Murray CSO Control Project

King County to begin the alternatives selection process for CSO Control in the Murray basin

To protect Puget Sound and public health, King County is identifying CSO control options for Barton, Murray, North Beach, and South Magnolia. These locations are top priority because people are most likely to come in contact with water during recreational activities such as swimming.

Barton and Murray Pump Station CSO Project Areas
Murray CSO basin area (located north of the Barton CSO basin area)

King County has identified several approaches to CSO control for these projects. These include the following:

Conveyance/treatment --Sending flows from the basin to a regional treatment plant.
Storage --Retaining flows during storms to prevent CSOs. Following the storm event, flows are sent for secondary treatment following the event.
On-site treatment --Providing primary treatment for flows exceeding system capacity during large storms.
Demand management (stormwater flow reduction) --Implementing one or more methods of limiting stormwater flow into the sewer system.
Combination of approaches--These options can be used alone or in combination, depending on local conditions at North Beach.

Beginning fall 2009, King County’s CSO Beach Project team will begin work to evaluate alternatives, approaches combined with potential sites, for CSO Control projects in all four basins.

Why are CSOs a problem at Murray?

Like many cities around the country (external link), 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 Barton and Murray Pump Stations. 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. These discharges are called combined sewer overflows or CSOs. When this happens, about 90 percent of the overflow is stormwater and the rest is dilute sewage.

On a 7-year average, Murray has five overflows per year 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 less than one untreated discharge per location per year to meet state regulations. The county is in the process of identifying CSO control approaches for Barton and Murray in West Seattle as well as for two other locations on Puget Sound: South Magnolia and North Beach. These locations are top priority because people are most likely to come in contact with water during recreational activities such as swimming.

Schedule

Evaluate alternatives for CSO control: 2009-2010
Alternative selection and environmental review: December, 2010
Final design & permitting: 2011-2013
Construction: Begins late 2013

How you can participate in the alternatives selection process

Check the Web – People can watch this Web page for updated information and announcements of community meetings
Sign up for updates – You can join our listserv to get notices when community meetings and updates are posted for each basin
Give us your input – Learn about alternatives being developed for each basin and provide input during the selection process

Related information

Upgrades needed to Murray Avenue Pump Station
Murray Ave Pump Station Upgrade
Upgrading the Murray Avenue Pump Station will help alleviate some CSO volumes. 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 emergency 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. Moreover, capacity may be inadequate for future demand. Learn more about the Murray Avenue Pump Station Upgrade project.