Site Characterization for Explosives
Contamination at a Military
Firing Range Impact Area
THOMAS F. JENKINS, MARIANNE E. WALSH, PHILIP G. THORNE,
PAUL H. MIYARES, THOMAS A. RANNEY, CLARENCE L. GRANT,
AND JOHN R. ESPARZA
would coincidentally target soils with the highest
INTRODUCTION
levels of HMX. Comparative environmental risk
factors were not evaluated, though.
Background
Our experience from an earlier investigation at
A study conducted in 1994 by the Army revealed
CFB-Valcartier (Canadian Force Base) shows that
that the impact areas at the inland firing ranges of
the concentrations of residues on impact ranges
Fort Ord were contaminated with residues of high
are highly correlated with individual tank targets
explosives. The contaminant present at the high-
(Fig. 3, Jenkins et al. 1997a). Like Fort Ord, the
est concentration was HMX (octahydro-1,3,5,7-
major residual contaminant at CFB-Valcartier was
tetranitro-1,3,5,7-tetrazocine), with much lower
HMX because 66-mm M72 LAWs (Lightweight
concentrations of RDX (hexahydro-1,3,5-trinitro-
Anti-Armor Weapons, Fig. 4) were extensively
1,3,5-triazine), TNT (2,4,6-trinitrotoluene), and two
used. These rockets contain octol, a melt cast
known environmental transformation products of
explosive composed of a 70:30 mixture of HMX
TNT--4-amino-2,6-dinitrotoluene (4-AmDNT)
and TNT. Inspection of debris at ranges 44 and 48
and 2-amino-4,6-dinitrotoluene (2-AmDNT)--also
at Fort Ord, and discussions with explosives ord-
being found (Fig. 1). The ranges had been actively
nance disposal (EOD) personnel, told us that the
used at the time of this study. One soil had an HMX
LAW was used extensively. Unlike CFB-Valcartier,
concentration as high as 1100 mg/kg, but, even in
various other ordnance was fired as well, includ-
this sample, the concentration of RDX was only
ing many munitions that contained Composition
11 mg/kg. However, the number of soil samples
B, which is made of RDX and TNT.
analyzed in the 1994 study was quite limited rela-
One important criterion that must be specified,
tive to the size of the impact areas, and the study
before decisions can be made about the need to
was not designed to provide sufficient spatial reso-
remediate specific locations within the site, is the
lution to delineate the extent of cleanup required
depth interval in the soil that is subject to the 0.5-
from either a depth or a surface area perspective.
mg/kg cleanup criterion for RDX. Our experience
Ranges 44 and 48 in site 39 were identified as
at CFB-Valcartier, and at other areas contaminated
areas of concern (Fig. 2). Recent results obtained
by explosives, suggests that there is a marked con-
by IT Corporation, but with incomplete documen-
centration gradient for explosives contaminants as
tation, indicated that RDX was not detectable in
a function of depth, the highest concentrations
the soil samples that they collected in 1997, while
being in the top 2 in. (5 cm) of soil (Jenkins et al.
HMX remained the predominant high explosive
1996, 1997a). This is true because explosives are
present.
solids at ambient temperature and were deposited
From a human health perspective, HMX was not
on the site as small particles. Samples analyzed
thought to be a major problem and remediation
for the 1994 study were reported at two depths, 0
goals were developed based on RDX. For example,
and 2.5 ft (0 and 0.8 m). It is uncertain whether
comparative drinking water criteria for HMX,
these samples were vertical composites over the
RDX, and TNT are shown in Table 1 (EPA 1996).
0- to 2.5-ft and 2.5- to 5-ft (0.8- to 1.6-m) intervals,
In addition, the 1994 study thought that HMX and
or over smaller depth intervals, near 0 and 2.5 ft.
RDX would be co-resident and that targeting soils
Because of the concentration gradient often found
with concentrations of RDX above 0.5 mg/kg
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