HARRISBURG, Pa. (WHTM) — A recent study of Midstate waterways shows bacteria levels can grow to magnificent levels after a steady rainfall.

Between June and mid-August, the Chesapeake Bay Foundation collected a series of 14 samples each from 10 waterway locations in Cumberland and Dauphin counties. Specifically, the samples were tested for E-coli and fecal coliform, both highly common and mostly naturally-occurring bacteria found in creeks and rivers. Results of the study showed a link between high bacteria levels and steady rainfall, which CBF concludes is caused by intense amounts of polluted runoff.

“Runoff can carry livestock and pet waste, untreated or partially treated human waste and other pollutants off the landscape and into our rivers and streams,” said Harry Campbell, executive director of the Chesapeake Bay Foundation’s Pennsylvania office. “We hope the takeaway from this study is that we all must do more to reduce polluted runoff and to use caution when considering going into the water within 48 hours of a heavy rain.”

Samples were collected from various sections of the Conodoguinet, Yellow Breeches and Swatara creeks as well as the Susquehanna River. In one instance, samples collected from the Yellow Breeches at South Middleton Township Park during a dry, non-rainy period revealed E-coli bacteria present at four times the EPA threshold for suitable swimming. The same area, when tested following a steady rain event on June 29, carried 10 times the acceptable levels of E-coli.

Similarly high levels of E-coli were detected in water samples collected on Aug. 2 following a steady rainfall along the Conodoguinet Creek in North Middleton Township and the Swatara Creek at Boathouse Park in Derry Township, among other locations.

Throughout the study, bacteria levels remained within the EPA standards for two sections of the Susquehanna River that were tested. Water samples were collected at both the Fort Hunter and West Fairview boat launches.

In the fecal coliform section of testing, which averages the density of bacteria over five collection periods, waterways as a whole fared better. While the Swatara Creek and Susquehanna River remained well below dangerous levels, the Cumberland County creeks were a mixed bag. The South Middleton Township Park section of the Yellow Breeches tested at three times the EPA acceptable levels of the bacteria while the Yellow Breeches at New Cumberland Borough Park and Conodoguinet Creek at North Middleton registered slightly higher than normal for the bacteria.Get breaking news, weather and traffic on the go. Download the ABC27 News App and the ABC27 Weather App for your phone and tablet.