EP
30 OCT 00
Develop an emission rate estimate using
project-specific models given in references
and
The emission rate estimate is used to
determine necessary emission control equipment for point sources. It is also used in dispersion
modeling for both point sources and area sources to determine if site emissions comply with
receptor point action levels. EPA's Office of Air Quality Planning and Standards Technology
Transfer Network (OAQPS-TTN) provides valuable information for estimating and measuring
emissions to the public at
a. Point Sources. These are stacks and vents on HTRW treatment process equipment.
Contaminants of concern include those present in the environmental medium undergoing
treatment, as well as chemicals used in the treatment process, or by-products of the treatment
process, which may be released to the air. Consult process engineering staff and
and to calculate emission rates from HTRW treatment process point sources. Be sure to
account for emission control technology if it is included in the design. Pilot-scale treatability
studies and existing full-scale treatment processes, where the processes and contaminants are
similar to the project under design, are valuable sources of information for estimating point
source emission rates.
These are ground level releases to the air over a specified surface area.
Examples of this type of a release on HTRW sites include excavations and associated material
handling activities, stockpiles, landfills, and lagoons. Emissions are calculated using models
specified in
and Emission rate modeling results can be made more realistic by
substituting site-specific data (e.g., moisture content, bulk density, particle size distribution, and
chemical and physical properties of the contaminants) for the default values specified in the
models.
Apply a two-tiered approach when performing
dispersion modeling for point sources. Do screening level modeling first, followed by refined
dispersion modeling if the results from the first model exceed receptor point action levels.
Dispersion modeling for area sources needs only to be done with screening level models.
a. Screening Models. TSCREEN or SCREEN3 are good screening level dispersion models
that can be applied to most HTRW remedial action scenarios for both point sources and area
sources. Both models are available to the public at no cost from the EPA's Support Center for
Regulatory Air Models (SCRAM) web site at
Models. Seek professional dispersion modeling support when doing refined
dispersion modeling for point sources when screening level modeling results exceed receptor
point action levels. Professional help is critical for selecting the model, evaluating
A-2
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