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The operator has committed to a mitigation contingency plan for downstream users should they <br />be effected by subsidence. <br />Groundwater Quantity: Effect on the Colorado River Alluvial Aouifer <br />Water quantity in the alluvium of the Colorado River aquifer is minimally affected by the mine <br />operations. The quantity of surface water and groundwater in the Roadside North and South <br />Portal facility azeas and adjacent azeas will not be adversely affected due to the recycling nature <br />of the ground and surface waters in the alluvial valley floor. Since the mines aze on the Colorado <br />River alluvial valley floor, the water pumped from the mines' old workings is essentially the <br />alluvial water already present in the river system. Additional water is added from the draining of <br />the coal aquifer as virgin coal seams aze mined to the south. Both waters aze circulated through <br />the mine workings, thus accumulating solids and salts, before being discharged into the Colorado <br />River. Approximately 0.7 cfs of mine discharge water is removed from the underground mine <br />workings and allowed sufficient time to settle out the solids before being discharged into the <br />Colorado River. The salts cannot be filtered out using this method. The salt loading result is <br />discussed more thoroughly in the previous discussion regazding ground water quality in the <br />Colorado River alluvium. <br />III. Topsoil <br />Soils resource information found in Volume 2, Tab 9, and the topsoil salvage and redistribution plan <br />in Volumes 3 and 5, Tabs 13 and 14, of the application have been reviewed for compliance by the <br />Division. <br />Since mining at this operation began prior to the Surface Mining Control and Reclamation Act, no <br />topsoil was salvaged in constmction of the mine benches. Topsoil from the loadout azea was used to <br />build the loadout stacker pad, although a small amount was stockpiled. The majority of the topsoil <br />salvaged was removed from the location of the Cameo refuse piles. <br />Soils in the general azea aze commonly high in sodium and occasionally saline. This is reflected in the <br />spazse vegetation which is primarily composed ofsalt-tolerant species and species such as greasewood, <br />which aze commonly found growing in sodic soils. The analyses of the stockpiled soil and the <br />material presently on the surface of the disturbed areas reflect the saline and sodic conditions of the <br />surrounding azea. <br />Upon completion of backfilling and grading operations, topsoil will be redistributed to a minimum <br />depth of six inches, with the exception of specified azeas where topsoil was not salvaged originally. <br />These azeas will be covered with a suitable amount of plant growth material and amended as <br />necessary. Prior to redistribution of the topsoil, the graded surface will be ripped to relieve <br />compaction and limit surface slippage. <br />Based on the results of a study conducted on the Roadside Refuse Disposal Area over a period of 10 <br />yeazs, and associated physical and chemical analysis which demonstrated that requirements of Rule <br />4.15 can be met with less than four feet of cover material, the Division has approved a variance from <br />the four foot refuse cover depth requirement of Rule 4.10.4(5). Technical Revision 16, approved by <br />the Division in January, 1994, approved minimum cover replacement depths of 18" on the RSRDA, <br />35 <br />