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1 <br /> Chevron <br /> UL Chevron <br /> 37 OCT - AM 10: 13 <br /> September 30, 1997 Chevron Pipe Line Company <br /> p 4000 Executive Parkway,Suite 400 <br /> San Ramon,CA 94583 <br /> P.O.Box 6059 <br /> San Ramon,CA 94583-0759 <br /> Mr. Michael J. Infurna,Jr. <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> P.O. Box 388 <br /> Stockton, California 95201-0388 <br /> "Results of Additional Soil and Groundwater <br /> Investigations and Request for Site Closure" <br /> Hanson Property (APN No. 252-040-02) <br /> 7750 Schulte Road, Tracy, California <br /> Dear Michael: <br /> Please find attached the subject report for the Hanson property located in Tracy, California,which <br /> was prepared by Geomatrix Consultants, Inc. (Geomatrix) on behalf of Chevron Pipe Line <br /> Company (CPL). The report summarizes both the previous environmental work performed by <br /> Aqua Science Engineers, Inc. and Geomatrix in 1995 and 1996,respectively, and also describes <br /> the more recent work conducted by Geomatrix between March and July 1997. <br /> Groundwater beneath the site is unaffected by benzene,toluene, ethylbenzene and xylenes <br /> (BTEX),polyaromatic hydrocarbons (PAHs), or total petroleum hydrocarbons characterized as <br /> gasoline or diesel based on two rounds of confirmatory groundwater sampling conducted at the <br /> site in June and July 1997. Low concentrations of PAHs are present in the soil. However, <br /> because no total extractable petroleum hydrocarbons (TEPH) or BTEX have been observed in <br /> site soil, the PAHs present in the soil do not appear to be related to CPL'S former pipeline. It <br /> should be noted that PAHs naturally occur in soil or from non-petroleum combustion sources. <br /> Geomatrix compared the concentrations in soil to health screening criteria (i.e., U.S. <br /> Environmental Protection Agency Region IX Preliminary Remediation Goals [PRGs]). The <br /> comparison showed that PAH concentrations in soil are significantly less than their respective <br /> residential PRGs. <br /> The work and analytical data described in the report are in accordance with CPL's Technical <br /> Approach to Site Evaluation and Decision-Making, Old Valley Pipeline Sites - Central Valley <br /> (March 20, 1997). The results of the recent work indicate that previous petroleum pipeline <br /> operations conducted adjacent to the site are unlikely to have represented a source of petroleum <br /> hydrocarbons in the site subsurface. <br />