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and dozing. These techniques will increase permeabilities of the material in <br />comparison to the original overburden. Due to truck dumping from the spoil <br />bench, large rock will settle near the bottom of the pit and provide a permeable <br />channel for groundwater flow. The hydraulic conductivity (K) of the spoil, as <br />measured in well GW -N27, is 40 ft /day, which is far greater than any <br />measurement made in the overburden. K values in the overburden generally <br />range from 3.0 to 5.5 ft /day. The New Horizon 41 site has had continued <br />seasonal irrigation from the North Lateral and its secondary ditch which flows <br />immediately north of the New Horizon 91 reclaimed areas. Water from this <br />irrigation and some added precipitation have moved through the spoil and <br />saturated it until it discharges at the low point of the base of the coal which is at <br />the Spoil Spring and the Pond 001 discharge. Flow from this point fluctuates in <br />response to the use of irrigation. It is believed that the spoil in the New Horizon <br />92 Mine area will remain relatively dry until irrigation is resumed from the West <br />Lateral Ditch. Once this irrigation is resumed, recharge will rapidly infiltrate into <br />the spoil, move to the southwest according to the basal gradient and develop a <br />spring at the low point of the lowwall crest, as was experienced at the New <br />Horizon 91 Mine. This point can be seen on Map 2.04.7 -1A, near the northwest <br />corner of the permit area near Tuttle Draw. This point was calculated in CAD <br />using the entire excavated area for the mine compared to the surface topography. <br />If any spring develops here, it would discharge into Tuttle Draw. The Morgan <br />property should not experience any spoil springs. <br />Although a large diameter HDPE pipe will be used to carry the ditch water <br />through the permit area, infiltration will begin when the permanent HDPE pipe <br />will be used in re- establishing irrigation in the reclaimed area. This will occur in <br />2003 for the area east of 2700 Road and will occur after 2010 for the remainder <br />of the mine area west of 2700 Road. It is estimated that full irrigation of the <br />reclaimed area will take place by year 2013. Although the pipe will be used to <br />carry the ditch flow until the end of its useful life in 30 -50 years, its use is not <br />relevant to the prediction of irrigation recharge since this recharge will occur <br />over 99% of the area even when the permanent pipe is in place. <br />From soil information, knowledge of the irrigation practices, discussions with <br />USGS, and the rainfall date for the site, the following recharge data has been <br />calculated: 2" from rain and snowmelt, 13" from irrigation and 1" from <br />underburden recharge and overburden recharge at the uphill spoil/overburden <br />contact. Total long -term recharge is therefore 16" per year. These predictions are <br />approximate but suffice in predicting the behavior of the groundwater in the <br />spoil. <br />The total affected area is roughly 768 acres. The volume of the reclaim spoil to <br />be recharged below the 5580 spoil spring elevation equals 2,778 ac.ft. as <br />determined from D.T.M. modeling of the spoil area and the pit bottom. Spoil <br />porosity of 15% is determined for the overburden. This yields a pore volume of <br />(0.15)(2778 ac.ft.) = 416 ac.ft. <br />32 <br />