Dispersion Models.

DOE-STD-3014-96

APPENDIX D

Figure D-2 is included to help the reader visualize the scenarios that are the end

points of the flowchart on Figure D-1. Figure D-2 contains more information

about important phenomena that must be addressed.

D.2.2 Dispersion Models. There is no "officially approved" model for the atmospheric

dispersion of hazardous chemical vapors. The two listed above, DEGADIS

(Reference 7) and SLAB (Reference 8), are in the public domain. The EPA has

developed a computer model, TSCREEN, that is suitable for several applications

in this area (Reference 9). Hanna et al. (Reference 10) evaluated 11 models

using data from nine field experiments. The EPA (Reference 11) and Touma

et al. (Reference 12) have also compared a number of heavy vapor models.

Each of the models mentioned in these references has various strengths and

weaknesses. The analyst must choose an appropriate model and justify its use.

D-6