Dames & Moore, 1999 - USDA Forest Service

Lead was present in the maintenance yard and lagoon area soil at concentrations exceeding 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 and USEPA guidelines for residential
sites, the exposure times expected at the site are significantly less than the assumed residential exposure
time upon which the guidelines are based. Therefore, concentrations of lead in soil in these two areas are
not expected to cause effects in exposed populations.
Total petroleum hydrocarbons were present in soil at the maintenance yard and lagoon area at levels
exceeding MTCA Method A level. Because no toxicity criteria exist for these complex mixtures. site-
specific risks were not evaluated. However, as with lead, exposure times and durations in these areas are
expected to be significantly lower than would be assumed for development of the Method A level. and
therefore TPH is soil at these locations is not expected to be of concern for the limited time period that
maintenance workers and recreational users are exposed populations. In addition, remedial actions in these
areas should significantly reduce soil TPH concentrations.
7.1.5.2 Sediment
Sediment sample results were divided into four.areas based on physical location, as follows: 1) Railroad
Creek adjacent to the Site, 2) Railroad Creek downgradient of the Site, 3) Copper Creek, and 4) Copper
Creek diversion. Constituents exceeding screening criteria in the four areas were selected as IHSs and
evaluated in the site-specific risk assessment.
Cancer risks and noncancer hazard quotients for all IHSs in all exposure areas were below the allowable
MTCA cancer risk and hazard quotient. Cancer risks ranged from 1.08 x lv7 for beryllium in all three areas
to 4.72 x lo4 for arsenic in Railroad Creek sediments adjacent to the site. The hazard quotients ranged from
6.25 x 10" for beryllium in all four areas to 1.68 x 10" for molybdenum in Railroad Creek sediments
adjacent to the site.
7.1.53 Air
Based on historical air monitoring data, the only constituent selected as an IHS for air during the screening
process was manganese. The site-specific hazard quotient calculated for manganese in air was 4.0 x lV1,
which is below the allowable MTCA hazard quotient. There were no cancer risks calculated for this media
since the IHS was not a carcinogen.
In order to evaluate current conditions and the potential for soiVtailings in each exposure area to be
transported to air via fugitive dust emissions, a simple USEPA model was utilized to develop a particulate
emission factor (PEF) for each exposure area. Each exposure area was then screened using conservative
cleanup criteria calculated from the PEF. Screening of constituent concentrations resulted in the elimination
of the vegetable garden, baseball field. wilderness area, maintenance yard, and tailings as areas of concern.
Constituents exceeding screening criteria in the remaining three surface soil areas were selected as IHSs and
evaluated in the site-specific risk assessment for transfers to air.
Cancer risks based on transfers from soil to air for all IHSs in all exposure areas were below the allowable
MTCA cancer risk and hazard quotient. Cancer risks ranged from 3.96 x lug for arsenic in the USFS guard
station soil (transferred to air) to 5.69 x 1 o4 for chromium in Holden village soil (transferred to air). There
were no hazard quotients calculated for this exposure pathway.
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17693405419Uuly 27.1999:5:16 PMDRAFT FINAL RI REPORT
7-36 DAMES & MOORE