Proposed dam fix could save Litchfield an estimated $150,000

The dam at the east end of Woodbury Pond in June in Litchfield. Joe Phelan/Kennebec Journal

LITCHFIELD — Litchfield officials are now exploring a long-term fix for the Woodbury Pond Dam that could be roughly $150,000 cheaper than initial repair plans.

Problems began to show this spring, when dam keeper Terry Averill witnessed settling of the stone riprap next to the right side of the upstream training wall. He also noted seepage along that wall, starting at about 7 feet and intensifying at 7-and-a-half feet.

Since then, Topsham-based engineering firm Wright-Pierce surveyed the site and presented Litchfield with a report, along with estimated repair costs. The firm was also assisted by geotechnical engineering consultants from Haley & Aldrich.

Tests confirmed that the water was traveling through this wall and exiting beneath the downstream training wall, and engineers also noted that the riprap had settled between their visits in May. They found that the problem was caused by a loss of materials in the embankment within a 10-foot area, and recommended that the pond’s elevation not go beyond 7 feet until measures are taken against the leak.

They pitched a two-phase approach to tackling the problem. The first phase would stabilize the situation, and involves installing sandbags along the affected area as well as pressure grouting this area to temporarily stabilize the dam. This part of the plan also involves regularly monitoring the dam and embankment and noting any changes in seeping or settling.

Phase one was estimated to keep the area stable for up to two years.

Residents in June approved adding $55,000 to the municipal budget to help with the first phase of the dam’s repair.

Phase two would be a long-term repair strategy. Engineers suggested three options: Installing a concrete core within the existing dam embankment, installing a steel sheet pile cutoff wall on the upstream face of the dam, or installing a concrete secant pile wall on the upstream face of the dam.

Litchfield selectmen discussed approval of phase one during a Monday meeting, but opted not to sign off until engineers could provide a more precise financial estimate. Altogether, costs for this phase were originally estimated at between $79,500 and $142,000.

The dam at the east end of Woodbury Pond recently in Litchfield. Joe Phelan/Kennebec Journal

Town Manager Kelly Weissenfels said Wednesday that the town’s Public Works Director Larry Nadeau suggested moving forward with the steel sheet pile cutoff wall option for phase two. He said this option would allow the town to skip the pressure grouting step and only install sandbags as part of phase one.

“The grouting costs up to $150,000,” Weissenfels said, “so rather than putting money into that procedure, which would give us two or so years, we hope to instead go straight to the steel sheet wall, and that way it would save us $150,000. That’s our hope.”

Looking ahead, he said the next step would be to authorize engineers to conduct a geotechnical survey and find out if the steel sheet option would work.

In the meantime, the town will pursue seeking the permitting and monitoring required to install sandbags at the site. Once a permit is obtained and the sandbags are installed, Weissenfels said the dam’s issues will be kept at bay for approximately seven months, at which point engineering work will ideally be finished and officials could obtain permits for the long-term fix.

Nothing has been finalized at this point, he said, but said it will be brought to the Select Board on July 12.

Weissenfels said they are still exploring the costs for the long-term fix, and that initial estimates are roughly $300,000. In order to help fund this fix, he said the town will explore grants as well as the Maine Municipal Bond Bank’s Dam Repair and Reconstruction Fund.

“It’s great news in terms of economics,” Weissenfels said. “There’s a little bit of risk involved if the leak increases, and that’s why monitoring the dam is important.”