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OCR for page 120
7
Realizing Future Capabilities
During the past two decades, advances in computing and microelectronics
have stimulated the production of an impressive array of tools and techniques for
noninvasive characterization of the shallow subsurface. These advances have
made existing tools and techniques faster, cheaper, or more effective. However,
there have been relatively few fundamental innovations with regard to the phe-
nomena being observed or the sensing devices that convert those phenomena into
electrical signals. Additional research and development (R&D) is needed to en-
hance and extend current capabilities, to develop fundamentally new measure-
ments, and to close the aforementioned gap between the state of the practice and
the state of knowledge.
Some of R&D areas are short-term (e.g., 3 to 5 years) opportunities for
advances that can be achieved using existing knowledge and technologies in
other words, enabling the state of the practice to be closer to the state of the art.
These include the automation of tools and techniques and the development of
methods for monitoring properties, processes, and temporal variations. Others are
of a long-term (e.g., 10 to 20 years), high-risk nature, but they offer the potential to
enhance significantly our ability to "see into the earth." The long-term needs deal
primarily with the discovery of fundamentally new phenomena that can provide
information about subsurface conditions and the development of new sensing tech-
niques for making measurements at a distance. In this section, the recommenda-
tions for R&D are presented in order from short term to long term.
The resource industries (particularly oil) have invested heavily in R&D be-
cause they are profit driven; breakthroughs in exploration can dramatically in-
crease profits. In comparison to the gross expenditures on characterization ef-
forts, the near-surface characterization industry invests relatively little in R&D.
120
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REALIZING FUTURE CAPABILITIES
121
The committee believes that lack of investment results because site characteriza-
tion activities do not generate revenue for the client but are required in a wide
range of environmental and engineering situations. In this situation, R&D is often
a cost without commensurate short-term benefits. This is exacerbated by the
"low-bid" nature of most specific site characterization efforts (Shuirman and
Slosson, 1992), a situation not likely to change. As a result, the private sector
usually defers needed R&D in favor of activities that produce more immediate
benefits in the form of cost reduction. As such, the committee believes that it is in
the interest of the nation to increase the federal government' s investment in R&D
and to provide incentives and mechanisms for increased private sector invest-
ment. Finally, because much of the research is based in universities and federal
laboratories, it will be important to provide for effective communications be-
tween researchers and industry to ensure that both short-term and long-term R&D
products are of great value to the near-surface characterization industry.
Government agencies should be encouraged to increase their in-
vestment in near-surface characterization R&D in the areas appropri-
ate to their mission.
For example, this includes:
.
Agencies (e.g., the Department of Defense and the Department of En-
ergy) that are required to deal with near-surface problems (hazardous waste,
construction, etc.) at their own sites;
· Agencies (e.g., the Environmental Protection Agency, the Department of
the Interior, the Department of Transportation, and the U.S. Army Corps of
Engineers) responsible for oversight of the environment, resource development,
transportation, and infrastructure where near-surface characterization can be an
integral part of their business; and
· Agencies for which basic research either is their primary mission (e.g.,
the National Science Foundation) or is critical to their mission (e.g., the U.S.
Geological Survey).
In addition, research programs supported by federal agencies should take
advantage of advisory boards to ensure that R&D expenditures are producing
innovations that will be of value to the site characterization process.
The federal government already supports some of the R&D that is needed to
deal with proliferating societal issues ranging from land mines to hazardous
waste to underground construction. A mechanism should be developed to stimu-
late private sector investment in R&D in spite of the cost-driven nature of the
industry and its size (usually small consulting firms) and application-specific
nature.
OCR for page 122
22
SEEING INTO THE EARTH
Government and industry should cooperatively investigate mecha
nisms for coordination and support of site characterization research.
One possible mechanism is a quasi-governmental entity that could be em-
powered to collect funds from site characterization contractors and clients. On
the other hand, the site characterization industry may have special characteristics
that demand an entirely new model. Initially it would be useful to define the
needs and characteristics of the industry (particularly the economic structure)
prior to designing a solution that optimally meets these needs.
In addition to traditional forms of R&D support, universities and government
labs should be encouraged to form more partnerships with industry to develop
tools and techniques that will enhance everyday field applications. This will help
effect the transition between the state of knowledge and the state of practice.
To ensure rapid technical transfer from research to practice, research could
be carried out by teams that include both practitioners (e.g., geobiologists, geo-
chemists, geophysicists) and clients (e.g., environmental scientists, civil engi-
neers). Such research teams should communicate their results to the scientific,
engineering, and user communities in widely available venues and in forms suit-
able for more immediate adoption.
AUTOMATION OF TECHNIQUES
Research and development efforts applied to automation of data acquisition,
data processing, and decision making could produce rapid improvement in all
aspects of near-surface characterization and should be given a high priority for
research funding.
Automation can be applied to data acquisition (e.g., robotics), data process-
ing, and decision making (e.g., use of expert systems and other decision tools for
survey planning and data interpretation). The benefits of automation include ease
of use, consistency, quality assurance, and cost reduction. It also could enable
more rapid technology transfer of the latest tools and techniques from the re-
search lab to the field, thus enabling the state of the practice to be nearer to the
state of the science. Finally, automation could help the site characterization in-
dustry deal with periodic shortages of trained professionals in specialized fields.
At present, for example, there is a potential shortage of individuals with
advanced education in shallow-exploration geophysics. Low enrollments in uni-
versity programs for the past decade, coupled with employment opportunities in
the oil and mining industries, may make it difficult for site characterization
companies to hire enough qualified professionals. However, computers can help
design a site survey, automate data acquisition, check the quality of data, process
the data, model the data, and provide a rough interpretation. For example, the
Geophysics Advisor Expert System (Olhoeft, 1992) can help select appropriate
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REALIZING FUTURE CAPABILITIES
123
geophysical tools to apply to EPA Superfund site problems (and in the process,
educate site managers and contractors). However, such systems are guides and
will not replace the need for skilled professionals; the uniqueness of sites makes
it difficult to include every possibility in such systems. Another example is a
tunnel detection system (Olhoeft, 1993) that automatically tests data quality
through 12 consistency tests (and, if necessary, indicates what might be wrong
with the data and ways to correct them). The system also processes the data for
the normal logistical, operational, and instrumental artifacts; manipulates and
models the data; and provides a graphical output of the most likely location for
detection of a tunnel. At each step, the program provides quantitative data pro-
cessing, modeling, and interpretive (uncertainty and confidence) indicators. These
types of automation and decision support systems can provide the expertise to
complement the skills of practitioners and help alleviate personnel shortages.
Automation also can make an important contribution to work in hazardous
environments. Not only can robotic technology make it possible to avoid putting
humans in dangerous situations, but expert systems and decision support tools
can further enhance the quality of data by making real-time decisions about
optimizing acquisition parameters. Ultimately, such systems could improve data
quality, lower cost, and enhance safety.
These are only a few examples of automation techniques that could provide
expertise, guide the characterization process, and ensure quality control. The
necessary capability to develop such techniques exists in universities and govern-
ment laboratories, and the techniques could be rapidly embedded in systems for
broad use. Impediments to broader development and use of these automated
systems include the issue of deciding how such systems should be certified, who
should be authorized to conduct the certification, and how the systems will be
updated.
Automation will not replace skilled practitioners; however, it can signifi-
cantly increase the knowledge base that practitioners use to accomplish their
jobs. By producing a better result, more rapidly and at lower cost, robotics and
decision support systems could be the key to more and more effective use of
site characterization methods. Therefore, automation of site characterization pro-
cesses should be pursued on two broad fronts simultaneously. Experts in univer-
sities and government laboratories should move aggressively to develop tech-
niques and systems for automation of activities and decision-making processes.
At the same time, the key regulatory bodies should develop certification policies
and procedures using experts from the legal, technical, and political arenas. Re-
search and development should include (but not be limited to) the following:
.
Expert systems to provide advice and guidance in designing characteriza-
tion surveys, optimizing parameters, estimating probability of success, validating
decisions, and justifying costs;
OCR for page 124
24
SEEING INTO THE EARTH
· Automated data acquisition instruments to ensure competent use, enable
field processing and interpretation, and provide quality control;
Expert systems, decision trees, and pattern recognition software to guide
data processing sequences;
· Decision support systems to assist in interpretation, incorporating effec-
tive use of modeling and simulation to validate possible interpretations and pro-
vide quantitative estimates of uncertainty;
.
.
Policies and procedures for certifying the validity and effectiveness of
automation tools; and
· Guidelines for regulatory adoption of the appropriate and proper use of
certified automation tools.
MONITORING TEMPORAL VARIATIONS
Many site characterization problems involve changes with time. Examples
include monitoring engineered barriers to confirm containment of contaminants,
analyzing changes in soil moisture to assess water fluxes, or surveying an envi-
ronmental remediation site to characterize the reduction in the extent of subsur-
face contamination. A single observation or survey at a characterization site may
show the distribution of materials in question at that point in time, but it will not
provide information about changes from earlier conditions or help predict future
evolution.
In many cases, properly designed multiple surveys can detect and monitor
small changes in properties with higher resolution than is possible within a single
survey. Significant advances can result from the development of exploration
strategies (using existing tools) for acquiring, processing, and interpreting time-
varying information. In the long term, research also is needed to develop mea-
surement technology that will allow monitoring new processes such as in situ
leaching or bioremediation.
Uses for time-varying information include the following:
· The ability to predict changes that may occur in response to human activ-
ity (or lack thereof) is essential to design and defend remediation plans.
· Baseline data and historical information often are needed to assess liabil-
ity or responsibility. Where baseline information does not exist, data from re-
peated measurements sometimes can be extrapolated backwards to provide in-
sight into history.
.
Monitoring the remediation process might either verify that the plan is
working or provide a quantitative basis for changing the plan to improve the
chances of success.
Observing contaminant transport in the subsurface has been done almost
exclusively through the use of monitoring wells. However, certain situations may
OCR for page 125
REALIZING FUTURE CAPABILITIES
125
preclude the use of monitoring wells. Even where wells are allowed, they often
may not be the most-cost effective solution, and in many cases they provide
limited areal coverage. Noninvasive methods could provide an economical means
for large-scale, long-term monitoring and also reveal the dynamics of subsurface
processes; for example:
· Monitoring of the land surface by remote sensing techniques could pro-
vide much information about the subsurface conditions in the top meter or so.
· Changes in moisture conditions at the surface could indicate subsurface
heterogeneity. Soil-gas surveys could monitor microbial activity or assess the
success of remediation schemes.
· Repeat geophysical surveys could indicate changes in the distribution of
subsurface fluids, which is particularly useful in monitoring contaminant move-
ment (e.g., DNAPL remobilization) during site remediation activities.
Noninvasive monitoring for prolonged periods of time should be considered
an integral part of site characterization, underground construction, and remedia-
tion projects that require monitoring.
Noninvasive techniques could augment traditional invasive monitoring and
enhance our ability to test and develop an understanding of subsurface processes.
In some cases, noninvasive methods are the only alternative. The following R&D
efforts are needed for this to become common practice:
· Geological noise and other factors limit the resolution of a survey method.
If the noise does not change with time, then changes in key properties often can
be detected with higher resolution than the properties themselves can be mapped.
The development of processing and interpretation techniques that take advantage
of differential measurements would allow existing tools and survey methods to
be used effectively for monitoring.
· As new remediation techniques are developed (in situ leaching, bio-
remediation, etc.), monitoring properties indicative of the progress of a remedia-
tive actions might be difficult using existing characterization tools and survey
methods. Fundamentally new tools (such as magnetic resonance imaging and
seismic-electric techniques) offer the promise of making measurements previ-
ously thought impossible. Monitoring needs for the next decade could require a
long-term, sustained program of fundamental research into "exotic" measure-
ment technologies.
PROPERTIES AND PROCESSES
Site characterization historically has focused on mapping the subsurface
geometry (e.g., location of anomalies, shapes of boundaries). Physical, chemical,
and biological properties and processes (including coupling between processes)
OCR for page 126
26
SEEING INTO THE EARTH
are at least as important as geometry; however, there has been limited research
into the noninvasive measurement of such properties and processes and their
distribution. Developing the ability to observe these properties and processes
noninvasively will require long-term research, from the perspective of both un-
derstanding the phenomena and developing the methodology to measure and
interpret these phenomena.
Until recently, measurements of properties (e.g., the bearing strength of the
foundation material at a construction site) usually have been done on samples
obtained by drilling or other intrusive means. Today there is a growing demand
for nonintrusive surveys that measure in situ properties (chemical and biological
as well as mechanical). For example, no longer is it sufficient to find the top of
the saturated zone; now it also is necessary to determine water quality or identify
contaminants. In the future, solutions to environmental and engineering problems
of the shallow subsurface also will depend on understanding and observing in situ
chemical and biological processes and the interactions between them.
Characterization methods used to find anomalies or map subsurface geom-
etry actually are detecting variations in properties or mapping boundaries be-
tween areas of different properties. However, quantitative relationships between
the phenomena being observed and the values of the in situ properties usually are
not well defined and often involve ambiguity. Therefore, although the location of
the variations or boundaries can be mapped, relatively little information about the
properties themselves (such as the specific contaminant being mapped) can be
determined. The problem is worse if the target involves a chemical or biological
process because, in many cases there is little knowledge about the relationship
between the in situ process and the phenomena observable at the surface. An
example would be the situation wherein a biological agent was introduced into a
region containing a chemical pollutant. We know little about whether the biologi-
cal process produces any effect that is potentially measurable, let alone how to
measure it.
As part of a basic research program, there needs to be a signifi
cant effort directed toward quantification of physical and chemical
realities of what is being sensed as well as possible interactions be
tween in situ properties and processes.
Some noninvasive methods for subsurface characterization are well under-
stood. For instance, there is a good correlation between seismic measurements
and the elastic properties of the material being sensed. This is not the case for
many other measurements. Fundamental studies should be initiated and expanded
to include the following:
· Understand subsurface processes and the interactions between them, and
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REALIZING FUTURE CAPABILITIES
127
identify the measurable properties that might be associated with these processes
or combinations of processes.
Establish theoretical and phenomenological relationships between the
properties and processes of interest and the phenomena that could be measured
noninvasively at the surface.
· Develop instruments and techniques that will allow these phenomena to
be measured with useful resolution and adequate signal-to-noise ratio.
.
.
Produce the interpretive tools and procedures to invert the surface mea-
surements into an accurate description of the properties or processes at depth.
Fundamental studies should be supplemented by variable-scale testing, rang-
ing from laboratory examination of cores to full-scale integrated surveys of stan-
dard test sites. The National Geotechnical Test Site Program, supported by the
National Science Foundation and the Federal Highway Administration and man-
aged by the National Council for Geo-Engineering and Construction, might serve
as a useful model. Other test sites (e.g., those at the University of Arizona,
Stanford University, and the Idaho National Environmental Engineering Labora-
tory) have been established for specific research projects. These test sites can be
used to develop new techniques and to validate models.
OPPORTUNITIES FOR INNOVATIVE MEASUREMENTS
Most existing technologies measure physical phenomena and are used to
interpret physical properties and processes. Few methods exist to monitor the
chemical or biological properties and processes that are becoming increasingly
important, particularly in areas such as groundwater management and hazardous
waste mitigation. The discovery of fundamentally new measurement technolo-
gies, the ability to observe fundamentally new phenomena, and better interaction
between disciplines are essential for nonintrusive site characterization to meet
current and future needs.
Nonintrusive characterization methods inherently rely on "action at a dis-
tance." Furthermore, the action at a distance must occur rapidly compared to the
time scale of the process in order for the measurement to reflect current conditions.
For example, biological agents working on organic pollutants at depth might pro-
duce a volatile by-product that can migrate to the surface where it could be mapped
with a soil-gas survey. However, if the rate of propagation of the volatile product is
slower than the action of the biological agent, the soil-gas survey could be describ-
ing conditions that have changed by the time of the survey.
The measurement of physical phenomena on the surface to infer physical
properties at depth is relatively well developed. However, many of the challenges
in site characterization for environmental applications involve interpreting sur-
face measurements to infer chemical and biological properties and processes at
depth. Methods for accomplishing the latter are not as well developed, and in
OCR for page 128
28
SEEING INTO THE EARTH
many cases, there are no quantitative measurements that can yield information
about such properties or processes.
Some physical phenomena can be interpreted to yield such information (for
example, subtle features in a ground penetrating radar signal are linked to the
chemistry of certain subsurface pollutants); however the relationships between
the phenomena and the properties or processes generally are not well understood.
There are a few geochemical measurements that also can provide information
about in situ properties (the use of "sniffers" to sample gases emanating from the
soil), but again the connection between the source and the observation is not
always well understood. Furthermore, in many cases involving geochemical mea-
surements, the time scale of the phenomenon is long relative to the process being
monitored (e.g., the soil-gas survey mentioned above), in which case the mea-
surements may be of little practical use.
In the future, the committee expects subsurface biological activity to become
a major issue; however, the ability to relate surface observations to biological
properties and processes is even more limited. A few physical measurements
indirectly involve biological agents (for example, spectral imaging can be used to
interpret the health of plants that, in turn, can indicate depth to water table).
However, there are few, if any, ways to infer biological agents or activity at depth
directly from physical observations on the surface. It may be possible to use
geochemical observations to infer geobiological properties or processes, but at
the present time the capabilities of most of these methods are limited and their
efficacy has not been demonstrated. Such measurements also are subject to the
time-delay problems mentioned above.
The committee believes that the lack of progress in these areas is the result of
insufficient research directed to the connections between the physical phenomena
and the chemical or biological property or process; part of this is probably a lack
of understanding or appreciation of the importance of these problems. However,
the problem may be more deeply rooted in the lack of communication between
geophysicists, geochemists, and geobiologists. Fragmentation in the traditional
earth sciences is well documented (there are 32 separate professional societies
that are members of the American Geological Institute and even more that do not
participate in this organization), but the gap between fields and geochemistry or
(especially) geobiology is even greater. Therefore, any increase in support for
research in mapping chemical or biological properties must be accompanied by a
commitment to truly effective cross-disciplinary interaction.
Long-term research to develop fundamentally new noninvasive
tools and techniques should be given a high priority, with emphasis on
research done by multidisciplinary teams.
Among the challenges in site characterization technologies in the coming
decades will be measurement, both direct and indirect, of geochemical and
OCR for page 129
REALIZING FUTURE CAPABILITIES
129
geobiological properties and processes. Meeting this challenge will require long-
term investment in high-nsk research leading to
· A better understanding of the relationship between chemical and biologi-
cal properties and processes and physical phenomena that can be measured with
existing instruments;
.
The discovery of fundamentally new measurement technologies that can
measure a physical phenomenon that has a causal relationship with
subsurface chemistry or biology;
make a direct chemical or biological measurement that is diagnostic
of conditions at depth; and
3. the ability to observe fundamentally-new phenomena; and
· Better data fusion and integrated processing, modeling, and visualization
of data from all three specialties.
Development of these innovative techniques and measurements will require
the following:
· Research to be done by multidisciplinary teams;
· Cross-disciplinary education of specialists to enhance their ability to work
effectively on multidisciplinary teams;
.
Facilities such as well-controlled test sites that support multidisciplinary
development and validation of measurement, processing, interpretation, and mod-
eling systems; and
· More effective communication and interaction between the biological,
chemical, and physical specialists within the site characterization community.
Progress in promoting more effective use of existing tools for noninvasive
characterization and improving and developing new techniques should lead to a
greater understanding of the shallow subsurface and the applications that depend
on this understanding.
REFERENCES
Olhoeft, G. R., 1992. Geophysics Advisor Expert System (version 2.0): U.S. Geological Survey
Open-File Report 92-526, 21 pp. and floppy disk.
Olhoeft, G. R., 1993. Velocity, attenuation, dispersion and diffraction hole-to-hole radar processing,
in Proceedings of the Fourth Tunnel Detection Symposium on Subsurface Exploration Technol-
ogy, Colorado School of Mines, Golden, Colorado, 26-29 April 1993, R. Miller, ea., U.S. Army
Belvoir Research, Development and Engineering Center, pp. 309-322.
Shuirman, G., and Slosson, J. E., 1992. Forensic Engineering, Environmental Case Histories for
Civil Engineering and Geologists, Academic Press, Inc., San Diego, California, 296 pp.
OCR for page 130
Representative terms from entire chapter:
realizing future
