Eagle Harbor West CDF Liner and Cover

ERDC TN-DOER-C18

August 2000

pumped under the cover during filling, and volatile emissions from this component of the remedia-

tion system were adequately controlled.

Eagle Harbor West CDF Liner and Cover. A 0.4-ha nearshore CDF was

used for placement of material dredged from the Eagle Harbor, WA, West

Harbor Operable Unit, a part of the Wycoff/Eagle Harbor Superfund site. A

plan and typical cross-sections for this site are shown in Figures 8 and 9,

respectively. This site utilized selective placement of contaminated material To view figure

below the water table and an engineered liner and cover (Verduin et al. 1998). larger, click here

The containment berm was constructed using select fill (40 percent gravel; less

Figure 8

than 5 percent fines) placed by conveyor between riprap training dikes. Soft

materials were removed from below the dike prior to its construction by

excavating a key trench. A 60-mil HDPE liner was placed over the footprint

of the CDF to an elevation of +10.0 mean lower low water (MLLW) to raise

the water table from +6.0 MLLW to allow for additional volume retained in a

saturated condition. Edges of the liner were overlapped a minimum of 0.3 m To view figure

(1 ft) and the upper edge of the liner was anchored in a trench excavated into larger, click here

the inner side of the dike. Geotextile fabric was used on the inside face of the

dike to cushion the liner from damage from the sharp edges of the training dike

Figure 9

riprap. "Ecology blocks" were used to anchor the liner in place prior. Dredged

material was placed in the CDF mechanically by clamshell equipment and front-end loaders. A

surface cover of 1.5 m (5 ft) of compacted structural fill was placed to bring the fill to grade.

Bremen and Hamburg, Germany, CDF Covers, Liners, and Leachate Collection.

Since the middle 1980's a concept of integrated dredged material disposal has been implemented

at the ports of Bremen and Hamburg, Germany, involving dewatering and separation of dredged

material and disposal of dewatered material in "silt mounds." Several million cubic meters of

material are dredged each year, most of which is contaminated to some degree. Sediments that are

predominantly fine-grained are placed in dewatering fields, while those with a significant fraction

of sand (presently about 50 percent) are sent to mechanical dredged material processing plants. The

separated sand is used beneficially, while the dewatered silt, from both the separation plants and

dewatering fields, is placed in the silt mounds.

A series of 15 small CDFs are used as dewatering fields at the Port of Bremen.

Following placement and dewatering in these facilities, the dredged material

is re-handled to an upland CDF for final disposal. Each of the dewatering

fields is about 100 by 200 m and is used annually to dry approximately 700,000

cu m of wet dredged material. An aerial view is shown in Figure 10 (PIANC

To view figure

1997). The fields were constructed on an older CDF using the previously

larger, click here

placed dredged material. During construction, the bottoms and the slopes were

covered with a sealing liner of 0.30 m of conditioned dredged material.

Figure 10

Drainpipes were installed in a sand layer above the sealing layer to collect

percolating water and discharge it to another pond for treatment.