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Section 780.21(c) Continued. <br />The yield per acre previously calculated times the 1,985.1 acre <br />tributary area to the proposed sedimentation ponds is 6.0 acre-feet. <br />The total amount of required sediment storage volume for the <br />sedimentation ponds is 66.9 acre-feet. Therefore, all of the assumed <br />annual yield per acre in the proposed permit area will be detained by <br />sedimentation ponds, and there will be an effect of pond detention on <br />water quantity in the intermittent draws draining the proposed permit <br />area. A breakdown of assumed annual yield vs. pond detention is <br />given below: <br /> Total Assumed Tributary Assumed <br /> Vatershed Annual Pond Annual <br />Receiving Area Yte ld Area Detention Percent <br />Stream (ac) (ac-ft) (ac) (ac-ft) Detention <br />Bolton Draw 4,352 13.1 145.7 2.2 16.8 <br />Bush Draw 3,072 9.2 182.0 0.5 5.0 <br />• Villiams Draw 2,880 B.6 499.4 1.5 17.4 <br />Sudduth Drar 2,304 6.9 81.0 0.2 2.9 <br />These calculations indicate that the percentage of runoff to be <br />detained by sedimentation ponds in Bolton, Bush, Williams and Sudduth <br />Draws are 16.8, 5.4, 17.4 and 2.9 percent, respectively. <br />Salt Load Studv <br />The length of data record on water quality during the baseline period <br />was insufficient to determine the cumulative hydrologic effect of <br />increased dissolved salt load on receiving streams in the proposed <br />permit and adjacent area. There was no discharge of leachate water <br />from the existing mine pit and no discharge from the newly <br />constructed sedimentation ponds during the baseline period, and thus <br />no data on these discharges were available. The continuing <br />hydrologic monitoring program will provide data on salt loading <br />780-126 eeeR <br />Revised - January, 1991 <br />