LITCHFIELD — Officials hope to receive a finalized design from Calderwood Engineering for a permanent solution for the Woodbury Pond dam, which began showing signs of seepage last spring, by the end of the month.
Once dam keeper Terry Averill discovered the seepage last year, the town began working with Topsham-based engineering firm Wright-Pierce and geotechnical consultants Haley & Aldrich, who identified a loss of material within 10 feet of the fill.
Residents then approved a $55,000 mandate to repair the dam at the town hall last June.
The dam’s problems, if left unchecked, could make the road through the dam impassable and lower water levels in some of Tacoma’s five lakes, negatively impacting wildlife, flora and fauna. surrounding property values.
At first, city officials considered installing sandbags and pressure grouting, which would stabilize the area for two years while they find a permanent solution. The city then elected to simply install the sandbags, without pressure injection, a decision that saved the city approximately $150,000.
The sandbags were placed along the east wall of the dam last October, but in December Averill said seepage was still occurring.
City Manager Kelly Weissenfels said Tuesday that a small amount of leaking is currently occurring at the dam.
“The sandbags aren’t perfect,” he said, “but they’re stable and we’re monitoring them to make sure they stay that way.”
In January, the select committee unanimously approved a $22,500 deal with Calderwood Engineering for final design and construction supervision.
Weissenfels said engineers are working to answer some questions from the Select Board regarding the connection of the sheet pile to the dam and expects to deliver the updated plan before the next board meeting on April 25. Sheet piles are structural sections that provide soil retention.
“The tricky part of the engineering with the sheet pile is the connection of the sheet pile to the concrete wall of the dam, and that’s the part they wanted to provide a bit more detail on,” he said. “They want to make sure they get that final attachment concept right, and that’s the last piece that’s left.”
Once the design is finalized, the city will put the project out to tender. Contractors will have until fall 2023 to complete the project, instead of the end of this year, Weissenfels said.
“It’s to allow bidders to mitigate more risk by allowing more time to acquire materials if they need them,” he said. “Our hope is that if someone is able to get the materials faster, they’ll get the job done sooner, but we want to give them the opportunity to have that amount of time to get those materials at a cheaper price. .”
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