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

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sites have had exceedences of the pH standard and two sites have had exceedences of boron. Manganese was exceeded commonly in both Tuttle and Calamity Draws, as well as at sites located along tributaries to each drainage (SW -N6, SW -N7, NPDES 001 and 006, and SW -N102). Based on a classification of salinity hazard for and and semi -arid areas (National Academy of Sciences, 1972), surface water in Calamity and Tuttle Draws all fall within the category of water that can be used for tolerant plants on permeable soils with careful management practices (TDS from 2000 to 5000 mg/1). According to this classification system, water supplied by the West Lateral irrigation ditch (TDS 500 mg/1) will have no detrimental effects on plants. Using mean values for sodium adsorption ratio (SAR) and specific conductance (SC, umbos/cm at 25°C) from each site determined for both the irrigation and non -irrigation season, water classifications were made based on guidelines proposed by the U.S. Salinity Laboratory (1954). During periods of irrigation (mid-April through mid-October), all surface water sites exhibit a low sodium hazard and a medium to high salinity hazard. Between irrigation seasons (with the exception of West Lateral Irrigation Ditch sites), all sites can be classified as having a low sodium hazard and a high to very high salinity hazard. As a result of the request made by OMLR to Peabody in a letter on May 4, 1986, Peabody revised the list of parameters that were analyzed for at all surface and ground water monitoring sites. The revised list included analyses for silver (total recoverable) and hexavalent chromium (total recoverable). The list was temporarily revised in order to determine whether silver and chromium were present in monitored water in sufficient and frequent enough concentrations to warrant further sampling for each, based on stream standards for the San Miguel River. During 1987, Peabody had its contract laboratory (ACZ Laboratories, Steamboat Springs, Colorado) perform total recoverable analyses for silver and hexavalent chromium on two sample sets collected at each surface water site. In addition, Peabody collected water quality samples in April and October of 1987 at two points on the San Miguel River; 1) upstream of the confluence with Calamity Draw (San Miguel #2); and 2) downstream of the confluence with Tuttle Draw (San Miguel #1). The results of each silver and chromium analyses performed at each surface water monitoring site can be found in Attachment 2.04.7-11 (Peabody Appendix 7-9). The results of the additional analyses for silver and chromium showed that total recoverable chromium never exceeded 10 ug/1; and that silver exceeded 10 ug/1 once each (20 ug/1 at sites SW -N3, SW -N7 and SW -N102). Compared to standards adopted for the nearest applicable reach of the San Miguel River (Segment 5), all analyses for chromium (total recoverable) were well below the standard (25 ug/1). Unfortunately, the detection limit used by the laboratory for silver (total recoverable) was 10 ug/1, significantly higher than the standard (.1 ug/1). With respect to Colorado Department of Health (CDOH) receiving stream standards (CDOH, 1983, revised 1986), Tuttle and Calamity Draws lie within the Stream Segment 12 of Region 10 of the San Miguel River. Because the listed parameters (physical and biological, only) are not applicable to both Tuttle and Calamity Draws, the nearest segment (downstream) in which applicable standards have been promulgated (Segment 5) are used to compare surface water quality of Calamity (SW -N103) and Tuttle Draws (SW -N3, NPDES 001 and NPDES 006). Exceedences were observed at three sites: 1) iron at San Miguel #1 (downstream of Turtle Draw); 2) zinc and manganese at SW -N103; and 3) nickel at NPDES 006. Based on the rigorous comparisons made, it is evident that water delivered by the West Lateral Irrigation Page 2.04.7-27 March 2017 (TR -77)