AEPA
United States Industrial Environmental Research EPA-600/7-79-115
Environmental Protection Laboratory May 1979
Agency Research Triangle Park NC 27711
Assessment of Road
Carpet for Control
of Fugitive Emissions
from Unpaved Roads
Interagency
Energy/Environment
R&D Program Report
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EPA-600/7-79-115
May 1979
Assessment of Road Carpet for Control
of Fugitive Emissions from Unpaved Roads
by
T. R. Blackwood
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45407
Contract No. 68-02-3107
Program Element No. EHE624A
EPA Project Officer: Dennis C. Drehmel
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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ABSTRACT
Historically, emissions from unpaved roads have been controlled
by watering, oiling, and chemical soil stabilization. An analy-
sis of the forces which produce emissions shows that if fine
material can be reduced, fine particle emissions (<15 vim) will
also be reduced. A new concept for control has been proposed
which utilizes a stable, rot-resistant, water permeable fabric to
separate road ballast from subsoil. Fine material is not accu-
mulated in the ballast due to gravitational and hydraulic forces
during normal rainfall. Preliminary studies indicate that fine
material will pass through the fabric without "blinding" and
fines in the subsoil do not "pump into the ballast from the
subsoil. Economic evaluations show that roads constructed with
the fabric are cheaper for emissions control than conventional
control methods. The effectiveness of control cannot be calcu-
lated; however, continuing research is anticipated. Construction
and testing of a prototype road is anticipated in early 1979.
111
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CONTENTS
Paqe
Abstract
Figures vi
Tables vii
1. introduction 1
2. Summary and Recommendation 2
3. Description of Concept 3
Background 3
The road carpet concept for emissions control .... 5
4. Theory of Emissions from Unpaved Roads 7
Factors affecting emissions 7
Estimation of emissions from unpaved roads 10
5. General Theory of Road Carpet Operation 14
Pumping of solids 15
Removal of fines contaminating the ballast 16
6. Economics of the Road Carpet Concept 20
References 26
Appendix
A. Raw data for determination of flow characteristics of
suspended solids through BIDIM fabric 28
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FIGURES
Number Page
1 This concept employs a road carpet which spreads the
vehicular load, prevents moisture from eroding the
graded area, and keeps the dirt from reaching the
tires where it can be picked up and dispersed. ... 5
2 The siphoning action of the road carpet aids in sub-
surface soil consolidation even in the presence
of an ascending gradient 14
3 This picture, taken one year after installation of
BIDIM fabric, shows the ballast remains clean with
minimum contamination. The lower insert shows the
result of fine soil particles being pumped up into
the ballast 15
4 Blockage of fabric due to bentonite clay in water. . . 17
5 Blockage of fabric due to Hoytville clay in water. . . 17
6 Laboratory instrument used to evaluate in-plane flow
of slurries through fabrics 18
7 Design curves for 18 metric ton axle load 24
VI
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TABLES
Number Page
1 Average Surface Coal Mine Respirable Particulate
Emissions 4
2 Tests of Unpaved Road Emissions 8
3 In-Plane Water Transport of Fabrics 18
4 Comparison of Flowrates Through BIDIM Fabric 19
5 Capital Costs of Unpaved Road Construction 21
6 Capital Cost of Construction of Unpaved Road Using
Fabric 22
7 Operating Costs of Watering and Oiling Control Options 23
8 Amortized Costs of Dust Control on Unpaved Roads ... 25
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SECTION 1
INTRODUCTION
Fugitive emissions from vehicular movement on unpaved industrial
haul roads are the major source of respirable emissions from
urban quarrying. Current control methods, which include water
wetting, treatment with surface agents, soil stabilization,
paving, and traffic control, have their own merits and limita-
tions. Environmental problems could result from surface agents
(such as oil) leaching into streams. Safety problems could
result from slippery and dangerous road conditions. High
initial cost and subsequent maintenance and repair costs make
otherwise effective control measures (such as paving) impractical,
A new concept for emissions control has been proposed based on
the use of a civil engineering fabric which is synthetic, stable,
water-permeable, rot-resistant and usually employed in road
stabilization. Laid below the haul road overburden, this tough
fabric termed "Road Carpet" separates the fine soil particles in
the roadbed from the coarse aggregate. This action prevents the
fine material from reaching the road surface so that dust emis-
sions are reduced.
This report describes the theory of operation of this concept to
control of emissions from unpaved roads. Preliminary test data
are included, and the economics of application are presented.
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SECTION 2
SUMMARY AND RECOMMENDATION
The "road bed" concept has the potential for preventing virtually
all of the emissions from unpaved roads at little or no additional
cost over conventional controls. Any dust which falls to the
road will be restricted, and most emissions that might occur
would come from the grinding action of the vehicles over a short
period of time. Any fines (less than 15 ym) in the road surface
would be removed during rainfall by being washed into the road
ballast. Fine dust which enters the ballast will pass through
the fabric either into the subsoil or to the edge of the road.
Fines in the subsoil cannot be pumped up into the ballast
because of the siphoning action of the fabric. Thus essentially
all of the sources of fine dust are eliminated from the road
surface. Preliminary measurements have shown that emissions
increase when the concept is reversed. Preliminary economics
indicate that roads constructed using fabric stabilization are
40% to 50% cheaper than conventional roads on soft soil. For
firm soil, the road with fabric is 10% more expensive and may
require replacement during the life of a quarry or mine. How-
ever, maintenance would be insignificant for the road with
fabric compared to the conventional costs of dust control. For
permanent or temporary roads, this new concept is cheaper over
the life of the plant for soft soil. On firm soil, the permanent
road with fabric may be cheaper depending upon inflation and the
life expectancy of the fabric. For temporary roads, the concept
would be about 10% more expensive; however, firm subsoil is
unusual for temporary roads.
It is recommended that a prototype of this concept be installed
at a quarry and that experiments be conducted to evaluate the
following:
• The reduction in fine dust (less than 15 ym) compared
to the same unpaved road with no control, watering and
oiling (if possible).
• Deterioration of the road containing fabric, including
ballast replacement.
• Factors which may improve the concept for emissions
control.
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SECTION 3
DESCRIPTION OF CONCEPT
BACKGROUND
Health hazards and haze problems are associated with fugitive
emissions from industrial processing. Emissions of particulates
and other pollutants from open source industries, which emit air
pollutants primarily in a nonpoint source manner, have drawn
increased attention in recent years because of frequently
encountered fugitive emission problems. Consequently, new con-
cepts for controlling fugitive particles are being sought.
Sources of Emissions
From an industrial standpoint, the hauling of raw materials from
mines or quarries to processing plants by large rubber-tired
hauling vehicles over unpaved haul roads is responsible for a
major portion of the fugitive dust generated by quarrying and
mine operations.
Emissions occur due to comminution, vortex entrainment, and
saltation. Comminution is the grinding of the aggregate between
the truck tires and the road surface. Vortex entrainment suspends
the smaller particles as the truck creates a wind over the road.
As large aggregate falls on a dusty road surface (kicked up from
the tires), the smaller particles are suspended from the impact;
this is called saltation.
In the crushed limestone industry, for example, total particulate
emissions from vehicular movement on unpaved roads (between quarry
and plant) contribute approximately 66% of the overall emissions
and 35% of the respirable emissions, i.e., particles smaller than
7 pm (1). Similarly, for an average surface coal mine, the
transport and unloading operations contribute 40.8% of the over-
all respirable particulate emissions (2), as shown in Table 1.
(1) Chalekode, P. K., T. R. Blackwood, and S. R. Archer. Source
Assessment: Crushed Limestone State of the Art. EPA 600/2-
78-004e, U.S. Environmental Protection Agency, Cincinnati,
Ohio, April 1978. 61 pp.
(2) Rusek, S. J., S. R. Archer, R. A. Wachter, and T. R. Black-
wood. Source Assessment: Open Mining of Coal State of the
Art. EPA 600/2-78-004x, U.S. Environmental Protection
Agency, Cincinnati, Ohio, September 1978. 87 pp.
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TABLE 1. AVERAGE SURFACE COAL MINE RESPIRABLE
PARTICULATE EMISSIONS (2)
Percent of
respirable
Operation emissions
Drilling 11.9
Coal loading 14.8
Transport and unloading 40.3
Blasting 31.9
Augering 0.6
Total ^100
These emission sources are important because most quarrying
occurs in urban areas and mining is an important part of the
national economy. Since the price of raw materials, especially
aggregate and construction materials, is a function of the haul
distance from the plant to the consumer, most quarries are
located near the mass of population which consumes its product.
Quite often several quarries surround the urban area which can
make these emission sources a constant problem in attaining
acceptable urban air quality.
Conventional Methods of Emission Control
Emissions from hauling operations are proportional to the
condition of the road surface and the volume and speed of
vehicular traffic (3). Control measures include methods to
improve road surfaces, suppress dust, or minimize the effect of
vehicular traffic by means of operations changes. Currently
available control measures, which include water wetting, treat-
ment with surface agents, soil stabilization, paving, and traffic
control, each has its own merits and limitations (3). Watering,
for example, may be totally ineffective on warm and windy days
because of rapid evaporation. Excessive watering may result in
muddy, slippery road surfaces which create hazardous conditions
for haulage vehicles.
The most commonly applied form of surface treatment is oiling.
Although the frequency of application is significantly reduced,
a potentially adverse environmental impact may result due to
oil leaching into streams. Oiling is usually supplemented by
(3) Ochsner, J. c., P. K. Chalekode, and T. R. Blackwood. Source
Assessment: Transport of Sand and Gravel. EPA600/2-78-
004y, U.S. Environmental Protection Agency, Cincinnati, Ohio
October 1978. 62 pp.
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watering and, again, improper application can cause slippery,
dangerous road conditions. Other surface treatments include
the application of hygroscopic chemicals (which absorb moisture
from the air). These chemicals dissolve in the moisture which
they absorb and form a clear liquid that resists evaporation.
However, since they are water soluble, their use in areas of
frequent rainfall may require repeated application. Additionally,
these agents may contribute to increased corrosion of expensive
haulage vehicles.
Soil stabilizers usually consist of a water-dilutable emulsion
of either synthetic or petroleum resins which acts as an
adhesive or binder. Substantial success has been reported by
quarry operators using one such soil stabilizer. In addition to
the environmental benefits, operators report considerable savings
and operating benefits over traditional watering methods including
reduced labor costs, lower maintenance costs on haulage vehicles,
and safer road conditions. Daily applications of these chemicals,
however, are required to effectively control dust emissions.
Paving is probably the most effective means of reducing some of
the particulate emissions, but it may be impractical due to
high initial cost and subsequent maintenance and repair costs.
Operational methods that would result in reduced emissions
include the reduction of traffic volume, control of traffic
speed, and replacement of smaller haulage vehicles with larger
capacity units.
THE "ROAD CARPET" CONCEPT FOR EMISSIONS CONTROL
A new, effective, and economical technique is desired for the
control of fugitive particle emissions. This project involves
the application of nonchemical road stabilization as a control
option. The concept uses a stable, water-permeable, rot-resistant
polyester fabric ("road carpet") laid below haul road overburden
to separate the roadbed from the coarse aggregate as shown in
Figure 1.
COARSE AGGREGATE
GRADED AREA (CLAY)
Figure 1. This concept employs a road carpet which spreads the
vehicular load, prevents moisture from eroding the
graded area, and keeps the dirt from reaching the
tires where it can be picked up and dispersed.
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The fundamental concept behind the use of a fabric roadbed
stabilizer, or road carpet, for the control of fine particle
emissions from haul roads is the prevention of vortex entrain-
ment and saltation effects by the separation of fine roadbed
materials from the coarse aggregate. Large aggregate is held
from settling, while fines (less than 70 ym) are filtered by
gravitation and hydraulic action. Road carpet can be made from
spun-bonded, thin-film polypropylene on nylon sheet (Celanese),
continuous filament polyester fibers needled to form a highly
permeable fabric (Monsanto Company), or other synthetic materials
spun or needle punched. The mechanical interlocking of fibers
makes a formed fabric with the durability and toughness required
for the proposed use. Designed for road construction use, this
fabric is laid over poor load-bearing soils to help support and
contain the overburden aggregate. It spreads the concentrated
stress from heavy-wheeled traffic over a wider area, siphons
away ground water, and contains fine soil particles in the road-
bed that can otherwise contaminate road ballast.
Use of road carpet results in no health or safety hazards or in
any other unfavorable environmental impact. In the development
of these fabrics, various synthetic polymers, including nylon,
propylene, and polyester were screened and evaluated. Fabrics
made from any of these products generally are resistant to mildew,
mild acids, and alkali, and are rot and vermin proof. Polyester
was chosen by Monsanto Company because of the following distinct
advantages (4):
• resistance to chemicals, including those found in soils
• constant properties over a wide range of temperature
• high melting point
• little change in properties wet or dry
• low moisture absorption
• high abrasion resistance
• high modulus of elasticity and excellent resilience
• excellent creep resistance.
Thus, use of road carpet precludes any environmental damage due
to leaching of hazardous chemicals or heavy metals.
(4) BIDIM® Engineering Fabric for Soil Stabilization and Drain-
age. Product Brochure published by Monsanto Company,
St. Louis, Missouri. 24 pp.
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SECTION 4
THEORY OF EMISSIONS FROM UNPAVED ROADS
FACTORS AFFECTING EMISSIONS
Once fugitive particles are airborne, they must be collected in
order to be suppressed. The most effective approach to solving
the emissions problem is thus to prevent the particles from
becoming airborne. For unpaved roads within industrial process-
ing areas, roads are usually constructed to serve haul trucks for
a limited period of time (e.g., 4 to 6 months). These roads are
usually created by bulldozing and grading a path from the working
site (mine or quarry) to the processing plant (crusher or tipple),
To create traction and to prevent subsidence of the road, a
coarse aggregate is usually placed on the graded surface. The
emissions are generated by comminution, vortex entrainment, and
saltation of the large aggregate. These mechanisms are related
to air turbulence and the mechanical forces of tires on the road
surface. Emissions, Eu (g/vehicle), are affected by several
factors which can be used to relate dependent and independent
variables in equation form:
• vehicle speed (V), km/hr
• number of wheels/vehicle (N)
• particle size distribution (P), %
• surface moisture (M), or P.E. index
• vehicle weight (T), metric tons
• vehicle cross section (A), m2
• tire width (W), m
• length of unpaved road (L), m
A literature search yielded only scattered quantitative informa-
tion on emissions from unpaved roads. Most of the reported
studies were directed toward quantifying the influence of
vehicle speed on unpaved road emissions.
Vehicle Speed
Table 2 lists results of various tests conducted on emissions
from unpaved roads.
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TABLE 2. TESTS OF UNPAVED ROAD EMISSIONS
Investigator
Sampling site
Type
of road
Vehicle
speed ,
kra/hr
Emission
factor,
g/veh-m
Particle size
distribution, urn
Anderson, C. (5)
School of Engineering,
University of Wew Mexico (5)
Pedco-Environmental
Specialists, Inc. (6)
Bernalillo County, NM Dirt
University of NM Dirt
Sante Fe, NM
Engineering Research Institute, Powshiek County, IA
Iowa State University
Puget Sound Air Pollution
Control Agency (7)
Duwamich Valley, WA
Dirt
Dirt
Gravel
48
40
24
40
56
64
16
32
48
0.14 to 0.20
0.26
0.01
19
28
56
0.99
1.55
0.62
0.12
0.03
2.40
2.48
0.65
0.68
0.08
3.92
1.47
0.12
No designated size distribution.
<6
<3
<2
_a
~a
<10
<2
a
<2
Midwest Research Franklin County, KS Gravel
Institute (8)
Gravel
Gravel
• Morton County, KS Dirt
Dirt
Wallace County, KS Dirt
48
48
64
48
64
48
1
0
0
1
1
0
1
1
1
2
1
1
0
0
0
6
5
3
.135
.950
.770
.0
.05
.882
.705
.22
.025
.33
.25
.05
.597
.597
.512
.82
.35
.72
2
2
2
2
2
2
>30
to
<2
^30
to
<2
>30
to
<2
>30
to
<2
>30
to
<2
>30
to
<2
30
30
30
30
30
30
(5) Anderson, C. Air Pollution from Dusty Roads. In: Proceedings of the 1971 Highway
Engineering Conference, (Bulletin No. 44-NMSO-EES-44-71, Las Cruces, New Mexico, 1971.
12 PP.
(6) Investigation of Fugitive Dust Sources, Emissions, and Control. Contract 68-02-0044, U.S.
Environmental Protection Agency, Research Triangle Park, North Carolina, May 1973. 152 pp.
(7) Roberts, J. W., A. T. Rossano, P. T. Boseerman, G. C. Hofer, and H. A. Waiters. The
Measurement, Cost and Control of Traffic, Dust and Gravel Roads in Seattle's Duwamish Valley.
In: Proceedings of the Annual Meeting of the Pacific Northwest International Section of the
Air Pollution Control Association, Paper No. AP-72-5, Eugene, Oregon, 1972. 10 pp.
(8) Cowherd, J., Jr., K. Axetell, Jr., C. Guenther, F. Bennett, and G. Jutze. Development of
Emission Factors for Fugitive Dust Sources. EPA-450/3-74-037, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, June 1974. 172 pp.
The study conducted by the Puget Sound Air Pollution Control
Agency can be used to predict a mathematical relationship for
the emission of respirable particles from unpaved roads. Their
results show that emissions of particles less than 2 um in
diameter are proportional to the vehicle speed (V), and those
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less than 10 ym in diameter are proportional to the square of
the vehicle speed (V2). Based on this study, one could expect
emissions of respirable particles (less than 10 ym) to be propor-
tional to (aV2 + bV) where a and b are constants. Then
Eu = (aV2 + bV) (1)
where E = emissions, g/vehicle
V = vehicle speed
a, b = constants
Number of Wheels
A vehicle moving on an unpaved road generates dust in proportion
to the number of its wheels. Thus,
EU - N (2)
where N = number of wheels per vehicle
particle Size Distribution of the Road Surface Material
particles greater than 100 ym are moved by saltation and surface
creep3 and are deposited in or near the affected area.
Particles less than 10 ym are moved by the wind, mostly by sus-
pension, and are carried over long distances from their sources.
Thus, smaller particles from unpaved road emissions have a
significant impact on ambient air particulate levels. Wind-
tunnel studies and open-field measurements show that the propor-
tion of movement by suspension is approximately equal to the
proportion of particles less than 100 ym found in the soil (9).
Hence,
Eu « P (3)
where P = percent of particles (less than 100 ym) in the road
surface material (0 cm to 10 cm depth)
aSaltation refers to movement of particles (100 ym to 500 ym) in
a series of short bounces, and surface creep refers to the
rolling and sliding of particles (greater than 500 ym) along
the surface of the ground. Soil movement in saltation occurs
below a height of 0.6 m to 1.0 m above ground level; over 90%
of the soil transported by saltation is below a height of
0.3 m from ground level (9).
(9) Chepil, W. S. Dynamics of Wind Erosion: I. Nature of the
Movement of Soil by Wind. Soil Science, 60(4):305-320, 1945.
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Surface Moisture
As particle moisture increases, the cohesive force between
particles increases, and therefore, the rate of soil entrainment
decreases. The rate of soil movement varies inversely as the
square of its moisture content (10). However, soil surface
moisture is assumed to be proportional to the Thornthwaite
Precipitation-Evaporation (PE) Index. The PE Index is determined
from the total annual rainfall and mean annual temperature (11).
(4)
Vehicle Weight, Vehicle Cross Section, and Tire Width
No quantitative data are available in the literature describing
how these factors influence unpaved road emissions.
Distance of Unpaved Road
A vehicle generates dust in proportion to the length of unpaved
road. Thus,
Eu a L (5)
where L = the length of unpaved road.
ESTIMATION OF EMISSIONS FROM UNPAVED ROADS
General Expression for Emissions
Based on available data in the literature, emissions from unpaved
roads can be expressed as follows:
K (aV2 + bV) (P) (N)
Eu = (PEP f(T,A,W)L (6)
where E = emissions, g/vehicle
K = constant of proportionality
Equation 6 is too general to be evaluated with the limited data
available.
(10) Chepil, W. S., W. H. Siddoway, and D. V. Armburst. Climat-
ic Factor for Estimating Wind Erodability of Farm Fields.
Journal of Soil and Water Conservation, 17:162-165, 1962!
(11) Thornthwaite, T. W. Climates of North American According t
a New Classification. Geographical Review, 21:633-635, 193?
**• •
10
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The overall emissions (Q) due to vehicle traffic are the sum of
the emissions from four basic sources (i.e., vortex entrainment,
comminution, saltation, and creep) . Both saltation and creep
are related to the slippage of material between the time of the
vehicle and the roadway, as is comminutive action. In essence,
the general entrainment model is as follows (where Q is expressed
in g/s) :
Q = QA + QB + Qc + QD (7)
where CL = emissions due to vortex forces (air compression and
expansion)
QR = emissions due to comminution (grinding of the road
by tires)
Qr = emissions due to saltation
Q = emissions due to creep
Qc and QD are functions of the same parameters as QB; consequently,
the general model reduces to the following (with different
internal constants for Qn) :
D
Q = QA + QB (8)
Emissions Due to Vortex Entrainment
As a vehicle passes, air compression and expansion result in a
draft that "pumps" dust into the air. An expression has been
developed for wind erosion from flat storage piles. The follow-
ing expression for coal was derived based upon the results of
wind tunnel experiments conducted at the Pittsburgh Mining and
Safety Center (12)
0.336V3P2s°-35
E =
c - (PE
where E = emissions due to wind erosion of a coal storage
pile, g/s
V = wind speed, m/s
P = bulk density, g/cm3
s = surface area, m2
PE = Precipitation-Evaporation Index
(12) Singer, J. M., F. B. Cook, and J. Gurma. Dispersal of Coke
and Rock Dust Deposits. Bureau of Mines RI-7642, U.S.
Department of the Interior, Pittsburgh, Pennsylvania, 1972.
32 pp.
11
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For a typical haul -road vehicle of 21 metric tons, the 2.4-meter
wide truck displaces a 3-meter width of air over the average
length of travel (2.2 km) (3). If this displaced air can be
raised to two-thirds of the average vehicle speed, 32 km/hr (3) ,
with a soil bulk density of 2 g/cm3 in a PE index region of 100,
then the emission due to vortex entrainment is 0.58 g/s. For the
2.2-km road, the vehicle will travel 248 seconds; hence, the emis-
sion factor is 0.07 grams per vehicle-meter.
Emissions Due to Comminution
Slippage between truck tires and the road surface will suspend
the material in the slippage zone. The larger (greater than
100 urn) material will fall back to the surface rapidly while the
fines (less than 15 ym) will remain suspended for great distances
Material between 15 ym and 100 ym will carry for limited distances
generally less than 20 meters. MRI has determined that emissions
from unpaved roads can be related to vehicle speed and soil
siltiness as shown in Equation 10 (13).
E = 0.23(S) (V/13) (365 - R/365)
where E = emissions, gram per vehicle-meter
R = days of rainfall over 0.03 cm, per year
V = vehicle speed, m/s
S = soil siltiness, %
Soil siltiness is a function of particle size distribution in
soil and affects the depth of soil disruption in the slippage
zone. Vehicle speed also contributes to the depth of soil
displacement. A general model for comminution may take the
form of Equation 11:
(10)
= (k,) = klVWZp (1
where ki = emissions constant
L = length of vehicle travel
W = width of tires
Z = thickness of soil disturbed
p = soil density
T = time of travel
V = vehicle speed, L/T
(13) Cowherd, C. Development of Emission Factors for Fugitive
Dust Sources. EPA-450/3-74-037, U.S. Environmental Protect
tion Agency, Research Triangle Park, North Carolina,
June 1974. 172 pp.
12
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Because the large particles (greater than 100 pm) suspended by
this process result in saltation and creep, the emissions
constant will include this contribution. The thickness of soil
disturbed will be proportional to the vehicle speed and soil
siltiness (5). Thus, the emission rate becomes:
Qn = k2V2SWp = k3V2S (12)
o
where k2, k3 = constants
Equation 12 is similar to that developed by MRI since the factor
(365 - R/365) is an adjustment for the frequency of dry days
when emissions would occur. Use of Equation 10 at the average
conditions of 12% silt and 120 "wet" days (13) yields 1.27 grams
per vehicle-meter. Thus, the effects of vortex entrainment
(0.07 grams per vehicle-meter) are small.
Comminution, or slippage between the road and tire, is the major
part of the problem of unpaved road emissions. While it is not
feasible to eliminate the slippage, the emissions could be
reduced if the fine material (less than 15 um) was eliminated
from the slippage zone. The fine material in the road ballast
comes from three sources as follows:
1) Dirt from the vehicle tires, body, or payload may fall off
and be deposited on the roadway.
2) Soil particles can be pumped up through the road ballast
during rainfall. When the surface drys out, the soil will
be dispersed by the traffic.
3) The ballast may be ground up by the action of the vehicle
tires on the road surface. This material can eventually
become small enough to be suspended.
13
-------
SECTION 5
GENERAL THEORY OF ROAD CARPET OPERATION
An important characteristic of road carpet is its ability to
transport water along the plane of the fabric. This siphoning
action aids in subsurface consolidation. Figure 2 shows a
laboratory model in which the polyester fabric made by Monsanto
Company is placed in direct contract with silty soil. Water
contacting the fabric flows to the edges of the road, even if
there is an ascending gradient. The flow is not materially
affected by the existence of a load. The random entanglement of
the polyester filaments and the low fabric density still enable
groundwater and rain to pass freely through the fabric.
Since the fabric filters selectively, particles larger than
70 ym are held back, while smaller waterborne fines pass through
without clogging or binding. Fine particles which may settle
on the roadway pass through the fabric and re-entrainment is
prevented. This feature shows that the concept has the potential
capability of reducing emissions of fine particles (less than
1 ym) by at least 90%.
Road carpet will prevent pumping of soil particles to the
surface by carrying water out of the ballast. As this water
flows through the ballast, it will pick up the fines due to
material spillage and grinding of the ballast.
41M-]
Figure 2. The siphoning action of road carpet aids in sub-surface
soil consolidation even in the presence of an
ascending gradient (4).
14
-------
PUMPING OF SOLIDS
The road carpet prevents the fine material in the soil from
reaching the road ballast. As shown in Figure 3, the ballast
of a railroad is uncontaminated when the fabric is installed.
Rain is removed rapidly from the ballast to the edge of the road-
way, and the soil remains stable. At a site in Georgia, an
unpaved road was observed to drain free of water after a severe
storm in just over four hours, while an adjacent road without
the fabric remained wet.
Figure 3.
This picture, taken one year after installation of
BIDIM® fabric, shows the ballast remains clean with
minimum contamination (4) . The lower insert shows
the result of fine soil particles being pumped up
into the ballast.
-------
REMOVAL OF FINES CONTAMINATING THE BALLAST
When fine material enters the ballast, from either the aggregate
or traffic, rainfall should carry it down to the fabric. If the
fines do not pass through the fabric, they will build up and
eventually contaminate the ballast. However, preliminary studies
indicate that some fines do pass through some of the fabrics. In
tests of clay blockage rates with vertical water flow, BIDIM and
Cerex fabrics reached a limited blockage of 4 to 18% of the
fabric area. Other fabrics, as shown in Figures 4 and 5, became
essentially plugged up with the clay and bentonite solutions
(private communication, C. J. Setzer, Monsanto Triangle Develop-
ment Center, Research Triangle Park, NC). These results indicate
that the fabric will pass the particles vertically and could be
consolidated into the sub-surface or carried out through the
fabric in a horizontal direction.
To further evaluate the particle transport characteristics of the
fabric, tests were conducted on the horizontal flow through the
fabric. The fabric to be tested was placed in the apparatus
shown in Figure 6, which resembles a bell jar. A constant head
of water was maintained and the horizontal flow measured. In-
plane (horizontal flow) transmissability for several fabrics
was deduced from these tests and is given in Table 3 (personal
communication C. J. Setzer, Monsanto Triangle Research Center,
RTF). In-plane transmissability of water is four to nine times
higher for BIDIM than other fabrics. Additional flow studies
were conducted with typical road dirt suspended in the water
solutions. During the assessment of the transport of sand and
gravel (3), samples of road dirt were collected throughout the
United States to evaluate the composition and dustiness of
unpaved roads near quarries. Since the quarries were in urban
areas, a composite of these samples could be representative of
"typical" unpaved road dust. This composite was suspended in
water and, after settling of the large aggregate (greater than
70 ym), the slurry was sent to the bell jar to measure the in-
plan flow of the slurry. A load equivalent to 0.2 m to 0.25 m
of aggregate was placed on the fabric. Further details are
provided in Appendix A.
Table 4 compares the vertical and horizontal flow rates for the
BIDIM fabric with and without the presence of solids (i.e., clean
water vs slurry). The horizontal flow is reduced to about 40%
of the initial clean water flowrate, but the fabric is not
completely occluded. It is anticipated that, in the real world,
pulsations of flow and channeling may increase the effective
flow rate. This was verified in experimental work by momentarily
raising the pressure on the fabric. Pulsations would result from
the compression and expansion of the fabric under the load of
vehicles. A 17% increase in flow was observed due to these
pulsations. Channeling is a common phenomenon due to the nonhomo-
genicity of the aggregate and soil adjacent to the fabric.
16
-------
50-
40-
TYPAR
MIRIFI
o
—I
m
2
o
a:
20
,10
-CEREX
J_
-BIDIM C22
_L
0.04 0.08 0.11 0.15 0.19 0.23
CUMULATIVE FLOW, m3
0.26
0.30
Figure 4. Blockage of fabric due to bentonite clay in water.
0.04
0.11 0.15 0.19 0.23
CUMULATIVE FLOW, m3
0.26
0.30
Figure 5. Blockage of fabric due to Hoytville clay in water
17
-------
CONSTANT HEAD
OF 30cm MAINTAINED
SLURRY FEED
(100% OF PARTICLES
LESS THAN SOpm)
Figure 6.
r
' FL
J
J
y
1
IFFLUENT
OW >
I
V
i
+— — BtLL .
PRESSURE
y i
1
EFRUENT
AK
APPLIED
-FABRIC
QAMPI r
iM/VlrLL
Laboratory instrument used to evaluate
in-plane flow of slurries through fabrics,
TABLE 3. IN-PLANE WATER TRANSPORT OF FABRICS
Transmissability ,
Fabric 10~3 cm2/s
BIDIM C22
BIDIM C34
BIDIM C38
MIRAFI 140
TYPAR
16
26
36
4
1
18
-------
TABLE 4. COMPARISON OF FLOWRATES THROUGH BIDIM FABRIC
Flowrate, m/mfn
FabricFabric
Direction C-22 c-34
Vertical:
Clean water 22 15
Slurry3 19 13
Horizontal:
Clean water
Slurry'5
1.7
0.69
1.9
0.88
Slurry contains bentonite clay;
flow rate is the limit at
steady state.
Slurry contains typical road
dirt; flow rate is the limit
at steady state.
Particle Separation by Size
The holes in the fabric are approximately 70 ym in diameter and
will pass particles up to that size depending upon particle
shape. Because the fabric does not "blind," the effective size
of the holes is not reduced significantly, and all particles
smaller than 15 ym (the size of interest) should pass through the
fabric vertically. If the soil is soft (cone penetrometer less
than 1,000 kpa), these particles would be consolidated with the
existing soil. When firm soil (soil penetrometer greater than
1,200 kpa) is present, consolidation would be difficult.
Because the presence of the fine soil particles does not plug the
fabric during horizontal water flow, some if not all of the fines
could be purged along with normal water flow. The median
particle size which passed through the fabric during the hori-
zontal flow tests was about 3 ym. Particles as large as 20 ym
also came through the fabric. This means that only the very
small particles would pass horizontally over firm soil; however,
some channeling would exist and carry off the intermediate size
particles (3 to 15 ym).
19
-------
SECTION 6
ECONOMICS OF THE ROAD CARPET CONCEPT
Capital and operating costs of various control options differ with
each alternative. Cost comparisons have been made between the
cost of new roads constructed with a fabric base and conventional
subsurface preparation.
For very soft soil (cone penetrometer index less than 600 kpa)
the thicker the fabric the cheaper the road, since the fabric
spreads the stress and can replace 0.5 to 0.75 meters of rock.
For soft soil (cone penetrometer index less than 1,000 kpa), the
road with fabric is only 40% to 50% cheaper. On firm or existina
aggregate-covered roads, the road would cost about 10% more.
The maintenance cost of a conventional road would be higher than
that for one containing road carpet; this will offset the
difference in capital costs.
Tables 5 and 6 provide estimates of road construction capital
costs. Table 7 shows the cost of two common control options,
watering and oiling. The amortized costs for conventional control
measures and for the new concept are summarized in Table 8. The
life expectancy of the fabric in the road is unknown; experience
indicates that 12 years would not be an unreasonable estimate.
A haul road may last for the life of the plant (25 yr) with
proper maintenance.
The road constructed with fabric is cheaper than either waterinct
or oiling. Better data would be required on ballast replacement
and watering costs due to the high inflation trends which are
presently occurring. With conventional roads, a higher percent-
age of the yearly cost is required for perpetual care. This
would make an even higher capital cost more attractive, if the
life expectancy were better than anticipated.
The following is an explanation of Table 8. The annual cost of
conventional road (25-yr life) is $7,600 per kilometer. Waterin*
and ballast replacement would add $6,750 to give $14,400 for an
ordinary road. Adding $7,600 to the oiling and ballast replace-
ment would give $13,800. This indicates that of the two options
watering or oiling, oiling is cheaper. By comparison, a fabric '
unpaved road would amortize over 12 years to $9,600 and with onl
ballast replacement, the annual cost would be $11,200. This
indicates that the fabric unpaved road is cheaper than oiling o
watering; however, rebuilding the road at the end of 12 years
20
-------
would amortize at $30,300 per km per year. In the 13th year,
watering would be cheaper than the fabric road ($28,800 vs
$35,300) but the cost of watering will continue to increase as it
did for the previous 12 years.
TABLE 5. CAPITAL COSTS OF UNPAVED ROAD CONSTRUCTION
Assumption:
Road width = 10 m; road length = 1.6 km
Soft Soil requires a minimum of 0.36 m of aggregate for
18 metric ton axle loads on 10:00-20 tires (as shown in
Figure 7). A grader and pan would be required.
Item Cost, $
0.15 m of excavation (3 km haulage) 3,500
requires 4 days at 8 hr/day and
$110/hr
No. 57 aggregate fill requires 51,500
12,443 metric tons at $4.14/metric
ton (FOB)
330 man-hours of haulage of aggregate 8,300
(500 trips at 48 km/hr and 16 km of
haulage)
Grading of surface (5 days with 10 2,200
trucks)
Taxes and permits 5,075
Total $70,600
Firm Soil requires a minimum of 0.20 m of aggregate, which
is equivalent to 7,100 metric tons of aggregate and 190 hr
of haulage. This decreases the cost of a 1.6 km road to
$43,900.
21
-------
TABLE 6. CAPITAL COST OF CONSTRUCTION OF UNPAVED ROAD USING FABRIC
Assumption:
Road width = 10 m; road length = 1.6 km
Minimum thickness of aggregate is 0.15 m for 18 metric ton
axle loads on 10:00-20 tires (as shown in Figure 7). Fabric
can be laid with no surface preparation on firm or soft soil.
Item Cost/ $
17,000 m2 of fabric at $0.86/m2 (FOB) 14,700
Installation (3 men for 1 hr at $20/hr), 2,800
transportation to site (48 km), and
freight (57 rolls at $50/roll;
2 truck loads)
0.15 m of No. 57 aggregate fill; 22,100
5,330 metric tons at $4.14/metric ton
(FOB)
140 hours of aggregate haulage (200 trips 3,600
at 48 km/hr and 16 km of haulage)
Surface grading (3 days with 10 trucks) 1,300
Taxes and permits 3,600
Total $48,100
22
-------
TABLE 7. OPERATING COSTS OF WATERING AND OILING CONTROL OPTIONS
WATERING
Assumptions;
Truck nets 1.6 km/hr including water loading time.
Water applied each day when rainfall is less than
0.1 cm or two out of three days (U.S. average).
Plant operates 130 days/year.
Item
Amortized cost of watering trucks
($12,000 over 10 yr at 17% interest)
Maintenance and repair of watering truck
Manpower for watering 2.2 km of road, two
times daily at $25/hr
Water (1 cm or 156,000 liter)
Total for 2.2 km road
Road repair (24 hr of grading and 3-5%
of ballast replaced per year)
Total per km of road
OILING
Cost, $
2,600/yr
1,000/yr
5,960/yr
680/yr
10,200/yr or
4,640/km-yr
2,100/km
6,750/yr
Assumptions;
Typical application for haul road trucks is 0.19 cm
of oil per month. For 6 months of operation on a
9-m wide road (1 km long), 104,000 liters of oil
would have to be applied at $0.055 per liter.
Item
Oiling service (1 km)
For dusty road surfaces (0.3 cm of dust),
0.27 cm of oil would be applied with an
asphaltic sealer. This material would
require application twice during 6 months
of operation but would cost about $0.092
per liter.
Item
Cost of asphaltic oiling service (1 km)
Ballast replacement (3-5%/yr)
Lowest expected cost for oiling (1 km)
Cost, $
5,800/yr
Cost, $
4,600/yr
1,600/yr
6,200/yr
23
-------
o.ioh
i i
7 14 21 28 34 41 48 55 62 69
SHEAR STRENGTH, kPa
138 276 414 552 690 827 965 1^03
CONE PENETROMETER INDEX, kPa
Figure 7. Design curves for 18 metric ton axle
load on 10:00-20 tires for BIDIM fabric.
24
-------
TABLE 8. AMORTIZED COSTS OF DUST CONTROL ON UNPAVED ROADS
Type of road and/or dust control Cost, $/km~
Unpaved road on firm soil (no control); $27,400 4,750
over 25 years (17% interest)
Watering and ballast replacement 6,750
Oiling and ballast replacement 6,200
Ordinary road with watering and ballast 11,500
replacement
Ordinary road with oiling and ballast 10,950
replacement
Fabric unpaved road/ $30,000 over 12 years 6,000
(17% interest)
Ballast replacement 1,600
Fabric road with ballast replacement 7,600
Fabric replacement (amortized cost in 12 years 18,900
at 17% interst and 10% inflation)
Cost of fabric road in 13th year with ballast 24,400
replacement
Cost of conventional road with watering and 28,000
ballast replacement in 13th year
Cost of conventional road with watering and 25,900
ballast replacement in 12th year
Cost of fabric road in 12th year with ballast 11,500
replacement
25
-------
REFERENCES
Chalekode, P. K., T. R. Blackwood, and S. R. Archer. Source
Assessment: Crushed Limestone State of the Art. EPA-600/2-
78-004e, U.S. Environmental Protection Agency, Cincinnati,
Ohio, April 1978. 61 pp.
Rusek, S. J., S. R. Archer, R. A. Wachter, and T. R. Black-
wood. Source Assessment: Open Mining of Coal State of the
Art. EPA-600/2-79-004x, U.S. Environmental Protection
Agency, Cincinnati, Ohio, September 1977. 87 pp.
Ochsner, J. C., P. K. Chalekode, and T. R. Blackwood. Source
Assessment: Transport of Sand and Gravel. EPA-600/2-78-
004y, U.S. Environmental Protection Agency, Cincinnati,
Ohio, October 1977. 62 pp.
BIDIM® Engineering Fabric for Soil Stabilization and Drain-
age. Product Brochure published by Monsanto Company,
St. Louis, Missouri. 24 pp.
Anderson, C. Air Pollution from Dusty Roads. In: Proceed-
ings of the 1971 Highway Engineering Conference, (Bulletin
No. 44-NMSU-EES-44-71, Las Cruces, New Mexico, 1971. 12 pp.
Investigation of Fugitive Dust Sources, Emissions, and
Control. Contract 68-02-0044, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, May 1973.
152 pp.
Roberts, J. W., A. T. Rossano, P. T. Bosserman, G. C. Hofer,
and H. A. Watters. The Measurement, Cost and Control of
Traffic, Dust and Gravel Roads in Seattle's Duwamish Valley.
In: Proceedings of the Annual Meeting of the Pacific
Northwest International Section of the Air Pollution Control
Association, Paper No. AP-72-5, Eugene, Oregon, 1972. 10 pp
Cowherd, J., Jr., K. Axetell, Jr., C. Guenther, F. Bennett,
and G. Jutze. Development of Emission Factors for Fugitive
Dust Sources. EPA-450/3-74-037, U.S. Environmental Protec-
tion Agency, Research Triangle Park, North Carolina, June
1974. 172 pp.
Chepil, W. S. Dynamics of Wind Erosion: I. Nature of the
Movement of Soil by Wind. Soil Science, 60 (4) :305-320, 1945
26
-------
10. Chepil, W. S., W. H. Siddoway, and D. V. Armburst. Climat-
ic Factor for Estimating Wind Erodability of Farm Fields.
Journal of Soil and Water Conservation, 17:162-165, 1962.
11. Thornthwaite, T. W. Climates of North American According to
a New Classification. Geographical Review, 21:633-635, 1931,
12. Singer, J. M., F. B. Cook, and J. Gurma. Dispersal of Coke
and Rock Dust Deposits. Bureau of Mines RI-7642, U.S.
Department of the Interior, Pittsburgh, Pennsylvania, 1972.
32 pp.
13. Cowherd, C. Development of Emission Factors for Fugitive
Dust Sources. EPA-450/3-74-037, U.S. Environmental Protec-
tion Agency, Research Triangle Park, North Carolina,
June 1974. 172 pp.
27
-------
APPENDIX A
RAW DATA FOR DETERMINATION OF FLOW CHARACTERISTICS
OF SUSPENDED SOLIDS THROUGH BIDIM FABRIC
28
-------
This test work was initiated at the request of Tom Blackwood at
the Dayton Laboratory who is looking at a new application for
Bidim. For this application Bidim would underlay an 8-10 in.
gravel road bed used by large trucks in mining operations. The
fabric will help control a dust pollution problem by carrying
fine silt particles generated by abrasion away from the road bed.
The installation could need a supply of water which could wash
the fines down through the gravel to the fabric.
To evaluate the fabric, a modified lateral flow permeameter and
a dilute slurry of fine soil particles were used to test the
fabric. Soil particle sizes, before and after passage through
the fabric, and flow rates were measured.
SLURRY PREPARATION
The soil was supplied by Tom Blackwood in eight plastic contain-
ers. These were blended.
Two kinds of slurries were used. The first slurry was composed
of about 12-15 Ib of the soil-rock blend in 14 gallons of water.
This slurry was agitated vigorously during the experiment and
relatively large soil particles were kept in suspension. This
slurry caused rapid blinding of the fabric because the mean
particle size was too large to pass through the fabric pores
(approximately 70 y).
The second slurry was an attempt to reduce the mean particle size
to <70 u and to have the concentration of fines between 5-20 g/&.
To accomplish this the blended soil was sieved through the No. 20
seive. These fines (>841 ym) were stirred into 14 gal of water.
This slurry was allowed to settle for about 10 min before using.
The concentration of suspended particle was about 18 g/£. Fur-
ther stirring of the 14 gal slurry tank was minimized.
APPARATUS
Modifications to the Advanced Drainage System (ADS) equipment and
to the Planar Permeameter (PP) were necessary to perform this
test. The constant head tank (CHT) was also modified. The gen-
eral arrangement of equipment used for these experiments is given
in Figure A-l.
PROCEDURE
1 - Stir slurry in tub vigorously. Wait 10-15 min before
starting pump. Allow CHT to overflow 30 min.
2 - Install pre-wet fabric. Rubber gaskets were not used to seal
interface between plate and fabric. Apply combined force
of 3.35 psi on fabric. Open bleed valve on PP.
29
-------
—-fry"*1
mtm ytt})}h
1 SLURRY TUB 18 in. x 22 in. x 15 in. DEEP 10
2 MIGHTY MITE PUMP (2D-N) 11
3 BIPASS BAFFLE 12
4 BIPASS VALVE 13
5 ADS CHAMBER D = 8 in. L = 16 in. 14
w/4 in. I.D. RESTRICTION PLATE 15
6 GRAVITY SUPPLY TUBE TO CHT 16
7 CHT D = 6 in. L - 9 1n. (STRIPPER NOT SHOWN) 17
8 CHT OVERFLOW D = 9-1/2 in L = 9 in. 18
9 CHT OVERFLOW TUBE
CHT OVERFLOW BAFFLE
SUPPLY TUBE TO PP
PP PRESSURE CAP
PP BASE PLATE W/OVERFLOW TROUGH
FABRIC SPECIMEN D - 4-1/4 in.
BLEED VALVE
BLEED TUBE 1/4 in. O.D.
FABRIC DRAIN TUBE
SLURRY RECYCLING CONTAINER
Figure A-l. Apparatus used for testing slurry flow.
-------
3 - Initiate flow in PP supply tube by removing plug on inside
of CHT. Start run timer with initial flow of slurry out of
bleed tube.
4 - Measure flow rate from fabric drain tube. After 2, 20, and
60 min lapse times, slurry samples are to be collected from
the fabric drain tube and the bleed tube.
5 - Recycle slurry out of PP by pouring into CHT overflow
every 2-3 min.
RESULTS
Run Data; C-34 Bidim Fabric
Preliminary runs were made to develop techniques prior to this
single run.
Area of fabric under compression, 10.21 in.2
Compressive force, 3.35 psi
Hydraulic head, 30 cm of water
Flow through the PP bleed tube, 390 mJl/min
Temperature in the CHT, 23.7°C, RT = 0.916
Elapsed time, Flow, Elapsed time, Flow,
min cc/min min cc/min
1 950 45 575
5 875 50 560
10 810 55 540
15 750 60 520
20 710 65 510
25 675 75 485
30 645 90 450
35 620 100 435
40 600
Run Data; C-22 Bidim Fabric
Temperature in the CHT, 22.6°C, RT = 0.940
Experimental constants same as for C-34
Elapsed time, Flow, Elapsed time, Flow,
min cc/min min cc/min
2 590 50 350
10 520 55 335
15 480 60 325
20 450 70 305
25 430 80 290
30 410 90 275
35 390 100 260
40 375 110 245
45 360 120 235
31
-------
After 120 min, the pressure was momentarily increased to 48.1 psi
then returned to 3.35 psi where the flow was checked.
125 min 275 cc
135 min 233 cc
This suggests that pumping action may stimulate and improve the
fabric's performance.
COMPARATIVE DATA
The PP was used to generate transmissability and permeability
values for a variety of fabrics using pure water. These tests
used a constant hydraulic head of 30 cm. The RT was 0.990 and
1.017 for C-22 and C-34 Bidim fabrics. However, the load on the
fabric was varied every 5 min so the flows did not reflect any
creep that would probably occur in 120 min.
C-22 flow after 5 min lapse time:
max 650 cc/min, min 502 cc/min, mean 566 cc/min
C-34 flow after 5 min lapse time:
max 982 cc/min, min 840 cc/min, mean 903 cc/min
QUANTIMET ANALYSIS OF SLURRY USED IN PLANAR PERMEAMETER
Slurry samples (100-200 mi) were collected at the bleed tube
(#16, Figure A-l) and at the fabric drain tube (#17, Figure A-l)
at various time intervals during the testing of C-22 and C-34
fabrics. The samples were labeled by fabric weight, lapse time,
and "BP" if sample was taken at the bleed tube.
The Quantimet was programmed to view 30 different fields each
having an area of 110,178 ym2 and count the number of "features,"
soil particles between 1 and 100 ym in equivalent circular diam-
eter, a standard way of sizing irregular shaped particles. The
computer also calculated the total particle volume. Using this
information the relative concentrations of solid particles in
each slurry could be determined.
The obvious problem was being sure a typical drop from 100-200 mJl
of sample was being taken. The microscopist did check success-
fully for reproducibility on several of the odd samples.
The original water suspension was allowed to air dry on the slide
and was replaced by a silicone and then stirred for uniform dis-
persion. The results are given in Table A-l.
32
-------
TABLE A-l. PARTICLE SIZE DISTRIBUTION THROUGH FABRIC
Sample
I.D.
34-.1
34-1 BP
34-20
34-20 BP
34-60
34-60 BP
22-2
22-2 BP
22-20
22-20 BP
22-60
22-60 BP
Equivalent circular
diameter, y
Max
15.48
21.90
12.74
21.77
17.88
16.95
22.02
20.69
17.07
13.14
11.55
14.10
Min
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
1.
617
617
617
617
617
617
617
617
617
617
617
617
Mean
3.
3.
3.
3.
3.
3.
3.
3.
3.
2.
3.
3.
367
660
219
214
516
404
891
604
309
697
251
181
Median
3
3
3
3
3
3
4
3
3
3
3
3
.866
.977
.842
.846
.915
.896
.042
.945
.851
.782
.822
.815
Particle Solid
volume, concentration,
y3 d/t
73,255.
116,471
38,550.
72,283.
99,534.
103,304
204,057
171,430
64,500.
27,404.
46,121.
40,863.
4
8
6
9
8
5
2
5
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
060
069
004
043
072
079
12
11
065
027
050
038
Note: C-22 fabric was tested first then the slurry reused for
fabric C-34. Quantimet analysis performed on 2-9-79,
and 2-13-79.
Calculation for sample 22-2:
p VS
Concentration = (g/£) = —
VL
V_ = volume solid
VL = volume liquid
p = 4.2 x ID-2 g/cm3 or 2.65 lb/ft3
L = max equivalent circular diameter
[ci = (4.2 x 10-2 g/cm3) x (Vy3) x (1 x IQ-^ Cm3/u3)
30 x (1.1 x 10~3 cm2) x (Lcm) x (1 x 10~3 Vcm3)
= 4.2 x 10-""* 204,057
3.3 x 10~5 x 2.2 x 10~3
• 1-3 * »- * ^^>
=0.12 g/i
Wilsford E. Artz
Monsanto Triangle Park
Research Center
33
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-79-115
2.
3. RECIPIENT'S ACCESSION NO.
TITLE AND SUBTITLE
Assessment of Road Carpet for Control of Fugitive
Emissions from Unpaved Roads
6. REPORT DATE
May 1979
6. PERFORMING ORGANIZATION CODE
7. AUTMOR(S)
T.R. Blackwood
8. PERFORMING ORGANIZATION REPORT NO
MRC-DA-896
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45407
10. PROGRAM ELEMENT NO.
EHE624A
NO.
68-02-3107
12. SPONSORING AGENCV NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PI
Final; 8/78 - 4/79
PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/13
1OTEJ
919/541-2925.
IERL-RTP project officer is Dennis C. Drehmel, Mail Drop 61"
ABSTRACT rp^ rep0rt gives results of an assessment of the use of carpeting to con-""
trol fugitive emissions from unpaved roads. Historically, emissions from unpaved
roads have been controlled by watering, oiling, or chemical soil stabilization. An
analysis of the forces which produce emissions shows that, if fine material can be
reduced, fine particle emissions (<15 micrometers) will also be reduced. A new
concept for control has been proposed: it utilizes a stable, rot-resistant, water-
permeable fabric to separate road ballast from subsoil. Fine material is not accu-
mulated in the ballast due to gravitational and hydraulic forces during normal rain-
fall. Preliminary studies indicate that fine material will pass through the fabric
without blinding, and that fines in the subsoil do not pump into the ballast from the
subsoil. Economic evaluations show that roads constructed with the fabric are
cheaper for emissions control than with conventional control methods. The effect-
iveness of control cannot be directly calculated; however, research is continuing.
Construction and testing of a prototype road in anticipated in 1979.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Pollution
Roads
Dust
Carpets
Fabrics
8. DISTRIBUTION STATEMENT
Unlimited
b.IDENTIFIERS/OPEN ENDED TERMS
Pollution Control
Stationary Sources
Unpaved Roads
Particulate
Road Carpets
19. SECURITY CLASS (This Report!
Unclassified
Unclassified
c. COSATI Held/Group
13B
11G
HE
21. NO. OF PAGES
39
22.
EPA Form 2220-1 (»-73)
34
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