A state Assembly committee will hold a public hearing Wednesday on whether sand mining and illegal dumping have impacted Long Island’s water quality.

The hearing in Smithtown, convened by the Assembly’s Environmental Conservation Committee, headed up by Assemb. Steven Englebright (D-Setauket), will examine whether existing laws regulating sand mining and dumping are strong enough to protect groundwater — the sole source of drinking water for Long Island’s nearly 3 million residents.

Englebright said the issue of mining sand — and the fill or debris that can end up in the resulting holes — has been of concern to him since his days as a Suffolk County legislator in the 1980s.

He also said he was influenced by reading news reports over the past two years about dumping and sand mining in Suffolk County.

“Each of those stories has been a reminder to me of the importance of attending to the issue,” he said.

The subcommittee will hear testimony from experts, politicians, environmentalists and others as state legislators weigh whether laws should be changed to provide more protection to the environment.

Current law allows for exemptions from a sand-mining permit if the activity is part of a building project — an exemption that can give an unscrupulous developer cover, Englebright said.

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“The law never anticipates someone will have ill motives, and the agencies don’t have enough personnel to be watchful,” he said.

Experts have said sand mining can pose a threat to groundwater, since the resulting hole can present an opportunity for dumping improper debris.

Contaminants in the debris can then leach into the underground aquifer system.

Towns also have the option to create regulations on the practice within their borders.

Brookhaven Town has been embroiled in litigation against the Brookhaven Rail Terminal over allegations that the terminal was improperly mining sand on its property, creating an environmental hazard. And Suffolk prosecutors this year issued subpoenas to towns seeking records on sand mining.

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The state Department of Environmental Conservation, which regulates sand mining, this year began an investigation into properties on Furrows Road in Holbrook over allegations of illegal sand mining.

The hearing will begin at 11:30 a.m. in the legislative auditorium of the William H. Rogers Building, 725 Veterans Memorial Hwy., Smithtown.