Preliminary Public Dose Evaluation in Support of the Development of the
November 2012
Rare Element Resources Bear Lodge Project
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is expected that this pathway is not important, particularly when compared to
inhalation.
For this public dose evaluation, the inhalation of radon and particulates emitted from the
BLP is considered the most important pathway leading to potential public doses and the
only pathway considered.
4.1
Atmospheric Dispersion Model
There are many atmospheric dispersion models that could be used to estimate off-site impacts
from radon and particulate emissions from the BLP, including MILDOS-AREA, CAP-88,
AERMOD, and CALPUF. For this evaluation, AERMOD was chosen because of its ability to
consider complex terrain and surface effects and it is the EPA’s preferred model for both simple
and complex terrain.
AERMOD is a steady-state plume model that incorporates air dispersion based on planetary
boundary layer turbulence structure, scaling concepts including treatment of both surface and
elevated sources, and both simple and complex terrain. This assessment used BREEZE
AERMOD Version 7.6 air dispersion modeling software which couples the AERMOD computer
code to a user-friendly graphical user interface. Output from the AERMOD model was converted
to dose by using the dose conversion factors discussed below.
4.1.1
AERMOD Parameters
Most of the input parameters, including terrain and metrological data were obtained from Trinity
Consultants of Albuquerque, New Mexico. Source parameters, such as area size and location,
were established using Autocad files provided by RER.
4.1.2
Meteorology
The metrological data used was from Spearfish, South Dakota —Surface Station 72660 and
Upper Air Station 94043—from fourth quarter 2010 through third quarter 2011. Data from
Spearfish were used because this is the closest station to BLP with an acceptable uptime (greater
than 90 percent) over a one year period. The meteorological data files were pre-processed by
Trinity Consultants for use in BREEZE–AERMOD. Site-specific data are being collected but are
not complete at the time of this model development. This report is considered a preliminary
evaluation because it is expected that meteorological data from the Bear Lodge and Upton sites
will be used in future assessments.
4.1.3
Terrain Data
Terrain (topographical) data for the AERMOD model was analyzed using AERMAP, the
AERMOD terrain data pre-processor, prior to its use in AERMOD. The terrain data 7.5 minute
DEM files were obtained from Trinity Consultants with a 30 meter (m) resolution.
