EPA s Vapor Intrusion Database

Transcription

1 EPA s Vapor Intrusion Database Characterization and Evaluation of Attenuation Factors for Chlorinated VOCs in Residences Helen Dawson, PhD Rich Kapuscinski, PhD March 20,

2 Acknowledgements OSWER support Rich Kapuscinski, OSRTI, OSWER Henry Schuver, ORCR, OSWER Ian Hers, Golder Associates William Wertz, formerly NYDEC Jeffrey Kurtz, Envirogroup 3/20/2012 2

3 Outline Vapor attenuation factor definition Database contents & limitations Database screening Empirical attenuation factor distributions Summary 3/20/2012 3

4 Vapor Attenuation Factor AF VI c c IA, VI SV AF EMP, VI c IA, VI c csv Backgd 3/20/2012 4

5 Subslab TCE Concentration (ug/m3) All Six Bldgs UA03 UA18 UA19 UA21 UA22 UA24 Groundwater Attenuation Factor Indoor Air TCE Concentration (ug/m 3 ) Variability in Indoor Air and Subsurface Vapor Concentrations 100 Variability of TCE in Indoor Air Over Time Within Buildings at Lowry Air Force Base 10 UA03 UA18 UA19 1.0E+00 Variability in TCE Attenuation Factors for Residential Buildings at Lowry Air Force Base 1 UA21 UA22 UA24 1.0E-01 Max E-02 95th % Sample Date 1.0E-03 75th % 50th % 25th % Variability of TCE in Subslab Vapor Within and Among Buildings at Lowry Air Force Base 1.0E-04 5th % E-05 Min 1000 UA03 SS 100 UA18 SS UA19 SS 1.0E UA21 SS UA22 SS UA24 SS Building 0.1 Sample Date 3/20/2012 5

6 Database Contents Data Set Attribute Full Database CHC VOCs in Residences EPA Regions represented 1, 2, 5, 6, 7, 8, 9, 10 1, 2, 5, 7, 8, 9, 10 States represented Sites represented Buildings represented Attenuation factors 2,929 2,487 AF ss 1,582 (54%) 1,231 (49%) AF gw 1,021 (35%) 952 (38%) AF sg 235 (8%) 213 (9%) AF cs 91 (3%) 91 (4%) 3/20/2012 6

7 Database Limitations Reflects only a subset of the hundreds of vapor intrusion sites identified nationwide Types and amount of data pairings differ among sites A relatively high percentage of the total data pairings come from a small group of sites, primarily from four EPA regions 3/20/2012 7

8 Database Screening Purpose: Identify indoor air subsurface vapor sample pairings representative of vapor intrusion Focus on chemicals of site-specific concern (subsurface concentrations > RL) Examine consistency of building-specific results (consistent AFs for multiple VOCs) Screen indoor air or subsurface vapor to minimize influence of background 3/20/2012 8

9 Indoor Air Concentration (ug/m 3 ) Theoretical Influence of Background on Indoor Air Concentrations 1000 Observed Indoor Air Concentration Alpha = Background Indoor Air Conc. = 1 ug/m Subslab Concentration (ug/m 3 ) 3/20/

10 Indoor Air Concentration (ug/m3) Indoor Air Concentration (ug/m3) Indoor Air Concentration (ug/m3) Indoor Air Concentration (ug/m3) Database Screening: Effect on Distribution of Subslab Soil Gas Attenuation Factors 1.E+04 1.E+03 1.E+02 1.E+01 IA > RL IA < RL Alpha = 1.0 Alpha = 1E -1 CHC in Residences 1.E+00 Alpha = 1E -2 1.E E E+04 1.E E+03 1.E E E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 Alpha = 1E -3 Alpha = 1E -4 Alpha = 1E -5 IA > RL IA < RL SS > RL; AF consistency Subslab (ug/m3) 1.E+02 Alpha = E+01 Alpha = 1E -1 1.E+00 1.E E E+04 1.E E+03 1.E E E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 Subslab (ug/m3) 1.E+02 1.E+01 Alpha = 1E -2 Alpha = 1E -3 Alpha = 1E -4 Alpha = 1E -5 IA > RL IA < RL Alpha = 1.0 Alpha = 1E -1 1.E+00 Alpha = 1E -2 IA > Bkgd 1.E E+04 1.E E+03 1.E E E E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E+02 Subslab (ug/m3) 1.E+01 Alpha = 1E -3 Alpha = 1E -4 Alpha = 1E -5 IA > RL IA < RL Alpha = 1.0 Alpha = 1E -1 1.E+00 Alpha = 1E -2 1.E -01 Alpha = 1E -3 Alpha = 1E -4 1.E -02 Alpha = 1E -5 SS > 50X Bkgd 1.E E E E E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 3/20/2012 Subslab (ug/m3) 11

11 Frequency Subslab Soil Gas Attenfaion Factor Identifying Data Sets Less Influenced by Background Frequency Cumulative Probability Baseline 1.E-02 SS > 10X Bkgd SS > 50X Bkgd Source Strength Screen SS > 100X Bkgd 1.E-03 SS > 500X Bkgd IA > Bkgd 1.E+00 Baseline Screen 1.E-01 Indoor Air Screen Baseline IA > Bkgd SS > 10X Bkgd SS > 50X Bkgd SS > 100X Bkgd SS > 500X Bkgd Series E-04 Log. (Baseline) 0 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 Subslab Soil Gas Attenuation Factor 1.E Z-Score 3/20/

12 Screens Determined Best for Limiting Influence of Background Subslab soil gas Groundwater Exterior Soil Gas (SS > 50X Bkgd) (GW > 1000X Bkgd) (SG > 50X Bkgd) Crawlspace (IA > Bkgd) 3/20/

13 SS > 50X Bkgd BillingsPCE DenverPCEBB Endicott Georgetown Harcros/Tri State Hopewell Precision Jackson LAFB Orion Park Raymark SCM-Cortlandville West Side Corporation Subslab Soil Gas Attenuation Factor Subslab Soil Gas Attenuation Factor Inter- and Intra-Site Variability 1.0E E-01 Max 1.0E E-03 95th % 75th % 50th % 25th % 5th % 1.0E-04 Min 1.0E-05 Overall median = 0.003; overall 95 th percentile = Median varies by more than one order of magnitude across the 12 sites. Range from the 5th to 95th percentile values exceeds two orders of magnitude. 3/20/

14 Subslab Soil Gas Attenuation Factor Subslab Soil Gas Attenuation Factor by Foundation 1.0E E-01 Max 1.0E E-03 95th % 75th % 50th % 25th % 5th % 1.0E-04 Min 1.0E-05 SS > 50X Bkgd Basement Slab-On-Grade Poured concrete foundations (basement or slab on grade) have similar vapor attenuation characteristics. 3/20/

15 Subslab Soil Gas Attenuation Factor Subslab Soil Gas Attenuation Factor by Chemical 1.0E E-01 Max 1.0E E-03 95th % 75th % 50th % 25th % 5th % 1.0E-04 Min 1.0E-05 SS > 50X Bkgd TCE PCE 111TCA 11DCE The median and 95 th percentile are within a narrow range for each CHC. 3/20/

16 Groundwater Attenuation Factor Groundwater Attenuation Factor Inter- and Intra-Site Variability 1.E+00 1.E-01 1.E-02 Max 1.E-03 1.E-04 1.E-05 1.E-06 95th % 75th % 50th % 25th % 5th % Min 1.E-07 Overall median = 7E-05 ( ); overall 95th percentile = Median varies by more than two orders of magnitude across the 24 sites. Range from the 5th to 95th percentile values exceeds two orders of magnitude. 3/20/

17 Groundwater Attenuarion Factor Groundwater Attenuation Factor by Soil Type 1.0E E E E E E E-06 Max 95th % 75th % 50th % 25th % 5th % Min 1.0E-07 Fine Coarse V.Coarse AFs for finer-grained soil < AFs for coarser-grained soil. Pattern is generally consistent with the conceptual model for vapor intrusion. 3/20/

18 Groundwater Attenuation Factor Groundwater Attenuation Factor by Water Depth 1.0E E E E E E E-06 Max 95th % 75th % 50th % 25th % 5th % Min 1.0E-07 < 1.5 m m 3-5 m > 5 m Depth to Groundwater AFs generally decrease with increasing depth to water through 5 m bgs. Pattern is generally consistent with the conceptual model for vapor intrusion. 3/20/

19 Exterior Soil Gas Attenuation Factor Soil Gas Attenuation Factor Inter- and Intra-Site Variability 1.E+01 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 Max 95th % 75th % 50th % 25th % 5th % Min 1.E-05 1.E-06 Overall median = 0.004, slightly larger than AF ss (0.003); Overall 95 th percentile = 0.3 >> AF ss (0.03). 3/20/

20 Crawlspace Attenuation Factor Crawlspace Attenuation Factor Inter- and Intra-Site Variability 1.E+01 Max 1.E+00 95th % 75th % 50th % 25th % 1.E-01 5th % Min 1.E-02 IA > Bkgd Grants Jackson LAFB Lockwood Generally little attenuation occurs between the crawlspace and indoor air space. 3/20/

21 Groundwater (GW > 1000X Bkgd) Exterior Soil Gas (SG > 50X Bkgd) Subslab Soil Gas (SS > 50X Bkgd) Crawlspace (IA > Bkgd) Attenuation Factor Comparative Summary of Attenuation Factors 1.E+01 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 Max 95th % 75th % 50th % 25th % 5th % Min 1.E-07 Pattern is generally consistent with the conceptual model for vapor intrusion (e.g., AF SS > AF gw,). 3/20/

22 Summary EPA s vapor intrusion database represents the most comprehensive compilation of vapor intrusion data for CHCs in residences available at this time. The analyses show that it is important to consider the influence of background sources. 3/20/

23 Summary (continued) The attenuation factor distributions obtained for groundwater and subslab soil gas are generally consistent with the conceptual model for vapor intrusion. The ranges of attenuation factors obtained for each medium after screening span several orders of magnitude. 3/20/

24 Contact Information Helen Dawson (703) Rich Kapuscinski (703) /20/