Table 12. Firing record for 19972000 at Fort Lewis.1
Historical firing records
DODIC2
20003
Round
1997
1998
1999
Total
Firing records for the six most heavily used
rounds indicated that the 105-mm artillery round
81-mm
C256
1,997
2,112
2,789
2,075
8,973
was the item most heavily fired, followed by the
105-mm
C445
10,585
3,166
9,505
7,458 30,714
--4
120-mm
C623
474
--
359
833
81-mm mortar and the 155-mm artillery round
120-mm
C788
--
75
288
--
363
(Table 12). Estimates of range loading of explo-
107-mm
C697
219
128
262
216
825
sives residues from each type of round can be
155-mm
D544
207
7,564
261
841
8,873
made by making several assumptions and using
1 Records encompass the available electronic database from Janu-
known low-order detonation rates (Table 13). For
ary 1997 through July 2000 and include the most commonly fired
example, firing records indicate that 7458 105-
items as indicated by Del Larson, Range Operations Officer.
mm howitzer rounds were fired into the Fort Lewis
2 Department of Defense Identification Code.
impact area in 2000 (Table 12). On average, about
3 Data through July 2000 only.
4 No record of firing for this item in this year.
0.07 percent of those fired undergo a low-order
detonation (Table 13). Thus, for 2000, we esti-
mate that five of these 105-mm rounds would have
Table 13. Mean dud and low-order detonation rates for
munitions items commonly used at Fort Lewis.1
undergone a low-order detonation. If we assume
that all the 105-mm rounds contained Composi-
Items
Duds
Low orders
tion B as the main charge, then each round would
2
Round
DODIC
tested
(%)
(%)
contain about 1252 g of RDX. If half of the main
charge remained undetonated for each low-order
81-mm
C256
9,122
2.16
0.22
105-mm
C445
10,003
4.39
0.07
detonation, then 3130 g of RDX would be depos-
3
120-mm
C623, C788
--
--
--
ited on the Fort Lewis range from low-order deton-
2
107-mm (4.2-in.)
C697
1,518
2.24
0.02
ations of 105-mm howitzer rounds in 2000.
155-mm
D544
6,216
2.75
0.02
We can estimate the amount of residue depos-
1 Rates based on test data acquired by U.S. Army Defense Ammu-
ited from high-order detonations as well. For the
nition Center, McAlester, Oklahoma (Dauphin and Doyle 2000).
total number of 105-mm rounds fired in 2000, we
2 Department of Defense Identification Code.
estimate that 327 were duds and five rounds were
3 No data.
low-order detonations (Table 13). Thus, about
7126 rounds underwent high-order detonations.
At this point, there is no experimentally derived esti-
mates, efforts should be made to locate and remove the
mate of the amount of explosives residue that is pro-
debris from low-order detonations as soon as possible.
duced from the detonation of a 105-mm round; however,
This action alone may substantially reduce the amounts
there are estimates for 60-mm mortars that also con-
of explosives residues contaminating surface soils at
tain Composition B. Each 60-mm round has 258 g of
impact ranges.
RDX or about 20.6% of the RDX present in the 105-
mm round. Experiments conducted by firing 60-mm
SUMMARY AND CONCLUSIONS
rounds onto a snow-covered range indicate that about
0.00007% of the RDX originally present in the round
Three training areas were sampled at Fort Lewis,
remains undetonated and is deposited on the range (Jen-
Washington: an impact area within the hand grenade
kins et al. 2000). If we assume that this same percent-
range, a 105-mm howitzer firing point, and a portion
age would apply to high-order detonations of 105-mm
of the impact area within the heavy artillery and mortar
rounds, then each detonation would deposit about 0.88
range. A set of eleven water samples also was analyzed
mg of RDX. Multiplying this by the 7126 high-order
from monitoring wells and seeps that are adjacent to
detonations results in an estimate of about 6.2 g of RDX
the artillery impact area. Soil samples were also col-
deposited in 2000.
lected at a hand grenade range at Fort Richardson,
It is important to remember that these are prelimi-
Alaska.
nary estimates and source terms for rounds other than
With respect to the two hand grenade ranges, RDX
60-mm mortars are being developed from additional
was detected in all of the 96 soil samples collected,
detonation experiments. However, it appears that even
both surface and shallow subsurface. The median and
a small number of low-order detonations contribute a
maximum concentrations of RDX in surface soils at
these sites were 1560 g/kg and 51,200 g/kg at Fort
very large percentage of the total explosives residues
Lewis, and 28.9 g/kg and 518 g/kg at Fort Richard-
deposited. If the 0.00007% figure is correct, then one
low-order detonation in which half of the explosive is
son. TNT and HMX concentrations were also detect-
not destroyed contributes as much residue as about
able in most soils from these two grenade ranges
700,000 high-order detonations. Based on these esti-
Overall, concentrations of explosives-related con-
25
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