Nitrogen, phosphorus, and sediment flowing off agriculture and urban/suburban landscapes, is the major source of pollution damaging Pennsylvania rivers and streams.
Sampling of 10 southcentral Pennsylvania waterways this summer found elevated levels of bacteria that can be considered as a surrogate for nutrients and sediment that are carried into rivers and streams as polluted runoff. The laboratory results prove that polluted runoff is real and must be reduced.
Elevated levels of E. coli bacteria, which the Environmental Protection Agency (EPA) says show an increased risk to human health, were found in more than half of the streams tested, especially when sampled within 48 hours of heavy rains. Some of those E. coli results were more than 10 times above the level the EPA considers to be acceptable for swimming. Also, the average of test results for fecal coliform bacteria in dry conditions for a 30-day period, were over the Pennsylvania Department of Environmental Protection's acceptable threshold at three sites.
While emphasis was on gathering water samples after rain events of more than 0.25 inches, sampling in dry conditions illustrates the magnitude of polluted runoff that rain events can deliver. Samples were collected from early June through mid-August from the Conodoguinet, Swatara, and Yellow Breeches creeks, and the Susquehanna River. Sources of the bacteria found in the streams were not determined. Testing was done by ALS Environmental Laboratory in Middletown.
Elevated bacteria numbers after rain events not only suggest waiting 48 hours after a rainstorm to enter the water, they demonstrate the importance of reducing polluted runoff damaging rivers and streams. Some of the ways to reduce the amount of polluted runoff include planting trees along streams and streets and in backyards, planting cover crops on farm fields, fencing cattle out of streams, and picking up after our own animals.
The map and chart below includes data for E. coli levels from sites in Cumberland, and Dauphin Counties in Pennsylvania. Learn more about this project or select a site on the map below to view the results.
E. coli (cfu/100ml) Geometric Mean: 0 to 126 126 to 235 235 to 400 400 to 480
E. coli Bacteria Data
|Red values||= E. coli counts greater than 235 cfu/100 ml. The EPA considers waters over the 235 cfu/100 ml threshold to be unsuitable for swimming.|
|Red values||(underlined and italicized) = E. coli counts greater than 2,419. 2419 is the maximum amount countable in a single sample using this methodology.|
|Light blue background||= .25 inches or more of rainfall within the 24 hours before water samples were collected.|
|Lavender background||= .25 inches or more of rainfall within the 48 hours before water samples were collected.|
E. coli are bacteria that are found in the intestines of warm-blooded animals and humans. Their presence in surface water is a strong indication of recent sewage or animal waste contamination. Counts are expressed as cfu or colony-forming units. Counts greater than 235 cfu/100 ml in fresh water indicate conditions not suitable for swimming at public beaches, by the U.S. Environmental Protection Agency (EPA). All samples were tested at the ALS Environmental Laboratory in Middletown, PA. NELAP certification #PA 22-293; methodology S9223B-04.
Fecal Coliform Bacteria Data
Fecal coliform are bacteria that are found in the intestines of warm-blooded animals and humans. Their presence in water may not be directly harmful and does not necessarily indicate the presence of feces. It does indicate an increased likelihood of harmful pathogens in the water. Counts are expressed as cfu or colony-forming units. Geometric mean counts (far right column) greater than 200 cfu/100 ml water (shown in red) indicate conditions over the threshold of what the Pennsylvania Department of Environmental Protection considers to be acceptable. Here, Geometric mean is the average of five test results in dry conditions over a 30-day period. All samples were tested at the ALS Environmental Laboratory in Middletown, PA. NELAP certification #PA 22-293; methodology S9222D-97.