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entitled 'Groundwater Contamination: DOD Uses and Develops a Range of 
Remediation Technologies to Clean Up Military Sites' which was released 
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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]

www.gao.gov/cgi-bin/getrpt?GAO-05-666.

To view the full product, including the scope and methodology, click on 
the link above. For more information, contact Anu K. Mittal at (202) 
512-3841 or mittala@gao.gov.

[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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