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CRDA-1 Road <br />SOIL LOSS CALCULATION <br />AREA <br />R <br />K <br />I LS I C I P <br />A <br />Adjacent Area- CRDA-1 Road <br />30 <br />0.24 <br />11.4 <br />0.192 <br />1.0 <br />15.77 <br />Reclaimed CRDA-1 Road <br />30 <br />0.24 <br />2.16 <br />0.194 <br />1.0=3.02 <br />It can be seen from the above calculation that the revegetated CRDA-1 Road may lose <br />about 3.02 tons per acre per year to erosion. The CRDA-1 Road adjacent area, which <br />represents the baseline conditions, may lose 15.77 tons per acre per year. Based on this <br />demonstration, the CRDA-1 Road is not contributine suspended solids in excess of Dre- <br />mining levels. <br />Conclusions: <br />The three reclaimed and revegetated areas are not contributing suspended solids in <br />excess of the pre -mining levels. Additionally, untreated drainage from the disturbed <br />areas is required to meet the State and Federal water quality standard requirements <br />applicable after the sedimentation ponds and treatment facilities are removed. Run-off <br />from the reclaimed areas ultimately flow into the Colorado River with no notable <br />negative impacts to water quality. <br />The three reclaimed areas encompass a total of 0.006 square miles and runoff from <br />those areas will flow into the Colorado River. The total drainage basin of the Colorado <br />River is 240,000 square miles. The reclaimed areas account for 0.000003% of the total <br />Colorado River Drainage basin. <br />The very small drainage area of the three reclaimed areas would not have any <br />measurable impact on the quality or quantity of water in the Colorado River. The <br />vegetation on site will help reduce the sediment load that enters the Colorado River. <br />The soils on site do not have any physical or chemical constituents that would degrade <br />water quality. There is no reason to believe oil and grease will contaminate runoff from <br />the reclaimed areas since there is no oil or grease storage areas within the reclaimed <br />areas. <br />SL -10 Tab -7, Page 3 03/06/2017 <br />