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61/31/2603 17:09 2799186 DOTY & ASSOCIATES PAGE 06 <br />Mr. Christopher C. LaRue <br />Page 6 <br />January 28, 2003 Doty & Associates <br />western boundary of the proposed mine site and south of the well (663 feet) will <br />contribute flow to the well because there are other producing wells in the area. The <br />flow from this length of drain is approximately 50 gallons per minute. <br />In order to include the effects of the flow delivered to the well by the drain, we <br />assumed that the drain flow of 50 gallons per minute directly enters the well and that <br />only 450 gallons per minute would be produced from the formation. The pumping rate <br />of the image well representing the slurry wall was also reduced to 450 gallons per <br />minute. As can be seen on Figure 4, drawdowns in the well are lessened in this model <br />of the system performance (the predicted drawdown is reduced from 6.9 feet to 6.2 <br />feet). Again, this is nearly the total saturated thickness penetrated by the well 18 feet) <br />and our prediction is probably an under-estimate of the actual drawdown because of <br />partial penetration effects. <br />CONCLUSIONS <br />Our evaluation of hydrologic conditions and review of the application materials lead us <br />to conclude the following. <br />1. The Off Partnership Well No. 12992 is completed in highly transmissive <br />alluvium associated with the South Platte River. The hydraulic conductivity of <br />the alluvium is on the order of 0.31 cm/s, or somewhat lower. The saturated <br />thickness in the vicinity of the well is 28 feet. Although partially penetrating, <br />the well appears capable of producing its full adjudicated right of 500 gallons <br />per minute. This is a very senior right with a first use date of 1905. <br />2. The well is located approximately 184 feet west of a proposed slurry wall that <br />is intended to be essentially impermeable to water flow. <br />3. Our calculations predict a drawdown in the well of nearly the full saturated <br />interval penetration if the slurry wall is constructed 16.9 feet and 8 feet, <br />respectively). Our prediction Ilkely under-estimates the true drawdown because <br />of partial penetration and aquifer thinning effects, perhaps by as mach as a foot <br />due to aquifer thinning alone. In addition, our prediction is based on a <br />published hydraulic conductivity value thatthe publication suggests is probably <br />somewhat lower at this location. Therefore, we conclude that the well will <br />probably not be able to produce its adjudicated right if the wall is installed. <br />4, Our calculations predict that a french drain installed outside the slurry wall will <br />only raise the water table at the well by approximately 0.7 feet. Given the <br />factors listed in the previous conclusion, we are of the opinion that the well will <br />probably not be able to produce its adjudicated right even if a french drain is <br />installed to minimi2e the impact of the slurry wall.