Coulee Dam Wastewater Treatment Plant Improvement

Varela improves wastewater treatment for Coulee Dam and vicinity

The City of Coulee Dam’s wastewater treatment facility was constructed in 1970, with a major upgrade in 1976.

The facility served not only the residents of Coulee Dam, but also of Elmer City, and the residents of the developments of Lone Pine, Grandview Village, and Riverview as well as the U.S. Bureau of Reclamation complex.

The facility is regulated by the Environmental Protection Agency rather than the Washington State Department of Ecology because it is located within the boundaries of the Confederated Colville Tribes Reservation.

Initial Facility Planning efforts addressed aging equipment, manpower-intensive processes, and standards for redundancy and reliability.

The City worked with Varela to implement and construct a new extended aeration treatment system. Other components included a screwpress biosolids dewatering system, ultraviolet disinfection, and headworks screening.

Residents and businesses around Coulee Dam now benefit from a more efficient wastewater treatment facility with increased capacity, effective pretreatment, better disinfection, and less troublesome disposal of solid matter.

Treatment improvements and scope included:

• 0.195 MGD average and 0.72 MGD peak hour wastewater influent capacity
• Preliminary treatment improvements facility with fine screening
• Anoxic selector tanks for conditioning existing activated sludge prior to treating the influent wastewater
• 165,000 gallon aeration basin, oxidation ditch with fine bubble diffusers
• Ultraviolet disinfection system
• FKC Screwpress for dewatering biosolids.