0An Evalution of Contaminant Vapor Intrusion Into Buildings Through a Study of Field Data

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Soil Vapor Intrusion...
A Decade of Regulatory Requirements Experiences
Paul W. Locke MA DEP Bureau of Waste Site
Cleanup One Winter Street Boston, MA
02108 617-556-1160 Paul.Locke_at_state.ma.us
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Late 1980s
Hillside School, Needham Mass
Wowthat can happen?
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MADEP Regulatory Response

1. Place concern on radar screen
2. Incorporate into cleanup standards
3. Obtain real world data to gauge
   scope/parameters of problem
4. Provide tools/toolbox to regulated community

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1 On the Radar Screen
Training/awareness agency staff and regulated
community Regulatory requirement to notify MADEP
if pathway likely or confirmed
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2 Incorporate into Cleanup Standards
Lowest of 3 or IAQ Background, whatever is
higher
Air
Transport Model
Groundwater
Lowest of 3 or GW background or PQL, whatever
higher
GW Standard
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1993 Standards Transport Model
Johnson Ettinger
Assumed 10 Henrys Law Equilibrium Condition
GW to Soil Gas
Soil Gas to Indoor Air
? 5 x 10-4
crude and limited application of JE
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Calculated GW Standards (1993)
Compound Standard (?g/L)
TCE 300
1,1,1-TCA 4000
PCE 3000
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1996 Evaluation

• Are these Standards Really Protective?
• Lets take a Look at our Files

GW Conc
Soil Gas Conc
Indoor Air Conc
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MADEP Records Review
Database Search
DEP Files 6000
Potential Sites Evaluated 177
Adequate Data 59 sites
BTEX 23 (39)
Chlorinated 36 (61)
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Findings Were the 1993 Standards Generally
Conservative Protective?
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Petroleum Sites?
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Chlorinated Solvent Sites?
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Proposed Revisions(2004)
Chemical-Specific Evaluations
Conservative Pathway Scenario
Conservative Site/Soil Properties
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Key JE Inputs (MADEP 2004)

• Groundwater
• 7 feet below grade
• 1 foot below basement floor

• Building Depressurization
• ?P 4 Pa (40 g/cm-s2)
• 0.45 air exchanges/hour

• Sand, total porosity
• n 0.43

• Vadose Zone Moisture Content
• ?w ????

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Moisture Level Below Buildings
Dry Soils?
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Vadose Zone Soil Moisture
What is a realistic, conservative value..
beneath buildings?
Little study data available, but.
Fair amount of chemical analytical data from soil
samples beneath buildings!
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0.06
Moisture (w/w) to Soil Moisture(v/v)
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Proposed Revisions to Current MADEP Groundwater
Standards (Soil Vapor Pathway)
Up to an order of magnitude lower for some
chlorinated solvents
Public Comment Period Ended December 10, 2004
Stay Tuned..
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4 Provide Tools Toolboxes Site-Specific
Evaluations
Guidance Documents Rules of Thumb
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Site-Specific Pathway Evaluation
(Mandatory when gt Generic GW Standard)

• Key Tools
• Soil Gas Assessment
• Indoor Air Analysis
• Vertical Profiling

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MADEP Recommended Approach
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MADEP Guidelines for Soil Gas Evaluation
Compound Screen out levels ppmV Screen out levels ppmV Screen out levels ppmV Screen out levels ppmV
Compound PID (eV) PID (eV) PID (eV) FID
Compound lt10 10-11.4 gt11.4 FID
Toluene 11 12 12 10
Ethylbenzene 4 4 4 3
Xylenes 25 26 24 22
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MADEP Guidelines for Obtaining Soil Gas Samples
Infiltration displaces/ solubilizes soil gases
place probe below bldg/pavement for
representative samples
enclosed space
grass
pavement
building
foundation
foundation cracks
diffusing vapors
depth to
vadose zone
groundwater
Negative bias
capillary zone
dissolved chemical in
groundwater
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Real World Example of Negative Bias TCE Soil
Gas Data from 2 Homes
Date Interior Exterior 9/96 397 /
281 24 / lt1 12/96 16 / 80 lt1 / lt1
3/97 6 / 64 lt1 / lt1 6/97 19 / 226
lt1 / lt1 8/97 157 / 594 4 / lt1
All data ppb v/v TCE
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Obtaining Indoor Air Samples
Winter months usually worst case - Other times
may not rule out pathway
Stack Effects
windows closed
frost layer
Furnace combustion
Vapors
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Groundwater/Vertical Profiling
well
Infiltration
fresh water lens
groundwater flow
VOC plume
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For More Information..

• BWSC.Information_at_state.ma.us or
  BWSC.Regulation_at_state.ma.us
• Characterizing Risks Posed by Petroleum
  Contaminated Sites Implementation of the MADEP
  VPH/EPH Approach
• www.mass.gov/dep/bwsc/files/02-411.pdf
• Indoor Air Sampling and Evaluation Guide
• www.mass.gov/dep/ors/files/indair.pdf
• MCP Numerical Standards GW-2
• www.mass.gov/dep/bwsc/files/standard /gw2/gw2.htm