HDR Engineering Inc 7/9/2019 - Laserfiche WebLink

FYR (developed by the Civil and Environmental Engineering Department at the University of Washington). • The subconsultant will use these new runoff projections in the Everett Yield Analysis Model to simulate municipal water supply, downstream flows for fish, transmission infrastructure, and hydropower generation provided by Spada Reservoir. • Safe yield will be evaluated for three scenarios (similar to those evaluated in the 2007 CWP): - Unconstrained Yield -This scenario investigates the amount of water available to Everett when Spada is operated with water supply as the priority. The yield is constrained by the natural inflows of the Sultan River, the available capacity in Spada Reservoir, and existing instream flow requirements for fish. In this scenario, Spada Reservoir can be drawn down to the level of 1,240 feet. - Yield Constrained by Transmission Upstream of Chaplain Reservoir-This scenario investigates the amount of water available to Everett when Spada is operated with water supply as the priority. The yield is constrained by the natural inflows of the Sultan River, available capacity in Spada Reservoir, existing instream flow requirements, and the flow capacities of Tunnel #1 (from the Diversion Dam to Chaplain Reservoir), pipeline to Chaplain Reservoir, and Blue Mountain Tunnel (from Jackson Powerhouse to Chaplain Reservoir). In this scenario, Spada Reservoir can be drawn down to the level of 1,240 feet. - Yield Constrained by Hydropower Operations and Spada Minimum Elevation of 1,380 ft-This scenario investigates the amount of water available to Everett when Spada is operated with hydropower as the priority. The yield is constrained by natural inflows of the Sultan River, available capacity in Spada Reservoir, existing instream flow requirements, the flow capacities of Tunnel#1, the pipeline to Chaplain Reservoir, and Blue Mountain Tunnel, and a minimum pool level in Spada Reservoir of 1,380 feet. • HDR will review results and conclusions from recent regional climate change influenced water supply yield studies in the region, including the Tacoma Integrated Resource Plan and the Central Puget Sound Forum Regional Resiliency Project. • HDR and its subconsultant will conduct a one-half day workshop with Everett staff. The focus of the workshop will be how the updated safe yield results differ from the 2007 analysis with respect to Everett water supply, changes in projected demand, and instream flow requirements. During this workshop, the team will agree on conclusions related to the safe yield of the system. 2. The subconsultant will assist HDR in preparing a draft memorandum outlining the process and findings for City review and comment. 3. HDR will Incorporate the City's review comments into a final technical memorandum. 9.3 City Responsibilities 1. Provide input based on Everett's participation in the Forum's Regional Resiliency Project. Provide relevant data in the City's possession, and seek data as needed from the Snohomish County PUD. Everett Comprehensive Water Plan June 12, 2019 Exhibit A—Scope of Services Page 13 of 30