_GENERAL DOCUMENTS - C1981017 (304)

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COLORADO DEPARTMENT OF PUBLIC HEALTH& ENVIRONMENT Water Quality Control Division WQCD-PE-B2 Cherry Creek Drive South Denver, Colorado 80222-1530 RATIONALE STORMWATER DISCHARGES ASSOCIATED WITH METAL MINING OPERATIONS AND MINE-WASTE REMEDIATION GENERAL PERMIT IN COLORADO COLORADO DISCHARGE PERMIT NUMBER COR-040000 L INTRODUCTION The permit is for the regulation of stormwater runoff associated with metal mining operations and mine-waste remediation projects. The term "metal" is used to distinguish this permit from the general permit for coal mining with surface discharge only, and the general stormwater permit for sand and gravel mining and processing (and other nonmetallic minerals). Other terms are defined in the permit. This Rationale will briefly explain the background of the stormwater program, activities which are covered under this permit, how to apply for coverage under this permit, and the requirements of this permit. IL CHANGES IN RENEWAL PERMIT The following major changes have been made to this permit during renewal: A. Mine-Waste Remediation: Stormwater Management Plan ("SWMP) requirements have been added that specifically address stormwater concerns for operations that undertake mine-waste remediation and seek eventual permit certification termination. These are described below at Section IV.B and W.B. B. Termination of Permit Coveraze: Provisions have been added to describe the criteria and process for termination of permit coverage. These are described below at Section W.H. C. SWMP Format Chanjees: The SWMP contents and requirements have been amended to eliminate redundancies. SWMPs that were prepared in accordance with previous requirements are not required to be amended to conform to the new SWMP format. The format of the SWMP has changed, but the essence of the requirements remains the same. D. Duplication:Redundancies between the permit and Rationale have been reduced. E. Allowable Non-Stormwater Discharges: Several additions have been made to the list of non-stormwater discharges which are allowed under this permit. These are described below at Section W.A. F. Other changes: Minor changes and clarifications have been made throughout the permit and Rationale. In general, they do not affect the substance of the requirements. III. BACKGROUND The federal Clean Water Act requires that industrial stormwater discharges be regulated 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 Water Quality Control Division ("the Division") has stormwater regulations (5 CCR 1002-2, 6.1.0) in place. These regulations specifically include mining operations where stormwater has come into contact with any overburden, raw material, intermediate products, byproducts, finished products or waste products, as industrial facilities which must obtain stormwater discharge permits.