Water Supply Overview

Transmission & Supply Plan (TSP) Overview

Cascade’s 2019 Transmission and Supply Plan Extension updates the 2012 Transmission and Supply Plan, which describes Cascades current water supplies and operations and development of additional water supplies to meet the needs of Cascade members through 2060. The 2019 Transmission and Supply Plan Extension says no significant changes are expected, and forecasts indicate sufficient water supply to meet current and future needs.

Download the 2019 Transmission and Supply Plan Extension

Download the 2012 Transmission and Supply Plan

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 Bellevue and Sammamish for operating and maintaining the BIP.

Cascade administers regional water conservation services on behalf of its members. The 2019-2022 Conservation Program has a goal of achieving water savings of 0.4 million gallons per day (mgd) in terms of annual average consumption.