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Ms. Vicki McCartney Project No. 8800401A.0201 <br /> 1 October 26,2004 <br /> Page 3 <br /> depth of 90 feet bgs. Groundwater samples were collected from hydropunch borings <br /> advanced adjacent to each CPT boring location. Four discrete water samples were <br /> collected from each hydropunch boring. Soil encountered beneath the site during this <br /> t investigation consists of interbedded gravelly sand, sand, silty sand, sandy silt, silt, <br /> sandy clay, silty clay and clay. There appears to be laterally continuous sand beds at <br /> -. depths of approximately 8 to 15 feet bgs and 28 to.40 feet bgs. Below these sand <br /> 1 horizons are many discontinuous thin layers of clay and other stiff, fine-grained material. <br /> PROBLEM ASSESSMENT <br /> This section provides information requested by the California RWQCB characterizing <br /> the extent of impact at the site based on the results of previous investigations. This <br /> information provides the basis for making remedial action/ decisions. <br /> _ Soil Conditions <br /> Shallow soil at the s e t site h s een impacted with el hydrocarbons at <br /> concentrations up to 2 m �r (µg/1) of otal e oleum hydrocarbons as v <br /> rA <br /> gasoline (TPHg), ^� '2-7-2--k:cg��l o benzene, and s / f MtBE. The highest 3 <br /> hydrocarbon concentrations have been present in soil beneath the western dispenser <br /> islands. Appendix A contains historical soil chemical analytical data. <br /> IJ Groundwater Conditions <br /> i Hydrocarbons have been reported in groundwater beneath the site at concentrations up to <br /> 25,700 pg/l of TPHg (well MW-1), 1,820 µg/l of benzene (well MW-1), and 41,000 µg/l <br /> yr of MtBE (well MW-5). On August 12, 2004, TPHg range hydrocarbons were reported <br /> in wells MW-1, MW-3, and MW-5 at. concentrations of 1,100, 150, and 54 pg/1, <br /> respectively. Benzene was reported in all wells except MW-2 at concentrations ranging <br /> from 0.79 µg/1 (MW-3) to 86 µg/l (MW-1). MtBE is reported at concentrations ranging <br /> from 13 µg/1 (MW-3) to 2,500 µg/l (MW-2) in all wells at the site. 'In CPT borings <br /> CPT-3 and CPT-4 advanced in September 2003, groundwater samples collected at <br /> } <br /> 25 feet bgs had concentrations of MtBE at 7,600 and 12,000 µg/1, respectively. <br /> N:IsacDP120041Pr1188018800401A.4ad.doc Shaw Environmental,Inc. <br /> t <br />