Laserfiche WebLink
10% of this amount, since irrigation will not be used on the majority of the area <br />and the fresh - placed spoil will be relatively dry. <br />Spoil spring discharge (Spoil Spring Recharge) (Seepage into Low Wall) <br />Seepage into Low Wall = (10 ft. thick permeable sandstone bed in low wall) <br />(8500 ft. wide seepage area)(0.10 ft. per day seepage velocity)(1 /43,560 cu. ft. to <br />ac. ft.)(365 days per year) = 72 ac.ft. <br />Spoil Spring Discharge = (563 ac.ft. recharge) — (72 ac.ft. seepage into low wall) <br />= 490 ac.ft. In the year 2000, the NPDES 001 discharge at the New Horizon 91 <br />Mine showed an average flow of 271,000 gallons per day or 320 acre -feet per <br />year. The NPDES 001 discharge is for practical purposes composed entirely of <br />spoil water. The New Horizon Mine 2 irrigated spoil area is bigger, therefore the <br />predicted flow of 490 acre -feet per year for this area is a reasonable maximum <br />flow when compared to what is being observed at the 91 Mine. <br />Realistic case time to spring discharge (Pore Volume) /(Recharge Volume) <br />_ (416 ac.ft.) / (490 ac.ft.) = 0.8 years to actual spring flow after full irrigation is <br />resumed on the reclaimed land in 2013. This is the most realistic case of when <br />the spoil spring will begin to flow. <br />In both the worst case and the more realistic discharge scenario, it may begin to <br />discharge slightly sooner since irrigation may begin on the eastern portion of the <br />reclaimed area sooner than 2013, thus contributing some discharge. Also, <br />recharge from precipitation has not been factored in the spoil prior to 2013. <br />Assuming that the permanent pipe is installed in the year 2003 and has a life of <br />30 years, the pipe would be replaced by the ditch in the year 2033. At this time <br />recharge would increase slightly since water from the ditch would provide <br />additional infiltration, however, the ditch area is so small (0.87 acres) compared <br />to the area of the spoil (768 acres) and the area of irrigation (422 acres), that the <br />increase in infiltration would be negligible. Therefore, the worst case prediction <br />for flow in the spoil spring at the New Horizon Mine 2 is 952 acre feet per year, <br />while the most realistic flow for the spoil spring is 490 acre feet per year. This is <br />a potential flow of 1.31 cfs (worst case) and 0.68 cfs (realistic case). <br />In both cases, the flow is higher than the previously calculated spoil spring flow <br />from when the New Horizon Mine 2 covered a smaller area. That flow was 0.57 <br />cfs. The greater flow at New Horizon Mine 2 will lead to a lower impact on area <br />water quality due to dilution. <br />Overall, there should be no detrimental impacts from the mining operation on <br />groundwater flow and recharge rates. It is definite that ground water flow and <br />recharge in the spoil material will be increased, since the overburden aquifers <br />have historically had very low flow rates and also poor quality. These aquifers <br />34 <br />