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Ms. Erica Crosby <br />Division of Minerals and Geology <br />April 5, 2006 <br />Page 17 of 21 <br />b. If baseline measurements for one or more wells consistently show fluctuations <br />that are greater than 2 feet above and below the averages, the applicant will <br />propose revised trigger points, via a technical revision, to account for larger-than- <br />expected pre-exposure fluctuation. <br />5. In conformance with Rule 3.1.6(1), please quantify the maximum pumping rate and <br />duration of pumping expected for de-watering activities in the 10-acre Phase 1 Area; <br />and quantify the horizontal and vertical extent of drawdown expected from de- <br />watering activities at the time of maximum excavation. In addition, the Division <br />requests that the Applicant provide a representative cross-sectional diagram that <br />shows the Phase 1 Pit at maximum excavation, static groundwater level and <br />expected drawdown. Finally, based on the results of the drawdown analysis, please <br />provide a Map or Exhibit which shows the location(s) of all groundwater users within <br />the radius of expected drawdown during a time of maximum disturbance. The Map <br />or Exhibit should also include all available data on each well such as well <br />completion, well type, well depth, well registration number, pumping rate, baseline <br />water level, etc. Please respond. <br />The maximum expected pumping rate from Phase 1 is approximately 1,000 gpm, <br />and it is expected that pumping will be necessary for approximately 24 months. <br />Included as Attachment 10 is a representative cross-section that shows Phase 1 at <br />maximum excavation. <br />The contour maps presented in the March 6, 2006 modeling report (see Attachment <br />6) address the drawdown aspects of this question. The mined area will be <br />approximately 10-acres in size and it is expected that the dewatering will occur <br />throughout this area. The vertical extent is assumed to be down to as close to <br />bedrock as is possible, that being about 15 feet from the ground surface over much <br />of the area. <br />Exhibit C-1 shows all registered wells, well permit numbers, and unregistered wells <br />whose location is approximately known, within the radius of expected drawdown. <br />The requested detailed information (completion type, pumping rate, baseline water <br />level, etc.) for all registered wells in the area is available via records at the State <br />Engineer's Office, which we have obtained would be happy to provide copies to the <br />Division upon request. Including all of this information on Exhibit C-1, however, <br />does not appear relevant to the requirements of Rule 3.1.6(1), especially given the <br />modeling results discussed in Attachment 6. If additional information is required, <br />please explain how each of the requested items are relevant to the Division's <br />requirements. <br />6. In accordance with Rule 3.1.6(1), please provide an assessment of possible <br />hydrologic impacts to the Brighton Ditch based on planned de-watering activities at <br />the Wattenberg West Pit. Information to be included in the assessment should <br />include, but not be limited to the following: <br />• Ownership of the ditch. <br />• /s the ditch lined or unlined? <br />What is the annual flow regime of the ditch? <br />