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3. Groundwater <br />Since the mine will encounter water in the mining operation approximately 10' below the current <br />ground surface, pit pumping is needed. As described in the previous section, an electric powered <br />pump will be placed at the low point of the sediment pond. Trenches will be dug around the <br />perimeter of the excavated pit, which will keep the groundwater from contacting the active pit <br />area, thus keeping it clean. This water will be delivered to the sump and then the sediment pond, <br />where the pond pump will pump the water into the 8" pipe to the 33 Road Drain. This will be the <br />discharge point for the CDPHE permit. <br />Pumping is expected to be from 1500 to 2000 gallons per minute during the initial stages of each <br />pit and, after one month, the rate should drop to less than 1000 gallons per minute. <br />United has received a combined storm water process and process water discharge permit <br />specifically for sand and gravel mining for this site. The 33 Road Drain enters the Colorado <br />River a short distance downstream and southwest of the permit area. <br />All discharges from pumping water will be regulated under a combined storm water /process <br />water permit that will be approved by the Colorado Department of Public Health and <br />Environment. If the water quality is out of compliance, water will not be discharged until it is in <br />compliance. <br />The permit area is basically a zone of recent gravels in the floodplain of the Colorado River, <br />deposited over the past 1000 to 10000 years. Below this gravel zone is the very thick and <br />impermeable Mancos Shale, which forms the base of the lower Colorado River valley. The <br />gravels are approximately 30 -50% cobble size with a maximum size of approximately 12 inches. <br />The amount of material below 100 mesh is approximately 5 %- 15 %. The overlying alluvial <br />deposits consist of a basal gravel unit overlain by generally finer- grained alluvium and <br />windblown silts and clays, which comprise the overburden layer. At the Otter Creek site, gravel <br />deposits range in thickness from 5.5 to 29 feet with finer -grain overburden deposits ranging in <br />Otter Creek Pit December 12 G - <br />