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Probable Hydrologic Consequences - Chimnry Rock Mine <br />An exception is noted that the quality in the well A-1, located west of the former east pit area, has <br />shown elevated levels of TDS, conductivity, sodium, magnesium, manganese, iron, calcium, and <br />sulfate in December 1994. Compared to other wells in the area this well has traditionally <br />demonstrated elevated levels of these constituents. This well is continuing to be monitored as part <br />of the current monitoring program. <br />Sulfate concentrations in wells W-10 and W-16 (Appendix I)from 1985 to 1991 could be <br />attributed to the physical and chemical weathering of the waste soils and mine overburden <br />generated during mining operations in the North (Revision 1) Pit and used as backfill in the East <br />Pit and Barren Ridge areas. Mine overburden, composed of sulfide minerals, namely pyrite, <br />chemically reacts upon exposure to water and air. Sulfide ions in the pyritic material become <br />oxidized and soluble sulfate ions are formed. These sulfate ions are transported to the groundwater <br />via infiltration of precipitation and surface runoff. <br />Depending on the mineralogy of the mine overburden, the surface runoff i~ltrating the ground <br />can be quite varied in ionic content. Natural attenuation by various chemical, physical, and <br />biological processes occurs as the water migrates through the soil. The higher concentrations of <br />various constituents at well A-1 can be attributed to the shallowness of the well, and the close <br />proximity of the mine overburden pile. <br />Utilizing the water quality data that has been obtained, potential impacts to Stollsteimer Creek <br />were analyzed. WeI1sW6 and W 16 have had PHREEQC 1 modeling analyses performed to attempt <br />to predict future electroconductiviry and total dissolved solids (TDS) levels in the water samples <br />from the wells and therefore in the spoils aquifer. Subsequently, the predicted TDS values for the <br />spoils aquifer were utilized in predicting stream loading of TDS. Although no impacts are <br />apparent in surface and alluvial waters, the predictions and analyses area "worst-case" analyses <br />of the potential impacts to Stollsteimer Creek. <br />Saturation indices (SI) were calculated for the average constituent concentrations in well W6 <br />(upgradient, Fruitland Formation well) and well W 16 (formerly installed in the spoils) to <br />determine the potential for increases in the TDS concentration. Well W-6 is utilized in this <br />analysis since the water in the well is representative of the underburden flow from the Fruitland <br />Formation. Well W-16 water represents the water that has migrated into the spoil from <br />precipitation, infiltration and underburden flow and indicates the quality of the spoil effluent from <br />these sources. This calculation was performed utilizing the PHREEQCI (Parkhurst, 1995) <br />geochemical modeling program. The program utilized the WATEQ4 (Plummer and others, 1976) <br />parameters database for the molecular weight of the constituents. This analyses duplicates the <br />methodology utilized in the Williams and Clark 1994 study. The result of the modeling are <br />included in Appendix II. <br />~s~`t, G~°~ ,~ <br />~ S V Il ~R ~"f'M /~ f'.~ <br />Revised hydrologic-05305-23-0(806AM) 1~ ~^J <br />