United States
Environmental Protection
Agency
Air and Radiation
(6604J)
402-R-93-069
September 1993
oEPA EPA's Map of Radon Zones
WISCONSIN
Printed on Recycled Paper
-------
-------
EPA'S MAP OF RADON ZONES
WISCONSIN
RADON DIVISION
OFFICE OF RADIATION AND INDOOR AIR
U.S. ENVIRONMENTAL PROTECTION AGENCY
SEPTEMBER, 1993
-------
-------
ACKNOWLEDGEMENTS
This document was prepared by the U.S. Environmental Protection Agency's (EPA's)
Office of Radiation and Indoor Air (ORIA) in conjunction with the U.S. Geological Survey
(USGS). Sharon W. White was the EPA project manager. Numerous other people in ORIA
were instrumental in the development of the Map of Radon Zones, including Lisa Ratcliff,
Kirk Maconaughey, R. Thomas Peake, Dave Rowson, and Steve Page.
EPA would especially like to acknowledge the outstanding effort of the USGS
radon team — Linda Gundersen, Randy Schumann, Jim Otton, Doug Owen, Russell
Dubiel, Kendell Dickinson, and Sandra Szarzi - in developing the technical base for the
Map of Radon Zones.
ORIA would also like to recognize the efforts of all the EPA Regional Offices in
coordinating the reviews with the State programs and the Association of American State
Geologists (AASG) for providing a liaison with the State geological surveys. In addition,
appreciation is expressed to all of the State radon programs and geological surveys for their
technical input and review of the Map of Radon Zones.
-------
-------
TABLE OF CONTENTS
I. OVERVIEW
II. THE USGS/EPA RADON POTENTIAL
ASSESSMENTS:INTRODUCTION
III. REGION 5 GEOLOGIC RADON POTENTIAL
SUMMARY
V. PRELIMINARY GEOLOGIC RADON POTENTIAL
ASSESSMENT OF WISCONSIN
V. EPA'S MAP OF RADON ZONES - WISCONSIN
-------
-------
OVERVIEW
Sections 307 and 309 of the 1988 Indoor Radon Abatement Act (IRAA) direct EPA to
identify areas of the United States that have the potential to produce elevated levels of radon.
EPA, the U.S. Geological Survey (USGS), and the Association of American State Geologists
(AASG) have worked closely over the past several years to produce a series of maps and
documents which address these directives. The EPA Map of Radon Zones is a compilation of
that work and fulfills the requirements of sections 307 and 309 of IRAA. The Map of Radon
Zones identifies, on a county-by-county basis, areas of the U.S. that have the highest potential
for elevated indoor radon levels (greater than 4 pCi/L).
The Map of Radon Zones is designed to assist national, State and local governments
and organizations to target their radon program activities and resources. It is also intended to
help building code officials determine areas that are the highest priority for adopting radon-
resistant building practices. The Map of Radon Zones should not be used to determine if
individual homes in any given area need to be tested for radon. EPA recommends that all
homes be tested for radon, regardless of geographic location or the zone designation of
the county in which they are located.
This document provides background information concerning the development of the
Map of Radon Zones. It explains the purposes of the map, the approach for developing the
map (including the respective roles of EPA and USGS), the data sources used, the conclusions
and confidence levels developed for the prediction of radon potential, and the review process
that was conducted to finalize this effort.
BACKGROUND
Radon (Rn222) is a colorless, odorless, radioactive gas. It comes from the natural
decay of uranium that is found in nearly all soils. It typically moves through the ground to
the air above and into homes and other buildings through cracks and openings in the
foundation. Any home, school or workplace may have a radon problem, regardless of
whether it is new or old, well-sealed or drafty, or with or without a basement. Nearly one out
of every 15 homes in the U.S. is estimated to have elevated annual average levels of indoor
radon.
Radon first gained national attention in early 1984, when extremely high levels of
indoor radon were found in areas of Pennsylvania, New Jersey, and New York, along the
Reading Prong-physiographic province. EPA established a Radon Program in 1985 to assist
States and homeowners in reducing their risk of lung cancer from indoor radon.
Since 1985, EPA and USGS have been working together to continually increase our
understanding of radon sources and the migration dynamics that cause elevated indoor radon
levels. Early efforts resulted in the 1987 map entitled "Areas with Potentially High Radon
Levels." This map was based on limited geologic information only because few indoor radon
measurements were available at the time. The development of EPA's Map of Radon Zones
and its technical foundation, USGS' National Geologic Radon Province Map, has been based
on additional information from six years of the State/EPA Residential Radon Surveys,
independent State residential surveys, and continued expansion of geologic and geophysical
information, particularly the data from the National Uranium Resource Evaluation project.
1-1
-------
Purpose of the Map of Radon Zones
EPA's Map of Radon Zones (Figure 1) assigns each of the 3141 counties in the
United States to one of three zones:
o Zone 1 counties have a predicted average indoor screening level > than
4 pCi/L
o Zone 2 counties have a predicted average screening level > 2 pCi/L and
^ 4 pCi/L
o Zone 3 counties have a predicted average screening level < 2 pCi/L
The Zone designations were determined by assessing five factors that are known to be
important indicators of radon potential: indoor radon measurements, geology aerial
radioactivity, soil parameters, and foundation types.
The predictions of average screening levels in each of the Zones is an expression of
radpn potential in the lowest liveable area of a structure. This map is unable to estimate
actual exposures to radon. EPA recommends methods for testing and fixing individual homes
based on an estimate of actual exposure to radon. For more information on testing and fixinq
elevated radon levels in homes consult these EPA publications: A Citizen's Guide to Radon
the Consumer's Guide to Radon Reduction and the Home Buyer's and Seller's Guide to
Radon.
EPA believes that States, local governments and other organizations can achieve
optimal risk reductions by targeting resources and program activities to high radon potential
areas. Emphasizing targeted approaches (technical assistance, information and outreach
efforts, promotion of real estate mandates and policies and building codes, etc.) in such areas
addresses the greatest potential risks first.
EPA also believes that the use of passive radon control systems in the construction of
new homes in Zone 1 counties, and the activation of those systems if necessitated by follow-
up testing, is a cost effective approach to achieving significant radon risk reduction.
The Map of Radon Zones and its supporting documentation establish no regulatory
requirements Use of this map by State or local radon programs and building code officials is
voluntary. The information presented on the Map of Radon Zones and in the supporting
documentation is not applicable to radon in water.
Development of the Map of Radon Zones
The technical foundation for the Map of Radon Zones is the USGS Geologic Radon
Province Map. In order to examine the radon potential for the United States the USGS
began by identifying approximately 360 separate geologic provinces for the U S The
provinces are shown on the USGS Geologic Radon Province Map (Figure 2) Each of the
geologic provinces was evaluated by examining the available data for that area- indoor radon
measurements, geology, aerial radioactivity, soil parameters, and foundation types As stated
previously, these five factors are considered to be of basic importance in assessing radon
1-2
-------
a
o
S3
fl
o
§D
•9 .^
I'3
.o o
£:§
c c
-§ o
e °-
_ C
o
k-l
3
03
5i
•c.
"QI
o^
-S
g
.0
!
"5
T3
C
D
JU
-S
~~.*
V.
5
•^
•Q
O
"S
a>
N
|
o
•S
c
•C
J^
1
8,
t
o
Ol
o
1
1
Ol
1
n
6
"c
0
o
"p
1
(J
•&
.w
g-
6
?
i
j)
."o
1
Q.
C
O
e
-S
§
fe
I
o
!
.s
a
1
^.
*» -Q
fv, O
°1
o
-------
00
O)
CO
-------
potential and some data are available for each of these factors in every geologic province. The
province boundaries do not coincide with political borders (county and state) but define areas
of general radon potential. The five factors were assigned numerical values based on an
assessment of th'eir respective contribution to radon potential, and a confidence level was
assigned to each contributing variable. The approach used by USGS to estimate the radon
potential for each province is described in Part II of this document.
EPA subsequently developed the Map of Radon Zones by extrapolating from the
province level to the county level so that all counties in the U.S. were assigned to one of
three radon zones. EPA assigned each county to a given zone based on its provincial radon
potential. For example, if a county is located within a geologic province that has a predicted
average screening level greater than 4 pCi/L, it was assigned to Zone 1. Likewise, counties •
located in provinces with predicted average screening levels > 2 pCi/L and < 4 pCi/L, and
less than 2 pCi/L, were assigned to Zones 2 and 3, respectively.
If the boundaries of a county fall in more than one geologic province, the county was
assigned to a zone based on the predicted radon potential of the province in which most of
the area lies. For example, if three different provinces cross through a given county, the
county was assigned to the zone representing the radon potential of the province containing
most of the county's land area. (In this case, it is not technically correct to say that the
predicted average screening level applies to the entire county since the county falls in
multiple provinces with differing radon potentials.)
Figures 3 and 4 demonstrate an example of how EPA extrapolated the county zone
designations for Nebraska from the USGS geologic province map for the State. As figure 3
shows, USGS has identified 5 geologic provinces for Nebraska. Most of the counties are
extrapolated "straight" from their corresponding provinces, but there are counties "partitioned"
by several provinces -- for example, Lincoln County. Although Lincoln county falls in
multiple provinces, it was assigned to Zone 3 because most of its area falls in the province
with the lowest radon potential.
It is important to note that EPA's extrapolation from the province level to the
county level may mask significant "highs" and "lows" within specific counties. In other
words, within-county variations in radon potential are not shown on the Map of Radon
Zones. EPA recommends that users who may need to address specific within-county
variations in radon potential (e.g., local government officials considering the
implementation of radon-resistant construction codes) consult USGS' Geologic Radon
Province Map and the State chapters provided with this map for more detailed
information, as well as any locally available data.
Map Validation
The Map of Radon Zones is intended to represent a preliminary assessment of radon
potential for the entire United States. The factors that are used in this effort -indoor radon
data, geology, aerial radioactivity, soils, and foundation type « are basic indicators for radon
potential. It is important to note, however, that the map's county zone designations are not
"statistically valid" predictions due to the nature of the data available for these 5 factors at the
county level. In order to validate the map in light of this lack of statistical confidence, EPA
conducted a number of analyses. These analyses have helped EPA to identify the best
situations in which to apply the map, and its limitations.
1-5
-------
Figure 3
Geologic Radon Potential Provinces for Nebraska
Lincoln County
Bill Modern: Low
Figure 4
NEBRASKA - EPA Map of Radon Zones
Lincoln County
Zsat I Zoae 2 Zone 3
1-6
-------
One such analysis involved comparing county zone designations to indoor radon
measurements from the State/EPA Residential Radon Surveys (SRRS). Screening averages
for counties with1 at least 100 measurements were compared to the counties' predicted radon
potential as indicated by the Map of Radon Zones. EPA found that 72% of the county
screening averages were correctly reflected by the appropriate zone designations on the Map.
In all other cases, they only differed by 1 zone.
Another accuracy analysis used the annual average data from the National Residential
Radon Survey (NRRS). The NRRS indicated that approximately 6 million homes in the
United States have annual averages greater than or equal to 4 pCi/L. By cross checking the
county location of the approximately 5,700 homes which participated in the survey, their
radon measurements, and the zone designations for these counties, EPA found that'
approximately 3.8 million homes of the 5.4 million homes with radon levels greater than or
equal to 4 pCi/L will be found in counties designated as Zone 1. A random sampling of an
equal number of counties would have only found approximately 1.8 million homes greater
than 4 pCi/L. In other words, this analysis indicated that the map approach is three times
more efficient at identifying high radon areas than random selection of zone designations.
Together, these analyses show that the approach EPA used to develop the Map of
Radon Zones is a reasonable one. In addition, the Agency's confidence is enhanced by results
of the extensive State review process -- the map generally agrees with the States' knowledge
of and experience in their own jurisdictions. However, the accuracy analyses highlight two
important points: the fact that elevated levels will be found in Zones 2 and 3, and that there
will be significant numbers of homes with lower indoor radon levels in all of'the Zones. For
these reasons, users of the Map of Radon Zones need to supplement the Map with locally
available data whenever possible. Although all known "hot spots", i.e., localized areas of
consistently elevated levels, are discussed in the State-
specific chapters, accurately defining the boundaries of the "hot spots" on this scale of map is
not possible at this time. Also, unknown "hot spots" do exist.
The Map of Radon Zones is intended to be a starting point for characterizing radon
potential because our knowledge of radon sources and transport is always growing. Although
this effort represents the best data available at this time, EPA will continue to study these
parameters and others such as house construction, ventilation features and meteorology factors
in order to better characterize the presence of radon in U.S homes, especially in high risk
areas. These efforts will eventually assist EPA in refining and revising the conclusions of the
Map of Radon Zones. And although this map is most appropriately used as a targeting tool
by the aforementioned audiences -- the Agency encourages all residents to test their homes
for radon, regardless of geographic location or the zone designation of the county in
which they live. Similarly, the Map of Radon Zones should not to be used in lieu of
testing during real estate transactions.
Review Process
The Map of Radon Zones has undergone extensive review within EPA and outside the
Agency. The Association of American State Geologists (AASG) played an integral role in
this review process. The AASG individual State geologists have reviewed their State-specific
information, the USGS Geologic Radon Province Map, and other materials for their geologic
content and consistency.
1-7
-------
In addition to each State geologist providing technical comments, the State radon
offices were asked to co-mment on their respective States' radon potential evaluations In
particular, the States were asked to evaluate the data used to assign their counties to specific
zones. EPA and USGS worked with the States to resolve any issues concerning county zone
''eeignattons. In a few cases, States have requested Changes in connty zone delations The
requests were based on additional data from the State on geology, indoor radon
measurements, population, etc. Upon reviewing the data submitted by the States, EPA did
make some changes in zone designations. These changes, which do not strictly follow the
methodology outlined in this document, are discussed in the respective State chapters
EPA encourages the States and counties to conduct further research and data collection
efforts to refine the Map of Radon Zones. EPA would like to be kept informed of any
changes the States, counties, or others make to the maps. Updates and revisions will be
handled in a similar fashion to the way the map was developed. States should notify EPA of
any proposed changes by forwarding the changes through the Regional EPA offices that are
listed in Part II. Depending on the amount of new information that is presented EPA will
consider updating this map periodically. The State radon programs should initiate proper
notification of the appropriate State officials when the Map of Radon Zones is released and
when revisions or updates are made by the State or EPA.
1-8
-------
THE USGS/EPA RADON POTENTIAL ASSESSMENTS: AN INTRODUCTION
by
Linda C.S. Gundersen and R. Randall Schumann
U.S. Geological Survey
and
Sharon W. White
U.S. Environmental Protection Agency
BACKGROUND
The Indoor Radon Abatement Act of 1988 (15 U.S.C. 2661-2671) directed the U.S.
Environmental Protection Agency (EPA) to identify areas of the United States that have the
potential to produce harmful levels of indoor radon. These characterizations were to be based
on both geological data and on indoor radon levels in homes and other structures. The EPA
also was directed to develop model standards and techniques for new building construction
that would provide adequate prevention or mitigation of radon entry. As part of an
Interagency Agreement between the EPA and the U.S. Geological Survey (USGS), the USGS
has prepared radon potential estimates for the United States. This report is one of ten
booklets that document this effort. The purpose and intended use of these reports is to help
identify areas where states can target their radon program resources, to provide guidance in
selecting the most appropriate building code options for areas, and to provide general
information on radon and geology for each state for federal, state, and municipal officials
dealing with radon issues. These reports are not intended to be used as a substitute for
indoor radon testing, and they cannot and should not be used to estimate or predict the
indoor radon concentrations of individual homes, building sites, or housing tracts. Elevated
levels of indoor radon have been found in every State, and EPA recommends that all homes
be tested for indoor radon.
Booklets detailing the radon potential assessment for the U.S. have been developed for
each State. USGS geologists are the authors of the geologic radon potential booklets. Each
booklet consists of several components, the first being an overview to the mapping project
(Part I), this introduction to the USGS assessment (Part II), including a general discussion of
radon (occurrence, transport, etc.), and details concerning the types of data used. The third
component is a summary chapter outlining the general geology and geologic radon potential
of the EPA Region (Part III). The fourth component is an individual chapter for each state
(Part IV). Each state chapter discusses the state's specific geographic setting, soils, geologic
setting, geologic radon potential, indoor radon data, and a summary outlining the radon
potential rankings of geologic areas in the state. A variety of maps are presented in each
chapter—geologic, geographic, population, soils, aerial radioactivity, and indoor radon data by
county. Finally, the booklets contain EPA's map of radon zones for each state and an
accompanying description (Part V).
Because of constraints on the scales of maps presented in these reports and because the
smallest units used to present the indoor radon data are counties, some generalizations have
been made in order to estimate the radon potential of each area. Variations in geology, soil
characteristics, climatic factors, homeowner lifestyles, and other factors that influence radon
concentrations can be quite large within any particular geologic area, so these reports cannot
be used to estimate or predict the indoor radon concentrations of individual homes or housing
II-l Reprinted from USGS Open-File Report 93-292
-------
tracts. Within any area of a given geologic radon potential ranking, there are likely to be
areas where the. radon potential is lower or higher than that assigned to the area as a whole,
especially in larger areas such as the large counties in some western states.
In each state chapter, references to additional reports related to radon are listed for the
state, and the reader is urged to consult these reports for more detailed information. In most
cases the best sources of information on radon for specific areas are state and local
departments of health, state departments responsible for nuclear safety or environmental
protection, and U.S. EPA regional offices. More detailed information on state or local
geology may be obtained from the state geological surveys. Addresses and telephone
numbers of state radon contacts, geological surveys, and EPA regional offices are listed in
Appendix C at the end of this chapter.
RADON GENERATION AND TRANSPORT IN SOILS
Radon-(223Rn) is produced from the radioactive decay of radium (226Ra), which is, in turn,
a product of the decay of uranium (238U) (fig. 1). The half-life of 222Rn is 3.825 days. Other
isotopes of radon occur naturally, but, with the exception of thoron (220Rn), which occurs in
concentrations high enough to be of concern in a few localized areas, they are less important
in terms of indoor radon risk because of their extremely short half-lives and less common
occurrence. In general, the concentration and mobility of radon in soil are dependent on
several factors, the most important of which are the soil's radium content and distribution,
porosity, permeability to gas movement, and moisture content. These characteristics are, in
turn, determined by the soil's parent-material composition, climate, and the soil's age or
maturity. If parent-material composition, climate, vegetation, age of the soil, and topography
are known, the physical and chemical properties of a soil in a given area can be predicted.
As soils form, they develop distinct layers, or horizons, that are cumulatively called the
soil profile. The A horizon is a surface or near-surface horizon containing a relative
abundance of organic matter but dominated by mineral matter. Some soils contain an E
horizon, directly below the A horizon, that is generally characterized by loss of clays, iron, or
aluminum, and has a characteristically lighter color than the A horizon. The B horizon
underlies the A or E horizon. Important characteristics of B horizons include accumulation of
clays, iron oxides, calcium carbonate or other soluble salts, and organic matter complexes. In
drier environments, a horizon may exist within or below the B horizon that is dominated by
calcium carbonate, often called caliche or calcrete. This carbonate-cemented horizon is
designated the K horizon in modern soil classification schemes. The C horizon underlies the
B (or K) and is a zone of weathered parent material that does not exhibit characteristics of A
or B horizons; that is, it is generally not a zone of leaching or accumulation. In soils formed
in place from the underlying bedrock, the C horizon is a zone of unconsolidated, weathered
bedrock overlying the unweathered bedrock.
The shape and orientation of soil particles (soil structure) control permeability and affect
water movement in the soil. Soils with blocky or granular structure have roughly equivalent
permeabilities in the horizontal and vertical directions, and air and water can infiltrate the soil
relatively easily. However, in soils with platy structure, horizontal permeability is much
greater than vertical permeability, and air and moisture infiltration is generally slow. Soils
with prismatic or columnar structure have dominantly vertical permeability. Platy and
prismatic structures form in soils with high clay contents. In soils with shrink-swell clays, air
II-2 Reprinted from USGS Open-File Report 93-292
-------
T3
g
I
O
I
*•*
T3
eo
a
O
s
ft
Js-o
S3
•s
K O
e
COCO.
(U >
•C >»
8
oo c
f^ on
-------
and moisture infiltration rates and depth of wetting may be limited when the cracks in the
surface soil layers swell shut. Clay-rich B horizons, particularly those with massive or platy
structure, can form a capping layer that impedes the escape of soil gas to the surface
(Schumann and others, 1992). However, the shrinkage of clays can act to open or widen
cracks upon drying, thus increasing the soil's permeability to gas fiow during diier periods.
Radon transport in soils occurs by two processes: (1) diffusion and (2) flow (Tanner,
1964). Diffusion is the process whereby radon atoms move from areas of higher
concentration to areas of lower concentration in response to a concentration gradient. Flow is
the process by which soil air moves through soil pores in response to differences in pressure •
within the soil or between the soil and the atmosphere, carrying the radon atoms along with it.
Diffusion is the dominant radon transport process in soils of low permeability, whereas flow
tends to dominate in highly permeable soils (Sextro and others, 1987). In low-permeability
soils, much of the radon may decay before it is able to enter a building because its transport
rate is reduced. Conversely, highly permeable soils, even those that are relatively low in
radium, such as those derived from some types of glacial deposits, have been associated with
high indoor radon levels in Europe and in the northern United States (Akerblom and others,
1984; Kunz and others, 1989; Sextro and others, 1987). In areas of karst topography formed
in carbonate rock (limestone or dolomite) environments, solution cavities and fissures can
increase soil permeability at depth by providing additional pathways for gas flow.
Not all radium contained in soil grains and grain coatings will result in mobile radon
when the radium decays. Depending on where the radium is distributed in the soil, many of
the radon atoms may remain imbedded in the soil grain containing the parent radium atom, or
become imbedded in adjacent soil grains. The portion of radium that releases radon into the
pores and fractures of rocks and soils is called the emanating fraction. When a radium atom
decays to radon, the energy generated is strong enough to send the radon atom a distance of
about 40 nanometers (1 nm = 10'9 meters), or about 2x10"* inches—this is known as alpha
recoil (Tanner, 1980). Moisture in the soil lessens the chance of a recoiling radon atom
becoming imbedded in an adjacent grain. Because water is more dense than air, a radon atom
will travel a shorter distance in a water-filled pore than in an air-filled pore, thus increasing
the likelihood that the radon atom will remain in the pore space. Intermediate moisture levels
enhance radon emanation but do not significantly affect permeability. However, high
moisture levels can significantly decrease the gas permeability of the soil and impede radon
movement through the soil.
Concentrations of radon in soils are generally many times higher than those inside of
buildings, ranging from tens of pCi/L to more than 100,000 pCi/L, but typically in the range
of hundreds to low thousands of pCi/L. Soil-gas radon concentrations can vary in response to
variations in climate and weather on hourly, daily, or seasonal time scales. Schumann and
others (1992) and Rose and others (1988) recorded order-of-magnitude variations in soil-gas
radon concentrations between seasons in Colorado and Pennsylvania. The most important
factors appear to be (1) soil moisture conditions, which are controlled in large part by
precipitation; (2) barometric pressure; and (3) temperature. Washington and Rose (1990)
suggest that temperature-controlled partitioning of radon between water and gas in soil pores
also has a significant influence on the amount of mobile radon in soil gas.
Homes in hilly limestone regions of the southern Appalachians were found to have higher
indoor radon concentrations during the summer than in the winter. A suggested cause for this
phenomenon involves temperature/pressure-driven flow of radon-laden air from subsurface
II-4 Reprinted from USGS Open-File Report 93-292
-------
solution cavities in the carbonate rock into houses. As warm air enters solution cavities that
are higher on the hillslope than the homes, it cools and settles, pushing radon-laden air from
lower in the cave or cavity system into structures on the hillslope (Gammage and others,
1993). In contrast, homes built over caves having openings situated below the level of the
home had higher indoor radon levels in the winter, caused by cooler outside air entering the
cave, driving radon-laden air into cracks and solution cavities in the rock and soil, and
ultimately, into homes (Gammage and others, 1993).
RADON ENTRY INTO BUILDINGS
A driving force (reduced atmospheric pressure in the house relative to the soil, producing
a pressure gradient) and entry points must exist for radon to enter a building from the soil.
The negative pressure caused by furnace combustion, ventilation devices, and the stack effect
(the rising and escape of warm air from the upper floors of the building, causing a
temperature and pressure gradient within the structure) during cold winter months are
common driving forces. Cracks and other penetrations through building foundations, sump
holes, and slab-to-foundation wall joints are common entry points.
Radon levels in the basement are generally higher than those on the main floor or upper
floors of most structures. Homes with basements generally provide more entry points for
radon, commonly have a more pronounced stack effect, and typically have lower air pressure
relative to the surrounding soil than nonbasement homes. The term "nonbasement" applies to
slab-on-grade or crawl space construction.
METHODS AND SOURCES OF DATA
The assessments of radon potential in the booklets that follow this introduction were
made using five main types of data: (1) geologic (lithologic); (2) aerial radiometric; (3) soil
characteristics, including soil moisture, permeability, and drainage characteristics; (4) indoor
radon data; and (5) building architecture (specifically, whether homes in each area are built
slab-on-grade or have a basement or crawl space). These five factors were evaluated and
integrated to produce estimates of radon potential. Field measurements of soil-gas radon or
soil radioactivity were not used except where such data were available in existing, published
reports of local field studies. Where applicable, such field studies are described in the
individual state chapters.
GEOLOGIC DATA
The types and distribution of lithologic units and other geologic features in an
assessment area are of primary importance in determining radon potential. Rock types that
are most likely to cause indoor radon problems include carbonaceous black shales, glauconite-
bearing sandstones, certain kinds of fluvial sandstones and fluvial sediments, phosphorites,
chalk, karst-producing carbonate rocks, certain kinds of glacial deposits, bauxite, uranium-rich
granitic rocks, metamorphic rocks of granitic composition, silica-rich volcanic rocks, many
sheared or faulted rocks, some coals, and certain kinds of contact metamorphosed rocks.
Rock types least likely to cause radon problems include marine quartz sands, non-
carbonaceous shales and siltstones, certain kinds of clays, silica-poor metamorphic and
H-5 Reprinted from USGS Open-File Report 93-292
-------
igneous rocks, and basalts. Exceptions exist within these general lithologic groups because of
the occurrence of localized uranium deposits, commonly of the hydrothermal type in
crystalline rocks or the "roll-front" type in sedimentary rocks. Uranium and radium are
commonly sited in heavy minerals, iron-oxide coatings on rock and soil grains, and organic
materials in soils and sediments. Less common are uranium associated with phosphate and
carbonate complexes in rocks and soils, and uranium minerals.
Although many cases of elevated indoor radon levels can be traced to high radium and
(or) uranium concentrations in parent rocks, some structural features, most notably faults and
shear zones, have been identified as sites of localized uranium concentrations (Deffeyes and '
MacGregor, 1980) and have been associated with some of the highest reported indoor radon
levels (Gundersen, 1991). The two highest known indoor radon occurrences are associated
with sheared fault zones in Boyertown, Pennsylvania (Gundersen and others, 1988a; Smith
and others, 1987), and in Clinton, New Jersey (Henry and others, 1991: Muessie and Bell
1988).
NURE AERIAL RADIOMETRIC DATA
Aerial radiometric data are used to quantify the radioactivity of rocks and soils.
Equivalent uranium (eU) data provide an estimate of the surficial concentrations of radon
parent materials (uranium, radium) in rocks and soils. Equivalent uranium is calculated from
the counts received by a gamma-ray detector from the 1.76 MeV (mega-electron volts)
emission energy corresponding to bismuth-214 (»
-------
FLIGHT LINE SPACING OF SURE AERIAL SURVEYS
2 KU (1 VILE)
5 KH (3 HILES)
2 * 5 KM
ES 10 EU {£ UILES)
5 k 10 IM
NO DATA
Figure 2. Nominal flightline spacings for NURE aerial gamma-ray surveys covering the
contiguous United States (from Duval and others, 1990). Rectangles represent I°x2° quadrangles.
-------
Figure 2 is an index- map of NURE 1° x 2° quadrangles showing the flight-line spacing .
for each quadrangle. In general, the more closely spaced the flightlines are, the more area
was covered by the aerial gamma survey, and thus, more detail is available in the data set.
For an altitude of 400 ft above the ground surface and with primary flightline spacing
typically between 3 and 6 miles, less than 10 percent of the ground surface of the United
States was actually measured by the airborne gamma-ray detectors (Duval and others, 1989),
although some areas had better coverage than others due to the differences in flight-line
spacing between areas (fig. 2). This suggests that some localized uranium anomalies may not
have been detected by the aerial surveys, but the good correlations of elJ patterns with
geologic outcrop patterns indicate that, at relatively small scales (approximately 1:1,000,000
or smaller) the National eU map (Duval and others, 1989) gives reasonably good estimates of
average surface uranium concentrations and thus can assist in the prediction of radon potential
of rocks and soils, especially when augmented with additional geologic and soil data.
The shallow (20-30 cm) depth of investigation of gamma-ray spectrometers, either
ground-based or airborne (Duval and others, 1971; Durrance, 1986), suggests that gamma-ray
data may sometimes underestimate the radon-source strength in soils in which some of the
radionuclides in the near-surface soil layers have been transported downward through the soil
profile. In such cases the concentration of radioactive minerals in the A horizon would be
lower than in the B horizon, where such minerals are typically concentrated. The
concentration of radionuclides in the C horizon and below may be relatively unaffected by
surface solution processes. Under these conditions the surface gamma-ray signal may indicate
a lower radon source concentration than actually exists in the deeper soil layers, which are
most likely to affect radon levels in structures with basements. The redistribution of
radionuclides in soil profiles is dependent on a combination of climatic, geologic, and
gee-chemical factors. There is reason to believe that correlations of eU with actual soil
radium and uranium concentrations at a depth relevant to radon entry into structures may be
regionally variable (Duval, 1989; Schumann and Gundersen, 1991). Given sufficient
understanding of the factors cited above, these regional differences may be predictable.
SOIL SURVEY DATA
Soil surveys prepared by the U.S. Soil Conservation Service (SCS) provide data on soil
characteristics, including soil-cover thickness, grain-size distribution, permeability, shrink-
swell potential, vegetative cover, generalized groundwater characteristics, and land use. The
reports are available in county formats and State summaries. The county reports typically
contain both generalized and detailed maps of soils in the area.
Because of time and map-scale constraints, it was impractical to examine county soil
reports for each county in the United States, so more generalized summaries at appropriate
scales were used where available. For State or regional-scale radon characterizations, soil
maps were compared to geologic maps of the area, and the soil descriptions, shrink-swell
potential, drainage characteristics, depth to seasonal high water table, permeability, and other
relevant characteristics of each soil group noted. Technical soil terms used in soil surveys are
generally complex; however, a good summary of soil engineering terms and the national
distribution of technical soil types is the "Soils" sheet of the National Atlas (U.S. Department
of Agriculture, 1987).
II-8 Reprinted from USGS Open-File Report 93-292
-------
Soil permeability is commonly expressed in SCS soil surveys in terms of the speed, in
inches per hour (in/hr), ^t which water soaks into the soil, as measured in a soil percolation
test. Although in/hr are not truly units of permeability, these units are in widespread use and
are referred to as "permeability" in SCS soil surveys. The permeabilities listed in the SCS
surveys are for water, but they generally correlate well with gas permeability. Because data
on gas permeability of soils is extremely limited, data on permeability to water is used as a
substitute except in cases in which excessive soil moisture is known to exist. Water in soil
pores inhibits gas transport, so the amount of radon available to a home is effectively reduced
by a high water table. Areas likely to have high water tables include river valleys, coastal
areas, and some areas overlain by deposits of glacial origin (for example, loess).
Soil permeabilities greater than 6.0 in/hr may be considered high, and permeabilities less
than 0.6 in/hr may be considered low in terms of soil-gas transport. Soils with low
permeability may generally be considered to have a lower radon potential than more
permeable soils with similar radium concentrations. Many well-developed soils contain a
clay-rich B horizon that may impede vertical soil gas transport. Radon generated below this
horizon cannot readily escape to the surface, so it would instead tend to move laterally,
especially under the influence of a negative pressure exerted by.a building.
Shrink-swell potential is an indicator of the abundance of smectitic (swelling) clays in a
soil. Soils with a high shrink-swell potential may cause building foundations to crack,
creating pathways for radon entry into the structure. During dry periods, desiccation cracks in
shrink-swell soils provide additional pathways for soil-gas transport and effectively increase
the gas permeability of the soil. Soil permeability data and soil profile data thus provide
important information for regional radon assessments.
INDOOR RADON DATA
Two major sources of indoor radon data were used. The first and largest source of data is
from the State/EPA Residential Radon Survey (Ronca-Battista and others, 1988; Dziuban and
others, 1990). Forty-two states completed EPA-sponsored indoor radon surveys between 1986
and 1992 (fig. 3). The State/EPA Residential Radon Surveys were designed to be
comprehensive and statistically significant at the state level, and were subjected to high levels
of quality assurance and control. The surveys collected screening indoor radon measurements,
defined as 2-7 day measurements using charcoal canister radon detectors placed in the lowest
livable area of the home. The target population for the surveys included owner-occupied
single family, detached housing units (White and others, 1989), although attached structures
such as duplexes, townhouses, or condominiums were included in some of the surveys if they
met the other criteria and had contact with the ground surface. Participants were selected
randomly from telephone-directory listings. In total, approximately 60,000 homes were tested
in the State/EPA surveys.
The second source of indoor radon data conies from residential surveys that have been
conducted in a specific state or region of the country (e.g. independent state surveys or utility
company surveys). Several states, including Delaware, Florida, Illinois, New Hampshire, New
Jersey, New York, Oregon, and Utah, have conducted their own surveys of indoor radon. The
quality and design of a state or other independent survey are discussed and referenced where
the data are used.
II-9 Reprinted from USGS Open-File Report 93-292
-------
U
a.
'y
CD
~ .5
8
t/a
o
•o
CO
o
o
•o
CO
3
CO
I
s
(U
^
"S
u
OS
a
&>
v
c
o
4_»
•>
I
en
3
E
-------
Data for only those counties with five or more measurements are shown in the indoor
radon maps in the state chapters, although data for all counties with a nonzero number of
measurements are listed in the indoor radon data tables in each state chapter. In total, indoor
radon data from more than 100,000 homes nationwide were used in the compilation of these
assessments. Radon data from State or regional indoor radon surveys, public health
organizations, or other sources are discussed in addition to the primary data sources where
they are available. Nearly all of the data used in these evaluations represent short-term (2-7
day) screening measurements from the lowest livable space of the homes. Specific details
concerning the nature and use of indoor radon data sets other than the State/EPA Residential
Radon Survey are discussed in the individual State chapters.
RADON INDEX AND CONFIDENCE INDEX
Many of the geologic methods used to evaluate an area for radon potential require
subjective opinions based on the professional judgment and experience of the individual
geologist. The evaluations are nevertheless based on established scientific principles that are
universally applicable to any geographic area or geologic setting. This section describes the
methods and conceptual framework used by the U.S. Geological Survey to evaluate areas for
radon potential based on the five factors discussed in the previous sections. The scheme is
divided into two basic parts, a Radon Index (RI), used to rank the general radon potential of
the area, and the Confidence Index (CI), used to express the level of confidence in the
prediction based on the quantity and quality of the data used to make the determination. This
scheme works best if the areas to be evaluated are delineated by geologically-based
boundaries (geologic provinces) rather than political ones (state/county boundaries) in which
the geology may vary across the area.
Radon Index. Table 1 presents the Radon Index (RI) matrix. The five factors—indoor
radon data, geology, aerial radioactivity, soil parameters, and house foundation type—were
quantitatively ranked (using a point value of 1, 2, or 3) for their respective contribution to
radon potential in a given area. At least some data for the 5 factors are consistently available
for every geologic province. Because each of these main factors encompass a wide variety of
complex and variable components, the geologists performing the evaluation relied heavily on
their professional judgment and experience in assigning point values to each category and in
determining the overall radon potential ranking. Background information on these factors is
discussed in more detail in the preceding sections of this introduction.
Indoor radon was evaluated using unweighted arithmetic means of the indoor radon data
for each geologic area to be assessed. Other expressions of indoor radon levels in an area
also could have been used, such as weighted averages or annual averages, but these types of
data were not consistently available for the entire United States at the time of this writing, or
the schemes were not considered sufficient to provide a means of consistent comparison
across all areas. For this report, charcoal-canister screening measurement data from the
State/EPA Residential Radon Surveys and other carefully selected sources were used, as
described in the preceding section. To maintain consistency, other indoor radon data sets
(vendor, state, or other data) were not considered in scoring the indoor radon factor of the
Radon Index if they were not randomly sampled or could not be statistically combined with
the primary indoor radon data sets. However, these additional radon data sets can provide a
means to further refine correlations between geologic factors and radon potential, so they are
II-11 Reprinted from USGS Open-File Report 93-292
-------
TABLE I. RADON INDEX MATRIX, "ppm eU" indicates parts per million of equivalent
uranium, as indicated by NURE aerial radiometric data. See text discussion for details.
JJ.-N \_isxi.f\o.u>ivj jvfvuwiN Jr*_; i crN i Lt\ i , ^
FACTOR
INDOOR RADON (average)
AERIAL RADIOACTIVITY
GEOLOGY*
SOIL PERMEABILITY
ARCHITECTURE TYPE
POINT VALUE
1
<2pCi/L
< 1.5 ppm eU
negative
low
mostly slab
2
2-4pCi/L
1.5 - 2.5 ppm eU
variable
moderate
mixed
3
>4pCi/L
> 2.5 ppm eU
positive
high
mostly basement
'GEOLOGIC FIELD EVIDENCE (GFE) POINTS: GFE points are assigned in addition to points
for the "Geology" factor for specific, relevant geologic field studies. See text for details.
Geologic evidence supporting: HIGH radon +2 points
MODERATE +1 point
LOW -2 points
No relevant geologic field studies 0 points
SCORING:
Radon potential category
LOW
MODERATE/VARIABLE
HIGH
Probable average screening
Point range indoor radon for area
3-8 points
9-11 points
12-17 points
<2pCi/L
2-4pCi/L
>4pCi/L
POSSIBLE RANGE OF POINTS = 3 to 17
TABLE 2. CONFIDENCE INDEX MATRIX
INCREASING CONFIDENCE
FACTOR
INDOORRADON DATA
AERIAL RADIOACTIVITY
GEOLOGIC DATA
SOIL PERMEABILITY
^
POINT VALUE
1
sparse/no data
questionable/no data
questionable
questionable/no data
2
fair coverage/quality
glacial cover
variable
variable
3
good coverage/quality
no glacial cover
proven geol. model
reliable, abundant
SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10 - 12 points
POSSIBLE RANGE OF POINTS = 4 to 12
II-12 Reprinted from USGS Open-File Report 93-292
-------
included as supplementary information and are discussed in the individual State chapters. If
the average screening indoor radon level for an area was less than 2 pCi/L, the indoor radon
factor was assigned 1 point, if it was between 2 and 4 pCi/L, it was scored 2 points, and if
the average screening indoor radon level for an area was greater than 4 pCi/L, the indoor
radon factor was assigned 3 RI points.
Aerial radioactivity data used in this report are from the equivalent uranium map of the
conterminous United States compiled from NURE aerial gamma-ray surveys (Duval and
others, 1989). These data indicate the gamma radioactivity from approximately the upper 30
cm of rock and soil, expressed in units of ppm equivalent uranium. An approximate average
value of elJ was determined visually for each area and point values assigned based on
whether the overall eU for the area falls below 1.5 ppm (1 point), between 1.5 and 2.5 ppm
(2 points), or greater than 2.5 ppm (3 points).
The geology factor is complex and actually incorporates many geologic characteristics. In
the matrix, "positive" and "negative" refer to the presence or absence and distribution of rock
types known to have high'uranium contents and to generate elevated radon in soils or indoors.
Examples of "positive" rock types include granites, black shales, phosphatic rocks, and other
rock types described in the preceding "geologic data" section. Examples of "negative" rock
types include marine quartz sands and some clays. The term "variable" indicates that the
geology within the region is variable or that the rock types in the area are known or suspected
to generate elevated radon in some areas but not in others due to compositional differences,
climatic effects, localizeddistribution of uranium, or other factors. Geologic information
indicates not only how much uranium is present in the rocks and soils but also gives clues for
predicting general radon emanation and mobility characteristics through additional factors
such as structure (notably the presence of faults or shears) and geochemical characteristics
(for example, a phosphate-rich sandstone will likely contain more uranium than a sandstone
containing little or no phosphate because the phosphate forms chemical complexes with
uranium). "Negative", "variable", and "positive" geology were assigned 1, 2, and 3 points,
respectively.
In cases where additional reinforcing or contradictory geologic evidence is available,
Geologic Field Evidence (GFE) points were added to or subtracted from an area's score
(Table 1). Relevant geologic field studies are important to enhancing our understanding of
how geologic processes affect radon distribution. In some cases, geologic models and
supporting field data reinforced an already strong (high or low) score; in others, they provided
important contradictory data. GFE points were applied for geologically-sound evidence that
supports the prediction (but which may contradict one or more factors) on the basis of known
geologic field studies in the area or in areas with geologic and climatic settings similar
enough that they could be applied with full confidence. For example, areas of the Dakotas,
Minnesota, and Iowa that are covered with Wisconsin-age glacial deposits exhibit a low aerial
radiometric signature and score only one RI point in that category. However, data from
geologic field studies in North Dakota and Minnesota (Schumann and others, 1991) suggest
that eU is a poor predictor of geologic radon potential in this area because radionuclides have
11-13 Reprinted from USGS Open-File Report 93-292
-------
been leached from the upper soil layers but are present and possibly even concentrated in
deeper soil horizons, generating significant soil-gas radon. This positive supporting field
evidence adds two GFE points to the score, which helps to counteract the invalid conclusion
.digested by the radiometric data. No GFE points ; -e awarded if there are no documented
field studies for the area.
"Soil permeability" refers to several soil characteristics that influence radon concentration
and mobility, including soil type, grain size, structure, soil moisture, drainage, slope, and
permeability. In the matrix, "low" refers to permeabilities less than about 0.6 in/hr; "high"
corresponds to greater than about 6.0 in/hr, in U.S. Soil Conservation Service (SCS) standard
soil percolation tests. The SCS data are for water permeability, which generally correlates
well with the gas permeability of the soil except when the soil moisture content is very high.
Areas with consistently high water tables were thus considered to have low gas permeability.
"Low, "moderate", and "high" permeability were assigned 1, 2, and 3 points, respectively.
Architecture type refers to whether homes in the area have mostly basements (3 points),
mostly slab-on-grade construction (1 point), or a mixture of the'two. Split-level and crawl '
space homes fall into the "mixed" category (2 points). Architecture information is necessary
to properly interpret the indoor radon data and produce geologic radon potential categories
that are consistent with screening indoor radon data.
The overall RI for an area is calculated by adding the individual RI scores for the 5
factors, plus or minus GFE points, if any. The total RI for an area falls in one of three
categories—low, moderate or variable, or high. The point ranges for the three categories were
determined by examining the possible combinations of points for the 5 factors and setting
rules such that a majority (3 of 5 factors) would determine the final score for the low and
high categories, with allowances for possible deviation from an ideal score by the other two
factors. The moderate/variable category lies between these two ranges. A total deviation of 3
points from the "ideal" score was considered reasonable to allow for natural variability of
factors—if two of the five factors are allowed to vary from the "ideal" for a category, they
can differ by a minimum of 2 (1 point different each) and a maximum of 4 points (2'points
different each). With "ideal" scores of 5, 10, and 15 points describing low, moderate, and
high geologic radon potential, respectively, an ideal low score of 5 points plus 3 points for
possible variability allows a maximum of 8 points in the low category. Similarly, an ideal
high score of 15 points minus 3 points gives a minimum of 12 points for the high category.
Note, however, that if both other factors differ by two points from the "ideal", indicating
considerable variability in the system, the total point score would lie in the adjacent (i.e.,
moderate/variable) category.
Confidence Index. Except for architecture type, the same factors were used to establish a
Confidence Index (CI) for the radon potential prediction for each area (Table 2). Architecture
type was not included in the confidence index because house construction data are readily and
reliably available through surveys taken by agencies and industry groups including the
National Association of Home Builders, U.S. Department of Housing and Urban
Development, and the Federal Housing Administration; thus it was not considered necessary
11-14 Reprinted from USGS Open-File Report 93-292
-------
to question the quality or validity of these data. The other factors were scored on the basis of
the quality and quantity of the data used to complete the RI matrix.
Indoor radon data were evaluated based on the distribution and number of data points and
on whether the data were collected by random sampling (State/EPA Residential Radon Survey
or other state survey data) or volunteered vendor data (likely to be nonrandom and biased
toward population centers and/or high indoor radon levels). The categories listed in the CI
matrix for indoor radon data ("sparse or no data", "fair coverage or quality", and "good
coverage/quality") indicate the sampling density and statistical robustness of an indoor radon '
data set. Data from the State/EPA Residential Radon Survey and statistically valid state
surveys were typically assigned 3 Confidence Index points unless the data were poorly
distributed or absent in the area evaluated.
Aerial radioactivity data are available for all but a few areas of the continental United
States and for part of Alaska. An evaluation of the quality of the radioactivity data was based
on whether there appeared to be a good correlation between the radioactivity and the actual
amount of uranium or radium available to generate mobile radon in the rocks and soils of the
area evaluated. In general, the greatest problems with correlations among eU, geology, and
soil-gas or indoor radon levels were associated with glacial deposits (see the discussion in a
previous section) and typically were assigned a 2-point Confidence Index score. Correlations
among eU, geology, and radon were generally sound in unglaciated areas and were usually
assigned 3 CI points. Again, however, radioactivity data in some unglaciated areas may have
been assigned fewer than 3 points, and in glaciated areas may be assigned only one point, if
the data were considered questionable or if coverage was poor.
To assign Confidence Index scores for the geologic data factor, rock types and geologic
settings for which a physical-chemical, process-based understanding of radon generation and
mobility exists were regarded as having "proven geologic models" (3 points); a high
confidence could be held for predictions in such areas. Rocks for which the processes are
less well known or for which data are contradictory were regarded as "variable" (2 points),
and those about which little is known or for which no apparent correlations have been found
were deemed "questionable" (1 point).
The soil permeability factor was also scored based on quality and amount of data. The
three categories for soil permeability in the Confidence Index are similar in concept, and
scored similarly, to those for the geologic data factor. Soil permeability can be roughly
estimated from grain size and drainage class if data from standard, accepted soil percolation
tests are unavailable; however, the reliability of the data would be lower than if percolation
test figures or other measured permeability data are available, because an estimate of this type
does not encompass all the factors that affect soil permeability and thus may be inaccurate in
some instances. Most published soil permeability data are for water; although this is
generally closely related to the air permeability of the soil, there are some instances when it
may provide an incorrect estimate. Examples of areas in which water permeability data may
not accurately reflect air permeability include areas with consistently high levels of soil
moisture, or clay-rich soils, which would have a low water permeability but may have a
11-15 Reprinted from USGS Open-File Report 93-292
-------
significantly higher air permeability when dry due to shrinkage cracks in the soil. These
additional factors were applied to the soil permeability factor when assigning the RI score, but
may have less certainty in some cases and thus would be assigned a lower CI score.
The Radon Index and Confidence Index give a general indication of the relative
contributions of the interrelated geologic factors influencing radon generation and transport in
rocks and soils, and thus, of the potential for elevated indoor radon levels to occur in a
particular area. However, because these reports are somewhat generalized to cover relatively
large areas of States; it is highly recommended that more detailed studies be performed in
local areas of interest, using the methods and general information in these booklets as a guide'
11-16 Reprinted from USGS Open-File Report-93-292
-------
REFERENCES CITED
Akerblom, G., Anderson, P., and Clavensjo, B., 1984, Soil gas radon-A source for indoor radon
daughters: Radiation Protection Dosimetry, v. 7, p. 49-54.
Deffeyes, K.S., and MacGregor, I.D., 1980, World uranium resources: Scientific American
v. 242, p. 66-76.
Durrance, E.M., 1986, Radioactivity in geology: Principles and applications: New York, N.Y., .
Wiley and Sons, 441 p.
Duval, J.S., 1989, Radioactivity and some of its applications in geology: Proceedings of the
symposium on the application of geophysics to engineering and environmental problems
(SAGEEP), Golden, Colorado, March 13-16,1989: Society of Engineering and Mineral
Exploration Geophysicists, p. 1-61.
Duval, J.S., Cook, B.G., and Adams, J.A.S., 1971, Circle of investigation of an airborne
gamma-ray spectrometer: Journal of Geophysical Research, v. 76, p. 8466-8470.
Duval, J.S., Jones, W.J., Riggle, F.R., and Pitkin, J.A., 1989, Equivalent uranium map of
conterminous United States: U.S. Geological Survey Open-File Report 89-478,10 p.
Duval, J.S., Reimer, G.M., Schumann, R.R., Owen, D.E., and Otton, J.K., 1990, Soil-gas
radon compared to aerial and ground gamma-ray measurements at study sites near Greeley
and Fort Collins, Colorado: U.S. Geological Survey Open-File Report 90-648,42 p.
Dziuban, J.A., Clifford, M.A., White, S.B., Bergstein, J.W., and Alexander, B.V., 1990,
Residential radon survey of twenty-three States, in Proceedings of the 1990 International
Symposium on Radon and Radon Reduction Technology, Vol. HI: Preprints: U.S.
Environmental Protection Agency report EPA/600/9-90/005c, Paper IV-2,17 p.
Gammage, R.B., Wilson, D.L., Saultz, R.J., and Bauer, B.C., 1993, Subtereanean transport of
radon and elevated indoor radon in hilly karst terranes: Atmospheric Environment
(in press).
Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1988a, Correlation between geology, radon
in soil gas, and indoor radon in the Reading Prong, in Marikos, M.A., and Hansman,
R.H., eds., Geologic causes of natural radionuclide anomalies: Missouri Department of
Natural Resources Special Publication 4, p. 91-102.
Gundersen, L.C.S, Reimer, G.M., Wiggs, C.R., and Rice, C.A., 1988b, Map showing radon
potential of rocks and soils in Montgomery County, Maryland: U.S. Geological Survey
Miscellaneous Field Studies Map MF-2043, scale 1:62,500.
Gundersen, Linda C.S., 1991, Radon in sheared metamorphic and igneous rocks, in Gundersen,
Linda C.S., and Richard B. Wanty, eds., Field studies of radon in rocks, soils, and water:
U.S. Geol. Survey Bulletin no. 1971, p. 39-50.
H-17 Reprinted from USGS Open-File Report 93-292
-------
Henry, Mitchell E., Kaeding, Margret E., and Monteverde, Donald, 1991, Radon in soil gas and
gamma-ray activity of rocks and soils at the Mulligan Quarry, Clinton, New Jersey, in
Gundersen, Linda C.S., and Richard B. Wanty, eds., Field studies of radon in rocks,
soils, and water: U.S. Geol. Survey Bulletin no. 1971, p. 65-75.
Klusman, R. W., and Jaacks, J. A., 1987, Environmental influences upon mercury, radon, and
helium concentrations in soil gases at a site near Denver, Colorado: Journal of
Geochemical Exploration, v. 27, p. 259-280.
Kovach, E.M., 1945, Meteorological influences upon the radon content of soil gas: Transactions,
American Geophysical Union, v. 26, p. 241-248.
Kunz, C, Laymon, C.A., and Parker, Q, 1989, Gravelly soils and indoor radon, in Osborne,
M.C., and Harrison, J., eds., Proceedings of the 1988 EPA Symposium on Radon and
Radon Reduction Technology, Volume 1: U.S. Environmental Protection Agency Report
EPA/600/9-89/006A, p. 5-75-5-86.
Muessig, K., and Bell, C., 1988, Use of airborne radiometric data to direct testing for elevated
indoor radon: Northeastern Environmental Science, v. 7, no. 1, p. 45-51.
Ronca-Battista, M., Moon, M., Bergsten, J., White, S.B., Holt, N., and Alexander, B., 1988,
Radon-222 concentrations in the United States—Results of sample surveys in five states:
Radiation Protection Dosimetry, v. 24, p. 307-312.
Rose, A.W., Washington, J.W., and Greeman, D.J., 1988, Variability of radon with depth and
season in a central Pennsylvania soil developed on limestone: Northeastern Environmental
Science, v. 7, p. 35-39.
Schery, S.D., Gaeddert, D.H., and Wilkening, M.H., 1984, Factors affecting exhalation of radon
from a gravelly sandy loam: Journal of Geophysical Research, v. 89, p. 7299-7309.
Schumann, R.R., and Owen, D.E., 1988, Relationships between geology, equivalent uranium
concentration, and radon in soil gas, Fairfax County, Virginia: U.S. Geological Survey
Open-File Report 88-18,28 p.
Schumann, R.R., and Gundersen, L.C.S., 1991, Regional differences in radon emanation
coefficients in soils: Geological Society of America Abstracts With Programs, v. 23,
no. 1, p. 125.
Schumann, R.R., Peake, R.T., Schmidt, K.M., and Owen, D.E., 1991, Correlations of soil-gas
and indoor radon with geology in glacially derived soils of the northern Great Plains, in
Proceedings of the 1990 International Symposium on Radon and Radon Reduction
Technology, Volume 2, Symposium Oral Papers: U.S. Environmental Protection Agency
report EPA/600/9-91/026b, p. 6-23-6-36.
JJ-18 Reprinted from USGS Open-FUe Report 93-292
-------
Schumann, R.R., Owen,'D.E., and Asheir-Bblinder, S., 1992, Effects of weather and soil
characteristics on temporal variations in soil-gas radon concentrations, in Gates, A.E., and
Gundersen, L.C.S., eds., Geologic controls on radon: Geological Society of America
Special Paper 271, p. 65-72.
Sextro, R.G., Moed, B.A., Nazaroff, W.W., Revzan, K.L., and Nero, A.V., 1987,
Investigations of soil as a source of indoor radon, in Hopke, P.K., ed., Radon and its
decay products: American Chemical Society Symposium Series 331, p. 10-29.
Sterling, R., Meixel, G., Shen, L., Labs, K., and Bligh, T., 1985, Assessment of the energy
savings potential of building foundations research: Oak Ridge, Tenn., U.S. Department of
Energy Report ORNL/SUB/84-0024/1.
Smith, R.C., H, Reilly, M.A., Rose, A.W., Barnes, J.H., and Berkheiser, S.W., Jr., 1987,
Radon: a profound case: Pennsylvania Geology, v. 18, p. 1-7.
Tanner, A.B., 1964, Radon migration in the ground: a review, in Adams, J.A.S., and Lowder,
W.M., eds., The natural radiation environment: Chicago, EL, University of Chicago
Press, p. 161-190.
Tanner, A.B., 1980, Radon migration in the ground: a supplementary review, in Gesell, T.F.,
and Lowder, W.M. (eds), Natural radiation environment m, Symposium proceedings,
Houston, Texas, v. 1, p. 5-56.
U.S. Department of Agriculture, 1987, Principal kinds of soils: Orders, suborders, and great
groups: U.S. Geological Survey, National Atlas of the United States of America, sheet
38077-BE-NA-07M-00, scale 1:7,500,000.
U.S. Department of Energy, 1976, National Uranium Resource Evaluation preliminary report,
prepared by the U.S. Energy Research and Development Administration, Grand Junction,
Colo.: GJO-11(76).
Wanty, Richard B., and Schoen, Robert, 1991, A review of the chemical processes affecting the
mobility of radionuclides in natural waters, with applications, in Gundersen, Linda C.S.,
and Richard B. Wanty, eds., Field studies of radon in rocks, soils, and water: U.S.
Geological Survey Bulletin no. 1971, p. 183-194.
Washington, J.W., and Rose, A.W., 1990, Regional and temporal relations of radon in soil gas to
soil temperature and moisture: Geophysical Research Letters, v. 17, p. 829-832.
White, S.B., Bergsten, J.W., Alexander, B.V., and Ronca-Battista, M., 1989, Multi-State
surveys of indoor 222Rn: Health Physics, v. 57, p. 891-896.
JJ-19 Reprinted from USGS Open-File Report 93-292
-------
APPENDIX A
GEOLOGIC TIME SCALE
Eon or
Eonothem
Phanerozoic2
(B)
A
(A)
Subdivisions {and their symbols)
Era or
Erathem
Cenozoic 2
(Cz)
vlesozoic2
(Mi)
aleozoic2
(Pi)
^f Ot»f OJO.C 31
Prottroiotc fYl
Pfonfotoic IXI
Arch»n IW)
Artluinrtr)
Arth.m IUI
Period, System,
Subperiod, Subsystem
Quaternary
(Q)
Suoperiod or
Terriarv Subsystem (N)
(Tj Paleogene2
Subceriod or
Subsystem (Pi)
Cretaceous
(K)
Jurassic
U)
Triassic
OS)
Permian
-------
^APPENDIX B
GLOSSARY OF TERMS
Units of measure
pCi/L (picocuries per liter)- a unit of measure of radioactivity used to describe radon
concentrations in a volume of air. One picocurie (10-12 curies) is equal to about 2.2 disintegrations
of radon atoms per minute. A liter is about 1.06 quarts. The average concentration of radon in
U.S. homes measured to date is between 1 and 2 pCi/L.
Bq/m3 (Becquerels per cubic meter)- a metric unit of radioactivity used to describe radon
concentrations in a volume of air. One becquerel is equal to one radioactive disintegration per
second. One pCi/L is equal to 37 Bq/m3.
ppm (parts per million)- a unit of measure of concentration by weight of an element in a
substance, m this case soil or rock. One ppm of uranium contained in a ton of rock corresponds
to about 0.03 ounces of uranium. The average concentration of uranium in soils in the United
States is between 1 and 2 ppm.
in/hr (inches per hour)- a unit of measure used by soil scientists and engineers to describe the
permeability of a soil to water flowing through it It is measured by digging a hole 1 foot (12
inches) square and one foot deep, filling it with water, and measuring the time it takes for toe water
to drain from the hole. The drop m height of the water level in the hole, measured in inches, is
then divided by the time (in hours) to determine the permeability. Soils range in permeability from
2° ^ ** ^ ^ " ^ United Sta'es have permeabiS
Geologic terms and terms related to the study
aerial 1 radiometnc, aeroradiometric survey A survey of radioactivity, usually gamma rays
taken by an aircraft carrying a gamma-ray spectrometer pointed at the ground surface.
alluvial fan A low, widespread mass of loose rock and soil material, shaped like an open fan
and deposited by a stream at the point where it flows from a narrow mountain valley out onto a
alluvium, alluvial General terms referring to unconsolidated detrital material deposited bv a
stream or other body of running water. y
alpha-track detector A passive radon measurement device consisting of a plastic film that is
sensitive to alpha particles. The film is etched with acid in a laboratory after it is exposed The
etching reveals scratches or "tracks", left by the alpha particles resulting from radon decay which
can then be counted to calculate the radon concentration. Useful for long-term (1-12 months)
radon tests. }
amphibolite A mafic metamorphic rock consisting mainly of pyroxenes and(or) amphibole and
n-21 Reprinted from USGS Open-File Report 93-292
-------
argillite, argillaceous Terms referring to a rock derived from clay or shale, or any sedimentary
rock containing an appreciable amount of clay-size material, i.e., argillaceous sandstone.
arid Term describing a climate characterized by dryness, or an evaporation rate that exceeds the
amount of precipitation.
basalt A general term for a dark-colored mafic igneous rocks that may be of extrusive origin,
such as volcanic basalt flows, or intrusive origin, such as basalt dikes.
batholith A mass of plutonic igneous rock that has more than 40 square miles of surface
exposure and no known bottom.
carbonate A sedimentary rock consisting of the carbonate (COs) compounds of calcium,
magnesium, or iron, e.g. limestone and dolomite.
carbonaceous Said of a rock or sediment that is rich in carbon, is coaly, or contains organic
matter.
charcoal canister A passive radon measurement device consisting of a small container of
granulated activated charcoal that is designed to adsorb radon. Useful for short duration (2-7 days)
measurements only. May be referred to as a "screening" test
chert A hard, extremely dense sedimentary rock consisting dominantly of interlocking crystals of
quartz. Crystals are not visible to the naked eye, giving the rock a milky, dull luster. It may be
white or gray but is commonly colored red, black, yellow, blue, pink, brown, or green.
clastic pertaining to a rock or sediment composed of fragments that are derived from preexisting
rocks or minerals. The most common clastic sedimentary rocks are sandstone and shale.
clay A rock containing clay mineral fragments or material of any composition having a diameter
less than 1/256 mm.
clay mineral One of a complex and loosely defined group of finely crystalline minerals made up
of water, silicate and aluminum (and a wide variety of other elements). They are formed chiefly by
alteration or weathering of primary silicate minerals. Certain clay minerals are noted for their small
size and ability to absorb substantial amounts of water, causing them to swell. The change in size
that occurs as these clays change between dry and wet is referred to as their "shrink-swell"
potential.
concretion A hard, compact mass of mineral matter, normally subspherical but commonly
irregular in shape; formed by precipitation from a water solution about a nucleus or center, such as
a leaf, shell, bone, or fossil, within a sedimentary or fractured rock.
conglomerate A coarse-grained, clastic sedimentary rock composed of rock and mineral
fragments larger than 2 mm, set in a finer-grained matrix of clastic material.
cuesta A hill or ridge with a gentle slope on one side and a steep slope on the other. The
formation of a cuesta is controlled by the different weathering properties and the structural dip of
the rocks forming the hill or ridge.
daughter product A nuclide formed by the disintegration of a radioactive precursor or "parent"
atom.
11-22 Reprinted from USGS Open-File Report 93-292
-------
delta, deltaic Referring -to a low, flat, alluvial tract of land having a triangular or fan shape,
located at or near the mouth of a river. It results from the accumulation of sediment deposited by a
river at the point at which the river loses its ability to transport the sediment, commonly where a
river meets a larger body of water such as a lake or ocean.
dike A tabular igneous intrusion of rock, younger than the surrounding rock, that commonly cuts
across the bedding or foliation of the rock it intrudes.
diorite A plutonic igneous rock that is medium in color and contains visible dark minerals that
make up less than 50% of the rock. It also contains abundant sodium plagioclase and minor -
quartz.
dolomite A carbonate sedimentary rock of which more than 50% consists of the mineral dolomite
(CaMg(CO3)2), and is commonly white, gray, brown, yellow, or pinkish in color.
drainage The manner in which the waters of an area pass, flow off of, or flow into the soil.
Also refers to the water features of an area, such as lakes and rivers, that drain it.
eolian Pertaining to sediments deposited by the wind.
esker A long, narrow, steep-sided ridge composed of irregular beds of sand and gravel deposited
by streams beneath a glacier and left behind when the ice melted.
evapotranspiration Loss of water from a land area by evaporation from the soil and
transpiration from plants.
extrusive Said of igneous rocks that have been erupted onto the surface of the Earth.
fault A fracture or zone of fractures in rock or sediment along which there has been movement
fluvial, fluvial deposit Pertaining to sediment that has been deposited by a river or stream.
foliation A linear feature in a rock defined by both mineralogic and structural characteristics. It
may be formed during deformation or metamorphism.
formation A mappable body of rock having similar characteristics.
glacial deposit Any sediment transported and deposited by a glacier or processes associated
with glaciers, such as glaciofluvial sediments deposited by streams flowing from melting glaciers.
gneiss A rock formed by metamorphism hi which bands and lenses of minerals of similar
composition alternate with bands and lenses of different composition, giving the rock a striped or
"foliated" appearance.
granite Broadly applied, any coarsely crystalline, quartz- and feldspar-bearing igneous plutonic
rock. Technically, granites have between 10 and 50% quartz, and alkali feldspar comprises at least
65% of the total feldspar.
gravel An unconsolidated, natural accumulation of rock fragments consisting predominantly of
particles greater than 2 mm in size.
heavy minerals Mineral grains in sediment or sedimentary rock having higher than average
specific gravity. May form layers and lenses because of wind or water sorting by weight and size
11-23 Reprinted from USGS Open-File Report 93-292
-------
and may be referred to as a "placer deposit." Some heavy minerals are magnetite, garnet, zircon,
monazite, and xenotime.
igneous Said of a rock or mineral that solidified from molten or partly molten rock material. It is
one of the three main classes into which rocks are divided, the others being sedimentary and
metamorphic.
intermontane A term that refers to an area between two mountains or mountain ranges.
intrusion, intrusive The processes of emplacement or injection of molten rock into pre-existing
rock. Also refers to the rock formed by intrusive processes, such as an "intrusive igneous rock".
kame A low mound, knob, hummock, or short irregular ridge formed by a glacial stream at the
margin of a melting glacier; composed of bedded sand and gravel.
karst terrain A type of topography that is formed on limestone, gypsum and other rocks by
dissolution of the rock by water, forming sinkholes and caves.
lignite A brownish-black coal that is intermediate in coalification between peat and
subbituminous coal.
limestone A carbonate sedimentary rock consisting of more than 50% calcium carbonate,
primarily in the form of the mineral calcite (CaCOs).
lithology The description of rocks in hand specimen and in outcrop on the basis of color,
composition, and grain size.
loam A permeable soil composed of a mixture of relatively equal parts clay, silt, and sand, and
usually containing some organic matter.
loess A fine-grained eolian deposit composed of silt-sized particles generally thought to have
been deposited from windblown dust of Pleistocene age.
mafic Term describing an igneous rock containing more than 50% dark-colored minerals.
marine Term describing sediments deposited in the ocean, or precipitated from ocean waters.
metamorphic Any rock derived from pre-existing rocks by mineralogical, chemical, or structural
changes in response to changes in temperature, pressure, stress, and the chemical environment.
Phyllite, schist, amphibolite, and gneiss are metamorphic rocks.
moraine A mound, ridge, or other distinct accumulation of unsorted, unbedded glacial material,
predominantly till, deposited by the action of glacial ice.
outcrop That part of a geologic formation or structure that appears at the surface of the Earth, as
in "rock outcrop".
percolation test A term used in engineering for a test to determine the water permeability of a
soil. A hole is dug and filled with water and the rate of water level decline is measured.
permeability The capacity of a rock, sediment, or soil to transmit liquid or gas.
phosphate, phosphatic, phosphorite Any rock or sediment containing a significant amount
of phosphate minerals, i.e., minerals containing PO4.
11-24 Reprinted from USGS Open-FUe Report 93-292
-------
physiographic province A region in which all parts are similar in geologic structure and
climate, which has had a uniform geomorphic history, and whose topography or landforms differ
significantly from adjacent regions.
placer deposit See heavy minerals
residual Formed by weathering of a material in place.
residuum Deposit of residual material.
rhyolite An extrusive igneous rock of volcanic origin, compositionally equivalent to granite.
sandstone A clastic sedimentary rock composed of sand-sized rock and mineral material that is
more or less firmly cemented. Sand particles range from 1/16 to 2 mm in size.
schist A strongly foliated crystalline rock, formed by metamorphism, that can be readily split into
thin flakes or slabs. Contains mica; minerals are typically aligned.
screening level Result of an indoor radon test taken with a charcoal canister or similar device,
for a short period of time, usually less than seven days. May indicate the potential for an indoor'
radon problem but does not indicate annual exposure to radon.
sediment Deposits of rock and mineral particles or fragments originating from material that is
transported by air, water or ice, or that accumulate by natural chemical precipitation or secretion of
organisms.
semiarid Refers to a climate that has slightly more precipitation than an arid climate.
shale A fine-grained sedimentary rock formed from solidification (lithification) of clay or mud.
shear zone Refers to a roughly linear zone of rock that has been faulted by ductile or non-ductile
processes in which the rock is sheared and both sides are displaced relative to one another.
shrink-swell clay See clay mineral.
siltstone A fine-grained clastic sedimentary rock composed of silt-sized rock and mineral
material and more or less firmly cemented. Silt particles range from 1/16 to 1/256 mm in size.
sinkhole A roughly circular depression in a karst area measuring meters to tens of meters in
diameter. It is funnel shaped and is formed by collapse of the surface material into an underlying
void created by the dissolution of carbonate rock.
slope An inclined part of the earth's surface.
solution cavity A hole, channel or cave-like cavity formed by dissolution of rock.
stratigraphy The study of rock strata; also refers to the succession of rocks of a particular area.
surficial materials Unconsolidated glacial, wind-, or waterborne deposits occurring on the
earth's surface.
tablelands General term for a broad, elevated region with a nearly level surface of considerable
extent.
11-25 Reprinted from USGS Open-File Report 93-292
-------
terrace gravel Gravel-sized material that caps ridges and terraces, left behind by a stream as it
cuts down to a lower level.
terrain A tract or region of the Earth's surface considered as a physical feature or an ecological
environment.
till Unsorted, generally unconsolidated and unbedded rock and mineral material deposited directly
adjacent to and underneath a glacier, without reworking by meltwater. Size of grains varies greatly
from clay to boulders.
uraniferous Containing uranium, usually more than 2 ppm.
vendor data Used in this report to refer to indoor radon data collected and measured by
commercial vendors of radon measurement devices and/or services.
volcanic Pertaining to the activities, structures, and extrusive rock types of a volcano.
water table The surface forming the boundary between the zone of saturation and the zone of
aeration; the top surface of a body of unconfined groundwater in rock or soil.
weathering The destructive process by which earth and rock materials, on exposure to
atmospheric elements, are changed in color, texture, composition, firmness, or form with little or
no transport of the material.
11-26 Reprinted from USGS Open-FUe Report 93-292
-------
APPENDIX C
EPA REGIONAL OFFICES
EPA Regional Offic-ps
EPA Region 1
JFK Federal Building
Boston, MA 02203
(617) 565-4502
EPA Region 2
(2AIR:RAD)
26 Federal Plaza
New York, NY 10278
(212) 264-4110
Region 3 (3AH14)
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8326
EPA Region 4
345 Courtland Street, N.E.
Atlanta, GA 30365
(404) 347-3907
EPA Region 5 (5AR26)
77 West Jackson Blvd.
Chicago, IL 60604-3507
(312) 886-6175
EPA Region 6 (6T-AS)
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7224
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7604
EPA Region 8
(8HWM-RP)
999 18th Street
One Denver Place, Suite 1300
Denver, CO 80202-2413
(303) 293-1713
EPA Region 9 (A-3)
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1048
EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
(202) 442-7660
Alabama 4
Alaska IQ
Arizona 9
Arkansas .....6
California 9
Colorado g
Connecticut j
Delaware 3
District of Columbia 3
Florida 4
Georgia 4
Hawaii 9
Idaho jo
Illinois 5
Indiana 5
Iowa 7
Kansas .• , 7
Kentucky 4
Louisiana g
Maine ^
Maryland 3
Massachusetts i
Michigan 5
Minnesota 5
Mississippi 4
Missouri 7
Montana g
Nebraska 7
Nevada 9
New Hampshire.... i
New Jersey 2
New Mexico g
New York 2
a. North Carolina 4
North Dakota g
Ohio 5
Oklahoma g
Oregon IQ
Pennsylvania 3
Rhode Island i
South Carolina 4
South Dakota g
Tennessee 4
Texas g
Utah ............""g
Vermont i
Virginia 3
Washington 10
West Virginia 3
Wisconsin 5
Wyoming g
n-27 Reprinted from USGS Open-File Report 93-292
-------
STATE RADON CONTACTS
May, 1993
Alabama James McNees
Division of Radiation Control
Alabama Department of Public health
State Office Building
Montgomery, AL 36130
(205)242-5315
1-800-582-1866 in state
Charles Tedford
Department of Health and Social
Services
P.O. Box 110613
Juneau.AK 99811-0613
(907)465-3019
1-800-478-4845 in state
AtiZQOa John Stewart
Arizona Radiation Regulatory Agency
4814 South 40th St
Phoenix, AZ 85040
(602) 255-4845
Arkansas LeeGershner
Division of Radiation Control
Department of Health
4815 Markham Street, Slot 30
Little Rock, AR 72205-3867
(501) 661-2301
California J. David Quinton
Department of Health Services
714 P Street, Room 600
Sacramento, CA 94234-7320
(916) 324-2208
1-800-745-7236 in state
Colorado Linda Martin
Department of Health
4210 East llth Avenue
Denver, CO 80220
(303) 692-3057
1-800-846-3986 in state
Connecticut Alan J. Siniscalchi
Radon Program
Conneci,vUt Department of Health
Services
150 Washington Street
Hartford, CT 06106-4474
(203) 566-3122
Delaware MaraiG.Rejai
Office of Radiation Control
Division of Public Health
P.O. Box 637
Dover, DE 19903
(302) 736-3028
1-800-554-4636 In State
District Robert Davis
of Columbia DC Department of Consumer and
Regulatory Affairs
614 H Street NW
Room 1014
Washington, DC 20001
(202) 727-71068
Florida N. Michael Gilley
Office of Radiation Control
Department of Health and
Rehabilitative Services
1317 Winewood Boulevard
Tallahassee, PL 32399-0700
(904)488-1525
1-800-543-8279 in state
Richard Schreiber
Georgia Department of Human
Resources
878 Peachtree St, Room 100
Atlanta, GA 30309
(404) 894-6644
1-800-745-0037 in state
Hawaii Russell Takata
Environmental Health Services
Division
591 Ala Moana Boulevard
Honolulu, ffl 96813-2498
(808) 586^700
n-28 Reprinted from USGS Open-File Report 93-292
-------
Idaho PatMcGavarn
Office of Environmental Health
450 West State Street
Boise, ID 83720
(208) 334-6584
1-800-445-8647 in state
Richard Allen
Illinois Department of Nuclear Safety
1301 Outer Park Drive
Springfield, IL 62704
(217)524-5614
1-800-325-1245 in state
Lorand Magyar
Radiological Health Section
Indiana State Department of Health
1330 West Michigan Street
P.O. Box 1964
Indianapolis, IN 46206
(317) 633-8563
1-800-272-9723 In State
Donald A. Plater
Bureau of Radiological Health
Iowa Department of Public Health
Lucas State Office Building
Des Moines, IA 50319-0075
(515) 281-3478
1-800-383-5992 In State
Kansas Harold Spiker
Radiation Control Program
Kansas Department of Health and
Environment
109 SW 9th Street
6th Floor Mills Building
Topeka, KS 66612
(913)296-1561
Kentucky JeanaPhelps
Radiation Control Branch
Department of Health Services
Cabinet for Human Resources
275 East Main Street
Frankfort, KY 40601
(502) 564-3700
Iowa
Louisiana Matt Schlenker
Louisiana Department of
Environmental Quality
P.O. Box 82135
Baton Rouge, LA 708o4-2135
(504) 925-7042
1-800-256-2494 in state
Maine Bob Stilwell
Division of Health Engineering
Department of Human Services
State House, Station 10
Augusta, ME 04333
(207)289-5676
1-800-232-0842 in state
Maryland Leon J. Rachuba
Radiological Health Program
Maryland Department of the
Environment
2500 Broening Highway
Baltimore, MD 21224
(410)631-3301
1-800-872-3666 In State
Massachusetts William J. Bell
Radiation Control Program
Department of Public Health
23 Service Center
Northampton, MA 01060
(413) 586-7525
1-800-445-1255 in state
Michigan SueHendershott
Division of Radiological Health
Bureau of Environmental and
Occupational Health
3423 North Logan Street
P.O. Box 30195
Lansing, MI 48909
(517) 335-8194
Minnesota Laura Oatmann
Indoor Air Quality Unit
925 Delaware Street, SE
P.O. Box 59040
Minneapolis, MN 55459-0040
(612)627-5480
1-800-798-9050 in state
11-29 Reprinted from USGS Open-File Report 93-292
-------
Mississii
Missouri
Montana
Silas Anderson
Division of Radiological Health
Department of Health
3150 Lawson Street
P.O. Box 1700
Jackson, MS 39215-1700
(601) 354-6657
1-800-626-7739 in state
Kenneth V. Miller
Bureau of Radiological Health
Missouri Department of Health
1730 East Elm
P.O. Box 570
Jefferson City, MO 65102
(314)751-6083
1-800-669-7236 In State
Adrian C. Howe
Occupational Health Bureau
Montana Department of Health and
Environmental Sciences
Cogswell Building A113
Helena, MT 59620
(406)444-3671
Joseph Milone
Division of Radiological Health
Nebraska Department of Health
301 Centennial Mall, South
P.O. Box 95007
Lincoln, NE 68509
(402)471-2168
1-800-334-9491 In State
Stan Marshall
Department of Human Resources
505 East King Street
Room 203
Carson City, NV 89710
(702) 687-5394
New Hampshire David Chase
Bureau of Radiological Health
Division of Public Health Services
Health and Welfare Building
Six Hazen Drive
Concord, NH 03301
(603) 271-4674
1-800-852-3345 x4674
Nebraska
New Jersey Tonalee Carlson Key
Division of Environmental Quality
Department of Environmental
Protection
CN415
Trenton, NJ 08625-0145
(609)987-6369
1-800-648-0394 in state
New Mexico William M. Floyd
Radiation Licensing and Registration
Section
New Mexico Environmental
Improvement Division
1190 St. Francis Drive
Santa Fe,NM 87503
(505) 827-4300
New York William J. Condon
Bureau of Environmental Radiation
Protection
New York State Health Department
Two University Place
Albany, NY 12202
(518)458-6495
1-800-458-1158 in state
North Carolina Dr. Felix Fong
Radiation Protection Division
Department of Environmental Health
and Natural Resources
701 Barbour Drive
Raleigh, NC 27603-2008
(919) 571-4141
1-800-662-7301 (recorded info x4196)
North Dakota Arlen Jacobson
North Dakota Department of Health
1200 Missouri Avenue, Room 304
P.O. Box 5520
Bismarck, ND 58502-5520
(701) 221-5188
Ohio Marcie Matthews
Radiological Health Program
Department of Health
1224 Kinnear Road - Suite 120
Columbus, OH 43212
(614) 644-2727
1-800-523-4439 in state
11-30 Reprinted from USGS Open-File Report 93-292
-------
Oklahoma
Oregon
Pennsylvania
Puerto Rico
Rhode Island
South Carolina
Gene Smith
Radiation Protection Division
Oklahoma State Department of
Health
P.O. Box 53551
Oklahoma City, OK 73152
(405) 271-5221
George Toombs
Department of Human Resources
Health Division
1400 SW 5th Avenue
Portland, OR 97201
(503)73W014
Michael Pyles
Pennsylvania Department of
Environmental Resources
Bureau of Radiation Protection
P.O. Box 2063
Harrisburg, PA 17120
(717) 783-3594
1-800-23-RADON In State
David Saldana
Radiological Health Division
G.P.O. Call Box 70184
Rio Piedras, Puerto Rico 00936
(809) 767-3563
Edmund Arcand
Division of Occupational Health and
Radiation
Department of Health
205 Cannon Building
Davis Street
Providence, RI02908
(401) 277-2438
Bureau of Radiological Health
Department of Health and
Environmental Control
2600 Bull Street
Columbia, SC 29201
(803)734^631
1-800-768-0362
South Dakota MikePochop
Division of Environment Regulation
Department of Water and Natural
Resources
Joe Foss Building, Room 217
523 E. Capitol
Pierre, SD 57501-3181
(605)773-3351
Tennessee Susie Shimek
Division of Air Pollution Control
Bureau of the Environment
Department of Environment and
Conservation
Customs House, 701 Broadway
Nashville, TN 37219-5403
(615)532-0733
1-800-232-1139 in state
Texas Gary Smith
Bureau of Radiation Control
Texas Department of Health
1100 West 49th Street
Austin, TX 78756-3189
(512) 834-6688
Utah John Hultquist
Bureau of Radiation Control
Utah State Department of Health
288 North, 1460 West
P.O. Box 16690
Salt Lake City, UT 84116-0690
(801) 536-4250
Vermont Paul demons
Occupational and Radiological Health
Division
Vermont Department of Health
10 Baldwin Street
Montpelier, VT 05602
(802)828-2886
1-800-640-0601 in state
Virgin Islands Contact the U.S. Environmental
Protection Agency, Region n
in New York
(212)264^110
n-31 Reprinted from USGS Open-File Report 93-292
-------
Virginia Shelly Ottenbrite
Bureau of Radiological Health
Department of Health
109 Governor Street
Richmond, VA 23219
(804) 786-5932
1-800-468-0138 in state
Washington Kate Coleman
Department of Health
Office of Radiation Protection
Airdustrial Building 5, LE-13
Olympia, WA 98504
(206) 753-4518
1-800-323-9727 In State
West Virginia BeattieL.DeBord
Industrial Hygiene Division
West Virginia Department of Health
151 llth Avenue
South Charleston, WV 25303
(304) 558-3526
1-800-922-1255 In State
Wisconsin Conrad Weiffenbach
Radiation Protection Section
Division of Health
Department of Health and Social
Services
P.O. Box 309
Madison, WI53701-0309
(608) 267-4796
1-800-798-9050 in state
Wyoming Janet Hough
Wyoming Department of Health and
Social Services
Hathway Building, 4th Floor
Cheyenne, WY 82002-0710
(307) 777-6015
1-800-458-5847 in state
11-32 Reprinted from USGS Open-File Report 93-292
-------
STATE GEOLOGICAL SURVEYS
May, 1993
Alabama Ernest A. Mancini
Geological Survey of Alabama
P.O. Box 0
420 Hackberry Lane
Tuscaloosa, AL 35486-9780
(205) 349-2852
Alaska Thomas E. Smith
Alaska Division of Geological &
Geophysical Surveys
794 University Ave., Suite 200
Fairbanks, AK 99709-3645
(907)479-7147
Arizona Larry D. Fellows
Arizona Geological Survey
845 North Park Ave., Suite 100
Tucson, AZ 85719
(602) 882-4795
Arkansas Norman F. Williams
Arkansas Geological Commission
Vardelle Parham Geology Center
3815 West Roosevelt Rd.
Little Rock, AR 72204
(501) 324-9165
California James F. Davis
California Division of Mines &
Geology
801 K Street, MS 12-30
Sacramento, CA 95814-3531
(916)445-1923
Colorado Pat Rogers (Acting)
Colorado Geological Survey
1313 Sherman St., Rm 715
Denver, CO 80203
(303)866-2611
Connecticut Richard C. Hyde
Connecticut Geological & Natural
History Survey
165 Capitol Ave., Rm. 553
Hartford, CT 06106
(203) 566-3540
Delaware Robert R. Jordan
Delaware Geological Survey
University of Delaware
101 Penny Hall
Newark, DE 19716-7501
(302) 831-2833
Florida Walter Schmidt
Florida Geological Survey
903 W. Tennessee St.
Tallahassee, FL 32304-7700
(904)488-4191
William H. McLemore
Georgia Geologic Survey
Rm. 400
19 Martin Luther King Jr. Dr. SW
Atlanta, GA 30334
(404) 656-3214
Hawaii Manabu Tagomori
Dept. of Land and Natural Resources
Division of Water & Land Mgt
P.O. Box 373
Honolulu, ffl 96809
(808) 548-7539
Idaho Earl H. Bennett
Idaho Geological Survey
University of Idaho
Morrill Hall, Rm. 332
Moscow, ID 83843
(208) 885-7991
Illinois Morris W. Leighton
Illinois State Geological Survey
Natural Resources Building
615 East Peabody Dr.
Champaign, IL 61820
(217) 333^747
Indiana Norman C. Hester
Indiana Geological Survey
611 North Walnut Grove
Bloomington, IN 47405
(812) 855-9350
Iowa Donald L. Koch
Iowa Department of Natural Resources
Geological Survey Bureau
109 Trowbridge Hall
Iowa City, IA 52242-1319
(319) 335-1575
Kansas Lee C. Gerhard
Kansas Geological Survey
1930 Constant Ave., West Campus
University of Kansas
Lawrence, KS 66047
(913) 864-3965
n-33 Reprinted from USGS Open-File Report 93-292
-------
Kentucky Donald C. Haney
Kentucky Geological Survey
University of Kentucky
228 Mining & Mineral Resources
Building
Lexington, KY 40506-0107
(606)257-5500
Louisiana William E. Marsalis
Louisiana Geological Survey
P.O. Box 2827
University Station
Baton Rouge, LA 70821-2827
(504)388-5320
Maine Walter A. Anderson
Maine Geological Survey
Department of Conservation
State House, Station 22
Augusta, ME 04333
(207)289-2801
Maryland Emery T. Cleaves
Maryland Geological Survey
2300 St. Paul Street
Baltimore, MD 21218-5210
(410) 554-5500
Massachusetts Joseph A. Sinnott
Massachusetts Office of
Environmental Affairs
100 Cambridge St, Room 2000
Boston, MA 02202
(617) 727-9800
Michigan R. Thomas Segall
Michigan Geological Survey Division
Box 30256
Lansing, MI 48909
(517) 334-6923
Minnesota PriscillaC. Grew
Minnesota Geological Survey
2642 University Ave.
St. Paul, MN 55114-1057
(612) 627-4780
Mississippi S. Cragin Knox
Mississippi Office of Geology
P.O. Box 20307
Jackson, MS 39289-1307
(601) 961-5500
Missouri James H. Williams
Missouri Division of Geology &
Land Survey
111 Fairgrounds Road
P.O. Box 250
Rolla, MO 65401
(314) 368-2100
Montana Edward T. Ruppel
Montana Bureau of Mines & Geology
Montana College of Mineral Science
and Technology, Main Hall
Butte, MT 59701
(406)4964180
Nebraska Perry B. Wigley
Nebraska Conservation & Survey
Division
113 Nebraska Hall
University of Nebraska
Lincoln, NE 68588-0517
(402)472-2410
Nevada Jonathan G. Price
Nevada Bureau of Mines & Geology
Stop 178
University of Nevada-Reno
Reno, NV 89557-0088
(702) 784-6691
New Hampshire Eugene L.Boudette
Dept. of Environmental Services
117 James Hall
University of New Hampshire
Durham, NH 03824-3589
(603) 862-3160
New Jersey Haig F. Kasabach
New Jersey Geological Survey
P.O. Box 427
Trenton, NJ 08625
(609) 292-1185
New Mexico Charles E. Chapin
New Mexico Bureau of Mines &
Mineral Resources
Campus Station
Socorro.NM 87801
(505) 835-5420
New York Robert H. Fakundiny
New York State Geological Survey
3136 Cultural Education Center
Empire State Plaza
Albany, NY 12230
(518)474-5816
n-34
Reprinted from USGS Open-File Report 93-292
-------
North Carolina Charles H. Gardner
North Carolina Geological Survey
P.O. Box 27687
Raleigh, NC 27611-7687
(919) 733-3833
North Dakota John P. Bluemle
North Dakota Geological Survey
600 East Blvd.
Bismarck, ND 58505-0840
(701) 224-4109
Ohio Thomas M. Berg
Ohio DepL of Natural Resources
Division of Geological Survey
4383 Fountain Square Drive
Columbus, OH 43224-1362
(614) 265-6576
Oklahoma Charles J. Mankin
Oklahoma Geological Survey
Room N-131, Energy Center
lOOE.Boyd
Norman, OK 73019-0628
(405) 325-3031
Oregon Donald A. Hull
Dept. of Geology & Mineral Indust.
Suite 965
800 NE Oregon St. #28
Portland, OR 97232-2162
(503)731-4600
Pennsylvania Donald M. Hoskins
Dept. of Environmental Resources
Bureau of Topographic & Geologic
Survey
P.O. Box 2357
Harrisburg,PA 17105-2357
(717) 787-2169
Puerto Rico Ram6n M. Alonso
Puerto Rico Geological Survey
Division
Box 5887
Puerta de Tierra Station
San Juan, P.R. 00906
(809) 722-2526
Rhode Island J. Allan Cain
Department of Geology
University of Rhode Island
315 Green Hall
Kingston, RI02881
(401) 792-2265
South Carolina Alan-Jon W. Zupan (Acting)
South Carolina Geological Survey
5 Geology Road
Columbia, SC 29210-9998
(803) 737-9440
South Dakota CM. Christensen (Acting)
South Dakota Geological Survey
Science Center
University of South Dakota
Vermillion, SD 57069-2390
(605) 677-5227
Tennessee Edward T. Luther
Tennessee Division of Geology
13th Floor, L & C Tower
401 Church Street
Nashville, TN 37243-0445
(615) 532-1500
Texas William L. Fisher
Texas Bureau of Economic Geology
University of Texas
University Station, Box X
Austin, TX 78713-7508
(512)471-7721
Utah M. Lee Allison
Utah Geological & Mineral Survey
2363 S. Foothill Dr.
Salt Lake City, UT 84109-1491
(801)467-7970
Vermont Diane L. Conrad
Vermont Division of Geology and
Mineral Resources
103 South Main St.
Waterbury,VT 05671
(802)244-5164
Virginia Stanley S. Johnson
Virginia Division of Mineral
Resources
P.O. Box 3667
Charlottesville, VA 22903
(804) 293-5121
Washington Raymond Lasmanis
Washington Division of Geology &
Earth Resources
Department of Natural Resources
P.O. Box 47007
Olympia, Washington 98504-7007
(206) 902-1450
11-35 Reprinted from USGS Open-File Report 93-292
-------
WestJ/irginia Larry D.Woodfbrk
West Virginia Geological and
Economic Survey
Mont Chateau Research Center
P.O. Box 879
Morgantown, WV 26507-0879
(304) 594-2331
Wisconsin James Robertson
Wisconsin Geological & Natural
History Survey
3817 Mineral Point Road
Madison, WI 53705-5100
(608)263-7384
Wyoming Gary B. Glass
Geological Survey of Wyoming
University of Wyoming
Box 3008, University Station
Laramie, WY 82071-3008
(307) 766-2286
11-36 Reprinted from USGS Open-File Report 93-292
-------
EPA REGION 5 GEOLOGIC RADON POTENTIAL SUMMARY
by
R. Randall Schumann, Douglass E. Owen, and Sandra L. Szarzi
U.S, Geological Survey
EPA Region 5 comprises the states of Illinois, muiana, Michigan, Minnesota, Ohio, and
Wisconsin. For each state, geologic radon potential areas were delineated and ranked on the
basis of geologic, soil, housing construction, and other factors. Areas in which the average
screening indoor radon level of all homes within the area is estimated to be greater than 4 pCi/L
were ranked high. Areas in which the average screening indoor radon level of all homes within
the area is estimated to be between 2 and 4 pCi/L were ranked moderate/variable, and areas in
which the average screening indoor radon level of all homes within the area is estimated to be
less than 2 pCi/L were ranked low. Information on the data used and on the radon potential
ranking scheme is given in the introduction chapter. More detailed information on the geology
and radon potential of each state in Region 5 is given in the individual state chapters. The
individual chapters describing the geology and radon potential of the six states in EPA Region 5,
though much more detailed than this summary, still are generalized assessments and there is no
substitute for having a home tested. Radon levels, both high and low, can be quite localized, and
within any radon potential area homes with indoor radon levels both above and below the
predicted average will likely be found.
Radon potential in EPA Region 5 is controlled by three primary factors. Bedrock
geology provides the source material for the overlying glacial deposits, and in areas with no
glacial cover, directly provides the parent material for the soils. Glacial geology (fig. 1) is an
important factor because glaciers redistributed the bedrock and glacially-derived soils have
different soil characteristics from soils developed on bedrock. Climate, particularly precipitation
and temperature, in concert with the soil's parent material, controls soil moisture, the extent of
soil development and weathering, and the types of weathering products that form in the soils.
The following is a brief, generalized discussion of the bedrock and glacial geology of EPA
Region 5 as they pertain to indoor radon. More detailed discussions may be found in the
individual state geologic radon potential chapters.
Western and southern Minnesota are underlain by deposits of the Des Moines and Red
River glacial lobes. Des Moines lobe tills are silty clays and clays derived from Upper
Cretaceous sandstones and shales, which have relatively high concentrations of uranium and high
radon emanating power. Deposits of the Red River lobe are similar to those of the Des Moines
lobe, but also contain silt and clay deposits of glacial Lake Agassiz, a large glacial lake that
occupied the Red River Valley along the Minnesota-North Dakota border. The Upper
Cretaceous Pierre Shale provides good radon source material because, as a whole, it contains
higher-than-average amounts of uranium (average crustal abundance of uranium is about 2.5
parts per million). Glacial deposits of the Red River and Des Moines lobes generate high
(> 4 pCi/L) average indoor radon concentrations (fig. 2) and have high geologic radon potential
(fig. 3). Northern Wisconsin, the western part of the Upper Peninsula of Michigan, and part of
northern Minnesota are underlain by glacial deposits of the Lake Superior lobe. Parts of northern
Minnesota are also underlain by deposits of the Rainy and Wadena lobes (fig. 1). The
underlying source rocks for these tills are Precambrian volcanic rocks, metasedimentary and
metavolcanic rocks, and granitic plutonic rocks of the Canadian Shield. The volcanic,
metasedimentary, and metavolcanic rocks have relatively low uranium contents, and the granitic
rocks have variable, mostly moderate to high, uranium contents. The sandy tills derived from the
HI-1 Reprinted from USGS Open-File Report 93-292-E
-------
J2
9
N
-------
1X1 S
T3 £3
e o
-
8 p^ts
* § o
p £ .B
\
eS C "
w
2 >L
11 .
E c *>
.
2 c "" to
« a wi S
w o 4> go
c -s ex, eo
TO pm ~*
«a "
« r* S^
*- g «« O
i_ O ft) T3
O "O '& W
O ** C *"
*O OM 3 O
C i O OJO
—• CO O CO
ISO'S «*- fe
C C O >
O CO
I
O
o s
E U "S "o
-------
o
rt
<
CO
Kt
I
§
T3
U
'So
o
1
en
I
-------
volcanic, metase.dimentary, and metavolcanic rocks have relatively high permeability, but
because of their lower uranium content of and lower emanating power, they have mostly
moderate to locally high radon potential (fig. 3). Sandy, granite-rich tills in northern Minnesota
generally have high radon potential. Granites and granite gneisses, black slates and graphitic
schists, and iron-formation are associated with anomalous uranium concentrations and locally
high radon in northern Wisconsin and adjacent northwestern Michigan. In central Wisconsin,
uraniferous granites of the Middle Proterozoic Wolf River and Wausau plutons are exposed at
the surface or covered by a thin layer of glacial deposits and cause some of the highest indoor
radon concentrations in the State. An area in southwestern Wisconsin and adjacent smaller parts
of Minnesota, Iowa, and Illinois, is called the "Driftless Area" (fig. 1). It is not covered by
glacial deposits but parts of the area were likely overrun by glaciers at least once. The Driftless
Area is underlain by Cambrian and Ordovician limestone, dolomite, and sandstone with
moderate to high radon potential.
Glacial deposits in southern Wisconsin, northern and central Illinois, and western Indiana
are primarily from the Green Bay and Lake Michigan lobes. The Green Bay and Lake Michigan
lobes advanced from their source in the Hudson Bay region of Canada and moved southward,
terminating in Illinois and Iowa. These tills range from sandy to clayey and are derived
primarily from shales, sandstones, and carbonate rocks of southern Wisconsin, the western
Michigan Basin, and the northern Illinois Basin. A small part of eastern Illinois and much of
western Indiana are covered by deposits of the Huron-Erie lobe, and west-central Illinois is
covered by glacial deposits of pre-Wisconsinan, mostly Illinoian, age. The Huron-Erie lobe
entered Illinois from the east and moved westward and southwestward into the State. Huron-Erie
lobe and pre-Wisconsinan glacial deposits are derived from Paleozoic shale, sandstone, siltstone,
carbonate rocks, and coal of the Illinois Basin, and they are commonly calcareous due to the
addition of limestones and dolomites of northern Indiana and Ohio and southern Ontario. In
contrast, Lake Michigan lobe deposits contain significant amounts of dark gray to black
Devonian and Mississippian shales of the Michigan Basin, accounting for the high clay content
of Lake Michigan lobe tills. Unglaciated southernmost Illinois is part of the Mississippi
Embayment of the Coastal Plain and has low geologic radon potential.
Wisconsin-age glacial deposits in Indiana were deposited by three main glacial lobes—
the Lake Michigan lobe, which advanced southward as far as central Indiana; the Huron-Erie
lobe; and the Saginaw sublobe of the Huron lobe (labeled Huron lobe on fig. 1), which advanced
from the northeast across northern Ohio and southern Michigan, respectively. Michigan lobe
deposits are clayey near Lake Michigan, sandy and gravelly in an outwash and morainal area in
northwestern Indiana, and clayey to loamy in west-central Indiana. Saginaw sublobe deposits are
loamy and calcareous and are derived primarily from carbonate rocks and shale. The Huron-Erie
lobe advanced from the northeast and covered much of northern and central Indiana at its
maximum extent Eastern Indiana and western Ohio are underlain by tills of the Huron-Erie lobe
that are derived in part from black shales of the Devonian Ohio Shale and Devonian-
Mississippian New Albany Shale, but also include Paleozoic limestone, dolomite, sandstone,
siltstone, and gray shale. Black shales and carbonates underlie and provide source material for
glacial deposits in a roughly north-south pattern through central Ohio, including the Columbus
area, and extend south of the glacial limit, where the black shales form a prominant arcuate
pattern in northern Kentucky that curves northward into southern Indiana and underlies glacial
deposits in east-central Indiana. The overall radon potential of this area is high. Eastern Ohio is
underlain by Devonian to Permian shales and limestones with moderate to high radon potential.
m-5 Reprinted from USGS Open-File Report 93-292-E
-------
The Michigan Basin covers all of the Southern Peninsula and the eastern half of the
Northern Peninsula of Michigan, as well as parts of eastern Wisconsin and northeastern Illinois,
northern Indiana, and northwestern Ohio. Glacial deposits include silty and clayey tills of the
Lake Michigan, Huron, and Huron-Erie lobes (fig. 1). Huron lobe tills are sandy to gravelly and
calcareous, containing pebbles and cobbles of limestone, dolomite, and some sandstone and
Shale, with boulders of igneous and metamorphic rocks and quartzite. Tills of the Huron-Erie
and Lake Michigan lobes are derived from similar source rocks but are more silty and clayey in
texture. Source rocks for these tills are sandstones, gray shales, and carbonate rocks of the
Michigan Basin, which are generally poor radon sources. In the Southern Peninsula, the
Devonian Bell, Antrim, and Ellsworth Shales, and Mississippian Sunbury Shale locally contain
organic-rich black shale layers with higher-than-average amounts of uranium, except for the
Antrim Shale, which is organic rich throughout. These shales underlie and constitute source rock
for glacial deposits in the northern, southeastern, and southwestern parts of the Southern
Peninsula, and are locally exposed at the surface in the northern part of the Southern Peninsula.
Because of generally moist soils, soils developed on tills derived from black shales in Michigan
generate moderate to locally high radon, with higher values more common in the southern part of
the State (fig. 2).
Glaciated areas present special problems for radon-potential assessment because bedrock
material in the central United States was commonly transported hundreds of km from its source.
Glaciers are quite effective in redistributing uranium-rich rocks; for example, in Ohio, uranium-
bearing black shales have been disseminated over much of western Ohio and eastern Indiana,
now covering a much larger area than their original outcrop pattern, and display a prominent'
radiometric high. The physical, chemical, and drainage characteristics of soils formed from
glacial deposits vary according to source bedrock type and the glacial features on which they are
formed. For example, soils formed from ground moraine deposits tend to be more poorly
drained and contain more fine-grained material than soils formed on kames, moraines, or eskers,
which are generally coarser and well-drained. In general, soils developed from coarser-grained
tills are poorly structured, poorly sorted, and poorly developed, but are generally more highly
permeable than the bedrock from which they are derived.
Clayey tills, such as those underlying parts of western and southern Minnesota, have
relatively high emanation coefficients and usually have low to moderate permeability, depending
on the degree to which the clays are mixed with coarser sediments. Tills consisting of mostly
coarse material tend to emanate less radon because larger grains have lower surface area-to-
vplume ratios, but because these soils have generally high permeabilities, radon transport
distances are generally longer. Structures built in these materials are thus able to draw soil air
from a larger source volume, so moderately to highly elevated indoor radon concentrations may
be achieved from comparatively lower-radioactivity soils. In till soils with extremely high
permeability, atmospheric dilution may become significant, and if the soils have low to moderate
radium contents, elevated indoor radon levels would be less likely to occur. Soil moisture has a
significant effect on radon generation and transport and high levels of soil mois.ture generally
lower the radon potential of an area. The main effect of soil moisture is its tendency to occlude
soil pores and thus inhibit soil-gas transport. Soils in wetter climates from northern Minnesota to
northern Michigan generally have lower radon potential than soils derived from similar tills in
the southern parts of those states or in Indiana and Illinois, in part because of higher soil moisture
conditions to the north.
ffl-6 Reprinted from USGS Open-File Report 93-292-E
-------
PRELIMINARY GEOLOGIC RADON POTENTIAL ASSESSMENT OF WISCONSIN
R. Randall Schumann
U.S. Geological Survey
INTRODUCTION
This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
deposits of Wisconsin. The scale of this assessment is such that it is inappropriate for use in
identifying the radon potential of small areas such as neighborhoods, individual building sites, or
housing tracts. Any localized assessment of radon potential must be supplemented with additional
data and information from the locality. Within any area of a given radon potential ranking, there
are likely to be areas with higher or lower radon levels than characterized for the area as a whole.
Indoor radon levels, both high and low, can be quite localized, and there is no substitute for testing
individual homes. Elevated levels of indoor radon have been found in every state, and EPA
recommends that all homes be tested. For more information on radon, the reader is urged to
consult the local or State radon program or EPA regional office. More detailed information on state
or local geology may be obtained from the State geological survey. Addresses and phone numbers
for these agencies are listed in chapter 1 of this booklet
PHYSIOGRAPHIC AND GEOGRAPHIC SETTING
The landscape of Wisconsin ranges from flat plains to dissected uplands. Elevations range
from 595 m (1952 ft) at Timms Hill, near Ogema, to 177 m (580 ft) along the shore of Lake
Michigan in eastern Wisconsin (Dutton, 1976). Parts of two major physiographic provinces are
represented in Wisconsin: the Superior Upland province in the northern part of the State and the
Central Lowlands province in the south. Within the State these are further subdivided into
physiographic regions (fig. 1). The Superior Lowland and Northern Highland regions are parts of
the Superior Upland province; the Western Upland, Central Plain, and Eastern Ridges and
Lowlands regions (fig. 1) are included in the Central Lowlands province.
The Western Upland is a dissected highland in the southwestern part of Wisconsin. Most
of this area lies within the Driftless Area, which is not covered by glacial deposits and is generally
more dissected than the glaciated parts of the State. Most of the area is underlain by nearly flat-
lying sandstone and dolomite, with the notable exception of the Baraboo Range in Columbia and
Sauk Counties (fig. 2 is a map of counties), which is composed primarily of quartzite (Crowns,
1976). Numerous caves have formed in dolomite in southwestern Wisconsin.
The Central Plain is a crescent-shaped belt of relatively flat landscape, interrupted only
locally by pinnacles and hills resulting from differential erosion of the sandstone. Much of the area
is covered by glacial drift, and the central part of the region is a flat-lying plain occupying the
former basin of glacial Lake Wisconsin, covering most of Adams and Juneau Counties and parts of
nearby counties. Wetlands are common in the central and eastern parts of the Central Plain.
The Eastern Ridges and Lowlands comprises gently rolling plains with tilted limestone
ledges (forming cuestas), moraines, and drumlins providing local relief. Wetlands and part of the
bed of glacial Lake Oshkosh cover the northern part of the area. This region contains the State's
greatest density of population, as it contains most of Wisconsin's major cities, including
Milwaukee, Green Bay, and Madison. Figure 3 is a map showing population distribution by
county.
IV-1 Reprinted from USGS Open-File Report 93-292-E
-------
-------
LAKE SUPERIOR
LOWLAND
NORTHERN!
HIGHLAND !
CENTRAL PLAIN
WESTERN
UPLAND
-
EASTERN
RIDGES AND
\
\ LOWLANDS I
V j
...; \
0 25 50 75 100 miles
'
50
100
l
150
km
Figure 1. Physiographic regions of Wisconsin (after Martin, 1916).
-------
Figure!. Wisconsin counties.
-------
POPULATION (1990)
C3 0 to 25000
E3 25001 to 50000
E3 50001 to 100000
H 100001 to 500000
• 500001 to 959275
Figure 3. Population of counties in Wisconsin (1990 U.S. Census data).
-------
-------
The Northern Highland (fig. 1) is an undulating plain sloping gently toward the south with
occasional hills and ridges, including Timms Hill, Pearson Hill, Rib Mountain, and Sugarbush
Hill, the highest points in the State. The Northern Highland is underlain by Precambrian rock of
the North American Shield (also referred to as the Canadian Shield) and covered by Pleistocene
glacial deposits. The area is heavily forested and contains numerous lakes and wetlands.
The Lake Superior Lowland is located on the southern shore of Lake Superior and slopes
toward the lake. The edge of the Lowland is marked by a steep escarpment with local relief as
much as 107 m (350 ft), which has formed rocky cliffs and waterfalls where bedrock is exposed
(Crowns, 1976).
GEOLOGY
The discussion of geology is divided into three sections: bedrock geology, glacial geology,
and a discussion of uranium in rocks and soils. "Bedrock" refers to pre-glacial rock units, which '
are covered by glacial deposits in most parts of the State. A bedrock geologic map (fig. 4) shows
rock units that underlie glacial deposits or are exposed at the surface in some areas. The glacial
deposits are composed of material derived from underlying bedrock and from rock units to the
north and northeast. The discussion of bedrock geology is summarized from Button (1976),
Ostrom (1976), Mudrey and others (1982), and Sims (1992). The section on glacial geology is
summarized from Frye and others (1965), Hadley (1976), and Richmond and Fullerton (1983a,
1983b, 1984,1991). For more detailed discussions and maps of the geology, the reader is
encouraged to consult these and other reports.
Bedrock geology: Wisconsin's bedrock geology divides the State into two major areas: an
area of Precambrian rock, mostly metamorphic and igneous, in the north, and an area of Paleozoic
sedimentary rock that overlies the older rock in the south, east, and west (fig. 4). The
northwesternmost area of Precambrian rock in Wisconsin is composed of a thick sequence of
volcanic and sedimentary rock (fig. 4). Beds of shale, sandstone, and conglomerate are
interbedded with thick, massive basaltic and some andesitic lava flows. Gabbros with essentially
the same composition as the lavas also underlie this area. A thick sequence of Precambrian
sedimentary rock called the Lake Superior Sandstone, consisting of shale, sandstone, and
conglomerate, also occurs in this area (fig. 4).
The Gogebic Range, in Bayfield, Ashland, and Iron Counties (figs. 2,4), is underlain by
Middle Precambrian quartzite, iron-formation, and locally, dolomite. South and east of the
Gogebic Range are gneisses, metavolcanic rock of mafic to intermediate composition, and lesser
amounts of metasedimentary rock and iron-formation. The western edge of the Precambrian rock
area is underlain by quartzite (fig. 4). The southwestern part of the area lies along the Black River
and contains mainly gneisses and schists with local areas of felsic and mafic intrusive rock and
iron-formation. The south-central part of the area contains numerous exposures of Precambrian
bedrock at the surface in the Wausau and Wisconsin Rapids area. Rocks in this area are primarily
felsic and mafic igneous intrusive and volcanic rock, with lesser amounts of gneiss and quartzite.
The southeastern part of the area is dominated by the Wolf River batholith, an extensive area of
primarily granite and quartz monzonite (Fig. 4). Precambrian rock exposed outside of the
northeastern part of the State includes outcrops of quartzite, iron-formation, and slate in the
Baraboo area in Sauk and Columbia Counties (fig. 4). Precambrian granite and rhyolite directly
underlie glacial deposits in Marquette, Green Lake, and Waushara Counties.
IV-5 Reprinted from USGS Open-File Report 93-292-E
-------
-------
0 2^5 SO mi
0 25 50 75 km
Figure 4. Generalized bedrock geologic map of Wisconsin (after Mudrey and others, 1982, and
Sims, 1992).
-------
-------
GENERALIZED BEDROCK GEOLOGIC MAP OF WISCONSIN
EXPLANATION
E~JH1 Devonian dolomite and shale
I' i' H Silurian dolomite
^^i Ordovician Maquoketa Formation-shale and dolomite
[S51 Ordovician Sinnipee Group-dolomite with some limestone and shale
j^Hj Ordovician St Peter Formation-sandstone with some limestone, shale, and
^^m conglomerate
FTTTJ Ordovician Prairie du Chien Group-dolomite with some sandstone and
1 ' ' '' shale
1 1 Cambrian sandstone with some dolomite and shale
CvC'3 Proterozoic Y sandstone and conglomerate with some shale
FT71 Proterozoic Y basalt, andesite, and felsite (includes Upper Archean
lk-ij metagabbro in Iron and Ashland Counties)
E;!?] Proterozoic Y granite and syenite (in Wolf River Batholith and Wausau
and Stettin plutons)
VO&YA Proterozoic Y anorthosite
|xx"xi ProterozoicX quartzite
PPffPfl Proterozoic X metasedimentary rocks (argillite, siltstone, quartzite,
graywacke) and iron-formation
[Y-^ci Proterozoic X granite, granodiorite, tonah'te, and some quartz diorite and
Fl V'1"1 granite gneiss
t»»1 ProterozoicX gneiss and amphiboh'te
l»!V!«»i Proterozoic X mafic to felsic volcanic and metavolcanic rocks
Proterozoic X. gabbro and metagabbro (includes Upper Archean
metagabbro in Eau Claire County)
Lower Proterozoic and Upper Archean gneiss, migmatitic gneiss,
amphiboh'te, and some granitic gneiss and granite
Lower to Middle Proterozoic and Upper Archean mylonite (in Eau Pleine
shear zone)
-------
-------
Lower Paleozoic sedimentary rock overlies Precambrian rock in the western, southern, and
eastern parts of the State"(fig. 4). They consist of a sequence of alternating clastic (sandstone,
shale) and carbonate (limestone, dolomite) rock ranging in age from Cambrian to Devonian.
Upper Cambrian rocks (fig. 4) include the Mount Simon (sandstone), Eau Claire (sandstone and
shale), Wonewoc (sandstone), Lone Rock (sandstone, shale, and dolomite), Mazomanie
(sandstone), St Lawrence (dolomite and siltstone), and Jordan (sandstone) Formations. The
oldest Ordovician rock overlies Cambrian rock on the west, south, and east, and includes the
Prairie du Chien Group and the St Peter Formation (fig. 4). The Prairie du Chen Group comprises
the Oneota Dolomite and the Shokapee Formation. The Shokapee Formation consists of the New
Richmond Sandstone Member (composed of sandstone, sandy dolomite, and shale) and the
Willow River Dolomite. The St Peter Formation is composed of sandstone, shaly conglomerate,
and shale. It is overlain by the Ordovician Sinnipee Group, consisting of dolomite, shaly
dolomite, and shale, and the Maquoketa Shale (fig. 4).
Silurian rock includes thin-to thick bedded dolomites occurring in a wide band along the
State's eastern coastline from the Door Peninsula southward to the Illinois border. Devonian rock
occurs in a small area in southeastern Wisconsin near Milwaukee (fig. 4) and consists of dolomite,
shaly limestone, and shale.
Glacial geology: More than three-quarters of Wisconsin's land area is covered by
Pleistocene (and possibly older) glacial deposits ranging in thickness from less than one to more
than 100 meters. Pre-Wisconsinan deposits are exposed along the southern border of the State in
Green and Lafayette Counties (fig. 5). These deposits, along with Altonian (earliest Wisconsinan)
drift in the same area, are thought to have been deposited by glaciers which entered the area from
the east. Late Altonian drift to the north of the Driftless Area (fig. 5) was deposited by the Lake
Michigan and Green Bay lobes, which moved westward across the State, and by the Superior and
Des Moines lobes, which entered from the northwest, moving southeastward. This unit consists
of sandy to loamy till containing fragments of gabbro, felsite, red sandstone, and limestone in the
west, and granite, gneiss, schist, and sandstone in central Wisconsin.
During the Woodfordian substage (middle to late Wisconsinan), ice advanced from the
north, northeast, and east in several distinct lobes and sublobes, leaving a prominent moraine that
stretches across the State from Minnesota to Illinois. The Lake Michigan and Green Bay lobes
advanced roughly south-southeastward along the troughs of Lake Michigan and Green Bay
(fig. 5). The Lake Michigan lobe deposits are primarily clayey tills containing clasts of limestone
and dolomite. The Green Bay lobe deposited silty- and sandy-clay loam tills and loamy tills
containing clasts of limestone and dolomite, with locally scattered clasts of igneous and
metamorphic rocks (Richmond and Fullerton, 1984). The Chippewa, Wisconsin Valley, and
Langlade sublobes of the Superior lobe advanced from the north and northeast across the Lake
Superior basin and northern Michigan. These lobes deposited mainly clayey, silty, sandy till
derived from granite, mafic metavolcanic rocks, gabbro, and schist
Deposits of the Grantsburg sublobe of the Des Moines lobe, which entered the State from
the west, are found in Burnett and Polk counties (fig. 5). Till from the Grantsburg sublobe
contains fragments of limestone, shale, and other rocks from northwestern Minnesota, and red
sandstone, basalt, and gabbro from the Lake Superior district (Wright and others, 1973). As the
ice retreated near the end of the Woodfordian stage, many of the glacial lakes in Wisconsin were
formed, including ancestral Lake Michigan, known as Lake Chicago, and Lake Wisconsin.
During late Wisconsinan time, the Superior lobe advanced southwestward along the Lake Superior
basin, carrying mostly basalt, gabbro, and red sandstone, the Green Bay lobe
IV-8 Reprinted from USGS Open-File Report 93-292-E
-------
-------
EXPLANATION
=r=
^J Glacial lake deposits
fU Superior lobe
|j Chippewa sublobe
£| Wisconsin Valley sublobe
J Langlade sublobe
U Grantsburg sublobe
^ Green Bay lobe
^ Lake Michigan lobe
U Pre-Late Wisconsinan
ii glacial deposits
"I Driftless Area
0 25 50 75 100 miles
50
i
100
150
km
Figure 5. Glacial lobes and deposits in Wisconsin (after Richmond and Fullerton, 1983 1984
1991; and Thwaites, 1960).
-------
-------
re-advanced as far as the southern end of modern Lake Winnebago, and the Lake Michigan lobe
advanced down the Lake Michigan Basin as far as Milwaukee (Hadley, 1976). The final retreat of
ice from Wisconsin occurred about 9,500 years ago.
Loess deposits (windblown silt derived from glacial drift) ranging in thickness from 0 to
5 m occur over much of the State. Most of the loess occurs in the south-central and western parts
of Wisconsin, including most of the Driftless Area. The thickest deposits occur along the
Mississippi River on the State's western border.
Uranium geololgy: Schnabel (1976) describes a fragment of a quartz-pebble conglomerate,
presumed to be from the Precambrian McCaslin Formation, found near Mt. McCaslin in
southeastern Forest County containing 0.75 percent (7500 ppm) uranium (U). Two other samples
of conglomerate also presumed to be from the McCaslin Formation contain 0.12 and 0.33 percent
U (Kalliokoski, 1976), but no other radioactive conglomerate samples have since been found in
this area and outcrops of the McCaslin Formation are also low in radioactivity. Sandstone of the
Cambrian Tunnel City Group in the vicinity of Tomah, Monroe County, yielded as much as 6 ppm
U (Schnabel, 1976), probably associated with glauconite (Kalliokoski, 1976; Wisconsin
Geological Survey, 1956). Elevated uranium (for purposes of this report, "elevated" is defined as
greater than 2.5 ppm U) and elevated soil-gas radon concentrations are associated with glauconitic
sediments in a number of areas, such as the Atlantic and Gulf Coastal Plain (Gundersen and
others, 1991). Rocks of granitic composition in the northeast and north-central part of the State,
particularly rocks of the Wolf River Batholith, contain sufficient uranium to generate radon at
levels of concern. In particular, the Red River quartz monzonite in southern Shawano and
northern Waupaca Counties and the Wausau Syenite Complex in Marathon County host a number
of radioactive anomalies (Kalliokoski, 1976). Shear zones in contact with Wolf River Batholith
rocks, such as in Marathon County, may be areas of localized uranium enrichment (Kalliokoski,
1976). Glacial drift containing granitic rock fragments as a major constituent may contain elevated
uranium concentrations.
SOILS
Soils of the orders Entisols, Inceptosols, Mollisols, Alfisols, Spodosols, and Histosols can
be found in Wisconsin (Hole, 1976a, 1976b). Figure 6 shows major soil regions of Wisconsin.
Soils of southwestern Wisconsin (fig. 6A) are silty and clayey soils developed on sedimentary
rocks. Much of this area is covered by loess. Soils of southeastern Wisconsin (fig. 6B) are silty
to sandy soils developed on calcareous glacial drift. Most soils of this area have accumulations of
calcium carbonate (CaCOa) at 0.5 to 1.5 m depth. The amount of carbonate in the soils roughly
follows the carbonate content of the parent tills, which decreases westward from more than 50
percent north of Milwaukee to less than 15 percent in Marquette County (Hole, 1976a). The soils
also contain considerable clay in the eastern pert of the region. Soils of the Central Sandy Plain
(fig. 6C) are sandy soils developed on coarse glacial deposits. Most of these soils are excessively
drained, but some areas are poorly drained, especially in areas underlain by glacial lake deposits,
many of which are now occupied by wetlands. The Western Sandstone Uplands and Valleys area
occupies much of the Driftless Area (fig. 6D) and contains mostly silty and sandy loams. Some of
the Cambrian sandstones in this area contain significant amounts of glauconite, giving the
sandstone a green color ("greensands") that is also imparted to the soils developed from this unit
(Hole, 1976b).
IV-10 Reprinted from USGS Open-File Report 93-292-E
-------
-------
Figure 6. Soils of Wisconsin. A, Soils of Southwestern Wisconsin; B, Soils of Southeastern
Wisconsin; C, Soils of the Central Sandy Plain; D, Soils of the Western Sandstone
Uplands and Valleys; E, Soils of the Northern and Eastern Sandy and Loamy reddish
Drift Uplands and Plains; F, Soils of the Northern Silty Uplands and Plains; G, Soils of
the Northern Loamy Uplands and Plains; H, Soils of the Northern Sandy Uplands and
Plains; I, Soils of the Northern and Eastern Clayey and Loamy Reddish Drift Uplands
and Plains; J, Soils of Stream Bottoms and Major Wetlands (from Hole, 1976a, b).
-------
Soils of the Northern and Eastern Sandy and Loamy Reddish Drift Uplands and Plains lie
on either side of-Green Bay (fig. 6E). Depth to the dolomite bedrock is very small in many parts
of this soil area. These soils are distinct from soils in nearby areas because they are "pink" rather
than reddish or brown in color. Some of the soils are developed on glacial lake deposits and
consist of silty to very fine sand with little or no clay accumulation in the B horizon. Carbonate
content of these soils ranges from fairly high on the Door Peninsula to only a few percent in the
northwestern part of the region (Hole, 1976b). Soils of the Northern Silty Uplands and Plains
(fig. 6F) consist of silt to silty loam about 0.6 m thick covering acidic reddish-brown till, sand,
gravel, outwash, and Precambrian bedrock. The silty material was probably originally loess
(Hole, 1976b). Soils of the Northern Loamy Uplands and Plains (fig. 6G) are forest soils
developed on glacial drift These loams, sands, and sandy loams probably incorporated
windblown sUt into the soil layers during formation, as there is no discrete loess cover on these
soils as in other areas. These soils have weak argillic horizons (clayey subsurface layers) and
spodic horizons formed from accumulations of organic matter and iron oxides (Hole, 1976b).
Soils of the Northern Sandy Uplands and Plains (fig. 6H) are developed on glacial
deposits, mostly outwash, giving the soils a sandy to stony texture. Soils of the Northern and
Eastern Clayey and Loamy Reddish Drift Uplands and Plains (fig. 61) are red clay soils bordering
Lake Superior, Green Bay, and Lake Michigan. These soils are associated with Valderan glacial
deposits of the Superior, Green Bay, and Lake Michigan lobes. The red clays and silts are colored
by glacially-ground Precambrian iron-formation (Hole, 1976b). In the north the clayey soils are
associated with sandy soils. These soils contain from 15 percent (near Lake Superior) to 30
percent calcium carbonate (near Lake Michigan). Soils of Stream Bottoms and Major Wetlands are
scattered across the State (fig. 6J). These soils are poorly drained and generally have water tables
at or near the surface.
A generalized map of soil permeability (fig. 7) was compiled using maps and reports by
Hole (1976a, 1976b), Wisconsin Department of Natural Resources and Wisconsin Geological and
Natural History Survey (1987), and U.S. Soil Conservation Service county soil surveys. Soil
permeability is generally low in soils developed on glacial lake deposits and in soils of regions A,
I, and the western part of region F (figs. 6A, 6F, and 61). Soils of regions C, D, G, and H (figs.
6C, 6D, 6G, and 6H) have generally high permeability in U.S. Soil Conservation Service
percolation tests (fig. 7).
INDOOR RADON DATA
Indoor radon data from 1191 homes sampled in the State/EPA Residential Radon Survey
conducted in Wisconsin during the winter of 1986-87 are given in Table 1 and shown in figure 8.
Data are only displayed in figure 8 for those counties with 5 or more data values. The maximum
value recorded in the survey was 89 pCi/L in Grant County. Counties with average screening
indoor radon levels equal to or greater than 4 pCi/L include Dodge, Door, Grant, Iron, Langlade,
Marathon, Polk, Portage, Price, Rock, Shawano, St. Croix, Walworth, Washington, Waukesha,
and Waupaca (fig. 8; Table 1). In four counties (with 5 or more measurements)—Dodge, Rock,
Walworth, and Waukesha—50 percent or more of the homes tested had indoor radon levels
exceeding 4 pCi/L (Table 1).
IV-12 Reprinted from USGS Open-File Report 93-292-E
-------
SOIL PERMEABILITY (in/hr)
High (>6)
I I Low(<0.6)
Moderate (0.6-6)
0
1
0
25
i
50
50 75
i i
I
100
10
1
150
100 miles
km
Figure 7. Generalized soil permeability map of Wisconsin. Compiled by Kevin M. Schmidt,
U.S. Geological Survey, from Hadley and Pelham (1976), Wisconsin Department of
Natural Resources and Wisconsin Geologic and Natural History Survey (1987), and
U.S. Soil Conservation Service county soil survey data.
-------
Bsmt. & 1st Floor Rn
%24pCi/L
12
13
OtolO
mo20
25 KSSSSSSfrl 21 to 40
5 E3 41 to 60
1 H 61 to 80
0 i 81 to 100
16 ' ' Missing Data
(< 5 measurements)
100 Miles
Bsmt & 1st Floor Rn
Average Concentration (pCi/L)
10
32
13
_d 0.0 to 1.9
2.0 to 4.0
4.1 to 10.0
1 1 10.1 to 13.4
16 I I Missing Data
(< 5 measurements)
100 Miles
Figure 8. Screening indoor radon data from the EPA/State Residential Radon Survey of Wisconsin,
1986-87, for counties with 5 or more measurements. Data are from 2-7 day charcoal canister tests.
Histograms in map legends show the number of counties in each category. The number of samples
in each county (see Table 1) may not be sufficient to statistically characterize the radon levels of the
counties, but they do suggest general trends. Unequal category intervals were chosen to provide
reference to decision and action levels.
-------
TABLE 1. Screening indoor radon data from the State/EPA Residential Radon Survey of
Wisconsin conducted during 1986-87. Data represent 2-7 day charcoal canister measurements
from the lowest level of each home tested.
COUNTY
ADAMS
ASHLAND
BARRON
BAYFELD
BROWN
BUFFALO
BURNETT
CALUMET
CfflPPEWA
CLARK
COLUMBIA
CRAWFORD
DANE
DODGE
DOOR
DOUGLAS
DUNN
EAU CLAIRE
FLORENCE
FOND DU LAC
FOREST
GRANT
GREEN
GREEN LAKE
IOWA
IRON
JACKSON
JEFFERSON
JUNEAU
KENOSHA
KHWAUNHE
LA CROSSE
LAFAYETTE
LANGLADE
LINCOLN
MANrrowoc
MARATHON
MARINETTE
MARQUETTE
MENOMINEE
MILWAUKEE
NO. OF
MEAS.
2
8
1^
8
2i
8
^
18
A
8
5
87
12
8
9
13
20
13
22
6
10
6
2
1
5
2
15
2
21
5
26
4
19
4
18
71
13
4
2
124
MEAN
2.<
l.(
1.'
1.1
2.2
3.2
2.1
3.2
3.7
1.4
2.1
3.8
3.2
4.8
6.5
2.3
2.1
3.5
2.4
3.2
2.4
13.4
3.3
10.3
0.9
4.4
1.6
2.2
2.6
1.9
1.3
2.5
3.2
4.0
3.2
1.4
5.2
2.4
2.1
4.5
3.1
GEOM
MEAN
2.^
0.8
1.:
0.9
1.7
2.5
IA
3.2
2.2
1.2
1.8
3.C
2.0
4.0
2.7
1.0
2.1
2.8
1.5
2.5
1.0
4.9
2.4
2.5
0.9
2.3
1.2
1.9
2.3
1.5
0.8
2.2
2.9
2.8
2.4
1.2
3.0
1.4
1.3
3.4
2.1
MEDIAN
2.6
i.:
l.i
1.1
1.6
3.(
1.7
3.]
2.7
1.6
2.C
3.7
2.2
4.0
2.4
1.2
2.0
3.2
1.8
2.7
1.4
3.7
3.2
10.3
0.9
1.4
1.6
2.2
2.6
1.3
1.3
2.5
3.5
2.9
2.3
1.1
3.2
1.1
2.0
4.5
2.4
STD.
DEV.
l.<
0.5
0.<
0.6
1.6
1.6
1.5
1.2
4.2
0.6
1.2
2.3
2.9
3.6
8.8
3.0
0.6
2.5
2.3
2.1
3.1
26.9
2.4
14.1
0.0
5.8
.3
2
:.6
.6
.1
.2
.3
3.0
2.7
0.9
6.5
2.8
1.9
4.2
2.6
MAXIMUM
3.6
U
3.8
2'
7.;
6X
4.6
4.'
18.5
1.8
4.6
6.3
12.9
14.8
25.1
9.6
3.1
11.3
7.5
7.2
8.4
89.1
7.0
20.2
0.9
14.5
2.5
5.1
3.7
5.5
2.8
6.4
4.5
11.9
6.9
3.7
37.1
10.1
4.3
7.5
15.3
%>4pCi/L
0
0
0
0
1]
25
11
33
33
0
13
40
25
50
38
22
0
20
15
41
17
40
33
50
0
40
0
7
0
14
0
8
25
26
25
0
38
23
25
50
27
%>20pCi/L
0
0
0
0
0
0
0
0
0
0
0
0
0
0
13
0
0
0
0
0
0
10
0
50
0
0
0
0
0
0
0
0
0
0
0
0
3
0
0
0
0
-------
TABLE 1 (continued). Screening indoor radon data for Wisconsin.
COUNTY
MONROE
OCONTO
ONHDA
OUTAGAMffi
OZAUKEE
PEPIN
PIERCE
POLK
PORTAGE
PRICE
RACINE
RICHLAND
ROCK
RUSK
SAUK
SAWYER
SHAWANO
SHEBOYGAN
ST. CROIX
TAYLOR
TREMPEALEAU
VERNON
VILAS
WALWORTH
WASHBURN
WASHINGTON
WAUKESHA
WAUPACA
WAUSHARA
WINNEBAGO
WOOD
NO. OF
MEAS.
7
30
8
23
12
4
6
9
30
10
31
3
18
4
7
34
30
20
10
11
8
2
45
8
1
16
58
39
7
25
16
MEAN
1.2
1.6
3.0
2.7
3.2
• 3.8
2.4
4.5
4.1
5.1
2.6
1.4
4.5
1.7
3.7
2.5
4.2
2.1
4.0
1.7
3.8
5.1
3.2
5.8
5.8
4.9
6.3
4.7
0.9
3.0
2.0
GEOM.
MEAN
1.0
0.9
2.6
2.2
3.0
3.4
1.4
2.9
2.9
2.6
1.9
1.2
3.0
1.6
2.8
1.9
2.8
1.6
1.8
1.2
1.8
4.0
1.7
4.2
5.8
1.8
4.4
2.8
0.6
2.2
1.6
MEDIAN
1.0
0.8
2.7
2.1
3.0
2.9
2.6
3.2
2.7
3.5
2.0
1.5
4.4
1.6
3.4
2.6
2.6
1.5
2.1
1.0
1.1
5.1
1.5
4.2
5.8
1.4
4.5
3.2
1.3
2.2
1.7
STD.
DEV.
0.8
1.8
1.6
1.6
1.4
2.2
1.5
5.1
3.8
6.4
2.3
0.8
3.3
0.5
2.6
1.6
4.3
1.6
4.5
1.7
5.0
4.4
7.1
6.3
0.0
9.2
5.4
4.6
0.6
2.2
1.2
MAXIMUM
2.6
7.2
6.1
6.2
5.9
7.0
4.1
17.1
16.7
21.5
10.7
2.1
14.3
2.4
7.5
6.0
20.5
5.2
13.3
6.3
14.9
8.2
48.2
21.0
5.8
37.3
33.0
21.2
1.3
8.7
4.3
%>4pCi/L
0
13
25
22
17
25
17
22
30
30
26
0
56
0
29
24
33
20
30
9
38
50
13
50
100
25
64
46
0
20
6
%>20pCi/L
0
0
0
0
• o
0
0
0
0
10
0
0
0
0
0
0
3
0
0
0
0
0
2
13
0
6
2
3
0
0
0
-------
GEOLOGIC RADON POTENTIAL
•" - $
An aeroradiometric map of Wisconsin (fig. 9) indicates that equivalent uranium (elJ)
concentrations in surficial materials are 1.0 ppm or less over most of the northern two-thirds of the
State, with the exception of an area in the northeastern part of Wisconsin that is underlain by
granite and granite-rich glacial deposits from the Wolf River Batholith and associated rocks
(fig. 4). Many of the areas with an eU of 0.5 ppm or less, particularly in the northern part of the
State, are wetlands or other areas with high water tables. Equivalent uranium concentrations in
most of the southern third of the State range from 1.5 to 3.0 ppm (fig. 9). The higher values in
this area appear to be associated with carbonate bedrock and carbonate-derived glacial deposits.
These rocks (granites and carbonates) have the highest radon potential in the State.
Rocks of the Wolf River Batholith, particularly those of quartz monzonite and syenite
composition, and glacial deposits containing these rocks as a major constituent, have high geologic
radon potential. Glacial deposits covering the bedrock in this area are generally thin. Other
Precambrian granites in northeastern Wisconsin may generate locally high radon levels. Areas of
iron-formation, as in the Gogebic Range in Ashland and Iron Counties, may generate locally high
indoor radon levels. Metamorphic rocks of mafic composition have low radon potential, but
because these rocks are intruded by granites and intensely sheared in many places, and fragments
of these rocks are mixed together in glacial tills, the area in northeastern Wisconsin underlain by
Precambrian rocks, excluding the Wolf River rocks, has a moderate or variable radon potential.
Ordovician limestones and dolomites along the eastern, southern, and western parts of the
State, particularly those of the Sinapee and Prairie du Chien Groups, also have high geologic radon
potential. Although carbonate rocks are generally relatively low in uranium content, residual soils
formed by weathering and dissolution of much of the calcium carbonate contain heavy mineral
concentrates, including uranium minerals. This concentrating mechanism, along with the locally
nigh rock and soil permeabilities developed in fissures and solution cavities, allow carbonate rocks
and soils to generate locally high radon levels. In the southwestern part of the State, the carbonate
bedrock is exposed and moderately to highly weathered near the surface. Loess in this area may
also be a source of locally high radon levels. In the southeastern part of Wisconsin, the bedrock is
covered with glacial deposits derived mostly from the carbonate bedrock. The glacial deposits are
relatively thin over most of these rocks, with thicker glacial cover east of a line from Green Bay
through western Walworth County. Clay-rich soils along the shore of Lake Michigan from
Milwaukee north to Kewaunee (fig. 61) give this area a low radon potential. South of Milwaukee,
the soils are also clay-rich, but have more silt and higher surface radioactivity. This area has a
moderate geologic radon potential.
Soils and glacial deposits derived from Cambrian sandstones have a moderate radon
potential. These deposits cover a large area, and within this area, indoor radon values are expected
to range from low to locally high. Areas underlain by greensands (glauconite-bearing sandstones)
and soils derived from them (see figure 6D) are most likely to generate locally high indoor radon
levels. Sandstones of the Bayfield Group in the Superior Lowland (fig. 1) have generally low
radon potential (Bayfield County had an indoor radon average of 1.1 pCi/L). The Precambrian
volcanic rocks immediately south of this area also have low to moderate radon potential, but the
glacial deposits overlying these rocks generate moderate and locally high indoor radon levels,
probably because the soils have moderate to high permeability. This area has an overall moderate
or variable geologic radon potential.
IV-17 Reprinted from USGS Open-File Report 93-292-E
-------
Figure 9. Aerial radiometric map of Wisconsin (after Duval and others, 1989). Contour lines at
1.5 and 2.5 ppm equivalent uranium (eU). Pixels shaded from 0 to 6.0 ppm eU at 0.5 ppm eU
increments; darker pixels have lower eU values; white indicates no data.
-------
SUMMARY
V. '" *
Nine areas of Wisconsin were delineated based on bedrock and glacial geology,
radioactivity, soil permeability, and indoor radon data (fig. 10), and assigned Radon Index (RI)
and Confidence Index (CI) scores (Table 2). A thorough discussion of the methods and data used
in determining the RI and CI is given in the introduction chapter to this booklet
Area SL, named for the Superior lobe and underlain primarily by sandstones and volcanic
rocks, has moderate geologic radon potential (RI=10) with moderate confidence (CI=9). Radon
levels are probably generally lower in the northern part of this area and generally somewhat higher
in the southern part Bayfield County has a generally low radon potential. Area CWL, underlain
by deposits of the Chippewa, Wisconsin Valley, and Langlade sublobes of the Superior lobe, has
moderate/variable geologic radon potential (RI=10) with high confidence (CI=10). Areas
underlain by granites or granite-derived glacial deposits, and areas in close proximity to shear
zones, may have locally high indoor radon levels. Areas underlain by mafic volcanic rocks will
likely have low to moderate indoor radon levels. Area OGD, older glacial deposits, has moderate
geologic radon potential (RI=10) with moderate confidence (CI=9). Areas underlain by granite
bedrock or granite-rich glacial deposits, and areas underlain by greensands, may have locally high
radon levels. Area WRB, the Wolf River Batholith, has high geologic radon potential (RI=13)
with high confidence in the prediction (CI=10).
Area GBL, underlain by deposits of the Green Bay lobe, has moderate radon potential
(RI=10) with moderate confidence (CI=9). Average radon levels in this area are uniformly
moderate (2-4 pCi/L), and most homes are expected to have indoor radon levels in this range, but
individual homes may have low to high radon levels depending on local conditions. Area CS is
unglaciated and underlain by Cambrian sandstones. This area has moderate geologic radon
potential (RI=10) with moderate confidence (CI=9). Areas underlain by greensands may have
locally high radon levels. Area OC, underlain by Ordovician carbonate rocks, includes areas
covered by glacial deposits in the eastern part of the area and areas where the bedrock is exposed in
the western part. This area has an overall high radon potential (RI=12) with moderate confidence
(CI=9). Area RBC, underlain by red-brown clayey soils, has low radon potential (RI=8) with
moderate confidence (CI=9). Area CRC, underlain by clay-rich carbonate soils, has moderate
geologic radon potential (RI=10) with moderate confidence (CI=9). Generally lower soil
permeability and thicker glacial cover in this area appear to be the primary factors responsible for
the slightly lower average indoor radon levels in this area compared to area OC to the west
This is a generalized assessment of the State's geologic radon potential and there is no
substitute for having a home tested. The conclusions about radon potential presented in this report
cannot be applied to individual homes or building sites. Indoor radon levels, both high and low,
can be quite localized, and within any radon potential area there will likely be areas with higher or
lower radon potential that assigned to the area as a whole. Any local decisions about radon should
not be made without consulting all available local data. For additional information on radon and
how to test, contact your State radon program or EPA regional office. More detailed information
on state or local geology may be obtained from the State geological survey. Addresses and phone
numbers for these agencies are listed in chapter 1 of this booklet.
IV-19 Reprinted from USGS Open-File Report 93-292-E
-------
TABLE 2. Radon Index (RI) and Confidence Index (CI) scores for geologic radon potential areas
of Wisconsin. See figure 10 for locations and abbreviations of areas.
AREA
SL
FACTOR RI CI
INDOOR RADON 2 3
RADIOACTIVITY 1 2
GEOLOGY 2 2
SOIL PERM. 2 2
ARCHITECTURE 3
GFE POINTS 0
TOTAL 10 9
RANKING MOD MOD
GBL
FACTOR RI CI
INDOOR RADON 2 3
RADIOACTIVITY 1 2
GEOLOGY 2 2
SOIL PERM. 2 2
ARCHITECTURE 3
GFE POINTS 0
TOTAL 10 9
RANKING MOD MOD
RADON INDEX SCORING:
CWL
RI
2
1
2
2
3
0
10
MOD
CS
RI CI
2 3
1 2
2 2
2 2
3
0
10 9
MOD MOD
CI
3
2
3
2
—
—
10
HIGH
oc
RI CI
2 3
2 2
3 2
2 2
3
0
12 9
OGD
RI
2
1
2
2
3
0
10
MOD
HIGH MOD
CI
3
2
2
2
—
—
9
MOD
RBC
RI CI
2 3
1 2
1 2
1 2
3
0
8 9
LOW MOD
Probable screening
Radon potential category
LOW
MODERATE/VARIABLE
HIGH
Point ranee
3-8
9-11
> 11
points
points
points
WRB
RI
3
2
3
2
3
0
13
HIGH
CI
3
2
3
2
—
~
10
HIGH
CRC
RI
2
2
2
1
3
0
10
MOD
indoor
CI
3
2
2
2
—
—
9
MOD
radon averaee for area
<2pCi/L
2-4pCi/L
>4pCi/L
Possible range of points = 3 to 17
CONFIDENCE INDEX SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10 - 12 points
Possible range of points = 4 to 12
IV-20 Reprinted from USGS Open-File Report 93-292-E
-------
GEOLOGIC
RADON POTENTIAL
High
,>*i Moderate or Variable
Low
RBC
0
1
1
0
25
50
50 75
I
100
100
1
1
150
miles
km
Figure 10. Geologic radon potential areas of Wisconsin. SL, Superior Lobe; CWL, Chippewa,
Wisconsin Valley, and Langlade sublobes of the Superior Lobe; OGD, older glacial
deposits; WRB, Wolf River Batholith; GBL, Green Bay Lobe; CS, Cambrian
sandstones; OC, Ordovician carbonate rocks; RBC, red-brown clayey soils; CRC,
clay-rich carbonate soils.
-------
REFERENCES CITED IN THIS REPORT
AND GENERAL REFERENCES RELATED TO RADON IN WISCONSIN
Blackburn, W.H. and Mathews, G.W., 1982, Evaluation of uranium anomalies in the McCaslin
Syncline, northeastern Wisconsin: U.S. Department of Energy, National Uranium
Resource Evaluation Report GJBX-222(82), p. 43-67.
Crowns, Byron, 1976, Wisconsin through 5 billion years of change: Wisconsin Rapids, WI:
Wisconsin Earth Science Center, 318 p.
Dutton, C.E., 1976, Precambrian geology, in Dutton, C.E., and Ostrom, M.E. (eds), Mineral and
water resources of Wisconsin: Report prepared by the U.S. Geological Survey and the
Wisconsin Geological and Natural History Survey for the U.S. Senate Committee on
Interior and Insular Affairs: U.S. Government Printing Office, p. 11-22.
Duval, J.S., Jones, W.J., Riggle, F.R., and Pitkin, J.A., 1989, Equivalent uranium map of the
conterminous United States: U.S. Geological Survey Open-File Report 89-478,10 p.
Frye, J.C., Willman, H.B., and Black, R.F., 1965, Outline of glacial geology of Illinois and
Wisconsin, in Wright, H.E., Jr., and Frey, D.G. (eds.), The Quaternary of the United
States: Princeton, NJ, Princeton University Press, p. 29-41.
Gundersen, L.C.S., Peake, R.T., Latzke, G.D., Hauser, L.M., and Wiggs, C.R., 1991, A
statistical summary of uranium and radon in soils from the Coastal Plain of Texas,
Alabama, and New Jersey, in The 1990 International Symposium on Radon and Radon
Reduction Technology, Atlanta, Ga., 19-23 February 1990, Proceedings, Vol. 3:
Symposium Poster Papers: Research Triangle Park, N.C., U.S. Environmental Protection
Agency Rept EPA600/9-91-026c, p. 6-35-6-47.
Hadley, D.W., and Pelham, J.H., 1976, Glacial deposits of Wisconsin: Wisconsin Geological
and Natural History Survey Map 10, scale 1:500,000.
Hadley, D.W., 1976, Glacial geology, in Dutton, C.E., and Ostrom, M.E. (eds), Mineral and
water resources of Wisconsin: Report prepared by the U.S. Geological Survey and the
Wisconsin Geological and Natural History Survey for the U.S. Senate Committee on
Interior and Insular Affairs: U.S. Government Printing Office, p. 38-55.
Hole, F.D., 1976a, Soils of Wisconsin: Wisconsin Geological and Natural History Survey
Bulletin 87,223 p.
Hole, F.D., 1976b, Soil guide for Wisconsin land lookers: Wisconsin Geological and Natural
History Survey Bulletin 88, 66 p.
Hudson, T.B. and Nelson, R.S., 1989, Analysis of radon concentrations and Pleistocene deposits
in Illinois: Transactions of the Illinois State Academy of Science 82, Suppl., p. 49.
IV-22 Reprinted from USGS Open-File Report 93-292-E
-------
Kalliokoski, J., 1976, Uranium and thorium occurrences in Precambrian rocks, Upper Peninsula
of Michigan and northern Wisconsin, with thoughts on other possible settings: Report
prepared for the U.S. Energy Research and Development Administration, Grand Junction,
CO, GJBX 48(76), 294 p.
Kochis, N.S., Orlovsky, SJ. and Leavitt, S.W., 1989, Radon emanations in surficial geologic
deposits of Kenosha, Racine and Waukesha counties in southeastern Wisconsin:
Geological Society of America, Abstracts with Programs, v. 21, no. 4, p. 18.
Martin, Lawrence, 1916, The physical geography of Wisconsin: Wisconsin Geological and "
Natural History Survey Bulletin 36,549 p.
Mudrey, M.G., Jr., Brown, B.A., and Greenberg, J.K., 1982, Bedrock geologic map of
Wisconsin: Wisconsin Geological and Natural History Survey, scale 1:1,000,000.
Ostrom, M.E., 1976, Paleozoic rocks, in Dutton, C.E., and Ostrom, M.E. (eds), Mineral and
water resources of Wisconsin: Report prepared by the U.S. Geological Survey and the
Wisconsin Geological and Natural History Survey for the U.S. Senate Committee on
Interior and Insular Affairs: U.S. Government Printing Office, p. 23-37.
Paull, R.K., and Paull, R.A., 1977, Geology of Wisconsin and upper Michigan including parts of
adjacent states: Dubuque, Iowa, Kendall/Hunt Publishing Company, 232 p.
Richmond, G.R., and Fullerton, D.S. (eds.), Quaternary Geologic Atlas of the United States:
U.S. Geological Survey Miscellaneous Investigations Map 1-1420, sheet NL-15,
Minneapolis 4°x6° quadrangle, 1983a; sheet NL-16, Lake Superior 4°x6° quadrangle, 1984;
sheet NK-15, Des Moines 4°x6° quadrangle, 1991; sheet NK-16, Chicago 4°x6°
quadrangle, 1983b; scale 1:1,000,000.
Routledge, R.E., Parrish, I.S. and Leigh, O.E., 1982, Ashland Quadrangle, Wisconsin,
Michigan, and Minnesota: U.S Department of Energy, National Uranium Resource
Evaluation Report PGJ/F-084(82), 31 p.
Schnabel, R.W., 1976, Uranium-thorium, in Dutton, C.E., and Ostrom, M.E. (eds), Mineral and
water resources of Wisconsin: Report prepared by the U.S. Geological Survey and the
Wisconsin Geological and Natural History Survey for the U.S. Senate Committee on
Interior and Insular Affairs: U.S. Government Printing Office, p. 132.
Scott, M.R., Rotter, R.J. and Salter, P.P., 1985, Transport of fallout plutonium to the ocean by
the Mississippi River: Earth and Planetary Science Letters, v. 75, p. 321-326.
Steck, D.J., 1987 , Geological variation of radon sources and indoor radon concentrations along
the southwestern edge of the Canadian Shield: Health Physics, v. 52, p. S40.
IV-23 Reprinted from USGS Open-FUe Report 93-292-E
-------
Steck, D.J., 1988, Geological variation of radon sources and indoor radon along the southwestern
edge of the Canadian Shield, in M. A. Marikos and R.H. Hansman (eds), Geologic causes
of natural radionuclide anomalies: Proceedings of GEORAD Conference, St Louis, MO,
April 21-22,1987, Missouri Department of Natural Resources Special Publication 4,
p. 17-23.
Sims, P.K., 1976, Precambrian tectonics and mineral deposits, Lake Superior region: Economic
Geology, v. 71, p. 1092-1127.
Sims, P.K., 1992, Geologic map of Precambrian rocks, southern Lake Superior region,
Wisconsin and northern Michigan: U.S. Geological Survey Miscellaneous Investigations
Map 1-2185, scale 1:500,000.
Thwaites, F.T., 1960, Ice age deposits of Wisconsin: Wisconsin Geological and Natural History
Survey map, scale approximately 1:2,730,000.
Wisconsin Geological Survey, 1956, Uranium prospecting in Wisconsin: Wisconsin Geological
Survey Information Circular 2,6 p.
Wisconsin Geological and Natural History Survey, 1981, Bedrock geology of Wisconsin:
Wisconsin Geological and Natural History Survey map, scale approx. 1:2,725,000.
Wisconsin Department of Natural Resources and Wisconsin Geological and Natural History
Survey, 1987, Groundwater contamination susceptibility in Wisconsin: Wisconsin
Geological and Natural History Survey map, scale 1:1,000,000.
Wright, H.E., Jr., Matsch, C.L., and Gushing, E.J., 1973, Superior and Des Moines lobes, in
Black, R.F., Goldthwait, R.P., and Willman, H.B. (eds), The Wisconsinan Stage:
Geological Society of America Memoir 136, p. 153-85.
IV-24 Reprinted from USGS Open-File Report 93-292-E
-------
EPA's Map of Radon Zones
The USGS' Geologic Radon Province Map is the technical foundation for EPA's Map
of Radon Zones. The Geologic Radon Province Map defines the radon potential for
approximately 360 geologic provinces. EPA has adapted this information to fit a county
boundary map in order to produce the Map of Radon Zones.
The Map of Radon Zones is based on the same range of predicted screening levels of
indoor radon as USGS1 Geologic Radon Province Map. EPA defines the three zones as
follows: Zone One areas have an average predicted indoor radon screening potential greater
than 4 pCi/L. Zone Two areas are predicted to have an average indoor radon screening
potential between 2 PCi/L and 4 PCi/L. Zone Three areas are predicted to have an average
indoor radon screening potential less than 2 pCi/L.
Since the geologic province boundaries cross state and county boundaries, a strict
translation of counties from the Geologic Radon Province Map to the Map of Radon Zones
was not possible. For counties that have variable radon potential (i.e., are located in two or
more provinces of different rankings), the counties were assigned to a zone based on the
predicted radon potential of the province in which most of its area lies. (See Part I for more
details.)
WISCONSIN MAP OF KADON 7fWT7g
The Wisconsin Map of Radon Zones and its supporting documentation (Part IV of this
report) have received extensive review by Wisconsin geologists and radon program experts.
The map for Wisconsin generally reflects current State knowledge about radon for its
counties. Some States have been able to conduct radon investigations in areas smaller than
geologic provinces and counties, so it is important to consult locally available data.
Although the information provided in Part IV of this report -- the State chapter entitled
"Preliminary Geologic Radon Potential Assessment of Wisconsin" - may appear to be quite
specific, it cannot be applied to determine the radon levels of a neighborhood, housing tract
individual house, etc. THE ONLY WAY TO DETERMINE IF A HOUSE HAS
ELEVATED INDOOR RADON IS TO TEST. Contact the Region 5 EPA office or the
Wisconsin radon program for information on testing and fixing homes. Telephone numbers
and addresses can be found in Part II of this report.
V-l
-------
------- |