Using E. coli to spot potential health risks
We test for E. coli, a common bacterium found in the guts of warm-blooded animals, including humans. While most strains are harmless, its presence may signal other pathogens that can cause illness from water contact.
While we can’t guarantee water safety, we give you the tools to assess the risks yourself.
Understanding water risk levels
The different colored icons and bacteria ranges represent risk thresholds, which are based on the statistical chances of getting sick if you come in contact with water in these bacteria ranges.
Clean for swimming
Swimming is defined as any recreation or other water use in which there is prolonged and intimate contact with the water with a significant risk of ingestion of water. These include, but are not limited to, wading, swimming, diving, surfing and water skiing.
Clean for boating only
Boating is defined as any recreation or other water use in which contact with the water is either incidental or accidental. These include but are not limited to fishing, including human consumption of fish, boating and limited contact incident to shoreline activities.
Not clean for either
When water is labeled not clean for either, it means that engaging in activities like swimming or boating may pose health risks. Contamination or elevated bacteria levels make any contact with the water potentially harmful.
From river to report: our process
Monitoring typically occurs from late May to October, when people use the water for recreation the most.
Volunteers across different partner organizations are trained annually on proper sampling techniques to collect a representative sample and avoid contamination. Most groups also collect Quality Control samples to verify sampling, handling, and lab processing techniques.
Most samples are analyzed using the Colilert system from IDEXX, an EPA-approved method used globally for millions of tests each year.
Results are posted to this site’s map within 24 hours after the sample was taken.
Your trusted water quality partner
Established in 2009, our lab processes bacteria samples from over 80 locations in Massachusetts and Vermont during the swimming and boating season, providing fast, reliable data for public and decision-makers.
About us