Rotterdam Harbor

Marina del Ray material (Mesa 1995). Actual placement was initiated fol-

lowing completion of the berms, so the geotextile bags were not actually

required as a control measure; but the project proved to be a valuable field

demonstration of this innovative concept.

The sediments were dredged using a clamshell and placed in a split-

hull scow lined with two layers of geotextile (a nonwoven inner liner and

a woven outer shell) forming a container. Following completion of filling

of a barge, the geotextile material was brought over the top of the barge,

and the edges were sewn closed to form the completed container. Modifi-

cations were made to the scow bulkheads to reduce the width and length

of the filled volume to allow easier release of the filled bags.

The first geocontainer was filled with approximately 1,900 cu yd of

material. Because of drainage of the sandy sediment during transport and

subsequent bridging action, the first container failed to fall completely

from the barge. Water jets were finally employed to fluidize the material

and release the bag. Subsequent bags were only filled with approximately

1,300 cu yd, and additional fabric was used in forming the containers,

providing more "slack" in the containers to help with release. A total of

44 containers were placed (Figure 36).

All contaminated materials were successfully placed within the

subaqueous dikes, and the dikes have performed as intended. Bathymetric

and sediment profiling image camera monitoring confirmed that approxi-

mately 98 percent of the contaminated material was retained behind the

subaqueous dike, and that the thickest deposits immediately outside the

dike were generally less than 5 cm (the regulatory limit set for the project

in advance).

Rotterdam Harbor

As a consequence of local effluent discharge from chemical industries

sited around the 1st Petroleum Harbor in the Port of Rotterdam, the harbor

basin contained heavily contaminated material. Several options (upland,

open water, dredged pits, and confined behind a sheet-piled dam) were

considered for disposing of the contaminated material as described by

Kleinbloesam and van der Weijde (1983). The alternative finally selected

was a CAD project that consisted of excavating pits in the 1st Petroleum

Harbor, dredging the contaminated material, disposing of it in the pits,

and capping and lining the pit with clean material (Figure 37). The plan,

called the Putten Plan, had to be executed so that dispersion of pollutants

into the surface water and groundwater was very low, but acceptable. Spe-

cial dredging equipment was used for the disposal operation, and studies

were conducted to determine the dispersion of the contaminants.

The first dredge pit was 550 by 120 m at the bottom and was 15 m deep

with a capacity of 1.4 million m3. The silt from the pit dredging was dis-

posed at sea, and the sand was used at various landfill projects. Two addi-

tional pits were dredged; the contaminated dredged material was taken to

the first pit, and the clean material was used or discharged at sea. A third

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Chapter 10 Case Studies