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Richard J. Wenning is the Practice Director for
Environmental Management & Risk Services at The Weinberg Group
in San Francisco, CA.
For
scientists, environmental managers, and environmental
policy-makers in the United States engaged in the
investigation or remediation of contaminated sediments, four
reports reflect their call for focused and concerted actions
to address contaminated sediments in our nation’s waterways.
First was USEPA’s 1998 Report to Congress on the incidence and
severity of sediment contamination in the United States 1.
Prepared in conjunction with both the National Oceanic and
Atmospheric Administration (NOAA) and the Army Corps of
Engineers, the Agency estimated that approximately 96
watersheds containing over one billion cubic yards of
contaminated sediments warranted some level of assessment and
management (Figure 1). More than two-thirds of these
watersheds, representing nearly 15 percent of the nation’s
lake acreage and 5 percent of its river miles, already had
fish consumption advisories in place.
Less
than one year later, USEPA published its Contaminated
Sediment Management Strategy 2. The strategy
described the Agency’s work plan for actions needed to bring
about assessment and reduction of the ecological and human
health risks posed by contaminated sediments. The strategy
established four goals: source control and prevention of
further sediment contamination; reduction in the volume of
in-place contamination; use of environmentally sound remedial
measures; and, promotion of scientifically sound sediment
management tools for pollution prevention, source control,
remediation, and dredged material management.
At
nearly the same time, the National Research Council (NRC)
reported on the concerns of technical experts that currently
available technologies for cleanup of contaminated sediments
in U.S. ports, harbors, and waterways were capable of
addressing only the less severe aspects of the problem. New
technologies and innovative programs were needed to address
potentially highly toxic sediments in a manner that would
minimize or reduce human exposures and injuries to aquatic
resources 3.
The
fourth, and latest, report in this series was issued by the
NRC earlier this year. Its Risk Management Strategy for
PCB-Contaminated Sediments summarized the current state of
knowledge of human health and ecological impacts posed by PCB
contaminated sediments and provided recommendations for a
wide-range of investigation and research activities as part of
a strategy to reduce the risks 4. The NRC
Committee selected the framework developed by the
Presidential/Congressional Commission on Risk Assessment and
Risk Management 5 (Figure 2), and refined the
framework for application to managing the risks posed by
PCB-contaminated sediments, potential remediation options, and
risks that remain when remediation is complete (Figure 3).
The
NRC report made strong recommendations in support of the use
of a risk-based decision framework. This included an emphasis
on the use of sound risk management principles, extending
beyond the more traditional risk assessment approach. The NRC
Committee also acknowledged that all remedial options have
advantages and disadvantages and, in particular, that dredging
cannot be expected to remove all contaminants. The NRC report
recommended that all risks of implementation for each remedial
option under consideration should be considered, including
risks occurring both during and after the implementation phase
of the remedy. Finally, the NRC Committee recommended that
the net environmental benefit of each remedial option should
be considered and compared.
In
the context of the Superfund program, where the fate of the
majority of contaminated sediment problems rest, the USEPA
faces, perhaps, its most complex environmental challenge to
date. Using the Agency’s estimates for the fraction of
material deemed sufficiently toxic to fish and wildlife to
require removal or isolation, treatment, and disposal, the
projected costs to the Superfund program for cleanup are
enormous. Many experts have concluded that the magnitude of
the problem could be on the order of several billions of
dollars, or more. Using USEPA’s (1998) estimate of 1.2
billion cubic yards of contaminated sediment and a mean
dredging cost up to $250/cubic yard, nationwide remediation
costs could exceed $5 trillion in the United States.
What is the appropriate
approach to investigation, assessment, and remediation of
contaminated sediments? Who should be involved? What are the
important technical, regulatory, and public policy
requirements? What level of investigation and assessment is
required to define appropriate remedies? What are appropriate
remedies? And, how should they be evaluated for short- and
long-term effectiveness?
USEPA
Sediment Forum
To
address these and other difficult questions, the USEPA Office
of Emergency and Remedial Response (OERR) hosted an open
technical forum for discussion of five key aspects of
investigation and remediation of contaminated sediments at
hazardous waste sites. The five aspects are community
involvement, hazard assessment, site characterization,
remedial effectiveness, and risk management.
The purpose of the forum was to
facilitate an open exchange of information and viewpoints
among experts involved in the cleanup of contaminated
sediments. Thirty panelists with recognized expertise in each
of the five disciplines led discussions involving nearly 400
participants representing industry, state and federal
environmental agencies, engineering companies, health
consulting firms, academic institutions, environmental groups,
and Native American interests.
The
forum provided participants with a unique opportunity to
explore the important science and policy issues currently
under consideration by the Agency for making site-specific
risk management decisions. With USEPA staff in the Superfund
Program office currently engaged in drafting guidance on
assessment methods for contaminated sediment at hazardous
waste sites, forum participants could highlight key technical
considerations, the lessons learned, and coax further
considerations by the Agency on several difficult issues. The
new guidance is anticipated in draft form in early 2002.
The specific aims of the USEPA
sediment management forum were to:
-
Provide a forum for
stakeholders to express opinions on USEPA program policies
and guidance that address sediment remediation;
-
Identify the key site
information and data that should be collected and evaluated
to make informed site-specific cleanup decisions;
-
Identify issues that need to
be resolved, additional data that needs to be gathered and
evaluated, and research that needs to be performed; and,
-
Share information and the
lessons learned as a result of managing sites involving
contaminated sediments.
Five Aspects of
Contaminated Sediment Management
Accordingly, the
forum was organized to facilitate the sharing of information
and discussion of key technical issues across five important
aspects:
Community involvement. Nearly twenty years of CERCLA
program experience has taught both the regulated and
regulatory communities that community involvement is a
critical element in the decision-making process at hazardous
waste sites. Citizens groups, Native American tribes, and
other special interest groups are increasingly recognized as
important stakeholders with special interests often
misunderstood or inadequately considered during both the
investigation and remediation stages.
Effects on human health and ecological resources. For
risk managers and the public to understand the scientific
issues that support effective remedial solutions, there
remains an urgent need for clear communication and education
across several disciplinary boundaries. The CERCLA program
has taught us that scientifically defensible, site-specific
risk assessment and environmental analysis still founder when
discussions turn to scientific and engineering uncertainties.
And often at times, these efforts fail to adequately address
the questions important to stakeholders.
Site characterization. Site-specific investigations,
assessments, and remediation of contaminated waterways imply
the development of site-specific conceptual site (or,
sediment) models to guide the entire process. But, the
investigation methods and technologies that should be employed
to understand site-specific conditions are often viewed by the
public and by regulatory agencies as time consuming or, at
worst, as delay-tactics by PRPs. At issue is defining the
appropriate breadth and level of detail required of
site-specific investigations to characterize both
retrospective and prospective temporal and spatial trends of
the contamination.
Remedy effectiveness. Even in a perfect world where
technical experts agree on both the environmental impacts and
site characteristics, there would remain considerable
disagreements over the efficacy of different remediation
technologies and appropriate methods for evaluation of the
long-term effectiveness of selected remediation options.
Furthermore, ongoing releases from uncontrolled or non-point
sources, natural disasters (e.g., severe flooding), and
incomplete or inadequate site characterization can undermine
the long-term success of the chosen remedy.
Risk management frameworks. The various risk
management frameworks emerging among different state and
federal agencies, industry groups, and academic institutions
require convergence, at least on the basic principles.
Achieving consensus among these different stakeholder groups
may be the first, and largest, challenge among all concerned
parties.
Forum Themes:
Community Involvement
Involvement of the local community in the investigation,
assessment, and decision-making process has become an
increasingly important activity for both potential responsible
parties and regulatory agencies. A public involvement plan
that incorporates the concerns of environmental organizations
and other special interest groups, and particularly those of
Native Americans, is increasingly recognized by experts as an
essential early step in contaminated sediment management
strategies throughout the country.
Among
the two essential elements of a community involvement program,
project advisement and education, education may be the most
critical component. According to Larry McShea, from Alcoa,
Inc., the complex nature of contaminated sediment issues
requires that community advisory panels get involved early in
the process to allow adequate time to gain an understanding of
the technical and policy issues before important decisions are
made. The significant complexities that all stakeholders
must grapple with include the evaluation and selection of
sediment management options, assessment of human exposures and
adverse health effects, ecological risk concerns, and societal
issues related to use restrictions on public access waterways.
Jennifer Sutter from Oregon DEQ concurred, noting the success
of Technical Advisory Panels (TAPs) comprised of local
environmental and engineering experts; local, state, and
federal agencies; and the interested public. TAPs can provide
a link between the public and oversight agencies and also
provide a forum for independent peer-review of regulatory and
PRP activities, thereby building confidence and trust among
the various stakeholder groups. She also noted the value of
reaching out to local interest groups to provide updates at
their meetings and on “their turf”, which tended to reach more
people and were more appreciated than the typical formal
public meetings.
The
community involvement approach used by USEPA Region 6 for the
Calcasieu Estuary in Louisiana represents another approach to
community involvement. Among the four key components of USEPA
Region 6’s approach, involvement of local government early in
a local leadership role may be most important. Other
components include the establishment of outreach activities
such as local advertising of significant events and findings,
workshops, and opening of local information offices. The
release of environmental data as it becomes available and
ahead of formal reports, which may be months away, builds
trust. And the last component, frequent communication with
potentially responsible parties to facilitate open
communication on difficult issues, was a common theme
throughout the discussion on community involvement.
The
concept of community extends not just to affected
municipalities, cities, and towns but also to sensitive
populations and special interest groups. According to Tom
Nelson, environmental specialist representing the Onieda
Nation in Wisconsin, the management of contaminated waterways
in Indian Country poses special challenges often ignored or
inadequately addressed by decision-makers. Tribal societies
differ across the country, defying generalizations and
requiring tribe-specific considerations during the assessment
phase and when promoting the final remedy. Incorporating
their concerns and needs likely will continue to pose a
challenge to environmental agencies and other stakeholders.
Forum Themes:
Assessing Human Health and Ecological Risks
Consensus is building among
technical experts and regulatory authorities that risk-based
approaches to investigation and remediation of contaminated
sediments should be favored for their cost-effectiveness and
ability to prioritize public health and ecological concerns.
Difficulties arise, however, over the uncertainties and often
considerable conservatism required to fill data gaps in both
human health and ecological risk assessments.
The age-old argument between
reliance on best-case or worst-case assessments of current and
prospective exposures and health risks remains at the heart of
this debate. Most experts would concur with decisions that
err on the side of safety. At issue is the appropriate
magnitude of that margin of safety and the degree of
resolution required in the assessment to distinguish that
margin.
The
importance of developing more realistic approaches for
characterizing the extent of exposure at contaminated sediment
sites was emphasized in presentations by Natalie Wilson, from
N.D. Wilson and Associates, and Dr. Todd Bridges, from the
U.S. Army Corps of Engineers. The application of
unnecessarily simplistic approaches to characterizing the
punctuated nature of exposure to mobile receptors like fish
often leads to erroneous conclusions about the true risks to
ecological and human receptors. The example presented by Dr.
Bridges for the NY Bight emphasized that assumptions that
constrain the movement of highly mobile receptors to the
confines of relatively small
contaminated sites results in highly exaggerated
assessments and generates uncertainties that significantly
undermine confidence in the decision-making process.
The
weight-of-evidence approach advocated by Dr. Charles Menzie,
from MenzieCura & Associates, highlights one mechanism for
early agreement among stakeholders regarding the magnitude of
that inevitable margin of safety. The framework used in
Massachusetts relies on reaching a consensus among
stakeholders on appropriate assessment and measurement
endpoints in waterway assessments. Dr. Lucinda Jacobs at
Exponent concurs, adding that advancements in risk assessment
such as the use of a tiered assessment approach and
quantitative uncertainty analysis can significantly reduce
uncertainty and minimize data gaps.
Nonetheless, as Dr. Frank Bolen from the University of
Connecticut cautions, weight-of-evidence approaches, as well
as other site characterization methods, still require careful
consideration of the level of precision necessary to answer
the question of environmental fate, impacts on ecosystems, and
the subsequent scope of the remediation effort.
Another approach, which deviates from risk-based assessment
methods, involves the use of numerical sediment quality
guidelines and sediment toxicity testing to predict the
probability of adverse effects to bottom-dwelling benthos.
According to Dr. Chris Ingersoll from USGS, a commitment to
large data collection efforts involving matching sediment
chemistry and laboratory toxicity analyses can effectively
reduce uncertainties regarding characterization of the extent
of adverse ecological impact of contaminated sediment.
Additionally, the generation of site-specific data to evaluate
the applicability of nationwide or regional-based sediment
quality guidelines could be a cost-effective means for making
sediment management decisions.
However, there is considerable debate among experts on the
accuracy and appropriate use of numerical criteria, and
particularly on whether sediment quality guidelines are
effective at predicting sediment toxicity and adverse
ecological effects across different marine and freshwater
environments. Dr. Alan Burton, from Wright State University,
noted that experience thus far indicates that there can be
considerable differences between the nature and magnitude of
adverse effects on indicator species observed in the
laboratory and the effects observed under actual field
experimental conditions. Furthermore, Dr. Robert Engler, from
the U.S. Army Corps of
Engineers, observed that numbers alone cannot be used as
benchmarks and cleanup goals because they address only the
effects side of the risk paradigm without consideration of
causality or the extent of exposure.
Much
as the NRC (2001) report indicated, technical and policy
discussions on sediment risk assessment methods, the utility
of numerical criteria, and the role that both of these tools
should play in decision-making at contaminated sediment sites
remain unresolved and capable of provoking considerable debate
among experts.
Forum
Themes: Site Characterization
If
each Indian tribe is unique and different, then certainly no
two waterways are alike either. There is broad consensus that
site characterization methods must be site-specific and
tailored to explore and evaluate a waterways’ unique
environmental and biological conditions. In fact, several
sets of unique conditions may be evident in larger waterways
such as the Hudson River or Fox River, each requiring their
separate and focused investigations and assessments.
At
present, the debate concerning appropriate site
characterization methods swings widely between those experts
who seek to generalize waterway behavior into a basic model
framework, and those experts who seek to establish key
measurement indicators and advocate implementation of a full
suite of characterization tools. One issue in this debate is
the importance of distinguishing between site characterization
efforts that generate need-to-know information from those that
produce nice-to-know information. Risk-based decision-making,
at a minimum, requires site-specific environmental data. And
regardless of the focus, site characterization must adequately
address the spatial, temporal, and exposure aspects of a
risk-based management paradigm, and provide sufficient
quantification of the uncertainties associated with the chosen
characterization methods to inform decision-makers of possible
limitations and data gaps.
The
importance of problem formulation early in the investigation
process was evident to all forum participants. Regardless of
the approach, Dr. John Connolly, from Quantitative Environment
Analysis, advocates the application of the scientific method
to establish and ask the important questions in a
hypothesis-testing framework. But, there are some
difficulties with regard to the practical aspects of this
approach to site characterization beyond mass balance modeling
and source control investigations.
Source
investigation during site characterization is one area of
general agreement among experts. Site characterization must
address ongoing sources because the success of any future
remediation activities by risk managers requires no net inputs
to the affected environment. Bioavailability and contaminant
flux also must be well understood. Food web transfers and
pathways of human exposure must be evaluated and the linkage
to contaminated sediment conditions confirmed at the site.
Sediment stability, particularly the risk of remobilization
during severe natural climatic events (e.g., flooding), must
be evaluated.
Forum
Themes: Remedy Effectiveness
For contaminated sediments
requiring remediation, remedy selection often hinges on the
decision whether to dredge sediments, promote natural recovery
of the affected waterway, or cap contaminated materials in
place. Considerations of long- and short-term remedy
effectiveness are important issues that stakeholders should
consider for all management options. A brief review of
waterway projects completed to date suggests that these three
options do not provide the level of environmental protection
and finality required by all stakeholders.
Representing the considerable expertise of the Army Corps of
Engineers on this subject, Dr. Michael Palermo observed that
the current debate about dredging contaminated sediments
focuses on concerns regarding short-term potentially negative
impacts on wildlife and human health. For example, while
capping may impose lower short-term environmental impacts than
dredging, severe natural climatic events and unintentional
man-made disturbances that violate the in-situ barrier may
pose considerable longer-term risks. And, in the case of
dredging, downstream losses of contaminated material and their
short-term impacts during the removal process need to be
balanced against the long-term capability for the ecology of
the affected water way to recover.
The
third remediation option, monitored natural recovery (formerly
referred to as natural attenuation, or by its sharpest critics
as the no action alternative), is gaining serious
consideration as a reasonable approach for some
contaminants. But as James Chapman, from USEPA Region 5, and
Dr. Victor Magar, from Battelle, observed in their case
studies, more research is needed to improve understanding of
natural processes and to advance the lessons learned at
several successful project sites such as in Lake Hartwell,
South Carolina to other sites. In some cases, the reasons why
natural processes fail to fully attenuate contamination under
conditions that appear ideal for natural processes are not
completely understood. It is on this basis, according to
Emily Green, representing the Sierra Club, that activities
that appear to reflect the no-action alternative are
unsatisfactory.
There
is general agreement with Dr. Palermo’s five criteria for
evaluating short- and long-term effectiveness of capping and
dredging/disposal options. The time to achieve remediation
goals must be considered. Contaminant releases during and
following construction activities must be evaluated to
understand whether the remedy has the potential to do more
harm than good. The permanence of the remedy must be forecast
under several reasonable and worst-case scenarios. The high
cost typically associated with the majority of contaminated
sediment projects does not tolerate remedy failure. And,
finally, the implementation of the remedy approach must be
practicable to the specific areas of concern at the site.
Forum
Themes: Risk Management Frameworks
Several contaminated sediment management frameworks in various
stages of development are available from a wide range of
stakeholders at the present time. Managing the risks posed by
contaminated sediments at hazardous waste sites is likely to
remain elusive long after the technical issues related to site
characterization, risk assessment methods, and remediation
technologies have been resolved.
Four
common themes are evident among different proposed
frameworks. Risk management should address the need for
source control, strive to reduce in-place contamination, use
scientifically sound investigation, assessment, and
remediation methods, and involve implementation of
environmentally sound management options. A successful
framework should involve all concerned stakeholders and
provide each with a forum to express opinions, concerns, and
share ideas. The framework may have a national set of guiding
principles, but must be flexible and tailored to
waterway-specific conditions and solutions.
Echoing some of the eleven recommendations specified in NRC’s
(2001) risk management strategy for PCB-contaminated
sediments, forum experts agreed that a site-specific risk
management framework should comprehensively evaluate the broad
range of risks posed by the occurrence of contaminants in
sediments and any proposed remedial action. Management
options should be risk-based. Source control measures are
relevant to the remedial decision-making process. There
should be no presumptive remedies or undue focus on a single
preferred remedial option. Engineering and other less
intrusive options are likely to be necessary to address the
range of human health and ecological concerns at a site.
A
similar set of what could be called “guiding principles” is
described in the detailed decision-making framework proposed
by the Sediment Management Work Group. (Figure 4). The
framework and several supporting technical documents can be
found on their web site at
www.smwg.org.
Finally, the overall framework for managing risks will likely
extend far beyond the project lifetime because of the need for
long-term monitoring to evaluate the effectiveness of the
management approach and to ensure adequate, continuous
protection of public health and the environment. The scope
and duration of post-remediation monitoring will be a function
of the level of site-specific uncertainty between the
occurrence of contamination and its direct link to measurable
adverse ecological effects and human health impacts.
Closing
Considerations
A
synopsis of the meeting and copies of the presentations given
by invited panelists will be made available by USEPA OERR on
the internet. Documents will appear on the Superfund web site
at
www.epa.gov/superfund/
before the end of this summer.
The
next steps in the technical dialogue process initiated by the
Superfund Sediment Team within USEPA’s Office of Emergency and
Remedial Response will likely include regional workshops
around the country to further explore the issues in each of
the five focus areas. Special technical forums are likely to
explore topics such as sediment transport, ecotoxicology,
bioavailability, fish consumption surveys, remediation
technologies, and specific sediment contaminants. New
technical and policy documents anticipated from USEPA over the
next year likely will include guidance on sediment
remediation, a risk-based policy framework for contaminated
sediments, and a proposed contaminated sediment research plan.
There
also is an expectation among forum participants for more
frequent dialogue, information exchange and joint research
activities among technical experts from industry, academia,
and regulatory agencies; between different state and federal
regulatory agencies; and with citizen groups, environmental
organizations, and other special interest stakeholders.
Technical and policy changes
are underway to address the calls for action heralded in the
four USEPA and NRC reports published within the past four
years. Over the next few years we are likely to see more
integration and greater consensus among diverse technical and
policy experts on appropriate sediment characterization
methods, site-specific risk assessment methods (both human
health and ecological), and site-specific remediation
technologies and management techniques. The USEPA’s sediment
management forum was an important step in the right direction.
To learn more about USEPA
progress on its national contaminated sediment management
strategy, look to USEPA’s web site located at
www.epa.gov/ost/cs.
The Army Corp of Engineers maintains a wealth of information
on dredged material assessment and management methods on its
Dredging Operations and Environmental Research (DOER) web
site located at
www.wes.army.mil/el/dots.
Other resources for further understanding of the various
sediment management issues include the Sediment Management
Work Group’s web site located at
www.smwg.org,,
and the National Environmental Policy Institute’s National
Sediment Dialogue forum located at
www.nepi.org/sediments.htm.
References
1. USEPA,
The Incidence and Severity of
Sediment Contamination in Surface Waters of the United States,
EPA 823-R-97-006, -007, and -008 (January, 1998).
http://www.epa.gov/OST/cs/congress.html .
2. USEPA,
Contaminated Sediment Management Strategy: Reinventing
Government to Streamline Decision-Making, EPA
823-F-98-004 (April, 1998).
http://www.epa.gov/OST/cs/manage/stratndx.html .
3. National
Research Council, Contaminated Sediments in Ports and
Waterways: Cleanup Strategies and Technologies, Committee
on Contaminated Marine Sediments, Marine Board, Commission on
Engineering and Technical Systems (June, 1998).
http://www.nap.edu/books/0309054931/html/
4. National
Research Council, A Risk Management Strategy for
PCB-Contaminated Sediments, National Academy Press,
Washington, D.C. (January, 2001).
www.nap.edu/openbook/0309073219/html/4.html .
5. Presidential/Congressional
Commission on Risk Assessment and Risk Management,
Framework for Environmental Health Risk Management: Final
Report. Washington, D.C. (January, 1997).
http://www.riskworld.com/Nreports/1996/risk_rpt/Rr6me001.htm.
Figure 1. Probable
Areas of Concern identified by the U. S. Environmental
Protection Agency in the 1998 Report to Congress on
contaminated sediments in the continental United States.
Source: The Incidence and Severity of Sediment
Contamination in Surface Waters of the United States
(September, 1997).
Figure 2. The
Presidential/Congressional Commission on Risk Assessment and
Risk Management (1997) framework for environmental health risk
management.
Figure 3. The NRC
(2001) Technical Committee’s refinement of the
Presidential/Congressional (1997) framework for application to
the risk management of PCB-contaminated sediments.
Figure 4.
The sediment management decision-making framework proposed by
the Sediment Management Work Group (www.smwg.org).
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