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' Groundwater Investigation,Monitor Well Destruction and Installation,and Interim Remediation Pump Test Report Boyett Petroleum,419 S.Main St,Manteca,CA January 30,2004 . Page 6 interbedding and clay horizons. A clay to silty clay horizon of variable thickness was encountered in the CPT borings from approximately 22 to 28 feet bgs; this clay horizon appears to be continuous across the site. A continuous, coarse sand horizon was encountered in the borings at approximately 28 to 53 feet bgs. At depths greater than 53 feet bgs to the maximum depth of the investigation, the soils encountered by the borings were predominantly continuous horizons of interbedded sands and clay intercalated with relatively thin silt horizons. The CPT boring logs indicate that the clay units underlying the site vary in composition from dominantly ' stiff to very stiff clay to silty/sandy clay. The silty units vary in grain size composition and range from clayey silt to sandy silt. Sand units appear to form continuous sand horizons of variable thickness and range in composition from clayey sands to medium/coarse-grained sands with gravels. ' 35.2 Laboratory Analyses The laboratory analytical results of the groundwater and soil samples collected from the direct push ' borings are presented in Table 1 and Table 2, respectively. Laboratory analytical results for groundwater samples collected during the October 2003 groundwater investigation are presented in Figure 4, Appendix A. MTBE isoconcentration contours in groundwater are shown in Figure 5, Appendix A. Copies of ' laboratory analytical results and chain-of-custody records for the groundwater and soil samples collected during the October 2003 investigation are included in Appendix F. I Table 1 Direct Push Boring Groundwater Sample Analytical Results Sample Number 3761E-CPT3- 3761E-CPT3- 3761E-CPT3- 3761B-CPT3- 29'-10/23103 44'-10/23103 71'-10/23103 121'-10/23/03 ' Sample Interval feet 24 -29 39-44 66-71 1 116-121 Analyte Units AWLL /1, µg2 Benzene <1.0 <0.5 Q.5 <0.5 Toluene <1.0 <0.5 <0.5 <0.5 ' Ethyl benzene <1.0 <0.5 <0.5 <0.5 Total Xylenes <2.0 <1.0 <1.0 1 <l.0 TPI-1-0 <50 <50 <50 <50 ' MTBE 330 1.5 2.3 <0.5 Ethanol(Et0 <10 <5.0 <5.0 <5.0 Tertiary-Butanol (TBA <10 <5.0 <5.0 <5.0 Di-isopropyl Ether DFPE <1.0 <0.5 <0.5 <0.5 ' Ethyl tertiary-Butyl Ether(ETBE) <1.0 <0.5 <0.5 <0.5 Tertian -Am 1 methyl Ether AME <1.0 Q.5 <0.5 <0.5 1,2-Dichloroethane 1,2-DCA <1.0 <0.5 <0.5 <0.5 1,2-Dibromoethane(EDB) <1.0 <0.5 <0.5 <0.5 1 ' �� CONDOR