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<br />r - 7 - <br />` '/; <br />~~• 2. Y~ Page 2.05-110 of the PHC states that solute concentrations for leachate <br />- - } I from the reclaimed spoils will start to decline after about 140 years <br />and will return to baseline levels after about 235 years. The leachate <br />study showed that significant decreases in EC levels occur when the <br />ratio of the volume of leachate to the weight of the spoil material is <br />.9 liters per kilogram with a return to baseline EC levels when the <br />ratio is about 1.5 1/kg. We have found apparent discrepancies in the <br />way the above time frames were Calculated and the results of the Teach <br />~ study. From the data obtained in the leach study the Division made the <br />following calculations. <br />~' <br />`\~ ` h = Average height of spoil in feet = 60 feet <br />', Column volume = 1 foot x 1 foot x 60 feet <br />.~ Total volume = 60 cubic feet <br />Bulk density of backfill = T.45 gm/cc = 1.45 kg/1. <br />1 cubic foot overburden = 28.3 1. x 1.45 kg/1.= 41.0 kg <br />60 feet3 x 41.0 kg = 2462 kg total overburden <br />For column <br />Thus, it would take .9 1. x 2462 kg or 2216 1. to flush a 60 foot <br />~~ column at a ratio of .9 1./kg <br />,\ . <br />~• ; Average annual rain fall = 3 inches = .25 feet = <br />,, 7.142 liters per year per square foot <br />Thus, ~~ = 310 years <br />' Therefore, to flush the spoils at a rate of .9 1./kg would take <br />\, 310 years. And to Flush 1.5 1./kg would take 310 x 1.67 = or <br />'\ 516 years. Why is the calculation submitted in the application more <br />~ appropriate than the Division's calculations? Pi ease explain the <br />\ variables used in the calculation and the rationale for using them. <br />~ What was the basis for the assumed effective porosity of .45? Please <br />1 submit supporting data if available.. <br />3.>l; Page 2.05-107 states that fifty ,p rcent of the recharge to the <br />i backfilled areas will evelrt+ral'~y infiltrate the bedrock aquifers. This <br />appears to conflict with backfill spoil investigations submitted <br />5a ` earlier this year which indicate most infiltrating water discharges as <br />-^ 1 springs. Please address this apparent discrepancy and support the <br />c) ,? assumption with sufficient calculations. This should be submitted as a <br />water balance with appropriate calculations. <br />n <br />/'/J' ; <br />~~ ~~ <br />