United States
Environmental Protection
Agency
Air and Radiation
(6604J)
402-R-9S-047
September 1993
&EPA EPA's Map of Radon Zones
NEBRASKA
Printed on Recycled Paper
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EPA'S MAP OF RADON ZONES
NEBRASKA
RADON DIVISION
OFFICE OF RADIATION AND INDOOR AIR
U S ENVIRONMENTAL PROTECTION AGENCY
SEPTEMBER, 1993
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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.
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TABLE OF CONTENTS
I. OVERVIEW
II THE USGS/EPA RADON POTENTIAL
ASSESSMENTS:INTRODUGTION
III REGION 7 GEOLOGIC RADON POTENTIAL
SUMMARY
V PRELIMINARY GEOLOGIC RADON POTENTIAL
ASSESSMENT OF NEBRASKA
V. EPA'S MAP OF RADON ZONES - NEBRASKA
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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 arid 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 shoiild 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
inap (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.
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of t^p Map nf 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
radon 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 fixing
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 ot
new homes in Zone 1 counties, and thfe 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.
ryvHnpmopt "f thft MaP nf 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
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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 their 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 Ration Zones by .extrapolating i,rom 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 correcj 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.
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Figure 3
Geologic Radon Potential Provinces f.o r Nebraska
Lincolfl County
ink
Uoictate
Figure 4
NEBRASKA - EPA Map of Radon Zones
Zoae 1 Zone 2 Zone 3
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One such analysis involved comparing county zone designations to indoor radon
measurements from the State/EPA Residential Radon Surveys (SRRS). Screening averages
for counties with 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. '< , >
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In addition to each State geologist providing technical comments, the State radon
offices were asked to comment 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
designations. In a few cases, States have requested changes in county zone designations. 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.
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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
(PartTV). 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). iU
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
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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
ecology 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 (2"Rn) is produced from the radioactive decay of radium (226Ra), which is, in turn,
a product of the decay of uranium (»U) (fig. 1). The half-life of «Rn is 3.825 days. Other
isotopes of radon occur naturally, but, with the exception of thoron -(«°Rn), 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 shnnk-swell clays, air
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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 flow during, drier 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" 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 ot
buildings, ranging from tens of PCi/L to more than 100,000 PCi/L, but typically m the range
of hundreds to low thousands of PCi/L. Soil-gas radon concentrations can vary m 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 a,r from subsurface
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solution cavities in the parbonate rock into houses. As warm air enters solution cavities-that
are higher on the hillsiqpe than the homes, it cools and settles, pushing radon-laden air from
lower in the cave or cavity system into structures on the hillslppe (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 riot 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, glaucomte-
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
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rocks and basalts. Exceptions exist within these general lithologic groups because of
ccu^« of localized uranium deposits, commonly of the hydro-thermal type m
cwstalline rocks or the "roll-front" type in sedimentary rocks Uranium and radium are
c^rnonly sited in heavy minerals, iron-oxide coatings on rock and soil grams and organic
maTcriaS in soils and sediments. Less common a,e uranium associated with phosphate and
carbonate complexes in rocks and soils, and uranium minerals.
Xugh many cases of elevated indoor radon levels can be traced to high radium and
(or) u anium concentrations in parent rocks, some structural features, -^^"^
shear zones have been identified as sites of localized uranium concentrations (Deffeyes and
MacG^egor 1980) and have been associated with some of the highest reported indoor radon
bveMlundlrsen 1991). The two highest known indoor radon occurrences are , «o«a ed
with sheared fault zones in Boyertown, Pennsylvania (Gundersen and others, 1988a Smith
and others, 1987), and in Clinton, New Jersey (Henry and others, 1991; Muessig 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 ™C*«™IO™°\™«™
parent materials (uranium, radium) in rocks and soils. Equivalent uranium is calculated from
Sie counts received by a gamma-ray detector from the 1 .76 MeV (mega-electron volts)
emission energy corresponding to bismuth-214 (»
-------
FLICUT LINE SPACING OF SURE AEKI AL SURVEYS
2 KM (I KILE)
5 KM (3 HUES)
2 i 5 KH
10 KU (6 lilLES)
5 t' 10 IV
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 flightlme 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 eU 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
geochemical 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, shrmk-
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).
H-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), at 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 60,00,0 homes were tested
in the State/EPA surveys.
The second source of indoor radon data comes 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 fronvUSGS Open-File Report 93-292
-------
-------
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
divi'ded 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 tfie 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 relipd 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 .
- 11-11 Reprinted from USGS Open-File Report 93-292
-------
TABLE I. RADON INDEX MATRIX, "ppm eU" indicates parts per million of'equivalent
umnium, as indicated by NURE aerial radiometric data. See text discussion for details.
INCREASING R ADQN POTENTIAL
POINT VALUE
FACTOR
INDOOR RADON (average)
> 2.5 ppm eU
ositive
1.5 - 2.5 ppmeU
< 1.5 ppm eU
mostly basement
AERIAL RADIOACTIVITY
••^"^^™
GEOLOGY*
•••••^^™«*«^"«»«"^^""«^^"
SOIL PERMEABILrrY
ARCHITECTURE TYPE
*OFOT jOOIC FIELD EVIDENCE (GFE) POINTS: GFE points are assigned in addition to points
°^4JSS3£5 factor forspecific, relevant geologic field studies. See text for details.
HIGH radon +2 points
MODERATE +1 point
LOW -2 points
No relevant geologic field studies 0 points
Geologic evidence supporting:
SCORING:
Radon pot?nfal category
LOW
MODERATE/VARIABLE
HIGH
3-8 points
9-11 points
12-17 points
Probable average screening
<2pCi/L
2-4pCi/L
>4pCi/L
POSSIBLE RANGE OF POINTS = 3 to 17
CONFIDENCE INDEX MATRIX
TABLE 2.
INCREASING CONFIDENCE
poiNT_yALUE
2
FACTOR
fair coverage/quality pod coverage/quali
sparse/no data
INDOOR RADON DATA
uestionable/no data
roven geol. model
MIB«««—""•"•••"••"^^"^••^^
reliable, abundant
uestionable
••^™——•—
questionable/no data
AERIALRADIOAC11 Vil
•«••«•—«^IP^—M^^i—"ii^^*^^"•"^
GEOLOGIC DATA
MMM—W—M^i^—•
SOIL PERMEABILITY
SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10 -12 points
POSSIBLE RANGE OF POINTS = 4 to 12
n-12 Reprinted fiom 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 fdr 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, 1989j. 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 eU 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 of in areas with geologic and climatic settings similar
enough that they could be applied with full confidence. For example, areas of tne 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 sUidies in North Dakota and Minnesota (Schumann and others, 1991) suggest
that eU is a poor .predictor of geologic radon potential in this area because radioriuclides have
H-13 Reprinted from USGS Open-File Report 93-292
-------
been leached from the upper soil layers but are present and possibly even concentrated m
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
suggested by the
-------
to question the quality or validity of these data. The other factors were stored 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 rado'n 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-ppint 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 on}y 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 inco'rrfcct 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, SoU 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, E.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, LA., 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. TJI: 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.SM 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.
JI-17 Rqwinted from USGS Open-File Report 93-202
-------
Henry, Mitchell E., Kaeding, MargretE., and Monteverde, Donald, 1991, Radon uvsoil 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, C, 1989, Gravelly soils and indoor radon, *" 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, L, 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 Grecman, D.J., 1988, Variability of radon with depth and
season in a central Pennsylvania soU 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.
IJ-18 Reprinted ftom USGS Open-File Report 93-292
-------
Schumann, R;R., Owen, D.E,, and Asher-Bolinder, S., 1992, Effects of weather and soil
characteristics on temporal variations in soil-gas radon concentrations, in Gates, A.E., and
Gundersen, L.C.SM 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., II, 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, fll., 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 HI, Symposium proceedings,
Houston, Texas, v. 1, p. 5-56.
U.S. Department of Agriculture, 1987, Principal lands of soils: Orders, suborders, and great
groups: U.S. Geological Survey, National Atias 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.WM Alexander, B.V., and Rohca-Battista, M., 1989, Multi-State
surveys of indoor 222Rn: Health Physics, v. 57, p. 891-896.
n-19 Reprinted fiomUSGS Open-File Report 93-292
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APPENDIX A
GEOLOGIC TIME SCALE
Subdivisions (and their symbols)
Eon or
Eonothem
Phsnerozoic2
Proterozoic
(B)
Archean
(A)
Era or
E rathe m
Cenozoic
(CD
Mesozoic2
(Mi)
Paleozoic
(Pi)
MiOOIt
E«"V
t«"Y
Arct*«an (U1
Period, System,
Subperiod. Subsystem
Quaternary
IQ)
Nee>B«n* 2
Subperiod or
I-..:.-. Subsystem (N)
rn Paleogene
(" Suboe'iod or
Subsystem (Pt)
Cretaceous
(K)
Jurassic
(J)
Triassic
CR)
Permian
(P)
Pennsylvanian
Carboniferous 'P'
(C) Mississippian
(M)
Devonian
(D)
Silurian
IS)
Ordovician
Cambrian
(C)
Epoch or Series
Holocene
Pleistocene
Pliocene
Miocene
Oligocene
Eocene
Paleocene
Late
Early
Late
Middle
Early
Late
Middle
Early
Late
Early
Late
Middle
Early
Late
Early
Late
Middle
Early
Late
Middle
Early
Late
Middle
Early
Late
Middle
Early
Upper
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Lower
Upper
Middle
Lower
Upper
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Middle
Lower
None defined
Age estimates
of boundaries
in mega-annum
(Ma)1
— 1.6 (1.6-1.9)
5 (4.9-5.3)
24 (23-26)
38 (34-38)
55 (54-56)
66 (63-66)
95 (95-97)
138 (135-141)
205 (200-215)
240
290 (290-305)
-330
360 (360-365)
410 (405-415)
435 (435-440)
500 (495-510)
.570 3
900
1600
2500
3400
3800?
.nd Wostr.ligr.phic «gt .ssignm.nts. Aot bound.*.* not eto«rfy br»ck.t»d by existing
J^wSwi «•«*•««««*« "*Jl^{1977)- D«i9n«iton m-y- "^fw M
of th» torg«f unit th»
(PC,. . tirn.
Inlonn*! tlm« wrm without ipeofie rank.
USGS Open-FDe Report 93-292
-------
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'*2curies) 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 pQ/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, in 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, fillingit with water, and measuring the time it takes for the water
to drain from the hole. The drop in 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
less than 0.06 in/hr to greater than 20 in/hr, but most soils in the United.States have permeabilities
between these two extremes. "
Geologic terms and terms related to the study of radon .
'' • • '
aerial radiometric, 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
plain or broader valley. May also form at the junction with larger streams or when the gradient of
the stream abruptly decreases.
alluvium, alluvial General terms referring to unconsolidated detrital material deposited by a
stream or other body of running water.
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
plagioclase.
H-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.
day 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.
n-22 Reprinted from USGS Open-File Repeat 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 pluitonic 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-sidecl 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 in 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 feldsparrbearing 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 of 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-FileReport 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 irto which rr ~^s ars dlv: J^ the others t ing 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, imbedded 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-
n-24 Reprinted from USGS Open-File 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. ^
pl?.cer 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, eompositionally 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 (Uthification) 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 studyof rock strata;also refers to the succession of rocksof aparticular area.
surficial materials Unconsolidated glacial, wind-, or waterborne deposits occurring «n the
earth's surface.
tablelands General term for a broad, elevated region with a nearly level surface of considerable
extent
11-25 Reprintedfrom 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 vanes 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 unconftned 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.
n-26 Reprinted from USGS Open-File Report 93-292
-------
APPENDIX C
EPA REGIONAL OFFICES
F.PA Regional Offic«
State
F.PA Region
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, TL 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 ....,..:.. 10
Arizona ». --9
Arkansas............. ..... 6
California ;.-9
Colorado..... 8
Connecticut •. —• 1
Delaware........ • -.3
District of Columbia 3
Florida . -4
Georgia ±....... .4
Hawaii --9
Idaho.... i ..: 10
Illinois..... ....5
Indiana ..1...5
Iowa ; •"• -.7
Kansas : ;.....,7
Kentucky..... 4
Louisiana.. , ,...- ;•<>
Maine.......:... ....'• —-1 ,
Maryland. • 3
Massachusetts 1
Michigan 5
Minnesota............... •••••5
Mississippi..... - -4
Missouri.... »••• 7
Montana. ::• »8
Nebraska ,. ,..-....i ..7
Nevada , 9
New Hampshire 1
New Jersey — 2
• New Mexico, , •• 6
New York 2
North Carolina - 4.
North Dakota..: ...8
Ohio........... ..........5
Oklahoma 6
Oregon • 10
Pennsylvania...;. .........3
Rhode Island ,....,..1
South Carolina ...........: 4
South Dakota.... -8
Tennessee 4
Texas • •••&
Utah » 8
Vermont •—1
Virginia............. v-3
Washington 10
West Virginia : 3
Wisconsin • ....;..5
Wyoming......... ..8
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
Arizona John Stewart
Arizona Radiation Regulatory Agency
4814 South 40th St.
Phoenix, AZ 85040
(602)2554845
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
Connecticut 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
pf 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, FL 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, HI 96813-2498
(808) 586-4700
n-28 Reprinted ftom USGS Open-File Report 93-292
-------
Idaho
Illinois
Indiana
fowa
Kansas
Kentucky
PatMcGavam
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
LorandMagyar
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. Hater
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
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
JeanaPhelps
Radiation Control Branch
Department of Health Services
Cabinet for Human Resources
275 East Main Street
Frankfort, KY 40601
(502) 564-3700 ,
Louisiana Matt Schlenker
Louisiana Department of
Environmental Quality
P.O. Box 82135
Baton Rouge, LA 70884-2135
(504)925-7042
1-800-256-2494 in state
Maine BobStilwell
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
n-29 Reprinted from USGS Open-File Report 93-292
-------
Mississippi 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
Missouri 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
Montana Adrian C. Howe
Occupational Health Bureau
Montana Department of Health and
Environmental Sciences
Cogswell Building A113
Helena, MT 59620
(406)444-3671
Nebraska 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
Nevada 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
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 Stale 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 Alien 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
H-30 Reprinted from USGS Open-File Report 93-292
-------
Oklahoma Gene Smith,
Radiation Protection Division
Oklahoma State Department of
Health
P.O. 60x53551
Oklahoma City, OK 73152
(405)271-5221
Oregon George Toombs
Department of Human Resources
Health Division
1400 SW 5th Avenue
Portland, OR 97201
(503)731^4014
Pennsylvania 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
Puerto Rico David Saldana
Radiological Health Division
G.P.O. Call Box 70184
Rio Piedras; Puerto Rico 00936
(809)767-3563
Rhode Island EdmundArcand
Division of Occupational Health and
Radiation
Department of Health
205 Cannon Building
Davis Street
Providence, RI02908
(401)277-2438
South Carolina
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 MikePochdp ,
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 I ••
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.p. 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
' , ' i
Virgin Islands Contact the U.S. Environmental
Protection Agency, Region n
in New York
. (212)264-4110
H-31 Reprinted frontUSGS 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 KateColeman
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 BealtieL. 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 Weifferibach
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
n-32 Reprinted firom USGS Open-File Report 93-292
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STATE GEOLOGICAL SURVEYS
May, 1993
Alabama Ernest A. Mancini
Geological Survey of Alabama
P.O.BoxO
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 lames F. Davis
California Division of Mines &
Geology
801 K Street, MS 12-30
Sacramento, CA 95814-3531
(916)445-1923
Colorado Pat Rogers (Acting) t
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 S'irvey
903 W. Tennessee St.
Tallahassee, FL 32304-7700
(904)488^191 ~
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, HI 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. Leightpn
Illinois State Geological Survey
Natural Resources Building
615EastPeabodyDr.
Champaign, IL 61820
(217)333-4747
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, JA 52242-1319
(319)335-1575
Kansas LeeC.Gerhard
Kansas Geological Survey
1930 Constant Ave., West Campus
University of Kansas
Lawrence.KS 66047
(913) 864-3965
H-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
Mains 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 SL Paul Street
Baltimore, MD 21218-5210
(410) 554-5500
Massachusetts Joseph A. Sinnott
Massachusetts Office of
Environmental Affairs
100 Cambridge SL, 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 Priscilla C. Grew
Minnesota Geological Survey
2642 University Ave.
SL 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)496-4180
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
DepL 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
H-34 Reprinted fiom 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
600EastBlv
-------
West Virginia Laity D. Woodfork
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
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EPA REGION 7 GEOLOGIC RADON POTENTIAL SUMMARY
' ' ' .. ' - V -• ' by ' . - .. , --• .; ' '• • •
R. Randall Schumann, James K. Otton, and Sandra L. Szarzi
s ';> U.S. Geological Survey „
EPA Region 7 includes the states of Iowa, Kansas, Missouri, and Nebraska. 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 7 is given in the individual state chapters. The individual chapters describing the geology
and radon potential of the four states in EPA Region 7, 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,ycan be quite localized, and within any radon potential are,a homes
with indoor radon levels both above and below the predicted average will likely be found. ;
Figure 1 shows the geologic radon potential areas in EPA Region 7. Figure 2 shows
average screening indoor radon levels in EPA Region 7 by county, the data for each state are
from the State/EPA Residential Radon Survey and reflect screening charcoal canister
measurements. Figure 3 shows the geologic radon potential of areas in Region 7, combined and
summarized from the individual state chapters. Many rocks and soils in EPA Region7 contain
ample radon source material (uranium and radium) and have soil permeabilities sufficient to
produce moderate or high radon levels in homes. The following sections summarize the geologic
radon potential of each of the four states in Region 7. More detailed discussions may be found in
the individual state radoh potential chapters for the states in Region 7.
IOWA
Pre-Blinoian-age glacial deposits cover most of Iowa, and are at or near the surface in the
southern, northwestern, and much of the northeastern parts of the state. These deposits generally
consist of calcium-carbonate-rich loam and clay loam till containing pebbles and cobbles of granite,
gabbro, basalt, rhyolite, greenstone, quartzite, chert, diorite, and limestone. Pre-Illinoiantills are
covered by from less than 1 m to more than 20 m of Wisconsinan loess (windblown silt) in
western, southern, and eastern Iowa. Ulinoian glacial deposits occur a relatively small area along
the Mississippi River in southeastern Iowa. These deposits consist of loamy to locally sandy till
containing elasts of limestone and dolomite, with lesser amounts of igneous and metamorphic
rocks, sandstone, and coal fragments, niinoian deposits are covered by 1-5 m of loess.
Wisconsinan drift is .represented by the Gary and tazewell drifts, consisting of calcareous loamy
till containing clasts of shale, limestone, and dolomite, with minor amounts of basalt, diabase,
granite, chert, and sandstone. Gary drift (now called the Dows Formation), which represents
deposits of the Des Moines lobe, is generally not loess-covered; Tazewell drift is covered by as
much as 2 m of loess.
ffl-1 Reprinted from USGS Open-File Report 93-292-G
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The aeroradioaetiyity signature of surface deposits in Iowa, especially the Des Moines lobe
deposits and other areas in which the loess cover is dicotitinuous or absent, seems lower than
would be expected in light of the elevated indoor radon levels. This may be because much of the
radium in the near-surface soil horizons may have been leached and transported downward in the
soil profile, giving a low surface radiometric signature while generating significant radon at depth
(1-2 m? or greater) to produce elevated indoor radon levels. For example, a large area of low
radioactivity (< 1.5 ppm eU) in the northern part of the State corresponds roughly to the Des
Moines lobe and the lowan erosion surface, an area directly east of the Des Moines lobe,in
northeastern Iowa that is underlain by Pre-Illinoian glacial deposits and loess. However, these
areas have high geologic radon potential. Most of the remainder of the State has eU values in the
1.5-2.5 ppm range. In general, soils developed from glacial deposits can be more rapidly leached
of mobile ions than their bedrock counterparts, because crushing and grinding of the rocks by
glacial action gives soil weathering agents (mainly moisture) better access to soil and mineral grain
surfaces. Grinding of the rocks increases the mobility of uranium and radium in the soils by
exposing them at grain surfaces, enhancing radionuclide mobility and radon emanation. In
addition, poorly-sorted glacial drift may in many cases have higher permeability than the bedrock
from which it is derived. Cracking of clayey glacial soils during dry periods can create sufficient
permeability for convective radon transport to occur. This may be an important factor causing
elevated radon levels in areas underlain by clay-rich glacial deposits.
. Loess-covered areas have a higher radiometric signature than loess-free areas, and also
appear to correlate roughly with higher average indoor radon levels than loess-free areas, although
all areas of Iowa have average indoor radon levels exceeding 4 pCi/L. The Loess-Covered Drift
Plains, which cover northwestern Iowa and all of southern Iowa, are underlain by Pre-HUnoian
and Illinoian glacial deposits, and loess. The Loess-Covered Drift Plains have overall high radon
potential. Valley bottoms with wet soils along the Mississippi and Missouri Rivers may have
locally moderate to low radon potential because the gas permeability of the soils is extremely low
due to the water filling the pore spaces.
The Paleozoic Plateau, in northeastern Iowa, is underlain primarily by Ordovician
carbonate and Cambrian sandstone bedrock covered by varying amounts of Quaternary glacial
deposits and loess. It was originally thought to have been unglaciated because it is deeply
dissected and lacks glacial landforms. However, small patches of Pre-Dlinoian drift have been
preserved on uplands, indicating that at least part of the area had been glaciated. The Paleozoic
Plateau also has high geologic radon potential. Soils developed from carbonate rocks are derived
from the residue that remains after dissolution of the calcium carbonate that makes up the majority
of the rock, including heavy minerals and metals such as uranium, and thus they may contain
somewhat higher concentrations of uranium or uranium-series radionuclides than the parent rock.
Residuum from weathered carbonate rocks may be a potential radon source if a structure is built on
such a residual soil, or if the residuum constitutes a significant part of a till or other surficial
deposit. In some areas underlain by carbonate bedrock, solution-features such as sinkholes and
caves increase the overall permeability of the rocks in these areas and generally increase the radon
potential of these rocks, but few homes are built directly over major solution features.
KANSAS •' .",.-• . ''".''•: '. "'. •
Almost all of the bedrock exposed at the surface in Kansas consists of sedimentary units
ranging in age from Mississippian to Quaternary. Igneous rocks native to Kansas and exposed at
ffl-5 Reprinted fromUSGS Open-File Report 93-292-G
-------
the surface are .small localized exposures of Cretaceous lamproite in Woodson County and
Cretaceous kimberlite in Riley County. Sedimentary rocks of Mississippian age underlie the
extreme southeastern corner of the State. They consist primarily of limestones but also include
shale, dolomite, chert, sandstone, and siltstone. Penrisylvanian rocks underlie approximately the
eastern one-quarter of the State. They consist of an alternating sequence of marine and nonmanne
shale, limestone, sandstone, and coal, with lesser amounts of chert and conglomerate. The shales
range from green and gray (low organic content) to black (organic rich). Permian rocks are
exposed in east-central and southern Kansas and consist of limestone, shale, gypsum, anhydrite,
chert, siltstone, and dolomite. Red sandstone and shale of Permian age underlie the Red Hills
along the southern border of Kansas.
The Mississippian, Pennsylvanian, and Permian rocks in eastern Kansas have relatively
low uranium contents, generally low to moderate permeability and have generally low to moderate
geologic radon potential. Homes situated on Pennsylvanian and Permian carbonate rocks
(limestones and dolomites) may have locally elevated indoor radon levels if the limestones have
developed clayey residual soils and(or) if solution features (karst topography), are present in the
area. Because of the geologic variability of these units, the Mississippian, Pennsylvanian, and
Permian rock outcrop area has been ranked moderate or variable in overall geologic radon
potential. Homes sited on Pennsylvanian black shale units may be subject to locally high indoor
radon levels. This may be the case in the Kansas City area, part of which is underlain by black
shales.
Some elevated indoor radon levels in the northern part of the Permian outcrop area,
specifically in Marshall, Clay, Riley, Geary, and Dickinson Counties, may be related to faults and
fractures of the Mid-Continent Rift and Nemaha Uplift Many of the subsurface faults reach and
displace the surface sedimentary rock cover, and the density and spacing of faults and fractures
within the rift zone is relatively high. Fault and shear zones are commonly areas of locally elevated
radon because these zones typically have higher permeability than the surrounding rocks, because
they are preferred zones of uranium mineralization, and because they are potential pathways
through which uranium-, radium-, and(or) radon-bearing fluids and gases can migrate.
Cretaceous sedimentary rocks underlie much of north-central and central Kansas, and
consist of green, gray, and black shale, sandstone, siltstone, limestone, chalk, and chalky shale.
A discontinuous layer of loess of varying thickness covers the Cretaceous rocks in many areas,
particularly in the western part of the Cretaceous outcrop area. Cretaceous rocks in Kansas contain
sufficient uranium to generate elevated indoor radon levels. Soils developed on Cretaceous rocks
have low to moderate permeability, but the shale-derived soils with low permeability to water likely
have moderate permeability to soil gas when they are dry due to desiccation cracks. Areas
underlain by these rocks have an overall high radon potential. Tertiary rocks cover much of
western Kansas, though they are covered by loess deposits in many areas. Tertiary rocks consist
of nonmarine sandstone, siltstone, and shale; volcanic ash deposits; and unconsolidated gravel,
sand, silt, and clay. Areas underlain by the Tertiary Ogallala Formation have a moderate
radioactivity signature and a moderate to high radon potential.
Loess ranging from 0 to more than 30 meters in thickness covers as much as 65 percent of
the surface of Kansas and is thickest and most extensive in the western and north-central parts of
the State and in proximity to glacial deposits in the northeastern corner of the State. Possible
sources for the loess include: (1) glacial outwash, (2) sand dunes in the Arkansas and Cimarron
River valleys or elsewhere (such as the Sand Hills of Nebraska), and (3) erosion of Tertiary
sedimentary rocks by wind and rivers. Radon potential of loess-mantled areas depends on the
m-6 Reprinted from USGSOpen-FUe Report 93-292-G
-------
f
thickness and source of the loess. In areas of very thin loess cover, the radon potential of the
underlying bedrock is significant, and the loess both generates radon and transmits radon from the
underlying bedrock, whereas if the loess is more than 7-10 m thick, it is probably the sole radon
source for homes in the area. Loess-covered areas underlain by Cretaceous and Tertiary bedrock
appear to have variably moderate to high radon potential across the State, and locally elevated ,
indoor radon levels may be expected anywhere within areas underlain by these units. Areas
underlain by loess-covered Pennsylvanian and Permian rocks appear to generate mainly moderate
to locally elevated indoor radon levels. .
Areas of windblown sand in the Arkansas and Cimarron River valleys have low uranium
contents and low radon potential, but few homes are built directly on the sand dunes. The dune
sands are intermixed with loess in parts of the Arkansas and Cimarron valleys, and the radon
potential may be related to the relative proportions of sand, loess, and bedrock within these areas.
Area's underlain by dune sand are expected to have lower radon levels, areas with considerable
loess content are expected to have moderate to locally elevated radon levels. Where sand or loess
is thin or absent, the radon levels in homes on Tertiary or Cretaceous bedrock are also expected to
generally fall into the moderate to high category.
The area within the glacial limit in northeastern Kansas is underlain by discontinuous
glacial drift and loess. The glacial deposits consist of a clay, silt, or sand matrix with cobbles and
boulders of igneous and metamorphic rocks derived from as far away as the Lake Superior Region
and southwestern Minnesota. The glacial deposits are discontinuous and till thickness varies
markedly within the area, most likely because post-glacial erosion has removed and redistributed
significant amounts of drift Because the, loess in this area is likely derived from nearby glacial
drift, and because glacial deposits are known to generate elevated indoor radon levels throughout
the northern Great Plains, this area should be considered to have a moderate to locally high radon
potential.
MISSOURI '
Missouri lies within the stable midcontinent area of the United States. The dominant
geologic feature is the Ozark uplift in the southeastern part of the state which forms the Ozark
Plateau Province Pfecambrian crystalline rocks form the core of the'uplift and crop out along its
eastern side. Paleozoic sedimentary rocks dip away from this core in all directions. To the north,
northwest, and west of the uplift these sedimentary sequences are folded into broad arches and
sags. The Precambrian core of the Ozark uplift is primarily granite and rhyolite. Much of this rock
is slightly enriched in uranium (2.5-5.0 ppm). The Precambrian core is surrounded by Cambrian
' and Ordovician sandstone, dolostone, shale, cherty dolostpne, chert, and limestone.
Pennsylvanian sandstone, shale and clay crop out in the north-central part of the uplift. To the
north and west of the uplift, Mississippian and Pennsylvanian shale, limestone, sandstone, clay,
coal, and fire clay occur. Silurian and Devonian sedimentary rocks crop out in central Missouri
along the Missouri River and along the Mississippi River northeast of St Louis and in Cape
Girardeau and Perry Counties south of St. Louis.
Uraniferous granites and rhyolites, and residuum developed on .carbonate rocks in the
Ozark Plateau Province are likely to have significant percentages of homes with indoor radon levels
exceeding 4 pCi/L. The most likely areas are those where elevated eU values occur. Where
structures are sited on somewhat excessively drained soils in this area the radon potential is further
increased. Extreme indoor radon levels may be expected where structures are sited on uranium
m-7 Reprinted from USGS Open-File Report 93-292-G
-------
occurrences and where the disturbed zone around a foundation is connected to solution openings in
carbonate rocks or to open zones in soil and bedrock caused by mine subsidence.
The Ozark Plateau Province has a moderate overall radon potential. Several areas of
somewhat excessively drained soils, scattered uranium occurrences, residual carbonate soils in
which uranium has been concentrated, and areas of karst may generate locally elevated indoor
radon levels in this area. The St. Francois Mountains have high radon potential owing to elevated
levels of uranium in soils developed on granitic and volcanic rocks throughout these mountains and
substantial areas of somewhat excessively to excessively drained soils.
The permeability of soils and subsoils in karst areas has been enhanced by solution
openings in and near carbonate pinnacles and by zones of solution collapse. Where soils
developed on such carbonate rocks are thin, foundations may encounter open bedrock fractures in
the limestone. Karst underlies parts of the City and County of St Louis and may locally cause
elevated indoor radon levels. Elevated eU and significant karst development occur in Perry and
Cape Girardeau Counties. Structures sited on locally highly permeable karst soils with elevated eU
in these two counties will likely have elevated indoor radon levels. Broad karst areas have formed
by dissolution of carbonate rocks in the central and western Ozark Plateau, the southern Osage
Plain, and along the Mississippi River from Cape Girardeau County to Rails County. These
carbonate regions have overall moderate radon potential. However, areas of intense karst
development, elevated uranium in residual soils developed on carbonate, and large areas of
somewhat excessively drained to excessively drained soils may cause locally high indoor radon
levels to occur.
Several very thin, highly uraniferous (as much as 180 ppm), black, phosphatic shales
occur in the Devonian and Pennsylvanian sedimentary rock sequences in the unglaciated Osage
Plain of southwestern Missouri. Elevated indoor radon levels may be expected where the
foundations of structures intercept the thin Pennsylvanian uraniferous shales or the Chattanooga
Shale in the southwestern part of the state from Kansas City south to McDonald and Barry
Counties and in north-central Missouri in Boone, Randolph and Macon Counties, or where they
intercept well-drained alluvium derived from these rocks. Because these uraniferous shales are so
thin, such circumstances are likely to be very site- or tract-specific; thus detailed geologic and soil
mapping will be necessary to outline areas of potential problems. Where these shales are jointed or
fractured or soils formed on them are somewhat excessively drained on hillslopes, the radon
potential is further increased. Residuum developed on limestones associated with these
uraniferous shales may also have elevated uranium levels and have significant radon potential. The
unglaciated Osage Plain province has a low overall radon potential; however, areas of thin soils
underlain by the uraniferous shales in this province have high radon potential with locally extreme
values possible.
Along the Missouri and Mississippi River valley floor, alluvial deposits (silt, sand, and
gravel) dominate. Loess deposits .occur on the flanks of the river valleys in several areas and are
especially widespread in Platte, Buchanan, Holt, and Atchison Counties along the Missouri River
north of Kansas City. Alluvium and loess along the upper Missouri River Valley upstream from
Kansas City seem to be producing elevated indoor radon levels that may be related to the somewhat
elevated uranium content of these materials and, possibly, to elevated radon emanation and
diffusion associated with well-drained loess deposits. Detailed studies of indoor radon data in this
area would be necessary to determine more closely the origin of elevated indoor radon levels.
Thin, somewhat excessively drained soils developed on limestone that occur as part of one soil
m-8 Reprinted from USGS Open-File Report 93-292-G
-------
association in the southern suburbs of Kansas City may also be related to elevated indoor radon
levels in Jackson County. .-,.•'
The northernmost part of the Mississippi Embayment occupies the southeastern corner of
the state and forms the Coastal Plain Province, or southeastern lowlands. This area is underlain by
Tertiary and Quaternary alluvium. The Coastal Plain 1 evince has a low radon potential overall.
Only one value exceeding 4 pCi/L is reported for a six-county area, and very poorly drained soils
are widespread. However, some aeroradiometric anomalies occur in this area, and some
excessively drained soils occur locally. Elevated indoor radon levels may be associated with these
locales, Althpugh elevated elJ occurs over some of the sedimentary rocks in this province, the
high soil moisture, the very poorly drained soils, and the low indoor radon values all point towards
low radon potential. ; •
The surficial geology north of the Missouri River is dominated by glacial deposits covered
with a thin veneer of loess; however, several areas of residual soils developed on underlying
sedimentary rocks occur in the eastern and western parts of this region. Residual soils are those
soils formed by weathering of the material beneath the soil. These surficial deposits (both glacial
deposits and residuum) are generally 50-200 feet thick, but they locally exceed 200 feet along the
northern edge of the state. The dissected till plain of northern Missouri has moderate overall radon
potential, although elevated indoor radon levels are common in areas of similar geology in adjacent
states, particularly Iowa, Nebraska (fig. 1), and minois. Except for counties along the Missouri
River, the indoor radon data for the counties in the dissected till plain are sparse and appear to be
generally in the low to moderate range.
NEBRASKA
Rocks ranging in age from Pennsylvanian to Quaternary are exposed in Nebraska. ,
Pennsylvanian rocks are exposed in southeastern Nebraska and include limestones, shales, and
sandstones. Only some of the Upper Pennsylvanian strata are exposed in Nebraska; these rocks
are a repeated sequence of marine shales and limestones alternating with nonmarine sandstones and
shales, and thin coals. Exposed Permian rocks consist of green, gray, and red shales, limestone,
and gypsum. Exposures of Pennsylvanian and Permian rocks are generally limited to valley sides
along streams because much of the eastern part of the State is mantled with Pleistocene glacial
deposits and loess. Black shales of Pennsylvanian age may constitute a significant radon source
where the shales are a source component of the glacial tills.
Cretaceous rocks are exposed in much of eastern Nebraska, in parts of northern and
northwestern Nebraska, and along the Republican River Valley, Lower Cretaceous rocks consist
of sandstones, shales, and thin coals. Upper Cretaceous rocks consist primarily of shale,
limestone, and sandstone. The Upper Cretaceous Pierre Shale consists of gray, brown, and black
shales, with thin layers of bentonite, chalk, limestone, and sandstone. Although the permeability
of soils developed on the Pierre Shale is listed as low, the shales-contain numerous fractures and
partings and are likely to have sufficient permeability for radon transport during dry periods. The
stratigraphically lowest unit in the Pierre Shale is the Sharon Springs Member, a black shale of
widespread occurrence in Nebraska, South Dakota, Kansas, and Colorado. The Sharon Springs
Member is exposed in a relatively broad area along the Niobrara and Missouri Rivers from Keya
Paha to Cedar Counties and along the Republican River in southern Nebraska. The gray-shale
units of the Pierre Shale, while riot as uraniferous as the black shale of the Sharon Springs
Member, generally contain higher-than-average (i.e., >2.5 ppm) amounts of uranium and are
m-9 Reprinted from USGS Open-File Report 93-292-G
-------
correlated with elevated indoor radon levels in several areas. Outcrops of the Pierre Shale in the
northwestern corner of Nebraska have the highest surface radioactivity in the State. Areas
underlain by Cretaceous rocks, particularly the Pierre Shale, have overall high radon potential.
Tertiary rocks have the most widespread exposure in the State. The White River Group
consists of mudstone, siltstone, sandstone, and thin layers of volcanic ash, and is exposed in the
North and South Platte valleys and in northwestern Nebraska. The Arikaree Group overlies the
White River Group and consists of siltstone and sandstone. The Tertiary Ogallala Group covers
about two-thirds of the State. It consists of sandstone, siltstone, gravel, sand, silt, clay, and thin
volcanic ash layers. The Ogallala is covered by the Sand Hills, an area of Quaternary windblown
sand deposits, in the north-central part of Nebraska. Pre-Sand Hills sediments of Pliocene and
Quaternary age also overlie portions of the Ogallala in this area. The Ogallala, Arikaree, and White
River Groups all have high surface radioactivity (for purposes of this report, high radioactivity is
defined as greater than 2.5 ppm eU) and are known to host uranium deposits. Soils developed on
the Tertiary units have moderate permeability and generate moderate to locally high indoor radon.
The White River and Arikaree Groups have significant amounts of uranium-bearing volcanic glass
and may be somewhat more likely to generate elevated indoor radon concentrations. Areas
underlain by Tertiary sedimentary rocks have overall moderate radon potential. Some homes in
this area are likely to have high indoor radon levels, particularly those sited on uranium-bearing
parts of the White River and Arikaree Groups in northwestern Nebraska.
Eastern Nebraska and southern Nebraska south of the Platte River are underlain by
Permian through Tertiary rocks mantled with Pleistocene glacial deposits of Pre-Dlinoian age and
loess. The glacial deposits generally consist of a clay, silt, or sand matrix with pebbles and
cobbles of limestone, igneous rocks, and quartzite. Source material for the glacial deposits
includes locally-derived Permian and Pennsylvanian limestone and shale and Cretaceous sandstone
and shale as well as lesser amounts of sandstone, limestone, shale, and igneous and metamorphic
rocks from bedrock sources to the north and northeast. Of the source rocks underlying the glacial
deposits and those to the north and northeast, Cretaceous sandstones and shales, Pennsylvanian
black shales, and Precambrian crystalline rocks all contain sufficient amounts of uranium-series
radionuclides (uranium and(or) radium) to generate radon at elevated levels.
Loess covers most of the glacial deposits in eastern Nebraska as well as bedrock in the
south-central part of the State. Loess is a generally good radon source because it consists of silt
and clay-sized particles, which are more likely to be associated with radionuclides and have higher
emanation coefficients than larger sized particles, and it typically has moderate permeability.
Average indoor radon levels are consistently greater than 4 pCi/L in areas underlain by loess-
mantled glacial drift. The majority of homes in the area underlain by loess-mantled bedrock in the
south-central part of the State also have radon levels exceeding 4 pCi/L, but indoor radon levels
are likely to be more variable from house to house in south-central Nebraska, depending on the
distribution, thickness, or weathering extent of the loess. Areas underlain by glacial drift and most
areas underlain by loess have overall high radon potential. The area mapped as loess between the
Platte River and the Sand Hills in the central part of the State has generally moderate radon
potential Homes sited on thicker loess along the north side of the Platte River in Dawson and
Buffalo Counties may have locally high indoor radon levels. The Sand Hills have low smf ?ce
radioactivity and generally low radon potential.
m-10 Reprinted from USGS Open-File Report 93-292-G
-------
PRELIMINARY GEOLOGIC RADON POTENTIAL ASSESSMENT OF NEBRASKA
,, • by i • • ••" ' •. '
R.RdhdallSchuMann -
. '' , US. Geological Survey
INTRODUCTION ,
Many of the rocks and soils in Nebraska have the potential to generate levels of indoor
radon exceeding the U.S. Environmental Protection Agency's guideline of 4 pCi/L. In a survey of
2027 homes conducted during the winter of 1989-90 by the State of Nebraska and the EPA, 54
percent of the homes had indoor radon levels exceeding this value. Areas of Nebraska have
geologic radon potentials ranging from low to high.
This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
. deposits of Nebraska. 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
Most of Nebraska (the western four-fifths of the State) is part of the Great Plains
physiographic province, characterized primarily by flat and dissected plains. The eastern one-fifth
of Nebraska (east of the glacial limit) is part of the Central Lowlands Province, consisting of
rolling hills. Nebraska's topography comprises several types of land surfaces (fig. 1). Most of
western and central Nebraska are characterized by plains, regions of relatively flat uplands, and
dissected plains, regions of hilly land that have been eroded by water and wind, resulting in
moderate to steep slopes, sharp ridge crests, and remnants :of the original plain (Nebraska
.Conservation and Survey Division, 1986). Rolling hills occupy the eastern part of the State and a
small area in the northwestern corner of Nebraska (fig. 1). In eastern Nebraska they consist of
ridges and valleys formed by glaciers and modified by subsequent erosion and deposition. Most
of the hills are covered by windblown silt, called loess. The Sand Hills are a region of low- to
high-relief sand dimes, most of which have been stabilized by vegetation. Valleys are regions of
low relief along major drainages. Some of the valleys are bordered by rugged bluffs and
escarpments with steep and irregular slopes, and the broader valleys in western and northwestern
Nebraska have recognizable valley side slopes between the bluffs and valley floors (fig. 1)
(Nebraska Conservation and Survey Division, 1986).
Nebraska is. divided into 93 counties (fig. 2). The population density is generally low;
most counties have less than 10,000 inhabitants (fig. 3). Counties with populations greater than
100,000 include Douglas and Lancaster Counties, representing the Omaha and Lincoln areas,
respectively (fig. 3). •
IV-1 Reprinted from USGS Open-File Report 93-292-G
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GEOLOGY
Bedrock geology: Rocks ranging in age from Pennsylvanian to Quaternary are exposed in
Nebraska. Pennsylvanian rocks are exposed in southeastern Nebraska (fig. 4) and include
limestones, shales, and sandstones. Only some of the Upper Pennsylvanian strata are exposed in
Nebraska; these rocks are a repeated sequence of marine shales and limestones alternating with
nonmarine sandstones and shales (Burchett, 1979). Several thin coal seams occur within the
exposed Pennsylvanian strata in Cass, Otoe, Johnson, Nemaha, Pawnee, and Richardson
Counties. Pennsylvanian shales include gray, greenish-gray, red (iron-rich), and black (organic-
rich) shales (Burchett, 1979). Only the lower portion of the Perrnian series is exposed^
Nebraska. Exposed Permian rocks consist of green, gray, and red shales, limestone, and gypsum
(Burchett, 1983). Exposures of Pennsylvanian and Permian rocks are generally limited to valley
sides along streams because much of the eastern part of the State is mantled with Pleistocene glacial
deposits and loess. ^ , "
Cretaceous rocks are exposed in much of eastern Nebraska, in parts of northern and
northwestern Nebraska, and along the Republican River Valley (fig. 4). Lower Cretaceous rocks
are represented by the Dakota Group, which consists of sandstones, shales, and thin coals. Upper
Cretaceous rocks include the Colorado and Montana Groups (Condra and Reed, 1959; Burchett,
1986). The Colorado Group includes the Graneros Shale, Greenhorn Limestone, Carlile Shale,
and Nibbrara Formation (consisting of the Smoky Hill Chalk and Fort Hays Limestone). The
Montana Group overlies the Colorado Group and includes the Pierre Shale, Fox Hills Sandstone,
and Lance Formation. The Pierre Shale consists of gray, brown, and black shales, .with thin layers
of bentonite, chalk, limestone, and sandstone (Condra and Reed, 1959). The stratigraphically
lowest unit in the Pierre Shale is the Sharon Springs Member, a black shale of widespread
occurrence in Nebraska, South Dakota, Kansas, and Colorado. The Lance Formation consists of
continental sandstone, shale, and thin coals. ;
Tertiary rocks have the most widespread exposure in the State. The White River Group
consists of mudstone, siltstone, sandstone, and thin layers of volcanic ash. White River rocks are
exposed in the North Platte and South Platte valleys and in northwestern Nebraska (fig. 4). The
•Arikaree Group overlies the White River Group and consists of siltstone and sandstone (Swinehart ,
and others, 1985). The Tertiary Ogallala Group covers about two-thirds of the State (fig. 4). It
consists of sandstone, siltstone, gravel, sand, silt, clay, and thin volcanic ash layers. The Ogallala
is covered by the Sand Hills in the north-central part of Nebraska. Pre-Sand Hills sediments of
Pliocene and Quaternary age also overlie portions of the Ogallala inlthis area (Swinehart and
Diffendal, 1990). , , ,
Glacial geology: Pleistocene glacial deposits of Pre-Illinoian age (Richmond and others,
1991) cover approximately the eastern one-fifth of Nebraska (fig, 5). The glacial deposits
generally consist of a clay, silt, or sand matrix with pebbles and cobbles of limestone, igneous
rocks, and quartzite (Reed and Dreeszen, 1965). Most of the tills are calcareous (containing
layers, nodules, or cements of calcium carbonate, CaCOs) and many contain layers or grain —
coatings of iron oxides. Source material for the glacial deposits includes locally-derived Permian
and Pe'nnsylvanian limestone and shale and Cretaceous sandstone and shale, as well as lesser
amounts of sandstonerlimestone, shale, and igneous and metamorphic rocks from bedrock
sources to the north and northeast Loess (windblown silt of glacial, periglacial, and non-glacial
IV-5 Reprinted from USGS Open-Hie Report 93-292-G
-------
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Era
Cenozolc
Mesozoic
Paleozoic
Period
Quaternary
\
Tertiary
.Cretaceous
Jurassic
Triassic
Permian
Pennsylvanian
Mississippian
' Devonian
Silurian
Ordovician
Cambrian
Prccambrian
Epoch
Holocene
Pleistocene
Pliocene
Miocene
Oligocene
Eocene
Paleocene
Late
Cretaceous
Early
Cretaceous
. Ages in
millions
of years'
0 01
—20
5
24-
37
' 5S
67
. / •
—•-^•™»4flfl .™™™™~
i!3fl
Group
or
Formation
OgallaU
Ankarce
White River
. - Lithology
, Sand, silt, gravel and clay
f Sand, gravel and silt
Sand, sandstone, siltslone and some
gravel
Sandstone and siltstone
Sillstone, sandstone and clay in lower
pan
Rocks of this age are not identified in Nebraska.
Lance
Fox Hills
Pierre
Niobrara
Carlile
Greenhorn-
Graneros
Dakota.
Sandstone and siltstone
Shale, some sandstone in west
Shaly chalk and limestone
Shale; in some areas, contains
sandstones in upper part
Limestone and shale
Sandstone and shale
Sillstone, some sandstone
Sillstone
Limestones, dolomites, shales
and sandstones
'Estimated ages of time boundaries from the Geological Society or America. 1983 Geologic Time Scale
Figure 4 (continued) DESCRIPTION OF GEOLOGIC UNITS IN NEBRASKA
(modified from Nebraska Conservation and Survey Division, 1986).
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origin) covers most of the glacial deposits in eastern Nebraska as well as bedrock in the south-
central part of the State (fig. 5). , . .
Uranium geology: Uranium in commercial, as well as significant but non-commercial
grades, occurs in Nebraska in rocks and sediments of Tertiary, Cretaceous, and Pennsylvanian
age, and in Pleistocene glacial deposits derived from these rocks. Uranium in concentrations as
high as 3 percent (Gjelsteen and'Collings, 1988), occurs in the White River Group in Dawes
County. Uranium is currently being solution mined from a subsurface deposit in the Chadron
Formation-of the White River Group at Crow Butte near Crawford (Collings and Knode, 1984).
A sample of the Brule Formation (upper part of the White River Group) from Noddings Ridge,
north of Chadron, was found to contain as much as 0.43 percent (4300 ppm) uranium (Dunham,
1955; Dickinson, 1991). Overall, the White River Group is estimated to contain an average of 7.7
ppm uranium (Gjelsteen and Collings, 1988). The sources of the uranium in the Tertiary deposits
is thought to be the volcanic ash layers (Zielinski, 1983) and volcanic glass in the bulk sediments,
especially in the White River and Arikaree Groups. The Arikaree Group is also known to host
local uranium occurrences in western South Dakota (Denson and Gill, 1956). The Tertiary
Ogallala Group is considered favorable for uranium, and higher-than-average uranium
concentrations have been found in groundwater samples taken from the Ogallala aquifer in eastern
Colorado (Nelson-Moore and others, 1978).
Several shales in the State also contain above-average amounts of uranium (average crustal
abundance of uranium is about 2.5 ppm (Carmichael, 1989) and. non-organic-rich shales generally
contain 1-4 ppm uranium). The Sharon Springs Member of the Pierre Shale, an organic-rich black
shale, locally contains as much as 100 ppm uranium (Tourtelot, 1956), with an average uranium
content of about 15 ppm (Kepferle, 1959). The Sharon Springs Member is exposed to the
northeast and southeast of the Sand Hills (part of the areas labeled Pierre Shale on figure 4).
Altered shales in the Cretaceous Niobrara Formation have anomalous concentrations of uranium
where they are directly overlain by the Chadron Formation of the White River Group. Samples of
altered Niobrara Formation in southwestern South Dakota yielded 300 ppm uranium (Tourtelot,
1956). Many of the Pennsylvanian black shales underlying the glacial deposits in the southeastern
corner of Nebraska contain significant amounts of uranium. The black shale beds are generally
thin and scattered throughout the Pennsylvanian sequence. About 20 of the Pennsylvanian black
shale beds contain more than 30 ppm uranium; several contain about 100 ppm uranium; and a few
thin black shales locally contain as much as 170 ppm uranium (Swanson, 1956). Many of the
Pennsylvanian black shales contain small, irregularly distributed phosphatic nodules or concretions
that comprise approximately 5 percent of the shale unit The phosphate nodules typically contain
150-200 ppm uranium, and a few contain as much as 1000 ppm uranium (Swanson, 1956).
i "
SOILS
Soils of the Entisol and Mollisol orders occur in.Nebraska. Approximately the eastern one-
sixth of Nebraska is covered by Udolls, moist silt loam to silty clay loam soils with black, organic-
rich surface horizons and subsurface horizons that have been leached of calcium carbonate (U.S.
Soil Conservation Service, 1987). These soils have low to moderate permeability (fig. 6). The
remainder of the State exclusive of the Sand Hills is covered by Ustolls, drier soils with subsurface
accumulations of salts or carbonates. These soils are mostly silt loams, silty clay loams, and loams
developed on loess and a combination of loess and eolian sand on sandstone residuum (Elder, >
1969). These soils have mostly moderate permeability (fig. 6),
IV-9 Reprinted from USGS Open-Hie Report 93-292-G
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Soils in the Sand Hills region are classified as Entisols, soils with little or no development
of pedogenic horizons. The soils are sands or sandy loams with high permeability (fig. 6) that
absorb precipitation rapidly; there is very Me runoff (Kuzila, 1990).
INDOOR RADON DATA
Indoor radon data from 2027 homes sampled in the State/EPA Residential Radon Survey
conducted in Nebraska during the winter of 1989-90 are shown in figure 7 and listed in Table 1.
The data are derived from short-term (2-7 day) screening measurements using charcoal canister
radon detectors placed in the lowest level of the home (in Nebraska, usually the basement). Data
are only displayed in figure 7 for those counties with 5 or more data values. The maximum value
recorded in the survey was 123.4 pCi/L in Dakota County (Table 1). Average indoor radon
concentrations exceed 4 pCi/L in most counties in eastern and southern Nebraska (fig. 7).
Merrick County, which is underlain almost entirely by alluvium (fig. 5), has a low radon average
(1.9 pCi/L). Counties underlain by the Sand Hills have low (<2.0 pCi/L) to moderate (2-4 pCi/L)
indoor radon averages (fig. 7). Counties in the panhandle have mostly moderate 19 locally high
indoor radbn averages (fig. 7). The percentage of homes sampled in each county with indoor
radon concentrations exceeding 4 pCi/L generally foUows the same trend as the averages (fig. 7).
A high percentage of homes have indoor radon levels exceeding 4 pCi/L in eastern Nebraska, a
moderate to high proportion of homes exceed 4 pCi/L in southern Nebraska, generally low
proportions of homes exceed 4 pCi/L in the Sand Hills, and a moderate proportion of homes
exceed 4 pCi/L in the panhandle (fig. 7).
GEOLOGIC RADON POTENTIAL
A comparison of bedrock and surficial geology (figs. 4,5) with aerial gamma radioactivity
(fig. 8) and indoor radon distributions (fig. 7) indicates areas and lithologies with differing radon
potentials. Three primary types of bedrock or surficial deposits are likely to generate moderate to
high amounts of radon in Nebraska: (1) Tertiary sandstones; (2) shales, especially organic-rich
black shales; and (3) glacial deposits and loess. The Tertiary Ogallala, Arikaree, and White River
Groups all have high surface radioactivity (for purposes of this evaluation, high radioactivity is
defined as greater than 2.5 ppm eU) and are known to host uranium deposits. Soils developed on
the Tertiary units have moderate permeability (fig. 6) and generate moderate to locally high indoor
radon. The White River and Arikaree Groups have significant amounts of uranium-bearing
volcanic glass and may be somewhat more likely to generate elevated indoor radon concentrations.
Outcrops of the Pierre Shale in the northwestern comer of Nebraska have the highest
surface radioactivity in the State, averaging 3.0-3.5 ppm eU (fig. 8) and displaying several
prominent anomalies in the 6.0 ppm or greater range (Duval and others, 1989). Although the
permeability of soils developed on the Pierre Shale is listed as low (fig. 6), the shales contain
numerous fractures and partings and are likely to have sufficient permeability for radon transport
during dry periods. The Sharon Springs Member of the Pierre Shale is exposed along the
Niobrara and Missouri Rivers from Keya Paha to Cedar Counties and along the Republican River
in southern Nebraska (fig. 4). Black shales of Pennsyryanian age underlie glacial deposits in
southeastern Nebraska and may constitute a significant radon source where the shales are a source
component of the tills.
Eastern Nebraska and southern Nebraska south of the Platte River are underlain by
Permian through Tertiary rocks mantled with glacial deposits and loess. These deposits have a
IV-11 Reprinted from USGS Open-Hie Report 93-292-G
-------
Bsmt. & 1st Floor Rn
%>4pCi/L
11 CZ3 OtolO
10 C3 11 to 20
16JS3S1 21 to 40
23 Y/////SA 41 to 60
21 61 to 80
5 • 81 to 100
7 |~1 Missing Data or < 5 measurements
100 Miles
28
48
Bsmt. & 1st Floor Rn
Average Concentration (pCi/L)
1 •
7 r~l
0.0 to 1.9
2.0 to 4.0
4.1 to 10.0
10.1 to 11.8
Missing Data or < 5 measurements
100 Miles
Figure 7. Screening indoor radon data from the EPA/State Rf sid^2
Nebraska 1989-90 for counties with 5 or more measurements. Data are from 2-7
were chosen to provide reference to decision and action levels.
-------
TABLE 1. Screening indoor radon data froni the EPA/State Residential Radon Survey of
Nebraska conducted during 1989-90. Data represent 2-7 day charcoal canister measurements
from the lowest level of each home tested.
COUNTY
ADAMS
ANTELOPE
ARTHUR
BANNER
ELAINE
BOONE
BOXBUTTE
BOYD
BROWN
BUFFALO
BURT
BUTLER
CASS
CEDAR
CHASE
CHERRY
CHEYENNE
CLAY
COLFAX
CUMING
CUSTER
DAKOTA
DAWES
DAWSON
DEUEL
DIXON
DODGE
DOUGLAS
DUNDY
FILLMORE
FRANKLIN
FRONTIER
FURNAS
GAGE
GARDEN
GARFffiLD
GOSPER
GRANT
GREELEY
HALL
HAMILTON
NO. OF
MEAS.
75
20
4
6
5
17
37
11
6
81
13
9
10
32
15
40
45
14
10
26
40
27
34
40
5
17
16
148
7
6
14
8
12
10
2J
c
4
2
li
10?
18
MEAN
4.7
4.8
1.0
3.4
1.5
6.1
2.8
7.2
2.3
4.8
9.5
4.2
i 8.2
9.0
4.2
2.0
3.5
7.0
5.0
6.3
3.6
11.8
4.3
2.6
3.1
8.8
5.4
6.4
2.6
1.1
6.1
2.S
4.5
6.(
3.(
3.5
4.<
0.6
.-•• ?.:
25
5.'
GEOM.
MEAN
3.7
3.3
0.8
2.7
0.7
5.0
2.2
5.0
2.0 v
3.4
7.7
3.1
6.7
6.3
3.3
1.4
3.0
5.3
3.0
4.7
3.0
5.6
3.3
2.1
2.1
7.0
4.2
4.9
2.3
5.1
5.1
U
3.(
5.(
1.6
2.5
3.<
0.:
4.6
2.(
4.'
MEDIAN
4.2
3.8
1.0
2.2
0.4
5.7
2.2
4.2
2.5
4.2
8.6
2.8
7.6
7.8
4.6
1.8
2.8
5.4
2.6
4.6
3.2
5.9
3.6
2.3
3.6
9.4
4.6
5.3
2.1
5.4
5.3
3.6
, 4.2
5.7
•1.1
3.5
5.(
0.6
3.<
2.5
4.:
!'1X
DEV.
3.4
3.4
0.7
2.6
2.3
3.6
1.8
7.2
1.2
3.8
5.6
3.8
5.1
6.4
1.9
1.6
2.2
5.4
4.7
5.5
2.2
' 23.3
3.0
1.8
2.4
5.5
4.0
5.9
1.5
6.7
3.7
1.8
2.6
3.5
3.8
1.6
- 3.1
0.6
9.'.
1.6
4.(
MAXIMUM
19.7
12.6
1.9
8.2
5.5
14.8
9.3
26.2
3.6
24.4
19.3
12.7
15.9
24.5
9.1
9.8
12.7
20.0
14.4
24.6
11.5
123.4
13.9
8.4
6.3
19.4
16.2
51.7
4.8
20.1
13.3
4.9
8.8
12.:
16.9
5.<
8.2
l.(
42.8
9.(
17.0
0>4pCi/L
52
40
0
33
20
59
19
64
0
. 54
77
33
70
72
60
5
24
57
40
58
28
63
38
13
, 20
82
50
65
-29
,67
64
25
58
70
21
44
, 50
0
44
12
50
o>20pCi/L
0
0
0
0
0
0
0
9
0
1
0
0
0
9
0
0
0
0
0
4
0
15
0
0
0
0
0
4
0
17
0
0
0
0
0
0
0
0
6
0
0
-------
TABLE 1 (continued). Screening indoor radon data for Nebraska.
]
COUNTY 1
HARLAN
HAYES
HITCHCOCK
HOLT _.
HOOKER
HOWARD
JEFFERSON
JOHNSON
KEARNEY
KEITH
KEYA PAHA
KIMBALL
KNOX
LANCASTER
LINCOLN
LOGAN
LOUP
MADISON
MCPHERSON
MERRICK
MORRILL
NANCE
NEMAHA
NUCKOLLS
OTOE
PAWNEE
PERKINS
PHELPS
PIERCE
PLATTE
POLK
RED WILLOW
RICHARDSON
ROCK
SALINE
SARPY
SAUNDERS
SCOTTS BLUFF
SEWARD
SHERIDAN
SHERMAN
SIOUX
STANTON
TO. OF
MEAS.
8
8
10
34
15
13
7
1
17
31
6
17
25
74
77
11
6
89
4
21
26
16
7
19
7
2
9
24
14
11
6
25
7
15
9
33
8
113
7
33
8
6
11
MEAN
5.2
4.4
4.2
2.4
1.3
2.8
6.2
21.0
4.3
3.9
1.3
2.8
7.9
6.0
22
1.7
1.5
6.4
1.7
1.9
22
5.4
7.8
7.6
5.2
3.5
3.3
3.0
7.4
3.3
6.2
4.2
5.2
0.8
8.3
5.6
6.9
3.5
5.1
3.8
4.0
3.4
4.9
3EOM.
MEAN
4.5
3.4
2.9
1.1
2.0
6.0
21.0
3.5
3.0
0.8
2.1
5.0
4.9
1.6
1.0
0.9
4.3
0.9
1.3
1.3
4.1
6.3
6.3
4.'
3.5
1.6
2.4
3.7
2.6
5.5
3.5
4.0
0.5
6.6
4.5
6.2
2.8
4.9
2.6
3.7
1.9
2.4
MEDIAN
5.3
4.0
•4.4
1.3
1.9
6.2
21.0
3.8
3.5
1.1
2.3
5.0
5.6
1.7
1.6
0.9
5.5
1.3
1.4
2.0
5.0
4.6
7.6
5.
3.5
3.6
2.8
4.8
2.6
5.3
3.4
5.:
0.'
9.6
4.0
6.5
2.9
4.9
2.9
4.2
1.6
3.1
5TD.
DEV. 1
2.7
3.2
2.7
0.8
2.0
1.8
0.0
2.5
2.9
1.0
2.8
8.7
3.2
1.7
1.3
1.4
5.3
1.7
2.1
1.9
3.6
5.3
4.0
2.5
0.0
2.7
1.7
7.4
2.6
3.6
2.7
3.5
0.8
4.9
4.4
3.3
2.5
1.3
3.6
1.6
4.5
4.9
MAXIMUM
9.4
11.0
9.6
84
'. 23
6.0
9.9
21.0
10.1
15.0
3.1
12.7
40.9
15.2
10.7
4.0
3.6
31.2
3.8
10.0
, 7.7
13.7
16.2
15.2
9.3
3.5
8.5
6.5
22.9
9.1
13.2
13.0
11.5
3.3
14.3
24.2
10.9
17.3
6.8
18.4
6.3
12.4
13.8
8»4pCi/L '
63
50
60
18
b~
23
100
100
47
42
0
12
64
72
10
0
0
60
0
10
15
63
86
79
57
0
44
21
57
18
83
44
71
0
67
48
63
28
86
30
63
17
36
&>20pCi/L
0
0
0
0
0
0
0
100
0
0
0
0
8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3
0
0
0
0
0
0
0
-------
TABLE 1 (continued). Screening indoor radon data for Nebraska.
COUNTY
THAYER
THOMAS
THURSTON
VALLEY
WASHINGTON
WAYNE
WEBSTER
WHEELER
YORK
NO. OF
MEAS.
6
10
4
13
8
18
12
6
12
MEAN
4.2
1.5
8.3
4.0
8.3
9.3
4.0
1.4
5.8
GEOM.
MEAN
3.4
1.2
7.7
3.5
5.2
7.1
2.4
0.8
4.5
MEDIAN
3:6
1,1
9.7
4.2
4.6
7.2
3.5
1.3
5.1
STD.
DEV.
2.9
1.3
3.1
1.9
12.0
6.4
3.1
1.1
4.1
MAXIMUM
9.0
5.0
10.2
7.0
37.9
20.2
9.0
3.0
15.9
%>4pCi/L
33
10
75
54
63
72
42
0
67
%>20pCi/L
0
,0
0
0
13
6
0
0
0
-------
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gamma radioactivity signature averaging between 2.0 arid 2.5 ppm equivalent uranium (eU), with
scattered areas less than 2.0 ppm'and scattered anomalies greater than 3.0 pprru locally as high as
6.0 ppm (fig. 8). Of the source rocks underlying the gllcial deposits and those to the north and
northeast, Cretaceous sandstones and shales, Penrtsyiyanian black shales, and Precambrian
crystalline rocks all contain significant amounts-of uranium-series radionuch'des (uranium and(or)
radium) to generate radon at elevated levels;! In generalf soils developed from glacial deposits are
rapidly weathered, because crushing and grinding of the rocks by glacial action can enhance and ,
speed up soil weathering processes (Jenny, 1935). Grinding of the rocks increases the mobility of
uranium and radium in the soils by exposing them at grain surfaces, enhancing radionuclide
mobility and radon emanation. In addition, poorly-sorted glacial drift may in many cases have
higher permeability than the bedrock from which it is derived. Cracking of clayey glacial soils
during dry periods can create sufficient permeability for convective radon transport to occur.
Loess is a generally good radon source because it consists of silt and clay-sized particles, which
are more likely to be associated with radionuch'des and have higher emanation coefficients than
larger sized particles (Megumi and Marhuro, 1974), and it typically has moderate permeability
(fig. 6). , •' . ; '
The area mapped as loess between the Platte River and the Sand Hills in the central part of
the State (fig. 5) has surface radioactivity in the 2.5-3.0 ppm eU range (fig. 8), which is more
similar to the surface radioactivity of the Tertiary bedrock in the Panhandle area than to other loess-
covered areas in eastern and south-central Nebraska. The Sand Hills have low surface
radioactivity (fig. 8) and generally low radon potential.
SUMMARY '
For the purposes of this assessment, Nebraska is divided into five geologic radon potential
areas (fig. 9) and each area assigned a Radon Index (RI) and Confidence Index (CI) score
(Table 2). The Radon Index is a semiquantitative measure of radon potential based on geologic,
soil, and indoor radon factors, arid the Confidence Index is a measure of the relative confidence of
the RI assessment based on the quality and quantity qf data used to make the predictions (see the
Introduction chapter to this booklet.for more information on the methods arid data used).
Area 1, the Sand Hills, has a low radon potential (RI=8) with high confidence (CI=12).
Area 2 is underlain by Tertiary sedimentary bedrock in the Nebraska Panhandle and on the
northeastern side of the Sand Hills (fig. 9). Area 2 has a moderate radon potential (RI=11) with
high confidence (CI=12). Some homes in this area are likely to have high indoor radon levels,
particularly those sited on uranium-bearing parts of the White River and Arikaree Groups in
northwestern Nebraska. Area 3 is underlain by Tertiary bedrock covered by varying thicknesses
of loess. Area 3 has a moderate radon potential (RI=11) with high confidence (CI=l2). Homes
sited on thicker loess along the north side of the Platte River in Dawson and Buffalo Counties may
have locally high indoor radon levels. Area 4 is underlain by Cretaceous Pierre Shale bedrock,
including the uranium-bearing Sharon Springs Member. The gray-shale units of the Pierre Shale,
while not as uraniferous as the black shale units of the Sharon Springs Member, generally contain
higher-than-average (i.e., >2.5 ppm) amounts of uranium and are correlated with elevated indoor
radon levels in several areas. Area 4 has an overall high radon potential (RI=12) with high
confidence (CI=12). Area 5 is underlain by loess-mantled glacial drift in eastern Nebraska arid
loess-mantled Tertiary and Cretaceous bedrock in south-central Nebraska. Average indoor radon
levels are consistently greater than 4 pCi/L in areas underlain by loess-mantled glacial drift The
IV-17 Reprinted from USGS Open-File Report 93-292-G
-------
majority of homes in the area underlain by loess-mantled bedrock in the south-central part of the
State also have radon levels exceeding 4 pCi/L, but indoor radon levels are likely to be more
variable from house to house in south-central Nebraska, depending on the distribution, thickness,
or weathering extent of the loess. Area 5 has an overall high radon potential (RI=13) with high
confidence (CI=12). .
This is a generalized assessment of Nebraska'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
D21 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-18 Reprinted fitom USGS Open-File Report 93-292-G
-------
TABLE 2. Radon Index (RI) and Confidence Index (CI) scores for geologic radon potential areas
of Nebraska. See figure 9 for locations of areas;
RADON POTENTIAL AREAS
FACTOR
INDOORRADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
RANKING
1-Sand
Hills
RI CI
1
1
1
3
2
0
8
LOW
3
3
3
3
12
HIGH
2-Tertiary
Bedrock
RI CI
2
3
2
2.
2
0
11
MOD
.3
3
3
3
12
HIGH
3-Loess
over Tertiary
RI CI
2
3
2
2
2
0
11
MOD
3
3
3
3
12
HIGH
4-Pierre 5-Glacial Drift
Shale & Loess
RI CI RI CI
3
3
3
1
2
0
12
HIGH
3
3
3
3
12
HIGH
3
2
3
,2
3
0
13
HIGH
3
3
3 -•
3
12
HIGH
RADON INDEX SCORING: ,
1 Radon potential category
Probable screening indoor
Point range radon average for area
LOW " 3-8 points <2pCi/L
MODERATE/VARIABLE' - 9-11 points 2 - 4 pCi/L
HIGH > 11 points >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-19 Reprinted from USGS Open-File Report 93-292-G
-------
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-------
; REFERENCES USED IN THIS REPORT .
AND GENERAL REFERENCES PERTAINING TO RADON IN NEBRASKA
Burchett, R.R., 1979, The Mississippian and, Pennsylyanian (Carboniferous) Systems in the
United States—Nebraska: U.S. Geological Survey Professional Paper 1110-P, 15 p.
Burchett, R.R., 1983, Surface to subsurface correlation of Pennsylvanian and Lower Permian
rocks across southern Nebraska: Nebraska Geological Survey Report of Investigations
No. 8, 24 p.
Burchett, R.R., and Pabian, R.K., (compilers), 1991, Geologic bedrock map of Nebraska:
Nebraska Geological Survey, scale 1:1,000,000.
Carmichael, R^s!, 1989, Practical Handbook of physical properties of rocks and minerals: Boca
Raton, Fla., CRC Press, 741 p.
Collings, S.P., and Knode, R.H., 1984, Geology and discovery of the Crow Butte uranium
deposit, Dawes County, Nebraska, in Practical Hydromet '83: Proceedings of the 7th
Annual Symposium on Uramum and Precious Metals, American Institute of Mining
Engineers, p. 5-14. _ ,
Condra, G.E., and Reed, E.G., 1959, The geological section of Nebraska (with revisions by E.G.
Reed): Nebraska Geological Survey Bulletin 14-A, 82 p.
Denson, N.M-, and Gill, J.R., 1956, Uranium-bearing lignite and its relation to volcanic tuffs in
eastern Montana and^North and South Dakota, in Page. L.R., Stocking, H.E., and Smith,
H.B (eds), Contributions to the geology of uranium and thorium by the United States
Geological Survey and Atomic Energy Commission for the United Nations international
conference on peacefuluses of atomic energy, Geneva, Switzerland, 1955: U.S.
Geological Survey Professional Paper 300, p. 413-418.
Dickinson, K.A., 1991, Uranium and diagenesis in evaporitic lacustrine mudstone of the
Oligocehe White River Group, Dawes County, Nebraska: U.S. Geological Survey
Bulletin 1956, 25 p.
Dunham, R.J., 1955, Uranium minerals in the Oligocene gypsum near Chadron, Dawes County,
Nebraska: U.S. Atomic Energy Commission report TEI-525, 31 p. ;,
Duval, J.S., JonesvW.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.
Elder, J.A., 1969, Soils of Nebraska: University of Nebraska Conservation and Survey Division
Resource Report No. 2, ,60 p.
Gjelsteen, T.W., and Collings, S.P., 1988, Relationship between groundwater flow and uranium
mineralization in the Chadron Formation, northwest Nebraska: Wyoming Geological
Association 39th Field Conference Guidebook, p. 271-284.
IV-21 Reprinted from USGS Open-File Report 93-292-G
-------
Kepferle, R.C., 1959, Uranium in Sharon Springs Member of Pierre Shale, South Dakota and
northeastern Nebraska: U.S. Geological Survey Bulletin 1046-R, p. 577-604.
Kuzila, M., 1990, Soil Associations and Series, in Bleed, A. and Flowerday, C. (eds), An Atlas
of the Sand Hills: Resource Atlas No. 5a, 2nd edition., Conservation and Survey
Division, University of Nebraska-Lincoln, p. 58-66.
Megumi, K., and Mamuro, T., 1974, Emanation and exhalation of radon and thoron gases from
soil particles: Journal of Geophysical Research, v. 79, p. 3357-3360.
Nebraska Conservation and Survey Division, 1986, Groundwater atlas of Nebraska: Nebraska
Conservation and Survey Division Resource Atlas No. 4,32 p.
Nelson-Moore, J.L, Collins, Donna Bishop, and Hornbaker, A.L., 1978, Radioactive mineral
occurrences of Colorado and bibliography: Colorado Geological Survey Bulletin 40,
1054 p.
Reed, E.G., and Dreeszen, V.H., 1965, Revision of the classification of the Pleistocene deposits
of Nebraska: Nebraska Geological Survey Bulletin 23,65 p.
Richmond, G.M., Fullerton, D.S., and Christiansen, Ann Coe (editors), 1991, Quaternary
geologic map of the Des Moines 4°x6° quadrangle, United States: U.S. Geological Survey
Miscellaneous Investigations Map 1-1420, sheet NK-15, scale 1:1,000,000.
Struempler, A.W., 1989, Radon in outside air, buildings, water, and soil in northwestern
Nebraska, in A. Zechmann (ed), Proceedings of Nebraska Academy of Sciences, 99th
annual meeting Lincoln, NE, Apr. 14-15, 1989, p. 55.
Swanson, V.E., 1956, Uranium in marine black shales of the United States, in Page. L.R.,
Stocking, H.E., and Smith, H.B. (eds), Contributions to the geology of uranium and
thorium by the United States Geological Survey and Atomic Energy Commission for the
United Nations international conference on peaceful uses of atomic energy, Geneva,
Switzerland, 1955: U.S. Geological Survey Professional Paper 300, p. 451-456.
Swinehart, J.B., Souders, V.L., DeGraw, H.D., and Diffendal, R.F., Jr., 1985, Cenozoic
paleogeography of western Nebraska, in Flores, R.M. and Kaplan, S.S. (eds), Cenozoic
Paleogeography of west-central United States: Rocky Mountain Section, Society of
Economic Paleontologists and Mineralogists, Denver Colorado, p. 209-229.
Swinehart, J.B. and Diffendal, R.F., Jr., 1990, Geology of the pre-dune strata, in Bleed, A. and
Flowerday, C. (eds), An Adas of the Sand Hills: Resource Atlas No. 5a, 2nd edition.,
Conservation and Survey Division, University of Nebraska-Lincoln, 29-42..
Tourtelot, H.A., 1956, Radioactivity and uranium content of some Cretaceous shales, central
Great Plains: Bulletin of the American Association of Petroleum Geologists, v. 40,
p. 62-83.
IV-22 Reprinted from USGS Open-File Report 93-292-G
-------
U.S. Soil Conservation Service, 1987, Soils: U.S. Geological Survey National Atlas sheet
38077-BE-NA-07M-00, scale 1:7,500,000. : r
Zielinski, R.A., 1983, Tuffaceous sediments as source rocks for uranium—A case study of the
White River Formation, Wyoming: Journal of Geochemical Exploration, v. 18,
p. 285-306. : ,
IV-23 Reprinted from USGS Open-File Report 93-292-G
-------
-------
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 USGS' 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.) , " ,
V - . - .
NEBRASKA MAP OF RADON ZONES / '
The Nebraska Map of Radon Zones and its supporting documentation (Part IV of this
report) have received extensive review by Nebraska geologists and radon program experts.
The map for Nebraska 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 Nebraska" — 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 7 EPA office or the
Nebraska radon program for information on testing and fixing homes. Telephone numbers
and addresses can be found in Part II of "this report. .-"'.•;
V-l
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