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• 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 arid and semi-arid areas (National Academy of Sciences, 1972), surface water in Calamity and Tuttle Draws all fall within the category ofwaterthat can be used for tolerant plants on permeable soils with careful management practices (TDS from 2000 to 5000 mg/I). According to this classification system, water supplied by the West Lateral irrigation ditch (TDS 500 mg/l) will have no detrimental effects on plants. Using mean values for sodium adsorption ratio (SAR) and specific conductance (SC, umhos/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 listwas 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 foreach, based on stream standards forthe 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 waterquality samples in April and Octoberof 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 Peabody Appendix 7-9. The results of the additional analyses for silver and chromium showed that total recoverable chromium never exceeded 10 ug/I; and that silver exceeded 10 ug/I once each (20 ug/I at sites SW-N3, SW-N7 and SW-N102). Compared to standards adopted forthe nearest applicable reach ofthe San Miguel River(Segment5), all analyses forchromium (total recoverable) were well (Revised 6/28101) 2.04.7-35