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Page 13 <br />All of the above considerations make AAI believe that the fly ash deposits (both in pure state as <br />well as mixed state with spoils) in the Ash -Pit will yield a greater overall safety factor compared <br />to spoils backfill. Therefore, AAI's preference to simulate the spoils backfill in the Ash -Pit in a <br />comparative study with other pits was justified for the sake of simplicity of modeling and <br />conservatism. <br />Truiillo Comment 2. Based on the "depth -based" approach, spoil of coarser/heavier particles are <br />deposited at the bottom with finer/lighter particles are deposited at the top. It is unsure to the <br />Division how Trapper plans to implement this during backfilling and grading of the L- and A - <br />pit. Please provide the Division with discussion on how Trapper plans to backfill and regrade to <br />ensure spoil participle distribution matches that which has been modeled using the "depth -based" <br />approach. <br />Trapper Response to Trujillo Comment 2. The in -pit spoils are segregated based on particle size <br />and density automatically, once end -dumping from haul trucks or dozer -pushing are performed <br />to backfill the pit. The layered strength approach is based on empirical field strength <br />observations made at other coal spoil deposits, where end -dumping has been used to backfill the <br />coal spoils. Therefore, no specialized placement plan is needed to be performed by Trapper to <br />achieve the depth -based strength matrix used in AAPs simulations. Routine end -dumped and <br />dozer -pushed spoils are anticipated to attain the fine -to -medium -to -coarse (and respective <br />strength) arrangements from top -to -bottom of the in -pit backfill matrix. <br />Please get back to us with any questions, comments or concerns. <br />Sincerely, <br />orrest Luke <br />Environmental Manager <br />Trapper Mining Inc. <br />c PR -09 binder <br />File 109.2.3.4 <br />