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