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PRETANK OQSURE SITE ASSESSMENT 3725 Tracy Boulevard, Tracy, CA Delta Project No. 40-89-012 Page 4 LFollowing removal of the steel tanks in 1985, soil samples were collected from below the three tanks. In addition, water samples were collected from the bottom of the excavation. The results are included in the analytical report prepared by Canonie Engineers (Appendix B). Samples were analyzed for total extractable hydrocarbons, benzene, toluenes, xylenes, ethylene dibromide, and organo-lead. In summary, soil samples indicated a TPH range of nondetectable (at 1 ppm) to 40 ppm in soils, and from not detected to 0.7 ppm in water. Organo-lead, ethylene dibromide, benzene, and toluene were below detectable levels in all soil samples analyzed. Xylenes were detected in the water sample at a concentration of 66 part per billion (ppb) and in one soil sample at a concentration of 1.2 ppb. The depth represented by these samples is not known. 2.4 Snill/Leak History We are not aware of any leaks or spills that have been reported by this site. At this time, we are not able to estimate the quantity of hydrocarbons that may have been introduced to the environment. In-line leak detectors are currently used to monitor the double-walled tank annulus and dispensing lines. The monitoring systems have been checked annually to verify proper function and operations since installation in 1985. All systems have passed each annual test (personal communication, Mr. Bert Russell, Shell Oil Company, 1988). 2.5 Well inventory An inventory of existing water supply wells within a one-half mile radius of the site was conducted by reviewing California Department of Water Resources records. A total of 22 wells were identified. T le ear drilled and s f each of the res ective wells identified, eneral the wells 'used for domestic water supply have an average depth of approximately 200 feet and are cased for the first 1.00__feet__ In addition, there appears to be a water supply well 1 Iocated on site of unknown construction and depth. The well appears to have been installed approximately at the time of regional site construction and was taken out of use during 1974 when public sewer and water service were connected to the facility. 2.�Underzroun4 Utilities Public utilities are located below Tracy Boulevard and are present as illustrated on Figure 2. Approximately location where utilities enter on the site are also indicated. It is unknown at this time whether or not the facility utilized an on-site septic system