OXFORD — The Welchville Dam is in danger of failing, according to engineer Myron Petrosky, of MBP Consulting in Portland.
“The condition is awful. It is in the state of imminent failure,” Petrosky told the Board of Selectmen at its May 18 board meeting.
“If the dam fails I would expect the pond levels (Whitney and Hogan) to drop about five to six-feet at least,” he told selectmen.
Whitney and Hogan ponds, which are popular summer destinations off Route 26 and home to several campgrounds, lay parallel to each other and are interconnected at the northern end. The outlet leads to the Little Androscoggin River and on to the Welchville Dam.
The 170-acre Whitney Pond has a maximum depth of 24 feet, while the slightly larger 177-acre Hogan Pond has a depth of 34 feet.
The dam, that was constructed sometime in the early to mid-1800s, is located in the Welchville section of Oxford on Route 26 by the intersection of Route 121, has been repaired a number of times since 2010 and rebuilt in the 1990s. But Petrosky said the time has come to either replace it or build a new dam.
Petrosky said he viewed pictures of the dam from several years ago when he was hired in 2015 to repair the Welchville Dam for $8,000 and compared them with view of the same segments of the dam taken on May 18.
“Today it’s in much worse condition. You’re losing significant parts.”
Petrosky, who just completed the replacement of the Pleasant Lake Dam in Casco, reported that the costs for the Welchville Dam could be about $1.4 million to repair the dam or about $900,000 to build a new dam.
The state of Maine and U.S. Army Corps of Engineers classify the Welchville Dam as a low-hazard structure. That means the if the dam fails it would results in no probable loss of life, no inundation of habitual properties, and low economic (infrastructure) losses.
According to a report issued to the town in January, the dam on the Little Androscoggin River in Welchville village had planking, structural timbers and rock fill falling away. Erosion has caused the center of the dam to sag over a foot in the past two decades.
Petrosky told the Advertiser Democrat that should the dam fail, it could have the following consequences:
1. A drop of the water level in Hogan and Whitney ponds and potential impact on property values. Same size of the water level drop in the ponds (or maybe larger) can be expected if the dam removed. Thompson Lake is well above and will not be affected by the Welchville Dam.
2. Environmental impact: The release of sediment accumulated upstream of the dam and contamination of the downstream river reaches (water and the shores). This sediment discharge could be centuries old and toxic.
3. Sudden failure of the dam and wave (or wall) of water rushing downstream could result in potential drowning of people doing pleasure activities in the downstream river reaches (boaters, fishermen and bird watchers).
The biggest cost in the dam replacement would be the coffer dam, which is installed to dry the area where the new construction takes place and control any seepage, Petrosky said. This was done in 1994 to replace missing timbers and a stone field.
If the work is to be done this year, it would not happen until the fall, said Chairman Scott Owens.
Town Manager Becky Lippincott expressed concern for the resents of Hogan and Whitney ponds.
“All these people depend on the water and all of a sudden they have a puddle.”
Lippincott said she will contact several agencies to help determine whether the dam can be taken out entirely, how it would affect other water bodies if the dam is taken out and other possible fixes.