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suspended solids because settleable solids and suspended solids comprise the same relative <br />proportion of the source sediment in pre-mining and post-mining conditions. <br />Trapper's 20-acre study areas. Trapper ran SEDCAD 4 for a 20-acre study area having <br />sedimentologic characteristics representative of each bond release parcel. SEDCAD 4 calculated <br />the peak settleable solids concentration of runoff flowing to a single discharge point at the down- <br />stream end of each 20-acre study area. SEDCAD 4 was run for pre- and post-mining conditions. <br />The Division believes use of 20-acre study areas is a valid approach for modeling sedimentation in <br />the reclaimed drainages in the bond release area because it enables applying each block's actual <br />vegetative cover data to the SEDCAD run for each block. <br />Trapper's conclusion from SEDCAD+. Trapper's SEDCAD 4 modeling concluded that the <br />computed postmining peak settleable solids generated from each block is much less than the <br />computed premining value. Trapper considers that the lower postmining sediment yields are a result <br />of a lazge amount of vegetative cover on the reclaimed lands. <br />The Division's field observations made during inspections over the years and observations <br />made during the bond release inspection of October 1999. The Division searched for any field <br />evidence of erosion and sediment accumulation during the bond release inspection. Observations <br />made during the bond release field inspection, as well as observations made during previous regular <br />inspections, indicated that the vegetation on the reclaimed slopes had stabilized the soil. No sediment <br />accumulations, such as deltas and fans, were observed. There was no general erosional instability <br />observed. The Division's Feld observations appeared to corroborate Trapper's hydrologic modeling <br />results of postmining sediment yields be^^ing less than pre ning yields. <br />~cr,Lt~} ~ISLY ~.l~c--~~~"~ <br />Division's finding that post-mining sediment yield does not exceed pre-mining yield. Based on <br />Trapper's SEDCAD 4 modeling~using baseline data~fhe Division finds that the lands proposed for <br />Phase II bond release aze not contributing suspended solids to streamflow or runoff outside the <br />permit azea in excess of premining levels. <br />Summary and Conclusions <br />Trapper requested Phase II bond release from the lands delineated on Map 1.0, titled "Phase II Bond <br />Release-Pazcel (SL-2) Parcel/Block Delineation", of the bond release submittal, received October <br />6, 1999. The Division reviewed the bond release application, the mine permit, and inspected the <br />lands. Based on the review and inspections, the Division finds that on the bond release lands <br />Trapper has: <br />1. Replaced topsoil in accordance with the approved reclamation plan. <br />2. Established vegetation that meets the approved success standard for vegetative covert' <br />Trapper Mine <br />Phase II Bond Release Page 11 12/21/99 <br />