ML15272A313

Enclosure - Amendment 1 to the Flood Hazard Reevaluation Report for the Calvert Cliffs Nuclear Power Plant, Units 1 and 2

ML15272A313
Person / Time
Site:	Calvert Cliffs
Issue date:	09/23/2015
From:	Exelon Generation Co
To:	Office of Nuclear Reactor Regulation
References
Download: ML15272A313 (91)

Text

Enclosure Amendment 1 to the Flood Hazard Reevaluation Report for the Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (90 pages)

AMENDMENT 1 TO THE FLOOD HAZARD REEVALUATION REPORT iN RESPONSE TO THE 50.54(f) INFORMATION REQUEST REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2.1: FLOODING for the Calvert Cliffs Nuclear Power Plant 1650 Calvert Cliffs Parkway Lusby, Maryland Exeton.

Exelon Generation Co., LLC 300 Exelon Way Kennett Square, PA 19348 Prepared by:

~j ENERCON Ezrellence-Eveyprvij&~ Eve~yd~

Enercon Services, Inc.

1601 Northwest Expressway, Suite 1000 Oklahoma City, OK 73118 Submitted Date: September 08, 2015 Printed Name Affiliation Siqnature Date Anubhav Gear ENERCON  ?' V Oq bC~g"j Preparer.

Verifier: Abiot Gemechu ENERCON . -I *"L Approver: Pat Brunette ENERCON 09*=,**

C) {*'li Sheldon Waiters Exefon *[ 0 _. 4[ eq *l Lead Responsible Engineer:

Branch Manager Mike Gahan Exelon ** * ')Idoi ,'

Senior Manager Design Engineering Doug Lauver Exelon )

Joe Bellini Exelon ./ -

91101v5 Exelon Corporate

Amendment 1 to CCNPP Exelon Generation Co. Flood Hazard Reevaluation Report September 08, 2015 Table of Contents 1 AMENDMENT

SUMMARY

........................................................................... 6 1.1 Background ...................................................................................... 6 1.2 Summary of Amendments ...................................................................... 6 2.1 REEVALUATED LOCAL INTENSE PRECIPITATION ANALYSIS (Superseded by this Amendment) ............................................................................................... 8 2.1.1 Site Description............................................................................. 8 2.1.2 Probable Maximum Precipitation (Superseded by this Amendment)................... 8 2.1.3 Hydrologic Modeling ....................................................................... 8 2.1.4 Hydraulic Modeling......................................................................... 8 2.1.5 Effects of Local PMP (Superseded by this Amendment)................................ 8 2.1.6 Conclusion (Superseded by this Amendment).......................................... 10 2.1.7 References (Additional References) .................................................... 11 2.4 REEVALUATED PROBABLE MAXIMUM STORM SURGE ANALYSIS (Superseded by this Amendment)....................................................................................... 26 2.4.1 Introduction................................................................................ 26 2.4.2 Probable Maximum Storm Surge Evaluations.......................................... 26 2.4.3 Results..................................................................................... 38 2.4.4 Conclusions............................................................................... 38 2.4.5 References (Additional References)..................................................... 39 2.9 COMBINED EFFECT FLOODING (Superseded by this Amendment).......................... 79 3 COMPARISION OF CURRENT AND REEVALUATED FLOOD CAUSING MECHANISMS (Superseded by this Amendment) ...................................................................... 80 3.1 Local Intense Precipitation (Superseded by this Amendment)........................... 82 3.4 Storm Surge (Superseded by this Amendment) .......................................... 83 3.9 Combined Effects Flooding (Superseded by this Amendment).......................... 85 4 INTERIM FLOOD PROTECTION MEASURES FOR AUXILLARY AND TURBINE BUILDINGS (Superseded by this Amendment) ............................................... ....................... 90 5 ADDITIONAL ACTIONS (Superseded by this Amendment)..................................... 90 List of Tables Table 2.1-1. Local Intense PMP Depths at CCNPP Site (Superseded by this Amendment)....12 Table 2.1-2. Time of Concentration Calculations................................................... 13 Table 2.1-3. PMP Peak Flow Rates for Sub-Basins (Deleted by this Amendment) .............. 13 Table 2.1-4. HEC-RAS Output Table (Superseded by this Amendment) ......................... 14 Table 2.1-5. Comparison of Elevation at Building Entrances and Water Levels (Superseded by this Amendment) ........................................................................................... 17 Calvert Cliffs Nuclear Power Plant Pg Page 2 off990

Amendment 1 to CCNPP Exelon Generation Co. Flood Hazard Reevaluation Report September 08, 2015 Table 2.1-6. Comparison of PMP Estimates (New Table).......................................... 18 Table 2.4-1. PMH Parameters for Critical Hurricane Track (Superseded by this Amendment).. 41 Table 2.4-2. Summary of HHA Results (Superseded by this Amendment) ....................... 42 Table 2.4-3. Comparison of Parameters and Results for Storm Surge and Wave Runup Analyses (Superseded by this Amendment).................................................................... 43 Table 2.4-4. Summary of Topographic and Bathymetric Data Used as Input for CCNPP Storm Surge Model (New Table) .................................................................................... 44 Table 2.4-5. Wind Drag Coefficient Sensitivity (New Table)........................................ 45 Table 2.4-6. Range of PMH Design Storm Parameters (New Table)...... ........................ 46 Table 2.4-7. Scenarios Evaluated to Determine Worst Case PMH (New Table)................. 47 Table 3.0-1. Current Design Basis Flood Elevations for Safety-Related and Important-to-Safety SSCs (Superseded by this Amendment) ............................................................ 86 Table 3.0-2. Summary of Licensing Basis and External Flooding Study (New Table) ........... 87 Table 3.0-3. Local Intense Precipitation (New Table)............................................... 88 Table 3.0-4. Probable Maximum Storm Surge (PMSS) (New Table).............................. 89 List of Figures Figure 2.1-1. Site Locations........................................................................... 19 Figure 2.1-2. General Site Terrain and Drainage Flow Directions ................................. 19 Figure 2.1-3. Sub-Basin Drainage Area Map........................................................ 19 Figure 2.1-4. Fitting of PMP Depths (Superseded by this Amendment)........................... 20 Figure 2.1-5. Schematic of HEC-HMS Model (Superseded by this Amendment) ................ 21 Figure 2.1-6a. Hydrograph at Sub-1 (Deleted by this Amendment) ............................... 22 Figure 2.1-6b. Hydrograph at Sub-2 (Deleted by this Amendment) ............................... 22 Figure 2.1-6c. Hydrograph at Sub-3 (Deleted by this Amendment) ............................... 22 Figure 2.1-6d. Hydrograph at Sub-4 (Deleted by this Amendment) ............................... 22 Figure 2.1-6e. Hydrograph at Sub-5 (Deleted by this Amendment) ............................... 22 Figure 2.1-6f. Hydrograph at Sub-6 (Deleted by this Amendment)................................ 22 Figure 2.1-6g. Hydrograph at Junction J-1l(Deleted by this Amendment)......................... 22 Figure 2.1-6h. Hydrograph at Junction J-2 (Deleted by this Amendment) ........................ 22 Figure 2.1-6i. Hydrograph at Diversion (Deleted by this Amendment) ............................ 22 Figure 2.1-6j. Hydrograph at Outlet-I (Deleted by this Amendment).............................. 22 Figure 2.1-6k. Hydrograph at Junction J-3 (Deleted by this Amendment)......................... 22 Figure 2.1-61. Hydrograph at Outlet-2 (Deleted by this Amendment).............................. 22 Figure 2.1-7a. HEC-RAS Model Cross Section Plan (Deleted by this Amendment) ............. 23 Figure 2.1-7b. HEC-RAS Cross Section Plan (Deleted by this Amendment) ..................... 23 Figure 2.1-8. Schematic of HEC-RAS Model........................................................ 23 Calvert Cliffs Nuclear Power Plant Pg Page 3 off990

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.1-9. Local PMP Maximum Water Level Profiles (Superseded by this Amendment) .... 24 Figure 2.1-10. Maximum PMP Water Levels (Deleted by this Amendment)...................... 25 Figure 2.1-1 a. Rating Curves and Cross Section Plot at Cross Section 1722 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.1-1lib. Rating Curves and Cross Section Plot at Cross Section 1509 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.1-1lic. Rating Curves and Cross Section Plot at Cross Section 1412 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.1-1lid. Rating Curves and Cross Section Plot at Cross Section 1336 of Downstream-2 (Deleted by this Amendment) ........... ........................................... 25 Figure 2.1-1lie. Rating Curves and Cross Section Plot at Cross Section 1103 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.1-1llf. Rating Curves and Cross Section Plot at Cross Section 1075 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.1-11lg. Rating Curves and Cross Section Plot at Cross Section 648 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.1-1llh. Rating Curves and Cross Section Plot at Cross Section 489 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.1-1Ili. Rating Curves and Cross Section Plot at Cross Section 382 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.1-1 lj. Rating Curves and Cross Section Plot at Cross Section 321 of Downstream-2 (Deleted by this Amendment) ....................................................... 25 Figure 2.4-1. Plan View of Intake Structure and Forebay........................................... 49 Figure 2.4-2. Cross Section of Intake Structure..................................................... 49 Figure 2.4-3. Representative Equivalent Slope for Intake Structure of CCNPP 1 & 2 (Deleted by this Amendment) ........................................................................................... 49 Figure 2.4-4. Storm Tracks for Historical Hurricanes (Superseded by this Amendment) ........ 50 Figure 2.4-5. Evalauted Delft3D Model Storm Track for PMH at CCNPP Site (Superseded by this Amendment) ........................................................................................... 51 Figure 2.4-6. Delft3D Model Grids for CCNPP Strom Surge Model (Superseded by this Amendment)

............. ....................................................................................... 52 Figure 2.4-7. Delft3D Model Storm Surge Results at the Intake Deck (Superseded by this Amendment) ........................................................................................... 53 Figure 2.4-8. SLOSH Model Storm Surge Results Showing the Maximum Surge Level for HHA Iteration No. 2 (Deleted by this Amendment)........................................................ 54 Figure 2.4-9. Delft3D-WAVE (SWAN) Grids or CCNPP Strom Surge Model (New Figure).....55 Figure 2.4-10. Schematic of Calibration Steps/Processes (New Figure).......................... 56 Calvert Cliffs Nuclear Power Plant Pg 4 off990 Page

Amendment 1 to CCNPP Exelon Generation Co. Flood Hazard Reevaluation Report September 08, 2015 Figure 2.4-11. Hurricane Isabel (2003) and Hurricane Irene (2011) Storm Tracks used for Calibration and Verification of the CCNPP Storm Surge Model (New Figure).................... 57 Figure 2.4-12. Tidal Stations used for CCNPP Storm Surge Delft3D Model Calibration (New Figure)

............. ....................................................................................... 58 Figure 2.4-13. Observed and Simulated Tide Water Level - Chesapeake Bay Bridge Tunnel, VA (New Figure) ........................................................................................... 59 Figure 2.4-14. Observed and Simulated Tide Water Level - Solomons Island, MD (New Figure) 60 Figure 2.4-15. Observed and Simulated Tide Water Level - Tolchester Beach, MD (New Figure)

............. ....................................................................................... 61 Figure 2.4-16. Calibrated Spatially Varying Manning Roughness Coefficient (New Figure) .... 62 Figure 2.4-17. Water Level Recording Station used for CCNPP Storm Surge Delft3D Model Calibration (New Figure) .............................................................................. 63 Figure 2.4-18. Wave Recording Station used for CCNPP Storm Surge Delft3D Model Calibration (New Figure) .................................................................... ....................... 64 Figure 2.4-19. Hurricane Isabel: Modeled and Observed Maximum Water Surface Elevation Agreement (New Figure).............................................................................. 65 Figure 2.4-20. Hurricane Irene: Modeled and Observed Maximum Water Surface Elevation Agreement (New Figure).............................................................................. 66 Figure 2.4-21. Hurricane Isabel: Modeled and Observed Water Surface Elevation at Tolchester Beach, MD (New Figure) .............................................................................. 67 Figure 2.4-22. Hurricane Isabel: Modeled and Observed Water Surface Elevation at Baltimore, MD (New Figure) ........................................................................................... 68 Figure 2.4-23. Hurricane Isabel: Modeled and Observed Water Surface Elevation at Annapolis, MD (New Figure) ........................................................................................... 69 Figure 2.4-24. Hurricane Isabel: Modeled and Observed Water Surface Elevation at Kiptopeke, VA (New Figure) ........................................................................................... 70 Figure 2.4-25. Delft3D-WAVE Model Boundaries, Buoy Stations and WlS Stations (New Figure) 71 Figure 2.4-26. Critical PMH Track Direction and bistance from CCNPP to PMH Storm Center (New Figure).................................................................................................. 72 Figure 2.4-27. Storm Surge Elevation in Chesapeake Bay during the Peak of PMH (New Figure)

............. ....................................................................................... 73 Figure 2.4-28. Significant Wave Height in Chesapeake Bay during the Peak of PMH (New Figure)

............. ....................................................................................... 74 Figure 2.4-29. Peak Period in Chesapeake Bay during the Peak of PMH (New Figure) ........ 75 Figure 2.4-30. Significant Wave Height and Wave Vector in Chesapeake Bay during the Peak of PMH (New Figure)..................................................................................... 76 Figure 2.4-31. Wave Length in Chesapeake Bay during the Peak of PMH (New Figure)........ 77 Figure 2.4-32. Cross Section Schematic of Wave Activity on CCNPP Units 1l&2 Pump House (New Figure).................................................................................................. 78 Calvert Cliffs Nuclear Power Plant Pg Page 5 off990

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 I AMENDMENT

SUMMARY

1.1 Background In response to the nuclear fuel damage at the Fukushima-Dai-ichi power plant due to the March 11, 2011, earthquake and subsequent tsunami, the United States Nuclear Regulatory Commission (NRC) established the Near Term Task Force (NTTF) to conduct a systematic review of NRC processes and regulations, and to make recommendations to the NRC for its policy direction. The NTTF reported a set of recommendations that were intended to clarify and strengthen the regulatory framework for protection against natural phenomena.

On March 12, 2012, the NRC issued an information request pursuant to Title 10 of the Code of Federal Regulations, Section 50.54 (f) (10 CFR 50.54(f) or 50.54(f) letter) (Reference 2.1-1 8) which included six (6) enclosures:

1. [NTTF] Recommendation 2.1: Seismic Hazard Analysis

2. [NTTF] Recommendation 2.1: Flooding Reevaluation

3. [NTTF] Recommendation 2.3: Seismic Walkdown

4. [NTTF] Recommendation 2.3: Flooding Walkdown

5. [NTTF] Recommendation 9.3: Emergency Preparedness

6. Licensees and Holders of Construction Permits - Contact Information for Licensees In Enclosure 2 of the NRC issued information request (Reference 2.1-18), the NRC requested that licensees 'reevaluate the flooding hazards at their sites against present-day regulatory guidance and methodologies being used for early site permits (ESP) and combined operating license reviews'.

Constellation Energy Nuclear Group, LLC submitted the Flood Hazard Reevaluation Report (FHRR) for Calvert Cliffs Units 1 and 2 to the NRC (Accession Number ML13078A010) on March 12, 2013.

The FHRR provides the information requested in the March 12, 50.54(f) letter; specifically, the information listed under the 'Requested Information' section of Enclosure 2, paragraph 1 ('a' through The FHRR indicated that two reevaluated flood causing mechanisms, Local Intense Precipitation (LIP) and Probable Maximum Storm Surge (PMSS) exceeded the current design basis flood for Calvert Cliffs Units 1 and 2. The FHRR also indicates that flooding due to the LIP and the PMSS events do not cause immediate flooding at Calvert Cliffs. Interim measures to mitigate flooding from LIP and PMSS events were also proposed in the FHRR. The interim actions have been completed and are procedurally governed. This was communicated to the NRC in September 2013 (Accession Number ML1325A151).

1.2 Summary of Amendments The 50.54(f) letter suggests utilizing present-day guidance and methodologies following the Hierarchical Hazard Assessment (HHA) approach. The HHA approach is also in accordance with NRC guidance NUREG/CR-7046 (Reference 2.1-2). The 50.54(f) letter indicates:

Reevaluate the flood hazard based on present day regulatory guidance and methodologies for each flood causing mechanism. Using any new site-related information and site details identified in Step 1, evaluate all possible flood causing mechanisms. Documentation of all methodologies should be discussed. This step of the process reiterates the current hierarchical hazard Calvert Cliffs Nuclear Power Plant Pg 6 off990 Page

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 assessment (HHA) used by U.S. Nuclear Regulatory Commission (NRC) staff. The HHA is described as a progressively refined, stepwise estimation of the site-specific hazards that evaluates the safety of the site with the most conservative plausible assumptions consistent with available data.

(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 2b) is higher than the original design flood elevation for the selected flood causing mechanism. If not, use this flood elevation for this causal mechanism in Step 3.

(d) Determine if the site-related parameters can be further refined. If yes, perform reevaluation (repeat step 2c). If no, use this flood elevation for this causal mechanism in Step 3.

(e) Determine if all flood causing mechanisms have been addressed. If yes, continue to Step 3. If no, select another flood causing mechanism (Step 2a).

As described in NUREG/CR-7046, HHA approach is a progressive stepwise approach.

NUREG/CR-7046 suggests starting the analysis using the most conservative simplifying assumptions that will maximize the flood hazard. If the most conservative analysis results in an adverse effect or exposure of any SSCs, a re-analysis using site-specific data and conservative assumptions should be performed. The re-analysis may require several iterations or analyses.

The FHRR for Calvert Cliffs Units 1 and 2 submitted on March 12, 2013 utilizes conservative assumptions and approaches in evaluating flood hazards. As part of this Amendment and in accordance with the HHA approach presented in the 50.54(f) letter and NUREG/CR-7046 guidance, Constellation Energy Nuclear Group, LLC further reevaluated the LIP and PMSS flood causing mechanisms. This amendment is limited to reevaluation of LIP (Section 2.1 of FHRR) and PMSS (Section 2.4 of the FHRR) flood causing mechanisms. Other flood causing mechanisms discussed in the FHRR are not impacted by this amendment. Sections 2.9, Combined Effect Flooding, 3.0 Comparison of Current and Reevaluated Flood-Causing Mechanisms, 3.1 Local Intense Precipitation, 3.4 Storm Surge, 3.9 Combined Affect Flooding, Section 4 Interim Evaluation and Actions Taken or Planned and Section 5 Additional Actions are also amended.

As indicated in the FHRR, reevaluations of LIP and PMSS are performed using present-day guidance and methodologies following the HHA approach outlined in NUREG/CR-7046. Similarly, the reevaluation performed as part of this Amendment apply present-day regulatory guidance and methodologies being used for ESP and calculation reviews including current techniques, software, and methods used in present-day standard engineering practice to develop the flood hazard.

The results of reevaluation performed as part of this Amendment indicated that the flood causing mechanisms, LIP and PMSS are bounded by the current design basis flood for Calvert Cliffs Units 1 and 2. Reevaluated LIP and PMSS are discussed in detail in Sections 2.1 and 2.4 of this Amendment respectively.

Calvert Cliffs Nuclear Power Plant Pg 7 off990 Page

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 2.1 REEVALUATED LOCAL INTENSE PRECIPITATION ANALYSIS (Superseded by this Amendment)

LIP is an extreme precipitation event at the site location. The LIP is equivalent to the 1-hour, t-mi2 PMP as described in the NUREG/CR-7046.

As indicated in the FHRR, LIP was evaluated utilizing probable maximum precipitation (PMP) estimates obtained from the NOAA Hydrometeorological Reports (HMR) 51 and 52. The 1-hour, 1-mi2 PMP obtained from HMRs 51 and 52 is 18.48 inches. A site-specifiC PMP study was completed for Calvert Cliffs Units 1 and 2, which produced a 1-hour 1-mi2 rainfall depth of 11.70 inches. As part of the FHRR, Constellation chose to use the more conservative HMR-52 1-hour 1-mi2 rainfall value of 18.48 inches. For a more accurate LIP flood determination and an assessment of available margin, the LIP updates reported in this Amendment are based on the site-specific 1-hour 1-mi 2 rainfall depth of 11.70 inches. The HMR 51 and HMR 52 rainfall depth is no longer the basis for the LIP flood analysis. Instead, a site-specific LIP analysis is being used.

The site-specific LIP is determined in Calculation CEC-008-CALC-02, "Site-Specific LIP PMP Evaluation for Calvert Cliffs Nuclear Power Plant Units I and 2" (Reference 2.1-16). The effects of the LIP, which are the resulting impacts from the flood water surface elevations and flow depths, are determined in Calculation CEC-008-CALC-03 "Local Intense Precipitation Drainage Study for Calvert Cliffs Nuclear Power Plant Units 1 and 2" (Reference 2.1-17). The effects of the LIP are computed for the safety-related structures at Calvert Cliffs Units I and 2. The assumptions associated with the site-specific LIP analysis are listed in Calculation CEC-008-CALC-03 (Reference 2.1-17).

2.1.1 Site Description Not Impacted by this Amendment and Remains Valid 2.1.2 Probable Maximum Precipitation (Superseded by this Amendment)

The site-specific LIP at Calvert Cliffs Units 1 and 2 is evaluated in Calculation CEC-008-CALC-02 (Reference 2.1-16). As indicated in the FHRR, the LIP estimates are derived using the generalized HMRs No. 51 and 52. Use of LIP estimates from HMRs 51 and 52 resulted in water surface elevations above plant entrances. The LIP estimates are refined by using a site-specific hydrometeorological study in lieu of the generalized hydrometeorological studies of HMRs 51 and

52. The approach and methodology utilized in the site-specific hydrometeorological study is outlined in detail in Calculation CEC-008-CALC-03 (Reference 2.1-17).

2.1.3 Hydrologic Modeling Not Impacted by this Amendment and Remains Valid 2.1.4 Hydraulic Modeling Not Impacted by this Amendment and Remains Valid 2.1.5 Effects of Local PMP (Superseded by this Amendment)

The inputs for the analysis are described below.

o Site-specific LIP Calvert Cliffs Nuclear Power Plant Pg 8 off990 Page

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 aOther Inputs - All other inputs used in the site-specific LIP analysis were obtained from the LI P Calculation 25794-000-KOC-0000-00001I (Reference 2.1-15) developed as part of the FHRR. The HEC-HMS hydrologic model and the HEC-RAS hydraulic model were utilized for the site-specific LIP reevaluation. Both HEC-HMS and HEC-RAS models were obtained from the existing Calculation 25794-000-KOC-0000-00001I (Reference 2.1-15).

The Effects of LIP analysis performed as part of this amendment utilizes the same methodology for hydrologic and hydraulic analyses as described in the FHRR. As discussed earlier, the only change is utilizing more refined site-specific PMP as compared to generalized PMP estimates obtained from HMRs 51 and 52. HMRs 51 and 52 provide generalized and smoothed LIP values over a large geographic domain that covers the United States east of the 105th meridian. Specific characteristics unique to the site were not addressed. Calculation CEC-008-CALC-02 (Reference 2.1-16) considered characteristics specific to the site, and produced PMP values that explicitly considered the meteorology of the LIP storm type which would result in the 1- and 6-hour 1-mi 2 values. Additionally, several new storms have been analyzed and included in this site-specific LIP analysis that were not included in the HMRs. This provided a higher level of confidence in the final values. Comparison between 1-hour site-specific PMP and generalized PMP from HMRs 51 and 52 is shown in Table 2.1-6.

The HEC-HMS model was utilized to estimate rainfall-runoff resulting from the site-specific LIP. The hydrologic model (i.e., HEC-HMS model) used as part of this amendment was developed in Calculation 25794-000-KOC-0000-00001 (Reference 2.1-15). The only change to the HEC-HMS model obtained from Calculation 25794-000-KOC-0000-00001 is the local intense precipitation.

The frequency storm option of the HEC-HMS meteorological model was used in the FHRR. For a frequency storm with a 6-hour total storm duration, the HEC-HMS meteorological model requires precipitation input at 5-minute, 15-minute, 1-hour, 2-hour, 3-hour, and 6-hour durations. Because LIP values at 2-hour and 3-hour interval were not given, a logarithmic regression was fit to the LIP data points to obtain precipitation values at 2-hour and 3-hour storm durations, see Figure 2.1-4.

The local intense precipitation values were replaced with new site specific LIP values obtained from Calculation CEC-008-CALC-02 (Reference 2.1-16). The HEC-HMS model schematic of Calvert Cliffs Units 1 and 2 drainage area is shown in Figure 2.1-5. Flow hydrographs at locations, "J-2",

"Outlet-I", and "Outlet-2" were used for inputs into the water level analysis using the HEC-RAS model. As indicated in the FHRR, all areas are conservatively considered impervious with curve number of 98. Therefore, no roof storage was considered as a conservative approach.

The HEC-RAS model was used to determine the water surface elevation at Calvert Cliffs Units 1 and 2 resulting from the revised site specific LIP time series discharge. The HEC-RAS model of this calculation was developed in Calculation 25794-000-KOC-0000-0000 1 (Reference 2.1-15).

The only changes to the HEC-RAS model obtained from Calculation 25794-000-KOC-0000-00001 are the flow hydrograph, downstream boundary conditions, lateral weir coefficients, and computational method. Calculation 25794-000-KOC-0000-00001 utilizes the steady state HEC-RAS computational method. However, in Calculation CEC-008-CALC-03 (Reference 2.1-17) the unsteady state HEC-RAS computational method with mixed flow regime was used. HEC-RAS provides steady or unsteady flow modeling. Steady flow modeling iteratively solves the energy equation while unsteady flow modeling is based on finite difference approximations of the St. Venant equations.

The unsteady flow St. Venant equations are more physically correct than the energy equation which is used to compute steady flow. From a numerical standpoint, the energy equation has an advantage in that it can be analytically solved, yielding an exact solution. The unsteady flow Calvert Cliffs Nuclear Power Plant Pg 9 off990 Page

Amendment 1 to CON PP Fiood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 equations must be reduced to a discrete form (finite difference approximation) to solve, so there is some built-in error. However, ifdone correctly, this error is inconsequential for river models.

The biggest difference is that steady flow models does not take into account the effects of in-channel and off-line storage in the attenuation of the flood wave. This can be quite significant.

2.1.6 Conclusion (Superseded by this Amendment)

The critical structures at the Calvert Cliffs Units 1 and 2 site consist of the Emergency Diesel Generator (EDG) buildings, utility buildings, and the reactor complex, which consists of the turbine building, the auxiliary building, two maintenance & service buildings, and two reactors. The elevation of the entrances and the floor of the safety-related facilities range from 45 to 45.5 feet MSL. The ground and entrance elevations for safety-related structures, peak water levels, maximum water depth, channel velocity, and freeboard above entrance floor elevation are summarized in Table 2.1-5. Site Specific LIP HEC-RAS water surface profiles for upstream, downstream-I, and downstream-2 reaches are shown in Figure 2.1-9. The HEC-RAS summary output table is provided in Table 2.1-4.

1. The maximum water surface elevations at all locations on the site due to the site-specific LIP event at Calvert Cliff Units 1 and 2 result from a resulting maximum water depth of 1.64 ft.

2. The maximum water surface elevation in the vicinity of the power block area due to the site-specific LIP event is 44.86 ft MSL.

3. The maximum reevaluated water surface elevation due to the site-specific LIP event is below the station floor elevation of 45 ft MSL, as shown in Table 2.1-5.

The predicted flood flow velocities from the HEC-RAS model are shown in Table 2.1-4. For the Downstream-2 reach between Cross Sections 1799 and 583 that cover most of the power block area, the flow velocity (in the main channel) ranges from 0.61 ft/s and 10.64 ft/s. Similarly, for the Downstream-i reach between Cross Sections 140 and 689, which cover the southeastern side of the power block, the flow velocity ranges from 0.04 ft/s to 6.62 ft/s. The maximum permissible mean velocity threshold for concrete surfaces is greater than 18 feet/second. Since the power block is mostly concrete paved, there is no safety concern as a result of scouring. The contributing drainage area to the Calvert Cliffs Units 1 and 2 power block is generally gradual and is mostly covered with an impervious surface, with some woods areas. Therefore, associated risk of sediment and debris being brought to the site is relatively low under the LIP storm event. There is a relatively steep slope between cross-section 123 and 109, which are located east of the Intake Structure and are farther away from the power block area. While velocities at these steep slope reach up to 47.65 ft/s, the slope is covered with stone riprap. The reported high velocity occurs along the steep slopes and only within the Downstream -1 channel. Left overbank represents the area east of the Intake Structure retaining wall. There is no flow in the left overbank area of cross sections 123 and 109. Erosion, if any, will be limited in the channel portion of cross-sections 123 and 109. In an unlikely event, if erosion reached the left overbank, the Intake Structure is protected by existing retaining wall. Therefore, high velocity with channel portions of cross sections 123 and 109 does not affect any safety-related functions or equipments.

Consideration of wind-wave action for the site LIP event is not explicitly required by NUREG/CR-7046 and judged to be a negligible associated effect because of limited fetch lengths and flow depths. Since the site has impervious cover for much of the surrounding area around the power block, any increase in groundwater levels is not expected to cause an impact to safety-related structures. The maximum reevaluated LIP flood elevation is bounded by the current design basis Calvert Cliffs Nuclear Power PlantPae1of9 Page 10 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 (0DB) at the lA EDG Building. Other buildings were not analyzed for LIP in the CDB. Therefore, LIP was considered to be not bounded in these areas. However, a site review concluded that safety-related structures in these areas are protected to elevation 45.0 feet MSL. No manual actions are credited in current licensing basis for LIP flood or required to the 45.0-foot protection level.

Therefore, warning time for LIP is not a relevant flood parameter.

2.1.7 References (Additional References) 2.1-15 Calculation 25974-000-KOC-0000-00001, Local PMP Drainage Study, Revision 0 2.1-16 Calculation CEC-008-CALC-02, Site-Specific LIP PMP Evaluation for Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 1 2.1-17 Calculation CEC-008-CALC-03, Local Intense Precipitation Drainage Study for Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 1 2.1-18 U.S. Nuclear Regulatory Commission, Letter to Licensees, 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, March 12, 2012 Calvert Cliffs Nuclear Power PlantPae1of9 Page 11 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Table 2.1-1: Local Intense PMP Depths at CCNPP Site (Superseded by this Amendment)

Time (Minute) ]PMP Depth (inch) 360 24.8 180 19.26 120 17.25 60 11.7 15 6.1 5 3.9 Calvert Cliffs Nuclear Power PlantPae1of9 Page 12 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 2.1-2: Time of Concentration Calculations Not Impacted by this Amendment and Remains Valid Table 2.1-3: PMP Peak Flow Rates for Sub-Basins Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Calvert Cliffs Nuclear Power PlantPae1of9 Page 13 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Table 2.1-4; HEC-RAS Output Table (Superseded by this Amendment)

River [Reach [River StaJ PofiIe ].9i~~!J MInChEI ~ VeiChni f~~a TopWidth Froude#ChI

_________ ___________ 1.1 _______ I.p!~L..J Ut] ~ (fth] ~ (It] __________

UoStream CCPMPLUPj13 MaxWS 10.

IOO.L9*. 49.2_7 1.64 o7.i 49.07 49.70! 49.821 50.08' 0.023586 4.99', 21.09' 261.15:

496i 50.44 0.055218 8.38' 24.14,, 303.73' 49.36 142.80, 48.25*

4919 49743 0.042181 Up£tream IXPMP UP" 7124285' i:arWS 48.541 UpStream CCPM-U 120.571' M"" W Up~teamCCPM-UP115857 MarcWS 2.58 48.14' UpStream CCPMP- UP 1112' 'amrWS 47.42~ 49.57' 0.0444994 7.28 15.64, 237.79; 47:741 2.26 129.49i 47.641 48.794 47.34 Q0.05694 UpStream CCPMPUP 106428' 1*arrWS 47.13 4.j 49.13; 0,001715.

UpStreamfi CCPMP-U 11.7143' MarrS 12.28 4838 48.95' 0.044582: 71.7 1499 191.92303; UpStream .CCPMP-IJP 1796.599 1'amS 302.598' 43725w 7.51 189.61; 228.39i UpStream 2 CPMPU 9D.2817'70112 48 : 44.91:0.0452659 207*i 47.23: 46.31i 02.31 71.4 175.96.11822.55 125.691 463829  : 44.8:62 0.004678 7.38' 1741 861 2411 02.3 UpSlream CCPP P 7.514 Max WS 478 484688 0.012 82.3 UpiStramCcMPU 8#D2.5722' MaxWS: 1286 4 61.41,. 46.34' UpStream* CCPP-P*N 78.1428' MarrS 47.6 48.30~ 60.047350 124.507 46.318 4742 48.12 0.0477929 2.38 UpStrea2 CCPP-UP * .2 685" amW 44.95 124.08 45.951 2.403 184.815 45.721 7.53 160.87' 5160.3 UpStream cCMP UP2 64 1"limW 472 47975 0.049510 7.7,2 16.34.0 4938:*

175.87* 45.26 44.88, UpStream* CCPP-UP2 5.!111'* MaxS 44.87, 4.01 .47.798_0.053026 7.88 151942, 4&22.

UpStream CCP 7P 54.N22 MarWS*

UpStream2 CCPM-U 43333N2rW 44.86' 467 476' .056948mo~

44.861 192.33' 45.203 8211 152.21 43.52' 448 44.85! 4625 464 84 0.0080912 102*

UpStreamCPPUP3.66 MaxWvS 44.86. 8.48 164.63* 41700 1503.23 44.34, 6.562i 167.1--7 46936--

4637,i 0.0010378

• 23 43.25; 44.85 i 46.391 0.0001534 0.28 44.851 1.72 44.08;* i*7218 0.27 201.85'. 43.28 46.18' 0-1--.001715 DiStream2: CCF'P-LDN2 ;!7992 MaxWS 44.85i 186.47 43.431 Dn*team2' CtI~P-:DN2 179.7 MaWS 44.851 i 44.94 o..O0OO76 44.84! 38.02 13.24- 44836 0723 44.84 S 44.89:-0.00024613 0.22 17.3 43.32 44.841 1 4-4.86'* o0000 44.86j 0.0o0074 448 164.70 4-3.28-6 44.80..... 0101*3 Calvert Cliffs Nuclear Power PlantPae1of9 Page 14 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Table 2.1-4: HEC-RAS Output Table (Superseded by this Amendment) (Continued)

River .Rec . Rive Ste Proflla QTtlMnCE .. Ee r1WS .. Ee .. SeeVlCn k~e o it Froude 1I Chi

- _____ 2 ,j j f] (t I) I i) I (tf) I (l/) I (qi] I (t Dnstream 2l £CPI'IP- DM211286.8' IMaxWS 43.444 43._42 44.79 0.96 121.07 87.22 183 124.30 0.16

_0.54

.22954 43.40 4,4.45 44.59, 45.04[ 0.00895 6.33k 38.45- 3.406 1.21 214.48 43.37 44.38 0.71 225.91 43.33 44.31 44.29 44.52 0.004725 4.15' 67.61* 150.17;

_4..3_7: 7.71 1S8 0.94 229.72 43.26 .44.23_... 44.23 _4438_.004~o515.. 3.79 .79.92_. 231.99* 0.85 119.07 43.23 44.15 44.18: 0.o0092 1.58. 87.60. 252.53; 0.38 DnStrea2IXMP-:DN2 127.4 MxW 297.94 43.16' 43.96' 44.13 44.45. 0.016294 6.25* 55.80 145.24 1.57 Dn~tream 2 CCMP-PN2 25 MxS 43.88 4 4.0 1.63 36948; 45.22 0089 6*.50 ..4i8.22f 12.27.i-o* 2.91 DnSt~ea2 CCPMP-DN2 1254 MaxW DnStreanv2 CII'P-0M 21"8' MxS 1.46 184.99 42.67 _4356. 43.73, _0.00_3759. 3.54 56. 74 157.21 0.83 DnStream2. PMFP-DN2 116.2 MaxW RI at SlriPn DnSbeaiii2CCMPIDN2 1189.6 M*axS 169.23 42.33 43.60 4368.._. 0.__01253. 2.45, 7_9.40 184:27 0.51 DnStremarn l*PP-QN2.116 MaWS 167.91 4208 43.63: 43.67 0.000555 1,84, 105.85 226.03 0.34 DnStream 2 CCPMP-DN2 114166' MaxW 143.19 42.00 43.64 1.44 114.48, 2508 0.24 DnStream fXPtMEDN2 112337 MaS 118.02 42_00 43.66 43: .67' io2 1.05'...127.38 ... 265.01_ 0.16 Dn~trea2 CCPMP-D.M2 1103 MxS 101.80 41.00 43.66; '4367' 0.000046 0.73* 178.36 232.60 0.09 103 73 41.07 43.66 43.66 0.000036 0.61 200.86 200.56 0.08 DnStrea 2. CPMP-DN2 109' aW 108.47 42.00 43.65 43.66 0.000071 0.74 148.79 111.40 0.11 DOiStrearn 2. CCPM DN2 105 MaxWS 112.53 42.00 43.63 43.66* 0.0003261 1.54. 74.68 63.12 0.23 DriStrearn2 CCMP, DM2 1059.33 MaxWS 118.23 41.70 43.44 43.63 0.001537 3.53 34.26 29.64 0.55 66.63 41.30 43.30 43.36; 0o-00434: 1.93' 36.38 29.44 0.27 DnSlream'2 CCPMP-D2 102 MaW 127.18 41.05 41.78 42.59 45.36. 0.107840 15.34 8.75 21.61 3.87 DnSre'am 2 CCt*P- DN21085MaW 40.39 40.96 41.42 43.04 0.075820 11.66: 11.45 33.46 3.22 129818 44.48-0539-346 17.21 8.11. *4.3*2-5:-

DrlStra2 CC*PMPDM2 989 MxW 6.71 131.74 38.78 39.11 39.59 43.56 0.364728, 17.21 8.24 44.57 6.46 Dn~ram'2 CCPMP-N288 MaW 132. 04 17.13 8.39 43.07 6.30 131.19 36.90 37.28 37.75 40.55' 0.210588 14.99 9.71 42.15 5.07 131.86* 36__.44; 3.6.83 38_.100.10t07434' 10.86 13:.46 41.47_ 3.11 DnSteam 2 CCPP-DN2 05 Max VS 132.47 35.00 35.51: 35.99 *:02. 0.1*0580 13.08! 11.26: 37.05 3.72 133.09 34.05 34.61 3514 37.39, 0.101697i 13.64 10.61 32.14 3.70 Dn~tream2 CCPMP DM2 58 xVS: 133.70 33.11 33.69 34.29 37.13 0.117869 15.10: 9.49 27.86 4.02 Ontea2CP, -N255 Ma1/ 14.14 10.38, 26.09. 3.40 134.93 31.21' 31.90 3256 36.28~ 0.138444: 17.21 8.48 21.15 4.20 113.78. 29,60 31.31 31.58 32.06, 0.008623 7.27 18.25 28.52 1.22 107._49 2800.oo 31..3,4 a000429 2.45: 55.78 43.06 0.29 D~rea 2 PMP D2546. Max V/ 31.27 28.67i 31.28 0.000187, 1.50o 51.19, 45.81 0.19 104.20 31.22: 0.002159 3.86; 31.45 44.80 0.62 30.81 31.36 33.033 0.051---713- 12.04' 13.99 32.67. 2.89 2933 30.30: 3-.88 138.32 29.53' 10.45 14.08 40.82 2_55 138.32 29.29 29.72 30.92 0.074734 10.47 13.96' 44.06 2.58 200.25 43.24 44.95 44.97 0.000170 1.-2* 189.68 214.4 0.18 43.27 44.92 0.000108' 0.94 170.15 201.51 0.14 118.37 43.30 44.91 0.000094 0.86 154.44 193.62: 0.13 110.96 43.34 0.13 4-337? 4i89! 4490§ 08 -0.12 99.14 43.40 44.88 0.12 43.41. 44.89 0.080090 0.78. 128.26j 203.32.

4489 0000084_ 0.12 43.42 44.88 0.76. 129.01 206.49 0.12 92.37 44.088 0.000082 0.74 129.96 209.85 4-3-44" 44.87' 44.88, 0.00007 071i iA :

• 0.70* 131i8A 2i-s.55' 0.11 DnStream if CCPMP- DM11601.5' Max V/S 88.37 43.45, Calvert Cliffs Nuclear Power PlantPae1o9 Page 15 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Table 2.1-4: HEC-RAS Output Table (Superseded by this Amendment) (Continued)

River

.... ]Rec 1.. .. .. 1 .. .I.

4. RIverSt~alProfile Toa

• l i~E

{* .;l-*CiV/S G;~vEGSp (ft ]111!{L (ft}/

VeiChn

] jfA*J

{L..i!

FlWAe

{rat_____]_

o",',~t rue C OnStra1i CCP*MI- DN1 16.2" Max WS 104.28i S 44.90; 00000951 DnStrearnl CCPt.IP-DNI 648 MaxWS 9.14*s:*...... 43.37i 43.40o. 44.891 4..

4..88: 0831 134.49! 182,35 DnStrearn 'I CCPMP- DN1 638.7" 0.8 "1-28. 26.... 203.325 0.11 MaxWS 93.82 43.421 44.88:

')nStrearnl CCPMP-ON1 629.4" MaxWS OnStrearni ~CPMP-DN1 62111" MaxWS

7T7: 0.000082: 0.74* 12&9.6 209.85*

OnStrearn 1 CCP$P- DN1 61118" MaxW$ - ..4-4.88:io.0oo-y7 0.11 DnStrea'nl CCPMP-PN1 601.5" MaxWS OnStream 1 CCPMP-DN1 592.2" MaxWS 0.11 9....

37k- 43.4.. 4.87.

3 *:* 0.63 134._28 220.87j DnStream 1 CrJ'~4P- ONi 582.9" M4~ WS OnStream 1 CC~MP- DNI 573.6" M~xWS , 44.891 0.0000719 0.10 DnStream 1 CC~MP- ONi 584.3" 88.37 43].45- 44.-87g 0.4 3588i 0485 MexWS 6i 6 DnStream 1 CCPMP- DN1 555 Max WS  ; 4.90; 0.000015 0.09 DnStream 1 CCPMP- ONi 545.571" Max WS OnStream 1 CCPNIP- ONi 53& 142" MaxWS 89.68T 43.70: 44.87' 0.08

8 0.90005_60. 0.07 DnStrearnl CCPMP-DN1 526.714" MexWS DnStreaml CCPMP-DNI 517.285" MaxWS 81.91! 43.T: 44.88 44.88& 10000388 Q4! 159.82 191.72' DnStrean 1 CCPMP- ONi 507.957" Max WS 1 2954.95§ -517686 0.11 OnStrearn 1 CCPO.4P- DM1 498.428~ MaxWS 1.63oi05.4i- 412212 DnStrearnl CCPMP-DNI 489 MaxWS 0.213 DnStrearn 1 CCPMP- DNi 472.8" MaxWS i8.574 OnStream 1 CCPMP- DN1 456.6" MaxWS 43.48 44.88. 0750' 878.07 1080.26 0.16*

OnStrearn 1 CCPMP- DN1 440.4" MaxWS -0.191 72898 297 1120 OnStrearn 1 CCPNP- DN1 424.2" MaxWS 443i44.90.i 1100053o

.--I *. .... 2 0.26 DnStreafnl CCPMP-DN1 408 MaxWS 6329*1!43*.53: 44.89 .......

DnStrearnl CCPMP-DN1 399.333" MaxWS 3862.21 43.56, 44.89 DnStreaml CCPMP-DN1 390.666" MaxWS 141 .9 5 43593 44.89: 44.13; 0.000908 DnStreaxi 1 CCPMP- DN1 382 MaxWS 1.51; 48.30, 50371 0.09 OnStrearn 1 CCPMP- DM1 373285" Max WS 62.22! 43.61: 44.89 DnStream 1 CCPMP- DM1 364.571" MaxWS 1.750 1 890 5275.3 OnStream 1 CCPMP- DM1 355857" MaxWS S44.88! 0.0009688 DnStreaail CCPMP-DN¶ 347.142" MaxWS 0.69 11.5 41.86; 44.89:

DnStream.1 CCPMP-DNI 338.428" MaxWS DnStrearnl CCPMP-DN1 329.714" MaxWS 14.11! 39387 44.5:73 OnStrearni CCPt"IP-DN1 321 MaxWS 4326 43.92 0.0029761 1.514 20.5 40857 DnStrearnl CCPNP-DN1 312.4" MaxWS DnStreain 1 CCPMP- DM1 3038" MaxWS i 42489 0,000066 0.14 DnStrea~n 1 CCPMP- DM1 295.2" MaxWS 16908 4370 44; 3.84 OnStreatni CCPMP-DN1 286.6" MaxWS DnStrea~,1 CCPMP-DN1 278 MaxWS DnStreaml CCPMP-DN1 268.6" MaxWS 4421 i.67' 11000000 DnStreainl CCPMP-DN1 2592" MaxWS -0.90 42.72 2081.6 0.79 DnStrearn I CCPMP- DM1 - _____

DnStreamT CCPHP-DN1 249.8" MaxWS 0.13 DnStreaml CCPMP-DN1 240.4" MaxWS DnStream 1 CCPMP- DM1 231 MaxWS 1.68 OnStrearni ~XPMP-DN1 196 t%4axWS 0.95 DnStreaml CCPMP-DN1 166 MaxWS 0.38 DRStrearnl CcPMP-DN1 149 MaxWS DnStreaml CCf -DM1 140 Ma~rWS DnStreainl CCPMP-DN1 131 MaxW$ 3.94 DnStreainl CCPMP-DN1 127." MaxWS DnStrearril QFMP-QN1 123 MaxWS DnS~ream1 £CPMP-DN1 119" MaxWS 0.16 DnStrearnl CCPt"IP-DNI 115 MaxWS DnStreainl CCPMP-DMI 112." MaxWS DnStream1IGCPt~1P-0N1i109 MaxWS 11.47*

Calvert Cliffs Nuclear Power PlantPae1of9 Page 16 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Table 2.1-5 Comparison of Elevation at Building Entrances and Water Levels (Superseded

_______________ ______ by this Amendment) ___ ____

Current Reevaluated Entrance Design Flood Level :3)Freeboard (1)Duration Critical Structures Floor Basis Computed Max. Channel above of flooding Elev. Flood in this Water Velocity Entrance at Level Amendment Depth (ft) (ft/s) Floor Ely. Entrances (ft) (hr)

______________ft-MSL ft-MSL ft-MSL ___ __ ___

Not South Service Building 45 discussed 44.86 1.16 1.36 0.14 N/A

_____in CDB ___ __ ___ ___

Not Turbine Building 45 discussed 44.81 1.11 -0.9(2) 0.19 N/A

______ in CDB _ _ _ _ _ _ _ _ _ _ _

Not Auxiliary Building 45 discussed 44.86 1.51 0.61 0.14 N/A

______ in CDB _ _ _ _ _ _ _ _ _ _ _

Not Auxiliary Building 45 discussed 44.81 1.31 1.18 0.19 N/A

______ in CDB _ _ _ _ _ _ _ _ _ _ _

Not Auxiliary Building 45 discussed 44.79 1.64 0.71 0.21 N/A

______in CDB ___ __ ___ ___

Not Auxiliary Building 45 discussed 44.76 1.26 1.32 0.24 N/A

______ in CDB _ _ _ _ _ _ _ _ _ _ _

Not Turbine Building 45 discussed 43.64 0.64 5.40 1.36 N/A

_______ ______ in CDB _ _ _ _ _ _ _ _ _ _ _

DislGnrtr 45.5 44.8 43.64 0.64 5.40 1.86 N/A Buildin _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

(1)Durations of flooding at entrances were not reported as the area surrounding the power block will remain dry during the LIP event.

( 2)Negative velocity show discharge in HEC-RAS model going the opposite direction than downstream direction, which is the primary flow direction.

( 3)Freeboard= Entrance Floor Elevation - Peak Water Surface Elevation Calvert Cliffs Nuclear Power PlantPae1o9 Page 17 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Table 2.1-6 Comparison of PMP Estimates (New Table)

PMP Duration and Area Generalized PMP Site-specific LIP PMP (FHRR) (Reference 2.1-16) 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, 1- square mile 18.48 inch 11.70 inch Calvert Cliffs Nuclear Power PlantPae1of9 Page 18 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.1-1: Site Locations Not Impacted by this Amendment and Remains Valid Figure 2.1-2: General Site Terrain and Drainage Flow Directions Not Impacted by this Amendment and Remains Valid Figure 2.1-3: Sub-Basin Drainage Area Map Not Impacted by this Amendment and Remains Valid Calvert Cliffs Nuclear Power PlantPae1of9 Page 19 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.1-4 Fitting of PMP Depths (Superseded by this Amendment)

(Deleted "from HMR51 & HMR52" from the title) 30 J 25 4

,* y = 4.9613In~x) - 6.5022 o 20

• -Log. (Precipitation Data

• ,- Points)

• " 15 10 0 i 110 100 1000 Log (Duration, Minutes)

U V

• Calvert Cliffs Nuclear Power PlantPae2of9 Page 20 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.1-5 Schematic of HEC-HMS Model (Superseded by this Amendment)

-Pmpos~roed forU 3 Vdehib b.Te Calvert Cliffs Nuclear Power PlantPae2of9 Page 21 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.I-6a Hydrograph at Sub-I Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2,1-6b Hydrograph at Sub-2 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.1-6c Hydrograph at Sub-3 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.I-6d Hydrograph at Sub-4 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.1-6e Hydrograph at Sub-5 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.1-6f Hydrograph at Sub-6 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.I-6g Hydrograph at Junction J-1 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.I-6h Hydrograph at Junction J-2 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.1-6i Hydrograph at Diversion Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.1-6j Hydrograph at Outlet-I Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.1-6k Hydrograph at Junction J-3 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Figure 2.1-61 Hydrograph at Outlet-2 Deleted- No Longer Applicable because of revised HEC-HMS model with site-specific PMP Calvert Cliffs Nuclear Power PlantPae2of9 Page 22 of 90

Amendment 1 to CCNPP Exelon Generation Co. Flood Hazard Reevaluation Report September 08, 2015 Figure 2.1-7a HEC-RAS Model Cross Section Plan Deleted- No Longer Applicable because of revised HEC-RAS model with site-specific PMP Figure 2.1-7b HEC-RAS Cross Section Plan Deleted- No Longer Applicable because of revised HEC-RAS model with site-specific PMP Figure 2.1-8 Schematic of HEC-RAS Model Not Impacted by this Amendment and Remains Valid Calvert Cliffs Nuclear Power PlantPae2of9 Page 23 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.1-9 Local PMP Maximum Water Level Profiles (Superseded by this Amendment)

L W

CrI 1

J

• SaWS S

I~i-t

• iJ Calvert Cliffs Nuclear Power PlantPae2of9 Page 24 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.1-10 Maximum PMP Water Levels Deleted- No Longer Applicable because of revised HEC-RAS model with site-specific PMP Figure 2.1-11a Rating Curves and Cross Section Plot at Cross Section 1722 of Downstream-2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-sp3ecific PMP Figure 2.1-11b Rating Curves and Cross Section Plot at Cross Section 1509 of Downstream -2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-sp*ecific PMP Figure 2.1-11c Rating Curves and Cross Section Plot at Cross Section 1412 of Downstream-2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-sp*ecific PMP Figure 2.1-l1d Rating Curves and cross Section Plot at Cross Section 1336 of Downstream-2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-sp*ecific PMP Figure 2.1-lie Rating Curves and Cross Section Plot at Cross Section 1103 of Downstream -2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-sp*ecific PMP Figure 2.1-11f Rating Curves and Cross Section Plot at Cross Section 1075 of Downstream-2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-sp*ecific PMP Figure 2.1-11g Rating Curves and Cross Section Plot at Cross Section 648 of Downstream-2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-sp*ecific PMP Figure 2.1-11h Rating Curves and Cross Section Plot at Cross Section 489 of Downstream-2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-sp*ecific PMP Figure 2.1-11i Rating Curves and Cross Section Plot at Cross Section 382 of Downstream-2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-specific PMP Figure 2.1-11j Rating Curves and Cross Section Plot at Cross Section 321 of Downstream-2 Deleted- No Longer Applicable because of revised HEC-RAS model with site-specific PMP Calvert Cliffs Nuclear Power PlantPae2of9 Page 25 of 90

Amendment 1 to CCNPP Exelon Generation Co. Fiood Hazard Reevaluation Report September 08, 2015 2.4 REEVALUATED PROBABLE MAXIMUM STORM SURGE ANALYSIS (Superseded by this Amendment) 2.4.1 Introduction Not Impacted by this Amendment and Remains Valid 2.4.2 Probable Maximum Storm Surge Evaluations The reevaluated PMSS analysis utilizes a different modeling approach than the one used in the FHRR. The FHRR utilizes the SLOSH model used by the National Hurricane Center for storm surge prediction. According to the NRC, a two-dimensional model capable of modeling hurricane wind and pressure fields, such as Delft3D, is necessary to model a hurricane storm surge over complex topography. PMSS Analysis performed as part this amendment utilizes two dimensional Delft3D model. Delft3D is an advanced numerical modeling program that is caPable of simulating flows, sediment transpOrts, waves, water quality, morphological developments and ecology. As part this amendment, the Delft3D-FLOW and Delft3D-WAVE (SWAN) modules are used to simulate the coupled effects of flow movement (surge) and wave propagation (wave spectra, height, period, and setup) through a water body (Atlantic Ocean and Chesapeake Bay) when acted upon by external forcing funCtions (wind fields, atmospheric pressure fields, and tides) at the planetary boundary. The physical features of the numerical model are created from regional and local bathymetry and topography. The model is calibrated and validated to observed tides and historical hurricane storms (Hurricanes Isabel and Irene). The antecedent water level conditions, including 10 percent exceedance high tide and potential sea level rise, are included in the numerical model.

The existing storm surge analysis performed as part of the FHRR utilizes a SLOSH model, which is a depth-averaged two dimensional finite difference model on curvilinear polar, elliptical, or hyperbolic grid schemes. Some of the limitation of the SLOSH program are: 1) the SLOSH model utilizes a simplified parametric wind model, based on pressure and radius of maximum winds to calculate the wind stresses over water that generate storm surge values for the model,

2) grid resolution and bathymetry used in SLOSH are coarse, for example, the Chesapeake Bay has a grid resolution of approximately 0.7 miles, 3) the SLOSH model results are within +/-20 percent and does not take into account river flow, rainfall, wind-wave interaction and wave setup, and 4) topographic inundation is performed utilizing low resolution topography data.

Storm surge generation is a very site specific process and depends on prevailing storm tracks, pressures, shoreline shap.e, and bathymetry. The revised PMSS analysis (Reference 2.4-24) utilizes hurricane parameters based on NWS 23 methodology and high resolution bathymetrical data obtained from the National Oceanic and Atmospheric Administration (NOAA) and the United States Geological Survey (USGS) at the vicinity of Calvert Cliffs Units 1 and 2. Moreover, the storm surge model is calibrated and validated for historical hurricane events. Therefore, software error of 20 percent will not be added as compared to the SLOSH model.

The methodology used in the PMSS analysis performed as part of this amendment is consistent with the following standards and guidance documents:

• NUREGICR-7046, 'Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America" (Reference 2.4-15). This guidance document provides present-day methodologies and technologies that can be used to estimate design-basis floods at nuclear power plants for a range of flooding mechanisms. Sections 3.5, 3.6, Appendix E, Calvert Cliffs Nuclear Power PlantPae2of9 Page 26 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 and Appendix F of NUREG/CR-7046 provide additional guidance and an illustrative case study for a PMSS analysis.

ANSI/ANS-2.8-1992, "Determining Design Basis Flooding at Power Reactor Sites ANS-2.8-1 992" (Reference 2.4-19, Section 7, "Probable Maximum Surge and~Seiche Flooding").

This document provides a methodology for estimating storm surges and seiches at estuaries and coastal areas on oceans and large lakes. ANSI/ANS-2.8-1992, Appendix C gives a simplified method of estimating surges on the AtlantiC and Gulf Coasts. Specifically the document calls for:

oUse of a two-dimensional coupled hydrodynamic ocean circulation and wave model, both driven by a planetary boundary layer (PBL) that provides atmospheric forcing.

o Use of the steady-state hurricane parameters for defining the hurricane wind and pressure field, such as the parameters described in NOAA, National Weather Service (NWS) Technical Report 23 (Reference 2.4-7).

o Incorporation of detailed bathymetric, topographic, and hydrologic data into the model with proper sensitivity testing for bottom friction coefficients, wind stress coefficients, and other applicable model parameters.

oValidation of the model with reproduction of one or more large floods with particular importance that model simulation and associated parameters use the largest reported historical floods near the site. The model shall demonstrate to be conservatively applicable for the probable maximum hurricane condition.

• NUREG-0800, "Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants (LWR Edition)" (Reference 2.4-26). This regulatory document provides guidance to NRC staff in performing safety reviews under 10 CFR Part 50 and 10 CFR Part

52. Section 2.4.5 provides general guidance for estimating flooding due to storm surge and seiche. The technical rationale given in the document requires the following:

o Appropriate consideration of the most severe natural phenomena historically reported for the site and surrounding area, with sufficient margin for the limited accuracy, quantity, and time period in which the historical data have been accumulated.

o Appropriate combinations with the effects of the natural phenomena.

o Use of a deterministic approach to assess design basis (and for this calculation, potentially beyond design basis events) and the impact on the safety functions to be performed. Such an approach will account for. the practical physical limitations of natural phenomena that contribute to the severity of a given event. It also specifies a level of conservatism to assess the severity of floods to provide a level of assurance that the most severe hydrologic site characteristics have been identified and that the site's physical characteristics be taken into account when determining its acceptability for a nuclear power plant when considering the potential for flooding.

Note that the acceptance criteria of NUREG-0800 are based on meeting the relevant requirements of NRC regulations 10 CFR Part 100, 10 CFR 100.23, 10 CFR Part 50, and 10 CFR 52.17(a)(1)(vi). However, the technical rationale for the application of these acceptance criteria provides appropriate consideration and justification for the methods applied in this calculation.

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Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015

• JLD-ISG-2012-06, "Guidance for Performing a Tsunami, Surge and Seiche Hazard Assessment Revision 0" (Reference 2.4-27). JLD-ISG-2012-06 provides the most recent guidance and was developed specifically for the evaluation of Section 50.54(f) flooding reevaluations for coastal flooding mechanisms. Because this guidance forms the basis of NRC's evaluations, it is appropriate to address the analytical approach presented therein. Furthermore, the approach is not new; ANSI/ANS 2.8-1992 presents a similar approach (as it applies to coastal surge).

JLD-ISG-2012-06 guidance allows for the application of NWS 23 PMH in determining the design storm for hurricane surge modeling. However, the guidance specifically prescribes analyzing storm sizes (i.e. the Radius of Maximum Wind [RMW]) beyond the parameter guidance provided in NWS 23. Section 3.2.1.1 of JLD-ISG-2012-06 states:

Surge elevation increases with increasing hurricane size. In addition, based on site-specific topographyor bathymetry, the increase in storm surge with increasinghurricane size may reach an upper bound. Thus, this behavior should be further investigated by varying the PMH size (radius of maximum wind) beyond the upperbound specified in NWS 23 for a PMH approaching the site (Irish et al., 2008; Resio and Westerink, 2008). ANSI/ANS-2.8-1992, Section 7, provides additionalguidance on the critical combinations of PMH parameters.

ANSI/ANS-2.8-1 992 applies a similar approach to extrapolating key parameters:

7.2.1.4 CriticalCombination of Parameters Various combinations of the given ranges of the radius of maximum winds, R, and fonward speeds, T, and the maximum 10-mmn sustained 33-ft wind (Vx), which varies with different values of R and T, should be input to the hurricane surge calculation to determine those critical combinations of parametersthat would result in the most severe flood condition.

7.2.4 Requirements for Review To facilitate an independent review, the probable maximum meteorological winds and associated parametersdetermined for each of the meteorological events (PMH, PMWS, and moving squall line), the following should be included:

(1) Detailed analyses of actual historical storm events in the general region of the site.

(2) Modifications and extrapolations of data to reflect a more severe meteorological wind system than actually recorded, insofar as these modifications and extrapolations are deemed "reasonablepossible"of occurringon the basis of meteorologicalreasoning.

(3) Sufficient bases and information to ensure that the parameterspresented are the most severe combination.

Additionally, NUREG/CR-7046, Appendix H 3.1 and ANS 2.8-1 992, Section 9.2.2.1, states that the following combination of flood-causing events provides an adequate design basis for shore locations:

"H 3.1 Shore Location, Combination of:

1) Probable maximum surge and seiche with wind-wave activity.

2) Antecedent 10 percent exceedance high tide."

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Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Therefore, the criteria for PMSS with wind-wave activity and the antecedent 10 percent high tide including potential sea level rise were evaluated. The wave runup associated with the wind-wave activity was evaluated in Calculation CEC-008-CALC-10, "Probable Maximum Storm Surge (PMSS) Wave Runup" (Reference 2.4-25).

2.4.2.1 Topographic and Bathymetric Data Delft3D computer software uses high resolution topographic data through grid refinement, domain decomposition, nesting, and triangulation interpolation techniques allowing accurate representation of the bathymetry of Chesapeake Bay and the coastline at the Atlantic Ocean.

High resolution bathymetry and topography data for storm surge modeling at Calvert Cliffs Units 1 and 2 are available from various governmental agencies. For the Atlantic Ocean, the General Bathymetric Chart of the Ocean (GEBCO) (Reference 2.4-30) gridded bathymetric data was used.

The GEBCO 1-km resolution bathymetry is the best global bathymetry currently available for the open Atlantic Ocean. The shallow-water bathymetry at Chesapeake Bay and near shore of the Atlantic Ocean were obtained from NOAA's National Ocean Service (NOS) (Reference 2.4-31).

The local topography that include the Calvert Cliffs Units 1 and 2 site and surrounding areas was based on Light Detection and Ranging (LiDAR) discrete-return point cloud data that is obtained from the USGS (Reference 2.4-32). The density of the NOAA and USGS data is found to be appropriate for storm surge modeling of Chesapeake Bay and the near shore and offshore zones of the Atlantic coast. Table 2.4-4 identifies each data type and its source.

Additional site features such as the Intake Channel and Intake'Deck were incorporated into the local topography.

Current licensing basis is provided in Mean Sea Level (MSL) vertical datum. Therefore, data gathered from different sources is converted to MSL and then imported into the Delft3D model.

Calculation CEC-008-CALC-05 provides the detailed approach and methodology. According to the Calvert Cliffs Calculation 124832-F-2 (Reference 2.4-33), the MSL datum is 0.64 ft higher than the National Geodetic Vertical Datum of 1929 (NGVD 29). Therefore, a conversion factor of "NGVD29 = MSL + 0.64 feet" was used.

2.4.2.2 Storm Surge Model Grid Delft3D uses a gridded domain to solve two-dimensional and three-dimensional flow problems with the capability of coupling a model with wave simulation algorithms. As part of this amendment, a sufficiently large coarse domain was selected to ensure all potentially significant regions and features that could affect the storm surge results in Chesapeake Bay were captured and appropriate boundary conditions analyzed. As shown on Figure 2.4-6, the boundaries of the coarse grid were located on the deep water of the Atlantic Ocean, sufficiently far from Calvert Cliffs Units 1 and 2 to prevent reflection at boundaries from impacting results at the site. Due to the size of the area under study, five FLOW domains were considered necessary: one coarse domain with coarse resolution and four refined grids of increasingly finer grid resolution. The four more refined grids shown on Figure 2.4-6 were included within the coarse grid using domain decomposition tool within Delft3D-FLOW. In domain decomposition, the model conveys the information from the coarse grid to provide boundary conditions for the finer grids, which will vary with time during the evolution of the simulation. The finer resolution grids were only c~reated for Chesapeake Bay and close to the Calvert Cliffs Units 1 and 2 site. The refined grid in the vicinity of Calvert Cliffs Units I and 2 has a grid resolution of 8m. Additionally, four refined grids were generated for the Delft3D-WAVE model as shown on Figure 2.4-9. The nesting modeling approach in the Delft3D-WAVE program was used to insert the refined wave grids into the coarse grid domain.

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Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 In general, the Delft3D-FLOW and Delft3D-WAVE grid cell sizes were selected to be small enough to accurately model the storm surge dYnamics during PMH but *large enough to maintain an acceptable runtime for the simulations. The Delft3D-FLOW and Delft3D-WAVE grids are shown on Figures 2.4-6 and 2.4-9, respectively 2.4.2.3 Delft 3D Model Calibration Calibration and validation of a storm surge model are critical to the success of storm surge modeling, the defensibility of the technical approaches that are taken, and ultimately to acceptance of storm surge results. As required by NUREG/CR-7046, the parameters of a given model may need to be calibrated using data from large historical storm events, and then validated with comparatively large storm events not used in the calibration. To verify the prediction capability of the Delft3D model, Calibration and validation are performed by comparing the Delft3D output with observed historical storm surges, tides, significant wave heights, and wave periods during historical hurricane events.

A numerical model that accounts for the regional characteristics of Chesapeake Bay was built using the Delft3D-FLOW and Delft3D-WAVE software to predict the storm surge and wave dynamics at Calvert Cliffs Units 1 and 2. Some selected parameters of the Delft3D-FLOW and Delft3D-WAVE models were calibrated by varying the parameters until a stable running model was obtained and a reasonable agreement between the simulated results and observed conditions was achieved. A typical calibration procedure is shown on Figure 2.4-10.

Hurricane Isabel (September 6 to 20, 2003) and HurriCane Irene (August 20 to 28, 2011) were used for calibration and verification of various Delft3D model parameters, respectively. Hurricane Irene and Hurricane Isabel were selected because of the strength of the hurricanes, availability of calibration data (water level and wave characteristics), and the track of the storms and resulting stormi surge in Chesapeake Bay. Hurricane Irene and Hurricane Isabel tracks are shown on Figure 2.4-11.

The Delft3D models were calibrated and validated for the following three cases:

1) Delft3D calibration for tides

2) Delft3D calibration for Hurricane Isabel

3) Delft3D validation for Hurricane Irene Development of Atmospheric Forcing - Historical Hurricane Wind~and Pressure Fields Historical hurricane tracks within a 200-mile radius of the Calvert Cliffs Units 1 and 2 station are provided on Figure 2.4-4. Examining the historical data from 1900 to present, as shown in Figure 2.4-4, most historical hurricanes move in a northerly direction. One important note is that Eastern-type hurricanes that travel to the east of Chesapeake Bay generate a maximum surge in the southern portion of the Bay, whereas western-type hurricanes that pass to the west of Chesapeake Bay create the highest surge in the northern part of,the Bay. For .calibration of the Delft3D storm surge model HurriCane Irene, which was a Western-type, and Hurricane Isabel, which was an Eastern-type were examined. Hurricane Irene (August 20 to 28, 2011) and Hurrcane Isabel (September 6 to 20, 2003) were used for calibration and verification of various Delft3D model parameters, respectively.

Refer to Figure 2.4-11 for Hurricane Irene and Hurricane Isabel tracks. Hurricane Isabel is considered to be one of the most significant tropical cyclones to affect portions of northeastern Calvert Cliffs Nuclear Power PlantPae3of9 Page 30 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 North Carolina and east central Virginia. Hurricane Isabel passed to the west of Chesapeake Bay perpendicular to the coast and created the highest surge in the northern part of the Bay.

Hurricane Isabel made landfall near Drum Point, North Carolina as a Category 2 hurricane.

Hurricane Isabel had a significant impact on Chesapeake Bay with a maximum surge of 2.48 m in Chesapeake City, MD. Hurricane Irene first made landfall in North Carolina as a Category 1 hurricane and then continued north-northeastward, just offshore of Chesapeake Bay, and made another landfall very near Atlantic City, New Jersey.

The historical hurricane parameters and track position data for hurricane Irene and Isabel were obtained from NOAA and from Unisys Weather. Atmospheric forcing (wind and pressure data) for Hurricanes Isabel and Irene was generated using the parametric wind and pressure field model described in Memorandum HUR 7-97 (Reference 2.4-28). The wind model can (approximately) reproduce the wind field and pressure field of historical hurricanes with meteorological parameters including hurricane path, atmospheric pressure, and radius of maximum wind. These parameters were assembled in Calculation CEC-008-CALC-06 (Reference 2.4-21) from the NOAA National Hurricane Center.

Delft3D Calibration for Tides Prior to storm surge simulations, the Delft3D model was calibrated first with respect to the bottom friction coefficient by simulating tide characteristics from September 15, 2013 to October 15, 2013.

The model was forced by tidal constituents at its open boundary that were assembled for the open boundary grids. In addition to the open boundary tidal constituents, semi diurnal, diurnal, and long period earth tidal forces were also applied to interior cells of the model domain to model the contribution of the earth gravitational forces on the water level.

To model freshwater flow interactions with Chesapeake Bay, river boundary conditions were created as a time series discharge function. Contrary to land boundaries, the boundary condition for rivers creates a boundary segment that allows a non-zero flux. Chesapeake Bay receives freshwater inflow from eight major rivers and from more than 150 creeks. Because most of these creeks are ungauged and small, only freshwater measurements from the major rivers are used as a flow boundary condition. The majority of the flow is derived predominantly from Susquehanna, Potomac, Rappahannock, and James Rivers. The flow contribution from these four major rivers is modeled as an inflow boundary. During tidal calibration, Delft3D-WAVE and wind and atmospheric pressure forcing in Delft3D-FLOW were turned off.

For this amendment, a one-month period simulation was run in order to span a complete spring-neap tidal cycle. A simulation time step of 1-minute was used and outputs are produced at 6-minute time steps. The simulated 6-minute tidal levels were used for comparison with resynthesized tidal water levels at tidal gauge stations around the Chesapeake Bay area to ensure that the model was correctly modeling the tidal forcing from the Atlantic Ocean.

Resynthesized tidal water levels for tidal calibration were obtained from the XTide tidal constituents assembled by Deltares.

In deep water, the speed and direction of propagation of the tides is primarily controlled by the ocean bathymetry and bottom roughness. Spatial variability of Manning's roughness on the ocean floor requires that this parameter be considered a calibration parameter in both the tidal and surge model evaluations.

For the Calvert Cliffs Units 1 and 2 Delft3D model, initially a Manning's roughness n coefficient value of 0.02 was specified for the entire grid area in the Delft3D model. A Manning's n of 0.02 is a typical value for coastal modeling application as indicated in the Delft3D-FLOW User Manual.

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Amendment 1 to CCNPP Exelon Generation Co. Flood Hazard Reevaluation Report September 08, 2015 During the calibration process, the Manning's roughness coefficient was adjusted for optimal simulation results during tidal calibration using values between 0.008 and 0.025.

Simulated time series tidal water surface elevations were compared with resynthesized tidal elevations in terms of amplitude and phase at selected locations throughout the domain area.

The modeled - resynthesized agreement was evaluated using the Root Mean Square Error (RMSE) and Nash-Sutcliffe Efficiency (NSE). Figure 2.4-12 shows the locations of the tidal stations used for tidal calib-ration. The 20 stations on Figure 2.4-12 provide a strong spatial coverage in Chesapeake Bay and coastline of the Atlantic Ocean for assessment of the model performance.

Using the best fit Manning's roughness values, modeled water surface elevations show an excellent agreement at the majority of the calibration tidal stations with an average RMSE and NSE of 0.061 meters (0.2 ft) and 0.922, respectively. Figures 2.4-13, 2.4-14, and 2.4-15 compare the Delft3D-FLOW simulated water levels against resynthesized tidal waters for some selected tidal stations. Calibrated spatially variable Manning roughness coefficients in the Chesapeake Bay region are shown on Figure 2.4-16.

Delft3D Calibration and Verification during Hurricane Events (Hurricane Irene and Isabel)

Once the Calvert Cliffs Units 1 and 2 Delft3D-FLOW tidal model was calibrated, Hurricane Irene and Hurricane Isabel were simulated to calibrate and validate other physical parameters of the Delft3D-FLOW and Delft3D-WAVE (SWAN) model. The Calvert Cliffs Units 1 and 2 Delft3D storm surge model was calibrated by varying the wind drag coefficient, in the case of Delft3D-FLOW, and only if necessary, the JONSWAP bottom friction and depth-breaking gamma coefficient in the case of Delft3D-WAVE (SWAN), until Delft3D computed water surface elevation and wave characteristics (wave height and period) matched the results of the observed or reported values of the historic storms as closely as possible. For the calibration and validation of the wind drag coefficients, Delft3D was run using only the FLOW module. For the calibration and validation of the wave parameters, Delft3D was run using both the FLOW and WAVE modules.

The wind drag coefficient was used as the calibration parameter in the Delft3D-FLOW model with atmospheric wind and pressure forcing. Six scenarios were run with the wind drag coefficients shown in Table 2.4-5. The wind drag coefficient was calibrated and validated through comparison to observations of maximum surge water levels. Modeled versus measured data agreement was evaluated using the RMSE, Coefficient of Determination (R2), and Mean Absolute Error (MAE).

Additionally, a time series graph between observed and simulated water levels was generated for a visual evaluation at selected locations throughout the domain area.

Figure 2.4-17 and 2.4-18 show the spatial distribution of water level and wave recording stations used for storm surge calibration/verification. Overall, the Delft3D storm surge model shows good performance at all calibration stations with a small RMSE. The storm surge model produces the best results in Chesapeake Bay near Calvert Cliffs Units 1 and 2 when using the wind drag parameterization from Scenario 2, shown in Table 2.4-5. Additional verification runs were performed using Hurricane Irene and calibrated parameters from Hurricane Isabel simulation to validate the calibration parameters. Delft3D modeled and observed maximum water surface elevation agreement during calibration (Hurricane Isabel) and verification (Hurricane Irene) are shown on Figures 2.4-19 and 2.4-20. Figures 2.4-21 through 2.4-24 compare the Delft3D-FLOW simulated water levels against observed water levels for some selected water level stations.

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Amendment 1 to CCNPP Exelon Generation Co. Fiood Hazard Reevaluation Report September 08, 2015 The Delft3D-WAVE (SWAN) model was set up to account for depth induced breaking, non-linear triad interactions, bottom friction based on the JONSWAP formulation, wind gr-owth, white capping, refraction, and frequency shift.

The initial conditions of the Delft3D-WAVE runs were set such that the significant wave height, peak wave period and wave direction are prescribed along the north, east, and south model boundaries_ as shown on Figure 2.4-25. Other wave boundary conditions such as Wave heights, periods, and direc:tions were based on wave conditions at historical buoy stations 41002, 44017, and 41048. These stations were selected for their Proximity to the model offshore boundaries. A uniform wave boundary condition (significant wave height, peak wave period, wave direction, and directional spreading) along the north, east, and south model boundaries was imposed as shown in Figure 2.4-25.

Wave height and wave period calibrations were performed by forcing the cOupled Delft3D-FLOW and Delft3D-WAVE (SWAN) model using Hurricane Irene and Hurricane Isabel wind and pressure fields. The Delft3D-WAVE model calibration and verification performance was evaluated by visually comparing Delft3D simulated wave characteristics (wave height and periods) against observed data and quantitative analysis of the simulated and observed wave characteristics (wave height and periods) in terms of percent difference and MAE. Delft3D-WAVE (SWAN) was run in non-stationary mode with a COUp~ling time interval of 1-minute.

2.4.2.4 Determination of Controlling PMSS Strom Event The U.S. Army Engineer Research and Development Center (Reference 2.4-29) has previously conducted a storm surge modeling study for the ChesaPeake Bay area. The study comPared the surge water surface elevations of different storm types such as hurricanes (tropical storms) and northeasterS (extra-tropical). The study performed simulations for forty-three (43) hurricanes and forty-three (43) northeaster storms affecting the Bay between 1954 and 2006. Northeaster storms were selected at the Ocean entrance of Chesapeake Bay based on criteria of peak wind speed being greater than 20 in/sec (40 knots) or 10 in/sec (20 knots) and durations exceeding 3 days.

The hurricanes were selected based on maximum wind speeds greater than 25 mn/sec (50 knots) in the ar~ea between 75 and 79 degrees W longitude and 36 and 39 degrees N latitude. For hurricanes, the largest storm surge levels occur at the east side of the bay and low-lying islands and at the southwest side of the bay in the tributaries, where water is pushed and trapped at these locations. The largest storm surge levels are normally generated by stronger hurricanes (Category 3 and above) with.a south-to-.north track Passing the bay. For northeasters, higher water levels occur in the south bay as water is driven southward by storms encounters flood tides entering the bay from the Atlantic Ocean. Outside the bay along the coast andL in the Delaware Bay, the ocean tides contribute to the water levels more than the northeasters. The study concluded that the storm surge produced under northeasters is comparatively smaller than the storm surge produced by hurricane events because of the relatively weaker wind associated with northeasters. TherefOre, hurricanes are the only storms selected for PMSS analysis for Calvert Cliffs Unis 1 and 2 as part of this amendment. This is also consistent with the approach used in the UFSAR (Reference 2.4-4).

2.4.2.5 Probable Maximum Hurricane PMSS is defined as a surge that results from a combination of meteorological parameters of a Probable Maximum Hurricane (PMH). The PMH is a hypothetical steady-state hurricane having a combination of values of meteorological parameters that will give the highest sustained wind speed that can occur at a coastal location. As part of this amendment, the design hurricane is selected in accordance with applicable guidance documents (NUREG/CR-7046 (Reference 2.4-Calvert Cliffs Nuclear Power PlantPae3of9 Page 33 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 15), NUREG 0800 (Reference 2.4-26), JLD-ISG-2012-06 (Reference 2.4-27)), which refer to the PMH methodology of NWS 23. JLD-ISG-2012-06 states that the PMH methodology of NWS 23 is acceptable for licensing decisions. Using the NWS 23 methodology, the critical PMH parameters of storm size, pressure, and wind fields are determined for a storm making landfall near the mouth of Chesapeake Bay. The ranges of PMH parameters obtained from NWS 23 for use in the deterministic storm surge evaluations at Calvert Cliffs Units 1 and 2 are provided in Table 2.4-6. A sufficient number of storm radii, headings, and forward speeds combinations are analyzed to determine the worst case storm (i.e., the PM H), as shown in Table 2.4-7. Atmospheric forcing (wind and pressure data) for multiple combinations of the PMH parameters were generated using the parametric wind and pressure field model described in Memorandum HUR 7-97 (Reference 2.4-28). The wind model can (approximately) reproduce the wind field and pressure field of the PMH with meteorological parameters including hurricane path, atmospheric pressure, and radius of maximum wind.

The screening for the critical PMH was conducted as follows:

1) Hold central pressure and peripheral pressure to the PMH criteria of 26.49 in. Hg and 30.12 in. Hg, respectively.

2) Synchronize the timing of the storm surge so that it arrives with the incoming high tide.

3) Test different track directions within the range of 152 to 197 degrees, as shown on Figure 2.4-5. For sensitivity, the track directions were extended beyond the range presented in NWS 23 to determine if hurricanes from the south and southwest would result in a higher surge at Calvert Cliffs Units 1 and 2. Review of historical hurricane tracks shown on Figure 2.4-4 show that a significant number of hurricanes approach Chesapeake Bay from the south and southwest direction. Ten track directions (152, 157, 162, 167, 172, 177, 182, 187, 192, and 197 degrees) were examined.

4) Test different radius of maximum winds within a range of 10 to 50 nautical miles (nm), as shown in Table 2.4-7. The radius of maximum wind sensitivity was extended beyond the range presented in NWS 23 to determine if hurricanes with larger radius of maximum winds increase the surge level at Calvert Cliffs Units 1 and 2.

5) Test different forward speeds within the range of 17 knots to 37 knots. For sensitivity, the forward speed was extended beyond the range presented in NWS 23 to determine if a lower forward speed along the South Carolina and North Carolina latitudes results in a larger surge at Calvert Cliffs Units 1 and 2. Therefore, for the critical PMH, the hurricane wind field for points preceding landfall (i.e., points 1 to 5 in the Delft3D track file) were generated by assuming the PMH travels at the minimum possible forward speed. This is approximately 8 knots for the South Carolina and North Carolina latitudes according to NWS 23. After landfall the forward speed was maintained at the critical forward speed determined from the range of 17 knots to 37 knots provided in Table 2.4-7. Track point locations are shown on Figure 2.3-5.

6) Test different track positions relative to the Calvert Cliffs Units 1 and 2 location as shown on Figure 2.4-26. Eight storm paths were evaluated by modifying the critical track path from Step 3. The storm paths are as follows:

a) A hurricane storm center passing directly over the Calvert Cliffs Units 1 and 2 site,

• b) A hurricane storm center passing at a distance of 5 nm west of the Calvert Cliffs Units I and 2 site (0.25 times RMWV) along the critical track direction c) A hurricane storm center passing at a distance of 13 nm west of the Calvert Cliffs Units 1 and 2 site (0.65 times RMWV) along the critical track direction d) A hurricane storm center passing at a distance of 18 nm west of the Calvert Cliffs Units 1 and 2 site (0.9 times RMWV) along the critical track direction Calvert Cliffs Nuclear Power PlantPae3of9 Page 34 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 e) A hurricane storm center passing at a distance of 22 nm west of the Calvert Cliffs Units 1 and 2 site (1.0 times RMW) along the critical track direction f) A hurricane storm center passing at a distance of 25 nm west of the Calvert Cliffs Units 1 and 2 site (1.25 times RMW) alon~g the critical track dir-ection g) A hurricane storm center passing ait a distance of 5 nm east of the Calvert Cliffs Units 1 and 2 site (-*0.25 times RMWV) along the critical track direction h) A hurricane storm center passing at a distance of 10 nm east of the Calvert Cliffs Units 1 and 2 site (-0.5 times RMW) along the critical track direction As the hurricane transitions from sea to land, the hurricane wind can lose its strength rapidly. This is due to two processes: 1) due to increased frictional .dissipation of kinetic energy at the lower boundary, and 2) change in the available energy supply, that is, the absence of vertical flux of sensible heat from the ocean to the atmosphere which oCcur after the center of a hurricane moves away from the warm water of the tropical oceans to land. ANSI/ANS-2.8-1 992 (Reference 2.4-

19) indicated that reasonable routing of the PMH upstream into estuaries and rivers should be performed and reductions to the hurricane wind should be accounted for as the hurricane traverses overland. TO take into account the weakening of the PMH as it traverses overland, the PMH wind fields generated using the parametric wind and pressure field mOdel were adjusted by an average sea-land transition reduction factor of 20.56 percent or a surface friction Coefficient (k)=0.833. Accordingly, the maximum gradient wind speed for locations 6 (assumed as landfall location) through 14 along the hurricane track were multiplied by 0.833. Track point locations are shown on FigUre 2.3-5. This adjustment was done for hurricanes making landfall west of the Chesapeake Bay entrance. For hurricanes making landfall on the east of the Chesapeake Bay entrance (i.e., track directions of 152, 157, and 162 degrees), most of the hurricane path will be on Chesapeake Bay water. Therefore, the PMH wind fields were not adjusted. This assumption is conservative.

2.4.2.6 Determination of Antecedent Water Level In accordance with NUREG/CR-7046, the PMSS is required to be evaluated coincidentally with an antecedent water level equal to the 10 percent exceedance high tide, initial rise, and long-term sea level rise. As described in ANSI/ANS-2.8-1992 (Reference 2.4-19), the 10 percent exceedance high tide is the high tide level that is equaled or exceeded by 10 percent of the maximum monthly tides over a continuous 21 year period. in accordance with AN SI/ANS-2.8-1992, 10 percent exceedance high tide can be determined from recorded tide data .or from predicted astronomical tide tables. If predicted tides are used, sea level anomaly shall be added.

The sea level anomaly (also known as initial rise) is an anomal'ous departure of the tide level from the predicted astronomical tide and is estimated by comparing long term recorded and predicted tides. Additionally, in accordance with NUREG/CR-7046, consideration Should be given to the long-term effect of sea level rise (in most of the cases for the lifetime of the plant). This effeCt should be included in calculation of the PMSS antecedent water level to establish whether the site can adequately accommodate potential changes in the design-basiS flood due to climate change.

The antecedent water level that includes the 10 percent exceedance high spring tide (1.53 ft MSL), initial rise (.1.1 ft), and long-term sea level rise (1.07 ft) were obtained from the PMSS analysis performed as part of the FHRR. This provided the initial Still Water Level (SWL) of 3.7 ft (the sum of 10 percent exceedance high .tide, initial rise and long term sea level rise), which was used as the antecedent water level. Because the Delft3D model was run with the influence of ambient tides, a tidal adjustm'ent equal to the difference between the initial SWL of 3.7 ft MSL Calvert Cliffs Nuclear Power PlantPae5of9 Page 35 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 (1.1278 m MSL) and simulated ambient high tide was added to Delft3D simulated PMSS elevation to ensure the ambient tidal elevation was equal to the intial SWL of 3.7 ft MSL.

Simple superposition of the high tide and storm surge ignoring their interaction can lead to substantial errors in both magnitude and timing of the peak surge due to the non-linear terms in the hydrodynamic equations. Therefore, all simulations were run with the influence of tides.

However, ifthe. peak of a hurricane storm surge arrives at low tide, the total amplitude of the storm surge will be less than if it arrives at high tide. To account for this possibility, one simulation without wind forcing was run to determine the timing of the tide at Calvert Cliffs Units 1 and 2. Then, the runs were synchronized such that the peak of the storm surge would arrive at high tide. This was accomplished by manually shifting the entire simulation "X"number of hours or minutes such that the storm surge peak would arrive at high tide 2.4.2.7 PMSS Determination The calibrated Delft3D model and calibrated storm surge parameters were used to determine the PMSS. Detailed approach, methodology and assumptions associated with the PMSS determination are discussed in Calculation CEC-008-CALC-09 (Reference 2.4-24).

The storm surge level at Calvert Cliffs Units 1 and 2 due to the worst case PMH was determined using guidelines in NWS 23. The characteristics of the PMH (forward speed, track direction, radius of maximum winds, central pressure) were determined in Calculation CEC-008-CALC-06, (Reference 2.4-21). The ranges of PMH parameters for use in the deterministic storm surge evaluations at CCNPP are provided in Table 2.4-6.

Multiple Delft3D model simulations, representing the range of meteorological hurricane parameters and storm track directions provided in Table 2.4-6, were performed to determine the "worst case" combination of meteorological hurricane parameters and storm track directiOns. The "worst case" combination of meteorological hurricane parameters and storm track directions are those that cause the probable maximum surge as the PMH approaches the site along a critical path at ani optimum rate of movement (i.e., forward speed). The various combinations examined in Delft3D are provided in Table 2.4-7.

For each storm simulation, the model simulations are evaluated to identify the combination of meteorological parameters and storm track direction that result in the worst case storm surge elevation. From the various Delft3D simulations listed in Table 2.4-7, the scenario that resulted in a maximum water surface elevation in the vicinity of the Calvert Cliffs Units 1 and 2 is taken as the critical or worst case simulation. A final round of Delft3D simulations were conducted by running the selected critical candidate PMH event using the coupled Delft3D-FLOW and Delft3D-WAVE model. Screening and the final round of Delft3D simulations show that the PMH with the following attributes produced the maximum surge at Calvert Cliffs Units 1 and 2:

• A central pressure of 26.49 inches of Mercury

• A peripheral pressure of 30.12 inches of Mercury

• A pressure deficit of 3.63 inches of Mercury (122.93 millibar)

• A radius of maximum winds of 20 nautical miles

• Variable forward speed of 8 knots (preceding landfall) and 17 knots (after landfall)

• A PMH track approaching from 192 degrees (clockwise from north) as shown on Figure 2.3-5

• A PMH storm center 5 nautical miles east of Calvert Cliffs Units I and 2 along the critical track of 192 degrees as shown on Figure 2.4-26 Calvert Cliffs Nuclear Power PlantPae3of9 Page 36 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 The summary of the worst case combination of meteorological hurricane parameters that were used to develop the PMH wind and pressure field is provided in Table 2.4-1. As discussed above the wind and pressure field for the worst case PMH was generated using the parametric wind and pressure field model descsribed in Memorandum HUR 7-97 (Reference 2.4-28). During the passage of the PM H event at the Calvert Cliffs Units 1 and 2 site, the elevation of the storm surge was calculated to be +14.85 ft MSL. During the. PMH, a maximum significant wave height of 10.14 ft (3.09 m) and wave period Of 4.62 seconds wer-e simulated in the forebay. MaXimum water surface elevation, significant wave height, .peak period, significant wave height and wave Vector, and wave length in Chesapeake Bay during the peak of the PMH are provided in Figures 2.4-27 through Figure 2.4-31 respectively.

2.4.2.8 Wave Runup Determination Wave runup is the uprush of water from wave action on the shore. It is expected that under PMSS conditions, the PMH hurricane winds will allow waves to directly impact the site and waves will runup the Calvert Cliffs Units 1 and 2 Intake Structure simultaneously with the storm surge.

Wave parameters such as wave height, wave period, and wave length from Calculation CEC-008-CALC-09 (Reference 2.4-24) were used to calculate wave runup and the maximum water surface elevation at the Intake Structure of Calvert Cliffs Units 1 and 2. During the passage of the PMH event at the Calvert Cliffs Units 1 and 2 site, the elevation of the storm surge was calculated to be +14.85 ft MSL. Because the maximum still-water level is +14.85 ft MSL and the deck E:levation is +10.0 ft MSL, the controlling depth of water on the Intake Deck is 4.85 ft.

Deep water waves from Chesapeake Bay cannot continue unbroken across the front edge of the intake deck as shown by the Delft3D-WAVE (SWAN) results. Although the significant wave height was calculated to be 10.14 ft (3.09 m) in the forebay, the maximum sustainable wave height on the intake deck Will be limited to less than 4.85 ft. Waves in the forebay, larger than 4.85 ft, will break and diminish in size while smaller waves may strike the intake structure pump house wall and runup the structure.

As per ANSI/ANS-2.8-1992 (Reference 2.4-19), the wave height for the runup calculation should be the lower of the maximum breaker height or the maximum wave height available after modification by refraction, shoaling, and bottom friction of the deep water wave. The wave characteristics simulated by the Delft3D-WAVE (SWAN) accounts for wave generation, propagation, breaking in both deep water (due to white capping) and in shallow water (due to bottom friction anid depth induced), refraction, diffraction, and reflection. The controlling wave height for wave runup analysis performed as part of this amendment use the maximum breaker height (Ha) calculated using Equation 11-4-3 of USACE Coastal Engineering Manual (CEM)(Reference 2.4-34). The maximum wave height is calculated to be 0.78* 4.85 ft = 3.78 feet or 1.15 meter.

Runup was estimated based on two methods and the more conservative wave runup from the two methods was used to compute the maximum water surface elevation at Calvert Cliffs Units I and 2. The methods used for estimating wave runup are:

• Method 1- Empirical Formulation for Runup on a Smooth Impermeable Slope described in the USACE CEM, EM 1110-2-1100, 2011 (Reference 2.4-34)

Calvert Cliffs Nuclear Power PlantPae3of9 Page 37 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015

• Method 2- Empirical Formulation for Runup on a Vertical Slope described in the USACE Shore Protection Manual, Volumes 1 and 2, 1984 (Reference 2.4-35) 2.4.3 Results During the passage of the PMH event at the Calvert Cliffs Units 1 and 2 site, the elevation of the storm surge was calculated to be +14.85 ft MSL. During the PMH, a maximum significant wave height of 10.14 ft (3.09 m) and wave period of 4.62 seconds were simulated in the forebay.

Although the significant wave height was calculated to be 10.14 ft (3.09 m) in the forebay, the maximum sustainable wave height approaching the Pump House will be limited to 0.78 times the water depth on the Intake Deck, which is 3.78 feet or 1.15 meter. The more conservative wave runup from Methods 1 and 2 was used to compute the maximum water surface elevation at Calvert Cliffs Units 1 and 2. The maximum wave runup is 11.32 ft using methodology from the Coastal Engineering Manual (Reference 2.4-34).

Using the H.3 combination from the NUREG/CR-7046 combination of flood-causing events, consisting of the probable maximum surge and seiche with wind-wave activity and the antecedent 10 percent exceedance high tide, the maximum water surface elevation at the Calvert Cliffs Units 1 and 2 pump house was calculated to be +26.17 ft MSL. The results of the wave runup calculations are shown schematically on Figure 2.4-32.

2.4.4 Conclusions The top of the Pump House is +28.5 ft MSL. Therefore, the maximum runup elevation of 26.17 ft MSL (or 26.81 ft NGVD29) does not overtop the Calvert Cliffs Units 1 and 2 Intake Structure Pump House roof during a PMH event.

Additionally, as described in the UFSAR, the design basis flood elevation for PMSS water surface elevation with wave activity is 27.5 ft MSL (or 28.14 ft NGVD 29). Therefore, the revaluated PMSS water surface elevation with wave activity is bounded by the design basis flood elevation.

As indicated in the UFSAR, the pressure distribution due to waves is a combination of hydrostatic and hydrodynamic components and the exposed safety-related structures are designed to withstand these effects. The re-evaluated wave height and runup are bounded by current design basis as summarized in Table 3.0-4. Therefore, the hydrodynamic loads at the screen house due to H.4.3 combinations are bounded by current design basis condition.

As indicated in the UFSAR and FHRR, approximately 3700 ft of the shoreline near the Calvert Cliffs Units 1 and 2 is protected against shoreline erosion. Therefore, the erosion/deposition is not a plausible hazard for Calvert Cliffs Units 1 and 2.

High winds could be generated concurrent to this combined effect flood. However, manual actions are not required to protect the intake structure from the PMSS so this concurrent condition is not applicable. The stillwater level is bounded by the current design basis stillwater level as summarized in Table 3.0-4. Therefore, impact to groundwater ingress is considered to be bounded.

The stillwater level is bounded by the current design basis stillwater level as summarized in Table 3.0-4 and SSC's important to safety are currently protected by means of permanent/passive measures. Therefore, flood event duration parameters are not applicable to the PMSS flood. The Calvert Cliffs Nuclear Power PlantPae3of9 Page 38 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 reevaluated peak flood elevation is bounded by the current design basis, therefore, other factors are not applicable to the PMSS flood.

2.4.5 References (Additional References) 2.4-19 ANSI/ANS-2.8-1992, American Nuclear Society, American National Standard for Determining Design Basis Flooding at Power Reactor Sites, Prepared by the American Nuclear Society Standards Committee Working Group ANS-2.8, La Grange Park, Illinois, 1992.

2.4-20 Calculation CEC-008-CALC-05, Delft3D Bathymetry and Geometry Calculation for Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 0.

2.4-21 Calculation CEC-008-CALC-06, Probable Maximum Storm (PMS) Parameters and Storm Track Calculation for Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 0.

2.4-22 Calculation CEC-008-CALC-07, Delft3D Mode! Geometry Calculation for Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 0.

2.4-23 Calculation CEC-008-CALC-08, Delft3D Surge Model Calibration Calculation for Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 0.

2.4-24 Calculation CEC-008-CALC-09, Probable Maximum Storm Surge Calculation for Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 0.

2.4-25 Calculation CEC-008-CALC-10, Wave Runup Calculation for Calvert Cliffs Nuclear Power Plant Units 1 and 2, Revision 0.

2.4-26 U.S. Nuclear Regulatory Commission, NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition - Site Characteristics and Site Parameters (Chapter 2), ML070400364, March 2007.

2.4-27 U.S. Nuclear Regulatory Commission, NRC JLD-ISG-2012-06, Guidance for Performing a Tsunami, Surge and Seiche Flooding Safety Analysis, Japan Lessons-Learned Project Directorate Interim Staff Guidance, Revision 0, June 2012.

2.4-28 H.M.S. Weather Bureau, 1968, U.S. Department of Commerce, E.S.S.A.,

Memorandum HUR 7-97, "Interim Report - Meteorological Characteristics of the Probable Maximum Hurricane, Atlantic and Gulf Coasts of the United States," H.M.S.

Weather Bureau, May 7, 1968.

2.4-29 Demirbilek et. al., "Numerical Modeling of Storm Surges in Chesapeake Bay",

International Journal of Ecology and Development, Vol. 10; No. S08; pp. 24-39, Summer 2008.

2.4-30 Provost, C. and F. Lyard, "The impact of ocean bottom morphology on the modelling of the long gravity waves, from tides and tsunami to climate," Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales, LEGOS/GRGS, Charting the Secret World of the Ocean Floor, The GEBCO Project 1903-2003.

2.4-31 National Oceanic Atmospheric Administration (NOAA), National Ocean Service, U.S.

Department of Commerce, Moose, Robert E., "The National Geodetic Survey Gravity Calvert Cliffs Nuclear Power PlantPae3of9 Page 39 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Network," NOAA Technical Report NOS 121 NGS 39, Rockville, Maryland, December 1986.

2.4-32 Maryland Department of Information Technology (MDIT, "Independent LiDAR Quality Control Report - Calvert County Area of Interest", MD iMap website, http ://webmaps.esraqc.ornqlLiDAR/portal/client/downloadlMetadatalCalvertl, accessed February 24, 2015.

2.4-33 Calvert Cliffs Phase I1: Storm Surge Analysis and Revised Runup Calculations, Calculation Number 124832-F-2, Revision 0.

2.4-34 U.S. Army Corps of Engineers (USACE), "Coastal Engineering Manual," EM 1110 1100, 2011.

2.4-35 United States Corps of Engineers (USACE), "Shore Protection Manual, Volumes 1 and 2," 1984.

Calvert Cliffs Nuclear Power PlantPae4of9 Page 40 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 2.4-1 PMH Parameters for Critical Hurricane Track (Superseded by this Amendment)

(Replaced "Storm Surge HHA Iteration Nos. 1 and 2" with "for Critical Hurricane Track" from the title)

Radius of Forward Time Latitude Longitude Maximum Wind Pressure Speed (hours) (degrees) (degrees) (Nautical Miles) Deficit (mb) (Knots) 0 16.701798 -81.490238 20 122.93 8 42 22.180020 -80.277310 20 122.93 8 72 26.092701 -79.380502 20 122.93 8 108 30.789361 -78.271250 20 122.93 8 135 34.311426 -77.401090 20 122.93 8 141 35.093583 -77.199861 20 122.93 17 153 38.420269 -76.336962 20 122.93 17 156 38.974082 -76.185520 20 122.93 17 158 40.081501 -75.877781 20 122.93 17 162 41.188905 -75.564895 20 122.93 17 168 42.849646 -75.083181 20 122.93 17 171 43.680254 -74.838990 20 122.93 17 174 44.510855 -74.591345 20 122.93 17 189 48.657788 -73.255649 20 122.93 17 Calvert Cliffs Nuclear Power PlantPae4of9 Page 41 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Table 2.4-2 Summary of HHA Results (Superseded by this Amendment)

Runup, PMSS with Loain Loato IRunup, Method 1 Method Excee 10%

Tdane Maximum RunpeEevtioiRnu Maiumu Ex2HcgeTdane Elevationtio

_______f ft ft (ft MSL) (ft MSL) (1)(ft NGVD29)

Toue oPup 111.32 8.68 [ 14.85 126.17 = (14.85 + 11.32) 1 26.81 (1)ft-NGVD29 = ft MSL + 0.64 ft Calvert Cliffs Nuclear Power PlantPae4of9 Page 42 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 2.4-3 Comparison of Parameters and Results for Storm Surge and Wave Runup Analyses (Superseded by this Amendment)

CNP fr~

UFSR FAR or FHRR CCNPP 1 Amended ParameterlResults 2 (Reference 2.4-4) ccP 3 aus HRVle (Rfrne241)Used!Com puted (Refrenc 2.412)in this Reportp)~

PMH Parameters and Results Ceta rsue135 mb 123 mb 124 - 55 mb 122.93 mb Deficit__ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Radius of Ma~ximum 26 nautical miles 10- 26 nautical 28 -40 nautical 10 -26 nautical Winds ____________miles miles miles Wave Runup Parameters and Results AneeetWtr2.82 ft NGVD* 4.4 ft NGVD 4.4 ft NGVD(') 4.34 ft NGVD Level PMSS Level 16.24 ft NGVD 17.6 ft NGVD 17.5 ft NGVD 15.49 ft NGVD Significant.Wave 11.4 ft 10.8 ft 10.9Wft*. 10.14 ft Height ___________

Breaking Wave Height N/A 7.6 ft 5.84 ft 3.78 ft Wave Runup 11.9 ft 15.6 ft(2) 13.8 ft 11.32 ft PMSS +Wave Runup 28.14 ft NGVD 33.2 ft NGVD 31.3 ft NGVD 26.81 ft NGVD

• ft-NGVD 29= ft-MSL + 0.64 ft Notes:

(1)Calculated for CCP 3.

(2)Wave runup value is calculated for the Makeup Water Intake Structure (MWIS).

(3)Values presented here are for Phase II Iteration No. 4.

Calvert Cliffs Nuclear Power PlantPae4of9 Page 43 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 2.4-4 Summary of Topographic and Bathymetric Data Used as Input for CCNPP Strom Surge Model (New Table)

Are taTyp Source Horizontal Coordinate Vertical/ Vertic Vertical Areauion Atati ahyer IOA T SyDataial Reslutin Sysem AD3MLL Tdalu Datuseod alTypeuio aUnesluio Unites N etrta Ocean 2014 (-90 m) 1-meter(I)

Regional Bathymetry GEBCO, 30 arc- WGS84 MSL Meters NA2 and 2008 second Topography ('-1 kin)

Chesape Bathymetry NOAA, 1 arc-second NAD83 MLLW Meters lm > 20m ake Bay 1997 (-30 m) depth and 0.20m < 20m depth( 1)

Regional Topography USGS, 1 arc-second NAD83 NAVD88 Meters 2.44 m( 3 )

- NEDs 2009 (-30 m)

Site Topography USGS, Nominal Maryland NAVD88 Feet 0.33-ft( 4 )

- LiDAR 2012 Pulse State Plane, Spacing NAD83 2 m(4 )

I*IL.1L/*J S INUO [lyUIUyl;4*J[llC surveys, [RUI[I!Oe[::UTI vaEnyrneEry, aria [r*lCKllFle ioa[nyrne[ry.

2 Acoustic methods, using sound waves, measure broad swathes of seabed (up to 10 kilometers across in very deep water) to accuracies of better than a meter or two. Very high accuracy systems measure swathes and shallow water but have a depth accuracy of up to a couple of centimeters.

3 The accuracy of the NED varies spatially because of the variable quality of the source DEMs. As such, the NED inherits the accuracy of the source DEMs. The most recently published figure of overall absolute vertical accuracy expressed as the root mean square error (RMSE) is 2.44 meters.

4 Tested 0.654ft at 95 percent confidence level in open terrain using RMSE

• 1.96 and tested 0.702ft at the 9 5 th percentile method.

Calvert Cliffs Nuclear Power PlantPae4of9 Page 44 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 2.4-5 Wind Drag Coefficient Sensitivity (New Table)

Wind Drag Break Wn rgCefcet Points (m/s) Wind___ DraCeffcint Scenario Manning's n A [B IC A l B [C 1 Spatially 0 33 90 0.00063 0.0025 0.0040 2() Varied as 0 27 90 0.00063 0.0030 0.0018 3 determined 0 33 90 0.00063 0.0024 0.0015 during tidal 4calibration 0 25 90 0.00063 0.0024 0.0015 5 0 25 90 0.00063 0.0030 0.0040 6 ______ 0 25 90 0.00063 0.0030 0.0015 (1)Scenario 2 was selected as the final set of calibration parameters Calvert Cliffs Nuclear Power PlantPae4of9 Page 45 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 2.4-6 Range of PMH Design Storm Parameters (New Table)

Parameter Value (units)

Storm Peripheral Pressure 30.12 inches of Mercury (1020 mbar)

Storm Central Pressure 26.49 inches of Mercury (897.05 m bar)

Storm Radius of Maximum Winds 10 - 26 (nautical miles)

Storm Forward Speed 17 - 37 (knots)

(1)Storm Track Direction 68 -152 (degrees)

U)'Track Directions below 152 degrees do not produce maximum storm surge at Calvert Cliffs Units I and 2 The track direction outside of the NWS 23 .range (152 degrees to 207 degrees) are presented for additional sensitivity Calvert Cliffs Nuclear Power PlantPae4of9 Page 46 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 2.4-7 Scenarios Evaluated to Determine Worst Case PMH (New Table) ____ _________

10% 1Hurricane Storm Exceedance Finest Peripheral Central RMW Center Distance Forward Track Run N FLOW High Tide, Grid Cell Pressure (in. Pressure (in. I(nautical Relative to CCNPP Speed Direction ID Grids SLR, IR Size JWaves L==) Hjjj) miles) (RMW) (knots) (degrees)1 Description 1 3 N 40wm N 30.12 26.40 26 0 17 152 Track directionl sensitivity 1 2 3 N 40wm N 30.12 26.40 26 0 17 157 Trsck direction sensitivity 2 3 3 N 40wm N 30.12 26.49 26 0 17 162 Track direction sensitivity 3 4 3 N 40wm N 30.12 . 26.49 26 0 17 167 Trsck direction sensitivity 4 6 3 N 40wm N 30.12 26.49 26 0 17 172 Track direction sensitivity, 6 6 3 N 40wm N 30.12 26.49 26 0 17 177 Track direction sensitivity 6 7 3 N 40wm N 30.12 26.49 26 0 17 182 Track direction sensitivity 7 9 3 N 40wm N 30.12 26.49 26 0 17 187 Track direction sensitivity 8 9 3 N 40 m N 30.12 26.49 26 0 17 192 Track direction sensitivity 9 10 3 N 40wm N 30.12 29.49 26 0 17 197 Track direction sensitivily 10 11 3 N 40wm N 30.12 26.49 10 0 17 192 RMW sensitivity 1 12 3 N 40wm N 30.12 26.49 15 017 192 RMW sensitivity 2 13 3 N 40Gm N 30.12 26.49 20 0 17 192 RMW sensitivity 3 14 3 N 40wm N 30.12 26.49 26 0 17 192 "RMW sensitivity 4 15 3 N 40wm N 30.12 26.49 26 0 17 192 R MW sensitivity 5 16 3 N 40wr N 30.12 26.49 30 0 17 192 RMW sensitivity 6 17 3 N 4Cm N 30.12 26.49 36 0 17 192 RMW sensitivity 7 18 3 N 40wm N 30.12 26.49 38 0 17 192 RMW sensitivity 8 SNautical convention is presented (North = 0 degrees)

Calvert Cliffs Nuclear Power PlantPae4of0 Page 47 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 2.4-7 Scenarios Evaluated to Determine Worst Case PMH (New Table) (Continued) 10% Hurricane Storm N i Exceedance Finest Peripheral Central RMW Center Distance Forward Track Run FLOW High Tide, Grid Cell Pressure (in. Pressure I(nautical Relative to Speed Direction 2

ID Grids J SLR, IR Size Waves H* (in. Hg) 1miles) CCNPP (RMW) (knots) (degrees) Description 19 3 N 40Gm N 30.12 26.49 20 0 17 192 Forward speed sensitivity 1 20 3 N 40 m N 30.12 26.49 20 0 22 192 Forward speed sensitivity 2 21 3 N 40 m N 30.12 26.49 20 0 27 192 Forward speed sensitivity 3 22 3 N 40 m N 30.12 26.49 20 0 32 192 Forward speed sensitivity 4 23 3 N 40 m N 30.12 26.49 20 0 37 192 Forward speed sensitivity 5 24 3 N 40 m N 30.12 26.49 20 0 V (8 and 17) 192 Forward speed sensitivity 6 12 Track path relative to CCNPP 25 3 N 40 m N 30.12 26.49 20 1.25RMW V (8Band 17) 12sensitivity1 26m 3N 4 30.2 2.49 20 1ORM V Band17) 192 Track path relative to CCNPP 26 3N 4N rn 3.12 26.9 20 1.0MW (8and17) 192sensitivity 2 Track path relative to CCNPP 27 3 N 40 m N 30.12 26.49 20 0.65RMW V (Band 17) 192 sensitivity 3 28 3N 4m N 0.1 26.9 2 0.5RMW V ((8and17) and17) 192 28 m 3N 4 3012 6.4 20 .25MW 192sensitivityTrack path relative to 4 CCNPP 29 3N 4 0.2 2.9 2 0RMW Track path relative to CCNPP 30 3 N 40Gm N 30.12 26.49 20 *02 W V (8 and 17) 192 Takpt eaiet CP (at CNPP)sensitivity 6 31 3 N 40 m N 30.12 26.49 20 -O.25RMW V (B and 17) 192 Trc sptelaitiveito CCP 31__N_0__N_0.2_2.4 V( n 7 9 a0-.RW ensitivity 7 32 Using Optimum values from 32 5 y5 m Y 30.12 26.49 20 -O.2fiRMW V (S and 17) 192 Scenartos 1-31 Notes: RMW = Radius of Maximum Wind, N Grids = Number of Grids Run in the Model, N = No, not included in the model run, Y = Yes, included in the model run, SLR = Sea Level Rise, IR= Initial Rise, V = Variable. Critical Scenarios are shown in bold 2

Added to the final simulated water surface elevation 3

PMH Centered at CCNPP Calvert Cliffs Nuclear Power PlantPae4of9 Page 48 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-1 Plan View of Intake Structure and Forebay Not Impacted by this Amendment and Remains Valid Figure 2.4-2 Cross Section of Intake Structure Not Impacted by this Amendment and Remains Valid Figure 2.4-3 Reprsentative Equivalent Slope for Intake Structure of CCNPP 1 & 2 Deleted- No Longer Used Calvert Cliffs Nuclear Power PlantPae4of9 Page 49 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-4 Storm Tracks for Historical Hurricanes (Superseded by this Amendment)

(Replaced "1955 Hurricane (Reference 2.406)" with "Historical Hurricane" from the title)

-- ch#S~)~ Nm~mW C~gm~4 ftim~w~e Calvert Cliffs Nuclear Power PlantPae5of9 Page 50 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-5: Evalauted Delft3D Model Storm Track for PMH at CCNPP Site (Superseded by this Amendment) (Replaced "SLOSH" with "Evaluated Delft3D" from the title)

UULF1U1 J 120 240 4~ ~7~]

I ~

Calvert Cliffs Nuclear Power PlantPae5of9 Page 51 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-6 Delft3D Model Grids for CCNPP Strom Surge Model (Superseded by this Amendment)

(Modified Title)

L OaDEFT3o FLOWG-ddMode t]om Calvert Cliffs Nuclear Power PlantPae5of9 Page 52 of 90

Amendment 1 to CCNPP Exelon Generation Co. Flood Hazard Reevaluation Report September 08, 2015 Figure 2.4-7: Delft3D Model Storm Surge Results at the Intake Deck (Superseded by this Amendment)

(Modified Title) 4.65 4.55 4,45 S4.25 4.15 Date Note: Time series data incudes the additional0.9156 meters ensure the ambient tidal elevation was equal to the l10% exceedance high tide Calvert Cliffs Nuclear Power PlantPae5of9 Page 53 of 90

Amendment I to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-8: SLOSH Model Storm Surge Results Showing the Maximum Surge Level for liHA Iteration No. 2 Deleted- No Longer Used Calvert Cliffs Nuclear Power PlantPae5of9 Page 54 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-9 DeIft3D-WAVE (SWAN) Grids or CCNPP Strom Surge Model (New Figure) o~I VCHW CO*fl - - -

""'a -. ~

a - a 4 J3D F-JOELF WVGrdM~od.IDm~

Calvert Cliffs Nuclear Power PlantPae5of9 Page 55 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-10 Schematic of Calibration StepslProcesses (New Figure) observations parameters Model compare forcing [

Calvert Cliffs Nuclear Power PlantPae5of9 Page 56 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-11 Hurricane Isabel (2003) and Hurricane Irene (2011) Storm Tracks used for Calibration and Verification of the CCNPP Storm Surge Model (New Figure)

Calvert Cliffs Nuclear Power PlantPae5of9 Page 57 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-12 Tidal Stations used for CCNPP Storm Surge Delft3D Model Calibration (New Fia ure)

Calvert Cliffs Nuclear Power PlantPae5of9 Page 58 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-13 Observed and Simulated Tide Water Level - Chesapeake Bay Bridge Tunnel, VA (New Figure)

--- Smuatd, ani ' = 0.0 -- Resynthesized 0

4 v 4 , s ~

Calvert Cliffs Nuclear Power PlantPae5of9 Page 59 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-14: Observed and Simulated Tide Water Level - Solomons Island, MD (New Figure)

GA 0.3

.~G2 A GA 8

• 0.3

-0.3 U

-a'

-0,3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

~.

~%O %4 o, 404 J'0440o44 4 04'0'4 Dat.

--- Simulated, Mannlngs N = 0.01 - Resynthesized Calvert Cliffs Nuclear Power PlantPae6of9 Page 60 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-15: Observed and Simulated Tide Water Level - Tolchester Beach, MD (New Figure) 04 I

- 03 0.2 0.1 I 0.0

-0.1

-02

~43

-04

"% "% "*k, "*%-'% "% "*,

Dale

- Resynthesized - - Simulated, Manning's N= 0.01 Calvert Cliffs Nuclear Power PlantPae6of9 Page 61 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-16: Calibrated Spatially Varying Manning Roughness Coefficient (New Figure) city. NJ Calvert Cliffs Nuclear Power PlantPae6of9 Page 62 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-17 Water Level Recording Station used for CCNPP Storm Surge Delft3D Model Calibration (New Figure)

Calvert Cliffs Nuclear Power PlantPae6of9 Page 63 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-18 Wave Recording Station used for CCNPP Storm Surge Delft3D Model Calibration (New Fiaurel Calvert Cliffs Nuclear Power PlantPae6of9 Page 64 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Agreement (New Figure)

Scenario 2 3.0S

• Chesapeake Bay Bridge, VA Kiptopeke, VA 2.5 . .- A Lewisetta, VA Cambridge, MD y =1.069x ,.

20R 2 =0.7376 S.."

i(. Annapolis,MD

-Baltimore, MD

-J L._ + Duck, NC 2.0 ~~ ~~--/oO.. .-

4oJ

• Se wells Point, VA

-a)

• Toichester Beach, VA

• -'3 1.0 555 . "*' "°55

• Atlantic City, NJ

-1:1 Line E 0.25 m Error Bound Linear 0.0 "

0.0 0.5 1.0 1,5 2.0 2.5 3.4 Obseved Observed Water Level (m-MSL)

Calvert Cliffs Nuclear Power PlantPae6of9 Page 65 of 90 (mMSL Levl ate

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-20 Hurricane Irene: Modeled and Observed Maximum Water Surface Elevation Agreement (New Figure)

• Chesapeake Bay Bridge, VA 3.0 - Kiptopeke, VA

-' A Lewisetta, VA

-J 2.5 Cambridge, MD y = 0.9932x 2.0 R2=0.9566 Annapolis, MD E

-Baltimore, MD 1.5

+ Duck, NC

-_J I..

4-i 1.0

• Sewelts Point, VA

• Toichester Beach, MD

-o 0.5 4-,

• Atlantic City, NI Co 0.0 Solomons Island. MD Em *,Yorktown, VA

• c'i

-0.5

• Windmill Point, VA

... Wrightsville Beach, NC

-1.0 1.0 0.0 1.0 2.0 3.0 - 1:1 Line Observed Water Level (m-MSL) 0.25 m Error Bound -

Calvert Cliffs Nuclear Power PlantPae6of9 Page 66 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-21 Hurricane Isabel: Modeled and Observed Water Surface Elevation at Tolchester Beach, MD (New Figure)

Calvert Cliffs Nuclear Power PlantPae6of9 Page 67 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-22 Hurricane Isabel: Modeled and Observed Water Surface Elevation at Baltimore, MD (New Figure) 2.5 ID LO 1.0 Dat Calvert Cliffs Nuclear Power PlantPae6of9 Page 68 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4.23 Hurricane Isabel: Modeled and Observed Water Surface Elevation at Annapolis, MD (New Figure) 2.5

- 2.0

-O.5 Dat Calvert Cliffs Nuclear Power PlantPae6of9 Page 69 of 90

Amendment 1 to CCNPP Fiood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-24 Hurricane Isabel: Modeled and Observed Water Surface Elevation at Kiptopeke, VA (New Figure) 2.0 1 .

0 4.5

-1.0 Date Calvert Cliffs Nuclear Power PlantPae7of9 Page 70 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-25 Delft3D-WAVE Model Boundaries, Buoy Stations and WlS Stations (New Figure)

Calvert Cliffs Nuclear Power PlantPae7of9 Page 71 of 90

Amendment I to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-26 Critical PMH Track Direction and Distance from CCNPP to PMH Storm Center (New Figure)

Calvert Cliffs Nuclear Power PlantPae7of9 Page 72 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-27 Storm Surge Elevation in Chesapeake Bay during the Peak of PMH (New Figure) water' eI* 19:4759 06-Apt-2015 01) 40 r

• kCCNPP Units I &2 4:1 39'.

3*S 38-

• =37.5 {10 37' 36.5-35.5 F

!  !  ! I

-7'4

• { 'i , i i i I i

?7.5 -77 -7865 -76 -75.5 74.5 xcoordinate Calvert Cliffs Nuclear Power PlantPae3of9 Page 73 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-28 Significant Wave Height in Chesapeake Bay during the Peak of PMH (New Figure) hsig wave height (ft) 06-Apr-20 15 19:47:59 40 r 30

• CCNPP Units I &2 39.51-25 391-38.51}-

381- 20 a) 37.5 1-15 Cu I-0 0

0 371-36.5 -

36 1-10 35.5tI-35-77L l

-75,5

-75

-76.5 -76 x coordinate Calvert Cliffs Nuclear Power PlantPae7of9 Page 74 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Figure 2.4-29 Peak Period in Chesapeake Bay during the Peak of PMH (New Figure) smoothed peak period (s) 06-Apr-201 5 19:47:59 40[ CCNPP UnitsIt&2 14 39.5k 12 39F 10 38.5k 381 8

37.5k O0 0

0m 6

37F 36.5k 4 36F 2

35.5k I l l 0 35'-

-77 -76.5 75.5 -75 x coordinate Calvert Cliffs Nuclear Power PlantPae7of9 Page 75 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-30 Significant Wave Height and Wave Vector in Chesapeake Bay during the Peak of PMH (New Figure) 06-Apr-201 5 19:47:59 4C F CNPP Units I &2 130 39.51I-391-25 38.51F

[

20 381-4) 4-,

ID 37.51-a-

15 0

0 0

371-A0 36.51-361-5 35.51-I l l 35L I i i I

'-77p -76.5 -76 -75.5 -75 x coordinate Calvert Cliffs Nuclear Power PlantPae7of9 Page 76 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.2-31 Wave Length in Chesapeake Bay during the Peak of PMH (New Figure) mean wave length (ft) 06-Apt-201 5 19:47:59 4 0r

• " CCNPP Units I &2 39.5' 200 39 38.5 K 150 38 Cu 37.5 I,-

K 100 37F 36.5 50 36 35.5 35- l il i

i 0

-77 -76.5 -76 -75.5 -75 x coordinate Calvert Cliffs Nuclear Power PlantPae7of9 Page 77 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Figure 2.4-32: Cross Section Schematic of Wave Activity on CCNPP Units l& 2 Pump House (New Figure) 50

-. ITqp Si*.tioni ot irwke Dedc 40

-Pump Roon Roof Elevzion

... Roof Elevatwio of Seik Building PMSS

~~~~/

I-I_= tN 1Aft

• ., .,,. ,-,.\

1.~ \ /

Uk- 3.J8 p*[*=11.2 *20 UO U

.... / ....../ .... e 10 House

4.85 U

-10

-20

-250 -200 -150 -100 -50 50 100 150 Di[stance from Clhesapeske ]Bay, Feet Note; Figure not to Scale Calvert Cliffs Nuclear Power PlantPae7of9 Page 78 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 2.9 COMBINED EFFECT FLOODING (Superseded by this Amendment)

Combined effect of different flood-causing mechanisms is evaluated based on the guidelines presented in RG 1.20 6 (Reference 2.9-I), NUREG/CR-7046 (Reference 2.9-2), NUREG/CR-6966 (Reference 2.9-3), NEl 12-08 (Reference 2.9-4) and ANSI/ANS-2.8-1992 (Reference 2.9-5).

Particularly,the evaluation is based on ANSI/ANS-2. 8-1992 (Reference 2.9-5) and NUREG/CR-7046 (Reference 2.9-2), which provides detailed guidance on selecting combined events criteriafor power reactorsite locations on inland streams, open or semi-enclosed bodies of water, and enclosed bodies of water.

Flooding reevaluations for different flood mechanisms are described in Sections 2.1 through 2.8. As identified in the CCNPP Units 1 & 2 UFSAR (Reference 2.9-6) and CCNPP Unit 3 COLA (Reference 2.9-7) and as described in this report, flooding in streams and rivers (Section 2.2), dam failure (Section 2.3), seiche (Section 2.5), ice-induced flooding (Section 2.7), and channel diversion (or shoreline erosion) (Section 2.8) would have no impact to any safety-related or important to safety SSCs of the CCNPP Units 1 & 2. These flood mechanisms are screened out as not applicable to the site based on topographic, geological, and hydrologic setup. Therefore, a combined effect flooding assessment for these mechanisms is not necessary.

Reevaluation of the local site-specific PMP event in Section 2.1 identifies that water surface elevations remains below the finish floor elevations for all critical structures surrounding the power block. The critical structures consist of the Emergency Diesel Generator Building, South Service Building, Turbine Buildings, and Auxiliary Building. Table 2.1-5 summarizes the results from the LIP analysis utilizing site-specific PMP.

The effects of PMSS are discussed in Section 2.4, which shows that the revaluated PMSS water surface elevation with wave activity of 26.17 ft MSL (or 26.81 ft NGVD 29) is below the design basis elevation of 27.5 ft MSL (or 28.14 ft NGVD 29).

NUREG/CR-7046, Appendix H43.1 and ANS 2.8-1992, Section 9.2.2.1, state that the following combination of flood-causing events provides an adequate design basis for shore locations:

H 3.1 Shore Location, Combination of:

1) Probable maximum surge and seiche with wind-wave activity.

2) Antecedent 10 percent exceedance high tide.

Therefore, the criteria for PMSS with wind-wave activity and the antecedent 10 percent high tide including potential sea level rise were evaluated. Section 2.4.2.6 provides detailed discussion on antecedent water level used as initial water level. Section 2.4.2.8 provides detailed discussion on methods used to calculate wave runup.

For the tsunami flooding evaluation, the guidance in NUREG/CR-7046 (Reference 2.9-2) and NUREG/CR-6966 (Reference 2.9-3) with respect to the 10 percent excee dance high spring tide and long-term sea level rise, as described in Section 2.6, are followed.

2.9.1 Conclusions Not Impacted by this Amendment and Remains Valid 2.9.2 References Not Impacted by this Amendment and Remains Valid Calvert Cliffs Nuclear Power PlantPae7of9 Page 79 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 3 COMPARISlON OF CURRENT AND REEVALUATED FLOOD CAUSING MECHANISMS (Superseded by this Amendment)

This section summarizes the comparison of current design basis fiood elevations at various safety-related and important-to-safety SSCs against corresponding reevaluated flood elevations from the same flood-causing mechanisms. As discussed in the FHRR, all flood-causing mechanisms except LIP and PMSS are either determined to be implausible or completely bounded by other mechanisms.

Reevaluation performed as part of this amendment indicated that the fiood causing mechanisms of LIP and PMSS are also completely bounded by the current licensing basis. Table 3.0-1 shows the comparison of flood elevations from all flood-causing mechanisms for the current and reevaluated design basis conditions.

There is no safety concern at the power block due to scouring during local intense precipitation as the power block is mostly concrete paved. Also, the risk of debris impact to CCNPP Units 1 & 2 is relatively low under the local intense precipitation event, as the contributing drainage area to the CCNPP Units 1 & 2 power block is mostly covered with an impervious surface with some woods areas. The steep slope between the power block and the substation is covered with riprap and protected by gabion baskets. Therefore, the potential for erosion affecting the safe functioning of the plant is expected to be low.

Per the March 12, 2012, 50.54(f) letter (NRC March 2012), Enclosure 2, the following flood-causing mechanisms were considered in the flood hazard reevaluation for Calvert Cliffs Units 1 and 2.

1. Local Intense Precipitation;

2. Flooding in Streams and Rivers;

3. Dam Breaches and Failures;

4. Storm Surge;

5. Seiche;

6. Tsunami;

7. Ice Induced Flooding; and

8. Channel Migration or Diversion.

Some of these individual mechanisms are incorporated into alternative 'Combined Effect Flood' scenarios per Appendix H of NUREG/CR-7046 (NUREG/CR-7046).

The March 12, 2012, 50.54(f) letter, Enclosure 2, requests the licensee to perform an integrated assessment of the plant's response to the reevaluated hazard if the reevaluated flood hazard is not bounded by the current design basis. This section provides comparisons with the current design basis flood hazard and applicable flood scenario parameters per Section 5.2 of JLD-ISG-2012-05 (NRC ISG-2012-05), including:

1. Flood height and associated effects

a. Stillwater elevation;

b. Wind waves and run-up effects;

c. Hydrodynamic loading, including debris;

d. Effects caused by sediment deposition and erosion (e.g., flow velocities, scour);

e. Concurrent site conditions, including adverse weather conditions; and

f. Groundwater ingress.

2. Flood event duration parameters shown in Figure 6 of JLD-ISG-2012-05)

Calvert Cliffs Nuclear Power PlantPae8of9 Page 80 of 90

Amendment 1 to CCNPP Exelon Generation Co. Flood Hazard Reevaluation Report September 08, 2015

a. warning time (may include information from relevant forecasting methods (e.g.,

products from !ocal, regio~nal, or national weather forecasting centers) and ascension time of the .flood hYdrograph to a pdint (e.g., intermediate Water surface elevations) triggering entry into flood procedures and actions by.,plant personnel);

b. Periotd of site preparation (after entry into flood procedures and before flood waters reach site grade);

c. Pe'riod of inundation; and

d. Period of recession (when flood waters completely recede from site and plant is in safe and stable state that can be maintained).

3. Plant mode(s) of operation during the flood event duration

4. Other relevant plant-specific factors (e.g., waterborne projectiles)

Per Section 5.2 of JLD-ISG-2012-05 (NRC ISG-2012-05), flood hazards do not need to be considered individually as part of the integrated assessment. Instead, the integrated assessment should be performed for a set(s) of flood scen~ario parameters defin~ed based on th~e results of the flood hazard reevaluations. In Some cases, only one controlling flood hazard may exist for a site. In this case, licensees Should define the flood scenario parameterS based on this controlling flood hazard. However,r sites that have a diversity of flood hazards to which the site may be exposed Should define multiple sets of flood scenario parameters to capture the different plant effects from the diverse flood parameters associated with applicable hazards. In addition, sites may use different flood Protection systems to protect against or mitigate different flood hazards. In such instances, the integrated assessment should define multiple sets of flood scenario parameters. If appropriate, it is acceptable to develop an enveloping scenario (e.g., the maximum water surface elevation and inundation duration with the minimum warning time generated from different hazard scenarios) instead of considering multiple sets of flood scenario parameters as part of the integrated assessment. For simplicity, the lcensee may'combine these flood parameters to generate a single bounding set of flood scenario parameters for use in the integrated assessment.

As discussed in the FHRR, all flood-causing mechanisms except LIP and PMSS are either determined to be implausible or completely bounded by Other mechanisms. Reevaluation performed as part of this amendment indicated that .the flood causing mec:hanisms of LIP and PMSS are also completely bounded by the current licensing basis.

Tables 3.0-1 through 3.0-4 summarize the parameters for the LIP and PMSS flood hazards and provide comparisons with the current design basis flood.

Calvert Cliffs Nuclear Power Plant Pg 811o9 Page of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 3.1 Local Intense Precipitation (Superseded by this Amendment)

The CCNPP Units I & 2 UFSAR (Reference 3.1-1) indicates that the site drainage design, which employs a network of surface ditches and underground culverts, allows storm water drainageaway from the site and eliminates any flooding impact to the site. The plant area has a site grade elevation of approximately 45.0 ft NGVD 29. Several entrance openings with roll-up doors for the Auxiliary and Turbine Buildings are located at site grade.

The UFSAR also evaluates a flooding elevation at the EDG and SBO Buildings, where site grading design provides a system of swales that direct surface runoff from the local PMP event to the Chesapeake Bay without producing drainage or flooding problems for the buildings. The runoff to the Chesapeake Bay does not depend on the site's storm drain system. The results of the runoff and backwater analyses indicate that during the PMP storm, the swale system will convey the surface runoff with a maximum water level of 44.8 ft NG VD 29 near the Diesel GeneratorBuildings (EDG and SBO0). This water level is below the floor grade of the Diesel GeneratorBuildings, which is 45.5 ft NG VD29, and thus eliminates the potential for flooding of the Diesel GeneratorBuildings during the local PMP event. The local PMP analysis used HMR 51 and HMR 52 and employed U.S. Army Corps of Engineers (USA CE) computer program HEC-1 and HEC-2 to compute surface runoff and peak water levels for the ditches and swales (Reference 3.1-1).

The reevaluated results due to the site-specific local intense precipitation are presented in Section 2.1. The reevaluation also utilizes site-specific PMP instead of HMR 51 and HMR 52 to obtain the point rainfall intensities and used USACE computer models HEC-HMS and HEC-RAS to simulate peak runoff and corresponding maximum water levels in the drainage paths within the power block area. The analysis is performed assuming underground storm drains and culverts, as well as roof drains are clogged and not functioning during the local PMP storm event. The resulting simulated water levels in the power block area varied between 43.64 ft MSL to 44.86 ft MSL. The HEC-RAS model results indicate that the area surrounding the power block will remain dry (i.e., flood free) during the site specific LIP event. Resulting simulated peak flow velocities varied between 0.61 ft/s to 5.39 ft/s, which are not expected to produce any erosion hazards as described in Section 2.1. Additionally, the majority of the contributing drainage area to the Calvert Cliffs Units 1 and 2 power block is mostly covered with concrete and gravel. Therefore, associated risk of sediment and debris being brought to the site is relatively low under the site specific LIP event.

3.1.1 References Not Impacted by this Amendment and Remains Valid Calvert Cliffs Nuclear Power PlantPae8of9 Page 82 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 3.4 Storm Surge (Superseded by this Amendment)

The PMSS constitutes the flooding design basis at the intake structure. The Calvert Cliffs Units 1 and 2 UFSAR (Reference 3.4-1) uses the following methodology to develop the PMSS elevation at the site:

PMH parameters were identified from NOAA technical report HUR 7-97, the predecessor to NWS Technical Report NWS 23. The PMH parameters include:

o Central pressure of 26.94 inches of Mercury o Asymptotic pressure of 30.12 inches of Mercury, which provides a central pressure deficit of 3.18 inches of Mercury or 107.7 millibar o Radius of maximum wind of 30 statute mi o Forward speed of 23 mile per hour o Maximum wind speed of 124.7 mile per hour at the radius of maximum wind o PMH path that approaches the coast from the east, curving northward after it passes inland west of Chesapeake Bay

• The PMH wind field developed from the PMH parameters used the methodology described in report HUR 7-97.

• The storm surge elevation in the open water in front of the Chesapeake Bay entrance was obtained following the methods described in USACE Technical Report 4. The maximum hurricane surge of 17.32 ft NGVD 29 coincidental with the normal high tide was obtained at the Chesapeake Bay entrance.

• Hurricane surge levels within the bay were evaluated adopting the methodology proposed by Bretschneider in USACE Miscellaneous Paper 3-59. The surge elevation of 15.6 ft NGVD 29 was obtained near the Calvert Cliffs Units 1 and 2 site.

• Coincident significant wave height and peak period were estimated at 11.4 ft and 9.0 seconds, respectively.

• Wave runup was confirmed by physical scale model tests, which show a maximum wave runup elevation of 27.1 ft NGVD 29 with a runup height of 9.5 ft corresponding to a maximum (1 percent) wave height of 14 ft. The final model tests included an adverse slope for the intake structure. The runup elevation from physical model tests did not overtop the intake structure top elevation at 28.5 ft NGVD 29.

The reevaluated maximum storm surge as part of this amendment uses NWS 23 to define the PMH parameters, which are used in the calibrated Delft3D storm surge model. As part of this amendment, the design hurricane is selected in accordance with applicable guidance documents (NUREG/CR-7046, NUREG 0800, JLD-ISG-201 2-06), which refer to the PMH methodology of NWS 23. JLD-ISG-2012-06 states that the PMH methodology of NWS 23 is acceptable for licensing decisions. Using the NWS 23 methodology, the critical PMH parameters of storm size, pressure, and wind fields are determined for a storm making landfall near the mouth of Chesapeake Bay. A sufficient number of storm radii, headings, and forward speeds are analyzed to determine the worst case storm (i.e., the PMH). Atmospheric forcing (wind and pressure data) were generated using the parametric wind and pressure field model described in Memorandum HuR 7-97. The Calvert Cliffs Units 1 and 2 Delft3D storm surge model was calibrated and validated to Hurricane Isabel and Irene storm events.

The PMH with the following attributes produced the maximum surge at Calvert Cliffs Units 1 and 2:

• A central pressure of 26.49 inches of Mercury Calvert Cliffs Nuclear Power PlantPae8of9 Page 83 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015

• A peripheral pressure of 30.12 inches of Mercury

• A pressure deficit of 3.63 inches of Mercury (122.93 millibar)

• A radius of maximum wind of 20 nautical miles

• Variable forward speed of 8 knots (preceding landfall) and 17 knots (after landfall)

• A PMH track approaching from 192 degrees (clockwise from north) as shown on Figure 2.4-5

• A PMH storm center 5 nautical miles east of Calvert Cliffs Units 1 and 2 along the critical track of 192 degrees as shown on Figure 2.4-26.

• The PMH parameters were evaluated in the calibrated Delft3D storm surge model. The final PMSS analysis uses a coupled Delft3D-WAVE and Delft3D-WAVE (SWAN) model.

Therefore, wave setup is automatically accounted for in the simulated storm surge level.

• The Delft3D simulation results show that the PMSS elevation throughout the simulation did not exceed the top elevation of the pump house 28.5 ft MSL. However, the lower deck is completely flooded, by as much as 4.85 ft of water during the PMH. No safety related equipment is affected by water in this area.

• Maximum wave height, wave length and wave period were simulated at grid points located in the Forebay. The maximum wave height was computed to be 3.09 meters (10.14 ft), the wave length was computed to be 33.10 meters (108.6 ft), and the wave period was computed to be 4.62 seconds. Although the significant wave height was calculated to be 10.14 ft (3.09 m) in the forebay, the maximum sustainable wave height on the intake deck will be limited to less than 4.85 ft. Waves in the forebay larger than 4.85 ft will break and diminish in size while smaller waves may strike the intake structure pump house wall and runup the structure.

• Wave runup was calculated using two methods. The more conservative wave runup was used to compute the maximum water surface elevation at Calvert Cliffs Units 1 and 2. The maximum wave runup is 11.32 ft.

• Using the NUREG/CR-7046 combination of flood-causing events, consisting of the probable maximum surge and seiche with wind-wave activity and the antecedent 10 percent exceedance high tide, the maximum water surface elevation at the Calvert Cliffs Units 1 and 2 pump house was calculated to be +26.17 ft MSL (+26.81 ft NGVD29) which is bounded by the Current Design Basis (COB) of +27.5 ft MSL (28.14 ft NGVD).

• The top of the Pump House is +28.5 ft MSL. According to the results of the runup calculation, the maximum runup elevation of 26.17 ft MSL (or 26.81 ft NGVD29) does not overtop the Calvert Cliffs Units 1 and 2 Intake Structure Pump House roof during a PMH event.

3.4.1 References Not Impacted by this Amendment and Remains Valid Calvert Cliffs Nuclear Power PlantPae8of9 Page 84 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 3.9 Combined Effects Flooding (Superseded by this Amendment)

Combined effect flooding is discussed as part of the reevaluation of flood-causing mechanisms, where applicable, based on the guidelines presented in RG 1.206 (Reference 3.9-1), NUREG/CR-7046 (Reference 3.9-2), NUREG/CR-6966 (Reference 3.9-3), NEI 12-08 (Reference 3.9-4) and ANSI/ANS-2.8-1992 (Reference 3.9-5). The combined effect for three flooding mechanisms, local intense precipitation, storm surge and tsunami, are compared to the current licensing basis in the following paragraphs. Other flooding mechanisms are screened out based on the topographic, geologic and hydrologic settings of the site and the surroundingregion.

The local PMP analysis performed for the EDG Building in the Units 1 & 2 UFSAR (Reference 3.9-6) conservatively assumed the entire contributing catchment area as impervious. The analysis then used a runoff curve number of 98 to represent the impervious surface condition. The reevaluated LIP analysis performed as part of this amendment utilizes site-specific PMP instead of rainfall obtained from HMR 51 and 52. To account for the saturated ground condition due to the antecedent rain, the reevaluation performed in Section 2.1 also used a runoff curve number of 98. This combined events condition is comparable to the reevaluation as summarized in Section 2.9.

CCNPP Units 1 & 2 UFSAR (Reference 3.9-6) used the normal high tide and sea level anomaly of approximately 2.82 ft NGVD 29 as the antecedent water level for the storm surge estimation. The estimated storm surge elevation of 16.24 ft NGVD 29 was then combined with the wind-wave runup (11.9 ft) on the intake structure. The maximum storm surge water level thus obtained was (16.24 + 11.9 =) 28.14 ft NGVD 29. This combined events condition is comparable to the reevaluation performed as part of this amendment as summarized in Section 2.9 of this amendment.

While the CLB qualitatively evaluates to screen out tsunami impacts to the plant, the reevaluation performed numerical model simulations of tsunami wave propagation, as documented in Section 2.6. Following the guidance in NUREG/CR-7046 (Reference 3.9-2) and NUREG/CR-6966 (Reference 3.9-3) the ambient conditions of 10 percent exceedance high spring tide with consideration of long-term sea level rise is used in the PMT estimate.

The results of the combined effects analysis has not introduced any additional flood hazards.

3.9.1 References Not Impacted by this Amendment and Remains Valid Calvert Cliffs Nuclear Power PlantPae8of9 Page 85 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 3.0-1 Current Design Basis Flood Elevations for Safety-Related and Important-to-Safety SSCs (Superseded by this Amendment)

Reevaluated.

Current Flood Level Current Flood Design Flooding Flood Critical Protection Computed in Mechanism Structure Basis Flood this Elevation Level Amendment ft MSL ft MSL ft MSL Containment Building, Auxiliary Building, Local Intense Emergency Diesel Not discussed Precipitation Generator Building, 45.0, 45.5(3) in COB, 4.83 43.64(3) - 44.86 Station Blackout Building(1), and Turbine Building(2)

Flooding in No Flooding No Flooding No Flooding No Flooding Streams and Expected Expected Expected Expected Rivers Upstream Dam No Flooding No Flooding No Flooding Failures Expected Expected Not Evaluated Expected Storm Surge (including Intake Structure 28.5 27.5 26.17 wave runup)

Seiche No Flooding No Flooding Not Evaluated No Flooding Expected Expected Expected Tsunami 11.5 (including runup) Intake Structure 28.5 No Flooding (No Flooding Expected Expected)

Ice Induced No Flooding No Flooding No Flooding Flooding Expected Expected Not Evaluated Expected Channel Migration or No Flooding No Flooding No Flooding No Flooding Diversio n(4 ) Expected Expected Expected Expected Notes:

(1) Station Blackout Building is augmented safety-related (2) Turbine Building is Seismic Category II (3) At the Emergency Diesel Generator and SBO Buildings (4) Shoreline protection measures exist and no erosion expected Calvert Cliffs Nuclear Power PlantPae8of9 Page 86 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co.

September 08, 2015 Table 3.0-2 - Summary of Licensing Basis and External Flooding Study Parameters (New Table)

Parameter j Current Licensing Basis [ FHRR FHRR Amendment No Local Intense- Precip~itation . ... .... .... .. .__

Ntmentioned in UFSAR for Calvert Cliffs Units 1 and 2 HMR 51 and HMR 52 Site-specific PMP Methodology HMR 51 and HMR 52 used in (1- mi 2, 1-hr -1 8.48 (1- mi2 , 1-hr-Calvert Cliffs Unit 3 COLA (1- inches) 11 .7inches) mi2, 1-hr -18.48 inches) I___________ __________

".=

' * . . Effects

. .. Local,. Intense,

• Precipi tation. _.  ! . -.- -,. .

Not mentioned in UFSAR for Calvert Cliffs Units 1 and 2.

Hydrologic Modeling using Steady Study Unsteady Study MehoolgyHEC-HMS Computer Hydraulic Model Hydraulic Model Mtoooy Software. Hydraulic Modeling (HEC-RAS computer (HEC-RAS using HEC-RAS Computer software) computer software)

Software in Calvert Cliffs Unit 3 COLA _______ ______

' ., Proba~ble Maximum Surge and .Seiche 2-Dimensional Hydrodynamic I 2-Dmensonal Hyrdnmcand More refined grid calibrated Methodology modeling (SLOSH computer Hyrdnmc storm surge model software)

______________________ {computer modeling (SLOSH software)sotae (Delft3D computer Calvert Cliffs Nuclear Power PlantPae8of9 Page 87 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 3.0-3 Local Intense Precipitation (New Table)

Flood Scenario Parameter Current Design Reevaluated as part of IBudd()o Budd()o

1. Max Stillwater Elevation (ft. MSL)

Basis (CDB)

Not discussed IAmendment this 43.64(° _

j iNoBune (NB)

B (D*in 0DB, 44.8(10) 44.86 See Note 1 o 2. Max Wave Run-up Elevation (ft. MSL) N/ASe Noe2N/A______

< ,* NA SeeNN/A

• -3. Max Hydrodynamic / Debris Loading Not Determined SeN/A N/A (bIbft) SeNote 3 "J 4. Effects of Sediment Deposition/Erosion N/A See Note 4 B "0

6 5. Concurrent Site Conditions Not Determined See Note 5 N/A

,T 6. Effects on Groundwater N/A See Note 6 N/A

= 7. Warning Time (hours) "N/A N/A N/A oSee Note 7 See Note 7 _______

_* 8. Period of Site Preparation (hours) N/A N/A

-*See Note 7 See Note 7N/

>* 9. Period of Inundation (hours) N/A N/A See Note 7 See Note 7N/

oo 10. Period of Recession (hours) N/A N/A

" N/

See Note 7 See Note 7N/

11. Plant Mode of Operations An SeNyt Ohr12. Other Factors N/A N/A N/A

_______________________________ ___________ SeeNote_ 9 _______

Notes for corresponding parameter:

1. The reevaluated flood elevation is bounded by the current design basis at the EDG and SBO buildings. UFSAR does not provides LIP water surface elevation at other critical structures. The reevaluation water surface elevation at other critical structures is below finish floor elevation of 45.0 ft MSL.

2. Consideration of wind-wave action for the LIP event is not explicitly required by NUREG/CR-7046 and is judged to be a negligible associated effect because of limited fetch lengths and flow depths.

3. The hydrodynamic and hydrostatic loads are bounded by the design basis maximum tornado wind load. The debris load for the LIP event is assumed to be negligible due to the absence of heavy objects at the plant site and due to low flow velocity, the factors combination of which could lead to a hazard due to debris load.

4. The flow velocities due to the LIP event are determined to be below the suggested velocities for the ground cover type (concrete and grave) at the plant area. Therefore, the erosion is not a plausible hazard for Calvert Cliffs Units 1 and 2.

5. High winds could be generated concurrent to a LIP event. However, manual actions are not required to protect the plant from LIP flooding so this concurrent condition is not applicable.

6. The majority of the plant area is paved or gravel and results in minimal infiltration, if any. Therefore, it is expected that infiltration of precipitation and groundwater seepage would likely be minimal.

Additionally, the event is a short-duration (1-hour precipitation) which limits the amount of soil infiltration.

7. SSC's important to safety are currently protected by means of permanent/passive measures.

Therefore, flood event duration parameters are not applicable to the LIP flood.

8. The reevaluated peak flood elevation is bounded by the current design basis. Current plant operations and procedures will still govern.

9. There are no other factors, including waterborne projectiles, applicable to the LIP flood.

10. At the EDG and SBO buildings Calvert Cliffs Nuclear Power PlantPae8of9 Page 88 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exelon Generation Co. September 08, 2015 Table 3.0-4 - Probable Maximum Storm Surae (PMSS* (New Table' Flood Scenario Parameter Current IDesign Basis 1Reevaluated as part of this

'JBoun'ded Not Bou~nded (B) or (CDB) J Amendment I (NB)

1. Max Stiliwater Elevation (ft. NGVD 29)1 B 16.24 15.49 SeNt S 2. Max Wave Run-up (Including Setup) 281B681SeNt S Eleyation (ft. NGVD 29)1 28.14____ 26.81_SeeNote_

o 3. MaX Hydlrodynamic and DebrisSeNoe3 eeot3B S Loading (Ib)SeNoe3 eeot3B o, 4. Effects of Sediment Deposition/Erosion See Note 4 See Note.4 B

._1 5. Concurrerit site Conditions N/A N/A o See Note 5 See NoteS N/

___6. Effects on. Groundwater See Note 6 See Note 6 B

7. Warning Time (hours) N/A N/A N/A

-o See Note 7 See. Note 7

-,' 8. Period of Site Preparation (hours) N/A N/A N/A C-See Note 7 See Note 7 ______

>* 9. Period of Inundation (hours) N/A .N/A N/A

____________________ See Note 7 See Note 7 _______

.2 10. Period of Recession (hours) 'N/A N/A N/A

____ __________________________ See Note 7 See Note 7

11. Plant Mode of Operations Any AnyAn Other See Note 8

___12..Other Factor's N/A N/A N/A Notes for corresponding parameter:

1. ft NGVD 29 =MSL +0.64

2. The reevaluated flood elevation is bounded by the current design basis.

3. As indicated in the UFSAR, the pressure distribution due to the waves is a combination of hydrostatic and hydrodynamic components and the exposed safety-related structures are designed to withstand these effects. The re-evaluated wave height and ruinup are bounded by the CDB.

Therefore, the hydrodynamic loads at the screen house due to H.4.3 combinations are bounded by CDB.

4. As indicated Units 1 and 2inis the UFSARagainst protected and FHRR, approximately shoreline erosion. 3700 ft of the shoreline near the Calvert Cliffs

5. High winds could be generated concurrent to this combined effect flood. However, manual actions are not required to protect the intake structure from the PMSS so this concurrent condition is not applicable.

6. The stillwater level is bounded by the current design basis stillwater level. Therefore, impact to groundwater ingress is considered to be bounded.

7. SSC's importanit to safety are currently protected by means of permanent/passive measures.

Therefore, flood event, duration parameters are not applicable to the PMSS flood.

8. The reevaluated peak flood elevation isbounded by the current desicin basis.

I

• Y Calvert Cliffs Nuclear Power PlantPae8of9 Page 89 of 90

Amendment 1 to CCNPP Flood Hazard Reevaluation Report Exeion Generation Co. September 08, 2015 4 INTERIM FLOOD PROTECTION MEASURES FOR AUXILLARY AND TURBINE BUILDINGS (Superseded by this Amendment)

Deleted- No Longer Applicable as results of reevaluated LIP and PMSS analysis are bounded by the current licensing basis.

5 ADDITIONAL ACTIONS (Superseded by this Amendment)

Deleted- No Longer Applicable as results of reevaluated LIP and PMSS analysis are bounded by the current licensing basis.

Calvert Cliffs Nuclear Power Plant Pg Of9 Page 90 of 90