Enhanced Natural Remediation of
White-Phosphorus-Contaminated Wetlands
through Controlled Pond Draining
MICHAEL R. WALSH, MARIANNE E. WALSH, AND CHARLES M. COLLINS
INTRODUCTION
in detail. This is the preferred method of remedia-
White phosphorus (P4) is a highly toxic chemi-
tion for Eagle River Flats as determined by the
cal that does not normally occur in the natural
Remediation Project Managers and described in
environment. When milligram quantities of
the site Record of Decision (CH2M Hill 1998).
white phosphorus (WP) are ingested by water-
fowl, the effect is devastating. In Eagle River Flats
BACKGROUND
(ERF), an estuarine salt marsh off Knik Arm near
Anchorage, Alaska, this devastation manifested
For over forty years, Eagle River Flats has been
itself in the deaths of thousands of waterfowl a
used by the U.S. military as a munitions impact
year. The "Flats," situated on Ft. Richardson, had
area. Among the many types of munitions fired
been used for many years by the U.S. military as a
into the ERF were rounds containing white phos-
munitions impact area. The use of white phos-
phorus. White phosphorus is classified as a "smoke"
phorus rounds for targeting and practice had re-
munition because of the formation of large clouds of
sulted in the deposition of unburned material in
condensed water vapor generated during burning
the many permanent ponds scattered throughout
of the chemical. The vapor cloud can serve both as
the area. Ft. Richardson biologists, alerted to the
an obscurant and for marking targets. These
die-offs in the early 1980s, did a preliminary
clouds are very useful for training, especially as
investigation to determine the extent of the prob-
the moving cloud can be used as a dynamic target
lem. When the magnitude of the situation was
during practice firings.
discovered, action to uncover the yet unknown
There are two common fusing systems for
cause was initiated, followed by efforts to devise
smoke rounds. The first, an aerial burst fuse, ena-
an acceptable remediation method.
bles the round to explode at a preset height above
This report discusses the characteristics of
the ground, allowing a much wider dispersal of
white phosphorus, which led to the problem at
the material, a higher burn rate, and more com-
Eagle River Flats, the physical processes of the
plete combustion. The second type of fuse is the
ERF that exacerbate the persistence of the chemi-
comparatively inexpensive, more commonly used,
cal in the environment, and some of the initial
point-detonating fuse. This type of fuse triggers on
treatment methods used to try to remediate the
impact with the ground. With point detonating
problem. The implementation of a composite
rounds, the dispersal is not as great, and some of
sampling method for determining the distribu-
the material is driven into the ground. The white
tion of the nonhomogeneous particulate contami-
phosphorus in a point-detonating round explod-
nant will also be discussed. Finally, the feasibility
ing in a muddy or permanently ponded area will
and implementation of a remote, semiautono-
not completely combust. These unburned particles
mous pond pumping system to enhance the natu-
of white phosphorus will embed in the saturated
ral remediation of the contaminant will be covered
sediments. As solid white phosphorus is extremely
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