United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/540/S2-85/003 Mar. 1988
&ER& Project Summary
Fugitive Dust Control
Techniques at Hazardous
Waste Sites: Results of Three
Sampling Studies to Determine
Control Effectiveness
Keith D. Rosbury, Kenneth Axetell, Jr., Stan R. Lueck, and Robert A. Zimmer
Data is presented for several methods
of controlling contaminated dust at
hazardous waste sites. Commercial
dust suppressant products were applied
to exposed areas and soil storage piles
to control wind erosion emissions.
Windscreens were also used to control
emissions from the storage piles. The
chemical dust suppressants were effec-
tive in controlling wind erosion emis-
sions in both applications. Windscreens
were effective in reducing windspeed
but did not produce commensurate
reductions in particulate concentrations
coming from the pile. Emissions gen-
erated by equipment movement during
active cleanup were controlled by
spraying the active work area with water
and with a water-surfactant mixture.
Emissions generated by loading soil into
a truck were controlled with an array of
spray nozzles mounted on the sides of
the truck bed. A similar array of foam
nozzles was also used to control loading
emissions. All of these methods were
effective in reducing emissions gener-
ated by active cleanup.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH.
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
Land surfaces contaminated with toxic
chemicals can lead to subsequent human
exposure through many routes. One of
these routes is entrainment of contam-
inated soil particles and transport offsite
in the air.
There are three basic mechanisms by
which soil containing toxic chemicals can
become entrained:
Wind erosion
Reentrainment by moving vehicles
Disturbance of the soil surface during
active clean-up of a hazardous waste
site
The purpose of this project.was to investi-
gate control measures for these potential
airborne dust sources at hazardous waste
sites.
A review of previous research in this
area revealed that most studies have
been concerned almost exclusively with
control of dust from vehicle reentrain-
ment. Therefore, the decision was made
that the present study would focus on
controls for airborne emissions from wind
erosion and active cleanup operations.
Three separate field studies were per-
formed concurrently at different sites to
evaluate fugitive dust control measures:
Active cleanup emissions resulting
from loading soil into a truck with a
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front-end loader, controlled with area
spraying and with a spray curtain.
Wind erosion of inactive surfaces,
controlled with chemical dust suppres-
sants.
Wind erosion of an inactive soil storage
pile, controlled with windscreens alone
and in conjunction with other control
measures.
The report contains the results of these
three field studies. Another report entitled
"Handbook of Dust Control at Hazardous
Waste Sites" incorporates the test results
into recommendations for controlling dust
at contaminated sites.
Methodology
Exposed Area Testing
Twenty-one test plots were prepared by
removing vegetation and topsoil from
areas 50 ft. x 50 ft. Several smaller 4 ft. x
8 ft. plots were also prepared. A tracer
was applied to the bare plot before the
plot was treated with a specific dust
suppressant. Zinc oxide and zinc sulfate
were used as tracer compounds. Soil
particles eroding from the exposed areas
were sampled along the perimeters of the
plots with saltation samplers. Samples
were also taken from the treated surface
of the plot with a vacuum apparatus. The
presence of zinc in either sample indi-
cated a failure of the "seal" formed by the
dust suppressant.
Storage Pile Testing
The test site contained a single pile of
shredded topsoil and a 75 ft. long, 8 ft.
high windscreen that could be readily
shifted to different positions around the
pile. Paniculate samplers were placed
upwind and downwind of the pile/screen
area to measure the particulate concen-
trations from wind erosion and the re-
duction in concentration due to the
windscreen and other controls. Wind-
speed and wind direction sensors were
also placed upwind and downwind of the
pile and screen. A large number of tests
were performed at different windspeeds
with and without the windscreen. From
the resulting values, the average reduc-
tion in net concentration (downwind
minus upwind) was determined for each
control alternative as a function of wind-
speed. Screen-to-pile distances of 5, 15,
and 25 m were tested.
Active Cleanup Testing
The operation selected for testing con-
sisted of a front-end loader (FEL) and
dump truck combination. The FEL scraped
material from the surface, turned and
traveled to the dump truck where the load
was dumped. Exposure profiling was used
to sample the dust emissions downwind
of the operation. The primary sampling
instruments were isokinetic profiler
heads utilizing a stacked filter concept.
Four control measures were evaluated.
Control measure 1 consisted of spraying
the active working area of the FEL and
dump truck with water (0.9 gal/yd2). For
control measure 2, application procedures
were identical to those used in the plain
water application, but a surfactant was
added to the water to form a 1:1000
dilution of surfactant to water. This
mixture was applied at a rate of 0.75
gal/yd2. Control measure 3 consisted of
an array of 12 spray nozzles on the sides
of the dump truck emitting a continuous
spray of the water/surfactant mixture.
This method was used to control emis-
sions from the dump cycle. The final
method, control measure 4, utilized 4
spray nozzles at the corners of the truck
bed to disperse a foam solution. The foam
spray operated only during each dump.
Quantities of liquid average 1.5 gal/yd3
and 0.4 gal/yd3 respectively for the last
two control measures.
Discussion of Results
Exposed Area Testing
Surface sampler (vacuum sample) re-
sults did not appear to be reliable based
on methodological problems. It is theo-
rized that the force of the vacuum may
have damaged the integrity of the "seal"
formed on the soil surface by the dust
suppressant products. Evaluation of the
saltation sample results shows varying
degrees of control among the products
tested. Most of the products dropped
below 100 percent effectiveness two to
four weeks after application. The gradual
upward trend in zinc concentration in the
samples indicates that a dust controlling
"seal" was initially formed but soon
began to deteriorate.
Storage Pile Testing
A total of 82 tests were taken47 with
the pile surface dry, 14 with watering,
and 21 with dust suppressant products
applied. Hourly average windspeeds
varied from 4.1 to 24.1 mph. Windspeed
reductions resulting from the windscreen
decreased as the screen-to-pile distance
increased. These reductions were fairly
independent of incoming windspeed and
were consistent with reductions reported
previously in the literature. The screen
did reduce windspeeds by the amount
anticipated, but this did not result in
commensurate reductions in particulate
concentrations coming from the pile.
Taken in total, the results indicate that
the windscreen did not produce consis-
tent or significant reductions in wind
erosion. An explanation for the wind-
screen's performance, developed after
review of all the data from this study, is
that wind erosion emission rates in the
less than 10 micrometer size range are
fairly constant at windspeeds above the
threshold of 7 mph (hourly average). The
additional emissions associated with high
wind erosion losses at high windspeeds
are larger particles that are not detected
by the type of sampler used in this study
(GCA RAM-1). The windscreen may be
effective in stopping or reducing the
movement of these larger particles, but
many of them do not stay airborne
because of their relatively large size.
Thus, they present less of a threat of
offsite exposure. Chemical dust suppres-
sants, without the windscreen, were very
effective in reducing wind erosion, re-
ducing concentration by 6 to 8 //g/m3.
The tests of the windscreen in combina-
tion with watering or chemical dust
suppressants inexplicably showed that
the screen was counterproductive.
Active Cleanup Testing
Water spraying over the area being
worked by the FEL and truck resulted in a
control efficiency of 42 and 64 percent for
less than 30 and less than 2.5 (TSP and
FP) micrometer size particles. Surprising-
ly, the emissions from the dump cycle
were reduced 63 and 70 percent for TSP
and FP. Adding surfactant to the water
increased control efficiencies slightly
while allowing the quantity of water used
to be reduced. TSP control efficiency for
the FEL travel/scraping increased from
42 to 69 percent with the addition of the
surfactant. Other control values had
smaller increases.
Both the spray curtain control measures
were shown to be less effective than the
area spray with the water/surfactant
mixture. However, a redesign of the
controls used may result in higher effi-
ciencies. Of the two, the water curtain
was somewhat better for control of dust
from the dump cycle than the foam
curtain. If one of these controls were used
in conjunction with the water/surfactant
area spray, the resulting control efficiency
would probably be significantly greater
than for either one alone.
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Drier conditions than were experienced
during testing would require greater
quantities of water. It is unlikely that the
goal of 100 percent control efficiency can
be obtained with these technologies,
potentially causing subsequent human
exposure impacts.
The full report was submitted in ful-
fillment of Contract No. 68-02-3512 by
PEI Associates, Inc., under the sponsor-
ship of the U.S. Environmental Protection
Agency and the U.S. Army Toxic and
Hazardous Materials Agency.
Keith D. Rosbury, Kenneth Axetell, Jr., StanR. Lueck, and Robert A. Zimmer are
with PEI Associates, Inc., Golden. CO 80401.
Stephen C. James is the EPA Project Officer (see below).
The complete report, entitled "Handbook: Dust Control Techniques at Hazardous
Waste Sites." (Order No. PB 86-190 105/AS; Cost: $11.95, 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:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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