Regional Wastewater System Biofilter Project

This project will construct an improved and cost-efficient system for effectively reducing sewer odors and preventing corrosion in manholes and sewer pipes.

Project Overview

Two independent sewer pipelines that serve the City of Battle Ground and over 7,300 homes in Clark County merge into a single pipeline along Salmon Creek Avenue. These pipelines generate odors that are currently being mitigated using several different treatment processes.

This project will construct a new biofilter that incorporates the latest technology to collect and treat the odorous air and minimize long term corrosion. Engineered biofilter media and a new air line connection to the sewer pipes will greatly increase the effectiveness of the new filter. The new filter will replace the existing facility south of Salmon Creek Avenue and east of Interstate 205.

The biofilter is estimated to save $200,000 to $250,000 in operation costs annually.

What is a Biofilter?

The biofilter is a “living system” that treats odors from the sewer and helps prevent corrosion. A fan pulls air from the sewer and pushes it through an engineered media — porous rock covered in a thin layer of bacteria that breaks down unpleasant odors in the air. Biofilter systems cost less than other odor control methods, are easy to maintain, and extend the life of the sewer by reducing corrosion.

Biofilter Benefits

  • Enhances the efficiency and effectiveness of foul air treatment.
  • Provides a permanent solution that requires little maintenance.
  • Reduces annual costs for odor control.
  • Provides a redundant system for the control of odors.

Project area.

This biofilter treats odors from air drawn out of the sewer.


In 2014, the Alliance adopted a comprehensive Capital Plan that brings the partners’ facility assets, including the regional biofilter, under Alliance ownership. Costs for the regional biofilter are covered in the Capital Plan. In total, the project is anticipated to cost $1.2 million.

Construction Impacts

Traffic - Construction will take place in two locations along NE Salmon Creek Avenue: at the entrance of Liberty Bible Church, just east of the I-205 overpass; and at NE 127th Street. Work at each location is expected to last approximately one week.

Odor - During the acclimation and testing period (Winter of 2017–2018) fugitive odors may escape. Report any related odors to us via e-mail at


Biofilter installation.

Project Schedule

Contact Us to Learn More

Adrienne DeDona, Public Outreach Manager
(360) 903-4792

Updated August 2017