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Swim Water Testing
The Town of Colchester performs water testing of E. coli annually, with 2025 testing taking place Mondays and Wednesdays starting June 18th and ending August 27th. E. Coli is a very effective indicator for the possible presence of more harmful bacteria that can cause human health problems. More information is provided below.
BEACH STATUS
BEACH | STATUS | LAST UPDATED | NOTES |
Bayside Beach | OPEN | 8/14/25 | |
Rossetti Beach | OPEN | 8/14/25 |
Status meanings:
OPEN - The area meets criteria suitable for swimming
CLOSED - The area does not meet criteria suitable for swimming (swimming not recommended)
2025 E. Coli Test Results (MPN/ 100 mL) | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Sample Date | 1-DP Delta Park | 4-PP Porter's Point | R1 Rossetti Beach 1 | R2 Rossetti Beach 2 | 6SW Spauldings West Beach | 7MS Moorings Stream | B1 Bayside 1 | B2 Bayside 2 | B3 Bayside 3 | 8SH Smith Creek | 9CT Camp Tee | 11CC Crooked Creek |
6/18 | 1.0 | 22.8 | 123.4 | 22.6 | 19.7 | 9.0 | 108.1 | 72.3 | 98.5 | 19.9 | 78.9 | 727.0 |
6/23 | 1.0 | 107.1 | 24.1 | 21.1 | 1413.6 | 76.7 | 196.1 | 135.4 | 47.4 | 26.2 | 9.8 | 23.8 |
6/25 | 29.9 | 4.1 | 13.1 | 19.7 | >2419.6 | 36.9 | 19.9 | 8.6 | 2.0 | 3.1 | 2.0 | 123.6 |
6/30 | 2.0 | 16.8 | 60.2 | 42.6 | 205.3 | 101.7 | 66.3 | 28.8 | 31.5 | 9.8 | 8.5 | 150 |
7/2 | 4.1 | 33.6 | 45 | 37.2 | 131.4 | 68.2 | 28.8 | 48.7 | 45.5 | 3.0 | 7.4 | 55.4 |
7/7 | 11.0 | 22.8 | 5.2 | 6.3 | 28.8 | 20.3 | 365.4 | 172.3 | 75.2 | 11.0 | 1.0 | 114.5 |
7/9 | <1.0 | 27.9 | 54.8 | 80.9 | 6.3 | 172.5 | 7.5 | 3.0 | 8.5 | 1.0 | 3.0 | 25.5 |
7/14 | 8.4 | 18.5 | <1.0 | <1.0 | 18.7 | 980.4 | 32.7 | 14.5 | 17.3 | 25.3 | 1.0 | 98.5 |
7/16 | 9.8 | 25.9 | 2.0 | 5.2 | <1.0 | 249.5 | 74.9 | 143.9 | 11.0. | 2.0 | <1.0 | 7.4 |
7/21 | 2.0 | 131.7 | 34.5 | 18.5 | <1.0 | 167.40 | 214.2 | 461.1 | 160.7 | 34.1 | 88.4 | 435.2 |
7/23 | <1.0 | 2.0 | 1.0 | 1.0 | 9.6 | 65.7 | 231 | 92.2 | 17.0 | 201.4 | 8.5 | 172.5 |
7/28 | 51.2 | 4.1 | 3.1 | 11.0 | 3.1 | 344.8 | 24.1 | 15.8 | 71.7 | 209.8 | 17.5 | 101.9 |
7/30 | 3.1 | 121.1 | 7.4 | 1.0 | 1.0 | 29.5 | 90.9 | 73.3 | 69.7 | 686.7 | 20.0 | 6.3 |
8/4 | - | - | 7.5 | 7.4 | - | - | 98.7 | 48.1 | 59.1 | - | - | - |
8/6 | 3.1 | 5.2 | 3.1 | 2.0 | 1.0 | 6.3 | 12.1 | 17.1 | 45.9 | 648.8 | 22.6 | <1.0 |
8/11 | 3.1 | <1.0 | <1.0 | <1.0 | 1.0 | <1.0 | 6.3 | 3.1 | 5.2 | 29.8 | 163.8 | 4.1 |
8/13 | 135.4 | 1.0 | 31.3 | 5.1 | 3.0 | 191.8 | 8.5 | 26.6 | 20.2 | 344.8 | 93.3 | 4.1 |
Past years' Test Data can be viewed here: 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024.
Want a comprehensive guide on healthy recreational waters and what these results mean? Click here!
The Vermont State Health Department recommends not swimming in water where E. Coli levels are higher than 235 most probable number of colonies (MPN) per 100 milliliters of water. When water samples come back with E. Coli levels higher than 235 MPN/100mL, those readings will appear in Bold.
For Bayside Beach and Rossetti Natural Area, multiple samples are taken each testing day. If two or more of the samples have unsafe E. Coli levels, the affected beach will have signs erected warning of these high levels. The beach closure will remain until new tests come back with safe E. Coli counts.
AS A GENERAL RULE: Swimmers should always stay clear of streams, and where streams and storm drains flow into the lake. A distance of at least 100 feet from stream and drain outflows is advised.
Want more Lake Champlain water quality data?
State parks perform their own E. Coli and Cyanobacteria water quality testing for Niquette Bay State Park. Results can be found at: https://vtstateparks.com/niquette.html. The Lake Champlain Basin Program also performs water quality testing in Malletts Bay from April through October as part of the Lake Champlain Long Term Monitoring Project. Since 1992, the program has tested for phosphorus, nitrogen, chloride, and other nutrients, and scientists also watch for signs of cyanobacteria (blue-green algae).
Have Questions?
For questions about Bayside or Rosetti Beach, please contact the Parks and Recreation Department at 802-264-5640.
For questions about swim water testing please contact the Department of Public Works at 802-264-5621.