Salmon Creek Treatment Plant Improvements Project

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 and improve odor control and operational reliability 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.

As our community grows, we will need to expand the plant’s capacity to meet the increasing flow of wastewater. Improvements will also be made to the odor control systems and several areas of the in-plant mechanical systems to keep the facility current with regulatory requirements and in good working order.

Increase in Treatment Capacity

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. Some older structures 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.

Odor Control

These improvements will also include installing a new odor control system, which involves collecting air from the first two treatment processes and adding biotrickling filters that treat the air. These methods have proven very effective in reducing odors. In order to help collect the air, aluminum covers will be added over the Primary Clarifiers.

Columbia River Outfall and Effluent Pipeline Project Map


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. The operations and maintenance costs associated with power and general maintenance for the odor control system will be factored into the annual operating costs for the plant. In total, the project is anticipated to cost approximately $24 million. Those costs are allocated to the two funding members of the Alliance partnership – the City of Battle Ground and the Clark Regional Wastewater District. The City and the District, in turn, make the final decisions on what rate and charge structures are appropriate for their customers in paying for the project. The City and District have included the project costs in long range financial planning efforts to ensure overall affordability of rates and charges for everyone.

Project Timeline

There is a great deal that needs to be completed before construction can begin, including detailed design and engineering, acquisition of the necessary permits, and selecting a construction contractor through a competitive bid process.

Project Timeline

Project Documents

Contact Us

For more information contact Adrienne DeDona, Public Outreach Manager, at (360) 903-4792 or

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