2017-08-08_REVISION - M1973021 - Laserfiche WebLink

Home Browse Search

1. Introduction This Technical Revision(TR)provides GEI Consultants, Inc. (GEI) revised highwall recommendations for quarry development within the South Quarry of the Aggregate Industries (AI) Morrison Quarry mine. This TR also presents the revised highwall configuration and demonstrates the highwall design and quarry development meet the minimum required factors of safety for rock stability (FOS > 1.2). It also summarizes the field mapping, investigation, and stability analyses performed in support of the highwall recommendations presented herein. The Morrison Quarry is currently operating under permit M-1973-021 from the Colorado Division of Reclamation, Mining, and Safety(DRMS). The first step toward maintaining wall stability and mitigating rock-fall hazards is to begin with a plan based on sound engineering applied to available geological data and planning to evaluate the long-term stability of highwalls. Equally important is the need for ongoing refinement of stability assessments, based on changes in wall geometry and geological conditions observed within the active South Quarry. As mining advances and mine design standards undergo operational changes, it is crucial any geotechnical assumptions be reviewed and modified by an experienced engineer or geologist to evaluate the integrity of the final highwall design and reduce the potential for highwall instability and rock-fall hazards. 1.1 Site Description The Morrison Quarry is a hard rock quarry, owned and operated by Al, located approximately half a mile west of Colorado Highway 8 and approximately half a mile north of U.S. Highway 285 in Morrison, Colorado. The mine site is located west of the Dakota hogback along the Front Range west of Denver, Colorado, in Section 10 of Township 5 South, Range 70 West of the 6th Principle Meridian. The site location map is shown in Figure 1. The Morrison Quarry consists of three cells;the North Quarry, the Central Quarry, and the South Quarry. Active mining no longer occurs within the North or Central Quarries. The North Quarry currently holds water utilized as mine process water. Within the North Quarry footprint, the North Repository acts as a repository area for waste material from mine operations and damaged or inoperable mine equipment. The North Quarry was mined to an approximate bottom elevation(El.)of 6220 feet above mean sea level (MSL)utilizing highwalls and benches at a nominal 1 horzontal:1 vertical (H:V) slope. The Central Quarry was mined to an approximate bottom El. 6330 utilizing highwalls and benches at a nominal 1 H:1 V or steeper slope. In 2016,reclamation was effectively completed within the Central Quarry when the southwest corner was backfilled even with the Aggregate Industries Morrison Quarry GEI Consultants, Inc. South Quarry Highwall Design Technical Revision 1 August 2017