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4-29

pentachlorophenol. Operations included wood storage and pole peeling, and a

treatment plant with pressure vessels, storage tanks, and drip racks. 

The site is relatively flat with elevations ranging from 43.2 feet to 53.8 feet above

mean sea level. The water table occurs at depths ranging from approximately 2 to

5 feet bgs. Surficial soils are part of the Beaumont Formation, which is composed

of clays, silts, and silty sands. The depositional environment was fluvial and

deltaic, and the deposits can be characterized as stream channel, point bar, mud

flat, and coastal marsh. The majority of the soils are composed of continuous and

noncontinuous clay to silty clay layers with two principal sand to silty-sand layers

located at average depths of 15 feet and 30 feet bgs. The various clay layers are

known to be fractured to various degrees. The site is intersected by at least three

and possibly four relatively minor surface faults with displacements of 2 to 5 feet.

At least one of these faults is known to be active.

The site was divided into separate soil and groundwater operable units during the

feasibility study. The soil operable unit consists of approximately 10,000 cubic

yards of contaminated soil that was excavated and stockpiled into a

bioremediation cell. The groundwater operable unit was addressed through a

pump-and-treat system consisting of 19 wells, pumps, a treatment plant, and three

groundwater infiltration galleries. The pump-and-treat system operated at an

average flow rate of 12 gallons per minute for 24 months. It removed

approximately 7,000 gallons of DNAPL out of approximately 11,500,000 total

gallons of extracted water. The pump-and-treat system was subsequently

discontinued due to a drastic decline in the amount of DNAPL recovered.

Previous information sources of subsurface data consisted mainly of a limited

number of boring logs and soil samples. In order to gather more information on

the horizontal and vertical extent of DNAPL that exists in the subsurface and to

refine the site conceptual model, the CPT/ROSTTM technology was selected as the

most cost effective option for data collection. A total of 101 pushes were completed

at an average depth of approximately 45 feet for data collection. The data from the

cone penetrometer portion of the tool, which is displayed similar to well logs,

were used in the construction of isopach and structure maps and fence diagrams

to aid in the characterization of the subsurface. Based on an extensive correlation

of the pushes, it was determined that the tool’s lithologic determinations were

internally consistent and correlated well with the existing data. Also, due to the

greatly increased number of data points, two and possibly three additional faults

were located.

The ROSTTM data, like that from the CPT portion of the tool, was provided in a

format similar to a well log with total fluorescence graphed versus depth.

Windows of the “waveform,” which consisted of a graphical presentation of the

breakdown of the total fluorescence into four wavelengths, were also presented on

this log for various peak fluorescence values. This enabled a quick identification of

the type of hydrocarbon contamination present at a given depth. Additionally,

another log was provided which displayed the total fluorescence signature and a 
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4-30

continuous breakdown of this signal into the four component wavelengths, which

allowed more detailed analyses of the different types of hydrocarbons.

The data from the ROSTTM portion of the tool was used to gain an understanding of

the vertical and horizontal extent of creosote contamination, and the relative

concentration of the creosote contamination in three dimensions. Due to the tool’s

ability to detect a wide range of hydrocarbon contamination, other sources of

hydrocarbon, such as diesel, gasoline, and oil, were also discovered. Interestingly,

four of the pushes, which are located adjacent to a known pipeline easement

exhibit a relatively strong oil-like signature at shallow depths. It is postulated that

this represents leaks in the pipeline. Because the focus of the investigation was

creosote, these signals were filtered out from the total fluorescence signal by

running the data through a FORTRAN program written specifically for that

purpose. Refinement of this filtering methodology, although effective, is currently

somewhat primitive and is undergoing further development.

When creosote was encountered, it was usually found at several depths within a

given push. The tops of the creosote occurrences were tabulated by depth and by

whether they occurred in a sand or a clay. It was determined that almost all of the

creosote hits occurred within the two sands zones, with the lower sand zone

registering the majority of the hits. The deepest creosote contamination that was

observed occurred at a depth of approximately 50 feet bgs. Based on these data,

the remediation strategy of the site has re-focused on the lower sand zone.

CPT/ROSTTM has proven cost-effective for the determination of lithology and the

delineation of creosote contamination at the North Cavalcade Superfund site. Also,

based on its performance at the site, its effectiveness appears to extend to the

identification of other less dense hydrocarbon signatures. The CPT/ROSTTM offers

advantages in both price and the rapidity with which the data can be acquired.

This technology is being evaluated for use at two additional creosote sites.

&RQWDFW

Joe Kordzi, USEPA Region VI, 214-665-7186

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Energy dispersive XRF is used to analyze trace metals (e.g., mercury, chromium,

lead, cadmium, copper, nickel, and arsenic) in soils, sludges, and groundwater.

The technique uses x-rays (high-energy electromagnetic radiation) to penetrate the

soil matrix and excite metals. Radiation emitted from fluorescence of the metals is

measured to quantify the concentrations of metals present in the soil.

XRF analyzers yield semiquantitative results with detection from a few to a few

hundred parts per million (ppm) depending on the soil matrix and the metals

being analyzed. XRF is generally considered a screening tool because of its

relatively high reporting limits. The XRF analyzer is easily transported to the field

and very fast (reportedly 5 to 40 samples per hour can be analyzed depending on

sample preparation and measurement times).
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4-31

2SHUDWLRQDO &RQVLGHUDWLRQV

Several manufacturers supply XRF analyzers including TN Spectrace (the

Spectrace 9000) and Metorex Inc. (the HAZ-MET 920, HAZ-MET 940, and the XMET series). XRF analyzers contain a radioactive source that may require special

handling. Although XRF methods do not require soil samples to be digested (as do

conventional analytical methods), some sample preparation (e.g., drying and

homogenization) may be required. XRF analyzers are susceptible to interference

from water, petroleum, and soil heterogeneity. Nontechnical personnel may

operate XRF analyzers with minimal training.

$SSOLFDWLRQV DQG &RVW

XRF methods are mostly used as screening tools for trace metals. Because of their

relatively high detection limits, these methods are best suited to site

characterizations requiring metal screening at relatively high levels.

The cost to rent an XRF analyzer is approximately $2,000/week. A comparative

conventional analytical method (inductively coupled plasma) is 30 to 40 percent

more expensive and requires that samples be digested. 

%HQHILWV

 No IDWs generated

 Easily transportable to the field

 Does not require digestion of soil samples

/LPLWDWLRQV

 Sample preparation required (e.g., drying and homogenization)

 Poor detection limits on some metals, especially as a result of matrix

interference

 Limited penetration depth

 Not well suited to measure liquid samples

 Radioactive source in the analyzer

&RQWDFWV

Jim Moore, TN Spectrace, (512) 388-9100, x208

James R. Pasmore, Metorex Inc., (541) 385-6748 or (800) 229-9209

 &RORULPHWULF )LHOG 7HVW .LWV

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Colorimetric field test kits are used to detect the presence or determine the

concentrations of contaminants in soil and water. Because detection limits are

generally in the low ppm range, field test kits are primarily used as a screening

tool for site characterization. Colorimetric field test kits may be used to screen for a

broad range of inorganic parameters, total hydrocarbons, selected organic

compounds, and selected explosive compounds. 
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4-32

Colorimetry is generally performed by mixing reagents in specified amounts with

the water or soil sample to be tested and observing the color change in the

solution. The intensity of the color change is an indicator of the concentration of

the chemical of interest. The color change is either observed visually (compared

with color charts) or electronically with a handheld colorimeter. 

It is important to understand the limitations of the specific test kit being used,

including the chemicals it can detect. Some kits are susceptible to interference from

both naturally occurring organic matter and other co-contaminants.

Specific vendor technologies discussed below include Handby, PetroFLAGTM,

PetroSenseTM, and Quick Testr field test kits. Handby field test kits are generally

used to screen for petroleum-derived substances in soil and water. Results are

quantified by comparison to substance-specific calibration photographs. Handby

kits are also available to quantify PAHs. The PetroFLAGTM test kit for soil is

primarily used to detect petroleum hydrocarbons with detection limits ranging

from 20 to 2,000 ppm. The PetroFLAGTM test kit can use either a conservative

calibration to estimate total hydrocarbons present or it can be calibrated to specific

hydrocarbons. The Dexsil Corporation, which markets the PetroFLAGTM test kit,

indicates that PAHs can be measured using the technology. The PetroSenseTM

PHA-100 Petroleum Hydrocarbon Analyzer (PetroSenseTM), marketed by FCI

Environmental Inc., combines fiber optic chemical sensor technology and digital

electronics to measure the vapor concentration of TPHs in soil and benzene,

toluene, ethylbenzene, and xylenes (BTEX) in water. Envirol Inc., markets Quick

Testr field test kits, which can estimate total cPAHs in soil. Quantitative results are

obtained by establishing a site-specific correlation between test kit and laboratory

results.

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The Handby Kit is susceptible to positive interference if extremely large quantities

of organic matter (e.g., peat) are present. The PetroFLAGTM is sensitive to a wide

range of hydrocarbons including natural waxes and oils. For both the Handby Kit

and PetroFLAGTM, the user must test background samples and calibrate the

equipment to detect only foreign (i.e., not naturally occurring) substances.

The Handby Kit analyzes a sample in less than 10 minutes; detection limits

typically range from 1 to 1,000 ppm for soil and 0.1 to 20 ppm for water.

Approximately 25 samples per hour can analyzed using the PetroFLAGTM field test

kit. The PetroSenseTM analyzer is very sensitive to turbidity and temperature in

water samples. Preconditioning and calibration for the PetroSenseTM take

approximately 30 minutes; sample analysis takes less than 10 minutes. The

PetroSenseTM probe may be lowered directly into a borehole for analyzing in situ

groundwater. The Quick Testr field test kit for cPAHs in soil reportedly takes less

than 20 minutes per sample to analyze. The Quick Testr must be used in

temperatures ranging from 40 to 110(F.

$SSOLFDWLRQV DQG &RVW

Test kits are most useful as screening tools. Colorimetric test kits are available for
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4-33

different media and contaminants. Prices vary with the type of kit. Most test kits

include some of the following equipment: hand-held analyzer, glassware,

reagents, and scales. The more expensive units use electronic colorimeters, and the

less expensive units usually use visual colorimetric matches. Handby kits for soil

or groundwater cost about $1,300 including enough reagent for 30 samples, and

$550 for an additional 30 samples. The PetroFLAGTM kit for soil costs about $800

with enough reagent for 10 samples, and $250 for an additional 10 samples. The

PetrosenseTM rents for about $150/week plus minimal costs for calibration

standards. The Quick Testr analyzer rents for about $275/week plus $40 per

sample for consumables.

%HQHILWV

 Rapid on-site screening tool

 Kits available for petroleum-derived substances and polynuclear aromatic

hydrocarbon (PNAs) 

 Useful for remote sampling 

 Generally requires minimal training

/LPLWDWLRQV

 Relatively high detection limits

 Possible interference by naturally occurring chemicals and other contaminants 

 Possible difficulty reading colorimetric matches under low light conditions

&RQWDFWV

Dexsil Corporation (PetroFLAGTM), (203) 288-3509, www.dexsil.com

Envirol, Inc. (Quick Testr), (801) 753-7946 or (435) 753-7946, www.environl.com

FCI Environmental Inc. (PetroSenseTM), (702) 361-7921

Handby Environmental Laboratory Procedures, Inc., (Handby Kit), (512) 847-1212 

 ,PPXQRDVVD\ 6FUHHQLQJ

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Immunoassay testing can be used in the field to detect target chemicals in soil and

other samples. Most immunoassay-based test kits for analyzing environmental

contaminants are of the competitive enzyme-linked immunosorbent assay (ELISA)

type. In competitive ELISAs, the sample to be tested is combined with a labeled

enzyme and an antibody to which both the contaminant in the sample and the

enzyme will bind. The contaminant and the enzyme compete for the limited

number of antibody binding sites that are available. Each will bind to a number of 
&KDSWHU 

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4-34

sites that is proportional to its concentration in the mixture, so the relative

concentration of the contaminant can be determined.

The relative concentrations of enzymes and contaminants are indicated by colorproducing reagents, which are added after the antibody with contaminants and

enzymes bound to it is separated from whatever material is left over. Color

development is catalyzed by the enzymes and then terminated by a stopping

reagent. A spectrophotometer reads the absorbance or reflectance of the antibodycontaminant-enzyme complex; the color detected by the spectrophotometer is

proportional to the enzyme’s concentration and inversely proportional to the

contaminant’s concentration. Thus, the concentration of contaminant in the soil or

other sample tested can be inferred.

2SHUDWLRQDO &RQVLGHUDWLRQV

Field immunoassay test kits can operate in temperature ranges from 40 to 100(F.

Soil moisture content in excess of 30 percent can decrease extraction efficiency.

Reactivity and/or interference from the surrounding soil matrix can have either a

positive or negative effect on results. A work environment protected from sunlight

and wind is recommended, and operator training by the manufacturer is

encouraged.

To effectively use immunoassay test kits for field screening at MGP sites, a sitespecific correlation study should be performed first. PAH immunoassay test

methods measure PAH compounds based on molecular structure. Laboratories

use gas chromotography/mass spectrometry (GC/MS) for ion identification to

quantify 16 different PAHs. The presence of any of the more than 30 PAHs can be

detected, but without identifying specific types or quantifying concentrations.

Immunoassay test kits should not be used at MGP sites where crude oil was used

as a fuel source because the widely varied composition of feedstocks for oil-fired

plants does not allow correlation to a standard based on simple feedstock. MGP

sites where coal was used as a fuel source yield much better correlation factors

between analytical laboratory data and immunoassay test kit data in field tests.

$SSOLFDWLRQV DQG &RVW

Immunoassay test kits may be an effective screening tool for PAHs, TPHs, and

other chemicals typically detected at coal-fueled MGP sites. Immunoassay test kit

cost per sample is $25-55 (excluding labor) depending on batch size and product

line. Field lab instrumentation can be rented for $450/week or purchased for

$1,700-2,000.

%HQHILWV

 Rapid, real-time analytical data on-site

 Can be used to select samples for laboratory analysis and to define limits of

contamination during an investigation

/LPLWDWLRQV

 Requires site-specific calibration
&KDSWHU 

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4-35

 Does not speciate individual PAHs

 Does not work effectively on MGP sites where crude oil was used as fuel

 Does not produce quantified concentrations of target substance being analyzed

 Requires a trial period or test runs to confirm satisfactory performance

&RQWDFW

Dwight Denham, Strategic Diagnostics, Inc., (714) 644-8650

&DVH 6WXG\

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In 1930, the Georgetown Coal Gas plant was demolished after about 20 years of

operation. The objectives of using immunoassay kits at the Georgetown Former

MGP Site were to evaluate the entire site quickly and to find areas with actionable

levels of PAHs, determine the extent and depth of each contaminated area, and

compare in-laboratory methods with immunoassay results in terms of accuracy,

cost, and time. Of the 36 samples analyzed at the site, the PAH immunoassay test

kits were consistent with in-laboratory results with the exception of five false

positives from the immunoassay test method. By not performing laboratory

analysis of the samples determined to be negative via immunoassay (as defined by

a concentration less than 1 ppm), a savings of approximately $4,000 would have

been realized. Used as a screening tool, the immunoassay results can be very

useful in determining which samples to send to a lab (immunoassay costs were

approximately one tenth of laboratory analysis).

 0RELOH /DERUDWRULHV

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Under the right conditions for field programs in which rapid site assessment is

necessary, mobile laboratories can provide rapid on-site, soil, air, and water

sample analyses.

Field characterization programs are often conducted in phases of field sample

collection and analysis. The results from the first phase are used to plan the

sampling strategy of the second phase. The results from the second phase are used

to plan sampling for a third phase, and so on until delineation of contaminants is

complete. The time spent between phases waiting for analytical results from

standard offsite laboratories translates into additional costs for repeated

mobilization/demobilization of drilling equipment and field personnel. Mobile

laboratories can provide same-day results for field sampling, allowing field

personnel to make quick decisions about the locations of subsequent sampling. It

is not necessary to demobilize then remobilize the sampling effort.

2SHUDWLRQDO &RQVLGHUDWLRQV

The analytical capabilities of mobile laboratories vary considerably among

companies. However, several laboratories are equipped to analyze PAHs in

addition to petroleum hydrocarbons and other common contaminants. Some

mobile laboratories are also equipped to analyze natural attenuation parameters in
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4-36

the field. Many natural attenuation parameters (e.g., dissolved oxygen, oxidationreduction potential, ferrous iron, hydrogen, methane, ethane, and ethene) require

rapid analysis for accurate reporting, so mobile laboratories can be very effective

for analyzing these parameters.

Several mobile laboratories can identify and quantify PAHs by SW846 Methods

8100, 8270, and 8310. Prior to selecting a mobile laboratory, it is important to

determine the quality of data required (e.g., are results from immunoassay methods

acceptable, or are gas chromatography/mass spectrometry procedures warranted).

Similar to offsite laboratories, mobile laboratories require trained chemists to run

analyses and perform QA/QC functions.

$SSOLFDWLRQV DQG &RVW

The decision to use a mobile rather than an offsite laboratory depends on a

number of factors, including quality of data required, number of samples to be

analyzed, types of analyses required, possibility of access to a fixed laboratory, and

cost of onsite versus offsite analysis.

If the mobile laboratory does not require specialized instrumentation, the cost of

sample analysis may be 10 to 15 percent less than the cost of sending samples

offsite and requesting rapid turnaround (Onsite Laboratories, 1998). It is important

to note that the cost of laboratory analyses at both onsite and offsite situations

varies markedly among laboratories and that unit costs depend on the number of

samples to be analyzed. Approximate laboratory rental costs are $2,500 to $3,000

plus $13 to $30 per sample for expenditures.

%HQHILWV

 Extremely rapid turnaround analytical results

 May reduce mobilization/demobilization charges for drilling and field

personnel

 Can rapidly perform time-critical analyses, such as for natural attenuation

parameters

/LPLWDWLRQV

 May be more efficient to send samples for rapid turnaround at an offsite

laboratory

 More expensive than standard turnaround analysis

 Not all mobile laboratories use USEPA analytical methods

()	&
*	&

Geophysical surveys encompass a broad group of tools historically used by the

geophysical, mining, and petroleum industries for mapping geological formations.

All of these tools operate from the surface to sense buried obstructions and objects,

changes in geologic formations, and/or the location of groundwater, thus

minimizing uncertainty about what might be unearthed during excavations and
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4-37

giving additional information to conceptual and numerical modeling of

groundwater flow. These tools are generally grouped into one of two categories:

surface geophysical and borehole geophysical.

Surface geophysical tools are nonintrusive and include:

 Electromagnetics

 Seismic Refraction

 Ground-Penetrating Radar

 Magnetometry/Metal Detection

Borehole geophysical tools are designed to be put into a well or borehole. They

include:

 Electrical Logging (including single-point and multi-electrodes)

 Mechanical Logging

 Sonic Logging

 Radiometric Logging

 Thermal Logging

 Video Logging

In general, all geophysical tools work on a “preponderance of evidence” basis.

That is, an individual geophysical method does not typically provide definite

results. Rather, several methods are used in conjunction at a site to provide

information concurrently through their results.

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Electromagnetic surveys (EMS) comprise two subclasses of surveys: 

magnetometer surveys and terrain conductivity electromagnetic surveys. Both

types of surveys are nonintrusive geophysical surveying techniques that have

traditionally been used to detect geologic features (e.g., formations with magnetic

properties). More recently, EMS has been successfully applied with groundpenetrating radar (GPR) surveys at former MGP sites to locate buried obstructions

and objects such as old underground storage tanks, buried sumps and pits, and

current and abandoned utility lines.

Magnetometer surveys are conducted by using an instrument that measures the

varying intensity of magnetic fields produced by natural objects (e.g., rocks) and

man-made objects (e.g., utility lines). Interpreting the magnetic readings produced

by the magnetometer allows conclusions to be drawn about the location of the

buried objects.

Terrain conductivity electromagnetic surveys are conducted by remote seismic

inductive electric measurements made at the surface. The apparent conductivity of
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4-38

subsurface formations and objects is measured by a conductivity meter consisting

of a receiver coil and a separate transmitter coil that induces an electric source field

in the ground. Lateral variations in conductivity values generally indicate a

change in subsurface conditions. The figure below is an example of an output from

a terrain conductivity electromagnetic survey.

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Soil factors that affect the accuracy of EMS include moisture content, iron content,

and dissolved salts and ions. EMS results can also be affected by electromagnetic

interference. Overall, EMS results are best interpreted in parallel with other

geophysical survey techniques, such as ground-penetrating radar surveys, that

provide correlating information.

$SSOLFDWLRQV DQG &RVW

EMS uses a nonintrusive source and detectors and is therefore ideal for screening

sites for buried objects. It is a fast, relatively inexpensive method to obtain

“ballpark” data. Under favorable conditions (low moisture, low iron content, low

electromagnetic interference), EMS’s resolution and accuracy improve. EMS is well

understood and provides reliable results.

The cost of an EMS survey varies depending upon access to the site (directly

related to the time required to perform the field work) and detail desired (e.g., the

target depth to which a survey is to be conducted). Typically, an EMS survey on a

1-acre site will take 3 to 4 days to complete, costing around $3,500.

%HQHILWV

 Provides reliable data

 Field tested and proven

/LPLWDWLRQV

 Requires expertise to plan, collect, and interpret data

 Data subject to interference from soil moisture

or clay in the subsurface and nearby

electromagnetic sources (e.g., power lines)

 May be problematic in iron-rich, deeply

weathered soils

&DVH 6WXGLHV

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Available historical information for PG&E’s Chico

former MGP site indicated multiple locations for

the historical buried feedstock tank. Terrain

conductivity electromagnetic surveys were

performed in conjunction with GPR to determine

whether the tank still existed and, if so, to better

estimate the tank’s location (thereby determining if

soil contamination observed in the general area
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4-39

might be from the tank or from a different former MGP structure). At the time of

the surveys, the site consisted of the former MGP sheet-metal generating building

and an adjacent substation. There was significant interference in the EMS survey

from the adjacent substation, but the GPR survey was able to place the location of

the former buried feedstock tank farther west than the location estimated from

historical Sanborn Fire Insurance maps.

6WRFNWRQ )RUPHU 0*3 6LWH

Terrain conductivity electromagnetic surveys were also used at PG&E’s Stockton

former MGP site to delineate debris-filled areas, covered pits and sumps, and

concealed foundations associated with the former MGP. The terrain conductivity

electromagnetic surveys correlated well with the estimated locations of former

MGP structures as determined by a GPR survey. 

&RQWDFW

Robert Doss, Pacific Gas and Electric Company, (415) 973-7601

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Seismic refraction is a nonintrusive geophysical surveying technique that can be

used to determine depth to bedrock, thickness of surficial fracture zones in

crystalline rock, extent of potential aquifers, and depth of the water table.

Seismic refraction surveys are conducted by measuring the velocity of elastic

waves in the subsurface. Elastic waves are generated by a source (hammer blow or

small explosion) at the ground surface, and a set of receivers is placed in a line

radiating outward from the energy source to measure the time between the shock

and the arrival. The velocity of the elastic waves in the subsurface increases with

increasing bulk density and water content. The depth of various strata and objects

may be calculated if their wave velocities are sufficiently different. The survey

data are processed and interpreted, typically along with other geologic

information and geophysical surveys, to provide a picture of subsurface

conditions. The following figure exemplifies the output from a seismic refraction

survey.
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4-40

Three-dimensional/three-component (3-D/3-C) seismic imaging can be an

extremely powerful tool for characterizing the hydrogeological framework in

which contaminants are found at MGP sites. 3-D/3-C seismic imaging is a

nonintrusive geophysical surveying technique that can delineate subsurface

geophysical features including: bedrock channels, clay layers, faults, fractures, and

porosity. In addition, 3-D/3-C seismic imaging can identify trench/pit boundaries

and differences in soils and wastes (Hasbrouck et al., 1996).

3-C imaging entails analysis of one-component compression-wave and twocomponent shear-wave data. Two-dimensional (2-D) seismic refraction surveys

use only one–component compression-wave data. The 3-D/3-C seismic imaging

uses shear-wave data to map much thinner features than can be detected with 2-D

surveys; 3-D/3-C imaging can determine anisotropy (i.e., preferred grain

orientation, periodic layering, and depositional or erosional lineation), which may

correlate to preferential contaminant transport pathways (Hasbrouck et al., 1996).

2SHUDWLRQDO &RQVLGHUDWLRQV

Interpretations of seismic refraction surveys are most reliable in cases where there

is a simple two- or three-layer subsurface in which the layers exhibit a strong

contrast in seismic velocity. For shallow investigations (i.e., up to approximately

10 feet deep), the energy source for the elastic waves is a hammer blow on a metal

plate set on the ground surface. For a deeper investigation or at sites with noise

interference (heavy machinery or highways), an explosive source is necessary.

High gravel content in the soil matrix may diminish the quality of the data.

3-D/3-C seismic imaging data can be processed so that cross sections are oriented

from any angle and specific zones of interest can be displayed and interpreted.

Specially developed 3-D/3-C software is necessary to process the data, and skilled

data interpretation is required (Hasbrouck et al., 1996).
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4-41

Overall, seismic refraction results are best interpreted in parallel with other

geophysical survey techniques (such as magnetometer surveys and

electromagnetic terrain surveys) or well logs, which provide correlating

information.

$SSOLFDWLRQV DQG &RVW

Where deep groundwater, consolidated materials, or both make test drilling

relatively expensive, it may be advantageous to get as much information as

possible by seismic refraction. Seismic refraction is a nonintrusive survey method

that is well understood and provides reliable results.

3-D/3-C seismic imaging can be used for subsurface characterization. The

relatively high cost of 3-D/3-C seismic imaging may be justified in situations

where site entry is restricted because of high levels of subsurface contaminants

and a three-dimensional picture of the sites’s subsurface is required without

intrusive sampling.

The cost of a seismic refraction survey varies depending upon access to the site

(directly related to the time required to perform the field work) and the level of

detail desired (e.g., the target depth to which the survey is to be conducted).

Typically, one week of seismic refraction surveys may yield 3 to 5 line miles of

interpreted data for approximately $10,000.

%HQHILWV

 Provides reliable data

 Field tested and proven

 Minimizes the number of times an area must be accessed for subsurface

characterization and maximizes the amount of information gathered

 3D/3C seismic refraction provides greater level of detail (e.g., thinner features)

than traditional 2-D seismic surveying results

/LPLWDWLRQV

 Requires expertise to plan, collect and interpret data

 Data subject to interference from complex geological strata

 3D-3C seismic refraction relatively expensive

 Needs to be correlated with other site-specific subsurface data such as drilling

logs 

 Heavy traffic or numerous surface obstructions can be problematic

&RQWDFW

Dennis Olona, U.S. Department of Energy, Albuquerque, NM, (505) 845-4296
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GPR is a nonintrusive geophysical surveying technique that has traditionally been

used to detect geologic features (e.g., fractures and faults). More recently, GPR has

been successfully applied with EMSs at former MGP sites to locate buried

obstructions and objects such as old foundations, underground storage tanks,

buried sumps and pits, current and abandoned utility lines, and concrete rubble.

GPR surveying emits high-frequency electromagnetic waves into the subsurface.

The electromagnetic energy that is reflected by buried obstructions is received by

an antenna at the surface and recorded as a function of time. The recorded patterns

are interpreted, typically along with other geologic information and geophysical

surveys, to provide a picture of subsurface conditions. The following figure is an

example of an output from a GPR. Results are best interpreted in parallel with

other geophysical survey techniques, such as magnetometer surveys and EMSs,

which provide correlating information.

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GPR uses a nonintrusive source and detectors and is therefore ideal for screening 

sites for buried objects. It is a fast, relatively inexpensive method to obtain

“ballpark” data. Under favorable conditions (low moisture, low iron content, low

electromagnetic interference), GPR’s resolution and accuracy is best. GPR is well

understood and provides reliable results.

The cost of a GPR survey varies depending upon access to the site (directly related

to the time required to perform the field work) and the level of detail desired (e.g.,

the target depth to which the survey is to be conducted). Typically, one week of

GPR surveys yields 5 to 7 line miles of interpreted data for around $10,000.
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%HQHILWV

 Field tested and proven

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 Requires expertise to plan, collect, and interpret data

 Data subject to interference from soil moisture or clay in the subsurface

 May be problematic in iron-rich, deeply weathered soils

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Historical information for PG&E’s Chico former MGP site indicated multiple

locations for the buried former feedstock tank. Ground-penetrating radar was used

in conjunction with EMS to determine whether the tank still existed and to verify

its location (in order to determine whether soil contamination observed in an area

might be from the tank or from a different former MGP structure). Although there

was significant interference in the EMS survey from an adjacent substation, the

GPR survey placed the location of the former buried feedstock tank farther west

than the location estimated from historical Sanborn Fire Insurance maps.

Interpretation of the survey data identified the location of the tank excavation but

was not able to confirm whether or not the tank was still in place.

&RQWDFW

Robert Doss, Pacific Gas and Electric Company, (415) 973-7601

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Magnetometry is a nonintrusive electromagnetic geophysical surveying technique

commonly used in the construction industry to detect and map buried drums,

metallic pipes, utilities, cables, and piping before excavation, demolition and/or

construction. This technology has also been applied to former MGP sites to

identify buried utilities before drilling and to survey and map historical MGP

structures such as buried piping, tanks, and other metal structures.

Magnetometer surveys use an instrument that measures the varying intensity of

magnetic fields produced by buried metallic objects. The magnetic readings

produced by the magnetometer can be interpreted so that conclusions can be

drawn about the location of the buried objects. The following figure is an example

output from a magnetometer survey.

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Soil factors that affect the accuracy of magnetometry include moisture content,

iron content, and dissolved salts and ions. In addition, magnetometry surveys are

typically depth limited and cannot distinguish among types of metallic objects.

Nonferrous objects are invisible to magnetometry survey instruments.
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$SSOLFDWLRQV DQG &RVW

Magnetometry uses a nonintrusive

source and detectors and is

therefore ideal for screening sites

for buried objects. It is a fast,

inexpensive method to obtain

“ballpark” data on the location of

buried metallic objects. Under

favorable conditions (low moisture,

low iron content, low

electromagnetic interference),

magnetometry resolution and

accuracy is best. Magnetometry is

well understood, well accepted, and

provides reliable results.

The cost of a magnetometry survey

varies depending upon access to the site (directly related to the time required to

perform the field work), the size of the area to be surveyed, and the level of detail

desired (e.g., the target depth to which the survey is to be conducted). Typically, a

magnetometry survey on a 1-acre site with 10-foot grid spacing will take 3 to 4

days to complete. Equipment rental may cost approximately $500 per month,

exclusive of labor (for both testing and data interpretation) and other related

expenses.

%HQHILWV

 Field tested and proven

 Widely accepted

/LPLWDWLRQV

 Details obtainable only at relatively shallow depths

 Cannot distinguish among metallic objects

 May be problematic in iron-rich, deeply weathered soils or where there is a lot

of scattered metal debris

 Nonferrous objects will not be visible to the technology

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Borehole geophysical methods are used to physically characterize sediments, rocks,

and fluids in boreholes and wells. Data are acquired by moving a string of

instruments up or down a borehole and measuring the response. Depending on the

specific information required, one or more borehole geophysics techniques may be

used in a single well. The radius of the investigation depends on the particular

instrument used.
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The tools discussed below include several categories of borehole survey

techniques:

 Electrical 

 Mechanical 

 Sonic 

 Radiometric 

 Thermal 

 Video

Borehole geophysical logging is a useful tool for site characterization. Because of

the mobilization effort required and because multiple logging techniques can be

used simultaneously, borehole geophysical surveys are most cost effective when

performed as part of a multiple-log suite. 

Geophysical logs provide a continuous profile of response versus depth in a well or

boring. Typically, direct soil sampling is undertaken only at 5-foot intervals. A

substantial amount of information can be obtained from a few logging runs into a

well. In addition, data can be correlated between adjacent wells. Examples of some

of the well logs that may be produced with the techniques discussed herein is

shown below.

In general, borehole logging is relatively expensive (including actual logging and

post processing), and equipment must be transported to the site. In addition, the

radius of the investigation may be small and may not be representative of the bulk

formation.
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Electrical logging includes electrical resistivity methods, induction logs, selfpotential logs, and fluid conductivity logs. Electrical resistivity relies on different

electrode configurations to give information on different zones around the

borehole. The characteristics (e.g., thickness, permeability, salinity) of a region

energized by particular current electrode configuration can be estimated by

measuring variations in current among electrodes. Many variations of electrical

resistivity logging exist in which different electrode configurations are used

including: normal logs, lateral logs, guard logs, and micrologs. Using empirical

constants specific to the particular rocks in the area and the drilling fluid, electrical

resistivity is also used to estimate porosity, water and hydrocarbon saturation, and

permeability.

An induction log is a profile of resistivity obtained by utilizing electromagnetic

waves. This technique is used in dry holes or boreholes that contain nonconductive

drilling fluid. Lithologic boundaries show up on induction logs as gradual changes

in apparent resistivity.

On self-potential logs, measurements of potential differences between an electrode

on the sonde (probe) and a grounded electrode at the surface are made in

boreholes filled with conductive drilling fluid. The self-potential effect originates

from the movement of ions at different speeds between two fluids of differing

concentration, in this case groundwater and drilling fluid. Self-potential logging

can be used to identify the boundaries between geological beds based on the

differing rates of penetration of drilling mud into the lithology. In hydrocarbonbearing zones, self-potential logs show less deflection than normal. 

Fluid conductivity logging uses an electrical conductivity probe to profile water

quality by depth. It is used to select sampling depths and also used in conjunction

with a flow-meter log (see Section 4.2.3.5.2, Mechanical Logging) to identify waterproducing zones.

2SHUDWLRQDO &RQVLGHUDWLRQV

The electrical logging techniques described here require an open borehole.

Borehole fluids must be electrically conducting if electrical resistivity and selfpotential logging are to be used. Induction logging, however, requires either a dry

borehole or nonconducting fluids in the borehole. Single-electrode logging yields a

poor response in saltwater aquifers and provides qualitative data elsewhere.

Multi-electrode logging permits quantitative data and estimates of formation

water salinity. Fluid conductivity logging yields less precise information in highly

saline waters.

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The cost of electrical logging is approximately $1,200-$2,500 per day. Five to seven

wells can be logged per day. Fluid conductivity logging is approximately $500-

$600 per well when performed as part of a multiple-log suite and approximately

$1,500-$2,500 per well when done alone.
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%HQHILWV

 Quantitative data may require corrections

/LPLWDWLRQV

 The electrical logging techniques described require an uncased borehole

 Electrical resistivity and self-potential techniques require conductive borehole

fluids

 Induction logging requires a dry borehole or borehole with nonconductive

fluids

 Induction logging may be complex and provide poor results in situations of

high-resistance formations, thin beds, and shallow wells

 Poor response in saltwater aquifers

 0HFKDQLFDO /RJJLQJ

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Flow-meter and caliper logging are two different types of mechanical logging.

Flow-meter or spinner logging incorporates mechanical flow meters to measure

horizontal and vertical groundwater flow rates. These flow rates can be used to

identify permeable zones in a formation. When used in conjunction with the

caliper log, the flow meter yields semiquantitative measurements of groundwater

into the borehole.

A mechanical flow meter measures the velocity of fluid in a borehole by means of

low-inertia impellers that are turned by the fluid flow. Turning of the impellers

causes a magnet mounted on the impeller shaft to rotate and generate electrical

signals. Mechanical flow meters are capable of measuring flow rates down to

about 2 feet per minute (ft/min). A newer electromagnetic flow meter uses

thermal principles to measure flow rates as low as 0.1 ft/min.

Mechanical flow-meter logging can be done under natural (non-pumping) or

forced-flow (pumping) conditions. Pumping flow-meter logs can be used to

estimate the relative transmissivity of different water-bearing zones; non-pumping

flow-meter logs can be used to identify the direction and magnitude of vertical

well-bore flow caused by vertical gradients.

Another common type of mechanical logging uses the caliper log, which measures

borehole diameter and roughness. The tool itself has a number of feelers (usually

four) attached. The feelers are electromechanical devices, held by springs against

the wall of the hole, that send information to the surface. The information from the

log is used mainly to estimate the volume of cement that might be required to seal

around a collapsed region, to verify well-construction details, and to provide

lithologic information. Information gained from the caliper log is used to estimate

velocity losses in the gap between the borehole wall and the flow-meter impeller,

thereby correcting velocity measured by the flow-meter log. The key use of the
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4-48

caliper log data is to correlate vertical velocity data to vertical flow data by

allowing the area of the borehole to be factored into the vertical profile.

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Flow-meter logging requires a minimum flow of approximately 2 ft/min. Caliper

logging requires an open borehole, which may be difficult to achieve in deep,

unconsolidated deposits. Conductor casing may be necessary to contain

unconsolidated sediments near the top of the well.

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The cost of flow-meter logging is roughly $500 to $600 per well when performed as

part of a multiple-log suite. The cost of flow-meter logging (with recommended

caliper logging) is $1,500 to $2,500 per well.

%HQHILWV

 Caliper log is widely available, rapid, and inexpensive

 Flow meter logging is relatively simple and inexpensive

/LPLWDWLRQV

 Flow-meter logging is relatively insensitive at low velocities

 Most applications of flow-meter logging require a pumping or flowing well

during the survey

 A caliper log is needed for interpretation of flow-meter logs

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Sonic logging, also known as continuous velocity or acoustic logging, is used to

determine the relative porosity of different formations. Sonic logging may also be

used to determine the top of the water table, to locate perched water-bearing

zones, and to assess the seal between a casing and formation material. 

A probe containing one or more transmitters that convert electrical energy to

acoustic energy is lowered into the borehole on a cable. The acoustic energy travels

through the formation and back to one or more receivers also located on the tool.

The acoustic energy is converted back to an electrical signal, which is transmitted

back to the surface by the receivers and recorded.

Sonic logging determines the seismic velocities of the formations traversed. The

average velocity of the acoustic wave passing through the formation depends on

the matrix material and the presence of fluid in the pore space. The speed of the

wave is slowed by the presence of pore fluid; therefore, sonic logging provides a

measure of fluid-filled pore space. The velocity of the solid matrix can be

determined by laboratory analysis of core samples.

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Sonic logging can be performed in a borehole cased with metal; however, the

results are most representative of formation properties if logging is performed in

an open borehole. The borehole must be fluid-filled for signal transmission to
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4-49

occur. Obtaining meaningful results in unconsolidated materials with low

groundwater velocities may be difficult.

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Sonic logging may be used for site characterization where information is needed

on the relative porosity of different formations and the location of water-bearing

zones. The cost of sonic logging is approximately $1,500 to $4,500 per well.

%HQHILWV

 Widely available

 Suitable for uncased or cased boreholes although the results are more

representative of the formation if the borehole is uncased

 Useful for characterizing rock aquifers to identify high-porosity zones that may

transmit water

 Allows porosity determination without use of radioactive source

/LPLWDWLRQV

 Interpretation of the data may require expertise

 The borehole must be fluid-filled

 Not applicable in shallow wells or in unsaturated conditions

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The radiometric logging techniques discussed here include neutron logging and

natural gamma (or gamma) logging. Neutron logging is used to estimate porosity

and bulk density, and, in the vadose zone, to locate saturated zones outside a

borehole or well casing. Natural gamma logs are used to evaluate downhole

lithology, stratigraphic correlation, and clay content of sedimentary rocks. 

Both logging techniques are based on the process by which particles of mass or

energy are spontaneously emitted from an atom. These emissions consist of

protons, neutrons, electrons, and photons of electromagnetic energy that are called

gamma rays. Radiometric logs either make use of the natural radioactivity

produced by the unstable elements U238, Th232, and K40, or radioactivity induced by

the bombardment of stable nuclei with gamma rays or neutrons. 

In neutron logging, nonradioactive elements are bombarded with neutrons and

stimulated to emit gamma rays. The sonde (probe) contains a neutron source, and

the neutrons collide with atomic nuclei in the wall rock and emit gamma rays,

which are measured by a gamma-ray detector also on the sonde. The amount of

gamma radiation from neutron logging correlates directly with the proportion of

water-filled pore space in a rock unit.
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Natural gamma radiation logging uses a detector mounted on a sonde to measure

the gamma rays produced by radioactive elements in a formation. Because

different types of formations contain different amounts of radioactive elements,

gamma logging is used primarily to determine lithology, stratigraphy, and the clay

or shale content of a rock. 

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Neutron and gamma logging techniques can be used in cased holes, which means

they offer a distinct advantage under some circumstances. Neutron logging

requires handling of a radioactive source.

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Neutron logging costs approximately $2,500 to $5,000 per well (depending on well

depth and the number of other logs run at the same time). Gamma logging costs

are on the order of $1,200 to $2,500 per well; approximately five to seven 100-foot

wells can be logged per day.

%HQHILWV

 Radiometric logging is suitable for both uncased and cased boreholes

 Specialized training is not required for gamma logging

 Radiometric logging is useful in characterizing rock aquifers to identify highporosity zones that may transmit water.

/LPLWDWLRQV

 Gamma rays detected using neutron and natural gamma logging come from the

formation only within a few feet from the well

 Lithology must be determined by other logs before porosity estimates can be

made using the neutron logging technique

 Neutron logging requires special training, transportation, and permits to allow

handling of a radioactive source; its availability is also limited

 Neutron logging may only be allowed in cased holes in some states (e.g.,

Oregon)

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Thermal logging is primarily used to locate water-bearing zones. It can also be

used to estimate seasonal recharge or a source of groundwater. A temperature

sensor, usually a thermistor mounted inside a protective cage, is lowered down a

water-filled borehole. The probe is lowered at a constant rate and transmits data

related to the temperature change with change of depth to surface. The natural

variation of temperature with depth is called the geothermal gradient. Waterbearing zones intersected by the borehole may cause changes in the geothermal

gradient, which is shown on the temperature log. Seasonal recharge effects may

also be detected because the influx of recharge water changes the natural

temperature regime. It is also possible to assess the source of groundwater if the

regional sources have characteristic temperatures.
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Thermal logging may be performed in an open or cased borehole; however, the

borehole must be fluid-filled. Thermal logging should be performed several days

after drilling is complete to ensure that water in the boring is representative of

ambient conditions.

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Thermal logging is often combined with other borehole geophysical methods. The

cost of thermal logging is approximately $500 to $600 per well (depending on the

total depth logged) as part of a multiple-log suite. The cost of temperature logging

when no other borehole geophysical methods are used is approximately $1,500 to

$2,000 per well. 

%HQHILWV

 Thermal logging is widely available, rapid, and inexpensive

 Data are easy to interpret unless internal borehole flow is present

/LPLWDWLRQV

 Temperature measured is that of borehole fluid, which may not be

representative of surrounding formation

 This technique requires a fluid-filled borehole

 Interpretation of log is complicated if internal borehole flow is present

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Video logging a borehole can provide visual inspection of the interior of a well,

detecting damaged sections of screen and confirming well construction details. In

uncased boreholes, video logs can detect fractures, solution cracks, and geological

contacts if turbidity in the well is low. 

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Video logging requires very low turbidity in the well for a successful survey. Both

monochrome and color videography are available; however, color is preferred

because interpretation of images is easier.

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Video logging is primarily used to detect fractured bedrock and the integrity of

screens and casing. Video logging may cost from $400 to $3,000 per well.

%HQHILWV

 Video logging allows visual inspection of well interior

 Video logging is useful for troubleshooting potentially damaged casings

/LPLWDWLRQV

 Video logging requires an open borehole and is therefore not useable with

unconsolidated formations
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 The borehole walls must be clean and the groundwater relatively clear

)*	&

Soil gas measurements can successfully predict actual concentrations of MGP

residues in soil and water. MGP residues are present in the soil as a gas because of

their vapor pressure and solubility. Measuring the amount and composition of

these gases can indicate the extent of source areas and groundwater plumes. Soil

gas investigations, used in conjunction with physical soil and groundwater

sampling, can provide a more thorough and cost-effective site investigation than

borings and well samples alone. Soil gas surveys are grouped in two categories: 

passive and active. Passive soil gas surveys measure the relative concentration of

contaminants through subsurface detectors sensitive to diffusion. Active soil gas

surveys relatively quickly withdraw soil vapors using a vacuum pump system to

analyze the concentration of contaminants in the vapor phase. The active gas soil

gas technique provides real-time concentration data; the passive soil gas technique

provides a time-integrated relative concentration that may detect less volatile

compounds. Each of these methods of soil gas sampling is discussed in more detail

below. 

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Passive soil gas surveys use subsurface detectors sensitive to diffusion to measure

the relative concentration of contaminants. Passive methods involve integrated

sampling over time and collection of the sample on an absorbent material. Because

sampling is integrated over time, fluctuations in soil gas availability resulting from

changing ambient and subsurface conditions are minimized. Passive soil gas

sampling does not disrupt the natural equilibrium of vapors in the subsurface as is

the case with active sampling methods. Passive gas sampling only provides

qualitative results because it does not measure the specific amount of

contamination per unit of contaminated material. Because passive soil gas

sampling occurs over a period of at least a few days, it can detect heavy organic

compounds with lower vapor pressures, such as PAHs.

Gore-Sorbers® and Emflux® are both patented technologies that use passive soil

gas principles. The Gore-Sorbers® Module uses a granular absorbent within an

inert Gore-Tex® membrane that only permits vapor transfer into the module. Each

thin, cord-like, module is placed in the shallow subsurface for a period of 2 to 4

weeks and then removed and shipped to a laboratory for analysis. Emflux®

samples consist of a sampler vial containing an adsorbent cartridge. The samplers

are placed at a depth of approximately 3 inches below grade for 72 hours, after

which they are removed and sent to a laboratory for thermal desorption and

analysis. Results of a passive gas survey is shown below.
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As opposed to active gas sampling, passive soil gas sampling can be used in areas

with relatively low soil permeability. Installation and retrieval of samples can be

accomplished with minimal training and equipment. Soil gas samples should be

taken at points deep enough to avoid background contamination from surface

spills or exhaust. Installations directly beneath concrete or paved surfaces should

be to a depth below the zone of lateral migration of soil gas to avoid misleading

results. Depths of at least 2 to 3 feet are typically sufficient to insure good

sampling. It may be difficult to obtain passive soil gas data for vertical

characterization; active soil gas sampling is often used to vertically characterize

contamination. Passive gas sampling may be applied directly in a saturated zone.

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Passive gas testing has been used for many different types of contaminants

(including MGP residues) and is becoming more popular because of its low cost

and flexibility in different types of soil. Using soil gas sampling data in

conjunction with other site-specific data can be a cost-effective method for

delineating MGP residues.

Passive soil gas testing is approximately $250 per sample location (including

analysis and reporting) and $50 to $100 per location for installation and retrieval.

%HQHILWV

 Easy to use

 Can be used in areas of relatively low permeability

 Can be more sensitive than active soil gas, soil, or groundwater sampling
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4-54

/LPLWDWLRQV

 May not correlate well with active soil sampling results

 Does not measure direct concentration

 Data at depth for vertical characterization may be difficult to collect

 Gore Sorber® passive detector must remain in situ for 14 days, whereas

Emflux® passive detector must remain in situ for only 3 days

&DVH 6WXG\

0F&OHOODQ $LU )RUFH %DVH $)%

Past disposal practices at McClellan AFB, located near Sacramento, California,

from 1936 to the late 1970s, contaminated the soil and groundwater of more than

3,000 acres. Contaminants include caustic cleaners, electroplating chemicals, heavy

metals, industrial solvents, low-level radioactive wastes, PCBs, and a variety of

fuel oils and lubricants.

As part of a test location for innovative technologies, McClellan AFB tested the

Gore-Sorber® Module, primarily to monitor VOCs (perchloroethylene [PCE] ,

trichloroethylene [TCE], and cis-1,2-dichloroethylene [CIS-1, 2-DCE]). A very good

correlation was observed between the relative contamination levels measured by

the survey and actual levels determined using active soil gas sampling (Elsevier

Sciences, 1997).

&RQWDFWV

Paul Henning, Quadrel Services (Emflux® Module), (800) 878-5510

Gore Technologies (Gore-Sorber®), Mark Wrigley (410) 392-3406 and Andre Brown

(415) 648-0438

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Active soil gas surveys use a vacuum pump to induce vapor transport in the

subsurface and to instantaneously collect samples of contaminants in the vapor

phase. Active soil gas surveys provide a snapshot of vapor concentration in the

subsurface, in contrast to passive soil gas surveys, which provide time-integrated

sampling data. 

Because active soil gas sampling provides real-time data, a relatively coarse

sampling grid is initially used; this grid can be refined in areas of interest (e.g.,

areas with relatively high contaminant concentrations) for additional sample

collection. The following figure shows a schematic of one type of active soil gas

sampling device. (Adapted from “Handbook of Vadose Zone Characterization and

Monitoring” by L.G. Wilson, et al., 1995.)
&KDSWHU 

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4-55

Other active soil gas sampling

methods also use a vacuum

pump; however, a gas sampling

bag, an evacuated canister/vial,

or a solid adsorbent may be

used instead of a gas sampling

syringe. The active soil gas

sampling method that uses a

solid adsorbent is similar to

passive soil gas sampling

techniques except that active

soil gas sampling uses vacuum

pressure instead of diffusion to

pull the vapor sample through

the solid adsorbent. 

2SHUDWLRQDO &RQVLGHUDWLRQV

The vacuum used in active soil

gas sampling disrupts the

equilibrium soil gas vapor in the

subsurface by forcibly drawing

the vapor and soil gas from the

soil matrix surrounding the

sampling point. Active soil gas sampling typically must be done at least 10 to 20

feet bgs; passive soil gas sampling, by contrast, typically occurs at 3 feet bgs. It

may be difficult to collect an active soil gas sample in an area of relatively low soil

permeability. Active soil gas surveys may not be used in the saturated zone and

may result in false negative or low soil gas concentration measurements in areas of

elevated soil moisture. 

Active soil gas sampling may be adversely affected by transient processes such as

barometric pressure changes, earth tides, and precipitation, as well as by

stationary features such as buried foundations. Active soil gas sampling data

should be interpreted to account for the fluctuations these transient processes may

create in the data.

Laboratory sample holding/extraction times are dependent on the specific active

soil gas sampling method used. The solid adsorbent active gas sampling method

requires relatively long sample holding/extraction times. The gas syringe active

gas sampling method (shown in the figure above) requires relatively short sample

holding/extraction times.

$SSOLFDWLRQV DQG &RVW

Active soil gas sampling is well suited to delineating areas of higher and lower

VOC concentrations. Passive soil gas sampling may be better suited to measuring

lower contaminant concentrations and less volatile compounds such as PAHs

because of the time-integrated nature of the sampling methodology. Active soil

gas sampling costs approximately $3,000 to 4,000 per day. 
&KDSWHU 

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4-56

%HQHILWV

 Provides real-time data 

 Provides rapid results that allow the user to converge on areas of interest

 Provides a direct measure of vapor concentration

 Can be used to evaluate vertical changes in soil gas concentrations 

/LPLWDWLRQV

 Requires samples collected at least 10 to 20 feet bgs

 Cannot be effectively used in areas of relatively low permeability

 May not be effective in detecting semivolatiles (e.g., PAHs)

 May be affected by barometric and other transient processes

 Subsurface equilibrium vapor conditions disrupted by vacuum

&RQWDFWV

Tracer Research, (800) 989-9929

Transglobal Environmental Geosciences, (800) 300-6010

+$!*

Three techniques for evaluating the movement and degradation of contaminants

in aquifers include a Push-Pull Natural Attenuation Test, a Partitioning Interwell

Tracer Test (PITT), and an In Situ Bio/Geochemical Monitor (ISM) test. Each of

these are discussed in more detail below.

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The push-pull natural attenuation test is an infrequently used single-well

injection/extraction test used to obtain quantitative information on in situ

microbial metabolic activity. A push-pull test is conducted in three steps:

1. Inject in an existing monitoring well a pulse of test solution consisting of water,

a conservative tracer, and microbial substrates (electron acceptors and donors).

2. Allow the test solution to interact with indigenous microorganisms and then

extract a slug of water/tracer/microbial substrates from the same well.

3. Measure the tracer, substrate, and product concentrations from the extracted

slug of the test solution/groundwater mixture, and use measurements to

calculate rates of microbial activities.

This method provides direct estimates of rates for microbial activity and mass

balances for reactants.
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The following figure shows an idealized breakthrough curve for a process

generating a single product from a single reactant. The curves show the typical

relationship between contaminant concentration and time, providing information

on the way advection, dispersion, diffusion, and biodegradation affect

contaminant movement within the aquifer.

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Push-pull tests require specially trained field personnel although an individual test

typically only requires a few hours, so several tests can be completed by a single

operator in a day. The test solution used during the injection phase of a push-pull

test is composed of various electron acceptors and donors (e.g., sodium bromide)

that depend on the objectives of the sampling. The tracer selected should have a

decay rate similar to or greater than the groundwater flow rate.

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Push-pull tests are ideal for situations in which quantifiable estimates of microbial

activity are desired for potential natural attenuation scenarios. 

The cost of push-pull tests for a site contaminated with BTEX is approximately

$12,000 to $15,000 for two to three wells, including analytical costs. The costs are

very dependent on the specific analyses required.

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 Can document microbial metabolism, loss of degraded contaminants,

production of degradation products, and estimates of zero- and first-order

decay constants

 Provides in situ data (versus in an artificial laboratory environment)
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 Can be used in wells that are already installed

 Can assay a wide variety of processes

 Is field tested

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 Is a fairly new test; not widely used

 Can be difficult to use when decay rate is slow relative to groundwater flow

rate

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The PITT is an in situ technology that measures the volume and percent

saturation of NAPL contamination trapped in water-saturated and vadose zone

sediments. The PITT technology is primarily used to:

 Quantify and locate NAPL contamination

 Assess the performance of remediation activities

 Quantify water saturation in the vadose zone

The technique is essentially a large-scale application of chromatography. The

migration of a partitioning tracer between an injection well and an extraction well

is retarded relative to a nonpartitioning tracer because it spends a portion of its

residence time in the immobile residual NAPL. The chromatographic separation of

the tracers indicates the presence of NAPL in the interwell zone and is used to

determine the volume of NAPL present. The figure below shows a typical

injection-extraction system. 

The PITT technique can be used before

and after an in situ remedial activity,

such as surfactant flooding, to estimate

the fraction of NAPL removed and the

volume of NAPL remaining.

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The PITT technique requires wells

situated so that the potential NAPL

source is within the radius of influence

of the wells used to inject/withdraw the

conservative and nonconservative

tracers. It is important for the tracers to

be nontoxic and to have nondetectable

background concentrations and for the

partitioning tracer to have an affinity for

the particular NAPL found at the site.
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4-59

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The PITT technique is ideal for in situ characterization of NAPL and is limited by

the well network available to perform the injection/withdrawal tests and the

project budget.

The cost of PITT technology may range from $100,000 to $400,000 depending on

the scale of the test.

%HQHILWV

 Provides quantitative estimates of NAPL volume

 Can be used to design remediation methods targeting a NAPL source

 Is relatively accurate compared with other in situ tests that utilize point values or

small aquifer volumes

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 Expensive

 Technology is patented

 Not economical for smaller sites

 Most application experience is with solvents 

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The PITT technique was used at Hill AFB in 1996 to demonstrate surfactant

remediation of a DNAPL-contaminated site. Partitioning interwell tracer tests

were used to estimate the volume of DNAPL in place and to assess the

performance of the surfactant remediation. Three constituents make up more than

95 percent of the DNAPL present at the site: TCE; 1,1,1-trichloroethane (1,1,1-

TCA); and PCE. Approximately 99 percent of the DNAPL source within the test

volume was recovered by the surfactant remediation leaving a residual DNAPL

saturation of only approximately 0.0004. The PITT technique successfully provided

quantitative estimates of DNAPL volume before and after an in situ remedial

activity at this site.

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Chemical and biochemical reactions affect the geochemical composition of

groundwater and the migration and persistence of inorganic and organic

contaminants. The ISM allows in situ measurement of biochemical reaction rates

and retardation factors for both soluble organic and inorganic compounds. The

ISM maintains the geochemical integrity of sediment and groundwater and may

be less expensive than collecting similar data via conventional tracer tests.

Installed below the water table, the ISM isolates a small section of the aquifer with

minimal disturbance of the geological medium. Groundwater is removed from the
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4-60

test chamber, reactants and tracers are added, and it is reinjected into the test

chamber. Samples are then collected for laboratory analysis to monitor the

biological and geochemical reactions occurring within the test chamber (Solinst,

1998).

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The ISM requires saturated aquifers with a hydraulic conductivity greater than 10-4

centimeters per second (cm/sec). The monitor is installed through the center of a

hollow-stem auger with a special “trap door” cutting head and pushed into the soil

using either a hydraulic ram or vibrating hammer. The ISM consists of a stainless

steel test chamber, open at the bottom and bounded at the top by a set of coarse and

fine mesh screens. These screens are used to draw groundwater into the test

chamber. A depth-adjustable central spike with a fine mesh screen extends into the

test chamber. In biodegradation studies, groundwater samples are collected via the

spike. To create a one-dimensional flow system in retardation studies, water is

injected through the spike and collected from the outer screens (Nielsen, 1996;

Solinst, 1998). 

The ISM has a relatively complex design and requires knowledgeable personnel to

design, implement, and interpret tests. A numerical model may be necessary to

estimate degradation rate constants from test data (Neilsen, 1996).

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The ISM can be used in aquifers with a hydraulic conductivity greater than 10-4

cm/s where in situ biochemical reaction rates and retardation factors must be

determined. The cost of ISM is approximately $3,000 for equipment purchase only,

not including installation, analyses, and trained personnel (Solinst, 1998). 

%HQHILWV

 Reduces the time and cost of obtaining site-specific biological and geochemical

data (as compared with injection-withdrawal and field tracer tests)

 Provides in situ measurement of biochemical reaction rates

 Provides estimated rates of denitrification during biodegradation

 Provides estimated retardation factors for organic and inorganic compounds

/LPLWDWLRQV

 Design, implementation, and interpretation of ISM tests are complex and

require knowledgeable personnel

 A numerical model may be necessary to help estimate the degradation rate

constant

 Typically applicable only with permeability greater than 10 -4 cm/sec

 Small aquifer volume tested means results may be affected by small-scale

variations in aquifer properties

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Solinst Canada Ltd., (800) 661-2023, www.solinst.com
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4-61

,-	

Listed below are other tools and techniques that offer a range of advantages for

expediting site characterization but do not fit in one of the categories previously

described. These tools include:

 Microscale solvent extraction

 PAH sample filtration

 Inverse specific capacity method

 Hand-augering/trenching/pot holing

 Noise and fugitive emission controls

 Information management

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Conventional laboratory analysis of PAHs in soil and water matrices may take 2

weeks from the time samples are received to the time the results are released.

Current EPA-approved Methods 8240, 8270, and 8310 require a 24-hour extraction

period before analysis can be run. EPRI has developed a technique for analysis

that requires smaller sample volumes and shorter laboratory turnaround times

than conventional techniques. Because microscale solvent extraction (MSE)

methods require smaller sample volumes, MSE analytical methods are ideal for

alternative collection methods that yield smaller sample volumes (e.g., GeoprobeTM

and HydropunchTM) (EPRI, undated). 

MSE methods are microextraction techniques used by a lab to prepare samples for

analysis by gas chromatography. Microextraction is defined as a single-step

extraction process with a high liquid-sample-to-solvent ratio. Historically,

microextraction techniques have been limited by extraction inefficiencies, in

precision, and elevated detection limits. However, recent MSE methods involve

multiple microextraction steps as needed to improve analyte recovery and reduce

detection limits. EPRI reports that the comparison of MSE results to standard

USEPA methods ranges from good to excellent. 

As a screening tool, MSE methods provide quantitative results for individual PAH

components at the site characterization or remediation stages of a project. Several

states have approved MSE methods for specific projects either in lieu of certified

laboratory analysis or as a percentage of samples being submitted to a certified

laboratory for confirmation analysis.

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MSE methods were originally developed for use at an on-site laboratory; therefore,

these methods can easily be used in an on-site laboratory to perform expedited

characterization of PAHs. 
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Soil sample volumes required for MSE analytical methods can be up to six times

smaller than those for conventional laboratory analysis. Turnaround times for

MSE methods range from 12 hours to 2 weeks; in contrast, laboratories following

conventional EPA protocol may have turnaround times ranging from 24 hours to 4

weeks.

Many conventional laboratories may not have instrumentation and protocol

readily available for MSE methods. Analytical laboratories chosen to use MSE

methods should be interviewed and audited prior to contracting and use. 

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MSE methods are applicable during the site characterization or remediation stages

of a project where quantified concentrations of PAHs are needed.

The cost of MSE depends on the laboratory (prices vary widely) and the types and

numbers of samples to be analyzed. Analytical costs can be as much as 50 percent

lower than costs for conventional analyses. In addition, using MSE methods may

significantly reduce overall project costs because of rapid turnaround times on lab

results (which could translate into fewer mobilizations/demobilizations of field

crews) and lower sample volumes (which permit alternative drilling/sampling

techniques to be implemented).

%HQHILWV

 Small sample volumes

 Fast laboratory turnaround times

 Minimal laboratory waste 

 Quantitative results for individual components 

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 Relatively new procedure

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Electric Power Research Institute, (800) 313-3774

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When monitoring wells are constructed or aquifers are disturbed (e.g., pumped at

rates higher than natural groundwater flow), small particles called colloids are

mobilized in the groundwater. Although it is common practice to require turbidity

during sampling to be less than 5 nephelometric turbidity units (NTUs), in practice

it may be difficult to acheive (unless low-flow sampling techniques are employed).

Artificially suspended particles become entrained in groundwater at flow rates

higher than the natural groundwater flow rate and these suspended particles may

bias concentration data higher than true concentration levels. PAHs are relatively

immobile, hydrophobic compounds that tend to sorb onto soil particles. Because

PAHs have low aqueous solubility values and a high affinity to sorb onto

artificially mobilized suspended particles, it may be more representative to filter
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4-63

PAH samples that are collected under high turbidity conditions (Backus, 1993; and

Saar, 1997). 

A standard environmental filter has a pore diameter of 0.45 micrometers (mm).

Research has shown that naturally transported colloids may have diameters up to

2 mm. Therefore, a drawback to sample filtering is that naturally transported

colloids may be filtered, in addition to the artificially mobilized colloids, and

contaminant concentrations may be understated depending on the importance of

natural colloid transport at a particular site (Backus, 1993). 

In deciding whether to filter groundwater samples or not, the potential for natural

and artificial colloid transport should be considered. Because sampling turbid

groundwater often necessitates the use of field filters, it is recommended that all

attempts be made to lower the turbidity (e.g., low-flow sampling) and thereby

avoid filtering altogether. Analysis of both filtered and unfiltered samples from

the same location may provide an indication of the relative impact of colloidal

transport; however, it cannot distinguish between natural and artificial colloidal

transport. 

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Turbidity is often highest in formations characterized by reducing conditions and

fine-grained or poorly sorted lithologies. Typically, filtering is not an issue with

samples collected from higher permeability (and presumably lower turbidity)

formations. For groundwater samples collected in a temporary monitoring well or

borehole, turbidity will most likely be relatively high, so it may be justifiable to

field filter because of the large amount of artificially entrained colloids (Backus,

1993).

The ultimate use of the sampling data should also be considered when deciding

whether or not to filter a groundwater sample. In general, the following guidelines

may be used in making this decision:

 Filtered samples should be used whenever groundwater samples are collected

to determine whether water quality has been affected by a hazardous

substances release that includes metals or chemicals susceptible to colloidal

transport.

 Samples should not be filtered when a water supply well is sampled.

 For data to be used in risk assessment, unfiltered samples should also be

considered if the hydrogeologist suspects that colloidal transport could be

significant.

 It is generally recommended that both filtered and unfiltered samples be

collected at the same time for comparison.

Several different filter types are available at equipment supply stores. Filtration

may occur in an open filter funnel with filter discs (the sample is pulled through

the filter with a vacuum system) or by using an in-line filter where the sample is

pushed through a self-contained, enclosed filter. Many different filter sizes are 
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4-64

available. A 0.45-mm filter should be used unless some information is known

regarding the distribution of natural and artificial colloids at a particular site.

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Field filtering of PAH samples is applicable to groundwater samples that have

relatively high turbidity levels (e.g., greater than 5 NTUs). One key drawback,

however, is that filtering also removes naturally transported colloids. The presence

of naturally transported colloids should be taken into consideration when

analyzing the results.

The cost of field filtering equipment is nominal compared with the cost of sample

analysis and may add a small labor cost to complete the field filtering. Analyzing

both filtered and unfiltered samples doubles analytical costs and raises the labor

costs associated with groundwater sampling.

%HQHILWV

 Eliminates the high bias in PAH concentration measurements introduced by

artificial colloidal entrainment 

 A simple technology requiring minimal training

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 PAH concentrations determined from filtered samples may not include naturally

transported colloids and create a low bias

 Dissolved or colloidal contaminants may adsorb onto the filter or apparatus

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The hydraulic conductivity of the interval yielding water to permanent monitoring

wells is routinely estimated by pumping tests or slug tests conducted in a well.

The inverse specific capacity method estimates the hydraulic conductivity of the

depth interval that provides the water sample in a temporary monitoring well. 

Specific capacity refers to the flow of water yielded by a well at a drawdown or

drop in the water surface. The specific capacity test is usually estimated by

pumping a well at a fixed rate and monitoring the drop in the level of water in the

well over time. The inverse specific capacity method sets the drawdown at a

predetermined level and then measures the yield required to maintain this

predetermined drawdown (Wilson, 1997).

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The inverse specific capacity test is conducted using the GeoProbeTM as a

temporary monitoring well. Once the GeoProbeTM (or similar technology) rods are

pushed to the desired depth, 1⁄4” plastic tubing, a peristaltic pump, and a

measuring cup collect the inverse specific capacity data. Typically, a peristaltic

pump can lift up to 40 feet of head; therefore, when groundwater is more than

approximately 40 feet bgs, the inverse specific capacity method is not feasible.
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Site-specific permeability data from conventional means (pumping or slug tests)

are needed to calibrate the inverse specific capacity data if quantitative data are

desired. In addition, the inverse specific capacity method is only appropriate for

zones with hydraulic conductivities ranging from 10 -1 to 10 -5 cm/sec (Wilson,

1997).

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The inverse specific capacity method can be used with any direct-push drilling

technique where groundwater can be sampled via suction lift using a pump on the

surface. The cost is negligible assuming that a peristaltic pump and push sampler

are already in use at the site. The typical time for a test ranges from 5 to 10

minutes.

%HQHILWV

 Provides quantitative estimates of hydraulic conductivity in a temporary

monitoring well

 Allows variation in horizontal hydraulic conductivity to be assessed in the

vertical direction for preferential pathway identification

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 Provides hydraulic conductivity estimates for a small volume of aquifer

 Requires hydraulic conductivity values from conventional monitoring wells on

site for calibration

 Only approved for zones having permeability ranging from 10 -1 to 10 -5 cm/sec

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Hand augering, trenching, and pot holing are well-accepted, simple techniques for

gathering shallow geologic information and for surveying and delineating wastes

from former MGP sites. All three methods require minimum equipment and result

in the gross collection of geologic and analytical information.

Hand augers are thin-tube cylinders that are driven by hand into the ground.

Typically 18 inches in length, hand augers split lengthwise to allow insertion of

three stainless steel or brass rings. When driven into the ground, soil is pushed

into the rings, which are then removed and used for sample analysis.

Trenching and pot holing both use equipment such as shovels or backhoes to

excavate soil. Trenching is basically excavation along a single axis, often designed

to create vertical walls that can then be mapped for geologic strata. Pot holing 

incorporates the random or sequential digging of pits and is typically used to

grossly delineate the extent of MGP residues. A photograph of a typical trench is

shown below.
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Trenching and pot holing are easy exploratory techniques that often do not require

regulatory (e.g., boring) permits. They are especially effective at large sites with

few above- or underground obstructions and where labor is inexpensive. Both

techniques will, however, create significant quantities of waste, which can be

costly to handle and dispose of if found to be hazardous.

Similar to trenching and pot holing, hand augering is effective at sites where labor

is inexpensive. In contrast to trenching and pot holing, hand augering is effective

for sites where there are significant above- or underground obstructions and/or at

sites where generation of wastes is a significant concern. In contrast to trenching

and pot holing, hand augering is limited to the depth to which the sampler can be

driven, often a maximum of 3 to 5 feet bgs.

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As noted above, trenching, pot holing, and hand augering are inexpensive if labor

is inexpensive. The costs for the techniques vary directly with local labor costs.

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 Can be used to expose buried objects

 Discrete and can get into tight locations (hand augering)

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 Hand augering and pot holing are depth limited

 Trenching and pot holing are visible to the public

 Borehole and slope stability may be a problem

 Waste management may be a problem with trenching and pot holing
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The MGP formerly operating at PG&E’s Marysville Service Center was originally

located in what is now an operating substation. Because of clearance restrictions

and operating limitations, standard drilling methods (e.g., hollow-stem auger

drilling) could not be conducted within the substation. Hand auger sampling was

initially performed within the substation in areas historically thought to contain

some former MGP structures (e.g., the generating and scrubbing building,

lampblack dump, and gas holder). Soil samples collected via hand augering

indicated that MGP residues did exist in soil within the substation. Partial

substation de-energizing was subsequently arranged, and limited access drilling

(via Precision Sampling’s limited-access direct-push drilling rig) was conducted to

approximately 28 feet bgs within the substation.

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Robert Doss, Pacific Gas and Electric Company, (415) 973-7601

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During site characterization and remediation, noise and/or emission controls may

be required for regulatory, political, and safety reasons. Sound barriers, such as

curtains or berming, may be necessary to minimize noise in residential areas

during 24-hour drilling or near school/community centers during the day. One

primary disadvantage of sound barriers and tenting to control noise is that

decreased air flow may result in the work area, so emission controls (such as

ventilation blowers) may have to be increased.

Construction activities such as grading, excavation, material handling, and travel

on unpaved surfaces can generate substantial amounts of dust. Water sweeping or

soil stabilization may be necessary at sites where airborne dust could pose a health

and safety risk. Foam suppressants and chemical applicants such as magnesium

chloride are also used to control dust. A site can be completely enclosed (tented) to

prevent dust migration off-site; however, ventilation of work areas may be

required.

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All alternatives to control noise and fugitive emissions should be considered. If, for

example, several days of 24-hour construction in a residential area are required, it

may be more cost effective to forgo noise control and place nearby residents in

hotels during the noisiest construction. Seasonal and diurnal constraints such as

cooler weather or the calmest periods of the day should be factored into the

remediation schedule. To control noise from generators and other construction

equipment, one alternative is to use an electrical power source or advanced muffler

systems. Monitoring the effectiveness of the controls is critical. Noise monitors are

readily available from field equipment catalogs and provide constant-readout,

time-averaged, or peak sound levels. Airborne emission levels are often monitored

visually or with the use of a hand-held meter that gives real-time measurements of
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dust, aerosols, fumes, and mists. Monitoring of noise or dust levels may occur at the

project site perimeter if off-site migration is the primary concern; monitoring may

take place close to sources if worker safety is the primary concern.

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Noise and/or fugitive emission controls should be used at any site where

regulatory, health, or community concerns dictate action. The cost and level of

effort to implement noise and/or emission controls vary widely. Water sweeping at

a smaller construction site may cost from $200 to $500 per day; renting and

installing a sound barrier around a drilling operation may cost $5,000; and

complete enclosure of a site could easily add tens of thousand of dollars to project

costs.

%HQHILWV

 Protects community and workers

 May satisfy regulatory requirements

 Limits noise and air pollution

 Minimizes migration/transport of contaminants during remediation

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 Noise emission control on a large scale may involve prohibitive cost and effort

 Controls may make investigations/remediations logistically more complex

and/or may limit the rate of completion

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There is a growing awareness of the importance of information management in

expediting and streamlining remedial action planning, coordination, and

execution. In particular, information management tools can:

 Ensure that the quality and integrity of environmental data are maintained

throughout the site investigation process.

 Facilitate data interpretation and remedial selection.

At the project level, information management tools allow geologists, engineers and

project managers to plot and view site characterization data quickly and efficiently.

At a management level, a database management system may provide a “big

picture” of critical issues, significantly improving an environmental manager’s

communications with decision makers both within their organizations and with

regulatory agencies. The efficiencies gained through the effective use of database

and information management systems allows resources to be shifted from laborintensive data manipulation to analyzing data through efficient management and

focusing on solutions and project closure.
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A variety of commercial software packages are available to support this type of

initiative. The most common characteristic of these systems is that the system

architecture is designed around a common premise that all project information can

be assigned a spatial address, converted to electronic formats, and entered into a

geographic information system (GIS) project database. 

The architecture of a GIS-based information management system must allow for

multi-level participation in information use since all information is derived from a

common database. Once construction of the database architecture is complete, any

portion of the database can be accessed depending on user needs but not changed.

This approach allows all information to be available in one location significantly

reducing time spent searching for information — a common challenge without

effective data management tools. The features and benefits of using a GIS-based

information management system are as follows:

Feature Benefit

Data associated with unique spatial address High quality data integrity

Information available electronically in one location Time accessing information reduced

Elimination of manual data handling Reduction in data transcription errors and

compounding of errors over the remainder of the

project

If correctly utilized, GIS-based information management systems can reduce cycle

times for completing site characterization and remediation activities. 

2SHUDWLRQDO &RQVLGHUDWLRQV

Prior to the purchase and/or development of an information or database

management system, specific project needs must be evaluated. Questions to be

answered include the following:

 What kind of data may be expected?

 How much data may be expected?

 Who will be the direct users of the package (e.g., one computer operator,

multiple personnel)?

 How would prospective system users interact with the system (e.g., readonly access)?

 What is the level of the users’ computer literacy?

 How would the data be manipulated (e.g., tables, boring logs, cross-sections,

figures, interaction with groundwater flow models)?

 How much would the client need to spend?

 What are the software’s system requirements (e.g., memory, coprocessor

speed)?
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4-70

The answers to these questions will aid the manager in selecting the right package

for the project. Options will range from sophisticated GIS packages such as

ArcInfo, to less sophisticated software packages built on common computer

software such as ACCESS and AutoCAD.

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Data and information management packages are applicable to all projects that

generate data. The level of sophistication required will vary, however, from site to

site. Smaller sites may be able to use common software packages such as ACCESS,

DBASE, LOTUS, and EXCESS to easily tabulate and sort data. Larger projects may

look towards more sophisticated, expensive software such as ArcInfo or BOSS

GMS. Costs, too, will vary considerably depending on the management system

purchase, associated hardware costs, and labor costs for data entry and system

maintenance.

%HQHILWV

 Helps ensures data quality and integrity

 Facilitates data use and interpretation

 Combined with electronic deliverables from analytical laboratories, may

reduce data entry costs

 May reduce labor costs associated with report preparation

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 System may act only as data repository

 No single system may be able to fulfill all project requirements

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The Public Service Electric and Gas Company (PSE&G) former Bordentown Gas

Works site is located in a mixed commercial and residential area in Bordentown,

New Jersey. The site was used as an MGP from approximately 1853 to 1900 and as

a gas distribution regulating station until 1960. Since the demolition and clearing

of structures, the site has remained vacant and remains the property of PSE&G. 

A pilot project was initiated by PSE&G as part of an ongoing joint effort between

PSE&G and the New Jersey Department of Environmental Protection (NJDEP) to

continue to streamline remedial processes associated with MGP cleanups. A

remedial investigation was previously conducted at the site, indicating that

remedial actions were required:

 Collect additional site characterization data to support PSE&G’s remedial

objective

 Conduct a remedial alternative analysis
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 Prepare and submit a remedial action selection report to NJDEP. The report

included a comprehensive evaluation of environmental conditions at the site

using a GIS-based data management system developed and applied by

Woodard & Curran, Inc.

The Woodard & Curran environmental data management system was selected to

aid in data evaluation to understand the site’s environmental conditions; facilitate

real-time interpretation of subsequent field work activities to complete site

characterization; streamline mapping and interpretation of geologic and

contaminant profiles; and assist in the evaluation of viable remedial options. The

system consisted of a customized software platform based on ESRI’s ArcView® as

the overall platform and GIS\Solutions’ GIS\KeyTM as the application software for

environmental data. The key benefit of utilizing ArcView® is that the software has

the ability to import information from a variety of software packages (including

those specifically designed for environmental data management) increasing the

robust performance of this system. 

The data management work performed by Woodard & Curran, Inc., on this project

consisted of the following tasks:

 Electronic loading of environmental data (approximately 10,000 records) into

the system

 Querying of data to understand site conditions and identify data gaps in

concert with the NJDEP

 Development of a supplemental investigation work plan to address data gaps

 Input of supplemental data (approximately 4,000 records) for use in mapping,

assessment of environmental conditions at the site, and identification of areas

of concern for evaluation of remedial alternatives

 Review of findings in a series of workshops with the NJDEP prior to

preparation of the remedial action selection report

This project resulted in improvements in the overall site investigation process,

including reductions in cycle time for data collection, compilation and

interpretation. Supplemental field work activities filled in the data gaps and

allowed the project team to focus on remedial alternatives. Field and laboratory

data were in the system within one week of completion and were available to the

project team for interpretation and analysis immediately thereafter. The project

team conducted technical workshops to keep NJDEP apprised of results

throughout the process. The data management system was used at project

meetings to conduct “what if” scenarios, creating contaminant isopleths and

assisting in understanding hydrogeologic features at the site. The final report

included a summary of findings and conclusions that were developed in concert

with NJDEP throughout the project. In summary, the application of the

information management system assisted the project team and resulted in the

following:
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 Reductions in time and cost required to complete the site investigation

 Increased reliability of data interpretation

 A simplified way of presenting site environmental data to NJDEP and

permitted them to be part of the project team evaluating site conditions and

remedial alternatives in real time

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Woerner Max, Public Service Electric and Gas Company, (973) 430-6413

Matt Turner, New Jersey Department of Environmental Protection, (609) 984-1742