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known. One approach to evaluating this potential is through use of a soil loss model 5�' <br /> such as the Universal Soil Loss Equation (USLE). Included in permit documentation for the Coal Basin Mine were calculations relating to S14iment pond sizing. Included was >`' <br /> one small area that had a 50 percent slope (2:1(h:v)). For this area, the consideration <br /> of soil erodibility, slope length, percent slope, ground cover and surface roughness <br /> along with rainfall events led to calculation of a projected yield of 286 tons of <br /> sediment/acre/year. It can be anticipated that the yield from 1:1 slopes with little or no <br /> cover would be even higher, and, very likely, much higher. The cumulative yield of <br /> sediment across the full extent of steep slopes left on the Coal Basin site certainly <br /> leaves no doubt as to the necessity to control that erosion, as is required by state and <br /> federal law and regulation and as was clearly to be addressed in the approved <br /> reclamation plan for Coal Basin. <br /> ASSESSMENT OF SUCCESS OF PRIOR REVEGETATION EFFORTS AT COAL <br /> BASIN <br /> EVALUATION OF 1997 MINE No. 4 STEEP SLOPE REVEGETATION <br /> Based on observations of 8 September 1998, 1 believe that the seedings of steep <br /> slopes at Mine No. 4 have reasonable expectation of proving successful. The <br /> prominence of young plants resulting from the seeding is low as would be expected in <br /> the first year. The road cut areas have reasonable stands that are relatively easily <br /> visible. The road fill outslopes are much more difficult to see the <br /> presence/development of small seedlings. The loose fill is in general a more difficult <br /> place to establish as a seedling because the steepness of slopes limit the degree to <br /> which incident moisture can enter the soil. These sites also tend not to have snow <br /> cover as long in winter. Taken together, these conditions leave available soil moisture <br /> at lower levels than less steeply sloping locations and rates of plant growth are <br /> consequently less. <br /> EVALUATION OF PREVIOUS TEST PLOT RESULTS (ORM MINES 1, 4 AND 5 J" <br /> 4 <br />