2021-09-07_REVISION - M1973021 (9)

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Exhibit D — Mining Plan: The mining plan presented in AM05 includes four phases: Phase I developed the Central Quarry, Phase 11 developed the North Quarry, Phase III developed the South Quarry, and Phase IV deepened the South Quarry. After review of this approach, the mining plan in AM07 reverts back to the four phases of mining presented in AM05 to be consistent with the approved mining and reclamation plans. The remaining phases, which are the focus of the Mining Plan, are Phase I II —South Quarry and West Quarry Development and Phase IV—South Quarry Deepening. AM05 Phase III and Phase IV have been modified to accommodate the need to manage groundwater and surface water as follows: • Phase III: For this phase, the bottom elevation has been modified to Elevation (El.) 6,500, the elevation where groundwater is anticipated to be encountered. Text has been added to this section to recognize permitting requirements, stipulate cessation of work in areas where groundwater is encountered before approvals are received, and plan a dewatering approach for stormwater and groundwater, if it is encountered. • Phase IV This phase has been defined as conceptual and will require a future permit amendment before work in this phase can begin. The decision to make this phase conceptual was based on the recognition that additional geotechnical and hydrogeologic investigations are necessary to understand geotechnical stability in saturated conditions and to better understand the hydrogeology in the area, information critical to defining a dewatering strategy. In addition, end uses of the South Quarry are still under consideration and require discussions with other potential stakeholders. The hydrogeologic investigations for dewatering will also support an analysis for potential reclamation requirements for a reservoir end use, specifically whether the pit will require sealing to State Engineer's Office (SEO) standards or if the bedrock in the pit meets "lined pit' permeability standards. To satisfy reclamation bonding requirements, it is assumed the pit will be used as a reservoir and no lining will be required. Again, this decision is subject to change, and final reclamation requirements will be defined in a future Permit Amendment. Exhibit E — Reclamation Plan. Recognizing that Phase IV is now conceptual, the Reclamation Plan has been updated to include the installation of a more permanent drainage structure after Phase III is completed. This structure will provide permanent drainage solutions for both stormwater and any encountered groundwater in the event that Phase IV is delayed or postponed. Exhibit G —Water Information. This exhibit has been updated to include a detailed discussion regarding how groundwater will be managed when it is encountered during Phase I II and IV mining activities. The discussion focuses on temporary dewatering approaches for Phase III during mining activities and proposes the installation of a permanent management structure in the event Phase IV is delayed. The section also provides details regarding the planned hydrogeologic investigations necessary to develop a comprehensive dewatering approach for Phase IV and evaluates potential reclamation requirements for a reservoir end use. Again, this section reiterates the need for well permits, substitute supply plans, and future additional permitting needs.