REP17188 - Laserfiche WebLink

Home Browse Search

MORRISON QUARRY DMG PERMIT NO. 73-21 (AM 004) CC/xC GEOTECHNICAL STABILITY EXHIBIT t/qN ~ ~ ~D INTRODUCTION D,V t Sro° °J hli°°1a/S & G°D% 9Y On behalf of Cooley Gravel Company (Cooley), Haley & Aldrich, Inc. (Haley & Aldrich) has prepared this Geotechnical Stability Exhibit as an attachment to the 1995 Notice of Intent to Continue Mining Operations/ Annual Report for the subject Regular (112) Mining and Reclamation Permit. This conforms to Rule 6, Section 6.5 and is also required to comply with the conditional approval of Permit Amendments Nos. 3 and 4. These Amendments describe in detail the Observational Method to mine slope design being implemented a[ the quarry whereby conservatively designed slope angles may be modified to steeper configurations based on ongoing collection of rock mass property data and updated slope stability evaluations. Specifically, this exhibit provides supplemental data required by the Division of Minerals and Geology (DMG) per Stipulation No. 4 in your letter of Conditional Approval of Amendment 4, dated 16 February 1995. BACKGROUND Mine Plan Amendments Nos. 3 and 4 revised the approach to slope design at the Morrison Quarry with the implementation of the Observational Method throughout the quarry. The significant changes presented in these Amendments were a reconfiguration of the East Highwall of [he Central Quarry to address slope instabilities in [hat area and [Ite provisional change in slope inclinations elsewhere to as steep as O.SH:1V. As a condition of the Atendments, the steeper slopes and revised configuration could be implemented only in accordance with specific, predetermined steps outlined in the Observational Method. Approval of the Amend- ments required annual reporting of geotechnical data, slope stability evaluations, and current mine conditions in areas where steeper slopes were utilized. The Observational Method as described in Mine Plan Amendments Nos. 3 and 4, is a step-wise approach to slope design by which new information is continually used'to upgrade previous analyses. This method was utilized as a practical approach to designing slopes in a rock mass which in some areas is poorly exposed and difficult to characterize. A key factor of the method is that baseline conditions are established during initial evaluations; observed conditions are then compared with the baseline. Annual reports are presented as a required condition of permit approval and to provide [he opportunity for regular regulatory oversight of mining activities. The Observational Method is applicable to any slope in the quarry which is more aggressive than an 80-ft highwall and 80-f[ bench configuration (steeper than 1H:1V). Additionally, the method is applied to the East Highwall in the special slope remediation area if the slope is altered from [he previously approved slope configuration shown in the approved Amendments. G:\.0?W\R09i00.300