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• Along this reach, a significant portion of the ditch banks are heavily vegetated with willow, wild rose <br />and a variety of grasses that commonly exhibit high rates of transpiration. <br />Interestingly, two reaches showed a gain in discharge. Between Site SW-N104 (5) and the <br />"cemetery" box (8), an increase in flow of 1.5 percent (from 19.4 to 19.7 cfs) was observed. Also, <br />between the "halfway" box (10) and the "bend" box (11), a 12.6 percent increase in flow was <br />observed (from 15.9 cfs to 17.9 cfs). <br />Most reaches along the West Lateral lose irrigation flow to diversions, evapotranspiration and, of <br />course, seepage. The reaches that showed a loss inflow had water being withdrawn along each <br />reach through diversions on the day the study was performed, as well as significant lengths of <br />heavily vegetated bank sides. Seepage of irrigation wateroccurs along the entire reach of the West <br />Lateral, probably occurring at higher rates and volumes along the "ridge-top" reach where the ditch <br />was excavated through the shallow soils into the highly fractured sandstone. <br />The two reaches where the ditch featured gains in flow are portions of the general "ridge-top" <br />segment of the West Lateral. The ditch channel bottom in this reach is largely fractured and <br />weathered sandstone, and likely results in relatively large amounts of seepage. This seepage, in <br />combinationwithtocalized intensive "flooding-type" irrigation, travels laterally through the shallow <br />soils and fractured sandstone eventually flowing back into the West Lateral slightly downstream. <br />The combination of fractured, weathered sandstone channel bottoms in the ditch and localized <br />"flood-type" irrigation along these two gaining reaches likely resulted in the measured gains in flow. <br />WaterQuality. Surface water Site SW-N1041iesonthe West Lateral irrigationditchjustupstream <br />of the northeastern boundary ofthe New Horizon 2 mining area (see Map 2.04.7-1 ). Monitoring of <br />water quality atthis site (when the ditch is on) was conducted on a monthly basis since July of 1986. <br />Waterquality data collected at this site since 1986 is contained in Appendix B ofAttachment 2.04.7- <br />1. <br />The irrigation water sampled over time at SW-N 104 exhibited a calcium bicarbonate sulfate type <br />(see Peabody Appendix 7-8). The mean pHvalue at SW-N104 is 8.09, ranging from 7.71 up to 8.42. <br />TDS averaged only 179 mg/I, and ranges between 116 and 264 mg/I. TSS averaged 56 mg/I, <br />varying from 8.0 to 106 mg/I. FeT, Fep and MnT average 1.21 mg/I, .02 mg/I and .04 mg/I, <br />• respectively. <br />(Revised 6/28iot) 2.04.7-31 <br />