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Report-Sod and Groundwater investigation C s Car Wash 6320 Pacific Sc St Stockton CA ' lime 12,3998 Page-4 4 INVESTIGATION RESULTS 4 1 FIELD OBSERVATIONS/SITE GEOLOGY Field observations made during the investigation include visual observations pertaining to site geology and the detection of petroleum hydrocarbons by the OVA-PID and/or by odor OVA-PID measurements and the presence or absence of petroleum hydrocarbon odor are noted on the soil boring logs, included in Appendix B of this report Inter-bedded clay, silt, and sand are present in the shallow subsurface of the Canepa's Car Wash site From the surface to a depth of approximately 8 feet bgs, a black, organic-rich clay was encountered Below the clay, sandy clays, and clayey silts were encountered Beginning at about 23 5 feet bgs and ' extending down to between 33 and 38 feet are silty-sand lenses, which appear to be discolored to bluish- gray The discoloration is possibly due to the presence of petroleum hydrocarbons Below the discolored silty-sand and extending down to 70 feet were inter-bedded clay, silt, and sand with a moderate to strong gasoline odor Groundwater was encountered at approximately 40 feet Groundwater yields are greater lin the inter-bedded silty and sandy sequences from 40 feet to at least 70 feet bgs (total drilling depth) In soil boring SB-2, clean quartz rich sand was encountered beginning at approximately 70 feet A cross-section of the site in shown in Figure 3 and the Soil Boring Logs are located in Appendix B Positive OVA-PID readings were not observed at or above the instrument detection Iimit of one part per million total organic vapors in the soil samples collected from 5 feet bgs to SB-1 and 5, 10, and 15 feet in SB-2 Gasoline odors in the soil were noted in both borings, beginning at a depth of approximately 23 5 feet bgs and continuing to the total depth of the boring Weathered gasoline odor was noted beginning at 23 5 feet and fresh gasoline odor was noted beginning at approximately 26 feet and continuing the depth of the borings OVA-PID measurements are shown on the Soil Boring Logs in Appendix B 4 2SO IL GAS SCREENING I Simulprobe soil gas screening samples were collected at 15 and 30 feet bgs in SB-1, and at 15, 26, and 35 feet in SB-2 Each screening sample was collected by purging the Simulprobe and line for approximately 5 minutes OVA-PID readings collected at 15 and 30 feet in SB-I were 0 ppm and 1,050 ' ppm respectively OVA-PTD readings of a sample of soil collected at the same depths and placed in a plastic bag (bagged samples) were 5 ppm and 100 ppm, respectively OVA-PID readings for soil gas collected at I5 feet bgs in SB-2 were 10 ppm OVA-PID readings for soil gas collected at 26 and 35 feet in SB-2 exceeded the upper limit of the OVA-YID of 2,000 ppm OVA-PID readings of bagged samples collected at the same three depths were 10, 35, and 2,000+ ppm, respectively Soil gas samples were not collected for laboratory analysis A summary of the soil gas screening sample results and the laboratory analysis of the soil samples collected from corresponding depths is provided in Section 4 4 The OVA- PID readings are listed in fable I located below, and on the Soil Boring Logs located in Appendix B t� CONDOR