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6.4.4(c) <br /> It is expected that all stormwater will percolate into the fractured ground within 72 hours; please <br /> refer to Exhibit G for additional discussion on water handling. All disturbed areas of the site will <br /> be surrounded by a stormwater berm >24- in height to minimize sediment leaving the site. These <br /> stormwater berms will also serve to divert upland stormwater flows from entering the disturbed <br /> areas of the site. <br /> The active mining pit will behave as a sediment settling sump following major storm events. In <br /> the event that pooled water is observed beyond 72 hours after a rain event, stormwater will be <br /> pumped to the closest adjacent drainage following ample time for sediment settling. Only <br /> sediment free water will be discharged, and all discharges will occur within the bounds of the <br /> site's CDPHE discharge permit. Tentative discharge locations are shown on Map C-3. By using <br /> this method, no excess stormwater will accumulate within the mining area beyond 72 hours; an <br /> event that is highly unanticipated and none-the-less prepared for. Mining traffic will avoid sump <br /> areas. <br /> An additional 3-foot safety and stormwater berm will be installed around the crest of each phase <br /> of mining using overburden and topsoil material. This berm will prevent stormwater from <br /> entering the pit by collecting and directing stormwater towards throughgoing preexisting <br /> drainages. <br /> 6.4.4(d) <br /> Mining will occur in four phases as shown on Map C-3. A new phase will not be opened until <br /> mining in the previous phase is complete; however, pre-mine stripping may occur while the <br /> previous phase transitions from mining to reclamation activities. <br /> Blasting and mining will occur in 20-foot benches. The final blasts along each phase's mining <br /> extent will be excavated and promptly backfilled to create a final 2.01-1:1.0V slope. Therefore, the <br /> maximum active highwall during mining will be 20 feet tall and 1,200 feet long during phases 3 <br /> and 4. Once a bench is reclaimed, it is no longer considered a highwall. As shown on the Map C- <br /> 4 cross sections, mined benches will create an overall 2.01-1:1.0V mining slope that, when <br /> backfilled and reclaimed, becomes a uniform 2.0H:1.0V reclamation slope. <br /> Siskin Pit <br /> January 2024 D-5 Lewicki 8( Associates <br />