Comparison of Empirical Attenuation Factors to Modeled Attenuation Factors Study Area Site Background Site Background Site Location Site Location Background on Vapor Migration Pathway and Sampling Approach Background on Vapor Migration Pathway and Sampling Approach Co-located indoor air, ambient air, groundwater and soil gas samples (sub-slab and at depth) were collected from 26 commercial and residential building locations in the Study Area between August 2002 and July 2004. Samples were analyzed for the chemicals of potential concern (COPCs) identified in the Draft Human Health Risk Assessment (Target VOCs). Chlorinated and petroleum hydrocarbons were detected in groundwater, soil gas, indoor air, and ambient air. Indoor air sampling results for Target VOCs were adjusted for contributions from background by subtracting the chemical concentration detected in ambient air, likely to have infiltrated the building Depth to groundwater is 8 to 10 feet below ground surface (bgs) 17 geotechnical samples were collected throughout the area. Soil type is generally sandy loam/loamy sand with interbeds of silt loam. Building types range from residential construction with basements or crawl spaces to commercial office or commercial warehouses with slab-on-grade construction. Statistics for Target VOCs Statistics for Target VOCs Conducted a thorough building evaluation prior to developing the Sampling Plan to identify any potential sources of indoor air contamination. Collected groundwater samples, soil gas samples, and ambient air samples with every indoor air sample to assist in determining the source of chemicals found in indoor air. Subtracted ambient air concentrations from indoor air concentrations to account for background. *The Regulatory Agency would not allow correction due to national indoor air background values. Used soil gas data qualitatively as in indicator of whether chemicals detected in indoor air are coming from the groundwater or from an indoor air source. *The Regulatory Agency would not allow the soil gas data to be used quantitatively. Efforts Taken to Minimize or Quantify Background Contributions Efforts Taken to Minimize or Quantify Background Contributions Sample Collection Information Groundwater Soil Gas Indoor Air Ambient Air Sample Duration 20-30 min via low- flow 24 hours 24 hours 24 hours Direct push, in-situ MW - Low-flow (purge at <300 ml/min, sample at <100 ml/min) Analytical Method SW 846-8260 SIM to meet RL goals of Inhalation Pathway Interim Measure Action Levels (IPIMALs) TO-14A w/SIM to meet RL goals of ALs TO-14A w/SIM to meet RL goals of IPIMALs TO-14A w/SIM to meet RL goals of IPIMALs Number of co- located samples 40 32 51 24 Field Sample Method GIVF Sampling - direct push soil gas sampling or permanent soil gas port soil gas sampling (purge then sample). Tier 3 Sampling - Sub- slab soil gas, purge then sample. All methods utilized 6L Summa Canisters. 6L Summa Canisters 6L Summa Canisters Sampling Information Sampling Information Summary of Multi-Media Sampling Results Summary of Multi-Media Sampling Results There is a large range of AFs across the site and no consistent relationship with elevated groundwater and indoor air. The strongest correlation exhibited by the data is the relationship between ambient air and indoor air concentrations. The data show an inverse correlation between groundwater concentrations and measured AFs, indicating that background indoor air/ambient air concentrations are often not related to changes in groundwater (source vapor) concentrations, especially at low (sub-ppb) concentrations. Ambient air concentrations have a significant impact on measured AF and mask measured AFs. At sites with variable subsurface, building construction, and urban ambient air concentrations, it may be difficult to verify that JEM is a reliable predictor of indoor air concentrations. This is especially true at sites with low groundwater concentrations and significant background concentrations in ambient and/or indoor air. Co-located and co-collected indoor air, ambient air, sub-slab soil gas, and groundwater samples should be collected in order to determine if the indoor air concentrations are associated with VI or background. Lessons Learned Lessons Learned Chris Waldron & Kim Prestbo PIONEER Technologies Corporation 360.570.1700 Amy Sidell Philip Services Corporation 425.227.6121 [email protected] [email protected] Collecting groundwater samples from temporary wells using direct push technology. Soil gas sample collection from a permanent soil gas port designed like a miniature monitoring well with sand pack and screen. Sample Collection Sample Collection Chemicals have been detected in soil at the PSC facility. Dense non-aqueous phase liquid (DNAPL), which is primarily comprised of chlorinated solvents, is likely to be present in groundwater at the property adjacent to the west of the site. Chemicals in groundwater appear to have migrated beyond the boundary of the facility towards the southwest. Chemicals associated with releases of chlorinated solvents and petroleum products have been detected in groundwater at Philip Services Corporation’s (PSC’s) former TSD facility and in the surrounding area, a mixed industrial and residential neighborhood in South Seattle. These chemicals are thought to have been released to groundwater from past operations on the PSC property dating back to the 1950’s, including storage of chemical products in underground storage tanks and processing and storage of chemical products in above ground containers without containment prior to environmental regulation. The results of numerous environmental investigations indicate that: PSC is currently implementing an interim measure to protect the health of residents and workers potentially exposed to chemicals migrating from shallow groundwater into indoor air. Freq. Min Max Freq. Min Max Freq. Min Max Freq. Min Max 1,1,1-Trichloroethane 6/32 5.44 82.4 24/32 0.41 480.0 27/32 0.20 14.0 18/32 0.18 0.56 1,1-Dichloroethane 20/32 1.8 265.0 8/32 0.63 610.0 1/32 0.22 0.22 4/32 0.15 0.42 1,1-Dichloroethylene 11/32 0.05 4.46 6/32 0.11 0.59 1/32 0.22 0.22 0/32 -- -- 1,2,4-Trimethylbenzene 4/32 2.68 48.6 25/32 0.18 28.0 32/32 0.76 190.0 32/32 0.35 6.0 1,2-Dichloroethane 7/32 0.1 1.92 1/32 8.1 8.1 13/32 0.14 2.2 2/32 1.3 1.4 1,3,5-Trimethylbenzene 3/32 1.52 10.3 21/32 0.21 3.6 32/32 0.24 89.0 26/32 0.18 1.8 2-Hexanone 0/32 -- -- 14/32 0.67 19.0 4/32 0.8 8.6 11/32 1.2 3.2 Benzene 11/32 0.76 13.35 25/32 0.42 6.6 32/32 1.2 12.0 32/32 0.95 6.7 Chloroethane 5/32 67.3 552.0 8/32 0.28 17.0 2/32 0.28 0.38 2/32 0.48 0.55 Chloroform 1/32 1.76 1.76 15/32 0.13 20.0 24/32 0.2 4.6 4/32 0.2 0.98 cis-1,2-Dichloroethylene 21/32 1.1 265.0 4/32 0.63 460.0 1/32 0.13 0.13 0/32 -- -- Cumene 0/27 -- -- 0/27 -- -- 1/27 20.0 20.0 1/27 20.0 20.0 Ethylbenzene 4/32 2.18 2930.0 23/32 0.28 130.0 32/32 0.56 26.0 32/32 0.49 9.7 Naphthalene 3/32 9.87 20.8 0/32 -- -- 0/32 -- -- 0/32 -- -- Propylbenzene 3/32 1.46 16.30 0/32 -- -- 1/32 48.0 48.0 0/32 -- -- sec-Butylbenzene 2/32 1.42 2.48 0/32 -- -- 0/32 -- -- 0/32 -- -- Tetrachloroethene 13/32 0.05 2.69 25/32 1.1 280.0 27/32 0.23 3.6 17/32 0.2 12.0 Toluene 4/32 1.06 119.0 30/32 0.54 110.0 32/32 5.1 300.0 32/32 3.3 28.0 trans-1,2-Dichloroethylene 7/32 1.06 7.21 0/32 -- -- 0/32 -- -- 0/32 -- -- Trichloroethene 26/32 0.03 400.0 18/32 0.26 370.0 28/32 0.19 27.0 28/32 0.3 29.0 Vinyl Chloride 25/32 0.02 176.0 11/32 0.1 3.9 4/32 0.04 0.1 18/32 0.081 0.68 Ambient Air (ug/m 3 ) Analyte Groundwater (ug/L) Soil Gas (ug/m 3 ) Indoor Air (ug/m 3 ) Note – Frequency is based on number of co-located stations. In cases where more than one media sample were collected, maximum at each station was used for statistics. Calculating Empirical Attenuation Factors Calculating Empirical Attenuation Factors Empirical groundwater to indoor air AFs were calculated for Target VOCs detected in both groundwater and indoor air during co-located sampling events as follows: ) / ( @ _ ) / ( 3 3 m g WT SG Max m g IA AF r Groundwate corrected corrected m m = Where: vGroundwater AF corrected = Measured attenuation factor for groundwater to indoor air (corrected for ambient air) vIA corrected = Measured indoor air concentration corrected for ambient air. vMax_SG@WT = source vapor concentration predicted by Johnson and Ettinger Model (JEM) based on maximum co-located detected groundwater concentration. Comparison of Measured TCE AFs to EPA VI Guidance Figure 3b Default Values Comparison of Measured TCE AFs to EPA VI Guidance Figure 3b Default Values Notes: 1) Default values based on Figure 3b from Draft Guidance for Evaluating Vapor Intrusion to Indoor Air Pathway (EPA, 2002). 2) Empirical AF (TCE_AF_C) calculated for TCE detected in groundwater and indoor air (adjusted for ambient air concentrations). 3) Average TCE Predicted by JEM = average of JEM predicted AF at 10 ug/L for basement and slab-on-grade scenario, assuming sand beneath foundation and loamy sand above water table with depth to groundwater of 305 cm. 1.00E-07 1.00E-06 1.00E-05 1.00E-04 1.00E-03 1.00E-02 1.00E-01 1.00E+00 0.01 0.1 1 10 100 1000 10000 Groundwater Concentration ug/L Measured AF Chlor inated Compounds Petr oleum Compounds Correlation of Measured AFs with Groundwater Concentrations Correlation of Measured AFs with Groundwater Concentrations Range of Values Measured in Groundwater (Source Vapor), Soil Gas, Indoor Air and Ambient Air Range of Values Measured in Groundwater (Source Vapor), Soil Gas, Indoor Air and Ambient Air 0.01 0.1 1 10 100 1000 10000 100000 1000000 Vapor Concentration (ug/m3) Max SG @ WT Soil Gas Indoor Air Ambient Air Corrected IA No consistent AFs measured across site. AFs for all target VOCs detected in groundwater and adjusted indoor air range from 8E-07 to 8E-02. Site-specific JEM AFs for target VOCs range from 1E-04 (slab- on-grade) to 7E-04 (basement). AFs for about 32% of target VOCs fall within the range of JEM-predicted AFs for this area (1E-04 to 7E-04). AFs for about 50% of target VOCs fall above predicted JEM range. AFs for about 18% of target VOCs fall below predicted JEM range. TCE and vinyl chloride most consistently measured in groundwater. TCE most consistently detected in both groundwater and indoor air, but no consistent correlation with elevated indoor air. Vinyl chloride not detected in indoor air above ambient concentrations at any location. Vinyl Chloride 0.1 1 10 100 1000 10000 PCE Vapor Concentration (ug/m3) Max SG @ WT Soil Gas Indoor Air Ambient Air Corrected IA 0.01 0.1 1 10 100 1000 10000 100000 1000000 TCE Vapor Concentration (ug/m3) Max SG @ WT Soil Gas Indoor Air Ambient Air Corrected IA Trichloroethene (TCE) Note: Measured AF for All TCs detected in groundwater and Indoor Air ( Measured AF for All TCs detected in groundwater and Indoor Air (adjusted) adjusted) Tetrachloroethene (PCE) 1.00E-06 1.00E-05 1.00E-04 1.00E-03 1.00E-02 1.00E-01 0 5 10 15 20 25 30 Depth to Contamination from Foundation Vapor Attenuation Factor Sand Loamy Sand Sandy Loam Loam TCE_AF_C Average TCE Predicted by JEM General Observations General Observations