2016 Bacteria Testing—Maryland Data

Adults and children wade in the river at Cascade Falls.

Waders at the Cascade Falls swimming hole in the Patapsco Valley State Park in Howard County, Maryland. On June 22, 2016, when this photo was taken, the bacteria level in the water was over 130 times higher than federal safety levels.

CBF Staff

Excrement in our streams and rivers is not just a problem in Baltimore City. While media attention recently has focused on sewage leaks in Baltimore, water monitoring this summer in 40 streams and rivers in five counties outside of the city found elevated levels of fecal bacteria, some equivalent to or higher than levels in Baltimore. At some beautiful swimming holes, readings were over 450 times higher than federal safety limits.

Clearly, polluted runoff is a problem—not only in urban areas, but in the suburbs and even in the countryside. Marylanders are waking up to the seriousness of this problem. Pete and Janet Terry are talking of selling their home on the Bird River in Baltimore County—where bacteria levels in feeder streams spiked to unsafe levels this summer. A camp director in Harford County kept his kids from swimming at the Kilgore Falls swimming hole after storms.

Local governments, businesses and citizens must do more to reduce polluted runoff. Localities need dedicated sources of funding to clean up this mess.

2016 is the second year of the water monitoring project in Maryland. View the 2015 enterococci data reported by Hood College (Frederick County), Harford Community College, and Howard Community College.

The map and chart below includes 2016 data for enterococci levels from sites in Baltimore City, Baltimore, Carroll, Frederick, Harford, and Howard Counties in Maryland. Learn more about this project or select a site on the map below to view the results.


Enterococci (cfu/100 ml)   Average: 0 to 61 61 to 600 600 to 2,419 2,419 to 13,243



Red values = Enterococci bacteria counts greater than 61 cfu/100 ml in fresh water. At the time of sampling the site was not healthy for "moderate" bathing use, according to EPA standards. Readings above 151 cfu are not suitable for any bathing or "full body contact." More on the EPA standards.
Red values (underlined and italicized) = Enterococci bacteria counts greater than the 2,419 maximum detection limit for analysis performed that day.
Light blue background = .5 inches or more of rainfall at least 24 hours before collecting water samples


Enterococci are bacteria that are found in the GI tract of warm-blooded animals, which includes all birds and mammals. Their presence in surface water indicates recent contamination with fecal waste. Counts are expressed as cfu or colony-forming units. Counts greater than 61 cfu/100 ml in fresh water indicate conditions not suitable for recreational use by the U.S. Environmental Protection Agency (EPA). Water samples were taken within 24 hours of a rainstorm of .5 inches or more. Exact rainfall amounts on individual sampling days are available. All samples tested at biology laboratories of partner colleges. None of the laboratories is certified by the EPA for bacteria testing.

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