Gunpowder River Water Quality Update June 22nd, 2022

Gunpowder Riverkeeper is proud to provide up-to-date water quality information to residents of Baltimore and Harford counties along the Gunpowder and Bush River Watersheds. 

For a map based on Bacteria Monitoring Results and more information on this monitoring work, please visit:

In partnership with Community Environmental Laboratories, an EPA-certified water testing laboratory located in Harford County, we have the capacity to sample various access points along the river for their respective E. Coli levels. Our water monitoring results help inform the public on where they can recreate safely along the River and provide indicators for possible stormwater or point-source pollution. 

The EPA’s Safe Swimming Criteria for Maximum Probable number of E. Coli is 126 MPN (geometric mean) and 235 MPN (single sample).

On June 22nd, Gunpowder Riverkeeper sampled at 5 locations along the Gunpowder River including; Monkton (Monkton Rd/Rt. 138), Pot Rocks (Belair Rd/Rt 1), Jericho Bridge (Jerusalem Mill), Town Creek and Foster’s Branch (Mariner’s Point Park). We sampled in dry conditions, however the area has received 0.66 inches of rainfall since our most recent monitoring efforts. We’ve outlined our results and pictures from our sample sites below: 

Monkton – 80 MPN

Pot Rocks Bel Air Rd/ Rt 1. – 50 MPN

Jericho Bridge – 130 MPN 

Town Creek – 30 MPN 

Foster’s Branch – 130 MPN

According to the Maryland Department of the Environment’s fact sheet on the EPA’s water quality criteria, at the EPA’s Safe Swimming threshold of 126 MPN (geometric mean) / 235 MPN (single sample), it is estimated that 36 individuals out of 1000 swimmers may contract a water-borne gastroenteritis illness. 

When our samples indicate E.Coli counts over the EPA’s criteria, it is recommended that the public avoid contact with the water within that area of the Gunpowder River until further sampling is conducted. The Maryland Department of the Environment also advises to avoid swimming in the river within 48 hours of a heavy rainfall event. For more advised precautions, see the Department’s tips for swimmers

For additional water quality monitoring in the Gunpowder, Little Gunpowder, Bird and Bush Watersheds:

Harford County Health Department Recreational Water Sampling

Baltimore County Department of Health Water Sampling 

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