Parrot's Beak, Rotterdam CDF Liner and Leachate Collection

ERDC TN-DOER-C18

August 2000

The silt mounds themselves are essentially upland CDFs, acting as covers

constructed over previously used conventional CDFs. A double seal liner is

installed at the base of the silt mound (essentially on top of the old CDF),

consisting of 2.5-mm-thick HDPE, heat-sealed, with a 1.5-m-thick layer of

compacted silt. Dewatered dredged material is placed in layers with interme-

diate layers of separated sand acting as drainage layers. A double seal is also

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installed as a cover layer, with a topsoil layer for planting a vegetative cover.

A cross-section of this arrangement is shown in Figure 11.

Figure 11

Parrot's Beak, Rotterdam CDF Liner and Leachate Collection: The

Papegaaiebek (Parrot's Beak) site in Rotterdam, The Netherlands, is a 40-ha

upland CDF specially designed for highly contaminated dredged material from

Rotterdam Harbor. The site has been filled with approximately 1.5 million

cubic meters of fine-grained material, and hydraulic pipeline dredges or

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hydraulic off-loaders were used for the filling. A plan view of the site and a

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typical cross-section of the dike used are shown in Figure 12.

Figure 12

This CDF was designed with a liner and leachate collection system. The liner for Parrot's Beak

consisted of 2-mm-thick HDPE sheeting. The liner material was placed in overlapping strips (see

Figures 13 and 14), extending across the bottom of the basin and onto the inside face of the dike.

A crane was used to unroll the strips, which were then held in place with sandbags. The edge of

the liner was anchored in a trench excavated along the dike crest (Figure 15). Seams were then

heat-welded (Figure 16). The leachate collection system consisted of 100-mm-diam perforated pipe

placed at 50-m spacings.

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Figure 13

Figure 14

Figure 15

Figure 16

Once dredged material was initially placed in the site, an inner compartment was constructed for

the most highly contaminated sediment, separated from the remainder of the CDF by an interior

filtration dike. Clean fine-grained dredged material was used to form the main berm for the interior

dike and was left in a layer above the membrane within the interior compartment. The upper portion

of the interior dike section consisted of a sand core with geotextile placed on the inside face which

acted as a filter for excess water flowing from the interior compartment to the main CDF.

Venice Lagoon CDF "Diaphragm" Liner and Cover. A confined site with special lateral

containment measures was constructed as a part of the overall remediation of the Venice, Italy,