Sensor Technologies Used During

Site Remediation Activities -

Selected Experiences

((((Cce
Solid Waste EPA 542-R-05-007 

and Emergency Response September 2005 

(5102G) www.clu-in.org 

Internet Address (URL) • www.epa.gov/ 

Recycled/Recyclable • Printed with Vegetable Oil Based Inks on Process Chlorine Free Recycled Paper (minimum 50% Postconsumer)

Sensor Technologies Used During Site Remediation Activities – 

Selected Experiences 

i 

TABLE OF CONTENTS 

Section Page

ACRONYMS AND ABBREVIATIONS....................................................................................... ii 

NOTICE AND DISCLAIMER...................................................................................................... iv 

1.0 INTRODUCTION ...............................................................................................................1 

1.1 What are Sensors?....................................................................................................1 

1.2 Purpose of Report ....................................................................................................1 

1.3 Methodology............................................................................................................2 

2.0 OVERVIEW OF SENSORY SYSTEMS............................................................................3 

2.1 Characterization or Monitoring................................................................................3 

2.2 Automation ..............................................................................................................4 

3.0 EXAMPLES OF REMEDIATION SITES THAT HAVE USED SENSOR 

TECHNOLOGIES ...............................................................................................................5 

3.1 Site Characterization................................................................................................5 

3.2 Monitoring ...............................................................................................................5 

3.3 Automation ..............................................................................................................5 

4.0 REFERENCES ....................................................................................................................9 

Appendices

1 Sensor Technology Case Study – Use of Membrane Interface Probe Technology for 

Detection of VOCs at the Sol Lynn/Industrial Transformer Superfund Site 

2 Sensor Technology Case Study – 2D-Recon and EOL Geophysical Survey Techniques 

for Characterizing Hydrocarbon-Contaminated Soils at the Hotel Pier Site 

3 Sensor Technology Case Study – Use of Capacitance Probes to Measure Soil Moisture at 

the Badger Army Ammunitions Plant 

4 Sensor Technology Case Study – Use of In-Situ Sensors to Monitor Ground Water 

Velocity at the China Lake Naval Air Weapons System Site 

5 Automation Technology Case Study – Programmable Logic Controllers and Ozone 

Analyzers at the Moffett Federal Airfield Site 

6 Sensor Technology Case Study – Automated Sampling and Analysis of Trichloroethene 

and Hexavalent Chromium Using the Burge System at the North Indian Bend Wash and 

Nevada Test Sites 

7 Automation Technology Case Study – Supervisory Control and Data Acquisition Using 

Programmable Logic Controllers at the Sprague Road Superfund Site 

LIST OF TABLES 

Table Page

1 Selected Case Studies on Sensor Technologies...................................................................6 
ii 

ACRONYMS AND ABBREVIATIONS 

1, 2-DCE 1, 2-dichloroethene 

2D-Recon Two-dimensional gradiometer 

ASTM American Society of Testing and Materials 

BAAP Badger Army Ammunition Plant 

Bgs Below ground surface 

BRL Basic relay logic 

BTEX Benzene, toluene, ethyl benzene, and total xylenes 

COC Contaminant of concern 

CPU Central Processing Unit 

CPU Central Processing Unit 

Cr-VI Hexavalent chromium 

DA Data acquisition 

DBG Deterrent Burning Ground 

DELCD Dry electrolytic conductivity detectors 

EC Electrical conductivity 

ECD Electron capture detector 

EOL Electromagnetic offset log 

EPA U.S. Environmental Protection Agency 

FID Flame ionization detector 

ft/day Feet per day 

GC Gas chromatograph 

HMI Human machine interface 

HOA Hand-off-auto 

Hz Hertz 

IrriMAX Vendor-supplied standard calibration model 

LED Light emitting diode 

LPZ Low permeability zones 

MFA Moffett Federal Airfield 

MIP Membrane interface probe 

mL/min Milliliters per minute 

mV Millvolts 

NELP Navy Environmental Leadership Program 

NIBW North Indian Bend Wash 

NPDES National Pollutant Discharge Elimination System 

NTS Nevada Test Site 

o

C Degrees Centigrade 

Ogden Ogden Environmental and Energy Services Co., Inc. 

OSHA Occupational safety and health administration 

PC Anywhere (communications software) 

PC Personal computer 

PID Photoionization detector 

PLC Programmable logic controller 

PLC Programmable logic controllers 

ppb Parts per billion 

R&D Research and development 
iii 

RI Remedial investigation 

SCADA Supervisory control and data acquisition 

SDI Serial data interface 

Sol Lynn Sol Lynn/Industrial Transformer Superfund 

Sprague Road Sprague Road Ground Water Plume Superfund 

SRI Supplemental remedial investigation 

TCE Trichloroethene 

THM Trihalomethanes 

USDA U.S. Department of Agriculture 

UST Underground storage tank 

UV Ultraviolet light 

VC Vinyl chloride 

VECTOR Variably Emitting Controlled Thermal Output Recorder 

VOC Volatile organic compounds. 

WBZ Water bearing zones 

WBZ Water bearing zones 
iv 

NOTICE AND DISCLAIMER 

Preparation of this report has been funded by the U.S. Environmental Protection Agency (EPA) 

Technology Innovation and Field Services Division under EPA Contract Number 68-W-02-034. 

This document represents the views of the authors. However, this document has undergone EPA 

and external review by experts in the field. 

A limited number of printed copies of the report are available free of charge and may be ordered 

via the Web site, by mail, or by fax from the following source: 

EPA/National Service Center for Environmental Publications 

P.O. Box 42419 

Cincinnati, OH 45242-2419 

Telephone: (513) 489-8190 or (800) 490-9198 

Fax: (513) 489-8695 

This document is not U.S. EPA policy, guidance or regulation. It does not create or impose any 

legally binding requirements. The information is not intended, nor can it be relied upon, to 

create any rights enforceable by any party in litigation with the United States or any other party. 

The information provided may be revised periodically without public notice. Use or mention of 

trade names does not constitute endorsement or recommendation for use. Standards of Ethical 

Conduct do not permit EPA to endorse any private sector product or service. 

For further information about this report, please contact the EPA’s Office of Superfund 

Remediation and Technology Innovation: 

Ellen Rubin 

(703) 603-0141 

rubin.ellen@epa.gov 
1 

1.0 INTRODUCTION 

1.1 WHAT ARE SENSORS? 

A sensor is a device that produces a discernable response to external stimulus. Some examples 

of sensors are thermometers, photoelectric cells, pressure transducers, and smoke detectors. 

Electronic sensors respond to stimulus by producing standardized electrical signals. This enables 

them to interface with devices that display a readable output or larger systems providing sensory 

input to a decision-making device. For example, sensors may be used inside a storage tank to 

supply information on fluid levels to a system controller who would in turn use this information 

to make decisions on starting or shutting down pumps that fill or drain the tank. Sensors can be 

used in environmental remediation for the following activities: 

• Characterization 

• Monitoring 

• Automation 

When properly applied, sensors can provide long-term benefits for remediation projects by 

reducing manpower requirements, reducing analytical costs, and generating information that 

facilitates process optimization. 

1.2 PURPOSE OF REPORT 

Environmental remediation includes many activities that require measurement and monitoring of 

parameters such as contaminant concentrations, media characteristics, and systemic parameters. 

In recent years, there has been an increase in the number and types of sensor technologies used 

during site remediation. These include technologies that are used for performing real-time and 

continuous measurements, remote monitoring, remote operation, and system automation. 

The U.S. Environmental Protection Agency (EPA) prepared this report to provide an overview of 

several types of sensor technologies and a summary of selected experiences with using the 

technologies during site remediation activities. The report highlights the applications, 

implementation, strengths and limitations, and lessons learned from actual projects that have 

used one or more sensor technologies as part of an overall site remediation strategy. Appendices 

one through seven provide case studies for specific sites that have used sensor technologies 

during site remediation activities. 

This report does not provide guidance on the selection of a specific type or vendor of sensor 

technology; these technologies are most cost-effective under specific environmental, chemical, 

and physical conditions. Numerous site-specific considerations, such as site geology, soil, and 

aquifer characteristics, chemical, physical, and biological parameters of affected media, and 

chemicals of concern, among many others, can impact the overall cost-effectiveness of a system. 
2 

1.3 METHODOLOGY 

In preparing this report, EPA collected available information on sensor technologies for remedial 

projects performed at Superfund sites, federal/military sites, and other sites. EPA attempted to 

compile information that was readily available and current for each project as of Summer/Fall 

2004, however, in some cases, EPA was not able to confirm the available information. Some 

case studies include information provided primarily by the technology vendor, with limited input 

from a regulatory authority. In addition, for many of the projects, there were gaps in the types of 

information available (e.g., for some sites, performance data were not available, or there was a 

limited amount of data that independently evaluated sensor performance). This report is not a 

comprehensive review of all available sensor technologies or vendors. 
3 

2.0 OVERVIEW OF SENSORY SYSTEMS 

Sensory systems used for automation, characterization, and monitoring can consist of a number 

of different components, including mechanical sensors, electronics, analytical (chemical) 

sensors, control systems, telemetry systems, and software. These components may be used alone 

or together to form relatively simple or highly complex systems. 

Mechanical sensors by definition contain moving parts. For instance, turbine flow meters 

contain turbines that rotate as water flows through a pipe. Flow rate is measured by counting the 

number of revolutions per minute. When coupled with electronic transmitters, flow meters can 

form sensory systems that are able to measure and communicate flow data to a control unit or 

display. Other examples of mechanical sensors include floats (used in tank float switches) and 

pressure gauges. 

Electronic sensors are electrically powered and can measure a variety of parameters such as 

pressure, specific gravity, the presence of liquid (water level meters and interface probes), pH, 

temperature, and conductivity. 

Analytical sensors are typically used to measure chemical parameters such as contaminant 

concentrations. Some examples of analytical sensors include pH probes, and optical sensors 

used for colorimetric measurement 

Control systems that work in conjunction with sensors include programmable logic controllers 

(PLC) and other electronic microprocessor devices. Control systems are able to receive sensory 

inputs, process information, and trigger specific actions. 

Telemetry systems facilitate system control or data acquisition from remote locations. They can 

be radio or telephone based. Radio-based systems use radiofrequency communication devices to 

send and receive information. Telephone-based systems use modems to send and receive 

information through telephone lines. 

2.1 CHARACTERIZATION OR MONITORING 

Sensors used in characterization are typically used to measure environmental parameters. For 

example, a membrane interface probe may be used to detect and locate subsurface 

contamination; an electrochemical probe may be used to measure ground water parameters such 

as pH; and a thermometer may be used to measure sample temperature. Sensors in monitoring 

are typically used to measure both environmental and systemic parameters. For example, an 

anemometer may be used to measure wind velocity at a site; a water-level sensor may be used to 

measure long term fluctuations in ground water elevation; and a flow meter may be used to 

monitor flow through a pipe. 
4 

2.2 AUTOMATION 

Automation systems use sensory devices to measure parameters necessary for proper system 

operation. Some examples of these parameters are water levels in wells and tanks, temperature, 

pressure drop, flow rate, and effluent concentration. These parameters are then used by 

microprocessor devices such as PLCs to make operational decisions including starting up or 

shutting down components of the remediation system. 

Additional Sources of Information about Sensor Technologies 

Field Analytic Technologies Encyclopedia (FATE) – an online encyclopedia intended to provide 

information about technologies that can be used in the field to characterize contaminated media, 

monitor the progress of remedial efforts, and in some cases, perform confirmation sampling and 

analysis for site close out. FATE includes information on several types of fiber optic chemical 

sensors. http://fate.clu-in.org/index.htm 

Measurement and Monitoring Technologies for the 21st Century (21 M2) – through this initiative, 

EPA's Office of Solid Waste and Emergency Response (OSWER) will identify and deploy promising 

measurement and monitoring technologies in response to waste management and site cleanup program 

needs by matching existing and emerging technologies with OSWER program and client needs. 

Current projects include open path monitoring and sampling for contaminated sediments, as well as a 

summary of available literature on measurement and monitoring technologies. 

http://www.cluin.org/programs/21m2/

Remediation and Characterization Technology Database (EPA REACHIT) – an online database 

with powerful search options for information on treatment and characterization technologies, plus 

updated information from remediation projects undertaken by EPA. The database includes the 

following information for characterization technologies (as of March 2004): 158 technology vendors, 

241 technologies, and 186 vendor source sites. http://www.epareachit.org

EPA’s “A Review of Emerging Sensor Technologies for Facilitating Long-Term Ground Water 

Monitoring of Volatile Organic Compounds” – This report summarizes the status of emerging 

sensor technologies for facilitating long-term ground water monitoring for volatile organic compounds 

(VOCs). It also describes a number of factors, including regulatory acceptance and cost-effectiveness, 

that influence the applicability of these technologies. http://www.clu-in.org/s.focus/c/pub/i/1040/ 

Superfund Innovative Technology Evaluation (SITE) Program – established by EPA to aid 

engineers, scientists and other remediation professionals in the efficient monitoring, characterization 

and remediation of hazardous wastes. In this program, technologies are field-tested to assess 

performance. Cost and performance data are then presented in technology evaluation reports. 

http://www.epa.gov/ORD/SITE/
5 

3.0 EXAMPLES OF REMEDIATION SITES THAT HAVE USED SENSOR 

TECHNOLOGIES 

Table 1 identifies seven case studies on sensor technologies that illustrate their use in site 

characterization, monitoring, and process automation. The sites discussed in these case studies 

used the following types of technologies: 

3.1 SITE CHARACTERIZATION 

• Membrane Interface Probe – for contaminant concentrations 

• Geophysical surveys – for evaluation of hydrocarbon contamination 

3.2 MONITORING 

• Capacitance probe – for soil moisture content 

• VECTOR technology – for ground water flow velocity 

• Burge System – for sampling and analysis 

3.3 AUTOMATION 

• Ozone analyzers and SCADA with PLC – for ground water pump and treat operation 

• SCADA with PLC – for ground water pump and treat operation 

Five of the seven case studies present characterization and monitoring sensor technologies; the 

other two (Moffett Federal Airfield, and Sprague Road Superfund Site) discuss sensor-dependent 

automation technologies. The technologies discussed in this report are commercially available, 

and have had at least one full-scale implementation. Projects for which case studies were 

completed were selected based on information in available databases and Internet resources, such 

as EPA’s Clu-In Web site (www.cluin.org), and discussions with remediation project managers 

(RPMs), staff of both EPA Headquarters and Regional Offices, project managers from other 

Federal, state, and local government agencies, consultants, and vendors. 

Each case study includes site background information, an overview of the sensor technology 

used and the goal for using the technology, a brief summary of remedial efforts at the site, 

information about the implementation of the sensor technology, and lessons learned. In addition, 

each case study presents cost data for the specific sensor technology. Where actual cost data are 

not available, estimated information is provided. Conclusions in the case studies are not limited 

to site-specific details. In most cases, conclusions include site-specific information and general 

information about the technology that might benefit potential users. References used in 

preparation of each case study are provided at the end of the case study. 
6 

TABLE 1. SELECTED CASE STUDIES ON SENSOR TECHNOLOGIES 

Site Name 

Technology 

Employed 

Time Period 

of Use 

Media of 

Concern Contaminants 

Goal for Use of 

Technology 

Sol Lynn/ Industrial Transformer Superfund Site, Houston, Texas

Membrane Interface Probe 

January – June 2001

Ground water TCE and its 

degradation products

Delineate ground water contamination and screen locations requiring further characterization. 

MIP technoidentify higregions in sas well as dthe contamvarious wat

Hotel Pier Site, Pearl Harbor, Hawaii

Geophysical survey techniques – 2DRecon and 3D EOL 

Not provided Soil and 

ground water 

Hydrocarbon contamination

Characterize areas of hydrocarbon contamination and assist in evaluation of remedial alternatives.

Electromagcharacterizecontaminatconcept thawith hydrocresistivity t

Badger Army Ammunition Plant, WI (SubSite BAAP-06- Deterrent Burning Ground) 

Capacitance probe (for soil moisture content) 

2004 – ongoing 

Soil Munitions 

based compounds 

Measure soil moisture levels beneath a cap, to assess potential for leaching contaminants to GW at 100-110 ft bgs. 

A nutrient iencouraged degradation contaminatThe capacitsentinels agflooding of that could pthe ground bgs. 
7 

TABLE 1. SELECTED CASE STUDIES ON SENSOR TECHNOLOGIES 

Site Name 

Technology 

Employed 

Time Period 

of Use 

Media of 

Concern Contaminants 

Goal for Use of 

Technology 

China Lake Naval Weapons Station, CA velocity) 

VECTOR technology (for ground water flow 

1999 – ongoing (data through September 2004) 

Ground water Not provided Monitor GW 

flow along southern property boundary, with potential for transport to nearby municipal well fields. 

Each velocwith an abothat records predeterminDownloadeaccompanywhich transground watdirection.

Moffett Federal Airfield, CA (West-side Aquifers) 

Ozone analyzers and Programmable Logic Controllers (PLCs) in a ground water pump and treat system 

2001 – ongoing (data through September 2004) 

Ground water TCE Automate pump 

and treat system and monitor ozone in aqueous and gaseous media. 

The ozone conjunction ensure that of ozone is water, (2) tsystem is memission stambient air safety and h(OSHA) sta

North Indian Bend Wash: Jan 2002 – July 2003 

Ground water TCE Analyze TCE in 

influent and effluent of ground water treatment plant on a daily basis. 

The TCE mused to promonitoring effluent frotreatment s

North Indian Bend Wash, AZ, and Nevada Test Sites, NV 

Burge System – (optical sensor) 

Nevada Test Site: December 2003 and March 2004 

Ground water Cr-VI Analyze Cr-VI in 

ground water (pilot test). 

The Cr-VI used for samanalysis of water in a pis currently site near Ri
8 

TABLE 1. SELECTED CASE STUDIES ON SENSOR TECHNOLOGIES 

Site Name 

Technology 

Employed 

Time Period 

of Use 

Media of 

Concern Contaminants 

Goal for Use of 

Technology 

Sprague Road Superfund Site, TX 

PLC and SCADA

2003 – ongoing

Ground water Cr-VI Automation of 

pump and treat system.

PLCs used pumps. Thsensors and sensory datcontrol decon or shut vcommunicanetwork andesktop comdata loggerrecording ssuch as flow flow.
9 

4.0 REFERENCES 

EPA. 2004. 21M2 - Measurement and Monitoring Technologies for the 21st Century. 

http://www.cluin.org/programs/21m2/ (Includes quarterly literature search). 

WPI. 2004. Sensor Technology Information Exchange. www.sentix.org. (Includes searchable 

database of sensor information) 

Federal Remediation Technology Roundtable. 2004. Field and Innovative Sampling and 

Analysis Technology Matrix, version 1.0. www.frtr.gov. 

EPA. 2004. Field Analytic Technologies Encyclopedia (FATE). www.fate.cluin.org. (Includes 

section on technologies) 

EPA. 2004. REmediation And CHaracterization Innovative Technologies (EPA REACH IT). 

www.epareachit.org. 

EPA. 2004. Environmental Technology Verification (ETV) Program. 

www.epa.gov/etv/index.htm. 

Vendor Web Sites 

• Advantech at www.advantech.com

• Ametech, Inc. at http://www.drexelbrook.com/

• Analytical Measurements, Inc. at http://www.anyliticalmeasurements.com

• Bowles Corporation, Inc. at http://www.bowles-corp.com/cet.htm

• Burge Environmental at http://www.burgenv.com/index.html

• Campbell Scientific at www.campbellsci.com/sensors.html

• Clean Earth Technology at http://www.bowles-corp.com/cet.htm

• Conor Pacific at http://www.conorpacific.com/

• Containment Solutions at http://www.containmentsolutions.com/

• Control Development at http://www.controldevelopment.com/

• Controlotron at http://www.controlotron.com/

• Diversified Remediation Controls, Inc. at http://www.drc1.com/prod01.htm

• Foxboro at http://foxboro.com

• Geophysical Survey Systems, Inc. at http://www.geophysical.com/SIR20.htm

• Geo-Sense at http://www.geo-sense.com/

• GE Industrial Systems at http://www.geindustrial.com/cwc/gefanuc/
10 

• Gundle/SLT Environmental Inc. at http://www.gseworld.com/

• Horiba at http://global.horiba.com/analy_e/u-20_series/

• Hydrotechnics at http://www.hydrotechnics.com/index_6.htm

• I-CORP International, Inc. at http://www.geosynthetic.com/

• Instrumentation Northwest, Inc. at http://inwusa.com/xlseries.htm

• KPSI at http://www.psih.com/

• Leakwise7 at http://www.leakwise.com/

• North East Environmental Products, Inc. at http://www.neepsystems.com/

• Omega at http://www.omega.com/

• PERMA-PIPE, Inc. at http://www.permapipe.com/

• Physical Sciences, Inc. at http://www.psicorp.com/

• Raychem Corporation at http://www.raychem.com/products/chemlex/tracetek.htm

• Remediation Service, Inc. at http://www.rsi-save.com

• Remote Possibilities at http://www.remotepossibilities.com/

• Revere Control at http://www.reverecontrol.com

• Rockwell Software at http://www.software.rockwell.com/rsviewstudio/

• SAIC at http://www.saiceemg.com/harrisburg/ers-siteboss.htm

• Sensaphone, Inc. at http://www.sensaphone.com/

• Strison Wireless Systems at http://strison.com

• SubSurface Leak Detection, Inc. at 

http://www.subsurfaceleak.com/zcorr_logger_prod.html

• Tracer Research Corporation at http://tracertight.com/

• Troxler Electronic Laboratories at http://www.troxlerlabs.com/ap200.html

• Turner Designs, Inc. at http://www.turnerdesigns.com/

• Tyco Thermal Controls, Inc. at http://tycothermal.com/

• Waste Technologies of Australia, Party Limited, at http://www.wastetechnologies.com/

• Wonderware at www.wonderware.com

• YSI at http://www.ysi.com

• ZISTOC Corporation at http://www.zistos.com/
Appendix 1 

Sensor Technology Case Study 

Use of Membrane Interface Probe Technology for Detection of VOCs 

at the Sol Lynn/Industrial Transformer Superfund Site 

Sensor Technology Case Study 

Use of Membrane Interface Probe Technology for Detection of VOCs at the 

Sol Lynn/Industrial Transformer Superfund Site 

1-1 

Summary Information [1, 5, 6] 

The membrane interface probe (MIP) is a semiquantitative field-screening tool for the 

detection of volatile and semi-volatile organic 

compounds. It facilitates quantitative 

measurement, but the results produced at any 

given location are relative and not absolute. It is 

often used as a precursor to future more accurate 

analysis. For instance, site characterization with 

MIP could paint a qualitative picture of 

subsurface contamination that distinguishes 

between areas of low, medium or high 

contamination. This could then be used to 

develop a plan for media sampling and 

laboratory analysis to assess the amount of 

contamination. 

MIP technology works by advancing the MIP 

through the strata to be explored. The MIP 

heats the matrix in contact with it and volatilizes 

contaminants. Volatilized contaminants enter 

the probe through a membrane covered window 

and are transported to the surface by a 

continuous draft of inert carrier gas. The 

contaminated gas stream is conveyed to a 

measurement device which then produces a 

quantitative result. The result is fed to a 

computer which displays it on the screen as a 

real-time graph of detected contamination 

versus depth of probe penetration. The 

computer also logs this data for future use. 

The Sol Lynn/Industrial Transformer Superfund 

(Sol Lynn) site is located about 6 miles 

southeast of downtown Houston, Texas. 

Historical operations at the site resulted in 

contamination of several water bearing zones 

with trichloroethene (TCE). The 1988 record of 

decision selected a pump and treat remedy for 

this site which operated for several years before 

ongoing groundwater monitoring revealed that it 

was ineffective. A supplemental remedial 

investigation (SRI) was initiated in 2001 to 

better understand the nature and extent of 

contamination. During this SRI, MIP 

technology was used to detect subsurface 

volatile organic compounds (VOC). 

MIP exploration was conducted at 99 locations 

between January 17, 2001, and June 5, 2001. A 

truck mounted Geoprobe® rig was used for 

probe advancement. Equipment used in 

combination with the probe included an MIP 

controller, a field computer (to display and log 

real-time measurements), and a gas 

chromatograph (GC) for gas-phase detection. 

Real time results made it possible to employ a 

dynamic method of site investigation that 

steered locations of subsequent investigations. 

MIP showed limited use as a quantitative tool. 

Technology Description [1, 5, 6, 8] 

MIP is a semi-quantitative screening tool for 

detection of volatile and semi-volatile organic 

compounds. Strictly speaking, the probe in 

itself has no sensory capability; it merely 

transfers vaporized samples of subsurface 

contaminants to gas-phase detectors at the 

surface. However, MIPs are used in tandem 

with electrical conductivity (EC) sensors. The 

two have been integrated into a single probe that 

is still called an MIP. Present day MIPs both 

serve as collection devices for subsurface 

contaminants, as well as measure soil EC. The 

primary use of the EC sensor in this probe is to 

map stratigraphy. 

The MIP is manufactured by Geoprobe®

Systems. It is a pen shaped device with 

stainless steel construction consisting of an EC 

sensor, a heater block, and a semi-permeable 
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-2 

membrane. Figure 1 displays an MIP. The 

membrane is a replaceable steel-impregnated 

thin-film polymer approximately 6.35 mm in 

diameter, and sits on the probe’s heater block. 

The block is raised at the leading edge to protect 

the membrane. Teflon tubing conveys carrier 

gas to and from the probe. Power wires supply 

electrical energy to the heater block, and control 

wires facilitate sensory feedback from the EC 

unit to the field computer. A model MP3500 

surface unit - called the MIP controller - 

monitors and controls carrier gas supply. The 

MIP controller feeds clean nitrogen gas to the 

probe, and conveys contaminant laden gas to the 

gas detector. A model FC4000 field computer 

interfaces with the EC sensor and the gas 

detector to acquire and log all sensory data. 

Figure 2 displays the field computer, the MIP 

controller, and the gas detector. The field 

computer has a screen which provides a 

graphical display of real-time measurements as 

the probe advances through the soil. This tells 

the operator the location of the contaminant, the 

relative concentration, and the type of soil in 

which the contaminant is located. 

This technology exploits the phenomenon of gas 

transfer across membranes to detect subsurface 

contamination. The membrane used in an MIP 

is semi-permeable, which means that the 

passage of substances through it is selective. 

The membrane retains liquids, but allows 

compounds in their gaseous state to pass 

through. Cross-membrane transfer of gaseousphase contaminants occurs through the process 

of diffusion motivated by a concentration 

gradient across the membrane. The heater block 

speeds this transfer by elevating the temperature 

of the surrounding matrix. The block is heated 

to approximately 120 degrees Centigrade (o

C). 

Heat from the block vaporizes contaminants in 

the surrounding matrix causing higher vapor 

pressures, and consequently higher 

concentration gradients. Once past the 

membrane, contaminants are transported to a 

detection unit by a continuously flowing stream 

of carrier gas. Carrier gas sweeps behind the 

membrane at a constant flow rate of 35-45 

milliliters per minute (mL/min). Travel time 

from the membrane to the detector is 

approximately 30-60 sec (depending on the 

length of trunk line and flow rate). 

The ability to detect a contaminant depends on 

the type of gas detectors being used. Any 

laboratory grade gaseous phase detector with an 

analog output of 1-5 Volts may be used. Most 

commonly used detectors include the 

photoionization detector (PID), electron capture 

detector (ECD), and the flame ionization 

detector (FID). Each of these detectors is best 

suited to a group or type of contaminant. The 

ECD is usually used for the detection of 

chlorinated contaminant (such as TCE, PCE, 

etc.); the PID is best suited for the detection of 

aromatic hydrocarbons (BTEX compounds); 

and the FID is best used for straight chained 

hydrocarbons (such as methane, butane, etc.). 

These detectors may be used in series with the 

least destructive detector being first and the 

most destructive detector coming last. The MIP 

field computer (FC4000) system can process up 

to four detector signals simultaneously. Figure 

2 shows a GC -housing a PID and an FID- being 

used as a gas-phase detector. 

The essential components of an MIP 

characterization effort are: (1) a direct push 

mechanism (such as Geoprobe® or Cone 

Penetrometer [CPT]); (2) an MIP; (3) an MIP 

controller; (4) gaseous phase detectors; and (5) a 

data display and logging system. 

MIP exploration typically requires a three-man 

crew including a geologist. Though not an 

unchangeable standard, MIP advancement is 

usually accomplished one foot at a time. The 

waiting periods between subsequent 

advancements typically last a minute. This is 

necessary for sample collection and transfer to 

the surface detector. 
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-3 

Figure 1 

Membrane Interface Probe 

Source: Geoprobe® Systems 
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-4 

Figure 2 

MIP Detection Equipment 

Source: Geoprobe® Systems 

Site Information [1, 4, 6] 

The Sol Lynn site is located about 6 miles 

southeast of downtown Houston, Texas. 

Historical activities at the site lead to 

contamination of the groundwater with TCE. 

Following a remedial investigation (RI) and 

feasibility study, a pump-and-treat system was 

designed to address the groundwater problem at 

the site. The system was installed in 1990. 

After several years of monitoring the 

contaminant plume, it became evident that the 

pump-and-treat system had failed to mitigate the 

problem or achieve plume containment. As a 

result, the pump-and-treat system was shut 

down in 1999. 

An SRI was initiated in late 1999 to gain a 

better understanding of the hydrogeology and 

contaminant distribution at the Sol Lynn site. 

The site hydrogeology at Sol Lynn was found to 

be extremely complex. While the first RI had 

concluded that there were only 3 water bearing 

zones (WBZ) at the site, the SRI found that 

there were in fact 9 WBZs in the first 200 feet 

below ground surface (bgs). Shallow 

groundwater at the site occurred within the more 

permeable units of the Beaumont formation. 

The surficial hydrogeologic units were a part of 

the upper Chicot aquifer. Each of the WBZs 

was separated by low permeability zones (LPZ) 

which acted like aquitards between the 

individual WBZs. 

Gas Chromatograph MP3500 MIP Controller 

FC4000 

Field 

Computer 
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-5 

TCE was the primary contaminant of concern 

(COC) in groundwater. TCE by-products, 

primarily 1, 2-dichloroethene (1, 2-DCE) and 

vinyl chloride (VC), were also present in 

groundwater. 

MIP was used to delineate groundwater 

contamination at the site and serve as a field 

screening tool to identify locations requiring 

additional characterization. 

Ninety-nine MIP advancements were made at 

the site between January 17, 2001, and June 5, 

2001. Figure 3 displays MIP advancement in 

progress at Sol Lynn. 

A truck mounted Geoprobe® 5410 unit was used 

for probe advancement. A Model 14A 

Shimadzu GC was used for gas-phase detection. 

The GC housed an ECD and PID detector. The 

ECD was particularly sensitive to chlorinated 

compounds. The FC4000 Geoprobe® field 

computer was used for data display and logging. 

The system displayed membrane temperature, 

probe advancement rate, and plotted EC and 

contaminant response versus depth. The system 

produced data that was readily transferable to 

spreadsheet programs such as Microsoft Excel. 

The steps in a typical advancement included 

setup over the desired location, anchoring 

equipment in place, performing preadvancement response tests on the MIP, MIP 

advancement, and response monitoring. The 

locations for MIP exploration were not entirely 

predetermined. In many instances the location 

of the next MIP advancement was based on the 

results of the previous. 

Since one objective of the investigative effort 

was to delineate the extent of the contaminant 

plume, the general methodology used in 

determining exploratory locations was to move 

outwards in the direction of decreasing 

contamination. The original plan anticipated a 

total of 82 MIP advancements, but the dynamic 

nature of the exploration effort lead to a total of 

99 advancements. 

The advancement rate at Sol Lynn was 

approximately one foot per minute. This 

coupled with the waiting period between 

advancements resulted in an approximate 2.5 to 

3-hour duration for complete penetration at any 

given location. As a result, 3 to 4 locations 

could be explored per day. The depth of MIP 

penetration was limited by its physical 

durability. Soil resistance made direct push 

advancement infeasible beyond a certain depth. 

At some locations, direct push was not possible 

beyond 20 ft bgs. The actuating force for 

advancement beyond this depth involved impact 

loading using a hydraulic hammer. The MIP 

had a limited tolerance for this type of loading, 

and that is why its durability restricted the depth 

of exploration. The average depth of MIP/EC 

exploration at Sol Lynn was 42.86 ft bgs, and 

the maximum depth was 64.10 ft bgs. 

Gaseous phase detectors quantified MIP carrier 

gas contaminant concentrations in millvolts 

(mV). The measurements represented a family 

of contaminants rather than one specific 

contaminant. Analytical results from 

groundwater samples collected in the vicinity of 

specific MIP advancements later revealed that 

the minimum detection limit of MIP exploration 

at that site was greater than 100 parts per billion 

(ppb) of total volatiles. 

A response test was performed at every new 

location prior to MIP advancement. This was 

done to evaluate the condition of the membrane. 

The test involved immersing the probe in a 

standard solution and observing the response on 

the detectors. The response was compared to 

that of previous tests. A decline in response 

indicated the need for membrane replacement. 

Figure 4 presents an example of the same test 

being performed at a Geoprobe® facility. 
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-6 

Figure 3 

MIP Probe Advancement Using a Geoprobe® Direct Push Rig 

Source: Tetra Tech EM Inc. 

Source: Tetra Tech EM Inc. 
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-7 

Figure 4 

MIP Response Test 

Source: Geoprobe® Systems 

MP3500 

MIP 

Controller 

Laptop 

Computer 

(running 

same 

software as 

the FC4000 

field 

computer)

Gas 

Chromatograph 

MIP Immersed 

in Standard 

Solution
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-8 

Cost [2, 4] 

The total cost of the investigative field effort at 

Sol Lynn was approximately $150,000. 

However, part of this cost did not pertain to MIP 

exploration. Costs quoted by contractors 

offering MIP field services varied from roughly 

$3,000 to $3,700 per day. On an average, 250 

to 300 feet of strata could be explored in one 

day. Costs could be influenced by factors such 

as the depth of penetration, and the media to be 

penetrated. There could be a surcharge for 

requiring penetration beyond a certain depth. 

Similarly there could be a surcharge to 

compensate for equipment wear if impact 

loading were used for MIP advancement. A 

typical probe withstands approximately 1,000 ft 

of cumulative advancement through clays and 

sands. However, probe advancement through 

gravel would likely result in shorter life spans 

and consequently, additional charge for 

exploration. Difficulty in accessing locations 

for MIP exploration could be another factor 

increasing cost. Equipment mobilization and 

demobilization charges varied from $2 to $15 

per mile. 

Conclusions [1, 2, 3, 4] 

In general MIP technology worked well as a 

screening tool at Sol Lynn. Although 

repeatability of measurement was observed in a 

few cases, MIP was not found to be 

significantly useful as a quantitative tool. There 

were a few instances when highly contaminated 

media were encountered. In such cases 

contaminant concentrations were found to lie 

outside the detectors’ range of measurement. 

The results of MIP exploration at Sol Lynn 

played a large role in developing the monitoring 

well plan for the site. 

The remainder of this section discusses 

important issues about MIP. These are not 

necessarily site-specific issues, and include 

general opinions gleaned from contractors that 

offer MIP field services. Two such contractors 

are Plains Environmental and Applied Research. 

Plains Environmental was the contractor at Sol 

Lynn, and Applied Research was contacted to 

serve as an alternate source for this case study. 

Although theoretically suitable for any VOC, 

there seemed to be agreement that MIP worked 

especially well for chlorinated VOCs. 

Chlorinated VOC in-situ detection limits were 

stated to range from 200 to 500 ppb. The use of 

MIP as a field screening tool would not be 

advisable at in-situ concentrations below the 

aforementioned. Variation in detection limits 

were attributed to probe peculiarities, 

contaminant chemistries, and specifics of the 

strata being penetrated. At the other end of the 

spectrum, extremely high in-situ concentrations 

could also be troublesome with MIP 

exploration. Penetrating a zone of free-phase 

contamination could lead to saturation of the 

MIP carrier gas trunk line. Once saturated, 

further exploration would not be possible until 

the line were completely purged. Purging could 

take from a few to several minutes. Purging is 

not a special procedure; it is implemented by 

simply letting the system operate without 

advancing the probe. While the probe remains 

in place, cross-membrane contaminant transfer 

continues until the contaminants’ gaseous phase 

in the vicinity of the membrane is depleted. 

Once the ingress of contaminants has stopped, 

the continuing flow of nitrogen carrier gas 

renders the trunk line purged in the duration it 

takes to flush an entire tube volume. An MIP 

carrier gas trunk line would be considered 

purged when the detectors read zero. In 

extreme cases, purging could be impracticable. 

In such cases, the trunk line would have to be 

replaced to facilitate further exploration. 

There seemed to be some difference of opinion 

in the preferred method of MIP advancement. 

One contractor stated that they preferred to use 

CPT instead of Geoprobe® rigs for MIP 
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-9 

exploration. This was because CPT rigs were 

said to provide considerably greater pushing 

force, which consequently afforded penetration 

to greater depths. CPT rigs also made it 

possible to use a wider variety of probes in 

combination with MIP/EC probes to collect 

additional geological data. Another contractor 

stated that they preferred to use Geoprobe® rigs 

for MIP advancement because those rigs 

facilitated impact loading which permitted 

deeper penetration than possible with direct 

push. 

As implied by the sensitivity of various 

detectors to different contaminant groups, 

knowledge of existing contaminant types in the 

media to be explored was considered 

advantegeous. Prior knowledge of 

contamination not only facilitates selection of 

the most suitable detectors, but also lets one 

evaluate the applicability of MIP as an 

exploration tool. In general, dry electrolytic 

conductivity detectors (DELCD) and ECDs are 

considered best suited for detection of 

halogenated VOCs. PIDs though able to detect 

low molecular weight VOCs including 

halogenated VOCs, cannot distinguish between 

halogenated and non-halogenated VOCs. FIDs 

are characterized by low sensitivity, but are 

useful for detecting straight chained 

hydrocarbons. The likelihood of detection 

decreased with increasing molecular weight. 

Another detector that has been used with MIP is 

the mass spectrometer. This showed promise 

when it was first used in the mid nineties, but -

according to a contractor- has been sparingly 

used since. 

According to the lead agency’s contractor there 

seems to be a deficiency of quantitative 

guidance to predict the effectiveness of MIP in 

detecting any given compound in a given strata. 

Since the working principle is based on 

vaporization of contaminants, it is likely that the 

contaminant’s boiling point, and Henry’s Law 

constant could help predict its response to MIP. 

Consequently, it might be safe to doubt the 

effectiveness of MIP for contaminants with 

boiling points above the temperature (120 o

C) 

attained by its heating block. One contractor 

stated that MIP could be expected to lose 

effectiveness with compounds at least as heavy 

as xylenes (which have a boiling point of 

140 oC). The same contractor also verified that 

MIP was unable to detect dichlorobenzene 

which has a lower molecular weight than 

xylenes, but a higher boiling point (172 to 

174 oC). However, this does not imply that MIP 

will work for any compound with a boiling 

point less than 120 oC. Heavier compounds that 

volatilize and pass through the membrane could 

still condense in the trunk line and drop out of 

the carrier gas before they reach the detector. 

Given the current incomprehensive knowledge 

on the potential for this technology, one might 

best be served by discussing their investigative 

needs with the MIP vendor before assuming the 

applicability of MIP to their site. 

Contact Information 

Lead Agency: 

EPA Region 6 

Remedial Project Manager 

Mr. Ernest R. Franke, PE 

Phone: 214-665-8521 

Email: franke.ernest@epa.gov

State Agency: 

Texas Commission on Environmental Quality 

Project Manager 

Ms. Carol Dye, P.G. 

Phone: (512) 239-1504 

Email: cdye@tceq.state.tx.us

Lead Agency’s Contractor: 

Tetra Tech EM, Inc. 

Project Manager 

Mr. Timothy Startz 

Phone: (214) 740-2064 

Email: tim.startz@ttemi.com
Sol Lynn/Industrial Transformer Superfund Site, Houston, Texas

1-10 

MIP Vendor: 

Geoprobe® Systems 

Mr. John Terpening 

Phone: (800) 436-7762 

Email: terpeningj@geoprobe.com

MIP Contractor (at Sol Lynn): 

Plains Environmental 

Mr. Lynn Newcomer 

Phone: (800) 542-0445 

Email: lynn@plains.kscoxmail.com

MIP Contractor (Alternate Source): 

Applied Research 

Mr. Ray Reed 

Phone: (281) 290-6493 

Email: rreed@ara.com

References 

The following references were used in the 

preparation of this report: 

1. Telephone Conversation. Bill Gagnon, SKA 

Consultants, with Chitranjan Christian, Tetra 

Tech EM Inc., Response to Questions on use 

of MIP Technology at Sol Lynn. May 26, 

2004. 

2. Telephone Conversation. Ray Reed, 

Applied Research, with Chitranjan 

Christian, Tetra Tech EM Inc., Response to 

Request for Information on MIP 

Technology. April 26, September 15, and 

16, 2004. 

3. Telephone Conversation. Neal Van Wyck, 

Applied Research, with Chitranjan 

Christian, Tetra Tech EM Inc., Response to 

Questions on MIP Effectiveness. September 

15, 2004. 

4. Telephone Conversation. Lynn Newcomer, 

Plains Environmental, with Chitranjan 

Christian, Tetra Tech EM Inc., Response to 

Questions on MIP Technology. September 

15, 2004. 

5. E-mail from John Terpining, Geoprobe®

Systems, to Chitranjan Christian, Tetra Tech 

EM Inc., Response to Request for 

Information on MIP Technology. July 28, 

2004. 

6. Tetra Tech EM, Inc., 2003. Supplemental 

Remedial Investigation Report. Sol 

Lynn/Industrial Transformer Site. Houston, 

Texas. December 2002. 

7. Worldwide web resource. Chemical 

Database. ChemFinder. 

http://chemfinder.cambridgesoft.com

8. Worldwide web resource. Geoprobe®

Systems. 

http://www.geoprobesystems.com/what_is/w

hat_is.htm

Acknowledgements 

This report was prepared for the U.S. 

Environmental Protection Agency’s Office of 

Solid Waste and Emergency Response, Office 

of Superfund Remediation and Technology 

Innovation. Assistance was provided by Tetra 

Tech EM Inc. under EPA Contract No. 

68-W-02-034. 
Appendix 2 

Sensor Technology Case Study 

2D-Recon and EOL Geophysical Survey Techniques 

for Characterizing Hydrocarbon-Contaminated Soils at the Hotel Pier Site 

Sensor Technology Case Study 

2D-Recon and EOL Geophysical Survey Techniques for 

Characterizing Hydrocarbon-Contaminated Soils 

at the Hotel Pier Site

2-1 

Summary Information 

Surface and subsurface geophysical surveys 

were completed at the Hotel Pier site on Pearl 

Harbor Naval Base in Hawaii to characterize 

hydrocarbon contamination and help evaluate 

remedial alternatives. Geophysical resistivity 

surveys were useful for characterizing 

hydrocarbon contamination sites because soil 

with hydrocarbons within the soil pores 

(contaminated areas) have a relatively higher 

resistivity to electromagnetic current than 

similar soil without hydrocarbons within the soil 

pores (uncontaminated areas). A surface twodimensional gradiometer (2D-Recon) survey 

was used initially to measure relative resistivity 

and determine the probable plume boundaries 

across a 7-acre site. The subsurface 3D 

electromagnetic offset log (EOL) survey was 

then completed to define and map resistivity 

using a 10-foot grid spacing over 1.4 acres of 

the Hotel Pier site. 

Surface and subsurface geophysical surveys 

took place in January 1999. The 2D-Recon 

survey was completed in 2 days while the EOL 

survey required an additional 7 days for data 

acquisition. Final data processing and reporting 

required approximately two months to complete. 

The geophysical surveys at the Hotel Pier site 

provided additional surface and subsurface 

information on the extent of hydrocarbon 

contamination in a rapid manner. Geophysical 

surveys provide the greatest characterization 

value for sites with large and complex 

hydrocarbon contamination. 

Technology Description [10, 11] 

While 2D-Recon is used to determine the 

horizontal extent of subsurface contamination, 

3D EOL is used to determine vertical variations 

in contaminant distribution. 2D EM surveys 

and EOL surveys have been used for over 15 

years to identify and model hydrocarbon 

contamination associated with leaking 

underground storage tank (UST) sites. 

2D-Recon 

The 2D-Recon survey (a surface 

electromagnetic [EM] gradiometer technique) 

evolved from geophysical techniques developed 

for petroleum and mining exploration. Such 

techniques were used to detect subsurface zones 

with unusually high contrasts in electrical 

resistivity. 

2D-Recon measurements are made by moving a 

surface EM gradiometer along closely spaced 

transects around and over suspected areas of 

contamination. The data acquired is processed 

to filter noise and produce a horizontal outline 

of subsurface contaminant plumes. 

The surface EM gradiometer data acquisition 

system uses pairs of EM sensor coils normally 

aligned vertically; one sensor near the ground 

surface and the other sensor five feet above it. 

Figure 1 shows sensor coils mounted on a golf 

cart for faster data collection. Each pair of coils 

measures the difference in signal voltage (or the 

voltage gradient) between the coils. Anomalies 

in soil resistivity are indicated by large changes 

in the voltage gradient, and imply the presence 

of subsurface contamination. 
Hotel Pier Site, Oahu, Hawaii

2-2 

Figure 1 

2D-Recon Survey Data Acquisition 

Source: Pritchard Geophysics 

EOL 

The EOL survey is an established 

electromagnetic induction technique which 

measures resistivity variations in the subsurface. 

For example, all free hydrocarbons are highly 

resistive while subsurface waters are much 

lower in resistivity. By measuring resistivity 

variations of the subsurface, one can predict the 

presence of hydrocarbon plumes. The 

resistivities are plotted to provide a three 

dimensional information on subsurface 

contamination. 

The EOL survey utilizes a very large surface 

transmitter coil at low frequency to induce a 

magnetic field in the subsurface. A receiver coil 

is placed in a nearby well and measures the 

signal. The strength of the measured signal is 

proportional to the resistivity of the soil it 

passed through. This measurement is 

transmitted to a data collection unit on the 

surface. The measurements are taken and 

recorded at 0.1 foot intervals. Figure 2 shows a 

typical layout for an EOL system. Once 

measurements are made at a location, the 

transmitter coil is moved to a new data point on 

the surface for another set of measurements. 

Once all the necessary data has been collected, 

it is edited to eliminate extraneous noise. The 

data is then normalized to eliminate differences 

caused by data acquired from separate receiver 

wells. 
Hotel Pier Site, Oahu, Hawaii

2-3 

Figure 2 

3D EOL Typical Setup 

Source: Gehm Environmental 

Once this is done, apparent resistivity and 

second order resistivity logs are generated 

versus depth. These logs are then interpreted to 

identify contaminated zones. 

Site Information [1, 2, 3, 4, 5, 6]

The Hotel Pier site is located at Fleet Industrial 

Supply Center, Pearl Harbor Naval Base, Oahu, 

Hawaii. A non-time-critical removal action was 

proposed for the Hotel Pier site and EOL was 

completed as part of the remedial site evaluation 

for the site. Previous investigations at the site 

included an underground storage tank (UST) 

investigation, soil gas survey, a site 

reconnaissance, and a remedial investigation 

(RI). The RI for the site concluded that a plume 

of free product existed and that local 

groundwater was impacted with petroleum 

constituents. Preliminary fate and transport 

calculations conducted under the RI suggested 

that free product might be releasing to the 

surface waters of Pearl Harbor. 

In addition, several fuel spills have occurred at 

the Hotel Pier site. The most recent fuel spill 

occurred in July 1997 when an estimated 1,500 

to 3,500 gallons of diesel fuel leaked from a 

damaged fuel line. As a result of historic fuel 

leaks, elevated levels of benzene, toluene, ethyl 

benzene, and total xylenes (BTEX) were 

detected in soils and groundwater samples 

collected from soil borings located across the 

site. Based on the RI and other site 

investigations, the subsurface free product 

contamination at the Hotel Pier site may be 

associated with the historic spills, leaking 

subsurface product lines, or the preferential 

pathways for plume migration along subsurface 

electrical and sewer utility lines. 

Hotel Pier site has a gentle relief with elevations 

from 2 to 10 feet above mean sea level. Pearl 

Harbor is essentially a series of drowned river 

valleys that formed between the Waianae and 

Koolau Volcanoes through a complicated 

history of rising and falling sea levels, 

subsequent erosion and deposition of alluvial 

Well 

EOL 

Collector 

Contaminant 

Plume 

EOL 

Transmitter 

Coil 
Hotel Pier Site, Oahu, Hawaii

2-4 

material, and additional deposition of 

pyroclastic ash from eruptions at Salt Lake and 

Makalapa. Pearl Harbor is underlain primarily 

by soils of the lualualei-fill land-ewa 

associations which are well-drained and fine- to 

moderately-fine textured soils. The primary 

surface soil across Hotel Pier site is composed 

of fill material with brown silt with angular tuff 

and coral fragments, and occasional basalt 

fragments. 

2D-Recon at the Hotel Pier Site 

The 2D-Recon survey used present EM noise 

fields generated by existing overhead power 

lines as the source field. The EM fields may 

penetrate into the ground to depths of 300 feet. 

In cases and sites where electrical noise is low 

or weak, a temporary EM power source can be 

supplied for the survey by hanging a temporary 

line between buildings or other aboveground 

objects. The 2D-Recon technology components 

included two sensor coils (upper and lower), a 

laptop computer with data acquisition software, 

and a measuring wheel to record distance and 

location. The lower sensor measures the 

resistive change in the earth and the upper 

sensor is used to account for and correct errors 

in the power readings of the lower sensor. The 

2D-Recon survey coils and components were 

mounted on a rented electric golf cart for fast 

and effective data collection (Figure 1). The 

2D-Recon survey measured resistivity changes 

in the soil and geology below it as the sensors 

were moved over the surface. The data was 

processed to develop a 2-D aerial picture of the 

subsurface hydrocarbon contamination. 

3D EOL at the Hotel Pier Site 

The 3D EOL geophysical survey used a surface 

source coil (transmitter) with an area of 

approximately four square meters. The surface 

source coil was constructed with more than 30 

loops of low resistance wire and connected to a 

transmitter power unit consisting of a 1,600 watt 

60 hertz gas-powered generator and a power 

amplifier capable of up to 12 ampere output. 

The amplifier was set at a 5.00 amperes signal 

and the transmitter coil and receiver were tuned 

to around 270 Hertz (Hz) with a narrow 

bandwidth. This tuning procedure, along with 

choosing EM receiver wells in low noise level 

areas, can filter out most of the excess and 

unwanted electrical noise and allows the EOL 

technology to be used in and around most 

manmade structures and other sources of 

subsurface electrical noise. A grid pattern with 

approximately 10-foot spacing was used to 

survey a central 100 feet by 600 feet area of the 

Hotel Pier site (1.4 acres). Figure 3 shows the 

EOL transmitter and receiver locations for the 

Hotel Pier site. The transmitter coil was a 

portable, self-contained unit that was placed at 

each grid point one at a time, and the electrical 

signal transmitted. 

The EM receiver was mounted on a 2-inch 

diameter, 4-foot long probe and connected to a 

wire-line winch and EOL data acquisition 

system. To receive the induced signal from the 

transmitter, the receiver was mechanically 

pulled up through the receiver well hole 

measuring the primary and secondary EM fields 

produced at the transmitter coil location. A 

large, long wavelength response was created 

representing the primary EM field. 

Superimposed on this response were responses 

related to the secondary EM fields caused by 

eddy currents moving around the boundaries of 

resistivity contrasts in the earth. 

The EM receiver was mounted on a 2-inch 

diameter, 4-foot long probe and connected to a 

wire-line winch and EOL data acquisition 

system. To receive the induced signal from the 

transmitter, the receiver was mechanically 

pulled up through the receiver well hole 

measuring the primary and secondary EM fields 

produced at the transmitter coil location. A 

large, long wavelength response was created 

representing the primary EM field. 
Hotel Pier Site, Oahu, Hawaii

2-5 

Figure 3 

EOL Survey Transmitter and Receiver Locations 

Source: Gehm Environmental 

Superimposed on this response were responses 

related to the secondary EM fields caused by 

eddy currents moving around the boundaries of 

resistivity contrasts in the earth. 

The raw data were computer processed to 

remove the primary field and calculate and 

verify the secondary fields. The secondary 

fields were converted to apparent resistivity 

measured in ohm-meters to compare directly to 

the physical properties in the earth. The 

computer processed data were presented in both 

three dimensional figures and as depth-specific 

slices and cross sectional views across the Hotel 

Pier site. 

System Operation 

Calibration and maintenance checks on the EOL 

transmitter and receiver tools were typically 

performed at the beginning of each day of 

survey and at changes between receiver well 

locations. The portable generator required 

typical oil and fuel checks. Both 2D-Recon and 

EOL data acquisitions were collected in real 

time, therefore it was obvious when the 

equipment was not properly functioning. Each 

completed resistivity logging data set was 

uniquely named and saved to a laptop computer. 

The primary operation and maintenance tasks 

involved making routine checks of the wiring 

and wiring connects and the transmitter's output 

and signal level. 

EOL measurements were not affected by 

asphalt, reinforced concrete features, or buried 

steel utility lines and pipelines. However, the 

Hotel Pier site had several underground product 

fuel lines and sewer lines with cathodic 

protection that could have potentially interfered 

with the EOL survey. To avoid interference, the 

cathodic protection was turned off at the 

beginning of each day and turned back on at the 

end of each day, allowing an 8 to 10 hour time 

interval for the EOL survey to be conducted 

without interference. 
Hotel Pier Site, Oahu, Hawaii

2-6 

Cost [ 7, 9] 

A complete 2D-Recon survey costs about 

$2,500 per day with coverage of between two to 

five acres per day, depending on data point 

density. Mobilization and demobilization are 

additional costs. The 2D-Recon produces 

qualitative data and the data are available within 

two days of the final data collection. 

A complete EOL geophysical survey costs about 

$10,000 per day including all materials, 

supplies, equipment rentals, data acquisition, 

two field staff, one geophysicist, data 

processing, and report preparation. The daily 

rate of data acquisition is dependent on the 

contamination depth, groundwater depth, and 

overall logging time at each EOL location. 

Based on observations at three sites (North 

Island, San Diego; Makalapa Field, Hawaii; and 

Hotel Pier site, Hawaii), between 50 to 100 

individual EOL survey locations (0.1 to 0.25 

acres per day) can be completed during an eight 

hour day. Mobilization and demobilization and 

completion of any additional monitoring wells 

are added costs. Final data processing and 

reporting, performed using Silicon Graphics’ 

ShowCase and word processing software, 

required approximately two months to complete. 

At Hotel Pier, 2D-Recon and EOL surveys cost 

approximately $10,000 and $90,000 

respectively. 

Conclusions [8] 

Data from the 2D-Recon and EOL survey were 

used to characterize the lateral extent of the 

hydrocarbon plume and define the general 

boundaries of larger subsurface anomalies. 

Qualitative results were presented in graphical 

format using five-color resistivity maps 

correlating to low, average, above average, high, 

and very-high resistivity values (Figure 4). The 

project geophysicist stated that the high and 

very high resistivity features identified in plan 

view depth intervals and in cross-section may be 

associated with the soils with hydrocarbon filled 

pores. Many of the high resistivity anomalies 

were found to be positioned around and along

utility and pipeline corridors which are known 

to be preferential conduits for hydrocarbon 

movement. 

Post EOL survey soil sampling was completed 

but locations were limited to areas outside of the 

buildings and depths only reached fifteen feet 

below ground surface. Laboratory analytical 

data identified hydrocarbon contaminated soil 

which agreed with the resistivity model. 

Multiple anomalies were identified from the 2DRecon and EOL surveys that likely would not 

have been identified through traditional 

subsurface soil sampling. The remedial 

alternative selection criteria and feasibility and 

effectiveness of a subsurface barrier to control 

hydrocarbon seepage into the harbor were 

supported through this survey. 

Technology Performance and Factors 

Factors that affected the performance of this 

technology at the Hotel Pier site were (1) the 

experience of the data acquisition team (two or 

three field staff), (2) experience and interpretive 

skills of the senior geophysicist, (3) availability 

of the Senior Geophysicist to be on site during 

the field data acquisition and to provide quality 

control, (4) access to all areas of the site (inside 

and outside of buildings), (5) timing and 

logistics to complete additional monitoring 

wells at specific locations within a few days, 

and (6) other site-specific factors such as depth 

to groundwater, inherent resistivity of the 

contaminated and uncontaminated areas, nature 

and amount of overhead and buried utilities, and 

general size of the contaminated area. The 

overall qualifications and capability of the 

geophysicist to generate good data and process 

the data into a usable and accurate model were 

paramount. 
Hotel Pier Site, Oahu, Hawaii

2-7 

Figure 4 

Apparent Resistivity Map from 2D-Recon Survey 

Source: Gehm Environmental (Best available copy) 

A weakness of EOL surveys is the need for site 

characterization data to distinguish and calibrate 

the soil resistivity measurements. A significant 

contrast between the resistivity of contaminated 

and the non-contaminated material is needed in 

order to have a high degree of confidence in the 

data. 

Some subsurface site characterization data is 

necessary to discern the initial resistivity 

measurements. For example, subsurface 

geology information from monitoring well 

boring logs, previous subsurface sampling, and 

groundwater monitoring are all potentially 

valuable characterization data helpful for an 

EOL survey. 

Suitable existing EM receiver wells for the EOL 

receiver will not be available at all hydrocarbon 

contaminated sites; therefore time and costs may 

be needed to properly install new EM receiver 

wells. The most suitable EOL receiver wells are 

clean monitoring wells located just outside the 

central edge of the plume. The radial coverage 

from a receiver well is dependent on site 

geology and subsurface features but is 

approximately 200 to 300 feet. 

One improvement that has occurred during the 

last 15 years is the phased approach in which 

the geophysical survey begins with a more cost 

effective 2-D surface gradiometer survey. Then, 

if contamination and site logistics concur, the 
Hotel Pier Site, Oahu, Hawaii

2-8 

survey proceeds to the more labor-intensive and 

costly 3D EOL survey. Smaller, more portable 

laptop computers and the use of commonly 

available database software packages have 

helped with the data acquisition and storage of 

large data sets. 

Lessons Learned 

A site should have a potentially large and 

complex area of hydrocarbon contamination to 

afford the use of surface and subsurface 

geophysics. The 2D-Recon and EOL 

geophysical surveys can quickly provide 

additional subsurface information on the extent 

of hydrocarbon contamination. Data are 

collected in real time allowing for on-site 

qualitative assessments of the plume boundaries, 

appropriate locations for new monitoring wells, 

and subsurface sampling efforts which may all 

help to expedite the entire remediation effort. 

Though the geophysical survey techniques 

provided information on hydrocarbon entrained 

in the soil, additional analysis was needed to 

determine the fraction of it that was mobile and 

recoverable. 

The EOL technology performance was 

evaluated at North Island Navy Base under the 

Navy Environmental Leadership Program 

(NELP) in 1997. 

Contact Information 

Owner’s Contractor 

Tetra Tech EM Inc. 

Mr. J. Edward Surbrugg, Ph.D. 

Phone (406) 442-5588 

Email: edward.surbrugg@ttemi.com

Technology Vendor 

Gehm Environmental 

Mr. Dave Gehm, President 

Phone: (660) 882-3485 

Email: dgehm@gehm.com

Technology Vendor 

Pritchard Geophysics 

Mr. James Pritchard, Ph.D. 

Phone: (972) 851-3433 

Email: jip.gp-1@worldnet.att.net

Navy Contact 

Pacific Division, Pearl Harbor 

Naval Facilities Engineering Command 

Ms. Michelle Yoshioka, Remedial Project 

Manager 

Phone: (808) 472-1413 

Email: michelle.yoshioka@navy.mil

References 

The following references were used in the 

preparation of this report: 

1. Gehm Corporation. 1995. Technical 

Details and Case Histories, Electromagnetic 

Offset Log (EOL), by: James I. Pritchard, 

Technical Director. December. 

2. Gehm Environmental. 1999. 3-D 

Resistivity Survey, Electromagnetic Offset 

Log (EOL), Hotel Pier Area, Pearl Harbor 

Naval Base, Oahu, Hawaii. March. 

3. Macdonald, G.A., A.T. Abbott, and F.L. 

Peterson. 1983. “Volcanoes in the Sea.” 

University of Hawaii Press. Honolulu. 2nd 

Edition. 

4. Ogden Environmental and Energy Services 

Co., Inc. (Ogden). 1994. “Remedial 

Investigation/Feasibility Study Draft Report 

for Subsurface Fuel Investigation, Naval 

Base Pearl Harbor, Hawaii.” 

5. Tetra Tech EM Inc. 1996. Electromagnetic 

Offset Logging at Naval Aviation Deport 

Buildings 379 and 397. Demonstration 

Evaluation Report. Navy Environmental 

Leadership Program. November 25. 
Hotel Pier Site, Oahu, Hawaii

2-9 

6. U.S. Department of Agriculture (USDA). 

1972. “Soil Survey of Island of Kuai, Oahu, 

Maui, Molokai, and Lanai, State of Hawaii.” 

U.S. Department of Agriculture, Soil 

Conservation Service in Cooperation with 

University of Hawaii. August. 

7. E-mail from Edward Surbrugg, Tetra Tech 

EM Inc., to Chitranjan Christian, Tetra Tech 

EM Inc., Response to Questions on Cost. 

January 13, 2005. 

8. E-mail from Michelle Yoshionka, Naval 

Facilities Engineering Command, to Ellen 

Rubin, EPA, Office of Superfund 

Remediation and Technology Innovation, 

Response to Request for Comments. 

November 3, 2004. 

9. E-mail from James Pritchard, Pritchard 

Geophysics, to Ellen Rubin, EPA, Office of 

Superfund Remediation and Technology 

Innovation, Response to Request for 

comments. September 10, 2004. 

10. Worldwide web resource. Gehm 

Environmental. 

http://www.gehm.com/eol.htm. 

Electromagnetic Offset Log. 

11. Worldwide web resource. Gehm – Prichard 

Environmental Surveys. 

http://www.gpesurveys.com/2-d-reconsurveys.html. 2D Recon Surveys. 

Acknowledgements 

This report was prepared for the U.S. 

Environmental Protection Agency’s Office of 

Solid Waste and Emergency Response, Office 

of Superfund Remediation and Technology 

Innovation. Assistance was provided by Tetra 

Tech EM Inc. under EPA Contract No. 

68-W-02-034. 

Appendix 3 

Sensor Technology Case Study 

Use of Capacitance Probes to Measure Soil Moisture 

at the Badger Army Ammunitions Plant 

Sensor Technology Case Study 

Use of Capacitance Probes to Measure Soil Moisture 

at the Badger Army Ammunitions Plant 

3-1 

Summary Information [1, 2, 3, 4, 5, 6, 10, 12] 

There are several devices that can be used to 

measure soil moisture content in the vadose 

zone. Some of these devices include dielectric 

permittivity probes, radio-frequency probes, 

lysimeters, tensiometers, and capacitance 

probes. This case study focuses on capacitance 

probes. 

Capacitance probes have long been used to 

measure soil moisture in the agricultural 

industry for irrigation scheduling. They have 

also been used in environmental applications as 

part of containment type remedies. They 

measure soil moisture content by measuring the 

capacitance (a measure of charge storing 

capacity) of the soil around them. 

Capacitance probes are being used to monitor 

the moisture content in soil at the Badger Army 

Ammunition Plant (BAAP). The BAAP is a 

7,354 acre site located in Sauk County, 

approximately 7 miles south of Baraboo, 

Wisconsin. Intermittent war-time plant 

operations over a 33 year period resulted in 

contamination of the site with munitions based 

compounds. The remedial approach at Badger 

was to address sub-sites individually. This case 

study presents use of soil moisture sensors used 

at sub-site BAAP-06 also called the Deterrent 

Burning Ground (DBG). 

The DBG is located in the northeastern portion 

of BAAP. The DBG was a former two-acre 

borrow pit that was used as a landfill for 

demolition debris, and for the open burning of 

deterrents, structural timbers, asphalt shingles, 

cardboard, papers, and office waste. The 

primary contaminants are volatile organic 

compounds and munitions based compounds. 

The most contaminated soil in the top 15 feet of 

the waste pit was removed. The remedy for the 

site included the construction of a 7-acre lowpermeability cap above the contaminated zone. 

This was to prevent leaching of contaminants 

into the groundwater during large rainfall 

events. Another component of the remedy 

involved in-situ bioremediation of residual 

contamination in the vadose zone. 

The bioremediation system was installed in the 

summer of 2003. The system supplies water 

and nutrients to native microbes in the vadose 

zone through an infiltration gallery. 

Capacitance probes were used to measure soil 

moisture in the vadose zone to evaluate overall 

system performance. In addition, capacitance 

probes provided the sensory means to observe 

the potential for excessive infiltration, and thus 

prevent inadvertent contamination of the 

underlying groundwater. 

Four capacitance probes were installed at 

BAAP. The probes continuously measure soil 

moisture content, and four separate dataloggers 

periodically retrieve measured data from their 

respective probes. The data is downloaded from 

the datalogger and examined to understand soil 

moisture response during infiltration. 

Inferences from soil moisture data are used to 

determine the need for modification in 

infiltration gallery operation. 

To date, the system has not been able to detect 

infiltration beyond the first two feet beneath the 

infiltration gallery. This is possibly due to the 

lack of a detectable moisture front during 

infiltration. 

Technology Description [1, 2, 3, 4, 7, 8] 

Capacitance probes use the principal of 

electrical capacitance to measure soil moisture. 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-2 

Capacitance is a measure of a device’s ability to 

store electrical charge. A device that can store 

charge is called a capacitor and consists of two 

metal plates separated by a dielectric substance 

(or insulator). The device’s capacitance 

depends on the dielectric substance used. When 

an alternating current is applied to a capacitor, it 

charges and discharges sequentially causing an 

apparent change in the frequency of applied 

current. This change in frequency is a function 

of the device’s capacitance, and by measuring 

the altered frequency, one can determine the 

device’s capacitance. 

The soil-sensor system is in essence a capacitor. 

The sensor’s electrodes serve as the plates, and 

the soil around the sensors serves as the 

dielectric substance. The capacitance of the 

sensor-soil system is a function of the moisture 

in the soil. By measuring the capacitance of the 

system, the probe in essence measures the 

amount of moisture in the soil. 

Capacitance probes have been used to measure 

soil moisture in the agricultural industry for 

several years. The technology has been 

commercial for at least 15 years. 

The probe consists of vertically spaced sensor 

assemblies enclosed in a snug-fitting PVC 

access tube (Figure 1). The number of sensors 

used in a probe, and the sensor spacing along 

the access tube can be varied as desired. 

Different manufacturers have different 

constraints on the maximum number of sensors 

allowed in a probe. Probes in the agricultural 

industry are typically 3 feet long and rarely 

exceed 6 feet in length. The access tubes are 

installed in direct contact with the lithology 

using a suitable augur method. 

Once the access tube is in place, the sensor 

assembly can be inserted into it. However, the 

sensors typically need to be normalized before 

this. Alternately, one can purchase normalized 

sensors for an additional charge. Normalization 

is a process through which sensor outputs are 

standardized to lie on a common scale. 

Normalization is necessary because there is a 

slight variation in outputs produced from sensor 

to sensor. EnviroSMARTTM probes are 

normalized using vendor-supplied software to 

set the sensor’s maximum output to 1, and its 

minimum output to zero. The maximum 

corresponds to complete saturation, and the 

minimum corresponds to zero moisture content. 

Therefore normalized probes produce outputs 

on a unitless zero to 1 scale. 

Probe installation involves drilling a hole to the 

required depth. After the probe casing is 

lowered into the hole, a bung is inserted to seal 

off the bottom. The sensors and controlling 

electronics are then inserted into the casing. 

Finally the cap is installed to seal-in the sensors 

and associated electronic devices. The cap is 

weather proof, but cannot withstand continuous 

submergence. The cap contains a desiccant to 

prevent moisture from entering the casing. The 

probe head is typically not flush mounted with 

the ground. It usually sits about 5 inches above 

ground level. 

After the probe has been installed in place and 

all the necessary electrical connections have 

been made, the sensors may be field-calibrated. 

Field calibration in essence involves correlating 

the sensor’s normalized output to actual soil 

moisture. However, according to the vendor, 

field calibration is a rare practice. Most of the 

time customers use the vendor-supplied 

standard calibration model (IrriMAX) which 

converts retrieved output data to approximated 

volumetric soil moisture contents. Sometimes 

normalized results produced by the sensors meet 

the customer’s requirements, in which case not 

even the standard calibration model is used. 

However, field-calibration is recommended for 

applications that need accurate measurement of 

volumetric soil moisture content. Field 

calibration takes into account all the 

peculiarities of the soil surrounding a given 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-3 

Figure 1 

Soil Moisture Probe 

Source: Campbell Scientific Inc. 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-4 

sensor thereby minimizing measurement error. 

It involves developing a mathematical 

relationship between the sensor’s normalized 

output and actual soil moisture content. Data 

required for this correlation is obtained by 

sensory measurement followed immediately by 

collection of a soil sample for laboratory 

analysis. The EnviroSMARTTM probe’s user 

manual provides instructions on deriving this 

mathematic relationship. Once derived, a 

spreadsheet program such as Microsoft Excel 

can be used to convert sensor outputs to 

volumetric soil moisture content. 

The table below provides specifications of the 

probes used at the Badger site. These probes 

were manufactured in Australia by Sentec Inc. 

and marketed in the United States by Campbell 

Scientific Inc. 

EnviroSMARTTM Probe Specification 

Parameter Value 

Maximum Cable 

Length 

200 ft 

Maximum Sensors 

per Probe 

16 

Accuracy (field 

calibration) 

R2 =0.99 

Precision (+/-) 0.03% by volume 

Measurement Range Oven-dry to saturation 

Temperature Effects (+/-) 3% (at 

temperatures between 

41o and 95oF) 

Operating 

Temperature Range 

32o to 158oF 

Time to Read One 

Sensor 

1.1 seconds 

Sphere of Influence 99% of measurement 

within 3.94 inch radius 

from the outside of the 

access tube 

Sensor Diameter 2 inches 

Access Tube 

Diameter 

2.22 inches 

Site Information [2, 5, 10, 12] 

BAAP is a 7,354 acre site located in Sauk 

County, approximately 7 miles south of 

Baraboo, Wisconsin. The BAAP site contains 

several sub-sites. The DBG, where the probes 

were installed, is one of the sub-sites at BAAP. 

The lithology at the site comprises layers of 

sand and gravel with interspersed layers of silt. 

The first water bearing zone is encountered 

approximately 100 to 110 feet below ground 

surface (bgs). 

A low permeability cover was part of the 

remedy for the DBG. The low permeability 

cover reduced surface water infiltration through 

the contaminated vadose zone, thereby 

preventing the leaching of contaminants into the 

groundwater. The other component of the 

remedy involved bioremediation of 

contaminants in the vadose zone. 

Bioremediation of the vadose zone involved the 

supply of water and nutrients to sustain 

contaminant-degrading microbial communities. 

Water and nutrients were supplied through 

infiltration galleries constructed approximately 

four feet beneath the surface of the low 

permeability cap. 

Capacitance probes were installed in June 2003 

(as part of the bioremediation system) to 

monitor infiltration. In addition to serving as 

indicators for conditions favoring 

bioremediation, the capacitance probes were 

expected to provide the sensory means to 

recognize excessive infiltration into the vadose 

zone. The probes spanned the entire depth of 

the vadose zone, extending from the ground 

surface to a few feet above the water table. 

Figure 2 presents a section of the installed 

probes at Badger. Each installed probe was 

approximately 100 feet deep, but the deepest 

sensor in each probe laid only 50 feet bgs. 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-5 

Figure 2 

Soil Moisture Probe Assembly 

Note: Modified from as-built drawing (Shaw Environmental, Inc. 2004) 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-6 

Two infiltration galleries were constructed in 

the remediation area. One measured 100 feet by 

80 feet, and the other located southeast of the 

first measured 320 feet by 100 feet. Of the four 

Sentek EnviroSMARTTM probes used at the site, 

one was installed beneath the smaller gallery, 

two were installed beneath the larger gallery, 

and one was installed in an area adjacent to both 

galleries to serve as a control. 

Sonic drilling was used to drill 4-inch-diameter 

holes for each of the probes. Segments of the 

access tube were then spliced together and 

lowered into the borehole. Each segment was 

approximately 6.8 feet long and had a 2.22-inch 

outside diameter. The deepest segment had a 

PVC cap at the bottom to provide a moisturetight seal. The segments were spliced together 

using glued PVC slip joints. PVC centralizers 

were installed at each slip joint and at the 

bottom of the assembled access tube. After the 

access tube was in place, a kaolinite claycement grout was used to fill the annular space 

between the borehole and the access tube. The 

grout was placed along the entire length of 

borehole from the bottom of the borehole to the 

ground surface. After the grout had set, the 

sensors and related electronics were lowered 

into each tube. Each probe contained 14 

sensors. Sensor spacing varied along the length 

of the probe. In general, the spacing increased 

with increasing depth. 

The data retrieval system included a serial data 

interface (SDI) operating at a baud rate of 1,200 

to receive and record data from each soil 

moisture sensor. A Campbell Scientific Model 

CR510-2M datalogger was used to query each 

probe’s SDI and store soil moisture data for 

future retrieval. The datalogger could be 

programmed to record soil moisture 

measurements in intervals that ranged from as 

small as five minutes to greater than one week. 

The Intelligent Probe Utility Software provided 

by Campbell Scientific, Inc. was used to 

normalize each sensor through the probe’s SDI. 

The probes were not field-calibrated. 

System Operation [1, 2, 11] 

The infiltration gallery operated only one day 

per quarter to simulate percolation caused by 

precipitation. The moisture probes, however, 

operated continuously to measure soil moisture 

response during, and after infiltration gallery 

operation. The only human effort in operation 

of the moisture probes involved data retrieval 

from the dataloggers. Soil moisture 

measurements were automatically collected 

from the probes by the dataloggers at 30-minute 

intervals for a period of up to 4 weeks. 

Soil moisture data downloaded from the 

dataloggers was closely examined to gain an 

understanding of the changes in soil moisture 

content during infiltration gallery operation. To 

date, the only observed spikes in soil moisture 

content were observed in the upper two feet of 

soil beneath the infiltration gallery. 

Over the months, there was a decreasing trend 

in soil moisture measured by some of the deeper 

sensors. This supported the claim that the low 

permeability cap was reducing the amount of 

infiltration through the contaminated zone. 

System maintenance included periodic checks 

for probe cap seal, and changing the desiccant in 

the cap as necessary. The probe head 

enclosures were replaced with watertight 

enclosures to prevent recurrence of sensor 

malfunction previously caused by the entrance 

of moisture into the probes. 

Cost [4, 6, 9] 

Costs for installation of the probes at the Badger 

site were not available. However, a cost 

estimate for a similar system is presented in 

Table 1. 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-7 

TABLE 1 

ESTIMATE FOR A TYPICAL SYSTEM USING ONE SOIL MOISTURE PROBE 

EnviroSMARTTM 

Item Qty Unit Unit Price ($) Subtotal ($) 

EnviroSmart Probe 1 (50 feet long) 1 ea 2,837 2,837

Sensors 2 16 ea 200.00 3,200

SDI-12 Interface 1 ea 375.00 375

Interface Cable 3 ($20 + $0.23/ft) 50 ft 0.23 12

Yellow Cutting Edge 1 ea 10.25 10

Expandable Bung 1 ea 19.00 19

Gel Bags 1 set 34.00 34

Ferrite Beads 1 pack 12.60 13

Normalization Container 1 ea 157.00 157

Programming Cable 1 ea 120.00 120

Probe Utility Software 1 ea 63.00 63

Datalogger (Campbell Scientific CR510-2M) 1 ea 895.00 895

TOTAL 4 6,840

Note: 

1

 Cost varies with length 

2

 Number of sensors in a probe can vary from 1 to a maximum of 16 

3

 Cable runs from the datalogger to the SDI-12 interface 

4

 Cost does not include installation 

Source: Campbell Scientific Inc. 2004 Price List 

There are several variables that affect the cost for 

installing such a system. However, the two major 

variables are depth of installation and number of 

sensors used. The depth of installation (or the 

length of probe) directly impacts total cost of the 

system. Shorter probes are less expensive than 

longer ones. The depth of installation also 

influences the cost of drilling. For shallow probes 

not exceeding 7 feet in length, the hole may be 

drilled using the installation kit purchased (or 

rented) from the supplier. On the other hand, 

deep installations such as the one at Badger 

require drilling rigs, and more involved probe 

installation methods. The cost of the system also 

depends on the number of sensors used per probe. 

The number of sensors can vary from 1 to a 

maximum of 16. As in other systems, the number 

of probes purchased influences the selling price 

per probe. Optimizing datalogger use by using 

the maximum number of probes per datalogger 

can reduce unit cost per probe. 

The estimate presented in Table 1 assumes that 

the probe contains 16 sensors that interface with 

a Campbell Scientific Model CR510-2M 

datalogger, the deepest sensor being 50 feet 

deep. In practice the datalogger to be used 

depends on requirements of the application, and 

not the probe. The simplest datalogger that can 

be used with this probe is Campbell Scientific’s 

Model CR200. The estimate does not include 

drilling or probe installation. 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-8 

Conclusions [1, 2, 4, 10] 

According to the owner’s contractor, Sentek’s 

capacitance probes were used at Badger because 

they were the only probes amenable to deep 

installation. 

The cap on the probe’s access tube is 

weatherproof but does not provide a watertight 

seal when submerged. This should be taken into 

account while designing systems that use this 

probe. Moisture entry into a probe caused it to 

malfunction at Badger. This resulted in 

replacement of the then-existing probe-head 

enclosures with watertight enclosures. The 

vendor recommends replacement of the desiccant 

inside the access tube’s cap as needed to prevent 

moisture build-up. 

Sensors can be removed and re-used as desired. 

The access tube might have to be abandoned in 

place (depending on the depth of installation), the 

sensors, according to the Vendor, can always be 

removed and used at another location. 

Modification of installed probes by adding or 

removing sensors is also possible. Addition of 

sensors to an existing probe would be constrained 

by the space available inside the access tube, and 

the maximum number of sensors (16) that can be 

used per probe. 

According to the Vendor, most customers are 

satisfied with normalized outputs or the vendorsupplied standard calibration model. 

Nevertheless, in applications where accurate soil 

moisture measurement is required, fieldcalibration is essential. Field-calibration is a 

tedious and time consuming process, and should 

not be neglected in budgetary estimates. It is 

important to note that deep installations (such as 

those at Badger) can make field-calibration 

impractical. This is because collecting a deep soil 

sample within the sensor’s zone of measurement, 

immediately following sensory measurement, can 

be difficult if not impossible. For this reason, one 

must discuss the requirements of the application 

with the vendor before incorporating the probe 

into the design for a remediation system. 

The access tubes supplied by the vendor 

required splicing using glue and slip joints. 

According to the owner’s contractor, this 

method of splicing presented problems during 

installation. Since glue was used, care had to be 

taken not to strain the joint until the glue had 

dried. This increased the time and effort 

required to install the access tubes. In this 

regard, the owner’s contractor was of the 

opinion that threaded PVC pipe would have 

made for a better access tube. At one location, 

an obstruction was encountered at a slip joint in 

the access tube during sensor installation. The 

inner walls of the access tube had to be reamed 

to smooth the slip seams before the sensors 

could be re-inserted. In another instance, grout 

entered the access tube presumably through a 

separated slip joint. The access tube was 

abandoned in place, and a new access tube had 

to be installed a few feet away from the first 

one. 

To date there have been no observed spikes in 

measured soil moisture beyond the first two feet 

beneath the infiltration gallery. Although this 

seems to imply that there is no infiltration 

beyond this point, this is not necessarily the 

case. Soil vapor vents used to monitor 

biological activity have detected gases in 

concentrations indicative of enhanced biological 

activity. This suggests successful nutrient 

delivery, and consequently infiltration of water 

to the remediation zone. It can be theorized that 

infiltration may not have been detected due to 

the lack of a saturated front, and the resulting 

irregular migration of moisture through the soil 

pores. Whatever the migratory path, it appears 

that the moisture did not pass sufficiently close 

(3.94 inches from the outside of the access tube) 

to the probes to be detected. 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-9 

Contact Information 

Federal Oversight Agency 

EPA Region 5 

Office of RCRA 

Corrective Action Project Manager 

Mr. Bob Egan 

Phone: (312) 886-6212 

Email: egan.robert@epa.gov

State Oversight Agency 

Wisconsin Department of Natural Resources 

Site Contact 

Mr. Steve Ales 

Phone: (608) 275-3310 

Email: Stephen.Ales@dnr.state.wi.us

Owner’s Contractor 

Shaw Group 

Project Manager 

Mr. Doug Rubingh 

Phone: (303) 741-7665 

Email: doug.rubingh@shawgrp.com

Probe Vendor 

Campbell Scientific, Inc. 

Applications Engineer 

Mr. David Meek 

Phone: (435) 750-9555 

Email: davemeek@campbellsci.com

References 

The following references were used in the 

preparation of this report: 

1. Telephone Conversation. David Meek, 

Campbell Scientific Inc., with Chitranjan 

Christian, Tetra Tech EM Inc., Response to 

Questions on Soil Moisture Probe. June 22, 

July 1, and September 13, 2004. 

2. Telephone Conversation. Doug Rubingh, 

Shaw Group Inc., with Chitranjan Christian, 

Tetra Tech EM Inc., Response to Questions 

on Sensor Technology use at the Badger 

Army Ammunitions Plant. June 22 and July 

1, 2004. 

3. Email from Corey White, Sentek Sensor 

Technologies, to Chitranjan Christian, Tetra 

Tech EM Inc., Response to Questions on 

EnviroSMARTTM operation. July 5, 2004 

4. Email from David Meek, Campbell 

Scientific Inc., to Chitranjan Christian, Tetra 

Tech EM Inc., Response to Questions on 

EnviroSMARTTM Cost. July 26, and August 

6, 2004. 

5. Email from Doug Rubingh, Shaw 

Environmental, Inc., to Chitranjan Christian, 

Tetra Tech EM Inc., Response to Questions 

on Probe Operation at Badger Army 

Ammunitions Plant. August 11, 2004, and 

July 25, 2005. 

6. Email from Jason Ritter, Campbell 

Scientific Inc., to Chitranjan Christian, Tetra 

Tech EM Inc., Response to Questions on 

EnviroSMARTTM Cost. July 16, 2004. 

7. Campbell Scientific Inc. 2004. 

EnviroSMARTTM Soil Water Content 

Probes Instruction Manual. July. 

8. Campbell Scientific Inc. 2004. Product 

Literature. Soil Volumetric Water Content 

Probes Models EasyAG® and 

EnviroSMARTTM. July. 

9. Campbell Scientific Inc. 2004. 2004 U.S. 

Price List. July. 

10. Shaw Environmental Inc. 2004. Draft 

Corrective Measures Implementation 

Report, Enhanced Biodegradation and 

RCRA Cap/Cover System, Deterrent 

Burning Ground, Badger Army Ammunition 

Plant, Baraboo, Wisconsin. Revision 1. 

January. 
Badger Army Ammunitions Plant, Baraboo, Wisconsin 

3-10 

11. Shaw Environmental Inc. 2004. Draft 

Operation and Maintenance Manual, Final 

Remedy Enhanced Biodegradation System, 

Deterrent Burning Ground, Badger Army 

Ammunition Plant, Baraboo, Wisconsin. 

Revision 1. April. 

12. Worldwide web resource. Badger Army 

Ammunitions Plant. 2003. Propellant 

Burning Ground. April. 

http://www.badgeraap.org/sites/pbg/pbg.htm

Acknowledgements 

This report was prepared for the U.S. 

Environmental Protection Agency’s Office of 

Solid Waste and Emergency Response, Office 

of Superfund Remediation and Technology 

Innovation. Assistance was provided by Tetra 

Tech EM Inc. under EPA Contract No. 

68-W-02-034. 
Appendix 4 

Sensor Technology Case Study 

Use of In-Situ Sensors to Monitor Groundwater Velocity 

at the China Lake Naval Air Weapons System Site 

Sensor Technology Case Study 

Use of In-Situ Sensors to Monitor Groundwater Velocity 

at the China Lake Naval Air Weapons System Site

4-1 

Summary Information [1, 2, 3, 4, 5, 6, 7, 8, 9, 

10] 

Variably Emitting Controlled Thermal Output 

Recorder (VECTOR) technology is used to 

measure groundwater flow speed and direction 

in three dimensions. It works on the principle of 

heat perturbation, whereby measured 

displacements in the heat-flow field around the 

probe are used to calculate groundwater 

velocity. The measurement range for velocity 

magnitude is 0.01feet per day (ft/day) to 2.00 

ft/day. Three-dimensional directional 

measurement has an accuracy of (+/-) 5 degrees. 

These probes are installed in situ, much like a 

monitoring well, using a suitable method such 

as hollow stem auger drilling. Following 

installation, the system is connected to 120 volt 

power supply. Once all of the necessary 

electrical connections have been made, the 

probe is turned on, calibrated and allowed to 

collect flow data. 

VECTOR technology is being used at the China 

Lake Naval Weapons Station to monitor 

groundwater flow in various water bearing 

zones (WBZ) along the southern boundary of 

the property. 

VECTOR probes were installed in 1999. Data 

from the probes were used to monitor local 

groundwater flow as well as seasonal and 

background impacts to local flow fields (such as 

agricultural or municipal pumping) located 

several thousands of feet away from the probes. 

Quarterly site visits to download stored data 

from automatic data collection devices 

constituted the only human effort in system 

operation. Although the option for remote 

access via telephone or cellular phone was 

available, this was not used at China Lake. 

Once downloaded, the data was analyzed using 

HTFlow, the analysis software provided with 

the VECTOR system. 

Although a few probes have stopped operating 

since their installation in 1999, they have 

generally lasted longer than their predicted oneyear lifespan. Operation to date has resulted 

only in minor data corruption, attributed to 

system wear and electrical anomalies. 

The probe requires a minimum five-foot 

saturated thickness above it to function 

properly. This has been a limitation at China 

Lake, where saturated thicknesses are usually 

less than 10 feet. 

Technology Description [1, 4, 5, 6, 7, 8, 9] 

VECTOR technology is used to measure 

groundwater flow velocity (Darcy velocity). It 

is a full-scale technology and VECTOR systems 

are available for purchase from Hydrotechnics 

Inc. Probes are generally made to order with 

lead times on delivery ranging from one to five 

weeks. 

Since velocity is a vector characterized by 

magnitude and direction (three dimensional in 

this case), this document uses the term 

“velocity” to imply both magnitude and 

direction. 

Following in-situ installation, the probe is fieldcalibrated. Field-calibration is usually 

performed just once in the lifetime of a probe 

provided there is no drastic change in the 

probe’s environment. For instance, a 50 degree 

change in groundwater temperature caused by a 

local thermal influence, or a significant change 

in saturated zone composition through intrusion 

of another liquid may warrant re-calibration. 
China Lake Naval Air Weapons System Site, California 

4-2 

Calibration includes heating the probe to a 

steady temperature approximately 25 degrees 

Centigrade (oC) above the ambient groundwater 

temperature. As groundwater flows past the 

heated probe an equilibrium temperature 

distribution forms on the probe’s surface. The 

analysis software supplied with the VECTOR 

system then correlates measured temperature 

distribution to groundwater velocity. Just as the 

coldest side of a wet finger held up in the air 

indicates which way the wind is blowing, the 

coldest side of the submerged probe indicates 

the direction from which the groundwater is 

flowing. 

The VECTOR system is made up of several 

different components: a probe, a power source, 

wiring to transmit data, a data collector often 

called a datalogger, and data analysis software 

(HTFlow). Some of these components come 

with differing capabilities depending on the 

requirements of the application. The datalogger 

can be connected to a maximum of 12 probes 

and the power supply can be tailored to 

accommodate any number of probes. Figure 1 

depicts a typical VECTOR system. 

The VECTOR probe is a cylinder measuring 

2.375 inches in diameter and 36 inches in length 

connected to industry-standard flush-mounted 

Schedule 40 PVC well pipe. Alternating current 

(110 Volt) runs a power supply which is used to 

constantly heat the probe with about 60 watts, 

maintaining it at a temperature between 20 and 

30 o

C above ambient groundwater temperature. 

An integrated array of 30 carefully calibrated 

temperature sensors or thermistors forms the 

outermost layer of the probe. This layer 

measures temperature variations along the 

surface of the probe caused by groundwater 

flow. These thermistors are extremely sensitive 

and can accurately measure differential 

temperature to within (+/-) 0.01 o

C. 

The VECTOR probe has the following 

measurement capabilities: 

Minimum Darcy Velocity = 0.01 feet per 

day (ft/day) 

Maximum Darcy Velocity = 1.00 ft/day 

Resolution = 0.001 ft/day 

Minimum Flow Rate Measured = 0.01 ft/day 

Max. Flow Rate Measured = approximately 

2 ft/day 

Thermistor Accuracy = (+/-) 0.01 o

C 

Directional Accuracy = (+/-) 5 degrees 

The probes are installed in direct contact with 

saturated soil using a method of drilling that 

allows uniform collapse of the lithology around 

the probe. According to the manufacturer, 

hollow-stem auger drilling has so far yielded the 

most consistent results. Although this method 

of drilling disturbs the lithology, there is the 

certainty that a saturated sand lithology will 

uniformly collapse around the VECTOR probe 

when the auger flights are removed. Other 

drilling techniques have successfully been used 

for installation in deeper and more difficult 

formations. Good results have also been 

obtained using mud-rotary drilling. According 

to the manufacturer, resonant sonic drilling has 

the potential to replace hollow-stem auger 

drilling as the method of choice. 

Groundwater flow direction measurements 

made by the probe are relative to the probe’s 

reference direction which is carefully recorded 

during installation of the probe. Conversion of 

the probe’s directional measurements to 

azimuths is performed by HTFlow. 

The datalogger currently supplied with the 

VECTOR probe is a CR10X datalogger 

manufactured by Campbell Scientific. Although 

there are other similar dataloggers, the 

manufacturer recommends use of the CR10X 

because of the variety of remote downloading 

capabilities it offers. The CR10X datalogger 
China Lake Naval Air Weapons System Site, California 

4-3 

Figure 1 

Vector System Layout 

Source: Hydrotechnics Inc. 
China Lake Naval Air Weapons System Site, California 

4-4 

requires a simple wall-mounted 12 Volt direct 

current power source for operation. To make 

communication possible, an interface box 

(Campbell Scientific Model SC32B) must be 

used. The data logger comes with industrystandard software allowing a user to program 

data collection schedules as well as 

simultaneously manage data collection from 

several probes. The datalogger can be fitted 

with a modem that communicates through 

landlines or cellular phones to facilitate remote 

data acquisition. 

Site Information [3, 8, 9] 

The VECTOR system was used at the Naval Air 

Weapons Station in China Lake, California. 

The concern at China Lake was the proximity of 

the site to the municipal well fields in the City 

of Ridgecrest. The closest well field was 

located less than a mile south of Inyokern Road 

which marks the boundary between China Lake 

and the City of Ridgecrest. Although no 

contamination was found along the boundary, 

the VECTOR probes were installed to monitor 

the potential for off-site migration of 

contaminants to safeguard against the possibility 

of their detection at a later date. 

The Navy’s monitoring well network included 

64 wells (5 equipped with pressure transducers) 

screened in the shallow WBZ, 36 wells (3 

equipped with pressure transducers) screened in 

the intermediate WBZ, 23 wells screened in the 

deep WBZ, and 9 VECTOR probes installed at 

four strategic locations along the facility’s 

property boundary in the shallow and 

intermediate WBZs. 

The probes were installed in 1999 using hollow 

stem auger drilling. They were installed 50 feet 

and 180 feet bgs in the permeable (sand and 

gravel) portions of the shallow and intermediate 

WBZs respectively. Data collected from the 

nine VECTOR probes and pressure transducers, 

coupled with the water level measurements 

collected quarterly from the fence line 

monitoring well network facilitated the 

following: 

(1) Determination of the direction and rate of 

groundwater movement from the China 

Lake Complex to the City of Ridgecrest 

(2) Monitoring changes in horizontal and 

vertical groundwater gradients and velocities 

(3) Evaluating the interconnectivity between the 

three WBZs (shallow, intermediate, and 

deep) 

According to the Owner’s contractor, VECTOR 

technology in concert with other monitoring 

programs in place at China Lake, provided a 

cost-effective approach to monitoring horizontal 

and vertical groundwater movement (within the 

different WBZs) from the China Lake Complex 

to the municipal well field. 

The VECTOR probes, coupled with the pressure 

transducers in adjacent monitoring wells, 

collected hourly measurements of groundwater 

velocity and groundwater level data to provide 

temporal continuity to the network of 123 wells 

that were being used to monitor groundwater 

flow within an 84-square mile area. 

The entire field effort for installation of the 

VECTOR systems, including well drilling, 

probe installation, and electrical connections 

took place over a two-week period. The 

VECTOR manufacturer provided installation 

services during this period. No problems were 

encountered during probe installation. 

The electronics were housed in weatherproof 

NEMA4 enclosures next to electrical utility 

poles that served as power sources. The locked 

enclosure allowed limited access for 

downloading data and adjusting probe power 

levels. All power and control wiring to the 

probes were run below ground to allow for 

unimpeded site access. 
China Lake Naval Air Weapons System Site, California 

4-5 

System Operation [3, 8] 

Following initial calibration, probe operation 

required no human supervision. The datalogger 

continuously logged probe data and recorded 

hourly averages. Stored data was manually 

downloaded for analysis every three months. 

Data retrieval involved connecting the 

datalogger to a laptop computer through an 

interface box. The supplied software was then 

used to download the data onto the laptop 

computer’s hard drive. Downloaded data was 

analyzed in the office using HTFlow. 

According to the Owner’s contractor, the probes 

operated as expected. Minor flaws in recorded 

data were distinguishable and could be excluded 

from analysis. The HTFlow software was able 

to calculate a “fit error,” for calculated 

velocities. This error was presented as an upper 

and lower confidence interval bounding the 

velocity curve. It was a useful feature for 

determining the quality of retrieved velocity 

data. In addition, error analysis allowed users to 

separate the few data flaws caused by electrical 

anomalies from real measurements. 

Being a relatively new and untested technology 

(first installed in 1996), the expected lifespan 

for a constantly operating submerged probe was 

not known. Although the probes were said to 

have life expectancies ranging from one to two 

years, nearly all probes installed at this site 

operated without malfunction for at least five 

years. Recently, however, several of the probes 

ceased to function. The Owner’s contractor 

attributed their failure to possible electrical 

problems resulting from earth moving 

operations on site rather than probe malfunction. 

Over the operating life of the probes, there were 

only minor problems involving the data logging 

and retrieval system, including some data loss 

caused by power surges. 

Cost [5, 7] 

Incurred costs for installation of the nine-probe 

VECTOR system at China Lake were not 

available. However, the estimated cost 

(excluding well drilling) in 2004 dollars is 

approximately $50,000. Table 1 presents a cost 

estimate for a similar three-probe VECTOR 

system. Unit prices are in 2004 dollars. This 

estimate is based on the assumption that the 

purchaser would have total ownership of the 

equipment and all data processing. This type of 

procurement is beneficial when equipment 

rental costs for long-term groundwater 

monitoring exceed that of outright ownership. 

Based on Table 1, the unit price for installation 

was $8,145 per probe. This included material 

and installation costs for the VECTOR probes 

and datalogger; assuming that the well had 

already been drilled. Consequently, drilling 

costs were not part of this estimate. 

Material costs account for the bulk (82 percent) 

of the total capital cost of the technology. In 

comparison, installation costs are small at only 

18 percent of the total capital cost. Although 

costs for operation were not available, the main 

cost components are expected to include energy 

and quarterly site mobilization for data 

download. 

Some factors that influence capital costs are: 

(1) Number of probes. The unit cost of 

implementing this technology is inversely 

proportional to the number of probes 

purchased. 

(2) Production volume and demand for the 

VECTOR system. High production and low 

demand would decrease costs, while low 

production and high demand would increase 

costs. 
China Lake Naval Air Weapons System Site, California 

4-6 

TABLE 1 

COST ESTIMATE 

Typical System Using Three Vector Probes 

Description Qty Unit Cost ($) Total ($) 

VECTOR In Situ Permeable Flow Sensor includes downhole multiplexer, lab-calibration with associated files, and 

introductory technical support. 3 Each 3,080 9,240

Campbell Scientific CR10X Data Logger (with 2 (two) meg 

memory option, RS232 optically isolated interface, manual, 

12V power supply and all com port connection cables) 1 Each 2,650 2,650

60V/1.5A Protek DC adjustable digital readout power supply 

for single-probe operation 3 Each 400 1,200

Probe/cable packaging and handling, basic insured groundshipping w/2-3 week advance notice 3 Each 65 195

VECTOR System assembly, down-hole installation with 

driller assistance, establish reference direction, assistance 

with cable burial and well head completion, all cable/power 

connections, enclosure installation, and initial probe 

powering for field calibration 5 Days 900 4,500

NEMA-4 weather-proof hinged enclosure for power supply 

and/or datalogger. Construction with cooling fans and backplate mounted instruments 1 Each 350 350

HTFLOW software license (Free to US Government) 1 Each 300 300

 

TOTAL 24,435

UNIT COST (per Probe) 8,145

Source: Hydrotechnics Inc. Estimate # 1802 from Richard Fagioli 

(3) Peripheral costs. Some components of the 

VECTOR system (such as the data logger) 

are manufactured by a different entity. 

Capital costs of the VECTOR system would 

therefore be influenced by price changes in 

peripherals. 

According to the manufacturer, apparent, large 

up-front capital costs are an obstacle to probe 

use. Though the technology might have an 

initially high capital cost, the minimal operation 

and maintenance costs imply increasing costbenefit over time. For example, if a one-timeonly snapshot measurement of groundwater 

flow were required at a site, VECTOR 

technology might prove more expensive than a 

three-point piezometric analysis. On the other 

hand, if continuous measurements were required 

over a period of time and over differing flow 

scenarios, cost analysis would reveal the 

benefits of using VECTOR technology over 

conventional methods. 

In general, the level of effort and associated 

costs for implementing VECTOR technology 

are less than those for setting up and performing 

a week-long constant rate discharge test 

representing a location of equal size. 
China Lake Naval Air Weapons System Site, California 

4-7 

Conclusions [3, 5, 8, 10] 

Information presented in this section was 

derived from conversations with the Navy’s 

contractor at China Lake, and the technology 

vendor. 

This section summarizes technology strengths, 

weaknesses, and useful facts learned through 

implementation at China Lake. This section 

also includes useful knowledge gained from 

implementation at other sites, as provided by the 

vendor. 

The accuracy in measurement of groundwater 

flow direction is a function of the magnitude of 

velocity and the geometry of flow past the 

probe. HTFlow can graphically illustrate the 

potential margin of error in measured flow 

direction at a given point in time. Another 

factor influencing directional accuracy is the 

diligence exercised by the field-installer in 

recording the compass orientation of the probe’s 

reference meridian. This is thought to be the 

greatest contributor to error in directional 

measurement. Discounting human error, these 

probes usually have (+/-) 5 degree azimuthal 

accuracy at low groundwater flow velocities. 

This is considered more than sufficient for 

typical hydrogeologic applications. Another 

important factor in directional measurement is 

magnetic declination. After the orientation of 

the probe’s meridian has been determined using 

a compass, a correction must be applied. This is 

because compass measurements are in reference 

to the earth’s magnetic poles, while true 

azimuths are in reference to its geographic 

poles. 

Continued accuracy of groundwater flow 

measurement is contingent on the assumption 

that groundwater temperature will remain 

relatively constant. Strictly speaking, 

measurement is only valid at the temperature at 

which the probe was calibrated. As a result, one 

must be cognizant of heat sources in the vicinity 

that could alter groundwater temperature after 

calibration. Early tests on shallow probes 

installed in very thin aquifers revealed 

detrimental effects related to diurnal heating and 

cooling of overlying soils. To mitigate these 

effects, the probes must be installed in a 

lithology that provides at least 4 feet of 

saturated overburden. 

The probes have never been installed in aquifers 

deep enough to experience more than about 30 

pounds per square inch (or 70 feet of water 

column) of pressure. Therefore, it is not known 

whether depth is a limiting factor in probe 

function. Though there are no theoretical limits, 

the depth of installation is currently restricted by 

the length of cable connecting the probe to the 

datalogger. The present configuration allows 

for a maximum cable length of about 500 feet. 

Improper installation of the probe can produce 

errors in measurement. Improper installation 

could include a situation where the probe is in 

contact with a different lithology than 

presumed. This can be avoided by maintaining 

accurate lithologic logs while drilling the well. 

Improper installation may also constitute a 

probe encompassed by disturbed soil with 

hydraulic properties differing from the 

surrounding lithology. Minimizing surface 

disturbances during probe installation, and 

careful removal of the drilling augur can prevent 

this from happening. 

Factors affecting the life span of the probe are 

not known. However, the manufacturer believes 

that the longevity of the thermistors used in the 

probe possibly has the greatest influence on the 

probe’s life span. The manufacturer estimates a 

one to two year lifespan. However, the probes 

at China Lake lasted at least five years. 

VECTOR systems function best in a wide 

variety of sands. This includes any material 

with grain sizes from 0.050 mm to 1.5 mm or 

U.S. Standard Sieve Series No. 270 to No. 12. 
China Lake Naval Air Weapons System Site, California 

4-8 

However, usable results have also been obtained 

in other lithologies. 

In general, the VECTOR system has widespread 

potential application. Its potential uses include 

monitoring ambient groundwater flow, 

monitoring the capture zone of a groundwater 

extraction system, and monitoring bulk 

hydraulic conductivities of aquifer media during 

remedial processes that require such 

measurement. 

The cost-benefit of VECTOR technology is a 

function of the user’s needs. According to the 

manufacturer, the technology is generally 

underutilized in that customers typically use it 

to measure fewer parameters than it is capable 

of. For example, the probe in combination with 

pressure transducers in nearby wells can be used 

to measure and monitor changes in bulk 

hydraulic conductivity. However, if a user does 

not need to measure this parameter, the probes 

ability to measure it will not be considered a 

benefit. 

Limitations 

VECTOR technology allows users to manually 

regulate the power supplied to the probe; users 

are expected to record any change made, in 

HTFlow. Erroneous results could be produced 

if a user did not record the new power level. 

Any lithology that does not produce a laminar 

groundwater flow past the probe’s surface is 

inappropriate for the VECTOR. Fractured or 

solid bedrock, unsaturated sediments, 

excessively high groundwater flow velocities or 

grossly heterogeneous lithologies primarily 

consisting of cobbles and coarse glacial deposits 

will yield poor results. Conversely, super fine 

sediments such as silts and clays will also yield 

poor results because local convection will play a 

greater role in heat transfer than groundwater 

advection. However, thin lenses of these kinds 

of sediments within a suitable lithology can be 

accounted for when performing data analysis by 

simply isolating those thermistors in direct 

contact with the lenses. 

This technology cannot be used in environments 

such as open boreholes, open streams, rivers, 

and open channels. 

This technology is not suitable in any thermally 

heterogeneous environment such as within a 

narrow permeable reactive barrier, or near a 

formation with thermal properties differing from 

the surrounding lithology. 

Improvements 

Although the VECTOR was originally designed 

for emplacement in direct contact with a 

saturated granular lithology, efforts are 

underway to produce a tool that will measure 

three dimensional flow within any packed and 

backfilled open-borehole configuration. 

The VECTOR manufacturer is also beta-testing 

their own down-hole datalogger (VeComm) 

system for use with the probes. 

Contact Information 

Owner 

Department of the Navy 

Southwest Division 

Naval Facilities Engineering Command 

Remedial Project Manager 

Mr. Mike Cornell 

Phone: (619) 532-4208 

Email: michael.j.cornell@navy.mil

State Oversight Agency 

Department of Toxic Substances Control 

Project Manager 

Ms. Laurie Racca 

Phone: (916) 255-3668 

Email: LRacca@dtsc.ca.gov
China Lake Naval Air Weapons System Site, California 

4-9 

Owner’s Contractor: 

Tetra Tech EM Inc. 

Project Manager 

Mrs. Kathy Monks 

Phone: (505) 881-3188 ext 101 

Email: kathy.monks@ttemi.com

Technology Vendor: 

HydroTechnics, Inc. 

P.O. Box 92828 

Albuquerque, NM 87199 

Mr. Richard Fagioli 

Phone: (505)797-2421 

Email: richf@hydrotechnics.com

References 

The following references were used in the 

preparation of this report: 

1. Campbell Scientific, Inc. CR10X 

Measurement and Control Module – 

Operators Manual. Revision 9/01. 2001. 

2. Tetra Tech EM Inc. 1999. Proposed 

Revised Approach for Hydrologic 

Investigation Along Boundary Fence Line, 

Naval Air Weapons Station, China Lake, 

California. March. 

3. Telephone Conversation. Kathy Monks, 

Tetra Tech EM Inc., with Chitranjan 

Christian, Tetra Tech EM Inc., China Lake 

Response to Questions on VECTOR 

Technology. April 28, 2004. 

4. Telephone Conversation. Craig Knox, 

Campbell Scientific, Inc., with Chitranjan 

Christian, Tetra Tech EM, Inc., Response to 

Questions on CR10X datalogger. May 20, 

2004. 

5. E-mail from Richard Fagioli, Hydrotechnics 

Inc., to Chitranjan Christian, Tetra Tech EM 

Inc., Response to Questions on VECTOR 

technology. May 21, 2004. 

6. E-mail from Richard Fagioli, Hydrotechnics 

Inc., to Chitranjan Christian, Tetra Tech EM 

Inc., Response to Additional Questions on 

VECTOR technology. May 26, 2004. 

7. E-mail from Richard Fagioli, Hydrotechnics 

Inc., to Chitranjan Christian, Tetra Tech EM 

Inc., Cost Estimate for VECTOR 

technology. June 14, 2004. 

8. E-mail from Kathy Monks, Tetra Tech EM 

Inc., to Chitranjan Christian, Tetra Tech EM 

Inc., Response to Questions on China Lake. 

June 11, 2004. 

9. Worldwide web resource. Hydrotechnics 

Inc. http://www.hydrotechnics.com/ 

10. Monks, K. and M. Godwin. 2001. “A CostEffective Approach to Multi-Parameter 

Hydrologic Monitoring to Characterize 

Groundwater Flow Conditions.” 2001 

International Containment & Remediation 

Technology Conference and Exhibition. 

DOE/EM-0620. http://www.em.doe.gov. 

Acknowledgements 

This report was prepared for the U.S. 

Environmental Protection Agency’s Office of 

Solid Waste and Emergency Response, Office 

of Superfund Remediation and Technology 

Innovation. Assistance was provided by Tetra 

Tech EM Inc. under EPA Contract No. 

68-W-02-034. 

Appendix 5 

Automation Technology Case Study 

Programmable Logic Controllers and Ozone Analyzers 

at the Moffett Federal Airfield Site 

Automation Technology Case Study 

Programmable Logic Controllers and Ozone Analyzers 

at the Moffett Federal Airfield Site

5-1 

Summary Information [3] 

Ozone analyzers and a programmable logic 

controller (PLC) are used in an ozone/hydrogen 

peroxide groundwater treatment system to 

monitor system performance. This case study 

presents the use of real-time ozone analyzers in 

conjunction with a PLC in a pump and treat 

system. The ozone analyzers work in 

conjunction with the PLC to ensure that (1) the 

correct dosage of ozone is applied to the influent 

water, (2) the offgas treatment system is 

meeting the air emission standards, and (3) that 

the ambient air meets occupational safety and 

health administration (OSHA) standards. 

In addition to the ozone analyzers, this case 

study presents the use of a PLC as well as a 

supervisory control and date acquisition 

interface. The supervisory control portion of the 

system consists of a PLC, which receives inputs 

from various sensors and instruments and 

operates the treatment system based on a set of 

programmed instructions. The data acquisition 

portion of the system consists of remote 

computers, the human machine interface (HMI), 

which stores all system operational data to assist 

the system operators during system 

troubleshooting, data logging for National 

Pollutant Discharge Elimination System 

(NPDES) and other reports, and system 

optimization. 

This case study is based on the treatment system 

as initially designed and operated. Subsequent 

process modifications occurred, however they 

are not relevant to the PLC or ozone analyzers 

discussed in the case study. 

Air strippers have commonly been used to treat 

TCE contaminated groundwater in pump and 

treat remedies. Air strippers remove 

contamination from the liquid phase and transfer 

it to the gas phase. Regulations do not always 

require treatment of this gas phase prior to 

discharge. Concerns about TCE emissions from 

phase-transfer processes have made destructive 

treatment options more prevalent. The ex situ 

ozone advanced oxidation process discussed 

here is one such treatment option to reduce 

atmospheric TCE emissions. 

Additionally, ozone has been increasingly 

applied via sparging to oxidize groundwater and 

soil contaminants in situ. Monitoring of ozone 

emissions from these systems is important both 

for system optimization and worker safety. 

Based on information received from the vendor, 

the ozone analyzer costs range from $2,500 to 

$15,000 and are generally reliable and require 

little maintenance. Typical problems result 

from nuisance shutdowns due to high levels of 

ambient ground level ozone. 

Technology Description [4] 

PLCs enable facility automation. However, 

they depend on field devices for sensory input. 

The ozone analyzer is one such device used at 

the Moffett Federal Airfield (MFA). 

PLC 

A PLC is a computer system that monitors 

inputs, makes decisions based on its program, 

and controls outputs to automate a process or 

machine. PLCs consist of input modules or 

points, a Central Processing Unit (CPU), and 

output modules or points. Input modules accept 

a variety of digital or analog signals from 

various field devices (such as level sensors or 

ozone analyzers) and converts them into a logic 

signal that can be used by the CPU. The CPU 

makes decisions and executes control 

instructions based on program instructions in 
Moffett Federal Airfield Site, Santa Clara County, California 

5-2 

memory. Output modules convert control 

instructions from the CPU into a digital or 

analog signal that can be used to control various 

field devices (such as valves or switches). PLCs 

can be networked with other computer systems 

for data acquisition or display. 

Ozone Analyzer 

Ozone analyzers are devices that can be used to 

measure ozone concentration in gaseous media. 

The media sampling system consists of inlet 

needle valves for sample and zero gas 

collection, a flow meter, a solenoid valve, and a 

sample chamber. The zero gas is collected from 

atmospheric air that passes through a scrubber 

containing an ozone destruction catalyst to 

remove any background ozone concentration. 

The unit measures ozone concentration by 

comparing the absorption of the sample with the 

zero gas. Depending on the position of the 

solenoid valve, zero or sample gas is forced 

through the solenoid valve, the sample chamber, 

and flow meter. The intensity of the ultraviolet 

light (UV) traversing the sample chamber is 

attenuated as prescribed using the Beer-Lambert 

Law, that is, the presence of ozone reduces the 

intensity of the UV light, the amount of UV 

light reduction corresponds to the ozone 

concentration. The ratio of the intensities is 

determined and the results are processed by the 

microcomputer to determine the ozone 

concentration. Since the concentration 

determined by the photometer is based solely on 

the ratio of light intensities, the actual intensity 

of the light is not important. Slow changes in 

light intensity due to lamp aging or dirt buildup 

in the optics will not affect the concentration 

reading. 

Site Information [1, 2, 3, 5, 6] 

MFA is located in Santa Clara County, 

California, at the southern end of San Francisco 

Bay. From the 1930s until its closure in 1994, 

the base was operated by the Navy as Naval Air 

Station Moffett Field. In 1994, the base was 

transferred to the National Aeronautics and 

Space Administration (NASA) and continues to 

operate as a federal airfield. MFA was placed 

on the national priorities list (NPL) in 1987. 

In 1991, the EPA and other agencies divided 

MFA into six operable units (OUs). OU4 

consisted of the west-side aquifers. These 

aquifers were contaminated with a mixture of 

gasoline and diesel from several leaking USTs, 

as well as tetrachloroethylene (PCE) and its 

breakdown products from an on-site dry cleaner. 

However, in 1992, the EPA determined that the 

west-side aquifers were affected by a regional 

plume (primarily TCE and its daughter 

products) that emanated from the adjacent 

Middlefield Ellis Whisman (MEW) NPL site. 

As a result, EPA determined that the west-side 

aquifers were subject to the 1989 record of 

decision (ROD) already written for the MEW 

site, directing remediation of the west-side 

aquifers. Consequently, OU4 was deleted and 

has since been referred to as the west-side 

aquifers. 

The west-side aquifers consisted of two highly 

heterogeneous interconnected aquifer zones of 

alluvial channel deposits composed of sand and 

gravel incised in and interbedded with clayey 

floodplain deposits. The aquifers extended from 

5 to 65 feet below ground surface. 

The MEW site ROD designated pump-and-treat 

with air stripping as the remedy. A subsequent 

explanation of significant differences in 1996 

allowed the use of liquid-phase granular 

activated carbon (GAC). Design of the westside aquifers treatment system (WATS) was 

completed in 1997 and construction was 

completed in 1998. Table 1 lists the 

contaminants, concentrations, and treatment 

requirements for extracted water at the WATS. 
Moffett Federal Airfield Site, Santa Clara County, California 

5-3 

Table 1 

Influent Contaminant Concentrations 

West-Side Aquifers Treatment System 

Contaminant 

Average Influent 

Concentration 

(μg/L)1

Federal MCL 

(μg/L) 

California MCL 

(μg/L) 

NPDES 

Treatment 

Requirement

(μg/L) 

Trichloroethene (TCE) 1,850 5 5 5 

Tetrachloroethene (PCE) 24 5 5 5 

Vinyl Chloride 31 2 0.5 0.5 

1,1-Dichloroethene 

(1,1-DCE) 

26 7 6 5 

Cis-1,2-Dichloroethene 

(1,2-DCE) 

270 70 6 5 

Trans-1,2-Dichloroethene 

(1,2-DCE) 

10 100 10 5 

1,1-Dichloroethane 

(1,1-DCA) 

6 N/A 5 5 

1,1,1-Trichloroethane 

(1,1,1-TCA) 

1 200 200 5 

Freon 113 21 N/A 1,200 5 

TPH-purgeable 180 N/A N/A 50 

TPH-extractable 11 N/A N/A 50 

Notes: 

1 Based on operational sampling data from December 1998 through March 2000 

μg/L Micrograms per liter 

MCL Maximum contaminant level 

N/A Not applicable—no MCL for this parameter 

NPDES National Pollutant Discharge Elimination System 

TPH Total petroleum hydrocarbons 

Source: Tetra Tech EM Inc. 
Moffett Federal Airfield Site, Santa Clara County, California 

5-4 

Remediation System 

The WATS consists of eight extraction wells 

piped to a treatment system located north of 

Building 45. All system equipment is controlled 

by a PLC. The extraction wells maintained a 

constant groundwater drawdown to maximize 

extraction rates from each well. Contaminated 

water collected in two on-site sumps near 

Hangar 1 was also treated in the WATS. 

Contaminated water was pumped from the 

extraction wells and treated to remove 

groundwater contaminants to levels specified in 

the MFA NPDES permit before being 

discharged to the MFA storm sewer. 

Extracted groundwater was first passed through 

bag filters, which remove sediment from the 

influent. Then, ozone and hydrogen peroxide 

were mixed with the water in three 1,400-gallon 

reaction tanks (ozone and hydrogen peroxide 

combine to form hydroxyl radicals that are 

stronger oxidants than ozone and hydrogen 

peroxide alone. The hydroxyl radicals destroy 

about 99 percent of the influent contaminants). 

The remaining contaminants were removed by 

the air stripper and GAC units and the treated 

water was discharged to the MFA storm sewer 

under an NPDES permit. Offgas from the 

oxidation tank, consisting of a mixture of 

unreacted ozone and oxygen, was heated and 

treated with a proprietary ozone destruction 

catalyst. Figure 1 presents a simplified process 

flow diagram of the WATS. 

Control System 

PLC control and sensors served five main 

functions on the system, (1) they allowed the 

system to operate automatically, (2) they shut 

down the system if water or offgas treatment 

was not functioning correctly, (3) they shut 

down the system before an unsafe worker safety 

condition, such as an ozone leak, existed, 

(4) they allowed remote monitoring of system 

status, allowing the operator to schedule site 

visits, and (5) they logged operational data, 

which could then be mined and trended to 

troubleshoot problems or optimize system 

performance. A pump-and-treat system of the 

complexity at the WATS would be extremely 

difficult to operate manually or even with a 

solid-state control system. 

In order to maintain a constant groundwater 

drawdown, a capacitance-type level probe was 

used in each extraction well to continuously 

monitor the water level and relay this data to the 

PLC. The PLC then sent a signal to a flow 

control valve. If the water level was rising, the 

flow control valve opened slightly to increase 

the pumping rate, and thus the drawdown. 

Conversely, if the water level was decreasing, 

the flow control valve closed slightly to 

decrease the pumping rate. This automatic 

adjustment of well flow rate adjusted for 

changes in well yield due water table 

fluctuations caused by precipitation events. 

The PLC was also used to regulate ozone and 

hydrogen peroxide dosage which was critical to 

obtaining maximum destruction efficiencies. 

This was accomplished using an influent 

flowmeter which measured the flowrate into the 

treatment system. The PLC processed this 

information and calculated the corresponding 

hydrogen peroxide injection rate and sent a 

signal to the hydrogen peroxide pump to inject 

the correct dosage. The gas flow rate into the 

oxidation tanks was constant, but ozone 

percentage of gas varied to achieve the proper 

ozone/hydrogen peroxide ratio for optimal 

treatment. Thus, the PLC also processed the 

water flow rate, calculated the correct ozone 

concentration, and sent a signal to the ozone 

generator which converted oxygen into the 

proper percentage of ozone sparged into the 

tanks to maintain the correct dosage. 
Moffett Federal Airfield Site, Santa Clara County, California 

5-5 

Figure 1 

West-Side Aquifers Treatment System 

Ozone/Peroxide 

Reaction Tanks 

Air Stripper

Ozone 

Analyzers 

Air 

Compressor 

Ozone 

Generator 

Oxygen 

Generator 

From Bag Filters and 

Extraction Wells 

To Granular 

Activated Carbon 

Filters and Discharge 

Granular 

Activated 

Carbon Vessels Air Stripper

Ozone/Peroxide 

Reaction Tanks 

Hydrogen PLC Enclosure

Peroxide 

Tank 
Moffett Federal Airfield Site, Santa Clara County, California 

5-6 

The universal shutdown interlock programmed 

into the PLC shut down the entire WATS, 

including the eight extraction pump motors, 

based on activation of any of the following 

system alarms: 

y High-high bag filter differential pressure 

(indicates that the bag filters are 

clogged) 

y Low hydrogen peroxide flow (indicates 

that the hydrogen peroxide pump has 

failed) 

y Low hydrogen peroxide tank level 

(indicates that the hydrogen peroxide 

tank is nearly empty) 

y Air compressor general fault 

y Air receiver low pressure 

y Low ozone generator voltage 

y Ozone generator fault 

y Oxygen low flow 

y Low oxidation tank inlet ozone 

concentration (ensures that correct 

dosage of ozone is injected into the 

oxidation tanks) 

y High-high ozone generator discharge 

temperature (prevents the ozone 

generator from overheating) 

y Low catalytic oxidizer temperature 

(indicates that the ozone destruction 

system is not functioning) 

y Low-concentration ozone analyzer 

general failure (indicates that the 

analyzer has malfunctioned) 

y High catalytic oxidizer exhaust ozone 

concentration (indicates that the ozone 

destruction system is not working 

properly) 

y High air stripper sump level (indicates 

that the air stripper drain is clogged) 

y Low air stripper blower pressure 

(indicates that the air stripper is not 

functioning) 

y High-high secondary containment sump 

level (indicates that a spill has occurred 

within the treatment pad) 

These alarms were selected to activate the 

universal shutdown interlock because they 

indicate that a spill could occur, that the system 

may not be treating the water effectively, or that 

the offgas treatment system may not be working 

correctly. Immediately shutting down the 

system in response to any of these alarms would 

avoid spills, the discharge of untreated water, or 

the discharge of untreated offgas. 

An ozone analyzer continuously monitored the 

ozone concentration in the ambient air. If an 

ozone leak occurred, it could immediately 

endanger the health of any on-site worker. 

Thus, when the ozone analyzer detected an 

ambient air ozone concentration of 0.1 ppm, the 

entire system (including the ozone generator, 

presumably the source of the ozone) would shut 

down, well before the OSHA permissible 

exposure limit of 0.1 ppm could be exceeded for 

an 8-hour time-weighted average (TWA). 

Data Acquisition 

The WATS PLC was connected via modem to 

remote PC-based human-machine interfaces 

(HMI) at offsite locations. This allowed the 

system operator to view system status. Thus, 

some troubleshooting could be conducted from 

offsite. Additionally, the operator could 

remotely view the status of various parameters, 

such as bag filter pressure drop, and hydrogen 

peroxide volume to remotely schedule bag filter 

changeouts and chemical deliveries 

respectively. Finally, the operator could 

remotely turn extraction wells on or off as 

needed. Figure 2 presents the HMI for a typical 

extraction well that shows the current pump 

status (auto), pump discharge pressure (17.27 

psi), flow rate (5.91 gpm), and water level -1.36 

feet mean sea level). 

The HMI logged all system parameters, such as 

flowrates, extraction well water levels, and 

pressures, on a remote computer. This 

information was useful in the preparation of the 
Moffett Federal Airfield Site, Santa Clara County, California 

5-7 

Figure 2 

Human Machine Interface 

Extraction Well Status Screen 

Process Variable Trending Screen
Moffett Federal Airfield Site, Santa Clara County, California 

5-8 

NPDES reports and quarterly progress reports, 

where individual well flow rates could be 

plotted for each reporting period. The 

extraction well water level data could be trended 

over any user-defined period. Figure 2 displays 

a typical process variable trending screen on the 

HMI. 

The datalogging also maintained a record of all 

alarms and the causes of all system shutdowns, 

which significantly simplified system 

troubleshooting. Otherwise, with such a 

complex system, it could often be difficult to 

determine what equipment failure or process 

variable initiated the system shutdown 

sequence. Reviewing the data logs allowed the 

operator to quickly identify the initial cause or 

causes of the problem. 

Design of the WATS began in 1996, before use 

of the internet was widespread. Thus, the HMI 

was originally connected to the PLC via 

modem. In 2001, the HMI was upgraded to an 

internet-based version which allowed easier 

access to the system operating conditions. The 

internet-based version had a firewall and was 

password-protected to prevent unauthorized 

system modifications. 

Ozone Analyzers 

The most complex of these sensors were the two 

ozone analyzers. There were two ozone 

analyzers (Figure 3), a high concentration ozone 

analyzer and a low concentration ozone 

analyzer. Both worked in the same manner. 

The ozone analyzers (PCI Model LC-400 and 

HC-400) provided a digital readout of ozone 

concentrations. The high concentration ozone 

analyzer measured percent ozone (0 percent to 

15 percent) in oxygen from the ozone generator. 

The low concentration ozone analyzer measured 

ozone in ppm from 0.001 ppm to 10 ppm. The 

high concentration ozone analyzer measured the 

actual ozone concentration of the gas that was 

sparged into the oxidation tanks. The PLC 

compared this value to the target ozone 

concentration based on the influent water flow 

rate. If the concentration was not within 10 

percent of the target ozone concentration, the 

system shut would down before partially-treated 

water was released. 

The offgas ozone analyzer measured the ozone 

concentration in the system offgas. The Bay 

Area Air Quality Management District 

(BAAQMD) limit for nonpermitted ozone 

emissions was 1 pound per day. The offgas 

ozone analyzer monitored the ozone 

concentration in the system offgas. When the 

offgas ozone concentration exceeded 9 ppmv 

(based on the maximum concentration the unit 

can detect without damage), the PLC would shut 

down the entire system. At 9 ppm, the WATS 

ozone emissions would be about 0.026 pound 

per day. 

System Operation [7] 

The pump and treat system has been in 

operation since 1998 and has treated 

approximately 190,000,000 gallons of 

contaminated water. The PLC control system 

has not experienced significant problems and 

has not required maintenance. 

The ozone analyzers required little maintenance. 

The units were factory-calibrated. For reasons 

stated previously (that is, always comparing the 

UV absorption by sample to absorption by a 

zero gas), the units did not require field 

calibration. However, there were some minor 

maintenance items. First, the zero gas and the 

sample gas particulate filters required 

replacement every 6 months (this depended on 

the site gas quality). Second, the UV bulbs 

required annual replacement. An internal check 

warned the operator when UV bulbs were 

nearing the end of their operational life. 
Moffett Federal Airfield Site, Santa Clara County, California 

5-9 

Figure 3 

Ozone Monitors 

The gas scrubber that produced zero gas for the 

ozone analyzers did not required maintenance. 

However, future maintenance could be required 

depending on exposure of the zero gas scrubber 

to ozone and potential catalyst poisons. 

Both ozone analyzers were replaced with newer 

models in fall 2004 as replacement parts became 

hard to find. The high concentration ozone 

analyzer was replaced with a Mini-HiCon 

manufactured by IN USA, Inc. The low 

concentration analyzer was replaced with a 

Series 930 ozone analyzer manufactured by 

Aeroqual Ltd. 

Cost [3, 6, 7] 

According to the construction contractor, the 

instrumentation and controls system installation 

cost was $95,454 (Tetra Tech 2001). However, 

this number may not reflect the total control 

system installation cost, some of which is likely 

lumped in with the $319,060 system startup 

cost. Tetra Tech estimates that the actual 

installation and startup cost for the 

instrumentation and control system was 

approximately $200,000. The ozone analyzers 

cost approximately $15,000 at the time of 

installation. However, costs have decreased 

considerably since then and now range from 

$2,500 to $15,000 depending on sensitivity of 

the instrument, the input/output options, and the 

type of enclosure (NEMA 3, NEMA 4X, etc.) 

Operation and maintenance cost for the PLC 

and HMI system are minimal. Once the 

software license is purchased and the system is 

programmed, installed, and debugged, O&M 

costs are similar to the costs of operating several 

PCs with internet access. 

System changes or upgrades can be more costly, 

especially when a programming subcontractor is 

unfamiliar with the system and must learn the 

system operations as well as familiarize 

himself/herself with the program. 

Ozone analyzer O&M costs are approximately 

$500 per year in parts and approximately 16 

hours in labor. 

Lessons Learned [1, 2, 3, 5, 6]

The primary troubleshooting problem with the 

offgas ozone analyzer occurred during system 

startup and shakedown when the unit began 

displaying extremely variable ozone 

concentrations (from 0.00 ppmv to exceeding 
Moffett Federal Airfield Site, Santa Clara County, California 

5-10 

100 ppmv, beyond the range of the instrument). 

It was determined that the zero gas ozone 

destruction catalyst had become poisoned (due 

to hydrochloric acid in the oxidation tank 

offgas). Thus, the zero gas actually contained 

ozone. Replacement of the catalyst remedied 

the problem. 

Another problem with the ozone analyzer 

resulted from high ground-level ozone 

concentrations due to normal sources, such as 

automobile exhaust. The ambient air ozone 

analyzer is designed to detect leaks in the ozone 

injection system and shut the system when 

worker safety is at risk. However, using the 

OSHA 8-hour TWA as the system shutdown 

criteria would potentially delay system 

shutdown during a catastrophic leak. To 

prevent such a delay in system shutdown, the 

more conservative National Institute for 

Occupational Safety and Health (NIOSH) 

instantaneous recommended exposure limit of 

0.1 ppm was chosen as the system shutdown 

criteria. Using this instantaneous criterion, the 

system would respond immediately to a leak in 

the ozone piping or failure of the ozone offgas 

destruction. 

However, during the first few years of system 

operation, numerous system shutdowns 

occurred because of high ambient ozone 

concentrations. The offgas ozone destruction 

system was found to be functioning correctly 

and leak testing of all ozone piping (via pressure 

testing and soap) did not identify any leaks. 

After further investigation, it was determined 

that the cause of the shutdowns was elevated 

background ozone concentrations, which are 

common urban areas. In fact, in 1998, the 

maximum instantaneous ozone concentration in 

Santa Clara County was 0.15 ppm, and the 

highest 8-hour TWA was 0.11 ppm. 

To balance the need for minimizing nuisance 

system shutdowns with worker safety, the 

ambient ozone system shutdown setpoint was 

adjusted from a 0.1 ppm for one instantaneous 

reading, to 0.1 for a 1-minute rolling average 

(approximately 2 readings). This change 

eliminated nuisance shutdowns while 

maintaining worker safety. 

Conclusions [5, 6, 7] 

PLC system control and instrumentation at the 

WATS has been a success to date in that there 

have been no exceedences of the BAAQMD 

ozone discharge requirements or exceedences of 

the NPDES permit due to incomplete oxidation 

of the chlorinated solvents, and there have been 

no spill events. Additionally, system 

troubleshooting has been greatly simplified by 

studying the datalogs of system shutdown. 

However, programming the HMI requires 

advanced programming knowledge of the 

system software (Wonder Ware). Making 

minor changes to the HMI often required a 

significant effort and could be expensive as it 

required specialized contractors. Newer 

versions of HMI software have incorporated 

more user-friendly programming tools that 

should allow minor changes to the HMI to be 

made more easily. 

During system startup, Tetra Tech conducted 

proof of performance testing of the ozone offgas 

analyzer using a handheld ozone analyzer 

(Bionics TG-800). The handheld monitor uses 

an entirely different method for ozone detection 

(gas membrane galvanic cell) and its range of 

detection was substantially different (0 to 2 

ppmv, in 0.05 ppmv increments) than the low 

concentration ozone analyzer. Based on a 

comparison of results, Tetra Tech was able to 

determine that the analyzers were accurate to 

within 0.05 ppmv. 
Moffett Federal Airfield Site, Santa Clara County, California 

5-11 

Contact Information 

State Agency: 

San Francisco Bay Regional Water Quality 

Control Board 

Remedial Project Manager 

Ms. Adriana Constantinescu 

Phone: (510) 622-2353 

Email: avc@rb2.swrcb.ca.gov

Owner: 

Department of the Navy 

Base Realignment and Closure Program 

Management Office West 

Ms. Andrea Espinoza 

Phone: (619) 532-0911 

Email: andrea.espinoza@navy.mil

Owner’s Design Contractor: 

Tetra Tech EM Inc. 

Project Engineer/Project Manager 

Mr. David J. Berestka, P.E. 

Phone: (303) 312-8856 

Email: david.berestka@ttemi.com

Owner’s O&M Contractor: 

Tetra Tech FW, Inc. (formerly Foster Wheeler 

Environmental) 

Technical Lead 

Mr. Michael Klosky, P.E. 

Phone: (770) 825-7144 

Email: mklosky@ttfwi.com

References 

The following references were used in the 

preparation of this report: 

1. Bay Area Air Quality Management District 

(BAAQMD). 1997. Letter Regarding 

West-Side Aquifer Treatment System. From 

Robert E. Cave, Air Quality Engineer II, 

Permit Services Division. To Stephen Chao, 

BRAC Environmental Coordinator, 

Engineering Field Activity West, 

Department of the Navy. March 10. 

2. California Air Resources Board (CARB). 

1999. Summaries of Ozone Data (1980-

1998), Santa Clara County. March 26. 

http://www.arb.ca.gov/aqd/OLDozone/ 

A1C43.htm

3. PCI Ozone & Control Systems. 1993. 

Ozone Monitor Operating and Instruction 

Manual, Models LC-400, HC-400. 

November. 

4. Siemens Energy & Automation, Inc. 

Siemens Technical Education Program 

(STEP) 2000 series. Basics of PLCs. 

5. Tetra Tech EM Inc. (Tetra Tech). 2000. 

Final Operation and Maintenance Manual 

for the West-side Aquifers Treatment 

System. DS.0310.14581-01. October 20. 

6. Tetra Tech. 2001. Draft Final Interim 

Remedial Action Report, West-side 

Aquifers Treatment System (WATS), 

Moffett Federal Airfield, Moffett Field, 

California. DS.0310.14585-01. January 12. 

7. E-mail from David Berestka, Tetra Tech EM 

Inc., to Chitranjan Christian, Tetra Tech EM 

Inc., Draft Case Study. November 9, 2004. 

Acknowledgements 

This report was prepared for the U.S. 

Environmental Protection Agency’s Office of 

Solid Waste and Emergency Response, Office 

of Superfund Remediation and Technology 

Innovation. Assistance was provided by Tetra 

Tech EM Inc. under EPA Contract No. 

68-W-02-034. 

Appendix 6 

Sensor Technology Case Study 

Automated Sampling and Analysis of Trichloroethene and Hexavalent 

Chromium Using the Burge System 

at the North Indian Bend Wash and Nevada Test Sites 

Sensor Technology Case Study 

Automated Sampling and Analysis of Trichloroethene and Hexavalent Chromium 

Using the Burge System at the North Indian Bend Wash and Nevada Test Sites

6-1 

Summary Information [1, 2, 3, 4, 5, 6, 7, 8, 9, 

10] 

The research and development (R&D) of 

automated sampling and analysis systems 

described in this report began in 1988 and 

initially focused on a device called an optrode 

developed by Lawrence Livermore National 

Laboratory, for the analysis of volatile 

chlorinated hydrocarbons. 

As the etymology of “optrode” suggests; it is an 

instrument that provides a pathway for light. 

Although sometimes incorrectly used in a 

broader sense, the term optrode was originally 

meant to refer to a colorimetric instrument that 

measured a rate of change in light intensity as 

the compound of interest (analyte) diffused into 

the optical pathway through the instrument’s 

semi-permeable membrane. Following beta 

testing, Burge Environmental made the optrodebased analytical system available to the 

environmental industry in March 1998. The 

system was only able to detect trichloroethene 

(TCE). Since then the vendor has developed the 

skeletal technology to permit the use of other 

sensors to measure various analytes. 

There are several sensors today that use 

analytical methods suited to specific, or 

sometimes an entire range of analytes. 

However, they sometimes never make it past the 

R&D stage due to the lack of a suitable platform 

for field deployment. This report discusses a 

modifiable automated sampling and analysis 

platform developed by Burge Environmental. 

The report focuses on two systems in particular. 

One is an optrode based system developed for 

the analysis of TCE, and the other is a nonoptrode based colorimetric system developed 

for the analysis of hexavalent chromium 

(Cr-VI). 

Case studies on these systems cover 

implementation of this technology at two 

different sites: (1) The North Indian Bend Wash 

(NIBW) Superfund site; and (2) The Nevada 

Test Site (NTS). The implementation at the 

NIBW site involved sampling the influent and 

effluent of a groundwater treatment plant and 

analyzing the samples for TCE on a daily basis. 

The field effort at the NTS was a pilot test 

preceding deployment of the Cr-VI sampling 

and analysis system for groundwater monitoring 

at the Hanford site along the Columbia River 

near Richland, Washington. 

Implementation of this technology at both sites 

proved to be satisfactory. Lessons were learned 

along the way and improvements have been 

made. 

This technology is potentially useful in 

situations requiring frequent sampling and 

generation of large amounts of data. Since this 

technology has not yet been approved by the 

U.S. Environmental Protection Agency (EPA) 

for regulatory monitoring, it has limited 

application in compliance monitoring. 

However, it has been used in the past to 

augment regulatory monitoring for groundwater 

and treatment processes. 

Technology Description [1, 3, 5, 6] 

The Burge system facilitates automated 

sampling and on-site analysis for monitoring of 

groundwater or treatment processes. The 

system was specifically designed for 

deployment of sensors in the field. 

The system essentially consists of two separable 

modules; a sampling module and an analytical 

module. As their names suggest, the sampling 

module is responsible for sample acquisition, 
North Indian Bend Wash Site and Nevada Test Sites 

6-2 

and the analytical module quantifies the amount 

of analyte present in the acquired sample. The 

system also has a waste module that manages 

wastes produced during analysis and system 

purging. The entire system is powered by a 12 

Volt energy source. 

Sampling Module 

The sampling module is built to suit the 

sampling effort. For instance, the module used 

to sample the effluent of a wastewater treatment 

system might consist of a peristaltic pump with 

associated tubing for sample conveyance. A 

groundwater sampling module on the other hand 

may be significantly more complex especially if 

it involved sampling at multiple depths. The 

sampling module would be built to fit into or 

just above the well casing and would include 

valves, pneumatic tubing, conveyance tubing, 

and electrical wiring. 

In general most sampling modules are 

pneumatically actuated. Compressed air serves 

as the driving force to convey liquids from one 

point to another. High pressure air (15 pounds 

per square inch [psi]) drives sample collection. 

Analytical Module 

Figure 1 presents an illustration of a wellsampling and analysis module. The illustration 

shows the sampling module inside the well and 

the analytical module to its right in a subsurface 

enclosure. The enclosure also contains the 

battery power source shown connected to the 

solar cell on the surface. The waste module and 

compressed air tank are seen to the left of the 

well. 

The analytical module is in essence a miniature 

laboratory small enough to fit in a two-foot 

cube. The module can be configured for use 

with multiple sensors. In practice, the module 

may be located within the monitoring well, 

adjacent to the monitoring well, or both. The 

analytical module houses interconnected vials 

used to hold samples, store reagents, and 

facilitate proper chemical reaction. Low 

pressure compressed air (1.5 psi) drives fluids in 

the analytical system from one stage to the next. 

Although the specifics of the analytical system 

vary with the analyte, the module in general 

facilitates reagent component storage, reagent 

blend preparation, sample preparation, sample 

dilution, reactant mixing, system flushing, and 

measurement using a sensor. Reagent storage 

containers typically vary in size from 250 to 500 

milliliters. However the amount of reagent 

stored can be increased to reduce the frequency 

of reagent replacement. Assuming one sample 

per day, reagent storage is usually designed to 

last at least 6 weeks. 

According to Burge Environmental, the 

analytical platform is flexible enough to even 

allow the integration of sensors manufactured 

by other entities. Some of the analytical 

methods available for use are: (1) molecular 

spectroscopy; (2) electrochemical measurement; 

(3) colorimetric measurement, and (4) photoionization. 

The analytical process consists of three 

important stages: (1) instrument calibration; 

(2) sample analysis; and (3) post-test calibration 

check. 

Instrument calibration is generally performed 

before the first analysis, after which calibration 

is performed manually (from the remote 

computer) only as required. For instance, recalibration may be necessitated by a change in 

the ambient temperature recorded by the 

instrument’s thermometer. Calibration involves 

analysis of samples bearing known 

concentrations of the analyte. Analytical results 

are compared with the known concentrations 

and the instrument is adjusted to minimize the 

difference between the two. Samples used for 

calibration represent a minimum (zero), a 
North Indian Bend Wash Site and Nevada Test Sites 

6-3 

Figure 1 

Burge Groundwater Sampling and Analysis System 

Source: Burge Environmental 
North Indian Bend Wash Site and Nevada Test Sites 

6-4 

maximum (varies), and a mid analytical range. 

The analytical range is designed such that the 

required detection range for the analyte falls 

between the minimum and the maximum, and is 

bisected by the mid. The analytical module 

produces the minimum-, maximum-, and midcalibration samples from varying blends of 

stored standard solution and prepared blanks. 

Blanks are analyte-free samples that are made in 

the analytical module by passing contaminated 

water through the appropriate treatment 

medium. The treatment medium in the TCE 

analytical module is activated carbon, and in the 

Cr-VI analytical module is granular ferric 

hydroxide. All process wastes are pumped to a 

waste storage tank. 

Sample analysis is a two or three stage process 

involving the transfer of a metered volume of 

prepared sample to the analytical cell followed 

by measurement using a sensor. 

To verify the validity of the result of analysis, 

the module performs a post-test mid-calibration 

check. This involves analysis of a prepared 

mid-calibration sample soon after analysis of the 

acquired media sample. If the result of post-test 

mid-calibration shows more than 20 percent 

deviation from the true value, the module marks 

the previous result for review. 

TCE Analysis 

Analysis for TCE involves a colorimetric 

measurement technique that uses a device called 

an optrode. The optrode consists of a U-tube, a 

light source and a collector. The U-tube is 

constructed of a semi-permeable material with a 

reflective inner surface. Being in essence an 

optic fiber, the u-tube allows the passage of 

light from one end to the other with 

undiminished intensity. A green light emitting 

diode (LED) at one end of the u-tube serves as 

the light source and a collector at the other end 

measures the intensity of exiting light. The 

optrode is located in the head space (volume 

above liquid level) of the sample vial. 

Prior to every analysis, the optrode is filled with 

a freshly prepared solution of a TCE-specific 

reagent. When an aqueous sample is introduced 

into the vial containing the optrode, an 

equilibrium results between the liquid and vapor 

phases of volatile contaminants in that sample. 

Vapor in the headspace permeates the wall of 

the optrode and enters the reagent. The reagent 

reacts with TCE forming a red colored product. 

This product absorbs light produced by the 

green LED as it passes through the u-tube. 

Consequently, the intensity of light exiting the 

u-tube decreases. As the reaction proceeds and 

more product is formed, the collector records 

continuously diminishing light intensity. At the 

end of the three-minute reaction period, the 

instrument uses the measured rate of decrease in 

light intensity to estimate the concentration of 

TCE in the aqueous sample. 

The detection limit of the TCE analytical 

module is 1 ppb. However, since chloroform 

interferes with TCE analysis, the TCE detection 

limit is a function of the amount of chloroform 

present in the sample. 

Cr-VI Analysis 

The analysis package used for Cr-VI also uses a 

colorimetric technique. However, the technique 

does not involve the measurement of a reaction 

rate and thus does not use an optrode. 

The analytical cell is a cylindrical tube with a 

green LED at one end and a collector at the 

other. Metered portions of the sample and 

reagent (1,2-diphenylcarbazide) are mixed in a 

reaction cell. Cr-VI in the sample reacts with 

the reagent to form a red colored product. The 

intensity of the coloration is directly 

proportional to the amount of Cr-VI present in 

the sample. After a predetermined waiting 

period, the red liquid is transferred to the 
North Indian Bend Wash Site and Nevada Test Sites 

6-5 

analytical cell. The red liquid absorbs green 

light produced by the LED causing a decrease in 

intensity of green light measured by the 

collector. This decrease in intensity is used to 

estimate the concentration of Cr-VI in the 

sample. 

The detection limit of the Cr-VI analytical 

module was found to be 1 ppb during precision 

tests. However, detection limit can be reduced 

by increasing the length of the optical path 

through the sample. 

Control System 

The control system for the sampling and 

analysis modules comprises level sensors, 

electrically actuated valves, and an on-board 

logic controller. The logic controller interfaces 

with a personal computer (PC) through an RS232 interface to receive instructions and transfer 

data. Figure 2 presents a schematic of an 

optrode-based analytical system. 

Figure 2 

Schematic of the Analytical System 

Source: Burge Environmental 
North Indian Bend Wash Site and Nevada Test Sites 

6-6 

The system has fail-safe provisions. A 

watchdog program continuously monitors 

system components and shuts down the system 

if a malfunction is detected. An error code on 

the PC screen identifies the component of the 

system that caused shutdown. 

Remote operation of the system is facilitated by 

PCAnywhere (communications software). This 

commercially available software developed by 

Symantec makes it possible for the user’s PC to 

communicate with the system’s PC over a 

phone line. The graphical user interface used to 

operate the system was developed by Burge 

Environmental. The program allows the user to 

monitor system operation, perform analytical 

system calibration, actuate sampling and 

analysis, view results, and store data in a 

Microsoft Excel spreadsheet. 

Construction 

Components of the sampling and analysis 

system including all containers and electrical 

components are typically housed in an insulated 

weather-proof box unless they are being used 

indoors. Figure 3 provides an illustration of 

both an indoor and an outdoor system. 

Other than the above common features, each 

system usually has to be custom-designed to suit 

a given site. This is due to variations in client 

requirements, site infrastructure, and the nature 

of the system being tied-in to. For example, at a 

site where electricity is easily available, there 

would be no need for an autonomous solar-cell 

and battery power supply. Similarly, where a 

phone connection is easily available for an 

indoor system, the data transfer system would 

not need radio telemetry. In extremely cold 

climates, below ground construction and 

allowance for a space heating system would 

influence system enclosure design. Reasons 

such as these are what force the vendor to be 

flexible; and the very same reasons preclude the 

manufacture of a standardized off-the-shelf 

system. 

Site Information [1, 2, 6, 9] 

This report presents two different sites to 

illustrate implementation of both the TCE and 

Cr-VI systems. 

The TCE system had been previously used to 

monitor both groundwater and treatment 

processes. This report presents a site that used 

sampling and analysis modules to test the 

influent and effluent of a groundwater treatment 

system. 

The Cr-VI analytical system became available 

for use more recently. A groundwater sampling 

and Cr-VI analytical system was designed for 

use at the Hanford site near Richland, 

Washington and was deployed in mid July, 

2004. However, before this, as a precursor to 

full-scale implementation, a pilot-scale test of 

the system was performed at the Nevada Test 

Site near Las Vegas, Nevada. This report 

presents details of this pilot test. 

From this point forward in this report, the 

sampling and analysis system will be called the 

Burge system. 

North Indian Bend Wash Site 

Groundwater at the North Indian Bend Wash 

(NIBW) Superfund site in Arizona was 

contaminated with several volatile organic 

compounds (VOC). A groundwater pump and 

treat system was being used to extract and treat 

contaminated groundwater. TCE was the 

primary contaminant of concern. 

The groundwater treatment system used airstripping and carbon adsorption to remove 

VOCs from the groundwater. The treatment 

plant was operated by the City of Scottsdale and 
North Indian Bend Wash Site and Nevada Test Sites 

6-7 

Figure 3 

Sampling and Analysis System Photos 

Indoor Wall-Mounted Sampling and Analysis System for Process Monitoring. Source: Burge Environmental 

Outdoor Sampling and Analysis System for Groundwater Monitoring – Used at the Nevada Test Site. Source: Burge 

Environmental 
North Indian Bend Wash Site and Nevada Test Sites 

6-8 

processed 10.7 million gallons of water per day. 

The Burge system was installed as part of an 

agreement with the EPA to allow reduced 

regulatory monitoring at the facility. 

The Burge system was installed at the plant in 

January 2002 to monitor pre- and post-treatment 

concentrations of TCE in extracted 

groundwater. Influent and effluent monitoring 

served as a measure for treatment plant 

performance. Effluent monitoring also served 

to warn against accidental discharge above the 

regulatory threshold of 5 ppb. The influent 

water had a TCE concentration averaging 100 to 

120 parts per billion (ppb) and the effluent had a 

concentration below the laboratory’s detection 

limit (0.5 ppb). The Burge system tapped 

directly into the influent line for influent sample 

acquisition. Since the treatment plant effluent 

outlet was much farther away, the facility 

provided a continuously flowing open loop 

system to make fresh effluent water 

continuously available to the Burge system. 

The Burge system tapped into this open loop for 

sample acquisition. 

The Burge system performed daily analysis of 

influent and effluent waters, and performed a 

post-test mid-calibration check after each 

analysis as a quality control measure. The 

calibration process used a blank, 6 and 12 ppb 

standards and a 6 ppb post-test check standard. 

The calibration curve range was selected to 

bracket the regulatory threshold concentration 

of 5 ppb. Consequently influent water 

underwent dilution prior to analysis. 

Burge Environmental remotely operated the 

system from their office in Tempe, Arizona. 

Operation included setting times to initiate 

sampling and analysis, as well as retrieving and 

reviewing testing data. All other functions 

including sampling, calibration and analysis 

were automated. 

Nevada Test Site

As a precursor to full scale implementation at 

the Hanford site, the Cr-VI Burge system was 

pilot-tested at the Nevada Test Site near Las 

Vegas, Nevada. These tests were conducted in 

December 2003 and March 2004. 

The sampling module used a peristaltic pump to 

collect water samples from storage containers. 

The module facilitated sampling from four 

different sources. 

Communication between the Burge system and 

the remote PC was made possible through a 

wireless modem link. This was functionally 

equivalent to using a serial cable. One modem 

was connected to the on-board logic controller 

in the field deployment box, and the other was 

connected to a PC at a remote facility. The 

modems required line of sight, and had a 12-

mile communication range. The radio modem 

in the field deployment box was powered by the 

system’s 12-Volt power supply. The PC in the 

remote facility hosted a data acquisition and 

control software developed by Burge 

Environmental. 

The test system included a waste module that 

was used to remove and store all analytical 

process wastes. There were two waste streams 

created by the monitoring system. One was 

water from the monitoring wells used to rinse 

the sampling lines. The other waste stream 

contained leftover reagents, standards, and 

sample after an analytical run. 

The test system was not an exact replica of the 

system to be used at Hanford because it had the 

benefit of operator supervision. The 

communication system used at Hanford was 

more involved because system monitoring, 

control, and data acquisition was to be based in 

Arizona while the field unit was located in 

Washington. A combination of a wireless 

modem link and a phone line was required to 
North Indian Bend Wash Site and Nevada Test Sites 

6-9 

link the field unit to the monitoring station. The 

wireless modems linked the Burge system to the 

on-site PC. Telephone modems linked the onsite PC to the remote PC. Figure 4 provides an 

illustration of the Burge system used at Hanford. 

System Operation [1, 2] 

This section discusses operation of the Burge 

systems installed at the two sites. 

North Indian Bend Wash Site 

System operation was automated and did not 

demand supervision. However, Burge 

Environmental remotely monitored the system 

as part of the service offered with the contract. 

Daily monitoring was performed in ten minutes 

and was meant to observe system function and 

view test results. Results of the post-test midcalibration determined the validity of the test. If 

the result was within 20 percent of the true 

concentration of the standard, the test was 

considered valid. On the other hand, deviation 

beyond the stipulated 20 percent limit resulted 

in either repeating a test, or re-calibrating the 

instrument. Table 1 presents monthly average 

TCE concentration for treatment plant influent, 

treatment plant effluent, and the mid-calibration 

standard (6 ppb). 

The system experienced only two mechanical 

problems from January 2001 to July 2003. Both 

problems were attributed to malfunctioning 

valves. 

Maintenance involved a site visit once every 

three weeks to visually inspect the system and 

discuss system performance with the treatment 

plant operator. Other maintenance activities 

included refilling reagents and standards. 

Maintenance frequency was therefore a function 

of storage capacity and sampling frequency. 

Temperature was the main factor that affected 

performance. Varying temperatures sometimes 

made sample analysis invalid because the test 

temperature was different than the calibration 

temperature. As a result the instrument had to 

be re-calibrated several times. Other instances 

of failed tests were triggered by factors such as 

insufficient reagent, insufficient standard, and 

power surges. Tests were repeated in each case. 

Nevada Test Site

The system was tested at the Nevada Test Site 

on two different occasions. The first testing 

event spanned December 1, 2 and 3, 2003, and 

the second spanned March 16, 17, 18 and 19, 

2004. During these events the system 

underwent extensive laboratory and field 

testing. Since the implementation at the NTS 

was a supervised limited-duration operation, 

there was no need for system maintenance. 

The well-sampling module was not tested at the 

NTS. Samples to be analyzed were prepared 

and stored in a container. A peristaltic pump 

delivered the sample from the storage container 

to the analytical module. In order to simulate 

site-specific sample chemistry, some of the 

samples were prepared using groundwater from 

the Hanford site. All samples tested by the 

analytical module were also tested by an 

analytical laboratory. The average 

concentration of Cr-VI measured by the Burge 

system in 11 separate tests was 1,161 ppb. The 

standard deviation of the results was 2.1 

percent. The result of laboratory analysis for 

the same sample was 1,200 ppb. The sampling 

module operated autonomously using its own 

power supply unit. Power supply constituted a 

solar cell and a battery. The battery was sized 

to facilitate four days of continuous operation 

without solar recharging and was found to have 

more than sufficient capacity for uninterrupted 

operation. 
North Indian Bend Wash Site and Nevada Test Sites 

6-10 

Figure 4 

Hanford Field Implementation Conceptual Model 

Source: Burge Environmental 
North Indian Bend Wash Site and Nevada Test Sites 

6-11 

Table 1 

North Indian Bend Wash Analytical Results 

TCE Concentration Monthly Averages (October 2002-April 2003) 

Treatment Plant Effluent Treatment Plant Influent 

Burge System Laboratory 4 Burge System 1 Laboratory 2, 4

MidCalibration 3

Month Average Concentration (ppb) 

October <1 <0.5 109 112 6.6 

November <1 <0.5 98 118 6.3 

December <1 <0.5 106 113 5.9 

January <1 <0.5 105 106 5.2 

February <1 <0.5 111 132 5.5 

March <1 <0.5 110 138 6.2 

April <1 <0.5 106 122 6.2 

Note: 

TCE Trichloroethene 

ppb Parts per billion 

1

 Based on an average of at least 28 samples per month 

2

 Based on an average of 4 to 5 samples per month 

3

 Mid-calibration standard sample had 6 ppb TCE concentration 

4

 Laboratory analysis used EPA Method 8260B 

Source: Burge Environmental 

The system performed well at the NTS. The 

analytical module –as seen above- demonstrated 

precision and good agreement with the results of 

laboratory analysis. 

Cost [1, 4] 

Actual costs for implementation at the NIBW 

site and the NTS were not available. 

Approximate present day costs for various 

components of a Burge system are presented in 

the following table: 

Burge System Cost Estimate 

Item Cost Range 

Sample acquisition 

system 1 $500-$3,000

Base system (includes 

analytical system) 2 $10,000 – $12,000

Burge System Cost Estimate 

Item Cost Range 

Solar cells & batteries 

(sold without markup) 3 $1,500

Wireless modems 4 $3,200

TOTAL $10,000 – $19,700

Note: 

1

 Depends on whether sample acquisition is 

from a treatment process or a well 

2

 Depends on the type and number of sensors 

3

 Only for remote system where no power is 

available 

4

 Only for remote units where no phone line is 

available 

Source: David Hoffman, Burge Environmental, 

Inc. 
North Indian Bend Wash Site and Nevada Test Sites 

6-12 

The bare cost for purchase of a Burge system 

could therefore range from $10,000 to $19,700. 

Installation costs are sensitive to several factors 

and could vary. The main operation and 

maintenance cost items would include: 

(1) monthly fee for monitoring and data 

acquisition services provided by Burge 

Environmental; (2) monthly fee for a telephone 

line; (3) reagent and standard solution 

replacement; and (4) treatment media (activated 

carbon or granular ferric hydroxide) 

replacement. 

If the unit is leased instead of purchased, Burge 

Environmental estimates total cost for lease, 

operation, and services at $1,000 per month. 

Conclusions [1, 2] 

This section discusses the advantages and 

disadvantages of this technology, and its 

potential uses based on information provided by 

the vendor and one of its users. 

Although the Burge system uses the same 

method for colorimetric analysis of Cr-VI as the 

EPA-approved method, it is not yet recognized 

by the EPA as suitable for regulatory 

monitoring. Consequently, neither the TCE nor 

the Cr-VI analytical system can currently 

replace laboratory analysis. However at the 

NIBW site, the combined effect of the facility’s 

track record and the use of the Burge system 

resulted in reduced regulatory monitoring. 

The Burge system is currently more of an 

optimization and management tool than a 

regulatory tool. Its potential applications 

include treatment process monitoring, long term 

groundwater monitoring, and breakthrough 

monitoring in permeable reactive barriers. 

Though never used in this capacity, the Burge 

system, according to Burge Environmental, is 

amenable to integration into larger systems 

controlling facility operation. In such a role, the 

Burge system might be used to trigger 

independent alarms, or provide input to a 

supervisory control system. 

Customers have never sought autonomous 

control of the Burge system and have always 

required that it be operated and maintained by 

Burge Environmental. As a result, Burge 

Environmental provides remote oversight of 

system operation, and keeps system automation 

at a minimum. However, further automation 

can be incorporated upon request. For example, 

though the system does not currently flag results 

that do not meet testing standards it can be 

programmed to check for compliance of results 

with testing standards. Similarly, the system 

can be programmed to trigger an alarm or call 

an operator if an analytical result exceeds a 

compliance limit. 

According to Burge Environmental, system 

operation is easy to learn, and new users can be 

walked through and taught to operate the control 

program in about 15 minutes. System 

troubleshooting however is more complex and 

requires substantial knowledge of the Burge 

system. 

To reduce the amount of waste produced, the 

Burge system does not purge well volumes 

while sampling monitoring wells. Analysis 

usually requires 500 ml of sample for TCE and 

20 ml of sample for Cr-VI. According to Burge 

Environmental the sample is acquired at a rate 

that is not significant enough to produce 

drawdown in the well, or alter chemical 

equilibrium in a way that invalidates the sample 

as being representative of the groundwater in 

the formation. 

Mechanical problems experienced by the Burge 

system during previous field deployments have 

included air compressor malfunction, valve 

malfunction, and analytical system clogging due 

to excessive solids. The solids problem was 

solved by using an in-line filter. 
North Indian Bend Wash Site and Nevada Test Sites 

6-13 

The Burge system had minor problems with 

hardness-related scale formation at the NIBW 

site. Although the analytical system itself is 

protected by inline solids removal, the sample 

acquisition line needs to be monitored for scale 

when sampling water with high hardness. 

Monitoring durations for sample collection has 

been an effective method of checking for scale. 

According to Burge Environmental, none of 

their submerged sample acquisition systems 

have had problems with scale or biofouling. So 

far the longest duration of submergence for any 

of their system components has been 6 months. 

Temperature is the most important 

environmental variable influencing TCE 

analysis. The Cr-VI analytical system on the 

other hand is not as sensitive to temperature. 

Although possible, the Burge system does not 

adjust analytical results for temperature. To 

mitigate temperature effects, the Burge system 

incorporates sufficient engineering controls and 

testing strategies. Engineering controls include 

thermal insulation of outdoor units, space 

heating, construction below the frost line in 

extremely cold environments, and a 

thermometer to record temperatures during 

testing. The validity of a test rests on the 

proximity of temperature during testing to the 

temperature during calibration. Temperature 

variations can be minimized by constraining 

testing to a certain part of the day. 

Although the use of an optrode for headspace 

analysis of TCE negates turbidity-related 

problems, it inherits problems associated with 

vapor-phase analysis. Headspace analysis 

operates on the assumption that TCE vapor in 

the headspace is at equilibrium with its 

dissolved phase during sample analysis. This 

complicates analysis, as changes in sample 

chemistry can affect equilibration times. TCE 

analysis therefore requires greater diligence to 

detect potentially flawed results. The validity of 

questionable results has in the past been 

confirmed by test repetition. Consistency in 

results during repetitions is considered a strong 

indicator of equilibrium. According to the 

NIBW facility’s representative, the TCE 

analytical system seemed to perform better at 

high, than with low concentrations. 

Carbon dioxide was identified as a hurdle in 

TCE analysis. Groundwater samples bearing 

high carbonate concentrations when brought to 

the surface tend to re-equilibrate under the 

reduced hydrostatic pressure. This reequilibration sometimes results in the release of 

carbon dioxide into the head space. According 

to Burge Environmental, carbon dioxide was 

found to inhibit the migration of TCE across the 

optrode’s semi-permeable membrane. 

The shelf life of reagents used in the Burge 

system was cause for concern during early 

stages of development. However, the TCE 

system now stores components with indefinite 

shelf lives separately and uses them to prepare 

fresh reagent prior to sample analysis. The 

reagent used in the Cr-VI system on the other 

hand has a finite shelf life. 

According to Burge Environmental, none of the 

analytical modules have experienced problems 

with method contamination. Method 

contamination can theoretically result from 

leakage of standard solution into the sample, or 

residual contamination from a previous analysis. 

According to Burge Environmental, the Burge 

system has sufficient controls in place – 

including long flushing cycles- to prevent this 

from occurring. 

Although not an issue at the sites in this case 

study, it is important to note that the presence of 

cosolvents or surfactants in an aqueous sample 

can affect the measurement of TCE. Since both 

co-solvents and surfactants affect the 

partitioning of TCE into the vapor phase, it is 

possible that the Burge system would 

underestimate TCE concentration when such 

compounds are present in the water sample. 
North Indian Bend Wash Site and Nevada Test Sites 

6-14 

The Burge system has not yet been able to 

resolve the problem posed by trihalomethanes 

(THM) in the analysis of the TCE. The TCE 

optrode is unable to distinguish between THMs 

and TCE. However, since THMs in the 

environment have usually been related to 

chlorination activities (such as disinfection), this 

has not been much cause for concern. At the 

NIBW site, chlorination of some of the wells to 

discourage biological growth resulted in 

elevated concentrations of THMs in the 

treatment plant influent. The Burge system 

detected this as elevated concentrations (1 to 2 

ppb) of TCE. 

At the end of their current field deployments the 

system will undergo testing for compliance with 

American Society of Testing and Materials 

(ASTM) requirements for analytical systems. 

The standards to be met will be the similar to 

those required of EPA Method 8021. This will 

be the first in a series of steps towards 

recognition by the EPA as a technology capable 

of regulatory monitoring. 

Contact Information 

North Indian Bend Wash Site 

City of Scottsdale 

Mr. Mark Seamans 

Phone: (480) 312-0390 

Email: mseamans@ci.scottsdale.az.us

Nevada Test Site 

Bechtel Laboratories 

AMSI Program 

Senior Scientist 

Dr. Rick Venedam 

Phone: (702) 295-5487 

Email: venedarj@nv.doe.gov

Federal Oversight Agency - North Indian 

Bend Wash Site 

EPA Region 9 

Remedial Project Manager 

Ms. Melissa Pennington 

Phone: (415) 972-3153 

Email: pennington.melissa@epamail.epa.gov

State Oversight Agency - North Indian Bend 

Wash Site 

Arizona Department of Environmental Quality 

State Project Manager 

Mr. William DePaul 

Phone: (602) 771-4654 

Email: wad@ev.state.az.us

Sampling and Analysis Technology Vendor 

Burge Environmental 

Mr. David Hoffman 

6100 South Maple Avenue, Suite 114 

Tempe, AZ 85283 

Phone: (480) 968-5141 

Email: burgeenv@globalcrossing.net

References 

The following references were used in the 

preparation of this report: 

1. Telephone Conversation. David Hoffman, 

Burge Environmental, with Chitranjan 

Christian, Tetra Tech EM, Inc., Response to 

Questions on the Burge Sampling and 

Analysis System. June 18 - 22, 29, July 9, 

23, August 6 and 23, 2004. 

2. Telephone Conversation. Mark Seaman, 

City of Scottsdale, with Chitranjan 

Christian, Tetra Tech EM Inc., Response to 

Questions on Burge System Operation at the 

North Indian Bend Wash site. June 29, 

2004. 

3. E-mail from David Hoffman, Burge 

Environmental, to Chitranjan Christian, 

Tetra Tech EM Inc., Response to Questions 

on the Burge System. June 28, 2004. 
North Indian Bend Wash Site and Nevada Test Sites 

6-15 

4. E-mail from David Hoffman, Burge 

Environmental, to Chitranjan Christian, 

Tetra Tech EM Inc., Response to Questions 

on Cost. July 12, 2004. 

5. Burge, Scott and Hoffman, David. 2003. 

“Automated Monitoring of Chloroform and 

Trichloroethylene Using a Halocarbon 

Specific Optrode.” American Laboratory. 

November. 

6. Burge Environmental. 2004. Cr(VI) 

Detection System. Results of the 

Laboratory and Field Tests at Nevada Test 

Site. April. 

7. Worldwide web resource. Burge 

Environmental. 

http://www.burgenv.com/about.htm. 

Optrode Background. 

8. Worldwide web resource. Burge 

Environmental. 

http://www.burgenv.com/case.htm#doe_ 

monitoring. DOE Phase I SBIR Summary. 

Ground water monitoring system for 

multiple sensors. 

9. Worldwide web resource. Burge 

Environmental. 

http://www.burgenv.com/case_indianbend_

wash.htm. North Indian Bend Wash 

Superfund Site Case Study. 

10. Worldwide web resource. Burge 

Environmental. 

http://www.burgenv.com/case_edwards_afb.

htm. Edwards Air Force Base Case Study. 

Acknowledgements 

This report was prepared for the U.S. 

Environmental Protection Agency’s Office of 

Solid Waste and Emergency Response, Office 

of Superfund Remediation and Technology 

Innovation. Assistance was provided by Tetra 

Tech EM Inc. under EPA Contract No. 

68-W-02-034. 

Appendix 7 

Automation Technology Case Study 

Supervisory Control and Data Acquisition Using Programmable Logic 

Controllers at the Sprague Road Superfund Site 

Automation Technology Case Study 

Supervisory Control and Data Acquisition Using Programmable Logic Controllers 

at the Sprague Road Superfund Site

7-1 

Summary Information [1, 2, 3, 4, 5, 6, 8, 9] 

Programmable logic controllers (PLC) are used 

to automate processes. Before the 

commercialization of PLC technology, process 

automation was achieved by hard-wired relays 

and timers, also called basic relay logic (BRL). 

Any change in process operation required 

rewiring of the control circuits. PLC technology 

changed the emphasis in automation from 

hardware to software. Though skilled 

electricians were still required to integrate the 

PLC into the control system, the logic that drove 

process automation was embedded in computer 

programs as opposed to hard-wired circuits. 

PLC technology is being used at the Sprague 

Road Ground Water Plume Superfund (Sprague 

Road) site to operate the remediation system. 

The site is located in Ector County outside the 

northwest city limits of Odessa, Texas, and 

consists of three inactive or abandoned metal 

plating facilities located within 1 mile of each 

other: Machine & Casting, Inc. (M&C), Leigh 

Metals (LM), and National Chromium 

Corporation (NC). 

Historical operations at those facilities resulted 

in contamination of the groundwater with 

hexavalent chromium. The contaminant plumes 

beneath each facility are physically distinct, but 

due to their proximity the remedial approach 

was to address the three facilities as one single 

site. The selected remedy for the Sprague Road 

site was groundwater extraction, treatment (ion 

exchange) and re-injection. 

The system was designed for continuous 

operation with minimal human intervention, and 

continuous centralized monitoring over the 

anticipated ten-year remediation period. This is 

facilitated by a supervisory control and data 

acquisition (SCADA) system. 

PLC technology is used at this site to facilitate 

supervisory control over the extraction, 

treatment and re-injection system. However, the 

control system encompasses much more than 

just the PLC. Sensory equipment, actuators, and 

the PLC form the bone structure of the control 

system. Sensors are the “eyes,” of the control 

system, and provide the PLC with information 

on the status of the system. The PLC is the 

decision-making unit of the control system and 

uses its programmed instructions to processes 

sensory information ultimately leading to a 

response. The response may be: to do nothing; 

to command an actuator to start an associated 

device; or to command an actuator to stop an 

associated device. 

Sensors at this site include liquid level and 

pressure sensing devices. Actuators include 

switchgears and hand-off-auto (HOA) switches 

that start and shut down pumps, or open and 

close solenoid valves. All pumps at this site 

have manual overrides, that is, the “hand,” 

mode. An actuator will respond to PLC 

commands only when the HOA switch is placed 

in the “auto,” mode. 

The data acquisition (DA) system is comprised 

of a network of three personal computers (PC) 

that interface with the PLC at each of the three 

sites. A program called Lookout installed on 

each of the PCs accomplishes the “data 

acquisition,” from the PLCs and depicts the 

information on user interface screens. Lookout 

is essentially a window into the sensory 

information available to the PLC. 

The remediation and automation system has 

been in operation since September 2003, and 
Sprague Road Superfund Site, Odessa, Texas 

7-2 

there have been no PLC breakdowns as of this 

case study (Fall 2004). The DA system 

malfunctioned in April 2004. The cause was 

software-related, but the exact nature of it was 

never determined. The SCADA system was 

operational within two weeks of the observed 

malfunction. The time taken to implement the 

solution was small compared to that consumed 

by administrative tasks and logistical hurdles. 

The remediation system itself functioned 

normally during this time. 

Technology Description [2, 3, 6] 

PLCs, also referred to as programmable 

controllers, are in the computer family. They 

are most commonly used in commercial and 

industrial applications. Figure 1 shows the PLC 

used at the Sprague Road site. 

A PLC monitors inputs, makes decisions based 

on its program, and controls outputs to automate 

a process or machine. PLCs consist of input 

modules or points, a Central Processing Unit 

(CPU), and output modules or points. An input 

accepts a variety of digital or analog signals 

from various field devices (sensors) and 

converts them into a logic signal that can be 

used by the CPU. The CPU makes decisions 

and executes control instructions based on 

program instructions in memory. Output 

modules convert control instructions from the 

CPU into a digital or analog signal that can be 

used to control various field devices (actuators). 

A programming device is used to input the 

desired instructions. These instructions 

determine what the PLC will do for a specific 

input. An operator interface device allows new 

control parameters to be entered. 

DA systems go hand-in-hand with PLC 

technology. A DA system refers to DA 

software and the computer system hosting the 

software. DA software can be loaded on any 

personal computer (PC) that meets the 

software’s minimum requirements. Some 

examples of DA system software are: 

(1) Lookout developed by National Instruments; 

(2) InTouch developed by Wonderwear; 

(3) Intellutions developed by GE Fanuc; 

(4) Cimplicity developed by GE Fanuc; and 

(5) Iconics developed by Iconics Inc. 

The DA system interfaces with the PLC and 

continuously gathers real-time process 

information. The DA system uses this 

information to update graphical or numerical 

depictions of system status on the user interface 

screen. DA systems can be programmed to 

maintain electronic records of desired process 

data at any desired interval, and generate 

reports. The total amount of data that can be 

recorded would be limited only by the host 

computer’s hard disk storage space. The DA 

system does not control any components of the 

remediation system. 

Site Information [1, 3, 4, 5, 8, 9] 

The site is located in Ector County outside the 

northwest city limits of Odessa, Texas, and 

consists of three inactive or abandoned metal 

plating facilities (M&C, LM and NC) located 

within 1 mile of each other. 

Past waste management practices at those 

facilities led to contamination of the 

groundwater with hexavalent chromium. The 

plumes associated with each facility were 

physically distinct, but the three facilities were 

collectively termed the Sprague Road Ground 

Water Plume Superfund (Sprague Road) site. 

The selected remedy was a comprehensive 

approach for all three facilities. It entailed 

extraction of contaminated groundwater through 

three localized networks, treatment by an ion 

exchange process at LM, followed by 

distribution of treated water for re-injection at 

the three facilities. 
Sprague Road Superfund Site, Odessa, Texas 

7-3 

Figure 1 

Control Cabinet Housing PLC 

Remediation System 

A network of recovery wells (7 at M&C, 27 at 

LM, and 23 at NC) formed the ground water 

recovery system. Recovery systems at M&C 

and NC each pumped contaminated ground 

water into local collection tanks. Pumps 

transferred water from these collection tanks to 

the treatment system. The recovery wells at LM 

pumped water directly to the treatment system. 

The treatment system was located at LM and 

included a surge tank, a pump tank, pumps, bag 

filters, and an ion exchange system. The ion 

exchange system consisted of two banks, each 

consisting of five resin tanks. Resin tanks 

within a bank were connected in parallel, and 

the two banks were connected in series. At any 

given time one bank acted as the worker (or 

primary) resin, and the other acted as the 

polisher (or secondary) 

The injection system consisted of three separate 

networks of injection wells (8 at M&C, 8 at LM, 

and 27 at NC), and a vadose zone flushing 

system at NC. Injection pumps in the treatment 

building at LM delivered treated water to each 

of these networks. 

PLC with CPU, input, 

output, power, interface, 

and communication 

modules 
Sprague Road Superfund Site, Odessa, Texas 

7-4 

System monitoring data along with groundwater 

monitoring, and hydrogeological modeling was 

used to periodically modify operation of the 

remediation system to address the current state 

of the plume in the most efficient manner. 

The process flow diagram of the remediation 

system is shown in Figure 2. 

Control System 

System control was shared by three local control 

centers, one each at M&C, LM, and NC. The 

three control centers communicated through 

telemetry making real time data globally 

available. However, field devices associated 

with a given facility could only be actuated by a 

local control center. The M&C and NC control 

centers had supervisory control over extraction 

pumps, injection well shutoff valves, and 

transfer pumps at their respective facilities. The 

LM control center performed similar functions 

at the LM facility, except that it also controlled 

operation of the treatment system, and injection 

pumps. The control centers were prefabricated 

air-conditioned metal buildings that contained a 

motor control center, panelboards, a control 

cabinet housing the PLC, and a desktop 

computer that displayed real time system 

information and recorded operating data. 

The PLC at each facility was a SIMATIC S7-

300 manufactured by Siemens. The PLC’s 

central processing unit was a CPU-315-2-DPnew. The PLC had digital input modules – each 

capable of receiving 16 inputs- as well as analog 

input modules – each capable of receiving 8 

inputs. The number of modules used at a given 

control center depended on the number of local 

field sensors providing input. The PLC also had 

digital output modules, each permitting output 

to 16 different devices. The number of output 

modules depended on the number of field 

device actuators to be controlled by the PLC. 

The PLC had an interface module that permitted 

interface with other devices to receive 

programming or transfer system status 

information. 

Each PLC had a communication module. The 

communication module had its own processor 

dedicated to information exchange. This 

module facilitated communication between 

PLCs, and with the internet through various 

available protocols. At this site the three PLCs 

used their communication modules to 

communicate with each other through a wireless 

industrial Ethernet link. A PLC at M&C was 

therefore able to recognize a high level in a tank 

at LM and respond by shutting down the 

appropriate transfer pump at M&C. 

Each PLC contained custom- programmed 

instructions on the appropriate response to be 

taken based on the input received from sensory 

devices. For example if the PLC at M&C 

received a low level signal from the level sensor 

in an extraction well, it would respond with an 

output signal to the corresponding pump 

actuator telling it to shut down that pump. 

Some of the functions performed by the PLC 

included: 

(1) Start and shut down of groundwater 

extraction pumps based on the water 

levels in the extraction wells. 

(2) Start and shut down of transfer pumps 

based on the water levels in receiving 

and supplying tanks. 

(3) Opening and closing of injection well 

valves based on the water levels in the 

injection wells. 

(4) Start and shut down of transfer pumps 

based on the presence or absence of 

radio communication between facilities. 

(5) Shut down of ion exchange system feed 

pumps based on the differential pressure 

across the bag filters. 

(6) Complete system shutdown during alarm 

conditions such as high-high (above 

high), or low-low (below low) levels in 

tanks. 
Sprague Road S

7-5 

Figure 2 

Process Flow Diagram 
Sprague Road Superfund Site, Odessa, Texas 

7-6 

Data Acquisition System 

The DA system at Sprague Road consisted of 

three desktop computers – one at each facility – 

running the Enterprise version of a DA software 

(Lookout) developed by National Instruments. 

This version of Lookout was necessary for the 

development of applications facilitating process 

monitoring through the internet. Lookout was 

used to develop the facility-specific applications 

that performed the required DA functions at 

those facilities. The computers hosting the DA 

software were all Dell PCs with 2.0 gigahertz 

Pentium 4 processors. Each PC was connected 

to its local PLC through a communication port. 

The DA software retrieved real-time system 

status information from the PLC and graphically 

depicted this information on the various userinterface screens. 

Some of the functions performed by the DA 

system included: 

(1) Displaying operating status (on or off) of 

extraction, transfer, and injection system 

pumps. 

(2) Displaying water levels in tanks as a 

percentage of total volume. 

(3) Displaying water level status (high or low) 

in injection and recovery wells. 

(4) Displaying injection well valve status 

(open or closed). 

(5) Computing and displaying flow rates 

(gallons per minute) through each 

extraction well, injection well, and transfer 

pump. 

(6) Displaying fluid pressure at various nodes. 

(7) Displaying presence or absence of radio 

communication between facilities. 

(8) Recording minimum, average, and 

maximum flow rates. 

(9) Recording totalized flow. 

(10) Summarizing data and automatically 

printing daily, weekly, and monthly 

reports. 

The DA system is in the process of being 

improved to provide internet access to real-time 

system-status information. When this update 

has been made, authorized users will be able to 

access the system’s website from anywhere in 

the world to view the various user interface 

screens showing real-time process information. 

System Operation 

The system has been in operation since 

September 2003. As of May 16, 2004, 

97,160,690 gallons of water were recovered, 

treated and re-injected. 

The only maintenance associated with the 

supervisory control system was the replacement 

of PLC input/output fuses. There had been no 

PLC malfunctions since system startup. The 

DA system malfunctioned in April 2004. The 

cause of the malfunction was never determined, 

but it apparently resulted in corruption of the 

DA application. The problem was fixed by 

updating the Windows operating system, 

installing the latest Windows service packs, then 

re-installing the DA application. Since the DA 

system played no role in supervisory control, the 

remediation system functioned normally even 

when the DA system was inoperable. 

The flexibility offered by PLC technology was 

evidenced during the initial stages of system 

operation. The radio antennae used for remote 

communication between the three PLCs 

occasionally lost contact with each other. When 

this occurred there was the potential for transfer 

pumps at M&C and NC to flood tanks at LM. 

To facilitate safe system operation, the 

automation logic had to be modified. PLC 

programmers were able to easily change the 

program to cause transfer pumps at M&C and 

NC to shut down when communication was lost 

with LM. 
Sprague Road Superfund Site, Odessa, Texas 

7-7 

Cost [6, 7, 8] 

The total cost for purchase and installation of 

the control system at Sprague Road was 

$415,000. This included labor and materials 

costs for the motor control centers, panelboards, 

control cabinets, sensors, DA system, PLCs and 

peripherals. The actual portion of this cost that 

was spent on PLC and DA system purchase and 

installation was not available. However, the 

table below provides the estimated cost of PLC 

hardware at one of the facilities (LM) at 

Sprague Road. The unit price for each 

component is the manufacturer’s listed price. 

PLC (SIMATIC S7-300) COST ESTIMATE 

Item Qty

Unit 

Price 

($) 

Subtotal

($) 

CPU 1 1,760 1,760

Digital input module 5 198 990

Digital output 

modules 3 275 825

Analog input 

module 1 765 765

Interface module 1 230 230

Communications 

processor 1 1,780 1,780

Power supply 

module 1 365 365

TOTAL1 6,715

Note: 

1

 Cost does not include installation 

Unit Price Source: Siemens Energy and 

Automation 

Lessons Learned [3, 8] 

According to the lead agency’s contractor, the 

following were lessons learned with respect to 

construction of the SCADA system at the 

Sprague Road site. 

The bid should require that all project submittals 

be approved by the prime contractor prior to 

mobilization by the subcontractors. The 

subcontractors must bear the burden of meeting 

every requirement of the submittal process, 

including accuracy, relevance, detail, 

completeness and timely submission. The sheer 

volume of submittals associated with such 

projects requires the above measures to ensure 

strict compliance with design specifications, and 

timely approval by the engineer. 

Subcontracts for this type of work should be 

“performance-based.” This implies payment for 

services based on the achievement of project 

milestones as opposed to payment for time and 

effort. Subcontractors would therefore be 

compelled to complete all tasks on schedule in 

order to maintain their profit margins. 

The inclusion of a professional Electrical 

Engineer in the design, procurement and 

oversight team proved to be absolutely critical 

to the successful installation of the SCADA 

system. 

After about a year of operation, it was suggested 

that the project could have benefited from 

certain SCADA system functions that were not 

believed to be essential during system design. 

One such function was for the system to contact 

the plant operator via telephone or pager if a 

problem occurred. Another was remote access 

to the SCADA system via direct dial that would 

allow programmers to fix DA software glitches, 

or modify the SCADA program from remote 

locations. This was thought to be potentially 

more cost effective than having programmers 

travel to the site to fix problems. 
Sprague Road Superfund Site, Odessa, Texas 

7-8 

In general, it is important to remember that the 

overall functionality of the SCADA system is 

only as good as the information being provided 

to it. The selection, installation, and 

maintenance of the sensors that communicate 

with the PLC are therefore just as important as 

the PLC itself. 

Conclusions [3, 6] 

Information in this section was derived from 

conversations with the project Electrical 

Engineer. 

The complexity and scale of the pump and treat 

system at Sprague Road makes manual 

operation impractical. This section uses BRL 

technology as a benchmark to discuss system 

automation using PLC technology. 

The main advantage of PLC technology is its 

flexibility. System automation is based in 

software as opposed to hard wiring in the older 

basic relay logic (BRL) technology. PLC 

technology makes it possible to change the 

operating logic of the system merely by 

modifying the programmed instructions. On the 

other hand changing the operating logic of a 

system using BRL would require re-wiring and 

the addition of relays and interlocks. This is a 

tedious and complex task. 

PLC technology requires a lot less space than 

BRL technology. For example, if BRL were 

used at Sprague Road, the control cabinet could 

be at least twice its current size. 

PLC technology is relatively inexpensive 

compared to BRL. For example a $1,500 

investment in a PLC would purchase a lot more 

process control power than BRL technology of 

equal cost. 

A drawback to using PLC technology is the high 

level of skill and sophistication required of 

those who implement this technology. PLCs are 

programmed by educated and skilled computer 

programmers. In addition, various PLC 

manufacturers market their own PLC 

programming software. Even though 

programming in different software 

environments may lack conceptual differences, 

there often are differences in method. Therefore 

an expert programmer in one software 

environment may not be as skilled in another. 

This somewhat restricts the options available 

when looking for programmers after a specific 

PLC has been selected. On the other hand, BRL 

does not require the same level of skill. Any 

skilled electrician experienced with control 

panel wiring would be able to interpret design 

drawings to efficiently implement BRL 

technology irrespective of who the components 

are manufactured by. 

Another drawback to PLC technology is 

centralized control. If the PLC breaks down, the 

entire process shuts down. A damaged relay in 

BRL on the other hand only leads to shut down 

of the component controlled by it. For example 

if a groundwater extraction pump were 

controlled by BRL, break down of a relay would 

only affect the one pump, and the rest of the 

system would function normally. 

PLC technology is weaker than BRL in its 

weatherability. PLCs require greater 

environmental controls than BRL to function 

normally. 

Generally system reliability can be increased by 

blending PLC and BRL technology. However, 

this type of blend may not be required for a 

system such as that used as Sprague Road. This 

is because there is no noticeable consequence to 

system shut down for a few days or even a week 

at a time. Critical systems on the other hand 

would benefit from backup automation circuitry 

in the event of PLC failure. One method uses 

parallel processing to add reliability to the 

control system. This essentially means two 

PLCs are simultaneously used to control the 
Sprague Road Superfund Site, Odessa, Texas 

7-9 

same process. One is the primary and the other 

serves as a backup. The backup PLC takes over 

when the primary fails. The two techniques 

used for this type of redundancy are called “hot 

backup,” and “fault tolerant backup.” Other 

than the few inherent software-depended 

operational differences, these terms for 

redundancy techniques can be used 

interchangeably. The system at Sprague Road is 

not critical enough to require such measures. 

Contact Information 

Lead Agency: 

EPA Region 6 

Remedial Project Manager 

Mr. Vincent Malott 

Phone: (214) 665-8313 

Email: malott.vincent@epa.gov

State Agency: 

Texas Commission on Environmental Quality 

Project Manager 

Mr. Subhash Pal 

Phone: (512) 239-4513 

Email: spal@tceq.state.tx.us

Lead Agency Contractor: 

Tetra Tech EM, Inc. 

Project Manager 

Mr. Keith Westberry 

Phone: (214) 740-2034 

Email: keith.westberry@ttemi.com

Project Electrical Engineer: 

Frank J. Dillard and Associates 

Mr. Frank Dillard, P.E. 

Phone: (713) 526-5054 

Email: dillard1@netropolis.net

PLC Technology Manufacturer: 

Siemens Energy and Automation 

Mrs. Diana Bowman 

Phone: (423) 262-2510 

Email: diana.bowman@siemens.com

References 

The following references were used in the 

preparation of this report: 

1. EPA, 2000. Superfund Record of Decision. 

Sprague Road Ground Water Plume Site, 

Ector County, Texas. September 2000. 

2. Siemens Energy & Automation, Inc. 

Siemens Technical Education Program 

(STEP) 2000 series. Basics of PLCs. 

3. Telephone Conversation. Terry Nauman, 

Wunderlich-Malec, with Chitranjan 

Christian, Tetra Tech EM Inc., Sprague 

Road Response to Questions on Data 

Acquisition System. May 12, 2004. 

4. Telephone Conversation. Andrew Long, 

Laguna Construction Company, with 

Chitranjan Christian, Tetra Tech EM Inc., 

Sprague Road Response to Questions on 

Data Acquisition System. May 12, 2004. 

5. Telephone Conversation. Ronald McClung, 

Tetra Tech EM Inc., with Chitranjan 

Christian, Tetra Tech EM Inc., Sprague 

Road Response to Questions on Supervisory 

Control and Data Acquisition System. May 

12, and May 17, 2004. 

6. Telephone Conversation. Frank Dillard, 

Frank J. Dillard and Associates, with 

Chitranjan Christian, Tetra Tech EM Inc., 

Response to Questions on Supervisory 

Control and Data Acquisition System. May 

14, and May 17, 2004. 

7. Telephone Conversation. Diana Bowman, 

Siemens Energy and Automation, with 

Chitranjan Christian, Tetra Tech EM Inc., 

Response to Questions on Cost of PLC 

Components. May 17, 2004 

8. Tetra Tech EM, Inc., 2003. Remedial 

Action Report. Sprague Road Ground 

Water Plume Superfund Site, Odessa, Ector 

County, Texas. September 2003. 
Sprague Road Superfund Site, Odessa, Texas 

7-10 

9. Tetra Tech EM, Inc., 2004. Ground Water 

Recovery, Treatment, and Injection System 

Operation and Maintenance Plan. Sprague 

Road Ground Water Plume Superfund Site, 

Odessa, Ector County, Texas. June. 

Acknowledgements 

This report was prepared for the U.S. 

Environmental Protection Agency’s Office of 

Solid Waste and Emergency Response, Office 

of Superfund Remediation and Technology 

Innovation. Assistance was provided by Tetra 

Tech EM Inc. under EPA Contract 

No. 68-W-02-034.