Quebecers worried about the health of Lake Memphremagog are in Vermont today in a last-ditch effort to halt the expansion of a garbage dump on the U.S. side of the lake.

The Coventry landfill expansion project has gotten pushback over environmental concerns that wastewater from the landfill's treatment plant is polluting the lake, which straddles the Quebec-Vermont border.

Those concerns increased in September, when Vermont admitted it hasn't been monitoring the lake to track the effect of the treated wastewater that's discharged into it.

The lake is the source of drinking water for at least 170,000 people in the Eastern Townships, including the City of Sherbrooke.

The Quebec delegation — including the CAQ MNA for Orford, Gilles Bélanger, representatives of Sherbrooke and the MRC of Memphremagog — is asking the environmental commission that deals with state land use and development to boost monitoring of the landfill's effect on the lake.

"I know people from Vermont are people who love Lake Memphremagog, and they protect the environment, so I'm very confident there will be additional requirements at the monitoring level," said Michel Cyr, head of water management for the city of Sherbrooke, who is part of the Quebec delegation.

"I have confidence they'll ask for more analysis and more monitoring requirements."

Lake Memphremagog, as seen from the shore of Eagle Point in Derby, Vt. in 2010, is the main source of drinking water for people in Sherbrooke and other municipalities in the Eastern Townships. (Toby Talbot/Associated Press)

The company that operates the landfill — which is five years from reaching capacity — got its permit to expand by about 20 hectares last fall, but it needs a final go-ahead from the environmental commission and Vermont's land use regulator.

Cyr said the environmental commission has given no indication of when it will make a decision on the landfill expansion.