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. " 4.3,2 State Surface Water Qqality Standards baseline data or criteria accepted within the research community. Such criteria will be discussed in further detail under sections dealing with specific contaminants. 4.3.2 STATE SURFACE WATER QUALITY STANQARDS The federal Clean Water Act, as amended (33 U.S.C. 466, et seq.), declares that "it is the national goal that wherever attainable, an interim goal of water quality which provides for the protection and propagation offish, shellfish, and wildlife and provid~s for recreation in and on the water be achieved by July 1,1983..." (Senate Committee on Enviromnent and Public Works 1982). In accordance with this Act, each state must designate the uses for which its surface waters shall be protected and must prescribe the water quality standards necessary to sustain the designated uses (New Mexico Water Quality Control Commission 1991). Each of the three states of the San Juan River basin has therefore assigned designated uses and standards to the San Juan River and its tributaries (New Mexico Water Quality Control Commission 1991, New Mexico Water Quality Control Commission 1992, Utah Department of EnvirOnmental Quality 1992, Toole 1992, Colorado Water Quality Control Commission 1993a, Colorado Water Quality Control Commission 1993b). Each state has approached the task of assigning use designations and standards in a somewhat different manner, making a comparison of all standards for the basin cumbersome. In general, each state has three sets of information that need to be referenced in order to determine the standards for a given section of river or stream. The first set lists the water use olassifications that a state has chosen, the second lists the water quality standards that apply to each classification, and the third assigns a classification to each section of water. Depending on the state, these ~e sets of information may be combined or given in separate tables. A particular stretch of water may have multiple use classifications, with the most stringent standards taking precedence; fisheries standards are normally, though not always, the most restrictive. The following sections list the classifications and standards for each state. New Mexico - New Mexico has chosen 11 use classifications for its waters (Table 4). In assigning classifications to its surface waters, the state has divided the San Juan basin into seven broad sections (Table 5), each with its own standards for pH, dissolved oxygen, temperature, and fecal coliform. All New Mexico waters within the San Juan basin have been designated as fisheries and as such must meet the standards for trace elements, chlordane, and cyanide that have been prescribed for the protection of aquatic life (section 3-101-J, of Table 6). All waters within the basin are also classified for livestock and wildlife watering and therefore must meet the radium-226 + radium-228 limit of 30.0 picocuries per liter (pCi/l) in addition to trace element requirements (New Mexico Water Quality Control Commission 1991). In accordance with section 305(b) of the Clean Water Act (Appendix 6) (Senate Committee on Environment and Public Works 1982), New Mexico has evaluated its surface waters to determine which sections do not support their use classifications. The state's assessment of its water depends primarily on ambient physical and chemical data. The state also uses fish tissue data from a study begun in 1991, but data from biological surveys and biomonitoring tests have not yet been formally incorporated into New Mexico's assessment protocol (New Mexico Water Quality Control Commission 1992). The EP A recommends that even a single exceedance of a chronic criterion in a three-year period indicates that aquatic uses are "not supported." New Mexico, though, has chosen to designate uses as ''partially supported" when waters show exceedances of chronic criteria for toxicants, unless exceedances of other criteria indicate that impairment is serious enough to warrant the designation of "not supported" (New Mexico Water Quality Control Commission 1992). New Mexico has compiled a list of those sections of rivers and streams within the San Juan basin whose uses are not fully supported (Table 7). Th~ table also includes the toxicants that have been found at acute or chronic levels within these waters, as well as the probable sources of these toxicants. Acco(ding to the New Mexico Water Quality Control Commission's evaluation, none of the surface 22