Surficial geology along the Spokane River, Washington and its relationship to the metal content of sediments (Idaho-Washington stateline to Latah Creek confluence): Geologic units

The Spokane River flows westward into eastern Washington out of the
northern end of Lake Coeur d'Alene in northern Idaho. The river and
lake lie downstream of the Coeur d'Alene mining district, where over
56 million metric tonnes of metal-enriched tailings were disposed into
the Coeur d'Alene River between 1886 and 1968 (Long, 1998).
Geochemical analyses of riverine sediments in the Spokane River
by the Washington Dept of Ecology (Johnson, 1999), the US Geological
Survey (Grosbois and others, 2001; Box and others, in prep.) and an EPA
contractor (URS Greiner, 2000, 2001) have indicated that Spokane River
sediments are variably enriched in metals derived from those tailings.
In this report we present a surficial geologic map (plates 1 through 8)
of the unconsolidated deposits within and along the Spokane River in
eastern Washington between the Idaho stateline and the confluence with
Latah Creek about 20 miles downstream. Existing sample datasets for
sediments and soils in and along the Spokane River are also located on
the map and the surficial geologic unit that was sampled is noted.
This work was undertaken in cooperation with the Washington Department
of Ecology and the Environmental Protection Agency.