Transmission and Supply Plan (2011)
The Cascade Water Alliance has issued its draft Transmission and Supply Plan (TSP) which fulfills Cascade’s responsibility to submit a water system plan to the state. In addition, the plan supplements information on regional water supply provided by each of its members in their respective water system plans. The plan describes Cascade’s current water supplies and operations and also its future plans for development of additional water supplies.
Cascade is a public, non-profit corporation comprised of eight member cities and special districts within King County. This includes the cities of Bellevue, Issaquah, Kirkland, Redmond and Tukwila and the Covington Water District, the Sammamish Plateau Water and Sewer District and the Skyway Water and Sewer District. It serves about 400,000 residents and more than 22,000 businesses.
As outlined in the TSP, Cascade currently contracts with the Seattle Public Utilities (SPU) for delivery of water to seven of its eight members. This water will decline over time beginning in 2024. Cascade’s existing capital facilities for delivery of municipal water supplies consist solely of the Bellevue-Issaquah Pipeline. Individual members own operate and maintain their own water distribution systems. Five of the eight have their own independent supplies. It is anticipated that the current mix of supplies will meet member needs through 2023.
“In recent years, the downturn in housing and economic activity has affected demands for water throughout the Puget Sound region, and this effect is expected to persist for the next several years. This is a change from past planning efforts when rapid growth was occurring,” says Lloyd Warren, chair of the Cascade Board of Directors. “This, coupled with our conservation efforts, means the demand for water in Cascade’s service area is forecast to remain constant through 2020 at about 40 million gallons per day. After that, the demand begins to rise again.”
After evaluating a wide range of water supply options (about 27) to meet long term needs, the preferred and recommended supply portfolio is:
- Continued production from member supplies serving their respective service areas;
- Continued use of water from Seattle Public Utilities under the block contract;
- Beginning in 2024, deliver of Green River supply from Tacoma Public Utilities (TPU);
- Beginning in 2024 additional Green River supply from Covington Water District’s share in the Regional Water Supply System (formerly the Tacoma second Supply Project) over and above water used within that district’s own service area; and
- Beginning in 2030 or as needed, water from Cascade’s planned Lake Tapps Municipal Water Supply project.
Click here to view:
TSP Executive Summary
Transmission and Supply Plan
TSP Appendices
SEPA DNS and checklist
The results of Cascade's demand projection and supply alternative process can be viewed in materials presented to the Connections Working Group.
