Fulton Schools of Engineering P. C. Johnson 2011€¦ · VI is a dynamic process reflecting vapor source, subsurface, building, occupant, and weather characteristics Similar to, but

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P. C. Johnson 2011Fulton Schools of Engineering

University of Washington Superfund Research Program

Agency Seminar Series at EPA Region 10

"Temporal Changes in Vapor Intrusion Behavior and Implications for Conventional Pathway Assessment Paradigms"

June 15, 2011Dr. Paul Johnson, Professor

School of Sustainable Engineering and the Built Environment, Fulton Schools of EngineeringArizona State University

contact information- [email protected]

Please note- These presentation slides were made available by Dr. Paul Johnson.Contact Dr. Johnson with questions or for permission to print these slides-

beyond educational purposes..


Changes in VI Behavior with Time:In-Progress Results from a Multi-Year Study

Paul C. JohnsonEmma LuoPaul Dahlen

Chase HoltonIra A. Fulton Schools

of Engineering

Kyle GorderErik Dettenmaier

Hill AFB


Vapor intrusion (VI) is a possibility wherever buildings are in close proximity to impacted soils or groundwater

VI is a dynamic process reflecting vapor source, subsurface, building, occupant, and weather characteristics

Similar to, but also different from radon intrusion.

Potential consequences range from concentrations of no significance, to unacceptable long-term/chronic exposures, and occasionally to short-term impacts (explosion, acute effects).

Vapor Intrusion (VI) Overview

?�


Common VI Scenarios• Buildings overlying

CHC-impacted groundwater is more typical than over DNAPL sources.

• Many well-publicized neighborhood-scale sites (CDOT, Redfields, Hill AFB, NY sites, etc.).

• Most available empirical data corresponds to these types of situations

Chlorinated Hydrocarbon Spill SitesHill AFB, Utah


Empirical Experience (CHC Sites)

1.E-03

1.E-02

1.E-01

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

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+08

Indo

or A

ir C

once

ntra

tion

(ug/

m3) EPA Data (IA > RL)

Alpha = 1.0

Alpha = 1E-1

Alpha = 1E-2

Alpha = 1E-3

Alpha = 1E-4

Alpha = 1E-5

Groundwater Vapor (ug/m3)

U.S. EPA’s Vapor Intrusion Database: Preliminary Evaluation of Attenuation Factors

0.1 – 10 ppbv

OSWER Draft - March 4, 2008 - http://iavi.rti.org/OtherDocuments.cfm

10 – 10,000 g/L in ground water

What’s Important Here? Does it help?•Unacceptable impacts occur at some sites at very low GW concentrations•Little to no impact occurs at other sites with very high GW concentrations


Common VI Scenarios• A few buildings overlying

NAPL-impacted soils is more typical scenario. Few neighborhood-scale settings.

• Potential short-term consequences more severe than for CHC sites.

• Oxygen resupply, source-building separation, and physical features may be major factors.

• Low conc. sources not expected to pose significant risks.

• Potential risks associated with methane often overlooked. P

etro

leum

Hyd

roca

rbon

Spi

ll Si

tes

Greenpoint, Brooklyn, NY

Page


Petroleum Hydrocarbon

Sites -Range of Behaviors(all-or-nothing)

Abreu and Johnson (2005, 2006)

O2

O2

O2

HC

HC

HCSig

nific

ant

Bio

atte

nuat

ion

Insi

gnifi

cant


PCJ’s VI TaxonomyVI Sites

Chlorinated -Recalcitrant

VadoseSource (High

Strength)

GW Source (High

Strength)

GW Source (Low

Strength)

Petroleum HC -Aerobically Bio-D

Low O2Behave

Like CHC

NAPL Source (High

Strength)

GW Source (Low

Strength)

High/low – what chemical(s)? CH4 Issues?

Prob. low risk, but Is it really a plume?

No bio-attenuation

How many buildings?


Indoor Air Samples(Cindoor)

Groundwater Samples

Sub-slab Soil Gas Samples (Csub-slab)

Near-Source Soil Gas Samples (Csoil-gas)

Outdoor Air Samples

Soil Core

Near-building soil gas samples (Cgw)

VI Pathway Assessment: MLE Approach[v1.0, 1.1, 2.0 Paradigms]

Models • Heavy weighting on indoor air data

• Decisions made using a few samples, (typically 24-h or less time-averaged indoor air)

• Sometimes short sampling windows or seasonal data (i.e., fall, winter, spring, summer, rainy, dry)

• Some use of passive samplers and sorbent tubes for longer durations; low use of point-in-time and point-in-space sniffers (i.e., TAGA, HAPSITE) for indoor source identification


Conventional Beliefs Underlying VI Pathway Assessment Practice

•Temporal changes in VI impacts occur, with variations spanning about an order-of-magnitude

•24-h duration samples address any short-term fluctuations in indoor air concentrations

•A few 24-h samples sprinkled across longer time will identify any longer-term (seasonal) temporal changes

•Consistency in results across a few samples provides confidence that VI is understood. Other results can be averaged or anomalies discarded.

•Multi-day or multi-week samples might be better, but not yet clear how to do this right

•Can identify indoor sources via inventories


• Factors that might induce temporal changes have been identified, but quantitative cause-effect relationships are not known (and are difficult to discern with existing data)

• Some higher-frequency/longer-term indoor radon data available

• Some higher-frequency/longer-term soil gas data available

• Some lower-frequency/longer-term/multi-building indoor air data for groundwater/soil contaminants available

• Difficulty an assessing changes in VI behavior using typical data sets, given analytical variability and confounding by indoor air sources

Background: State-of-the-Science


So…given this background:

•Is there a scientific foundation for our current approach to sampling (and for conventional VI wisdom)?

•Is it possible to design practicable sampling plans that are sufficiently robust under conditions of unknown temporal behavior?

•Do we need new tools or approaches for assessing the vapor intrusion pathway?

So…given this background:

•Is there a scientific foundation for our current approach to sampling (and for conventional VI wisdom)?

•Is it possible to design practicable sampling plans that are sufficiently robust under conditions of unknown temporal behavior?

•Do we need new tools or approaches for assessing the vapor intrusion pathway?

Questions

Studies of Changes in VI Behavior with Time

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Study through Simulation•3-D transient numerical code

•Incorporating actual driving forces (wind, barometric pressure)

•Looking at effects of site conditions (depth, soil type, biodegradation, etc.)

Study through Simulation•3-D transient numerical code

•Incorporating actual driving forces (wind, barometric pressure)

•Looking at effects of site conditions (depth, soil type, biodegradation, etc.)

Ongoing Temporal Behavior Studies

Study through Monitoring•Residence over dilute chlorinated solvent plume

•Intensive monitoring

•High frequency/long duration monitoring of indoor air, building characteristics, and driving factors

Study through Monitoring•Residence over dilute chlorinated solvent plume

•Intensive monitoring

•High frequency/long duration monitoring of indoor air, building characteristics, and driving factors

-20

-15

-10

-5

0

5

10

15

20

42 49 56 63 70 77

Time [d]

Subs

lab

- Ind

oor

P [P

a]

Location 3

ASU/H. Luo et al. (2007-present) (ASU/Hill AFB SERDP project)P. C. Johnson 2011Fulton Schools of Engineering

SERDP-Funded Project

Topic 1: Temporal variations in indoor air

concentration, and differences between variations for indoor

and subsurface sources?

Dissolved chlorinated solvent groundwater plume

Capillary fringe

Topic 2: Relationship between groundwater

concentrations and indoor air concentrations?

Topic 3: Spatial and temporal variability in

sub-slab concentrations and factors that affect

them?

Topic 6: Indoor chemical sources?

Topic 4: Changes with time in chemical vapor emissions from

impacted groundwater?

Topic 5: Alternate assessment

approaches to point-in-time and point-in-

space sampling{

Emphasis on Studying Temporal Changes

* - Topics 1 – 4 driven by current regulatory guidance approaches


Hill AFB Situation:

About 3000 homes above dissolved CHC plumes (10 –100 ug/L; mean about 30 ug/L)

About half of the home-owners have opted for indoor monitoring at least once

Hill AFB Off-Site Plumes


Sun Devil Manor[Layton, UT]

10 – 30 ug/L TCE and 1,1 DCE in GW10 – 30 ug/L TCE and 1,1 DCE in GW

P. C. Johnson 2011Fulton Schools of Engineering P. C. Johnson 2011Fulton Schools of Engineering

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Monitoring Network+ Multi-level soil gas and groundwater sampling points

• Indoor air monitoring (VOCs, radon)

• Differential pressures, soil moisture, soil temperature

• Weather (wind, barometric pressure, rainfall, outdoor temp)

• HVAC operation, indoor T, exchange rate (SF6) P. C. Johnson 2011Fulton Schools of Engineering

• Indoor air: 4000+ indoor air samples across 14 months at 2 h and 4 h intervals

• Snapshots: soil gas and groundwater, 6 events over 9 months

• Weather: wind, outdoor temp, relative humidity, rainfall, sampled every 15 min for 9 months

• Building Dynamics: diff press, indoor air temp HVAC operation, indoor temp, sampled every 2 min or 10 min across 9 months

• Soil Conditions: soil temperature and soil moisture monitored every 10 min for 9 months

• Radon: every 2 hours for about 3 months and 3 soil gas snapshots

• Indoor Air Exchange Rate: measured about every 30 min over 3 months

Data Collected to Date

www.schiffner.com


Dissolved chlorinated solvent groundwater plume

Capillary fringe

Soil Cores

Conventional Groundwater

Samples

Discrete Soil Gas and

Groundwater Samples

Indoor Air Monitoring

Weather Monitoring

Differential Pressure

Res

ults

Pre

sent

atio

n

Technical ApproachField Laboratory Studies


Sub-Slab Shallow Groundwater

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

0

10

20

30

40

50

60

-30 0 30 60 90 120 150 180 210 240 270

[ft] [g/L]

Time [d]

TCE in Groundwater Beneath Foundation

IGW-1

IGW-2

IGW-3

IGW-4

IGW-5

IGW-6

GW Elevation (1-16)


August 2010 Nov 2010 Dec 2010

Feb 2011 April 2011 May 2011

TCE in Soil Gas at 6-ft Below-slab Depth


TCE at Sub-slab Soil Gas Depth

August 2010 Nov 2010 Dec 2010

Feb 2011 April 2011 May 2011

Page


January 2011

Soil Gas Snapshots: Radon 1.8 m (6 ft) Below Slab

Radon [pCi/L]

-2 0 2 4 6 8 10 12 14-4

-2

0

2

4

6

8

10

1435 1494 1531

14691620

1797

N/A

N/A N/A

1500

900

1240

N/A

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N

[m]

[m] 0

200

400

600

800

1000

1200

1400

1600

1800

2000

-2 0 2 4 6 8 10 12 14-4

-2

0

2

4

6

8

10

1546 1466 N/A

16481649

1822

N/A

N/A N/A

1381

869

1175

N/A

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N

[m]

[m]

Radon [pCi/L]

0

200

400

600

800

1000

1200

1400

1600

1800

2000

April 2011


-2 0 2 4 6 8 10 12 14-4

-2

0

2

4

6

8

10

1400 1256 1432

13041556

1420

N/A

1290 1400

1350

690

550

1270

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N

[m]

[m] 0

200

400

600

800

1000

1200

1400

1600

1800

2000

-2 0 2 4 6 8 10 12 14-4

-2

0

2

4

6

8

10

1529 1413 1423

15111723

1600

N/A

1334 1405

1306

677

481

1357

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N

[m]

[m]

Radon [pCi/L]

0

200

400

600

800

1000

1200

1400

1600

1800

2000

January 2011 April 2011

Soil Gas Snapshots: Radon 0.9 m (3 ft) Below Slab


January 2011

-2 0 2 4 6 8 10 12 14-4

-2

0

2

4

6

8

10

933 97 182

362135

17

56

1020 910

760

N/A

145

1170

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N

[m]

[m]

Radon [pCi/L]

0

200

400

600

800

1000

1200

1400

1600

1800

2000

-2 0 2 4 6 8 10 12 14-4

-2

0

2

4

6

8

10

1090 35 68

58087

6

29

1019 904

791

N/A

129

1257

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N

[m]

[m]

Radon [pCi/L]

0

200

400

600

800

1000

1200

1400

1600

1800

2000

January 2011 April 2011

Soil Gas Snapshots: Radon at Sub-slab Depth



Groundwater Samples



Outdoor Air Samples

Soil Core


Wind, temperature, barometric pressure, rainfall HVAC

systems, resident behaviors (seconds-minutes-hours)

Source history and seasonal influences

(weeks-months-years)

Source and some surface effects


}}}

Changes with Time?Buildings and their Surroundings are Dynamic Systems

Surface drivers and proximity to foundation entry points (minutes-hours-months)


0.01

0.10

1.00

10.00

100.00

-180 -120 -60 0 60 120 180 240

[ppb

v]

Time [d]

Hapsite Data TD Tube Data (4 h) IST Studies (manip) GSI Study (manip) August 2010 SS November 2010 SS December 2010 SS February 2011 SS January 2011 SS March 2011 SS

Radon

TCE Indoor Air ConcentrationsAutomated data acquisition

SF6 release

Manipulation

Other SERDP/ ESTCP Projects


0.01

0.10

1.00

10.00

-27 -26 -25 -24 -23 -22

[ppb

v]

Time [d]

0.01

0.10

1.00

10.00

140 145 150 155 160 165 170

[ppb

v]

Time [d]

TCE Indoor Air Concentrations

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TCE vs. Radon Indoor Air Concentrations

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

170 180 190 200 210 220 230 Rad

on in

Indo

or A

ir [p

Ci/L

]

Time [d]

0.01

0.10

1.00

10.00

170 180 190 200 210 220 230

[ppb

v]

Time [d]

2-h samples


Observations and Thoughts

Observations ThoughtsTemporal concentration behavior appears to be “structured” and not random or statistically distributed

Typical sampling plans not robust enough for

these conditions

This is very different from the behavior

conceptualized and anticipated by guidance.

Different monitoring tools and paradigms are

needed.

Over some time periods the temporal behavior has a repeatable daily pattern

There are periods of relative VI inactivity with sporadic VI activity

There are periods of relative VI activity with sporadic VI inactivity


0

500

1000

1500

2000

125 135 145 155 165 175 185 195 205 215 225

SF6 [

ppb v

]

Time [d]

SF6 Snapshots

SF6 released at a constant rateDaily fluctuations in SF6 conc. correspond to variations of about 2X in EB = 18 to 28 d-1 (50% of the time in the data set; VB=350 m3)

Air Exchange Rate (EB)

20 exchanges/day


Snapshot of Sub-Slab SF6

January 2011 (120 d SF6)700 ppbv indoor air concentration -2 0 2 4 6 8 10 12 14

-4

-2

0

2

4

6

8

10

4 57 592

629

650

100

2 1

4

N/A

1

2

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N [m

]

[m] 0

50

100

200

400

600

800

SF6 [ppbv]


April 2011 (180 d SF6)1000 ppbv indoor air concentration -2 0 2 4 6 8 10 12 14

-4

-2

0

2

4

6

8

10

17 53 388

757

185

94

1 1

4

N/A

0

1

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N

[m]

[m] 0

50

100

200

400

600

800

SF6 [ppbv]

Snapshot of Sub-Slab SF6


April 2011

Soil Gas Snapshot: Radon Sub-Slab

-2 0 2 4 6 8 10 12 14-4

-2

0

2

4

6

8

10

1090 35 68

58087

6

29

1019 904

791

N/A

129

1257

Garage

Living Area

Building Foundation

Restroom

Stairs

Laundry Room

N

[m]

[m]

Radon [pCi/L]

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Page



Groundwater Samples



Outdoor Air Samples

Soil Core


Wind, temperature, barometric pressure, rainfall HVAC

systems, resident behaviors (seconds-minutes-hours)

Source history and seasonal influences


Source and some surface effects


}}}

Changes with Time?Buildings and their Surroundings are Dynamic Systems

Surface drivers and proximity to foundation entry points (minutes-hours-months)


Comprehensive long-term data set (only one of its kind) – illustrates previously unanticipated intermittent VI behavior

Data show that current pathway snapshot-style assessment schemes are not likely to be robust.

Tracer release conclusively shows that indoor air sources can cause soil gas plumes and storage in the subsurface.

Data will be useful for evaluating cause-effect relationships

Key Results to Date


In Progress - Data Mining: Cause-Effect Relationships

Wind Speed (m/s)

>8.0

6.0-8.0 3.0-6.0

1.0-3.0

0.5-1.0

0.0

0.2

0.4

0.6

0.8

1.0

0 60 120 180 240

Dai

ly R

ainf

all [

in]

Time [d]

Daily Rainfall Snapshot

-20 -10

0 10 20 30 40

0 60 120 180 240 Out

door

Tem

pera

ture

[°C

]

Time [d]


For building-specific pathway assessment:•Quick/reliable identification of indoor sources (portable/sensitive tools)

•Proven means of manipulating buildings in short-term to overcome time variability of natural driving forces (i.e., forced depressurization, T. McHugh and this study) – is the short-term behavior of these tests indicative of long-term and could history of indoor sources still confound the test?

•Practicable longer-term real-time monitoring, with occupant awareness (real-time needed to spot the inadvertant introduction of new indoor sources)

Lessons-LearnedThoughts about Needs for the Future


Continued monitoring under natural conditions through 12/2011

Dissipation of indoor SF6 source soil gas plume and impact to indoor air

Manipulated building conditions in 2012 – depressurize to eliminate building changes as a driving factor:

•This allows assessment of changes in groundwater release rate with time

•Also allows evaluation of building depressurization as a VI assessment tool

Next Steps – SERDP Project

Indoor Air Samples (Cindoor)

Groundwater Samples



Outdoor Air Samples

Soil Core



Transition PlanOpen Access for Other Projects:•SERDP ER-1687 Vapor Intrusion from Entrapped NAPL Sources and Groundwater Plumes: Process Understanding and Improved Modeling Tools for Pathway Assessment (Illangasekare, CSM)

•ESTCP ER-0702 Application of Advanced Sensor Technology to DoD Soil Vapor Intrusion Problems (Reisinger, Burris, Hinchee IS&T)

•ESTCP ER-0707 Protocol for Tier 2 Evaluation of Vapor Intrusion at Corrective Action Sites (McHugh/GSI)

•ESTCP ER-0830 Development of More Cost-Effective Methods for Long-Term Monitoring of Soil Vapor Intrusion to Indoor Air Using Quantitative Passive Diffusive-Adsorptive Sampling Techniques (McAlary/Geosyntec)

•ESTCP ER-1025 Use of Compound-Specific Stable Isotope Analysis to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs (McHugh/GSI)

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Thanks to:

SERDP (for funding!)

Kyle Gorder and Erik Dettenmaier, Hill AFB for collaborations/monitoring/supporting/etc.


University of Washington Superfund Research Program

Agency Seminar Series at EPA Region 10

"Temporal Changes in Vapor Intrusion Behavior and Implications for Conventional Pathway Assessment Paradigms"

June 15, 2011Dr. Paul Johnson, Professor

School of Sustainable Engineering and the Built Environment, Fulton Schools of EngineeringArizona State University

contact information- [email protected]

Please note- These presentation slides were made available by Dr. Paul Johnson.Contact Dr. Johnson with questions or for permission to print these slides-

beyond educational purposes.