Boulder's Stormwater Quality Program

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

Addressing Water Quality Issues

The stormwater quality program works to address issues related to water quality through the urban corridor of the city with the goals of regulatory compliance and improved urban stream health.

The city has a state municipal separate storm sewer system (MS4) permit for stormwater that flows through the city stormwater system and is not treated before entering the creek. The city’s program description document related to this permit is publicly available for review and comment by contacting the Stormwater Quality Program.

Stream Monitoring

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.

The city has been conducting water quality monitoring on Boulder Creek for over 30 years. Boulder creek is used for recreation (class 1A), agriculture, and domestic water supply as defined by the Colorado Department of Public Health and Environment. In order to protect these essential stream functions the city conducts water quality monitoring at 15 location along Boulder Creek and its tributaries in order to assess water quality conditions, and monitor compliance with state regulations. Further information on the city’s water quality monitoring program can be found in the Keep it Clean Partnership’s annual water quality report which summarizes the water quality monitoring efforts and results for Boulder Creek and the greater St. Vrain watershed.

Biological monitoring utilizes living organisms (bioindicators) to evaluate the health of the aquatic environment. Aquatic insects, known as benthic macroinvertebrates, are a widely used bioindicator for assessing the health of aquatic ecosystems. Benthic macroinvertebrates are used to detect changes in their aquatic environment based on the abundance and composition of macroinvertebrate families present. The City of Boulder has monitored benthic macroinvertebrates in Boulder Creek since 1995 and is currently conducting monitoring at nine locations.

Boulder Stormwater Review and Oversight Process

The City of Boulder implements a stormwater review and oversight process in accordance with the State of Colorado Phase II MS4 General Permit. The City’s oversight process starts with development review and continues through construction and permanent operations and maintenance.

All proposed development projects are subject to the requirements of the City of Boulder Design and Construction Standards (DCS). Development review applications are processed and overseen by City of Boulder Planning and Development Services.

DCS Chapter 7 – Stormwater Design details the design standards, process, and documentation requirements pertaining to stormwater management for new development and redevelopment. The following forms and checklists supplement the Stormwater Design DCS Chapter:

The City of Boulder follows the Mile High Flood District, Urban Storm Drainage Criteria Manual and associated Excel design tools (Detention Design and UD-BMP).

The City of Boulder also encourages reference to the City and County of Denver Ultra-Urban Green Infrastructure Guidelines when appropriate for site conditions.

All new development and redevelopment projects in the City of Boulder are required to implement erosion and sediment control measures in accordance with an erosion control plan.

Projects that disturb greater than 1 acre of land must have an approved Stormwater Management Plan and apply for a City of Boulder Erosion Control Permit.

How to Report a Spill


  • If you witness someone spilling or dumping any substance within the City of Boulder, or notice an existing spill or discharge please report the spill.
  • All information is kept confidential and callers may also remain anonymous when reporting an illicit discharge.
  1. Phone
    • The Stormwater Quality Team can be reached at 303-916-5563
    • City of Boulder Public Works can be reached at 303-441-3200 during and after normal business hours, and your call will be directed.

Tips for Reporting a Spill

  • Estimate the amount of discharge
  • Note the characteristics of the discharge (color, odor, etc.)
  • Never get too close to a strange discharge because it can be dangerous!
  • If applicable and when possible, take information on the vehicle or person(s) dumping the waste

What is considered an illicit discharge or spill?

This is any discharge into a storm sewer system that is not composed of entirely stormwater. Per Boulder Revised Code, no person is allowed to discharge into or upon the stormwater utility system, any public highway, street, sidewalk, alley, land, public place, stream, ditch or other watercourse or into any cesspool, storm or private sewer or natural water outlet. All stormwater drains go directly to our waterways without treatment. Please help us protect our waters!

Common illicit discharges

  • Paint
  • Sediment
  • Grease
  • Petroleum products
  • Sewage
  • Sediment from construction activities

Where does a spill into the storm drain really go?

Please Remember: The storm drain systems are separate from wastewater systems; they drain to our rivers, streams, creeks, and gulches without any treatment. The storm drain system is different from the sanitary sewer system because the sanitary sewer does go through treatment before is enters our rivers and streams.

Resources for Proper Waste Disposal