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Section 780.21 (b) Continued. <br />• outcropping in and recharged at narrow bands along the top of dip <br />slopes (see discussion of dip slopes under Section 779.14), and is <br />normally under confining conditions as a result of the presence of <br />thick, impermeable shale layers above. One low-yielding aquifer, a <br />zone of saturated sandstone above the Wadge Seam, will be disturbed <br />by mining activities. A detailed discussion on ground water occur- <br />rence and quality and aquifer characteristics is set forth under <br />Section 779.15. The lithologic, physical and chemical charac- <br />teristics and stratigraphic relationships of the aquifer are dis- <br />cussed in detail under Section 779.14. The overburden at the <br />existing and proposed operations in the Energy Mines No. 1 and 2 is <br />not saturated. <br />Potential Impacts on Ground Water Quality. Mining activities have <br />the potential of creating changes in the ground water quality in <br />terms of Total Dissolved Solids (TDS) concentrations, ion balance, <br />• pH and toxicity. The potential mechanisms of impact are: 1) <br />blasting and moving the overburden and placement in previous cuts <br />and excess spoil stockpiles; 2) exposure of toxic, acid- or alka- <br />linity-producing material; and 3) detention of surface water on <br />spoil. The mechanical breakdown, removal and replacement of over- <br />burden material by methods including blasting, ripping and movement <br />by draglines, shovels, trucks, dozers and scrapers will not only <br />increase the permeability of the overburden, but will result in a <br />greater surface area of the overburden material exposed to water. <br />The increased permeability and exposure of water to surface areas <br />of the material can cause a possible increase in the TDS concen- <br />tration and a change in the ion balance of the water in the spoils <br />as a result of the leaching of soluble constituents. If water from <br />these spoils comes in contact with a ground water aquifer recharge <br />zone, there is the possibility that increased quantities of dis- <br />solved solids can enter the ground water aquifer, elevate its TDS <br />concentration and change its ion balance. <br />• <br />780-165 <br />