2008-09-05_HYDROLOGY - C1996084 - Laserfiche WebLink

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STATE, OF COLORADO DIVISION OF RECLAMATION, MINING AND SAFETY Department of Natural Resources 1313 Sherman St., Room 215 Denver, Colorado 80203 D COLORADO t ON OF Phone: (303) 866-3567 RECLAMATION FAX: (303) 832-8106 MINING SAFETY September 5, 2008 Bill Ritter, Jr. Governor Colorado Department of Public Health and Environment Harris D. Sherman Water Quality Control Division Executive Director Ronald W. Cattany WQCD-P-132 Division Director 4300 Cherry Creek Drive South Natural Resource Trustee Denver CO 80222-1530 RE: General Permit for Coal Mining, COG-850000 Dear Mr. Neuhart: As we have discussed in two recent phone conversations, the Division of Reclamation, Mining, and Safety has some concerns about effluent limits as set forth in the recently issued General Permit for Coal Mining, effective July 1, 2008. We concur with the daily maximum limitations as established for storm runoff up to the 10-year, 24-hour storm event for settleable solids (.5 ml/1) and no limitation for total suspended solids (NA). However, we would question imposing limits for both the 30- day average for TSS (30mg/1) and the 7-day average for TSS (45 mg/1). As we discussed, from a practical standpoint, storm runoff from disturbed areas of a coal operation can be, and normally is, high in TSS even while meeting the .5 settleable solids limitation for any particular discharge. Sediment ponds at coal operations are designed using state-of-the-art computer programs that model and estimate settleable solids in effluent using a 24-hour volume weighted average method in addition to a peak sediment concentration for settleable solids. No estimate of TSS is made, likely due to the fact that storm runoff up to the 10-year, 24-hour storm event has always been eligible for the alternate limitation of .5 ml/I settleable solids with proper burden of proof of the storm timing and size. As I mentioned, our Rule 4.05.6(3)(a) requires coal mining sediment ponds to "contain or treat the runoff or inflow entering the pond as a result of the 10-year, 24-hour precipitation event..." Rule 4.05.2(7) requires that "discharges of water from areas disturbed by surface coal mining and reclamation operations shall be made in compliance with the Colorado Water Quality Control Act, 25-8-101 to 703 as amended and regulations promulgated pursuant thereto, and with effluent limitations for coal mining promulgated by the United States Environmental Protection Agency set forth in 40 CFR Part 434, (July1, 1993). This rule does not include later amendments to or editions of the incorporated material." It is important that DRMS personnel understand what limitations apply and when they apply in order to determine compliance with our Rules, and also to properly meet our Office of Office of Mined Land Reclamation Denver - Grand Junction - Durango Active and Inactive Mines