Laserfiche WebLink
87. Under Section 2— Slopes Stability, the application states the tallest mining highwall and <br /> the tallest waste rock landform scenarios were chosen for modeling. However, the <br /> highwall was modeled at 475 feet tall, whereas the tallest highwall depicted on Exhibit C <br /> maps is approximately 650 feet tall (in the phase 3 quarry area) and 500 feet tall (in the <br /> phase 2 quarry area). Additionally, the tallest waste rock landform slope was modeled at <br /> 600 feet tall, whereas the tallest waste rock landform slope depicted on Exhibit C maps <br /> is approximately 800 feet tall (during mine phase 3). Please update the analyses <br /> accordingly or explain why the scenarios modeled are sufficient. <br /> Please see the revised GALENA models in the revised Geotechnical Stability Exhibit. These <br /> models are developed using cross sections of the mining and reclamation plans shown on the <br /> Exhibit C maps and accurately reflect heights and distances. Highwalls will be limited to 25-feet <br /> tall as prior mining benches will be concurrently reclaimed to 2.01-1:1.OV final slopes and will thus <br /> no longer be considered highwalls. <br /> 88. According to Figure C-5— End of phase 3 and Figure F-1 — Reclamation, the toes of the <br /> proposed waste rock landforms will be located within approximately 50 feet of the <br /> northern permit boundary. Additionally, the proposed eastern and southern extents of <br /> the larger waste rock landform appear to be located within 30 feet of the eastern and <br /> southern permit boundaries. Per Rule 6.5(3), please demonstrate through appropriate <br /> geotechnical and stability analyses that off-site areas will be protected, with appropriate <br /> factors of safety incorporated into the analysis, from slope failure of the waste rock <br /> landforms during mining and reclamation. <br /> Additionally, please describe how the operation will work to prevent off-site impacts in <br /> these areas during construction, maintenance, and reclamation of the waste rock <br /> landforms. How will the permit boundaries be delineated in these areas to provide clear <br /> visual guidance for site workers? <br /> Boundaries will be clearly marked by stakes and signs to prevent mining related activities from <br /> leaving the permitted area. The initial lift of the WRL will be built and reclaimed very early in the <br /> operation and will provide a significant buffer between the adjacent property and the operation. <br /> The initial WRL lift will also provide significant stormwater protection via stabilizing vegetation <br /> and coarse blasted rock. This method of reclaiming and stabilizing the WRL as it is constructed <br /> will prevent sediment debris flows. <br /> Rule 6.5(3) is addressed by the Geotechnical Stability exhibit. The WRL slope stability was <br /> analyzed under a variety of conditions to demonstrate that a sufficient factor of safety was <br /> achieved to ensure no offsite impact from a slope failure. <br /> 89. Please provide a slope stability monitoring plan to include, at a minimum, the type and <br /> frequency of monitoring to be conducted to assess any potential slope stability issues <br /> during mining operations. <br /> Piezometers will be installed in the WRL during construction. Their location will be monitored <br /> annually via GPS to monitor slopes. These piezometers will ensure that any movement of the <br /> WRL is detected. See the revised Geotechnical Stability Exhibit for details. <br /> Appendix 3 — Preliminary Blast Plan: <br /> December 2021 28 a Lewicki 81 Associates <br />