. Thus, the bottom of the conservatively estimated ice thickness of 20.60 in (1.72 fi) would still be approximately 20.28 ft above the bottom of the intake channel to the ESWS pumphouse. The reevaluation analysis and the design basis (WCNOC, 2015) screened out ice formation as a potential flood hazard. Rev 1 3.3.8 Flooding Resulting from Channel Migration or Diversion The rivers and creeks in the vicinity of the WCGS site are the Neosho River, Wolf Creek, and Long Creek. A qualitative assessment of the streams and rivers in the vicinity of the WCGS site, in conjunction with the information presented in the USAR (WCNOC, 2015), indicated that Rev 1 safety-related SSCs at the WCGS site would not be affected by diversion of flows from the Neosho River, Wolf Creek, or Long Creek.

This hazard reevaluation also indicated that any potential diversion of cooling water would not adversely affect safety-related SSCs at the WCGS site. The cooling water is provided by Wolf Creek Lake, and the intake channel is protected from potential ice blockage by diffusing warmed water in front of the ESWS intake trash racks (WCNOC, 2015). The UHS is contained by a Rev 1 submerged Seismic Category I dam in Wolf Creek Lake and is fully functional for safe shutdown of the WCGS site. The UHS will provide a sufficient volume of water to safely shut down and maintain shutdown of the WCGS site as long as the sediment volume in the UHS is limited to 130 acre-ft (WCNOC, 2015, Section 2.4.11.6). The sources of the makeup water to the cooling Revi1 lake are Wolf Creek and the Neosho River (WCNOC, 2015, Section 2.4.8.2). Significant morphological changes in the Neosho River are not expected to affect the water supply from the John Redmond Reservoir, and Wolf Creek was also not expected to diverge due to the topography in the area.

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4.0 COMPARISON OF CURRENT DESIGN BASIS AND REEVALUATED FLOOD HAZARDS Section 4. 0 has been prepared in response to Request for Information Item i .e. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a): Provide a comparison of current and reevaluated flood-causing mechanisms at the site. Provide an assessment of the current design basis flood elevation to the reevaluated flood elevation for each flood-causing mechanism. Include how the findings from Enclosure 4 of this letter (i.e.,

Recommendation 2.3 flooding walkdowns) support this determination. If the current design basis flood bounds the reevaluated hazard for all flood-causing mechanisms, include how this finding was determined.

4.1 COMPARISON OF FLOOD-CAUSING MECHANISMS Rev 1 The flood-causing mechanisms evaluated under the current design basis in the USAR include the.

effects of local intense precipitation, probable maximum flood on Wolf Creek Lake, including wave run-up at the site, seismically induced potential dam failure, probable maximum storm surge and seiche flooding, probable maximum tsunami flooding, ice flooding, and channel diversions (WCNOC, 2015). The flood hazard reevaluation includes the same evaluations of the Rev 1 flooding mechanisms as presented in the current design basis, including a combined-effects flood. Note that the USAR terminology differs from the terminology used in current NRC guidance, but the same mechanisms are evaluated. The flooding mechanisms, from both the USAR and the reevaluation, are listed in Table 4-1.

The conditions under which the flooding analyses were performed and the methods used to perform the analyses were slightly different between CLB analyses and the reevaluation analyses. The differences are highlighted in Table 4-1 through Table 4-4. Table 4-4 focuses on the additional parameters (i.e., flood duration, dynamic loads, debris loading, and sedimentation) that are required to be evaluated since the issuance of NRC Recommendation 2.1.

4.2 COMPARISON OF FLOOD EFFECTSReI The current design basis, as presented in the USAR (WCNOC, 2015), indicates that the site is Rev I not affected by flooding. The WCGS site has a grade elevation of 1,099.5 fi, and a floor elevation of 1,100 ft.

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Local Intense Precipitation The current design basis LIP analysis assumes that the site drainage system is not functional during the LIP event. The design basis LIP water level for the safety-related buildings is 1,099.92 ft (WCNOC, 201 5), which is below the plant floor elevation of 1,100 ft. Because the maximum design water level due to LIP is below the plant floor elevation, hydrostatic and hydrodynamic forces are not evaluated for safety-related SSCs. However, the design basis does include hydrostatic loads on safety-related structures for groundwater levels at plant grade (WCNOC, 2015). Rev I The reevaluated on-site LIP ponding levels range from 1,100.03 ft to 1,100.38 ft adjacent to safety-related SSCs (Table 3-1). These values exceed the design basis water levels.

Since the LIP rainfall depth and distribution used for the reevaluation are the same those used for the LIP event used for the current design basis, the design basis roof loading evaluation is considered to bound the roof loading for the reevaluated flood hazard.

Potential pathways along which surface water runoff could reach safety-related SSCs include 40 different doors, vaults, and manholes. Table 3-2 and Table 3-3 present the resulting flood elevations, duration of flood, and the dynamic and static loads for these pathways. The Revision 0 FHRR presented flooding results for Cases 5 and 6. Case 7 includes site updates and model Rev 1 refinements and is presented as the most refined simulation for this Revision 1 FHRR. For Case 7, the maximum flood depth outside of an entrance to a Seismic Category I building on the powerblock (Auxiliary Building pressure door) was approximately 1.01 ft. The associated duration of flooding above a depth of 0.5 ft at this location was 0.5 hrs, with a corresponding maximum velocity 3 of 1.2 ft/s, a maximum hydrostatic force of 32 lb/ft, and a maximum Rev 1 hydrodynamic force of 3 lb/ft. Figure 4-1 illustrates a timeline for flooding adjacent to powerblock building doors.

For other doors, hatches, manholes, and vaults associated with safety-related SSCs, the simulated maximum flood depth is 1.43 ft at ESWS manholes MHE5A and MHE5B. The associated Rev 1 duration of flooding above a depth of 0.5 ft is 10.0 hrs, with a corresponding maximum velocity SThe Auxiliary Building pressure door is located at the end of an alleyway between the Fuel Building and the Hot 1Rev 1 Machine shop. Consequently the dominant flow velocities are away from the Auxiliary Building pressure door.

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of 0.6 ft/s, a maximum hydrostatic force of 64 lb/fl, and a maximum hydrodynamic force of less Rev 1 than one pound per foot.

The potential for sedimentation and debris loading on safety-related SSCs due to the LIP was screened out qualitatively, as discussed in Section 3.3.1.3. Rev 1 Flooding~ in Rivers and Streams The normal operating level at the Wolf Creek Lake is 1,087 ft. Snyder's synthetic unit hydrograph was used for the design basis to determine that the peak flow rate for the spillways is 22,845 cfs (WCNOC, 2015, Section 2.4.3.5) for a sequential flood event with an antecedent Rev 1 standard project flood followed by a PMP, which is analogous to a combined-effects precipitation flood event. The maximum water surface elevation in Wolf Creek Lake (i.e., the pooi elevation) due to the design PMF event is 1,095 ft at the plant site, which occurs approximately 158 hrs after the start of the event (WCNOC, 2015, Figure 2.4-23). This would exert a lateral force of 42,713 lb/ft on the face of the pumphouse (reported as a depth-integrated Rev 1 force per linear foot along the pumphouse face to the bottom of the ESWS pumphouse at elevation 1,058.0 fi). The coincident wind-wave activity of the design PMF results in a maximum run-up of 0.8 ft at the plant site shore. The resulting design run-up elevation is 1,095.8 ft when added to the PMF pool elevation (Table 4-3). The design maximum wave run-up elevation on the vertical wall of the intake structure of the ESWS is 1,100.2 ft.

In the reevaluation, the simulated outflow from Wolf Creek Lake over the service spillway was 23,021 cfs. The maximum water level in the lake resulting from the PMF was 1,093.54 ft, which occurred approximately 47.5 hrs after the start of the event, and was less than the design value (1,095 ft). The shorter duration to the peak water level is not considered a controlling parameter since the reevaluated maximum water level was bounded by the design basis and no procedural actions are required by the site due to increases in lake level due to a PMF. The reevaluated lake levels including wind-generated wave run-up at the WCGS shoreline and the ESWS pumphouse were 1,094.37 ft and 1,098.43 ft, respectively (Table 4-3). The reanalyzed water levels, including wind-waves, were less than the design water levels (1,095.8 ft), which is less than the plant grade elevation (1,099.5 ft). Therefore, hydrodynamic and hydrostatic loads at the plant were not calculated for safety-related structures on the powerblock. However, hydrostatic loads at the ESWS pumphouse were calculated. The maximum static load for the peak simulated water levels was 39,408 lb/ft, which is less than the design basis hydrostatic loading of 42,713 lb/ft. Rev 1 Wolf Creek Nuclear Operating Corporation *1*

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This represents a depth-integrated force from the stiliwater level to the bottom of the ESWS Rev 1 pumphouse (elevation 1,058.0 fi).

The reevaluation analysis for the river hydraulic model included simulations representing potential debris build-up at the Wolf Creek Lake Dam auxiliary and service spillways. The potential impact of debris was simulated with ten percent blockage of the auxiliary spillway and 50, 20, and ten percent blockage of the service spillway. Peak water levels with 50 and 20 percent blockage of the service spillway exceeded the design basis PMF elevation of 1,095 ft.

However, simulated peak water levels for 50, 20, or ten percent blockage of the service spillway did not exceed the plant grade elevation of 1,099.5 ft. The 50 percent and 20 percent cases (Cases 7 and 8) were not considered realistic due to the dimensions of the spillways.

It was expected that debris caused by runoff associated with the PMF would not adversely impact the intake structure of the ESWS pumphouse. Additionally, the baffle dikes provide a defense for the ESWS pumphouse against debris that could be floating in Wolf Creek Lake due to the PMF. The source area for debris generation would essentially be limited to a small contributing area on the east side of the plant and it is expected that any debris generated by that area would be small in size (e.g., tree branches) and would not affect the ESWS pumphouse.

Furthermore, the intake structure is equipped with trash racks, which protect the ESWS pumphouse from loss of flow due to debris.

The reevaluation analysis also included a simulation representing sediment build-up within Wolf Creek Lake, which considered a loss in the capacity of Wolf Creek Lake due to sedimentation over a period of 40 years. This is equivalent to approximately 1,080 acre-ft of sediment. The peak water levels with lake sediments did not exceed the design basis PMF elevation of 1,095 ft.

Combined-Effects Flooding~

The design water level for combined-effects flooding is 1,095.80 ft and 1,100.20 ft for the WCGS shoreline and the ESWS pumphouse, respectively (Table 4-3), which occurs approximately 158 hrs after the start of the event (WCNOC, 2015, Figure 2.4-23). The ]Revi1 analogous values determined during the reevaluation were 1,095.46 ft and 1,099.52, respectively, which occurs approximately 68 hrs after the start of the event. The reevaluated flood levels are less than, and bounded by, the design water levels.

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The design loads on the roofs of safety-related structures are based on a 100-year snowpack with the probable maximum winter precipitation superimposed on it, which results in the maximum combined loading calculated as 153 pounds per square foot (psf) (WCNOC, 2015; Section Rev 1 2.4.2.3.3). Ground loads due to the all-winter snowfall were considered in the hazard revaluation using the event combinations of ANSI/ANS 2.8 (ANS, 1992) Alternatives II and III for the combined-effects flood. It was determined that the ground loading using the snow water equivalence method could reach was 169.4 psf, which is slightly higher than the design roof loading. However, the maximum reevaluated ground loading is due to an April event that only generated 4.3 in of snow (the remainder being due to coincident April rainfall) and is not considered to be equivalent to a roof load, because the total combined water and snow column would not be stored on the roofs. All other months (November through March) resulted in ground loadings that were less than the design roof loading. Therefore, it was determined that the design roof loadings bounded the reevaluated ground loadings.

Dam Breaches and Failures Failure of dams located above the John Redmond Reservoir will not adversely affect any safety-related facilities at the WCGS site (WCNOC, 2015). In the most critical case, which postulates Rev 1 the domino-type failure of the John Redmond, Marion, Cedar Point, and Council Grove Reservoirs, the maximum flood stage of the Neosho River was estimated to be 1,044.55 ft at a distance of about 5.0 miles downstream from the John Redmond Dam (WCNOC, 2015, Case b.3 Rev 1 of Section 2.4.4.1).

As stated in the USAR, the topographic ridge between the Neosho River and Wolf Creek valleys below John Redmond Dam will separate the postulated flood levels in the Neosho River valley from any facilities at the site, with the exception of the Wolf Creek Lake dam. The maximum water elevation on the downstream slope of the Wolf Creek Lake Dam, due to the postulated combined maximum flood-causing events in the Neosho and Cottonwood River basins, is conservatively established at elevation 1,049.6 ft. This flood stage is well below surface grades of any Seismic Category I facilities at the site and is about 50 ft below the plant grade elevation Rev 1 of 1,099.5 ft (WCNOC, 2015).

The reevaluated flood level resulting from the failure of all dams upstream of the John Redmond Reservoir was 1,076.70 ft, which is substantially greater than the design value due to the more conservative method used (i.e., the Volume Method per JLD-ISG-2013-01), but still far less than plant grade elevation (1,099.5 ft) and the service spillway elevation for the Wolf Creek Lake Wolf Creek Nuclear Operating Corporation *t-Flood Hazard Reevaluation Report Pg 3o 0 145262/135031I/15 Rev. 1 (October 21, 2015) Page53 o-10

Dam (1,088.00 fi). Therefore, dam failure was screened out for the reevaluation, as was done in the design basis.

Storm Surg~e and Seiche, Tsunami, and Ice-Induced Flooding~

Storm surge and seiche, tsunami, and ice-induced flooding were screened out as potential flooding events in the current design basis in the USAR (WCNOC, 2015). In the reevaluation, Rev 1 storm surge and seiche, tsunami, and ice-induced flooding were also screened out.

Channel Diversion Channel diversion is screened out as a potential flooding event in the design basis. In the design basis, there is no indication that Wolf Creek or its tributaries would be diverted from its present course of flowing into Wolf Creek Lake. In addition, supply of makeup water to the plant is available to be pumped from the Neosho River, if the supply from Wolf Creek is temporarily cutoff. In the reevaluation analysis, channel diversion was similarly screened out and it was determined that safety-related SSCs at the WCNOC site would not be affected by the diversion of flows from the Neosho River, Wolf Creek, and Long Creek.

4.3 SUPPORTING DOCUMENTATION Calculation briefs in support of the flood hazard reevaluation at the WCGS site have been prepared, on which the reevaluated flood levels are based. Additionally, the Wolf Creek Nuclear Operating CorporationPost FukushimaFlooding,Walkdown Report (WCNOC, 2012) provides further information regarding the design basis flood hazard levels, as well as flooding protection and mitigation features.

According to the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012), safety-related SSCs that are credited in the CLB for protecting the plant from external flood hazards were identified, inspected, and evaluated to be adequate. According to the report (WCNOC, 2012), "The walkdown visual inspection has verified that there is reasonable assurance the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The Wolf Creek external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard."

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4.3.1 Technical Justification of the Flood Hazard Analysis All flooding reevaluation analyses described in this report have been undertaken with consideration and implementation of current techniques, software, and methods used in present-day standard engineering practice to develop the flood hazard. The technical basis for the various scenarios modeled under the HHA approach and the key assumptions utilized in the determination of the reevaluated flooding levels for each flood-causing mechanism are discussed individually in Section 3.0.

4.3.2 Technical Justification of the Walkdown Results With respect to the implementation and conclusions of the flooding hazard reevaluation, results from the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) have been taken into consideration. According to the report (WCNOC, 2012), "The walkdown visual inspection has verified that there is reasonable assurance the flood protection features are available, functional, and capable of performing their specified functions as set forth in the CLB. The Wolf Creek external flood protection features are effective and able to perform their intended flood protection function when subject to a design basis external flooding hazard."

Based on the reevaluated flood hazard results, the effects of flood levels that are not bounded by the CLB on the pertinent flood protection and mitigation features described in Section 2.6 and as identified in the Wolf Creek Nuclear OperatingCorporationPost Fukushima Flooding Walkdown Report (WCNOC, 2012) are provided below.

Top ogranhy The walkdown evaluated the state of the 2012 site layout and topography against the design basis. The analysis presented in the Revision 0 FHRR accounted for the site layout and topography as documented by a 2012 aerial and ground survey. Updates to the site layout and topography through July 2015 are incorporated in this Revision 1 FHRR, as discussed in Rev 1 Sections 2.1.2.1 and 2.4.2. No credit was taken for underground drainage in either the analysis prepared for the Revision 0 FHRR or the analysis prepared for the Revision 1 FHRR. Table 3-1 through Table 3-3 indicate that peak ponding levels determined in the reevaluated LIP analysis result in potential propagation pathways to safe shutdown equipment. These flooding effects are Wolf Creek Nuclear Operating Corporation 1 Flood Hazaird Reevaluation Report Pg 5o 0 145262/135031/15 Rev. 1 (October 21, 2015) Pag 5 of10 N

mainly attributed to short duration ponding caused by the peak intensity of the rainfall and the Rev 1 mild slopes of the site grading.

Doors Credited pressure doors were evaluated during the flooding walkdown. The hazard reevaluation determined localized ponding exceeding the design plant floor elevation of 1,100 ft at doors that are potential pathways to safety-related systems and components in the following structures:

Auxiliary Building, Communication Corridor Building, Fuel Building, Hot Machine Shop, Turbine Building, Condensate Storage Tank Pipe House, and the Refueling Water Storage Tank Valve House.

Structures / Floors / Walls / Penetrations / Vaults The walkdown evaluated the state of credited flood protection boundaries related to the hydrostatic design basis of plant grade. The hazard reevaluation determined localized ponding exceeding the design basis at Seismic Category I structures, as indicated in Table 3-1.

Therefore, the hydrostatic design basis for Seismic Category I structures, which is based on the design groundwater level of plant grade (elevation 1,099.5 ft), inspected during the walkdown is not bounded for the following Seismic Category I structures: Auxiliary Building, Control Building, Diesel Generator Building, Fuel Building, Reactor Building, Refueling Water Storage Tank, ESWS manholes (MHE1A, MHE1B, MHE2A, MHE2B, MIIE3A, MHE3B, MHE4A, MHE4B, MHE5A, and MHE5), and the Emergency Fuel Oil Tank Access Vaults.

ESWS Pumphouse and Forebay The credited flood protection features associated with the ESWS pumphouse were evaluated during the flooding walkdown. The ESWS pumphouse forebay was considered restricted access during the flooding walkdowns, but was inspected by divers as an SSC scheduled in the preventative maintenance program meeting the frequency requirements of NRC Regulatory Guide 1.127. The results of the hazard reevaluation for flood elevation, including wave run-up, are bounded by the design basis. Therefore, the evaluations performed during the walkdown are still applicable to the ESWS pumphouse.

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Sumo Pumps & Motors Credited sump pumps and motors in Seismic Category I buildings were evaluated during the flooding walkdown due to the design basis of controlling groundwater inleakage. As discussed previously, the hazard reevaluation determined localized ponding exceeding the design plant floor elevation of 1,100 ft at potential pathways to safety-related systems and components. The sump pumps are credited to control groundwater inleakage, not the propagation of water into the Seismic Category I buildings due to external ponding because the design basis determined there was no ponding exceeding the plant floor elevation. The capacity of these pumps could be evaluated, if necessary, for handling water that enters the building due to ponding during the LIP event.

4.4 CONCLUSIoNs The flood hazard reevaluation for the river flooding event is bounded by the design basis. In addition, the reevaluated combined-effects analysis is also bounded by the design basis.

Hydrostatic loads were computed for the design basis of the ESWS pumphouse during river flooding and bound the reevaluated loadings. The reevaluation analysis of dam break, storm Rev 1 surge and seiche, tsunami, and ice flooding are screened out in the reevaluation and in the design basis.

The LIP modeling in support of the Revision 1 FHRR accounts for changes to the site layout and grading through July 2015. The results of the updated LIP modeling performed for this Revision Rev I 1 FHRR do not change the overall conclusions of the Revision 0 FIIRR.

The current design basis flood levels for LIP do not bound the reevaluated flood levels. The maximum reevaluated flood level for LIP was 1,100.38 ft, which is above the plant floor entrance elevation of 1,100 ft, whereas the maximum design flood level for LIP flooding is Rev 1 1,099.92 ft. Thus, the reevaluated. LIP flood levels are approximately 0.46 ft higher than the CLB values. The highest level of floodwater in the reevaluated LIP flooding analysis occurs in the small alleyway between the Fuel Building, the Auxiliary Building, and the Hot Machine Shop. Additional evaluation of flooding in this area may be performed as part of a focused LIP evaluation (NRC, 2015Sa).

Although the effects of wind-wave action in the powerblock area are screened out as a significant contributor to the LIP flood hazard, it is understood that small wind-waves could Wolf Creek Nuclear Operating Corporation VL-Flood Hazard Reevaluation Report Pae5Lo 0 145262/135031/15 Rev. 1 (October 21, 2015) Page,57 of 10

occur on the transient flows around buildings during a LIP event. Additionally, building settlement may lower the elevation of an entryway below the design value of 1,100 ft.

Therefore, a focused LIP evaluation (NRC, 201 5a) should consider any small differences Rev 1 between the stillwater levels and the plant floor elevation. This should be considered when evaluating the potential mitigation required for a LIP event.

Removing the unused rail tracks or modifying the grading of the site near safety-related structures may improve site drainage and could be considered during a focused LIP evaluation Rev 1 (NRC, 2015a).

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5.0 INTERIM EVALUATION AND ACTIONS Section 5. 0 has been prepared in response to Request for Information Item 1.d. of NRC Recommendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a): Provide an interim evaluation and actions taken or planned to address any higher flooding hazards relative to the design basis, prior to completion of an integrated assessment or focused LIP evaluation if/as Rev 1 required per the forthcoming guidance (NRC, 2015a).

5.1 EVALUATION OF THE IMPACT OF THE REEVALUATED FLOOD LEVELS ON STRUCTURES, SYSTEMS, AND COMPONENTS Except for flooding levels due to a LIP event, the flooding levels of all other potential flood-causing mechanisms, as presented in Section 3. 0, do not exceed the elevations of the exterior entrances of SSCs at the WCGS site. The design basis for the LIP event did not include hydrostatic and hydrodynamic loads because the maximum calculated water level near the Rev 1 safety-related buildings is 1,099.92 ft (WCNOC, 2015), which is below the plant floor elevation of 1,100 ft (WCNOC, 2015). However, the design basis did consider hydrostatic loads due to groundwater levels equivalent to plant grade.

For the reevaluation analysis, the most refined simulated conditions result in ponded water adjacent to Seismic Category I buildings with elevations above the plant floor elevation (1,100 ft) at several entrances. Additionally, water levels exceeded critical elevations at several manhole covers. The flood depths, associated durations, flow velocities, as well as hydrostatic and hydrodynamic forces that are computed in the reevaluation analysis are not bounded by the design basis LIP analysis. Water levels computed in the reevaluation indicate potential flow of water into Seismic Category I buildings. Debris loading and sedimentation during a LIP event were screened out in the reevaluation analysis.

5.2 ACTIONS TAKEN TO ADDRESS FLOOD HAZARDS NOT COMPLETELY BOUNDED BY THE CURRENT DESIGN BASIS HAZARD Request for Information Item 1.d. of NRC Recommendation 2.1 specifies that the flooding reevaluation contain an interim evaluation and actions taken or planned to address any higher flooding hazards relative to the design basis, if necessary (NRC, 2012a), prior to completion of Rev 1 an integrated assessment or focused LIP evaluation (NRC, 2015a).

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Based on the results of the site walkdowns and the indicated ponding levels during a LIP event (exceeding doorway entrance elevations and design hydrostatic loads), interim actions are necessary to preliminarily evaluate the need for mitigation (e.g., sand bags), while a focused LIP evaluation (NRC, 201 5a) is conducted to further evaluate the need for mitigation in the case of a Rev 1 LIP event.

The temporary mitigation measures for the interim action will consider parameters, such as the effect of small wind-waves (a few inches) that could occur on the transient flows around buildings during a LIP event and building settlement that may lower the elevation of an entryway below the design value of 1,100 ft. The focused LIP evaluation (NRC, 2015a) and interim measures to mitigate ponding during a LIP event will be tracked by Wolf Creek's corrective Rev I action program.

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6.0 ADDITIONAL ACTIONS Section 6.0 has been prepared in response to Request for Information Item i.e. of NRC Reconmmendation 2.1, Enclosure 2 of the 10 CFR 50.54(f) letter (NRC, 2012a): Provide additional actions beyond Request for Information item 1.d taken or planned to address flooding hazards, if any.

At this time, there are no additional actions beyond Request for Information Item 1.d. of NRC Recommendation 2.1 (Section 5.0) which have been taken or are planned to address flooding hazards at WCGS.

The plant response to the reevaluated LIP flood levels will be considered and evaluated in accordance with the forthcoming guidance (NRC, 2015a) from the NRC regarding closure of Rev 1 actions associated with Near-Term Task-Force Recommendation 2.1, Flooding.

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7.0 REFERENCES

1. American Nuclear Society (ANS), 1992, "Determining Design Basis Flooding at Power Reactor Sites," ANSI/ANS-2.8-1992, La Grange Park, Illinois.

2. Chow et al., 1988, Chow, Ven Te, David R. Maidment, and Larry Mays, "Applied Hydrology," McGraw-Hill Book Company, 1988.

3. Dean, R.G. and R.A. Dalrymple, 1991, "Water Wave Mechanics for Engineers and Scientists," World Scientific Publishing Co. Pte. Ltd., 1991.

4. Environmental Systems Research Institute (ESRI), 2009, ArcGIS ArcMap 9.3 Computer Program, 2009.

5. Environmental Systems Research Institute (ESRI), 2012, ArcGIS ArcMap 10.1 Computer program, 2012.

6. Environmental Systems Research Institute (ESRI), 201 3a, "US Topo Maps by National Geographic," Website: <http://goto.arcgisonline.com/maps/USATopoMaps>, Date Accessed: December 24, 2013.

7. Environmental Systems Research Institute (ESRI), 2013b, "World Street Map," Website:

<http ://goto.arcgisonline.com/maps/ World_StreetMap>, Date Accessed: December 24, 2013.

8. Environmental Systems Research Institute (ESRI), 2013 c, "ArcGIS Imagery," Website:

<http ://www. arcgis, com/home/item.html?id=a5 fef63 51 7cd4a099b43 7e5 5713 d3 d54>,

Date Accessed: October 18, 2013

9. Federal Emergency Management Agency (FEMA), 1996, "Flood Insurance Study, City of Burlington, Kansas, Coffey County, Community Number 200063," Revised:

September 20, 1996.

10. Federal Emergency Management Agency (FEMA), 2013, "Numerical Models Meeting the Minimum Requirement of National Flood Insurance Program," Website

<http ://www.fema.gov/national-flood-insurance-program-flood-hazard-mapping/numerical-models-meeting-minimum-requirement-0>, Date Accessed:

September 4, 2013.

11. FLO-2D Software, Inc. (FLO-2D), 2012, "FLO-2D Reference Manual," September 2012.

12. FLO-2D Software, Inc. (FLO-2D), 2014, "Revisions, Enhancements and Bug Fixes to the R[

FLO-2D Pro Model and Processor Programs Since October 1, 2012", March 2014. Rv Wolf Creek Nuclear Operating Corporation 1 .

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13. Kansas Biological Survey (KBS), 2010, "Bathymetric Survey of Wolf Creek Reservoir (Coffey County Lake), Coffey County, Kansas," Applied Science and Technology for Reservoir Assessment (ASTRA) Program, Report 2009-12 (December 2009), Revised January 2010.

14. Kansas Department of Agriculture (KDA), 2011, "Kansas Department of Agriculture Fact Sheet," Division of Water Resources, Water Structures Program, 2011.

15. National Oceanic and Atmospheric Administration (NOAA), 2013, National Geophysical Data Center, "Historical Tsunami Event Database," Website:

<http://www.ngdc.noaa.gov/hazard/ tsu_db.shtml>, Date Accessed: June 17, 2013.

16. National Weather Service (NWS), 1982, "Application of Probable Maximum Precipitation Estimates - United States East of the 1 0 5 th Meridian," Hvdrometeorological Report No. 52: August 1982.

17. Nuclear Regulatory Commission (NRC), 1 977, "Design Basis Floods for Nuclear Power Plants," Regulatory Guide 1.59, Revision 2, Washington, D.C., 1977.

18. Nuclear Regulatory Commission (NRC), 1996, "NRC Information Notice 96-3 6:

Degradation of Cooling Water Systems Due to Icing," Date of Publication: June 12, 1996, Website: <http ://www.nrc.gov/reading-rm/doc-collections/gen-commlinfo-notices/i1996/in9603 6.html>, Date Accessed: September 3, 2013.

19. Nuclear Regulatory Commission (NRC), 2009, "Tsunami Hazard Assessment at Nuclear Power Plant Sites in the United States of America," NUREG/CR-6966. PNNL-1 7397, NRC Job Code J3301, Washington, D.C., March 2009.

20. Nuclear Regulatory Commission (NRC), 2011, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America," NUREG/CR-7046, PNNL-20091, NRC Job Code N6575, Washington, D.C., November 2011.

21. Nuclear Regulatory Commission (NRC), 2012a, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," Washington, D.C., March 12, 2012.

22. Nuclear Regulatory Commission (NRC), 2012b, "The Estimation of Very-Low Probability Hurricane Storm Surges for Design and Licensing of Nuclear Power Plants in Coastal Areas," NUREG/CR-7 134, NRC Job Code N6676, Washington, D.C., October 2012.

23. Nuclear Regulatory Commission (NRC), 2012c, Guidance for Performing the Integrated Assessment for External Flooding," JLD-ISG-2012-05, NRC Interim Staff Guidance (ML12311A214), Washington, D.C., Revision 0, November 30, 2012.

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24. Nuclear Regulatory Commission (NRC), 2013a, "Wolf Creek Generating Station, Unit 1," Website: <http ://www.nrc.gov/info-finder/reactor/wc.html>, November 16, 2012.

Date accessed: August 9, 2013.

25. Nuclear Regulatory Commission (NRC), 2013b, "Guidance for Assessment of Flooding Hazards Due To Dam Failure," JLD-ISG-2013-01, NRC Interim Staff Guidance (ML13151A153), Washington, D.C., Revision 0, July 29, 2013.

26. Nuclear Regulatory Commission (NRC), 2013c, "Guidance for Performing a Tsunami, Surge, or Seiche Hazard Assessment," JLD-ISG-2012-06, NRC Interim Staff Guidance (ML12314A412), Washington, D.C., January 4, 2013.

27. Nuclear Regulatory Commission (NRC), 2015a, "Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for Beyond-Design-Basis External Events," Letter to Licensees (ML15174A257), September 1, 2015.

Rev 1

28. Nuclear Regulatory Commission (NRC), 2015b, "Closure Plan for the Reevaluation of Flooding Hazards for Operating Nuclear Power Plants," COMSECY- 15-0019 (ML15153A104), June 30, 2015.

29. Peinke et al., 2004, J. Peinke, S. Barth, F. Bottcher, D. Heinemann, and B. Lange, "Turbulence, a Challenging Problem for Wind Energy," Physica A, Volume 338 pp. 187-193, 2004.

30. United States Army Corps of Engineers (USACE), 1987, "11MR52 Probable Maximum Storm (Eastern United States) User's Manual," USACE, Davis, California, April 1987.

31. United States Army Corps of Engineers (USACE), 2002, "Engineering and Design, Ice Engineering," EM 1110-2-1612, Washington, D.C., October 30, 2002.

32. United States Army Corps of Engineers (USACE), 2004, "Ice Engineering, Method to Estimate River Thickness Based on Meteorological Data," ERDC/CRREL Technical Note 04-3, June 2004.

33. United States Army Corps of Engineers (UJSACE), 2008, "Coastal Engineering Manual,"

Engineer Manual 1110-2-1100, Washington, D.C., 2008.

34. United States Army Corps of Engineers (USACE), 2010a, "Hydrologic Engineering Center (HEC), HEC-HMS Version 3.5 Computer Program Build 1417, Release Date:

August 2010.

35. United States Army Corps of Engineers (USACE), 2010Ob, Hydrologic Engineering Center (HEC), HEC-RAS Version 4.1 Computer Program, Release Date: January 2010.

36. United States Army Corps of Engineers (USACE), 2013a, National Inventory of Dams, Website: <http://geo.usace.army.mil/pgis/tf?.p=397:1 :112429380233301>, Date Accessed: November 4, 2013.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Pg 4o 0 145262/135031/15 Rev. 1 (October 21, 2015) Page 6 of 10

37. United States Army Corps of Engineers (USACE), 2013b, "Ice Jams Database, Total Number of Events by River for the State of KS," Website:

<http ://rsgisias.crrel.usace.anmy.mil/apex/f?p=273 :39:748147269460901: :NO: :P3 9_STA ST:KS>, Date Accessed: June 19, 2013.

38. United States Geological Survey (USGS), 2012a, "The National Map US Topo New Strawn Quadrangle, Kansas-Coffey Co. 7.5-Minute Series," 2012.

39. United States Geological Survey (USGS), 2012b, "The National Map US Topo Burlington Quadrangle, Kansas-Coffey Co. 7.5-Minute Series," 2012.

40. United States Geological Survey (USGS), 2012c, "Earthquake Hazards Program," Date of Publication: November 1, 2012, Website:

<http://earthquake.usgs.gov/earthquakes/states/kansas/history.php>, Date Accessed:

June 19, 2013.

41. United States Geological Survey (USGS), 2013, "National Map Viewer and Download Platform," Website: <http://nationalmap.gov/viewer.html>, Date Accessed: June 27, 2013.

42. Wolf Creek Nuclear Operating Corporation (WCNOC), 2012, "Wolf Creek Nuclear Operating Corporation Post Fukushima Flooding Walkdown Report," Enclosure to ET 12-003 1, November 2012.

43. Wolf Creek Nuclear Operating Corporation (WCNOC), 2013, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 26, March 2013.

44. Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Rev I Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March 2015.

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TABLES Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report p 145262/135031/15 Rev. 1 (October 21, 2015) Page 66 of 105 kz1 l

TABLE 2-1: LIST OF POWERB3LOCK STRUCTURES AND THEIR ELEVATIONS STRUCTURE j T SAFETY-RLTD T I(t ELEVATION Auxiliary Building Yes 1,100.00 Communication Corridor No 1,100.00 Condensate Storage Tank, Pipe No/No 1,100.00 House Door Control Building Yes 1,100.00 Diesel Generator Building Yes 1,100.00 Emergency Fuel Oil Tanks and Ys1097 Access Vaults Ys1097 ESW Access Vaults (5) Yes 1,098.00 - 1,100.00 Rev I ESWS Manholes (10) Yes 1,097.00- 1,099.50 ESWS Pumphouse Pressure Doors Yes 1,100.00 Fuel Building Yes 1,100.00 Hot Machine Shop No 1,100.00 Radwaste Building No 1,100.00 Reactor Building, Tendon Gallery Yes!/No 1,100.27 Access Shaft Reactor Makeup Water Storage Tank, No/Yes 1,100.00 Valve House Door Refueling Water Storage Tank, Valve YsYs1100 House Door Turbine Building No 1,100.00 Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Page 67 of 105 F'E 145262/135031/15 Rev. 1 (October 21, 2015)

TABLE 2-2: EXISTING WOLF CREEK DESIGN PARAMETERS 1 Plant Grade Elevation DESIGN PARAMETER 1 VALUE 1,099.5 ft Top of Slab Elevation for Safety-Related Structures 1,100.0 ft Top of Wolf Creek Dam Elevation 1,100.0 ft Crest Elevation of Wolf Creek Dam Main Spiliway 1,088.0 ft Lowest Elevation of Exterior Entrances to any Safety- 1,097.0 ft Rev I Related Structure (ESWS manholes) _______________

Elevation of Service Water Intake Structure 2' 1,058.0 ft Top of UHS Baffle Dike 1,094.0 ft Top of Submerged UHS dam 1,070.0 ft Local Intense Precipitation 28.79 in (6-hr cumulative rainfall)

Probable Maximum Precipitation (for the watershed) 32.8 in (48-hr PMP)

Design Precipitation Rate for Roof Drainage 3 19 in (in one hr)

Maximum PMF Water Level at the Site, Including 1,095.8 ft Wave Run-up Maximum PMF Water Level at the ESWS 1102f Pumphouse, Including Wave Run-up 1102f Wind Speed for Wave Run-up 40 mph (overland)

LT-2 Notes:

1Maximum LIP flood levels for the powerbiock area are at or below 1,099.92 ft, which does not cause flooding Rev 1 into any safety-related SSCs. As a result, flood durations were not evaluated in the design basis.

2 h invert elevation of the sump of the ESWS pumphouse is 1,058.0 ft with a minimum design water surface elevation of 1,068.0 ft. The top of slab elevation of the operating deck of the ESWS facility is 1,100.0 ft. The pump discharge line leaving the pumphouse is at elevation 1,091.5 ft. The intake structure of the ESWS pumphouse is designed to withstand a water elevation of 1,102.5 ft.

3 h design basis reports maximum snow loads on roofs. The load of the 48-hr winter PMP is 103.0, 98.8, 111.3, and 127.9 lb/ft 2 for the months of December, January, February, and March, respectively (WCNOC, 2015, Rev 1 Section 2.4.2.3.3). Note also that rainfall in excess of 7.4 inches per hour would (by design) overflow the roof curb and the building walls to the site drainage system (WCNOC, 2015; Section 2.4.2.3).

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Rev 1 Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March 2015.

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TABLE 2-3: CURRENT DESIGN BASIS FLOOD ELEVATIONS DUE TO ALL FLOOD MECHANISMS 1 FLOODING MECHANISM Local Intense Precipitation

]WATER LEVEL (ft) 1,099.92 2- Rev 1 Lake Flooding 1,095.00

• Combined-Effects Flooding1,9.0/,0.24 (WCGS ShorelineiESWS Pumphouse)1,9.0/,0.2 Dam Failure Flooding on the Neosho River 1,044.55 5 Storm Surge and Seiche Flooding N/A 6 Tsunami Flooding N/A 6 Ice Flooding N/A 6 Channel Diversion Flooding N/A 6 LT-3 Notes:

SConsistent with 10 CFR 54.3, the Current Design Basis (CDB) information (as defined in 10 CFR 50.2) is included within the Current Licensing Basis (CLB) documented in the USAR (WCNOC, 2015). The CLB and CDB flood levels are equivalent. Rev 1 2 The highest estimated water level resulting from a LIP event is 1,099.92 ft, calculated near the safety-related buildings in the powerblock area (WCNOC, 2015).

SThe maximum PMvF water level in Wolf Creek Lake is 1,095.00 ft. This stillwater level is assumed to be constant across the lake.

4 obnd-fet Flooding includes PMIF flooding preceded by a standard project flood event (50 percent of PMiP) and wave run-up. The water level of 1,095.80 ft includes the maximum wind-wave run-up at the WCGS shoreline. The maximum water level, including wave run-up, at the ESWS pumphouse is 1,100.20 ft (WCNOC, Rev 1 2015, Section 2.4.10).

5Awater level of 1,044.55 ft is reported for the confluence of the Wolf Creek with the Neosho River, based on an unsteady flow model simulating a domino-type failure of the John Redmond, Council Grove, Cedar Point, and Marion Dams with standard project floods (50 percent of PMP).

6 NA= Not Applicable.

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March Rev 1 2015.

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S.I

TABLE 3-1: WATER LEVELS AND PONDING DEPTHS DUE TO LOCAL INTENSE PRECIPITATION PEAK PONDING FODHIH BULIGSAFETY- WATER BULIGRELATED?9 ELEVATION ABOVE 1,100 FT (ft) (ft)

Auxiliary Building Yes 1,100.38 0.38 Communications Corridor No 1,100.25 0.25 Condensate Storage Tank No 1,100.37 0.37 Control Building Yes 1,100.35 0.35 Demineralized Water Storage Tank No 1,100.37 0.37 Diesel Generator Building Yes 1,100.03 0.03 Fuel Building Yes 1,100.35 0.35 Hot Machine Shop No 1,100.35 0.35 Rev 1 Radwaste Building No 1,099.91 Reactor Building Yes 1,100.38 0.38 Reactor Makeup Water Storage Tank No 1,099.90 Refueling Water Storage Tank Yes 1,100.12 0.12 Turbine Building No 1,100.47 0.47 LT-4 Wolf Flood creek HazardNuclear Operating Corporation Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 70 of 105 KI*

TABLE 3-2: LOCAL INTENSE PRECIPITATION FLOODING AT DOORS TO SEISMIC CATEGORY I BUILDINGS GROUND TIlRESDIOLD MAXIMUM FLOOD MAXIMUM DURATION2 MAXIMUM MAXIMUM 3 MAXIMUM 3 DOOR NUMBER'! ASSET NUMBER STRUCTURE DESCRIPTION ELEVATION ELEVATION ELEVATION DEPTII OF FLOOD VELOCITY HYDROSTATIC FORCE HYDRODYNAMIC FORCE (ft) fit) (ft) (ft) (hours) (ft/s) (Ib/ft) (Ib/ft) 1 1195/I1198 Auxiliary Building Door

________ ________ (Pressure Door/Alcove Door) 1,099.33 1,100.00 1,100.35 1.01 0.5 123 2 13011 Auxiliary Building Door1,9.0 110010996.2 OO1583

__________ _________ (Missile Door) 1,099.40 1,100.0 1,099.960.52_<0.5_1.5_8_

3 13012/13013 Auxiliary Building Door 19.4 10.010.306 . . 11

_________(Pressure Door/Alcove Door) 1,099.44 1,100.0 1,100.3_0.600.2_2._11_1 4 33031 ~Communication Corridor 33031______(Double Door/Hollow Core Door) 072 1,098.98 1,100.00 1,100.05 0.89 1.0 072 302 Communication Corridor 1093 ,0.01100 .907071 33042______(Roll Up Door) 1093 ,0.01100 .907071 6 33043 Communication Corridor 1093 ,0.01100 .509092

________(Hollow Core Door) 1,099_0_1,00.0 1,100.8_0.8_0.9_09_22_

7 32013/32018 Control Building ,096 110.0,1 .4036.01.8 4 3 (Pressure Door/Alcove Door)1,9.0 ,0.011004.300 8 52011 Diesel Generator Building 1,099.35 1,100.00 1,099.90 0.57 0.1 2.8 10 10

_____________________________ (Missile Door)_________________________

9 52031 Diesel Generator Building 1091 ,0.01099 .405161 (Missile Door) 1,09.7_,10.0_,09.9_0640._16_3_

Rev1 10 61011 Fuel Building1,9.7 110010981.010 (Hollow Core Door) 1090 1,0.0,9.8070.01.7 15 5 11 61021 Fuel Building1.82

________ ________ (Hollow Core Door) 1,099.36 1,100.00 1,099.56 0.50 0.11.82 12 61022 Fuel Building0.51

_________(Roll Up Door) 1,099.58 1,100.00 1,100.05 0.41 0.00.51 13 13342 Hot Machine Shop 1090 1,0.0,1.8091.62326 11 (Hollow Core Door)1,9.0 11001,018.10623 14 13321 Hot Machine Shop 1092 1,0.0,9.2061.40.9 12I (Hollow Core Door)1,9.9 110010992.604 15132 Hot Machine Shop 1,099.32 1,100.00 1,099.94 0.61 0.1 121 15 13322 ~~~(Roll Up Door) _______________

16 16402 43092 ~ Stair T-2 (Hollow Core Door) 1,099.35 1,100.00 1,100.09 0.70 0.5 101 101 17 4102 Stair T-3 17______43102_______ (Hollow Core Door) 1,099.35 1,100.00 1,100.10 0.72 0.5 1.0 16 1 LT-12 Notes:

SSome of these doors are to non-Seismic Category I buildings that have entrances to Seismic Category I buildings behind them. The ESWS sod pumphouse and miscellaneous yard buildings are not included in this table.

2 Flooding duration was computed based sos threshold depth of 0.5 ft.

3 Hydrostatie and hydrodynamie forces are reported in force per unit1width. Multiplying the reported forces by the width of a structure or wall provides the total force exerted on the wall. Hydrodynamie forces set in the direction of flow velocity. Consequently, the reported hydrodynamic forces should be interpreted as a conservative estimate. In eases where flow velocity is directed away from the building or tank (i.e., off the roof and sway fr'om the building or tank), the hydrodynamic force acting on the door is zero.

Wolf Cseck Flood HlazrdNuclear Operating Reevalutions Corporation Report 1452621135531/15 Rev. 1 (Ootober 21, 2515) Page 7t or105

TABLE 3-3: LOCAL INTENSE PRECIPITATION FLOODING AT OTHER DOORS, HATCHES, MANHOLES, AND VAULTS FOR SAFETY-RELATED SSCs GRONDTHESHLD MAIMM FOO MXIUM LOD URTIO MXIUM MAXIMUM MAXIMUM ITEM'l ASSET GRUDTRSOD MXMM3OD MXMMFOD DRTO AIU HYDROSTATIC 4 HYDRODYNAMIC 4 NUMBER STRUCTURE DESCRIPTION ELEVATION ELEVATION ELEVATION DEPTH OF FLOOD 3 VELOCITY .FORCE FORCE (ft) (ft) (ft) (ft) (hours) (flI second) (lb/ft) (lb/ft)

I 91011 Condensate Storage Tank Pipe HousetDoor 1,099.31 1,1I00.00 1,100.37 1.06 1.8 1.0 35 1 2 Z055 Emergency Fuel Oil Tanks and Access Vaults 1,099.51 1,099.75 1,099.78 0.31 0.0 0.5 3 <1 7 MHEIA ESWS Manhole 2 1,099.53 1,099.50 1,099.92 0.47 0.0 0.5 7 <1 8 MHEIB ESWS Manhole 2 1,099.57 1,099.50 1,099.93 0.35 0.0 0.5 4 <1 9 MHE2A ESWS Manhole'2 1,097.51 1,098.00 1,097.73 0.22 0.0 0.7 1 <1 2

10 MHE2B ESWS Manhole 1,097.80 1,098.00 1,097.78 0.13 0.0 0.3 <1 <1 i11 MI-E3A ESWS Manhole 2 1,097.03 1,097.00 1,097.51 0.19 0.0 0.4 1 <1 2

12 MHE3B ESWS Manhole 1,097.11 1,097.00 1,097.51 0.19 0.0 0.4 1 <1 13 MHE4A ESWS Manhole'2 1,096.79 1,097.00 1,097.73 0.83 1.4 2.2 22 9 14 MHE4B ESWS Manhole 1,096.89 1,097.00 1,097.73 0.83 1.4 2.2 22 9 15 MHE5A ESWS Manhole'2 1,097.23 1,097.75 1,098.29 1.43 10.0 0.6 64 <1 16 MHE5B ESWS Manhole 2 1,097.29 1,097.75 1,098.29 1.43 10.0 0.6 64 <1 17 KI051 ESWS Pumphouse Pressure Door A 1,099.34 1,100.00 1,099.49 0.11 0.0 0.8 <1 <1 18 KI041 ESWS Pamphouse Pressure Door B 1,099.54 1,100.00 1,099.79 0.17 0.0 0.4 <1 <1 21 N/A Reactor Building Tendon Gallery Access'Shaft 1,099.22 1,1I00.27 1,100.23 1.09 6.4 0.7 37 <I Rev I 22 91031 Reactor Makeup Water Storage Tank Valve House Door 1,099.34 1,1I00.00 1,099.86 0.53 <0.05 1.7 9 3 23 91021 Refueling Water Storage Tank Valve House Door 1,099.18 1,100.00 1,099.93 0.74 0.9 3.4 17 20 24 N/A ESW Vertical Loop Chase 1,099.58 1,100.50 1,100.29 0.94 1.1 0.8 28 <1 25 AVI IESW Access Vault 1,098.59 1,100.00 1,099.39 1.00 5.8 1.3 31 2 26 AV2 ESW Access Vault 1,096.62 1,098.00 1,097.34 0.65 1.1I 4.0 13 25 27 AV3 ESW Access Vault 1,098.87 1,099.50 1,099.55 0.44 0.0 1.2 6 1 28 AV4 ESW Access Vault 1,097.86 1,098.50 1,098.28 0.73 1.9 2.5 17 8 29 AV5 ESW Access Vault 1,098.09 1,098.50 1,099.19 0.44 0.0 1.2 6 1 LT-10 Notes:

SSeveral items have been abandoned in place due to the site projects. These items have been removed fr'om the table and new items have been added for Rev. 1 of the FHRR. Therefore, several item numbers in the above table are skipped in order for numbering to align with prior analyses.

' Items 7 through 16 (the ESWS Manholes) are designed to be watertight, as discussed in the Wolf Creek Nnclear OperatingCorporationPost FukushirnaFlooding Walkdow'n Report (WCNOC, 2012).

SFlooding duration was computed based on a threshold depth of 0.5 ft.

4Hydrostatic and hydrodynamic forces ure reported in force per unit width. Multiplying the reported forces by the width of a stracture or wall provides the total force exerted on the wall. Hydrodynamnic forces act in the direction of flow velocity. Consequently, the reported hydrodynamic forces should be interpreted as a conscrvative estimate. In cases where flow velocity is directed away from the building or tank (i.e., off the roof and away from the building or tank), the hydrodynatnic force acting on the door is zero

Reference:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2012, "Wolf Creek Nuclear Operating Corporation Post Fukushima Flooding Walkdown Report," Enclosure to ET 12-0031, November 2012.

Wolfrck Nuclear OperatingCoq~oaution Flood HacardRceavaluaion Rcportae72o t 145262/135031/I15 Res. i (Otoaber 21. 2015) Pg 2o 0

TABLE 3-4: WATERSHED SUBBASIN CHARACTERISTICS AND HEC-HMS MODELING RESULTS DANG ARA RUNOFF LA IE2 PRECIPITATION PEAK 4 DRBASINAG AmiEA LAGRTIM DEPTH 3 RUNOFF SU AI m) NUMBER I (Minutes) (in) (cfs)

SB1 7.035 92 47.30 36.70 50,817 SB2 2.470 90 31.05 36.70 21,131 SB3 1.934 85 44.77 36.70 14,246 SB4 16.250 92 23.08 36.70 151,880 SB5 3.450 82 85.97 36.70 17,932 LT-5 Notes:

SSCS Runoff Curve Number after calibration 2Lag time after calibration and reduction by 33 percent to account for nonlinearity effects in accordance with guidance in NRC N1UREG/CR-7046.

3Precipitation depth is for the 72-hr PMv~P.

" Runoff hydrograph ordinates from HEC-HMS output are increased by five percent for Case 5.

Reference:

Nuclear Regulatory Commission (NRC), 2011, "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America," NUREG/CR-7046. PNNL-20091, NRC Job Code N6575, Washington, D.C., November 2011.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 73 of 105

TABLE 3-5:

SUMMARY

OF HIEC-HMS AND HEC-RAS SIMULATION CASES CASE 1RAINFALL ILOSSESICHANNELS RUNOFF TRANSFORMATION RUIG TRUH NONLINEARITY EFFECTS PERCENT SPILL WAY SEI NT IO 1Ys/o (YES/NO) (YES/NO) (YES/NO) (YES/NO) 1 BLOCKED (E/O

__________________HEC-HMS Modeling _______

1 No No No No 0 No 2 No Yes Yes No 03 ~ No 3 No Yes Yes Yes 0 No 4 Yes Yes Yes Yes 0 3*Y No 5 Yes Yes No Yes 03 No HEC-RAS Modeling 1 No No No No 0 No 2 No Yes Yes No 0 No 3 No Yes Yes Yes 0 No 4 Yes Yes Yes Yes 03No 5 Yes Yes No Yes 0 No 6 Yes Yes No Yes 0 No 7 Yes Yes No Yes 50/10 No 8 Yes Yes No Yes 2/04No 9 Yes Yes No Yes 1/04No 10 Yes Yes No Yes 0 Yes LT-6 Notes:

' Nonlinearity effects include a decrease in lag time by 33 percent, and an increase in peak discharge. A five percent increase in discharge is used for Case 5 results as input into the HEC-RAS model.

2 Routing through channels is not used in HEC-HMS Cases 1 and 5. However, channels are represented in the HEC-RAS simulations. HEC-HMS simulated discharge from subbasins is used in the HEC-RAS simulations to avoid the potential of double accounting for delays in flow through channels.

SThe spillways are assumed to be unobstructed.

4"The first number is the percent of the service spillway that is blocked. The second number is the percent of the auxiliary spiliway that is blocked.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Page 74 of 105 U, d 145262/135031/15 Rev. 1 (October 21, 2015)

TABLE 4-1: COMPARISON OF MODELING APPROACHES FOR 1CURRENT LICENSING BASIS AND FLOODING REEVALUATION ANALYSIS CONSIDERATION REEVALUATED HAZARDS CURRENT LICENSING BASIS Local Intense Precipitation Calculation based on HMVR No. 52 Calculation based on HMR No. 52 (LIP) values values LIP Flooding Characterization FLO-2D Model USACE HEC-RAS PMP for the Wolf Creek Calculation based on HMR No. 52 Calculation based on HMR No. 33 Watershed values values PMP Rainfall Hyetograph Time period of 72 hrs with 48 hrs with 1-hr increments 5-minute increments HEC-HMS was not used for the USAR analysis. The USACE Rainfall-Runoff Model USACE HEC-HMS developed 1-hr Snyder unit hydrographs for 3 subbasins scaled from the Neosho River watershed.

Transformation Method SCS Synthetic Unit Hydrograph SndrsUiHyogahMtd MethodSndrsUiHyrgahMto PMFlos, tanforatin, nd Include loss, transformation, and Include loss and transformation, PMrossutasfratogn routing through the channels and with routing through Wolf Creek ruigthrough Wolf Creek Lake and dam. Lake and dam River Hydraulic Model USACE HEC-RAS USACE Water Surface Profiles 2 The Tennessee Valley Authority The Mthodwasuse olue to Software was used to compute the determine the water surface Dam Break Flooding elvto nNoh ie tte water surface elevation at the Wolf elevtio onNeoho ive atthe Creek confluence with the Neosho Wolf Creek confluence. Rvr Combined Effects Flooding ANSRECR992 anthds ANS, 1976 method LT-8 Notes:

SDue to changes in regulatory requirements since the original design basis, some of the mechanisms considered and the methodologies used in the reevaluation analysis are different from the original design basis analysis. Therefore direct comparison is not practicable in all cases.

2 Stated in USAR Section 2.4.3.5 (WCNOC, 2015). Rev 1

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March Rev 1 2015.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report Page 75 of 105 IF-145262/135031/15 Rev. 1 (October 21,2015)

TABLE 4-2: COMPARISON OF CURRENT LICENSING BASIS AND) FLOODING REEVALUATION ANALYTICAL INPUTS ANALYTICAL INPUT REVALUATED HAZARDS CURRENT LICENSING BASIS Local Intense Precipitation 19.0 in 19.0 in (1-hr, 1 mi2 value)

Probable Maximum PrcpttinfrWaese'36.70 in (72-hr PMP) 32.80 in (48-hr PMP)

Wolf Creek Lake Dam outflow: Wolf Creek Lake Dam outflow:

Input for River Hydraulics 23,813 cfs 22,845 cfs Model Wolf Creek Lake inflow: Wolf Creek Lake inflow:

215,128 cfs 82,089 cfs Spillway Elevations for Wolf Creek Lake Dam1,8.f!1,9.ft10.0t/,9.5t (Service /Auxiliary1,8.ft1005f1,80f/,9.5t Spillways)

Maximum Sustained Overland 10-minute, 2-year 38.65 mph 40.00 mph 2 Wind Speed Maximum Sustained Overwater 10-minute, 2-year 46.38 mph 1 Not computed Wind Speed _______________ ______________

LT-9 Notes:

' The maximum storm duration of HMR No. 33 (used in the design basis) is 48 hrs and the maximum storm duration of HMR No. 52 (used for the reevaluation analysis) is 72 hrs.

2 Wind speed used for wave height calculation.

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March Rev I 2015.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report FE 145262/135031/15 Rev. 1 (October 21, 2015) Page 76 of 105

~J1

TABLE 4-3: COMPARISON OF CURRENT LICENSING BASIS AND REEVALUATED FLOOD LEVELS 1 REEVALUATED WATER CURRENT LICENSING BASIS FLOODING MECHANISM LEVEL WATER LEVEL (ft) (ft)

Flooding Due2 to Local Intense Precipitation 1,100.38 1,099.92 Rev 1 Lake Flooding Due to PMF 1,093.54 1,095.00 Wave Run-up Coincident with Stillwater level + Stillwater level +

PMF Wave Run-up Wave Run-up WCGS Shoreline 1,094.37 1,095.8 ESWS Pumphouse 1,098.43 1,100.2 1,076.70 ft on the Neosho River at confluence of Wolf 1,044.55 ft on the Neosho Creek based on River at confluence of Wolf Dam Failure Flooding Instantaneous Transport of Creek based on dynamic Reservoir Storage (Volume modeling Screening Method)

Storm Surge and Seiche Flooding Dismissed Dismissed Tsunami Flooding Dismissed Dismissed Ice Flooding Dismissed Dismissed Channel Diversion Flooding Dismissed Dismissed Combined-Effects Flooding3 500-yr rainfall + PMP + SPF + PMP + Wave Run-up Wave Run-up WCGS Shoreline 1,095.46 1,095.80 ESWS Pumphouse 4 1,099.52 1,100.20 LT-7 Notes:

Consistent with 10 CFR 54.3, the Current Design Basis (CDB) information (as defined in 10 CFR 50.2) is included within the Current Licensing Basis (CLB) documented in the USAR (WCNOC, 2015). The CLB and CDB flood Rev 1 levels are equivalent.

2 The values reported are the highest water levels adjacent to safety-related buildings on the powerbiock.

SPMP = Probable Maximum Precipitation, SPF = Standard Project Flood = 50 percent PMP.

4 h intake structure for the ESWS Pumphouse is designed to withstand a high water elevation of 1, 102.50 ft (WCNOC, 2015, Section 2.4.10). Revi1

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit 1, Revision 28, March Rev 1 2015.

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 77 of 105 U,> Ii

TABLE 4-4: COMPARISON OF VARIOUS FLOODING PARAMETERS BETWEEN THE CURRENT LICENSING BASIS AND THE FLOOD REEVALUATION FLOOD CONDITION REEVALUATED FLOOD HZR fCURRENT LICENSING AI Local Intense Precipitation Flood Depth 1.43 ft 1 0.42 ft 2 Flood Duration 10.0 hrs i N/A 3 Maximum Flow Velocity 4.0 ft/s 4 N/A 3 Rev 1 Hydrostatic Loading 64 lb/ft 1 N/A 3 Hydrodynamic Loading 25 lb/ft 4 NA3 Debris Impact Loading Debris Screened Out 5 N/A 3 Flood Elevation with Sedimentation Sedimentation Screened Out 6 N/A 3 Probable Maximum Flood Flood Elevation 1,093.54 ft 7 1,095.0 ft 7 ,'

Flood Duration N/A 9 N/A 3 Maximum Flow Velocity N/A 9 N/A 3 Hydrostatic Loading 39,409 lb/ft 10 42,713 lb/ft"1 Hydrodynamic Loading N/A 12 N/A 3' 11 Flood Elevation with Debris/Spillway 1,094.37 ft 13 N/A 3 Blockage Flood Elevation with Sedimentation 1,093.54 ft 7 N/A 3, 14 Combined-Effects Flooding Flood Elevation 15 1,095.46/1,099.52 ft 1,095.8/1,100.2 ft Flood Duration N/A 9 N/A 3 Maximum Flow Velocity N/A 9 N/A 3 Hydrostatic Loading N/A 16 N/A 3' 16 Hydrodynamic Loading N/A 12 N/A 3, 16 LT- 11 Notes:

1 Simulated values at ESWS Manholes MHTE5A and MHE5B (Table 3-3, Items 15 and 16).

2 This flood depth results in a maximum water elevation of 1,099.92 ft, which does not flood any safety-related SSCs (WCNOC, 2015).

Rev 1 3These parameters are not included in the CLB.

4~Maximum simulated value at ESW Access Vault AV2 (Table 3-3, Item 33).

Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report p-145262/135031/15 Rev. 1 (October 21, 2015) Page 78 of 105

TABLE 4-4: COMPARISON OF VARIOUS FLOODING PARAMETERS BETWEEN TILE CURRENT LICENSING BASIS AND THE FLOOD REEVALUATION (CONTINUED) 5 These forces are screened out due to simulated low velocities and flow directions away fr'om safety-related SSCs.

SThe potential for increased flooding due to sedimentation was screened out due to negligible sediment source area Rv1 and low velocities limiting scour.

7 The peak stage simulated for Wolf Creek Lake, not including the effects of wind-waves.

8 The CLB value is from the USAR (WCNOC, 2015, Table 2.4-16).

Rev 1 9 Safety-related SSCs are not flooded, so these flooding affects are not applicable.

• 0 Hydrostatic forces are computed for the ESWS pumphouse only. This force is a depth-integrated force for the ESWS pumphouse from the stillwater level down to the bottom of the ESWS pumphouse (elevation 1058.0 fi).

• 1Although no values are reported in the current version of the USAR (WCNOC, 2015), the Design Basis analysis for the pumphouse reports a hydrostatic force of 42,713 lb/fl, corresponding to a lake level of 1095.0 ft. The Design Rev 1 Basis analysis also screens out hydrodynamic loads due to the stagnant nature of Wolf Creek Lake.

12Hydrodynamic forces are not applicable to the ESWS pumphouse because adjacent water is stagnant (i.e., Wolf Creek Lake). Hydrodynamic forces due to wind-waves are not computed in the reevaluation because wind-wave run-up levels in the reevaluation are bounded by the CLB run-up levels (1100.2 ft; WCNOC, 2015, Section 2.4.10). Rev 1 13 This is the peak stage simulated for Wolf Creek Lake with ten percent of the auxiliary and service spillways blocked.

14 The maximum fill over a period of 40-years is provided in the USAR (WCNOC, 2015).

15 The two flood elevations correspond to the lake shoreline and the pumphouse, respectively. Flood elevations for both locations include wind-wave effects. Rev 1 16The intake structure of the ESWS pumphouse can withstand a water elevation of 1,102.5 ft (WCNOC, 2015, Section 2.4.10).

References:

Wolf Creek Nuclear Operating Corporation (WCNOC), 2015, "Updated Safety Analysis Report (USAR)," Wolf Creek Generating Station (WCGS) Unit i, Revision 28, March Rev 1 2015.

Wolf Creek Nuclear Operating Corporation * ,*

Flood Hazard Reevaluation Report Pg 9o 0 145262/135031/1 5 Rev. 1 (October 21, 2015) Pag.7 of10

FIGURE S Wolf Creek Nuclear Operating Corporation p5 Flood Hazard Reevaluation Report 145262/135031I/15 Rev. i (October 21, 2015) Page 80 of 105 r~j

U Coordinate System: NAD 1983 State Plane Kansas South FIPS 1502 Feet Legend Projection: Lambert Conformal Conic l

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'*" Kansas City 25* 12.5 0 25 50 Miles RF: 1:1,166,670 A Wolf Creek Generating Station

+' Airport General Location of the Site PREPARED FOR River/Stream i Highways Wolf Creek Flood Hazard StateRoads

Reference:

Reevaluation Report Stte RadsBackgrounc

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Reference:

Image Source: ESRI 2013a. Environmental Systems Research Institute Flood Hazard Reevaluation Report (ESRI), "US Topo Maps by National Geographic".

Website: httpJ/goto.arcgisonline.comlmapslUSA.jUopo..Maps Date Accesed December24, 2013 R3' ENGINEERS Paul Associates, /Inc.

/CONSULTANTS C. Rizzo CM Page 82 of 105

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LEGEND: NOTE.

BACKGROUND IMAGE MODIFIED

1. AUXILIARY BUILDING

2. COMMUNICATION CORRIDOR FROM: GOOGLE EARTH, 2013.

3. CONDENSATE STORAGE TANK

4. CONTROL BUILDING SCALE

5. DIESEL GENERATOR BUILDING

6. EMERGENCY FUEL OIL TANKS 100 0 100 FEET

7. FUEL BUILDING

8. HOT MACHINE SHOP

9. RADWASTE BUILDING FIGURE 2-3

10. REACTOR BUILDING LOCATIONS OF BUILDINGS 1 1. REACTOR MAKE-UP WATER STORAGE TANK

12. REFUELING WATER STORAGE TANK IN THE POWERBLOCK AREA

13. TURBINE BUILDING PREPARED FOR WOLF CREEK FLOOD HAZARD REEVALUATION REPORT A REMOVED CALL-OUT FOR ESWS VALVE HOUSE [-IIN* Paul C. Rizzo Associates, Inc.

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WOLF CREEK GENERATING STATION WOLF CREEK LAKE WATER DEPTHS PREPARED FOR WOLF CREEK KANSAS BIOLOGICAL SURVEY, 2010, "BATHYMETRIC FLOOD HAZARD REEVALUATION REPORT SURVEY COUNTY REPORT OF WOLF CREEK RESERVOIR (COFFEY LAKE), COFFEY COUNTY, KANSAS,"

2009-12 (REVISED JANUARY 2010).

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Reference:

Image Source: ESRI 2013a, Environmental Systems Research Institute (ESRI), "US Topo Maps by National Geographic".

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FLOOD HAZARD REEVALUATION REPORT THE TIME INCREMENT OF HYETOGRAPH IS FIVE MINUTES.

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WOLF CREEK FLOOD HAZARD REEVALUATION REPORT TIM [QPaul C. Rizzo Associates, Inc.

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DATE ACCESSED: JUNE 27, 201.3. WOLF CREEK

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W-- Neosho Watershed Neosho Watershed Dams Lii WCGS - WOLF CREEK GENERATING STATION

REFERENCES:

1. IMAGE SOURCE: ESRI, 2013c, ENVIRONMENTAL SYSTEMS RESEARCH INSTITUTE (ESRI), "ARCGIS IMAGERY,"

WEBSITE: <http://www.orcgis.com/home/

item.html?id =a5fef635 17cd4aO99b437e557 13d3d54>,

DATE ACCESSED: OCTOBER 18, 2013.

2. HUC BASIN SOURCE: USGS, 2013.

UNITED STATES GEOLOGICAL SURVEY (USGS), "NATIONAL MAP VIEWER AND FIGURE 3-12 DOWNLOAD PLATFORM," WEBSITE:

<http://viewer.nationalmap.gov/viewer/>, LOCATION OF DAMS NEAR THE SITE DATE ACCESSED: JUNE 27, 2013.

PREPARED FOR

3. USACE, 201.3a, UNITED STATES ARMY CORPS OF ENGINEERS (USACE),

NATIONAL INVENTORY OF DAMS, WEBSITE: WOLF CREEK

< http//geo.usace.army.mil/pgis/

FLOOD HAZARD REEVALUATION REPORT f?p=397: 1 :112429380233301 :::::>,

DATE ACCESSED: NOVEMBER 4, 2013.

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IMAGE SOURCE: ESRI, 2013c, WOLF CREEK ENVIRONMENTAL SYSTEMS RESEARCH FLOOD HAZARD REEVALUATION REPORT INSTITUTE (ESRI), "ARCOIS IMAGERY,"

WEBSITE: <http://www.arcgis.com/home/

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DATE ACCESSED: OCTOBER 18, 2013. ENGINEERS / CONSULTANTS / CM Page 101 of 105

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I I .... - I BY I 012Q14 I APPPA\VFf RY I ,JML I-%-1 CA) IFILE 13-5031 -A22 Beginning of Rainfall Flooding Deeper Than 0.5 ft Flood Depths 3 Near Doors to End of Rainfall (Peak Rainfall Intensity) at Some Doors to Safety- Safety-related Buildings on the Related Buildings on the Powerblock Are Below 0.5 ft Powerblock 3 i i) i)

Initiation of Site Recession of Preparation Period of Inundation 2 Water from Site Procedures 1

+ _____

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6

, <5 minutes Flooding Event Time (hours)

NOTES:

1. NRC JLD-ISG-201 2 (NRC, 201 2C) USES THE PHRASE "SITE PREPARATION FOR FLOOD EVENTS" FOR CONDITIONS THAT, WHEN MET. INITIATE FLOOD PROCEDURES OR NOTIFICATION OF IMPENDING FLOOD. A MORE GENERAL TERM OF "INITIATION OF SITE FIGURE 4-1 PREPARATION PROCEDURES" IS USED HERE.

2. THE TIMING OF FLOOD DEPTHS AT EACH DOOR IS UNIQUE. THE TIMES INDICATED ARE DURATION OF FLOODING FOR INTENDED TO BE REPRESENTATIVE AND BOUNDING OF THE DURATION OF FLOODING.

THE LIP FLOOD ANALYSIS

3. 0.5 FT REPRESENTS THE DIFFERENCE BETWEEN THE GRADE ELEVATION (1,099.5 Fr)

AND THE FLOOR ELEVATION (1,100 FT) FOR BUILDINGS ON THE POWERBLOCK. PREPARED FOR WOLF CREEK FLOOD HAZARD REEVALUATION REPORT NUCLEAR REGULATORY COMMISSION (NRC), 2012C, "GUIDANCE FOR PERFORMING THE INTEGRATED ASSESSMENT FOR EXTERNAL FLOODING," JLD-ISG-2012-05, NRC INTERIM STAFF GUIDANCE (ML12311A214), WASHINGTON DC, REVISION 0, NOVEMBER 30, 2012.

[Q Pau~l C.'Rzz°-Asso-ciates_-Inc" ENGINEERS / CONSULTANTS / CM Pa~e 102 of 105

APPENDIX A FLO-2D PRO SOFTWARE QUALIFICATIONS Wolf Creek Nuclear Operating Corporation Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 103 of 105

~22J

FLO-2D PRO MODELING SOFTWARE QUALIFICATIONS The FLO-2D Pro computer program was developed by FLO-2D Software, Inc., Nutrioso, Arizona. FLO-2D Pro is a combined two-dimensional (2D) hydrologic and hydraulic model that is designed to simulate river overbank flows, as well as unconfined flows over complex topography and variable roughness, split channel flows, and urban flooding. FLO-2D is a FEMA-approved software (FLO-2D, 2012). FLO-2D Pro is a physical process model that routes rainfall-runoff and flood hydrographs over unconfined flow surfaces using the dynamic wave approximation to the momentum equation. The model has components to simulate riverine flow, including flow through culverts, street flow, buildings and obstructions, levees, sediment transport, spatially variable rainfall and infiltration and floodways.

Application of the model requires knowledge of the site, the watershed, and engineering judgment. This software has been used to simulate local intense precipitation, propagation of storm surge, seiches, and riverine flow through overland flow and channels to establish stillwater levels at various flood hazard reevaluation project sites.

The major design inputs to the FLO-2D Pro computer model are digital terrain model of the land surface, inflow hydrographs, and/or rainfall data, Manning's roughness coefficient, and soil hydrologic properties, such as the SCS curve number. The digital terrain model of the land surface is used in creating the elevation grid system over which flow is routed. The specific design inputs depend on the modeling purpose and the level of detail that is desired.

This FLO-2D Pro Overland Flow component simulates overland flow and computes flow depth, velocities, impact forces, static pressure, and specific energy for each grid. Predicted flow depth and velocity between grid elements represent average hydraulic flow conditions computed for a small time step. For unconfined overland flow, FLO-2D applies the equations of motion to compute the average flow velocity across a grid element (cell) boundary.

By using a 2D model, floodwater is routed in a natural manner without being "forced" to flow in predefined directions. This allows for a more accurate flood analysis than is possible with one-dimensional (iD) models. The FLO-2D Reference Manual (FLO-2D, 2012) describes the FLO-2D model as follows: "FLO-2D is a physical process model that routes rainfall-runoff and flood hydrographs over unconfined flow surfaces or in channels using the dynamic wave Wolf Creek Nuclear Operating Corporation F L>

Flood Hazard Reevaluation Report 145262/135031/15 Rev. 1 (October 21, 2015) Page 104 of 105 **_1

approximation to the momentum equation." Additionally, the FLO-2D Basic model is approved by FEMA for use in Flood Insurance Studies (FEMA, 2013; FLO-2D, 2012).

NRC JLD-ISG-2013-01 (NRC, 2013a) provides guidance for dam failure analysis. Within this guidance, the NRC comments about the advantages of 2D modeling methodologies. These comments, though directed towards dam failure modeling within the context of NRC JLD-ISG-2013-01 (NRC, 2013a), provide a perspective on 2D modeling that is relevant for a LIP analysis as well. Section 9.1.2 of NRC JLD-ISG-2013-01 (NRC, 2013a) states:

"In fact, flood flows through extremely flat and wide flood plains may not be modeled adequately as one-dimensional flow. Velocity of the flow across the floodplain may be just as large as that of flow down the channel. If this occurs, a two-dimensional flow model will better simulate the physical processes."

Section 9.2 of NRC JLD-ISG-2013-01 (NRC, 2013a) states:

"In general, as the flood plain widens, one-dimensional analysis becomes less reliable.

Accurate estimates of flood elevation in areas of changing topography and near large objects (i.e. buildings and other structures) in the flow field will typically require localized two-dimensional analysis, in areas of particular interest or sensitivity."

Section 9.2 of NRC JLD-ISG-2013-01 (NRC, 2013a) further gives the NRC staff position as:

"For estimating inundation at or near a NPP [Nuclear Power Plant] site, two-dimensional models are generally preferred by the NRC staff. However, use of one-dimensional models may be appropriate in some cases. Therefore, use of one-dimensional models will be accepted on a case-by-case basis, with appropriate justification."~

As a 2D model that simulates rainfall runoff, FLO-2D is sufficient for meeting the guidance presented in NRC NUREG/CR-7046 (NRC, 2011) for flooding analyses.

Wolf Creek Nuclear Operating Corporation *E*

Flood Hazard Reevaluation ReportPae]0of15*

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