The Dalles Wastewater Treatment Plant Expansion

Mortenson Construction and Kennedy/Jenks are the progressive design/build team for the upgrade of the City of The Dalles Wastewater Treatment Plant. The project will provide firm capacity at the Influent Pump Station, a new Headworks facility including Grit Chamber, Bar Screens, and Primary Filtration. Also as part of the project, the team will design and construct a new 210,000-gallon Anaerobic Digester, and micro-turbine which will provide heat and power for the plant thru renewable digester gas. With the plant’s location so close to the city center the team will provide aesthetic improvements creating an artistic barrier.

Project Description:

In January of 2016, Mortenson Construction and Kennedy/Jenks were awarded the $9 million Progressive Design-Build project for the City of The Dalles Wastewater Treatment Facility.

The project will provide for the design and construction of a new influent pump station, plant headworks facility, conversion of an existing 180,000-gallon biosolids storage vessel (Digester #2) with a floating cover into an anaerobic digester with a fixed roof, and aesthetic improvements to the treatment facility.

Currently, the plant provides secondary treatment and ultraviolet (UV) disinfection followed by discharge to the Columbia River. Current dry weather flows range from 2.3-4.15 million gallons per day (MGD) with a current Peak Instantaneous Flow (PIF) of 7.7 MGD. As the facility expands, PIF flows are projected to be 10.8 MGD in 2022, 11.9 MGD in 2030, and 13.2 MGD at buildout.