stable in saturated conditions, this results in the
vation, and the Ft. Richardson Directorate of Public
deposition and long-term storage of particles in
Works, Environmental Resources Branch, were
permanently wetted areas. Unfortunately, these
called on to assist in the investigation. Over the
are the same areas frequented by dabbling water-
course of the summer of 1990, explosives compo-
fowl.
nents such as RDX, TNT, and 2,4 DNT were elimi-
Waterfowl mortality at Eagle River Flats was
nated from consideration either because of their
first recognized in 1980 (Tweten 1989). Studies
absence in the sediment and water of Eagle River
conducted from 1980 to 1989 quantified the magni-
Flats or because they were not acutely toxic in the
tude of the problem and narrowed the range of
quantities available. Observation of smoke eman-
possible agents, but the causal agent remained elu-
ating from sediment samples collected at ERF led
sive. However, important clues had emerged. The
investigators to focus on white phosphorus, a sub-
birds being affected were almost exclusively dab-
stance previously dismissed. Analysis of the sedi-
bling waterfowl, such as shovelers, pintails, teal,
ment samples and subsequent analysis of fatty tis-
mallards, and swans. Most of the deaths were
sues and gizzards of dead waterfowl from ERF
occurring in or near the permanently ponded areas
indicated that the causal agent for the waterfowl
where these birds feed. Although a definitive cause
mortality is white phosphorus (Racine et al.
of the deaths was not identified, explosives com-
1992a,b). The mechanism was hypothesized as
pounds were postulated as the most likely cause of
being the selection of WP particles through sieving
the waterfowl mortalities, and it was recommend-
of the sediments in permanently ponded areas by
ed that firing into ERF cease (ESE 1990). Despite
dabbling waterfowl. Deaths were greater during
the cessation of firing in February of 1990, the
the fall and spring migrations, when large num-
waterfowl deaths continued unabated over the
bers of birds were feeding during brief stopovers
course of several years.
at ERF. The pieces of the puzzle were coming to-
In 1990, scientists from the U.S. Army Cold
gether. The next step was to determine what areas
Regions Research and Engineering Laboratory
of ERF were contaminated and to better under-
(CRREL) were requested to participate in the
stand the nature of the contaminant.
investigation of the waterfowl mortality because
of their experience with Alaskan wetlands and
Extent of contamination of Eagle River Flats
explosives chemistry. Investigators from Dart-
From 1990 to 1993, analysis of surface sediment
mouth College, the U.S. Fish and Wildlife Service,
samples taken at approximately 25-m intervals
the Alaska Department of Environmental Conser-
along transects through sections of Eagle River
Flats identified several areas that are con-
taminated with white phosphorus (Ra-
cine et al. 1993a and 1993b). Three areas,
Knik Arm
Area C, the Bread Truck (BT) Pond, and
Area D
Racine Island (Fig. 1), had the highest
Pond 109 (BT)
Eagle River
rates of detections and samples with the
Pond 730
highest concentrations. In these areas
Pond 155
white phosphorus concentrations varied
Pond 183
widely (Table 1), with relatively few sam-
Pond 146
ples having concentrations large enough
OB/OD Pad
to present an acute lethal dose of white
(EOD Pad)
phosphorus to a duck. When samples
were taken at close intervals (1 to 5 m)
Pond 256
Area C
around sample points with high white
Pond 258
phosphorus concentration, we again ob-
Area A
served extreme heterogeneity, with non-
Pond 290
detectable concentrations within a few
meters of high concentration samples
Otter Creek
(over 100 g/g). This pattern of con-
Area B
Racine
0
1000 m
tamination led us to believe that most of
Island
the white phosphorus was located in
"hot spots," probably at the point of im-
Figure 1. Map of Eagle River Flats.
pact of a WP-containing projectile.
2
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