Groundwater Contamination
DOD Uses and Develops a Range of Remediation Technologies to Clean Up Military Sites Gao ID: GAO-05-666 June 30, 2005To date, the Department of Defense (DOD) has identified nearly 6,000 sites at its facilities that require groundwater remediation and has invested $20 billion over the past 10 years to clean up these sites. In the past, DOD primarily used "pump-and-treat" technologies to contain or eliminate hazardous contaminants in groundwater. However, the long cleanup times and high costs of using pump-and-treat technologies often make them expensive and ineffective for groundwater remediation. As directed by Public Law 108-375 and as agreed, GAO (1) described current DOD groundwater remediation technologies and (2) examined whether any new technologies are being used or developed outside the department that may have potential for DOD's use and the extent to which DOD is researching and developing new approaches to groundwater remediation. GAO provided the Department of Defense with a draft copy of the report for its review and comment. DOD generally agreed with the contents stating that the report is an accurate summary of DOD's use and field tests of remedial technologies. DOD also provided technical clarifications that have been incorporated, as appropriate.
DOD has implemented or field-tested all of the 15 types of generally accepted technologies currently available to remediate contaminated groundwater, including several alternatives to pump-and-treat technologies. Some of these technologies, such as bioremediation, introduce nutrients or other materials into the subsurface to stimulate microorganisms in the soil; these microorganisms consume the contaminant or produce byproducts that help break down contaminants into nontoxic or less-hazardous materials. DOD selects the most suitable technology for a given site on the basis of several factors, such as the type of contaminant and location in the subsurface, and the relative cost-effectiveness of a technology for a given site. DOD has identified a number of contaminants of concern at its facilities, each of which varies in its susceptibility to treatment. GAO did not identify any alternative groundwater remediation technologies being used or developed outside DOD that the department has not considered or used. Most of the new approaches developed by commercial vendors and available to DOD generally use novel materials applied to contaminated sites with existing technologies. DOD actively researches and tests new approaches to groundwater remediation largely by developing and promoting the acceptance of innovative remediation technologies. For example, DOD's Strategic Environmental Research and Development Program supports public and private research on contaminants of concern to DOD and innovative methods for their treatment.
GAO-05-666, Groundwater Contamination: DOD Uses and Develops a Range of Remediation Technologies to Clean Up Military Sites
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Report to Congressional Committees:
June 2005:
Groundwater Contamination:
DOD Uses and Develops a Range of Remediation Technologies to Clean Up
Military Sites:
[Hyperlink, http://www.gao.gov/cgi-bin/getrpt?GAO-05-666]
GAO Highlights:
Highlights of GAO-05-666, a report to congressional committees:
Why GAO Did This Study:
To date, the Department of Defense (DOD) has identified nearly 6,000
sites at its facilities that require groundwater remediation and has
invested $20 billion over the past 10 years to clean up these sites. In
the past, DOD primarily used ’pump-and-treat“ technologies to contain
or eliminate hazardous contaminants in groundwater. However, the long
cleanup times and high costs of using pump-and-treat technologies often
make them expensive and ineffective for groundwater remediation.
As directed by Public Law 108-375 and as agreed, GAO (1) described
current DOD groundwater remediation technologies and (2) examined
whether any new technologies are being used or developed outside the
department that may have potential for DOD‘s use and the extent to
which DOD is researching and developing new approaches to groundwater
remediation.
GAO provided the Department of Defense with a draft copy of the report
for its review and comment. DOD generally agreed with the contents
stating that the report is an accurate summary of DOD‘s use and field
tests of remedial technologies. DOD also provided technical
clarifications that have been incorporated, as appropriate.
What GAO Found:
DOD has implemented or field-tested all of the 15 types of generally
accepted technologies currently available to remediate contaminated
groundwater, including several alternatives to pump-and-treat
technologies. Some of these technologies, such as bioremediation,
introduce nutrients or other materials into the subsurface to stimulate
microorganisms in the soil; these microorganisms consume the
contaminant or produce byproducts that help break down contaminants
into nontoxic or less-hazardous materials. DOD selects the most
suitable technology for a given site on the basis of several factors,
such as the type of contaminant and location in the subsurface, and the
relative cost-effectiveness of a technology for a given site. DOD has
identified a number of contaminants of concern at its facilities, each
of which varies in its susceptibility to treatment. The table below
shows the technologies DOD used to remediate contaminated groundwater.
GAO did not identify any alternative groundwater remediation
technologies being used or developed outside DOD that the department
has not considered or used. Most of the new approaches developed by
commercial vendors and available to DOD generally use novel materials
applied to contaminated sites with existing technologies. DOD actively
researches and tests new approaches to groundwater remediation largely
by developing and promoting the acceptance of innovative remediation
technologies. For example, DOD‘s Strategic Environmental Research and
Development Program supports public and private research on
contaminants of concern to DOD and innovative methods for their
treatment.
Technologies DOD Components Used for Groundwater Remediation:
[See Table 1]
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[End of section]
Contents:
Letter:
Results in Brief:
Background:
DOD Has Implemented or Field-tested a Wide Range of Technologies to
Remediate Sites Contaminated with Groundwater:
DOD Is Proactively Using and Developing New Approaches to Groundwater
Remediation:
Agency Comments:
Appendixes:
Appendix I: Objectives, Scope, and Methodology:
Appendix II: Technologies for the Remediation of Contaminated
Groundwater:
Ex-situ Technologies:
In-situ Technologies:
Appendix III: Groundwater Remediation Experts Consulted:
Appendix IV: Comments from the Department of Defense:
Appendix V: GAO Contact and Staff Acknowledgments:
Tables:
Table 1: Technologies DOD Components Used for Groundwater Remediation:
Table 2: Technologies Available for the Treatment of DOD's Contaminants
of Concern:
Figures:
Figure 1: Example of a Site with Contaminated Groundwater:
Figure 2: Selected Phases and Milestones in DOD's Environmental Cleanup
Process:
Figure 3: Example of a Conventional Pump-and-Treat System:
Abbreviations:
CERCLA: Comprehensive Environmental Response, Compensation, and
Liability Act:
DNAPL: dense nonaqueous phase liquids:
DOD: Department of Defense:
EPA: Environmental Protection Agency:
ESTCP: Environmental Security Technology Certification Program:
ITRC: Interstate Technology and Regulatory Council:
LNAPL: light nonaqueous phase liquids:
RCRA: Resource Conservation and Recovery Act:
SERDP: Strategic Environmental Research and Development Program:
Letter June 30, 2005:
The Honorable John Warner:
Chairman:
The Honorable Carl Levin:
Ranking Minority Member:
Committee on Armed Services:
United States Senate:
The Honorable Duncan L. Hunter:
Chairman:
The Honorable Ike Skelton:
Ranking Minority Member:
Committee on Armed Services:
House of Representatives:
The Department of Defense (DOD) has identified close to 6,000 sites at
its active, closing, and formerly used defense facilities where the
groundwater has been so contaminated by past defense activities and the
improper disposal of hazardous wastes that cleanup (remediation) of the
site is required.[Footnote 1] Groundwater--the water found beneath the
earth's surface that fills pores between soil particles, such as sand,
clay, and gravel, or that fills cracks in bedrock--accounts for about
50 percent of the nation's municipal, domestic, and agricultural water
supply. When groundwater becomes polluted, it can endanger public
health or threaten the environment. DOD estimates that cleanup of its
contaminated sites will cost billions of dollars and may take decades
to complete because of the extent of the contamination and the
complexity of groundwater systems.
DOD identifies, investigates, and cleans up contaminated groundwater
through its Defense Environmental Restoration Program. This program was
established by section 211 of the Superfund Amendments and
Reauthorization Act of 1986, which amended the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA) of
1980. In fiscal year 2004, DOD obligated approximately $1.7 billion for
environmental restoration activities, including groundwater
remediation, on active, closing, and formerly used defense facilities.
Multiple DOD entities--the Air Force, Army, Defense Logistics Agency,
and Navy--are responsible for groundwater remediation on active DOD
facilities.[Footnote 2] In addition, the U.S. Army Corps of Engineers
(Corps) is responsible for groundwater remediation on properties
formerly owned, leased, or used by the military.[Footnote 3] The Air
Force has the greatest number of sites with contaminated groundwater
needing remediation, followed by the Navy, Army, Corps, and Defense
Logistics Agency.[Footnote 4] DOD must carry out its groundwater
remediation program in a manner consistent with section 120 of CERCLA.
Section 120 addresses the cleanup of federal facilities and, among
other things, provides for participation in cleanup decisions by the
state in which a federal facility is located. Personnel from the
installation where the contamination is located work with DOD-hired
contractors; regulators (federal, state, local, or tribal); and other
stakeholders to evaluate and select appropriate technologies to achieve
cleanup goals (e.g., treatment or containment of contaminants). DOD may
use a single technology or a combination of technologies to clean up
the groundwater at a particular site.
In the past, DOD primarily used traditional "pump-and-treat"
technologies to contain or eliminate hazardous contaminants in
groundwater. Pump-and-treat technologies extract contaminated
groundwater for treatment in above-ground (ex-situ) facilities and are
often used to prevent the further spread of contamination in the
groundwater. However, according to DOD, the Environmental Protection
Agency (EPA), and groundwater remediation experts we consulted, pump-
and-treat often is expensive because of long cleanup times,
inefficiencies in removing contaminants from the subsurface, and the
costs associated with disposing of the contaminant and treated water.
Recently, DOD has begun to use alternatives to pump-and-treat
technologies that rely on a variety of biological, chemical, or
physical processes to treat the contaminated groundwater underground
(in-situ).
As directed by Public Law 108-375,[Footnote 5] and as agreed with your
offices, this report (1) describes the groundwater remediation
technologies that DOD is currently using or field-testing and (2)
examines whether any new groundwater remediation technologies are being
used outside the department or are being developed by commercial
vendors that may have potential for DOD's use, and the extent to which
DOD is researching and developing new approaches to groundwater
remediation. In addition, this report provides limited information on
the key characteristics, benefits, and limitations of selected
groundwater remediation technologies in appendix II.
To determine the range of groundwater remediation technologies DOD is
currently using or field-testing, we developed a questionnaire that we
sent to the DOD components responsible for DOD's groundwater cleanup
efforts--the Air Force, Army, Corps, Defense Logistics Agency, and
Navy. In the questionnaire, we listed 15 technologies that are
currently available for the treatment of contaminated groundwater and
asked the DOD components to indicate which of the technologies they
have used and to provide examples of specific groundwater remediation
projects.[Footnote 6] We developed this list of technologies by
reviewing existing lists developed by the National Research Council,
EPA, and others, as well as by working with a groundwater remediation
consulting firm and five nationally recognized groundwater remediation
experts. To identify DOD components involved with groundwater
remediation activities, we met with department officials responsible
for developing policy on groundwater remediation and for researching
and developing groundwater remediation technologies. We reviewed
documents, reports, and guidance on groundwater remediation from DOD,
EPA, and the National Academy of Sciences; and visited an Air Force
groundwater remediation project and a facility DOD uses to test
innovative groundwater remediation technologies. In addition, we
attended a national groundwater remediation conference, and spoke with
a number of commercial vendors of groundwater remediation technologies
about their products and efforts to develop innovative approaches to
groundwater remediation. Information presented in this report is based
on publicly available documents and information provided by government
officials, independent consultants, and experts. We did not review
nonpublic research and development activities that may be ongoing in
private laboratories. A more detailed description of our scope and
methodology is presented in appendix I. We performed our work from
January 2005 through May 2005, in accordance with generally accepted
government auditing standards.
Results in Brief:
DOD has implemented or field-tested all of the 15 types of generally
accepted technologies currently available to remediate groundwater.
These various remediation technologies include both in-situ and ex-situ
treatments, each of which relies on biological, chemical, or physical
processes to clean up groundwater. Of these 15 types of technologies,
the Navy reported that it has used all 15 and the Air Force, Army, and
Corps have used 14 each. The Defense Logistics Agency, which has
significantly fewer sites to clean up than the other DOD components,
reported using 9 of the 15 technologies. According to department
officials, DOD selects the most suitable technology for a given site on
the basis of a number of factors, such as the type of contaminant and
its location in the subsurface, and the relative cost-effectiveness of
a technology for a given site. DOD has identified a number of
contaminants of concern at its facilities, each of which varies in its
behavior and susceptibility to treatment by the various technologies.
Some of the contaminants, such as chlorinated solvents, can potentially
be treated using 14 of the 15 technologies, while others, such as
metals, can only be treated effectively with 7 of the 15 technologies.
According to analyses conducted by groups such as EPA and the Federal
Remediation Technologies Roundtable, the cost-effectiveness and
performance of each technology can vary significantly depending, in
part, on site-specific conditions. A more detailed description of each
of the technologies we identified for cleaning up groundwater is
presented in appendix II.
We did not identify any alternative technologies for groundwater
remediation being used or developed outside of DOD that it has not
considered or employed. However, we did identify a number of new
approaches to groundwater remediation being developed by commercial
vendors--most of which are also being explored or used by DOD--that are
based on modifications of or enhancements to existing technologies.
Most of the new approaches involve the use of novel materials applied
to contaminated sites using existing technologies. For example, DOD has
recently used molasses and vegetable oils at several bioremediation
projects to stimulate microorganisms in the subsurface to biodegrade
contaminants. Other alternative approaches being developed by
commercial vendors usually involve modifying the design of existing
technologies. For example, DOD is exploring the use of nanoscale rather
than granular sized metals to clean up sites contaminated by
chlorinated solvents. In addition, we found that DOD is actively
involved in researching and testing new approaches to groundwater
remediation, largely through its efforts to develop and promote the
acceptance of innovative technologies. For example, DOD maintains
several programs--such as the Strategic Environmental Research and
Development Program--to support the research, development, and testing
of innovative cleanup approaches. This program, a DOD-funded basic and
applied research program, supports public and private research on
contaminants of concern to DOD and innovative methods for their
treatment, as well as a variety of other activities. DOD also pursues
innovative solutions to groundwater remediation through its
Environmental Security Technology Certification Program. This program
field-tests and validates promising innovative environmental
technologies and transfers these technologies to the commercial sector.
DOD also works with various stakeholders, including the regulatory
community, to promote understanding and acceptance of innovative
remediation approaches. For example, DOD participates in the Interstate
Technology and Regulatory Council, a state-led coalition that works
with the private sector, regulators, and other stakeholders to increase
the regulatory acceptance of new environmental technologies.
Background:
DOD sites that require cleanup are often contaminated by many different
types of hazardous materials, have contamination in more than one
medium (e.g., soil, surface water, or groundwater), and may encompass
several acres or even square miles. Groundwater stored in subsurface
formations called aquifers can become contaminated in a number of ways.
For example, contamination can occur when a liquid hazardous substance
soaks down through the soil. Often, groundwater contamination is
difficult to address because of the complexity of groundwater systems.
The subsurface environment can be composed of numerous layers of
diverse types of material--such as sand, gravel, clay, and solid rock-
-and fractured layers through which groundwater flows. These variations
in the subsurface often affect how groundwater flows through a
contaminated site and can influence how contaminants are spread and
accumulate in the subsurface. Chemical properties of the contaminant
also influence its distribution in the subsurface. Typically,
contaminated sites consist of a source zone where the bulk of the
contaminant is concentrated and a plume of contamination that develops
beyond the source of contamination as a result of groundwater flowing
through the contaminated site. See figure 1 for an illustration of a
site with contaminated groundwater.
Figure 1: Example of a Site with Contaminated Groundwater:
[See PDF for image]
[End of figure]
DOD Facilities Can Have Significant Groundwater Contamination:
According to DOD, the Air Force has identified more than 2,500 sites on
its active and closing installations with contaminated groundwater; the
Navy has identified more than 2,000 sites; the Army has identified
about 800 sites; and the Defense Logistics Agency has identified 16
sites. In addition, DOD has identified more than 500 contaminated
groundwater sites on formerly used defense sites for which the Corps is
responsible for cleanup. Contamination on DOD facilities can pose a
threat to military personnel, the public, and the sustainability of
DOD's training and testing ranges. DOD first initiated its
environmental restoration efforts in 1975. Over the last 10 years, DOD
has invested approximately $20 billion for the environmental
restoration of contaminated sites, including remediation of
contaminated groundwater on and around active, closing, and formerly
used defense facilities.[Footnote 7]
DOD Cleanup Activities Generally Follow the CERCLA Process:
DOD's policies for administering cleanup programs are outlined in its
guidance for managing its environmental restoration program and
generally follow the CERCLA process for identifying, investigating, and
remediating sites contaminated by hazardous materials.[Footnote 8]
According to DOD's guidance, department officials are required to
involve EPA, relevant state and local government officials, and the
public, among others, at specified points in the cleanup process. See
figure 2 for more information on the phases of DOD's environmental
cleanup process.
Figure 2: Selected Phases and Milestones in DOD's Environmental Cleanup
Process:
[See PDF for image]
Note: These phases may overlap or occur simultaneously, but cleanup
activities at DOD facilities generally occur in the order shown.
[End of figure]
Once DOD identifies potential contamination on one of its facilities,
it initiates a preliminary assessment to gather data on the
contaminated site. If DOD finds evidence that the site needs
remediation, it consults with EPA to determine whether the site
qualifies for inclusion on the National Priorities List.[Footnote 9] If
EPA places a DOD facility on the National Priorities List, CERCLA
requires DOD to begin the next phase of cleanup within 6 months. During
this next phase, called a remedial investigation/feasibility study, DOD
characterizes the nature and extent of contamination and evaluates the
technical options available for cleaning up the site.
DOD also pursues a remedial investigation/feasibility study for sites
that do not qualify for the National Priorities List but require
decontamination. Data collected during the remedial investigation
influences DOD's development of cleanup goals and evaluation of
remediation alternatives. During the feasibility study, often conducted
concurrently with the remedial investigation, DOD identifies applicable
regulations and determines cleanup standards that will govern its
cleanup efforts. CERCLA requires that sites covered by the statute be
cleaned up to the extent necessary to protect both human health and the
environment. In addition, cleanups must comply with requirements under
federal environmental laws that are legally "applicable" or "relevant
and appropriate" as well as with state environmental requirements that
are more stringent than the federal standards. Furthermore, CERCLA
cleanups must at least attain goals and criteria established under the
Safe Drinking Water Act and the Clean Water Act, where such standards
are relevant and appropriate under the circumstances.
Once cleanup standards have been established, DOD considers the merits
of various actions to attain cleanup goals. Cleanup actions fall into
two broad categories: removal actions and remedial actions. Removal
actions are usually short term and are designed to stabilize or clean
up a hazardous site that poses an immediate threat to human health or
the environment. Remedial actions, which are generally longer term and
usually costlier, are aimed at implementing a permanent remedy. Such a
remedy may, for example, include the use of groundwater remediation
technologies. Also during the feasibility study, DOD identifies and
screens various groundwater remediation technologies based on their
effectiveness, feasibility, and cost. At the conclusion of the remedial
investigation/feasibility study, DOD selects a final plan of action--
called a remedial action--and develops a Record of Decision that
documents the cleanup objectives, the technologies to be used during
cleanup, and the analysis that led to the selection. If EPA and DOD
fail to reach mutual agreement on the selection of the remedial action,
then EPA selects the remedy. If the cleanup selected leaves any
hazardous substances, pollutants, or contaminants at the site, DOD must
review the action every 5 years after the initiation of the
cleanup.[Footnote 10] According to DOD policy, this may include
determining if an alternative technology or approach is more
appropriate than the one in place. DOD continues remediation efforts at
a site until the cleanup objectives stated in the Record of Decision
are met, a milestone referred to as "response complete." Even if DOD
meets the cleanup objectives for a site, in some cases the site may
require long-term management and monitoring to ensure that it does not
become contaminated from residual sources of pollution.
DOD Has Implemented or Field-tested a Wide Range of Technologies to
Remediate Sites Contaminated with Groundwater:
DOD has implemented or field-tested all of the 15 types of generally
accepted technologies currently available to remediate groundwater.
These 15 technologies include 6 ex-situ and 9 in-situ technologies,
each of which can be used to treat a variety of contaminants. All of
these groundwater remediation technologies rely on a variety of
biological, chemical, or physical processes to treat or extract the
contaminant. DOD guidance directs department officials to consider cost-
effectiveness and performance when selecting technologies for cleanup.
Fifteen Ex-situ and In-situ Technologies Are Currently Available for
Groundwater Cleanup:
We identified a range of ex-situ and in-situ technologies that DOD can
employ to clean up a contaminated groundwater site. Ex-situ
technologies rely on a pump-and-treat system to bring the contaminated
water above ground so that it can be treated and the contaminants
removed. Some ex-situ technologies destroy the contaminant, while
others remove the contaminant from the groundwater, which is
subsequently disposed of in an approved manner. The decontaminated
water can be discharged to surface water, used as part of a public
drinking water supply, injected back into the ground, or discharged to
a municipal sewage plant. We identified 6 categories of ex-situ
technologies:
* Advanced oxidation processes often use ultraviolet radiation with
oxidizing agents--such as ozone or hydrogen peroxide--to destroy
contaminants in water pumped into an above-ground treatment tank.
* Air stripping separates volatile contaminants from water by exposing
the water to large volumes of air, thus forcing the contaminants to
undergo a physical transformation from liquid to vapor
(volatilization). There is no destruction of the contaminant;
therefore, the contaminant must be removed and disposed of properly.
* Bioreactors are above-ground biochemical-processing systems designed
to degrade contaminants in water using various microorganisms, an
approach similar to that used at a conventional wastewater treatment
facility. Contaminated groundwater flows into a tank or basin where it
interacts with microorganisms that degrade the contaminant.
* Constructed wetlands are artificially built wetland ecosystems that
contain organic materials, plants, microbial fauna, and algae that
filter or degrade contaminants from the water that is pumped into the
wetland.
* Ion exchange involves passing contaminated water through a bed of
resin media or membrane that exchanges ions in the contaminants, thus
neutralizing them into nonhazardous substances.
* Adsorption (mass transfer) involves circulating contaminated water
through an above-ground treatment vessel containing a sorbent material-
-such as activated carbon--that removes the contaminant from the water.
(See app. II for more information on key characteristics of these ex-
situ technologies.)
Figure 3: Example of a Conventional Pump-and-Treat System:
[See PDF for image]
[End of figure]
Similarly, we identified nine in-situ technologies that can be used to
remediate contaminated groundwater. In contrast to ex-situ
technologies, in-situ technologies treat contaminants within the
subsurface. Some in-situ technologies--such as bioremediation and
chemical treatment--destroy the contaminant within the subsurface by
altering the contaminant's chemical structure and converting the toxic
chemical to a nontoxic form (e.g., benzene to carbon dioxide). Other in-
situ technologies--such as multiphase extraction and enhanced recovery
using surfactant flushing--facilitate the removal of the contaminant
from the subsurface for treatment above ground. Still other
technologies--such as air sparging--combine in-situ treatments with
extraction techniques.
* Air sparging introduces air or other gases into the subsurface to
remove the contamination from the groundwater through volatilization
(converting a solid or liquid into a gas or vapor that may be treated
at the surface), and in some configurations may also introduce oxygen
into the contaminated area to stimulate in-situ biological breakdown
(i.e., bioremediation) or ozone to achieve chemical oxidation of the
contaminant.
* Bioremediation relies on microorganisms living in the subsurface to
biologically degrade groundwater contaminants through a process called
biodegradation. Bioremediation may be engineered and accomplished in
two general ways: (1) stimulating native microorganisms by adding
nutrients, oxygen, or other electron acceptors (a process a called
biostimulation) or (2) providing supplementary pregrown microorganisms
to the contaminated site to augment naturally occurring microorganisms
(a process called bioaugmentation).
* Enhanced recovery using surfactant flushing involves the injection of
active agents known as surfactants[Footnote 11] into contaminated
aquifers to flush the contaminated groundwater toward a pump, which
removes the contaminated water and surfactant solution to the surface
for treatment and disposal of the contaminants.
* Chemical treatments inject various substances into the groundwater
that can chemically oxidize or reduce contaminants into less-toxic or
nonhazardous materials.
* Monitored natural attenuation involves using wells and monitoring
equipment in and around a contaminated site to track the natural
physical, chemical, and biological degradation of the contaminants.
Although not necessarily considered a treatment technology, this
approach is often used to monitor contaminant concentrations to ensure
that human health and the environment are not threatened.
* Multiphase extraction uses a series of pumps and vacuums to
simultaneously remove from the subsurface combinations of contaminated
groundwater, free product (i.e., liquid contaminants floating on top of
groundwater), and hazardous vapors. This technology can be used to
remove contaminants from above and below the groundwater table, thereby
exposing more of the subsurface for treatment.
* Permeable reactive barriers are vertical walls or trenches built into
the subsurface that contain a reactive material to intercept and
remediate a contaminant plume as the groundwater passes through the
barrier.
* Phytoremediation relies on the natural hydraulic and metabolic
processes of selected vegetation to remove, contain, or reduce the
toxicity of environmental contaminants in the groundwater.
* Thermal treatments involve either pumping steam into the aquifer or
heating groundwater to vaporize or destroy groundwater contaminants.
Vaporized contaminants are often removed for treatment using a vacuum
extraction system.
(See app. II for more information on key characteristics of these in-
situ technologies.)
Although most in-situ technologies have the advantage of treating a
contaminant in place, these technologies may afford less certainty
about the extent and uniformity of treatment in contaminated areas when
compared with some ex-situ technologies. For example, enhanced recovery
using surfactant flushing has not been used extensively and has limited
data on its remediation effectiveness, whereas air stripping has been
widely used for several decades to remove certain contaminants, and its
benefits and limitations as a water treatment technology are well-
understood. In some cases, a combination of in-situ and ex-situ
technologies may be used (either concurrently or successively) to clean
up a site if a single technology cannot effectively remediate an entire
site with its range of contaminants and subsurface characteristics.
According to the National Research Council, integration of technologies
is most effective when the weakness of one technology is mitigated by
the strength of another technology, thus producing a more efficient and
cost-effective solution.[Footnote 12]
DOD Has Used the Full Range of Groundwater Remediation Technologies
Identified:
As shown in table 1, the DOD components involved in groundwater
remediation activities reported using the full range of technologies
that we identified as currently available for groundwater remediation.
Specifically, the Navy reported that it has used all 15 of the
currently available technologies; the Air Force, Army, and Corps
reported using 14 each. The Defense Logistics Agency has used 9 of the
available technologies for the cleanup of the limited number of
contaminated groundwater sites for which it is responsible.
Table 1: Technologies DOD Components Used for Groundwater Remediation:
Technology: In-situ: Air sparging[A];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: Yes;
Navy: Yes.
Technology: In-situ: Bioremediation[B];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: Yes;
Navy: Yes.
Technology: In-situ: Enhanced recovery/surfactant flushing[C];
Air Force: Yes;
Army: No;
Army Corps of Engineers: No;
Defense Logistics Agency: Yes;
Navy: Yes.
Technology: In-situ: Chemical treatments[D];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: Yes;
Navy: Yes.
Technology: In-situ: Monitored natural attenuation;
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: Yes;
Navy: Yes.
Technology: In-situ: Multiphase extraction[E];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: Yes;
Navy: Yes.
Technology: In-situ: Permeable reactive barriers[F];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: Yes;
Navy: Yes.
Technology: In-situ: Phytoremediation[G];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: No;
Navy: Yes.
Technology: In-situ: Thermal treatments[H];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: No;
Navy: Yes.
Technology: Ex-situ: Advanced oxidation processes[I];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: No;
Navy: Yes.
Technology: Ex-situ: Air stripping;
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: Yes;
Navy: Yes.
Technology: Ex-situ: Bioreactors;
Air Force: No;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: No;
Navy: Yes.
Technology: Ex-situ: Constructed wetlands;
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: No;
Navy: Yes.
Technology: Ex-situ: Ion exchange[J];
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: No;
Navy: Yes.
Technology: Ex-situ: Adsorption (mass transfer);
Air Force: Yes;
Army: Yes;
Army Corps of Engineers: Yes;
Defense Logistics Agency: Yes;
Navy: Yes.
Source: Department of Defense responses to GAO data collection
instrument.
Notes: This table focuses on technologies used to treat contaminants
found in groundwater. It excludes technologies used (1) to treat and
dispose of the byproducts of groundwater remediation--such as emissions
of potentially harmful volatile gases; (2) exclusively to treat
contaminated soil (such as soil washing or excavation), although soil
remediation is often conducted in conjunction with groundwater
remediation; and (3) primarily to physically contain a contaminant--
such as soil capping. See appendix II for more information on the key
characteristics, benefits, and limitations of each of these
technologies.
[A] Includes related remedial approaches and technologies, such as co-
metabolic air sparging, oxygen and ozone sparging, in-well air
stripping, and soil vapor extraction. Soil vapor extraction, although
not technically a groundwater remediation technology, is often used
with air sparging to extract or capture emissions that result from
treating contaminated groundwater.
[B] Includes related bioremedial approaches, such as bioaugmentation,
biostimulation, co-metabolic treatment, enhanced aerobic
biodegradation, enhanced anaerobic biodegradation, and biobarriers.
[C] Includes related remedial approaches that use co-solvents to
improve the solubility of surfactants in the subsurface, and other
technologies, such as hydrofracturing and pneumatic fracturing, that
attempt to increase the permeability of the subsurface.
[D] Includes various remedial approaches and technologies that
chemically oxidize or reduce contaminants in-situ, as well as the in-
situ immobilization and stabilization of soluble metals.
[E] Includes the related technologies of bioslurping and dual-phase
extraction.
[F] Includes both biotic and abiotic passive and reactive treatment
barriers.
[G] Includes the related technologies of phytostabilization,
phytoaccumulation, phytoextraction, rhizofiltration, phytodegradation,
rhizosphere degradation, organic pumps, and phytovolatization.
[H] Includes related heating technologies, such as steam flushing,
conductive heating, and electrical resistance heating.
[I] Includes the related technologies of ultraviolet oxidation,
ultraviolet photolysis, and photocatalysis.
[J] Includes technologies that use ion exchange resins or membranes to
remove contaminants from groundwater, including dissolved metals and
nitrates.
[End of table]
According to department officials, DOD selects the most suitable
technology to clean up a contaminated site based on a number of
factors, including the type of contaminant, its location and
concentration at different levels in the subsurface, and its chemical
and physical composition.[Footnote 13] These officials identified a
number of contaminants of concern, such as federally regulated
chlorinated solvents (commonly found in metal degreasers) and fuels
used for military aircraft and vehicles. DOD officials also consider
some other hazardous materials that are not regulated by the federal
government--such as the rocket propellant perchlorate--to be
contaminants of concern because they are regulated by some states, such
as California, where DOD has active, closing, or formerly used defense
sites that need groundwater remediation.
According to the groundwater remediation experts we consulted, some of
DOD's contaminants of concern, such as chlorinated solvents, can
potentially be treated using 14 of the 15 technologies, while others,
such as metals, can be treated with only 7 of the 15 technologies. For
example, many chlorinated solvents do not readily dissolve in water;
and because they are often more dense (heavier) than water, they
migrate downward and pool at the bottom of aquifers, thereby limiting
the number of technologies that can treat them. Alternatively, some
contaminants composed of petroleum hydrocarbons (e.g., jet fuel, diesel
fuel, and motor gasoline) float on top of the water table because they
are less dense (lighter) than water, and technologies such as air
sparging or multiphase extraction can often effectively treat or
extract them through processes such as volatilization or free product
recovery. See table 2 for information on which of the 15 technologies
can potentially treat each of DOD's contaminants of concern.
Table 2: Technologies Available for the Treatment of DOD's Contaminants
of Concern:
Technology: In-situ: Air sparging;
Chlorinated solvents[A]: Yes;
Explosives[B]:;
Fuels[C]: Yes;
Metals[D]: No;
Oxygenates[E]: Yes;
Propellants[F]: No.
Technology: In-situ: Bioremediation;
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: Yes;
Oxygenates[E]: Yes;
Propellants[F]: Yes.
Technology: In-situ: Enhanced recovery/surfactant flushing;
Chlorinated solvents[A]: Yes;
Explosives[B]: No;
Fuels[C]: Yes;
Metals[D]: No;
Oxygenates[E]: Yes;
Propellants[F]: No.
Technology: In-situ: Chemical treatments;
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: Yes;
Oxygenates[E]: Yes;
Propellants[F]: Yes.
Technology: In-situ: Monitored natural attenuation;
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: Yes;
Oxygenates[E]: Yes;
Propellants[F]: Yes.
Technology: In-situ: Multiphase extraction;
Chlorinated solvents[A]: Yes;
Explosives[B]: No;
Fuels[C]: Yes;
Metals[D]: No;
Oxygenates[E]: Yes;
Propellants[F]: No.
Technology: In-situ: Permeable reactive barriers;
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: Yes;
Oxygenates[E]: Yes;
Propellants[F]: Yes.
Technology: In-situ: Phytoremediation;
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: No;
Oxygenates[E]: Yes;
Propellants[F]: Yes.
Technology: In-situ: Thermal treatments;
Chlorinated solvents[A]: Yes;
Explosives[B]: No;
Fuels[C]: Yes;
Metals[D]: No;
Oxygenates[E]: Yes;
Propellants[F]: No.
Technology: Ex-situ: Advanced oxidation processes;
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: No;
Oxygenates[E]: Yes;
Propellants[F]: No.
Technology: Ex-situ: Air stripping;
Chlorinated solvents[A]: Yes;
Explosives[B]: No;
Fuels[C]: Yes;
Metals[D]: No;
Oxygenates[E]: Yes;
Propellants[F]: No.
Technology: Ex-situ: Bioreactors;
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: No;
Oxygenates[E]: Yes;
Propellants[F]: Yes.
Technology: Ex-situ: Constructed wetlands;
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: Yes;
Oxygenates[E]: Yes;
Propellants[F]: Yes.
Technology: Ex-situ: Ion exchange;
Chlorinated solvents[A]: No;
Explosives[B]: No;
Fuels[C]: No;
Metals[D]: Yes;
Oxygenates[E]: No;
Propellants[F]: Yes.
Technology: Ex-situ: Adsorption (mass transfer);
Chlorinated solvents[A]: Yes;
Explosives[B]: Yes;
Fuels[C]: Yes;
Metals[D]: Yes;
Oxygenates[E]: Yes;
Propellants[F]: No.
Sources: Department of Defense and several groundwater remediation
experts.
Notes: This table presents the contaminants of concern to DOD.
Depending on their concentrations, these contaminants can pose health
risks to humans. The ability for any one technology to effectively
treat a contaminant is greatly influenced by site-specific conditions.
Some technologies are generally less effective or currently less
utilized to treat contaminants.
[A] Includes, but is not limited to, perchloroethene (PCE),
trichloroethene (TCE), dichloroethene (DCE), vinyl chloride (VC), and
chloroform (CF).
[B] Includes, but is not limited to, trinitrotoluene (TNT);
dinitrotoluene (DNT); cyclotrimethylene trinitramine, cyclonite, and
hexogen (RDX); and octogen and cyclotetramethylene-tetranitramine
(HMX).
[C] Includes gasoline, diesel fuel, jet fuel, and BTEX. BTEX is an
acronym for benzene, toluene, ethylbenzene, and xylene--a group of
volatile organic compounds commonly found in petroleum hydrocarbons,
such as gasoline.
[D] Includes, but is not limited to, arsenic, barium, cadmium,
chromium, copper, lead, mercury, selenium, silver, and zinc.
[E] Includes, but is not limited to, oxygen-bearing chemicals that can
be added to fuel to bring additional oxygen to the combustion process.
These include ethers such as methyl tertiary butyl ether (MTBE) and its
related compounds.
[F] Includes, but is not limited to, materials such as ammonium
perchlorate and potassium perchlorate that are used in the
manufacturing and testing of solid rocket propellants and other
munitions such as flares.
[End of table]
Technology Selection Is Also Influenced by Cost and Performance:
According to DOD guidance on groundwater remediation, department
officials should consider cost-effectiveness and performance of various
groundwater remediation options when selecting the most suitable
cleanup technology. A number of factors influence total cleanup costs
for a given site, such as how long the cleanup is expected to take and
the horizontal and vertical extent of the contamination. In addition,
according to the National Research Council, actual cleanup costs
associated with each technology depend on site-specific hydrogeologic,
geochemical, and contaminant conditions.[Footnote 14] Thus, a
particular technology may be the most cost-effective solution for one
site and not necessarily for another similarly contaminated site. The
National Research Council and others have also found that performance
of most technologies, including time for total cleanup, also depends on
complexities within the site's subsurface (i.e., site heterogeneities)
as well as contaminant characteristics. For example, the effectiveness
of certain in-situ technologies--such as air sparging--decrease as site
heterogeneity increases because the air will naturally follow certain
pathways that may bypass the contaminant. Similarly, the effectiveness
of many in-situ technologies may be limited by the presence of some
chlorinated solvents that, if heavier than water, can migrate into
inaccessible zones in the subsurface. Alternatively, in-situ thermal
treatments that use conductors to heat the soil are not as sensitive to
heterogeneity in the subsurface and contaminant characteristics because
thermal conductivity varies little with the properties of subsurface
materials and certain contaminants are more easily volatilized at
elevated temperatures. However, equipment and energy costs may make
this approach more costly than other in-situ technologies.
While overall conclusions on the cost-effectiveness of each groundwater
remediation technology are difficult to reach, a few groups have
attempted to estimate costs for various technologies. For example, EPA
has developed a technology cost compendium for several technologies
based on cost data from various public and private remediation
projects.[Footnote 15] Similarly, the Federal Remediation Technologies
Roundtable--a federal consortium of representatives from DOD, EPA, and
other federal agencies--has attempted to evaluate the relative overall
cost and performance of selected remediation technologies in general
terms.[Footnote 16] However, according to DOD officials and other
experts we consulted, these efforts to compare technologies are of only
limited utility because of the site-specific nature of technology
decisions.
DOD Is Proactively Using and Developing New Approaches to Groundwater
Remediation:
We did not identify any alternative groundwater remediation
technologies being used outside the department that DOD has not already
either employed or tested on some scale (laboratory or pilot). However,
we did identify a number of new approaches to groundwater remediation
being developed by commercial vendors, but these approaches are based
on modifications of or enhancements to existing technologies. Most of
these new approaches are being used or field-tested by DOD and involve
novel materials that are applied to contaminated sites using existing
technologies. In addition, we found that DOD is generally aware of new
approaches to groundwater remediation, in part through its efforts to
develop remediation technologies with the commercial sector. DOD also
works with various stakeholders, including the regulatory community, to
promote understanding and acceptance of innovative remediation
approaches. Some DOD officials and groundwater remediation experts
believe additional resources may be needed in order to develop and
advance DOD's process for selecting the most appropriate technology at
a site.
Most New Approaches Employ Novel Materials or Modifications to Existing
Technologies:
Most of the new remediation approaches commercial vendors have
developed and made available to DOD use existing technologies to apply
novel materials to contaminated sites. These materials typically
accelerate the breakdown of contaminants through biological or chemical
processes. In particular, multiple commercial vendors have developed
proprietary compounds used during bioremediation to stimulate
microorganisms in the subsurface to biodegrade contaminants. Some of
these compounds are designed to slowly release oxygen or other
nutrients into the subsurface in an effort to prolong their
availability, which microorganisms need to biodegrade the contaminants.
DOD has also field-tested several novel compounds for bioremediation
that are derived from food-grade materials such as molasses or
vegetable oils. These compounds can be injected into the contaminated
site using pre-existing wells or other existing techniques such as
direct push injection:
* The Army used a compound developed by a commercial vendor to
stimulate the bioremediation of chlorinated solvents at a contaminated
site at its Rocky Mountain Arsenal. This compound reacted with the
contaminated groundwater to produce lactic acid, which native
microorganisms used to produce the hydrogen that ultimately led to the
biological degradation of the contaminants. In addition, the Air Force
reported using oxygen-releasing compounds to stimulate aerobic
biodegradation at several of its cleanup sites, including a site in
Florida contaminated by spilled fuel.
* DOD has also field-tested the use of molasses during bioremediation
to treat chlorinated solvents at Vandenberg and Hanscom Air Force
bases. In addition, DOD reported using vegetable oils to stimulate
microorganisms in order to treat groundwater contaminated by
chlorinated solvents and perchlorate at a variety of locations,
including naval facilities in Massachusetts, Rhode Island, and South
Carolina.
Commercial vendors have also developed innovative approaches for
chemically treating contaminants in the subsurface. For example,
several vendors have developed proprietary approaches for delivering
oxidants, such as molecular oxygen and ozone with or without hydrogen
peroxide, into the subsurface to achieve in-situ chemical oxidation of
a variety of contaminants, including fuels and chlorinated solvents.
These oxidants are often delivered underground using variations of
existing air sparging technologies and a variety of injection
technologies. In addition to achieving in-situ chemical oxidation of
target contaminants, the use of ozone with or without hydrogen peroxide
can enhance the aerobic biodegradation of contaminants because it
increases oxygen levels in the subsurface. Commercial vendors have also
developed approaches to directly injecting other chemicals that are
oxidizing agents, such as persulfate and permanganate, into the
subsurface using existing technologies such as injection wells and
direct push-probe technologies.
DOD is exploring with the commercial sector other innovative approaches
to groundwater remediation that involve modifying the engineering,
design, or application of existing technologies. For example, DOD is
currently working with the commercial sector to explore innovative uses
of nanoscale metallic materials--such as zero-valent iron and palladium
impregnated iron--to improve the efficacy of in-situ chemical
treatments of chlorinated solvents commonly found on DOD
facilities.[Footnote 17] In the past, DOD used metallic materials, such
as zero-valent iron in granular form, to fill trenches dug into the
ground (a form of a permeable reactive barrier) to chemically reduce
chlorinated solvent plumes. The iron reacts with chlorinated solvents,
transforming them into benign products, such as ethane and ethene.
Treating contaminant plumes located deep within the subsurface is often
difficult, costly, and technically impossible using this approach.
Because of their size, nanoscale particles can be mixed with other
materials--such as vegetable oil and water--and injected deep into the
subsurface using existing technologies to treat contaminant sources or
plumes. Furthermore, nanoscale particles have high surface areas
relative to their volume (i.e., more metal is available to contact and
react with the contaminants), which will lead to increased rates of
reaction and more effective treatment.
DOD Supports the Development of New Technologies with the Commercial
Sector through Several Programs:
We found that DOD is actively involved in researching and testing new
approaches to groundwater remediation, largely through its efforts to
develop and promote the acceptance of innovative groundwater
remediation technologies. According to the National Research Council,
research on innovative remediation technologies is sponsored almost
exclusively by federal agencies such as DOD and, in some circumstances,
by individual companies and industry groups that have joined with
federal:
agencies in seeking more cost-effective solutions to common
problems.[Footnote 18] In particular, the DOD-funded Strategic
Environmental Research and Development Program (SERDP) supports public
and private research on contaminants of concern to DOD and innovative
methods for their treatment, among other activities. Created in 1990,
the program primarily focuses on issues of concern to DOD, although it
is jointly managed by DOD, EPA, and the Department of Energy.[Footnote
19] In fiscal year 2004, SERDP spent about $49 million to fund and
manage projects in a variety of areas, including 27 projects related to
groundwater remediation.
In response to technology needs and requirements generated by each of
the DOD components, SERDP funds research projects in private, public,
and academic settings on the fundamentals of contaminant behavior,
environmental toxicity, and the advanced development of cost-effective
innovative groundwater remediation technologies, among other things.
For example, SERDP has funded research projects to examine such issues
as the innovative use of vegetable oils for bioremediation; zero-valent
iron based bioremediation of explosives; and the behavior of, and
treatment options for, several emerging groundwater contaminants not
yet regulated by the federal government, such as 1,4-Dioxane (found in
solvents), N-Nitrosodimethylamine (found in rocket fuel), and
trichloropropane (used as a degreaser and paint stripper). In addition,
SERDP holds workshops with the scientific, engineering, academic,
regulatory, and DOD-user communities to discuss DOD's issues and
identify needs for future research, development, and testing of
groundwater remediation techniques.
[SIDEBAR]
National Environmental Technology Test Site at Dover Air Force Base:
[See PDF for image]
Source: Dover National Environmental Technology Test Site, Tim McHale.
[End of figure]
At Dover Air Force Base, DOD has constructed three double-walled
underground test areas (referred to as cells) that enable researchers
to inject common soil and groundwater pollutants into a natural
geologic setting as test constituents, without allowing the test
constituents to come into contact with the surrounding environment.
These test cells, known as the Groundwater Remediation Field
Laboratory, include one large test cell and several smaller ones, all
sharing the same outer containment cell area. The cells are constructed
of interlocking steel sheet pilings with sealed grouted joints that
extend from the ground's surface to a depth of 40 feet. This safe
testing area is in an area with "ideal geology," according to the site
program manager, because it has a shallow aquifer contained by a clay
layer, which prevents the migration of contaminants. This laboratory is
the only place in the United States that offers such a test setting. A
variety of technologies have been tested here for cleaning up a range
of contaminants. For example, tests for cleanup of TCE are under way
using a combination of three technologies: soil vapor extraction,
bioremediation, and air stripping.
[End of sidebar]
DOD also pursues innovative solutions to groundwater remediation
through its Environmental Security Technology Certification Program
(ESTCP). This program, founded in 1995, field-tests and validates
promising innovative environmental technologies that attempt to address
DOD's highest-priority environmental requirements, including
groundwater remediation.[Footnote 20] Using a process similar to that
of SERDP, ESTCP solicits proposals from public and private researchers
to field- test laboratory-proven remediation technologies that have
broad DOD and market application. Once ESTCP accepts a proposal, it
identifies a military partner, which provides a site on a DOD
installation where the researcher can field-test the technology and
document the technology's cost, performance, and reliability. In fiscal
year 2004, ESTCP spent about $35 million to fund and manage its
program, including 36 projects on groundwater remediation. These
projects include the demonstration of an enhanced recovery technology
using innovative surfactants, emulsified zero-valent nanoscale iron to
treat chlorinated solvents, and an ion exchange technology for the
removal and destruction of perchlorate. ESTCP and SERDP have co-located
offices and, according to DOD officials, the two programs work together
to pursue the development of innovative groundwater remediation
technologies from basic research through advanced field-testing and
validation. ESTCP often funds the demonstration of technologies that
were developed by private or public researchers with financial support
from SERDP.
In addition to funding the development of innovative technologies, DOD
works with various stakeholders, including the regulatory community, to
promote the understanding and acceptance of these technologies. For
example, DOD participates in the Interstate Technology and Regulatory
Council (ITRC), a state-led coalition that works with the private
sector, regulators, and other stakeholders to increase the regulatory
acceptance of new environmental technologies. ITRC develops guidance on
innovative environmental technologies and sponsors training for
regulators and others on technical and regulatory issues related to
environmental cleanup technologies and innovative groundwater
remediation approaches. According to ITRC, these efforts are designed
to help regulators streamline their review process and enable wider
acceptance of innovative environmental technologies across state
boundaries. In 2004, ITRC and DOD signed a memorandum of understanding
on the relationship between the two organizations. As a result of the
agreement, DOD now provides several liaisons to the ITRC's board of
advisers and helps the group develop materials and training courses on
innovative groundwater remediation technologies. According to a DOD
official, the department's partnership with ITRC has led to enhanced
cooperation among state regulators, DOD personnel, and community
stakeholders and increased the deployment of innovative technologies at
DOD cleanup sites.
Although DOD is actively involved in the research and development of
innovative technologies, some groundwater remediation experts and some
DOD officials with whom we consulted believe that additional resources
may be needed to develop and advance DOD's process for selecting the
most appropriate technology at a site. These individuals believe that a
better understanding of the nature and extent of contamination at a
site is critical for selecting appropriate technologies for cleanup.
Furthermore, these experts and some DOD officials believe that
additional resources may be appropriate for examining and improving
methods and engineering approaches for optimizing the performance of
the 15 types of groundwater remediation technologies that are currently
available. Other groundwater remediation experts and some DOD officials
suggested that more resources may be needed to further develop
innovative approaches to emerging groundwater remediation issues, and
to educate DOD personnel and regulators on these approaches.
Agency Comments:
DOD generally agreed with the content of the report, stating that the
report is an accurate summary of DOD's use and field tests of remedial
technologies; DOD also provided technical clarifications that we have
incorporated, as appropriate.
We are sending copies of this report to appropriate congressional
committees; the Secretary of Defense; the Administrator of EPA; and
other interested parties. We will also make copies available to others
upon request. In addition, the report will be available at no charge on
GAO's Web site at [Hyperlink, http://www.gao.gov].
If you or your staff have any questions about this report, please
contact me at (202) 512-3841 or [Hyperlink, mittala@gao.gov]. Contact
points for our Offices of Congressional Relations and Public Affairs
may be found on the last page of this report. GAO staff who made major
contributions to this report are listed in appendix V.
Signed by:
Anu K. Mittal:
Director, Natural Resources and Environment:
[End of section]
Appendixes:
Appendix I: Objectives, Scope, and Methodology:
This report (1) describes the groundwater remediation technologies that
the Department of Defense (DOD) is currently using or field-testing and
(2) examines whether any new groundwater remediation technologies are
being used outside the department or are being developed by commercial
vendors that may have potential for DOD's use, and the extent to which
DOD is researching and developing new approaches to groundwater
remediation. In addition, this report provides limited information on
the key characteristics, benefits, and limitations of selected
groundwater remediation technologies.
To address the first objective, we developed a questionnaire that we
sent to the DOD components responsible for DOD's groundwater cleanup
efforts--the Air Force, Army, U.S. Army Corps of Engineers, Defense
Logistics Agency, and Navy. In the questionnaire, we listed groundwater
remediation technologies and asked these DOD components to indicate
which technologies they have implemented and still currently use. We
also asked the components to provide examples of specific groundwater
remediation projects. We developed the list of technologies based on a
review of reports and existing lists developed by the National Research
Council, Environmental Protection Agency (EPA), Federal Remediation
Technology Roundtable, and others, as well as through discussions with
a groundwater remediation consulting firm and several nationally
recognized groundwater remediation experts. To better understand DOD's
processes for environmental cleanup and technology development, we met
with officials from the offices of the Deputy Undersecretaries of
Defense for Installations and Environment and for Science and
Technology. We also reviewed documents, reports, and guidance on
groundwater remediation from the Office of the Secretary of Defense and
the various DOD components involved in groundwater remediation. To
obtain information on how DOD uses groundwater remediation technologies
to treat contaminants of concern, we toured several bioremediation
projects at Dover Air Force Base and spoke with a groundwater
remediation program manager for the Air Force.
To address our second objective, we contracted with consultants from
the Washington, D.C., office of Malcolm Pirnie Inc. to gather
information from commercial vendors on the range of currently available
groundwater remediation technologies. We also attended a national
groundwater remediation conference, where we spoke with a number of
vendors of groundwater remediation technologies about their products,
efforts to develop innovative approaches to groundwater remediation,
and remediation work they may have performed for DOD. In addition, we
collected and reviewed reports and studies from these vendors to better
understand the range of technologies available to DOD. We also
consulted with four nationally recognized groundwater remediation
experts--two from academia and two from industry--to provide
information on innovative remediation technologies currently available
or under development by the commercial sector. We selected these
experts on the basis of their independence, knowledge of and experience
with groundwater remediation technologies, and recommendations from the
National Academy of Sciences and others. In addition, we consulted with
a senior groundwater remediation official from EPA's Groundwater and
Ecosystem Restoration Division, who is an expert on technologies used
for groundwater remediation.
Through these sources, we identified 15 technologies that are currently
available commercially for the treatment of contaminated groundwater.
For the purposes of this report, we defined a technology as a distinct
technical method or approach for treating or removing contaminants
found in groundwater. We did not consider any modifications or
enhancements to a technology, such as variations in the material or
equipment used during treatment, to be a separate technology. To
determine whether there were any technologies currently being used
outside of DOD, we compared the list of 15 currently available
technologies with information provided to us by DOD officials on
technologies currently used by DOD for groundwater remediation.
To identify the extent to which DOD supports the research and
development of new approaches to groundwater remediation, we
interviewed officials from the Strategic Environmental Research and
Development Program and the Environmental Security Technology
Certification Program. We reviewed reports, project portfolios, and
other documents developed by these two programs. To gain a better
understanding of DOD's efforts to field-test innovative approaches to
groundwater remediation, we visited a DOD National Environmental
Technology Test Site, located in Delaware, where private and public
researchers can test innovative groundwater remediation technologies.
We observed several ongoing research projects and interviewed an
official responsible for managing the test facility. To gain a better
understanding of DOD's relationship with the Interstate Technology and
Regulatory Council, we reviewed a memorandum of understanding between
the two organizations and interviewed an official that serves as DOD's
liaison to the council.
Information presented in this report is based on publicly available
documents and information provided by government officials, independent
consultants, and experts. We did not review nonpublic research and
development activities that may be under way in private laboratories.
We reviewed data for accuracy and consistency, and corroborated DOD-
provided data to the extent possible. We assessed the reliability of
the DOD-provided data by reviewing related documentation, including
DOD's annual reports to Congress on its Defense Environmental
Restoration Program and information provided by consultants.
We performed our work from January 2005 through May 2005, in accordance
with generally accepted government auditing standards.
[End of section]
Appendix II: Technologies for the Remediation of Contaminated
Groundwater:
Ex-situ Technologies:
1. Advanced oxidation processes often use ultraviolet light irradiation
with oxidizers such as ozone or hydrogen peroxide to produce free
radicals, which break down and destroy chlorinated solvents, fuels, and
explosive contaminants as water flows through a treatment reactor tank.
Depending on the design of the system, the final products of this
treatment can be carbon dioxide, water, and salts. An advantage of
advanced oxidation processes is that it destroys the contaminant,
unlike some other technologies, which only shift the phase of the
contaminant into something more easily handled and removed. There are
some limitations to these processes; for instance, maintenance of the
treatment equipment can be a problem if certain substances--such as
insoluble oil or grease--are allowed into the system. Also, the
handling and storage of oxidizers can require special safety
precautions. The cost of this type of remediation is largely dependent
on the volume and flow rate of groundwater to be treated, energy
requirements, and chemicals utilized. Operations and maintenance costs
are also a factor in the overall cost of this approach. For the
purposes of this report, advanced oxidation processes also include the
related technologies of phyotolysis and photocatalysis.
2. Air stripping involves the mass transfer of volatile contaminants
from water to air by exposing contaminated water to large volumes of
air, so that the contaminants, such as chemical solvents, undergo a
physical transformation from liquid to vapor. In a typical air stripper
setup, called a packed tower, a spray nozzle at the top of a tower
pours contaminated water over packing media or perforated trays within
the tower. At the bottom of the tower, a fan forces air up through the
tower countercurrent to the water flow, thus stripping the contaminants
from the water. The contaminants in the air leaving the tower must then
be removed and disposed of properly. Air strippers can be combined with
other technologies for treatment of groundwater. Advantages of this
technology include its potential to effectively remove the majority of
the volatile organic contaminants of concern. Moreover, this mature
technology is relatively simple and design practices are standardized
and well-documented, and, in comparison with other approaches, this
technology is often less expensive. However, maintenance can be an
issue with this technology if inorganic or biological material clogs or
fouls the equipment, and process energy costs can be high.
3. Bioreactors are biochemical-processing systems designed to degrade
contaminants in groundwater using microorganisms, through a process
similar to that used at a conventional wastewater treatment facility.
Contaminated groundwater flows into a tank or basin, where it interacts
with microorganisms that grow and reproduce while degrading the
contaminant. The excess biomass produced is then separated from the
treated water and disposed of as a biosolids waste. This technology can
be used to treat, among other things, chlorinated solvents,
propellants, and fuels. Potential advantages of bioreactors include
relatively low operations and maintenance costs and the destruction,
rather than mass transfer of, the contaminants. Moreover, regulators
and other stakeholders generally accept bioreactor technology as a
proven approach for remediation. Nonetheless, there are some
limitations to the use of bioreactors, including decreases in
effectiveness if contaminant concentrations in the influent water are
too high or too low to support microorganism growth and if nuisance
microorganisms enter the system. Additionally, the sludge produced at
the end of the process may need further treatment or specialized
disposal. Bioreactor cost is influenced by the upfront capital needed
for installation, setup, and start-up, as well as the operations and
maintenance costs associated with longer-term treatment.
4. Constructed wetlands use artificial wetland ecosystems (organic
materials, microbial fauna, and algae) to remove metals, explosives,
and other contaminants from inflowing water. The contaminated water
flows into the wetland and is processed by wetland plants and
microorganisms to break down and remove the contaminants. Wetlands,
intended to be a long-term remediation approach, can be created with
readily available equipment and generally can operate with low
maintenance costs. Furthermore, because this technology provides a new
ecosystem for plant and animal life, it is generally popular with the
public. However, this approach is often more suitable for groundwater
that is ultimately discharged to the surface rather than reinjected
into the ground. Also, the long-term effectiveness of this treatment is
not well-known, as aging wetlands may lose their ability to process
certain contaminants over time. Temperature, climate, and water flow
rate may negatively impact the processes that break down the
contaminants. Applicability and costs associated with constructed
wetlands vary depending on site conditions, such as groundwater flow
rate, contaminant properties, landscape, topography, soil permeability,
and climate.
5. Ion exchange involves passing contaminated water through a bed of
resin media or membrane (specific to the particular contaminant) that
exchanges ions in the contaminants' molecular structure, thus
neutralizing them. This approach can be useful for dissolved metals
(e.g., hexavalent chromium) and can be used to treat propellants such
as perchlorate. Once the ion exchange resin has been filled to
capacity, it can be cleaned and reused (following a process called
resin regeneration). Ion exchange is usually a short-to medium-term
remediation technology. This technology allows contaminated water to be
treated at a high flow rate and can completely remove the contaminants
from the water. However, some substances--such as oxidants or suspended
solids--in the incoming water may diminish the effectiveness of the ion
exchange resins. Furthermore, different resin types can be needed for
different contaminants. Among the factors influencing costs are
discharge requirements, the volume of water to be treated, contaminant
concentration (as well as the presence of other contaminants), and
resin regeneration. For the purposes of this report, ion exchange
includes technologies that use ion exchange resins or reverse osmosis
membranes to remove contaminants from groundwater, including dissolved
metals and nitrates.
6. Adsorption (mass transfer) technologies involve passing contaminated
water through a sorbent material--such as activated carbon--that will
capture the contaminants (through either adsorption or absorption),
thus removing or lessening the level of contaminants in the water. The
contaminated water is pumped from the aquifer and passed through the
treatment vessel containing the sorbent material. As the contaminated
water comes into contact with the sorbent surface, it attaches itself
to that surface and is removed from the water. Benefits of this
technology include its ability to treat contaminated water to
nondetectable levels and its potential for treating low to high
groundwater flow rates as well as multiple contaminants simultaneously.
However, some contaminants may not be sorbed well or the sorbent unit
may require disposal as hazardous waste. Furthermore, this approach is
impractical if the contaminant levels are high due to higher costs
resulting from frequent changing of the sorbent unit. If the
concentrations of contaminants are low or flow rates for treatment can
be kept low, then adsorption technology may be a cost-effective
approach.
In-situ Technologies:
1. Air sparging introduces air or other gases into a contaminated
aquifer to reduce concentrations of contaminants such as fuel or
chlorinated solvents. The injected air creates an underground air
stripper that removes contaminants by volatilization (a process similar
to evaporation that converts a liquid or solid into a gas or vapor).
This injected air helps to transport the contaminants up into the
unsaturated zone (the soil above the water table, where pores are
partially filled with air), where a soil vapor extraction system is
usually implemented to collect the vapors produced through this
process. This technology has the added benefit of often stimulating
aerobic biodegradation (bioremediation) of certain contaminants because
of the increased amount of oxygen introduced into the subsurface.
Typically, air sparging equipment is readily available and easily
installed with minimal disturbance to site operations. However, this
technology cannot be used if the contaminated site contains
contaminants that don't vaporize or are not biodegradable. In some
cases, this technology may not be suitable for sites with free product
(e.g., a pool of fuel floating on the water table) because air sparging
may cause the free product to migrate and spread contamination. Also,
this technology is less effective in highly stratified or heterogeneous
soils since injected air tends to travel along paths of least
resistance in the subsurface, potentially bypassing areas of
contamination. This technology can be less costly than ex-situ
technologies because it does not require the removal, treatment,
storage, or discharge of groundwater. For the purposes of this report,
air sparging includes the related remedial approaches of co-metabolic
sparging, sparging using other gases, and in-well air stripping.
2. Bioremediation relies on microorganisms to biologically degrade
groundwater contaminants through a process called biodegradation. It
may be engineered and accomplished in two general ways: (1) stimulating
native microorganisms by adding nutrients, oxygen, or other electron
acceptors (a process called biostimulation); or (2) providing
supplementary pregrown microorganisms to the contaminated site to
augment naturally occurring microorganisms (a process called
bioaugmentation). This technology mainly focuses on remediating organic
chemicals such as fuels and chlorinated solvents. One approach, aerobic
bioremediation, involves the delivery of oxygen (and potentially other
nutrients) to the aquifer to help native microorganisms reproduce and
degrade the contaminant. Another approach, anaerobic bioremediation,
circulates electron donor materials--for example, food-grade
carbohydrates such as edible oils, molasses, lactic acid, and cheese
whey--in the absence of oxygen throughout the contaminated zone to
stimulate microorganisms to consume the contaminant. In some cases,
pregrown microbes may be injected into the contaminated area to help
supplement existing microorganisms and enhance the degradation of the
contaminant, a process known as bioaugmentation. A potential advantage
of bioremediation is its ability to treat the contaminated groundwater
in place with naturally occurring microorganisms, rather than bringing
contaminants to the surface. By using native microorganisms, rather
than injecting additional ones, cleanup can be more cost-effective at
some sites. However, heterogeneous subsurfaces can make delivering
nutrient/oxygen solutions to the contaminated zone difficult by
trapping or affecting movement of both contaminants and
groundwater.[Footnote 21] Also, nutrients to stimulate the
microorganisms can be consumed rapidly near the injection well, thereby
limiting the microorganisms' contact with the contaminants, or
stimulating biological growth at the injection site. In summary, this
technology avoids the costs associated with bringing water to the
surface for treatment; instead, the main costs associated with
bioremediation include: delivery of the amendments to the subsurface
(which varies depending on the depth of contamination), the cost of the
amendments themselves, and monitoring of the treatment. For the
purposes of this report, bioremediation includes the related
bioremedial approaches of bioaugmentation, biostimulation, co-
metabolic treatment, enhanced aerobic biodegradation, enhanced
anaerobic biodegradation, and biobarriers.
3. Enhanced recovery using surfactant flushing speeds contaminant
removal in conventional pump-and-treat systems by injecting
surfactants[Footnote 22] into contaminated aquifers or soil to flush
the contaminant toward a pump in the subsurface (some distance away
from the injection point); this pump removes the contaminated water and
surfactant solution to the surface for treatment and disposal of
contaminants. Surfactants are substances that associate with organic
compounds such as fuels and chlorinated solvents and significantly
increase their solubility, which aids cleanup of contaminated aquifers
with less flushing water and pumping time. This technology is
applicable to both dense and light nonaqueous phase liquids (DNAPL and
LNAPL).[Footnote 23] Benefits of enhanced recovery approaches include
the rapid removal of contaminants, which may significantly reduce
cleanup times. However, regulatory issues may require special attention
due to extra scrutiny for obtaining approvals to inject surfactant
solutions; a greater degree of site characterization is often required
to satisfy both technical and regulatory requirements. In addition,
subsurface heterogeneities and low permeability can interfere with the
effective delivery and recovery of the surfactant solution.
Furthermore, to the extent that mobilization of organic liquid
contaminants is achieved, this approach may be better for LNAPLs than
DNAPLs, as LNAPLs tend to migrate upward and DNAPLs downward, possibly
trapping them in previously uncontaminated subsurface areas. In
addition to the high cost of surfactant solutions, another factor
influencing the overall cost of this approach may be the treatment of
the surfactant solution that is pumped out of the aquifer. For the
purposes of this report, this technology includes related remedial
approaches that use co-solvents such as ethanol to improve the
solubility of surfactants in the subsurface.
4. Chemical treatments include remediation technologies that chemically
oxidize or reduce contaminants when reactive chemicals are injected
into the groundwater. This approach converts contaminants such as fuels
and explosives into nonhazardous or less-toxic compounds. Depending on
the extent of contamination, this process involves injecting chemicals
into the groundwater and generally takes a few days to a few months to
observe results in rapid and extensive reactions with various
contaminants of concern. Additionally, this technology can be tailored
to the site and does not require rare or complex equipment, which may
help reduce costs. Generally, there are no unusual operations and
maintenance costs; however, in-situ chemical treatment may require
intensive capital investment for large contaminant plumes or zones
where repeated applications or large volumes of reactive chemicals may
be required; major costs are associated with injection-well
installation (cost influenced by well depth), procurement of the
reactive chemicals, and monitoring. Additionally, site characterization
is important for the effective delivery of reactive chemicals, as
subsurface heterogeneities may result in uneven distribution of the
reactive chemicals. For the purposes of this report, chemical treatment
also includes various remedial approaches and technologies that
chemically oxidize or reduce contaminants in- situ, as well as those
that result in the in-situ immobilization and stabilization of soluble
metals.
5. Monitored natural attenuation is a relatively passive strategy for
in-situ remediation that relies on the naturally occurring physical,
chemical, and biological processes that can lessen concentrations of
certain contaminants in groundwater sufficiently to protect human
health and the environment. The changes in contaminant concentrations
are observed through various wells that are placed throughout the
contaminated groundwater zone to monitor the level of contamination
over time and its migration from its initial location in the
subsurface. Some chlorinated solvents and explosives may be resistant
to natural attenuation; however, it can still be used in cases of
nonhalogenated chlorinated solvents and some inorganic compounds. If
appropriate for a given site, natural attenuation can often be less
costly than other forms of remediation because it requires less
infrastructure, construction, and maintenance. Furthermore, it is less
intrusive because fewer surface structures are necessary and it may be
used in all or selected parts of a contaminated site, alone or in
conjunction with other types of remediation. However, compared with
active techniques, natural attenuation often requires longer time
frames to achieve remediation objectives.
6. Multiphase extraction uses a series of pumps and vacuums to remove
free product,[Footnote 24] contaminated groundwater, and vapors from
the subsurface, treat them, and then either dispose or reinject the
treated groundwater. Specifically, one or more vacuum extraction wells
are installed at the contaminated site to simultaneously pull liquid
and gas from the groundwater and unsaturated soil directly above it.
This type of vacuum extraction well removes contaminants from above and
below the groundwater table, and can expose more of the subsurface for
treatment, notably in low permeability or heterogeneous formations. The
contaminant vapors are collected in the extraction wells and taken
above ground for treatment. This approach can be used to treat organic
contaminants--such as chlorinated solvents and fuels--and can be
combined with other technologies, particularly above-ground
liquid/vapor treatment, as well as other methods of in-situ remediation
such as bioremediation, air sparging, or bioventing. Potential
advantages of this technology include its applicability to groundwater
cleanup in low permeability and heterogeneous formations and its
minimal disturbance to site-specific conditions. However, the system
requires complex monitoring and specialized equipment, and it may be
difficult or problematic to implement the most effective number of
pumps. A major contributor to this technology's cost is operations and
maintenance, which may run from 6 months to 5 years, depending on site-
specific factors. For the purposes of this report, multiphase
extraction includes the related technologies of bioslurping and dual-
phase extraction.
7. Permeable reactive barriers are vertical walls or trenches built
into the subsurface that contain a reactive material to intercept and
remediate a contaminant plume as the groundwater passes through the
barrier. This technology can be used to treat a wide range of
contaminants and is commonly used to treat chlorinated solvents and
heavy metals. Reactive barriers usually do not require above-ground
structures or treatment, allowing the site to be used while it is being
treated. However, its use is limited by the size of the plume since
larger contaminant plumes are often more difficult to intercept for
treatment. Moreover, the barrier may lose effectiveness over time as
microorganisms or chemicals build up on the barrier, making
rehabilitation or media replacement necessary. The depth of the
contaminated groundwater zone and the required barrier may also present
some technical challenges. Underground utility lines, rocks, or other
obstacles can increase the difficulty of installing a barrier and drive
up capital costs. Additionally, because permeable reactive barriers do
not treat the contaminant source, but simply the plume, treatment may
be required for extended time periods, thus increasing overall cleanup
costs. For the purposes of this report, permeable reactive barriers
include biotic and abiotic, as well as passive and active treatment
barriers.
8. Phytoremediation is the use of selected vegetation to reduce,
remove, and contain the toxicity of environmental contaminants, such as
metals and chlorinated solvents. There are several approaches to
phytoremediation that rely on different plant system processes and
interactions with groundwater and contaminants. One approach to
phytoremediation is phytostabilization, which uses plants to reduce
contaminant mobility by binding contaminants into the soil or
incorporating contaminants into plant roots. Another approach is
phytoaccumulation, where specific species of plants are used to absorb
unusually large amounts of metals from the soil; the plants are later
harvested from the growing area and disposed of in an approved manner.
A similar process is called rhizofiltration, where contaminated water
moves into mature root systems and is circulated through their water
supply. Another process can remove contaminants by evaporating or
volatilizing the contaminants from the leaf surface once it has
traveled through the plant's system. Phytoremediation offers the
benefit of only minimally disturbing the environment and can be used
for the treatment of a wide range of contaminants. However, specific
plant species required for particular contaminants may be unable to
adapt to site conditions due to weather and climate, and
phytoremediation may not be an effective approach for deep
contamination. While maintenance costs, including cultivation,
harvesting, and disposal of the plants, are substantial for this
technology, phytoremediation typically has lower costs than alternative
approaches. For the purposes of this report, phytoremediation includes
phytostabilization, phytoaccumulation, phytoextraction,
rhizofiltration, phytodegredation, rhizosphere degredation, organic
pumps, and phytovolitilization.
9. Thermal treatments involves either pumping steam into the aquifer or
heating groundwater in order to vaporize chlorinated solvents or fuels
from the groundwater. The vaporized contaminant then rises into the
unsaturated zone and can be removed via vacuum extraction for
treatment. There are three main approaches for heating the groundwater
in-situ. The first, radio frequency heating, uses the electromagnetic
energy found in radio frequencies to rapidly heat the soil in a process
analogous to microwave cooking. The second, electromagnetic heating,
uses an alternating current to heat the soil and may include hot water
or steam flushing to mobilize contaminants. The third uses heating
elements in wells to heat the soil. Thermal treatments may be applied
to a wide range of organic contaminants and sites with larger volumes
of LNAPLs or DNAPLs as well as sites with low permeability and
heterogeneous formations. However, the presence of metal and subsurface
heterogeneities in the contaminated site may interfere with this
process. The heating and vapor collection systems must be designed and
operated to contain mobilized contaminants, to avoid their spread to
clean areas. The major costs incurred for thermal treatments are for
moving specialized equipment to the site, developing infrastructure to
provide power, and providing energy to run the system. For the purposes
of this report, thermal treatments include related soil-heating
technologies, such as steam flushing, conductive heating, and
electrical resistance heating.
[End of section]
Appendix III: Groundwater Remediation Experts Consulted:
Dr. John Fountain:
Professor and Head, Department of Marine, Earth and
Atmospheric Sciences:
North Carolina State University:
Raleigh, North Carolina:
Dr. Robert E. Hinchee:
Principal Civil and Environmental Engineer:
Integrated Science and Technology Inc.:
Panacea, Florida:
Dr. Michael C. Kavanaugh:
Vice President:
National Science and Technology Leader:
Malcolm Pirnie Inc.:
Emeryville, California:
Dr. Robert L. Siegrist:
Professor and Division Director:
Environmental Science and Engineering Division:
Colorado School of Mines:
Golden, Colorado:
Dr. John T. Wilson:
Senior Research Microbiologist:
Ground Water and Ecosystems Restoration Division, National Risk
Management Research Laboratory:
Office of Research and Development:
U.S. Environmental Protection Agency:
Ada, Oklahoma:
[End of section]
Appendix IV: Comments from the Department of Defense:
DIRECTOR OF DEFENSE RESEARCH AND ENGINEERING:
3030 DEFENSE PENTAGON:
WASHINGTON, D.C. 20301-3030:
JUN 22 2005:
Ms. Anu Mittal:
Director, Natural Resources and Environment:
U.S. Government Accountability Office:
444 G Street, N.W.:
Washington, D.C. 20548:
Dear Ms. Mittal:
This is the Department of Defense (DoD) response to the GAO draft
report, "GROUNDWATER CONTAMINATION: DoD Uses and Develops a Range of
Remediation Technologies to Clean Up Military Sites," dated May 31,
2005 (GAO Code 360539/GAO-05-666).
The draft report has been reviewed for technical accuracy. It
accurately reports the Department's usage of technologies to treat
groundwater at installations and those actions being taken to research
and test novel approaches to address groundwater contaminants.
Sincerely,
Signed by:
Ronald M. Sega:
[End of section]
Appendix V: GAO Contact and Staff Acknowledgments:
GAO Contact:
Anu K. Mittal, (202) 512-3841:
Staff Acknowledgments:
In addition to the contact above, Richard Hung, Lynn Musser, Jonathan
G. Nash, Omari Norman, and Diane B. Raynes made key contributions to
this report. Jessica A. Evans, Katherine M. Raheb, and Carol Herrnstadt
Shulman also made important contributions to this report.
(360539):
FOOTNOTES
[1] Remediation of a contaminated site involves efforts to remove,
destroy, or isolate contaminants found in the groundwater. In some
cases, disposal practices at these sites predate the enactment of
relevant environmental cleanup statutes.
[2] The Navy oversees environmental restoration on Marine Corps
facilities.
[3] The Corps may also participate in groundwater remediation
activities on active Army installations, some Air Force installations,
and properties that are scheduled for closure as part of the Base
Realignment and Closure Act process.
[4] For the purposes of this report, we have defined a "site" as a
specific area of contamination and a "facility" as a geographically
contiguous area under DOD's ownership or control within which a
contaminated site or sites are located. A single DOD facility may
contain multiple sites requiring cleanup.
[5] Ronald W. Reagan National Defense Authorization Act for Fiscal Year
2000, Pub. L. No. 108-375, § 316, 118 Stat. 1811, 1843 (Oct. 28, 2004).
[6] See appendix II for more information on each of the 15
technologies.
[7] Some of DOD's sites are considered megasites--defined by EPA as
sites requiring investments of over $50 million to achieve cleanup.
[8] DOD carries out some groundwater remediation as corrective action
under the Resource Conservation and Recovery Act of 1976 (RCRA).
According to DOD, while RCRA and CERCLA contain somewhat different
procedural requirements, these differences do not substantively affect
the outcome of remedial activities.
[9] This list represents EPA's highest priorities for cleanup
nationwide, including public and private sites considered by EPA to
present the most serious threats to human health and the environment.
To make its determination, EPA uses a hazard-ranking system to evaluate
the severity of the contamination by examining the nature of the
contaminants, the pathways through which they can move (such as soil,
water, or air), and the likelihood that they may come into contact with
a receptor--for example, a person living nearby. According to DOD's
Defense Environmental Programs, Annual Report to Congress, Fiscal Year
2004, DOD has 152 facilities that are listed or proposed for listing on
the National Priorities List.
[10] 42 U.S.C. § 9621(c). The applicable EPA regulation differs from
the statute: It requires the five-year reports only if contaminants
will remain at the site "above levels that allow for unlimited use and
unrestricted exposure." 40 C.F.R. § 300.430(f)(4)(ii).
[11] Surfactants, or surface active agents, are molecules with two
structural units: one with an affinity for water and one with an
aversion to water. This molecular combination is useful for dissolving
some contaminants and enhancing their mobility by lowering the
interfacial tension between the contaminant and the water.
[12] For more information, see National Research Council, Water Science
and Technology Board, Contaminants in the Subsurface: Source Zone
Assessment and Remediation (Washington, D.C., 2004).
[13] A contaminant may exist in aqueous (dissolved in water),
nonaqueous, solid (sorbed), or gaseous form.
[14] For more information, see National Research Council, Contaminants
in the Subsurface: Source Zone Assessment and Remediation (Washington,
D.C., 2005).
[15] For more information, see EPA, Office of Solid Waste and Emergency
Response, Remediation Technology Cost Compendium--Year 2000
(Washington, D.C., 2001).
[16] For additional information, see the online version of the Federal
Remediation Technologies Roundtable Treatment Technologies Screening
Matrix at http://www.frtr.gov/scrntools.htm.
[17] Nanoscale refers to miniscule particles that measure less than 100
nanometers in diameter. In comparison, an average human hair typically
measures 10,000 nanometers in diameter.
[18] See National Research Council, Water Science and Technology Board,
Environmental Cleanup at Naval Facilities: Adaptive Site Management
(Washington, D.C., 2003).
[19] SERDP's goals include supporting basic and applied research and
development of environmental technologies; providing information and
data on environmental research and development activities to other
governmental and private organizations in an effort to promote the
transfer of innovative technologies; and identifying technologies
developed by the private sector that are useful for DOD's and DOE's
environmental restoration activities.
[20] According to ESTCP, the program "provides an independent, unbiased
evaluation of the cost, performance, and market potential of state-of-
the-art environmental technologies based on field demonstrations
conducted under DOD operational conditions."
[21] Heterogeneities can cause wide variability in hydraulic properties
such as hydraulic conductivity--a measure of the volume of water that
will pass through an area at a given time. These changes in hydraulic
properties enhance the dispersion of a dissolved contaminant spread.
Heterogeneities can also create preferential pathways for contaminant
migration.
[22] Surfactants are molecules with two structural units: one with an
affinity for water and one with an aversion to water. Surfactants are
especially useful for dissolving some contaminants and enhancing their
mobility by lowering the interfacial tension between the contaminant
and water.
[23] Nonaqueous-phase liquids are liquids that do not mix with, or
dissolve in, water. Dense nonaqueous-phase liquids (DNAPL) fall to the
bottom of a body of water; chlorinated solvents are typical examples.
Conversely, light nonaqueous-phase liquids (LNAPL) gather on top of the
water. Gasoline and fuel oil are examples of LNAPLs.
[24] Free products are liquid contaminants floating on top of
groundwater.
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