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Project update

February 28, 2017

With the excavation complete and concrete pours underway, the project is halfway done!

King County contractors finished excavating the tank area at the intersection of S. Hanford St. and S. 27th Ave. S. in mid-January. The resulting hole is 50 feet deep – big enough to house the facility’s 340,000 gallon underground storage tank. The tank will help reduce overflows of sewage and stormwater into Puget Sound during heavy rains. Read more

Upcoming construction activity

Beginning as early as March 6th, King County’s contractors will begin to install a 30 foot pipe under S. Hanford St. They will be using a technique called pipe ramming, in which compressed air is used to drive a hammer that pushes or ‘rams’ a pipe through the ground. The pipe will be rammed in three sections with a break after each, during which the contractor will weld the sections of pipe together. The pipe ramming of each section will take about an hour and the complete installation of the pipe should take approximately 4 days in total.

King County’s contractor pours the concrete base slab of the new Rainier Valley storage tank.King County’s contractor pours the concrete base slab of the new Rainier Valley storage tank.


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Contact Caryn Sengupta at:


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To learn more about how we installed pipe under Rainier Ave. S. without having to close the road for long periods of time, watch this video on microtunneling.

Combined sewer systemWhy does sewage overflow on the rainiest days?

Project description

This project will keep sewage and stormwater out of the Duwamish River. A new sewer pipe will be installed near the intersection of Rainier Avenue South and South Bayview Street to send sewage and stormwater from a pipe that gets full during storms to another pipe that has more room. 

A storage tank at the intersection of South Hanford Street and South 27th Avenue will catch any remaining extra sewage and stormwater to keep sewage and stormwater out of the Duwamish River. 

New and reused pipe at S. Bayview St.New and reused pipe at South Bayview Street (  , May 2014)

new storage tank at S. Hanford St.Underground storage tank at South Hanford Street (  , May 2015)

Project schedule

Project scheduleProject schedule (  , May 2015)

Project location


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