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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale - Pagt 3, Permit No. C0~1034142 Table Value Standards (IYS) refers to Table III of the Basic Standards and Metlutdolories for Surface Water. For the metals listed with TVS standards, three sets of standards may apply depending upon the receiving stream class~ation -those for protection of I) aquatic hfe use, 2) agricultural use and 3) drinking water use. Table Value Standards for the protection of aquatic life can be divided into tx+o categories -those that are dependent upon the stream hardness, and those that are rot. Standards for the ,protection of agricuhural and water supply uses are aU hardness independent For Segment 136 of the Williams Fork River, aquatic life use, . agricultural use and drinking water use standards aPP1Y• For hardness dependent metals standards, the numerical value of the aquatic life use based standard will depend upon the rnmbined efllucnt/receiving stream hardness below the dischar~ie point. The hardness values to be used art those which trorrapond to the lower 95th percent confidence limit of the mean hardness value at the periodu low-flow criteria, as detmnined from a regression analysis of site-sped data. If data for such an analysis is not available, or if a regression analysis it not appropriate, other methods may be used. Nardness data is available for the Williams Fork River upstream of the discharges from the CECfacility. These data were supplied by the permittee in the application for renewal. The sample, taken on May 31, 1990, reponed a hardness in the Williams Fork River to be 100 mg/l as CaCOr This value will be used to calculate hardness-dependent standards. The following table su»vnarizes the metals standards for all uses. The most stringent of these will be used in ca~ulating eJ)luem limitations. Table I//-1 Metals Standards Summary -Williams Fork River, Segment 13b ajthe Lower Yampa/Green River Sub-basin of the Lower Colorado River Basin, AU Concentrations An ug/l Arsenic 360 ISO SO - 100 Cadmium 9.87 1.13 10 10 Copper 17.74 11.82 - lOg7 200 Iron - 1000+ - 300,:+ - Lend 95.85 3.89 50 - 100 Manganese - 1000+ - S0+* 200 Mercury 2.4 0.01 ^ 2.0 - - Nickel 922.22 95.58 - - 200 Selenium 135 17 /0 - - Sikver 2.03 0.32 50 - - Zinc 117 106 - 5000 2000 + Aquatic Life Use standards are based upon the dissolved method ojanalysis, except for iron and manganese standards, which are based upon the total recoverable method, and the mercury standard, which is based upon the rota[ method. ++ Drinking Water Use standards are based upon the total recoverable method of analysis, except for iron and manganese standards, which are based upon the dissolved method.