taminated ponds has also been shown to be mini-
ERF was a chemical deterrent. Methyl anthra-
nilate (Rejex-itTM) is an encapsulated bird repel-
mal. Investigations by Lawson et al. (1996a,b)
show that intra-pond and drainage gully trans-
lent that is applied to the contaminated ponds
port of white phosphorus, when it occurs, is not
and settles to the bottom (Clark et al. 1993, Po-
in the form of discrete, macroscopic particles.
chop et al. 1999). The repellent is released when
Rather, white phosphorus concentrations were
the micro-capsules are broken by feeding ducks.
sufficiently low to indicate that the white phos-
The repellant required multiple applications, due
phorus was sorbed to suspended sediment or
to microbial degradation of the capsule material,
organic matter. Observations of native fish (stickle-
and was very expensive. Further development
backs) and invertebrates (chironomids and amphi-
was postponed pending results from other, ongo-
pods) at ERF indicate that these organisms' lives
ing studies.
Physical barriers. Geotextile barriers were test-
are not adversely affected by the low concentra-
tions of white phosphorus found in permanently
ed in field trials in Eagle River Flats (Henry et al.
ponded areas (Bouwkamp 1995, U.S. Army Envi-
1995). The geotextile barriers were used as a
ronmental Hygiene Agency 1994 and 1995).
physical barrier to penetration by the bills of dab-
The physical system has a negative impact on
bling ducks, thus preventing them from feeding
the ability to remediate ERF. The periodic high
in the underlying contaminated sediments. A reli-
tides wet and cool areas that are undergoing dry-
able method for anchoring the material against
ing and warming. This effectively blocks the pro-
ice movement and a solution to the problem of
cess of natural attenuation of the contaminant.
trapped methane gas was not identified at the
Some attenuation has occurred, most notably in
time of field testing. The installation of the barri-
the mudflat areas and the intermittent ponded
ers was labor intensive and exposed the workers
areas between the mudflats and permanent
to potential dangers from unexploded ordnance.
ponds, since the cessation of firing of WP in ERF.
There was also concern that the barriers would be
However, the contaminant persists in the perma-
subsequently damaged by artillery firing, ero-
nent ponds, requiring remediation efforts to
sion, or movement of ice, which would again
resolve the problem.
expose the contaminated sediments to waterfowl.
Capping was also considered and tested.
AquaBlokTM is a composite of bentonite, gravel,
Treatment methodologies
A number of options have been proposed for
and polymers that is applied to pond bottoms.
treating the white phosphorus contaminated sed-
It hydrates after application and expands, sealing
iments in Eagle River Flats since the agent was
the pond bottom sediments. This material acts as
first identified. Many treatment ideas were reject-
a physical barrier to the penetration of the bills
ed as either impractical or not feasible. Other
of dabbling ducks while they are feeding (Fig. 3).
ideas, while at first promising, failed when sub-
Vegetation appears to reestablish readily in the
jected to either bench scale or field tests. The vari-
AquaBlok material based on observations of the
ous treatment options are summarized below.
treatment site on Racine Island (Pochop and
They can be divided into three basic types: (1)
Cummings 1994, Pochop et al. 1996, 1999). Cost
barriers that prevent the waterfowl from ingest-
of application of AquaBlok to large areas by heli-
ing the contaminant (i.e., breaking the pathway),
copter was very expensive, and consistency of ap-
(2) contaminant removal where the white phos-
plication difficult to maintain. Possible use of
phorus-laden sediment is physically removed
AquaBlok or clean gravel was retained as a poten-
from the salt marsh, and (3) alteration of habitat
tial treatment option for very localized, hard-to-
that either prevents waterfowl from ingesting the
treat areas.
contaminant or that leads to removal of the con-
Removal of contaminated sediment: dredging
taminant through in-situ sublimation and oxida-
tion. A detailed summary of all the remedial alter-
Use of a remote controlled dredge offered the
natives considered can be found in Section 3 of
possibility of physical removal of the white-phos-
Operable Unit C: Final Feasibility Study Report
phorus-contaminated sediment from the pond
(CH2M Hill 1997b).
bottoms and the deposition of the sediment at an
upland treatment site where the sediment can be
Barriers
allowed to dry and the white phosphorus allowed
Chemical barrier deterrent. One of the first treat-
to sublime and oxidize (Fig. 4). Additionally, the
ment methodologies developed and tested at
deepening of the pond by dredging would place
5
Previous Page
