Proposed Changes to EPA s Spreadsheet Version of Johnson & Ettinger Model (and some new spreadsheet tools) Workshop Integrating Observed & Modeled Vapor Attenuation The 15th Annual AEHS West Coast Conference, San Diego, California March 2005 Helen E. Dawson, PHD Regional Superfund Hydrogeologist US EPA Region VIII Denver, CO 303-312-7841 dawson.helen@epa.gov 1
Overview of Changes Current EPA s JE Model (8 spreadsheets): GW-SCREEN, GW-ADV SG-SCREEN, SG-SDV SL-SCREEN, SL-ADV NAPL-SCREEN, NAPL-ADV Toxicity lookup table in each spreadsheet Many hard-wired properties Difficult to update One Spreadsheet: GW-, SG-, and SL-SCREEN & ADV combined into one spreadsheet One toxicity lookup table No hard-wired properties NAPL spreadsheets still separate New Tools: Proposed Spreadsheet for Table 1 (Preliminary Screening) Spreadsheet for Table 2 (generic screening) 2
US EPA Condensed Guide to Assessing the Vapor Intrusion Pathway Tier 1: Preliminary Screening Tier 1 Preliminary Screening VOCs in subsurface? (Table 1) (1) Inhabited buildings (and/or areas of future development) overlie VOCs? (2) Immediate action warranted? (3) Proceed to Tier 2 Generic Screening Proceed with Appropriate Action Vapor Intrusion Pathway is Incomplete Data Needed: - List of VOCs in subsurface - Initial conceptual model of subsurface contamination - Current (and/or potential future) land use over contamination Table 1: Check if present Notes: (1) Table 1 lists chemicals with saturated vapor concentrations that are sufficiently toxic (10 times an incremental lifetime cancer risk greater than 10-6 or a non-cancer hazard quotient greater than 1.0) to result in potentially unacceptable indoor air inhalation risks through vapor intrusion. If any of the chemicals listed in Table 1 are present in ground water, soil or soil vapor, or suspected to occur in a NAPL phase in the unsaturated zone, the guidance recommends proceeding to Question 2. (2) Use professional judgment in evaluating the potential for vertical and horizontal vapor migration to identify potentially impacted buildings or areas of concern. EPA recommends the assessment include any buildings (or areas of future development) within 100 feet horizontally or vertically of known subsurface contamination. Also consider whether there exist any naturally occurring or anthropogenic subsurface pathways that are expected to have a high gas permeability and be of sufficient volume and proximity to a building (or area of future development) to facilitate vapor intrusion. Examples include fractures, macropores, utility conduits and subsurface drains that intersect vapor sources or vapor migration pathways and intersect the building foundation. Additionally, if the source of contamination is groundwater, consider migration of the contaminant plume when evaluating the potential for future risks. (3) Immediate action (e.g., forced ventilation, air filtration/purification, or evacuation) may be warranted if (a) occupants report odors (e.g., chemical, solvent, or gasoline odors) or (b) physiological effects (e.g., dizziness, nausea, vomiting, confusion, etc.), or (c) if residents' basements are wetted by shallow groundwater known to be contaminated with chemicals listed in Table 1, or (d) if NAPLs known to contain chemicals listed in Table 1 are in close proximity to the building foundation.
Table 1 Spreadsheet OSWER VAPOR INTRUSION GUIDANCE Table 1. Chemicals Sufficiently Toxic to Pose an Inhalation Risk via Vapor Intrusion View Selected Chemicals Target Indoor Air Conc. Basis Saturated Vapor Conc. Sufficiently Toxic? Check (x) Cia, target C = cancer Cv Cv.Cia,target? If Present CASN Chemical (ug/m 3 ) NC = noncancer (ug/m 3 ) (yes/no) x 83329 Acenaphthene 2.10E+02 NC 2.07E+04 No x 75070 Acetaldehyde 1.11E+00 C 2.14E+09 Yes x 67641 Acetone 3.50E+02 NC 7.19E+08 Yes x 75058 Acetonitrile 6.00E+01 NC 2.01E+08 Yes x 156592 cis-1,2-dichloroethylene 3.50E+01 NC 1.06E+09 Yes x 75343 1,1-Dichloroethane 5.00E+02 NC 1.21E+09 Yes x 107062 1,2-Dichloroethane 9.36E-02 C 4.20E+08 Yes x 75354 1,1-Dichloroethylene 2.00E+02 NC 3.13E+09 Yes x 127184 Tetrachloroethylene 4.12E-01 C 1.66E+08 Yes x 156605 trans-1,2-dichloroethylene 7.00E+01 NC 1.74E+09 Yes x 79005 1,1,2-Trichloroethane 1.52E-01 C 1.67E+08 Yes x 71556 1,1,1-Trichloroethane 2.20E+03 NC 8.88E+08 Yes x 79016 Trichloroethylene 1.11E+00 C 5.19E+08 Yes x 75014 Vinyl chloride (chloroethene) 2.77E-01 C 1.00E+10 Yes 4
US EPA Condensed Guide to Assessing the Vapor Intrusion Pathway Tier 2: Generic Screening Tier 2 Generic Screening Additional Data Needed: Measured or reasonably estimated (e.g., from contoured data) VOC concentrations in ground water and/or soil vapor samples. Location and extent of significant subsurface contamination. Is there a source of vapors in the unsaturated zone under buildings or areas of concern? (4) [GW] Generic Screening Level? (Table 2) (5) OR [SG] Generic Screening Level? (Table 2) (5) Notes: (4) If there is a suspected vapor source in the unsaturated zone (e.g., NAPL or contaminated soil) underlying buildings or areas of concern, soil vapor data are needed to evaluate the potential for vapor intrusion into buidlings overlying the unsaturated zone source. Where a groundwater plume extends beyond a vadose zone source, groundwater data may be used for screening, provided the potential for lateral vapor migration in the unsaturated zone is considered. (5) Table 2 provides target screening levels for ground water and soil vapor corresponding to indoor air concentrations at an incremental lifetime cancer risk greater than 10-6 or a noncancer hazard index greater than 1.0 assuming a residential exposure scenario. The downloadable Q4 spreadsheet may be used to obtain screening level concentrations for other cancer risk levels or for a commercial exposure scenario. The ground water screening leves assume a generic attenuation factor of. The deep soil gas screening levels assume a generic attenuation factor of. The shallow soil gas screening levels assume a generic attenuation factor of. Table 2: Generic Screening Levels Use of the generic ground water screening levels is not recommended if NAPLs are present at or above the water table within 100 feet of buildings or areas of concern, or if contaminated ground water wets the buidlings' basements. If ground water concentrations approach screening levels, consider collecting confirmatory soil vapor samples in a selected number of representative locations to provide an additional line of evidence for screening. In evaluating the available site data, consider whether the DQOs used in collecting the data are consistent with the DQOs for the vapor intrusion pathway (aee Appendx A). For example, detection limits associated with the subsurface data should be low enough to detect volatile contaminants at levels of potential concern. Also consider whether the subsurface samples were appropriately collected (see appendices on Ground Water and Soil Vapor Sampling) and whether the nature and extent of of contmination in groundwater and/or the unsaturated zone is adequately characterized to ensure that all contaminants of concern and significant areas of contamination have been identified. Proceed to Tier 3 External Site-Specific Screening Vapor Intrusion Pathway Is Incomplete or Does Not Pose an Unacceptable Risk to Human Health
US EPA Condensed Guide to Assessing the Vapor Intrusion Pathway Tier 3: External Site-Specific Screening Tier 3 External Site-Specific Screening Additional Data Needed: VOC concentrations in soil vapor and/or ground water samples at nearest accessible location to buildings Depth to vapor source Unsaturated zone soil type(s) Site-specific building height and floor area (or select default values for either a residential or commercial setting) Are near-building subsurface data available? (6) Is Johnson & Ettinger Conceptual Model applicable to the site? (7) Subsurface Concentration Site-Specific Screening Level? (8) Notes: (6) Data for this level of screening should be collected from locations as close to the buildings or areas of concern as possible.. A sufficient number should be collected to ensure the samples are representative and that spatial variability in the samples is adequately addressed (see Ground Water and Soil Vapor Sampling appendices). Ground water samples should be collected at the water table. Soil vapor samples need to be collected from a depth at least 3(?) feet below the level of the building foundation, preferably at various depths to obtain vertical profiles of the soil vapor concentrations. If biodegradation is suspected, as for petroleum hydrocarbons, EPA recommends collection of soil gas samples from depths as shallow as possible (though at least 3(?) feet below the level of the building foundation) to obtain samples representative of the degree of biodegradation that is occurring in the unsaturated zone. Additionally, EPA recommends collection of vertical soil vapor profiles, including O2 and CO2 as well as VOC concentrations to provide additional lines of evidence for screening biodegradable compounds. (7) Key elements of the Johnson Ettinger Model are described in Appendix G. Of greatest importance are... Site-Specific Screening Levels JE-Model derived Near-building data (8) The site specific screening levels are obtained from the Q5 spreadsheet that allows the user to input the source medium, chemical name, depth to source, up to three layers of soil types (with default properties), a limited set of building parameters (constrained by reasonableness checks), and either a residential or commercial set of exposure parameters. The spreadsheet fully documents all inputs and outputs and provides reasonableness checks on the inputs. Proceed to Tier 4 Internal Site-Specific Assessment Vapor Intrusion Pathway Is Incomplete or Does Not Pose an Unacceptable Risk to Human Health
Q5: Semi-Site-Specific Screening Levels EPA Johnson & Ettinger Spreadsheet Model Q5: Do media concentrations exceed semi-site specific criteria? Graph from J&E model Alpha from graph 4 Soil types: sand loam Depth to contamination Fig. 3 (a,b) Attenuation factor: (SG & GW specific) Tables 3 (a,b,c) http://www.epa.gov/superfund/program s/risk/airmodel/johnson_ettinger.htm 8
US EPA Condensed Guide to Assessing the Vapor Intrusion Pathway Tier 4: Internal Site-Specific Assessment Tier 4 Internal Site-Specific Assessment Collect In-Building Samples (Indoor air [IA] or subslab [SS] or both) [IA], ([SS] Target Concentrations? No Further Action Monitor Line of Evidence Evaluation [IA] x [SS] Decision Matrix Mitigate Phased Subslab Investigation Phased Indoor Investigation Indoor Air Conc. & Subsurface Conc. Relationships Indoor/Outdoor Background Investigation Site- Specific Modeling Other Internal and External Assessment Tools [IA] attributable to vapor intrusion? Implement Remedial Action or Institutional Controls Vapor Intrusion Pathway Is Incomplete or Does Not Pose an Unacceptable Risk to Human Health
OSWER VAPOR INTRUSION GUIDANCE Table 1. Chemicals Sufficiently Toxic to Pose an Inhalation Risk via Vapor Intrusion Preliminary Screening View Selected Chemicals Target Indoor Saturated Vapor Sufficiently Air Conc. Basis Conc. Toxic? Check (x) Cia, target C = cancer Cv Cv.Cia,target? If Present CASN Chemical (ug/m 3 ) NC = noncancer (ug/m 3 ) (yes/no) x 83329 Acenaphthene 2.10E+02 NC 2.07E+04 No x 75070 Acetaldehyde 1.11E+00 C 2.14E+09 Yes x 67641 Acetone 3.50E+02 NC 7.19E+08 Yes x 75058 Acetonitrile 6.00E+01 NC 2.01E+08 Yes x 156592 cis-1,2-dichloroethylene 3.50E+01 NC 1.06E+09 Yes x 75343 1,1-Dichloroethane 5.00E+02 NC 1.21E+09 Yes x 107062 1,2-Dichloroethane 9.36E-02 C 4.20E+08 Yes x 75354 1,1-Dichloroethylene 2.00E+02 NC 3.13E+09 Yes x 127184 Tetrachloroethylene 4.12E-01 C 1.66E+08 Yes x 156605 trans-1,2-dichloroethylene 7.00E+01 NC 1.74E+09 Yes x 79005 1,1,2-Trichloroethane 1.52E-01 C 1.67E+08 Yes x 71556 1,1,1-Trichloroethane 2.20E+03 NC 8.88E+08 Yes x 79016 Trichloroethylene 1.11E+00 C 5.19E+08 Yes x 75014 Vinyl chloride (chloroethene) 2.77E-01 C 1.00E+10 Yes Generic Screening External Site- Specific Screening Internal Site- Specific Assessment