United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-94/064
June 1994
EPA Project Summary
Soil and Fill Laboratory
Support—1991, Florida Radon
Research Program
C.E. Roessler, Ryan Richards, Ha Nguyen, D.L. Smith, and C. Vonada
This report presents the results of
soil analysis laboratory work by the
University of Florida in support of the
Florida Radon Research Program
(FRRP). Analyses were performed on
soil and fill samples collected during
1991 by the FRRP Research House pro-
gram and the New House Evaluation
Program (NHEP). Work included tex-
tural classification, and particle size,
moisture, radium-226, and emanation
coefficient determinations.
During this period, 124 samples rep-
resenting 45 sites were submitted. For
North Florida sites (Gainesville vicin-
ity), radium-226 concentrations were,
in all but two sites, <1 pCi/g. At one
site, moderately elevated radioactivity
fill (3 pCi/g) was found over low activ-
ity (<1 pCi/g) surficial substrate. At an-
other site, the near-surface substrate
was moderately elevated in radioactiv-
ity (5 pCi/g), but the associated fill
sample was of low radioactivity. Cen-
tral Florida sites (Polk County) were
characterized by predominantly mod-
erately elevated (1-10 pCi/g) or elevated
(>10 pCi/g) fill over either low activity
or moderately elevated substrate.
This work resulted in the following
conclusions:
I.The observations for North Florida
support earlier conclusions (1989 and
1990 studies) that a large proportion
of the fill actually used in Florida con-
struction is of a low radium content.
2. Elevated radium concentrations do
occur in some soil and fill samples in
actual house construction.
3. Fill with elevated radioactivity can be
an issue in selected circumstances
(such as the Central Florida NHEP
sites).
4. Mining-related lands (such as reclaimed
overburden and/or sand tailings areas)
may present a radon source.
5. Other, related studies indicate that, at
some locations, the source of near-
surface soil gas radon may be zones
of elevated radium occurring at depths
greater than being sampled for the
NHEP.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
This report gives results of laboratory
analyses of soils performed by the Uni-
versity of Florida in support of the Florida
Radon Research Program (FRRP). Physi-
cal and radiological characteristics were
determined on samples collected during
1991 by the Research House Program
and the New House Evaluation Program
(NHEP) of the FRRP.
This work is a continuation of efforts to
characterize the radon* source potential and
the permeability characteristics of Florida
soil and fill materials. In 1989, a survey of
* In this summary, "radon" is used to designate the radon
isotope, radon-222. "Radium" is used to denote the
radium isotope, radium-226.
-------
35 sites gave results of analyses of state-
wide fill materials at construction sites
(66.7%) and native surficial soil at con-
struction or existing house sites (33.3%).
In addition, in-situ permeability and soil
gas radon were measured at a sub-set of
these sites. Work in 1990 emphasized in-
situ permeability and soil gas radon mea-
surement and soil sampling at 23 state-
wide sites as prepared for construction.
(See Figures 1, 2, and 3.)
In 1991, the research contractors for
the NHEP program submitted samples
collected at construction sites in areas of
suspected elevated radon potential in
North Florida (Alachua County) and Cen-
tral Florida (primarily Polk County).
Samples were also received from the
Alachua County and Polk County FRRP
Research House sites.
Methodology
Samples were collected to represent
both the sub-slab fill material and the up-
per layer (<1 m) of the underlying sub-
strate. Laboratory work included textural
classification, particle size measurements,
moisture determination, and radium and
radon emanation coefficient analyses.
Samples were subjected to classification
by texture and appearance, determination
of size distributions by sieve analysis, and
classification by sedimentation analysis
(hydrometer analysis). For radiological
analysis of soil samples, dried portions were
sealed in a container, counted with a high
resolution gamma-ray spectrometry system
shortly after sealing, held for ingrowth of
radon and its short-lived decay products,
and counted at least one more time. Ra-
dium concentrations and radon emana-
tion coefficient were calculated from the
activity associated with the 295.21, 351.92
and 609.31-keV peaks of the short-lived
radon daughters. The radium concentra-
tion was based on the projected equilib-
rium radon-222 activity; radon emanation
coefficient was determined from the pair
of values corresponding to pre-ingrowth
and equilibrium radon concentrations.
Results and Discussion
A total of 124 samples were received
as summarized in Table 1.
Geological Nature of the
Samples
Within Alachua County (North Florida),
three major geological units prevail as
surficial lithologies. In certain portions of
the county, particularly in the western half,
Columbia County
Kilometers
0 80 160 240 320
0 50 100 150 200
Miles
Figure 1. Sampling locations - North Florida.
-------
Hillsborough
County
Kilometers
0 80 160 240 320
0 50 100 150 200
Miles
Figure 2. Sampling locations - Central Florida.
-------
North Florida
16-.
14-
» 12-
™ 10-
° 8-
- 6-
1 4-
2-
n.
/
/
/
'
'
/
'
/
y
/
/
/
,
/
,
,
/
/
/
'
'
'
'
/
V.
-?
> — p
l")'
"7
y g
_> f. — f / e. — f A
< - 1 pCi/g
0 nOi/n Fill
: = 1 pCi/g
1 -10
Substrate
> 10
Central Florida
5-
CO 4-
fn «
Number of
D ->• M (j.
X
/
X
/
/
^
/
^c
==>
^
n
7 /
^ /
/
L
i
p /
p /
/ s~
y
< = 1 pCi/g 1-10 > 1 0
Substrate
3 — 7i
< - 1 pCi/g
-10pCi/g
0 pCi/g Fill
Figure 3. Distribution of soil-fill radioactivity combinations.
Table 1. Summary of Sites and Samples
Origin Sites Samples
N FL NHEP
C FL NHEP
Total NHEP
26
16
42
83
29
112
N FL Research House
C FL Research House
Total Research House
TOTAL
1
2
~3
45
5
7
72
124
limestone of the Eocene Ocala Group is
exposed. Overlying the limestone in the
central and eastern portions of the county
are rocks of the Miocene Hawthorn Group.
These rocks consist of discontinuous
lenses of unconsolidated sands, phos-
phatic clays, clayey sands, limestone, and
dolomite. A thick sequence of relatively
recent sand from beach processes exists
in much of eastern Alachua County to
cover the Hawthorn sediments. Thin allu-
vial sands cover all three major units
throughout much of the county in the up-
per 0.3 to 1.0 m (1 to 3 ft). Throughout the
exposures of Hawthorn sediments in
Florida, geological evidence of reworking
and mixing of surficial units exists. Ac-
cordingly, silty clayey sands and sandy
clays are common and difficult to distin-
guish or correlate. By virtue of positive
clay content, all of the North Florida NHEP
samples are considered to be from the
Hawthorn group. Certain samples had
higher clay compositions and could be
attributed to zones or lenses of clayey or
silty sands.
In Polk county (Central Florida), the geo-
logical surface of most of the area is some
component of the Hawthorn group of sedi-
ments with the best known being the Bone
Valley formation of phosphatic sands and
clays. The surface of the easternmost por-
tion of the county consists of marine ter-
race sands of recent age. Some surficial
materials in Polk County are tailings from
the beneficiation of minerals extracted from
the Hawthorn Group. This material has
undergone a sizing process that results in
an inordinate sorting to yield a relatively
uniform-sized sand fill. The Central Florida
NHEP samples are consistent with a Haw-
thorn origin. Some of the samples had
relatively high clay contents (>25%) and
could be attributed to a zone richer in
clays. The deeper Research House site
samples were markedly uniform in size
and low in silt and clays suggesting that
they are sand tailings from mineral
beneficiation.
Radiological Characteristics
The radium content of soil-fill samples
is summarized in Table 2.
For the North Florida sites sampled dur-
ing this reporting period, the radium con-
centrations of samples from the upper 0.9
m (3 ft) were less than 1 pCi/g at 25
(96%) of the 26 sites. Note that, in related
studies being conducted in North-central
Florida, the source of near-surface soil
gas radon at some locations appears to
be zones of elevated radium concentra-
tions occurring at depths greater than 1
m. Only one fill sample had a radium
concentration in excess of 1 pCi/g.
For the Central Florida sites sampled
during this reporting period, 63% of the
native soil and 92% of the fill samples had
radium concentrations exceeding 1 pCi/g,
and concentrations as high as 30 pCi/g
were observed. Thus in this particular re-
gion, fill materials currently in use do con-
tain elevated radium concentrations.
Soil-fill radioactivity combinations are
summarized in Table 3. North Florida sites
were characterized by the predominant
occurrence of low activity (<1 pCi/g) fill
over low activity surficial substrate. On
the other hand, the Polk County (Central
Florida) sites were characterized by the
predominant occurrence of moderately el-
evated (1-10 pCi/g) and elevated (>10
pCi/g) activity fill over either low or moder-
ately elevated substrate. Only one Central
Florida site had low activity fill; this oc-
curred in combination with a moderately
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Table 2. Summary of Radium-226 Content Soil and Fill Samples
Native Soil
Cone, pd/g
Distribution of Sites
<1 pd/g
1-10
>10
FHISoil
Cone, pd/g
Distribution of Sites
<1 pd/g
1-10
>10
NFL
0.2 - 5.5
25 (96.2%)
1 (3.8%)
0 (0.0%)
26
0.2 - 3.2 0.
17 (94.4%)
1 (5.6%)
0 (0.0%)
lls
CFL
0.7-10.8
6 37.5%)
8 (50.0%)
2 (12.5%)
76
7-29.5
r (8.3%)
6 (50.0%)
5 (41.7%)
72
* Manatee site
Table 3. Summary of Soil-Fill Radioactivity Combinations
Fill
Substrate
NFL
A < =1 pd/g
B 1-10
C >10
CFL
A < =1 pd/g
B 1 -10
C >10
A
<1
16
1
0
17
0
r
0
1
B
1-10
1
0
0
^
3
2
1
6
C
>10
0
0
0
~°
2
3
0
~5
Total
17
1
0
18
5
6
1
12
elevated substrate at a single site sampled
in Manatee County.
Conclusions
This project led to the following conclu-
sions:
I.The observations for North Florida
support earlier conclusions (1989 and
1990 studies) that a large proportion
of the fill actually used in Florida con-
struction is of a low radium content.
2. Elevated radium concentrations do oc-
cur in some Florida soil and fill samples
in actual house construction.
3. Fill with elevated radioactivity can be
an issue in selected circumstances (this
was observed at the Central Florida
NHEP sites).
4. Mining-related land (such as reclaimed
overburden and/or sand tailings areas)
may present a radon source. These
soils may have characteristics different
from undisturbed soils and directly ex-
cavated fills.
5. Other studies being conducted in
North-central Florida indicate that at
some locations the near-surface soil
gas radon may originate from depths
greater that the 0.6 to 0.9 m (2 to 3 ft)
being sampled for the NHEP.
* Manatee site
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C. Roessler, R. Richards, H. Nguyen, D. Smith, and C. Vonada are with the
University of Florida, Gainesville, FL 32611.
David C. Sanchez is the EPA Project Officer (see below).
The complete report, entitled "Soil and Fill Laboratory Support—1991, Florida
Radon Research Program," (Order No. PB94-163243; Cost: $17.50; 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
Official Business
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