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Surface Water -Probable Hydroloeic Consequences <br />•The mining activities at the Eckman Park Mine and Mine # 1 have the potential to impact the surface seater <br />hydrologic system as follows: <br />• Increases in dissolved and suspended solids concentrations in surface waters as a result of <br />increased runoff and groundwater discharge from disturbed areas. <br />• Alteration of the surface water ion balance due to contribution of disturbed area runoff and <br />groundwater d ischarge. <br />• Temporary changes in the volume and timing of surface water discharges. <br />Increaser) Dissolved and Suspended Solids Concentrations <br />Mining-related disturbance, particularly the removal of surface vegetation and topsoil, results in temporary <br />increases in erosion and surface runoff from disturbed areas. In addition, increased leaching typically occurs as <br />runoff volumes increase and unweathered materials are exposed to surface water. The temporary increase in <br />surface erosion and leaching results in increased concentrations of dissolved and suspended solids in the runoff <br />water. <br />• <br />The problem of increased levels of suspended solids in the surface runoff was effectively mitigated by construction <br />and operation of sedimentation control structures. The sedimentation control structures are operated to affect <br />compliance with the effluent limitations of the NPDES permit. Under the stringent limitations of the NPDES <br />permit, the suspended solids concentrations of the discharge will be lower than natural baseline conditions. <br />Successful completion of reclamation activities as described under Section 780.18 provides effective surface <br />erosion control and results in runoff characteristics similar to the pre-mining conditions. <br />Increases in the concentration of dissolved solids tends [o result from increased leaching of disturbed overburden <br />material aitd from evaporation of water impounded in sumps and sedimentation control structures. Since no <br />effective treatment method is available, surface <br />• <br />1996 Permit Ren. Permit Renewal 780-144-24 Revised 3/18/97 <br />