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CAMBRIA Three of the CPT borings were drilled to 80 fbg or beyond A sand layer was encountered in each of these borings The top of this sand layer was encountered at approximately 72 to 77 fbg This sand layer appears to be continuous across the site This sand layer is not shown on the Delta cross-sections, as none of the wells at this site extend to this depth Cambria plotted soil and groundwater sample analytical data on the cross-section to show which constituents and concentrations were detected at which depths CONCLUSIONS Soil and groundwater results from boring CPT-1, drilled in the former UST location, delineate the vertical extent of petroleum hydrocarbons and MTBE in this source area These constituents do not extend to 60 5 fbg in soil and 72 fbg in groundwater Groundwater analytical data collected from the site's monitoring wells have shown groundwater concentrations to be low or below detection limits In general, the site monitoring wells were constructed with screened intervals of approximately 20 to 40 fbg, except for well MW-10, which is screened from 30 to 45 fbg Groundwater analytical data collected from all four of the CPT borings contained elevated levels of petroleum hydrocarbons at the approximate depth of 50 fbg TPHg concentrations at this depth ranged from 2,530 to 439,000 ppb, and benzene levels were reported at 517 to 13,200 ppb Based on the soil types encountered at this depth, there does not appear to be any reason why we would find elevated levels of petroleum hydrocarbons at this depth and not detect them 10 feet above in the monitoring wells One possible explanation for this is that previous SVE remediation performed at this site cleaned up the shallow soils, down to 40 fbg, but this remedial effort was not able to clean up saturated soils beneath that depth Elevated levels of petroleum hydrocarbons were also detected in deeper groundwater samples collected at approximately 74 fbg Groundwater samples from CPT-3 and CPT-4 contained TPHg at concentrations of 19,900 and 10,400 ppb, respectively, and benzene concentrations of 2,940 and 132 ppb, respectively Groundwater samples from CPT-1 did not contain detectable levels of petroleum hydrocarbons at 72 and 79 fbg, and a groundwater sample from this depth was not collected from CPT-2 The detection of petroleum hydrocarbons at this depth coincides with the top of a sand layer encountered at depths ranging from 72 to 77 fbg It appears that petroleum hydrocarbon concentrations decline rapidly beneath the top of this sand layer There is an order of magnitude drop in TPHg and benzene concentrations between the 74 fbg and 80 fbg groundwater samples from CPT-4 In CPT-3, the decline in 0779 6