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• Lnmted Subsurface Investigation Report- Chevron ion Service Station #9-1$48 October 28, 1997 uarterl Monitonn Groundwater monitoring wells G-1 through C-3 have been monitored and sampled since July 1991 by Blaine Tech Services, Inc. Samples are currently analyzed for Total Petroleum Hydrocarbons as gasoline (TPHg), for benzene, toluene, ethylbenzene, total xylenes (BTEX), and for methyl tert-butyl ether (MTBE) First quarter 1997 groundwater samples collected from C-1 'through C-3 did not contain detectable concentrations of TPHg or BTEX compounds Groundwater samples from wells C-1 and C-3 did not contain concentrations of MTBE However, the groundwater sample from well C-2 contained concentrations of MTBE at 1,100 parts per billion or ppb Monitorinl� Historical monitoring data indicate depth to groundwater has fluctuated from approximately 12 to 20 feet below ground surface (bgs) During the first quarter 1997 monitoring, groundwater was measured at 12 29 to 13 37 feet bgs Historically, groundwater now has been toward the northeast at approximate gradients of 0 002 to 0 008 ft/ft FIELD ACTIVITIES Field work was performed in accordance with the GR Site Safety Plan #6392 01, dated August 23, 1997 GR Field Methods and Procedures are included in Appendix A Underground Service Alert (USA) was notified, and a private utility locator was contracted to clear the boring Iocations prior to GeoProbeO activities Four off-site exploratory soil borings (B1 through B4) were advanced on August 25, 1997 The borings were advanced to a depth of 24 feet bgs The borings were advanced by Fisch Environmental Exploration Services (C57 #683865) using a Geoprobe® rig equipped with a 1 5- inch diameter sampler A G-R geologist observed the drilling activities, described the encountered soil, collected soil samples at 5-foot intervals for possible chemical analyses, and prepared a log of each boring Logs of the soil borings are included in Appendix B Locations of the borings are shown on Figure 2 The Geoprobe® equipment advances the sampler hydraulically, and does not generate any soil cuttings Following,collection of grab groundwater samples, the borings were backfilled to ground surface with neat cement Grab groundwater samples were collected from borings BI through B4 Sample handling procedures are described in Appendix A The samples were delivered under chain-of-custody to Sequoia Analytical (ELAP #1210) in Redwood City, California 639201-3 2