Gratiot County, Michigan: drinking water report. Gratiot County in central Michigan has about 41,000 residents in a deeply agricultural community.
Gratiot County in central Michigan has about 41,000 residents in a deeply agricultural community. Alma and St. Louis are the main towns. Nearly all water comes from groundwater, with many residents on private wells. The county's flat terrain, sandy soils, and intensive farming create a textbook scenario for agricultural groundwater contamination.
The Velsicol Chemical Company operated a plant in St. Louis that manufactured PBB (polybrominated biphenyls) and DDT. In 1973, PBB was accidentally mixed into animal feed, contaminating Michigan's dairy and meat supply in one of the state's worst environmental disasters. According to Michigan EGLE's 2024 site investigation, soil and groundwater contamination from the Velsicol plant includes PBB, DDT, and other chlorinated pesticides. The Pine River, which runs through St. Louis, remains contaminated.
Agricultural nitrate compounds the issue. A 2024 EGLE private well testing report found 18% of tested wells in Gratiot County exceeding the nitrate MCL. The sandy soil provides minimal filtration between farm fields and the aquifer.
Gratiot County's combination of chemical industry contamination and agricultural nitrate makes private well testing essential. If you are in the St. Louis area, testing for PBB and chlorinated pesticides is warranted given the legacy contamination.
Check your water for available data. For the range of contaminants in this county, reverse osmosis provides the broadest protection. Our water filter guide covers systems suited to contaminated rural groundwater. Get your detailed report for local data, and visit our Michigan page for statewide context.
Drinking water is one exposure route. These federal datasets also cover Gratiot County, MI.
The EPA places Gratiot County, MI 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.
69% of homes in Gratiot County, MI were built before 1980, and 31% 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 Gratiot County, MI 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