By Dawn De Busk

Staff Writer

CASCO — The nonprofit group that protects the water quality of Thompson Lake requested that Casco use its voice to help the Town of Oxford put into place a maintenance plan for the dam.

Thompson Lake Environmental Association (TLEA) co-presidents spoke to the Casco Board of Selectmen, providing the board with an update of milfoil removal campaigns, runoff prevention and concern about the worsening condition of the Thompson Lake Dam.

The dam is entirely owned and controlled by the Town of Oxford. The Town of Casco has representatives on the Thompson Lake Advisory Committee.

TLEA’s two co-presidents, Marcia Matuska and Kathy Cain, provided the selectmen with a slideshow and a 5- to 10-minute overview of  the association’s work and most pressing concerns.

Matuska did most of the speaking, starting with water clarity and ending with piecemeal repairs on the Thompson Lake Dam.

“In 2018, an engineer rated the dam from poor to fair condition,” she said.

“Whoever is on the dam committee, we hope you’ll put in a maintenance plan,” Matuska said.

Although the east end of the dam is slated to be replaced, there are other items that cannot go much longer without being repaired, she said. She listed holes in the concrete that are leaking water and could simply be sealed up as well as a large leak that has left a puddle several feet deep and could cause underground erosion.

“There are trees and plants growing in the concrete—that is concerning to us,” she said.

“We don’t have a voice,” she said.

“We we know the dam committee is a committee that suggests. We’d like to see a maintenance plan put in place. The east dam is going to be replaced. We would like to see other issues addressed rather than it be done piecemeal,” Matuska said.

The board has in the past discussed a better approach to the maintenance on the dam, which borders the towns of Oxford, Otisfield and Casco.

Earlier in the presentation, Matuska talked about the importance of courtesy boat inspectors to keep new invasive aquatic species out of the lake as well as the continued campaigns to mitigate existing milfoil.

“You do know that we have variegated leaf milfoil in Thompson Lake. We’ve had this since the early 1980s,” she said.

She showed slides of the reduction of milfoil outbreaks over the years in Otisfield Cove and Hancock Cove and at Pine Point, where it is thought the infestation originated.

“Since the beginning of the milfoil projects, we have removed over 160 tons of milfoil, and that does not include the milfoil that was gotten rid of by milfoil tarps,” she said.

Most of the milfoil removal was done by vacuum pumps. Hand-pulling was another technique that continues to be employed.

“We are concerned about new invasive species getting into the lake. We help with this by hiring courtesy boat inspectors,” Matuska said.

The boat inspectors are set up at three points of entry into the lake. Those three boat ramps are at Pismo Beach in Oxford, the boat ramp off Route 121 in Otisfield, and the Thompson Lake Marina.

“The marina on the Casco side [of the lake] is our busiest spot,” Matuska said. 

Last year in 2018, 1,000 boats were inspected compared to 1,232 this summer, she said.

“We don’t want any more invasive species,” she said.

“As you know, Thompson Lake is one of the cleanest lakes in Maine and we have been monitoring the water quality for many, many years,” she said.

“From May through October, twice a month, we measure the clarity of the water,” she said. “Anywhere from 24 to 27 feet you can see down into the lake so that is extraordinarily clear.”