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Ms. Erica Crosby <br />June 7, 2006 <br />Page 2 <br />~~ <br />CIVIL RES'7JURCES, LLC <br />4. The applicant states that topsoil will be replaced to the proposed high water line. Please <br />indicate at what elevation this will be within the reservoir. <br />Topsoil will be replaced to an approximate elevation of three to four feet below the existing ground <br />surface (elevation 4937) <br />5. Hall Irwin commits to replacing 10" of topsoil for all of Phases 1 and 2, for the perimeter of the <br />water storage reservoir in Phase 3 and as necessary in the landscape sales yard. Please <br />explain if the future development area will receive topsoil prior to revegetation of the area. <br />The future development area will not receive topsoil prior to revegetation of the area. <br />6. In accordance with Rule 3.1.6(1)(a), please explain how disturbance to the hydrologic balance <br />will be minimized during the mining and reclamation. Please explain how Hall-Irwin will comply <br />with Colorado Water Laws governing injury to existing water rights. Per Rule 6.4.7(2)(b), identify <br />and characterize the aquifer to be mined in or through. Define or predict the cone of depression <br />expected for any areas to be dewatered and dry mined during the life of the operation. <br />Civil Resources addressed this question in our groundwater model, in our May 8, 2006 letter addressed <br />to you and in our May 11, 2006 letter addressed to Tom Schreiner. <br />It appears that the ParkerlDersham site is within the 100•year floodplain of the South Platte <br />River. Please provide the flood elevations(s) to be expected under a "worst case" Flooding <br />scenario and specific mitigation measures that will be implemented to minimize the potential for <br />any offsite impacts. Legible copies of the Flood Insurance Rate Maps ("FIRM") through the <br />mine reach would facilitate the Division's review. <br />Civil Resources addressed this question iri our letter to you dated March 31, 2006. The site is within <br />the effective 100-year floodplain currently recognized by FEMA. Refer to the attached FIRM. Flood <br />elevations range from 4944 feet to 4948 feet above mean sea level based on USGS mapping. This <br />equates to approximately zero to two feet of flood depth on average over the site. Flow velocities in this <br />shallow flooding area would be in the range of zero to two feet per second and would not pose an <br />erosion risk. Therefore, specific mitigation measures to prevent downstream impacts during the 100- <br />yearflood event are not necessary. <br />8. Please explain how water from dewatering of the ParkerlDersham site will be managed to <br />protect against pollution of surface of groundwater both during and after the mining operation <br />(Rule 6.4.7(2)(c)). <br />Hall-Irwin will operate in accordance with their Spill Prevention Control and Countermeasure Plan. <br />If you have any questions, please do not hesitate to call. <br />Sincere) , <br />Danna Ortiz, LEED AP <br />Planner <br />cc: Jeff Gregg, Hall-Irwin Corporation <br />