2023-10-31_REVISION - M1973021 - Laserfiche WebLink

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Ninth Technical Revision(TR09)to Permit M-1973-021,Holcim-WCR,Inc.Morrison Quarry 9 Exhibit D — Mining Plan Rationale for Technical Revision Amendment No. 05 (AM05) identified a four-phase mining approach focused on: 1) developing the quarry in a manner that will disturb only limited areas each time; 2) facilitating reclamation of mined slopes in inactive areas in a timely manner; and 3) accommodating mine operation considerations. Phases I and II were established to develop the Central and North Quarries; mining operations in these areas are complete, and reclamation activities are ongoing. Phases III and IV focused on development of the West and South Quarries. Phase III is underway and was the subject of the Amendment No. 07 (AM07). This mining plan modification addresses the Phase III mining plan, specifically the mining plan below El. 6,600. This TR focuses mining below this elevation in an area referred to as the Satellite South Pit, with proposed mining advancing to approximate El. 6,480. The northern portion of the South Quarry will remain at current elevation and will continue to be the location of the main Haul Road for West Quarry activities. This area will, if needed, provide additional area for material stockpiling. In addition, based on water level measurements in the surrounding monitoring wells, the modification to the Phase III Mining Plan discusses anticipated exposure to groundwater and associated management in the Satellite South Pit below El. 6,600. As was discussed in AM07, Holcim-WCR, Inc. intends to further develop the South Quarry below elevations approved in AM07, as modified by this TR09, referred to as Phase IV on the mining plan. This Phase will be addressed in a future amendment. Other changes to the mining plan include revisions to drainage in the South Quarry, specifically modifications to the South Quarry West Wall drainage design (a draft Drainage Report was submitted as an appendix to AM07). Phase III Work Completed to Date To date, Phase III mining operations have resulted in lowering the South Quarry to approximately El. 6,600. In accordance with previous amendments, the South Quarry West Wall benches above El. 7,000 were mined at a 40-foot highwall and 60-foot bench (60H:40V) configuration and mostly reclaimed. Below El. 7,000, mining has advanced on the South Quarry West Wall, East Wall, and South Wall using various configurations within the maximum 60-foot highwall and minimum 40-foot bench (40H:60V) configuration approved in AM07. As of the date of this TR submission, mining activities have advanced in the West Quarry at approximate El. 7,320 using a 60HA0V bench configuration approved in AM07. Annual geotechnical observations and performance monitoring of exposed highwalls is conducted to support the development of an annual Geotechnical Addendum and assess highwall stability. The most recent Geotechnical Addendum (HDR, December 2022) stated that, for areas surveyed in support of the addendum, no conditions were observed that indicate the potential for large-scale slope failures. Completed South Quarry reclamation and mining activities are identified in Exhibit D- 1. October 2023 1 2