Columbia-Pacific Northwest Region

Kachess Dam - Safety of Dams Modification Project Environmental Assessment

Questions and Answers

Aerial View of Kachess Reservoir, Washington

Is this environmental assessment related to the Kachess Drought Relief Pumping Plant (KDRPP) project?
The Kachess environmental assessment study is unrelated to KDRPP. The environmental assessment is a Safety of Dams study to reduce the risk of potential failure modes associated with internal erosion along the Kachess Dam outlet works conduit.

The KDRPP project is a surface-water supply project. Reclamation and the Washington State Department of Ecology are studying ways to improve water resources management in the Yakima River basin.

Will the proposed work at the dam impact my property?
We do not anticipate any impacts to property. Details of the exact work and impacts will be forthcoming once they are understood. Reclamation makes every effort possible to ensure there is clear and open communication with the public.

What is the safety concern at Kachess Dam?
Voids have formed along the outlet works as a result of internal erosion along the seepage path. Reclamation proposes to line the outlet works and to provide a filter for the seepage and a berm to weight the filter.

What is the schedule for the proposed modification?
Reclamation anticipates performing premodification work in 2023. Modification work will begin in 2024, and we anticipate concluding the work in 2026.

Who owns and operates Kachess Dam?
Reclamation owns and operates Kachess Dam.

When was the dam built?
The dam was originally constructed between 1910 and 1912.

What is an earth-fill dam?
An earth-fill dam (also known as an earthen dam) is its construction involves using materials obtained from earth and rock materials obtained from borrow areas located near the dam site.