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Additionally, as discussed under Item 20 below, the anticipated hydraulic head on the <br />Whirlwind bulkhead seal is low (a maximum of about 38 vertical feet) and the seal <br />has been designed to handle approximately four times this hydraulic pressure. As <br />previously discussed in Item 4, recharge to the Brushy Basin sandstone lenses is <br />limited to a small area on the southwest side of Beaver Mesa and would be expected <br />to be very low in even a wet year. Therefore, it is very unlikely that the hydraulic <br />head on the seal would increase above projected maximum levels. <br />10) The Mine Plan Map C-2 denotes stormwater drainage from the ore pad will go to a <br />sump and then be directed to the treatment pond facility. Since the approval of the <br />water treatment plant was completed under the NOl, please address how the <br />stormwater from this area will be directed to the treatment plant since the <br />configuration is now different. <br />The revised treatment plant layout is shown on Map C-2 in Attachment C. It is very <br />similar to the original configuration, but there is considerably less earthwork involved. <br />The Untreated Water Pond was replaced by an "Untreated Water Tank" of similar size. <br />Stormmwater from the ore pad area will be directed to a sump that will overflow to the <br />Untreated Water Tank during large storm events. Required freeboard and storage <br />capacities for the 100-year storm event are discussed in the November 17th As-Built <br />Report; these requirements will also be included in the Stormwater Management Plan. <br />All three lines that connect with the Untreated Water Tank (i.e., 6-inch waterline from <br />the ore pad, 3-inch waterline from the mine, and 2-inch return waterline to the mine) <br />will have a low section where the pipe goes under 5/10 Road. The pipes will be <br />equipped with connections that will allow the standing water in these short sections of <br />pipe to be blown into the tank using compressed air. This will be done prior to and <br />during winter when the water would otherwise freeze in these non-draining sections. <br />Compressed air is readily available at the mine since it is used for underground drilling <br />operations. <br />11) Ore Pad Construction: The Applicant proposes compaction of the upper twelve <br />inches of soil on the ore pad to decrease permeability and calls out a specification for <br />compaction to 90 percent maximum dry density based on a standard Proctor. The <br />Division requires compaction for soil liners to 95 percent of maximum dry density. <br />This is not an onerous requirement as most soils suitable for use as liners reach 90 <br />percent density in stockpile, and compacting to 95 percent will result in a significant <br />decrease in permeability compared to 90 percent. The Division further requires that <br />for a project the size of the ore pad, a minimum of one Proctor test on a <br />representative sample of the soil, and a minimum of two density tests on soil <br />following compaction. <br />In order for soil to be effective as a liner it must behave plastically. The upper twelve <br />inches of soil to be compacted on the ore pad must have a minimum plasticity index of <br />10 percent. If there are no onsite soils that meet this criterion, the Operator must use <br />imported soil or soil amendments to increase plasticity, or propose other liner <br />T~nergs- T'ucls Reso~~rccs C;t~r~t~rat~ic~n =t4 l..!~~i{:aa~ Cioulev~ar~l, Suite EiOC) 9 <br />L~al:c~~~c>i~ci. CSC:) 8f} i ~~ Pht~ne: 303-{)7~-2 i =10 <br />