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material is composed of lime which has cementitious properties in the presence of water. This ultimately <br /> will result in a greater factor of safety of the fill area and the use of just spoil in the stability analysis is a <br /> more conservative approach. I concur with this response based on what has been provided. Finally, these <br /> comments match with what was observed on the Division's pre-site inspection in November 2018. The <br /> Division walked and inspected the fly ash pit and it was noted that the ash fill was solidified and more <br /> compact than what is observed in adjacent spoil. <br /> Trapper's response is adequate and satisfies the Division's Comment 1. This item is resolved. <br /> Division 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 Division <br /> how Trapper plans to implement this during backfilling and grading of the L- and A pit. Please provide <br /> the Division with discussion on how Trapper plans to backfill and regrade to ensure spoil participle <br /> distribution matches that which has been modeled using the "depth-based"approach. <br /> Trapper states that the"depth-based"approached occurs naturally as part of the baclfilling operations. <br /> Routine end-dumped and dozer-pushed spoils are anticipated to attain the fine-to-medium-to-coarse <br /> arrangements from top-to-bottom of the in-pit backfill matrix. This information is based on site specific <br /> information of other backfilled areas and is logical. <br /> Trapper's response is adequate and satisfies the Division's Comment 2. This item is resolved. <br /> This concludes my review of Trapper's proposed AOC variance and associated engineering report <br /> submitted with PR-09.If you have any questions, feel free to contact me. <br /> Sincerely, <br /> Zach Trujillo <br /> Environmental Protection Specialist <br /> (303) 866-3567 ext. 8164 <br /> Zach.Trujillo@state.co.us <br /> Trapper Mine PR-09 Memo Jame 17,2020 <br />