Chloride in Maine well water
In Maine, chloride was detected in 99% of 1,169 tested private well samples.
Chloride mainly comes from road salt and water softener discharge. Above 250 mg/L water tastes salty and corrodes plumbing. Rising chloride in a well usually means road salt is reaching the aquifer.
By county, from individual samples
Public monitoring samples against the EPA limit; counties with at least 30 samples.
| County | Samples | Detected | Above EPA limit | Median | Highest |
|---|---|---|---|---|---|
| Penobscot | 64 | 100% | no limit | 6.1 | 88 mg/L |
| Washington | 79 | 100% | no limit | 3.8 | 23 mg/L |
| Cumberland | 380 | 100% | no limit | 29.1 | 2,020 mg/L |
| Franklin | 30 | 100% | no limit | 1.91 | 36 mg/L |
| Hancock | 41 | 100% | no limit | 4.43 | 227 mg/L |
| Kennebec | 44 | 100% | no limit | 15.1 | 939 mg/L |
| Somerset | 57 | 100% | no limit | 4.21 | 115 mg/L |
| York | 90 | 99% | no limit | 9.4 | 870 mg/L |
| Androscoggin | 60 | 98% | no limit | 3.56 | 140 mg/L |
| Aroostook | 88 | 97% | no limit | 9.25 | 98 mg/L |
| Oxford | 206 | 96% | no limit | 6.9 | 380 mg/L |
- North Washington UT, Washington County100% detected of 34
- Oxford, Oxford County100% detected of 54
- Paris, Oxford County100% detected of 32
- Windham, Cumberland County100% detected of 326
- Fryeburg, Oxford County91% detected of 70
Sources
- Individual samples from the USGS Water Quality Portal and state monitoring, summarized per geography. chloride counts and shares are listed on each county and town page with their sources.