Flooding and erosion have threatened the treatment plant, putting residents at risk of being exposed to millions of gallons of raw sewage. Parametrix worked with the City of Montesano to implement bioengineered protections, such as log jacks, to slow erosion and protect from flood damage.
“What made this project unique was the urgent need for a viable solution and the innovative approach our team identified to effectively protect the treatment plant,” said Parametrix Project Manager Matt Kastberg. “The idea was to install launchable log jacks above the ordinary high-water line. As the bank below the log jacks eroded, the jacks fell into the river along the bank and thus slowed erosion. This bought us time to design and permit a longer-term solution, which included installing 200 in-water log jacks.”
Natural processes were mimicked to protect streambanks by deflecting energy and depositing sediment, resulting in aquatic habitat enhancement and improved channel complexity. This was a collaborative effort between local, state, federal, and tribal agencies.
As a result, the previously encroaching Wynoochee River is moving away and the riverbanks along the treatment plant are growing.
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“The fix is working, and this method is now being utilized on other projects,” Kastberg said.
The city continues to monitor the riverbank along the Montesano Wastewater Treatment Plant. The innovative log jack solution is expected to extend the life of the treatment plant by 15 to 30 years.
Parametrix is a 100 percent employee-owned firm providing solutions in engineering, planning, and environmental sciences. The company is comprised of 600 employee-owners serving clients from locations across the Western United States.