Cascade Water Alliance plans switch to Tacoma supply; city briefed on long‑range pipeline costs and timeline
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Summary
Issaquah’s mayor told the council that Cascade Water Alliance expects to enter a wholesale contract with Tacoma Public Utilities; the change shifts timing for a transmission main and delays the need for a Lake Tapps treatment plant into the 2060s, but carries an estimated $700 million transmission cost and other implementation steps.
The Issaquah mayor reported at the Jan. 7 council meeting that Cascade Water Alliance is prepared to enter a contract with Tacoma Public Utilities (TPU) after multiyear negotiations with both Seattle Public Utilities and Tacoma.
Under the proposed arrangement, Cascade would receive 15 million gallons per day immediately under a wholesale agreement and could obtain an additional roughly 12 million gallons per day under a temporary market price contract phased in between 2041 and 2062. The mayor said TPU’s water is fluoridated and meets current quality standards.
The proposed TPU contract would require construction of a transmission main from Tacoma to Cascade’s system earlier than previously planned. The mayor estimated the transmission main construction would be undertaken in the 2030s and cost approximately $700 million. Cascade forecasts the need to add eight full‑time employees to plan, build and maintain the new pipeline and related infrastructure. The shift to TPU would allow the Lake Tapps water treatment plant project to be delayed to the 2060s under current demand projections.
Why it matters: The wholesale supplier change affects long‑term infrastructure timing, regional planning and costs that Cascade members will need to address. The proposed transmission main is a large, multi‑jurisdictional capital project with significant planning and financing implications.