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Johnson and Ettinger(1991) Model for Subsurface Vapor Intrusion into Buildings I Solid ... Paget of 2 V 4o saq� http://www.ePa.ciov/oswer/riskassessnient/airmodel/johnson_ettinger.htm 'Sc Last updated on Friday, July 10, 2009 T3 Waste and Cleanup Risk Assessment �t You are here: EPA Home OSWER Waste and Cleanup Risk Assessment Johnson and Ettinger(1991) Model for Subsurface Vapor Intrusion into Buildings Johnson and Ettinger ( 1991) Model for Subsurface Vapor Intrusion into Buildings 1 Concerns have been raised about the potential for subsurface contamination in either soil or 4 ground water adversely impacting indoor air quality. In September 1998, EPA developed a series of models,fo=estimatin.g indoor air concentrations-and associated,health risks from subsurface vapor intr_uslo into buildings These models were based on the analytical' .-8c solutions ofr]ohnson_and;Ettiog .(19.9_1)Tforzcontaminant partitioning and=subsurface,vapor transport into buildingss.Since that time, revisions to the mode'Is have been made and a series of new modelszha a been added. Data for any chemical may be edited, new chemicals added, or existing chemicals deleted=fromlthe Chemical Properties Lookup Table within the VLOOKUP worksheet. To begin,an editing session the user must unprotect (unseal) the worksheet,(.the-password=iszABC" in capital letters); editing of individ` uaai el me ents or addition and deletion of chemicals may then proceed. 1 The models have been revised toincorporate thedefault values recommended in Appendix:G of the EPA-OSWERDraft-Guidance for Evaluating'th'e'Vapor Intrusionrto.Indoor�Air Pathway (November, 2002). The revisions� include new'—r value'cs intermediate variables for estimating the soil vapor permeability and the degree of water saturation in the capillary zone above the water table. In addition, new. human health benchmarks have been added for some chemicals and revised for others. Finally, a series of automatic checks have been added to the models to prevent the use of inappropriate initial soil or ground water contaminant concentrations (i.e., soil concentrations_greater__- -thanti soillsaturati�'entration or ground water concentr..atiorfs`greater.than.,the-solubility limit). The 3-phase soil contamination models listeb owtheoretically partition the^contamination into three-discrete phases: 1) in solution with water, 2) sor d to the soil organic-carbon, and 3) in vapor phase within the soil ai��flled pores. The 3-phase models replace the old models previously available on this website. These models have been constructed in Microsoft® Excel and are applicable when NAPL is not present in subsurface'soils-or-in-groundwater. r In addition to the 3-phase models discussed above, two new models have been added allowing the user to estimate vapor intrusion into buildings from measured soil gas data. These models are also constructed in Excel and are included in the 3-phase odelzir p files listed below. The User's Guide also shown below covers use of both the 3-phase models and the soil gas models. When NAPL is present in soils, the contamination includes a fourth or residual phase. In such cases, the new NAPL models listed below can be used to estimate the rateof vapor intrusion into buildings and the associated health risks. The new NAPL models use a numerical approach for simultaneously solving the time-averaged soil and building vapor concentration for each of up to ten soil contaminants. This involves a series of iterative calculations for each contaminant. The NAPL models are available in Excel. The NAPL model User's Guide that accompanies the new models is also listed below. c I http://www.epa.gov/oswer/riskassessment/ainnodel/J*ohnson_ettinger.htm 6/7/2011