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M -5- 3. Solute Leaching In an attempt to quantify the amount of solute leaching from backfilled mine Al pits, the applicant performed a leaching study on overburden material ~II~~ 1;~}- collected from the Eckman Park Mine. One of the most important results of a ~ leaching study such as this is to estimate an anticipated "worst case" value ~ ,Y for total dissolved solids concentration of leachate percolating through the la,p I lV~ reclaimed spoils pits. An anticipated "worst case" TDS value for spoils p./~ leachate should be included to this section. W ~ ~ u -permit-aFp-Nra#~en~. ~~~ y Pa. 4. Solute Transport The applicant has qualitatively discussed the mechanism of increased dissolved solids transport from the backfilled mine pits to the undisturbed overburden aquifer system. However, a quantitative interpretation of effects has not `~~~;.~~ been presented. A numeric projection of anticipated impacts of spoils eater P ~J discharge on the ambient hydrologic system should be produced and supporting data and calculations should be Included 1n the permit application. B. Surface Mater Effects ,,/ 1. Runoff and Erosion ~~,~,~~i,,~° A quantitative evaluation of the anticipated increase to runoff and erosion Sec rates for all disturbed areas should be presented along with supporting data P1~ and calculations. 2. Sediment and Otssoived Salt Load The applicant should include a numeric estimation of the change in sediment and dissolved salt load on receiving streams due to existing and proposed mining activities both during mining and post-reclamation. m e4n~ m~,n~' C. Additional Cortments on Probable Hydrologic Consequences ~ y 1. There is some concern within the Division as to the potential impacts of the Mine No. 3 and Middle Creek Detention Basins on the water quality of the alluvial aquifer system within the permit and adjacent areas. Both detention basins are located adjacent to alluvial deposits and are projected by the applicant to be in hydrologic communication with the alluvial ground water system. Therefore, the "Probable Hydrologic Consequences" section of the permit application should be expanded to include a discussion of potential S water quality effects of the detention basins on the alluvial ground water system. The discussion should include detailed geologic cross sections h'b~ C~~ extending at least 500 feet adjacent to the basins, clearly identifying the b relationship between the basins and adjacent undisturbed bedrock, backfilled) overburden material, and alluvial deposits. Additionally, the discussion should Include an estlmatlon of contribution from water percolating through reclaimed spoils into the basins, an estlmatlon of seepage rates out of the basins, and a predicted "worst case" value of total dissolved solids of water contained within the detention basins.