Environmental Health
Minimum Isolation Distances
When you install your well, drainfield, and/or septic tank, you must observe minimum isolation distances as indicated in the table below. In some cases, isolation distances must be increased.
Note: If your property is hilly, the well should be located up hill from the drainfield or upstream from your drainfield site.
| Item |
Septic |
Drainfield |
Well** |
|---|---|---|---|
| Property Line |
10 feet |
10 feet |
- |
| Building Foundation (no basement) |
5 feet |
10 feet |
3 feet |
| Basement Wall |
10 feet |
15 feet |
3 feet |
| Water Supply Well* (25 feet deep or more) |
50 feet |
100 feet |
- |
| Lake or Stream |
25 feet |
50 feet |
** |
* Isolation distances will be increased for wells serving other than individual dwellings, and may be increased if wells are drawing water from an unprotected aquifer.
** A well cannot be located in an area subject to flooding.
For more information, please contact:
- Your Area Sanitarian (based on your Township)
- Washtenaw County Environmental Health Division - (734) 222-3800
