E. coli fouls 100 Colorado waterways. But managers aren’t sure how big the threat is to people playing in streams — The #Colorado Sun

Boulder Creek. Photo credit: Susan from Alameda, CA, USA – CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=2536150

From The Colorado Sun (Sharon Udasin):

The Colorado Department of Public Health and Environment has registered more than 100 waterbody segments on its impaired waters list due to alarmingly high E. coli levels

…public health officials are taking this fecal bacterium quite seriously, as summer temperatures make Colorado’s waterways ideal breeding grounds for Escherichia coli. Policymakers and scientists across the state are working to decipher which types of microbes are lurking in the water, and whether they actually pose a significant threat to human health…

100 waterways considered “impaired” by E. coli

The Colorado Department of Public Health and Environment has registered more than 100 waterbody segments on its impaired waters list due to alarmingly high E. coli levels. While only certain strains of E. coli cause illness in humans, officials do not yet have the capacity to pinpoint in any real-time fashion where and when these strains congregate.

Among the newest segments on the list is the stretch of Boulder Creek between the mouth of Boulder Canyon and 13th Street…

Prior to the latest update in January, the CDPHE had considered only the portion from below 13th Street to its confluence with South Boulder Creek to be impaired…

The city of Boulder isn’t sure where the contamination is coming from, but a team led by Candice Owen, the stormwater quality supervisor, is trying to figure it out. She and her team will be taking more frequent dry weather discharge samples toward the end of the recreation season, when E. coli concentrations are typically highest, she said. The city also recently began posting precautionary signs along the creek, in English and Spanish, indicating the periodic presence of bacteria…

The CDPHE’s Monitoring and Evaluation list, or M&E list, includes waterways in which two, three, or four water samples have exceeded the EPA’s recreational-waters standard of 126 colony-forming units (cfu) per 100 milliliters. For more serious violations, in which there is “overwhelming evidence” of contamination, waterways end up on the state’s list of impaired waters, officially known as 303(d). The Water Quality Control Division defines overwhelming evidence as exceeding water quality standards by more than 50%.

While EPA standards consider recreational waters to be impaired if E. coli levels exceed 126 cfu per 100 mL – as opposed to 235 cfu per 100 mL necessary for swim beach closures – the CDPHE warns that risk of becoming ill still exists in these waters.

CDPHE recommends that people take precautions if they choose to swim in impaired waterways, mainly by avoiding swallowing water and washing their hands upon exiting. To minimize further contamination of the waterways, the department advises showering before entering, taking children on frequent bathroom breaks and staying out of the water when ill with gastrointestinal symptoms…

Confluence Park Denver

Boulder Creek is far from alone in its E. coli problems – with quite a formidable competitor at Confluence Park in Denver, where the South Platte River and Cherry Creek come together.

When storm drains undergo flushing or sediment in streams is stirred up, so, too, are the E. coli lurking in these spaces, explained Jon Novick, environmental administrator at the Denver Department of Public Health and Environment. Like Owen, Novick said pinpointing the bacteria’s exact sources is difficult, but he noted that raccoons congregate near the park and homeless individuals also camp along the river…

…Denver has launched a number of initiatives aimed at tackling the problem – particularly within the stormwater outfalls where “urban drool,” like irrigation return flows and other untreated water tends to accumulate, Novick said. For example, he said, the city has installed UV filtration systems that are quite effective in eliminating E. coli from sewage during dry weather…

Confluence Park samples collected on July 14 indicated that E. coli levels were above recreational standards at both the Cherry Creek and South Platte River testing sites, which Novick attributed to that day’s storm. The Cherry Creek spot is typically the greater offender of the two, due to its shallow water level, sandy bottom and shaded environment, he said…

Nonetheless, Novick acknowledged that officials don’t really know whether exposure to E. coli in impaired waters actually leads to illness. Public health agencies do not typically survey bathers to find out if swimming in the creek has made them sick, he said.

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