Options if Required Volume is Too Large (cont.)

projects that collectively can afford the cap required. Other options involve

creating a contained aquatic disposal (CAD) site, either by creating berms from

clean material (perhaps dredged from the disposal site creating additional

capacity) or potentially using geotextile fabric containers. Use of geosynthetic

fabric containers (GFCs) to contain the contaminated sediments is also an option

to reduce the amount of cap required. However, this is a fairly recent develop-

ment, and specific guidelines for this application are not yet available. Clausner

et al. (1996) summarize the present state of knowledge and critical issues for

geotextile container use with contaminated dredged material.

Good advance planning can be used to create a "natural" CAD site. As

described in Chapter 6, over a several-year time period, the New England

Division created a series of capped mounds in a circle. The de facto CAD site in

the center was then used for a rather large project. This technique greatly

reduced the potential spread of the contaminants and allowed a low cap volume

to contaminated sediment volume ratio. Fredette (1994) describes this project in

detail.

H12

Appendix H Level-Bottom Capping Projects