SYRCL has been working with Cranmer Laboratories to perform the collection and testing of total coliform and E.coli bacteria at 5 popular swimming holes throughout the Yuba River Watershed. In addition to the grab samples for bacteria, basic water quality parameters are also measured including dissolved oxygen, pH, conductivity, air temperature, turbidity, and water temperature. The study included testing at Bridgeport, Purdon Crossing, Edwards Crossing, Highway 49 Bridge, and Oregon Creek Swimming Hole during the months of June, July, and August. SYRCL’s interest in collecting this data is to monitor the health of the river for swimming and recreational purposes during the summer months.
According to the EPA, coliforms are bacteria that are naturally present in the environment and used as an indicator that other potentially harmful bacteria may be present. Taking this into account, the numbers reported for total coliform are a ratio of active cells vs. inactive cells after going through the laboratory procedures. The reported number for E.coli is the count per 100 milliliters of water. E.coli is a single species within the fecal coliform group and is an important water quality indicator because it is only found in the feces of warm blooded mammals. Common sources of such pollution are untreated sewer discharges, failing septic systems, pets and wildlife, storm water, ill swimmers, and improperly disposed boat wastes. We all can help prevent this pollution of our rivers and streams by picking up after your pets at the river, avoiding swimming when ill with diarrhea, and maintaining septic tanks regularly.
EPA Contact Recreation Guidelines indicate E.coli levels should remain lower than 235 MPN/100mL. There are no EPA guidelines for total coliform levels. The month of July shows an elevated reading of E.coli at the Oregon Creek Swimming Hole (see graph above). This bacteria sample was quickly followed up a few days later to determine if this reading was a “hit” or a possible sewage leak. What we call a “hit” is an elevated reading due to wildlife, pets, storm water, ill swimmers, or improperly disposed boat wastes. A “hit” is not a prolonged event, such as a sewage leak. If the second sampling on July 15 was found elevated, we would have followed-up with more samplings, advisories for the public, and a notification to authorities. The second sample did not show an elevated reading, and therefore the E.coli concentration was not a prolonged event and did not trigger an advisory.
In years past, SYRCL collaborated with the State Water Resource Control Board (SWRCB) to test for bacteria contamination at popular swimming holes throughout the Yuba watershed as part of a “Safe to Swim Study.” If you would like to see the study written by SWRCB on the South Fork of the Yuba River and the North and Middle Forks please follow the hyperlinks.