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Rifle Gravel Pit#1 May 2023 <br /> confluence of the ditch and the pond will be located where the ditch enters the eastern <br /> boundary of the property. <br /> • A six-foot wide fringe of 5:1 slope will be left at the inner edge of the perimeter berm, and <br /> planted with wetland reclamation species after mining activity is complete. The intention <br /> is for the six-foot wide fringe to be nearly inundated during high-water periods as the <br /> water table rises, and then to be progressively exposed as the water table drops during <br /> the growing season. The remainder of the pit slope to the bottom of the pond will not <br /> exceed 3H:1 V slopes. Note that this reclamation effort follows local Garfield County <br /> guidelines and standards (LUC Section 7-1002.1-1). Formal wetland mitigation per <br /> USACE standards is not required, as no impacts to jurisdictional wetlands are 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 /> control, and aggregate dewatering. This perimeter berm will essentially provide a zero <br /> discharge of water or sediment-laden water off-site. <br /> Scott will comply with the State Engineer Office's (SEO) rules and regulations regarding any <br /> water depletions that may occur during mining operations from water lost with mined <br /> aggregate and water used for dust suppression. A copy of the SEO permit applications to <br /> address depletions is included in Attachment C. <br /> Any agricultural return flows in the tailwater ditch, which are estimated at<2 cubic feet per <br /> second (cfs) during peak irrigation season, will be incorporated into the pond, mixed with the <br /> alluvial aquifer, and eventually migrate laterally through the permeable gravels into the <br /> larger Colorado River water table. Given the minimal flows in the ditch, the large size of the <br /> pond (estimated at 6 acres within one year), and the highly permeable nature of the gravel, <br /> the agricultural return flows will have a negligible effect on water levels in the pond. As <br /> excavation proceeds, the tailwater ditch will be subsumed into the expanding pond <br /> boundaries, until under final conditions the discharge point will be where the ditch enters the <br /> eastern boundary of the property. <br /> 5.2.4 Explosives <br /> Explosives will not be used during mining or reclamation of the property. <br /> 29 <br />