7.1.4 Regulatory Considerations

material will be a source of volatile emissions during various stages of CDF

operation and flow equalization as follows:

a. Delta formed during primary settling of dredged material slurries.

b. Dredged material in filled primary settling facilities after ponded water is

drawn off.

c. Delta formed during mechanical disposal of dredged material in in-water

or nearshore flow equalization facilities.

d. Dredged material in upland flow equalization facilities for mechanically

dredged material.

The rate at which chemicals volatilize from exposed dredged material is

affected by many factors. Geotechnical properties such as porosity and water

content, chemical factors such as water and air diffusivities, and environmental

factors such as wind speed and relative humidity all affect volatilization rates. In

addition, processes such as air-water-solids chemical partitioning, diffusion of

thermal energy, evaporation of water, and desiccation cracking of the dredged

material can have pronounced impacts on volatile emission rates for exposed

sediment.

7.1.4 Regulatory Considerations

As dredged material is placed in the CDF, volatiles may escape through the

air/water interface, and volatiles may escape from dredged material as the drying

dredged material is exposed to the air. However, there are no known instances

where volatiles from CDFs have posed a potential release sufficient to trigger the

regulatory application of the Clean Air Act (CAA). Importantly, the CAA

regulates emissions from a point source (stack), and the CAA regulates only a few

paramters such as particulates and carbon dioxide. Neither of these scenarios

apply to CDFs. Nevertheless, there are occasions where workers might be

exposed to volatile emissions while undertaking management actions at the CDF

such as dike rehabilitation using dredged material from the CDF, dewatering

using specialized equipment or trenching equipment to dewater the dredged

material.

This chapter on emissions is designed to ensure that worker safety measures

are properly undertaken to meet standards of exposure established by the

Occupational Safety and Health Administration (OSHA). The approach for

evaluation of the volatile pathway involves prediction of a flux rate of

contaminants to air and calculation of the concentration of contaminants in air

(mass/cubic meter), considering dispersion because of atmospheric processes such

as wind. The receptor of concern for volatile emissions is humans working on site

or humans adjacent to the CDF. The predicted air quality or exposure

concentration data can be compared with OSHA standards. The dispersion

models provided consider dispersion occurring at a height of 1.8 m (6 ft) above

the dredged material surface or adjacent ground surface.

7-4

Chapter 7

Guidance for Evaluation of Volatile Emissions