ML15041A469

Enclosure 2 to NLS2015006: SL-012450, Rev. 0, Cooper Nuclear Station Flood Hazard Reevaluation Report, Cover Through Page 2-31

ML15041A469
Person / Time
Site:	Cooper
Issue date:	01/26/2015
From:	Karas T M Sargent & Lundy
To:	Nebraska Public Power District (NPPD), Office of Nuclear Reactor Regulation
Shared Package
ML15041A523	List: ML15041A468 ML15041A469 ML15041A470 NLS2015006, Enclosure 2 to NLS2015006: SL-012450, Rev. 0, Cooper Nuclear Station Flood Hazard Reevaluation Report, Page 2-91 Through End
References
11784-017, NLS2015006 SL-012450, Rev 0
Download: ML15041A469 (80)

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NLS2015006 Enclosure 2 Enclosure 2 Cooper Nuclear Station Flood Hazard Reevaluation Report (Redacted Version)

N Nebraska Public Power District Always there when you need us Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-01 2450 Revision 0 Project No.: 11784-017 January 2015 Z] Safety-Related LI Non-Safety-Related 13 -3g-C v t; 6. LLI" CdVLL C 55 East Monroe Street -Chicago, IL 60603 USA ° 312-269-2000 www.sar-qentlundy.com Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 LEGAL NOTICE This report was prepared by Sargent & Lundy, L.L.C. ("S&L"), expressly for the sole use of Nebraska Public Power District ("Client")

in accordance with the agreement between S&L and Client. This Deliverable was prepared using the degree of skill and care ordinarily exercised by engineers practicing under similar circumstances.

Client acknowledges: (i) S&L prepared this Deliverable subject to the particular scope limitations, budgetary and time constraints, and business objectives of the Client; (2) information and data provided by others may not have been independently verified by S&L; and (3) the information and data contained in this Deliverable are time-sensitive and changes in the data, applicable codes, standards, and acceptable engineering practices may invalidate the findings of this Deliverable.

Any use or reliance upon this Deliverable by third parties shall be at their sole risk.Legal Notice ii Sargent: AE. Lunndty Nebraska Public Power District Coooer Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-01 2450 Revis~on 0 Droject No.: 117~84-01 7 SIGNATURES Preparer: Section I Reviewer: Section I Reviewer: Section I (Client comment resolution)

Preparer: Sections 2 and 3 (except Section 2.3)Reviewer: Sections 2 and 3 (except Section 23)Preparer: Section 2.3 Reviewer: Section 2.3 Preparer: Sections 4 and 5 Approver: T. M. Karts M. Kaiseruddin ,l. W. Dingier M. Salehi N. M. Patel eLj- ol N. M. Patel M. Salehi M. NIenaber(NPPD)

B. E. Jelke Date Date Date Date D at e Date Tate\12 e1201/ -Date Date Date Signatures iii

' '

Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 TABLE OF CONTENTS LEGA L NOTICE .......................................................................................................................................

II SIG NATURES .........................................................................................................................................

III TABLE O F CO NTENTS .........................................................................................................................

IV LIST TABLES .........................................................................................................................................

IX LIST O F FIG URES .................................................................................................................................

XI LIST O F ACRO NYM S AND ABBREVIATIO NS ...............................................................................

XV INTRO DUCTIO N I PURPOSE ..............................................................................................................

XlX 1. SITE INFORMATION RELATED TO THE FLOOD HAZARD .......................................................

1-1 1.1 Detailed Site Inform ation ......................................................................................................

1-1 1.1.1 Site Layout ........................................................................................................

.. 1-1 1.1.2 Spatial Data Sets ............................................................................................................

1-2 1.1.3 Elevation of Structures, System s, and Com ponents (SSCs) .........................................

1-2 1.1.4 Topography

....................................................................................................................

1-2 1.1.5 M issouri River and Tributaries

........................................................................................

1-2 1.2 Current Design Basis Flood Elevations

..............................................................................

1-4 1.2.1 Sum m ary of CNS External Flood Design and Licensing Basis ......................................

1-4 1.2.2 CLB Local Intense Precipitation (LIP) ............................................................................

1-6 1.2.3 CLB Flooding in Stream s and Rivers .............................................................................

1-7 1.2.4 CLB Dam Breaches and Failures ...................................................................................

1-7 1.2.5 C LB Storm Surge ...........................................................................................................

1-7 1.2.6 CLB Seiche .............................................................................................................

1-7 1.2.7 CLB Tsunam i ..................................................................................................................

1-7 1.2.8 CLB Ice-Induced Flooding ..............................................................................................

1-7 1.2.9 CLB Channel M igration or Diversion

..............................................................................

1-7 1.2.10 CLB Com bined Effects ...................................................................................................

1-8 Table of Contents iv Srngeritl

& i-rndv' j Nebraska Public Power District SL-01 2450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 1.2.11 CLB Associated Effects ..................................................................................................

1-8 1.3 Flood-Related Changes and Flood Protection Changes .................................................

1-10 1.4 Changes to the W atershed or to the Local Area ..............................................................

1-11 1.5 Current Design Basis Flood Protection and Mitigation Features ...................................

1-12 1.6 Additional Site Detail ...........................................................................................................

1-16 1.7 References

...........................................................................................................................

1-17 1.8 Tables ...................................................................................................................................

1-18 1.9 Figures ..................................................................................................................................

1-21 2. FLOOD HAZARD REEVALUATION

.............................................................................................

2-1 2.1 Local Intense Precipitation (LIP) ..........................................................................................

2-1 2.1.1 Probable Maxim um Precipitation Depths .......................................................................

2-1 2.1.2 Drainage Areas and Local Drainage Parameters

...........................................................

2-2 2.1.3 Peak Discharges

............................................................................................................

2-3 2.1.4 Hydraulic Model Setup ...................................................................................................

2-3 2.1.5 Effect of LIP ....................................................................................................................

2-6 2.1.6 References

.....................................................................................................................

2-6 2 .1 .7 T a b le s .............................................................................................................................

2 -8 2 .1 .8 F ig u re s .........................................................................................................................

2 -1 5 2.2 Flooding in Stream s and Rivers (PM F) ..............................................................................

2-32 2.2.1 Probable Maxim um Precipitation (PM P) ......................................................................

2-33 2.2.2 PM P Runoff Hydrographs

............................................................................................

2-35 2.2.3 W ater Level Determ inations .........................................................................................

2-37 2.2.4 Com bined Effects .........................................................................................................

2-44 2.2.5 Associated Flooding Impacts .......................................................................................

2-46 2.2.6 References

...................................................................................................................

2-48 2 .2 .7 T a b le s ...........................................................................................................................

2 -5 1 2 .2 .8 F ig u re s .........................................................................................................................

2 -6 2 Table of Contents V Luundv Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 2.3 Dam Breaches and Failures .........................................................................................

2-91 2.3.1 Flood Protection Level at the CNS Site ........................................................................

2-93 2.3.2 Hydrologic Evaluation

...................................................................................................

2-93 2.3.3 Hydraulic Evaluation

.....................................................................................................

2-97 2.3.4 Com bined Effects .......................................................................................................

2-100 2.3.5 Associated Flooding Impacts .....................................................................................

2-101 2.3.6 References

.................................................................................................................

2-105 2 .3 .7 T a b le s .........................................................................................................................

2 -1 0 8 2 .3 .8 F ig u re s .......................................................................................................................

2 -1 2 7 2.4 Storm Surge .......................................................................................................................

2-154 2.4.1 References

.................................................................................................................

2-154 2.5 Seiche .................................................................................................................................

2-155 2.5.1 References

.................................................................................................................

2-155 2.6 Tsunam i .............................................................................................................................

2-156 2.6.1 References

.................................................................................................................

2-156 2.7 Ice-Induced Flooding ........................................................................................................

2-157 2.7.1 Methodology

...............................................................................................................

2-157 2.7.2 Most Severe Historical Ice Jam Event ........................................................................

2-157 2.7.3 Upstream Breach of an Ice Dam ................................................................................

2-158 2.7.4 Downstream Ice Jam and Resulting Backwater

.........................................................

2-158 2.7.5 Effect of Ice-Induced Flooding ....................................................................................

2-158 2.7.6 References

.................................................................................................................

2-159 2 .7 .7 F ig u re .........................................................................................................................

2 -1 6 0 2.8 Channel M igration or Diversion

.......................................................................................

2-162 2.8.1 Historical Channel M igration or Diversion

..................................................................

2-162 2.8.2 Regional Topographic Evidence ................................................................................

2-163 2.8.3 Ice Causes .................................................................................................................

2-165 2.8.4 Flooding of Site Due to Channel M igration or Diversion

............................................

2-165 2.8.5 Human-Induced Changes of Channel Diversion

........................................................

2-166 Table of Contents vi f.- r-ger'tt C-;. L~undy -"

Nebraska Public Power District SL-01 2450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 2.8.6 Conclusions

................................................................................................................

2-166 2.8.7 References

.................................................................................................................

2-167 2 .8 .8 F ig u re s .......................................................................................................................

2 -1 7 0 2.9 Com bined Effects ..............................................................................................................

2-185 2.9.1 References

.................................................................................................................

2-185 3. COMPARISON OF CURRENT AND REEVALUATED FLOOD-CAUSING MECHANISMS

..... 3-1 3.1 Local Intense Precipitation

...................................................................................................

3-1 3.2 Flooding in Stream s and Rivers ...........................................................................................

3-1 3.3 Dam Breaches and Failures .................................................................................................

3-2 3.4 Storm Surge ...........................................................................................................................

3-3 3.5 Seiche .....................................................................................................................................

3-3 3.6 Tsunam i ..................................................................................................................................

3-3 3.7 Ice-Induced Flooding ............................................................................................................

3-3 3.8 Channel M igration or Diversion

...........................................................................................

3-4 3.9 Com bined Effects ..................................................................................................................

3-4 3.10 Associated Effects ................................................................................................................

3-4 3.10.1 Hydrostatic and Hydrodynamic Loads ............................................................................

3-4 3.10.2 Debris Loads ..................................................................................................................

3-5 3.10.3 Erosion and Sedimentation

............................................................................................

3-5 3.11 Other Pertinent Factors ........................................................................................................

3-5 3.11.1 Flood Duration ................................................................................................................

3-5 3.11.2 Overtopping

....................................................................................................................

3-5 3 .1 1 .3 In u n d a tio n .......................................................................................................................

3 -6 3.12 Conclusions

...........................................................................................................................

3-6 3.13 References

.............................................................................................................................

3-6 3.14 Tables .....................................................................................................................................

3-7 Table of Contents vii v iS rvg~ it e : .L-undvy Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 4. INTERIM EVALUATION AND ACTIONS TAKEN OR PLANNED ................................................

4-1 4.1 Regulatory Background

........................................................................................................

4-1 4.2 Evaluation of the Impact of the Reevaluated Flood Levels on Structures, Systems, and Components (SSCs) .............................................................................................................

4-1 4.3 Interim Evaluation and Actions Taken or Planned for CNS ..............................................

4-2 4 .3 .1 D a m F a ilu re ....................................................................................................................

4 -2 4.3.2 Channel Migration or Diversion

......................................................................................

4-3 4.4 Reference

...............................................................................................................................

4-3 5. ADDITIONAL ACTIONS ................................................................................................................

5-1 Table of Contents viii Zargent: G. Lundly -

Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 LIST TABLES T a ble 1.8-1 : M isso uri R ive r D a m s ........................................................................................................................

1-19 Table 1.8-2: D esign Evaluation S um m ary ...........................................................................................................

1-19 Table 1.8-3: M issouri R iver D rainage A rea ..........................................................................................................

1-20 Table 2.1-1: PMP Values and Intensities at the CNS Site .....................................................................................

2-9 T a b le 2 .1-2 : P e a k D isc h a rg e ..................................................................................................................................

2 -9 Table 2.1-3: Drainage Area and Peak Flow at each Cross Section -Zone A .....................................................

2-10 Table 2.1-4. Drainage Area and Peak Flow at each Cross Section -Zone B .....................................................

2-11 Table 2.1-5: Drainage Area and Peak Flow at each Cross Section -Zone C .....................................................

2-12 Table 2.1-6: Drainage Area and Peak Flow at each Cross Section -Zone D .....................................................

2-13 T a ble 2 .1-7 : P M P W ate r Levels ............................................................................................................................

2-14 Table 2.2-1: Point 3 (shown in Figure 2.2-4) Adjusted Precipitation Depths Based on HMR 52 .........................

2-52 Table 2.2-2: Model Input Parameter Definitions and References

........................................................................

2-53 Table 2.2-3: Summary of Unsteady Computational Parameters

..........................................................................

2-55 Table 2.2-4: Location of Inflow Hydrographs

........................................................................................................

2-55 Table 2.2-5: Comparison of Manning's Roughness Coefficients used in the Model to Standard Values ............

2-56 Table 2.2-6: NSE Coefficient Summary and Peak Discharge Comparison for 2011 Validation Simulation

........ 2-56 Table 2.2-7: Inflow Hydrograph Location Summary for PMF Simulations

...........................................................

2-57 Table 2.2-8: PMF Simulations Peak Magnitude and Time at RM 556.16 ............................................................

2-59 T able 2.2-9: M onitoring Point S um m ary ...............................................................................................................

2-59 Table 2.2-10: Calculation of Wind-Driven Waves and Wind Setup Approaching CNS ........................................

2-60 Table 2.2-11: Submerged Embankment Results .................................................................................................

2-60 Table 2.2-12: Wave Runup Approaching CNS Main Building Complex ...............................................................

2-61 T able 2.2-13: Forces on Intake S tructure .............................................................................................................

2-6 1 List of Tables ix Sargent & Lun*rdy'-

Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 T able 2 .2-14 : D eb ris Im pact Load s ......................................................................................................................

2-6 1 Table 2.3-1: Salient Features of Missouri River Mainstem Dams ......................................................................

2-109 Table 2.3-2: Dam Break Parameters for Hypothetical Dams .............................................................................

2-110 Table 2.3-3: HEC-HMS Model Input Parameters and Definitions

.........................................

2-113 Table 2.3-4: Hypothetical Dam Outflow Summary from HEC-HMS Model ........................................................

2-115 Table 2.3-5: 500-Year Flow on Missouri River at Drainage Locations

...............................................................

2-118 Table 2.3-6: Peak Flow at HEC-RAS Inflow Locations

......................................................................................

2-119 Table 2.3-7: Non-System Dam Failure Peak Stage at CNS and Plant Flood Protection Level .........................

2-121 Table 2.3-8: Peak Stage/Flow at CNS for Combined System and Non-System Dam Failure ...........................

2-121 Table 2.3-9: Maximum Average Velocities at CNS -Combined System and Non-System Dam Failure ...........

2-122 Table 2.3-10: Refined Maximum Velocity at CNS -Fort Peck Hydrologic and Non-System Dam Failure ........ 2-122 Table 2.3-11: Calculation of Wind-Driven Waves and Wind Setup Approaching CNS ......................................

2-123 Table 2.3-12: Summary of Wind Setup, Wave Runup, and Total Water Levels at SSCs ..................................

2-123 Table 2.3-13: Summary of Water Depth above Roof at Important Plant Structures

..........................................

2-124 Table 2.3-14: Summary of Water Depth above Bridge Deck at Important Bridges ...........................................

2-124 Table 2.3-15: Resultant Forces and Elevations on Main Building Complex Structures

.....................................

2-125 Table 2.3-16: Resultant Forces and Elevations on Intake Structure

..................................................................

2-125 T able 2 .3-17 : D ebris Im pact Loads ....................................................................................................................

2-126 Table 3.14-1: Current Licensing Flood Elevations and Reevaluated Flood-Causing Mechanisms

.......................

3-8 Table 3.14-2: D ebris Im pact Loads Sum m ary .......................................................................................

................

3-9 List of Tables X 3argent & Luncdy" c Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 LIST OF FIGURES F ig u re 1 .9 -1 : S ite L o ca tio n ..................................................................................................................................

1-2 2 Figure 1.9-2: M issouri R iver T ributaries

.........................................................................................................

.1-23 Figure 1.9-3: O verhead View of C N S 1 ..........................................................................................................

1-24 Figure 1.9-4: Overhead View of CNS 2 ................................................................................................

.... 1-25 Figure 1.9-5: Missouri River Reservoir System ..........................................

..........

..........1-26 Figure 1.9-6: Missouri River Path in 1879 at the Site of CNS ..............................................................................

1-27 Figure 1.9-7: Aerial Photograph of the Plant Site in 1971 ....................................................................................

1-28 Figure 1.9 Aerial Photograph of CNS Showing Flooding .................................................................................

1-29 Figure 2 .1-1: Location of S ecurity Barriers ...........................................................................................................

2-16 Figure 2.1-2: D rainage A reas for LIP Evaluation

..................................................................................................

2-17 Figure 2.1-3: Offsite Drainage Area behind USACE Levee .................................................................................

2-18 Figure 2.1-4: Cross Sections for LIP Evaluation

-Zone A ....................................................................................

2-19 Figure 2.1-5: Cross Sections for LIP Evaluation

-Zone B ....................................................................................

2-20 Figure 2.1-6. Cross Sections for LIP Evaluation

-Zone C ...................................................................................

2-21 Figure 2.1-7: Cross Sections for LIP Evaluation

-Zone D ...................................................................................

2-22 Figure 2.1-8: HEC-RAS Cross Sections for Zone A .............................................................................................

2-23 Figure 2.1-9: HEC-RAS Cross Sections for Zone B (sheet 1 of 2) ......................................................................

2-24 Figure 2. 1-10: HEC-RAS Cross Sections for Zone C (sheet 1 of 6) ....................................................................

2-26 F ig u re 2 .2 -1 : L o ca tio n M a p ...................................................................................................................................

2 -6 3 Figure 2.2-2: PMP Position 1 -Sheet a (see subsequent Sheets b, c, and d for PMP Positions 2 to 4) .............

2-64 Figure 2.2-3: Geographic Distribution of Basins of Influence for Missouri River Drainage above CNS ..............

2-68 Figure 2.2-4: PMP Spatial Distribution over Platte River Basin (P3 Centroid; 41.35N, 96&20W) ...........

...........

2-69 Figure 2.2-5: Antecedent Final Model PMF Hydrographs for P1, P2, P3, and P4 ...............................................

2-70 List of Figures xi 13S lgerit C LUundc' Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 Figure 2.2-6: Subsequent Storm Final Model PMF Hydrographs for P1, P2, P3, and P4 ...................................

2-71 F igure 2 .2-7 : M issouri R iver Junctions

.................................................................................................................

2-72 Figure 2.2-8: Full Floodplain PMF Hydrographs for Gavins Point Release of 160,000 cfs ..................................

2-73 Figure 2.2-9: PMF Hydrographs for 2-D Model Upstream Boundary RM 556.16 ................................................

2-74 Figure 2.2-10: PMF Downstream Boundary Condition Rating Curve RM 510.03 ................................................

2-75 Figure 2.2-11: Study Area Overview for the 2-D Model .......................................................................................

2-76 Figure 2.2-12: Spatial Distribution of Land Use Classes to Determine Manning's Roughness Coefficients

....... 2-77 Figure 2.2-13: C om putational M esh O verview .....................................................................................................

2-78 Figure 2.2-14: C om putational M esh Near C N S ....................................................................................................

2-79 Figure 2.2-15: 2-D M odel Inflow H ydrographs

.....................................................................................................

2-80 Figure 2.2-16: Comparison of Discharge Hydrographs through the Study Reach ...............................................

2-81 Figure 2.2-17: Contours of Maximum Water Surface Elevation for PMF Event -Large Scale ...........................

2-82 Figure 2.2-18: Contours of Maximum Water Surface Elevation for PMF Event -Small Scale ............................

2-83 Figure 2.2-19: Contours of Maximum Depth for PMF Event -Overview ..............................................................

2-84 Figure 2.2-20: Contours of Maximum Depth for PMF Event -Small Scale .........................................................

2-85 Figure 2.2-21: Contours of Maximum Velocity for PMF Event -Small Scale ......................................................

2-86 Figure 2.2-22: Fetches from Embankment Points of Interest ...............................................................................

2-87 Figure 2 .2-23: Labeled P oints of Interest .............................................................................................................

2-88 Figure 2.2-24: Main Building Complex and Locations of Interior Runup Calculations

.........................................

2-89 Figure 2.2-25: Expected Maximum Extent of Wave Runup at Representative Locations

...................................

2-90 Figure 2.3-1: Non-System Dams Downstream of Gavins Point Dam ................................................................

2-128 Figure 2.3-2: Inconsequential Non-System Dams Downstream of Gavins Point Dam ......................................

2-129 Figure 2.3-3: HEC-HMS Plan for Missouri River below Gavins Point Dam to Omaha, NE ...............................

2-130 Figure 2.3-4: HEC-HMS Plan for Missouri River from Omaha, NE to CNS .......................................................

2-131 List of Figures Xii Sare --_ L-undV-Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 Figure 2.3-5: Dam Failure Hydrographs at Gavins Point Dam due to System Hydrologic Dam Failure ............

2-132 Figure 2.3-6: Dam Failure Hydrographs at Gavins Point Dam due to System Sunny-Day Dam Failure ...........

2-133 Figure 2.3-7: Selected Dam Failure Hydrographs at Gavins Point Dam due to System Dam Failure ...............

2-134 Figure 2.3-8: Estimated Peak Stage and Peak Flow at CNS for Non-System Dam Failure ..............................

2-135 Figure 2.3-9: Estimated Peak Stage at CNS due to System and Non-System Dam Failure .............................

2-136 Figure 2.3-10: Estimated Peak Discharge at CNS due to System and Non-System Dam Failure ....................

2-137 Figure 2.3-11: Velocity Distribution Segments at HEC-RAS Cross Section 532.65 (CNS Site) ........................

2-138 Figure 2.3-12: Max. Right Bank Velocity & Total Discharge

-Fort Peck Hydrologic Failure (RM 532.65) ........ 2-139 Figure 2.3-13: Max. Channel Velocity & Total Discharge

-Fort Peck Hydrologic Failure (RM 532.65) ............

2-140 Figure 2.3-14: Max. Left Bank Velocity & Total Discharge

-Fort Peck Hydrologic Failure (RM 532.65) ...........

2-141 Figure 2.3-15: W S E L w ith Fetch O verlay ...........................................................................................................

2-142 Figure 2.3-16: Fetch Directions for Waves Approaching Plant East and Plant West ........................................

2-143 Figure 2.3-17: Fetch Directions for Waves Approaching Plant North and Plant South ......................................

2-144 Figure 2.3-18: Plan View of Pressure Calculation Surfaces for Main Building Complex ...................................

2-145 Figure 2.3-19: Cross Sections and Channel Bank Locations at CNS RMs 532.65, 532.53, and 532.49 ..........

2-146 Figure 2.3-20: Max. Right Bank Velocity & Total Discharge

-Fort Peck Hydrologic Failure (RM 532.49) ........ 2-147 Figure 2.3-21: Water Surface Elevation

& Total Discharge

-Fort Peck Hydrologic Failure (RM 532.65) .........

2-148 Figure 2.3-22: Max. Right Bank Bed Shear & Total Discharge

-Fort Peck Hydrologic Failure (RM 532.49) .... 2-149 Figure 2.3-23. Inundation Map for Fort Peck Hydrologic Dam Failure Scenario (Large-Scale Map) ................

2-150 Figure 2.3-24: Inundation Map for Fort Peck Hydrologic Dam Failure Scenario (Medium-Scale Map) .............

2-151 Figure 2.3-25: Inundation Map for Fort Peck Hydrologic Dam Failure Scenario (Small-Scale Map) .................

2-152 Figure 2 .3-26 : B ridge Location M ap ...................................................................................................................

2-153 Figure 2.7-1: Hydrologic Unit Code (HUC) for Different Watersheds Upstream and Downstream of the Site.. 2-161 F ig u re 2 .8-1: 187 9 La nd C o ve r ...........................................................................................................................

2 -17 1 List of Figures xiii ýýySg tr r-.. Ltndy, Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 Figure 2.8-2: 1940 Aerial Photography

......................................................................................................

.2-172 Figure 2.8-3: 1965 Aerial Photography

......................................................................................................

.2-173 Figure 2.8-4: 1993 Aerial Photography

...............................................................................................................

2-174 Figure 2.8-5: 1999 Aerial Photography

.........................................................

.....................................................

2-175 Figure 2.8-6 2003 Aerial Photography

...............................................................................................................

2-176 Figure 2.8-7: 2005 Aerial Photography

...............................................................................................................

2-177 Figure 2.8-8: 2010 Aerial Photography

...............................................................................................................

2-178 Figure 2.8-9: Hydric Soils ...................................................................................................................................

2-179 Figure 2.8-10: Geom orphic Soil Description

......................................................................................................

2-180 Figure 2.8-11 : Soil Textures ..............................................................................................................................

2-181 Figure 2.8-12: 2011 Landsat Thematic Mapper Surface Reflectance On-demand

...........................................

2-182 Figure 2.8-13: 2012 Aerial Photography

.............................................................................................................

2-183 Figure 2.8-14: 2011 Flood Breach Locations

.....................................................................................................

2-184 List of Figures xiv Sagmret & LunldV-Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 LIST OF ACRONYMS AND ABBREVIATIONS Acronym or Abbreviation 1-, 2-, 3-D ac ac-ft ACES AEC AEP ANS ANSI ASCE BSNP BWR CFR CEDAS CEM cfs CLB CNS COL CRREL DEM ERP ESP ESPA ESRI FEMA FHR Explanation one-dimensional, two-dimensional, three-dimensional acre acre-feet Automated Coastal Engineering System U.S. Atomic Energy Commission annual exceedance probability American Nuclear Society American National Standards Institute American Society of Civil Engineers bank stabilization and navigation project boiling water reactor Code of Federal Regulations Coastal Engineering Design & Analysis System Coastal Engineering Manual cubic feet per second Current Licensing Basis Cooper Nuclear Station combined operating license Cold Regions Research and Engineering Laboratory digital elevation model Elevated Release Point early site permit early site permit application Environmental Systems Research Institute Federal Emergency Management Agency flood hazard reevaluation List of Acronyms and Abbreviations xv S.ar-gont:: lLundly ,-

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-01 2450 Revision 0 Project No.: 11784-017 Acronym or Abbreviation FIS ft fps FSAR GI GIS HEC-HMS HEC-RAS HHA Hmo HMR hr HTab HU HWM in in/hr IPEEE ISFSI ISG LiDAR LIP LOB m mi min mph MPF Explanation flood insurance study feet feet per second Final Safety Analysis Report Generic Issue geographical information system Hydrologic Engineering Center Hydrologic Modeling System Hydrologic Engineering Center River Analysis System Hierarchical Hazard Assessment spectral significant wave height Hydrometeorological Report hour Hydraulic Table hydrologic unit high-water mark inch inch per hour Individual Plant Examination for External Events Independent Spent Fuel Storage Installation Interim Staff Guidance Light Detection and Ranging Local Intense Precipitation Left Overbank meter mile minute mile per hour Multi-Purpose Facility List of Acronyms and Abbreviations xvi-Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-01 2450 Revision 0 Project No.: 11784-017 Acronym or Abbreviation MSL MWe MWt NAVD88 NCDC NCHRP NDNR NEmbE NGVD29 NID NLSWE NOAA NPPD NRC NRCS NSE NTTF NWS PA PBL PMF PMP PMT psf RCIC RHR RG RM Explanation mean sea level megawatt electric megawatt thermal North American Vertical Datum of 1988 National Climatic Data Center National Cooperative Highway Research Program Nebraska Department of Natural Resources north embankment east National Geodetic Vertical Datum of 1929 National Inventory of Dams Non-linear Shallow Water Equation National Oceanic and Atmospheric Administration Nebraska Public Power District U.S. Nuclear Regulatory Commission Natural Resources Conservation Service Nash-Sutcliffe efficiency coefficient Near-Term Task Force National Weather Service Protected Area planetary boundary layer Probable Maximum Flood Probable Maximum Precipitation Probable Maximum Tsunami pound per square foot Reactor Core Isolation Cooling Residual Heat Removal Regulatory Guide River Mile List of Acronyms and Abbreviations xvii Sar-gernt C- LundV' ,

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-01 2450 Revision 0 Project No.: 11784-017 Acronym or Abbreviation ROB SCS SER SGTS SSC Tp tpd UMRSFFS USACE USACE-OD USAR USBR USCG USDA USGS VBS WEmbN WEmbS WEmbW VVRF WSEL Explanation Right Overbank Soil Conservation Services Safety Evaluation Report Standby Gas Treatment System structure, system, and component peak wave period tons per day Upper Mississippi River System Flow Frequency Study U.S. Army Corps of Engineers USACE Omaha District Updated Safety Analysis Report United States Bureau of Reclamation United States Coast Guard United States Department of Agriculture United States Geological Survey vehicle barrier system west embankment north west embankment south west embankment west width reduction factor water surface elevation List of Acronyms and Abbreviations xviii S~ar-genb i&. Lundy V Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 INTRODUCTION I PURPOSE Following the accident at the Fukushima Dai-ichi nuclear power plant resulting from the March 11, 2011, Great T6hoku Earthquake and subsequent tsunami, the U.S. Nuclear Regulatory Commission (NRC) established the Near-Term Task Force (NTTF). The NTTF Charter tasked the NTTF with conducting a systematic and methodical review of NRC processes and regulations to determine if the agency should make additional improvements to its regulatory system. Ultimately, a comprehensive set of recommendations was developed.

In response to the NTTF recommendations and pursuant to Sections 161 .c, 103.b, and 182.a of the Atomic Energy Act of 1954, as amended, and Title 10 of the Code of Federal Regulations (10 CFR), Section 50.54(f), the NRC has requested information from all operating power plant licensees.

The purpose of the request is to gather information to: " Reevaluate seismic and flooding hazards at U.S. operating reactor sites.* Facilitate the NRC's determination if there is a need to update the design basis and structures, systems, and components (SSCs) important to safety to protect against the updated hazards at operating reactor sites.* Address Generic Issue (GI) 204 regarding flooding of nuclear power plant sites following upstream dam failures.The information request relating to flooding hazards requires licensees to reevaluate their sites applying present-day regulatory guidance and methodologies being used for early site permit (ESP) and combined operating license (COL) reviews, including current techniques, software, and methods used in present-day standard engineering practice to perform the flood hazard studies. The results are compared against the site's current licensing basis (CLB) for protection and mitigation from external flood events.This report describes the flooding reevaluation performed for Cooper Nuclear Station (CNS). This report satisfies the information requested by Enclosure 2 (Recommendation 2.1: Flooding) of U.S. NRC letter, 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-lchi Accident, dated March 12, 2012 (Reference 1.7-1).Introduction

/ Purpose xix Sargenwt & LuncdI-I Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 1. SITE INFORMATION RELATED TO THE FLOOD HAZARD 1.1 DETAILED SITE INFORMATION Cooper Nuclear Station (CNS) is located on the Nebraska portion of a 1,090-acre (ac) site (Reference 1.7-2, Section 1.1) in Nemaha County, Nebraska and Atchison County, Missouri.The plant, located approximately 55 miles (mi) south-southeast of Omaha, Nebraska and 100 mi north-northwest of Kansas City, Kansas, is on the west bank of the Missouri River at River Mile (RM) 532.5 located midway between the villages of Brownville and Nemaha, Nebraska.

ArcMap was used to show the location of the plant (see Figure 1.9-1). This portion of the Missouri River is referred to as the Lower Brownville Bend. The U.S. Army Corps of Engineers (USACE) has stabilized the channel near the plant using pile dikes and bank protection.

This control prevents meandering of the river within the alluvial flood plain (Reference 1.7-3, Section 4.1).The Missouri River flows past the site in a southeasterly direction under open-river conditions, there being no downstream dams to control the stage of the river. In the vicinity of CNS, levees with crest elevations of approximately 902 feet (ft) mean sea level (MSL) control the river section during flood stages. River flow is controlled by a series of flood control dams on the upper Missouri River, which are operated by the USACE for a number of authorized purposes, including flood control, navigation, irrigation, power, water supply, water quality control, recreation, and fish and wildlife.

The Platte River (see Figure 1.9-2) is a major source of flow and joins the Missouri River south of Omaha, Nebraska.Maximum water surface elevation (WSEL) at the CNS site, as reported by the USACE, was 899 ft MSL in 1952 prior to the installation of the upstream control dams. Peak flood flow in 1952 was 414,000 cubic feet per second (cfs), which would have been reduced to approximately 100,000 cfs if today's controls had been in place at that time.The site coordinates are approximately 400 21' north latitude and 950 38' west longitude (Reference 1.7-4, Chapter II, Section 2.1). See Figure 1.9-1, Figure 1.9-3, and Figure 1.9-4 for various views of the plant.1.1.1 Site Layout CNS consists of a single boiling water reactor (BWR) with a capacity of 836 megawatt electric (MWe) / 2,419 megawatt thermal (MWt) and first went into service on July 1, 1974 (Reference 1.7-4, Chapter I, Section 1.0).The principal structures of the station consist of the Reactor Building, Turbine Building (including service area appendages), Control Building, Radwaste Building, Augmented Radwaste Building, Intake Structure, Diesel Generator Building, Drywell and Suppression Chamber, Miscellaneous Circulating Water System Structures (e.g., circulating water conduits, seal well, etc.). (See Reference 1.7-4,Section XII.) Aside from the Intake Structure, the nearest building to the river channel edge is approximately 200 ft away (Reference 1.7-5, Section 2.1).Site Information Related to the Flood Hazard 11 Sýng~rM &. LunC1V Nebraska Public Power District SL-01 2450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 1.1.2 Spatial Data Sets Elevations in Section 1 are referenced to MSL for consistency with the CNS Updated Safety Analysis Report (USAR). In this context, MSL is equated to Plant Datum and is distinct from other geodetic vertical datums. Reference 1.7-3 notes that Plant Datum is the same datum used in the USAR.1.1.3 Elevation of Structures, Systems, and Components (SSCs)The station site grade level of 903 ft MSL has been raised 13 ft above the natural grade level of 890 ft MSL, in order to bring final grade 1 ft above the existing 902 ft MSL levee constructed by the USACE (Reference 1.7-4, Chapter II, Section 4.2.2.2).The levee is situated at a nominal elevation of 902 ft MSL. The finished floor elevation is given as 903.5 ft MSL for all Class I structures (Reactor Building, Turbine Building, Diesel Generator Building, Control Building, Radwaste Building, Intake Structure and Controlled Corridor).

The Z-Sump is at 890 ft MSL, and the Elevated Release Point (ERP) tower foundations are at 891 ft MSL (Reference 1.7-3, Section 4.0).1.1.4 Topography Prior to the construction of CNS, the site was nearly flat with only one or two feet of relief over the majority of the area. General grade elevation was approximately 890 ft MSL. A bluff, approximately 150 ft above the floodplain, running north-south, is located about one mile west of the river near the plant area. An earthen levee parallels the west (right) river bank at a distance of approximately 500 ft.Surface drainage of the site was poor because of the lack of natural relief. The levee also inhibits surface runoff from the area behind the levee to the river (Reference 1.7-6, Section 2.2).Federal Levee R548 is adjacent to the CNS main plant area. The top elevation of the levee near the site is approximately 902 ft MSL, 1 ft below the nominal plant grade of 903 ft MSL. The levee extends north of the plant, where it terminates at the higher ground near the bluffs. South of CNS, the levee follows the right bank of the Missouri River, curving around to the west and running parallel to the left bank of the Nemaha River, which is a tributary to the Missouri River, and turning north where it meets the higher ground near the town of Nemaha. The top elevation of the levee varies from approximately 902 ft MSL near CNS to approximately 897 ft MSL on the southern end, with top elevations of the levee as low as 894 ft MSL locally. The area enclosed by the levee and the higher bluffs to the west is 4000 ac (Reference 1.7-7, Section 5.1.8).1.1.5 Missouri River and Tributaries The Missouri River Basin drains 529,000 square miles (mi 2), including about 9,700 mi 2 located in Canada. The Basin spans 10 states, including all of Nebraska, most of Montana, Wyoming, North Dakota, and South Dakota; about half of Kansas and Missouri; and smaller parts of Iowa, Colorado, and Minnesota.

The Missouri River is fed from several major tributaries, including the Yellowstone, Platte, Kansas, Grand, and Osage Rivers. The Missouri River extends 2,619 mi from its uppermost source at Browers Spring on Hell Roaring Creek and 2,321 mi from Three Forks, Montana, where the Site Information Related to the Flood Hazard 1-2 Sargenat & Lunrdvc Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Jefferson, Madison, and Gallatin Rivers converge.

The Missouri River is the longest river in the United States, draining one-sixth of the country. The Missouri River Mainstem System (System) consists of six dams and reservoirs on the Missouri River located in Montana, North Dakota, South Dakota, and Nebraska.

The six System dams are Fort Peck Dam in Montana; Garrison Dam in North Dakota; Oahe Dam, Big Bend Dam, and Fort Randall Dam in South Dakota; and Gavins Point Dam in South Dakota and Nebraska.

The System has a capacity to store 73.1 million acre-feet (ac-ft) of water, which makes it the largest reservoir system in North America. Runoff from upstream of the System is stored in the six reservoirs.

Water is released from the System as needed for downstream flow support. Released water from the most downstream dam in the System, Gavins Point Dam, flows down the Missouri River, which includes the Bank Stabilization and Navigation Project (BSNP) from Sioux City, Iowa to the mouth near St. Louis, Missouri (Reference 1.7-8 and Figure 1.9-5).The location of six System dams is noted in Table 1.8-1. There are no dams or similar structures on the Missouri River downstream of the plant site. (See Figure 1.9-2 and Figure 1.9-5 and Reference 1.7-4, Chapter II, Section 4.2.2.1.)Site Information Related to the Flood Hazard 1-3 Sargent iM LundyI-Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 1.2 CURRENT DESIGN BASIS FLOOD ELEVATIONS This section summarizes key flood and plant information found in the CNS USAR.1.2.1 Summary of CNS External Flood Design and Licensing Basis The safety equipment needed to maintain a safe shutdown includes the Diesel Generators, which are near plant grade (903.5 ft MSL), Reactor Core Isolation Cooling (RCIC) and Residual Heat Removal (RHR) pumps located in the Reactor Building basement (859.7 ft MSL); RHR service water booster pumps located in the Control Building basement (882.5 ft MSL); various electrical equipment and switchgear needed to operate decay heat removal systems at elevations ranging from 903.5 to 905.0 ft MSL; and the service water pump motors located at 907.5 ft MSL in the Intake Structure (Reference 1.7-2, Section 2.4.3). The protection of building openings to 906.0 ft MSL, 2.5 ft above the finished floor elevation, is accomplished by deploying temporary flood control barriers.

These barriers are deployed at critical grade level openings around and within the Main Building Complex. Engineered flood barriers are used; however, sandbags are available for contingencies, as needed, to supplement the engineered barriers.

The material and equipment necessary to implement these protective measures are available at CNS and are inventoried on an annual basis. Special flood fighting equipment includes two portable gasoline-powered pumps and 100 ft minimum (per pump) of non-collapsible hose (Reference 1.7-4, Chapter II, Section 4.2.2.2).See Table 1.8-2 for a summary of the design evaluation.

1.2.1.1 Flood Levels (USAR)Information on riverine flooding in the CNS USAR is based on independent studies performed by the USACE and by the U.S. Atomic Energy Commission (AEC). Information from the USACE study is summarized in the USAR and its predecessor, the Final Safety Analysis Report (FSAR). The AEC study is summarized in the CNS Safety Evaluation Report (SER). These studies are discussed in subsequent sections of this report.The projected upper limit of elevation for a 1,000-year flood discharge is 900 ft MSL and for a 10,000-year flood discharge is 902 ft MSL. The Probable Maximum Flood (PMF) is established at 903 ft MSL with a projected return frequency estimated to be in excess of 1,000,000 years. The PMF is derived by centering a probable maximum rainstorm critically over the drainage area above Brownville.

The USACE has estimated that the peak discharge for the PMF is 600,000 cfs (Reference 1.7-4, Chapter II, Section 4.2.2.1).

This estimate is based on a qualitative judgment that the peak of a PMF event should be between two to three times the peak of a standard project flood. Preliminary estimates of standard project conditions on the Missouri and Platte Rivers were used in estimating the PMF peak of 600,000 cfs at CNS (Reference 1.7-4, Chapter II, Section 4.2.2.1).

Table 1.8-3 summarizes the approximate drainage area (mi 2) for locations of interest along the Missori River.The effects of a sustained wind in conjunction with a PMF were evaluated by USACE using the procedures described in the U.S. Army Coastal Engineering Research Technical Report 4. Assuming a Site Information Related to the Flood Hazard 1-4 Sargent & Lunldy-Nebraska Public Power District SL-01 2450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 45-mile per hour (mph) overwater wind speed and a 903 ft MSL PMF WSEL, the significant shallow-water wave height was computed to be 4.0 ft. The 1% wave height was computed to be 6.7 ft. The runup was computed to be 6.7 ft on a smooth vertical wall located in shallow water and 4.8 ft on a one-on-three riprapped slope. The fetches are of sufficient length that the above waves could be generated with winds from the north through east through south. It should be noted, however, that these wave height values are based on relationships derived from studies made on lakes and oceans, and it is believed that the same parameters would not produce waves as high as those computed above in highly turbulent, fast-flowing river flood waters (Reference 1.7-4, Chapter II, Section 4.2.2.1).The wave action, as mentioned above, will not affect the plant proper since the nearest building is located about 200 ft from the river edge and is surrounded by grade to elevation 903 ft MSL. Wave energy would be dissipated before reaching any of the main buildings.

Wave action at the Intake Structure will not affect the safe shutdown of the plant since the service water pumps and controls are protected by massive reinforced concrete walls and slab up to elevation 919 ft MSL (Reference 1.7-4, Chapter II, Section 4.2.2.2).Flooding caused by ice blockage is considered credible only at river levels significantly lower than the PMF. Flooding caused by ice blockage would cause water surface elevations below those of the PMF.(Reference 1.7-4, Chapter II, Section 4.2.2.1.)The failure of a large upstream dam is not considered probable.

These dams are massive earthen structures with impervious core walls, large freeboard for wave action, and adequate spillways.

The dams are located in a zone of low seismic activity.

The Gavins Point Dam, closest dam to the site, is over 275 mi upstream (Reference 1.7-4, Chapter II, Section 4.2.2.1).These dams are under constant inspection by local USACE personnel and are inspected once a year by a team of professionals.

If seismic failure occurred in spite of these circumstances, the failure would most probably be caused by other than instantaneous failure of a major portion of the dam. Under these circumstances, overtopping of Gavins Point Dam, although conceivable, is not likely to occur (Reference 1.7-4, Chapter II, Section 4.2.2.1).1.2.1.2 USACE Study The USACE estimated a PMF elevation between 902 ft MSL and 903 ft MSL at CNS. This is based on a Probable Maximum Precipitation (PMP) event occurring upstream of Brownville, Nebraska and a resulting flow rate in the Missouri River of 600,000 cfs. The rainfall event producing this flow rate is described in FSAR Question 2.1 as originating over the Platte River Basin (Reference 1.7-9).1.2.1.3 AEC Study Safety Evaluation Report The AEC performed an independent PMF study for CNS, which is summarized in the CNS SER. Based on detailed PMF estimates in the general region of the site, AEC staff conservatively estimated the peak PMF discharge to be about 1,000,000 cfs. This estimate was conservatively considered to reflect the total runoff potential represented by the large drainage area downstream of the USACE dams, plus the relatively minor component that could be contributed by releases from these dams. AEC staff Site Information Related to the Flood Hazard 1-5 Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 concluded that the dams should remain intact during a PMF. Additionally, AEC staff constructed an analytical water surface profile model of the Missouri River from below CNS to the Brownville Bridge a few miles upstream and estimated the PMF still WSEL at the site would be 901.2 ft MSL. The model was verified by reproducing historical flood high-water marks using estimates of floodplain geometry and flood runoff rates. Coincident wave action induced by an assumed 45-mph wind was estimated to produce a maximum WSEL of 909.2 ft MSL at the Intake Structure and 905 ft MSL on the other exposed safety-related structures.

AEC staff did not consider seismically induced dam failure coincident with PMF credible but considered the effects of a seismically induced failure of one of the largest upstream dams concurrent with flood levels of one half of the PMF and concluded that the water level that could result at CNS is less than the AEC staffs estimated PMF (Reference 1.7-2, Section 2.4.3).This information has been incorporated into the USAR. (See Section 1.2.1.1 of this report.)1.2.1.4 Conclusions The 906 ft MSL level for which the station committed to provide protection bounds both the AEC and USACE studies. Therefore, 906 ft MSL should be considered the Current Licensing Basis (CLB) still WSEL due to Missouri River flooding.

The wave impact design basis outside of the intake structure is 909.2 ft MSL (Reference 1.7-4, Chapter II, Section 4.2.2.2).The immediate station area grade is at elevation 903 ft MSL. This is 4 ft above the flood of record, 1 ft above the existing levee, and equal to the highest projected level of the maximum probable natural flood. Overtopping of the levee would occur before flooding of the station would occur (Reference 1.7-4, Chapter II, Section 4.6).Failure of an upstream dam is considered improbable.

However, in the unlikely event that such a failure does occur, it would be approximately three days before the water would reach the site, which is sufficient time to provide protection or to conduct a safe and orderly shutdown of the plant. High water resulting from failure of an upstream dam would overtop the levee before flooding the station.(Reference 1.7-4, Chapter II, Section 4.6).1.2.2 CLB Local Intense Precipitation (LIP)From Hydrometeorological Report No. 33 (HMR-33) dated April, 1956 by the U.S. Department of Commerce -Weather Bureau and the USACE (Reference 1.7-10), it was determined that the PMP for the CNS site area is 23.5 inches (in) total rainfall for a 24-hour period. This bounding PMP value was obtained from HMR-33 Figure 17 (August). (See Reference 1.7-4, Chapter II, Section 3.1.3). An independent evaluation by the AEC determined that the PMP 1-hour rainfall rate was 9.7 in per hour (Reference 1.7-2, Section 3.4).Class I and Class II buildings are protected from the effects of precipitation through the use of roof drains and overflow scuppers.

The Reactor Building, Diesel Generator Building, and Control Building use-4-in roof drains and 6-in scuppers.

The remaining local site drainage is designed such that any excess rainfall not immediately absorbed into the ground will flow away from the buildings to be discharged into drywells or low lying areas adjacent to the plant site. Therefore, this configuration can safely remove the accumulated water from the PMP rate described in the USAR, Chapter II, Site Information Related to the Flood Hazard 1"6 Sar-genrlt

& Lrundvc Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 Section 3.1.3, and can also accommodate the 9.7 in per hour (Reference 1.7-11 and Reference 1.7-4, Chapter II, Section 3.2.3) rate estimated by the AEC without adverse effects on the safety-related systems necessary for safe shutdown (Reference 1.7-4, Chapter II, Section 3.2.3).1.2.3 CLB Flooding in Streams and Rivers Refer to Section 1.2.1.1.2.4 CLB Dam Breaches and Failures The USAR (Reference 1.7-4, Chapter II, Section 4.2.2.1) notes that a dam failure was not considered a credible event. The maximum expected still water level at the site associated with a postulated dam failure was 906 ft MSL, with a minimum warning time of three days (Reference 1.7-4, Chapter II, Section 4.2.2.2).

No associated effects (wind-wave, debris, etc.) were considered in the dam failure scenario.1.2.5 CLB Storm Surge The CLB is silent on flooding effects from storm surge. However, due to its location, the storm surge flooding mechanism can be screened out for CNS.1.2.6 CLB Seiche The CLB is silent on flooding effects from seiche. However, due to its location, the seiche flooding mechanism can be screened out for CNS.1.2.7 CLB Tsunami The CLB is silent on flooding effects from tsunami. However, due to its location, the tsunami flooding mechanism can be screened out for CNS.1.2.8 CLB Ice-Induced Flooding Flooding caused by ice blockage is considered credible only at river levels significantly lower than the PMF. Flooding caused by ice blockage would produce WSELs below those of the PMF (Reference 1.7-4, Chapter II, Section 4.2.2.1).

Thus, the CLB does not include quantitative parameters for ice-induced flooding, but the ice-induced flooding effects are bounded by the PMF.1.2.9 CLB Channel Migration or Diversion The CLB discusses this mechanism only with respect to channel migration away from the site due to levee failure on the opposite river bank and the potential loss of the heat sink. Channel migration toward the site was not considered credible.Changes in river alignment have occurred in the past as a result of meteorological events. The river channel at present is stabilized as a result of permanent revetments constructed under the supervision Site Information Related to the Flood Hazard 1-7 Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 of the USACE over a number of years; thereby, making it extremely unlikely that the river would be diverted at Brownville Bend. If, however, in spite of these controls, the river should be diverted, it would most likely occur as a result of the failure of a major upstream dam -either Oahe Dam or Fort Randall Dam, although dam failure is not considered credible in the CLB. The closer of the two dams, Fort Randall Dam, is almost 350 mi upstream from the plant site and there would be a three-day warning before the river reached a peak flood stage at CNS. While the river is at peak flood stage at the site, the postulated diversion of the Missouri River might occur upstream.

During peak flood stage, reactor shutdown procedures could begin and continue as the flood water slowly receded. With the river diverted and the flood waters fully receded, what might remain in front of the Intake Structure would be a large body of still water cut off from the upstream flow and possibly cut off at a point downstream.

After the river diversion occurs, the resulting isolated body of water in the vicinity of the site, fed by groundwater inflow, would retain essentially the same stage characteristics that apply to the current open river as long as the main channel were retained in the existing valley. It was concluded that there would be an adequate supply of water to affect a safe shutdown of the plant (Reference 1.7-4, Chapter II, Sections 4.2.3.1 and 4.2.3.2).

The AEC concurred with these findings in the CNS SER, which states that it was considered unlikely that major channel diversions would occur (Reference 1.7-2, Section 2.4.5).1.2.10 CLB Combined Effects Combined effects of different flood-causing mechanisms are discussed in Section 1.2.1 through 1.2.8, where applicable.

1.2.11 CLB Associated Effects Section 9 of Reference 1.7-12 defines "Flood height and associated effects" as: The maximum still WSEL plus the following factors:* Wind waves and runup effects." Hydrodynamic loading, including debris." Effects caused by sediment deposition and erosion.* Concurrent site conditions, including adverse weather conditions.

• Groundwater ingress.* Other pertinent factors 1.2.11.1 Wind Waves and Runup Effects The CLB values for wind waves and runup is 909.2 ft MSL at the Intake Structure and 905 ft MSL for other exposed safety-related structures (Reference 1.7-4, Chapter II, Section 4.2.2.2).Site Information Related to the Flood Hazard 1-8 Sargent: r LEundVy Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 1.2.11.2 Hydrostatic and Hydrodynamic Loads The principal structures are designed to withstand hydrostatic loads up to the flood protection level of 906 ft MSL with margin (Reference 1.7-4, Chapter II, Section 4.2.2.2).The CLB is silent on hydrodynamic loads.1.2.11.3 Debris Loads The CLB is silent on flooding debris loads (Reference 1.7-4); however, the CLB does discuss a runaway barge (Reference 1.7-4, Chapter II, Section 4.3).In summary, the Intake Structure and Class I equipment located inside are qualified to withstand a barge impact. Additionally, a barge that impacts the Intake Structure guide wall will, therefore, have little if any effect on plant operations.

1.2.11.4 Erosion and Sedimentation Effects of erosion and sedimentation during extreme flooding events are not analyzed in the CLB.1.2.11.5 Concurrent Site Conditions The CNS CLB (Reference 1.7-4) does not specifically discuss evaluation of concurrent site conditions.

1.2.11.6 Groundwater Ingress The CNS CLB does not specifically address or quantify groundwater in-leakage from the site subsurface water table. Groundwater level is monitored/logged once per shift based on level indicators located within site well(s) providing plant water supply. According to CNS personnel, site groundwater level normally fluctuates between 875 ft MSL to 885 ft MSL with the highest recorded level of 900.8 ft MSL during the May 2011 Missouri River flood event (Reference 1.7-5, Section 3.7).1.2.11.7 Other Pertinent Factors The Maintenance Procedure directs the CNS maintenance personnel in the installation of temporary flood control barriers and features.

The procedure provides a system of primary barriers at the openings of the outside walls of the Main Building Complex to seal the buildings up to elevation 906 ft MSL. Secondary barriers are provided strategically inside the buildings to control any minor leakage past the primary barriers and to segregate the building complex into small areas that can be more easily protected (Reference 1.7-5, Section 3.5.)Site Information Related to the Flood Hazard 1-9 S' Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 1.3 FLOOD-RELATED CHANGES AND FLOOD PROTECTION CHANGES The plant design features and their functional requirements that provide protection against the design basis external flood mechanisms are provided in the USAR (Reference 1.7-4). The credited flood protection related attributes of the overall plant configuration that support the design for mitigation against external flooding have not changed from the time of initial licensing.

Enhancements to procedural guidance supporting the implementation of protective actions against external flooding have been made over time. The temporary barriers deployed in Procedure 7.0.11 (Reference 1.7-13) now consist of engineered flood barriers.

The use of these barriers, instead of the original sandbag barriers, has resulted in a significant reduction of the barrier deployment time and effort.Changes to the hydrosphere around the CNS site and physical changes to the CNS site (e.g., security changes, buildings, etc.) are discussed in Section 1.4 of this report.Site Information Related to the Flood Hazard 1-10 Ear-gert', or -ud I ,

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 1.4 CHANGES TO THE WATERSHED OR TO THE LOCAL AREA As shown in Figure 1.9-6, the river was much wider and further to the east than it is today as illustrated in Figure 1.9-7 and Figure 1.9-8 Reference 1.7-14).The CNS site is located in the floodplain of the Missouri River at approximate Missouri River Mile 532.5.As a result of the location, the site is subjected to hydrometeorological events relevant to inland sites.The Missouri River Basin upstream of CNS and downstream of Gavins Point Dam combined with Platte River Basin, as discussed in Section 2.2 of this report, encompasses approximately 132,657 mi 2.Changes in watershed properties particularly affect the estimation of the PMF and upstream dam failure flooding.

It is expected that watershed characteristics do change through the years, with the expansion of urban areas and change in land use and land cover. However, all of the changes that may have occurred in the past were captured in the current flooding hazard reevaluation.

The reevaluation took into account the existing watershed conditions, which were incorporated through the hydrologic and hydraulic model calibration efforts. It should be noted that since the construction and operation of CNS, there has been no major upstream dam or impoundment on the Missouri River or tributaries constructed or proposed.Any changes in local area that may have occurred in the past, including the vehicle barrier installed for a security measure, were incorporated in the LIP analysis of the current flooding hazard reevaluation.(See Section 2.1 of this report.)Site Information Related to the Flood Hazard 1-11 Saýrgenvt

e. Lundly -c Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 1.5 CURRENT DESIGN BASIS FLOOD PROTECTION AND MITIGATION FEATURES The general ground elevation surrounding CNS Class I structures, which corresponds to the PMF event elevation, is elevated 13 ft above the natural floodplain to 903 ft MSL (Reference 1.7-4, Chapter II, Section 4.2.2.2).

The finished floor elevation of all Class I structures is placed at elevation 903.5 ft MSL, or 0.5 ft above the PMF event. These structures were designed for a hydraulic load equivalent to a groundwater elevation of 903 ft MSL and reviewed for integrity for a river elevation up to 906 ft MSL.Grade level openings on exterior walls of the buildings (except for the Intake Structure) are protected from wave effects and WSELs up to 906 ft MSL with flood barriers erected per CNS Procedures 7.0.11 (Reference 1.7-13) and 5.1, Flood (Reference 1.7-15), as previously discussed in Section 1.2.11.7 of this report.The CNS Flood Protection Feature Inspections, in accordance with the request from the U.S. Nuclear Regulatory Commission (NRC) as defined in the Recommendation 2.3, Flooding, Enclosure 4 of the 50.54(f) letter dated March 12, 2012 (Reference 1.7-5) found that the CNS flood protection active and passive features, e.g., walls, floors, roofs, penetration seals, doors, check valves, etc., were confirmed to be installed per design, functional, in good material condition, and appropriately controlled procedurally to ensure continued functionality.

The following CNS safety-related plant structures and procedures have been identified as protected from flooding as noted: Intake Structure The maximum water level on the outside of the Intake Structure of 909.2 ft MSL (PMF plus wave effects) will not affect safe operation of the Service Water pump motors. The Intake Structure is built with a floor elevation of 903.5 ft MSL. The Service Water pump motors are positioned approximately 4.5 ft above the floor and are protected by 24-inch-thick concrete walls to an elevation of 919 ft MSL. Therefore, direct wave action will be dissipated and the water level in the room would be below the elevation of the Service Water pump motors (Reference 1.7-4, Chapter II, Section 4.2.2.2).Reactor Building The Reactor Building is protected from wave effects and flood water by grade level building walls and by temporary flood barriers to elevation 906 ft MSL.Emergency Diesel Generator Building The Emergency Diesel Generator Building is protected from wave effects and flood water by grade level building walls and by temporary flood barriers to elevation 906 ft MSL.Radwaste Building The Radwaste Building is protected from wave effects and flood water by grade level building walls and by temporary flood barriers to elevation 906 ft MSL.Site Information Related to the Flood Hazard 1-12 Sarger, & Lundv.

Nebraska Public Power District SL-01 2450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 Control Building The Control Building is protected from wave effects and flood water by grade level building walls and by temporary flood barriers to elevation 906 ft MSL.Controlled Corridor The Controlled Corridor is protected from flood water by grade level Reactor and Turbine Building walls to elevation 906 ft MSL.Turbine Building The Turbine Building is protected from wave effects and flood water by grade level building walls and by temporary flood barriers to elevation 906 ft MSL.Z-Sump (Below ERP Tower)As noted in the USAR (Reference 1.7-4, Chapter II, Section 4.2.2.2), the top of floor drain Z-Sump, at the base of the ERP tower, is located at elevation 891 ft MSL and, therefore, is within postulated flood levels. The Z-Sump contains equipment essential to the operation of the Standby Gas Treatment System (SGTS) and, therefore, the sump must remain functional whenever Secondary Containment is required.

Although the ground elevation at the sump is only 890 ft MSL, the Z-Sump will not be affected by flooding since the sump penetrations are sealed and the proper functioning of the sump is monitored when flood levels reach 890 ft MSL.Diesel Fuel Storaqe Tanks As noted in the USAR (Reference 1.7-4, Chapter II, Section 4.2.2.2);

there is sufficient fuel in the Diesel Oil Storage Tanks to ensure seven days of operation of a single diesel generator powering a single critical division of safe shutdown loads. This time duration is sufficient to obtain more fuel, if needed. The two storage tanks are buried and their appendages are protected by a substantial cover. The manholes providing access to the Diesel Oil Transfer Pumps, the capped fill connections, and the tank vents are all located above 906 ft MSL. The design and installation of the tanks ensure flotation does not occur when empty during the PMF.The following CNS plant structures have been identified as important to the protection of the various safety-related structures and equipment and are also protected from flooding as noted: Augmented Radwaste Building The Augmented Radwaste Building is protected from wave effects and flood water by grade level building walls and by temporary flood barriers to elevation 906 ft MSL.Boiler Room The Boiler Room is protected from wave effects and flood water by grade level building foundation walls and by temporary flood barriers to elevation 906 ft MSL.Site Information Related to the Flood Hazard 1-13 f..Saegert a LundV' Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 Fan Room The Fan Room is protected from wave effects and flood water by grade level building foundation walls and by temporary flood barriers to elevation 906 ft MSL.Water Treatment Plant The Water Treatment Plant is protected from wave effects and flood water by grade level building foundation walls and by temporary flood barriers to elevation 906 ft MSL.Tool Crib The Tool Crib is protected from wave effects and flood water by grade level building foundation walls and by temporary flood barriers to elevation 906 ft MSL.Machine Shop The machine shop is protected from wave effects and flood water by grade level building foundation walls and by temporary flood barriers to the elevation of 906 ft MSL.Multi-Purpose Facility (MPF) Building The MPF Building is protected from wave effects and flood water by grade level building foundation walls and by temporary flood barriers to the elevation of 906 ft MSL.Other Site Structures Various site out-buildings and structures classified as not important to safe operation and shutdown of the plant are located at base elevations lower than the PMF elevation of 903 ft MSL. Per CNS Procedure 5.1, Flood (Reference 1.7-15), evaluation of the protection of these assets is determined by NPPD plant management by implementing actions based on various parameters, including plant safety, asset value, importance to overall long-term power generation, etc.Procedures Upon reaching an actual river level of 895 ft MSL or receiving a river level forecast of 902 ft MSL within the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />, the site flooding procedure is implemented.

Apart from implementing temporary protection up to 906 ft MSL as previously discussed, the procedure directs the discharge of liquid radwaste as required to provide room for handling flood leakage. The floor and equipment drains and portable gasoline pumps are used to control leakage past the primary and secondary barriers.Site Information Related to the Flood Hazard 1-14 Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 A plant shutdown is initiated under any of the following conditions:

• Floodwaters either reach 902 ft MSL, or are forecast to reach 902 ft MSL within the next 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> (as from the 10,000 year flood or an upstream dam failure).* Floodwater accumulates in either Diesel Generator Room, any of the four Reactor Building Quads, or the Control Building basement." Plant conditions warrant reactor to be shut down.(Reference 1.7-4, Chapter II, Section 4.2.2.2)Site Information Related to the Flood Hazard 1-15 Sargent; C. Lundly ,

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 1.6 ADDITIONAL SITE DETAIL All available site details have been noted.Site Information Related to the Flood Hazard 1-16 Sargertm V LzruncId Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017

1.7 REFERENCES

1.7-1. U.S. Nuclear Regulatory Commission, 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, 2012.1.7-2. Safety Evaluation of the Cooper Nuclear Station. Docket 50-298. 02-14-73.1.7-3. NPPD Engineering Evaluation Number 12-035, Revision 0, "Review of 2012 Topographic Survey of CNS," March 2013.1.7-4. Cooper Nuclear Station USAR, Revision xxvi7.1.7-5. Nebraska Public Power District, Flooding Walkdown Submittal Report for Resolution of Fukushima Near-Term Task Force 10 CFR 50-54 (f) Section 2.3 Flooding Response.1.7-6. Nebraska Public Power District, Columbus, Nebraska, Engineering Criteria Document for Cooper Nuclear Station. June, 3, 1970.1.7-7. Calculation 2012-12283, Revision 0, Evaluation of Local Probable Maximum Precipitation (PMP).1.7-8. United States Coast Guard, Mississippi River and Tributaries Waterways Action Plan Missouri River Annex 2011.1.7-9. Cooper Nuclear Station, FSAR Question Number 2.1, Amendment Number 9.1.7-10. Hydrometeorological Report No. 33, Dated April 1956.1.7-11. Cooper Nuclear Station, FSAR Question Number 2.3.6, Amendment 17.1.7-12. U.S. Nuclear Regulatory Commission, "Interim Staff Guidance for Performing the Integrated Assessment for External Flooding," JLD-ISG-2012-05, November 30, 2012.1.7-13. CNS Operations Manual, Maintenance Procedure 7.0.11, Flood Control Barriers, Revision 29, Dated 02-19-14.1.7-14. Calculation 2014-00225, Revision 0, Task 810- Missouri River Channel Geomorphic Evaluation at CNS.1.7-15. CNS Emergency Procedure 5.1 Flood, Revision 13.1.7-16. Hydrodynamic Computer Modeling to Predict Missouri River Probable Maximum Flood Elevations and Flow Velocities at Cooper Nuclear Station, NEDC 11-076, Revision 1, Dated August 08, 2011.1.7-17.ArcMap Version 9.3.1 (Build 3000). ESRI, Redlands, CA.Site Information Related to the Flood Hazard 1-17 Sargernt & L-uncdyt, Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 1.8 TABLES The tables associated with Section 1 are presented on the following pages.Site Information Related to the Flood Hazard 1-18 Sargert & Lundyv I-Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Table 1.8-1: Missouri River Dams Name Location Near River Mile Gavins Point Yankton, South Dakota 811 Fort Randall Lake Andes, South Dakota 880 Big Bend Chamberlain, South Dakota 987 Oahe Pierre, South Dakota 1072 Garrison Bismarck, North Dakota 1389 Fort Peck Glasgow, Montana 1771 Note: 1. Plant location:

River Mile 532.5 Table 1.8-2: Design Evaluation Summary CNSComn Condition Evaluation Comment PMF Peak Flow Rate 1 600,000 cfs PMP Event centered above Brownville, NE.PMF Still Water Surface Elevation Plant site elevated +/-903 ft MSL. First floor of all Class I 903 ft MSL (21 buildings at 903.5 ft MSL.Flood barriers not needed at intake since critical PMF + Wave Runup at Intake Structure equipment is elevated above 906 ft MSL and protected 909.2 ft MSL from wave impacts.Class I buildings' grade level openings at 903.5 ft MSL PMF + Wave Action Main Plant Complex No impact protected by flood barriers from standing water up to 906 ft MSL.Notes: 1.The USACE estimated a higher river stage during the PMF than the AEC, despite the fact it used a lower flow rate (600,000 cfs versus 1,000,000 cfs). Details of the methodology utilized by the AEC to develop its stage flow relationship were not described, except for a statement in the SER text that the AEC constructed an "Analytical Model". The analysis conducted by CNS in 2011 is consistent with the USACE stage discharge estimates (Reference 1.7-16).This elevation is based on a steady flow rate of 600,000 cfs. See Reference 1.7-4, Chapter II, Section 4.2.2.1.See Reference 1.7-5, Section 2.7.2.3.Site Information Related to the Flood Hazard 1-19 Sar~gent. LundJV I ý Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Table 1.8-3: Missouri River Drainage Area Location Drainage Area (Missouri River) (Approximate (Square Miles)Above Fort Peck Dam 57,500 Above Garrison Dam 181,400 Above Oahe Dam 243,490 Above Fort Randall Dam 263,480 Above Gavins Point Dam 279,480 Above Mouth of Platte River 323,530 Platte River at Mouth 90,200 At Cooper Nuclear Station 414,600 Reference 1.7-4, Chapter II, Section 4.2.2.1 Site Information Related to the Flood Hazard 1-20 S-arge~nt; 45 Lunch/,I-

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 1.9 FIGURES The figures associated with Section 1 are presented on the following pages.Site Information Related to the Flood Hazard 1-21 Sargent & L-undly-Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 1.9-1: Site Location MWICIUMC 1.1-If Site Information Related to the Flood Hazard 1-22 Sar'get S Lundcv Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 1.9-2: Missouri River Tributaries GARR/,.O.N

• OAHE BIG BEND.-FT RANDALL/ { -'-- GAVINS POIWr LOU1S 1965 Reference 1.7-4, Figure 11-4-1 Site Information Related to the Flood Hazard 1-23 SaPgent: Lundy'

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 1.9-3: Overhead View of CNS I Site Information Related to the Flood Hazard 1-24 Sargent & L unVd Nebraska Public Power District Cooper Nuclear Station FLOOD HAzARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 1.9-4: Overhead View of CNS 2 Site Information Related to the Flood Hazard 1-25 Sar-gerW 8 Luncdy' Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 1.9-5: Missouri River Reservoir System Missouri River Mainstem Reservoir System IWWRecký Mewt-voir Reference 1.7-8 Site Information Related to the Flood Hazard 1-26 Sar-ge* & Lunrdv Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-01 2450 Revision 0 Project No.: 11784-017 Figure 1.9-6: Missouri River Path in 1879 at the Site of CNS q Ii-26~ ~il ,ln ~" EiU3 Land Coe:USACE MR:P lhttp://mor'Fverrecovery.usace.army.mil/mrrpgis/i I lReference 1.7-14 (Note: Current river path is overlaid and is in faded blue.)Site Information Related to the Flood Hazard 1-27 Saýgrget 4% L-undy'r Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 1.9-7: Aerial Photograph of the Plant Site in 1971 0 2.000 4,000 Feet Reference 1.7-14 (This photograph was taken after construction of C 1974. The river channel and banks looked much like they do today.)r opening in Site Information Related to the Flood Hazard 1-28 Sýngrvc 4 LunVd Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 1.9-8: Aerial Photograph of CNS Showing Flooding Feet ReleZac ondmadiUGiRO Soot ...........

q....-Z iý;c... ... Z o. .. .. ... ..... 6Tso Reference 1.7-14 (This Figure shows a satellite image of the Missouri River taken on July 9, 2011 and the effect of the maximum releases from Gavins Point Dam during the 2011 flood. Flood waters had inundated the floodplain in many of the areas where the Missouri River had once meandered within the boundaries of the levees. There was visible flooding east of the eastern levee due to the upstream levee breaches.

There was also visible standing water on the west side of the river, west of the levee, likely due to interior drainage.

There is no evidence that a new channel was beginning to form. The resolution of the image is such that it is not possible to discern the status of the bank stabilization structures.)

Site Information Related to the Flood Hazard 1-29 Sa3r~gent

&4 L-undy Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 2. FLOOD HAZARD REEVALUATION

2.1 LOCAL

INTENSE PRECIPITATION (LIP)Probable Maximum Precipitation (PMP), also known as Local Intense Precipitation (LIP), is the measure of the extreme precipitation (high intensity/short duration) at a given location.

Evaluation of the flooding hazards to the safety-related Systems, Structures, and Components (SSCs) at Cooper Nuclear Station (CNS) due to LIP is presented in this section of the report. U.S. Nuclear Regulatory Commission (NRC) guidelines NUREG/CR-7046 (Reference 2.1-1), NRC Regulatory Guide 1.59 (Reference 2.1-2), and ANSI/ANS-2.8-1992 (Reference 2.1-3) form the basis for the approach and methodology used in this evaluation.

The analysis was performed with the conservative assumption that the local storm drainage system (culverts, ditches, storm sewers, dry wells, etc.) would not be functional during the LIP event.The LIP flood effects on CNS were determined by performing site-specific hydrologic and hydraulic analyses.

The rational method (Reference 2.1-4) with conservative runoff coefficients (i.e.,1.0) was used for computation of peak PMP runoff from different drainage areas of the plant site. The U.S. Army Corps of Engineers (USACE) Hydrologic Engineering Center River Analysis System (HEC-RAS)computer program (Reference 2.1-5) was used to determine the maximum water surface elevation and flow velocity.

Due to the relatively short duration of the flooding event and the shallow depth of inundation, the effects of wind-waves were not considered.

Reference 2.1-6 defines Plant Datum as the same as Datum used in the USAR (which is MSL).The vertical datum used for this section (i.e., Section 2.1) was the CNS Plant Datum. The National Geodetic Vertical Datum of 1929 elevation (NGVD29) is equal to Plant Datum elevation plus 0.11 feet [ft] (Reference 2.1-6). The North American Vertical Datum of 1988 elevation (NAVD88) is equal to NGVD29 elevation plus 0.26 ft (Reference 2.1-6). The NAVD88 elevation is equal to Plant Datum elevation plus 0.37 ft. All directions are with respect to the Plant North direction, which is oriented to the west of the true north direction.

The effect of LIP on CNS was not evaluated previously in the Updated Safety Analysis Report (USAR, Reference 2.1-7). As presented in Section 4.2.2.2 of the USAR, the finished floor elevation of Principle Class 1 Structures (SSCs) is at 903.5 ft Plant Datum (903.87 ft NAVD88) and the general site grade elevation is at 903.0 ft Plant Datum (903.37 ft NAVD88).2.1.1 Probable Maximum Precipitation Depths As prescribed in NUREG/CR-7046 (Reference 2.1-1), the LIP used in the analysis is the 1-hour, 1-square mile PMP at the CNS site. Parameters to estimate the LIP were obtained from the U.S.National Weather Service (NWS) Hydrometeorological Reports HMR 51 and HMR 52 (see References 2.1-8 and 2.1-9).The estimated depths from HMR 51 are for precipitation durations 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and longer and drainage areas from 10 to 20,000 square miles. These estimates were used with procedures outlined in HMR 52 to determine PMP depths of various durations less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and Local Intense Precipitation (LIP)2-1Sa-er &L nv-Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 drainage areas up to 1 square mile for the site. Table 2.1-1 presents the PMP depths and intensities for various durations at the CNS site.2.1.2 Drainage Areas and Local Drainage Parameters The CNS site is located on the west (right) bank of the Missouri River near Brownville, Nebraska, at approximate River Mile (RM) 532.5. The latest available topographic survey (Reference 2.1-6) for the plant site area was used for delineation of drainage areas (zones). The main plant area is relatively flat without well-defined flow paths, and is delineated into drainage areas considering drainage away from the Central Building Complex in all directions.

The majority of the plant area perimeter is bounded by 9 to 10 rows of jersey barriers (Figure 2.1-1) with variable longitudinal spacing (1 inch to 36 inches). A portion of the security barrier south of the plant is formed by Kontek concrete block barriers.

The jersey barriers are 12.5 ft long and 32 inches (in) high and the Kontek blocks are 10 ft long and 3 ft high. Due to the variability in opening size, potential for barrier relocation, and potential for staggered openings between barrier rows; conservatively, openings between barriers were not considered flow paths for this analysis.Figure 2.1-2 shows the four drainage areas considered in the main plant area, identified as Zones A, B, C, and D. All safety-related facilities at CNS are located within these four zones. Peripheral portions of the main plant area that are not directly connected to, or that do not affect the safety-related facilities, were not included in the PMP zones. These small areas located along the periphery of the main plant area would generate a relatively small amount of runoff that would drain away from these areas without affecting the runoff draining away from the safety-related facilities.

Zone A is located on the east side of the plant, near the Missouri River. The Intake Structure is located along the downstream (eastern) boundary of Zone A. The grade elevation in this zone varies from 902 ft (902.37 ft NAVD88) to 903.5 ft (903.87 ft NAVD88). Although runoff could flow to the south where the grade slopes down toward the area of the discharge canal and sludge pond, all runoff from Zone A is considered to flow over the eastern boundary to the river on the south side of the Intake Structure, resulting in conservative estimates for the maximum water level in Zone A.Zone B is located on the north side of the main plant area. Security barriers are located along the northern edge of the zone at the downstream boundary, with relatively high elevations on the west side and lower elevations on the east side toward the river. The grade elevations at the downstream boundary of Zone B range from 902.5 ft (902.87 ft NAVD88) on the west side, to 897 ft (897.37 ft NAVD88) and below on the east side. Due to multiple obstructions on the western side of Zone B (i.e., tanks, buildings, etc.), the flow paths on the west side of some cross sections were considered blocked and not used for conveyance.

Additionally, due to the relatively high grade elevation and security barriers downstream of the tanks, the areas between the tanks were designated as ineffective flow areas within the HEC-RAS model. All runoff from Zone B was considered to drain away from the main plant through the area between the Condensate Storage Tank and the Fabrication Shop, and discharge over the top of the security barriers on the east side of the northern boundary.

Overtopping of the barriers was considered at the downstream boundary of Zone B.Local Intense Precipitation (LIP)2-2 i& 1 ly Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 Zone C is located on the south side of the main plant area. Runoff from this zone drains over the southern periphery of the main plant area to the low elevation area near the discharge canal, where it can flow unobstructed to the Missouri River. The grade elevations at the downstream boundary of Zone C range from 904 ft (904.37 ft NAVD88) to 902 ft (902.37 ft NAVD88), and all runoff from Zone C was considered to exit the zone on the west side of the storage tanks and buildings located near the downstream (southern) boundary.Zone D is located on the west side of the main plant area. The security barriers (32 inches high) are located at the western edge of this zone and act as an obstruction.

As runoff accumulates behind the barriers and causes ponding in Zone D, runoff will flow to the south. Overtopping of the barriers along the western boundary of Zone D was not considered in this analysis due to the relatively high elevations of the top of barriers.

Although the flow path along the west side of the East Warehouse between the security barriers and the building has the capacity to convey the entire peak flow from Zone D, it is expected that some runoff will flow into Zones B and C. Flow-balancing calculations were performed to determine the quantities of runoff flowing to these zones.The offsite drainage area was delineated (Figure 2.1-3) considering Federal Levee R548 that is adjacent to CNS with a top elevation of approximately 902 ft (902.37 ft NAVD88). The levee extends north of the plant, where it terminates at the higher ground near the bluffs. South of CNS, the levee follows the right bank of the Missouri River, curving around to the west, running parallel to the left bank of the Nemaha River, and turning north where it meets the higher ground near the town of Nemaha.The area enclosed by the levee and the higher bluffs to the west measures 4000 acres (ac). The effect of runoff from the offsite drainage area on PMP water levels near CNS is discussed in Section 2.1.4.2.1.3 Peak Discharges To compute the peak runoff, time of concentration for each zone was estimated using the Kerby Equation (Reference 2.1-10). For each zone, flow length, average slope, and roughness coefficient were estimated and used as input for the Kerby Equation.

The surfacing in the main plant area is mostly gravel and concrete or asphalt-paved, and the roughness coefficient was considered to be 0.02 (Reference 2.1-4).The estimated times of concentration are presented in Table 2.1-2. Using the PMP values corresponding to the time of concentration, the applicable PMP intensity for each zone was estimated.

Employing the rational method (Reference 2.1-4), peak runoff for each of the zones was estimated.

A conservative runoff factor value of 1.0 (indicating 100% runoff without any infiltration or other losses) was used in the rational method.2.1.4 Hydraulic Model Setup For computations of water levels, the HEC-RAS Version 4.1 computer program (Reference 2.1-5) was used. Separate HEC-RAS runs for each zone were performed.

The site features and flow obstructions in each drainage area are characterized by cross sections (Figure 2.1-4 through Figure 2.1-7) and used in the hydraulic analysis.Local Intense Precipitation (LIP)2-3 Sarngent:

E undyV-c Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 The surfacing in the main plant area is primarily gravel and concrete or asphalt-paved.

Reference 2.1-4 recommends Manning's roughness coefficients ranging from 0.011 to 0.025 for such surfaces.Conservatively, a Manning's roughness coefficient of 0.030 was used to account for minor obstructions.

The flow at each cross section was computed by prorating the peak discharge of the entire zone based on the drainage area upstream of that cross section. Table 2.1-3 through Table 2.1-6 present the peak flow at each cross section for Zones A through D, respectively.

For Zones A, C, and D, the critical depth was considered as the downstream boundary condition to account for the flow transition from the relatively flat main plant area, over the peripheral boundary and down a steep slope. Critical depth was considered for the downstream boundary condition in Zone B to account for the flow over the security barriers, which were considered to act as a weir. The present-day regulatory guidance (References 2.1-1 and 2.1-11) does not provide combined-events criteria governing the coincident water level in an adjacent river during the LIP event. The normal river water level at CNS is well below elevation 890 ft (880.37 ft NAVD88), and the CNS USAR defines the normal summer water level as 880 ft (890.37 ft NAVD88 [Reference 2.1-7]).The 25-year water level in the Missouri River at CNS is 898.04 ft (898.41 ft NAVD88 [Reference 2.1-12]).The 25-year water level is well below the lowest elevation of any cross section considered in the evaluation and will not affect drainage from the site during an LIP event. Therefore, there is no backwater effect from the Missouri River at the downstream boundary for Zones A, B, and C. Zone D discharges to the floodplain behind the USACE levee, and is not affected by water levels in the Missouri River or the offsite area.Runoff from the offsite drainage area will pond on the floodplain behind the USACE levee. Comparing the total PMP runoff volume with the storage volume available behind the levee showed that the maximum surface elevation of the ponded water level will be less than 892 ft (892.37 ft NAVD88).Therefore, water levels at the boundary of the main plant area, during an LIP event, will not be affected by runoff from the offsite drainage area.Several temporary trailers are installed in the main plant area at CNS. The trailers are accounted for in the analysis as complete obstructions.

Sensitivity runs with and without the trailers performed using HEC-RAS indicated that these trailers have a negligible effect on the PMP water levels estimated for this analysis.Initially, the maximum water levels for each zone were computed without considering the cross flow between the adjacent zones. Subsequently, a trial-and-error flow-balancing exercise was performed to determine the cross flows that result in matching water levels at the interface between zones.2.1.4.1 LIP Runoff Water Levels without Cross Flow between Zones The resulting maximum water level in each zone during an LIP event, without consideration of cross flow between zones, is summarized below: Local Intense Precipitation (LIP)2-4 S~argent 4e L-undyV I-Nebraska Public Power District SL-01 2450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017* Zone A maximum water level = 903.05 ft (903.42 ft NAVD88)* Zone B maximum water level = 903.35 ft (903.72 ft NAVD88)" Zone C maximum water level = 903.59 ft (903.96 ft NAVD88)* Zone D maximum water level = 903.80 ft (904.17 ft NAVD88)2.1.4.2 Water Levels with Cross Flow between Zones Preliminary water level estimates without consideration of cross flow showed the water levels in Zones B and D differ by nearly 6 inches. Through a process of trial-and-error, a cross flow of 63 cubic feet per second (cfs) is considered to flow from Zone D to Zone B (Figure 2.1-5). A cross flow of 63 cfs was chosen because it represents all of the peak flow at the upstream-most cross section of Zone D and provides closely matching (less than a 1-inch difference) final water surface elevations between Zones B and D.Cross flow can occur from Zone D to Zone C upstream of the East Warehouse, and from Zone C to Zone D downstream of the East Warehouse (Figure 2.1-6). Cross flow from Zone D into Zone B was deducted from Zone D before the cross flow balancing between Zones C and D was performed.

Cross flow from Zone C into Zone A (Figure 2.1-7) was estimated following the cross flow balancing between Zones C and D.The maximum water level in Zone B is approximately 5 inches higher than the maximum water level in Zone A. The broad-crested weir equation (Reference 2.1-13) was used to estimate the cross flow from Zone B to Zone A. The potential for submerged weir flow was checked using Figure 5-15 of Reference 2.1-14. A total cross flow of 108 cfs enters Zone A at the upstream boundary and was applied to every cross section in the zone. Conservatively, the flows at cross sections in Zone B and Zone C were not reduced to account for this flow out of the zone. Figure 2.1-8 through Figure 2.1-10 present the results of the hydraulic analysis for all HEC-RAS cross sections considering cross flow between two adjacent zones. The resulting maximum water level in each zone during an LIP event, considering cross flow between zones, is summarized below.* Zone A maximum water level = 903.19 ft (903.56 ft NAVD88)* Zone B maximum water level = 903.47 ft (903.84 ft NAVD88)* Zone C maximum water level = 903.50 ft (903.87 ft NAVD88)" Zone D maximum water level = 903.50 ft (903.87 ft NAVD88)2.1.4.3 Velocity The maximum velocity obtained from the HEC-RAS output for each zone is summarized below.* Zone A maximum velocity = 3.64 feet per second (fps)* Zone B maximum velocity = 4.49 fps" Zone C maximum velocity = 2.87 fps* Zone D maximum velocity = 5.02 fps Local Intense Precipitation (LIP)2-5 & r-.ir-dV Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 The HEC-RAS simulations were performed under subcritical flow conditions; however, the results indicated that there could be supercritical flow conditions in Zone B and Zone D. Additional HEC-RAS test runs using a mixed-flow regime resulted in no change to the maximum water levels estimated for these zones. Since the subcritical flow dominates in the upstream areas, upstream water levels are controlled by water levels downstream, not the upstream boundary condition.

However, the velocities at some cross sections are affected when a mixed-flow regime is employed.In Zone D, supercritical flow occurs in the area located between the Warehouse and the security barriers at Cross Section D500, with a maximum velocity of 5.12 fps. The model indicated that a hydraulic jump occurs between Cross Sections D500 and D400. The Froude number is close to 1.0, indicating that the hydraulic jump is weak; however, the potential for erosion exists due to turbulence at the location of the jump. In Zone B, supercritical flow occurs on the steep slope at the periphery of the main plant area at Cross Section B200. The velocity at this location is 9.34 fps; hence, there is a potential for erosion of the sloped surface. Both of the locations that have potential for site erosion are located around the periphery of the plant, away from safety-related SSCs, and would not affect any CNS safety-related facilities.

2.1.5 Effect

of LIP Table 2.1-7 presents a summary of the Maximum Water Levels in all zones at different cross sections.These water levels consider cross flow between zones for steady-state, subcritical flow conditions.

The maximum estimated water level due to LIP at CNS is 903.50 ft (903.87 ft NAVD88), which is equal to the finished floor elevations for Principal Class 1 Structures.

While significant inundation above the finished floor elevations is not expected, the potential for minor flooding at the entrances of these structures may exist during the peak of the event.Reference 2.1-14 recommends a maximum permissible flow velocity of 6.0 fps to prevent erosion of channels with fine-gravel surfacing.

The potential for erosion in the main plant area is low, as the velocities do not exceed 6 fps and are generally less than 3 fps. Velocities on the steep slope at the periphery of the main plant area may cause local erosion of the sloped surface, but there would be no effect on safety-related facilities.

Due to the relatively short duration of the flooding event and the shallow depth of inundation, the effects of wind-waves were not considered.

Additionally, debris loading and transportation were not considered in the analysis due to the relatively low velocity and shallow depth of LIP flood waters near CNS safety-related facilities, and due to the lack of debris sources in the CNS main plant area.2.1.6 References 2.1-1. Design-Basis Flood Estimation for Site Characterization at Nuclear Power Plants in the United States of America, NUREG/CR-7046, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, November 2011.2.1-2. Regulatory Guide 1.59, Design Basis Floods for Nuclear Power Plants, Revision 2, Office of Standards and Development, U.S. Nuclear Regulatory Commission, August 1977.Local Intense Precipitation (LIP)2-6 Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 2.1-3. American Nuclear Society, ANSI/ANS-2.8-1992, Determining Design Basis Flooding at Power Reactor Sites, July 1992.2.1-4. Handbook of Applied Hydrology, VenTe Chow, McGraw -Hill Inc., 1964.2.1-5. Hydrologic Engineering Center's River Analysis System (HEC-RAS)

Version 4.1 for Windows.U.S. Army Corps of Engineers, 2010.2.1-6. NPPD Engineering Evaluation Number 12-035, Revision 0, "Review of 2012 Topographic Survey of CNS," March 2013.2.1-7. Updated Safety Analysis Report (USAR -2.7), Cooper Nuclear Station, Site and Environs, Hydrology, Site Flooding Protection, Dated 01/16/01.2.1-8. Hydrometeorological Report No. 51 (HMR 51), Probable Maximum Precipitation estimates, United States East of the 1 0 5 th Meridian, National Weather Service, National Oceanic and Atmospheric Administration (NOAA), June 1978.2.1-9. Hydrometeorological Report No. 52 (HMR 52), Application of Probable Maximum Precipitation Estimates

-United States East of the 105th Meridian, National Weather Service, National Oceanic and Atmospheric Administration (NOAA), August 1982.2.1-10. Hydrology and Hydraulic Systems, Ram S. Gupta, Second Edition, Waveland Press, Inc., 2001.2.1-11. Standard Review Plan, Revision 4, NUREG-0800, Section 2.4.2 Floods, United States Nuclear Regulatory Commission (USNRC), March 2007.2.1-12. Upper Mississippi River System Flow Frequency Study, Hydrology and Hydraulics, Appendix F, Missouri River, U.S. Army Corps of Engineers, Omaha District, November 2003.2.1-13. Handbook of Hydraulics, Ernest F. Brater, Horace W. King, Sixth Edition, McGraw-Hill, Inc., 1976.2.1-14. Engineering Manual EM 1110-2-1601, "Engineering and Design -Hydraulic Design of Flood Control Channels," Table 2-5, p 2-16, U.S. Army Corps of Engineers, 1991.Local Intense Precipitation (LIP)2-7 sMgm r Lunidy-'

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-01 2450 Revision 0 Project No.: 11784-017 2.1.7 Tables Tables associated with Section 2.1 are presented on the following pages.Local Intense Precipitation (LIP)2-8 Sarenit & LunrdyI-Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Table 2.1-1: PMP Values and Intensities at the CNS Site 1 hr, Point PMP Depth PMP PMP Duration and Area Location Source PMP Intensity Ratio (in) (in/hr)24 hr, 10 mi 2 -HMR 51 -Figure 20 33.3 1 hr, point location -HMR 52 -Figure 24 18.2 18.2 30 min, point 0.765 HMR 52 -Figure 38 13.9 27.8 15 min, point 0.534 HMR 52 -Figure 37 9.7 38.8 5 min, point 0.338 HMR 52 -Figure 36 6.2 74.4 Table 2.1-2: Peak Discharge Drainage Flow Slope Time of Rainfall Peak Zone Area Concentration Intensity Discharge (acres) Length (ft) ( (min) (in/hr) (cfs)A 2.61 130 0.0077 4.0 74.4 194 B 5.30 280 0.0036 6.9 59.7 316 C 4.00 285 0.0035 7.0 59.1 236 D 6.29 650 0.0031 10.6 46.2 291 Note: 1. A 5-minute time of concentration is applied to any drainage area in which the estimated time of concentration is less than 5 minutes.Local Intense Precipitation (LIP)2-9 S~ar-get:,1C' L-undIV -I Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-01 2450 Revision 0 Project No.: 11784-017 Table 2.1-3: Drainage Area and Peak Flow at each Cross Section -Zone A Column: (1) (2) (3) (4)Peak Flow (cfs) Peak Flow (cfs)Cross Section Upstream Ratio Upstream Flow Profile: Flow Profile: Area (ac) Area to Total Area Initial (Without Final (With Cross Flow) Cross Flow)A800 1.04 0.398 77 185 A700 1.22 0.467 91 199 A600 1.47 0.563 109 217 A500 1.73 0.663 129 237 A400 1.98 0.759 147 .255 A300 2.23 0.854 166 274 A200 2.46 0.943 183 291 A100 2.61 1.000 194 302 Notes: 1. Column (2) = Column (1) Total Area; Total Area = 2.61 ac 2. Column (3) = Column (2) x Peak Flow; Peak Flow = 194 cfs 3. Column (4) = Column (3) + 108 cfs from Zone B and Zone C (Cross Flow)Local Intense Precipitation (LIP)2-10 Sargent; V& LundtV11' Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Table 2.1-4: Drainage Area and Peak Flow at each Cross Section -Zone B Column: (1) (2) (3) (4)Peak Flow (cfs) Peak Flow (cfs)Cross Section Upstream Ratio Upstream Flow Profile: Flow Profile: Area (ac) Area to Total Area Initial (Without Final (With Cross Flow) Cross Flow)B1200 0.75 0.142 45 108 B1100 1.16 0.219 69 132 B1000 1.49 0.281 89 152 B900 2.13 0.402 127 190 B800 2.38 0.449 142 205 B700 2.81 0.530 168 231 B600 3.41 0.643 203 266 B500 3.65 0.689 218 281 B400 4.10 0.774 244 307 B300 4.65 0.877 277 340 B200 4.95 0.934 295 358 B100 5.30 1.000 316 379 Notes: 1. Column (2) = Column (1) / Total Area; Total Area = 5.30 ac 2. Column (3) = Column (2) x Peak Flow; Peak Flow = 316 cfs 3. Column (4) = Column (3) + 63 cfs from Zone D (Cross Flow)Local Intense Precipitation (LIP)2-11 Sagrgen 4,% Lundly 1 Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Table 2.1-5: Drainage Area and Peak Flow at each Cross Section -Zone C Column: (1) (2) (3) (4)Peak Flow (cfs) Peak Flow (cfs)Cross Section Upstream Ratio Upstream Flow Profile: Flow Profile: Area (ac) Area to Total Area Initial (Without Final (With Cross Flow) Cross Flow)C1200 1.08 0.270 64 65 C1100 1.19 0.298 70 72 C1000 1.37 0.343 81 84 C900 1.74 0.435 103 109 C800 2.11 0.528 124 130 C700 2.50 0.625 148 154 C600 2.69 0.673 159 165 C500 2.95 0.738 174 180 C400 3.26 0.815 192 170 C300 3.48 0.870 205 154 C200 3.82 0.955 225 145 C100 4.00 1.000 236 156 Notes: 1. Column (2) = Column (1) /Total Area; Total Area = 4.00 ac 2. Column (3) = Column (2) x Peak Flow; Peak Flow = 236 cfs 3. Column (4) = final profile resulting from cross flow balancing with Zone D Local Intense Precipitation (LIP)2-12 Sarge~nt;

-& Lunly, I Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Table 2.1-6: Drainage Area and Peak Flow at each Cross Section -Zone D Column: (1) (2) (3) (4)Peak Flow (cfs) Peak Flow (cfs)Cross Section Upstream Ratio Upstream Flow Profile: Flow Profile: Area (ac) Area to Total Area Initial (Without Final (With Cross Flow) Cross Flow)D2000 1.36 0.216 63 0 D1900 1.66 0.264 77 14 D1800 1.81 0.288 84 21 D1700 2.18 0.347 101 38 D1600 2.38 0.378 110 47 D1500 2.82 0.448 130 67 D1400 3.42 0.544 158 95 D1300 3.96 0.630 183 120 D1200 4.12 0.655 191 126 D1100 4.23 0.672 196 131 D1000 4.40 0.700 204 137 D900 4.78 0.760 221 152 D800 4.94 0.785 229 160 D700 5.19 0.825 240 171 D600 5.30 0.843 245 176 D500 5.46 0.868 253 184 D400 5.66 0.900 262 222 D300 5.82 0.925 269 258 D200 6.08 0.967 281 298 D100 6.29 1.000 291 308 Notes: 1. Column (2) = Column (1) /Total Area; Total Area = 6.29 ac 2. Column (3) = Column (2) x Peak Flow; Peak Flow = 291 cfs 3. Column (4) = final profile resulting from cross flow balancing with Zone C Local Intense Precipitation (LIP)2-13 Caren &Lunay, ,-

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Table 2.1-7: PMP Water Levels Zone A Water Zone B Water Zone C Water Zone D Water Cross Level Cross Level Cross Level Cross Wat)Section Level(f) Section Level(f) Section Level(f) Section Level(f)A800 903.19 B1200 903.47 C1200 903.50 D2000 903.50 A700 903.17 B1100 903.46 C1100 903.48 D1900 903.50 A600 903.16 B1000 903.45 C1000 903.49 D1800 903.50 A500 903.14 B900 903.40 C900 903.47 D1700 903.50 A400 903.07 B800 903.39 C800 903.45 D1600 903.50 A300 903.02 B700 903.35 C700 903.44 D1500 903.50 A200 902.84 B600 903.33 C600 903.43 D1400 903.50 A100 902.55 B500 903.32 C500 903.43 D1300 903.49-B400 903.17 C400 903.42 D1200 903.49-B300 902.54 C300 903.38 D1100 903.49-B200 900.51 C200 903.15 D1000 903.47-B100 899.79 C100 902.30 D900 903.15 D- 800 903.06 D- 700 902.85 D- 600 902.51 D500 902.16 D400 902.02 D300 902.01 D- 200 901.76 D- 100 901.51 Note: 1. Water levels are all in Plant Datum; add 0.37 to convert to ft NAVD88.Local Intense Precipitation (LIP)2-14 Sargent i& Lunch/y I.-

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 2.1.8 Figures Figures associated with Section 2.1 are presented on the following pages.Local Intense Precipitation (LIP)2-15 Sargenvt:

& Lunwdv I-Nebraska Public Power District Cooper Nuclear Station FLOOD HAzARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-1: Location of Security Barriers Local Intense Precipitation (LIP)2-16 Sargen~t S LunrdyV Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-2: Drainage Areas for LIP Evaluation Local Intense Precipitation (LIP)2-17 13"vig"rft AL L-u"cly Nebraska Public Power District SL-012450 Cooper Nuclear Station Revision 0 FLOOD HAZARD REEVALUATION REPORT Project No.: 11784-017 Figure 2.1-3: Offsite Drainage Area behind USACE Levee i" ........... ...

i I IIo I LUSACE LEVEE-' \", /--CNS PLANT i. -I 4' .S -RDRAIAGE AREA BOUNDARY* (AREA =4000 AC)J X.i "" ACE LEVEE" Loa Ines Prcptto LP i 2 1 I -j, , ,I**I. ..=1, I = , I, I=1=,,IWl ,I. I~l IIIl=lIl~

l ll 3000' 0' 3000' 6000'GRAPHIC SCALE Local Intense Precipitation (LIP)2-18__Sar'gerlt 5, Lunndv Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-4: Cross Sections for LIP Evaluation

-Zone A Local Intense Precipitation (LIP)2-19 13--oftrift M t-u"cfy I , I Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-5: Cross Sections for LIP Evaluation

-Zone B Local Intense Precipitation (LIP)2-20 n-,JA-rW.

ML t---"v 1, Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-6: Cross Sections for LIP Evaluation

-Zone C Local Intense Precipitation (LIP)2-21L-undy '

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPoRT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-7: Cross Sections for LIP Evaluation

-Zone D Local Intense Precipitation (LIP)2-22 r-~JE~,r1b~

L..r~dy Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-8: HEC-RAS Cross Sections for Zone A------ ------17-Local Intense Precipitation (LIP)2-23 Sa-Urv ea.L L-undl ý Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-9: HEC-RAS Cross Sections for Zone B (sheet I of 2)Z-eB u!tlt%l .'433 ,1 4++ \ ,30 r C-.H, I-: SMvw.30 I I-.40,4,3314)33.3439 4)81,1101 41310(033 0.3010, 3404 L1 *441w 30 4)E 4.3313 M 313"i t A.1 S131333 III 13330.33.131 1.9 LG rI- 'tnd E34304330-V 50 3 1033 '30. 3(3 330 030 .0)3 3 33 33(3 330 3(0' 3433 0033 1033331 (00 2W0 330 0 W30 330-MI014 Local Intense Precipitation (LIP)2-24 Sarqge vt IS "nldL -

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-9: HEC-RAS Cross Sections for Zone B (sheet 2 of 2)Zo-oB E. F s F-(-.~14 m , kv4-10,1 týýZoBeB 411,;-.-.V.EGrl.blbl*8 F.- WS~~0S4~201 ,o (l.CObblb OS I~.S 14520,40 1,0l*blbobI, 1'('(4 ES -I, h0bo 1*41' W 0 1101 tt}l) 300 Local Intense Precipitation (LIP)2-25 SBoarge 4% Lundv --I Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-10: HEC-RAS Cross Sections for Zone C (sheet I of 6).8°4.134 ZmneC C 11W L..0 .3233 fIG 3.34a333.33349 WFk3 1 3349 W F,.W,8I,0 3 3%0 1;0 2.33 232 360 C-133 Lopnd EG F. 3 333 3333 WS F384333(c3--9 3.333.st.gn iý--t2 I ' .....' .......l W 38 200 25 ZoneC"1 L3033d INS N33333339 fI 3.33333033 3333.333.33 B333k33 90 i-3333 0333 333 433 4333330 38, 0 103 03 3il*3¶3333333383

• 033f-------

Local Intense Precipitation (LIP)2-26 Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-10: HEC-RAS Cross Sections for Zone C (sheet 2 of 6)IN-ZowOC ZonrC'AIX G Fo1.41)0)BS R.)310 3)04 LgOd (0)00010)1)1305 WO F 1),., 1313.)))0l4 000)0)0 0)23 305 W20410 ZoneC ZoneC C200 1111W1 (00 010 30-M(4 ~4W908 I 10 )-, (1110304 0)5 0102 101413000 00003 0 o,0 0))I( 110 00030 WO H10)1000 il1(H 908 1300]I i 9(11 D06 c- I , 0 IN0 2W0 30 M0 0 80.)400,)0 100 34 3 00 " 4 0050 SAX)1)0(n, Local Intense Precipitation (LIP)-2-27 E3ýý-gýrvb M ""CIV I , I Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-10: HEC-RAS Cross Sections for Zone C (sheet 3 of 6)Z.OU.DH U1433 WS "",Ie* (1'G'4 33l43WS-Eu Ssi-- 46**0 Foe *Inc4u,6**~

., i 1*t 319* 1(0 3(3 W2 Zoned U3 SloWB, *3*, EGF 94k1.9,.13 A. M-90*-------~~1~

0~'319410*1*1 Ull, AKI ,xl 41. 1.-l Local Intense Precipitation (LIP)2-28ý"ar'g M Lundu ' ' '

Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-10: HEC-RAS Cross Sections for Zone C (sheet 4 of 6)101,00 ZmO10 Z-teD U12 910;9Oo*L"-dn EI G .,. F 0 0, L"g-d I d Wl 11 101000 o0ed10 100,0 10F.00I004.101~1 WI 1.100 10010.1019 10.1.110, Zo03d 410; no.0 L1..0 1 0'60 2W1.10cý ým I 110 100 110 00. 210 000 110 410 II,,.,, 110 Local Intense Precipitation (LIP)2-29 Oal-""tv ML "ndV, Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-10: HEC-RAS Cross Sections for Zone C (sheet 5 of 6)1one0.Zon~e'3S002 3l33 L.gWon EG 31.10 3(n'Wf Ws F04. 4 i3it~{~001 03 Co roe 0100.3O 0.S 1 0003w (13 0.01,0.8 CO Foal Ondeseg 220 30 3k0n40 9 330 Fne 30oo00~~e..n,.0-0214{.Zono')12.4,,, 333 Loon')43000, 3n3 Looo')(.1,.1 LCl,, IOFl40.I L..e£G 111Weo 1--014S308Fn" 4.1 L-o~d 013-3.3 11313 353 2103 2143 3330 lOll 5140.1.1 3313 10301 S.-00n In 50 1303 3314 20.3 25030(3 0143 Local Intense Precipitation (LIP)2-30 3~gInr*& Lu-rfV Nebraska Public Power District Cooper Nuclear Station FLOOD HAZARD REEVALUATION REPORT SL-012450 Revision 0 Project No.: 11784-017 Figure 2.1-10: HEC-RAS Cross Sections for Zone C (sheet 6 of 6) Zoned EG ECFrwdh~a~y WSFeji ih.kg I n.j (cc ci, II 0) cliii 200 '00 II) hO 5Ic~',~ (0)I 10, l Local Intense Precipitation (LIP)2-31 Sarge- L-unchI