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Mazch 6, 2006 Mr. Jeff Keller Asphalt Paving Company 14802 W. 44`~ Avenue Golden, Colorado 80401 Dear Jeff: Martin and Wood Water Consultants, Inc. 602 Park Point Drive, Suite 275, Golden, CO 80401 Phone: (303) 526-2600 . Fax: (303) 526-2624 www.martinandwood.com Re: Wattenberg Pit Phase I Mining Modeling Project Number 625.1 This letter report presents the results of our modeling investigations carved out on the approximately 10-acre Phase I mining to be conducted at the proposed Wattenberg Pit located immediately west of the Town of Wattenberg in Weld County, Colorado. This modeling has been done pursuant to the request for additional modeling contained in the December 13, 2005 letter from the Division of Minerals and Geology. Specifically, there was expressed a desire to see determinations made as to the levels of drawdowns that would be expected from the dewatering activities at this small pit. To conduct our analyses, we have utilized the MODFLOW model that was previously constructed for two prior rounds of modeling investigations at the site. That previous work addressed the potential impacts on the local water table from the mine phases that would involve slurry wall installation and mining dry mining within the slurry walled aeeas. The primary changes to the existing model involved removal of the slurry wall areas and then simulation of the dewatering of the Phase I area via modeled drains. The model in this configuration was run until we had developed essentially steady-state conditions that would represent the maximum drawdowns that would be imposed by the dewatering and mining. In the model the drains were set 0.5 feet above the bottom of the simulated alluvial aquifer. The aquifer in this area, as per the test boring results and the subsequent water level monitoring, is quite limited, with only some three- to hve- feet of saturation. Further, the data indicates that the alluvial aquifer pinches out immediately to the west of the pit and the model configuration reflects this with a no-flow boundary simulated along the western edge of the model domain. Two sets of simulations were carved out for these investigations. The first included just the Phase I pit, while the second included the Phase II and III slurry wall lined pit area, which will lie between the Phase I azea and the Town of Wattenberg. This second simulation was carried out as it is not yet cleaz that the Phase I mining will be completed before the Phase II and II slung wall is installed. The model results from the first simulations are presented in Figures 1 and 2, which present the drawdowns in the vicinity of the Phase I operations, first without the background map so that the drawdown contours can more readily be observed, and then with the prior map superimposed in the background to provide a frame of reference far the extent of the contours. Note that on both figures the location of the Wattenberg Improvement Association ("WIA") well is also presented.