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The two reaches where the ditch featured gains iri 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 />combination with localized 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 />Water Quality. Surface water Site SW-N1041ies on the West Lateral irrigation ditchjust upstream <br />of the northeastern boundary of the New Horizon 2 mining area (see Map 2.04.7-1 ). Monitoring <br />of water quality at this site (when the ditch is on) was conducted on a monthly basis since July of <br />1986. Water quality data collected at this site since 1986 is contained in Appendix B of Attachment <br />2.04.7-1. <br />The irrigation water sampled over time at SW-N104 exhibited a calcium bicarbonate sulfate type <br />(see Peabody Appendix 7-8). The mean pH value at SW-N104 is 8.09, ranging from 7.71 up to <br />8.42. TDS averaged only 179 mg/I, and ranges between 116 and 264 mg/I. TSS averaged 56 <br />mg/I, varying from 8.0 to 106 mg/I. FeT, Feo and MnT average 1.21 mg/I, .02 mg/I and .04 mg/I, <br />respectively. <br />Surface water Site SW-N105 lies about midway between Sites SW-N104 and SW-N106 on the <br />West Lateral. Water quality data collected at this site since 1986 were compiled and are presented <br />in Appendix B of Attachment 2.04.7-1 <br />The water type determined at Site SW-N105 was a calcium bicarbonate sulfate (see Peabody <br />Appendix 7-8). The pH averaged 8.04 at SW-N105, and fell between 7.72 and 8.42 units. The <br />mean value determined for TDS was 185.7 mg/I, and TDS ranged from 142 to 278 mg/I. TSS <br />averaged 67 mg/I, and ranged from 4.0 to 204 mg/I. FeT, Fep and MnT averaged 1.48 mg/I, 02 mg/I, <br />1.08 mg/1, respectively. <br />Site SW-N106 was the most downstream surface water site established on the West Lateral <br />Peabody Appendix 7-9 contains the water quality data collected at this site since July of 1986. As <br />(Revised 25 Jul 2002) 2.04.7-33 <br />