Water release causes flooding below Casco dam
By Dawn De Busk
CASCO — More water than was anticipated rushed downstream of the Pleasant Lake Dam, when the cofferdam was opened in order to lower lake levels.
A cofferdam is the temporary structure which holds back water so that construction can occur on a dam or on marine vessels.
Within a few days of the water being released, two bridges on the town’s all-terrain vehicle (ATV) trail system were under water and Woods Road, used by Hancock Lumber, was also flooded, according to Casco Town Manager Dave Morton.
The integrity of the dam, which has been constructed to replace the old dam, did withstand the water pressure, Morton said.
However, a small amount of erosion occurred as the water flowed forcefully around the wings of the dam, he said. Any erosion will be resolved when the dam construction is wrapped up because the contractor will backfill the banks on both sides of the dam, Morton said.
Also, a culvert failed as a result of the water release. The culvert is part of the Maine Department of Inland Fisheries and Wildlife’s construction project.
The dam was purposely opened to reduce water levels in Pleasant Lake and Parker Pond. That happened on Monday, Feb. 6.
“The lake level has been held back for two months. It was 18 to 20 inches above the high-water mark,” Morton said.
The higher-than-usual water levels ended up impacting some residential houses in Otisfield, on the north end of Pleasant Lake.
“So, the contractor decided to let some water out,” Morton said. “The basic portion of the dam is completed. They let some water out the coffer dam. A separate coffer dam has started to let water out. The force of the water coming through undermined the rest of the dam,” he said
“The culvert failed a few days ago,” he said.
“It resulted in a lot of water coming out of the lake. The lake has come down eight or nine inches in two days,” Morton said. “The water was going through the sluice way, the open gate. The water started going around the end of the dam,” he said.
Morton spent last Wednesday afternoon watching the trees near the dam in case the root system was compromised and those trees toppled. That did not happen, he said.
“But there were some problems. The ATV bridge is under water,” Morton said.
“It spoiled the opportunity for the snowmobile club to do their rodeo over the weekend,” he said, adding the club was forced to cancel the event.
In addition, another bridge on the Pole Line trail system was under water, he said.
Also, Woods Road, which is used by Hancock Lumber, had water running over it late last week. That road has flooded at least a dozen times during extreme storm events, he said.
“Ultimately, I don’t know what damage will be done to the road, to ATV bridge, to the snowmobile bridge,” Morton said.
“Those are things we want to explore in terms of helping those organizations once the water recedes,” he said. “The good news is the lake is going down,” Morton said.
Warning signs have been posted at all public access points on Pleasant Lake and Parker Pond. The signs let the public know to be aware of shifting ice because of fluctuating water levels. There are warnings posted on the town’s website, too.
The contractor on the dam replacement project is T-Buck Construction.
Prior to the decision to release the water, the contractor helped the homeowner to remedy the flooding situation by jacking up the foundation of the home, which sits on concrete tubes.
As far as the construction on the dam resuming, it is an only-time-will-tell situation.
“They will let the water run before they think about reconstructing the cofferdam,” Morton said.
The crews will need to wait until the lake level equalizes and inclement weather will play a factor in the timing.
Morton stressed that the recent developments will not be a setback to the dam construction, which is a project shared jointly by the towns of Otisfield and Casco.
“There is not setback to the town’s project,” he said.
“It has put on hold the (installation of) the pipe for the Inland Fisheries” project, he said.
The state piggybacked on the dam-replacement project with its plans to install a sleeve in a culvert, which would allow fish to swim past when the sluice-style dam is closed and inaccessible.
“There is a lot of water. You take eight inches of water out of those two lakes in that period of time and it’s a lot of water,” he said.
“The good news is our dam stood up well,” Morton said.