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at this time. <br /> In accordance with Rule 3.03.1(3)(b) and with Section III.A.7.a. of the Division's 1995 Guideline <br /> Regarding Selected Coal Mine Bond Release Issues, Trapper submitted two evaluations to <br /> demonstrate that runoff from each bond release block will result in equivalent or lesser sediment <br /> contribution as compared to baseline conditions and similar undisturbed lands. <br /> Trapper's bond release application compares pre- and post-mining sediment yields by calculating <br /> expected sediment yields for both conditions. Trapper used the LISLE (Universal Soil Loss <br /> Equation), and SEDCAD 4 for Windows calculation methods. The LISLE calculates expected <br /> average annual soil loss per acre of land (rate of erosion), based on slope, rainfall pattern, soil <br /> type and vegetation type. SEDCAD 4 calculates the expected settleable solids concentration in <br /> runoff from a precipitation event. Trapper's two sets of pre-mining and post-mining sediment <br /> control demonstration models comprise Appendix 3 (SEDCAD 4)and Section 1.4 (USLE), of the <br /> bond release application. <br /> LISLE Comparison: Only the "C" factor varies between the pre-mining and the post-mining <br /> calculations; all other variables are constant for pre-and post-mining. The C factor takes into <br /> account land use, vegetative canopy cover, effective cover and grass type. The pre-mining <br /> calculation utilized baseline vegetation cover values from the permit application (Table 2.3-13 <br /> and 4.4-2). The post-mining calculation uses vegetation cover data for the disturbed area collected <br /> in 2017. <br /> The variables used in the calculations are reasonable for making the comparison. The comparison <br /> therefore is technically valid. A chief cause of soil loss is transport of solids in suspension. The <br /> comparison indicates the total drainage area does not yield more suspended solids than pre-mining <br /> 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 /> Permit Number C 19 81010 <br /> SL19 <br />