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Idlewild Market May 23, 1996 Page -4- the previous over-excavation The sample location, including the laboratory results are shown on Geologic Cioss Section A-A', Figure 3, Appendix A 5 0 SESOIL MODELING RESULTS S 1 Toluene Tolueae was modeled using a 25 year simulation without applying a degradation rate SESOIL predicted that it would take approximately 17 years for toluene to reach the capillary fringe under the conditions described above The predicted concentration of toluene at the capillary fringe is 0 3 µg/ml dissolved, 0 14 µg/g adsorbed, and 0 09 µg/cm3 air in pores (see Run 1 - Toluene, Appendix B) The primary maximum contaminant level(MCL)for toluene,as defined by the U S Environmental Protection Agency, Drinking Water Standards, is 1 0 µg/ml I5 2 Ethyl Benzene Ethyl benzene was modeled using a 100 year simulation without applying a degradation rate SESOIL predicted that it would take approximately 44 years for ethyl benzene to reach the capillary fringe under the conditions described above The predicted concentration of ethyl benzene at the capillary fringe is 0 45 µg/inl dissolved, 0 35 go/o adsorbed, and 0 11 dig/cm3 air in pores (see Run 2 -Ethyl Benzene, Appendix B) The primary MCL for ethyl benzene, as defined in the California Code of Regulations, Title 22, Drinking Water Regulatory Criteria, is 0 68 4g/ml 5 3 Xylene IXylene was modeled using two simulations The first simulation for xylene was a 100 year run without applying a degradation rate The second simulation for xylene was a 50 year run using a conservative I degradation rate of 10% of the published biological degradation rate for xylene(Geraghty & Milner) The input values foi biodegradation for xylene were 0 00019254/day in groundwater and 0 00247553/day in soil ISESOIL predicted that it would take approximately 22 years for xylene to reach the capillary fringe for both simulations, regardless of biodegradation The predicted concentration of xylene, without biological I degtadation, at the capillary fringe is 6 9 ttg/ml dissolved, 4 2 µg/g adsorbed, and 1 9 µg/cm' air in pores (see Run 3 - Xylene, Appendix B) The predicted concentration of xylene, with degradation, at the capillary fringe is 7x10 ' pg/ml dissolved, 4 4x10' }Lg/g adsorbed, and 19x10' µg/cm' air in pores (see I Run 4 - Xylene, Appendix B) Tne primary MCL for xylenes, as defined in the California Code of Regulations, Title 22, Di inking Water Regulatory Criteria, is 1 75 µg/ml I I �g7 CONDOR