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Door County Private Well Monitoring Program
Past Testing Results
The common contaminants that are tested for in the study have been bacteria in the form of Total Coliform and E. coli and Nitrate. The following table summarizes the results from 2019 - 2022. The numbers displayed show the percentage of Door County wells indicating various levels of contaminants compared to Wisconsin averages.
Water Quality Standard (Level Detected) | Spring 2023 (195 wells) | Fall 2022 (196 wells) | Spring 2022 (260 wells) | 2021 (217 wells) | 2020 (295 wells) | 2019 (148 wells) | Wisconsin Average |
| Total Coliform (0 MPN/100 ml) | 95% | 92% | 90% | 76% | 86% | 84% | 17% (>0 MPN/ 100 ml) |
| Total Coliform (1-10 MPN/100 ml) | 5% | 6% | 6% | 14% | 9% | 10% | |
| Total Coliform (10-100 MPN/100 ml) | 0% | 2% | 3% | 6% | 3% | 4% | |
| Total Coliform (>100 MPN/100 ml) | <1% | 1% | 1% | 3% | 1% | 1% | |
| E.coli (0 MPN/100 ml) | 100% | 100% | 99% | 98% | 99% | 100% | 5% (>0 MPN/ 100 ml) |
| E.coli (1-10 MPN/100 ml) | 0% | 0% | <1% | 1% | 1% | 0% | |
| E.coli (10-100 MPN/100 ml) | 0% | 0% | 0% | <1% | 0% | 0% | |
| E.coli (>100 MPN/100ml) | 0% | 0% | 0% | 0% | 0% | 0% | |
| Nitrate (0 mg/L) | 77% | 74% | 80% | 75% | 72% | 71% | 8% (>10 mg/L) |
| Nitrate (2-5 mg/L) | 16% | 18% | 16% | 11% | 16% | 16% | |
| Nitrate (5-10 mg/L)(>10 mg/L) | 5% | 7% | 4% | 12% | 12% | 11% | |
| Nitrate (>10 mg/L) | 3% | 1% | 0% | 2% | <1% | 2% | |
| Arsenic (<2 µg/L) | 89% | 92% | 88% | 89% | 90% | 99% | 5% (>10 µg/L) |
| Arsenic (2-5 µg/L) | 10% | 7% | 11% | 9% | 6% | 1% | |
| Arsenic (5-10 µg/L) | 0% | 1% | 1% | 1% | 3% | 0% | |
| Arsenic (>10 µg/L) | <1% | 0% | 0% | 1% | <1% | 0% |