conclude that treatment of the sediment with
encapsulated repellent may be a viable strategy
cle to the particles per unit mass of sediment, the
to prevent ducks from using WP-contaminated
amount of time spent feeding, the duck's rate of
areas. If used as a hazing tool on Eagle River
feeding, and its efficiency in recovering particles
Flats, methyl anthranilate beads should be
of a certain size. Literature-based values for feed-
employed over contaminated areas greater than
ing rate and efficiency are available, but refine-
900 m2 at an application rate of 0.017 kg of active
ment of the particle size distribution per unit
ingredient per square meter.
mass of sediment is still needed on a site-specific
The water column data on methyl anthranilate
basis.
release show that loss of the repellent material is
constant over time. However, in the field the data
Collins, C.M. (1994) Pond draining treatability
suggest a high level of integrity between 0 and 5
study. In Interagency expanded site investigation:
days, whereupon there is catastrophic failure of
Evaluation of white phosphorus contamination and
the bead, resulting in significant loss of methyl
potential treatability at Eagle River Flats, Alaska
anthranilate. Given the organic nature of the shell
(C.H. Racine and D. Cate, Ed.). CRREL Contract
(gel alginate), we suggest that the integrity of the
Report to U.S. Army Garrison, Alaska, Director-
bead is attacked by microbes as a nutrient source.
ate of Public Works, FY93 Final Report, p. 323
The field failure rate for all beads tested to date is
332.
about 5 days and cannot generally be improved
Pond draining is an option under consider-
upon so long as a biodegradable gel alginate cap-
ation for treating pond bottom sediments con-
taminated with WP. Pond draining would accom-
sule is used.
plish two distinct functions: 1) it would remove
the pond as habitat for dabbling waterfowl,
Clark, L., J.L. Cummings, C.H. Racine, B.B.
Steele, and L.R. Reitsma (1995) Integrated risk
reducing the time the waterfowl spend feeding in
assessment model for determining white phos-
a contaminated area, thus reducing the chances of
phorus encounter rate by waterfowl. In Interagency
WP poisoning; and 2) it would subaerially expose
expanded site investigation: Evaluation of white phos-
WP-contaminated pond bottom sediments.
phorus contamination and potential treatability at
A field test was conducted to determine the in-
Eagle River Flats, Alaska (C.H. Racine and D. Cate,
situ conditions of pond bottom sediments under
Ed.). CRREL Contract Report to U.S. Army,
drying conditions. The test results indicated that
Alaska, Directorate of Public Works, FY94 Final
pond bottom sediments may dry sufficiently to
Report, p. 403410.
permit WP concentration in the sediment to
The objective of this study was to develop a
decrease. Surveys of potential pond draining
simple method for risk assessment using WP
locations were conducted. Based on the surveys
encounter rate by dabbling ducks feeding in ERF.
of the gullies in the vicinity of the Bread Truck
The general model, M = cFW, relates the probabil-
Pond, a drainage ditch connecting one or more
ity of mortality M to F, the proportion of time a
gullies with the Bread Truck Pond could be con-
duck spends feeding, and W, the probability of
structed to drain the pond. The drainage ditch
encountering a WP particle (c is a proportionality
would be excavated to a depth of 1 m and would
constant relating F and W). Data from telemetry
be between 50 and 150 m long, depending on
studies, in which about 10% of the transmitter-
location chosen. The drainage ditch would be
collared ducks died (M), and feeding effort data
excavated by explosives owing to the danger of
for mallards indicated that 80% of their time is
UXO. Because of the extensive bulrushwetland
spent feeding. Using c = 1 and solving for W M/
complex connected to the C pond along its east
Fc, the marsh-wide probability of encountering a
and northeast side, it does not lend itself to drain-
lethal dose of WP is predicted to be 0.125. This
ing. A detailed survey of the eastern end of the
value is in line with the percentage of all pond
Bread Truck Pond should be conducted next
and marsh sediment samples having concen-
summer to confirm that the pond is hydrologic-
trations greater than 1 g/g ( the level at which
ally isolated from the C/D area. A preliminary
we can find actual WP particles). This model still
pumping test should be conducted to confirm the
requires refinement to account for differential use
feasibility of draining the pond prior to the con-
of specific habitats or site-specific feeding partic-
struction of a permanent drainage ditch. A drain-
ularly since remediation would be site-specific.
age ditch would then be designed and construct-
Therefore, another model is proposed that relates
ed that would lower the maximum water level
37
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