2008-01-28_REVISION - M1997054 (34)

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Mr. Berhan Keffelew - Re.: Parkdale Quarry, Amendment #1, Adequacy Letter Response -January 28, 2008 Page 2 of 6 III) EXHIBIT D Mining-Plan 1) The current depth of ,the sand and gravel pit will -generally be 35 to.- 40 feet. The - operator proposes to excavate dewatering . trenches, around the perimeter of the mining area. Groundwater' collected in the trenches - will be . conveyed to a settling pond and pumped to Tallahassee Creek or the Arkansas -River as directed by-the State-approved discharge permit. The rate of transmissivity of-the sand and gravel strata can be found. in the draft groundwater report previously provided to the, DRMS. No -well pump test was conducted. A variance for installation of pumping equipment was granted by' the State. The pumps and all,ancillary support equipment have been included in the revised bond calculation. The pump associated with the well is an 8-inch centrifugal pump, diesel- fueled and trailer mountedto cycle- groundwater in a closed loop system. The dewatering . pump is a vertical turbine pump rated for 2,000 gpm. The well completion report, cross section, and the pump variance letter are attached as Exhibit 11I.1. 2) The attached sandstone description (Exhibit 111.2) is intended to amend the Mining and Reclamation Plans to include detailed information about the sandstone quarry.. At . this time, no mining is proposed within the sandstone quarry. The disturbance limit has been revised to include the sandstone area since it is currently permitted for mining and, may be considered for mining by Front Range Aggregates in the future. If mining is proposed, a technical revision and bond will be submitted for the sandstone quarry. 3) The bond calculations have been modified to include the. removal of the processing plant in the eastern portion of the gravel- pit, including the removal of the conveyer belts extending westward. Two concrete supports exist where the conveyer belt is elevated over a road. No additional. concrete supports are anticipated. 4) To date, the operator is in compliance. with all air-emissions permits. Two inspections, have been performed resulting in zero violations.. The NESCO system uses a high- efficiency spray to physically knock-down dust particles. The sand and. gravel dust control system applies water at a rate of 1.43 gallons per minute with anestimated. operation of 2,500 hours per year, equaling 9.2 acre-feet of water per year. The quarry will use an estimated 7.4 acre-feet of water for 2,000. hours of dust control operation per year. The total volume for dust control- is 16.6 acre-feet. 5) The sediment ponds will generally be. located- along the northern portion of the' sand and gravel mining area. As the mining operation progresses the settling ponds may be reconfigured or relocated within the mining area, but are expected to remain the same approximate size and. in the same general location. The current settling ponds are approximately one acre combined.. The operator intends to backfill these settling ponds once they are no longer needed to support the mining operation. 6) The Mining Plan Map (Exhibit C-2) has been revised and -includes two additional topsoil stockpiles. One topsoil stockpile will generally be located northwest of the gravel mining area within the disturbance limit. A second topsoil stockpile will generally be located west of the quarry mining area within the-disturbance limit. The mining operator agrees to seed topsoil stockpiles that will be in place for 180 days or more. For. bonding purposes, the addition of these two stockpiles will decrease the haul distance required for placing topsoil during.reclamation. -'Therefore the unit cost of $1.05 used in the original amendment bond calculation was unchanged.