Table 18. Risk-based concentrations in soil (g/g) and maxi-
mum concentrations detected on the Washington Impact
Area.
Risk-based concentrations*
Max conc.
Analyte
Industrial
Residential
detected
Event
TNT
190
21
130
Low-order detonation
RDX
52
5.8
340
Low-order detonation
HMX
10,000
3,900
40
Low-order detonation
NG
410
46
17
Firing point
2,4-DNT
4,100
160
9.5
Unknown
*http://www.epa.gov/reg3hwmd/risk/riskmenu.htm
for 2,4-DNT and 2,6-DNT, respectively, if the dilution
physical evidence of numerous high-order detonations.
attenuation factor is one, and 0.57 g/g and 0.25 g/g
At each impact area that we visit in the future, we will
if the dilution attenuation factor is 20. The highest
continue this kind of biased sampling to further enhance
concentrations we found for these two analytes were
our understanding of the relative importance of each
9.50 and 0.42 g/g in a sample not associated with a
potential source of contamination. Source areas must
known firing event.
be identified prior to assessing the potential for
migration to water. However, biased or authoritative
Recommendations for future sampling plans
sampling does not provide adequate baseline data to
The sampling approach we used for this preliminary
evaluate the extent of contamination, which usually
survey was biased because we are researching the
requires a probabilistic sampling design to estimate
sources of explosives residues in soils of impact areas.
mean concentrations
To accomplish this research we focused on low-order
When designing a sampling plan to estimate mean
detonations and locations with written history or
concentrations of explosives in soil, the following
Table 19. Naturally occurring cleanup levels and maximum concentrations detected on the Wash-
ington Impact Area.
Concentration (g/g)
Naturally
Alaska DEC
Naturally
occurring
cleanup levels
EPA risk based
occurring
in Alaska†
concentrations
Max. conc.
in U.S.*
Migration to
detected
Element
Soil
Soil
Sediment
Ingestion
Industrial
Residential
(Event)
Antimony (Sb)
0.66
41
3.6
820
31
30 (TOW)
Barium (Ba)
580
595
811
7,100
1,100
140,000
5,500
790 (Crater)
Cadmium (Cd)
0.35
1.3
2.6
100
5
1,000
39
18 (TOW)
Chromium (Cr)
54
50 (t)
115(t)
510(+6)
26 (+6)
6,100 (+6)
230 (+6)
45 (Mortar)
Copper (Cu)
25
24
37
82,000
3,100
1,100 (Mortar)
Iron (Fe)
26,000
35,000
37,000
610,000
23,000 39,000 (Mortar)
Lead (Pb)
19
12
12
400 to 1,000
140 (TOW)
Nickel (Ni)
19
24
37
2,000
87
41,000
1,600
45 (TOW)
Zinc (Zn)
60
70
157
30,000
9,100
610,000
23,000
300 (TOW)
*Lower 48 states (Sposito 1989)
(t) total
(+6) oxidation state +6
†Gould et al. (1984, 1988)
32
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