tions, Part 264, and no significant environmental
WP is the primary cause of waterfowl mor-
or human health risks were determined, remedia-
WP was deposited in the sediment primarily
tion of OB/OD Pad is not included in the FS.
during range firing activities.
Craters in ERF potentially indicate the level
of range firing activity.
The OUC FS is intended to provide the U.S.
WP particles are not homogeneous through-
Army Alaska, U.S. Environmental Protection
Agency, and Alaska Department of Environmen-
The detection frequencies and concentra-
tal Conservation (the Agencies) and the public
tions for WP in sediment are highest in Area
with an assessment of the remedial alternatives,
C, Bread Truck, and Racine Island.
including their relative strengths and weakness-
WP particles can break down (sublime/oxi-
es. The overall goal is to provide sufficient infor-
dize) when exposed to air, but are long last-
mation to the decision makers so that they can
ing in water-saturated sediment.
select a proposed alternative to be applied to
Waterfowl are exposed to WP from the sedi-
OUC. The decisions will be used to develop a
ment of ponds and sedge marshes while
proposed plan and a Record of Decision (ROD) to
they are feeding.
achieve remediation at OUC. There were five
Dabbling ducks and swans are the primary
steps used to prepare this FS:
receptors of WP.
Develop remedial action objectives (RAOs). The
Predation and human exposure to WP by
overall remedial objective is the protection
consumption are not high-level concerns at
of the environment and human health.
Develop pond groups. Twenty-two ponds at
Permanent ponds, with associated sedge
ERF were identified for remediation. They
marsh, having confirmed presence of WP or
were divided into six pond groups on the
moderate to high crater density and observed
basis of physical site characteristics and ex-
moderate to high dabbling duck and swan
pectation of similar response to remediation.
use are the most significant exposure areas
This pond grouping forms the geographical
(called hot ponds).
basis of making decisions.
The movement of WP through Eagle River to
Develop remedial alternatives. Five remedial
Knik Arm appears to be minimal.
alternatives were developed.
Evaluate each remedial alternative against nine
Open Burning/Open Detonation Pad
criteria as required by the National Contingency
Open Burning/Open Detonation Pad is about
Compare alternatives for each pond groups. This
3.2 ha (about 8 acres) in size and consists of a
gravel pad placed as fill at the edge of ERF. Open
tive would perform under the NCP criteria
burning and open detonations of explosive mate-
at each pond group. Because of differing
rials historically have occurred on this pad.
physical characteristics, each pond group is
The following are major findings of the RI for
expected to perform differently under each
The groundwater is at a depth of 6 to 11 m
alternative. Thus, a different alternative may
below the surface, the gradient is shallow,
be ultimately selected for each pond group.
west, toward ERF.
Remedial action objectives
The site investigation detected only a limited
As introduced in the OUC RI report, the overall
number of organic chemicals and metals in
remedial objectives at ERF are the protection of
the environment and human health. There are
OB/OD Pad will meet clean closure require-
three specific RAOs:
Reduce dabbling duck mortality. This RAO
The ecological and human health risk assess-
addresses the single most important issue
ments found very low risks associated with
exposures to these chemicals at the meas-
dabbling ducks have been the most affected,
their mortality will be assessed specifically
Because OB/OD Pad meets clean closure guid-
in support of the achievement of this goal.
ance from Title 40 of the Code of Federal Regula-
Mallards have been chosen as the indicator