Draft Environmental Impact Statement for Roca Honda Mine

Chapter 3. Affected Environment and Environmental Consequences
Regarding worker safety in the mine itself, radon-222
exposures are regulated by the Mine Safety and Health
Administration (MSHA), the Federal enforcement agency
responsible for the health and safety of America’s miners.
These exposures are limited at 4 working level months
(WLM). With proper ventilation and personal protection
equipment (PPE), worker exposures would be below this
level. If the operator cannot demonstrate compliance, the
mine will be shut down. Furthermore, smoking is not
allowed in underground uranium mines (Schierman, 2012).
The tools used to evaluate the dose to any member of the
public (i.e., the environmental consequence) are prescribed
by Federal law.
40 CFR 61.23 states…“Compliance with the
emission standard in this subpart shall be determined
and the effective dose equivalent calculated by the
U.S. Environmental Protection Agency (EPA)
computer code COMPLY-R”.
COMPLY-R is a computer program that may be used to demonstrate compliance with the national
emissions standards for hazardous air pollutants (NESHAPS) in 40 CFR 61, Subpart B. It can
also be used as a predictive tool to evaluate potential but unmeasurable impacts of a proposed
uranium mine provided reasonable assumptions and site-specific information where available are
used as input to the computer program. COMPLY-R requires the following information as input:
• The number of radon-222 release points, typically mine vents
• The radon-222 release rate
• The release height from the ground surface of each release point
• Mine vent diameter
• Volumetric flow rate from each release point or vent
• Distance from each release point to each receptor
• Ventilated and ambient air temperatures
• Annual average wind speed or wind frequency distribution data
Working Level Month
The working level month (WLM) is
a common unit of exposure of
miners’ lung tissue to one type of
radioactivity called alpha
emissions. The WLM is when
human lungs have been exposed for
170 hours (a typical month’s work)
to air which has 3.7 kBq of radon-
222. This is air with an alpha dose
rate of one working level (WL).
The average person in the general
public is estimated to be subject to
0.2 WLM per year, which adds up
to a total exposure of approximately
15–20 WLM in a typical lifetime.
In humans a relationship has been
established between lung
cancer and radon-222 exposure for
levels of 100 WLM and above.
Realistic and reasonable results from the COMPY-R computer code are dependent on realistic
and reasonable input parameters. The use of site-specific information as input to COMPLY-R is
clearly the most realistic and should be used when available. There are cases where site-specific
information is not available and estimates are necessary. A description of each input item
identified above is provided below. Site-specific information is identified and, in cases where
estimates are needed, the assumptions and methods to derive these estimates are provided.
The following information was provided by RHR in two documents entitled “Modeling of Dose
Due to Radon Emissions from the Proposed Roca Honda Mine, New Mexico” (SENES, 2012a)
190 DEIS for Roca Honda Mine, Cibola National Forest