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No details regarding spillways are available nor designed for the Bradford Mesa Quarry. Outfall <br /> structure designs and locations will be included in a technical revision to the Division if a <br /> combined process and stormwater discharge permit is required and pursued with CDPHE. <br /> 18. It is anticipated that over the life of mine that fine sediment will accumulate in the <br /> bottoms of the ponds/sumps decreasing the infiltration rates of collected storm water. <br /> Please provide information on how the built up sediment will be dealt with and what will <br /> be done to insure that water will not be detained for longer than 72 hours. While it is <br /> stated that water will not detained for longer than 72 hours it is not clear what measures <br /> will be taken to insure this. <br /> Fine sediment will be removed as needed from the sumps throughout the site. Material removed <br /> from the sumps will be placed in the mining strip that is actively being filled at that time. <br /> Although the sump will be lined with fines that will periodically require removal after <br /> accumulation, the lack of consistent precipitation in the area paired with the known low rain <br /> values will ensure that captured water either evaporates or will infiltrate the very porous ground <br /> surface. These details are included on page D-19. <br /> 19. The Applicant states that the ponds are designed for a 100 year 24-hr event. Please <br /> clarify if this volume calculation takes into account that moisture may accumulate in the <br /> ponds/sumps prior to the storm event (wet weather preceding the 100 year event). <br /> The calculated available storage volume of the processing area sump is able to hold three back- <br /> to-back 100-year storm events. The calculated available storage volume of the dump sump will <br /> hold two back-to-back storm events. It should be noted that the MSHA required safety berms at <br /> the crest of the dump slope—through each lift of development—effectively precluded <br /> stormwater which falls on the dump surface from running down the sloped surface of the dump. <br /> Instead, precipitation on the horizontal dump surface is directed west towards the active mining <br /> area and/or the processing area. Therefore, both sumps will be capable of holding 100-year event <br /> stormwater from their drainage areas in addition to other moisture also temporarily captured for <br /> less than 72 hours in either of the sumps. These details are included on pages D-19, G-1, G-2, <br /> and G-3. <br /> 20. Please clam if the topsoil stockpiles are to be separate from the overburden stockpiles. <br /> Temporary topsoil stockpiles and overburden stockpiles will be separate. The stockpiles that <br /> serve as the sediment capture structure in the processing area will be made up of overburden <br /> topped with topsoil and seeded with the approved native seed mix detailed in Exhibit E as they <br /> will remain in the final reclamation. <br /> 21. The Division requests the Applicant replace clover, as cover crop for topsoil stockpiles, <br /> with a native species, or utilize the final reclamation seed mix to help establish a <br /> beneficial seed bank or contact the local office of the Natural Resource Conservation <br /> Service (NRCS) to get a formal recommendation. Please provide the updated seed <br /> mixture, in pure live seed(PLS),per acre for the topsoil stockpile stabilization. <br /> Bradford Mesa—Preliminary Adequacy Response 6 <br />