City surrenders to beavers to reduce roadway flooding

By Dan Aznoff | May 04, 2017
Courtesy of: Adopt A Stream Foundation Ambitious beavers like this one along Penny Creek have been blamed for the flooding that has created havoc for commuters along 35th Ave. SE for decades.

If you can’t beat them you might as well join them may be the solution that will finally end the floods that cover a major arterial through Mill Creek.

The city’s public works department has begun the installation of flexible levelers that will allow beavers to build dams across Penny Creek at 144th Street SE to the north of the bridge in the Highland Trails neighborhood. The levelers will allow water to flow through the beaver dams and not back up over 35th Ave. SE.

“One of the goals of the city’s Surface Water Utility program is to rehabilitate stream and drainage corridors to benefit wildlife habitat,” said Marci Chew, Mill Creek surface water specialist. “This solution will enable us to prevent flooding while preserving the beaver habitat.

Beavers have been blamed for many of the woes of travelers on the Mill Creek portion of 35th Avenue SE. The beaver dams hold back the flow of water under the bridge at 144th Street SE as it curves into 30th Avenue SE. Flooding from the wetlands has been responsible for road closures that flood across 35th Avenue SE by Thomas Lake.

City work crews had previously removed beaver dams on a weekly basis from spring through the fall, according to Chew.

The Hydraulic Project Approval permit from the Washington State Dept. of Fish and Wildlife, allowed public work crews to install the two flexible levelers that will allow the beavers to build a dam across the creek.

Designed by beaver specialists, the flexible leveler is a system made from double-walled corrugated plastic pipe, which extends 20-feet from the wetland area and under the beaver dam. The mouth of the pipe will be protected by cattle fencing to prevent beavers from entering it or blocking it. The pipe is also anchored in place and staked every six feet to prevent movement.

If successful, water will be able to flow out of the wetlands without an impact to the beavers. Staff from the surface water and public works departments will work with Beavers Northwest, a beaver conservation and education organization, to build and install the flexible levelers.

“Our crew will watch how they are built and designed, which will enable us to do this in the future without requiring a consultant,” said Chew. “There are several beaver dams along Penny Creek, and beavers continue to multiple. This will help us manage the problem without impacting the habitat.”

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