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VGIIL off;, �µ7CL11Vt; .-- 510 420 1707; Nov-9-_99 16;33; Page 28/29 r' Indoor Air Risks and hazards for exposure of adults and children to volatile chemicals in indoor air were also calculated assuming the site is used for a residential setting. The Johnson-Ettinger 11rlodeI w „ted to calculate risks and hazards from exposure to volatiles in indoor air, at the request of DTSC personnel(U.S.EPA, 1997). 'the model was run assuming the followir parametecm depth rs: 1) 1 S below grade to bottom of enclosed space floor,2)430 cm depth below grade to the water table(this corresponds to the shallowest depth to groundwater that was encountered during drilling in the Phase H investigation), 3) a silty clay soil type directly above the water table and within the vadose zone (SIC), based on data collected during the Phase II investigation, 4) an average soil/groundwater temperature of 16.6 degrees Celsius(U.S. EPA, 1997),5)a default vadose zone soil dry bulk density of 1.3 g/cm3, 6) a default vadose zone soil total porosity of 0.43 (unitless), 7)a default vadose zone soil water-filled porosity of 0.3 cm3/stn3, 8) the depth below grade to top of contamination was assumed to be the depth at which the Tnaximum concentration of each COPCs was reported, corresponding with the greatest calculated risk/hacard, 9) a default soil organic carbon fraction of 0.002, 10)a default averaging time for carcinogens of 70 years, 11)a default averaging time for non- carcinogens of 30 years, 12) a default 30-year exposure duration, and 13) a default exposure frequency of 350 days/per year; COPCs in soil and groundwater were individually entered into the Johnson Ettinger model and the resulting incremental'ride from vapor intrusion into indoor air, and/or hazard quotient calculated. The incremental risks and hazards based on all COPCs found in svil rind groundwater were then summed for the cumulative risk and hazard for this pathway. Separate calculations of risks and hazards from volatilization Of COPCs from groundwater collected immediately off-site were also. made. These results are described in the Risk Characterization section below. TOXICITY VALUES AND SUMMARY TABLES Toxicity values for COPCs were obtained from the following sources (in order of preference): 1) California Environmental Protection Agency, Criteria for Carcinogens (Cal/EPA, 1994), 2) the Integrated Risk Information System maintained by the U.S. EPA(1999),and 3)U.S. EPA's Health Effects Assessment Summary'fables(1997). Cal/EPA's Hot Spots Unit Risk and Cancer Potency values(1999)and the DTSC PFA Guidance Manual(1994)were also consulted for toxicity values used in the PEA. Where toxicological data was not available from these sources,the U.S.EPA-1998 Preliminary Remediation Goals table was consulted for toxicological information(Smucker, 1998). All reference concentrations from these toxicological data sources were converted to reference doses in accordance with accepted{methods (DTSC; 1994). In addition, oral slope factors and reference doses were used as surrogate val ues to estimate systemic toxicity as a result of dermal exposures to COFCs becaur;e dermal toxicity values are not currently available for any chemicals. A summary table with cancer potency factors and reference doses for all COPCs and each route of exposure, including the source and date of toxicity values are provides!in Appendix C. Toxicity values based on cross route extrapolation are also included in the summary table in Appendix C. Toxicity values included in the Johnson-Ettinger model for indoor air were first compared with the toxicity values in the Table in C-1; the most current toxicity values were used in the assessment. 1f COPCs were not included in the database of chemicals included with the Johnson-Ettinger model, 973699[k,peu.wpd-[119/99 22