Valley wells around Mazomanie are shallow, with a median of 100 feet and water only about 23 feet down. Black Earth wells run deeper. Both towns were in the western Dane nitrate project and saw the 2018 flood. Test after high water, and use a DNR-licensed pump installer for pump work.
Updated October 2026
Typical wells here
- Town of Mazomanie: 284 wells, median 100 ft (58–164), casing 82 ft, water level about 23 ft down.
- Town of Black Earth: 142 wells, median 178 ft (138–246), casing 79 ft, water level about 71 ft down.
- Roxbury has no town figure in the depth table yet.
The Black Earth Creek valley sits on sandstone, while the ridges above are capped with dolomite. Wells in the valley reach water much closer to the surface.
Water quality notes
- Mazomanie, Black Earth and Roxbury were in Dane County’s 2024–25 western Dane testing project. Of its 1,292 volunteer samples, 90% had detectable nitrate and 10% were over the 10 mg/L standard. The highest was 26.7 mg/L.
- After the 2018 Black Earth Creek flood, PHMDC gave out free test kits here. That lab closed in 2025.
- If floodwater reached your casing, stop drinking the water and test for coliform before using it again. DNR says disinfection is best done by a licensed driller or pump installer.
Testing near Black Earth and Mazomanie
- Wisconsin State Laboratory of Hygiene (WSLH), Madison: bacteria $35, nitrate $35, arsenic $38. Kits ship free; you pay return shipping. 608-224-6202.
- UW-Stevens Point lab: homeowner package $78 (bacteria, nitrate and basic chemistry). 715-346-3209.
- PHMDC still helps you read results: 608-243-0357.
Permits and rules
- New well: a Dane County well location permit from PHMDC ($226, 608-242-6515) plus the DNR well construction notification ($50.50).
- In a floodplain, the casing must end 2 feet above the regional flood elevation.
- A well unused for more than 90 days must be filled and sealed by a licensed pro.
When you need a licensed professional
Wisconsin rules require a DNR-licensed pump installer for pump and pressure-tank work on a drinking-water well; check with DNR if you’re unsure. You can check a contractor’s license in the DNR directories.
- Disinfection after a flood
- Raising a low casing
- Cloudy water or sand after heavy rain
- Bacteria that come back
Related
- Wells around Cross Plains
- Wells around Sauk City and Prairie du Sac
- Typical well depths by town
- Common well problems
- Where to test your well water
Sources
