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The water type at SW-N102 during the two seasons was a calcium sulfate. Even as levels of each <br />major ion increased after the irrigation season ended, the relative proportions of each ion remained <br />consistent (Attachment 2.04.7-10 (Peabody Appendix 7-8)). The mean value of pH during irrigation <br />was 7.7, while averaging slightly lower during periods of no irrigation (7.39). <br />Mean TDS also increased after the irrigation season ended, averaging 1900 mg/I during this period <br />in comparison to a mean TDS of 1,176 mg/I during the irrigation season. <br />After the irrigation season ended, TSS, FeT and Fep all averaged slightly higher (12.5 mg/1,.88 mg/I <br />and .39 mg/1, respectively) than during the irrigation season (6.8 mg/I, .49 mg/I and .08 mg/I, <br />respectively). These higher averages for these constituents at SW-N102 after the irrigation season <br />ended probably reflect the gradual recession of tail water discharge (hence, higher concentrations) <br />after irrigation ceases. <br />Surface water Site SW-N103 was situated in Calamity Draw about .6 miles downstream of <br />SW-N101. It was the furthest downstream monitoring site Peabody routinely monitored for water <br />quality in Calamity Draw. Monitoring for water quality at SW-N103 began in July of 1986 <br />(Attachment 2.04.7-11 (Peabody Appendix 7-9)). <br />The water type at Site SW-N103 for both seasons was a calcium magnesium sulfate (Attachment <br />2.04.7-10 (Peabody Appendix 7-8)). This water type was very similar to waters sampled upstream <br />in Calamity Draw at Site SW N101. During periods of irrigation, the major ions at SW N103 were <br />slightly lower than shown at SW-N101. This suggested that contributions to flow in Calamity Draw <br />between these sites due to irrigation tail water provided a dilution effect. <br />Little variability between the seasons for pH was detected at SW-N103. During irrigation, pH <br />averages 7.84 and ranges from 6.84 up to 8.10 units. After the irrigation season, pH averages 7.88 <br />and ranges between 7.50 and 8.06 units. <br />Similar to previously discussed surface water monitoring sites, the mean of TDS during the <br />non-irrigation season was more than double (3,135 mg/1) the mean for this constituent during the <br />irrigation period (1,371 mg/1). Again, the higher levels of the major ions in Calamity Draw at this site <br />after irrigation stops explains this trend. <br />2.04.7-38