Severn River Association warns swimmers of high bacteria levels

Memorial Day weekend is a popular time for swimmers to hit local beaches and watering holes throughout the region, but with high levels of fecal bacteria reported last week, one local waterway advocate is warning residents not to come into contact with the water.

Anne Arundel County always has a preemptive advisory in place, warning people not to swim or come into contact with water at beaches for at least 48 hours after a 1/2 inch or more rain fall. Between Tuesday and Saturday 1.45 inches of rain fell, most of it mid-week, according to the National Weather Service.


On the county's website there are currently no advisories or closures listed for local beaches.

However, the Severn River Association issued a warning of its own Sunday morning — "It certainly isn't safe to swim in local waters this Memorial Day weekend."


The reason, the group said in the post to Facebook, is high levels of fecal matter in the water. The page cited data collected Wednesday and Thursday from Operation Clearwater, a water monitoring program run by Anne Arundel Community College's Environmental Center. Nine out of 11 beaches tested along the Severn had bacteria levels that were unsafe for swimming.

The program primarily tests for enterococci, an indicator of fecal contamination. Enterococci bacteria are found in the gastrointestinal tracts of warm-blooded animals, according to Operation Clearwater's webpage. A count of more than 104 colony-forming units per 100 milliliter of water means the water isn't fit for recreational uses, such as swimming.

The program's director Tammy Domanski said last week's readings were high, though not historically high for a significant rainfall. Rain washes the bacteria from the land into the water, resulting in higher readings after a storm.

What did make last week's round of testing stand out was that sites which typically stay below the unsafe swimming threshold even after a storm were above it, Domanski said. More testing will be required to determine why.

"From one week I can't draw conclusions," Domanski said.

The Operation Clearwater data is available at