|
Ninth Technical Revision (TR09) to Permit M-1973-021, Holcim- WCR, Inc. Morrison Quarry
<br />
<br />
<br />
<br />January 2024 | 3
<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 />(Error! Reference source not found.1), using the same mining methods described in AM05 and
<br />AM07. The sequence of mining activities remains unchanged from AM07, which described mining as
<br />generally occurring on two "fronts" simultaneously: one continues South Quarry development, and
<br />one develops the West Quarry. Mining plan and approved maximum bench configurations above El.
<br />6,600, summarized below, remain unchanged with this amendment:
<br />· Above El. 7,000: 60H:40V Benches
<br />· El. 7,000 to El. 6,600: 40H:60V Benches
<br />This TR changes the mining plan below El. 6,600. The initial bench configurations approved in
<br />AM07, 40H:40V 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 40H:40V 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 40H:40V 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-1c
<br />present the Phase III cross sections for the South and West Quarries.
|