ML19011A111

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Supplement to the Flooding Hazard Reevaluation Report in Response to 50.54(F) Information Request Regarding Near-Term Task Force Recommendation 2.1: Flooding
ML19011A111
Person / Time
Site: Millstone  Dominion icon.png
Issue date: 12/18/2018
From: Lockett B, Wang B
Zachry Nuclear
To:
Dominion Energy Nuclear Connecticut, Office of Nuclear Reactor Regulation
References
18-E05
Download: ML19011A111 (39)
v • d • e


Text

Serial No.18-447 Docket Nos. 50-336/423 Enclosure SUPPLEMENT TO DOMINION FLOODING HAZARD REEVALUATION REPORT FOR MILLSTONE POWER STATION UNITS 2 AND 3 IN RESPONSE TO 50.54(F) INFORMATION REQUEST REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2.1: FLOODING DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNITS 2 AND 3

Zachry Nuclear ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FLOODING HAZARD REEVALUATION REPORT FOR MILLSTONE POWER STATION UNITS 2 AND 3 IN RESPONSE. TO 50.54(F) INFORMATION REQUEST REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2.1: FLOODING REVISION 0 QA CLASSIFICATION: NON-SAFETY RELATED

~ww Prepared by: _ _ _ __

Bin Wang

_[_ _ _ _ _ _ __ 12/17/2018 Date Co-Prepared by: -&1 (/:. ~

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___ 12/17/2018 David M. Leone Date Co-Reviewed by: ~ ~ ~~

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Approved by: ~ \ , . ~ ' , { , ~ I¥ I'; J Jtf' 1

Sombat Pornpraseft Dale Client: Dominion/Millstone Power Station Zachry Nuclear Job No. : 112074 Page 1 of 16 Total number of pages including Attachments - 38

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ZACHRY NUCLEAR ENGINEERING EVALUATION,18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 REVISION HISTORY Revision Revision Description 0 Original Issue.

Bin Wang was responsible for preparing the front matter of the EE, Section 1.0, Sections 3.0 through 5.0 and Section 7.0.

Bryan J. Lockett was responsible for preparing Sections 2.0 and 6.0.

Stephen F. Superson was the overall responsible reviewer, and in particular co-reviewed the front matter of the EE and Section 2.0 and 6.0.

David Leone was responsible for reviewing Section 1.0, Sections 3.0 through 5.0 and Section 7.0.

This Engineering Evaluation, while in accordance with Zachry Procedure N0302, Rev. 01, is formatted and presented in such a manner as to be consistent with the expectations of Dominion and the Nuclear Regulatory Commission (NRC). This re-formatting will include header, footer, and page number adjustments that will allow for easy topic recognition while not violating any Zachry branding guidelines. The Engineering Evaluation Verification Form will not be included as an attachment to this document, but will instead be kept in records with this EE, as a separate document.

This document replaces in its entirety the Engineering Evaluation previously submitted via Zachry Transmittal 01OMPS/112074/D18252.

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ZACHRY NUCLEAR ZAC=I BIY ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 TABLE OF CONTENTS EVALUATION TITLE SHEET ....................................................................................................................... 1 REVISION HISTORY .................................................................................................................................. 2 TABLE OF CONTENTS .............................................................................................................................. 3 1.0 Purpose...................................................................................................................................... 4 2.0 Site Information Supplemental Information ............................................................................ 4 3.0 Storm Surge Stillwater Elevation at AEP of 1 E-4 for MPS ...................................................... 5 3.1 Methodology ..................................................................................................................... 5 3.2 Results ............................................................................................................................. 7 4.0 Combined Effects Flood Analysis for Stillwater at AEP of 1 E-4 ............................................ 9 4.1 Methodology ..................................................................................................................... 9 4.2 Results ........................................................................................................................... 1O 4.3 Conclusions .................................................................................................................... 12 5.0 Comparison of Current Design Basis and Reevaluated Flood Causing Mechanisms ....... 12 5.1 Storm Surge ................................................................................................................... 12 5.2 Combined Effects Flooding ............................................................................................. 13 6.0 Supplement to Interim Evaluations and Actions (FHRR Section 4.1 and 4.5) ..................... 14 6.1 Combined Effects Flooding Supplemental Information .................................................... 14 6.2 Conclusion Supplemental Information ............................................................................ 14 7.0 References ............................................................................................................................... 14 TOTAL NUMBER OF PAGES IN EVALUATION BODY ............................................................ 16 ATTACHMENTS Total Pages A. Tables 10 B. Figures 12 TOTAL NUMBER OF PAGES IN ATTACHMENTS .................................................................. 22 TOTAL NUMBER OF PAGES IN EVALUATION ..................................................................... 38 Page 3 of 16 Revision O

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ZACHRY NUCLEAR ZACIIIIW ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 1.0 Purpose The purpose of this engineering evaluation is to supplement Sections 2 and 3 of the existing Dominion Flood Hazard He-evaluation Report (FHRR) for Millstone Power Station (MPS) Units 2 and 3 (Zachry Engineering Evaluation 14-E16, 2015a), focusing on additional Probabilistic Storm Surge Analysis (PSSA) at the 1x104 (1 E-4) Annual Exceedance Probability (AEP). The 1E-4 PSSA was performed in response to NRC and MPS discussions during review of the FHRR (Zachry 2015a) presenting the 1E-6 PSSA results. During the review of the FHRR (Zachry, 2015a), NRC and MPS agreed to focus on a more frequent AEP to reduce the epistemic uncertainty around the reevaluated flood elevation estimate. The storm surge and combined effects flood analysis presented in this document refines estimates of error and uncertainty around an AEP of 1E-4, which is an AEP used in probabilistic flood analyses by the U.S. Army Corps of Engineers in independent studies of coastal flood risk.

This supplement provides additional information to FHRR Sections 2.4, 2.9, 3.4, 3.9, 4.1 and 4.5 and does not supersede information previously provided in the FHRR.

This document summarizes the results and findings based on the two calculations below:

  • Annual Exceedance Probability (AEP) 1.0E-04 for Probabilistic Storm Surge Analysis (PSSA) for Millstone Power Station (Zachry calculation 18-075, 2018a); and
  • Combined Effects (CE) Flood Analysis for Storm Surge Annual Exceedance Probability 1 E-4 for Millstone Power Station (Zachry calculation 18-110, 2018b).

MPS is located at the shoreline of Long Island Sound with 41.311 degrees (0 ) North (Latitude) and -

72.168° West (Longitude) in Waterford, Connecticut. MPS is subject to coastal storm surge flooding

_due to its proximity to the Long Island Sound.

Vertical datum: Two vertical datums were used for this report: 1) North American Vertical Datum of 1988 (NAVD88) and 2) Mean Sea Level (MSL), the pla,nt datum. MSL is interchangeable with National Geodetic Vertical Datum of 1929 (NGVD29) (see "Introduction" of Zachry, 2015a), wh,ich was not specifically referenced or used in this report. Conversion relationship is defined as (Zachry, 2018b):

Elevation in feet, MSL plant datum = Elevation in feet, NAVD88 + 0.99 foot.

2.0 Site Information Supplemental Information This section is a supplement to Section 1.3 of the MPS FHRR (Zachry, 2015a). As a result of the Fukushima Daiichi incident, the NRC issued order EA~ 12-049 which notified existing and future commercial licensees to modify all licenses with regard to requirement for mitigation strategies for beyond-design-basis external events. Specifically, the objective of this order was to ensure licensees provide sufficient 'mitigating strategies, onsite portable equipment and consumables (FLEX Equipment) to maintain or restore core cooling, containment, and Spent Fuel Pool "(SFP) cooling capabilities until resources can be brought from off site to sustain these functions indefinitely.

Subsequent to issuing the Dominion Flooding Hazard Reevaluation Report for Millstone Power Station Units 2 and 3 (Engineering Evaluation 14-E16R1 ), Millstone constructed a Type I, Beyond Design Basis (BOB) Storage Building to store the FLEX Equipment. The BOB Storage Building Page 4 of 16 Revision 0

ZACHRY NUCLEAR ZACIRIY ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 is designed as a seismic, tornado-missile protected structure with missile-protected door construction. The purpose of the BDB Storage Building is to protect the onsite portable equipment used to maintain or restore key safety functions for the Unit 2 and Unit 3 reactors from applicable site-specific external events and provide reasonable assurance that the equipment will remain deployable following such an event.

Millstone has developed station documents which describe and document the Beyond Design Basis mitigating strategies, procedures, guidance, training, staging, or equipment installation needed for the strategies. These have been developed in accordance with NEI 12-06, "Diverse and Flexible Coping Strategies (FLEX) implementation Guide" to ensure the plant's ability to cope with an extended loss of alternating current (AC) power (ELAP) concurrent with a loss of normal access to the ultimate heat sink (LUHS). Implementing procedures provide guidance to station personnel for the preparation, response and recovery from significant storms and other hazardous phenomena to maintain operation of the Station, maintain a safe condition for personnel, prompt transition to high priority actions, prevent or mitigate damage and achieve restoration of the site as quickly as possible, and support employee and community restoration effort which include utilization of FLEX Equipment.

3.0 Storm Surge Stillwater Elevation at AEP of 1E-4 for MPS This section is a supplement to Section 2.4 of the MPS FHRR (Zachry, 2015a). This PSSA calculated a mean stillwater elevation and confidence intervals associated with an AEP of 1E-4 in the nearshore area around MPS (Zachry, 2018a). Please note that the methodology used for the development of the 1E-4 stillwater in this calculation is specific to this AEP level. To develop mean stillwater levels for other AEP values (i.e., recurrence intervals such as 1E-5 or 1E-3),

additional sensitivity tests on key input parameters (such as probability functions and/or logic tree branch weighting factors) will be needed.

3.1 Methodology The 1E-4 PSSA calculation (Zachry, 2018a) followed the framework of the Joint Probability Method (JPM) for calculating tropical cyclone-induced storm surge flood frequency curves. The JPM was combined with Optimal Sampling (OS) technique with Response Surface (RS) method, as used by previous federal coastal flood evaluation projects such as the Federal Emergency Management Agency (FEMA) risk mapping project for parts of New York and New Jersey (FEMA, 2014) and the post-Sandy North Atlantic Coast Comprehensive Study (NACCS) performed by the U.S. Army Corps of Engineers (USAGE, 2015).

The 1 E-4 PSSA adopted a logic tree approach with a total of 96 branches or paths (Figure 1 and Table 1) to evaluate potential variability and epistemic uncertainty of the final flood frequency curve. Nodes on the logic tree define the input parameters such that each path results in a distinctive stillwater flood frequency curve. The weighting factors (Figure 1) represent the final selected weighting scheme, mainly based on sensitivity test results and engineering judgment.

The final weight assigned for each flood frequency curve was computed as the product of all the connecting nodal weighting factors along each path. A weighted average flood frequency curve was calculated with confidence intervals (see Section 3.1 of Zachry, 2018a for more details).

Steps to calculate the mean 1E-4 storm surge stillwater elevation at MPS include:

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ZAC=i *IV ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3

  • Compile two sources of storm surge numerical modeling data: (1) JPM-OS set simulated for the PMSS calculation (Zachry, 2015b) using the MPS site-specific Advanced Circulation (ADCIRC) model; and (2) NACCS modeling results of 1,050 tropical cyclone tracks (USAGE, 2015). The model grid used by USAGE is large, covering the Atlantic coast from Virginia to Maine and the large number of the synthetic hurricanes modeled with ADCIRC and STWAVE (Steady-State Spectral Wave Model) coupled provide a valuable addition to the simulated results generated by the site-specific model (Zachry, 2015a and Zachry 2015b)
  • Compile source hurricane tracks and develop probability distribution functions for hurricane parameters (i.e., intensity metric including maximum wind speed (Vm) in knots and central pressure deficit (CPD) in millibars (mb), heading (Fdir) in degrees (0 ), forward speed (Fspd) in knots or kilometers per hour (km/hr), and radius of maximum winds (RMW) in nautical miles (nm) or kilometers (km)) based on two separate data sources:

o Synthetic hurricane tracks generated by WindRiskTech (WRT), which was used to develop the MPS PMH and PMSS calculations (Zachry, 2014; Zachry, 2015b) and summarized in the original MPS FHRR (Zachry, 2015a); and o Historical hurricane tracks based on National Oceanic and Atmospheric Administration (NOAA) Reanalysis database, HURDAT and Extended Best Track Data (EBTD) (see Sections 6.5.2 and 6.5.3 of Zachry, 2018a for more details).

  • Compute storm recurrence rates with upper and lower bounds for both WRT and historical hurricane datasets;
  • Develop discrete probability values for the hurricane parameters at specified intervals;
  • Assemble two JPM sets of synthetic hurricanes: (a) full JPM set using the MPS site-specific model results; and (b) full JPM set using the NACCS model results. Each synthetic hurricane has a distinctive probability value that includes the parameter combination, storm recurrence rate, landfall rate and tidal conditions.
  • Perform the JPM-OS-RS calculation to interpolate and/or extrapolate the simulated storm surge response to the full parameter space as specified by the full JPM sets (MPS-based and NACCS-based sets), using the storm surge response factors developed using the MPS model results.
  • Develop error and uncertainty parameters based on tidal conditions, modeling error, hurricane intensity variability and/or correction factors, which were based on sensitivity analysis results and engineering judgment and are applicable to the AEP of 1 E-4 specifically;
  • Calculate each flood frequency curve with error and uncertainty incorporated;
  • Calculate the weighted mean flood frequency curve and confidence intervals based on the logic tree branch weights (using the selected weighting scheme);
  • Calculate a separate extratropical flood frequency curve with confidence intervals based on water levels at Save Point 756_ from 100 simulated historical extratropical cyclones Page 6 of 16 Revision 0

ZACHRY NUCLEAR ZACIU&Y ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 (USAGE, 2015; see Figure 6 of Zachry, 2018a for location of Save Point 756, which is just south of Millstone Point); and

  • Combine the tropical and extratropical flood frequency curves.

Note that the selection of hurricane parameter probability distributions and error/uncertainty parameters was specifically intended to develop a mean stillwater elevation at AEP of 1E-4. The curves shown in this document are not intended to be extrapolated beyond the vicinity of AEP of 1E-4.

3.2 Results MPS modeling results from the JPM-OS set (Zachry, 2015b), which consists of a total of 71 synthetic storm tracks, were used for calculating storm surge values of the full MPS model-based JPM set. The output node is located at a nearshore point location between the Unit 2 and Unit 3 Intake Structures (see Figure 1 of Zachry, 2018a). The NACCS modeling results of 1,050 synthetic tropical cyclones were extracted at Save Point 756, which is located south of the plant, in the Long Island Sound (see Figure 6 of Zachry, 2018a; USAGE, 2015). Branches 1 through 60 use the MPS model results and Branches 61 through 96 use the NACCS model results (Figure 1 and Table 1).

Hurricane Data Sources Input for the WRT-based logic tree branches (Branches 1 through 4, 11 through 14, 21 through 24, 31 through 34, 41 through 44, and 51 through 54) was based on the Probable Maximum Hurricane (PMH) calculation using the WRT synthetic hurricane tracks (see Section 6.3.1 of Zachry, 2018a; Zachry, 2014; Zachry, 2015a). The data was spatially filtered to a 200-kilometer circular (offshore) zone centered at point location 40.825°N (Latitude) and 72.66°W (Longitude) near Hampton, New York (southeastern shore of Long Island) (Zachry, 2014; Zachry, 2015a).

Input for the historical data-based logic tree branches (Branches 5 through 10, 15 through 20, 25 through 30, 35 through 40, 45 through 50, 55 through 60, and 61 through 96) was developed based on the HURDAT data filtered by a 300-kilometer circular zone centered at MPS. HURDAT data was filtered to the time period between 1938 and 2016. The EBTD data was filtered to data points east of Longitude -82° to remove the data within the Gulf of Mexico. The period of record for the EBTD data is from 1988 to 2016 (Section 6.3 of Zachry, 2018a).

Storm Recurrence Rate The MPS model-based (i.e., node i1) branches (1 through 60) use the WRT storm recurrence rate of 5.1 E-4 storms per year per kilometer (storm/yr/km) or 9.4E-4 storms per year per nm, with upper and lower bound values of 7.1E-4 and 3.1E-4 storm/yr/km. The NACCS model-based (node i2) branches (61 through 96) use the historical hurricane storm recurrence rate of 4.3E-4 storms per year per kilometer (storm/yr/km), with upper and lower bound values of 6.3E-4 and 2.3E-4 storm/yr/km (See Section 6.4 of Zachry, 2018a).

Probability Distributions

  • The WRT-based branches use the non-parametric distributions developed in the PMH calculation (Zachry, 201-4, FHRR Section 2.4 of Zachry, 2015a and Zachry, 2015b) assuming parameter Page 7 of 16 Revision 0

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ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 independence and the 3-million (3M) vector set to calculate JPM parameter combination probabilities assuming complete dependence between the four parameters, Vm, Fdir, Fspd and RMW.

The historical data-based branches use the univariate probability distribution for each hurricane parameter. For Fdir and intensity parameters (Vm and CPD), multiple distributions were used to evaluate potential variability. For Fpsd, only one distribution Nakagami was selected, which appeared to be the best fit of the source data. RMW distributions were developed based on its dependence on the intensity parameter (Vm for i1-related paths or CPD for i2-related paths). The logic tree used both heading-independent and heading-dependent paths to assess the variability of this assumption. Source historical data was separated based on the heading parameter, Fdir, into two categories: 1) westerly tracks, west of -10° (i.e, 10° west of north) and 2) north/northeasterly tracks (i.e., east of -10°).

JPM-OS-RS Calculation The full JPM sets for the MPS model and the NACCS model (Section 6.6 of Zachry, 2018a) were assembled based on the parameter intervals presented below.

MPS Site-specific Model-based Branches (1 through 60) used 5 landfall locations, 11 headings, 12 forward speeds, 11 maximum wind speeds and 17 radii of maximum winds, which resulted in a total number of 123,420 JPM storms, calculated as:

5 (LF) x 11 (Fdir) x 12 (Fspd) x 11 (Vm) x 17 (RMW) = 123.420.

NACCS Model-based Branches (Nos. 61 through 96) used 130 NACCS master tracks (which cover 6 different headings), 1O forward speeds, 16 central pressure deficit values and 17 radii of maximum winds, which resulted in a total number of 353,600 JPM storms, calculated as:

130 (tracks) x 10 (Fspd) x 16 (CPD) x 17 (RMW) = 353,600.

A distinct AEP value was calculated for each individual JPM synthetic track based on the storm recurrence rate, landfall probability, storm parameter combination and tidal condition.

The RS method was used to interpolate and/or extrapolate modeled surge response for any storm parameter combination in the full JPM set. For the MPS-based logic tree branches, the 71 MPS ADCIRC model simulated OS storms were used to derive the surge response factors along each parameter space (Vm, Fspd, and RMW). For the NACCS-based logic tree branches, the surge response factors were also derived for CDP, Fspd and RMW (with units consistent with the NACCS synthetic tropical cyclone tracks) based on the 71 MPS ADCIRC simulations. A test flood frequency curve was developed, which was similar to the published NACCS AEP curves at Save Point 756. This comparison indicates the approach of using NACCS model results combined with MPS model surge response factors is reasonable (see Section 6.6 of Zachry, 2018a).

Error and Uncertainty Estimates Ten MPS model-based and 6 NACCS model-based flood frequency curves were calculated without error and uncertainty. Error and uncertainty parameters were developed for each path and incorporated into the frequency curves using FEMA's "surge_stat" program, which uses two terms (a constant "a" parameter and a proportional "b" parameter) (Section 6.7 of Zachry, 2018a).

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ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 To include potential variability due to linearly regression of a slightly non-linear behavior of the surge error function, a "b"-vector was also adopted for this analysis to fit the underlying data with a fourth order polynomial function. Attachment B (Tables) of Zachry, 2018a provides the summary of the "a" and "b" values (or vectors) required by "surge_stat". Different tidal scenarios were incorporated as a different error term in each branch. Storm recurrence rates were applied as constants to adjust the AEP values of each calculated JPM curve.

Combined Tropical and Extratropical Curve The overall storm surge flood frequency curve resulted in a stillwater level at 1E-4 AEP of 16.1 feet, MSL at a nearshore point location between the MPS Unit 2 and 3 intake structures (Figure 3), with no projected sea level rise included. The final mean storm surge elevation at AEP of 1 E-4 was 16.6 feet, MSL, which includes 0.45 foot to account for a 50-year, linear-extrapolated sea level rise at MPS (Figure 2, which also illustrates confidence levels). Please refer to Figures 60 through 63 of the 1E-4 PSSA calculation (Zachry, 2018a).

4.0 Combined Effects Flood Analysis for Stillwater at AEP of 1E-4 This section is a supplement to Section 2.9 of the original MPS FHRR (Zachry, 2015a) 4.1 Methodology MPS Unit 2 and Unit 3 intake structures are located at the site's western shoreline. Foundation walls of the intakes are partially submerged under normal daily tides. Unit 2 Turbine Building has a typical site grade of 14 feet, MSL and is at a minimum distance of approximately 200 feet from the shoreline. Unit 3 Turbine Building has a typical site grade of 24 feet, MSL and is at a minimum distance of approximately 400 feet from the shoreline.

  • During a typical tropical cyclone surge event, MPS is likely to experience southernly onshore winds for an extended period of time. The wind and pressure differential from the storm system can bring significant storm surge above astronomical tides and wind-generated waves in the Long Island Sound. The stillwater level near the shoreline will likely consist of astronomical tides, storm surge, and wave setup. Deep water waves are likely to break at the shoreline (e.g., the bulkhead along MPS or shallow rock outcrops). Deep water waves will be reflected by vertical surfaces and cause wave run up, such as along the exterior walls of the Unit 2 and Unit 3 Intake Structures.

When the foreshore of the site is inundated, shallow water waves will propagate towards Unit 2 Turbine Building and could cause potential wave overtopping of the concrete flood wall protecting the western side of the Unit 2 Turbine Building. The combination of wave direction and dissipation of wave energy due to the various non-safety related buildings indicate that wave effects are negligible in the Unit 2 main site/ power block area, including the eastern wall of the Unit 2 Turbine Building. Therefore, wave effects were calculated on the western side only for Unit 2 Turbine Building.

The combined effects flood calculation (Zachry, 2018b) used a deterministic approach to calculate wave runup, total water level, overtopping and flood loads associated with the 1E-4 stillwater elevation at MPS (Section 3.0 of this document). Steps to develop the combined effects flood elevations, overtopping flow, and hydrostatic, hydrodynamic and debris impact loads include:

  • Evaluate hurricane parameters that are representative for a tropical cyclone to induce a stillwater flood elevation consistent with the mean 1E-4 flood (i.e., stillwater elevation of Page 9 of 16 Revision O

ZACHRY NUCLEAR ZACIUIV ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 16.6 feet, MSL, including sea level rise, in the nearshore area between Unit 2 and 3 intake structures) (Figure 3; Figure 1 of Zachry, 2018a);

  • Develop a set of synthetic storms for hydrodynamic and wave numerical model simulation with storm parameter combinations that are representative for the AEP of 1E-4 and will likely generate storm surge elevations in the vicinity of the 1 E-4 stillwater elevation determined in the PSSA calculation (Zachry, 2018a) ;
  • Perform hydrodynamic and wave numerical modeling and extract results to determine the storm surge response and coincident wave activity around the 1E-4 stillwater elevation;
  • Identify the storm that is most representative of the storm conditions that will likely produce the 1 E-4 stillwater elevation at MPS;
  • Calculate total water levels at Unit 2 and Unit 3 intake structures including wave runup; calculate total water level at Units 2 and 3 Turbine Buildings including wave runup;
  • Calculate wave overtopping at the Unit 2 Turbine Building flood wall based on modeled water level and wave time series (assuming failure of the existing wall panels);
  • Calculate maximum flood loads against Units 2 and 3 Intakes and Unit 2 Turbine Building.

The European Overtopping Manual (EurOtop, 2016) was used for calculating wave runup, total water levels (i.e., the calculated flood level in the existing FHRR, Zachry, 2015a) and overtopping rate and volume to the Unit 2 Turbine Building. Additional reference documents were used for calculating flood loads, debris impact load and standing wave loads (ASCE, 201 O; FEMA, 2011; FEMA, 2012).

4.2 Results The MPS model-based JPM set (with 123,420 synthetic storm tracks) was used to evaluate "average" hurricane parameters that are representative of the stillwater at AEP of 1E-4. Branches 25 and 26 from the logic tree were used. Branch 25 is a representative branch for heading-intensity independent scenarios; Branch 26 is a representative branch for heading-intensity dependent scenarios. Both branches are based on historical hurricane data. A set of parameter combinations was compiled for numerical modeling, informed by the calculated average 1 E-4 storm parameters. The calculation used a coupled ADCIRC+SWAN (Simulating WAves Nearshore) model to perform a total of 1O synthetic simulations, as presented in Table 2, which were named as "CE" storms. Figure 3 presents the model grid around Unit 2 and Unit 3. Figure 4 presents the modeled synthetic storm tracks on an area map. The simulated peak stillwater elevations, maximum significant wave height, and time series of stillwater, current, wave characteristics, and wind speed were examined to identify CE-2, with a heading of -20°, Vm of 11 O knots, Fspd of 15 knots, and RMW of 30 nm, as a representative storm for evaluating combined effects associated with the stillwater level at AEP of 1 E-4 at MPS (Section 3.1 of Zachry, 2018b; Attachment D.2 of Zachry, 2018b). The slightly westerly heading of CE2 generates peak wind-wave actions coincident with peak storm surge, due to the hydrological setting of the site location in the Long Island Sound. The simulated stillwater elevation in the Long Island Sound, between the Units 2 and 3 Intake Structures, is 16. 7 feet, MSL, which is consistent with the calculated mean stillwater of 16.6 feet, MSL at AEP of 1E-4 (Zachry, 2018a).

Figure 5 presents three time series (i.e., stillwater, significant wave height, current velocity) at three representative locations around Units 2 and 3 Intake Structures and Unit 2 Turbine Building.

Figure 6 presents a snap shot of the stillwater elevation around the power block and intake Page 10 of 16 Revision O

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- ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 structures approximately at the time of peak storm surge at MPS due to CE-2. Figure 7 presents the wave height and direction at the time of peak wave height around MPS. The Combined Effects calculation (Attachment C of Zachry, 2018b) provides additional snap shots and time series.

Stillwater elevations, current velocities, calculated wave runups and total water levels from the CE2 simulation are summarized at selected locations around MPS in Table 3. Total water levels were calculated as the sum of Stillwater (including wave setup) and wave runup. Wave runup (exceeded by 2 percent of the incoming waves) for Unit 3 Turbine Building was estimated using an iterative method along a selected transect (red line in Figure 8; calculation presented in Attachment E of Zachry, 2018b). For other locations, wave runup (exceeded by 2 percent of the incoming waves) was estimated proportionally with a constant factor of 1.93 using significant deep water wave height (EurOtop, 2016).

Total water levels at the west side of Unit 2 and Unit 3 Turbine Buildings are 19.8 feet, MSL and 22.2 feet, MSL, respectively. Total water levels at the south side of Units 2 and 3 Intakes are up to 37.2 feet, MSL and 42.6 feet, MSL, respectively. Stillwater levels elsewhere in the Unit 2 main site / power block area are approximately the same as the west side, based on the modeling results. Therefore, the stillwater level value reported for the west side of the Unit 2 Turbine Building is also applicable to the Unit 2 main site/ power block area.

The Unit 2 Turbine Building has an internal flood wall with a top elevation of 22 feet, MSL and siding panels above the wall that, if in place, would protect the interior of Unit 2 Turbine Building from flooding. Assuming the siding is not present (e.g., due to wind or other effects), wave overtopping of the flood wall due to intermittent wave splashing on the west wall of Unit 2 Turbine Building was estimated using the method outlined in the EurOtop Manual (EurOtop, 2016) and adopting a 3-stage approach based on wave crest and stillwater elevations. The three consecutive stages (e.g., periods of time) are (1) prior to foreshore inundation; (2) during foreshore inundation; and (3) post-inundation (see Section 2.7 of Zachry, 2018b). The overtopping analysis was performed along a selected transect (green line in Figure 8 of Attachment B; calculation presented in Attachment G of Zachry, 2018b). The calculated cumulative overtopping volume during Stages 1 and 3 was 1,324 gallons and 2,655 gallons, respectively. The calculated overtopping volume during Stage 2 was estimated to be 22 gallons (with obliquity) or 4,862 gallons (without obliquity). Therefore, the total overtopping volume is approximately 4,000 gallons inside the Unit 2 Turbine Building, with obliquity effects included.

The total overtopping volume is approximately 8,840 gallons inside Unit 2 Turbine Building, with obliquity effects conservatively ignored.

Hydrostatic, hydrodynamic, debris impact and standing wave loads were individually calculated.

The maximum hydrostatic pressure was calculated to be 3,002 and 3,014 pounds-per-square-foot (psf) for the south sides of the Unit 2 Intake Structure and the east sides of the Unit 3 Intake Structure, respectively. The maximum hydrostatic pressure was calculated to be 224 psf for the west side of Unit 2 Turbine Building. The maximum hydrodynamic pressure against the Unit 2 Intake Structure was calculated as 34 psf at the west side and 59 psf at the south side. The maximum hydrodynamic pressure against the Unit 3 Intake Structure was calculated as 5.0 psf at the south side and 32 psf at the east side. The maximum hydrodynamic pressure against the Unit 2 Turbine Building was calculated as 224 psf.

a Two types of objects were used: a 2,000-pound (lbs) log or 5,291-lbs container for evaluating debris impact, based on current velocity. Debris impact loads were calculated to be 13,800 lbs or 36,508 lbs on the south side of Unit 2 Intake, due to a log or a container, respectively. Debris Page 11 of 16 Revision O

ZACHRY NUCLEAR DIV ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 impact loads w~re calculated to be 10,200 lbs or 26,984 lbs on the east side of Unit 3 Intake, due to a log or a container, respectively.

Standing (non-breaking) wave loads were calculated for Units 2 and 3 Intake Structures using both significant wave height and maximum wave height. Tables 4 and 5 summarize the different types of loads at various structures at MPS, based on significant wave height and maximum wave height, respectively.

Duration of significant flooding (including stillwater and wave runup) around the intake structures and Unit 2 Turbine Building was estimated to be up to 4.5 to 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. Duration of significant wave overtopping at Unit 2 Turbine Building flood wall was estimated to last approximately 7 to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> in total.

4.3 Conclusions The overall storm surge flood frequency curve resulted in a stillwater level at 1E-4 AEP of 16.1 feet, MSL at a nearshore point location between MPS Unit 2 and 3 intake structures, with no projected sea level rise included. The final mean storm surge elevation at AEP of 1E-4 was 16.6 feet, MSL, which includes 0.45 foot to account for a SO-year, linear-extrapolated sea level rise at MPS (Figure 2, which also illustrates confidence levels).

Calculated combined effects results are summarized in Tables 3 through 5 of this document (see Section 5.0 and Tables 6 through 10 of Zachry, 2018b). The combined effects flood stillwater elevations (including wave setup) range from 16.8 to 17.1 feet around Unit 2 and Unit 3 Intake Structures and from 17.5 to 17.7 feet MSL around Unit 2 and Unit.3 Turbine Buildings. Wave runup heights range from 2.3 to 4.5 feet on the west side of the Unit 2 and 3 Turbine Buildings to more than 20 feet around the Unit 2 and 3 Intake Structures. Except for the west side of the Unit 2 Turbine Building, wave effects were judged to be negligible within the Unit 2 main site I power block area due to the distance from the shoreline and the presence and density of buildings and structures. The stillwater level value reported for the west side of the Unit 2 Turbine Building is applicable to the Unit 2 main site/ power block area.

Unit 2 Turbine Building overtopping volume can reach up to 1.4 and 3.2 percent of the available storage (i.e., 280,000 gallons) inside the building, with and without obliquity considered, respectively. The Unit 3 total water level, 22.2 feet MSL, is lower than the Unit 3 average site grade of 24 feet, MSL. Therefore, the total water level only reaches the foreshore approaching the Unit 3 Turbine Building and does not impact the Unit 3 Turbine Building or any other buildings in the Unit 3 main site I power block.

5.0 Comparison of Current Design Basis and Reevaluated Flood Causing Mechanisms This section supplements Section 3.4 (Storm Surge) and 3.9 (Combined Effect Flood) of the MPS FHRR (Zachry, 2015a). It also supplements Tables 3.0-1 and 3.0-2 of MPS FHRR (Zachry, 201 Sa) with the 1E-4 PSSA results (see Tables 6 and 7, Attachment A of this document). Please refer to the MPS FHRR (Zachry, 201 Sa) for more detailed discussion of MPS current design basis for flooding.

5.1 Storm Surge Page 12 of 16 Revision O

    • ---~---- - -----" ------ ------- ----- --------

ZACHRY NUCLEAR ZAC=l nlV ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 The 1E-4 PSSA (Zachry, 2018a) calculated the mean 1E-4 stillwater elevation of 16.6 feet MSL at a nearshore location around MPS (Figure 3), which is applicable to both Units 2 and 3. The MPS FHRR (Zachry, 2015a) summarizes the current design basis elevation for storm surge stillwater as 18.2 feet MSL at MPS Unit 2*and at 19.7 feet MSL at MPS Unit 3. The mean 1 E-4 stillwater elevation is, therefore, bounded by the current design basis at MPS Units 2 and 3.

5.2 Combined Effects Flooding The synthetic storm track CE2 produced a stillwater elevation of 16. 7 feet MSL in the nearshore area (Table 3; Figures 5 and 6). Stillwater elevations including wave setup varies spatially. The simulated stillwater elevations varied between 16.8 and 17.1 feet MSL around the Intake Structures (Table 3; Figures 5 and 6). The simulated stillwater elevations caused by CE2 were 17.5 feet MSL and 17.7 feet MSL at the Unit 2 Turbine Building and at the Unit 3 foreshore approaching the Unit 3 Turbine Building, respectively (Table 3; Figures 5 and 6).

The 1E-4 Combined Effects calculation (Zachry, 2018b) calculated the mean 1 E-4 combined effect elevation (i.e., total water level, also referred to as "reevaluated flood level" in the MPS FHRR, which is stillwater level and wave effects combined) for the storm surge to be:

  • 19.8 feet, MSL at the west side of Unit 2 Turbine Building (Table 3);
  • \ 37.2 feet, MSL at the south side of Unit 2 Intake Structure {Table 3);
  • 22.2 feet, MSL at the foreshore approaching the Unit 3 Turbine Building (Table 3);
  • 42.6 feet, MSL at the south side of Unit 3 Intake Structure (Table 3).
  • Except for the west side of the Unit 2 Turbine Building, wave effects were judged to be negligible within the Unit 2 main site / power block area due to the distance from the shoreline and the presence and density of buildings and structures.

The MPS FHRR (Zachry, 2015a) summarizes the current design basis elevation for MPS Unit 2 combined effect flooding (total water level) as:

  • 25.1 feet at the MPS Unit 2 Turbine Building and other MPS Unit 2 buildings (Section 3.9 of Zachry, 2015a);
  • 42.5 feet at the vertical Wall of the Intake Structure (Section 3.9 of Zachry, 2015a).
  • The MPS FHRR (Zachry, 2015a) summarizes the current design .basis elevation for MPS Unit 3 combined effects flooding (total water level) as:
  • 23.8 feet at the MPS Unit 3 buildings (not including intake structure) (Section 3.9 of Zachry, 2015a);
  • 41.2 feet at the vertical wall of the Intake Structure (Section 3.9 of Zachry, 2015a).

The 1E-4 combined effects flood elevations are, therefore, bounded by the current design basis at MPS Units 2_ and 3, with the exception of the MPS Unit 3 Intake Structure. The MP3 Intake Structure would still have an available physical margin of 0.8 feet to the unsealed cable Page 13 of 16 Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 penetrations. Internal water levels within the intake structures are analyzed in NAI Calculation NAl-1996-001, Rev. 1 (MP2) and NAI Report NAl-1996-002, Rev. 1 (MP3) (Zachry 2018c and 2018d).

The overall conclusions reported in the FHRR regarding flood-related loading and debris impact forces for the 1E-4 AEP remain unchanged (Zachry, 2015a).

6.0 Supplement to Interim Evaluations and Actions 6.1 Combined Effects Flooding Supplemental Information This section is a supplement to Section 4.1 of the MPS FHRR (Zachry, 2015a).

Based on the AEP of 1 E-04, the Combined Effects Flooding analysis produced stillwater elevations of 17.5 feet, MSL and 17.7 feet, MSL for MPS Unit 2 and Unit 3, respectively. The calculated 1E-4 stillwater elevations are below the current licensing basis stillwater elevations, which are 18.1 feet, MSL and 19. 7 feet, MSL for MPS Unit 2 and Unit 3, respectively. The 1 E-4 combined effects flood elevations are, therefore, bounded by the current design basis at MPS Units 2 and 3, with the exception of the MPS Unit 3 Intake Structure. However, the 1E-4 stillwater elevations are below the current flood protection levels, including at the MPS Unit 3 Intake Structure.

The equipment and planned actions for Millstone site to address combined effects flooding are contained in Design Change MPG-13-00010, Rev .. 1 (Dominion, 2014) and the Engineering Technical Evaluations ETE-CPR-2012-0008/9 for Millstone Unit 3 and 2 respectively (Dominion, 2018a and 2018b). These were updated as part of the implementation of the FLEX strategies to respond to a loss of ultimate heat sink (UHS) event for Beyond Design Basis flooding.

The MP2 and MP3 Intake Structures were re-analyzed in Zachry, 2018c and 2018d respectively, for 1.0E-04 Annual Exceedance Probability (AEP) results and no changes were required to the existing designs.

6.2 Conclusion Supplemental Information This section is a supplement to Section 4.5 of the MPS FHRR (Zachry, 2015a).

The impact from combined effects flooding at an AEP of 1.0E-04 are within the current licensing basis designs and/ or mitigation strategies developed as part of the FLEX strategies therefore no supplemental changes to the original FHRR are noted.

For Sections 4.2 and 4.3 of the original FHRR (Zachry, 2015a), the site procedures, Dominion, 2017a, 2018c, and 2018d were updated to implement station flood protection features based on notifications of an imminent LIP event or tsunami (tsunami warning from NOAA's/NWS National Tsunami Warning Center) and to initiate required actions.

7.0 References Dominion, 2014. Design Change MPG-13~00010, Revision 1, BOB Storage Building/Millstone Power Station/Units 2&3, 2014.

  • Page 14 of 16 Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Dominion, 2017a, Millstone Power Station Common Operating Procedure, C OP 200.6, Revision 008-00, Storms and Other Hazardous Phenomena (Preparation and Recovery), 2017 Dominion, 2018a. Engineering Technical Evaluation No. ETE-CPR-2012-0008, Revision 6, Beyond Design Basis - FLEX Strategy Basis Document and Final Integrated Plan (Millstone Unit 3), 2018.

Dominion, 2018b. Engineering Technical Evaluation No. ETE-CPR-2012-0009, Revision 6, Beyond Design Basis - FLEX Strategy Basis Document and Final Integrated Plan (Millstone Unit 2), 2018.

Dominion, 2018c. Millstone Power Station Abnormal Operating Procedure AOP 2560, Revision 018-00, Storms, High Winds and High Tides, 2018 Dominion 201 Sd. Millstone Power Station Abnormal Operating Procedure AOP 3569, Revision 024, Severe Weather Conditions ASCE, 2010. "Minimum Design Loads for Buildings and Other Structures," ASCE/SEI 7-10, American Society of Civil Engineers (ASCE), 2010.

EurOtop, 2016. Manual on wave overtopping of sea defenses and related structures, the EurOtop team, Second Edition, 2016. Document downloaded www.overtopping-manual.com in 2018.

FEMA, 2011. "Coastal Construction manual: Principles and Practices of Planning, Siting, designing, Constructing and Maintaining Residential Buildings in Coastal Areas," FEMA 55, Federal Emergency Management Agency, 2011.

FEMA, 2012. "Engineering Principles and Practices for Retrofitting Flood-Prone Residential Structures,"

FEMA-P-259, Federal Emergency Management Agency, 2012.

FEMA, 2014. Region II storm surge project- joint probability analysis of hurricane and extratropical flood hazards, Federal Emergency Management Agency, September 2014.

USACE, 2015. Coastal Storm Hazards from Virginia to Maine, North Atlantic Coast Comprehensive Study, US Army Corps of Engineering Engineer Research and Development Center, November 2015.

Zachry, 2014. Zachry Calculation No.14-034, Revision 0, Probable Maximum Hurricane for Millstone Power Station, GZA GeoEnvironmental, Inc., 2014.

Zachry, 2015a. Zachry Engineering Evaluation No. 14-E16 Dominion Flooding Hazard Reevaluation Report for Millstone Power Station Units 2 and 3 in Response to 50.54(F) Information Request Regarding Near-Term Task Force Recommendation 2.1: Flooding, Revision 1, Zachry Nuclear, Inc., 2015.

Zachry, 201 Sb. Zachry Calculation No.14-161, Revision 0, Probabilistic Storm Surge for Millstone Power Station, GZA GeoEnvironmental, Inc., 2015.

Zachry, 2018a. Zachry Calculation No.18-075, Revision 0, Millstone Power Station Annual Exceedance Probability 1.0E-4 for Probabilistic Storm Surge Analysis, GZA GeoEnvironmental, Inc., 2018.

Zachry, 201 Sb. Zachry Calculation No.18-110, Revision 0, Combined Effects Flood Analysis for Storm Surge Annual Exceedance Probability 1E-4 at Millstone Power Station, GZA GeoEnvironmental, Inc.,

2018.

Page 15 of 16 Revision O

ZACHRY NUCLEAR ZAClda'V ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Zachry, 201 Sc. NAI Calculation NAl-1996-001, Revision 1, MP2 Intake Structure Refined Beyond Design Basis Inundation Analysis, Numerical Applications, Inc., 2018.

Zachry, 201 Sd. NAI Report NAl-1996-002, Revision 1, MP3 Intake Structure Service Water Pump Room Available Physical Margin during Beyond Design Basis Inundation, Numerical Applications, Inc., 2018.

Page 16 of 16 Revision O

. - - - - - - - -~-- *-- - *------ ---*- --- -- - - - -

oav ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Attachment A Tables Table 1: Logic Tree Branches Defined by Node Identifiers ................................................................... 2 Table 2: Summary Results for Ten Simulated Synthetic Hurricanes for Combined Effects ................... 5 Table 3: Wave Runup and Total Water Level. ....................................................................................... 6 Table 4: Flood Loads Results based on Significant Wave Height .......................................................... 7 Table 5: Flood Loads Results based on Maximum Wave Height .......................................................... 8 Table 6: Summary of the Comparison of Current Design Basis and Reevaluated (1 E-4 AEP) Flood Causing Mechanisms for MPS Unit 2 ..................................................................................................... 9 Table 7: Summary of the Comparison of Current Design Basis and Reevaluated (1 E-4 AEP) Flood Causing Mechanisms for MPS Unit 3 ................................................................................................... 1O.

Note: Tables presented in Attachment A are from Zachry Calculations 201 Ba and 201 Bb.

Zachry EE 18-EOS Attachment A, Page 1 of 1O Revision 0

ZACHRY NUCLEAR RIV ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Table 1: Logic Tree Branches Defined by Node Identifiers Antecedent Dependent Radius of Path Surge Water Forward or Maxir:num Error and ID Interpolation SRR Level Heading Speed Independent Intensity Winds Uncertainty (I) (R) (T) (H) (F) (D) (VP) (W) (E) 1 il rl t1 hl fl dl vpl vpl el 2 il rl tl hl fl dl vpl vpl e2 3 il rl tl hl fl d2 vp2 vp2 el 4 il rl t1 hl fl d2 vp2 vp2 e2 5 il rl tl h2 f2 d3 vp3 vp3 e3 6 il rl t1. h2 f2 d4 vp4 vp4 e3 7 il rl tl h2 f2 d4 vp5 vp5 e3 8 il rl t1 h3 f2 d3 vp3 vp3 e3 9 il rl t1 h3 f2 d4 vp4 vp4 e3 10 il rl tl h3 f2 d4 vp5 vp5 e3 11 il rl t2 hl fl dl vpl vpl el 12 il rl t2 hl fl dl vpl vpl e2 13 il rl t2 hl fl d2 vp2 vp2 el 14 il rl t2 hl fl d2 vp2 vp2 e2 15 il rl t2 h2 f2 d3 vp3 vp3 e3 16 il rl t2 h2 f2 d4 vp4 vp4 e3 17 il rl t2 h2 f2 d4 vp5 vp5 e3 18 il rl t2 h3 f2 d3 vp3 vp3 e3 19 il rl t2 h3 f2 d4 vp4 vp4 e3 20 il rl t2 h3 f2 d4 vp5 vp5 e3 21 il r2 tl hl fl dl vpl vpl el 22 il r2 t1 hl fl dl vpl vpl e2 23 il r2 t1 hl fl d2 vp2 vp2 el 24 il r2 t1 hl fl d2 vp2 vp2 e2 25 il r2 t1 h2 f2 d3 vp3 vp3 e3 26 il r2 t1 h2 f2 d4 vp4 vp4 e3 27 il r2 t1 h2 f2 d4 vp5 vp5 e3 28 il r2 tl h3 f2 d3 vp3 vp3 e3 29 il r2 t1 h3 f2 d4 vp4 vp4 e3 30 il r2 tl h3 f2 d4 vp5 vp5 e3 31 il r2 t2 hl fl dl vpl vpl el 32 il r2 t2 hl fl dl vpl vpl e2 33 il r2 t2 hl fl d2 vp2 vp2 el 34 il r2 t2 hl fl d2 vp2 vp2 e2 35 il r2 t2 h2 f2 d3 vp3 vp3 e3 36 il r2 t2 h2 f2 d4 vp4 vp4 e3 37 il r2 t2 h2 f2 d4 vp5 vp5 e3 38 il r2 t2 h3 f2 d3 vp3 vp3 e3 39 il r2 t2 h3 f2 d4 vp4 vp4 e3 40 il r2 t2 h3 f2 d4 vp5 vp5 e3 41 il r3 tl hl fl dl vpl vpl el 42 il r3 t1 hl fl dl vpl vpl e2 Zachry EE 18-EOS Attachment A, Page 2 of 1O Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Antecedent Dependent Radius of Path Surge Water Forward or Maximum Error and ID Interpolation SRR Level Heading Speed Independent Intensity Winds Uncertainty (I) (R) (T) (H) (F) (D) (VP) (W) (E) 43 il r3 t1 hl fl d2 vp2 vp2 el 44 il r3 t1 hl fl d2 vp2 vp2 e2 45 il r3 t1 h2 f2 d3 vp3 vp3 e3 46 il r3 t1 h2 f2 d4 vp4 vp4 e3 47 il r3 t1 h2 f2 d4 vpS vpS e3 48 il r3 tl h3 f2 d3 vp3 vp3 e3 49 il r3 t1 h3 f2 d4 vp4 vp4 e3 50 il r3 t1 h3 f2 d4 vpS vpS e3 51 il r3 t2 hl fl dl vpl vpl el 52 il r3 t2 hl fl dl vpl vpl e2 53 il r3 t2 hl fl d2 vp2 vp2 el 54 il r3 t2 hl fl d2 vp2 vp2 e2 55 il r3 t2 h2 f2 d3 vp3 vp3 e3 56 il r3 t2 h2 f2 d4 vp4 vp4 e3 57 il r3 t2 h2 f2 d4 vpS vpS e3 58 il r3 t2 h3 f2 d3 vp3 vp3 e3 59 il r3 t2 h3 f2 d4 vp4 vp4 e3 60 il r3 t2 h3 f2 d4 vpS vpS e3 61 i2 r4 t1 h4 f3 dS vp6 vp6 e4 62 i2 r4 tl h4 f3 d6 vp7 vp7 e4 63 i2 r4 tl h4 f3 d6 vp8 vp8 e4 64 i2 r4 t1 hS f3 dS vp6 vp6 e4 65 i2 r4 t1 hS f3 d6 vp7 vp7 e4 66 i2 r4 tl hS f3 d6 vp8 vp8 e4 67 i2 r4 t2 h4 f3 dS vp6 vp6 e4 68 i2 r4 t2 h4 f3 d6 vp7 vp7 e4 69 i2 r4 t2 h4 f3 d6 vp8 vp8 e4 70 i2 r4 t2 hS f3 dS vp6 vp6 e4 71 i2 r4 t2 hS f3 d6 vp7 vp7 e4 72 i2 r4 t2 hS f3 d6 vp8 vp8 e4 73 i2 rs t1 h4 f3 dS vp6 vp6 e4

74. i2 rs t1 h4 f3 d6 vp7 vp7 e4 75 i2 rs t1 h4 f3 d6 vp8 vp8 e4 76 i2 rs t1 hS f3 dS vp6 vp6 e4 77 i2 rs tl hS f3 d6 vp7 vp7 e4 78 i2 rs t1 hS f3 d6 vp8 vp8 e4 79 i2 rs t2 h4 f3 dS vp6 vp6 e4 80 i2 rs t2 h4 f3 d6 vp7 vp7 e4 81 i2 rs t2 h4 f3 d6 vp8 vp8 e4 82 i2 rs t2 hS f3 dS vp6 vp6 e4 83 i2 rs t2 hS f3 d6 vp7 vp7 e4 84 i2 rs t2 hS f3 d6 vp8 vp8 e4 85 i2 r6 t1 h4 f3 dS vp6 vp6 e4 86 i2 r6 t1 h4 f3 d6 vp7 vp7 e4 Zachry EE 18-EOS Attachment A, Page 3 of 1O Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Antecedent Dependent Radius of Path Surge Water Forward or Maximum Error and ID Interpolation SRR Level Heading Speed Independent Intensity Winds Uncertainty (I) (R) (T) (H) (F) (D) (VP) (W) (E) 87 i2 r6 t1 h4 f3 d6 vp8 vp8 e4 88 i2 r6 t1 hS f3 dS vp6 vp6 e4 89 i2 r6 t1 hS f3 d6 vp7 vp7 e4 90 i2 r6 tl hS f3 d6 vp8 vp8 e4 91 i2 r6 t2 h4 f3 dS vp6 vp6 e4 92 i2 r6 t2 h4 f3 d6 vp7 vp7 e4 93 i2 r6 t2 h4 f3 d6 vp8 vp8 e4 94 i2 r6 t2 hS f3 dS vp6 vp6 e4 95 i2 r6 t2 hS f3 d6 vp7 vp7 e4 96 i2 r6 t2 hS f3 d6 vp8 vp8 e4 Note: Node identification (e.g., t1) as shown in Figure 1.

Zachry EE 18-EOS Attachment A, Page 4 of 1O Revision 0

I ZACHRY NUCLEAR ZACIH IY ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Table 2: Summary Results for Ten Simulated Synthetic Hurricanes for Combined Effects Nearshore West ofTB2 West ofTB2 Central Maximum Radius of Antecedent (Point 2) (Point 10) (Point 10)

Forward Forward v Simulation Landfall Pressure Wind Maximum Water Maximum Maximum Peak Direction Speed ID Location Deficit Speed Vm Winds Level (ft, Stillwater Stillwater Significant

(*) (kt)

(mb) (kt) (nm) NAVD88) Level (ft, Level (ft, Wave MSL) MSL) Height (ft)

CEl 3 -40 79 110 15 30 1.16 18.2 18.5 1.6

'I CE2 3 -20 79 110 15 30 1.16 16.7 17.1 1.1 CE3 3 0 79 110 15 30 1.16 14.5 15.1 0.7 CE6 3 -20 103 125 15 30 1.16 21.0 21.3 2.8 CE7 3 -20 86 110 5 30 1.16 14.0 14.5 0.4 CE8 3 -20 72 110 25 30 1.16 16.9 17.6 1.2 CEll 3 -20 100 110 15 45 1.16 19.1 19.3 1.8 CE13 6 -20 128 51 15 100 1.16 7.1 n/a n/a CE14 6 -40 116 47 15 100 1.16 6.9 n/a n/a .,,

  • I CE15 3 -20 79 110 15 30 2.16 17.7 18.1 1.4 '

Note: 0 denotes degrees; mb denotes millibars; kt denotes knots; nm denotes nautical miles; and ft denotes feet. "n/a" denotes foreshore not flooded and results not available. Refer to Figure 3 for output node locations. TB2 stands for Unit 2 Turbine Building.

Zachry EE 18-E05 Attachment A, Page 5 of 1 O Revision O

ZACHRY NUCLEAR ZACllllV ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Table 3: Wave Runup and Total Water Level Maximum Flow Stillwater Elevation Wave Runup, Ruz% Total Water Level Location 1 Velocity (feet, MSL) (feet) (feet, MSL)

(feet/ second)

West Side 5.2 16.8 19.9 36.7 Unit 2 Intake Structure South Side 6.9 16.9 20.3 37.2 East Side 5.1 17.1 25.1 42.2 Unit 3 Intake Structure South Side 2.0 16.9 25.7 42.6 Unit 3 Turbine 2 West Side n/a 17.7 4.5 22.2 4 Building 2 Unit 2 Turbine West Side 1.3 17.5 2.3 19.8 Building 3 Notes:

1. See Figure 13 and Figure 23 in Attachment C of Zachry, 2018b for locations of structures.
2. Runup calculation sheet in Attachment E of Zachry, 2018b.
3. Except for the west side of the Unit 2 Turbine Building, wave effects are judged to be negligible in the Unit 2 main site/ power block areas.
4. 22.2 feet, MSL occurs at the foreshore approaching the Unit 3 Turbine Building. The Unit 3 main site/ power block average site grade is 24 feet, MSL.

Zachry EE 18-EOS Attachment A, Page 6 of 1O Revision O

i ,

I, 1,*!

l ,'

ZACHRY NUCLEAR ZACIU~ ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Table 4: Flood Loads Results based on Significant Wave Height Location Hydrostatic Current Velocity Standing Wave Composite Debris Load Debris Load Considering a Pressure Hydrodynamic Pressure Pressure Considering a Log of Shipping Container of 5,291 Structure (psf) 1 Pressure (psf) (psf) 3 (psf) 4 2,000 lb lb (lb) 3 (lb) 3 Stillwater 0 34 691 725 10,400 27,513 Unit 2 Intake Elevation West Side Bottom of 2,995 34 442 3,471 N/A N/A Structure 2 Stillwater 0 59 707 766 13,800 36,508 Unit 2 Intake Elevation South Side Bottom of 3,002 59 467 3,528 N/A N/A Structure 2 Stillwater 0 5 898 903 4,000 10,582 Unit 3 Intake Elevation South Side Bottom of 3,002 5 570 3,577 N/A N/A Structure 2 Stillwater 0 32 877 909 10,200 26,984 Unit 3 Intake Elevation East Side Bottom of 3,014 32 556 3,602 N/A N/A Structure 2 Unit2 Stillwater 0 224 N/A 224 21,200 N/A Turbine Elevation Building West Bottom of Side 5 224 224 N/A 448 N/A N/A Structure 2 Notes: 1) psf = pounds per square foot (lb/ft2 )

2) Toe Elevation at Unit 2 and Unit 3 intake structures= -30.0 ft MSL. Toe Elevation at Unit 2 Turbine Building= 14 ft MSL
3) Debris loads assumed to act at the maximum stillwater elevation. Standing wave pressures are based on significant wave height.
4) The composite pressure at a given location is the sum of the hydrostatic pressure, current velocity hydrodynamic pressure and standing wave pressure.
5) Flood loads except for hydrostatic load do not apply to other sides of Unit 2 Turbine Building and structures in the Unit 2 main site/ power block area (see Table 3, note 3).

Zachry EE 18-E05 Attachment A, Page 7 of 10 Revision 0

ZACHRY NUCLEAR ZACIUI V ENGINEERING EVALUATION 18-E05 2 AND 3 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS Table 5: Flood Loads Results based on Maximum Wave Height Standing Debris Load Debris Load Considering a Hydrostatic Current Velocity Composite Wave Considering a Log of Shipping Container of 5,291 Structure Location Pressure Hydrodynamic Pressure Pressure 2,000 lb lb (psf) 1 Pressure (psf) (psf) 4 (psf) 3 (lb) 3 (lb) 3 Unit 2 Intake Stillwater 0 34 1,168 1,202 10,400 27,513 West Side Elevation Bottom of N/A 2,995 34 738 3,767 N/A Structure 2 Unit 2 Intake Stillwater 13,800 36,508 0 59 1,196 1,255 South Side Elevation Bottom of N/A 3,002 59 781 3,842 N/A Structure 2 Unit 3 Intake Stillwater 10,582 0 5 1,512 1,517 4,000 South Side Elevation Bottom of N/A 3,002 5 953 3,960 N/A Structure 2 Unit 3 Intake Stillwater 10,200 0 32 1,477 1,509 East Side Elevation 26,984

  • Bottom of 3,014 32 929 3,975 N/A N/A Structure 2 Unit 2 Turbine Stillwater N/A 0 224 N/A 224 21,200 Building West Elevation Side 5 Bottom of 224 224 N/A 448 N/A N/A '1 Structure 2 Notes: 1) psf = pounds per square foot {lb/ft2)
2) Toe Elevation at Unit 2 and Unit 3 intake structures = -30.0 ft MSL. Toe Elevation at Unit 2 Turbine Building = 14 ft MSL.
3) Debris loads assumed to act at the maximum stillwater elevation. Standing wave pressures are based on maximum wave height.
4) The composite pressure at a given location is the sum of the hydrostatic pressure, current velocity hydrodynamic pressure and standing wave pressure.
5) Flood loads except for hydrostatic load do not apply to other sides of Unit 2 Turbine Building and structures in the Unit 2 main site/ power block area (see Table 3, note 3).

Zachry EE 18-E05 Attachment A, Page 8 of 1O Revision O

ZACHRY NUCLEAR ZAClldlV ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Table 6: Summary of the Comparison of Current Design Basis and Reevaluated (1 E-4 AEP) Flood Causing Mechanisms for MPS Unit 2 Flooding Flood Critical Structure Current Design Basis Flood Level Current Flood Protection Reevaluated lE-4 AEP Flood Mechanism (Per FSAR) (MSL) Elevation (MSL) Level (MSL)

[2) 21.3 ft (Stillwater plus wave 17.5 ft at east side of MPS2; IVIPS2,exceptlntake crest) 22 ft Structure 25.1 ft 19.8 ft at west side of IVIPS2 Combined (Wave runup)

Effects for AEP of lE-4 22 ft 26.5 ft (standing wave inside Wave runup up to 37.2 ft at the IVIPS2 Intake Structure except 26.5 ft (at one Intake Structure) Intake structure -

service water pump motor)

IVIPS2,exceptlntake 18.2 ft Storm Surge 22 ft 17.5 ft Structure [3]

(Stillwater Elevation) for AEP of lE-4 Diesel Generator & Intake 18.2 ft 22 ft 16.9 ft Structure [3)

Notes:

1. This table is a supplement to Table 3.0-1 of the MPS FHRR (Zachry, 2015a). "ft" denotes "feet". Flood level is location dependent;
2. Flood Protection Elevation 22 ft. assumes that there is sufficient warning time to close all MPS2 flood gates;
3. Current Design Basis Flood Level considers stillwater level plus wave runup. Wave action in conjunction with wave runup is projected to cause higher levels in some locations and was independently calculated.

Zachry EE 18-EOS Attachment A, Page 9 of 1O Revision O

ZACHRY NUCLEAR ZACll *F.?' ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Table 7: Summary of the Comparison of Current Design Basis and Reevaluated (1 E-4 AEP) Flood Causing Mechanisms for MPS Unit 3 Flooding Flood Critical Structure (Per Current Design Basis Flood Current Flood Protection Reevaluated lE-4 AEP Flood Level Mechanism FSAR) Level (MSL) Elevation (MSL} (MSL}

23.8 ft (near MPS3 except at 22.2 ft (site grade at 24 ft MSL MPS3, except Intake front of Intake Structure) protects against wave run up Structure Combined [2] except at Intake) 24 ft (25.5 ft for SW Effects for AEP Pumps) of lE-4 41.2 ft (at seaward wall of Intake Structure) Wave runup up to 42.6 ft at the Intake Structure Intake structure

[2]

MPS3, except Intake 19.7 ft 17.7 ft Storm Surge Structure [2]

(Stillwater 24 ft (25.5 ft for SW Elevation) for Pumps)

AEP of lE-4 19.7 ft Intake Structure 17.1 ft

[2]

Notes:

1. This table is a supplement to Table 3.0-2 of the MPS FHRR (Zachry, 2015a). ft" denotes "feet". Flood level is location dependent;
2. Current Design Basis Flood Level considers stillwater level plus wave runup. Wave action in conjunction with wave runup is projected to cause higher levels in some locations and was independently calculated.

Zachry EE 18-EOS Attachment A, Page 1 O of 1 O Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Attachment B Figures Figure 1: Weighted Mep.n and Confidence Levels for All Tropical Hazard Curves - Final Selected Weighting Scheme ................................................................................................................................. 2 Figure 2: Combined Tropical and Extratropical Storm Surge for AEP 1E-4 with 50-year Sea Level Rise at MPS ..............................................*.................................................................................................... 4 Figure 3: Refined ADGlRC+SWAN Model Mesh with Bathymetry ................................... ,...................... 5 Figure 4: Ten ADClRC+SWAN Simulated Synthetic Hurricane Tracks for Combined Effects Calculation

.................................................................................................................., ........................................... 6 Figure 5: Stillwater Elevation, Significant Wave Height and Depth-averaged Velocity at Selected Locations- CE2 .................................................................................................................................... 7 Figure 6: Stillwater Elevation at Approximate Time of Peak Surge (Time = 51.25 hour2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />) - CE2 ............ 10 Figure 7: Significant Wave Height and Direction at Approximate Time of Peak Significant Wave Height (Time = 53.00 hour0 days <br />0 hours <br />0 weeks <br />0 months <br />) - CE2 .................................................................................................................. 11 Figure 8: Transects for Wave Runup at Unit 3 Turbine Building and Wave Overtopping at Unit 2 Turbine Building for CE2 ................................................................................................................................... 12 Note: Figures presented in Attachment Bare from Zachry Calculations 2018a and 2018b.

Zachry EE 18-E05 Attachment B, Page 1 of 12 Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Figure 1: Weighted Mean and Confidence Levels for All Tropical Hazard Curves - Final Selected Weighting Scheme Sto rm Surge Storm Rate Antecedent Intensity- Fdir VmaxorCPD Error /

lnterp. Fdir PDF Fspd PDF Rmax PDF Landfalling (storm/yr/km) Water Level Dep. PDF Uncertainty (ft, NAVD88) (H) (F) {W)

(R) (T) (D) (VP) (E)

(I)

Zachry EE 18-E05 Attachment B, Page 2 of 12 Revision 0

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Notes for Figure 1:

1. Branches are not replicated at "parallel" nodes for clarity. This tree structure yields a total of 96 end nodes, which correspond to 96 storm surge flood hazard curves.
2. "*" denotes nodes that were based on WRT synthetic hurricane data.
3. "BE" stands for Best Estimate. "Upper" stands for upper bound; "Lower" stands for lower bound.
4. "0.5/0.5" denotes half probability for high and low tides each. "0.33/0.33/Q.33" denotes one third probability for high, mean and low tides each.
5. "t-Loc scale" stands fort-Location scale distribution; "Beta" stands for Beta Distribution.
6. "Nakagami" stands for Nakagami distribution.
7. "h-dep" and "h-indep" stand for heading dependent and independent intensity metric (Vmax or CPD), respectively.
8. "gev" stands for generalized extreme value distribution; "kernel" stands for non-parametric kernel function.
9. "Vmax-dep" and "CPD-dep" stand for Vmax- and CPD-dependent Rmax distribution functions, respectively.
10. "w_xi" denotes weighting factors, where "x" corresponds to the column ID on the header row (e.g., (T) for antecedent water levels or tidal conditions in this analysis). The values shown in this figure represent the final selected weighting scheme. Please note that weighting factors vary between different scenarios.
11. The tree structure yields a total of 96 end nodes, which correspond to 96 storm surge flood hazard curves.

Zachry EE 18-EOS Attachment B, Page 3 of 12 Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Figure 2: Combined Tropical and Extratropical Storm Surge for AEP 1E-4 with 50-year Sea Level Rise at MPS 23 22 21 E::I C

n, C

n, 20 a: 19 U'I

ii:

18

£ C

0

  • .;::. 17 n,

QI iij 16 QI n,

l*.;::. 15 U'I 14

- Combined Mean

84% confidence level 12

  • * * * * *95% confidence level 11 1.E-03 1.E-04 1.E-05 Annual Exceedance Probability Zachry EE 18-EOS Attachment B, Page 4 of 12 Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Figure 3: Refined ADCIRC+SWAN Model Mesh with Bathymetry Negative values in the bathymetry scale indicate positive topographic elevations.

Zachry EE 18-EOS Attachment B, Page 5 of 12 Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Figure 4: Ten ADCIRC+SWAN Simulated Synthetic Hurricane Tracks for Combined Effects Calculation

,,.,. r L "" .,.

  • Toror1t I 0 1'1 r., ps,

,TATES ndi.snap,ol

  • o c;oh .WTtb\.l J Kan eaa.Qty C1ACi nnat1 f

'" 1 , R l<t.Ml cin d ti oi l 1 CI 0

H,d t Dall CE-Au etinc J k "111*

an Anton lo 0

rr Miami HIIV n 0

CUDA Note : This figure presents the tracks summarized in Table 2.

Zachry EE 18-E05 Attachment B, Page 6 of 12 Revision 0

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Figure 5: Stillwater Elevation, Significant Wave Height and Depth-averaged Velocity at Selected Locations - CE2 (a) West Side of Unit 2 Intake Structure

...J Cl)

~

15

~ - - ~ -West - ~Side

- -of ~ Unit

-- 2~ Intake

-- Structure

~ - - ~ - - ~~ 20 -.

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15 :E C'l

~ 10 .Q) oj

> 10 ~

Q)

...J 5 ct!

s:

s:-

Q) ct! 0 .Q>

Cl) 0 10 20 30 40 50 60 70 Time (hour)

Time (hour)

Zachry EE 18-E05 Attachment B, Page 7 of 12 Revision 0

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 (b) South Side of Unit 3 Intake Structure (Figure 5 continued)

-~ 15

~

South Side of Unit 3 Intake Structure

.----------,--------r------..----,------,-----,----.--, 20 .-

~

15 .E

~ 10 O>

  • a:;

Q)

> 10 ~

Q) 5 >

co

....Q)

...J

_,----...~ __J 5 $:

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co 0 s:

0 10 20 30 40 50 60 70 Time (hour)

- 2.----------,---------r------..----,------,-----,----.--,

4?

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1.5 0

a5 1

.....C

§ 0.5 ~\\\1~

u o1___ J....__ _ _i___=====::[___ _ J __ __ J _ ~~ ~

0 10 20 30 40 50 60 70 Time (hour)

Zachry EE 18-EOS Attachment B, Page 8 of 12 Revision 0

ZACHRY NUCLEAR ENGINEERING EVALUATION 18- E05 SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 (c) West Side of Unit 2 Turbine Building (Figure 5 continued)

..-.. 20 West Side of Unit 2 Turbine Buildin

. - - - - - - - - ~ - - - - - - r - - - - - - - , - - - - - . - - - - - - - - - , , - - - ~ - - - - . - - - ----r-, 3 ..-.

~

~

~

~-

15

~

E 2 -~

a3 10 IQ)

~ 5 J1 ~

~ I s s O . _ __ ____.__ _ ___.__ _ __ . __ _ __.___ _--',Uc...__ __uu.u.u.u_ _ __.__. o ~

0 10 20 30 40 50 60 70 Time (hour)

(/J 1 .--------~------r----~---~-----,---~---~

-*g

¢?

~

i1 Q) 0.5

( \

OL_____.____

0 10

__1__ _ __ . _ __ _ _.J.....__ _--1-1_

20 30 40 50

~

__ _ : .-1.U.U..U.,,L . __

60

_J_J 70 Time (hour)

Note: Red cu rve fo r significant wave height. Top blue curve for stillwater elevation. Bottom blue curve fo r current velocity. Additional time series plots available in Calculation 18-110 (Zachry, 2018b).

Zachry EE 18-E05 Attachment B, Page 9 of 12 Revision 0

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-E05 SUPPLEMENT TO DOM INION FHRR FOR MPS UNITS 2 AND 3 Figure 6: Stillwater Elevation at Approximate Time of Peak Surge (Time = 51.25 hour2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />) - CE2 Zachry EE 18-E05 Attachment B, Page 1O of 12 Revision O

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Figure 7: Significant Wave Height and Direction at Approximate Time of Peak Significant Wave Height (Time= 53.00 hour0 days <br />0 hours <br />0 weeks <br />0 months <br />)- CE2 II I t I I 1111111,,,

\\11111/111

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\ \ 1 1 1 1 1 / t l l l l, llttllllllll lltlltlttlfl t I I I I f I t I I t t I I f / / / / I I I I I I f I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I

/ I I/I/Ill Zachry EE 18-EOS Attachment B, Page 11 of 12 Revision 0

ZACHRY NUCLEAR ENGINEERING EVALUATION 18-EOS SUPPLEMENT TO DOMINION FHRR FOR MPS UNITS 2 AND 3 Figure 8: Transects for Wave Runup at Unit 3 Turbine Building and Wave Overtopping at Unit 2 Turbine Building for CE2 Zachry EE 18-EOS Attachment B, Page 12 of 12 Revision 0

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