Summary and Recommendations

11 Summary and

Recommendations

Summary

This report presents technical guidance for subaqueous dredged material

capping. The guidance is summarized as follows:

a. Capping is the controlled accurate placement of contaminated

material at an open-water disposal site, followed by a covering or

cap of clean isolating material. Within the context of capping, the

term "contaminated" refers to material that needs isolation from

the benthic environment, while the term "clean" refers to material

found to be suitable for open-water disposal.

b. A capping operation must be treated as an engineered project with

carefully considered design, construction, and monitoring to en-

sure that the design is adequate.

c. There is a strong interdependence between all components of the

design for a capping project. By following an efficient sequence

of activities for design, unnecessary data collection and evalu-

ations can be avoided, and a fully integrated design is obtained.

d. The basic criterion for a successful capping operation is simply that

the cap thickness required to isolate the contaminated material

from the environment can be successfully placed and maintained.

e. The contaminated sediment must be characterized from physical,

chemical, and biological standpoints. Physical characteristics are

of importance in determining the behavior of the material during

and following placement at a capping site. Chemical and biologi-

cal characterization data for the contaminated material to be

capped are useful in determining potential water column effects

during placement and acceptable exposure times before placement

of the cap begins.

The capping sediment must also be characterized from the physical,

chemical, and biological standpoints. Physical characteristics

determine the behavior during placement of the cap and long-term

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Chapter 11 Summary and Recommendations