EAGLE RIVER FLATS FY 00
4
face sediment. Also, we re-sampled previously identified hot spots to see if
the white phosphorus concentrations had declined.
The main pond of Area C (Pond 183) has been pumped for four consecu-
tive seasons. This year (2000), the pond was dewatered by pumping in
early May and the sediments dried significantly until a series of flooding
tides July 2 to 4. Sediments remained wet through July and August due to
frequent precipitation and tidal flooding in August. Despite cool surface
sediment temperatures (mean of 14.8C) during the time that the sediment
was unsaturated, we measured a 56% loss of mass of the white phosphorus
particles we planted in May 2000 and recovered in August 2000. White
phosphorus concentration the middle of Area C (C100 m grid), as deter-
mined by composite sampling, has declined from 0.07 g/g in June 1997 to
0.00055 g/g in August 2000. A milestone was reached at Miller's Hole, the
crater produced when a white phosphorus-containing UXO was detonated
on 20 May 1992. In samples of the surface sediment collected from the
bottom of the crater in August 2000, white phosphorus was undetectable
for the first time since we began sampling the crater when the concentra-
tion was over 2000 g/g. However, Pond 183 is not completely decontami-
nated. White phosphorus is still detectable in discrete samples collected
from the DWRC Pen 5, although only four samples have concentrations
greater than 0.001 g/g (in 1996 all 48 samples were greater than 0.001 g/
g). A few more favorable drying seasons should complete the decontami-
nation of Pond 183.
We installed a datalogger and resampled Pond 146, adjacent to Canoe
Point in Area C, in an area that was dredged in 1996 but still had high white
phosphorus concentrations in 1999. Particles planted in Pond 146 declined
in mass by 27%; composite samples showed a greater loss, with one sample
declining from 7.31 g/g in June 1999 to 0.001 g/g in August 2000.
Pond 155, to the Northeast of Pond 183 in Area C, is located within a
bulrush marsh, and the sediments do not dry significantly. This year, planted
particles did show a 32% decrease in mass, as compared to last year when
no change was found. A grid for collecting composite samples was estab-
lished in 1998, but no decline in white phosphorus concentration is evident.
Ponds 258 and 256 in Area A were drained for the third consecutive sea-
son and both showed drying and a decline in the mass of planted white
phosphorus particles of 89 and 92%, respectively.
Pond 730 in Area C/D was drained by pumping for the second year, but
minimal drying occurred because of frequent flooding from the Bread Truck
ditch. Pond 75 in Coastal East was drained this year because we found
white phosphorus in a composite sample collected in 1999. This pond also
floods from the Bread Truck ditch and minimal drying occurred.
The former Bread Truck pond experienced 20 flooding tides between June
and August, which eroded more of the pond and further enlarged the blasted
ditch. After the flooding tides at the beginning of June, both the north and
south sides of the pond dried. Planted white phosphorus declined by 79%
and 32% for the north and south sides, respectively. White phosphorus is
barely detectable in the composite samples collected from the north and
south sides of the pond.
Because of the death of telemetry birds in the Aquablok treated pond
(#285) on Racine Island, we were asked to take composite samples of the
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