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RULE 2 PERMITS <br /> different. However,the Wilson Creek stations consistently showed chloride concentrations five to <br /> ten times higher than other stations. Chloride is usually absent in groundwater seepage but can be <br /> present in high concentrations in mineral springs. Since such springs have not been reported along <br /> Wilson Creek, some other source may be causing these high levels. Since the geology of the three <br /> drainage basins is very similar, water quality differences may relate to agricultural or other <br /> disturbances in the area. Additionally, the natural slumping of bank areas above the USGS gage <br /> on Wilson Creek may significantly impact the results of this parameter. <br /> Dissolved solids concentrations showed incremental increases of 40 mg/1 to 50 mg/1 per mile of <br /> flow. These increases represented the inflow of total dissolved solids from groundwater seepage, <br /> agricultural drainage, dissolving elements found in the streambed, and the concentrating effect of <br /> evaporation of the stream water. <br /> Seasonal water quality variations in the streams were evident in the sample results. As streamflow <br /> decreased to the baseflow period of fall and winter,the stream source changed from mainly surface <br /> runoff caused by snowmelt and rainfall to mainly groundwater seepage. This change is reflected <br /> by changes in water quality. Alkalinity,which is a measure of dissolved carbonate and bicarbonate <br /> ions, showed somewhat of a direct relation to the proportion of surface runoff and decreased in the <br /> fall. Sulfates, which are the product of the oxidation of sulfur minerals and are typically found in <br /> groundwater, increased in the fall. These changes usually occurred as surface runoff decreased, <br /> rather than as groundwater flow increased. Magnesium and sodium also showed seasonal <br /> fluctuations, with magnesium decreasing and sodium increasing in the fall. Chloride <br /> concentrations decreased in the fall in a manner similar to other elements, but with somewhat <br /> different timing. <br /> Iron was present in normal quantities. Since no deposits of"iron boy" were observed along any of <br /> the streams,acid drainage problems are not evident or expected. All the cadmium,lead,chromium, <br /> and arsenic results were below their respective toxic thresholds of 0.01 mg/1, 0.03 mg/1, 0.05 <br /> mg/1, and 1 mg/1 (NAS, 1972). In addition, all the mercury and selenium analyses were below <br /> their toxic thresholds of 0.00005 mg/1 and 0.23 mg/1, respectively, as indicated by the presence <br /> of aquatic life. Toxicities of zinc and copper vary widely in water of different hardness.Laboratory <br /> experiments and field bioassays have shown high levels of calcium, such as those found in these <br /> drainages, to inhibit the toxicity of these metals. Based on hardness and alkalinity the waters in <br /> these drainages are not toxic to aquatic life. No unusual water quality constituents were detected <br /> by this sampling program. <br /> Sampling for water quality constituents has continued since the 1974-1975 data collection period. <br /> The USGS has collected data at Taylor Creek, Wilson Creek and Goodspring Creek for a host of <br /> water quality parameters as a part of the continuing EMRIA Program. Colowyo has also collected <br /> data for Taylor Creek and Goodspring Creek for the period 1978 to present. These data continue <br /> to reflect the high variability by month of specific conductance, total dissolved solids, total <br /> suspended solids and the other constituents of concern. Table 2.04.7-20 is a comparison of USGS <br /> and Colowyo data. The raw data from which these calculations were derived are included in <br /> Exhibit 7A. The data in Table 2.04.7-20 are revealing in that the USGS effort has been much more <br /> intensive than the Colowyo effort, but the results are quite similar. <br /> Rule 2 Permits 2.04-26 Revision Date: 12/20/19 <br /> Revision No.: TR-135 <br />