Recent Trends and Critical Issuesfor Assessment of Vapour

Intrusion Pathway

Dr. Ian HersGolder Associates Ltd.

SoilContamination

WaterTable

Chemical vaporMigration

SABCS Soil Vapour ForumJuly 8, 2008,

Vancouver, BC

GOLDER ASSOCIATES

?

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

NAPL Source

Fresh-water lens (non-contaminatedgroundwater)

Infiltration

Precipitation

Diffusion

Volatilisation

DryWet

Layers

Oxygen

Capillary TransitionZone

Water table fluctuations

Wind Background

Cracks

Mixing

Building Conditions

Bio Layer

AdvectionSnow

Stack Effect

As go from source to indoor air measurementsthere is compounding effect of variability

CSM

GOLDER ASSOCIATES

The Recent Context

Vapor intrusion (VI) is a potential exposure pathway atsites with volatile chemicals (many sites!)

Perception and potential for breathing “toxic” vapoursmakes this a challenging pathway

Increasing number of sites with demonstrated VIincluding several high profile sites with large chlorinatedsolvent plumes below residential areas

VI has caught the attention of regulators, lawyers andpublic (several large lawsuits, Cambridge Ontario 100M,Quebec site 250 M, Redfields 400 M)http://www.tceblog.com/posts/1147841386.shtml

GOLDER ASSOCIATES

Johnson & Ettinger Model(1991) [The beginning of the end…]

Johnson & Ettinger Model(1991) [The beginning of the end…]

Early Guidance (1990’s)(MA 1992, ASTM E-1739 1995, CCME2000 [Limited knowledge of pathway…]

Early Guidance (1990’s)(MA 1992, ASTM E-1739 1995, CCME2000 [Limited knowledge of pathway…]

• It has been a 20 yearprocess for:

►Recognition

►Science

►Experience

►Guidance

• Knowledge improvingbut questions (andmisconceptions!) remain

Experience (~ 2000 on)(“Colorado” Sites, Endicott, NY)[We need to take this pathway seriously …]

Experience (~ 2000 on)(“Colorado” Sites, Endicott, NY)[We need to take this pathway seriously …]

HistoricalOverview

Recent Guidance (2005 on)(USEPA 2002, Health Canada 2004, CA2005, NJ 2005, ITRC 2007, ASTM 2008?)[Hmmm…Lot of different approaches]

Recent Guidance (2005 on)(USEPA 2002, Health Canada 2004, CA2005, NJ 2005, ITRC 2007, ASTM 2008?)[Hmmm…Lot of different approaches]

Early IAQ Concerns (1970’s &early 1980’s) (VOCs as Carcinogens)Early IAQ Concerns (1970’s &early 1980’s) (VOCs as Carcinogens)

Early Experience (1980’s)(Love Canal, 1985; Hillside MA School 1989)Early Experience (1980’s)(Love Canal, 1985; Hillside MA School 1989)

IAQ = indoor air quality

GOLDER ASSOCIATES

What do we know(from observations)

Many chlorinated solvent sites with significant VIimpacts, much smaller number of petroleumsites (aerobic biodegradation)

Large degree spatial variability in groundwaterand soil vapour; and temporal variability in soilvapour and indoor air

Significant VI impacts for range of building typesand foundations (buildings generallydepressurized, flux controlled by soil)

USEPA VI database has contributed significantto understanding of pathway – 4 yrs, 44 sites,over 2000 data points

GOLDER ASSOCIATES

Comparison J&E –AFsto Empirical Data

(Groundwater AF, Chlorinated hydrocarbons)(proposed alpha)

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

0 3 6 9 12 15Depth to Vapor Source below Foundation (m)

Alp

ha

Alliant - 11 DCE - C

Bay Area 1 - TCE - L

Bay Area 2 - TCE - L

CDOT - TCE, 111 TCA, 11 DCE - SI

Davis - TCE, cis-12-DCE - S

Eau Claire - TCE - S

Hamilton Sunstrand - 11 DCE - S&G

Hopewell Precision - TCE - S&G

LAFB - TCE & 11DCE - LS

Lockwood - TCE & PCE - L

MADEP 1 TCE - S

MADEP 2 TCE - S

Mountain View TCE - LS

Redfields 11 DCE - S to SI

Twins Inn TCE,cis-DCE,11 DCE - S

Uncasville PCE - S

Harcros-Tri State PCE - S

Site 1 TCE - S&G

Endicott TCE S&G

Wall Township PCE - S

Sand (Coarse-grained)

Loamy Sand

Sandy Loam

Loam (Fine-grained)

Light Blue = Sand & gravel a = 1.5E-4 Red = Loam a = 3.8E-5

Dark Blue = Sand a = 7.7E-5 Green = Clay a = 7.1E-6

Orange = Loamy Sand a = 1.6E-5 Median alphas provided

HC AF curves fordifferent soil types

GOLDER ASSOCIATES

Redfield, Single Point vs AverageAlpha (Redfield Site)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1.0E-06 1.0E-05 1.0E-04 1.0E-03

Attenuation Factor

Cu

mu

lati

ve

Perc

en

t

Singe Point Alphas Average Alpha Geomean Alpha

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

Ma

r-9

7

Ju

l-9

8

De

c-9

9

Ap

r-0

1

Se

p-0

2

Ja

n-0

4

Ma

y-0

5

Oct-

06

Sample Date

Att

en

ua

tio

nF

ac

tor

H1 H2 H3 H4 H5

Courtesy David Folkes, Envirogroup

GOLDER ASSOCIATES

Groundwater Alpha - Residential & Commercial - All Data

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07

Predicted vapor conc. from groundwater (ug/m3)

Gro

un

dw

ate

r-A

irA

lph

a

TCEPCE1,1-DCE1,1,1-TCABenzeneEthylbenzeneTolueneXylenes

100 ug/m310 ug/m31 ug/m3

Normalized Groundwater Alpha - Residential & Commercial - All Data

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

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/m3)

Gro

un

dw

wate

r-a

irA

F

TCEPCE1,1-DCE1,1,1-TCABenzeneEthylbenzeneTolueneXylenes

Filter all other chemicalsFilter TCE

Normalized tobackground

GOLDER ASSOCIATES

Comparison J&E - AFs to Chlorinated andPetroleum Hydrocarbon Empirical Data

(soil vapour aresidential, filtered)

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 2 4 6 8 10Distance building to vapour measurement (m)

So

ilV

ap

ou

rA

lph

a

Soil vapour chlorinated solventSoil vapour PHCSubslab vapourSand (coarse-grained)Loamy SandSandy LoamLoam (fine-grained)

Subslab Data (417 points,

filtered from 1549)

Most of this data couldn't be

distinguished from background

Chlorinatedsolvents

HC AF curves

BTEX (support lower alpha factor)

GOLDER ASSOCIATES

Soil Vapor Alpha - Residential- Chlorinated Solvent - Filtered

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+02 1.E+03 1.E+04 1.E+05 1.E+06

Measured vapor conc. (ug/m3)

Alp

ha

Jackson PCE - LS

MADEP1 TCE - S

Mountainview TCE - LS

Uncasville PCE - S

Harcros-Tri States PCE - S

Grants PCE and TCE - S

Site 1 TCE - S&G

Raymark 11 DCE - S&G

Endicott TCE - S&G

GOLDER ASSOCIATES

Wall Township, NJ

PCE in groundwater

Dry cleaners source of two large PCEplumes (1.5 by 2 miles!), sand, depth togroundwater = 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/m3, Commercial ~ 1500 ug/m3

GOLDER ASSOCIATES

LEGEND

PCE concentration indoor air (ug/m3)

Wall Township, Indoor Air

Max indoor PCEconcentration!:Residentialhouses ~ 2000ug/m3,Commercial (1building) ~ 1500ug/m3

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

Intrusive, cost, temporalvariability moderate to high,background issues

Most direct indication (onlyfor existing building)

Air

Intrusive, cost, small scalespatial variability can be high

Closer to receptor, avoidslateral variability

Subslabvapour

Spatial variability moderate tohigh, temporal variabilitymoderate, method issues

Avoids partitioning, moredirect indication exposure,may integrate sources

Externalsoilvapour

Partitioning uncertain, notrepresentative if unsaturatedzone source

Data may be available, lowcost, moderate temporalvariability

Groundwater

Partitioning highly uncertain,high spatial variability

Data may be available, lowcost, low temporal variability

Soil

Con’sPro’sMedia

GOLDER ASSOCIATESGolder Associates Ian Hers, 2004

Relationship Groundwaterand Soil (or lack thereof) (Paul Johnson)

GOLDER ASSOCIATES

1.E-02

1.E-01

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-02 1.E+00 1.E+02 1.E+04 1.E+06

Predicted F1 in Soil Vapour (mg/m3)

Me

asu

red

F1

inS

oil

Va

po

ur

(mg

/m3)

Difference depth soil gas & soil > 0.5 mVm/Vp 50th = 2.1E-5, 90th = 3.6E-3Difference depth soil gas & soil < 0.5 mVm/Vp 50th = 9.3E-5, 90th = 7.4E-3

1:1 1:10 1:100

Meta-data Analysis –Co-located soil-soil vapor

Approximate relationship between measured & predicted vaporconcentrations. Measured vapor > 10X less than predicted.

Keypoints:

F1 (TPHg) vaporconcentrationspredicted using3-phase model,

foc = 0.005

CPPI Database

GOLDER ASSOCIATES

Soil Vapour Data

More direct indication of potential exposure, canintegrate sources (if in right location!), potentiallyless conservative, but …

Significant challenge is observed spatial and temporalvariability in soil vapour concentrations: Capping effect of building

“Rain shadow” and drier soils below building

“Oxygen limitations” leading to reduced biodegradation

Barometric pumping

Influence of building (subslab fill, utilities, advection)

Deeper near source data least affected by variability(shallow external data may not be representative)

Poor sampling methods also a problem

GOLDER ASSOCIATES

Endicott Case StudyBill Wertz, NYDEC

Bill Wertz, NYDEC

Courtesy JustinDeming, BillWertz, NYSDEC,EPA/AEHSWorkshopMarch 2008

GOLDER ASSOCIATES

OutlineEndicott Case Study

Bill Wertz, NYDEC

GOLDER ASSOCIATES

Vol. Water Content vs. Y

Y

Vol. Water Content

0

2

4

6

8

0.0 0.1 0.2 0.3 0.4 0.5

0.22

0.26

0.3

0.34

0.38

-10 0 10 20 30 40-5

0

5

10

0.5 0.5

1.5 1.5

2.5 2.5

3.5 3.5

4.5 4.5

5.5 5.5

6.5 6.5

-10 0 10 20 30 40-5

0

5

10

SCS Loam

Vol. Water Content

Dep

th(m

)

Steady State~ 3 yr

InitialCondition Vol. Water Content

Hydraulic Head

0

2

4

6

8

Ksat = 1.39E-04cm/sec

FC = 0.235Res.Sat=0.15

SEEP-W Modeling

GOLDER ASSOCIATES

Courtesy Todd McAlary, AEHS/EPA Mar 08 Workshop

GOLDER ASSOCIATES

Temporal Trends

H-009 Sub-Slab Trends TCE

0

50

100

150

200

250

300

O N D J F M A M J J A S O N

ug

/m3

Subslab ASubslab BSubslab C

Courtesy Bill Wertz, NYDEC

GOLDER ASSOCIATES

Where to Sample Vertically?Conceptual Hydrocarbon Vapour Profile

Blayne Hartman, H&P Geochemistry

GOLDER ASSOCIATES

Aerobic Biodegradation

0

2

4

6

8

10

12

14

16

18

1.E+00 1.E+02 1.E+04 1.E+06

Benzene Vapor Concentration (mg/m3)

Dep

thb

elo

wg

rou

nd

(ft)

Below Building #1

Below Building #2

Below Building #3

Below Building #4

Adjacent Building #1

Adjacent Building #2

Buildingfoundation depth

Santa Maria House, CA(Paul Lundegard, Unocal

Oil Seeps)

Paulsboro House, NJ (BP)(Gasoline NAPL, sand,

sm. silt)

Subslab

Beside

Santa Maria, CA Study(Is O2 Transport BelowHouse Slow or Fast)

Paul Johnson, ASU, Paul Lundegard, Unocal and Paul Dahlen, Golder

O2

10

8

6

4

2

0

De

pth

(ft)

0 5 10 15 20Ci (%)

CH4

slab

GOLDER ASSOCIATES

Biodegradation

Golder Associates Ian Hers, 2004

Todd Ririe slide or anotherChatterton slide

Diffusion most important, wind inducedO2 recharge also important. Rainfall

can affect recharge

Paul Johnson, ASU, Paul Lundegard, Unocal and Paul Dahlen, Golder

GOLDER ASSOCIATES

Biodegradation

Golder Associates Ian Hers, 2004

Todd Ririe slide or anotherChatterton slide

GOLDER ASSOCIATES

Biodegradation

Golder Associates Ian Hers, 2004

Todd Ririe slide or anotherChatterton slide

GOLDER ASSOCIATES

Biodegradation

Golder Associates Ian Hers, 2004

Todd Ririe slide or anotherChatterton slide

GOLDER ASSOCIATES

Guidance Overview

Health Canada – tiered approach based on soil,groundwater and soil vapour; supporting PQRAand SSRA spreadsheets

Alberta and Ontario – Tier 1 soil andgroundwater guidelines, Tier 2 soil vapour

Draft USEPA 2002 OSWR VI Guidance – currentstatus will not be updated, but several whitepapers/tools to be produced

ITRC VI Guidance (2007) – multiple lines ofevidence

ASTM E2600 – Phase 1 screeening approach andpre-emptive mitigation

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Health Canada VI Guidance

Preliminary Screening forpathway completeness

Secondary Screening usingAttenuation factor (AF)“alpha” curve approach for soiltype and depth

Adjustments for: Aerobic biodegradation (10X)

Mass flux for groundwater

Source depletion for soil

Building properties

Tier 3 process? (not defined)

Vapour Intrusion Factors

1.E-05

1.E-04

1.E-03

1.E-02

0 10 20 30

Depth to Contamination (m)

Vap

or

Att

en

uati

on

Rati

o

Sand

Loam

Soil vapour AF =Cair/Cvapour (measured)

Groundwater AF =Cair/Cvapour (predicted)

GOLDER ASSOCIATES

Proposed Bioattenuation Adjustmentsfor Health Canada Guidance(simpler approach may be adopted)

Media Contamination Criteria Bioattenuation Adjustment Factors(BAF)

Groundwater Dissolved - Low Benzene < 0.1 mg/LF1 < 5 mg/LF2 < 1 mg/L

100X for Ds > 1 m

Dissolved – High Benzene < 1 mg/LF1 < 15 mg/LF2 < 5 mg/L

10X for Ds > 1 m100X for Ds > 3 m

NAPL 10X for Ds > 5 m

Soil Vapour Dissolved Cg < 1 mg/L 10X for Ds > 1 m100X for Ds > 1 m, Dp < 1 m

Transition dissolved& NAPL

Cg > 1 mg/LCg < 50 mg/L

10X for Ds > 2 m

NAPL Cg > 50 mg/L 10X for Ds > 5 m

Soil All 20X for Ds > 1 m

Note: BAFs may only be applied when there is no significant capping effect.

Cg = BTEX + F1 + F2 + CH4

Ds = Separation distance between contamination source and buildingDp = Distance from contamination to soil gas probe

GOLDER ASSOCIATES

Pathway Assessment –Possible Future Refinements

Need better screening approach to categorizesites

No brainer – there is a problem

Likely a problem – lets not think to much about it

Grey zone – more assessment needed

Not a problem – let’s move on (biodegradation criticalhere – source strength, depth, capping effect)

One size does not fit all, more flexibility needed inmedia and models that may be used(biodegradation, source depletion, buildingproperties)

GOLDER ASSOCIATES

Pathway Assessment –Possible Future Refinements

Need to get a better handle on soil vapour spatialand temporal variability and influence of building –more research is needed in this area

Sampling and analysis tools and practice needs tobe improved – hopefully next session willcontribute to this

Updated surrogate approach for TPH

Greater standardization for mitigation design

Use of more sophisticated models

GOLDER ASSOCIATES

Meta-data Analysis –Influence of Background

Often will not beable to see above

the noise!(especially if some

bioattenuation)

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01 1.E+03 1.E+05 1.E+07 1.E+09

Source Vapor Concentration/Background Air Conc

Alp

ha

Vapor-derived ("inherent")

High Source

Strength

Low Source

Strength

Empirical alpha

Benzene Site Data

emp= Cairbackground / Cvapour source + inherent

ACC = 1.5 ug/m3

0.001

GOLDER ASSOCIATES

3-D Numerical Model(this is a slicethrough the house)Abreu & Johnson,ES&T, 2005

Modeling Study(Illustrates spatial variability& effect of biodegradation)

Building

Vapors

What if you sample out here?

V. High gasoline concentrations

Oxygen

Slightly lower gasoline concentrations

GOLDER ASSOCIATES

First Nations Site Strategic SoilVapour Sampling

Kwadahcha

0

1

2

3

4

5

6

7

8

0 500 1000 1500

TVOC Vapor Conc. (mg/m3)

De

pth

be

low

gro

un

d(m

)

0 5 10 15 20

O2 and CO2 (%)

TVOC

O2

CO2

Kwadahcha

0

1

2

3

4

5

6

7

8

0 5 10 15 20

Vapor Conc. (mg/m3)

De

pth

be

low

gro

un

d(m

)

0 5 10 15 20

O2 and CO2 (%)

Decane

O2

CO2

Diesel NAPL above water table, sand and gravel,teacherage with basement

Health Canada protocol requires minimum depth ½way between building and contamination

PHC, O2, CO2,CH4 profileshelpful toevaluate

biodegradation!

GOLDER ASSOCIATES

RISC Model SummaryBoundary layer modelfor O2 flux (Ko)

Advection & DiffusionBuilding

RISC Model

GOLDER ASSOCIATES

RISCOutput

Golder Associates Ian Hers, 2004

Cs = 400mg/m3

Cs = 1600mg/m3

%

First order decay aromatics= 20 day-1

Aliphatics = 1000 day-1

%

GOLDER ASSOCIATES

Soil Vapor Methods

Similar or higher level of care than groundwater

Preference small diameter probes

Carefully seal boreholes

Leak tracer tests to test seals andsampling trains

“Geoprobe”

Helium tracer test

GOLDER ASSOCIATES

Soil Vapour Tool Box

Low flow (100-200 ml/min) and low vacuum (< 5in H20) purging and sampling

Vacuum chamber (lung box) sampling warranted insome cases

Analytical methodscarefully chosen(sorbent tubes,Summa canisters – hardware key issue)

QC samples (equip-ment blanks,duplicates)

GOLDER ASSOCIATES

8. Screening Using Field Detectors

GeoEnvirologic Course June 5, 2008

GOLDER ASSOCIATES

GeoEnvirologic Course June 5, 2008

Courtesy Todd McAlary, AEHS/EPA Mar 08 Workshop