The Suffolk County Department of Health has launched expanded testing of private wells near the former Grumman aerospace facility in Calverton amid ongoing concerns over groundwater contamination.

The new round of testing is a critical step for homeowners who rely on private wells, which are not subject to the same routine monitoring as public water systems. The county is now targeting an expanded area — up to 3 miles from the former plant — after previous testing by the U.S. Navy revealed the presence of contaminants, known as PFAS, or “forever chemicals,” in a significant number of wells.

PFAS are a group of man-made chemicals linked to health risks including cancer, liver damage and developmental issues. In the Navy’s earlier testing, 17 of 30 wells within a 1-mile radius of the site tested positive for PFAS, though levels reportedly remained below thresholds requiring remediation.

Still, environmental advocates are pushing for more aggressive action and transparency.

"At this point, we know there’s contamination. We know it’s caused by Navy Grumman operations,” said Adrienne Esposito, of Citizens Campaign for the Environment. “But we still, even after over a decade, do not know the extent, the width, and the length of this contamination."

The expanded study could include testing at up to 160 homes. However, it will not include the 128 homes that were recently connected to public water, which is regularly tested and regulated.

Suffolk County health officials confirmed that the new sampling initiative began earlier this month. The results will help determine how far the contamination plume has traveled — and what actions may be needed next to ensure the safety of local drinking water.