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Framework for Dredged Material Management
May 2004
the material desiccates through evapotranspiration, it becomes aerobic and oxidized,
mobilizing some contaminants as described previously. At this point, the surface layer
has characteristics similar to that of material in an upland CDF.
The bottom of an in-water CDF below the low-tide or groundwater elevation
remains saturated and anaerobic, favoring insolubility and contaminant attraction to
particulate matter. After dewatering of the dredged material above the flooded zone
ceases and consolidation of the material in the flooded zone reaches its final state, water
movement through the flooded material is minimal and the potential for migration of
contaminants is low.
The intermediate layer between the saturated and unsaturated layers will be a
transition zone and may alternately be saturated and unsaturated as the water surface
fluctuates. The depth of this zone and the volume of dredged material affected depend on
the difference in tide elevations and on the permeability of the dike and of the dredged
material. With low-permeability material, the volume of CDF material impacted by this
pumping is very small compared with the in-water CDF's total volume.
5.3.3 Analysis of Pathways for CDFs
Guidance for analysis of contaminant pathways for CDFs is provided in the
Upland Testing Manual or UTM (USACE 2003). This manual is a resource document
providing detailed testing procedures and approaches for evaluation of potential
contaminant migration pathways from diked confined disposal facilities (CDFs).
Consideration of pathways for migration of contaminants from the site and potential
contaminant impacts is required to determine the need for operational or engineered
measures to control contaminant releases. During the 1980s and 1990s, a number of
evaluation procedures and laboratory tests were developed for CDF pathway evaluations
and serve as the technical basis for procedures in the UTM (Environmental Laboratory
1987, Francingues and Averett 1988, Palermo et al. 1989, Brannon et al. 1990, and Myers
1990).
The UTM uses a tiered approach similar to that long used for evaluation of open
water placement of dredged material (USEPA/USACE 1991 and 1998). The pathways of
concern for CDFs include effluent discharges to surface water during filling operations,
rainfall surface runoff, leachate into groundwater, volatilization to the atmosphere, and
direct uptake by plants and animals on site and subsequent cycling through food webs.
Additional discussion of the respective CDF pathways including appropriate testing
protocols and evaluation procedures are given in the following paragraphs.
5.3.4 Effluent Discharge
The effluent from a CDF may contain both dissolved and particulate-associated
contaminants. A large portion of the total contaminant concentration is tightly bound to
the particulates. Effluent from a CDF is considered a dredged material discharge under
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