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r <br /> Preliminary Subsurface Investigation <br /> City of Stockton, former Westem Pacific Railroad Property,Stockton, CA <br /> May 27, 1992 <br /> W0601 AD <br /> rsamples collected from wells MW-1 through MW-3 were analyzed for California Title 22 <br /> Metals, Volatile Organics (EPA method 8240), and Semi-Volatile Organics. (EPA method 8270). <br /> rThese soil samples were selected for laboratory analysis based on: 1) areas where the presence <br /> of priority pollutant metals and volatile organics in the soil and groundwater beneath the former <br /> rWestern Pacific Railroad property were suspected; and 2) due to the poor mobility of the <br /> contaminants, the 5 foot sample was selected. <br /> 1 <br /> 6.0 RESULTS OF LABORATORY ANALYSIS <br /> 6.1 Soil <br /> Laboratory analysis recorded certain priority pollutant metals above method detection levels in <br /> rthe composite soil samples collected from grid sections A through F at 5.5 feet below grade. <br /> Although none of the levels detected exceeded the Total Threshold Limit Concentration (TTLC) <br /> values as listed in Title 22 of the California Code of Regulations, some of the samples contained <br /> arsenic concentrations that were ten times greater than the Soluble Threshold Limit <br /> rConcentration (STLC) maximum limit. Because of the sample dilution factor of 10 used in the <br /> waste extraction test protocol, it was considered possible that these samples exceeded the STLC <br /> rfor arsenic (Marshack, 1989) therefore, these samples (WPRR-A, -B, -C, and -E) were <br /> reanalyzed for soluble arsenic using a citric acid extraction test. The results of the STLC <br /> ranalyses detected soluble arsenic concentrations ranging from 0.33 to 0.97 ppm. None of these <br /> ' concentrations exceed the 5 ppm STLC maximum limit for arsenic. No volatile or semi-volatile <br /> organics were detected in any of the samples analyzed by EPA method 8240 and 8270, <br /> respectively. The laboratory results for the soil samples are presented in Table 3. Laboratory <br /> reports, chain of custody documentation, and laboratory QA/QC data, are included in Appendix <br /> r G. <br /> R041392.SAY 10 <br /> r <br />