Walla Walla to Overhaul $10M Wastewater Treatment Plant

Aging infrastructure at the city's treatment facility will be replaced over the next year.

Published on Mar. 4, 2026

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The city of Walla Walla, Washington is moving forward with a $10 million overhaul of its wastewater treatment plant. The project will focus on rehabilitating two primary digesters, replacing the facility's boilers, and installing a new waste burner to manage excess biogas.

Why it matters

The wastewater treatment plant is critical infrastructure for the city, and the upgrades will help extend the life of the aging facility, improve efficiency, and reduce environmental impacts through the use of captured biogas.

The details

The project will replace mixing and heating systems in the plant's two primary digesters, which have become corroded after over two decades of use. New protective coatings will also be applied. The facility's boilers will be replaced with a system that can use the plant's own biogas as a primary fuel source, and a new waste burner will be installed to manage excess gas.

  • The project is currently 90% through the design phase.
  • Construction is scheduled to run from July 2026 to July 2027.

The players

City of Walla Walla

The local government overseeing the wastewater treatment plant upgrades.

Washington State Department of Ecology

Providing a $7 million loan to fund the project.

Washington Public Works Board

Providing additional financial support for the wastewater treatment plant overhaul.

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What’s next

Construction on the $10 million wastewater treatment plant overhaul is scheduled to begin in July 2026 and be completed by July 2027.

The takeaway

The city of Walla Walla is making critical investments to modernize its aging wastewater treatment infrastructure, which will improve efficiency, reduce environmental impacts, and extend the life of this essential public utility.