EAGLE RIVER FLATS FY 00
42
1996, 1998, and 1999 we sampled a 5.46- 20-
in Area C/D. Pond 75 in Coastal East, from
which a positive composite sample (0.029 g/
m area including this pen, taking discrete
g) was collected last year (M.E. Walsh et al.
samples at the nodes of a 1.82-m-square grid
2000), was drained by explosively excavating
(M.E. Walsh et al. 1997). The 1998 and 1999
a ditch between Pond 75 and the pump in
samplings revealed dramatic reductions in
Pond 730. Sublimation/oxidation conditions
white phosphorus concentrations (Fig. III-2-
were monitored using dataloggers and
7). We resampled this grid in August 2000.
planted particles in both of these ponds.
In 1999 we collected eight sets of subsur-
face samples in Area C (seven from within
Pond 285 (Racine Island)
pond 183 and adjacent bulrush marsh and one
Pond 285 was first sampled in 1993 by C.H.
from pond 146) at locations that were sampled
Racine (Fig. III-2-1). Four samples were col-
in 1992 and where white phosphorus was de-
lected, all of which contained white phospho-
tectable over most of the core length (M.E.
rus (0.001 to 0.42 g/g). This pond was treated
Walsh et al. 2000). We obtained the subsur-
i n 1994 and 1995 by covering it with
face samples while the ponds were pumped
A q u a b l o k . Prior to application of the
dry by digging holes 30 cm deep and using a
Aquablok, DWRC sampled the area at 10-m
corer to take sediment samples from the wall
intervals for a total of 29 samples, which were
of each hole at 0-, 5-, 10-, 15-, 20-, 25-, and 30-
analyzed in duplicate at the Waterways Ex-
cm depths. White phosphorus was still detect-
periment Station, Vicksburg, MS. Of these,
able at only two of the eight locations. At lo-
five samples were blank (Table III-2-1). The
cation #615, which is within the bulr ush
maximum concentration found in the positive
marsh, we detected white phosphorus at sam-
samples was 36 g/g, indicating the likely
pling depths of 5 cm (0.00084 g/g), 10 cm
(0.003 g/g), and 25 cm (0.0018 g/g). At lo-
presence of discrete white phosphorus par-
ticles. DWRC collected samples again in 1995,
cation #53, which is adjacent to the dredge
10 months after covering with Aquablok. Fif-
channel in Pond 146, white phosphorus was
teen samples were collected from the perim-
detectable along the entire length of the core
eter of the treated area. Six samples were
(Table III-2-3). In August 2000 we resampled
blank, and the remaining samples ranged
location #53.
from 0.0017 to 0.017 g/g. When we visited
Two sets of subsurface samples were taken
the pond in August 2000, we found that most
from the bottom of Miller's Hole (Fig. III-2-
of the pond has transformed to bulrush
3), the crater produced when a white phos-
marsh, with open water on the east and west
phorus mortar round was detonated in May
sides. Small pools punctuate the marsh. We
1992. At this site we used a small shovel to
collected five grid composite samples, three
collect sediment at 0- to 10-cm depth and 10-
from the west side and two from the east side
to 20-cm depths.
(Fig. III-2-6). We also collected eight discrete
samples from pools that were too small for a
Laboratory Analysis of Sediments for White
grid composite sample (less than 20 m in one
Phosphorus Residues
dimension).
In the laboratory each composite sample
was thoroughly mixed by stirring and knead-
ing. To obtain an estimate of average white
Discrete Surface and Subsurface Sampling
Area C
phosphorus concentration, a 200-g subsample
We collected discrete surface and subsur-
was taken from each composite and analyzed
face samples from sites that had high concen-
using solvent extraction (100 mL isooctane)
trations of white phosphorus prior to drain-
a n d gas chromatography (EPA SW-846
age of the ponds. We again intensively
Method 7580). If concentrations were high, the
sampled the location of the DWRC Pen #5 in
remainder of each composite was rinsed
Area C (Fig. III-2-3), used from 1992 to 1993
through a 30-mesh sieve (0.59-mm sieve open-
for the evaluation of methyl anthranilate. In
ing) to remove the fine-grain sediment. Ma-
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