More than a "Do-Nothing" Remedy

[Lenny Siegel <lsiegel@igc.apc.org>]

NATURAL ATTENUATION: MORE THAN A DO-NOTHING REMEDY

Hazardous substances undergo some degree of natural attenuation under
virtually all conditions. Therefore, the question for responsible
parties, regulators, and communities is not whether natural attenuation
should take place, but whether, where, and when natural processes are
sufficient to protect public health and the environment.

Natural attenuation is being proposed as a remedy at an increasingly
large number of sites across the U.S. Particularly at leaking fuel tank
sites, it is becoming the remedy of choice. The rush toward natural
attenuation, led by polluters who are out primarily to save money, has
blindsided the environmental movement. There are few "enviro" experts on
the subject. Activists have had little opportunity to react. And
policies are being established without much input from public
stakeholders. Yet there are many instances where natural attenuation
makes sense as a remedial response.

For these reasons, CAREER/PRO is beginning a project designed to inform
public stakeholders about natural attenuation as a cleanup remedy and to
bring their views into the debate over its desirability. We will be
producing fact sheets on the subject, and we are organizing, later this
year, a "National Stakeholders Forum on Natural Attenuation."

Meanwhile, U.S. EPA's "Monitored Natural Attenuation" directive, which I
reviewed in a separate report, is a major step in the right direction.
It makes clear, in two ways, that natural attenuation, to be accepted as
a remedy, must be much more than a do-nothing remedy. First, it
establishes procedures for predicting and ensuring that natural
attenuation is taking place at a sufficient level. Second, it says that
natural attenuation is more likely to be acceptable if used in
conjunction with more active remedial actions.

The directive briefly suggests that a reduction in concentration induced
by plume migration, in itself, is not likely to be acceptable. That's
good. I think most public stakeholders subscribe to the aphorism,
"Dilution is not the solution to pollution!" 

I would have reinforced that position by renaming and refocusing the
guidance on the actual breakdown of hazardous substances. Since EPA's
definition of "natural attenuation" includes various forms of dilution,
including dispersion and volatilization, I would have called the policy
"Monitored Degradation." Where chemical or biological degradation is
documented, that's actually permanent treatment, preferable to "dig and
haul" or "pump and treat," which simply move contamination to other
places. (The contamination removed through carbon filters is usually
incinerated!)

I'm reserving judgment on the attenuation of inorganics, such as metals
and tritium, the radioactive form of water. This is a rather new
approach, and I think we need to learn more about it before embracing it
or ruling it out.

Note that I don't suggest "Monitored Natural Degradation." That's
because, as EPA suggests, natural degradation will often be complemented
- by location or over time - by active measures. The monitoring required
to support active measures and the criteria for acceptance are
fundamentally the same for active and natural degradation. So I would
have preferred that they be addressed in the same directive.

Beyond the directive, there may be a need to establish consensus, or at
least precedent, for general principles on the acceptability of natural
degradation as a remedy. I am assuming, of course, that the degradation
is documented through monitoring, and that conditions exist for
degradation to continue until remedial objectives are reached.

Here are some possibilities, some of which are already included in or
implied in the EPA directive:

* Degradation, not dilution, should be documented. 

* Investigation and remediation should address all possible
contaminants. For example, natural degradation of petroleum is
insufficient if MTBE is present in hazardous quantities.

* Sources, such as free product, should be removed. (There are some
experts who believe that the removal of free petroleum product is
unnecessary to limit risk at some sites, but I remain skeptical.)

* Degradation must apply to breakdown products that are as toxic,
persistent, or mobile (or moreso) than the original contaminants.

* Hazards from flammable breakdown products, such as methane, must be
evaluated and controlled.

* Natural attenuation is acceptable where contaminants are breaking down
faster than they are spreading AND they are unlikely to reach (at
hazardous levels) human or ecological receptors. I don't think the fact
that contaminants are unlikely to migrate across property lines - such
as from a large Air Force Base - should play a role in such decisions.

* Where than last condition is NOT met, then monitored natural
attenuation should be compared to other remedies, such as
pump-and-treat. 

This is not a simple comparison. Today there is widespread recognition
that groundwater extraction may contain or reduce contamination, but it
is unlikely to bring groundwater contamination down to regulatory
standards within a reasonable time frame. At some sites, following
source removal, natural attenuation may clean up groundwater nearly as
fast as more expensive active measures.

However, the same conditions that limit the effectiveness of extraction,
such as the elusiveness of dense non-aqueous phase liquids - portions of
TCE plumes, for example - may hinder natural degradation. Natural
attenuation, therefore, should be subject to the same stringent
questioning as pump-and-treat.

Furthermore, it is shortsighted to accept natural degradation simply
because it's expected to achieve similar objectives as active
remediation, as we know it today. The demand for faster, more complete,
more cost-effective cleanup is the principal driver of the development
of innovative remedial technologies. Take that demand away, and those
technological opportunities will be lost. Until the discovery of the
MTBE problem, the development of technologies for responding to
petroleum releases had virtually ground to a halt.

One benefit of EPA's monitoring strategy, therefore, is that responsible
parties seeking to employ natural attenuation as a remediation strategy
still have to jump through the regulatory hoops. They still must invest
in sampling, modeling, and other studies, over a long period of time.
That creates at least a small incentive for the use of new technologies.

(Of course, there are other sites or portions of sites that will require
active measures in any case, so the demand for new cleanup technologies
is not wholly dependent on natural attenuation policy.)

Finally, the potential transfer or change of use of a property should be
considered in evaluating the sufficiency of natural attenuation. For
legal reasons, including liability, there are advantages to carrying out
complete cleanups quickly, rather that waiting for natural processes to
take their course. Where new uses are possible, letting contamination
degrade slowly may limit the use - and thus the value - of the property.
On the other hand, where those issues are resolved, the sampling system
required for monitored degradation may be less intrusive than a
full-blown extraction system, allowing more flexible use.

Once responsible parties and communities recognize that monitored
degradation is another tool in the remediation toolbox, not just a
do-nothing remedy, then all parties have to work together to understand
when it's appropriate to use. Polluters might not save all the money
that they hoped, but hopefully we'll end up with a better strategy for
protecting public health and the environment.

-- 

Lenny Siegel
Director, SFSU CAREER/PRO (and Pacific Studies Center)
c/o PSC, 222B View St., Mountain View, CA 94041
Voice: 650/961-8918 or 650/969-1545
Fax: 650/968-1126
lsiegel@igc.apc.org