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comparison therefore is technically valid. A chief cause of soil loss is transport of solids in <br /> suspension. The comparison indicates the total drainage area does not yield more suspended <br /> solids than pre-mining conditions. <br /> The LISLE is an empirical formula approximating expected sediment yield from a parcel of land. <br /> It is reasonable to hypothesize that the LISLE is useful for discriminating between two <br /> significantly different yield rates. However, it is not useful for discriminating between two yield <br /> rates of similar magnitude. For the bond release parcels in SL 19, Trapper calculated a pre-mining <br /> sediment yield rate of 2.30 tons per acre per year and a post-mining rate of 0.72 tons per acre per year. <br /> The calculation indicates that the post-mining soil loss rate is 31% of the pre-mining rate. The <br /> considerable difference between these two calculated rates indicates the post-mining rate is less than <br /> the pre-mining rate. This conclusion is only valid if Trapper used reasonable variables in the LISLE <br /> calculations. <br /> The variables employed in the LISLE equation and their definitions are presented in the table <br /> below: <br /> Table 5. USLE Variables and their Definitions. <br /> Variable Definition <br /> R Climatic erosivity factor due to precipitation <br /> K Soil erodibility under a standard condition <br /> LS Slope length and steepness factor <br /> C Cover management/land use <br /> P Support practices factor <br /> The Division finds Trapper's selected USLE variables reasonable. The variables are similar to <br /> those found acceptable by the Division for Trapper's previous bond releases. The lands in SL 19 <br /> are similar to lands in previous bond releases. Trapper's basis for selecting each variable and the <br /> Divisions review of each variable is presented in the table below: <br /> Permit Number C 1981010 <br /> SL19 <br />