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Stpten{er 2000 Kerr Ctwpnry'Pmrial Bord Rdeae'Hy6dogC RelanrrriaeEwGatiar • 2 K =0.28 (clay loam) 2.3 LENGTH SLOPE FACTOR (LS) The LS factor accounts for the effects of hillslope length (L) and hillslope gradient (S) on erosive and transport forces. The following equation was used to determine the LS factor. For slopes <9% LS = (L/72.6)"' r. (10.8 x sin(s)+0.03) For slopes >9% LS =(L/72.6)'" x (16.8 x sin(s) +0.5) Where: L =Slope length S =Slope angle m = 0.3 for slopes G3% 0.4 for slopes = 4% 0.5 for slopes > 5% and < 10% 0.6 for slopes > 10% Average slope lengths and angles for the ctrtrent reclaimed conditions for all three major mine disturbance areas were determined from recent aerial topography maps. Slope lengths and angles for the premirring conditions were determined from the Pre-Mme Topography Map (Map 35a) in the Kerr Mining and Reclamauon Plan document. LS factors for each sub-drainage within the three major mine disturbance areas were determined and then averaged for each azea. The closed contour furrows constructed during reclamation on the steeper slopes in the 720 Pit and Pit 1 areas were taken into account when deterntinutg representative slope lengths. LS calculations are snmm~n~rd in Attachment 1, Calculation Spreadsheets. 2.4 ,COVER MANAGEMENT FACTOR ICI The cover management factor represents the effects of vegetation, management, and erosion-control practices on erosion and soil loss. C factors deterrtrinations for the premising and reclaimed conditions for the three major mine disturbance areas were based on cover data from the Report of Findings- Reclamation Monitoring (ESOO Associates, 1999). C factors for various vegetation types and cover percentages were detemtined from Table S.A.3 in Applied Hydrology and Sedimentology for Disturbed Areas, Barfield, Warner, and Haan. The selected C factors and their basis aze suntnurrzxd by Table 1. TABLE 1 C Factors Area % Canopy Type % Ground C and Hei ht Cover Factor Mart Pit Reclaimed (Pre 1986 Reclamation! 0°,5 G 57°h 0.05 Mart Pit Premising (Alkali Sagebrush and Sagebrush- 25%/0.5m G 44%/56 0.075 Grass) °~ 720 Pit Reclaimed (1995 Reclamation) 0% W 64% .07 720 Pit Premising (Alkali Sagebrush and Sagebrush- 25%/0.5m G 44%/56 .079 Grassl % Pit 1 Reclaimed 11996 Reclamation) 0% W 67°h .07 Pit 1 Premising (Alkali Sagebrush and Sagebrush-Grassl 25%/0.5m G 44%/56 .074 Notes: % Ground Cover includes litter and standing dead. G -Majority of ground cover is grass W - Ma'orit of round cover is broadleaf Ma¢gnery Wr~or ' P. ~ Ba< 774018 Stem/mt Sprirg, (T780477 ° (970) 8796260 x~ emnnis.Ad ew.>v.r~ ~ xw,m~ vnix~n.