2020-06-04_PERMIT FILE - C1981008A (2)

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mg/1, varying from 8.0 to 106 mg/1. FeT, FeD and MnT average 1.21 mg/1, .02 mg/1 and .04 mg/1, respectively. Surface water Site SW -N105 lies about midway between Sites SW -N104 and SW -N106 on the West Lateral. Water quality data collected at this site since 1986 were compiled and are presented in Appendix B of Attachment 2.04.7-5. The water type determined at Site SW -N105 was a calcium bicarbonate sulfate (Attachment 2.04.7-10 (Peabody Appendix 7-8). The pH averaged 8.04 at SW -N105, and fell between 7.72 and 8.42 units. The mean value determined for TDS was 185.7 mg/1, and TDS ranged from 142 to 278 mg/l. TSS averaged 67 mg/1, and ranged from 4.0 to 204 mg/1. FeT, FeD and MnT averaged 1.48 mg/1, 02 mg/1, 1.08 mg/1, respectively. Site SW -N106 was the most downstream surface water site established on the West Lateral. Attachment 2.04.7-11 (Peabody Appendix 7-9) contains the water quality data collected at this site since July of 1986. As mentioned for both Sites SW -N104 and SW -N105, the water type determined for SW -N106 was a calcium bicarbonate sulfate. At Site SW -N106, pH averaged 8.08 units, and ranged between 7.68 and 8.41 units. The mean value determined for TDS was 179.7 mg/1, and TDS varied from 112.0 to 270.0 mg/l. TSS averages 107.7 mg/L, ranging from 16.0 to 406 mg/1. FeT, FeD and MnT average 1.52 mg/ 1, .02 mg/l and .05 mg/1, respectively. From the previous discussions of water quality at Sites SW -N104, SW -N105 and SW -N106, the irrigation water monitored in the West lateral showed little chemical variability as flow was monitored in the downstream direction. Of the parameters mentioned, only total suspended solids (TSS) and dissolved iron (FeD) showed trends of slight increases (mean values) as irrigation water progresses down the ditch. Relationships Among Flow, TSS and TDS The interrelationships among certain physical and chemical parameters in surface water often control the chemical quality. Generally, as the discharge (flow) of a stream increases, so does the concentration of total suspended solids (TSS). For streams that commonly experience elevated levels of TSS (104 to 105 in semi -arid environments), total dissolved solids (TDS) commonly is inversely related to TSS, that is, as TSS level increase, TDS concentration will decrease. This inverse relationship between TSS and TDS will result in lower proportions of dissolved constituents while conserving the total chemical load of the water. In order to investigate the significance of relationships among flow, TSS and TDS in streams monitored at the New Horizon 2 area, simple linear regression correlation analyses were performed on flow, TSS and TDS values collected simultaneously at each surface water site. Using flow as the independent variable, discharge was regressed against TSS and TDS. Also, using TSS as the independent variable, TSS was regressed against TDS. TSS showed little to no correlation with flow. The range of correlation coefficients (r2 values) determined for flow versus TSS during the irrigation season were from .000 to .298. For periods between the irrigation seasons, r2 values ranged from .000 to .447. These calculated correlation coefficients indicated that discharge (instantaneous measurements) has no relationship with levels of TSS in the monitored streams at the New Horizon 2 mining area. Page 2.04.7-25 March 2017 (TR -77)