Hancock County, Mississippi: drinking water report. Hancock County on Mississippi's westernmost coast has about 48,000 residents in communities including
Hancock County on Mississippi's westernmost coast has about 48,000 residents in communities including Bay St. Louis and Waveland. The county draws water from the Miocene aquifer and shallower sand aquifers. Stennis Space Center – NASA's primary rocket engine test facility – occupies a 125,000-acre buffer zone in the northern part of the county, and the former Mississippi Test Operations used hazardous materials that have affected local groundwater.
Stennis Space Center's operations and associated military activities (the Naval Construction Battalion Center is co-located) have generated multiple contamination sites. According to NASA's 2024 environmental report, TCE and perchlorate from rocket engine testing have been detected in groundwater monitoring wells on the facility. PFAS from firefighting foam use at the co-located military facilities has been found at 32 ppt in boundary monitoring wells.
The county's coastal location adds saltwater intrusion risk. A 2024 MDEQ groundwater study found chloride concentrations increasing in production wells along the Bay St. Louis coastline, driven by sea level rise and increased pumping demand during the post-Katrina population rebound.
Hancock County residents near Stennis Space Center should be aware of the potential for perchlorate and PFAS in groundwater. The NASA buffer zone limits residential development near the facility, but the contamination plume extends beyond the buffer in some areas.
Check your water for data at your location. For the combination of rocket-fuel-related contaminants, PFAS, and coastal minerals, reverse osmosis provides the broadest household protection. Our water filter guide covers systems rated for perchlorate removal. Pull your detailed report for local data, and visit our Mississippi page for statewide patterns.
Drinking water is one exposure route. These federal datasets also cover Hancock County, MS.
The EPA places Hancock County, MS in Zone 3 - the EPA's lowest-risk category, with a predicted average indoor radon level below 2 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.
28% of homes in Hancock County, MS were built before 1980, and 6% 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 Hancock County, MS averages 8.2 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
11 public water systems serving Hancock County, MS have EPA lead testing on record. The reported lead sample skews toward systems that already flagged a problem, so its exceedance rate is not directly comparable with other areas. 5 water systems serving Hancock County, MS carry a health-based EPA Safe Drinking Water Act violation.
| Most-cited violation type | Systems affected |
|---|---|
| Total Trihalomethanes (TTHM) | 2 |
| Lead and Copper Rule Revisions | 2 |
| Ground Water Rule | 2 |
| Haloacetic Acids (HAA5) | 1 |
| Revised 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.