Windham County, Connecticut: drinking water report. Windham County in northeastern Connecticut – the "Quiet Corner" – has about 117,000 residents in…
Windham County in northeastern Connecticut – the "Quiet Corner" – has about 117,000 residents in communities including Willimantic, Putnam, and Danielson. Most water comes from small municipal systems and private wells drawing from glacial and bedrock aquifers. The county's textile mill history left contamination at numerous sites along the Quinebaug and Shetucket Rivers.
Mill-era contamination includes chlorinated solvents, petroleum products, and heavy metals at sites throughout the river valleys. According to Connecticut DEEP's 2024 site assessment database, Windham County has 42 properties with documented groundwater contamination, many tied to former textile finishing and dyeing operations that used solvents freely.
The Windham Airport has documented AFFF use, and CT DEEP's 2024 PFAS investigation found PFOS at 11 ppt in monitoring wells near the facility. Naturally occurring arsenic in bedrock wells is another concern – the USGS's 2024 New England bedrock study found that 10% of wells in Windham County's metamorphic rock formations exceeded the 10 ppb MCL.
Windham County's many small water systems and high proportion of private wells mean water quality is a local issue rather than a county-wide one. If you are on a private well, testing for arsenic, VOCs (if near a former mill site), and PFAS gives you the full picture.
Check your water for any available data. For the range of contaminants possible in this area, reverse osmosis provides the broadest household protection. Our water filter guide covers well water systems for New England geology. Get your detailed report for context, and visit our Connecticut page for statewide data.
Drinking water is one exposure route. These federal datasets also cover Windham County, CT.
The EPA places Windham County, CT in Zone 2 - a moderate-risk category, with a predicted average indoor radon level between 2 and 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 Windham County, CT averages 5.8 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
Across 37 public water systems serving Windham County, CT with EPA lead testing on record, 7 (18.9%) reported a 90th-percentile lead result above the EPA's 15 ppb action level, and the median is 7.9 ppb. 30 water systems serving Windham County, CT carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Lead and Copper Rule Revisions | 25 |
| Revised Total Coliform Rule | 13 |
| Lead and Copper Rule | 8 |
| Arsenic | 2 |
| Total Coliform Rule | 1 |
Source: EPA Lead and Copper Rule 90th-percentile tap sampling and EPA SDWIS Safe Drinking Water Act enforcement records, aggregated from the public water systems serving this county. Figures are counts of water systems, not a test of any individual home or tap.