United States
Environmental Protection
Agency
Air and Energy Environmental
Research Laboratory
Research Triangle Park NC 27711
April 1991
Research and Development
<&EPA The 1991 International
Symposium on Radon
and Radon Reduction
Technology:
Volume 5. Preprints
Session IX: Radon Occurrence in
the Natural Environment
Session X: Radon in Schools
and Large Buildings
April 2-5, 1991
Adam's Mark Hotel
Philadelphia, Pennsylvania
-------
The 1991 International
Symposium on Radon and
Radon Reduction Technology
"A New Decade of Progress"
April 2-5,1991
Adam's Mark Hotel
Philadelphia, Pennsylvania
Sponsored by:
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
and
U. S. Environmental Protection Agency
Office of Radiation Programs
and
Conference of Radiation Control Program Directors, Inc.
(CRCPD)
Printed on Recycled Paper
-------
The 1991 International Symposium on Radon
and Radon Reduction Technology
Opening Session
Opening Remarks Symposium Co-Chairpersons
Introduction Charles M. Hardin, CRCPD, Inc.
Welcome Edwin B. Erickson,
EPA Region III Administrator
An Overview of the NAS Report on Radon Dosimetry Jonathan Samet
New Mexico Tumor Registry
iii
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The 1991 International Symposium on Radon
and Radon Reduction Technology
Table of Contents
Session I: Government Programs and Policies Relating to Radon
The Need for Coordinated International Assessment of the
Radon Problem - the IAEA Approach
Friedrich Steinhausler, International Atomic Energy Agency, Austria 1-1
The European Research Program and the Commission of
European Communities
Jaak Sinnaeve, Belgium
United Kingdom Programs
Michael O'Riordan, National Radiological Protection Board, UK I-3
The U.S. DOE Radon Research Program: A Different Viewpoint
Susan L. Rose, Office of Energy Research, U. S. DOE I-4
U.S. EPA Future Directions
Margo Oge, U.S. EPA, Office of Radiation Programs I.5
Session I Posters
The State Indoor Radon Grants Program: Analysis of Results
After the First Year of Funding
Sharon Saile, U.S. EPA, Office of Radiation Programs IP-1
EPA Radon Policy and Its Effects on the Private Sector
David Saum and Marc Messing, INFILTEC
Evaluation of EPA's National Radon Contractor Proficiency Program
and Network of Regional Radon Training Centers
G. Lee Salmon, U.S. EPA, Office of Radiation Programs IP_3
State Certification Guidance
John Hoornbeek, U.S. EPA, Office of Radiation Programs IP-4
The U.S. EPA Radon Measurement Proficiency (RMP) Program
Jed Harrison, U.S. EPA, Office of Radiation Programs ip.5
iv
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Session II: Radon-Related Health Studies
Residential Radon Exposure and Lung Cancer in Women
Goran Pershagen, Karolinska Institute, Sweden 11-1
An Evaluation of Ecologic Studies of Indoor Radon and Lung Cancer
Christine Stidley, University of New Mexico II-2
Comparison of Radon Risk Estimates
Richard Hornung, NIOSH II-3
Lung Cancer in Rats Exposed to Radon/Radon Progeny
F. T. Cross and G. E. Dagle, Pacific Northwest Laboratory II-4
Startling Radon Risk Comparisons
JoAnne D. Martin, DMA-RADTECH, Inc II-5
Estimated Levels of Radon from Absorbed Polonium-210 in Glass
Hans Vanmarcke, Belgium II-6
Expanded and Upgraded Tests of the Linear-No Threshold Theory
for Radon-Induced Lung Cancer
Bernard L. Cohen, University of Pittsburgh II-7
Session II Panel: Risk Communication
Apathy vs. Hysteria, Science vs. Drama: What Works in Radon
Risk Communication
Peter Sandman, Rutgers University II-8
American Lung Association's Radon Public Information Program
Leyla Erk McCurdy, American Lung Association II-9
Ad Council Radon Campaign Evaluation
Mark Dickson and Dennis Wagner, U.S. EPA, Office of
Radiation Programs 11-10
Developing a Community Radon Outreach Program: A Model for
Statewide Implementation
M. Jeana Phelps, Kentucky Cabinet for Human Resources 11-11
V
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Session II Posters
Occupational Safety During Radon Mitigation: Field Experience and
Survey Monitoring Results
Jean-Claude F. Dehmel, S. Cohen & Associates; Peter Nowlan,
R. F. Simon Company; Eugene Fisher, U.S. EPA,
Office of Radiation Programs UP„1
Consumer Cost/Benefit Analysis of Radon Reductions in 146 Homes
Kenneth D. Wiggers, American Radon Services, Ltd IIP-2
The Effect of Passive Cigarette Smoke on Working Level
Exposures in Homes
Raymond H. Johnson, Jr. and Randolph S. Kline, Key Technology, Inc.;
Eric Geigerand Augustine Rosario, Jr., Radon QC IIP-3
Session III: Measurement Methods
Quality Assurance of Radon and Radon Decay Product Measurements
During Controlled Exposures
Douglas J. Van Cleef, U.S. EPA, Office of Radiation Programs 111-1
Current Status of Glass as a Retrospective Radon Monitor
Richard Lively, MN Geological Survey, and Daniel Steck,
St. John's University
Soil Gas Measurement Technologies
Harry E. Rector, GEOMET Technologies, Inc IH-3
Results From a Pilot Study to Compare Residential Radon Concentrations
with Occupant Exposures Using Personal Monitoring
B. R. Litt, New Jersey Department of Environmental Protection,
J. M. Waldman, UMDNJ, and N. H. Harley and P. Chittaporn,
New York University Medical Center HI.4
Rapid Determination of the Radon Profile in a Structure by
Measuring Ions in the Ambient Atmosphere
W. G. Buckman and H. B. Steen III, Western Kentucky University ni-5
Intercomparison of Activity Size Distribution Measurements with
Manual and Automated Diffusion Batteries - Field Test
P. K. Hopke and P. Wasiolek, Clarkson University; E. O. Knutson,
K. W. Tu, and C. Gogolak, U. S. DOE; A. Cavallo and K. Gadsby,
Princeton University; D. Van Cleef, NAREL III-6
vi
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Influence of Radon Concentrations on the Relationship Among Radon
Measurements Within Dwellings
Judith B. Klotz, NJ State Department of Health 111-7
The Use of Indoor Radon Measurements and Geological Data in Assessing
the Radon Risk of Soil and Rock in Construction Sites in Tampere
Anne Voutilainen and Nona Makelainen, Finnish Centre for
Radiation and Nuclear Safety 111-8
Session III Panel: Detection of Radon Measurement Tampering
Policy and Technical Considerations for the Development of EPA
Guidance on Radon and Real Estate
Lawrence Pratt, U. S. EPA, Office of Radiation Programs 111-9
State Property Transfer Laws Now Include Radon Gas Disclosure
Michael A. Nardi, The Nardi Group 111-10
Update of AARST Real Estate Testing Guidelines
William P. Brodhead, WPB Enterprises 111-11
Real Estate Transaction Radon Testing Interference
Dean Ritter, ABE Testing 111-12
How to Determine if Radon Measurement Firms are Providing
Accurate Readings
Herbert C. Roy and Mohammed Rahman, New Jersey Department
of Environmental Protection 111-13
Grab Sampling as a Method of Discovering Test Interference
Marvin Goldstein, Building Inspection Service, Inc 111-14
Exploring Software Device Management Routines that Ensure the Overall
Quality of Continuous Working Level and Continuous Radon Monitor
Performance in a Field Environment
Richard Tucker, Gemini Research, and Rick Holland,
Radonics, Inc 111-15
Use of Grab Samples as a Quality Assurance Tool to Enhance Overall
Radon Measurement Accuracy and Reproducibility
Brian Fimian, Radonics, Inc., and Richard Tucker, Gemini Research 111-16
vii
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Session III Panel: Short-Term/Long-Term Measurement
Predicting Long-Term Indoor Radon Concentrations from Short-Term
Measurements: Evaluation of a Method Involving Temperature Correction
T. Agami Reddy, A. Cavallo, K. Gadsby, and R. Socolow,
Princeton University 111-17
Correlation Between Short-Term and Long-Term Indoor Radon
Concentrations in Florida Houses
Susan E. McDonough, Southern Research Institute 111-18
Relationship Between Two-day Screening Measurements of Radon-222
and Annual Living Area Averages in Basement and
Nonbasement Houses
S. B. White, N. F. Rodman, and B. V. Alexamder, Research Triangle
Institute; J. Phillips and F. Marcinowski, U. S. EPA, Office of
Radiation Programs 111-19
The Use of Multiple Short-Term Measurements to Predict Annual Average
Radon Concentrations
Frank Marcinowski, U. S. EPA, Office of Radiation Programs III-20
Session III Posters
Characterization of Structures Using Simultaneous Single Source
Continuous Working Level and Continuous Radon Gas Measurements
Brian Fimian and John E. McGreevy, Radonics, Inc IIIP-1
Pennsylvania Department of Environmental Resources Radon in Water
Measurement Intercomparison
Douglas Heim and Carl Granlund, Pennsylvania Department of
Environmental Resources IIIP-2
A Field Comparison of Several Types of Radon Measurement Devices
Elhannan L. Keller, Trenton State College IIIP-3
Radon and Water Vapor Co-Adsorption on Solid Adsorbents
Neguib M. Hassan, Tushar K. Ghosh, Sudarshan K. Loyalka,
and Anthony L. Hines, University of Missouri-Columbia, and
Davor Novosel, Gas Research Institute IIIP-4
Calibration of Modified Electret Ion Chamber for Passive Measurement
of Radon-222 (Thoron) in Air
P. Kotrappa and J. C. Dempsey, Rad Eiec, Inc IIIP-5
viii
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Unit Ventilator Operation and Radon Concentrations in a
Pennsylvania School
William P. Brodhead, WPB Enterprises IIIP-6
Session IV: Radon Reduction Methods
Causes of Elevated Post-Mitigation Radon Concentrations in Basement
Houses Having Extremely High Pre-Mitigation Levels
D. Bruce Henschel, AEERL; Arthur G. Scott, AMERICAN
ATCON, Inc IV-1
A Measurement and Visual Inspection Critique to Evaluate the
Quality of Sub-Slab Ventilation Systems
Richard W. Tucker, Gemini Research, Inc.; Keith S. Fimian,
Radonics, Inc IV-2
Correlation of Diagnostic Data to Mitigation System Design and
Performance as Related to Soil Pressure Manipulation
Ronald F. Simon, R. F. Simon Company IV-3
Pressure Field Extension Using a Pressure Washer
William P. Brodhead, WPB Enterprises IV-4
A Variable and Discontinuous Subslab Ventilation System and Its
Impact on Radon Mitigation
Willy V. Abeele, New Mexico Environmental Improvement Division IV-5
Natural Basement Ventilation as a Radon Mitigation Technique
A. Cavallo, K. Gadsby, and T.A. Reddy, Princeton University IV-6
Attic Pressurization - A Radon Mitigation Technique for Residential Structures
Myron R. Edelkind, Southern Mechanical IV-7
Section IV Posters
Radon Mitigation Failure Modes
William M. Yeager, Research Triangle Institute; D. Bruce Harris, AEERL;
Terry Brennan and Mike Clarkin, Camroden Associates, Inc IVP-1
Mitigation by Sub-SlabDepressurization Under Structures Founded on
Relatively Impermeable Sand
Donald A. Crawshaw and Geoffrey K. Crawshaw, Pelican
Environmental Corporation IVP-2
ix
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A Laboratory Test of the Effects of Various Rain Caps on Sub-Slab
Depressurization Systems
Mike Clarkin, Camroden Associates, Inc IVP-3
Analysis of the Performance of a Radon Mitigation System Based on
Charcoal Beds
P. Wasiolek, N. Montassier, P. K. Hopke, Clarkson University;
R. Abrams, RAd Systems, Inc IVP-4
Control of Radon Releases in Indoor Commercial Water Treatment
D. Bruce Harris and A. B. Craig, AEERL IVP-5
Session V: Radon Entry Dynamics
A Modeling Examination of Parameters Affecting Radon and Soil Gas
Entry Into Florida-Style Slab-on-Grade Houses
G. G. Sextro, Lawrence Berkeley Laboratory V-1
Effect of Winds in Reducing Sub-Slab Radon Concentrations Under
Houses Laid Over Gravel Beds
P. C. Owczarski, D. J. Holford, K. W. Burk, H. D. Freeman, and
G. W. Gee, Pacific Northwest Laboratory V-2
Radon Entry Into Dwellings Through Concrete Floors
K. K. Nielson and V. C. Rogers, Rogers and Associates
Engineering Corporation V-3
Radon Dynamics in Swedish Dwellings: A Status Report
Lynn M. Hubbard, National Institute of Radiation Protection, Sweden V-4
Soil Gas and Radon Entry Potentials for Slab-on-Grade Houses
Bradley H. Turk, New Mexico; David Grumm, Yanxia Li, and Stephen
D. Schery, New Mexico Institute of Mining and Technology;
D. Bruce Henschel, AEERL V-5
Direct Measurement of the Dependence of Radon Flux Through
Structure Boundaries on Differential Pressure
D. T. Kendrick and G. Harold Langner, Jr., U.S. DOE/Chem-Nuclear
Geotech, Inc V-6
Radon Resistance Under Pressure
William F. McKelvey, Versar, Inc.; Jay W. Davis, Versar A/E, Inc V-7
Recommendations to Reduce Soil Gas Radon Entry Based on an
Evaluation of Air Permeability of Concrete Blocks and Coatings
J. S. Ruppersberger, U. S. EPA, Office of Research and Development V-8
X
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Session V Posters
A Simple Model for Describing Radon Migration and Entry Into Houses
Ronald B. Mosley, AEERL VP-1
Effect of Non-Darcy Flow on the Operation of Sub-Slab
Depressurization Systems
R. G. Sextro, Lawrence Berkeley Laboratory VP-2
Effects of Humidity and Rainfall on Radon Levels in a Residential Dwelling
Albert Montague and William E. Belanger, U. S. EPA;
Francis J. Haughey, Rutgers University VP-3
Session VI: Radon Surveys
Factors Associated with Home Radon Concentrations in Illinois
Thomas J. Bierma and Jennifer O'Neill, Illinois State University VI-1
Radon in Federal Buildings
Michael Boyd, U. S. EPA, Office of Radiation Programs VI-2
Radon in Switzerland
H. Surbeck and H. Volkle, University Perolles; W. Zeller, Federal
Office of Public Health VI-3
A Cross-Sectional Survey of Indoor Radon Concentrations in 966 Housing
Units at the Canadian Forces Base in Winnipeg, Manitoba
D. A. Figley and J. T. Makohon, Saskatchewan Research Council VI-4
Radon Studies in British Columbia, Canada
D. R. Morley and B. G. Phillips, Ministry of Health; M. M. Ghomshei,
Orchard Geothermal Inc.; C. Van Netten, The University of
British Columbia VI-5
The State of Maine Schools Radon Project: Results
L. Grodzins, NITON Corporation; T. Bradstreet, Division of Safety
and Environmental Services, Maine; E. Moreau, Department of
Human Services, Maine VI-6
Radon in Belgium: The Actual Situation and Plans for the Future
A. Poffijn, State University of Gent VI-7
A Radiological Study of the Greek Radon Spas
P. Kritidis, Institute of Nuclear Technology - Radiation Protection VI-8
xi
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Session VI Posters
A Cumulative Examination of the State/EPA Radon Survey
Jeffrey Phillips, U. S. EPA, Office of Radiation Programs VIP-1
Seasonal Variation in Two-Day Screening Measurements of Radon-222
Nat F. Rodman, Barbara V. Alexander, and S. B. White, Research
Triangle Institute; Jeffrey Phillips and Frank Marcinowski,
U. S. EPA, Office of Radiations Programs VIP-2
The State of Maine School Radon Project: Protocols and Procedures of
the Testing Program
Lee Grodzins and Ethel G. Romm, NITON Corporation;
Henry E. Warren, Bureau of Public Improvement, Maine VIP-3
Results of the Nationwide Screening for Radon in DOE Buildings
Mark D. Pearson, D. T. Kendrick, and G. H. Langner, Jr., U. S. DOE/
Chem-Nuclear Geotech, Inc VIP-4
Session VII: State Programs and Policies Relating to Radon
Washington State's Innovative Grant: Community Support Radon Action
Team for Schools
Patricia A. McLachlan, Department of Health, Washington VII-1
Kentucky Innovative Grant: Radon in Schools Telecommunication Project
M. Jeana Phelps, Kentucky Cabinet for Human Resources;
Carolyn Rude-Parkins, University of Louisville VII-2
Regulation of Radon Professionals by States: the Connecticut Experience
and Policy Issues
Alan J. Siniscalchi, Zygmunt F. Dembek, Nicholas Macelletti, Laurie
Gokey, and Paul Schur, Connecticut Department of Health Services;
Susan Nichols, Connecticut Department of Consumer Protection;
Jessie Stratton, State Representative, Connecticut
General Assembly VII-3
New Jersey's Program - A Three-tiered Approach to Radon
Jill A. Lapoti, New Jersey Department of Environmental Protection VII-4
Session VII Posters
Quality Assurance - The Key to Successful Radon Programs in the 1990s
Raymond H. Johnson, Jr., Key Technology, Inc VIIP-1
xii
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Radon in Illinois: A Status Report
Richard Allen and Melanie Hamel-Caspary, Illinois Department
of Nuclear Safety VIIP-2
Session VIII: Radon Prevention in New Construction
Long-Term Monitoring of the Effect of Soil and Construction Type on
Radon Mitigation Systems in New Houses
D. B. Harris, U. S. EPA, Office of Research and Development VIII-1
A Comparison of Indoor Radon Concentrations Between Preconstruction
and Post-Construction Mitigated Single Family Dwellings
James F. Burkhart, University of Colorado at Colorado Springs;
Douglas L. Kladder, Residential Service Network, Inc VIII-2
Radon Reduction in New Construction: Double-Barrier Approach
C. Kunz, New York State Department of Health VIII-3
Radon Control - Towards a Systems Approach
R. M. Nuess and R. J. Prill, Washington State Energy Office VIII -4
Mini Fan for SSD Radon Mitigation
David Saum, INFILTEC VIII-5
Building Radon Mitigation into Inaccessible Crawlspace New
Residential Construction
D. Bruce Harris and A. B. Craig, AEERL; Jerry Haynes, Hunt
Building Corporation VIII-6
The Effect of Subslab Aggregate Size on Pressure Field Extension
K. J. Gadsby, T. Agami Reddy, D. F. Anderson, and R. Gafgen,
Princeton University; A. B. Craig, AEERL VIII-7
Session VIII Posters
Radon Prevention in Residential New Construction: Passive Designs
That Work
C. Martin Grisham, National Radon Consulting Group VIIIP-1
Preliminary Results of HVAC System Modifications to Control Indoor
Radon Concentrations
Terry Brennan and Michael Clarkin, Camroden Associates;
Timothy M. Dyess, AEERL; William Brodhead, Buffalo Homes VIIIP-2
xiii
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Correlation of Soil Radon Availability Number with Indoor Radon and
Geology in Virginia and Maryland
Stephen T. Hall, Radon Control Professionals, Inc VIIIP-3
Session IX: Radon Occurrence in the Natural Environment
Combining Mitigation and Geology: Indoor Radon Reduction by
Accessing the Source
Stephen T. Hall, Radon Control Professionals, Inc ix-1
A Comparison of Radon Results to Geologic Formations for the
State of Kentucky
David McFarland, Merit Environmental Services
Geologic Radon Potential of the United States
Linda Gunderson, U. S. Geological Survey
Technological Enhancement of Radon Daughter Exposures Due to
Non-nuclear Energy Activities
Jadranka Kovac, University of Zagreb, Yugoslavia
A Site Study of Soil Characteristics and Soil Gas Radon
Richard Lively, Minnesota Geological Survey; Daniel Steck,
St. John's University IX-5
Geological Parameters in Radon Risk Assessment - A Case History
of Deliberate Exploration
Donald Carlisle and Haydar Azzouz, University of California
at Los Angeles IX-6
Session IX Posters
Geologic Evaluation of Radon Availability in New Mexico: A Progress Report
Virginia T. McLemore and John W. Hawley, New Mexico Bureau of Mines
and Mineral Resources; Ralph A. Manc^go, New Mexico
Environmental Improvement Division
Paleozoic Granites in the Southeastern United States as Sources
of Indoor Radon
Stephen T. Hall, Radon Control Professionals, Inc IXP-2
Comparison of Long-Term Radon Detectors an<^ Their Correlations with
Bedrock Sources and Fracturing
Darioush T. Gharemani, Radon Survey Systems, Inc IXP-3
jciv
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Geologic Assessment of Radon-222 in McLennan County, Texas
Mary L. Podsednik, Law Engineering, Inc IXP-4
Radon Emanation from Fractal Surfaces
Thomas M. Semkow, Pravin P. Parekh, and Charles O. Kunz, New York
State Department of Health and State University of New York
at Albany; Charles D. Schwenker, New York State Department
of Health IXP-5
National Ambient Radon Study
Richard Hopper, U. S. EPA, Office of Radiation Programs IXP-6
Session X: Radon in Schools and Large Buildings
The Results of EPA's School Protocol Development Study
Anita L. Schmidt, U. S. EPA, Office of Radiation Programs X-1
Diagnostic Evaluations of Twenty-six U. S. School - EPA's School
Evaluation Program
Gene Fisher, U. S. EPA, Office of Radiation Programs X-2
Extended Heating, Ventilating and Air Conditioning Diagnostics in
Schools in Maine
Terry Brennan, Camroden Associates X-3
Mitigation Diagnostics: The Need for Understanding Both HVAC and
Geologic Effects in Schools
Stephen T. Hall, Radon Control Professionals, Inc X-4
A Comparison of Radon Mitigation Options for Crawl Space School Buildings
Bobby E. Pyle, Southern Research Institute; Kelly W. Leovic, AEERL X-5
HVAC System Complications and Controls for Radon Reduction in
School Buildings
Kelly W. Leovic, D. Bruce Harris, and Timothy M. Dyess, AEERL;
Bobby E. Pyle, Sourthe Research Institute; Tom Borak, Western
Radon Regional Training Center; David W. Saum, INFILTEC X-6
Radon Diagnosis and Mitigation of a Large Commercial Office Building
David Saum, INFILTEC X-7
New School Radon Abatement Systems
Ronald F. Simon, R. F. Simon Company X-8
Design of Radon-Resistant and Easy-to-Mitigate New School Buildings
Alfred B. Craig, Kelly W. Leovic, and D. Bruce Harris, AEERL X-9
XV
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Session X Posters
Design and Application of Active Soil Depressurization (ASD) Systems
in School Buildings
Kelly W. Leovic, A. B. Craig, and D. Bruce Harris, AEERL; Bobby E.
Pyle, Southern Research Institute; Kenneth Webb, Bowling Green
(KY) Public Schools XP-1
Radon in Large Buildings: Pre-Construction Soil Radon Surveys
Ralph A. Llewellyn, University of Central Florida XP-2
Radon Measurements in North Dakota Schools
Thomas H. Morth, Arlen L. Jacobson, James E. Killingbeck,
Terry D. Lindsey, and Allen L. Johnson, North Dakota State
Department of Health and Consolidated Laboratories XP-3
Major Renovation of Public Schools that Includes Radon Prevention:
A case Study of Approach, System Design and Installation, and
Problems Encountered
Thomas Meehan XP-4
The State of Maine School Radon Project: The Design Study
Henry E. Warren, Maine Bureau of Public Improvement;
Ethel G. Romm, NITON Corporation XP-5
Design for the National Schools Survey
Lisa Ratcliff, U. S. EPA, Office of Radiation Programs XP-6
xvi
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Session IX:
Radon Occurrence in the Natural Environment
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IX-1
combtntno MTTTfiftTiON * nFni.nny:
INDOOR radon REDUCTION BY ACCESSING THE SOURCE
by: Stephen T. Hall
Radon Control Professionals, Inc.
Reston, Virginia 22094
ABSTRACT
Soil radon testing has shown that radon sources are concentrated
in narrow linear areas congruent with local geology in the Eastern
Piedmont, which should also hold true in any folded mountain belt
region with heterogenous geology.
In existing buildings, if mlcrornanometer tents indicate poor
communication in the sub-slab environment, soil radon concentration
gradients can be mapped with instantaneous sub-slab radon measurements.
By then orienting these difficult-to-mitigate homes on a geologic map,
we have been able to predict the location of the radon source adjacent
to foundation walls. Tapping these source areas with a multi-duct sub-
slab depressurization system has been shown to be effective in
achieving optimum radon reductions.
By using this method of radon soil testing for the construction of
new large buildings, such as schools, to locate areas of sub-slab
depressurization, maximum indoor radon reductions can be achieved with
minimal Installations.
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and therefore the contents do not
necessarily reflect the views of the Agency and no official endorsement
should be inferred.
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In large buildings, such a? schools and office buildings, and
in homes without: good sub-slab air-flow communication, e.g. no
aggregate, we have achieved significant indoor radon reductions by
sub-slab ventilation at the source of maximum soil radon
concentrations using quantitative diagnostic tests which Incorporate
the correlation between radon soil testing and local geology.
Recent measurements of soil radon availability number?, by the
author (1) have yielded correlations between indoor radon levels In
homes, office buildings, and schools and the various geologic units
in the Coastal Plain, Piedmont, and Mesozolc Basin. The radon
availability number was determined using the equations of Nazaroff,
et al (2) and Tanner (3), whereby radon availability number Is a
function of soil radon content, permeability, and diffusion
coefficient. The equipment used consists of a Pylon radon monitor
with attached Lucas cell and soli probe developed by the author.
The probe has an ln-llne flow meter and pressure gauge (which must
have an appropriate range for the permeability values Inherent In
the particular soils being measured) and a drying tube, cut-off
valve, and Swaglok connector which attaches to the In-ground section
of the probe assembly. This ln-ground section consists of a three
foot long metal tubing surrounded near Its base by an Inflatable
packer to prevent atmospheric dilution.
Because soli permeabilities In the Piedmont, Coastal Plain, and
the Mesozoic Basin of Northern Virginia and Maryland are low enough
that radon migration is predominately diffusion driven, it was
decided to calculate the radon availability number based upon the
soil radon concentration and diffusion coefficient of the soil.
Soils were then tested around a number of basement homes and schools
remediated by RCP. Therefore good data was available on the
original radon values and construction characteristics.
Determined radon availability numbers, plotted against Indoor
radon levels, revealed two distinct populations (Figure 1). The
lower population (I.e. those with a higher radon availability number
to indoor radon ratio) consists entirely of buildings having one or
more of the following four factors:
1. A vented crawlspace,
2. A tight or sealed slab-wall contact,
3. A controlled fill around basement walls that has a low radon
availability number,
4. No basement.
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180-
160-
140"
120 H
100-1
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60
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io ao
RADON AVAILABILITY NUMBER, KBq/m2
Figure 1. Correlation between soil test results (radon availability number)
and indoor radon concentration.
Interestingly, the author had previously discovered In the
George Mason University (GMU) Radon Study, that in the same geologic
setting, basement homes with crawlspaces tended to have lower indoor
radon than those without crawlspaces. Apparently this Is a function
of the fact that crawlspaces are normally attached at one end of the
basement and have fresh air vents to the outside, at least In the
local area studied. Crawlspace? are also usually separated from the
rest of the basement by a wall, thereby acting as a decoupled unit
without the decrease in Indoor air pressure that the basement
exper iences.
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The upper population (i.e. those with a lower radon
availability number to indoor radon ratio) consists entirely of
homes and schools with none of the factor? inherent in the lower
population. It is this trend that one would want to use to predict
magnitudes of indoor radon problems, based upon soil tests for homes
or buildings without any radon mitigating factors. Figure 2-7
(highest values darkened), illustrates that both slab-wall
separation radon measurements (Interior semi-c1rcles) In partially
completed schools have corroborated the location of maximum r.idon
potentials determined from soil tests.
In most cases, elevated sub-slab radon levels and soil test
results have been shown to be concentrated in linear areas for the
various geologic units around the DC metro area, which should also
hold true in any folded geologic region with heterogenous geology.
These linear areas or "bands" can be one foot to a few tens of feet
wide. Importantly, the orientation of the high radon potential
lineations correlate well with the trend of local rock layers
(generally N30°E), or with the trend of local shear fractures
(generally N45°W to N60°w). For example, a boundary between high
and low radon potentials Is shown in Figure 2, along a N60°W
fracture trend and in Figure 3, along a N45°W fracture trend.
Figure 4 shows a diagonal band through the central area of the
school along a N45°W trending fracture pattern. Figures 5 and 6
show correlations between high radon potentials and N30°E trending
rock layers; both revealing a linear band through the interior area
of the school.
v*n Jil.
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Figure 2. Footprint plan of a school showing highest soil radon potentials
(RAN) and indoor slab/wall joint radon concentrations darkened.
Highest soil radon potentials follow N60°W fracture trends.
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Figure 3. Footprint plan of a school shoving highest soil radon potentials
(RAN) and indoor slab/wall joint radon concentrations darkened.
Highest soil radon potentials follow N45°W fracture trends.
/
/
A
I • | ~
/
/
ML /
/
y- /
/
s—r^'l # n
\
vO
/
/
/
G
/
\ J
/
N
/
•»
/
o
Figure 4. Footprint plan of a school showing highest soli radon potentials
(RAN) and Indoor slab/wall joint radon concentrations darkened.
Highest soil radon potentials follow N45°W fracture trends.
-------
rcr-
c/e
O
"3"
I
T
_i J
/
> M. —0L
• • '
-d.
Figure 5. Footprint plan of a school showing highest soil radon potential;
(RAN) and Indoor slab/wall joint radon concentrations darkened.
Highest soil radon potentials follow N30°E trending rock layers,
\
\
— \
\
"ol__ \
\
\
\
©
Figure 6. Footprint plan of a school showing highest soli radon potentials
(RAN) and indoor slab/wall joint radon concentrations darkened.
Highest soil radon potentials follow N30°E trending rock layers.
-------
Foe the construction of new large buildings, sucli schools,
radon soil testing has proven valuable In locating tin- <>urf-3 of
maximum radon availability. By locating sub-slab ventilation points
in the vicinity of these areas maximum indoor radon reductions can
be achieved with minimal sub-slab ventilation installations.
In existing homes with a footprint area of less than 200 0 ft2,
if sub-slab mlcroinanometer tests indicate good air-flow permeability
(good sub-slab communication), the location of ventilation points is
not critical because one fan with one penetration will draw r
-------
Figure 6 illustrates a similar house situation where high ration
potentials are parallel to N30°E rock layers and generally increase
toward the SE. Sub-slab ventilation as shown brought Indoor radon
levels from 30 pCi/1 to 1.5 pCl/1.
N—
0 474
1282
(?) 1825
@)59
///// / ^ {///// /
/ / / ' , ,/>=
Sub-slab
ventilation
sys tem
(D 1325
@627
JLZ.
iZZZZS/
Highest radon
potential
rock layers
1255
Footing
Footing
Figure 8. Footprint plan of a home shoving numerical values of sub-slab
and blockvall radon concentrations that indicate that: the radon
source is following N30°R rock layers, delineated by dash lines.
Sub-slab ventilation systems penetrations are shown as darkened
circles.
Figure 9 shows a workplace building with a footprint area less
than 2000 ft2 where micromanometer readings indicated no sub-slab
communication because the slab was poured directly on compacted
clay. Construction material radon levels tested negative, However,
3ub-slab radon levels Increase towards the SE, congruent with local
rock layers oriented N30°E. Thirteen slab penetrations with 2" pipe
were necessary to deplete most oŁ tlie source from the SE end of the
building because the negative pressure field around each penetration
was so small due to the very poor communication. Indoor radon,
which initially vas measured as high as 120 pCi/1, was reduced to
less than \ pcl/l.
-------
(*) Sub-slab radon levels, pCi/1
¦ ^ Wall penetration radon levels, pCi/1
Figure 9. Footprint plan of a home showing numerical value:1, of sub-slab
and blockvall radon concentrations that indicate that the radon
source is following N30°E rock layers. Sub-slab ventilation
systems penetrations are shown as darkened circles.
Therefore, by knowing local geology and by tapping these high
radon potential source areas with a multi-duct, single fan, sub-slab
ventilation system optimum radon reductions can be achieved in
buildings with poor sub-slab communication. Likewise by combining
geologic knowledge with sub-slab and blockvall radon measurements in
large buildings such as schools, the radon source can be located to
determine where to place sub-slab ventilation systems that will
achieve maximum radon reductions.
-------
REFERENCES
1. Hall, S. Correlation of soli radon availability number
with indoor radon and geology in Virginia and Maryland.
In: Proceedings of the EPA/USGS Soli Gas Meeting,
September 14-16, Washington, D.C.
2. Nazaroff, W, Moed, B., and Sextro, R, Soil as a source of
Indoor radon: generation, migration, and entry. In: W.
Nazaroff and A. Nero (ed.), Radon and Its Decay Products
In Indoor Air. John Wiley and Sons, New York, N.Y., 1988.
pp. 82-90.
3. Tanner, A. B. Measurement of radon availability from
soli. In: Geologic Causes of Natural Radionuclide
Anomalies, Proceedings of the GEORAD Conference, St.
Louis MO, Apr. 21-22. 1987, MO Dept. of Nat, Resources,
Dlv. of Geology and Land Survey, Spec. Pub. No. 4. pp.
139-146.
-------
IX-2
TITLE; A Comparison of Radon Results to Geologic Formations for the
State of Kentucky
AUTHOR: David McFarland, Merit Environmental Services
This paper was not received in time to be included in the
preprints so only the abstract has been included. Please check
your registration packet for a complete copy of the paper.
A large bank of radon results for the state of Kentucky
are compared to the local geologic formation. These results
are discussed in detail. The topic of elevated radon levels
as a result of native building materials (for the study area)
is also addressed.
-------
TITLE:
Geologic Radon Potential of the United States
AUTHOR: Linda Gunderson, U.S. Geological Survey
This paper was not received in time to be included in the
preprints so only the abstract has been included. Please check
your registration packet for a complete copy of the paper.
A ^CQlapt radon map depicting the major geologic provinces relevant to radon has been
constructed for the United States. Indoor radon daia from ihe Sutc/EPA Indoor Radon Survey and
from other sources were compared with bedrock and surficial geology, aerial radiometric data, soil
properties, and soil and water radon studies to designate and rank the different provinces. The
map depicts areas of the country thai have the potential for indoor radon (l) less than the national
avenge of 2 pCi/L, (2) greater than the national average, and (3) greater than 4 pCl/L. The areas
of the country with the highest radon potential are listed below:
(1) The Proteroroic rocks of the Appalachians and Roches: These uraniferous metamophosed
sedin\ents, volcanics, and granite intrusives and carbonates are highly deformed and often sheared.
Shear zones in these rocks cause the highest Indoor radon problems in the United States.
(2) (jiacia; deposits of the northern Midwest, particularly those derived from uranium-tearing
shales, and glacial lake deposits. The clay-rich tills and lake clays have high radon emanation
coefficients, in pan because of their high specific surface areas, and exhibit higher-thiri-expected
permeabilities due to desiccation cracking when dry.
t?) Devonian and Cretaceous black shales: The Chatanooga and New Albany Shales arid their
equivalents in Ohio, Tennessee, and Kentucky and some members of the Pierre Shale in the Great
Plains are often moderately uraniferous and have high emanation coefficients and high fracture
permeability.
(4) Phosphorites: Natural and m&nmade accumulations of phophorttes in Florida, phospharlc clays
;n Georgia ajid Alabama, and the Permian Phosphona Formation in Wyoming, Idaho, Utah, and
Montana are typically associated with uniformly high concentrations of uranium or anomalously
high concentrations uf uranium caused by diagenesis.
-------
TITLE: Technological Enhancement of Radon Daughter Exposures Due to
Non-nuclear Energy Activities
AUTHOR: Jadranka Kovac, University of Zagreb, Yugoslavia
This paper was not received in time to be included in the
preprints so only the abstract has been included. Please check
your registration packet for a complete copy of the paper.
Natural radioactivity is a part of our natural surrounding and
concentrations of natural radionuclides in the environment increase
with the development of technologies. This is the case with phosphate
ore processing in fertilizer industry and during coal combustion in
coal-fired power plants. A major source of exposure to the population
in the vicinity of non-nuclear industries results from inhalation of
P2P
the Rn daughters. Exposure to radon daughters has been also associ-
ated with lung disorders that include cancer among workers. For that
reason the radon daughter concentrations in different atmospheres are
discussed in this paper.
Working levels were measured as "grab samples" for several years
at several stations on-site and off-site of the coal-fired power
plant as well as the phosphate fertilizer plant, both located in
Croatia. The average maximums, minimums, and mean values of working
levels are presented, and measurement techniques are reviewed.
-------
IX- 5
A STTF. STUDY OF SOIL CHARACTERISTICS AND SOTT, GAS RADON
by: Richard Lively, Minnesota Geological Survey, 2642
University Ave. St. Paul, MN 55114, and Daniel Steck,
Dept. of Physics, St. John's University, Collegeville,
MN 56321
ABSTRACT
In regional surveys, indoor radon is usually the parameter of
interest, but occasionally soil gas radon at depths of 1 meter or
less is also measured. At statewide scales, even limited data sets
can be used to infer relationships between geology and soil gas or
indoor radon. However, predicting the radon potential of a single
house or even an area the size of a neighborhood is more
difficult. As the size of a surveyed area decreases, site-specific
variables become more significant.
We recently completed a study of two residential
neighborhoods within 7 kilometers of each other near Rochester,
Minnesota. Eight holes were augered into glacial sediments to
maximum depths of 4.5 meters and samples collected for grain-size
analysis, measurement of radon parent/daughter nuclides and radon
emanation. A total of 65 homes in the areas were provided with two
alpha-track registration detectors for 1 year of indoor
monitoring.
Positive correlations were observed between the average soil
radon, the average indoor radon, and the precursor/daughter
radionuclides. The study area with the most topographic relief
also had the highest radionuclide contents, the most variability
with depth, and some variation with time and soil moisture; these
results were not observed at the low-relief site. The type of
study described would best be applied to site-specific
preconstruction screening, rather than to predicting radon in
existing structures.
-------
introduction
This project was designed to collect data on soil type and soil
characteristics, radon and other related nuclides at several
depths, and porosity and permeability. At the same time, radon
levels in basements and living areas of homes built on the soils
were also measured.
Two areas were chosen for the pilot study (Figure 1) St. Marvs
Hills on the west side of Rochester consists of modern, single-
family homes on 1/2-acre to 2-acre lots on the west side of a
bedrock hill composed of St. Peter Sandstone, Decorah Shale and
Galena limestone, with a total vertical relief of about 40 meters
The bedrock surface is covered by 2 and 6 meters of glacial
sediment and loess. Essex Park, about 6.5 kilometers northeast of
St. Marys Hills is a mix of modern, single-family and multiple-
residence homes on 1/2-acre lots. The topography is subdued with
about 9 meters of relief. Depth to the bedrock (Prairie du Chien
Group) is between 3 and 18 meters. The profiles for each area and
locations of the sample holes are shown in Figure 2.
Sixty-four owners of single-family homes participated in the
study, 45 from Essex Park and 19 from St. Marys Hills. Each
received two radon detectors, one for the basement and one for a
first-floor living area. Exposures lasted from 9 to 12 months.
METHODOLOGY
The test holes were drilled in October 1988 using a truck-
mounted Giddings soil auger with a 5-cm-diameter bit and core
tube. Sediment samples collected during drilling were placed in
sealable plastic bags.
The following is a summary of the analyses and methods used to
study the sediment samples.
1. Moisture content and bulk density: the wet weights were
measured within 2 days after collection. Soils were dried for a
minimum of 24 hours at 70°C and reweighed. The results are only
approximate, because they do not reflect moisture lost prior to
measurement.
2. Solid particle density: these measurements were based on a
procedure from Luetzelschwab and others (1). These results
combined with the wet and dry bulk densities can be used to
approximate the pore volume in a sample of soil.
3. Grain-size fractions: the soils were screened into
fractions consisting of a bulk sample (undifferentiated as to
grain size), >149 H (sand and gravel), 149-63 p. (very fine sand)
and <63 11 (silt and clay by Wet sieving) .
4. Mineralogy: the mineralogy was determined by examining the
>149 |i. grain-size fraction with a binocular microscope.
5. Radon: radon emanatlon was measured from the bulk soil
samples, the <63 |l, and the 63-149 p. fractions using a charcoal
trap system modified from an unPublished report by Dr. J.N.
-------
Andrews, University of Bath, England. Scatter in the bulk fraction
is thought to result from inhomogeneous radium in the sediment.
The reproducibility of the other duplicate analyses was very good,
and replicate analyses of radium standards varied by less than
10% .
6. 210Po — 210Pb: Polonium-210 was extracted from the sediment
with a leaching technique modified from Eakins and Morrison (2),
Blake and Norton (unpub.), and D.R. Engstrom (unpub.). The 210po
was assumed to be in radioactive equilibrium with the 21(^Pb.
7. Radium and thorium: 1-kilogram sediment splits from each
depth were analyzed for 226Ra and 232Th by gamma-ray spectroscopy
using a high-resolution germanium detector. The measured
activities reflect total radium and thorium in the sediments.
8. Radon concentrations in the soil at multiple depths were
measured by (1) pumping air from isolated intervals through a
liquid scintillation cocktail (active sampling) and by (2)
extended monitoring of isolated intervals with alpha-track
detectors (passive sampling). Inflatable rubber packers on the
outside of hollow PVC pipe were used to isolate each collection
point. Each alpha track detector was wrapped in Saran Wrap® to
keep out water vapor but still allow diffusion of radon. Initial
data from alpha-track detectors is not included in the tables
because of large variance in the calibration constant for the
detectors used at that time and our doubts about the integrity of
the original packers. In 1989, a redesigned system for both the
active and passive sampling was used with more reliable packers
and flexible barriers, which prevented vertical air movement if a
packer failed.
SOIL CHARACTERISTICS
The sediments within the Rochester area are the result of
glacial processes and include tills, outwash, colluvium, and
loess. Loess, ranging from 0.6 to 2.8 meters thick, covers all of
the sample sites except Hole B in St. Marys Hills. The glacial
tills below the loess are oxidized; some show the reddish-brown
colors of ferric iron to depths of about 4.3 meters (Figure 3).
Moisture ranged from a low of 6.8 weight percent in the loess
to a high of 20 weight percent, also in loess. Soil moisture
increased slightly with depth, but not in all holes and not more
than a few percent. Between the initial sampling in 1988 and
measurement of radon in 1989, Hole B (St. Marys Hills) collected
water in the bottom meter. This could have been due to seepage
from the sediment or water infiltrating from the surface.
There is a fairly broad range of grain-size distributions in
the sediment samples, but the means within and between the sites
were not statistically different. The available data do not allow
us to distinguish between the relative effects of deposition and
post-depositional soil development on the grain-size distribution.
-------
Mineralogically the sediments are very similar, being
predominantly composed of quartz, feldspar, biotite, and
muscovite. Rock fragments form up to 50% of the >149 (i size
fraction and include granite, limestone, quartzite, sandstone and
metamorphic and volcanic rocks. Varying percentages of magnetite
pyrite, hematite, and limonite were also observed. '
RADIOMETRIC RESULTS
Radon concentrations in the soil gas at St. Marys Hills
generally increase with depth and range from 17 to 71 kBq/m3 (Table
1), with an average of 44 ± 13. In Hole A, both active and passive
radon samples were collected. Below 1 meter, the two methods gave
concentrations that were, within error, identical. The lower radon
value at sample point A1 using the active monitor was probably due
to leakage around the original packer. A second group of passive
monitors was placed in Hole B during August-November and produced
results that were significantly lower than the July-August
measurements. Hole B also contrasts with the other St. Marys Hills
data in that radon decreases with depth. These trends appear
related to increased water retention in the clayey soil of Hole B
as well as collection of water in the lower meter.
In Essex Park the radon levels range from 3 to 42 kBq/m3 with
an average of 26 ± 7 kBq/m3 (Table 2). The level of 3 kBq/m3 was
obtained at a depth of 0.2 meters in Hole G; at a depth of one
meter the lowest concentration was 13 kBq/m3. Some of the holes
show an increase in radon with depth; others show relatively
uniform levels. Some of the radon concentrations measured by the
active sampling are as much as 30% lower than concentrations
measured with the passive monitors. However, the means are not
statistically different.
A second set of measurements in Hole G during August-November
showed lower radon levels than during July-August and correspond
to the decrease observed in Hole B at St. Marys Hills. Although
the decrease can be attributed to higher water retention in the
soil during a rainy fall it 1S difficult to be sure as only one
hole was measured within each area during the late fall.
Radon emanation was measure^ on the bulk samples, the 63-14 9 u.
and the <63 |J. fractions as described above. Replicate analyses
gave reproducible results with standard deviations comparable to
the error associated with counting statistics. A number of
factors, such as moisture, radium content, and location of radium
either on grain interiors or secondary coatings, control the
amount of radon emanated (3) f however, on the average, higher
radon emanation would be e*Pected to produce higher radon
concentrations in the soil
-------
63-14 9 (I measurements were considered representative of all the
sand-size fractions.
Differences between the radon emanation rates of the two sites,
were comparable with those of the radon concentrations. The
average radon emanating from the soils in St. Marys Hills is just
over twice that emanating from the Essex Park soils. The
difference in means is statistically significant at the 0.025
confidence level. Although emanation rates in St. Marys Hills were
divided fairly evenly between the 63-149 |X and <63 size
fractions, in Essex Park the emanation rates for 9 out of 10
samples was highest in the <63 p. fraction. The variation of
emanation rates in Essex Park was much smaller than in St. Marys
Hills, in accordance with the more uniform radon concentrations in
Essex Park.
The sum of the emanation rates from the grain-size fractions
should be comparable with the emanation rate measured from each of
the bulk samples. In Essex Park this was the case, but in St.
Marys Hills, although most were comparable, some soils, such as
A6, had a bulk emanation rate that was larger than either the
individual or the sum of the fractional emanations. The overall
agreement between the bulk and weighted fractional emanations
indicates that the assumption that the 63-149 JX size represents
the total sand fraction is reasonable for these samples.
Other radionuclides measured included 232Th, 226^a^ ancj 210po
(Tables 5 and 6). Both the mean and standard deviation of 232Th are
equivalent for both sites. Radium and 210Pb values were higher in
St. Marys Hills than in Essex Park and were also more variable
both within and between sites than was thorium. If post-
depositional migration altered the radionuclide distributions, it
did not affect thorium, which is not mobile under near-surface
geochemical conditions. Uranium isotopes, however, respond to
weathering and changing oxidation/reduction environments, leading
to separation from daughter radionuclides and altered distribution
patterns. The relatively uniform distributions of radionuclides in
Essex Park sediments are consistent with little post-depositional
migration, whereas the uneven distributions in St. Marys Hills
indicate significant migration, possibly related to enhanced
weathering of the sediments on the hill slope.
The activity ratio 210Pb/226Ra in the sediment can be a useful
indicator of relative radon loss. A ratio smaller than one implies
that radon has moved away from the radium source, resulting in
less 210pb activity relative to 22^Ra. All but one of the samples
(A6) have activity ratios less than unity; in fact the overall
activity ratio is about 0.5, with St. Marys Hills having a
somewhat higher mean value (significant at the 0.05 confidence
level). Lower activity ratios could also result from only partial
recovery of polonium from the sediment, with the apparent effect
of reducing the Pb/Ra activity ratio. Sample A6, with an activity
ratio of 1.25, is at present an anomaly because the individual
-------
... * 210dk ,nH 226Ba, as well as the activity ratio, are
activities of "Opb and other samples,
much greater than those of tne
the lowest activity ratios were not
Contrary to where radon could easily escape into the
always near t e su j_n Essex Park with the lowest activity
atmosphere. T e san y moved away from its source even at
ratios imply t a ra qpfTniiibrium between 226Ra and 2i0pb could
depths of 3 meters. migration of radium during weathering of
also result from downward be partially related to
the sediments or cou , o0lonium from the sediment, we were not
inefficient extrac 1 directly with either 226r3 or 210Pb
able to compare e different (volume vs. mass), and the
because the units were ond in depth_
samples did not always corr
i -Mai detector to measure the total gamma
We also used a ls in several of the holes. in general
activity at 2- oo i relationship followed the pattern of
the activity versus p sediment except near the surface, where
radium and polonium l ,ations of potassium. Total gamma
there may have been a peared higher in St. Marys Hills, in
activity in the se im measurements, but not all holes were
accordance wit .nCj.icate that subsurface gamma activity
measured. The resu simple screening technique, which
is a potential y use a spectroscopy system that det ermines
could be improved by u 9 and identifies the isotopes present,
the energy of the radiation
INDOOR radon
The summary of the indoor radon information is given in Table
7 . Of the 64 homeowners who were given the two detectors, 48
returned them. Of those, 17 weŁe from the St. Marys Hills area and
31 from the Essex Park area • The mean indoor radon levels of St.
Marys Hills and Essex Park &re different and significant at the
0.025 level for a two-sided t-test. The higher average indoor
radon in St. Marys Hills corresponds to the higher average
radionuclide contents in the sediments of St. Marys Hills and to
the higher radon emanation rates. The range of indoor radon
concentrations is similar f°r both areas. each has ieveiS that
exceed 370 Bq m~3 and levels that are less than 37 Bq m-3. Although
this reduces the probability Pr^dicting radon levels for
individual homes, there is 3 good correlation between the average
soil radon concentrations, p#rerit/daughter radionuclides, and
indoor radon levels.
CONCLUSIONS
Our primary objective in t ls study was to measure, in two
different areas, radionuclides^elated to and including radon at
several depths within unconsolidated sediments, and to see what,
if any, correlation existed between the characteristics of the '
sediment and indoor radon of measurements were
made in glacially derived o? ated material. None were obtained
-------
from the limestone bedrock, which was encountered in only three
holes. We think that within the study areas the glacial sediments
are the primary source of indoor radon and that bedrock probably
is not a significant source. A more extensive study is needed to
determine which homes were built on or near bedrock and collect
additional data on the radon and other radionuclide levels.
Radium-226, 210Pb, radon emanation, and downhole radon levels
all have statistically higher averages in St. Marys Hills
sediments than those in Essex Park. Indoor radon levels also were
statistically higher in St. Marys Hills, and had a positive
correlation with the radionuclides in the soil. The mineralogy,
moisture levels, and bulk densities were similar in both areas and
did not correlate with the radionuclide distribution. Texturally
the sediments were variable but showed similar average contents of
gravel, sand, and silt/clay; however, more work is needed before
firm conclusions can be made about the effect of grain-size
distribution on the radionuclide content and distribution within
the sediments.
All of the techniques used to assess the radon potential were
consistent with each other and could be applied individually or
collectively to other areas. We believe that at these sites near
Rochester mineralogical characteristics of the sediments and the
location of samples within the stratigraphic column were only
partially responsible for the observed distribution of
radionuclides. We suggest that post-depositional transport of
uranium and radium related to weathering processes contributed to
the observed distributions. The redistribution of radionuclides
was more extensive in the St. Marys Hills area probably owing to
the greater vertical relief. In both areas 226Ra/210Pb activity
ratios indicate migration of radon independent of the
parent/daughter movement.
Predicting radon source areas in regions where sediments are
more than a couple of meters thick should not be be based solely
on identification of geological materials or on near-surface radon
measurements. Evidence for the secondary transport and
redistribution of radionuclides is not shown on geologic maps, and
near-surface radionuclide characteristics may differ from those at
basement depth. The data from this study, although limited in
area, indicate that measurement of radon or related radioactive
nuclides in soils can be a useful preconstruction indicator of
potential indoor radon problems. Survey methods could involve
active measurements at depths greater than 1 meter of soil gas
radon, subsurface gamma spectroscopy and 226Ra in the sediment.
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and therefore the contents do not
necessarily reflect the views of the Agency and no official
endorsement should be inferred.
-------
references
1. Luetzelschwab, J.W., Helweick, K.L., and Hurst, k. a. Radon
concentrations in five Pennsylvania soils. Health Physics 56-
181, 1989.
2. Eakins, J.D., and Morrison, R.T. a new procedure for the
determination of Lead-210 in lake and marine sediments.
International Journal of Applied Radiation and Isotopes. 29-
531, 1989.
3. Nazaroff, W.W., and Nero, A.V., Jr. Radon and its decay
products in indoor air. J. Wiley & Sons, 1988. 518 pp.
4. Olsen, B.M. Bedrock geology, Plate 2 of 9. Balaban, N.H.,
editor. Geologic atlas of Olmsted County, Minnesota Geological
Survey County Atlas Series, Atlas C-3, Scale 1:100,000.
5. Hobbs, H.C. Surficial geology, Plate 3 of 9. Balaban, N.H.,
editor. Geologic atlas of Olmsted County, Minnesota Geological
Survey County Atlas Series, Atlas C-3, Scale 1:100,000.
Partial funding for this project was provided the the Center for
Urban and Regional Affairs, University of Minnesota, Minneapolis.
-------
TABLE 7. SUMMARY OF RADON LEVELS (Bq/m3) IN HOMES WITHIN THE STUDY AREA
Geometric Arithmetic
Mean Mean Min. Max.
St. Marys Hills
Rn Index No.t
180
* +
1.8
220
70
610
Rn Basement
250
* +
2.1
270
40
1100
Rn 1s* Floor
130
* +
3.0
160
30
400
Essex Park
Rn Index No.
60
* +
2.5
90
10
390
Rn Basement
80
*
4-
2.4
130
15
650
Rn 1st Floor
40
* +
2.7
70
10
280
J The radon index number is a weighted average of the two radon measurements in the house. The weighting factor
for each floor was an estimate of the amount of time an occupant spends on each floor.
-------
TABLE 1. DOWNHOLE RADON MEASUREMENTS, ACTIVE & PASSIVE - ST. MARYS HILLS
Sample No.
Depth (m)
Average
Date
mo/yr
Active
Date
mo/yr
Passive
/kRn/m3^
Date
44 ± 13
Passive
A1-1
10/88
17
±
2
7-8/89
29 ± 4
__
_
A2-2
10/88
40
+
3
7-8/89
40 ± 6
-
__
A3-3
10/88
61
+
4
7-8/89
57 ± 8
-
A4-4
10/88
68
+
6
7-8/89
71 ± 9
-
--
B1-1
-
-
7-8/89
42 ± 6
8-11/89
25
+ 2
B2-2
-
-
7-8/89
41 ± 6
8-11/89
28
+ 2
B3-3
-
-
7-8/89
29 ± 4
8-11/89
20
+ 1
B4-4
-
-
7-8/89
water
8-11/89
5
± 0.4
C1-1
—
-
7-8/89
26 ± 3
—
„
C2-2
-
-
7-8/89
44 ± 6
-
—
D1-1
—
-
7-8/89
44 ± 6
—
D2-2
—
-
7-8/89
46 ± 6
-
..
D3-3
-
-
7-8/89
53 ± 7
-
-
Error values are one standard deviation based on counting statistics.
TABLE 2. DOWNHOLE RADON MEASUREMENTS, ACTIVE & PASSIVE - ESSEX PARK
Sample No.-
Date
Active
Date
mo/yr
Passive
Date
Passive
E1 -1
8/89
22
±
2
7-8/89
15
±
2
_
E2-2
8/89
21
±
2
7-8/89
22
±
3
—
_
E3-3
8/89
21
±
2
7-8/89
18
±
3
-
—
F1-1
8/89
15
±
2
7-8/89
21
±
3
—
F2-2
8/89
26
±
3
7-8/89
32
+
4
-
F3-3
8/89
27
±
3
7-8/89
24
±
3
_
F4-4
8/89
27
+
3
7-8/89
36
±
5
—
G1-1
(0.2)*
8/89
3
±
0.3
7-8/89
18
+
3
8-11/89
20 ± 1
G2-2
(1.2)*
8/89
23
±
2
7-8/89
31
±
4
8-11/89
28 ± 2
G3-3
(2.2)*
8/89
24
±
2
7-8/89
33
±
4
8-11/89
23 ± 2
G4-4
(3.2)*
8/89
31
±
3
7-8/89
42
+
6
8-11/89
collapsed
H1-1
8/89
13
+
1
7-8/89
23
+
3
_
H2-2
8/89
21
±
2
7-8/89
25
±
4
H3-3
8/89
19
+
1
7-8/89
25
+
4
-
H4-4
8/89
17
r>r>
+
1
Ł +
7-8/89
23
OR
+
+
3
7
-
-
'Depth (meters) of active radon measurements in Hole G. Error values are one standard deviation based on counti^T
statistics. uuiiimy
tAverage does not include sample from depth 0.2 meters.
-------
TABLE 3.
EMANATION RESULTS -
ST. MARYS
HILLS
Sample No.
Bulk Emanation
Sum of Emanation
Emanation
Emanation
Depth (m)
from Sand &(Silt+Clay)*
63-149 n
<63 p.
(Bq/kg)
(Bq/kg)
(Bq/kg)
(Bq/kg)
A1-1.3
7.6 ± 0.4
14.7 ± 0.7
16.7 ± 0.9
f14.6 + 1.0
A2-2.1
t10.6 ± 0.7
14.3 ± 0.7
11.0 + 0.8
t16.9 1 1.0
A3-2.9
20.1 ± 1.0
18.0 1 0.9
15.9 ± 0.9
21.3 ± 0.9
A4-3.5
20.2 ± 0.9
22.4 ± 1.1
19.1 ± 1.0
26.8 1 1.2
A5-4.0
11.0 ± 0.6
12.3 ± 0.6
11.4 ± 0.7
14.5 + 1.0
A6-4.6
138.2 ± 3.3
17.5 ± 0.9
t13.7 ± 0.8
t20.3 + 1.3
B1-1.9
15.6 ± 0.7
9.5+ 1.2
6.6 ± 0.6
t11 2 ± 1.7
B2-3.4
11.1 ± 0.8
12.2 ± 0.6
20.2 ± 0.9
11.9 1 0.6
B3-4.6
13.8 ± 0.7
11.1 ± 0.6
f15.0 ± 0.8
t10.9 ± 0.6
C2-1.8
18.8 ± 1.0
11.4 ± 0.6
21.7 ± 1.0
11.2 + 0.6
C2-2.9
11.0 ± 0.6
12.0 + 0.6
19.5 ± 0.8
f11 -2 + 1.7
D1-1.2
18.2 ± 0.7
12.1 ± 0.6
32.4 ± 2.0
11.4 1 0.7
D2-2.7
34.0 ± 2.0
27.1 ± 1.4
21.8 ± 1.0
30.9 + 1.0
Average
17.7 ± 9.2
-
-
-
'Emanation measured on 63-149 n. size and applied to total sand fraction; emanation from <63 |i size includes both
silt and clay. Sum is the measured emanation times the weight percent of each size fraction.
tThe number is mean of replicate measurements; error is the standard deviation about the average.
TABLE
4. EMANATION RESULTS - ESSEX PARK
Sample No.
Bulk Emanation
Sum of Emanation
Emanation
Emanation
Depth (m)
from Sand &(Silt+Clay)*
63-149 p.
<63 |4.
(Bq/kg)
(Bq/kg)
(Bq/kg)
(Bq/kq)
E1-1.9
t6.3 ± 0.6
6.8 ± 0.7
NS*
16.5 1 1.0
E2-3.1
8.2 ± 0.5
12.3 ± 1.2
11.41 0.7
14.9 1 0.8
F1-1.8
9.8 ± 0.7
12.7 ± 1.2
35.5 1 1.4
10.1 1 0.6
F2-3.1
11.8 ± 0.6
9.3 ± 0.6
5.0 + 1.0
9.41 1.0
F3-4.3
8.8 ± 0.6
8.0 ± 0.8
t2.2 1 0.6
10.0 + 0.7
G1-1.9
7.4 ± 0.6
5.6±0.8
3.1 1 0.4
10.6 1 0.6
G2-3.3
7.2 + 0.5
6.3 ± 0.8
2.7 + 0.4
9.5 + 0.7
G3-4.4
f10.5 ± 0.7
6.7 + 0.8
t1.2 + 0.5
f10.7 1 0.8
H1-1.8
5.6 ± 0.7
5.6 + 0.8
2.8 + 0.4
9.4 + 0.6
H2-3.3
4.7 ± 0.8
5.2 ± 0.8
2.3 1 0.4
9.7 + 0.7
H3-4.3
5.2 ± 0.5
4.8 ± 0.7
2.0 + 0.4
10.0 + 0.7
Average
7.8 ± 2.3
-
-
-
'Emanation measured on 63-149 n size and applied to total sand fraction; emanation from <63 n size includes both
silt and clay. Sum is the measured emanation times the weight percent of each size fraction.
|The number is mean of replicate measurements; error is the standard deviation about the average.
^NS indicates insufficient sample for measurement.
-------
TABLE 5. RADIUM-22 6, LEAD-210 AND THORIUM-232 IN ST. MARYS HILLS
Sample No.
Depth (m)
Ra-226
(Bg/kg)
Pb-210
(Bq/kg)
Th-232
(Bq/kg)
21°pb/226Ra
±=10%
A1-1.3
82
±
10
t24.9
± 0.7
32
±
14
0.30
A2-2.1
77
±
10
t18.8
± 2.6
48
±
18
0.24
A3-2.9
74
±
09
37.8
± 0.6
29
+
15
0.51
A4-3.5
64
±
09
37.2
± 0.5
55
±
19
0.58
A5-4.0
45
+
07
26.4
± 0.5
23
+
17
0.59
A6-4.6
117
±
12
f146
± 46
38
±
18
1.25
B1-1.9
30
±
6
23.7
± 0.6
33
+
16
0.79
B2-3.4
47
±
8
26.4
± 0.5
55
±
15
0.56
B3-4.6
42
±
7
27.0
± 0.7
55
±
14
0.64
C1-1.8
60
+
9
39.9
± 0.8
45
+
19
0.67
C2-2.9
39
±
7
25.8
± 0.6
34
+
16
0.66
D1-1.2
39
±
7
32.3
± 0.7
42
+
17
0.83
D2-2.7
79
±
9
+54.9
± 7
44
±
13
0.69
Average
61
±
25
40
± 33
41
+
11
0.64 ± 0.25
fThe number is the mean of replicate measurements, error is the standard deviation about the average.
TABLE 6. RADIUM-226, LEAD 210 AND THORIUM-232 IN ESSEX PARK
Sample No. Ra-226 Pb'?1? Th-232 210Pb/226Ra
Depth (m) (Bq/kg) (Bq/kg) (Bq/kg) ±=10%
ljcijiii \nt)
E1-1.9
27
H' a
+
/
6
16.1
± 0.4
29
+
10
0.60
E2-3.1
21
±
5
10.9
i+
o
32
±
11
0.52
F1-1.8
39
+
7
19.4
± 0.5
49
+
17
0.50
F2-3.1
36
+
7
18.4
± 0.8
64
±
20
0.51
F3-4.3
33
+
7
16.1
± 0.7
50
+
17
0.49
G1-1.9
26
+
5
13.3
± 0.3
30
+
14
0.51
G2-3.3
25
±
7
14.4
± 0.4
37
±
12
0.58
G3-4.4
28
+
6
+ 11.9
± 0.2
29
+
13
0.42
H1-1.8
30
+
5
12.8
± 0.4
33
±
15
0.43
H2-3.3
23
4*
5
6.5
± 0.3
32
+
14
0.28
H3-4.3
25
±
6
9.2
± 0.4
31
±
10
0.37
Average 28 ± 6 14 ± 4 38 ± 12 0.47 ± 0.09
fThe number is the mean of replicate measur6m0r>ls' err°r's the standard deviation about the average.
-------
\
/j| Essex Park \
Rochester
¦
St. Marys Hills
Scale
0 1 5 tan
II 1 1
Figure 1. Map showing study areas near Rochester,
Olmsted County, Minnesota
-------
Plan View
St. Marys Hills
Elevation (meters asl):
370
Loess
C,D
360
? Contact ?
Glacial Till
Decorah Shale;
350
? Contact ?
Platteville Fm
340'
P? ? Contact ?
Glenwood Shale
? Contact ?
•'•'¦'St. Peter Sandstone
? Contact ?
Prairie du Chien
Essex Park
Elevation (meters asl):
320
Plan View
ground surface
310
Glacial Till
Prairie du Chien Group (Ls)
0 st 100 «
, „ . i i i Vertical exageration - 8x
Horizontal Scale ' ' 1
Figure 2. Profiles and location of sample holes. Modified from
Plates 2 and 3, Olmsted County Atlas (4,5).
-------
Hole A
St. Marys Hills
Hole B Hole C
Loess
Oxidized glacial
sediment
Unoxidized
glacial
sediment
Hole D
Loess
Clay
Hole E
Sandy glacial
sediment
Unoxidized
glacial
sediment
Sample
Interval
Essex Park
HoleF
HoleG
rfeOr
HoleH
-PWP
w«>*v
•/.•An
yy.'«
W;S»S
W • S • S1
- b*S*V
:<&•
•VV;«
^•A'S
»•¦¦¦¦• I
W»S"%
Figure 3. Borehole lithology and sample locations
based on field identifications.
-------
IX-fi
GEOLOGICAL PARAMETERS IN RADON RISK ASSESSMENT - A CASE HISTORY
OF DELIBERATE EXPLORATION
By: Donald Carlisle and Haydar Azzouz *
Department of Earth and Space Sciences
University of California Los Angeles
Los Angeles, California 90024
ABSTRACT
Geological exploration has identified an unsuspected radon-prone belt in southern
California. Detailed analysis of aeroradiometric (NARR) data in relation to geological
units, soil-gas radon, soil permeability, and finally indoor radon has identified the Rincon
Shale and soils derived predominantly from the Rincon Shale in Santa Barbara County as
anomalous in uranium and radon. Roughly 76% of our screening tests to date from homes
on the Rincon Shale exceed 4 pCi/1 and 26% exceed 20 pCi/1. Measurements under
"normal" living conditions show 42% exceeding 4 pCi/1. An estimated 4,000 plus homes
are at this level of risk; extensive new construction on the Rincon Shale is limited only by
domestic water supply.
Unusually good correlations between aeroradiometry, soil-gas radon at 75 cm depth
adjusted for soil-gas permeability, geology, and indoor radon concentrations reflect the
unmetamorphosed character of sedimentary host rocks and the tendency for anomalous
uranium concentrations to be disseminated throughout a geological unit rather than in erratic
mineralized zones. Under these circumstances, deliberate geological exploration can be a
more efficient approach to radon risk identification than simple random sampling or non-
random testing of homes and by the same token geological parameters can facilitate radon
risk assessment on undeveloped lands.
The work described in this paper was not funded by the U.S. Environmental Protection
Agency and therefore the contents do not necessarily reflect the views oif'the Agency and no
official endorsement should be inferred.
* Present address of Haydar Azzouz: GSI Environmental, Huntington Beach, California
1
-------
RATIONALE
Two very different questions can be asked about the incidence and distribution of
indoor radon concentrations:
1. What is the probability distribution of indoor radon concentrations among the
entire stock of homes in a given region or in the country as a whole?
2. What is the probability of occurrence and the location of radon-prone areas within
this given region? This latter question is of much greater interest to individuals.
Answers to the first kind of question, regional probability or frequency distribution, are
usually estimated by statistical analysis of measurements from a simple random sample or
probability sample of homes in the area of interest. Simple random sampling aims ideally to
avoid bias by making every home equally selectable and, as a consequence, obliterating
differences among sub-populations which may, or may not, exist within the whole. Ex-
post-facto analysis of existing measurements from private and/or public sources is a less
expensive and less reliable substitute. Aggregate regional frequency distributions so
obtained are usually shown as approaching log-normality with characteristic arithmetic
means from 0.8 to 11.3 pCi/1, geometric means from 0.6 to 3.3 pCi/1, and geometric
standard deviations from 2.1 to 3.4 pCi/1. In reality the distributions are commonly very
irregular, particularly at higher concentrations, and undoubtedly represent multiple
populations each with its own characteristic frequency distribution.
The alternative approach, which we among others have taken, is to purposely explore
for radon-prone areas using geological reasoning along with inexpensive, practical
techniques modified from mineral exploration, engineering, or research methodology
already in use or in the literature. In other words we have directly addressed the second
kind of question: the probability of occurrence and the location of radon-prone sub-
populations. There is now an extensive literature on sources, distribution, and
measurement of radon in soils, and on its contribution to indoor radon which we will not
cite in detail: a recent primary reference is Nazaroff, et al. (1). The following very brief
summary establishes the principal assumptions for our work.
Given that the overwhelming preponderance of indoor radon is derived from underlying
soils and rocks, and ultimately from U-238, the detection of anomalous natural radon
sources is in large measure the detection of anomalous uranium concentrations and therefore
quite analogous to the exploration for mineral deposits in general. Uranium is an ubiquitous
element, present in trace amounts in all soils and rocks in concentrations ranging from as
little as 0.2 ppm (parts per million) or less in sandstones, from 1 to 20 ppm in common
igneous rocks, and to as much as 200 ppm, rarely 500 ppm in black shales. Ore-grade
concentrations average from 500 to 28,000 ppm, locally much higher, across mineralized
zones which are comparatively small, erratic and difficult to find.
2
-------
Geological controls for uranium distribution are reasonably well known in principle.
Lithological and geochemical methods of exploration, including radiometrics, are
particularly useful but must take into account the differing geochemical properties of the
several isotopes within the U-238 decay series and the consequent likelihood of departure
from secular equilibrium. Uranyl ions produced during oxidative weathering, for example,
are extremely soluble and mobile in contrast with the insoluble Th-234 and Th-230
compounds. Ra-226 behaves as an alkaline earth: its daughter Rn-222 is an inert gas.
Natural secular disequilibrium is commonly found 1) where the deposition of uranium-
bearing sediments or rocks (or the later introduction of uranium into host sediments or
rocks) has taken place very recently - crudely less than ten million years or so - in which
case the radioactive decay products will not have "grown in" completely and will be
"deficient" relative to uranium content and 2) where the soluble uranyl ion has been leached
from the near surface by weathering while thorium has not in which case the uranium decay
products, and their associated radioactivity, may appear to be excessive in relation to
uranium. Radium too can migrate from its source under near-surface conditions, in the
same way as other alkaline earths. Radon gas, of course, moves easily unless confined
which is why the radon content of soil gas close to the surface of the ground approximates
that of ambient air even though radon content at depths of a meter or so ranges up to
hundreds, thousands, or tens of thousands of pCi/1. Nevertheless, radon anomalies in soil-
gas samples taJcen from comparable depths are often reasonably indicative of uranium
anomalies nearby.
The predominant source of gamma radiation in the U-238 series detected by ground or
airborne scintillometry is Bi-214 and as a result this isotope is the most widely used
geochemical pathfinder in uranium exploration. The fact that Bi-214 is separated from Rn-
222 in the decay series by only two extremely short-lived isotopes, Po-218 and Pb-214
helps to maintain a correlative relationship between radon and the observed Bi-214 gamma
radiation in spite of the fugacity of radon and in spite of the fact that gamma radiation is
essentially blocked by 20 cm or so of typical soil. Airborne gamma-ray spectrometry is an
excellent uranium reconnaissance tool. Standard practice is to calculate an apparent uranium
concentration from Bi-214 gamma-ray intensity as if secular equilibrium actually obtained
and to report this apparent concentration as "equivalent uranium" (eU). This same technique
and terminology is equally useful for concentrations of radon (eRn), radium (eRa) or other
precursors of Bi-214 in upper layers of the soil.
Geological controls influencing near-surface radon concentration, given the distribution
of radium in the underlying soil must take into account: 1) the proportion of Rn-222
newly-produced from Ra-226 able to escape from the solid mineral phase into soil gas - the
"emanating fraction," 2) the distribution of fractures, shear zones or other pathways which
facilitate upward radon migration and 3) soil-gas permeability. Of these three, soil-gas
permeability is the most easily quantified for a particular site. Gas permeability of soils
ranges over eight orders of magnitude in the extreme case of gravels and clays, although in
typical soil categories the range is reduced to about four or five orders of magnitude (5X10
-10 cm2 for sjjt. ciay mixtures to 5 X 10" cm2 for coarse sand). Variations in the
emanating fraction are too costly to evaluate and probably relatively insignificant for
purposes of radon exploration. Fractures or other pathways are essentially impossible to
quantify as controls but sometimes are recognizable visually or by geological inference as
confounding factors in particular sites. The seasonal cracking of montmorillonite-rich soils
to depths of as much as a meter, as in the case of Rincon-derived soils, may be characteristic
3
-------
of an entire formation and more important than soil permeability. Moisture content is a
major non-geological variable - though not the only one - because of its affect on both the
emanating fraction and soil-gas permeability. An optimum moisture content for combined
radon emanation and migration has been observed by Stranden, et al. (2) at about 25%.
Recognizing all these complexities, and lesser ones, it can nevertheless be argued 1) that
radium concentration or soil-gas radon concentration is a good measure of the "source
strength" for radon in the soil and 2) that soil-gas permeability is a first approximation of the
rate at which radon-bearing soil gas can reach the foundation of a building. A radon index
number (RIN) which includes only the two parameters, soil radium concentration and soil-
gas permeability was first suggested by DSMA Atcon, Ltd. (3). Tanner (4) subsequently
proposed a radon availability number (RAN) defined as the product of soil-gas radon
concentration, mean radon migration distance, and soil porosity. At about the same time
Kunz, et al. (5) developed a simplified RIN based empirically on comparisons with indoor
radon measurements in New York State. The Kunz formulation which we have adopted
here is:
RIN = 10(C) (K)1/2
where: C is soil-gas radon concentration (pCi/1)
K is the soil-gas permeability (cm2)
The factor 10 was inserted by Kunz, et al. merely to make the RIN
roughly comparable with their typical indoor radon levels.
A "depth factor," less than or equal to 1, is added by Kunz for areas
where the depth to the water table, bedrock or substantially less
permeable soil is known to be less than 10 feet.
The purpose of our work has been to test the practicality of deliberate radon exploration
using aeroradiometrics, analyzed to the optimum, as a reconnaissance tool followed by
application of the Kunz, et al. formulation and, where appropriate, by detailed site studies
in a large populated portion of Southern California where the indoor radon risk inferred
from random and non-random home tests has been purported to be very low.
For our study we chose the part of Southern California encompassed by the Los
Angeles Sheet of the Geological Map of California. This is a one-degree by two-degree
sheet (34° to 35° latitude, 118° to 120° longitude) including roughly the northern half of
Los Angeles and extending from about 8 miles east of Pasadena to about 18 miles west of
Santa Barbara.
We were fortunate in that shortly after initiating our analysis of aeroradiometric data, the
California Department of Health Services began a three-month alpha track survey in a
random sample of homes in a portion of our study area in northwestern Los Angeles -
southeastern Ventura counties. Through DHS efforts 82 homeowners (out of a total of 171
DHS participants) made their properties available to us for brief examination, for soil and
soil-gas sampling adjacent to the house and for surface gamma-ray measurements. The
4
-------
indoor radon measurements became available after our field measurements and the^ Vw-
the basis for calibration of our methodology. "
METHODOLOGY
AERORADIOMETRIC RECONNAISSANCE DATA
Be°innine in the mid 1970's, the U.S. Department of Energy sponsored the National
Airborne Radiometric Reconnaissance (NARR) to provide a semi-quantitative evaluation of
SSlreTemen^s^bution in the United States as part of the National Uranium
Resource Evaluation (NURE) ^ "4° for.
potassium, Tl-208 for thorium, and Bi-214 (using the 1.76 MeV photopeak) for uranium
typically by means of helicopter at an average of 400 feet or less above ground surface fitted
with a gamma-ray spectrometer and large crystal detectors Primary flight knes are typically
oriented east-west about 3 miles apart; tie lines are typically north-south and about 12 miles
apart. Radiometric data were corrected for live time, aircraft and equipment background,
cosmic background, Compton scatter, altitude, barometnc pressure and temperature. In
California the corrected data were statistically evaluated m terms of individual geological
units as shown on the The Geologic Map of (^if^a. Smnsucal data were reported on eU
»Tt, tc ctn and on their ratios to 0.01. The compiled data were also presented as
pseudo-contour maps, stacked profiles, anomaly maps, and "geological histograms" which
are frequency distributions of the e-concentrations and their ratios for each geological unit
Stacked orofiles show eU along each flight line and are the most site-specific graphic
presentation of the data. Extrapolations can be made to specific sites between flight lines
With varying degrees of reliability. We have done this using the appropriate geological
histograms and eU anomaly maps as a basis for choking the extrapolations. The wde
spacing of flight lines, particularly the north-south tie lines, and the small scale of the
graphical reproductions introduce large uncertainties^ the longer extrapolations. A striking
case in point is the community of Summerland which is almost entirely on radon-nch
Rincon Shale but also entirely between flight lines andtherefore not shown as eU
anomalous on the aeroradiometnc diagrams or maps. The point we would make, however,
is that our geological approach led us directly to Summerland, among other areas, as soon
as we identified the Rincon Shale as eU and Rn-anomalous in the areas where we had data.
Aeroradiometric data for the Los Angeles Sheet were plotted by geological unit and
informally subdivided into six categories having mean values between 1,0 -1.9 ppm eU and
6.0 - 6.9 ppm eU.
Perhaps the main value of extrapolation between flight lines is that it makes possible the
comDarisons of aeroradiometric data with soil-gas radon concentrations and with indoor
measurements both of which we discuss next.
5
-------
SOIL-GAS RADON CONCENTRATION
We used the method of Reimer (6) to obtain soil gas samples: A stainless steel probe,
0.80 cm OD, 0.16 cm ID, is pounded into the soil to a depth of 75 cm, an O-ring fitting
with a septum is attached and three successive 10 cc samples of soil gas are extracted by
hypodermic syringe through the septum after purging the probe. The small diameter of the
probe ensures minimal disturbance of the subsurface environment. The 75 cm depth is a
compromise between probe refusal or bending and the more ideal depth of 1 to 1.5 m where
radon concentration in soil-gas tends to reach an equilibrium value. It also enables sampling
from the lower B or upper C horizon. Samples were always collected during the day, not
during periods of unstable weather or strong winds, and not after precipitation until dry
conditions are allowed to return. Special care was taken to sample natural soil away from
any filled zone. The time of sampling was recorded
Soil-gas samples were then taken to the laboratory for radon measurement by injecting
the sample through a valve and septum device into a Lucas cell radon/radon daughter
detector (RDA 200, manufactured by EDA Instruments, Inc.). Measurements were made 3
to 24 hours after soil gas sampling, more than sufficient time for decay of Ra-220 (thoron).
Earlier experiments showed that radon daughters in the original soil-gas sample or generated
up to the time of injection into the Lucas cell are plated out in the hypodermic syringe. Since
there is also some adsorption of radon, particularly on the syringe plunger, and other
potential complications, the entire assemblage of components for sampling and analysis was
calibrated as configured against known radon-bearing gas samples from the EPA operated
chamber at Las Vegas, Nevada. Each Lucas cell was partially evacuated to a standard
pressure prior to sample injection. Early experiments also showed that truly consistent
results require 25 minutes of counting in the Lucas cell detector. Counts up to 5 minutes
were found to be insufficiently consistent for the research stage of our work and were
omitted from the calculations. Even at moderate concentrations of radon, however, this
long counting period results in appreciable contamination of the Lucas cells, as Reimer
points out, and for reconnaissance purposes much shorter counting periods may be
acceptable.
The formula used to calculate radon concentration is:
C = (N30-N5 - CB)/(TxSV xDFxCF)
where: C = Rn-222 concentration in pCi/1
N30 = Counts in 30 minutes
N5 = Counts in 5 minutes
CB = Cell background prior to sample injection
T = Counting period: 25 minutes
6
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SV = Sample volume: 0.01 liters
DF = Decay factor for radon for elapsed sampling-to-counting time:
from standard table.
CF = "Cell Factor" in cpm/pCi from calibration of configured
apparatus using known radon chamber samples.
Prior to sampling in the study area, the following indications of precision and
reproducibility were obtained from a test plot:
1) Radon measured from soil-gas samples at 75 cm depth from 9 probe sites within a
square meter yielded a Gaussian distribution, arithmetic mean =1,071 pCi/1, standard
deviation = 106 pCi/1 (coefficient of variation = 10 %).
2) Radon measured from five soil gas samples consecutively drawn from one probe site
in the same plot yielded a Gaussian distribution, arithmetic mean = 1,052 pCi/1, standard
deviation = 85 pCi/1 (coefficient of variation = 8 %).
Standard procedure in the primary subarea was to occupy three probe sites within 0.5 to
4 meters of each house and to take three soil-gas samples at 75 cm depth from each site. If
the first two radon analyses from a given probe site were within ten percent of each other,
the third sample was discarded, otherwise it was measured. The soil-gas radon value
reported for each house location is the mean of the three probe sites. The variation
coefficient for each house location ranged from 1.1 % to 63.3 % with a mean of 18.5 %.
SOIL-GAS PERMEABILITY
Recent studies including those of Kunz and Tanner previously cited have adopted a
quantitative determination of soil-gas permeability based upon measured gas flow under
measured differential pressure during pumping of gas from the ground or pumping of air
into the ground. However this apparently rigorous method rests upon assumptions about
the size and geometry of the soil volume from which the gas is drawn or pumped into even
in the case of uniform soil profiles. It is unclear even in presumably homogeneous soils
whether the geometry of the soil volume should be assumed to be spherical or
hemispherical, for example. Many soils are not only layered but are randomly penetrated by
fractures, root cavities or animal burrows or contain irregular layers of varying permeability.
In-situ measurement of water permeability is not truly indicative of in-situ gas
permeability nor are gas permeability measurements on reconstructed soils.
Bearing in mind cost and practicality we have adopted the technique of permeability
estimation based upon grain size distribution determined by screening the dried soil. This
method is eminently suitable for reconnaissance work and perhaps as good as any for
rfptailw* follow-on studies, It has the advantage not only of simplicity but also of avoiding
Ae^ntiXtoge errors that might arise during flow-guage-volume pumping
measurements due to openings in the sod or zones of varying permeability which are
7
-------
entirely site-specific on a small scale and therefore not necessarily representative of the area
under consideration.
Soil samples taken at depths of 25 to 35 cm from the same sites as soil-gas samples
were oven dried overnight at 100 degrees C. and sieved by mechanical shaker. Soil types
were categorized and permeabilities were assigned on the basis of published tables, e.g.
Sextro, et al. (7). Because of the large number of samples involved we did not perform
wet separation of clay and silt. Even more significant is the disregard of moisture content
and degree of compaction or cementation of the soil. Perhaps the permeability assigned in
this way should be called pseudo-permeability or at best equivalent permeability but the
method is as likely as any to provide a basis for comparison with reasonable cost.
Moreover it should be noted that permeability appears in the RIN formulation, above, only
as its square root
RESULTS FROM THE PRIMARY SUBAREA IN NORTHWESTERN LOS ANGELES -
SOUTHEASTERN VENTURA COUNTIES
HOUSE CHARACTERISTICS IN THE PRIMARY SUBAREA
Mention was made above of the 82 homes in the DHS three-month alpha track survey
which were made available to us for soil-gas radon and soil permeability measurements.
Questionnaires about house design and use were completed by all participants. None of the
houses had indoor measurements in excess of 2.9 pCi/1 and we were not able to show that
any of the adjacent soils had more than normal gamma-ray activity at the ground surface
using a hand-held scintillometer with a one cubic inch T1 activated Nal crystal. None of the
82 houses have a basement and only 4 % have crawl space construction; the rest are slab-
on-grade. Ventilation patterns were approximately similar during the test period which was
characterized by mild coastal and near-coastal Southern California weather. It would appear
that in this survey building characteristics and meteorological factors probably had less-than-
average influence on indoor radon levels.
AERORADIOMETRIC DATA, SOIL-GAS RADON, RIN AND INDOOR RADON IN
THE PRIMARY SUBAREA: CORRELATIVE RELATIONSHIPS
Figure 1 shows the relationship observed between airborne equivalent uranium (eU) and
soil-gas radon concentrations obtained by soil probe from the vicinities of the 82 houses in
the primary subarea. The strength of the correlation probably reflects the proximity of Rn-
222 and Bi-214 in the decay series but was somewhat surprising and encouraging
nevertheless.
Figure 2 shows the relationship observed between indoor radon and soil-gas radon for
the 82 houses in the primary subarea. Again the correlation is very encouraging in spite of
some scatter. We believe that it probably reflects in part the similarity between house
parameters noted above. However it may also reflect the relatively well-ventilated character
8
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y • 875 04x - I 160.0, R-squared. 757
4Q00J
3500-1
300CM
2500-1
3 200Ch
| i 50oJ
OO
5004
Airborne Equivalent Uranium (eU) pprn
Figure 1. Soil-gas radon in relation to airborne equivalent radon in the primary stud}' area.
y - .OOlx ~ .394, R-squared: .503
OO
C
a
O O
Figure 2. Indoor radon in relation to soil-gas radon in the primary study area.
y - ,639x ~ .273, R-squared. .663
25
CD
(ZD
u
a
GD
CO
aoo
25
3 5
RIN
«
Figure 3. Indoor radon in relation to RIN in the primary study area.
9
-------
of nearly all homes in the region because, even though some soil-gas radon concentrations
were between 2,000 and 4,500 pCi/1, the maximum indoor radon level was only 2.9 pCi/1.
Figure 3 shows the relationship observed between indoor radon and the RIN value. The
essential difference between soil-gas radon and RIN is that soil-gas permeability is taken
into account in the latter. It is not surprising therefore that the correlation of indoor radon
with RIN value is even better than with soil-gas radon.
Equivalent uranium extrapolated from the NARR data in the primary subarea shows a
range of 1.5 to 5.8 ppm eU, an arithmetic mean (AM) of 2.9 ppm, a geometric mean (GM)
of 2.8 ppm, and an arithmetic standard deviation (ASD) of 0.86 ppm. For soil-gas radon
concentrations the range is from 206 to 4,390 pCi/1 and the remaining statistics are: AM =
1,388 pCi/1, GM = 1,162 pCi/1 and ASD = 859 pCi/1. Indoor radon shows a range of 0.2
to 2.9 pCi/1, and AM = 1.2 pCi/1, GM = 0.99 pCi/1, ASD = 0.70 pCi/1. All three frequency
distributions are skewed toward a log-normal pattern but are quite irregular and the sample
size is insufficient to demonstrate log-normality.
DISCOVERY OF THE RADON-PRONE RINCON SHALE BELT
AERORADIOMETRIC INDICATIONS
As shown in Figure 1 the primary subarea yielded relatively low airborne eU values. In
fact none of the 82 houses tested is underlain by a geological unit with a truly anomalous
mean eU level: the highest category is 4.0 to 4.9 ppm eU. However the excellent
correlations between eU, soil-gas radon and indoor radon at the low levels observed
demanded that we re-examine the aeroradiometric map.
In the northwestern Los Angeles - southeastern Ventura region itself there are a few
geological units in category 5.0 to 5.9 ppm eU but these are predominandy in undeveloped
terrain. However, to the west of the primary subarea, passing through major parts of Santa
Barbara city and vicinity, there is a pronounced east-westerly trending belt with eU in
category 6.0 to 6.9 ppm and an adjacent belt in category 5.0 to 5.9 ppm eU. Both of these
belts coincide with the generalized unit "ML" (Lower Miocene) as shown on the Los
Angeles Geological Map Sheet. ML in this area could encompass parts or all of three
geological formations and several members. Lithology pointed to two possible uranium-
rich candidates: the dark, moderately organic Rincon Shale and the lower Monterey
Formation which is locally organic and locally phosphate-bearing. Uranium tends to
associate with organic matter and with phosphate. Probe soil-gas sampling and analysis,
followed by radon screening tests in a handful of houses, veiy rapidly identified the Rincon
Shale as the undoubted source of most, if not all, of the anomalous airborne signature.
10
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RADON IN THE RINCON SHALE
To date we have made soil-gas radon measurements at 68 sites on the Rincon Shale
extending from near the easterly boundary 01 banta Barbara County to Gaviota on the west-
a strike length of about 48 miles. The range of radon concentrations is from 1,240 to
16,200 pCi/1, with an AM of 4,480 pCi/1, of 3,817 pCi/1, and an ASD of 1,891 pCi/1.
The mean values are more than three times higher than the means of soil-gas radon
concentrations in the primary study or in non-Rincon units in Santa Barbara County and
elsewhere in Southern California that we have tested to date. It may be geologically
significant that the highest soil-gas radon concentrations appear to be near the middle of this
belt, near Santa Barbara itself, though more data need to be obtained on the east and the
west to confirm this pattern. The frequency distribution of soil-gas radon values is
bimodal.
INDOOR RADON MEASUREMENTS IN HOUSES ON THE RINCON SHALE
We have now tested 79 homes in Santa Barbara County, the great majority in easterly
c « vtzrhxn citv Montecito and Summerland. Thirty three of these homes are on the
Santa Sliehtlv over 76 % of the homes on the Rincon Shale have screening test
\ trt 7 ria\, activated charcoals) in excess of 4 pCi/1. Twenty six percent exceed
results, (three3i to7.iw measurements of from one to six months duration, under
SSffiSwl 42 % exceeding 4 pCVl and none exceeding 20 pCi/i
cnme of the worst situations were mitigated prior to completion of the follow-on
although so t on Rincon Shale has a follow-on measurement exceeding
is on a sUde area with a badly cracked slab-on-grade at the time of
Keller of the Geology Department, University of California Santa Barbara has
our statistics very closely by providing single activated charcoal detectors to
confirmed . on a^d off the Rincon Shale (8). An estimated 4,000 plus homes
areattheindicated level of risk; extensive new construction on the Rincon Shale is limited
only by domestic water supply*
COMPARISONS BETWEEN AREAS AND DISCUSSION
Fitmres 4 5 and 6 illustrate relationships between the same parameters as figures 1,2
5vri»nt that these fieures represent the two areas combined, i.e. the primary study
SIkmm nlus the Santa Barbara Rincon Shale area on the same graphs. The Santa Barbara
?Wv dltlroutsTc Sated with a tick on the circular data symbols. We do not yet
have all threecategories of data on more than a few houses, hence the small number of
11
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y - 755 447* - 868.733, R-squared. 831
7000.
5000.
- 4000.
OCT
2000.
Airborne Equivalent Uranium (eU) ppm
Figure 4. Soil-gas radon in relation to airborne equivalent radon in the entire study area.
y - 003x - 2.693, R-squared: .472
45-
35.
30.
25.
" ~ 20.
0
1000
2000
3000
5000
6000
7000
Soli Gas pCi/l
Figure 5. Indoor radon in relation to soil-gas radon in the entire study area.
y - 1.992* - 1.532, R-jquared: .724
40-
25
20
10
18
8
10
14
16
0
2
6
12
4
2
RIN
Figure 6. Indoor radon in relation to RIN in the entire study area.
12
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Santa Barbara points. The considerable range in indoor radon relative to soil-gas radon or
RIN illustrates the very considerable influence of building design and use in this radon-
prone area.
The purpose of combining the data in figures 4, 5 and 6 is not only to make the
comparison between areas more visible but also to show that the two areas actually represent
two quite different populations. Note that the regression lines shown for the combined data
depart considerably from the regression lines for the primary subarea data. The existence of
sub-populations needs to be kept in mind whenever attempts are made to use regional
frequency distributions of radon occurrence as a basis for predicting national or regional
radon risk.
The correlations that we have obtained regionally between aeroradiometry, soil-gas
radon at 75 cm depth adjusted for soil-gas permeability, geology, and indoor radon
concentrations are apparently better than those reported from other places. In our opinion
this probably reflects the fact that the unmetamorphosed sedimentary rocks that we find in
much of coastal and central California tend either to have or not to have anomalous uranium
concentrations disseminated more or less throughout the unit This is not to say that erratic
uranium-rich zones do not occur in these same rocks: there are many examples of small
quite rich uranium concentrations in the Monterey, in the Sespe and several other
unmetamorphosed formations. The locations of these erratic concentrations are extremely
difficult to predict but, unlike some situations in metamorphosed terrains for example, such
concentrations are few and far between. Anomalous amounts of uranium disseminated
throughout a rock unit can affect a large number of homes but it is especially in these
circumstances that deliberate geological exploration can be a more efficient approach to
radon risk identification than simple random sampling or non-random testing of homes.
Judging by experience in the mineral industry, exploration based upon geological models
of occurrence is infinitely more likely to find anomalous occurrences than is random
sampling. Models for geological predictability can also contribute to radon risk assessment
on undeveloped tracts of land.
13
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REFERENCES
1. Nazaroff, W. W. and Nero, A. V. (eds.). Radon and its Decay Products. John
Wiley & Sons, Inc., 1988.
2. Stranden, E, Kolston, A. K. and Lind, B. Radon exhalation: moisture and
temperature dependence. Health Physics. 47: 480-484, 1984.
3. DSMA Atcon Ltd. Review of existing instrumentation and evaluation of
possibilities for research and development of instrumentation to determine future
levels of radon at a proposed building site. INFO-0096, Atomic Energy Control
Board, Ottawa, Ontario, 1983. 30 pp.
4. Tanner, A. B. Measurement of radon availability from soil. In: M. A. Markos and
R. H. Hansman (eds), Geological Causes of Natural Radionuclide Anomalies.
Missouri Department of Natural Resources, Division of Geology and Land Survey.
Spec. Pub. No. 4, 1987. p. 139 - 146.
5. Kunz, C., Laymon, C. A. and Parker, C. Gravelly soils and indoor radon.
Presented at EPA Symposium on Radon and Radon Reduction Technology, Denver,
CO. Oct. 17 - 21, 1988.
6. Reimer, G. M. Reconnaissance techniques for determining soil-gas radon
concentrations: An example from Prince Georges County, Maryland. Geophysical
Research Letters. 17: 809-812. 1990.
7. Sextro, R. G., Moed, B. A., Nazaroff, W. W„ Revzan, K. L. and Nero, A. V.
Investigations of soil as a source of indoor radon. In: P. K. Hopke (ed.), Radon
and its Decay Products: Occurrence, Properties and Health Effects. American
Chemical Society, Washington, D.C., 1987. p. 10 -29.
8. Burns, M. Radon may lurk in 2,000 homes, tests find. Santa Barbara News-
Press. February 4, 1991.
14
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Session IX:
Radon Occurrence in the
Natural Environment - POSTERS
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IXP-1
GEOLOGIC EVALUATION OF RADON AVAILABILITY IN NEW MEXICO:
A Progress Report
by: Virginia T. McLemore and John W. Hawley
New Mexico Bureau of Mines and Mineral Resources
Socorro, NM 87801
and
Ralph A. Manchego
New Mexico Environmental Improvement Division
1190 St. Francis Dr.
Santa Fe, NM 87503
ABSTRACT
The New Mexico Bureau of Mines and Mineral Resources and the Radiatio
Licensing and Registration Section of the New Mexico Environmental Improvement Division
in cooperation with the U.S. Environmental Protection Agency (EPA) have been evaluatin »
geologic and soil conditions that may contribute to elevated levels of indoor radon
throughout New Mexico. During the first phase of this evaluation, New Mexico lands have
been subdivided into three provisional radon-availability categories (high, moderate and
low). Data sources include 1) aerial radiometric sui^eys; 2) uranium-resource evaluations-
3) reports on lithologic character and structure of major geologic units, 4) hydrogeologic and
geochemical information; and 5) soil surveys (including data on particle size, clay minerals
moisture regimes and permeability). This information was used in selection of private homes
tested during an initial random survey of indoor radon in 1989. The New Mexico rado
survey was unique in that it was the first in the nation to successfully use a decentralized
strategy in the attempt to place charcoal canisters randomly across a state. Results of 1775
homes tested throughout New Mexico during January to March, 1989 indicated that 24<7
had indoor-radon screening results exceeding the recommended EPA guideline of 4
picocuries per liter of air (pCi/L). Visits were also made to about 50 home sites in north-
central New Mexico where preliminary surveys (random and volunteer) indicated that
geologic and soil conditions were the major factors contributing to elevated indoor r-winn
levels (>10 pCi/L). n
Studies to date suggest that elevated radon levels are commonly associated with
hillside building sites where floors and walls are contiguous to geologic units such as highly-
fractured bedrock of varying lithology, limestones with solution enlarged joints, or thick
pumice deposits. Bedrock units, associated alluvial-colluvial deposits, and ground water that
contain high concentrations of uranium and thorium locally make a significant contribution
and need further study. Some homes built on clay-rich expansive soils also have elevated
levels of radon. Areas that have been tested in the vicinity of uranium mines and mills have
relatively low levels of indoor radon (below 10 pCi/L). A better understanding of the natural
factors that affect indoor radon concentrations in New Mexico will only be gained through
integrated, site-specific investigations which combine more comprehensive indoor-radon
-------
measurements and home construction information with data on geology, hydrology and soils.
INTRODUCTION
Concern about public health risks to the general population of the State of New
Mexico from exposure to radon gas and its decay products in homes, schools, places of
employment and office buildings, has been raised over the past few years by the medical,
scientific communities, and government agencies. Concern raised by these interest groups
has subsequently alerted the general public. While other factors such as cigarettes
contribute to lung cancer deaths each year, airborne radon gas exposures may be
accountable for 15% to 20% of all lung cancer deaths in the United States.
In 1989, in an effort to evaluate the levels of radon which contribute to public health
risks associated with radon exposure in New Mexico, the Radiation Licensing and
Registration Section (RLRS) of the Environmental Improvement Division (EID) and the
Environmental Protection Agency (EPA) initiated a random radon-screening survey of
private homes throughout the State. Such a screening test offers the homeowner an
indication of indoor levels of radon gas at a given point in time. This test is of short
duration and does not provide information over a long period of time. The EPA
recommends that exposure levels be calculated in terms of an annual average before any
further action is undertaken. The short screening test is only an indication of the indoor-
radon level; and, for this reason, the charcoal canisters are placed in individual homes where
they would produce the highest measurements or "worst case conditions." Therefore, tests
are conducted in the winter months when closed-house conditions are most likely to be
observed. If these screening tests show radon levels of 4 picocuries per liter of air (pCi/L)
or above, then it is recommended that long term testing be conducted. If follow-up testing
confirms high radon levels, the EPA suggests that a mitigation program should be
undertaken. This report outlines the methods used in the random selection of homes for
radon-exposure measurements, and gives a preliminary interpretation of the results from this
screening.
Results from 1775 houses tested during January to March of 1989 indicate that about
24% of those tested had radon screening results at or above the EPA "action-level" guideline
of 4 pCi/L. All of the results of this radon survey indicate "worst case" screening conditions
for radon gas tests. The resulting numbers only indicate the homes with a potential radon
problem. About 5% of the homes tested had concentrations greater than 10 pCi/L and only
about one percent exceeded 20 pCi/L with a maximum value of about 105 pCi/L.
The New Mexico radon survey was unique in that it was the first in the nation to
successfully use a decentralized strategy in the attempt to place charcoal radon test canisters
randomly across a State. The eighteen states which had previously participated jointly with
EPA in randomly placing canisters in owner-occupied homes had relied upon centralized
phone calling and canister distribution. Additionally, New Mexico utilized Environmental
Improvement Division staff resources (central office, district and field offices) in placing the
canisters as well as volunteers from the City of Albuquerque Environmental Health staff and
other organization volunteers. This strategy was selected since EID District and Field office
staff were known to be familiar with the population centers in their areas as well as with the
more isolated areas. Project staff predicted that increasing the proximity of staff to
-------
a akn increase the success of the canister placement. Other
s.TsTaShTcantracTe°d outside private companies in their canister placement program
states nau emiti , t workine from one central location.
" Had New Mexico's"^clntralized program resulted in the placement of 50 canisters in two
, , * in he nilot survey. Past experience in other states had resulted in a pilot
days for use in th p ^ whUe Qther states required an average of tWo to
Emonths to place over 2000 canisters, New Mexico successfully placed 1775 canisters
'eSS Staff believe^that the decentralized radon canister placement method used in New
_ . " ° ' mst effective, utilizes existing staff, can be implemented m a more timely
^lX'CO,LT nrovdef indoor radon analytical results more quickly to Health and
fashion and pr Staff a|sQ recomme„d that the decentralized
EnvironmeM staff ^ ^ ^ sparse and widdy dislribule(, p0pUiations.
RaCCw . > exnerience has demonstrated the usefulness of such a strategy.
New aspect of the New Mexico survey was the evaluation of geologic,
Another impo P contribute to elevated levels of indoor radon
SOU and c™ ^ work was done b the staff Qf the Office of State Geologist, New
throughout the state. Mineral Resources (NMBMMR). During the first phase of
Mexico Bureau of Mines; and MmeraU^ur«»^ ^ ^ ^ radon.availabiH
this investigation, N[ew ™ ^ Da(a SQurces inciucJed 1) aerial radiometric surveys;
categories (high, moderate reports on lithology and structure of major geologic
2) uranium-resource evaluations,:>) report^™ ^ ^ ^ (jnduding da,a on
units; 4) hydrogeologic and g® regimes and permeability). This information was used
for the initial screening survey jus,
discussed.
PRELIMINARY STUDIES (1986-1988)
Preliminary studies prior to the 1989 survey involved 1) random, short-term screening
during the winter of 1986-1987 of homes in north-central New Mexico, and 2) a 1988
statewide evaluation of natural conditions that could significantly influence elevated indoor
radon levels.
Preliminary Screening Survey of Homes
In order to evaluate the distribution and concentration of radon gas throughout the
State of New Mexico, the Radiation Licensing and Registration Section (RLRS) of the
NMEID, in conjunction with the four district offices began the screening survey of randomly
pre-selected homes in New Mexico. "
NMEID staff provided the man hours for the screening process. Materials for testinc
were provided by EPA, training for EID personnel was handled by EPA staff. Materials for
public outreach and educational materials were also provided by EPA. The list of homes
was randomly selected by the EPA Statistical Staff. Homeowners' names, phone numbers
and addresses after being randomly selected by EPA staff, were used to do the screening
Another important aspect of the screening survey was a study of the geographic
-------
distribution of radon gas in an indoor environment. A preliminary study was conducted in
the winter months of 1986-1987 by EID staff in the north-central areas of the State using
working level meters in volunteer homes. Either a 24- or a 48-hour period was used to
determine the average radon gas concentration and these two values were averaged for
reporting purposes. Standard EPA protocol was adhered to throughout the screening
process. Results of this preliminary survey were tabulated by counties.
Preliminary Evaluation of Natural Conditions Influencing Indoor Radon (1988); New
Mexico Bureau of Mines and Mineral Resources
A major objective of the preliminary phase of this study was to identify and
characterize areas in New Mexico where natural conditions (e.g. geology, hydrology, and
soils) had the potential for making significant contributions to elevated indoor radon values.
Such areas needed to be identified so that a larger percentage of radon detectors could be
allocated to those localities during the 1989 survey conducted by the NMEID in cooperation
with the EPA. This phase of the investigation (McLemore and Hawley, 1988) was
conducted by the New Mexico Bureau of Mines and Mineral Resources-Office of State
Geologist (NMBMMR).
Rocks and soils in New Mexico were initially grouped into three radon-availability
categories based on geologic and hydrologic interpretations, which are specific to New
Mexico conditions. Subsequently, each county and the major cities in the state were given
a radon-availability rating based on the predominant availability category established for
geologic units in that area (Tables 1 and 2, Fig. 1).
TABLE 1. PRELIMINARY RADON-AVAILABILITY RATING FOR COUNTIES IN
NEW MEXICO.
High
Moderate
Low
Los Alamos
Luna
McKinley
Rio Arriba
Dona Ana
Hidalgo
Bernalillo
Catron
Cibola
Chaves
Colfax
Eddy
Grant
Lea
Curry
De Baca
Guadalupe
Harding
Mora
Sandoval
Santa Fe
Socorro
Taos
Otero
Roosevelt
San Miguel
Lincoln
San Juan
Torrance
Valencia
Sierra
Quay
Union
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TABLE 2. PRELIMINARY RADON-AVAILABILITY RATING FOR SOME OF THE
LARGEST CITIES IN NEW MEXICO (POPULATION FROM WILLIAMS, 1986;
POPULATION IN PARENTHESES FROM U.S. CENSUS BUREAU FOR 1990 AS
REPORTED IN THE ALBUQUERQUE JOURNAL, JANUARY 26, 1991).
population
r; County 1984 estimates Classification
3 (1990)
Albuquerque
Bernalillo
Santa Fe
Santa Fe
Las Cruces
Dona Ana
Roswell
Chaves
Farmington
San Juan
Hobbs
Lea
Clovis
Curry
Carlsbad
Eddy
Alamogordo
Otero
Gallup
McKinley
Los Alamos-
White Rock
Los Alamos
Las Vegas
San Miguel
Grants-Milan
Cibola
Rio Rancho
Sandoval
Artesia
Eddy
Lovington
Lea
Silver City
Grant
Portales
Roosevelt
Deming
Luna
350,575 (384,736)
moderate
52,274 ( 55,859)
high
50,275 ( 62,126)
high
45,702 ( 44,654)
high
37,332 ( 33,997)
low
35,029 ( 29,115)
moderate
33,424 ( 30,954)
moderate
28,433 ( 24,952)
high
27,485 ( 27,596)
low
20,959
high
19,040
high
15,364
low
12,823
moderate
12,310 ( 32,505)
moderate
11,938
low
11,704
moderate
11,014
low
10,456
low
10,609
high
It should be emphasized that, even in counties with moderate and high availability
ratings, many houses may have very low levels of indoor radon. Procedures used in
developing the preliminary rating scheme are discussed in more detail in the following
sections.
RADON AVAILABILITY AS A FUNCTION OF GEOLOGY AND SOILS
Introduction
The first step in formulating a sample plan for the survey of indoor radon levels in
New Mexico was to evaluate the rocks and soils for radon-availability (McLemore and
-------
Hawley, 1988). Major geologic factors influencing radon-availability include 1) lithology
and uranium or radium content of bedrock and unconsolidated geologic deposits, 2) rock
structure (faults and fractures), 3) porosity and permeability, and 4) nature of the water
in both the saturated and unsaturated zones. Texture, structure, mineralogy, and
moisture regimes of surficial soils (~ upper 2 meters of unconsolidated earth materials)
are also major factors influencing radon availability (Brookins, 1986, 1990; Brookins and
Enzel, 1989).
The primary information sources used were published reports and unpublished
records in the NMBM&MR files including data from 1) aerial radiometric surveys, 2)
geologic maps, 3) uranium resource surveys, and 4) soil surveys. Other sources of
information include special reports on geochemical and groundwater investigations, and a
limited amount of data on indoor radon concentrations. This information was compiled
by McLemore and Hawley (1988) in order to provide the EPA and the NMEID with a
preliminary estimate of radon-availability for their 1989 program to randomly sample
individual New Mexico homes.
In the fall of 1989 about 50 sites in north-central New Mexico with elevated
indoor radon levels (10-105 pCi/L) detected in the random survey were visited as part of
a cooperative study with the EPA on indoor-radon mitigation strategies. At that time,
detailed observations were also made of on-site geologic and soil conditions that could
contribute to indoor radon. This is the only follow-up verification of preliminary test
results made to date.
Aerial Radiometric Surveys
Aerial radiometric surveys provide (Duval, 1988) a regional estimate of uranium
concentrations in the surficial rocks and soils and correlate well with the amount of radon
in the ground (Peake and Schumann, in press). However, it must be emphasized that the
amount of radon that is available to enter a house from the ground is dependent upon
many other variables. The primary source for aerial radiometric data in New Mexico is a
series of reports prepared as part of the National Uranium Resource Evaluation
(NURE) program. The NURE program was established in 1974 and terminated in 1984
and the main objectives were 1) to provide an assessment of the uranium resources in
the United States and 2) to identify areas of uranium mineralization.
Aerial radiometric data are dependent upon a constant altitude above the ground.
However, in some areas of New Mexico where there are steep mountains and deep
canyons, constant altitude could not be maintained, resulting in erroneous measurements.
Both airplanes and helicopters were used to collect data in New Mexico and helicopters
were able to better maintain constant altitude than airplanes.
The NURE aerial radiometric data has been released in reports based on 1° x 2°
topographic quadrangles and on magnetic tape. The quadrangle reports include a brief
narrative and graphs of the flight line data, uranium anomaly maps, and histograms of
the radioactivity data by lithology. Aerial gamma-ray contour maps of regional surface
concentrations of uranium, potassium, and thorium in New Mexico has been recently
published by the U.S. Geological Survey at a scale of 1:750,000 (Duval, 1988). A colored
contour map of the state showing radiometric equivalent uranium (eU) concentrations
was also prepared by the U.S.G.S. at a scale of 1:1,000,000 from the computerized aerial
-------
radiometric data. Copies of this map are available for inspection at the NMBM&MR
and NMEID.
Several problems exist with the aerial radiometric data. Most 1° x 2° auad
in New Mexico were flown with east-west flight line spacings of three miles Ho fan^ s
parts of the Tularosa and all of the Carlsbad, Raton, and Ft. Sumner quadrancIeT(Wrt
of Chaves, Colfax, De Baca, Dona Ana, Eddy, Guadalupe, Lincoln, Sierra Taos and
Torrance Counties) were flown with six mile spacings. Large unmeasured'areas exist
between these flight lines and localized anomalies may be overlooked In addition
all areas of New Mexico were flown. The largest area of no data is in the vicinity of th
White Sands Missile Range north of Las Cruces and west of Alamoeordo nrimnrik,
Dona Ana and Otero Counties. ^
In the southwestern part of New Mexico, atmospheric inversions are known to
occur frequently and may result in uncompensated U-air anomalies. Atmospheric nlum
generated by copper smelters in southwestern New Mexico and southeastern Arizona S
also may result in uranium anomalies in the surveys. The effect of these atmospheric
anomalies in predicting elevated levels of indoor radon is unknown
The extremely high uranium anomalies in the aerial radiometric data (>5 nnm
eU) near Grants, Cibola County, are a result of high values measured over mill tailing
four uranium mill sites. The computer-generated aerial radiometric maps produced bv **
the U.S. Geological Survey exaggerate the significance of these anomalies; the actual
area affected by the mill tailings is small. Surveys conducted by the NMEID and
Homestake Mining Company suggest that mill tailings have not contributed to indoor
radon levels in nearby houses. Capping of mill tailings and other remedial measures ar
in progress in this area of New Mexico. e
General Geologic and Soils Information
Information on the type and distribution of the lithologic and structural units in
New Mexico is important in identifying areas of radon-availability for indoor-radon
generation. Published geologic maps, primarily the New Mexico Geological Societv
(1982) State Map and NMBMMR State Uranium Resources Map (McLemore and
Chenoweth, 1988), were used in the preliminary phase of the study.
There are very few direct measurements of radon or radium concentrations in th
rocks and soils of New Mexico; however, data on uranium concentrations in rocks and ^
soils of New Mexico is more plentiful. Rocks with uranium concentrations exceeding 5
ppm U are sufficient to produce elevated levels of indoor radon (Peake and Hess 1987"*
In New Mexico, most rock types could provide a source for indoor radon. '
In addition to lithology, structural features also play an important role in manv
areas. Fault zones and other areas of highly jointed rocks are likely sites of uranium
mineralization; and they also provide a pathway for radon to migrate into houses (Oede
et al., 1987). Karst (rock dissolution) features in carbonate and gypsiferous terranes ma"
also provide pathways for migration of radon. Highly permeable and porous rocks and y
soils (such as pumice, poorly welded tuffs, sand and gravel, and expansive clays) are also
potential source materials that need to be evaluated throughout the state.
-------
Uranium Occurrences
Areas of uranium and thorium occurrences (as well as mine-mill sites) are well
known in New Mexico (McLemore, 1983; McLemore and Chenoweth, 1989). The
majority of these areas are found in relatively unpopulated parts of the state; however,
there are a number of important exceptions. Uraniferous coals in the Gallup area,
McKinley County, were once mined for uranium, and the host rocks are probably a good
source for radon. Other areas, such as northern Santa Fe County, and White Signal in
Grant County, occur at sites of uranium mineralization near or at the surface that could
provide radon in nearby houses. Some indurated caliche (calcrete) horizons in soils and
surficial geologic formations may also be sources of elevated uranium-radium-radon
levels. More detailed studies of the correlation of known uranium and thorium
occurrences, population distribution, and indoor radon levels are required.
Soil Surveys
Soil textural, permeability, and mineral data from soil surveys prepared by the
U.S. Soil Conservation Service are an important data base for any assessment of radon
availability. Well-drained, permeable soils, typically with hydraulic conductivity
measurements exceeding 6 in/hr, provide excellent pathways for radon. Many areas of
elevated radiometric- equivalent uranium (eU) concentrations shown on the aerial
radiometric map are also associated with permeable soils. However, the soil permeability
data used in this preliminary study is generalized and based on very few actual
measurements of hydraulic conductivity. Also soil-moisture regimes vary significantly on
a seasonal as well as an annual basis, and they can materially affect permeability values.
Clay-rich soils with high shrink-swell potential develop wide and deep desiccation cracks
when dry (a typical condition in New Mexico) and provide pathways for rapid soil-gas
transfer. These soils, however, are very impermeable when moist.
Other Sources of Information
Other information sources were examined to support interpretations of
aforementioned data. The NURE geochemical data consists of uranium analyses of
stream sediment and ground water samples (McLemore and Chamberlin, 1986).
Geochemical reconnaissance maps showing the distribution of uranium for each 1° x 2°
quadrangle in New Mexico were used to identify areas of high uranium concentrations.
Most of these areas correlate well with areas identified using aerial radiometric data. A
few problems exist with the NURE geochemical data. Uranium concentrations in stream
sediments are actually displaced and diluted values. Very little information, such as host
rock and depth of the ground water samples, is available. In addition, many populated
areas of New Mexico were not sampled and no data exists.
Ground water data, such as depth, flow direction, and chemical composition,
provide additional information on hydrogeologic conditions which may affect the levels of
indoor radon. Other data such as distribution and character of geothermal areas were
also used in this assessment. In Idaho, houses built in geothermal areas have higher
levels of indoor radon (Ogden et al., 1987). This relationship is being tested in New
-------
Mexico at present (James Witcher, New Mexico State University, personal commun.,
Feb., 1990).
Only a limited amount of indoor radon measurements are available on a statewide
basis. Much of the data from past studies (prior to 1988) are confidential, at least on a
site-specific scale. However, all available published and unpublished data were reviewed
during this preliminary investigation.
PRELIMINARY CLASSIFICATION OF RADON AVAILABILITY
Prior to placement of detectors in the winter of 1989 random survey, the rocks
and soils in New Mexico were geographically grouped into three radon-availability
categories according to interpretations of available geologic data (Tables 1, 2; Fig. 1;
McLemore and Hawley, 1988). These relative radon-availability categories are specific to
New Mexico and should be regarded as provisional until many more "on-site" radon
investigations are completed. Because the risk of inhaling or ingesting a dangerous
amount of radon is controlled by many factors besides geology and soil conditions, "risk"
considerations played no part in this preliminary evaluation of "radon-availability." It
should be also emphasized that any category area will contain a significant number of
localities where one or both of the other two categories occur.
High Radon-Availability Category /Provisional^
The provisional high radon-availability category included areas where the rocks
and soils were believed to have the greatest potential for generation of indoor radon.
These areas included rocks which typically exceed 2.7 ppm eU on the areal radiometric
map and, generally (but not always) included well drained, permeable soils. The limit of
2.7 ppm eU was chosen on the basis of prior experiences of EPA elsewhere in the
country (T. Peake, USEPA, personal commun., Sept., 1988).
The "high category" included many outcrop areas of Proterozoic granitic rocks
with average uranium concentrations of 3-17 ppm (Sterling and Malan, 1970; Brookins
and Delia Valle, 1977; Brookins, 1978; Condie and Brookins, 1980; McLemore, 1986;
McLemore and McKee, 1988). Other lithologic units in the high-availability category
include:
a. Tertiary rhyolitic and andesitic volcanic rocks in southwestern New Mexico. The
rocks contain anomalously high uranium concentrations (Walton et al., 1980;
Bornhorst and Elston, 1981)- example, a sample of the Alum Mountain
andesite near Silver City, Grant County, contained 35.1 ppm U (Bornhorst and
Elston, 1981). A sample of the Bandelier Tuff in the Jemez Mountains in north-
central New Mexico contained 14.8 ppm U (Zielinski, 1981).
b. Tertiary alkalic intrusive rocks in central and eastern New Mexico (New Mexico
Geological Society, 1982). Many uranium and thorium occurrences are associated
with these units (McLemore and Chenoweth, 1989).
c. Sedimentary rocks. Some Paleozoic and Mesozoic sandstones, shales, and
limestones locally contain high concentrations of uranium (Brookins and Delia
Valle, 1977; Dickson et al., I977)-
-------
d. Coal. Some Cretaceous coals in the San Juan Basin contain 3-9 ppm U (Frank
Campbell, NMBM&MR, personal commun., Oct. 3, 1988).
e. Permeable basin-fill sediments of Tertiary to Quaternary age. Although only very
few analyses of these rocks are reported, they need to be (at least locally)
considered as radon sources (Brookins, 1990; Brookins and Enzel, 1989).
f. Any areas of intense shearing and faulting, especially in areas of uraniferous rocks.
A few areas in New Mexico contain rocks with greater than 5 ppm eU from the
aerial radiometric map. These areas typically merited a high availability ranking; but
there is one exception, the Grants area. The Grants anomaly is a result of uranium mill
tailings and has been assigned a moderate availability ranking.
Most of the aerial radiometric anomalies (>5 ppm eU) can be explained
geologically. The Gallup anomaly is the only one near a major city. It is a result of
uraniferous coals, some of which were mined for uranium. The other anomalies occur in
sparsely populated areas. The Vermejo Park anomaly is associated with a uraniferous
Proterozoic granite and pegmatites; epithermal uranium veins may occur in the area
(McLemore, 1990; Goodknight and Dexter, 1984; Reid et al., 1980). The anomalies in
the Cornudas Mountains, Otero County and at Laughlin Peak, Colfax County are
associated with Tertiary alkalic intrusives; uranium and thorium veins occur in the area
(McLemore and Chenoweth, 1989; Zapp, 1941; Staatz, 1982, 1985, 1986, 1987). Several
anomalies occur in southern Socorro County, east of Las Cruces in Dona Ana County,
west-central Hidalgo County, and in the Black Range that are associated with Tertiary
rhyolitic and andesitic volcanics. Only two of these anomalies are associated with known
uranium occurrences: the Nogal cauldron in Socorro County (Berry et al., 1982) and
Bishop Cap in Dona Ana County (McLemore and Chenoweth, 1989; McAnulty, 1978).
One of the aerial radiometric anomalies, north of Gallup in McKinley County,
cannot be readily explained by geological interpretations. It correlates with the Tertiary
Chuska Sandstone, Cretaceous Menefee Formation, and associated surficial cover; no
mining activity is in the area. Field examination of this area of the Navajo Reservation
and indoor-radon testing is needed, but was not part of the preliminary investigation.
Moderate Radon-Availability Category (Provisional)
This provisional category included areas where preliminary evaluation of geology
and soils data indicated that rocks and soils only have a moderate potential for
generation of elevated indoor radon. These localities include rocks with 2.3-2.7 ppm eU
on the areal radiometric map (Duval, 1988) and are dominated by areas underlain by
moderately permeable soils. This category includes many outcrop areas of Proterozoic
metamorphic rocks, Paleozoic and Mesozoic sedimentary rocks, and Tertiary-Quaternary
sedimentary rocks. Some rocks and soils in the Pecos Valley area in eastern New Mexico
are rated moderate even though they have less than 2.3 ppm eU. Numerous high
uranium ground water anomalies occur in that area, suggesting that uranium is highly
mobile and could result in elevated levels of indoor radon.
-------
Low Radon-Availability Category
This category includes the remaining parts of New Mexico where the rocks and
soils are believed to have low radon availability. These areas include rocks with less than
2.3 ppm eU on the aerial radiometric map (Duval, 1988) and include areas dominated by
soils of low permeability. Some houses in these areas may still have elevated levels of
indoor radon, but there were no obvious geologic reasons for predicting their existence in
the preliminary assessment of radon availability.
PRELIMINARY CLASSIFICATION BY COUNTY
The EPA's nationwide survey of indoor radon levels in houses required that each
county be ranked for radon-availability. Ranking by counties was required for two
reasons: (1) Population statistics required to establish a sample allocation plan are
available for each county throughout the United States. (2) It provides a way to
standardize the reporting of indoor radon surveys throughout the country.
New Mexico is the fifth largest state in the United States, yet it contains only 33
counties. Some of these counties are as large or larger than some states in the eastern
United States. The geology and terrain of New Mexico are quite diverse (New Mexico
Geological Society, 1982), and major geologic and landform units cut across most county
boundaries, creating obvious problems in ranking counties for radon-availability.
Using the procedure described in the previous section, each county in New Mexico
was ranked according to the predominant availability category established for
combinations of geologic and soil units in the state (high, moderate, or low). If a county
was represented by more than one availability category, the county was assigned the
highest classification where that category represented more than 25% of the total county
area. Some exceptions are explained below. Preliminary county rankings are listed in
Table 1. Similar procedures were used in evaluating counties in other states.
Since New Mexico is sparsely populated in most places and is geologically diverse
the major cities in terms of population (preliminary census data, 1984) were also assessed
for radon-availability (Table 1). Some cities were rated higher than the rest of the
county. In order to emphasize population distributions, counties with large urban-
suburban populations were assigned the higher classification (Table 2).
Preliminary Ranking of Counties
Ten counties were assigned a high-availability rating for elevated indoor radon
(Table 1). Large areas of these counties typicai]y contain rocks and soils with greater
than 2.7 ppm eU and the soils are permeable. Two counties, Dona Ana and Santa Fe
Counties, were assigned a high ranking even though the majority of the rocks in the
county contain 2.3-2.7 ppm eU. This ^as because the major cities in both counties (Las
Cruces and Santa Fe) were ranked as having a radon-availability potential. The
preliminary ranking indicated that GalluP in McKinley County was the most likely area in
New Mexico to encounter a large number of houses with elevated levels of indoor radon
Testing to date has not been detailed enough to test whether or not this prediction is
-------
valid.
Thirteen counties were assigned to the moderate-availability category (Table 1).
Large areas of these counties contain rocks and soils with 2.3-2.7 ppm eU. Soil
permeabilities and lithologies vary. Three counties, Chaves, Eddy, and Lea, were
assigned a moderate rating because cities in these counties were rated moderate even
though most geologic evidence suggests a low ranking. In addition, NURE ground-water
data suggested that uranium in ground water is highly mobile and could contribute radon.
A study of uranium and radium mobility in ground water in southeastern New Mexico
indicates that uranium and radium concentrations correlate with high chloride
concentrations; however, higher radium concentrations occurred in chemically reducing
ground water, which is not common in New Mexico (Hecrzeg et al., 1988).
Four counties, Colfax, San Juan, Grant, and Sierra, contain large areas of rocks
that exceed 2.7 ppm eU and could be assigned a high rating. A moderate rating was
assigned to these counties because 1) the uranium-bearing rocks and soils of many areas
are reported to be moderately permeable to impermeable, 2) the cities in these areas are
rated moderate, not high, and 3) the areas containing rocks exceeding 2.7 ppm eU are in
sparsely populated portions of the county.
Ten counties were assigned a low availability (Table 1). These counties are
underlain by rocks with less than 2.3 ppm eU. However, the lithology and permeability
of the rocks and soils vary. Undoubtedly, some houses in these counties will exceed the
EPA's recommended action level, but there are no obvious geologic reasons for
predicting their existence.
THE 1989 STATEWIDE SURVEY
The primary objective of this survey was to locate and identify areas within the
State of New Mexico which may have homes with elevated indoor levels of radon and to
characterize radon levels statewide. A secondary objective was to determine how geology
affects radon levels and to determine whether or not geology can be used to predict
indoor radon levels. This was a "screening" survey.
The target population in this survey was restricted to owner-occupied homes
selected at random from telephone listings. This eliminated high-rise structures from the
survey. Since radon concentrations tend to be low in such structures and the intent of
this survey was to identify areas where radon could be a potential problem, the
elimination of high-rise structures from the survey should provide the most efficient use
of the sampling detectors. The type of dwellings that were excluded from the survey
were mobile homes, group quarters, and apartments. The survey was restricted to
owner-occupied dwellings to simplify procedures in gaining permission to sample radon.
Although this type of selection essentially negates a true random sampling for statistical
purposes, the study had to be structured to fit workable sampling parameters.
Radon measurements were made with charcoal canisters supplied by EPA.
Measurements were made under closed-house conditions and in the lowest liveable area
of the dwelling in conformance with EPA screening measurement protocols. Samples
were analyzed by EPA's laboratory in Montgomery, Alabama. Alpha track detectors
were utilized at 10% of the homes utilizing the charcoal canisters for radon daughter
-------
determination.
The previously defined radon-availability categories (based on geology and soils)
were used by the EPA in allocation of detectors in the random sampling program.
Three thousand canister detectors for sampling radon and 562 Alpha track
detectors for sampling radon daughters were available for use in this survey. Table 3
gives an account of distribution of charcoal canisters by county. Fifty of the charcoal and
five of the alpha track detectors were used to conduct a pilot study of fifty homes to
evaluate participant response rate and workability of survey forms. This pilot study was
conducted before initiating the main part of the survey.
Allocation of radon detectors in the study phase utilizing 2,250 sampling devices
was initially based on population or number of households. Sample size was then
adjusted by the EPA based on evaluation of the natural (geologic and soils) conditions
Given the final sample sizes for each district, the expected allocation to counties
was proportional to number of homes in the county. Consider, for example, Socorro
County in District 1. The number of detectors expected to be placed in homes in
Socorro County, on the average over all possible samples, was 200.
Upon receiving a list of randomly selected homes for the survey from the EPA,
each potential participant was sent a letter. This letter explained how the NMEID
planned to conduct the radon survey and was accompanied by general information on the
radon issue (e.g. EPA, 1986). The letter also informed the potential participant that a
telephone interviewer would contact him or her in the near future to discuss the
participation. These letters were mailed in batches at the District level.
Approximately one week after the notification letter was mailed out, a telephone
interviewer called potential participants and discussed participation. The
control/screening form, which was used in conducting the telephone interview was used to
log all the calls, times of contact, whether or not the homeowner wished to participate.
All pertinent information was logged on the screening form. For details of canister
distribution see Table 3.
The information recorded on the field survey form was entered into the State's
computer. Information from the laboratory data form was stored in EPA's computer
system. The EPA provided this information to the State of New Mexico in a computer
readable format. All information from the combined data base are available to both the
EPA and the State of New Mexico. Summary statistics and data analyses was generated
from this data base (e.g. Table 3; Fig. 2).
In the ongoing final phase of the study, the remainder of the charcoal canisters
and additional alpha track sampling detectors are being used to sample in high suspect
areas of counties which did not receive high priority sampling in the initial phase. These
sampling detectors are also being used to establish boundaries of problem areas
identified in the initial phase. This has been accomplished by concentrated sampling
efforts in these problem areas. Alpha track sampling detectors not used will be returned
to EPA. At the writing of this report this phase was still in progress; and the data are
not available for citation. An additional 200 charcoal canisters are needed for concurrent
sampling in homes being tested with alpha track detectors to determine seasonal impacts
on radon concentrations in homes. The alpha track detectors would remain in place
during the entire testing period while charcoal canisters will be changed during seasonal
periods.
-------
Quality assurance for the radon measurements taken in this survey were
established by collecting duplicate radon samples in 5% of the homes tested. Standard
estimates for the data was provided by laboratory analysis of radon samples containing
known concentration of radon. Blank samples were submitted to the laboratory at a rate
of 2 percent of the total number of samples collected.
For classification the State is subdivided into the four EID Districts. The New
Mexico plan implemented the survey utilizing EID district as well as central office staff
resources; and the survey was coordinated from district offices. EID district staff are
familiar with the population centers in their Districts, as well as with isolated homes in
their areas. Knowledge of home location proved to be invaluable in the sparsely
populated areas of New Mexico.
TABLE 3. RESULTS OF EID SCREENING SURVEY BY COUNTY IN NEU MEXICO.
County
<4
pCi/L
o
V
<¦4-
A
PCi/L
>10.<20 pCi/L
>20 pCi/L
TOTAL
no.
X
no.
%
no.
%
no.
X
BernaliIlo
267
70.6
85
22.5
22
5.8
4
1.1
378
Catron
16
94.1
1
5.9
0
0.0
0
0.0
17
Chaves
41
82.0
9
18.0
0
0.0
0
0.0
50
Cibola
8
53.3
7
46.7
0
0.0
0
0.0
15
Colfax
43
51.2
31
36.9
8
9.5
2
2.4
84
Curry
35
83.3
6
14.3
1
2.4
0
0.0
42
De Baca
12
92.3
1
7.7
0
0.0
0
0.0
13
Dona Ana
75
92.6
6
7.4
0
0.0
0
0.0
81
Eddy
39
81.3
9
18.8
0
0.0
0
0.0
48
Grant
48
87.3
6
10.9
1
1.8
0
0.0
55
Guadalupe
6
100.0
0
0.0
0
0.0
0
0.0
6
Harding
9
90.0
1
10.0
0
0.0
0
0.0
10
Hidalgo
8
53.3
6
40.0
1
6.7
0
0.0
15
Lea
47
94.0
3
6.0
0
0.0
0
0.0
50
Lincoln
16
94.1
1
5.9
0
0.0
0
0.0
17
Los Alamos
30
76.9
8
20.5
1
2.6
0
0.0
39
Luna
35
70.0
12
24.0
2
4.0
1
2.0
50
McKinley
29
63.0
15
32.6
1
2.2
1
2.2
46
Mora
11
61.1
6
33.3
1
5.6
0
0.0
18
Otero
35
79.5
8
18.2
0
0.0
1
2.3
44
Quay
5
55.6
4
44.4
0
0.0
0
0.0
9
Rio Arriba
55
78.6
9
12.9
5
7.1
1
1.4
70
Roosevelt
36
90.0
4
10.0
0
0.0
0
0.0
40
Sandoval
55
78.6
7
10.0
6
8.6
2
2.9
70
San Juan
158
88.3
20
11.2
0
0.0
1
0.6
179
San Miguel
34
54.0
22
34.9
4
6.3
3
4.8
63
Santa Fe
40
54.1
28
37.8
5
6.8
1
1.4
74
Sierra
39
100.0
0
0.0
0
0.0
0
0.0
39
Socorro
30
81.1
7
18.9
0
0.0
0
0.0
37
Taos
19
40.4
20
42.6
5
10.6
3
6.4
47
Torrance
7
58.3
5
41.7
0
0.0
0
0.0
12
Union
18
66.7
8
29.6
1
3.7
0
0.0
27
Valencia
27
100.0
0
0.0
0
0.0
0
0.0
27
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DISCUSSION BASED ON PRELIMINARY DATA ANALYSIS
Figure 2 is a map showing distribution by county of major radon-level classes in
percent (<4 pCi/1; 4-10 pCi/I; 10-20 pCi/1; and >20 pCi/1) determined during the 1989
random-screening survey of 1775 homes. Table 3 lists the results of the screening survey
of the four major radon-level classes showing both the percentage distribution within the
four classes and the number of canisters allocated per county.
In this preliminary state survey, only nine counties (Bernalillo, Colfax, Hidalgo,
Los Alamos, Luna, Mora, Santa Fe, San Miguel, and Taos) had a significant percentage
(>5%) of homes with indoor-radon measurements greater than 10 pCi/1. All but two of
these counties (Hidalgo and Luna) are clustered in the north-central part of the state.
This is the Southern Rocky Mountain region identified in earlier phases of radon
research where radon-availability could be relatively high in many areas (Tables 1 and 2).
The southwestern Basin and Range region, including Hidalgo and Luna Counties, is also
an area where moderate to high radon-availability conditions have been predicted. Seven
of these counties were predicted as having moderate to high radon availability conditions;
only Mora and San Miguel Counties were predicted as having low radon-availability
conditions (McLemore and Hawley, 1988).
Lower indoor-radon measurements throughout the central and southern part of
New Mexico also generally fit the radon-availability projections made in early phases of
this study. Radon levels above the EPA "action level" of 4 pCi/1 were not detected in this
preliminary survey in three counties, Guadalupe, Valencia and Sierra. Twelve other
counties (Catron, Chaves, Cibola, De Baca, Dona Ana, Eddy, Harding, Lea, Lincoln,
Roosevelt, Quay and Torrance) had no indoor-radon measurements above 10 pCi/1. All
of these counties except Dona Ana were predicted as having low to moderate radon
availability conditions (McLemore and Hawley, 1988). However, extreme caution should
be used in interpreting the data summarized in this report as well as the projections of
radon-availability discussed earlier (see also McLemore and Hawley, 1988). The very
small number of charcoal canisters allocated to most areas of the State (Table 3), the
very uneven distribution of canisters (most concentrated in small urban areas within very
large county areas), and the very short-term nature (24-48 hrs) of the radon-
measurement period are representative of the significant factors that contribute
uncertainty to this type of investigation.
Visits made to about 50 individual homes in north-central New Mexico indicate
that geologic and soil conditions were the major factors contributing to elevated indoor-
radon levels (>10 pCi/L). Studies to date suggest that elevated radon levels are
commonly associated with hillside building Slt^s where floors and walls are contiguous to
geologic units such as highly-fractured bedrock of varying lithology, limestones with
solution enlarged joints, or thick pumice deposits. Bedrock units, associated alluvial-
colluvial deposits, and ground water that contain high concentrations of uranium and
thorium locally make a significant contrition and need further study. Some homes
built on clay-rich expansive soils also have elevated levels of radon. Areas in the vicinity
of uranium mills and mines that have b^en tested have relatively low levels of indoor
radon (below 10 pCi/L). A better understanding of the naturaj factors that affect jn(joor
radon concentrations in New Mexico will °n y be gained through integrated, site-specific
-------
investigations which combine more comprehensive indoor-radon measurements and home
construction information with data on geology, hydrology and soils.
ACKNOWLEDGMENTS
The authors wish to acknowledge the effort of the dedicated professionals in the
health field who contributed to the New Mexico Radon Survey. The survey's success was
dependent on the volunteer work of these professionals. Special thanks to the
Environmental Improvement Division field staff and the Albuquerque Environmental
Health Department for their valuable help with telephone calls, mailing and other tasks
associated with the survey, and special thanks to the community volunteers in District III
and IV. Finally, the authors wish to thank the homeowners of the State of New Mexico
for allowing us to come to their homes and to be involved with this ambitious project.
Without their cooperation and interest the New Mexico Radon Survey would not have
been possible.
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and therefore the contents
do not necessarily reflect the views of the Agency and no
official endorsement should be inferred.
REFERENCES
Berry, V. P., Nagy, P. A., Spreng, W. C., Barnes, C. W., and Smouse, P. Uranium
resource evaluation, Tularosa quadrangle, New Mexico. U.S. Department of
Energy Quadrangle Report GJQ-014(82). 22 pp. 1982
Bornhorst, T. J., and Elston, W. E. Uranium and thorium in mid-Cenozoic rocks of the
Mogollon-Datil volcanic field, southwestern New Mexico. P. C. Goodell and A. C.
Waters (eds.). Uranium in volcanic and volcaniclastic rocks. American
Association of Petroleum Geologists, Studies in Geology 13, pp. 145-154. 1981.
Brookins, D. G. Radiogenic heat contribution to heat flow from potassium, uranium,
thorium in the Precambrian silicic rocks of the Florida Mountains and the Zuni
Mountains, New Mexico. New Mexico Bureau of Mines and Mineral Resources,
Open-file Report 98. 13 pp. 1978.
Brookins, D. G. Indoor and soil Rn measurements in the Albuquerque, New Mexico
area. Health Physics, v. 51, no. 4, pp. 529-533. 1986.
Brookins, D. G. Controls on indoor radon levels in the Albuquerque, New Mexico area.
Geological Society of America, Abstracts with Programs, v. 22, no. 3, pp. 10.
1990.
Brookins, D. G., and Delia Valle, R. S. Uranium abundance in some Precambrian and
Phanerozoic rocks from New Mexico. Rocky Mountain Association of Geologists,
-------
Guidebook to the 1977 field conference, pp. 353-362. 1977.
Brookins, D. G., and Enzel, Y. Soil radon and uranium: Correlation with high indoor
radon in the Albuquerque, New Mexico area. Geological Society of America
Annual Meeting Abstracts, pp. A145. 1989. '
Condie, K. C., and Brookins, D. G. Composition and heat generation of the
Precambrian crust in New Mexico. Geochemical Journal, v. 14, pp. 95.99 1980
Dickson, R. E., Drake, D. P. and Reese, T. J. Measured sections and analyses of
uranium host rocks of the Dockum Group, New Mexico and Texas. U.S. Enerev
Research and Development Administration, Report GJBX-9(77), 68 pp. 1977
Duval, Joseph S. Aerial gamma-ray contour maps of regional surface concentrations "of
uranium, potassium, and thorium in New Mexico. U.S. Geological Survey
Geophysical Investigation Map GP-979, scale 1:750,000. 1988.
Environmental Protection Agency (EPA). A citizen's guide to radon. EPA-86-004
Washington, DC (8/86). 1986.
Goodknight, C. S., and Dexter, J. J. Evaluation of uranium anomalies in the
southwestern part of the Costilla massif, Taos County, New Mexico. In Reports
on field investigations of uranium anomalies. U.S. Department of Energy Reno
GJBX-1(84), pp. IVI-IV28. 1984. port
Herczeg, A. L., Simpson, H. J., Anderson, R. F., Trier, R. M., Mathieu, G. G., and Deck
B. L. Uranium and radium mobility in ground waters and brines within the '
Delaware Basin, southeastern New Mexico, USA. Chemical Geology (Isotone
Geoscience Section), v. 72, pp. 181-196. 1988.
McAnulty, W. N. Fluorspar in New Mexico. New Mexico Bureau of Mines and Miner 1
Resources, Memoir 34, 64 pp. 1978.
McLemore, V. T. Uranium and thorium occurrences in New Mexico-distribution
geology, production, and resources with selected bibliography. New Mexico
Bureau of Mines and Mineral Resources, Open-file Report OF-183, 950 pn 1933
McLemore, V. T. Geology, geochemistry, and mineralization of syenites in the Red Hill *
southern Caballo Mountains, Sierra County, New Mexico-preliminary S'
observations. New Mexico Geological Society, Guidebook to the 37th field
conference, pp. 151-159. 1986.
McLemore, V. T. Uranium in the Costilla massif. New Mexico Geological Society
Guidebook to the 42 Field Conference, p. 17-18. 1990.
McLemore, V. T., and Chamberlin, R. M. National uranium resource evaluation
(NURE) data. New Mexico Bureau of Mines and Mineral Resources 12 on
1986. ' u *
McLemore, V. T., and Chenoweth, W. L. Uranium resources in New Mexico. New
Mexico Bureau of Mines and Mineral Resources, Resource Map 18. 1989
McLemore, V. T., and Hawley, J. W. Preliminary geologic evaluation of radon
availability in New Mexico. New Mexico Bureau of Mines and Mineral Resource
Open-file Report OF-345, 28 pp. 1988. s'
McLemore, V. T., and McKee, C. Geochemistry of the Burro Mountains syenites and
adjacent Proterozoic granite and gneiss and the relationship to a Cambrian-
Ordovician alkalic magmatic event in New Mexico and southern Colorado. New
Mexico Geological Society, Guidebook to the 39th field conference pn 83 88
1988.
-------
New Mexico Geological Society. New Mexico highway geologic map. New Mexico
Geological Society, text, scale 1:1,000,000. 1982.
Ogden, A. E., Welling, W. B., Funderburg, R. D., and Boschult, L. C. A preliminary
assessment of factors affecting radon levels in Idaho. In B. Graves (ed.), Radon,
radium, and other radioactivity in ground water. Lewis Publishers, Inc., Chelsea,
Michigan, pp. 83-96. 1987.
Peake, R. T., and Hess, C. T. Radon and geology: Some observations. In D. D.
Hemphill (ed.), Trace substances in environmental health. University of Missouri,
Columbia, pp. 186-194. 1987.
Peake, R. T., and Schumann, R. R. Regional radon characterizations. U.S. Geological
Survey, Bulletin, in press. 1990.
Reid, B. E., Griswold, G. B., Jacobsen, L. C., and Lessand, R. H. National uranium
resource evaluation, Raton quadrangle, New Mexico and Colorado. U.S.
Department of Energy, Quadrangle Report GJQ-5(80), 83 pp. 1980.
Staatz, M. H. Geologic map of the Laughlin Peak area, Colfax County, New Mexico.
U.S. Geological Survey, Open-file Report 82-453, scale 1:12,000. 1982
Staatz, M. H. Geology and description of the thorium and rare-earth veins in the
Laughlin Peak area, Colfax County, New Mexico. U.S. Geological Survey,
Professional Paper 1049-E, 32 pp. 1985.
Staatz, M. H. Geologic map of the Pine Buttes quadrangle, Colfax County, New Mexico.
U.S. Geological Survey, Geologic Quadrangle Map GQ-1591, scale 1:24,000. 1986.
Staatz, M. H. Geologic map of the Tres Hermanos Peak quadrangle, Colfax County,
New Mexico. U.S. Geological Survey, Geologic Quadrangle Map GQ-1605, scale
1:24,000. 1987.
Sterling, D. A., and Malan, R. C. Distribution of uranium and thorium in Precambrian
rocks of the southwestern United States. American Institute of Mining
Engineering, Society of Mining Engineers, Transactions, v. 247, pp. 255-259. 1970.
Walton, A. W., Salter, T. L., and Zetterlund, D. Uranium potential of southwestern New
Mexico (southern Hidalgo County), including observations in crystallization history
of lavas and ash tuffs and the release of uranium from them. U.S. Department of
Energy, Report GJBX-169(80), 114 p. 1980.
Williams, J. L., 1986, Population distribution. In J.L. Williams (ed.), New Mexico in
Maps, 2nd edition. University of New Mexico, Albuquerque, pp. 150-152. 1986.
Zapp, A. D. Geology of the northeastern Cornudas Mountains, New Mexico.
Unpublished M.S. thesis, University of Texas, Austin, 63 pp. 1941.
Zielinski, R. A. Experimental leaching of volcanic glass. Implications for evaluation of
glassy volcanic rocks as sources of uranium. In P. C. Goodell and A. C. Waters
(eds.), Uranium in volcanic and volcaniclastic rocks. American Association of
Petroleum Geologists, Studies in Geology 13, pp. 1-12. 1981.
-------
Shipruck
)Capultn
Colfax
0 Gr«nvill«
Cimarron
P»»imont«
Mora
Stead
O Pueblo
McKinlev
CmxwiixjKri
$ f» ,
j Santa |
Fe !
Albuquerque
i Guadalupe
VZ/////////A
Rayland
Torrance
Valencia
0 Quemado
Roosevel
Catron
Lincoln
Socorro
Chaves
Carriio/o
RoswellO
iRuidoso
Caproch
O Glenwood
Truth or
Consequences
Sierra
mgton
Hillsboro
Hobbg
Carlsbad
O-iUi^bur o
mgm
Dona
Ana
Luna
Mm*
El Paso
HIGH RADON AVAILABILITY
FIGURE 1: RADON AVAILABILITY IN NEW MEXICO
Note: Preliminary rating
-------
29
4 i
mm,
I : 51
Colfax 37 | • 00,.^o 1
2 | „ * C1W
g*J|:::Un,on gH|
v.y Mora' - si\ §»*;
Piftt-tiohl* :
0 Harding t j
A. on I' : : .1
oc«»m»
0 Ajl«C
n*»w«
Rio Arriba •*»«*»»
San Juan
Rw'-RVIV
C>ro»20 pCi/L
FIGURE 2: RESULTS OF EID SCREENING SURVEY BY COUNTY
IN NEW MEXICO
Note on patterns. Counties where some measurements were >20 =
dark dot pattern or 10-20 = light dot pattern. Counties where all
measurements were <10 = white or <4 = diagonal line pattern.
-------
I
RADON CONTROL PROFESSIONALS, INC. IXP
11920 Fieldthorn Ct. INSl Rpn
Reston, Va. 22094 1
(703)471-9459 '-r™ I'-..*-0
hPA TR.\I\ej)
PALEOZOIC GRANITES IN THE SOUTHEASTERN UNITED STATES
AS SOURCES OF INDOOR RADON
Stephen T. Hall
Geology Department, George Mason University
Radon Control Professionals, Inc.
Isotopic age determinations of Paleozoic granites
predominantly in the Piedmont Province have revealed three
general groups by age: Taconic (480-435 Ma), Acadian (380-340
Ma), and Hercynian (330-230 Ma). Whole rock and trace element
chemistries and isotopic ratios indicate that with time each of
the three groups of granites experienced greater degrees of
assimilation of continental crust. During this process,
incompatible trace elements such as uranium and thorium quickly
become depleted in the continental crustal rocks and hence are
enriched in the granitic melt. In addition, it has been
demonstrated that U4+ can be readily oxidized to the more mobile
U6+ by hydrothermal activity associated with metamorphism and
even weathering.
Since the Hercynian granites are post-metamorphic, they
often contain the highest levels of uranium-238, the parental
source for radon-222. The older granites, however, have probably
experienced a significant uranium loss during metamorphism and
the U6+ has migrated until it reached a lower fOs buffered zone
in the surrounding country rock.
-------
Map oŁ the Southeastern US shoving Paleozoic (480-230 million
year old) granites darkened
-------
HERCYNIAN ARC
Ul'tt,
Map of the Southeastern US showing Hercynlan (3:30-230 oil 11 ion
year old) granites only
-------
8018 Ratios
wwwvv
5-6.5
] 6.5-7.5
>7.5
#
$
0 IOC
BU.OMI Ttff
Sr87/Sr86
Initial Ratios
<0.704
mm 0.704 -0.705
EHHHD 0.705-0.706
Egjgg >0.706
Maps of the Southeastern US shoving O18 ratios and Srs"VSrB6
ratios oŁ Hercynian granites increasing inland indicating a
greater involvement of continental crust and higher initial
uranium content
-------
10-*
10-
0 8
6 +
0 6
6+ Schoepite
UO,(OH), H,0
6+ :
UO,OH
6+ :
Huo:?
o
>
r.
ui
10*
•0 2
10*'
0 4f~
H,0
10"
¦0 8
10
12
14
6 7 8
0
2
4
pH units
Eh-pH diagram of the IJ-Oa-HaO system showing stability of U4""
compounds Including uranlnite (non-mobile uranium-bear iiig
mineral) at lower fOa (oxygen fugacity)
-------
Uroriinite
'///.{/A
pH
Eh-pH diagram of the U-Os-HaO-COi system showing stability of U4*
compounds including uraninite (non-mobile uranium-bearing
mineral) at lower fOa (oxygen fugacity)
-------
-10
jQ
U. -30
o»
-40
400"
-60
fOs-temperature diagram showing magnetite stability at lower fOa
stability than uraninite- Since many Hercynian granites contain
magnetite, they have probably retained their original uraninite
-------
chemical compositions of some Kercynlan granites indicating
uranium concentrations in the 3-8 ppm range
Mean Compositions of Surface Samples
Winnsboro
Rion
Liberty Hill
Liberty Hill
Rolesville
Castalia
Louisb
gran i te
(6)
(16)
coarse
(15)
f ine
(4)
(18)
(3)
(1)
io. ot bampies
U ppm
(st. dev.)
2 .6b
(0.4 3)
5.23
(1.58)
2.87
(0.71)
4.55
(0.67)
3.99
(1.56)
4.34
(1.74)
3.07
Th ppm
(st. dev.)
14 . 64
(2.48)
31.55
(3.62)
14.57
(4.05)
28.7
(3.88)
17.83
(4.51)
13.76
(3.57)
30.8J
Si02
(st. dev.)
72.91
(3.30)
72.73
(1.71)
67.25
(3.18)
71. 72
(1-29)
71.18
(2.91)
75.26
(3.43)
72.53
(st. dev.)
5.47
(0.27)
5.36
(0.25)
5.66
(0.48)
5.53
(0.18)
4.52
(0.46)
4.22
(0.53)
5.11
Mean Compositions of Core Samples
No. of Samples
WIN1
Rion
(17)
KER1
LH Łine
(I)
KER2
LH coarse
(5)
KER3
LH coarce
(9)
KER3
LH fine
(3)
Upprn
(st. dev.)
7.32
(1.90)
5.65
3.11
(0.02)
2.32
(0.08)
6.59
(4.40)
Th ppm
(st. dev.)
33.58
(4.40)
21.33
14.18
(0.90)
11.64
(2.02)
29.25
(8.36)
Si02
(st. dev.)
72.65
(1.08)
73.82
66.31
(0.41)
67.22
(2.43)
72.12
(2.32)
K2O
(st. dev.)
5.50
(0.31)
5.27
5.02
(0.18)
5.17
(0.25)
5.41
(0.14)
AVERAGE COMPOSITIONS FROM PETEFSUURG BATHOLITH
SURE ACE PET1 CORE
NO. SAMPLES (36) (11)
U ppn
7. 6
<4.8
(st dev)
(«• 1)
(0.6)
Th ppn
18.7
U.9
(st dev)
(7.2)
(2.6)
Si02
7 1. '1 U
67. 06
(st dev)
(3.03)
(1.47)
K20
5.05
5. 38
(st dev)
(0.83)
( 1. 08)
-------
V
? \
"v.—
. - - X'-
%
^ >
SV ^X % A» -'
s s __ ,/J-
-- -- %m /
Vx
% %X
*,> \
°'°V
*<Ł* s
*N 0Q$*
Map of Paleozoic giani tts of the Southeastern us with Hercynian
granites darkened and uranium (upper numbers) and thorium (lower
numbers) contents
-------
IXP-3
COMPARISON OF LONG TERM RADON DETECTORS AND THEIR
CORRELATIONS WITH BEDROCK SOURCES AND FRACTURING
BY:
DARIOUSH T. GHAHREMANI, PH.D.
RADON SURVEY SYSTEMS, INC.
10357 LIBERTY RD. CLEVELAND, OHIO 44087
ABSTRACT
Radon prospecting for mapping soil gas radon hot spots provides
an additional correlation method which can be used with other
geochemical tracers to support the genetic association between
radon presence at the surface and bed rock sources and fracturing
at depth.
Anomalous radon concentration at the surface can be caused either
by proximity of shallow burial of rocks rich in uranium and
radium mineralization or by migration of gases from deep sources.
The working hypothesis is based on the fact that radon generated
at depth can be transported by other gases or dissolved in
solution and reach the surface. Areas with high densities of
micro-fracturing of the rocks can enhance the migration and
therefore higher than average radon concentration can be
expected.
In Ohio as well as many parts of the Appalachian basin, the main
source of radon has been found to be the organic rich black
radioactive sections of Ohio and Olentangy shales. Other sources
of radon in Ohio and other glaciated regions are the till and
tillits (glacial sand and gravel deposits) which covers most of
the state.
Results of studies within the intense bed rock fracturing
indicated that: 1- there is a good correlation between micro-
fracturing of the rocks and higher than average radon
concentrations at the surface. 2- Areas closer to the regions
with shallow burial of organic rich members of Ohio shale
revealed anomalous radon activities in the soil. 3- Atmospheric
parameters showed a measurable influences on the short term
measurements. 4- Sites with high soil gas radon concentrations
correlated with nearby indoor radon measurements in the study
area.
-------
INTRODUCTION
^ ~ v^r, made to investigate the occurrences of
Many studies hav trations within Ohio and parts of the
soil gas radon . Thousands of locations have been
Appalachian .si y establish the regional background and to
visited in °h^° (Hot Spots). The working hypothesis is
search for ra OIL__ vields will be optimized where natural
that natural g .L c]cs is greatest. Such fracturing would
fracturing o toward the ground surface at a greater rate
allow the gas to leak ¦t°wa* enCe of this gas in the soil, by
than elsewhere, mechanisms, produce conditions whereby the
various geoch coil gas is also enhanced compared to other
radon activity in the soil ya
areas.
^ ronnrted herein represents a state of the art
The case hi V p order to detect areas of gas leakage from
radon proCe.__ cmrface sources in Ohio. Radon anomalies are
bedrock or n radioactive materials such as radium and
caused by ae Y . near surface environment by ascending
uranium transp hvdrocarbons affect the microgeochemistry
hydrocarbons a way as tQ enhance precipitation of
near the surr from circulating ground-water. The exact
radioactive understood and may involve several
mechanisms a P Radon which is an intermediate daughter of
interacting factors. Raa°erleSj has faeen wl(Jely uged tQ lQcate
subsurface3 mineral deposits, geothermal monitoring, earthquake
prediction and environmental studies.
methodologies
Radiometric measurements in the soil gas were accomplished bv
using several short and long term techniques to monitor alpha
and gamma activities in the ground. Radioactivity caused by soil
man made sources were also investigated in order to establish
correlation between deep gas migration and near surface soil
or
a
gas radon anomalies
An area of one square Kilometer was selected for this study where
geological and environmental parameters related to gas movement
in the ground could be evaluated. Topographic features included
many east-west stream gullies, valleys, and drainages caused by
bed rock fracturing. These features are intersecting a major
lineament (large fracture) trending in a NW-SE direction in the
study area adjacent to the N-S trend of a major river in
northern Ohio (Figures 1/ 2/ ar*d 3).
Figure 4 shows the location of sampling sites in the study area.
A square grid was laid out with 100 stations using spacing of loo
meter outside the anomalies, reduced to 50 and 20 meter near and
-------
C«n*dl«rt 8HI«Jd
W
Michigan Baatn
OUtll«r
'i.J
r
Art of outcrop of Mlddl* and
Upptr Otfvonlan rockt
ArM of Outcrop of ProcatmbHan
roekt
0 100 200 mllit
y 1 1 i i 1
0 100 200 300 fcllomttort
Figure 1, Structural setting and areas of Devonian shales out-
crop in Ohio and Appalachian basin (Modified from Schwietering,
1979). The small dot indicates the approximate location of the
study area.
-------
Ai
Sharon Cgi
< 2
0 o
Me«dvi||e 8h
MISS.
0 p
1 <
Shtrpiytn. 8h
I'
Orange villa Sh
3 o
o Ł
/ Sunburv Sh
Ber«a Ss "
Z
Bedford
<
z
o ^
Cleveland Sh
o
It
Chagrin
UJ
n
W CO
Huron Sh
3
Olentangy Sh
Oel*war» ~
|Mff luroi ftc\ M
~jHu "°n |»i"»
ES Sandstone
1 I Predominantly "normal" shale
C3I Transitional
¦I Predominantly radioactive shale
Feet
500
20
Figure 2, Generalized stratigraphic column for Devonian
Mississippian rocks and composite cross section of Devonian
shale sequence in eastern Ohio. Sub-surface distribution
of black radioactive shale is indicated by the black nat-t-^m
Unpatterned portions of the section represent non-radioacti^
gray shale and sandstone. Arrow at the top indicates the aon
roxinate part of the section that is equivalent to that under-
lying the study area (Adapted from Majchszak, 1977)
-------
Figure 3, Topographic map of the study area (boxed outline) with
respect to regional and local structural and topographic features.
The NW-SE lineament is shown by line L-L .
-------
above anomalies. At each sampling site marKea on topographic map,
long term Track Etch alpha tracks were used to cover areas of
previously detected radon anomalies by short term and Kodak long
term film cup detectors, a scintillometer reading of total gamma
activity and a soil sample was taken. Also atmospheric parameters
were recorded during the entire survey period.
RESULTS
Soil gas radon results are summarized in figure 4. Radon readings
are reported in units of tracks per sguare millimeter and are
normalized to equivalent 30*~days^ exposure. The data ranged from
55 to 666 tracks per square millimeter with a STD of 107. Figure
4 shows readings with at least one STD above the background
values.
Nearly 15% of the sites revealed values more than one STD above
background mean, while 2% of the sites are identified as
anomalous as represented by the larger triangle symbols in
Figures 4, and 5). The actual activities at these sites are
greater than 538 tracks per sguare millimeter as compared to the
background mean of 217 track per square millimeter.
The background activity in the area was higher than other parts
of the state due to several factors including: intensive bed rock
fracturing, glacial coverage, and elevated radium or uranium
concentrations by the action of ground water percolating in the
radioactive black shales (Cleveland and Huron members of Ohio
shale), a common bed rock type buried shallowly near the surface
in northeast Ohio found to act as source rocks for radon mainly
in eastern Ohio (Majchszak, 1977; Janssens, A. & deWitt, W.1976).
Figure 5 is a modified version of Figure 3 in which categories of
anomalous, intermediate, and background values are defined as
values equal to greater than mean plus 3 STD, values between mean
plus one and three STD's and values within one STD respectively.
Also shown symbol it ically in Figure 5 are the results of the
early preliminary radon surveys with long term Kodak film cups ,
located in the inner outlined area. The maximum values detected
by each technique are slightly displaced, but the two are
generally consistent in locating localized soil gas anomalies
(Figure 5) .
The arrangements of anomalous and intermediate values are
suggestive of control by bed rock fracturing. E-W fractures are
well expressed in the topography of tributary streams draining
the adjacent hill slopes (Figure 3). The anomalous sites are
mostly located in the vicinity of intersections between the NW-SE
lineament discovered during the course of this study and numerous
-------
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it*
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tM M ^
-------
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•
A
A A A
•
•
•
7
•
•
•
•
•
• •
~
~
•
6
o
o
H] ®
®
o
%
•
5
~
•
(B+1cr)
OBkg.
i
X>(B+3cr)
A (B+3 *>(B+1ir)
• Bkg. X
«S (B+tcr)
100m
Figure 5, Map of Kodak and Track Etch results at the study
area, schematically distinguished according to the categories
of anomalous, intermediate, and background as defined in the
text. In the legend, the symbols in the upper row refer to
Kodak results whereas the symbols in the lower row refer to
Trach Etch results. The inner outlined area is the site of a
Kodak film-cup survey undertaken prior to the more extensive
Track Etch survey. Several sampling sites are camion to the
two surveys. T-T* line is showing the trend of lineament in
the study area.
-------
E-W fractures. These anomalous sites are marked with large
triangles for Tract Etch detectors and squared symbols for kodak
film detectors located in the center of the study area and along
the NW-SE lineament trend (Figures 4 and 5).
Evidence of deep gas migration compare to shallow sources of
thorium or uranium mineralization included the very low
correlation coefficient between radon values and scintillometers
readings (Figure 6) . Comparing this map to statistical criteria
previously described in Figure 5, there are few differences
except sites A7, A9, and A10, which have been increased from
background to intermediate status, and sites D3, G5, and J4,
which have been decreased from intermediate to background status.
CONCLUSIONS
Radon anomalies in the soil gases of many areas in eastern Ohio
result from vertical migration of gases from subsurface sources
(Figure 7) . The migration pathways are primarily controlled by
bed rock fracturing particularly in areas of two or more fracture
intersections.
The near surface sources of radon can be differentiated from
deeper sources by the compositional characteristics of liberated
gases and laboratory analyses of soil or rock samples within
anomalous radon concentrations. Main source rocks for radon gas
detected in the study area are the black radioactive members
(Cleveland and Huron) of Ohio shale underlying the entire eastern
Ohio. Other sources of near surface contaminations such as
glacial till (sand and gravel channels), contaminated soils or
man made sources common to many industrial sites in the state
were found to be insignificant in this study area.
Environmental parameters showed a measurable effect on the short
term measurements compared to long term alpha tracks used in this
study.
The high background level and occurrences of several anomalous
sites at this study area or regions with similar geological
characteristics could be considered as sites with potential
environmental hazard. This hazard may be prevalent wherever
radioactive black shales are present at shallow depth bellow the
surface or sites in proximity of intense bedrock fracturing in
Ohio and adjacent states.
-------
~ ~
A A A A
• •
A a
4 A
A
A A
• • •
kX>(Bt 3a)
± x '(B'lffl • Bkg X ! ( B * 1
-------
Figura ~J
BADON DiitribuHon Over Permeobl* Frgctuf Zonei
Hypothetical model of radon distribution in
soil gases over fractured zones in bedrock.
GAS MIGRATION
WklHS
Figure 7, Radon distribution over permeable fracture zones . Hypothetical
model of radon distribution in soil gases over fractured zones in bedrocks
within Ohio and Appalachian basin.
-------
ACKNOWLEDGEMENTS
The author wishes to thank Drs. W. Alter and R. Oswald of
Terradex Corp. for providing the TE monitors used for this study.
references
Janssens, A. and deWitt, W., Jr. 1976, Potential natural gas
resources in the Devonian shales of Ohio. Ohio Geol. Surv. Note
3, 12 PP.
Majchszak, F.L., 1977, Progress report on characterization of the
Devonian black shales in Ohio, Preprints, First Eastern Gas
Shales Symposium, Morgantown Energy Research Center, Morgantown,
West Virginia, PP. 510-519.
Schwietering, J.F. 1979, Devonian shales of Ohio and their
eastern and southern equivalents. U.S. Dept. Energy, METC/CR-
79/2. 68 PP.
-------
IXP-4
GEOLOGIC ASSESSMENT OF RADON-222 IN McLHNNAN COUNTY. TEXAS
Mary L. Podsednik
Law Engineering, Inc.
7616 LBJ Freeway, Suite 600
Dallas, Texas 75251
ABSTRACT
Geologic parameters controlling the distribution and transport of radon were
evaluated in McLennan County, Texas. Laboratory analysis of selected rock samples
identified phosphate zones in the Austin Formation and shales and bentonites in the Lake
Waco Formation as probable source rocks. Geophysical logging techniques utilizing
gamma logs were supplemental in identifying the Lake Waco Formation as a source rock
based on relative radioactivity between selected geologic formations. Emanation of radon
from representative soil types was evaluated by using large area activated charcoal
cannisters. The Houston and Houston Black clay soils had the greatest radon flux
concentrations potentially resulting from increased surface area and more efficient transport
of radon through desiccation cracks typical of these soils. Analysis of groundwater
indicated that radon concentrations were greatest in the Austin Formation, particularly when
samples were collected after rainfall events. Radon concentrations were shown to be
greatly increased in wells located near stream discharge points owing to a flushing of the
aquifer flow system, including the unsaturated zone, during periods of infiltration.
Elevated indoor radon concentrations were found to be most commonly associated with
homes overlying the Austin Formation which has been identified as a source rock and is
characterized by high shrink-swell soils, abundant faulting and fracturing, and foundation
failure caused by the high shrink swell soils. These characteristics allow for the production
of radon and efficient transport from the subsurface to the indoor environment.
-------
INTRODUCTION
Several localities in Texas have been identified as target areas with the potential for
elevated indoor radon concentrations based on generalized geology maps and aerial gamma
spectroscopy. These areas include the south Texas uranium district, Llano region, east
Texas lignite belt, Panhandle shales, and Big Bend intrusives (see Figure 1)(1). However,
a soil gas survey conducted by the United States Geological Survey indicated anomalous
radon concentrations associated with the Austin Formation and adjoining outcrop belts,
which comprise a major portion of the study area in McLennan County, Texas. Therefore,
the objectives of this investigation are to examine the potential sources of radon in
McLennan County, Texas; to interpret radon flux variation in soils with respect to soil type,
thickness, permeability and underlying geology; to quantify the distribution of radon in
shallow groundwater systems; and to analyze indoor radon concentrations on a county-
wide basis.
LOCATION
The area of investigation is located in McLennan County, Texas characterized by
northeast-southwest striking outcrop belts of Comanchean and Gulfian age Cretaceous
Henosits of limestone, chalk, shale, and marl. These units are typically shallow marine
deposits wi h™he exception if the fluvial deltaic deposits of the Woodbme format™ and
Sal deposits of the Quaternary age alluvium. Figure 2 represents a stratigraphic column
characteristic of the study area.
The studv area lies within the Balcones Fault Zone, a northeast-southwest striking
system characterized by normal faults, down-thrown to the east Slickensided faults,
calcSe filled fractures and conjugate fractures are most commonly associated with the
Austin and Ozan Formations. However, bedding plane separation and stress release
fractures exist in all units.
Groundwater occurrence and flow occurs through fractured bedrock in the
weathered zone and through porous sand and gravel of alluvial and terrace deposits. The
SeSe generally unconfined except where impermeable soils exist which may result in
Snorarilv confined conditions. Regional groundwater flow systems are recharged
eSv from the Austin Formation and possibly from the Lake Waco Formation which
Pt«noL,nhirallv hi eh areas. Hydraulic communication occurs as regional flow between
Sbw groundwater in the Austin and Ozan Formations (2) and as local flow between the
Austin and South Bosque Formations (3).
Distribution of soils within the study area relate primarily to underlying geologic
influences where deep, clay-rich soils develop from shales and marls, and shallow, silty
clay soils develop from limestones and chalk.
Climate within the study area is of a modified marine sub-humid environment,
characterized by hot summers and dry winters. Average annual precipitation is 33 inches
and average annual lake evaporation is 65 inches (4).
METHODS
Methodology employed in this investigation involved the laboratory analysis for
Radium-226 (hereafter referred to as radium) in rock and soil samples and Radon-222
(hereafter referred to as radon) in groundwater samples. Radon flux was determined by
-------
Panhandle Shales
/feast Texas
Study A'"0"118 Be"
Area /
Uano Inirusives
Big Bend
Intruslves
Figure 1 Areas in Texas with potential for elevated indoor radon concentrations (1).
System
Series
Group
Formation
Member
Lithology
Taylor
Ozan
Austin
Bruceville
c
CO
Atco
"5
O
Eagle Ford
South Bosque
Lake Waco
Bouldin
CO
Cloice
CRETACEOU
Bluebonnet
Woodbine
Woodbine
PeDDer *
c
«
Q)
XI
Del Rio
Mainstreet
u
Paw Paw
CO
Washita
Georgetown
Weno
i i; ii; 111; i; i !?d
E
o
O
Denton
Fort Worth
Duck Creek
"The Woodbine Formation exists in the northern study area
while the Pepper Formation exists in the southern area
Figure 2
Stratigraphy of the study area.
-------
using large area activated charcoal cannisters (LAACC) supplied by the Environmental
Protection Agency (EPA) (5). After sample collection, the charcoal was evaluated for
radon by determining the concentrations of daughter products. Indoor radon
concentrations were measured using charcoal cannisters supplied by an EPA proficient
laboratory.
SOURCE ANALYSIS
Rock units were evaluated for source rock potential based on radium concentrations
of selected rock samples and relative in-situ gamma radioactivity of boreholes completed in
outcropping formations. The following sections describe the results and interpretation
specific to each formation, from oldest to youngest, analyzed in this investigation.
WOODBINE GROUP
The Woodbine Group is comprised of the Woodbine Formation which forms a thin
outcrop of sand and shale in the northern study area and the Pepper Formation which forms
a thin outcrop of dark shale and sand stringers in the southern study area. Radium
concentrations in samples obtained from the Woodbine Formation range from 1.31 pCi/g to
1.87 pCi/g for shale and sand samples, respectively (see Figure 3a and 3b). Radium
concentrations in samples obtained from the Pepper Formation range from 2.06 pCi/g to
3.88 pCi/g for shale and sand samples, respectively (see Figure 3a and 3b).
Austin
Woodbine Woodbine Waco Waco Bosque
Sh«le S«nd BentonKe Shale
Figure 3.
Ranges of radium concentrations in rock samples.
-------
Sediment sources for the Woodbine Group include igneous, metamorphic, and
sedimentary rocks from southeastern Oklahoma and southwestern Arkansas in addition to
high grade metamorphics contributed by longshore currents from the Appalachians (6).
Uranium present in the original source rocks was redeposited in the Woodbine sands
resulting in the higher radium concentrations identified in the sand and sand stringers. The
shales were deposited in a slightly reduced depositional environment with a decreased
influx of sediment from the provenance described above. Therefore, slightly lower radium
concentrations are characteristic of the shales.
The gamma log from a borehole completed in the Lake Waco and Pepper
Formations indicates a sharp decrease in radioactivity at the Lake Waco/Pepper Formation
contact (see Figure 4a). The distinct change at the contact represents a lithologic
unconformity and a characteristic change in the aqueous geochemistry at the time of
deposition. Radioactivity in the Pepper Formation increases slightly with depth possibly
indicating that the lower units were deposited in a more restricted environment favorable for
uranium precipitation.
LAKE WACO FORMATION
The rock samples were obtained from the Cloice Member of the Lake Waco
Formation which consists of alternating black shale, limestone, and bentonite. Shale
deposition occurred in a reduced depositional environment while limestone deposits are
representative of fresh water influx (7). The bentonite unit, with radium concentrations
ranging from 2.28 pCi/g to 7.40 pCi/g was deposited during periods of volcanic ash
distribution and probably represent radium concentrations of the original volcanics (see
Figure 3c). The black shales with radium concentrations ranging from 3.79 pCi/g to 8.92
pCi/g indicate a reduced depositional environment favorable for precipitation of uranium
(see Figure 3d).
The gamma log from a borehole completed in the Lake Waco and Pepper
Formations indicates that the Lake Waco Formation has relatively greater radioactivity than
the Pepper Formation (see Figure 4a). This correlation coincides with the radium
laboratory data indicating higher radium concentrations in samples obtained from the Lake
Waco Formation. This gamma log also shows a peak associated with a bentonite unit
encountered in the borehole and lesser peaks associated with shales.
The gamma log from a borehole completed in the Lake Waco Formation indicates
that radioactivity increases slightly with depth (see Figure 4b). The peaks appear to
correspond to bentonite or shale units and troughs represent limestone units. The upper
portion of the log represents the Bouldin Member of the Lake Waco Formation which is a
limestone dominated sequence having lower radioactivity. The lower portion of the log
represents the Cloice Member of the Lake Waco Formation which is a shale dominated
sequence with increased radioactivity.
Radium laboratory results and comparison of relative radioactivity from gamma
logs indicates that shales and bentonites from the Lake Waco Formation have the greatest
potential as source rocks in the study area.
SOUTH BOSQUE FORMATION
The South Bosque Formation consists of a massive dark gray shale containing
sulfate deposits in the form of pyrite crystals which indicate deposition in a reduced
environment (8). Radium concentrations were relatively low with 2.15 pCi/g (see Figure
-------
5
_ 6
5
sz 7
Hentomte
lake Wacf
Pepper
BO 100 120 140 160 180 200
Gamma Radioactivity (CPS\
y
C
WiMiln'icrt Lake Waai
Ł
3
20 40 60 80 100 120 140 if,o
Gamma Radioactivity (CPS)
B
Wealhered
Bentonite
South Bosque
50 60 70 80 90 '00 110
Gamma Radioactivity (CPS)
Wraih«rm1 Austin
Sl«gh|/y W«alhei-ed
Austin
0 10 20 30 40 50 60 70
Gamma Radioactivity (CPS)
r- 6
O.
0)
Q 7
fl
Soil
^ Hl8^y
Weathpffri
_Soil and Clay
Weather 0*an
20 30 40 50 60 70 80
Gnmma Rad>oactivity (CPS)
D
Figure 4 Representative gamma logs from wells completed in the Lake Waco/Pepper
Formations (A), Lake Waco Formation (B), South Bosque/Lake Waco
Formation (C), Austin Formation (D), and Ozan Formation (E).
-------
3e). Although reduced conditions were in existence at the time of deposition, the lack of
volcanics and true black shale deposition resulted in low uranium precipitation.
The gamma log of the South Bosque Formation indicates three zones of high
radioactivity (see Figure 4c). The upper soil zone may represent colluvium originating
from the adjacent escarpment which is known to contain phosphate nodules at the South
Bosque-Austin Formation contact. These phosphate nodules sampled from the base of the
Austin Formation for radium analysis contain 7.67 pCi/g which is comparable to the
radium analyses from the Lake Waco shale. The middle radioactive zone is represented by
a weathered bentonite unit with increased radioactivity resulting from original radionuclides
present in the volcanics. The lower radioactive zone possibly represents a shale unit
associated with the Lake Waco Formation.
AUSTIN FORMATION
The Austin Formation is composed of chalk with thin alternating marl units and
bentonite seams (9). This unit is highly fractured due to the proximity of the Balcones
Fault Zone and contains localized deposits of pyrite, calcite, and phosphate nodules.
Radium concentrations ranged from 0.40 pCi/g to 1.69 pCi/g in the rock matrix and had
concentrations of 0.62 in the pyritic zone, 0.13 for calcite filled fractures, 0.19 pCi/g for
slickensided fractures, and 7.67 pCi/g for phosphate zones (see Figure 3f). Phosphates are
located throughout the Austin Formation as a minor constituent and nodules occur at the
upper and lower geologic contacts.
The gamma log of the Austin Formation indicates slightly increasing radioactivity
with depth (see Figure 4d). Distinct peaks and troughs indicate lithologic changes from
bentonite or marl units to chalk. The upper fractured zone shows decreased radioactivity
which may indicate leaching of radionuclides by infiltrating water. Groundwater sampled
from the Austin Formation maintained greater radionuclide concentrations than the
remaining aquifers sampled in the study area. This may indicate that leaching and
dissolution of radionuclides in the Austin Formation is more pronounced and transport
through fractures more efficient.
OZAN FORMATION
The Ozan Formation consists of a massive dark gray montmorillonitic clay that is
highly fractured with secondary calcite and hematite deposits along fracture faces. The
samples obtained for radium analysis consist of matrix rock material and range from 0.89
pCi/g to 1.11 pCi/g (see Figure 3g). Locally higher concentrations may be present along
fractures where secondary precipitation of radionuclides may have occurred.
The gamma log for the Ozan Formation indicates greater radioactivity in the upper
weathered zone followed by decreasing radioactivity with depth (see Figure 4e). Previous
hydrogeologic investigations show that the Austin Formation recharges the Ozan Formation
through a regional groundwater flow system (2, 10). Groundwater from the Austin
Formation, which contains higher radionuclide concentrations, may distribute and
reprecipitate radionuclides in the Ozan Formation particularly along fracture faces. This
would result in greater radioactivity in the weathered zone.
SOIL ANALYSIS
Soils were analyzed for radon flux which is defined by the EPA as the rate at which
radon emanates from the soil for a given area and time interval (5). Twenty three selected
-------
sites comprise three east-west transects and represent thirteen soil types and nine geologic
formations. Moisture content was analyzed for each sample to identify the relationship
between radon flux and moisture. Radon flux measurements were repeated along the
southern transect to identify the effects climatic variations.
RESULTS
The flux concentrations in the study area range from 0.34 pCi/m^s to 10 40
pCi/m^s, which are comparable to flux concentrations at an inactive phosphogypsum stack
with flux concentrations ranging from 0.57 pCi/m^s to 14.5 pCi/m^s (11). The highest
flux concentrations in the study area, ranging from 2.27 pCi/m^s to 10.40 pCi/m^s are
represented by Houston and Houston Black clay soils and have relatively high moisture
content ranging from 5.48 percent to 20.92 percent. The Houston and Houston Black clay
soils have low permeability, high moisture retention, and high shrink-swell potential owing
to a fine grained montmorillonitic texture and composition. The underlying geology for the
sites with the highest radon flux include the Austin, Pepper, South Bosque, and Ozan
formations.
INTERPRETATION
Previous findings show that water present in intergranular spaces increase radon
production by limiting the recoil range, but decreases diffusion by limiting migration (121)
The clay soils represented in the study area exhibit these properties within the soil matrix
However, the residual nature and expansive property of these soils provide both a continual
source and an efficient mode of transport for radon emanation. Desiccation cracks
developed during dry periods are able to transport radon by initial recoil from the fissure
faces, while diffusive transport occurs from interconnected pores adjacent to the fissure
wall (see Figure 5). The clay matrices between desiccation cracks generate significant
concentrations of radon because of higher moisture content but emanation of radon through
diffusive transport is negligible because of the low permeability and the presence of water
LAACC
Desiccation Cracks
Rn-222 Emanation \
from Fracture Faces
and Clay Matrix J
Clay Matrix
Figure 5. Diagrammatic illustration of radon emanation from the clay matrix and
desiccation cracks. The presence of desiccation cracks allows for increased
surface area from which radon may emanate in addition to more efficient
transport of radon to the surface.
-------
Two storm types that prevail in the study area include high intensity, short duration
storms in the summer and early fall; and low intensity, long duration storms in the winter
and early spring (4). During the summer and fall soils tend to be dry and desiccated.
Water infiltrating into the soil matrix and desiccation cracks may force soil gas upwards
causing a temporary increase in flux concentrations. Desiccation cracks will probably
remain open because of the short duration of storms and a period will exist when increased
flux occurs as a result of increased radon production in surface soil layers. Low intensity,
long duration storms of winter, however, will reduce the size and distribution of
desiccation cracks, causing infiltration to be primarily through the soil matrix. During the
rainfall event, radon may be pushed upward by a rising water table and trapped by
saturated clays at the surface and radon flux will be reduced except where openings exist.
However, as desiccation cracks begin to form, radon flux concentrations will increase until
the soil becomes dry in the area at the surface and near desiccation cracks.
Transect I in southern McLennan County was analyzed over two sampling periods
for radon flux and moisture content in order to evaluate the effects of climatological
differences on flux concentrations. The first sampling date represented a dry period (one
month since significant rainfall) with temperatures near 100 degrees. The second sampling
date represented an extremely dry period (2.5 months since significant rainfall) with
temperatures near 85 degrees. Results show that a general decrease in moisture content
during the second sampling period correlates with a slight reduction of radon flux, which
contradicts an EPA study indicating that increased moisture correlates with decreased radon
flux (5). This variation may be explained by decreased radon emanation produced from the
areas near desiccation cracks during the dryer period caused by radon being recoiled more
frequendy into adjacent grains and less frequently into the pore space.
Sample locations representing the highest radon flux values, were evaluated for
radium concentrations in the upper two to six inches of soil. The primary objective of this
analysis was to determine if the source of radon flux originated from the upper soil matrix
or from a deeper source.
Radium concentrations in soil samples ranged from 0.31 pCi/g to 0.89 pCi/g with a
mean of 0.51 pCi/g and a median of 0.48 pCi/g. These values are low in relation to radon
flux concentrations indicating a source other than the immediate soil matrix. The findings
of the present investigation, therefore, identify bedrock, fissure faces in soils, and radon
equilibration at the air-water interface in groundwater as potential sources contributing to
radon flux and validates the significance of desiccation cracks and fractures in rock and soil
as primary means of radon transport in the study area.
GROUNDWATER ANALYSIS
Groundwater from twenty-two shallow, large diameter wells and three springs was
analyzed for radon concentrations. The results indicate a relationship between radon in
groundwater and precipitation, temperature, aquifer efficiency, and topographic location of
the well. Table 1 represents the laboratory results from each well and spring in addition to
the sampling date and formation name.
The highest concentrations of radon in groundwater from the aquifers analyzed
occurs in the Austin and Georgetown Formations. These are fractured chalk and limestone
aquifers, respectively, which would generally be assumed to contain lower radionuclide
concentrations. Four sampling periods which represent significant climatic variations were
-------
utilized in this evaluation. Precipitation, temperature, aquifer efficiency, and topographic
location appear to be the major factqrs affecting radon concentrations in groundwater in the
study area.
TABLE 1
RADON CONCENTRATIONS IN groundwater
Well or Spring"
Radon
Location
(pCi/L)
I
72.4
2
52.4
3
39.3
4 **
306.0
4
9.0
5 **
20.9
5
7.2
6
171.0
7
296.0
8
1.6
9
45.9
10
3.9
11
0.4
12
11.2
13
23.8
14
6.3
15 **
3.7
15
0.0
16 ~*
8.4
16
1.6
17
7.2
18 **
19.4
18
11.9
19
7.5
20
6.7
21
15.2
22
7.4
23*
5.3
24 «
113.0
25*
211.0
Date
7-06-89
7-06-89
7-06-89
7-06-89
9-06-89
7-06-89
7-06-S9
7-0^89
7-06-89
7-06-89
7-06-89
7-06-89
9-06-89
9-06-89
8-14-89
8-14-89
8-14-89
9-06-89
8-14-89
9-06-89
8-14-89
8-14-89
9-06-89
8-14-89
8-14-89
8-14-89
8-14-89
9-06-89
10-9-89
10-9-89
Aquifer
O/an
Ozan
Oran
Austin
Austin
Austin
Austin
Austin
Austin
South Bosque
Like Waoo
Lake Waco
Del Rio
Georgetown
Ozan
Ozan
Ozan
Ozan
Austin
Austin
Austin
Tcrracc/South Bosque
Terrsce/Soulh Bosque
Terrace/Lake Waco
South Bosque
Woodbine
Terrace/Woodbine
Austin (Proctor Spring)
Austin (Indian Spring)
Georgetown (Osage Spring)
•« Wells sampled over two sampling periods
PRECIPITATION AND TEMPERATURE
In the two months prior to the first sampling date, 12.9 inches of rain was recorded
by the National Weather Service in Waco, Texas. An additional .9 inches was recorded
within three days of the first sampling date, which is characterized by higher radon
concentrations. The second and third sampling dates, characterized by lower radon
concentrations, were during dry periods of the year and very little precipitation was
recorded prior to these dates. Double asterisks (**) on Table 2 represent wells that were
sampled on two separate dates. Wells 4 and 5 had significant decreases in radon
concentrations from the first sampling date to the third sampling date. Wells 15, 16, and
18 had only slight decreases in radon concentrations from the second sampling date to the
third sampling date. Precipitation appears to be a significant factor in transporting
radionuclides through the groundwater flow system and works in conjunction with aquifer
efficiency. Samples 23 and 24, representing spnng samples in the Austin Formation,
indicate a significant increase in radon from the third sampling date to the fourth sampling
date, which occurred the day after a precipitation event. In addition, radon variation in the
spring samples may be caused by a 40 degree decrease m temperature between the third
and fourth sampling dates. The agitation provided by the dispersive nature of the spring in
addition to high temperatures (99 degrees) on the third sampling date resulted in greater
radon loss to the atmosphere, whereas colder temperatures on the fourth sampling date
assisted in increasing radon solubility factors.
-------
AQUIFER EFFICIENCY AND TOPOGRAPHIC LOCATION
Aquifer efficiency refers to hydraulic conductivity and transmissivity of the
aquifers. Based on well recovery rates observed after pumping, the Austin Formation with
98 percent recovery, appears to be the most effective at transport efficiency. The distinct
and abundant interconnected fractures provide more efficient transport routes for
radionuclides and supports higher radon concentrations in groundwater. The Ozan, with
65 percent recovery, and the Eagle Ford, with 59 percent recovery, appear to have tighter
flow systems which would result in decreased radon in groundwater by maintaining longer
residence times exceeding the half-life of radon. Therefore, radon concentrations detected
in the chalk and limestone aquifers may have been sourced from areas outside the
immediate well bore while radon concentrations observed in the shales are representative of
an area within the near vicinity of the well bore.
The topographic location of a well may have a significant impact on the radon
concentrations detected (see Figure 6) In this investigation wells located near entrenched
stream valleys or discharge areas were characterized by higher radon concentrations than
wells located near topographic divides. During precipitation events, water may infiltrate
into the subsurface and absorb radionuclides encountered in the unsaturated zone. This
infiltration will ultimately result in a water table rise and groundwater flow will temporarily
be increased towards the down-gradient wells. Radionuclides in solution in the
groundwater will increase in the down-gradient wells by the culmination of radionuclides
obtained from the unsaturated zones and by dislodging radionuclides that are absorbed to
particles. The divide wells, because of shorter flow paths from the recharge area, slower
rates of groundwater flow, and thin soils, have decreased radionuclide concentrations in
groundwater following precipitation events. As the water table begins to decline,
radionuclides in the groundwater will begin to absorb to particles and fracture faces in what
will become the unsaturated zone, and radionuclide concentrations in groundwater will
decrease.
High Water
Low Water
I Divide Well
¦ Table | ~~.T "
¦Shorter Flow Path
•Shallow Gradient
-Shallow Soils
-Decreased Rn-222
Down Gradient Well
-Longer Flow Path
-Steeper Gradient
-Thick Soils
-Increased Rn-222
Figure 6. Diagrammatic cross section of groundwater flow showing radon variations
between divide wells and down-gradient wells. The culmination of
recharged water, longer flow paths, and steeper gradients transport radon
from the up-gradient direction to the down-gradient well.
-------
INDOOR ANALYSIS
_Voinated for indoor radon concentrations in order to determine
. Flft^hr" r^lo ical parameters and areas where homes are subject to high
the relationship ^tweengwlog PQmes tested were distributed throughout the county,
indoor radon concen^a"°nS- the Waco area. The resulting radon concentrations range
with heavier concentrationsi in t indoor radon concentrations occur in homes
from 0.0 pCi/1 to 10.5 pOJ. Formation (see Figure 7). The home with the
located in Waco i on Houston Black soils overlying the Austin
highest indoor radon value is }y expansive and typically produce foundation
Formation. The soils at this s t h wh}ch radon may ^ introduced into the indoor
failureresultingincrackedsiao cQnsistedof aslabfoundation but subsequent addition
environment, . to foundation failure. Cracks are visible throughout the
of pier ^trances corners, windows, and between the wall and ceiling,
home, particularly ^wr emran , on wUh fractures in the Austin, the soil, and
Therefore, a for radon transport and entry,
the home provided optimum condition
McLennan County
Kef
KQt
Qal
Kgy
Kwc
Kef
Kau
Oal
Ko
s
0
Figure 7 Distribution of indoor radon concentrations exceeding 4.0 pCi/L. The
Austin Formation appears to have the greatest potential for high indoor
radon concentrations.
Homes with indoor radon concentrations above the EPA recommended guideline of
4.0 pCi/1, in addition to those located over the Austin Formation, include the lower Lake
Waco Formation, upper Pepper Formation, and the Woodbine Formation. High radon flux
in the soils overlying the Lake Waco and Pepper Formations, and associated foundation
failure due to the instability of the soil, introduced a source and mode of transport into the
structures. In the Woodbine Formation, the radon flux results and source rock potential
were low. However, the sandy nature of the underlying bedrock and gravelly nature of the
underlying soils may have produced efficient transport mechanisms by diffusive flow
resulting in a high indoor radon value.
-------
Homes overlying the Austin Formation in the study area appear to have the greatest
potential for indoor radon concentrations exceeding the EPA recommended guideline. The
Austin Formation is a highly faulted and fractured formation which contains phosphatic
zones identified as potential source rocks in this investigation and is associated with high
shrink-swell soils causing foundation instability. These characteristics are favorable for
elevated indoor radon concentrations.
CONCLUSIONS
Phosphatic zones in the Austin Formation and shales and bentonites of the Lake
Waco Formation have been identified as the potential source rocks in the study area based
on laboratory results from radium analysis. In-situ gamma logs indicate that the Lake
Waco Formation and the South Bosque Formation contain the greatest amounts of relative
gamma radioactivity.
Results from radon flux analysis in soils indicates that the greatest potential exists in
relation to Houston and Houston Black clay soils. These high shrink-swell potential soils
allow for increased permeability and surface area which result in increased emanation rates
and high radon flux concentrations.
Radon in groundwater is greatest in the Austin Formation. A clear relationship
exists between radon concentrations in groundwater and frequent precipitation events, low
temperatures, lower topographic location of the well, and high aquifer efficiency.
Indoor analyses indicate anomalies associated with the Austin, Woodbine, and
lower Lake Waco Formations. This is the result of high shrink-swell soils and associated
foundation failure which allow for efficient transport of radon into structures. The Austin
Formation has the highest potential for elevated indoor radon concentrations because of
high shrink-swell soils, foundation failure, common faults and fractures, and an identified
source rock.
REFERENCES
1. Cech, I.M., Prichard, H.M., Mayerson, A., and Lemma, M. Pattern of
distribution of radium 226 in drinking water of Texas. Water Resources Research,
v. 23, no. 10, pp. 1987-1995.
2. Barrett, D.P. A hydrogeologic assessment of the Ozan Formation, central Texas,
unpublished masters thesis, Baylor University, Waco, Texas, 141pp., 1988.
3. Panisczyan, F. Recognition, genesis, and engineering geology of weathered Eagle
Ford shale, central Texas, unpublished masters thesis, Baylor University, Waco,
Texas, 183pp., 1989.
4. Larkin, T.J. and Bomar, G.W. Climatic atlas of Texas. Texas Department of
Water Resources, LP-192, 151pp., 1983
5. Hartley, J.N. and Freeman, H.D. Radon flux measurements on Gardinier and
Royster phosphogypsum piles near Tampa and Mulberry, Florida. EPA 520/5-85-
029, U.S. Environmental Protection Agency, Richland Washington, 61pp., 1986.
-------
6. Oliver, W.B. Depositional systems in the Woodbine Formation (Upper
Cretaceous). Northeast Texas Bureau of Economic Geology Report of
Investigations, no. 73, University of Texas at Austin, 28pp„ 1971
7. Charvatt, W.A. The nature and origin of the bentonite rich Eagle Ford rocks,
central Texas: unpublished masters thesis, Baylor University, Waco, Texas, 220
pp., 1985.
8. Chamness, R.S. Stratigraphy of the Eagle Ford Group in McLennan County,
Texas, unpublished masters thesis, Baylor University, Waco, Texas, 85pp„ 1963.
9 Seewald, K.O. Stratigraphy of the Austin chalk, McLennan County, Texas,
unpublished masters thesis, Baylor University, Waco, Texas, 47pp., 1959.
10. Barquest, B.A. Hydrogeologic assessment of the Austin Chalk, unpublished
masters thesis, Baylor University, Waco, Texas, 147pp., 1989
11. Horton, T.R., Blanchard, R.L., and Windham, S.T. A long-term study of radon
and airborne particulates at phosphogypsum stacks in central Florida. EPA 520/1-
87-19-1, U.S. Environmental Protection Agency, Montgomery, Alabama, 41pp.,
1988.
12 Durrance, E.M. Radioactivity in geology: principles and applications. Chichester,
England, Ellis Horweel Ltd., 441pp., 1986.
The work described in this paper was not funded by the U.S. Environmental Protection Agency and therefore
the intents do not necessarily reflect the views of the Agency and no official endorsement should be inferred.
-------
IXP-5
RADON EMANATION FROM FRACTAL SURFACES
Thomas M. Semkowa,b, Pravin P. Parekha,b, Charles 0. Kunza,b
and Charles D. Schwenkera
a) Wadsworth Center for Laboratories and Research, New York State Department of
Health, Albany, NY 12201-0509
b) School of Public Health, State University of New York at Albany, Albany, NY
ABSTRACT
A fractal theory of radon emanation is developed for the precursor Ra distributed
uniformly throughout the sample. The main ingredient of the theory is the a recoil from
fractally rough surface. A relation between emanating power and the specific surface area is
derived and discussed in detail. It is suggested that the emanating power measurements can
be used to determine the fractal dimension of the surface on the scale from tens to hundreds
of nanometers. The theory is in good agreement with some of the experimental data, while
the discrepancy with the remaining data is attributed to radon implantation. A new process
of penetrating recoil is suggested and the role of indirect recoil is modified. The need of
using the median projected radon ranges rather than extrapolated ranges is discussed.
-------
INTRODUCTION
It is well established that radon emanates from solids predominantly by a recoil
temperatures that do not substantially differ from the room temperature. The recoil effects
have been shown to explain many features of radon emanation, e.g., (1,2). At temperatures
much greater than normal, however, processes such as solid-state diffusion, dehydration
decomposition, structural changes, and sintering begin to contribute to radon emanation
(3). Since the recoil occurs from a solid region close to the surface into the air space, the
emanation is essentially a surface phenomenon. In 1923 Hahn and Miiller suggested that
the emanation technique could be used in surface-area determinations (4). In 1939 Flugge
and Zimens published the first emanation theory; they showed that the recoil emanating
power En from a spherical grain of radius ro having uniform distribution of precursor Ra is
proportional to 3R/tq , where R is the recoil range (5). The 3/ro factor is a ratio of surface
to volume S/V of a sphere and it was assumed that it represents real surfaces. Thus, for
sufficiently large grains one obtains (5)
Er = \rV' (1)
While the above assumption appears quite intuitive, the formal derivation of equation 1 for
realistic surfaces was made only recently (Ref. 1, eq. 23). The S/V can also be expressed as
PqA, where po [g • cm-3] is the solid state density and A [m2 -g-1] is the specific surface area
Several authors have studied the emanating powers of 22Q| 222Rn from various solids
having uniform distribution of precursor Ra as a function of A (6-10). The specific sur-
face areas were determined by gas adsorption (BET) technique (11). Linear relationships
between Er and S/V have been deduced from these experiments but the exact nature of
this proportionality remained elusive. This is illustrated in Fig. 1 where we plot the ratio
of theoretical slope from eq. 1 to the experimental slope, i.e., Rp0A/4ER vs. the maximum
specific surface area measured. The ranges were calculated from the semiempirical relation-
ship by Flugge and Zimens (5). It is seen from Fig. 1 that approximately the greater the A
measured the greater the discrepancy between theory and experiment, which is as high as a
factor of 31 for a specific surface area of several hundreds m2 • g-1.
Other two processes that have escaped a clear understanding are Rn implantation and
indirect recoil. Flugge and Zimens (5) suggested that the recoiling Rn atoms have sufficient
kinetic energy to implant themselves into another grain provided the grains are sufficiently
small and close to each other so that the recoils will not stop in the surrounding air. The same
authors estimated that the maximum emanating power from powders is therefore ~ 0 01
This is, however, in contrast with experiments. In fact, most of the data shown in Fig i
-------
Q_
X
LU
\
>-
QC
O
LU
IE
a
_i
o
Q_
O
_l
CO
JO
1 1
1 1 1 1
1 1 1
.
1 ¦
2
25
-
¦
-
3
4
¦
¦
15
5
¦
7 ¦
¦ 6
¦
8
5
" 9
-
¦
.
-5
i 1
1 i 1
i
-50 50 150 250
fl [m2/g]
350
450
Figure 1. Ratios of the slopes of emanation curves from the old theory and from the
experiments plotted vs. the maximum specific surface area A measured. Point numbers refer
to the systems: 1,2 220Rn/MgO (6), 3 220Rn/MnO2 (7), 4 220Rn/ZrO2 (8), 5 220Rn/Al2O3
(9), 6 220Rn/MgO (8), 7 220Rn/NiO (7), 8 220Rn/ThO2 (8), 9 222Rn/brick (10).
are for finely dispersed solids and the values of Er often exceed 0.5. This discrepancy led
Quet and Bussiere to conclude: "The absolute emanating powers of the various samples are
too high for a powder. We must consider the possibility for radon to escape anomalously
from the solid at room temperature" (6). This situation can be helped with the concept of
indirect recoil by Zimens (12): the recoils implanted into the solid may subsequently diffuse
back through the region of radiation damage caused by the implantation (see also Ref. 3,
p. 54). This is, however, inconsistent with 222Rn implantation experiments into monocrystals
and some geological samples performed by Lambert et aI. (13) and Lambert and Bristeau
(14), which indicated that the Rn recoils once implanted do not easily diffuse out. Using
the authors' statement: "Simple radioactive measurements show that the diffusion of radon
is very low within various monocrystals and that it cannot explain the emanating power of
rocks" (14).
-------
We have just described that, in spite of general consensus that recoil is a predominant
mechanism of radon release, the exact nature of the relationship between the emanating
power and the surface area as well as implantation and indirect recoil remain unclear. The
purpose of this paper is to try to explain some of these discrepancies. The models of Rn
emanation based on Euclidean geometry either fail to describe the emanating surface properly
or express the surface with the parameters that are not sufficient. We therefore use the
fractal geometry of Mandelbrot (15) to describe the emanating surface. In the subsequent
sections we discuss briefly the principles of fractal geometry and use it to derive a fractal
theory of Rn emanation. We then discuss the meaning of fractal dimension determined from
emanation measurements in relation to the fractal dimension obtained from gas adsorption
measurements. We discuss the relationship between the emanating power and specific surface
area in detail. The fractal model of radon emanation leads us to suggest a new interpretation
of implantation and indirect recoil. Finally, we address the question of the use of Rn recoil
ranges in emanation. In this paper we are interested only in uniform distribution of Ra in
the samples.
FRACTAL THEORY OF RADON EMANATION
Principles of Fractal Geometry
A concept of self-similarity is central to fractal geometry: the fractal object contains
features of different sizes that are invariant under ordinary geometric scaling (Ref. 15, p. ig)
i.e., they look similar at different magnifications. The number of features of size r is pro-
portional to r~D, where D is the fractal dimension (Ref. 15, p. 37). The value of D is
normally a noninteger and it lies somewhere between the topological dimension Dt and the
dimension of the embedding Euclidean space E: Dt < D < E. For lines Dt = 1 and E = 2
so 1 < D < 2; for surfaces Dt = 2 and E = 3, so 2 < D < 3. Another important point is
that, if two sets with fractal dimensions Da and D\, intersect, the fractal dimension of the
intersection is usually Da+D^ — E (Ref. 15, p. 365). We illustrate these concepts by plotting
several alternate Koch curves in Fig. 2 (Ref. 15, p. 48). The fractal dimensions are given
next to each curve. If the fractal surface D is intersected with a plane, the fractal dimension
of the resulting curve is D + 2 — 3 = D — 1. Since the curves in Fig. 2 are considered as cuts
through the fractal surfaces, the dimensions of the corresponding surfaces are obtained by
adding 1 to the curve dimensions and are given in parentheses in Fig. 2. A comprehensive
analysis of surfaces of many materials revealed that most of them are fractals at least in the
molecular range (16).
-------
1.25 (2.25)
Figure 2. Alternative Koch curves describing the cuts through the fractal surfaces.
The fractal dimensions are given by each curve followed by fractal dimensions of the corre-
sponding surfaces (in parentheses).
-------
f nt interest to radon emanation is the volume of points with
An important concep ^ in p.g 3 At each point of
a touUenle/a drcle of radius r. The volume enclosed by an outer envelope of the circle,
is given by (Ref. 15, P- 358) ^ = ^ ^_D ^
. , 1 ^nnstant For real fractal surfaces this constant can be
where B is a certain t eore Ka ^ ^ adsorbatej and determining the monolayer volume
eliminated by covering diameter of the adsorbate molecule,
tTrrr: *»-*
V(D = n.)® <»>
Equation 3 and its modifications have been used extensively in studying multilayer adsorption
on fractal surfaces (17,18). _
• wa 9 fractal surfaces have an internal porosity that first increases
As can be seen^i Fig. 2^actaUu ^ ^ ^ = 2 and 3 ^ ^ = g ^
and then decreases For D = 3 we have such an extreme roughness that
have a flat surface with no porosi ^ SQ the intemal porosity is again zero.
the fractal surface
-------
Figure 3. Volume of points with distances < r from a fractal (D = 1.2).
AIR
SOLID
Figure 4. Volume of points with distances < R from a surface. R is a recoil range.
Arrows abbreviate the processes: 1 direct recoil, 2 implantation, 3 indirect recoil, and 4
penetrating recoil.
-------
ratio of V(R) to the total solid-state volume V. Using eq. 3 and the fact that V(a) = So,
where S is the BET value of surface area we get
Ti,. .f ft » w ""
of surface.
Eauation 4 is modelless. However, we must consider emanation from particular shapes
• to calculate the proportionality constant in eq. 4. We have chosen emanation from
in order to ca are manifold> The emanation from a
plates as a ^problem so the integration is simple. Also, smaJ! grains
plate is essen y ^ ^ ^ platelets or needles in addition to spheres. Using the
forrmdas for" emanation from a plate (22) and performing the integration over the entire
fractal regime one obtains (23)
1
ER= 4
2d~1 (t)D~2
4-D\RJ
R p- , 2r0 > R (5a)
p _ i _ D- ~ , R>2r0, (5b)
Er - l 4 — Ł)
• half thickness of a plate (or geometric radius of an object). In deriving eq. 5
we Neglected the edge effects (1) and assumed cancellation of certain terms.
,, . frw lareer than the recoil range Er oc S/V. For
objectlfsrnaller than "r,"En asymptotically approaches 1 «d i.: independent of S/V. The
surface-to-volume ratio for a fractal object can be expressed as (23)
s_ _ (6a)
V ro\a)
C ffik)
i< = —'
r volume ratio of an outer shape (a hull) and it is equal to 6 for a cube,
where C is a surface-to-volu ^ ^ ^ p|aU, Using eq. 5a,6a, the emanating power can
3 for a sphere, 2 for a cylinder, an
then be expressed as a function of radius ro
P K (—)3~° ¦ 2n>R. (7)
bR~ 4-D\2nJ
, , „„ 7 6b reduce to the familiar Euclidean formulas R/4r„ and 1 -ra/R,
F°rC : Tm 3 emanation is com(,K te (Es = 1). The D = 3 limit can be
respectively [22). ^ eviuUS section. For D = 3 the surface has an
understood by recalling the iscussion sections with well developed microporosity,
extreme roughness and is composed of thin soM
-------
so all Rn can emanate into pores. Equations 5,7 describe what fraction of Rn atoms recoil
out of the surface. They do not describe the implantation processes from Fig. 4, which will
be discussed later.
Recoil Ranges
In emanation studies fixed values of recoil ranges R have usually been assumed. The
ranges are traditionally deduced from a semiempirical relationship by Fliigge and Zimens
(FZ) (5). Their approach has been questioned; we refer the reader to a work of Baulch
and Duncan (24) for a detailed discussion. The point is that FZ ranges are those which
one might call extrapolated. In reality the range has a distribution due to range and angle
straggling of recoiling atoms penetrating the medium. The quantity that is best measured
experimentally is the median projected range /2m. It is the penetration depth to stop 50%
of the beam, projected on the beam direction. Here we use a theory of Lindhard, Scharff
and Schi0tt (LSS) to calculate the range Rm and its variance crm (25,26)
D _ em \jMi + Mi M2 „
m ~ 2 * r » 2 >7 ry 1
7T Noh Ml + -A/2 P2
3
am _ j 2 Mj mi + \m2
Rm V ^ Mi Mi + M2
In eq. 8 M is the atomic mass, Z is atomic number, E is kinetic energy, p is the density, m is
the electron mass, Nq is the Avogadro number, % is the rationalized Planck constant, e is the
basis of natural logarithm, and indexes 1 and 2 refer to a beam (recoil) and a target (solid),
respectively. The LSS ranges are in good agreement with experimental ranges of 222Rn in
A1 at energies of ~ 100 keV (27), which, in fact, is of interest to emanation.
It is instructive to compare the R of FZ with Rm of LSS. For 222Rn recoil in glass
we get 37 and 26 nm, for 220Rn recoil in MgO we get 37 and 21 nm, respectively. The FZ
values are larger and thus they may be referred to as extrapolated. Considering the Rn
emanation, we calculated the emanating power from a plate assuming a Gaussian straggling
and neglecting the channeling effects. The result is (23)
^ = <9>
where erf(x) is an error function. For 222Rn in glass we get from eq. 8b Rmly/2am « 3 and
erf(3) « 1. Therefore the Rm values should be used for ranges in emanation. Equation 9
is valid for features that have sizes of Rm or larger. As can be seen from eq. 5a, this is
particularly important for D close to 2. For features smaller than Rm a particular value of
(8a)
(8b)
-------
range is less important because most of the Rn emanates anyway. This is the case for D
approaching 3 and eq. 5,7 show that Er is then only a weak function of range.
APPLICATIONS AND DISCUSSION
a . ,, emanating power should scale as r0D 3. Therefore from
Equation 7 shows tha e ^ ^ ^ ^ ^ dimemi o{
a logarithmic plot of Er . ^ ^ p.g g the data of Barretto (28) who
the emanating surface, lo i u tions Qf Lipari volcanic glass. The straight line is
measured Er for sieve-separa e si Euclidean formula one would expect the slope of
a least-squares fit ^ ^ data.^ ± ^ ^ ^ ^ ^ ^ D = ^ ± 0 06i
this line to ^ determined to give a quantitative fit to the data.
The constant C from.eq. reasonable shape of the hull. We also used the LSS
The result is C = 9-8> to° lg 26nm In order to improve the fit, one has to realize
value of 222Rn range in glass ^ ^ wide and are indicated by horizontal lines in
that the size ranges for each d Qn the (unknoWn) weight vs. size distribution
Fig. 5. The emanation wi « gcales as rD~\ the contribution to emanation
in each size fraction, am ^ fraction. One then has to integrate eq. 7 over
is greater from smaller sizes in ea• & constant weight vs. size distribution in each
the appropriate distribution. . and repeated the fit. The result is D = 2.28±0.10
fraction, integrated eq. 7 acco g ^ . ^in the error of the fit. The value of C is
with C = 3.1. The two va ues ^ shapes of the particles. It is remarkable that,
close to 3 indicating approxima ^ ^ quantitative agreement with the data with only
under a reasonable assump ion, q. that processes such as implantation were not
two fit parameters: D an • ^ ^ ^ ^ ^ yalue o{ D and large rQ> gmall D
significant, which is easy to jus J gQ the impiantation in the same grain must have
indicates a moderate surface 1 « . was largely prevented by Rn stopping in the
''ces were tens ot "m or more (Bm(air)=47 "m
for 222Rn). a fractal surface with a rather low
We conclude that the ipaxii v° ^ ^ ^ compared with similar geological and glassy
fractal dimension in the vicim y(20 29) The values of D are: 2.14 ± 0,06
materials with D determine y ^ ^ 2 21 ± 0 01 for crushed
for Madagascar quartz, z.io x . , lags The emanating power thus emerges
quartz, and 2.35 ± O.U for crushed Cornng8 ^ ^ ^ ^
M Wout the sample-
-------
L±J
4*101 102 103
luml
Figure 5. Emanating power Er plotted vs. the average size of the grains. Horizontal
bars are the size ranges in each fraction (not the errors). The lower rightmost point is a
lower limit on size.
When implying that there is a fractal dimension D associated with a surface, we are
faced with a question of a range of its self-similarity. It is instructive to compare this with
gas adsorption techniques (30). In that case one covers the surface with molecules of size a
and using the BET method, for instance, one can deduce a monolayer coverage. Thus the
lower limit of self-similarity is a. If the fractality was determined for particle sizes between
rmin and rmax, the upper limit of self-similarity is armaz/rmin, for particles with size rmax
(30). It does not imply that the self-similarity does not extend higher. It only says that
the adsorption is not sensitive to self-similarity above the upper limit. A typical range of
self-similarity determined from gas adsorption thus lies between a fraction of a nm to tens
of nm.
For Rn emanation the situation is as follows. Equation 5a shows that Er Rm, Er is sensitive
-------
to D. For Rm > 2ro we have to look at eq. 5b. Some sensitivity to D is still there but
for plate only. For a sphere eq. 5b would give Er = 1 identically, and the sensitivity to Ł>
would be lost. Hence, for realistic particles one can say that the lower limit of self-similarit
is approximately Rm/2. Suppose a self-similarity was determined for particle radii betvve^
rmin and rmax . Using the concept of self-similarity we scale the rmin particle up to the r
particle by a scaling factor of rmax/rmin . So if the lower limit of self-similarity is Rm/2 The
upper limit for particle rmax is Rmrmax/2rmin • The range of self-similarity by eman&ti
technique is thus
( 1 » 1 ft Tmax \
\ 2 m ' 2 m Tmin ) ' (10)
for particle with radius rmax . Applying these concepts to the data of Barretto (28) and us'
Rm = 26 nm, rmin = 94 /mi, and rmax = 2000 /xm, we get a range of self-similarity between
~ 13 to ~ 280 nm. The emanation technique for D determination thus complements the
adsorption technique by being sensitive between tens to hundreds of nanometers
We now turn to a dependence of Er on S/V and use eq. 5a to analyze the data of QUe
and Bussiere (6). These authors made a comprehensive investigation of 220Rn ema t'
from MgO labelled with 228Th. The samples were prepared by coprecipitation of 228Xh * °
Mg(OH)2. The precipitates were then heated for several hours at difFerent temperatur^^
several hundreds °C to make the final samples. The samples were composed of fine ^
of MgO. Besides the Er, specific surface areas A by BET (11) and De Boer V-t adsorptio^
curves (31) were determined, as well as the electron-microscopy images were taken It l0°
also determined that the Er was not dependent on Rn transport in the samples by showT^
that the measured activity of 220Rn increased linearly with the sample mass.
We reproduce Quet and Bussiere (6) emanating-power data in Fig. 6. The curve h
a linear section, between points 8 and 16, and it deviates from linearity between points
and 7. The slope of the linear section is about 25 times lower than the one predicted th^
Euclidean emanation theory (eq. 1). This discrepancy between theoretical and experim * °
slopes has been described in the Introduction and the factor of 25 for 220Rn/MgO s t<»
is reproduced as point 2 in Fig. 1. Point 1 in Fig. 6 can also be assigned a "slope" wh* i,
results in a discrepancy factor of 31, depicted as point 1 in Fig. 1.
In the following we focus on three points from Fig. 6: point 14 lying on the line
section, point 7 at the onset of departure from linearity, and the rightmost point number ^
Some of the experimental and theoretical parameters for these three points are reD
in Table 1. Equation 6a shows that S/V can increase when r0 decreases or D increases W
thus conclude from eq. 5a that the linear section in Fig. 6 has a constant D and a decre' ' °
ro. Each point corresponds to a distribution in ro . In this case it does not matter howey0^
because the experimental S/V already takes care of that distribution. One would ^
D > 3 to fit eq. 5a to the linear part of Fig. 6. We therefore look at the Rn implantat^^16
improve the fit. We use a concept of implantation threshold fe introduced by Tham^
-------
0.5
0.4
0.3
en
Ixl
0.2
0.1
0.0
0 100 200 300 400
R (m2/g)
Figure 6. Emanating power Er plotted vs. the specific surface area A for the system
230Rn/MgO (6). Points 1, 7, 8, 14, 16 are discussed in the text.
et a1. (32) and also employed in Ref. 1. By definition, /e is a fraction of a range required for
permanent implantation. Thus using
Re = (l~fe)Rm (Ha)
the implanted fraction is Erc and the emanating power in the presence of implantation is
Er^-Er.. (lib)
Now we have two parameters: D and fe to determine. However, since eq. 5a,lib intersect
the origin, there are many combinations of D and fe that would fit the data. We have to look
for an alternative way of finding D. It can be deduced from the V-t curves reported by Quet
and Bussiere (6). Using the standard V-t curve by De Boer (31), we transformed the data
to isotherms, i.e., weight W of N2 adsorbed vs. the ratio of the pressure to saturation pres-
sure p/po. Then, using the BET method (11), we determined the weight Wm for monolayer
coverage. Finally, we plot the reduced isotherms, i.e., WfWm vs. the p/po in Fig. 7. This
-------
TABLE 1. SUMMARY OF EMANATING POWER DATA4
Variable
Name
14
Value for pointb
7
1
Obtained
from
Er
emanating power
0.179
0.313
0.405
experimental
A ,m2 • g-1
specific surface
137
242
384
BET isotherm (nj
area
D
fractal dimension
2.4
2.6
2.9
fractal BET
isotherm (18)
ro , nm
average grain
35
31
23
electron
radius
micrographs
slope
theory/exp.
25.3
25.6
31.4
eq. lc
slope
theory/exp.
4.5
2.7
1.5
eq. 5ad
fe
implantation
0.34
0.69
~ 0.99
eq. 5a,Ha,bXimately
D & 2.9 for point 1.
Now we return to the discussion of the linear section of the curve from Fig. g Using
D = 2.4 and eq. 5a, the ratio of theoretical slope to the experimental slope is now 4 5 for
any point on the curve including point 14. This is a considerable improvement froxn a factor
of 25, and the remaining deviation is attributed to Rn implantation. Using eq. 5a,lia b one
can fit the data exactly yielding the implantation threshold fe = 0.34. It is intere8t'ing to
note that the previously assumed value was 0.3 (32,1).
We also used the electron micrographs from Ref. 6 to estimate approximate the
average sizes of the grains. As it turns out, the samples are composed of very grajn8
with approximate average radii of 35, 31, and 23 nm for samples number 14, 7 an(J j
-------
0 I I I , I I I L
0.0 0.2 0.4 0.6 0.8 1.0
P/Po
Figure 7. Reduced isotherms (adsorbed weight vs. the pressure) for Nj adsorption
on MgO (6). Point abbreviations: ~ point 14, A point 7, O point 1 (point numbers from
Fig. 6 and Table 1). Solid curves are for the fractal BET model (18) with D values (starting
from the top): 2, 2.2, 2.4, 2.6, 2.8, 3 (all for number of layers n = oo), and 3 (n = 20).
TABLE 2. FACTORS AFFECTING RADON IMPLANTATION AND PENETRATING
RECOIL.
Case
Grain
Water
Fractal
Implantation
Penetrating
radiusa
present
dimension
recoil
1
> i?m(air)
no
low
low
low
2
< Rm(air)
no
low
high
low
3
any
no
high
low
high
4
any
yes
any
low
low
a) Rm{air) = 47 fim is a median projected range of Rn in air
-------
, A,„,rdinC to our discussion above, the bending of the curve from Fig. 6 is
respectively. A g decrease of r0. We repeat the fits to points 7 and 1, with
thus due to increase o theoretical to experimental slopes are now
the values of D ^ J. implantation threshoUs are 0.69, and ~ 0.99 for points T,
2.7 and 1.5, or a ^ ^ ^ .ncreasiiig D and decreasing r„ the discrepancy
and 1, respectiv y. diminishing; due to decrease of implantation. The value of
between theory for D approaching 3 eq. 5a,lib
L v« senitive to D and the implantation threshold probably loses its straightforward
interpretation. ^ ^ ^ ^ discrepancy between fractal theory
The importan is between !.5 to 4.5. Thamer et al. (32) studied the
of radon emanation and p ^ Łs(wet)/Eji(dry)). They found the range
water effects in En emana ion uae tbe recoils are believed to stop in water, this
of water effects between . ^^ ^ impUnUtion.
supports very n ^ impiantotion process. As mentioned in the In-
We now turn to th ^ Umbert and Bristeau (14) studied the implantation
troduction, Lambert et a . V ; diffusion back through the radiation-damaged zone
of into variou^materials and ^ ^ ^ ^
(damage diffusion), in y or mica no diffusion was detected, for limestone
monocrystal 1'7±0'7^ basalt 0-2% diffused (at 300°C). Korselsen made a
3.1 ± 2.7% difFused (at 300 )' o{ inert gases jn tungsten as a function of kinetic
systematic study of sticking pro ^ ^ sticking probability ranged from
energy in the range 40 eV to e Brown and Davies found that sticking probability
~f *5 keV' for Ag A»-
, • j wu«re it was lower (35).
which do not form oxides, where
Rn emanation. Consider emanation from a plate and
Let us apply the range is proportional to kinetic energy (eq. 8a)
we get (23) _ Et_
fe ~ Eq '
where ft is the threshold energy for implantation and ft is the recoil energy. Using
eq! 6b,7,11a,b with C = 1 and /) = 2 we get
_ ^Ei^Rrn ^12b)
hRm 4 Eq ro
e K w 3 keV and Eq = 86 keV, for 222Rn recoil. So the
Recalling the discussion above we us ^ ^ reduce(j by a factor ~ 29 due to Rn implantation,
emanating power would be expec e ^ ^ ^ ^ ^ implantation was
However, for Quet and Bussiere a a ^ ^ penetrating recoils from Fig. 4
between 1.5-4.5. We therefore suggest
-------
(arrow 4) rather than the indirect recoils (arrow 3) that are responsible. With an increase
of D from 2.4 to 2.9 surface roughness increases and, as can be seen from Fig. 2, the surface
acquires a large number of small irregularities. The recoiling Rn atoms can penetrate these
irregularities through losing their energies. This process diminishes the implantation and
the ratio of theoretical to experimental slopes decreases from 4.5 to 1.5.
The indirect recoil mechanism (12) is nothing else than the damage diffusion. The
experiments described above showed that this damage diffusion occurs only for the smallest
energies (< 3 keV). Therefore it can occur at the very late stage of energy-loss process,
after most of the energy was lost due to penetrating recoil. Then, the indirect recoil (or
lowered sticking probability) prevents the implantation. For pure implantation with kinetic
energies > 3 keV there is little chance for any indirect recoil. This is especially true for
220Rn whose short half life (55 s) precludes any significant damage diffusion. Some of the
implanted 222Rn recoils can be leached out at a slow rate with water introduced after the
implantation (36). When water is originally present in the sample, implantation is expected
to significantly decrease owing to recoils stopping in the water. The processes of implantation
and penetrating recoil can occur in the same grain or into the neighboring grains depending
on the sizes of the grains, average interstitial separation relative to the recoil range in air,
surface roughness, and presence of water. A summary of different situations is given in
Table 2.
CONCLUSIONS
1. A fractal theory of radon emanation has been developed for the case when precur-
sor Ra is distributed uniformly throughout the sample. The emanating power was
expressed either as a function of surface-to-volume ratio (eq. 5a) or an outer-shape ra-
dius (eq. 5b,7). Fractal dimension of the surface enters the equations as a parameter.
2. It has been shown how the emanating power measurements can be used to determine
the fractal dimension of the emanating surface. The range of self-similarity that can
be determined is between a few tens to a few hundreds of nanometers, which extends
the range determined by the gas adsorption.
3. With no Rn implantation present, fractal theory gives a good agreement with emanat-
ing powers from Lipari volcanic glass. When Rn implantation is present, the theory
differs from emanating powers from MgO by a factor of 1.5-4.5, which is a typical
range of water effects in emanation.
4. Careful examination of our results and the implantation experiments from the literature
led us to suggest that the implantation and penetrating recoil are the results of most
-------
of the energy loss. The indirect recoil may be present at the very last stage of energy
ot the en gy ^ ^ ^ ^ ^ penetratl„g recoil. Consequently, the
penetr^ing recoil may be responsible for diminished incantation in material, with
rough surfaces.
5. The need of using the median projected ranges (LSS) rather than extrapolated range,
(FZ) for Rn recoil was emphasized.
o funded bv the U.S. Environmental Protection
Age»cr^h"t cdteldo 1 necessarily reflect the views of the agency and no
official endorsement should be inferred.
acknowledgments
f f f *1 a-eometry has been independently suggested to one of us (T.M.S.)
The concept of fractal g Alben for fruitful discussion,
by A.B. Tanner. Thanks are due to K. AlBen
REFERENCES
grains,
in radon
1. Semkow, T.M. Recoil-emanation theory applied to radon release from mineral
Geochim. Cosmochim. Acta. 54: 425, 1990.
2 Semkow, T.M. and Parekh, P.P. The role of radium distribution and porosity i
emanation from solids. Geophys. Res. Lett. 17: 837, 1990.
3 Balek, V. and Tolgyessy, J. Comprehensive Analytical Chemistry. Vol. XII. Thermal
Analysis. Part C. Emanation Thermal Analaysis and Other Radiometric Emanation
Methods. Elsevier, New York, 1984.
4 Hahn O. and Miiller, 0. Eine neue methode zum studium der oberflache und
oberflachenanderung feinverteilter niederschlage. Z. f. Elektroch. 29: 189, 1923.
5. Fliigge, S. and Zimens, K.E. Die bestimmung von korngroBen und von diffusionskon-
stanten aus dem emaniervermogen. (Dietheorie der emaniermethode.) Z.Phys. Chem.
t-» 17Q 1Q39.
' ^ j „ „oiire P Pouvoir emanateur de solides finement dmsea. II.-Oxyde3
6. Quet, C. and Bus ' . pr^KiltioI1 de l'hydroxyde, coprecipitation de thorium
de magnesium ex-hy y • temperature ambiante d'oxydes d'aire specifique
228, texture et pouvo.r emanateur a la temp
J. Chim. Phys. 72. 823, 1975.
-------
7. Gourdier, J.-F., Bussiere, P. and Imelik, B. Cinetique chimique. - Sur la relation entre
pouvoir emanateur et surface specifique de solides finement divises, et son utilisation
pour l'etude cinetique du frittage. C. R. Acad. Sc. Paris C. 264: 1625, 1967.
8. Zhabrova, G.M. and Shibanova, M.D. An investigation by a radiation method of oxide
catalysts during their preparation and thermal treatment. Kinetika i Kataliz. 2: 668,
1961 (Engl, transl. p. 602).
9. Jockers, K. Emaniervermogen und oberflachengroBe verschiedener aluminiumhydrox-
yde und aluminiumoxyde. Z. Anorg. Allg. Chemie. 265: 49, 1951.
10. Bossus, D.A.W. Emanating power and specific surface area. Rad. Prot. Dos. 7: 73,
1984.
11. Brunauer, S., Emmett, P.H. and Teller, E. Adsorption of gases in multimolecular layers.
J. Am. Chem. Soc. 60: 309, 1938.
12. Zimens, K.E. Oberflachenbestimmungen und diffusionsmessungen mittels radioaktiver
edelgase. III. Der vorgang der emanationsabgabe aus dispersen systemen. Folgerungen
fur die auswertung von EV-messungen und fur die deutung der ergebnisse. Z. Phys.
Chem. A. 192: 1, 1943.
13. Lambert, G., Bristeau, P. and Polian. G. Geophysique.-Mise en evidence de la faiblesse
des migrations du radon a l'interieur des grains de roche. C. R. Acad. Sc. Paris D.
274: 3333, 1972.
14. Lambert, G. and Bristeau, P. Migration des atomes de radon implantes dans les
cristaux par energie de recul. J. de Phys. C. 5: 137, 1973.
15. Mandelbrot, B.B. The Fractal Geometry of Nature. Freeman, New York, 1983.
16. Avnir, D., Farin, D. and Pfeifer, P. Molecular fractal surfaces. Nature. 308: 261, 1984.
17. Pfeifer, P., Wu, Y.J., Cole, M.W. and Krim, J. Multilayer adsorption on a fractally
rough surface. Phys. Rev. Lett. 62: 1997, 1989.
18. Pfeifer, P., Obert, M. and Cole, M.W. Fractal BET and FHH theories of adsorption:
a comparative study. Proc. R. Soc. Lond. A. 423: 169, 1989.
19. Levitz, P., Van Damme, H. and Fripiat, J.J. Growth of adsorbed multilayers on fractal
surfaces. Langmuir. 4: 781, 1988.
20. Avnir, D., Farin, D. and Pfeifer, P. Surface geometric irregularity of particulate mate-
rials: the fractal approach. J. Colloid Interf. Sci. 103: 112, 1985.
21. Kurbatov, J.D. Evaluation of the surface area of catalysts of cubic form by the ema-
nation method. J. Phys. Chem. 45: 851, 1941.
-------
22. Quet, C„ Rousseau-Violet, J. and Bussiere, P. Pouvok emanateurd<, recul de.particulea
isolees des solides finement divisfe. Rzdiochem. RaAoanal. Lett. 9. 9, 1972.
23. Semkow, T.M. Unpublished.
, t 'PVip rance-enerffy relation for &~recoil atoms. Austr&l,
24. Baulch, D.L. and Duncan, J.F. I he range energy
J. Chem. 10: 112, 1957.
25. Lindhard, J. and Scharff, M. Energy dissipation by ions in the keV regum. Phys. Rev.
124: 128, 1961.
™ t • Ah H 1 Scharff M. and Schi0tt, H.E. Range concepts and heavy ,on ranges.
26. Lindhard, J , Schartt ^ ^ ^ ^ 3J(U). ^ l%3
(Notes on atomic collisions, n.) m j
t n • c i A Domeii B. and Uhler, J. The range of 222Rn ions of keV
27 Bergstrom, I., Davies, J.A., L»om J,
energies in aluminium and tungsten. Art-v f. Fys,k. 24. 389, 1963.
a r Fmanation characteristics of terrestrial and lunar materials and
28' fh:»^loteffect''on the U-Pb system discordance. Ph.D. Thesis, Rice University,
Houston, Texas, 1972.
A • n n j Porin D Chemistry in noninteger dimensions between two and three.
adsorbents. ?X Chen, P„, «= "*3.
™ j a nir D Chemistry in noninteger dimensions between two and three.
30' [^fractal* theor^of heterogeneous surfaces. X CHem. Phy, 79: 3558, 1983. Erratum.
ibid. 80: 4573, 1983.
r T insen B G and De Boer, J.H. Studies on pore systems in catalysis.
31- iThTadforptioTo, nitrogen; apparatus and calculation. J. Catalysis. 3-. 32, 1964.
B T Nielson K.K. and Felthauser, K. The effects of moisture on radon
32, Imrli'on deluding the effects on diffusion. US DOt Report BuMines OFR 184-82,
iVT/S Report PB83-136358, 1981.
33 Lowell S. Introduction to Powder Surface Area. J. Wiley k Sons, New York, 1979.
/ V 1 n P V The ionic entrapment and thermal desorption of inert gases in tungsten
eV to 5 keV. Can. X Ph.s . 4* 364, 1964.
i? nA navies J A The effect of energy and integrated flux on the retention
35' anTrange oT^'ions injected at keV energies in metals. Can. X Phys. 41: 844,
1963. ...
36. Fleischer, R.L. Theory of alpha recoil effects on radon release and .sotop.c d,sequilib-
rium. Geochim. Cosmochim. Acta. 47. 77 ,
-------
IXP-6
TITLE: National Ambient Radon Study
AUTHOR: Richard Hopper, EPA - Office of Radiation Programs
This paper was not received in time to be included in the
preprints and the abstract was not available. Please check your
registration packet for a complete copy of the paper.
-------
Session X:
Radon in Schools and Large Buildings
-------
X-l
TITLE: The Results of EPA's School Protocol Development Study
AUTHOR: Anita L. Schmidt, EPA - Office of Radiation Programs
pap©r was not received in time to be included m th©
preprints so only the abstract has been included. Please check
your registration packet for a complete copy of the paper.
ABSTRACT
In April 1989, EPA released interim guidance, " Radon Measur0m- *.
in Schools-An Interim Report (EPA520/1-89-010). This guidan^
based in part on data from an intensive study of radon < Va®
limited number (five) of schools in Fairfax County VirainiT mv*
Radon Division of the Office of Radiation Programs subsim,a«IVe
conducted the School Protocol Development study to y
additional data to update and revise as necessary the guidan^t
procedures for radon measurmeents in schools. 8
This study consisted of two phases. Phase I was a screenino ^
of 130 schools in 16 states using 2-day, weekend charcoal can?«* *
measurements. Based on the results of these measurement.
schools in 7 States were selected for Phase II. This was" a v
long, comprehensive study investigating short-term and lone +r~
measurements using a variety of devices under different condi?!^*™
Various factors that influence these measurements, such as bull 2?*'
structure and ventilation systems, will be evaluated. Th*
results of this study will be presented. rihal
-------
X-2
TITLE: Diagnostic Evaluations of Twenty-six U.S. Schools -- EPA's
School Evaluation Program
AUTHOR: Gene Fisher, EPA - Office of Radiation Programs
This paper was riot received in time to be included in the
preprints so only the abstract has been included. Please check
your registration packet for a complete copy of the paper.
As part of a coordinated radon in schools technology development
effort, EPA's School Evaluation Team has performed on site
evaluations of twenty six schools in eight regional locations
throughout the United States. This paper presents the results
and preliminary conclusions of these evaluations which represent
the most schools to date diagnosed for both sub-slab and HVAC
characteristics. Also reported are carbon dioxide and building
shell tightness measurements which further characterize the
building dynamics, in addition to these technical issues,
physical and institutional problems which affect the selection
and implementation of radon mitigation strategies are identified.
Specific determination of soil depressurization and existing hvac
systems as radon control methods and remedial recommendations
were developed for each school. Results of this two year study
indicate that EPA should consider a new direction in large
building radon abatement — a holistic approach that considers
total indoor air quality, comfort, cost, and energy issues.
NOTES:
This presentation will incorporate 35 mm slides (pictoral,
graphic, and text types), and is expected to take a full 2 0
minutes.
-------
X-3
TITLE: Extended Heating, Ventilating and Air Conditioning Diagnostics
in Schools in Maine
AUTHOR: Terry Brennan, Camroden Associates
This paper was not received in time to be included in the
preprints so only the abstract has been included. Please check
your registration packet for a complete copy of the paper.
. ^ aMMS the effects of HVAC system operation the indoor
An extensive ^ Mariy schools In the School Evaluation Program
r«don I0WI3 WMOO ¦ d)Wed or monotoning outside air on the
nave been found to have ^ ^ ^ Mm ichoo)5 had ^ al#atllwl
ventilation system. uofeeslonal HVAC and control contractor#.
This condition was ^ tnd outside airflow., preesum
Measurements were m ^ and hMih, redon levels. Exhaust
differentia acroM » Z« were taMigMl. A hM
ventilationjwmupa^ w , room that had leaky window sash as the
-------
X-4
MTTTfiftTtnN ntafiNnRTrrs: the nff.d fok uNPFKSTANrmin
BOTH HVAC AND GEOLOGIC EFFECTS IN SCHOOLS
by: Stephen T. Hall
Radon Control Professionals, Inc.
Reston, Virginia 22094
ABSTRACT
Experience in the remediation of schools has shown that in
some, highest indoor radon levels were located near large central
HVAC return ducts arid were attributed to the predominance of and
the proximity to negative HVAC pressure. Successful sub-slab
depressurization systems were Installed, however, in rooms with
lower Indoor but greatest sub-slab radon levels, closest to the
source. This shows the Inadequacy of using indoor radon levels
alone as a basis for remediation. Wings of other schools with
radon problems have window heating units in rooms of equal uize
and no central HVAC system. Highest Indoor radon levels
correlated well with highest sub-slab radon levels due to the
equivalent effects of the window units anc| the predominance of
geology.
Diagnostic tests in other schools have revealed: blockwall
radon transport to upper floors; elevated blockwall radon
adjacent to sub-slab sources; and elevated indoor radon above a
cravlspace caused by HVAC induced negative pressure.
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and therefore the contents do not
necessarily reflect the views of the Agency and no official
endorsement should be inferred.
-------
M.,r vlV, rnndocted radon sMl analyses at
... r_c*. ti-,vf.e Y^*s " w,,rH on sites In the Washington,
in the P'-j- • chool an,j numerous other c0"' ty HD) to predict indoor radon
approximately 20 3 • d Montgomery C tloir. with Indoor radon In
DC area (Hor^ern Virginia showed correlation.^
ŁSctJes\n «t»o«phlc ^0fmden^a„I„yre»eala1 dl„n.Stlc, ana mediation m
Control P"ŁesslHtheJ large buildings.
20-30 schools and Ar^nce oŁ the effects of both the location
PXDerlence has shown the mp .| tl«m of Indoor radon. In general,
! tnnrces and HVAC-lnduced ^^trib - fllstrlbutea HVAC pressures are
«« rU'letS both contrition..
Effective remedla ^ highest indoor radon levels were
Kftnli, uith central HVAC uys ^ -« sub-slab radon measurements
l5 SOr; 3la e return duct,- ^ indoor radon levels indicating
located near la g nelghborlng rooms wit docts hgd a more important
were often pressure created by the * gtreftqth lFlgure3 1# 2, and 3.
that the ne5^^levated Indoor radon than ent3 Vere available, Indoor
contribution to ele^e SOBe alpha track wasui ^ charcoal tests
in all Łl9utes' tn the center oŁ each ¦ comparison. Both sub-slab radon
ra40n levels. sho«n l.i «lntet «««" "I™ (>levels, aajacer,t to seat-
««•"-;ri,uS'"' ^js^srsrsapass
Installed *n rooms ^the*inadequacy of using Indoor radon levels alone as a
i.« fhP source. This snow
to the source,
basis for remedlation.
-------
SPRINGBROOK HIGH SCHOOL
69
1 °
1168
3.5
2.8
•
9.8
C 025
FIGURE 1. Springbrook High School - Indoor radon levels not correlated with sub-
slab radon levels due to HVAC effects predominant over geologic source
effects. In all Figures, indoor radon levels are in the center oŁ each
room. Both sub-slab radon levels, adjacent to circles, and blockvall
radon levels, adjacent to semi-circles, are underlined.
-------
OJ
U)
o
CTN
cn
cn
rt
o *
N)
LJ
(Jj
FIGURE 2. whltter Woods Elementary school - indoor radon levels not correlated
with sub-slab radon levels due to HVAC effects predominant over
geologic source effects
-------
T3 (3D
U)
n»|n>
12
»
H
o
C5
M
<
H
Cj
C
z
H
o
o
X
w
n
X
FIGURE 3. Rldyevlev Junior High School - Indoor radon levels not correlated with
sub-slab radon levels due to HVAC effects predominant over geologic
source effects
-------
The .chool shown In rW«r«
3 has a
with openings for return
a pl'-'nnm Crllill'l Wll-11 oprum 11-- > ^v.^v.j.«,
ie school snowy "Y'nrm'has no windows or return openings In the plenum
alI. The roc,
» room with i-i ^'1* "^nrPmPnts between tins room wn... the door
".Mtna Differential pressure »ea-'"r-Łicant difference until a nearby outside
closed and the h.ll«Y .h.«« (TaMe 1). .e suggested sub-slab
t5Ł r.«thrc,-« »r. ^uCn."s-r
isrs-ffsss sn^« - .oo,,.
table 1.
RIDGEVIEW JUNIOR HIGH SCHOOL
A p effect FROM OPEN DOORS
room 119
HVAC ON
time, sec.
30
60
90
120
indoor/hallway, Ł^P,
INCHES HaO COLUMN
-.001
-.001
-.001
-.001
ADJACENT OUTSIDE
DOOR OPENED:"SnE
air rushed outside
150
180
210
+ ,017
+ .020
+ .020
Wings of two other schools with radon problems have equivalent vinrt
coll units in rooms of equal size and no central hvac system. Hiqhest *an
radon levels correlated well with highest sub-slab radon'levels du
equivalent effects of the window units. (Figures 4 and 5). This was vettfi
an outside corner room in Francis Scott Key High School (Figure 4) with 1 n !2,b*
indoor radon and 132 pCi/1 sub-slab radon, the lowest source strength * 1
Sub-slab/indoor radon ratios were approximately 100/1. The rooms with i Un<5.
* a N60°W trend, correlative with local shear fr»^ated
' - •«» Elevated
V-V4.J.
radon level
equivalent e
an outside corner
Indoor radon and 132 pCi/i suu -x-
Sub-slab/indoor radon ratios were approximately 100/1. lne rouma
radon are aligned along a N60°W trend, correlative with local shear"fr*'=-h<*Cea
(2). In Cannon Road Elementary School (Figure 5), rooms with elevated0
levels are aligned along a N30°E trend, correlative with local rock lav*r*d°n
foliation (2). Thus in schools with equivalent hvac effects, geoloqlc V* 0r
appears to dictate Indoor radon concentrations. ^ s°utce
-------
T
T)
50
>
Z
n
M
CO
w
n
O
H
*
M
kJ
CD
X
W
n
a:
o
o
tr1
u*
C5
09
*?
d
Kn
as
u» •
M o
17
cn
URS
O)
:cj ir
figure 4. Francis Scott Key High School - Indoor radon levels proportional to
sub-slab radon levels due to equivalent HVAC effects and predominant
geologic control
-------
CANNON ROAD ELEMENTARY SCHOOL
•*3
i—«
a
5a
171
cO CO O
a> w ai
o crs
i—» i ~
O CO o
tXi ' 3-
»—• w
Cj C*"
!2J
O »-< O
O ^ 'i'
cn
H-* I—'
i*D CI*
< 3
.*& "j
'A rr
!li'
C*»
~ »-c
rt O
•t" C
»jQ '—'
< 1
UJ
t—' »-•
¦t r1
re
< ^
:> •-'
o 9^
«T 5
iX T
O <
r.c
7 f""?"
cf O
16 12
-------
Martin Luther King Junior High School (Figure 6) revealed Indoor radon
migration through blockwalls from the first floor to the second floor. Rooms
near the center of the school and In the southeast corner had both first and
second floor radon levels equivalent to adjacent blockwall radon levels, showing
that second floor radon problems were caused by vertical migration through
blockwalls. Sub-slab depressurization with appropriately placed blockwall
penetrations remediated the school.
-------
MARTIN LUTHER KING JUNIOR HIGH
o xz **
4^ M
—« O
4-5 > ©
f—<
Wall
penetration iJ?
Wall
penetration
tl 33
. - , r^H
I 1/ penetration
Drain
id
rf} O -i->
c Xi co
fp ^
C W-l
•>' i
c ro
o
tJ'O o
rj a; >
M C O
—< -C
r—¦1 /C
»—» 4->
.T! o:
> o —.
0 ^
0(0 0
rH O
CQ I-H
VI-4
1 a.1
<0 »o
m C
«—I o
o cro
O * 0)
r c w
o o
CO I *—»
-h m
X VA
o
x-i .c •
M O ? ^7
O O 4/
C * U
o tn >-»
*0 "•"*
ecu
c> O -H c
c u rHI a>
0)
icj to *0 O O
rs —« >
J M-l c © Ł O
H u o *o
rO 0) O *TJ
X CO M m
W
05
o
Cl4
-------
Two schools (Figures 7 arid ft) showed appzoxiirtftely equivalent hi nek -
wall/sub-slab radon concentrations revealing radon migration into blockvalls
directly from the sub-slab source. This shows the need to assess blockvall radon
measurements to determine when blockvall penetrations are required based upon
high blockvall/sub-slab radon ratios.
-------
SPRINGBROOK HIGH SCHOOL
109
O 734
386
5.9
8.7
it
3.6
1210
>34
FIGURE 7. Springbrook High School - Blockvall radon concent rat. ions correlating
with adjacent sub-slab radon levels y
-------
RIDGEVIEW JUNIOR HIGH SCHOOL
276
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-------
in one school radon problems existed over one end of a room (Fl04) under 1 =» 1
by the unvented end of a crawlspace (Figure 9). Table 2 shows the results ?
indoor/outdoor Ap measurements with a micromanometer. A Tygon tube was run f
the high pressure port of the micromanomcter to outside a window, sealed sh°f
with tape, while the low pressure port was open to first the room'and then th
crawlspace. An aquarium stone was attached to the high pressure tube outside l-6
minimize wind effects. The differential pressures vet p. then measured in both th°
room and the crawlspace by turning the central HVAC system on with the exhaust
fan off and then with the exhaust fan on. Results reported in Table 2 show that
the HVAC system created a negative pressure in the room resulting in radon levels
nearly as high as a two-day average within 60 seconds. The exhaust fan, blovlna
from the room Into the crawlspace, diminished this effect. In the crawlspace
the HVAC system created an equal negative pressure with the exhaust off but
higher radon levels. However, the exhaust fan created a positive pressure in the
crawlspace greatly diminishing the radon levels. Theoretically pressurizing the
crawlspace with outside air would optimally reduce crawlspace radon levels.
However warm summer outside air entering the cool crawlspace causes condensation
problems so remediation was achieved by adding another crawlspace vent below the
problem room and running an exhaust line from a roof-mounted fan Into tho
crawlspace, as shown In Figure 9, to draw radon from the crawlspace at a high
enough rate to overcome the increase In radon levels from depressurlzatlori.
WHITE OAK MIDDLE SCHOOL
exis ting
vent
ven
existing
[^exhaust
fan
PrflnUrlZation
FIGURE 9. White Oak Middle School - Crawlspace area outlined with dashed line
existing exhaust fan exhausts indoor air into crawlspace.
-------
TABLE 2. WHITE OAK MIDDLE SCHOOL - A P AND RADON DEPENDENCY ON HVAC AND
EXHAUST FAN
INDOOR/OUTDOOR, A P,
TIME, SEC. INCHES HaO COLUMN Rn, pCi/1
ROOM F1Q4;
HVAC ON, 15 -.005
EXHAUST FAN 30 -.008
OFF 60 -.010 4.5
HVAC ON, 15 0
EXHAUST ON 30 0
60 -.002
120 -.005 <0.1
rwfcwi. SPACE:
HVAC ON, 15 -.005
EXHAUST OFF 30 -.008
60 -.010 13.0
HVAC ON, 15 +.050 1.4
EXHAUST ON 30 +.100 <0.1
-------
REFERENCES
1. Hall, S. Correlation of soil radon availability number with indoor rad
and geology in Virginia and Maryland. In: Proceedings of EPA/USGS Soil °
Gas Meeting, September 14-16, 1988, Washington, D.C.
2. Hall, S. Combining mitigation and geology: indoor radon reduction by
accessing the source. In: Proceedings of the Annual Meeting of the
American Association of Radon Scientists and Technologists, October 15
17, 1989, Ellicott City, MD.
-------
X-5
A COMPARISON OF RADON MITIGATION OPTIONS FOR
CRAWL SPACE SCHOOL BUILDINGS
Bobby E. Pyle
Southern Research Institute
Birmingham, AL 35255
Kelly W. Leovic
U.S. Environmental Protection Agency
Air & Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
ABSTRACT
School buildings that are constructed over crawl spaces can present
unique challenges to radon mitigation since they are often quite
large (at least 4,000 ft2 in area) and may contain support walls
with footings that extend below the soil surface. The perimeter
walls in the crawl space can also be extensive (on the order of 500
to 1,000 lineal ft). In this research project, natural ventilation
using the existing vents in the foundation walls, depressurization
and pressurization of the crawl space, and active soil
depressurization under a polyethylene liner covering the soil were
compared in a wing of a school building in Nashville, Tennessee.
The wing has four classrooms constructed over a crawl space area of
4,640 ft2. The building and crawl space were monitored throughout
each mitigation phase with continuous sampling devices that
recorded radon levels both in the crawl space and in the rooms
above, in addition to environmental conditions such as temperatures
and pressure differences in the building.
Results showed that active soil depressurization was the most
effective technique for reducing radon levels in both the crawl
space and the rooms above. Crawl space depressurization was also
very effective in reducing radon levels in the rooms above the
crawl space; however, radon levels in crawl space increased during
depressurization.
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administrative review
policies and approved for presentation and publication.
-------
INTRODUCTION AND BACKGROUND
J.r» J. X\V-/4^ W W * —
ri.2 4-n Table 1 for metric conversion factors)
This 29,266 ft ( „.»«. oriainallv constructed in 1954, with
Nashville school building 1964. The original building and
subsequent additions m 1957 and 1964. ?^Qn and the 1964
the first Edition are ŁŁŁ»*Ł* =ver a crawl space connected
four-classroom Edition ^ walkway. Initial charcoal
to the slab-on-grade SChool in 1989 indicated that the 18
canister measurements in oresented the most severe radon
slab-on-grade rooms measured presented deviation of ? 5
problems, averaging 34. p / i/L were subsequently measured
pCi/L. in fact, levels °™r "O^Ci/L in ^ ^
in some of the sla?"° J the crawl space were relatively much
classrooms constructiVtcill* with a standard deviation of 0.7 pCi/L.
lower, averaging 9.7 pci/i. efforts during the summer of 1989
As a result, initial slab-on-grade wings with active
focussed on reducing iev Post-mitigation measurements
subslab depressurizati I ^d levels in the slab-on-grade
during February 1990 ina ^ ^ thig time plans were initiated
rooms averag®^e°®f^ctiveness of various mitigation techniques in
the crawl space wing.
the crawl spa^e
4.640 ft2 in area, and the
The crawl space is af? 80 in. with a total air volume of
height ranges from 4fe ^ view of the crawl space is shown
approximately 25,500 ft .The Plan ^ .g excellent and the
in Figure 1. Acpfs? COTnplex (i.e., no inaccessible areas,
surface of the soil is not P g Qf goil) ^ The floor of the
rock outcroppmgs, or iary ^ suspended concrete slab poured
classrooms over the ^fwlspace „' ^ b a network of steel
over corrugated st/t0 Lternal concrete block support walls in
trusses. There are two i ^ ^ goil Th wall d not
the crawl space that ext however, the walls effectively
penetrate the sla.b°J® into three sections, as shown in Figure
subdivide the crawl spa.ze e different from that found in
1. This type of cons^u^anv existing houses, the floor is composed
residential houses, in ma y ^ boards or plywood sheathing)
of wood decking (either x y This t of houSe construction
supported by wooden floor 3 ^ nearly impossible to seal all
has been shown to be Q^ite x J e and the rooms overhead (3,4) .
the openings between thee Contain any heating, ventilating,
Since the crawl space «o ductwork or any asbestos, it was of
and air-conditioning (HVA ) x space in this school building
interest to determine lf ^P suri ti or
could be sealed _rawl space volume as a mitigation option.
depressurization of the crawi sp«
• „onHiated naturally with eight block vents
The crawl space ls.v®"V„est sides of the building). Each of
(four each on the east an screened opening with the same
these foundation wall vents i6 _n<) Qr approximately 128
gross area as a c°nc5®Ł® tests carried out on the crawl space
in.1 Fan „ 40?™fm-8?feSulted in an effective leakage area
according to ASTM t>
-------
(ELA) at 0.016 in. WC of pressure difference of 251 in.2 with the
vents open and 83 in.2 with the vents sealed (using closed-cell foam
board and caulking). Thus, the vents were providing approximately
168 in.2 of total open area, or about 21 in.2 per vent. This value
is consistent with that measured in houses using similar techniques
(5). The important point is that the leakage area independent of
the block vents is very low (83 in.2) compared to that measured in
15 houses in the same geographic area which ranged from 198 to 424
in.2 with a mean of 262 in.2 (5) . Thus, this building was thought
to be an ideal candidate to test a variety of possible mitigation
techniques.
METHODOLOGY
Mitigation systems typically installed in crawl space houses
include: isolation of the crawl space from the rooms above,
isolation and depressurization or pressurization of the crawl
space, isolation and ventilation of the crawl space (either natural
or forced) , and active soil depressurization either directly in the
soil or under a plastic membrane (SMD) covering the exposed soil
(4). Each of these mitigation techniques (with the exception of
the forced ventilation and direct soil depressurization techniques)
was tested in this school crawl space in an effort to compare their
effectiveness when applied to a building having a larger size and
a different construction type (concrete slab over the crawl space).
Initial baseline testing was carried out before any
modifications were made to the building. Following the baseline
measurements, the accessible openings (e.g., utility penetrations)
from the crawl space to the upstairs rooms were sealed with a
combination of closed-cell foam and urethane caulking. The block
vents were also sealed with rigid closed-cell foam board and
caulking. Following testing with the vents closed, a network of 4
in. PVC ducting was installed as shown in Figure l. The fan
installed is rated at 200 cfm at 1.5 in. WC. The fan and the air
distribution network were used to test the effectiveness of crawl
space pressurization and depressurization as mitigation options for
the building. After the crawl space depressurization and
pressurization tests were completed, two suction pits approximately
24 in. in diameter and 12 to 18 in. in depth were excavated in each
of the three sections of the crawl space for a total of six suction
pits as shown in Figure 1. Each suction pit was covered with a
piece of 36 in. square by 1 in. thick marine grade plywood. The
plywood covers were supported at the corners by four common bricks.
Both the suction pits and the exposed soil were covered with two-
ply high-density polyethylene sheeting. The plastic film was
installed in three pieces, one in each section of the crawl space.
No attempt was made to seal the plastic to the outer or inner
foundation walls. The edges of the plastic were cut approximately
12 in. wider than necessary in the event that sealing to the walls
was necessary. The excess material was then simply folded up the
walls or allowed to fold back upon itself. The network of PVC
ducting was connected to the suction pits to complete the active
soil depressurization systems, as in previous house research (3).
-------
a.- „ foct.infl oeriod, several parameters were
Throughout the entir datalogging device. The parameters
monitored continuousPressure differentials between Room 116 and
monitored include: Pre® . t and west sides; pressure
outside the building on ¦the east ^ interior;
differentials between Room ll6 and the sub-poly region
pressure differentials tures outdoors, in Room 116, in the
during the SMD testing; temp ^ ^ direction; the outdoor
crawl space, and in the s°-4' . d the radon levels in both Room
relative humidity and rainf , ^ these parameters was sampled
116 and the crawl space. E totaied at the end of every 30
every 6 seconds and measurements and their locations are
minute interval. ^hese " t were accumulated in the datalogging
summarized in Table 2. The da ^ ^ a personal computer and
device and periodically dow analysis. Initial testing of
stored on magnetic disics ior and continued through July 20,
the building began on Marcn i, g hours) . The datalogger was
1990, for a total of: 152 y ^ tQ January 17f 1991, in order
reinstalled from ' tems during winter conditions. The
to evaluate the mitigati
-------
pressure difference was reduced to -1.5 Pa and the average
classroom pressure difference was reduced to -2.5 Pa as seen in
Figure 3. The average radon levels in the classroom and crawl
space were 10.6 and 29.1 pCi/L, respectively, as shown in Figure 2.
It is apparent that the flowrate of outdoor air into the crawl
space is not sufficient to raise the pressure in the crawl space
above the outdoor pressure and could only negate about 60% of that
produced by the stack effect in the crawl space and about 50% of
that produced in the classroom. It is possible that by doubling
the flowrate (to around 500 cfm) the crawl space and the classroom
could have been pressurized above the outdoor conditions and the
radon levels further reduced. However, this option did not appear
as a desirable year-round solution in view of the fact that
unconditioned air was being used for pressurization.
Crawl Space Depressurization
Following the crawl space pressurization testing, the fan was
reversed so that air was withdrawn from the crawl space and
exhausted above the roof of the building. In this configuration,
the fan flowrate increased slightly to 279 cfm or about 0.7 ACH.
The negative pressures in the classroom were similar. However, the
pressure differential in the crawl space increased by approximately
73% (from -1.5 to -2.6 Pa) . The radon levels in the classroom were
reduced by about 94% (from 10.6 to 0.6 pCi/L) even though the
levels in the crawl space increased by a factor 1.8 (from 29.1 to
53.6 pCi/L). Therefore, while depressurizing the crawl space
lowered the levels in the classroom, it nearly doubled the levels
in the crawl space. This was not unexpected since a similar
technique applied to a residential house increased the levels in
the crawl space by about a factor of 3 (4, 5).
Active Soil Depressurization
The third type of mitigation system implemented was active soil
depressurization under a plastic membrane covering the exposed soil
(SMD). The total flowrate exhausted from under the plastic liners
was 2 60 cfm when using all six suction points shown in Figure 1.
As seen in Figure 2, the radon levels in the classroom were reduced
within a matter of hours to around background (0.5 pCi/L), and in
the crawl space the levels decreased to 3.5 pCi/L. In an attempt
to determine if fewer suction points could be used, the two suction
points in the central sector of the crawl space were disconnected
and the suction pipes to both the fan and the suction pits were
capped. The results are shown in Figure 2. The decrease in the
crawl space levels is probably not significant, and the levels in
the classroom are the same within the level of uncertainty of the
measurement. The results from the SMD mitigation technique are
quite similar to those found when the same method is applied to
residential houses (4, 5, 6), where the area of the exposed soil is
typically in the range of 1,000 to 2,000 ft2. In this building the
area is much larger (4,640 ft2); however, the resulting reduction
in the radon levels using SMD is seen to be as good as that
achieved in smaller crawl spaces. The next important research step
-------
is to apply the SMD technique to crawl space areas on the order
10,000 ft2 or larger.
ppgm.TS r>F WINTEP MFftSTTRKMENTS ...
u6rP reoeated during the winter (December
The above measurements w inPorder to determine if the results
18, 1990, to January 17,199 > ^ summer measurements. a brief
were consistent with the spr g ts the results of previous
analysis of the wiriter -t of the SMD system during cold
measurements and the inwgr y analyzed and documented m a
weather. These data will be a*alysis q{ the data> the
fver«e"Pirw'eatherdradon levels both in Koom H6 and in the crawl
space are shown in Figure 2.
paCp1ine ^oacurements
+-o reproduce the open vent (natural
No attempt was made t f to fee an umlSUal operating
ventilation) condition »s The results for the closed vent
mode for wintertime condi ^ as those obtalned in the
mode in winter were ible exception that the winter radon
spring/summer, with the po ^ &s high as the previous values
levels in the crawl space w The iower readings could be
(63.4 pCi/L compared to 8/. p / measurements were carried
due in part to the fact that the.wi,^ polyethylene liners The
out after the soil was c«0 s covering the soil could act as a
presence of the plastic 11 halation. The lower readings could
partial barrier to soil ga winter measurement period was much
shorter measurement period.
nr*ui spaCe pxessurizatjoD
i BMre oressurization levels were much the
The wintertime crawl sp Łese resuits indicate that, with the
same as obtained previously. ^ radon reductions achieved
CSM Sltntfchnfque ari still less than desirable.
„rn,,i gr^e peprgssurjnation
,„rjna cold weather conditions gave very
Using this technique ° i^ed in the spring/summer tests. The
similar results to those o.» classroom and the crawl space were
wintertime levels in both the c« ^ ^ increased stack effect
somewhat higher aJd cou^ ld weather. In order for this technique
normally expected during = year-round, It is obvious that the
to be successfully appii*' be done during extreme temperature
installation and testing » an adequate amount of air is
conditions in «der to en
exhausted from the crawi ^
snii Depressuri^atioa
levels measured with the SMD system
The wintertime raaon ^ levels measured previously,
operative were almost idein x 0® «as within the unc«tainty of
The average level in we
-------
the measurement techniques, and the levels in the crawl space were
slightly lower than before. These results clearly indicate that
the SMB technique is not only effective but stable in its ability
to lower the radon levels in both the classroom and the crawl space
under varying weather conditions.
CONCLUSIONS
The results of this project indicate that the SMD technique is
the most effective in reducing elevated levels in both the crawl
space and the classrooms. In this application, the crawl space was
large but fairly simple in geometry. Access to the exposed soil
areas was excellent and, with the exception of the two internal
support walls, did not contain a large number of obstructions such
as support piers or utility pipes lying on the soil. The topology
of the soil surface in this crawl space was relatively smooth.
Other crawl spaces may have some or all of the complications that
were absent in this application (7) . Application of the SMD
technique in these more difficult crawl spaces needs further
investigation.
Depressurization of the crawl space is effective in reducing
levels in the classrooms; however, the levels in the crawl space
will be increased by at least a factor of 2 and perhaps as much as
a factor of 3. This could pose a problem in buildings that have
nonsealable openings from the crawl space into the occupied rooms
above (e.g., HVAC ducts in the crawl space, wooden floors over the
crawl space, or doors or other entry openings from the crawl space
into the rooms above) or if the crawl space is occupied on a
regular basis. In this building the overhead floor was a poured
concrete slab with very few openings to the classrooms above that
helped to contribute to the effectiveness of crawl space
depressurization.
Pressurization of the crawl space was found to be less effective
in reducing the radon levels than natural ventilation. This method
may be more effective if larger quantities of air are supplied to
the crawl space; however, this may result in increased energy
losses and perhaps could increase the risk of damage to utility
lines in cold weather.
Natural ventilation of the crawl space also appears to be
ineffective in reducing the radon levels to acceptable levels.
Increasing the ventilation through larger or more numerous vents
may increase radon reduction; however, the effectiveness of this
method depends to a large extent on the wind patterns outdoors.
Also, this method can easily be defeated by closing vent openings
during the colder periods.
The number of school buildings constructed over crawl spaces is
not quantified at the present, although EPA research in over 40
schools has shown that only 7 of the buildings contain crawl spaces
(in combination with slab-on-grade substructures). There is little
information available regarding crawl space characteristics, such
as floor construction, number of vents, number of piers and support
walls, and the presence of HVAC ductwork or asbestos in the crawl
-------
space. While the SMD technique appears to be the method of choice
for reducing levels in both the crawl space and the rooms above,
further investigations need to be carried ou in crawl spaces tha.t
are not as simple as the one used in this study to determine if it
can indeed be applied successfully in non-ideal conditions.
references
r, P Harris, and B.E. Pyle, Radon
1 rraia A.B., K.W. Leovic, D.e. q public Schools in
Diagnostics and at the 1990 International
Nashville, Tennessee. Pres tion Technology, Atlanta,
symposium on Radon and Radon
GA, February 19-23,
fpa's Radon Reduction Research In
2. Leovic, K. W., SUM«y of E™A_600/8-90-072, U.S. Environ-
Schools During 1989 so- * and Energy Engineering
mental Protection A9*j^a'rch Triangle Park, NC, October
Research Labora1tory' a.
1990, (NTIS PB91-102038).
.^¦i- « c S. Fowler, F.E. Belzer III,
3 Pvle, B.E., A.D. *on Mitigation Techniques in
' m.C. Osborne, and T. combination Houses in Nashville,
crawl Space, Basement, ana 1988 symposium on Radon
Tennessee. In: ^Technology- Volume 1. Symposium Oral
and Radon Beduct^nn? pyie, B.E. and A:°:tioi ^EPA/600/8-90/061, U. S. Environ-
Nashville DemoI}str?^n^v Air and Energy Engineering
mental ProtTriangle Park, NC, July 1990,
Research
(NTIS PB90-257791).
. ancj a. G. Scott, Testing of
5 Findlay, W.O., A.?^®rTeChAiques in Central Ohio Houses:
indoor ^don Reduction TechniqpA_600/8Q50f
Phase 2 (Winter 1988 198 > < Air and Energy Engi-
Environmental Protecting ^ Research Trlangle Park, NC,
SayriSlo tmis NO. PB90-222704) .
6. Brennan, T., »• Spi-Bufldingt, »'C-
^UdTAs^eS AtUnf. «. XprU 17-18,
» « craia and D.W. Sauro, Radon Mitigation
7. Leovic, K.W. / A:®;icult-T'o-Mitigate Schools. Presented at
Experience Dl?^iional symposium on Radon and Radon
Reduction «. »-». 1990.
-------
TABLE 1. METRIC CONVERSION FACTORS
Non-Metric
cubic foot (ft3)
cubic feet per minute (cfm)
degrees Fahrenheit (°F)
foot (ft)
inch (in.)
inch of water column
(in. WC)
square foot (ft2)
square inch (in.2)
Times
28.3
0.47
5/9 (°F-32)
0.30
2.54
248
picocurie per liter (pCi/L) 37
0. 093
6. 452
Yields Metric
liters (L)
liter per second (L/s)
degrees centrigrade (°C)
meter (m)
centimeters (cm)
pascals (Pa)
becquerels per cubic
meter (Bq/m3)
square meter (m2)
square centimeters (cm2)
TABLE 2. SUMMARY OF MEASUREMENTS
Parameter
Differential Pressure
Radon
Temperature
Location
Room 116 to Outdoors
Room 116 to Crawl space
Room 116 to Subpoly
Room 116
Crawl Space
Room 116
Crawl space
Soil
Outdoors
Wind Speed and Direction
Relative Humidity
Rainfall
Outdoors
Outdoors
Outdoors
-------
N
-TO SLAB-ON-GRADE
WEATHER STATION POLE
VENTS
/
4"PVC
ROOM 116
24'
ROOM 119
ROOM 117
15' —
—
ROOM 11!
80'
VENTS
CN
A
o
CNI
Figure 1. Plan view of the crawl space and installed ductine
network.
-------
V«nt» Op«n V«nt» Closed C/S Praia c/S Dtpctn 6-Pt SMD
4-Pt SMD
ClaSS (Spring/Summer)
ClaSS (Winter)
Crawl (Spring/Summer)
Crawl (winter)
Figure 2. Average radon levels in the crawl space and in
Room 116 during each of the mitigation testing
periods (both spring/summer and winter).
-------
Vents Open Vents Closed OS Press OS Depress
Room-to-Outdoors M Crawl space-to-0utdoor4_ Tout
Tcrawl ""** Troom
Figure 3.
Average pressure differences between both the crawl
space and outdoors and Room 116 and the outdoors
during each of the mitigation testing periods.
-------
X-6
HVAC SYSTEM COMPLICATIONS AND CONTROLS FOR
RADON REDUCTION IN SCHOOL BUILDINGS
by: Kelly W. Leovic, D. Bruce Harris, and Timothy M. Dyess
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
Bobby E. Pyle
Southern Research Institute
Birmingham, AL 35255
Tom Borak
Western Radon Regional Training Center
Ft. Collins, CO 80523
Dave W. Saum
Infiltec
Falls Church, VA 22041
ABSTRACT
School mitigation research to date has emphasized reduction of radon levels using active
subslab depressurization (ASD). Although ASD has proven successful in a number of schools, it is not
reasonably applicable in all school buildings since many schools do not have a layer of clean, coarse
aggregate under the slab or may have many subslab barriers that would require an unreasonable
number of ASD suction points. Additionally, mitigation options that have relatively low installation and
operating costs need to be researched for application to schools with moderately elevated radon levels
(4 to 20 picocuries per liter, pCi/L). Since many schools are designed with heating, ventilating, and
air-conditioning (HVAC) systems that can provide outdoor air to the building, research has been
initiated to determine the feasibility of using HVAC systems to pressurize the building interior to reduce
elevated levels of radon in selected schools.
This paper discusses case studies of four schools where the U.S. Environmental Protection
Agency's (EPA) Air and Energy Engineering Research Laboratory (AEERL) has recently initiated long-
term research on the ability of HVAC systems to reduce elevated levels of radon. The schools are
located in the states of Colorado, Maryland, Virginia, and Washington. Depending on the school
building floor plan and HVAC system design, a specific wing or the entire building was selected for
research. Two of the schools have unit ventilators in the rooms being researched and two have central
air-handling systems. Initial results indicate that, when sufficient outdoor air is supplied by the HVAC
system, radon levels can be reduced. The amount of radon reduction depends on the specific HVAC
system design and operation.
This paper has been reviewed in accordance with the U.S. EPA's peer and administrative
review policies and approved for presentation and publication.
BACKGROUND
Previous research efforts on radon reduction in schools have presented theoretical aspects and
limited short-term data on radon mitigation using HVAC systems (1,2, 3); however, long-term research
on the feasibility of radon mitigation using HVAC system pressurization is limited. As a result, in the
summer of 1990 AEERL's Radon Mitigation Branch initiated several projects in an effort to better
understand school HVAC systems and their ability to reduce radon levels in schools while also
improving overall indoor air quality.
-------
. raHr>n mitiaation using HVAC systems, four schools (or wings of
To initiate this res®ar^h he schoQ, wings contain wall-mounted unit ventilators in each
the schools) were s®lect®dw . gnd tw0 of the schools have central air-handling systems
classroom (Maryland and Wash g , schools had been part of previous research efforts
(Colorado and Virginia). The Man/ washinaton schools were identified during field studies in the
by AEERL (1, 4), and the Colorado and schools (one in Mary.and and two in
summer of
19g° These four schools, in ^ar'® ln a few of the schools future research will
Ohio), will be studied in more d d ASD in reducing elevated levels of radon. Metric
also include a comparison of HVAL systems, *
conversion factors are presented in Table .
CASE STUDIES
, • CD discuss four schools located in Colorado, Maryland, Virginia, and
The following case studies nrmat;on on each school, each case study includes an HVAC
Washington. add,^°®;initia^ measurements, and future research plans for the school. The
sum^ry^har^c^eristics of these schoo.s are displayed in Table 2.
COLORADO SCHOOL
^nctmrted in 1956 and includes seven classrooms and various other
The original building was construe ^ ^ approximately 15,750 ft2 of floor space as
support offices and storage rooms w 1 300 h2 boiler room located in a basement in the
shown in Figure 1. Th® or'9'na'faDDroximately 11 ft below grade and contains the HVAC system,
southwest corner. Th® b°'le/n7°^'! QPn grade construction. In 1958 an additional six classrooms, a
The remainder of the building is s'^ <3 totaling about 9,500 ft2 were added to the original
kitchen, several grooms,,^upp wgg adde(j tQ the end of the 1958 addition. The last
building. In 1976, a 2,1 °° " mea ^ ^ was added t0 the southwest end of
addition to the building was m 1982 t int of the building is approximately 29,000 ft2 , with
in all classrooms from January 15 to 17, 1990, averaged 6.6
E-Perm measur®r?e"tSrT»nd a maximum of 12.3 pCi/L. Most of the rooms were remeasured
pCi/L with a minimum of 4.8 pu/L 19gQ yhese )ater meaSurements averaged 7.6 pCi/L
during followup tests from February a maximum value of 10.2 pCi/L The results of both sets of
:^u,itra"sheownBon .he .loo,plans in 1 and 2. restively.
HVAC PescriptiQ".
ncludes a central air handler with a single fan and individual
The building HVAC system i operates by time control with the system operating
controls in each of the rooms. The H ^ ^ ^ ^ approximate,Y 15 hours at night. This
approximately 9 hours during the day* ^ weekend when the school is not occupied. The
schedule is apparently mainta.neJ e ^ wpp|y ducts are located below the slabs and are
HVAC registers are located in tne i undQd by poured concrete. In those areas where these
composed of cylindrical cardboara au the cardboard tubing and the surrounding concrete,
ducts were visible, large gaps were to cardboard tubing has deteriorated to the point that the
It is highly likely that in most locati ^ Sjnce radon ,eve|S may build up in the supply ducts
supply air is in direct contact witn tn ^ ^ megsured in future studies to determine the
when the HVAC fan is not operatino, t"®
relative contribution to bu.ld.ng radon le e .
arh classroom exits through grilles into the hallway with the hallway of
The return air from eacn ci« m From the hallway the return air is ducted into a central
the building serving as a return »ir p ^ ^ ^ handler in the basement. The air in the gym is
subslab return-air tunnel that leaas northwest corners of the room directly into the return
returned through floor grilles in the nortneas
-------
air tunnel. The tunnel varies in size from about 3 by 3 ft up to 4 by 4 ft in cross section and can be
accessed in the boiler room. The tunnel has numerous penetrations by utility lines that lead to direct
soil contact and probably represent a major radon source. There is a provision for outdoor air to the
air handler located at roof level with the air ducted directly into the HVAC fan chamber through a
control damper. Visual observation of the outdoor air intake damper from inside the fan chamber with
the fan operating indicated that the damper did not open during fan operation. Subsequent
investigation by the school maintenance staff confirmed that the control rod for the fresh-air intake
damper did not operate properly, and this was repaired. However, it is not clear what control system
operates the damper. During the cold winter days the damper may be only partially opened depending
on the outdoor temperature.
Results of Initial Measurements
Room pressure differentials were investigated primarily in the kindergarten room using an
electronic micromanometer. These measurements were made before the outdoor air damper was
repaired. The differential pressure in the kindergarten room relative to the subslab was measured to
be -0.005 in. WC with the HVAC on and the door to the hall open. When the door was closed the
differential pressure dropped to -0.003 in. WC. The differential pressure between the kindergarten
room and the hallway was -0.005 in. WC with the HVAC on and the door closed. The pressure of the
room relative to outdoors was -0.005 in. WC. Differential pressure was not measured with the HVAC
system off. However, it appears that the HVAC system is depressurizing the classroom relative to
both the subslab region and outdoors. This indicates that, even in the warm summer months when
the HVAC system is used for ventilation purposes only, it causes room depressurization which results
in soil gas flow from the subslab regions into the room.
Radon concentrations under the slab and at several possible entry points were measured using
a Pylon AB5 in a "sniff" configuration. The subslab radon levels measured through 0.5 in. diameter
holes drilled through the slab in the kindergarten room and the office in Room 6 were about 700 pCi/L.
Levels of about 300 pCi/L were measured in a crack in the slab adjacent to one of the air supply
registers in the kindergarten room. Sniffing in one of the supply registers in the gym showed levels
of about 15 pCi/L with the air handler off and about 25 pCi/L with the fan on. Measurements in the
wall cracks of the air return tunnel showed levels of between 50 and 100 pCi/L with the fan off.
These levels increased to about 350 pCi/L when the fan was turned on and the tunnel depressurized.
This indicates that the depressurization of the return duct can increase radon entry from the soil
through the cracks and penetrations in the tunnel walls.
Examination of the air handler fan chamber identified a relatively large crack (about 0.1 in.
wide) in the slab. The investigators sealed the accessible part of the crack with duct tape for a length
of roughly 4 ft and sealed the hose of the Pylon under the tape. The levels were measured to be
about 700 pCi/L with the fan off and about 800 pCi/L with the fan on. The AB5 was placed in the fan
chamber to sniff the air in the chamber. The radon levels were about 70 pCi/L with the fan off and
increased to 350 to 700 pCi/L with the fan on, indicating that the slab crack into the fan chamber is
a major radon entry route. It was also observed that the crack was very clean with little or no dust
filling in the crack. Apparently there is sufficient air flow out of the crack (or turbulence in the air
above) to keep the crack clean. The pressure in the fan chamber relative to the boiler room was
measured to be approximately -2 in. WC.
Over the 1990 Christmas break a series of E-Perm measurements were made in all classrooms
of this school with the outdoor air damper for the HVAC system opened and closed. Measurements
were also made in another school in the district that has the same design but has not been shown to
have elevated levels of radon. In both schools the first set of measurements were made with the
outdoor air dampers closed (December 21-26, 1990), and the second set were made with the damper
open (December 27-31, 1990). The weather during the second measurement period was exceptionally
cold and, as a result, it appears that the damper in the school with the radon problem did not open as
-------
. ^ tKo mpasurements with the damper open were repeated in this school on
2 - - —¦
Itc in Table 3 opening the outdoor air damper reduces average
As indicated by the resu"ts jt'does not bring the average of the average classroom
classroom radon levels in School l. 2 show on(y g sliflht decrease in average radon
levels to below 4 pCi/L. 1he resu,w ^ measurements in the return air duct
classroom levels with the outdoo schools. These results support the theory that the
exceed average levels in the classr fadon ,eve)s partlCularly in School 1. Opening the
radon^levels in the tunnel but not enough to reduce average classroom levels
to below 4 pCi/L.
Figure Plans
F.^.ira nana
l 1 n January 1991 to collect continuous radon levels (in
A datalogger was installed tn Schoo i djfferentia) pressure( and meteorological data.
Room 6, the supply, and the return' 'radon source strengthS in Schools 1 and 2. Once a
Measurements will also be made to comp ^ damper opened gnd c,osed< the slab crack jn
measurements repeated.
MARYLAND SCHOOL
>h ASD in 1988 and is discussed in detail in Reference 5.
This school was mitigated witn addition to the school (Building B in Reference 5) indicated
Previous measurements in a .our levels o. over 20 pCi/L to below 2 pCi,L;
that the unit ventilators in the classrooms^cou since ra(jon levels increased at night
however, school personnel had indicate that radon levels are typically well below
when the unit ventilators were off • Measu^ ^ ^ ^ schoo| presents an ldeal opportunity to
co^p^re^SD^nd uni^vernTator pressurization in the same school.
mv/aC gyrt1?™ Description
,• ^ •= a W classroom addition, as shown in Figure 3. Each of the
The area being studied is a tou ^ ^ tQ pfovjde outdoor air when the
classrooms has a w«n-moun»J unit vent ^ ^ ^ schoo| |3600 c(m) acco[di„0 to schoo,
damper is open. Although there is
trials it is never used.
officials it is never used.
Investigation of the unit ventilators revealed that, although the design drawings called f
minimum of 16% outdoor air, the outdoor air dampers for two of the four units were not openin°f *
all. After repairs, flow hood measurements for the units in Rooms 107 and 108 indicated that ab **
120 cfm of outdoor air was being supplied by each unit with the outdoor air damper in minim°Ut
(roughly 10% open) position. With the restroom exhaust estimated to be 50 cfm, Classroom 107 Um
at a neutral pressure. With the outdoor air dampers open to 100% outdoor air, Room 107 was
+ 0.003 in. WC relative to the outdoors, and the air flow into the unit ventilator was 450 cfm 'a'h
doors and windows in the room were shut during the data collection.
Results of Initial Measurements
A datalogger was installed in Rooms 105 - 108 over the holiday break (December 21 to 31
1990) in order to collect preliminary data on the unit ventilators operating with the ASD system ff
Measurements were made over successive 3-day periods with the unit ventilators operated as follo° •
-------
1) setback (no outdoor air), 2) normal operation (with evenino setback), and 3) continuous day
operation with no setback (outdoor air provided for entire period). The fans for these units do not run
during setback unless room temperatures drop below 60°F. The radon levels measured in Room 108
during these three conditions are shown in Figure 4. As seen by these data, radon levels remain well
below 4 pCi/L while the unit ventilator is operated continuously but rise above 4 pCi/L during the
setback modes. Note that during the day-plus-setback operation, radon levels rise at night and drop
to about 4 pCi/L during the day.
Future Plans
A datalogger was re-installed in Rooms 107 and 108 to study unit ventilator operation over a
longer time period while the school is occupied. Continuous data being collected include: radon levels,
room to subslab differential pressure, unit ventilator damper position, and indoor/outdoor temperatures.
VIRGINIA SCHOOL
This school was constructed in 1987 in an area with a known radon problem. As a result,
various steps were taken by designers to reduce the likelihood of elevated levels of indoor radon and
to facilitate post-construction mitigation if needed. (The construction of this school is covered in detail
in Reference 4.) Initial post-construction charcoal canister measurements were made in October 1988
in all ground floor classrooms: all measurements were below 2 pCi/L, as shown in Figure 5. These
measurements were repeated in December 1990, and radon levels were consistently higher: 13 of the
rooms measured 4 pCi/L or higher as shown in Figure 6. Note that levels in the east wing of the
school tend to be highest. This is consistent with the higher subslab radon levels measured during
construction (4).
HVAC System Description
This school has eight air-handling units serving eight zones. The units are designed to provide
a total of 72,600 cfm with a minimum of 16,010 cfm outdoor air. Total building exhaust is 9,506
cfm. This design should maintain the building at a positive pressure; however, the HVAC system is
Variable Air Volume (VAV), and outdoor supply is reduced if the temperature drops below a given level.
Results of Initial Measurements
Differential pressure data showed the room to be at a negative pressure relative to the subslab,
thus the air-handling units were not adequately pressurizing the building as intended. A datalogger was
placed in a conference room December 21, 1990, to collect continuous radon, differential pressure,
and temperature data. These results, displayed in Figure 7, show that radon levels are about 5 pCi/L
when the room is at a negative pressure relative to the subslab. Radon levels tend to drop slightly as
the room-to-subslab differential pressure approaches zero.
Future Plans
The datalogger will remain in this school to collect additional continuous data. School
personnel are also considering installation of an ASD system to reduce radon levels on a continual
basis. If the ASD system is installed, its effectiveness in reducing radon levels will be compared with
that of HVAC pressurization.
WASHINGTON SCHOOL
This school has 16 classrooms, a multipurpose room (gym/cafeteria), and several special
purpose rooms and offices. Eight of the classrooms are built over a crawl space, and the remaining
eight are slab-on-grade.
-------
. Mara made over all four seasons (spring, summer, fall, and winter)
Several radon mMSuwments wff charcoal canisters, short and lono term E-perms,
under a number of ventilation condition measurements are to be presented at the 1991
R^'and Radon Reduction Techno,o0v ft . Paper entitled -The Results
of EPA's School Protocol Development Study (6).
of EPA'S ^cnooi nwvwvv. « .
i. • w* hniit over the crawl space did not have elevated
Measurements indicated that the eig ^ ejflht slab.on.Qrade classrooms that had
radon levels. As a result, researcJ^0CU® , out of this part of the school is shown in FiQure 8.
consistently measured above 4 pCi/L. Y ^ ^ schoo, (Ro0ms 139-142). and the desiQn
These classrooms were located m tne no school contained several classrooms
drawinos indicated the presence of particularly clear on specific sub,lab
additions, and the '^Ch^b foundations included both poured concrete footings and thickened
foundation locations. The sudsibd tvu
slab footings.
, . tho _,ah ai0ng the perimeters of the classrooms in each
There was a utility tunnel ,ocated b 4 H high with a dirt floor. The walls of the tunnel
wino This tunnel was approximately 4 u w y tQ the soi| Accesses to the tunnels
" of poured concrete and !»<• Rooms 127 and 128 in the east section. The
rnnVrcontaTnei4t0hea'M.m p^s'that connected the boiler with the unit ventilators in each of the
rooms.
HVAC Svs^m Description
The HVAC system in this school consists of heating-only, three-speed unit ventilators located
in each room. Each room had an electronic thermostat that controlled the outdoor air damper and the
heating valve in the unit ventilator. Each unit had a low-limit thermostat that shuts off the outdoor air
damper when the supply air temperature falls below 60° F. The units appeared to be in excellent
torkins order in Rooms 139-142. Rooms 141 and 142 •«*Ł«•'"'"J?"*'™ •*>«»' ducted to
the roof through the storage/coat closets. The turbine for *°°™J*2J"as .,n°Perab|e (not turning)
during the investigation, but school maintenance perso"n^tPnR^ 39 A passive
exhaust was located in Room 140, and there was no exhaust in Room 139 (library).
There was no automatic shutoff of the ventilators, nor was there an automatic temperature
setback control. It appeared that each unit fan ran continuously and the unit cabinets and thermostats
were inaccessible without special tools (a hex key); thus thefan sp®®ds a"d temperature settings could
not be adjusted by the teachers. The unit ventilator fans could be shut off at the electrical panelboard.
The piping was routed to each unit ventilator through tunnels under the slab, as seen in Figure
8 The return air for the unit ventilator was not isolated from the slab over the tunnel, thus any
opening in the slab (e.g., a pipe sleeve, crack) would allow air from the tunnel to enter the unit
ventilator and mix with the room air return and outdoor air. A high radon level in the tunnel could be
the source of elevated radon levels in the room. Some openings were found around pipe penetrations.
and radon levels in the tunnel averaged about 55 to 60 pCin-
Results of Inifol Measurements
Air flow quantities were measured for each unit venti'ato^ and static pressure readings (relative
.a , nraccnm) were taken in Rooms 139-142. The readings were taken for the various
at'na modes of each unit ventilators: 1) unit ventilator off; 2J unit ventilator on low, medium, high
fan soeed- and 3) unit ventilator with outdoor air damper opened and closed. In addition to these unit
static pressure was measured with the hallway door opened and
dosed The results of the differential pressure and flow are shown 'n Tables 4 through
7, and the results of the differential pressure measurement displayed graphically m Figures 9
-------
through 12. These measurements indicate that the optimal operating mode for the reduction of soil
gas infiltration would require the unit ventilator to be on (any speed) with the outdoor air damper in
the open (or 100%) position, and with the hallway door closed. It appears that no other operating
mode, or door position, would allow for pressurization of the room. Only Room 139 (library) could be
pressurized with the outdoor air damper in the minimum (roughly 10% open) position, with the hallway
door closed (probably due to the lack of any exhaust system in the room). With the unit ventilator on,
the outdoor air damper open, and the hallway door closed, pressures in those rooms with wind turbine
or passive exhausts (140-142) ranged from +0.020 to +0.036 in. WC. These pressures should be
adequate to prevent soil gas infiltration into the rooms.
To determine the ability of the unit ventilators to reduce radon levels during normal occupancy,
a datalogger was installed in this school from November 29, 1990, to January 8, 1991. Continuous
radon levels were measured in Rooms 139, 140, and 141, and in the tunnel. Differential pressures,
temperatures, wind speeds and directions, classroom door openings and closings, and unit ventilator
operations were also monitored. These data are currently being analyzed. For a general comparison,
a summary of the data is displayed in Table 8. The results shown in this table were obtained over a
2 week period (December 2 through December 15, 1990). During the first week (December 2 through
8, 1990) the classrooms were operated in a normal manner with the classroom doors into the hall
closed about 75% of the time (note that the doors were usually closed after class and throughout the
weekend). During the second week (December 9 through 15) the teachers were asked to keep their
classroom doors closed as much as possible during class. As seen in Table 4, the percent of time the
doors were closed increased to about 90%. The average radon level was reduced by approximately
50% as a result of the pressurization of the classrooms produced by the unit ventilators.
These data indicate that if the classroom-to-hall doors are kept closed, radon levels in the
classrooms can be reduced. The slightly lower levels in Room 139 (the library) are probably due to a
combination of factors including: a lower source strength, no exhaust (passive or turbine), and the
library door is closed more frequently than the classroom doors.
Future Plans
Data collected from the datalogger are being analyzed. Depending on the need to keep the
classroom-to-hall doors closed to achieve adequate mitigation with the unit ventilators, the school will
make a final decision on the mitigation approach.
CONCLUSIONS
The initial data collected in these four schools confirmed that pressurization of classrooms
(using the HVAC system) reduces average radon levels. Pressurization, however, did not consistently
reduce the levels to below 4 pCi/L in all the classrooms studied. The schools used in this study are
a small sample, but the HVAC systems found in these schools are expected to have a great deal in
common with those installed in most school buildings constructed in the U. S. since the 1950s.
Those buildings with central air handling units are designed to be pressurized. It was found
that modifications to the control systems by owners and deterioration of the system components have
resulted in these systems no longer operating to pressurize the classrooms. These systems were
contributing to depressurization of the building interiors, thus increasing the potential for the entry of
radon-laden soil gas. (In one case, it appears that radon entry into the subslab return air duct is also
contributing to elevated radon levels in the building.) A change in the control strategy, returning them
to original operations, should allow for pressurization of the classrooms and a reduction in radon levels.
However, it should be noted that most control strategies will close outdoor air dampers in cold weather
to reduce the likelihood of freezing the heating coil.
Unit ventilators are designed and operated in such a manner that the outdoor air damper is
-------
modulated based on indoor and supply air temperatures. They were observed in this study to
pressurize a classroom but usually only when the classroom door to the hallway was closed and the
outdoor air damper was open. This may not be sufficient to reduce radon levels consistently below
4 pCi/L without additional efforts to reduce other negative pressures in the building.
Research in these schools and additional schools over the next year will focus on determinina
the optimal HVAC system operation for radon reduction. Limitations of HVAC pressurization will also
be studied, and in some of the schools HVAC pressurization will be compared with ASD.
REFERENCES
1. Leovic, K.W., Craig, A.B., and Saum, D.W. The influences of HVAC design and operation on
radon mitigation of existing school buildings. In: Proceedings of ASHRAE IAQ'89, The Human
Equation: Health and Comfort. San Diego, 1989, NTIS PB89-218-762.
2. Turner, W.A., Leovic, K.W., and Craig, A.B. The effects of HVAC system design and operation
on radon entry into school buildings. Presented at the 1990 International Symposium on Radon
and Radon Reduction Technology. Atlanta, 1990.
3 Brennan, T., Turner, W.A., and Fisher, G. Building HVAC/Foundation Diagnostics for Radon
Mitigation in Schools: Part 1. In: Proceedings of Indoor Air '90, Toronto, 1990,
4. Witter (Leovic), K., Craig, A.B., and Saum, D.W. New-construction techniques and HVAC
over-pressurization for radon reduction in schools. In: Proceedings of ASHRAE IAQ'88
Atlanta, 1988.
5 Saum, D. W., Craig, A. B., and Leovic, K. W., Radon Mitigation in Schools: Part 2. American
Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Journal Vol 32
No.2, pp. 20-25, 1990. ' ' '
6 Schmidt, A. The results of EPA's school protocol development study. To be presented at the
1 991 International Symposium on Radon and Radon Reduction Technology, Philadelphia April
1991.
ACKNOWLEDGMENTS
The authors would like to express their appreciation to all the school officials who h
graciously permitted them to conduct measurements in their school buildings. 6
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TABLE 1. METRIC CONVERSION FACTORS
Non-Metric Times
cubic foot per minute (cfm) 0.47
degree Fahrenheit (°F) 5/9 (°F-32)
foot (ft) 0.305
inch (in.) 2.54
inch of water column (in. WC) 248
picocurie per liter (pCi/L) 37
square foot (sq ft) 0.093
square inch (sq in.) 0.00065
Yields Metric
liter per second (L/s)
degrees Centigrade (°C)
meter (m)
centimeters (cm)
pascals (Pa)
becquerels per cubic
meter (Bq/m3)
square meter (m2)
square meter (m2)
TABLE 2. SUMMARY OF SCHOOLS*
State
Colorado
Approximate
Size of Area
Under Study
so ft
HVAC
Initial
Radon Levels
DCi/L
29,000
central
5-12
Maryland
3,500
unit
ventilators
14-20
Virginia
1,200
central
2-7
Washington
5,000
unit
ventilators
3-21
• Substructure of all schools is slab-on-grade.
TABLE 3. E-PERM MEASUREMENTS IN COLORADO SCHOOLS 1 AND 2
Dates
Dec 21-26
Outdoor
Air Damper
closed
Dec 27-31 open in 2
open & closed
in 1
Classrooms
10.8 2.9
7.0 2.5
Radon Levele. pCi/L
Boiler Room
_L_ _2_
Return Air Duct
2
2.5
3.5
2.6
2.0
13.5
14.6
6.6
7.8
Jan 1-2
open in 1
4.6 -
2.5
7.5
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TABLE 4. DIFFERENTIAL PRESSURE AND FLOW MEASUREMENTS IN ROOM 139
DATA TAKEN: August 22, 1990
DIFFERENTIAL PRESSURE MEASUREMENTS. ROOM TO OUTDOORS I'm. wr|
Room-to-Hall Door Closed
Outdoor Air Damper Position
Unit Ventilator Speed Setting:
Off Low Medium
Open (100%)
Closed (10% open)
Room-to-Hall Door Open
Open (100%)
Closed (10% open)
AIR QUANTITY MEASUREMENT (cfm)
Outdoor Air Damper Position
-0.001
-0.001
-0.001
-0.001
Low
0.053
0.01
-0.001
-0.002
0.054
0.009
-0.001
-0.003
Medium
Open (100%)
Outdoor Air
Supply Air
-H'flh
0.056
-0.012
0
-0.001
Hiah
460
1175
470
1306
500
1285
Closed (10% Open)
Outdoor Air 30 47 109
Supply Air N/A N/A N/A
Percent Outdoor Air
Outdoor Air Damper Open 39% 36% 39%
Outdoor Air Damper Closed 3% 4% go^
Outdoor Air Per Student (cfm - Based on 20 Students)
Outdoor Air Damper Open 23 24 25
Outdoor Air Damper Closed 225
Avg Leak Area (in.2) = 73 2
OBSERVATIONS: Room 139 (Library) could be pressurized with the unit ventilator, regardless of
the outdoor air damper position, but only when the room-to-hall door was
closed. It does not have an exhaust vent like the other rooms, thus it is easier
to pressurize.
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TABLE 5. DIFFERENTIAL PRESSURE AND FLOW MEASUREMENTS IN ROOM 140
DATA TAKEN: Auoust 22, 1990
DIFFERENTIAL PRESSURE MEASUREMENTS. ROOM TO OUTDOORS (in. WC>
Room-to-Hall Door Closed
Unit Ventilator Speed Setting:
Outdoor Air Damper Position Off Low Medium High
Open (100%)
Closed (10% open)
0
0
0.02
-0.002
0.021
-0.001
0.024
-0.002
Room-to-Hall Door Open
Open (100%)
Closed (10% open)
0.001
0.001
0
-0.004
-0.003
-0.002
-0.001
-0.008
AIR QUANTITY MEASUREMENT (cfm)
Outdoor Air Damoer Position
Low
Medium
Hiah
Open (100%)
Outdoor Air
Supply Air
361
1200
438
1263
449
1380
Closed (10% Open)
Outdoor Air
Supply Air
45
1090
23
1135
44
1197
Percent Outdoor Air
Outdoor Air Damper Open
Outdoor Air Damper Closed
30%
4%
35%
2%
33%
4%
Outdoor Air Per Student (cfm - Based on 20 Students)
Outdoor Air Damper Open 18
Outdoor Air Damper Closed 2
22
1
22
2
Avg Leak Area (in.2) =
101.1
OBSERVATIONS: Room 140 could be pressurized with the unit ventilator, only with the outdoor
air damper in the fully open position, and the room-to-hall door closed. This
room has a passive vent and is more difficult to pressurize.
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TABLE 6. DIFFERENTIAL PRESSURE AND FLOW MEASUREMENTS IN ROOM 141
DATA TAKEN: August 22, 1990
Room-to-Hall Door Closed
Outdoor Air DamDer Position
Unit Ventilator Speed Setting:
Off Low Medium
Hiah
Open (100%)
Closed (10% open)
0 0.03
-0.003 -0.002
0.034
-0.002
0.036
-0.003
Room-to-Hall Door Open
Open (100%)
Closed (10% open)
-0.002 -0.005
-0.002 -0.002
-0.001
-0.003
-0.001
-0.003
AIR QUANTITY MEASUREMENT (cfm)
Outdoor Air Damoer Position
Low Medium Hiah
Open (100%)
Outdoor Air
Supply Air
495
1001
580 657
1097 1160
Closed (10% Open)
Outdoor Air
72
87 94
Supply Air
Percent Outdoor Air
Outdoor Air Damper Open
Outdoor Air Damper Closed
N/A
49%
7%
Outdoor Air Per Student (cfm - Based on 20 Students)
Outdoor Air Damper Open 25
Outdoor Air Damper Closed 4
N/A
53%
8%
29
4
N/A
57%
8%
33
5
Avq Leak Area (in.2)
=
113.0
OBSERVATIONS: Room 141 could be pressurized with the unit ventilator, only with the outdoor
air damper in the fully open position, and the room-to-hall door closed. This
room has a wind turbine exhaust and is more difficult to pressurize.
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TABLE 7. DIFFERENTIAL PRESSURE AND FLOW MEASUREMENTS IN ROOM 142
DATA TAKEN: August 22, 1 990
DIFFERENTIAL PRESSURE MEASUREMENTS. ROOM TO OUTDOORS (in. WC)
Room-to-Hall Door Closed
Unit Ventilator Speed Setting:
Outdoor Air Damper Position Off Low Medium High
Open (100%)
Closed (10% open)
Room-to-Hall Door Open
Open (100%)
Closed (10% open)
AIR QUANTITY MEASUREMENT (cfm)
Outdoor Air Damper Position
0 0.03
-0.003 -0.002
-0.002
-0.002
Low
-0.005
-0.002
0.034
-0.001
-0.001
-0.003
0.036
-0.003
-0.001
-0.003
Medium
High
Open (100%)
Outdoor Air
Supply Air
Closed (10% Open)
Outdoor Air
Supply Air
Percent Outdoor Air
Outdoor Air Damper Open
Outdoor Air Damper Closed
266
1123
150
1078
20%
14%
Outdoor Air Per Student (cfm - Based on 20 Students)
Outdoor Air Damper Open 11
Outdoor Air Damper Closed 8
230
1218
160
1250
19%
13%
12
8
251
1362
184
1306
18%
14%
13
9
Avq Leak Area (in.2) =
OBSERVATIONS:
46.2
Room 142 could be pressurized with the unit ventilator, only with the outdoor
air damper in the fully open position, and the room-to-hall door closed. This
room has a wind turbine exhaust vent and is more difficult to pressurize
although the turbine was inoperable during these measurements. The outdoor
air damper appears not to open fully.
-------
TABLE 8. AVERAGE RADON LEVELS IN WASHINGTON SCHOOL DURING 1 WEFK nc
NORMAL OPERATION AND 1 WEEK OF TESTING OPERATION
Location'
Room 139
Room 140
Room 141
Normal Operation
Persent
Average Time Door
Radon (max) Closed
(pCi/L) (%)
2.6 (26.7)
5.3 (29.2)
4.5 (32.1)
76
74
75
Test Operation
Average
Radon (max)
(pCi/L)
1.4 (16.5)
3.2 ( 7.4)
2.2 (25.0)
Persent
Time Door
Closed
(%>
97
92
88
Subslab Radon
Sniff
Measurement
(Aug. 1990)
(DCi/H
400
500
700
Average
Tunnel
4.1
55.6 (202.8)
75
2.3
60.8 (129.2)
92
533
N/A
Data for Room 142 not available; Pylon inadvertently "unplugged."
-------
KINDERGARTEN
(8.8)
p (T&)i 1
food
STORE
KM 1
(55)
KM 2
(6.0)
KM J
(e.#)
W.RM
(8.8)
STORE
KIT-
CHEN
(4.8)
(50)-
ta_
BT
¦2)
PI
RM 5
(7.0)
RM 4
(7.2)
MEDIA
CENTER
(7.0)
(7.3).
CYM
CT
GYU S
DOWN
RU «
RM 7
PRI | OFT
LOUNGE
(6.6)
Ry 12
RM 9
RM 11
RM 10
t :: j
coach orr (5.6)
ART TEACH OFF ((.I)
•-DUPLICATE
SCALE
H 50'
Figure 1. Results of January 1990 radon measurements
in Colorado school, pCi/L.
KINDERGARTEN
(7.2)
T '
T1
RM 1
(7.7)
RM 2
(7.5)
RM 3
(8.1)
GYU S
DOWN
FOOD
RM 6
STORE
KIT-
CHEN
RM 7
PRJ i ofT
(«-3) i (6.fl)
LOUNGE S
RM 5
COACH Off (5.8)
RM 4
RM 12
RM 11
RM 10
Figure 2. Results of February 1990 radon measurements
in Colorado school, pCi/L
-------
Room 108
20.3
Room 106
Room 107
20.3
Figure 3. Results of initial radon measurements
Cc-tinjous Setback
Day ~ Setback
Continuous Day
356 358 360 362 364
1990 Julian Day
Figure 4. Continuous radon measurements
in Maryland school.
-------
N
i
1 .0
~ n
"S'Tn
0.9
"~t$
O.i 0.7 1
12j^ fct]
i 0.6
m
r W
0.4
C.6
LI
0.5
0.9
^ 1-5
F-igure 5. Results of October 1988 radon measurements in Virginia school, pCi /L
As/
/
1.4
1.3 "
H ¦
- SL.4
I I
T .HUl,-!-'
3.0 2.0
3 y
\ 3'
.3/3.4
3.0
3.5 \
/ 2.6
3.5 \
Figure 6. Results of December 1990 radon measurements in Virginia school, pCi/L.
-------
o
Z3
c
o
o
a?
b
00
CO
CD
5-
O.
4->
C
0>
J-
a>
S-
o
C3
a.
o
"O
ro
ce:
5 -
School Starts 1/2/91
Radon in Conference Room
Subslab Pressure
-Positive Pressure over Slab (warm weather)
355 358 361 364 2
1990 and 1991 Julian Days
Radon in Room
Subslab Pressure
Figure 7. Continuous radon and differential
pressure in Virginia school.
- UMT VfVTVAJO*
B - 1VMA ACCESS
d
i
127
fa
128
I
129
a
3
rr
Figure 8. Partial floorplan showing utility tunnel
and room locations in Washington school.
-------
E -001
OFF
HIGH
LOW MEDIUM
UV Speed Setting
¦ O A(100% )DOOR - CLOSED CD OA(10Ci)DOOR-CLOSED
E O A(100®i>)DOOR - OPEN Q OAriO<*)DOOR-OPEN
Figure 9. Differential pressure measurements
in Room 139, August 1990.
3
0 06
+¦>
3
o
i
&
cc
O)
i_
Z5
S-
CL
0.05
0.04
0.03
0.02
to 0.01
c
o>
s-
a;
o -0.01
OFF
HIGH
LOW MEDIUM
UV Speed Setting
¦ OACIOO^ODOOR-CLOSED ~oA(109i)DOOR-CLOSED
E OA(l 009fc )DOOR -OPEN Q OA(10fc)DOOR-OPEN
Figure 10. Differential pressure measurements
in Room 140, August 1990.
-------
0 06
- 0.05
j y VI//
OFF
LOW MEDIUM
UV Speed Setting
H OA(100%)DOOR-CLOSED [Z3oA(10^)DOOR-CLOSED
E3 OA(100?«)DOOR-OPEN O OA(10~f)DOOR-OPEN
HIGH
Figure 11. Differential pressure measurements
i'n Room 141, August 1 990.
0.06
0.05
V 0.04
: o.o3
OFF
HIGH
LOW MEDIUM
UV Speed Setting
¦ OA(l00%)DOOR-CLOSED [Z3 OA(10%)DOOR -CLOSED
22 OA(100%)DOOR-OPEN O OA(10%)DOOR-OPEN
Figure 12. Differential pressure measurements
in Room 142, August 1990.
-------
X - 7
RADON DIAGNOSIS IN A LARGE COMMERCIAL OFFICE BUILDING
by: David Saum and Marc Messing
Infiltec
Falls Church, VA 22041
ABSTRACT
Large commercial office buildings present a significant
challenge to the commercial radon mitigator. A radon problem in
a Washington, DC area was recently analyzed with a number of
diagnostic techniques in a attempt to get a quick understanding
of the nature of the problem while operating within a limited
budget. The building has 7 stories, is 5 years old and it has a
VAV type HVAC system with 21 air handler zones. The diagnosis
was carried out using and integrated approach combining: 1)
multiple short term radon screening to look for hot spots, 2)
continuous radon monitoring in a few sites to identify day/night
radon variations, 3) pressure tests across doors to identify
localized depressurization, and 4) continuous pressure in hot
spots monitoring to identify building HVAC cycles. This
integrated approach identified different mitigation solutions in
each zone. Mitigation options have been presented to the
building owners, but a final decision on mitigation has not been
made at the time this paper was written.
-------
BACKGROUND
Radon mitigators may need to use a wide variety of
diagnostic tools to analyze radon problems in large office
buildings. These buildings generally have sophisticated HVAC
systems and complex foundation structures that are not generally
found in homes or schools. For quick, cost effective radon
diagnosis in large office buildings, it may b necessary to use a
variety of radon and pressure measurement equipment. This paper
describes an attempt to diagnose a building using: 1) multiple
short term radon screening to look for hot spots, 2) continuous
radon monitoring in a few sites to identify day/night radon
variations, 3) pressure tests across doors to identify localized
depressurization, and 4) continuous pressure monitoring in hot
spots to identify building HVAC cycles.
The ground floor of this Washington, DC Metro area 7 story,
5 year old building is underground except for a loading dock
area. The HVAC system is a VAV type with 3 air handlers on each
floor, supplies in most rooms, and a return plenum overhead.
Figure 1 shows the floor plan of the basement and each of the
three HVAC zones is outlined. There are a number of areas in the
basement with slab-to-slab walls that may cross the boundaries of
the HVAC zones.
Previous radon tests were made with alpha-track monitors
deployed for three months during the summer and winter of 1989.
Rooms indicated on Figure 1 are locations of radon tests. Table
1 lists all of the radon test results. When some radon levels
above 4 p/Ci/L were found, all the building VAV units were
adjusted to- supply a minimum airflow of 30%, and booster fans
were installed in the fresh air supply ducts. All of this work
was assumed to guarantee that the building would be under a
positive pressure while the HVAC system was on. No further radon
tests were performed after these modifications, and one of the
goals of the Infiltec work was to determine if the HVAC
modifications have made a change in the radon levels. Additional
goals include a determination of the pressure balances inside the
building and suggestions for mitigation if elevated radon levels
are found.
RADON MEASUREMENTS
In order to determine if the radon levels had changed since
the HVAC modifications were performed, radon tests were conducted
by Infiltec over the period 9/6 to 9/14 with electret passive
monitors in 23 rooms and continuous radon monitors (CRMs) in two
rooms. The electrets were read out every few days to check the
average radon levels and the CRMs recorded hourly data so that
the short term fluctuations could be monitored. Table 1 lists
the electret results and Figures 2 and 3 show the hourly radon
data in 2 zones.
1
-------
PERIOD 9/6-9/7
A quick 24 hour test was performed to get a snapshot of the
building and to check out areas such as elevator shafts and HVAC
rooms that had not been tested before. This data is shown in the
first data column of Table 1. No new sources were found but the
shop area which had shown the highest radon levels in previous
tests was not as high as the rooms in zones B and C.
PERIOD 9/6-9/10
A longer electret test (second data column in Table 1) over
the weekend was performed in more rooms with the hope of finding
sources in the building when the HVAC system shut down over the
weekend. Unfortunately, it was found that during the weekend the
HVAC system operates with the same cycling as a weekday because
of partial weekend occupancy. However, the longer tests showed
continued elevated levels of radon in most rooms in zones A and
B, and the shop showed the highest levels.
PERIOD 9/6-9/14
Adding 4 more days to the electret test (third data column
in Table 1) resulted in a surprising lowering of radon levels in
zones A and B, but the shop room stayed at about 6 pCi/L. When
the electret data is analyzed for the levels between 9/10-9/14
(fourth data column in Table 1) it can be seen that the radon
levels have dropped substantially in both of these zones during
this period, while the levels in zone A have not changed very
much.
Figure 2 shows what happened to the radon levels in one room
in zone B which is expected to be representative of most of the
rooms in this zone. On the evening of September 10 the radon
levels fall from about 4 pCi/L to about 2.5 pCi/L and remain
there. The electret data suggest that this is what happened in
all the rooms in zones B and C. One possible explanation is that
the onset of cooler weather on 9/10 may have changed the VAV
settings to bring in more fresh air. At present the reason for
this sudden change in radon levels is unknown but it seems to
have only affected the radon levels in zones B and C. Since
Figure 2 shows that the radon levels in zone B do not show a
day/night fluctuation, it seems that radon is being constantly
pulled into these zones during the day and that when the HVAC
system shuts down at night there is no significant increased or
decreased entry.
Figure 3 shows that the radon levels in the shop area
exhibit extreme day/night fluctuations with peaks up to 30 pCi/L
at night and decreasing to 1 or 2 pCi/L during the day. The
shaded area on this graph shows the radon levels during occupied
hours (7 am to 5 pm), and the average radon during occupied hours
is not very much different from the average levels during
occupied hours because the HVAC system comes on a t 7 am and it
takes several hours to sweep the radon from this room. Some of
this effect may be due to time lag in the CRM response. Note
that Table 1 shows that radon levels in the rest of zone A rooms
are quite low. There seems to be a strong radon source in the
2
-------
shop that is suppressed during the day by either positive
pressure or ventilation, but when the HVAC system shuts down this
source raises the levels in the shop very quickly.
PRESSURE MEASUREMENTS
Figure 4 shows a recording of the pressure difference
between the shop and the subslab gravel layer. This data was
measured through a small hole drilled through the slab in the
shop. The graph shows that there is a positive pressure in the
shop (relative to the subslab) during the day of 0.01 to 0 02
inches of water column ("wc) and when the HVAC system is shut
down at night there is still a positive pressure of about 0 002
"wc. The pressure in the shop relative to the hall was measured
at about 0.007 "wc lower than the hall during the day (Table 1)
and Figure 4 suggests that zone A is generally well pressurized
by the HVAC system. It is generally assumed that if there is anv
positive pressure in a room relative to the subslab that all
radon entry will be suppressed. Therefore it is surprising that
the shop appears to be at a slight positive pressure even at
night when the radon is entering. This suggests that the radon
source is not in the subslab and that it may be somewhere in the
walls. We have been unable to locate the entry point and it mav
be necessary to conduct further investigations when the HVAC
system is not pressurizing the room.
Subslab radon measurements were made through three drilled
holes in the shop floor and levels of 130 to 280 pCi/L were found
(Table 2). These radon levels are very low. From our experience
we have generally seen subslab radon levels in problem buildincrs
ranging from 500 to 80, 000 pCi/L. It appears that the subslab
radon may be diluted by the positive room pressurization induced
flow or that there is a hot spot somewhere that we have not
located.
Figure 5 shows the pressures measured through a hole drilled
through the slab in room H0228A in HVAC zone B. Again we see
good HVAC pressurization during the day (0.01 to 0.01 "wc) and
nighttime pressure around zero, with the exception of a half hoi
negative period (about -0.006 "wc) just before the HVAC system
comes on in the morning. Note that several days of data were
recorded and each daily pressure cycle is almost identical to the
one shown. Table 1 pressure measurements made under the doors in
zones B and C show that the only rooms that are significantlv
negative are the HVAC and electrical rooms. When these rooms
were investigated for possible radon sources, drains were found
that had large gaps around them leading directly to the subslab
When radon measurements were taken in these drains, levels of
about 250 pCi/L were found (Table 2) together with significant
air flow into the HVAC rooms. It seems reasonable to believe
that the negative pressure in the HVAC rooms pulls in radon
during the day and distributes it around zones B and C, and that
when the HVAC system goes down at night this radon does not decav
enough to show any decrease in levels. "
Pressure in the HVAC rooms (relative to the halls) in zone>
B and C were measured on 9/10 at -0.050 and -0.026 "w
3
-------
respectively. The significant decrease in zone C negative
pressure may be the reason that this zone had lowest radon levels
during the 9/10-9/14 electret monitoring. It is assumed that
this lower pressure was present during that previous time period.
The lower pressure would have reduced the flow of soil gas from
the drain hole in the zone C HVAC room. Zone B radon entry may
not have changed but there may be some communication between the
air in the two zones and the zone B radon reduction may be caused
by zone C.
CONCLUSIONS AND RECOMMENDATIONS
Based on the diagnostic measurements, the following
conclusions and recommendations were made:
1. The radon levels appear to be generally lower now than
they were during the 1989 summer and winter alpha-track
measurements. Of course, these radon measurements may not be
representative of the longer term, since they only covered one
week and we already have seen significant variations that appear
to be due to HVAC changes resulting from weather changes. Long
term (3 month) winter radon measurements are definitely recommend
for confirmation.
2. The building appears to be generally under positive
pressure (relative to the subslab) in most rooms while the HVAC
system is on. Only a few rooms were found to be significantly
negative relative to the hallway and subslab. No continuous
pressure measurements were made in HVAC zone C but all other
measurements suggest that it is just as positive as zones A and
B.
3. At night during HVAC shutdown there appears to be very
little negative pressure, but this may change as the weather gets
colder and the "stack effect" becomes stronger. In order to
investigate this possible effect it would be necessary to do
continuous radon and pressure measurements during cold weather.
If this stack effect causes significant radon entry during the
night, the HVAC system might be turned on earlier in the morning
(e.g. 6 am) to flush out the building. Another option is to run
the basement air handlers continuously during the night to
guarantee a continuous positive pressure over the slab.
3. The negative pressure in the pump room and the HVAC
equipment rooms should be eliminated if possible. Since a very
wide range of depressurization was measured in these rooms (from
0.8 to 0.008" wc), it is assumed that there is a balancing
problem that could be corrected.
4. The radon source in the shop was not found and it might
be easier to locate when the HVAC system was shut down. It is
difficult to locate it during the day because the positive
pressure in the shop appears to suppress the radon entry.
5. The drain openings in the HVAC equipment rooms should be
sealed to prevent radon and soil gas entry. Sealing could
probably be done with a non-shrink grout or with a pourable
4
-------
polyurethane caulk. This may be the primary solution to the
radon problem in zones B and C, but it cannot be guaranteed
because radon tends to build up behind sealing and emerge at
other entry points. A combination of reducing depressurization
and sealing is likely to be most effective. It is not clear
whether the porous block walls in the HVAC rooms are also a
source and it may be necessary to seal them too.
6. The standard radon reduction technique of subslab
depressurization (SSD) may not be necessary in this building if
all rooms can be pressurized, the major soil gas leaks can be
closed, and any radon that enters when the HVAC system is shut
down can be countered by bringing up the HVAC system early enough
to flush it out. The shop area might be treated with SSD if the
source is located, and a small exterior exhaust fan could
probably be located in the bermed area next to the shop.
DISCLAIMER
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and therefore the contents do not
necessarily reflect the views of the Agency and no official
endorsement should be inferred.
5
-------
Table 1
Radon and Pressure Test Results by Room
Room
or zone
Tested
HVAC ZONE A
Shop (Pylon)
H0001 pump
Custodial
H0138 Locksmith
Elect
Kitchen elevator
Kitchen storage
Freight elevator
cable chase
H0001 storage
H, 168 HVAC
H0168 electrical
HVAC ZONE B
H0226 electrical
H022 6 HVAC
H0256
H0266 (Pylon)
H0244
H0229B
HVAC ZONE C
H0407 electrical
H0407 HVAC
H0470
H0440
H0450
H0495
H0308
H0310
H0318
H0324
Electret
9/6-9/7
(pCl/L)
Test Type and Date
« BSE *^51 Sias'3
pC 1 /LJ_ (pCl/L) (pCl/L) (" WC)
' " " ' * v -'J V- 1 1
-------
Custodial
H-
iQ
C
H
(D
00
0)
W
(C
3
(D
3
r+
(U
D
03
C
H-
H1
a
H-
a
U3
H0001
Pump Room
HVAC Room
HTf -•
HVAC ZONE A ]
Shop
loading dock
berms
H0146
H0100
rms
Locksmith
HO 13
Freight Elevator
B- ^
'H Sfferr 11
Kitchen - Elevator
Kitchen - Storage
3 HVAC zones per floor
7 floors
VAV type HVAC
Night shut down (10pm-6am)
Ceiling return plenum
Some walls slab-to-slab
j below grade
H0244
H0450
H0470
¦A0495
HVAC ZONE B
front
entrance
H0407
HVAC & Elect
H0440
below grade
H0229B
~ HVAC ZONE C "
~.T~^f"rri.~' -It)
H0266
H0256
H0226 HVAC & Electrical
i.iuuVJL--1— .. .. 1
H0310
-------
6
\
b
Cl
c
o
~o
CO
cr
VAVs creating more dilution due to milder weather?
13
September 1990 Day
15
Hourly estimates from Pylon with Lucas cell
Figure 2 Continuous Radon in zone tJ, Koom H0226
30
O
Q_
C
o
X)
CO
en
20
Average radon = 5.9 pCi/L during all. hours
Average radon = 5.1 pCi/L during oqtupied hours
Average radon = 6.4 pCi/L during ui occupied hours
10
13
September 1990 Day
Hourly estimates from Pylon with PRD
Occupied hours (7 am to 5 pm)
Figure 3 Continuous Radon in Zone A, Shop Room
8
-------
Pressure Across Slab
(measured through drilled hole)
+0.10" wc
in o
Room Pressurized
1
co n;
+ 0.020" wc •§
<- 0.000
0.020" wc
+0.002"
pressure
during nighi
setback
:0.010
Room Depressurized
0.10" wc
9/13/90
2-4 23 22- 2.1 IP if It 17
<- TIKE <-
15 /4- 13 /2.
9/12/90
-------
Pressure Across Slab
(measured through drilled hole)
'in j •
<- +0.10" wc
*1
H-
iQ
C
M
(t>
(Jl
O
O
3
r+
H-
3
C
o
c
CO
T)
H
CD
CO
CO
c
n
(D
H-
3
tSJ
o
p
(D
a
o
o
3
33
O
to
to
cn
TIME
Room Pressurized
<- +0.020" wc —
- ZERO PRESSURE
-0.020" wc
0.010" wc
-0.006" wc
Negative pressure
^pike for
1/2 hour each
morning
Room Depressurized
. C- .
I3 It tt IO ? $¦
5 Ac
<- -0.10" wc
% i 2* a? m %\
20 l
-------
X-8
TITLE: New School Radon Abatement Systems
author: Ronald F. Simon, R.F. Simon Company
This paper was not received in time to be included in the
preprints so only the abstract has been included. Please check
your registration packet for a complete copy of the paper.
This paper describes the methods used to develop a state-of the-art Radon
Abatement system- (1) all aspects of design and implementation from proper
sizing radon ventilation ductwork (RVD) in relationship to the amount of free air
available in sub-slab aggregate, (2) review of electrical systems with their
monitoring devices from the very basic to the more sophisticated type of
installation, (3) review abatement designs for their durability and application as
well as methods and techniques.
Building codes will also be reviewed for commercial construction applications,
spot-lighting the usage of specific materials and techniques and their impact on the
industry.
-------
X-9
DESIGN OF RADON RESISTANT AND EASY-TO-MITIGATE
NEW SCHOOL BUILDINGS
by: Alfred B. Craig, Kelly W. Leovic,
and D. Bruce Harris
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Research Triangle Park, North Carolina 27711
ABSTRACT
The Air and Energy Engineering Research Laboratory's (AEERL)
radon mitigation research, development, and demonstration program
was expanded in 1988 to include the mitigation of schools.
Application of technology developed for house mitigation has been
successful in many but not all types of school buildings. School
mitigation studies carried out to date in the AEERL program have
been reviewed in order to determine those architectural features
which affect radon entry and ease of mitigation. This paper
details those features having the most effect and recommends the
design parameters which should be most cost-effective in
controlling radon in new school buildings.
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administrative review
policies and approved for presentation and publication.
-------
INTRODUCTION
The Air and Energy Engineering Research Laboratory (AEERT ^ ^
the U.S. Environmental Protection Agency (EPA) has been develoninf
and demonstrating radon mitigation technology in houses E Ł5
existing and new, since 1985. In 1988, the program was expanded
to include radon mitigation in existing schools in Sk
intervening 3 years, detailed diagnostic studies have been earn !
out in about 40 schools in 8 states and mitigation studies ™
of these schools. Walk-through examinations and revi^wt 2
architectural drawings have been conducted in manv °T
schools. y aaaitional
Over the past year, architectural features of the
studied have been carefully reviewed in an attempt to id»n?°iS
those features which affect radon entry and ease of mitiaa?- y
Results of the studies are currently being used to develoo a
for construction of radon resistant and easy-to-mitiqate schmi '®
This new guidance document will be available later this vear
purpose of this paper is to briefly summarize some of the A* •
and construction features which have been identified as imn®ign
in this study. raPortant
Nearly all new schools being built today are slab-nr> ^
(SOG), and this paper is limited to this archit2c?n2 ?
substructure. However, what is stated for sog schools nor™??
applies to schools with basements and is applicable to them J11*"
if any, new schools are being built today with crawl SDac'fte W'
they are not covered in this paper. p es» so
DESIGN FEATURES WHICH AFFECT RADON ENTRY
Two design features are known to affect the rate of
entry into large buildings—slab cracks and penetration^**011
pressure differentials resulting from the buildina «***?**
construction and the design and operation of the he*!-?1
ventilating, and air conditioning (HVAC) system. ne«tingf
SLAB CRACKS AND PENETRATIONS
Slab cracks, expansion joints, and penetrations in school«
similar to those in houses as is their control. These
eliminated by a change of building design, or their effects
minimized by proper sealing. Great care should be taken iJan,be
design to minimize slab cracking. sl«b
Sealing is even more difficult in existing schools th»
houses since the cracks are frequently hidden and cannot be rita*
found. However, this is not true in new school construction 2 y
all cracks and openings in the slab are readily accessible at
stage of construction. son»e
-------
Expansion joints are the largest source of cracks in SOG
construction. Where codes do not require them, they should be
eliminated since, in most cases, they serve no useful purpose. A
slab is at its largest size during curing in the first few hours
after pouring due to the heat of hydration of the cement. As a
result, the only slab which can be larger at a later date
(requiring an expansion joint) is one that is poured and cures in
extremely cold weather. Allowance for shrinkage, the other
function of an expansion joint, is better accomplished using pour
joints (without expansion joints) or control saw joints, both of
which are much easier to seal than are expansion joints. Where
pour joints are used without expansion joints, both slabs should
have a tooled edge to make possible a good polyurethane (PU) seal.
Control saw joints, pour joints, and expansion joints, where
used, should be carefully sealed with a flowable PU caulk applied
according to the manufacturer's specifications. With expansion
joints, the top l/2-in.* should be removed to make space for a good
PU seal.
A second source of openings in the slab are utility line
penetrations. These can be minimized by running all utility lines,
except sanitary sewer, overhead in the area above the drop ceiling,
a practice found in some existing schools visited in our mitigation
studies. Overhead utility lines are recommended in radon-prone
areas in order to minimize slab penetrations by utility lines.
Utility penetrations, when present, must be carefully sealed. If
any type of wrapping has been put around a utility pipe to protect
it from the concrete, it frequently allows soil gas passage. This
type of wrap must be designed so as to not allow any soil gas
passage or it must be removed after the concrete is set and the
resulting space filled with a PU caulking.
In some design situations, utility pipes penetrate the slab
in groups to enter pipe chases. In these situations, great care
should be taken to design and construct in such a way that no slab
openings are left between the pipes.
HEATING, VENTILATING, AND AIR CONDITIONING SYSTEMS
Most schools being built today are air conditioned. This
usually results in the use of large HVAC systems supplying many
rooms. These large systems are always built with provisions for
ventilation by the addition of outdoor air to the air handling
system. This results in pressurization of the building as long as
the circulating fan of the air handler is in operation and an
adequate quantity of outdoor air is being brought into the system
continuously. Pressurization by this means will significantly
reduce radon-containing soil gas entry as long as the circulating
fan is operating and fresh air is being brought in. When the
^*)Readers more familiar with metric units may use the factors at
the end of this paper to convert to that system.
-------
is usually the case during night or
circulating fan. g°®s °tb' k radon-containing soil gas can enter
weekend temperature rases has been found to reach high levels
the building and in some^cases « fan Qf the HyAC system
~ /-i a^firootns. Once tne c horning when heating or
stopped and the radon in
starrs ----- entry is stoppea anu m
cooling is called fo / ^ period of time by the outdoor air
the building is diluted system. If the radon level reached
being brought in by t dilution process can take several
during the night is ng , o{ which are being reported at this
hours. studie_SimUend at determining under what conditions the HVAC
meeting, are awed at detern ^ ycontrol radon to a satisfactory
system can be .T.efp®^ hvac svstem design and operation as a radon
mitigatior^approach cannot be determined until these studies are
completed.
AI have been found to be an entry route for
Return air dv^c.ts These should never be routed below the
radon-containing sol 9 * under neqative pressure when the HVAC
floor since they * ceiling plenum is used as an unducted
fan is running. ^ns penetrating the slab and ending
return air space, any capped with a solid block. Otherwise
in the plenum sho^ Pn reach the plenum through the block
radon-containing beiow the slab. Radon levels can also
wall which is very p ^ the glafa when the circulating fan
is1iffUandnthen be brought into the room when the circulating fan
comes back on.
comes bacK
v«o heated and air conditioned using unit
Buildings can ith hot water or steam from a boiler
ventilators (UVs) s^ppli ®ished from a central chiller. All UVs
and with chilled water fur addition at the unit. Use of
are designed f:or fresn ^ thig type of system 1S slmiiar
iTtZl'Tparacentral HVAC system.
* - larae rooms such as kitchens, lunchrooms,
Exhaust systems tor w y and ghops create special problems
gymnasiums, »ultipu^])0® aative pressure and cause radon-containing
since they can c^eate.^eg.n This can be eliminated by supplying
soil gas to be br°ught in. ig removed by the exhaust system,
more conditioned ou^oor ai^ bfi an expensive solution, it is the
Although this may PP soil gas entry,
only known way to ensure
^rvj-ain exhaust fans which frequently cause
Restrooms also c°n«i rooms. This can be minimized by
elevated radon lev®1® „ smaii as code requirements will allow,
keeping the exhaust fan a* d any pers0n spends in
In addition, since the Exposure in this area is relativeiy
a restroom is prebumcu
^Hit^ioninq are frequently ventilated by
Schools usually mounted in the plenum above the
the use of exhaust fans usual y
-------
hall ceiling. The use of exhaust fans should be minimized in
radon-prone areas since this will usually result in a radon
problem. Rooms should always be ventilated by bringing in outdoor
air rather than by exhausting room air.
DESIGN FEATURES AFFECTING EASE OF MITIGATION
WITH ACTIVE SUBSLAB DEPRESSURIZATION (ASD)
The most successful mitigation technique for existing schools
has been the use of ASD, the same as in existing houses. This is
true as long as the school has aggregate under the slab. Since the
presence of aggregate can be required in new school construction
(and is, in fact, common practice), then it is logical that, until
similar information for other mitigation options becomes available
for performance and cost comparison, ASD should be the mitigation
system of choice in new schools. Thus the rest of this paper will
dwell on factors which affect the ease of application and the
effectiveness of ASD in new schools.
In a paper which the authors presented at the last symposium
in Atlanta(l), two schools mitigated in Nashville, TN, were
compared. One required 16 suction points to mitigate 15 rooms,
whereas 15 rooms were mitigated to a lower radon level in the
second school with only 1 suction point. This striking difference
in ASD effectiveness was the motivation for these authors'
beginning to review the factors which affect the ease of mitigation
in schools and has led to this paper.
In the authors' experience, pressure field extension (PFE),
is the most valuable diagnostic tool in determining the ease of
application of active subslab depressurization (ASD) to mitigation
of houses, schools, and large buildings. PFE measurements are even
more important in large buildings than in houses since much larger
subslab areas are involved and subslab barriers frequently exist
that are not normally found in houses. For example, PFE
measurements led to the prediction of the difference in ease of
application of ASD to the two previously discussed Nashville
schools which was then confirmed by the results obtained. Thus PFE
is used as a surrogate for ease of mitigation in the subsequent
discussion in this paper.
A review of the PFE measurements that have been made on all
of the schools in EPA's program, examination of their architectural
drawings, and many discussions of the factors affecting flow of
gases through aggregate beds with fellow scientists working on
radon have led to the identification of the following factors which
affect PFE:
Aggregate
Bulk density (or void volume)
Particle size (both average size and particle size
distribution)
Type (naturally occurring stone from moraine
deposits or crushed bed rock)
-------
Layer thickness and uniformity of thickness
Subslab barriers
Subslab suction pit s^e
STanfl^uSn of'openings in slabs (both
planned and unplanned)
These factors are discussed in the following sections.
aggregate
anrrrpaate listed above are known to
The four ProP?rJ1®| through stone beds. Bulk density is
affect the flow of a g size distribution and type of stone
actually controllediy pa aravel, which is rounded, packs more
i;;iS:iSy°^ with its greater variation in
shape).
• « -j-^ntative conclusions are postulated on the
effect^of "aggregate properties on PFE:
PFE is proportional to^average
particle*size distribution.
- narticle size distribution range the
greater^hevoid volume and hence the greater the PFE.
3. The smoother Reshape Ł th. ^^void
volume; ® pE for the same average particle size
and particle size distribution than crushed aggregate.
,„vr.v at Princeton University to verify and
AEERL is sponsoring work first report of this work is being
quantify these effects. in a poster paper given at this
made by Kenneth Gadsby in
» y \
1.
2 .
symposium(2).
SUBSLAB BARRIERS
+ differences between mitigation of houses
one of the greatest d ^ subslab barriers which are
and schools is the pre Qther large buildings and are rarely
commonplace in schools " ents made in schools have shown a
found in houses. P*& the preSence or absence of these
very strong c°r.rel*^°"ce is determined by a review of the
barriers. Their Pr®s®nructurai drawings. Based on school plans
foundation plan m the tst designs can be divided into the four
reviewed to date, Ł®u"^a, * Figures 1,3,5,and 6. These types
types shown schematicaiiy and the number Qf suction points
determine the ease of _tors are the same. They are presented
necessary assuming 3 to mitigate by ASD starting with the
in the order of difficulty
most difficult.
-------
The type shown in Figure 1 (schematic) is the most common and
unfortunately the most difficult to mitigate. In this type, all
walls around each room extend below the slab to footings in
undisturbed soil resulting in the same number of compartments under
the slab as number of classrooms above the slab. A section of this
type of wall is shown in Figure 2. PFE measurements made in
Nashville showed that some PFE could be achieved through one
subslab wall but not two. Unfortunately, installation of a suction
point in every other room was not sufficient to mitigate the
intervening rooms, and it is now believed that a suction point will
normally be necessary in every room in this type of school.
Obviously, this is not a recommended footing configuration for new
schools built in radon-prone areas.
In the plan shown in Figure 3, the hall walls extend through
the slab to footings, but the walls between rooms are set on the
slab. The slab under these walls are normally thickened slab
footings as shown in Figure 4. Aggregate continues under these
thickened sections; consequently, they do not adversely affect PFE.
One suction point on each side of the hall will mitigate a number
of rooms in this configuration, the number depending on other
variables which affect PFE (such as type of aggregate). A third
suction point might be needed in the hall but it is unlikely if the
rooms on each side of the hall are adequately mitigated. In this
type of structure, the bar joists for the roof are placed
perpendicular to the hall and rest on the hall walls. The walls
between the rooms do not carry any roof load and consequently can
rest satisfactorily on thickened slab footings.
Figure 5 shows a footing configuration found in three schools
mitigated by EPA. in this configuration, the walls between the
rooms go through the slab to footings but the hall walls set on
thickened slab footings. In this case, the roof bar joists are
placed parallel to the hall and rest on the walls between the
rooms. The aggregate continues under the hall for the full length
of the building; consequently, PFE can be achieved down the hall
and into the individual rooms. With this configuration, the
suction point is best put in the hall, and the number of rooms that
can be mitigated will depend on other variables (such as type of
aggregate).
The final configuration found to date, shown in Figure 6, was
used in the Two Rivers Middle School in Nashville. In this
configuration, no walls go through to footings: all sit on
thickened slab footings. This is referred to architecturally as
post and beam construction and is commonly used in buildings which
are very wide and very long, such as supermarkets. Posts on both
sides of the hall at Two Rivers go through to footings and are tied
together with overhead beams which in turn carry the roof bar
joists. The posts and beams can be either reinforced concrete as
in Two Rivers, or more commonly steel as in supermarkets. In this
configuration, the aggregate is continuous under the entire
-------
pff can reach long distances if other
ponditionsnareCproper. At Two Rivers, PFE easily extended 130 ft,
conditions are P*"°P _-i.iaated 15 ooo ft2 to less than l picocune
Tr "C\vcJu recently arranged to have a hospital
buildina under construction install a suction point in the center
of a 200 by 250 ft slab (50,000 ft') underlaid withi carefully placed
or a ^uu uy *=> ^ ,gTM #5 stone). Some time this spring,
coarse crushed aggregate (Abin wo bw / better feel
pff of this slab will be measured, and EPA will have a setter reel
for iusfhSw much PFE can be achieved under a very large slab with
optimum aggregate and a large suction pit.
SUBSLAB SUCTION PIT SIZE
The importance of the size and geometry of the suction system
under the Slab has been the subject of considerable debate and
under tne years. However, it has been the
disagreement t-hat everything else being the same, the
authors experi n ^ greater the PFE. Although this is not
t?oqimportant in houses, it becomes much more important in large
slabs such as schools.
Tn an existing school, the size that can readily be dug
In an 9 lab is about 40 in. in diameter. However,
through a Ł essentially no limit to the size of
in new construction there is essen ^ that ^
the pit which increasing effectiveness is the size of
controlling factor surrounding aggregate. With
interface between tfhe.hh°1®^s( craig) designed the suction pit
™ Thepff "ons^ied b/digging out an a?ea
shown in Figure 7. ine^e ^ suction pit is desired. Four
of about 6 ft s<| , . size are placed in a square 4 ft on
concrete blocks< a* 4*4 ft piece of 3/4-in. treated plywood,
a side and cover f the piy^ood is even
Th:Kdjr hnttom of the slab to bl poured. The aggregate is filled
with the bottom of the siaD to jj v ^ ^ intQ the hQle> ^
level with the_P^W° ' tone wm be about 30° leaving most of the
angle of reP°se of th guction ipe is installed under the plywood
hole open. The 6 1 * . to a convenient place for the riser.
as shown in Figure nossible to separate the location of the
This arrangement makes it possime uw
suction pit from that of the riser.
rtniv as a form for the slab over the hole.
The plywood serves V after setting is more than sufficient
The strength of the concrete ^ unusually high loading.
S that caas4e,Łtthhe0ls!aUbniu? need reinforcing.
Perforated pipe can a^^^fons^show®^that the Suction pit
described above. interface equivalent to about 200 ft of
has an air to aggregate ^e^face^ eq^ diameter per Uneal foot.
perforated pipe 10 n f either system will
As a result, it is planned to compare these two
be about the same. it is believed that the suction
u"s i|n Ui cant lCycheaper to'install than the perforated pipe.
-------
AMOUNT OF SUCTION APPLIED
The amount of PFE also depends on the level of suction applied
to the suction pit. The amount of vacuum which can be applied
depends on fan size and the air leakage rate from all sources into
the subslab area. Theoretically, if the subslab aggregate envelope
is completely airtight, very little air will need to be moved to
get very large PFE. The top and sides of the envelope can be well
sealed, resulting in only a small amount of air leakage. However,
the bottom of the envelope, the compacted soil under the aggregate,
has variable permeability depending on composition and compaction.
Consequently, the air infiltration into the envelope from this
source is variable. Given a choice of subaggregate conditions, the
underlayment should be made as impermeable as reasonably possible.
For a given subaggregate, the more the soil is compacted, the less
the resultant permeability. In areas where the subaggregate fill
is highly permeable, such as with sand in Florida or with near-
surface moraine in many areas, it may be necessary to overlay the
permeable material with a compacted layer of impermeable clay.
The size of the suction fan needed can best be determined
experimentally. Table 1 lists the performance characteristics of
various sizes of one commercial exhaust fan (Kanalflakt). Note
that the larger fans can achieve a higher negative pressure than
the smaller ones. One wing of the Two Rivers Middle School (15,000
ft2) was mitigated by a T3B fan which had a flow of 150 cfm at 1.97
in. WC when installed in this system. In choosing a fan size, it
is better to err on the high side rather than the low side.
SIZE AND LOCATION OF OPENINGS IN SLABS
Expansion joints, pour joints, control saw cracks, and pipe
penetrations are discussed in an earlier section. Several other
types of slab penetrations can also affect radon entry, one such
source is an open sump connected to perforated pipe installed under
the slab for groundwater protection. All sumps must be sealed in
order to keep out soil gas which may contain radon. One good
solution for this is the use of a sewage ejector pit as a sump pit
since they always have vaportight lids.
Floor drains can also be a source of radon entry if connected
to a septic system (which is rare in the case of schools but they
do exist). In this case, care should be taken in the design to
make sure that the floor drain is trapped and will always be full
of water. Lines of conventional sewer systems have not been found
to contain radon since they are tightly sealed.
If electrical conduit is routed under the slab, care must be
taken to make sure that any conduit connections under the slab are
vaporproof. The same is true for any other subslab conduit.
-------
CONCLUSIONS
Study of the architectural features, diagnostic studies, and
mitigation results for the existing schools that have been
mitigated as part of the AEERL school mitigation program has
resulted in identifying many factors which affect radon entry and
ease of mitigation. Results of these studies have led to tentative
conclusions on how to design new schools which are radon resistant
and easy to mitigate. Many of these findings can be considered as
sufficiently sound that they can be recommended for incorporation
in new school buildings. Others need field verification in schools
either currently under construction or in the design phase. Work
is underway to accomplish this in the next 2 to 3 years.
REFERENCES
r^airr a r K W Leovic, D.B. Harris, and B.E. Pyle, Radon
Diagnostics and'Mitigation in Two Public Schools in Hashyille,
2S presented at the 1990 International Symposium on
RadSn and Radon Reduction Technology, Atlanta, GA, February
19-23, 1990.
v t t a Reddv, D.F. Anderson, R. Gafgen, and A.B.
C?aiq The Effect'of Subslab Aggregate size on Pressure Field
Extension To be given at the 1991 International Symposium
of Radon and Radon Reduction Technology, Philadelphia, PA,
April 2-5, 1991.
CONVERSION FACTORS
Readers more familiar with the metric system may use the following
factors to convert to that system.
Honnatrifi Multiplied by Yields Metric
0.00047 m5s
ft 0.30 »
11, 0.093 «
HP ?-46 "
in 0.025 ¦
xn • pa
in. WC 249
-------
wall*
9ub«l*l> footlmjs
-------
Figure 3. Hall and outside walls are load-bearing.
igure 4. Section of wall resting on thickened slab footing.
-------
ZRooa w«11b
SuMltt footings
Figure 5. Walls between rooms and outside walls are load-bearing.
subtl&b footing*
Figure 6. Outside walls and posts are load-bearing.
-------
Traatad plywood ahaat
Concrata block
Sec*.'on *
Figure 7. Design for large suction pit.
TABLE 1. KANALFLAKT FAN PERFORMANCE
FAN ATR FLOW fcftnl VS STATIC PRESSURE fin. WO pIPE
MODEL
HP
RPM
0
1/8
1/4
3/8
1/2
3/4
I
1-1/2
Tl Turbo 5
1/40
2800
158
143
125
114
90
45
T2 Turbo 6
1/20
2150
270
255
235
200
180
140
110
T3A Turbo 8
1/15
2150
410
375
340
285
225
180
135
T3B Turbo 8
1/10
2300
520
500
470
445
415
310
230
200
T4 Turbo 10
1/6
2400
700
670
640
612
582
470
410
250
T5 Turbo 12
1/8
1250
900
801
718
624
557
456
359
254
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Session X:
Radon in Schools and Large Buildings -- POSTERS
-------
XP-1
DESIGN AND APPLICATION OF ACTIVE SOIL DEPRESSURTZATTHM
(ASD^ SYSTEMS IN SCHOOL BUILDINGS
by: Kelly W. Leovic, A.B. Craig, and D. Bruce Harris
U.S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Research Triangle Park, NC 27711
Bobby E. Pyle
Southern Research Institute
Birmingham, AL 35255
Kenneth Webb
Bowling Green Public Schools
Bowling Green, KY 42101
ABSTRACT
During 1990, building investigations and subslab pressure
fipld extension (PFE) measurements were made by the U.S.
Environmental Protection Agency's (EPA) Air and Energy Engineering
Research Laboratory (AEERL) in several school buildings located in
Tnlorado Kentucky, Maine, and Washington. The recommended ASD
svsllldesignfor each school was based on the construction
characteristics of each building including: subslab material and
fan selection^ subslab barriers (i.e., footings), utility tunnels,
active vs. passive soil depressurization, and interior vs. exterior
suction points.
These school research projects, together with previous
mitigation research by the authors in nearly 40 schools over the
oast few years, are discussed in terms of the influences that
various building construction features have on the design of the
ASD system. Specific examples and data for recent or on-going
research projects in Kentucky and Maine are presented.
This paper has been reviewed in accordance with the U.S. EPA's
peer and administrative review policies and approved for
presentation and publication.
-------
INTRODUCTION
School characteristics that influence radon entry and
subsequent mitigation have been discussed in previous papers on
radon diagnostics and mitigation in schools (1,2,3,4,5). The
purpose of this paper is to detail the effects of some of the more
significant school construction characteristics and how these
characteristics can influence designs of ASD systems. The ASD
systems designs should be applicable for other schools with similar
characteristics.
The school building construction characteristics discussed in
this paper include: subslab materials and fan selection, subslab
barriers (i.e., footings), utility tunnels, active vs. passive
subslab depressurization systems, and interior vs. exterior suction
points. Following a general discussion of how each building
characteristic can affect ASD system design, specific examples and
data from recent or on-going research in Kentucky and Maine schools
are presented. Conversion factors are displayed in Table 1.
This paper focuses on radon mitigation with ASD systems rather
than radon reduction through heating, ventilating, and air
conditioning (HVAC) system pressurization and/or dilution. The
authors recognize that for acceptable indoor air quality a minimum
of 15 cfm of outdoor per person should be delivered to occupied
classrooms according to ASHRAE guidelines (6) ; however, many
schools are not designed and/or operated to provide adequate
conditioned outdoor air for pressurization or ventilation and, as
a result, reduction of radon levels using an HVAC system is not a
current option without an extensive (and expensive) retrofit.
Although it is strongly recommended that such schools take the
necessary steps to meet minimum ASHRAE indoor air quality
guidelines as soon as possible, installation of a properly designed
and operated ASD system will reduce radon levels in many schools at
a relatively low cost (5).
SUBSLAB MATERIAL AND FAN SELECTION
Initial experience with radon mitigation in schools has
indicated that in schools with at least 4 in. of clean, coarse
subslab aggregate (at least 0.75 in. in diameter with few fines)
the ASD system normally requires larger fans and pipe sizes than
typical ASD systems in houses because of the greater air flow
through the aggregate (2) . However, many schools do not have
subslab aggregate and the slab may be poured over a tightly packed
material such as sand or clay.
Example - Maine School
In one school currently being researched by the EPA in Maine,
a multi-point ASD system was installed with both a conventional
radon mitigation fan and a high vacuum fan to make direct
performance evaluations between the two fans. This 1968 addition
-------
to the existing school is slab-on-grade construction with radiators
for heating and an exhaust fan for ventilation. No conditioned
outdoor air is provided to any classroom in this wing.
The wing being researched has seven classrooms, a library, and
a multi-purpose room with a storage area. Suction points were
installed in four of the seven classrooms, and two points were
installed in the library. (The multi-purpose room has a separate
ASD system.) All six suction points and overhead piping for the
classroom and library ASD system are 4 in. diameter PVC piping and
are manifolded overhead in the dropped ceiling. A suction pit
(approximately 1 ft deep and 2 to 3 ft in width) was excavated at
each point. The two fans were installed near an outside door. One
fan is a standard radon mitigation fan (0 in. WC at 520 cfm and 1
in. WC at 230 cfm) and the other fan is a high pressure, low flow
fan (3 0 in. WC at 0 cfm and approximately 5 in. WC at 3 0 cfm) being
evaluated for its applicability in low permeability soils.
Data were collected from late November 1990 through mid-
January 1991 while the high suction fan was in operation. The
suction pressure of the fan was varied to determine the effect on
radon levels. Continuous radon levels were measured in each of the
seven classrooms by State of Maine Indoor Air Program employees
using Honeywell Model A9000A monitors. Figure 1 displays the
results of the average radon levels in each classroom under the
following conditions: 1) ASD fan off, 2) fan at 1 in. WC, 3) fan at
2 in. WC, and 4) fan at 4.5 to 5 in. WC. The results show that fan
suction pressures of 1 and 2 in. WC are not sufficient to reduce
radon levels in these rooms. In fact, in some of the classrooms
levels are slightly higher with the fan operating at 1 or 2 in. wc
than with the fan off. These increases in radon levels are likely
attributed to typical variations in radon rather than any
detrimental effects caused by operating the fan at low suction
pressures.
The data for all seven classrooms in the wing are averaged in
Figure 2 for each of the four fan suctions. Radon levels averaged
approximately 7 pCi/L with the ASD fan off and with the fan at 1
and 2 in. WC. indicating little, if any, change in the three
conditions. Adjusting the fan to increase suction to 4.5 to 5 in.
WC decreased average radon levels in the seven classrooms to below
3 pCi/L.
A datalogger was installed in this school in January 1991 to
collect continuous radon, differential pressure, and temperature
data for each of the fans. These data will be part of a long-term
research project that will compare different mitigation techniques
in all three wings of this school.
SUBSLAB BARRIERS
Subslab barriers, such as below grade footings, can increase
the cost and complexity of ASD systems. PFE measurements in
schools have indicated that in many instances one suction point
-------
will be required for each area surrounded by below-grade subslab
footings. If the school has relatively permeable subslab material,
it may be possible to reach across one subslab barrier. The PFE
will need to be determined on a case by case basis for each school
(or school design if more than one school is constructed from a set
of plans). The different types of subslab barriers and their
effects on subslab PFE are discussed thoroughly in Craig's paper to
be presented at this Symposium (7).
UTILITY TUNNELS
In many slab-on-grade schools, utility lines are located below
the slab in utility tunnels that typically run parallel to the
corridor either down the center of the corridor or along the
perimeter wall of the classrooms. These tunnels vary in size from
about 1 ft wide and 0.5 ft deep to 5 ft wide and 5 ft deep (to
allow entry by maintenance workers). These tunnels may or may not
have poured concrete floors, and even tunnels with concrete floors
typically have many openings to the soil. In many classrooms with
unit ventilators or fan coil units, the piping from the utility
tunnel penetrates the slab under the unit creating a radon entry
route around each penetration. Limited studies have looked at
utility tunnel depressurization for reducing radon levels in the
classrooms above (8). Since utility tunnels are very common in
slab-on-grade schools, depressurization of the tunnels could
present a relatively easy and inexpensive mitigation technique if
no friable asbestos is present in the tunnel (because of increased
air movement), the tunnel contributes to elevated radon levels in
the room, and the tunnel is not too leaky.
Example - Kentucky School
This Kentucky school is slab-on-grade construction with the
utility lines in the wing under study located in a relatively small
tunnel that runs along the perimeter wall on each side of the
corridor. Pipes from the tunnel connect to the wall-mounted unit
ventilators in each classroom. PFE across the corridor is poor
since below grade footings are present along the corridor under
each of the interior walls. The soil under the slab is a reddish
brown clay with some rock fragments. Subslab sniffs with a Pylon
AB-5 monitor showed a wide range of levels from below 1000 to over
9000 pCi/L. The subslab radon levels in the four rooms of interest
averaged about 4000 pCi/L. A radon sniff measurement in one of
the tunnels was about 1000 pCi/L.
During the building investigation it was noted that there was
an access to the utility tunnel outdoors on one side of the
corridor. It was determined that, if depressurization of this
tunnel from the outdoors could reach into the four classrooms
serviced by the utility lines on this side of the corridor, this
would be a relatively easy and inexpensive radon mitigation
technique. (No asbestos was present in tunnel.) School
maintenance personnel covered the tunnel access with a sheet of
plywood and attached a mitigation fan to depressurize the tunnel.
-------
The results of the subslab to classroom pressure differentials are
presented in Table 2. As seen by the negative pressures measured
in the middle of three of the four rooms, this tunnel
depressuri2ation system was a very simple and effective means of
creating a negative pressure under the slab.
pre-mitigation radon levels in the four classrooms affected by
the tunnel depressurization averaged 5.3 pCi/L in June 1990, and
with the tunnel depressurization fan operating, levels in August
1990 averaged 1.8 pCi/L. Since data from school personnel indicate
that this school tends to have higher radon levels in winter than
summer, these measurements were repeated in January and February of
1991.
This school is an example of how a very simple and inexpensive
approach can sometimes be effective in reducing radon levels
depending on building design. The material costs for this system
were approximately $300 and approximately io labor hours were
required. A standard one-point ASD system installed in another
wing of the school covered three classrooms and cost $500 in
materials and required about 3 0 labor hours, not including
diagnostics.
ACTIVE VS. PASSIVE SOIL DEPRESSURIZATION SYSTEMS
Research of passive soil depressurization (PSD) in schools is
limited. Since there can be significant negative pressures to
overcome from building exhausts and the stack effect, experience
suggests that active systems are preferred to passive systems in
existing schools.
Vvample - Maine School
An ASD system was installed in the basement of a three-story
wing of a Maine school. Each floor of this wing is about 3000 sq
ft in area, and the basement is about 4 ft below grade. N°
building design drawings were available to provide information on
subslab fill or footings^ although excavation of the suction pits
indicated that the material under the slab is mostly fine-grained
sand. The basement contains occupied classrooms, and in the 1000
sq ft area affected by the ASD system, HVAC is provided by ceiling
mounted unit ventilators. Inspection of the unit ventilators
indicated that they were not operated to bring in outdoor air. ^
vertical ventilation shaft runs from the basement to the roof and
is a likely contributor to the stack effect in this three-story
building. It was thought that this building might present a good
opportunity to compare PSD and ASD because of the building height*
Subslab PFE measurements made in the basement with the ASD fan
on and off. Subslab pressures were measured at the 2 suction
points, and at 11 test holes distributed throughout an area of
about 1000 sq ft. As seen in Figure 3 and Table 3, although
negative subslab pressures can be achieved at the suction points
with PSD, this negative pressure does not extend to any of the test
-------
holes within the 1000 sq ft area. When the fan is activated (to
Pressures of about -2.5 in. WC at the suction points) the negative
Pressure field extends throughout the area to points that were
Positive with PSD.
PSD needs merit further study in new schools where it is known
that the slab is underlain with a layer of clean, coarse aggregate;
however, these results, together with previous experience in house
mitigation, indicate that its applicably will be very limited in
existing schools. Because of the reliability and effectiveness of
ASD in consistently reducing elevated radon levels (even when
ne9ative pressures in the building are caused by building exhausts
and the stack effect) it is recommended over PSD in existing
schools.
INTERIOR VS. EXTERIOR SUCTION POINTS
Radon mitigation research in slab-on-grade houses in Ohio has
shown generally comparable results for ASD points placed inside the
house and exterior to the house; however, it was found that
interior points were preferable in the larger houses (9) .
Evaluation and comparison of PFE results in schools with both
interior and exterior ASD points is limited. In schools where
accessibility totheclassroom interior is limited (e.g., due to
chalkboards), placement of exterior ASD points needs to be
investigated for effectiveness.
^Karnple - Kentucky School
. In another wing of the Kentucky school discussed above (in
utility Tunnels section) suction was applied in a teachers lounge
that was located between two classrooms (Nos. 2 and 3) . The results
PFE measurements in classrooms 2 and 3 are shown in Table 4.
Results indicated that PFE was relatively good. To compare these
PFE results with suction applied from the exterior, a hole was
drilled from the exterior of Room 3 to the subslab area.
suction applied at this exterior point, no effect was apparent at
the test hole located in Room 3, compared to a pressure of -0.016
ln« WC when suction was applied to the interior point. As a result,
school officials chose to install an interior ASD point in the
teachers' lounge to mitigate Rooms 2 and 3 and the teachers'
lounge.
Pre-mitigation radon levels in Rooms 2 and 3 and the teachers'
lounge averaged 8.2 pCi/L in June 1990. With the ASD system
operating, levels in August 1990 averaged 1.3 pCi/L in Rooms 2 and
3- (No data are available for the teachers' lounge.) These
Measurements were repeated in January and February 1991.
The comparison of PFE for interior and exterior suction points
in this school indicates that interior suction produces a much more
effective pressure field under the slab. The area of the three
rooms is approximately 2100 sq ft (the size of a large house) so
these results are somewhat consistent with previous house data (9) .
-------
Future research should repeat these measurements in additional
school buildings, particularly in those with clean, coarse
aggregate under the slab.
CONCLUSIONS
1. In the Maine school with low permeability material (sand)
under the slab, a higher suction fan was required in order to
adequately depressurize the subslab area and reduce radon levels.
2. Results from the Kentucky school show that utility tunnel
depressurization may be an effective and relatively inexpensive
technique for reducing elevated radon levels if the tunnel does not
contain asbestos, is a contributor to elevated indoor radon levels,
and is not too leaky.
3. Since there can be significant negative pressures to overcome
from building exhausts and the stack effect, previous experience
and the measurements in the Maine school suggest that active
subslab depressurization systems are typically preferred to passive
systems in existing schools.
4. in the Kentucky School studied, pfe was greater when suction
was applied to an interior point rather than from the building
exterior. Interior vs. exterior PFE should be researched in
additional schools, especially those with clean, coarse subslab
aggregate.
REFERENCES
1. Fisher, E., F. Blair, T. Brennan, and W. Turner, The school
evaluation program. Presented at the 1990 International
Symposium on Radon and Radon Reduction Technology, Atlanta,
February 1990.
Leovic, i A. B.Craig, and D. w. Saum, Characteristics of
schools with elevated radon levels. in: Proceedings of the
1988 Symposium on Radon and Radon Reduction Technology, EPA-
600/9-89-006a (NTIS PB89-167-480). March 1989. gy'
Leovic, K.W., A. B. Craig, and D. W. Saum, Radon mitigation in
schools. American Society of Heating, Refrigerating and Air-
1990 jr"o-45gineerS' InC* JOUrnal* Vol« 32' No- January
°'B' Harris- Radon diagnostics
for schools. Presented at the 83rd Air and Waste Management
Association Annual Meeting, Pittsburgh, June 1990.
U.S. Environmental Protection Agency. Radon reduction
techniques in schools - interim technical guidance. U.S. EPA
?p^^^?!fio!n,enr?lr\nClii6Ve:Lopnent and Radiation Programs.
EPA 520/1 89—020 (NTIS PB90-160086). October 1989.
-------
6. ASHRAE 1989. Ventilation for acceptable indoor air quality.
Standard 62-1989. American Society of Heating, Refrigerating
and Air-Conditioning Engineers, Inc., Atlanta, 1989.
7. Craig, A.B., K. W. Leovic, and D. B. Harris, Design of radon
resistant and easy-to-mitigate new school buildings. To be
presented at the 1991 International Symposium on Radon and
Radon Reduction Technology, Philadelphia, April 1991.
8. Leovic, K.W., A. B. Craig, and D. W. Saum, Radon mitigation
experience in difficult-to-mitigate schools. Presented at
the 1990 International Symposium on Radon and Radon Reduction
Technology, Atlanta, February 1990.
9. Henschel, D.B., A. G. Scott, A. Robertson, and W. 0. Findlay,
Evaluation of sub-slab ventilation for indoor radon reduction
in slab-on-grade houses. Presented at the 1990 International
Symposium on Radon and Radon Reduction Technology, Atlanta,
February 1990.
ACKNOWLEDGMENTS
The authors would like to express their appreciation to all
the school officials who have graciously permitted them to conduct
measurements in their school buildings.
-------
TABLE 1. METRIC CONVERSION FACTORS
Non-Metric
cubic foot per minute (cfm)
foot (ft)
inch (in.)
inch of water column
(in. WC)
picocurie¦per liter
(pCi/L)
square foot (sq ft)
TABLE 2.
Location.date
Pit at Fan Base,6/90
Center Room 19,6/90
Center Room 17,6/90
Center Room 19,7/90
Center Room 14,7/90
Tiroes
0.47
0.305
2.54
248
37
0.093
0 -0.007
15 -0.001
45 0.000
15 -0.001
105 0.000
Yields Metric
liter per second
(L/s)
meter (m)
centimeters (cm)
pascals (Pa)
becquerels per
cubic meter (Bq/m3)
square meter (m2)
. WC)
-0.750
-0.045
-0.028
-0.030
-0.003
SUBSLAB PRESSURES WITH TUNNEL FAN OFF AND ON
Distance (ft) Fan Off fin, wr) Fan On fin
Subslab pressures were not measured in iC ,,
Rooms 14 and 17). Ro°® 15 (located between
-------
TABLE 3. SUBSLAB PRESSURES WITH ASD FAN OFF AND ON
Location Fan Off (in. WC) Fan On (in. WC)
Suction Point l -o.oio -2.53
Suction Point 2 -0.012 -2.52
Test Point Fb 0.012 -0.010
Test Point Fc 0.009 -0.038
Test Point Fd 0.003 -0.019
Test Point Fe 0.005 -0.015
Test Point Ff 0.001 -0.005
Test Point Fg 0.002 -0.005
Test Point Fh 0.006 -0.017
Test Point Fi 0.002 -0.339
0.005 -0.016
0.003 -0.024
0.000 -0.156
Test Point Fj
Test Point Fk
Test Point Fm
TABLE 4. PFE MEASUREMENTS FROM SCHOOL INTERIOR
Location 'in- WC) Suction On (in. WC)*
Room 2 -0.002 -0.010
llZ 3 -0.000 -0.016
* Suction applied in teachers' lounge located between
Rooms 2 and 3.
-------
ROOM NUMBER
ES FAN AT 1 IN. EZ3 FAN AT 2 IN
l>0;: 3 FAN AT 4.5 TO 5 IN
ASD OFF
FIGURE 1. Comparison of radon levels at various fan pressures.
ASD OFF FAN AT 1 IN. FAN AT 2 IN. FAN AT 4.5-5 IN
FAN SUCTION
FIGURE 2. Comparison of average radon levels at various fan pressures.
-------
N
4
Fg
(+0.002/—0.005)
(+0.001/—0.005)
Fh
( + 0.006/—0.01 7)
Fj
(+0.005/-0.01 6)
(+0.002/-0.339)
SHELVES
Fm
(0.000/-0.156)
A13 VENT^
(+0.003/-0.024)
\ X
Fe (+0.005/-0.015)
Fd (+0.003/-0.019)
SUCTION POINT §2
C—0.012/—2.52)
SUCTION POINT #1
(—0.010/-2.53)
Fb (+0.012/—0.010)
FC (+0.009/—0.038)
BOYS'
RESTROOM
Figure 3. Results of PFE measurements in Maine school
(in. WC fan off/in. WC fan on).
-------
XP-2
RADON IN LARGE BUILDINGS:
PRE—CONSTRUCTION SOIL RADON SURVEYS
by: Ralph A. Llewellyn
Department of Physics
University of Central Florida
Orlando, FL 32816
ABSTRACT
Attempts to correlate individual soil radon and/or radium
concentrations with the subsequent concentrations of radon measured
in structures constructed on the sites of the tests have had only
occasional, or perhaps even coincidental success. High
concentrations in the soil may or may not result in elevated levels
in buildings, and vice versa. over the past two years the UCF
Radon Project has been conducting an intensive radon screening of
all buildings (>40) on the campus, a relatively compact
concentration occupying about 300 acres of a 1200 acre site.
Analysis of these data suggest that perhaps the earlier-
difficulties in obtaining correlations between soil radon/radium
measurements and radon concentrations in structures has been simply
a failure to measure at a sufficient number of locations for a long
enough duration. A contour 'map1 of average radon concentrations
in the campus buildings was used as a guide for measuring soil
radon for periods of several months in the areas where the
construction of three large new buildings was Dlanned. The results
were used to predict the levels that to be expected an completion
and to suggest appropriate radon-resistant construction measures.
Two of the structures incorporating such suggestions are now under
construction.
-------
INTRODUCTION
UCF RADON PROJECT
In mid-1989 the environmental physics group at the University
of Central Florida initiated a research program with objectives
that included learning more about the distribution of radon
concentrations in large buildings and discovering reliable methods
for predicting the potential for radon diffusion into large
buildings that might be constructed on particular sites. (1) The
results of work directed to the first of these objectives,
presented at the 1990 International Symposium on Radon and Radon
Reduction Technology, revealed that radon concentrations often do
not decrease nearly as rapidly as would be expected from standard
diffusion theory as one moves upward in large structures,
suggesting that protocols for guiding radon measurements in large
buildings should call for similar sampling rates, at least through
the first 5 or 6 floors.
Work on the second of these objectives was conducted
throughout 1990 using the construction sites of three major
buildings on the University's main campus as "laboratories". The
concentration of radon in the soil gases at measured over a period
of several months at several locations on each site and soil
samples were collected for radium assay. All three buildings, an
87,000 ft2 fieldhouse, a 60,000 ft2 art complex, and a 90,000 ft2
student center, are now under construction. In each case the final
design and/or construction techniques used incorporated features
and methods intended to respond to the degree of potential radon
hazard at the site.
SOIL GAS RADON STUDY
SAMPLING PROCEDURES
Radon
Radon gas in the soil was collected at each measurement
location using standard EPA-type charcoal canisters (F&J Specialty
Products, Inc. model RA40V). At each location a sampling station
was installed to hold the canisters in clean, reproducible
positions. A typical installed sampling station is shown in cross-
section in the Appendix.
Each canister was exposed for approximately 72 hours.
Preparation and subsequent measurement of the canisters conformed
to protocols established by the U. S. Environmental Protection
Agency in "EERF standard operating procedures for Rn-222
measurement using charcoal canisters" (520/5-87-005). Analysis of
the radon concentration of each canister was performed in the UCF
Department of Physics using a research quality nuclear radiation
analysis system. The system was regularly calibrated with a
standard radon source whose activity is traceable to a National
Institute of Standards and Technology primary standard.
-------
Radium
Four soil samples were taken at the site of each sampling
station, one each at the surface and at one foot depth intervals
as the holes for installing the stations were dug. The purpose was
to analyze the soil for 22<5Ra, the parent radioisotope of "2Rn, in
order to obtain information regarding the possible origin of any
radon gas that might subsequently be detected at the site.
Analysis of the radium in the soil samples is based on measuring
the eguilibrium activity of radon. The same calibrated nuclear
radiation counting system is used as is employed for the analysis
of the charcoal canisters. Preparation and analysis of the soil
samples involves, among other things, a 20-day holding period for
the sealed sample holder in order to allow time for the
establishment of eguilibrium between 226Ra and 222Rn. For that
reason and because the available time on the nuclear radiation
measuring system was fully taken by soil gas radon measurements
most of the soil samples have yet to be analyzed for 226Ra. The
long half-life of that isotope ensures that the analyses, when
performed, will not be adversely affected by the several months of
soil sample storage time. The very high radon concentrations
measured on the east half of Pegasus Circle make radium
concentration measurements of soil samples from that area very
important. Radium concentrations in the soil will be the subject
of a separate report.
SITES
Pegasus Circle
Six sampling stations were established and operated within
Pegasus Circle, the planned location of the new student center
facility. These sites are shown on the diagram below and detailed
in Table 1.
Pegasus
Circle
94
o
o 90
+
\
O
Q
O
95
91
93
N
Benchmark
(campus center)
-------
Table 1. Pegasus Circle Site
Sampling
Station
Location
90
91
93
94
95
96
10 m north (0°) of campus center benchmark
30 m west (270°) of campus center benchmark
30 m east (90°) of campus center benchmark
60 m east (90°) of campus center benchmark
90 m east (90°) of campus center benchmark
92 m northeast (45°) of campus center benchmark
Fieldhouse
Three sampling stations were operated at locations adjacent to
the construction pad for the fieldhouse. They are shown on the
diagram below and detailed in Table 2.
©
71
70 © 4.
Benchmark
(#1 70 54)
Construction
Pad
o 72
FIELDHOUSE
Table 2. Fieldhouse Site
Sampling
Location
Station
70
6.2 m west (270°) of benchmark #1 (70 54)
71
48 m from benchmark #1 at 49.6° E of N
72
126 m from benchmark #1 at 9° S of E (99°
Art Complex
Four sampling stations were established and operated around
the construction site of the art complex. Their locations are
-------
shown in the diagram and detailed in Table 3.
83
82
ART
COMPLEX
+-
o 81
N
f
80
+
Table 3. Art Complex
Sampling
Station
Location
80
81
82
83
125 m § 11° W of N from —=======
120 m @ 69° E of N fTom siteCh™arlc (N101200,E6800)
55 m § 48' W of N frrvm L ^ 0
60 m § 63° W of n from site 82** (N101850'E7°00
NOTE: The sampling station numbers in the diagrams and in Tables
1, 2, and 3 are identifiers used by the database UCF RADONBASE.
RESULTS
The graphs that follow record the radnn *. •
measured in the soil gas since the commencement of the stud^uitil
its conclusion at each of the sampling stations assnpiaf0H ^
three construction sites identified above. (5)in reviewing ty,*
graphs, note that the EPA maximum concentration for buTidTŁr« !f
pCi/€. The graphs for each construction sitem ?g J? 4
in the order (1) Pegasus Circle, (2) Fieldhon<^L and *S5
Complex. Preceding the graphical radon concentrat-ion d'cni t
each sampling station at the fieldhouse and art cQniniflY\LrIS'
composite graph of the data from all associated <=* * there is a
that enables comparisons of the radon levels at- t-h ^ in^ -S ml?s
results from the Pegasus Circle sampling st M ^hat location. The
two composite displays, one showing the d **11 ?? ln
stations where the higher concentrations of raH rom e ^ e®
a second containing data from the statW TVS?**? &nd
concentrations. °ns that had the lower
-------
50.0
CL
Site 90
Site 91
2 20.0 -
Ld :
Site 95
10.0
0.0
100
150
50
DAY NUMBER
Figure 1 SOIL RADON CONCENTRATION Pegasus Circle Low Concentration Sites February 1 - July 31, 1990
-------
300.0 n
Q_
200.0 -
Site 94
W 100.0 -
Site 96
Site 93
0.0
t—i—i—|—r
50
t—i—r
i—i—i—i—r
T
T
100
50
DAY NUMBER
Figure 2 SOIL RADON CONCENTRATION Pegasus Circle High Concentration Sites February 1 - July 31 1990
-------
10.00
8.00
Q.
Z
o 6.00
Site 71
Site 70
77 4.00
Ld
2.00
Site 72
0.00
IT
0 10 20 30 40 50
DAY NUMBER
Figure 3 SOIL RADON CONCENTRATION Field House March 15 - April 30 1990
-------
25.00
Q_
10.00
LjJ
O
Site S3
Site 82
Site 81
5.00
Site 80
cr
0.00
30
40
50
DAY NUMBER
Figure 4 SOIL RADON CONCENTRATION ART COMPLEX June 15 - July 31, 1990
-------
The radon concentration measurements at each site show both
the short term effects of rainfall and the longer term effects of
soil moisture. Heavy rain appears to quickly "wash" radon out of
the soil, probably owing to the solubility of the gas in water and
the rise of the water table following rainfall, which may partially
block migration of the gas in the soil. The concentration soon
returns to or even above pre-rainfall levels, however, and does so
more quickly than could be accounted for by the re-establishment of
secular equilibrium with radium in the soil. This effect can be
seen very clearly in the composite graph of radon concentrations at
the art complex site. Note, in particular, the period around Day
22.
The slow downward trend of the radon concentration at some
stations may be associated with a gradual average decline in soil
moisture over the 1990 spring and summer. This suggestion is based
only on field observations, however, and is not the result of soil
moisture measurements.
While not a part of this particular project, the Pegasus
Circle area would provide an excellent region for conducting
research on the transport of radon in the soil and the effects of
rainfall, soil moisture, wind speed and direction, and atmospheric
pressure on it. The establishment of a set of sampling stations
associated with an automated weather station in Pegasus Circle for
long-term study of this interaction is a goal of the UCF Radon
Project.
WORK IN PROGRESS
Based on what appears to be effects on soil radon
concentration arising from rainfall, changes in soil moisture,
atmospheric pressure fluctuations, and surface wind speed an
direction, the next phase of the project will involve searches for
correlations between those parameters and radon concentration in
the soil gas. The results of this work will be presented at future
meetings.
CONCLUSION
The results presented above suggest that earlier difficulties
in obtaining correlations between soil radon/radium measurements
and radon concentrations in structures subsequently built on the
sites tested may in part be due simply to a failure to measure at
a sufficient number of locations for a long enough period of time.
Better data should more informed radon-protection strategies in the
design and construction of large buildings.
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and, therefore, the contents do not
necessarily reflect the views of the Agency and no official
endorsement should be inferred.
-------
REFERENCES
Llewellyn, R.A. UCF Radon Project: Main Campus Screening
Report (unpublished draft) University of Central Florida,
Orlando, Florida 1989.
Ronca-Battista, M., Magno, P., Windham, S., and Sensintaffar,
E Inerim indoor radon and decay product measurement
protocols. EPA 520/2-86-04, U.S. Environmental Protection
Agency, Washington, D.C., 1986. 50 pp.
Ronca-Battista, M., Magno, P., and Nyberg, P. Interim
protocols for screening and followup radon and radon decay
product measurements. EPA 520/1-86-014, U.S. Environmental
Protection Agency, Washington, D.C., 1987. 22pp.
Gray, D. and Windham, S. EERF standard operating procedures
for radon-222 measurement using charcoal canisters. EPA
520/5/87-005, U.S. Environmental Protection Agency,
Montgomery, Alabama, 1987. 30 pp.
Llewellyn, R.A. UCF Radon Project: Radon Analysis of Soils at
UCF Construction Sites, Report No. 3 (unpublished) University
of Central Florida, Orlando, Florida, 1991.
-------
XP-3
RADON MEASUREMENTS IN NORTH DAKOTA SCHOOLS
By: Thomas H. Morth
Arlen L. Jacobson
James E. Killingbeck
Terry D. Lindsey
Allen L. Johnson
North Dakota State Department of Health
and Consolidated Laboratories
Division of Environmental Engineering
1200 Missouri Avenue
P.O. Box 5520
Bismarck, ND 58502-5520
ABSTRACT
Through the Environmental Protection Agency's State Indoor
Radon Grant (SIRG) Program, the State of North Dakota conducted a
survey for the presence of radon in schools throughout the state,
from January to April of 1990.
Two main reasons for undertaking this project were:
1. Elementary and secondary school students' theoretically
higher risk from exposure to radon and its progeny;
2. Results of the 1988 state-wide random survey showed 63% of
the homes tested as having screening measurements greater
than or equal to 4.0 pCi/1, suggesting radon's presence in
other types of structures.
The results of this school survey revealed that 6.1% of the
rooms tested had radon levels greater than or equal to 4.0 pCi/1,
differing from the residential survey by a factor of ten.
The position is advanced that this survey is representative of
schools in the upper midwest and that its data will be important in
developing testing, diagnosis, and mitigation protocols in schools
and larger public buildings.
This paper has been reviewed in accordance with the U.S.
Environmental Protection Agency's peer and administrative review
policies and approved for presentation and publication.
-------
BACKGROUND
in the winter and spring of 198, the North Dakota State
Department of Health and Consolidated Laboratories (the
Department), in conjunction with the Environmental Protection
Aaencv (EPA) undertook a state-wide residential radon survey,
ills holes 'were measured with two-day charcoal canisters An
average concentration of 7.0 picocurres of radon per liter of
^ ? ^,nri /l) was recorded, with 59% of these homes
4.0 - 20.0 pCi/1 range, and 4% having
20.0 pCi/1 or greater.
These results indicated a potential for high radon levels
throughout the state, with 51 of 53 counties reporting 25% or
greater of home screening measurements at or above the EPA action
level of 4.0 pCi/1 (Figure !)•
These screening measurements were confirmed by analysis of
year-long alpha-track detectors placed m addition to the charcoal
canisters in 175 of the above homes. 47.4% of these homes had at
least one alpha-track result above 4.0 pCi/1.
North Dakota 1988 Random Survey
% > 4 P C / I. I | 0 - 2 4 L-'-y'l 2 5 - 4 9
II I I I H g O 74 ¦¦§ 7 5 10
Figure l.
-------
Given these results, and the potentially more harmful effects
of radiation from radon and it's progeny on younger people, it was
decided to explore cumulative exposures to children based on where
the majority of their time was spent in addition to that spent in
their homes, notably their schools. A grant deviation was applied
for and approved by EPA to enable screening measurements to be
performed this past testing season rather than delay the study
another year. This led to the Department conducting a state-wide
radon in schools survey in the winter/spring of 1990 under an EPA
State Indoor Radon Grant (SIRG).
STUDY DESIGN
Since the residential state-wide survey was conducted using
48-72 hour charcoal canister screening measurements, it was decided
to be consistent with this approach for the initial testing in
schools. The canisters were to be EPA style, cylindrical open-
faced of the same testing window duration. For consistency, one
vendor to supply and analyze the canisters was to be chosen. Other
criteria for a vendor included: being listed in the EPA Radon
Measurement Proficiency Program (RMP) and having the capacity to
analyze up to thousands of canisters within a meaningful amount of
time.
Bids were submitted by approximately 20 prospective vendors.
The contract was eventually awarded to Home Radon Detection, Inc.
(HRDI), whose bid allowed the purchase and analysis of over 7,000
canisters by funds allocated under the SIRG. Terms of the contract
called for the solicitation of schools for participation in the
survey by the Department. The Department was to analyze the
testing plan submission by the schools for correct room placement,
number, control and duplicate canisters, etc. An approved plan
would then be returned to the school showing approved test room
locations. The vendor was then notified as to the address of the
school and the number to be sent to that address. After testing,
the canisters would be returned postage-paid directly to the vendor
for analysis. Results of this analysis were to be furnished to
both the school and the Department.
Since the clientele to be solicited for this survey do not
normally fall exclusively under the jurisdiction of a health
agency, the State Department of Public Instruction was notified and
informed of the proposed project and given the opportunity to be
the lead agency, as a matter of professional courtesy. They
declined this, and provided the Department with all school district
contact individuals and mailing addresses. At that time, December
1989, the number of public and private school districts numbered
approximately 350 for the entire state.
-------
It was decided to contact school districts and make the
district responsible for the individual schools within that
district, rather than us contacting each individual school. This
was a far more efficient method, as many districts had a
considerable number of school buildings, and worked within the
normal educational chain of informational flow.
METHODOLOGY
SOLICITATION
All 350 school districts within the state were contacted by
mail and offered the opportunity to participate in the survey.
There was no cost to the districts for this program as it was under
the SIRG, 75% federal and 25% state-matching funded. However,
since school testing was and is not mandated under North Dakota or
federal regulation, only 130 districts submitted applications for
testing under the 1990 grant year.
In September 1989, at a school administrator's conference, the
Department made a radon presentation and included a copy of the EPA
publication "Radon Measurements in Schools - An Interim Report" in
the informational packet for each attender.
This publication was referenced in the application packet sent
to each school district; pertinent sections related to testing were
duplicated and included as part of the packet. Other enclosures
were:
Individual school information sheets (Form 1).
Summary district application form to be dated and signed
by a district official (Form 2).
Instructions on completing the above two forms.
A sample completed application.
As part of the application, floor plans of all levels of all
school buildings to be tested showing proposed test locations were
requested.
REVIEW
Current EPA school testing protocols call for testing in all
frequently used rooms at or below ground level. Ten percent of
these rooms were to be tested with duplicate canisters; an
additional five percent of canisters were to be set aside as
controls. To maximize the radon levels obtained under screening
measurements, it is also suggested the testing be performed during
periods of relative inactivity, such as over a weekend. The
Department followed these protocols with the following exceptions:
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Testing in rooms or areas of high humidity such as bath
or locker rooms was strongly discouraged due to the
effects of moisture on canister analysis accuracy;
To maximize the number of tests to be performed under the
grant, not all support rooms, such as offices,
conference rooms, etc., were tested, but a represent-
ative sampling thereof - virtually all classrooms
were tested, however - this was felt to be a more
critical area of concern;
These protocols call for placement of a canister for
every 2,000 square feet of area in an "open-
classroom" school or gymnasium. In this survey,
canister placement in gymnasiums was often for areas
of greater than 2,000 square feet.
A two stage, primary and secondary, review process was
performed on each application. If more information or
clarification was needed, the district official was contacted by
mail or phone. Upon approval, written notification to the district
was provided along with approved floor plan showing test locations
and room summary enclosures. At this time, the vendor (HRDI) was
also notified and given the district contact, mailing address, and
total number of canisters to be delivered.
Care had to be exercised so as to time the approval of schools
so that the number of canisters to be analyzed would not exceed the
capacity of the vendor. This technique was negated to some degree
by the school districts not testing as soon as possible after
receipt, but waiting until the "perfect" testing weekend.
Canisters were therefore delayed in being sent to some schools
until "outstanding" ones were returned for analysis.
RECORD MANAGEMENT
To maintain a quality assurance program, the vendor was not
informed as to which canisters were duplicates and controls until
after analysis. The Department sent separate quality assurance
forms to each district for each school, to be returned to the
Department upon completion of testing, listing canister numbers and
locations of controls and duplicates. This procedure established
an accounting redundancy between the Department, the schools, and
the vendor.
Upon receipt of results from the vendor, data was input to
personal computers utilizing a dBASEIV software system. Rationale
for database structure was one main district record; multiple
schools per district; and multiple results per school.
-------
Radon results were further broken down by the type of room use
cateqory and organized in such a manner that results for a
particular category could be split and analyzed separately. This
was done to allow for the theoretically variable harmful effects of
radon based on age of incidence of exposure. It is, therefore,
beneficial to know whether a particular classroom was in a primary
or secondary school.
RESULTS
Due to widely variant climatic extremes within North Dakota
all buildings, including schools, are well insulated, well sealed'
and generally energy efficient. Some of the schools tested during
this survey were constructed around the time of admission to
statehood, in 1889, while others were built within the past year.
A wide range of construction styles and techniques are, therefore,
encompassed. The majority of existing school structures appear to
be slab-on-grade or "ranch" style, primarily to achieve lower
construction costs and to allow for handicapped accessibility.
130 out of the 350 school districts participated in the 1990
school survey; however, virtually all of the larger districts did
so. It is estimated that radon exposures to 50% of the state's
students were analyzed. In these 130 districts, 273 buildings were
tested. Out of 7,011 approved test locations in these 273
buildings, 6,983 canisters were placed and analyzed - a rate of
99.60 %.
Results showed mean levels to be considerably less than those
discovered for residences - less than 2.0 pCi/1 for any room use
category - resulting in a extremely skewed distribution to the
lower end of the scale. These results are further delineated in
Tables 1, 2, and 3.
Table
1. Canister Use
Control canisters
Duplicate canisters
Room canisters*
Basement 156
1st Floor 5,896
Total
323
608
6,052
6,983
(323/6052 -
(608/6052 =
5.34%)
10.05%)
* Definitive rooms or
2,000 square
feet of floor
area.
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Table 2. Placement
and Results
by Room Category
Room category
Number
% of
Number >
% of room cat.
6052
4.0 pCi/1
> 4.0 pCi/1
Classrooms:
Elementary
1,981
32.7
137
6.9
Secondary
1,856
30.7
94
5.1
3,837
231
Support rooms:
General*
426
7.0
22
5.2
Physical Ed
32
0.5
4
12.5
Kitchen
204
3.4
12
5.9
Lunchroom
128
2.1
6
4.7
Lounge
185
3.1
12
6.5
Library
192
3.2
11
5.7
Office
581
9.6
43
7.4
Multi-purpose
119
2.0
8
6 . 7
Gymnasium
348
5.8
20
5.7
2 .215
138
Totals
6,052
100.1
369**
* General
support rooms include: conference, counselor,
bath, auditorium, locker,
apartment, custodial,
storage
, etc.
in pCi/1
** Results
(x)
of 6,052
rooms
X
< 4.
0
5,683
93.90%
4 .
0 <
x < 20.0
363
6.00%
X
> 20
.0
6
0. 10%
66.2 pCi/1
was the highest
measurement.
74 districts (74/130
= 56.
9%) had at least one test
result
> 4.
0 pCi/1.
102 buildings (102/273 = 37.4%) had at
least one test
result
> 4.
0 pCi/1.
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Table 3. Statistical Analysis
Room
Category
Number*
Arith
Mean
Arith
Std Dev
pCi/1
Geom
Mean
pCi/1
pCi/1
Total
Elem class
Sec class
Support
6,660
2 ,206
2 , 068
2 , 386
1. 53
1.61
1.40
1.58
1.95
1. 56
1 .96
2 . 24
0 . 98
1.04
0 . 87
1.01
* Including duplicate canisters, but not controls.
School districts were sent results by the vendor soon after
project completion. Confirmatory correspondence was also sent to
each district, listing the schools, and the rooms within the
schools that had screening measurement results > 4.0 pCi/1.
Procedures were referenced from "Radon Measurements in Schools";
additionally, the Department recommended retesting at 5 - 10 year
intervals and following school building remodeling or additions.
No mitigation was recommended at this stage, but rather
confirmatory testing for rooms with screening measurements > 4.0
pCi/1. Suppliers of alpha-track detectors were listed in the
Department's letter along with the statement that there was
currently no funding anticipated for this follow-up testing under
future state grants.
In participatory studies such as this, a great deal of trust
must be placed in the personnel on site to properly place
canisters, record data, and maintain qualitatively and
quantitatively effective sampling techniques. Placement of the
canisters in this study was performed by administrators, building
superintendents, selected educators, and school science clubs.
The Department was available to answer questions from the
project inception until its conclusion, greatly reducing the number
of errors that inevitably occur. The high analysis percentage
(99.6) is indicative of this effort.
EVALUATION
RESULTS
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METHODOLOGY
The following are ways in which it is thought the survey could
have been run more effectively:
1. In addition to the sample completed application forms,
it would have been illustrative to include a sample
floor plan showing correct canister placement.
2. Consistency between the approved test locations and
their identity on the vendor analysis forms should
have been stressed. Oftentimes a room was identified
by number (101, 102, etc.) or use (Math, English,
etc.) and then reported by educator (Ms. Smythe, Mr.
Johnson, etc.).
3. Some extraneous information was asked for on Form 1.
The total number of classrooms in a school was
requested, not just those at or below ground level.
This was asked to get an idea of the construction
style of a building, but this could be inferred from
the floor plans we requested. This data was also
thought to have informational value in the event a
school chose to conduct optional testing. While this
would have been useful, this Form would not appear to
be the appropriate place to bring up the point of
optional testing. Questions 3, 5, and 7 on Form 1
could therefore have been eliminated.
4. A split on Form 1 between class and support rooms
was asked for without a great deal of delineating
criteria. Some additional definition would have been
helpful.
5. Some school officials took the protocols for testing
in all frequently occupied rooms literally, and
submitted plans showing placement in all areas, in-
cluding closets, storage, boiler rooms, etc. A list
of types of rooms not to test would have been helpful.
6. Testing of some schools did extend into April, which
even in North Dakota is at or beyond the end of the
heating season. This was brought about by the earlier
noted tendency by some school officials to wait for
the "perfect" weekend, delaying the entire queue, and
by the timing of the grant approval after the first of
the year, so that the survey began somewhat advanced
into the testing season. Starting the SIRG programs
at the beginning of the Federal fiscal year
(October 1) would help to increase the length of the
testing season as opposed to delaying a study until
the beginning of the next school year.
-------
7 Some school officials were reluctant to sign the
summary application Form 2 as they were unsure as to
what thev were committing to by signing. Form 2
Should have stated that they were agreeing to follow
the protocols for screening measurements only.
R North Dakota has an open records law; the results of
*nv school would be open to examination by anyone,
romoromising the implied confidentiality between
the Department and the school district. The policy
was to refer questions on results to the district,
hut if pressed, the Department would have had to
release them. A statement on the application summary
form to this effect would have explicitly stated this
position and avoided future misunderstandings.
CONCLUSIONS
There would appear to be an anomaly between the results of the
residential state survey and the radon in schools survey. The
initial assumption was that much higher levels oŁ radon would be
found in the schools and that more rooms would have been identified
as being above the action level. A variety of reasons may have an
effect on this situation:
1 School rooms generally have a larger volume than
residential rooms.
2 School rooms are generally better ventilated as a
result of increased traffic and more effective HVAC
(Heating, Ventilating, and Air Conditioning) systems.
3 Whereas it is estimated that 95% of all homes in North
Dakota have basements1, the majority of schools in the
state appear to be of slab-on-grade construction.
Only 156 tested rooms (156/6052 = 2.6%) were basement
rooms. Of these 156, 16 (10.3%) had levels greater
than or egual to 4.0 pci/l.
In Mav 1990, an EPA diagnostic/mitigation team headed by Mr.
Fisher Washington D.C., examined three Minot, North Dakota
schools where elevated levels had been indicated by the SIRG
qrreenino measurements. Diagnostic work was linked to a possible
correlation between elevated radon levels and elevated C02 levels
'thin the rooms in question. Mitigation recommendations were made
Ti the individual schools by this team. HVAC supply-exhaust air
flow adjustments were recommendations common to all schools.
i g environmental Protection Agency, Radon-Resistant
Cgnstructiga (EPA/600/8-88/087 July 1988), p. 4.
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FUTURE ACTIONS
To continue the logic behind the impetus for school testing,
future grant applications will be directed toward completion of
screening measurements in schools and licensed day care centers
across the state. Confirmatory measurements were recommended to
schools prior to potential mitigation. These results will be
illustrative in determining the actual exposure to students and
young people from radon gas.
-------
references
n s Environmental Protection Agency,
1. RMon-R^^n-^^g§fi;20/i:87-2 0, 1987.
Washington, D.C., E?A 52U/
¦r, Qrhools - An interim _Re&ort, U.S.
2. RaciojiJ^yLyiL^ Aqency, Washington, D.C.,
Environmental Protection
EPA 520/1-89-010, 1989.
• lrntial New Construction, U.S.
3. gton, D.C.,
Environmental Prot®^OQ
EPA/600/8-88/087, 1988.
s b Hoffman, M., Alexander, B.,
4. Bergsten, J., White, • g^.anSorl/ s., and Kooyman, C.
Holt, N., Pantulla, ^don Assessment Program, Volume II.
Support of the State Triangle institute, Research
RTI/7804/06-02F, Re^"Ch ir
Triangle Park, NC,
_ _ environmental Protection Agency, Office
5. Fisher, Gene, U.b- nn-site, Minot, ND area school
of Radiation Programs, on si
investigations.
-------
Form 1.
RADON IN SCHOOLS TESTING QUESTIONNAIRE/APPLICATION
1. Name of School District and Address/Location (including City and County):
2. Name of School building and Address/Location (including City and County):
3. Total number of classrooms in building:
4. Total number of classrooms on or below the ground level:
5. Total number of support rooms:
(e.g. library, cafeteria, administrative, etc.):
6. Total number of support rooms on or below the ground level:
7. Total number of classrooms/support rooms (add Items 3 & 5 above):
8. Total number of classrooms/support rooms on or below the ground level:
(Add Items 4 and 6 above):
9. Subtotal number of test devices required for this building
(minimum-1 classroom in contact with the ground):
10. Number of control test devices required
(5% of total shown in Item 9):
11. Number of duplicate test devices required
(10% of total shown in in Item 9):
12. Total number of test devices required for testing this
school building (Items 9+10+11):
13. Attach sketches/drawings of the school buildings showing proposed placement
of test devices for radon testing.
Please refer to pages A-l to A-5 when planning the placement of your test devices.
14. School district contact for radon in schools testing program:
(Contact Person) (Contact Telephone No)
-------
Form 2 .
SCHOOL DISTRICT SUMMARY QF__RADQN_TESTING REQUIREMENTS
School 8ui1ding/
Location
(City and County)
Subtotal
Devices
j Required
(11 em 9)
Controls
Requi red
(Item 10)
i
1
Duplicates
Requi red
(Item 11)
J Total
iDevices
Requi red
For Schooli
I
I
i
I
I
I
TOTALS
1
r
CERTIFICATION
I hereby certify that the
School District will follow the EPA protocols, referenced in "Radon Measurements in
Schools - Interim Report."
Typed Name of School " County
District Official
Signature of SchooT
District Official
Date
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XP-4
MAJOR RENOVATION OF PUBLIC SCHOOLS THAT INCLUDES
RADON PREVENTION: A Case Study of Approach, System Design and
Installation; and, Problems Encountered
By: Thomas Meehan
-------
An increasing number of schools had been identified by
1989 with radon concentrations in excess of U.S. EPA guidelines.
As some data suggests that children may be more susceptible to
radiation induced cancer than adults. The State of Connecticut
Department of Health Services recommended in April 1989 that all
local education agencies and districts test their schools for
radon. One school district that followed these recommendations
identified high levels in an elementary school that was scheduled
for major renovations. The local education agency agreed to
mitigate existing building and utilize radon-resistant new
construction techniques for the additional buildings planned.
Many problems were encountered while attempting to install these
systems, and utilize techniques recommended by the EPA for
installation of radon reduction systems. An outline of this
experience with recommendations for avoiding similar problems
is presented.
- 1 -
-------
After initial testing identified high radon levels in the
school, maintenance workers attempted to lower the levels by
sealing openings and cracks in the slab and foundation, isolating
an open dirt tunnel, yet not allowing for release of any trapped
gases, and putting a fan in the boiler room window to bring
outside air in. More testing was performed and the levels were
still high.
Since major renovations were slated, the school district
asked architects to design systems to address the existing build-
ing and utilize radon resistant techniques for new buildings
planned.
We were invited to submit a bid to install systems to the
architects specifications and secured the job.
In reviewing the prints and specifications of the mitigation
systems, it was evident that, although the systems were superbly
designed, knowledge of EPA protocols were lacking.
The most prevalent was the fan location. The architect
chose to mount in-line duct fans horizontally above the ceiling
within the building.
We discussed this matter with the general contractor and
the architect, pointing out the potential problems of condensa-
tion build-up in a horizontally mounted fan. Also discussed,
were EPA protocols suggesting the mounting of fans outside the
occupied envelope to avoid potential release of radon gas inside
the building on the positive pressure end of the exhaust.
After the general contractor and architect discussed the
matter among themselves, the decision to mount the fans vertically
was agreed upon, but that the fans were to remain inside, stating
the change would cost too much.
As a sub-contractor, we could not push the subject without
alienating ourselves.
Another aspect of the job discussed was the decision to use
Schedule 80 for all above ground pipe on a system that would
have relatively low pressure. They decided to stay with the
larger and more costly pipe for reasons not explained.
- 2 -
-------
Although work on the existing building has not begun, another
potential problem we feel that might arise is in reference to the
lack of diagnostics.
When we are invited to bid to do work on existing schools
and large buildings, mitigation systems are designed in conjunction
with thorough diagnostics of the building consisting of:
1. Communication testing with micromometer
2. Sniffing with Pylon AB-5 to identify hot spots
3. Use of blower door to identify air balancing affects.
A follow-up paper we will be writing will cover these areas
in more detail.
What we have learned to date, in reference to doing work on
State funded School Radon Mitigation, might assist you on your
next project.
In the decision to engage your company in large scale radon
mitigations, there are many things that must be taken into
consideration. These can be broken down into three categories.
1. Bid process
2. Job Orientation and Familiarization
3. Actual Work
There are many things to consider in each of these areas.
The following are what we feel are important factors that must
be addressed.
1. Bid Process - Pre bid on site inspection is strongly
advised. There are always characteristics unique to each con-
struction site that are not explained on the blueprint or in the
specifications.
When putting a bid together, always verify any State or
Federal wage rate requirements. If there are, obtain the
classification of your workers in writing from the State Labor
Department.
Another important aspect is the insurance and bonding
requirements. These can vary depending upon the project.
Generally, a $1,000,000 liability and workman's compensation
coverage is required.
One of the most important factors to consider, are the
payment schedules. Most government and State jobs give no
- 3 -
-------
money up front and will make payments on a scheduled basis, a
minimum of 30 days from the date of requisition. This also
involves elaborate paperwork that is required for each payment.
It is very important to have the proper funding in place prior
to acceptance of large scale jobs. Be sure to check on performance
penalt ies.
2. Job Orientation & Familiarization - Once a job has been
secured and contracts signed, it is key to the sucess of the job
that you spend time with the following:
Materials - Obtain a locked in price, purchase materials and
get them stored on site. This will allow you to submit bills for
materials purchased, and avoid any future price increases. Also,
request specification sheets on all materials purchased and retain
for job file. When possible, locate supply houses near the job
site and obtain an account to avoid costly delays.
The most important person related to your work, other than
employees, is the job superintendent. It is important to establish
a working relationship with him. Be sure to let him know your
capabilties and possible short comings related to the job.
Review the entire job with him, if possible. Going over potential
problems you might see that he does not realize (EPA Protocols).
It is very important to go through this entire process with
another key employee in case you are unavailable.
3. Actual work - It is important to have two people very
familiar with blueprint reading. The need will also arise to
coordinate your work along with other contractors on the job.
Some potential problems that can occur are: pouring founda-
tion prior to placement of piping. Be sure to coordinate with
concrete workers so the appropriate steps can be taken to insure
access through foundation in the appropriate place. (Core bore
drilling is expensive).
Check all foundation prints on the interior of the building
for footings. The prints might not show this, but a dip in the
piping may be required where footings are present.
- 4 -
-------
Exact measurements are a necessity. Do not rely on one
measurement. Measure pipe placement from two locations. Where
piping comes through a slab, measure from four points. (Concrete
cutters are expensive).
In reviewing the prints throughout the course of the job,
if you see anything that might create future problems, discuss
this with the superintendent or architect.
- 5 -
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XP-5
The State of Maine School Radon Project: The Design Study
by: Henry E. Warren, Director
Division of Safety & Environmental Services
Bureau of Public Improvement
Augusta, ME 04333
Ethel G. Romm, President
Chief Executive Officer
NITON Corporation
Bedford MA 01730
ABSTRACT
The State of Maine, with a population of 1,222,000, has a public school enrollment of
212,000 students (K through 12) in 14,500+ rooms in about 800 buildings in some 160 public
school systems. A proposal to study the radon in the school systems was requested by the state.
An advisory team was formed, expert on schools, HVAC systems, geology, radon testing and
radon mitigation. This group, meeting with experts from NITON Corporation, the chosen testing
firm, formulated a comprehensive program to provide thorough testing and, where necessary,
retesting, within the constraints of a frugal budget. A quality control program was initiated. So
too were plans for informing the public. This paper will describe the major choices and decisions
on such questions as: Should the program be spread over several years? Is a statistical sampling
of rooms sufficient? Should one test in the summer? Who should set out the tests? How should
the tests be monitored?
-------
INTRODUCTION
The State of Maine, with a population of 1,222,000, has a public school enrollment of 212,000
students (K through 12) in some 160 public school systems. A proposal and bid was requested by
the state to test for radon in the entire Maine school system. NITON Corporation was chosen as
the testing firm.
Henry E. Warren, Director of the Division of Safety & Environmental Services of the Bureau of
Public Improvement for the State of Maine formed an advisory team: Expert in schools— Roy
Nesbitt, Director of Maine School Facilities; HVAC systems— William A. Turner, PE; geology
—Ted Bradstreet, geologist; radon in Maine —Eugene Moreau, Manager of Indoor Air Quality,
Department of Human Services. This group met with experts from NITON Corporation, who
have much experience in testing schools and other large buildings, and formulated a
comprehensive program to provide thorough testing and, where necessary, retesting, within the
constrains of a frugal budget. A quality control program was initiated. So, too, were plans for
informing the public. This paper discusses the many choices and decisions made by the group.
Many questions had to be decided. The two critical questions were: How many tests should be
made and who should place and retrieve them? The answers to these determined the costs, and
thus the extent of the testing.
PLANNING
FUNDAMENTAL DECISIONS
How Many Tests?
Determining the number of radon tests required for large buildings is counter-intuitive. It
would seem reasonable to expect that testing the four corner rooms of a school will reveal any high
levels that may exist. Maine had thus first proposed "4000 tests for approximately 900 buildings."
In the view of NITON and the experts consulted, a program with this proportion is very nearly
a waste of money. Four tests that read less than 4 pCi/L do not mean the building itself is below
the EPA's action level, only that those four rooms are below the action level. Any other room
nearby or any cluster of rooms may be higher and only testing them all reveals which ones.
The location of high radon in large buildings cannot, unfortunately, be predicted, so that every
occupied room on the ground or over crawl space must be tested. To uncover radioactivity, the
EPA protocol is one's best assurance.
The group recommended: A short-term screening test done over a week-end in (a) every
(b) frequently occupied (c) room (d) on the ground or (e) over crawl space. If the budget was
limited, use the 4000 tests to do fewer buildings correctly, rather then do them all badly.
The State of Maine chose to follow the EPA protocol and do each building properly to the limit
of its budget.
-------
Who should place and retrieve the tests?
To the extent that school personnel could do this task, the costs would drop dramatically and
more tests could be done. Travel costs alone, for example, can be prohibitive in a state as large,
rural, and winter-bound as Maine, 303 miles from North to South.
Most experts would agree that in many, perhaps most, situations, a professional radon tester is
always to be desired. For example, in real estate transfers of homes and commercial property,
there are too many questions of placing the test at proper height, in which areas, how the heating
system affects numbers and locations, how stone foundations and fireplaces affect placement, and
how to maintain closed building conditions, not to mention matters of tampering.
A school, however, poses none of these problems, whose solution requires training and
experience. The question of placement, for instance, is minor. Every classroom or school office
has a desk, which is exactly the height EPA calls for, 30".
NITON had already had substantial experience in helping public schools to test. Although its
products are used almost exclusively by professionals—environmental firms, inspectors, and the
like—the company had earlier been approached by a number of Massachusetts public school
systems to devise a low-cost system. The schools of Massachusetts had very little money but
wanted to test. Without in-school testers, they could not have tested at all.
The program NITON had developed for non-professionals was further refined for Maine. It
involved reading and marking all floor plans, an 800 Number Help Line, continuous follow-
through, etc. These are described elsewhere in this program under Protocols and Procedures (1).
Because school personnel placed and harvested the tests, the State of Maine was able to afford
a test for every designated schoolroom in the state within one year.
Why were short-term charcoal canisters chosen?
The EPA's Interim Protocol for Schools recommends both short-term screening tests (two days
or over a week-end) and Alpha Tracks (three months) (2). There are three reasons why the short-
term charcoal screening test was chosen for Maine schools:
1. The cost of an Alpha Track is typically about twice that of a charcoal canister.
2. In buildings where people work or go to school, the HV and HVAC systems typically have
a set-back cycle during the evenings, week-ends, holidays, and school vacations, making Alpha
Tracks inappropriate for long-term testing in these structures. With a 168-hour week, and the
systems set back 120 to 136 or more of those hours, ATs will generally give a false high or a false
low, and take many months to do it. That is, ATs are skewed in these buildings from 3 to 1 to 7
to 1 or more in the direction of the radon values of the off or set-back cycle. These concentrations
may be very much higher or very much lower than during hours of occupation. The problem is
aggravated since during the week-ends and vacations, radon can build up to values that may be 10
times the mid-week evening set-back value.
3. More importantly, a short-term test will efficiently find high radon levels in a short time. In
addition, tests are less likely to be misplaced or forgotten. Any tests that are lost or mishandled
can be quickly and inexpensively replaced and the test promptly redone, again over a weekend. If
an AT is lost, the three months of testing is lost and the next three-month test has to start again. If
the air handling equipment is on its regular mid-week cycle, the set-back cycle dominates by a
-------
factor of only 2 to 1 (16 hours set back, 8 hours on). If the system is kept on continuously as this
Maine protocol calls for, the occupied conditions are more nearly met.
One should not have to wait many months to learn of occupied rooms with high radon levels.
In Maine, 8.7% of rooms were found to be more than 4 pCi/L, 1.9% were more than 10, and
0.7% were more than 20 pCi/L, and results were available within a week, including the testing.
OPERATIONS ORGANIZATION
Where should the tests po?
NITON read and marked the plans of every school building. For details, see Protocols and
Procedures (1).
When should the tests be done?
Schools were tested from late Friday afternoon to early Monday morning, a time period
recommended by the EPA that is becoming standard practice for testing schools (3). NITON vials
are calibrated from 24-72 hours for screening.
This week-end period assures that outside windows and doors will be kept shut to maximize the
radon potential. It is also felt that students will not tamper with the tests.
Heating and ventilation cycles on?
When there are sufficient funds, one would ideally screen test all rooms with all systems down,
to learn how much radon is entering the building; then one would retest, with HV or HVAC
systems on, to learn the effectiveness of these systems at clearing away radon gas or creating
negative pressure and sucking it in. Given an extremely limited budget, the group felt it was most
important to learn what the radon levels were when students and adults were actually occupying
the building. It was decided to request that the Heating and Ventilating be on continuously. The
instructions were made part of the Data Entry Sheet.
Test in spring and fall, or continue through summer?
With testing scheduled to begin at the end of February, the question of continuing the testing
through the summer or waiting until fall to recommence the testing came up.
Based on preliminary evidence, the EPA Interim School Protocol calls for testing in the
wintertime only (4). Warren checked with Maria Van der Werff, Radon Coordinator, EPA,
Region #1 and William Turner, PE, who agreed with NITON that mounting evidence was
showing that summer testing was valid.
For example, NITON had done comparison testing of 89 rooms in 5 schools in Massachusetts
six months apart and found slightly higher readings in the summer; 80% of the rooms were within
1 pCi/L (5). Summer is, in fact, an excellent time for two-day screen testing. The custodians have
more time, there are fewer distractions, and it costs very little to put the HVAC onto continuous
cycle for the short test period.
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MANAGEMENT OF NON-PROFESSIONALS
HOW TO KEEP THE PROGRAM ON SCHEDULE?
Even with professionals, schedules need to be set up. With non-professionals, schedules have
to be far more detailed, and people need to be monitored very closely and continuously. Maine had
previously provided free radon tests to several schools, most of whom had never returned their
tests to the lab, or had returned them months after exposure. Maine was particularly concerned
with this point. The system devised worked for 98.5% of the tests.
NITON was given the name, principal's name, and phone number of every school in the State
of Maine. Many schools were in towns and cities, with facilities maintenance staffs. Some were
out on islands or Indian reservations with no staffs. Some were one-room schoolhouses, with no
principal and no custodian. NITON devised a checking system that kept track of all of them at
every stage in the program, from sending in floor plans to returning tests.
RE-TESTING: WHERE AND HOW
It was already known that some areas of Maine were high in radon; 60 pCi/L in basements was
not so rare in those parts. When the first very high readings showed up in schools there, the EPA
was called in and mitigation begun.
The decision was made to retest every room with a reading over 3 pCi/L. Ideally, one would
want a sensitive electronic continuous radon monitor to give hour-by-hour results in every such
room, but the cost is high.
A cost-effective way to retest is the use of NITON vials to learn day and night readings. The
NITON vial is calibrated to 8 hours, and is extremely sensitive as well as accurate at low levels (a
liquid scintillation counter counts virtually 100% of 5 decaying particles). At 1 pCi/L, the
Standard Deviation is 10%; in retests, all tests are counted to a Standard Deviation of 2% at 3
pCi/L. Thus, a reading may be taken during the school day, when the building is occupied, and
another in the same room at night, when the systems are set back. Rooms confirmed to be high
would then be candidates for careful diagnosis of all conditions, beginning with the HVAC.
QUALITY CONTROL
QUALITY ASSURANCE FOR TESTING VIALS
To test the tests, two procedures were used. Side-by-side NITON vials were set out in
some 150 rooms. In addition, 50 of the 4" charcoal canisters (75 gr) were supplied by the State of
Maine and analyzed in the Maine Radon Lab. More information on this is given in the presentation
on Results in the State of Maine School Radon Project (6).
DATA REPORTING
It was decided that test results would be sent to Henry Warren's office within two business
days of the arrival of the tests at the lab. In addition, NITON would make the data available on
discs for further analysis.
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PUBLIC RELATIONS
The decision was made to tell the public of results as they were learned. Disclosure of even
high radon values can be made without arousing undue alarm provided it is done early. This has
been proven again and again in towns and school systems where such information was provided to
the public early, instead of being withheld and then "revealed" by an outside source.
Note: The wisdom of this policy was demonstrated in the towns in the Sebago Lake region,
where the radon was in excess of occupational levels for uranium mines, yet there was no hue and
cry to close the schools, as there has been in areas where high results have been kept secret for too
long.
ACKNOWLEDGEMENTS
H.W.and E.R. wish to acknowledge with gratitude the contributions of the following to the
success of this study: William Bell, Maria Van der Werff, Roy Nesbitt, William Turner, and the
planners from NITON, who include Lee Grodzins and Anne McGuineas.
The work described in this paper was not funded by the U.S.
Environmental Protection Agency and therefore the contents do
not necessarily reflect the views of the Agency and no official
endorsement should be inferred.
REFERENCES
1 Grodzins L., Warren, H.E., and Romm, E.G. Protocols and Procedures of the State of
' Maine School Radon Project. Poster Presentation at EPA 1991 International Symposium on
Radon and Radon Reduction Technology, Philadelphia, PA. April 2-5,1991.
t ppa Radon Measurements in Schools: An Interim Report. U.S. Environmental Protection
Agency Office of Radiation Programs, Washington, DC. EPA 520/1-89-010. Sect. VI.D.
Pg. 1-9.
i ppa Radon Measurements in Schools: An Interim Report. U.S. Environmental Protection
Agency, Office of Radiation Programs, Washington, DC. EPA 520/1-89-010. Sect.VI.D.l.
a ppa Radon Measurements in Schools: An Interim Report. U.S. Environmental Protection
Agency, Office of Radiation Programs, Washington, DC. EPA 520/1-89-010. Sect. VI.B.
< rmrlzins L Radon in Schools in Massachusetts. EPA 1990 International Symposium on
Radon and Radon Reduction Technology, Atlanta, GA. February 19-23,1990.
Grodzins L , Bradstreet, T., Moreau, E. The State of Maine School Radon Project: Results.
ppa 199i International Symposium on Radon and Radon Reduction Technology,
Philadelphia, PA. April 2-5,1991.
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TITLE: Design for the National Schools Survey
AUTHOR: |_-jsa Ratcliff, EPA - Office of Radiation Programs
This paper was not received in time to be included in the
preprints and the abstract was not available. Please check your
registration packet for a complete copy of the paper.
('U.S. GOVERNMENT PRINTING OFFICE: 1991-518-1 87/?0568
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