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rr �) • Quik Stop No 121 Additional On-Site and Offsite Soil and Groundwater Investigation Page 5 Subsurface Conditions The subsurface conditions encountered at CPT-1 (located on-site)were found to be composed of alternating layers of silty sand and sand, with some silty clay and clay from the surface to approximately 32 feet The material was found to be dense with localized areas of very dense material From 32 feet to 42 feet, a dense sand to gravelly sand was encountered (Figure 3) This granular unit was followed by a 12-foot interval of sand, sandy silt to silty clay From 54 feet to 66 feet, a very stiff clayey silt to clay was encountered, with some localized "hard pan" material Below 66 feet and extending to the bottom of the bore hole, a very dense sand to gravelly sand was encountered Refusal occurred at 79 5 feet The off-site CPT sounding hole (CPT-2), located approximately 325 feet to the southeast of the site, also encountered alternating layers of clay, silty clay, sand and gravelly sand to a depth of approximately 43 feet Below this interval and extending to a depth of 62 feet, the soil becomes less granular, consisting of silty sand to silty clay and clay There were several localized areas of hard pan material encountered CPT-2 was terminated at 62 feet due to refusal • As previously mentioned, no sounding data was collected at CPT-3 (located north of the site), due to a faulty sounding cone However, observation of hydraulic response at this location indicate similar alternating sequences of silty clay, silty sand and sand to a depth of 35 feet Grab water samples were collected from all three CPT locations A grab water sample (CPT-3), was collected from CPT-3 using a hydropunch and opening the screen interval from 12 to 16 feet The sounding logs were reviewed and sample points selected prior to collecting water samples at CPT-1 and CPT-2 Water sample CPT-1W was collected from a gravelly sand lens ata depth of 35 to 38 feet Two water samples were collected from different depths at CPT-2 Water sample CPT-2W was collected from a sand lens at a depth of 17 to 20 feet and CPT-2WA was collected from a gravelly sand at a depth of 37 to 40 feet Copies of the CPT sounding logs and computer print data are attached in Appendix A Laboratory Analysis CCI submitted a total of four CPT water samples to North State Environmental of South San Francisco, California, a state-certified laboratory for analysis All samples were analyzed for total petroleum hydrocarbons as gasoline(TPHg), benzene, toluene, ethylbenzene and xylenes (BTEX), using EPA Test Methods 8015 and 8020, and volatile organic compounds using EPA Test Method 8260 Three water samples were also collected from the on-site wells and submitted to Entech Analytical Laboratory, located in Sunnyvale, California These three samples were also analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene