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The water sample was also analyzed at PG&E's chemical laboratory in San Ramon for glycol compounds. The results of these analyses were transmitted to the San Joaquin County Local Health District in a letter date March 23, 1988, and are summarized in Table 1. The chemical analyses of the samples indicated that petroleum hydrocarbons were present in the three soil samples and the water sample collected from the site. Benzene and toluene were not detected in samples S-1 and S4. The water sample(S4)also contained levels of diethylene glycol,triethylene glycol, and tetraethylene glycol;however, these glycol compounds are not regulated per Chapter 11, Title 22 of the California Code of Regulations nor are they contained in the water quality goals listed in Central Valley Regional Water Quality Control Board report entitled"The Designated Level Methodology for Waste Classification and Cleanup Level Determination", dated October 1986 (revised September 1991). On May 19, 1988, Groundwater Technology Inc. performed three exploratory soil borings in the immediate vicinity of the reboiler discharge line (Figure 2). The purpose of this study was to evaluate the vertical extent of petroleum hydrocarbons in the soils and to determine the feasibility of using in-situ bioremediation techniques to remediate the affected soils. Selected soil samples from each borehole were analyzed for total petroleum hydrocarbons by EPA Methods 8015 and 418.1,triethylene glycol by EPA Method 8015, and benzene,toluene, ethylbenzene and xylenes by EPA Method 8020. In addition, one soil sample was analyzed for volatile organic compounds by EPA Method 8240, polychlorinated biphenyls by EPA Method 8080, and semivolatile compounds by EPA Method 8270. The chemical analytical results of these soil samples (Table 2)indicate that petroleum hydrocarbon compounds were present in the shallow soils adjacent to the discharge line. Triethylene glycol was reported in one soil sample at a concentration of 12,000 mg/kg. The results of the analyses for the other compounds indicate very low to non-detectable concentrations of volatile organic compounds and non-detectable concentrations of PCB's and semivolatile compounds. In response to a request by PG&E's Gas Production and Storage Department, TES prepared a work plan entitled "Work Plan, Subsurface Investigation, PG&E's Lathrop Gas Dehydrator Station" which addressed additional site assessment activities at the site. The work plan was submitted to SJCPHSD for approval on October 29, 1992. cca/08/18/93/9449arpt.doc/mkn4 1-5