Figure 9. Grain size analysis for spoils sample (1995).
Table 7. Contaminant removed as a function
A rough estimate can be obtained from observa-
of lethal doses (1995).
tions of the quantity of sediment in the settlement
basin. At the cessation of dredging activities in late
Lethal
Single
Mortality
September, the quantity of material in the Basin
dose
species
observed
Multispecies
would fill about one third of the area to the 60-cm
Species
(mg) mortality
(%)
mortality
level. This is equivalent to about 1650 m3. Material
Teal
1.5
2400
26
624
was removed to a depth of 75 to 100 cm from the
Mallard
4
900
37
333
water level at the time of dredging.
Pintail
3
1200
37
444
From this quantity and the results of the sedi-
Total
9002400
100
1401
ment sampling analysis, a rough estimate of the
WP mass transfer can be made:
CONTRACT DEPLOYMENT
Total solids removed:
In 1996, a local environmental firm was con-
1650 m3
tracted to complete dredging of the 1-ha area
begun in 1994. The main objective of CRREL's
Avg. sample (hit) concentration:
6.16 g/kg (6.16 ppb)
participation in this phase of the project was to
monitor the removal of the white phosphorus-
Percent spoils hits:
contaminated bottom sediments. Other tasks
19%
were to monitor the fate of the contaminated
spoils sediments in the retention basin, to meas-
Possible quantity of contaminated spoils:
0.19 1650 = 313.5 m3
ure WP concentrations in the spoils line prior to
deposition in the retention basin as well as in the
Mass transfer of P4:
decanted sediment in the basin, and post-remedi-
= 313.5 6.16 106 = 2 cm3
ation sampling within the basin, to determine the
2 1.82 103 = 3600 mg
efficiency of natural remediation on the sediment
To put this number in perspective, it should be
within the basin. In addition, CRREL assisted the
considered in terms of lethal doses. Table 7 was
contractor in equipment deployment, operations
constructed using estimates based on Reitsma and
instruction, and guidance during the initial phase
Steele (1995) and toxic dose levels were based on
of operation.
Sparling et al. (1995). The quantity of white phos-
Limited sampling and testing were conducted
phorus transferred from the Flats to the basin
in the basin and on the spoils entering the basin.
given here is conservative due to the sampling
Datalogger stations were reinstalled in the basin
apparatus, as described above.
to monitor such parameters as air and soil tem-
9
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