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 Table 6-1
Summary of Data Requirements for Prediction of the Quality of
Leachate from Confined Dredged Material Disposal Areas
Data Required
Source of Data
Project information; site
Thickness of dredged material
design
Thickness of dikes, vadose zone, and aquifer
Site design; site selection
Project information; site
Ponded area in disposal site
design
Project information; site
Dredged material solids concentration
design
Grain size distribution of dredged material
Project information
Grain size distribution of foundation soils, dike materials, and aquifer Site selection; site design
Organic content of dredged material
Project information
Organic content of foundation soils, dike materials, and aquifer
Site selection; site design
Acid Volatile Sulfides (AVS) and salinity of dredged materials
Project information
Bulk sediment chemistry of dredged materials
Project information
Bulk chemistry of foundation soils
Site selection
Groundwater velocity
Site selection
Climate
NOAA
Partitioning coefficients of contaminant in dredged material and
Leaching tests; literature
foundation soils
6.1.5 Disposal Area Design
When the quality of the leachate from a CDF is of concern, the design,
operation, and management of the site should be carefully considered. This
includes aspects relating to the design features, dewatering, and the disposal
sequence of materials in the CDF. Procedures for such evaluations are presented
in Engineer Manual 1110-2-2-5027 (HQUSACE 1987) and should be considered
prior to the evaluation of the leachate for the project.
6.1.6 Summary of Tiered Evaluations for Leachate
A flowchart illustrating the tiered evaluation for leachate is shown in Figure
6-3. If a decision cannot be reached in Tier I, Tiers II and III provide evaluation
methods and laboratory tests for evaluating potential leachate impacts. If a
decision about leachate cannot be reached in Tiers I through III, a site-specific risk
assessment is available in Tier IV.
The Tier II evaluation of leachate quality is a screening procedure based on
solubility and partitioning. Attenuation and diffusion that will occur in the vadose
and groundwater zones is considered. Conservative procedures (i.e., those that err
on the side of environmental protection) are employed in Tier II to identify
scenarios when testing or testing for some classes of contaminants would not be
needed.
6-6
Chapter 6
Leachate to Groundwater
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