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Stormwater ​Program Overview

The City of Thornton has implemented a stormwater management program to protect our surface and groundwater quality. Federal and State regulatory factors played a significant role in its structure. The Colorado Water Quality Control Act (25-8-101 et seq., C.R.S. 1973, as amended) triggered the Colorado Department of Public Health and Environment to establish the Colorado Water Quality Control Commission (CWQCC) and the Colorado Water Quality Control Division (CWQCD). The CWQCC was charged with developing water quality regulations, standards, and classifications of State waters for designated uses. The CWQCD was created to administer and enforce these regulations through a discharge permit system.

In March of 2001, the CWQCD finalized Colorado's stormwater program, establishing the Municipal Separate Storm Sewer System (MS4) permit. MS4 permits were issued to the majority of the metro Denver area communities. 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).

The City's MS4 permit requires that control measures be implemented for the following activities: