ARCHIVED REPORTS XR0000211 - Laserfiche WebLink

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NECTIONTHRE]E inhalation of particulates PRGs are to be used for a single medium (e g soil, air, or water) The exposure pathway calculations for soil exposure assume that there is no paving and that the site is bare soil PRGs do not consider impact to groundwater The following table compares EPA Region IX PRGs (EPA Region IX, 1998) for soil for residential and industrial sites with the 95% UCL concentrations calculated for the chemicals of concern in the surface soil at the site(Table 3-1) Residential Sod PRG Industrial! Soil PRG Shop 10 Surface Soil mg/ko mg/kg 95% UCL mgNg Benzene 062 1 4 071 Toluene 520 520 25 88 Ethylbenzene 230 230 1422 Xylene fm-xylene) 210 210 49 65 The 95% UCL concentrations in the surface soil are significantly lower than EPA Region on 1xs health- based PRGs for industrial sites The 95% UCL for benzene exceeds the residential soil PRG Residential soil PRGs are not appropriate for the site because they assume that individuals will have direct contact with the soil through ingestion, dermal absorption, inhalation of particulates, and inhalation of volatiles for 30 years at 350 days per year The residential soil PRG also assumes that a child will be located on site for six years PRGs do not consider impact to groundwater Fate and transport modeling was used to evaluate potential impacts to groundwater beneath the site j M.3 Groundwater Data Details on the groundwater sampling and analysis can be found in other reports (Woodward-Clyde 1990, Alton Geoscience, 1992,Environmental Assessors, Inc 1994, Geocon, 1995, and PSI, 1997 and 1998) Groundwater data (Table 2-2) were evaluated based on sampling dates and well screen intervals Table 3-3 presents the statistical data for groundwater samples collected from 1987 through 1998 Table 3-4 summarizes the older groundwater samples that were collected from 1987 through 1992 The more recent groundwater data that was collected from 1993 through 1998, are summarized in Table 3-5 The depth to the groundwater table was at approximately 57 feet bgs in the late 1980s and early 1990s when the first monitoring wells were installed The groundwater table steadily decreased to approximately 68 feet bgs in 1993,below the screen interval The wells that were installed in 1992 and w°odwMd4lPm T%I 907W73008NAWMCKTQ"8K RT%SHMEP#7 DOCWFMB-N T3009 %SNA 3-3