New London County, Connecticut: drinking water report. New London County on Connecticut's southeastern coast has a population of about 270,000.
New London County on Connecticut's southeastern coast has a population of about 270,000. Water sources include the Thames River watershed, local reservoirs, and groundwater wells. The county hosts Naval Submarine Base New London (Groton) – the U.S. Navy's primary submarine base and the first submarine base established in the country. General Dynamics Electric Boat, which builds the Navy's submarines, operates a major shipyard adjacent to the base.
Naval Submarine Base New London has confirmed PFAS contamination from AFFF firefighting foam use. According to the Navy's 2024 environmental investigation, monitoring wells on the base detected PFOS at concentrations up to 350 ppt. The contamination plume extends into the surrounding area, and the Navy has conducted testing of private wells in Groton neighborhoods near the base boundary.
Electric Boat's manufacturing operations introduce industrial solvents, metals, and other process chemicals to the local contamination picture. Connecticut has adopted PFAS action levels of 12 ppt for combined PFOA and PFOS, stricter than federal MCLs. A 2024 Connecticut DEEP report documented PFAS detections above state action levels in three public water systems in the county.
Groton residents near the submarine base face the most direct PFAS exposure risk. The Navy has been conducting outreach and testing, but household filtration adds protection during the characterization and remediation process.
Check your water for the latest data on your system. For PFAS, reverse osmosis provides the strongest household defense. Our water filter guide identifies systems certified for the concentration ranges found near military bases. Pull your detailed report for trends, and visit our Connecticut page for statewide context.
Drinking water is one exposure route. These federal datasets also cover New London County, CT.
The EPA places New London County, CT in Zone 1 - the EPA's highest-risk category, where the predicted average indoor radon level is above 4 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
Modelled annual fine-particle pollution (PM2.5) in New London County, CT averages 5.7 µg/m³, within the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide