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erosional features indicates successful vegetation establishment and erosion control. Three sparsely <br />vegetated small areas were observed on the far western portion of the CR 93-94 bond release block. <br />These aeeas correlated to repaired backfilled highwall settlement cracks, were very limited in size, <br />and showed evidence of vegetation becoming established. <br />Suspended Solids: <br />TMI used two methods to compare pre-mining and post-mining sediment yields on the bond release <br />blocks. TMI used the Universal Soil Loss Equation (LISLE) and the SEDCAD 4 computer model. The <br />LISLE provides a rough approximation of expected sediment yield from a parcel of land. The LISLE is <br />useful for discriminating between two yield rates that are significantly different. For the two bond <br />release blocks, TMI calculated apre-mining sediment yield rate of 0.86 tons per acre per yeaz and a <br />post-mining sediment yield rate of 0.13 tons per acre per year using the LISLE formula. The post- <br />miningmodel indicates less suspended solids would leave the reclaimed site than in the pre-mining <br />condition. One significant explanation for the reduction in sediment load is the shift from an annual <br />wheat crop pre-mining to a perennial alfalfa grass hay crop post-mining. The Division believes that <br />TMI used appropriate variables in its sediment yield demonstrations and considers that the calculations <br />adequately represent the pre-mining and post-mining conditions. <br />TMI used the SEDCAD 4 computer model to demonstrate that post-mining settleable solids are less <br />than pre-mining settleable solids from the bond release blocks. Although Section 3.03.1(3)(b) of the <br />Regulations specifies "suspended solids" be used to determine post and pre-mining sediment yields, the <br />Division finds TMI's use of settleable solids acceptable since SEDCAD 4 does not calculate total solids, <br />but instead calculates total sediments and settleable solids. TMI compazed total sediment for pre-mining <br />and post-mining conditions. TMI's SEDCAD 4 mode] showed that the computed post-mining peak <br />settleable solids generated from each bond release block is less than the compared pre-mining value. <br />The Division concurs with TMI's calculation and corroborates the model with field observations. No <br />serious erosional features, large gullies, or sediment fans were encountered during the bond release <br />inspection. One small gully was encountered during the inspection. This gully was shallow, <br />approximately 9 to 12 inches deep, short duration, approximately 50 feet long, approximately 4-6 inches <br />wide and not currently active, as noted by the proliferation of grass species growing in the bottom and <br />along the sides of the gully. <br />Drainages and sedimentation ponds located within and down slope of the bond release blocks aze not <br />included in this bond release application. Portions of Coyote and No Name drainages and associated <br />sediment ponds remain in the permitted azea and are not a part of this Phase II bond release. Portions of <br />the West Buzzazd, East Buzzard, and Far East Buzzard drainages that pass through CR 82-92 and CR <br />93-94 bond release blocks are included in this Phase II bond release. The West Buzzazd, East Buzzazd <br />and Far East Buzzard ponds remain and are not a part of this Phase II bond release. <br />Trapper Mine, SL-03, Findings ~ April 19, 2002 <br />