King County to replace aging Lincoln Park sewer line

King County will start a four-month construction project this weekend to replace more than a mile of sewer line that runs through West Seattle's Lincoln Park. The aging line was damaged after heavy rains and high flows on Jan. 17 and Feb. 6, causing sewage leaks in Lincoln Park.

The county is moving quickly to replace the 50-year-old line after Wastewater Treatment Division inspectors discovered extensive wear and corrosion throughout much of the pipe, which pushes wastewater from the Barton Street Pump Station north of the Fauntleroy ferry dock through a 6,250-foot pipeline to the county's Murray Avenue Pump Station at Lowman Beach Park.

To keep the system operating normally during construction, crews installed a temporary 6,000-foot-long, 18-inch-diameter surface pipeline along the beach. The pipeline will carry wastewater from an interim pumping facility at Barton to a manhole south of Lowman Park where it will be discharged back into the system and go to the West Point Treatment Plant in Seattle.

When the temporary pipe and pumping station begin operating this weekend, the county will no longer need to bypass the damaged line using trucks to haul wastewater from Barton to the Alki Treatment Plant. The temporary pipe will also enable the county to stop bypassing about a million gallons of wastewater a day to an outfall in Puget Sound, which will protect water quality.

Contractors will begin permanent repairs next week. Installation of a new, 24-inch plastic pipe inside the existing line will take about a month to complete. Lining the old pipe is more efficient and cost-effective because the old pipe will not need to be dug out and removed.

When the pipe lining work is finished, the system will once again begin normal operations and the temporary pipe along the beach will be removed.

But because the new pipe lining will restrict capacity, King County will need to spend three additional months installing a second 24-inch pipe that will run parallel to the newly repaired line. Two pipes will add enough capacity to increase system reliability, and allow periodic inspections of each of the pipes.

Contractors will begin trenching along the beach in March, starting from the south end of Lincoln Park heading north. King County and City of Seattle Parks and Recreation are coordinating efforts to get the work finished as quickly as possible.

The county will also be holding meetings with neighborhood groups and the public to answer questions and address concerns.

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 more than 40 years.