United States
                Environmental Protection
                Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
                Research and Development
EPA/600/SR-94/052
June 1994
EPA       Project Summary
                Characteristics  of Florida Fill
                Materials and  Soilsó1990
               C.E. Roessler, R. Morato, D.L. Smith, and J. Wherett
                 This report presents results of labo-
               ratory work by the University of Florida
               in support of the Foundation Fill Data
               Base project of the Foundation Fill Ma-
               terials Specifications Task Area of the
               Florida Radon  Research  Program
               (FRRP). Work included determination
               of radon concentrations  in  soil  gas
               samples and physical and radiological
               characterization of soil/fill samples to
               provide data for further use in model-
               ing radon production, transport,  and
               entry.  This work adds to the 35-site,
               54-sample data base developed in an
               earlier study by the University of Florida
               under the  State  University System
               Board of Regents Radon Research Pro-
               gram.  The  earlier  study  emphasized
               materials being used as fill at construc-
               tion sites; only one-third of the samples
               were native surficial soil at construc-
               tion or existing house sites. The study
               being reported here emphasized sites
               as prepared for construction. Twenty-
               three sites were sampled. Two sites
               were  selected in each of 11 regions
               designated to represent population cen-
               ters covering the range of geographic,
               topographic, and geological features in
               Florida. Also included was a Brooksville
               school construction site being studied
               in another FRRP project.
                  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
   The most prevalent source of elevated
 indoor radon* in Florida is from the entry
 of radon-bearing  soil gas from beneath
 the structure. Radon in this soil gas origi-
 nates from radium in underlying and sur-
 rounding soil and fill materials. The radon
 source potential  of a particular site is a
 function  of the soil gas radon concentra-
 tion and the radon transport characteris-
 tics of the substrate. Transport character-
 istics  determine the ease with which this
 soil gas can be moved into a  structure
 and the extent to which the exhausted soil
 gas radon  can be replenished.  The ease
 of movement of  radon-bearing soil gas
 can be characterized in terms of the soil
 air permeability coefficient. Permeability is
 also an important parameter in the design
 and  performance of the sub-barrier de-
 pressurization method of radon mitigation.
   Alternative soil characteristics can also
 be used to estimate  radon  source term
 and entry.  Soil radium concentration and
 radon emanation coefficient jointly deter-
 mine  the radon production. Particle size
 distribution influences the air permeability
 and radon  diffusion coefficient of the soil.
 Soil classification  can be a qualitative in-
 dicator of the other, quantitative, param-
 eters.
   Initial  work to characterize the radon
 source potential and the permeability char-
 acteristics of Florida soils  and fill materi-
 als was conducted by  the University  of
 Florida as part of the State University Sys-
 tem Board of Regents  Radon  Research
 * In this report, the term "radon" is used to designate the
 radon isotope, radon-222, and the term "radium" is
 used to designate the radium isotope radium-226.

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Program.  This  report presents data for
appearance, physical characteristics, and
radiological characteristics for fill material
samples collected at 23 sites in  11 desig-
nated regions of the State of Florida. In
addition, a sand fill sample was collected
at the  Brooksville school  site. The  data
from this  laboratory work are  presented
for further use in modeling radon produc-
tion, transport, and entry under the FRRP
Foundation  Fill Materials Specifications
task effort.

Field  Measurements and
Sampling
  Sampling  regions were designated to
represent  population centers covering the
range of geographic, topographic, and geo-
logical  features in  Florida.  Typically two
sampling  sites  were designated per re-
gion. One additional  sampling location,
Brooksville,  was included because  of a
FRRP  project involving  a  school under
construction in that vicinity.
  Sites were selected, field work was per-
formed, and results  were reported by
Geohazards, Inc. under a separate FRRP
contract. Most of the sampling sites  con-
sisted of sites that had been leveled and
contoured  for construction with fill (if any)
in place. A small number of sites were on
raw  land  or in the  vicinity  of existing
houses.
  Sites were typically visited twice. At the
initial visit, in-situ permeability,  penetrom-
eter,  and density measurements were per-
formed, and alpha-track  soil  gas radon
detectors were  deployed.  In addition,  soil
gas samples were collected in conjunc-
tion with the in-situ permeability measure-
ments  at  the maximum  depth  at which
these measurements were made (0.30 to
0.75  m or  12 to  30 in.). Soil samples were
also  collected for laboratory classification
and measurement of physical and radio-
logical  properties. Soil samples were col-
lected at a depth of 0.61  m (2 ft) or shal-
lower, but usually 0.3  m (1  ft) or deeper.
Approximately 6 weeks later, the sites were
revisited, the alpha track detectors were
retrieved, and additional soil gas samples
were collected.

Laboratory Measurements
  Samples were classified by texture and
appearance  with  reference to the grain
size  scale used by  American  geologists
(the  modified Wentworth  scale). Perme-
ability values were determined for samples
in  dry unconsolidated,  dry compacted,
moist unconsolidated,  and moist com-
pacted states.  Size distributions were de-
termined by sieve analysis. The samples
were  also classified by  sedimentation
analysis.
  The radon concentration in soil gas was
determined by using a  radon scintillation
cell counting system to analyze the cells
that had  been  filled during  soil gas sam-
pling in the field. For radiological analysis
of soil samples, dried portions were sealed
in a container,  counted with a high  resolu-
tion  gamma-ray spectrometry system
shortly after sealing, held for ingrowth of
radon-222, and counted at least one more
time. Radon emanation  coefficient and ra-
dium-226  concentration were  calculated
from the activity associated with the 295-,
352-,  and  609-keV peaks  of  the  short-
lived  radon daughters.  The  radium-226
was  based on the  projected equilibrium
radon-222 activity; radon emanation coef-
ficient was determined from  the  pair of
values corresponding to pre-ingrowth and
equilibrium radon concentrations.

Appearance and Physical
Characteristics
  All  of the regional soil  samples were
sand or sandy materials with loamy sand
and clayey sand the more  prevalent ma-
terials. In contrast,  the  Brooksville school
site samples were clay.  Most of the sandy
samples had  moisture contents  in  the
range of 2-10%; the clay  samples had
moisture contents on the order of 30- 40%.
Laboratory permeability measurements are
reported for four combinations of compac-
tion and moisture  for each sample and
ranged from below the detection level to
48.71 x 10"12m2. In-situ permeabilities were
measured at four depths and ranged from
<0.0005 to 1050 x  10'12m2. Particle size
data are reported  for  46 samples. The
predominant particle size  was  noted for
each sample as  a simple screening clas-
sification.  Sieve  analyses for  eight size
categories  based on seven sieve sizes
ranged from 0.074  to 2.00 mm. The re-
sults of sedimentation (hydrometer) analy-
sis are presented in terms of the fractions
classified as sand, silt, and  clay.

Radiological  Characteristics
  Soil gas radon concentrations  include
both the initial  sampling at a single depth
at the two primary  stations at each site
and the later sampling in the vicinity of the
alpha tract burial  stations. At  11  sites,
samples were collected  at two depths at
the alpha tract (second visit). At 10  of the
sites, no soil gas sample was collected at
the second visit; this was  usually due to
the fact that the buried alpha track detec-
tors  could not be  located  as a result of
construction activities between the two vis-
its.
  Soil gas radon  concentrations ranged
from a few to  over  10,000 pCi/L. The data
were  not submitted to statistical analysis;
however, some observations can be made
by inspection:

  1) The  two primary stations  at  a  site
     generally had comparable  levels on
     the same sampling date.
  2) About half of  the 13 alpha track sta-
     tions (sampled  6 weeks  later)  had
     levels that were noticeably different
     from those at the  primary stations.
     However, since the two types of sta-
     tion were not sampled at the  same
     visit, it is not possible to  determine
     whether this  is  a  time effect or  a
     spatial effect.
  3) In  the limited multi-depth  sampling
     at 11 alpha track stations, concen-
     trations  generally increased with
     depth in the  range of 0.30-0.75 m
     (12-30 in.) when the  concentrations
     were greater  than 100 pCi/L.

  Radium-226 concentrations were  2 pCi/
g or less in 87% of the samples and less
than 1 pCi/g in 67%. One  exception was
the Bartow samples which had concentra-
tions on the order  of 11-13 pCi/g. At this
site, the upper 0.6 m (2 ft) consisted of
white/grey sand with pebbles and cobbles
and appeared to be a fill material placed
over the original natural soil. The  other
exceptions were  the  Brooksville samples
(clay) and the Tallahassee A samples
which had concentrations on the order of
2-4 pCi/g. The fact  that soil gas  radon
concentrations at some of the sites where
soil  concentrations were  <1  pCi/g  ap-
proached  or  exceeded  1000  pCi/L sug-
gests a radon source deeper than that
from which the soil sample was taken.
  Results of  emanation coefficient mea-
surements  ranged  from a few  to  about
40%.  Since most  of these samples  had
low radium concentrations,  the associated
emanation coefficient determinations have
a high degree of uncertainty.

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   C.E. Roessler, R. Morato, D.L Smith, and J.  Wherett are with The University of
     Florida, Gainesville, FL 32611.
   David C. Sanchez is the EPA Project Officer (see below).
   The complete report, entitled "Characteristics of Florida Fill Materials and Soilsó
     1990," (Order No.  PB94-176906; 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

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