More than a "Do-Nothing" Remedy

[Lenny Siegel <lsiegel@cpeo.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@cpeo.org