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JAN-09-01 TUE ]0.40 AM DMG DURRNGO FIELD OFFICE FAX N0. 970+247+5104 P, 02 ' ~~. ~, i~~e~iv~l JOHN F. ABEL, .,R. DEC 2 62000 370 LOOKOUT VIEW COURT MINING ENGINEER GOLDEN, C060G01 30127&d4D7 Durango Field Ottioe Fnxz7sa~e3 .1H.b~a~HOmo mm Division of Minerals & Geologq October 31, 2000 Mr. 47arren 0. Wilcox jj(/_, Gunnison Gravel {.jr ~ fL~~~l P.0. Box 42 ~ ~,~f`ti Gunnison, CO 81230 Reference: Dickerson Quarry slope stability evaluation Dear Warren: The ;strength of the fresh granite and fracture set orientations present in the Dickerson Quarry and the quarry expansion geometry are generally favorable for the long term stability of the planned overall 63° slope angles (2 vertical to I horizontal) for the plan~ied expansion. Figure 1 presents the planned quarry expansion. The only potentially adverse fracture set strikes from N33°W to N38°W and dips from 20° to 38°NE. This joint set is more westerly striking and steeper dipping where exposed in the existing quarry and more northerly striking and flatter dipping where exposed ir. outcrops c;. the west side cf the property. It is recommended that the ultimate slope in the southwest corner of the quarry be flattened to 45° in order to assure the long term stability of the northeast facing 'section of the ultimate quarry wall. GEOLOGIC INPUT Fresh granite is exposed on the west wall the existing quarry. The existing quarry and the Dickerson property are shown on Figure 2. The fresh granite forms an over 30-foot high overhanging face at the base of the west highwall. The fresh granite is overlain by 40 to 60 feet of weak decomposed granite and capped with up to 10 feet of the West Elk volcanic breccia. The breccia thins and disappears to the south and west across the property. Figure 3a shows the decomposed granite sitA ng on the overhanging fresh granite face, with a detached block of the massive West El Y. breccia in the foreground. Figure 3a also shows the northeast dip of the contact between the decomposed and fresh granite. Figure 3b shows the slot bulldozed back approximately 100 feet westward into the decomposed granite and thin breccia capping in the center of the present west quarry wall. Figure 3b also indicates the thinning of the decomposed granite and West ElY.