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MAR. -28' 91(FRI) 15:2D WRIGHT WATER TEL~303 480 1020 P. 004 Dave Beny and Mike Boulay Mazch 28, 1997 Page 3 CDMG has been made awaze of flows of up to a few hundred gpm, but never the amount being experienced by the West Elk Mine. Dave Berry stressed that increased total dissolved solids (TDS) loading to the North Fork is of considerable interest to CDMG, not only in terms of what happened in 1996, but in terms of what might occur in the future. Dave specifically said that a"worst-case scenario" for future inflows would be helpful. He indicated that duo to time constraints, CDMG would rely heavily on WWE's analysis of this issue. He suggested that we not overlook the fact that there aze special salinity requirements on the Colorado River and that we pay particulaz attention to low flows. WWE noted that fault inflows have had TDS values as high as 3,000 mg/L from the 1" Southeast headgate fault, and that B Fast Mains fault inflows were typically around 2,000 mg/L. All of us agreed that with typical values is the river of between 100 mg/L and 200 mg/L, the high fault water flows have the potential to measurably increase TDS levels in the river, partieulazly during low flow conditions. Dave asked if there aze mechanisms that could be added to the MCC treatment process at Ponds MB-1 and MB-2R that would reduce TDS concentrations, WWE replied that removal of TDS would require reverse osmosis, or an equivalent treatment, and is not economically feasible. Update: WWE has conducted analyses of TDS loading to the North Fork during 1996. Our evaluation showed that, although TDS levels in the North Fork were measurably increased by MCC's discharges, the annual salinity loading during 1996 was well within the assumptions used in the 1992 CHIA. Fur[hermore, the annual salinity loading for the West Elk Mine used in the CHIA is still appropriate even under worst-case conditiottr-primarily due to the discontinuous nature of MCC's pond discharges, There was considerable discussion regarding the water quality and water balance data that appears in MCC's annual hydrology reports (AHRs). Dave expressed some concern with the quality of the data in the AHRs. Mike and Dave mentioned that they have recently requested that MCC provide laboratory "back-up" shcets for the past three yeazs so that CDMG can better understand how discrepancies in the quantity/quality data reporting have occurred. As stated by Dave: "We want to know that the data that we are relying on aze good." WWE responded by indicating that MCC has always "opened its file cabinets" to us, and that we have not had a concem with the quality of the data. Since the meeting, MCC has agreed to provide CDMG with copies of [he laboratory "back-up" sheets far water years 1993, 1993, and 1995. MCC is currently processing this request. Following this discussion, Dave stressed that CDMG is genuinely coacemed that MCC will encounter more significant inflows as they move to the east and to the north. Dave emphasized that CDMG's interests in the nature of these inflows and their sources is faz from academic, because CDMG has liability for overseeing the permitting of the West Elk Mine. Dave emphasized that CDMG sees the PHC issues as very serious because they potentially relate to MCC's ability to continue to mint due to physical constraints.