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4. Drainage Facilities i • The overall design of the sediment control system is to do the following: 1) ensure that water pumped from the dewatering trench into the wetland to the north will be clean and that the wetland will be maintained. 2) contain the mnoff from all disturbed areas for the 100 year - 24 hour storm. 3) keep undisturbed water from entering the site for all storms up to the 100 year 24 hour event. As described in the general discussion of the mine plan, a 2' topsoil berm will be used along the east side of the permit area to isolate water on and off the property. The slopes of this berm will be 2H:1V. The irrigation ditch north of the access road and the 30' high topsoil stockpile will prevent any water from the south from entering the property. The area west and north of the permit area drain away from it and no undisturbed water can enter the permit area in these locations. Since the operation involves pure excavation of the resource, all water from the pi[ areas and facility areas will be detained within the 10 acre permit for the 100 year event. [t is estimated that the pumping operation may move 5000 to 6000 gallons per minute into the wet- , land initially, which will likely lessen to approximately 500 gallons per minute once the site is somewhat dewatered. These flow estimates are dependent upon the ability of water to flow through the gravel itself, which will not be exactly known until the operation is started. It is expected that the pump will deliver the water to a perforated PVC pipe that will border the southern edge of the wetland, as shown on Map E-1. The perforations will evenly distribute water to the wetland. All discharges will be regulated under a combined storm water/process water permit [ha[ has been ap- plied for with the Colorado Department of Health. As described earlier in this section and shown on Detail A, the water must go through two sets of gravel berms to get to the pump. The pumped water will be frequently monitored for compliance with [his permit. If the water quality is out of compli- ance, water will not be pumped until it is in compliance. The U.S. Army Corps of Engineers was also contacted for approval on two items related to this per- mit: First, United wanted the Corps to evaluate the design in the permit in regarding the preserva- tion of [he wetland. Second, the 30' high topsoil stockpile and the product stockpiles will be located in the 100 year floodplain. Although the floodplain is very wide at this point and no one in the area Piceance Pit 7/01 18