Laserfiche WebLink
will be routed to the pond, and any discharges features to be installed. In addition, explain how the <br />pond will be reclaimed. <br />16. Please locate and describe in further detail the dewatering trenches that will be constructed to <br />facilitate dewatering of the site. Provide the sizing of the trenches and the pint of discharge. <br />17. The applicant states that for Cells B and C, water will be pumped to an existing sediment pond across <br />the Big Thompson River at the Brownwood Pit (M-1979-059). <br />• It appears that the proposed sediment pond will facilitate the dewatering of Cell B. Does the <br />applicant mean Cells C and D will be pumped across the river? <br />• Please describe in further detail how the water from Cells C and D will be conveyed to the <br />Brownwood Pit. Describe how the conveyance structure will be protected from high runoff <br />in the Big Thompson River and provide any ditch or conveyor designs. <br />• Please state if an Army Corps of Engineers 404 permit will be required for the conveyance <br />structure. <br />• The applicant will need to demonstrate that the Brownwood pit sediment pond can handle the <br />water conveyed from the Gardels Pit. In addition, the Brownwood pit permit will need to be <br />revised to account for the additional water from the Gardels pit and all conveyance structures <br />to be constructed. <br />• Please revise the exhibits to depict the location of the conveyance structures. <br />18. The applicant states that a drainage ditch occurs down the western side of Cell D. The applicant <br />proposes to relocate the ditch to the eastern side of Cell D to avoid capturing flow during the mining <br />of Cell D. Please inform the Division as to the owner of the ditch. The applicant will need to submit <br />a notarized agreement between the applicant and the owner of ditch that is to be removed and <br />relocated. In addition, please provide designs and drawings of the relocated ditch. <br />Rule 6.4.5 Exhibit E- Reclamation Plan <br />19. Cell A is to be reclaimed to approximate historic grade. Under Exhibit I-Soils, the Fluvaquents Soils <br />(33) it states that a water table exists at a depth of less than 12". In order to backfill above the water <br />table in Cell A, the operator will need to backfill at a minimum 12" above the groundwater table. In <br />order to determine the final grade of the pit, the applicant will need to provide the depth to <br />groundwater in this area and depict the contour intervals on the pre-mining map. <br />20. The applicant proposes to line Cell D with a compacted clay liner. Please explain how the clay will <br />be excavated and placed in the pit to ensure stable slopes. In particular, please explain how lifts will <br />be placed, how thick the clay liner will be and how it will be compacted to ensure the material is <br />placed in a stable configuration. <br />21. Exhibit F depicts a cross section of the compacted clay liner. The top of the liner is below grade. The <br />top of the liner should be at least three feet above the highest possible groundwater elevation. Please <br />provide borehole data as to the groundwater elevation in this area. If the liner is too low, and water <br />was to fill the pond to an elevation above the top of the liner fill, the operator could loose water to the <br />alluvial aquifer. <br />22. Please explain how the lined Cell D pit will achieve the postmining land use of general agriculture. <br />In particular, please state what surface water rights exist or will be used to divert water into the ponds <br />to achieve the post mining land use. <br />23. The rerouted drainage ditch to the north and southeast side of Cell D appears to cross over the mining <br />limits noted on Exhibit F, Reclamation Plan Map. The ditch relocation is different than noted on <br />Exhibit C-2, Mine Plan Map. Please clarify this discrepancy and revise the exhibits accordingly. <br />