Water Supply Overview

Transmission & Supply Plan (TSP) Overview

Cascade is in the process of extending its existing Transmission and Supply Plan that was originally adopted in July 2012, fulfilling Cascade’s responsibility to the Washington State Department of Health (DOH). It supplements information on regional supply provided by each of its members in their respective individual water system plans. The plan describes Cascade’s current water supplies and operations and also its plans for development of additional water supplies to meet the needs of Cascade members through 2060. The Cascade TSP was approved by the King County Council in February 2013 and by DOH in March 2013.

Cascade has wholesale water purchase contracts with Seattle Public Utilities (SPU) and Tacoma Public Utilities (TPU). Cascade anticipates that the current mix of wholesale purchases and member independent supplies will meet all member needs for decades to come.

Cascade’s regional water service area coincides with the individual service areas of its members. Individual Cascade members are Cascade’s source of quality. Each member owns, operates and maintains its own water distribution systems, including water treatment for their independent water sources (five members have their own independent supplies), maintenance of water quality within their reservoirs and distribution systems; and local monitoring of water quality conditions (some monitoring is shared with SPU or other water systems). At this time Cascade’s existing capital facilities for delivery of municipal water supplies consist solely of the Bellevue-Issaquah Pipeline (BIP) which provides transmission of water purchased from SPU to Issaquah and
Sammamish Plateau. Cascade has agreements with the Cities of Bellevue and Sammamish for operating and maintaining the BIP.

Cascade administers regional water conservation services on behalf of its members. The 2014-2019 Conservation Program has a goal of achieving water savings of 0.6 million gallons per day (mgd) in terms of annual average consumption and 1 mgd during the peak season.

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