City staff monitoring E. coli levels in Boulder Creek
Along with many streams on the Front Range and throughout Colorado, Boulder Creek is impaired for E. coli, meaning E. coli levels in Boulder Creek sometimes exceed the level deemed safe for recreational use by the U. S. Environmental Protection Agency.
The city routinely monitors E. coli in Boulder Creek, but because Boulder Creek is not regulated as a swim beach this data isn’t used to prohibit recreation. Instead, community members are encouraged to be educated on the risks of recreating in Boulder Creek and how to reduce those risks.
Escherichia coli (E. coli) are a large and diverse group of bacteria that typically live in the digestive tracks of warm-blooded animals. Most strains of E. coli are harmless, but some can make you sick. Measuring for E. coli is easier than measuring for all possible pathogens in waterbodies, so it is widely used as an indicator of the presence of bacteria and viruses that can make people sick. E. coli concentrations provide information about the possible presence of pathogens but does not provide information about where the E. coli is coming from.
When wading or swimming in any natural water body, including Boulder Creek, you may be exposed to E. coli and other microorganisms. Most types of E. coli do not cause illness, but there are certain strains that can cause gastrointestinal illness and symptoms can include nausea, vomiting, stomachache, diarrhea, headache and fever. Boulder Creek does periodically exceed the level of E. coli deemed safe for recreational use by the U.S. Environmental Protection Agency.
Use these tips to help reduce the chance of getting sick while swimming:
Everyone can help reduce pollution in Boulder Creek and other creeks in Boulder. Stormwater run-off goes directly into our creeks without being treated. Trash, debris and pollution you see on streets, sidewalks and parks is therefore likely to end up in the creeks.
The city has explored using infrastructure designed to prevent raccoons from entering the stormwater system. Due to limited effectiveness, safety concerns and cost, the city determined this was not a viable solution. They city’s Bear Protection Ordinance requires bear-resistant containers if trash and compost are put out the night before pickup.
The city provides pet waste bag stations and dog waste receptacles. A Pet Waste Removal Fine and educational Let’s Doo It Campaign encourages community members to understand the importance of picking up after pets. About 80,000 pounds of dog waste is left behind on OSMP trails annually.
The city’s Universal Zero Waste Ordinance requires all properties in Boulder to have waste services that provide separated compost, recycling and trash so that waste can be properly managed. The city regularly cleans up creeks and has a restaurant outreach program to promote proper waste and fats, oils and grease (FOG) disposal practices.
The city will continue to operate its robust illicit discharge detection and elimination (IDDE) program and respond to all observed and reported illicit discharges.
The city did not find any direct connections between the sanitary and stormwater sewer systems. However, there was evidence of human sources in multiple outfall investigations. The city saw improper disposal of diapers and human waste and found positive results for human genetic markers in the stormwater system. Human fecal contamination is more likely to cause illness than other sources of bacteria and should be taken seriously.
The city performs routine pipe condition assessments and repairs on sanitary and stormwater pipes. In addition to maintaining properly functioning pipes, these assessments and repairs protect water quality by preventing sewage from directly or indirectly entering Boulder’s surface waters or stormwater system.
The city also regularly performs trash pickup along Boulder Creek, maintains trash receptacles and maintains multiple public restroom facilities adjacent to Boulder Creek. Restroom accessibility has been increased by adding a restroom south of the 6th Street Bridge crossing.
While E. coli typically lives in the digestive tracks of warm-blooded animals, it can become naturalized, which means it will exist in the natural environment on its own. This means that once E. coli is present in an area, like in the stormwater system pipes and on the stream bottom, it can continue to grow. This results in more E. coli, beyond what has been introduced by the other listed bacteria sources. While naturalized E. coli found in the environment is less of a health risk than E. coli from fecal contamination, it is not possible to differentiate between the two. The best use of time and resources for the city and community is to focus our efforts on controllable sources of bacteria.
Dry-weather flow is water in the stormwater system that did not come from rainfall. While not a direct source of E. coli, dry-weather flows can mobilize E. coli in the stormwater system and flow into Boulder Creek. The most common sources of dry-weather flow included:
Sources of dry-weather flow are dispersed and episodic and are sometimes necessary (groundwater sump pumps). No single solution will eliminate dry-weather flow in the stormwater system. The city assists in repairing leaking ditches, implementing the city’s Water Efficiency Plan, supporting community water conservation efforts and maintaining irrigation equipment on city properties. The most effective dry-weather flow reduction strategy is a combined effort between the city and the community.
The City of Boulder’s stormwater group has routinely monitored the health of Boulder Creek for over 30 years. Boulder Creek E. coli is currently monitored at least monthly at six locations within the city. This monitoring allows the city to evaluate current conditions, examine long-term trends and better understand the health of Boulder Creek as the city grows and changes.
In addition to routine monitoring, the city has conducted outfall investigations to further understand Boulder Creek’s E. coli levels. Outfall investigations have focused on identifying sources of E. coli from priority stormwater pipe networks that drain to Boulder Creek following the steps outlined in the 2019 E. coli Total Maximum Daily Load (TMDL) Implementation Plan. The plan and other study reports can be provided upon request.
The city’s stormwater group plans to continue routine E. coli monitoring in Boulder Creek and investigating possible sources of E. coli, particularly any evidence of human waste. The city is currently reviewing and compiling findings to date from five years of implementing the 2019 TMDL Implementation Plan. This analysis will inform specific next steps for the program and will be shared on this web page by the end of 2024.
Bacteria concentrations can vary dramatically within short periods, but the following trends for Boulder Creek have been identified using the city’s routine E. coli monitoring data.
Additional results and discussion can be found in the Keep It Clean Partnership water quality report.
Yes, the city monitors E. coli in Boulder Creek monthly at six locations within city limits. Weekly samples are taken between August and October when E. coli levels are typically highest. The E. coli samples are analyzed at the city’s water quality laboratory.
The city does not post its E. coli monitoring results in real time because the analysis takes over 24-hours to complete and concentrations can vary dramatically within a short time. Therefore, the city focuses on trends rather than individual results. More analysis and discussion can be found in the Keep it Clean Partnership water quality report and the raw data is available upon request.
Investigations have found that there is no single or easily controllable source of E. coli causing the impairment in Boulder Creek. Instead, a variety of dispersed sources have been identified.
Boulder Creek may be periodically closed to recreation because of high flows, but Boulder Creek does not close due to high E. coli concentrations because it is not regulated as a swim beach. E. coli levels are highly variable, even for samples taken in close proximity, and with the rate of water moving in the creek and the 24 hours required to analyze a sample, the sample results are not meaningful to make real-time management decisions. Instead, community members are encouraged to be educated on the risks of recreating in Boulder Creek and how to mitigate those risks.
Boulder Creek became impaired for E. coli in 2004 when monitoring data found E. coli concentrations periodically exceeded the state’s standard for E. coli. Following the Clean Water Act, streams get placed on a state’s list of impaired waters when water quality standards are exceeded. All stream impairments can be found on the Colorado Department of Health and Environment’s Impaired Waterways webpage.
Impairments are typically followed by a Total Maximum Daily Load (TMDL) planning document that establishes the maximum amount of a pollutant a waterbody can receive without exceeding water quality standards. The city was the first in Colorado to develop a TMDL for E. coli in 2011. The city also developed a TMDL implementation plan to guide the city’s efforts to understand the sources of E. coli in Boulder Creek and evaluate mitigation strategies. The plan was most recently updated in 2019.
A stream can get delisted from the state’s impaired waters list if it meets the water quality standard for a period of time. E. coli impairments are difficult to delist, unless there is a single point source that is controllable. In an urban environment like Boulder, there are many dispersed sources, some of which are controllable, but many of which are not. Boulder’s goals are to maintain stable or decreasing long-term trends in Boulder Creek, to ensure that the city’s infrastructure is not directly contributing to the problem, to work with the community to mitigate other sources, and to meet our stormwater permit requirements.
