TIC 2018-04-09 Item 2A - Agreement - Water Reservoir and Pump Station Study with Carollo Engineers

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Highline water district intertie Water district 75 intertie Water district #75 intertie EXHIBIT A CITY OF TUKWILA PRELIMINARY WATER RESERVOIR AND PUMP STATION FEASIBILITY STUDY The City of Tukwila (City) has proposed leasing storage from Highline Water District (Highline) rather than construct a City owned 1.3 MG reservoir and pump station, which was identified in the City's 2013 Comprehensive Water Plan. In 2014, the City and Carollo evaluated sites for a City owned reservoir and identified Cerini Hill (abandoned SWAT training facility) as the preferred location for the planned $7,180,000 reservoir and pump station. This study will consider the operational and cost effectiveness of leasing storage from Highline. • Carollo Engineers, Inc. will be referred to as "Consultant" in this document. • City of Tukwila will be referred to as "City" in this document. • Highline Water District will be referred to as "Highline" in this document. • The City will obtain water quality on Highline's finished water quality in electronic format. No water quality data will be collected. • No new water quality data will be collected as part of the study. • The 2013 Water System Plan hydraulic model will be used as the basis for the analysis. • The City will obtain costs for leasing storage from Highline. • All costs will be AACE Class V estimates. TASKS 1. Summarize Water Quality - Summarize finished water quality from Highline and the City. It is assumed the City will obtain the water quality data and provide it electronically. Compare water quality to primary and secondary drinking water standards. No mixing study or evaluating the corrosively either Highline or City water will be conducted as part of this work. However, the data will be reviewed to confirm data availability for a future study. Additional data collection will be recommended, if needed. 2. Purpose of Storage - Establish City's potential uses for the Highline reservoir (emergency storage, fire storage, equalizing, etc.). Estimate the frequency of use, volume of storage and flow rates required for each potential use. o Meeting No. 1 — Storage Uses - Review water quality and identify storage uses for leased reservoir with City staff. Establish criteria for hydraulic modeling and comparison of alternatives. o Meeting No. 3 — Highline Coordination - Meet with Highline Staff to discuss leasing storage. Review purpose of uses, potential operations, and known infrastructure challenges. Identify limitations by either Highline or the City. 3. System Analysis o Update hydraulic model - Update the hydraulic model to incorporate piping changes identified in the 2016 Pipeline Asset Management Update project. Develop potential PRV settings for the Highline intertie based on the potential storage uses. Update pw://Carollo/Documents/Client/WA/Tukwilaho933Aoo/Project Mgmt/Contracts/Tukwila Reservoir Analysis Scope of Work docx Page 1 of 2 8