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DNAPL Source Zones

Mark L. Brusseau University of Arizona

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Superfund Basic Research Program University of Arizona

•

(NIEHS), an institute of the National Institutes of

•

contamination

Funded and administered by the National Institute of Environmental Health Sciences

Health (NIH)

Hazardous wastes investigated include: arsenic, chlorinated hydrocarbons, and mine tailings

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The DNAPL Problem

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•

•

Primary Source of Contaminant Mass

Site Characterization

Remediation

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The Source-Zone Issue

that is the question… To Remediate or Not To Remediate---

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Recent Studies

• 2002. DNAPL Source Reduction: Facing theChallenge.

• 2003. The

• 2004.

.

Interstate Technology and Regulatory Council.

Environmental Protection Agency. DNAPL Remediation Challenge: Is There a Case for Source Depletion?

National Research Council. Contaminants in the Subsurface: Source Zone Assessment and Remediation

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Summary

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•

Complete Mass Removal Not Possible

Is Partial Removal [Mass Reduction] Beneficial?

Need To Define Objectives

Cost/Benefit Analysis

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Key Questions

•

•

•

Expected Degree of Mass Reduction?

Impact of Specified MR on Mass Flux?

Impact of Mass Flux Reduction on Risk?

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Answers

• Need to Understand the Impact of Source-zone Architecture and Dynamics on Mass Flux Behavior

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Research Needs • SERDP/ESTCP

of Chlorinated Solvent Sites. 2001.

–

– Processes

–

Expert Panel Workshop on Research and Development Needs for Cleanup

Focus Research on Source-Zone Issues

Source-zone Architecture and Mass Transfer

Pore-scale Processes

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Research Needs

•

– between mass reduction and mass flux

– multiple (pore, column, intermediate, field) scales

– Distribution and mass-transfer behavior of DNAPLs in heterogeneous (low-permeability or fractured) systems

UA/SBRP Expert Panel DNAPL Workshop. 2005.

Source-zone mass flux processes, and the relationship

Distribution and mass-transfer behavior of DNAPLs at

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Continued

– of aging and the relative contributions of trapped

dissolved mass

–

(real-world) settings

– associated upscaling

Long-term mass flux behavior, including the influence

DNAPL, sorbed mass, and matrix-associated

Impact of co-contaminants on phase properties (wettability, interfacial tension) in complex, natural

Mathematical modeling at multiple scales, and

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Mass Flux

Source Zone

Contaminant Flux

High Concentration

Low Concentration Source Zone

ContaminantFlux

High Concentration

Low Concentration

High Concentration

Low Concentration

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Flux Reduction vs. Mass Removal

0

1

0 100

l (%)

i

I l

I l

13

0.25

0.5

0.75

25 50 75

Mass Remova

M a s

s Fl

ux R

edu c

to n Non- dea Mass Transfer

dea Mass Transfer

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Factors Influencing Mass Flux

• ield Dynamics

•

•

•

Flow-F

DNAPL Distribution and Configuration

Dissolution Dynamics

Mass Transfer and Transformation Processes

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Measuring Mass Flux

• lux in the Field

•

Measuring Mass F

Lynn Wood Presentation

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Predicting Mass Flux Reduction

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•

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Flux Reduction-Mass Removal Relationships

Understand Impacts of Source-zone Architecture and Dynamics on Mass Flux

Priority Research Need

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Intermediate-Scale Experiments

• • • •

• •

Examine Heterogeneous Systems Permeability Variability Non-uniform NAPL Distribution Multiple Mass-transfer Processes

Controlled/Well-defined Systems Evaluate Flux vs. Mass Removal Behavior

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UA-PNNL Experiments •

– – –

• saturation in-situ (mass removal)

• i– – –

Multiple methods to measure aqueous concentrations (mass flux):

Depth specific ports [e.g., multilevel sampling ports] Vertically integrated ports [e.g., fully screened MWs] Flow-cell effluent [e.g., extraction well]

Dual-energy gamma system to measure NAPL

Additional characterizat on methods: Non-reactive tracer test Dye tracer test Visualization of dyed TCE

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Flow-cell Schematic

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Flow Cell

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TCE Concentrations

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Mass Flux-Mass Removal

0

1

0

n

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

20 40 60 80 100

Mass Removed (%)

Mas

s Fl

ux R

educ

tio

Sand- Well Sorted Sand- Poorly Sorted

Homogeneous P.M., Uniform NAPL

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Mass Flux-Mass Removal

0

1

0

(%)

i

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

20 40 60 80 100

Mass Removed

Mas

s Fl

ux R

educ

tion

Homogeneous P.M. Un form NAPL Heterogeneous P.M. Non-uniform NAPL

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Pore-scale Research

• – – – –

• – –

Topics: Multi-phase Fluid Displacement Wetting/Non-wetting Fluid Distributions Fluid-Fluid Interfacial Areas Mass-transfer Processes

Methods: High-Resolution Imaging--- MRI/NMR; X-ray Pore-scale Modeling--- Network, Lattice-Boltzmann

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GeoSoilEnviroCARS

• research facility at theAdvanced Photon Source, Argonne, IL

• DOE, State of Illinois

Synchrotron-based

Supported by NSF,

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Synchrotron X-ray CT Images

NAPL = white

Solids = dark gray, Water = black,

Solids = gray, Water = blue, NAPL = red

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Examples of NAPL Ganglia

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Time Series

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Acknowledgements

•

• McColl, Michele Mahal, Mart Oostrom

NIEHS SBRP

Greg Schnaar, Justin Marble, Colleen

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A. Lynn Wood Michael C. Brooks

U.S. EPA/ORD/NRMRL

Measurement and Use of Contaminant Flux as an

Assessment Tool for DNAPL Remedial Performance

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in the Field Methods:

¾ Multi-Level Sampler (MLS) Transects ¾

¾ ) ¾ Integral Pumping Test (IPT) ¾

Measuring Contaminant Mass Flux

Passive Flux Meters (PFM) Horizontal Flow Treatment Wells (HFTWs

Modified Integral Pumping Test (MIPT)

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et al

Contaminant Flux Estimates by MLS Transects

(from Newell ., 2003)

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MLS Transect Method

• – i

– – ll l–

• – – – –

Advantages: Generates spatial informat on on concentration distributions Methods exist to estimate uncertainty Sma waste vo umes produced Conventional

Disadvantages: Requires independent estimation of water flux Contaminant measures are instantaneous Interrogates small volumes of aquifer Data must be spatially integrated to obtain contaminant mass flows

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Well

lWell

Contaminant Mass Flux Measurements by Horizontal Flow Treatment Wells ( HFTWs )

(from Huang et al. 2004 and Goltz et al. 2004)

Downflow

Upf ow

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(HFTW) Method

• – – – – –

• –

) – – – –

Horizontal Flow Treatment Well

Advantages: Generates water flux and contaminant mass flux estimates Interrogates large volumes of aquifer Can be used in deep aquifers Does not extract groundwater Can estimate horizontal and vertical aquifer conductivities

Disadvantages: Does not provide spatial information (difficult to quantify uncertaintyAssumes aquifer is homogeneous Uses tracers to estimate interflow Does not function in all wells Underestimates maximum resident contaminant concentrations

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Passive Flux Meters (Hatfield et al., 2004)

Sorbent (with Tracers

(minimize vertical flow)

Tube for flow bypass

Retrieval wire

q = f(depth)

J = f(depth)

activated carbon)

Viton Washers

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Passive Flux Meter Concepts ContaminantWater Flux

q0

Tracer ElutedTracer Remaining

Flux Contaminant Sorbed

(Hatfield et al., 2004)

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Passive Flux Meter Method

• –

– – l – l– – i

• – l–

– –

Advantages: Generates spatial information on cumulative water and contaminant mass flux Methods exist to estimate uncertainty Generates loca estimates of horizontal aquifer conductivity Small waste vo umes are produced Passive Inexpens ve

Disadvantages: Interrogates small vo umes of aquifer Data must be spatially integrated to obtain contaminant mass flows and total water discharge Uses resident tracers to estimate groundwater flux Does not function in all wells

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Integral Pumping Test(Bockelmann et al. 2001, 2003; Schwarz et al., 1998; Teutsch et al. 2000;

Ptak et al. 2000)

Measured mass fluxesat control cross-sectionsPumping tests

ResidualNAPL-phase

Q, C(t)

mass flux

C

t

C

t

Mea

sure

men

ts(f

ield

sca

le)

Fiel

d si

te

Q, C(t)

Comparison andInterpretation

Control

Plane I

flux 1

Control

Plane II

flux 2

Measured mass fluxesat control cross-sectionsPumping tests Measured mass fluxesat control cross-sectionsPumping tests

ResidualNAPL-phase

Q, C(t)

mass flux

C

t

C

t

Mea

sure

men

ts(f

ield

sca

le)

Fiel

d si

te

Q, C(t)

ResidualNAPL-phase

Q, C(t)

mass flux

C

t

C

t

Mea

sure

men

ts(f

ield

sca

le)

Fiel

d si

te

Q, C(t)

Comparison andInterpretation

Control

Plane I

flux 1

Control

Plane II

Comparison andInterpretation

Control

Plane I

flux 1

Control

Plane II

flux 2flux 2

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Integral Pumping Method

• – – –

• – ( l) – – – –

) – –

Advantages: Generates contaminant mass flow estimates Interrogates large volumes of aquifer Can be used in deep aquifers

Disadvantages: Costly wastewater disposaRequires lengthy time execution Assumes aquifer is homogeneous Does not estimate water flux Does not provide spatial information (difficult to quantify uncertaintySubject to the limitations of sampling configuration Underestimates maximum resident contaminant concentrations

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Modified Integral Pumping Test

J = q0c

Interpreted from concentration –time

series

x

y

q0 i

well

Estimate q0 directly from IPT results

Observat on point

Pumping

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Diff

eren

ce in

Ele

vatio

n

Modified Integral Pumping TestSuperposition of Uniform flow and multiple Sink terms

0.00003

0.00002

0.00001

0

-0.00001

-0.00002

-0.00003

∆ φ − = o

T B q ∆ x +

4π T 1 ∑

i = 1

n

iQ

q = o

r i w

r obs [ 2 [

2

ln

∑ ln 4π B ∆ x i = 1

− Q n

At ∆φ = 0,

i ]

]

r i w

r obs [ 2 [

2 i

]

]

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035

Q*ln(ε )

Flux Well 1 Flux Well 2 Flux Well 3

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2) Measure Elevations = f(Q)

1) Measure Q = f(t)

Elev(t0) Elev(Q1)

Q

t

Elev(Q3)Pumping Well Observation Well

Elev(Q2)

Modified Integral Pumping Test

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Modified Integral Pumping Method

• – – – –

• – ( l) – – –

) – –

Advantages: Generates contaminant mass flow estimates Interrogates large volumes of aquifer Can be used in deep aquifers Estimates water flux

Disadvantages: Costly wastewater disposaRequires lengthy time execution Assumes aquifer is homogeneous Does not provide spatial information (difficult to quantify uncertaintySubject to the limitations of sampling configuration Underestimates maximum resident contaminant concentrations

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Assessing DNAPL Source Remediation Performance

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Source Remediation = Contaminant Flux Management

Pre-Remediation: Control

c)

Control

c)

Post-Remediation:

Jc=qw•C

Most contaminated

Least contaminated

Source Zone

Plane

Contaminant Flux (J

Source Zone

Plane

Contaminant Flux (J

Flux = Flow • Concentration

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Pre-Remediation:

Dissolved Plume

DNAPL

DNAPL

DNAPL

MASS DEPLETION RESPONSE

Source Zone

Control Plane Compliance Plane

Dissolved

Partial Mass Removal + Enhanced Natural Attenuation:

Source Zone Plume

Dissolved

Partial Mass Removal:

Source Zone Plume

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Field Demonstrations

Laboratory Experiments

Mathematical Modeling

Impacts of DNAPL Source Zone Treatment: Experimental and Modeling Assessment of

Benefits of Partial Source Removal

…assess the benefits of aggressive in situ DNAPL source-zone remediation

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Project Team

• • •

l Air Force Institute of Technology • • •

Mike Annable – University of Florida Michael Brooks – EPA/ORD/NRMRL Ron Falta – Clemson University

• Mark Go tz – Jim Jawitz – University of Florida Suresh Rao – Purdue University Lynn Wood – EPA/ORD/NRMRL

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DNAPL Field Sites 99

999

9/

99

Fort Lewis, Washington Pre-Remedial Flux 10/03 Resistive Heating 12/03-8/04 Post-Remedial Flux 8/05

Hill AFB, Utah Pre-Remedial Flux 5/02 Surfactant Flushing 6/02 Post-Remedial Flux 6/03&10/04

CFB, Canada Pre-Remedial Flux 5/04&7/04 In-situ Chemical Oxidation 6 05 Post-Remedial Flux 4/06

Jacksonville, Florida Pre-Remedial Flux 6/04 Cosolvent Flushing 6-7/04 Post-Remedial Flux 5/06

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Nor

thin

g (fe

et)

lls

iWells

ii i

Hill AFB OU2

293070

293090

293110

293130

293150

293170

Flux We

Observat on

Approx mate Flow D rect on

U2-154

U2-153

U2-117

U2-216

U2-155

U2-157

U2-152

U2-150

U2-148

U2-116

U2-149

U2-151

Layton, Utah

1870620 1870640 1870660 1870680 1870700 1870720

Easting (feet)

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1

10

1

10

1

10

100

0

TCE Concentration Time Series

TC

E C

once

ntra

tion

(mg/

L)

Elapsed Time (Hours)

May ‘02

q0

q0

q0

100

1000

100

1000

0.1

20 40 60 80 100

Jun ‘03

Oct ‘04

U2-154

U2-152

U2-150

U2-148

U2-116

U2-149

U2-151

U3-153

U2-155

U2-157

= 1.7 cm/d

= 2.9 cm/d

= 3.2 cm/d

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l

C

C

t

t

Adapted from Bockelmann et al. (2003)

Interpretation of CT series

Pumping well

Plume boundary

Pumping wel

Plume boundary

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May '02 Jun '03 Oct '03

Hill AFB OU2 Layton, Utah TCE Flux Summary 10

TC

E F

lux

(g/s

quar

e m

/day

)

1

0.1

0.01 154 152 150 148 116 149 151 153 155 157

Flux Well

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56

0 10 20 30 40 50 60 70 80 90

0 10 20 30 40 50 60 70 80 90

57

i l

0

1

2

3

4

5

6

7

8

9

10

154 152 150 116 151 153 157

154 152 150 116 151 153 157

Well

Flux Meter - Darcy Velocity (cm/day)

Ele

vatio

n (f

eet) 4660

4665

4670 Pre Remedial Flux Measurement Test May 2002

Second Post Remed al F ux Measurement Test October 2004

4660

4665

4670

148 149 155

148 149 155

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0 10 20 30 40 50 60 70 80 90

0 10 20 30 40 50 60 70 80 90

58

4660

4665

4670

4660

4665

4670

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

154 152 150 116 151 153 157

154 152 150 116 151 153 157

Flux Meter – Log TCE Flux (gram/square meter/day)

Ele

vatio

n (f

eet)

Second Post Remedial Flux Measurement October 2004

Pre Remedial Flux Measurement May 2002

148 149 155

148 149 155

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0

1

2

3

4 (

Hill AFB OU2 Darcy Velocity Comparison

May 2002 June 2003 Oct 2004

PFM MIPT PFM PFMMIPT MIPTD

arcy

Vel

ocity

cm/d

ay)

Layton, Utah

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Well-Averaged Flux Summary

0.001

0.01

0.1

1

10

0.001 0.01 0.1 1 10

lux (g / m2 / day)

l2 /

day)

IPT F

FM F

ux (g

/ m

TCE 5/02

TCE 6/03

DCE 6/03

TCE 10/04

DCE 10/04

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NAPL Area 1

NAPL Area 2

NAPL Area 3

Fort Lewis EGDY Area 1 Source Zone of Ft. Lewis Plume

Tacoma, Washington

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B09

Fort Lewis EGDY Area 1

5,216,710

5,216,720

5,216,730

5,216,740

5,216,750

5,216,760

5,216,770

5,216,780

536,390 536,400 536,410

LC-213 LC-214

LC-212

C08 LC-211

LC-207

LC-206

LC-205

LC-209

LC-204

D14

LC-210

LC-203

LC-208

LC-202

LC-215

LC-201

Tacoma, Washington

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10

20

63

0

0

1

2

PFM Velocity Field (cm/hr) University of Florida

Fort Lewis EGDY Area 1

33

13

Dep

th (f

t bgs

)

23

20 40 60 80 100 120 140 160 180

0.2

0.4

0.6

0.8

1.2

1.4

1.6

1.8

2.2

2.4

2.6

2.8

Tacoma, Washington

Distance along transect (ft)

63

10

20

64

0

0 100 120 140 160 180

-2 hr-1) University of Florida

Fort Lewis EGDY Area 1

33

13

Dep

th (f

t bgs

)

23

-0.005

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

0.055

0.06

0.065

0.07

20 40 60 80

PFM TCE Flux (mg cm

Tacoma, Washington

Distance along transect (ft)

Range: <0.1 to 20 g/ sqm /day; Transect average 2 g / sqm / day.

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Fort Lewis EGDY Area 1

Flux Well

-1)

Tacoma, Washington

Ft Lewis Modified Integrated Pump Test - Oct/Nov 2003

0.01

0.10

1.00

10.00

100.00

201 202 203 204 205 206 207 211 212 213

Dar

cy F

lux

(cm

hr

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Fort Lewis EGDY Area 1

0.01

0.1

1

10

201 202 203 204 205 206 207 211 212 213

TCE

Flux

(g m

-2 d

-1 )

IPT

Average Pre-Remedial Flux, Oct/Nov 2003 Tacoma, Washington

0.0001

0.001

Flux Well

PFM

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•

• in flux at Hill AFB

• methods to date are comparable

Summary

Modified IPT method is being used to measure pre- and post-remedial flux Approximately an order of magnitude decrease

Flux estimates based on flux meter and IPT

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Acknowledgements

•

• Research and Development Program (SERDP)

Onsite Assistance – Hill AFB EMR/URS, Utah – LFR, Florida – US Army Corps of Engineers Seattle

District/Fort Lewis Public Works, Washington – University of Waterloo, Canada

Project Funding: Strategic Environmental

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