Laserfiche WebLink
Rifle Gravel Pit#1 June 2023 <br /> location), where the material will be stockpiled for washing, processing, and <br /> subsequent sale. <br /> • Any agricultural return flows in the tailwater ditch, which are estimated at <2 cubic <br /> feet per second (cfs) during peak irrigation season, will be discharged into the pond, <br /> mixed with the alluvial aquifer, and migrate laterally through the permeable gravels <br /> into the larger Colorado River water table. Given the minimal flows in the ditch, the <br /> large size of the pond (estimated at approximately 6 acres within one year), and the <br /> highly permeable nature of the gravel, the agricultural return flows will have a <br /> negligible effect on water levels in the pond. As excavation proceeds, the tailwater <br /> ditch will be subsumed into the expanding pond boundaries, until under final <br /> conditions (Figure 11, Exhibit C6)the confluence of the ditch and the pond will be <br /> located where the ditch enters the eastern boundary of the property. <br /> • A six-foot wide greenbelt area with a 5:1 slope will be constructed at the inner edge <br /> of the perimeter berm, and planted with wetland reclamation species after mining <br /> activity is complete. The intention is for the six-foot wide greenbelt area to be nearly <br /> inundated during high-water periods as the water table rises, and then to be <br /> progressively exposed as the water table drops during the growing season. The <br /> remainder of the pit slope to the bottom of the pond will not exceed 3:1 slopes. <br /> • The greenbelt area slope of 5:1 will be visually apparent due to the shallow water <br /> covering the fringe. The deeper slopes will be maintained at no steeper than 3:1. <br /> During mining operations, Scott will utilize the GPS receiver in the excavator to see <br /> the excavated profile and make sure that the requirements of the permit are being <br /> met, including the 3:1 maximum slope. Scott will also use a handheld rover and <br /> check the slopes as excavation occurs to ensure that all requirements of the mining <br /> permit are being met, including the 3:1 maximum slope. <br /> • The six-foot wide greenbelt area with a 5:1 slope will be species surfaced using the <br /> topsoil retained from Phase 1 (566 CY) and planted with wetland reclamation <br /> species using a mix of seed and containerized stock. The remainder of the pit slope <br /> to the bottom of the pond will not exceed 3:1 slopes. Note that this reclamation effort <br /> follows Garfield County LUC standards (LUC Section 7-1002.1-1). Formal wetland <br /> mitigation per USACE standards is not required, as no impacts to wetlands are <br /> proposed. <br /> 5.2.3.2 Water Diversions and Impoundments <br /> As previously described, the Last Chance Ditch tailwater channel, which currently terminates <br /> on the property west of the Affected Lands and Permitted Area, will be incorporated into the <br /> excavated pond where aggregate is being removed. The irrigation return flows in the ditch <br /> will be mixed with the alluvial groundwater that fills the pond, and the water will continue to <br /> migrate laterally through the underlying permeable gravels to reach the Colorado River. The <br /> exact point where the tailwater channel enters the pond will migrate as the excavated <br /> boundaries of the pond expand; under final conditions the Last Chance Ditch tailwater <br /> channel will discharge directly into the pond at the point where the ditch enters the property <br /> on the eastern boundary. <br /> 5.2.3.3 Water Handling and Dewatering <br /> The perimeter berm, installed during Phase 1, will keep all on-site activities from impacting <br /> adjacent properties including, but not limited to stormwater, process wash water, dust- <br /> 29 <br />