The discharge standards under the NPDES refer to specific potential contaminants. A series of water quality goals are associated with each potential contaminant. Goals for a specific situation depend on the established use of the water body. The regulated contaminants vary from state to state. Schultz has classified more than fifty water quality parameters into four groups based on the frequency of their use in state ACLs and associated NPDES water quality standards (Schultz 1972).
All state water quality standards classify the following nine parameters: dissolved oxygen (D), pH, coliform, temperature, floating solids (oil-grease), settleable solids, turbidity-color, taste-odors, and toxic substances. In 50 to 99 percent of the state standards, three groups of parameters are categorized. In most regions, these frequently sampled parameter groups (radioactivity, total dissolved solids, and U.S. Public Health Service Drinking Water Standards) are sampled less frequently than the first nine. Sixteen parameters, eleven of which are heavy metals and other toxic substances, are found in the 20 to 49 percent of the state standards. Eighteen parameters appear in less than 20 percent of the state standards.
Table 4.5.3 shows the optimum and maximum values of water quality characteristics related to type of use published by California as an example of water quality goals.
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