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 7.1.5 Data Requirements
Data requirements for volatile emissions evaluations include those variables
specific to the proposed CDF operation. The predictive equations and models
used to evaluate volatilization require many assumptions, site variables, operating
variables, and chemical properties. The information used in volatile evaluations
should be specific to the proposed CDF and disposal operation. Project specific
information such as CDF size, area of each deposit event, exposure, wind speed,
temperature, and physical and chemical characteristics of the dredged material are
required for evaluating air quality as a result of volatilization. A summary of the
data requirements for volatile emissions predictions is given in Table 7-1.
Table 7-1
Variables for Volatile Emissions Evaluation
1. Total area of CDF
2. Available area for each deposit event
3. Disposal frequency
4. Daily worker exposure period to exposed material
5. Daily worker exposure period to ponded material
6. Air exchange control volume
7. Bulk density of dredged material
8. Contaminant concentration in pore water
9. Contaminant concentration in ponded water
10. Wind-driven currents in ponded water (assumed to be 3% of wind speed)
11. Wind speed and direction
12. Fetch length
13. Average weight of worker
14. Minute ventilation
15. Molecular wt. of air
16. Molar volume of air
17. Universal gas constant
18. Contaminant diffusivity in water
19. Atmospheric pressure
20. Temperature
21. Total porosity of dredged material
22. Air-filled porosity of drying material
23. Partitioning coefficient
24. Henry's Law constant of contaminant
25. Vapor pressure of contaminant
26. Molecular weight of contaminant
27. Solubility of contaminant
28. Water depth
29. Receptors
30. Receptors location
7.1.6 Summary of Tiered Evaluations for Volatile Emissions
A flowchart illustrating the tiered evaluation for volatilization is shown in
Figure 7-2. If a decision regarding volatile emissions cannot be reached based on
the evaluation of existing information in Tier I, Tier II provides a method for
volatile emissions screening based on conservative assumptions. Tier III consists
of a laboratory test for prediction of volatile flux rate from exposed sediment.
Both the Tier II and Tier III evaluations consider dispersion of the volatile
emissions at the CDF as a part of the evaluation. The evaluations in Tiers II and
III will be sufficient for evaluation of volatile emissions in the vast majority of
cases. As with all pathways, Tier IV evaluations involve consideration of
volatilization within the framework of a risk assessment.
7-5
Chapter 7
Guidance for Evaluation of Volatile Emissions
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