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year, 24 hour storm event (Rule 4.09.2(7). Additionally, Rule 4.09.2(7) requires that <br />drainage from the fill be diverted into channels designed for the 100 year, 24 hour <br />storm event. No diversion of flow is proposed at this time for either the south side <br />drainage from the fill or the northeast drainage from the fill. In a phone call on <br />March 31, 2009 with Trapper Mine personnel, the Division discussed possible <br />changes to the drainage design for Horse Gulch Fill to incorporate the 100 year <br />channels to meet the requirements of 4.09.2(7). Also discussed was utilizing two rip <br />rap down drains as recommended by the Agapito report. Should these changes be <br />implemented, please provide revised surface drainage calculations, including <br />SEDCAD design information. <br />Trapper's Response: Trapper has incorporated the changes discussed by phone <br />with DRMS. A riprap channel has been added to the south and the face diversions <br />on the Horse Gulch Fill flow either to the north riprap channel or the south riprap <br />channel. In addition, a diversion has been added to the north. This diversion <br />(NHGFD) captures runoff from the fill and diverts into the reconstructed West <br />Flume drainage. The SEDCAD run for this case also includes a look at the <br />reconstructed drainage to insure that the flow from a 100 year, 24 hour event can be <br />safely passed. Given the relative large size of reconstructed drainages, the model <br />shows that this storm event is easily passed. The reference point on the West Flume <br />reconstructed drainage was conservatively chosen at Northing 406,000. SEDCAD <br />runs for all of the diversions are enclosed as well as a revised Figure T-1 that shows <br />the diversions in plan view and a table of design criteria. The diversion depths <br />include 1.0 foot of freeboard. <br />8. Division's Comment: Table 4.9-3 reflects the projected bank cubic yards of topsoil <br />to be salvaged and replaced; however, the K pit area, Horse Gulch Fill and Buttress <br />Fill are not included with the costs associated with tables 1.4-8 and 1.4-9...Please <br />acknowledge if the costs... include the costs of topsoil salvaging and replacement in <br />these areas. <br />Trapper's Response: In Table 1.4-8, Summary of topsoil replacement costs, the area <br />designated as G pit includes the 2012 projected disturbed portion of G pit, the <br />projected disturbance in K pit and both the Horse Gulch Fill and the Buttress fill <br />areas. The total of 1,064,040 cubic yards calculated for this line item represents <br />approximately 32% of the total bond topsoil replacement quantity and equates to <br />659.5 acres. <br />9. Division's Comment: A summary of estimated revegetation quantities and costs is <br />associated with Table 1.4-10.... Please acknowledge if the costs in Table 1.4-10 <br />include the costs to revegetate the K Pit, Horse Gulch Fill and Buttress Fill or revise <br />the costs to reflect the revegetation of these areas. <br />Trapper's Response: In Table 1.4-10, Summary of estimated revegetation quantities <br />and costs, the line item noted as G pit shows the full 659.5 acres that includes all of <br />the G Pit, K Pit, Horse Gulch Fill and Buttress Fill areas.