Figure 24. Ordnance retention receptacle.
be evacuated while actively dredging. Post-dredg-
After much work on the equipment, all systems
ing sampling is the only current method of mea-
were integrated and operational. A last-minute
suring dredge area contamination. This is being
requirement that a box be placed between the
done by other researchers (Lawson and Brockett
dredgehead and pump delayed initiation of dredg-
1993) and thus will not be discussed here. How-
ing for about a week. The device, called a "boom
ever, at the outflow from the basin, effluent can be
box" (Fig. 24), reduces the velocity of the flow over
sampled and contaminant levels measured.
a length of about 1.2 m up to a factor of seven. The
The best method of determining whether the
theory is that heavier objects, such as mortar
dredge is removing WP from the Flats is to ana-
rounds, will drop out before reaching the pump.
lyze material that is being pumped to the reten-
A self-dumping feature was built in to allow dis-
tion basin. Due to safety considerations, material
posal of any collected debris.
within the basin cannot be sampled during active
dredging and no sampling can easily occur on the
dredge, so a tap was put into the spoils line just
INSTRUMENTATION AND SAMPLING
below the top of the berm (Fig. 25). This tap con-
sisted of a pitless adapter, a ball valve, and a 1-m
Several parameters related to the dredging pro-
length of 1/2-in. (1.27 cm) Tygon tubing. A 5-gal.
cess need to be monitored to ensure that the pro-
PE bucket was used to collect spoils for integrated
cess is effective and that there is no collateral con-
samples, which were collected hourly. Storage of
tamination occurring due to dredging activities.
samples was simplified due to the low ambient
Process efficacy can be determined by sampling
temperature: it did not get above 7C during
of the spoils and the retention basin sediments.
dredging operations. Samples were shipped over-
Pond recontamination due to dredging is a more
difficult parameter to measure because of the ex-
night to CRREL upon cessation of operations for
analysis there. A standard operation procedure for
tremely hazardous nature of the operation. The
sample collection and storage is included in Ap-
most obvious area that may become contaminated
pendix C.
is near the dredge during dredging operations.
To measure the basin parameters that will af-
Unfortunately, the area around the dredge must
27
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