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West EIk Mine <br />WWE has reviewed the salinity (TDS) loading analysis in the 1992 Cumulative Hydrologic <br />• Impacts Anatysis (CHIA) for the North Fork in the context of MCC's 1996 discharges. In the <br />CHIA, CDMG calculated the cumulative TDS (salinity) loading to the North Fork from coal <br />mines located in the North Fork valley. The assumptions used for MCC's contribution were a <br />discharge rate of 1,000 gpm (2.23 cfs) and a TDS concentration of 2,500 mg/L. When <br />assessing calendar year 1996, the total volume discharged from ponds MB-1 and MB-2R was <br />approximately 433 acre feet, which translates to an average continuous discharge rate of <br />approximately 270 gpm. Additionally, the TDS concentration of the B East Mains fault water <br />was typically around 2,000 mg/L. Consequently, the annual salinity loading to the North Fork <br />from the West Elk Mine for 1996 was 3,290 tons, well below the value assumed in the CHIA <br />as shown in Table 57. <br />Furthermore, even considering the "worst case" scenario, the annual salinity load is just over <br />half of the value calculated in the CHIA. This result stems primarily from the discontinuous <br />nature of the pond discharges. While discharge rates from the ponds are commonly above <br />2,000 gpm, the discharges occur roughly one quarter of the time. The TDS concentration was <br />assumed to be equivalent to that of the 14SE Headgate fault water. This is extremely <br />conservative for an annual calculation when considering that imported water, with a much <br />lower TDS concentration, comprises a major component of the discharge volume. <br /> <br />Table 57 TDS Concentrations and Loads Relative to'I992 CHIA Analysis <br />Scenario Avg. TDS Annual Salt Percent of <br /> Continuous Concentration Loading CHIA <br /> Discharge Rate (mg/L) (tons/year) Loading <br /> (gpm) <br />1996 270 2, 000 1,180 21 % <br />"Worst Case" 500 3,000 3,290 58% <br />1992 CHIA 1,000 2,500 5,670 --- <br />Water Quality Impacts from January 1997 Through Start-up of New Pumping <br />Facility <br />Relative to water quality from January through late 1997, North Fork water will not be <br />tangibly affected by mine outflows, for these reasons: <br />1. MCC presently has the capability to reliably treat between 200 gpm and 300 gpm of <br />mine water outflow in the sedimentation ponds. This treatment capacity is backed <br />up by the storage capabilities of the sealed sumps to handle upset conditions. <br />2. MCC has separated "clean" flows in the mine from those flows which would likely <br />fail to comply with the NPDES limits. In late summer 1996, the mine flows that <br />• exceeded the NPDES limits were direc[ed [o [he seated sump, white the "clean" <br />2.05-203 Rev~sedJun. 1995 PR06: Revised Nov. 1998 TR80; I/98 PR08 <br />