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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Numeric standards of chemical and physical parameters for stream reaches in <br /> <br /> <br />the basin are based on ambient stream conditions characterized on the basis <br /> <br /> <br />of available stream water quality data (Colorado Department of Health, <br /> <br /> <br />1981). Data for proposing standards for numerous stream reaches were quite <br /> <br /> <br />limited. Inorganic constituents in the stream standards classification <br /> <br /> <br />system include ammonia, chloride, cyanide, hydrogen, sulfide, sulfate, <br /> <br />nitrite, and nitrate. Trace metals include arsenic, cadmium, chromium, <br /> <br /> <br />copper, iron, lead, manganese and zinc. Actual numeric standards values <br /> <br />for each stream reach are given in the standards list for the basin <br /> <br /> <br />(Oolorado Department of Health, 1981). <br /> <br />Most streams in the upstream part of the South Platte River basin are <br /> <br /> <br />characterized by small dissolved solids concentrations, providing stream <br /> <br />quality that is excellent for most water uses. Calcium and bicarbonate are <br /> <br /> <br />commonly the dominant ions. Streams in this part of the basin carry low <br /> <br /> <br />sediment concentrations, flowing over relatively non-erodible rocks such as <br /> <br />granite (Colorado Department of Health, 1980). <br /> <br />Concentrations of many water quality constituents tend to increase in the <br /> <br />South Platte River as it flows through the Denver metropolitan area. This <br /> <br /> <br />might be attributed largely to municipal and industrial wastewater <br /> <br /> <br />discharges and non-point source contributions such as lawn irrigation and <br /> <br /> <br />urban runoff (Denver Regional Council of Gcvernments, 1977). Approximately <br /> <br /> <br />56 municipal and 98 industrial dischargers may affect water quality in the <br /> <br /> <br />South Platte River in the Denver metropolitan area (Colorado Department of <br /> <br /> <br />Health, 1980). Urban runoff also increases levels of fecal coliforms, <br /> <br /> <br />ammonia, biochemical oxygen demand (BOD), and trace metals of streams <br /> <br /> <br />draining the Denver metropolitan area. As streams flow through weathered <br /> <br />sedimentary rock formations, "natural" but often unquantifiable changes in <br /> <br /> <br />major ion concentrations occur (Hall and others, 1980). <br /> <br />Certain water quality conditions of concern have been noted in the Clear <br /> <br />Creek sub-basin. At its confluence with the South Platte River, fecal <br /> <br />-37- <br />