Re: Feedback requested on DNAPLs

[Marsden and June Chen <doobage@localnet.com>]

Some comments on the treatment technologies.
1. Alcohol or cosolvent flushing; and 2. Surfactant flushing. - I'll asume
that we are only dealing with contaminated soil in the vadose zone, since
treatment of chlorinated organics under the water table will present other
complex problems.
If these are ex situ treatment, i.e., the contaminated soil is treated and
the extracted contamination and spent alcohol, cosolvent and surfactant are
collected and disposed of in a safe manner, we would all think that we have
died and have entered environmental heaven.
But one will discover that many of the cases will propose in situ flushing,
and such flushing could generate secondary and possibly greater
environmental problems.
Some thoughts on in situ flushing: a) if the stratigraphy does not contain a
solid, thick clay layer underlaying the contaminated soil, any flushing will
transport the chlorinated organics rocket-like to the ground water table,
with resultant significant contamination of the aquifer; b) if there is a
clay layer with sufficient integrity, great pains must be taken to construct
MULTIPLE (possibly redundant)extraction wells in both the vertical and
horizontal planes on the periphery of the contaminated soil to ensure that
all introduced flushing agents and chlorinated organics in solution will be
brought to the surface. One outcome could be the rapid transport of the
contaminants to the top of clay and depending on the conditions there, it
might be difficult to collect the "runoff". But any one who has been in the
Superfund game long enough may agree with the statement that the PRP's -
both private sector, federal government and others will debate to the bitter
end (that one instead of twenty (say) extraction wells will be sufficient
for adequate exraction). And with the weasly and weak kneed conditions of
many, many federal and State regulatory agencies, it doesn't require much
brain power to conclude that it will be ONE WELL more often than not; c)
what physical or chemical effects will alcohol, cosolvent or surfactant have
on the chlorinated solvents?
3. In situ oxidation. I'm not sure what this means - there is another term,
bioventing, which pumps ambient air into the contaminated soil with the
"guaranteed" results that the resultant oxidation will remedy all
chlorinated solvents contamination - I've yet to see results that confirm
such guarantees.
4. Soil Vapor Extraction. Requires a closed system - but my verdict is still
out on this technology, since the end point of one such remedial activity is
some distance away, therefore proof of its adequacy has not yet been
attained - the intial results were encouraging, as high concentrations of
contaminants were measured in the off-gases.
6. In-well stripping. It is purported that this technology has been backed
up by equations and that the mathematics bear out that in-well stripping
will be efficient in removing chlorinated solvents from an aquifer. But
imagine the following - the well's extraction screen is its lowermost part,
the contaminated water is pumped up through the riser, circulated, stripped
of the contaminants in an above ground system then routed back into the
riser (down) from where it is released via a screen into the vadose zone at
or some level above the water table. Very shortly after pumping of the
contaminated water begins and the rapid reintroduction of the "clean" water
to the vadose zone, saturation of the environs of the well will occur and
further pumping and reintroduction will result in a loop - i.e., a great
volume of water, if not all, that will be pumped and reintroduced after
saturation will begin to re-enter the extraction screen. I am sure that
contaminated water from the aquifer will also be pumped - but not to the
degree that it should be, to ensure that the in-well sparging will be an
effective remedy. The pundits have maintaned that the mathematics supports
in-well sparging, which has yet to be submitted, but data from strategically
located pressure gauges in test runs seem to support my lay man's lauguage.
Then there is the requirement for multiple monitoring wells (again redundant
ones if necessary) down gradient of the in-well sparger to ensure that all
water leaving the plane of the sparger (or vicinity) have in fact been
stripped of contamination. (See 1 & 2 above regarding monitoring wells).
7. Steam injection - same problems as 1 & 2 above.
Getting late - Will respond to the other items in you e-mail some other
time.


Susan Gawarecki wrote:

> To members of the CPEO-military list:
>
> I am working with the Interstate Technology Regulatory Cooperation
> (ITRC) work group to incorporate stakeholder perspectives into a
> document of technical and regulatory guidelines for remediating sites
> contaminated with Dense Non-Aqueous Phase Liquids (DNAPLs).  The purpose
> is to help responsible parties, regulators and contractors make better
> remediation decisions and be more effective in dealing with the public's
> concerns.
>
> Common DNAPLs include chlorinated solvents, PCBs, and coal tar/creosote
> components.  We are primarily concerned with the chlorinated solvents,
> such as Tetrachloroethylene (PCE), Trichloroethylene (TCE), 1-2
> Dichloroethylene (DCE), Vinyl Chloride (VC), and Trichloroethane (TCA).
>
> A variety of treatment technologies will be examined.  These include:
> 1. Alcohol or cosolvent flushing
> 2. Surfactant flushing
> 3. In situ oxidation
> 4. Soil vapor extraction and deritives
> 5. Air sparging
> 6. In-well stripping
> 7. Steam injection
> 8. Electrical heating
> 9. In situ vitrification
> 10. Electrokinetics
> 11. Bioremediation
> 12. Physical containment/isolation
> 13. Reactive barrier walls
> 14. Pump and treat
>
> We are also looking at site characterization technologies such as ground
> penetrating radar, cone penetrometer, soil coring, tracer tests, bore
> hole technologies / down hole logging, dye technologies, and combined
> technologies.
>
> I am interested in stakeholder perspectives on both the issue of DNAPL
> contamination and the different technologies that might be used for site
> characterization and remediation.
>
> Please forward your comments on any of the above to me at loc@icx.net.
> Your experiences and opinions, both good and bad, with specific sites,
> contaminants, and remediation techniques are welcome.  If you would
> prefer to talk to me directly, send me your phone number and best time
> to call (with time zone).
>
> Regards,
> Susan Gawarecki
> --
> ==================================================
> Susan L. Gawarecki, Ph.D., Executive Director
> Oak Ridge Reservation Local Oversight Committee, Inc.
> 136 South Illinois Avenue, Suite 208
> Oak Ridge, Tennessee  37830
> Phone (423) 483-1333; Fax (423) 482-6572; E-mail loc@icx.net
> VISIT OUR UPDATED WEB SITE:  http://www.local-oversight.org
> ==================================================