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Ms. Erica Crosby <br />Division of Minerals and Geology <br />6.4.7 Exhibit G-Water Information <br />May 1, 2006 <br />Page 4 of 5 <br />6. In accordance with Rule 3.1.6(1), the applicant will need to affirmatively state that <br />the planned de-watering activities will not result in a negative impact on the normal <br />operation of the Brighton Ditch. Also, the applicant shows on Exhibit C-3, Mine Plan <br />that the Phase 1 excavation will be two hundred (200) feet away from the Brighton <br />Ditch. The Division recommends that the applicant locate and mark the 200-foot <br />setback prior to excavation in this area. Please respond. <br />Asphalt Paving Company's dewatering plans will not result in a negative impact on <br />the normal operation of the Brighton Ditch. Asphalt Paving Company commits to <br />marking the 200-foot setback line from the Brighton Ditch prior to excavation in <br />Phase 1. Please note that per the previously submitted Agreement with the Brighton <br />Ditch Company (see original application package), Asphalt Paving Company is <br />allowed to perform mining-related activities (such as stockpiling) as close as 50 feet <br />to the Brighton Ditch. <br />9. Based on their May 3, 2005 "Ground water Modeling Study", Martin and Wood <br />Water Consultants, Inc. suggest that the Phase 1 de-watering and mining activities <br />will have no significant impacts on the surrounding water table conditions, especially <br />if the Phase 2 and 3 slurry wall is installed prior to the completion of the Phase 1 <br />mining. The Division concurs and requests that the applicant commit to 100% <br />installation of the slurry wall around the Phase 2 and 3 areas prior to excavation in <br />the Phase 1 area. (In the absence of this commitment, the applicant will need to <br />model the expected groundwater conditions in the affected land and surrounding <br />area assuming de-watering of all 3 phases of the operation at the same time). <br />Please respond. <br />Asphalt Paving Company cannot commit to installation of the slurry wall around <br />Phases 2 and 3 prior to the dewatering of Phase 1. We are confident, however, that <br />the planned Phase 1 dewatering of 10 acres with only a few feet of saturated gravel <br />will not significantly affect off-site water users, based on our understanding of the <br />modeling results and Asphalt Paving Company's previously stated commitment to <br />the well monitoring and mitigation plan. <br />In their Phase 1 modeling report dated March 6, 2006 (included as an attachment to <br />the first Adequacy Review response letter, dated April 5, 2006), Martin and Wood <br />Water Consultants, Inc. modeled the Phase 1 dewatering plan two ways. First, <br />assuming that the slurry wall around Phases 2 and 3 is not installed at the time of <br />Phase 1 dewatering (see Figures 1 and 2 in their March 6`h report); and second, <br />assuming that the slurry wall is installed prior to Phase 1 dewatering (see Figures 3 <br />and 4). With respect to the first scenario, their report concludes: "As can readily be <br />determined from the Figures, the drawdown impacts from the Phase 1 dewatering <br />will be minimal". Although the report later concludes, as you note, that impacts <br />would be even more insignificant if the slurry wall were installed first, it also <br />concludes that there will be "no significant impact" either way because of the high <br />transmissivity of this aquifer. <br />