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backfill groundwater is generally of poorer quality than surface Flows so that discharge may result in localized <br />increases in concentration of dissolved solids in receiving drainages. Water discharging from saturated backfill at <br />.spoil springs drains to the surface sediment control system and also typically exhibits increased concentrations of <br />dissolved solids. The suspended solids level of disturbed area runoff is controlled by detention in sediment ponds <br />prior to discharge to receiving streams. Retention of surface runoff and backfill discharge in sedimentation ponds <br />ma}• fiirtlier increase the total concentration of dissolved solids due to the effects of evaporation. The potential <br />impacts to surface water systems are evaluated in more detail in the Probable Hydrologic Consequences section. <br />Surface Water Protection and Mitigation Measures <br />Increases in suspended and dissolved solids, temporary decreases in runoff volumes, and minor changes in the <br />timing and volume of surface water discharges are the major potential surface water impacts which may result <br />from the mining operations. With the exception of potential increases in dissolved solids concentrations, all <br />anticipated surface water impacts will be localized and effectively confined to the permit and adjacent areas by the <br />planned mitigation measures. Potential increases in the concentration of dissolved solids will carry through the <br />sedimentation pond discharge to the receiving drainage, since there are no effective treatment methods available. <br />However, as described in more detail in the probable hydrologic consequences sections, the relatively low amounts <br />invoh~ed render the resultant overall impact on the surface hydrologic system insignificant, except during low-flow <br />• or no-flow discharge periods in Foidel Creek. <br />The principle surface water protection and mitigation measures which were utilized to prevent significant adverse <br />impacts included a number of general operation practices as well as specific drainage and sediment control <br />procedures. Practices wliicli were significant in minimizing potential adverse surface water impacts included the <br />following: <br /> <br />1996 Permit Ren. Permit Renewal 780-144-7 Revised 3/18/97 <br />