quenched in the water and allowed to settle
remedial technology applied at a hot pond
into pond or marsh bottom sediments.
should be used as a preliminary indication that a
Waterfowl are exposed to WP from the sediments
hot pond has been eliminated. The future moni-
of ponds and sedge marshes while they are feeding.
toring activities should become primary mecha-
Some WP particles match the size of food (such
nisms for evaluating the main remedial goal of
as seeds and macroinvertebrates) sought by
reducing waterfowl mortality over the entire ERF.
dabbling ducks and swans. As the waterfowl
forage for food in pond and marsh bottom
OB/OD Pad
sediments, it is possible that they cannot dif-
OB/OD Pad is about 4 ha in size and consists of
ferentiate between WP and their normal food
a gravel pad as fill on the edge of ERF. Open burn-
source.
ing and detonation of explosive materials histori-
Dabbling ducks and swans are the primary recep-
cally have occurred on this pad. Materials have
tors of WP. Dabbling ducks and swans both
included fuses, high-explosive projectiles, smoke
forage for food in pond and marsh bottom
pots, mortar rounds, star cluster, flares, mines,
sediments. In addition, mortality rates of
rocket motors, shaped charges, detonation cord,
dabbling ducks have been observed to be sig-
dynamite, and some flammable solids. Existing
nificantly higher than mortality rates of other
records indicate that no liquids were disposed of
waterfowl in ERF as well as other Upper
there. Disposal was either on the surface or in an
Cook Inlet marshes. Telemetry data in 1996
excavated pit.
suggest that the mortality rate among mal-
A site investigation of the soil and ground-
lards was about 35%.
water at OB/OD pad was completed in 1996. Sur-
Predation and human exposure to WP by con-
face and subsurface soils were sampled. Nine
sumption are not high-level concerns at present.
monitoring wells were installed and developed,
There has been no verified mortality resulting
and groundwater samples were taken. Soil and
from predators feeding on WP-contaminated
ground water samples were analyzed for an
waterfowl carcasses. Although a dead eagle
extensive list of volatile and semivolatile organic
chemicals and metals. Very few chemicals were
rent predator mortality appears low. In addi-
detected in either the soil or the groundwater. All
tion, the results of analyses of tissue collected
detected chemicals had concentrations consider-
from dabbling ducks taken by hunters near
ably below their action levels for clean closure. In
ERF do not indicate a threat to humans ingest-
addition, the ecological and human health risk
assessments indicate that the risks are very low.
ing the meat.
The following are major findings for OB/OD
Permanent ponds and associated sedge with con-
firmed presence of WP or moderate to high crater
Pad:
density and observed moderate to high dabbling
The groundwater is at a depth of 6 to 11 m below
duck and swan use are the most significant expo-
the surface, and the gradient is shallow, with
sure areas (such as ponds are referred to as hot
groundwater moving toward the southwest, tow-
ponds). According to the conceptual site
ard ERF. Groundwater movement patterns
model, areas of greatest concern are where
are likely influenced by the tides and the
there is a source (WP-contaminated sedi-
river.
ment), a receptor (dabbling duck or swan),
The site investigation detected only a limited
and a potential for exposure (foraging for
number of organic chemicals and metals in the
food). Twenty-two hot ponds, which include
soil and groundwater. In many cases, observed
a total area of 23 ha, have been identified in
soil concentrations were similar to reference
these areas: A, C, C/D, Bread Truck, and
area values.
Racine Island.
The OB/OD Pad will meet clean closure require-
The movement of WP through Eagle River to Knik
ments. The detected chemicals were all con-
Arm appears to be minimal. WP has been de-
siderably below their clean closure action
tected in the sediments traveling through the
levels.
gullies, but there is no evidence to suggest
The ecological and human health risk assess-
that WP would be detected in Knik Arm.
ments found very low risks associated with expo-
An integrated process of evaluating remedial
sures to these chemicals at the measured concen-
success for ERF should be implemented once
trations.
remedial action is initiated. Data specific to the
At OB/OD Pad, the USARAlaska should pro-
16
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