2021-10-08_REVISION - M1987026 - Laserfiche WebLink

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will see on the Exhibit C Phase I Mining Map originally provided that the O/B disposal cell is 200 feet away from the house. Please see the additional new map enclosed with this letter, specifically identifying this house in relation to the proposed permit boundary and affected areas. Please also see the additional map enclosed with this letter, showing the 200-foot setbacks to the north and south of the overhead powerlines, within which no permit-related activity will be carried out. These overhead electric lines effectively divide the 112c permit, with all current and proposed Phase I activity limited to the south of the electric lines and their south setback. There will be no mining-related activity carried out in the northern half of the permit (i.e., on lands lying to the north of the powerlines or their north setback), until Colorado Quarries has received approval for any permit revision for activity there. As such, maps reflecting Phase I activities and features will largely exclude the northern half(Phase 11), and will be clearly labeled. There are currently no activities proposed in the NW part of the 112c permit area, or anywhere in the northern part of the 112c permit,though no activities are planned or locations known, at this time. The operator reiterates that the north part of the permit will eventually contain affected land. Exhibit D—Mining Plan Topsoil:The approximate "average"thickness of topsoil to be stripped from affected areas is expected to be 6 to 12 inches. Topsoil depth varies greatly across this rolling site, but this depth range is being used as a practical quantity to strip, stockpile and replace. Assuming the minimum depth of 6 inches removed, the volume of soil is estimated to be 16,133 cubic yards. This will be stripped during Phase I mining, and placed in the temporary stockpile area or placed directly on areas that are ready for final, concurrent reclamation. The stockpile area is shown on the Phase I Mining Map. All stockpiled topsoil will be respread, and the stockpile area reclaimed. It should be noted that the area upon which topsoil will be respread is smaller than the area from which it was stripped, Overburden:The overburden depth varies, as previously stated,from zero up to 40 feet, though its average depth is closer to 10-15 feet. It will need to be fully removed above the area to become the expanded quarry area. Eventually this volume could reach an estimated 200,000 cubic yards. This will be incrementally stripped and hauled for permanent placement, either in the permanent O/B disposal area north of the quarry, operations pad fill, or minor amounts used for runoff berms or road fills. The O/B disposal area will receive the majority of this material, and is shown on the Phase I Mining Map and Reclamation Map. Overburden that has been moved will be placed in the permanent disposal area, shaped with proper sideslope gradient, topsoiled and revegetated. The obsidian deposit in the quarry does not produce groundwater, but tends to impound meteoric water faster than it infiltrates. While the operator will place an earthen berm above the quarry as an upland diversion to deflect runoff from entering the quarry, precipitation and the operator's dust mitigation could cause water to pond in the pit floor. Occasionally the pit will be need to dewatered by pumping, which will be captured by the "upper" sediment pond proposed, immediately below the operations pad in the permit area (see the Phase I Mining Map). The lower stormwater pond shown on the maps, outside the permit area was constructed many years ago to help control runoff from a wide upland area (including from the 110 permit) before it reached the town. These drainageways and the pond area are nearly always dry. Though it seems that including it on the maps was misleading, we felt it necessary to show it on the maps since all ephemeral drainageways, including"ponds" should be shown. This lower, existing catchment area is not intended