ML15093A283

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Enclosure 1: Local Intense Precipitation Evaluation Report for Oyster Creek, Rev. 6
ML15093A283
Person / Time
Site: Oyster Creek
Issue date: 07/03/2013
From: Lehrer M
AMEC Environment & Infrastructure
To:
Office of Nuclear Reactor Regulation
Shared Package
ML15093A289 List:
References
RA-15-015, RS-15-063 RCN:LIP-122
Download: ML15093A283 (18)
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Text

Enclosure 1 Oyster Creek Nuclear Generating Station Local Intense Precipitation Evaluation Report Revision 6 (17 pages)

LOCAL INTENSE PRECIPITATION EVALUATION REPORT, Rev. 6 for the OYSTER CREEK NUCLEAR GENERATING STATION Route 9 South, PO Box 388, Forked River, NJ 08731 A- Exelon..

Exelon Generation Company, LLC (Exelon)

P.O. Box 805387 Chicago, Illinois 60680-5387 Prepared by:

AMEC Environment & Infrastructure, Inc.

502 West Germantown Pike, Suite 850, Plymouth Meeting, PA 19462 Revision 6 Submittal Date: June 24, 2013 Printed Name Affiliation Signature Date Originator: Matthew Lehrer AMEC 6124/13 Verifier: Petr Masopust AMEC 6/24/13 Approver: Jeffrey Mann AMEC 6/24/13 Valmicky Samlal/Ruben got:1E~

Lead Responsible Engineer:

Martinez Exelon Branch Manager Exelon O 12L g Senior Manager Design Engineering: Howle Ray Exelon Corporate Acceptance: Joseph V. Bellini Exelon I4110rA "7/lt/13 RCN: LIP-122 Page 1 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 Contents

1. List of Acronym s ......................................................................................................................................... 3
2. PURPOSE .................................................................................................................................................... 3
a. Background ............................................................................................................................................. 3
b. Site Description ...................................................................................................................................... 4
c. Vertical Datum ....................................................................................................................................... 5
d. Sum m ary of Current Licensing Basis Flood Hazards ........................................................................ 6
3. M ETHODOLOGY ......................................................................................................................................... 7
a. M odeling Approach ................................................................................................................................ 7
b. Topography .......................................................................................................................................... 10
c. Land Cover ........................................................................................................................................... 10
d. Probable M axim um Precipitation ........................................................................................................ 11
4. RESULTS .................................................................................................................................................... 12
5. CONCLUSIONS .......................................................................................................................................... 16
6. REFERENCES ............................................................................................................................................. 16 Figure 1: Oyster Creek Nuclear Generating Station Location ........................................................................ 5 Figure 2: FLO-2D M odel Boundary ............................................................................................................. 9 Figure 3: 1-HR PM P Distribution for Oyster Creek Station .......................................................................... 12 Figure 4: Locations of Doors ............................................................................................................................ 15 Table 1: Assigned M anning's Roughness Coefficients (n-values) ............................................................... 10 Table 2: 1-HR PM P Distribution for Oyster Creek Station .......................................................................... 11 Table 3: LIP Predicted Flooding Results at the Oyster Creek Station ......................................................... 13 Table 4: LIP Predicted Flooding Results at the Main Doors and Bays of Site Buildings .............................. 13 Table 5: LIP Predicted Flooding Results at the Main Doors and Bays of the Site Buildings ........................ 14 RCN: LIP-122 Page 2 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6

1. List of Acronyms ASME American Society of Mechanical Engineers CLB Current Licensing Basis DEM Digital Elevation Model ft Foot / Linear Foot fps Feet per second GIS Graphical Information System HMR 51 Hydrometeorological Report 51 HMR 52 Hydrometeorological Report 52 HSG Hydrologic Soil Group IPEEE Individual Plan Examination of External Events Lb Pound Force LiDAR Light Detection and Ranging LIP Local Intense Precipitation MSL Mean Sea Level Datum NAVD 88 North American Vertical Datum of 1988 NRC Nuclear Regulatory Commission NRCS Natural Resources Conservation Service OCNGS Oyster Creek Nuclear Generating Station PMP Probable Maximum Precipitation PMF Probable Maximum Flood RAI Request for Additional Information IR Issue Report SEP Systematic Evaluation Program Sq mi Square Miles UFSAR Updated Final Safety Analysis USDA United States Department of Agriculture WRF Width Reduction Factor WSE Water Surface Elevation
2. PURPOSE
a. Background AMEC Environment & Infrastructure, Inc. (AMEC) on behalf of Exelon Corporation (Exelon) performed an evaluation of site runoff generated from a Local Intense Precipitation (LIP) event to supplement the on-going flooding studies at Oyster Creek Nuclear Generating Station (OCNGS). AMEC performed this work under a Quality Assurance (QA) Program that conforms to the requirements of ASME NQA-1 and 10.CFR.50 Appendix B. The LIP evaluation was performed in accordance with the Nuclear Regulatory Commission's (NRC's) "Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America", dated November 2011 (NUREG/CR-7046) (Reference 10).

NUREG/CR-7046 (Reference 10) identifies the LIP under causative mechanisms for design based floods and states that these mechanisms or causes be investigated to estimate the design-basis flood for nuclear RCN: LIP-122 Page 3 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 power plant sites. Local flooding is associated with inundation caused by localized, short-duration, intense rainfall events. The focus of this study was to evaluate the adequacy of the site's grading, drainage, and runoff-carrying capacity. It was assumed for this analysis that all active and passive drainage system components (e.g., pumps, gravity storm drain systems, small culverts, inlets, etc.) are non-functional during the local intense rainfall event, per Case 3 in NUREG/CR-7046 (Reference 10). As such, only overland flow and open channel systems were modeled and considered in the local flooding analysis.

Per NUREG/CR-7046 (Reference 10), the LIP event is defined as a 1-hour/i-square mile Probable Maximum Precipitation (PMP). The PMP is the greatest depth of precipitation, for a given duration, that is theoretically possible for a particular area and geographic location (Reference 10). The PMP is not derived from historic rainfall records, although historic atmospheric conditions and patterns are considered. The 1-hour PMP event was developed using Hydrometeorological Report 52 (HMR 52) (Reference 8).

b. Site Description OCNGS is located on the coastal pine barrens of New Jersey, in Lacey and Ocean Townships, Ocean County.

The plant site is located to the west of Route 9, and is bounded by Oyster Creek in the north, south, and east. The site is approximately 35 miles north of Atlantic City, New Jersey and 45 miles east of Philadelphia, Pennsylvania (Reference 4).

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Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 Figure 1: Oyster Creek Nuclear Generating Station Location

c. Vertical Datum Elevations provided in this report are presented in the North American Vertical Datum of 1988 (NAVD 88) and the Mean Sea Level Datum (MSL) to relate calculated results to the Current Licensing Basis (CLB) documents. The topographic, photogrammetric and survey data used for the calculations are in the NAVD 88 datum.

A conversion was required to compare elevations reported in the MSL and NAVD 88 datums. According to the NOAA Center for Operational Oceanographic Products and Services website (Reference 9) the datum shift from MSL to NAVD 88 for the OCNGS latitude and longitude (39.8222, -74.203) requires an adjustment based on the closest benchmark location. The closest benchmark location is the Inside Barnegat Inlet Station, 8533615 (Reference 9). Equation 1 shows the datum conversion to convert the MSL elevation to the NAVD 88 datum.

Equation 1 Elevation in ft NAVD 88 = Elevation in ft MSL - 0.02 ft RCN: LIP-122 Page 5 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6

d. Summary of Current Licensing Basis Flood Hazards The OCNGS grade elevation is 22.98 ft NAVD 88 (23.00 feet MSL), and the water intake structure invert is at elevation 5.98 ft NAVD 88 (6.00 feet MSL). According to the site's Updated Final Safety Analysis Report (UFSAR), the current Probable Maximum Flood (PMF) in the Oyster Creek watershed would generate a peak water surface elevation at the site of approximately 5.28 ft NAVD 88 (5.30 feet MSL) (Reference 4).

The site topography generally slopes from Route 9 to the west toward OCNGS with a station grade elevation of 22.98 ft NAVD 88 (23.00 feet MSL). The floor elevations of the reactor and turbine buildings are 6 inches above grade at elevation 23.48 ft NAVD 88 (23.50 feet MSL). Two entrances to the emergency diesel generator building are at elevation 22.98 ft NAVD 88 (23.00 feet MSL). A 6-inch high asphalt dike is provided at these entrances to provide protection against external flooding of the emergency diesel generator building up to an elevation of 23.48 feet NAVD 88 (23.50 feet MSL). The plant site grading generally slopes away from the high point in the center of the island toward the intake to the north and west, the discharge canal to the south and west, and Route 9 to the east (Reference 4). Per AMEC's field observations during a site visit on April 27, 2012, the switchyard, located on the west bank of the intake and discharge canals across from the station, is generally flat with an estimated grade of 1%. The eastern half of the switchyard slopes toward the northeast toward a 2-ft high earthen berm along the eastern and northern fence line. The western half of the switchyard drains toward the west to a drainage ditch, just outside of the fence line.

Per Oyster Creek Station's UFSAR, Section 2.4.2.3 (Reference 4), an LIP investigation was previously performed. The UFSAR indicates that runoff resulting from LIP partly drains off the site through the existing storm water sewers and partly drains away as overland flow towards the outer periphery of the plant site.

Due to the time lag between the runoff and rainfall, some local site ponding is predicted to occur; however, this predicted ponding does not result in flooding of the site. Based on the information provided in the UFSAR (Reference 4) the flood elevation for the PMP was established at 23.48 ft NAVD 88 (23.50 ft MSL).

The USFAR did not provide details on the methodology and assumptions used in evaluating the LIP flood elevation.

Additional information regarding the licensing basis LIP flooding evaluation is discussed in the August 2000 AmerGen reply letter to Request for Additional Information (RAI) on Individual Plan Examination of External Events (IPEEE) at OCNGS (Reference 2). According to the 2000 AmerGen reply letter, the initial site drainage analysis prior to the IPEEE was performed in 1982 (Reference 2). This analysis was performed for a 6-hour point PMP of 27 inches (Reference 2). The analysis considered the site topography and the existing storm sewer drainage system consisting mostly of 8-inch diameter sewers leading into a 10-inch diameter sewer to a 30-inch diameter outfall into the discharge canal north of the emergency diesel generator building (Reference 2). The 2000 AmerGen reply letter indicates the methodology and assumptions for performing the hydrologic analysis and calculation of flood depths were not provided (Reference 2). This prior analysis concluded that the local site flooding would occur 5 inches above grade elevation of 23.00 feet MSL (Reference 12).

The 2000 AmerGen reply letter (Reference 2) indicates a drainage analysis using the updated PMP criteria was performed under the IPEEE for OCNGS. As part of the evaluation, a site walkdown was performed to confirm the site configuration per the design drawings. Changes in site configuration that were identified RCN: LIP-122 Page 6 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 during this site walkdown included new catch basins and pipes, as well as change in drainage patterns due to the construction of an administration building. The site drainage analysis was performed using criteria from Hydrometeorological Report 51 and 52 (HMR 51 and HMR 52) for a 1-hour PMP of 18 inches and 24-hour PMP of 35 inches (Reference 2). The storm sewer system and changes in site configuration were incorporated in the analysis; however, the methodology and assumptions for performing the hydrologic analysis and calculation of flood depths were not discussed in detail (Reference 2). The results of the analysis showed that a water surface elevation of 23.60 feet MSL could occur in areas adjacent to the north, east, and south sides of the reactor building (Reference 2). However, the analysis did not indicate whether this calculated water surface elevation was the result of the 1-hour or 24-hour PMP. The analysis concluded that water intrusion in other buildings would not lead to severe accidents, since the turbine building or diesel generator building would not be affected by the flooding (Reference 2). The analysis also concluded the only potential water entry would be the reactor building; however, the entrances are kept closed during normal operation (Reference 2). The 2000 AmerGen reply letter (Reference 2) indicates the interior of the reactor building is maintained at a negative pressure of 0.25 inches of water (Reference 2). The analysis states that the force exerted on the airlock doors by approximately one inch of water along the base is negligible compared to the pressure of 0.25 inches of water over the entire door surface, and therefore would remain in place minimizing water intrusion into the building (Reference 2).

3. METHODOLOGY
a. Modeling Approach This evaluation uses a two-dimensional (2D) hydrodynamic model, FLO-2D, to evaluate the flow characteristics of the runoff caused by an LIP event. The FLO-2D model was created with boundaries along the centerline of Route 9 to the east, OCNGS to the north and south, and the access road just west of the switchyard fence line. The switchyard was included in the study area to evaluate the potential effects of LIP on the safety-related systems, structures, and components (SSCs) in this area. Figure 2 shows the exterior boundary of the FLO-2D model and land marks referenced in this document.

The FLO-2D model consists of 66,664 10-ft by 10-ft grids elements. The 10-ft by 10-ft grid size was chosen to provide an adequate level of detail to reflect the hydrodynamic effects at the site, while requiring a reasonable amount of computational resources. Based on Table 1.1 of the FLO-2D Data Input manual, the optimal number of grid elements is 150,000 (Reference 5). If the grid size were reduced to 5 ft by 5 ft, the model would have approximately 267,000 grid elements, which is greater than the optimal number of grid elements. The FLO-2D model required the following inputs to evaluate LIP (Reference 5):

" Topography to characterize grading, slopes, drainage divides, and low areas of the site;

" Manning's Roughness Coefficients (n-values) to characterize the land cover of the site and its effects on flow depths and velocities; and

" 1-hour PMP Event to characterize the local intense precipitation event (volume, distribution, and duration).

The model was run with the above inputs to evaluate the adequacy of the site grading and runoff carrying capacity during the local intense precipitation event. The model provides information on the following parameters:

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Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6

  • Flood elevations;
  • Flood depths;
  • Flooding conditions;
  • Velocity vectors (magnitude and direction);
  • Resultant static loads; and
  • Resultant impact loads.

It was assumed that all active and passive drainage system components (e.g., pumps, gravity storm drain systems, small culverts, inlets, etc.) are non-functional or completely blocked during the LIP event, per Case 3 in NUREG/CR-7046 (Reference 10). NUREG/CR-7046 discusses that it is extremely rare that the passive site drainage network would remain completely unblocked during the LIP event. Assuming blocked conditions was considered reasonable during a LIP event because the expectation is that: 1) a significant volume of debris/sediment would be transported, delivered, and accumulated at drainage structures and 2) conveyance capacity of the drainage system is very limited, even if completely open, relative to the peak flow rates during a LIP event. Furthermore, the NRC would require the utility to provide substantial justification for crediting partial or full conveyance from drainage structures (Reference 10).

The LIP evaluation was conducted independently of external high-water events. That is, the LIP event was assumed to have occurred non-coincidental to a river flood. Therefore, backwater or tailwater was not considered. Per recommendations provided by NUREG/CR-7046, runoff losses were ignored during the LIP event to maximize the runoff from the event. The site is predominantly impervious and, therefore, accounting for losses would have very minimal impact on the results. The soil types in previous surfaces are classified by the USDA-NRCS as being within Hydrologic Soil Group (HSG) A, which is characterized as having saturated infiltration rates ranging from 0.6 inches per hour to 20.00 inches per hour (Reference 13).

However, given the majority of the site is impervious, the saturation infiltration rates can be considered toward the low end of this range and negligible compared to the rainfall intensity for an LIP event. If included, the NRC would require the utility to provide justification for crediting losses (Reference 10). Only overland flow and open channel systems were modeled and considered in the LIP flooding analysis.

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Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 Figure 2: FLO-2D Model Boundary RCN: LIP-122 Page 9 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6

b. Topography The FLO-2D model was constructed from a digital elevation model (DEM) produced from available photogrammetric survey data and a supplemented with a field survey completed to characterize grading, slopes, drainage divides, and low areas of the site.

A digital CAD file of the photogrammetric survey data collected in 2004, was provided by Exelon (Reference 3). The survey data provided 1-foot contours of the site. AMEC accepted the survey data through a commercial grade dedication process under AMEC's Quality Assurance Program.

AMEC considered the photogrammetric survey sufficient as a baseline for the LIP evaluation. A supplemental field survey of the site was completed to incorporate site features that were not identified by the photogrammetric survey. The features included depressions/low points and isolated concrete barriers.

The field survey was performed in July of 2012 by a Professional Land Surveyor licensed in the State of New Jersey (Reference 14).

The supplemental field survey data was incorporated into the photogrammetric survey using AutoCAD Civil3D software to produce the DEM. The DEM was clipped to match the FLO-2D model limits shown in Figure 2 above.

c. Land Cover The FLO-2D model uses Manning's Roughness Coefficients (n-values) to characterize the site's surface roughness and calculate effects on flow depths and velocities. Land cover for the site was evaluated using interpretation of orthoimagery that was verified in the field by AMEC during subsequent visits to the site.

N-values were assigned to each land cover type and based on ranges described on page 22 of the FLO-2D Reference Manual (Reference 6). The assigned n-values are provided in Table I below.

Table 1: Assigned Manning's Roughness Coefficients (n-values)

Land Cover Surfaces of Oyster Creek Station" Recommended Range Assigned n-value %Coverage of n-values2 Bermuda and dense grass, dense vegetation 0.17 - 0.48 0.32 39%

Shrubs and forest litter, pasture 0.30 - 0.40 0.40 26%

3 Asphalt, Concrete, or Buildings 0.02 - 0.05 0.035 14%

Gravel 4 0.05 9%

Water surfaces 0.02 12%

'Land cover surface per orthoimagery and field verification.

2Recommended ranges of Manning's n-values per page 22 of the FLO-2D Reference Manual provided in Appendix A.

3Building obstructions are accounted for in the model through the use of Area and Width Reduction Factors (Reference 6)

'Gravel surfaces were assigned a n-values from the upper range for Asphalt/Concrete to reflect the roughness of the material.

SWater surfaces assigned a n-values from the lower range for Asphalt/Concrete to reflect its smoothness.

As noted in Table 1, the n-values assigned to gravel and water land cover surfaces are values from the recommended range for asphalt/concrete to reflect their surface roughness. Gravel is assigned the higher end of the range to account for typical irregularities in the gravel surface. The Manning's n-value for water is assigned the low end of this range to account for internal friction. Shrubs and forest litter were assigned a RCN: LIP-122 Page 10 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 Manning's n-value at the upper end of the recommended range to account for the observed dense brush surface. The rest of the land cover surface categories were assigned the middle of their respective recommended ranges.

A sensitivity analysis was performed on the n-values to evaluate the effect this parameter has on the maximum water surface elevation. As part of the analysis, the upper and lower ranges of the Manning's n-values presented in Table 1 were run through the FLO-2D model. The results indicate that the difference in water surface elevations between the upper and lower range of the Manning's n values presented in Table 1 are within +/- 0.08 ft. This also suggests that the LIP peak flood levels for much of the site are controlled by floodwaters ponding or backing-up at constrictions (e.g., catch basins and small culverts),

reducing the affect of surface friction on flow depths and reinforcing the reasons discussed previously for the increases above the current design basis.

d. Probable Maximum Precipitation The 1-hour PMP event distribution was developed using HMR 52. Per NUREG/CR-7046 (Reference 10), the LIP event is defined as a 1-hour/i-square-mile PMP event. The total PMP depth per square mile for the 1-hr event was extrapolated from the PMP depth contour map provided in Figure 24 of HMR 52 (Reference 8).

The distribution of the 1-hr PMP was developed for the 5-, 15-, and 30-minute time intervals, with the 60-minute interval being the 1-hr PMP depth. The depth for each time interval was calculated using the ratios obtained from Figures 36, 37, and 38 of HMR 52 (Reference 8). The 1-hr PMP distribution is provided in Table 2 and Figure 3 below. The 1-hour PMP event was run through the FLO-2D model to calculate the subsequent site flooding.

Table 2: 1-HR PMP Distribution for Oyster Creek Station Time Percent Total PMP Cumulative Depth Reference (minutes) (%) (inches) 0 0% 0.00 5 33.46% 6.05 HMR 52, Page 94, Figure 36 15 52.58% 9.50 HMR 52, Page 95, Figure 37 30 75.46% 13.64 HMR 52, Page 96, Figure 38 60 100% 18.07 HMR 52, Page 79, Figure 24 RCN: LIP-122 Page 11 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 1-hr PMP Distribution 20 18 716 -

E14 a0 0 10 20 30 40 50 60 Time (minutes)

Figure 3: 1-HR PMP Distribution for Oyster Creek Station

4. RESULTS The LIP flooding evaluation, as per the Case 3 assumptions of NUREG/CR-7046, Section 3.2 (Reference 10) produced results that include flooding depths, water surface elevations, velocities, resultant static loads, and resultant impact loads that could be expected for an LIP event at the site. The maximum resultant impact load and maximum resultant static load are expressed as pounds force per unit width. Multiplying these loads by the horizontal width of the structure within the grid element will provide the magnitude of the resultant force. Detailed calculations, results, and figures are presented in AMEC Calculation Package LIP-OYS-001 (Reference 1). The calculated maximum results of the LIP evaluation are presented in Table 3.

The FLO-2D model shows peak LIP flood elevations around the plant (reactor and turbine buildings) ranging between 21.40 and 23.93 feet NAVD 88 (21.42 and 23.95 feet MSL). This is 2.08 feet lower to 0.45 feet higher than the design-basis peak LIP flood elevation of 23.48 feet NAVD 88 (23.50 feet MSL). In comparing available information from the design-basis evaluation (References 2 and 4), the difference appears to be attributable to assumptions and methods used in developing the design-basis flood levels. The design-basis flood evaluation appears to have included the effects of the storm sewer system being operational during the event. According to the FLO-2D model output, features such as grated catch basins, and other constrictions/obstructions, control much of the flooding during an LIP event. The design basis evaluation appears to have assumed the storm sewer conveyance was uninhibited.

Results provided in this report are direct outputs from the FLO-2D model. The FLO-2D model reports results to the hundredth of a foot. However, based on the sensitivity analysis of Manning's n values, an accuracy of

+/- 0.1 foot should be taken into consideration when evaluating the reported results.

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Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 Table 3: LIP Predicted Flooding Results at the Oyster Creek Station Max. Max. Max. Resultant Max. Water Surface Elevation Flooding Max. Velocity Resultant Building Name Depth Impact Load ft (NAVD 88) ft (MSL) ft ft/sec. lb/ft lb/ft Diesel Generator Building 13.59 - 23.13 13.61 - 23.15 0.10 - 0.47 0.10- 1.20 0.01- 0.36 0.32- 6.96 Storage Building 22.45 - 22.65 22.47 - 22.67 0.17-0.58 0.20-0.76 0.01-0.77 0.88- 10.47 XFMR (Transformers) 21.41 - 22.37 21.43 - 22.39 0.13 -0.51 0.45 - 1.18 0.07-0.96 0.50-8.19 Pre-Treatment Building 22.13 - 22.58 22.15 - 22.60 0.13-0.58 0.26- 1.01 0.08- 1.36 0.56- 10.64 Old Machine Shop 22.58 - 23.12 22.60 - 23.14 0.10-0.67 0.13 -0.72 0.02-0.81 0.32 - 13.97 Security Building 22.66 - 23. 10 22.68 - 23.12 0.10- 1.71 0.00-0.99 0.01- 1.21 0.32-91.73 Office Building 22.72 - 22.90 22.74 - 22.92 0.10-0.75 0.17-0.62 0.02-0.25 0.32- 17.54 Reactor Building 22.72 - 23.93 22.74 - 23.95 0.72- 1.77 0.16-0.54 0.02-0.34 16.28 - 97.56 Mac Facility 23.92 - 23.92 23.94 - 23.94 0.92-0.92 0.16-0.62 0.04-0.53 26.30 - 26.61 Respirator Facility 22.70 - 23.92 22.72 - 23.94 0.70-0.92 0.57- 1.75 0.04-6.67 7.69- 16.13 Storage Tank T-12-4 22.39 - 23.39 22.41 - 23.41 0.13-0.92 0.14- 1.30 0.01- 2.11 0.50-26.32 T.B.Dirty Oil Tank 20.07 - 23.21 20.09 - 23.23 0.10-0.37 0.00- 1.37 0.01- 1.74 0.32- 12.66 Cond Storage Tank 18.58 - 22.64 18.60 - 22.66 0.14-2.31 0.49-2.23 0.26-4.44 0.57 - 166.83 Chlorination Facility 13.81 - 22.57 13.83 - 22.59 0.10- 1.63 0.28- 1.81 0.02-3.45 0.32- 11.46 Turbine Building (T.B.) 21.40 - 22.70 21.42 - 22.72 0.10- 2.31 0.21- 1.14 0.02-4.44 0.33 - 166.83 The maximum predicted LIP flooding results at critical entrances to the site buildings are provided in Table 4.

Table 4: LIP Predicted Flooding Results at the Main Doors and Bays of Site Buildings Max. Max. Max.

Reference Max. Water Surface Max. Resultant Resultant Door No. Grid Element Elevation Flooding Velocity Impact Static No. Depth Load Load ft (NAVD 88) ft (MSL) ft ft/sec. Ib/ft Ib/ft Door 1 24458 22.59 22.61 0.59 0.43 0.24 10.79 Door 2 26887 22.63 22.65 0.63 0.46 0.30 12.37 Door 3 23275 22.59 22.61 0.59 0.28 0.05 10.93 Door 4 26895 23.08 23.10 0.12 0.47 0.06 0.48 Door 5 22982 22.59 22.61 0.59 0.28 0.04 10.84 Door 6 27829 22.72 22.74 0.72 0.32 0.13 16.25 Door 7 30020 22.72 22.74 0.72 0.40 0.23 16.30 Door 8 31919 22.71 22.73 0.71 0.37 0.19 15.61 Door 9 26009 23.92 23.94 0.92 0.25 0.08 26.61 Door 10 20654 22.47 22.49 0.47 0.23 0.06 6.94 Door 11 20647 22.46 22.48 0.46 0.27 0.04 6.53 Door 12 19802 23.13 23.15 0.13 0.15 0.01 0.56 Door 13 18979 23.11 23.13 0.11 0.36 0.04 0.38 RCN: LIP-122 Page 13 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 The predicted LIP flooding depths and duration above the station grade elevation at the critical entrances to the site buildings are provided in Table 5.

Table 5: LIP Predicted Flooding Results at the Main Doors and Bays of the Site Buildings Reference Max. Flooding Depth Flooding Duration Rrec Max. Water Surface Above the Station Above the Station Door No. Elmn Elevation 1 Grade (Elevation Grade (Elevation 2

Element 23.50 ft MSL2 23.50 ft MSL )

No.

ft (NAVD 88) ft (MSL) ft hrs Door 1 24458 22.59 22.61 -0.89 0.00 Door 2 26887 22.63 22.65 -0.85 0.00 Door 3 23275 22.59 22.61 -0.89 0.00 Door 4 26895 23.08 23.10 -0.40 0.00 Door 5 22982 22.59 22.61 -0.89 0.00 Door 6 27829 22.72 22.74 -0.76 0.00 Door 7 30020 22.72 22.74 -0.76 0.00 Door 8 31919 22.71 22.73 -0.77 0.00 Door 9 26009 23.92 23.94 0.44 1.26 Door 10 20654 22.47 22.49 -1.01 0.00 Door 11 20647 22.46 22.48 -1.02 0.00 Door 12 19802 23.13 23.15 -0.35 0.00 Door 13 18979 23.11 23.13 -0.37 0.00 1 Reference 1 2

Plant grade elevation of 23.50 ft MSL per UFSAR Section 2.4 (Reference 4) converted to 23.48 ft NAVD 88.

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Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6 Figure 4: Locations of Doors RCN: LIP-122 Page 15 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6

5. CONCLUSIONS Per the UFSAR, the OCNGS grade elevation is 22.98 ft NAVD 88 (23.00 feet MSL) (Reference 4). The floor elevations of the reactor and turbine buildings are 6 inches above grade at elevation 23.48 ft NAVD 88 (23.50 feet MSL) (Reference 4). According to the UFSAR (Reference 4), the previous LIP investigation concluded that the LIP water surface elevations would not exceed the finished floor elevation of the plant.

The results show that the predicted maximum LIP flooding water surface elevations at the main doors and bays of the site buildings range between 22.46 and 23.92 feet NAVD 88 (22.48 and 23.94 feet MSL), which is 1.02 ft lower to 0.44 ft higher than the station grade elevation. The results in Table 5 show that the approximate water surface elevation at Door 9 could remain above the first floor elevation for approximately 1.26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br />. However, the approximate water surface elevations at the other doors evaluated in this study appear to be below the first floor elevation.

Based on the results of AMEC's LIP flooding evaluation (Reference 1), the need for incorporation of additional flood protection measures should be further evaluated for Door 9, since it appears the LIP flooding elevation exceeds current protection level per the CLB documents at this location. The LIP flooding event is a short-duration storm and the site may have little to no advance flood warning prior to an LIP event taking place.

Interim evaluation and actions taken or planned to address any higher flooding hazards relative to the design basis will be dispositioned through the Corrective Active Program (CAP), prior to completion of the integrated assessment. Issue Report (IR) #01445360 has been generated.

6. REFERENCES
1. AMEC Calculation Package LIP-OYS-O01 (2013). Oyster Creek Nuclear Generating Station Local Intense Precipitation.
2. AmerGen Energy Company, LLC (August 2000). Oyster Creek Generating Station, Docket No. 50-219, Reply to RAI on IPEEE.
3. Birdsall Services Group (2004), Oyster Creek Nuclear Generating Station Photogrammetric Survey.
4. Exelon Nuclear, Oyster Creek Nuclear Generating Station (2009). Oyster Creek Nuclear Generating Station Updated Final Safety Analysis Report (OCNGS UFSAR), Revision 17.
5. FLO 2D (2009). Data Input Manual. Version 2009.06
6. FLO 2D (2009). Reference Manual. Version 2009.
7. GPU Nuclear Corporation (December 1995). Oyster Creek Individual Plant Examinationfor External Events (IPEEE).
8. U.S. Department of Commerce, National Oceanic and Atmospheric Administration, and U.S.

Department of the Army Corps of Engineers (1982). HydrometeorologicalReport No. 52 (HMR-52),

Application of Probable Maximum Precipitation Estimates - United States East of the 1 0 5 th Meridian.

RCN: LIP-122 Page 16 of 17

Local Intense Precipitation Evaluation Report Oyster Creek Nuclear Generating Station Exelon Corporation June 24, 2013 Rev 6

9. United State Department of Commerce, National Oceanic and Atmospheric Administration (NOAA)

(2003). Published Bench Mark Sheet for 8533615 BARNEGAT INLET (INSIDE) NEW JERSEY. Available at http://tidesandcurrents.noaa.gov/benchmarks/8533615.html, accessed 10/5/12.

10. United States Nuclear Regulatory Commission (2011). NUREG/CR-7046, Design-Basis Flood Estimationfor Site Characterizationat Nuclear PowerPlants in the United States of America
11. U.S. Nuclear Regulatory Commission (January 1983). NUREG-0822, Integrated Plant Safety Assessment Systematic EvaluationProgram, Oyster Creek Nuclear GeneratingStation.
12. U.S. Nuclear Regulatory Commission (July 1988). NUREG-0822 Supplement No.1, Integrated Plant Safety Assessment Systematic Evaluation Program, Oyster Creek Nuclear GeneratingStation.
13. United States Department of Agriculture, Natural Resources Conservation District (October 12, 2012). Custom Soil Resource Report for Ocean County, New Jersey.
14. ACT Engineers, Inc. (August 14, 2012). Survey Report for Oyster Creek Nuclear Power Station Local Intense PrecipitationFlooding Hazard Analysis, Lacey and Ocean Townships, Ocean County, New Jersey.

RCN: LIP-122 Page 17 of 17

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