Recent Trends and Critical Issues for Assessment of Vapour - PowerPoint PPT Presentation

Recent Trends and Critical Issues for Assessment of Vapour Intrusion Pathway SABCS Soil Vapour Forum July 8, 2008, Vancouver, BC Dr. Ian Hers Golder Associates Ltd. Chemical vapor Migration Soil Water Contamination Table

Assessment Challenge � Identify buildings/sites with potentially complete pathway for vapour intrusion (VI) � Determine whether indoor vapour presents adverse impacts/risks to those in buildings � Use the right tool kit of methods ? and approaches � Do this is way that is sufficiently certain, efficient and cost effective GOLDER ASSOCIATES

Precipitation CSM Stack Effect Background Wind Building Conditions Snow Advection Oxygen Mixing Infiltration Cracks Wet Dry Bio Layer Layers Diffusion Fresh-water lens (non- contaminated Capillary Transition Volatilisation groundwater) Zone NAPL Source Water table fluctuations As go from source to indoor air measurements there is compounding effect of variability GOLDER ASSOCIATES

The Recent Context  Vapor intrusion (VI) is a potential exposure pathway at sites with volatile chemicals (many sites!)  Perception and potential for breathing “toxic” vapours makes this a challenging pathway  Increasing number of sites with demonstrated VI including several high profile sites with large chlorinated solvent plumes below residential areas  VI has caught the attention of regulators, lawyers and public (several large lawsuits, Cambridge Ontario 100M, Quebec site 250 M, Redfields 400 M) http://www.tceblog.com/posts/1147841386.shtml GOLDER ASSOCIATES

Historical Early IAQ Concerns (1970’s & Early IAQ Concerns (1970’s & early 1980’s) (VOCs as Carcinogens ) Overview early 1980’s) (VOCs as Carcinogens ) Early Experience (1980’s) Early Experience (1980’s) (Love Canal, 1985; Hillside MA School 1989) (Love Canal, 1985; Hillside MA School 1989) • It has been a 20 year process for: Johnson & Ettinger Model Johnson & Ettinger Model (1991) [The beginning of the end…] (1991) [The beginning of the end…] ► Recognition ► Science Early Guidance (1990’s) Early Guidance (1990’s) (MA 1992, ASTM E-1739 1995, CCME (MA 1992, ASTM E-1739 1995, CCME ► Experience 2000 [Limited knowledge of pathway…] 2000 [Limited knowledge of pathway…] ► Guidance Experience (~ 2000 on) Experience (~ 2000 on) (“Colorado” Sites, Endicott, NY) (“Colorado” Sites, Endicott, NY) • Knowledge improving [We need to take this pathway seriously …] [We need to take this pathway seriously …] but questions (and Recent Guidance (2005 on) Recent Guidance (2005 on) misconceptions!) remain (USEPA 2002, Health Canada 2004, CA (USEPA 2002, Health Canada 2004, CA 2005, NJ 2005, ITRC 2007, ASTM 2008?) 2005, NJ 2005, ITRC 2007, ASTM 2008?) IAQ = indoor air quality [Hmmm…Lot of different approaches] [Hmmm…Lot of different approaches] GOLDER ASSOCIATES

What do we know (from observations)  Many chlorinated solvent sites with significant VI impacts, much smaller number of petroleum sites (aerobic biodegradation)  Large degree spatial variability in groundwater and soil vapour; and temporal variability in soil vapour and indoor air  Significant VI impacts for range of building types and foundations (buildings generally depressurized, flux controlled by soil)  USEPA VI database has contributed significant to understanding of pathway – 4 yrs, 44 sites, over 2000 data points GOLDER ASSOCIATES

Comparison J&E –AFs to Empirical Data (Groundwater AF, Chlorinated hydrocarbons) (proposed alpha) 1.E-02 HC AF curves for Alliant - 11 DCE - C Bay Area 1 - TCE - L different soil types Bay Area 2 - TCE - L CDOT - TCE, 111 TCA, 11 DCE - SI Davis - TCE, cis-12-DCE - S 1.E-03 Eau Claire - TCE - S Hamilton Sunstrand - 11 DCE - S&G Hopewell Precision - TCE - S&G LAFB - TCE & 11DCE - LS 1.E-04 Lockwood - TCE & PCE - L Alpha MADEP 1 TCE - S MADEP 2 TCE - S Mountain View TCE - LS Redfields 11 DCE - S to SI 1.E-05 Twins Inn TCE,cis-DCE,11 DCE - S Uncasville PCE - S Harcros-Tri State PCE - S Site 1 TCE - S&G 1.E-06 Endicott TCE S&G Wall Township PCE - S � = 1.5E-4 � = 3.8E-5 Light Blue = Sand & gravel Red = Loam Sand (Coarse-grained) � = 7.7E-5 Dark Blue = Sand Green = Clay a = 7.1E-6 Loamy Sand � = 1.6E-5 = Loamy Sand Median alphas provided Orange Sandy Loam 1.E-07 Loam (Fine-grained) 0 3 6 9 12 15 Depth to Vapor Source below Foundation (m) GOLDER ASSOCIATES

Redfield, Single Point vs Average Alpha ( Redfield Site) 100% 90% 80% 1.E-03 Cumulative Percent 70% Attenuation Factor 1.E-04 60% 50% 1.E-05 40% 1.E-06 30% 1.E-07 20% Mar-97 Jul-98 Dec-99 Apr-01 Sep-02 Jan-04 May-05 Oct-06 10% Sample Date H1 H2 H3 H4 H5 0% 1.0E-06 1.0E-05 1.0E-04 1.0E-03 Attenuation Factor Singe Point Alphas Average Alpha Geomean Alpha Courtesy David Folkes, Envirogroup GOLDER ASSOCIATES

Groundwater Alpha - Residential & Commercial - All Data 1.E+00 1 ug/m 3 10 ug/m 3 100 ug/m 3 1.E-01 Groundwater-Air Alpha 1.E-02 1.E-03 1.E-04 TCE PCE 1.E-05 1,1-DCE 1,1,1-TCA Benzene 1.E-06 Ethylbenzene Toluene Xylenes 1.E-07 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 Normalized Groundwater Alpha - Residential & Commercial - All Data Predicted vapor conc. from groundwater (ug/m 3 ) 1.E+00 Filter TCE Filter all other chemicals 1.E-01 Groundwwater-air AF 1.E-02 Normalized to 1.E-03 background 1.E-04 TCE PCE 1.E-05 1,1-DCE 1,1,1-TCA Benzene 1.E-06 Ethylbenzene Toluene Xylenes 1.E-07 1.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 Predicted Vapor Conc. from Groundwater/ 90th Background (ug/m 3 ) GOLDER ASSOCIATES

Comparison J&E - AFs to Chlorinated and Petroleum Hydrocarbon Empirical Data (soil vapour aresidential, filtered) 1.E+00 Soil vapour chlorinated solvent Subslab Data (417 points, Soil vapour PHC filtered from 1549) Subslab vapour 1.E-01 Sand (coarse-grained) HC AF curves Loamy Sand Sandy Loam Soil Vapour Alpha Loam (fine-grained) 1.E-02 Chlorinated solvents 1.E-03 1.E-04 BTEX (support lower alpha factor) 1.E-05 Most of this data couldn't be distinguished from background 1.E-06 0 2 4 6 8 10 Distance building to vapour measurement (m) GOLDER ASSOCIATES

Soil Vapor Alpha - Residential- Chlorinated Solvent - Filtered 1.E-01 Jackson PCE - LS 1.E-02 MADEP1 TCE - S Mountainview TCE - LS Uncasville PCE - S 1.E-03 Harcros-Tri States PCE - S Alpha Grants PCE and TCE - S Site 1 TCE - S&G 1.E-04 Raymark 11 DCE - S&G Endicott TCE - S&G 1.E-05 1.E-06 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 Measured vapor conc. (ug/m 3 ) GOLDER ASSOCIATES

Wall Township, NJ PCE in groundwater  Dry cleaners source of two large PCE plumes (1.5 by 2 miles!), sand, depth to groundwater = 20’  Dry cleaners decommissioned prior to 1991  PCE detected in private wells 1997  Indoor air testing began 2001  Max indoor PCE concentration!: Residential ~ 2000 ug/m 3 , Commercial ~ 1500 ug/m 3 GOLDER ASSOCIATES

Wall Township, Indoor Air  Max indoor PCE concentration!: Residential houses ~ 2000 ug/m 3 , Commercial (1 building) ~ 1500 ug/m 3 LEGEND PCE concentration indoor air (ug/m 3 ) GOLDER ASSOCIATES

Wall Township, Indoor Air David Brehner, AWMA Pittsburgh, 2006 GOLDER ASSOCIATES

Wall Township, Indoor Air GOLDER ASSOCIATES

Pro’s & Con’s Different Media Media Pro’s Con’s Soil Data may be available, low Partitioning highly uncertain, cost, low temporal variability high spatial variability Ground Data may be available, low Partitioning uncertain, not water cost, moderate temporal representative if unsaturated variability zone source External Avoids partitioning, more Spatial variability moderate to soil direct indication exposure, high, temporal variability vapour may integrate sources moderate, method issues Subslab Closer to receptor, avoids Intrusive, cost, small scale vapour lateral variability spatial variability can be high Air Most direct indication (only Intrusive, cost, temporal for existing building) variability moderate to high, background issues GOLDER ASSOCIATES

Relationship Groundwater and Soil (or lack thereof) (Paul Johnson) GOLDER ASSOCIATES Golder Associates Ian Hers, 2004

Meta-data Analysis – Co-located soil-soil vapor Measured F1 in Soil Vapour (mg/m 3 ) 1.E+07 Difference depth soil gas & soil > 0.5 m Vm/Vp 50th = 2.1E-5, 90th = 3.6E-3 CPPI Database 1.E+06 Difference depth soil gas & soil < 0.5 m Vm/Vp 50th = 9.3E-5, 90th = 7.4E-3 1.E+05 1.E+04 F1 (TPH g ) vapor 1.E+03 concentrations 1.E+02 predicted using 1.E+01 3-phase model, 1.E+00 f oc = 0.005 1:1 1:10 1:100 1.E-01 1.E-02 1.E-02 1.E+00 1.E+02 1.E+04 1.E+06 Predicted F1 in Soil Vapour (mg/m 3 ) Key Approximate relationship between measured & predicted vapor points: concentrations. Measured vapor > 10X less than predicted. GOLDER ASSOCIATES