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Ninth Technical Revision(TR09)to Permit M-1973-021,Holcim-WCR,Inc.Morrison Quarry
<br /> 2.3 Updated Phase III Mining Approach
<br /> Mining and reclamation will proceed in the West and South Quarries from the present configuration
<br /> (Exhibit D-1), using the same mining methods described in AM05 and AM07. The sequence of
<br /> mining activities remains unchanged from AM07, which described mining as generally occurring on
<br /> two "fronts" simultaneously: one continues South Quarry development, and one develops the West
<br /> Quarry. Mining plan and approved maximum bench configurations above El. 6,600, summarized
<br /> below, remain unchanged with this amendment:
<br /> • Above El. 7,000: 60HA0V Benches
<br /> • El. 7,000 to El. 6,600: 401-1:60V Benches
<br /> This TR changes the mining plan below El. 6,600. The initial bench configurations approved in
<br /> AM07, 40HA0V benches, remain unchanged; however, the modifications to the mining plan focus
<br /> on the South Quarry mining efforts below this elevation in an area referred to as the Satellite South
<br /> Pit(refer to Exhibit D-1, purple shading). In this area, based on water levels evaluated in 2022
<br /> geotechnical borings (refer to Attachment A, Geotechnical Stability Exhibit) and MW-2019-02, the
<br /> piezometer located south of the South Quarry, exposure to groundwater is anticipated in the Satellite
<br /> South Pit. Last, the South Quarry West Wall drainage design, presented in AM07, has changed and
<br /> the revised design is presented as an Appendix to this TR and discussed below.
<br /> Satellite South Pit Development
<br /> South Quarry mining activities will be focused on lowering the southern portion of the South Quarry,
<br /> referred to as the Satellite South Pit, from El, 6,600 to approximate El. 6,480. Mining in this area will
<br /> be completed in accordance with AM07 which identified 40HA0V benches and application of the
<br /> Observational Method. Under this approach, operations will mine to an initial 40-foot bench and 40-
<br /> foot highwall configuration. This initial configuration meets the required DRMS factor of safety (FOS)
<br /> of 1.25 or greater(refer to Attachment A, Geotechnical Stability Exhibit) for both competent bedrock
<br /> and larger deposits of poor quality rock (e.g., talc gneiss) that are present in this area below El.
<br /> 6,600. Using the observational method presented in AM07, if routine geotechnical observations
<br /> identify favorable conditions for potentially steeper configurations, a qualified geotechnical
<br /> professional will conduct additional mapping or laboratory testing necessary to conduct a stability
<br /> evaluation to support a steeper(i.e. 40H:60V) bench configuration. If evaluations result in a FOS
<br /> greater than 1.25, the results of this analysis will be presented in a technical revision that will be
<br /> submitted to DRMS for review and approval. Planning for the 40HA0V bench configuration, a
<br /> maximum of two additional benches will be formed in the South Quarry between El. 6,480 and
<br /> 6,600.
<br /> A temporary spur road, currently constructed on the east edge of the South Quarry, from the existing
<br /> Main Haul Road to the southern edge of the South Quarry, will continue to be used to access the
<br /> Satellite South Pit benches below El, 6,600 and haul material to the Central Quarry for stockpiling
<br /> and processing. The pit will be lowered by existing western, southern, and eastern benches, and
<br /> creating a new northern bench to approximate El. 6,480.
<br /> Exhibit D-1 presents the revised Phase III buildout configuration plan view, and Exhibit D-1A— D-1 C
<br /> present the Phase III cross sections for the South and West Quarries.
<br /> October 2023 1 3
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