for us to judge it acceptable for use again this
year. In addition, moisture content and densities
daunting contracting delays, but they were
drilled and installed the last week in September.
were tested near the percolation tests to complete
Seven wells, each 6 m deep by 10 cm in diameter,
the characterization of the Retention Basin liner.
were placed at the corners and down the middle
Moisture contents ranged from around 30% to
of the EOD Pad. As work had ceased before com-
around 70%. Densities generally ran around 0.9
g/cm3 (55 lb/ft3).
pletion of the wells, no attempt was made to
instrument the wells with depth sensors. A
Some erosion had occurred around the con-
groundwater-sampling plan will need to be devel-
crete splash pad at the spoils line outlet, so a
oped prior to sampling for chemical analysis.
wooden weir was constructed along one side and
The final task was to develop a remote-
flow channels around the remaining sides were
controlled coring machine for use in the Flats.
blocked with stones. Finally, the geotextile silt
This was to be a follow-on to the drill machine.
fence at the drop inlet structure was subjectively
Because of the delays in the drill project, develop-
checked with a knife to assure integrity. It was left
ment of the coring unit is delayed until FY
in place and covered with a tarp to reduce expo-
96. Work has been initiated in conjunction with
sure to UV rays. Later problems with low super-
TARDEC on retrofitting an M501 Hawk missile
natant salinity levels forced us to forego the use of
loader for this task using carry-over funds.
the silt fence because of clogging.
In summary, it was a frustrating field season,
Continued problems with the dredge equip-
with two of the three tasks coming very close to
ment and the unique environment at the Flats
completion, but being foiled by contract delays.
precluded its full operation until September. At
The only positive aspect to this situation is that a
that time, the slurry pump had been reconfig-
ured, the dredge sensors reprogrammed, the elec-
wet field season and contract delays in other pro-
trical work finished, spoils line repaired, the
grams resulted in the equipment not being need-
boom box removed, a new grate system installed
ed as much this season as it will be next season.
on the dredgehead, and the lateral winch dead-
With the wells in place, a full season's data can be
men anchored. During dredge operations, 160
collected during next year's dredge deployment.
spoils-line sediment samples and 23 supernatant
(water) samples were obtained and analyzed,
Walsh, M.R. (1996) Dredging as a remediation
with a total of 26 sediment sample WP hits and
strategy for white phosphorus contaminated
one water hit. The average concentrations were
sediments at Eagle River Flats. In Interagency
6.16 and 4 g/kg for the sediment and water sam-
expanded site investigation: Evaluation of white phos-
ple hits, respectively. Approximately 1650 m3 of
phorus contamination and potential treatability at
Eagle River Flats, Alaska (C.H. Racine and D. Cate,
material was dredged from Clunie Inlet and Area
Ed.). CRREL Contract Report to U.S. Army,
C between and adjacent to Clunie and Canoe
Alaska, Directorate of Public Works, FY95 Final
Points. Using the results of the analysis of the
Report, p. 311344.
spoils, about 1420 lethal doses of WP were
This project covers the second deployment of
removed during dredging (based on a 37% mal-
the dredging system and the various factors in-
lard, 37% pintail, 26% teal mix). The fine particle
volved in dredging and remediation of the spoils.
size of the suspended solids in the supernatant
diminishes the lethality of any WP returned to the
This season's work can be divided into three cate-
Flats.
gories: continued investigation of the hydrologi-
The attenuation study was initiated and some
cal properties of the Retention Basin, dredge
data obtained from the instrumentation installed
operations, and initiation of the attenuation
in the Retention Basin. Six particles were planted
study in the Basin.
The hydrological studies of the Basin liner
in partially dewatered spoils in four locations,
were conducted in mid-June. They consisted of
two adjacent to instrumentation stations, on 28
constant-head percolation tests, in-situ density
September. The dataloggers were allowed to
tests, and moisture content tests. The percolation
operate until 7 December. At that time, the tem-
tests were run over a period of up to 9 days.
perature was well below zero and the spoils had
While most tests indicated a percolation rate
frozen solid. Only partial drying of the sediments
below the acceptable level of 106 cm/s, one test
occurred before freezeup, so definitive data will
exceeded that level (<5 106 cm/s). However,
not be collected and analyzed until next spring.
the overall performance of the liner was sufficient
Because of equipment problems, it was not
72
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