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It is estimated that pumping will not be required for this operation due to the method of mining <br /> which will allow all water encountered to remain within the area of the future lake. Any necessary <br /> discharges will be regulated under a combined storm water/process water permit that has been <br /> applied for with the Colorado Department of Public Health and Environment. Water will not be <br /> pumped during this operation from any location to another. <br /> The Farnsworth Collection Ditch will easily handle the base flow from the adjudicated spring. The <br /> ditch is a minimum of 5' high, 1.5H:1V side slopes, minimum bottom width of 2.5',with somewhat <br /> vegetated bottom and sides. The slope of the channel is approximately 0.55%. Using a maximum <br /> base flow of 0.6 cfs(from Farnsworth), and a Manning's n of 0.025, flow capacity to a height of 5 <br /> feet is 400 cfs, from Manning's equation. The Ditch crosses 4005 Lane in a 18" CMP with 4' of <br /> head above the culvert to the edge of the road. The total flow must pass through this culvert. The <br /> headwater to depth ratio used is 3.0, which is conservative, since the actual ratio is 5.5/1.5 =3.67. <br /> The maximum flow under these conditions is 18 cfs, which is still considerably more than the <br /> design flow of 4.45 + 0.6 = 5.05 cfs. Therefore,the ditch and culvert combination is adequate. It <br /> should be noted that the culvert is approximately 40%plugged in the pre-mine condition and must <br /> be cleaned prior to startup. <br /> 20 <br /> North Fork Pit March 04 <br />