1995-03-17_GENERAL DOCUMENTS - M1973021

Home Browse Search

Cooley Gravel Company 17 March 1995 Page 2 of 9 Morrison Quarry - 1994 Annual Report Mine plan Amendment No. 4 changed the overall mine development to allow remining in the North Quarry area, and a revised configuration in the Central and South Quarry areas. Additionally two water storage reservoirs were incorporated as part of the reclamation plan. This amendment continued the use of the Observational Method as an approach to determine stable slope configurations. Reporting requirements associated with the steeper slope configurations were required similar to mine plan Amendment No. 3. The Observational Method as described in Amendments No. 3 and No. 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,then observed conditions are compared with the baseline. Annual reports are presented as a required condition of permit approval and to provide the 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 bench and 80 ft highwall configuration(steeper than 1H:1V). Additionally,the method will be applied to the East Highwall in the special slope remediation area if the slope is altered from the previously approved configuration shown in the approved amendments. GEOTECHNICAL DATA COLLECTION AND SUMMARY During the subject report year, additional geotechnical data was collected in the active Central Quarry area in the form of: 1) drilling and logging four new exploratory core borings; 2) obtaining new ground water level data; 3) performing borehole packer tests to evaluate bedrock hydraulic conductivity (permeability); and 4)performing geologic mapping along the West Highwall. The core borings, ground water level data and permeability testing were all related to conceptual design of the proposed Permanent Reservoir No. 1 that may be constructed for the Town of Morrison in the Central Quarry following mining. The geologic mapping was performed in support of evaluations prior to construction of 80 ft high by 40 ft wide benches along the West Highwall of the Central Quarry beginning with the highwall above the existing bench at approximately El. 6,560 ft. Core Borings The locations of the four new core borings are depicted in the attached Figure 1., Borehole Location Map. The borings were labeled CH-CR1 through CH-CR4 to designate core holes (CH) drilled for the proposed Central Quarry Reservoir (CR). Typed core boring logs are provided in Attachment A, Core Boring Reports, which include detailed rock mass data collected by a Haley & Aldrich geologist who logged the core borings. A summary of important geological/geotechnical data included on the detailed logs is also included herein. M8267.200 2