Bacteria monitors receiving training and testing kits at the June kick-off meeting. Bacteria monitoring coordinator, Kelsey Bitter, is second from left.
For the fifth consecutive summer, the fecal bacteria levels in the Little Falls watershed have exceeded the Maryland State Standards for recreational water use - even for infrequent human contact. According to our 16-week study conducted at eight sites, the Little Falls Branch, the Willett Branch and the Minnehaha Branch fail to meet the criteria for safe water play at all locations.
Willet Branch Levels Still Highest in Watershed
Willett Branch bacteria levels reached as high as 24,190 MPN, the highest number our tests can count. The tests were conducted each week at two sites on the Willett Branch, which runs through downtown Bethesda underground emerging into the daylight by the Bethesda Pool near the Little Falls Parkway. In 2024, Montgomery County identified the Hyatt Hotel in downtown Bethesda as a point source of fecal bacteria. Hotel waste water was being sent into the storm drain system. The problem was fixed in December 2024, but the Willett Branch numbers are still higher than other sites in the watershed.
While the Little Falls Branch sites never reached the level of fecal bacteria pollution seen in the Willett Branch, all five sites regularly saw numbers in excess of 1,200 MPN, three times the maximum number for safe water play. Little Falls Branch runs through the Town of Somerset and the Little Falls Stream Valley Park and into the Potomac River at Little Falls and is a popular stream for wading and other recreation.
Minnehaha creek included for testing this year
Minnehaha Results, 2025, with counts and geometric mean. Our normal test cannot count numbers above 2,419 so the geometric mean is most likely much higher.
The Minnehaha creek at Glen Echo was added to the testing sites this year after a request from residents of Glen Echo. The test site is in the Glen Echo National Park.
The site tested with the same variation of bacteria levels that we saw in other sites - passing nine times, and exceeding the Maryland state standards for safe water play seven times. The lowest counts were in July and August and were as low as 85 MPN; the highest numbers were above 2,419 - the highest number our normal testing can count. Despite seven weeks of passing numbers, the site is still not considered “suitable for recreational use” as the geometric mean (shown on the chart to the right) is still over 125 MPN per 100 ml.
Bacteria Pollution is a serious health threat for humans
Fecal bacteria pollution is odorless and invisible to the naked eye. Our streams look lovely, the water is clear and they rarely have a bad odor. Yet, they are not safe for human recreation. Ingesting the water can cause extreme diarrhea or other gastronomical symptoms. Open sores can lead to rashes and other infections. When the levels are higher than the Maryland State standard, people are advised to stay out of the creek - no swimming, or total immersion at all - and to wash carefully if they do come in contact with the water.
The Complete Report is HERE. More information about our Bacteria Monitoring Program is HERE.
thank you
Thank you to Kelsey Bitter, our bacteria monitoring program coordinator, for the great job she did this summer. Thank you to her and Woody Stanley for the end-of-season report. The 2025 water quality data was collected by volunteer citizen scientists every week this summer. The findings in the report would not have not been possible without their dedicated effort. In no particular order, the LFWA extends a thank you to David Batson, Mark Cheng, Emily Cordas, Will Dolan, Susie and Amelia Hodges, Madelyn Lash, Leanne McDougal, Bobby Pestronk, Dan and Corrina Spealman, Emily, Will and Averill Simone, Julie Steinberg, Matt Stiglitz, Karen Thornton, Sally Winthrop, and Binh Wrona