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4.0 Data Evaluation <br /> 4.1 Aerially Deposited Lead Investigation <br /> 4.1.1 Lead Concentration and Distribution <br /> Soil samples collected from the site were reported to contain lead (Table 1). The source for the <br /> lead is not known. However, studies along the transportation corridors have attributed elevated <br /> lead concentrations within soil to accumulation of dust and debris containing lead from leaded <br /> gasoline emissions (Coltrin, et al., 1993). <br /> The elevated lead concentrations decreased with depth. A summary of the distribution of the <br /> elevated lead concentrations is presented below. The data set is restricted to those samples <br /> reported to contain greater than or equal to 50 mg/kg lead, a level selected because it is ten times <br /> the STLC. <br /> Distribution of Samples from Distribution of Samples from Distribution of Samples from All <br /> Total Sample Population with Interval with Greater Samples with Greater <br /> Greater Than 50 mg/kg Lead Than 50 mg/kg Lead Than 50 mglkg Lead <br /> Sample <br /> Interval Number Percentage Number Percentage Number Percentage <br /> 0.1 meters 17 of 165 10.3 17 of 55 30.9 17 of 35 48.6 <br /> 0.3 meters 15 of 165 9.1 15 of 55 27.3 15 of 35 42.9 <br /> 0.6 meters 3 of 165 1 4.6 3 of 55 1 5.5 3 of 35 8.6 <br /> The number of samples reported to contain elevated lead concentrations decreased with depth. <br /> This is typical of accumulations of aerially deposited lead, as reported by Coltrin and others <br /> (1993), where concentrations of lead were observed to decrease with depth. <br /> Lead concentrations were compared to TTLC and STLC values to evaluate whether the soil <br /> would be considered a California-hazardous waste, should it become a waste. Generally, TTLC <br /> and STLC values for lead are used to judge whether a waste is a California-hazardous waste <br /> based on the total and soluble concentration of lead within the waste. The TCLP values are used <br /> to judge whether a waste is a Resource Conservation and Recovery Act (RCRA)-hazardous <br /> waste (also known as a Federal hazardous waste)based on the soluble concentration of lead <br /> within the waste. <br /> SacDP-N:IrmtcjpllProjectsl8218712641Reponll20Austin report.doc 4-1 <br /> S/?1101 <br />