ARCHIVED REPORTS XR0001483 - Laserfiche WebLink

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440 West Charter Way, Stockton, California June 29, 1992 Texaco Environmental Services Page 2 All wells were sealed with cement grout to the surface Construction details of the soil vapor extraction wells are presented on the drill logs in Attachment I GROUNDWATER MONITORING On May 15, 1992, water table elevations at the site were an average of 0 75 foot higher than levels reported the previous quarter The estimated flow_direction of the groundwater is divergent from MW-2 but dominantly to the east Figure 2 is a potentiometric surface map constructed from the May 15, 1992 monitoring data Table 1 presents a cumulative summary of the most recent and four preceding quarterly monitoring events GROUNDWATER SAMPLING Prior to water-sample collection, the groundwater monitoring wells were purged until pH, temperature and conductivity readings were stabilized or until dry (Table 2) A Teflon" sampler, cleaned with an industrial detergent and distilled water, was used for the groundwater ' sampling The water samples were then transferred to 40-milliliter glass vials with Teflon"- septum caps, preserved on ice, and transported to a California state-certified laboratory, accompanied by a chain-of-custody manifest The water samples were analyzed using modified EPA methods 50301802018015, which measure concentrations of total petroleum hydrocarbons-as-gasoline (TPH-G), and benzene, toluene, ethylbenzene and xylenes IBTEX} MW-1 was not sampled due to the presence of SP GROUNDWATER ANALYTICAL RESULTS Concentrations of TPH-G in the May 15, 1992 groundwater samples ranged from 190 parts per billion (ppb) to 81,000 ppb, benzene concentrations ranged from 2 6 ppb to 18,000 ppb (Figures 3 and 4) Analytical results, along with results from the four previous sampling events are presented in Table 3 Copies of the laboratory analyses reports are presented in Attachment Il CROEJNpWA3`ER TECHNOLOGY