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COLORADO DEPARTMENT OF PUBLIC HEALTH & ENVIRONMENT -Water Quality Control Division Ratiowle -Page I ] Permit No. COR-040000 VII. CHANGES AFTER PUBLIC NOTICE (cont.) stormwater discharges assoriated with mining activity still occur, the owner or operator is still responsible for the continued (albeit reduced) delivery of pollutants to the stream. 2. The differentiation between stormwater and process water at a mine or mill site. One commentor requested that the Rationale be expanded to make clear which sources of water ar a mine site are stormwater (covered by this permit) and which sources are process water" (nor covered by this permit). Response: "Process water" is a term used by the Division to refer to waters which when discharged, are required to have conventional permits with numeric effhtent limits. These include wastewaters that were generated or used in an industrial process, or domestic wastewater. They also include mine drainage and many other sources of water from speafic industrial categories that are defined and set forth in federal regulation (40 CFR subchapter N). Several sources of precipitation-induced runoff from active mine sites are included in the 40 CFR, subchapter N, part 440, Effhtem Limitation Guidelines. The confusion between stormwater and process water at mine sites arises because the regulatory definitions overlap somewhat. Currently, this overlap is addressed in a Division Policy document "Definition of Process Water and Stormwater at Non-Coal Mining Sites (policy number WQP-17). " Since this overlap in definitions is also a subject of current national litigation, the Division believes that the policy document is the appropriate place for the Lengthy discussion. This policy is available from the Division. 3. Exemptions from perrnittirt¢ or termination criteria Several commenton requested that exemptions of one kind or another be included in the general permit. Two commentors questioned the assertion that stormwater discharges from inactive mines contribute to water quality problems, specifically in San Juan County. A few commeraors asked for an exclusion from permit requirements if it can be demonstrated that the aposed material would not be expected to degrade water quality. One commeruor requested exemption from permit requirements if the mine has been inanive since 1973 and the site is less than 2 acre. Response: Essentially, the Division is unable to grant exemptions to permitting requirements in a permit document. The federal and state rules (40 CFR 122.26 and 5 CCR 1002-2, § 6.4.2, respectively) set out which circumstances and which activities require permit coverage. Permits are lower in the regulatory hierardty than rules, and carutor gram an exemption which is in confiia with rules. Exemptiosns would require a rules change at both the federal and state levels, as the state rule primarily repeats the federal rule. Change in the state rule alone is limited to being no less stringent than federal rules. Re¢ardinr the stormwater contributions to water aualiN problems in San Juan County: Contrary to the assenion that there is no evidence that stormwater discharges from mine workings contribute to the water quality problems in San Juan County, information supports the conclusion that these sources are significant. Analysis of water quality data in the Upper Mimes River basin by the Division had shown that precipitation- induced runoff from inactive mine/mill sites is a significant pan of the zinc loading in the Mimes River. The contribution from these San Juan County sites appears to be most acute during the early spring snow-melt flush. The data were generated by monitoring water quality above and below individual sites, as well as extensive data collected by the Colorado River Watch Program on Cemeru Creek, Mineral Creek and the Upper Mimes River. In addition, an unpublished PhD dissertation concluded that the majority of zinc loading in the Cemem Creek watershed is contributed by old mine waste dumps (Caruso, 1995). Cement Creek has no aquaric life due in part to the toxic levels of zinc. Rerardine an exemption for uncontaminated stormwater: The regulations state that permits are required for: "...mining operations....that discharge stormwater comaminated by contact with or that has come imo contact with, a~ overburden, raw material, iruermediate products, finished products, byproducts or waste products located on the site... (5 CCR 1002-2 § 6.4.2(5)(c)(iii)) (emphasis added). However, after funkier