Coyote Valley Dam/Lake Mendocino - Major Deviation to the Water Control Manual - Draft Environmental Assessment/FONSI (PDF)
PROJECT LOCATION AND DESCRIPTION
This study area is located on the east fork of the Russian River near the city of Ukiah, California. The Russian River drains an area of 1,485 square miles; approximately two-thirds of the drainage area is in Sonoma County, and the remainder is in Mendocino County. The Coyote Valley Dam (CVD) project (also known as Lake Mendocino Dam) was authorized by Section 204 of the Federal Flood Control Act of 1950, and includes sediment, flood control, and domestic and agricultural water supply pools with a total storage capacity of 199,000 acre-feet. The existing project, completed in 1957, consists of a 160-feet-high earth-filled dam and a reservoir with a storage capacity of 122,400 acre-feet. Because local interests considered it unnecessary at the time of construction, an additional water-supply portion of the authorized project (77,000 acre-feet) was deferred. Increased development has subsequently renewed interest in the additional water that would be supplied by that deferred portion of the project.
TOTAL COST $ 5,798,000
FEDERAL COST $ 2,899,000
NON-FEDERAL COST $ 2,899,000
TOTAL FEDERAL COST THROUGH FY 2018 $ 705,000
FY 2019 BUDGET $ 0
COST TO COMPLETE $ 2,194,000
*Study cost in current Feasibility Cost Sharing Agreement (FCSA). See information below regarding estimated remaining study costs, which are greater than the amounts above.
FY 19 AND FY 20 ACCOMPLISHMENTS
- Feasibility study is inactive, pending additional funds.
ISSUES AND OTHER INFORMATION
- The Mendocino County Inland Water and Power Commission (MCIWPC) is the Non-Federal Sponsor (NFS) for this study.
- Key documentation and milestones to date for the feasibility study are: Feasibility Cost Sharing Agreement (FCSA) executed (October 2005), Public Scoping Meeting Report (December 2007), CVD Topographic & Bathymetric Surveys (December 2008), Hydrologic and Hydraulic Modeling of Coyote Valley Dam for With and Without Failure of the Dam (July 2009), Preliminary Water Supply Evaluation (March 2013), Planning Charrette (December 2014), Draft Preliminary Analysis of Economic Justification for Continuation of the Feasibility Study (Sep 2016).
- Potential alternatives identified for modifying CVD to increase water supply are: full dam raise, partial dam raise, modifying operations, reservoir dredging, outlet works/spillway modifications, or combinations of these. Full or partial dam raise would likely require auxiliary dam and new spillway.
- Construction Costs: Estimated minimum cost to enlarge and provide additional water storage to fully-authorized levels at the Coyote Valley Dam and Reservoir project is at least $320 million. This rough estimate is based on 2015 update to 1974 cost estimate and does not account for potential dam safety issues.
- Economics: Based on draft preliminary economic analysis, costs for the full dam raise could increase to $560 million before non-CVD alternatives for water supply would challenge the dam raise as the least costly alternative per acre feet per year.
- Dam Safety: CVD is assigned a Dam Safety Action Classification (DSAC) of 3. Per Ch. 24 of ER 1110-2-1156, Safety of Dams – Policy and Procedures, water supply study at projects where a DSAC 1, 2, or 3 is currently assigned to the dam, requires approval of the USACE Dam Safety Officer (DSO) to proceed with study. The San Francisco District is developing this approval request in coordination with MCIWPC.
- Study Costs and Schedule: A rough estimate for remaining 50% Fed/50% non-Fed cost-shared study costs is $5.5 million. A rough estimate is that the study will take 4-5 years to complete after the study resumes. Detailed scope, schedule, and budget for completing the study will be developed after receiving additional funds to resume study.
- Construction Cost-Sharing: This will likely be a multipurpose project with elements of water supply and ecosystem restoration. Construction costs for water supply elements would be 100% non-federal, with potential for upfront federal financing and non-federal repayment. Construction costs for ecosystem restoration elements would be 65% federal/35% non-federal.
- 2ND District, Rep. Jared Huffman
- 5TH District, Rep. Mike Thompson
POINT OF CONTACT
- Deputy for Project Management, Edwin S. Townsley, (415) 503-6593.
Updated on 31 January 2019
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