King County celebrates final major clean-water project for ending overflows into Lake Washington

2005 Archived News

After more than three years of construction, King County today celebrated with the Rainier Beach community completion of its last major clean-water project to control overflows of untreated stormwater and sewage into Lake Washington.

The $77 million "Henderson/Martin Luther King Combined Sewer Overflow (CSO) Project" features a giant 15-foot-diameter pipe that will hold millions of gallons of dirty water until it can be treated and will significantly reduce untreated discharges of combined stormwater and sewage.

Before this project, rainy weather contributed to 30 million to 60 million gallons of combined waste and stormwater overflowing to Lake Washington every year from King County combined sewer overflows.

"With the project complete, CSOs will be dramatically reduced, and our beaches will be cleaner and safer," said King County Executive Ron Sims. "Completing this project upholds a clean-water legacy that residents established when they founded our regional wastewater treatment utility more than 40 years ago. These new facilities will add safeguards to protect water quality as we increase our attention on restoring Puget Sound. "

Sims thanked the Rainier Beach community, including neighboring Rainier Beach High School, for its patience and help during construction activities.

Along with helping to protect the water quality of Lake Washington, the completed project provides many needed improvements to the Rainier Beach sewer system, much of which is more than 50 years old. The project includes more than two miles of tunnels and pipelines and expands the Henderson Pump Station and flow regulator facilities. Improvements include:

• The Henderson Pump Station can now push more than 20 million gallons a day of combined stormwater and wastewater away from Lake Washington.
• The package of pipelines tunneled and trenched along South Henderson Street and South Norfolk Street run from the shore of Lake Washington, beneath Martin Luther King Jr. Way South, under Interstate 5 and below the railroad tracks south of the King County International Airport.
• The huge 15-foot-diameter Beacon Hill Tunnel running two-thirds of a mile under 42nd Avenue South allows for critical storage and treatment.
• Two flow-regulator facilities at each end of the Beacon Hill Tunnel control water entering and leaving the storage facility.

During storms, the new tunnel under Beacon Hill can hold 4 million gallons of dirty water. After the storm settles down, the system will send flows to either the West Point Treatment Plant in Seattle or the South Treatment Plant in Renton. The tunnel runs two-thirds of a mile at depths of 30 to 100 feet beneath 42nd Avenue South.

"Here and in other older areas of Seattle, sewers were built to carry both sewage and stormwater. During wet weather, the stormwater overwhelms these combined sewers, and that causes overflows to our waterways," said Sims. "Our new CSO control system will reduce both the volume and the frequency of untreated flows into Lake Washington. Because of these new facilities, Lake Washington will be cleaner and healthier for the Rainier Beach community and the rest of our region to enjoy for generations to come.

In addition to the Rainier Beach neighbors, Sims also thanked the businesses of the Norfolk Industrial Park, and construction and design firms HDR Engineering, Jacobs Civil, and Tri-State Construction, NW Boring/Kenny JV, and Strider Construction. He also thanked Wastewater Treatment Division Project Manager Rick Andrews, Director Don Theiler and Capital Improvement Manager Christie True.

More information about the project is available on the county Web site: http://dnr.metrokc.gov/wtd/henderson-cso/. For high resolution photographs of project construction, click on: http://dnr.metrokc.gov/wtd/henderson-cso/drawings_photos.htm.

King County's Wastewater Treatment Division protects public health and water quality by serving 17 cities, 17 local sewer utilities and more than 1.4 million residents in King, Snohomish and Pierce counties. Formerly called Metro, the regional clean-water agency now operated by King County has been preventing water pollution for 40 years.