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Slope Stability and Setback Exhibit – Windsor East Mine September 21, 2022 <br />TETRA TECH 2 <br />The mine slope and a reclamation slope were considered during this stability analysis for the respective sections. Tetra <br />Tech understands that Martin Marietta plans to concurrently backfill along the highwall slope using compacted <br />overburden from the site. Backfill will be placed in lifts and compacted to a minimum of 95% of maximum dry density as <br />determined by standard Proctor. The grade modeled for the reclamation slope was 3H:1V and the highwall is assumed to <br />be 1H:1V. <br />Select sections were modeled with a planned 8-foot-high temporary stockpile placed 8 feet from the crest of the <br />reclaimed slope section. The stockpile will consist of overburden or topsoil material excavated from the mining process <br />and will be constructed at a 3H:1V slope. <br />3.1 ANALYZED SECTIONS <br />Critical manmade structures within 200 feet of proposed mining limits were modeled during this evaluation. A critical <br />structure is defined by the DRMS as a manmade structure that poses a potential human safety risk, major environmental <br />impact, or major repair cost if the slope were to fail. The cross sections and profiles were created using data referenced <br />above and proposed mining plans shown on Figure A in Attachment C. This plan shows the proposed site layout and <br />locations to critical structures, easements, and the topography in the area. Sections were created at critical structures in <br />the vicinity, and the estimated depth to bedrock from the subsurface studies was used to create the profile for the slope <br />stability analysis. <br />A total of twelve slope stability models were prepared to evaluate the risk of damage to critical manmade structures for <br />this evaluation as shown in Attachment C. Below is a description of the 12 model sections: <br />Section 1 <br />Section 1, (Figures 1a to 1f) evaluated the proposed setback from the farm access road and northern permit boundary to <br />the north side of Cell B. This section also included analysis of a proposed temporary stockpile shown on Figures 1c and <br />1d. <br />Section 2 <br />Section 2, (Figures 2a to 2f) evaluated the proposed setback from County Road 23 and the western permit boundary to <br />the west side of Cell B. This section also included analysis of a proposed temporary stockpile shown on Figures 2c and 2d. <br />Section 3 <br />Section 3, (Figures 3a to 3d) evaluated the proposed setback from the future right-of-way for Crossroads Boulevard to <br />Cell B. <br />Section 4 <br />Section 4, (Figures 4a to 4d) evaluated the proposed setback from the future right-of-way for Crossroads Boulevard to <br />Cell A. <br />Section 5 <br />Section 5, (Figures 5a to 5d) evaluated the proposed setback from the future right-of-way for Crossroads Boulevard to <br />Cell B. <br />Section 6 <br />Section 6, (Figures 6a to 6d) evaluated the proposed setback from the future right-of-way for Crossroads Boulevard to <br />Cell C. <br />Section 7 <br />Section 7, (Figures 7a to 7h) evaluated the proposed setback from the easement of an abandoned pipeline to Cells A and <br />C. <br />Section 8 <br />Section 8, (Figures 8a to 8d) evaluated the proposed setback from the eastern property boundary and existing Parsons <br />Mine excavation to Cell A. <br />