Draft Supplemental Watershed Plan No. 9 and Environmental Assessment for the Rehabilitation of Silver Lake Flat Dam American Fork-Dry Creek Watershed Utah County, Utah Sponsoring Local Organizations: North Utah County Water Conservancy District Utah Division of Wildlife Resources Prepared by: McMillen, LLC Prepared for: U.S. Department of Agriculture Natural Resources Conservation Service In cooperation with: U.S. Department of Agriculture U.S. Forest Service Uinta-Wasatch-Cache National Forest August 2013 NRCS Silver Lake Flat Dam Rehabilitation Title and Document Status: Draft Supplemental Watershed Plan No. 9 and Environmental Assessment (Draft Plan-EA) for the Rehabilitation of Silver Lake Flat Dam. The Project is located in Utah County, Utah. Lead Agency: U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Cooperating Agencies: USDA U.S. Forest Service (USFS) Uinta-Wasatch-Cache National Forest (UWCNF) Sponsoring Local Organizations: North Utah County Water Conservancy District (NUCWCD) and Utah Division of Wildlife Resources (UDWR) Authority: This Draft Plan-EA has been prepared under the authority of the Watershed Protection and Flood Prevention Act, Public Law (PL) 83-566, as amended (16 U.S.C. 1000-1008, 1010 and 1012) and in accordance with Section 102(2)(c) of the National Environmental Policy Act of 1969, PL 91-190, as amended (42 U.S.C. 4321 et seq.). Abstract: Silver Lake Flat Dam (#UT00276) was originally built in 1971 and was designed and constructed as a high hazard (Class “C”) dam due to the high probability of loss-of-life if the dam should fail. The dam was planned and built for the primary purpose of irrigation water storage but has incidental benefits to flood control, sediment retention, and recreation. In accordance with the rehabilitation provisions of NRCS’s Small Watersheds Program, Silver Lake Flat Dam is eligible for rehabilitation funding due to its high hazard class and outdated infrastructure. This project is needed to rehabilitate the Silver Lake Flat Dam to meet current NRCS and Utah State Dam Safety regulations and current engineering standards. The need for the project is to extend the life of the dam for 71 years starting in 2017 to continue to provide economic benefit through the primary use of water storage. The purpose of the project is to continue to provide rural water supply for irrigation, recreation, and fish and wildlife uses, in a manner that minimizes the risk of loss of human life, is cost efficient, and environmentally acceptable. The preferred alternative includes the rehabilitation of the dam and replacement of the spillway in the same location. Rehabilitation of the dam would consist of measures to meet current NRCS and Utah Dam Safety regulations, current engineering standards and extend the life of the dam for 71 years starting in 2017. Rehabilitation of the dam would include installing new riprap on the upstream face, placing additional fill on the downstream face for stability, raising the auxiliary spillway elevation 2.5 feet, replacing the existing spillway, installing new toe drains, replacing two low-level outlet gates, installing a seepage monitoring system, clearing vegetation around the dam and reservoir, and installing improvements to the dam access road for construction equipment access. The estimated construction cost for the rehabilitation of the dam is $3,538,000. Comments: NRCS has completed this Draft Plan-EA in accordance with the National Environmental Policy Act (NEPA). Reviewers should provide their comments to NRCS during the allotted Draft Plan- EA review period. Comments need to be submitted by September 25, 2013. Please send comments to: Greg Allington – McMillen, LLC 1401 Shoreline Dr. Boise, ID 83616 (208) 342-4214 office / (208) 342-4216 fax [email protected] Draft Plan-EA August 2013 NRCS Silver Lake Flat Dam Rehabilitation Non-Discrimination Statement: The U.S. Department of Agriculture (USDA) prohibits discrimination against its customers. If you believe you have experienced discrimination when obtaining services from USDA, participating in a USDA program, or participating in a program that receives financial assistance from USDA, you may file a complaint with USDA. Information about how to file a discrimination complaint is available from the Office of the Assistant Secretary for Civil Rights. USDA prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex (including gender identity and expression), marital status, familial status, parental status, religion, sexual orientation, political beliefs, genetic information, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) To file a complaint of discrimination, complete, sign, and mail a program discrimination complaint form, available at any USDA office location or online at www.ascr.usda.gov, or write to: USDA Office of the Assistant Secretary for Civil Rights 1400 Independence Avenue, SW. Washington, DC 20250-9410 Or call toll free at (866) 632-9992 (voice) to obtain additional information, the appropriate office or to request documents. Individuals who are deaf, hard of hearing, or have speech disabilities may contact USDA through the Federal Relay service at (800) 877-8339 or (800) 845-6136 (in Spanish). USDA is an equal opportunity provider, employer, and lender. Persons with disabilities who require alternative means for communication of program information (e.g., Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). Draft Plan-EA August 2013 NRCS Silver Lake Flat Dam Rehabilitation SUPPLEMENTAL WATERSHED PLAN AGREEMENT NO. 9 (TO BE INCLUDED IN FINAL PLAN-EA) Draft Plan-EA August 2013 NRCS Silver Lake Flat Dam Rehabilitation TABLE OF CONTENTS SUMMARY OFFICE OF MANAGEMENT AND BUDGET FACT SHEET ................................................. S-1 S.1 Project Title .................................................................................................................... S-1 S.2 County, State .................................................................................................................. S-1 S.3 Congressional District .................................................................................................... S-1 S.4 Sponsoring Local Organizations .................................................................................... S-1 S.5 Authority ........................................................................................................................ S-1 S.6 Cooperating Agency ....................................................................................................... S-1 S.7 Purpose and Need for Action ......................................................................................... S-1 S.8 Description of the Preferred Alternative ........................................................................ S-2 S.9 Resource Information ..................................................................................................... S-2 S.10 Alternative Plans Considered ......................................................................................... S-3 S.11 Project Costs by Purpose and Funding Source ............................................................... S-3 S.12 Project Benefits .............................................................................................................. S-3 S.13 Net Economic Benefits ................................................................................................... S-3 S.14 Period of Analysis .......................................................................................................... S-4 S.15 Project Life ..................................................................................................................... S-4 S.17 Major Conclusions ......................................................................................................... S-6 S.18 Areas of Controversy and Issues to be Resolved ........................................................... S-6 CHAPTER 1.0 INTRODUCTION ........................................................................................................ 1-1 1.0 Introduction .................................................................................................................... 1-1 1.1 Purpose and Need Statement .......................................................................................... 1-1 1.2 Scope of Draft Plan-EA .................................................................................................. 1-2 1.3 Project Background ........................................................................................................ 1-3 1.4 Project Area and Existing Dam Conditions ................................................................... 1-4 CHAPTER 2.0 AFFECTED ENVIRONMENT ....................................................................................... 2-1 2.1 Climate ........................................................................................................................... 2-1 2.1.1 Silver Lake Flat Dam Local Climate .............................................................................. 2-1 2.2 Geology and Soils .........................................................................................................