Calculation of Site Specific Groundwater to Indoor Air Volatilization Factors (GIVFs)

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1 Calculation of Site Specific Groundwater to Indoor Air Volatilization Factors (GIVFs) Philip Services Corporation, Seattle, Washington former TSD Facility Indoor Air Interim Measure Ongoing in Mixed Residential/ Commercial/ Industrial Neighborhood March 2004

2 Georgetown Community Study Area

3 Site Background Information Chemical releases to groundwater were likely the result of industrial operations at the property dating to the 1950s. VOCs are the primary set of COPCs at the site, primarily chlorinated hydrocarbons and petroleum hydrocarbons. The results of numerous environmental investigations indicate that: Chemicals have been detected in soil at the Georgetown facility. Chemicals in groundwater appear to have migrated beyond the boundary of the facility towards the southwest. Groundwater studies show that 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.

4 Background on GIVFs PSC was required to implement inhalation pathway interim measures. PSC developed a site-specific approach for evaluating and addressing the inhalation pathway for interim measure implementation. The approach consisted of two steps: Develop site-specific groundwater to indoor air volatilization factors (GIVFs) that represent the relationship of VOCs in groundwater and indoor air. GIVFs were used to develop groundwater Inhalation Pathway Interim Measure Action Levels (IPIMALs), and GIVFs were used to determine, via the Inhalation Pathway Interim Measure (IPIM) Decision Tree, if indoor air concentrations of VOCs would potentially be above levels of concern. The IPIM Decision Tree is a tiered approach for evaluating locations west-southwest of the Georgetown facility on a quarterly basis at least until a final remedy for the site is implemented.

5 Decision Tree for Developing GIVFs

6 The GIVF Approach Co-located indoor air, ambient air, groundwater and soil gas samples were collected from 10 building locations in the GIVF Study Area and were analyzed for the chemicals of potential concern (COPCs) identified in the Draft Human Health Risk Assessment. The results of these chemical analyses were used to develop GIVFs for target compounds (TCs), which are the subset of COPCs considered the most reliable tracers for representing volatilization from groundwater to indoor air. Prior to calculating TC-specific GIVFs, indoor air sampling results for TCs were adjusted for contributions from background by subtracting the maximum of either: 1. The chemical concentration detected in ambient air, likely to have infiltrated the building or 2. The median or mean of the 25th and 75th percentiles from national background indoor air sources, compiled from peer-reviewed literature values. TC-specific GIVFs were calculated by dividing the measured indoor air concentration by the co-located groundwater concentration for each TC and building location.

7 Efforts Taken to Minimize or Quantify Background Contributions Conducted thorough building evaluation prior to developing Sampling Plan. Removed VOC emitting substances (e.g., cleaners, solvents, glues) where possible prior to sampling. 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.

8 Sampling Information Sample Collection Groundwater Soil Gas Indoor Air Ambient Air Information Sample Duration min via low-flow 24 hours 24 hours 24 hours Field Sample Method Low-flow (purge at <300 ml/min, sample at <100 ml/min) Pre-Tier 3 Sampling - 6L Summa Canisters 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 Analytical Method SW SIM to meet RL goals of IPIMALs TO-14A w/sim to meet RL goals of IPIMALs 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

9 GIVFs (IA Corrected) GIVFs (Indoor Air Corrected by Subtracting Ambient Air) GIVF (ug/m3/ug/l) 1.00E E E E E E-03 1,1,1- Tr ic hlor oe t ha ne 1,1- Dic hlor oe t ha ne 1,2,4-Trimethylbenzene 1,2-Dichloroethane 1,3,5-Trimethylbenzene Benzene Chloroethane Ethyl Benzene Tetrachloroethene Tolue ne Trichloroethene Vinyl Chloride EPA Table 2 - alpha= TCE EPA Table 2 - alpha= TCE 1.00E E-05

10 GIVFs (No Correction) GIVFs with No Correction of Indoor Air by Subtracting Ambient Air GIVF (ug/m3/ug/l) 1.00E E E E E E- 03 1,1,1- Tr ic hlor oe t ha ne 1,1- Dic hlor oe t ha ne 1,2,4-Trimethylbenzene 1,2-Dichloroethane 1,3,5-Trimethylbenzene Benzene Chloroethane Ethyl Benzene Tetrachloroethene Tolue ne Trichloroethene Vinyl Chloride EPA Table 2 - alpha= TCE EPA Table 2 - alpha= TCE 1.00E E- 05

11 Comparison of GIVFs for TCE Comparison of Ambient Air Corrected and UnCorrected GIVFs for TCE 1.00E E+01 GIVF (ug/m3/ug/l) 1.00E E E- 02 TCE GIVF AA Corre ct e d TCE GIVF NOT AA Corre c t ed EPA Table 2 - alpha=0.001 EPA Table 3 - alpha= E E- 04

12 Empirical GIVFs Versus JEM GIVFs

13 Summary of GIVF Results Co-located multi-media sampling is essential to determine the source of indoor air concentrations. Ambient Air Sampling Ambient air concentrations have a significant impact on indoor air concentrations. At some locations, ambient air concentrations also appear to have a significant impact on sub-slab soil gas sample results.

14 IPIM Decision Tree Used to Define IPIM Actions Each quarter PSC evaluates groundwater data to determine if new buildings need to be sampled or may require the installation of a depressurization system.

15 Status of IPIMs Completed to Date Summary of IPIMs Number of Buildings Evaluated Complete No Access or Removed from IPIM List Total Buildings in Study Area 209 Buildings to be Sampled (Tier 3) Buildings where IMs will be Installed (Tier 4) Buildings Evaluated in Tier 3 that moved to Tier 4 2 0

16 Lessons Learned Ambient air and potential indoor air sources of VOCs are very important confounding factors that should be addressed when evaluating the VI pathway. When collecting indoor air samples, co-located and co-collected ambient air, sub-slab soil gas, and groundwater samples should also be collected in order to determine if the indoor air concentrations are associated with VI or background. Even with co-located and co-collected samples, the results are often very difficult to interpret at a single location. However, trends can be identified if sampling is performed at multiple locations.

17 Authors Carolyn Mayer & Amy Sidell Philip Services Corporation Chris Waldron & Kim Prestbo PIONEER Technologies Corporation