Analysis of Haul Road Emission Test Data

8/3/2019 Analysis of Haul Road Emission Test Data

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Analysis of Haul Road Emission Test Data forDetermining Dispersion Modeling

Updated June 2004

Prepared by:

Arron Heinerikson Principal Consultant

Trinity Consultants

9777 Ridge DriveSuite 380

Lenexa, KS 66219www.trinityconsultants.com

(913) 894-4500

June 2004


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ANALYSIS OF HAUL ROAD EMISSION TEST DATA FORDETERMINING

DISPERSION MODELING PARAMETERS (UPDATED JUNE, 2004)

Arron Heinerikson and Abby Goodman

Trinity Consultants25055 West Valley Parkway, Suite 101

Olathe, Kansas 66061

INTRODUCTION

Many regulatory agencies require aggregate facilities to complete air quality dispersion

modeling analyses before issuing permits. One of the most subjective and time-consuming

aspects of air dispersion modeling is the modeling of sources that are fugitive in nature like

those found at a typical aggregate facility. Fugitive sources can include fugitive dust from

conveyor transfer points, haul roads and open storage piles, as well as emissions from

crushers/screens and truck loading and unloading. The current and proposed EPA air dispersion

models, Industrial Source Complex Model (ISCST3)1and Aermic Model (AERMOD)2, are able

to estimate ambient concentrations from these types of fugitive sources. The models allow for

categorization of sources into point, area, volume, or open pit sources (open pit sources are only

available in ISCST3).

The National Stone, Sand, and Gravel Association (NSSGA) is in the process of developing a

document that provides step-by-step instructions on how to appropriately model fugitive sources

from aggregate facilities. Methodologies for correctly characterizing fugitive sources are

necessary due to the models sensitivity to certain input parameters and the lack of guidance for

modeling fugitive sources. Incorrect characterization of fugitive sources can lead to unrealistic

model-predicted concentrations. Often, the impacts of fugitive sources are exaggerated to the

point of causing facilities to limit utilization of plant equipment to be able to demonstratemodeled compliance with air quality standards, while nearby monitors show only minimal

concentrations.

Many types of sources will be reviewed in the NSSGA document, including haul roads. It is

critical that haul roads are characterized correctly in a modeling analysis. Texas Commission of

Environmental Quality (TCEQ) guidance notes that if haul road sources are incorrectly

characterized, the model will over predict and may incorrectly identify road emissions as the

major cause of air pollution at the facility.3

This document provides methods for appropriately characterizing haul road sources such that the

modeled parameters, and thus calculated concentrations, accurately reflect the sources in

question. Discussions on regulatory guidance are included as well as summaries of the data andtechnical theory used to develop the suggested methodologies. The methodologies presented

should be adapted to fit site specific characteristics as shown in the following sections.

1Users Guide for the Industrial Source Complex (ISC3) Dispersion Models, Volume II Description of

Model Algorithms. EPA-454/B-95-003b, September 1995.

2Users Guide for the AMS/EPA Regulatory Model AERMOD. August 10, 2002.3Texas Commission of Environmental Quality (TCEQ) Air Quality Modeling Guidelines RG-25 (Revised).

February 1999.


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NSSGA ESH Forum (Updated June 2004) - Page 2

HAUL ROADS

Emissions from haul roads are caused by the force of the haul truck wheels pulverizing surface

materials. The surface particles are then lifted and thrust into the air by the rolling wheels. The

truck accelerating through the wind causes a turbulent wake. The dust is then mixed in the wake

before dispersing further by the motion of the wind, as shown in Figure 1.

FIGURE 1. EXAMPLE HAUL ROAD

CURRENT HAUL ROAD MODELING GUIDANCE

There is limited written guidance on how to model fugitive sources and more specifically haul

roads, further stressing the importance of consistent source characterization methodologies that

are based on source specific data and sound model theory. The limited written guidance

available is presented below.

A small number of state agencies have provided written guidance on how to model haul roads.

New Mexico, North Carolina, Oklahoma, and Texas suggest modeling haul roads as volume

sources. Whereas, the following states suggest modeling haul roads as an area source:

Missouri, Nebraska, Nevada, South Carolina, and Vermont. In contrast, Louisiana providesguidance on modeling haul roads as several point sources.

Several state agencies, such as Texas, Oklahoma, and Louisiana, also recommend that haul

roads should only be included in modeling analyses of annual averaging periods. These states,

as well as AP-42 Section 13.2.2, place low confidence on short-term haul road emission rates

unless site-specific data is used.

As a part of Texass model refinement processes, the TCEQ has developed a new procedure for

modeling low-level fugitive sources with release heights less than 10 meters. They allow

facilities to apply an adjustment factor of 0.6 to the emission rate of each fugitive source to

minimize the apparent tendency of the model to exaggerate modeled concentrations from low-

level fugitive sources.4

It is important to note the small number of states that provide written guidance on how to model

haul roads. In addition, even fewer states provide written guidance on determining the haul road

modeled parameters, such as release height and initial vertical dimension.

4Texas Commission of Environmental Quality (TCEQ), Interoffice Memorandum, March 6, 2002.


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Texas is the only state that provides specific written guidance for determining the appropriate

modeling parameters for a haul road source. The TCEQ guidance for determining haul road

volume source parameters is summarized below.5

1. Determine the adjusted width of the haul road. The adjusted width is the actual width of the

road plus 6 meters. The additional width represents turbulence caused by the vehicle as it

moves along the road.

2. Determine the height of the volume source. The height is 2 times the actual height of the

vehicle generating emission (i.e. the haul truck).

3. Determine the initial horizontal dimension (yo).

a. If the haul road is represented by a single volume source, yo = adjusted width / 4.3

b. If the haul road is represented by adjacent volume sources,yo = adjusted width / 2.15

c. If the haul road is represented by alternating volume sources, yo = twice the adjusted

width, measured from the center point of the first volume source to the center of the next

represented volume source / 2.15

4. The initial vertical dimension = height of the volume source / 2.15

5. The release height = height of the volume source / 2. This represents the center point of the

volume source.

40 CFR Part 51, Appendix W6indicates that ISCST3 (EPAs current model) and AERMOD

(EPAs proposed model) are the guideline models for short-term dispersion model analyses and

the ISC Users Guide, Volume 2 indicates that line sources, such as haul roads, can be modeled

with either volume or area sources.7

Mr. Richard Daye, EPA Region 7, references a study performed in December 1995 that found

model performance treating roadways as area sources is indistinguishable from modelperformance using volume sources.8 In addition, Mr. Daye notes the mathematical approach of

the area source is more defensible than volume sources in this situation. The volume source

algorithm uses the virtual distance approach for both the initial vertical and initial horizontal

dimensions, which is known to provide biased results in some circumstances.9

The federal and state guidance provided here was used in conjunction with current haul road

studies to develop the set of methodologies presented in this paper.

5Texas Commission of Environmental Quality (TCEQ) Air Quality Modeling Guidelines, RG-25 (Revised).

February 1999.6Chapter 40 Code of Federal Regulations Part 51 Appendix W.

7Users Guide for the Industrial Source Complex (ISC3) Dispersion Models, Volume II Description ofModel Algorithms. EPA-454/B-95-003b, Addendum, February 2002, Page 1-47 and 1-50.

8Modeling Fugitive Dust Impacts From Surface Coal Mining Operations Phase III. EPA-454/R-96-002,

December 1995.9Telephone Correspondence between Mr. Richard Daye, EPA Region 7, and D. Wilson and D. Doll.

July 2, 1997.


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CURRENT HAUL ROAD STUDIES

NSSGA sponsored PM10 emission factor tests at two aggregate facilities in Georgia. The tests

were performed by Air Control Techniques, P.C. in an effort to develop an equation that can

accurately quantify PM10

emission factors for aggregate facility haul roads. The data gathered

in this study were combined with previously gathered data to derive an industry specific haul

road emission factor equation. This study will be referred to as the January 2002, Haul Road

Emission Factor Test Program.10

Haul Road Emission Factor Test Program Background

The tests were performed at the Lafarge/Blue Circle plant in Cumming, Georgia and the Martin

Marietta Aggregates, Inc. plant in Forsyth, Georgia. The haul roads selected for the tests were

chosen based on maximum haul road traffic.

Air Control Techniques, P.C. used an upwind/downwind profiling system to measure PM10

emissions from the haul roads. Four PM10

ambient monitors were located on a 24-foot tower

16 feet from the downwind edge of the haul road. The PM10 ambient monitors were located at

the following heights: 5 ft, 10 ft, 15 ft, and 24 ft. One PM10 ambient monitor was located 16 ft

from the upwind side of the haul road. The upwind monitor was at a height of 10 ft. In

addition, meteorological monitoring stations were located at elevations of 6 and 30 ft on the

downwind side of the haul road. See Figure 2 for a depiction of the haul road PM10 ambient

monitor and meteorological monitor network.

A total of 20 one-hour tests were performed at each of the plants. The following parameters

were gathered for each test:

Road surface moisture content

Road silt content Road particulate size distribution

Number of truck passes along the haul road

Wind Speed

Wind Direction

Truck Speed

Production Data

Ambient PM10 Concentration (g/m3) for each monitor height (upwind and downwind)

10Haul Road Emission Factor Test Program for the National Stone, Sand, and Gravel Association. Air

Control Techniques, P.C., January 2002, ACTPC Job Number 707.


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FIGURE 2. UPWIND/DOWNWIND PROFILE SAMPLING SYSTEM11

The types and sizes of trucks that were present during each test were also recorded. The trucks

from both quarries were either 50 or 65 ton haul trucks with heights ranging from 14 feet

2 inches to 15 feet 2 inches.

Wet suppression was used for fugitive dust control of the haul roads at both facilities.

11Haul Road Emission Factor Test Program for the National Stone, Sand, and Gravel Association. Air

Control Techniques, P.C., January 2002, ACTPC Job Number 707, Page 5.


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Haul Road Emission Factor Test Program Implications on Modeling

Trinity reviewed the concentration and meteorological data collected for the haul road emission

factor test program to determine the concentration profiles of the plume generated by the quarry

haul trucks. If the behavior of the plume is understood, more accurate dispersion modeling input

parameters can be developed, such that more accurate modeled concentrations can be predicted.

Defining the Plume. A review of the downwind monitored concentration data (monitors

at 5, 10, 15, and 24 feet) revealed the following:

A plot of monitored concentration versus the height of the monitor revealed that the

concentrations were uniform with height. Further, the mean and standard deviation of the

monitored concentrations (four monitor heights) for each test run were calculated. It was

found that, on average, the standard deviation was less than 20 percent of the mean value for

each test at the Cumming quarry and less than 15 percent of the mean value for each test at

the Forsyth quarry. The data suggests that at the locations and heights of the monitors,

concentrations resulting from the plume were independent of height above ground, and do

not have a gaussian distribution in the vertical (z) dimension. Figures 3 and 4 provide plots

of concentration versus height for each run at the Cumming and Forsyth locations,

respectively.

During six of the twenty test runs at the Cumming Quarry, the wind was not blowing

towards the monitors during the time periods that the trucks were driving by the monitors.

Consequently, one would assume that there would have been a noticeable decrease in

monitored concentrations for those time periods. However, the monitored concentrations

for these situations were indistinguishable from the data obtained when the wind was

blowing towards the monitors. This data indicates that wind direction does not have a

measurable impact on the plumes dispersion at the locations and heights of the monitors,

and thus the concentrations in the plume are equivalent in the vertical dimension at the

locations of the monitors.


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FIGURE 3. CUMMING QUARRY DOWNWIND CONCENTRATION VERSUS HEIGHT

Cumming Quarry

Downwind Concentration vs. Height

0

20

40

60

80

100

120

140

5 10 15 20 25

Height (ft)

Concentration(ug/m3)

Series1Series2Series3

Series4Series5Series6Series7Series8Series9Series10Series11Series12Series13Series14Series15Series16Series17Series18

Series19Series20

FIGURE 4. FORSYTH QUARRY DOWNWIND CONCENTRATION VERSUS HEIGHT

Forsyth Quarry

Downwind Concentrations vs. Height

0

20

40

60

80

100

120

140

160

5 10 15 20 25

Height (ft)

Concentration(ug/m3)

Series1Series2Series3Series4Series5Series6Series7Series8

Series9Series10Series11Series12Series13Series14Series15Series16Series17Series18Series19Series20

The data from the upwind (10 foot) monitor was also reviewed and provided the following:

These data were very similar in magnitude to the downwind monitor concentrations. More

specifically, there was no statistically significant difference between the mean concentration

(average of four monitored concentrations, one from each height) calculated for a given run

using the downwind monitor values versus the upwind monitor concentration.

Over 25 percent of the time, the upwind monitor measured a higher concentration than any

of the four downwind monitors. This further substantiated that the wind direction was not


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impacting the monitored concentrations at the locations of the monitors. The data provides

that the plume generated is not measurably different in the horizontal or vertical dimensions

at least to a distance equivalent to the height off the tallest monitor (24 feet) and the distance

between the upwind and downwind monitors (82 feet).12 This type of plume behavior has

been defined as a cavity region.13 A cavity region is a region characterized by very chaotic

flow with considerable turbulence that is rapidly changing every few seconds. Cavity

regions are generated by mechanical turbulence and zones of turbulent eddies. The

development of such a region behind a haul truck could be explained by the turbulent eddies

created by the truck moving down the road.

Simulating the Plume. Now that the concentration profile behind the moving truck has beenestablished, one can determine the most representative method of simulating this type of plume

in the regulatory models, ISCST3 and AERMOD. According to the data reviewed above, the

plume resembles a cavity region with uniform concentrations in both the vertical and horizontal.

Cavity region calculations are usually discussed in terms of building downwash produced by

wind flow over and around buildings. Downwash of a plume due to wind flow over and around

buildings brings the plume down on the lee side of the building and recirculates the plume in theturbulent flow downwind of the building. A side view of this situation is provided as Figure 5.

Wind tunnel studies show that there is a cavity region directly downwind of the building

followed by a turbulent wake region before the flow returns to normal.

FIGURE 5. CHARACTERISTIC WIND FLOW PATTERNS AROUND AN OBSTACLE (SIDE VIEW)

Further, Figure 6 provides the view from above of flow patterns around a cube (similar to a

truck) exposed to a wind. The wind patterns are similar to those generated by a truck driving on

a haul road.

12Monitored concentrations at the 24ft level were the highest of the four downwind readings, 20 percent of

the time in both data sets, suggesting the cavity most likely extends further than 24 feet.13Dispersion of the recirculated cavity mass is based on building geometry and is assumed to be uniformly

mixed in the vertical.AERMOD: Description of Model Formulation. EPA-454/R-02-002d, October 2002.


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FIGURE 6. WIND PATTERNS RESULTING FROM WIND FLOW AROUND A CUBE (TOP VIEW)14

Algorithms to simulate building downwash have been incorporated into the ISCST3 and

AERMOD dispersion models. However, the algorithms do not take effect until the wake region.That is, the models do not perform cavity region calculations. Enhanced versions of ISCST3

and AERMOD that include the Plume Rise Model Enhancement (PRIME) can make cavity

calculations. These versions of the models are referred to as ISC-PRIME and

AERMOD-PRIME. The PRIME versions of the models have been proposed to be regulatory

guideline models but have not yet been approved.15

The plumes generated from haul roads appear to behave similar to plumes that are downwashed

on the lee side of a building. Downwash calculations in the models may only be made for point

sources, not area or volume source types. As such, the data suggests that the most representative

method of modeling emissions from haul roads is a continual series of point sources and

associated buildings. ISC-PRIME (Version 01228) was used to model a line of point sources

and structures to simulate emissions from the haul road. As there are an infinite number of

combinations of structure and point source combinations that could be used, dimensions of

14Atmospheric Science and Power Production, Technical Information Center Office of Scientific and

Technical Information United States Department of Energy. Page 250, 1984.15CALPUFF is a regulatory approved model that is commonly used for modeling of Class I impacts,

beyond 50 km. CALPUFF does incorporate the PRIME algorithms.


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measurable parameters were used as a starting point for the analysis. The parameters that were

fixed in the analysis included:

Buildings

Width = Road width (m) = 50 feet

Length: Assumed that a haul road length of 300 feet would be sufficient to minimize end

effects. Buildings were square and set end-to-end. Length of each = 300 feet divided by 6

buildings = 50 feet.

Point Sources

Diameter = Diameter of building = 50 feet Velocity = 0.001 m/s (simulating no vertical momentum) Temperature = Ambient (simulated by entering 459.6 F) Location = Centered in each building Emission Rate = Divided a unit emission rate (1 lb/hr) equally over 6 point sources = 0.167

lbs/hr each

To determine concentrations in the modeled plumes cross section, receptors were placed at a

distance of 16 feet from the source with flagpole heights varying in 0.1 meter increments from 0

meters to 10 meters (32.8 feet). Figure 7 describes the sources, buildings, and receptors

modeled.

The variables that remain include stack height and structure height. As there is no data to justify

using different heights for these variables, the assumption was made that the point source and

structure height should be equal. The point source and structure height (source height) were

then varied to determine the height that would result in a modeled concentration profile most

closely representing the monitored concentration profile. As described previously, the

monitored data provides the following:

Concentrations resemble a cavity region At a receptor located 16 feet from the edge of the structure, the standard deviation of the

modeled concentrations between ground level and 24 feet should vary by no more than 15 to20 percent of the mean value (referred to in this analysis as the Target Height).

A typical meteorological condition was established from the onsite data which included a wind

speed of 1.54 meters/second, an ambient temperature of 39 F (277 Kelvin), a stability class of

4, and a mixing height of 441 meters (which did not impact the analysis). To simulate the

source, the source height was first set to the actual average height of the truck (14.7 feet). The

modeled concentrations, provided as Case 1 in Table 1, resulted in a target height of 19.7 feet.

As this is less than 24 feet, the source height was increased to 15.7 feet, 16.7 feet, and 17.7 feet,

Cases 2, 3, and 4 respectively, until a modeled Target Height greater than 24 feet was found.

Finally, the source height was lowered to 17.5 feet, Case 5, such that the Target Height of

approximately 24 feet was achieved. These results are also provided in Table 1.


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FIGURE 7. HAUL ROAD MODELED AS A SERIES OF DOWNWASHED POINT SOURCES

Point Sources

(Circles)

Receptors

Buildings

(Squares)

TABLE 1. RESULTS OF SOURCE HEIGHT VARIABILITY IN ISC-PRIME

Case 1 Case 2 Case 3 Case 4 Case 5

Source & Building Height (ft) 14.7 15.7 16.7 17.7 17.5

Target Height (ratio of standarddeviation to the mean is 20%) ft

19.7 21.0 22.3 24.3 23.9

Ratio of modeled source height to

truck height (14.7 ft)

1.00 1.07 1.14 1.20 1.19

Table 1 provides that to recreate the monitored concentration profile resulting in both a cavity

height of 24 feet, and a ratio of standard deviation to the mean of 20%, a source release height to

truck height ratio of approximately 1.19 is necessary.

The results of modeling a haul road using the point source and building dimensions and relative

locations shown in Figure 7, as well as the source parameters for Case 5 in Table 1, are provided

in Figure 8 .


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FIGURE 8. MODELED CONCENTRATIONS RESULTING FROM A HAUL ROAD MODELED

AS A SERIES OF DOWNWASHED POINT SOURCES USING ISC-PRIME

0.00 5.00 10.00 15.00 20.00 25.00 30.00

X - Distance from source in meters

0.00

5.00

10.00

15.00

20.00

Z-Heightabovegroundinmeters

60

90

120

150

180

210

240

Ground level

Ratio of Standard Deviation to the Mean is20% at 24 feet (7.3 meters) above Ground

Point

Source

with

Structure

Figure 8 provides modeled concentrations versus height above ground and distance from the

source. Discrete receptors were placed at distances ranging from 0 meters to 30 meters from the

source, with flagpole receptor heights varying from 0 to 20 meters above ground.

Although the proposed method will represent the monitored concentrations, additional studiesare suggested with monitors located at heights greater than 24 feet as well as distances greater

than 16 feet from the source. Visual observations by the authors would suggest that the cavity

region may extend to twice the height of the truck.

As the PRIME versions of ISCST3 and AERMOD are not yet approved by all regulatory

authorities, methods for modeling haul roads using the current versions of ISCST3 or AERMOD

are also being provided. Although volume and area sources have gaussian concentration

profiles, they are more representative of a haul road plume than a point source without

downwash cavity calculations. As such, volume and area source types have long been the

suggested method for modeling haul roads as was stated above in the summary of regulatory

guidance available. Traditionally, a volume source was used to model haul road concentrations

because until version 3 of the ISCST model was released in 1995 there were significant flaws

with the area source algorithm. Some states have retained this methodology. With the

flexibility available in defining area source size parameters, area sources have become a popular

method of modeling haul roads. In addition, EPA has demonstrated that modeling haul roads as

an area source results in the same model performance as modeling them as a volume source.16

16Modeling Fugitive Dust Impacts From Surface Coal Mining Operations Phase III. EPA-454/R-96-002,

December 1995.


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Using either an area source or a volume source, the source should initially be defined to

encompass the cavity region created by the haul truck. The data reviewed in this study indicates

that the cavity is at least 24 feet in the vertical and 82 feet in the horizontal.

When using either the area or volume source types, the release height must also be specified. In

this case, the data alone does not reveal what this height should be. Absent quantifiable data,

video and photographs of quarry haul roads using similar trucks were reviewed to determine if

any indication of a point of maximum concentration could be determined. The photos suggest

that at a given point, the plume is in the shape of a sphere centered in location at a height of

approximately the height of the truck. The visual data also appears to support the conclusion

that the particulate emissions are equally mixed in the plume (cavity region) as the opacity of the

plumes appear constant throughout the sphere. Consequently, a release height of the center of

the sphere, or cavity, is suggested, which in this case is the average truck height (average of 14.2

and 15.2 feet = 14.7 feet). Figure 9 shows the cavity as defined by the monitored data.

FIGURE 9. CAVITY REGION CREATED BY MONITORED HAUL TRUCKS

4.3 z = 29.4 ft

Average Release Height =

14.7 ft

4.3 y = 82 ft

TCEQ guidance suggests that the plume thickness (height) be calculated as twice the height of

the vehicle generating the emissions (2 14.7 feet = 29.4 feet = 9.0 meters) rounded to the

nearest meter (9 meters).


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Since the monitoring data clearly shows that the cavity extended much farther than twice the

truck width in the horizontal direction, it is reasonable to assume that had monitoring data been

available at 29 feet or higher, it would have been proven that the cavity would have extended to

at least 29 feet. Consequently, it is suggested that the plume thickness be estimated as at least

twice the truck height until additional data becomes available.

The initial vertical dimension (zo) would then be determined by the following equation:

Plume Thickness (feet) = 2 height of haul truck in feet

zo (feet) = Plume Thickness (feet) /4.3

= (2 height of haul truck in feet)/4.3

= (height of haul truck in feet)/2.15

Note that for a volume source, this is consistent with current ISC guidance17. That is, zo is

equal to the structure (truck) height / 2.15 for a source on or adjacent to a structure (truck).

Proposed source parameters for characterizing haul roads as either area sources or volumesources are as follows:

Area Source (ISCST3/AERMOD)

Adjusted haul road width (feet) = Width of haul road (feet) + 32 feet

zo (feet) = (2 height of haul truck in feet)/ 4.3

Release height (feet) = height of haul truck in feet

Location = Area source centered on coordinates of the actual haul road.

Volume Source (ISCST3/AERMOD)

yo (feet) = (Width of haul road in feet + 32 feet)/4.3 zo (feet) = (2 height of haul truck in feet)/ 4.3


Locations = Series of volume sources centered on the haul road centerline, spaced width of

haul road in feet + 32 feet apart.

Figure 10 provides modeled concentrations versus height above ground and distance from thesource using the same meteorological data and receptors as used for Figure 8 as well as the

following model inputs:

Area source width = 82 feet (25 meters) Area source length = 300 feet (91 meters)

Total area = 24,600 ft2 Emission Rate (per unit area) = 1 lb/hr / 24,600 ft2 = 4.065 E-05 lbs/hr/ft2 Release Height = Average truck height = 14.7 feet (4.5 meters) zo = 2 Avg. truck height / 4.3 = 6.8 feet (2.1 meters)

17Users Guide for the Industrial Source Complex (ISC3) Dispersion Models, Volume I Users

Instructions. EPA-454/B-95-003a, Table 3-1, September 1995, Page 3-30


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FIGURE 10. MODELED CONCENTRATIONS RESULTING FROM A HAUL ROAD MODELED

AS AN AREA SOURCE

0.00 5.00 10.00 15.00 20.00 25.00 30.00

X - Distance from source in meters

0.00

5.00

10.00

15.00

20.00

Z-Heightabovegroundinmeters

60

70

80

90

100

110

120

130

Ground level

Ratio of Standard Deviation to the Mean is20% at 26.2 feet (8 meters) above GroundRatio of Standard Deviation to the Mean is

15% at 23 feet (7 meters) above Ground

AreaSource

As mentioned previously, based on the data available, the modeled source characteristics are

conservative estimates since the cavity region is likely to extend beyond the limits currently

measured in this data set, which would lead to larger adjusted widths and zo.

Comparing Figure 8 and Figure 10 visually reveals the difference between modeling a haul road

as a source initially existing as a cavity region using ISC-Prime versus a source with Gaussian

dispersion from the point of generation respectively. In Figure 8, there is a large region of

constant concentration whereas in Figure 10 the concentration is highest at the center and

decreases in all directions from this center line concentration.


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CONCLUSIONS

The following methods for modeling haul roads have been developed:

Point Source(s) with Building(s) (ISC-PRIME and AERMOD-PRIME)

Point Source Height (feet) = 1.19 Height of haul truck (feet)

Point Source Diameter (feet) = Series of point sources with overall length equal to the length

of the road. Each point sources diameter equal to the road width (feet). Point Source Velocity = 0.01 m/s (simulating no vertical momentum) Point Source Temperature = Ambient (simulated by entering 459.6 F) Point Source Location = Centered in building, with a separation distance such that the point

sources do not overlap Point Source Emission Rate = Divide emission rate equally over all point sources

Building Height (feet) = 1.19 Height of haul truck (feet)

Building Width (feet) = Road width (feet)

Building Length (feet) = Series of buildings with overall length equal to the length of the

road. Each buildings length equal to the road width (feet).

Area Source (ISCST3/AERMOD)

Adjusted haul road width (feet) = Width of haul road (feet) + 32 feet

zo (feet) = (2 x height of haul truck in feet)/ 4.3


Location = Area source centered on coordinates of the actual haul road.

Volume Source (ISCST3/AERMOD)

yo (feet) = (Width of haul road in feet + 32 feet)/4.3 zo (feet) = (2 x height of haul truck in feet)/ 4.3

Release height (feet) = height of haul truck (feet)

Locations = Series of volume sources centered on the haul road centerline, spaced width of

haul road in feet + 32 feet apart.

These source characterizations provide a methodology for re-creating the monitoring data from

the January 2002, Haul Road Emission Factor Test Program. NSSGA is planning to perform

additional monitoring studies. When this data becomes available, it should be incorporated into

the overall data set, and the conclusions should be re-evaluated to determine if refinements to

the proposed source characterizations can be made.

Documents

Analysis of Haul Road Emission Test Data