Framework for Dredged Material Management
regarding potential for human health effects and for beneficial uses of the site or dredged
material. Levels of contaminants in the biomass are compared with Federal criteria for
food or forage. Risk assessment may also be performed to evaluate the potential effects
of plant and animal uptake on sensitive species subject to primary or secondary exposure
(Cura, Wickwire, and McArlde in preparation).
From the test results, appropriate management strategies can be formulated
regarding where to place dredged material to minimize plant or animal uptake or how to
control and manage the species on the site so that desirable species that do not take up
and accumulate contaminants are allowed to colonize the site, while undesirable species
are removed or eliminated.
5.3.8 Volatilization to Air
Contaminant transport from in situ sediment to air is a relatively slow process,
because most contaminants must first be released to the water phase prior to reaching the
air. Potential for volatilization should be evaluated in accordance with regulatory
requirements of the Clean Air Act. Thibodeaux (1989) discusses volatilization of organic
chemicals during dredging and disposal and identifies four locales where volatilization
Dredged material exposed directly to air.
Dredging site or other water area where suspended solids are elevated.
Ponded CDF with a quiescent, low-suspended solids concentration.
Dredged material covered with vegetation.
In cases where highly contaminated sediments are disposed, airborne emissions
must be considered to protect workers and others who could inhale contaminants released
through this pathway.
Rate equations based on chemical vapor equilibrium concepts and transport
phenomena fundamentals have been used to predict chemical flux (Thibodeaux 1989;
Semmler 1990). Computerized programs have been developed utilizing these rate
equations for the evaluation of volatile emissions from dredged material (Myers,
Schroeder and Estes in preparation (b)). Since the original publication of this document,
considerable effort has also been directed to testing procedures for direct measurement of
volatile emissions (Price et al. 1997; Price et al. 1998; Price et al. 1999, USACE 2003).
Emission rates are primarily dependent on the chemical concentration at the
source, the surface area of the source, and the degree to which the dredged material is in
direct contact with the air. The magnitude of release from exposed dredged material is
initially higher than for ponded conditions. This is of limited duration however.
Volatilization from ponded areas occurs at a lower rate, but is continuous, and may result
in a higher mass flux over time.