1998 CPEO Brownfields List Archive

From: Career/Pro <cpeo@cpeo.org>
Date: 27 Oct 1998 10:28:52
Reply: cpeo-brownfields
Subject: National Stakeholders' Forum on MNA Report
On August 31-September 1, CPEO, with financial support from the Air Force and other agencies, conducted the National Stakeholders' Forum on Monitored
Natural Attenuation.  We believe the event was extremely successful, and once again we would like to express our appreciation not only to the co-sponsors, but to the speakers and other participants.  The forum report follows.  The formatted version of this report, and CPEO fact sheets on natural attenuation are available online at: http://www.cpeo.org/pubs/index.html


          Report of the National Stakeholders' Forum on
                  Monitored Natural Attenuation
             Center for Public Environmental Oversight
  San Francisco Urban Institute, San Francisco State University 

                         October, 1998 

The National Stakeholders' Forum on Monitored Natural 
Attenuation, held near San Francisco August 31 and September 1, 
1998, brought together nearly 250 scientists, activists, and 
government officials. Organized by the Center for Public 
Environmental Oversight (CPEO), with sponsorship from the Air 
Force, the Navy, U.S. EPA, and the Department of Energy, the 
Forum offered a balanced series of informative presentations on 
natural attenuation as a cleanup strategy, and it provided the 
public stakeholder participants with perhaps their only 
opportunity to influence national policy on natural attenuation. 

The racially diverse community participants, many of whom live 
near federal facilities, represented communities from throughout 
the U.S. Most indicated their appreciation for the opportunity 
to gain a wider understanding of the science and policy of 
natural attenuation, as well as the chance to network with 
people from other areas of the country with similar problems. 
Participants from all constituencies recognized the value of the 
Forum's unique format: Large numbers of people representing 
federal responsible parties, regulators, consultants, academia, 
and the public nationally were able to exchange their views 
openly and respectfully. 

To guide national policy development, organizers of the Forum 
laid out four questions for participants: 

1.   What are the advantages and disadvantages of monitored
     natural attenuation as a remedy? 

2.   When and where is monitored natural attenuation

3.   How does one predict and verify the effectiveness of
     natural attenuation? 

4.   What should be done if natural attenuation doesn't work as

Forum planners did not seek consensus. There was no formal 
voting. Rather, the Forum provided opportunities for those 
present to express themselves, in breakout groups as well as 
plenary sessions, and CPEO recorded those points of view. 

Panelists consisted of community activists, regulators, 
academics, and scientists in the employ of the Departments of 
Energy and Defense. They represented differing points of view, 
but each brought his or her own expertise to the podium. 
Community representatives, for example, not only stressed the 
importance of community concerns, but they showed how grassroots 
activists could, over time, achieve a serious level of technical 

Other speakers stressed the importance of factoring in all 
scientific aspects when considering natural attenuation as a 
remedy. They described how cleanup teams study contamination in 
the subsurface environment, pointing out how difficult it is to 
know exactly what's going on underground. Speakers agreed that 
natural attenuation, to some degree, always occurs at 
contamination sites. While project scientists must estimate the 
extent of natural attenuation processes, the question for 
decision-makers is whether such processes are sufficient to 
achieve cleanup goals. Finally, panelists explored the 
terminology used to describe natural processes. Though some 
found the term "natural attenuation" acceptable, others felt it 
confused degradation with other natural paths to reduce 
contaminant concentration. 

Forum participants offered a wide range of comments on Monitored 
Natural Attenuation in general and specifically on EPA's interim 
policy, but the public stakeholders who spoke out tended to 
agree on key issues. Below is CPEO's summary of those comments. 

The Importance of Trust 

Public participants indicated widespread suspicion of Monitored 
Natural Attenuation as a cleanup strategy, but they did not 
challenge the science presented by its proponents. In fact, at 
first Forum organizers were frustrated by comments that centered 
on what seemed to be other issues, such as risk assessment, 
institutional controls, and the general absence of trust for 
government officials, particularly those working for agencies, 
such as the Departments of Defense and Energy, which have large 
contamination problems. 

In reviewing the Forum record, however, that response stands out 
as the key lesson of the event: Decision-makers who believe 
monitored natural attenuation is the best remedial response at a 
site must win the trust of the public long before they propose 
it as a remedy. 

Many traditional remedial strategies, such as "dig and haul" or 
"pump and treat," are superficially simple. Most people 
understand the basic concepts. They can see whether it's 
happening. The case for monitored natural attenuation, on the 
other hand, relies upon complex analysis before and after the 
fact. Before remedy selection, site characterization must show 
that natural attenuation is likely to achieve remedial 
objectives. Once natural attenuation is endorsed, long-term 
monitoring must continue until those objectives are reached. 
Both characterization and monitoring depend upon multiple lines 
of evidence, most of which involve variables that are difficult, 
at best, for the average person to understand. 

Furthermore, at least one public participant pointed out that in 
practice decision-makers often rely upon only two lines of 
evidence, but use the term multiple to reinforce the perceived 
certainty that natural attenuation is proceeding with enough 
strength, speed, and stamina to complete the job. 

Typically, when natural attenuation is under consideration, 
experts working for the responsible party present charts, 
graphs, and arguments designed to show that Monitored Natural 
Attenuation will achieve comparable results to other, more 
expensive remedial options. In fact, at the forum one Air Force 
scientist presented a graph showing that the rate of contaminant 
mass reduction in one major plume using natural attenuation 
wasn't much different than the estimated rate using conventional 
remedies. That graph demonstrated, he suggested, that Monitored 
Natural Attenuation was worth considering at that site. 

However, from the public stakeholders' point of view, the only 
sure thing in the presentation was that natural attenuation 
would save the polluter - in this case the Air Force - a great 
deal of money. They had no way to independently test the Air 
Force's projection. And in fact, many were aware that even in 
the best of situations the Air Force comparison was fraught with 
technical uncertainty. As one speaker pointed out, "It's dark 
down there." That is, it's difficult to measure what's going on 
throughout the subsurface environment. Finally, they had no way 
to know whether there might be a third approach, with a better 
graph, waiting in the wings. 

If, as many of the Forum participants indicated, people are 
already mistrustful of responsible parties - and often 
regulators - around issues they better understand, such as land 
use and health, they are unlikely to believe the promises of 
even the most knowledgeable, articulate experts. Natural 
attenuation is suspect, therefore, wherever the rest of the 
restoration program is suspect. It takes more than pretty 
pictures or sound science to win support where there is little 

On the other hand, at those facilities where the public believes 
that officials are both honest and willing to shape their 
decisions to meet public concerns, the public appears willing to 
evaluate the lines of evidence for natural attenuation, or any 
other remedy, on their merits. 

Not surprisingly, public representatives at the forum 
underscored the importance of public participation in the 
screening and selection of remedial alternatives. The people who 
design and approve a natural attenuation strategy for a 
groundwater plume will be long gone by the date at which 
remedial objectives are expected to be reached, but most of the 
residents or their descendants will still have to live with the 
results. Public stakeholders also bring to the table local 
expertise and frequently an institutional memory that the 
scientific or regulatory experts lack. However, seeking public 
approval may present a "Catch 22" for the proponents of 
monitored natural attenuation. To win endorsement, they must 
increase the possibility of rejection. 

To support such public participation, attendees called for a 
printed primer and more events like the Forum, to discuss the 
science and implications of natural attenuation. Though many of 
the participants said that they valued the technical 
presentations, some expressed frustration that speakers at the 
Forum were too technical, hard to follow, and difficult to 

Relationship to Other Remedies 

Monitored natural attenuation seemed to be most acceptable to 
public stakeholders when regarded as just another tool in the 
remediation toolbox. As suggested in EPA's policy, natural 
attenuation may complement other remedies. 

One participant, for example, argued that "enhanced" natural 
attenuation was more acceptable than the other kind, although he 
didn't provide a sharp line distinguishing the two. While some 
other participants, in their written comments, complained that 
too many people were focusing on the semantics of the term 
"monitored natural attenuation," it's clear that "natural 
attenuation" still carries with it the baggage with which it was 
first widely publicized, as a "do-nothing" remedy. 

Another stakeholder proposed that monitored natural attenuation 
be approved as a remedy only in conjunction with other remedies, 
though she allowed that there might be exceptions. While some 
argued that other remedies were usually required for technical 
reasons, others echoed the perceptual importance of visibly 
"doing something" at a site. In other words, the presence of a 
visible physical or engineered remedy at a site demonstrates 
that action is actually being taken. 

In particular, numerous people supported source removal as 
essential for natural attenuation to work. However, at the Forum 
this was not up for debate. All of the proponents of natural 
attenuation made the case for source removal. No one - as others 
have elsewhere - suggested letting natural processes deal with 
free product contaminants. 

A number of speakers challenged the Defense Department's 
perceived policy of always considering monitored natural 
attenuation as a possible remedy for groundwater contamination. 
While an Air Force spokesman said that current guidance simply 
required that site characterization efforts collect the data 
necessary to evaluate the extent of natural attenuation, the 
critics felt that natural attenuation was almost a presumptive 
remedy, that budgets would be built and characterization would 
be biased on the assumption that natural attenuation was a 
front-running option. They argued that natural attenuation 
should be on a equal footing with other approaches. 

Some participants expressed concern that reliance upon natural 
attenuation would undermine the development and use of 
innovative alternatives. In a site-specific evaluation of 
alternatives, monitored natural attenuation might look like it 
better satisfies remediation criteria - such as the nine 
criteria of the National Contingency Plan - than pump-and-treat, 
but there may be other, less well known options. A Cape Cod 
participant explained that residents in one neighborhood didn't 
want intrusive extraction systems in their yards, so they tended 
to support monitored natural attenuation as the local remedy. 
They were unaware of other options, such as horizontal wells, 
that might meet their needs while accelerating the removal of 

Some speakers raised the fear that natural attenuation might be 
approved at some sites now, because better alternatives are not 
yet proven. Then, when new technologies emerge that better 
satisfy remediation criteria, it's unlikely that the remedy will 
be reopened, even at five-year review. They asked: If monitored 
natural attenuation is approved as the best of a collection of 
uninspiring alternatives at a large number of sites, what 
incentive is there for anyone to invent better approaches? If 
new alternatives are developed, will there be any incentive to 
employ a new remedy at a monitored natural attenuation site? 

At least, EPA's policy discusses the need for contingency 
remedies should monitoring demonstrate that natural attenuation 
is not working as expected. Participants liked that idea, but 
they showed concern that monitoring might not be good enough or 
soon enough to flag problems before they get out of hand. 
Because natural attenuation is frequently much less costly than 
other approaches, they expressed concern that budgets built on 
the assumption that natural attenuation will do the job may 
actually lock it in as a remedy, even when it doesn't work. One 
participant suggested a performance bond that would guarantee 
that money is available should it be necessary to call upon 
contingency remedies. 

Destructive vs. Non-Destructive Remedies 

Public stakeholders expressed strong preference for degradation 
as opposed to other forms of natural attenuation, such as 
dilution, dispersion, and volatilization. Many believed the non-
destructive forms of attenuation should not be acceptable, and 
one tried to pin that down by asking what share of attenuation 
should be attributable to degradation for it to be considered 
the principal process. Another asked that the record of decision 
for each site specify the dominant attenuation process 
anticipated there. 

Similarly, some participants were uncomfortable with the goal of 
"plume stabilization," considering it just another form of 
containment. They felt that treatment or removal, as currently 
required by regulations, was more desirable. 

As a result of these preferences, some participants appeared 
more willing to accept monitored natural attenuation at 
petroleum sites, where degradation of the principal contaminants 
is more widespread and better documented, than at sites with 
volatile organic compounds. Few responded to the Department of 
Energy's description of the natural attenuation of inorganic 
substances - it was too new and too different. Those who did 
respond thought that metals should be dealt with in a separate 
policy, since degradation does not occur (except with 

No matter what the principal contaminant, participants were 
concerned that remedies address all contaminants - such as MTBE 
(methyl tertiary butyl ether) in gasoline or whatever sits in a 
landfill - and that the persistent formation of toxic breakdown 
products, such as vinyl chloride, was an unacceptable result. 

Land Use 

Finally, a number of participants - particularly from 
communities with closed and closing military bases - expressed 
concern that natural attenuation, as a slow, uncertain remedy, 
could delay the transfer and/or reuse of contaminated 
properties. While long-term pump-and-treat as a groundwater 
remedy may be essentially as cumbersome as natural attenuation, 
"dig-and-haul" is a much faster way to deal with soils. And 
sometimes pump-and-treat can reduce or limit the size of a 
plume, making it easier to reuse or transfer property which does 
not lie over the contamination, even if the achievement of 
cleanup objectives remains a long way off. Some noted that any 
step in the remedial process that delays unrestricted use of 
property represents a real or potential economic loss to the 
community or property owner receiving the property. 

Several participants felt the land and water use control as a 
component of remedial action is a significant area with many 
unresolved issues. They noted that the Defense Department, as 
evidenced by discussions at the most recent meeting of the 
Defense Environmental Response Task Force, is just beginning to 
grapple with complex issues surrounding institutional controls. 
Since monitored natural attenuation often depends upon the 
implementation of land and water use restrictions, participants 
from various constituencies urged the organization of a similar 
forum to discuss institutional controls. 


On the whole, forum participants recognized that the adoption of 
monitored natural attenuation often requires more scientific 
review than conventional, engineered remedies. They expressed 
concern, however, that the open discussion of natural 
attenuation does not begin early enough in the remediation 
decision-making process. Many also felt that natural 
attenuation, as it is currently being defined, does not 
accurately depict the remedial strategy. For the most part, 
public stakeholders are willing to accept uncertainty when 
reviewing proposed remedies, but they are much less open to 
unconventional or complex remedies when they mistrust decision-

That is, the uncertainty and technical complexity surrounding 
monitored natural attenuation magnify the mistrust found at many 
major contamination sites. To compensate for that uncertainty, 
the public wants contingency plans in place should monitored 
natural attenuation not perform as advertised. Community members 
want a clear mechanism for revisiting remedies if better 
alternatives are developed. 

Researchers at the forum may have been disappointed that public 
participants chose not to focus on the scientific questions to 
which they devote their professional lives. They brought 
questions of their own to the table, instead. Until communities, 
responsible parties, and regulators better address the causes 
and consequences of mistrust, then proposals to rely upon 
monitored natural attenuation to address complex or significant 
contamination sites will be greeted, more often than not, with 

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