OXFORD — A local pond association is requesting that the town significantly lower the water level in Hogan and Whitney ponds to combat an especially virulent milfoil infestation. 

Eurasian milfoil is a non-native underwater plant, considered one of the most problematic aquatic invasives in the United States. The plant grows rapidly in huge clumps at the surface that quickly choke out other plant species and obstruct swimming and boating.

In an Aug. 31 letter to the town, Hogan and Whitney Ponds Association Treasurer Richard Auren asked the town to drop the water level on the two ponds “as much as physically possible” beginning Oct. 21 and to maintain a low level until ice out next spring.

According to Town Manager Michael Chammings, however, the town already flushes the ponds during the winter, in order to minimize seasonal flooding. The town has used the method since voters approved a Welchville Dam water level strategy in 2008. 

“We’re already opening it up longer than they’re asking us to,” Chammings said.

The two ponds feed the Little Androscoggin River, which is controlled at the Welchville Dam. The town is working on restoring the old wooden dam with a new concrete cap.

Because of the project, the water levels may have to remain low later into the spring, Chammings said.

The Board of Selectmen will hold a hearing on the issue when a construction schedule is finalized, he said.

In order for the drawdown to be effective, the water is lowered enough to expose the plants and dry out the soil before a hard freeze, Auren said in his letter.

In a telephone interview last week, Auren said he knew that the town dropped the water level over the winter but wanted it taken down even farther.

“We need to drop it way down,” Auren said. “If you talk to anybody who’s been on the pond any length of time, it can go much farther down than what they do in the winter.”

The association has been dealing with the infestation in Hogan Pond for years and has poured time and money into hiring divers to both remove the plants by their roots and cover them with mats underwater.  

This summer, however, the milfoil “came back with a vengeance,” overwhelming volunteers’ efforts to control it, Auren said. The infestation is particularly bad in the southern end of Hogan Pond, he reported. 

“We feel like we’ve lost control of the situation,” Auren said.

According to Peter Lowell, the executive director of the Bridgton-based Lakes Environmental Association, the drawdown method has been used to some success elsewhere in Western Maine. 

By dropping water levels in the Songo River between Brandy Pond and Sebago Lake in Naples over the past six year, the LEA has been able to manage an out-of-control milfoil infestation in the waterway.

By pairing water level drawdowns with aggressive eradication efforts, LEA has been able to reduce milfoil levels in the upper Songo River from acres to a few dozen plants, he said.

The success of the measure is entirely dependent on site-specific conditions, and there is no guarantee it will be able to cut down on the milfoil, said John McPhedran, with the Maine Department of Environmental Protection’s invasive aquatic species program. 

Even if the measure succeeds in killing some of the plants, it might not get all or even the majority, McPhedran warned. 

“You may, with the right weather conditions, affect the exposed area, but next year, you still may have a good population of the plants that then refragment and recolonize that area,” he said. 

pmcguire@sunjournal.com