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r_ monitoring wells were installed at and in the vicinity of the Exxon site. As of the date of this report, ten groundwater monitoring wells, four groundwater extraction wells, one groundwater re-injection well, two piezometers, two sots vapor monitoring wells, and four soil vapor extraction wells had been installed at and in the vicinity of the former Exxon Service Station Remedial systems for groundwater extraction, treatment and re-injection and soil vapor extraction had been designed for the former Exxon Service Station and permits submitted to PHS/EHD and the Regional Water Quality Control Board (RWQCB) by December of 1987, but following public hearings and meetings with regulatory agencies, as of the date of preparation of this report, approval for the installation of remedial systems had still not been granted. Regional groundwater flow was stated by Mr. Michael Collins of the PHS/EHD to be to the northeast due to the effects of groundwater pumping for agricultural uses, and groundwater flow direction determined from water level measurements collected at the Exxon site has been described to be consistently to the north/northeast (Mr Terry Winsor, of EA Engineering, Science and Technology, the investigators of the Exxon site, pers. Comm ). Groundwater sample analytical results indicate the presence of free-phase petroleum hydrocarbons in monitoring wells MW3 and MW6, located in the northeastern comer of the former Exxon Service Station, and significant concentrations of dissolved petroleum hydrocarbons in monitoring wells located to the northeast of the Exxon site. For example, groundwater samples collected from monitoring well MW10, installed in Rose Mane Lane approximately 75 feet to the northeast of the Exxon site, contained 35,000 ug/I of total petroleum hydrocarbons as gasoline (TPH-G) in August 1989. in addition, off-site investigation of groundwater quality by EA had involved the installation of groundwater monitoring wells immediately downgradient of the Shell Service Station, and the 7-11 convenience store (MW8 and MW9, respectively) Maximum concentrations of TPH-G in groundwater samples collected downgradient of the Shell Service Station and 7-11 Convenience Store were 120,000 ug/l and 35,000 ug/1, respectively. Soil samples collected from well MW8 contained up to 3,800 mg/kg TPH-G. McLaren/Hart believes that the groundwater flow direction in the vicinity of the Exxon Service Station has been well established to be to the north/northeast, away from the subject property, and is not believed to have impacted the subject site. 2.12 Shell Service Station Four underground storage tanks were removed from the active Shell Service Station in May, 1990, and soil samples collected from beneath the underground storage tanks contained up to 4,300 mg/kg of TPH-G Based on the results of the tank removal soil sampling, four groundwater monitoring wells and two soil vapor extraction wells were installed at the Shell site, and maximum concentrations of petroleum hydrocarbons in groundwater samples iiiaicdi 4