Leaburg fish ladder needs $900,000 in repairs

Scuba divers from Northwest Underwater Contractors did an underwater survey of the Leaburg Dam’s fish ladder last April that revealed erosion has undermined the structure’s concrete foundation.

LEABURG: Scuba divers inspecting Leaburg Dam’s left bank fish ladder had bad news after an underwater inspection of the structure last summer. They reported that some seventy feet of the concrete foundation had been undermined.

The fish ladder, constructed in the 1960’s, was poured directly on the river bottom, which is comprised of cobbles, sand, and gravel. Riprap was placed adjacent to the fish ladder in an effort to prevent erosion. Divers found the undermining ranged from four feet to more than fifteen horizontal feet, measured from the riverside foundation to the face of the fish ladder.

That means a substantial portion of the foundation is unsupported. In addition, measurements revealed that twelve vertical feet of riprap, which helped protect the fish ladder, has also been washed away from the riverside face of the fish ladder over the years.

In response, the Eugene Water & Electric Board contracted with a structural engineering firm, Metzler Engineering Group has been retained to design repairs to the left bank fish ladder. The work would include installation of sheet piling along the riverside face of the fish ladder as well as filling all below-foundation voids with concrete. Estimated total cost of work, including EWEB labor, consultant, and construction contractor, is $900,000.

Due to fish migration concerns, the in-water work must be completed by April 30th. If delayed, according to a report to the EWEB board by Mel Damewood, Engineering Manager; and Debra Smith, Assistant General Manager, “EWEB would be at risk of incurring additional major damage during the spring high flow season. To mitigate this risk by preserving an adequate construction schedule, it may be necessary to award a construction contract without Board approval. If delays are significant, it may also be necessary to forego conventional formal bidding processes in favor of obtaining quotes from select contractors.”

The fish ladder issues are in addition to prior problems at the site. Last year, the lift mechanism for rollgate 2 on the dam failed, requiring an estimated $1 million repair project that is still in process.