United Statas Air and Radiation 402-R-93-038
Environmental Protection (6604J) September 1993
Agency
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EPA S MAP OF RADON ZONES
LOUISIANA
RADON DIVISION
OFFICE OF RADIATION AND INDOOR AIR
U.S. ENVIRONMENTAL PROTECTION AGENCY
SEPTEMBER, 1993
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ACKNOWLEDGEMENTS
This document was prepared by the U.S. Environmental Protection Agency's (EPA's)
Office of Radiation and Indoor Air (ORIA) in conjunction with the U.S. Geological Survey
(USGS). Sharon W. White was the EPA project manager. Numerous other people in ORIA
were instrumental in the development of the Map of Radon Zones, including Lisa Rate I iff,
Kirk Maconaughey, R. Thomas Peake, Dave Rowson, and Steve Page
EPA would especially like I© acknowledge the outstanding effort of the USGS
radon team — Linda Gundersen, Randy Schumann, Jim Otton, Doug Owen, Russell
Dubiel, Kendeli 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
L OVERVIEW
II. THE USGS/EPA RADON POTENTIAL
ASSESSMENTS: INTRODUCTION
III. REGION 6 GEOLOGIC RADON POTENTIAL
SUMMARY
V. PRELIMINARY GEOLOGIC RADON POTENTIAL
ASSESSMENT OF LOUISIANA
V. EPA'S MAP OF RADON ZONES -- LOUISIANA
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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
(AASGl have worked closely over the past severa. years to produce a series of maps and
documents winch 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 1RAA. The Map of Radon
Zones identifies, on a county-by-county basis, areas of the U S thai have the highest potenti
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 (he zone designation of
the county in which they are located.
This document provides background information concern mi; 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 1 985, 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.
I-l
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MAP OF RADON ZONES
FACT SHEET
PURPOSE;
Sections 30? and 309 of' IRAA directed EPA to list and identit\ areas of the U S w ith the potential for elevated indoor
radon levels.
EPA's Map of Radon Zones assigns each of the 3141 counties in the United Stales to one of three zones based on radon
potential
Zone I counties have a predicted average indoor s -reenrog level greater than 4 pCt L tred)
Zone 2 counties have a predicted average screening level between 2 and 4 pCi/L (orange)
Zone 3 counties have a predicted average screening level less than 2 pCi L (yellow)
AUDIENCES:
• National, State and local governments and organizations -to assist in targeting their radon prognm activities and
resources.
• Building code officials
to help determine areas that are the highest priority for adopting radon-resistant building practices.
MAP DEVELOPMENT;
Five Factors were used to determine radon potential
indoor radon measurements, geok»g>. aerial radioactivity. soil permeability and foundation type.
• Radon potential assessment is based on geologic provinces
Radon Index Matrix is the quantitative assessment of radon potential
Confidence Index Matrix shows the quantity and quality of the data used to assess radon potential
• Geologic Provinces were adapted to county boundaries for the Map of Radon Zones.
MAP DOCUMENTATION:
• Detailed booklets are available for every State:
Booklets discuss the matrices and data used in every State.
• State booklets are an essential tool in employing the maps' information.
IMPORTANT POINTS;
• All homes should test for radon, regardless of geographic location or zone designation
• There are main- thousands of individual homes with elevated radon levels in Zones 2 and 3. Elevated levels can be
found in Zone 2 and 3 counties.
• All users of the map should carefully review the map documentation for information on within-county variations in
radon potential and supplement the map with locally available informatiw-before making any decisions.
• The map is not to be used in lieu of testing during real estate transactions.
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Figure 1
EPA Map of Radon Zones
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Figure 2
GENERALIZED GEOLOGIC RADON POTENTIAL OF THE UNITED STATES
by the U.S. Geological Survey
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Geologic Radon
Potential
{Predicted Average
Screening Measurement)
| I LOW (< 2 pCI/L)
r^J MODERATE/VARIABLE
(2 - 4 pCI/L)
HIGH (> 4 pCI/L)
6/93
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potential and some data are available for each of these factors in every geologic province. The
province boundaries do not coincide with political borders (county and state) bus 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 10 the county level so thai 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, il 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, wit tain-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.
1-5
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Figure 3
Figure 4
NEBRASKA
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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 Slates 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 pCt/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
1-7
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In addttion 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 resolv.e 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
bv
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 Ac! 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 arc not intended to he 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 Stale, and EPA recommends that all homes
he 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, soi!
characteristics, climatic factors, homeowner lifestyles, and other factors that influence radon
concentrations can be quite large within any particular geologic area, so these reports cannot
be used to estimate or predict the indoor radon concentrations of individual homes or housing
II-1 Reprinted from USGS Open-File Report 93-292
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tracts. Within any 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,
especialiy 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
stale, and the reader ts urged to consult these repels for more detailed information. In most
cases the best sources of information on radon for specific areas are state and local
departments of health, state departments responsible for nuclear safety or environmental
protection, and U.S. EPA regional offices, More detailed information on state or local
geology may be obtained from the state geological surveys Addresses and telephone
numbers of state radon contacts, geological surveys, and EPA regional offices are listed in
Appendix C at the end of this chapter.
RADON GENERATION AND TRANSPORT IN SOILS
Radon (:::Rn) is produced from the radioactive decay of radium (::6Ra). which is, in turn,
a product of the decay of uranium (-"'U) (fig I) The half-life of ":Rn is 3.825 days Other
isotopes of radon occur naturally, but, with the exception of thoron 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
ciays, 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
11-2 Reprinted from USGS Open-File Report 93-292
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Uranlum-238
1.17 mln.
Rsdlum-226 fa
1602 years
21 mln.
18.7 mln.
Lead-210
19.4 years
STABLE
Figure I. The uranium-238 decay series, showing the half-lives of elements and their modes of decay (after Wanty and
Schoen, 1991), a denotes alpha decay, (1 denotes beta decay.
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and moisture infiltration rates and depth of wetting may be limited when the cracks in the
surface soil layers swell shut. Clay-rich B horizons, particularly those with massive or platv
structure, can form a capping layer that impedes the escape of soil gas to the surface
(Schumann and others, 1992) However, the shrinkage of clays can act to open or widen
cracks upon drying, thus increasing the soil's permeability to gas flow during drier periods.
Radon transport in soils occurs by two processes: (1) diffusion and (2) flow (Tanner,
1964). Diffusion is the process whereby radon atoms move from areas of higher
concentration to areas of lower concentration in response to a concentration gradient Flow is
the process by which soil air moves through soil pores in response to differences in pressure
within the soil or between the soil and the atmosphere, carrying the radon atoms along with it.
Diffusion is the dominant radon transport process in soils of low permeability, whereas flow
tends to dominate in highly permeable soils (Sextro and others, 198?). 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; Kurtz 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 gram 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 2x 10* inches—this is known as alpha
recoil (Tanner, 1980) Moisture in the soil lessens the chance of a recoiling radon atom
becoming imbedded in an adjacent grain Because water is more dense than air. a radon atom
will travel a shorter distance in a water-filled pore than in an air-filled pore, thus increasing
the likelihood that the radon atom will remain in the pore space. Intermediate moisture levels
enhance radon emanation but do not significantly affect permeability. However, high
moisture levels can significantly decrease the gas permeability of the soil and impede radon
movement through the soil.
Concentrations of radon in soils are generally many times higher than those inside of
buildings, ranging from tens of pCi/L to more than 100,000 pCi/L, but typically in the range
of hundreds to low thousands of pCi/L Soil-gas radon concentrations can vary in response to
variations in climate and weather on hourly, daily, or seasonal time scales. Schumann and
others (1992) and Rose and others (1988) recorded order-of-magnitude variations in soil-gas
radon concentrations between seasons in Colorado and Pennsylvania. The most important
factors appear to be (1) soil moisture conditions, which are controlled in large part by
precipitation; (2) barometric pressure; and (3) temperature. Washington and Rose (1990)
suggest that temperature-controlled partitioning of radon between water and gas in soil pores
also has a significant influence on the amount of mobile radon in soil gas.
Homes in hilly limestone regions of the southern Appalachians were found to have higher
indoor radon concentrations during the summer than in the winter. A suggested cause for this
phenomenon involves temperature/pressure-driven flow of radon-laden air from subsurface
II-4 Reprinted from USGS Open-File Report 93-292
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solution cavities in the carbonate rock into houses. As warm air enters solution cavities that
are higher on the hillslope than the homes, it cools and settles, pushing radon-laden air from
lower in the cave or cavity system into structures on the hillslope (Gammage and others.
1993) In contrast, homes built over caves having openings situated below the level of the
home had higher indoor radon levels in the wintei, 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 siab-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 "n on basement" 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: (I) 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 sot I-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-nch volcanic rocks, many
sheared or faulted rocks, some coals, and certain kinds of contact metamorphosed rocks
Rock types least likely to cause radon problems include marine quartz sands, non-
carbonaceous shales and siltstones, certain kinds of clays, silica-poor metamorphic and
II-5 Reprinted from USGS Open-File Report 93-292
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igneous rocks, and basalts. Exceptions exist within these general liihologic groups because of
the occurrence of localized uranium deposits, commonly of the hvdroibermal 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 grams, 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 (Deffeves and
MacGregor, 1980) and have been associated with some of the highest reported indoor radon
levels (Gundersen, 1991) The two highest known indoor radon occurrences are associated
with sheared fault zones in Boyertown, Pennsylvania (Gundersen and others, 1988a, Smith
and others, 1987), and in Clinton, New Jersey (Henry and others, 1991, Muessig and Bell,
1988).
NURE Aerial Radiometric Data
Aerial radiometric data are used to quantify the radioactivity of rocks and soils.
Equivalent uranium (eU) data provide an estimate of the surficial concentrations of radon
parent materials (uranium, radium) in rocks and soils. Equivalent uranium is calculated from
the counts received by a gamma-ray detector from the 1.76 MeV (mega-electron volts)
emission energy corresponding to bismuth-214 (;"Bi), with the assumption that uranium and
its decay products are in secular equilibrium Equivalent uranium is expressed in units of
parts per million (ppm) Gamma radioactivity also may be expressed in terms of a radium
activity; 3 ppm eU corresponds to approximately 1 picocurie per gram (pCi/g) of radium-226
Although radon is highly mobile in soil and its concentration is affected by meteorological
conditions (Kovach, 1945; Klusman arid Jaacks, 1987; Schery and others, 1984; Schumann
and others, 1992). statistical correlations between average soit-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 lo 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
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F LI CUT LIKE SPACING Of SOKE AEKIAl SURVEYS
m l U {1 MILE}
¦ i n (3 HUES)
m Z k $ K M
EE 10 EV (6 HUES)
M 5 k 10 IS
¦i NO DIT A
Figure 2, Nominal flightline spacings for NURE aerial gamma-ray surveys covering the
contiguous United States (from Duval and others, 1990). Rectangles represent l°x2° quadrangles.
-------
Figure 2 is an index map of NURE r x 2° quadrangles showing the flight-line spacing
for each quadrangle. In general, the more closely spaced the fhghtlines are, the more area
was covered by the aerial gamma survey, and thus, more detail is available in the data set.
For an altitude of 400 ft above the ground surface and with primary flightline spacing
typically between 3 and 6 miles, less than 10 percent of the ground surface of the United
Slates was actually measured by the airborne gamma-ray detectors (Duval and others, 1989),
although some areas had better coverage than others due to the differences in flight-line
spacing between areas (fig. 2) This suggests that some localized uranium anomalies may not
have been detected by the aerial surveys, but the good correlations of eU patterns with
geologic outcrop patterns indicate that, at relatively small scales (approximately 1 1,000.000
or smaller) the National eU map (Duval and others, 1989) gives reasonably good estimates of
average surface uranium concentrations and thus can assist in the prediction of radon potential
of rocks and soils, especially when augmented with additional geologic and soil data.
The shallow (20-30 cm) depth of investigation of gamma-ray spectrometers, either
ground-based or airborne (Duval and others, 1971; Durrance, 1986), suggests that gamma-ray
data may sometimes underestimate the radon-source strength in soils in which some of the
radionuclides in the near-surface soil layers have been transported downward through the soil
profile. In such cases the concentration of radioactive minerals in the A horizon would be
lower than in the B horizon, where such minerals are typically concentrated. The
concentration of radionuclides m the C horizon and below may be relatively unaffected by
surface solution processes. Under these conditions the surface gamma-ray signal may indicate
a lower radon source concentration than actually exists in the deeper soil layers, which are
most likely to affect radon levels in structures with basements. The redistribution of
radionuclides in soil profiles is dependent on a combination of climatic, geologic, and
geochemical factors. There is reason to believe that correlations of eU with actual soil
radium and uranium concentrations at a depth relevant to radon entry into structures may be
regionally variable (Duval, 1989, Schumann and Gundersen, 1991). Given sufficient
understanding of the factors cited above, these regional differences may be predictable
Soil Survey Data
Soil surveys prepared by the U.S. Soil Conservation Service (SCS) provide data on soil
characteristics, including soil-cover thickness, grain-size distribution, permeability, shrink-
swell potential, vegetative cover, generalized groundwater characteristics, and land use. The
reports are available in county formats and State summaries. The county reports typically
contain both generalized and detailed maps of soils in the area
Because of time and map-scale constraints, it was impractical to examine county soil
reports for each county m the United States, so more generalized summaries at appropriate
scales were used where available. For State or regional-scale radon characterizations, soil
maps were compared to geologic maps of the area, and the soil descriptions, shrink-swell
potential, drainage characteristics, depth to seasonal high water table, permeability, and other
relevant characteristics of each soil group noted. Technical soil terms used in soil surveys are
generally complex; however, a good summary of soil engineering terms and the national
distribution of technical soil types is the "Soils" sheet of the National Atlas (U.S. Department
of Agriculture, 1987).
11-8
Reprinted from USGS Open-File Report 93-292
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Soil permeability ts commonly expressed in SCS soil surveys in terms of the speed, in
inches per hour (ln/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 >vell with gas permeability Because data
on gas permeability of soils is extremely limited, data on permeability to water ts 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.
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STATE/EPA RESIDENTIAL RADON
SURVF.Y SCRFPNINr. MRACI IRnMPNTS
//X/A
' a
X \...l
Eslimaicd Percent of Houses will) Screening Levels Greater ihati 4 pCi/L
0
20 and >
IV SUtasot IMU1-N1t.NI .NY. »
-------
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 polentia! 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
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TABLE 1. RADON INDEX MATRIX, "ppm eU" indicates parts per million of equivalent
uranium, as indicated by MURE aerial radiometric data. See text discussion for details.
INCREASING RADON POTENTIAL ^
FACTOR
POINT VALUE
I
2
3
INDOOR RADON (average)
<2 pCi/L
2-4 pCi/L
> 4 pCi/L
AERIAL RADIOACTIVITY
< 1.5 ppm eU
1.5 - 2.5 ppm eU
> 2.5 ppm eU
GEOLOGY*
negative
variable
positive
SOIL PERMEABILITY
low
moderate
high
ARCHITECTURE TYPE
mostly slab
mixed
mostly basement
^GEOLOGIC FIELD EVIDENCE (GFE) POINTS: GFE points are assigned in addition to points
for the "Geology" factor for spetific, relevant geologic field studies. See text fox details.
Geologic evidence supporting: HIGH radon +2 points
MODERATE +1 point
LOW -2 points
No relevant geologic field studies 0 points
SCORING:
KadonjaasimaLaiasfitt-
LOW 3-8 points
MODERATE/VARIABLE 9-11 points
HIGH 12-17 points
POSSIBLE RANGE OF POINTS = 3 to 17
Probable average screening
Point range indoor radon for area
< 2 pCi/L
2-4 pCi/L
>4 pCi/L
TABLE 2. CONFIDENCE INDEX MATRIX
INCREASING CONFIDENCE
FACTOR
POINT VALUE
I
2
3
INDOOR RADON DATA
sparse/no data
fair coverage/quality
good coverage/quality
AERIAL RADIOACTIVITY
questionable/no data
glacial cover
no glacial cover
GEOLOGIC DATA
questionable
variable
proven geol. model
SOIL PERMEABILITY
questionable/no data
variable
reliable, abundant
SCORING; LOW CONFIDENCE 4-6 points
MODERATE CONFIDENCE 7-9 points
HIGH CONFIDENCE 10-12 points
POSSIBLE RANGE OF POINTS = 4 to 12
II-12 Reprinted from USGS Open-File Report 93-292
-------
included as supplementary information and are discussed in the individual State chapters If
the average screening indoor radon level for an area was less than 2 pCi/L, the indoor radon
factor was assigned I 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 NURJE 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 fails 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-nch 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
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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 RJ scores for the 5
factors, plus or minus GFE points, if any The total RJ for an area falls in one of three
categories—low, moderate or variable, or high The point ranges for the three categories were
determined by examining the possible combinations of points for the 5 factors and setting
rules such that a majority (3 of 5 factors) would determine the final score for the low and
high categories, with allowances for possible deviation from an ideal score by the other two
factors. The moderate/variable category lies between these two ranges. A total deviation of 3
points from the "ideal" score was considered reasonable to allow for natural variability of
factors—if two of the five factors are allowed to vary from the "ideal" for a category, they
can differ by a minimum of 2 (1 point different each) and a maximum of 4 points (2 points
different each). With "ideal" scores of 5, 10, and 15 points describing low, moderate, and
high geologic radon potential, respectively, an ideal low score of 5 points plus 3 points for
possible variability allows a maximum of 8 points in the low category. Similarly, an ideal
high score of 15 points minus 3 points gives a minimum of 12 points for the high category
Note, however, that if both other factors differ by two points from the "ideal", indicating
considerable variability in the system, the total point score would lie in the adjacent (i e.,
moderate/variable) category.
Confidence Index. Except for architecture type, the same factors were used to establish a
Confidence Index (CI) for the radon potential prediction for each area (Table 2). Architecture
type was not included in the confidence index because house construction data are readily and
reliably available through surveys taken by agencies and industry groups including the
National Association of Home Builders, U.S. Department of Housing and Urban
Development, and the Federal Housing Administration, thus it was not considered necessary
11-14 Reprinted from USGS Open-File Report 93-292
-------
to question the quality or validity of these data, The other factors were scored on the basis of
the quality and quantity of the data used to complete the RI matrix.
Indoor radon data were evaluated based on the distribution and number of data points and
on whether the data were collected by random samplme (Siate/EPA Residential Radon Survey
or other state survey data) or volunteered vendor data (likely to be nonrandom and biased
toward population centers and/or high indoor radon levels). The categories listed in the CI
matrix for indoor radon data ("sparse or no data", "fair coverage or quality", and "good
coverage/quality") indicate the sampling density and statistical robustness of an indoor radon
data set. Data from the State/EPA Residential Radon Survey and statistically valid state
surveys were typically assigned 3 Confidence Index points unless the data were poorly
distributed or absent in the area evaluated.
Aerial radioactivity data are available for all but a few areas of the continental United
States and for part of Alaska. An evaluation of the quality of the radioactivity data was based
on whether there appeared to be a good correlation between the radioactivity and the actual
amount of uranium or radium available to generate mobile radon in the rocks and soils of the
area evaluated In general, the greatest problems with correlations among eU, geology, and
soil-gas or indoor radon levels were associated with glacial deposits (see the discussion in a
previous section) and typically were assigned a 2-point Confidence Index score Correlations
among eU, geology, and radon were generally sound in unglaciated areas and were usually
assigned 3 CI points Again, however, radioactivity data in some unglaciated areas may have
been assigned fewer than 3 points, and in glaciated areas may be assigned only one point, if
the data were considered questionable or if coverage was poor
To assign Confidence Index scores for the geologic data factor, rock types and geologic
settings for which a physical-chemical, process-based understanding of radon generation and
mobility exists were regarded as having "proven geologic models" (3 points); a high
confidence could be held for predictions in such areas. Rocks for which the processes are
less well known or for which data are contradictory were regarded as "variable" (2 points),
and those about which little is known or for which no apparent correlations have been found
were deemed "questionable" (1 point)
The soil permeability factor was also scored based on quality and amount of data. The
three categories for soil permeability in the Confidence Index are similar in concept, and
scored similarly, to those for the geologic data factor Soil permeability can be roughly
estimated from grain size and drainage class if data from standard, accepted soil percolation
tests are unavailable; however, the reliability of the data would be lower than if percolation
test figures or other measured permeability data are available, because an estimate of this type
does not encompass all the factors that affect soil permeability and thus may be inaccurate in
some instances. Most published soil permeability data are for water, although this is
generally closely related to the air permeability of the soil, there are some instances when it
may provide an incorrect estimate Examples of areas in which water permeability data may
not accurately reflect air permeability include areas with consistently high levels of soil
moisture, or clay-rich soils, which would have a low water permeability but may have a
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significantly higher air permeability when dry due to shrinkage cracks in the soil. These
additional factors were applied to the soil permeability factor when assigning the RI score, but
may have less certainty in some cases and thus would be assigned a lower CI score.
The Radon Index and Confidence Index give a general indication of the relative
contributions of the interrelated geologic factors influencing radon generation and transport in
rocks and soils, and thus, of the potential for elevated indoor radon levels to occur in a
particular area. However, because these reports are somewhat generalized to cover relatively
large areas of States, it is highly recommended that more detailed studies be performed in
local areas of interest, using the methods and general information in these booklets as a guide.
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REFERENCES CITED
Akerblom, G., Anderson, P., and Clavensjo, B., 1984, Soil gas radon-A source for indoor radon
daughters: Radiation Protection Dosimetry, v. 7, p. 49-54.
Deffeyes, K.S., and MacGregor, I.D., 1980, World uranium resources: Scientific American,
v. 242, p. 66-76,
Durrance, E.M., 1986, Radioactivity in geology: Principles and applications: New York, N.Y.,
Wiley and Sons, 441 p.
Duval, J.S., 1989, Radioactivity and some of its applications in geology: Proceedings of the
symposium on the application of geophysics to engineering and environmental problems
(SAGEEP), Golden, Colorado, March 13-16,1989: Society of Engineering and Mineral
Exploration Geophysicists, p. 1-61.
Duval, J.S., Cook, B.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, WJ.» 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. Ill: Preprints: U.S.
Environmental Protection Agency report EPA/600/9-90/Q05c, 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 tenants; Atmospheric Environment
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Gundcrsen, L.C.S., Reimer, G.M., and Agard, S.S., 1988a, Correlation between geology, radon
in soil gas, and indoor radon in the Reading Prong, in Marikos, M.A., and Hansman,
R.H., eds.. Geologic causes of natural radionuclide anomalies: Missouri Department of
Natural Resources Special Publication 4, p. 91-102.
Gundersen, L.C.S, Reimer, G.M., Wiggs, C.R., and Rice, C.A., 1988b, Map showing radon
potential of rocks and soils in Montgomery County, Maryland: U.S. Geological Survey
Miscellaneous Field Studies Map MF-2043, scale 1:62,500.
Gundersen, Linda C.S., 1991, Radon in sheared metamorphic and igneous rocks, in Gundcrsen,
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.
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Henry, Mitchell E., Kaeding, Margret E., and Monteverde, Donald, 1991, Radon in soil gas and
gamma-ray activity of rocks and soils at the Mulligan Quarry, Clinton, New Jersey, in
Gundersen, Linda C.S., and Richard B. Wanty, eds., Field studies of radon in rocks,
soils, and water: U.S. Geol. Survey Bulletin no 1971, p. 65-75.
Klusman, R. W., and Jaacks, J. A., 1987, Environmental influences upon mercury, radon, and
helium concentrations in soil gases at a site near Denver, Colorado: Journal of
Geochemical Exploration, v. 27, p. 259-280.
Kovach, E.M., 1945, Meteorological influences upon the radon content of soil gas: Transactions,
American Geophysical Union, v. 26, p. 241-248.
Kunz, C., Laymon, C.A., and Parker, C., 1989, Gravelly soils and indoor radon, in Osborne,
M.C., and Harrison, J., eds., Proceedings of the 1988 EPA Symposium on Radon and
Radon Reduction Technology, Volume 1: U.S. Environmental Protection Agency Report
EPA/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 m radon emanation
coefficients in soils: Geological Society of America Abstracts With Programs, v. 23,
no. 1, p. 125.
Schumann, R.R., Peake, R.T., Schmidt, K.M., and Owen, D.E., 1991, Correlations of soil-gas
and indoor radon with geology in glacially derived soils of the northern Great Plains, in
Proceedings of the 1990 International Symposium on Radon and Radon Reduction
Technology, Volume 2, Symposium Oral Papers: U.S. Environmental Protection Agency
report EPA/600/9-9l/026b, p. 6-23-6-36.
n-18 Reprinted from USGS Open-File Report 93-292
-------
Schumann, R.R., Owen, D.E., and Asher-Bolinder, S., 1992, Effects of weather and soil
characteristics on temporal variations in soil-gas radon concentrations, in Gates, A.E., and
Gundersen, L.C.S., eds., Geologic controls on radon: Geological Society of America
Special Paper 271, p. 65-72.
Sextro, R.G., Moed, B.A., Nazaroff, W.W., Revzan, K.L., and Nero, A.V., 1987,
Investigations of soil as a source of indoor radon, in Hopke, P.K., ed., Radon and its
decay products: American Chemical Society Symposium Series 331, p. 10-29.
Sterling, R„ Meixel, G„ Shen, L., Labs, K., and Bligh, T., 1985, Assessment of the energy
savings potential of building foundations research: Oak Ridge, Terau U.S. Department of
Energy Report ORNL/SUB/84-0024/1.
Smith. R.C., II, Reilly, M.A., Rose, A.W., Barnes, J.H., and Berkheiser, S.W., Jr., 1987,
Radon: a profound case: Pennsylvania Geology, v. 18, p. 1-7.
Tanner, A.B., 1964, Radon migration in the ground: a review, in Adams, J.A.S., and Lowder,
W.M., eds., The natural radiation environment: Chicago, HI., University of Chicago
Press, p. 161-190.
Tanner, A.B., 1980, Radon migration in the ground: a supplementary review, in Gesell, T.F.,
and Lowder, W.M. (eds), Natural radiation environment HI, Symposium proceedings,
Houston, Texas, v. 1, p. 5-56.
U.S. Department of Agriculture, 1987, Principal kinds of soils: Orders, suborders, and great
groups: U.S. Geological Survey, National Atlas of the United States of America, sheet
38077-BE-NA-07M-00, scale 1:7,500,000.
U.S. Department of Energy, 1976, National Uranium Resource Evaluation preliminary report,
prepared by the U.S. Energy Research and Development Administration, Grand Junction,
Colo.: GJO-ll(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 mRn: Health Physics, v. 57, p. 891-896.
n-19
Repnot®d from USGS Open-File Report 93-292
-------
APPENDIX A
GEOLOGIC TIME SCALE
Subdivisions (and their symbols}
Eon or
Eonoihem
era or I Period, System.
Erithem [ Subpariod. Subsystem
jpoch or Series
Age estimates
of boundaries
in mega-annum
(Mai '
CvnoiDie 1
(CD
Quaternary 3
IQI
Pdaneroioie3
Mesozoic
(Mi)
Ttnisry
m
Neojene 1
Suaoencd or
SuMvwn IN)
Hoiocene
Pleistocene
Pliocene
Miocene
Psisogeni
SuSDe'iod or
Sut»ylt*m (Pil
Oligocena
Eocene
Paleocene
Cretaceous
IK)
Late
Upper
Early
Jurassic
(J)
Triassic
fS>
Paleozoic'
IPJ
Permian
(P)
Late
Middle
Early
Late
Middle
Early
Late
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Early |
Upper
Lower
Carboniferous
Systems
(C)
Pennsylvania!!
(P)
Mississippian
IM)
Devonian
fD(
Proterozoic
(Bi
Are he an
(A)
Lai*
m«o<*
UU
f
i fV}
Silurian
IS)
Ordovician
<0!
Late
Middle
Early
Late
Early
Late
Middle
Early
Late
Middle
Early
Late
Middle
Early
Cambrian
fCl
Late
Upper
Middle
Lower
Upper
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Middle
Lower
Upper
Middle I Middle
Early
Lower
None defined
Non# defined
Nona defined
None defined
None defined
None defined
Bf*.Ajeh«nn (pA(
- 0.010
- 1.6
(1.6-1.9)
- 5
(4.9-5.3)
- 24
(23-26}
- 38
(34-36)
- 55
(54-56)
- 66
(63-66)
96
(95-97)
138
(135-141)
¦ 205 (200-2151
-2*0
290 (290-305)
-330
360 (360-365)
410 (405-415)
435 (435-440)
500 (495-510)
.570 '
900
1600
2500
3000
3400
3800 7
1 Ranges reOect uncertainties of isotope ami bioatratigraphie age assignments. Age boundaries not doeety bracketed by existing
data shown by •> Decay constants and iselepse ratios emptoy®d are etied in Sieiger and Jiger pS77). Designation m.y. m*6 Iof an
Interval el time.
'Modifier* (fewer, middle, upper or earty, middle. Ibis) when us«d with tfws® hems are Mormal divisions of the larger unit: the
first letter of the modifier Is lowercase.
'Recks eidei than 578 Ma also called Precambrian (p€). a time i»rm witteui specific fand.
* Informal time term w&ixwl specific rank.
USGS Open-FiJe Report 93-292
-------
APPENDIX B
GLOSSARY OF TERMS
'Tn!ts of measure
pCi/L (picocurics 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.
im/tir (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.
the study of fBdsii
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.
13-21 Reprinted from USGS Open-File Report 93-292
-------
argillite, argillaceous Terms referring to a rock derived from clay or shale, or any sedimentary
rock containing an appreciable amount of clay-size material, i.e., argillaceous sandstone.
arid Term describing a climate characterized by dryness, or an evaporation rate that exceeds the
amount of precipitation.
basalt A general term for a dark-colored mafic igneous rocks that may be of extrusive origin,
such as volcanic basalt flows, or intrusive origin, such as basalt dikes.
batholith A mass of plutonic igneous rock that has more than 40 square miles of surface
exposure and no known bottom.
carbonate A sedimentary rock consisting of the carbonate (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 small container of
granulated activated charcoal that is designed to adsorb radon. Useful for short duration (2-7 days)
measurements only. May be referred to as a "screening" test
chert A hard, extremely dense sedimentary rock consisting dominantly of interlocking crystals of
quartz. Crystals are not visible to the naked eye, giving the rock a milky, dull luster. It may be
white or gray but is commonly colored red, black, yellow, blue, pink, brown, or green.
clastic pertaining to a rock or sediment composed of fragments that are derived from preexisting
rocks or minerals. The most common clastic sedimentary rocks are sandstone and shale.
clay A rock containing clay mineral fragments or material of any composition having a diameter
less than 1/256 mm.
clay mineral One of a complex and loosely defined group of finely crystalline minerals made up
of water, silicate and aluminum (and a wide variety of other elements). They are formed chiefly by
alteration or weathering of primary silicate minerals. Certain clay minerals are noted for their small
size and ability to absorb substantial amounts of water, causing them to swell. The change in size
that occurs as these clays change between dry and wet is referred to as their11 sh rink-swell1'
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. Hie
formation of a cuesta is controlled by the different weathering properties and the structural dip of
the rocks forming the hill or ridge.
daughter product A nuclide formed by the disintegration of a radioactive precursor or "parent"
atom.
n-22
Reprinted from USGS Open-File Report 93-292
-------
delta, deltaic Referring 10 a low, flat, alluvial tract of land having a triangular or fan shape,
located at or near the mouth of a river. It results from the accumulation of sediment deposited by a
river at the point at which the river loses its ability to transport the sediment, commonly where a
river meets a larger body of water such as a lake or ocean.
dike A tabular igneous intrusion of rock, younger than the surrounding rock, that commonly cuts
across the bedding or foliation of the rock it intrudes.
diorite A plutonic igneous rock that is medium in color and contains visible dark minerals that
make up less than 50% of the rock. It also contains abundant sodium plagioclase and minor
quartz.
dolomite A carbonate sedimentary rock of which more than 50% consists of the mineral dolomite
(CaMg (003)2), and is commonly white, gray, brown, yellow, or pinkish in color.
drainage The manner in which the waters of an area pass, flow off of, or flow into the soil.
Also refers to the water features of an area, such as lakes and rivers, that drain it
eolian Pertaining to sediments deposited by the wind.
esker A long, narrow, steep-sided ridge composed of irregular beds of sand and gravel deposited
by streams beneath a glacier and left behind when the ice melted.
evapotranspiration Loss of water from a land area by evaporation from the soil and
transpiration from plants.
extrusive Said of igneous rocks that have been erupted onto the surface of the Earth.
fault A fracture or zone of fractures in rock or sediment along which there has been movement.
fluvial, fluvial deposit Pertaining to sediment that has been deposited by a river or stream.
foliation A linear feature in a rock defined by both mineralogic and structural characteristics. It
may be formed during deformation or metamorphism.
formation A mappable body of rock having similar characteristics.
glacial deposit Any sediment transported and deposited by a glacier or processes associated
with glaciers, such as glaciofluvial sediments deposited by streams flowing from melting glaciers.
gneiss A rock formed by metamorphism in which bands and lenses of minerals of similar
composition alternate with bands and lenses of different composition, giving the rock a striped or
"foliated" appearance.
granite Broadly applied, any coarsely crystalline, quartz- and feldspar-bearing igneous plutonic
rock. Technically, granites have between 10 and 50% quartz, and alkali feldspar comprises at least
65% of the total feldspar.
gravel An unconsolidated, natural accumulation of rock fragments consisting predominantly of
particles greater than 2 mm in size.
heavy minerals Mineral grains in sediment or sedimentary rock having higher than average
specific gravity. May form layers and lenses because of wind or water sorting by weight and size
n-23
Reprinted from USGS Open-File Report 93-292
-------
and may tie 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 arc 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 tedded 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 (CaCOj).
lithology The description of rocks in hand specimen and in outcrop on the basis of color,
composition, and grain size.
loam A permeable soil composed of a mixture of relatively equal parts clay, silt, and sand, and
usually containing some organic matter.
loess A fine-grained eolian deposit composed of silt-sized particles generally thought to have
been deposited from windblown dust of Pleistocene age.
mafic Term describing an igneous rock containing more than 50% dark-colored minerals.
marine Term describing sediments deposited in the ocean, or precipitated from ocean waters.
metamorphic Any rock derived from pre-existing rocks by mineralogical, chemical, or structural
changes in response to changes in temperature, pressure, stress, and the chemical environment
Phyllite, schist, amphibolite, and gneiss are metamorphic rocks.
moraine A mound, ridge, or other distinct accumulation of unsorted, imbedded glacial material,
predominantly till, deposited by the action of glacial ice.
outcrop That part of a geologic formation or structure that appears at the surface of the Earth, as
in "rock outcrop".
percolation test A term used in engineering for a test to determine the water permeability of a
soil. A hole is dug and filled with water and the rate of water level decline is measured.
permeability The capacity of a rock, sediment, or soil to transmit liquid or gas.
phosphate, phosphatic, phosphorite Any rock or sediment containing a significant amount
of phosphate minerals, i.e., minerals containing PO4.
n-24 Reprinted from USGS Open-File Repon 93-292
-------
physiographic province A region in which all parts are similar in geologic structure and
climate, which has had a uniform geomorphic history, and whose topography or landforms differ
significantly from adjacent regions.
placer deposit See heavy minerals
residual Formed by weathering of a material in place.
residuum Deposit of residual material.
rhyolite An extrusive igneous rock of volcanic origin, compositionally equivalent to granite.
sandstone A clastic sedimentary rock composed of sand-sized rock and mineral material that is
more or less firmly cemented. Sand particles range from 1/16 to 2 mm in size.
schist A strongly foliated crystalline rock, formed by metamorphism, that can be readily spit into
thin flakes or slabs. Contains mica; minerals are typically aligned.
screening level Result of an indoor radon test taken with a charcoal canister or similar device,
for a short period of time, usually less than seven days. May indicate the potential for an indoor
radon problem but does not indicate annual exposure to radon.
sediment Deposits of rock and mineral particles or fragments originating from material that is
transported by air, water or ice, or that accumulate by natural chemical precipitation or secretion of
organisms.
semiarid Refers to a climate that has slightly more precipitation than an arid climate.
shale A fine-grained sedimentary rock formed from solidification (lithification) of clay or mud.
shear zone Refers to a roughly linear zone of rock that has been faulted by ductile or non-ductile
processes in which the rock is sheared and both sides are displaced relative to one another.
sbrink-swetl 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.
surficiai materials Unconsolidated glacial, wind-, or waterbome deposits occurring on the
earth's surface.
tablelands General term for a broad, elevated region with a nearly level surface of considerable
extent.
Reprinted from USGS Open-File Report 93-292
-------
terrace gravel Gravel-sized material that caps ridges and terraces, left behind by a stream as it
cuts down to a lower level.
terrain A tract or region of the Earth's surface considered as a physical feature or an ecological
environment.
till Unsorted, generally unconsolidated and unbedded rock and mineral material deposited directly
adjacent to and underneath a glacier, without reworking by meltwater. Size of grains varies greatly
from clay to boulders.
uraniferous Containing uranium, usually more than 2 ppm.
vendor data Used in this report to refer to indoor radon data collected and measured by
commercial vendors of radon measurement devices and/or services.
volcanic Pertaining to the activities, structures, and extrusive rock types of a volcano.
water table The surface forming the boundary between the zone of saturation and the zone of
aeration; the top surface of a body of unconfined groundwater in rock or soil.
weathering The destructive process by which earth and rock materials, on exposure to
atmospheric elements, are changed m color, texture, composition, firmness, or form with little or
no transport of the material.
11-26
Reprinted from USGS Open-File Report 93-292
-------
State
Contact
Phone Number
Address
Florida
N. Michael
Gil ley
(904)488-1525
Florida Dept. of Health
Bureau of En v. Toxicology
2020 Capital Circle. SE (Bin 22)
Tallahassee, FL 32399
Georgia
Stephanie
Siniard
(404)651-5120
Georgia Dept. Natural Resources
Pollution & Systems Div./P2AD
7 ML King Jr. Drive, Suite 450
Atlanta. GA 30334
Guam
Peter Cruz
(671)646-8863
Guam EPA
PO Box 122439-GMF
Barrigada. Guam 96911
Hawaii
Russell
Takata
(808) 586-4700
Hawaii Dept. of Health
Radiation & IAQ Branch
591 Ala Moana Blvd.
Honolulu. HI 96813
Idaho
Kara Bishop
(208) 332-7319
Idaho Indoor En v. Program
PO Box 83720
Boise. ID 83720
Illinois
Richard
Allen
(217) 786-7127
Illinois Dept of Nuclear Safety
1035 Outer Park Drive
Springfield, IL 62704
Indiana
Michele
Starkey
(317)633-0150
Indiana State Dept of Health
Indoor & Radiological Health
2 North Meridian St, 5th Floor
Indianapolis, IN 46204
Iowa
Donald
Plater
(515)281-3478
Iowa Dept of Public Health
Lucas State Office Building
321 E. 12th Street
Des Moines. IA 50319
Kansas
Vick Cooper
(785)296-1561
Kansas Dept. of Health & Em-
Radiation Control Program
Forbes Field, Bldg. 283
Topeka. KS 66620
Kentucky
Douglas
Jackson
(502) 564-4856
Kentucky Dept. of Health Svcs.
Env. Management Branch
275 East Main Street
Frankfort. KY 40621
-------
State
Contact
Phone Number
Address
Louisiana
Matt
Schlenker
(504) 925-7042
Louisiana Dept. of En v. Quality
PO Box 82135
Baton Rouge. LA 70884-2135
Maine
Robert
Stil well
(207) 287-5676
Maine Radiation Control Program
#10 State House Station
157 Capitol Street
Northampton, MA 01060
Maryland
Massa-
chusetts
William Bell
(413) 586-7525
Massachusetts Dept of Public Health
Western MA Regional Office
23 Service Center
Jamaica Plain. MA 02130
Michigan
Sue
Hendershott
(517)335-8194
Michigan Dept of Env Quality
Drinking Water & Rad. Pro. Div
PO Box 30630 - CPH Mailroom
Lansing. Ml 48909
Minnesota
Laura
Oatmann
(651)215-0911
Minnesota Dept. of Health
Div. of Environmental Health
PO Box 64975
St. Paul. MN 55164
Mississippi
Silas
Anderson
(601) 354-6657
Mississippi Dept. of Health
Div Rad. Health & Radon Program
3150 Lawson Street
Jackson. MS 39213
Missouri
Gary McNutt
(314)571-6102
Missouri Dept. of Health
Bureau of Environmental Equity
930 Wildwood Drive
Jefferson City, MO 65109
Montana
Brian Green
(406) 444-6768
Montana Dept of Env Quality
Occ & Rad Health Quality
PO Box 200901
Helena, MT 59620
North
Carolina
Dr. Felix
Fong
(919) 571-4141
North Carolina Div of Radiation
Protection
PO Box 27687
Raleigh, NC 27611
-------
Stale
Contact
Pimm Number
Address
North
Dakota
Ken Wangter
(701)328-5188
North Dakota Dept. of Health
Environmental Health Section
PO Box 5520
Bismarck, ND 58502
Nebraska
Joe Milone
(402)471-2168
Nebraska Dept. of Health
Environmental Health Protection
301 Centennial Mall, South
Lincoln. NE 68509
Nevada
Adrian
Howe
(702) 687-5394
Nevada State Health Division
Radiological Health Section
1179 Fairview Drive, Suite 102
Carson City, NV 89701
New
Hampshire
David Chase
(603)271-4674
New Hampshire Dept. of
Radiological Health
Health & Welfare Building
6 Hazen Drive
Concord, NH 03301
New Jersey
Anita
Kopera
(609) 984-5543
New Jersey Dept. of Environmental
Protection
Rad, Protection Prog,, DESHAP
25 Arctic Parkway CN415
Trenton. NJ 08625
New
Mexico
Jcrrie Moore
(505) 841-9474
New Mexico Radon Program
Environmental Division
4131 Montgomery, NE
Albuquerque, NM 87109
New York
Adela
Salame-Alfie
(518)458-6495
New York State Health Dept.
Bureau of Env. Radiation
Two University Place, Rm 240
Albany. NY 12203
Ohio
Mark
Needham
(614)466-0061
Ohio Dept. of Health
Bureau of Diag. Safety & Per Cert.
PO Box 118
Columbus. OH 43215
Oklahoma
Stephen
Fernandez
(405)271-7634
Oklahoma Dept. of Env. Quality
1000NE 10th Street
Oklahoma City. OK 73117
-------
Stale
Contact
Phone Number
Address
Oregon
Ray D. Paris
(503) 731 -4014
Oregon Dept. of Human Resources
Health Division
800 NE Oregon Street, Suite 260
Portland, OR 97232
Pennsyl-
vania
Mike Pyles
(717)783-3594
Pennsylvania Dept of Env. Protection
Rachel Carson State Office Bldg.
400 Market Street, 13th Floor
Harrisburg. PA 17101
Puerto Rico
Jose Font
(787) 767-3563
Puerto Rico Radiological Health
Division
G.P.O. Call Box 70184
Rio Piedras 00936
Rhode
Island
Edmond
Arcand
<401) 222-2438
Rhode Island Dept of Health
Office of Occ. & Rad, Health
3 Capitol Hill, Room 206
Providence, RI 02908
South
Carolina
Albert Craft
(803) 734-4634
South Carolina Dept of Health &
Environment
Radiological Lab.
2600 Bull Street
Columbia, SC 29201
South
Dakota
Barbara
Regynski
(605)773-7171
South Dakota Dept of Eriv & Natural
Resources
Joe Foss Building
523 E. Capitol. Room 217
Pierre, SD 57501
Tennessee
Marsha
White
(615)532-0733
Tennessee Dept of Env. &
Conservation
Div.of Pollution Pre/Env. Awareness
401 Church Street, 8th Floor,
L&C Annex
Nashville, TN 37143
Texas
Gar>' L.
Smith
(512)834-6688
Texas Dept of Health
Bureau of Radiation Control
1100 West 49th Street
Austin, TX 78756
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State
Contact
Phone Number
Address
Utah
John
Hultquist
(801)536-4250
Utah Dept of Hnv, Quality
PO Box 144850
Sail Lake City. UT 84114
Vermont
Paul
demons
(802)865-7730
Vermont Dept of Health
Occ. & Rad, Health Division
108 Cherry Street
Burlington, VT 05402
Virginia
Leslie
Foldesi
(804)786-5932
Virginia Dept of Health
Bureau of Radiological Health
1500 E. Main Street, 240
Richmond, VA 23218
Washington
John
Erickson
(360) 664-4536
Washington State Dept of Health
Division of Radiation Protection
PO Box 47827
Olympia. WA 98504
West
Virginia
Beattie
Debord
(304)558-2981
West Virginia Bureau of Public
Health
Office of Env. Health Services
815 Quarrier Street. Suite 418
Charleston. WV 25301
Wisconsin
Conrad
Weiffenbach
(608) 267-4796
Wisconsin Division of Health
Dept. of Health & Family Svcs.
1 West Wilson Street. PO Box 309
Madison. WI 53701
Wyoming
Debi Nelson
(307) 777-6015
Wyoming Dept of Health
2300 Capitol Avenue
Hathaway Bldg,. Room 486
Cheyenne. WY 82002
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State Geological Surveys Contacts
ALABAMA
Geological Survey of Alabama
420 Hackberry Lane P.O. Box 0
Tuscaloosa, AL 35486-9780
(205) 349-2852
Fax: (205) 349-2861
Web site: http://www.gsa.tuscaloosa.al.us/
Donald F. Oltz. State Geologist &. Director
ALASKA
Alaska Division of Geological and Geophysical Surveys
794 University Avenue, Suite 200
Fairbanks. AK 99709-3645
(907)451-5000
Fax:(907)451-5050
Web site: http://wwwdggs.dnr.state.ak.us/
Milton A. Wiitse, Director, Geologist VI
ARIZONA
Arizona Geological Survey
416 West Congress Street, Suite 100
Tucson, AZ 85701
(520) 770-3500
Web site: http://www.azgs.state. az.us
Larry D. Fellows, Director & State Geologist
ARKANSAS
Arkansas Geological Commission
Vardelle Parham Geology Center. 3815 West Roosevelt Road
Little Rock, AR 72204
(501)296-1877
Fax: (501)663-7360
William V. Bush, State Geologist & Director
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CALIFORNIA
California Division of Mines and Geology
SOI K Street
Sacramento, CA 95814
(916)445-1923
Fax: (916)445-5718
Web site: http://www.consrv.ca.gov/drng/index.html
James F. Davis, State Geologist
COLORADO
Colorado Geological Survey
1313 Sherman Street. Room 715
Denver, CO 80203
(303) 866-26] 1
Fax: (303)866-2461
Web site: http://www.dnr.state.co.us/geosurvey/
Vicki J. Cowart. State Geologist and Director
CONNECTICUT
Connecticut Geological and Natural History Survey
Natural Resources Center, Dept. of Environ. Protection, 79 Elm St.
Hartford, CT 06106-5127
(860)424-3540
Allan Williams. Acting Director
DELAWARE
Delaware Geological Survey
University of Delaware
Newark. DE 19716-7501
(302)831-2833
Fax:(302) 831-3579
Web site: hup://www.udel.edu/dgs/dgs.html
Robert R. Jordan. State Geologist & Director
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FLORIDA
Florida Geological Survey
903 Wesi Tennessee Street
Tallahassee, FL 32304-7700
(850)488-4191
Fax: (850)488-8086
Web site; http://www.dep.state.fl.us/geo/
Waller Schmidt. Chief & State Geologist
GEORGIA
Georgia Geologic Survey
Room 400. 19 Martin Luther King Jr. Dr.. S.W.
Atlanta, GA 30334
(404)656-3214
William H. McLemore, State Geologist & Branch Chief
HAWAII
Hawaii Division of Water and Land Development
P.O. Box 373
Honolulu. HI 96809
(808) 587-0230
Fax: (808) 587-0283
Web site: http://kumu.icsd.hawaii.gov/dlnr/wclcome.hlml
Andrew Monden. Chief Engineer
IDAHO
Idaho Geological Survey
Morrill Hall. Room 332. University of Idaho
Moscow, ID 83844-3014
(208)885-7991
Fax: (208) 885-5826
Earl H. Bennett, State Geologist
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ILLINOIS
III inois State Geological Survey
Natural Resources Building, 615 East Peabody Drive
Champaign. 1L 61820-6964
(217)333-4747 *
Fax: (217) 244-7004
Web site: http://www.isgs.uiuc.edu/Lsgshome.htrnl
William W. Shifts, Chief
INDIANA
Indiana Geological Survey
611 North Walnut Grove
Bloomington. IN 47405
(812)855-5067
Fax:(812)855-2862
Web site: http://www.indiana.edu/~igs/
Norman Hester, Director & State Geologist
IOWA
Iowa Geological Survey Bureau/1 DNR
109 Trowbridge Hall
Iowa City, 1A 52242-1319
(319)335-1575
Fax:(319)335-2754
Web site: http://www.igsh.uiowa.edu/
Donald L. Koch. State Geologist & Bureau Chief, Geological Survey Bureau
KANSAS
Kansas Geological Survey
1930 Constant Avenue, Campus West, University of Kansas
Lawrence, KS 66047-3726
(913)864-3965
Web site: http://www.kgs.ukans.edu
Lee C. Gerhard. State Geologist and Director
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KENTUCKY
Kentucky Geological Survey
228 Mining and Mineral Resources Building. University of Kentucky
Lexington. KY 40506-0107
(606) 257-5500
Web site: http://www.uky.eda/KGS/home.hmi
Donald C. Haney. Slate Geologist & Director
LOUISIANA
Louisiana Geological Survey
University Station, Box G
Baton Rouge, LA 70893-4107
(504) 388-5320
Fax: (504)388-5328
Web site: http://www.dnr.state.la.us/min/geosur.htm
Chacko John, Acting Director
MAINE
Maine Geological Survey, Natural Resources Information & Mapping Center
22 State House Station
Augusta. ME 04333-0022
(207) 287-2801
Fax: (207) 287-2353
Web site: http://www.state.me.us/doc/nrimc/nrimc.htm
Robert G. Marvinnev. Director and State Geologist
MARYLAND
Maryland Geological Survey
2300 St, Paul Street
Baltimore, MD 21218
(410)554-5500
Fax:(410)554-5502
Web site: http://mgs.dnr.md.gov/
Emery T. Cleaves, Director/State Geologist
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MASSACHUSETTS
Executive Office of Environmental Affairs
100 Cambridge St.. 2Oth Floor
Boston, MA 02202
(617) 727-5830 ext.305
Fax:(6!7j727-2754
Richard N. Foster. State Geologist
MICHIGAN
Michigan Geological Survey Division. Dept. of Environmental Quality
Box 30256. 735 E, Hazel St.
Lansing. MI 48909
(517)334-6907
Fax:(517)334-6038
Web site: http://ww\v.deq.state.mi.us/gsd/
MINNESOTA
Minnesota Geological Survey
University of Minnesota. 2642 University Avenue
St. Paul. MN 55114-1057
(612)627-4780
Fax:(612)627-4778
Web site: http://www.geo.unm.edu/mgs/index.html
"David L. Southwick, Director, Professor, Geology & Geophysics
MISSISSIPPI
Mississippi Office of Geology
Southport Center, 2380 Highway 80 West, P.O. Box 20307
Jackson. MS 39289-1307
(601)961-5500
Fax: (601}96i-5521
Web site: http://www.deq.state.ms.us
S. Cragin Knox, State Geologist
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MISSOURI
Missouri Division of Geology and Land Survey
111 Fairgrounds Road. P.O. Box 250
Rolla. MO 65401-0250
(573) 368-2100
Fax:(573)368-21!I
Web site: http://www.state.mo.us/dnr/dgls/dglshp.htm
James H, Williams. Director & State Geologist
MONTANA
Montana Bureau of Mines and Geology
Montana Tech of the Univ. of Montana, 1300 West Park Street
Butte, MT 59701-8997
(406)496-4180
Fax: (406) 496-4451
Web site: http://mbmgsun.mtech.edu
John C. Steinmetz. Director & State Geologist
NEBRASKA
Nebraska Conservation and Survey Division
113 Nebraska Hall, University of Nebraska
Lincoln. HE 68588-0517
(402)472-3471
Fax: (402)472-2410
Web site: http://csd.unl,edu/csd.html
Perry B. Wigley, Director/State Geologist
NEVADA
Nevada Bureau of Mines and Geology
University of Nevada, Reno, MS 178
Reno. NV 89557-0088
(702) 784-6691
Fax:(702)784-1709
Web site: http://www.nbmg.unr.edu
Dr. Jonathan G. Price. Director/State Geologist
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NEW HAMPSHIRE
New Hampshire Dept. of Environmental Services
P.O. Box 2008
Concord. NH 03302-2008
(603)271-3406
Fax:(603)271-7894
Web site: http://www.state.nli.us/des/descover/htm
Eugene L. Boudette, State Geologist
NEW JERSEY
New Jersey Geological Surv ey
CN-427
Trenton. NJ 08625-0427
(609)292-1185
Fax: (609)633-1004
Web site: http://www.state.nj.us/dep/njgs/index.htm!
Halg F. Kasabach, State Geologist
NEW MEXICO
New Mexico Bureau of Mines and Mineral Resources
Campus Station
Socorro, NM 87801
(505)835-5420
Fax:(505)835-6333
Web site: http://geoinfo.nmt.edu
Charles E. Chapin, Director & State Geologist
NEW YORK
New York State Geological Survey
3140 Cultural Education Center, Empire State Plaza
Albany, NY 12230
(518)474-5816
Fax:(518)486-3696
Robert H. Fakundiny, State Geologist & Chief
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NORTH CAROLINA
North Carolina Geological Survey
P.O. Box 27687
Raleigh, NC 27611-7687
(919)733-2423
Fax:(919)733-0900
Web site: http://www.ehnr.state.nc.us/EHNR/DLR/JEFF/rockl.htm
Charles H. Gardner. Director & State Geologist
NORTH DAKOTA
North Dakota Geological Survey
600 East Boulevard Avenue
Bismarck, ND 58505-0840
(701)328-8000
Fax: (701) 328-8010
Web site: http://www.state.nd/ndgs/NDGS.HomePage.html
John P. Bluemle. State Geologist
OHIO
Ohio Division of Geological Survey
4383 Fountain Square, Building B
Columbus, OH 43224
(614)265-6576
Fax: (614)447-1918
Web site: http://www.dnr.state.oh.us/odnr/geo survey,'
Thomas M. Berg. State Geologist & Division Chief
OKLAHOMA
Oklahoma Geological Survey
100 East Boyd. Room N-131
Norman. OK 73019-0628
(405)325-3031
Fax: (405) 325-7069
Web site: http://www.ou.edu/special/ogs-pttc/
Charles J. Mankin, Director
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OREGON
Oregon Department of Geology and Mineral Industries
800 NE Oregon St., -28
Portland. OR 97232
(503)731-4100
Fax:{503}73 2-4066
Web site: http://sarvis.dogami.state.or.us/homepage/
Donald Hull. Director/State Geologist
PENNSYLVANIA
Pennsylvania Geological Survey
P.O. Box 8453
Harrisburg. PA 17105-8453
(717) 787-2169
Fax:(717)783-7267
Web site: http://www.dcnr.state.pa.us/topogeo/defauit.htm
Donald M. Hoskins. Director & State Geologist
PUERTO RICO
Bureau of Geology, Department of Natural and Environmental Resources
P.O. Box 9066600
Puerta de Tierra, PR 00906-6600
(787)722-2526
Fax:(787)723-4255
Lisbeth Hyman, Director
RHODE ISLAND
Office of Rhode Island State Geologist
Department of Geology, The University of Rhode Island
Kingston. RI 02881
(401) 874-2265
Fax: (401) 874-2190
Web site: http://www.uri.edu/artsci/gel/rigeolst.htm
J. Allan Cain, State Geologist & Professor of Geology
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SOUTH CAROLINA
South Carolina Geological Survey
5 Geology Road
Columbia, SC 29210-4089
(803) 896-7700
Fax: (803) 896-7695
C. W. Clcndenin, Jr.. State Geologist & Chief, Geological Survey
SOUTH DAKOTA
South Dakota Geological Survey
Science Center. University of South Dakota
Vermillion, SD 57069-2390
(605) 677-5227
Fax: (605)677-5895
Web site: http://www. sdgs,usd.edu/
TENNESSEE
Tennessee Division of Geology
401 Church St.
Nashville, TN 37243-0445
(615)532-1500
Fax: (615) 532-1517
Ronald Zurawski, Stale Geologist
TEXAS
Texas Bureau of Economic Geology
University of Texas at Austin. University Station. Box X
Austin. TX 78713-8924
(512)471-1534
Fax: (512)471-0140
Web site: http://www.utexas.edu/research/beg/
Noel Tyler, Director
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UTAH
Utah Geological Survey
1594 W. North Temple, Suite 3110. P.O. Box 146100
Salt Lake City. UT 84114-6100
(801)537-3300
Fax:(801)537-3400
Web site: http://www.ugs.state.ut.us
M. Lee Allison, Director
VERMONT
Vermont Geological Survey
Agency of Natural Resources, 103 South Main St., Laundry Building
Waterbury, VT 05671-0301
(802)241-3496
Fax: (802)241-3273
Web site: http://www.state.vt.us/anr/geoiogy/vgshmpg.htm
Laurence Becker. State Geologist & Director
VIRGINIA
Virginia Division of Mineral Resources
P.O. Box 3667
Charlottesville, VA 22903
(804)293-5121
Fax:(804)293-2239
Stanley S. Johnson, State Geologist and Division Director
WASHINGTON
Washington Division of Geology and Earth Resources
Washington Department of Natural Resources, P.O. Box 47007
Oiympia, WA 98504-7007
(360) 902-1450
Fax:(360)902-1785
Web site: http://www.wa.gov/dnr/htdocs/ger/ger.html
Raymond Lasmanis, State Geologist & Division Manager
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WEST VIRGINIA
West Virginia Geological and Economic Survey
Mont Chateau Research Center, P.O. Box 879
Morgan town. WV 26507-0879
(304) 594-2331
Fax: (304) 594-2575
Web site: http://www.wvgs.wvnet.edu/
Larry D. Woodfork. Director & State Geologist
WISCONSIN
Wisconsin Geological and Natural History Survey
3817 Mineral Point Road
Madison. Wl 53705
(608)262-1705
Fax: (608) 262-8086
Web site: http://wwiv.uwex.edu/wgnhs/
lames M, Robertson, Director and State Geologist
WYOMING
Wyoming State Geological Survey
P.O. Box 3008
Laramie, WY 82071
(307) 766-2286
Fax: (307) 766-2605
Web site: http://www-wwTC.uwyo.edu/wds/wsgs/wsgs.html
Gary B. Glass, Director/Stale Geologist
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EPA REGION 6 GEOLOGIC RADON POTENTIAL SUMMARY
by
Linda C.S. Gundersen. James K. Otton. Russell F. Dubiei. and Sandra L. Szarzi
U.S. Geological Survey
EPA Region 6 includes the states Arkansas, Louisiana, New Mexico, Oklahoma, and
Texas. For each state, geologic radon potential areas were delineated and ranked on the basis of
geology, soils, housing construction, indoor radon, 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 6 is given in the individual state chapters. The individual chapters
describing the geology and radon potential of the states in Region 6, though much more detailed
than this summary, still are generalized assessments and there is no substitute for having a home
tested. Within any radon potential area homes with indoor radon levels both above and below the
predicted average likely will be found.
Figure 1 shows a generalized map of the physiographic/geologic provinces in Region 6.
The following summary of radon potential in Region 6 is based on these provinces. Figure 2
shows average screening indoor radon levels by county calculated from the State/EPA Residential
Radon Survey. Figure 3 shows the geologic radon potential areas in Region 6, combined and
summarized from the individual state chapters.
ARKANSAS
The geologic radon potential of Arkansas is generally low to moderate. Paleozoic marine
limestones, dolomites, and uraniferous black shales appear to be associated with most of the
indoor radon levels greater than 4 pCi/L in the State.
Ordovician through Mississippian-age sedimentary rocks, including limestone, dolomite,
shale, and sandstone, underlie most of the Springfield and Salem Plateaus. Black shales and
residual soils developed from carbonate rocks in the Springfield and Salem Plateaus are moderate
to locally high in geologic radon potential. The Ordovician limestones, dolomites, black shales,
and sandstones have moderate (1.5-2.5 ppm) to high (>2.5 ppm) equivalent uranium (eU, from
acroradioactivity surveys) and some of the highest indoor radon in the State is associated with
them. The Mississippian limestones and shales, however, have low (<1.5 ppm) equivalent
uranium with very localized areas of high eU, but also have moderate to high levels of indoor
radon associated with them. Black shales and carbonaceous sandstones within the Mississippian,
Devonian, and Ordovician units of the plateaus are the likely cause of the local areas of high eU.
The Chattanooga Shale and shale units within the Mississippian limestones may be responsible for
some of the high indoor radon levels found in Benton County. Limestones are usually low in
radionuclide elements but residual soils developed from limestones may be elevated in uranium and
radium. Karst and cave features are also thought to accumulate radon.
The Boston Mountains, Arkansas Valley, Fourche Mountains, and Athens Plateau are
underlain predominantly by Mississippian and Pennsylvanian sandstones and shales with low to
ffl-1
Reprinted from USGS Open-File Report 93-292-F
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Figure I. Geologic radon potential areas of EPA Region 6. 1,4, 7-Creiaceous marine rocks; 2 Jemez Mountains; 3, 11-Southern r,h k> Muimutiir; 5, 15
Tertiary OgaJlala Formation (High Plains); 6-Granrs uranium bell; 8, 9-Ptains and Plateaus (Triassic, Cretaceous and Quaternary deposits: I!) -Dmil-Mogul Ion
volcanic field; 12-Tertiary volcanic and Cretaceous sedimentary rocks; 13 Laic Paleozoic marine limestones; I4-Enstward extension til ihe Basin ajid Range
Province; 16 Central Oklahoma and Texas (Paleozoic marine sediments); 17- Wichita Mountains; 18, 19 Cretaceous Central Texas ami Llano Uplift; 2(1-
Northem Coastal Plains (Old Uplands (LA)); 21-Soulhcrn Texas Plain; 22-Coastal Plain (TX)/01d Uplands (LA): 23-Ozark Plateau; 24 Lower Arkansas River
Valley; 25-Ouachita Mountains; 26, 29-Salem Plateau; 27-Springfield Plateau; 28-Boslon Mountains; 30 Crowley's Ridge; 3t-Fi»itidie Mmntiairis; 32 Athens
Plateau; 33—Cenlral Ouchita Mountains; 34-Mississippi Alluvial Plain; 35, 37-Terraces; 36-Prairies.
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100 Mies
Indoor Radon Screening
Measurements: Average (pCi/L)
~ 0.0 to 1.9
42 E3 2.0 to 4.0
12 ¦ 4.1 to 7.5
149 t I Missing Data or < 5 Measurements
Figure 2. Screening indoor radon average for counties with 5 or more measurements in EPA Region 6. Data are from 2-7 day
charcoal canister tests. Data for all states are from the EPA/State Residential Radon Survey. Histograms in map legends show the
number of counties in each category.
-------
Milts
Figure 3. Geologic radon potential areas of EPA Region 6. For more detail, refer to individual state radon potential chapters.
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moderate radon potential. Although the indoor radon average for these provinces is low, there are
a number of counties in these provinces with screening indoor radon averages slightly higher than
I pCi/L and maximum readings greater than 4 pCi/L. The marine black shales are probably
uranium-bearing. Further, carbonaceous sandstones of the Upper Atoka Formation and Savanna
r'oi mation have high (>2.5 ppmi eU associated with ti.em. Uranium also occurs i.. the Jackfork
Sandstone in Montgomery Count)' and in the Atoka Formation in Crawford County. These rocks
are the most likely sources for the indoor radon levels. Radon from a hydrocarbon source in these
rocks should not be ruled out. The presence of radon and uranium in some natural gas, petroleum,
and asphaltite is well known and could contribute radon to indoor air in some locations.
The Central Ouachita Mountains are underlain by intensely-deformed Ordovician and
Silurian shales and sandstones with minor chert and limestone. These rocks generally have low to
moderate radon potential. Aeroradiometric signatures of 2.5 ppm eU or more are associated with
the Ordovician black shales and possibly with some syenite intrusions. Indoor radon in the Central
Ouachita Mountains is low to moderate and permeability of the soils is low to moderate.
The West Gulf Coastal Plain is generally low in radon potential. Some of the Cretaceous
and Tertiary sediments have moderate eU (1.5-2.5 ppm). Recent studies in the Coastal Plain of
Texas, Alabama, and New Jersey show that glauconite and phosphate in sandstones, chalks,
marls, and limestones, as well as black organic clays, shales, and muds, are often associated with
high concentrations of uranium and radon in the sediments, and could be sources for elevated
indoor radon levels. Several formations within the Gulf Coastal Plain of Arkansas contain these
types of sediments, especially parts of the upper Cretaceous and lower Tertiary section, but
average indoor radon levels in this area are not elevated. The Quaternary sediments of the Coastal
Plain have low eU and the indoor radon average is low for the Gulf Coastal Plain overall.
The Mississippi Alluvial Plain and Crowley's Ridge have low to locally moderate radon
potential. The southern half of the Mississippi Alluvial Plain is made up predominantly of
quartzose sediments, has generally low eU, and has low indoor radon. The northern half of the
alluvial plain, however, includes the loess of Crowley's Ridge, which appears to have high
equivalent uranium associated with it, and possibly a high loess content in the surrounding
sediments in general. The northeastern comer of Arkansas appears to be crossed by the large belt
of loess that continues into Kentucky and Tennessee and shows as a distinct area of high eU on the
aeroradiometric map of the United States. Some areas of high eU may also be due to uranium in
phosphate-rich fertilizers used in agricultural areas. Several of the counties in the northern part of
the alluvial plain have maximum indoor radon values greater than 4 pCi/L and indoor radon
averages between 1 and 2 pCi/L, which are generally higher than those in surrounding counties.
LOUISIANA
The geology of Louisiana is dominated by ancient marine sediments of the Gulf Coastal
Plain and modern river deposits from the Mississippi River and its tributaries. Louisiana is
generally an area of low geologic radon potential. The climate, soil, and lifestyle of the inhabitants
of Louisiana have influenced building construction styles and building ventilation which, in
general, do not allow high concentrations of radon to accumulate. Many homes in Louisiana are
built on piers or are slab-on-grade. Overall indoor radon is low; however, several parisiics had
individual homes with radon levels greater than 4 pCi/L. Parishes with indoor radon levels greater
than 4 pCi/L are found in different parts of the State, in parishes underlain by coastal plain
sediments, terrace deposits, and loess.
m-5
Reprinted from USGS Open-File Report 93-292-F
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In the Coastal Plain of Louisiana the glauconitic, carbonaceous, and phosphatic sediments
have some geologic potential to produce radon, particularly the Cretaceous and lower Tertiary-age
geologic units located in the northern portion (Old Uplands) of the State. Soils from clays, shales,
and marls in the Coastal Plain commonly have low permeability, so even though these sediments
may be a possible source of radon, low permeability probably inhibits radon availability. Some of
the glauconitic sands and silts with moderate permeability may be the source of locally high indoor
radon. Moderate levels of radioactivity {1.5-2.5 ppm ell) are associated with areas underlain by
the Eocene through lower Oligocene-age Coastal Plain sediments, but do not follow formation
boundaries or strike belts in a systematic manner. The pattern of moderate radioactivity in this area
does appear to follow river drainages and the aeroradioactivity pattern may be associated with
northwest- and northeast-trending joints and or faults which, in tum. may control drainage
patterns. Part of the pattern of low aeroradioactivity in the Coastal Plain may be influenced by
ground saturation with water. This area receives high precipitation and contains an extensive
system of bayous and rivers. Besides damping gamma radioactivity, ground saturation can also
inhibit radon movement.
The youngest Coastal Plain sediments, particularly Oligocene and younger, have
decreasing amounts of glauconite and phosphate and become increasingly siliceous (silica-rich),
and thus, are less likely to be significant sources of radon. However, the possibility of roll-front
uranium deposits in sedimentary rocks and sediments of Oligocene-Miocene age, analogous to the
roll-front uranium deposits in Texas, has been proposed. Anomalous gamma-ray activity has been
measured in the lower Catahoula sandstone, but no uranium deposits have yet been identified.
The fluvial and deltaic sediments in the Mississippi Alluvial Plain are low in geologic radon
potential. They are not likely to have elevated amounts of uranium and the saturated to seasonally
wet conditions of the soils, as well as the high water tables, do not facilitate radon availability.
Coarse gravels in the terraces of the Mississippi Alluvial Plain have locally very high permeability
and may be a source of radon.
Loess units in the northern portion of the Mississippi fioodplain can easily be identified by
their radiometric signature on the aeroradioactivity map of Louisiana. Loess is associated with
high radiometric anomalies throughout the United States. Radiometric anomalies also seem to be
associated with exposures of loess in Iberia, Lafayette, eastern Acadia, and northern Vermilion
Parishes, in the southeastern part of the Prairies. Loess tends to have low permeability, so even
though these sediments may be a possible source of high radon, the lack of permeability,
particularly in wet soils, may inhibit radon availability.
NEW MEXICO
An overriding factor in the geologic evaluation of New Mexico is the abundance and
widespread outcrops in local areas of known uranium-producing and uranium-bearing rocks in the
State. Rocks known to contain significant uranium deposits, occurrences, or reserves, and rocks
such as marine shales or phosphatic limestones that are known to contain low but uniform
concentrations of uranium, all have the potential to contribute to elevated levels of indoor radon. In
New Mexico, these rocks include Precambrian granites, pegmatites, and small hydrothermal veins;
the Pennsylvanian and Permian Cutler Formation, Sangre de Cristo Formation, and San Andres
Limestone; the Triassic Chinle Formation; the Jurassic Morrison Formation and Todilto Limestone
Member (Wanakah Formation); the Cretaceous Dakota Sandstone, Kirtland Shale, Fruitland
Formation, and Crevasse Canyon Formation; the Cretaceous and Tertiary Ojo Alamo Sandstone;
m-6 Reprinted from USGS Open-File Report 93-292-F
-------
Tertiary Ogallala Formation and Popotosa Formation (Santa Fe Group); Tertiary alkalic intrusive
rocks and rhyolitic and andesitic volcanic rocks such as the Alum Mountain andesite; and the
Quaternary Bandelier Tuff and Valles Rhyolite.
Several areas in New Mexico contain outcrops of one or more of these rock units that may
contribute to elevated radon levels. The .southern and western rims of the San Juan Basin expose a
Paleozoic to Tertiary sedimentary section that contains the Jurassic, Cretaceous, and Tertiary
sedimentary rocks having a high radiometric signature and that are known to host uranium deposits
in the Grants uranium district, as well as in the Chuska and Carrizo Mountains. In north-central
New Mexico, the Jemez Mountains are formed in part by volcanic rocks that include the Bandelier
Tuff and the Valles Rhyolite; this area also has an associated high radiometric signature, in
northeastern New Mexico, Precambrian crystalline rocks and Paleozoic sedimentary rocks of the
southern Rocky Mountains and Tertiary volcanic rocks and Cretaceous sedimentary rocks are
associated with radiometric highs. In southwestern New Mexico, middle Tertiary volcanic rocks
of the Datil-Mogollon region are also associated with high radiometric signatures. Remaining areas
of the Colorado Plateau, the Basin and Range, and the Great Plains are associated with only
moderate to low radiometric signatures on the aeroradiometric map; these areas generally contain
Paleozoic to Mesozoic sedimentary rocks, scattered Tertiary and Quaternary volcanic rocks, and
locally. Tertiary sedimentary rocks.
The southern extension of the Rocky Mountains and uplifted Paleozoic sedimentary rocks in
central New Mexico; Upper Cretaceous marine shales and uranium-bearing Jurassic fluvial
sandstones of the Grants uranium belt in the northeastern part of the State; and Tertiary volcanic
rocks in the Jemez Mountains, just west of the southern Rocky Mountains, have high radon
potential. Average screening indoor radon levels are greater than 4 pCi/L and aeroradioactivity
signatures are generally greater than 2.5 ppm eU. Rocks such as Precambrian granites and uplifted
Paleozoic strata, Jurassic sandstones and limestones, or Cretaceous to Tertiary shales and volcanic
rocks that are known to contain or produce uranium are the most likely sources of elevated indoor
radon levels in these areas. The remainder of the State has generally moderate radioactivity,
average screening indoor radon levels less than 4 pCi/L. and overall moderate geologic radon
potential.
OKLAHOMA
The geology of Oklahoma is dominated by sedimentary rocks and unconsolidated
sediments that vary in age from Cambrian to Holocene. Precambrian and Cambrian igneous rocks
are exposed in the core of the Arbuckle and Wichita Mountains and crop out in about 1 percent of
the State. The western, northern, and central part of the State is underlain by very gently west-
dipping sedimentary rocks of the northern shelf areas. A series of uplifts and basins flank the
central shelf area. The Gulf Coastal Plain forms the southeastern edge of the State.
Most of the rocks that crop out in the central and eastern part of the State are marine in
origin; they include limestone, dolomite, shale, sandstone, chert and coal of Cambrian through
Permian age. Norsmarine rocks of Permian and Tertiary age, including shale, sandstone, and
conglomerate, are present in the western part of the central Oklahoma Hills and Plains area; sand,
clay, gravel, and caliche dominate in the High Plains in the western part of the State. The Gulf
Coastal Plain is underlain by Cretaceous nonmarine sand and clay and marine limestone and clay.
Some of these units locally are moderately uranium-bearing.
m-7 Reprinted from USGS Open-File Report 93-292-P
-------
Surface radioactivity across the State varies from less than 0.5 ppm to 5.0 ppm eU. Higher
levels of equivalent uranium {>2.5 ppm) are consistently associated with black shales in the
southeastern and westernmost Ouachita Mountains, the Axbuckle Mountains, and the Ozark
Plateau; with Permian shale in Roger Mills, Custer, Washita, and Beckham Counties; with granites
and related rocks in the Wichita Mountains: and with Cretaceous shale and associated limestone in
the Coastal Plain. Low eU values (<1.5 ppm) are associated with large areas of dune sand
adjacent to rivers in western Oklahoma; with eolian sands in the High Plains in Cimarron and Ellis
Counties; and with Mississippian and Pennsylvanian rocks in the Ouachita Mountains, the Ozark
Plateau, and the eastern part of the central Oklahoma plains and hills.
Areas of Oklahoma ranked as locally moderate to high are underlain by black, phosphatic
shales and associated limestones in the northeastern part of the State and near the Arbuckle
Mountains; the Upper Permian Rush Springs Formation in Caddo County; and granites, rhyolites,
and related dikes in the Wichita Mountains in the southwestern part of the State. Areas ranked as
generally low are underlain by Paleozoic marine sedimentary rocks in central and northwestern
Oklahoma and by Tertiary continental sedimentary rocks on the High Plains.
Well-drained alluvial terraces along some rivers {for example, along the Arkansas River
west of Tulsa); steep, thin, sandy to gravelly soils developed on sandstone on river bluffs (for
example, bluffs in the southeastern suburbs of Tulsa); and clayey loams on uraniferous shales (in
the northeastern corner of the State) are responsible for a significant percentage of elevated indoor
radon levels in those areas. Thus, in addition to soils derived from rocks with elevated uranium
content, soils in selected parts of counties where river terraces and sandstone bluffs occur might
also have elevated radon potential.
Soil moisture may have an additional effect on radon potential across the State. Indoor
radon values tend to be higher west of Oklahoma City where rainfall is less than 32 inches per year
and lowest in the southeastern corner of the State, where rainfall ranges from 32 to 64 inches per
year. Indoor radon values in northeastern Oklahoma, where rainfall is also high, include many
readings greater than 4 pCi/L, but the effects of uraniferous bktk shales and weathered limestone
soils on indoor radon may increase the levels overall and counter the effects of regional variation in
soil moisture. High permeability, dry soils, and moderate uranium content may be responsible for
elevated indoor radon readings in Beaver County.
TEXAS
The geologic radon potential of Texas is relatively low to moderate overall. The relatively
mild climate throughout much of the State, especially in the most populous areas, and the
predominance of slab-on-grade housing seems to have influenced the overall potential. Significant
percentages of houses with radon levels exceeding 4 pCi/L are restricted primarily to the High
Plains and the Western Mountains and Basins provinces. However, no physiographic province in
Texas is completely free from indoor radon levels greater than 4 pCi/L.
Elevated indoor radon can be expected in several geologic settings in Texas. Granites and
metamorphic rocks in central Texas, Tertiary silicic volcanic and tuffaceous sedimentary rocks in
western Texas, dark marine shales in east-central Texas and the Big Bend area, sand and caliche
associated with the OgaUala Formation and overlying units in the High Plains of Texas, sediments
of Late Cretaceous age along the eastern edge of central Texas, and residual soils and alluvium
derived from these units are likely to have significant percentages of homes over 4 pCi/L. Except
for the High Plains and the Western Mountains and Basins Provinces, these rocks generally make
HI-8 Reprinted from USGS Open-File Report 93-292-F
-------
up only a relatively small percentage of the surface area of the various physiographic provinces.
However, the outcrop belt of Upper Cretaceous sedimentary rocks of the East Texas Province
passes near some substantial population centers. Extreme indoor radon levels (greater than 100
pCi/L) may be expected where structures are inadvertently sited on uranium occurrences. This is
more likely to occur in more populated areas along the outcrop belt of the Ogallala Formation at the
edge of the Llano Estacada in the northern and central parts of the High Plains and Plateaus
Province. In this outcrop area, sedimentary rocks with more than 10 ppm uranium are relatively
common.
The northern part of the High Plains and Plateau Province has moderate radon potential.
Uranium occurrences, uranium-bearing calcrete and silcrete, and uranium-bearing lacustrine rocks
along the outcrop belt of the OgaLlala Formation and in small upper Tertiary lacustrine basins
within the northern High Plains may locally cause very high indoor radon levels. Indoor radon
data are elevated in many counties in this area . Equivalent uranium values in this area range from
1.0 to 4.0 ppm. An area of elevated eU along the Rio Grande River is included in this radon
potential province. The southern part of the High Plains and Plateaus Province has low radon
potential overall as suggested by generally low eU values and low indoor radon. This area is
sparsely populated and existing indoor radon measurements may not adequately reflect the geologic
radon potential. An area of low eU covered by the sandy facies of the Blackwater Draw
Formation in the northeastern corner of the Western Mountains and Basins Province is included in
this radon potential area. Some parts of this province that may have locally elevated indoor radon
levels include areas of thin soils over limestone and dolomite in the Edwards Plateau of the
southern part of this province, and areas of carbonaceous sediments in the southeastern part of this
province.
The Western Mountains and Basins Province has moderate indoor radon potential overall.
Although average indoor radon levels are mixed (low in El Paso County, but high in three southern
counties), areas of elevated eU are widespread. Uranium-bearing Precambrian rocks, silicic
volcanic rocks, and alluvium derived from them may locally cause average indoor radon levels in
some communities to exceed 4 pCi/L. Some indoor radon levels exceeding 20 pCi/L may also be
expected. Exceptionally dry soils in this province may tend to lower radon potential. In very dry
soils, the emanating fraction of radon from mineral matter is lowered somewhat.
The Central Texas Province has low radon potential overall; however, areas along the
outcrop belt of the Woodbine and Eagle Ford Formations and the Austin Chalk along the east edge
of this province, and areas of Precambrian metamorphic and undifferentiated igneous rocks in the
Llano Uplift in the southern pan of this province have moderate geologic radon potential.
Structures sited on uranium occurrences in the Triassic Dockum Group in the western part of this
province may locally have very high indoor radon levels.
The East Texas Province has low radon potential overall. Soil moisture levels arc typically
high; soil permeability is typically low to moderate; and eU levels are low to moderate. A few
areas of well-drained soils and elevated eU may be associated with local areas of moderately
elevated indoor radon levels.
The South Texas Plain has low radon potential due to generally low eU and low to
moderate soil permeability. Some structures sited on soils with slightly elevated uranium contents
in this province may locally have elevated indoor radon levels, but such soils are generally also
clay rich and this may mitigate radon movement The Texas Coastal Plain has low radon potential.
Low aeroradioacrivity, low to moderate soil permeability, and locally high water tables contribute
to the low radon potential of the region.
ffl-9 Reprinted from USGS Open-File Report 93-292-F
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PRELIMINARY GEOLOGIC RADON POTENTIAL ASSESSMENT OF LOUISIANA
by
Linda C.S. Gundersen
U.S. Geological Survey
INTRODUCTION
Louisiana has an overall low indoor radon potential. Only a few rock types in the State
have uranium and radium concentrations that might produce elevated indoor radon. Further, the
climate, soil, and lifestyle of the inhabitants have influenced building construction styles and
building ventilation which, in general, do not allow high concentrations of radon to accumulate.
Indoor radon data from 1314 homes sampled in the State/EPA Residential Radon Survey
conducted in Louisiana during the winter of 1990-91 had an average of 0.5 pCi/L and 0.8 percent
of the homes tested had indoor radon levels exceeding 4 pCi/L.
This is a generalized assessment of geologic radon potential of rocks, soils, and surficial
deposits of Louisiana. The scale of this assessment is such that it is inappropriate for use in
identifying the radon potential of small areas such as neighborhoods, individual building sites, or
housing tracts. Any localized assessment of radon potential must be supplemented with additional
data and information from the locality. Within any area of a given radon potential ranking, there
are likely to be areas with higher or lower radon levels than characterized for the area as a whole.
Indoor radon levels, both high and low, can be quite localized, and there is no substitute for testing
individual homes. Elevated levels of indoor radon have been found in every State, and EPA
recommends that all homes be tested. For more information on radon, the reader is urged to
consult the local or State radon program or EPA regional office. More detailed information on state
or local geology may be obtained from the state geological survey. Addresses and phone numbers
for these agencies are listed in chapter 1 of this booklet.
PHYSIOGRAPHIC AND GEOGRAPHIC SETTING
The physiography of Louisiana is in part a reflection of the underlying geology (fig. 1).
Louisiana is divided into two major physiographic regions: The Coastal Plain and the Mississippi
Alluvial Plain. For the purposes of this report, however, we will refer to the major topographic
areas of the State of which there are six (fig. 2). The Old Uplands area is equivalent to the Coastal
Plain, whereas the other areas refer to specific morphologic areas formed by the Mississippi River
and its tributaries, which include: the Floodplain, the Terraces, the Prairies, and the Delta. The
area of the Cheniers is influenced both by the river and ocean. The Cheniers is characterized by
beach and dune ridges of sand overlying clay and mud marsh deposits. Elevation is at or near sea
level and the landscape is flat-lying except for the beach ridges (called cheniers). The Delta is a
complex coastal area in which the Mississippi River deposits sediment and has systems of levees
designed to maintain the river in its current channel. Elevation is at or near sea level and the delta
plain is flat. The Floodplain consists of the meandering channels of the Mississippi River,
including recent alluvial deposits and natural levees. Elevation is from sea level up to several tens
of feet, and the topography is gently rolling. The Prairies and Terraces are characterized by older
alluvial, terrace, and deltaic deposits which vary in elevation from 5 to 400 feet and consist of flat-
lying to hilly terrain. The Old Uplands contains low hills of ancient marine sediments and the
IV-1 Reprinted from USGS Open-File Report 93-292-F
-------
¦ V.I
+S.S. *. Z A
Catahou
Formation
wmmM
ip-Tfd»°o\ ;#h»*%4/®a«• a»\ s
wm&mi
Brikman ^97^ geologic maP of" Louisiana (after Snead and McCulloh 1984; King and
-------
Lousiana General Geology Map
Description of Unite
LITHOLOGY
Qh: Alluvium: jiray lo brown clay anil silly clay, some sand and gravel. Natural levees: gray and brown sill, sill)
clay, and very fine sand. Delta plain.fresh marsh pray 10 black clay of very high organic eonsem. some peal. Dcim
plain, saltne marsh of gray lo black clay of high organic conteni and some peat. Chemci plain, fresh marsh : j;r:t\ in
brown to black clay and silt of high organic conteni, Chenier plain, saline marsh: gray to brown to black clay and
silt of mode rale organic content. Chenkrs: white lo light gray fine sand and shell fragments. Dewewille Terrace
gray mixed with brown to red clay and silty clay, some sand and gravel locally.
Qp: Prairie terraces: light gray to light brown clay, sandy clay, silt, sand and some gravel. Braided stream
terraces: light gray, tan, and brown fine to coarse sand, some clay, silt, and gravel (west side of Mississippi Valley
in northeastern Louisiana. Intermediate terraces: light gray to orange-brown clay, sandy clay, and sift, much sand
and gravel locally.
Tpc : High terraces: thin sheets of tan to orange sandy clay. silt, and clayey sand with a large amount of basal.
sandy gravel.
Tin : ft founts Creek Member: gray to green silty clays, siltstones. and silts with abundant sand beds, some lignite
and Senses of black chert gravel. Castor Creek Member, gray to dark gray calcareous clays which may weather 10
black soil, lignitic clays and non calcareous clayey silts. Williamson Creek Member: while to gray sills, siltstones.
silly clays, and sand beds, some lenses of black chert gravel. Dough Hills Member: gray to yellow silty clays, light
gray calcareous clays which may weather to black soil, some siliceous silt and volcanic ash beds. Carnahan Bayou
Member: yellow to gray silts lone, sandstone, and clays with thin tuffaceous beds, some lenses of black chert gravel
and petrified wood locally. Lena Member, gray calcareous clays which may weather to black soils, siltstones.
tuffaceous clays and some volcanic ash beds.
Catahoula Formation: gray to white sandstone, loose quartz sand, tuffaceous sandstone, volcanic ash. and brown
sandy clays, petrified wood locally.
To: Vicksburg Group; (Undifferentiaied) brown to gray lignitic clays with thin imerbeds of ligniie or micaceous
sands, calcareous . dark shale, petrified wood, and bluish fossiliferous clay locally.
Te3: Jackson Group: (Undifferentiated) light gray to brown lignitic. clays with intcrbeds of lixnonuic. glauconitic
sands or lignite, at base, calcareous, glauconitic. shaley and fossiliferous beds may weather to black soil.
Te2: Claiborne Group: CockfteldFormation: brown lignitic clays, sills, and sands, some sideritic glaucomtc may
weather to brown ironstone in lower part. Cook Mountain Formation: greenish gray sideritic, glauconitic clay in
upper part may weather to brown ironstone, yellow to brown clays and fossiliferous marl in lower part may weather
to black soil. Ironstone concretions near base. Sparta Formation: white to light gray massive sands with
interbedded clays, some thin interbeds of lignite or lignitic sands and shales. Cane River Formation: brown silly
clay with basal glauconitic, fossiliferous silts which may weather to ironstone locally.
Tel: Wilcox Group: gray to brown lignitic sands and silly to sandy lignitic clays, many seams of lignite, some
limestone and glauconite, underlain by fossiliferous marine units.
Tx : Midway Group: (Undifferentiated), dark gray to black shale, glauconitic sands and silly clays with several
lenses of coquinic limestone.
uK: Fossiliferous limestone and marl.
-------
Chert isrs
f~£] Delta
| j Floodplairt
123 Old Uplands
~ Prairies
°- e Terraces
Figure 2. Topographic areas of Louisiana (modified from Newton, 1972).
-------
highest elevation in Louisiana at 535 feet. Elevation is generally above 200 feet and the terrain is
hilly to gentJy rolling.
Population distribution and land use in Louisiana reflects in part the geology, topography,
and climate of the State. The 1990 population is approximately 4,219,973, with a population
density of 92 per square mile; 69 percent of the population is urban (fig. 3). The climate of
Louisiana is subtropical with some influence by continental weather patterns. The summers are hot
and humid and the winters are mild, with occasional influxes of Arctic air. From June through
November, Louisiana is prone to tropical storms and hurricanes. Average temperature ranges from
64°F in the north to 71 °F in the southern portion of the State. Precipitation ranges from 48 to 64
inches per year (fig. 4).
GEOLOGY AND SOILS
The geology of Louisiana is dominated by the ancient marine sediments of the Gulf Coastal
Plain and the recent river deposits from the Mississippi River and its tributaries. The following
discussion of geology and soils is derived from Snead and McCulloh (1984); Soil Conservation
Service (1987) and selected Parish reports; and Richmond and others (1990). A map of general
soil areas is given in figure 5.
The Coastal Plain
The area known as the Old Uplands is underlain predominantly by Coastal Plain deposits
of Cretaceous to Tertiary age. The majority of these rocks and sediments are marine sandstone,
siltstone, shale, sand, silt, clay, limestone, and marl. The soils of the Old Uplands consist of
decomposition residuum of the ancient Coastal Plain sediments and rocks. They are usually moist,
gently to moderately sloping, with well developed clay horizons and low organic matter content in
the subsurface. Permeability is generally controlled by grain size and clay content.
The oldest rocks exposed in Louisiana are Upper Cretaceous limestone and marl exposed in
two interior salt domes of the Old Uplands. The oldest Tertiary rocks exposed are the Midway
Group, which consists of gray to black carbonaceous shales and glauconitic sands. These rocks
are also exposed in the same two salt domes. Both of these units cover only a minor surface area
in Louisiana.
The Midway Group is succeeded by the sediments of the Wilcox Group, consisting of gray
to brown lignitic sand and silty to sandy lignitic clay, lignite, minor limestone, and glauconite.
This group underlies northwestern Louisiana west of the Red River. Soils are generally clayey,
fine to medium sands and sandy clays that are slowly to moderately permeable.
The Claiborne Group underlies a large area between the Red River and the Mississippi
Alluvial Plain. It consists of several distinct formations, many of which weather to ironstone or
have ironstone concretions. The Cane River Formation is a brown silty clay with basal
glauconitic, fossiliferous silts. Soils are silty clay and clayey silt with slow permeability. Massive
white sands interbedded with clays, lignite, and shales make up the Sparta Formation. Soils are
medium-grained sand, clayey sand, and minor sandy clays of slow to moderate permeability. The
Cook Mountain Formation consists of sideritic. glauconitic clay and fossiliferous marl. Soils are
dominated by clay and are slowly permeable. The top of the Claiborne Group is the Cockfield
Formation, which includes lignitic clays, silts, and sands with some glauconite. Soils are sandy
loams and silty, sandy clays of slow to moderate permeability.
rv-5
Reprinted from USGS Open-File Report 93-292-F
-------
POPULATION (1990)
Q 0 to 10000
~ 10001 to 25000
0 28001 to 50000
¦ 50001 to 100000
¦ 100001 to 496938
Figure 3. Population of counties in Louisiana (1990 U.S. Census dam).
-------
48"'
w
60"
SO'
60"
Figure 4. Annua! precipitation in Louisiana (Facts on File, 1984).
-------
Figure 5. Generalized map showing soil areas of Louisiana (redrawn from map supplied by the Louisiana State University Remote
Sensing and Image Processing Lab, 1992, from U.S. Soil Conservation Service soil survey data).
-------
GENERALIZED SOIL MAP OF LOUISIANA
EXPLANATION
COASTAL PLAIN-gently to moderately sloping, usually moist, clay, clay loam, silty
clay loam, silt loam, silt, and fine sand, slowly to locally moderately permeable.
++ +
+++
++ +
GULF COAST FLATWOODS-poorly drained silty and clayey loams, frequently
saturated.
GULF COAST PRAIRIES-loamy soils with clayey subsoils, slowly permeable.
SOUTHERN MISSISSIPPI VALLEY SILTY UPLANDS-loess and loessal soils: silt and
silty loams with very minor sand and clay, somewhat poorly drained, seasonally wet in
the northern part of the State to typically wet in the southern part, generally slowly
permeable.
RECENT ALLUVIUM-poorly to moderately drained, slowly to moderately permeable,
loam, silt, and sand in floodplains. On levees, poorly drained, slowly permeable, loams,
silt loams and silty clay loams in the south; well drained, highly permeable, loams and
sands in the north.
MARSH-Fresh water and salt water marshes containing clay, silt, and peat, usually
saturated.
-------
The Jackson Group consists of light gray to brown Hgnitic clays with inter beds of
limonitic, glauconitic sands or lignite. Near the base of the unit are calcareous, glauconitic. shaly
and fossiliferous sediments that typically weather to a black soil. Soils are silly clays and
micaceous fine sandy days that are slowly permeable. The Jackson Group is exposed in a narrow
band which crosses central Louisiana south of the Claiborne Group.
The Vicksburg Group and Catahoula Formation also form narrow bands of outcrop just
south of the Jackson Group. The Vicksburg Group consists of brown to gray lignitic clays with
thin interbeds of lignite or micaceous sands, calcareous, dark shale, petrified wood, and local blue
fossiliferous clay. Soils are silty clay and micaceous fine sandy clay that are slowly permeable.
The Catahoula Formation is characterized by gray to white sandstone, unconsolidated quartz sand,
tuffaceous sandstone, volcanic ash, and brown sandy clays, with petrified wood locally. Soils are
clayey, fine to medium sand and fine sandy, silty clay that are slowly to moderately permeable.
On the geologic map of Louisiana included in this report (fig. 1), the Miocene-age Coastal
Plain sediments have been placed in one group and form a discontinuous line of exposures in
Central Louisiana across the southern pan of the Coastal Plain and the easternmost Terraces. The
Lena Member is composed of gray calcareous clays (which may weather to black soils), siltstones,
tuffaceous clays arid some volcanic ash beds. The Carnahan Bayou Member consists of yellow to
gray siltstone, sandstone, and clays with thin tuffaceous beds and local lenses of black chert gravel
and petrified wood. The Dough Hills Member has gray to yellow silty clays, light gray calcareous
clays which may weather to black soil, and some siliceous silt and volcanic ash beds. The
Williamson Creek Member consists of white to gray silts, siltstones, silty clays, and sand beds
with some lenses of black chert gravel. These units axe succeeded by the Castor Creek Member
which consists of gray to dark gray calcareous clays (which may weather to black soil), lignitic
clays, and noncalcareous clayey silts. The Blounts Creek Member consists of gray to green silty
clays, siltstones, and silts with abundant sand beds, minor lignite, and lenses of black chert gravel.
Soils are clays, smectitic clays with high shrink-swell potential, sandy clays, fine sands, and
clayey sands. Permeability is generally slow.
The Mississippi Alluvial Plain
The soils underlying the Mississippi Alluvial Plain are characterized by high organic
contents, reflect the grain size of the particular environment of deposition, and generally are moist
to seasonally wet and have high water tables. Permeability expressed in the Soil Conservation
Service parish reports is water permeability and is not applicable to gas permeability in water-
saturated sediments.
The two areas known as the Terraces on the physiographic map consist of several different
terrace deposits formed by the progressive change in relative sea level and aggradation of the
Mississippi Delta, The High Terraces are tan to orange clay, silt, and sand with a large amount of
basal gravel. The Intermediate Terraces are light gray to brown clay, sandy clay, silt, and locally
extensive deposits of sand and gravel. Soils in the terraces are silty and clayey loams that are
frequently saturated and poorly drained. The Prairie Terraces underlie most of the areas known as
the Prairie and the Terraces on the topographic areas map (fig. 2). They show little dissection in
contrast to the other terrace deposits, are generally finer grained, and are composed of gray to
brown clay, sandy clay, silt, sand, and some gravel. Soils in the Prairies are generally loamy in
surface layers and have clayey subsoils of slow permeability.
Two major alluvial plains, the Mississippi and the Red River, cover a significant portion of
Louisiana and are made up of approximately equal amounts of alluvial and natural levee deposits at
IV-10 Reprinted from USGS Open-File Report 93-292-F
-------
the surface. Alluvial sediments are predominantly gray to brown clay and silty clay, with some
sand and gravel. They are poorly drained, frequently flooded, and have slow permeability. They
are deposited in the overbank flood areas adjacent to natural levees and, in the lower valleys of the
Mississippi, arc predominantly backswamp organic clay and silt. Sandy channel and point bar
deposits of the river also occur but tend to be covered by levee deposits. Natural levees of gray
and brown silt, silty clay, and very fine sand form along the present and former courses and
distributaries of the rivers. The levee deposits slope away from the river channel and merge with
the alluvial deposits. In the south, levee soils are silt loams and silty clay loams of slow
permeability. To the north in both the Red River and Mississippi Floodplains, levee soils are well
drained loams and sands with high permeability. In the northern pan of the Mississippi Alluvial
Plain, braided stream terraces of light gray, tan, and brown, fine to coarse sand, some clay, silt,
and gravel cover extensive areas and arc considered glacial outwash of the ancestral Arkansas
River. Along streams of intermediate size, including the northwestern edge of the Mississippi
Alluvial Plain and along the Sabine River, a Quaternary unit known as the Deweyville Terrace is
found. It consists of gray, brown, and red clay and silty clay, with some sand and gravel locally.
The Delta Plain forms the southeastern extension of Louisiana into the Gulf Coastal waters.
It consists of freshwater marsh with gray to black clay of very high organic content and some peat.
This is rimmed with saline marsh of gray to black clay with high organic content and some peat.
The northern part of the Cheniers is freshwater marsh of gray to brown and black clays and
silts of high organic content. Saline marsh with gray, brown, and black clay and silt of moderate
organic content is found in the southern part. The cheniers themselves are white to light gray, fine
sand and shell fragments that form linear ridges, especially along the coast.
Loess
Loess is a windblown silt deposit and it is exposed in three principal areas in Louisiana: the
northern Mississippi Alluvial Plain, the eastern part of the Prairies, and the eastern Terraces. Loess
is the main component of the Southern Mississippi Valley Silty Uplands soil area (fig. 5), Loess is
tan to reddish brown massive silt with some clay and minor amounts of very fine sand. Soils
derived from loess are silt loams, somewhat poorly drained, and are typically wet in the southern
part of the State and seasonally wet in the north. They have generally low permeability.
RADIOMETRIC DATA
An aeroradiometric map of Louisiana (fig. 6) was compiled from spectral gamma-ray data
acquired during the U.S. Department of Energy National Uranium Resource Evaluation (NURE)
program (Duval and others, 1989). For the purposes of this report, low equivalent uranium (eU)
on the map 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 appears to be associated
with Coastal Plain sediments in the north-central and northwestern parts of the State and in the
coastal marshes that border the southern part of the State. Moderate eU is found throughout the
Mississippi Alluvial Plain and the coastal prairies and some parts of the Coastal Plain. Moderate
eU also appears to correlate well with the loess deposits found in the northern Floodplain and in
the southeastern part of the Prairies. Very small, local areas of high eU (fig. 6) are found in the
Prairies and the Mississippi Alluvial Plain. In the Prairies, these local areas of high eU seem to be
associated with distinct exposures of loess. Some of the moderate to high equivalent uranium may
be cultural and the result of uranium in phosphate fertilizers, a common occurrence in heavy
1V-11 Reprinted from USGS Open-File Report 93-292-F
-------
Figure 6. Aerial radiometric map of Louisiana (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.
-------
agricultural areas, or associated with cities, such as the radiometric anomaly over Alexandria.
Naturally-occurring radioactive materials in the form of pipe scale, which can be concentrated in
active and abandoned oil-industry pipe yards, may also be a local source of some of the anomalies.
INDOOR RADON DATA
Indoor radon data from 1314 homes sampled in the State/EPA Residential Radon Survey
conducted in Louisiana during the winter of 1990-91 are shown in figure 7 and presented in
Table 1. A map of parishes is included for reference (fig. 8). Data are shown on the maps only
for those parishes with 5 or more data values. The maximum value recorded in the survey was 8
pCi/L in Rapides Parish. The average for the State was 0.5 pCi/L and 0.8 percent of the homes
tested had indoor radon levels exceeding 4 pCi/L. The most notable parishes include West Carrol
and Union, which have indoor radon averages greater than 1 pCi/L. Seven parishes have
maximum indoor radon levels greater than 4 pCi/L; they are West Carrol, Union. Ouachita, Caddo,
Rapides, Lafayette, and St Tammany. The majority of these parishes are underlain by alluvium
and deltaic sediments. Overall, Louisiana ranks as the second lowest state in the State/EPA
Residential Radon Survey; only Hawaii had a lower state radon average.
GEOLOGIC RADON POTENTIAL
An examination of the aerial radioactivity map for Louisiana, its State geologic map, and
the indoor radon map allows us to make some observations about the geologic radon potential of
the State. Overall indoor radon is low; however, several parishes had individual homes with radon
levels greater than 4 pCi/L (fig. 7). Parishes with maximum indoor radon levels exceeding 4 pCi/L
are found in areas of the State underlain by coastal plain sediments, terrace deposits, and loess.
A study of the radon in the Coastal Plain of Texas, Tennessee, and Alabama (Peake and
Gundersen, 1989; Gundersen and others, 1991) suggests that glauconitic, phosphatic, and
carbonaceous sediments, and sedimentary rocks equivalent to those, in Louisiana can cause
elevated levels of indoor radon. Ground surveys of radioactivity and radon surveys of soil in the
above-mentioned study indicate that the upper Cretaceous through lower Tertiary Coastal Plain
sediments are sources of high radon (> 1000 pCi/L) and uranium. Soils from clays, shales, and
marls commonly have low permeability, so even though these sediments may be a possible source
of radon, slow permeability probably inhibits radon availability. Some of the glauconitic sands
and silts with moderate permeability may be the source of locally high indoor radon. Moderate
levels of radioactivity are found on the NURE radiometric map (fig. 6) in areas underlain by the
Eocene through lower Oiigocene-age Coastal Plain sediments, but do not follow formation
boundaries or strike belts in a systematic manner. The pattern of moderate radioactivity in this area
does appear to follow river drainages and according to R.P. McCulloh (Louisiana Geological
Survey, pers. comm., 1992) the aerial radioactivity pattern may be associated with northwest- and
northeast-trending joints and(or) faults which in turn may control drainage patterns. Part of the
pattern of low radioactivity in the Coastal Plain may be influenced by ground saturation with water.
This area receives high precipitation and contains an extensive system of bayous and rivers.
Besides damping gamma radioactivity, ground saturation can also inhibit radon movement.
Loess deposits in Tennessee were also examined by Peake and Gundersen (1989) and high
levels of radon were extracted from both dry and moist loess soils. On the radioactivity map of
Louisiana, the loess units can easily be traced, following the highest of the moderate uranium
FV-13 Reprinted from USGS Open-File Report 93-292-F
-------
Bsmt & 1 st Floor Radon
% > 4 pCi/L
"*"-"-"-"-"3 0 to 5
1 H 5 to 10
iB 11 to 15
8 I I Missing Data or < 5 Measurements
Bsmt & 1st Floor Radon
Average Concentration (pCi/L)
*.-.-.-.-.-1 o.O to 0.5
14 ES33 0.6 to 1.0
2 ¦ 1.1 to 1.5
8 I S Missing Data or < 5 Measurements
Figure 7. Screening indoor radon data from the EPA/State Residential Radon Survey of
Louisiana, 1990-91, for parishes with 5 or more measurements. Data are from 2-7 day charcoal
canister tests. Histograms in map legends show the number of parishes in each category. The
number of samples in each parish (see Table 1) may not be sufficient to statistically characterize
the radon levels of the parishes, but they do suggest general trends. Unequal category intervals
were chosen to provide reference to decision and action levels.
-------
TABLE 1. Screening indoor radon data from the EPA/State Residential Radon Survey of
Louisiana conducted during 1989-90. Data represent 2-7 day charcoal canister measurements
from the lowest level of each home tested.
NO. OF
GEOM.
STD.
PARISH
MEAS.
MEAN
MEAN
MEDIAN
DEV.
MAXIMUM
%>4 pCi/L
%>20 pCi/L
ACADIA
13
0.5
0.2
0.4
0.6
1.6
0
0
ALLEN
5
0.2
0.1
0.1
0.4
0.8
0
0
ASCENSION
23
0.4
0.3
0.4
0.5
1.5
0
0
ASSUMPTION
5
0.3
0.1
0.0
0.6
1.3
0
0
AVOYELLES
6
0.2
0.2
0.2
0-2
0.4
0
0
BEAUREGARD
8
0.4
0.3
0.4
0.6
1.7
0
0
BLENVTLLE
15
0.2
0.2
0.2
0.5
1.5
0
0
BOSSIER
35
0.6
0.3
0.4
0.5
1.8
0
0
CADDO
83
0.7
0.4
0.5
1.1
7.6
2
0
CALCASIEU
60
0.3
0.2
0.2
0.7
2.3
0
0
CALDWELL
13
0.3
0.2
0.1
0.5
1.6
0
0
CAMERON
2
0.3
0.2
0.3
0.5
0.6
0
0
CATAHOULA
7
0.3
0.2
0.5
0.5
0.8
0
0
CLAIBORNE
16
0.5
0.3
0.4
0.7
2.1
0
0
CONCORDIA
7
0.4
0.3
0.4
0.6
1.4
0
0
BE SOTO
6
0.4
0.3
0.5
0.5
1.1
0
0
EAST BATON ROUGE
170
0.4
0.3
0.4
0.5
2.4
0
0
EASTCARROLL
9
0.9
0.3
0.3
1.1
2.8
0
0
EAST FELICIANA
5
0.2
0.2
0.2
0.4
0.6
0
0
EVANGELINE
6
0.3
0.2
0.2
0.4
1.0
0
0
FRANKLIN
9
0.8
0.5
0.7
0.9
2.9
0
0
GRANT
9
0.6
0.5
0.4
0.6
1.5
0
0
IBERIA
12
0.4
0.2
0.4
0.6
1.5
0
0
IBERVILLE
7
0.5
0.3
0.3
0.6
1.3
0
0
JACKSON
2
0.8
0.7
0.8
0.2
0.9
0
0
JEFFERSON
104
0.3
0.2
0.3
0.5
2.4
0
0
JEFFERSON DAVIS
8
0.4
0.3
0.5
0.3
0.9
0
0
LA SALLE
10
0.3
0.2
0.2
0.7
2.0
0
0
LAFAYETTE
71
0.8
0.4
0.5
1.0
5.0
3
0
LAFOURCHE
12
0.6
0.4
0.5
0.8
2.4
0
0
LINCOLN
11
0.6
0.5
0.6
0.4
1.3
0
0
LIVINGSTON
29
0.5
0.3
0.3
0.7
3.0
0
0
MADISON
2
1.4
0.7
1.4
1.6
2.5
0
0
MOREHOUSE
12
0.8
0.4
0.8
0.9
2.7
0
0
NATCHITOCHES
27
0.6
0.3
0.4
0.6
2.3
0
0
ORLEANS
51
0.3
0.2
0.3
0.5
1.4
0
0
OUACHITA
44
0.6
0.3
0.4
0.8
4.1
2
0
PLAQUEMINES
3
0.4
0.2
0.0
0.9
1.4
0
0
POINTE COUPEE
6
0.1
0.1
0.1
0.1
0.3
0
0
RAPIDES
47
0.6
0.3
0.5
1.2
8.0
2
0
RED RIVER
4
0.8
0.7
0.9
0.4
1.3
0
0
-------
TABLE 1 (continued). Screening indoor radon data for Louisiana.
PARISH
NO. OF
MEAS.
MEAN
GEOM.
MEAN
MEDIAN
STD.
DEV.
MAXIMUM
%>4 pCi/L
%>20 pCi/L
RICHLAND
8
0.6
0.3
0.3
0.8
2.4
0
0
SABINE
8
0.2
0.1
0.1
0.3
0.7
0
0
ST. BERNARD
18
0.2
0.2
0.3
0.3
0.7
0
0
ST. CHARLES
15
0.2
0.2
0.2
0.3
0.7
0
0
ST. JAMES
12
0.4
0.3
0.4
0.4
1.1
0
0
ST. JOHN
11
0.2
0.2
0.3
0.5
0.9
0
0
ST. LANDRY
28
0.3
0.2
0.3
0.5
1.5
0
0
ST. MARTIN
8
0.3
0.2
0.3
0.3
0.8
0
0
ST. MARY
17
0.2
0.2
0.2
0.3
1.0
0
0
ST. TAMMANY
73
0.5
0.3
0.4
1.0
5.2
3
0
TANGIPAHOA
18
0.3
0.2
0.1
0.6
2.2
0
0
TENSAS
6
0.1
0.1
0.0
0.4
0.8
0
0
TERREBONNE
35
0.4
0.3
0.5
0.4
1.5
0
0
UNION
12
1.1
0.6
0.6
1.4
4.5
8
0
VERMILION
13
0.5
0.3
0.4
0.9
3.0
0
0
VERNON
15
0.3
0.2
0.3
0.4
1.2
0
0
WASHINGTON
7
0.7
0.5
0.7
0.4
1.0
0
0
WEBSTER
14
0.4
0.3
0.2
0.5
1.1
0
0
WEST BATON ROUGE
7
0.6
0.4
0.6
0.3
0.9
0
0
WEST CARROLL
7
1.4
0.6
0.5
1.9
5.3
14
0
WEST FELICIANA
3
1.5
1.4
1.7
0.6
1.9
0
0
WINN
5
0.3
0.2
0.3
0.4
0.7
0
0
-------
Figure 8. Parishes of Louisiana (Facts on File, 1984).
-------
anomalies in the northern portion of the Mississippi Floodplain. On the National Radiometric Map
of the United States (Duval and others. 1989) loess throughout the United States is associated with
high radiometric anomalies. Radiometric anomalies in the southeastern part of the Prairies also
seem to be associated with the exposure of loess as mapped on the Louisiana State Geologic Map
(Snead and McCulloh, 1984) in Iberia, Lafayette, eastern Acadia, and northern Vermilion
Parishes, Loess tends to have low permeability, so even though these sediments may be a possible
source of high radon, the permeability may inhibit radon availability.
The youngest Coastal Plain sediments, particularly Oligocene and younger, have
decreasing amounts of glauconite and phosphate and become increasingly siliceous and less likely
to be significant sources of radon. However, the possibility of roll-front uranium deposits in
sedimentary rocks and sediments of Oligocene-Miocene-age. analogous to the roll-front uranium
deposits in Texas, has been proposed by McCulloh (1982). McCulloh (1982) also reports surface
gamma anomalies from the lower Catahoula sandstone measured by private industry. Thus far,
uranium deposits have not been reported.
The fluvial and deltaic sediments in the Mississippi Alluvial Plain are low in geologic radon
potential. They are not likely to have elevated amounts of uranium and the saturated to seasonally
wet conditions of the soils, as well as the high water tables, do not facilitate radon availability.
SUMMARY
For the purposes of this assessment, Louisiana has been divided into six geologic radon
potential areas based on physiography and geology. Each area has been assigned a Radon Index
(RI) and a Confidence Index (CI) score (Table 2). The RJ is a semi-quantitative measure of radon
potential based on geology, soils, radioactivity, architecture, and indoor radon. The CI is a
measure of the relative confidence of the RI assessment based on the quality and quantity of the
data used to assess geologic radon potential (see the Introduction chapter to this regional booklet
for more information on the methods and data used).
Examination of the indoor radon and geologic data reveals that Louisiana is generally an
area of low radon potential. The climate, soil, and lifestyle of the inhabitants of Louisiana have
influenced building construction styles and building ventilation which, in general, do not allow
high concentrations of radon to accumulate. Many homes in Louisiana are built on piers or are
slab-on-grade. Glauconitic, carbonaceous, and phosphatic sediments of the Coastal Plain,
particularly the Cretaceous and lower Tertiary-age geologic units located in the northern portion of
the State, have some geologic potential to produce radon. Other areas to consider as possible
sources of radon include Oligocene-Miocene age units that may host roll-front uranium deposits,
and loess deposits. Several areas of moderate to high equivalent uranium occur in the Mississippi
Alluvial Plain and the Prairies, and appear to be associated with loess.
This is a generalized assessment of the State's geologic radon potential and there is no
substitute for having a home tested. The conclusions about radon potential presented in this report
cannot be applied to individual homes or building sites. Indoor radon levels, both high and low,
can be quite localized, and within any radon potential area there will likely be areas with higher or
lower radon potential that assigned to the area as a whole. Any local decisions about radon should
not be made without consulting all available local data. For additional information on radon and
how to test, contact your State radon program or EPA regional office. More detailed information
on state or local geology may be obtained from the state geological survey. Addresses and phone
numbers for these agencies are listed in chapter 1 of this booklet.
IV-18 Reprinted from USGS Open-File Report 93-292-F
-------
TABLE 2. RI and CI for major physiographic and geologic areas of Louisiana.
Cheniers Delta Floodplain
FACTOR
RI
CI
RJ
CI
RI
CI
INDOOR RADON
1
2
1
2
1
2
RADIOACTIVITY
1
3
2
3
2
3
GEOLOGY
I
2
1
2
1
2
SOIL PERM.
2
2
I
2
2
2
ARCHITECTURE
I
-
1
-
1
-
GFE POINTS
0
-
0
-
0
-
TOTAL
6
9
6
9
7
9
LOW
MOD
LOW
MOD
LOW
MOD
Old Uplands
Prairies
Tenaces
FACTOR
RJ
CI
RI
CI
RI
CI
INDOOR RADON
1
2
1
2
I
2
RADIOACTIVITY
1
3
2
3
*)
3
GEOLOGY
2
2
1
2
0
4b
2
SOIL PERM.
2
2
2
2
2
2
ARCHITECTURE
1
-
1
-
1
-
GFE POINTS
0
-
0
•
0
-
TOTAL
7
9
7
9
8
9
LOW MOD LOW MOD LOW MOD
RADON INDEX SCORING:
Radon potential category
-Point ranee
LOW 3-8 points
MODERATE/VARIABLE 9-11 points
HIGH > 11 points
Probable screening indoor
radon average for area
< 2 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
2-4 pCi/L
> 4 pCi/L
Possible range of points = 4 to 12
IV-19 Reprinted from U8GS Open-File Report 93-292-F
-------
REFERENCES USED IN THIS REPORT
AND GENERAL REFERENCES PERTAINING TO RADON IN LOUISIANA
Demas, C.R., Curwick, P.B. and Demcheck, D.KL, 1989. The use of radon-222 as a tracer of
transport across the bed sediment-water interface in Prien Lake, Louisiana, in G.E. Mallard
(ed), U.S. Geological Survey Toxic Substances Hydrology Program; proceedings of the
technical meeting, Phoenix. Arizona. September 26-30, 1988: Proceedings of U. S.
Geological Survey Toxic Substances Hydrology Program, Technical Meeting. Phoenix,
AZ, Sept. 26-30, 1988, Water-Resources Investigations, p. 291-300.
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, 1980, 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, 1980, Aerial gamma ray and magnetic survey, Jackson quadrangle,
Mississippi and Louisiana: U.S. Department of Energy National Uranium Resources
Evaluation Report GJBX-153(80).
EG&G Geometries, 1980, Aerial gamma ray and magnetic survey, Alexandria quadrangle.
Louisiana and Texas: U.S. Department of Energy National Uranium Resources Evaluation
Report GJBX-152(80).
Facts on File, Inc., 1984, State Maps on File.
Gabelman, J.W„ 1972, Radon Emanometry of Starks Salt Dome, Louisiana [abstr.]: EOS ,
v. 53, p. 530.
Gundersen, L.C.S., Peake, R.T., Latske, 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 Proceedings of the 1990 Symposium on Radon and Radon
Reduction Technology, 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.
King. P.B., and Beikman, H.M., 1974, Geologic map of the United States: U.S. Geological
Survey, scale 1:2,500,000.
Kraemer, T.F., 1986, Radon in unconventional natural gas from Gulf Coast geopressured-
geothermal reservoirs: Environmental Science & Technology, v. 20, p. 939-942.
McCulloh. R. P., 1982, A preliminary assessment of Louisiana's uranium potential: Proceedings
of the Louisiana Academy of Sciences, v. 45, p. 156-172.
Newton, M. B., Jr., 1972, Atlas of Louisiana: Louisiana State University, School of Geoscience,
Miscellaneous Publication 72-1, 196 p.
IV-20 Reprinted from USGS Open-File Report 93-292-F
-------
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.
Richmond, G.M., Weide, D.L.. and Moore, D.W. (eds.), 1990, Quaternary Geologic Map of the
White Lake 4°x6° Quadrangle, United States: Quaternary Geologic Atlas of the United
States, U.S. Geological Survey Miscellaneous Investigations Map 1-1420 (NH-15), scale
1:100,000.
Scott, M.R., Rotter, R.J. 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.
Snead, J. I., and McCulloh, R.P., 1984, Geologic Map of Louisiana: Louisiana Geological
Survey, Williams and Heintz Map Corp., one plate with text, scale 1:500,000.
Soil Conservation Service, 1987, Principal kinds of Soils: National Atlas of the United States of
America, U.S. Geological Survey, 38077-BE-NA-07M-00, scale 1:7,500,000.
Troutman, A., 1956, The oil and gas fields of southeast Louisiana: Five Star Oil Company Report.
342 p.
IV-21 Reprinted from USGS Open-File Report 93-292-F
-------
EPA's Map of Radon Zones
The USGS' Geologic Radon Province Map is the technical foundation for EPA's Map
of Radon Zones. The Geologic Radon Province Map defines the radon potential for
approximately 360 geologic provinces EPA has adapted this information to fit a county
boundary map in order to produce the Map of Radon Zones.
The Map of Radon Zones is based on the same range of predicted screening levels of
indoor radon as USGS" Geologic Radon Province Map. EPA defines the three zones as
follows: Zone One areas have an average predicted indoor radon screening potential greater
than 4 pCi/L. Zone Two areas are predicted to have an average indoor radon screening
potential between 2 pCi/L and 4 pCi/L. Zone Three areas are predicted to have an average
indoor radon screening potential less than 2 pCi/L.
Since the geologic province boundaries cross state and county boundaries, a strict
translation of counties from the Geologic Radon Province Map to the Map of Radon Zones
was not possible. For counties that have variable radon potential (i.e., are located in two or
more provinces of different rankings), the counties were assigned to a zone based on the
predicted radon potential of the province in which most of its area lies. (See Part I for more
details )
LOUISIANA MAP OF RADON ZONES
The Louisiana Map of Radon Zones and its supporting documentation (Part IV of this
report) have received extensive review by Louisiana geologists and radon program experts.
The map for Louisiana generally reflects current State knowledge about radon for its counties.
Some States have been able to conduct radon investigations in areas smaller than geologic
provinces and counties, so it is important to consult locally available data.
Although the information provided in Part IV of this report -- the State chapter entitled
"Preliminary Geologic Radon Potential Assessment of Louisiana" -- 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 6 EPA office or the
Louisiana radon program for information on testing and fixing homes. Telephone numbers
and addresses can be found in Part II of this report.
V-l
-------
LOUISIANA - EFA Map of Radon Zones
The purpose ol this map Is to assist National. State and local organizations
to target their resources and to implement radon-resistant build >ng cod«s
This map in not intended !o datormine if a hooe in a given lone shouid be tested
for radon. Homos with olovatod levels of radon have been found in ail Itiree
zones. A// homos sftooM t>9 fesJed, ngtrdloss of zortm designation.
¦ »t rom*
Mmm ImuPM
AUJtt
i *w«4
I mtt I ~ newt*,,
A
'X L,w*i*nt3
"V KIWUD '
\ V
>iaowA
tMES >
v fiWiBOWSi \; ; ¦
IMPORTANT: Consutt the publication etitilkxJ 'Preliminary Geologic ftadon
Potential Assessment ol Loussisna* before using this map. This
document contains information of! ?®dort potential variations within counties
EPA also (recommends that this map be Rijpplemf»ntf>d with any available
loca! data in order to further understand a/id predic! the radon potential ol n
specrfic area
Zone 3
------- |