The Wastewater Division of the City of Ellensburg's Public Works Department operates and maintains seventy-seven miles of underground sewer pipe. This extensive piping system serves over 5,100 residential and almost 500 non-residential customers by managing wastewater flows from sinks, showers and bathing, dish and clothes washers, toilets, and industrial processes. Wastewater flows from homes and businesses through sewer pipes that lead to the Wastewater Treatment Plant. The Wastewater Treatment Plant processes an average of 3.85 million gallons of wastewater each day.
The Wastewater Treatment Plant is governed by a wastewater permit issued by the Washington State Department of Ecology.