United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/S7-88/005 May 1988
AEPA Project Summary
Clinton, New Jersey, Radon
Mitigation Follow-up and
Long-term Monitoring
Joseph Carvitti
During 1986, the U.S. Environ-
mental Protection Agency demon-
strated radon reduction techniques
in 10 houses in Clinton, New Jersey.
Initial radon levels in the 10 houses
ranged from 400 to 2200 pCi/l. Radon
reductions of more than 95% were
achieved by using a variety of
subslab ventilation techniques.
Since January 1987 the radon
levels in the 10 houses have been
monitored with alpha track detectors.
The detectors have been installed
and removed quarterly. Three
detectors were used on the lowest
level of each house, and three on the
next higher level. Results of the
comparison between the radon
concentration measured during the
first and second quarters of 1987
showed that most of the houses had
slightly higher concentrations during
the second quarter. These results
are contrary to expected trends.
Two houses with slightly elevated
radon levels received additional
radon reduction applications at the
end of the second quarter of 1987. In
one house, the radon concentration
was successfully reduced, and in the
other, essentially unchanged.
This Project Summary was
developed by EPA's Air and Energy
Engineering Research Laboratory,
Research Triangle Park, NC, to an-
nounce 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
Data are being collected on the radon
levels in 10 houses in Clinton, New
Jersey. The U.S. Environmental Pro-
tection Agency had previously screened
these 10 houses for indoor radon and
had retrofitted them with mitigation
systems. The monitoring phase of this
activity occurred in the spring of 1986,
mitigation systems were installed in the
fall of 1986, in time for the winter heating
season. All work in 1986 was performed
by Research Triangle Institute (RTI) and
is documented in the report, "Devel-
opment and Demonstration of Indoor
Radon Reduction Measures for 10
Homes in Clinton, New Jersey,"
EPA/600/8-87/027 (NTIS PB87-215
356).
To compile a complete data base
showing the effects of the radon
reduction systems installed in Clinton in
1986, EPA contracted with PEI
Associates, Inc., to perform follow-up
radon monitoring. Alpha track detectors
(ATDs) were installed in each house in
January 1987 and retrieved in April 1987
Other ATDs were installed in April 1987
and retrieved in July 1987 Charcoal
canisters (CCs) were also installed in
each house in April 1987, and a special
study entailed installation of additional
CCs at some of the houses in June and
July 1987.
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Radon Monitoring with Alpha
Track Detectors
ATDs were obtained from Terradex
Corporation in Glenwood, Illinois. The
detectors use radiation-sensitive plastic
to record the energy transferred by alpha
particles emitted during radon decay.
Each detector is self-contained in a
small lattice-topped plastic casing and
is provided with a paper filter to prevent
entry of particles formed during radon
decay. Radon, a gas, passes through the
paper filter and releases an alpha particle
as it decays. The alpha particles
released while inside the detector
transfer their energy to the plastic as
they strike it and produce an energy
track etching. The tracks are later
counted, and the number of counts is
converted to a radon concentration. The
exposure period of the detector is taken
into account during this count.
The ATDs were deployed in each
house to obtain a long-term average
radon concentration. The planned
exposure period was 3 months. Sixty-
six SF detectors, numbered consecu-
tively from 474801 to 474850, 477611 to
477613, and 477638 to 477650, were
obtained for subsequent deployment on
April 16 and 17, 1987, and analysis at the
1pCi/l sensitivity level The detectors
were received in sealed aluminum
packages.
Six ATDs were deployed in each
study house. Triplicate detectors were
placed in two different locations
representing high-use areas of each
house. The detectors were either placed
on a shelf or hung from an interior wall or
ceiling beam. An effort was made to
place the detectors near the middle of
the house, away from exterior walls and
windows. The detector number was
recorded as each ATD was deployed
The detectors were deployed at random,
without regard for maintaining a
consecutive number sequence in each
house, to minimize bias during analysis
and reporting of results. To assist in
record-keeping and retrieval, the
aluminum packages for each house were
clipped together in separate groups. This
allowed the field installer to recheck the
accuracy of recorded information in the
office.
The detectors were retrieved on July
20 and 23, 1987. When retrieved, each
detector was placed in its original
aluminum package, sealed with tape, and
sent to the supplier for analysis. The six
extra detectors were also returned to the
supplier as blanks after the packages
had been opened and labeled as if they
had been deployed with the others.
Radon Monitoring with
Charcoal Canisters
CCs were obtained from the EPA
Office of Radiation Program's (ORP)
Eastern Environmental Radiation Facility
in Montgomery, Alabama. The CCs are
filled with a measured amount of
activated carbon and fitted with a screen
to prevent spilling. Each CC is self-
contained in a steel container with a filter
to prevent entry of particles formed in
the monitoring environment. The radon
passes through the filter and adsorbs on
the carbon. As the radon decays, the
decay products remain on the carbon.
Because the decay products are gamma
emitters, the amount of radon that had
decayed on the carbon can be calculated
by measuring the activity of the decay
products on the carbon.
The CCs are deployed by removing
the tape seal and placing the CC in the
monitoring area. The exposure period for
CCs is 2 to 3 days. Two CCs were
deployed in each house included in the
special study phase following the second
quarter alpha track testing. These
samples were taken at the completion of
the additional remediation to estimate the
benefit of the additional measures.
Additional Mitigation
Between June 29 and July 3, 1987,
special studies were performed at two of
the study houses to determine if
additional remediation could be
achieved. The two houses subjected to
this special study were C7-E and C10-
D. The results obtained during the first
sampling period had shown that both
houses still had elevated radon
concentrations with respect to the target
concentration of 4pCi/l. The first
sampling period produced 3-month
average results of 10.8 and 9 1 pCi/l on
the upper and lower levels of house C7-
E, respectively; and 4.8 and 10.8 pCi/l on
the upper level and basement of house
C10-D, respectively. The goal of the
special studies was to reduce radon
levels in both houses to below the target
concentration of 4pCi/l.
Most of the time during the special
study was spent on house C7-E, which
was of different construction from that of
all the other houses in the Clinton radon
study. Grab samples were collected at
numerous locations within the crawl
space and the exterior walls of the house
by using Lucas cells A Pylon monitor
operated continuously was also used oi
the outside of the house to investig^|
the possibility of reentrainment from tro
suction exhaust point. All sample results
which were assessed qualitatively
indicated that two exterior block walls c
the slab-on-grade had high rado
levels, and that these walls were nc
affected by the block wall suction syster
previously installed in the house
Reentrainment had not been observec
The additional remediation warranted b
these results was to apply a suction t
these two walls to contain high rado
concentrations. Suction was applied t
the two exterior block walls by fir:
increasing the fan size in the suctio
system and then installing a 4-in. (1
cm) PVC pipe in the corner of the tw
adjoining walls. This 4-in. (10 cm) pip
was then joined to the existing block wj
suction system. Because of acces
limitations, the new pipe was run on th
outside of the house. Pressure different!;
measurements at the completion of th
installation indicated that the two bloc
walls were adequately connected to th
suction system. The cost to install th
additional remediation system was aboi
$500, including skilled labor an
supplies.
Work in house C10-D was concei
trated in the basement, where tr
previously installed system consisted
two subslab suction points: one at it
sump and the other at the opposite er
of the basement. Investigations i
possible remedies consisted of meast
ing the negative pressure field below tl
slab, measuring the negative pressure
the block walls, and using Lucas cells
collect grab samples for qualitatn
analysis. These investigations reveal*
that the negative pressure field below tl
basement slab was adequately di
tributed throughout the entire area ai
that the negative pressure extended in
some of the block walls. Three of tl
walls, those closest to the slab-o
grade portion of the house, howev<
showed no indication of negati'
pressure. Based on the mvestigatio
conducted, the additional necessa
remediation consisted of sealing the ar
around the sump and most of the see
between the floor and walls of t
basement. In addition, the three bio
walls determined to be without negati
pressure were connected directly to t
suction system by tapping into t
intersecting corner of two of the walls a
installing a 4-in. (10 cm) PVC pipe t
tween the corner and the subslab sucti
system. Measurements were made
determine the requirements to delh
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adequate suction to all portions of the
ubslab area and basement block walls.
The cost to perform the additional
remediation was minimal (based on the
use of two tubes of sealant), and is not
considered an increase in the original
cost of remediation.
Results and Discussion
Based on the control samples and the
triplicate ATDs, the results reported by
the analytical laboratory appear to be
good. Table 1 presents the AID average
concentration for both sampling periods
for each house and compares these
levels with the premitigation levels
measured by charcoal canisters. Results
of the comparison between periods
generally show radon levels similar to
thos.e measured during the first sampling
period, but results for most of the houses
indicate slightly higher concentrations
during the second period. These results
are contrary to expected trends: for the
first period, samples were collected
during the heating season, when radon
concentrations are assumed to be higher
than in other seasons. The results for the
second sampling period in House C2-B
are significantly higher than those for the
first period. The second-period results
at House C5-B are also significantly
higher than the first-period results. All
other second-period results, although
slightly different, are not significantly
different from results obtained during the
first sampling period.
The data presented in Table 1 reveal
a condition that warrants further attention.
Table 1 shows a second period radon
concentration of over 11 pCi/l on both
levels of the house C2-B. This leads to
the conclusion that the radon reduction
system in house C2-B experienced
reduced effectiveness during the second
period.
Although a direct comparison of pre-
and post-mitigation concentrations re-
sults in only partially valid conclusions
(because the measurements were made
during different seasons and house
conditions), the data in Table 1 indicate
that substantial reductions have been
achieved in many study houses.
Based on CC samples collected
shortly after the additional remediation
was completed in the two houses
included in the special study, an
improvement was shown in the radon
levels in house C10-D, but little or no
improvement in the levels was measured
in house C7-E. Because of the short-
term nature of the charcoal canister
measurements, however, the effect of the
additional remediation in these two
houses cannot be fully assessed until
after an additional 3-month ATD
average concentration is obtained.
Table 1
Comparison of Radon Levels Between Sampling Periods
ATD Average Period 1,
House No. Jan-April, 1987, pCi/l
ATD Average Period 2, Concentrations at Beginning of
April-July, 1987, pCi/l Study, March 1986, pCi/l
C1-A
C2-B
C3-C
C4-A
C5-A
C6-B
C7-&
C8-A
C9-B
c JO-DC
2.6*
2.9b
5.0
33
5.4
4.2
3.4
3.6
5.4
8.5
7.2
8.4
10.8
9.1
1.5
1.7
6.3
6.0
4.8
10.8
3.73
3.8"
15.6
11.6
4.8
5.5
2.9
3.1
8.6
11.6
9.4
9.2
72.0
72.3
1.8
2.7
3.7
3.8
3.3
72.8
22546
697
7790
7500
635
936
426
797
670
7357
aupsfa/rs.
bDownstairs.
cModifications to radon reduction systems in houses C7 and C10 were completed at the end of the
second period and are therefore not reflected in these results
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Joseph Carvitti is with PEI Associates, Inc., Cincinnati, OH 45246
Michael C. Osborne is the EPA Project Officer (see below).
The complete report, entitled "Clinton, New Jersey, Radon Mitigation Follow-
up and Long-term Monitoring," (Order No. PB 88-198 528/AS; Cost:
$12.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
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
U.S.OFFICIAL MAR
Official Business
Penalty for Private Use $300
EPA/600/S7-88/005
•0000329 PS
U S i««R PROTECTION *S6«CY
CHICAGO
* U S GOVERNMENT PRINTING OFFICE 1988—548-013/87058
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