About ESI 8

Project need

King County Wastewater Treatment Division protects public health and the environment by collecting and cleaning wastewater and recovers valuable resources for a thriving Puget Sound region. ESI 8 is breaking down due to age and corrosion and needs to be repaired to prevent failure, overflow, or disruption of service. Completing this project will support the reliability of a key part of the regional wastewater treatment system on the Eastside for 50 years to come.

See video footage and LiDAR scans 1, 2, and 3 of the pipe.

Maintaining sewer service during the repair

To repair ESI Section 8, all the sewage it carries (approximately 55 million gallons per day during the dry season) will be diverted into a temporary bypass pipe. This bypass pipe system will allow crews to work inside the existing pipe while maintaining sewer service to the community.

To limit disruptions to neighbors and commuters, the temporary bypass pipe will be installed at the ground surface along an inactive segment of the Eastside Rail Corridor (ERC) and will then cross below I-405 via a deep tunnel. The temporary system will reconnect with the standard wastewater system near Coal Creek Parkway, on the east side of I-405.

An example of an above-ground temporary bypass pipe system. This system is used to maintain services while pipes are rehabilitated. 

How we rehabilitate

After installing the temporary bypass pipe, we will then rehabilitate ESI 8 by “sliplining,” a rehabilitation method that pushes a slightly smaller reinforced pipe inside of the existing pipe. This method allows us to repair the pipeline without disturbing roads, trails, or sensitive environmental areas. The sliplining work will take place underground and won’t be visible to the public.

Construction crews inspect a new reinforced pipe as it is installed through a process called “sliplining.”

Most of the visible construction activity will take place at the north and south ESI 8 access points, staging areas, and along the temporary bypass pipe route (see map below). We will share more information about construction impacts before work begins.

We have an opportunity to implement a different contracting method that other agencies, including other King County Departments, have successfully used before. One key component of this delivery method is the early collaboration on constructability with the contractor.

Read more about it here.