CALIFORNIA, Md. – Elevated bacteria levels following summer rainstorms — along with a separate blue crab die-off in the lower Potomac River — are raising health and environmental concerns in Maryland, according to watershed groups and state officials.
Most Sites Fail Bacteria Standards
According to a July 10 report from the Arundel Rivers Federation, all monitored sites failed water quality standards for recreational swimming except for Arundel on the Bay and Columbia Beach.
“Every site failed this week except for two on the mainstem bay,” the group stated. Samples are collected Thursday mornings and processed by Anne Arundel Community College. Results are measured against the EPA’s recommended limit of 104 cfu/100mL for enterococcus bacteria, which signals the possible presence of harmful pathogens.
The group warned that “bacteria levels can increase after major rain events” and advised the public to avoid swimming for 48 hours after rainfall, avoid entering the water with open wounds.
Upper Potomac River Shows Sustained Contamination
The Upper Potomac Riverkeeper reported July 11 that most of its sites failed Maryland’s geometric mean standard of 126 MPN for E. coli, even if some single samples were within acceptable limits.
“There are several sites that are below the 410 and even the 126 level as a single sample,” the group said. “But most of the sites failed the geometric mean limit of 126.”
The geometric mean reflects contamination trends over time and is used to evaluate overall public health risk. “If the geo-mean is red and the single sample is red, then there is a very high risk,” the group added. “This is especially for children and adults with immune deficiencies.”…