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​Stormwater Quality​

​​​​​​​​​​​​​​​​​​​​The Colorado Water Quality Control Act (25-8-101 et seq., CRS 1973, as amended) established the Colorado Water Quality Control Commission (CWQCC) within the Colorado Department of Public Health and Environment (CDPHE) to develop water quality regulations and standards, classifications of State waters for designated uses, and water quality control regulations. The Act also established the Colorado Water Quality Control Division (CWQCD) to administer and enforce the Act and administer the discharge permit system. Violations of the Act are subject to significant monetary penalties, as well as criminal prosecution in some cases. 

Colorado's stormwater management regulations have been implemented and are included in Regulation No. 61 Colorado Discharge Permit System (CDPS) Regulations (CWQCC 2009).  The Colorado's stormwater program was finalized in March 2001, establishing stormwater permitting requirements. The regulation resulted in a large number of Municipal Separate Storm Sewer System (MS4) permits issued to almost all of the metro Denver area communities. MS4 permit holders are required to develop, implement, and enforce a Stormwater Management Program designed to reduce the discharge of pollutants from the MS4 to the maximum extent practicable, to protect water quality, and to satisfy the appropriate water quality requirements of the Colorado Water Quality Control Act (25-8-101 et seq., C.R.S.) and the Colorado Discharge Permit Regulations (Regulation 61).

In compliance with provisions of the Colorado Water Quality Control Act and the Colorado Discharge Permit Regulations; the City of Thornton is required to obtain a permit, which authorizes the City to discharge stormwater.  Such discharges are allowed in accordance with the conditions of the City’s MS4 Permit and the City’s Stormwater Management Program.

The MS4 Permit requires the City of Thornton to implement six minimum control measures. These minimum control measures are as follows... 

​Public Education and Outreach

MS4s are required to educate their community on the pollution potential of common activities, and increase awareness of the direct links between land activities, rainfall-runoff, storm drains, and their local water resources. Most importantly the requirement is to give the public clear guidance on steps and specific actions that they can take to reduce their stormwater pollution-potential.

Public Participation and Involvement

MS4s are required to follow all State, and local public notice requirements when implementing their stormwater program.

​Illicit Discharge Detection and Elimination

Illicit discharges are generally any discharge into a storm drain system this is not composed entirely of stormwater. The exceptions include discharges from emergency fire fighting activities and discharges specifically authorized by a separate permit.

Construction Site Runoff Control

Stormwater runoff from construction activities can have a significant impact on water quality. As stormwater flows over a construction site, it picks up pollutants like sediment, construction debris, and chemicals such as gas, fertilizer, and paint. Polluted stormwater runoff can harm or kill fish and other wildlife. Sedimentation can destroy aquatic habitat and high volumes of runoff can cause stream bank erosion.

Post Construction Site Runoff Control

MS4s are required to address post-construction stormwater runoff from new development and redevelopments that disturb one or more acres. This primarily includes developing strategies to implement a combination of structural and non-structural BMPs, an ordinance to address post-construction runoff, and a program to ensure adequate long-term operation and maintenance of Best Management Practices (BMPs).​

​​Pollution Prevention / Good Housekeeping

MS4s are required to develop and implement an operation and maintenance program with the ultimate goal of preventing or reducing pollutant runoff from municipal operations into the storm sewer system. The program includes employee training on how to incorporate pollution prevention/good housekeeping techniques into municipal operations such as parks and open space maintenance, fleet and building maintenance, new construction and land disturbances, and stormwater system maintenance.