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Image by CDC
Image by CDC

E-Coli Monitoring

Fecal coliform bacteria (E-Coli) are found in the feces of warm-blooded animals such as people, pets, and wildlife.  E-Coli contamination in streams can come from leaking sewer pipes, pet waste, and wildlife. As the amount of fecal coliform bacteria in the water increases, the risk of contracting a waterborne illness increases.  

E-Coli Results

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We test one site at Cabin John Creek in Cabin John Local Park for now, with plans to expand to three sites in summer 2023. We test in warm weather from June to mid-September when bacteria thrive.

The following are benchmarks are used throughout the Potomac River watershed for reporting E-coli levels:

  • HIGH - FAILS, Avoid Contact (deemed unsafe by MD State Standards for water play)

  • MODERATE - PASSES, but use Caution

  • LOW - PASSES, Have fun!


We suggest avoiding contact with creeks 72 hours after a heavy rain. We also recommend keeping your face out of the creek and always hosing down your dog and kids!... or a shower after playing in the creek in the summer.

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Our lab work is done by the Anacostia Riverkeeper’s water quality lab.

What do I do?

During the summer months, E-Coli thrives in warm weather. We are not alone, many places around DC and the Potomac have elevated levels of E-Coli in the summer. Check out TheSwimGuide which we will be posting our data to soon.

If you have a dog, the best thing you can do is pick up the poop! Please pick up after your pet anywhere outside (yard, sidewalk, street, parks, woods) -- you'll be helping Cabin John Creek! Stormwater just flushes it into the storm drains which end up in our creeks.

From DNA testing of water samples, it is estimated that at least 20% of bacteria in waterways comes from dogs. Dog poop has few nutrients yet bacteria love it. Other sources include wildlife and sewer leaks. 

Report any sewage leaks to WSSC!


We’ll be testing each summer on Wednesday mornings from June through mid-September at the picnic table by the creek in Cabin John Local Park (off of MacArthur Blvd near one lane bridge). 


Want to help? Volunteers can help by driving the sample to Pierce Mill in Rock Creek Park for handoff to the Anacostia Riverkeeper before 10am each Wednesday. We also need volunteers to post results in trail kiosks and our communities. If we get enough volunteers, we can expand to other locations.


Email if you can help on bacteria testing.


Made possible through the Montgomery County Watershed Restoration and Outreach Grant program funded

through the Montgomery County Water Quality Protection Fund”,

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Additional Info

WSSC also performs testing in the Spring and Fall each year as required by their Sanitary Sewer Overflow Consent Decree. Samples are analyzed for human fecal markers and one animal (bird/gull) fecal marker.  In 2022, all human fecal markers were non-detect. WSSC test sites in Cabin John Creek are at MacArthur Boulevard and Cabin John Regional Park. 


Any health alerts or sewage leaks will be posted on the WSSC site or their Sewer Alert Map

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