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At Site SW-N7, the means of TSS and Fe are lower when irrigation occurs (9.7 mg/l and .33 <br /> mg/l, respectively) than during the period of no irrigation (64.3 mg/l and .50 mg/l, <br /> respectively). The mean for Fe is higher during irrigation (.04 mg/1) than the one value <br /> obtained for Fe (.01 mg/1) during the non-irrigation period. <br /> During the periods of non-irrigation, total manganese averages almost nine times (.90 <br /> mg/1) the mean determined for this constituent during the irrigation season (.11 mg/1). <br /> Calamity Draw. Surface water monitoring Site SW-N101 is located in Calamity Draw upstream <br /> of the eastern boundary of the Nucla East mining area (see Exhibit 7-1). Monitoring of <br /> water quality at this site was initiated in July of 1986 for purposes of collecting <br /> baseline information for the Nucla East mining area (see Appendix 7-9). Table 7-48 is a <br /> statistical summary of all baseline water quality collected at this site. Figure 7-29 <br /> presents a Schoeller diagram of mean milliequivalent values representative of both seasons <br /> (irrigation and non-irrigation) collected at Site SW-N1O1. <br /> For both seasons, the water type at Site SW-N101 is a calcium magnesium sulfate. As <br /> previously seen at surface water sites established at the Nucla Mine, the mean <br /> milliequivalent values for each major ion increase during periods of non-irrigation. <br /> Average pH measured at SW-N101 is less during periods of no irrigation (7.64) compared to <br /> the mean pH representative of the irrigation season (7.82). However, the pH range is <br /> larger (7.23 - 8.05) during the non-irrigation months than when irrigation is occurring <br /> (7.44 - 7.98). <br /> Average TDS dramatically increases at SW-N101 when irrigation shuts down, being almost <br /> three times the mean (2,942 mg/1) determined at this site when irrigation occurs (1 ,026 <br /> mg/1). Upon perusal of Figure 7-29, it is evident that the increases in the major ions <br /> that occur after irrigation stops greatly influences this increase in TDS, while the <br /> relative proportions (percent milliequivalents) of each ion remain fairly constant. <br /> Based on the period of record, TSS, Fe and Fe all average greater (71.3 mg/l , 1 .79 mg/l <br /> and .48 mg/l , respectively) during the irrigation season than the non-irrigation period <br /> (28.3 mg/l, 1 .12 mg/l, and .15 mg/l , respectively). The opposite is true for MnT, <br /> averaging 1.43 mg/l when irrigation has ceased (mid-October through mid-April) compared to <br /> a mean of .40 mg/l during irrigation. <br /> 7-143 Revised 04/11/88 <br />