Stormwater Quality

Stormwater runoff is the water that flows over the ground as the result of rain, snowmelt, hail and sleet. Buildings, streets, driveways, parking lots, sidewalks and patios prevent the water from soaking into the ground. These structures are referred to as impervious surfaces. Runoff is collected by storm sewer infrastructure such as inlets and pipes and is then transported to multiple drainage basins throughout Thornton including, Big Dry Creek, Brantner Gulch, Todd Creek, Grange Hall Creek, Niver Creek, and their tributaries; all of which ultimately flow to the South Platte River. As water flows over the ground, it picks up everything in its path, such as sediment, oil, grease, litter and chemicals, taking it all to the basins without treatment.

Report an illicit discharge

Report illicit discharges through MyThornton.

Contractor Resources

Construction Site and Post-Construction resources.

Volunteer Opportunites

Volunteer with the City Stormwater Quality team.

Recognizing Illicit Discharges

Illicit Discharges, or illegal dumping, are a significant cause of stormwater pollution. When trash, fertilizer, antifreeze, paint, pet and lawn waste, and other pollutants enter the stormwater system water quality diminishes.

Common signs of an illicit discharge at stormwater drains include unusual color or cloudiness of the water, oil sheen, algae, strong/pungent or musty odor, dead vegetation or inhibited growth, dead animals, floating debris, pipe corrosion, surface scum or foam, stains on channel bottom or sides.

Stormwater Capital Improvement Projects (CIP)

The CIP program provides for cost-effective design and construction of capital projects. The city's CIP includes projects that provide an enhancement to the quality of life for citizens or result in the reduction of the cost of ongoing maintenance. The City maintains a five-year plan, which is updated annually. 

Projects include improvements to transportation, city facilities, trails, water, storm sewer, and sanitary sewer systems. This site contains major CIP projects that are of interest to the public. The city also performs ongoing maintenance projects not included on this site. Please click the link above for more information on current and future CIP projects.