For eight months a 100-foot portion of Burnett Avenue North, that connects with North Sixth Street, will be closed for rehabilitating old corroded sewage pipe operated by King County.
A large eight-foot-wide sewer under Logan Avenue in Renton, that carries wastewater from everywhere along Lake Washington south of Kirkland, is in serious need of new lining to extend the life of the pipes. The project is estimated to cost $32 million, paid for and constructed by King County.
The closure of Burnett Avenue North is for an excavation pit to aligning a temporary bypass with the end of the sewer line. That bypass will be above ground and near the Renton Landing, behind a screen wall.
Councilmember Ryan McIrvin remarked at the transportation meeting on April 1 how the closure is probably a lot smaller than it could have been, since the line runs under Logan Avenue.
There’s also a few small closures around manholes on Logan Avenue along the sewer line expected in the coming months, according to King County.
The 3,700 feet of pipe carries the sewage to the King County South Treatment Plant in Renton. The pipe, called the Eastside Interceptor, was constructed in 1962.
King County staff informed Renton city council of the project at Committee of the Whole in August 2018. At that meeting, King County staff showed Renton city councilmembers photos of the steel that reinforces the pipe, which is exposed due to corrosion.
This lining is anticipated to extend the life of the sewer by 50 years or more, according to King County.
The project requires a large sewer bypass for the volume that usually flows through the pipe, which will be able to carry 45 million gallons a day. The pipe goes along Boeing property and then installed into the bike lane on the west side of Logan Avenue, protected by Jersey barriers.
Alternate bike and pedestrian routes will be posted, said Norm Mah, spokesperson with King County Wastewater Treatment Division.
Mah said about 75 percent of the bypass will be above ground, the rest being under intersections, driveways and travel lanes.
Councilmember Randy Corman was surprised at the Transportation Committee meeting April 1 that a bypass could handle the capacity for thousands of homes’ sewage.
Mah said in an email that the bypass system is made to handle average rainfall of the last four summers. He said that King County staff will monitor rainfall and have methods of switching back to the Eastside Interceptor should rain exceed the limits on the bypass.
The bypass is also pressurized, according to both city staff at that meeting and Mah, so the velocity will mean less volume in the tubes at any given time.
Corman asked city staff to double check the safety of the project to make sure the bypass could handle that level of flow and not be exposed to outside circumstances, such as a car crash colliding with the above-ground line.
Mah said the bypass pipe will be at 25 percent of its pressurized capacity and that aside from traffic barriers, King County staff will monitor on-site 24/7 during operation to protect from such a collision.
The project will happen in four phases: staging the construction area, installing the bypass for two months, installation of the new lining for four months, and then two months of bypass removal.
Noise and odor concerns have been posed throughout the project. Mah said these are primary considerations in using electric systems wherever possible, the screen wall, and additional noise mitigation measures that will be implemented as necessary.
According to the King County page on the project, there may be instances where people notice odors and noise.
The pumps for the bypass will also be electric, instead of diesel.
Mah also said mobile odor units will be able to provide temporary odor management along the project’s length.
“The County will be available to address any community member concerns and implement additional measures as the need arises,” Mah said.
Renton Public Works Administrator Greg Zimmerman said during the city transportation meeting they will make sure other businesses and residents are aware of the work closing 100 feet of Burnett Avenue. He said they’ve been working closely with King County on this project.
This is a two-part project, the first of which was completed in 1988. More information is available here.