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Broken Arrow Investments, LLC Derr Pit, Adequacy Review Comment Responses, File No. M-2008-017 10117108 <br />-4- <br />stock piles will be separated and stored in individual piles. Please refer to the revised <br />Exhibits C & D. <br />11. Include a topsoil handling plan that addresses removal, stockpiling, and <br />placement of topsoil. In addition, verify that the volumes proposed to be <br />stripped equal stockpile volumes. <br />Response: <br />Clarification is provided in the mining plan narrative for the removal, stockpiling, and <br />placement of topsoil. The volumes proposed to be stripped are equal to the stockpile <br />volumes. The sizes of the stockpiles have been revised on the mining plan map. <br />Please refer to the revised Exhibits C & D. <br />12. The mining plan calls for installing dewatering trenches along the perimeter of <br />each mining area in phases 2-7. Please explain how dewatering will be <br />accomplished in each phase to a depth of 70 to 90 feet with a 3HA V slope on <br />the outside half of each phase. <br />Response: <br />The dewatering trench around the perimeter of the phase being mined will be placed <br />at the toe of the 3H:1 V mining slope. As the phase is mined deeper the dewatering <br />trench will be lowered and moved laterally along the 3H:1 V mining slope toward the <br />center of that phase. Once the interior area becomes small enough where the 3H:1 V <br />mining slopes from three to four sides are encroaching upon the portable plant and <br />haul roads another phase will be opened to continue mining. The slurry wall is <br />anticipated to be installed prior to Phase 2 being mined, and it is expected minimal <br />dewatering will be required in the subsequent phases due to the slurry wall cutting off <br />groundwater infiltration into the pit. Please refer to the revised Exhibit D. <br />13. The mining plan states that there will be a minimum 150 foot setback from <br />existing oil and gas facilities. The Division requires a minimum 200 foot <br />setback from every permanent man-made structure unless an executed <br />damage waiver agreement has been submitted per Rule 6.4.19(a). If an <br />agreement cannot be reached then an engineering evaluation can be used to <br />demonstrate that mining will not result in structural damage per Rule 6.4.19(b). <br />Response: <br />A 200 foot setback will be maintained from the existing oil and gas facilities until a <br />finalized surface use agreement is in place with Kerr-McGee / Anadarko. We are <br />working on finalizing the surface use agreement with Kerr-McGee / Anadarko and <br />will provide the agreement to DRMS once it is finalized. When the agreement is <br />finalized setbacks will be maintained per the agreement. We have also provided a <br />slope stability report indicating acceptable setbacks that are less than the 200 foot <br />setback required by the DRMS for permanent man-made structures. Please refer to <br />the revised Exhibit D. <br />14. Please describe in detail how mining will progress during each phase and from <br />phase to phase with a 70-90 foot highwall. Include enough information in the <br />text and on the maps for the Division to calculate the maximum interior <br />highwall dimensions that will require 3HAV slope. This information is <br />necessary to assist us with our financial warranty calculation. <br />4 1400 W 122nd Avenue - Suite 120 • Westminster CO 80234 • Ph: 303-457-0735 • Fax: 303-920-0343 <br />111