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Walstrum Spur Amendment, Exhibit D-Mining Plan revised September 2021 <br /> Stormwater resulting from precipitation falling on disturbed areas of the Spur Amendment will be drained to the <br /> Existing Quarry using ditches and topography. Water impoundments consisting of natural ponding areas and <br /> detention basins to store and treat stormwater will continue to be used. The active mine level elevation will be <br /> sloped to drain from east to west towards the Existing Quarry to utilize stormwater controls already in place in the <br /> Existing Quarry. As the Spur Amendment progresses, Best Management Practices will be adjusted as needed to <br /> handle stormwater. When necessary, stormwater will be discharged in accordance with the site discharge permit. <br /> No stormwater collected will be held for more than 72 hours unless evaporative loss is accounted for in the <br /> existing water supply plan. <br /> See Exhibit G Water Information for more details on drainage and stormwater runoff. <br /> 3.4 Work Area <br /> 6.4.4(d) the size of area(s) to be worked at any one time. <br /> The working faces in the Spur Amendment will start small and slowly grow to approximately 3,000 linear feet on <br /> horizontal benches. As mining progresses, the upper benches will be concurrently reclaimed while lower benches <br /> are mined. See Figure D-1 for a vertical depiction of a set of benches. As the benches on the west side of the <br /> Spur Amendment are developed, they will be integrated into the Existing Quarry. Exhibit C-3 shows how the <br /> disturbance due to mining activities will look when a mining elevation of approximately 7,800 feet is achieved. <br /> 3.5 Timetable <br /> 6.4.4(e) An approximate timetable to describe the mining operation. The timetable is for the purpose of <br /> establishing the relationship between mining and reclamation during the different phases of a mining operation. <br /> An Operator/Applicant shall not be required to meet specific dates for initiation, or completion of mining in a phase <br /> as may be identified in the timetable. This does not exempt an Operator/Applicant from complying with the <br /> performance standards of Section 3.1. If the operation is intended to be an intermittent operation as defined in <br /> Section 34-32-103(6)(a)(11), C.R.S., the applicant should include in this exhibit a statement that conforms to the <br /> provisions of Section 34-32-103(6)(a)(11), C.R.S. Such timetable should include: 112(2)(h) <br /> (i) an estimate of the periods of time which will be required for the various stages or phases of the <br /> operation; <br /> (ii) a description of the size and location of each area to be worked during each phase; and <br /> (iii) outlining the sequence in which each stage or phase of the operation will be carried out. <br /> The total combined area of the Existing Quarry and Spur Amendment have been divided into four stage areas. <br /> These stage areas are illustrated on Exhibit C-3. Table D-2 presents a summary of the stages. This estimated <br /> mining timetable is based on an average year. Each individual year can vary widely from the average. <br /> Table D-2-Estimated Timetable <br /> Stage • • Approximate <br /> I Existing Quarry affected area -20-50 265 <br /> J Spur Amendment affected area -30-50 229 <br /> S Undisturbed area for visual Life of the mine 255 <br /> screening and buffer <br /> Y Texaco Placer Life of the mine 1 <br /> Spur Amendment Timetable <br /> Mining in the Spur Amendment area is expected to begin soon after all required permits are obtained. <br /> oTETRA TECH Page 5 1 9 <br />