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33 Total Lead <br /> Only one of the six samples analyzed exhibited detectable concentrations of total lead A <br /> concentration of 6 16 mg/kg was detected in sample SGS1 This concentration is well below the <br /> RMAC for total lead <br /> 4.0 CONCLUSIONS AND RECOMMENDATIONS <br /> Of the locations sampled and analyzed at the Pacific Avenue Car Wash site, three exhibited <br /> detectable concentrations of petroleum hydrocarbon compounds These three locations centered <br /> ' around the fuel distribution island and may be the result of a distribution pipeline fuel leak The <br /> petroleum compounds were detected at depths of 15 feet bgs, approximately 11 feet below the fuel <br /> distribution pipeline <br /> ' The soils encountered at the site consisted primarily of clayey material reminiscent of unweathered <br /> marine clay This clay was moist during the sample collection period Clay materials similar to that <br /> encountered at the Pacific Avenue Car Wash site, posses very low hydraulic perrneabilities Typical <br /> hydraulic conductivity valves for this type of clay in both consolidated and unconsolidated aquifer <br /> systems range from 10" to 10,7 meters per day (Davis, 1969, Dunn and Leopold, 1978, Freeze and <br /> Cherry, 1979) These type of clay material usually retard the vertical movement of the chemical <br /> compounds in the soils Presently however, not enough site characterization data exists to <br /> adequately rationalize or explain the detection of significant compound concentrations at the 15 foot <br /> depth The existence of the petroleum compounds could be due to several conditions, such as 1) <br /> migration through clay possessing extremely low permeability over a lengthy period of time, 2) <br /> migration through fractures in the clay, 3) deposition by floating product on top of a fluctuating <br /> groundwater table or 4) deposition by an alternate source at a depth greater than the suspected <br /> source <br /> TreaTek recommends that additional site investigation activities be conducted at the site to <br /> adequately define the areal and vertical extents of the compound presence and to potentially <br /> determine the compound migratory pathways, migration mechanisms and the source of <br /> contaminates Additionally, the site investigation activities would provide information from which the <br /> most effective remedial alternative can be selected <br />' 5.0 LIMITATIONS <br />' The conclusions reached in this report are based on the available analytical data, known site and <br /> regional geophysical conditions and the TreaTek Project Manager's professional experience Since <br /> the project's objective was to confirm or deny the presence of petroleum hydrocarbon compounds <br />' within the shallow soils at the site, TreaTek feels that these objectives were met Until additional <br /> data is available, no additional conclusions can be reached <br />