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t3.0 GROUNDWATER MONITORING .; 3.1 Groundwater Sampling Activities JJW commissioned Del-Tech to conduct groundwater monitoring and sampling activities on December 17, 1999. Prior to purging the five wells and collecting groundwater samples, the ' depth to static groundwater was measured and recorded in the four of the five wells (excluding MW-2). The current groundwater gradient and flow directions are presented in Table I and Figure 3. Following water depth measurements, a 12-volt DC pump was used to purge the ' groundwater monitoring wells until at least two or more of the readings for temperature, pH, conductivity, and oxidation-reduction potential (ORP) approximately stabilized. Approximately 5 to 36 gallons were purged from each well, which corresponded to three well volumes. ' Following well purging and recharge, ground-water samples were collected with polyethylene, well-dedicated, disposal bailers and poured into precleaned 40 milliliter glass vials and one liter amber glass jars. Following collection, the water samples were immediately placed on ice in a ' cooler. Specific site conditions and sampling parameters can be found in the Well Sample Field Logs included in Appendix B. Del-Tech did not experience any ambient petroleum-like odors above the monitoring wells except a gasoline odor in the new well MW-5. ' The groundwater samples were transported under chain-of-custody to BSK Analytical Laboratories, a State of California certified analytical laboratory (Certification No. 1180). BSK analyzed the groundwater samples for the following parameters per the San Joaquin County ' Environmental Health Division directive: - Total petroleum hydrocarbons as gasoline (EPA method 8015 modified); t - The aromatic volatile fuel components BTEX (EPA method 8020); Cumulative groundwater analytical results are summarized in Table Il. The analytical ' laboratory data sheets can be found in Appendix A. 3.2 Groundwater Sample Laboratory Analytical Results ' Laboratory analyses indicated that aromatic volatile hydrocarbons (BTEX) and total petroleum hydrocarbons as gasoline (TPH-g) were detected in wells MW-2 and MW-5 above method ' detection limits. Groundwater samples collected from MW-1, MW-3 and MW-4 did not contain TPHg or BTEX components above method detection limits. At the direction of the San Joaquin County Environmental Health Division, the water samples are no longer analyzed for the ' petroleum oxygenate MTBE since it has not been a factor at this site. Monitor well MW-2 contained 1400 µg/l_ of TPH-g and 29 gg/L of benzene. MW-5 had levels of TPH-g at 1800 µg/l_ and benzene at 5.2 µg/L. See Table 11 for Cumulative Groundwater Analytical Results. The analytical laboratory data sheets can be found in Appendix A. 1 ; r 2 JJW GEOSCIENCES Inc.