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calculations are reasonable for making the comparison; as such, the comparison appears <br />technically valid. Also, the variables are similar to those the Division has found to be reasonable <br />in TMI's previous bond releases, and the lands in SL-09 are similar to some of the lands in <br />previous bond releases. <br />In the SEDCAD 4 comparison, TMI utilized baseline data for selecting parameters for the <br />SEDCAD 4 runs of pre-mining conditions and 2008 data in the bond release submittal for the <br />runs of post-mining conditions. The Division's review of each of the parameters shows that <br />the parameters reasonably represent the conditions in the field for the pre-mining conditions <br />and the post-mining conditions. <br />TMI ran SEDCAD 4 for a 20-acre study area having sedimentologic characteristics <br />representative of each bond release parcel. SEDCAD 4 calculated the peak settleable solids <br />concentration of runoff flowing to a single discharge point at the down-stream end of each <br />20-acre study area. The Division believes use of 20-acre study areas is a valid approach for <br />modeling sedimentation in the reclaimed drainages in the bond release area because it enables <br />applying each block's actual vegetative cover data to the SEDCAD run for each block. The <br />total sediment load calculated for the pre-mining block A, D&H RSC 20-acre study area was <br />8.7 tons of sediment and 20.8 tons of sediment for pre-mining block D&F RSAB. The total <br />sediment load calculated for the post-mining block A, D&H RSC 20-acre study area was 4.0 <br />tons of sediment and 9.3 tons of sediment for the post-mining block D&F RSAB. TMI's <br />SEDCAD 4 modeling concluded that the computed post-mining peak settleable solids <br />generated from each block is much less than the computed pre-mining value. <br />Observations made during the bond release inspection, as well as observations made during <br />previous inspections, indicated that the vegetation on the reclaimed slopes had stabilized the <br />soil. There was no major erosional instability observed. The Division's field observations <br />appeared to corroborate TMI's hydrologic modeling results of post-mining sediment yields <br />being less than pre-mining yields. <br />Based on TMI's SEDCAD 4 modeling using baseline data, the Division finds that the lands <br />proposed for Phase II bond release are not contributing suspended solids to streamflow or <br />runoff outside the permit area in excess of pre-mining levels. <br />Summary and Conclusions <br />Based upon a review of the mine permit, the applicant's bond release application, and site <br />inspections, the Division finds that Trapper Mining, Inc. has replaced topsoil and established <br />permanent vegetative communities that support the post-mining land use in accordance with the <br />approved reclamation plan. The Division finds both methods Trapper Mining, Inc. provided for <br />demonstrating that the reclaimed lands are not contributing suspended solids to streamflow or <br />runoff outside the permit area in excess of pre-mining levels are valid. <br />Trapper Mine Page 9 December 2, 2008 <br />Phase III Bond Release