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Li • <br />�'. is a . :S'4r"D r1 <br />D. Stream Buffer Zones <br />Tlie Division previously approved surface'o`r underground mining <br />activities within 100 feet of or ;through a'perennial stream or stream with a <br />' '`= biological commurirty This decision was based on finding that the <br />original str "earn channel' would be restored, water quality and quantity <br />would not' be adversely:affected, and appropriate riparian vegetation <br />would bereestablished:`'he buffer zone variance was granted for the <br />former water pump station on Trout Creek, aridTfor the facilities area along <br />Oak Creek [Rule 4.05.18(1)]. For these areas, the Division also finds that: <br />'a) the surface coal 'mining operations will not -cause or contribute to the <br />violation' of applicable water quality :standards, and b) during and after <br />mining, the water quantity and quality, and other environmental resources <br />of the stream shall not be adversely affected [Rule 4.05.18(1]. <br />Probable Hydrologic ConsegUerices.(PHC) of Mining <br />Section 2.5 in Volume 3 Of the PAP contains an assessment of the <br />hydrologic consequences of the Edna Mine. Those consequences (with <br />PHC page number or other reference) are summarized below. <br />ti <br />' Projected Impacts <br />1. Post - mining infiltration rate of meteoric water — Annually, 1.95 <br />=inches ofineteroic •water'will infiltrate from the ground surface <br />into the subsurface (PAR page 2.5 -88). <br />2. Spoil saturation - The infiltrating water will saturate spoil in the <br />toe (northwestern, down -dip end) of each backfilled pit (PAP, <br />Exhibit 2.5 -25). <br />Spoil ,leachate quality - As the infiltrated water percolates through <br />the spoil;::it will become mineralized to form a spoil leachate <br />having an average total dissolved solids (TDS) concentration of <br />3000 mg/1 (PAP, page 2.5 -96). This compares to TDS of less than <br />600 ing/1 in this stratigraphic sequence prior to mining. <br />4. Discharge of leachate from pit - From the spoil in each <br />backfilled pit, the leachate will discharge into the bedrock in the <br />walls of the toe of the pit, and to the ground surface as spoil <br />' F s - *springs (PAP, sEXhibit 2.5-25). <br />,; t' - <br />5. Leachate impacts on bedrock ground water - Leachate discharging <br />into bedrock in the toe of the pit will not cause material damage to <br />bedrock aquifers because the bedrock receiving the leachate is an <br />unmined wedge of bedrock that would transmit the leachate less <br />than 1000 feet to the bedrock's outcrop on the banks of Trout <br />C1980 -001 Edna Mine Permit Renewal No. 6 23 <br />