United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
P.O. Box 93478
Las Vegas NV 89193-3476
EPA/600/4-89/023
June 1989
Research and Development
EPA
Geophysics Advisor
Expert System
Version 1.0
DO NOT DE-SENSITIZE!!
DISK ENCLOSED.
V EJBD
. ARCHIVE
EPA
\ 600-
* 4-
89-
023
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GEOPHYSICS ADVISOR EXPERT SYSTEM: VERSION 1.0
by oositOHf
Gary R. Olhoeft
U.S. Geological
Denver, Colorado 80225
Interagency Agreement Number DW14932497
Project Officer
Aldo T. Mazzella
Advanced Monitoring Systems Division
Environmental Monitoring Systems Laboratory
Las Vegas, Nevada 89193-3478
This study was conducted in cooperation with
the U.S. Geological Survey
^^*s1 Libraries
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89193-3478
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NOTICE
The information in this document has been funded
wholly or in part by the United States Environmental
Protection Agency under Interagency Agreement Number
DW14932497 to the United States Geological Survey.
It has been subjected to the Agency's peer and
administrative review, and it has been approved for
publication as an EPA document. Mention of trade
names or commercial products does not constitute
endorsement or recommendation for use.
ii
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ABSTRACT
This expert system computer program is designed to assist and educate
non-geophysicists in the use of geophysics at hazardous waste sites. It is
not meant to replace the expert advice of competent geophysicists. The
program is written to run on any IBM-PC-DOS compatible computer and to be
simple to use. The program asks questions about the geology at a site, the
contamination problem, and cultural noise. The program considers the
following geophysical methods: electromagnetic induction, d.c. resistivity,
seismic, magnetic, ground penetrating radar, soil gas, gravity, and
radiometric techniques. Based upon the answers given to the questions,
the program recommends what types of geophysical methods will most likely
be useful at the site to solve such problems as the location of the
contamination and hydrogeological characterization of the site.
This report was submitted in fulfillment of Interagency Agreement
Number DWU932497 by the U.S. Geological Survey under the sponsorship
of the U.S. Environmental Protection Agency. This report covers a period
from Hay 1987 to May 1989, and work was completed as of May 1989.
iii
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CONTENTS
Computer Program on Floppy Diskette Front Cover
Notice ii
Abstract ill
Introduction 1
Geophysics Advisor Expert System 1
Recommendations 2
Example of Computer Printout 2
iv
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INTRODUCTION
This expert system computer program was created for the U S
Environmental Protection Agency, Environmental Monitoring Systems
Laboratory, Las Vegas, Nevada. The expert system is designed to
assist and educate non-geophysicists in the use of geophysics at
hazardous waste sites. It is not meant to replace the expert advice
of competent geophysicists.
GEOPHYSICS ADVISOR EXPERT SYSTEM
The geophysics expert program asks questions about a site and the
contamination problem. Questions about the types of cultural noise are al™
addressed. Over 90 questions are in the prograE. The tot.I"u.E of ques ons
asked, however, varies depending upon the answers to initial questions The
program considers the following geophysical methods: electromagne c LuItL,
,™J! i Ir grOU" pen!tratine radar' magnetic, seismic, soil gas,
gravity, and radiometnc techniques. Based upon the answers given, the program
SvTSS ±MlLPeL°f,!e?phy!icS "J11"" li^ b* «"ful at Ihe sUe ?o
ot the contamination and hydrogeological
M K
!" °5 th' !Uu- A relative numerical ranking of the varius
P ' 6 °re P°sitive number i^icatin the best or
« -h u ang e est or
better methods to consider. The methods are also ranked into three general
SJ2f?Se8'fJll5i' meth°d Teivlng a rec°m^nded, not recommended, or
uncertain effectiveness evaluation. The program also annotates why the
various geophysical techniques will likely work or not work at the site.
in Ihl r±±a T S" PrOg^m wil1 indicate "y apparent inconsistencies
in the responses to the questions. The user can go back to any specific
-5 -ngK ^ anSWer'. " 3 large number of ^consistencies are
If a site is very complicated with many things happening, it is
thee°Z±m ^?t "^ be br°ken d°Wn int° SeV"al ^site'proolems, and
the roram should be run separately for each problem. The program is
gl^-Ka aCd C°Py Printout of a11 ^e questions and answers
I ***\ \^ ^i"*6"' A" ^"P16 °f 3 C<>mPUter Output of the
is included. The output can also be stored on a computer file.
ann , ^ progra™ if written to run on any IBM-PC-DOS compatible computer
and o be very simple to use. It is written in True Basic and by itself
requires about 200 kilobytes of memory. About 512 kilobytes of memory is
required when the overhead of a typical DOS operating system "
To run the program, place the floppy diskette in drive A:, tvne 'A"
olow6rhS '•' ;Ent"' ^ then type 'EXPERT' and press the "Enler'^ey
Follow the instructions shown on the screen from that point on. Press
Ctrl Break' to exit the program at any point (this is not recommended when
nVtnT n™1S Writ1in« lo th? "* >' Quali^ Assurance requirements mandate
inrlvnJY S ° * ^ available in co-piled form and the datafile be
encrypted. However, the program and datafile are not copy protected and may
be freely copied. This program is not subject to U.S. Copyright Law
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RECOMMENDATIONS
A second version of the program (2.0) is currently under development.
Version 2.0 will improve the system by adding a database of the physical
and chemical properties of the top 100 chemicals on the hazardous substances
list. The current version 1.0 asks questions about the properties of the
contaminants, such as "Are the organics miscible with water?" Version 2.0
will present a list of contaminants to select from (such as benzene). For
the top 100 contaminants, it will know the answers to the questions. For
other contaminants, it will still ask the questions about the properties.
Version 2.0 will be available in 1990.
The consideration of other geophysical methods, such as the self or
electrokinetic potential technique, is currently being reviewed and may be
added in the next version of the program.
EXAMPLE OF COMPUTER PRINTOUT
The example on the following pages is a computer printout of the
program. It was based upon initial information of an actual investigation.
The problem was to find buried transformers possibly containing PCB's. The
advisor expert program recommended ground penetrating radar, magnetometer,
and electromagnetic induction methods. In the actual field investigation,
magnetometer and electromagnetic induction methods were used with good
success. Ground penetrating radar equipment was not available for use at
the site. Based upon the field results, it too would have worked with good
success in finding the buried transformers.
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An example of Llic computer printout of the program is shown below
and on the following pages.
NOTICE
The Information In this program has been funded wholly or In part by the
United States Environmental Protection Agency under Interagency agreement
DW14932497-01-1 to the United States Geological Survey. It has been subject
to the Agency's peer and administrative review, and it has been approved for
publication as an EPA document. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.
U.S. Geological Survey preliminary computer program for Geophysics Advisor
Expert System. Written In True BASIC 2.03 to run under Microsoft MS-DOS 2.0
or later on IBM-PC or true compatible computers with 512k or greater memory
available to the program. No source code Is available.
Use of brand names and model numbers is for the sake of description only, and
docs not constitute endorsement by the U.S. Geological Survey.
Although this program has been used by the U.S. Geological Survey, no
warranty, expressed or Implied, Is made by the USGS as to the accuracy and
functioning of the program and related program material nor shall the fact of
distribution constitute any such warranty, and no responsibility Is assumed by
the USGS In connection herewith.
(press any key)
NOTE: You may leave this program at any time by pressing Control-Break.
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SITE NAME: Test Site
This is an example of a test run with the expert advisor program. The problem
was to find buried transformers possibly containing PCBs.
EXPLANATION: (This is the first question.)
QUESTION: The source of contamination was:
ANSWERS:
Unknown
Single event
Continuous leak (fixed)
Continuing leak
EXPLANATION: 'Surface spill' includes all types of contamination that start at
the surface (such as an oil slick or any others than those listed separately).
'Not a spill or leak' is something like an intact, lost barrel of waste.
If several sources are involved, do one session for each...
QUESTION: The contaminants originated from:
ANSWERS:
Unknown
Surface spill
Land treatment facility
Surface impoundment
Leaking landfill
Leaking underground storage tank
Leaking underground pipeline
Leaking trench
Deep injection well
Not a spill or leak
EXPLANATION: For 'Yes' or 'no1 questions like this,
'Unknown' means you don't know and don't care.
'Maybe' is closer to 'Yes' than 'no',
and 'Need to know' means you'd like to know this.
QUESTION: Did the contaminants reach the surface? (or are they on the surface?)
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
QUESTION: Are the contaminants in the unsaturated subsurface? (above the water
table)
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
QUESTION: Are the contaminants in the saturated subsurface?
(at or below the water table)
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
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QUESTION: Do the underground sources (trenches, pipelines, barrels, wells,
tanks, etc.) need to be located?
ANSWERS:
Unknown
No
Maybe
yes
EXPLANATION: Magnetic metals include iron, nickel and many (but not all)
steels. Aluminum, copper, brass, plastic, wood, and glass are non-magnetic.
QUESTION: Do the underground sources (trenches, pipelines, barrels, wells,
tanks, etc.) contain magnetic materials?
ANSWERS:
Unknown
No
Maybe
Yes
EXPLANATION: An areal search is a search across the surface of the earth for
the location of the contaminant problem.
A depth search is a search for the location of the contaminant problem versus
depth.
QUESTION: Is this an areal search, a depth search, or both?
ANSWERS:
Unknown
Areal
Depth
Both
EXPLANATION: 'Container' includes barrels and drums as well as pond and trench
liners.
QUESTION: Are the contaminants in a plume or in a container?
ANSWERS:
Unknown
Surface plume
Subsurface plume
Intact container
Leaky container
Both
QUESTION: What is the form of the container?
ANSWERS:
Unknown
Barrel
Drum
Box
Pipeline
Pond liner
Trench
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SHEET "hat materlal ls the "ntainer or liner made from?
Unknown
Clay
Magnetic metal
Nonmagnetic metal
Rubber
Glass
Wood
Paper
Plastic
Concrete
QUESTION: What is the condition of the container?
ANSWERS:
Unknown
Leaking
Intact
Need to know
QUESTION: Do you need to locate the containers?
ANSWERS:
Unknown
No
Maybe
Yes
QUESTION: Are radioactive contaminants present?
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
QUESTION: Are non-radioactive inorganic contaminants present?
ANSWERS:
Unknown
No
Maybe
yes
Need to know
EXPLANATION: 'Organics' includes hydrocarbons.
QUESTION: Are organics present?
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
EXPLANATION: Soluble or insoluble in water.
Soluble means they chemically dissolve in water (such as alcohol)
QUESTION: Are the organics water soluble or insoluble?
ANSWERS:
Unknown
Insoluble
Soluble
Mixed
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ANSWER™'
sa
°rganics water
physically nix with water
or immiscible?
Unknown
Miscible
Immiscible
Mixed
EXPLANATION: Lighter than water means they float. Heavier than water means they
*: Are the organics heavier or lighter than water?
-Unknown
Neither
Heavier than water
Lighter than water
Both
««„ i-v, r'7' are ne9atively charged in water.
means they are positively charqed in water
QUESTION: Are the organics polar?
ANSWERS:
Unknown
Nonpolar
Anionic
Cationic
Mixed
** * llquid lf the
preferentiallv water-wet or organic-wet?
the
Unknown
Neither
Water
Organic
Both
ANSWERS :
Unknown
Water
Soil
Gas
All
adsorbed
solids,
organics bein? ^dified by any processes?
Unknown -----
No
Maybe
Yes
Need to know
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EXPLANATION: Volatile means they produce a gaseous vapor at room temperature.
(typically that means they may smell.)
QUESTION: Are the organics volatile?
ANSWERS:
Unknown
Non volatile
Volatile
Both
EXPLANATION: Organics present at the surface means in the air, on the ground
or in leaking containers at the surface.
QUESTION: Are there volatile organics present at the surface in the area of
study?
ANSWERS:
Unknown
No
Maybe
Yes
QUESTION: How old is the organic/hydrocarbon contamination?
ANSWERS:
Unknown
Hours
Days
Weeks
Months
Years
EXPLANATION: Empty means land with few or no manmade features of any kind.
Rural means farm country (or 2 or less houses per acre suburbs).
Suburban means 3 or more houses per acre site density.
Urban means high density center-city housing and utility density.
Industrial means setting with high building and utility density.
Landfill means low surface density, high subsurface density clutter.
Military means active military base with many interference sources.
Service station means gasoline/diesel service station or refinery.
Choose the lowest density of buildings and utilities that characterize the
site itself.
QUESTION: What is the environment at the site?
ANSWERS:
Unknown
Empty
Rural
Suburban
Urban
Industrial
Landfill
Military base
Service station
EXPLANATION: Metallic objects such as fences, pipelines, and electrical or
telephone (above or below ground) wires will interfere with some geophysical
techniques.
Small metallic objects such as pop cans are not a problem unless present in
large continuous piles.
Magnetic, electrical and electromagnetic techniques are biased around metallic
objects.
QUESTION: Are there any metallic objects on or near the site?
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ANSWERS:
Unknown
No
Maybe
------ Yes -----
Need to Know
EXPLANATION: Metallic objects such as fences, pipelines, and electrical or
telephone (above or below ground) wires will interfere with some geophysical
techniques.
Small metallic objects such as pop cans are not a problem unless present in
large continuous piles.
Magnetic, electrical and electromagnetic techniques are biased around metallic
objects.
QUESTION: What is the average horizontal spacing between metallic objects?
(such as fences, pipelines or wires)
ANSWERS:
Unknown
<3m <10ft
------ 3-10m 10-30ft -----
10-30m 30-100ft
30-100m 100-300ft
>100m >300ft
EXPLANATION: Metallic objects such as fences, pipelines, and electrical or
telephone (above or below ground) wires will interfere with some geophysical
techniques.
Small metallic objects such as pop cans are not a problem unless present in
large continuous piles.
Magnetic, electrical and electromagnetic techniques are biased around metallic
objects.
QUESTION: How much of the areal extent of the site surface is covered by
metallic objects? (such as metallic trash or metallic-sheet buildings)
ANSWERS:
Unknown
None
10-25%
25-501
50-751
>75%
QUESTION: Are metallic well casings installed at the site?
ANSWERS:
Unknown
------ No -----
Maybe
Yes
EXPLANATION: In this context, buildings means current or former buildings or
their foundations.
QUESTION: How much of the site is covered by buildings?
ANSWERS :
Unknown
None
10-25%
25-50%
50-75%
>75%
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EXPLANATION: 'Difficult' means it is difficult to walk around the site.
'Walking' means most of the site is available to access on foot.
'ATW means access by all terrain vehicle is possible.
'4-WD' means four-wheel drive jeeps can drive over most of the site.
'2-WD van' means two-wheel van-like vehicles can drive over most of the site.
QUESTION: What is the site access like?
ANSWERS:
Unknown
Difficult
Walking
ATV
4-WD
------ 2-WD van (easy access) -----
EXPLANATION: 'Inaccessible' includes site access problems due to property
ownership and trespass, excessive safety hazards such as explosive hazard, and
difficulties due to quicksand, swamp or other similar problems.
QUESTION: How much of the site is inaccessible?
ANSWERS :
Unknown
------ None -----
10-25%
25-50%
50-75%
>75%
QUESTION: What is the annual precipitation?
ANSWERS:
Unknown
<5cm <2in
5-20cm 2-8in
20-50cm 8-20in
------ >50cm >20in -----
EXPLANATION: (If so, what is the wet season?)
QUESTION: Does most precipitation occur in one season of the year?
ANSWERS :
------ Unknown -----
No
Spring
Summer
Fall
Winter
QUESTION: Are there natural organics present? (from forest, jungle, farm,
swamp, etc.)
ANSWERS:
Unknown
------ No -----
Maybe
Yes
EXPLANATION: Radio, TV and radar transmissions may interfere with some
geophysical methods.
In this context, also consider nearby active airports, police stations, and
10
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other non-commercial radio stations.
Arc-welders in welding shops may also qualify as 'radio' transmitters.
QUESTION: Are there radio, TV or radar transmitters within 2 km of the site?
ANSWERS:
Unknown
No
Maybe
Yes
EXPLANATION: Some sounds may interfere with some geophysical methods.
Sources of acoustic noise include railroads, heavily travelled roads, airport
flight paths, and industrial plants.
Continuously windy sites also qualify as acoustically noisy.
QUESTION: Is the site acoustically noisy?
ANSWERS:
Unknown
No
Maybe
Yes
EXPLANATION: These permeability features may modify the results of a soil gas
survey.
QUESTION: Are streams (past or present), utility or other trenches, glacial
scours or drains present in the site?
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
EXPLANATION: Concrete will interfere with some geophysical techniques.
QUESTION: How much of the areal extent of the site is surfaced by concrete?
ANSWERS:
Unknown
None
<25%
25-50%
50-75%
>75%
EXPLANATION: Asphalt will interfere with some geophysical techniques.
QUESTION: How much of the areal extent of the site is surfaced by asphalt?
ANSWERS:
Unknown
None
<25%
25-50%
50-75%
>75%
EXPLANATION: Some geophysical techniques require topographic correction for
proper interpretation.
QUESTION: What is the range of topographic relief across the site?
ANSWERS:
Unknown
10m >30ft
11
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QUESTION: Are there sinkholes or evidence of subsidence present at the site?
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
QUESTION: What is the approximate area of the site?
ANSWERS:
Unknown
<100 sq-m <3 acres
100-1,000 3-30
1,000-10,000 30-300
>10,000 sq-m >300 acres
QUESTION: Is this a four-season site with freezing winters?
ANSWERS:
Unknown
No
Maybe
Yes
QUESTION: What is the average depth of freeze?
ANSWERS:
Unknown
<0.3m 3m >10ft
QUESTION: What is the average depth to bedrock?
ANSWERS:
-Unknown
<3m <10ft
3-10m 10-30ft
10-30ra 30-100ft
>30m >100ft
QUESTION: Do you need to determine the average depth to bedrock?
ANSWERS:
Unknown
No
Maybe
Yes
QUESTION: Is the zone of interest above or below the bedrock interface?
ANSWERS:
Unknown
Above —-
At
Below
All
12
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QUESTION: What is the average depth to the water table?
ANSWERS:
-Unknown
<3m <10ft
3-10m 10-30ft
10-30m 30-100ft
>30m >100ft
QUESTION: Do you need to determine the average depth to the water table?
ANSWERS :
Unknown
------ No -----
Maybe
Yes
QUESTION: Is the zone of interest above or below the water table?
ANSWERS :
Unknown
------ Above -----
At
Below
All
EXPLANATION: In this context, consider lakes, rivers and other permanent
surface water bodies.
QUESTION: How much of the surface areal extent of the site is covered by water?
ANSWERS :
Unknown
------ Hone -----
10-25%
25-50%
50-75%
75-90%
>90wt%
QUESTION: How much of the surface areal extent of the site is regularly
irrigated?
ANSWERS :
Unknown
------ None— ---
10-25%
25-50%
50-75%
75-90%
>90%
EXPLANATION: Resistivity in ohm-meters or (conductivity in millimho/meter)
QUESTION: What is the electrical resistivity of the ground water?
ANSWERS :
------ Unknown -----
<30 ohm-m (>30 mmho/m) [not fresh]
>=30 ohm-m (<30 mmho/m) [fresh]
13
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EXPLANATION: 'Brine layers' include seawater intrusions and other salty waters.
QUESTION: Are there brine layers present at the site?
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
EXPLANATION: Some geophysical techniques are influenced by rock and soil type.
The sequence gravel to clay indicates coarse to fine particle size.
QUESTION: What is the dominant soil type at the site?
ANSWERS:
Unknown
Rock - no soil
Gravel
Sand
Till
Clay
EXPLANATION: The presence of clay helps some geophysical techniques and
hinders others.
Clay in this context means mineralogical clay (such as montnorillonite) not
engineering-size-fraction 'clay'.
The depth penetration of ground penetrating radar in particular is strongly
limited by clay.
QUESTION: Is clay present at the site? (exclude a basal clay below depths of
interest)
ANSWERS:
Unknown
No
Maybe
Yes
Need to know
EXPLANATION: 'Quickly' means in less than one day.
QUESTION: Does rainfall on the site surface sink in slowly or quickly?
ANSWERS:
Unknown
Run off
Pond
Sink in slowly
Sink in quickly
EXPLANATION: Resistivity in ohm-meters or (conductivity in millimho/meter).
QUESTION: What is the average electrical resistivity of the site in ohm-meters?
ANSWERS:
Unknown
<1 ohm-m (>1000 mmho/m)
1-10 (100-1000)
10-30 (33-100)
30-100 (10-33)
100-300 (3-10)
>300 ohm-m (<3 mmho/m)
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SITE: Test Site
0014 Ground penetrating radar methods recommended.
0010 Magnetic methods recommended.
0010 Electromagnetic induction methods recommended.
0001 Resistivity effectiveness is uncertain.
0000 Soil gas effectiveness is uncertain.
0000 Seismic effectiveness is uncertain.
0000 Gravity methods not recommended.
-010 Radiometric methods not recommended.
15
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SITE: Test Site
Site specific comments: 0010 Electromagnetic induction methods recommended.
Use time domain EN for deep sounding.
EN induction methods work well in locating underground sources.
Metal detectors methods work well in locating underground sources that are
less than 3 meters deep. EM techniques are better for areal searches.
EM methods may find magnetic metallic containers.
Metal detectors may find magnetic metallic containers buried less than 3
meters deep. EM methods may find metallic containers.
Metal detectors may find shallow metallic containers buried less than 3 meters
deep. Metallic objects interfere with EM techniques.
Too many metallic objects for EM.
EM techniques will require topographic correction.
0010 Electromagnetic induction methods recommended. EMI are electromagnetic
techniques that induce currents in the earth. They measure the magnetic field
generated by the induced currents. The electrical conductivity of the earth
is proportional to the magnetic field generated from the induced currents.
The depth of investigation is a function of the instrument coil spacing and
orientation, frequency of measurement, and the electrical conductivity of the
ground. By measuring and mapping the changes in electrical conductivity, EMI
techniques may directly locate plumes of inorganic contaminants, clay lenses,
metallic objects such as buried drums, and inhomogeneities in geology such as
fractures. EMI techniques are ineffective in areas with many fences,
pipelines, telephone cables, and other metallic interferences. EMI techniques
require topographic correction. EMI techniques are readily available
commercially, relatively inexpensive, and require 1 or 2 man crews. EMI
methods acquire data very quickly over large areas, whereas resistivity
methods are preferred for sounding to acquire depth information. For further
information, see: Keller, G.V. and Frischknecht,F., 1966, Electrical methods
in geophysical prospecting, NY, Pergamon, 517p. Greenhouse, J. and Harris,
R., 1983, Migration of contaminants in ground water at a landfill: a case
study, 7. DC, VLF, and inductive resistivity surveys, J.Hydrol., v.63,
p. 177-197. McNeil1, J.D., 1988, Advances in electromagnetic methods for
groundwater studies, in Proc.Symp.Appl.Geophys.Engr.& Environ.Probl., Golden,
CO, Soc.Engr.6 Min.Explor.Geophys., p.252-348.
16
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SITE: Test Site
Site specific comments: 0014 Ground penetrating radar methods recommended.
Radar has very high resolution for locating underground sources (trenches,
barrels, tanks, pipelines, etc.)- Radar may find magnetic metallic containers.
Radar has the highest resolution to find containers.
Radar can detect some kinds of organics.
Radar may require topographic correction.
Perform radar during winter to exploit high resistivity of frozen ground.
Radar may find depth to bedrock.
Radar may determine the depth to the water table.
Radar may determine the depth to the clay.
0014 Ground penetrating radar methods recommended. GPR measures changes in
the propagation of electromagnetic energy in the ground. Such changes
typically occur from changes in water content and bulk density. Thus, GPR is
a sensitive indicator of soil stratigraphy, bedrock fracturing and an
excellent way to map the water table. GPR may sometimes directly detect
organic contaminants either by changes in scattering properties (the texture
of the radar record) or dielectric contrast (such as oil floating on water).
GPR works well in high resistivity environments such as dry or fresh-water
saturated coarse sand or granite. Low resistivity salt water and clays such
as montmorillonite severely limit the depth of penetration and effectiveness
of GPR. In clay-free soil with resistivity above 30 ohm-m, GPR can provide
vertical sections of the earth to depths of 30 meters with resolution of a few
centimeters. For further information, see: Olhoeft, G.R., 1984, Applications
and limitations of ground penetrating radar, in Expanded abstracts, 54th
Annual Int'l. Meeting and Expo, of the Soc. of Explor.Geophys., Atlanta,
p. 147-148. Olhoeft, G.R., 1986, Direct detection of hydrocarbon and organic
chemicals with ground penetrating radar and complex resistivity, in Proc. of
the NWWA/API Conf. on Petroleum hydrocarbons and organic chemicals in ground
water — prevention, detection and restoration, Nov.12-14, Houston, p.284-304.
Olhoeft, G.R., 1988, Selected bibliography on ground penetrating radar, in
Proc.Symp.Appl.Geophys.Engr.b Environ.Probl., Golden, CO, Soc.Engr.4
Mm. Explor.Geophys., p. 462-520.
17
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SITE: Test Site
Site specific comments: 0001 Resistivity effectiveness is uncertain.
DC resistivity techniques are better for depth searches.
Resistivity techniques will require topographic correction.
0001 Resistivity effectiveness is uncertain. Resistivity techniques
use electrodes in contact with the ground to measure electrical resistivity
(reciprocal of conductivity). The depth of investigation is a function of the
electrode spacing and geometry, (larger spacings see deeper). By measuring
and mapping the changes in electrical resistivity, these techniques may
directly locate plumes of inorganic contaminants, clay lenses, metallic
objects such as buried drums, and inhomogeneities in geology such as
fractures. Resistivity techniques are ineffective in areas with many fences,
pipelines, telephone cables, and other metallic interferences. Resistivity
techniques require topographic correction, are readily available commercially,
relatively inexpensive, and require 1 or 2 man crews. Resistivity methods are
preferred for sounding to acquire depth information, whereas EM induction
provides easier and faster areal mapping. For further information, see:
Greenhouse, J. and Harris, R., 1983, Migration of contaminants in ground water
at a landfill: a case study, 7. DC, VLF, and inductive resistivity surveys,
J.Hydrol., v.63, p.177-197. Complex resistivity measures resistivity as a
function of frequency. It can detect organic contaminants when they react
with clay minerals, but it is much more time consuming and expensive than DC
resistivity. Olhoeft, G.R., 1986, Direct detection of hydrocarbon and organic
chemicals with ground penetrating radar and complex resistivity, in
Proc.NWWA/API Conf.Petroleum hydrocarbons and organic chemicals in ground
water — prevention, detection and restoration, Nov.12-14, Houston, p.284-304.
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SITE: Test Site
Site specific comments: 0000 Seismic effectiveness is uncertain.
Seismic methods may require topographic correction.
0000 Seismic effectiveness is uncertain. Seismic techniques measure
changes in the propagation of elastic compressional or shear energy in the
ground. They may be operated in reflection or refraction modes. They are
sensitive to changes in density and water content. They are most useful in
defining subsurface geological and hydrological structure. They cannot detect
contaminants directly, though they may locate trenches or other disturbed
burial zones in the ground. In urban environments, high noise or difficult
coupling (such as through concrete or asphalt) may make their use prohibitive.
Seismic and radar techniques are complementary as seismic works well in clay
soils where radar does not, and radar works well in loosely compacted sandy
soil where seismic does not. Basic references are: Mooney, H.N., 1973,
Handbook of engineering geophysics, vol.1, seismic: Bison Instruments,
Minneapolis, MN, 216p. Romig, P.R., ed., 1986, Special issue - engineering
and ground water, Geophysics, v.51, p.221-323. Hasbrouck, W.P., 1987,
Hammer-impact, shear-wave studies, in Shear-wave exploration, S.H.Danbom and
S.N.Domenico, eds., Tulsa, SEG, p.97-121. Ensley, R.A., 1987, Classified
bibliography of shear-wave seismology, in Shear-wave exploration, S.H.Danbom
and S.N.Domenico, eds., Tulsa, SEG, pp.255-275. Lankston, R.W., 1988, High
resolution refraction data acquisition and interpretation, in
Proc.Symp.Appl.Geophys.Engr.& Environ.Probl., Golden, CO, Soc.Engr.4
Min.Explor.Geophys., p.349-408. Steeples, D.W. and Miller, R.D., 1988,
Seismic reflection methods applied to engineering, environmental and ground
water problems, ibidem, p.409-461.
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SITE: Test Site
Site specific comments: 0010 Magnetic methods recommended.
Magnetics are good for locating underground sources (trenches, barrels, tanks,
pipelines, etc.) containing or filled with magnetic metals.
Magnetics are good at finding magnetic materials.
Too many metallic objects for magnetics.
0010 Magnetic methods recommended. Magnetic techniques measure perturbations
in the earth's natural magnetic field near magnetic objects such as iron drums
or barrels. Magnetic techniques cannot locate non-metallic materials nor
non-magnetic metallic objects. Large concentrations of iron or steel fences,
utilities, culverts, vehicles or buildings may interfere with the technique.
High iron content soils (such as greensands, basalts, red hematitic soils) may
be sufficiently magnetic to hide objects detectable under other soil
conditions. Basic references include: Benson, R.C., Glaccum, R.A., and Noel,
M.R., 1983, Geophysical techniques for sensing buried wastes and waste
migration, National Water Well Association, Dublin, OH, 236p. Hinze, W.J.,
1988, Gravity and magnetic methods applied to engineering and environmental
problems, in Proc.Symp.Appl.Geophys.Engr.S Environ.Probl., Golden, CO,
Soc.Engr.fi Min.Explor.Geophys., p.1-108.
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SITE: Test Site
Site specific comments: 0000 Gravity methods not
recommended.
0000 Gravity methods not recommended. Gravity techniques
measure changes in the gravitational field of the earth. These changes are
interpreted in terns of changes in density and porosity in the ground.
Microgravity techniques may be useful in locating trenches, voids, and
incipient subsidence problems. They cannot directly detect contaminants.
Gravity techniques require accurate location and topographic surveying,
removal of regional gradients, and correction for tidal effects. Basic
references are: Butler, O.K., 1984, Microgravimetric and gravity gradient
techniques for detecting subsurface cavities, Geophysics, v.49, p.1084-1096.
Rodrigues, E.B., 1987, Application of gravity and seismic methods in
hydrogeological mapping at a landfill site in Ontario, in Proc. of the First
National Outdoor Action Conference on Aquifer Restoration, Ground Water
Monitoring and Geophysical Methods, Nay 18-21, 1987, Las Vegas, NWWA, Dublin,
Ohio, p.487-503. Hinze, W.J., 1988, Gravity and magnetic methods applied to
engineering and environmental problems, in Proc.Symp.Appl.Geophys.Engr.i
Environ.Probl., Golden, CO, Soc.Engr.& Min.Explor.Geophysi, p.1-108.
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SITE: Test Site
Site specific comments: -010 Radiometric methods not
recommended. There are no radioactive materials present.
~01° . Radiometric methods not recommended. Radiometric
techniques measure the radiation emmitted from radioactive isotopes.
Radioactive contaminants may bo maakod by high background levels of natural
radioactivity or by roughly a meter of overlying soil cover (depending upon
the type and strength of the source). These are generally only useful at
radioactive waste disposal sites. However, they may be useful in locating
natural radioactive hazards (such as radon gas sources), early radium
processing plants, mining mill tailings, and other similar sites. Basic
references are: EG&G Idaho Inc., 1983, Low-level radioactive waste management
handbook series: Environmental monitoring for low-level waste-disposal sites
°^/L^3Tg' available from N>"S, Springfield, VA, var.pag.; Morse, J.G., '
ed., 1977, Nuclear methods in mineral exploration and production, NY, Elsevier
2 80p •
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