Final Site Information Package for National Remedy Review Board ...

4. Site Characteristics
The Upper Basin of the Coeur d’Alene River occupies approximately 300 square miles of
land surface in the Panhandle of northern Idaho. The area includes the SFCDR and
tributaries downstream to the confluence of the South and North Forks of the river. The
Upper Basin is also the primary source area for most of the mining-related waste materials;
therefore, within the Upper Basin, elevated concentrations of metals are present in waste
piles, stream beds, and floodplains primarily from the discharge or erosion of mill tailings
and other mine-generated waste into rivers and streams. The SFCDR and many of its
tributaries have undergone extensive channelization and additional alterations as a result of
mining-related activities and other anthropogenic activities, including the construction of
I-90.
Information provided in this section is based on the work documented in the 2001 RI and FS
Reports (USEPA, 2001c, 2001d) and the ROD for OU 3 (USEPA, 2002), and incorporates
additional study and monitoring data obtained from 2002 through 2009. Specific sources of
data used in this analysis include the BEMP for OU 3, the EMP for OU 2, the Coeur d’Alene
Basin Remedial Action Monitoring Program, U.S. Geological Survey (USGS) gauging station
data as reported on the USGS website, and the results of discrete sampling events.
4.1 Nature and Extent of Contamination
The long history of mining activities within the Upper Basin, combined with the dynamic
and complex hydrologic system and anthropogenic modifications to that system, have
resulted in widespread and commingled sources of contamination.
4.1.1 Sources and Locations of Mining Wastes
Contaminant sources as identified by BLM in 1999 are widespread in the Upper Basin,
extending up nearly every drainage area (Figure A-2) (USEPA, 2001c, 2001d). Several of
these sources are not discrete locations, but rather diffuse areas extending along river and
creek segments.
Contaminated media that potentially affect human health and the environment are surface
water, soil, sediments, and groundwater. During development of the 2001 FS Report
(USEPA, 2001d), the contaminated media were grouped by source type to help characterize
the nature and extent of contamination and to develop remedial alternatives. These
contaminant source types, based on the mining-related primary sources and secondary
sources, with estimated volumes (for OU 3), are as follows.
• Mining-related primary sources:
− Tailings: 11 million cubic yards
− Waste rock: 11.7 million cubic yards
− Adit drainage: 101 pounds of zinc per day
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