United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-96/126
November 1996
&EPA Project Summary
RAETRAD-F: Version 1.1 for
Analyzing Site-Specific
Measurements of Soil Radon
Potential Category for Florida
Houses
Vern Rogers, Kirk K. Nielson, Vern C. Rogers, and Rodger B. Holt
The RAETRAD-F (RAdon Emanation
and TRAnsport into Dwellings—Florida)
computer code provides a simple
means of analyzing site-specific soil
measurements to estimate upper-limit
indoor radon concentrations in a refer-
ence house at a site. The code uses
data from measured soil radium pro-
files, soil density and texture proper-
ties, water table depths, and soil radon
concentrations to estimate the poten-
tial indoor radon concentrations. It also
identifies the site's radon potential cat-
egory for use in lieu of its radon pro-
tection map designation.
This project summary was developed
by EPA's National Risk Management
Research Laboratory's Air Pollution
Prevention and Control Division, Re-
search Triangle Park, NC, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
The Florida Department of Community
Affairs, under the Florida Radon Research
Program (FRRP), has developed radon-
protective building standards to reduce ra-
don-related health risks. For residences,
these standards are given in the Florida
Standard for Passive Radon-Resistant
New Residential Building Construction.
This standard requires passive radon bar-
riers in counties that adopt it. An earlier
version of the standard contained more
detailed requirements for both passive and
active radon controls in areas identified
by a radon protection map to have el-
evated radon potential. Although no longer
part of the adopted standard, the radon
protection map and the related system for
selecting different levels of radon control
still provide useful guidance for residential
radon control. A protocol was also devel-
oped under the FRRP for measuring the
soil radon potential category of specific
sites in a way that corresponds to the
radon protection map designations.
The former standard required passive
radon barriers and active sub-slab ventila-
tion to reduce radon entry in regions that
are prone to elevated radon levels. Re-
gions requiring radon controls in new
house construction are identified by red or
yellow areas on the Florida Radon Pro-
tection Map. Regions where radon levels
in a reference house could exceed 8.3
pCi/L at a 95% confidence limit are identi-
fied as Red regions, requiring both active
and passive radon-protective features.
Regions where radon levels could exceed
4.0 pCi/L at a 95% confidence limit, but
not exceed 8.3 pCi/L, are identified as
Yellow regions, requiring only passive ra-
don-protective features. Regions with pro-
jected radon levels below 4.0 pCi/L at a
95% confidence limit require no special
building features beyond those required
by existing building codes. These regions
are identified as Green regions.
While the radon protection maps give
convenient regional guidance on the need
for special radon controls in new houses,
the building standard also recognizes mea-
surements of the radon potential category
of particular sites. Although site-specific
analyses are not generally required, they
can give valuable guidance in some cases.
For example, a prospective builder may
know of or suspect anomalous conditions
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at a site (from previous land use, soil or
mineral observations, etc.) that could in-
crease the radon potential above its
mapped category. Alternatively, the builder
may have reason to suspect that the land
has lower radon potential than its mapped
category, leading to the desire to reduce
or eliminate radon controls unless they
are specifically shown to be needed. In
either case, site-specific tests could help
lead to a more informed decision. The
decision should also consider the relative
costs of using conservative radon controls
versus testing, as well as the U.S. EPA
guidance on further reducing radon levels
even in the 0- to 4-pCi/L range.
The RAETRAD-F computer code was
developed for the Florida Department of
Community Affairs to analyze the site-spe-
cific measurements produced by the FRRP
protocol. The code's objective is to inter-
pret the measurements in terms of the
radon potential category of the site (Red,
Yellow, or Green) in a way that is consis-
tent with the radon protection maps.
RAETRAD-F is a special version of the
more general RAETRAD code. It contains
the reference house and corresponding
radium, water table, and statistical analy-
ses that correspond to the radon protec-
tion map calculations. RAETRAD-F uses
measured radium concentrations, soil den-
sity and texture, water table depths, and
soil gas radon concentrations to estimate
potential indoor radon levels and the ra-
don potential category of a site.
The RAETRAD Algorithm
RAETRAD-F computes potential indoor
radon concentrations as used in the ra-
don protection map. It first calculates the
geometric means and geometric standard
deviations of the measured soil radium
concentrations. It also determines the sea-
sonal water table distribution as defined
for the Florida Radon Protection Maps. It
then uses this information to compute best
estimates of indoor radon concentrations
for the different seasonal water table con-
ditions. After determining the geometric
mean annual radon concentration in the
reference house from seasonal values,
the variations among seasonal conditions
and among the radium concentrations are
used to estimate the potential radon con-
centration in the reference house at a
95% confidence limit.
RAETRAD-F employs an efficient, nu-
merical-analytical algorithm to solve the
steady-state air flow and radon genera-
tion and transport equations in two-dimen-
sional, elliptical-cylindrical geometry. It
uses complete, multiphase equations to
account for radon generation; radon ex-
change among solid, liquid, and gas
phases; and radon transport by diffusion
(concentration-driven) and advection (with
pressure-driven air flow).
Operating Environment
RAETRAD-F is designed to operate in
the Microsoft® Disk Operating System (MS-
DOS) environment only. As such, it will
not operate under the Microsoft® Windows
Operating environment. It is recommended
that the code be installed on a Microsoft/
Intel personal computer system equipped
with a mathematics co-processor, at least
4 Mbytes of RAM, and a printer.
RAETRAD-F Results
The RAETRAD-F output is divided into
four sections: site location, measurements,
results, and certification. The location sec-
tion shows the user-specified input infor-
mation with regard to the name of the
company performing the measurements,
the location of the test property, and the
name of the code user. This section also
gives the date and time of RAETRAD-F
analysis.
The measurements section shows the
user-specified input data for the soil char-
acteristics. These data include the indi-
vidual radium measurements, soil density
and texture data, soil radon measure-
ments, and water table information.
The results section is displayed in a
box following the location and measure-
ments sections. This section reports the
indoor radon potential in picocuries per
liter as well as the radon protection map
color category that corresponds to this
concentration. The user should note that
the indoor radon potential printed by
RAETRAD-F is an upper limit (95% confi-
dence limit) of the range of radon concen-
trations that could occur at the site, and is
therefore higher than the expected annual
average radon concentration. The code
determines the radon protection category
by comparing the indoor radon potential
concentration to the 4.0- and 8.3-pCi/L
cut points used in the radon protection
map.
The certification section at the bottom
of the printout allows both the RAETRAD-
F user and the agent for the company that
performed the measurements to certify that
the information used in the analysis is
correct.
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V. Rogers, K.K. Me/son, V.C. Rogers, and R.B. Holt are with Rogers & Associates
Engineering Corp., Salt Lake City, UT 84110-0330.
David C. Sanchez is the EPA Project Officer (see below).
The complete report, entitled "RAETRAD-F: Version 1.1 User's Guide for Analyzing
Site-Specific Measurements of Soil Radon Potential Category for Florida
Houses," (Order No. PB97-115364; Cost: $19.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air Pollution Prevention and Control Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information (G-72)
Cincinnati, OH 45268
Official Business
Penalty for Private Use $300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-96/126
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