Environmentalists say an expansion plan by a Calverton sand mine may put drinking water at risk.

A sand mining operation in Calverton is asking the state Department of Environmental Conservation for permits to dig vertically into Long Island's sole source aquifer.

The company wants to mine vertically by digging to a depth of 100 feet downwards—89 feet below ground water – to create an 8.5 acre lake.

Local civic groups and environmentalist say the results of the project may seriously harm the local groundwater.

"Sand mining below the groundwater table is absolutely absurd. We are supposed to be protecting our aquifer, not making it more vulnerable to contamination. The problem is when you expose the aquifer, every other activity in the sand mine pollutes the aquifer," says Adrienne Esposito, of Citizens Campaign for the Environment.

The Town of Riverhead banned sand mining more than 20 years ago, but the sand mine on the corner of Osborn and Youngs Avenues has a preexisting permit to mine 20 acres on the site.

However, with the new request for a vertical permit, the town would have to approve expanding a nonconforming use.

Environmentalists also say the sand mine abuts to a close landfill and they are concerned about contaminants leaching into the aquifer.

“Riverhead needs to be extra vigilant about protecting that source of drinking water - allowing the sand mine to go below ground water level is a threat to public health,” says Esposito.

News 12 reached out to Riverhead Town officials and the sand mine operators for comment, but has not heard back.