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• ft/day, which is far greater than any measurement made in the overburden. K values in the overburden <br />generally range from 3.0 to 5.5 fUday. The New Horizon #1 site has had continued seasonal irrigation <br />from the North Lateral and its secondary ditch which flows immediately north of the New Horizon #1 <br />reclaimed areas. Water from this irrigation and some added precipitation have moved through the <br />spoil and saturated it until it discharges at the low point of the base of the coal which is at the Spoil <br />Spring and the Pond 001 discharge. Flow from this point fluctuates in response to the use of irrigation. <br />It is believed that the spoil in the New Horizon #2 Mine area will remain relatively dry until irrigation <br />is resumed from the West Lateral Ditch. Once this irrigation is resumed, recharge will rapidly infiltrate <br />into the spoil, move to the southwest according to the basal gradient and develop a spring at the low <br />point of the lowwall crest, as was experienced at the New Horizon #1 Mine. This point is expected to <br />be N = 602,530, E = 1,112,350 @ elevation 5580'. Although a large diameter HDPE pipe will be used <br />to carry the ditch water through the permit area, infrltration will begin when the permanent HDPE pipe <br />will be used in re-establishing irrigation in the reclaimed area. This will occur in 2003 for the area east <br />of 2700 Road and will occur after 2010 for the remainder of the mine area west of 2700 Road. It is <br />estimated that full irrigation of the reclaimed area will take place by year 2013. Although the pipe will <br />be used to carry the ditch flow until the end of its useful life in 30-50 years, its use is not relevant to <br />the prediction of irrigation recharge since this recharge will occur over 99% of the area even when the <br />permanent pipe is in place. <br />• From soil information, knowledge of the irrigation practices, discussions with USGS, and the rainfall <br />date forthe site, the following recharge data has been calculated: 2"from rain and snowmelt, 13"from <br />irrigation and 1"from underburden recharge and overburden recharge at the uphill spoil/overburden <br />contact. Total long-term recharge is therefore 16" per year. These predictions are approximate but <br />suffice in predicting the behavior of the groundwater in the spoil. <br />The total affected area is 418 acres. The volume of the reclaim spoil to be recharged below the 5580 <br />spoil spring elevation equals 1512 ac.ft. as determined from D.T.M. modeling of the spoil area and the <br />pit bottom. Spoil porosity of 15% is determined for the overburden. This yields a pore volume of <br />(0.15)(1512 ac.ft.) = 227 ac.ft. <br />With a pore volume of 227 ac.ft. and assuming a total recharge of 16" per year from all sources over <br />the 418 acres of spoil, annual recharge equals (16/12)(418) = 557 ac.ft. per year after full irrigation in <br />2013. It should be noted that a portion of the reclaimed area will be restored to dry land pasture and <br />will therefore will not contribute irrigation recharge, however, other areas will have a greater recharge <br />than 16" total, therefore, the average of 16" over the reclaimed area is reasonable. From the year <br />2003 to 2013, the expected recharge should only be 10% of this amount, since irrigation will not be <br />used on the majority of the area and the fresh-placed spoil will be relatively dry. <br />• (Revised 6/Ol) 2.05.6 (3) - 21 <br />