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/AnE-:: <br /> GEOMATRIX <br /> petroleum and, therefore, not likely related to the former pipeline, the concentrations were <br /> compared to health screening criteria for information purposes. The low concentrations of <br /> PAHs detected in soil samples pose no significant risk to human health based on a comparison <br /> to the U.S. EPA Region IX Preliminary Remediation Goals (PRGs). PRGs are media-specific <br /> concentrations that are based on defined levels of carcinogenic or noncarcinogenic risk for a <br /> specific exposure scenario. The EPA Region IX has developed PRGs in soil for residential <br /> exposure scenarios based on an excess cancer risk of one-in-million (1 x 106) or a hazard index <br /> (for noncarcinogenic risk) of 1 (EPA Region IX, 1996). As shown in Table 3, the PAH <br /> concentrations or detection limits are significantly less than their respective residential PRGs. <br /> Groundwater beneath the site is unaffected by BTEX, PAHs, TRPH, or TEPH based on <br /> samples collected from well TW-1. This result is consistent with the finding that site soil is <br /> unaffected by petroleum. The low concentrations of PAHs detected in the grab groundwater <br /> sample from SB-2 are likely the result of interference from low concentrations of PNAs in soil <br /> particulates entrained in the relatively turbid sample. These detections were not confirmed by <br /> more representative groundwater data from well TW-1 from two sampling rounds. <br /> In summary, these results confirm that residual petroleum hydrocarbons associated with the <br /> former Old Valley Pipeline are not present in site soil or groundwater. It is recommended that <br /> the Hanson Property be closed by the PHS-EHD. <br /> L\WPD0CS\4097\ADDLINVB.D0C 9 <br />