Message from Mike: Chicken Bridge Testing

Looking ahead to the 2023 Swim Guide season, we are continuing to monitor the area upstream from Chicken Bridge and investigate E. coli issues identified in work for last year’s Swim Guide.  E. coli (Escherichia coli) is a bacteria found in the gastrointestinal tract of humans and animals, which in water is a strong indicator of fecal contamination, and high concentrations can be a sign of other disease-causing organisms. Although not all strains of E. coli are harmful, consumption of certain types can lead to gastrointestinal discomfort all the way to meningitis, septicemia, urinary tract, intestinal infections, and even severe or deadly disease in children and the elderly. Septic systems, public sewage, and agricultural runoff are all potential sources for E. coli. 

For the Chicken Bridge investigation, multiple rounds of water samples have been collected from Cane Creek, Big Branch, Terrell’s Creek, Collins Creek as well as from some smaller tributaries, both from road-accessible sites and where these streams meet the Haw. HRA uses an EPA-approved process for determining bacterial levels in water samples. A reagent is dissolved in a 100 mL sample, which is poured into a tray that automatically distributes the sample into 97 separate wells of different sizes. The tray is sealed and placed in an incubator for 24-28 hours. Results are calculated statistically using a Most Probable Number (MPN) analysis, which is based on the random dispersion of microorganisms per volume in a given sample. The sample trays are reviewed after incubation for E. coli growth, which is indicated by characteristic color changes and fluorescence. Large and small positive wells are counted and referenced to a table which indicates concentration levels. While we have not found levels consistently matching those from 2022, we will continue to monitor these sites and are equipped with DNA tests from Jonah Ventures, which will aid in identifying potential sources of pollution. We will continue to track levels at these creek locations along with our other monitoring.  

North Carolina currently does not have a regulatory standard for E. coli, instead using a system based on the broader group of fecal coliform bacteria. These standards are generally less stringent, and E. coli concentration has been shown to be a better predictor of swimming-related gastrointestinal illness. Given these regulatory standards, monitoring waterways for E. coli contamination is a primary task for HRA and Riverkeepers throughout the state. Dangerously high levels were detected in the Dan and Mayo Rivers in September 2022 by Dan Riverkeeper Dan Pulliam. Along the coast, rising sea levels and high tides combined with increased development are overwhelming aging infrastructure, sending stormwater and sewage into swimming waters as pipes corrode and systems overflow during heavy rain events. A key feature of the HRA Swim Guide is testing our sites for E. coli concentrations, as this bacteria can directly impact human and animal health.

Posted in From The River: Blog

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