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LFR Levine-Fricke The potential exposure pathways for human and ecological receptors include direct contact(e.g., dermal contact, ingestion)with soil, inhalation of airborne dust, direct contact with surface water, and for humans, ingestion of drinking groundwater. To evaluate potential human health risks associated with exposure to the elevated metals or to constituents that may be present in pyrolytic oil, the soil data can be compared to the PRGs for metals, VOCs, SVOCs, and dioxin. The data can also be compared to the U.S. EPA SSLs to evaluate the potential for metals in soil to leach and impact groundwater. A preliminary comparison of the data with PRGs indicates that arsenic is present in all the soil samples collected at concentrations exceeding the PRG for arsenic of 1.6 mg/kg. However, it should be noted that the arsenic concentration reported in the regional background sample was also above the PRG(Bradford 1996). Concentrations of metals other than arsenic in soil samples were reported below their respective PRGs. Concentrations of antimony, arsenic, cadmium, total chromium, and zinc in surface soil samples exceeded their respective SSLs. Only one soil sample(TT-T1-2-2) contained a significant(>4,000 pg/kg)concentration of VOCs and only two soil samples(TT-T1-2-1 and TT-T3-1-1)contained significant(>1,000 mg/kg) concentrations of oil and grease (see Appendix E for data). VOCs and SVOCs were not detected above PRGs or SSLs in soil samples collected from the Site. Potential human health risks associated with soil conditions at the Site will be evaluated further in the upcoming RI/FS to be conducted following implementation of source removal activities. The evaluation of potential ecological receptors is more complex, and screening criteria other than background concentrations are not necessarily appropriate. Evaluation of ecological risk typically involves more than one species and the endpoints may differ from those employed for evaluation of human health risk. The primary environmental impact from the tire fire appears to be to surface soil, which will be addressed through implementation of the selected remedial alternative. Site conditions and potential risks to ecological receptors associated with contaminants in soil and groundwater will be thoroughly evaluated during the comprehensive RI/FS to be conducted following implementation of source removal activities. 5.0 SUMMARY AND EVALUATION OF ALTERNATIVES The remedial action objective(RAO) for the Site is to remove or mitigate the source of contamination based on visual inspection of burnt material present in the 34 burn piles. The goal of the remedial action is to maximize removal of Class I non-RCRA hazardous waste, Class II designated waste, and potentially discolored soil from the project site, to provide immediate protection to human health and the environment by removal of readily accessible hazardous waste. This interim measure is advantageous because the hazardous material is easily identifiable and removal and off-site disposal of the waste is a practical and reliable response action. This action will also simplify and expedite the comprehensive RI/FS and Final RAP. Final_RAP_Tracy_9.18.03(final).doc Page 7