Plymouth County, Massachusetts: drinking water report. Plymouth County on Massachusetts' South Shore has about 530,000 residents in communities from
Plymouth County on Massachusetts' South Shore has about 530,000 residents in communities from Brockton to Plymouth. Most water comes from surface reservoirs and groundwater wells, with each town operating its own water department or district. The county's proximity to military installations – the former South Weymouth Naval Air Station and Camp Edwards on nearby Cape Cod – and its industrial history create overlapping contamination concerns.
The former South Weymouth Naval Air Station, now the SouthField mixed-use development, has documented PFAS contamination from AFFF. According to Massachusetts DEP's 2024 investigation, monitoring wells at the former base show PFOS at 35 ppt, and the contamination plume extends into adjacent Weymouth and Rockland groundwater. Several water systems in the area have been affected.
Brockton's surface water supply from Silver Lake and reservoir systems has tested clean for PFAS, but disinfection byproducts from treating nutrient-rich reservoir water are a recurring theme. A 2024 DEP compliance report noted elevated haloacetic acid levels in the Brockton distribution system during summer months.
Plymouth County's town-by-town water system structure means quality varies significantly depending on where you live. Systems near the former naval station face different challenges than those drawing from pristine South Shore reservoirs.
Check your water for data specific to your town and system. For disinfection byproducts, a carbon filter at the tap is effective. For PFAS, reverse osmosis adds the strongest protection. Our water filter guide covers both scenarios. Get your detailed report for local data, and visit our Massachusetts page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Plymouth County, MA.
The EPA places Plymouth County, MA 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.
64% of homes in Plymouth County, MA were built before 1980, and 27% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Plymouth County, MA averages 6.4 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 46 public water systems serving Plymouth County, MA with EPA lead testing on record, 2 (4.3%) reported a 90th-percentile lead result above the EPA's 15 ppb action level, and the median is 4.7 ppb. 22 water systems serving Plymouth County, MA carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Lead and Copper Rule | 8 |
| Revised Total Coliform Rule | 7 |
| Total Trihalomethanes (TTHM) | 4 |
| Ground Water Rule | 2 |
| Total Coliform Rule | 2 |
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.