Yaphank residents are concerned about a nearby composting plant's impact on groundwater.

The state Department of Environmental Conservation found elevated levels of contaminants, including manganese, in groundwater near the Yaphank composting facility.

Adrienne Esposito, of the Citizens Campaign for the Environment, says she has never seen such high levels of manganese on Long Island. She says the water could have a negative impact on someone's central nervous system if it's consumed.

"They're literally thousands and thousands of times above health standards," Esposito says.

Most nearby residents have been connected to public water, and the state DEC says there is no risk for them.

On Gerard Street, some homeowners who still use private wells say they're very concerned. One man says he will get his water levels tested this week.

In a statement, Long Island Compost says it is "a positive environmental force in the region, recycling more than half of Long Island's organic yard waste. We take that responsibility seriously and will work closely with the DEC in this matter."