7.3.1 Tier II Volatilization Screen

7.3.1 Tier II Volatilization Screen

The volatilization screen utilizes an electronic spreadsheet for the calculations

and considers the bulk concentration of contaminants in the dredged material and

variables specific to the proposed CDF operation (Table 7-1). Necessary data

include both site and operating conditions and COC chemical properties.

Chemical partitioning assumptions are used to give conservative estimates of the

maximum COC air concentrations and fluxes on- and off-site under both

submerged and exposed dredged material conditions. Project specific information

such as CDF size, area of each disposal event, exposure, wind speed, temperature

and physical and chemical characteristics of the dredged material are required for

the Tier II evaluation. Site-specific values for these variables are entered into the

appropriate cells of the spreadsheet and output provides information on predicted

contaminant fluxes. The results can be compared to OSHA standards. The

spreadsheet, along with documentation, can be downloaded as an ADDAMS

module from the USACE DOTS website at www.wes.army.mil/el/dots. If desired,

equations for manual screening calculations are also available (Myers in

preparation).

The volatilization calculations in the spreadsheet yield COC concentrations at

the interface surface between air and the ponded water or the dredged material in

the CDF. Thus, they are somewhat analogous to effluent concentrations at the

point of release, before mixing is considered. A screening model for evaluation of

dispersion is therefore included in the Tier II spreadsheet calculations for volatiles

(Section 7.5).

7.3.2 Tier II - Volatile Emissions Decision

After consideration of the Tier II volatile emissions screen and dispersion

information, one of the following conclusions is reached for volatile emissions

(Figure 7-2):

1. Information is sufficient to reach a decision regarding volatile emissions.

In this case either:

a. Volatile emissions, after consideration of dispersion, are below

applicable OSHA standards. No further emissions evaluation is

necessary.

b. Volatile emissions, after consideration of dispersion, exceed

applicable OSHA standards, and management actions should be

considered. A decision to implement management actions for

emissions, such as a surface cove or treatment, may require more

detailed information prior to design of such actions. If management

actions are selected, no further emissions evaluation is necessary.

2. Information is not sufficient to reach a decision regarding volatile

emissions. Further evaluation in Tier III, or management actions as an

alternative to further evaluation, should be considered. A decision to

implement management actions for emissions, such as capping or

7-9

Chapter 7

Guidance for Evaluation of Volatile Emissions