Escherichia coli (E. coli) is a surrogate measure, or indicator for fecal contamination in recreational waters. Indicator organisms themselves do not cause illness under normal conditions. Elevated bacteria levels generally occur in aquatic environments after rain events when bacteria from various sources are washed into the lakes. Potential sources of E. coli in lake water include:
- Foreshore beach sand
- Organic debris
- Leaking diapers, bather defecation
- Polluted stormwater runoff
- Sewage spills near the beach
- Sewer line break discharges
- Stream inflows
- Wild and domestic animal waste
We test beaches weekly from June through August for E. coli bacteria, which can indicate a health risk. We follow Minnesota Pollution Control Agency guidelines for beach closures. Two types of results will close a beach:
- Single-Sample Limit: A single result of over 1,260 organisms per 100 mL of water
- Geometric Mean: Five samples equally spaced over a 30-day period exceed 126 organisms per 100 mL of water
Elevated bacteria levels in MPRB lakes usually occur as a result of rain events and return to normal levels within 24 to 48 hours of the rain event.
We will re-sample, and reopen the beach only when bacteria levels are within state guidelines.
We also provide water quality information on the beach status hotline: 612-313-7713