Unite) States
             Environmental Protection
             Agency
Air and Radiation
(6604J)
402-R-B3-026
September 1993
vvEPA    EPA's Map of Radon Zones

              FLORIDA
                                                       Recycled/Recyclable
                                                       Printed on paparthat contains
                                                       at least 50% recycled fiber

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       EPA'S MAP OF RADON ZONES
                 FLORIDA
             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
        ASSESSMENTSiINTRODUCTION
  III. REGION 4 GEOLOGIC RADON POTENTIAL
                SUMMARY
V. PRELIMINARY GEOLOGIC RADON POTENTIAL
          ASSESSMENT OF FLORIDA
  V.  EPA'S MAP OF RADON ZONES » FLORIDA

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                                     OVERVIEW
       Sections 307 and 309 of the 1988 Indoor Radon Abatement Act (IRAA) direct EPA to
 identify areas of the United States that have the potential to produce elevated levels of radon.
 EPA, the U.S. Geological  Survey (USGS), and the Association of American State Geologists
 (AASG) have worked closely over the past several years to produce a series of maps and
 documents which address  these directives. The EPA Map of Radon Zones is a compilation of
 that work and fulfills the requirements of sections 307 and 309 of IRAA. The Map of Radon
 Zones identifies, on a county-by-county basis, areas of the U.S. that have the highest  potential
 for elevated indoor radon  levels (greater than 4 pCi/L).
       The Map of Radon Zones is designed to assist national, State and local governments
 and organizations to target their radon program activities and resources.  It is also intended to
 help building code officials determine areas that are the highest priority for adopting radon-
 resistant building practices.  The Map of Radon Zones should not be used to determine if
 individual homes in any given area need to be  tested for radon.  EPA recommends that all
 homes be tested for radon, regardless of geographic location or the zone designation of
 the county in which they are located.
       This document provides background information concerning the development of the
 Map of Radon Zones. It explains the purposes of the map, the approach for developing the
 map (including the respective roles of EPA and USGS), the data sources used, the conclusions
 and confidence levels developed for the prediction of radon potential, and the review  process
 that was conducted to finalize this effort.

 BACKGROUND

       Radon (Rn222) is a  colorless, odorless, radioactive gas. It comes from the natural
 decay of uranium that is found in nearly all soils.  It typically moves through the ground to
 the air above and into homes and other buildings through cracks  and openings in the
 foundation.  Any home,  school or workplace may have a radon problem, regardless of
 whether it is new or old, well-sealed or drafty,  or with or without a basement. Nearly one out
 of every 15 homes in the U.S. is estimated to have elevated annual average levels of indoor
 radon.
       Radon first gained  national attention in  early 1984, when  extremely high levels of
 indoor radon were found in areas of Pennsylvania, New Jersey, and New York, along the
Reading Prong-physiographic province. EPA established a Radon Program  in 1,985 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       .                  "

       EPA's Map of Radon Zones (Figure 1) assigns each of the 3141 counties in the
United States to one of three zones:

              o     Zone 1 counties have a predicted average indoor screening level > than
                    4 pCi/L

              o     Zone 2 counties have a predicted average screening level > 2 pCi/L  and
                    < 4 pCi/L

              o     Zone 3 counties have a predicted average screening level < 2 pCi/L

       The Zone designations were determined by assessing five factors that are known to be
important indicators of radon potential: indoor radon measurements, geology, aerial
radioactivity, soil parameters, and foundation types.
       The predictions of average screening levels in each of the Zones is an expression of
radon potential in the lowest liveable area of a structure.  This map is unable to estimate
actual exposures to  radon.  EPA recommends methods for testing and fixing individual homes
based on an estimate of actual exposure to radon. For more  information on testing and  fixing
elevated radon  levels in homes consult these EPA publications: A Citizen's Guide to Radon,
the Consumer's Guide to Radon Reduction and the Home Buyer's and Seller's Guide  to
Radon.
       EPA believes that States, local governments and other organizations can achieve
optimal risk reductions by targeting resources and program activities to  high radon potential
areas.  Emphasizing targeted approaches (technical assistance, information and outreach
efforts, promotion of real estate mandates  and policies and building codes, etc.) in such  areas
addresses the greatest potential risks first.
       EPA also believes that the use of passive  radon control systems in the construction of
new homes in Zone 1 counties, and the activation of those systems if necessitated by follow-
up testing, is a cost effective approach to achieving significant radon  risk reduction.
       The Map of Radon Zones and  its supporting  documentation establish no regulatory
requirements.  Use of this map by State or local  radon programs and building code officials is
voluntary.  The information presented on the Map of Radon Zones and  in the supporting
documentation  is not applicable to radon in water.

Development of the Map of Radon Zones

       The technical foundation for the Map of Radon Zones is the USGS Geologic  Radon
Province Map.  In order  to examine the radon potential for the United States,  the USGS
began by identifying approximately  360 separate geologic provinces for the  U.S.  The
provinces are shown on the USGS  Geologic Radon Province Map (Figure 2).  Each of the
geologic provinces was evaluated by examining the available  data for that area: indoor radon
measurements,  geology, aerial radioactivity,  soil parameters, and foundation  types. As stated
previously, these five factors are considered to be of basic importance in assessing radon
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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
                 Geologic  Radon Potential  Provinces  for Nebraska
         Lincoln County
            Sill
                    Ueicrile       Low
Figure 4
         NEBRASKA -  EPA Map  of  Radon  Zones
         Li ncola County
          Zeae 1     Zoat 2    last 3
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        One such analysis involved comparing county zone designations to indoor radon
 measurements from the State/EPA Residential Radon Surveys (SRRS).  Screening  averages
 for counties with at least 100 measurements were compared to the counties' predicted radon
 potential as indicated by the Map of Radon Zones.  EPA found that 72% of the county
 screening averages were correctly reflected by the appropriate zone designations on the Map.
 In all other cases, they only differed by 1 zone.
        Another accuracy analysis used the annual average data from the National Residential
 Radon  Survey (NRRS).  The NRRS  indicated that approximately 6 million homes in the
 United  States have annual averages greater than or equal to 4 pCi/L.  By cross checking the
 county  location of the approximately 5,700 homes which participated in  the survey, their
 radon measurements,  and the zone designations for these counties, EPA found that
 approximately 3.8 million homes of the 5.4 million  homes with radon levels greater than or
 equal to 4 pCi/L will  be found in counties designated as Zone 1.  A random sampling  of an
 equal number of cpunties 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 n.  Depending on the amount of new information that is presented, EPA  will
consider updating this map periodically.  The State radon programs should initiate proper
notification of the appropriate State officials when the Map of Radon Zones is released and
when revisions or updates are made by the State or EPA.
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    THE USGS/EPA RADON POTENTIAL ASSESSMENTS: AN INTRODUCTION
                                           by
                      Linda C.S. Gundersen and R. Randall Schumann
                                  U.S. Geological Survey
                                           and
                                    Sharon W. White
                           U.S. Environmental Protection Agency

BACKGROUND

    The Indoor Radon Abatement Act of 1988  (15 U.S.C. 2661-2671) directed the U.S.
Environmental Protection Agency (EPA) to identify areas of the United States that have the
potential to produce harmful levels of indoor radon.  These characterizations were to be  based
on both geological data and on indoor radon  levels in homes and other structures.  The EPA
also was directed to develop model  standards and techniques for new building construction
that would provide  adequate prevention  or mitigation of radon entry. As part of an
Interagency Agreement between the EPA and the U.S. Geological Survey (USGS), the USGS
has prepared  radon  potential estimates for the United States. This report is one of ten
booklets that  document this effort. The purpose and intended use of these reports is to help
identify areas where states  can target their radon program resources, to  provide guidance in
selecting the  most appropriate building code options for areas, and to provide general
information on radon  and geology for each state for federal, state, and municipal officials
dealing with  radon  issues.  These reports are not intended to be used as a substitute for
indoor radon testing,  and they cannot and should not be  used to estimate or predict the
indoor radon concentrations of individual homes, building sites, or housing tracts.  Elevated
levels of indoor radon have been found  in every State, and EPA recommends that all homes
be tested for  indoor radon.
    Booklets  detailing the radon potential assessment for the U.S. have been developed for
each State. USGS geologists are the authors of the geologic radon potential booklets. Each
booklet consists of several  components,  the first being an overview to the mapping project
(Part I), this introduction to the USGS assessment (Part II), including a general  discussion of
radon (occurrence, transport, etc.), and details concerning the types of data used.  The third
component is a summary chapter outlining the general geology and geologic radon potential
of the EPA Region  (Part III). The fourth component is an individual chapter for each state
(Part IV). Each state chapter discusses the state's specific geographic setting, soils, geologic
setting, geologic radon potential, indoor radon data, and a summary outlining the radon
potential rankings of geologic areas in the state. A variety of maps are presented in each
chapter—geologic, geographic, population, soils, aerial radioactivity, and indoor radon data by
county. Finally, the booklets contain  EPA's map of radon zones for each state and an
accompanying description (Part V).
    Because  of constraints  on the scales of maps presented in these reports and because the
smallest units used  to present the indoor radon  data are counties, some  generalizations have
been  made in order to estimate the radon potential of each  area.  Variations in geology, soil
characteristics, climatic factors, homeowner lifestyles, and other factors that influence radon
concentrations can be quite large within any particular geologic area, so these reports cannot
be used to estimate or predict the indoor radon concentrations of individual homes or housing


                                           II-1     Reprinted from USGS Open-File Report 93-292

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 tracts.  Within any are£ 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 repots related to radon are listed for the
 state, and the reader is urged to consult these reports tor 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 (M2Rn) is produced from  the  radioactive  decay of radium (226Ra), which is, in turn,
 a product of the decay of uranium (U8U) (fig. 1).  The half-life of 222Rn is 3.825  days. Other
 isotopes of radon occur naturally, but, with the exception of thoron (220Rn), which occurs in
 concentrations high enough to be of concern in  a few localized areas, they are less important
 in terms of indoor  radon risk because of their extremely short half-lives and less common
 occurrence.  In general, the concentration and mobility of radon in soil are dependent on
 several  factors, the most important of which are the soil's radium  content and distribution,
 porosity, permeability to gas movement, and moisture content. These characteristics are, in
 turn, determined by the soil's parent-material composition, climate, and the soil's age or
 maturity. If parent-material  composition, climate, vegetation, age of the  soil, and topography
 are known,  the physical and chemical properties of a soil in a given area can be predicted.
    As soils form, they develop distinct layers, or horizons, that are cumulatively called the
 soil  profile.  The A horizon  is a surface or near-surface horizon containing a  relative
 abundance of organic matter but dominated by mineral matter.  Some soils contain an E
 horizon, directly below the A horizon, that is generally characterized by loss  of clays, iron, or
 aluminum, and has a characteristically lighter color than the A horizon.   The  B horizon
 underlies the A or E horizon.  Important characteristics of B horizons include accumulation of
 clays, iron oxides, calcium carbonate or other soluble salts, and organic  matter complexes.  In
 drier environments, a horizon may exist within or below the B horizon that is dominated by
 calcium  carbonate,  often called caliche or calcrete.  This carbonate-cemented  horizon is
 designated the K horizon in  modern soil classification schemes. The C horizon underlies the
 B (or K) and is a zone of weathered parent material that does not exhibit characteristics of A
 or B horizons;  that is, it is generally not a zone of leaching or accumulation.  In soils formed
 in place  from the underlying bedrock, the C horizon is a zone of unconsolidated, weathered
 bedrock  overlying the unweathered bedrock.
    The  shape and  orientation of soil particles (soil structure) control permeability and affect
 water movement in the soil.  Soils with blocky or granular structure have roughly  equivalent
permeabilities in the horizontal and  vertical directions, and air and water can  infiltrate the soil
 relatively easily.  However, in soils  with platy structure, horizontal permeability  is much
greater than vertical permeability, and air and moisture infiltration is generally slow. Soils
with prismatic or columnar structure have  dominantly vertical permeability.  Platy and
prismatic structures form in soils with high clay contents.  In soils with  shrink-swell clays, air
                                   *•
                                           II-2     Reprinted from USGS Open-File  Report 93-292

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  and moisture infiltration rates and depth of wetting may be limited when the cracks in, the
  surface soil layers swell shut. Clay-rich B horizons, particularly those with massive or platy
  structure, can form a capping layer that impedes the escape of soil gas to the surface
  (Schumann and others, 1992).  However, the shrinkage of clays can act to open or widen
  cracks upon drying, thus increasing the soil's permeability to gas flow during drier periods.
        Radon transport in soils occurs by two processes: (1)  diffusion and (2) flow (Tanner,
  1964).  Diffusion is the process whereby radon atoms move from areas of higher
  concentration to areas of lower concentration in response, to., a concentration  gradient.  Flow is
  the process by which soil air moves through soil pores in response to differences in pressure
  within the soil or between the soil and the atmosphere, carrying the radon atoms along with it.
* Diffusion is the dominant radon transport process in soils of low permeability, whereas flow
  tends to dominate in highly permeable soils (Sextro and others, 1987).  In low-permeability
  soils, much of the radon may decay before it is able to enter a  building because its transport
  rate is reduced.  Conversely, highly  permeable soils, even those that are relatively low in
  radium, such as those derived from some types of glacial  deposits, have been associated with
  high indoor radon levels in  Europe and in  the northern United  States  (Akerblom and others,
  1984; Kunz and others, 1989; Sextro and others, 1987).  In areas of karst topography formed
  in carbonate rock (limestone or dolomite) environments, solution cavities and fissures can
  increase soil permeability at depth by providing additional pathways for gas flow.
      Not all radium contained in soil grains and grain coatings will result in  mobile radon
  when the radium decays. Depending on where the radium is distributed in the soil, many of
  the radon atoms may remain imbedded in the soil grain containing the parent radium  atom, or
  become imbedded in adjacent soil grains.  The portion of radium that releases radon into the
  pores and fractures of rocks and soils is called the  emanating fraction. When  a radium atom
  decays to radon, the energy generated is strong enough to send the radon atom a distance of
  about 40 nanometers (1 nm = 10'9 meters), or about 2xlO'6 inches—this is known as alpha
  recoil  (Tanner, 1980).  Moisture in the soil lessens the chance of a recoiling radon atom
  becoming imbedded in an adjacent grain.  Because water is more dense than air, a radon atom
  will travel a shorter distance in a water-filled pore than in an air-filled pore, thus increasing
  the likelihood that the radon atom will remain in the pore space.  Intermediate moisture levels
  enhance radon emanation but do not significantly affect permeability. However, high
  moisture levels can  significantly decrease the gas permeability  of the soil and impede radon
  movement through the soil.
      Concentrations of radon in soils are generally many  times  higher than those inside of
  buildings, ranging from tens of pCi/L to more than 100,000  pCi/L, but typically in the range
  of hundreds to low thousands of pCi/L. Soil-gas radon concentrations can vary in response to
  variations in climate and weather on hourly, daily, or seasonal  time scales.  Schumann and
  others (1992) and Rose and others (1988) recorded order-of-magnitude variations in soil-gas
  radon concentrations between seasons in Colorado and Pennsylvania.  The most important
  factors appear to be (1) soil moisture conditions, which are controlled in large part by
  precipitation; (2) barometric pressure; and (3) temperature.   Washington and Rose (1990)
  suggest that temperature-controlled partitioning of radon between  water and gas in soil pores
  also has a significant influence on  the amount of mobile radon in soil gas.
      Homes in hilly limestone regions of the southern Appalachians were found to have higher
  indoor radon concentrations during the summer than in the winter.  A suggested cause for this
  phenomenon involves temperature/pressure-driven flow of radon-laden air from subsurface

                                             II-4     Reprinted from USGS Open-File Report 93-292

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solution cavities in the carbonate rock into houses.  As warm air enters solution cavities that
are higher on the hillslope than the homes, it cools and settles, pushing radon-laden air from
lower in the cave or cavity system into structures on the hillslope (Gammage and others,
1993).  In contrast, homes built over caves having openings situated below the level of the
home had higher indoor radon levels in the winter, caused by  cooler outside air entering the
cave, driving radon-laden air into cracks and solution cavities  in the rock and  soil, and
ultimately, into homes (Gammage and others, 1993).

RADON ENTRY INTO BUILDINGS

    A driving force (reduced atmospheric pressure in the house relative to the soil, producing
a pressure gradient) and entry points  must exist for radon to enter a building from the soil.
The negative pressure caused by furnace combustion, ventilation devices, and the stack effect
(the rising and escape of warm air from the upper floors of the building, causing a
temperature and pressure gradient within the structure) during cold  winter months are
common driving forces.  Cracks and other penetrations through building foundations, sump
holes, and slab-to-foundation wall joints are common entry points.
    Radon levels in the basement are generally higher than those on the main  floor or upper
floors of most structures. Homes with basements generally provide more entry points for
radon, commonly have a more pronounced stack effect, and typically have lower air pressure
relative to the surrounding soil than nonbasement homes.  The  term "nonbasement" applies to
slab-on-grade or crawl space construction.

METHODS AND SOURCES  OF DATA

    The assessments of radon potential in the booklets that follow this introduction were
made using  five main types of data:  (1) geologic (lithologic); (2) aerial radiometric; (3) soil
characteristics, including soil moisture, permeability, and drainage characteristics; (4) indoor
radon data;  and (5) building architecture (specifically, whether  homes in each area are built
slab-on-grade or have a basement or crawl space).  These five factors were evaluated and
integrated to produce estimates of radon potential.   Field measurements of soil-gas radon or
soil radioactivity were not used except where such data were available in existing, published
reports of local field studies.  Where  applicable, such field studies are  described in  the
individual state chapters.

GEOLOGIC DATA

    The types and distribution of lithologic units and other geologic features in an
assessment area are of primary importance in determining radon potential.  Rock types that
are most likely to cause indoor radon problems include carbonaceous black shales, glauconite-
bearing sandstones, certain kinds of fluvial sandstones and fluvial sediments, phosphorites,
chalk, karst-producing carbonate rocks, certain  kinds of glacial deposits, bauxite, uranium-rich
granitic rocks, metamorphic rocks of granitic composition, silica-rich volcanic rocks, many
sheared or faulted rocks, some coals, and certain kinds of contact metamorphosed rocks.
Rock types  least likely to cause radon problems include marine quartz sands, non-
carbonaceous shales and siltstones, certain kinds of clays, silica-poor metamorphic and

                                           II-5     Reprinted from USGS Open-File Report 93-292

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igneous rocks, and basalts.  Exceptions exist within these general lithologic groups because of
the occurrence of localized uranium deposits, commonly of the hydrothermal type in
crystalline rocks or the "roll-front" type in sedimentary rocks. Uranium and radium are
commonly sited in heavy minerals, iron-oxide coatines on rock and soil grains, and organic
materials in soils and sediments. Less common are uranium  associated with phosphate and
carbonate complexes in rocks and soils, and uranium minerals.
    Although many cases of elevated indoor radon levels can be traced to high radium and
(or) uranium concentrations in parent rocks, some structural features,  most notably faults and
shear zones, have been identified as sites of localized uranium concentrations (Deffeyes and
MacGregor, 1980) and have been associated with some of the highest reported  indoor radon
levels (Gundersen, 1991).  The two highest known indoor radon occurrences are associated
with sheared fault zones in Boyertown, Pennsylvania (Gundersen and others, 1988a; Smith
and others, 1987), and  in Clinton, New Jersey (Henry and others, 1991; Muessig  and Bell,
1988).

NURE AERIAL RADIOMETRIC DATA

    Aerial radiometric  data are used to quantify the radioactivity  of rocks and soils.
Equivalent uranium (eU) data provide an estimate of the surficial concentrations of radon
parent materials (uranium, radium) in rocks and soils. Equivalent uranium is calculated from
the counts received by  a gamma-ray detector from the 1.76 MeV (mega-electron  volts)
emission energy corresponding to bismuth-214 (2"Bi), 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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                . FLIGHT LINE  SPICING OF  SURE  AERIAL  SURVEYS
                     2  IK  (1 VILE)
                     5  IK  (3 MILES)
                     2  k  5  k'« • .
                 E3 10 KU  (6 HUES)
                     5  t  10  CV
                     NO DATA
Figure 2. Nominal flightline spacings for NURE aerial gamma-ray surveys covering the
contiguous United States (from Duval and others, 1990). Rectangles represent I°x2° quadrangles.

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    Figure 2 is an index map of NURE 1° x 2° quadrangles showing the flight-line spacing
for each quadrangle.  In general, the more closely spaced the flightlines are, the more area
was covered by the aerial gamma survey, and thus, more detail is available in the data set.
For an altitude of 400 ft above the ground surface and with primary flightline spacing
typically between 3 and 6 miles, less than 10 percent of the ground surface of the United
States was actually measured by the airborne gamma-ray detectors (Duval  and others, 1989),
although some areas had better coverage than others due to the differences in flight-line
spacing between  areas (fig. 2).  This suggests that some  localized uranium  anomalies may not
have been detected by the aerial surveys,  but the good correlations of eU patterns with
geologic outcrop  patterns indicate that, at relatively small scales (approximately  1:1,000,000
or smaller) the National eU map (Duval and others, 1989) gives reasonably good estimates of
average surface uranium concentrations and thus can assist in the prediction of radon potential
of rocks and soils, especially when augmented with additional geologic and soil  data.
    The shallow  (20-30 cm)  depth of investigation of gamma-ray spectrometers, either
ground-based or airborne (Duval and others, 1971; Durrance, 1986), suggests that gamma-ray
data may sometimes underestimate the radon-source strength in soils in which some of  the
radionuclides in the near-surface soil  layers have been transported downward through the soil
profile.  In such cases the concentration of radioactive minerals in the  A horizon would be
lower than in the B horizon, where such minerals are typically concentrated.  The
concentration of radionuclides in the C horizon and below may be relatively unaffected by
surface  solution processes.  Under these conditions the surface gamma-ray  signal may indicate
a lower radon source concentration than actually exists in the deeper soil layers, which  are
most likely to affect radon levels in structures with basements.  The redistribution of
radionuclides in soil profiles is dependent on a combination of climatic, geologic,  and
geochemical  factors.  There is reason to believe that correlations  of eU with actual soil
radium  and uranium concentrations at a depth relevant to radon entry into  structures may be
regionally variable (Duval, 1989; Schumann and Gundersen, 1991).  Given sufficient
understanding of the factors cited above, these regional differences may be predictable.

SOIL SURVEY DATA

    Soil surveys prepared by the U.S. Soil Conservation Service  (SCS) provide  data on soil
characteristics, including soil-cover thickness, grain-size  distribution, permeability, shrink-
swell potential, vegetative cover, generalized groundwater characteristics, and land use.  The
reports are available in county formats and State summaries. The county reports typically
contain  both generalized and detailed maps of soils in the area.
    Because  of time and map-scale constraints, it was impractical to examine county soil
reports for each county in the United States, so  more generalized summaries  at appropriate
scales were used  where available.  For State or regional-scale radon characterizations, soil
maps were compared to geologic maps of the area, and the soil descriptions, shrink-swell
potential, drainage characteristics,  depth to seasonal  high water table, permeability, and other
relevant characteristics of each soil group noted. Technical soil terms used in soil surveys are
generally complex; however, a good summary of soil engineering terms and the national
distribution of technical soil  types is the "Soils" sheet of the National Atlas (U.S.  Department
of Agriculture, 1987).
                                           II-8      Reprinted from USGS Open-File Report 93-292

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     Soil permeability is commonly expressed in SCS soil surveys in terms of the speed, in
 inches per hour (in/hr), at which water soaks into the soil, as measured in a soil percolation
 test.  Although in/hr are not truly units of permeability, these units are in widespread use and
 are referred to as "permeability" in SCS  soil surveys.  The permeabilities listed in the SCS
 surveys are for water, but they generally correlate well with gas permeability. Because data
 on gas permeability of soils is extremely limited, data on permeability to water is  used as a
 substitute except in cases in which excessive soil moisture is known to exist. Water in soil
 pores inhibits gas transport, so the.amount of.radon.available to a home is effectively reduced
 by a high water table.  Areas likely to have high water tables include river valleys, coastal
 areas, and some areas overlain by deposits of glacial origin (for example, loess).
     Soil permeabilities greater than 6.0 in/hr may be considered high, and permeabilities less
 than 0.6 in/hr may be considered low in terms of soil-gas transport.  Soils with low
 permeability may generally be considered to have a lower radon potential than more
 permeable soils with similar radium concentrations.  Many well-developed  soils contain a
 clay-rich B horizon that may impede vertical soil gas transport.  Radon  generated below this
 horizon cannot readily escape to the surface, so it would  instead tend to move laterally,
 especially under the influence of a negative pressure exerted by'a building.
     Shrink-swell potential is an indicator of the abundance of smectitic (swelling) clays in a
 soil.  Soils with a high shrink-swell potential may cause building foundations to crack,
 creating pathways for radon entry into  the structure.  During dry periods, desiccation cracks in
 shrink-swell soils provide additional pathways for soil-gas transport and effectively increase
 the gas permeability of the  soil.  Soil permeability  data and soil profile data thus provide
 important information for regional radon  assessments.

 INDOOR RADON DATA

    Two major sources of indoor  radon data were used. The first and largest source of data is
 from the State/EPA Residential Radon  Survey (Ronca-Battista and others, 1988; Dziuban and
 others, 1990). Forty-two states completed EPA-sponsored indoor radon surveys between 1986
 and.J992 (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 th.6 professional judgment and experience of the  individual
geologist.  The evaluations are nevertheless based  on established scientific principles that are
universally applicable to any geographic area or geologic setting. This section describes the
methods  and conceptual framework used by the U.S. Geological Survey to evaluate areas  for
radon potential based on the five factors discussed in the previous sections.  The scheme is
divided into two basic parts, a Radon Index (RI), used to rank the general radon potential of
the area,  and the Confidence Index (CI), used to express the level of confidence in the
prediction based on the quantity and quality of the data used to make the determination.  This
scheme works best if the areas to be evaluated are delineated by geologically-based
boundaries (geologic provinces) rather than political ones  (state/county boundaries) in which
the geology may vary across the area.
    Radon Index.  Table  1  presents the Radon Index (RI)  matrix. The five factors—indoor
radon data, geology, aerial radioactivity, soil parameters, and house foundation type—were
quantitatively  ranked (using a point value of 1, 2,  or 3) for their respective contribution to
radon potential in a given area.  At least some data for the 5 factors are  consistently available
for every geologic province. Because  each of these main factors encompass a wide variety  of
complex  and variable components, the geologists  performing the  evaluation relied heavily on
their professional judgment and experience in assigning point values to each category and in
determining the overall radon potential ranking. Background information on these factors is
discussed in more detail in the preceding sections  of this introduction. -
    Indoor radon was evaluated using  unweighted arithmetic means of the indoor radon data
for each  geologic area to  be assessed.  Other expressions of indoor radon levels in an area
also could have been used, such as weighted averages or annual averages, but these types of
data were not consistently available for the entire  United States at the time of this writing, or
the schemes were not considered sufficient to provide a means of consistent comparison
across all areas. For this  report, charcoal-canister screening measurement data from the
State/EPA Residential Radon Surveys  and other carefully selected sources were used, as
described in the preceding section.  To maintain consistency, other indoor radon data sets
(vendor,  state, or other data) were not considered  in scoring the indoor radon factor of the
Radon Index if they were not randomly sampled  or could not be statistically combined with
the primary indoor radon  data sets.  However, these additional radon data sets can provide  a
means to further refine correlations between geologic factors and radon potential, so they are


                                           II-11     Reprinted from USGS Open-File Report 93-292

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TABLE 1. RADON INDEX MATRIX,  "ppm eU" indicates parts per million of equivalent
uranium, as indicated by NURE aerial radiometric data.  See text discussion for details.

                                 INCREASING RADON POTENTIAL   ^
FACTOR
INDOOR RADON (average)

AERIAL RADIO ACITVirY
GEOLOGY*
SOIL PERMEABILITY
ARCHITECTURE TYPE
POINT VALUE
1
<2pCi/L
< 1.5 ppm eU
negative
low
mostly slab
2
2 - 4 pCi/L
1.5 - 2.5 ppm eU
variable
moderate
mixed
3
>4pCi/L
> 2.5 ppm eU
positive
high
mostly basement
*GEOLOGIC FIELD EVIDENCE (GFE) POINTS: GFE points are assigned in addition to points
   for the "Geology" factor for specific, relevant geologic field studies. See text for details.
   Geologic evidence supporting:
            HIGH radon        +2 points
            MODERATE       +1 point
            LOW             -2 points
No relevant geologic field studies    0 points
SCORING:
            Radon potential category
            LOW
            MODERATE/VARIABLE
            HIGH
                                   Probable average screening
                      Point range     indoor radon for area
                      3-8 points
                      9-11 points
                     12-17 points
           <2pCi/L
           2-4 pCi/L
           >4pCi/L
                      POSSIBLE RANGE OF POINTS = 3 to 17
TABLE 2.  CONFIDENCE INDEX MATRIX
                                     INCREASING CONFIDENCE
FACTOR
INDOOR RADON DATA

AERIAL RADIOACTIVITY
GEOLOGIC DATA
SOIL PERMEABILITY
POINT VALUE
1
sparse/no data
questionable/no data
questionable
questionable/no data
2
fair coverage/quality
glacial cover
variable
variable
3
good coverage/quality
no glacial cover
proven geol. model
reliable, abundant
 SCORING:
 LOW CONFIDENCE
 MODERATE CONFIDENCE
 HIGH CONFIDENCE
 4-6  points
 7-9  points
10 -12 points
                      POSSIBLE RANGE OF POINTS = 4 to 12
                                     H-12     Reprinted from USGS Open-File Report 93-292

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included as supplementary information and are discussed in the individual State chapters.  If
the average screening indoor radon level for an area was less than 2 pCi/L, the indoor radon
factor was assigned 1 point, if it was between 2 and 4 pCi/L, it was scored 2 points, and if
the average screening indoor radon level for an area was greater than 4 pCi/L, the indoor
radon factor was assigned 3 RI points.
    Aerial radioactivity data used in this report are from the equivalent uranium map of the
conterminous United States compiled from NURE aerial gamma-ray surveys (Duval and
others, 1989).  These data indicate the gamma  radioactivity from  approximately the upper 30
cm of rock and  soil, expressed in units of ppm equivalent uranium.  An approximate average
value of 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

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 been leached from the upper soil layers but are present and possibly 'even concentrated in
 deeper soil horizons, generating significant soil-gas radon. This positive supporting field
 evidence adds two GFE points to the score, which helps to counteract the invalid conclusion
 suggested by the radiometric data.  No GFE points are awarded if there are no documented
 field studies for the area.
     "Soil permeability" refers to several soil characteristics that influence radon concentration
 and mobility, including soil type, grain size, structure, soil moisture, drainage, slope, and
 permeability.  In the matrix, "low" refers to permeabilities less than about 0.6 in/hr; "high"
 corresponds to greater than about 6.0 in/hr, in U.S. Soil Conservation Service (SCS) standard
 soil percolation tests.  The SCS data are for water permeability, which generally correlates
 well with the gas permeability of the soil except when the soil moisture content is very high.
 Areas with consistently high water tables were thus considered to have low gas permeability.
 "Low, "moderate", and "high" permeability were assigned 1, 2, and 3 points, respectively.
    Architecture type refers to whether homes in the area have mostly basements (3 points),
 mostly slab-on-grade construction (1 point), or a mixture of the'two.  Split-level and crawl
 space homes fall into  the "mixed" category (2 points).  Architecture information is necessary
 to properly interpret the indoor radon data and produce geologic radon potential categories
 that are consistent with screening indoor radon data.
     The overall RI for an area is calculated by adding the individual RI scores for the 5
 factors, plus or minus GFE points, if any.  The total RI  for an area falls in one of three
 categories—-low, moderate or variable, or high. The point ranges for the three categories were
 determined by examining the possible combinations of points for the 5 factors and setting
 rules such  that a majority (3 of 5 factors) would determine the final score for the low  and
 high categories, with allowances for possible deviation from an ideal score by the other two
 factors. The moderate/variable category lies between these two ranges. A total deviation of 3
 points from the "ideal" score was considered reasonable to allow for natural variability of
 factors—if two of the five factors are allowed to vary from the "ideal" for a category,  they
 can differ by a minimum of 2 (1 point different each) and a maximum of 4 points (2 points
 different each). With "ideal" scores of 5, 10, and 15 points describing low, moderate,  and
 high geologic radon potential, respectively, an ideal low score of 5 points plus 3 points for
 possible variability allows a maximum of 8 points  in the low category.  Similarly, an ideal
 high score of 15 points minus 3 points gives a minimum of 12 points for the high category.
 Note, however, that if both other factors differ by two points from the "ideal", indicating
 considerable variability in the system, the total point score would lie in the adjacent (i.e.,
 moderate/variable) category.
    Confidence Index. Except for architecture type, the same factors were used to establish a
 Confidence Index (CI) for the radon potential prediction for each area (Table 2). Architecture
 type was not included in the confidence index because house construction data are readily and
reliably available through surveys taken by agencies and industry groups including the
 National Association of Home Builders,  U.S. Department of Housing and Urban
Development, and the Federal Housing Administration; thus it was not considered necessary

                                           11-14     Reprinted from USGS Open-File Report 93-292

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 to question the quality or validity of these data. The other factors were scored on the basis of
 the quality and quantity of the data used to complete the RI matrix.
     Indoor radon data were evaluated based on the distribution and number of data points and
 on whether the data were collected by random sampling (State/EPA Residential Radon Survey
 or other state survey data) or volunteered vendor data (likely to be nonrandom and biased
 toward population centers and/or high indoor radon levels).  The categories listed in the CI
 matrix for indoor radon data ("sparse or no data",  "fair  coverage or quality", and "good
 coverage/quality") indicate the sampling density-and .statistical robustness of an indoor  radon
 data set.  Data from the State/EPA Residential Radon Survey and statistically valid state
 surveys were typically assigned 3 Confidence Index points unless the data were poorly
 distributed or absent in the area evaluated.
    Aerial radioactivity data are available for all but a few areas of the continental United
 States and for part of Alaska.  An  evaluation of the quality of the radioactivity data  was based
 on whether there appeared to be a  good correlation between the radioactivity and the actual
 amount of uranium or radium  available  to generate mobile radon in the rocks and soils of the
 area evaluated.  In general, the greatest  problems with correlations among eU, geology, and
 soil-gas or indoor radon levels were associated with glacial deposits (see the discussion in a
 previous section) and  typically were assigned a 2-point Confidence Index score. Correlations
 among eU, geology, and radon were generally sound in  unglaciated areas and were usually
 assigned 3 CI points.  Again, however, radioactivity data in some unglaciated  areas may have
 been assigned fewer than 3 points,  and in  glaciated areas may be assigned only one point, if
 the data were considered  questionable or if coverage was poor.
    To assign Confidence Index scores for the geologic  data factor, rock types and geologic
 settings for which a physical-chemical, process-based  understanding of radon generation and
 mobility exists were regarded as  having "proven geologic models" (3 points); a high
 confidence could be held for predictions in such areas.  Rocks for which the processes are
 less'well known or for which data are contradictory were regarded as "variable" (2 points),
 and those about which little is known or for which no apparent correlations have been found
 were deemed "questionable" (1 point).
    The soil permeability factor was also scored based on quality and amount of data.   The
three categories for soil permeability in  the Confidence Index are similar in concept, and
 scored similarly, to those for the geologic  data factor. Soil permeability can be roughly
 estimated from grain size and drainage class if data from standard, accepted soil percolation
tests are unavailable; however, the reliability of the data would be lower than if percolation
test figures or other measured permeability data are available, because an estimate of this type
does not encompass all the factors that affect soil permeability and thus may be inaccurate in
some instances.  Most published soil permeability data are for water; although this is
generally closely related to the air permeability of the soil, there are some instances when it
may  provide an incorrect estimate.  Examples of areas in which water permeability data may
not accurately reflect air permeability include areas with consistently high levels of soil
moisture, or clay-rich  soils, which would have a low water permeability but may have a

                                           11-15     Reprinted from USGS Open-File Report 93-292

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significantly higher air permeability when dry due to shrinkage cracks in the soil. These
additional factors were applied to the "soil permeability factor when assigning the RI score, but
may have less certainty in some cases and thus would be assigned a lower CI score.
    The Radon Index and Confidence Index give a general indication of the relative
contributions of the interrelated geologic factors influencing  radon generation and transport in
rocks and soils,  and thus, of the potential for elevated indoor radon levels-to occur in a
particular area.  However, because  these reports are somewhat generalized to  cover relatively
large areas of States, it is highly recommended that more detailed studies be performed in
local areas of interest,  using the methods and general information in these booklets as a guide.
                                           11-16     Reprinted from USGS Open-File Report 93-292

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                                REFERENCES CITED

Akerblom, G., Anderson, P., and Clavensjo, B., 1984, Son gas radon--A source for indoor radon
       daughters: Radiation Protection Dosimetry, v. 7, p. 49-54.

Deffeyes, K.S., and MacGregor, I.D., 1980, World uranium resources: Scientific American,
       v'242, p. 66-76.

Durrance, E.M., 1986, Radioactivity in geology:  Principles and applications: New York, N.Y.,
       Wiley and Sons, 441 p.

Duval, J.S., 1989, Radioactivity and some of its applications in geology: Proceedings of the
       symposium on the application of geophysics to engineering and environmental problems
       (SAGEEP), Golden, Colorado, March 13-16,1989: Society of Engineering and Mineral
       Exploration Geophysicists, p. 1-61.

Duval, J.S., Cook, E.G., and Adams, J.A.S., 1971, Circle of investigation of an airborne
       gamma-ray spectrometer:-Journal of Geophysical Research, v. 76, p. 8466-8470.

Duval, J.S., Jones, W.J., Riggle, F.R., and Pitkin, J.A., 1989, Equivalent uranium map of
       conterminous United States: U.S. Geological Survey Open-File Report 89-478,10 p.

Duval, J.S., Reimer, G.M., Schumann, R.R., Owen, D.E., and Otton, J.K., 1990, Soil-gas
       radon compared to aerial and ground gamma-ray measurements at study sites near Greeley
       and Fort Collins, Colorado: U.S. Geological Survey Open-File Report 90-648,42 p.

Dziuban, J.A., Clifford, M.A., White, S.B., Bergstein, J.W., and Alexander, B.V., 1990,
       Residential radon survey of twenty-three States, in Proceedings of the 1990 International
       Symposium on Radon and Radon Reduction Technology, Vol. JJJ: Preprints: U.S.
       Environmental Protection Agency report EPA/600/9-90/005c, Paper IV-2,17 p.

 Gammage, R.B., Wilson, D.L., Saultz, R.J., and Bauer, B.C.,  1993, Subtereanean transport of
       radon and elevated indoor radon in hilly karst terranes: Atmospheric Environment
       (in press).

 Gundersen, L.C.S., Reimer, G.M., and Agard, S.S., 1988a, Correlation between geology, radon
       in soil gas, and indoor radon in the Reading Prong, in Marikos, M.A., and Hansman,
       R.H., eds., Geologic causes of natural radionuclide anomalies: Missouri Department of
       Natural Resources Special Publication 4, p. 91-102.

 Gundersen, L.C.S, Reimer, G.M., Wiggs, C.R., and Rice, C.A., 1988b, Map showing radon
       potential of rocks and soils in Montgomery County, Maryland: U.S. Geological Survey
       Miscellaneous Field Studies Map MF-2043, scale 1:62,500.

 Gundersen, Linda C.S., 1991, Radon in sheared metamorphic  and igneous rocks, in Gundersen,
        Linda C.S., and Richard B. Wanty, eds., Field  studies of radon in rocks, soils, and water:
        U.S. Geol.  Survey Bulletin no. 1971, p. 39-50.
                                          TJ-17     Reprinted from USGS Open-File Report 93-292

-------
Henry, Mitchell E., Kaeding, Margret E., and Monteverde, Donald, 1991, Radon in soil gas and
       gamma-ray activity of rocks and soils at the Mulligan Quarry, Clinton, New Jersey, in
       Gundersen, Linda C.S., and Richard B. Wanty, eds., Field studies of radon in rocks,
       soils, and water:  U.S. Geol. Survey Bulletin no. 1971, p. 65-75.

Klusman, R. W., and Jaacks, J. A., 1987, Environmental influences upon mercury, radon, and
       helium concentrations in soil gases at a site near Denver, Colorado: Journal of
       Geochemical Exploration, v. 27, p. 259-280.

Kovach, E.M., 1945, Meteorological influences upon the radon content of soil gas: Transactions,
       American Geophysical Union, v. 26, p. 241-248.

Kunz, C., Laymon, C.A., and Parker, C., 1989, Gravelly soils and indoor radon, in Osborne,
       M.C., and Harrison, J., eds., Proceedings of the  1988 EPA Symposium on Radon and
       Radon Reduction Technology, Volume  1: U.S. Environmental Protection Agency Report
       EPA/600/9-89/006A, p. 5-75-5-86.

Muessig, 1C, and Bell, C., 1988, Use of airborne radiometric data to direct testing for elevated
       indoor radon: Northeastern Environmental Science, v. 7, no. 1, p. 45-51.

Ronca-Battista, M., Moon, M., Bergsten, J., White, S.B., Holt, N., and Alexander, B., 1988,
       Radon-222 concentrations in the United States—Results of sample surveys in five states:
       Radiation Protection Dosimetry, v. 24, p. 307-312.

Rose, A.W., Washington, J.W., and Greeman,  D.J.,  1988, Variability of radon with depth and
       season in a central Pennsylvania soil developed on limestone: Northeastern Environmental
       Science, v. 7, p. 35-39.

Schery, S.D., Gaeddert, D.H., and Wilkening,  M.H., 1984, Factors affecting exhalation of radon
       from a gravelly sandy loam: Journal of  Geophysical Research, v. 89, p. 7299-7309.

Schumann, R.R., and Owen, D.E., 1988, Relationships between geology, equivalent uranium
       concentration, and radon in soil gas, Fairfax County, Virginia: U.S.  Geological Survey
       Open-File Report 88-18,28 p.

Schumann, R.R., and Gundersen, L.C.S., 1991, Regional differences in radon emanation
       coefficients in soils:  Geological Society of America Abstracts With  Programs, v. 23,
       no.  1, p.  125.

Schumann, R.R., Peake, R.T., Schmidt, K.M., and Owen, D.E., 1991,  Correlations of soil-gas
       and indoor radon with geology in glacially derived soils of the northern Great Plains, in
       Proceedings of the 1990 International Symposium on Radon and Radon Reduction
       Technology, Volume 2, Symposium Oral Papers: U.S. Environmental Protection Agency
       report EPA/600/9-91/026b, p. 6-23-6-36.
                                         JJ-18     Reprinted from USGS Open-File Report 93-292

-------
Schumann, R.R., Owen, D.E., and Asher-Bolinder, S., 1992, Effects of weather and soil
       characteristics on temporal variations in soil-gas radon concentrations, in Gates, A.E., and
       Gundersen, L.C.S., eds., Geologic controls on radon: Geological Society of America
       Special Paper 271, p. 65-72.

Sextro, R.G., Moed, B.A., Nazaroff, W.W., Revzan, K.L., and Nero, A.V., 1987,
       Investigations of soil as a source of indoor radon, in Hopke, P.K., ed., Radon and its
       decay products: American Chemical Society Symposium Series 331, p. 10-29.

Sterling, R., Meixel, G., Shen, L., Labs, K., and Bligh, T., 1985, Assessment of the energy
       savings potential of building foundations research:  Oak Ridge, Term., U.S. Department of
       Energy Report ORNL/SUB/84-0024/1.

Smith, R.C., JJ, 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 Adas 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.
                                         H-19     Reprinted from USGS Open-File Report 93-292

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                                           APPENDIX  A
                                   GEOLOGIC TIME SCALE
Subdivisions (and their symbols)
Eon or
Eonothem
Phanerozoic2
Proterozoic
(BJ
Archean
(A)
Era or.
Erathem
Cenozoic
(Cz)
Mesozoic2
(Mz)
Paleozoic2
(Pi)
F,o»""o*(Zl
MKJBIi
Etrtv

MIOBM
fc»nv
Period, System,
Subperiod, Subsysiem
Quaternary
(Q)
Neooene J
Subperiod or
T^.-Y Subsystem (N)
m Psleogene
l" Suboeriodor
Subsystem (Pi)
Cretaceous
(K)
Jurassic
(J)
Triassic
Hi)
Permian
(P)
Pennsylvanian
Carboniferous 'P'
(C) Mississippian
(M)
Devonian
(D)
Silurian
(S)
Ordovician
(Q)
Cambrian
fC)
Epoch or Series
Holocene
Pleistocene
Pliocene
Miocene
Oligocene
Eocene
Paleocene
Late
Early
Late
Middle
Early
Late
Middle
Early
Late
Early
Late
Middle
Early
Late
Early
Late
Middle
Early
Late
Middle
Early
Late
Middle
Early
Late
Middle
Early
Upper
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Lower
Upper
Middle
Lower
Upper
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Middle
Lower
None defined
Nont defined
None defined

Nont defined


Age estimates
of boundaries
in mega-annum
(Ma)1



24 (23-26)


	 66 (63-66)

	 138 (135-141)


	 205 (200-215)


	 -240

	 290 (290-305)


	 -330

	 360 (360-365)


	 410 (405-415)


	 435 (435-440)


	 500 (495-510)


-570 3
	 900
	 1600
	 2500
	 3000
	 3400
	 3800?

data
                          of tsolopic and btostratigraphic ag» assignmtnt*. Aot boundaries not etowly bracketedby existing
                          •*> Ac ratios .mp.oy^ «. cited in S.eigtr and Jiger 0977). Designat-on m.y. U«K) for an


            Oowtr. mid*, uppr or why. midd... lat.) when used with thw* H.ms «t inform., division, of th. taroer unit: th.

first letter of tht modHiar is lowercase.
   'Bock* oWtr than 570 Ma alio caBe
-------
   its of measure
                                    APPENDIX  B
                               GLOSSARY OF TERMS
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 O.Q6 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.
                                          11-21      Reprinted ftom USGS Open-File Report 93-292

-------
 argillite, argillaceous  Terms referring to a rock derived from clay or shale, or any sedimentary
 rock containing an appreciable amount of clay-size material, i.e., argillaceous sandstone.

 arid Term describing a climate characterized by dryness, or an evaporation rate that exceeds the
 amount of precipitation.

 basalt A general term for a dark-colored mafic igneous rocks that may be of extrusive origin,
 such as volcanic basalt flows, or intrusive origin, such as basalt dikes.

 batholith  A mass of plutonic igneous rock that has more than 40 square miles of surface
 exposure and no known bottom.

 carbonate A sedimentary rock consisting of the carbonate (COs) compounds of calcium,
 magnesium, or iron, e.g. limestone and dolomite.

 carbonaceous  Said of a rock or sediment that is rich in carbon, is coaly, or contains organic
 matter.

 charcoal canister A passive radon measurement device consisting of a small container of
 granulated activated charcoal that is designed to adsorb radon. Useful for short duration (2-7 days)
 measurements only. May be referred to as a "screening" test

 chert  A hard, extremely dense sedimentary rock consisting dominantly of interlocking crystals of
 quartz. Crystals are not visible to the naked eye, giving the rock a milky, dull luster. It may be
 white or gray but is commonly colored red, black, yellow, blue, pink, brown, or green.

 clastic pertaining to a rock or sediment composed of fragments that are derived from preexisting
 rocks or minerals. The most common clastic sedimentary rocks are sandstone and shale.

 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 alumhium (and a wide variety of other elements). They are formed chiefly by
 alteration or weathering of primary silicate minerals. Certain clay minerals are noted for their small
 size and ability to absorb substantial amounts of water, causing them to swell. The change in size
 that occurs as these clays change between dry and wet is referred to as their "shrink-swell"
potential.

 concretion A hard, compact mass of mineral matter, normally subspherical but commonly
irregular in shape; formed by precipitation from a water solution about a nucleus or center; such as
 a leaf,  shell, bone, or fossil, within a sedimentary or fractured rock.

conglomerate A coarse-grained, clastic sedimentary rock composed of rock and mineral
fragments larger than 2 mm, set in a finer-grained matrix of clastic material.

cuesta A hill or ridge with a gentle slope on one side and  a steep slope on the other.  The
formation of a cuesta is controlled by the different weathering properties and the structural dip of
the rocks forming the hill or ridge.

 daughter product A nuclide formed by the disintegration of a radioactive precursor or "parent"
 atom.
                                          H-22      Reprinted from USGS Open-File Report 93-292

-------
 delta, deltaic Referring to a low, flat, alluvial tract of land having a triangular or fan shape,
 located at or near the mouth of a river. It results from the accumulation of sediment deposited'by a
 river at the point at which the river loses its ability to transport the sediment, commonly where a
 river meets a larger body of water such as a lake or ocean.
 dike A tabular igneous intrusion of rock, younger than the surrounding rocktthat commonly cuts
 across the bedding or foliation of the rock it intrudes.
 diorite A plutonic igneous rock that is medium in color and contains visible dark minerals that
 make up less than 50% of the rock. It also contains abundant sodium plagioclase and minor
 quartz.
 dolomite A carbonate sedimentary rock of which more than 50% consists of the mineral dolomite
 (CaMg(CO3>2), and is commonly white, gray, brown, yellow, or pinkish in color.
 drainage The manner in which the waters of an area pass, flow off of, or flow into the soil.
 Also refers to the water features of an area, such as lakes and rivers, that drain it.
 eolian  Pertaining to sediments deposited by the wind.
 esker  A long, narrow, steep-sided ridge composed of irregular beds of sand and gravel deposited
 by streams beneath a glacier and left behind when the ice melted.
 evapotranspiration Loss of water from a land area by evaporation from the soil and
 transpiration from plants.
 extrusive Said of igneous rocks that have been erupted onto the surface of the Earth.
 fault A fracture or zone of fractures in rock or sediment along which there has been movement.
 fluvial, fluvial deposit Pertaining to sediment that has been deposited by a river or stream.
 foliation A linear feature in a rock defined by both mineralogic and structural characteristics. It
 may be formed during deformation or metamorphism.
 formation A mappable body of rock having similar characteristics.
 glacial deposit Any sediment transported and deposited by a glacier or processes associated
 with glaciers, such as glaciofluvial sediments deposited by streams flowing from melting glaciers.
 gneiss A rock formed by metamorphism in which bands and lenses of minerals of similar
 composition alternate with bands and lenses of different composition, giving the rock a striped or
 "foliated" appearance.
 granite Broadly applied, any coarsely crystalline, quartz- and feldspar-bearing igneous plutonic
rock. Technically, granites have between 10 and 50% quartz, and alkali feldspar comprises at least
 65% of the total feldspar.
 gravel An unconsolidated, natural accumulation of rock fragments consisting predominantly of
particles greater than 2 mm in size.
 heavy minerals Mineral grains in sediment or sedimentary rock having higher than  average
 specific gravity. May form layers and lenses because of wind or water sorting by weight and size
                                          11-23      Reprinted from USGS Open-File Report 93-292

-------
and may be referred to as a "placer deposit." Some.heavy minerals are magnetite, garnet, zircon,
mohazite, and xenotime.
igneous Said of a rock or mineral that solidified from molten or partly molten rock material. It is
one of the three main classes into which rocks are divided, the others being sedimentary and
metamorphic.
intermonfane A term that refers to an area between two mountains or mountain ranges.
intrusion, intrusive The processes of emplacement or injection of molten rock into pre-existing
rock. Also refers to the rock formed by intrusive processes, such as an "intrusive igneous rock".
kame A low mound, knob, hummock, or short irregular ridge formed by a glacial stream at the
margin of a melting glacier; composed of bedded sand and gravel.
karst terrain A type of topography that is formed on limestone, gypsum and other rocks by
dissolution of the rock by water, forming sinkholes and caves.
lignite A brownish-black coal that is intermediate in coalification between peat and
subbituminous coal.
limestone A carbonate sedimentary rock consisting of more than 50% calcium carbonate,
primarily in the form of the mineral calcite (CaCOs).
lithology The description of rocks in hand specimen and in outcrop on the basis of color,
composition, and grain size.
loam A permeable soil composed of a mixture of relatively equal parts clay, silt, and sand, and
usually containing some organic matter.
loess A fine-grained eolian deposit composed of silt-sized particles generally thought to have
been deposited from windblown dust of Pleistocene age.
mafic Term describing an igneous rock containing more than 50% dark-colored minerals.
marine Term describing sediments deposited in the ocean, or precipitated from ocean waters.
metamorphic Any rock derived from pre-existing rocks by mineralogical, chemical, or structural
changes in response to changes in temperature, pressure, stress, and the chemical environment.
Phyllite, schist, amphibolite, and gneiss are metamorphic rocks.
moraine A mound, ridge, or other distinct accumulation of unsorted, unbedded glacial material,
predominantly till, deposited by the action of glacial ice.
outcrop That part of a geologic formation or structure that appears at the surface of the Earth, as
in "rock outcrop".
percolation test A term used in engineering for a test to determine the water permeability of a
soil. A hole is dug and filled with water and the rate of water level decline is measured.
permeability The capacity of a rock, sediment, or soil to transmit liquid or gas.
phosphate, phosphatic, phosphorite  Any rock or sediment containing a significant amount
of phosphate minerals, i.e., minerals containing PO4.
                                          11-24      Reprinted from USOSOpen-FUe Report 93-292

-------
physiographic province A region in which all parts are similar in geologic structure and
climate, which has had a uniform geomorphic history, and whose topography or landforms differ
significantly from adjacent regions.

placer deposit See heavy minerals

residual Formed by weathering of a material in place.

residuum Deposit of residual material.

rhyolite An extrusive igneous rock of volcanic origin, compositionally equivalent to granite.

sandstone A clastic sedimentary rock composed of sand-sized rock and mineral material that is
more or less firmly cemented. Sand particles range from 1/16 to 2 mm in size.

schist A strongly foliated crystalline rock, formed by metamorphism, that can be readily split into
thin flakes or slabs.  Contains mica; minerals are typically aligned.

screening level  Result of an indoor radon test taken with a charcoal canister or similar device,
for a short period of time, usually less than seven days. May indicate the potential for an indoor
radon problem but does not indicate annual exposure  to radon.

sediment Deposits of rock and mineral particles or fragments originating from material that is
transported by air, water or ice, or that accumulate by  natural chemical precipitation or secretion of
organisms.

semiarid Refers to a climate that has slightly more precipitation than an arid climate.

shale  A fine-grained  sedimentary rock formed from  solidification (lithification) of clay or mud.

shear zone Refers to a roughly linear zone of rock that has been faulted by ductile or non-ductile
processes in which the rock is sheared and both sides are displaced relative to one another.

shrink-swell clay See clay mineral.

siltstone A fine-grained clastic sedimentary rock composed of silt-sized rock and mineral
material and more or less firmly cemented.  Silt particles range from 1/16 to 1/256 mm in size.

sinkhole A roughly circular depression in a karst area measuring meters to tens of meters in
 diameter. It is runnel 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



                                            n-25    Reprinted from USGS Open-File Report 93-292

-------
terrace gravel  Gravel-sized material that caps ridges and terraces, left behind by a stream as it
cuts down to a lower level.
terrain A tract or region of the Earth's surface considered as a physical feature or an ecological
environment
till Unsorted, generally unconsolidated and unbedded rock and mineral material deposited directly
adjacent to and underneath a glacier, without reworking by meltwater. Size of grains varies greatly
from clay to boulders.
uraniferous Containing uranium, usually more than 2 ppm.
vendor data Used in this report to refer to indoor radon data collected and measured by
commercial vendors of radon measurement devices and/or services.
volcanic Pertaining to the activities, structures, and extrusive rock types of a volcano.
water table The surface forming the boundary between the zone of saturation and the zone of
aeration; the top surface of a body of unconfined groundwater in rock or soil.
weathering The destructive process by which earth and rock materials, on exposure to
atmospheric elements, are changed in color, texture, composition, firmness, or form with little or
no transport of the material.
                                           n-26      Reprinted from USGS Open-File Report 93-292

-------
                                          APPENDIX  C
                                  EPA REGIONAL OFFICES
EPA  Regional  Offices
State
EPA  Reeion
EPA Region 1
JFK Federal Building
Boston, MA 02203
(617)  565-4502

EPA Region 2
(2AIR:RAD)
26 Federal Plaza
New York, NY 10278
(212)  264-4110

Region 3 (3AH14)
841 Chestnut Street
Philadelphia,  PA 19107
(215)  597-8326

EPA Region 4
345 Courtland Street, N.E.
Atlanta, GA 30365
(404)  347-3907

EPA Region 5 (5AR26)
77 West Jackson Blvd.
Chicago, IL 60604-3507
(312)  886-6175

EPA Region 6 (6T-AS)
1445 Ross Avenue
Dallas, TX 75202-2733
(214)  655-7224

EPA Region 7
726 Minnesota Avenue
Kansas City, KS  66101
(913)  551-7604

EPA Region 8
(8HWM-RP)
999 18th Street
One Denver Place, Suite 1300
Denver, CO 80202-2413
(303)  293-1713

EPA Region 9 (A-3)
75 Hawthorne Street
San Francisco, CA 94105
(415)  744-1048

EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
(202)  442-7660
Alabama	4
Alaska	10
Arizona	..9
Arkansas	6
California	9
Colorado...	8
Connecticut	1
Delaware	....3
District of  Columbia	3
Florida	4
Georgia	4
Hawaii	9
Idaho	10
Illinois	5
Indiana	5
Iowa	7
Kansas	i	7
Kentucky	4
Louisiana	6
Maine	1
Maryland	3
Massachusetts	1
Michigan	5
Minnesota	5
Mississippi	4
Missouri	7
Montana	8
Nebraska	7
Nevada	9
New Hampshire	1
New  Jersey	2
New Mexico	6
New York	2
North  Carolina	4
North  Dakota	8
Ohio	5
Oklahoma	.........6
Oregon	10
Pennsylvania....	3
Rhode Island	1
South  Carolina	4
South  Dakota	8
Tennessee	4
Texas	.....6
Utah	8
Vermont	1
Virginia	3
Washington	.....10
West Virginia	.'..	3
Wisconsin	5
Wyoming	8
                                                n-27
       Reprinted from USGS Open-FUe Report 93-292

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                                STATE RADON CONTACTS
                                            May, 1993
Alabama       • James McNees
               Division of Radiation Control
               Alabama Department of Public health
               State Office Building
               Montgomery, AL 36130
               (205)242-5315
               1-800-582-1866 in state
               Charles Tedford  •
               Department of Health and Social
                 Services
               P.O. Box 110613
               Juneau.AK 99811-0613
               (907)465-3019
               1-800-478-4845 in state
Arizona        John Stewart
               Arizona Radiation Regulatory Agency
               4814 South 40th St.
               Phoenix, AZ 85040
               (602) 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 In State

    District Robert Davis
of Columbia DC Department of Consumer and
              Regulatory Affairs
            614 H Street NW
            Room 1014
            Washington, DC 20001
            (202) 727-71068

     Florida N. Michael Gilley
            Office of Radiation Control
            Department of Health and
              Rehabilitative Services
            1317 Winewood Boulevard
            Tallahassee, EL 32399-0700
            (904)488-1525
            1-800-543-8279 in state

    Georgia Richard Schreiber
            Georgia Department of Human
              Resources
            878 Peachtree St., Room  100
            Atlanta, GA 30309
            (404) 894-6644
             1-800-745-0037 in state

     Hawaii Russell Takata
            Environmental Health Services
              Division
             591 Ala Moana Boulevard
             Honolulu, ffl 96813-2498
             (808) 5864700
                                                11-28       Reprinted from USGS Open-File Report 93-292

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Idaho
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 Allen
                Illinois Department of Nuclear Safety
                1301 Outer Park Drive
                Springfield, IL 62704
                (217) 524-5614
                1-800-325-1245 in state
Lorand Magyar
Radiological Health Section
Indiana State Department of Health
1330 West Michigan Street
P.O. Box 1964
Indianapolis, IN 46206
(317) 633-8563
1-800-272-9723 In State

Donald A. Hater
Bureau of Radiological Health
Iowa Department of Public Health
Lucas State Office Building
Des Moines, IA 50319-0075
(515) 281-3478
1-800-383-5992 In State

Harold Spiker
Radiation Control Program
Kansas Department of Health and
  Environment
109 SW 9th Street
6th Floor Mills Building
Topeka, KS 66612
(913) 296-1561

JeanaPhelps
Radiation Control Branch
Department of Health Services
Cabinet for Human Resources
275 East Main Street
Frankfort, KY 40601
(502) 564-3700
    Louisiana  Matt Schlenker
              Louisiana Department of
                Environmental Quality
              P.O. Box 82135
              Baton Rouge, LA 70o84-2135
              (504)925-7042
              1-800-256-2494 in state

  .  .,.. Maine  Bob Stilwell
              Division of Health Engineering
              Department of Human Services
              State House, Station 10
              Augusta, ME 04333
              (207)289-5676
              1-800-232-0842 in state

    Maryland  Leon J. Rachuba
              Radiological Health Program
              Maryland Department of the
                Environment
              2500 Broening Highway
              Baltimore, MD 21224
              (410)631-3301
              1-800-872-3666 In State

Massachusetts  William J. Bell
              Radiation Control Program
              Department of Public Health
              23 Service Center
              Northampton, MA 01060
              (413) 586-7525
              1-800-445-1255 in state

    Michigan  Sue Hendershott
              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
                                                IE-29      Reprinted from USGS Open-File Report 93-292

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Mississippi      Silas Anderson
                Division of Radiological Health
                Department of Health
                3150 Lawson Street
                P.O. Box 1700
                Jackson, MS 39215-1700
                (601) 354-6657
                1-800-626-7739 in state

Missouri        Kenneth V. Miller
                Bureau of Radiological Health
                Missouri Department of Health
                1730 East Elm
                P.O. Box 570
                Jefferson City, MO 65102
                (314)751-6083
                1-800-669-7236 In State

Montana        Adrian C. Howe
                Occupational Health Bureau
                Montana Department of Health and
                 Environmental Sciences
                Cogswell Building A113
                Helena, MT 59620
                (406)444-3671
Nebraska       Joseph Milone
               Division of Radiological Health
               Nebraska Department of Health
               301 Centennial Mall, South
               P.O. Box 95007
               Lincoln, NE 68509
               (402)471-2168
               1-800-334-9491 In State

Nevada         Stan Marshall
               Department of Human Resources
               505 East King Street
               Room 203
               Carson City, NV 89710
               (702) 687-5394

New Hampshire David Chase
               Bureau of Radiological Health
               Division of Public Health Services
               Health and Welfare Building
               Six Hazen Drive
               Concord, NH 03301
               (603)271-4674
               1-800-852-3345 x4674
.   New Jersey  Tonalee Carlson Key
               Division of Environmental Quality
               Department of Environmental
                Protection
               CN415
               Trenton, NJ 08625-0145
               (609)987-6369
               1-800-648-0394 in state

  New Mexico  William M. Floyd
               Radiation Licensing and Registration
                Section
               New Mexico Environmental
                Improvement Division
               1190 St. Francis Drive
               Santa Fe, MM 87503
               (505) 827-4300

    New York  William J. Condon
               Bureau of Environmental Radiation
                Protection
               New York State Health Department
               Two University Place
               Albany, NY 12202
               (518)458-6495
               1-800-458-1158 in state

North Carolina  Dr. Felix Fong
               Radiation Protection Division
               Department of Environmental Health
                and Natural Resources
               701 Barbour Drive
               Raleigh, NC 27603-2008
               (919) 57M141
               1-800-662-7301 (recorded info x4196)

 North Dakota  Arlen Jacobson
               North Dakota Department of Health
               1200 Missouri Avenue, Room 304
               P.O. Box 5520
               Bismarck, ND 58502-5520
               (701)221-5188

         Ohio  Marcie Matthews
               Radiological Health Program
               Department of Health
               1224 Kinnear Road - Suite 120
               Columbus, OH 43212
               (614) 644-2727
               1-800-523-4439 in state
                                               H-30
        Reprinted from USGS Open-File Report 93-292

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Oklahoma
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)7344631
               1-800-768-0362
South Dakota MikePochop
             Division of Environment Regulation
             Department of Water and Natural
               Resources
             Joe Foss Building, Room 217
             523 E. Capitol
             Pierre, SD 57501-3181
             (605)773-3351

   Tennessee Susie Shimek
             Division of Air Pollution Control
             Bureau of the Environment
             Department of Environment and
               Conservation
             Customs House, 701 Broadway
             Nashville, TN 37219-5403
             (615) 532-0733
             1-800-232-1139 in state

       Texas Gary Smith
             Bureau of Radiation Control
             Texas Department of Health
             1100 West 49th Street
             Austin, TX 78756-3189
             (512) 834-6688
        Utah John Hultquist
             Bureau of Radiation Control
             Utah State Department of Health
             288 North, 1460 West
             P.O. Box 16690
             Salt Lake City, UT 84116-0690
             (801) 5364250
                                           *
    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)2644110
                                               11-31      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     Kate Coleman
                Department of Health
                Office of Radiation Protection
                Airdustrial Building 5, LE-13
                Olympia,WA 98504
                (206)753-4518
                1-800-323-9727 In State

 West Virginia    Beattie L. DeBord
                Industrial Hygiene Division
                West Virginia Department of Health
                151 llth Avenue
                South Charleston, WV 25303
                (304) 558-3526
                1-800-922-1255 In State

 Wisconsin       Conrad Weiffenbach
                Radiation Protection Section
                Division of Health
                Department of Health and Social
                 Services
                P.O. Box 309
                Madison, WI53701-0309
                (608)267-4796
                1-800-798-9050 in state

Wyoming       Janet Hough
                Wyoming Department of Health and
                 Social Services
                Hathway Building, 4th Floor
                Cheyenne, WY 82002-0710
                (307)777-6015
                1-800-458-5847 in state
                                               IE-32      Reprinted from USGS Open-File Report 93-292

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                            STATE GEOLOGICAL SURVEYS
                                            May, 1993
Alabama        Emest A. Mancini
               Geological Survey of Alabama
               P.O. Box 0
               420 Hackberry Lane
               Tuscaloosa, AL 35486-9780
               (205) 349-2852
               Thomas E. Smith
               Alaska Division of Geological &
                 Geophysical Surveys
               794 University Ave., Suite 200
               Fairbanks, AK 99709-3645
               (907)479-7147
Arizona         Larry D. Fellows
               Arizona Geological Survey
               845 North Park Ave., Suite 100
               Tucson, AZ 85719
               (602) 882-4795
Arkansas        Norman F. Williams
               Arkansas Geological Commission
               Vardelle Parham Geology Center
               3815 West Roosevelt Rd.
               Little Rock, AR 72204
               (501) 324-9165

California       James F. Davis
               California Division of Mines &
                 Geology
               801 K Street, MS 12-30
               Sacramento, CA 95814-3531
               (916)445-1923

Colorado        Pat Rogers (Acting)
               Colorado Geological Survey
               1313 Sherman St., Rm 715
               Denver, CO 80203
               (303) 866-2611

Connecticut     Richard C. Hyde
               Connecticut Geological & Natural
                 History Survey
               165 Capitol Ave., Rm. 553
               Hartford, CT 06106
               (203) 566-3540

Delaware        Robert R. Jordan
               Delaware Geological Survey
               University of Delaware
               101 Penny Hall
               Newark, DE 19716-7501
               (302) 831-2833
 Florida  Walter Schmidt
        Florida Geological Survey
        903 W. Tennessee St.
        Tallahassee, FL 32304-7700
        (904)488-4191
Georgia  William H. McLemore
        Georgia Geologic Survey
        Rm. 400
        19 Martin Luther King Jr. Dr. SW
        Atlanta, GA 30334
        (404) 656-3214

Hawaii  Manabu Tagomori
        Dept. of Land and Natural Resources
        Division of Water & Land Mgt
        P.O. Box 373
        Honolulu, ffl 96809
        (808) 548-7539

  Idaho  Earl H. Bennett
        Idaho Geological Survey
        University of Idaho
        Morrill Hall, Rm. 332
        Moscow, ID 83843
        (208) 885-7991

Illinois  Morris W. Leighton
        Illinois State Geological Survey
        Natural Resources Building
        615 East Peabody Dr.
        Champaign, IL 61820
        (217) 333^747

Indiana  Norman C. Hester
        Indiana Geological Survey
        611 North Walnut Grove
        Bloomington, IN 47405
        (812) 855-9350

  Iowa  Donald L. Koch
        Iowa Department of Natural Resources
        Geological Survey Bureau
        109 Trowbridge Hall
        Iowa City, IA 52242-1319
        (319) 335-1575

Kansas  Lee C.Gerhard
        Kansas Geological Survey
        1930 Constant Ave., West Campus
        University of Kansas
        Lawrence, KS 66047
        (913) 864-3965
                                              n-33
  Reprinted from USGS Open-File Report 93-292

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 Kentucky       Donald CHaney
                Kentucky Geological Survey
                University of Kentucky
                228 Mining & Mineral Resources
                  Building
                Lexington, KY 40506-0107
                (606)257-5500

 Louisiana       William E. Marsalis
                Louisiana Geological Survey
                P.O. Box 2827
                University Station
                Baton Rouge, LA 70821-2827
                (504) 388-5320

 Maine          Walter A. Anderson
                Maine Geological Survey
                Department of Conservation
                State House, Station 22
                Augusta, ME 04333
                (207) 289-2801
Maryland       Emery T. Cleaves
               Maryland Geological Survey
               2300 St. Paul Street
               Baltimore, MD 21218-5210
               (410) 554-5500
Massachusetts   Joseph A. Sinnott
               Massachusetts Office of
                 Environmental Affairs
               100 Cambridge St., Room 2000
               Boston, MA 02202
               (617)727-9800

Michigan       R. Thomas Segall
               Michigan Geological Survey Division
               Box 30256
               Lansing, MI 48909
               (517)334-6923

Minnesota      Priscilla C. Grew
               Minnesota Geological Survey
               2642 University Ave.
               St, Paul, MN 55114-1057
               (612)627-4780
Mississippi     S. Cragin Knox
               Mississippi Office of Geology
               P.O. Box 20307
               Jackson, MS 39289-1307
               (601)961-5500
      Missouri  James H. Williams
                Missouri Division of Geology &
                 Land Survey
                111 Fairgrounds Road
                P.O. Box 250
                Rolla, MO 65401
                (314) 368-2100

      Montana  Edward T. Ruppel
     	Montana Bureau of Mines & Geology
                Montana College of Mineral Science
                 and Technology, Main Hall
                Butte, MT 59701
                (406)496-4180

      Nebraska  Perry B. Wigley
                Nebraska Conservation & Survey
                 Division
                113 Nebraska Hall
                University of Nebraska
                Lincoln, NE 68588-0517
                (402)472-2410

        Nevada  Jonathan G. Price
                Nevada Bureau of Mines & Geology
                Stop 178
                University of Nevada-Reno
                Reno, NV 89557-0088
                (702) 784-6691

New Hampshire  Eugene L. Boudette
                Dept. of Environmental Services
                117 James Hall
               University of New Hampshire
                Durham, NH 03824-3589
                (603) 862-3160

    New Jersey  Haig F. Kasabach
                New Jersey Geological Survey
                P.O. Box 427
                Trenton, NJ 08625
                (609)292-1185

   New Mexico  Charles E. Chapin
                New Mexico Bureau of Mines &
                 Mineral Resources
                Campus Station
                Socorro.NM 87801
                (505) 835-5420

     New York  Robert H. Fakundiny
                New York State Geological Survey
                3136 Cultural Education Center
                Empire State Plaza
                Albany, NY 12230
                (518)474-5816
                                               IE-34      Reprinted from USGS Open-File Report 93-292

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 North Carolina  Charles H. Gardner
                North Carolina Geological Survey
                P.O. Box 27687
              .  Raleigh, NC 27611-7687
                (919)733-3833

North Dakota    John P. Bluemle
                North Dakota Geological Survey
                600 East Blvd.
                Bismarck,ND  58505-0840
                (701) 22A-4109
Ohio           Thomas M. Berg
               Ohio DepL of Natural Resources
               Division of Geological Survey
               4383 Fountain Square Drive
               Columbus, OH 43224-1362
               (614)265-6576

Oklahoma      Charles J. Mankin
               Oklahoma Geological Survey
               Room N-131, Energy Center
               100E.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     Ramdn M. Alonso
               Puerto Rico Geological Survey
                 Division
               Box 5887
               Puerta de Tierra Station
               San Juan, P.R. 00906
               (809) 722-2526

Rhode Island    J. Allan Cain
               Department of Geology
               University of Rhode Island
               315 Green Hall
               Kingston, RI02881
               (401) 792-2265
South Carolina Alan-Jon W. Zupan (Acting)
              South Carolina Geological Survey
              5 Geology Road
              Columbia, SC 29210-9998
              (803) 737-9440

 South Dakota C.M. Christensen (Acting)
              South Dakota Geological Survey
              Science Center
           -  - University of South Dakota
              Vermfflion, SD 57069-2390
              (605) 677-5227

    Tennessee Edward T. Luther
              Tennessee Division of Geology
              13th Floor, L & C Tower
              401 Church Street
              Nashville, TN 37243-0445
              (615)532-1500

        Texas William L. Fisher
              Texas Bureau of Economic Geology
              University of Texas
              University Station, Box X
              Austin, TX 78713-7508
              (512)471-7721

        Utah M. Lee Allison
              Utah Geological & Mineral Survey
              2363 S. Foothill Dr.
              Salt Lake City, UT 84109-1491
              (801)467-7970
     Vermont Diane L. Conrad
              Vermont Division of Geology and
                Mineral Resources
              103 South Main St.
              Waterbury.VT 05671
              (802) 244-5164
      Virginia Stanley S. Johnson
              Virginia Division of Mineral
                Resources
              P.O. Box 3667
              Charlottesville, VA 22903
              (804)293-5121
  Washington Raymond Lasmanis
              Washington Division of Geology &
                Earth Resources
              Department of Natural Resources
              P.O. Box 47007
              Olympia, Washington 98504-7007
              (206) 902-1450
                                               11-35      Reprinted from USGS Open-File Report 93-292

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  West Virginia  Larry D.Woodfoik
               West Virginia Geological and
                 Economic Survey
               Mont Chateau Research Center
               P.O. Box 879
               Morgantown.WV  26507-0879
               (304)594-2331

Wisconsin      James Robertson
               Wisconsin Geological & Natural
                 History Survey
               3817 Mineral Point Road
               Madison, WI 53705-5100
               (608)263-7384

Wyoming      Gary B. Glass
               Geological Survey of Wyoming
               University of Wyoming
               Box 3008, University Station
               Laramie, WY 82071-3008
               (307) 766-2286
                                                11-36      Reprinted from USGS Open-File Report 93-292

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              EPA REGION 4 GEOLOGIC RADON POTENTIAL SUMMARY
                                           by
              Linda C.S. Gundersen, James K. Otton, and R. Randall Schumann
                                 U.S. Geological Survey

       EPA Region 4 includes the states of Alabama, Florida, Georgia, Kentucky, Mississippi,
North Carolina, South Carolina, and Tennessee. For each state, geologic radon potential areas
were delineated and ranked on the basis of geologic, soil,Jiousing construction, and other factors.
Areas in which the average screening indoor radon level of all homes within the area is estimated to
be greater than 4 pCi/L were ranked high. Areas in which the average screening indoor radon
level of all homes within the area is estimated to be between 2 and 4 pCi/L were ranked
moderate/variable, and areas in which the average screening indoor radon level of all homes within
the area is estimated to be less than 2 pCi/L were ranked low. Information on the data used and on
the radon potential ranking scheme is given in the introduction to this volume. More detailed
information on the geology and radon potential of each state in Region 4 is given in the individual
state chapters. The individual chapters describing the geology and radon potential of the states in
EPA Region 4, though much more detailed than this summary, still are generalized assessments
and there is no substitute for having a home tested. Within any radon potential area homes with
indoor radon levels both above and below the predicted average will likely be found.
       Major geologic/physiographic provinces for Region 4 are shown in figure 1 and are
referred to in the summary that follows.  The moderate climate, use of air conditioning, evaporative
coolers, or open windows for ventilation, and the small proportion of homes with basements
throughout much of Region 4 contribute to generally low indoor radon levels in spite of the fact
that this area has substantial areas of high surface radioactivity.
       Maps showing arithmetic means of measured indoor radon levels are shown in figure 2.
Indoor radon data for Alabama, Georgia, Kentucky, Mississippi, North Carolina, South Carolina,
and Tennessee are from the State/EPA Residential Radon Survey.  Data for Florida are from the
Florida Statewide  Radon Study. County screening indoor radon averages range from less than 1
pCi/L to 4.6 pCi/L. The geologic radon potential areas in Region 4 have been summarized from
the individual state chapters and are shown in figure 3.

ALABAMA

The Plateaus
       The Interior Low Plateaus have been ranked high in geologic radon potential.  The
Mississippian carbonate rocks and shales that underlie this province appear to have high (>2.5 ppm
eU) to moderate (1.5-2.5 ppm eU) radioactivity associated with them.  The carbonates and shales
are also associated with most of the highest county indoor radon averages for the State, particularly
in Colbert, Madison, Lawrence, and Lauderdale Counties. The geologic units that may be the
source of these problems, as indicated by the radioactivity, appear to be parts of the Fort Payne
Chert, the Tuscumbia Limestone, the Monteagle, Bangor, Pride Mountain, and Parkwood
Formations, and the Floyd Shale.  Indoor radon levels in homes built on the St. Genevieve
Limestone, Tuscumbia Limestone, and Fort Payne Chert averaged between 3.0 and 4.3 pCi/L.
Soils developed from carbonate rocks are often elevated in uranium and radium. Carbonate soils
are derived from the dissolution of the CaCOs that makes up the majority of the rock.  When the
CaCOs has been dissolved away, the soils are enriched in the remaining impurities, predominantly
                                          m-1     Reprinted from USGS Open-FUe Report 93-292-D

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Figure 1. Geologic radon potential areas of EPA Region 4.  See next page for names of
numbered areas.

-------
 Figure 1 (continued). Geologic radon potential areas of EPA Region 4. Note: although some
 areas, for example, the Coastal Plain, are contiguous from state to state, they are sometimes
 referred to by slightly different names or are subdivided differently in different states, thus are
 numbered and labelled seperately on this figure.
 l-Jackson Purchase (Coastal Plain)
 2-Western Coalfield
 3-Mississippian Plateau
 4-Eastern Pennyroyal
 5-New Albany Shale
 6-OuterBluegrass
 7-Inner Bluegrass
 8-Cumberland Plateau (Appalachian Plateau)
 9-Mississippi alluvial plain
 10-Loess-covered Coastal Plain
 11-Eastern Coastal Plain
 12-Cherty Highland
 13-Highland Rim
 14-Nashville Basin
 15-Appalachian Plateau
 16-Ridge and Valley
 17-Unaka Mountains
 18-Blue Ridge Belt
 19-Brevard Fault Zone
20-Chauga Belt
21-Inner Piedmont
22-Kings Mountain Belt
23-Dan River Basin
24-Milton Belt
25-Charlotte Belt
26-Carolina Slate Belt
27-Wadesboro sub-basin
28-Sanfonl-Durham sub-basins
29-Raleigh Belt
30-Eastern Slate Belt
 31-Inner Coastal Plain
 32-Outer Coastal Plain
 33-Jackson Prairies
 34-Loess HiUs
 35-North Central Hills
 36-Flatwoods
 37-Pontotoc Ridge
 38-Black Prairies
 39-Tombigbee Hills
 40-Coastal Pine Meadows
 41-Pine Hills
 42-Interior Low Plateaus
 43-Inner Coastal Plain (Cretaceous)
 44-Northern Piedmont (faults, phylite and granite rocks)
 45-Wedowee and Emuckfaw Groups
46-InnerPiedmont/DadeviIle Complex
47-Southern Piedmont
48-Inner and Outer Coastal Plain (Tertiary Rocks)
49-Rome-Kingston Thrust Stack
 50-Georgiabama Thrust Stack (north of Allatoona Fault)
 51-Georgiabama Thrust Stack (south of Allatoona Fault)
 52-Litfle River Thrust Stack
 53-Coastal Plain (Cretaceous/Tertiary)
 54-Coastal Plain (Quaternary/Pliocene-Pleistocene gravels)
 55-Upper Coastal Plain
 56-Middle Coastal Plain
 57-Lower Coastal Plain
 58-Highlands
 59-Lowlands
 6Q-Dade County anomalous area.
                                                ffl-3     Reprinted from USGS Open-File Report 93-292-D

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                                                                         Indoor Radon Screening
                                                                      Measurements: Average (pCi/L)
                                                                               0.0 to 1.9
                                                                               2.0 to 4.0
                                                                               4.1 to 6.0
                                                                               6.1 to 13.8
                                                                               Missing Data
                                                                               or < 5 measurements
Figure 2.  Screening indoor radon averages for counties with 5 or more measurements in EPA
Region 4. Data for all states in Region4 except Florida from the State/EPA Residential Radon
Survey. Data for Florida are from the Florida Statewide Radon Study. Histograms in map
legend show the number of counties in each category.

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                                                                     GEOLOGIC
                                                                 RADON POTENTIAL
                                                               |   j LOW
                                                                H3 MODERATEA/ARIABLE
                                                                    HIGH
Figure 3. Geologic radon potential areas of EPA Region 4. For more detail, refer to individual
state radon potential chapters.

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base metals, including uranium. Rinds containing high concentrations of uranium and uranium
minerals can be formed on the surfaces of rocks affected by CaCOs dissolution and karstification.
Karst and cave morphology is also thought to promote the flow and accumulation of radon.
Because carbonate soils are clayey, they have a tendency to crack when they dry and may develop
very high permeability from the fractures. Under ii*.'    jnditions, however, the soils derived
from carbonates have generally low permeability.
       The Appalachian Plateaus region is ranked moderate in radon potential. Indoor radon is
generally low (< 2 pCi/L) to  moderate (2^.4 pCi/L). .Radioactivity is low to moderate and soil
permeability is moderate. The sandstone of the Pottsville Formation is not noted for being
uranium-bearing, but uraniferous carbonaceous shales interbedded with the sandstone may be the
cause of locally moderate to  high (>4 pCi/L) indoor radon. Cullman County had several indoor
radon measurements greater than 4 pCi/L, including one measurement of 19.8 pCi/L. Winston and
Walker Counties also had several indoor radon levels greater than 4 pCi/L in the Alabama
Department of Public Health data set
                                                                       s
Valley and Ridge
       The Valley and Ridge province has been ranked moderate in geologic radon potential.
Radioactivity is generally moderate in the Valley and Ridge, with high radioactivity occurring along
the southeastern border with the Piedmont. Indoor radon is highly variable, with generally low
county averages and one high county average. Most of the counties had a few readings greater
than4pCi/L. The soils of the Valley and Ridge have low to moderate permeability. The
permeability may be locally  high in dry clayey soils and karst areas.  Carbonate soils derived from
Cambrian-Ordovician rock units of the Valley and Ridge province cause known indoor radon
problems in eastern Tennessee, western New Jersey, western Virginia, eastern West Virginia and
central and eastern Pennsylvania.  Further, the Devonian Chattanooga Shale crops out locally in
parts of the Valley and Ridge. This  shale is widely known to be highly uraniferous and has been
identified as a source of high indoor radon in Kentucky.

Piedmont
       Where it is possible to associate high radioactivity and/or high indoor radon levels with
particular areas, parts of the  Piedmont have been ranked moderate to high in radon potential.
Radiometric anomalies occur over the Talladega Fault zone, which separates the Paleozoic
carbonates from the metamorphic rocks. Some of the metamorphic rocks in the Northern
Piedmont, including the Poe Bridge Mountain Group, the Mad Indian Group, parts of the
Wedowee Group, and the Higgins Ferry Group, also have high radioactivity associated with them.
In many cases the radiometric anomalies appear to be associated with rocks in fault zones, graphitic
schists and phyllites, felsic gneiss, and other granitic rocks. Furthermore, Talladega, Calhoun,
Cleburne, and Randolph Counties all have some high indoor radon measurements.  Uranium in
graphitic phyllite with an assay value of 0.076 percent UsOg has been reported from Cleburne
County and similar graphitic phyllites from the Georgia Piedmont average 4.7 ppm uranium.
Graphitic phyllites and schists in other parts of the Piedmont are known sources of radon and have
high indoor radon levels associated with them.  Another  source of uranium in Piedmont
metamorphic rocks is monazite, which contains high amounts of both uranium and thorium. It is a
common accessory mineral  in gneisses and granites throughout the Piedmont and its resistance to
weathering and high density result in local monazite concentrations in saprolite.  A uraniferous
monazite belt that crosses the Piedmont in northern Chambers and Tallapoosa County may provide
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a source of radon. Soils of the Northern and Southern Piedmont have moderate to high
permeability, whereas soils developed from mafic rocks of the Dadeville Complex have low
permeability. Because the Dadeville Complex consists primarily of mafic rocks with low
radioactivity and low permeability, the Dadeville Complex was ranked separately from other
Piedmont rocks and is ranked low in geologic radon potential.

Coastal Plain
       More than half of Alabama is covered by the sediments of the Coastal Plain.  Indoor radon
levels are generally less than 4 pCi/L and commonly less than 2 pCi/L in this province. Soil
permeability is variable-generally low in clays and moderate to high in silts and sands. A distinct
radiometric high is located over the central belt of marly sandy clay and chalk known as the Selma
Group. Within the Selma Group high radioactivity is associated with the Demopolis Chalk,
Mooreville Chalk, Prairie  Bluffs Chalk, and the Ripley Formation in central and western Alabama.
In eastern Alabama and into Georgia these rocks are dominated by the glauconitic sands and clays
of the Providence Sand, Cusseta Sand, and Blufftown Formation. These units have  overall
moderate geologic radon potential.
       As part of a study by the U.S. Geological Survey and the U.S. EPA to assess the radon
potential of the Coastal Plain sediments in the United States, data on radon in soil gas, surface
gamma-ray activity, and soil permeability were collected and examined. Data were collected in the
Alabama Coastal Plain along a transect running from just north of Montgomery, Alabama, to just
south of De Funiak Springs, Florida. The highest soil-gas radon concentrations and equivalent
uranium were found in the Cretaceous Mooreville Chalk, carbonaceous sands and clays of the
Providence Sand, and the  glauconitic sands of the Eutaw and Ripley Formations.  However,
permeability in many of these units is slow—generally less  than IxlO-12 cm2, and soil-gas radon
was difficult to collect.  Geologic units that have the lowest  soil-gas radon concentrations and eU
include the quartz sands of the Cretaceous Gordo Formation and quartz sands and residuum of the
undifferentiated upper Tertiary sediments.  Low to moderate radon and uranium concentrations
were measured in the glauconitic sands and clays of the Tertiary Porters Creek Formation and in
the glauconitic sands, limestones, and clays of the Tertiary Nanafalia, Lisbon Formation, and the
Tuscahoma Sand. The indoor radon in some counties underlain by the Selma Group is in the 2-4
pCi/L range with a few measurements greater than 4 pCi/L, higher than in most other parts of the
Alabama Coastal Plain. High uranium and radon concentrations in the sediments of the Jackson
Group, locally exceeding  8 ppm U, but generally in the 1-4 ppm U range, and high soil-gas radon
concentrations, are associated with faults and oil and gas wells in Choctaw County.  Indoor radon
measurements are generally low in these areas, but may be locally high.

FLORIDA

       Florida lies entirely within the Coastal Plain, but there are six distinctive areas in Florida for
which geologic radon potential may be evaluated—the Northern Highlands, Central  Highlands, the
Central and Northern Highlands anomalous areas, the Gulf  Coastal Lowlands, Atlantic Coastal
Lowlands, and an area here termed the Dade County anomalous area.
       The Northern Highlands province has generally low geologic radon potential. All counties
entirely within this province have average indoor radon levels less than 1 pCi/L. Leon County
averaged 1.7 and 1.8 pCi/L in the two surveys of the Florida Statewide Radon Study. Most of
these data likely come from Tallahassee, which lies within an area of moderately elevated eU. This
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area and those parts of southern Columbia, western Union, and northern Alachua County, which
are underlain by phosphatic rocks, and limited areas where coarse gravels occur in river terraces in
the western panhandle, are likely to have elevated radon potential.
       The Central Highlands province has variable geologic radon potential. Generally low
radon potential occurs in low eU areas in tl  aasterr a "  outhern part, of this province. Moderate
radon potential occurs in the western part of this province where uraniferous phosphatic rocks are
close to the surface. Localized areas in which uranium contents of soils and shallow subsoils
exceed 100 ppm are likely, and indoor radon levels may exceed 20 pCi/L or more where this
occurs. Alachua (lies in both the Central and Northern Highlands), Marion, and Sumter Counties
report indoor radon values exceeding 20 pCi/L. Excessively well-drained hillslopes may also
contribute to higher radon potential.
       The Gulf Coastal Lowland Province generally has low radon potential.  High rainfall and
high water tables cause very moist soils which inhibit radon movement. Equivalent uranium is low
in most areas except in some coastal bay areas of western peninsular Florida. Some isolated areas
of elevated radon potential may occur in these areas of higher eU.
       The Atlantic Coastal Lowland area generally has low radon potential. High rainfall and
high water tables cause very moist soils that inhibit radon movement Equivalent uranium is low in
most areas. In some beach sand areas in northern Florida, elevated  eU seems to be associated with
heavy minerals; however, there is no evidence to suggest that elevated indoor radon occurs in these
areas.
       An area in southwestern Dade County, underlain by thin sandy soils covering shallow
limestone bedrock, has equivalent uranium values as high as 3.5 ppm.  Unusually high levels of
radium are present in soils formed on the Pleistocene Key Largo Limestone and perhaps on other
rock formations in certain areas of the Florida Keys and in southwestern bade County. Areas of
elevated eU and elevated indoor radon in Dade County are likely related to these unusual soils.
These soils may be responsible for the modestly elevated eU in soils and for the elevated indoor
radon levels, and they may extend into Collier County as well.

GEORGIA

Piedmont and Blue Ridge
       The oldest rocks in Georgia form the mountains and rolling hills of the Blue Ridge
Province and most of the Piedmont Province.  These highly deformed rocks are separated by a
series of thrust faults superimposing groups of older rocks over younger rocks, comprising the
Georgiabama Thrust Stack. The igneous and metamorphic rocks in the Georgiabama Thrust Stack
north of the Altoona Fault have been ranked moderate overall in geologic radon potential, but the
radon potential of the area is variable.  Mafic rocks are expected to have low radon potential
whereas phyllite, slate, some metagraywacke, granitic gneiss and granite have moderate to high
radon potential.  Soil permeability is slow to moderate in most soils. Counties in this area have
average indoor radon levels that vary from low to high (< 1 pCi/L to > 4 pCi/L), but the
measurements are predominantly in the moderate range.  The highest indoor radon reading, 18.7
pCi/L, was measured in the northern Blue Ridge in Fannin County, which is underlain
predominantly by metagraywacke, slate, phyllite, and mica schists. Equivalent uranium
concentrations in rocks and soils of this area are moderate to high.
       The Georgiabama Thrust Stack south of the Alatoona Fault has also been ranked moderate
in geologic radon potential. The majority of this part of the Georgiabama Thrust Stack is underlain
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 by schist and amphibolite of the Zebulon sheet, which have generally low radioactivity where not
 intruded by granites or where not highly sheared, particularly south of the Towaliga Fault An area
 with distinctly low aeroradiometric readings which is underlain by mafic metamorphic rocks lies
 between the Brevard and Allatoona Faults in the northwestern Georgiabama Thrust Stack. All of
 Jic^e rocks have slow to moderate permeability, and ii Joor radon values are genei Jly low to
 moderate.  A central zone of biotite gneiss, granitic gneiss, and granite has elevated uranium
 concentrations and high equivalent uranium (>2.5 ppm) on the NURE map.  Soil permeability is
 generally low to locally.moderate, .Indoor radon levels are generally moderate. Recent soil-gas
 radon studies in the Brevard zone and surrounding rocks show that this zone may yield unusually
 high soil-gas radon where the zone crosses the Ben Hill and Palmetto granites. Surface gamma-
 ray spectrometer measurements yielded equivalent uranium from 4 to 17 ppm over granite and
 granitic biotite gneiss (Lithonia gneiss). Soil-gas radon concentrations commonly exceeded 2,000
 pCi/L and the highest soil-gas radon measured was 26,000 pCi/L in faulted Ben Hill granite.
 Undeformed Lithonia gneiss had average soil radon of more than 2,000 pCi/L. Mica schist
 averaged less than 1,000 pCi/L where it is undeformed. The Stone Mountain granite and mafic
 rocks yielded low soil-gas radon. The Grenville Basement granite and granite gneiss have
 moderate to locally high radon potential. Radioactivity is generally moderate to high and soil
 permeability is generally moderate.
       The Little River Thrust Stack is generally low to moderate in geologic radon potential. It is
 underlain primarily by mafic metamorphic rocks with low radon potential, but each belt contains
 areas of rocks with moderate to locally high radon potential. Metadacites have moderate radon
 potential and moderate radioactivity. Faults and shear zones have local areas of mineralization and
 locally high permeability. Granite intrusives may also have moderate radon potential.
 Aeroradioactivity is generally low and soil permeability is generally moderate.

Ridge and Valley
       The Rome-Kingston Thrust Stack is ranked low in geologic radon potential; however,
 some of the limestones and shales in this area may have moderate to high radon potential. Indoor
radon is variable but generally low to moderate.  Permeability of the soils is low to moderate.
Equivalent uranium is moderate to locally high, especially along the Carters Dam and Emerson
faults.  Carbonate soils of the Valley and Ridge Province are likely to cause indoor radon
problems. The Devonian Chattanooga Shale, which crops out locally in parts of the Valley and
Ridge, is highly uraniferous and has been identified as a source of high indoor radon levels in
Kentucky. Numerous gamma radioactivity anomalies are  associated with the Pennington
Formation, Bangor Limestone, Fort Paine Chert, Chattanooga Shale, Floyd Shale, the Knox
Group, and the Rome Formation.

Appalachian Plateau
       The Appalachian Plateau has been ranked low in geologic radon potential. Sandstone is the
dominant rock type and it generally has low uranium concentrations. Equivalent uranium is low to
moderate. Permeability of the soils is moderate and indoor radon levels are low.

Coastal Plain
       The Coastal Plain has been ranked low in radon potential, but certain areas of the Coastal
Plain in which glauconitic, carbonaceous, and phosphatic sediments are abundant may have
moderate geologic radon potential.  The highest soil-gas radon concentrations (>1000 pCi/L) and
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equivalent uranium (elJ) concentrations (>2 ppm) in studies of radon in soil-gas in the Coastal
Plain of Alabama were found in the carbonaceous sands and clays of the Providence Sand and the
glauconitic sands of the Eutaw and Ripley Formations. Low to moderate soil-gas radon and
uranium concentrations were measured in the glauconitic sands, limestones, and clays of the
Tertiary Nanafalia and Lisbon Formations, and the Tuscahoma Sand. Equivalent rock units in
Georgia are also likely to be sources of high radon levels. Equivalent uranium is moderate in the
Cretaceous and Tertiary-age sediments and low, with local highs, in the Quaternary sediments.
Radioactivity highs in much of the Coastal Plain are related to phosphate and heavy-mineral
concentrations. In the shoreline complexes and in several sediment units such as the Hawthorn
Formation, the phosphate concentrations are naturally occurring. In the Black Lands and in many
portions of the central Coastal Plain that have abundant agricultural activity, the radioactivity may
be related to the use of phosphate fertilizers. Indoor radon in the Coastal Plain is generally low.

KENTUCKY
       Three primary areas in Kentucky are identified as being underlain by rock types and
geologic features suspected of producing elevated radon levels:  (1) areas underlain by Devonian
black shales in the Outer Bluegrass region; (2) areas underlain by the Ordovician Lexington
Limestone, particularly the Tanglewood Member, in the Inner Bluegrass region; and (3) areas of
the Mississippian Plateau underlain by karsted limestones or black shales. In addition, some
homes underlain by, or in close proximity to, major faults in the Western Coalfield and Inner
Bluegrass regions may have locally elevated indoor radon levels due to localized concentrations of
radioactive minerals and higher permeability in fault and fracture zones.
Appalachian Plateau
       The black shale and limestone areas in the Mississippian Plateau region have associated
high surface radioactivity, and the Western Coalfield contains scattered radioactivity anomalies.
The arcuate pattern of radioactivity anomalies along the southern edge of the Outer Bluegrass
region corresponds closely to the outcrop pattern of the New Albany Shale. A group of
radiometric anomalies in the vicinity of Warren and Logan counties appears to correspond to
outcrops of the Mississippian Ste. Genevieve and St. Louis Limestones.  The clastic sedimentary
rocks of the Cumberland Plateau region are characterized by relatively low surface radioactivity and
generally have low indoor radon levels.
       In the Mississippian Plateau Region, locally elevated indoor radon levels are likely in areas
with high soil permeability, solution cavities, or localized concentrations of radioactive minerals in
karst regions, and in  areas underlain black shale along the State's  southern border. Of particular
concern are the Devonian-Mississippian Chattanooga Shale (equivalent to the New Albany Shale),
limestones in the Mississippian Fort Payne Formation, and the Mississippian Salem, Warsaw,
Harrodsburg, St. Louis, and Ste. Genevieve Limestones in south-central Kentucky.
       Caves, produced by limestone solution and relatively common in central Kentucky, are
natural concentrators of radon and can be a local source of high radon levels. Levels of radon
decay products approaching a maximum of 2.0 working levels (WL), which corresponds to about
400 pCi/L of radon (assuming that radon and its decay products are in 50 percent equilibrium), and
averaging about 0.70 WL, or about 140 pCi/L of radon, have been recorded in Mammoth Cave.
Although these levels are not considered hazardous if the exposure is of short duration, such as
would be experienced by a visitor to the cave, it could be of concern to National Park Service
employees and other persons that spend longer periods of time in the caves.  Another potential
hazard is the use of cave air for building air temperature control, as was formerly done at the
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Mammoth Cave National Park visitor center.  The cave air, which averages 54°F, was pumped into
the visitor center for cooling, but this process has been discontinued due to the relatively high
radioactivity associated with the cave air.

Coastal Plain
       The majority of homes in the Jackson Purchase Region (Coastal Plain) have low indoor
radon levels, although the area is underlain in part by loess with an elJ signature in the 2.0-3.0
ppm range. The poor correspondence with surface radioactivity in this area appears to be due to a
combination of low soil permeability and high water tables.  The Coastal Plain is the only part of
the State in which seasonal high water tables were consistently listed in the SCS soil surveys as
less than 6 ft, and commonly less than 2 ft.

MISSISSIPPI

       Examination of the available data reveals that Mississippi is generally an area of low radon
potential.  Indoor radon levels in Mississippi are generally low; however, several counties had
individual homes with radon levels greater than 4 pCi/L. Counties with maximum levels greater
than 4 pCi/L are concentrated in the northeastern part of the State within the glauconitic and
phosphatic sediments of the Tombigbee Hills and Black Prairies. Readings greater than 4 pCi/L
also  occur in the Mississippi Alluvial Plain, the eastern part of the Pine Hills Province, and in
loess-covered areas. Glauconitic and phosphatic sediments of the Coastal Plain, particularly the
Cretaceous and lower Tertiary-age geologic units located in the northeastern portion of the State,
have some geologic potential to produce radon. Based on radioactivity and studies of radon in
other parts of the Coastal Plain, the Black Prairies and Pontotoc Ridge have been assigned
moderate geologic radon potential; all other parts of Mississippi are considered to be low in
geologic radon potential.  The climate, soil, and lifestyle of the inhabitants of Mississippi have
influenced building construction styles and building ventilation which, in general, do not allow
high concentrations of radon to accumulate.

Coastal Plain
       A study of the radon in the Coastal Plain of Texas, Tennessee, and Alabama suggests that
glauconitic, phosphatic, and carbonaceous sediments and sedimentary rocks, equivalent to those in
Mississippi, can cause elevated levels of indoor radon. Ground-based surveys of radioactivity and
radon in soils in that study indicate that the Upper Cretaceous through Lower Tertiary Coastal Plain
sediments are sources of high soil-gas radon  (> 1,000 pCi/L) and soil uranium concentrations.
The high equivalent uranium found over the Coastal Plain sediments in northeastern Mississippi
supports the possibility of a similar source of high radon levels. Chalks, clays and marls tend to
have low permeability when moist and higher permeability when dry due to desiccation fractures
and joints.
       The youngest Coastal Plain sediments, particularly Oligocene and younger, have
decreasing amounts of glauconite and phosphate and become increasingly siliceous and therefore
less likely to be significant sources of radon. Some carbonaceous units may be possible radon
sources.
       Loess in Tennessee, and probably elsewhere, is known to generate high levels of radon in
both dry and saturated soils.  Both thin and thick loess units can easily be traced on the
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radioactivity map of Mississippi by following the highest of the moderate equivalent uranium
anomalies. Loess tends to have low permeability when moist and higher permeability when dry.

Mississippi Alluvial Plain
       The Mississippi Alluvial Plain contains several areas with locally high eU, as well as
having moderate radioactivity overall. These high eU areas are located close to the river in Bolivar
and Washington Counties.  The highest indoor radon level recorded in Mississippi in the
State/EPA Residential Radon Survey (2-2.8 pGi/L) occurs within Bolivar County and the second
highest radon level of homes measured to date in the State (16.1 pCi/L) occurs in Washington
County. It is not apparent from the data available whether the high eU and indoor radon levels are
correlative, and only a few indoor radon readings in each county are greater than 4 pCi/L. The
geology of the region is not generally conducive to high uranium concentrations, except possibly in
heavy-mineral placer deposits. Further, elevated radioactivity in  the Mississippi Alluvial Plain may
be due in part to uranium in phosphatic fertilizers. Locally high soil permeability in some of the
alluvial sediments may allow locally high indoor radon levels to occur.
       The southeastern half of Mississippi has low radioactivity and low indoor radon levels.
The few indoor radon readings greater than 4 pCi/L were between 4.1 and 5.8 pCi/L. The lowest
eU is associated with the coastal deposits and the Citronelle Formation, which are predominantly
quartz sands with low radon potential.  Slightly higher eU, though still low overall, is associated
with the Pascagoula and Hattiesburg  Formations and Catahoula Formation. Soils in this area are
variably poorly to well drained with slow to moderate permeabilities.
       The Chattanooga Shale and related sedimentary rocks in the northeastern part of the State
have the potential to be sources of high indoor radon levels. • In Tennessee and Kentucky, the
Chattanooga Shale has high uranium concentrations and is associated with high indoor radon levels
in those states.  The extent of these rocks in Mississippi is minor.

NORTH CAROLINA

Blue Ridge
       The Blue Ridge has been ranked moderate overall in geologic radon potential, but it is
actually variably moderate to high in radon potential. The province has highly variable geology
and because of the constraints imposed by viewing the indoor radon data at the county level, it is
impossible to assign specific geologic areas of the Blue Ridge to specific moderate or high indoor
radon levels. Average indoor radon levels are moderate (2-4 pCi/L) in the majority of counties.
However, two counties have indoor radon averages between 4.1 and 6 pCi/L (Cherokee and
Buncomb Counties) and three counties in the northern Blue Ridge (Alleghany, Watauga, and
Mitchell) have indoor radon averages greater than 6 pCi/L. These three counties are generally
underlain by granitic gneiss, mica schist, and minor amphibolite and phyllite. Transylvania and
Henderson Counties, which are underlain by parts of the Blue Ridge and Inner Piedmont, also
have indoor radon averages greater than 6 pCi/L.  The Brevard fault zone, Henderson Gneiss, and
 Ceasars Head Granite are possible sources of high indoor radon in these two counties. Equivalent
 uranium is variable from low to high in the Blue Ridge. The highest eU appears to be  associated
 with the Ocoee Supergroup in the southern Blue Ridge, rocks in the Grandfather Mountain
 Window, and metamorphic rocks in parts of Haywood and Buncomb Counties. Soils are
 generally moderate in permeability.
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        The Chauga belt and Brevard fault zone are ranked high in geologic radon potential. The
 Chauga belt consists predominantly of the Henderson Gneiss. High eU and high uranium in
 stream sediments appears to be associated with the Brevard fault zone, Henderson Gneiss, and
 Ceasars Head Granite in this area. Average indoor radon levels in the two counties that the main
 part of the Chauga belt and the southern portion of the Brevard fault zone passes through are high.
 The soils have moderate permeability.

 Piedmont
        The Inner Piedmont and Kings Mountain belts have been ranked moderate in geologic
 radon potential.  Indoor radon levels are generally moderate.  Granitic plutons, granitic gneiss,
 monazite-rich gneiss and schist, pegmatites, and fault zones appear to have high eU and high
 uranium concentrations in stream sediment samples. Many of the granitic plutons are known to be
 enriched in uranium and recent studies suggest that the soils developed on many of the uraniferous
 granitic plutons and related fault zones in the Blue Ridge and Piedmont are possible sources of
 radon. Measured soil-gas radon concentrations commonly exceeded 1,000 pCi/L in soils
 developed on the Cherryville Granite, Rolesville Suite, and the Sims, Sandy Mush, and Castalia
 plutons. Soils developed on the Rocky Mount, Spruce Pine, Toluca, Mt. Airy, and Stone
 Mountain plutons had relatively low soil-gas radon concentrations.  Soil permeabilities in the Inner
 Piedmont, Brevard fault zone, and Kings Mountain belt are variably low to moderate which,
 together with the large proportion of homes without basements, may account for the abundance of
 moderate indoor radon levels.
       Most shear zones in the Piedmont and Blue Ridge should be regarded as having the
 potential to produce very localized moderate to high indoor radon levels. Geochemical and
 structural models developed from studies of shear zones in granitic metamorphic and igneous rocks
 from the Reading Prong in New York to the Piedmont in Virginia indicate that uranium
 enrichment, the redistribution of uranium into the rock foliation during deformation, and high
 radon emanation, are common to most shear zones. Because they are very localized sources of
 radon and uranium, shear zones may not always be detected by radiometric or stream sediments
 surveys.
       The Charlotte belt has been ranked low in geologic radon potential but it is actually quite
 variable-dominantly low in the southern portion of the belt and higher in the northern portion of
 the belt Equivalent uranium is generally low, with locally high eU occurring in the central and
 northern portions of the belt, associated with the Concord and Salisbury Plutonic Suites.
 Permeability of the soils is generally low to moderate and indoor radon levels are generally low.
       The Carolina slate belt has been ranked  low in radon potential where it is underlain
primarily by metavolcanic rocks. Where it crops out east of the Mesozoic basins it has been ranked
moderate. Aeroradioactivity over the Carolina slate belt, uranium in stream sediment samples, and
indoor radon levels are markedly low. Permeability of many of the metavolcanic units is  generally
low to locally moderate.  East of the Wadesboro subbasin in Anson and Richmond Counties lies a
 small area of the  slate belt that is intruded by the Lilesville Granite and Peedee Gabbro. It has high
eU and high uranium concentrations in stream sediments, and moderate to high permeability in the
soils, and is a likely source of moderate to high indoor radon levels.
       The Raleigh belt has been ranked moderate in geologic radon potential.  Equivalent uranium
in the Raleigh belt is generally moderate to high and appears to be associated with granitic intrusive
rocks, including the Castalia and Wilton plutons and the Rolesville Suite.  A belt of monazite-
bearing rocks also passes through the Raleigh belt and may account for part of the observed high
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radioactivity. Soils have variably low to moderate permeability. Indoor radon levels are generally
moderate.

CoastalPlain
       In the Coastal Plain province, moderate to hi&'     is associated with the Cretaceous and
Tertiary sediments of the Inner Coastal Plain. Permeability of the soils is highly variable but
generally moderate to low, and may be locally high in sands and gravels. Seasonally high water
tables are common. Indoor radon levels-in the Coastal Plain are generally low. The Inner Coastal
Plain is ranked low in geologic radon potential but may be locally moderate to high, especially in
areas underlain by Cretaceous sediments. Glauconitic, phosphatic, monazite-rich, and
carbonaceous sediments and sedimentary rocks in the Coastal Plain of Texas, New Jersey, and
Alabama, similar to some Coastal Plain sediments in North Carolina, are the source for moderate
indoor radon levels seen in parts of the Inner Coastal Plain of these states.
       The Outer Coastal Plain has low elJ, low indoor radon levels, and is generally underlain by
sediments with low uranium concentrations.  Soil permeability is variable but generally moderate.
Seasonally  high water tables are common.  A few isolated areas of high radioactivity in the Outer
Coastal Plain may be related to heavy mineral and phosphate deposits in the shoreline sediments.
The area has been ranked low in geologic radon potential, but may have local moderate or high
indoor radon occurrences related to heavy minerals or phosphate deposits.

SOUTH CAROLINA

Blue Ridge and Piedmont
       The Blue Ridge and Piedmont Provinces have moderate geologic radon potential.  Possible
sources of radon include uraniferous granites, biotite and granitic gneiss, and shear zones. Soils
developed on many of the uraniferous granitic plutons and some fault zones within the Piedmont
and Blue Ridge of North and South Carolina yield high soil-gas radon (>1,000 pCi/L). In the
Blue Ridge, sheared graphitic rocks may be a local source for high indoor radon concentrations.
       More than 10 percent of the homes tested in Greenville and Oconee Counties, in the Blue
Ridge and Piedmont, have indoor radon levels greater than 4 pCi/L.  Greenville County also has
the highest  indoor radon measurement in the State, 80.7 pCi/L, the highest radioactivity, associated
with the Silurian-Devonian Ceasers Head Granitic Gneiss, and with biotite gneiss in the Carolina
monazite belt. In Oconee County, the Toxaway Gneiss and graphitic rocks in the Brevard Fault
Zone may account for the higher incidence of indoor radon levels exceeding 4 pCi/L and the higher
overall indoor radon average of the county. Average indoor radon levels in the Blue Ridge and
Piedmont are generally higher than in the rest of the State, and moderate to high radioactivity is
common. Most of the soils formed on granitic rocks have moderate permeability and do not
represent an impediment to radon mobility. Mafic rocks in the Blue Ridge and Piedmont have low
radon potential. These rocks have low concentrations of uranium, and soils formed from them
have low permeability.

CoastalPlain
       In the Coastal Plain Province, moderate to  high radioactivity is associated with the
Cretaceous and Tertiary sediments of the upper Coastal Plain. Glauconitic, phosphatic, monazite-
rich, and carbonaceous sediments and sedimentary rocks in the Coastal Plain of Texas, New
Jersey, and Alabama, similar to some of those in South Carolina, cause elevated levels of indoor
                                           ffl-14   Reprinted from USGS Open-File Report 93-292-D

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 ration. Orangeburg County is the only other county besides Greenville and Oconee Counties that
 has an average indoor radon level greater than 2 pCi/L. It is underlain by Lower Tertiary
 sediments in an extremely dissected part of the Coastal Plain.  Radioactivity is moderate to low.
 Soils are highly variable in the county because of the complicated erosion patterns. The few high
 values of indoor radon for this county create an overall higher indoor radon average for the county.
 These locally high readings may be due to local accumulations of monazite, glauconite, or
 phosphate that can occur within these particular sediments.
        The lower Coastal Plain has low to locally, high radioactivity and low indoor radon levels.
 Most of the sediments have low uranium concentrations with the exception of the uraniferous,
' phosphatic sediments of the Cooper Group and local, heavy-mineral placer deposits within some
 of the Quaternary units. The area has been ranked low in geologic radon potential overall, but the
 radon potential may be locally high in areas underlain by these uraniferous sediments.

 TENNESSEE

 Coastal Plain and Mississippi Alluvial Plain
        The Mississippi Alluvial Plain has low geologic radon potential. The high soil moisture,
 high water tables, and the lack of permeable soils lower the radon potential in spite of moderate eU
 values. Some areas with very sandy or excessively-drained soils may cause homes to have indoor
 radon levels exceeding 4 pCi/L.
       The loess-covered parts of the Coastal Plain have low radon potential in spite of moderate
 eU values and elevated soil-gas radon concentrations.  The radon potential is lowered by the high
 moisture content and low permeability of the soils.  The lack of basements in homes also lowers
 the potential.  If prolonged dry periods were to occur in this area, some homes might see a
 significant increase in indoor radon, especially those with basements or crawl spaces. The eastern
 Coastal Plain has moderate geologic radon potential. NURE data show elevated eU values
 compared to the rest of the Coastal Plain.  Soil-gas radon levels are locally elevated.

 Highland Rim and Nashville Basin
       The Highland Rim and Nashville Basin are underlain by sedimentary rocks of Paleozoic
 age, principally limestone, shale, chert, and dolostone. The part of the Highland Rim that is
 underlain by cherty limestone (Fort Payne Formation) has high geologic radon potential. This area
 has moderate to locally high eU and soils that are cherty and excessively well drained. The
 limestone and shale part of the Highland Rim has moderate radon potential.  The Nashville Basin
 has high geologic radon potential.  The elevated eU, the presence of abundant phosphatic soils,
 local karst, and the presence of generally well-drained soils all contribute to this high geologic
 radon potential.  Very high (>20 pCi/L) to extreme indoor radon values (>200 pCi/L) are possible
 where homes are sited on soils developed on the Chattanooga shale, on phosphate-rich residual
 soils, or on karst pinnacles.

Appalachian Plateau
       Sandstones and shales underlie most of the Appalachian Plateau, which generally has
 moderate geologic radon potential. These rocks are typically not good sources of radon and values
 for eU are among the lowest in the State.  However, many sandy, well-drained to excessively-
 drained soils are present in this region, and may be a source of locally elevated radon levels
 because of their high permeability.
                                           M-15    Reprinted from USGS Open-File Report 93-292-D

-------
Ridge and Valley
       Folded and faulted Paleozoic limestone, shale, chert, dolostone, and sandstone underlie
most of the Ridge and Valley region, with sandstone and cherty dolostone forming most of the
ridges and limestone and shale forming nx.  . of the /a  . ^. The Ridge and Valley region has high
geologic radon potential because of elevated eU values, karst, and well drained soils. Very high
(>20 pCi/L) to extreme indoor radon values (>200 pCi/L) are possible where homes are sited on
soils developed on black shales, phosphate.-rich residual soils, or karst pinnacles. Homes with
basements are more likely to yield elevated indoor radon levels than homes with slab-on-grade
construction.

Unaka Mountains
       The Unaka Mountains are underlain by siltstone, sandstone, conglomerate, quartzite,
phyllite, gneiss, granite, and metamorphosed volcanic rocks of Precambrian and Paleozoic age that
have moderate geologic radon potential. Values of eU are generally moderate, although they are
locally high.  Some very high (>20 pCi/L) to extreme (>200 pCi/L) indoor radon levels are
possible where homes are sited on phosphate-rich residual soils developed on phosphatic carbonate
rocks, or on pegmatite in the metamorphic rock areas, but the former are much less common in this
region than in the Nashville Basin and the Ridge and Valley region.
                                          ffl-16   Reprinted from USGS Open-File Report 93-292-D

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       PRELIMINARY GEOLOGIC RADON POTENTIAL ASSESSMENT OF FLORIDA
                                            by
                                      Jianes K. Otton
                                  U.S. Geological Survey

 INTRODUCTION

        Indoor radon in Florida has been studied intensively by various State and Federal agencies
 and university groups since the mid-1970s. This report relies heavily on this past work and on the
 geologic and soil data that have been gathered over the past several decades, especially in the
 uraniferous phosphate lands in Florida.
        This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
 deposits of Florida. 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.
       The Department of Community Affairs of the State of Florida is conducting a Florida
 Radon Research Program which includes development of a more detailed map of radon potential
 for the State. This map will supersede the more generalized assessment presented here.  For more
 information on radon, the reader is urged to consult the Florida 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

       Physiographically,  Florida is characterized by modest highlands that lie along the northern
 border of the State (northern highland province, fig.  1) and extend down the axis of the peninsula
 (central highland province). These highland areas are flanked by coastal lowland (the coastal
 lowland province) and are locally interrupted by smaller interior lowland areas.  The north-central
 part of the central highlands is characterized by a series of linear ridges and intervening valleys that
 parallel the Atlantic coast
       The lowland areas throughout the State are level to nearly level whereas the highland areas
 are nearly level to locally strongly sloping. Throughout virtually the entire State local relief is less
 than 100 feet and for most  of Florida it is less  than 25 feet. Only in the highland areas near and to
 the west of Tallahassee and locally in the central peninsula does local relief exceed 100 feet Many
 lowland areas are characterized by high seasonal water tables, and in the Everglades  of southern
 Florida, the water table is at or above the ground's surface much of the year.
       Average annual precipitation ranges from 40 to 64 inches across Florida with driest periods
 typically in the late fall and winter. Where crops are  grown, irrigation is required during the dry
periods.
                                          IV-1   Reprinted from USGS Open-File Report 93-292-D

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                           & Northern

                           Gulf    C0
Figure 1. Generalized physiographic map for the State of Florida (after Bond, 1987b). Northern
Highlands include all the highland areas from northern Alachua County west to Escambia County.
The Central Highlands extend from western Alachua County south to northern Dade County, w -
water (Lake Okeechobee).

-------
                           p
        Most of the population of Florida resides in coastal areas, notably along the Atlantic Coast
 from Miami north to West Palm Beach, the Jacksonville area, the Gulf Coast areas extending from
 Tampa south to Ft Meyers, and the Pensacdla area (fig. 2). The interior corridors extending from
 Gainesville to.Orlando and from Tampa to Orlando are also highly populated.  Florida has
 experienced rapid growth over the past 20 years. Outside of these urban areas the southern two-
 thirds of Florida is used extensively for agriculture with subtropical fruit, cash crops, and grazing
 being the dominant activities. In northern Florida cash crops, forest, and livestock are the
 dominant land use activities. Industrial minerals, principally phosphate and limestone, are the
 major mining products in Florida. Uranium is recovered from phosphate mining as a byproduct.

 GEOLOGIC SETTING

       The geology of Florida is dominated by fluvial, deltaic, and marine sedimentary rocks that
 range in age from Eocene to Holocene (fig. 3). The older sedimentary rocks, mostly limestone and
 dolomite, are exposed in a structural high centered on Levy County along the western side of
 peninsular Florida. Younger sedimentary rocks occur throughout southern Florida, along the
 Atlantic coast, and in coastal areas of the western panhandle.
       Uraniferous phosphatic sediments occur in the Alachua Formation, the Hawthorn Group
 and the Bone Valley Formation (Sweeney and Windham, 1979).  Although only a few occurrences
 of uranium minerals have been described in Florida, where these uraniferous phosphatic rocks are
 mapped, high concentrations of uranium (up to a few hundred ppm) in near-surface soils and
 bedrock are known to occur. For example, Espenshade (1958) describes such occurrences in an
 area south of Ocala. Soils containing a few tens to a few hundreds of ppm of uranium are likely to
 be strong sources of radon.  If homes are sited on such soils; high levels of indoor radon are
 likely.
       Surficial materials in southernmost Florida (fig. 4) are composed mostly of peat, sand, and
 limestone.  Sand and silt or sand, shell, and clay are the primary surficial materials along the
 Atlantic Coastal areas, south central Florida, and Gulf coastal areas from Lee County to Pinellas
 County and from Waukulla County to Escambia County. Clayey sand, limestone, and dolomite
 are the most common surficial materials from central Florida northward and westward to Jackson
 County.  Coarse sand, gravel, sandy clay and clay occur in northern Walton, Okaloosa, Santa
 Rosa, and Escambia Counties.
       Karst terrains have developed in areas underlain by limestone and dolomite in north-central
 and northern Florida (fig. 5). Karstified carbonate bedrock has been implicated in some elevated
 indoor radon occurrences elsewhere in the United States where the foundation of the house is dug
 in areas of thin soils and the foundation has encountered open fractures and solution cavities in the
 bedrock. These open fractures and solution cavities above the water table are excellent pathways
 for radon-bearing soil gas to migrate into the disturbed zones around foundations.
       Surface materials across most of the State are low in uranium content with most of the State
 showing less than 1.5 ppm equivalent uranium (eU) (fig. 6). A strip of land about 60 miles wide
 along the Atlantic Coastal margin extending from Jacksonville southward to Miami is almost
 entirely below 1.5 ppm. However, the highland areas in the north and north central part of the
 State generally range from 1.0 to 2.0 ppm eU.  Higher readings occur in an area underlain by
phosphatic rocks that extends discontinuously from southern Polk County northward to southern
 Columbia County, including an area of a few hundred square miles averaging greater than 5.5 ppm
 eU. The area of elevated activity mentioned above includes disturbed phosphate mining lands
                                          IV-3   Reprinted from USGS Open-File Report 93-292-D

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             POPULATION (1990)

           El  0 to 25000
           E3  25001 to 100000
           E3  100001 to 500000
           H  500001 to 1000000
           •  1000001 to 1937094
Figure 2. Population of counties in Florida (1990 U.S. Census data).

-------
Ts
                        EXPLANATION
Stratlgnphle Untt
Surfldal sands and
terrace sands, undl-
ferentfated.
Lake Flirt Mart.
Anastasla Formation.
Miami Limestone. K»y
Largo Limestone, Fort
Thompson Formation,
CaJoosahatcho* Forma-
tion. Tamlaml Formation
undmerenuated
CHronelle Formation,
Mfccosukee Formation
undifterentlated
•Charton Formation'.
Jackson BKifl Formation,
Rod Bay Formation.
Yellow RKw Formation.
Shoal River Formation,
ChlpoU Formation
undmerenttated
Bon* Valey Formation,
Alachua Formation, Fort
Preston Formation and
Hawthorn Formation
(Group) undWarantlatsd
SL Marks Formation.
CtiattahoochH Forma-
tion undffiemntialad
Suwannea Umestona.
Duncan Church B*ds,
•Byratrf Formation,
and Avon ParK Ums-
storw undltBrannated
Crystal Rhwr Formation,
WUston Formation.
IngBs Formation, and
Avon Park Umestons
umJitlorontialod
CMnsnl IKhology
Prlmarly quartz sands
with varying propor-
tions of sit, day,
organic malarial and
carbonate
Fosslltorou* Ume-
storw. marls and lesser
amounts of sand
and day
Clays and quartz sands
with lesser amounts of
sits and gravels
Shel mans, days and
quartz sands wWi minor
Imestones
Sands, sits and days
with lesser amounts of
Imestone, dolomite
and phosphorite
Impure Imestones
wtth sand and lesser
amounts of stt and
dolomite.
Limestones which may
be sightly sandy
ordolomitic
FosslUerous Ime-
stones and dolomite
Major
llthologlc
unH
Sand
Limestone
Sand and Clay
Marl and Sand
Phosphorttic
day and
sand
Limestone
Limestone
Limestone
and
dolomite
Series
Hokwene
Pleistocene
Pleistocene
Pliocene

Miocene
ODgocana
Eocene
System
Quaternary
Tertiary
                                                                          0     50 mi
   Figure 3. Generalized geologic map for the State of Florida (after Bond, 1987b). w - water.

-------
      Gravel and coarse sand
      Sandy clay and clay
      Medium to fine sand and silt
      Clayey sand
      Limestone and dolomite
      Sand, shell and clay
      Peat
                                        o
50 mi
Figure 4- Generalized surficial materials map for the State of Florida (after Bond, 1987b). w
water.

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                           The large portion of the State repre-
                           sents the area where the piezometric
                           surface is at or above land surface
                           and/or the clastic overburden is in
                           excess of 100 ft thick. It appears to
                           be the least probable area tor sinkhole
                           development.
                          This area is the portion of the State
                          characterized by stable prehistoric
                          sinkholes, usually fiat bottomed, steep
                          sided, both dry and containing water.
                          Modifications in geology and hydrology
                          may activate process again.

                          This portion of the State is charac-
                          terized by limestones at or very near
                          the surface. The density of sinkholes
                          in this area is high, however, the inten-
                          sity of surface collapse is moderate due
                          to the lack of overburden.  Exploration
                          by drilling and geophysical methods
                          for near-surface cavities can be
                          realistically accomplished.


                          This region has moderate overburden
                          above cavernous limestones and appre-
                          ciable water use. These areas nave
                          histories of steep-walled, wider sink-
                          hole collapse. A thick overburden or
                          high water table may lessen the pro-
                          bability of sinks occuring.
                                                              0
                                                              I
50 mi
Figure 5-  Map showing areas of karst development in the State of Florida (after Bond  1987b)
w- water.                                                                                                       }'

-------
•Id
S «J
S-o
  §
II
II
CS* jff
•Q S

w
If
o g
ll
13 .S
rt ^
ctf ^^



° I
go
1
CDT3
§£
S

-------
 in which the aeroradiometric signatures are locally very high (as much as 50 to 60 ppm eU).
 Coastal areas in Levy and Taylor Counties have anomalous eU (as much as 5 ppm). Another area
 in southwestern Dade County, underlain by thin sandy soils covering shallow limestone bedrock,
 has equivalent uranium values as high as 3.5 ppm. Modest levels of radioactivity (1.5 to 3 ppm
 eU) occur in southwestern and southeastern Collier County, northeastern Lee County,
 northwestern Charlotte County, and scattered areas throughout the northern highland counties.

 SOILS

       Sandy soils dominate much of the State of Florida (Caldwell and Johnson, 1982). Loamy
 soils or sandy soils with loamy subsoil are common in northwestern Florida. Depth to bedrock
 across most of Florida is typically greater than 60 inches.  However, in southernmost Florida the
 sandy soils are thin (typically 20 to 40 inches) and are underlain by carbonate bedrock.  Peaflands,
 also underlain by carbonate bedrock, are common in the Everglades and coastal areas.
       Coarse sandy and gravelly soils are largely restricted to areas underlain by the Citronelle
 Formation in the westernmost part of Florida's panhandle (northern Escambia, Santa Rosa,
 Okaloosa and Walton Counties). Here permeabilities in some soils may locally be much greater
 than 20 inches/hour (in/hr).
       Florida is characterized by thermic and hyperthermic udic  soils which are typically slightly
 moist in the summertime and very moist in the wintertime (Rose and others, 1991). For a sandy
 loam, a typical Florida soil, pore space saturation would be in the range of 24-44 percent under
 slightly moist conditions and 56-96 percent under very moist conditions. These data would
 suggest that in summertime, typical slightly moist conditions would favor radon emanation from
 soil mineral matter and that transport of radon would not be significantly inhibited. In winter, the
 higher pore saturation would tend to inhibit radon transport hi natural soils.

 INDOOR RADON DATA

       Indoor radon data for the State of Florida comes from the Florida Statewide Radon Study
 (FSRS) (Nifong, 1987).  Two different indoor radon surveys were made during the FSRS: a
population-based survey (Table 1) and a land-based survey (Table 2).  Additionally, soil-gas radon
and gamma radiation measurements were made during the FSRS. The population-based survey
used a stratified random sampling design based on the 1980 census and residential addresses   .
obtained from a vendor. The target number of homes sought in each county ranged from 16 to
 160. The number of devices mailed out per county ranged from 6 to 234. The actual number of
radon samplers returned by homeowners per county in the population-based survey ranged from 5
to 190. The measurements were made using charcoal canisters placed for three days by the
homeowner during the winter and spring of 1987.
       The land-based survey was based on the 7-1/2 minute quadrangles for the State and was
designed to give a relatively uniform geographic coverage across the State. Charcoal canisters
were placed for three days during the winter and early spring of 1986-1987 by survey personnel
after interviewing homeowners. Results from the land-based survey (average concentrations and
percent of homes greater than 4 pCi/L) are shown in figure 7.
       The indoor radon data from the FSRS show that a discontinuous zone of elevated indoor
radon levels extends from southwestern Dade County northwestward through Collier, Lee, and
Charlotte Counties, and northward to Columbia County. Leon County also shows evidence of
                                         IV-9   Reprinted from USGS Open-File Report 93-292-D

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"CABLE 1. Indoor radon results from the Florida land-based radon survey, by county.
County
Alachua
Baker
Bay
Bradford
Brevard
Broward
Calhoun
Charlotte
Citrus
Clay
Collier
Columbia
Dade
DeSoto
Dixie
Duval
Escambia
Flagler
Franklin
Gadsden
Gilchrist
Glades
Gulf
Hamilton
Hardee
Hendry
Hernando
Highlands
HUlsborough
Holmes
Indian River
Jackson
Jefferson
Lafayette
Lake
Number
of homes
109
20
41
23
85
43
12
82
81
28
43
20
55
23
21
66
51
26
14
18
25
6
14
23
32
19
93
42
137
15
30
34
2
4
97
Average
pCi/L
3.3
0.3
0.3
0.4
-0.5
0.5
0.3
1.0
1.1
- 0.5
0.7
2.2
1.0
0.8
0.6
0.3
0.7
0.6
0.4
0.6
1.4
0.3
0.3
0.5
0.9
1.4
0.9
0.3
1.1
0.7
0.5
0.7
0.4
0.6
0.5
Standard
Deviation
pCi/L
5.6
0.3
0.2
0.4
0.4
0.4
0.2
1.1
1.1
0.5
0.6
3.4
1.1
' 0.8
0.4
0.2
0.5
0.5
0.4
0.3
1.4
0.3
0.3
0.4
1.4
1.4
0.8
0.2
1.7
0.8
0.4
0.5
0.2
0.2
0.5
Maximum
pCi/L
29.5
1.2
1.1
1.4
3.2
1.8
0.9
5.3
•8.5
2.3
3.1
11.7
4.7
3.0
1.9
1.1
2.6
2.2"
1.3
1.4
6.2
1.0
1.2
1.4
7.5
4.7
3.6
0.9
9.9
3.3
1.7
2.2
0.5
0.8
3.1
Percent
Homes
>4pCi/L
17.4*
-
-
-
-
-
-
3.7*
1.2
-
-
15.0*
3.6
-
-
-
-
-
-
-
4.0
-
-
-
3.1
10.5
-
-
5.1*
-
-
.
-
-
-
Percent
Homes
>8pCi/L
_ 10.1
-
-
-
-
-
-
-
1.2
-
-
10.0
-
-
-
-
-
-
-
-

-
-
-
-
-
-
-
2.2
-
-
-
-
-
-
Percent
Homes
>12pCi/L
7.3
-
-
. -
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-

-
-
-
-
-
-
-
-
-
-
-
-
-
•-
*- Counties for which the proportion homes with measured concentrations at or above 4 pCi/L is
significantly different from zero.
                                          IV-10   Reprinted from USGS Open-File Report 93-292-D

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    TABLE 1 (continued). Indoor radon results from the Florida land-based survey, by county.
County
Lee
Leon
Levy
Liberty
Madison
Manatee
Marion
Martin
Monroe
Nassau
Okaloosa
Okeechobee
Orange
Osceola
Palm Beach
Pasco
Pinellas
Polk
Putnam
St. Johns
St. Lucie
Santa Rosa
Sarasota
Seminole
Sumter
Suwanee
Taylor
Union
Volusia
Wakulla
Walton
Washington

Total, all
counties
Number
of homes
144
21
65
4
5
48
176
29
43
29
39
18
72
37
68
74
81
157
50
39
29
36
78
31
47
27
19
13
68
16
34
19

3,050
Average
pCi/L
1.0
1.8
1.1
0.7
0.4
0.6
3.1
0.4
0.6
0.4
0.5
0.5
0.7
0.4
0.5
0.9
0.5
1.4
0.5
0.4
0.4
0.6
0.9
0.5
2.8
0.6
0.9
1.3
0.5
0.5
0.6
0.4

1.0
Standard
Deviation
pCi/L
1.0
3.1
0.9
0.5
0.4
0.6
4.5
0.3
0.7
0.2
0.4
0.4
0.6
0.3
0.4
1.4
0.7
2.2
0.3
0.3
0.3
0.5
0.7
0.4
5.0
0.6
1.0
2.3
0.4
0.4
0.5
0.3

2.1
Maximum
pCi/L
5.8
13.8
4.9
1.4
1.2
3.1
32.4
1.6
3.2
0.7
1.8
1.3
2.6
1.5
1.6
8.0
4.3
13.2
1.4
1.3
1.0
2.6
3.2
2.0
25.3
3.3
4.3
6.6
1.4
1.6
1.7
1.2

32.4
Percent
Homes
>4pCi/L
2.1*
9.5
1.5
-
-
-
22.2*
-
-
f
-
-
-
-
-
5.4*
1.2
11.5*
-
-
-
-
-
-
14.9*
-
5.3
15.4
-
-
-
-

3.8
Percent
Homes
>8pCi/L
-
4.8
_
-
-
-
9.1
-
-
-
-
-
-
_
-
1.4
.
2.6
_
-
_
-
-
-
4.3
-
-
-
-
_
-
_

1.3
Percent
Homes
>12pCi/L

4.8
_
_
_
_
5.1
_
_
• -
_
_
_
_
_
_
_
0.6
_
_
_
_
_
_
4.3 .
_
_
_
_
_
_
_

0.7
*- Counties for which the proportion homes with measured concentrations at or above 4 pCi/L is
significantly different from zero.
                                          IV-11   Reprinted from USGS Open-File Report 93-292-D

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 TABLE 2. Indoor radon results from the Florida population-based radon survey, by county.
County
Alachua
Baker
Bay
Bradford
Brevard
Broward
Calhoun
Charlotte
Citrus
day
Collier
Columbia
Dade
DeSoto
Dixie
Duval
Escambia
Flagler
Franklin
Gadsden
Gilchrist
Glades
Gulf
Hamilton
Hardee
Hendry
Hemando
Highlands
Hillsborough
Holmes
Indian River
Jackson
Jefferson
Lafayette
Lake
Number
of homes
67
15
51
13
166
127
13
39
49
39
51
8
71
15
12
126
90
5
9
11
15
6
11
9
15
13
46
37
134
11
46
11
8
12
44
Average
pCS/L
2.4
0.4
0.3
0.3
0.3
0.4
0.4
1.7
1.9
0.3
0.9
0.2
0.8
0.8
0.2
0.3
0.5
0.3
0.3
0.5
1.8
0.4
0.2
0.3
0.8
0.6
0.5
0.4
1.0
0.4
0.3
0.4
0.2
0.5
0.3
Standard
Deviation
pCi/L
3.0
0.2
0.2
0.4
0.3
0.5
0.3
1.4
2.9
0.2
1.1
0.0
1.0
0.9
0.1
0.3
0.2
0.2
0.2
0.6
2.2
0.4
0.0
0.1
1.1
0.7
0.3
0.3
2.0
0.3
0.2
0.2
0.1
0.2
0.3
Maximum
pCi/L
14.4
0.9
1.1
1.6
1.8
2.7
1.3
6.1
15.9
1.0
7.5
0.2
5.3
3.5
0.6
1.3
1.5
0.7
0.8
2.3
7.2
1.1
0.2
0.5
3.9
2.2
1.4
1.2
17.8
1.1
1.1
0.9
0.5
0.8
2.0
Percent
Homes
>4pCi/L
22.4*
-
-
-
-
-
-
10.3*
10.2*
-
2.0
-
1.4
-
-
-
-
-
-
-
13.3
-
-
-
-
-
-
-
3.7*
-
-
-
-
-
-
Percent
Homes
>8pCi/L
7.5
-
-
-
-
-
_
-
4.1
-
-
-
-
_
-
-
-
-
-
-
_
-
-
-
-
-
_
_
2.2
-
-
-
-
-
-
Percent
Homes
>12pCi/L
3.0
_
_
-
_
_
_
_
2.0
_
-
_
-
_
_
_
_
_
-
-
_
-
_
_
-
_
_
_
0.8
-
_
_
_
_
-
*- Counties for which the proportion homes with measured concentrations at or above 4 pCi/L is
significantly different from zero.
                                         IV-12   Reprinted from USGS Open-File Report 93-292-D

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TABLE 2 (continued). Indoor radon results from the Florida population-based survey, by county.
County
Lee
Leon
Levy
Liberty
Madison
Manatee
Marion
Martin
Monroe
Nassau
Okaloosa
Okeechobee
Orange
Osceola
Palm Beach
Pasco
Pinellas
Polk
Putnam
St. Johns
St Lucie
Santa Rosa
Sarasota
Seminole
Sumter
Suwanee
Taylor
Union
Volusia
Wakulla
Walton
Washington

Total, all
counties
Number
of homes
101
51
11
12
8
69
39
23
9
18
63
13
157
28
141
121
185
128
25
17
49
24
135
65
15
15
11
18
126
7
18
9

3,106
Average
pO/L
1.6
1.7
2.2
0.3
0.5
0.8
4.3
0.3
0.2
0.3
0.3
0.4
0.5
0.4
0.4
0.8
0.4
0.9
0.2
0.3
0.3
0.5
0.7
0.6
1.9
0.5
0.8
0.7
0.4
0.4
0.3
0.5

0.7
Standard
Deviation
pCi/L
3.2
1.7
4.1
0.2
0.6
1.7
5.6
0.1
0.0
0.2
0.2
0.3
0.7
0.3
0.4
1.4
0.4
1.7
0.1
0.1
0.3
0.6
0.8
0.7
2.6
0.9
0.7
0.5
0.3
0.4
0.2
0.3

1.5
Maximum
pCi/L
28.2
7.0
14.0
0.8
1.8
13.3
25.4
0.7
0.2
0.7
1.3
1.0
4.6
1.4
2.3
8.0
4.4
15.1
0.5
0.7
1.2
2.5
5.6
4.4
8.5
3.7
2.1
1.6
1.7
1.1
0.7
1.0

28.2
Percent
Homes
>4pCi/L
5.9*
13.9*
18.2
-
-
2.9
30.8*
-
-
-
-
-
1.9*
-
-
5.0*
0.5
3.1*
-
-
-
-
1.5
1.5
13.3
-
-
-
-
-'
-
-

2.6
Percent
Homes
>8pCi/L
2.0
-
9.1
-
-
1.5
18.0
-
-
-
-
-
-
-
-
0.8
-
1.6
-
-
-
-
-
-
6.7
-
-
.
-
-
-
-

0.8
Percent
Homes
>12 pCi/L
2.0
-
9.1
-
-
1.5
12.8
-
-
-
-
-
-
-
-
,
-
0.8
-
-
-
-
-
-
-
-
-
-
-
-
-
-

0.5
*- Counties for which the proportion homes with measured concentrations at or above 4 pCi/L is
significantly different from zero.
                                          IV-13   Reprinted from USGS Open-File Report 93-292-D

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          Bstnt. & 1st Floor Rn
             %>4pCi/L
57 L
               6 E3
                 1 B
                3D
OtolO
11 to 20
21 to 30
Missing Data
or < 5 measurements
                                  100 Miles
                Bsmt. & 1st Floor Rn
            Average Concentration (pCi/L)
  60
                   4E3
                    0 0
                   3D
   0.0 to 1.9
   2.0 to 4.0
   4.1 to 5.0
   Missing Data
   or < 5 measurements
                                   100 Miles
     Figure 7- Maps showing indoor radon data by county from the Florida State Radon Study, land-
     based survey, for counties with 5 or more measurements. Data are from 3-day charcoal canister
     tests. Histograms in map legends show the number of counties in each category. The number of
     samples in each county (See Table 2) 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.

-------
elevated indoor radon. All of these areas are marked by locally elevated equivalent uranium in soils
(fig. 6) suggesting that the presence of uranium in soils is a primary control on the distribution of
elevated indoor radon levels in Florida. Phbsphatic sedimentary rocks are a primary source for
uranium in soils in Florida, but phosphatic sedimentary rocks do not occur at or near the surface in
Dade and Collier Counties. Studies by other researchers (Cowart and Burnett, 1989; D.R. Muhs,
oral communication, 1990) suggest that unusually high levels of radium are present in soils formed
on the Pleistocene Key Largo Limestone and perhaps on other rock formations in certain areas of
the Florida Keys and in southwestern Dade County. Areas of elevated eU (fig. 6) and elevated
indoor radon in Dade County are likely related to these unusual soils.  These unusual soils may
extend into Collier County and may be responsible for the modestly elevated eU in soils and for the
elevated indoor radon levels.
       Counties along the Atlantic Coast of Florida are generally low in indoor radon, likely
reflecting the low content of uranium in soils. Nassau County, which has some soils with elevated
levels of uranium, does not have corresponding evidence of elevated indoor radon levels. Elevated
uranium levels in Nassau County soils are most likely related to heavy minerals in beach sands.
As uranium-bearing heavy minerals in beach sands are poor emanators of radon, such elevated
uranium levels in the soils may not contribute much to elevated soil-gas radon or elevated indoor
radon levels.
       Douglas Mose (George Mason University, written communication, 1989) has identified
scattered zip code areas in Palm Beach, Brevard, Orange, and Volusia Counties along or near the
Atlantic coast in which average indoor radon levels are greater than 4 pCi/L.  Modest eU anomalies
(1.5-3.0 ppm) occur in the latter three zip code areas (there is no eU data for the Palm Beach zip
code area).

GEOLOGIC RADON POTENTIAL

       The potential for elevated indoor radon levels in Florida was first noted for houses built on
phosphate mill tailings (Rowe, 1975; Florida Department of Health and Rehabilitative Services,
1978); however,  studies showed that elevated indoor radon levels also occurred in houses built on
nearby undisturbed phosphate lands  (Florida Department of Health and Rehabilitation Services,
1978). Workers who have evaluated geologic radon potential since then have largely attributed
most of the radon potential in the State to these phosphate-bearing rock formations (Smith and
Hansen, 1989) and have been successful in predicting local areas of elevated indoor radon levels
using detailed geologic maps of the  uraniferous Hawthorn Group (Roessler and others, 1993).
       The uranium (radium) content of soils probably plays the most important role in the
geologic radon potential of Florida.  Moisture content of soils influences both the emanating power
and the transport of radon in soils. The moisture content of soils across Florida varies from
slightly moist in the  summertime to very moist in the wintertime.  Highest rainfall normally occurs
in the warmest months when evapotranspiration is highest, whereas rainfall is less in late fall and
winter but evapotranspiration is dramatically reduced.  In lowland areas and in highland areas
where perched water tables exist, the moisture content of soils is also affected by the seasonal high
water table. Areas of persistent high soil moisture are likely areas of reduced radon potential.
       Slope may play a role in increased radon potential in some areas of Florida, principally the
highlands.  Soils on  slopes tend to drain more quickly and thus are drier.  Dry soils transmit radon
more effectively  than similar wet soils. Nowhere, however, are soils in Florida likely to be so dry
that radon emanation is significantly reduced (low soil pore water permits radon atoms leaving a
                                          IV-15   Reprinted from USGS Open-File Report 93-292-D

-------
mineral grain to cross the pore space and embed in another mineral grain). Most of the sloped
terrain in highland areas has been created by dissection of the highlands. Li highland areas
underlain by phosphatic sedimentary rocks, uraniferous phosphatic layers may be preferentially
exposed on hillslopes.
       Soil permeabilities across most of Florida are generally in the moderate (0.6-2.0 in/hr) to
moderately rapid (2.0-6.0 in/hr) range because of the predominance of sandy soils. However,
high average soil moisture across much of the State probably significantly reduces the gas
permeability of most soils. High soil permeability may be a factor in increasing radon potential by
convective flow of soil gas only in local areas underlain by well-drained coarse sand and gravel,
principally in the highlands of the western panhandle.
       Bedrock permeability may play a role in radon transport in certain areas of Florida. Karst
terrains in which limestone and dolomite bedrock  has been fractured and dissolved are areas where
bedrock permeability can be very high. However, areas where karst is abundant in the State also
typically have very thick soils or commonly have  high water tables. However, open fractures and
solution cavities in the limestone .or dolomite may become pathways for radon-bearing soil gas to
move towards slab foundations on hillslopes in highland areas where the soils are thin and water
tables are deep or in areas where grading has exposed karstified bedrock. Homes with basements
or crawl spaces in such areas may be more severely impacted than slab-on-grade homes.
       Overall, it appears that eU values of 1.5 ppm eU and above on the aeroradiometric map
(fig. 6) delineate areas where radon levels in soils  are most likely to be high enough to significantly
increase indoor radon levels. These areas are largely coincident with, but not exclusively limited
to, those areas of the State underlain by phosphatic sedimentary rocks. If so, then several areas of
Florida are predicted to have increased indoor radon potential. Other factors such as steep slope,
well-drained coarse sandy or gravelly soils, or karst topography may locally enhance this potential
and locally persistent high soil moisture will decrease this potential.

SUMMARY

       There are six distinctive areas in Florida for which geologic radon potential may be
evaluated-the Northern Highlands, the Central Highlands, the Central and Northern Highlands
anomalous areas, the Gulf Coastal Lowlands, the Atlantic Coastal Lowlands, and the Dade County
anomalous area (fig.  8). A relative index of radon potential (RI) and an index of the level of
confidence in the available data (CI) have been established (see discussion in the introductory
chapter of this volume). The six radon potential areas in Florida are evaluated in Table 3.
       The Northern Highlands province has generally low geologic radon potential.  All counties
entirely within this province have indoor radon averages less than 1 pCi/L. Leon County averages
1.7 and 1.8 pCi/L in  the two surveys in the FSRS. Most of these data probably come from
Tallahassee, which lies within an area of modestly elevated eU. This area and those parts of
southern Columbia, western Union, and northern  Alachua County that are underlain by phosphatic
rocks, and limited areas in which coarse gravels occur in river terraces in the western  panhandle,
are likely to have elevated radon potential.  The anomalous eU areas in the Northern Highlands are
delineated in figure 8 and evaluated in Table 3.
       The Central Highlands province has two different geologic radon potentials that are
delineated in figure 8 and evaluated in Table 3.  Generally low radon potential occurs  in low eU
areas in the eastern and southern parts of this province. Moderate radon potential occurs in the
western part of this province where uraniferous phosphatic rocks are close to the surface. These
                                           W-16   Reprinted from USGS Open-File Report 93-292-D

-------
anomalous areas in the Central Highlands are delineated in figure 8 and evaluated in Table 3.
Localized areas in which uranium contents of soils and shallow subsoils exceed 100 ppm are likely
and indoor radon levels may exceed 20 pCi/L or more where this occurs. Alachua (lies in both the
Central and Northern Highlands), Marion, and Sumter Counties report indoor radon levels
exceeding 20 pCi/L in the FSRS. Excessively well-drained hfflslopes may also contribute to
higher radon potential.                                                ~        • *«   j
       The Gulf Coastal Lowland Province generally has low radon potential. High rainfall and
high water tables cause generally very moist soils which inhibit radon movement Low eU values
exist in most areas except in some coastal bay areas of western peninsular Florida. Some isolated
areas of elevated radon potential may occur in these areas of higher eU (fig. 6).
       The Atlantic Coastal Lowland province generally has low geologic radon potential. High
rainfall and high water tables cause very moist soils that inhibit radon movement Low eU values
exist in most areas.  In some beach sand areas in northern Florida, elevated eU seems to be
associated with heavy minerals, but there is no evidence to suggest that elevated indoor radon
occurs in these areas.          .
       Unusually high eU'(fig. 6) and elevated indoor radon levels (Nifong,  1987) occur in
southwestern Dade County. This Dade County anomalous area seems to be associated with
unusual soils that can be readily mapped.
       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 than assigned to the area as a whole. Any local decisions about radon should
not be made without consulting all available local data. The State of Florida Department of
Community Affairs in Tallahassee has conducted a Florida Radon Research Program which
includes detailed mapping of radon potential for the State. For information on the status of radon
potential mapping in Florida, contact the Department of Community Affairs.  For additional
information on radon and how to test contact the 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-17   Reprinted from USGS Open-File Report 93-292-D

-------
                     I  I   Low potential


                           Moderate potential
Figure 8- Map showing radon potential areas in the state of Florida.  Refer to Figure 1 for
physiographic province names.  1- Dade County anomalous area.

-------
 TABLE 3. Radon Index (RI) and Confidence Index (CI) for geologic radon potential areas
  of Florida. See figure 8 for locations of areas. See the introductory chapter for discussion of RI
                                     andCI.
Northern
Highland
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
RANKING
RI
1
1
1
2
1
0
6
LOW
CI
2
3
1
3
.
-
9
MOD
Central
Highland
RI
1
1
1
2
1
0
6
LOW
CI
2
3
3
3

_
11
HIGH
Gulf
Lowland
RI
1
1
1
2
1
0
6
LOW
CI
2
3
1
3



MOD
Atlantic
Lowland
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
RANKING
RI
1
1
1
2
1
0
6
LOW
CI
2
3
1
3
.
-
9
MOD
Highland
Anomalous areas
RI
2
2
2
3
2
+1
11
MOD
a
2
2
2
2
1
0
11
HIGH
Dade
County
RI
2
2
2
2
1
0
9
MOD
CI
2
3
2
3


10
HIGH
- Not used in CI.

RADON INDEX SCORING:
Radon potential category
LOW
MODERATE/VARIABLE
HIGH
Point ranse
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-19  Reprinted from USGS Open-File Report 93-292-D

-------
                        REFERENCES CITED IN THIS REPORT
         AND GENERAL REFERENCES PERTAINING TO RADON IN FLORIDA

Abbott, T.A., and Smith, D.L., 1987, Distribution of surficial radioactivity backgrounds in
       Marion, Levy, and Citrus counties, Florida, in Carson, R.G., chairperson, 1987 program
       issue of the Fifty-first annual meeting of the Florida Academy of Sciences: Florida
       Scientist, v. 50, Suppl. 1, 26 p.

Abbott, T.A., Smith, D.L.,-and Browning, C.B., 1988, The distribution of radioactivity in the
       surficial geological formations of Levy, Marion, and Citrus Counties, Florida, in Natural
       Radiation and Technically Enhanced Natural Radiation in Florida: Florida Chapter, Health
       Physics Society, p. 2-16.

Bond, P.A., 1987a, Peatlands and the distribution of environmental radioactivity: Geological
       Society of America Abstracts with Programs, v. 19, no. 7, p. 594-595.

Bond, P.A., 1987b, Geology and waste disposal in Florida: Florida Geological Survey Map
       Series no. 112,1 plate with text.

Breland, J.A., H, and Fanning, K.A., 1982,226Ra and 222Rn in rivers and estuaries of western
       Florida: EOS, Transactions, American Geophysical Union, v. 63, p. 56.

Briel, L.I., 1976, An investigation of the U 234/U 238 disequilibrium in the natural waters of the
       Santa Fe River basin of North-central Florida: Ph.D. thesis, Florida State University,
       Tallahassee, 241 p., also Diss. Abstr. Int., v. 37, no. 7, p. 3305B.

Browning, C,  and Smith, D., 1986, Background radioactivity of geologic formations in North
       Florida, in Program issue, fiftieth annual meeting of the Florida Academy of Sciences,
       Gainesville, Florida, April 10-12,1986: Florida Scientist, v. 49, no. 1,30 p.

Burnett, W.C., Cowart, J.B., and Chin, P.A., 1987, Polonium in the surficial aquifer of west
       central Florida, in Graves, Barbara, ed., Radon, radium, and other radioactivity in ground
       water, NWWA conference, Somerset, NJ, Apr. 7-9,1987, Lewis Publishers, p. 251-269.

Burnett, W.C., and Gomberg, D.N., 1977, Uranium oxidation and probable subaerial weathering
       of phosphatized limestone from the Pourtales Terrace: Sedimentology, v. 24, p. 291-302.

CaldweU, R.E., and Johnson, R.W., 1982, General soil map Florida: U.S. Department of
       Agriculture, Soil Conservation Service, 1 plate with text.

Chhatre, R.M., Onoda, G.Y., Jr., and Whitney, E.D., 1980, Uranium distribution in phosphate
       processing: Transactions of the American Institute of Mining, Metallurgical, and Petroleum
       Engineers Incorporated, v. 268, p. 1769-1772.

Chin, P.A., Deetae, S. and Burnett, W.C., 1985, Release of uranium decay-series nuclides from
       Florida phosphate rock:  Geological Society of America Abstracts with Programs, v. 17,
       no. 7, p. 544-545.
                                         IV-20   Reprinted from USGS Open-FUe Report 93-292-D

-------
Chung, G.S., Evans, C.C., and Swart, P.K., 1985, Uranium as an indicator of diagenesis and
       water flow in the Pleistocene Miami Limestone: Geological Society of America Abstracts
       with Programs, v. 17, no. 7, p. 546.         •

Cowart, J.B., 1980, Variation of uranium isotopes in some carbonate aquifers, in Gesell, T.F.,
       and Lowder, W.M., eds., Natural radiation environment HI; Vol. 1, International
       symposium on the natural radiation environment, Houston,TX, April 23-28,1978, DOE
       Symposium Series 1, Report no. CONF-7840422, p. 711-723.

Cowart, J.B., 1980, Uranium isotopes in Floridan Aquifer waters; their distribution and
       significance: Geological Society of America Abstracts with Programs, v. 12, no. 7, p. 407.

Cowart, J.B., 1983, Use of dissolved uranium isotopes in determining the time of change in
       hydrologic conditions in the west central Florida area: Geological Society of America
       Abstracts with Programs, v. 15, no. 2, p. 58.

Cowart, J.B., and Burnett, W.C., 1989, Elevated radon generated in terra rosa in south Florida:
       Geological Society of America Abstracts with Programs, v. 21, p. A144.

Cowart, J.B., Burnett, W.C., LaRock, P.A., and Harada, K., 1988, Polonium-210 in Florida
       groundwaters and its possible relationship to the sulfur cycle: Geological Society of
       America Abstracts with Programs, v. 20, no. 7, p. A173.

Cowart, J.B., Kaufman, M.I., and Osmond, J.K., 1978, Uranium-isotope variations in
       groundwaters of the Floridan Aquifer and Boulder Zone of South Florida: Journal of
       Hydrology, v. 36, p. 161-172.

Crane, J.J., 1986, An investigation of the geology, hydrogeology, and hydrochemistry of the
       Lower Suwannee River basin: Florida Bureau of Geology, Report of Investigation 96,
       205 p.

Deetae, S., 1986, Release and transport of radium during weathering in central and North Florida:
       Ph. D. thesis, Florida State University, Tallahassee, Florida, 149 p.

Duval, J.S., Jones, W.J., Riggle, F.R., and Pitkan, J.A., 1989, Equivalent uranium map of the
       conterminous United States: U.S. Geological Survey Open-File Report 89-478,10 p.

Espenshade, G.H., 1958, Geologic features of areas of abnormal radioactivity south of Ocala,
       Marion County, Florida: U.S. Geological Survey Bulletin 1118,115 p.

Fanning, K.A., Breland, J.A., H and Byrne, R.H., 1982,  Radium-226 and radon-222 in the
       coastal waters of West Florida; high concentrations and atmospheric degassing: Science,
       v. 215, p. 667-670.

Fisher, D.R., 1978, Risk evaluation and dosimetry for indoor radon progeny on reclaimed Florida
       phosphate lands: Doctoral thesis, University of Florida, Gainesville, 140 p.
                                         IV-21   Reprinted from USGS Open-File Report 93-292-D

-------
Florida Department of Health and Rehabilitative Services, 1978, Study of radon daughter
       concentrations in structures in Polk and Hillsborough Counties: Florida Department of
       Health and Rehabilitative Services, Tallahassee, 111 p.

Fountain, R.C., and Hayes, A.W., 1979, Uraniferous phosphate resources of the southeastern
       United States: in De Voto, R.H., and Stevens, D.N., eds., Uraniferous phosphate
       resources and technology and economics of uranium recovery from phosphate resources,
       United States and free world; Volume 1, Uraniferous phosphate resources, United States
       and free world: U.S. Department of-Energy Report GJBX-110(79), p. 55-122.

Fred, C, and Stafford, R.E., 1988, A preliminary radon risk assessment of three Florida schools,
       in Proceedings of the 1988 symposium on radon and radon reduction technology, U.S.
       Environmental Protection Agency report no. EPA600/9-89/006, Paper X-l.

Gesell, T.F., and Prichard, H.M., 1977, Measurements of radon-222 in water and indoor airborne
       radon-222 originating in'water: in Breslin, A.J., ed., 3rd HASL radon workshop, New
       York, NY, Feb. 1977, Report no. HASL-325, p. 132-140.

Golden, J.C., Jr., 1968, Natural background radiation levels in Florida: Sandia Laboratories
       Research Report SC-RR-68-196.

Grosz, A.E., Cathcart, J.B., Macke, D.L., Knapp, M.S., Schmidt, Walter and Scott, T.M.,
       1989, Geologic interpretation of the gamma-ray aeroradiometric maps of central and
       northern Florida: U.S. Geological Survey Professional Paper 1461,48 p.

Gunning, S.P., 1978, The distribution of uranium in phosphorites of central Florida: Master's
       thesis, University of Florida, Gainesville, 77 p.

Hansen, J.K., 1988, The distribution of gamma radiation in the surficial deposits of the Florida
       panhandle: Master's thesis, University of Florida, Gainesville, 113 p.

Harada, Koh, Burnett, William C., LaRock, Paul A., and Cowart, James B., 1989, Polonium in
       Florida groundwater and its possible relationship to the sulfur cycle and bacteria:
       Geochimica et Cosmochimica Acta, v. 53, p. 143-150.

Hull, Robert, 1981, Uranium isotopic disequilibrium; its hydrological application to Floridian
       Aquifer waters of Northeast Florida: Master's thesis, Florida State University, Tallahassee,
       Florida., 86 p.

Humphreys, C.L., 1984, Uranium and radium isotopic distributions in ground waters and
       sediments of the land-pebble phosphate district and surrounding areas of west-central
       Florida: Master's thesis, Florida State University, Tallahassee, FL., 141 p.

Humphreys, C.L., 1987, Factors controlling uranium and radium isotopic distributions in ground
       waters of the west central Florida phosphate district, in Graves, Barbara, ed., Radon,
       radium, and other radioactivity in ground water, NWWA conference, Somerset, NJ, April
       7-9, 1987, Lewis Publishers, p. 171-189.
                                         IV-22   Reprinted from USGS Open-File Report 93-292-D

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Irwin, G.A., and Hutchinson, C.B., 1976, Reconnaissance water sampling for radium-226 in
       central and northern Florida, December 1974-March 1976: NTIS, Springfield, VA, Report
       no.: PB-262 376/AS, 20 p.

Johnson, W., 1977, Radioactivity and the Bone Valley Formation: in Brown, D.P., Gurr, T.M.,
       Crissinger, D.B., and Nettles, S., Environment of the Central Florida phosphate district,
       Lakeland, Fla., twenty-first field conference, Dec. 2-3,1977: Southeastern Geological
       Society Publication 19, p. 30-35.

Karfunkel, B.S., 1982, Orientation study in Hillsborough and Polk counties, West-central Florida:
       U.S. Department of Energy, Report no. GJBX-146-82; DPST-81-141-21, 21 p.

Kaufmann, R.F. Radioactivity in groundwater associated with uranium and phosphate mining and
       processing, in Hemphill, D.D., ed., Proceedings of University of Missouri's 15th annual
       conference on trace substances in environmental health, Columbia, MO, June 1-4,1981:
       Trace Substances in Environmental Health, v. 15, p. 87-95.

Kaufmann, R.F., and Bliss, J.D., 1978, Radium-226 in ground water of west central Florida:
       Water Resources Bulletin (Urbana), v. 14, p. 1314-1330.

May, A., and Sweeney, J.W., 1982, Assessment of environmental impacts associated with
       phosphogypsum in Florida: U.S. Bureau of Mines Report of Investigations 8639,19 p.

Metzger, Robert, McKlveen, J.W., Jenkins, Robert, and McDowell, W.J., 1980, Specific activity
       of uranium and thorium in marketable rock phosphate as a function of particle size: Health
       Physics, v. 39, p. 69-75.

Miller, R.L., and McPherson, B.F., 1987, Concentration and transport of phosphorus and
       radium-226 in the Peace River and Charlotte Harbor, southwestern Florida: Abstracts of
       papers; 194th ACS national meeting, Aug.30-SepL 4,1987, unpaginated.

Miller, R.L., and Sutcliffe, H., Jr., 1985, Occurrence of natural radium-226 radioactivity in
       ground water of Sarasota County, Florida: U.S. Geological Survey Water-Resources
       Investigations Report no. WRI84-4237, 34 p.

Nash, J.D., 1987, Florida; working with the phosphate factor: Environment, v. 29,
       p.  13, 15,  37,  38.

Nifong, G, D., 1987, Florida statewide radon study: Florida Institute of Phosphate Research
       Publication no. 05-029-057, 424 p.

Nifong, G.D., and Nagda, N.L., 1988, The Florida statewide environmental radiation study:  81st
       Annual meeting of the Air Pollution Control Association, June 20-24,1988, Dallas, Texas,
       Paper 88-76.2, 13 p.

Odom, A.L., and Mose, D.G., 1989, Radon potential risk maps for Florida, Georgia and
       Alabama: Geological Society of America Abstracts with Programs, v. 21, no. 3, p. 53.
                                         IV-23   Reprinted from USGS Open-FUe Report 93-292-D

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Osmond, J.K., and Cowart, J.B., 1977, Uranium series isotopic anomalies in thermal ground
       waters from Southwest Florida, in Smith, D.L., and Griffin, G.M., eds., The geothermal
       nature of the Floridan Plateau: Florida Bureau of Geology Special Publication 21,
       ,p. 13.1-147,

Osmond, J.K., and Cowart, J.B., 1985, Mass balances by uranium-series disequilibria in natural
       phosphate deposits and mine products: Geological Society of America Abstracts with
       Programs, v. 17, no. 7, p. 683.

Palacas, J.G., and Roberts, A.A., 1980, Helium anomaly in surficial deposits of South Florida;
       possible indicator of deep subsurface petroleum or shallow uranium-associated phosphate
       deposits: U.S. Geological Survey, Open-File Report 80-91,16 p.

Roessler, G.S., Hintenlang, D.E., and Roessler, C.E., 1990, Characterization of the radon source
       in southeastern United States: Progress report, June 1989-March 1990: University of
       Florida, 24 p. plus appendix.

Roessler, C.E., Revell, T.A., and Wen, M.J., 1990, Temporal patterns of indoor radon in north
       central Florida and comparison of short-term monitoring to long-term averages, in U.S.
       Environmental Protection Agency, The 1990 international symposium on radon and radon
       reduction technology: Volume n. Preprints, Paper II-P2-3,17 p.

Roessler, C.E., Mohammed, H., Richards, R., and Smith, D.L., 1993, Radon source studies in
       north Florida, in Environmental Health Physics: Proceedings of Twenty-Sixth Midyear
       topical meeting of the Health Physics Society, Jan. 24-28,1993: Richland, Washington,
       Columbia Chapter Health Physics Society, 8 p., 1 appendix.

Rose, A.W., Ciolkosz, E.J., and Washington, J.W., 1991, Effects of regional and seasonal
       variations in soil moisture and temperature on soil gas radon, in The 1990 International
       Symposium on Radon and Radon Reduction Technology, Proceedings, Vol. 3:
       Symposium Poster Papers: Research Triangle Park, N.C., U.S. Environmental Protection
       Agency Report EPA600/9-91-026c, p. 6-49--6-60.

Rowe, W.D., 1975, Preliminary findings radon daughter levels in structures constructed on
       reclaimed Florida phosphate land: U.S. Environmental Protection Agency Tech. Note
       ORP/CSD-75-4.

Schoenborn, W.A., Koontz, M.D., Nagda, N.L., and Nifong, G.D., 1987, Geology as a
       regional indicator of radon potential; the Florida experience: Geological Society of America
       Abstracts with Programs, v. 19, no. 7.

Smith, D.L., and Hansen, J.K., 1989, Distribution of potentially elevated radon levels in Florida
       based on surficial geology: Southeastern Geology, v. 30, p. 49-58.

Sweeney, J.W., and Windham, S.R., 1979, Florida: the new uranium producer: Florida
       Geological Survey Special Publication no. 22,13 p.
                                         IV-24   Reprinted from USGS Open-File Report 93-292-D

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Upchurch, S.B.,1986, Chemistry of ground waters on the Central Florida phosphate district, in
       Graves, B.J., Lehr, J.H., and Butcher, K., chairpersons, Proceedings of the National
       Water Well Association Focus conference on Southeastern groundwater issues,
       p. 201-215.

U.S. Environmental Protection Agency, 1975, Preliminary findings, radon daughter levels in
       structures constructed on reclaimed Florida phosphate land: U.S. Environmental Protection
       Agency, Office of Radiation Programs Report ORP/CSD-75-4,30 p.

Vonstille, W.T., and Sacarello, H.L.A., 1990, Assessment of health impacts of radon exposures
       in Florida, in U.S. Environmental Protection Agency, The 1990 international symposium
       on radon and radon reduction technology: Volume I. Preprints, EPA/600/9-90/005a, Paper
       A-H-4,  lip.
                                        IV-25   Reprinted from USGS Open-FUe Report 93-292-D

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                                EPA's Map of Radon Zones
       The USGS' Geologic Radon Province Map is the technical foundation for EPA's Map
 of Radon Zones.  The Geologic Radon Province Map defines the radon potential for
 approximately 360 geologic provinces.  EPA has adapted this information Jo 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.)

 FLORIDA MAP OF RADON ZONES

       The Florida Map  of Radon Zones and its supporting documentation (Part IV of this
 report) have received  extensive review by Florida geologists and radon program experts.  The
 map for Florida 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.
       One county designation in Florida does not strictly follow the methodology for
 adapting the geologic provinces to "county boundaries."  Leon county has been designated to
 Zone 2 based on elevated indoor radon levels that have been recorded from  this county and
 on the isolated geologic potential  to cause elevated indoor radon levels.
       Although the information provided in Part IV of this report - the State  chapter entitled
 "Preliminary Geologic Radon Potential Assessment of Florida" ~ 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 4 EPA office or the
 Florida radon program for information on testing and fixing homes.  Telephone numbers and
 addresses can be found in Part II of this report.
      The Department of Community Affairs of the State of Florida is conducting a Florida
Radon Research  Program which includes development of a more detailed map of radon
potential for the  State. This map  will supersede the more generalized assessment presented
here.
                                         V - 1

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