Renton to abandon 54-year-old Kennydale sewer line

Published 11:30 am Thursday, March 26, 2026

The city of Renton will replace a 54-year-old underwater sewer line with a land-based system for Kennydale residents, protecting Lake Washington.

The city will pay Consor North America Inc. up to $1,240,033 for the construction management and inspection services for the Kennydale Lake Line Sewer system improvement project. The proposed project will discontinue the existing in-lake sewer main and transition to a new system on dry land consisting of mains served by individual grinder pump stations installed on each property.

The current system, constructed in 1972, includes 4,680 feet of 8-inch low pressure main underwater in Lake Washington. The line runs on the lakebed next to the lake’s shore from a flush station next to Gene Coulon Park, which uses lake water to push sewage down the pipe, to a lift station at 3903 Lake Washington Blvd N.

The line serves 57 houses and Kennydale Beach Park. Renton Wastewater Utility Engineering Manager Joe Stowell said the pipe has been damaged over the years by driven piers for docks and snagged anchors.

“Quite frankly, it’s super difficult to get to to do any kind of repairs on it,” Stowell said. “It’s too close to shore to get to it from the water side with a barge and too far from the shore to get to it from the shore with a crane or any kind of equipment there. So it’s been a real challenge for us.”

Stowell said a 2018 study found the main was 80% clogged. A cleaning project with a barge and vactor truck was able to get most of the clogging material, but not all of it.

Instead of replacing the lake line, the city decided to take a new land-based system using technology not available in 1972: individual grinder pumps for each house pumping into a common force main, which feeds into the King County system. The city will be responsible for maintaining the pumps, which will be powered by the city’s electrical system.

“The system that we’re using is what they call a canned unit, so when you buy it, it has everything all in it, all ready to go,” Stowell said. “All you have to do is put it in the ground, tie it in, and put some electrical to it. They’re very reliable.”

The engineering firm will work with the wastewater department on the project. Stowell said they will need to pay close attention to Eastrail trail and property owner access, and all the permitting requirements, which is too much for the staff of six to manage alone.

“It is a challenging project. We’re working between the houses and water to put these grinder pumps in. We have to get the grinder pumps and the force main around to the access road and it is super narrow, and there’s other things in there as well,” Stowell said.

Lake lines are common on Lake Washington. Bellevue operates approximately 15 miles of lines, 15 pump stations and eight flush stations along the shoreline. In February 2026, Mercer Island issued an advisory to cease all wastewater in an area of North Mercer Island for nine hours due to a blockage in a lake line. Stowell said Renton is on the “leading edge” in solving the issues with lake lines.

“As an engineer, it’s a really, really cool, technical project,” Stowell said. “There aren’t many like this and we’re trying to do the best we can to keep everything on the right track.”

The project is expected to begin this summer and anticipated to be complete by the end of 2027.