Dames & Moore, 1999 - USDA Forest Service

arsenic in the USFS guard station soil (transferred to air) to 5.69 x lo4 for chromium in Holden Village soil
(transferred to air). There were no hazard quotients calculated for this pathway.
Surface Water and Fish
Hazard quotients for molybdenum in Copper Creek were 6.44 x 10.' for ingestion of water and 3.1 8 r 1 0.'
for ingestion of fish, both of which are below the allowable MTCA hazard quotient. There were no cancer
risks calculated for this media since the IHS was not a carcinogen.
See~s and Mine Portal Drainage
Seep and portal drainage data were evaluated separately. Noncancer hazard quotients for all IHSs in both
media were below the allowable MTCA hazard quotient. There were no cancer risks calculated for these
media since IHSs were not carcinogens. The hazard quotients ranged from 1.15 x 10.* for manganese in the
1500-level main portal drainage to 5.3 1 x 10" for cadmium in the 1500-level main portal drainage.
Lead was present in both seeps and the 1500-level main portal drainage at concentrations exceeding the
MTCA Method A level; however, because no toxicity criteria exist for this constituent, site-specific risks
could not be evaluated. While exposure concentrations exceed MTCA Method A level, the exposure
frequencies and water ingestion rates expected at the site are significantly less than those upon which the
cleanup criteria is based. Therefore, concentrations of lead in seeps and portal drainage are not expected to
cause effects in potentially exposed populations.
Cumulative Risk
MTCA requires the evaluation of cumulative risk when Method C levels are used. ,Evaluation of cumulative
cancer risk was accomplished by summing all cancer risks for each receptor population. Cumulative risk for
noncancer effects was evaluated by summing hazard quotients for each IHS associated with the same toxic
effect endpoint
Cumulative cancer risks for forest service workers (I. I6 x 10.~) are less than the acceptable level of I x 10"
(Table 7.1-43). Cumulative cancer risks for village residents/recreational users are 1.10 x 10". Ingestion of
soil from the "storage" location in the maintenance yard is the primary contributor to the cumulative risk
within the rounding error of 1 x 10". When. adjusted to the appropriate number of significant digits, the
cumulative risk is the same as the acceptable level of 1 x 10". In addition, this cum~ilative risk assumes that
the children exposed recreationally during the summertime grow up to become residents of Holden Village
who work in the maintenance yard. This assumption is obviously extremely conservative.
All noncancer hazard quotients are less than the acceptable level of one, with one exception. Using a
combination of extremely conservative exposure assumptions that are unlikely to occur resulted in the
cumulative hazard quotient for nephrotoxic effects (non-cancer kidney . effects) for village
residents/recreational users of 1.26. This is due primarily to cadmium in portal drainage. This cumulative
conservative risk evaluation assumes that the receptor ,is daily drinking one-half liter of 1500-level main
portal drainage water, one-half liter of seep water, and one-half liter of Copper Creek water, as well as
ingesting soil from the lagoon area and maintenance area, ingesting soil, and eating fish caught from onsite
areas on exposed days. This combination of exposures is extremely conservative and highly unlikely to
occur. The water ingestion rates used in the calculation of Method B criteria assumed that one-half of a
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& MOORE
17693405419Uuly 27.1999.5:16 PMDRAFT FINAL RI REPORT