Untted States
             Environmental Protection
             Agtncy
Air and Radiation
(6604J)
402-H-S3-044
September 1993
«xEPA    EPA's Map of Radon Zones

             MISSISSIPPI
                                                       Recycled/Recyclable
                                                       Printed on paper that contains
                                                       at least 50% recycled fiber

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       EPA'S MAP OF RADON ZONES
               MISSISSIPPI
             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 arid Indoor Air (ORIA) in conjunction with the U.S. Geological Survey
(USGS).  Sharon W. White was the EPA project manager. Numerous other people in ORIA
were instrumental in the development of the Map of Radon Zones, including Lisa Ratcliff,
Kirk Maconaughey, R. Thomas Peake, Dave Rowson, and Steve Page.

      EPA would especially like to acknowledge the outstanding effort of the USGS
radon team -- Linda Gundersen, Randy  Schumann, Jim Otton, Doug Owen, Russell
Dubiel, Kendell Dickinson, and Sandra Szarzi — in developing the technical base for the
Map of Radon Zones.

      ORIA  would also like to recognize  the efforts of all the EPA Regional Offices in
coordinating the reviews with the  State programs and the  Association of American State
Geologists (AASG) for providing  a liaison with the State  geological surveys.  In addition,
appreciation is expressed to all of the State radon programs and geological surveys for their
technical  input and review of the Map of Radon Zones.

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            TABLE OF CONTENTS
               I. OVERVIEW
     II. THE USGS/EPA RADON POTENTIAL
        ASSESSMENTS:INTRODUCTION
  III. REGION 4 GEOLOGIC RADON POTENTIAL
                SUMMARY
V. PRELIMINARY GEOLOGIC RADON POTENTIAL
         ASSESSMENT OF MISSISSIPPI
 V. EPA'S MAP OF RADON ZONES - MISSISSIPPI

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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 ever the pa.  jeveral 3     to produce  . 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 (Rn:~) is a colorless/  odorless, radioactive gas. It comes from the natural
decay of uranium that is found in  nearly all soils.  It typically moves through the ground to
the air above and into homes and other buildings through cracks and openings in the
foundation.  Any home,  school or workplace may have a radon  problem, regardless  of
whether it is new or old,  well-sealed or drafty, or with or without a basement. Nearly one out
of every 15  homes in  the U.S. is estimated to have elevated annual average levels of indoor
radon.
       Radon first gained national attention in early  1984, when extremely high levels of
indoor radon were found in areas of Pennsylvania, New Jersey,  and New York, along the
Reading Prong-physiographic province.  EPA established a Radon Program in 1985 to assist
States and homeowners in reducing  their risk of lung cancer from indoor radon.
       Since 1985, EPA and USGS  have been working together to continually increase our
understanding of radon sources and  the migration dynamics that cause elevated indoor radon
levels.  Early efforts resulted in the  1987 map entitled "Areas with Potentially High Radon
Levels."  This map was based on limited geologic information only because few indoor  radon
measurements were available at the  time. The development of EPA's Map of Radon Zones
and its technical foundation, USGS'  National Geologic Radon Province Map, has been based
on additional information from six years of the State/EPA Residential Radon Surveys,
independent State residential surveys, and continued expansion of geologic and geophysical
information, particularly the data from the National Uranium Resource Evaluation project.
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Purpose of the Map of Radon Zones

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

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

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

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

       The Zone designations were determined by assessing five factors  that are known to be
important indicators of radon potential: indoor radon measurements,  geology, aerial
radioactivity, soil parameters, and foundation types.
       The predictions of average screening levels in each of the Zones is an expression of
radon potential in the lowest liveable area of a structure.  This map is unable to estimate
actual exposures to radon.  EPA recommends methods for testing  and fixing individual homes
based on an estimate of actual exposure to radon. For more  information on testing and fixing
elevated radon levels in homes consult these EPA publications: A  Citizen's Guide 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
                    Underlie       Lo»
 Figure 4
         NEBRASKA -  EPA Map  of  Radon  Zones
         Lincoln County
          lose 1     Zone 2    lone 3
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       One such analysis involved comparing county zone designations to indoor radon
measurements from the State/EPA Residential Radon Surveys (SRRS).  Screening averages
for counties with at least 100 measurements were compared to the counties' predicted radon
potential as indicated by the Map of Radon Zones.  EPA found that 72% of the county
screening averages were correctly reflected by the appropriate zone designations on the Map.
In all other cases, they only differed by 1 zone.
       Another accuracy analysis used the annual average data from the National Residential
Radon Survey (NRRS).  The NRRS indicated that approximately 6 million homes in the
United States have annual averages greater than or equal to 4 pCi/L.  By cross checking the
county location of the approximately 5,700 homes which participated in the survey, their
radon measurements, and the zone designations for these counties, EPA found that
approximately 3.8  million homes of the 5.4 million homes with radon levels greater than or
equal to 4 pCi/L will be found in counties designated as Zone 1.  A random sampling of an
equal number of counties would have only found approximately 1.8 million homes greater
than  4 pCi/L.  In other words, this analysis indicated that the map approach is three times
more efficient at identifying high radon areas than random selection of zone designations.
       Together, these analyses show that the approach EPA used to develop the Map of
Radon Zones is a reasonable one. In addition, the Agency's confidence is enhanced by results
of the extensive State review process -- the map generally agrees with the States' knowledge
of and experience  in their own jurisdictions.  However, the accuracy analyses highlight two
important points:   the fact that elevated levels will be found in Zones 2 and 3, and that there
will  be significant  numbers of homes with lower indoor radon levels in all of the Zones.  For
these reasons, users of the Map of Radon Zones need to supplement the Map with locally
available data whenever possible. Although all known  "hot spots", i.e., localized areas of
consistently elevated levels, are discussed in the State-
specific chapters, accurately defining the boundaries of the "hot spots" on this scale of map is
not possible at this time. Also, unknown "hot spots" do exist.
       The Map of Radon Zones is intended to be a starting point for characterizing radon
potential because our knowledge of radon sources and transport is always growing. Although
this effort, represents the best data available at this time, EPA will continue to study these
parameters and others such as house construction, ventilation features and meteorology factors
in order to better characterize the presence of radon  in U.S homes, especially in high risk
areas.  These efforts will eventually assist EPA in refining and revising the conclusions of  the
Map of Radon Zones.  And although this map is most appropriately used as a targeting tool
by the aforementioned audiences — the Agency encourages all residents to  test their homes
for radon, regardless of geographic location or the zone designation of the county in
which they live.  Similarly, the Map of Radon Zones should not to be  used in lieu of.
testing during real estate transactions.

Review Process

       The Map of Radon Zones has undergone extensive review within EPA and outside  the
Agency. The Association of American State Geologists (AASG) played an integral role  in
this  review process.  The AASG individual State geologists have reviewed their State-specific
information, the USGS  Geologic Radon Province Map, and other materials for their geologic
content and consistency.
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       In addition to each State geologist-providing technical comments, the State radon
'offices were asked to comment on their respective States' radon potential evaluations.  In
 particular, the States were asked to evaluate the data used to assign their counties to specific
 zones EPA and USGS worked with the States to resolve any issues concerning county zone
 designations.  In a few cases, States have requested changes in county zone designations. The
 requests were based on additional data from the State on geology, indoor radon
 measurements, population, etc. Upon reviewing the data submitted by the States, EPA did
 make some changes in zone designations.  These changes, which  do not strictly follow the
 methodology outlined in this document, are discussed in the respective State chapters.
       EPA encourages the States and counties to conduct further research and data collection
 efforts to refine the Map  of Radon Zones.  EPA would like to be kept informed of any
 changes the States, counties, or others make to the maps.  Updates and revisions will be
 handled in  a similar fashion to the way the map was developed.  States  should notify EPA of
 any proposed changes by forwarding the changes through the Regional EPA offices that are
 listed in Part II.  Depending on the amount of new information that is presented, EPA will
 consider updating this map periodically.  The State radon programs should initiate proper
 notification of the appropriate State officials when the Map of Radon Zones is released and
 when revisions or updates are made by the State or EPA.
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  ~ THE USGS/EPA RADON POTENTIAL ASSESSMENTS: AN INTRODUCTION
                                           by
                      Linda C.S. Gundersen and R. Randall Schumann
                                  U.S. Geological Survey
                                           and
                                    Sharon W. White
                           U.S. Environmental Protection Agency

BACKGROUND

    The Indoor Radon Abatement Act of 1988 (15 U.S.C. 2661-2671) directed the U.S.
Environmental Protection Agency (EPA) to identify  areas of the United States that have the
potential to produce harmful levels of indoor radon.  These characterizations were to be based
on both geological  data and on indoor radon levels in homes and other structures.  The EPA
also was directed to develop model standards and techniques for new building construction
that would provide adequate prevention or mitigation of radon entry.  As part  of an
Interagency Agreement between the EPA and the U.S.  Geological Survey (USGS), the USGS
has prepared radon potential estimates for the United States.  This report is one of ten
booklets that document this effort.  The purpose and intended use of these reports is to help
identify areas where states can target  their radon program resources, to provide guidance in
selecting the most appropriate building code options for areas, and to provide  general
information on radon and geology for each state for federal, state, and  municipal officials
dealing with radon issues.  These reports are not intended to be used as a substitute for
indoor radon testing, and they cannot and should not be used to estimate or predict the
indoor radon concentrations of individual homes, building sites, or housing tracts.  Elevated
levels of indoor radon have been found in every State,  and EPA recommends that all homes
be tested for indoor radon.
     Booklets detailing the radon potential assessment for the U.S. have been developed for
each State. USGS geologists are the authors of the  geologic radon potential booklets.  Each
booklet consists of several components, the first being an overview to the mapping project
' (Part I), this introduction to the USGS assessment (Part II), including a general  discussion of
radon (occurrence, transport, etc.),  and details concerning the types of data used. The  third
component is a summary chapter outlining the general geology and geologic radon potential
of the EPA Region (Part III).  The fourth  component is an individual chapter  for each state
(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

                                            H-l     Reprinted from USGS Open-File Report 93-292

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 tracts.  Within any area of a given geologic radon potential ranking, there are likely to be
' areas where the radon potential is lower or higher than that assigned to the area as a whole,
 especially in larger areas such as the large counties in some western states.
     In  each state  chapter, references to additional reports related to radon are listed for the
 state, and the reader is urged to consult these reports for more detailed information.  In most
 cases the best sources of information on radon for specific areas are state and local
 departments of health, state departments responsible for nuclear safety or environmental
 protection, and U.S.  EPA regional offices. More detailed information on state or  local
 geology may be obtained from the state geological surveys.  Addresses and telephone
 numbers of state  radon contacts, geological surveys, and EPA regional offices are listed in
 Appendix C at the end of this chapter.

 RADON GENERATION AND TRANSPORT IN SOILS

     Radon (2"Rn) is produced from the radioactive decay of radium (226Ra), which is, in turn,
 a product of the decay of uranium (238U) (fig. 1). The half-life of :22Rn 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 w.den
 cracks upon drying, thus increasing the soil's permeability to gas flow during drier periods.
        Radon Transport in soils occurs by two processes: (1) diffusion and (2) flow (Tanner,
 1964) Diffusion is'the process whereby radon atoms move from areas of higher
 concentration to areas of lower concentration in response to a concentration gradient.  Flow is
 the process by which soil air moves through soil pores in response to differences in pressure
 within the soil or between the soil and the  atmosphere, carrying the radon atoms along with it.
 Diffusion is the dominant radon transport process in soils of low permeability, whereas flow
 tends to  dominate in highly permeable soils (Sextro  and others, 1987).  In low-permeability
 soils much of the radon may decay before it is able to enter a building because its transport
 rate is reduced.  Conversely, highly  permeable soils, even those that are relatively  low in
 radium  such as those derived from some types of glacial deposits, have been associated with
 high indoor radon levels in Europe and in the northern United States (Akerblom and others
  1984- Kunz and others, 1989; Sextro and others, 1987).  In areas of karst topography formed
 in carbonate rock (limestone or dolomite) environments, solution cavities and fissures can
  increase soil permeability at depth by providing additional pathways for gas flow
      Not all radium contained in soil grains  and grain coatings will result in  mobile radon
  when the radium decays. Depending on where the radium is distributed in the soil, many of
  the  radon  atoms may remain imbedded in the soil grain containing the parent radium atom or
  become imbedded in adjacent soil grains.  The portion of radium that releases radon into the
  pores and fractures of rocks and soils is called the emanating  fraction.  When  a radium atom
  decays to  radon, the energy generated is strong enough to send the radon atom a distance of
  about 40 nanometers (1  nm =  10* meters),  or about 2x10- inches-this is known  as alpha
  recoil (Tanner  1980).  Moisture in  the soil lessens the chance of a recoiling radon atom
  becoming imbedded in an adjacent  grain.  Because  water is more dense than air, a radon atom
  will travel a shorter distance in a water-filled pore than  in an air-filled pore, thus  increasing
  the likelihood that the radon atom  will remain in the pore space.  Intermediate moisture levels
  enhance radon emanation but do not significantly affect permeability.  However, n.gh
  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 m 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 so.l-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-driveti  flow of radon-laden air  from subsurface
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  solution cavities in the carbonate rock into houses.  As warm air enters solution-cavities that
 ' are higher on the hillslope than the homes, it cools and settles, pushing radon-laden air from
  lower in the cave or cavity system into structures on the hillslope (Gammage and others,
  1993). In contrast,  homes built over caves having openings situated below the level of the
  home had higher indoor radon levels in the winter, caused by cooler outside air entering the
  cave,  driving radon-laden air into cracks and solution cavities in the rock and  soil, and
  ultimately, into homes (Gammage  and others, 1993).

  RADON ENTRY INTO BUILDINGS

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

  METHODS  AND SOURCES OF  DATA

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

  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 tacks, and basalts.  Exceptions exist within these general lithologic groups because of
 the occurrence of localized  uranium deposits, commonly of the hydroth-ermal type in
 crystalline rocks or the "roll-front"  type in sedimentary  rocks. Uranium and radium are
 commonly sited in heavy minerals, iron-oxide coatings on rock and soil grains, and organic
 materials in soils and sediments.  Less common are uranium  associated with phosphate and
 carbonate complexes in rocks and soils, and uranium minerals.
    Although many cases of elevated indoor radon levels can be traced to high radium and
 (or) uranium concentrations in parent rocks, some structural features, most notably faults and
 shear zones, have been identified as sites of localized .uranium concentrations (Deffeyes and
 MacGregor, 1980) and have been associated with some of the highest reported indoor radon
 levels (Gundersen, 1991).  The two highest known indoor radon occurrences are associated
 with sheared fault zones in  Boyertown, Pennsylvania (Gundersen and others,  198-8a; 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 (elJ) 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 (214Bi), 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  NUKE AEKUL  SURVEYS
                     2  L'U (1  KILE)
                     5  EM (3  HUES)
                     2  fc 5 KM
                 E3  10  III (6  HUES)
                     5  t 10 IH
                     NO  DATA
Figure 2. Nominal flightiine 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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•  •  -Finite' 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.morearea
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 fhghthne pacing
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 other , 1989),
athougrSome areas  had better coverage than .others due to the differences in fl,ght-lme
  padng 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
 TsmaneO  he 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 da a.
     The shallow (20-30 cm) depth of investigation of gamma-ray spectrometers, either
 grounded  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
 falnuclide" n the  near-surface  soil  layers have been transported downward through the soi.
 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 ot
 radionuclides  in soil profiles is dependent on a combination of climatic,  geologic, and
 Leochemical factors. There is reason to believe that correlations of eU with actual soil
 fadTum 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.
           i
  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 shnnk-
  swell potential, vegetative cover, generalized groundwater characteristics, and landI 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, so 1
  maps were compared to geologic maps of the area, and the soil descriptions, :*™k-swell
  potential  drainage  characteristics, depth to seasonal high water table, permeability and other
          :characteristics of each soil group noted. Technical soil terms used m sod surveys are
          v complex- however, a good summary of soil engineering terms and the national
           onTftchnLl soil tyrfes is the "Soils" sheet of the National Atlas (U.S. Department
  of Agriculture, 1987).
                                              II-8     Reprinted from USGS Open-File Report 93-292

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

 INDOOR RADON DATA

      Two major sources of indoor radon data were used.  The first  and  largest source of data is
  from the State/EPA Residential Radon  Survey (Ronca-Battista and others, 1988; Dziuban and
  others, 1990). Forty-two  states completed EPA-sponsored indoor radon surveys between 1986
  and 1992 (fig. 3).  The State/EPA Residential  Radon Surveys were designed to be
  comprehensive and statistically significant at the state level,  and were subjected to high levels
  of quality assurance  and control.  The surveys collected screening  indoor radon measurements,
  defined as 2-7 day measurements using charcoal canister radon detectors placed in  the lowest
  livable area of the home.  The target population for the surveys included owner-occupied
  single family, detached housing units (White and others, 1989),  although attached structures
  such as duplexes, townhouses, or condominiums were included in  some of the surveys if they
  met  the other criteria and had contact with the ground surface.  Participants were selected
  randomly from telephone-directory listings. In total, approximately 60,000  homes were tested
  in the;State/EPA surveys.
      The second source of indoor radon data comes from residential surveys that have been
  conducted in a specific state or region of the country (e.g. independent state surveys or utility
  company surveys).  Several states, including Delaware, Florida, Illinois, New Hampshire, New
  Jersey,  New York, Oregon, and Utah, have conducted their  own surveys of indoor radon.  The
  quality  and design of a state or other independent survey are discussed and referenced  where
  the data are used.
                                             II-9     Reprinted from USGS Open-File Report 93-292

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    Data" for only those counties with five or more measurements are shown in the indoor
radon maps in the state chapters,  although data for all counties with a -nonzero number of
measurements are listed in the indoor radon data tables in each state chapter.  In total, indoor
radon data from more than 100,000 homes nationwide were used in the compilation of these
assessments.  Radon data from State or regional indoor radon surveys, public health
organizations,  or other sources are discussed in addition to the primary data sources where
they are available.  Nearly all of the data used in these evaluations represent short-term (2-7
day) screening measurements from the lowest livable space of the homes.  Specific details
concerning the nature and use of indoor radon data sets other than the State/EPA Residential
Radon Survey are discussed in the individual State chapters.

RADON INDEX AND  CONFIDENCE INDEX

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

                                          II-l 1     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.

FACTOR
S5SBSSSS5BS^S^aSS=5SS=5S
INDOOR RADON (average)

AERIAL RADIOACTIVITY
GEOLOGY*
SOIL PERMEABILITY
ARCHITECTURE TYPE
POINT VALUE
1
Sg^B jSgSSSBBSSSSBSBSBSS^™*^!!
<2pCi/L
< 1.5 ppm eU
negative

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
                      Point ranee
             LOW             /
             MODERATE/VARIABLE
             HIGH  -
                      3-8 points
                      9-11 points
                     12-17 points
     Probable average screening
      indoor radon for area
           <2pCi/L
           2-4pCi/L
           >4pCi/L
                       POSSIBLE RANGE OF POINTS = 3 to 17
         i

 TABLE 2.  CONFIDENCE INDEX MATRIX

FACTOR
INDOOR RADON DATA

AERIAL RADIOACTIVITY
GEOLOGIC DATA
SOIL PERMEABILITY

1
-•••-1 - -"-1 "' -*

questionable/no data
questionable
questionable/no data
POINT VALUE
2
fair coverage/quality

glacial cover
variable
variable
	 ^
3
good coverage/quality


proven geol. model
reliable, abundant
  SCORING:
LOW CONFIDENCE
MODERATE CONFIDENCE
HIGH CONFIDENCE
 4-6  points
 7-9  points
10 -12 points
                        POSSIBLE RANGE OF POINTS = 4 to 12
                                       II-12     Reprinted from USGS Open-File Report 93-292

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

                                            II-15    Reprinted from ,USGS Open-File Report 93-292

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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
-ortributions of the interrelated geologic factors influencing radon generation nd transport in
rocks and soils, and thus, of the  potential for elevated indoor radon levels to occur in a
particular area.  However, because these reports are somewhat generalized to cover relatively
large areas of States, it is highly recommended  that more detailed studies be performed in
local areas of interest, using the  methods and general information in these booklets as a guide.
                                           11-16    Reprinted from USGS Open-File Report 93-292

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                             .   REFERENCES CITED

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

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

Durrance, E.Mi, 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. HI: Preprints: U.S.
       Environmental Protection Agency report EPA/600/9-90/005c, Paper IV-2,17 p.

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

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

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

 Gundersen, Linda C.S., 1991, Radon in slieared metamorphic and igneous rocks, in Gundersen,
       Linda C.S., and Richard B. Wanty, eds., Field studies of radon in rocks, soils, and water:
       U.S. Geol. Survey Bulletin no. 1971, p. 39-50.
                                          JI-17     Reprinted from USGS Open-FUe 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, K., and Bell, C.,  1988, Use of airborne radiometric data to direct testing for elevated
       indoor radon: Northeastern Environmental Science, v. 7, no. 1, p. 45-51.

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

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

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

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

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

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

-------
Schumann, R.R., Owen, D.E., and Asher-BoHnder, 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. 6^-72.

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

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

Smith, R.C., H, Reilly, M.A., Rose, A.W., Barnes, J.H., and Berkheiser, S.W., Jr., 1987,
       Radon: a profound case: Pennsylvania Geology, v. 18,  p. 1-7.

Tanner, A.B., 1964, Radon migration in the ground: a review, in- Adams, J.A.S., and Lowder,
       W.M., eds., The natural radiation environment: Chicago, 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, 19,87, Principal kinds of soils: Orders, suborders, and great
       groups: U.S. Geological Survey, National Atlas of the United States of America, sheet
       38077-BE-NA-07M-00, scale 1:7,500,000.

U.S. Department of Energy, 1976, National Uranium Resource Evaluation preliminary report,
       prepared by the U.S. Energy Research and Development Administration, Grand Junction,
       Colo.: GJO-11(76).                                                             .

Wanty, Richard B., and Schoen, Robert, 1991, A review of the chemical processes affecting the
       mobility of radionuclides in natural waters, with applications, in Gundersen, Linda C.S.,
       and Richard B. Wanty, eds., Field studies of radon in rocks, soils, and water: U.S.
       Geological Survey Bulletin no. 1971, p. 183-194.

Washington, J.W., and Rose, A.W., 1990, Regional and temporal relations of radon in soil gas to
       soil temperature and moisture: Geophysical Research  Letters, v. 17, p.  829-832.

White, S.B., Bergsten, J.W., Alexander, B.V., and Ronca-Battista, M., 1989, Multi-State
       surveys of indoor 222Rn:  Health Physics, v. 57, p. 891-896.
                                          JJ-19     Reprinted from USGS Open-File Report 93-292

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                                           APPENDIX  A
                                   GEOLOGIC TIME SCALE
Subdivisions (and their symbols)
Eon or
Eonothem
Phanerozoic2
i
Proterozoic
(B)
Archean
(A)
Era or
Erathem
Cenoioic 2
(CD
Mesozoic2
(Mi)
Paleozoic
(Pi)

Miaoi*
£»rty

Middii
tiny
Period, System,
Subperiod. Subsystem
Quaternary
(Q)
Neoeene 2
SuSperiod or
Tr-T'-y Subsystem (N)
m Paleogene
11 Suboeriod or
Subsystem (Pi)
Cretaceous
(K)
Jurassic
(J)
Triassic
CR)
Permian
(P)
Pennsylvanian
Carboniferous 'P'
(C) Mississippian
/ (M)
Devonian
(D)
Silurian
(S)
Ordovician
(Q)
Cambrian
«C)
Epoch or Series
Holocene
Pleistocene
Age estimates
of boundaries
in mega-annum
(Ma)1

	 If. M fi-1 Q)
Pliocene |. E „««,,
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

None defined
None defined

	 24 (23-26)


	 66 (63-66)

	 138 (135-U1)

•
	 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?

           reflect
d.U
          of isoiopie and btostratigraphic age assignments. Age boundaries not closely bracketed by existing
           and isotopie ratios employed are cited in Steiger and Jager (1977). Designation m.y. used for an


r. middle, upper or early, middle, late), when used with these Hems are informal divisions of the larger unit; the

                           (p€). a time term without specific rank.
   'Informal time term without specific rank.
                                     USGS Open-File Report 93-292

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                                    APPENDIX  B
                               GLOSSARY OF TERMS
Units of measure
pCi/L (picocuries per liter)- a unit of measure of radioactivity used to describe radon
concentrations in a volume of air. One picocurie (10'12 curies) is equal to about 2.2 disintegrations
of radon atoms per minute. A liter is about 1.06 quarts. The average concentration of radon in
U.S. homes measured to date is between 1 and 2 pCi/L.

Bq/m3 (Becquerels per cubic meter)- a metric unit of radioactivity used to describe radon
concentrations in a volume of air. One becquerel is equal to one radioactive disintegration per
second. One pCi/L is equal to 37 Bq/m3.

ppm (parts per million)- a unit of measure of concentration by weight of an element in a
substance, in this case, soil or rock. One ppm of uranium contained in a ton of rock corresponds
to about 0.03 ounces of uranium.  The average concentration of uranium in soils in the United
States is between 1 and 2 ppm.

in/hr (inches per hour)- a unit of measure used by soil scientists and engineers to describe the
permeability of a soil to water flowing through it It is measured by digging a hole 1 foot (12
inches) square and one foot deep, filling it with water, and measuring the time it takes for the water
to drain from the hole. The drop in height of the water level in the hole, measured in inches, is
then divided by the time (in hours) to determine the permeability. Soils range in permeability from
less than 0.06 in/hr to greater than 20 in/hr, but most soils in the United States have permeabilities
between these two extremes.
Geologic terms and terms related to the study of radon

aerial radiometric, aeroradiometric survey A survey of radioactivity, usually gamma rays,
taken by an aircraft carrying a gamma-ray spectrometer pointed at the ground surface.

alluvial fan A low, widespread mass of loose rock and soil material, shaped like an open fan
and deposited by a stream at the point where it flows from a narrow mountain valley out onto a
plain or broader valley. May also form at the junction with larger streams or when the gradient of
the stream abruptly decreases.

alluvium, alluvial General terms referring to unconsolidated detrital material deposited by a
stream or other body of running water.

alpha-track detector A passive radon measurement device consisting of a plastic film that is
sensitive to alpha particles.  The film is etched with acid in a laboratory after it is exposed. The
etching reveals scratches, or "tracks", left by the alpha particles resulting from radon decay, which
can then be counted to calculate the radon concentration.  Useful for long-term (1-12 months)
radon tests.

amphibolite A mafic metamorphic rock consisting mainly of pyroxenes and(or) amphibole and
plagioclase.
                                          II-21     Reprinted from USGS Open-File Report 93-292

-------
• areillite; 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 (CO3) 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 smaU 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 dorninantly of interlocking crystals of
 quartz. Crystals are not visible to the naked eye, giving me rock a milky, dull luster. It may be
 white or gray but is commonly colored red, black, yellow, blue, pink, brown, or green.

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

 clay A rock containing clay mineral fragments or material of any composition having a diameter
 less than 1/256 mm.

 clay mineral One of a complex and loosely defined group of finely crystalline minerals made up
 of water, silicate and aluminum (and a wide variety of other elements). They are formed chiefly by
 alteration or weathering of primary silicate minerals. Certain clay minerals are noted for their small
  size and ability to absorb substantial amounts of water, causing them to swell. The change in size
 that occurs as these clays change between dry and wet is referred to as their shnnk-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 or
  the rocks forming the hill or ridge.

  daughter product  A nuclide formed by the disintegration of a radioactive precursor or "parent"
  atom.
                                            n-22     Reprinted from USGS Open-File 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 ofsediment deposited by a
 river-at the point at which the river loses its ability to transport the sediment, commonly where a
 riveAieets a larger body of water such as a lake or ocean.
 dike A tabular igneous intrusion of rock, younger than the surrounding rock, that commonly cuts
 across the bedding or foliation of the rock it intrudes.
 diorite  A plutonic igneous rock that is medium in color and contains visible dark muierals 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(C03)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 nvers, 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 Pr°ce^a^°cj£ers
  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
  rocL TechnicaUy, 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
                                             H-23     Reprinted from USGS Open-File Report 93-292

-------
•and may be referred to as a "placer deposit." Some heavy minerals are magnetite, garnet, zircon,
 monazite, and xenotime.

 igneous Said of a rock or mineral that solidified from molten or partly molten rock material. It is
 one of the three main classes into which rocks are divided, the others being sedimentary and
 metamorphic.

 intermontane  A term that refers to an area between two mountains or mountain ranges.

 intrusion, intrusive  The processes of emplacement or injection of molten rock into pre-existing
 rock. Also refers to the rock formed by intrusive processes, such as an "intrusive igneous rock".

 kame A low mound, knob, hummock, or short irregular ridge formed by a glacial stream at the
 margin of a melting glacier; composed of bedded sand and gravel.

 karst terrain A type of topography that is formed on limestone, gypsum and other rocks by
 dissolution of the rock by water, forming sinkholes and caves.

 lignite A brownish-black coal that is intermediate in coalification between peat and
 subbituminous coal.

 limestone A carbonate sedimentary rock consisting of more than 50% calcium carbonate,
 primarily in the form of the mineral calcite (CaCOs).

 lithology  The description of rocks in hand specimen and in outcrop on the basis of color,
 composition, and grain size.

 loam A permeable soil composed of a mixture of relatively equal parts clay, silt, and sand, and
 usually containing some organic matter.

 loess A fine-grained  eolian deposit composed of silt-sized particles generally thought to have
 been deposited from windblown dust of Pleistocene age.
          I
 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.


                                           E-24     Reprinted from USGS Open-File Report 93-292

-------
• physiographic province A region in which all parts are similar hi 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 (Uthification) of clay or mud.

 shear zone Refers to a roughly linear zone of rock that has been faulted by ductile or non-ductile
 processes in which the rock is sheared and both sides are displaced relative to one another.
          1
 shrink-swell  clay  See clay mineral.

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

 sinkhole A roughly circular depression in a karst area measuring meters to tens of meters in
 diameter. It is funnel  shaped and is formed by collapse of the surface material into an underlying
 void created by the dissolution of carbonate rock.

 slope  An inclined part of the earth's surface.

 solution cavity A hole, channel or cave-like cavity formed by dissolution of rock.

 stratigraphy The study of rock strata; also refers to the succession of rocks of a particular area.

 surficial materials Unconsolidated glacial, wind-, or waterborne deposits occurring on the
 earth's  surface.

 tablelands General term for a broad, elevated region with a nearly level surface of considerable
 extent.
                                            11-25     Reprinted from USGS Open-File Report 93-292

-------
terrace gravel  Gravel-sized material that caps ridges and terraces, left behind by a stream as it
cuts down to a lower level.
terrain A tract or region of the Earth's surface considered as a physical feature or an ecological
environment
till Unsorted, generally unconsolidated and unbedded rock and mineral material deposited directly
adjacent to and underneath a glacier, without reworking by melrwater.  Size of grains varies greatly
from clay to boulders.
uraniferous  Containing uranium, usually more than 2 ppm.
vendor data  Used in this report to refer to indoor radon data collected and measured by
commercial vendors of radon measurement devices and/or services.
volcanic Pertaining to the activities, structures, and extrusive rock types of a volcano.
water table The surface forming the boundary between the zone of saturation and the zone of
aeration; the top surface of a body of unconfined groundwater in rock or soil.
weathering The destructive process by which earth and rock materials, on exposure to
atmospheric elements, are changed in color, texture, composition, firmness, or form with little or
no transport of the material.
                                           11-26      Reprinted from USGS Open-File Report 93-292

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

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

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

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

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

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

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

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

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

EPA Region 10
1200 Sixth Avenue
Seattle, WA 98101
(202) 442-7660
Alabama	4
Alaska	10
Arizona	9
Arkansas	6
California	,	:....9
Colorado	:	'.	8
Connecticut	1
Delaware	....„ 3
District of  Columbia	3
Florida	4
Georgia	„•	4
Hawaii	9
Idaho	10
Illinois	5
Indiana	5
Iowa	7
Kansas	.•	7
Kentucky	4
Louisiana	6
Maine	1
Maryland	3
Massachusetts	1
Michigan	5
Minnesota	5
Mississippi	4
Missouri	'.	7
Montana	8
Nebraska	7
Nevada	9
New Hampshire	1
New  Jersey	2
New Mexico	6
NewYork	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
                                                 11-27      Reprinted from USGS Open-File 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

Alaska         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       Lee Gershner
               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 06106^474
            (203)566-3122

   Delaware Marai G. Rejai
            Office of Radiation Control
            Division of Public Health
            P.O. Box 637
            Dover, DE 19903
            (302) 736-3028
            1-800-554-4636 In State

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

     Florida N. Michael 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
            Richard Schreiber
            Georgia Department of Human
              Resources
            878 Peachtree St., Room 100
            Atlanta, GA 30309
            (404) 894-6644
             1-800-745-0037 in state
     Hawaii  Russell Takata
             Environmental Health Services
               Division
             591 Ala Moana Boulevard
             Honolulu, ffl 96813-2498
             (808) 586-4700
                                               H-28      Reprinted from USGS Open-File Report 93-292

-------
Idaho
Illinois
Indiana
Iowa
 Kansas
 Kentucky
PatMcGavarn
Office of Environmental Health
450 West State Street
Boise, ID 83720
(208) 334-6584
1-800-445-8647 in state
Richard 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, LA 50319-0075
(515) 281-3478
1-800-383-5992 In State

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

JeanaPhelps
Radiation Control Branch
Department of Health Services
Cabinet for Human Resources
275 East Main Street
Frankfort, KY 40601
 (502) 564-3700
   Louisiana  Matt Schlenker
              Louisiana Department of
               Environmental Quality
              P.O. Box 82135
              Baton Rouge, LA 70884-2135
              (504) 925-7042"
              1-800-256-2494 in state

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

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

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

    'Michigan  SueHendershott
              Division of Radiological Health
              Bureau of Environmental and
                Occupational Health
              3423 North Logan Street
              P.O. Box 30195
              Lansing, MI 48909
              (517) 335-8194

    Minnesota  Laura Oatmann
              Indoor Air Quality Unit
              925 Delaware Street, SE
              P.O. Box 59040
              Minneapolis, MN 55459-0040
              (612) 627-5480
              1-800-798-9050 in state
                                                 n-29      Reprinted from USGS Open-File Report 93-292

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

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

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

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

North Carolina Dr. Felix Fong
              Radiation Protection Division
              Department of Environmental Health
                and Natural Resources
              701 Barbour Drive
              Raleigh, NC 27603-2008
              (919) 571-4141
 •    •          1-800-662-7301 (recorded info x4196)

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

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

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•Oklahoma -      Gene Smith
                Radiation Protection Division
                Oklahoma State Department of
                 Health
                P.O. Box 53551
                Oklahoma City, OK 73152
                (405) 271-5221
 Oregon         George Toombs
                Department of Human Resources
                Health Division
                1400 SW 5th Avenue
                Portland, OR 97201
                (503)731-4014
 Pennsylvania    Michael Pyles
                Pennsylvania Department of
                  Environmental Resources
                Bureau of Radiation Protection
                P.O. Box 2063
                Harrisburg, PA 17120
                (717) 783-3594
                1-800-23-RADON In State

 Puerto Rico     David Saldana
                Radiological Health Division
                G.P.O. Call Box 70184 /
                Rio Piedras, Puerto Rico 00936
                (809) 767-3563
 Rhode Island    Edmund Arcand
                Division of Occupational Health and
                  Radiation
                Department of Health
                205 Cannon Building
                Davis Street
                Providence, RI02908
                (401) 277-2438
 South Carolina
                Bureau of Radiological Health
                Department of Health and
                  Environmental Control
                2600 Bull Street
                Columbia, SC 29201
                (803) 734^631
                1-800-768-0362
South Dakota MikePochop
             Division of-Environment Regulation
             Department of Water and Natural
               Resources
             Joe Foss Building, Room 217
             523 E. Capitol
             Pierre, SD 57501-3181
             .(605) 773-3351

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

       Texas Gary Smith
             Bureau of Radiation Control
             Texas Department of Health
             1100 West 49th Street
             Austin, TX 78756-3189
             (512) 834-6688
        Utah John Hultquist
             Bureau of Radiation Control
             Utah State Department of Health
             288 North, 1460 West
             P.O. Box 16690
             Salt Lake City, UT 84116-0690
             (801) 536-4250

    Vermont Paul demons
             Occupational and Radiological Health
               Division
             Vermont Department of Health
             10 Baldwin Street
             Montpelier, VT 05602
             (802) 828-2886
             1-800-640-0601 in state

Virgin Islands Contact the U.S. Environmental
             Protection Agency, Region II
             in New York
             (212)264-4110
                                                n-3i
       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   Beanie 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)267^796
                1-800-798-9050 in state

 Wyoming •     Janet Hough
           i     Wyoming Department of Health and
                  Social Services
                Hathway Building, 4th Floor
                Cheyenne, WY 82002-0710
                (307) 777-6015
                1-800-458-5847 in state
                                                 11-32      Reprinted from USGS Open-File Report 93-292

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                            STATE  GEOLOGICAL SURVEYS
                                            May, 1993
Alabama        Ernest A. Mancini
               Geological Survey of Alabama
               P.O. Box 0
               420 Hackberry Lane
               Tuscaloosa, AL 35486-9780
               (205) 349-2852

Alaska         Thomas E. Smith
               Alaska Division of Geological &
                 Geophysical Surveys
               794 University Ave., Suite 200
               Fairbanks, AK 99709-3645
               (907)479-7147

Arizona        Larry D. Fellows
               Arizona Geological Survey
               845 North Park Ave., Suite 100
               Tucson, AZ 85719
               (602) 882-4795
Arkansas       Norman F. Williams
               Arkansas Geological Commission
               Vardelle Parham Geology Center
               3815 West Roosevelt Rd.
               Little Rock, AR 72204
               (501) 324-9165

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

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

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

Delaware       Robert R. Jordan
               Delaware Geological Survey
               University of Delaware
                101  Penny Hall
               Newark, DE 19716-7501
               (302) 831-2833
Florida  Walter Schmidt
        Florida Geological Survey
        903 W. Tennessee St.
        Tallahassee, FL 32304-7700
        (904)488^191
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, JL 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
                                               H-33
   Reprinted from USGS Open-File Report 93-292

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• Kentucky "      Donald C. Haney
                Kentucky Geological Survey
                University of Kentucky
                228 Mining & Mineral Resources
                  Building
                Lexington, KY 40506-0107
                (606) 257-5500

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

 Mains          Walter A. Anderson
                Maine Geological Survey
                Department of Conservation
                State House, Station 22
                Augusta, ME 04333
                (207) 289-2801
 Mnryland       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.
                SL Paul, MN 55114-1057
                (612) 627-4780
 Mississippi      S. Cragin Knox
                 Mississippi Office of Geology
                 P.O. Box 20307
                 Jackson, MS 39289-1307
                 (601) 961-5500
      Missouri  James H. Williams
               Missouri Division of Geology &
                 Land Survey
               111 Fairgrounds Road
               P.O. Box 250
               Rolla, MO 65401
               (314) 368-2100

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

      Nebraska  Perry B. Wigley
               Nebraska Conservation &  Survey
                 Division
               113 Nebraska Hall
               University of Nebraska
               Lincoln, NE 68588-0517
               (402)472-2410
               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
                                                11-34      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) 224^109
Ohio           Thomas M. Berg
               Ohio DepL of Natural Resources
               Division of Geological Survey
               4383 Fountain Square Drive
               Columbus, OH 43224-1362
               (614) 265-6576

Oklahoma      Charles J. Mankin
               Oklahoma Geological Survey
               Room N-131, Energy Center
               lOOE.Boyd
               Norman, OK 73019-0628
               (405)3'25-3031

Oregon        Donald A. Hull
               DepL of Geology & Mineral Indust.
               Suite 965
               800 ME Oregon St. #28 /
               Portland, OR 97232-2162
               (503)73M600

Pennsylvania   Donald M. Hoskins
           '    Dept. of Environmental Resources
               Bureau of Topographic & Geologic
                  Survey
               P.O. Box 2357
               Harrisburg, PA 17105-2357
               (717) 787-2169

Puerto Rico    Ram6n M. Alonso
               Puerto Rico Geological Survey
                  Division
                Box 5887
                Puerta de Tierra Station
                San Juan, P.R. 00906
                (809) 722-2526

Rhode Island    J. Allan Cain
                Department of Geology
                University of Rhode Island
                315 Green Hall
                Kingston, RI02881
                (401)792-2265,
South Carolina Alan-Jon W.Zupan' (Acting)
              South Carolina Geological Survey
              5 Geology Road
              Columbia, SC 29210-9998
              (803) 7: '-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
               CharlottesviUe, 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
                                                n-35      Reprinted fiom 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
                                                 H-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, andR. Randall Schumann
                                 US. 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, housing construction, and other factors.
Areas in which the average screening indoor radon level of all homes within the area is estimated to
be greater than 4 pCi/L were ranked high. Areas in which the average screening indoor radon
level of all homes within the area is estimated to be between 2 and 4 pCi/L were ranked
moderate/variable, and areas in which the average screening indoor radon level of all homes within
the area is estimated to be less than 2 pCi/L were ranked low. Information on the data used and on
the radon potential ranking scheme is given in the introduction 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-File 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.
1-Jackson Purchase (Coastal Plain)  .
2-Western Coalfield
3-Mississippian Plateau
4-Eastern Pennyroyal
5-New Albany Shale
6-Outer Bluegrass
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-HighlandRim
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-Sanford-Durham sub-basins
 29-Raleigh Belt
 30-Eastern Slate Belt
                                               31-Inner Coastal Plain
                                               32-Outer Coastal Plain
                                               33-Jackson Prairies
                                               34-Loess Hills
                                               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-Inner Piedmont/Dadeville Complex
                                               47-Southem 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-Little 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
                                               60-Dade County anomalous area.
                                                  m-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
                                                               |   | LOW
                                                               E^l MODERATE/VARIABLE
                                                                   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 CaCO3 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 n..'    editions, 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
^e of locallymoderate to high (>4 pCi/L) indoor radon. Cullman ^^^^^
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


Va ^TheVafley 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
 than 4 pCi/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 sods 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.
               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 U3O8 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 e'J areas in L  - eastern 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 Dade 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 Kidge
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
 jifcse rocks have slow to moderate permeability, and iadoor radon vames are geneiolly 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 (eU) 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 ell 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 f ollowing 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 seveial 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 (22.8 pCi/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 CitroneUe 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 uraniurn,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 elJ 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 Yorlc 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-dominantiy 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.

 Coastal Plain                                                      .,,/-,           A
        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-nch, 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 eU, 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.

  Coastal Plain
         In the Coastal Plain Province, moderate to high radioactivity is associated with the
  Getaceous and Tertiary sediments of the upper Coastal Plain, Glaueonitic, 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


                                             m-14    Reprinted from USGS Open-File Report 93-292-D

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•radon. 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.
                                            ffl-15    Reprinted from USGS Open-File Report 93-292-D

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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 nv... of the \n  , *. 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.
                                            m-16    Reprinted from USGS Open-File Report 93-292-D

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    PRELIMINARY GEOLOGIC RADON POTENTIAL ASSESSMENT OF MISSISSIPPI
                                          by
                                 Linda C.S. Gundersen
                                 U.S. Geological Survey

INTRODUCTION

       Mississippi is among the states with the lowest average indoor radon levels in the United
States  Indoor radon measurements in 960 homes sampled in the State of Mississippi as part of the
State/EPA Residential Radon Survey have an average of 0.9 pCi/L.  Only a few geologic units
have high radioactivity and the potential to produce high radon. These include some of the
glaucomtic and phosphatic sediments of the Coastal Plain, particularly the Cretaceous and lower
Tertiary-age geologic units located in the northeastern portion of the State.  Further, the climate and
lifestyle of the inhabitants have influenced building construction styles and  building ventilation
which, in general, do not allow high levels of radon to accumulate.
       This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
deposits of Mississippi.  The scale of this assessment is such that it is inappropriate for use in
identifying the radon potential of small areas such as neighborhoods, individual building sites, or
housing tracts. Any localized assessment of radon potential must be supplemented with additional
data and information from the locality. Within any area of a given radon potential ranking, there
are likely to be areas with higher or lower radon levels than characterized for the area as a whole.
Indoor radon levels, both high  and low, can be quite localized, and there is no substitute for testing
individual homes. Elevated levels of indoor radon have been found in every state, and EPA
 recommends that all homes be tested. For more information on radon, the reader is urged to
 consult the local or State radon program or EPA regional office. More detailed information on stote
 or local  geology may be obtained from the state geological survey. Addresses and phone numbers
 for these agencies are listed in chapter 1 of this booklet

 PHYSIOGRAPHIC AND GEOGRAPHIC SETTING

        The physiography of Mississippi is in part a reflection of the underlying bedrock geology
 (fig. 1). Mississippi has two principal physiographic regions: the Gulf Coastal Plain and the
 Mississippi Alluvial Plain.                                           .
        The Gulf Coastal Plain can be divided into several distinct subprovmces (fig. 2).  Rugged
 forested uplands with local relief of 250 feet and a high point of 806 feet,  the highest point in ihe
  State make up the Tombigbee Hills.  The Black Prairie derives its name from the dark color of the
  soil; its grasslands are flat to gently rolling.  Pontotoc Ridge is the forested drainage divide
  between the Mississippi River basin and the Tennessee-Tombigbee basins. It reaches heights
  between 400 and 600 feet. The Flatwoods immediately west of Pontotoc  Ridge are generally flat
  lying and are covered by pasturelands and forest The North Central Hills is the most extensive
  upland in Mississippi, with elevations of 300 to 600 feet above sea level. It contains some of the
  most rugged terrain in  the Coastal Plain and is covered by forests and pasturelands. The Jackson
  Prairie is a narrow belt of flat to undulating grasslands and woodlands  that flanks the southern part
  of the North Central Hills. The Pine Hills region lies between 100 and 500 feet above sea level.
  Its surface is rolling hills with moderately high ridges; approximately 60 percent of the region is
  forested with pine and hardwood. The Coastal Meadows region marks the present coastal zone


                                             IV-1     Reprinted from USGS Open-File Report 93-292-D

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Figure 1.  Generalized geologic map of Mississippi (after Bicker, 1969).

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              GENERHLIZED GEOLOGIC MRP OF MISSISSIPPI EHPLRNRTION
      QUHTERNRRV
      Alluvium
      Coastal Deposits - Deltas of gravel, sand and clay.
      TERTIRRV


      Citronelle Formation - Gravelly sands at base overlain by clay and clayey sands.

      Pascagoula and Hattiesburg Formations - Clays, sandy clay, sand, siltstone, locally
      fossiliferous.
      Catahoula Formation - Bentonitic clay and noncalcareous sand with some tuff.

      Vicksburg Group and Chickasawhay Limestone - Argillaceous to arenaceous limestone,
      marl, clay and some sand.

      Forest Hill Formation and Red Bluff Clay - Glauconitic gray clay, marl and limestone which
      grades into thinly laminated, carbonaceous, silty clay, micaceous sand and some lignite.
Ill   Jackson Group - Glauconitic, calcareous, argillaceous sand arid marl, glauconitic, calcareous,
***^  micaceous sand clay, calcareous sand, glauconitic, argillaceous marl, gray, calcareous clay and
      chalky limestone.
      Cockfield Formation - Fine-medium grained lignitic clay, sand with some glauconite and
      carbonaceous clay.

      Cook Mountain Formation - Fossiliferous, glauconitic marl, limestone, glauconitic sand and
      sandy clay.


      Kosciusko Formation - Cross-bedded, fine-grained sand, clay and quartzite.


      Zilpha and Winona Formations - Carbonaceous clay and glauconitic sand.

      Tallahatta Formation and Neshoba Sand - Gray, siliceous sandy claystone and clay with
      micaceous sand that is glauconitic in places.

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Wilcox Formation - Micaceous, glauconitic, calcareous, silty marls and clays; glauconitic
sands and laminated marls, clays and silts; lignitic clay, lignite, glauconitic marls and some
bauxite-bearing sands.                  •

Naheola Formation - Carbonaceous, micaceous, silt, clay, sand and lignite, overlain by
glauconitic, micaceous, lignitic clay, silt and bauxitic clay.


Porters Creek Formation - Black, massive clay with minor glauconitic sand and marl.


Clayton Formation - Glauconitic sands at base and sandy clay with marl and limestone.
CRETRCEOUS


Prairie Bluff Chalk and Owl Creek Formation - Chalk with phosphatic fossil molds merging
into calcareous, glauconitic sand and clay of the Owl Creek formation.


Ripley Formation - Fine, glauconitic sand, clay, sandy limestone and micaceous chalk.


Demopolis Chalk - Chalk with lime and clay.


Mooreville Chalk - Thin interbedded chalk and chalky marl.


Coffee Sand - Glauconitic sand, sandy clay and calcareous sandstone.


Eutaw Formation - Laminated clay and glauconitic sand. Some thinly bedded sand and clay.


Tuscaloosa Formation - Marine-fluvial quartzose, chert gravels, quartz sand, silt and clay.
 DEUONIRN/MISSlSSIPPIflN
 Chester Group - Oolitic limestone, dark chert and laminated siltstone.
 Limestones, Chert and Shale - Limestones, shales, sandstones and cherts.

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                                                 COASTAL PINE MEADOWS
Figure 2. Physiographic areas of Mississippi (after Cross and others, 1974). .

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 and is relatively flat, with forest and pasturelands.  The Loess Hills region forms a ridge of
' forested hills with elevations greater than 300 feet along the edge of the Mississippi Alluvial Plain.
        Population distribution and land use in Mississippi reflect in part the geology, topography,
 and climate of the State. In 1990, the population of Mississippi was 2,573,216, including 47
 percent urban population (fig. 3). Average population density is approximately 55 persons per
 square mile  The climate of Mississippi is semi-tropical, with abundant rainfall and a long growing
 season promoted by moderate temperatures. Annual precipitation averages more than 50 inches
 and is shown in fig. 4 (Cross and others, 1974). Agricultural land use in the State of Mississippi
 includes production of cotton, soybeans, catfish, and rice.

 GEOLOGY AND SOILS

        The discussion in this section is based on Bicker (1969), Cross and others (1974), and
 Mancini and others (1989). Figure 1 is a generalized geologic map of Mississippi and figure 5
 shows the general soil areas in Mississippi. Comparison of geology with the physiographic
 province map and the general soils map demonstrates how much the underlying geology of
 Mississippi controls the soil types and topography seen at the surface.
        The oldest rocks in the State are Devonian and Mississippian in age, part of the Interior
 Plateaus Province, and crop out along the eastern margin of Tishomingo County in the Tombigbee
 Hills  They consist of the Chattanooga Shale and overlying limestones, shales, and cherts.  These
 rocks are in turn overlain by sandstone, shale, and limestone of the Chester Group.  Soils are clay
 to sand loams with moderate permeability.
         The Coastal Plain is underlain by marine and fluvial sediments from Cretaceous to Recent
 in age. The oldest formations of the Coastal Plain in Mississippi also form most of the Tombigbee
 Hills  They are the Cretaceous Tuscaloosa and Eutaw Formations and the Coffee Sand. The
 Tuscaloosa consists of fluvial sands and gravels with minor silt and clay. Soils are generally well-
 drained loamy sands with moderate to moderately rapid permeability.  The Eutaw formation
 consists of cross-bedded to thinly laminated glauconitic sand and clay, to thinly bedded fine sand
  and clay that is very glauconitic in places. The Tombigbee Sand Member, at the top of the
 formation, is a massive glauconitic sand. Soils are generally well-drained loamy sands with
  moderate permeability.  The Coffee Sand is a cross-bedded to massive glauconitic sand and sandy
  clay with some calcareous sandstones. Soils are generally loamy sands, well drained, with
  moderate to moderately rapid permeability.
         The Mooreville Chalk, in the Black Prairie province, consists of thin interbedded limestone
  and chalky marl. The chalk tends to form clay loams and silty clays that are slowly permeable.
  The Demopolis Chalk, consisting of marly chalk and clay, forms the black to dark brown clayey
  soils that give the Black Prairie its name. These soils have poor drainage, are subject to erosion,
  and are slowly permeable.
         Pontotoc Ridge and the Flatwoods are underlain by  the youngest Cretaceous and oldest
  Tertiary units  The Ripley Formation consists of sand, clay, chalk, and limestone that form
  Pontotoc Ridge. This unit is succeeded by the Prairie Bluff Chalk, Owl Creek Formation, and the
  Clayton Formation, which crop out in a thin band along the edge of the Flatwoods. The Prairie
  Bluff Chalk is a sandy chalk and calcareous clay with many phosphatic molds of fossils at the
  base. It merges into the calcareous glauconitic sand and clay of the Owl Creek Formation.  The
  Clayton Formation is a thin band of glauconitic sands, sandy clay, marl, and limestone.  Soils are
  clayey to sandy loams that are slowly to moderately permeable.


                                             W-6    Reprinted from USGS Open-File Report 93-292-D

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                                                   POPULATION (1990)

                                                  C3 0 to 10000
                                                  0 10001 to 25000
                                                  [22 25001 to 50000
                                                  H 50001 to 100000
                                                  • 100001 to 254441
Figure 3.  Population of counties in Mississippi (1990 U.S. Census data).

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      w
                 60
                                                                                        50"
Figure 4.  Average annual precipitation in Mississippi (after Cross and others, 1974, and Facts on
File, 1984).

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                                                                Generalized Soil Regions
         Delta:  sand, gravel, clay alluvium, seasonal saturation with water, slowly to moderately
         permeable                          .                 .

         Brown loam-thick loess:  fine silt, thick fragipan, subject to severe erosion, slowly permeable

         Thin loess: silty loam, slow permeability

         Upper coastal plain:  In the Tombigbee Hills: loamy sands, moderate to moderately rapid
         permeability;  clayey loam of slow permeability over chalk; In the North Central hills: sandy
         loams, clayey sands, clayey loams, moderately permeable

         Interior flatlands: clayey loam, clayey silt, poorly drained, slowly permeable

         Northern Blacklands: clay, silty clay, poor drainage, subject to erosion, slowly permeable

         Southern Blacklands: clayey loams, loamy clay, clayey sands, poor drainage, slowly
         permeable

         Lower coastal plain: sandy to clayey loams, loamy clay, clayey sands, poor drainage, slow
         permeability

         Coastal Flatwoods: loam, sand, well drained in places, moderately permeable
Figure 5. Generalized soil map of Mississippi (after Cross and others, 1974).

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       The Porters Creek and Naheola Formations underlie most of the Flatwoods and northern
edge of the North Central Hills. The Porters Creek Formation is a massive black clay with minor
glauconitic sand and marl.  The Naheola Formation is carbonaceous and micaceous silt, clay, sand
and lignite with glauconitic, bauxitic, and micaceous clay and silt.  Soils developed on these
formations are clayey loams and clayey silts that have poor drainage, are subject to erosion, and are
slowly permeable.
       The North Central Hills are underlain by Tertiary-age nonmarine to deltaic sediments
comprising a number of formations. The Wilcbx Formation underlies nearly half of this province.
It has highly variable lithology but generally consists of micaceous, glauconitic to calcareous sands
with silty marls and clays, lignitic clay, lignite, fossiliferous and glauconitic sands and marls,'and
some bauxitic clays. The soils formed on this unit are sandy loams, clayey sands, and clayey
loams with moderate permeability. The Tallahatta Formation forms the most rugged hills in the
province and consists of siliceous sandy claystone and clay with lenses of sand and sandstone,
micaceous sand and rare glauconite. The Neshoba Sand is included with the Tallahatta on the
geologic map and consists of coarse-grained, slightly glauconitic sand that forms sandy loams with
moderate to moderately rapid permeability.  Carbonaceous clay with some glauconitic sand make
up the Zilpha and Winona Formations. The soils have poor drainage and are slowly permeable.
The Kosciusko Formation is a thick, cross-bedded, fine grained sand with clay and some quartzite.
Soils are moderately permeable sandy loams.  This sand is followed by a thin band of outcrop of
the Cook Mountain Formation which consists of fossiliferous, glauconitic marl, limestone,
glauconitic sand, and carbonaceous clay. The Cockfield Formation is exposed along the southern
edge of the North Central Hills and consists of interbedded sand, lignitic clay, and lignite with rare
glauconite.
       The Jackson Prairies are underlain by the clays, sands, and marls  of the Jackson Group, as
well as the Forest Hill Formation, the Red Bluff Clay, the Chickasawhay Limestone, and the
Vicksburg Group.  The clays of the Jackson Group are massive, calcareous, sandy hi places, and
micaceous.  The sands are generally calcareous, glauconitic, and may be micaceous. The marls are
also glauconitic and argillaceous with some chalky .limestone. The Red Bluff Clay is glauconitic
clay and marl with some limestone, and the Forest Hill Formation is a sand with laminated fine
sand, carbonaceous clay, and some lignite.  This is overlain by the Vicksburg Group and
Chickasawhay Limestone, which are argillaceous  to arenaceous limestone, marl, and clay. Soils in
the Jackson Prairies are generally clayey loams, loamy clays, and clayey sands that are  slowly
permeable and poorly drained.
       The Pine Hills are underlain by the Catahoula, Hattiesburg, Pascagoula, and Citronelle
Formations.  The Catahoula is predominantly sand, sandstone, and bentonitic clay, with some
quartzite, gravel, and tuff. Locally fossiliferous clay, sandy clay, sand, and siltstone make up the
Hattiesburg and Pascagoula Formations, which tend to crop out in drainages in the southern part of
the Pine Hills. The Pleistocene-age Citronelle Formation, consisting of sand, gravel, and clay,
caps hill summits and the higher levels of the southern Pine Hills.  Soils in the Pine Hills are sandy
to clayey loams and sandy clays that are slowly to moderately permeable.
       The Coastal Meadows mark an area where the present shoreline of the Gulf of Mexico
meets land. The coastal deposits of this area consist of delta deposits of fine sands, silts, clays,
and gravel.  The soils are generally moderately well to poorly drained sandy and silty or clayey
loams with slow to moderate permeability.
                                           IV-10    Reprinted from USGS Open-File Report 93-292-D

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       The Mississippi Alluvial Plain consists of sand, gravel, and clay alluvial deposits of the
Mississippi River. They are subject to seasonal saturation with water. Soil permeability is
generally slow to moderate.
       Important areas of geology not shown on the general geologic map of Mississippi, but
which appear on the physiographic and soils maps, are the areas of thin and thick loess cover.
Loess is a windblown silt deposit. On the soils map, the loess has been divided into two distinct
units: the thin loess and the thick brown loess. The thin loess area is defined where the loess is
four feet or less in thickness and covers coastal plain deposits. It forms silty loam soils that are
slowly permeable. The thick brown loess area is defined where the loess deposits are more than
four feet thick.  The thick loess is very homogeneous and forms the Bluff Hills along the edge of
the Mississippi Alluvial Plain. Soils from the thick loess are fine silt, subject to severe erosion,
commonly have thick clay layers or fragipans that are slowly permeable. When loess soils are dry
and fractured they may have high vertical permeability.

RADIOACTIVITY

       An aeroradiometric map of Mississippi (fig. 6 ) was compiled from spectral gamma-ray
data acquired during the U.S. Department of Energy's National Uranium Resource Evaluation
(NURE) program (Duval and others, 1989). For the purposes of this report, low equivalent
uranium (eU) is defined as less than 1.5 parts per million (ppm), moderate eU is defined as
1.5-2.5 ppm, and high eU is defined as greater than 2.5 ppm. In figure 6, low eU is found in the
southeastern half of Mississippi associated with the upper Tertiary Coastal Plain sediments. These
are mostly sands and clays with some marls and limestone.  Moderate eU is associated with the
older Coastal Plain rocks and sediments, as well as the Mississippi Alluvial Plain and loess.  High
eU is associated with the upper Cretaceous, highly glauconitic and locally phosphatic chalks,
marls, and sands of the Mooreville Chalk, Coffee Sand, Demopolis Chalk, and the Ripley
Formation. This band of rocks is also highly radioactive in Alabama. A few small areas of high
eU occur .in the Mississippi Alluvial Plain near the river and do not appear to be correlative with
any particular geologic features. The NURE reports for the Greenwood and Jackson Quadrangles
(EG & G Geometries, 1980a, b) describe these anomalies as possibly cultural (associated with
pipelines, railroads, and cities). Further, heavy agricultural use of phosphatic fertilizers in the
Black Prairie and Mississippi Alluvial Plain may contribute significantly to the high radioactivity
seen in these areas.

INDOOR RADON

       Indoor radon data from 960 homes sampled in the State/EPA Residential Radon Survey
conducted in Mississippi during the winter of 1990-91 are shown in figure 7 and in Table 1. Data
are shown on figure 7 only for those counties with 5 or more data values.  A map of counties is
included for reference (fig. 8).  Of these data, 27 of the measurements were taken in basements.
The maximum value recorded in the survey was 22.8 pCi/L in Bolivar County.  The average for
the State was 0.9 pCi/L and 2.3 percent of the homes tested had indoor radon levels exceeding
4 pCi/L. Notable counties include Bolivar, Tishomingo, and Washington Counties, which have
maximum indoor radon levels greater than 10 pCi/L.  Overall, indoor radon levels in Mississippi
are among  the lowest of those in the. State/EPA Residential Radon Survey.
                                          IV-11   Reprinted from USGS Open-File Report 93-292-D

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Figure 6. Aerial radiometric map of Mississippi (after Duval and others, 1989). Contour lines at
    1.5 and 2.5 ppm equivalent uranium (eU). Pixels shaded at 0.5 ppm eU increments.

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                                                     Bsmt. & 1st Floor Rn
                                                        %>4pCi/L
                                            52 C
J
                                                        8 EH
                                                    20
OtolO
11 to 20
21 to 30
Missing Data
or < 5 measurements
                                                   100 Miles
                                                        Bsmt. & 1 st Floor Rn
                                                    Average Concenration (pCi/L)
                                           58 E

   0.0 to 1.9
   2.0 to 4.0
   4.1 to 6.0
   Missing Data
   or < 5 measurements
                                                    100 Miles
Figure 7.  Screening indoor radon data from the State/EPA Residential Radon Survey of
Mississippi, 1990-91, for counties with 5 or more measurements.  Data are from 2-7 day charcoal
canister tests.  Histograms in map legends show the.number of counties in each category. The
number of samples in each county (see Table 1) may not be sufficient to statistically characterize
the radon levels of the counties, but they do suggest general trends.  Unequal category intervals
were chosen to provide reference to decision and action levels.

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TABLE 1. Screening indoor radon data from the State/EPA Residential Radon Survey of
Mississippi, conducted during 1990-91. Data represent 2-7 day charcoal canister measurements
from the lowest level of each home tested.
COUNTY
ADAMS
ALCORN
AMITE
ATTALA
BENTON
BOLIVAR
CALHOUN
CARROLL
CfflCKASAW
CHOCTAW
CLAIBORNE
CLARKE
CLAY
COAHOMA
COPIAH
COVINGTON
DESOTO
FORREST
FRANKLIN
GEORGE
GREENE
GRENADA
HANCOCK
HARRISON
HINDS
HOLMES
HUMPHREYS
ISSAQUENA
ITAWAMBA
JACKSON
JASPER
JEFFERSON
JEFFERSON DAVIS
JONES
KEMPER
LAFAYETTE
LAMAR
LAUDERDALE
LAWRENCE
LEAKE
LEE
LEFLORE •
LINCOLN
NO. OF
MEAS.
12
47
4
5
7
12
3
5
1
5
3
7
5
10
6
7
21
38
1
11
9
10
9
47
62
4
31
1
26
40
8
4
3
19
2
11
18
14
3
9
70
10
6
MEAN
2.0
1.0
2.6
1.1
1.8
2.9
1.5
0.7
3.8
0.6
0.8
0.7
1.3
1.0
0.9
0.8
1.2
0.7
0.8
1.3
1.9
1.1
0.6
0.8
1.0
0.5
1.1
0.5
1.2
0.6
0.9
1.3
0.7
0.9
0.6
1.0
0.8
1.0
0.5
1.1
1.1
1.4
1.2
GEOM.
MEAN
1.1
0.8
1.3
0.8
1.2
1.1
1.0
0.7
3.8
0.5
0.7
0.6
0.9
0.7
0.8
0.7
0.9
0.6
0.8
1.0
/ 1.1
0.9
0.6
0.6
0.8
0.5
0.8
0.5
1.0
0.5
0.7
1.1
0.7
0.8
0.5
0.8
0.7
0.8
0.5
0.7
0.8
1.0
0.9
MEDIAN
0.7
0.5
0.9
0.5
0.9
0.7
0.6
0.5
3.8
0.5
0.5
0.5
0.5
0.5
0.7
0.7
0.6
' 0.5
0.8
0.6
0.5
0.8
0.5
0.5
0.6
0.5
0.5
0.5
0.9
0.5
0.5
1.1
0.6
0.5
0.6
0.8
0.5
0.6
0.5
0.5
0.5
1.0
0.7
STD.
DEV.
2.5
1.1
3.7
1.1
1.8
6.3
1.7
0.3
—
0.1
0.5
0.4
1.4
1.4
0.6
0.3
1.1
0.6
—
1.5
2.1
1.0
0.3
1.3
0.8
0.0
1.0
—
0.8
0.2
1.0
0.8
0.1
0.8
0.1
0.6
0.7
0.7
0.0
1.6
1.1
12
. i.o
MAXIMUM
7.3
6.8
8.1
3.0
4.6
22.8
3.5
1.3
3.8
0.8
1.3
1.6
3.8
4.9
2.0
1.4
5.0
3.5
0.8
4.6
5.8
3.7
1.4
8.0
4.5
0.5
3.6
0.5
2.7
1.2
3.4
2.3
0.8
3.7
0.6
2.2
3.2
2.7
0.5
5.4
5.3
4.0
3.1
%>4_pCi/L
17
4
25
0
29
8
0
0
0
0
0
0
0
10
0
0
5
0
0
9
22
0
0
4
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
11
3
. 10
0
%>20 pCi/L
0
0
0
0
0
8
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

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TABLE 1 .(continued). Screening indoor radon data for Mississippi.
LOWNDES
MADISON
MARION-
MARSHALL
MONROE
MONTGOMERY
NESHOBA
NEWTON
NOXUBEE
OKTIBBEHA
PANOLA
PEARL RIVER
PERRY
PIKE
PONTOTOC
PRENTISS
QUITMAN
RANKIN
SCOTT
SHARKEY
SIMPSON
SMITH
STONE
SUNFLOWER
TALLAHATCHE
TATE
TIPPAH
TISHOMINGO
TUNICA ,
UNION
WALTHALL
WARREN
WASHINGTON
WAYNE
WEBSTER
WILKINSON
WINSTON
YALOBUSHA
YAZOO
14
12
.

11
•;
2
'
2
18
8
13
8
9
9
26
c
25
4
23
5
7
12
6
3
5
15
25
3
14
5
15
71
8
5
3
7
6
8
1.2
0.6
1.9
0.5
0.6
0.5
0.6
2.2
2.0
1.6
1.3
0.8
0.8
1.1
2.0
0.9
0.5
0.7
0.6
1.3
0.5
1.3
1.2
0.7
0.7
1.3
0.8
1.6
0.7
1.5
1.0
1.6
1.2
1.3
1.2
0.6
0.6
1.1
1.2
1.0
0.6
0.9
0.5
0.6
0.5
0.6
1.5
1.3
1.2
0.9
0.7
0.7
0.9
1.0
0.8
0.5
0.6
0.6
1.0
0.5
0.9
O.S
0.7
/ 0.7
0.9
0.7
1.0
0.7
1.0
0.8
1.2
0.8
1.0
1.2
0.6
0.6
0.8
0.9
0.9
0.5
0.5
0.5
0.5
0.5
0.6
1.3
2.0
0.9
0.5
0.5
0.7
0.5
0.5
0.5
0.5
0.5
0.5
0.7
0.5
0.7
0.5
0.6
0.5
0.5
0.6
0.9
0.6
0.8
0.6
1.2
0.5
0.9
1.2
0.5
0.5
0.6
0.7
1.
0.2
3.
—
0.2
0.0
0.1
2.4
2.1
2.0
1.1
0.7
0.3
0.9
2.1
0.7
0.0
0.5
0.2
1.1
0.0
1.5
1.3
0.3
0.3
1.0
0.5
2.1
0.3
1.7
0.8
1.7
2.0
1.2
0,2
0.2
0.3
1.3
1.0
4.5
0.9
7.5
0.5
1.1
0.5
0.7
7.5
3.4
8.1
3.3
2.5
1.3
2.7
9.0
3.3
0.5
2.3
0.8
3.9
0.6
4.6
5.0
1.3
1.1
2.4
2.3
10.5
1.0
7.1
2.3
7.0
16.1
4.1
1.5
0.9
1.2
3.7
3.3
7
0
20
0
0
0
0
14
0
11
0
0
0
0
11
0
0
0
0
0
0
14
8
0
0
0
0
4
0
7
0
7
3
13
0
0
0
0
0
" 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0

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Figure 8.  Counties and county seats of Mississippi (from Facts on File, 1984).

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GEOLOGIC RADON POTENTIAL                                        .

       An examination of the aerial radioactivity map, state geologic map, and the indoor radon
map for Mississippi allows us to make some observations about the geologic, radon potential of the
State. Overall indoor radon levels are low; however, several counties had individual homes with
radon levels greater than 4 pCi/L (fig. 7).  Counties with maximum levels greater than 4 pCi/L are
concentrated in the northeastern part of the State on 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.

Coastal Plain
       A study of the radon in the Coastal Plain of Texas, Tennessee, and Alabama (Gundersen
and Peake, 1992) 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 soil-gas radon in that study indicate that the Upper
Cretaceous through Lower Tertiary Coastal Plain sediments are sources of high soil-gas radon
(> 1000 pCi/L) and uranium concentrations. The high equivalent uranium (fig. 6) found over the
Coastal Plain sediments in northeastern Mississippi supports the speculation that these deposits
may be 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 fractures and joints.
       The youngest Coastal Plain sediments, particularly Oligocene and younger, have
decreasing amounts of glauconite and phosphate and become increasingly siliceous and thus less
likely to  be significant sources of radon.  Some carbonaceous units may be possible sources of
high radon.
       In the above-mentioned study, loess in Tennessee was also examined, and high levels of
radon were extracted from both dry and saturated soils. On the radioactivity map of Mississippi
(fig. 6), the thin and thick loess units can  easily be traced 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 of locally high eU (fig 6), as well as
having moderate radioactivity overall. The high eU areas are located close to the river in Bolivar
and Washington Counties. The highest indoor radon level recorded in the State survey
(22.8 pCi/L) occurs in Bolivar County and the second highest indoor radon level 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 are correlative  and only a few homes in each county have indoor radon
levels greater than 4 pCi/L. The geology of the region is not indicative of high uranium
concentrations, except possibly in heavy-mineral placer deposits.  Further, radioactivity in the
Mississippi Alluvial Plain may in part be  due to uranium in phosphatic fertilizers.  Locally high
permeability in some of the alluvial sediments may be the source of high radon levels.
       The southeastern half of the State 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 (fig. 6), which are predominantly
quartz sands with little potential to generate elevated indoor radon levels.  Slightly higher  eU is
related to the Pascagoula and Hattiesburg Formations and Catahoula Formation, but is still low
                                           IV-17    Reprinted from USGS Open-File Report 93-292-D

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overall. Soils in this area are variably poorly to well drained, and have slow to moderate
permeability.
       The Chattanooga Shale and related sedimentary rocks in the northeastern part of the State
have the potential to generate 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 (Peake and Schumann, 1991). The extent of these rocks in Mississippi is minor.

SUMMARY

       For the purpose of this assessment, Mississippi has been divided into ten geologic radon
potential areas and each area assigned a Radon Index (RI) and a Confidence Index (CI) score
(Table 2). The RI is a relative measure of geologic radon potential based on geologic, soil,
radioactivity, architecture, and indoor radon data. The CI is a measure of the confidence of the RI
assessment based on the quality and quantity of the data used to assess geologic radon potential
(see the introduction chapter of this regional book for more information.)
       Examination of the available data reveals that Mississippi is generally an area of low
geologic radon potential.  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 elevated indoor radon levels. The Black Prairies
and Pontotoc Ridge have been assigned moderate geologic radon potential, based on radioactivity
and studies of radon in other parts of the Coastal Plain; all other parts of Mississippi are considered
to have low geologic radon potential.  Several areas of high equivalent uranium also occur in the
Mississippi Alluvial Plain near the river and may be associated with high indoor radon levels in
Bolivar and Washington Counties. 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 conpentrations-of radon to accumulate.
       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. For additional information on radon and
how to test, contact your State radon program or EPA regional office. More detailed information
on state or local geology may be obtained from the state geological survey. Addresses and phone
numbers for these agencies are listed in chapter 1 of this booklet.
                                           IV-18    Reprinted from USGS Open-File Report 93-292-D

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TABLE 2, RI and CI scores for geologic radon potential areas of Mississippi.
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
FACTOR
INDOOR RADON
RADIOACTIVITY
GEOLOGY
SOIL PERM.
ARCHITECTURE
GFE POINTS
TOTAL
Tombigbee
Hills
RI CI
1
2
2
2
1
0
8
1
3
2
2
8
LOW MOD
Flatwoods
RI CI
1
2
2
2
1
0
8
1
3
2
2
8
LOW MOD
Pine
Hills
RI CI
1
1
1
2
1
0
6
I '
3
3
10
Black
Prairies
RI CI
1
3
3
1
1
0
9
1
3
2
3
9
MOD MOD
North Central
Hills
RI CI
1
2
2
2
1
0
8
LOW
Coastal Pine
Meadows
RI CI
1 1
1 3
1 3
2 2
1
0
6 9
1
3
2
2
8
MOD


Pontotoc
Ridge
RI CI
1
3
2
2
1
0
9
1
3
2
2
8

MOD MOD
Jackson-
Prairies
RI CI
1
2
2
2
1
0
8
LOW
Loess
Hills
RI CI
1 1
2 3
2 2
1 3
j _
0
7 9
1
3
2
3
9

MOD
Mississippi
Alluvial Plain
RI CI
1
2
2
2
1
0
8
3
3
2
2
10
                  LOW  HIGH


RADON INDEX SCORING:

         Radon potential category
LOW MOD
LOW MOD
LOW HIGH
  Point range
 Probable screening indoor
   radon average for area
LOW
MODERATE/VARIABLE
HIGH
3-8 points
9-11 points
> 1 1 points
<2pCi/L
2 - 4 pCi/L
> 4 pCi/L
                          Possible range of points = 3 to 17

CONFIDENCE INDEX SCORING:
         LOW CONFIDENCE
         MODERATE CONFIDENCE
         HIGH CONFIDENCE
         4-6  points
         7-9  points
        10 - 12 points
                          Possible range of points = 4 to 12
                                      IV-19    Reprinted from USGS Open-File Report 93-292-D

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                        REFERENCES USED IN THIS REPORT         .
        " AND OTHER REFERENCES PERTAINING TO RADON IN MISSISSIPPI

Bicker, A.R., compiler, 1969, Geologic map of Mississippi: Mississippi Geological Survey, scale
       1:500,000.

Cross, R.D., Wales, R.W., and Traylor, C.T., 1974, Atlas of Mississippi: Jackson, Miss.,
      University of Mississippi Press, 187 p.

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.

EG&G Geometries, 1980a, Aerial gamma ray and magnetic survey, Greenwood quadrangle,
      Mississippi, Arkansas, and Louisiana: U.S. Department of Energy National Uranium
      Resources Evaluation Report GJBX-183(80).

EG&G Geometries, 1980b, Aerial gamma ray and magnetic survey, Jackson quadrangle,
      Mississippi and Louisiana:  U.S. Department of Energy National Uranium Resources
      Evaluation Report GJBX-153(80).

Facts on File Publications, 1984, State Maps on File: Southeast

Gundersen, L.C.S., Peake, R.T., Latzke, G.D., Hauser, L.M., and Wiggs, C.R., 1991, A
      statistical summary of uranium and radon in soils from the Coastal Plain of Texas,
      Alabama, and New Jersey, in The 1990  International Symposium on Radon and Radon
      Reduction Technology, Proceedings, Vol. 3: Symposium Poster Papers: Research
      Triangle Park, N.C., U.S. Environmental Protection Agency Rept. EPA600/9-91-026c,
      p. 6-35—6-47.

Gundersen, L.C.S., and Peake, R.T., 1992, Radon in the Coastal Plain of Texas, Alabama, and
      New Jersey, in Gates, A.E., and Gundersen, L.C.S., eds., Geologic controls on radon:
      Geological Society of America Special Paper 271, p. 53-64.

Mancini, E.A., Russell,  E.E., Dockery, D.T., Reinhardt, J., and Smith, C.C., 1989, Upper
      Cretaceous and Paleogene biostratigraphy and lithostratigraphy of the Eastern Gulf Coastal
      Plain:  28th International Geological Congress Field Trip Guidebook T372, American
      Geophysical Union, Washington, D.C., 122 p.

Peake, R.T., and Gundersen, L.C.S., 1989, The Coastal Plain of the eastern and southern United
      States—An area of low radon potential: Geological Society of America, Abstracts with
      Programs, v. 21, no. 2, p. 58.

Peake, R.T., and Schumann, R.R., 1991, Regional radon characterizations, in Gundersen,
      L.C.S., and Wanty, R.B., eds., Field Studies of Radon in Rocks, Soils, and Water: U.S.
      Geological Survey Bulletin 1971, p. 163-175.
                                        IV-20    Reprinted from USGS Open-File Report 93-292-D

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 Rose, A.W., 1981, Emanation of radon and other uranium daughters as a mechanism for
'       producing highly radiogenic leads in Mississippi Valley lead-zinc deposits:  Geological
       Society of America, Abstracts with Programs, V. 13, p. 540.

 Scott, M.R., Rotter, RJ,. and Salter, P.F., 1985, Transport of fallout plutonium to the ocean by
       the Mississippi River: Earth and Planetary Science Letters, v. 75, p. 321-326.

 Steele, S., 1979, Radon surveying; a technique for fault detection:  Geological Society of America,
       Abstracts with Programs, v. 11, p. 166-167.

 Steele, S., 1980, Anomalous radon emanation prior to Caruthersville, Missouri earthquake of June
       ' 10,  1979: Eos, American Geophysical Union, v. 61, p. 47.

 Steele, S.R., 1980, Exploratory radon survey of the northern Mississippi Embayment; indications
        of buried faults: Eos, American Geophysical Union, v. 61, p. 1194-1195  .

 Steele, S.R., Hood, W.C., and Sexton, J.L., 1982, Radon emanation in the New Madrid seismic
        zone, in McKeown F.A., and Pakiser, L.C., eds., Investigations of the New Madrid,
        Missouri, earthquake region:  U.S. Geological Survey Professional Paper  1236,
        p. 191-201.
                                           IV-21   Reprinted from USGS Open-File 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 to fit  a county
boundary map in order to produce the Map of Radon Zones.
       The Map of Radon Zones is based on the same range of predicted screening levels of
indoor radon as USGS1 Geologic Radon Province Map.  EPA defines the three zones as
follows:  Zone One areas have an average predicted indoor radon screening potential greater
than 4 pCi/L.  Zone Two areas are predicted to have an average indoor radon screening
potential between 2 pCi/L and 4 pCi/L.  Zone Three areas are predicted to have an average
indoor radon screening potential less than 2 pCi/L.
       Since the geologic province boundaries cross state and county boundaries, a strict
translation of counties from the Geologic Radon Province Map to the Map of Radon Zones
was not possible.  For counties that have variable radon potential (i.e., are located  in two or
more provinces of different rankings), the counties were assigned to a zone based on the
predicted radon potential of the province in which most of its area lies.  (See Part  I for more
details.)
MISSISSIPPI MAP OF RADON ZONES

       The Mississippi Map of Radon Zones and its supporting documentation (Part IV of
this report) have received extensive review by Mississippi geologists and radon program
experts.  The map for Mississippi  generally  reflects current State knowledge about radon for
its counties.  Some States have been able to conduct radon investigations in areas smaller than
geologic provinces and counties, so it is important to consult locally available data.
       Two county designations in Mississippi do not strictly follow the methodology for
adapting the geologic provinces to."county boundaries."  Although most of the area of
Pontotoc and Union counties is located in low radon potential areas, significant regions of
these counties have moderate radon potential areas and elevated radon measurements have
been recorded in these counties.  For this reason EPA and the Mississippi Department of
Health have designated these two  counties as Zone 2.
       Although the  information provided in Part IV of this report -- the State chapter entitled
"Preliminary Geologic Radon Potential Assessment of Mississippi" -- 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
Mississippi radon program for information on testing and fixing homes. Telephone numbers
and addresses can be found in Part II of this report.
                                          V-l

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 02
 
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