United States
Environmental Protection
Agency
Air and Radiation
(66O4J)
402-R-93-057
September 1993
&EPA EPA's Map of Radon Zones
OREGON
Printed on Recycled Paper
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EPA'S MAP OF RADON ZONES
OREGON
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
ASSESSMENTSrINTRODUCTION
III. REGION 10 GEOLOGIC RADON POTENTIAL
SUMMARY
V. PRELIMINARY GEOLOGIC RADON POTENTIAL
ASSESSMENT OF OREGON
V. EPA'S MAP OF RADON ZONES - OREGON
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OVERVIEW
Sections 307 arid 309 of the 1988 Indoor Radon Abatement Act (IRAA) direct EPA to
identify areas of the United States that have the potential to produce elevated levels of radon.
EPA, the U.S. Geological Survey (USGS), and the Association of American State Geologists
(AASG) have worked closely over the past several years to produce a series of maps and
documents which address these directives. The EPA Map of Radon Zones is a compilation of
that work and fulfills the requirements of sections 307 and 309 of IRAA. The Map of Radon
Zones identifies, on a county-by-county basis, areas of the U.S. that have the highest potential
for elevated indoor radon levels (greater than 4 pCi/L).
The Map of Radon Zones is designed to assist national, State and local governments
•and organizations to target their radon program activities and resources. It is also intended to
help building code officials determine areas that are the highest priority for adopting radon-
resistant building practices. The Map of Radon Zones should not be used to determine if
individual homes in any given area need to be tested for radon. EPA recommends that all
homes be tested for radon, regardless of geographic location or the zone designation of
the county in which they are located.
This document provides background information concerning the development of the
Map of Radon Zones. It explains the purposes of the map, the approach for developing the
map (including the respective roles of EPA and USGS), the data sources used, the conclusions
and confidence levels developed for the prediction of radon potential, and the review process
that was conducted to finalize this effort.
BACKGROUND
Radon (Rn2~) 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, USGS1 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 . .
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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 irdoor screeni-g 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
irhportant indicators of radon potential: indoor radon measurements, geology, aerial
radioactivity, soil parameters, and foundation types.
The predictions of average screening levels in each of the Zones is an expression of
radon potential in the lowest liveable area of a structure. This map is unable to estimate
actual exposures to radon. EPA recommends methods for testing and fixing individual homes
based on an estimate of actual exposure to radon. For more information on testing and fixing
elevated radon levels in homes consult these EPA publications: A Citizen's Guide to Radon,
the Consumer's Guide to Radon Reduction and the Home Buyer's and Seller's Guide to
Radon.
EPA believes that States, local governments and other organizations can achieve
optimal risk reductions by targeting resources and program activities to high radon potential
areas. Emphasizing targeted approaches (technical assistance, information and outreach
efforts, promotion of real estate mandates and policies and building codes, etc.) in such areas
addresses the greatest potential risks first.
EPA also believes that the use of passive radon control systems in the construction 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. AC stated
previously, these five factors are considered to be of basic importance in assessing radon
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potential and some data are available for each of these factors in every geologic province. The
province boundaries do not coincide with political borders (county and state) but define areas
of general radon potential. 'The five factors were assigned numerical values based on an
assessment of their respective contribution to radon potential, and a confidence level was
assigned to each contributing variable. The approach used by USGS to estimate the radon
potential for each province is described in Part II of this document.
EPA subsequently developed the Map of Radon Zones by extrapolating from the
province level to the county level so that all counties in the U.S. were assigned to one of
three radon zones. EPA assigned each county to a given zone based on its provincial radon
potential. For example, if a county is located within a geologic province that has a predicted
average screening level greater than 4 pCi/L, it was assigned to Zone 1. Likewise, counties
located in provinces with predicted average screening levels > 2 pCi/L and < 4 pCi/L, and
less than 2 pCi/L, were assigned to Zones 2 and 3, respectively.
If the boundaries of a county fall in more than one geologic province, the county was
assigned to a zone based on the predicted radon potential of the province in which most of
the area lies. For example, if three different provinces cross through a given county, the
county was assigned to the zone representing the radon potential of the province containing
most of the county's land area. (In this case, it is not technically correct to say that the
predicted average screening level applies to the entire county since the county falls in
multiple provinces with differing radon potentials.)
Figures 3 and 4 demonstrate an example of how EPA extrapolated the county zone
designations for Nebraska from the USGS geologic province map for the State. As figure 3
shows, USGS has identified 5 geologic provinces for Nebraska. Most of the counties are
extrapolated "straight" from their corresponding provinces, but there are counties "partitioned"
by several provinces ~ for example, Lincoln County. Although Lincoln county falls in
multiple provinces, it was assigned to Zone 3 because most of its area falls in the province
with the lowest radon potential.
It is important to note that EPA's extrapolation from the province level to the
county level may mask significant "highs" and "lows" within specific counties. In other
words, within-county variations in radon potential are not shown on the Map of Radon
Zones. EPA recommends that users who may need to address specific within-county
variations in radon potential (e.g., local government officials considering the
implementation of radon-resistant construction codes) consult USGS' Geologic Radon
Province Map and the State chapters provided with this map for more detailed
information, as well as any locally available data.
Map Validation
The Map of Radon Zones is intended to represent a preliminary assessment of radon
potential for the entire United States. The factors that are used in this effort —indoor radon
data, geology, aerial radioactivity, soils, and foundation type — are basic indicators for radon
potential. It is important to note, however, that the map's county zone designations are not
"statistically valid" predictions due to the nature of the data available for these 5 factors at the
county level. In order to validate the map in light of this lack of statistical confidence, EPA
conducted a number of analyses. These analyses have helped EPA to identify the best
situations in which to apply the map, and its limitations.
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.* Figure 3
Ge o-l og'ic" Radon Potential Provinces for Nebraska
Liocola County
tliittue let
Figure 4
NEBRASKA - EPA Map of Radon Zones
Lificolo County
Zeie 1 Zoae 2 Zoic 3
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One such analysis involved comparing county zone designations to indoor radon
measurements from the StaJe/EPA Residential Radon Surveys (SRRS). Screening averages
for counties with at least 100 measurements were compared to the counties' predicted radon
potential as indicated by the Map of Radon Zones. EPA found that 72% of the county
screening averages were correctly reflected by the appropriate zone designations on the Map.
In all other cases, they only differed by 1 zone.
Another accuracy analysis used the annual average data from the National Residential
Radon Survey (NRRS). The NRRS indicated that approximately 6 million homes in the
United States have annual averages greater than or equal to 4 pCi/L. By cross checking the
county location of the approximately 5,700 homes which participated in the survey, their
radon measurements, and the zone designations for these counties, EPA found that
approximately 3.8 million homes of the 5.4 million homes with radon levels greater than or
equal to 4 pCi/L will be found in counties designated as Zone 1. A random sampling of an
equal number of counties would have only found approximately 1.8 million homes greater
than 4 pCi/L. In other words, this analysis indicated that the map approach is three times
more efficient at identifying high radon areas than random selection of zone designations.
Together, these analyses show that the approach EPA used to develop the Map of
Radon Zones is a reasonable one. In addition, the Agency's confidence is enhanced by results
of the extensive State review process -- the map generally agrees with the States' knowledge
of and experience in their own jurisdictions. However, the accuracy analyses highlight two
important points: the fact that elevated levels will be found in Zones 2 and 3, and that there
will be significant numbers of homes with lower indoor radon levels in all of the Zones. For
these reasons, users of the Map of Radon Zones need to supplement the Map with locally
available data whenever possible. Although all known "hot spots", i.e., localized areas of
consistently elevated levels, are discussed in the State-
specific chapters, accurately defining the boundaries of the "hot spots" on this scale of map is
not possible at this time. Also, unknown "hot spots" do exist.
The Map of Radon Zones is intended to be a starting point for characterizing radon
potential because our knowledge of radon sources and transport is always growing. Although
this effort represents the best data available at this time, EPA will continue to study these
parameters and others such as house construction, ventilation features and meteorology factors
in order to better characterize the presence of radon in U.S homes, especially in high risk
areas. These efforts will eventually assist EPA in refining and revising the conclusions of the
Map of Radon Zones. And although this map is most appropriately used as a targeting tool
by the aforementioned audiences » the Agency encourages all residents to test their homes
for radon, regardless of geographic location or the zone designation of the county in
which they live. Similarly, the Map of Radon Zones should not to be used in lieu of
testing during real estate transactions.
Review Process
The Map of Radon Zones has undergone extensive review within EPA and outside the
Agency. The Association of American State Geologists (AASG) played an integral role in
this review process. The AASG individual State geologists have reviewed their State-specific
information, the USGS Geologic Radon Province Map, and other materials for their geologic
content and consistency.
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. In-addition to each State geologist providing technical comments, the State radon
offices were asked to comment on their respective States' radon potential evaluations. In
particular, the States were asked to evaluate the data used to assign their counties to specific
zones. EPA and USGS worked with the States to resolve any issues concerning county zone
designations. In a few cases, States have requested changes in county zone designations. The
requests were based on additional data from the State on geology, indoor radon
measurements, population, etc. Upon reviewing the data submitted by the States, EPA did
make some changes in zone designations. These changes, which do not strictly follow the
methodology outlined in this document, are discussed in the respective State chapters.
EPA encourages the States and counties to conduct further research and data collection
efforts to refine the Map of Radon Zones. EPA would like to be kept informed of any
changes the States, counties, or others make to the maps. Updates and revisions will be
handled in a similar fashion to the way the map was developed. States should notify EPA of
any proposed changes by forwarding the changes through the Regional EPA offices that are
listed in Part H Depending on the amount of new information that is presented, EPA will
consider updating this map periodically. The State radon programs should initiate proper
notification of the appropriate State officials when the Map of Radon Zones is released and
when revisions or updates are made by the State or EPA.
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• THE USGS/EPA RADON PQTENTfAL ASSESSMENTS: AN INTRODUCTION
by
Linda C.S. Gundersen and R. Randall Schumann
U.S. Geological Survey
and
Sharon W. White
U.S. Environmental Protection Agency
BACKGROUND
The Indoor Radon Abatement Act of 1988 (15 U.S.C. 2661-2671) directed the U.S.
Environmental Protection Agency (EPA) to identify areas of the United States that have the
potential to produce harmful levels of indoor radon. These characterizations were to be based
on both geological data and on indoor radon levels in homes and other structures. The EPA
also was directed to develop model standards and techniques for new building construction
that would provide adequate prevention or mitigation of radon entry. As part of an
Interagency Agreement between the EPA and the U.S. Geological Survey (USGS), the USGS
has prepared radon potential estimates for the United States. This report is one of ten
booklets that document this effort. The purpose and intended use of these reports is to help
identify areas where states can target their radon program resources, to provide guidance in
selecting the most appropriate building code options for areas, and to provide general
information on radon and geology for each state for federal, state, and municipal officials
dealing with radon issues. These reports are not intended to be used as a substitute for
indoor radon testing, and they cannot and should not be used to estimate or predict the
indoor radon concentrations of individual homes, building sites, or housing tracts. Elevated
levels of indoor radon have been found in every State, and EPA recommends that all homes
be tested for indoor radon.
Booklets detailing the radon potential assessment for the U.S. have been developed for
each State. USGS geologists are the authors of the geologic radon potential booklets. Each
booklet consists of several components, the first being an overview to the mapping project
(Part I), this introduction to the USGS assessment (Part II), including a general discussion of
radon (occurrence, transport, etc.), and details concerning the types of data used. The third
component is a summary chapter outlining the general geology and geologic radon potential
of the EPA Region (Part III). The fourth component is an individual chapter for each state
(Part IV). Each state chapter discusses the state's specific geographic setting, soils, geologic
setting, geologic radon potential, indoor radon data, and a summary outlining the radon
potential rankings of geologic areas in the state. A variety of maps are presented in each
chapter—geologic, geographic, population, soils, aerial radioactivity, and indoor radon data by
county. Finally, the booklets contain EPA's map of radon zones for each state and an
accompanying description (Part V).
Because of constraints on the scales of maps presented in these reports and because the
smallest units used to present the indoor radon data are counties, some generalizations have
been made in order to estimate the radon potential of each area. Variations in geology, soil
characteristics, climatic factors, homeowner lifestyles, and other factors that influence radon
concentrations can be quite large within any particular geologic area, so these reports cannot
be used to estimate or predict the indoor radon concentrations of individual homes or housing
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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 (~:Rn) is produced from the radioactive decay of radium (~6Ra), which is, in turn,
a product of the decay of uranium P8U) (fig. 1). The half-life of :"Rn is 3.825 days. Other
isotopes of radon occur naturally, but, with the exception of thoron ("°Rn), which occurs in
concentrations high enough to be of concern in a few localized areas, they are less important
in terms of indoor radon risk because of their extremely short half-lives and less common
occurrence. In general, the concentration and mobility of radon in soil are dependent on
several factors, the most important of which are the soil's radium content and distribution,
porosity, permeability to gas movement, and moisture content. These characteristics are, in
turn, determined by the soil's parent-material composition, climate, and the soil's age or
maturity. If parent-material composition, climate, vegetation, age of the soil, and topography
are known, the physical and chemical properties of a soil in a given area can be predicted.
As soils form, they develop distinct layers, or horizons, that are cumulatively called the
soil profile. The A horizon is a surface or near-surface horizon containing a relative
abundance of organic matter but dominated by mineral matter. Some soils contain an E
horizon, directly below the A horizon, that is generally characterized by loss of clays, iron, or
aluminum, and has a characteristically lighter color than the A horizon. The B horizon
underlies the A or E horizon. Important characteristics of B horizons include accumulation of
clays, iron oxides, calcium carbonate or other soluble salts, and organic matter complexes. In
drier environments, a horizon may exist within or below the B horizon that is dominated by
calcium carbonate, often called caliche or calcrete. This carbonate-cemented horizon is
designated the K horizon in modern soil classification schemes. The C horizon underlies the
B (or K) and is a zone of weathered parent material that does not exhibit characteristics of A
or B horizons; that is, it is generally not a zone of leaching or accumulation. In soils formed
in place from the underlying bedrock, the C horizon is a zone of unconsolidated, weathered
bedrock overlying the unweathered bedrock.
The shape and orientation of soil particles (soil structure) control permeability and affect
water movement in the soil. Soils with blocky or granular structure have roughly equivalent
permeabilities in the horizontal and vertical directions, and air and water can infiltrate the soil
relatively easily. However, in soils with platy structure, horizontal permeability is much
greater than vertical permeability, and air and moisture infiltration is generally slow. Soils
with prismatic or columnar structure have dominantly vertical permeability. Platy and
prismatic structures form in soils with high clay contents. In soils with shrink-swell clays, air
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and moisture infiltration.-rates and depth of wetting may be limited when the cracks in the
surface soil layers swell shut. Clay-rich B horizons, particularly those with massive or platy
structure, can form a capping layer that impedes the escape of soil gas to the surface
(Schumann and others, 1992). However, the shrinkage of clays can act to open or widen
cracks upon drying, thus increasing the soil's permeability to gas flow during drier periods.
Radon transport in soils occurs by two processes: (1) diffusion and (2) flow (Tanner,
1964). Diffusion is the process whereby radon atoms move from areas of higher
concentration to areas of lower concentration in response to a concentration gradient. Flow is
the process by which soil air moves through soil pores in response to differences in pressure
within the soil or between the soil and the atmosphere, carrying the radon atoms along with it.
Diffusion is the dominant radon transport process in soils of low permeability, whereas flow
tends to dominate in highly permeable soils (Sextro and others, 1987). In low-permeability
soils, much of the radon may decay before it is able to enter a building because its transport
rate is reduced. Conversely, highly permeable soils, even those that are relatively low in
radium, such as those derived from some types of glacial deposits, have been associated with
high indoor radon levels in Europe and in the northern United States (Akerblom and others,
1984; Kunz and others, 1989; Sextro and others, 1987). In areas of karst topography formed
in carbonate rock (limestone or dolomite) environments, solution cavities and fissures can
increase soil permeability at depth by providing additional pathways for gas flow.
Not all radium contained in soil grains and grain coatings will result in mobile radon
when the radium decays. Depending on where the radium is distributed in the soil, many of
the radon atoms may remain imbedded in the soil grain containing the parent radium atom, or
become imbedded in adjacent soil grains. The portion of radium that releases radon into the
pores and fractures of rocks and soils is called the emanating fraction. When a radium atom
decays to radon, the energy generated is strong enough to send the radon atom a distance of
about 40 nanometers (1 nm = 10'" meters), or about 2x10"* inches—this is known as alpha
recoil (Tanner, 1980). Moisture in the soil lessens the chance of a recoiling radon atom
becoming imbedded in an adjacent grain. Because water is more dense than air, a radon atom
will travel a shorter distance in a water-filled pore than in an air-filled pore, thus increasing
the likelihood that the radon atom will remain in the pore space. Intermediate moisture levels
enhance radon emanation but do not significantly affect permeability. However, high
moisture levels can significantly decrease the gas permeability of the soil and impede radon
movement through the soil.
Concentrations of radon in soils are generally many times higher than those inside 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
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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 into cracks and solution cavities in the rock and soil, and
ultimately, into homes (Gammage and others, 1993). . .
RADON ENTRY INTO BUILDINGS
A driving force (reduced atmospheric pressure in the house relative to the soil, producing
a pressure gradient) and entry points must exist for radon to enter a building from the soil.
The negative pressure caused by furnace combustion, ventilation devices, and the stack effect
(the rising and escape of warm air from the upper floors of the building, causing a
temperature and pressure gradient within the structure) during cold winter months are
common driving forces. Cracks and other penetrations through building foundations, sump
holes, and slab-to-foundation wall joints are common entry points.
Radon levels in the basement are generally higher than those on the main floor or upper
floors of most structures. Homes with basements generally provide more entry points for
radon, commonly have a more pronounced stack effect, and typically have lower air pressure
relative to the surrounding soil than nonbasement homes. The term "nonbasement" applies to
slab-on-grade or crawl space construction.
METHODS AND SOURCES OF DATA
The assessments of radon potential in the booklets that follow this introduction were
made using five main types of data: (1) geologic (lithologic); (2) aerial radiometric; (3) soil
characteristics, including soil moisture, permeability, and drainage characteristics; (4) indoor
radon data; and (5) building architecture (specifically, whether homes in each area are built
slab-on-grade or have a basement or crawl space). These five factors were evaluated and
integrated to produce estimates of radon potential. Field measurements of soil-gas radon or
soil radioactivity were not used except-where such data were available in existing, published
reports of local field studies. Where applicable, such field studies are described in the
individual state chapters.
i
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
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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).
NUKE 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 (2UBi), 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 (Kovach, 1945; Klusman and Jaacks, 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 NUKE AERIAL SURVEYS
2 KM (1 VILE)
5 KM (3 MILES)
2 t 5 k'M
E3 10 EM (6 UILES)
5 I- 10 IV
NO DATA
Figure 2. Nominal flightline spacings for NURE aerial gamma-ray surveys covering the
contiguous United States (fromDuval and others, 1990). Rectangles represent I°x2° quadrangles.
-------
" » , • • fc
" Figure 2 is an index, map.of NURE 1° x 2° quadrangles showing the flight-line spacing
for each quadrangle. In general, the more closely spaced the flightlines are, the more area
was covered by the aerial gamma survey, and thus, more detail is available in the data set.
For an altitude of 400 ft abov* the group'' surface ?"H 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
-------
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
"re referred to as "permeability" in SCS soil survey* 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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" Data for only those .counties with five or more measurements are shown in the indoor
radon maps in the state chapters, although data for all counties with a nonzero number of
measurements are listed in the indoor radon data tables in each state chapter. In total, indoor
radon data from more than 100,000 homes nationwide were used in the compilation of these
assessments. Radon data from State or regional indoor radon surveys, public health
organizations, or other sources are discussed in addition to the primary data sources where
they are available. Nearly all of the data used in these evaluations represent short-term (2-7
day) screening measurements from the lowest livable space of the homes. Specific details
concerning the nature and use of indoor radon data sets other than the State/EPA Residential
Radon Survey are discussed in the individual State chapters.
RADON INDEX AND CONFIDENCE INDEX
Many of the geologic methods used to evaluate an area for radon potential require
subjective opinions based on the professional judgment and experience of the individual
geologist. The evaluations are nevertheless based on established scientific principles that are
universally applicable to any geographic area or geologic setting. This section describes the
methods and conceptual framework used by the U.S. Geological Survey to evaluate areas for
radon potential based on the five factors discussed in the previous sections. The scheme is
divided into two basic parts, a Radon Index (RI), used to rank the general radon potential of
the area, and the Confidence Index (CI), used to express the level of confidence in the
prediction based on the quantity and quality of the data used to make the determination. This
scheme works best if the areas to be evaluated are delineated by geologically-based
boundaries (geologic provinces) rather than political ones (state/county boundaries) in which
the geology may vary across the area.
Ration Index. Table 1 presents the Radon Index (RI) matrix. The five factors—indoor
radon data, geology, aerial radioactivity, soil parameters, and house foundation type—were
quantitatively ranked (using a point value of 1, 2, or 3) for their respective contribution to
radon potential in a given area. At least some data for the 5 factors are consistently available
for every geologic province. Because each of these main factors encompass a wide variety of
complex and variable components, the geologists performing the evaluation relied heavily on
their professional judgment and experience in assigning point values to each category and in
determining the overall radon potential ranking. Background information on these factors is
discussed in more detail in the preceding sections of this introduction.
Indoor radon was evaluated using unweighted arithmetic means of the indoor radon data
for each geologic area to be assessed. Other expressions of indoor radon levels in an area
also could have been used, such as weighted averages or annual averages, but these types of
data were not consistently available for the entire United States at the time of this writing, or
the schemes were not considered sufficient to provide a means of consistent comparison
across all areas. For this report, charcoal-canister screening measurement data from the
State/EPA Residential Radon Surveys and other carefully selected sources were used, as
described in the preceding section. To maintain consistency, other indoor radon data sets
(vendor, state, or other data) were not considered in scoring the indoor radon factor of the
Radon Index if they were not randomly sampled or could not be statistically combined with
the primary indoor radon data sets. However, these additional radon data sets can provide a
means to further refine correlations between geologic factors and radon potential, so they are
II-ll Reprinted from USGS Open-File Report 93-292
-------
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.
FACTOR
INDOOR RADON (average)
AERIAL RADIO ACTIVITY
GEOLOGY*
SOIL PERMEABILITY
ARCHITECTURE TYPE
INCREASING RADON POTENTIAL ^
POINT VALUE
1
<2pCi/L
< 1.5 ppm eU
negative
low
mostly slab
2
2-4pCi/L
1.5 - 2.5 ppm eU
variable
moderate
mixed
3
>4pCi/L
> 2.5 ppm eU
positive
high
mostly basement
'GEOLOGIC FIELD EVIDENCE (GFE) POINTS: GFE points are assigned in addition to points
for the "Geology" factor for specific, relevant geologic field studies. See text for details.
Geologic evidence supporting:
HIGH radon
MODERATE
LOW
No relevant geologic field studies
+2 points
+1 point
-2 points
0 points
SCORING:
Radon potential category
Probable average screening
Point range indoor radon for area
LOW
MODERATE/VARIABLE
HIGH
3-8 points
9-11 points
12-17 points
<2pCi/L
2-4pCi/L
>4pO/L
POSSIBLE RANGE OF POINTS = 3 to 17
TABLE 2. CONFIDENCE INDEX MATRIX
INCREASING CONFIDENCE
FACTOR
POINT VALUE
1
INDOOR RADON DATA
sparse/no data
fair coverage/quality
good coverage/quality
AERIAL RADIOACTIVITY
questionable/no data
glacial cover
no glacial cover
GEOLOGIC DATA
questionable
variable
proven geol. model
SOIL PERMEABILITY
questionable/no data
variable
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
n-12 Reprinted from USGS Open-Hie 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 a.ea was greater than 4 pCi/L, the indoor
radon factor was assigned 3 RI points.
Aerial radioactivity data used in this report are from the equivalent uranium map of the
conterminous United States compiled from NURE aerial gamma-ray surveys (Duval and
others, 1989). These data indicate the gamma radioactivity from approximately the upper 30
cm of rock and soil, expressed in units of ppm equivalent uranium. An approximate average
value of eU was determined visually for each area and point values assigned based on
whether the overall eU for the area falls below 1.5 ppm (1 point), between 1.5 and 2.5 ppm
(2 points), or greater than 2.5 ppm (3 points).
The geology factor is complex and actually incorporates many geologic characteristics. In
the matrix, "positive" and "negative" refer to the presence or absence and distribution of rock
types known to have high uranium contents and to generate elevated radon in soils or indoors.
Examples of "positive" rock types include granites, black shales, phosphatic rocks, and other
rock types described in the preceding "geologic data" section. Examples of "negative" rock
types include marine quartz sands and some clays. The term "variable" indicates that the
geology within the region is variable or that the rock types in the area are known or suspected
to generate elevated radon in some areas but not in others due to compositional differences,
climatic effects, localizeddistribution of uranium, or other factors. Geologic information
indicates not only how much uranium is present in the rocks and soils but also gives clues for
predicting general radon emanation and mobility characteristics through additional factors
such as structure (notably the presence of faults or shears) and geochemical characteristics
(for example, a phosphate-rich sandstone will likely contain more uranium than a sandstone
containing little or no phosphate because the phosphate forms chemical complexes with
uranium). "Negative", "variable", and "positive" geology were assigned 1, 2, and 3 points,
respectively.
In cases where additional reinforcing or contradictory geologic evidence is available,
Geologic Field Evidence (GFE) points were added to or subtracted from an area's score
(Table 1). Relevant geologic field studies are important to enhancing our understanding of
how geologic processes affect radon distribution. In some cases, geologic models and
supporting field data reinforced an already strong (high or low) score; in others, they provided
important contradictory data. GFE points were applied for geologically-sound evidence that
supports the prediction (but which may contradict one or more factors) on the basis of known
geologic field studies in the area 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 all6w 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 sco'red on the basis of
the quality and quantity of the data used to complete the RI matrix.
Indoor radon data were evaluated based on the distribution and number of data points and
on whether the data were collected by random sampling (State/EPA Residential Radon Survey
or other state survey data) or volunteered vendor data (likely to be nonrandom and biased
toward population centers and/or high indoor radon levels). The categories listed in the CI
matrix for indoor radon data ("sparse or no data", "fair coverage or quality", and "good
coverage/quality") indicate the sampling density and statistical robustness of an indoor radon
data set. Data from the State/EPA Residential Radon Survey and statistically valid state
surveys were typically assigned 3 Confidence Index points unless the data were poorly
distributed or absent in the area evaluated.
Aerial radioactivity data are available for all but a few areas of the continental United
States and for part of Alaska. An evaluation of the quality of the radioactivity data was based
on whether there appeared to be a good correlation between the radioactivity and the actual
amount of uranium or radium available to generate mobile radon in the rocks and soils of the
area evaluated. In general, the greatest problems with correlations among eU, geology, and
soil-gas or indoor radon levels were associated with glacial deposits (see the discussion in a
previous section) and typically were assigned a 2-point Confidence Index score. Correlations
among eU, geology, and radon were generally sound in unglaciated areas and were usually
assigned 3 CI points. Again, however, radioactivity data in some unglaciated areas may have
been assigned fewer than 3 points, and in glaciated areas may be assigned only one point, if
the data were considered questionable or if coverage was poor.
To assign Confidence Index scores for the geologic data factor, rock types and geologic
settings for which a physical-chemical, process-based understanding of radon generation and
mobility exists were regarded as having "proven geologic models" (3 points); a high
confidence could be held for predictions in such areas. Rocks for which the processes are
less well known or for which data are contradictory were regarded as "variable" (2 points),
and those about which little is known or for which no apparent correlations have been found
were deemed "questionable" (1 point).
The soil permeability factor was also scored based on quality and amount of data. The
three categories for soil permeability in the Confidence Index are similar in concept, and
scored similarly, to those for the geologic data factor. Soil permeability can be roughly
estimated from grain size and drainage class if data from standard, accepted soil percolation
tests are unavailable; however, the reliability of the data would be lower than if percolation
test figures or other measured permeability data are available, because an estimate of this type
does not encompass all the factors that affect soil permeability and thus may be inaccurate in
some instances. Most published soil permeability data are for water; although this is
generally closely related to the air permeability of the soil, there are some instances when it
may provide an incorrect estimate. Examples of areas in which water permeability data may
not accurately reflect air permeability include areas with consistently high levels of soil
moisture, or clay-rich soils, which would have a low water permeability but may have a
II-15 Reprinted from USGS Open-File Report 93-292
-------
significantly higher air permeability when dry due to shrinkage cfacks 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 scored
The Radon Index and Confidence Index give a peneral indication of the reHtive
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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1 . • •
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concentration, and radon in soil gas, Fairfax County, Virginia: U.S. Geological Survey
Open-File Report 88-18,28 p.
Schumann, R.R., and Gundersen, L.C.S., 1991, Regional differences in radon emanation
coefficients in soils: Geological Society of America Abstracts With Programs, v. 23,
no. 1, p. 125.
Schumann, R.R., Peake, R.T., Schmidt, K.M., and Owen, D.E., 1991, Correlations of soil-gas
and indoor radon with geology in glacially derived soils of the northern Great Plains, in
Proceedings of the 1990 International Symposium on Radon and Radon Reduction
Technology, Volume 2, Symposium Oral Papers: U.S. Environmental Protection Agency
report EPA/600/9-91/026b, p. 6-23-6-36.
11-18 Reprinted from USGS Open-File Report 93-292
-------
Schumann, R.R., Owen, P.E., and Asher-Bolinder, S., 1992, Effects of weather and soil
characteristics on temporal variations in soil-gas radon concentrations, m Gates, A.E., and
" Gundersen, L.CS., eds., Geologic controls on radon: Geological Society of America
Special Paper 271, p. 65-72.
Sextro,TLG., Moed, B.A.,T*azaroff, W.W., Revzan, K.L., and Nero, A.V., 1987,
Investigations of soil as a source of indoor radon, in Hppke, P.K., ed., Radon and its
decay products: American Chemical Society Symposium Series 331, p. 10-29.
Sterling, R., Meixel, G., Shen, L., Labs, K., and Bligh, T., 1985, Assessment of the energy
savings potential of building foundations research: Oak Ridge, Tenn., U.S. Department of
Energy Report ORNL/SUB/84-0024/1.
Smith, R.C., H, Reilly, M.A., Rose, A.W., Barnes, J.H., and Berkheiser, S.W., Jr., 1987,
Radon: a profound case: Pennsylvania Geology, v. 18, p. 1-7.
Tanner, A.B., 1964, Radon migration in the ground: a review, in Adams, J.A.S., and Lowder,
W.M., eds., The natural radiation environment: Chicago, HI., University of Chicago
Press, p. 161-190.
Tanner, A.B., 1980, Radon migration in the ground: a supplementary review, in Gesell, T.F.,
and Lowder, W.M. (eds), Natural radiation environment HI, Symposium proceedings,
Houston, Texas, v. 1, p. 5-56.
U.S. Department of Agriculture, 1987, Principal 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.
U-19 Reprinted from USGS Open-File Report 93-292
-------
. APPENDIX A
GEOLOGIC TIME SCALE
Subdivisions (and their symbols)
Eon or
Eonothem
Phineroioic2
Protero:o!c
(el
Archean
(A)
Era or
Erathem
Cenoioic 2
(CD
Mesozoic3
(Md
Paleozoic2
(Pi)
uw
MxiSI*
*J£Sena
Uu
fcarty
Period, System,
Subperiod. Subsystem
Quaternary 2
(Q)
Neogene 2
Subperiod or
T.-:.T Subsystem (N)
m Paieooene
11 Subpenodor
Subsysttm (Pi)
Cretaceous
(K)
Jurassic
-------
• -,'..-• APPENDIX B
GLOSSARY OF TERMS
Units of measure
pCi/L (picocuries per liter)- a unit of measure of radioactivity used to describe radon
concentrations in a volume of air. One picocurie (1(H2 curies) is equal to about 2.2 disintegrations
of radon atoms per minute. A liter is about 1.06 quarts. The average concentration of radon in
U.S. homes measured to date is between 1 and 2 pCi/L.
Bq/m3 (Becquerels per cubic meter)- a metric unit of radioactivity used to describe radon
concentrations in a volume of air. One becquerel is equal to one radioactive disintegration per
second. One pCi/L is equal to 37 Bq/m3.
ppm (parts per million)- a unit of measure of concentration by weight of an element in a
substance, 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.
n-21 Reprinted from USGS Open-File Report 93-292
-------
argiilite, argillaceous Terms referring to a rock derived from clay or shale; or any sedimentary
rock containing an appreciable amount of clay-size material, ie., argillaceous sandstone.
arid Term describing a climate characterized by dryness, or an evaporation rate that exceeds the
amount of precipitation.
basalt A general term for a dark-colored mafic igneous rocks that may be of extrusive origin,
such as volcanic basalt flows, or intrusive origin, such as basalt dikes.
batholith A mass of plutonic igneous rock that has more than 40 square miles of surface
exposure and no known bottom.
carbonate A sedimentary rock consisting of the carbonate (COs) compounds of calcium,
magnesium, or iron, e.g. limestone and dolomite.
carbonaceous Said of a rock or sediment that is rich in carbon, is coaly, or contains organic
matter.
charcoal canister A passive radon measurement device consisting of a small container of
granulated activated charcoal that is designed to adsorb radon. Useful for short duration (2-7 days)
measurements only. May be referred to as a "screening" test
chert A hard, extremely dense sedimentary rock consisting dominantiy 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.
day A rock containing clay mineral fragments or material of any composition having a diameter
less than 1/256 mm.
clay mineral One of a complex and loosely defined group of finely crystalline minerals made up
of water, silicate and aluminum (and a wide variety of other elements). They are formed chiefly by
alteration or weathering of primary silicate minerals. Certain clay minerals are noted for their small
size and ability to absorb substantial amounts of water, causing them to swell. The change in size
that occurs as these clays change between dry and wet is referred to as their "shrink-swell"
potential.
concretion A hard, compact mass of mineral matter, normally subspherical but commonly
irregular in shape; formed by precipitation from a water solution about a nucleus or center, such as
a leaf, shell, bone, or fossil, within a sedimentary or fractured rock.
conglomerate A coarse-grained, clastic sedimentary rock composed of rock and mineral
fragments larger than 2 mm, set in a finer-grained matrix of clastic material.
cuesta A hill or ridge with a gentle slope on one side and a steep slope on the other. The
formation of a cuesta is controlled by the different weathering properties and the structural dip of
the rocks forming the hill or ridge.
daughter product A nuclide formed by the disintegration of a radioactive precursor or "parent"
atom.
11-22 Reprinted from USGS Open-Hie 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 man 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
), 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 man 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 ','piacer deposit" 'Some heavy minerals are magnetite, garnet, zircon,
monazitc, and xenotime.4
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 diviaed, 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".
karne A low mound, knob, hummock, or short irregular ridge formed by a glacial stream at the
margin of a melting glacier; composed of bedded sand and gravel.
karst terrain A type of topography that is formed on limestone, gypsum and other rocks by
dissolution of the rock by water, forming sinkholes and caves.
lignite A brownish-black coal that is intermediate in coalification between peat and
subbituminous coal.
limestone A carbonate sedimentary rock consisting of more than 50% calcium carbonate,
primarily in the form of the mineral calcite (CaCOa).
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
Phylfite, schist, amphibolite, and gneiss are metamorphic rocks.
moraine A mound, ridge, or other distinct accumulation of unsorted, imbedded glacial material,
predominantly till, deposited by the action of glacial ice.
outcrop That part of a geologic formation or structure that appears at the surface of the Earth, as
in "rock outcrop".
percolation test A term used in engineering for a test to determine the water permeability of a
soil. A hole is dug and filled with water and the rate of water level decline is measured.
permeability The capacity of a rock, sediment, or soil to transmit liquid or gas.
phosphate, phosphatic, phosphorite Any rock or sediment containing a significant amount
of phosphate minerals, ie., minerals containing PO4.
• .
n-24 Reprinted from USGS Open-Hie Report 93-292
-------
physiographic province A region in which* all parts are similar in geologic* structure and
climate, which has had a uniform geomorphic history, and whose topography or landforms differ
significantly from adjacent regions.
placer deposit See heavy minerals
residual Formed by weathering of a material in place.
residuum Deposit of residual material.
rhyolite An extrusive igneous rock of volcanic origin, compqsitionally equivalent to granite.
sandstone A clastic sedimentary rock composed of sand-sized rock and mineral material that is
more or less firmly cemented. Sand particles range from 1/16 to 2 mm in size.
schist A strongly foliated crystalline rock, formed by metamorphism, that can be readily split into
thin flakes or slabs. Contains mica; minerals are typically aligned.
screening level Result of an indoor radon test taken with a charcoal canister or similar device,
for a short period of time, usually less than seven days. May indicate the potential for an indoor
radon problem but does not indicate annual exposure to radon.
sediment Deposits of rock and mineral particles or fragments originating from material that is
transported by air, water or ice, or that accumulate by natural chemical precipitation or secretion of
organisms.
semiarid Refers to a climate that has slightly more precipitation than an arid climate.
shale A fine-grained sedimentary rock formed from solidification (lithification) of clay or mud.
shear zone Refers to a roughly linear zone of rock that has been faulted by ductile or non-ductile
processes in which the rock is sheared and both sides are displaced relative to one another.
shrink-swell clay See clay mineral.
siltstone A fine-grained clastic sedimentary rock composed of silt-sized rock and mineral
material and more or less firmly cemented. Silt particles range from 1/16 to 1/256 mm in size.
sinkhole A roughly circular depression in a karst area measuring meters to tens of meters in
diameter. It is funnel shaped and is formed by collapse of the surface material into an underlying
void created by the dissolution of carbonate rock.
slope An inclined part of the earth's surface.
solution cavity A hole, channel or cave-like cavity formed by dissolution of rock.
stratigraphy The study of rock strata; also refers to the succession of rocks of a particular area.
surficial materials Unconsolidated glacial, wind-, or waterborne deposits occurring on the
earth's surface.
tablelands General term for a broad, elevated region with a nearly level surface of considerable
extent . '
11-25 Reprinted from USGS Open-File Report 93-292
-------
• •
terrace gravel Gravel-sized material that caps ridges and terraces, left behind by a stream as it
cuts down to a lower level.
terrain A tract or region of the Earth's surface considered as a physical feature or an ecological
environment
till Unsorted, generally unconsolidated and imbedded 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.
n-26 Reprinted from USGS Open-File Report 93-292
-------
APPENDIX C
EPA REGIONAL OFFICES
EPA Regional Offices
State
F.PA
EPA Region 1
JFK Federal Building
Boston, MA 02203
(617) 565-4502
EPA Region 2
(2A1R:RAD)
26 Federal Plaza
New York, NY 10278
(212) 264-4110
Region 3 (3AH14)
841 Chestnut Street
Philadelphia, PA 19107
(215) 597-8326
EPA Region 4
345 Courtland Street, N.E.
Atlanta, GA 30365
(404) 347-3907
EPA Region 5 (5AR26)
77 West Jackson Blvd.
Chicago, IL 60604-3507 '
(312) 886-6175
EPA Region 6 (6T-AS)
1445 Ross Avenue
Dallas, TX 75202-2733
(214) 655-7224
EPA Region 7
726 Minnesota Avenue
Kansas City, KS 66101
(913) 551-7604
EPA Region 8
(8HWM-RP)
999 18th Street
One Denver Place, Suite 1300
Denver, CO 80202-2413
(303) 293-1713
EPA Region 9 (A-3)
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-1048
EPA Region 10
1200 Sixth Avenue
Seattle. WA 98101
(202) 442-7660
Alabama.... 4
Alaska 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
Dlinois 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 4 6
Utah ...8
Vermont 1
Virginia ..3
Washington 10
West Virginia ; 3
Wisconsin 5
Wyoming 8
H-27
Reprinted from USGS Open-File Report 93-292
-------
STATE RADON CONTACTS
May, 1993
Alabama James McNees
Division of Radiation Control
Alabama Department of Public Health
State Office Building
Montgomery, AL 36130
(205)242-5315
1-800-582-1866 in state
Charles Tedford
Department of Health and Social
Services
P.O. Box 110613
Juneau,AK 99811-0613
(907)465-3019
l-8(XM78-4845 in state
Arizona John Stewart
Arizona Radiation Regulatory Agency
4814 South 40th St
Phoenix, AZ 85040
(602)255-4845
Arkansas LeeGershner
Division of Radiation Control
Department of Health
4815 Markham Street, Slot 30
Little Rock, AR 72205-3867
(501)661-2301
California J. David Quinton
Department of Health Services
714 P Street, Room 600
Sacramento, CA 94234-7320
(916) 324-2208
1-800-745-7236 in state
Colorado Linda Martin
Department of Health
4210 East llth Avenue
Denver, CO 80220
(303)692-3057
1-800-846-3986 in state
Connecticut Alan J. Siniscalchi
Radon Program
Connecticut Department of Health
Services
150 Washington Street
Hartford, CT 06106-4474
(203)566-3122
Delaware MaraiG. Rejai
Office of Radiation Control
Division of Public Health
P.O. Box 637
Dover, DE 19903
(302)736-3028
1-800-554-4636 Li State
District Robert Davis
of Columbia DC Department of Consumer and
Regulatory Affairs
614 H Street NW
Room 1014
Washington, DC 20001
(202)727-71068
Florida N. Michael Gilley
Office of Radiation Control
Department of Health and
Rehabilitative Services
1317 Winewood Boulevard
Tallahassee, FL 32399-0700
(904)488-1525
1-800-543-8279 in state
Richard Schreiber
Georgia Department of Human
Resources
878 Peachtree St., Room 100
Atlanta, GA 30309
(404) 894-6644
1-800-745-0037 in state
Hawaii Russell Takata
Environmental Health Services
Division
591 Ala Moana Boulevard
Honolulu, HI 96813-2498
(808)5864700
II-28 Reprinted from USGS Open-File Report 93-292
-------
Illinois
Indiana
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 Allan
Illinois Department of Nuclear Safety
1301 Outer Park Drive
Springfield, IL 62704
(217)524-5614
1-800-325-1245 in state
Lorand Magyar
Radiological Health Section
Indiana State Department of Health
1330 West Michigan Street
P.O. Box 1964
Indianapolis, IN 46206
(317) 633-8563
1-800-272-9723 In State
Donald A. Plater
Bureau of Radiological Health
Iowa Department of Public Health
Lucas State Office Building
Des Moines, IA 50319-0075
(515)281-3478
1-800-383-5992 In State
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 BpbStilwell
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 LeonJ.Rachuba
Radiological Health Program
Maryland Department of die
Environment
2500 Broening Highway
Baltimore, MD 21224
(410)631-3301
1-800-872-3666 In State
Massachusetts William J. Bell
Radiation Control Program
Department of Public Health
23 Service Center
Northampton, MA 01060
(413) 586-7525
1-800-445-1255 in state
Michigan SueHendershott
Division of Radiological Health
Bureau of Environmental and
Occupational Health
3423 North Logan Street
P.O. Box 30195
Lansing, MI 48909
(517)335-8194
Minnesota Laura Oatmann
Indoor Air Quality Unit
925 Delaware Street, SE
P.O. Box 59040
Minneapolis, MN 55459-0040
(612)627-5480
1-800-798-9050 in state
n-29 Reprinted from USGS Open-File Report 93-292
-------
Mississippi -Silas Anderson ' •
Division of Radiological Health
Department of Health
3150 Lawson Street
P.O. Box 1700
Jackson, MS 39215-1700
(601)354-6657
1-800-626-7739 in state
Kenneth V.' Miller
Bureau of Radiological Health
Missouri Department of Health
1730 East Elm
P.O. Box 570
Jefferson City, MO 65102
(314)751-6083
1-800-669-7236 In State
Montana Adrian C. Howe
Occupational Health Bureau
Montana Department of Health and
Environmental Sciences
Cogswell Building A113
Helena, MT 59620
(406)444-3671
Nebraska Joseph Milone
Division of Radiological Health
Nebraska Department of Health
301 Centennial Mall, South
P.O. Box 95007
Lincoln, NE 68509
(402)471-2168
1-800-334-9491 In State
Nevada Stan Marshall
Department of Human Resources
505 East King Street
Room 203
Carson City, NV 89710
(702)687-5394
New Hampshire David Chase
Bureau of Radiological Health
Division of Public Health Services
Health and Welfare Building
Six Hazen Drive
Concord, NH 03301
(603)271-4674
1-800-852-3345 x4674
New Jersey Tonalee Carlson Key
Division of Environmental Quality
Department of Environmental
Protection
CN415
Trenton, NJ 08625-0145
(609)987-6369
1-800-648-0394 in state
New Mexico William M Floyd
Radiation Licensing and Registration
Section
New Mexico Environmental
Improvement Division
1190 St. Francis Drive
Santa Fe,NM 87503
(505)827-4300
NewYoik William J. Condon •
Bureau of Environmental Radiation
Protection
New York State Health Department
Two University Place
Albany, NY 12202
(518)458-6495
1-800-458-1158 in state
North Carolina Dr. Felix Fong
Radiation Protection Division
Department of Environmental Health
and Natural Resources
701 Barbour Drive
Raleigh, NC 27603-2008
(919) 571-4141
1-800-662-7301 (recorded info x4196)
North Dakota Alien Jacobson
North Dakota Department of Health
1200 Missouri Avenue, Room 304
P.O. Box 5520
Bismarck, ND 58502-5520
(701)221-5188
Ohio Marcie Matthews
Radiological Health Program
Department of Health
1224 Kinnear Road - Suite 120
Columbus, OH 43212
(614)644-2727
1-800-523-4439 in state
U-30 Reprinted from USGS Open-File Report 93-292
-------
Oklahoma
Oregon
Pennsylvania
Puerto Rico
Rhode Island
South Carolina
. Gene Smith > •
Radiation Protection Division
Oklahoma State Department of
Health
P.O. Box 53551
Oklahoma City, OK 73152
(405)271-5221
George Toombs
Department of Human Resources
Health Division
1400 SW 5th Avenue
Portland, OR 97201
(503)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 MikePochop
Division of Environment Regulation
Department of Water and Natural
Resources
Joe Fc.. Building, Room 217
523 E. Capitol
Pierre, SD 57501-3181
(605)773-3351
r
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 Hultqiiist
Bureau of Radiation Control
Utah State Department of Health
288 North, 1460 West
P.O. Box 16690
Salt Lake City, UT 84116-0690
(801)536-4250
Vermont Paul demons
Occupational and Radiological Health
Division
Vermont Department of Health
10 Baldwin Street
Montpelier.VT 05602
(802) 828-2886
1-800-640-0601 in state
Virgin Islands Contact the U.S. Environmental
Protection Agency, Region JJ
in New York
(212)264-4110
n-31 Reprinted from USGS Open-File Report 93-292
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Virginia • Shelly Ottenbrite • •
Bureau of Radiological Health
Department of Health
109 Governor Street
Richmond, VA 23219
(804)786-5932
1-800-468-0138 in state
Washington KateColeman
Department of Health
Office of Radiation Protection
Airdustrial Building 5, LE-13
01ympia,WA 98504
(206)753-4518
1-800-323-9727 In State
West Virginia Beanie L.DeBprd
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)267^796
1-800-798-9050 in state
Wyoming Janet Hough
Wyoming Department of Health and
Social Services
Hathway Building, 4th Floor
Cheyenne, WY 82002-0710
(307)777-6015
1-800-458-5847 in state
n-32 Reprinted from USGS Open-File Report 93-292
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STATE GEOLOGICAL SURVEYS
May, 1993
Alabama Ernest A. Mancini
Geological Survey of Alabama
P.O. Box 0
420 Hackbeny 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
Cojojadfl 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, DE19716-7501
(302)831-2833
Uaho.
Walter Schmidt
Florida Geological Survey
903 W. Tennessee St.
Tallahassee, FL 32304-7700
(904)488-4191
William H. McLemore
Georgia Geologic Survey
Rm. 400
19 Martin Luther King Jr. Dr. SW
Atlanta, GA 30334
(404)656-3214
Manabu Tagomori
Dept of Land and Natural Resources
Division of Water & Land Mgt
P.O. Box 373
Honolulu, HI 96809
(808)548-7539
Earl H. Bennett
Idaho Geological Survey
University of Idaho
Morrill Hall, Rm. 332
Moscow, ID 83843
(208) 885-7991
fllinojs Morris W.Leighton
• Illinois State Geological Survey
Natural Resources Building
615 East Peabody Dr.
Champaign, IL 61820
(217)333-4747
Norman C. Hester
Indiana Geological Survey
611 North Walnut Grove
Bloomington, IN 47405
(812)855-9350
Donald L. Koch
Iowa Department of Natural Resources
Geological Survey Bureau
109 Trowbridge Hall
Iowa City, IA 52242-1319
(319)335-1575
Lee C.Gerhard
Kansas Geological Survey
1930 Constant Ave., West Campus
University of Kansas
Lawrence, KS 66047
(913)864-3965
n-33 Reprinted from USGS Open-File Report 93-292
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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 SL 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 Ave.
SL Paul, MN 55114-1057
(612)627-4780
Mississippi S. Cragin Knox
Mississippi Office of Geology
P.O. Box 20307
Jackson, MS 39289-1307
(601)961-5500
Missouri James H. Williams
Missouri Division of Geology &
Land Survey
1 11 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
Jonathan G. Price
Nevada Bureau of Mines & Geology
Stop 178
University of Nevada-Reno
Reno, NV 89557-0088
(702)784-6691
New Hampshire Eugene L. Boudette
Dept of Environmental Services
117 James Hall
University of New Hampshire
Durham, NH 03824-3589
(603)862-3160
New Jersey Haig F. Kasabach
New Jersey Geological Survey
P.O. Box 427
Trenton, NJ 08625
(609)292-1185
New Mexico Charles E. Chapin
New Mexico Bureau of Mines &
Mineral Resources
Campus Station
Socorro.NM 87801
(505) 835-5420
New York Robert H. Fakundiny
New York State Geological Survey
3 136 Cultural Education Center
Empire State Plaza
Albany, NY 12230
(518)474-5816
n-34 Reprinted from USGS Open-File Report 93-292
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'North Carolina- Charles IL Gardner - *
North Carolina Geological Survey
P.O. Box 27687
Raleigh, NC 27611-7687
(919)733-3833
North Dakota John P. Bluemle
North Dakota Geological Survey
600 East Blvd.
Bismarck, ND 58505-0840
(701)224-4109
Ohio Thomas M. Berg
Ohio Dept. of Natural Resources
Division of Geological Survey
4383 Fountain Square Drive
Columbus, OH 43224-1362
(614)265-6576
Oklahoma Charles I. Mankin
Oklahoma Geological Survey
Room N-131, Energy Center
lOOE.Boyd
Norman, OK 73019-0628
(405) 325-3031
Oregon Donald A. Hull
Dept of Geology & Mineral Indust.
Suite 965
800 NE Oregon St. #28
Portland, OR 97232-2162
(503)731-4600
Pennsylvania Donald M. Hoskins
Dept. of Environmental Resources
Bureau of Topographic & Geologic
Survey
P.O. Box 2357
Harrisburg, PA 17105-2357
(717)787-2169
Puerto Rico RanuSn M. Alonso
Puerto Rico Geological Survey
Division
Box 5887
Puerta de Tierra Station
San Juan, PJL 00906
(809)722-2526
Rhode Island J. Allan Cain
Department of Geology
University of Rhode Island
315 Green Hall
Kingston, RI02881
(401)792-2265
Utah
South Carolina Alan-Jon W.Zupan (Acting)
South Carolina Geological Survey
5 Geology Road
Columbia, SC 29210-9998
, (803)737-9440
South Dakota CM. Christensen (Acting)
South Dakota Geological Survey
Science Center
University of South Dakota
Vermillion, SD 57069-2390
(605)677-5227
Tennessee Edward T.Luther
Tennessee Division of Geology
13th Floor, L&C Tower
401 Church Street
Nashville, TN 37243-0445
(615)532-1500
William L. Fisher
Texas Bureau of Economic Geology
University of Texas
University Station, Box X
Austin, TX 78713-7508
(512)471-7721
M. Lee Allison
Utah Geological & Mineral Survey
2363 S. Foothill Dr.
Salt Lake City, UT 84109-1491
(801)467-7970
Vermont Diane L. Conrad
Vermont Division of Geology and
Mineral Resources
103 South Main St
Waterbury.VT 05671
(802)244-5164
Virginia Stanley S. Johnson
Virginia Division of Mineral
Resources
P.O. Box 3667
Charlottesville, VA 22903
(804)293-5121
Washington Raymond Lasmanis
Washington Division of Geology &
Earth Resources
Department of Natural Resources
P.O. Box 47007
Olympia, Washington 98504-7007
(206)902-1450
R-35 Reprinted from USGS Open-File Report 93-292
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' \Hfcst 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 Mineral Point Road
Madison, WI 53705-5100
(608)263-7384
Wyoming Gary B. Glass
Geological Survey of Wyoming
University of Wyoming
Box 3008, University Station
Laranue, WY 82071-3008
(307)766-2286
1-36 Reprinted from USGS Open-File Report 93-292
------- An error occurred while trying to OCR this image.
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Hgure 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.
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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 comer of the
Olympic Peninsula has lower rainfall and lower soil moisture than does the rest of the 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 pQ/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.
ffl-3 Reprinted from USGS Open-File Report 93-292-J
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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 pO/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
uranifcrous, 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 valley s in Washington and Idaho
north, northwest, and east of Spokane may be expected to have average indoor radon screening
measurements above 4 pQ/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 overalliadon potential. Most populous areas are in the latter category.
m-4 Reprinted from USGS Open-File Report 93-292-J
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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 rhyolites 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 alluvium in die 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 tectonically 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 eolian 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 transrnissivity 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.
BI-5 Reprinted from USGS Open-File Report 93-292-J
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Rgurc 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-
Westem 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. The Cretaceous sandstone artd 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 Prccambrian 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 terrane is 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 metamorphic 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 metamorphic 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 metamorphic rocks, and Mesozoic intrusive
and volcanic rocks. The metamorphic rocks include metamorphosed granites and amphibolite.
ffl-7 Reprinted from USGS Open-File Report 93-292-J
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The mesozoic intnisives are msofly 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 anctialies occ< - in the '.u1 — vince. Aluv gh indoor radon data are
sparse, indoor radon in parts of the Fairbanks and Fairbanks Northstar Boroughs is high. Felsic
intnisives 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 ML
McKinley, a southeast-trending mountain belt that extends from the ML 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
intnisives 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 arid southeastward to the
Canadian border. These include Paleozoic mafic volcanic rocks together with their sedimentary
and mctamorphic 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 intnisives, and Quaternary glacial deposits including eolian sand and silL
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
arc highly deformed and variably metamorphosed.
This area has moderate radon potential overall, although the uncertainty is high. The
Aleutian-Alaska Range contains felsic intnisives 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.
CoastalTrough .;
The Coastal Trough Province (7, fig. 2) includes a series of Cenozoic deposraonal 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 mat 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
ffl-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.
ffl-9 Reprinted from USGS Open-File Repeat 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
(< 5 measurements)
Figure 3A. Screening indoor radon data from the State/EPA Residential Radon Survey and the
Oregon Radon Project, for counties with 5 6r 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.
-------
11 L
Bsmt & 1st Floor Indoor 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 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 OREGON
-.'•'•• by
James K. Otton
US. Geological Survey
INTRODUCTION
Oregon is a state of varied geologic and climatic settings and varied radon potential. This
assessment of the radon potential of the state relied heavily on data provided by studies of indoor
radon by the Oregon Division of Health and the Bonneville Power Administration (BPA), previous
work by Duval, Otton, and Jones (1989) and Otton and Duval (1990), and geologic information
derived from publications of the U.S. Geological Survey and the Oregon Department of Geology
and Mineral Industries. Much information in the geographic setting section is derived from the
National Atlas of the United States.
This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
deposits of Oregon. 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
Oregon is divisible into several physiographic provinces (fig. 1). The Coast Ranges lie
along the Pacific coast and are dominated by low mountains with a relief of 1000-3000 feet
Southward the Coast Ranges give way to the Klamath Mountains where relief is generally greater
than 3000 feet Throughout these two areas less than 20 percent of the surface is gently sloping.
The Willamette River Valley lies to the east of and parallels the Coast Ranges, but the valley dies
out a little south of the central part of the state. The river valley is an area of plains and hills where
50-80 percent of the land's surface is gently sloping and the rest is hilly. The local relief ranges
300-500 feet The Cascade Range lies east of the Willamette River Valley and the Klamath
Mountains. The western Cascades are characterized by high mountains where greater than 80
percent of the land is steeply sloping and relief exceeds 3000 feet The east side of the Cascades
(the high Cascades) is marked by open high mountains where 20-50 percent of the land is gently
sloping and the relief exceeds 3000 feet The Deschutes-Umatilla Plateau (fig. 1) is characterized
by tablelands of high relief (1000-3000 feet) where 50-80 percent of the land is gently sloping and
greater than 75 percent of the gently sloped areas are in the uplands. The Blue Mountains and
adjacent Joseph Upland are marked by open low (1000-3000 feet of relief) to open high (more than
3000 feet of relief) mountains where 20-50 percent of the area is gently sloping (fig. 1) and the rest
is steeply sloping. The eastem:boundary of the latter two areas is formed by the Snake River
IV-1 Reprinted from USGS Open-FUe Report 93-292-J
-------
KLAMATH
MOUNTAINS
Figure 1- Physiographic divisions of Oregon. (Modified from U.S. Geological Survey,
1969).
-------
Canyon along die. Oregon-Idaho bolder. South of the Blue Mountains are the High Lava Plains,
which are characterized by plains with high hills (500-1000 feet of relief) to low mountains (1000-
3000 feet of relief) (fig. 1). The Basin and Range area of south-central Oregon is characterized by
plains with high hills (500-1000 feet of relief), low mountains (1000-3000 feet of relief), and two
high mountain ridges (greater than 3000 feet of relief) near the southern border of the state. The
Owyhee Upland is underlain by tablelands of considerable relief (500-1000 feet). Fifty to eighty
percent of these latter three areas are gently sloping and the rest is steeply sloping.
Precipitation ranges from 48 to 96 inches per year throughout most of the Coast Ranges
and the Cascade Mountains. The Willamette River Valley receives 32 to 48 inches of rain per year.
Most of the rest of Oregon is relatively dry with the interior areas east of the Cascades receiving
only 8 to 16 inches of precipitation per year except for the Blue Mountains where 16 to 48 inches
of precipitation fall.
Most people in Oregon live in cities and towns extending along the Willamette River valley
from Portland to Eugene (fig. 2). The remainder of the population lives in coastal towns, in a
series of communities in valleys south of Eugene, and in scattered communities in north-central
and northeastern Oregon. Desert areas of southeastern Oregon are sparsely populated.
Most of the Coast Ranges and the Cascade Mountains are forest and woodland areas, but
some cropland and pasture areas occur adjacent to the coast The Willamette River valley is used
mostly for cropland and, to a lesser extent, for pasture, woodland, and forest The Deschutes-
Umatilla Plateau includes cropland, and grasslands used for grazing. The Blue Mountains contain
areas of grassland and semiarid shrublands used for grazing at lower altitudes and forest and
woodlands used for grazing at higher altitudes. The Basin and Range and Owyhee Plateau of
southeastern Oregon is dominated by desert shrubland used for grazing.
GEOLOGIC SETTING
The northern Coast Ranges are underlain principally by marine sedimentary rocks and
mafic volcanic rocks of Tertiary age (fig. 3). The southern part of the Coast Range is underlain by
Tertiary estuarine and marine sedimentary rocks that are commonly feldspathic and micaceous.
The Klamath Mountains are dominated by Triassic to Jurassic metamorphic, volcanic, and
sedimentary rocks but also contain some Cretaceous intrusive rocks. The metamorphic and
volcanic rocks are largely of mafic composition. Large masses of ultramafic rocks occur
throughout the Klamath area.
River alluvium and river terraces occur along most of the Willamette River valley, but many
of tiie hills that rise above the plains are underlain by Tertiary basalts and marine sedimentary
rocks. The western Cascades are dominated by Tertiary andesite and basalt flows and pyroclastic
rocks. The eastern Cascades are underlain by late Tertiary to Quaternary basaltic and andesitic
volcanic rocks and several recently active volcanoes. Extensive areas underlain by pumice and ash
occur near Crater Lake.
The Deschutes-Umatilla Plateau is underlain principally by Tertiary basalt, basaltic breccia,
tuffaceous sedimentary rocks and tuff. Thin surficial deposits composed of lacustrine sediments,
glaciofluvial outwash, loess, and pediment gravels form much of the northeastern part of this
plateau. The Blue Mountains and Joseph Upland are comprised mainly of Tertiary basalt and
andesite, tuffaceous sedimentary rocks, and tuff; however, Triassic and Jurassic sedimentary and
volcanic rocks and later intrusive rocks core uplifts in this area. The sedimentary and volcanic
rocks are weakly metamorphosed in many areas.
IV-3 Reprinted from USGS Open-File Report 93-292-J
-------
1
•o
5
CO
o
o\
O\
o
oo
•8
o
•a
cd
I
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EXPLANATION
•MUMMMyMd oaten* reek*
|t»b| MM***tflWM«MonCMCM»llMOI
GEJ
[••h1] flJ-11M:,-jl-_ —=_^- „. ...
Figures- Generalized geologic map for the State of Oregon. (Erom U.S. Geological
Survey, 1969).
-------
The High Lava Plains arc underlain by basalt flows of late Tertiary and.Quatemary age and
Tertiary silicic ash-flow tuff. The Basin and Range Province of Oregon is an area of basaltic to
andesitic volcanic rocks, silicic ash-flow tuffs, some of them welded tuffs, and sediments derived
from these units. Playa basins dot the landscape. The Owyhee Plateau is underlain by 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.
Aeroradiometric data for the state of Oregon (fig. 4) show that surface materials from the
Cascade Range westward contain generally less than 1.5 ppm equivalent uranium (eU), with the
exception of the Willamette River Valley, where eU values as much as 2.5 ppm are recorded
locally. The northern and southern Coast Ranges show significantly different signatures, with the
northern parts, underlain mostly by mafic volcanic rocks, being less than 0.5 ppm eU whereas the
southern part, underlain by micaceous and feldspathic sedimentary rocks, ranging from 0.5-1.5
ppm eU. The Klamath Mountains are mixed in their eU signature with some metamorphosed
sedimentary rocks and granites showing as much as 2.5 ppm, whereas the ultramafic rocks and
other metamorphosed mafic volcanic rocks and sedimentary rocks show less than 1 ppm eU. East
of the Cascades, much of the western part of the Basin and Range, and the Blue Mountains are
very low in eU, ranging from 0.0 to 1.5 ppm. A broad area of elevated eU values (as much as 3.5
ppm in Umatilla County) occurs northwest of the Blue Mountains in the Deschutes-Umatilla
Plateau in Sherman, Gilliam, Morrow and Umatilla Counties (fig. 5). Underlying bedrock in this
area consists of basalts of the Columbia basin. Basalts arc generally low in uranium content
(<1 ppm), however, if appears that the elevated eU signatures in this area are due to surficial
deposits of loess and eolian sand derived from the nearby Columbia River Valley. Sediment in the
Columbia River Valley is derived in large part from more uraniferous rocks in the northeast corner
of Washington and northern Idaho, transported to this part of the area by major late Pleistocene
floods.
In the eastern Basin and Range and the Owyhee Plateau, a patchwork of elevated (1.5-4.5
ppm) and low eU (0.5-1.5) values occurs. Elevated eU values appear to be associated with
Tertiary silicic volcanic centers and sediments derived from those rocks whereas lower eU values
are associated with basaltic and andesitic rocks. Two areas of uranium deposits near the Lakeview
area (southern Harney County) and the northern McDermitt caldera area (southern Malheur
County) are marked by fairly intense eU signatures (as much as 5.0 ppm).
Most uranium occurrences in Oregon are found in the Basin and Range Province where
they arc associated with rhyolitic volcanic centers; however, they are also scattered elsewhere in the
Blue Mountains, the Klamath Mountains, and the southern part of the Coast Ranges, where they
arc associated with various sedimentary, volcanic, and intrusive rocks.
SOILS
As part of an earlier study for the Bonneville Power Administration, Duval and others
(1989) evaluated permeability data in the county soil surveys for 24 of the 36 counties in the state
(fig. 6). They compiled a map of the highly permeable soil associations (those soil associations
dominated by soils with percolation tests greater than 6 in/hr) in those 24 counties (fig. 7). Highly
permeable soils occur mainly in the upper Willamette River valley, along parts of the Columbia
River valley, in the Milton-Ereewater area, and in some coastal areas.
IV-6 Reprinted from USGS Open-File Report 93-292-J
-------
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. Soils of the west flank .of the Coast Range and all of the Cascades are typically very moist
in the wintertime (pore space saturation ranges from 56-96 percent for a sandy loam and 74-99
percent for a silty clay loam) and moderately moist in the summertime (pore space saturation ranges
44-56 percent for a sandy loam and 58-74 percent for a silty clay loam) (Rose and others, 1990).
Within the Willamette River Valley, on the east flank of the Coast Ranges, and on the Deschutes-
Umatilla Plateau, soils are typically very moist in the winter (pore space saturation ranges 56-96
percent for a sandy loam and 74-99 percent for a silty clay loam) and slightly moist in the summer
(pore space saturation ranges 24-44 percent for a sandy loam and 39-58 for a silty clay loam). Li
the Blue Mountains and the westernmost Basin and Range the soils are very moist in the winter
(pore space saturation ranges from 56-96 percent for a sandy loam and 74-99 percent for a silty
clay loam) and moderately moist in the summer (pore space saturation ranges 44-56 percent for a
sandy loam and 58-74 percent for a silty clay loam). Li the southeastern quadrant of the state soils
are typically slightly moist in the winter (pore space saturation ranges 24-44 percent for a sandy
loam and 39-58 for a silty clay loam) and slightly dry in the summer (pore space saturation ranges
4-24 percent in a sandy loam and 6-39 percent for a silty clay loam).
INDOOR RADONDATA
Indoor radon data for Oregon were gathered during the Oregon Radon Project conducted
by the Oregon Division of Health during 1988-1990 (Table 1, fig. 8). Data are composed of 1,954
randomly-sampled 12-month alpha-track detector measurements. These data show that counties
whose major population centers lie along the Columbia River Gorge and the Willamette River
Valley generally have average indoor radon levels in the 2-4 pCi/L range. Polk County averages
7.2 pCi/L. Highest county maximum readings for the State also occur in this area. Three Pacific
coastal counties also range 2-4 pCS/L. Averages for three northeastern counties range 2-4 pCS/L
and Union County in the northeast has a single value of 3.3 pCi/L. Lake County in the south-
central part of the State averages 2.8 pCi/L.
Another source for indoor radon data in the State of Oregon is an extended study conducted
by the Bonneville Power Administration (BPA). Indoor radon tests were offered as part of BPA's
weatherization program, extended to homeowners across its service area (parts of the states of
Washington, Oregon, Idaho, Montana, and Wyoming). Three month, wintertime alpha-track
measurements were made in participants' homes starting in the fall of 1985. The resultant data
were gathered on a township location system and are portrayed in figure 9. Li this figure all those
townships with less than 5 measurements are shown but no data are given. For those townships
with at least 5 measured houses, the percentage of those homes greater than 5 pCi/L is represented
in 4 categories: 0 percent, 0-5 percent, 5-10 percent, and greater than 10 percent (5 pCi/L was used
as an index by BPA under the assumption that a 5 pCi/L wintertime measurement would
approximately equal a 4 pCi/L year-long measurement). Most of the indoor radon data for the
State of Oregon in the BPA data set come from the populous areas of western Oregon.
Examination of data tables for the townships in Oregon from this study (Bonneville Power
Administration, 1990) show the following:
1. Of 151 townships in Oregon with at least 5 measurements, 17 townships averaged
greater than 2 pCS/L and 2 averaged greater than 4 pCi/L.
2. Overall, 513 of 12,079 measurements (4.2 percent) for the State equalled or exceeded 4
pCi/L.
IV-11 Reprinted from USGS Open-File Report 93-292-J
-------
Bsmt& 1st Floor Rn
%>4pCi/L
14 r.".-.»->
10
OtolO
11 to 20
21 to 30
31 to 40
Missing Data
or < 5 measurements
Bsmt. & 1st Floor Rn
Average Concentration (pCi/L)
16 i-.-.-.-.*^ 0.0 to 1.9
10 L\\\M 2.0 to 4.0
1 B 4.1 to 7.2
9 I ' Missing Data
or < 5 measurements
100 Miles
Figure 8. Indoor radon data from the Oregon Radon Project conducted by the Qrgeon
Division of Health, 1988-90, for counties with 5 or more measurements. Data are from
12-month alpha-track tests. Histograms in map legends show the number of counties in
each category. The number of samples in each county (See Table 1) may not be sufficient
to statistically characterize the radon levels of the counties, but they do suggest general
trends. Unequal category intervals were chosen to provide reference to decision and action
levels.
-------
•TABLE 1. Indoor radon data from the Oregon Radon Project conducted by.the Oregon Division
of Health. Data represent randomly-sampledl2-month Alpha-track detector measurements
collected during 1988-1990.
COUNTY
BAKER
BENTON
CLACKAMAS
CLATSOP
COLUMBIA
COOS
CROOK
CURRY
DESCHUTES
DOUGLAS
GRANT
HARNEY
HOOD RIVER
JACKSON
JhhhERSON
JOSEPHINE
KLAMATH
LAKE
LANE
LINCOLN
LINN
MALHEUR
MARION
MORROW
MULTNOMAH
POLK
TILLAMOOK
UMATILLA
UNION
WALLOWA
WASCO
WASHINGTON
WHEELER
YAMfflLL
NO. OF
MEAS.
19
108
156
29
9
38
1
1
42
21
1
8
21
135
2
63
31
13
79
11
57
10
136
2
611
29
9
40
1
8
8
225
2
28
MEAN
3.2
12
22
1.4
2.6
1.9
0.1
0.8
0.8
0.7
1.0
1.4
1.5
1.0
0.7
0.7
0.6
2.8
1.6
1.6
1.3
1.3
2.0
1.4
3.3
72
23
2.6
3.3
22
0.9
1.7
0.6
3.4
GEOM
MEAN
1.9
0.9
1.6
0.8
2.3
12
0.1
0.8
0.5
0.6
1.0
1.0
1.1
0.7
0.6
0.5
0.5
1.7
1.0
12
0.9
1.4
1.3
1.3
2.1
.3-1
1.7
1.6
3.3
0.8
0.6
12
1.1
2.1
MEDIAN
1.5
0.9
1.6
0.5
22
1.1
0.1
0.8
0.5
0.4
1.0
1.0
0.8
0.7
0.7
0.4
0.4
1.8
0.9
0.9
0.9
1.4
12
1.4
2.1
2.4
2.4
1.7
3.3
0.3
0.5
12
0.6
1.9
STD.
DEV.
32
1.1
2.7
2.4
1.6
2.6
***
***
12
0.9
***
1.2
1.1
12
0.4
0.9
0.7
3.1
2.3
2.2
1.4
0.7
2.8
0.5
3.9
12.2
1.7
3.0
***
3.4
1.1
1.8
0.8
4.5
MAXIMUM
10.0
6.0
25.5
8.7
6.0
15.6
0.1
0.8
7.2
3.4
1.0
3.6
3.3
6.0
0.9
5.3
3.1
11.5
15.4
7.8
5.9
2.7
25.2
1.7
35.5
48.8
5.7
14.0
33
9.9
3.4
13.9
1.1
20.9
%>4pCi/L
32
4
15
14
11
11
0
0
2
0
0
0
0
4
0
2
0
15
8
9
7
0
13
0
25
31
11
20
0
13
0
6
0
18
%>20pCi/L
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
1
14
0
0
0
0
0
0
0
4
-------
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-------
3. Townships averaging greater than 2IpO/L are located along the Cblumbia River Valley,
in scattered areas in the upper Willamette River Valley; in some river valleys in the central and
southern Coast Range; and in the Milton-Ereewater area (northeast Umatilla County).
GEOLOGIC RADON POTENTIAL
The available data suggest that selected parts of several counties across the State are likely
to have average indoor radon levels above 2 pO/L and a few areas are likely to have average levels
above 4 pCj/L. In some counties these local areas may be sufficiently widespread to cause the
countywide average to exceed 2 or even 4 pCS/L.
In the central and southern Coast Range, elJ values are sufficiently elevated that, in spite of
high soil moisture due to high precipitation, elevated indoor radon levels are likely where soils are
highly permeable or steeply sloping. This can occur in many soils developed on coarse alluvial
deposits along the several river valleys that cut through the Coast Range. Soils formed on sand
dunes in coastal areas, although locally highly permeable, are less likely to produce high indoor
radon levels because of probable low soil-gas radon concentrations and high soil moisture.
Similarly, precipitation is also relatively high in the Willamette River Valley and the eU
signature of many soils is elevated compared to other areas west of the Cascades in Oregon and
Washington. Scattered areas in the upper Willamette River Valley where soils are well-drained,
steep, or soil textures permit high emanation of radon are likely to produce elevated indoor radon
levels. Such soils are most common in river terrace areas near the Willamette River but they also
occur in some broad valley areas without significant river deposits.
Areas along the Columbia River Gorge in various counties in northwest Oregon seem
susceptible to elevated indoor radon where the soils formed on river terrace deposits. Such soils
are often highly permeable, well-drained, and locally steep.
Houses sited on the highly permeable Yakima gravelly loam in the town of Milton-
Freewater in northeastern Umatilla County are likely to have elevated indoor radon levels. The
Yakima gravelly loam and the Pilot Rock silt loam (thin silt loam over gravel) underlie much of the
city of Pendleton in north-central Umatilla County and elevated indoor radon levels are likely in
this city.
Areas of elevated eU associated with silicic volcanic rocks in Harney and Malheur Counties
in southeast Oregon probably cause average indoor radon levels above 4 pQ/L. This area is very
sparsely populated. Most people in this area live on ranches and in small communities in river and
stream valleys. Few homes are located directly on soils developed on the uraniferous volcanic
rocks themselves. Where alluvium is derived from silicic volcanic rocks, elevated indoor radon
levels are likely.
SUMMARY
There are nine distinct geologic provinces in Oregon for which radon potential may be
evaluated: the Coast Range, the Klamath Mountains, the Willamette River Valley, the Cascade
Range, the Deschutes Umatilla Plateau, the Blue Mountains and Joseph Upland, the High Lava
Plains, the Basin and Range Province, and the Owyhee Plateau. A relative index of radon potential
(RI) and an index of the level of confidence in the available data (GO have been established (see
discussion in chapter 1 of this volume). The nine geologic provinces in Oregon are evaluated in
IV-15 Reprinted from USGS Open-FUe Report 93-292-J
-------
Table2. The ColumbiaRiver.Gorge, although not a distinctive geologic province, is considered-
separately (see discussion below). .
Theradon potential of the CoastRange is low overall due to high rainfall and high soil
moisture,andlowtomoderatelevelsofiraniuminthesoUsandrocksofthearea. Locally,
however, structures on steep or excessively well-drained soils especially along many of the nver
valleys may have elevated indoor radon levels (>4 pO/L). For example, houses in Oatsop,
Tfflamook, and Coos Counties show elevated indoor radon levels. The radon potential of the
Klamath Mountains is similar to that of the Coast Ranges.
The overall radon potential of the Willamette River Valley is moderate. The uranium
content of the soils is moderate, the soils locally include some with high emanating power, and
some of the soils are excessively well-drained (fig. 7). Tmn5ohiw.
Radon potential in the Cascade Range is low due to low uranium and high soil moisture.
However, houses sited on steep, excessively well-drained slopes are likely to have higher indoor
radon levels including many areas along the Columbia River gorge.
The Deschutes Umatilla Plateau has moderate radon potential. This area has elevated
uraniumin soils, includes many dry alluvial soils with high permeability, and includes many soils
that are likely to have high emanating power.
The Blue Mountains and Joseph Upland have moderate radon potential. The uranium
content of soils and rocks is generally low (fig. 4), but most populated areas are located on valley-
floor alluvium where highly permeable soils are producing locally elevated indoor radon levels.
The High Lava Plains have low radon potential overall, but the confidence in this
assessment is low due to sparse data. The western part of the High Lava Plains has generally low
uranium in soils. The eastern part of the Lava Plains includes some uraniferous silicic volcanic
rocks and they or alluvium associated with them may be responsible for elevated indoor radon
levels locally. . ...
The Basin and Range has moderate radon potential, but the data are sparse and the
confidence level is low. Although the soil uranium content is generally low in the western part of
the province, soils are fairly dry, river alluvium may be locally highly permeable, and some are
likely to have high radon emanating power. In the eastern part of the province many areaslare
uraniferous and some volcanic rocks host uranium deposits. These volcanic rocks and sediment
derived from themare likely to produce elevated indoor radon levels. Structures inadvertently sited
on uranium occurrences found locallyin this area may have very highindoor radon.levels.
The O wyhee Plateau has high radon potential, although the confidence level is low. Much
of the area is underlain by uraniferous soils and rocks and alluvium derived from them which are
likely to produce elevated indoor radon levels. Uranium prospects occur in many areas and
structures sited on them are likely to have very high indoor radon levels.
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-16 Reprinted from USGS Open-FUe Report 93-292-J
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TABLE 2. Radon Index (RI) and Confidence Index (CI) for geologic radon potential areas of •
Oregon. See figure 1 for locations of areas. See the introductory chapter for discussion of RI and
CI.
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERMEABILITY
ARCHITECTURE
GFE POINTS
TOTAL
RANKING
Coast
Range
RI CI
1
1
2
2
1
0
7
2
3
2
2
9
LOW MOD
Klamath
Mountains
RI CI
1
1
2
2
1
0
7
2
3
2
2
9
LOW MOD
Willamette
Valley
RI CT
2
2
2
2
1
0
9
2
3
2
2
9
MOD MOD
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERMEABILITY
ARCHITECTURE
GFE POINTS
TOTAL
RANKING
Cascade
Range
RI CI
1
1
2
2
1
0
7
2
3
2
2
9
LOW MOD
Deschutes
Umatilla
RI CI
2
2
2
2
1
0
9
2
3
2
3
10
MOD HIGH
Blue
Mountains
RI CI
2
1
2
3?
1
0
9
1
3
1
1
6
MOD MOD
- Not used in CI.
RADON INDEX SCORING:
Radon potential category
LOW
MODERATE/VARIABLE
HIGH
Point range
3-8 points
9-11 points
> 11 points
Probable screening indoor
radon average for area
<2pCi/L
2-4pCi/L
>4pCi/L
Possible range of points = 3 to 17
CONFIDENCE INDEX SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10 - 12 points
Possible range of points = 4 to 12
IV-17 Reprinted from USGS Open-File Report 93-292-J
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.TABLE 2 (continued)-Radon Index (RI) and Confidence Index (CI) for geologic radon potential
areas of Oregon. See figure'1 for locations of areas. See the introductory chapter for discussion
ofRIandd
FAfTTOR
INDOORRADON
RADIOACTIVI'IY
GEOLOGY
SOIL PERMEABILITY
ARCHITECTURE
GFE POINT5?
TOTAL
RANKING
High Lava
Plains
RT CI
n
1
2
2
1
0
7
LOW
1
3
1
1
6
LOW
Basin &
Range
RT CT
27
1
3
2
1
0
9
MOD
1 .
3
1
1
6
LOW
Owyhee
Upland
RT CI
11
3
2
2
1
0
9
MOD
1
3
1
1
6
LOW
Columbia
River Gorge
RI CI
3
1
2
3
1
0
10
MOD
2
3
2
1
8
MOD
- Not used in CI.
RADON INDEX SCORING:
Radon potential category
Probable screening indoor
Point ranee radon average for area
LOW 3-8 points <2pCi/L
MODERATE/VARIABLE 9-11 points 2-4pCi/L
HIGH > 11 points > 4 pCi/L
Possible range of points = 3 to 17
CONFIDENCE INDEX SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
4-6 points
7-9 points
10 - 12 points
Possible range of points = 4 to 12
IV-18 Reprinted from USGS Open-FUe Report 93-292-J
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. . REFERENCES CITED IN THIS REPORT
AND GENERAL REFERENCES'RELAVENT TO RADON IN OREGON
Berry, M. R., 1981, Geology of the Lakeview uranium district, Oregon in Goodell, P. C. and
Waters, A. C, eds., Uranium in volcanic and volcaniclastic rocks: AAPG Studies in
Geology 13, p. 55-62.
Bonneville Power Administration, 1990, Radon monitoring results from BPA's residential
conservation programs: Report No. 12: Portland, Oregon, Bonneville Power
Administration, unpaginated.
Bradley, R., 1982, Mining districts and mineral deposits of the Basin and Range Province of
Oregon: United States Geological Survey Open-File Report 82-0058,15 p.
Cathrall, J. B. and Tuchek, E. T., Charles Sheldon Antelope Range and Sheldon National
Antelope Refuge, Nevada and Oregon: in Marsh, S. P., Kropscot, S. J. and Dickinson,
R. G., eds., Wilderness mineral potential; assessment of mineral-resource potential in U.S.
Forest Service lands studied 1964-1984: U.S. Geological Survey Professional Paper 1300,
p. 765-767.
Dayvault, R. D., Castor, S. B. and Berry, M. R., 1985, Uranium associated with volcanic rocks
of the McDermitt Caldera, Nevada and Oregon, in Anonymous, Uranium deposits in
volcanic rocks; proceedings of a technical committee meeting, El Paso, TX, Apr. 2-5,
1984: Panel Proceedings Series-International Atomic Energy Agency ST1/PUB/690,
p. 379-409.
Duval, J. S., Otton, J. K., and Jones, W. J., 1989, Estimation of radon potential in the Pacific
Northwest using geological data: Portland, Oregon, Bonneville Power Administration,
146 p.
Duval, J. S., Jones, W. J., Riggle, F. R., and Pitkin, J. A., 1989, Equivalent uranium map of the
conterminous United States: U.S. Geological Survey Open-File Report 89-478,10 p.
Erdman, J. A. and Harrach, G. H., 1981, Uranium in big sagebrush from Western U.S. and
evidence of possible mineralisation in the Owyhee Mountains of Idaho: Journal of
Geochemical Exploration, v. 14, n. 1, p. 83-94.
Erikson, E. H., 1977, Preliminary study of the uranium favorability of Malheur County, Oregon:
U.S. Department of Energy Report No.: GJBX-91(77), 16 p.
Moed, B.A., Nazaroff, A.V., Nero, M.B., Schwehr, M.B., and Van Heuvelen, A., 1984,
Identifying areas with potential for high indoor radon levels: analysis of the National
Airborne Radiometric Reconnaissance data for California and the Pacific Northwest:
Berkeley, California, Lawrence Berkeley Laboratory Report No. LBL-16955,70 p.
IV-19 Reprinted from USGS Open-FUe Report 93-292-J
-------
Nero, A.V., Schwehr, M.B., Nazaroff, W.W., and Revzan, K.L., 1986, Distribution of airborne
radon-222 concentrations in U.S. homes: Science, v. 234, p.992-997.'
Otton, J. K., 1987, Indoor radon; geologic controls in Pacific Northwest: Geological Society of
America Abstracts with Programs, v. 19, n. 2, p. 122.
Otton, J. K. and Duval, J. S., 1990, Geologic controls on indoor radon in the Pacific Northwest,
in U.S. Environmental Protection Agency, The 1990 international symposium on radon
and radon reduction technology: Volume UL Preprints, unpaginated.
Peck. D. L., 1961, Geologic map of Oregon west of the 121st meridian: U.S. Geological Survey
Miscellaneous Investigations Map 1-325. Scale 1:500,000.
Peterman, Z. E., Coleman, R. G. and Bunker, C. M., 1981, Provenance of Eocene graywackes
of the Flournoy Formation near Agness, Oregon; a geochemical approach: Geology, v. 9,
n. 2, p. 81-86.
Rcimer, G. M., 1981, Helium soil-gas survey of a portion of the McDermitt Caldera complex,
Malheur County, Oregon: United States Geological Survey Open-File Report 81-0565,
10 p.
Ronkos, C J., 1981, Geology, alteration, and mineralization in the pyroclastic and sedimentary
deposits of the Bretz-Aurora Basin, McDermitt Caldera, Nevada-Oregon: Master' thesis,
Univ. of Nevada, Reno, unknown p.
Roper, M. W. and Wallace, A. B., 1981, Geology of the Aurora uranium prospect, Malheur
County, Oregon in Goodell, P. C. and Waters, A. C., eds., Uranium in volcanic and
volcaniclastic rocks: AAPG Studies in Geology 13, p.81-88
Rose, A. W., Ciolkosz, E. J., and Washington, J. W., 1990, Effects of regional and seasonal
variations in soil moisture and temperature on soil gas radon, in U.S. Environmental
Protection Agency, The 1990 international symposium on radon and radon reduction
technology: Volume ffl. Preprints, unpaginated.
Rytuba, J. J., 1977, Uranium content of tuffaceous sediments and opalite mercury deposits within
the McDermitt Caldera, Oregon-Nevada: Geological Society of America Abstracts with
Programs, v. 9, n. 4, p. 492.
Rytuba, J. J., 1979, Alteration aureole in McDermitt caldera in Nevada and Oregon: U. S.
Geological Survey Professional Paper 1150,79 p.
Rytuba, J. J. and Conrad, W. K., 1981, Petrochemical characteristics of volcanic rocks associated
with uranium deposits in the McDermitt caldera complex in Goodell, P. C. and Waters, A.
C, eds., Uranium in volcanic and volcaniclastic rocks: AAPG Studies in Geology, v. 13,
p. 63-72
IV-20 Reprinted from USGS Open-File Report 93-292-J
-------
Rytuba, J. J. and Glanzman, R. K., 1979, Relation of mercury, uranium, arid lithium deposits to
the McDermitt Caldera complex, Nevada-Oregon in Ridge, J. D., ed., Papers on mineral
deposits of western North America; proceedings of the Fifth quadrennial symposium of the
International Association on the Genesis of Ore Deposits; Volume 2: Nevada Bureau of
Mines Report 33, p. 109-117.
Rytuba, J. J., Glanzman, R. K. and Conrad, W. K., 1979, Uranium, thorium, and mercury
distribution through the evolution of the McDermitt Caldera complex in Newman, G. W.
and Goode, H. D., eds., Basin and Range symposium and Great Basin field conference,
Oct. 7-11,1979: Rocky Mountain Assoc. Geol., p. 405-412.
Rytuba, J. J., Minor, S. A. and McKee, E. H., 1981, Geology of the Whitehorse Caldera and
caldera-fill deposits, Malheur County, Oregon: United States Geological Survey Open-File
Report 81-1092,22 p.
U.S. Geological Survey, 1969, Mineral and Water Resources of Oregon: Report of the Committee
on Interior and Insular Affairs, Washington, U.S. Government Printing Office, 462 p.
U. S. Geological Survey and U. S. Bureau of Mines, 1984, Mineral resources of the Charles
Sheldon Wilderness Study Area, Humboldt and Washoe counties, Nevada, and Lake and
Harney counties, Oregon: U.S. Geological Survey Bulletin 1538,139 p.
Walker, G. W., 1977, Geologic map of Oregon east of the 121st meridian: U.S. Geological
Survey Miscellaneous Investigations Map 1-902, Scale 1:500,000.
Walker, G. W., 1980, Preliminary report on the Lakeview uranium area, Lake County, Oregon:
U. S. Geological Survey Open-File Report 80-532,59 p.
Walker, G. W., 1980, Uranium in the Lakeview area, Oregon: U.S. Geological Survey
Professional Paper 1175,43 p.
Walker, G. W., 1985, Geology of the Lakeview uranium area, Lake County, Oregon, in
Anonymous, Uranium deposits in volcanic rocks; proceedings of a technical committee
meeting, El Paso, TX, Apr. 2-5,1984: Panel Proceedings Series-International Atomic
Energy Agency STI/PUB/690, p.411-447 p.
Wallace, A. B. and Roper, M. W., 1981, Geology and uranium deposits along the northeastern
margin, McDermitt caldera complex, Oregon in Goodell, P. C. and Waters, A. C., eds.,
Uranium in volcanic and volcaniclastic rocks: AAPG Studies in Geology 13, p. 73-79.
Weissenberger, K. W., 1984, Lakeview uranium area, Lake County, Oregon; constraints on
genetic modelling from a district-scale perspective: Ph.D. thesis, Stanford Univ., Stanford,
CA,367p.
IV-21 Reprinted firom USGS Open-File Report 93-292-J
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Wakening, R.M. and Cummings,M.L., 1987, Mercury and uranium mineralization in the Clarno
and John Day formations, Bear Creek Butte area, Crook County, Oregon: Oregon
Geology, v. 49, n. 9, p. 103-110.
Wilson, R. D., Purdom, William, and Welton, Richard, 1989, Radon study of the Rogue Valley
region of southern Oregon: Ashland, Oregon, Southern Oregon State College, unknown p.
IV-22 Reprinted from USGS Open-File Report 93-292-J
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. EPA's Map of Radon Zones
The USGS1 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.)
OREGON MAP OF RADON ZONES
The Oregon Map of Radon Zones and its supporting documentation (Part IV of this
report) have received extensive review by Oregon geologists and radon program experts. The
map for Oregon generally reflects current State knowledge about radon for its counties. Some
States have been able to conduct radon investigations in areas smaller than geologic provinces
and counties, so it is important to consult locally available data.
Although the information provided in Part IV of this report — the State chapter entitled
"Preliminary Geologic Radon Potential Assessment of Oregon" — 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
Oregon 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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