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D <br />April 11, 2001 <br /> <br />~~ <br />Wallace H. Erickson <br />Environmental Protection Specialist <br />Division of Minerals and Geology <br />Department of Natural Resources <br />State of Colorado <br />701 Camino Del Rio, Room 125 <br />Durango, CO 81301 <br />Re: Response to DMG Letter February 23, 2001 <br />Surface Rock Pit, Permit No. M-1984-001 <br />Dear Mr. Erickson: <br /> <br />1334 Ute Avenue • Grand Junction, Colorado 81501 <br />(970) 241-6027 • Fax: (970) 256-7992 <br />~~~~~~ ~' <br />APh ~_ ~ ~i~i <br />Durango Field OffiCo <br />Division of Minerals & Geoiogq <br />This letter is in response to your February 23, 2001 letter, in regard to technical revision #1 (TR- <br />O])for the Surface Rock Pit. <br />Geotechnical Engineering Group, Inc., our subconsultant evaluating the geotechnicaUstability <br />issues of the quarry, prepared a letter addressing the geotechnical concerns identified by the <br />DMG staff. The letter from Mr. John Withers, P.E. of Geotechnical Engineering Group, Inc. is <br />attached for your review. Should you have technical questions concerning these issues, please <br />contact Mr. Withers directly at 970-245-4078. <br />There are three items that were discussed in the February 23, 2001 DMG letter that I want to <br />address. They include the following: <br />I . Page 2, paragraph 4, of the Mr. Jim Pendleton 02/22/01 letter, under sub-heading <br />"Stability of the Parcel A Highwall" addresses that Rhino Engineering should revise TR-O1 <br />application to include detailed mapping of the quarry area of Parcel A. I do not see the need for <br />detailed mapping of the quarry for the following reasons: <br />• the similarity of the bench/vertical wall configuration to the previous plan by Agapito <br />Associates, [nc., <br />• the understanding that final reclamation will not entail a "gentle slope" graded from <br />the bottom of the highwall to the top of the highwall. When mining commenced, the <br />material to final Bade the highwall area was to originate from the 60,000 cubic yard <br />stockpile area. I believe that all parties have since agreed that any disturbance to this <br />stockpile today may cause unnecessary degradation of stability that was achieved <br />through natural aging processes, and <br />• the findings of the rollout analysis of fractured rock from the highwall. <br />Serving Colorado & Utah <br />