Well Water in Washtenaw County, Michigan

Washtenaw County · Population ~375,000 (county); well-dependent areas vary · Aquifer: Glacial Drift / Saginaw Formation

Hardness: Moderate to Very Hard

Washtenaw County is home to Ann Arbor and the University of Michigan, but outside the city limits, thousands of homes rely on private wells. The county has unique contamination concerns: the ongoing 1,4-dioxane plume from the Gelman Sciences site has been migrating through groundwater for decades, and PFAS has been detected at multiple locations.

The 1,4-Dioxane Plume

Washtenaw County has a contamination issue found almost nowhere else in Michigan: a massive 1,4-dioxane groundwater plume originating from the former Gelman Sciences facility in Scio Township. 1,4-dioxane is a likely human carcinogen that has been migrating through the aquifer since the 1960s.

The plume extends several miles and has affected both municipal and private wells. If you're on a private well in Scio Township, Ann Arbor Township, or western Ann Arbor, test specifically for 1,4-dioxane. Standard water tests do not include it — you need to request it.

PFAS in Washtenaw County

PFAS has been detected in Washtenaw County groundwater at multiple locations. The university town's awareness level means more testing has been done here than in many Michigan counties, which is both good news (problems get found) and concerning (problems are being found).

See our PFAS guide for the full picture on Michigan PFAS contamination and testing.

Natural Water Quality

Setting aside the industrial contaminants, Washtenaw County's glacial drift aquifer produces water that is moderately hard to very hard with commonly elevated iron and manganese. Arsenic occurs naturally in some areas, particularly where wells tap deeper glacial deposits or the underlying Saginaw Formation.

Nitrates can be elevated in agricultural areas and near older septic systems.

What to Test For

Washtenaw County well owners should test for bacteria and nitrates annually. Test at least once for arsenic, hardness, iron, and manganese. If you're anywhere near the Gelman Sciences plume area, add 1,4-dioxane. Consider a PFAS panel regardless of location.

The Washtenaw County Health Department provides well water testing guidance and periodic screening events. See our testing guide for details.

Every well is different. Two wells on the same street can produce completely different water. The data on this page reflects documented conditions in the Washtenaw County area, but the only way to know what's in your water is to test it.

Sources

  • Michigan EGLE — Gelman Sciences 1,4-Dioxane Contamination Site
  • USGS — Glacial Aquifer Water Quality, Washtenaw County
  • Washtenaw County Health Department — Private Well Program
  • Michigan PFAS Action Response Team — Washtenaw County Data