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Historic Allen Mine waste materials appeaz to be the major contributors to saline alluvial ground water <br />quality in the vicinity of the New Elk Mine (PAW-3 and PAW-4) (Figure 3.2-3). Saline conditions were <br />• anticipated in the PHC, and conductivities and TDS concentrations have been far lower than expected. <br />During March and April of 1985, 500 feet of the Middle Fork of the Purgatoire River was diverted to the <br />north to create additional room for the coal stockpile at the New Elk Preparation Plant. The original <br />channel was backfilled with mine waste, and two alluvial wells, PAW-3 and PAW-4, were established to <br />monitor water elevation and chemical parameters. Water quality does not appear to deteriorate <br />significantly due to the presence of refuse in the backfll between PAW-3 and PAW-4 and measures of <br />salinity, sodium, and sulfate are far lower than predicted by the PHC. A threefold increase over historic <br />values in 'von quantities in PAW -3 and PAW-4 may be due to the steel casing of the wells. No further <br />monitoring is required for PAW-3 and PAW-4. Data on PAW-8 (Table B-5) and the Stiff Diagram <br />indicate that seepage from the current refuse disposal area contains similar concentrations of sodium, <br />potassium and calcium to the pre-law mine waste (PAW-4). Leaching may be a cause for lower values <br />from the old materials. Data from PAW-9 downstream of the New Elk facilities indicated dilution having <br />an effect on concentrations. <br />• <br />i• <br />3.2.4 New Elk Mine Water <br />During the third quarter of 1989, the New Elk Mine was sealed and access to the mine workings <br />terminated. Mine inflows are flooding the abandoned mine workings. Previous studies and reports <br />suggested an inflow of 177 gallons per minute (gpm) and calculated inflows ranged from 142 to 468 gpm <br />based on measurements taken at Station NEW-4. A number of approximations were made in the <br />calculation of rates of inflow. From mine maps, the dip of the mine floor was determined to be 5 percent, <br />and the water line crosses approximately 12,000 linear feet of mined areas. The available volume is based <br />on an average extraction of 60 per cent. The calculations assume that the entire mined area below the <br />water level measured in NEW-4 is flooded (i.e., no trapped air pockets). Figure 3.2-4, Mine Water Levels, <br />portrays a lineal increase in the mine water level (flooding of) in the sealed New Elk Mine through from <br />1994 through 2001. From mid-2001 through 2003, the rate of increase in mine water level appears to <br />have diminished, only to resume its previous rate of increase during 2004. Continued monitoring will <br />provide the information to clarify the phenomena, and permit a more accurate projection of hydrologic <br />consequences. <br />Inflow water quality information is being obtained at the sealed New Elk Mine (see NEW -2, Table B-7; <br />NEW-3, Table B-8; and NEW-4, Table B-9). Stiff diagrams of mine water quality are provided in Figure <br />3.2.5. This water is of relatively high conductivity, and high concentrations of total dissolved solids, <br />bicarbonate, and sodium. None ofthis water has been discharged from the sealed mine to date. <br />35 <br />