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~UU•i' 7 `.'/ d5 ill S `a nce from t:ae mine 51 t~ i nC~"ea;25. The S3 i t D~ Ulne Can 5g expected to migrate approximately 48.5 ft/year. Spoils springs and seeps will continue to develop at the base of the spoils placement area. Spoils water nut infiltrating the bedrock aquifers will discharge from these seeps. Spoils spring discharges will increase the salt load in the upper Foidel Creek drainage. Estimated salt load from the Little Middle Creek tract is expected to be approximately 700 tons/year. This value will decrease as the spoils are flushed by recharge water. The applicant predicts that the approximately 4,000 acres of backfilled spoils will produce spring flows ranging from 320 - 5,800 gpm (0.71 - 12.92 cfs). This assessment was based on a study of existing spring flows during the past bHO years. The Division developed an estimate of spring flows which showed a range of 425 gpm - 7,845 gpm (0.95 cfs - 17.5 cfs) based on infiltration rates of three inches (3")!year and bedrock recharge along the highwall. 4 flushing rate of 0.9 1/kg would result in flushing a 60 foot column of spoils in 310 years. Flushing the same column at 1.5 1/kg would take 516 years. Complete flushing of the spoils material will result in a return of total dissolved solids concentrations to background levels. No hydrologic or geologic changes are expected to occur to the Trout Creek or Twentymile Sandstones. The Twentymile Sandstone crops Lo the northeast of the proposed mine area and is separated from i4ine 1 and Eckman Park both areally and stratigraphically. The Twentymile Sandstone is hydrologically isolated from the Wadge overburden aquifer by approximately 700 feet of low permeability marine shales. The Fish Creek seam, removed in Mine 2, is stratigraphically above the Twentymile Sandstone. Sixty feet of siltatone and shale separate these strata. The low permeabilities of the intervening siltstones and shales will hydrologically isolate the Twentymile Sandstone from the overlying Fish Creek coal and replacement spoils material. No changes in the Duality or quantity of ground water in the Twentymile Sandstone is expected. The underlying Trout Creek Sandstone will not be affected by mining in the Eckman Park Mine complex. The recharge area of the Trout Creek Sandstone lies outside of the mine area and outside the Foidel Creek drainage. The Trout Creek sandstone is stratigraphically below the 'rladge coal seam and, therefore, will not be disturbed by mining. Higher potentiometric heads in the Trout Creek Sandstone aquifer than those in the post-mine spoils will prevent discharge from the mine into the Trout Creek Sandstone. 3. Surface lister Inr_reased erosion and runoff are short term consequences associated with the active mining operation. Chemical changes of the surface hydrologic system are long-term impacts associated with the development of spoils aquifers. Runoff and erosion increase during the period between vegetation removal and vegetation re-establishment on reclaimed slopes. The operator utilizes sedimentation ponds to prevent siltation of surface waters outside the permit Brea and a variety of operational procedures to minimize erosion on-site.