PERMFILE132508 - Laserfiche WebLink

Home Browse Search

Parkdale Project • 1 • Reclamation Permit Exhibit 6.5 - Geotechnical Stability Exhibit Agile's Parkdale Project includes mining from a granite quarry. The Granite Quarry will be developed sequentially as a benched side hill cut. As shown on the Mining Plan Map, the ultimate crest of the open pit would be at an elevation of about 6,000 feet AMSL and the pit floor would be at an elevation of about 5,800 feet. Pit high wall configuration will be controlled by several parameters, some of which include geologic and geotechnical controls, equipment constraints and safe operating practices. Bench heights and widths are determined by mining equipment limitations and the results of slope stability analysis. As mining progresses, slope movement monitoring will be instituted to evaluate the safety of high walls. In addition, operational procedures for controlling blasting and bench scaling will be instituted to facilitate mining of stable pit walls. Granite will be mined by conventional open pit methods including drilling, blasting, loading and hauling. At closure, the quarry area will have access to benches blocked with lazge boulders. Pit faces and benches will be left in as mined topography with the floor to be nearly level so as to be free draining. The proposed post-mining bench configuration includes 50 foot bench heights with no less than 50 foot depth for an overall slope angle of 45 degrees or less. The post-mining configuration of the highwall feature (200 feet total height) is well within reasonable and conservative engineering limits for a long term safety from the standpoint of overall slope stability. The fifty foot bench heights are also conservative design criteria for the rock type to be mined. The macro-crystalline feldspar granite rock shows a high resistance to weathering and degradation over time. A nearly vertical mining face of fifty feet is planned with standard operating procedures including removal of any fractured or otherwise unstable rock from the bench face as necessary. While no geotechnical testing has been performed on the granite to date, field examination of the rock outcrop has resulted in a "compazable or more competent" rock hardness rating when compared with other Royal Gorge area granites that have recently been tested via confined and unconfined compressive strength evaluations. The granite outcrop area portrays little evidence of shear or fault zones that may limit rock competency and no evidence of weakness planes due to foliation. Because of the above observations and the conservative design of the final pit slopes, it is the Applicant's opinion that a site specific detailed engineering analysis is not warranted to demonstrate a reasonable factor of safety during operations and at closure.