Winter Tests of Artillery Firing into
Eagle River Flats, Fort Richardson, Alaska
CHARLES M. COLLINS AND DARRYL J. CALKINS
over the years. The sediments are anoxic, allowing
INTRODUCTION
the particles of white phosphorus to persist for
The objective for the winter tests of artillery fir-
many years, posing a continual risk to waterfowl
ing into the Eagle River Flats (ERF) impact area
feeding in the ponds.
was to determine the physical effects of exploding
Firing into the impact area was suspended in
rounds on winter terrain. The winter ground con-
February 1990. However, there is a continuing need
ditions of interest include snow cover, ice cover, fro-
to conduct artillery training at Ft. Richardson, and
zen and unfrozen sediments and to some extent
Eagle River Flats is the only feasible impact range
water beneath the ice covers in the pond areas.
available. Renewed artillery firing would only use
Observations were based on the disturbance of the
high-explosive (HE) projectiles; the use of white
snow, ice and sediment layers caused by exploding
phosphorus would be discontinued. Continued fir-
105-, 81- and 60-mm high-explosive (HE) projec-
ing into ERF during the summer would cause re-
tiles with both point detonation and delay fuses.
distribution and mixing of the bottom sediments
To determine the effects of these projectiles, test
in the shallow ponds and make buried WP par-
firings using 105-mm howitzers and 60- and 81-
ticles accessible to feeding waterfowl. Winter fir-
mm mortars were conducted in a small portion of
ing into ERF has been proposed as a solution. The
ERF during March 1991.
purpose of this study was to determine if the snow
The purpose of these tests was to assess if sea-
cover, ice cover and frozen ground that exist over
sonal firing of HE projectiles into ERF could be
extensive areas of ERF during the winter would
resumed without significantly disturbing contami-
isolate the sediments containing white phospho-
nated sediments. Firing only during the winter,
rus particles and prevent them from being dis-
when the salt marsh is covered by a seasonal cover
turbed or brought nearer to the surface by the ex-
of snow, frozen ground and ice, might significantly
plosion of artillery projectiles.
reduce the disturbance of the sediments, compared
to the previous practice of year-round firing.
Environmental setting
Eagle River Flats, at the mouth of the Eagle
River, is an 860-ha estuarine salt marsh on the south
side of Knik Arm in upper Cook Inlet (Fig. 1). It is
BACKGROUND
approximately triangular in shape, 2.75 km wide
near the coast and 4 km long in an inland direc-
Historical perspective
In 1990 white phosphorus (WP) was identified
tion. It is bounded inland by a sharp topographic
as the cause of waterfowl mortality in Eagle River
and vegetation boundary of spruce- and birch-
Flats, a U.S. Army artillery impact range at Ft.
covered uplands. The salt marsh is composed of a
Richardson, Alaska (Racine et al. 1992, 1993). Wa-
complex of landforms and vegetation zones. Natu-
terfowl use ERF as a resting, feeding and staging
ral levees occur along the banks of the river, with
area during the spring and fall migration periods.
large expanses of sparsely vegetated mudflats
In the past ten years, thousands of waterfowl have
along either side of the river and near the shore of
died annually in ERF. The WP particles found in the
Knik Arm. The backwater areas away from the river
sediments of the shallow ponds were derived from
consist of zones of low sedge meadow, tall coarse
WP smoke projectiles fired into the impact area
sedge marsh and shallow open-water ponds (Racine
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