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Fontenelle Dam and Outworks Infrastructure CompleƟon Level II Study Prepared by: In associaƟon with: 1600 Specht Point Rd. #209 Fort Collins, CO 80525 Denver, CO Fort Collins, CO Raton, NM Fontenelle Dam and Outworks Infrastructure Completion Level II Study Prepared for: Wyoming Water Development Commission 6920 Y ellowtail Road Cheyenne, WY 82002 Prepared by: ~gineering Analytics, Inc. 1600 Specht Point Road, Suite 209 Fort Collins, Colorado 80525 (970) 488-3111 Fax (970) 488-3112 Project No. 110661 December 2018 Fontenelle Dam and Outworks Level II Study Wyoming Water Development Office TABLE OF CONTENTS INTRODUCTION AND OVERVIEW ........................................................................... 1 Purpose .................................................................................................................... 1 Scope ....................................................................................................................... 1 Project Meetings ..................................................................................................... 3 BACKGROUND ............................................................................................................... 5 OUTLET WORKS AND POWERPLANT .................................................................... 7 River Outlet and Hydroelectric Diversion .............................................................. 7 Spillway .................................................................................................................. 9 East Canal ............................................................................................................... 9 West Canal ............................................................................................................ 10 Site Visit................................................................................................................ 10 ALTERNATIVES ANALYSIS ...................................................................................... 12 Alternatives ........................................................................................................... 12 NEPA CONSIDERATIONS .......................................................................................... 24 NEPA .................................................................................................................... 24 Agency Coordination ............................................................................................ 26 December 2018 2 Engineering Analytics, Inc. Fontenelle Dam and Outworks Level II Study Wyoming Water Development Office Environmental Considerations .............................................................................. 27 Environmental Alternatives Evaluations .............................................................. 32 Permitting, Clearances, and Approvals ................................................................. 32 Summary ............................................................................................................... 34 HYDRAULIC ANALYSIS OF HISTORIC AND FUTURE OPERATIONS .......... 35 Historic Reservoir Operations ............................................................................... 35 Reservoir Potential Yield ...................................................................................... 42 Construction Reservoir Drawdown Scenarios ...................................................... 42 Issues Relative to Interstate Compacts ................................................................. 54 Future Operations.................................................................................................. 55 CONCEPTUAL DESIGNS AND COST ESTIMATES .............................................. 57 Riprap .................................................................................................................... 57 December 2018 iii Engineering Analytics, Inc. Fontenelle Dam and Outworks Level II Study Wyoming Water Development Office Soil Cement ........................................................................................................... 60 Submar Mats ......................................................................................................... 60 Contech Wave Attack Blocks ............................................................................... 60 Summary of Costs ................................................................................................. 60 SCHEDULING ................................................................................................................ 63 Riprap .................................................................................................................... 63 Soil Cement ........................................................................................................... 63 Submar .................................................................................................................. 65 Contech ................................................................................................................. 65 Schedule Variations .............................................................................................. 65 Power Generation Scheduling............................................................................... 69 Summary ............................................................................................................... 70 ECONOMIC ANALYSIS .............................................................................................. 71 Benefits Associated with the Proposed Project .................................................... 71 Valuation Methods ................................................................................................ 72 Direct Water Supply Analysis .............................................................................. 75 Drought Mitigation Analysis ................................................................................ 80 Drought Avoidance Analysis .............................................................................. 105 December 2018 iv Engineering Analytics, Inc. Fontenelle Dam and Outworks Level II Study Wyoming Water Development Office Cost Considerations ............................................................................................ 110 Summary of Benefits .......................................................................................... 113 CONCLUSIONS AND RECOMMENDATIONS ...................................................... 115 Conclusions ......................................................................................................... 115 Recommendations ............................................................................................... 116 Extreme Event Alternative .................................................................................. 118 REFERENCES .............................................................................................................. 119 December 2018 v Engineering Analytics, Inc. Fontenelle Dam and Outworks Level II Study Wyoming Water Development Office LIST OF TABLES Table 1-1. Interagency group meetings with their corresponding topics and dates. ........... 4 Table 4-1. Quantity of riprap for each 20-foot section placed in the dry. ........................ 15 Table 4-2. Quantity of riprap for each 20-foot section for placement in full reservoir. ... 16 Table 4-3. Quantity of soil cement for each 20-foot section. ........................................... 19 Table 4-4. Material quantification for placing Submar Mats in full reservoir according to surface area of the dam face requiring armoring. ............................................................. 20 Table 4-5. Required Material for placing Contech Wave Attack Blocks in the Full Reservoir ........................................................................................................................... 21 Table 4-6. Summary of criteria met for each of the alternatives. ..................................... 23 Table 5-1. List of endangered and threatened species and details. ................................... 28 Table 5-2. List of facilities and details.............................................................................. 28 Table 5-3. List of migratory birds and details................................................................... 29 Table 6-1. Fontenelle average monthly inflow and outflows. .......................................... 35 Table 6-2. Fontenelle monthly average, maximum, and minimum end-of-month