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SeptasMr 2000 Kerr Cmpvry'Pmriul BmdRdeae'Hybdodic R~dmrutim EwGMim~ ~ 3 <br />The majority of the vegetation prior to mining in all three areas was Alkali Sagebrush, with minor <br />areas of Sagebrush-Grass. The C factor for premising conditions was deterntised using a weighted <br />average. <br />2.5 SUPPORT PRACTICE FACTOR IPI <br />The P factor represenu practices designed to control erosion. For the existing reclaimed conditions, a <br />P factor of 0.8 was used to account for the rough soil conditions from disking along contour and seed <br />drilling. For the premising conditions, a P factor of 1.0 was used. <br />3.0 RESULTS AND CONCLUSIONS <br />Calculation spreadsheets showing all inpuu and resulu are included in Attachment 1, Calculation <br />Spreadsheeu. Table 2 summarizxs the calculation results. <br />TABLE 2 <br />Sediment Yield Calculation Results <br />Area Annual Sediment Yield <br />tons/acre/ ear <br />Marr Pit Reclaimed IPre 1986 Reclamation) 0.63 <br />Marr Pit Preminin fAlkali Sa ebrush and Sa ebrush-Grassl 1.05 <br />720 Pit Reclaimed 11995 Reclamationl 0.54 <br />720 Pit Premising (Alkali Sa ebrush and Sagebrush-Grassl 1.12 <br />Pit 1 Reclaimed (1996 Reclamationl 0.83 <br />Pit 1 Preminin (Alkali Sa ebrush and Sa ebrush-Grassl 2.39 <br />As indicated by Table 2, calculated sediment yields for the reclaimed conditions aze significantly less <br />(35 to 60 percent of premuting yields) [has for the prenilrting conditions for all three of the major <br />mine disturbance areas. This reduction u a reflection of a number of factors including: <br />• Overall reduction of slope gradienu insignificant portions of the 720 Pit and Pit 1 <br />• Reductions in effective hydraulic slope lengths in the 720 Pic and Pit 1 through the use of <br />closed contourfurrows <br />• Reductions in surface erosion, runoff, and sediment transporc potential through surface <br />roughening <br />• Increases in effective vegetative cover due to reductions in sagebrush densities (ie: sagebrush <br />provides canopy cover but limiu grotmd cover since antibiotic effects hinder establishment <br />and growth of grass and forb species directlyunder sagebnuh plane) <br />The significant reductions in calculated sediment yields provide reasonable evidence of effective <br />hydrologic reclaznation consistent with the applicable regulatory provisions of Rule 3.03.1(3)(6). <br />Mmrtgrrery Wham! ' P.Q Bar 774018 Srovr/nu Spring, 0080477 ' (970J 879-6?ti0 <br />U'.RP/61J/emyBadRdee'l/dikp Rdnm~ <br />vn/w~~ <br />