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Stormwater Quality

The stormwater quality program consists of public education, water quality monitoring, regulatory compliance, and source control. Many of these efforts are required by the city's municipal separate storm sewer system (MS4) permit. The city also participates in the Keep It Clean Partnership (KICP), a regional stormwater program providing public education and outreach.

Boulder Creek Watershed

The Boulder Creek Watershed drains approximately 440 square miles on the eastern slope of the Rocky Mountains. The basin is bordered on the west by the Continental Divide where headwater tributaries begin in the Indian Peaks Wilderness. Boulder Creek flows through the City of Boulder and out to the confluence with St. Vrain River, and eventually the South Platte River.

Boulder Creek is impacted by many activities associated with various land features and land uses.

The impacts include:

  • sedimentation from highway maintenance and bank erosion;
  • acid mine drainage from historic gold mines in the mountainous region of Boulder County;
  • pollutants associated with urban runoff;
  • stream channelization and reduced riparian habitat functions;
  • pollutants from agricultural runoff;
  • damage to riparian vegetarian and sedimentation from stream bank erosion from ranching practices; and
  • point sources from industrial and municipal discharges.

To better understand impacts to Boulder's surface water, the city regularly examines water quality to discover how the community's water resources are changing over time, and to help identify and mitigate potential sources of pollution.

Clean Water Act Background

The Clean Water Act (CWA) of 1972 mandated the development of federal programs to protect waters throughout the United States. The CWA initially focused on point-source pollution, such as wastewater treatment plant discharges. In the 1980s, the Environmental Protection Agency (EPA) began addressing other pollution sources referenced in the CWA, including non-point source discharges, such as stormwater flows.

During the time the Clean Water Act was amended to address stormwater quality, Boulder developed a Comprehensive Drainage Utility Master Plan (CDUMP) to address flood and stormwater issues. In 1989, Boulder's Stormwater Quality Program was developed as a component of the CDUMP to address water quality issues related to stormwater runoff.


Latest News

The city has a wasteload allocation under the 2011 Boulder Creek  E. Coli total maximum daily load (TMDL). The city has issued the 2019 update to the E. Coli TMDL Implementation Plan. pdf  

E. Coli in 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 pdf. 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 pdf and the May 2019 WRAB Memo pdf.

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

For more information, visit: 

KICP Doo Good

KICP Trash


Stormwater Quality Program Components

The Stormwater Quality Program monitors impacts due to urban runoff and tracks ambient conditions in Boulder Creek. 

Report A Spill

Boulder prohibits the release of substances other than stormwater into the storm sewer and local waterways. Common pollutants include restaurant grease, leaking gas or oil, and sediment from construction sites. To report a spill or illegal discharge into the storm sewer system or a waterway contact City of Boulder Water Quality and Environmental Services at 303-413-7350 or email [email protected]


Water Quality Monitoring

Poor water quality, sediment contamination and destruction of fish and wildlife habitats can lead to the decline and degradation of valuable natural resources. The Stormwater Quality Program monitors impacts due to urban runoff and tracks ambient conditions in Boulder Creek.

To better understand impacts to Boulder's surface water, water quality is examined to discover how the water resources are changing over time, and to help identify and mitigate potential sources of pollution.

Regulatory Compliance

The Stormwater Quality Program assures compliance with all state and federal water quality regulations related to stormwater. The City of Boulder's municipal separate storm sewer system operates with a permit from the Colorado Department of Public Health and Environment. In compliance with requirement Part I.D.1.b of the Phase II MS4 permit, the city’s Program Description Document is publically available for review and comment by contacting the Stormwater Quality Program. 

The permit sets requirements related to six minimum control measures:

  • public education and outreach;
  • public participation;
  • illicit discharge detection and elimination;
  • construction site runoff control;
  • post-construction runoff control; and
  • pollution prevention and good housekeeping.

In addition to stormwater regulations for municipalities, federal regulations require certain industrial facilities to obtain a stormwater discharge permit. City-owned facilities such as the Wastewater Treatment Facility and the Boulder Municipal Airport are included in these current Industrial Pretreatment regulations. Stormwater discharges associated with construction activities are also required to obtain a permit.

Source Control

The Stormwater Quality Program seeks to identify and reduce illicit discharges to the stormwater system.

Source Control activities include:

  • monitoring dry weather flows to the storm sewer system,
  • tracking hazardous materials spills,
  • regulating ground water discharges, and
  • participating in Boulder County's Household Hazardous Waste Program.