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<br />/1. Warcr Quafin• lmpacrt <br />New Elk Mine <br />Water quality impacts to the Purgatoire River at the New Elk (Allen) Mine are evaluated in the <br />1980 WWL report. Mine impacts included a 73 gallon per minute (gpm) discharge from the <br />Allen (New Elk) Mine and the effect of this discharge on Purgatoire stream and alluvium <br />quality. The WWL predictions also addressed the effect on water quality of the active waste <br />dump at the Allen Mine by a mathematical model. The model assumed that the worst quality <br />water discharging from the waste dump would be reflected by a sample acquired from a seep <br />on the waste dump. <br />Mining operations at the New Elk Mine have changed significantly since 1980. The portals are <br />sealed and there is no discharge from the New Elk (Allen) Mine at this time. The refuse <br />disposal area north of the highway was constructed in 1985 to handle waste from the coal <br />processing plant. The Probable Hydrologic Consequences section of the permit predicts the <br />water quality associated with backfilling of a portion of the Middle Fork of the Purgatoire with <br />coal waste following the 1984 diversion. The 1993 Annual Hydrology Report records the effect <br />of the coal development waste pile, the backfilled channel and the refuse disposal area, with <br />monitoring data collected in November, 1993. Both PRS-1, upstream, and PRS-2, downstream, <br />are calcium bicarbonate waters of low salinity and hardness and are slightly alkaline. Figure 9 <br />• shows average concentrations of major cations and anions above and below the New Elk Mine <br />using data collected annually for five to ten years. The upstream site, PRS-1, has slightly higher <br />concentrations of sulfate and bicarbonate, while the downstream site, PRS-4, has slightly higher <br />calcium and magnesium levels. <br />Table 10 compares the WWL conclusions projections of a worst case water quality, assuming <br />a base flow of 3 cfs and mean concentrations of parameters collected at Stonewall with <br />monitoring of PRS-4 on November 29, 1993, at approximately 13.11 cfs, for current activities <br />at the New Elk Mine. Even at the higher flow, the Middle Fork of the Purgatoire is exhibiting <br />slightly higher total dissolved solids, chloride calcium and bicarbonate than what was projected. <br />Presumably, part of the source of this discrepancy is the use of mean values for Stonewall water <br />quality. It is valuable to note, however that none of these parameters are at concentrations <br />which would jeopardize beneficial uses in the stream. <br /> <br />A re-examination of salinity loading from the New Elk Mine was made based on a contribution <br />of 2.37 x 10.6 cfs from the backfilled Purgatoire channel during low flow, 0.0086 cfs from the <br />development waste dump, and 0.569 cfs from the refuse disposal area (0.72" water from subsur- <br />face runoff/(12"/1') / 30 days discharge/year x 56.5 acres x 0.5042 acft/cfs). A worst case <br />29 <br />