TABLE OF CONTENTS MICHAEL R.PALERMO, PH.D., P.E.
U.S. Army Engineer Waterways Experiment Station Vicksburg, Mississippi
Potential for water column and benthic effects related to sediment contamination must be evaluated when considering open-water disposal of dredged material. Management options aimed at reducing the release of contaminants to the water column during disposal and/or subsequent isolation of the material from benthic organisms may be considered to control potential contaminant effects. Such options include operational modifications, use of subaqueous discharge points, diffusers, subaqueous lateral confinement of material, or capping of contaminated material with suitable material (Francingues and Palermo, 1984; USACE/EPA, 1992).
Subaqueous dredged material capping is the controlled, accurate placement of contaminated dredged material at an appropriately selected open-water disposal site, followed by a covering or cap of suitable isolating material. Capping of contaminated dredged material in open-water sites began in the late 1970s, and a number of capping operations under a variety of placement conditions have been accomplished. Conventional disposal equipment and techniques are frequently used for a capping project, but these practices must be controlled more precisely than for conventional disposal (see also Chapter 17).
This chapter provides an overview of methods for evaluation of subaqueous dredged material capping projects. Design requirements, a design sequence, site selection, equipment and placement techniques, geotechnical considerations, mixing and dispersion during placement, required capping sediment thickness, material spread and mounding during placement, cap stability, and monitoring are described.
More details on capping and related evaluation procedures are found in technical guidance documents prepared...
