2026 Orono Beach Testing
Lake Orono is tested for E. coli bacteria (Escherichia coli) twice per week from Memorial Day through Labor Day at the public beach. This measure determines fecal contamination in the lake. Elevated bacteria levels can be harmful to humans and can occur after significant rain events when bacteria sources are washed into the lake from land.
Note: We are the only Sherburne County lake that tests for bacteria. All counts are in MPN/100mL.
Counts below 235 MPN/100 mL are considered safe.
Date | North of Beach | Middle of Beach | South of Beach | Geometric Mean |
|---|---|---|---|---|
| 6/25/26 | 65.7 | 980.4 | 365.4 | |
| 6/23/26 | 214.3 | 1119.9 | 547.5 | |
| 6/16/26 | 195.6 | 34.5 | 111.2 | |
| 6/11/26 | 307.6 | 155.3 | 55.6 | |
| 6/9/26 | 290.9 | 72.7 | 79.8 | |
| 6/4/26 | 39.3 | 67.0 | 86.2 | |
| 6/2/26 | 85.7 | 3.1 | 14.2 | |
| 5/26/26 | 16.9 | 15.3 | 64.5 |
Minnesota Department of Health Recommended Water Quality Criteria
MDH recommends posting an advisory at the beach indicating swimming and wading are not recommended when laboratory or model results show E. coli counts exceed established standards.
Minnesota Lake Superior beach monitoring program sample standard (based on EPA guidelines):
- The geometric mean based on not less than 5 samples within a 30-day period shall not exceed 126 organisms per 100 milliliters, and
- A single water sample shall not exceed an E. coli count of 235 organisms per 100 milliliters.
Beach advisories
A beach advisory is typically posted to reduce the likelihood of people getting sick when increased bacterial levels in the water are found. Advisories may occur for a variety of reasons, for example, pollution events (such as breaks in sewage pipes or rainfall carrying pollutants into the water) or contamination of the water by bathers, pets, or wildlife. Advisories are removed when bacterial levels fall within the acceptable standard.
For more information see:
https://www.health.state.mn.us/communities/environment/recreation/beaches/monitoring.html