Geophysics for LUST sitesDale Werkema, Ph.D.Research Geophysicist

US EPA, ORDwerkema.d@epa.gov

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Why geophysics?

• Prior to expensive and invasive surgery we utilize medical imaging.

• Each medical imaging method is used for specific purposes.

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• Prior to expensive earth intrusive investigations (e.g., drilling, excavating,

etc.) we can utilize geophysical imaging.

• Each geophysical method is used for specific purposes

x-ray of knee MRI of knee

Landfill plume mapping Abandoned well mapping

images credit: Lee Slater

Outline

1. Finding Underground Storage Tanks (USTs)

and underground infrastructure

2. Mapping contaminant plumes

3. Monitoring active or passive remediation

4. High resolution characterization and Conceptual

Site Model (CSM) development

5. Online resources – under development

•Online Environmental Geophysics Textbook

•Decision Support Tools

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Geophysical methods include a set of tools

in the site investigator’s tool box.

Geometrics G-858 Cesium vapor magnetometer

• What are the physical properties of the target, i.e. UST and associated infrastructure?➢ metal?, ferrous metal? fiberglass?

• Any potential interference?

1. Finding USTs & subsurface infrastructure

Likely applicable geophysical methods:1. Magnetic 2. Electromagnetic3. Ground Penetrating Radar (GPR)

Geonics EM-61Mala GPR system

Net

Ambient

BodyAnomaly Anomaly

Body

NORTH

Geophex GEM2

Geonics EM-31

1. Finding USTs & subsurface infrastructure

Total MagneticField Intensity (nT)

1. Finding USTs & subsurface infrastructure

EM 31 Quadrature

Geonics EM-31

1. Finding USTs & subsurface infrastructure

Ground Penetration Radar (GPR) UST and utility examples

Note: Hyperbolic Reflections

500 MHz antenna

• pipes oriented perpendicular to the profile.

• Darker reflections show higher amplitude due to greater electrical property impedance.

• Faint reflections show muted or low amplitude reflections due to the attenuation of the GPR energy from electrically conductive material.

400 MHz antenna

telephonecable

2 steelpipes

steelpipe

PVCpipe

A)

B)

GSSI antenna

GPR sections from Bill Sauck

Archie's Law for Porous Media w/o clay

re = a f-m S-n rw

re = resistivity of the earth

f = fractional pore volume (porosity)

S = fraction of the pores containing fluid

rw = the resistivity of the fluid

n, a and m are empirical constants

Direct Current (DC) Resistivity

2. Mapping contaminant plumes

Current flowlines

Lines ofequal potential

MeasuredpotentialCurrent

source v

Resistivity Surveying

Resistivity (Ohm m)10 100

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Distance (m)

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-2

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pth

(m

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saltwater-saturated sands

Approximate location of ~0.3 m thick oil layer

SENW Offshore

Zone of immature oil contamination imaged as resistive layer

thinning of oil layer?InlandOil layer

Oil impact thins away from the shoreline

Oil

layer

Heenan, J., Slater, L.D., Ntarlagiannis, D., Atekwana, E.A., Fathepure, B.Z., Dalvai, S., Ross, C., Werkema, D.D., and Atekwana, E.A., Geophysics, 2014

2. Mapping contaminant plumesDeep Water Horizon Oil Spill Barrier Island Impact

DC Resistivity Results

DWH Barrier Island Time-Lapse

10Heenan, J., Slater, L.D., Ntarlagiannis, D., Atekwana, E.A., Fathepure, B.Z., Dalvai, S., Ross, C., Werkema, D.D., and Atekwana, E.A., Geophysics, 2014

Adaptation of field resistivity system to remote solar power acquisition

15 months resistivityave. resistance of anomaly vs. time

2. Mapping contaminant plumes

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De Ryck et a l., 1993

Monitoring or measuring passive or

active remediation using geophysics

3. Remediation monitoring

Maturity of plume should be considered

zone of hydrocarbon impact

Controlled Kerosene Spill

However…

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Residual LNAPL

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Aquitard –

Clay Unit

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Free LNAPL

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F r e e L N A P L

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Lab Field Lab Field

Direct Current Resistivity of mature LNAPL plume

Geophysical response is coincident with microbiology and geochemical changes

Werkema Jr., D.D., Atekwana. E.A., Endres, A., Sauck, W.A. and Cassidy. D.P., Geophysical Research Letters, 2003

16S rRNA gene community composition

Contaminated

Column

Control

Column

Bacteroidetes

Bacilli

Clostridia

Bacilli

-proteobacteria

Contaminated

Column

Control

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Bacteroidetes

Bacilli

Clostridia

Bacilli

-proteobacteria

clean contaminated

3. Remediation monitoring

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Soil Vapor Extraction (SVE) monitoring using Self-Potential (SP)

Vukenkeng C.A., Atekwana Estella.A., Atekwana, Eliot, A., Sauck, W.A., Werkema Jr., D.D., Geophysics, vol. 74, 2009

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Groundwater flow

Approximate plume boundary

Groundwater flow

Soil vapor extraction

system

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Former fire training facility, Oscoda, Michigan

Large quantities of fuel were burned.

1990s, the free product 0.3 m thick and > 200 m down gradient

3. Remediation monitoring

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DC Resistivity response to SVE systemGPR Response

to SVE System

Vukenkeng C.A., Atekwana Estella.A., Atekwana, Eliot, A., Sauck, W.A., Werkema Jr., D.D., Geophysics, vol. 74, 2009

3. Remediation monitoring

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Magnetic Susceptibility (MS)

Atekwana, Mewafy, Abdel Aal, Werkema, Revil, and Slater, Journal of Geophysical Research, 2014

MS measurements of the

accumulation of magnetite can be adopted as a non-invasive technology for

monitoring long-term natural attenuation of

crude oil in the subsurface

C1010

C1006

North Pool

South Pool

Rupture

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3. Remediation monitoring

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4. High Resolution CSM development

Groundhog burrow

GPR image depicting

the entrance shaft,

tunnel, ramp, and

chamber imaged with

the 400 MHz antenna

and the 900 MHz

antenna.

Sherrod, L., Sauck, W., Simpson, E., Werkema, D., Swiontek, J., Case histories of GPR for animal burrows mapping and geometry, Journal of Environmental and Engineering Geophysics, In press, 2018

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Manual picks chosen for

the identification of the

groundhog burrow system

through hyperbolic

reflections in the 400 MHz

data.

GPR detection and mapping of animal burrows

Environmental Geophysics web

presence: tech transfer, assistance, guidance, and

decision support tools

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ONLINE RESOURCES

Once finalized this will be found at:

www.epa.gov/environmental-geophysics

Beta version: https://clu-in.org/characterization/technologies/geophysics/

5. Models & Decision Support

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5. Models & Decision Support ONLINE RESOURCES

https://clu-in.org/characterization/technologies/geophysics/ Werkema Jr., D.D., Jackson, M., and Glaser, D., EPA/600/C-10/004, 2010

Geophysical Decision Support System (GDSS – Beta Version)

5. Models & Decision Support ONLINE RESOURCES

SEER – Scenario Evaluator for Electrical Resistivity

(a) hypothetic target consisting of a mature LNAPL

plume on the water table, and electrodes with 1-m

spacing at land surface

(b) the resultant electrical resistivity tomogram,

assuming normally distributed random standard

errors of 3%.

Terry, N., Day-Lewis, F., Robinson, J., Slater, L., Halford, K., Binley, A., Lane Jr., J., Werkema, D., 2017

5. Models & Decision Support ONLINE RESOURCES

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Concluding Thoughts

We can use, and are learning to use, geophysics to:

1. Find Underground Storage Tanks2. Direct detection of some contaminants3. Biological breakdown of contaminants and remediation4. CSM development5. Forward models and decision support systems help reduce uncertainty of

results and inform stakeholders

The geophysical response is a function of the geology, hydrogeology, biology, and chemistry of the subsurface.

➢ Look for physical property contrasts, understand the mechanism of that contrast and if geophysical methods have the requisite resolution to detect the contrast.

What are the physical property contrasts?

Are these contrasts geophysically detectable?

Mass removal (e.g., SVE)

Biodegradation

Initiation of

contamination

peak conductivity

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Mea

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d p

ara

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conduct

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Conta

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ant m

ass

incre

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Atekwana et. al., 2006

Acknowledgement & Collaborators

• John Lane, Fred Day-Lewis, Marty Briggs, Carole Johnson, Eric White, Terry Neal: USGS and University of Connecticut

• Lee Slater, Dimitris Ntgarlantis, Judy Robinson, Rutgers University

• Estella Atekwana & Eliot Atekwana: University of Delaware formerly OSU

• Gamal Abdel Aal: Assiut University, Egypt

• Andre Revil: Colorado School of Mines

• Barbara Luke: University Nevada-Las Vegas

• Bill Sauck & Silvia Rossbach: Western Michigan University

• Yuri Gorby: J. Craig Venter Institute

• Students:

• UConn: Emily Voyteck, John Ong, Rory Henderson

• UNLV: Meghan Magill, Nihad Rajabdeen, Lisa Hancock

• Rutgers: Jeff Heenan, Yves Robert-Personna, Sina Saneiyan, Sundeep Sharma, Angelo Lamousis,

• Oklahoma State U: Farag Mawafy, Ryan Joyce, Dalton Hawkins, Brooke Braind, Cameron Ross, Carrie Davis, Che-Alota Vukenkeng,

• Colorado School of Mines: Marios Karaoulis

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Disclaimer: Any use of equipment or trade names does not constitute endorsement by the USEPA