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j <br /> Pacific Gas and Electric Company Environmental Services <br /> P.O.Boz 7640 <br /> i San Francisco,CA 94120 <br /> May 26, 1989 4151972-7000 <br /> Direct Dial 4151972 Ig1� <br /> Telecopy 4151972-6888 l 3A <br /> Ms. Antonia R. J. Vorster, Senior Engineer MAY 3 01989 <br /> California Regional Water Quality Control Board - ENVIRONiAEiNTALHEALi' <br /> Central Valley Region PERMIT/SER\'i(-F^ <br /> 3443 Routier Road <br /> Sacramento, California 95827-3098 <br /> Dear Ms. Vorster: <br /> Subject: Site Investigation for the Former <br /> Manufactured Gas Plant Site at <br /> Tracy, California (SQ-SK-TRA) <br /> I have attached for your review and comment the report: " Site <br /> Investigation for the Former Manufactured Gas Plant Site at Tracy, <br /> California ", prepared by Pacific Gas and Electric Company's (PG&E) <br /> Technical and Ecological Services Department, dated April, 1989. <br /> The work was conducted according to the site investigation workplan <br /> that you approved on October 18, 1988. The objectives of the <br /> investigation were to: <br /> a) define the extent of manufactured gas plant (MGP) residues <br /> in the soil and groundwater at the Tracy site; <br /> b) identify the chemical composition of the MGP residues <br /> encountered at the site; <br /> c) define those hydrogeologic characteristics that could <br /> affect movement of any encountered MGP residues; and <br /> d) estimate the potential for the offsite migration of MGP <br /> residues. <br /> Analyses of the soil samples collected from the soil borings <br /> drilled on-site indicated that polynuclear aromatic hydrocarbons <br /> (PAH) and total petroleum hydrocarbons (TPH) were present in <br /> generally low concentrations (i.e. <10 ppm) across the site. <br /> Pockets of TPH were encountered in a few locations on the site; <br /> chemical compounds associated with the operation of the former <br /> manufactured gas plant appear to be confined to surficial soil less <br /> than four feet below grade. <br /> No PAHs were detected in groundwater samples from the on-site <br /> wells. Results from one well (OW-2) installed next to the location <br /> of the former underground gasoline storage tank indicated the <br /> presence of chemicals not associated with MGP residues such as TPH <br /> (0.9 ppm as gasoline) , benzene (294 ppb) , <br />