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5. Drainaee Facilities <br />The overall design of the sediment control system is to do the following: <br />1) ensure that water pumped from the dewatering trench into the Farnsworth Collection Ditch to the <br />south will be clean and that the wetland at the bottom will be maintained. <br />2) contain the runoff from all disturbed areas for the 100 yeaz - 24 hour storm. <br />3) keep undisturbed water from entering the site for all storms up to the 100 year 24 hour event. <br />As described in the general discussion of the mine plan, a 2' topsoil berm will be used along all <br />sides of the permit area to isolate water on and off the property except for the north side, which will <br />have a larger topsoil stockpile berm. The slopes of these berms will be 2H:1 V. The irrigation ditch <br />south of Farnsworth Collection Ditch will prevent any water from the south from entering the prop- <br />erty. A small irrigation ditch east of the permit azea also prevents any water from entering the site <br />from this direction. Since the operation involves pure excavation of the resource, all water from the <br />pit areas and facility azeas will be detained within the 10 acre permit for the 100 yeaz event. <br />It is estimated that the pumping operation may move 1000 to 2000 gallons per minute into the Ditch <br />initially, which will likely lessen to approximately 500 gallons per minute once the site is somewhat <br />dewatered. These flow estimates are dependent upon the ability of water to flow through the gravel <br />itself, which will not be exactly known until the operation is started. It is expected that the pump <br />will deliver the water to a PVC pipe that enter the Ditch, as shown on Map E-1. All dischazges will <br />be regulated under a combined storm water/process water permit that has been applied for with the <br />Colorado Department of Public Health and Environment. As described eazlier in this section, the <br />water must go through two sets of gravel berms to get to the pump. The pumped water will be fre- <br />quently monitored for compliance with this permit. If the water quality is out of compliance, water <br />will not be pumped until it is in compliance. <br />The U.S. Army Corps of Engineers was also contacted for approval on two items related to this per- <br />mit: First, United wanted the Corps to evaluate the design in the permit regazding the river crossing. <br />North Fork Pit Mazch 04 24 <br />