Salmon Creek Treatment Plant Secondary Treatment Improvements

The treatment plant is a vital part of the wastewater system – safeguarding public health, environmental quality, and our community’s economic future. This project will provide for a planned increase in treatment capacity for the facility.

Project Overview

The Salmon Creek Wastewater Treatment Plant receives and treats roughly 8–10 million gallons of wastewater per day from homes and businesses. All wastewater received at the plant is treated to a high standard before clean water, or effluent, is conveyed and discharged into the Columbia River.

The information in this web page is also available as a fact sheet (PDF).

Secondary Treatment Process Improvements

As part of this project, the Alliance will expand the biological treatment process to increase the plant’s treatment capacity from approximately 15 million gallons per day to 17.5 million gallons per day within the existing facility footprint. This will be accomplished by constructing a new Aeration Basin and Secondary Clarifier in the middle portion of the plant and an older structure will need to be demolished to make space for these new facilities. In addition to these new structures, improvements to several mechanical pumping and air supply systems will be made inside existing buildings.

Salmon Creek Treatment Plant Secondary Treatment Improvements


Planning, design and construction costs for the project are covered in the Alliance’s Capital Plan, which includes funding for all long-range planning projects such as this one. In total, the project is anticipated to cost approximately $13 million. Those costs are allocated to the Alliance partners that share ownership of the facility – the City of Battle Ground and the Clark Regional Wastewater District.


Construction is slated to begin in 2022 and be completed sometime in 2024. There is a great deal that needs to be completed before construction can begin, including discussions with the Washington State Department of Ecology, detailed design and engineering, acquisition of the necessary permits, and selecting a construction contractor through a competitive bid process. Permitting and Design are ongoing, and should last into 2021.

Salmon Creek Phase 5 Program Delivery Timeline

Construction Impacts

Construction on capacity increasing projects at the treatment plant will begin in 2022, but work on new odor control systems and existing facilities improvements is scheduled to begin much earlier. As construction continues on from the previous projects, you may notice more frequent traffic carrying in workers and materials, with levels varying based on the work planned for any particular day. Construction management staff will be on-site to ensure that the Contractor is in compliance with County standards for hours of operation and noise. More information will be made available as the project design is completed toward the end of 2021.

Contact Us

Dale Lough, Alliance Capital Program Manager, can be contacted at (360) 993-8856, or

Project information can be provided in other formats or languages upon request.