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GEOMA-rRIX <br /> Ms. Katie Hower <br /> Chevron Pipe Line Company <br /> February 17, 1999 <br /> Page 3 <br /> comparison to United States Environmental Protection Agency (U.S. EPA) Region IX <br /> E PreliminaryRemediation Goals RGs PRGs are media-specific concentrations that are <br /> � } p <br /> based on defined levels of carcinogenic or noncarcinogenic risk for a specific exposure <br /> scenario. U.S. EPA Region IX has developed PRGs for residential soil based on an excess <br /> cancer risk of one-in-one million(1x10')or a hazard index for noncarcinogenic risk of 1 (U.S. <br /> EPA Region IX, 1998). As shown in Table 3 the concentrations of the detected PAHs (pyrene <br /> and chryene) are several orders of magnitude less than their respective PRGs, indicating that <br /> the presence of these constituents in soil at the site, including the potential for additivity due to <br /> multiple constituents,-do not pose an unacceptable risk to future on-site residents. <br /> The grab groundwater data collected from B-1 indicate that groundwater is unaffected by <br /> dissolved petroleum constituents. Therefore,the petroleum-affected soil encountered in B-1 is <br /> not a current or potential future source of groundwater degradation. Because the residual <br /> petroleum hydrocarbons found in B-1 do not pose a risk to future on-site residents or a threat <br /> to groundwater quality,we recommend that the Dobler Property be closed by the SJCPHS. <br /> We appreciate the opportunity to provide CPL with our professional environmental consulting <br /> services. <br /> Sincerely, <br /> GEOMATRIX CONSULTANTS, INC. <br /> Mike R. Keim Dawn A. Z o, C.E. <br /> Project Scientist Principa ydro <br /> J geolag st <br />! MRK/nAZ/pp <br /> ]ADoc Safe13000s1C34991doblrpt.doc <br /> Attachments <br /> CC' Elizabeth T. Lu- CPL <br />{ <br /> I <br /> I <br />