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5.0 Conclusions and Recommendations Based on the laboratory results, current regulatory guidelines, and the judgment of IT the following conclusions and recommendations are offered. • Lead was reported in soil samples collected from the site. The source for the lead is not known. However, studies along the transportation corridors have attributed elevated lead concentrations within soil to accumulation of dust and debris containing lead from leaded gasoline emissions (Coltrin, et al., 1993). • Lead concentrations were compared to TTLC and STLC values to evaluate whether the soil would, should it become a waste, be considered a hazardous waste. No soil samples were reported to contain total lead concentrations that exceed the TTLC value of 1,000 mg/kg for lead. Soil samples collected from borings 5, 12, 13, 14, 17, 23, 24, 36, and 40 were reported to contain soluble lead at concentrations in excess of the STLC of 5 mg/1 by WET analysis. • A soil sample collected from boring 37 was reported to contain a total lead concentration in excess of 350 mg/kg, a level requiring waste disposal in a Class I facility. • The statistical evaluation resulted in the following data. Predicted Soluble Predicted Soluble Lead(WET) Lead(DIWET) Total Lead Mean Total Lead Concentration and Concentration and Concentration 90%UCL 90%UCL 90%UCL Sample Population (mg/kg) (mg/kg) (mg/1) (mg/1) All Samples 36.0 44.8 0.899 and 5.11 0.129 and 0.463 • Based on the statistical analysis, the soil, if treated as a whole and sampled on a composite basis from stockpiles generated during construction activities,may not be considered hazardous. However, if management of the soil within the variance is required based on soluble lead concentrations, the statistical data indicate that the soil would be allowed to be re-used within condition 1 of the variance, if the soil is excavated and treated as a whole (0 to 0.6 meters). This condition requires that the soil be used as fill beneath at least one foot of clean (non-hazardous) soil and five feet above the water table. This conclusion is based on the calculated 90%UCLs for total lead and DI WET data within the 0 to 0.6 meter(0 to 2 foot) data set. • Evidence of potential USTs within the areas surveyed at the northeast and northwest corners of the intersection was not reported by the geophysical surveys. The geophysical surveys did detect an anomaly in the area surveyed at the southwest corner of the SaeDP-N.IrancjpllProjectsl8?1811J641Reponll?O Au do repon.doc 5-1 S/?1101