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

SITE INFORMATION PACKAGE FOR NATIONAL REMEDY REVIEW BOARD
PART B, SECTION 11: PREFERRED ALTERNATIVE
benefit to water quality in the South Fork of the Coeur d’Alene. It was not designed to
provide for ecosystem recovery in Canyon Creek and, as a consequence, did not include
stream and riparian improvement actions. In contrast, Alternative 3+(d) includes extensive
stream and riparian improvement measures that would be completed in areas following
remediation to accelerate ecosystem recovery. The interim ecological remedy for OU 3 only
included stream and riparian improvement measures in limited areas.
Alternative 3+(d) is focused on reducing dissolved metals and particulate lead in rivers and
streams and risks to humans and wildlife associated with direct contact with miningcontaminated
materials. The anticipated benefits of the alternative in addressing these
priority issues are described below.
• Dissolved metals in surface water – Dissolved metals have harmful effects on fish and
other aquatic receptors. Approximately 20 miles of the SFCDR and 10 miles of
tributaries have limited and impacted fish populations. Species density and diversity
have been reduced throughout the Upper Basin, and Ninemile and Canyon Creeks have
been observed to be essentially devoid of fish and other aquatic life in areas of mining
impacts. Impacted species include the native bull trout, which is listed as threatened
under the ESA. The AWQC for zinc and cadmium have been exceeded throughout the
SFCDR downstream of areas of mining impacts. Following the implementation of
Alternative 3+(d), the AWQC ratios for dissolved zinc in the SFCDR at Elizabeth Park
and Pinehurst are estimated to be 1.7 and 1.5, respectively (Table B11-2). The estimated
reduction in AWQC ratios is a function of the reduction in dissolved zinc load estimated
for both Elizabeth Park and Pinehurst (65 percent and 62 percent, respectively) following
the implementation of Alternative 3+(d) (Table B11-2). Further reductions in the AWQC
ratios over time, eventually resulting in the attainment of ARARs, are expected as a
result of natural source depletion. The AWQC ratios are also correlated to a set of
defined “fishery tiers” for the Coeur d’Alene Basin (URS Greiner, 2001a) that relate to
the health of a fishery. Table B11-3 presents the definitions and AWQC ratio ranges for
these fishery tiers. The estimated post-remediation water quality for Alternative 3+(d)
represents a Tier 4 fishery, a significant improvement over the current Tier 3 ranking.
The primary differences between Tiers 3 and 4 are that in the Tier 4 fishery, salmonids
are successfully spawning and rearing and sculpin (which are generally absent or
present at very low densities under a Tier 3 fishery) are present at moderate to high
densities. This increase represents a significant improvement in ecosystem and fishery
health.
• Particulate lead in surface water – Particulate lead transported downstream from the
Upper Basin is a continuing source of contamination to the Lower Basin, Coeur d’Alene
Lake, and the Spokane River. Reduction of lead load in sediments transported and
deposited in downstream areas is necessary to prevent recontamination of cleaned-up
areas and to protect humans and wildlife from exposure. The source control and stream
and riparian improvement actions included in Alternative 3+(d) would reduce
particulate lead in surface water in the Upper Basin to a greater extent than would be
achieved with the interim ecological remedy for OU 3 alone.
• Direct contact with mining-contaminated wastes – Heavy metals are present in miningcontaminated
materials throughout the Upper Basin and can pose risks to humans and
B11-6