Dillon Wilke takes a water sample for E. coli at Hangman Creek.
On July 16th, we conducted a routine sample of Hangman Creek at People’s Park for E. coli. E. coli. is a type of bacteria that lives in the guts of all warm-blooded animals, including humans. Most strains are completely harmless but the presence of living E. coli outside of the gut and in standing water is an indicator of bad water quality and fecal contamination that may cause human illness. Because of the potential for adverse effects on human health, E. coli is tightly regulated by environmental agencies. In Washington State, the Department of Ecology has set maximum standards for E. coli in recreational water as 320 colony forming units (CFU)/100mL of water for a single sample and 100 CFU/100 mL as the geometric mean of at least 10 samples.
Water placed on “Petrifilm” is incubated to grow bacteria.
Every other week we take water samples from Hangman Creek and the Spokane River to test for E. coli. We place 1 mL of water on Petrifilm and place these samples in an incubator for 18-24 hours. Although this is not EPA approved, it does provide a quick and cheap method for screening for E. coli.
Our first sample at Hangman Creek came back as 30 CFU/1mL. That is the equivalent of 3,000 CFU/100mL. What does this mean? Put simply, on July 16th, Hangman Creek at People’s Park was not safe to swim of splash around in. However, there are a lot of caveats to this claim. A single 1 mL sample of water from a river is not necessarily representative of the entire river. It is possible that the random sample we took was uncharacteristic of the river as a whole. The E. coli levels in the surrounding area could have been much lower or non-existent. In order to get a better representative sample, we came back to the same place the next day to sample 100mL of the water and took the sample to Anatek laboratory. These results showed 139.1 CFU/100 mL, which is a whole order of magnitude decrease from the previous day’s sample, but still of some concern. We took both sets of samples after a heavy rainfall, which can cause pathogens and E. coli to wash into the river. Dry weather samples taken 7/31 show much lower results.
Living in the gut of warm-blooded animals, E. coli thrive in conditions that are often very different than surface water. This means, unless there is a continuous input of E. coli from animals or sewage, low levels of E. coli with occasional spikes are common in most water bodies. Circumstances that can lead to continuous high levels include: improper sewage discharge into the river, unenclosed livestock defecating in the river, or untreated human feces washing into the river. At this time, there is no conclusive evidence to the source of the high E. coli levels in Hangman Creek. It could have been a one-off brought on by the large rainstorm washing fecal matter into the river. Interestingly, the other spots we sampled on July 16th, showed elevated levels of E. coli but nowhere near the contamination at Hangman Creek. Because of the potential human health issues, more sampling and research must take place to identify any unique or preventable problems Hangman Creek has with E. coli contamination.
To minimize the risk of getting sick from playing in rivers and lakes, heed any advisories, take a shower afterwards, cover any open cuts or sores, and do not drink the water. Special precautions should be taken after rainstorms because fecal contamination is often higher at this time due to surface runoff.
If we find high results during our sampling events, we will report it on our Facebook Page and contact the appropriate state or local agency. In this case, we will be reporting our findings to the Washington State Department of Ecology that currently has a TMDL (cleanup plan) for fecal coliform in Hangman Creek.