[CPEO-MEF] Sampling ordnance residue on snow

[Lenny Siegel <lsiegel@cpeo.org>]

The U.S. Army's Cold Regions Research and Engineering Laboratory (CRREL)
has published a study that creatively investigates toxic residues from
explosive detonation. In March, 2000 it fired and detonated a small
number of mortar shells on two snow-covered ranges in the northeastern
United States. It collected snow samples with explosive residue and
analyzed for explosive compounds. Explosive ordnance disposal personnel
detonated three 81-mm mortar rounds at Camp Ethan Allen, Vermont, and an
Army team fired three 60-mm mortar rounds at a snow-covered target at
Fort Drum, New York - though only two of the latter landed in an
accessible area.

The official purpose of the initial study was to prove that snow-covered
ranges provide an opportune medium for collecting explosive residues. It
appears to have accomplished that well, so we can expect more studies
that use this basic approach. The data collected through such tests
should prove applicable for managing toxic releases on disposal and
impact ranges, in a variety of climates and terrains.

The new studies will incorporate lessons learned from these tests. For
example, future tests will be conducted in midwinter, "when the surface
soils are frozen and frost penetration is at its maximum," to keep soil
particles from contaminating samples, and on overcast days to minimize
phototransformation and snowmelt.

The study found low-concentration plumes of explosive residues on the
ground surrounding each detonation site, but the concentrations actually
varied significantly for seemingly identical pieces of ordnance. The
study explained the prevalence of RDX and HMX, compared to TNT, on
ranges where high explosives containing those compounds had detonated.
The CRREL researchers wrote:

"These results are similar to those observed on an anti-tank firing
range, where TNT residue concentrations were two orders of magnitude
lower than HMX, even though the explosive used (Octol) was 70:30
HMX:TNT.... At the time, the differences in residue concentrations were
attributed to differences in rates of dissolution and biotransformation.
Apparently, a higher percentage of the TNT is consumed in detonations of
Composition B, leaving higher concentrations of RDX and HMX in the
post-blast residue."

Furthermore, nitroglycerine, according to the tests, "is apparently less
completely consumed in the detonation than TNT and RDX...."

The sampling also showed that the highest concentrations of residue were
not found in the samples closest to the detonation point, but at an
intermediate distance. This may explain sampling conducted by others at
large-scale open detonation sites, such as the Sierra Army Depot, where
sampling has detected soil contamination below modeled levels. It may be
that sampling was conducted at the wrong distance from ground zero.

Finally, the researchers used the residue quantities from the small
sample zones to extrapolate ballpark estimates of the total mass of
explosive residues from each detonation. The totals turned out to be
very small, with the largest (by far) being .011% of the RDX in one of
the 81-mm mortar rounds. They cautioned that these numbers are highly
uncertain, but it appears to me that it's be possible in future tests to
collect residue from entire plumes. And even small percentage may prove
environmentally significant; the small quantities may add up at sites
with large numbers of detonation.

This imaginative new approach complements other methods of measuring
detonation releases, such as collecting gases and particles from
confined detonations. It allows the documentation of contaminant
distribution, and it may lead to the study of larger explosions. I
believe that this, in turn, should help determine the scalability of the
results of tests involving small explosive net weights. Already, the
CRREL researchers are obviously coming up with findings that should help
address both ongoing releases and cleanup at ranges and other
contamination sites.

Thomas F. Jenkins, Thomas A Ranney, Marianne E. Walsh, Paul H. Miyares,
Alan D. Hewitt, and Nicholas H. Collins, "Evaluating the Use of
Snow-Covered Ranges to Estimate the Explosive Residues that Result from
Detonation of Army Munitions, " Cold Regional Research and Engineering
Laboratory, U.S. Army Corps of Engineers, ERDC/CRREL TR-00-15, August,
2000.

The 20-page report is available as a 400K-plus PDF file at
http://www.crrel.usace.army.mil/techpub/CRREL_Reports/reports/TR00-15.pdf.

Lenny


-- 


Lenny Siegel
Director, Center for Public Environmental Oversight
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
http://www.cpeo.org


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