United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC
711
Research and Development
EPA/600/S8-90/070 Nov. 1990
Project Summary
Identification of Candidate
Houses for the North Florida
Portion of the Florida Radon
Mitigation Project
G.S. Roessler, D.E. Hintenlang, C.E. Roessler, and R.A. Furman
This study was conducted to
locate candidate houses for a
proposed radon mitigation demon-
stration project in North Florida. The
effort involved: I) identification of
target geographical areas, 2) radon
monitoring in identified clusters, and
3) house characterization.
A review of a statewide radiation
study completed in 1987 and a 1986 -
87 pilot study of the Gainesville area
indicated that North Florida target
areas could be selected on the basis
of the near-surface occurrence of the
Hawthorn geological formation.
Volunteer houses for radon
monitoring in Alachua and Marion
counties were obtained by announc-
ing the study in newspaper articles.
Single-sample screening measure-
ments were made in approximately
400 area houses by the charcoal
collector method. These houses were
targeted based on geological
evidence that they would have a high
radon potential. The levels observed
ranged from <0.1 to 128 pCi/L. The
arithmetic mean was 11.2 pCi/L,and
the geometric mean was 6.4 pCi/L. Of
the houses, 32% were <4 pCi/L, 51%
were between 4 and 20 pCi/L, and
17% were >20 pCi/L. Results were
similar in the two counties, and the
distributions were similar in both slab
and crawl-space (unspecified venti-
lation) construction.
Criteria for selecting houses for
further consideration included radon
screening measurement~at least 4
pCi/L (the U.S. EPA action level)-
ownership/occupancy-single-family,
owner-occupied; house characteris-
tics-detached, single-story, foun-
dation system entirely slab or entirely
crawl space, not >2000 ft2 (186 m2);
and water supply-community or
municipal. Sorting on these criteria
produced over 100 candidate houses
in the two counties for further
consideration in mitigation demon-
stration.
This Project Summary was
developed by EPA's Air and Energy
Engineering Research Laboratory
Research Triangle Park, NC to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
A statewide study in Florida has
identified a number of counties with
evidence of elevated indoor radon. These
counties are concentrated in two
geographic areas--the West Central
Florida phosphate mining region and
North Florida's Hawthorn formation
region.
The project reported here was
conducted to identify a candidate list of
houses to be considered for a North
Florida demonstration project. The work
was carried out in two adjacent populated
areas of North Central Florida the
Gainesville area (Alachua County) and
the Ocala area (Marion County).
^> Printed on Recycled Paper
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Procedures
The effort to identify candidate houses
for inclusion in the North Florida Radon
Mitigation Project involved:
Task I. Identification of Target
Geographical Areas,
Task 2. Radon Monitoring in
Identified Clusters, and
Task 3. House Characterization.
Task 1. Identification of Target
Geographical Areas
Existing geological information and
indoor radon monitoring data were used
to identify areas in Alachua and Marion
counties where sufficient clusters of 20-
30 houses having indoor radon levels
greater than 4 pCi/L (the EPA action
level) would likely be found.
The report of the 1986-87 Florida
Statewide Radiation Study was examined
to determine the general geographic
distribution of elevated indoor radon and
possible association with geology. In
addition, the results of an indoor radon
study of the Gainesville area by the
University of Florida during the winter of
1986-87 were examined for further
definition of potential target areas.
Prompted by the knowledge that
uranium can be associated with a local
geological formation of poorly
consolidated sands, clays, and limestone
called the Hawthorn formatioh and by the
general association of elevated indoor
radon with this formation in the two
studies, the available geological data
were used to draw approximate
boundaries of the near-surface occur-
rence of the Hawthorn formation on
vicinity and street maps for Gainesville
and Ocala. These maps were the basis
for determining whether neighborhoods
could be considered within a target area.
Task 2. Radon Monitoring in
Identified Cluster
Homeowners were solicited by
announcement of the study in newspaper
articles in the two counties. Homeowners
were informed of the purpose of the
survey and its relation to EPA's Florida
Radon Mitigation Project. Interested
homeowners were asked to fill out an
Information and Authorization Request
form that recorded basic characteristics
of their houses.
Indoor radon measurements were then
conducted in approximately 400 houses
located within the target areas.
Measurements were short-term sampling
(5 days) by the charcoal absorber
method.
The study involved eight weekly
sampling rounds of approximately 50
houses per week. Homeowners were
notified by letter of test results. Home-
owners whose screening measurements
exceeded 4 pCi/L received a form for
follow-up house characteristic inform-
ation which they were requested to
complete and return.
Task 3. House Characterization
The initial set of house characteristics
was obtained from the Information and
Authorization Request form completed by
or on behalf of the homeowner. Data from
these forms were entered into a data
base for further retrieval and
summarization.
Additional information on houses
exceeding 4 pCi/L was obtained from the
Construction Classification Questionnaire
which was sent to the homeowner along
with the results of the screening
measurement. A limited number of
houses were visited by project personnel,
and additional Information was obtained
by interviews, visual observation, and
radon grab samples from the indoor air
and wall cavities.
The data files were sorted to select
candidates for further consideration
meeting several criteria:
1. Indoor radon-screening values 4 pCi/L
or greater.
2. Ownership/occupancy:
a) single family,
b) owner-occupied, and
c) expected occupancy for 24
months.
3. House characteristics:
a) detached house
b) single story,
c) foundation/floor system entirely
slab or entirely crawl space, and
d) not more than 2000 ft2 (186 m2).
4. Water supply-community or muni-
cipal.
Results and Discussion
Task 1. Identification of Target
Areas
The Florida Statewide Radiation Study
conducted during 1986-87 identified
counties having definite evidence of
elevated radon potential. Two foci of
expected elevated indoor radon In Florida
include a West Central Florida region
coincident with the geological formation
known as the Bone Valley formation and
with near-surface occurrence of _the •
underlying Hawthorn formation, and'the' •
North Central Florida cluster of counties •
coincident with the near-surface •
occurrence of the Hawthorn formation •
and the geologically similar Alachua •
formation ; I
The North Central Florida area •
includes two heavily populated areas- •
Alachua County with Gainesville, its •
suburbs and several smaller cities, and •
Marion County with Ocala and suburbs. •
Examination of the Statewide Study •
monitoring results on a subcounty scale •
for Aiachua and Marion Counties •
Indicated that, within the limitation of the •
spatial resolution used, elevated radon •
areas correspond generally with the •
Hawthorn formation and with soils •
identified as phosphatic soils. I
A study conducted In:the Gainesville •
area during the winter of 1986-87 by the I
University of Florida provided further •
definition within the Gainesville area. I
Single screening measurements were I
made In 67 houses chosen to provide a I
geographic distribution within the area I
and represent both slab and crawl-pace I
houses in rough proportion to their I
occurrence in the community (about I
equal numbers). A significant fraction of I
the houses exceed 4 pCi/L and some I
exceed 20 pCi/L In the screening I
measurement. Similar distributions I
appeared in both slab and crawl-pace I
houses (not differentiated as to degree of I
ventilation). A greater likelihood of I
elevated radon is associated with the I
Hawthorn formation. • I
Based on (1) knowledge that uranium I
can be associated with the Hawthorn I
formation, (2) the observation of the I
Statewide Study, and !(3) the further
confirmation of the Gainesville study, it
was concluded that the Hawthorn
formation provides a relatively good basis
for the designation of target sampling
areas. However, the scale of mapping is
not adequate to accurately define ranked
areas on a block-to-block basis.
Task 2. Radon Monitoring in
Identified Clusters
The results of radon monitoring are
summarized in Table 1. About 67% of the
single sample screening measurements
in the target areas were 4 pCi/L or higher.
About 50% were between 4 and 20 pCi/L,
and about 17% were abfwe 20 pCi/L. The
highest levels were concentrated almost
entirely in the region of near-surface
occurrence of the Hawthorn formation.
Table 2 shows the distribution of
indoor radon concentrations by found-
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Average
Geometric Mean
Minimum
Maximum
11.3
6.7
0.4
128.0
•
11.0
6.1
0.0
75.5
—
11.2
6.4
0.0
128.0
tration
Range,
pCi/L
s/at>
Combi-
nation*
Space Slab
/Crawl
of this type were monitored.
- nouYes'T^f >'4y Sr betwe*n
oace houses (61% >4 nr-/A crawl"
ST^Sys^21"
'scepiible to "ado° enTe especia">'
>uses. are based on only 15
is/c3.
detached
2. Radon Monitoring in
^Identified Clusters
houses in th ""Dstsntial number of
areas with elevated'"ndon? *?* °Ca/a
^ngle, charcoal colle t raaon levels.
under clospri hm,« sarnples, taken
/ u lutiea nouse condition.? !„ iaixc"
400 houses in the se£rt*S^ ' near|y
showed that 32% w|f ^ ta!Set areas
were between 4 and 20 nr/1PC'7L> 51%
were >20pCi/L P ' and 17%
taken in tarnot
. Table
radon po.en.ia Thev H
represent the overall Inri
Cities and coun
truction.
•elusions
°f
"^ neces""ly
P''Cture l
•space 3
Characterization
rher
~...~ov.lle and Oca/a %L U/6S in the
consideration for a mitT r for furtner
stration project Thfs ?'*l9atlon demon-
by sorting hou«5<= Ah was developed
select owner -ocnmlL^ er/St/c data to
simple foundation Qtu81"9'6 story,
>2000 ft2 (18e ml(y^thhouses of not
concentrations of >4 nrv,lnld°0r radon
screening measurement Th yt * sin9'e
systems of the houTJl 6ufoundation
90%s.abandlV"°nSs0pnact2i;s "St "»
radon tev ST"8 W''th indo°
addition, many ParticinaL°r 9reater- '"
°Ption to have a qn H exercfsed the
measurement to asJS'.A alpha track
of the screening Seas?±e verification
results will beoin o ments; these
'nformatioS has als^h"9 ''" Short'y-
though visits by Pro11t rf" °btained
'""/ted number nf h Personnel to a
from each of thL ,US6S- 'nformation
incorporated into th C°U/d be
Screen/^ the Candidate
ou-/o siab and 10% crawl
Recommendations
candidate houses ,!Ll *base' Rank'ng
base would provided H detai(ed data
follow-up visits and • t°rter list for
homeowners d '"^views with
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Meeting Initial Criteria for
Crawl
Slab space
Total
Distribution of Radon
Concentrations:
4-20 pCiA-
>20pCi/U
~Totalhouses4pCirt-or
higher
.1
Location:
Alachua County
(Gainesville vicinity)
51
House Characterization and
F/na5'selection of Mitigation
Candidates
v *nr> rnuld then t»e nouac
A next step couia « screened r,st
characterization visits w |esu(ts o{ the
'^»«*ffS
SSation project partiapants.
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G Roessler.D. Hintenlang, C.Roessler, and Ft. Furman are with the University of
Florida's Department of Nuclear Engineering Sciences, Gainesville, FL
32611.
David C. Sanchez is the EPA Project Officer (see below).
The complete report, entitled "Identification of Candidate Houses for the North
Florida Portion of the Florida Radon Mitigation Project:' (Order No. PS 90-
274 077IAS; Cost: $23.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
ERA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S8-90/070
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