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EXECUTIVE SUMMARY • Groundwater monitoring-was conducted at 3931 Newton Road on July 27, 2004 The depth to groundwater was measured in five monitoring wells, and a water sample was collected from each well for laboratory analysis The samples were analyzed for Total Petroleum Hydrocaibons in the diesel range The water elevation data were contoured to yield a map of the piezometric surface Continuing the pattern of the past few quarters, the elevation contours form an arc in the southern part of the site area and the water table is tilted to the south Three monitor wells are located downgradient (south) of the former UST facility, and Total Petroleum Hydrocarbons in the diesel range were detected in all three wells Concentrations range from 130 parts per billion in GT-9 to 680 parts per billion in G]'-6 (identical to the concentration detected in this well in December 2003) Diesel was not detected in either GT-3, located adjacent to the UST facility, or in GT-5, located upgradient (west) of the facility No sample was collected from the Gillies domestic well 10 INTRODUCTION The project site is located in an industrial area on the northeast outskirts of Stockton near U S Highway 99 (Figure 1) Originally agricultural property,,the site was developed as a commercial Mtruck terminal in 1973 A diesel and gasoline fueling facility, consisting of two underground storage tanks (UST's), was formerly present on the south side of the storage yard (Figure 2) This facility was removed in 1989, and evidence of soil contamination was discovered Several thousand cubic yards of contaminated soil were removed from the UST excavation in 1990 and treated using above-ground enhanced bioremediation methods, and several phases of drilling have been completed since then to investigate the extent of groundwater contamination and residual soil contamination Groundwater monitoring is normally conducted on a quarterly basis, but no monitoring was performed during the first or second quarters of 2004, while the San Joaquin County Environmental Health Department(EHD) reviewed the report for the fourth quarter of 2003 and a subsequent request for site closure In a letter dated June 17, 2004, EHD denied that request and instructed Gillies Trucking to continue groundwater monitoring This report presents the results of the July 27 monitoring event 2.0 PROCEDURES Groundwater samples were collected from five of six monitoring wells after the depth to groundwater was measured and the wells were purged of standing water Depth measurements and purge data were recorded on the Well Monitor Report (Appendix A) The samples were collected in disposable plastic bailers and transferred to 1-liter amber bottles, then labeled and placed into a i 1