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Jared Ebert <br /> September 16, 2019 <br /> Page 2 of 11 <br /> Also, the language in Exhibit D was not revised with language describing the justification for differing <br /> stockpile dimensions, please revise Exhibit D with this information included. <br /> Al Response: Ineffective flow areas are also known as "backwater" areas. These areas flood when <br /> the water surface elevation increases, but do not actively convey flows downstream. Ineffective flow <br /> areas have essentially no flow velocity. Ineffective flow areas are typically found upstream and <br /> downstream of bridges and culverts as flow contracts and expands through the opening. Because they <br /> do not convey flow downstream, these areas can be filled or altered without impacting flood water <br /> surface elevations. Stockpiles in other locations, which are in active flow areas, are oriented to be <br /> parallel to the direction of flow to minimize impacts to the flood water surface elevations. Since the <br /> stockpiles are located in areas where alterations are not expected to impact the flood water surface <br /> elevations, their orientation and length are not restricted such as the stockpiles in active flow areas. A <br /> schematic figure demonstrating the ineffective flow areas around a bridge is presented below. <br /> Cross Section <br /> for. <br /> �•' Contracting Flow /.".' Cross Section <br /> _ 3 <br /> —'--`' — Cross Section <br /> r S- ----Ineffective <br /> 7 , Flow Area <br /> (Typical All <br /> V \01 • Shaded <br /> �7 Expanding Flow Areas) <br /> / Cross Section <br /> a <br /> Rule 6.4.4, Exhibit D — Mining Plan <br /> 9. The Table on page D-6 describes when in the mining process the disturbance could be at its <br /> maximum. The active mining area is shown to have a near vertical face of 800 feet and the highwall <br /> with adjacent cells walls will be 1,500 feet in length. However, page D-4 indicates the mining highwall <br /> may extend no more than 4,000 feet in length. Please explain the large difference in the highwall <br /> lengths discussed on page D-6 and D-4. At what point during the mining operation would the highwall <br /> reach 4,000 feet? <br /> a. Al Response: All tables have been revised to reflect a maximum of 1500 feet of highwall at any given <br /> time during the mining and reclamation process. <br /> Aggregate Industries—WCR,Inc <br /> 1687 Cole Blvd Suite 300 <br /> Golden,CO 80401 <br />