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iii iiiiuiiiiiu iii STATE OF COL" u99,~. J DIVISION OF MINERALS AND GEOLOGY Dcparlmern of Nawral Resources Ill 4 Sherman 51., Ronm 215 Denver. Colorado 80203 Vhnne: 1311)1 Bhh-}567 FA% (10J1 A}Z-H 106 DATE: November 12, 1997 TO: Byron Walker FROM: Erica Crosby~y l- L RE: Colowyo Coal Mine (C-81-019) Comments on CPDES Permit No. CO-004 t61 I~~~~ DEPARTMENT OF NATURAL RESOURCES ROy Romer Gmernor lames 5 Lochhead Evrcmive Director Michael B. Long Division Director Byron, per your request I have the following comments regarding the Colowyo draft CPDES Permit and Rationale as well as the comments from Colowyo in a letter dated September 30, 1997 to DOH. Colowyo is requesting that the language in the permit be changed from "process water" to "pit pumped water." The change in language could imply that the pit water is clean, and does not need to meet the water quality limits defined in the permit. It was discussed on numerous occasions between DMG, WQCD and Colowyo, that pit water is processing water and it does not qualify for the altemate effluent limits in the permit. As stated in the April 17, 1996 letter by Department of Health Water Quality Control Division, "In regard to pit pumpage one section you highlighted which states that `the National Coal Association... agreed with EPA that pumping from pits, wherever located, could be controlled to the extent that alternate storm limitations would not be necessary' reinforces our determination that pit pumping does not qualify for the alternate limits:' Colowyo continues to state that the ponds are designed to contain the 10-year/24-hour storm event, and manual discharge is necessary to avoid discharges over the emergency spillway and impose a stability concern to the pond. The ponds have primary risers that are designed to pass the flow from the 10-year/24-hour storm event. Colowyo has not demonstrated that water discharging from the dewatering gate will meet the effluent limitations in the permit. Colowyo should not be exempted from meeting the primary limitations when the manual gate is used, only when water discharges over the primary spillway. If Colowyo wants to use the gates, and claim the storm exemption, then they will need to demonstrate to the Division that it will meet the settable solid criteria set forth in the CPDS permit. 3. It may be prudent to inform WQCD of the delay in the permitting process of the sediment ponds. The language in the CDPS permit relies on the existing pond designs that will change when the new designs are approved. Let me know if you have any questions. r~ ~:, I;