The dam at the east end of Woodbury Pond on Tuesday in Litchfield. Joe Phelan/Kennebec Journal Buy this Photo

LITCHFIELD — With residents recently approving an additional $55,000 to help with the first phase of repair for the Woodbury Pond Dam, town officials are pursuing an eventual permanent fix for the dam.

Issues were first identified this spring when dam keeper Terry Averill observed settlement of the stone riprap next to the right side of the upstream training wall, as well as seepage on that wall starting at approximately 7 feet and intensifying at 7 1/2 feet.

Topsham-based engineering firm Wright-Pierce surveyed the dam and recently presented the town with a report of their findings and estimated repair costs. They visited the site May 5 and May 25, with environmental and geotechnical engineering consultants from Haley & Aldrich.

They conducted three dye tests to determine the location and movement of water through the embankment, which showed water traveling through the upstream training wall and coming out beneath the downstream training wall.

Engineers also saw increased settlement of the riprap adjacent to the upstream right side wall between their visits, and noted voids between individual riprap pieces in the area. Engineers determined the problem was related to a loss of materials within the embankment and that it appears to be localized within a 10-foot area.

They recommended that the pond elevation not exceed 7 feet until initial measures are taken against the leak.

They proposed a two-phase approach to fixing the problems, with the first phase involving a short-term fix and phase two being a long-term repair strategy.

The first phase would stabilize the impacted embankment and control water seepage. That involves installing sandbags along the upstream right side face of the dam embankment and training wall, as well as pressure grouting the affected area to temporarily stabilize the dam. In their report, the engineers wrote that the project was discussed with Gorham-based contractor Knowles Industrial Services, which helped provide cost estimates.

Engineers said work could be scheduled directly with Knowles and potentially finished in late summer, as the installation of sandbags and pressure grouting will take approximately two to three weeks and also require a 30-day approval period through the Maine Department of Environmental Protection and the U.S. Army Corps of Engineers.

The dam at the east end of Woodbury Pond on Tuesday in Litchfield. Joe Phelan/Kennebec Journal Buy this Photo

Because there are still unknown subsurface conditions that could impact that cost and effectiveness of this short term plan, engineers estimate that phase one could stabilize the dam for about one to two years, providing ample time to work on the long-term repair strategy, or phase two.

And because of these uncertainties, phase one also involves regularly monitoring the dam and embankment. If any changes in the seeping or settlement occur, the dam may require emergency repairs.

Altogether, costs for phase one are estimated between $79,500 to $142,000, with the budget for engineering support between $8,500 and $9,500, permitting and remediation oversight between $8,500 and $10,500, monitoring plan development between $1,500 and $2,000, and establishing monitoring points and quarterly monitoring between $6,000 and $10,000.

Estimates for the sandbags and pressure grouting, also included in the total budget, are between $55,000 and $110,000. According to the engineer’s report, these figures were provided by Knowles, with the low end of the quote accounting for a three-person crew working for six to eight days. The $110,000 estimate accounts for obstructions or unforeseen circumstances that could impact the time and scope of the project.

Town Manager Kelly Weissenfels said that officials are planning to speak with Monmouth about potentially sharing costs for phase one, as the municipality shares a portion of the dam’s water frontage.

He said money could also be saved by using town equipment to assist with laying sandbags, which are one cubic yard of sand each. A contractor would handle work for other aspects of this phase, such as grouting.

Engineers pitched three options for the long-term repair strategy: 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.

Initial rough estimates for the long-term repair range from $265,000 to $500,000 for construction, $60,000 to $85,000 for design and permitting, and $40,000 to $60,000 for construction administration and oversight The total budget estimate is between $365,000 and $645,000.

Weissenfels said the town may consider funding via the Maine Municipal Bond Bank’s Dam Repair and Reconstruction Fund to assist with the second phase, adding that he is hopeful that the short-term repairs will provide the town with ample time to begin saving for the project.

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