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2000 to 5000 mg/I). According to this classification system, water supplied by the West Lateral <br />irrigation ditch (TDS 500 mg/I) will have no detrimental effects on plants. <br />Using mean values for sodium adsorption ratio (SAR) and specific conductance (SC, umhos/cm <br />at 25°C) from each site determined for both the irrigation and non-irrigation season, water <br />classifications were made based on guidelines proposed by the U.S. Salinity Laboratory (1954). <br />During periods of irrigation (mid-April through mid-October), all surface water sites exhibit a low <br />sodium hazard and a medium to high salinity hazard. Between irrigation seasons (with the <br />exception of West Lateral Irrigation Ditch sites), all sites can be classified as having a low sodium <br />hazard and a high to very high salinity hazard. <br />As a result of the request made by OMLR to Peabody in a letter on May 4, 1986, Peabody revised <br />the list of parameters that were analyzed for at all surface and ground water monitoring sites. The <br />revised list included analyses for silver (total recoverable) and hexavalent chromium (total <br />recoverable). The list was temporarily revised in order to determine whether silver and chromium <br />were present in monitored water in sufficientand frequent enough concentrations to warrantfurther <br />sampling for each, based on stream standards for the San Miguel River. During 1987, Peabody <br />had its contract laboratory (ACZ Laboratories, Steamboat Springs, Colorado) perform total <br />recoverable analyses for silver and hexavalent chromium on two sample sets collected at each <br />surface water site. In addition, Peabody collected water quality samples in April and October of <br />1987 at two points on the San Miguel River; 1) upstream of the confluence with Calamity Draw <br />(San Miguel #2); and 2) downstream of the confluence with Tuttle Draw (San Miguel #1). The <br />results of each silver and chromium analyses performed at each surface water monitoring site can <br />be found in Peabody Appendix 7-9. The results of the additional analyses for silver and chromium <br />showed that total recoverable chromium never exceeded 10 ug/I; and that silver exceeded 10 ug/I <br />once each {20 ug/I at sites SW-N3, SW-N7 and SW-N102). Compared to standards adopted for <br />the nearest applicable reach of the San Miguel River (Segment 5), all analyses for chromium (total <br />recoverable) were well below the standard (25 ug/I). Unfortunately, the detection limit used by the <br />laboratory for silver (total recoverable) was 10 ug/I, significantly higher than the standard (.1 ug/I). <br />With respect to Colorado Department of Health (CDOH) receiving stream standards (CDOH,1983, <br />revised 1986), Tuttle and Calamity Draws lie within the Stream Segment 12 of Region 10 of the <br />(Revised 25 Jul 2002) 2.04.7-37 <br />