United States
Environmental Protection
Agency
Air and Radiation
(6604J)
402-R-93-022
September 1993
v>EPA ERA'S Map of Radon Zones
ALASKA
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EPA'S MAP OF RADON ZONES
ALASKA
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:INTRODUCTION
III. REGION 10 GEOLOGIC RADON POTENTIAL
SUMMARY
V. PRELIMINARY GEOLOGIC RADON POTENTIAL
ASSESSMENT OF ALASKA
V. EPA'S MAP OF RADON ZONES -- ALASKA
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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 and local governments
and organizations to target their radon program activities and resources. It is also intended to
help building code officials determine areas that are the highest priority for adopting radon-
resistant building practices. The Map of Radon Zones should not be used to determine if
individual homes in any given area need to be tested for radon. EPA recommends that all
homes be tasted for radon, regardless of geographic location or the zone designation of
the county in which they are located.
This document provides background information concerning the development of the
Map of Radon Zones. It explains the purposes of the map, the approach for developing the
map (including the respective roles of EPA and USGS), the data sources used, the conclusions
and confidence levels developed for the prediction of radon potential, and the review process
that was conducted to finalize this effort,
BACKGROUND
Radon (Rn~:) 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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Purpose of the Map of Radon Zones
EPA's Map of Radon Zones (Figure 1) assigns each of the 3141 counties in the
United States to one of three zones:
o Zone 1 counties have a predicted average indoor screening level > than
4 pCi/L
o Zone 2 counties have a predicted average screening level > 2 pCi/L and
< 4 pCi/L
o Zone 3 counties have a predicted average screening level < 2 pCi/L
The Zone designations were determined by assessing five factors that are known to be
important indicators of radon potential: indoor radon measurements, geology, aerial
radioactivity, soil parameters, and foundation types.
The predictions of average screening levels in each of the Zones is an expression of
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 lo Radon.
the Consumer's Guide to Radon Reduction and the Home Buyer's and Seller's Guide to
Radon.
EPA believes that States, local governments and other organizations can achieve
optimal risk reductions by targeting resources and program activities to high radon potential
areas. Emphasizing targeted approaches (technical assistance, information and outreach
efforts, promotion of real estate mandates and policies and building codes, etc.) in such areas
addresses the greatest potential risks first.
EPA also believes that the use of passive radon control systems in the construction of
new homes in Zone 1 counties, and the activation of those systems if necessitated by follow-
up testing, is a cost effective approach to achieving significant radon risk reduction.
The Map of Radon Zones and its supporting documentation establish no regulatory
requirements. Use of this map by State or local radon programs and building code officials is
voluntary. The information presented on the Map of Radon Zones and in the supporting
documentation is not applicable to radon in water.
Development of the Map of Radon Zones
The technical foundation for the Map of Radon Zones is the USGS Geologic Radon
Province Map. In order to examine the radon potential for the United States, the USGS
began by identifying approximately 360 separate geologic provinces for the U.S. The
provinces are shown on the USGS Geologic Radon Province Map (Figure 2). Each of the
geologic provinces was evaluated by examining the available data for that area: indoor radon
measurements, geology, aerial radioactivity, soil parameters, and foundation types. t\s stated,
previously, these five factors are considered to be of basic importance in assessing radon
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Figure 1
EPA Map of Radon Zones
LEGEND
Zone 1
Zone 2
Zone 3
buom reimtnary one ssigna ion. **' The purpose of this mop is to assist Notional, Stats and heal organizations to target their resources and to implement radon-resistant building codes.
This map is not intended to be used to determine if a home in a given zone should be tested for radon. Homes with elevated levels of radon hove been found
in all three zones, Alt homes should be tested, regardless of geographic location.
IMPORTANT: Consult the EPA Map of Radon Zones document (EPA-402—R-93—071) before using this mop. This document contains information on radon potential variations within counties.
EPA also recommends that this map be supplemented with any available local data in order to further understand and predict the radon potential of a specific area.
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Figure 2
GENERALIZED GEOLOGIC RADON POTENTIAL OF THE UNITED STATES
by the U.S. Geological Survey
Scale
Continental United States
and Hawaii
Geologic Radon
Potential
(Predicted Average
Screening Measurement) ,
LOW (< 2 pC!/L)
MODERATE/VARIABLE
(2-4pCI/L)
HIGH (>4pCI/L)
0 500
Miles
6/93
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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 Radon Zones by extrapolating from the
province level to the county level so that all counties in the U.S. were assigned to one of
three radon zones. EPA assigned each county to a given zone based on its provincial radon
potential. For example, if a county is located within a geologic province that has a predicted
average screening level greater than 4 pCi/L, it was assigned to Zone 1. Likewise, counties
located in provinces with predicted average screening levels > 2 pCi/L and < 4 pCi/L, and
less than 2 pCi/L, were assigned to Zones 2 and 3, respectively.
If the boundaries of a county fall in more than one geologic province, the county was
assigned to a zone based on the predicted radon potential of the province in which most of
the area lies. For example, if three different provinces cross through a given county, the
county was assigned to the zone representing the radon potential of the province containing
most of the county's land area. (In this case, it is not technically correct to say that the
predicted average screening level applies to the entire county since the county falls in
multiple provinces with differing radon potentials.)
Figures 3 and 4 demonstrate an example of how EPA extrapolated the county zone
designations for Nebraska from the USGS geologic province map for the State. As figure 3
shows, USGS has identified 5 geologic provinces for Nebraska. Most of the counties are
extrapolated "straight" from their corresponding provinces, but there are counties "partitioned"
by several provinces — for example, Lincoln County. Although Lincoln county falls in
multiple provinces, it was assigned to Zone 3 because most of its area falls in the province
with the lowest radon potential.
It is important to note that EPA's extrapolation from the province level to the
county level may mask significant "highs" and "lows" within specific counties. In other
words, within-GOimty 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 Pf-ofiaces for Nebraska
Lincoln County
MD ^ e i 2 s e
lew
Figure 4
NEBRASKA - EPA Map of Radoa Zones
Liicola County
Zone 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 (he 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,
1-8
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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!), this introduction to the USGS assessment (Part II), including a general discussion of
radon (occurrence, transport, etc.), and details concerning the types of data used. The third
component is a summary chapter outlining the general geology and geologic radon potential
of the EPA Region (Part III). The fourth component is an individual chapter for each state
(Part IV). Each state chapter discusses the state's specific geographic setting, soils, geologic
setting, geologic radon potential, indoor radon data, and a summary outlining the radon
potential rankings of geologic areas in the state. A variety of maps are presented in each
chapter—geologic, geographic, population, soils, aerial radioactivity, and indoor radon data by
county. Finally, the booklets contain EPA's map of radon zones for each state and an
accompanying description (Part V).
Because of constraints on the scales of maps presented in these reports and because the
smallest units used to present the indoor radon data are counties, some generalizations have
been made in order to estimate the radon potential of each area. Variations in geology, soil
characteristics, climatic factors, homeowner lifestyles, and other factors that influence radon
concentrations can be quite large within any particular geologic area, so these reports cannot
be used to estimate or predict the indoor radon concentrations of individual homes or housing
II-l Reprinted from USGS Open-File Report 93-292
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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
geology may be obtained from the state geological surveys. Addresses and telephone
numbers of state radon contacts, geological surveys, and EPA regional offices are listed in
Appendix C at the end of this chapter.
RADON GENERATION AND TRANSPORT IN SOILS
Radon (222Rn) is produced from the radioactive decay of radium (22SRa), which is, in turn,
a product of the decay of uranium (M8U) (fig. 1). The half-life of ^Rn is 3.825 days. Other
isotopes of radon occur naturally, but, with the exception of thoron (220Rn), which occurs in
concentrations high enough to be of concern in a few localized areas, they are less important
in terms of indoor radon risk because of their extremely short half-lives and less common
occurrence. In general, the concentration and mobility of radon in soil are dependent on
several factors, the most important of which are the soil's radium content and distribution,
porosity, permeability to gas movement, and moisture content. These characteristics are, in
turn, determined by the soil's parent-material composition, climate, and the soil's age or
maturity. If parent-material composition, climate, vegetation, age of the soil, and topography
are known, the physical and chemical properties of a soil in a given area can be predicted.
As soils form, they develop distinct layers, or horizons, that are cumulatively called the
soil profile. The A horizon is a surface or near-surface horizon containing a relative
abundance of organic matter but dominated by mineral matter. Some soils contain an E
horizon, directly below the A horizon, that is generally characterized by loss of clays, iron, or
aluminum, and has a characteristically lighter color than the A horizon. The B horizon
underlies the A or E horizon. Important characteristics of B horizons include accumulation of
clays, iron oxides, calcium carbonate or other soluble salts, and organic matter complexes. In
drier environments, a horizon may exist within or below the B horizon that is dominated by
calcium carbonate, often called caliche or calcrete. This carbonate-cemented horizon is
designated the K horizon in modern soil classification schemes. The C horizon underlies the
B (or K) and is a zone of weathered parent material that does not exhibit characteristics of A
or B horizons; that is, it is generally not a zone of leaching or accumulation. In soils formed
in place from the underlying bedrock, the C horizon is a zone of unconsolidated, weathered
bedrock overlying the unweathered bedrock.
The shape and orientation of soil particles (soil structure) control permeability and affect
water movement in the soil. Soils with blocky or granular structure have roughly equivalent
permeabilities in the horizontal and vertical directions, and air and water can infiltrate the soil
relatively easily. However, in soils with platy structure, horizontal permeability is much
greater than vertical permeability, and air and moisture infiltration is generally slow. Soils
with prismatic or columnar structure have dominantly vertical permeability. Platy and
prismatic structures form in soils with high clay contents. In soils with shrink-swell clays, air
II-2 Reprinted from USGS Open-File Report 93-292
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Polonlum
JT*!
i-218y*g
Radon-222
3.82 days
Lead-214
27mln- X
eismuth.214
138,4 days
STABLE
Uranlum-238
Ji billion years
R \ Protactlnlum-234
1.17 mIn.M „ , „.
UranIum-234
247,000 years
r 80,000 years
Radlum-226 fa
'1602 years
J
f
Figure 1. The uranium-238 decay series, showing the half-lives of elements and their modes of decay (after Wanty and
Schoen, 1991). a denotes alpha decay, p denotes beta decay.
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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"9 meters), or about,2x10"6 inches—this is known as alpha
recoil (Tanner, 1980). Moisture in the soil lessens the chance of a recoiling radon atom
becoming imbedded in an adjacent grain. Because water is more dense than air, a radon atom
will travel a shorter distance in a water-filled pore than in an air-filled pore, thus increasing
the likelihood that the radon atom will remain in the pore space. Intermediate moisture levels
enhance radon emanation but do not significantly affect permeability. However, high
moisture levels can significantly decrease the gas permeability of the soil and impede radon
movement through the soil.
Concentrations of radon in soils are generally many times higher than those inside of
buildings, ranging from tens of pCi/L to more than 100,000 pCi/L, but typically in the range
of hundreds to low thousands of pCi/L. Soil-gas radon concentrations can vary in response to
variations in climate and weather on hourly, daily, or seasonal time scales. Schumann and
others (1992) and Rose and others (1988) recorded order-of-magnitude variations in soil-gas
radon concentrations between seasons in Colorado and Pennsylvania The most important
factors appear to be (1) soil moisture conditions, which are controlled in large part by
precipitation; (2) barometric pressure; and (3) temperature. Washington and Rose (1990)
suggest that temperature-controlled partitioning of radon between water and gas in soil pores
also has a significant influence on the amount of mobile radon in soil gas.
Homes in hilly limestone regions of the southern Appalachians were found to have higher
indoor radon concentrations during the summer than in the winter. A suggested cause for this
phenomenon involves temperature/pressure-driven flow of radon-laden air from subsurface
II-4 Reprinted from USGS Open-File Report 93-292
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solution cavities in the carbonate rock into houses. As warm air enters solution cavities that
are higher on the hillslope than the homes, it cools and settles, pushing radon-laden air from
lower in the cave or cavity system into structures on the hillslope (Gammage and others,
1993). In contrast, homes built over caves having openings situated below the level of the
home had higher indoor radon levels in the winter, caused by cooler outside air entering the
cave, driving radon-laden air intd cracks and solution cavities in the rock and soil, and
ultimately, into homes (Gammage and others, 1993).
RADON ENTRY INTO BUILDINGS
A driving force (reduced atmospheric pressure in the house relative to the soil, producing
a pressure gradient) and entry points must exist for radon to enter a building from the soil.
The negative pressure caused by furnace combustion, ventilation devices, and the stack effect
(the rising and escape of warm air from the upper floors of the building, causing a
temperature and pressure gradient within the structure) during cold winter months are
common driving forces. Cracks and other penetrations through building foundations, sump
holes, and slab-to-foundation wall joints are common entry points.
Radon levels in the basement are generally higher than those on the main floor or upper
floors of most structures. Homes with basements generally provide more entry points for
radon, commonly have a more pronounced stack effect, and typically have lower air pressure
relative to the surrounding soil than nonbasement homes. The term "nonbasement" applies to
slab-on-grade or crawl space construction.
METHODS AND SOURCES OF DATA
The assessments of radon potential in the booklets that follow this introduction were
made using five main types of data: (1) geologic (lithologic); (2) aerial radiometric; (3) soil
characteristics, including soil moisture, permeability, and drainage characteristics; (4) indoor
radon data; and (5) building architecture (specifically, whether homes in each area are built
slab-on-grade or have a basement or crawl space). These five factors were evaluated and
integrated to produce estimates of radon potential. Field measurements of soil-gas radon or
soil radioactivity were not used except where such data were available in existing, published
reports of local field studies. Where applicable, such field studies are described in the
individual state chapters.
GEOLOGIC DATA
The types and distribution of lithologic units and other geologic features in an
assessment area are of primary importance in determining radon potential. Rock types that
are most likely to cause indoor radon problems include carbonaceous black shales, glauconite-
bearing sandstones, certain kinds of fluvial sandstones and fluvial sediments, phosphorites,
chalk, karst-producing carbonate rocks, certain kinds of glacial deposits, bauxite, uranium-rich
granitic rocks, metamorphic rocks of granitic composition, silica-rich volcanic rocks, many
sheared or faulted rocks, some coals, and certain kinds of contact metamorphosed rocks.
Rock types least likely to cause radon problems include marine quartz sands, non-
carbonaceous shales and siltstones, certain kinds of clays, silica-poor metamorphic and
11-5 Reprinted from USGS Open-File Report 93-292
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igneous rocks, and basalts. Exceptions exist within these general lithologic groups because of
the occurrence of localized uranium deposits, commonly of the hydrothermal type in
crystalline rocks or the "roll-front" type in sedimentary rocks. Uranium and radium are
commonly sited in heavy minerals, iron-oxide coatings on rock and soil grains, and organic
materials in soils and sediments. Less common are uranium associated with phosphate and
carbonate complexes in rocks and soils, and uranium minerals.
Although many cases of elevated indoor radon levels can be traced to high radium and
(or) uranium concentrations in parent rocks, some,structural features, most notably faults and
shear zones, have been identified as sites of localized uranium concentrations (Deffeyes and
MacGregor, 1980) and have been associated with some of the highest reported indoor radon
levels (Gundersen, 1991). The two highest known indoor radon occurrences are associated
with sheared fault zones in Boyertown, Pennsylvania (Gundersen and others, 1988a; Smith
and others, 1987), and in Clinton, New Jersey (Henry and others, 1991; 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 concentrations of radon
parent materials (uranium, radium) in rocks and soils. Equivalent uranium is calculated from
the counts received by a gamma-ray detector from the 1.76 MeV (mega-electron volts)
emission energy corresponding to bismuth-214 (2HBi), with the assumption that uranium and
its decay products are in secular equilibrium. Equivalent uranium is expressed in units of
parts per million (ppm). Gamma radioactivity also may be expressed in terms of a radium
activity; 3 ppm eU corresponds to approximately 1 picocurie per gram (pCi/g) of radium-226.
Although radon is highly mobile in soil and its concentration is affected by meteorological
conditions (KLovach, 1945; Klusman and Jaaeks, 1987; Schery and others, 1984; Schumann
and others, 1992), statistical correlations between average soil-gas radon concentrations and
average eU values for a wide variety of soils have been documented (Gundersen and others,
1988a, 1988b; Schumann and Owen, 1988). Aerial radiometric data can provide an estimate
of radon source strength over a region, but the amount of radon that is able to enter a home
from the soil is dependent on several local factors, including soil structure, grain size
distribution, moisture content, and permeability, as well as type of house construction and its
structural condition.
The aerial radiometric data used for these characterizations were collected as part of the
Department of Energy National Uranium Resource Evaluation (NURE) program of the 1970s
and early 1980s. The purpose of the NURE program was to identify and describe areas in the
United States having potential uranium resources (U.S. Department of Energy, 1976). The
NURE aerial radiometric data were collected by aircraft in which a gamma-ray spectrometer
was mounted, flying approximately 122 m (400 ft) above the ground surface. The equivalent
uranium maps presented in the state chapters were generated from reprocessed NURE data in
which smoothing, filtering, recalibrating, and matching of adjacent quadrangle data sets were
performed to compensate for background, altitude, calibration, and other types of errors and
inconsistencies in the original data set (Duval and others, 1989). The data were then gridded
and contoured to produce maps of eU with a pixel size corresponding to approximately 2.5 x
2.5 km (1.6 x 1.6 mi):
II-6 Reprinted from USGS Open-File Report 93-292
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FLICUT LINE SPACING Of SU«E AERIAL SURVEYS
2 KB (1 KILE)
5 KK (3 HUES)
2 t 5 k'H
10 KM (6 MILES]
5 ft 10 XH
NO DATA
Figure 2. Nominal flightline spacings for NUKE 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 NUKE 1° x 2° quadrangles showing the flight-line spacing
for each quadrangle. In general, the more closely spaced the flightlines are, the more area
was covered by the aerial gamma survey, and thus, more detail is available in the data set.
For an altitude of 400 ft above the ground surface and with primary flightline spacing
typically between 3 and 6 miles, less than 10 percent of the ground surface of the United
States was actually measured by the airborne gamma-ray detectors (Duval and others, 1989),
although some areas had better coverage than others due to the differences in flight-line
spacing between areas (fig. 2). This suggests that some localized uranium anomalies may not
have been detected by the aerial surveys, but the good correlations of 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, shrink-
swell potential, vegetative cover, generalized groundwater characteristics, and land use. The
reports are available in county formats and State summaries. The county reports typically
contain both generalized and detailed maps of soils in the area,
Because of time and map-scale constraints, it was impractical to examine county soil
reports for each county in the United States, so more generalized summaries at appropriate
scales were used where available. For State or regional-scale radon characterizations, soil
maps were compared to geologic maps of the area, and the soil descriptions, shrink-swell
potential, drainage characteristics, depth to seasonal high water table, permeability, and other
relevant characteristics of each soil group noted. Technical soil terms used in soil surveys are
generally complex; however, a good summary of soil engineering terms and the national
distribution of technical soil types is the "Soils" sheet of the National Atlas (U.S. Department
of Agriculture, 1987).
II-8 Reprinted from USGS Open-File Report 93-292
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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 60,000 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 from USGS Open-File Report 93-292
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STATE/EPA RESIDENTIAL RADON
SURVEY SCREENING MEASUREMENTS
0
Estimated Percent of Houses with Screening Levels Greater than 4 pCi/L
20 and >
'ITic Steles of Dfi,n,NI I.NJ.NY, and UT
have conducted Ihcir own surveys. OR &
SD dedincd to participate in Ihc SRRS.
These results arc based on 2-7 day screening
measurements in the lowest livable level and should not
be used to estimate annual averages or health risks.
Figure 3. Percent of homes tested in the State/EPA Residential Radon Survey with screening indoor radon levels exceeding 4 pCi/L.
-------
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
. jS-ssments. Radon data from State or regional ind^ or radon surveys, public h alth
organizations, or other sources are discussed in addition to the primary data sources where
they are available. Nearly all of the data used in these evaluations represent short-term (2-7
day) screening measurements from the lowest livable space of the homes. Specific details
concerning the nature and use of indoor radon data sets other than the State/EPA Residential
Radon Survey are discussed in the individual State chapters.
RADON INDEX AND CONFIDENCE INDEX
Many of the geologic methods used to evaluate an area for radon potential require
subjective opinions based on the professional judgment and experience of the individual
geologist. The evaluations are nevertheless based on established scientific principles that are
universally applicable to any geographic area or geologic setting. This section describes the
methods and conceptual framework used by the U.S. Geological Survey to evaluate areas for
radon potential based on the five factors discussed in the previous sections. The scheme is
divided into two basic parts, a Radon Index (RI), used to rank the general radon potential of
the area, and the Confidence Index (CI), used to express the level of confidence in the
prediction based on the quantity and quality of the data used to make the determination. This
scheme works best if the areas to be evaluated are delineated by geologically-based
boundaries (geologic provinces) rather than political ones (state/county boundaries) in which
the geology may vary across the area.
Radon Index. Table 1 presents the Radon Index (RI) matrix. The five factors—indoor
radon data, geology, aerial radioactivity, soil parameters, and house foundation type—were
quantitatively ranked (using a point value of 1, 2, or 3) for their respective contribution to
radon potential in a given area. At least some data for the 5 factors are consistently available
for every geologic province. Because each of these main factors encompass a wide variety of
complex and variable components, the geologists performing the evaluation relied heavily on
their professional judgment and experience in assigning point values to each category and in
determining the overall radon potential ranking. Background information on these factors is
discussed in more detail in the preceding sections of this introduction.
Indoor radon was evaluated using unweighted arithmetic means of the indoor radon data
for each geologic area to be assessed. Other expressions of indoor radon levels in an area
also could have been used, such as weighted averages or annual averages, but these types of
data were not consistently available for the entire United States at the time of this writing, or
the schemes were not considered sufficient to provide a means of consistent comparison
across all areas. For this report, charcoal-canister screening measurement data from the
State/EPA Residential Radon Surveys and other carefully selected sources were used, as
described in the preceding section. To maintain consistency, other indoor radon data sets
(vendor, state, or other data) were not considered in scoring the indoor radon factor cf the
Radon Index if they were not randomly sampled or could not be statistically combined with
the primary indoor radon data sets. However, these additional radon data sets can provide a
means to further refine correlations between geologic factors and radon potential, so they are
II-11 Reprinted from USGS Open-File Report 93-292
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TABLE 1. RADON INDEX MATRIX, "ppm eU" indicates parts per million of equivalent
uranium, as indicated by NURE aerial radiometric data. See text discussion for details.
INCREASING RADON POTENTIAL ^
FACTOR
INDOOR RADON (average)
AERIAL RADIOACTIVITY
GEOLOGY*
SOIL PERMEABILITY
ARCHITECTURE TYPE
POINT VALUE
1
<2pCi/L
< 1.5 ppm eU
negative
low
mostly slab
2
2 - 4 pCi/L
1.5 - 2.5 ppm eU
variable
moderate
mixed
3
> 4 pCi/L
> 2.5 ppm eU
positive
high
mostly basement
*GEOLOGIC FIELD EVIDENCE (GFE) POINTS: GFE points are assigned in addition to points
for the "Geology" factor for specific, relevant geologic field studies. See text for details.
Geologic evidence supporting: HIGH radon +2 points
MODERATE +1 point
LOW -2 points
No relevant geologic field studies 0 points
SCORING:
Radon potential category
Point ranee
Probable average screening
indoor radon for area
LOW
MODERATE/VARIABLE
HIGH
3-8 points
9-11 points
12-17 points
<2pCi/L
2-4pCi/L
>4pCi/L
POSSIBLE RANGE OF POINTS = 3 to 17
TABLE 2. CONFIDENCE INDEX MATRIX -
INCREASING CONFIDENCE
FACTOR
INDOOR RADON DATA
AERIAL RADIOACTIVITY
GEOLOGIC DATA
SOIL PERMEABILITY
POINT VALUE
1
sparse/no data
questionable/no data
questionable
questionable/no data
2
fair coverage/quality
glacial cover
variable
variable
3
good coverage/quality
no glacial cover
proven geol. model
reliable, abundant
SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10 - 12 points
POSSIBLE RANGE OF POINTS = 4 to 12
11-12
Reprinted from USGS Open-File Report 93-292
-------
included as supplementary information and are discussed in the individual State chapters. If
the average screening indoor radon level for an area was less than 2 pCi/L, the indoor radon
factor was assigned 1 point, if it was between 2 and 4 pCi/L, it was scored 2 points, and if
the average screening indoor radon level for an area was greater than 4 pCi/L, the indoor
radon factor was assigned 3 RI points.
Aerial radioactivity data used in this report are from the equivalent uranium map of the
conterminous United States compiled from NUKE aerial gamma-ray surveys (Duval and
others, 1989). These data indicate the gamma radioactivity from approximately the upper 30
cm of rock and soil, expressed in units of ppm equivalent uranium. An approximate average
value of eU was determined visually for each area and point values assigned based on
whether the overall eU for the area falls belpw 1.5 ppm (1 point), between 1.5 and 2.5 ppm
(2 points), or greater than 2.5 ppm (3 points).
The geology factor is complex and actually incorporates many geologic characteristics. In
the matrix, "positive" and "negative" refer to the presence or absence and distribution of rock
types known to have high uranium contents and to generate elevated radon in soils or indoors.
Examples of "positive" rock types include granites, black shales, phosphatic rocks, and other
rock types described in the preceding "geologic data" section. Examples of "negative" rock
types include marine quartz sands and some clays. The term "variable" indicates that the
geology within the region is variable or that the rock types in the area are known or suspected
to generate elevated radon in some areas but not in others due to compositional differences,
climatic effects, localizeddistribution of uranium, or other factors. Geologic information
indicates not only how much uranium is present in the rocks and soils but also gives clues for
predicting general radon emanation and mobility characteristics through additional factors
such as structure (notably the presence of faults or shears) and geochemical characteristics
(for example, a phosphate-rich sandstone will likely contain more uranium than a sandstone
containing little or no phosphate because the phosphate forms chemical complexes with
uranium). "Negative", "variable", and "positive" geology were assigned 1, 2, and 3 points,
respectively.
In cases where additional reinforcing or contradictory geologic evidence is available,
Geologic Field Evidence (GFE) points were added to or subtracted from an area's score
(Table 1). Relevant geologic field studies are important to enhancing our understanding of
how geologic processes affect radon distribution. In some cases, geologic models and
supporting field data reinforced an already strong (high or low) score; in others, they provided
important contradictory data. GFE points were applied for geologically-sound evidence that
supports the prediction (but which may contradict one or more factors) on the basis of known
geologic field studies in the area or in areas with geologic and climatic settings similar
enough that they could be applied with full confidence. For example, areas of the Dakotas,
Minnesota, and Iowa that are covered with Wisconsin-age glacial deposits exhibit a low aerial
radiometric signature and score only one RI point in that category. However, data from
geologic field studies in North Dakota and Minnesota (Schumann and others, 1991) suggest
that eU is a poor predictor of geologic radon potential in this area because radionuclides have
11-13 Reprinted from USGS Open-File Report 93-292
-------
been leached from the upper soil layers but are present and possibly even concentrated in
deeper soil horizons, generating significant soil-gas radon. This positive supporting field
evidence adds two GFE points to the score, which helps to Counteract the invalid conclusion
suggested by the radiometric data. No GFE points are awarded if there are no documented
field studies for the area.
"Soil permeability" refers to several soil characteristics that influence radon concentration
and mobility, including soil type, grain size, structure, soil moisture, drainage, slope, and
permeability. In the matrix, "low" refers to permeabilities less than about 0.6 in/hr; "high"
corresponds to greater than about 6.0 in/hr, in U.S. Soil Conservation Service (SCS) standard
soil percolation tests. The SCS data are for water permeability, which generally correlates
well with the gas permeability of the soil except when the soil moisture content is very high.
Areas with consistently high water tables were thus considered to have low gas permeability.
"Low, "moderate", and "high" permeability were assigned 1, 2, and 3 points, respectively.
Architecture type refers to whether homes in the area have mostly basements (3 points),
mostly slab-on-grade construction (1 point), or a mixture of the'two. Split-level and crawl
space homes fall into the "mixed" category (2 points). Architecture information is necessary
to properly interpret the indoor radon data and produce geologic radon potential categories
that are consistent with screening indoor radon data.
The overall RI for an area is calculated by adding the individual RI scores for the 5
factors, plus or minus GFE points, if any. The total RI for an area falls in one of three
categories—low, moderate or variable, or high. The point ranges for the three categories were
determined by examining the possible combinations of points for the 5 factors and setting
rules such that a majority (3 of 5 factors) would determine the final score for the low and
high categories, with allowances for possible deviation from an ideal score by the other two
factors. The moderate/variable category lies between these two ranges. A total deviation of 3
points from the "ideal" score was considered reasonable to allow for natural variability of
factors—if two of the five factors are allowed to vary from the "ideal" for a category, they
can differ by a minimum of 2 (1 point different each) and a maximum of 4 points (2 points
different each). With "ideal" scores of 5, 10, and 15 points describing low, moderate, and
high geologic radon potential, respectively, an ideal low score of 5 points plus 3 points for
possible variability allows a maximum of 8 points in the low category. Similarly, an ideal
high score of 15 points minus 3 points gives a minimum of 12 points for the high category.
Note, however, that if both other factors differ by two points from the "ideal", indicating
considerable variability in the system, the total point score would lie in the adjacent (i.e.,
moderate/variable) category.
Confidence Index. Except for architecture type, the same factors were used to establish a
Confidence Index (CI) for the radon potential prediction for each area (Table 2). Architecture
type was not included in the confidence index because house construction data are readily and
reliably available through surveys taken by agencies and industry groups including the
National Association of Home Builders, U.S. Department of Housing and Urban
Development, and the Federal Housing Administration; thus it was not considered necessary
11-14 Reprinted from USGS Open-File Report 93-292
-------
to question the quality or validity of these data. The other factors were scored on the basis of
the quality and quantity of the data used to complete the RI matrix.
Indoor radon data were evaluated based on the distribution and number of data points and
on whether the data were collected by random sampling (State/EPA Residential Radon Survey
or other state survey data) or volunteered vendor data (likely to be nonrandom and biased
toward population centers and/or high indoor radon levels). The categories listed in the CI
matrix for indoor radon data ("sparse or no data", "fair coverage or quality", and "good
coverage/quality") indicate the sampling density and statistical robustness of an indoor radon
data set. Data from the State/EPA Residential Radon Survey and statistically valid state
surveys were typically assigned 3 Confidence Index points unless the data were poorly
distributed or absent in the area evaluated.
Aerial radioactivity data are available for all but a few areas of the continental United
States and for part of Alaska. An evaluation of the quality of the radioactivity data was based
on whether there appeared to be a good correlation between the radioactivity and the actual
amount of uranium or radium available to generate mobile radon in the rocks and soils of the
area evaluated. In general, the greatest problems with correlations among eU, geology, and
soil-gas or indoor radon levels were associated with glacial deposits (see the discussion in a
previous section) and typically were assigned a 2-point Confidence Index score. Correlations
among eU, geology, and radon were generally sound in unglaciated areas and were usually
assigned 3 CI points. Again, however, radioactivity data in some unglaciated areas may have
been assigned fewer than 3 points, and in glaciated areas may be assigned only one point, if
the data were considered questionable or if coverage was poor.
To assign Confidence Index scores for the geologic data factor, rock types and geologic
settings for which a physical-chemical, process-based understanding of radon generation and
mobility exists were regarded as having "proven geologic models" (3 points); a high
confidence could be held for predictions in such areas. Rocks for which the processes are
less well known or for which data are contradictory were regarded as "variable" (2 points),
and those about which little is known or for which no apparent correlations have been found
were deemed "questionable" (1 point).
The soil permeability factor was also scored based on quality and amount of data. The
Ihree categories for soil permeability in the Confidence Index are similar in concept, and
scored similarly, to those for the geologic data factor. Soil permeability can be roughly
estimated from grain size and drainage class if data from standard, accepted soil percolation
tests are unavailable; however, the reliability of the data would be lower than if percolation
test figures or other measured permeability data are available, because an estimate of this type
does not encompass all the factors that affect soil permeability and thus may be inaccurate in
some instances. Most published soil permeability data are for water; although this is
generally closely related to the air permeability of the soil, there are some instances when it
may provide an incorrect estimate. Examples of areas in which water permeability data may
not accurately reflect air permeability include areas with consistently high levels of soil
moisture, or clay-rich soils, which would have a low water permeability but may have a
11-15 Reprinted from USGS Open-File Report 93-292
-------
significantly higher air permeability when dry due to shrinkage cracks in the soil. These
additional factors were applied to the soil permeability factor when assigning the RI score, but
may have less certainty in, some cases and thus would be assigned a lower CI score.
The Radon Index and Confidence Index give a general indication of the relative
contributions of the interrelated geologic factors influencing radon generation and transport in
rocks and soils, and thus, of the potential for elevated indoor radon levels to occur in a
particular area. However, because these reports are somewhat generalized to cover relatively
large areas of States, it is highly recommended that more detailed studies be performed in
local areas of interest, using the methods and general information in these booklets as a guide.
11-16 Reprinted from USGS Open-File Report 93-292
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REFERENCES CITED
Akerblom, G., Anderson, P., and Clavensjo, B., 1984, Soil gas radon—A source for indoor radon
daughters: Radiation Protection Dosimetry, v. 7, p. 49-54.
Deffeyes, K.S., and MacGregor, ID., 1980, World uranium resources: Scientific American,
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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
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Duval, J.S., Cook, E.G., and Adams, J.A.S., 1971, Circle of investigation of an airborne
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Duval, J.S., Jones, W.J., Riggle, F.R., and Pitkin, J.A., 1989, Equivalent uranium map of
conterminous United States: U.S. Geological Survey Open-File Report 89-478,10 p.
Duval, J.S., Reimer, G.M., Schumann, R.R., Owen, D.E., and Otton, J.K., 1990, Soil-gas
radon compared to aerial and ground gamma-ray measurements at study sites near Greeley
and Fort Collins, Colorado: U.S. Geological Survey Open-File Report 90-648,42 p.
Dziuban, J.A., Clifford, M.A., White, S.B., Bergstein, J.W., and Alexander, B.V., 1990,
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Gammage, R.B., Wilson, D.L., Saultz, R.J., and Bauer, B.C., 1993, Subtereanean transport of
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Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1988a, Correlation between geology, radon
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Gundersen, L.C.S, Reimer, G.M., Wiggs, C.R., and Rice, C.A., 1988b, Map showing radon
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U.S. Geol. Survey Bulletin no. 1971, p. 39-50.
JI-17 Reprinted from USGS Open-File Report 93-292
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Henry, Mitchell E., Kaeding, Margret E., and Monteverde, Donald, 1991, Radon in soil gas and
gamma-ray activity of rocks and soils at the Mulligan Quarry, Clinton, New Jersey, in
Gundersen, Linda C.S., and Richard B. Wanty, eds., Field studies of radon in rocks,
soils, and water: U.S. Geol. Survey Bulletin no. 1971, p. 65-75.
Klusman, R. W., and Jaacks, J, A,, 1987, Environmental influences upon mercury, radon, and
helium concentrations in soil gases at a site near Denver, Colorado: Journal of
Geochemical Exploration, v. 27, p. 259-280.
Kovach, E.M., 1945, Meteorological influences upon the radon content of soil gas: Transactions,
American Geophysical Union, v. 26, p. 241-248.
Kunz, C., Laymon, C,A., and Parker, C., 1989, Gravelly soils and indoor radon, in Osborne,
M.C., and Harrison, J., eds., Proceedings of the 1988 EPA Symposium on Radon and
Radon Reduction Technology, Volume 1: U.S. Environmental Protection Agency Report
EPA/60Q/9-89/006A, p. 5-75-5-86.
Muessig, K., and Bell, C., 1988,.Use of airborne radiometrie data to direct testing for elevated
indoor radon: Northeastern Environmental Science, v. 7, no. 1, p. 45-51.
Ronca-Battista, M., Moon, M., Bergsten, J., White, S.B., Holt, N., and Alexander, B., 1988,
Radon-222 concentrations in the United States—Results of sample surveys in five states:
Radiation Protection Dosimetry, v. 24, p. 307-312.
Rose, A.W., Washington, J.W., and Greeman, D.J., 1988, Variability of radon with depth and
season in a central Pennsylvania soil developed on limestone: Northeastern Environmental
Science, v. 7, p. 35-39.
Schery, S.D., Gaeddert, D.H., and Wilkening, M.H., 1984, Factors affecting exhalation of radon
from a gravelly sandy loam: Journal of Geophysical Research, v. 89, p. 7299-7309.
Schumann, R.R., and Owen, D.E., 1988, Relationships between geology, equivalent uranium
concentration, and radon in soil gas, Fairfax County, Virginia: U.S. Geological Survey
Open-File Report 88-18,28 p.
Schumann, R.R., and Gundersen, L.C.S., 1991, Regional differences in radon emanation
coefficients in soils: Geological Society of America Abstracts With Programs, v. 23,
no. 1, p. 125.
Schumann, R.R., Peake, R.T., Schmidt, K.M., and Owen, D.E., 1991, Correlations of soil-gas
and indoor radon with geology in glacially derived soils of the northern Great Plains, in
Proceedings of the 1990 International Symposium on Radon and Radon Reduction
Technology, Volume 2, Symposium Oral Papers: U.S. Environmental Protection Agency
report EPA/600/9-9l/026b, p. 6-23-6-36.
11-18 Reprinted from 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.S., eds., Geologic controls on radon: Geological Society of America
Special Paper 271, p. 65-72.
Sextro, R.G., Moed, B.A., Nazaroff, W.W., Revzan, K.L., and Nero, A.V., 1987,
Investigations of soil as a source of indoor radon, in Hopke, P.K., ed., Radon and its
decay products: American Chemical Society Symposium Series 331, p. 10-29.
Sterling, R., Meixel, G., Shen, L., Labs, K., and Bligh, T., 1985, Assessment of the energy
savings potential of building foundations research: Oak Ridge, Tenn., U.S. Department of
Energy Report ORNL/SUB/84-0024/1.
Smith, R.C., II, Reilly, M.A., Rose, A.W., Barnes, J.H., and Berfcheiser, S.W., Jr., 1987,
Radon: a profound case: Pennsylvania Geology, v. 18, p. 1-7.
Tanner, A.B., 1964, Radon migration in the ground: a review, in- Adams, J.A.S., and Lowder,
W.M., eds., The natural radiation environment: Chicago, El., University of Chicago
Press, p. 161-190.
Tanner, A.B., 1980, Radon migration in the ground: a supplementary review, in Gesell, T.F.,
and Lowder, W.M. (eds), Natural radiation environment ffl, Symposium proceedings,
Houston, Texas, v. 1, p. 5-56.
U.S. Department of Agriculture, 1987, Principal kinds of soils: Orders, suborders, and great
groups: U.S. Geological Survey, National Atlas of the United States of America, sheet
38077-BE-NA-07M-00, scale 1:7,500,000.
U.S. Department of Energy, 1976, National Uranium Resource Evaluation preliminary report,
prepared by the U.S. Energy Research and Development Administration, Grand Junction,
Colo.: GJO-11(76).
Wanty, Richard B., and Schoen, Robert, 1991, A review of the chemical processes affecting the
mobility of radionuclides in natural waters, with applications, in Gundersen, Linda C.S.,
and Richard B. Wanty, eds., Field studies of radon in rocks, soils, and water: U.S.
Geological Survey Bulletin no. 1971, p. 183-194.
Washington, J.W., and Rose, A.W., 1990, Regional and temporal relations of radon in soil gas to
soil temperature and moisture: Geophysical Research Letters, v. 17, p. 829-832.
White, S.B., Bergsten, J.W., Alexander, B.V., and Ronca-Battista, M., 1989, Multi-State
surveys of indoor 222Rn: Health Physics, v. 57, p. 891-896.
BE-19 Reprinted from USGS Open-File Report 93-292
-------
APPENDIX A
GEOLOGIC TIME SCALE
Subdivisions (and their symbols)
Eon or
Eonothem
Phanerozoie
Proterozoie
/m
Archean
(A)
Era or
Erathem
Cenozoie 2
(Cz!
Mesozoic2
(Mi)
"aleoioic
{P«
L.H
lrot»ro?oic {Zi
M.OdH
Pfoiwroioic m
£«.-ly
PfOt*f6?Oic CXS
Ut»
AfCh»»n fWt
MiOdlt
Areh*an IV!
t«ny
ArchMn (U!
Period, System,
Subperiod, Subsystem
Quaternary
(Q>
Neogene *
Subperiod or
Tertiary Subsystem (N)
CD Paieogene
Subpariod or
Subsystem {Pi)
Cretaceous
(K)
Jurassic
U)
Triassic
fS)
Permian
CP)
Pennsylvanian
Carboniferous (P)
Systems _,
'^) Mississippian
(M)
Devonian
(D)
Silurian
/Ci
Ordovician
i-».*-j.u/
M|ocene | . . ... ...
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
•io , (J*-J(3)
96 ,(95-97)
138 (135—141)
,", i ^U3 UUV-illSI
Upper |
Middle
Lower
Upper
Lower
Upper
Middle . 1
Lower
Upper
Lower
Uooer
Middle
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Middle
Lower
None defined
None defined
None defined
None defined
None defined
None defined
pr»-Arch«an (pA)
-•— **fifi fSfifi—'SfiflU
-..__ K7O '
— — "anAri
-------
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 pieocurie (10"^ curies) is equal to about 2.2 disintegrations
of radon atoms per minute. A liter is about 1.06 quarts. The average concentration of radon in
U.S. homes measured to date is between 1 and 2 pCi/L.
Bq/m3 (Becquerels per cubic meter)- a metric unit of radioactivity used to describe radon
concentrations in a volume of air. One beequerel is equal to one radioactive disintegration per
second. One pCi/L is equal to 37 Bq/rrA
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, filling it 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.
II-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.5 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 (COa) compounds of calcium,
magnesium, or iron, e.g. limestone and dolomite.
carbonaceous Said of a rock or sediment that is rich in carbon, is coaly, or contains organic
matter.
charcoal canister A passive radon measurement device consisting of a small container of
granulated activated charcoal that is designed to adsorb radon. Useful for short duration (2-7 days)
measurements only. May be referred to as a "screening" test
chert A hard, extremely dense sedimentary rock consisting dominantly of interlocking crystals of
quartz. Crystals are not visible to the naked eye, giving the rock a milky, dull luster. It may be
white or gray but is commonly colored red, black, yellow, blue, pink, brown, or green.
clastic pertaining to a rock or sediment composed of fragments that are derived from preexisting
rocks or minerals. The most common clastic sedimentary rocks are sandstone and shale.
clay A rock containing clay mineral fragments or material of any composition having a diameter
less than 1/256 mm. •
clay mineral One of a complex and loosely defined group of finely crystalline minerals made up
of water, silicate and aluminum (and a wide variety of other elements). They are formed chiefly by
alteration or weathering of primary silicate minerals. Certain clay minerals are noted for their small
size and ability to absorb substantial amounts of water, causing them to swell. The change in size
that occurs as these clays change between dry and wet is referred to as their "shrink-swell"
potential.
concretion A hard, compact mass of mineral matter, normally subspherical but commonly
irregular in shape; formed by precipitation from a water solution about a nucleus or center, such as
a leaf, shell, bone, or fossil, within a sedimentary or fractured rock.
conglomerate A coarse-grained, clastic sedimentary rock composed of rock and mineral
fragments larger than 2 mm, set in a finer-grained matrix of clastic material.
cuesta A hill or ridge with a gentle slope on one side and a steep slope on the other. The
formation of a cuesta is controlled by the different weathering properties and the structural dip of
the rocks forming the hill or ridge.
daughter product A nuclide formed by the disintegration of a radioactive precursor or "parent"
atom.
H-22 Reprinted from USGS Open-File Report 93-292
-------
delta, deltaic Referring to a low, flat, alluvial tract of land having a triangular or fan shape,
located at or near the mouth of a river. It results from the accumulation of sediment deposited by a
river at the point at which the river loses its ability to transport the sediment, commonly where a
river meets a larger body of water such as a lake or ocean.
dike A tabular igneous intrusion of rock, younger than the surrounding rock, that commonly cuts
across the bedding or foliation of the rock it intrudes.
diorite A plutonic igneous rock that is medium in color and contains visible dark minerals that
make up less than 50% of the rock. It also contains abundant sodium plagioclase and minor
quartz.
dolomite A carbonate sedimentary rock of which more than'50% consists of the mineral dolomite
(CaMg(CO3)2), and is commonly white, gray, brown, yellow, or pinkish in color.
drainage The manner in which the waters of an area pass, flow off of, or flow into the soil.
Also refers to the water features of an area, such as lakes and rivers, that drain it.
eolian Pertaining to sediments deposited by the wind.
esker A long, narrow, steep-sided ridge composed of irregular beds of sand and gravel deposited
by streams beneath a glacier and left behind when the ice melted.
evapotranspiration Loss of water from a land area by evaporation from the soil and
transpiration from plants.
extrusive Said of igneous rocks that have been erupted onto the surface of the Earth.
fault A fracture or zone of fractures in rock or sediment along which there has been movement.
fluvial, fluvial deposit Pertaining to sediment that has been deposited by a river or stream.
foliation A linear feature in a rock defined by both mineralogic and structural characteristics. It
may be formed during deformation or metamorphism.
formation A mappable body of rock having similar characteristics.
glacial deposit Any sediment transported and deposited by a glacier or processes associated
with glaciers, such as glaciofluvial sediments deposited by streams flowing from melting glaciers.
gneiss A rock formed by metamorphism 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 feldspar-bearing igneous plutonic
rock. Technically, granites have between 10 and 50% quartz, and alkali feldspar comprises at least
65% of the total feldspar.
gravel An unconsolidated, natural accumulation of rock fragments consisting predominantly of
particles greater than 2 mm in size.
heavy minerals Mineral grains in sediment or sedimentary rock having higher than average
specific gravity. May form layers and lenses because of wind or water sorting by weight and size
11-23 Reprinted from USGS Open-File Report 93-292
-------
and may be referred to as a "placer deposit" Some heavy minerals are magnetite, garnet, zircon,
monazite, and xenotime.
igneous Said of a rock or mineral that solidified from molten or partly molten rock material. It is
one of the three main classes into which rocks are divided, the others being sedimentary and
metamorphic.
intermontane A term that refers to an area between two mountains or mountain ranges.
intrusion, intrusive The processes of emplacement or injection of molten rock into pre-existing
rock. Also refers to the rock formed by intrusive processes, such as an "intrusive igneous rock".
kame A low mound, knob, hummock, or short irregular ridge formed by a glacial stream at the
margin of a melting glacier; composed of bedded sand and gravel.
karst terrain A type of topography that is formed on limestone, gypsurn 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
lithology The description of rocks in hand specimen and in outcrop on the basis of color,
composition, and grain size.
loam A permeable soil composed of a mixture of relatively equal parts clay, silt, and sand, and
usually containing some organic matter.
loess A fine-grained eolian deposit composed of silt-sized particles generally thought to have
been deposited from windblown dust of Pleistocene age.
mafic Term describing an igneous rock containing more than 50% dark-colored minerals.
marine Term describing sediments deposited in the ocean, or precipitated from ocean waters.
metamorphic Any rock derived from pre-existing rocks by mineralogical, chemical, or structural,
changes in response to changes in temperature, pressure, stress, and the chemical environment.
Phyllite, schist, amphibolite, and gneiss are metamorphic rocks.
moraine A mound, ridge, or other distinct accumulation of unsorted, unbedded glacial material,
predominantly till, deposited by the action of glacial ice.
outcrop That part of a geologic formation or structure that appears at the surface of the Earth, as
in "rock outcrop".
percolation test A term used in engineering for a test to determine the water permeability of a
soil. A hole is dug and filled with water and the rate of water level decline is measured.
permeability The capacity of a rock, sediment, or soil to transmit liquid or gas.
phosphate, phosphatic, phosphorite Any rock or sediment containing a significant amount
of phosphate minerals, i.e., minerals containing PO4.
11-24 Reprinted from USGS Open-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.
nlacer deposit See heavy minerals
residual Formed by weathering of a material in place,
residuum Deposit of residual material.
rhyolite An extrusive igneous rock of volcanic origin, compositionally equivalent to granite.
sandstone A clastic sedimentary rock composed of sand-sized rock and mineral material that is
more or less firmly cemented. Sand particles range from 1/16 to 2 mm in size,
schist A strongly foliated crystalline rock, formed by metamorphism, that can be readily split into
thin flakes or slabs. Contains mica; minerals are typically aligned.
screening level Result of an indoor radon test taken with a charcoal canister or similar device,
for a short period of time, usually less than seven days. May indicate the potential for an indoor
radon problem but does not indicate annual exposure to radon.
sediment Deposits of rock and mineral particles or fragments originating from material that is
transported by air, water or ice, or that accumulate by natural chemical precipitation or secretion of
organisms.
semiarid Refers to a climate that has slightly more precipitation than an arid climate.
shale A fine-grained sedimentary rock formed from solidification (Miifieation) 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-Ike cavity formed by dissolution of rock.
stratigraphy The study of rock strata; also refers to the succession of rocks of a particular area.
surficial materials Unconsolidated glacial, wind-, or waterborne deposits occurring on the
earth's surface.
tablelands General term for a broad, elevated region with a nearly level surface of considerable
extent.
II-25 Reprinted from USGS Open-File Report 93-292
-------
terrace gravel Gravel-sized material that caps ridges and terraces, left behind by a stream as it
cuts down to a lower level.
terrain A tract or region of the Earth's surface considered as a physical feature or an ecological
environment.
till Unsorted, generally unconsolidated and unbedded rock and mineral material deposited directly
adjacent to and underneath a glacier, without reworking by meltwater. Size of grains varies greatly
from clay to boulders.
uraniferous Containing uranium, usually more than 2 ppm.
vendor data Used in this report to refer to indoor radon data collected and measured by
commercial vendors of radon measurement devices and/or services.
volcanic Pertaining to the activities, structures, and extrusive rock types of a volcano.
water table The surface forming the boundary between the zone of saturation and the zone of
aeration; the top surface of a body of unconfined groundwater in rock or soil.
weathering The destructive process by which earth and rock materials, on exposure to
atmospheric elements, are changed in color, texture, composition, firmness, or form with little or
no transport of the material.
11-26 Reprinted from USGS Open-FUe Report 93-292
-------
APPENDIX C
EPA REGIONAL OFFICES
EPA Regional Offices
State
EPA Region
EPA Region 1
JFK Federal Building
Boston, MA 02203
(61?) 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 (SAR26)
77 West Jackson Blvd.
Chicago, IL 60604-3507
(312) 886-6175
EPA Region 6 (6T-AS)
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7224
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7604
EPA Region 8
(8HWM-RP)
999 18th Street
One Denver Place, Suite 1300
Denver, CO 80202-2413
(303) 293-1713
EPA Region 9 (A-3)
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1048
EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
(202) 442-7660
Alabama 4
Alaska 10
Arizona.... 9
Arkansas 6
California .9
Colorado 8
Connecticut 1
Delaware... 3
District of Columbia 3
Florida 4
Georgia 4
Hawaii 9
Idaho 10
Illinois 5
Indiana 5
Iowa 7
Kansas > 7
Kentucky 4
Louisiana 6
Maine 1
Maryland 3
Massachusetts ...1
Michigan 5
Minnesota 5
Mississippi 4
Missouri 7
Montana 8
Nebraska .....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 6
Utah 8
Vermont 1
Virginia 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
Alaslca
Arkansas
California
Colorado
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
John Stewart
Arizona Radiation Regulatory Agency
4814 South 40th St.
Phoenix, AZ 85040
(602) 255-4845
Lee Gershner
Division of Radiation Control
Department of Health
4815 Markham Street, Slot 30
Little Rock, AR 72205-3867
(501) 661-2301
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
Linda Martin
Department of Health
4210 East 11th 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 061064474
(203) 566-3122
Delaware Marai G. Rejai
Office of Radiation Control
Division of Public Health
P.O. Box 637
Dover, DE 19903
(302) 736-3028
1-800-554-4636 In State
District Robert Davis
of Columbia DC Department of Consumer and
Regulatory Affairs
614 H Street NW
Room 1014
Washington, DC 20001
(202) 727-71068
Florida N. Michael GiEey
Office of Radiation Control
Department of Health and
Rehabilitative Services
1317 Winewood Boulevard
Tallahassee, EL 32399-0700
(904)488-1525
1-800-543-8279 in state
Georgia 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
H-28
Reprinted from USGS Open-File Report 93-292
-------
Mate
Illinois
Iowa
Kansas
Kentucky
PatMcGavarn
Office of Environmental Health
450 West State Street
Boise, ID 83720
(208) 334-6584
1-800-445-8647 in state
Richard Allen
Illinois Department of Nuclear Safety
1301 Outer Park Drive
Springfield, EL 62704
(217) 524-5614
1-800-325-1245 in state
Lorand Magyar
Radiological Health Section
Indiana State Department of Health
1330 West Michigan Street
P.O. Box 1964
Indianapolis, IN 46206
(317)633-8563
1-800-272-9723 In State
Donald A. Plater
Bureau of Radiological Health
Iowa Department of Public Health
Lucas State Office Building
Des Moines, IA 50319-0075
(515)281-3478
1-800-383-5992 In State
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 Sue Henderehott
Division of Radiological Health
Bureau of Environmental and
Occupational Health
3423 North Logan S treet
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
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, MM 87503
(505) 827^300
New York William J. Condon
Bureau of Environmental Radiation
Protection ,
New York State Health Department
Two University Place
Albany, NY 12202
(518)458-6495
1-800-458-1158 in state
North Carolina Dr. Felix Pong
Radiation Protection Division
Department of Environmental Health
and Natural Resources
701 Barbour Drive
Raleigh, NC 27603-2008
(919) 571-4141
1-800-662-7301 (recorded info x4196)
North Dakota Arlen Jacobson
North Dakota Department of Health
1200 Missouri Avenue, Room 304
P.O. Box 5520
Bismarck, ND 58502-5520
(701) 221-5188
Mo 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
II-30
Reprinted from USGS Open-File Report 93-292
-------
Oklahoma
Oregon
Pennsylvania
Puerto Rico
Rhode Island
Soulh Carolina
Gene Smith
Radiation Protection Division
Oklahoma State Department of
Health
P.O. Box 53551
Oklahoma City, OK 73152
(405) 271-5221
George Toombs
Department of Human Resources
Health Division
1400 SW 5th Avenue
Portland, OR 97201
(503) 731-4014
Michael Pyles
Pennsylvania Department of
Environmental Resources
Bureau of Radiation Protection
P.O. Box 2063
Harrisburg, PA 17120
(717) 783-3594
1-800-23-RADON In State
David Saldana
Radiological Health Division
G.P.O. Call Box 70184
Rio Piedras, Puerto Rico 00936
(809) 767-3563
Edmund Arcand
Division of Occupational Health and
Radiation
Department of Health
205 Cannon Building
Davis Street
Providence, RI02908
(401) 277-2438
Bureau of Radiological Health
Department of Health and
Environmental Control
2600 Bull Street
Columbia, SC 29201
(803)734-4631
1-800-768-0362
South Dakota Mike Pochop
Division of Environment Regulation
Department of Water and Natural
Resources
Joe Foss Building, Room 217
523 E. Capitol
Pierre, SD 57501-3181
(605)773-3351
Tennessee Susie Shimek
Division of Air Pollution Control
Bureau of the Environment
Department of Environment and
Conservation
Customs House, 701 Broadway
Nashville, TN 37219-5403
(615) 532-0733
1-800-232-1139 in state
Texas Gary Smith
Bureau of Radiation Control
Texas Department of Health
1100 West 49th Street
Austin, TX 78756-3189
(512) 834-6688
Utah John Hultquist
Bureau of Radiation Control
Utah State Department of Health
288 North, 1460 West
P.O. Box 16690
Salt Lake City, UT 84116-0690
(801) 536-4250
Paul demons
Occupational and Radiological Health
Division
Vermont Department of Health
10 Baldwin Street
Montpelier, VT 05602
(802) 828-2886
1-800-640-0601 in state
Virgin Islands Contact the U.S. Environmental
Protection Agency, Region II
in New York
(212)264-4110
n-3i
Reprinted from USGS Open-File Report 93-292
-------
Virginia Shelly Ottenbrite
Bureau of Radiological Health
Department of Health
109 Governor Street
Richmond, VA 23219
(804) 786-5932
1-800-468-0138 in state
Washington Kate Coleman
Department of Health
Office of Radiation Protection
Airdustrial Building 5, LE-13
Olympia, WA 98504
(206) 753-4518
1-800-323-9727 In State
West Virginia BeattieL.DeBord
Industrial Hygiene Division
West Virginia Department of Health
151 llth Avenue
South Charleston, WV 25303
(304) 558-3526
1-800-922-1255 In State
Wisconsin . Conrad Weiffenbach
Radiation Protection Section
Division of Health
Department of Health and Social
Services
P.O. Box 309
Madison, WI53701-0309
(608) 267-4796
1-800-798-9050 in state
Wyoming Janet Hough
Wyoming Department of Health and
Social Services
Hathway Building, 4th Floor
Cheyenne, WY 82002-0710
(307) 777-6015
1-800-458-5847 in state
H-32 Reprinted from USGS Open-File Report 93-292
-------
STATE GEOLOGICAL SURVEYS
May, 1993
Alabama Emest A. Mancini
Geological Survey of Alabama
P.O. Box 0
420 Hackberry Lane
Tuscaloosa, AL 35486-9780
(205) 349-2852
Alaska Thomas E. Smith
Alaska Division of Geological &
Geophysical Surveys
794 University Ave., Suite 200
Fairbanks, AK 99709-3645
(907)479-7147
Arizona Larry D. Fellows
Arizona Geological Survey
845 North Park Ave., Suite 100
Tucson, AZ 85719
(602) 882-4795
Arkansas Norman F. Williams
Arkansas Geological Commission
Vardelle Parham Geology Center
3815 West Roosevelt Rd.
Little Rock, AR 72204
(501) 324-9165
California James F. Davis
California Division of Mines &
Geology
801 K Street, MS 12-30
Sacramento, CA 95814-3531
(916)445-1923
Colorado Pat Rogers (Acting)
Colorado Geological Survey
1313 Sherman St., Rm 715
Denver, CO 80203
(303)866-2611
Connecticut Richard C. Hyde
Connecticut Geological & Natural
History Survey
165 Capitol Ave., Rm. 553
Hartford, CT 06106
(203) 566-3540
Delaware Robert R. Jordan
Delaware Geological Survey
University of Delaware
101 Penny Hall
Newark, DE 19716-7501
(302) 831-2833
Florida Walter Schmidt
Florida Geological Survey
903 W. Tennessee S.
Tallahassee, FL 32304-7700
(904)488-4191
Georgia 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. Leighton
Illinois State Geological Survey
Natural Resources Building
615EastPeabodyDr.
Champaign, IL 61820
(217) 333-4747
Indiana Norman C. Hester
Indiana Geological Survey
611 North Walnut Grove
Bloomington, IN 47405
(812) 855-9350
Iowa Donald L.Koch
Iowa Department of Natural Resources
Geological Survey Bureau
109 Trowbridge Hall
Iowa City, IA 52242-1319
(319) 335-1575
Kansas Lee C.Gerhard
Kansas Geological Survey
1930 Constant Ave., West Campus
University of Kansas
Lawrence, KS 66047
(913) 864-3965
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
Maine Walter A. Anderson
Maine Geological Survey "
Department of Conservation
State House, Station 22
Augusta, ME 04333
(207)289-2801
Maryland Emery T. Cleaves
Maryland Geological Survey
2300 St. Paul Street
Baltimore, MD 21218-5210
(410) 554-5500
Massachusetts Joseph A. Sinnott
Massachusetts Office of
Environmental Affairs
100 Cambridge St, Room 2000
Boston, MA 02202
(617) 727-9800
Michigan R. Thomas Segall
Michigan Geological Survey Division
Box 30256
Lansing, MI 48909
(517)334-6923
Minnesota Priscilla C. Grew
Minnesota Geological Survey
2642 University Aye.
St. Paul, MN 55114-1057
(612) 627-4780
Mississippi S. Cragin Knox
Mississippi Office of Geology
P.O. Box 20307
Jackson, MS 39289-1307
(601) 961-5500
Missouri James H. Williams
Missouri Division of Geology &
Land Survey
111 Fairgrounds Road
P.O. Box 250
Rolla, MO 65401
(314)368-2100
Montana Edward T. Ruppel
Montana Bureau of Mines & Geology
Montana College of Mineral Science
and Technology, Main Hall
Butte, MT 59701
(406)496-4180
Nebraska Perry B. Wigley
Nebraska Conservation & Survey
Division
113 Nebraska Hall
University of Nebraska
Lincoln, NE 68588-0517
(402)472-2410
NgyMa Jonathan G. Price
Nevada Bureau of Mines & Geology
Stop 178
University of Nevada-Reno
Reno, NY 89557-0088
(702) 784-6691
New Hampshire Eugene L. Boudette
Dept. of Environmental Services
117 James Hall
University of New Hampshire
Durham, NH 03824-3589
(603)862-3160
New Jersey Haig F. Kasabach
New Jersey Geological Survey
P.O. Box 427
Trenton, NJ 08625
(609)292-1185
New Mexico Charles E. Chapin
New Mexico Bureau of Mines &
Mineral Resources
Campus Station
Socorro.NM 87801
(505) 835-5420
New York Robert H. Fakundmy
New York State Geological Survey
3136 Cultural Education Center
Empire State Plaza
Albany, NY 12230
(518) 474-5816
11-34
Reprinted from USGS Open-File Report 93-292
-------
j^orth...Carolina Charles H. Gardner
North Carolina Geological Survey
P.O. Box 27687
Raleigh, NC 27611-7687
(919)733-3833
MonhPakoia John P. Bluemle
North Dakota Geological Survey
600 East Blvd.
Bismarck, ND 58505-0840
(701)224-4109
Qhift Thomas M. Berg
Ohio Dept. of Natural Resources
Division of Geological Survey
4383 Fountain Square Drive
Columbus, OH 43224-1362
(614) 265-6576
Oklahoma Charles J. Mankin
Oklahoma Geological Survey
Room N-131, Energy Center
100E.Boyd
Norman, OK 73019-0628
(405)325-3031
Donald A. Hull
Dept. of Geology & Mineral Indust.
Suite 965
800 NE Oregon St. #28
Portland, OR 97232-2162
(503) 731-4600
Pennsylvania Donald M. HosMns
Dept. of Environmental Resources
Bureau of Topographic & Geologic
Survey
P.O. Box 2357
Harrisburg, PA 17105-2357
(717) 787-2169
Ramdn M. Alonso
Puerto Rico Geological Survey
Division
Box 5887
Puerta de Tierra Station
San Juan, P.R. 00906
(809) 722-2526
RhodcTsland J. Allan Cain
Department of Geology
University of Rhode Island
3 15 Green Hall
Kingston, RI 02881
(401) 792-2265
South Carolina Alan-Jon W. Zupan (Acting)
South Carolina Geological Survey
5 Geology Road
Columbia, SC 29210-9998
(803) 737-9440
South-Dakota C.M. Christensen (Acting)
South Dakota Geological Survey
Science Center
University of South Dakota
Vermillion, SD 57069-2390
(605) 677-5227
Tennessee Edward T.Luther
Tennessee Division of Geology
13th Floor, L & C Tower
401 Church Street
Nashville, TN 37243-0445
(615) 532-1500
Texas William L. Fisher
Texas Bureau of Economic Geology
University of Texas
University Station, Box "K
Austin, TX 78713-7508
(512) 471-7721
Utah. M. Lee Allison
Utah Geological & Mineral Survey
2363 S. Foothill Dr.
Salt Lake City, UT 84109-1491
(801)467-7970
2D1 Diane L. Conrad
Vermont Division of Geology and
Mineral Resources
103 South Main St.
Waterbury.VT 05671
(802)244-5164
Stanley S, Johnson
Virginia Division of Mineral
Resources
P.O. Box 3667
Charlottesville, VA 22903
(804) 293-5121
Washington Raymond Lasmanis
Washington Division of Geology &
Earth Resources
Department of Natural Resources
P.O. Box 47007
Olympia, Washington 98504-7007
(206) 902-1450
11-35
Reprinted from USGS Open-File Report 93-292
-------
West Virginia Larry 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 Miifcral 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
H-36
Reprinted from USGS Open-File Report 93-292
-------
EPA REGION 10 GEOLOGIC RADON POTENTIAL SUMMARY
by
James K, Otton, Kendall A. Dickinson, Douglass E. Owen, and Sandra L. Szarzi
U.S. Geological Survey
EPA Region 10 includes the states of Alaska, Idaho, Oregon, and Washington. For each
state, geologic radon potential areas were delineated and ranked on the basis of geologic, soils,
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 pG/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 to this volume. More detailed information on the geology and radon potential of each
state in Region 10 is given in the individual state chapters. The individual chapters describing the
geology and radon potential of the states in EPA Region 10, though much more detailed than this
summary, still are generalized assessments and there is no substitute for having a home tested.
Within any radon potential area homes with indoor radon levels both above and below the
predicted average likely will be found.
The geology and radon potential of the Pacific Northwest (fig. 1) and Alaska (fig. 2) is
diverse; thus the two areas will be considered separately. The Pacific Northwest includes eight
distinct major radon geologic provinces: the Coastal Range-Klamath Mountains, the Puget
Lowland-Willamette River Valley, the Cascade Range, the Columbia Plateau-High Lava Plains-
Blue Mountains, the northern Rocky Mountains, the Snake River plain, the middle Rocky
Mountains, and the northern Basin and Range-Owyhee Plateau (fig. 1). Maps showing indoor
radon averages for counties in the Pacific Northwest and boroughs in Alaska are shown in figures
3a and 3b. Averages range from less than 1.0 pCi/L to 14.9 pCi/L. Details of the indoor radon
studies are described in the individual state chapters.
PACIFIC NORTHWEST
Coastal Range-Klamath Mountains
The Coastal Range Province (1, fig, 1) extends from the Olympic Peninsula of Washington
south to the coastal parts of the Klamath Mountains in southwestern Oregon. In Washington, the
Coast Ranges are underlain principally by Cretaceous and Tertiary continental and marine
sedimentary rocks and pre-Miocene volcanic rocks. In Oregon, the northern part of the Coastal
Ranges is underlain principally by marine sedimentary rocks and mafic volcanic rocks of Tertiary
age. The southern part of the Coast Range is underlain by Tertiary estuarine and marine
sedimentary rocks, much of them feldspathic and micaceous. The Klamath Mountains (2, fig. 1)
are dominated by Triassic to Jurassic metamorphic, volcanic, and sedimentary rocks, with some
Cretaceous intrusive rocks. These metamorphic and volcanic rocks are largely of mafic
composition. Large masses of ultramafic rocks occur throughout the Klamath area. Sand dunes
and marine terraces are common along the coastal areas of this province.
The radon potential of the Coastal Range Province is low overall. Most of the area has
high rainfall and, as a consequence, high soil moisture. Uranium in the soils is typically low,
although soils of the Oregon part of the Coast Ranges tend to be higher in uranium than do soils of
HI-1 Reprinted from USGS Open-File Report 93-292-J
-------
Figure 1- Radon geologic provinces of the Pacific Northwest (generalized from state
chapters included in this report). 1- Coast Ranges; 2- Klamath Mountains; 3- Puget
Lowland; 4- Willamette River Valley; 5- Cascade Range; 6- Northern Rocky
Mountains; 7- Columbia Plateau; 8- Blue Mountains; 9- High Lava Plains; 10-
Basin and Range; 11- Owyhee Plateau; 12- Snake River Plain; and 13- Middle
Rocky Mountains.
-------
the Washington part. A few communities along the river valleys near the coast of Oregon may
have locally elevated indoor radon where highly permeable, excessively well-drained soils occur
on river alluvium with a modestly elevated uranium content. The northeastern corner of the
Olympic. Peninsula has lower rainfall and lower soil rr. nsture than dees the rest of 'he Coastal
Range Province. Here, highly permeable, excessively well-drained soils may cause locally
elevated indoor radon levels.
Puget Lowland-Willamette River Valley
The Puget Lowland (3, fig. 1) is underlain almost entirely by glacial deposits and Holocene
alluvium. Most of the glacial and alluvial material of the Puget Lowland is derived from the
Cascades to the east, and from the mountains of the Olympic peninsula to the west. River alluvium
and river terraces underlie most of the Willamette River valley (4, fig. 1). However, many of the
hills that rise above the plains of the Lowland are underlain by Tertiary basalts and marine
sediments.
The Puget Lowland overall has very low radon potential because of low uranium content of
soils and because high rainfall produces high soil moisture, which slows radon movement.
Houses in most townships in the Bonneville Power Administration study from Tacoma northward
average less than 1 pCi/L radon. Structures built on locally very steep or well-drained soils,
especially on the east side of the lowland area, may be among the few likely to have elevated
indoor radon levels. The geologic radon potential is moderate only in the southern part of the
Puget Lowland, south of Tacoma, where excessively drained soils and somewhat elevated uranium
in soils occur.
The Willamette River Valley has moderate radon potential overall. Much of the area has
somewhat elevated uranium in soils, and many areas have excessively drained soils and soils with
high emanating power. Studies by the Oregon Department of Health and the Bonneville Power
Administration indicate that houses in many counties and townships in the valley average between
2 and 4 pCi/L radon.
Cascade Range
The Cascade Range (5, fig. 1) can be divided into two geologic terranes: a northern terrane
composed principally of Mesozoic metamorphic rocks intruded by Mesozoic and Tertiary granitic
rocks, and a southern terrane composed of Tertiary and Holocene volcanic rocks. The Holocene
volcanic centers are responsible for locally thick volcanic-ash deposits east of the Cascade
Mountains. Within the southern terrane, the western Cascades are dominated by Tertiary andesite
flows, basalt flows, and pyroclastic rocks, whereas the eastern Cascades have many recently active
volcanoes and are underlain by late Tertiary to Quaternary basaltic and andesitic volcanic rocks.
Overall, the sparsely populated Cascade Range Province has low radon potential because of
the low uranium and high moisture contents of the soils. Areas that are exceptions to this include
the Columbia River Gorge, where highly permeable, excessively well drained soils underlie many
of the communities, and thus the radon potential is moderate. Much of the alluvium in the Gorge is
also derived from the upper Columbia River valley, where the uranium content of the geologic
materials is higher than the rocks within the Cascade Mountain Province itself. Studies by the
Oregon Department of Health and the Bonneville Power Administration show that indoor radon
levels in homes in population centers along the Columbia River average 2 to 4 pCi/L.
IH-3 Reprinted from USGS Open-File Report 93-292-J
-------
Columbia Plateau, High Lava Plains, and Blue Mountains
The Columbia Plateau (7, fig. 1) is underlain principally by Miocene basaltic and andesitic
volcanic rocks, tuffaceous sedimentary rocks and tuff. An extensive veneer of Pleistocene
glaciofluvial outwash, eolian, and lacustrine deposits covers these volcanic rocks. The High Lava
Plains (9, fig. 1) are underlain by Miocene basaltic and volcanic rocks like those of the Columbia
Plateau without the veneer of younger sedimentary rocks. The Blue Mountains (8, fig. 1) have
similar basaltic and andesitic rocks and also include significant outcrop areas of Triassic and
Jurassic sedimentary and volcanic rocks, weakly metamorphosed in many areas, and younger
intrusive rocks.
The Columbia Plateau, with its areas of extensive Pleistocene glacio-fluvial outwash,
eolian, and lacustrine deposits, contains locally highly permeable soils, soils with high emanating
coefficients, and elevated soil uranium levels. This area has generally moderate radon potential.
Although the Blue Mountains have relatively low uranium in soils, average indoor radon levels are
in the 2-4 pCi/L range, probably because most population centers occur in alluviated valleys with
highly permeable soils. This area has moderate radon potential. In contrast, the High Lava Plains,
with much lower uranium in soils and only local areas of highly permeable soils, have low overall
radon potential.
Northern Rocky Mountains
The Northern Rocky Mountains (6, fig. 1) comprise the mountainous terrane of the
northeast and north-central parts of Washington and northern and central Idaho. This area is
underlain by Precambrian and Paleozoic sedimentary rocks, and by Mesozoic metamorphic rocks;
all are intruded by Mesozoic and Tertiary granitic rocks. The largest intrusive mass, the Idaho
Batholith, is a complex of granitic rock units that range from diorite to granite. Highly
uraniferous, Late Cretaceous to early Tertiary granites crop out throughout the Northern Rocky
Mountains. An extensive, though dissected, veneer of Tertiary volcanic rocks crops out over
much of the central Idaho portion of the Northern Rocky Mountains.
The Northern Rocky Mountains Province has high radon potential. Excessively well
drained glaciofluvial outwash or coarse gravels in alluvial fans underlie many of the valleys
throughout the area. The granitic material in much of the outwash contains moderate to locally
high concentrations of uranium. Areas where uranium occurrences are found, such as in the
granitic and metamorphic terranes in the mountains north of Spokane, may have structures with
extreme levels of indoor radon. Buildings in most of the alluvial valleys in Washington and Idaho
north, northwest, and east of Spokane may be expected to have average indoor radon screening
measurements above 4 pCi/L.
Snake River Plain
The Snake River Plain (12, fig. 1) forms an arcuate depression in southern Idaho that is
underlain principally by basaltic volcanic rocks of generally low eU (1 ppm or less). However,
alluvium from neighboring mountains and silicic tuffaceous sedimentary rocks covers much of the
upper Snake River Valley near Wyoming and the western end of the Snake River Plain near Boise
and south of Mountain Home. These materials have eU values that range from 1.5-5.0 ppm.
Those areas underlain by basalt have low to locally moderate radon potential. However, those
areas where basalt is overlain by silicic tuffaceous sedimentary rocks and alluvium along the Snake
River Valley have high overall radon potential. Most populous areas are in the latter category.
III-4 Reprinted from USGS Open-File Report 93-292-J
-------
Middle Rocky Mountains
The Middle Rocky Mountains Province (13, fig. 1) forms a strip along the border between
Wyoming and Idaho and comprises two areas. The northern area is the Yellowstone Plateau, a
high-standing plateau area underlain mostly by rhyclites containing moderate amounts of uranium.
To the south are complexly faulted and folded mountain ranges of Paleozoic and Mesozoic
sedimentary rocks, including uranium-bearing phosphatic rocks.
The high average uranium content of the volcanic rocks of the Yellowstone area and the
coarse aUuvium in the valleys of the southern mountain areas suggest that this province has high
geologic radon potential.
Basin and Range Province, Owyhee Plateau
The very sparsely populated northern part of the Basin and Range Province (10, fig. 1) lies
along the southern and southeastern edge of Region 10. It is composed of teetonically extended
areas where linear mountain ranges alternate with valleys and less extended plateau areas. It is
underlain mainly by basaltic to andesitic volcanic rocks, silicic ash-flow tuffs, including some
welded tuffs, and sediments derived from these units. Several playa basins occupy the centers of
the valleys. The Owyhee Plateau of southwestern Idaho (11, fig. 1) consists of Tertiary and
Quaternary basalt, andesite, and rhyolite, and sediments derived from these units. A few caldera
complexes, some of them with associated uranium mineralization, occur within the Owyhee
Plateau. Some mountain ranges in the eastern part of this province are underlain mainly by
Paleozoic and Mesozoic sedimentary rocks. Based on the high aeroradiometric signature of most
of the exposed rock units and the presence of many highly permeable soil units, the radon potential
of this area is generally high .
ALASKA
Alaska can be divided from north to south into eight geologic radon provinces: the Arctic
Coastal Plain, the Arctic Foothills, the Arctic Mountains, Central Alaska, the Northern Plateaus (a
subprovince of Central Alaska), the Alaska-Aleutian Ranges, the Coastal Trough, and the Border
Ranges Provinces (fig. 2).
Arctic Coastal Plain
The Arctic Coastal Plain Province (North Slope, 1, fig. 2) consists primarily of Quaternary
sediment, most of of which is composed of alluvium, glacial debris, and eplian sand and silt. A
belt of Tertiary sedimentary rocks along the eastern third of the area separates the coastal plains
from the foothills to the south.
This area has low radon potential. No significant uranium occurrences are known in this
area, and the number of gamma-ray anomalies is low when compared with other parts of Alaska.
The coastal plain is unglaciated and contains tundra soils and permafrost These soils probably
have low gas transmissivity because of water or ice saturation.
Arctic Foothills
The Arctic Foothills Province (2, fig. 2) is largely composed of marine and nonmarine
Cretaceous sandstone and shale. The Cretaceous beds are folded into west-trending anticlines and
synclines. Part of the area was covered by glaciers.
ffl-5 Reprinted from USGS Open-File Report 93-292-J
-------
Figure 2- Physiographic provinces of Alaska (from the state chapter included in this
report). 1- Arctic Coastal Plain; 2- Arctic Foothills; 3- Arctic Mountains; 4- Central
Province, 4a- Seward Peninsula, 4b- Bering Shelf, 4c- Ahklun Mountains, 4d-
Western Alaska, 4e- Northern Plateaus; 5- Alaska-Aleutian Province; 6- Coastal
Trough; 7- Pacific Border Ranges; and 8- Coast Mountains.
-------
This area has low radon potential overall. Hie Cretaceous sandstone and shale that makes
up the foothills could produce relatively large amounts of radon but no evidence that they do is on
hand. The area contains no known uranium occurrences or deposits, and the part of the area where
airborne gamma-ray measurements were made shows a low number of anomalies. The tundra
soils have permafrost and apparent low gas transmissivity.
Arctic Mountains
The Arctic Mountains Province (3, fig. 2) is composed largely of upper Precambrian and
Paleozoic marine sedimentary rocks. They are cut by west-trending thrust faults with upthrown
sides to the south.
This area has moderate radon potential. The Precambrian and Paleozoic marine
sedimentary rocks that make up the Arctic Mountains probably are not producers of high levels of
radon as there is little or no phosphate rock or black shale in these sequences. There are no known
significant uranium occurrences in this area. However, stream sediments in this province contain
moderately high levels of uraniferous resistate minerals. The area has been glaciated, but much of
the terraneis bare rock without surficial glacial material. The soils are classified as rock land,
which includes glacial ice.
Central Province (exclusive of the Northern Plateaus subprovince)
The Central Province, an area of plains, plateaus, and rounded mountains, is geologically
complex. The Central Province is divided into five subprovinces: Western Alaska, Seward
Peninsula, Aklun Mountains, the Bering Shelf (4a-d, fig. 2) and the Northern Plateaus (5, fig. 2).
The Northern Plateaus are considered separately below.
Western Alaska is underlain mostly by Cretaceous marine sedimentary rocks and lower
Paleozoic sedimentary and metamorpMc rocks. A large area of Cretaceous and Tertiary volcanic
rock is present in the western part of this subprovince. The Seward Peninsula consists mostly of
Precambrian and Paleozoic metamorpMc rocks, with lesser amounts of Precambrian and Paleozoic
sedimentary rocks, Quaternary sediments, and Tertiary and Quaternary mafic volcanic rocks. The
Aklun Mountains are composed mostly of marine sedimentary rocks and small intrusive masses of
Jurassic and Tertiary age. The Bering Shelf is covered almost entirely by Quaternary surficial
sediments, with minor areas of Tertiary volcanic rocks.
Overall the Central Province has moderate radon potential as many radon-producing rocks
occur there. There are, for instance, several areas of uraniferous granites together with felsic
intrusive and volcanic rocks. In addition, the area contains a few uranium deposits of potentially
commercial size at Death Valley on the Seward Peninsula and in the Healy Creek coal basin. The
area also contains a significant number of gamma-ray anomalies. Nearly all of the area falls within
a belt of uraniferous stream sediments. The schist that produces high indoor radon near Fairbanks
is in this area. Little of the province has been glaciated. The soils are mostly of the Tundra type
with variable permafrost. Significant areas of rockland and subarctic brown forest soils occur.
The latter soils may have high gas transmissivity.
Northern Plateaus
The Northern Plateaus subprovince (5, fig. 2) is covered by flat-lying Tertiary basin-fill
(nonmarine clastic rocks), Quaternary surficial deposits, Precambrian through Cretaceous mostly
marine sedimentary rocks, Paleozoic and Precambrian metamorpMc rocks, and Mesozoic intrusive
and volcanic rocks. The metamorpMc rocks include metamorphosed granites and amphibolite.
IH-7 Reprinted from USGS Open-File Report 93-292-J
-------
The mesozoic intrasives are msotiy gabbro and diabase. The Tintina and Denali fault zones cross
this subprovince.
The Northern Plateaus subprovince has a moderate radon potential overall. A moderate
number of aeroradiometric anomalies occurs in the ;rv vince. Although indoor radon data are
sparse, indoor radon in parts of the Fairbanks and Fairbanks Northstar Boroughs is high. Felsic
intrusives are scattered in two belts, one intruding Paleozoic and Precambrian metamorphic rocks
in the southeast one-third of the subprovince and one intruding Lower Paleozoic and (or)
Precambrian sedimentary rocks along the northwest margin of the subprovince. The area contains
one known significant uranium and thorium deposit at Mount Prindle. Uranium is high in stream
sediments in the south-central part and along the northwest border of the subprovince.
Alaska-Aleutian Ranges and Coastal Mountains
The Alaska-Aleutian Ranges and Coastal Mountains Province (6, fig. 2) includes the
Aleutian Peninsula, a northeast-trending mountain belt in south-central Alaska that includes Mt.
McKMey, a southeast-trending mountain belt that extends from the Mt McKinley area
southeastward to Canada, and the Coast Mountains in the southeast. On the Aleutian Peninsula
from Unimak Pass westward, the bedrock consists mostly of Quaternary and Tertiary volcanic
rocks and Tertiary sedimentary rocks. Tertiary and Quaternary volcanic rocks are also common
northeast of the Pass, but other rocks, including Jurassic and Cretaceous sedimentary rocks and
Jurassic intrusive rocks of intermediate and felsic composition, are also common in this area. In
addition, large masses of Tertiary mafic volcanic rocks and Jurassic or Cretaceous intermediate
intrasives are found in the area west of Cook Inlet and southwest of Mount McKinley. A varied
assortment of Phanerozoic rocks are present in the Talkeetna Mountains and southeastward to the
Canadian border. These include Paleozoic mafic volcanic rocks together with their sedimentary
and metamorphic derivatives; Mesozoic mafic volcanic flows and tuffs, together with various units
of shale, conglomerate, graywacke, and slate; and Tertiary and Quaternary intermediate volcanic
rocks, Tertiary felsic intrusives, and Quaternary glacial deposits including eolian sand and silt.
The Coastal Mountains are composed mostly of ultramafic, intermediate, and silicic volcanic
intrusive rocks of varying ages, and Paleozoic through Mesozoic sedimentary rocks. These rocks
are highly deformed and variably metamorphosed.
This area has moderate radon potential overall, although the uncertainty is high. The
Aleutian-Alaska Range contains felsic intrusives and other rocks that are likely to be uranium-rich,
although no significant uranium occurrences are known in this area. However, the area has a
moderate to substantial number of anomalously uranium-rich stream sediment samples. Most of
the area is or was covered by glaciers and glacial outwash may be highly permeable in many areas.
Soils are mostly classified as rockland or tundra.
Coastal Trough
The Coastal Trough Province (7, fig. 2) includes a series of Cenozoic depositional basins
containing thick sequences of Tertiary continental clastic and volcanic rocks that generally overlie
Cretaceous or older sedimentary rocks penetrated by Tertiary intrusive rocks. Mesozoic
sedimentary rocks and Pleistocene, mostly glacial, deposits, occur in some areas.
The radon potential of this area is moderate overall, but locally high indoor radon levels
could occur near uranium occurrences. The Coastal Trough Province contains Tertiary continental
clastic rocks similar to units that produce uranium in the western conterminous United States. The
overall uranium content of these rocks is not high, but small uranium occurrences are found in the
HJ-8 Reprinted from USGS Open-File Report 93-292-J
-------
Susitna Lowlands and in the Admiralty trough in southeastern Alaska. Soils are mostly brown and
gray-brown podzolic forest soils, which could have high gas transmissivity. Heavy rainfall and
saturated soils in southeast Alaska likely retards soil gas migration.
Pacific Border Ranges
The Border Ranges Province (8, fig. 2) is generally south and west of the Coastal Trough
Province. Jurassic and Cretaceous sedimentary and metamorphic rocks with interbedded mafic
volcanic rocks and some gabbro make up most of the Border Ranges rocks. A fairly large area of
early Tertiary sedimentary, volcanogenic sedimentary rocks, and volcanic rocks is found in the
Prince William Sound area.
The Border Ranges Province generally has low radon potential, although some uranium-
bearing rocks and uranium occurrences are likely to be present The uranium deposit at Bokan
Mountain is associated with a uranium-rich peralkaline granite. The uranium content of stream
sediments in the Border Ranges is intermediate for Alaska, although data are absent from many
areas. Podzolic brown and gray-brown forest soils are common in the Border Ranges, and they
could have high gas permeability. However, in this part of Alaska annual rainfall is about 14 feet,
and water saturation likely retards gas flow in soils on all but the steepest slopes.
M-9 Reprinted from USGS Open-FUe Report 93-292-J
-------
Bsmt & 1st Floor Radon
Average Concentration (pCi/L)
0.0 to 1.0
1.1 to 1.9
2.0 to 3.0
3.1 to 4.0
4.1 to 14.9
Missing Data
{< S measurements)
Figure 3A. Screening indoor radon data from the State/EPA Residential Radon Survey and the
Oregon Radon Project, for counties with 5 or more measurements in the conterminous part of
EPA Region 10. Histograms in map legends show the number of counties in each category. The
number of samples in each county may not be sufficient to statistically characterize the radon
levels of the counties, but they do suggest general trends. Unequal category intervals were
chosen to provide reference to decision and action levels.
-------
Bsrrrt & 1st Floor Indoor Radon
Average Concentration (pCi/L)
1 0
11 L
0.0 to 1,0
1.1 to 1.9
2.0 to 3.0
3.1 to 4.0
4.1 to 6.4
Missing Data
(< 5 measurements)
Figure 3B. Screening indoor radon data from the State/EPA Residential Radon Survey of
Alaska, for counties with 5 or more measurements. Data are from 2-7 day charcoal canister tests.
Histograms in map legends show the number of counties in each category. The number of
samples in each county may not be sufficient to statistically characterize the radon levels of the
counties, but they do suggest general trends. Unequal category intervals were chosen to provide
reference to decision and action levels.
-------
PRELIMINARY GEOLOGIC RADON POTENTIAL ASSESSMENT OF ALASKA
by
Kendell A. Dickinson
US. Geological Survey
INTRODUCTION
The state of Alaska is characterized by complex geology and soils developed on rugged
terrain in cool, moist climates. It is a laige, sparsely populated area. Indoor radon data are only
available for (he populated areas. For many areas conclusions are very general because of the lack
of field studies and the generallaek of data. It is, however, hoped that the study will suffice as a
general guide to future studies and planning in terms of radon potential.
This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
deposits of Alaska. 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.
GEOGRAPHIC SETTING
Alaska occupies the great northwestern peninsula of North America; it is an extension of
the North American Cordillera. Alaska can be divided from north to south into the following
physiographic provinces (Wahrhaftig, 1965): The Arctic Coastal Plain, Arctic Foothills, Arctic
Mountains, Central province (including Northern Plateaus, Western Alaska, Seward Peninsula,
Bering Shelf, and Aklun Mountains subprovinces), Alaska-Aleutian Ranges (including the Coast
Mountains of southeastern Alaska), Coastal Trough, and Pacific Border Ranges (fig. 1).
The southeastern corner of southeastern Alaska lies about 500 miles from the State of
Washington, the nearest part of the conterminous 48 states. The southeast corner of southeast
Alaska lies about 1800 miles from the northwest end of the north slope and about 2300 miles from
Attu Island, Alaska's and the USA's most eastern point (west of 180 degrees E. longitude).
Alaska is the largest state in the USA and is the least populated of all the states. It occupies
591,000 square miles.
According to the 1990 census there were 550,043 people in Alaska, about one third of
whom live in Anchorage and about one half of whom live in Anchorage and Fairbanks combined.
Alaska averages about 1.1 people per square mile (fig. 2).
IV-1 Reprinted from USGS Open-FUe Report 93-292-J
-------
Figure 1. Physiographic provinces of Alaska (Wahrhaftig, 1965).
-------
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GEOLOGIC SETTING
The geology of Alaska varies widely (fig. 3). As many as 60 tectonostratigrapMc terranes
have been recognized in Alaska (Jones and others, 1987; Monger and Berg, 1987). Terranes were
defined by HoweE (1985) as "fault-bounded geologic entities of regional extent each characterized
by a geologic history distinct from neighboring terranes". These terranes were accreted to the
western North American craton during the last 200 million years and now form Alaska. Diverse
assemblages of igneous, metamorphic, and sedimentary rocks ranging fromPrecambrian to
Holocene make up these terranes. Numerous Tertiary basins that contain largely continental
deposits of coal-bearing clastic rock formed after the terranes were in place. Stone and Wallace
(1987) grouped the terranes into framework provinces each containing several terranes of similar
tectonic or geologic style. The tectonostratigraphic terrane boundaries are coincident with fault
zones in many areas.
The geology of Alaska is summarized below on the basis of the physiographic provinces
and subprovinces of Wahrhaftig (1955). Terrane summaries included for each physiographic
division were abstracted from Jones and others (1987) and Monger and Berg (1987). Rocks
characteristic of each terrane form the bedrock in much of Alaska, but they are not part of the
surface geology in some areas and do not play a direct role in radon generation in those areas.
Surficial deposits in the Arctic Coastal Plain consist mostly of alluvium, eolian sand, and
silt of Quaternary age. A belt of marine and nonmarine conglomerate, sandstone, shale, and
mudstone of Tertiary age that separates the coastal plain from the Arctic Foothills to the south is
found along the eastern 1/3 of the area. The Arctic Coastal Plain province is underlain by the
NorthSlope subterrane (Precambrian to Lower Paleozoic basement rocks overlain by
Mississippian through Triassic and younger Mesozoic sedimentary rocks).
Surface rocks in the Arctic Foothills province are largely composed of marine and
nonmarine Cretaceous sandstone and shale, but some Paleozoic and Mesozoic rocks are also
present The Cretaceous beds are folded into west-trending anticlines and synclines. The North
Slops (see above), Endicott Mountains (Sequences of Devonian clastic rocks, Mississippian shale
and carbonate rocks, and Upper Paleozoic and Mesozoic chert, argillite and calcareous rocks), and
DeLong Mountains (thick Devonian and Mississippian carbonates and younger sequences of chert
and argillite) subterranes of the Arctic terrane underlie the Arctic Foothills province.
The Arctic Mountains province (Brooks Range) is composed largely of upper Precambrian
and Paleozoic marine sedimentary rocks. These rocks are cut by west-trending thrust faults with
their upthrown sides to the south. The Endicott Mountains (see above) and Hammond subterranes
(polymetamorphosed assemblage of Middle Paleozoic and older carbonate rocks, calc-schist,
quartz-mica schist, quartzite, and metarhyolite intruded by Devonian gneissic granitic rocks)
underlie most of the province. Several other terranes underlie small parts of the province. Among
these are the Angayucham terrane. (complex assemblage of oceanic rocks, including: gabbro,
diabase, pillow basalt, tuff, chert, graywacke, argillite, and minor limestone; Mississippian to
Jurassic sedimentary rocks; Late Carboniferous and Late Jurassic volcanic basalts; and thrust
sheets of ultramafic rocks which are found throughout the section).
The Central province, a large area of plains, plateaus and rounded mountains, is
geologically complex. The Central province was divided into five physiographic subprovinces by
Wahrhaftig (1965). These are the Northern Plateaus, Western Alaska, Seward Peninsula, Aklun
Mountains, and Bering Shelf subprovinces. More than 20 different terranes underlie the Central
province (Jones and others, 1987).
IV-4 Reprinted from USGS Open-File Report 93-292-J
-------
EXPLANATION
SEDIMENTARY ROCKS
Quaternary (Recent
& pleistocene)
Lover Twtiiu>'
(OUgocene, Eocene,
VOLCANIC ROCKS
Cretaceous (In parts of
[I I Reeky Mtns. & Alaska in-
eludes Jurassic &Triassk)
:t Upper J^ilszGit (Fermisa,
L" j Stemsylsiaaaii SMIssi-
ssipplma)
(Metamorpble & igneous
rocks)
Figure 3. Generalized geologic map of Alaska (Kinney, 1965).
-------
The Seward Peninsula, on the western end of the Central province, consists mostly of
Precambrian and Paleozoic metamorphic rocks. There is, however, an area of Precambrian and
Paleozoic sedimentary rocks in the northwest part of the peninsula, a belt of Quaternary sediments
along its northern edge, and an area of Tertiary and Quaternary mafic volcanic rocks generally in
the center of the northeast part of the Peninsula. The Seward Peninsula is primarily underlain by
the Seward terrane (Mica schist, micaceous calc-schist, metavolcanics, marble, and high grade
gneissic rocks; rocks of probable Precambrian and known Devonian age are present but some ages
are uncertain), but parts are underlain by the Crazy Mountains (Cambrian quartzitic sandstone and
other younger Paleozoic sedimentary rocks) and Koyukuk terranes (andesitic volcanic rocks
together with conglomerate, graywacke, and mudstone). Small parts of the Peninsula are
underlain by other terranes (Jones and others, 1987).
The Bering Shelf, on the western end of the Central province and south of the Seward
Peninsula, is covered almost entirely by Quaternary surficial sediments and scattered areas of
Tertiary volcanic rocks. The Bering Shelf is underlain almost entirely by the Crazy Mountain
terrane (see above).
The Aklun Mountains subprovince lies south of the Bering Shelf. It is covered mostly by
Precambrian through Cretaceous marine sedimentary rocks, consisting of sandstone, shale, and
limestone. The Aklun Mountain subprovince also contains small felsic intrusive bodies of Jurassic
and Tertiary age. Southwest-trending faults and folds and at least one major southeast-trending
fault are present in the Aklun Mountains. The subprovince is mostly underlain by the Togiak
(Jurassic and Lower Cretaceous volcanic and volcaniclastic rocks including pillowed flows, tuffs,
breccias, conglomerates, graywackes, chert and a minor amount of Cretaceous limestone) and
GoodNews (chert, pillow basalt, tuff, limestone, and blocks of ultramafic rock; dated limestones
vary from Ordovician to Permian; lawsonite-bearing metamorphic rocks in some areas) terranes.
The eastern third of the Central province is covered by the Northern Plateaus subprovince.
About the western half of this subprovince underlies flat-lying Tertiary basin fill (nonmarine clastic
rocks) and Quaternary surficial deposits. The northeastern part of the northern plateaus
subprovince, along the Canadian border, is a complex area of Precambrian through Cretaceous
mostly marine sedimentary rocks and Paleozoic metamorphic rocks that contain fairly large areas of
Mesozoic intrusive and volcanic rocks. Much of the southern and southeastern parts of the
subprovince is composed of a large variety of Paleozoic and Precambrian metamorphic rocks that
were penetrated by felsic intrusions. The Tintina fault, which is generally followed by the Yukon
River, trends southeast through the central part of the area. The Denali fault, which forms the
southeast boundary of the subprovince, more or less parallels the Tintina. A complex grouping of
terranes underlies most of the northern plateaus. The southeastern part is underlain by Yukon-
Tanana (metamorphic rock including Paleozoic granitoid protoliths and Devonian marble) terrane.
The northern part is underlain by Crazy Mountain (see above); Tozitna (Paleozoic (?) and Mesozoic
gabbro, basalt, diabase, argillite, tuff, chert, and conglomerate; also includes Permian Limestone
and Mississippian radiolarian cherts); and Porcupine terrane (phyllite, slate, quartzite and carbonate
rocks overlain by sedimentary complex ranging from Cambrian (?) to Devonian in age) terranes.
The western part of the Northern Plateaus province includes the Ruby (phyllite, schist, marble,
quartzite, marble, amphibolite, granite, and metachert) and other terranes. The easternmost part of
this province, near the Canadian Border, is underlain by phyllite, slate, and siltstone that is part of
the North American craton (not an accreted terrane).
The largest subprovince of the Central province is Western Alaska (fig. 1). Large areas of
Cretaceous and lower Paleozoic sedimentary and metamorphic rocks are present in the western half
IV-6 Reprinted from USGS Open-File Report 93-292-J
-------
of this subprovince. The Cretaceous rocks are mostly marine conglomerate, graywacke,
sandstone, and siltstone. The lower Paleozoic rocks are both sedimentary and metamorphic and
consist of limestone, dolomite, siltstone, argillite, chert, schist, quartzite, and greenstone. A large
area of Cretaceous and Tertiary volcanic rock is present in the western part of this subprovince just
east of the Seward Peninsula. Prominent faults cross the western Alaska subprovince from east to
west. The Mulchatna, Kaltag, Farewell, and Iditarod-Nixon faults trend southwest through the
western half of this subprovince. The Western Alaska subprovince is underlain by a large number
of terranes. The largest of these are Koyukuk (andesitic flow tuffs, breccias, agglomerates,
conglomerates, graywacke, and mudstone; locally interbedded limestone contains Early Cretaceous
fossils); Kahiltna (Late Jurassic to Early Cretaceous deep marine graywacke, tuffs, pelitic rocks
and minor amounts of chert, limestone, and conglomerate); Nixon Fork (reefal and platform
carbonate rocks of Qrdovician to Upper Devonian age overlain by Permian, Triassic, and
Cretaceous sedimentary rocks); Dilinger (Paleozoic graptolitic shale, basinal carbonate rocks, and
turbiditic sandstone and shale together with overlying Jurassic sandstone and siltstone); Innoko
(Late Paleozoic and early Mesozoic chert, argillite, graywacke, and volcanic sandstone,
conglomerate, and tuff); and Minchumina (Qrdovician chert, argillite, and quartzite together with
chert as young as Devonian).
The Alaska-Aleutian province includes the Aleutian Peninsula, a northeast-trending belt in
south-central Alaska that includes Mt. McKinley, a southeast-trending belt that extends from the
Mt. McKinley area south eastward to Canada, and the Coast Mountains in southeastern Alaska.
On the Aleutian Peninsula from Unimak Pass westward, the bedrock consists mostly of
Quaternary and Tertiary volcanic rocks and Tertiary sedimentary rocks. Quaternary and Tertiary
volcanic rocks are also important east of the Unimak Pass but other rocks including Jurassic and
Cretaceous sedimentary rocks and Jurassic intrusive rocks of intermediate and felsic composition
are also important in this area. In addition, in the area west of Cook Met and southwest of Mount
McKinley, large bodies of Tertiary mafic volcanics and Cretaceous or Jurassic intermediate
intrusives are found. A varied assortment of Phanerozoic rocks is present in the area from Mt.
McKinley southeastward to the Canadian border. This assortment includes Paleozoic mafic
volcanic rocks and their sedimentary and metamorphic derivatives; Mesozoic mafic volcanic flows
and tuffs, together with various units of shale, conglomerate, graywacke, and slate; and Tertiary
and Quaternary intermediate volcanic rocks, Tertiary felsic intrusives, and Quaternary glacial
deposits including eolian sand and silt. The Alaska-Aleutian province is mostly underlain in the
west by the Peninsular (Paleozoic and Mesozoic igneous and sedimentary rocks including
limestone, argillite, basalt, tuff, andesitic flows, breccias, volcanic sandstone and siltstone, and
batholithic granitic rocks; also included is the andesitic arc assemblage), Kahiltna (see above), and
Crazy Mountain terranes (see above), and in the north by the Yukon-Tanana terrane (see above).
The Coastal Mountains in southeastern Alaska consist mostly of ultramafic, intermediate, and felsic
intrusives, Mesozoic mafic volcanic rock, and Mesozoic through Paleozoic sedimentary rocks.
The Tracy Arm (metamorphosed pelitic and quartzofeldspathic schist and paragneiss, marble,
amphibolite, and minor serpentinite) and Taku (variably metamorphosed upper Paleozoic and
Triassic basalt and local felsic volcanic rock, carbonate rock, and pelite; includes some undated
metamorphosed clastic and volcanic rocks) terranes underlie most of the Coast Mountains.
The Coastal Trough province includes a row of basins that were active centers of
deposition during the Cenozoic. The province includes the Cook Met and Copper River Basins in
southern Alaska and the Admiralty Trough in southeastern Alaska. These depositional basins
contain thick sequences of Tertiary continental clastic rocks that generally overlie Cretaceous or
IV-7 Reprinted from USGS Open-File Report 93-292-J
-------
older sedimentary rocks and have been penetrated and covered by Tertiary volcanic rocks.
Mesozoic sedimentary rocks are abundant in the area north of Cook Inlet basin and large areas of
Pleistocene, mostly glacial deposits, are found at the north end of Cook Inlet basin and in the
Copper River basin. Large areas of Tertiary volcanic rocks are present in the vicinity of Shelikof
Strait and the WrangeU Mountains in southern Alaska and on Admiralty, Kupreanof, and Wrangell
Islands in southeastern Alaska. The coastal trough province is bounded by regional faults such as
the Bruin Bay and Border Ranges faults that trend southwest in the Cook Met area and the
Clarence Strait and Chatham Strait faults that trend southeast in southeastern Alaska, In southern
Alaska the Coastal Trough province is underlain by Crazy Mountains (see above), Wrangellia (in
ascending order, Upper Paleozoic arc-related volcanic breccias, flows, and clastic rocks; Permian
limestone, pelMc rocks, and chert; Triassic black cherty argillite; a thick sequence of pillow basalt;
basinal spicuMc argillaceous and calcareous rocks; and predominantly clastic rocks of Jurassic and
Cretaceous age); Peninsular (see above); and fCahiltna (see above) terranes. In southeast Alaska
much of the Coastal Trough province is underlain by the Stikmia terrane (Mississippian, Permian,
Triassic and Jurassic marine and nonmarine volcanic and sedimentary rocks together with coeval
granodioritic batholithic rocks).
The Border Ranges province is generally south and west of the coastal trough province.
This province includes the Chilcat and Baranof Mountains and Prince of Wales Island in
southeastern Alaska. Cretaceous and Jurassic sedimentary and metamorphic rocks with
interbedded mafic volcanic rocks and some gabbro comprise most of the Border Ranges rocks. A
fairly large area of lower Tertiary sedimentary, volcanogenic, and volcanic rocks is found in the
Prince William Sound area. In southeastern Alaska, the Border ranges consist mostly of Paleozoic
metamorphic and Paleozoic to Mesozoic sedimentary rock together with some intermediate
intrusives of Cretaceous and Tertiary age. The metamorphic rocks are mainly Devonian Schist,
phyEite, marble, and amphibolite. The sedimentary rocks are mainly Paleozoic shale, siltstone,
graywacke, conglomerate, and limestone and a Cretaceous melange containing blocks of flysch,
greenstone, limestone, chert, granodiorite, schist, layered gabbro, and serpentinite in a pelitic
matrix. In southern Alaska the Border Ranges province is underlain primarily by the Chugach
(mostly weakly metamorphosed Cretaceous graywacke and slate interbedded locally with
radiolarian chert, gabbro, pillow basalt, and ultramafic rocks); Yakutat (Upper Mesozoic
graywacke and shale intercalated with lenses of chert, argillite, and volcanic rocks); Ghost Rocks
(strongly deformed assemblage of pillow lava, pillow breccia, and tuff with andesitic to basaltic
composition interbedded with Late Cretaceous to Oligocene sandstone and mudstone and intruded
by sparse plutons) terranes. In southeastern Alaska most of the Border Ranges province is
underlain by the Alexander terrane which includes the Admiralty (Devonian and Mississippian
basalt, carbonate rocks, and chert in contact with Ordovician flysch); Annette (variably
metamorphosed Ordovician to Triassic intrusive, extrusive, clastic and carbonate rocks); and Craig
(Pre-Ordovician metamorphic complex and Ordovician to Triassic mafic and felsic volcanic rocks
and terriginous clastic and carbonate rocks) subterranes.
Uranium deposits and radioactive anomalies: Table 1 lists the major uranium deposits and
other significant uranium occurrences in Alaska. Both igneous and sedimentary types are present,
but none are found in populated areas (fig. 4; table 1). Only the Bokan Mountain deposit has
actually produced uranium (MacKevett, 1963). As presently known, only the Death Valley and
Bokan Mountain deposits are potential U producers. In addition to the deposits listed in table 1,
many small radioactive mineral occurrences (several as U and Th bearing placer deposits) and
radioactive anomaEes were reported by Eakins (1969,1975). National Uranium Resource
IV-8 Reprinted from USGS Open-File Report 93-292-3
-------
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P°'
I ALASKA PENINSULA
170"
16O*
150s
JUNEAU
GULF OF ALASKA
Kaku
Sumit
Bokan Mtn.
200km
140°
\
130*
Figure 4. Uranium deposits of Alaska.
-------
Evaluation (NUKE) surveys enumerated 1520 radioactive anomalies in an area that covers about
2/3 of the State (Dickinson and others, 1983). It should be noted, however, that uranium
enrichment in the rock is not necessary to produce elevated radon to be in homes, and in the case of
very young uranium deposits, even Mgh concentrations of uranium may not cause elevated radon
in homes because the uranium would be in gross disequilibrium with its daughter products,
TABLE 1. Uranium deposits in Alaska,
Area Type of deposit Reserves Reference
Death Valley Epigenetic, sandstone 1M Ibs. t^Og Dickinson (1988)
Bokan Mountain Peralkatine granite 800 K Ibs. U30g MacKevett (1963)
Nenana Coal Field Epigenetic and other unknown Dickson (1981)
Mount Prindle Igneous unknown Armbrustmacher
(1989)
Keku Strait Epigenetic sandstone unknown Dickinson and
and phosphate Vuletich (1990)
SOILS AND SURHCIAL DEPOSITS
The soils of Alaska are controlled largely by the cool moist climate and the rugged terrane.
The soil terminology used below generally follows the nomenclature of the National Cooperative
Soil Survey Classification of 1967. The distribution of soils is summarized from the National
Atlas of the United States (U.S. Department of Agriculture, 1987; fig. 5).
About 2/3 of Alaska is covered by tundra. The tundra soils are largely aquepts and
cryaquepts of the Inceptisol order. These soils are characterized by undecomposed plant material,
generally Mgh moisture content, and the presence of permafrost in the area generaEy north of the
arctic circle (fig 6). Radon transmissivity in these soils is presumed to be poor because of the
water and ice content. No large population centers are found in these areas.
Soils classified as rockland, which includes glacial ice, cover about 1/4 of Alaska (fig. 5).
These surfaces are generally found in the rugged mountain ranges such as the Brooks, Alaska,
Aleutian, Chugach, Kenai, Wrangell, St Elias, and Coast Ranges. No significant populated areas
in Alaska are found on rockland.
Another group of Ihceptisols, cryochrepts (subarctic brown forest soils) and cryandepts
(brown podzolic or gray-brown podzolic soils) cover about 5 percent of the Alaskan area. The
cryochrepts are mostly distributed along the valleys of the Yukon and Tanana Rivers in central
Alaska and the cryandepts are on the Alaskan Peninsula. These soils rank high in radon
transmissivity, but are not common in populated areas.
Spodosols make up about 3-1/2 percent of the surface area of Alaska. These soils are
characterized by a low base content and a high content of amorphous material, aluminum, and
probably iron. They are formed under acid conditions, generally on porous parent material, and
they probably have relatively high gas transmissivity. Anchorage and Juneau are located in areas
with spodosols.
IV-10 Reprinted from USGS Open-File Report 93-292-J
-------
60
140"
130"
SOIL CLASSIFICATION
(SEE EXPLANATION)
140°
Figure 5. Generalized soils map of Alaska (after U.S. Department of Agriculture,
1987)
-------
FIGURE 5 (continued). GENERALIZED SOILS MAP OF ALASKA
EXPLANATION
1. Cryaquepts (formertly Tundra), These are the Aquepts of cold climates, Aquepts are seasonly
wetlneeptisols that have an organic surface horizon. Inceptisols are soils that have
weakly differentiated horizons; materials in the soil have been altered or removed
but have not accumulated. These soils are usually moist, but during the warm
season of the year some are dry part of the time (66.5 percent).
2. Rock Land is a miscellaneous land type that includes Cryandepts (see below), Cryumbrepts
(Umbrepts of cold regions), Cryaquepts (see above), Cryorthods (see below), ice
fields, and glaciers. These are generally shallow soils formed on moderately
sloping or steep slopes. Umbrepts are Inceptisols with crystalline clay minerals,
thick dark-colored surface horizons, and altered subsurface horizons that have lost
mineral materials and that are low in bases (24 percent).
3. Cryandepts (formerly brown podzolic or gray brown podzolic soils) are Andepts of cold
regions. Andepts are Inceptisols (see above) that have formed in ashy materials,
have low bulk density and large amounts of amorphous materials or both.
4. Cryorthods (formerly podzols)-- Orthods of cold regions. Orthods are Spodosols that have a
horizon in which organic matter plus compounds of iron and aluminum have
accumulated. Spodosols with low base supply that have in subsurface horizons an
accumulation of amorphous materials consisting of organic matter plus compounds
of aluminum and usually iron; formed in acidic, mainly coarse-textured materials in
humid and mostly cool or temperate climates (3.5 percent).
5, Cryopsamments and Quartzipsamments (formerly regosols)-- Cryopsarnments are Psamments
of cold regions, Quartzipsamments are Psamments that consist almost entirely of
minerals that are highly resistant to weathering, mainly quartz. Psamments are
Entisols that have textures of loamy fine or coarser sand, Entisols are soils with no
pedogenic horizons (1 percent)
6. Cryochrepts (former subarctic brown forest soils) are the Ochrepts of cold regions. Ochrepts
are Inceptisols that have formed in materials with crystalline clay minerals, have
light-colored surface horizons, and have altered subsurface horizons that have lost
mineral materials (5 percent).
-------
Entisols, soils with no pedogenic horizons, make up <1 percent of the Alaskan soils. They
are the cryopsamments and quartzipsamments that are found only along the south central and
southeast coastal plains. They probably have high gas transmissivity, but are not found in
populated areas except for the village of Cordova (fig. 5).
Glacial deposits: Nearly half (48 percent) of Alaska was previously covered by glaciers
and as a result nearly half of the State is covered by glacial deposits. About 7 percent of the land
area is presently covered by glacial ice (fig. 6). Glacial outwash areas have more permeable
sediment than do areas of till, but for most glaciated areas the distribution of various sediments has
not been mapped,
Stream and River deposits'. Stream and river sediments cover much of Alaska especially in
delta and basinal areas. Examples are the Yukon flats area and the Yukon delta. There also large
areas of Quaternary sediments along the drainages of most of the major rivers. These deposits are
complex mixtures of fine- and coarse-grained sediment. In general the fine-grained sediment is
impervious (has low gas transmissivity) and the coarse-grained sediments are pervious (have high
gas transmissivity). No data is available to allow generalization on the distribution of fine versus
coarse-grained sediment on an area by area basis.
INDOOR RADON DATA
Indoor radon data from Alaska are principally from the State/EPA Residential Radon
Survey. This survey was conducted during the fall and winter of 1988 and 1989 by the Division
of Geology and Geophysics (DGGS) of Alaska and the Environmental Protection Agency (EPA).
The EPA analyzed the detectors and provided survey design and consultation through its
contractor, Research Triangle Institute (RTI). DGGS provided information on demography,
geology, and geography, selected participating households, and distributed the canisters (Nye and
Kline, 1990).
The data for the Alaska indoor radon survey are organized by borough or by other area
designations (fig. 7), Figure 8 shows the indoor radon concentration data for those areas where
sufficient date, was obtained and table 2 lists the indoor radon data for all areas in which data were
collected in the State/EPA Residential Radon Survey. The southeast Fairbanks census area had the
highest percent of radon values over 4 pQ/L. Forty-eight percent of the measurements in the
southeastern Fairbanks area exceeded 4 pCi/L (fig. 8; table 2). Boroughs or other areas with
average screening indoor radon levels exceeding 4 pCi/L in the State/EPA survey include Southeast
Fairbanks, Yukon-Koyukuk, and Skagway-Yakutat- Angoon, although the latter is based on only
three measurements (fig. 8; table 2) and should not be considered representative of all indoor radon
levels in the area.
IV-13 Reprinted from USGS Open-File Report 93-292-J
-------
142°
134°
EXPLANATION
*•
Existing glaciers
Pleistocene glecicre
Boundaries of permafrost areas
170*
166° 158V 160
Figure 6, Peimafrost and glaciers map of Alaska (Wahrhaftig, 1965).
-------
TABLE 2. Screening indoor radon data from the EPA/State Residential Radon Survey of Alaska
conducted during 1988-89. Data represent 2-7 day charcoal canister measurements from the
lowest level of each home tested.
BOROUGH
ANCHORAGE
FAIRBANKS NORTHSTAR
HAINES .
JUNEAU
KENAIPEN1NSULA
KETCHJKANGATEWAY '
KODIAKBLAND
MATANUSKA-SUSITNA
SITKA
SKAGWAY-YAKDTAT-ANGOON
SOUTHEAST FAIRBANKS
VALDEXCORDOVA
WRANGELL-PETERSBURG
YUKON-KOYUKUK
NO. OF
MEAS.
282
281
12
137
135
56
27
60
24
3
31
31
35
13
MEAN
1.0
3.5
1.0
0.4
2.6
0.2
0.4
2.8
0.3
4.2
6.4
1.6
0.3
5.5
GEOM.
MEAN
0.6
1.7
0.5
0.3
1.1
0.2
0.2
1.6
0.2
2.6
4.1
0.6
0.2
2.5
MEDIAN
0.6
1.6
0.6
0.3
1.3
0.2
0.2
1.5
0.1
5.3
4.0
0.7
0.2
2.0
STD.
DEV.
1.6
12.3
1.2
0.6
3.9
0.3
0.6
3.2
0.4
3.3
6.4
2.1
0.5
7.8
MAX
16.4
191.9
4.1
4.1
26.3
2.0
2.4
15.3
1.8
6.9
28.5
9.0
. 2.6
27.9
%>4 pCi/L
3
13
8
1
18
0
0
22
0
67
48
6
0
31
%>20 pCi/L
0
2
0
0
1
0
0
0
0
0
6
0
0
8
GEOLOGIC RADON POTENTIAL
The occurrence of radon in Alaska is related to bedrock type, surface sediment type, soil .
type, and fault locations. Black shale and phosphatic rocks commonly have relatively high
uranium contents. Phosphate deposits were found in Paleozoic and Mesozoic rocks in the Arctic
Foothills province and in southeastern Alaska (Patton and Matzko, 1959; Dickinson, 1979a,
1979b). In addition, black shale beds were found in the Arctic Foothills province. Black shales
are generally high in U, but no data is available for these rocks. Felsic igneous rocks, scattered
around Alaska (Forbes, 1975; Jones and Forbes, 1977), generally contain 5-7 ppm U, which is
higher than the average of 3.5 ppm for crustal igneous rocks (Wedepohl, 1971). One example is
the Darby pluton on the Seward Peninsula which contains about 7 ppm U and is believed to be the
source or U for the Death Valley deposit (Dickinson and others, 1987). Similar rocks are found in
other parts of Alaska (Jones and Forbes, 1977). The Darby pluton is, like the rock in the Arctic
Foothills province, located in an area with very low population density.
There are examples of high radon potential along fault zones in the conterminous 48 states
(Gundersen, 1991). Special attention should be paid to faults as radon hazards in Alaska because
of their abundance. Many if not most of the nearly 60 tectonostratigrapHc terranes are separated
from one another by fault zones. Most of the faults are not in populated areas, however. One
exception is the Knik Fault which runs along the east side of suburban Anchorage. The Knik Fault
passes near a radiometric anomaly along Turnagain Arm near Anchorage. The anomaly is over
Quaternary sediment, but the exact location of the fault in this area is not known. A relation
between the fault and the anomaly could exist
IV-15 Reprinted from USGS Open-File Report 93-292-J
-------
Aleutian Islands
nee of Wales
hikan
Figure 7. Boroughs and other subdivisions for plotting indoor radon data of Alaska.
-------
Bsmt & 1st Floor Indoor Rn
Average Concentration (pCi/L)
0.0 to 1.9
2.0 to 4.0
4.1 to 6.4
Missing Data
or < 5 measurements
newt
100 Miles
Bsmt & 1st Floor Indoor Radon
% > 4 pCi/L
OtolO
11 to 25
26 to 50
51 to 75
Missing Data
or < 5 measurements
100 Miles
Figure 8. Screening indoor radon data from the EPA/State Residential Radon Survey of Alaska,
1988-89, for boroughs with 5 or more measurements. Data are from 2-7 day charcoal canister
tests. Histograms in map legends show the number of boroughs or other areas in each category.
The number of samples in each borough (See Table 2) may not be sufficient to statistically
characterize the radon levels of the areas, but they do suggest general trends. Unequal category
intervals were chosen to provide reference to decision and action levels.
-------
An eU radiometric map is not available for Alaska. However, the number of radioactive
anomalies for each of the 1:250,000 quadrangle map areas in about-two thirds of the State are
available (Dickinson and others, 1983; fig. 9). These results are based on the National Uranium
Resource Evaluation (NURE) studies (LKB Resources, 1978a, 1978b, 1979). Most of the
anomalies represent contrasts between rock types and in some cases between bedrock and ice or
water. None of these anomalies has been identified as an important uranium deposit; however,
their distribution is significant for radon evaluation. In each of 13 quadrangles from a total of 91,
more than 40 anomalies were discovered (fig. 9). These anomalies can be grouped into two belts
and two isolated areas. The largest anomaly belt begins in the Kateel River quadrangle and extends
eastward through Melozitna, Tanana, Betfles, Beaver, Fort Yukon, Black River and Coleen. This
area generally follows the drainage basin of the Yukon River and its tributaries, the Tanana,
Porcupine, and Koyukuk. The other anomaly belt follows the Anchorage, Valdez and McCarthy
quadrangles that are occupied by the Chugach and Wrangell Mountains and a southern extension of
the Copper River Basin. The Medfra quadrangle, west of the Mt. McKinley quadrangle, by itself
exhibited 58 anomalies, and the Tanacross quadrangle southeast of Fairbanks exhibited 42, The
North Slope, Northern Foothills, Brooks Range, and the Alaska Peninsula were not covered by
this study.
Figure 10 shows the uranium content of stream sediments based on analyses from the
Geochemical Atlas (Weaver, 1983). This data is summarized as follows: A 200-mile-wide area of
high values extends westward across the State from Norton Sound and the Seward Peninsula
eastward through central Alaska, including most of the Brooks Range, to the Yukon Flats area and
the Canadian Border. A smaller belt covers the Alaska Range with Mount McKinley
approximately at its center. Small areas of intermediate values are found in the Chugach, Kenai,
and Wrangell Mountains. Scattered areas of relatively high values are present in southeastern
Alaska. Three belts of generally low values can be seen. These are approximately the North
Slope, the Kuskokwin River drainage basin in the central part of the State, and the Cook Inlet-
Matanuska Valley-Copper River basin area.
The following section is reproduced directly from Nye and Kline (1990):
"Interior Alaska has the highest proportion of homes with elevated radon concentrations as well
as the individual homes with highest concentrations. In the interior, 3 percent of homes with
the sample population had screening levels higher than 20 pCi/L and 17.6 percent of homes
had radon screening levels that were higher than 4 pCi/L. Figure 3 [fig. 11, this report]
summarizes the responses to a request for home site geographic information which was
included with the report of test results that was sent to part participants in the survey. This
figure shows that 30 to 35 percent of homes built in the hills around Fairbanks have elevated
radon concentrations.
In the Fairbanks area, homes built in the hills adjacent to the valley floor with concrete slab
or basement structures which are in contact with bedrock yielded the highest measured radon
levels. These areas also included the highest proportion of homes with high radon. We do not
yet know the proportion of homes with basements in contact with bedrock that do not have
elevated radon concentrations. The data shown in Figure 3 [fig. 12, this report] homes located
on hillside sites, includes homes which are built on thick accumulations of windblown glacial
silt (loess). Thick accumulations of loess appear to be an effective barrier to radon migration.
Homes built on alluvium from the Tanana and Chena Rivers are also at lower risk High radon
concentrations in homes which are sited in bedrock are likely to result from high fracture
IV-18 Reprinted from USGS Open-File Report 93-292-J
-------
29 28 38 2~ 2 MO
I70* 168* 166" 16«* 1SZ* 160* 1SS* 156* 154
Figure 9. eU anomalies map of Alaska, From LKB Resources Inc. (1978a, 1978b, 1979).
-------
4.99->19.26 ppm
2.57 - 4.98 ppm
<1.37-2.56 ppm
Figure 10. Uranium in stream sediments map of Alaska. Modified from Weaver (1983)
-------
150 H
Region 1
Greater Anchorage Area Borough
50%
E
-5
|
2?
0 0.5 2 4 10 '20
2501
Region 3
Southeastern Alaska
220
150
100
50
Region 2
Interior Alaska and Fairbanks Area
50%
8.5%
23%
11%
3.6% 3.0%
0.5
10 20
125-1
100-
35%
Region 4
Southcentral Alaska
36%
10 20
10 20
501
Region 5
Northern and Western Alaska
0.5 2 4 10
RESULT IpCi/l]
20
100
80-
S5.
a) 60
40
3
§20
V—V Reg ion 2
a n Regions
A—£> Region 4
C—0 Region 5
0.5 2 4 10
RESULTlpCi/ll
20
Figure 11. Histograms summarizing results of radon screening measurements (Nye and Kline,
1990).
-------
§
u
60
40
20
0
60
40
20
0
60
40
20
0
Homes located on hilltops or ridge crests.
n=23
34.7%
Homes located on steep slopes.
n = 10
20%
Homes located on gradual slopes.
n-47
Homes located in flat areas.
n=l19
AH Fairbanks area homes.
n=204
20
Radon concentration [pCi/ll
Figure 12. Histograms summarizing radon screening measurements and local geography of
Fairbanks area homes (modified from Nye and Kline, 1990).
-------
permeability of the bedrock as well as relatively high uranium concentration in the schist which
comprises local bedrock. Low radon concentration in homes built on loess and alluvium may
reflect low soil gas permeability, low uranium concentrations of soils, or both.
Throughout interior Alaska homes constructed on bedrock seem to be at higher risk for
elevated radon concentrations. However, homes built on coarse glacial outwash deposits
which are well drained can also have high radon concentrations. Outwash gravels may have
sufficient porosity and permeability to allow significant amounts of soil gas to migrate into
overlying structures. Outwash gravel may also contain abundant pebbles and boulders of rock
types with higher uranium concentrations, including granitic rocks.
Based on survey data, south-central Alaska includes communities with a significant
proportion of homes with elevated radon concentrations. The maximum radon concentrations
detected in south-central Alaskan homes, however, are not as high as those measured in the
Fairbanks area. The geologic setting of south-central Alaskan homes with elevated radon
concentrations appears to be diverse. In some cases high radon screening levels can probably
be attributed to the presence of coarse, well-sorted, granite-rich outwash. In other cases such
concentrations appear to reflect proximity to bedrock.
Survey data indicate that Anchorage, southeastern Alaska, and northern and western Alaska
have very few homes with elevated radon concentrations. In Anchorage this may reflect the
abundance of fine-grained glacio-fluvial and glacio-rnarine sediments which underlie most of
the borough. Fine-grained sediments such as these are characterized by low permeability, slow
soil gas transport, and much reduced reservoir volume of soil gas; thus reducing the amount of
radon which can be drawn into the home. Some of the homes included in the survey were
located in the hills surrounding Anchorage. The fact that these homes also have low radon
concentrations suggests that the local bedrock has low concentrations of uranium. The lack of
homes with high radon in Anchorage probably reflects low gas permeability and pore volume
of local soils, and low rates of radon production.
The low concentrations of radon in homes throughout southeastern Alaska are not well
understood, geologically. Many of the underlying bedrock types should have sufficient
uranium to produce a significant amount of radon, and many homes are built on extremely
porous soils and fractured bedrock. The sample base includes homes in Juneau built on coarse
talus fans and homes in the Mendenhall Valley built on coarse outwash with a high proportion
of granitic cobbles. Similar materials in other regions have relatively high source
concentrations of radon in soil gas. A high proportion of southeastern homes are built on
pilings. Since these homes were structurally ineligible for the survey they do not influence the
data presented here.
The small number of homes with elevated radon concentrations in northern and western
Alaska may be due to several factors, including local soil conditions such as shallow
permafrost and high water tables. Also, most of the communities included in this survey are
sited on fine grained alluvial deposits such as overbank silt, rather than in upland areas where
bedrock is exposed at or near the surface. Additionally, air exchange is probably more efficient
in small homes during routine entry and exit" (Nye and Kline, 1990).
The data on which this study is based "do not reflect the fact that most homes in rural
Alaska were structurally ineligible for this survey because they are built on pilings. Also there are
many Alaskan communities which do not include homes which were eligible for this study under
EPA guidelines" (Nye and Kline, 1990).
IV-23 Reprinted from USGS Open-File Report 93-292-J
-------
A compelling geological reason for the high indoor radon values obtained from the
Fairbanks area is difficult to determine. The bedrock in the Mils around Fairbanks is Preeambrian
to Paleozoic metamorphic rock (formerly termed the Birch Creek Schist). No data is at hand to
suggest that the Birch Creek Schist is an abnormally high radon producer in the vicinity of
Fairbanks. The Fairbanks 1:250,000 quadrangle produced only two gamma-ray anomalies in
studies carried out during the NURE program. The Anchorage quadrangle produced 43 anomalies
and the Juneau quadrangle produced 12. It should be noted that these airborne gamma-ray
anomalies are based on measurement of Bismuth-214 decay and are more closely related to radon
than to uranium. If abnormal amounts of radon are being generated by a particular rock unit such
as the Birch Creek Schist, these values should show up in airborne Bi-214 measurements.
One of the two airborne radioactivity anomalies in the Fairbanks quadrangle was obtained
over Quaternary sediments about 35 miles northwest of Fairbanks, the other was obtained over the
Mississippian Totatlinika Schist about 55 miles south of Fairbanks. In addition, EaMns (1969)
reported four uranium occurrences in stream sediment concentrates in the Fairbanks quadrangle.
One is in the Easter Dome area where minor granitic bodies intruded the Birch Creek Schist about
10 miles northwest of Fairbanks. Stream concentrates contained as much as 70 ppm U in this
area. Another is in the Pedro Dome-Gilmore Dome area about 15 miles northeast of Fairbanks,
where high Au» Bi, and W contents are found in lodes and high Au contents are found in placers
that are associated with the Birch Creek Schist Panned concentrates from this area contained up to
660 ppm U and outcrop samples contained as much as 10 ppm U (EaMns, 1969). Placer deposits
are difficult to assess for radon potential because the amount of radon that escapes uraniferous
resistate minerals through the uranium decay series is not well known. In addition, houses are not
often built on placer deposits and houses built on the alluvium in the Fairbanks area were low in
radon. Two other U occurrences are the Liberty Bell Mine, 64 miles southwest of Fairbanks, and
at Grubstake Creek 57 miles southwest of Fairbanks. They are too remote to suggest high
uranium values in the Fairbanks area. None of these occurrences suggest abnormally high radon
potential from the Birch Creek Schist in the Mils around Fairbanks.
In the Anchorage quadrangle, most of the 43 airborne radiometric anomalies identified
during the NURE studies are in the Chugach Mountains, away from populated areas. One strong
anomaly, however, was located along Turnagain Arm near residential areas of Anchorage. TMs
anomaly, as noted above, is near the Knik fault. It is also located on alluvium that is related to
Cretaceous and/or Upper Jurassic deep water clastic rocks consisting of siltstone, graywacke,
arkose, conglomeratic sandstone, pillow basalt, and other rocks. This sequence and a melange of
other Cretaceous and Jurassic (?) rocks including flysch, greenstone, limestone, chert,
granodiorite, schist, layered gabbro, and serpentinite form the hills above Anchorage to the west.
Houses in these Mils generally have low indoor radon readings.
The Juneau quadrangle contains two NURE airborne radiometric anomalies. Only one of
these was near Juneau. It is located over the waters of Taku Met about 10 miles east of Juneau.
The anomaly is next to Mesozoic and Paleozoic onshore rocks and may have resulted from the
migration of subaerial radon gas from these rocks. The rocks consist of greenstone, graphitic
schist, slate, chert, graywacke, quartzite, phyllite interlayered with marble, and a small amount of
ampMbolite.
IV-24 Reprinted from USGS Open-File Report 93-292-J
-------
SUMMARY
The major physiographic provinces of Alaska are the land units used for radon potential
estimates, except for the Central province, which is divided into the Northern Plateaus subprovince
and an area made up of the remaining subprovinces (fig. 1). Each of these areas has a variety of
geology and probably contains rock units that produce significantly high levels of radon. A brief
summary of the estimated potential for radon in each province or group of subprovinces together
with a radon potential index is given below (table 3).
The scores, particularly those for the confidence index, are low, in part because of dearth
of data considering the large size of the areas. The indoor radon data is limited to populated areas
and does not represent the entire land area of the province evaluated. Nevertheless, in the absence
of adequate data these data are given some credibility. The aerial radioactivity is presented only in
number of significant anomalies compiled by the NUKE program for each 1:250,000 quadrangle
area (LKB resources, Inc., 1978a, 1978b, 1979). The geology for these anomalies has been
incompletely compiled, but is known in some cases. The aerial radiometric data is applicable
within the constraints of the method of compilation. The geology for each province or subprovince
is well known, but in some of the areas it is complex and indoor and(or) soil-gas radon
information is lacking. Broad assumptions on radon potential based on geology have been used
for the score compilation. Broad assumptions on water and ice saturation of the soils and its effect
on soil-gas transmissivity were also used in the evaluations. No points were assigned for geologic
field evidence because no documented field studies of radon in the geologic environment in Alaska
were available.
The relatively flat-lying Cretaceous and Tertiary sedimentary rocks that make up the Arctic
Coastal Plain could contain high radon producers, although there is no data to suggest they do, A
radon potential score (RI) of 6 and confidence index (CI) of 6 is given for this province. These
low values stem mostly from lack of data and the assumption that soil saturation with water and ice
reduces radon transmissivity (figs. 5, 6). No significant uranium occurrences are known in this
area and the number of gamma-ray anomalies is low for this area when compared with other parts
of Alaska (figs. 4,9). The area also is a low in radioactive resistate minerals in stream sediments
(fig. 10). The coastal plain is unglaciated and contains tundra soils and permafrost.
The folded Cretaceous sandstone and shale that makes up most of the Arctic Foothills
province could produce relatively large amounts of radon but, again, no evidence that they do is at
hand. The province was assigned an RI of 7 and a CI of 6. The area contains no known U
deposits (fig. 4), and the part of the area where airborne gamma-ray measurements were made
shows a relatively low number of anomalies (fig. 9). The stream sediments show varied amounts
of uraniferous placer sediments with some high values in the eastern part of the area (fig. 10). Part
of the area was covered by glaciers (fig. 6). The soils are tundra soils with permafrost and
apparent low gas transmissivity (fig. 5).
The Precambrian and Paleozoic marine sedimentary rocks that make up most of the Arctic
Mountains province probably are not producers of large amounts of radon inasmuch as there is
little phosphate rock or black shale in these sequences. An RI of 9 and a CI of 6 was estimated for
this area. There are no known significant uranium occurrences in this area. The stream sediments
are, however, moderately high in uraniferous resistate minerals (fig. 10). The area has been
glaciated (fig. 6), but much of the terrane is bare rock without surficial glacial material. The soils
are classified as rockland, which includes glacial ice.
IV-25 Reprinted from USGS Open-File Report 93-292-J
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The Central province excluding the Northern Plateaus subprovince is a vast area of varied
geology and undoubtedly contains many rocks that are significant radon producers and many that
are not. The area was assigned an RI of 11 and a CI of 6. Indoor radon was given a rank of 3,
but with a very low confidence level because of the small number of measurements for such a vast
area. The number of gamma-ray anomalies ranged from one in the Lake Clark quadrangle to 71 in
the Kateel River quadrangle (fig. 9), and the area was given 2 RI points in this category. For
geology, the area was given 3 points. It contains uranium deposits of potentially commercial size
at Death Valley on the Seward Peninsula and in the Healy Creek Coal basin (fig. 4). There are
several areas of uraniferous granites, felsic intrusives, and volcanic rocks in parts of this province
together with various uranium occurrences in the Darby Mountains (Foley and Barker, 1986).
Nearly all of the area lies within the belt of uraniferous stream sediment minerals (fig. 10). Little
of the Central Province has been glaciated. The soils are mostly of the tundra type with variable
permafrost. There are significant areas of rockland and Cryochrepts (subarctic brown forest soils),
which may have high gas transmissivity. Water and ice saturation probably limits soil-gas
transmissivity in some parts of the area. Soil permeability was ranked 2.
The Northern Plateaus subprovince, a large, geologically complex area, was assigned an
RI of 11 and a CI of 7. Three points were given for indoor radon because of the high levels in
parts of the Fairbanks and Fairbanks-Northstar boroughs. The Northern Plateaus subprovince
was separated from the rest of the Central province in order to emphasize the high indoor radon
levels in the Fairbanks area, even though that area represents only a small part of the subprovince,
and to point out that high indoor radon levels are likely to occur locally in other parts of the
Northern Plateaus as well as the remainder of the Central Province, though both areas are ranked
moderate in geologic radon potential overall. Radioactivity, as measured by the number of
anomalies, was rated 2. The number of anomalies for 1:250,000 quadrangles covering the
Northern Foothills ranged from lows of two each in Fairbanks and Big Delta to highs of 59 in
Tanana and 63 in Beaver. The schist that apparently produces high indoor radon near Fairbanks is
in the Northern Plateaus subprovince, but no airborne gamma-ray anomalies were found over the
schist in the Fairbanks area. There are, however, 10 anomalies over the schist in the Tanacross
quadrangle 130 to 200 miles to the southeast of Fairbanks. Felsic intrusives are scattered in two
belts, one intruding Paleozoic and Precambrian metamorphic rocks in the southeast one third of the
subprovince and one intruding Lower Paleozoic and (or) Precambrian sedimentary rocks along the
northwest margin of the subprovince. For geology the subprovince was rated 3. The area
contains one known significant uranium and thorium deposit at Mount Prindle (fig. 4;
Armbrustmacher, 1989). Uranium is high in stream sediments in the south-central part and along
the northwest border of the subprovince (fig. 10). Soil permeability was ranked 2. In order of
decreasing abundance the soils consist of Cryaquepts (tundra), Cryochrepts (former subarctic
brown forest soils), and rockland. Soil permeability is variable, depending on water and ice
saturation. The Cryochrepts and rockland may have fairly high gas transmissivity.
The Alaska-Aleutian Range was assigned an RI of 9 and a CI of 6 overall (table 3), though
the area contains some felsic intrusives and other rocks that could be locally significant radon
producers. Indoor radon was given a RI score of one and confidence index of one. No significant
uranium occurrences are known in this province. The number of radiometric anomalies is
relatively low. The McKinley quadrangle, for instance, only has six (fig. 9). The province,
however, is an intermediate to high producer of uraniferous stream sediments (fig. 10). Most of
the area is or was covered by glaciers. Soils are mostly classified as rockland or tundra (figs. 5, 6).
IV-26 Reprinted from USGS Open-File Report 93-292-J
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The Coastal Trough contains thick sequences of carbonized wood-bearing Tertiary
continental clastic rocks similar to units that produce uranium in the western conterminous United
States. Uranium content of these rocks is not high, however, especially in the Cook Met and
Copper River basins. There is a slight northward increase in uranium content of the Tertiary
sedimentary rocks in the Cook Met basin and small uranium occurrences are found in the Susitna
Lowlands (Dickinson and Campbell, 1978). There are also small uranium deposits in the
Admiralty trough in southeastern Alaska (Dickinson and Campbell, 1984; Dickinson and Vuletich,
1990). Stream sediments are low in radioactive minerals in the Cook Inlet and Copper River basin
areas, and data from Admiralty Trough, where there are very few surface exposures, is sparse.
Soils are mostly brown and gray-brown podzolic forest soils which could have high gas
transmissivity. Heavy rainfall in southeast Alaska may retard soil gas migration. The Coastal
Trough area was given an RE of 9 and a CI of 6 (table 3).
The rocks of the Border Ranges, which consist mostly of Cretaceous and Jurassic
sedimentary and metamorphic rocks, together with some mafic volcanic and intrusive rocks,
generally have low radon potential. The RI for this area is 7 and the CI is 6 (table 3). The uranium
deposit at Bokan Mountain is associated with a peralkaline granite and it illustrates that because of
the great geologic diversity some high radon producers are undoubtedly present. Uraniferous
mineral content of stream sediments is intermediate for the Border Ranges, although data are absent
for many parts of the area (fig. 10). The radioactive anomaly density is also low for the Border
Ranges, although the Port Alexander quadrangle contains 17 and over half of the area is ocean
water. Podzolic brown and gray-brown forest soils are common in the Border Ranges and they
could have high gas transmissivity. In southern Southeastern Alaska, where annual precipitation is
about 14 feet, water saturation probably retards gas flow in soils. Nearly all of the Border Ranges
province was glaciated or is presently occupied by glaciers.
This is a generalized assessment of the State's geologic radon potential and there is no
substitute for having a home tested. The conclusions about radon potential presented in this report
cannot be applied to individual homes or building sites. Indoor radon levels, both high and low,
can be quite localized, and within any radon potential area there will likely be areas with higher or
lower radon potential that assigned to the area as a whole. Any local decisions about radon should
not be made without consulting all available local data. For additional information on radon and
how to test, contact your State radon program or EPA regional office. More detailed information
on state or local geology may be obtained from the State geological survey. Addresses and phone
numbers for these agencies are listed in chapter 1 of this booklet.
IV-27 Reprinted from USGS Open-File Report 93-292-J
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TABLE 3. RI and CI scores for geologic radon potential areas of Alaska.
PROVINCE
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
RANKING
Arctic
Coastal Plain
RI CI
1
1
2
1
1
0
6
LOW
1
1
2
2
6
LOW
Arctic
Foothills
RI CI
1
2
2
1
1
0
7
LOW
1
1
2
2
6
LOW
Arctic
Mountains
RI CI
2
2
2
2
1
0
9
1
1
2
2
6
MOD LOW
Central*
RI CI
3
2
3
2
1
0
11
MOD
2
1
2
1
6
LO
PROVINCE
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
RANKING
Northern
Plateaus
RI CI
3
2
3
2
1
0
11
MOD
2
1
2
2
7
MOD
Alaska-
Aleutian
Ranges**
RI CI
2
2
2
2
1
0
9
MOD
2
1
2
1
6
LOW
Coastal
Trough
RI CI
2.
2
2
2
1
0
9
MOD
2
1
2
1
6
LOW
Border
Ranges
RI CI
1
2
2
1
1
0
7
LOW
2
1
2
1
6
LO1
*Excluding Northern Plateaus
**including the Coast Mountains
RADON INDEX SCORING:
Radon potential category
LOW 3-8 points
MODERATE/VARIABLE 9-11 points
HIGH > 11 points
Possible range of points = 3 to 17
Probable screening indoor
Point range radon average for area
< 2 pCi/L
2 - 4 pCi/L
>4pCi/L
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-28 Reprinted from USGS Open-File Report 93-292-J
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REFERENCES CITED IN THIS REPORT
AND GENERAL REFERENCES PERTAINING TO RADON IN ALASKA
Armbrustmacher, T.J., 1989, Minor element content, including radioactive elements and rare-earth
elements, in rocks from the syenite complex at Roy Creek, Mount Prindle area, Alaska:
U.S. Geol. Survey, Open-File Report 89-0146, lip.
Beikman, H.M., (Compiler), 1980: Geologic Map of Alaska: U.S. Geological Survey, scale
1:2,500,000.
Bennison, A.P.(Compiler), 1974, Geologic highway map of the State of Alaska and the State of
Hawaii: American Association of Petroleum Geologists, scale 1:3,500,000
Conner, Cathy, and O'Haire, Daniel, 1988, Roadside geology of Alaska: Mountain Press
Publishing Co., Missoula, Montana, 250 p.
Dickinson, K.A., 1978, Uraninite in siderite nodules from Tertiary continental sedimentary rocks
in the Healy Creek basin area, central Alaska: U.S. Geological Survey Circular 804B, p.
B98-B99.
1979a, Uraniferous phosphate occurrence on Kupreanof Island, southeast Alaska: U.S.
Geological Survey, Open-File Report, 2 p.
1979b, A uraniferous occurrence in the Tertiary Kootznahoo Formation on Kuiu Island,
southeast Alaska: U.S. Geological Survey, Open-File Report 79-1427, 5 p.
1984, Uranium geology of the Tertiary Kootznahoo Formation of the Admiralty Trough,
southeastern Alaska: Journal of the Alaskan Geological Society, v. 4, p. 1-11.
, and Campbell, J.A., 1978, Epigenetic mineralization and areas favorable for uranium
exploration in Tertiary continental sedimentary rock in south-central Alaska-A preliminary
report: U.S. Geological Survey Open-File Report 78-757,13 p.
, 1984, Uranium geology of the Tertiary Kootznahoo Formation of the southern part of the
Admiralty Trough, Southeastern Alaska: Alaska Geological Society Journal, v. 4, p. 1-11.
, and Vuletich, April, 1990, Diagenesis and uranium mineralization of the Lower Tertiary
Kootznahoo Formation in the northern part of Admiralty Trough, Southeastern Alaska:
U.S. Geological Survey Bulletin 1888, 12 p.
,Cunningham, K.D., and Ager, T.A., 1987, Geology and origin of the Death Valley
uranium deposit, Seward Peninsula, Alaska: Economic Geology, v. 82, pp. 1558-1574.
• Morone, J.F., and Roberts, M.E., 1983, Summary of radiometric anomalies in Alaska:
U.S. Geological Survey, Open-File Report 83-169.
Dickson, R.K. 1981, Uranium mineralization in the Nenana Coal Field, Alaska in short notes on
Alaskan Geology: Division of Geological and Geophysical Surveys, Geologic Report 73,
p. 37-42.
IV-29 Reprinted from USGS Open-File Report 93-292-J
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Eakins, G.R., 1969, Uranium in Alaska: Division of Mines and Geology, Department of Natural
Resources, State of Alaska, Report number 38,49 p.
, 1,975, Investigations of Alaska's uranium potential: Alaska State Department of Natural
resources, Division of Geological and Geophysical Surveys, GJQ-1627, Energy research
and development Administration, 37 p.
, 1977, Investigation of Alaska's uranium potential, Part 1, Reconnaissance program, west-
Central Alaska and Copper River Basin: Alaska State Department of Natural Resources,
Division of Geological and Geophysical Surveys, U.S. Energy Research and
Development Adminstration, Grand Junction Colorado, 58 p.
Fleischer R.L., and Mogro-Campero, Antonio, 1985, Association of subsurface radon changes in
Alaska and the northeastern United States with earthquakes: Geochimica et Cosmochimica
Acta, v. 49, p. 1061-1071.
Foley J.Y., and Barker, J.C., 1986, Uranium Occurrences in the Northern Darby Mountains,
Seward Peninsula, AK: U.S. Bureau of Mines Information Circular, 26 p.
Forbes, R.B., 1975, Investigation of Alaska's uranium potential, map of the granitic rocks of
Alaska, regional distribution and tectonic setting of Alaskan alkaline intrusive igneous
rocks: GJO-1627, Part 2,44p.
Gundersen, L.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 1971, p. 39-50.
Howell, D.G. (editor), 1985, Tectonostratigraphic terranes of the Circum-Paciflc region: Council
for Energy and Mineral Resources, Earth Science Series no, 1, p. 3-30.
Jones, B.K., and Forbes, R.B., 1977, Investigation of Alaska's uranium potential, Part 2,
Uranium and thorium in Granitic and alkaline rocks in western Alaska: Alaska State
Department of Natural Resources, Division of Geological and Geophysical Surveys, 66 p.
Jones, D.L., Silberling, N.J., Berg, H.C., and Plafker, George, 1981j Map showing
tectonostratigraphic terranes of Alaska, columnar sections, and summary description of
terranes: U.S. Geological Survey Open-File Report 81-792,20 p.
Jones, D. L., Silberling, N. J., Coney, P. J., and Plafker, George, 1987, Lithotectonic terrane
map of Alaska (west of the 141st Meridian): U.S. Geological Survey Miscellaneous Field
Studies Map MF-1874-A.
Kinney, D.M., 1966, Geology: U.S. Geological Survey, National Atlas of the United States of
America, Sheet no. 74.
Larson, R.E., 1974, Radon profiles over Kilauea, the Hawaiian Islands and Yukon Valley Snow
Coven Pure Applied Geophysics, v. 112, p. 204-208.
IV-30 Reprinted from USGS Open-FUe Report 93-292-J
-------
LKB Resource Inc., 1978a, NURE aerial gamma ray and magnetic reconnaissance survey, Cook
Inlet, Alaska area: U.S. Department of Energy, Open-File Report GJBX-108 (78),
v. 1-2.
_, 1978b, NURE aerial gamma ray and magnetic reconnaissance survey, Eagle-
Dillingham area, U.S. Dept. of Energy, Open-File Report, GJBX-113 (78), v. 1-2.
, 1979, NURE aerial gamma ray and magnetic reconnaissance survey, southeastern
area, Alaska: U.S. Dept of Engergy, Open-File Report, GJBX-48 (79), v. 1-2.
Monger, J.W.H., and Berg, H.C., 1987, Lithotectonic terrane map of western Canada and
southeastern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1874-
B.
Nye, C.J., and Kline, J.T., ,1990, Preliminary evaluation of data derived from the recently
completed Alaska home radon survey: Alaska Division of Geological and Geophysical
Surveys, Public Data File 90-6,14 p. ,
MacKevett, E.M., Jr., 1963, Geology and ore deposits of the Bokan Mountain Uranium-Thorium
Area, Southeastern Alaska: U.S. Geological Survey, Bulletin 1154,125 p.
Patton, W.P., and Matzko, J.J., 1959, Phosphate deposits in northern Alaska: U.S. Geological
Survey, Professional Paper 302-A, 17 p.
Staatz, M.H., Hall, R.B., Macke, D.L., and Brownfield, I.K., 1980, Thorium resources of
selected regions in the United States: U.S. Geological Survey Circular 824, 32 p.
Stone, David B., and Wallace Wesley K., 1987, A geological framework of Alaska: Episodes, v.
10, no. 4, p. 284-289.
U.S. Department of Agriculture, Soil Conservation Service, 1987, Soils: U.S. Geological Survey
National Atlas sheet 38077-BE-NA-07M-00, scale 1:7,500,000.
Wahrhaftig, Clyde, 1965, Physiographic divisions of Alaska: U.S. Geological Survey,
Professional Paper 482, 52 p.
Weaver, T.A. (project leader), 1983, Geochemical atlas of Alaska: Los Alamos National
Laboratory, Los Alamos, New Mexico, LA-9897-MS, UC-51, 49 plates.
Wedepohl, K.H., 1971, Geochemistry: New York, Holt, Rhinehart, Winston, 231 p.
Wiess, H.V., and Naidu, A.S., 1986, 210 Pb Flux in an Arctic coastal region: Arctic, v. 39,
p. 59-64.
Wilkening, M.H., Clements, W.E., and Stanley, D., 1972, 38 Radon-222 flux measurements in
widely separated regions, in the Natural radiation environment n, Conference 720805-P2:
United States Energy Research and Development Administration, v. 2, p 717-729.
IV-31 Reprinted from USGS Open-File Report 93-292-J
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Page Intentionally Blank
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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.)
ALASKA MAP OF RADON ZONES
The Alaska Map of Radon Zones and its supporting documentation (Part IV of this
report) have received extensive review by Alaska geologists and radon program experts. The
map for Alaska 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.
Two borough designations in Alaska do not strictly follow the methodology for
adapting the geologic provinces to "county boundaries." The majority of land area in Juneau
and Haines is in the moderate radon potential area of the Coast Mountain province. However,
the available indoor radon data from these areas indicate low indoor radon measurements
among the population centers. Therefore, the Alaska Department of Health and Social
Services, the Alaska Cooperative Extension Service and the EPA have assigned Haines and
Juneau to Zone 3.
Although the information provided in Part IV of this report — the State chapter entitled
"Preliminary Geologic Radon Potential Assessment of Alaska" — 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 10 EPA office or the
Alaska 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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ALASKA - EPA Map of Radon Zones
The purpose of this map is to assist National, State and local organizations
to target their resources and to implement radon-resistant building codes.
This map is not intended to determine if a home in a given zone should be tested
for radon. Homes with elevated levels of radon have been found in all three
zones. AM homes should be tested, regardless of zone designation.
KENAI PENINSULA
SKAGWAY-YAKUTAT-ANGOON
Zone 1
Zone 2
Zone 3
PRINCE OF WALES-OUTER KETCHIKAN
IMPORTANT: Consult the publication entitled "Preliminary Geologic Radon
Potential Assessment of Alaska" before using this map. This
document contains information on radon potential variations within counties.
EPA also recommends that this map be supplemented with any available
local data in order to further understand and predict the radon potential of a
specific area.
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