Routine Monitoring by Boulder's Stormwater Group

The city of Boulder’s stormwater group conducts routine water quality and biological monitoring in Boulder Creek to evaluate current conditions, examine long term trends, and gain a better understanding of the aquatic ecosystem of Boulder Creek.

Safe Recreating Information

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. Below are some tips to help reduce the chance of illness resulting from E. coli exposure while swimming:

  • Don’t get water in your mouth, eyes or open wounds
  • Stay out of the water if you are sick
  • Wash your hands and shower after being in the creek
  • Don’t swim within in 48 hours of a rainstorm

Four new signs informing the public about safe practices when recreating in the creek were posted along the Boulder Creek Bike Path in July 2020.

What Is E. coli?

Escherichia coli (E. coli) are a large and diverse group of bacteria that typically live in the digestive tracks of warm-blooded animals. When found in our surface waters (rivers, streams, and lakes) E. coli has been used as an indicator of fecal pollution, which can originate from a variety of sources including wildlife, livestock, pets, and sewage. Most strains of E. coli are harmless, but some can make you sick.

What the City Is Doing to Address E. coli

In 2019, the city developed an update to the previous E. Coli TMDL Implementation Plan. The plan lays out the actions the city is and plans to take to mitigate E. coli sources to Boulder Creek. Based on the TMDL Implementation Plan, the city is currently in the process of developing storm sewershed management plans (SMPs) to identify sources of E. coli within the city’s MS4 system. The first plan was developed for the University Hill area of the city and was completed in 2020. For more information, read the April 2019 WRAB Memo and the May 2019 WRAB Memo.

What is a TMDL?

A Total Maximum Daily Load (TMDL) establishes the maximum amount of a pollutant a waterbody can receive without exceeding water quality standards. TMDLs are created for surface waters that are impaired due to prior exceedances of water quality standards and serve as a starting point or planning tool for restoring water quality.

The city developed the Boulder Creek E. coli TMDL in 2011 in response to the creek’s placement on the impaired waters list for bacteria.

The state Water Quality Standard for E.coli in recreational water bodies, including Boulder Creek, is 126 CFU/100 mL. Boulder Creek sometimes exceeds this standard. Levels of E. coli fluctuate frequently.

What you can do to help reduce bacteria pollution

  • Pick up pet waste
  • Reduce irrigation overspray
  • Keep trash from wildlife
  • Report spills