skip to main content

Wastewater Treatment

King County, Washington

For questions about the Wastewater Treatment Division website, please send an e-mail message or contact us at:

King Street Center
201 S. Jackson St., Suite 500
Seattle, WA 98104-3855
Phone: 206-477-5371
Fax: 206-684-1741
Telecommunication device for the deaf (TTY): 711

Get Directions to our office location in Seattle, Washington.

Staff Contacts

History of Puget Sound Beach CSO Control Projects

Project Planning Phase (2007-2010)

Murray CSO Control Project

March 2012 Update
Design on the Murray CSO Control project began in 2011.
>> For current information on this project, view HERE.

Learn more about the decision process and recommended proposal completed in 2010.

Why are CSOs a problem at Murray?

Like many cities around the country, the older parts of King County's wastewater system carry both wastewater and stormwater to the treatment plant. When heavy rains fill the pipes, excess stormwater and sewage flow directly into Puget Sound near the Murray Pump Station. These events, called combined sewer overflows, or CSOs, help to avoid sewer backups into homes and businesses and onto streets during storms, but they are a public health and environmental concern. When a CSO happens, about 90 percent of the overflow is stormwater and the rest is dilute sewage.

In 2008, King County reported that the Murray CSO facility has five overflows per year on average that discharge a total of five million gallons into Puget Sound off Lowman beach.

King County's goal is to reduce the number of CSOs each year, with a long-term goal of no more than one untreated discharge per location per year on average to meet state regulations.

Proposed project

Murray CSO basin project area -- underground storageKing County recommends a project for combined sewer overflow (CSO) control in Murray

King County plans to design and build a storage tank beneath private property across from Seattle’s Lowman Beach Park. This facility will be designed to store approximately 1 million gallons of combined stormwater and wastewater during heavy rain when the Murray Pump Station may reach maximum capacity. After storms have passed, an underground pump will transfer stored flows to the pump station for conveyance to King County’s West Point Treatment Plant. This facility will reduce combined sewer overflows to Puget Sound off Lowman Beach Park.


Learn more about the project schedule.

New project web page

Contact us

Related information

Upgrades needed to Murray Avenue Pump Station
Murray Avenue Pump Station 
King County has operated the Murray Avenue Pump Station and sewer facilities for more than 40 years. This pump station is no longer considered reliable. It lacks backup generators to keep the pumps working during power outages, and it has no odor control. If equipment fails, raw sewage could flow onto the beach and into Puget Sound. Learn more about the Murray Avenue Pump Station Upgrade project.