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Dames & Moore, 1999 - USDA Forest Service

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Surface Soil<br />

Cancer risks and noncancer hazard quotients ingestion of all IHSs in all exposure areas were below the<br />

allowable MTCA cancer risk and hazard quotient. The cancer risks ranged from 8.91 s 10''~ for ber?.lliurn<br />

at the USFS guard station to 5.66 x lod for arsenic in the maintenance area. The hazard quotients ranged<br />

from 4.1 5 x lod for beryllium at the USFS guard station soil to 2.04 x 10" for copper in the lagoon area soil.<br />

Lead was detected in maintenance yard and lagoon area soil at concentrations exceeding the screening<br />

criteria (1070 mgkg in the maintenance yard and 620 mgkg in the lagoon area). However. because no<br />

toxicity criteria exist for this constituent, site-specific risks could not be evaluated. USEPA guidelines<br />

recommend a cleanup level of 400 mg/kg for lead in soil at residential sites based on prediction of blood<br />

lead levels in children. Neither of these sites is residential and exposure time is expected to be significantly<br />

less than an assumed residential exposure duration of 7 day per week exposures for 30 years. The highest<br />

exposure concentrations are less than three times higher than the USEPA recommended levels. Therefore,<br />

concentrations of lead in soil in these two areas are not expected to cause effects in exposed populations. In<br />

addition, remedial actions in these two areas will likely significantly reduce the concentrations present.<br />

Total petroleum hydrocarbons were present in soil at the maintenance yard and lagoon area at levels<br />

exceeding h4TCA Method A level. Exposure concentrations ranged from 140 mglkg gasoline range<br />

hydrocarbons in the maintenance yard to 12,000 mg/kg diesel range hydrocarbons in the maintenance yard.<br />

Because no toxicity criteria exist for these complex mixtures, site-specific risks were not evaluated.<br />

However, as with lead, exposure times and durations at the maintenance yard and lagoon area are expected<br />

to be significantly lower than would be assumed for development of the Method A level, and therefore TPH<br />

is soil at these locations are not expected to be of concern for the limited time period that maintenance<br />

workers and recreational users are exposed populations. In addition, remedial actions in these areas should<br />

significantly reduce soil TPH concentrations.<br />

Sediment<br />

Cancer risks and noncancer hazard quotients for all IHSs in all exposure areas were below the allowable<br />

MTCA cancer risk and hazard quotients. Cancer risks ranged from 1.08 x 10'~ for beryllium in all three<br />

areas to 4.72 x 10" for arsenic in Railroad Creek sediments adjacent to the site. The hazard quotients ranged<br />

from 6.25 x l O" for beryllium in all three areas to 1.68 x 10" for molybdenum in Railroad Creek sediments<br />

adjacent to the site.<br />

- Air'<br />

The site-specific hazard quotients calculated for manganese in air was 4.0 x lo-', which is below the<br />

allowable MTCA hazard quotient. There were no cancer risks calculated for this media since manganese<br />

was not a carcinogen.<br />

Particulate Emissions fiom Soil<br />

In order to evaluate current conditions and the potential for soiVtailings in each exposure area to be<br />

transported to air via fugitive dust emissions, a simple USEPA model was utilized to develop a particulate<br />

emission factor (PEF) for each exposure area. Cancer risks based on transfers from soil to air for all IHSs in<br />

all exposure areas were below the allowable MTCA cancer risk. Cancer risks ranged from 3.96 x lo4 for<br />

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1769MOS019Uuly 27.199QJ: 16 PMDRAFT FINAL RI REPORT

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