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COEUR D'ALENE BASIN, IDAHO - EPA WATER QUALITY MONITORING, 1972 TO 1986
Description:
The Region 10 Office of USEPA has conducted chemical and biological monitoring during low-flow conditions from 1972 to 1986 along the South Fork Coeur dAlene River in northern Idaho (17010303), a stream with a long history of severe metals pollution from mining activities. During 1986, metals analysis of sediments and tissues from the lower Coeur dAlene River and Coeur dAlene Lake was also conducted. Due chiefly to effluent controls at the Bunker Hill Complex, low-flow season South Fork concentrations of zinc, cadmium, and lead downstream of Kellogg were reduced during the 1970s. During the 1986 low-flow survey, metal loadings were primarily a result of nonpermitted inputs to the stream, chiefly from the vicinity of the Bunker Hill Central Impoundment Area and from Canyon Creek, a tributary near Wallace. Although levels of zinc and cadmium remain well above national criteria for protection of cold water biota in both the South Fork and lower mainstem of the Coeur dAlene, recovery of aquatic life has been substantial, with the lower mainstem now supporting a successful sports fishery. Sediments in the lower Coeur dAlene system remain heavily contaminated with toxic metals, although high levels in edible fish tissue were not found. The cessation or treatment of the major discrete CIA seep at the Bunker Hill Superfund Site is estimated to reduce mainstem summer low-flow zinc concentrations by over 150 ug/l. Allowable 1986 permit limits for metals (primarily cadmium) have the potential of increasing in-stream metals concentrations substantially above the levels resulting from nonpermitted sources. Water quality-based permits are particularly important for aquatic life protection of the South Fork upstream of Mullan and the mainstem downstream of the South Fork confluence. Hornig, C.E., D.A. Terpening, and M.W. Bogue. 1988. USEPA, Region 10, Seattle, WA. 14 pp. plus appendices.