2018-02-02_REVISION - C1981019 (9)

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PART II Permit- Page 30 Permit No. COR -030000 III. BACKGROUND As required under the Clean Water Act amendments of 1987, the Environmental Protection Agency (EPA) has established af•amework for regulating municipal and industrial stormwater discharges. This framework is under the National Pollutant Discharge Elimination System (NPDES) program (Note: The Colorado program is referred to as the Colorado Discharge Permit System, or CDPS, instead of NPDES,) The Wale), Quality Control Division ("the Division') has stormwater regulations (5CCR 1002-61) in place. These regulations require specific types oj'industrial facilities that discharge stormwater associated with industrial activity (industrial stormwater), to obtain a CDPS permit for such discharge. The regulations specifically include construction activities that disturb one acre of land or more as industrial facilities. Construction activities that are part of a larger common plan of development which disturb one acre or more over a period of time are also included. A. General Permits The Division has determined that the use ofgeneral permits is the appropriate procedure for handling most of the thousands of industrial stormwater applications within the State. B. Permit Ret uirrnents This permit does not impose numeric effluent limits or require submission of effluent monitoring data in the permit application or in the permit itself. The permit instead imposes practice -based effluent limitations for stormwater discharges through the requirement to develop and implement a Slormwater Management Plan (SWMP). The narrative permit requirements include prohibitions against discharges of non-stormwater (e.g„ process water). See Part LD.3 of the permit. The permit conditions for the SWMP include the requirement for dischargers to select, implement and maintain Best Management Practices (BMPs) at a permitted construction site that adequately minimize pollutants in the discharges to assure compliance with the terms and conditions of the permit. Part I.D.2 of the permit includes basic design standards for BMPs implemented at the site. Facilities must select, install, implement, and maintain appropriate BMPs, following good engineering, hydrologic and pollution control practices. BMPs implemented at the site must be adequately designed to control all potential pollutant sources associated with construction activity to prevent pollution or degradation of State waters. Pollution is defined in CDPS regulations (5CCR 1002-61) as man-made or man -induced, or natural alteration of the physical, chemical, biological, and radiological integrity of water. Utilizing industry -accepted standards for BMP selection that are appropriate for the conditions and pollutant sources present will typically be adequate to meet these criteria, since construction BMPs are intended to prevent the discharge of all but minimal amounts of sediment or other pollutants that would not result in actual pollution of State waters, as defined above. However, site-specific design, including ongoing assessment ofBMPs and pollutant sources, is necessary to ensure that BMPs operate as intended. The permit further requires that stormwater discharges from construction activities shall not cause, have the reasonable potential to cause, or measurably contribute to an excursion above any water quality standard, including narrative standards for water quality. This condition is the basis for all CDPS Discharge permits, and addresses the need to ensure that waters of the Slate maintain adequate water- quality, in accordance with water quality standards, to continue to meet their designated uses. It is believed that, in most cases, BMPs can be adequate to meet applicable water quality standards. If water quality impacts are noted, or the Division otherwise determines that additional permit requirements are necessary, they are typically imposed as follows: 1) at the renewal of this general permit or through a general permit specific to an industrial sector (if the issue is sector -based); 2) through direction from the Division based on the implementation of a TMDL (f the issue is watershed -based); or 3) if the issue is site-specific, through a revision to the certification from the Division based on an inspection or SWMP review, or through an individual permit.