by CRREL engineers. The design work was car-
possible to dredge the entire 0.85-ha area that had
been planned. However, by the end of the season,
ried out by District engineers using data gathered
the dredge system was operating reliably and ef-
from the testing. A 0.8-ha retention basin with
fectively. The ability of the dredge to remove con-
2-m berms was designed. The structure is lined
taminated material from the Flats has been dem-
with a peaty-silt soil, which reduces conductivity
to ≈ 1 106 cm/s below the 1 105-cm/s thresh-
onstrated, although the cost will be high. The per-
formance of the Basin as a remediation structure
old. A drop inlet structure is located at one corner
should be determinable by next July.
of the basin for decanting supernatant through a
weir and silt fence. Two concrete pads are con-
structed within the basin for spoils line outfall to
Walsh, M.R., E.J. Chamberlain, and D.E.
Garfield (1995) Dredging as a remediation strat-
prevent erosion of the basin liner. The basin will
egy for white phosphorus contaminated sedi-
be reusable with the removal of the treated spoils.
ments at Eagle River Flats, Alaska. In Interagency
Instrumentation was installed in the basin to
expanded site investigation: Evaluation of white phos-
monitor temperatures, water level, and soil mois-
phorus contamination and potential treatability at
ture. A tap was installed in the spoils line adjacent
Eagle River Flats, Alaska (C.H. Racine and D. Cate,
to the basin for spoils sampling.
Ed.). CRREL Contract Report to U.S. Army,
Owing to procurement delays, equipment
Alaska, Directorate of Public Works, FY94 Final
modifications dictated by the Safety Plan, and the
Report, p. 563632.
incomplete state of the equipment on delivery,
Investigations into the fate and persistence of
actual dredging did not commence until mid-
white phosphorus (WP) at Eagle River Flats,
October. Because of problems with some of the
Alaska, indicate that, although natural attenua-
equipment modifications and the onset of winter,
tion is occurring in areas where intermittent dry-
only about 2 hours of actual dredging over a 2-
ing takes place, permanently flooded areas are
day span was conducted during October 1994.
retaining lethal amounts of the chemical. Several
Two samples were taken from the spoils line, one
remediation strategies for these persistent areas
of which was highly contaminated with WP (2.7
g/g). Owing to the short amount of operational
were initiated during the 1994 field season, cover-
ing a range of methodologies, including covering
time in the 1994 field season, a judgment as to the
contaminated areas, siphoning small permanent-
feasibility of dredging cannot be made. However,
ly ponded areas, and dredging larger permanent
the ability of the dredging system to remove WP-
ponds. This project covers the preparations and
contaminated sediments has been demonstrated.
initiation of the dredging remediation operation.
Initial investigations centered on the feasibility
Walsh, M.R., and C.M. Collins (1997) Monitor-
of dredging in an active impact area. Discussions
ing of contract dredge operations at Eagle River
with several small dredge manufacturers indi-
Flats, Alaska. In Interagency expanded site investi-
cated that a remotely controlled dredge config-
gation: Evaluation of white phosphorus contamination
ured to minimize damage in the case of the deton-
and potential treatability at Eagle River Flats, Alaska
ation of an unexploded round would be feasible.
(C.M. Collins and D. Cate, Ed.). CRREL Contract
A list of technical specifications was developed
Report to U.S. Army, Alaska, Directorate of Public
and sent to the USARAlaska Contracting Office to
Works, FY96 Final Report, p. 73100.
be included in the RFQ for a dredge system lease.
Investigations into the fate and persistence of
CRREL engineers then worked with the Contract-
white phosphorus (WP) at Eagle River Flats
ing Officer in bid evaluation. The contract was
awarded to ChemTrack of Anchorage, Alaska.
permanently ponded areas of ERF. Several reme-
Design of the dredge spoils retention basin
diation strategies for these WP-contaminated
was a major task in the overall project. The cho-
areas were initiated or implemented in the 1994
sen site, the EOD Pad, is a Solid Waste Manage-
1996 field seasons, encompassing a range of
ment Unit within a RCRA site. As such, much site
methodologies, including covering contaminated
characterization work was required by the Resto-
areas, designing equipment for the draining of
ration Program Managers before approval was
large contiguous ponds, enhancing natural atten-
given for site use. Extensive testing and design
uation in intermittently flooded areas, pond
work, done in association with the U.S. Army
draining through explosive trenching, and dredg-
Engineer District, Alaska, was required. Site char-
ing. The objective of this project is to monitor the
acterization and extensive testing was conducted
commercial implementation of a small, remote-
73
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