Dames & Moore, 1999 - USDA Forest Service

did not have health-based MTCA Method A or Method B levels (due to an absence of inhalation toxicity
criteria) which could be used for screening. While these constituent concentrations appear to be elevated,
they are not expected to present an unacceptable risk to receptors via the inhalation route at the
concentrations present, particularly given the short expected exposure period for this area and likely ground
cover in the area.
Tailings
Historical and 1997 tailings samples from tailings piles 1, 2 and 3 were collected and analyzed. The
maximum concentrations observed, regardless of location, were used as the source concentrations for
comparison to the screening criteria based on soil ingestion. The background concentrations used for
screening were statistically derived or obtained from Natural Background Soil Metals Concentrarions in
Wushington State (Ecology, 1994) for the Yakima basin. In addition, for those constituents which did not
have an available area background or Ecology natural background level, background levels for the State of
Washington (Dragun, 1991) are presented for comparison purposes. No constituents are eliminated as lHSs
based on the Dragun ranges, however.
The tailings have been adequately characterized to complete the screening assessment. All results were
assumed to represent near surface conditions on the tailings piles. The results of the screening for this
exposure area are presented in Table 7.1-20. All constituents were eliminated as IHSs based on this
screening.
Particulate Emissions from Tailings
The tailings data were also screened for particulate emissions potential. The results of the particulate
emissions screening for this exposure area are presented in Table 7.1-21. All constituents were eliminated
as IHSs based on this screening. Aluminum, copper, lead, molybdenum, selenium, silver, thallium, zinc,
and cyanide did not have health-based MTCA Method A or Method B levels (due to an absence of
inhalation toxicity criteria) which could be used for screening. Silver concentrations appear to be within the
background range for the State of Washington. While other constituent concentrations appear to be
elevated, they are not expected to present an unacceptable risk to receptors via the inhalation route at the
concentrations present, particularly given the short expected exposure period for this area.
Air
Post-remediation air monitoring data collected in 1994 by the USFS were screened. All data collected was
used in the screening and the maximum detected concentrations were used as the source concentrations.
The data were collected from locations onsite, downwind, and upwind and are assumed to be representative
of conditions onsite and in and around Holden Village. Background air concentrations were not evaluated
in the screening due to a lack of information on site conditions at the time of sampling. It should be noted
that short-term air concentrations measured during this monitoring event are not necessarily comparable to
cleanup levels based on long-term exposures; however, the cleanup levels were utilized anyway as a very
conservative screening tool. The results of the screening for this exposure medium are presented in Table
7.1-22. Manganese was the only constituent selected as an IHS based on this screening.
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