Laserfiche WebLink
• pasture and will therefore will not contribute irrigation recharge, however, other areas will have a <br />greater recharge than 16" total, therefore, the average of 16" over the reclaimed area is <br />reasonable. From the year 2003 to 2013, the expected recharge should only be 10% of this <br />amount, since irrigation will not be used on the majority of the area and the fresh-placed spoil will <br />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}(8500 ft. wide seepage <br />area)(0.10 ft. per day seepage velocity)(1/43,560 cu. ft. to ac. ft.)(365 days per year) = 72 ac.ft. <br />Spoil Spring Discharge = (557 ac.ft. recharge) - (72 ac.ft. seepage into low wall) = 485 ac.ft. In the <br />year 2000, the NPDES 001 discharge at the New Horizon #1 Mine showed an average flow of <br />271,000 gallons per day or 320 acre-feet per year. The NPDES 001 discharge is for practical <br />purposes composed entirely of spoil water. The New Horizon #2 spoil area is much bigger, <br />therefore the predicted flow of 485 acre-feet per year for this area is reasonable compared to what <br />is being observed at the #1 Mine. <br />• Time to spring discharge = (Pore Volume)/(Recharge Volume) <br />_ (227 ac.ft.) / (485 ac.ft.) = 0.5 years to actual spring flow after full irrigation is resumed on the <br />reclaimed land in 2013. <br />It may begin to discharge slightly sooner since irrigation may begin on the eastern portion of the <br />reclaimed area sooner than 2013, thus contributing some discharge. Also, recharge from <br />precipitation has not been factored in the spoil prior to 2013. Assuming that the permanent pipe <br />is installed in the year 2003 and has a life of 30 years, the pipe would be replaced by the ditch in <br />the year 2033. At this time recharge would increase slightly since water from the ditch would <br />provide additional infiltration, however, the ditch area is so small (0.87 acres) compared to the area <br />of the spoil (418 acres), that the increase in infiltration would be negligible. Water will be seeping <br />from irrigation on the vast majority of the reclaimed spoil regardless of the ditch being in soil or a <br />pipeline. Therefore, the long term prediction for flow in the spoil spring at the New Horizon #2 Mine <br />is 485 acre feet per year. <br />Overall, there should be no detrimental impacts from the mining operation on groundwater flow <br />and recharge rates. It is definite that ground water flow and recharge in the spoil material will be <br />increased, since the overburden aquifers have historically had very low flow rates and also poor <br />• <br />REVISED MARCH 2006 2.05.6(3)-23 <br />