2011-06-02_APPLICATION CORRESPONDENCE - C2010089 (19)

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• • Murari P. Shrestha, P.E. August 25, 2010 Page 5 distances utilized in the IDS AWAS analysis were measured from the centroids for each mine site to the identified points of depletion, as presented in the attached Figure 1. For New Horizon North, well pumping depletions will occur to Tuttle Draw below the Holder Ditch and the Charlie Rice Ditch, as shown on Figures 2.A and 2.B. Return flows from the septic system will return to Tuttle Draw, based on the understanding that the septic system will be located near the southwest corner of the New Horizon North Mine area. For the Cyprus Block area, depletions will occur to Calamity Draw north of the mine area, and return flows occur to Calamity Draw slightly upstream of the point of depletion, as presented in Figures 2.A and 2.B. Figure 2.B also shows locations where augmentation deliveries can be made in accordance with Western Fuels' augmentation plan described in the Water Solutions, LLC report. The Glover lagged depletion analysis simulated an infinite aquifer for this analysis; boundary conditions other than the stream were not simulated. The equilibrium lagged depletions and accretions resulting from the operation of water supply wells at the New Horizon North and Cyprus Block are presented in the attached Table Nos. 3.A and 4.A and in the attached Figure Nos. 3.A and 4.A, respectively. As expected, lagged net depletions for both locations occur throughout the year but are greatest late in the irrigation season. Although the peak water use and return flows occurs in the month of June, the peak lagged depletion and return flow occurs in the month of August. We have also provided lagging factors for both depletions and return flows which can be used for the purposes of a water balance or water rights accounting. The lagging factors are presented in Table Nos. 3.B and 4.B and Figure Nos. 4.A and 4.B, respectively. Analysis of Timing Impacts of Dewatering Pumping Western Fuels pumps dewatering water from the mine to an above ground tank, which then drains to sediment control ponds, which then drain to surface streams. Water from the tank is used to fill trucks which apply the water for dust control purposes. Based on field investigations and information provided by Western Fuels, it appears that the water pumped from the existing New Horizon mine is largely influenced by irrigation operations up gradient of the mine. The water pumped from the pit is largely believed to be irrigation return flow. Field observations completed near the end of the 2009 irrigation season supported this claim based on inflow to the pit from near the surface, although it was noted that inflows to the pit in lesser quantities were also discharging from bedrock material as well. In order to validate this position, BBA reviewed pumping records from the New Horizon Mine and compared them with reported irrigation diversions from the CC Ditch, historically known as the Highline Canal (hereafter, "CC Ditch "). A comparison of the timing of irrigation diversions in the CC Ditch and the timing of pumping from the pit is presented in Table 5 and Figure 5. The peak pumping from the pit occurs approximately three months later than the irrigation diversions. It is our opinion that the difference in timing between the pumping in the pit and the irrigation diversions indicates that the pit is effectively intercepting lagged irrigation return flows. The lag of the irrigation return flows to the stream system would probably be slightly greater if it were not for the presence of the mine pit. Effectively, the dewatering from the pit delivers return flow water to the stream at a faster rate than it would otherwise occur, www.bbawater.com Bishop- Brogden Associates, Inc.