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Dames & Moore, 1999 - USDA Forest Service

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(RAOs) section of the Feasibility Study. This section is not intended to substitute or replace discussion on<br />

establishing RAOs at the Site, which are established as cleanup goals for protection of human health and the<br />

environment. The purpose of the comparison is to focus the discussion of laboratory results on specific<br />

areas related to the Site where background influences are considered and where chemicals occur at<br />

concentrations that are above background and preliminary chemical-specific ARARs. The background data<br />

and chemical-specific ARARs used in the evaluation of each media are provided in the following sections.<br />

5.1.1 Soil<br />

Soil samples were collected in the fall of 1998 from the Railroad Creek drainage generally upvalley of<br />

mining activities associated with the Holden Mine Site to assess area background metal concentrations.<br />

These data are discussed in Section 5.2. Site data were compared to area background concentrations as an<br />

initial step in the assessment of PCOCs.<br />

Published background soil data for the Yakima Basin (Ecology, 1994) is also available for comparison to<br />

Site data, where constituent background levels are not available. The MTCA (WAC 173-340) cleanup<br />

levels were also used for comparison. The preliminary chemical specific ARARs and TBCs for soils are<br />

shown in Table 5.1 - 1 and include:<br />

Railroad Creek drainage area background values<br />

• Background values for the Yakima Basin published by Ecology<br />

• MTCA Method A and Method B soil cleanup levels, where available<br />

MTCA establishes procedures for calculating cleanup levels at sites where releases of hazardous substances<br />

pose a threat to human health or the environment. MTCA Method A involves comparing measured<br />

compound of concern concentrations to cleanup standards developed for a limited number of compounds.<br />

Method A is intended to provide protective cleanup levels at sites undergoing routine actions or for sites<br />

with a limited number of compounds of potential concern. Method A values derived by Ecology were<br />

based on considerations of technical feasibility and aesthetics, as well as other considerations, and are not<br />

strictly based on toxicological properties. The Interim Interpretive and Policy Statement for total petroleum<br />

hydrocarbons (TPH) published by Ecology in 1997 allows the calculation of revised W H cleanup levels<br />

that are site-specific and protective of groundwater and human health.<br />

MTCA Method B presents cleanup levels for individual compounds of potential concern using applicable<br />

state and. federal laws or algorithms as specified in WAC 173-340-720 through 173-340-750. For<br />

remediation of potentially carcinogenic substances, cleanup levels are based on the upper bound of the<br />

estimated excess lifetime cancer risk of 1 .OE-06. For individual non-carcinogenic substances, cleanup<br />

levels are set at concentrations which are expected to result in no acute or chronic toxic effects to human<br />

health or the environment. Calculated cleanup levels are based on the most recent available reference doses<br />

and carcinogenic potency factors, in addition to standardization exposure parameters established by<br />

Ecology.<br />

Site soil was initially compared to area background levels. If the concentration was above background, the<br />

data were then compared to MTCA Method A if available. Where MTCA Method A levels were<br />

unavailable, Method B levels were used.<br />

\V)M-SEAI\VOLI\COMMOMWP\WPDATAUH)~PORTSWOLDEN-XRN-O.doc 5-2 DAMES<br />

& MOORE<br />

17693-005-0 19Uuly 28.<strong>1999</strong>;11:09 AMDRAFT FINAL. RI REPORT

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