United States Office Of Air Quality EPA-454/R-00-030

Environmental Protection Planning And Standards April 2001

Agency Research Triangle Park, NC 27711

Air

HOT MIX ASPHALT PLANTS

STAKEHOLDERS OPINIONS REPORT
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EPA-454/R-00-030

HOT MIX ASPHALT PLANTS

STAKEHOLDERS OPINIONS REPORT

This document was prepared by:

Emissions Monitoring and Analysis Division

Office of Air Quality Planning and Standards

United States Environmental Protection Agency

Research Triangle Park, NC

U.S. ENVIRONMENTAL PROTECTION AGENCY

Office of Air and Radiation

Office of Air Quality Planning and Standards

Research Triangle Park, North Carolina 27711

April 2001
-iiDISCLAIMER

This report has been reviewed by the Emissions Monitoring and Analysis Division of the

Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, and has

been approved for publication. Mention of trade names or commercial products is not intended to

constitute endorsement or recommendation for use.
-iiiPREFACE

This report was produced by the Source Measurement Technology Group of EPA’s Emissions

Measurement Center located in Research Triangle Park, NC. It is one of a series of twelve reports

prepared to document an EPA program to characterize emissions to the air from hot mix asphalt plants. 

These twelve reports and their associated EPA document numbers and publication dates are:

Document Title EPA Document

Number

Publication Date

Hot Mix Asphalt Plants

Emission Assessment Report EPA 454/R-00-019 December 2000

Hot Mix Asphalt Plants

Kiln Dryer Stack Instrumental Methods Testing

Asphalt Plant A, Cary, North Carolina EPA 454/R-00-020 April 2000

Hot Mix Asphalt Plants

Kiln Dryer Stack Manual Methods Testing

Asphalt Plant A, Cary, North Carolina

Volume 1 of 2 EPA 454/R-00-021a April 2000

Volume 2 of 2 EPA 454/R-00-021b April 2000

Hot Mix Asphalt Plants

Kiln Dryer Stack Instrumental Methods Testing

Asphalt Plant B, Clayton, North Carolina EPA 454/R-00-022 April 2000

Hot Mix Asphalt Plants

Kiln Dryer Stack Manual Methods Testing

Asphalt Plant B, Clayton, North Carolina

Volume 1 of 2 EPA 454/R-00-023a April 2000

Volume 2 of 2 EPA 454/R-00-023b April 2000

Hot Mix Asphalt Plants

Truck Loading and Silo Filling Instrumental Methods Testing

Asphalt Plant C, Los Angeles, California

EPA 454/R-00-024 May 2000

Hot Mix Asphalt Plants

Truck Loading and Silo Filling Manual Methods Testing

Asphalt Plant C, Los Angeles, California

Volume 1 of 8 EPA 454/R-00-025a May 2000

Volume 2 of 8 EPA 454/R-00-025b May 2000

Volume 3 of 8 EPA 454/R-00-025c May 2000

Volume 4 of 8 EPA 454/R-00-025d May 2000

Volume 5 of 8 EPA 454/R-00-025e May 2000

Volume 6 of 8 EPA 454/R-00-025f May 2000

Volume 7 of 8 EPA 454/R-00-025g May 2000

Volume 8 of 8 EPA 454/R-00-025h May 2000

Hot Mix Asphalt Plants

Technical Systems Audit of Testing at Asphalt Plant C

Asphalt Plant C, Los Angeles, California EPA 454/R-00-026 May 2000
Document Title EPA Document

Number

Publication Date

-ivHot Mix Asphalt Plants

Truck Loading Instrumental Methods Testing

Asphalt Plant D, Barre, Massachusetts EPA 454/R-00-027 May 2000

Hot Mix Asphalt Plants

Truck Loading Manual Methods Testing

Asphalt Plant D, Barre, Massachusetts EPA 454/R-00-028 May 2000

Hot Mix Asphalt Plants

Response to Comments on Testing Program for Asphalt Plants

C and D EPA 454/R-00-029 May 2000

Hot Mix Asphalt Plants

Stakeholders Opinions Report EPA 454/R-00-030 April 2001

These documents, including this Stakeholders Opinions Report document, are available for downloading,

on CD-ROM and in paper.

Downloads can be made from:

http//www.epa.gov/ttn/emc/asphalt.html

Copies of the CD ROM can be requested by mail at:

Emission Measurement Center, MD-19

US Environmental Protection Agency

Research Triangle Park, NC 27711

Paper copies of the reports can be obtained from:

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22161

Phone orders 1-800-553-6847 or (703) 605-6000; FAX orders (703) 605-6900

http://www.ntis.gov/products/environment.htm
-vACKNOWLEDGMENTS

Many individuals contributed to the development of this report. Ron Myers of the Emission

Measurement Center’s Source Measurement Technology Group of the Emissions Monitoring and Analysis

Division, Roy Smith of the Risk and Exposure Assessment Group of the Emissions Standard Division and

Gary Foureman of the National Center for Environmental Assessment of the Office of Research and

Development are the primary authors of the report. Bob McConnell of EPA’s Region I office, David

Mobley, Acting Director of EPA’s Emissions Monitoring and Analysis Division, Bill Lamason, Mike

Toney, Gary McAlister, and Candace Sorrell of EPA’s Emission Measurement Center, Ron Ryan and

Dennis Beauregard of EPA’s Emission Factor and Inventory Group, Laura Autry of EPA’s Air Quality

Trends Analysis Group, Jim Crowder and Mary Johnston of the Minerals and Inorganic Chemicals Group

of the Emissions Standard Division participated in the review.
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vii

Contents

Chapter 1

1.0 Project Background ......................................................... . 1-1

Chapter 2

2.0 EPA Response to Stakeholder Opinions .......................................... . 2-1

2.1 Response to opinions of Wisconsin Department of Natural Resources ................ . 2-1

2.2 Response to opinions of Connecticut Department of Environmental Protection .......... . 2-1

2.3 Response to opinions of Coalition Against the Asphalt Plant et al .................... . 2-1

2.3.1 Introduction (EPA interactions with citizens) .............................. . 2-1

2.3.2 Why are many citizen groups concerned about asphalt plants? ................. . 2-2

2.3.2.1 Asphalt health effects, epidemiological studies, and sound science ....... . 2-2

2.3.2.2 Differences in approach to assessing health impacts .................. . 2-2

2.3.2.3 Use of “best performance data” from sources ....................... . 2-3

2.3.3 Unresolved issues ................................................... . 2-3

2.3.3.1 Volatility content and temperature issues .......................... . 2-3

2.3.3.2 Issues relating to collection and analysis of emissions data ............. . 2-5

Background correction and enclosure problems ...................... . 2-5

“EPA’s flat denial of errors in the report” .......................... . 2-6

“Unfounded leaps of faith ...................................... . 2-6

Problems with witnessing tests .................................. . 2-6

2.3.4 Conclusions ....................................................... . 2-8

2.3.4.1 Performance of epidemiological study by EPA ...................... . 2-8

2.3.4.2 Include additional warnings in AP-42 ............................. . 2-8

2.3.4.3 Get tough with industries on excessive claims of CBI ................. . 2-8

2.4 Response to opinions of National Asphalt Paving Association ...................... . 2-9

Chapter 3

Stakeholder Opinions on Hot Mix Asphalt Plants Emission Assessment Report EPA 454/R-00-019,

December 2000 ............................................................ . 3-1

Wisconsin Department of Natural Resources

Connecticut Department of Environmental Protection

Citizens Against the Asphalt Plant et al

National Asphalt Pavement Association

Chapter 4

Hot Mix Asphalt Plants Response to Comment on Draft Emissions Assessment Report, AP-42 Section

and AP-42 Background Report ................................................. . 4-1

Chapter 5

Stakeholder Comments on Draft Emissions Assessment Report, AP-42 Section and AP-42 Background

Report ................................................................... . 5-1

Stephen F. Lynch

Coalition Against the Asphalt Plant

Massachusetts Department of Health

National Asphalt Pavement Association

Norman Ostroff, PhD, PE

Steven Zemba
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1-1

STAKEHOLDERS OPINIONS REPORT

Chapter 1

1.0 Project Background

This is the last in a series of EPA reports that document the development of methods to estimate

emissions from hot mix asphalt plants. The primary purpose of this report is to publish the opinions of the

stakeholders on the final “Hot Mix Asphalt Plants - Emissions Assessment Report.” The stakeholders

involved in the processes leading up to the publication of the Emissions Assessment Report include national

and State legislators, State and local environmental and health agencies, national and regional industry

associations, citizen public interest groups and industry technical consultants. As an adjunct to the

opinions of the stakeholders on the final Emissions Assessment Report, this report includes EPA’s

responses to stakeholder issues that had not been documented previously or that EPA believes require

additional clarification. Additionally, the stakeholder comments on the draft Emission Assessment Report

and EPA’s responses to these comments are included to round out the stakeholder opinions and EPA’s

assessment of the technical issues being raised.

The final “Hot Mix Asphalt Plants - Emissions Assessment Report” was published in December

2000. This report contains EPA’s final emissions estimates from the two hypothetical facilities of average

production using the two predominant US production methods. This report also includes the revised AP-42

section, the revised AP-42 background report and the July 1996 Emission Inventory Improvement Program

(EIIP) report for hot mix asphalt plants. The AP-42 section contains the final emission estimation methods

and the background report provides detailed information on the development of these emission estimation

methods. Additionally, the background report contains summary information from all reference material

(including more than 350 emission tests) used in the development of the emission estimation methods. The

1996 EIIP report describes preferred and alternative emission estimation techniques and provides concise

example calculations to aid in the preparation of emission inventories.

The Emissions Assessment Report presents a comprehensive inventory with respect to the emission

sources characterized and the pollutants addressed. The emission sources characterized include the kiln

stack, hot mix asphalt (HMA) storage silo, truck load-out, hot asphalt storage tank, hot asphalt storage

tank heater, aggregate handling, RAP crushing, diesel exhaust, and road dust. For each of these sources,

the emissions data presented address the criteria pollutants (PM, VOC, CO, SO2 and NO x ) and many of

the Clean Air Act hazardous air pollutants (19 PAH compounds, 27 volatile HAP compounds and 10 HAP

metals). While most of the emission estimates were based upon methodologies presented in the AP-42

section for hot mix asphalt plants, some emission estimates were based upon methodologies in other AP-42

sections (material handling, road dust and mobile sources) or journal articles (mobile source HAPs).

 Emissions characterization data from three separate projects were utilized in drafting the

Emissions Assessment Report. Although each of the projects involved characterizing air emissions from

hot mix asphalt plants, each had a somewhat different goal. The goal of one project was to obtain and use

existing emissions test data from State and local air pollution control agencies to improve AP-42 emission

factors for hot mix asphalt plants. The second project was undertaken to determine whether there were any

previously unidentified kiln stack HAP emissions and, if such were present, to quantify these emissions. 
1-2

The third project was designed to characterize the fugitive emissions resulting from silo filling and

transport truck loading operations.
2-1

Chapter 2

2.0 EPA Response to Stakeholder Opinions

This chapter presents EPA’s responses to the stakeholder opinions presented in Chapter 3 of this

report. For the purposes of brevity, a detailed response to all issues raised by stakeholders was not

prepared. However, each major issue cited by a stakeholder has been thoroughly evaluated and a brief

response is presented. For issues where there is previous documentation of the issue including EPA’s

evaluation and response, the reader is referred to the appropriate section(s) in the prior report(s).

2.1 Response to opinions of Wisconsin Department of Natural Resources

EPA agrees with Wisconsin’s point that the development of the additional technical information

that was presented in the Emissions Assessment Report was an ambitious project. Additionally, EPA

reviewed the guidance for emission inventories for hot mix asphalt submitted with Wisconsin’s opinion and

will forward this document to the EIIP Point Source chair person for the committee’s consideration.

2.2 Response to opinions of Connecticut Department of Environmental

Protection

EPA recognizes that representatives of the Connecticut Department of Environmental Protection

(DEP) were active participants in the development stages of the study, witnessed the emission test at Plant

D, and participated in the review process of the test reports and subsequent technical analyses. EPA

appreciates Connecticut DEP’s recognition that the scope of the project was comprehensive, the collection

and analysis protocols were appropriate, the objectives were well defined and the EPA staff were very

capable.

2.3 Response to opinions of Coalition Against the Asphalt Plant et al

This section responds to the opinions of the citizen groups that were presented in the “Minority

Report on Fugitive Emissions from Asphalt Plants” (Minority Report). We have organized and presented

our responses based on the headings in the Minority Report.

2.3.1 Introduction (EPA interactions with citizens)

The citizens have provided a reasonable synopsis of the opportunities EPA afforded to all the

stakeholder groups to assist in the development of emissions estimation methodologies for fugitive emission

sources at hot mix asphalt plants. However, in the second half of the introduction and several other

locations in the Minority Report, the citizens disparage EPA’s interactions with the citizens. We believe the

record shows that EPA provided an open and meaningful public participation process in the development

and performance of the emission testing program as well as for the review of data generated from the

testing. In doing so, EPA strived to balance its obligation to ensure responsible use of public monies with

the numerous requests made by the citizens groups, many of which added to the cost of the testing program. 

A genuine effort was put forth, aided by facilitators brought in to assist the group discussions and to reach

outcomes agreeable to all parties. We believe we succeeded in that regard to the greatest extent possible.
1Hazard Review, Health Effects of Occupational Exposure to Asphalt; U.S. Department of Health

and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute

for Occupational Safety and Health; DHHS (NIOSH) Publication No. 2001––110, December 2000.

2-2

2.3.2 Why are many citizen groups concerned about asphalt plants?

2.3.2.1 Asphalt health effects, epidemiological studies, and sound science

In serving the public, the Agency has an obligation to use sound science in forming opinions on the

toxicity of chemical compounds. One aspect of applying sound science is to utilize and/or consider all of the

available credible scientific information on the toxicity of a given compound; credible scientific information

includes reports published in peer-reviewed scientific journals, conference proceedings, or other similar

peer-reviewed vehicles. Anecdotal information such as that referred to in the second paragraph of this

section of the Minority Report is, by definition, information that does not originate from a scientifically

peer-reviewed report and must be considered only with reservation. The recently published NIOSH hazard

review on the health effects of occupational exposure to asphalt (http://www.cdc.gov/niosh/01-110pd.html)

is a good example of an inclusive study of credible scientific information; in particular, it cites and evaluates

about 40 studies in an effort to present an overall view of all of the credible scientific information on the

acute and chronic health effects of asphalt emissions.1 This report concludes that current data are not

sufficient for quantifying the acute and chronic health risks of exposure to asphalt, asphalt-based paint, or

asphalt fumes and vapors. The NIOSH report also cites specific limitations concerning the Hansen cohort,

the one specifically cited in the Minority Report. The conclusions of the NIOSH report are of utility to EPA

especially as NIOSH is concerned with worker populations (e.g., pavers and roofers) that are more heavily

exposed to asphalt emissions than the general population, and in whom any adverse effects would be more

likely to occur. Any future formal review of the health effects of asphalt emissions by EPA would closely

approximate the sound science effort by NIOSH.

2.3.2.2 Differences in approach to assessing health impacts

The authors of the Minority Report express concern that the Agency is concerned solely with

long-term average exposures and not “... peak, short-term exposures for acute effects.” We acknowledge

that the exposure guidelines issued by EPA for air pollutants concerning cancer and noncancer effects are

concerned with long-term exposures and, although a methodology has been under development for several

years, EPA has yet to institute methodologies for evaluating effects from short-term exposures. 

Additionally, as stated clearly in the introduction to AP-42, the emission factors in AP-42 are average

values since its’ primary purpose is to support the development of area wide emission inventories. 

However, the emission factors for fugitive emissions at hot mix asphalt plants provide adequate flexibility

to estimate short term emission rates when combined with reasonable information on asphalt volatility and

temperature. Furthermore, reasonable estimates of short term stack emissions associated with normal plant

operations can be derived from the available supporting data. The authors of the Minority Report may

wish to consider the conclusions of NIOSH in their recently promulgated Hazard Review on asphalt

emissions. After considering the currently available information on workers under short-term exposure

conditions, their recommendation for worker exposure over a 15 minute period was not altered from their

original estimate determined in 1977, at the rather high level of 5 mg/m 3 for total particulate.
2-3

2.3.2.3 Use of “best performance data” from sources

EPA does not agree with the citizens statement that “much of the data used for developing stack

emission factors was collected just after initial plant startup often during a preoperating test period where

the plant owner is demonstrating to the state regulatory authorities that the plant can operate for short

periods of time at the design operating rate while staying within the permitted emission limits.” While some

of the data used were from tests performed within 60 days of the plants’ initial start up (known as initial

compliance tests) and may be representative of the most favorable operating conditions, most of data were

from hot mix asphalt plant emission tests performed on facilities that had been in operation for many years. 

The data utilized were drawn from 278 tests reports for emission tests performed between 1987 and 1994. 

Given the slow production growth in the industry, it is unlikely that more than half of these tests were initial

compliance tests. Generally, emissions tests are only conducted during periods of representative 

performance. EPA and most State and local agencies do not consider periods of startup, shutdown and

malfunction to be representative conditions. As a result, testing is usually not conducted during these

events. By definition, periods of non-representative operations are brief. Additionally, it is likely that a

facility being forced to test because of compliance concerns would correct any significant problem prior to

conducting the test. However, facilities that are compliance concerns are the exception. While it is

recognized that these worst case conditions are not represented in the supporting data, the available

supporting data is representative of the general range of facilities in operation. This is substantiated by the

wide range of the data for those pollutants where there are more than about ten data points supporting the

emission factor.

2.3.3 Unresolved issues

2.3.3.1 Volatility content and temperature issues

The citizens are concerned about the volatility content of asphalts and hot mix asphalt load-out

temperature and present five specific issues as the following five questions. We address these concerns 

below specifically in regard to their impact on estimation of emissions using the emission estimation

methodologies presented in Appendix A of the “Hot Mix Asphalt Plants - Emission Assessment Report,”

EPA 454/R-00-019, which is the text of Section 11.1 of AP-42, Hot Mix Asphalt Production.

a. Why did the industry change the specification for the maximum allowable volatile content of

asphalt from 0.5% to 1.0%? What are the implications of this change?

b. How is this volatile content measured now and how was it measured in the past?

c. How is the volatile content affected by seasonal variations in oil refining practice?

d. How is the volatile content affected by the various classes of additives that are sold to improve the

performance of asphalt?

e. Are the maximum operating temperatures recommended by industry groups actually followed by

plant operators? If not, what are the variations in temperature and what is the consequence of

these variations?

Response to questions a and b

As the citizens note, the industry has recently started using ASTM Method D2872-88, Standard

Test Method for Effect of Heat and Air on a Moving Film of Asphalt - Rolling Thin-Film Oven Test -
2-4

RTFOT for assessing asphalt volatile content. In the past, the method commonly used was ASTM Method

D1754-97, Standard Test Method for Effect of Heat and Air on Asphaltic Materials - Thin-Film Oven Test

-TFOT). All information used to develop the emission estimation methodology for estimating load-out and

silo filling emissions, used to establish the default values for asphalt volatility which may be used in

estimating load-out and silo filling emissions when no volatility data are available, and specified for use in

the emission equation rely on the volatile content as determined by the RTFOT method. Therefore, the

industry’s change in the specification for the maximum allowable volatile content of asphalt from 0.5% to

1.0% is not relevant to appropriate application of the emission estimation methodologies nor are the

differences in the loss on heating obtained using the two methods of concern. 

Response to questions c and d

The five State DOT laboratory directors contacted for this project have stated that the independent

volatility assessments made by the states using the RTFOT method are conducted on samples of asphalt

that are to be used without further blending or addition of additives. State DOT’s routinely perform a

variety of quality assurance tests including the RTFOT method on a representative sampling of asphalts to

insure that materials used to construct State and Federal roadways in their State meet required

specifications. There are potential legal ramifications to industry for changing the physical properties of

asphalts after the State quality assurance samples have been obtained. Since State agencies obtain and

independently determine the volatility of samples of asphalt which will be used without further

modification, we conclude that there is no potential impacts of seasonal refining practices, crude stocks,

and asphalt blending and additives in regard to the application of the emission estimation methodologies. 

This information available from State DOT’s is superior to the use of assumed values and should be more

than adequate in evaluating the variations in asphalt volatility over time.

Response to question e. 

Since the emission estimation methodology for load-out and silo filling incorporates a variable for

actual measured load-out temperatures, the effect on emissions of exceeding the industry recommended

temperature guidelines as well as other load-out temperatures can be assessed (see, for example, Table 1 in

the Minority Report). The use of measured load-out temperature data is superior to the use of theoretical

extremes for load-out temperature. Facilities and/or their customers routinely monitor the hot mix asphalt

temperatures loaded into the trucks before leaving the plant property. If measured load-out temperatures

are not available, load-out temperatures for a given time can be approximated from other available

temperature records. Hot mix asphalt plants, for example, routinely monitor the mix temperature of their

heated aggregate and drum mix plants monitor the temperature of the product stored in silos. By

correlating historical measured mix temperature or silo temperatures with historical measured load-out

temperatures and combining this with plant records of mix temperature/silo temperature and RAP usage it

is possible to obtain improved estimates of load-out temperatures. 

General

We believe it may also be helpful to clarify the criteria for selecting appropriate values for asphalt

volatility and load-out temperature. The values selected should not be arbitrary (e.g., based upon industry

desired targets or industry or State maximum allowable specifications) but instead should be based upon

legitimate verifiable data that is suitable for the health or environmental endpoint of interest. For example,

health or environmental endpoints that are the result of long term exposures should rely on emissions

estimations based upon a measure of central tendency (e.g., average, median, mode or other appropriate
2-5

statistical measure) of the asphalt volatility and load-out temperature. Conversely, if the health or

environmental endpoint is the result of a short term exposure, a combination of reasonable upper bound

values for volatility and load-out temperature should be used to estimate emissions. As stated in the last

sentence of the first paragraph on page 105 of the “Response to Comment on Draft Emissions Assessment

Report, AP-42 Section and AP-42 Background Report,” the selection of these upper bound values should

include an assessment of the probabilities of simultaneous events occurring. While the use of multiple

worst case assumptions (as depicted in the two columns labeled “Citizens” in Table 1 of the Minority

Report) may be a shortcut to evaluate maximum potential emissions, generally these emission estimates are

an unlikely result.

Previous responses or relevant information on asphalt volatility and temperature issues are

contained in Chapter 4 of this report (see Section 3.2 from page 54 through page 63, Section 3.5.34 on

pages 88 and 89, Section 3.6.4 on pages 104 and 105, Section 3.6.6 on page 105 and Section 3.6.10 on

page 106). In addition, the document EPA 454/R-00-029, “Hot Mix Asphalt Plants Response to

Comments on Testing Program for Asphalt Plants C and D” published in May 2000 also contains

responses and relevant information on these volatility and temperature issues (Item 5 on pages 9 and 10 and

Items 52 and 53 from page 61 through 68). Lastly, Appendix B of the “Hot Mix Asphalt Plants - Emission

Assessment Report, EPA 454/R-00-019 which is the “Emission Factor Documentation for AP-42 Section

11.1, Hot Mix Asphalt Production,” clearly presents the methodology used as the basis for the final

emission factor equations recommended in the AP-42 section and the development of long term average

default values for volatility and temperature (Section 4.4.1, 4.4.2, 4.4.3 and 4.4.4 from page 4-114 through

4-123 and Tables 4-27 through 4-44 from page 4-286 through 4-307).

2.3.3.2 Issues relating to collection and analysis of emissions data

Background correction and enclosure problems

The citizens identify three issues related to the collection and analysis of the fugitive emissions

data. These issues include (1) the quality of the background emissions data obtained at Plant C, (2) the

methodology used to correct for background emissions due to truck operation (diesel exhaust and road dust

emissions), and (3) the effectiveness of the enclosure at Plant D to capture essentially all of the truck loadout emissions. The citizen groups have raised each of these issues during meetings held in Boston, in their

written comments on the draft test reports for Plants C and D, and in their comments on the Draft

Emissions Assessment Report. We understand the concerns of the citizens, the supporting arguments of the

citizens, and their proposed methods to address these concerns. However, we remain unconvinced by the

arguments that the collection and analyses of the fugitive emissions are flawed.

Previous responses and relevant information on the issues expressed in the Minority Report on the

collection and analysis of emissions data are contained in Chapter 4 of this report (see Section 3.1 from

page 43 through page 54, Section 3.3 from page 63 through 70 and Section 3.5.38 on pages 90 and 91). In

addition, the EPA Report No. 454/R-00-029, “Hot Mix Asphalt Plants Response to Comments on Testing

Program for Asphalt Plants C and D” published in May 2000 also contains responses and relevant

information on these collection and analysis issues (see in particular Item 11 on pages 17 and 18, Item 13

on page 19, Item 15 from page 21 to 26, Item 41 from page 41 through 50, Item 51 from page 56 through

61, Item 55 on pages 68 and 69, Item 57 on page 70 and Item 60 from page 72 through page 75).
2-6

“EPA’s flat denial of errors in the report”

In one section of the Minority Report entitled “EPA’s flat denial of errors in the report,” the

citizens express dissatisfaction with EPA’s earlier response to their prior comments regarding errors in the

draft reports distributed for review by the stakeholders. In particular, the citizens express dissatisfaction

with “incorrect references, missing and incorrectly referenced appendices and numerical and logical errors

in the analysis.” We recognize that there were a few incorrect references and missing and incorrectly

referenced appendices which we have acknowledged in the past and since corrected: nevertheless, we do not

believe that these should have significantly affected the stakeholders reviews of the approximately 14 draft

reports distributed. We appreciate the citizens identification of the two more significant errors they cite

which we previously corrected. The first error was created when calculations to determine average

emission concentrations for one of three test runs on a silo filling operation included time periods where no

asphalt was being loaded into the storage silo; the second was an incorrect maximum concentration for the

intermittent load-out test reported in an appendix of the report for Plant C which fortunately had no effect

on data elsewhere in the report. We routinely distribute draft reports to all interested stakeholders for their

review to integrate the various perspectives and ensure that we have not made inappropriate assumptions,

overlooked relevant information, etc. Considering the large volume of data processed for this project and

the tight time constraints on its generation, we do not find these few errors unreasonable.

“Unfounded leaps of faith”

The citizens believe the selection of docosane and tricosane as model compounds for asphalt

emissions from storage tanks is an “unfounded leap of faith.” They point out that docosane and tricosane

are not the major measured constituents of asphalt emissions and that EPA chose these compounds because

their Antoine’s coefficients produce a working loss estimate of 32 pounds per million gallons of asphalt

throughput for their approximate molecular weight. The use of docosane and tricosane as the model

compounds in the development of Antoine’s constants for asphalt for use in the TANKS program to

estimate working losses from storage tanks is based on sound scientific principles. EPA recognizes that the

specific compounds used are neither the major constituents of asphalt vapors nor major constituents of

liquid asphalt. As the citizens imply, our selection of these compounds to derive Antoine’s constants for

asphalt is based in part on the fact that the Antoine’s constants for the compounds produce working loss

emission estimates consistent with the actual test data from Plant C. In other words, when using the

Antoine’s constants and the molecular weights developed, the TANKS program predicts the emissions 

calculated from the maximum vapor concentrations for asphalt measured during silo emission testing at

Plant C. Each step of the development of the Antoine’s constant is clearly described in Section 4.4.5

beginning on page 4-123 of Appendix B of the “Hot Mix Asphalt Plants - Emission Assessment Report,”

EPA 454/R-00-019 which is the “Emission Factor Documentation for AP-42 Section 11.1, Hot Mix

Asphalt Production.” Previous responses or relevant information on emissions estimations methods for

asphalt storage tanks are contained in Chapter 4 of this report (Section 3.5.44 on page 93, Section 3.5.50

from page 96 through page 99, Section 3.7.2 on pages 115 and 116, Section 3.7.4 on page 116). While the

calculational details are preliminary, this basic methodology is described in the response to item 17 from

page 26 through 28 in the document EPA 454/R-00-029, “Hot Mix Asphalt Plants Response to Comments

on Testing Program for Asphalt Plants C and D” published in May 2000.

Problems with witnessing tests

The citizens raise a number of issues with regard to citizen observation of the emission tests at

Plants C and D: (1) it was difficult for the single witness allowed at Plant C to simultaneously observe
2-7

operations at several places in the plant; (2) certain information was withheld from the citizen observer onsite under a claim of confidentiality, (3) citizens were forbidden to take photographs to document their

observations, and (4) an EPA staff member commented during a dinner discussion that EPA had no

intention of regulating fugitive emissions from the asphalt industry.

The citizens were allowed unprecedented access to both Plant C and D. All process and emissions

sampling data were freely available to the observer for review during the test program. While EPA’s

Confidential Business Information (CBI) procedures precluded providing a hard copy of this information to

the observer, hard copy was available later after it cleared CBI review. In addition, the citizen observer

was considered an integral part of the test team during on site decision meetings to discuss issues that could

potentially affect the test program. During both of the emission tests, the number of observers (citizen

plus agency) greatly exceeded the number of operators at the plants. To minimize competing requests for

the plant operators’ attention, access to the plant operator was limited to the individual responsible for

obtaining the process operation data who was responsible for keeping the remainder of the test team

informed of plant operation changes. This limitation applied not only to the citizen observer but to the EPA

observers, the three EPA contractor organizations, and the industry observers as well.

While no photographs were taken prior to correcting the two ventilation system problems that

created the visible emissions condition observed by Dr. Nadkarni on the day before the first complete truck

load-out emission test run at Plant C, documentation (capture efficiency measurements and photographs)

have been supplied to the stakeholders that confirm that the capture of the emissions was not 100% and the

capture efficiency measurements have been used to correct the data for the emissions testing at this

emission point. Further responses to comments concerning the capture of emissions at both Plants C and D

are included in items 11, 13 and 14 of the report “Hot Mix Asphalt Plants Response to Comments on

Testing Program for Asphalt Plants C and D” (EPA 454/R-00-029) and sections 3.1.2 and 3.1.4 in

Chapter 4.

The citizens’ assertion that EPA prejudged the final outcome of the project is incorrect. During the

many teleconferences and meetings with the stakeholders (citizens, industry, and State agencies) prior to the

emissions test, the EPA office responsible for regulatory decisions clearly identified the criteria established

by the Clean Air Act Amendments of 1990 (CAAA) for developing emissions regulations. In particular,

they explained that two major criteria that trigger development of a regulation are (1) a determination that

one or more facilities in a source category are a “major source” of hazardous air pollutants (HAPs) and (2)

that there is a demonstrated technology to control these HAP emissions. It was also explained to the

stakeholders, that the CAAA defines a “major source” as any contiguous facility with emissions of more

than 10 tons of any one HAP or 25 tons of any combination of HAPs. The objective of testing at both

Plants C and D was to quantify the fugitive HAP emissions from hot mix asphalt plants and thereby

determine whether any hot mix asphalt plants could be a “major source.” Considering the substantial

emission testing resources being expended to quantify emissions from hot mix asphalt plants in order to

make the “major source” determination and that fact neither of the EPA staff present at the dinner is

responsible for regulatory decisions, it is unlikely that they would have stated that EPA had no intention of

regulating hot mix asphalt plant emissions.
2Partanen, T.J., Boffetta, P., Heikkila, P.R., Frentzel-Beyme, R.R., Heederik, D., Hours, M.,

Jarvholm, B.G., Kauppinen, T.P., Kromhout, H. Langart, S. 1995. Cancer risk for European asphalt

workers. Scand. J. Work Environ. Health 21(4): 252-258.

3Burstyn, I., Kromhout, H., Cruise, P.J. and Brennan, P. 2000. Designing an international

industrial hygiene database of exposures among workers in the asphalt industry. Ann. Occup Hyg. 44(1):

57-66.

2-8

2.3.4 Conclusions

2.3.4.1 Performance of epidemiological study by EPA

The Minority Report recommends that the government conduct community-based epidemiological

studies to elucidate health effects from exposure to asphalt emissions. Justification for such a study would

be helped by further definitive studies in worker populations in whom any adverse effects would be more

likely to occur. Results from such a study among workers could then trigger and provide direction for

studies at the community level. The authors of the Minority Report may want to refer to the work of

Partanen, et al. (1995)2 and Burstyn, et al. (2000)3 which describe the feasibility of such studies among

asphalt workers in more depth.

2.3.4.2 Include additional warnings in AP-42

The citizens recommend that EPA include the limitations regarding individual emission factors in

each table in AP-42. As the citizens point out, EPA recognizes the great reliance on AP-42 emission

factors by industry and state agencies in permitting and other processes. The introduction to AP-42

currently provides a detailed discussion regarding limitations for using the emission estimation

methodologies contained in the numerous tables in the more than 200 sections of AP-42. We do not believe

it is reasonable that every table include a statement that the emission estimation methods represent an

average of available data and do not represent “worst case” impact scenarios. Such statements would

introduce additional and unnecessary complexity into the tables that are already complex and such

statements are not likely to eliminate or reduce any existing misuse of the available methodologies.

2.3.4.3 Get tough with industries on excessive claims of CBI

The citizens recommend that the government challenge industry regarding unsubstantiated demands

for confidentiality of business information. We would again point out that all available information was

provided to the stakeholders in sufficient time for evaluation and comment prior to the next decision point

of the process. Prior to their observation of testing at Plant C, the citizens were provided with a copy of the

OAQPS CAA Confidential Business Information (CBI) Security Manual. This manual includes the

procedures followed by OAQPS to insure that CBI that is inadvertently received is protected. We

recognize that much of the information collected during our plant visits and emission tests is unlikely to be

claimed as CBI. However, we must still recognize the potential to collect some limited amount of CBI. 

The procedures used by OAQPS to protect and determine the CBI status of information collected during

inspections and testing is described on page 19 of the manual. These procedures incorporate the

requirements of Federal Rules established by Congress for insuring that information EPA needs from

businesses do not infringe on businesses ability to keep selected information confidential. As indicated in

third paragraph section “B. Original CBI,” all information collected by EPA during data-gathering visits or
2-9

tests must be forwarded to the responsible industry official for review to preclude the inadvertent release of

CBI. The sample letter on page 87 of the manual contains criteria for supporting a claim of confidentiality. 

EPA staff have no authority to presuppose what material obtained during a visit or test does not meet these

criteria. Industries are usually provided 45 days to respond to EPA’s requests to identify CBI. For all of

the information obtained during the hot mix asphalt fugitive emissions study, industry made no claims of

confidentiality. In addition, the information obtained by EPA was made available to all stakeholders less

than 30 days after it was submitted to the industry for clearance.

2.4 Response to opinions of National Asphalt Paving Association

EPA agrees that the methodologies published in the Emissions Assessment Report have resolved

the question of how best to estimate emissions from truck load-out and silo filling operations. Additionally,

EPA agrees that with the completion of this report there are now reliable emission estimation methodologies

for essentially all air emission sources at hot mix asphalt plants. EPA does not agree that the information

in the Emissions Assessment Report proves that there are no hot mix asphalt plants that are “major

sources.” However, when combined with facility production information and the appropriate pollutant

emissions evaluation criteria, the available methodologies in the report will allow State and local agencies

to determine the major source status of a facility.
2-10

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Chapter 3

Stakeholder Opinions on

Hot Mix Asphalt Plants

Emission Assessment Report

EPA 454/R-00-019

December 2000
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Lloyd Eagan, Director

Bureau of Air Management

Wisconsin Department of Natural Resources

Madison, WI
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Research Triangle Park, NC 27711 
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y y gy ppyg 

governing statutes and administrative rules to the relevant facts. 
common to all HMAs. 

This document is a revision of two previous documents. The HMA document was 

written in 1996 after discussions with the industry. This document was later updated in 

1998. This document uses much of the same information of the prior documents but also 

includes summary tables for the HMA source and emission factor. 

This guidance was developed by the Central Office and people that deal with hot mix 

asphalt plants from the South Central and Southeast Regions. This guidance is only 

applicable to the calculation of emissions for the air emission inventory. This guidance is 

not intended for use on asphalt plant permits because the focus of permits tends to be on 

potential to emit (PTE) and maximum total emissions (MTE) while the air emission 

inventory focuses on the calculation of actual emissions. This guidance furnishes. s 

information on the emission factors and information for calculating emissions from each 

hot mix asphalt plant. 

DATABASE NEEDS 

The Air Emissions Management System (AEMS) is the air management computer system 

used to calculate air emissions from all point sources. AEMS requires the identification 

of the device (i.e. the piece of equipment), the process (i.e., the type of fuel burned or 

material processed), and an eight digit source classification code (SCC) associated with 

the process. The database assigns a default emission factor unless some other data is 

placed into the database manually. The default emission factors are taken from four 

sections of AP-42, l/95 version. These four sections are 11 .l Hot Mix Asphalt Plants, 

1.3 Fuel Oil Combustion, 1.4 Natural Gas Combustion and 1.5 Liquefied Petroleum Gas 

Combustion. 

USEPA HMA DESCRIPTIONS 

(Note: This section taken from AP-42 Section 11.1 Hot Mix Asphalt Plants. Tables 1, 

2, and 3 were developed from diagrams of the HMA plants in this section. J 

There are different types of HMA set-ups. HMA paving materials can be manufactured 

by: (1) batch mix plants, (2) continuous mix (mix outside drum plants), (3) parallel flow 

drum plants and (4) counterflow drum mix plants. According to AP-42 Section 11.1 Hot 
appropriate hoppers of the cold feed unit. The material is metered from the hoppers 

onto a conveyor belt and is transported into a rotary dryer (typically gas or oil fired). 

Dryers are equipped with flights designed to shower the aggregate inside the drum to 

promote drying efficiency. 

As the hot aggregate leaves the dryer, it drops into a bucket elevator and is transferred to 

a set of vibrating screens where it is classified into as many as four different grades 

(sizes), and is dropped into individual “hot” bins according to size. To control aggregate 

size distribution in the final batch mix, the operator opens various hot bins over a weigh 

hopper until the desired mix and weight are obtained. Reclaimed asphalt pavement may 

be added at this point, also. Concurrent with the aggregate being weighed, liquid asphalt 

cement is pumped from a heated storage tank to an asphalt bucket, where it is weighed to 

achieve the desired aggregate-to-asphalt cement ratio in the final mix. 

The aggregate from the weigh hopper is dropped into the mixer (pug mill) and dry-mixed 

for 6 to 10 seconds. The liquid asphalt is then dropped into the pug mill where it is 

mixed for an additional period of time. Total mixing time is less than 60 seconds. Then 

the hot mix is conveyed to a hot storage silo or is dropped directly into a truck and hauled 

to the job site. 

As with most facilities in the mineral products industry, batch mix HMA plants have two 

major categories of emissions: ducted sources (those vented to the atmosphere through 

some type of stack, vent, or pipe), and fugitive sources (those not confined to ducts or 

vents but emitted directly into the ambient air). Ducted emissions are usually collected 

and transported by an industrial ventilation system having one or more fans or air 

movers, eventually to be emitted to the atmosphere through some type of stack. Fugitive 

emissions result from process and open sources and consist of a combination of gaseous 

pollutants and PM. 

The most significant source of ducted emissions from batch mix HMA plants is the rotary 

drum dryer. Emissions from the dryer consist of water as steam evaporated from the 

aggregate, PM and small amounts of volatile organic compounds (VOC) of various 

species (including hazardous air pollutants [HAP] derived from combustion exhaust 

gases. 
I

on the temperature of the asphalt cement and aggregate entering the pub mill. Organic 

vapor and its associated aerosol are also emitted directly to the atmosphere as process 

fugitives during truck loadout, from the bed of the truck itself during transport to the job 

site, and from the asphalt storage tank. In addition to low molecular weight VOCs, these 

organic emission streams may contain small amounts of polycyclic compounds. Both the 

low molecular weight VOCs and the polycyclic organic compounds can include HAPS. 

The ducted emissions from the heated asphalt storage tanks may include VOCs and 

combustion products from the tank heater. 

There are also a number of fugitive dust sources associated with batch mix HMA plants, 

including vehicular traffic generating fugitive dust on paved and unpaved roads, 

aggregate material handling and other aggregate processing operations. Fugitive dust 

may range from 0.1 pm to more than 300 pm in aerodynamic diameter. On average, 5 

percent of cold aggregate feed is less than 74 pm (minus 200 mesh). Fugitive dust that 

may escape collection before primary control generally consists of PM with 50 ,to 70 

percent of the total mass less than 74 pm. 

Table I 

Batch Mix HMA 

Emission Sources 

3-05-020-33 (proposed) 
aggregates, as well as the combustion products, move toward the other end of the drum in 

parallel. Liquid asphalt cement flow is controlled by a variable flow pump electronically 

linked to the new (virgin) aggregate and RAP weigh scales. The asphalt cement is 

introduced in the mixing zone midway down the drum in a lower temperature zone, along 

with any recycled asphalt (RAP) and particulate matter (PM) from collectors. 

The mixture is discharged at the end of the drum and is conveyed to either a surge bin or 

HMA storage silos. The exhaust gases also exit the end of the drum and pass on to the 

collection system. 

Parallel flow drum mixers have an advantage, in that mixing in the discharge end of the 

drum captures a substantial portion of the aggregate dust, therefore lowering the load on 

the downstream collection equipment. For this reason, most parallel flow drum mixers 

are followed only by primary collection equipment (usually a baghouse or venturi 

scrubber). However, because the mixing of aggregate and liquid asphalt cement occurs 

in the hot combustion product flow, organic emissions (gaseous and liquid aerosol) may 

be greater than in other processes. 

The most significant ducted source of emissions is the rotary drum dryer. Emissions 

from the drum consist of water as steam evaporated from the aggregate, PM, and small 

amounts of VOCs of various species (including HAPS) derived from combustion exhaust 

gases, liquid asphalt cement, and RAP, if utilized. The VOCs result from the incomplete 

combustion and from the heating and mixing of liquid asphalt cement inside the drum. 

The processing of RAP materials may increase VOC emissions because of an increase in 

mixing zone temperature during processing. 

Process tigitive emissions associated with batch plant hot screens, elevators, and the 

mixer (pug mill) are not present in the drum mix process. However, there may be slight 

tigitive VOC emissions from transport and handling of the hot mix from the drum mixer 

to the storage silo and also from the load-out operations to the delivery trucks. Since the 

drum process is continuous, these plants must have surge bins or storage silos. The 

tigitive dust sources associated with drum mix plants are similar to those of batch mix 

plants with regard to truck traffic and to aggregate material feed and handling operations. 
[Note: SCCs 3-05-020-33 and 3-05-020-34 have been proposed by DNR as additions to 

the USEPA SCC list.] 

3. Counterflow Drum Mix Plant 

In this type of plant, the material flow in the drum is opposite or counterflow to the I ’ ,, 

direction of exhaust gases. In addition, the liquid asphalt cement mixing zone is located. 

behind the burner flame so as to remove the materials from direct contact with hot 

exhaust gases. 

Liquid asphalt cement flow is controlled by a variable flow pump which is electronically 

limited to the virgin aggregate and RAP weigh scales. It is injected into the mixing zone 

along with any RAP and particulate matter from primary and secondary collectors. 

Because the liquid asphalt cement, virgin aggregate, and RAP are mixed in a zone 

removed from the exhaust gas stream, counterflow drum mix plants are will likely have 

organic emissions (gaseous and liquid aerosol) that are lower than parallel flow drum mix 

plants. A counterflow drum mix plant can normally process RAP at ratios up to 50 

percent with little or no observed effect upon emissions. 

The most significant ducted source of emissions is the rotary drum dryer in a counterflow 

drum mix plant. Emissions from the drum consist of water as steam evaporated from the 

aggregate, PM, and small amounts of VOCs of various species (including HAPS) derived 

from combustion exhaust gases, liquid asphalt cement, and RAP, if used. 

Because liquid asphalt cement, aggregate, and sometimes RAP, are mixed in a zone not 

in contact with the hot exhaust gas stream, counterflow drum mix plants will likely have 

lower VOC emissions tan parallel flow drum mix plants. The organic compounds that 

-1 *.,. 

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I 

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I 

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Table 3 

Counter Flow HMA 

Emission Sources 

AP-42, l/95 Figure 11.1.3 

Emission Source Source Classification Code 

Counter Flow Drum Mixer 3-05-002-05 

Cold Aggregate Bins 3-05-002-04 

Asphalt Cement Storage Heater 3-05-002-06 

3-05-002-07 

3-05-002-08 

Loader 3-05-002-04 

Fihe Aggregate Storage Pile 3-05-002-03 

Coarse Aggregate Storage Pile 3-05-002-03 

Conveyor from Counter Flow Drum 3-05-020-06 

Mixer to scalping screen I 

Conveyor from scalping screen to Cold 1 3-05-020-06 

Aggregate Bins I 

I 

Convevor from RAP Bin to i 3X15-020-06 I 

[Note: SCCs 3-05-020-33 and 3-05-020-34 have been proposed by DNR as additions to 

the USEPA SCC list.] 

DNR INFORMATION ON HMAs 

DNR has experience with asphalt plants specific to their operations in Wisconsin. .The 

following is a list of DNR observations regarding HMAs. 

1. Emissions from processes 

Processes are those sources ducted to a vent or to a piece of control equipment. 

For the most part emissions from these processes are assumed to be gaseous. 

Particulate matter emissions are assumed to be emitted from fugitive sources. 
burned at either the batch mix or drum mix asphalt plants. Information 

from AP-42 Sections 1.3 and 1.4 are used in calculating these emissions 

because these emission factors are supported through higher quality data 

(AP-42 gives them an A rating) as compared to the emissions for these 

pollutants in AP-42 Section 11.1 which have a D or E rating. [Note: 

USEPA assesses a quality rating of A (the best) to E (the worst) based on 

data compiled to support these emission factors.] These criteria emissions 

vary based on fuel burned. 

1. Natural Gas 

Information from AP-42 Section 1.4 using SCC code l-02-006-02 

for small industrial boilers for burners with a heat input rating of 

less than100 MMBtu/hr are used in the calculation of criteria 

pollutant from natural gas burning. SCC code l-02-006-01 is used 

for burners with a heat input rate greater than 100 MMBtu/hr. 

,. 

2. Distillate Fuel Oil 

Information from AP-42 Section 1.3 using SCC code l-03-005-02 

for boilers using distillate fuel oil The criteria pollutant from 

distillate fuel oil burning should be calculated. Please note that 

distillate fuel oils are #l, #2 and #4 (if made up solely of heavy 

distillate fuel oil). #l and #2 distillate fuel oils have a maximum 

sulfur content of 0.5% by weight. 

3 Waste Fuel Oil 

Waste fuel oil is any oil refined from crude oil or synthetic oil that 

becomes contaminated during use. It includes engine oil, gear oil, 

lubricating oil, hydraulic oil, cutting oil, transformer fluids and 

tempering or quenching oils. Waste fuel oil is divided into three 

categories: specification, off-specification and hazardous waste. 

Waste fuel oil can then be mixed with either distillate or residual 

fuel oils to obtain a required viscosity. 
2. 

Combustion should be calculated using information from AP-42 

Section 1.5 using SCC code l-02-010-02 for industrial boilers. 

You will need to know the amount of Liquified Petroleum Gas 

burned at the HMA in 1000 gallons in order to calculate these 

emissions. 

Fugitive Emissions 

A. Asnhalt Heaters 

Asphalt heaters are used to heat the liquid asphalt cement. These units are 

typically fired with fuel oil. Again the combustion emissions factors from 

AP-42 Section 1.4 (natural nas fired) and 1.3 (he1 oil fired) could be 

applied to the heaters, as appropriate to fuel burned. 

B. Fuel Oil Tank Heaters 

Fuel oil tank heaters are used to heat the waste oil/residual fuel oil. These 

units are typically fired with fuel oil. Again the combustion emissions 

factors from AP-42 Section 1.4 (natural gas fired) and 1.3 (fuel oil fired) 

could be applied to the heaters, as appropriate to fuel burned. Generally, 

the emissions from fuel oil tank heaters are small or insignificant. 

C. Roadways 

Asphalt plants may have either paved or unpaved roadways, depending on 

their location and whether they are permanent or portable units. The same 

emissions factors and fugitive dust control efficiencies applied to 

roadways in quarries and sand and gravel operations under the current 

nonmetallic mining guidance document should be used to characterize 

these emissions. 

D. Stockpiles 

Asphalt plants will have several stockpiles of different types of stone, sand 

and ground recycled asphalt (RAP). The same emissions factors and 

I- 
0200102 and (gas) 20200301 could be applied to the diesel/gas 

generators, as appropriate to fuel burned. 

F. HaulinFr/Loadinn to Bins 

Asphalt plants generally will have several bins that a loader operator is 

required to keep full by traveling between the storage piles and dumping 

into the bins. The same emissions factor and fugitive dust control 

efficiency applied to portable crusher operations can be applied to asphalt 

plants. The hauling emission factor (developed for crushers) is listed in 

the Nonmetallic Air Emissions Guidance document applicable to the 

calendar year the emission was reported. The SCC code applicable to this 

fugitive emission is 3-05-020-l 1. 

G. Screening 

Asphalt plants generally will have screen(s) that separate out over sized 

materials before it enters the mix. The same emissions factor and fugitive 

dust control efficiency applied to portable crusher operations can be 

applied to asphalt plants. The SCC Code applicable to screening is 3-05 

020-04. 

H. Soil Remediation 

Asphalt plants that remediate soil discharge ROG and benzene emissions. 

These emissions are calculated and recorded according to their permit 

requirements and can be entered into AEMS under a separate process 

number. The SCC code associated with asphalt plants should be entered. 

The emission factor for ROG should reflect the units of reporting. 

Typical HMA Plant 

There are similarities and differences between (1) batch mix plants, (2) parallel flow 

drum and (3) counterflow drum mix plants. Each HMA plant in AEMS should begin 

with similar devices and proceses and have the specific HMA tailored using the devices 

and processes specific to the type of HMA. Table 4 lists the HMA sources identified by 

should be removed for asphalt 

1-02-006-03 natural gas PM10 for natural gas should 

Newt Rowe, Analytical Scientist

State of Connecticut

Department of Environmental Protection

Hartford, CT
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STATE OF CONNECTICUT 

DEPARTMENT OF ENVIRONMENTAL PROTECTION 

March 12, 2001 

Mr. Ronald Meyers 

USEPA 

Mail Drop 19 

Research Triangle Park, NC 27711 

RE: Hot Mix Asphalt Plant Emissions Study 

Dear Mr Meyers: 

As a representative of the Connecticut DEP, I tracked the progress of the asphalt plant emissions study 

from the outset. As you know, I played an active role in the developmental stages of the study by 

attending meetings, participating in conference calls, providing written comments, and witnessing 

emissions testing. During the developmental stages of this project, I became very aware that the USEPA 

staff was conducting the project in an exemplary fashion. It was quite evident that the scope ofthe 

project was comprehensive, the collection and analysis protocols appropriate, the objectives well-defined, 

and the USEPA staff very capable. 

Given this, it was decided that my time could be more efficiently and effectively spent on Title V and 

NSR permitting as well as other areas where technical support was needed within the DEP. As such, I 

started to track the progress of the asphalt study. It was important to track the progress of the study since 

a moratorium on the issuance of permits to asphalt batch and drum mix plants had been put into effect in 

Connecticut. This moratorium was established to assure that the results ofthe USEPA asphalt study 

could be considered in the NSR permit application review process. I believe that there are six 

applications in-house to which the results of the hot mix asphalt study will be applied. 

To this end, the DEP has developed two sets of spreadsheets one for batch mix the other for drum mix 

plants. Each set contains eight individual tables, only natural gas and #2 fuel oil combustion are 

considered since the use of #4 or #6 fuel oil for a new or modified batch or drum mix plant in Connecticut 

would probably not be considered BACT. The eight tables are described briefly below: 

1) Dryer/Hot Screens/Mixers (as applicable) - Criteria Pollutants 

2) Dryer/Hot Screens/Mixers (as applicable) -HAPS (federal & CT) 

3) Load & Silo Filling Operations-Criteria Pollutants 

4) Load & Silo Filling Operations - Semivolatile HAPS (federal & CT) 

5) Load & Silo Filling Operations-Volatile Organic HAPS (federal & CT) 

6) Silo Filling & Storage Operations-Volatile Organic HAPS (federal & CT) 

7) Asphalt Hot Oil Heaters - VOC, PAH & PCDD/PCDF 

8) Premise-Wide Summary (Criteria Pollutant & federal HAP) 

If you have any questions, please contact me at (860)-424-3465 or by E-mail at 

Newt.Rowe@po.state.ct.us. 

Sincerely, 

Newt Rowe 

Analytical Scientist 

cc: Robert McConnell, USEPA Region 1 

( Pr,n,rd on Recycied Paper) 

79 Elm street * Hartfurd. CT 06106 5127 

http:l,dep.state.ft.us 
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Lloyd Fillion

Citizens Against the Asphalt Plant

Boston, MA

Ravi Nadkarni

Wrentham Environmental Coalition

Wrentham, MA

Henry W. Nowick

Nowick Environmental Associates

Springfield MA

Hyla Napadensky

Napadensky Energetics

Lutsen MN

Janet &Lou Zeller

Blue Ridge Environmental Defense League

Glendale Springs, NC

Jeff Gearhart

Ecology Center

Ann Arbor MI

Stephen F. Lynch

Massachusetts State Senator

First Suffolk District

Boston, MA
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Minority Report on Fugitive Emissions from

Asphalt Plants

Lloyd Fillion, Citizens Against the Asphalt Plant, Boston MA

Ravi Nadkarni, Wrentham Environmental Coalition, Wrentham MA

Henry W. Nowick, Nowick Environmental Associates, Springfield MA

Hyla Napadensky, Napadensky Energetics, Lutsen MN

Lou Zeller, Blue Ridge Environmental Defense League, Glendale Springs, NC

Janet Zeller, Blue Ridge Environmental Defense League, Glendale Springs, NC

Jeff Gearhart, Ecology Center, Ann Arbor MI

Stephen F. Lynch, Massachusetts State Senator, First Suffolk District, Boston MA
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1. “Emissions Testing: July 9 - 11, 1996" AIRx Testing, Ventura Ca - Job # 1030.

Minority Report on Fugitive Emissions from Asphalt Plants

Introduction

In the mid-1990s, several groups of citizens and environmental organizations began petitioning the

US EPA to quantify so-called "fugitive" emissions from bituminous concrete, or asphalt hot mix,

plants. These requests were based on observations and subsequent theoretical analysis suggesting that

such emissions could be significantly greater in their volume and concomitant impact on the local

environment than the word "fugitive" implied. In late 1996, the EPA decided to move forward with

its own testing after the asphalt industry failed to conduct their own testing in an open manner as they

had promised the EPA, producing a test report1

 which was heavily criticized by academic and

research scientists, public health officers, citizens, environmental activists and even from within the

EPA itself. The citizen or public representatives who participated in this program ultimately included

staff from public health departments in Chelsea, Massachusetts and Boston, Massachusetts,

engineering/science consultants from several diverse disciplines including chemists, environmental,

chemical and mechanical engineers, environmental organizations from Massachusetts, Connecticut,

North Carolina and Michigan, and citizen activists from those states and from Minnesota, New York

and Virginia. Additionally the Massachusetts Department of Public Health and one Massachusetts

State Senator with experience in construction provided comments. 

The EPA committed to providing an opportunity for citizens, along with industry and other

stakeholders, i.e., other government agencies, to help frame the test protocols. This opportunity was

provided through a series of conference calls and day long meetings and written communications. The

interaction was hosted and coordinated by the EPA’s New England Regional office, and continued

through the testing, compilation of test data, analysis and production of reports. The commitment of

the EPA was laudable; however, the several year long interactions were adversarial at best, with

hostility or distrust between the multi-state citizen group with its technical consultants and the

technical staff from EPA's Research Triangle Park (EPA-RTP). The barely contained rancor resulted

in most of the conference calls and meetings being conducted with mediators from the EPA’s New

England Regional Alternative Dispute Resolution Program.

At the point of testing, the EPA provided opportunity (travel and lodging) for only one citizen

technical advisor from the East Coast cluster of public commenters to witness the primary test which

took place in California at a drum style facility, the same facility that had been previously selected by

industry1

, code labeled by the EPA as "Plant C." At a secondary test in Massachusetts, at a batch

style facility labeled "Plant D,” three citizens were on site for the three days of testing. The primary

test observer was severely handicapped because of an inability to be at more than one place

simultaneously, a prohibition on citizen photography coupled with the EPA's reluctance and even

refusal to take requested photographs as had been promised the citizens, and the exclusion of the

citizen from certain meetings which occurred between plant personnel and EPA officers with their

testing consultants who were responsible for the test. It is against this less-than-open venture in

cooperation that the test and subsequent data are to be viewed.
2

2. E.G. Knox & E.A. Gilman, “Hazard proximities of childhood cancers in Great

Britain from 1953 -80", Journal of Epidemiology and Community Health, 1997, 51, 151-159.

3. Hansen ES, “Cancer incidence in an occupational cohort exposed to bitumen

fumes”. Scand J Work Environ Health 1989;15:101-5. Hansen ES. “Mortality of mastic

asphalt workers”. Scand J Work Environ Health 1991;17:20-4; Hansen ES, “Author’s reply”, 

Scand. J. Work Environ. Health,18: 135-41, (1992). 

Why are many citizen groups concerned about asphalt plants?

Hot Mix Asphalt plants (HMA plants) and asphalt terminals have numerous characteristics that result

in a large number of the general public being exposed to their hydrocarbon and particulate emissions.

This is in contrast to the general experience where workers in industrial plants are frequently exposed

to higher concentrations of pollutants for longer durations than the people who live near the plant.

In the case of asphalt plants, this generalization is not correct because such plants, of which there are

about 3,600 within the US, are often located in urban areas close to homes, schools and playgrounds

with minimal setbacks. Further, the plants operate around the clock when fulfilling certain types of

contracts so that while the workers might be exposed only eight hours per day, the neighbors breathe

in the fumes day and night. While the operation of an asphalt plant might be seasonal, particularly in

northern latitudes, the intensity of exposure during the peak production months is quite acute.

Anecdotal information collected by Boston Health Commission’s Office of Environmental Health and

by others shows that some individuals exposed to asphalt plant emissions have the same or similar

symptoms: asthma, nausea, headaches, skin rash, etc. This information is not sufficient to indicate

whether these physiological reactions were a result of hypersensitivity and allergies or whether this

was a reaction of non-allergic people to levels of hydrocarbon and fine particulates high enough to

elicit a response. Available epidemiological studies have shown statistically significant links between

exposure to hydrocarbons and/or metal fume and childhood leukemia2

 and between exposure to

asphalt fume and a variety of cancers. Dr. Eva Hansen3 measured excess cancers in asphalt workers

in Scandinavia. These included cancers of the mouth, esophagus, lung, and rectum. Dr. Hansen also

found increases in non-pulmonary cancer, liver cirrhosis, bronchitis, emphysema and asthma in asphalt

workers.

As a part of the interaction with the EPA, the multi-state citizen coalition held a conference call with

EPA-RTP to discuss health effects of asphalt fume and to see if they could regulate emissions from

HMA plants so that the exposure of the general population would be reduced. These discussions

were unsatisfactory. EPA-RTP has acknowledged that their limited resources permit the

consideration of only about 50 chemicals annually, out of a field of 50,000 chemicals not yet tested.

Asphalt fume, a complex emission, is comprised of over 2,000 individual chemicals. Since EPA’s

current approach is based on considering each chemical by itself, knowledge about the health effects

of each individual chemical will not be available for many decades. Further, even after this data has

been compiled, the synergistic interactions between these chemicals in a complex mixture will not be

available and would require further study. EPA-RTP suggested that the citizens undertake an

epidemiological study to establish a statistical link between exposure to asphalt emissions and health
3

4. There are probably political reasons for this reluctance. After all, the asphalt industry is at the

confluence of several large, powerful and politically active industries with a long reach into Washington DC. 

These include the oil industry who produces the asphalt during the refining of petroleum, the sand and gravel

business which produces aggregate, the other component of hot mix, the highway lobby and the State Departments

of Transportation or Highways who have a symbiotic relationship with the hot mix asphalt industry as the major

customer for the product. The article by Sarah Gibson (“How OSHA Dealt with Asphalt Fume”, New Solutions, 5-

1, 24 - 47, Fall 1994.) is essential reading for any one interested in learning how the industry dictated the final

OSHA standards for occupational exposure to asphalt fume. The industry also conducted a vehement, coordinated

attack on Dr. Hansen, the epidemiologist who has shown a significant relationship between exposure to asphalt

fume and various cancers, at an ACGIH Satellite Meeting on “Developing Occupational Exposure Values from

Toxicology and Epidemiology Studies” on March 6, 1998 in Seattle. Her use of statistics was vehemently

challenged by a statistician as a part of an industry presentation by an employee of Ashland Oil. The industry also

paid to bring other attackers to the meeting including an employee of a Scandinavian industry trade group and

another Scandinavian researcher whose results are somewhat different from Dr. Hansen’s.

5. “RESPONSE TO COMMENT ON DRAFT EMISSIONS ASSESSMENT REPORT,

AP-42 SECTION AND AP-42 BACKGROUND REPORT” released December 20, 2000. This

report and related information can be downloaded from: http://www.gov/ttn/emc/asphalt.html.

Copies of CD ROM can be requested by mail from Emissions Measurement Center, MD-19, US

EPA, Research Triangle Park, NC, 27711. Paper copies can be obtained from National Technical

Information Service, 5285 Port Royal Road, Springfield VA 22161. 1-800-553-6847. 

effects. EPA would not act to curb these emissions in the absence of such a study. For environmental

pollutants like asphalt fume, neither exposure nor toxicity are acute enough to cause immediate death.

The physiological response might take time (for example, cancer often takes several decades to

develop even with exposure to known carcinogens like tobacco smoke) or the irritants will produce

a variety of negative health responses in a general population which, while significant in terms of loss

of productivity and “life, liberty and pursuit of happiness”, don’t cause immediate death but still have

an effect on mortality and morbidity. To track asphalt plant neighbors on a national basis over a long

period of time is a massive job that is totally outside the ability and resources of any citizen group4

.

 

The current work is the culmination of an almost 6-year effort to quantify fugitive emissions from

HMA production/handling. On the one hand, EPA agreed to measure these emissions by collecting

and analyzing data from two plants, labeled Plant C, a large drum plant and Plant D, a batch plant.

For this we are grateful. On the other hand, the work has certain shortcomings and this Minority

Report presents a discussion of these issues which have not been resolved to our satisfaction. Given

the contentious and contradictory nature of the latest document “RESPONSE TO COMMENT ON

DRAFT EMISSIONS ASSESSMENT REPORT, AP-42 SECTION AND AP-42 BACKGROUND

REPORT”5, a point by point rebuttal has not been attempted; instead a few select examples are

presented to illustrate that these differences continue due to lack of valid response from EPA. The

discussion focuses on the major questions that this work was expected to answer which unfortunately

have not been answered. 

It should be noted that there is a difference between the EPA and the citizens in the way they

respectively approach the issue of asphalt fume emissions. The citizens approach the issue from a

public health perspective. Thus their concern is with both average exposures for long term effects
4

6. “Strengthening Science at the U.S. Environmental Protection Agency: Research

Management and Peer Review Practices (2000)”, National Research Council, National

Academy Press. http://www.nap.edu/openbook/030971275/html/

and also with peak, short-term exposures for acute effects; particularly since much of the anecdotal

information deals with the latter. The EPA’s approach, as stated in the latest response5 is to collect

data to primarily enable the estimation of emission inventories and for air quality planning, although

EPA acknowledges that the information could be used in other contexts, for example, in applications

to State authorities to build new plants. EPA’s published data on emission factors is not just an

average number for all plants when data from individual plants varies by orders of magnitude, as much

of this data is collected under ideal operating conditions. For example, much of the data used for

developing stack emission factors was collected just after initial plant startup often during a

preoperating test period where the plant owner is demonstrating to the state regulatory authorities

that the plant can operate for short periods of time at the design operating rate while staying within

the permitted emission limits. In these situations, it is not unusual to have engineers from the

equipment suppliers standing by to adjust and tune the equipment (as was the case at Plant C for

EPA’s test) to make sure that the equipment is operating optimally. Once the test is successfully

completed, these engineers depart and the on-going emissions are dependent on the skills of the plant

operators and their internal maintenance staff.

Of equal importance, and most critically, citizens and public health officers are inclined to consider

worst case scenarios while the EPA almost consistently opted to publish data that reflects the best

case scenario. Additionally, these numbers don’t show measures of variability despite our request.

Such measures are buried in the appendices.

Recently, the EPA has been criticized for the lack of science to back up their decision-making6

.

Specifically, National Research Council mentioned “weak scientific performance” and “weak scientific

credibility”. The problems uncovered by citizen reviewers in this case indicate that the current project

also suffers from similar shortcomings.

 

Unresolved Issues

Rather than repeat the arguments, pro and con, under each topic, the highlights of the positions of

the two sides will be presented in this discussion of unresolved issues with emphasis on issues that

concern the citizens. Additional details, particularly of the EPA position, are in the most recent

document5

. Specific references are provided to the Section number in this “Response to Comments”

report.

1. The issue of volatile content and operating temperature

If asphalt did not contain a volatile fraction, there would not be any emissions of hazardous

organic chemicals from hot asphalt. Unfortunately, all asphalts contain a volatile fraction

which evaporates at the operating temperature of between 275o and 375o F. Further, the

emissions increase exponentially as temperature increases. The issues here are as follows:
5

7. V.P. Puzinauskas & L.W. Corbett, of the Asphalt Institute, “Report on Emissions

from Asphalt Hot Mixes”, Paper presented at ACS Meeting, Chicago IL, August 1975.

a. Why did the industry change the specification for the maximum allowable volatile

content of asphalt from 0.5% to 1.0%? What are the implications of this change?

b. How is this volatile content measured now and how was it measured in the past?

c. How is the volatile content affected by seasonal variations in oil refining practice?

d. How is the volatile content affected by the various classes of additives that are sold

to improve the performance of asphalt?

e. Are the maximum operating temperatures recommended by industry groups actually

followed by plant operators? If not, what are the variations in temperature and what

is the consequence of these variations?

The above issues are repeated below as captions for the discussion to follow which delineates

the differing positions of the citizens and EPA in bold letters:

a. Why did the industry change the specification for the maximum allowable volatile

content of asphalt from 0.5% to 1.0%? What are the implications of this change?

Traditional grades of asphalt use “proxy” properties such as viscosity at 140o F for specifying

and differentiating between grades of asphalt. Under such specifications, the volatile content

is a “not to exceed” value, typically 0.5% for the most common grade of asphalt AC-20.

Certain users might allow a relaxation of these specifications. For example, in Massachusetts,

the Mass Highway Department will allow their engineer in the field to relax the requirement

for Loss on Heating from 0.5% to 1.0%. One of the problems with this type of specification

is that the volatiles content of different batches of asphalt meeting the same viscosity

specification will vary dramatically. For example, an article published by industry researchers7

shows that the volatiles content of two different batches of AC-20 varied from 0.053% to

0.5%, a variation of one order of magnitude. This means that the emissions of asphalt fume

would have also varied by an order of magnitude. Second, the “not to exceed” value for

volatiles content is “based on original asphalt”, i.e., before any blending. In other words, these

specifications apply to the material that is shipped from a refinery, not necessarily to material

that is shipped from a terminal to a hot mix plant. At a terminal, the terminal operator will

add various diluents for altering viscosity. The potential effect of these diluents is discussed

later in section d.

The old system of viscosity specification is being replaced by a new specification called

“Superpave”which is based on measuring the properties of hot mix under simulated service

conditions. This standard was jointly developed in concurrence with many parties including

the government. However, the newer Superpave specification increases the permissible

volatiles content to “not to exceed 1.0%”. 

Our concern is that the specification was changed by industry in order to make it easy and

feasible for the industry to meet it under widely varying production conditions; otherwise, it
6

would have remained at 0.5%. This means that the emissions from certain plants at certain

times of the year, will be quite a bit higher than what is now shown in these reports. This

increase is quantified in Table 1 later in this report. EPA’s position is that this change is not

relevant, and that anyone can use the volatility value they want in the equations presented.

EPA also believes that the average volatility content of asphalts is less than 0.5% based on

a set of samples analyzed in 1993 as a part of the SHRP program. (3.2.2) We strongly

disagree that the range of volatility values measured in the SHRP program in 1993 is the

relevant range for asphalts in use today after blending. Further, EPA arrives at conclusions

about volatility of asphalts used around the country based on the SHRP data. This

extrapolation would be correct only if equal quantities of each of the various asphalts in the

database were sold each year in the US. There is absolutely no information to support that

key assumption.

b. How is this volatile content measured now and how was it measured in the past?

The volatiles content of asphalt has traditionally been measured by the Thin Film Oven Test

(TFOT), but the industry is moving to a slightly different test, the Rolling Thin Film Oven

Test (RTFOT). We understand that a major reason for this change is because the results of

the Rolling Thin Film Oven Test are more predictable, i.e., the method produces results with

less systematic and random error. 

There are two problems with either of these tests. First, both tests measure loss in weight on

heating, which is not the same as measuring the volatiles content, particularly since some

asphalt samples will gain weight as a result a pickup of oxygen and nitrogen. Nevertheless,

because these tests are performed routinely, it is the only available data source for estimating

the volatile content of original asphalt. Second, the loss of weight number obtained from the

Thin Film Oven Test is lower than the loss of weight measured by the Rolling Thin Film Oven

Test. However, the limited data, published by PES in the Plant C test report Appendix B.8,

indicates that this difference is 0.16% at 325o

 F. (For example, if the TFOT measured loss

of weight as 0.3% and RTFOT measured the loss of weight as 0.46%, the difference would

be 0.16%). When this difference was measured at two other temperatures, it was found to

be less than 0.1%. 

Thus, EPA’s other explanation (3.2.2) that the volatiles specification was increased from

0.5% to 1% because of a change in the testing procedure from the Thin Film Oven Test to

the Rolling Thin Film Oven Test is not supported by data. The citizens don’t agree that a

change of less than 0.16% should cause a relaxation of the specification by 0.5%, a value

three times the measured change.

c. How is the volatile content affected by seasonal variations in oil refining practice?

Refinery operations change seasonally. For example, summer runs are designed to maximize

gasoline production while winter runs decrease gasoline production and maximize fuel oil

production. Seasonal variations in refining operations should affect the volatiles content of

asphalt. 
7

The citizens are concerned that no data is available on this subject. Similar concerns were

raised by the Mass Department of Public Health. Such data might provide further insight why

the specification was changed and might provide a better understanding of exposure suffered

by neighbors of such plants.

d. How is the volatile content affected by the various classes of additives that are sold

to improve the performance of asphalt?

In recent years, the industry has produced dozens of proprietary diluents and modifiers for

the purpose of blending and for improving asphalt properties. These additives fall into

different modifier families including the following: fibers, fillers, plastic/rubber, rejuvenating

oils, antistripping agents, extenders and antioxidants. A partial list includes hydrolene (Sun

Chemicals), Kraton polymers (Shell Chemicals), Elvaloy (Du Pont) and so on. The fibers and

fillers are not expected to change the volatility but all others, which interact chemically with

asphalt constituents, should alter the volatility of the asphalt, based on engineering principles.

These substances are added in significant amounts: one or several percent by weight of the

asphalt. In other words, the recommended amount of additive exceeds the percentage of the

volatile component. Not only are these additives light compounds, but they can also alter the

vapor pressure of the asphalt by increasing the volatility of some of the lighter components

which otherwise might not have volatilized in the temperature range of 275 to 375o

 F. 

The citizens are concerned that the measurement of loss of heating of the original asphalt can

bear little relation to the emissions from the asphalt that is actually used to prepare a hot mix.

EPA’s position is that this is not a significant issue. The two tests at Plant C and Plant D did

not use any additives so there is no available data.

e. Are the maximum operating temperatures recommended by industry groups actually

followed by plant operators? If not, what are the variations in temperature and what

is the consequence of these variations?

The second factor that increases asphalt fume emissions is operating temperature. As such,

emissions increase exponentially with temperature. State Highway Departments will specify

a minimum and a maximum temperature for HMA when delivered to the job site where the

pavement is being installed. In Massachusetts, this range is 275o

 to 325o F. Note that the

actual temperature of the asphalt leaving the plant and being loaded into a truck is higher.

The temperature has to be higher in order to compensate for cooling during transportation

to the job site and this issue becomes critical when delivering to a distant job site. Also, note

that there is no such restriction when delivering HMA for non-state supervised jobs. Also,

according to an engineer who was the general manager of an asphalt plant and a plant

designer internationally, who attended many of the planning meetings, many small private

contractors who drive small trucks will demand a higher temperature at loadout since a

smaller mass of HMA will cool faster. 

There are also other factors that will increase emissions. For example, when a plant switches

from one HMA mix formula to another, emissions will increase. The best example of this is
8

8. Ravi Nadkarni, Comments on EPA Reports on Asphalt Fume Measurements,

September 15, 1999.

9. “Hot Mix Asphalt Plants - Emissions Assessment Report” with Appendices A, B & C.

EPA-454/R-00-019, December 2000.

when a plant making hot mix with Recycled Asphalt Pavement (RAP) switches to a formula

without RAP. In the first instance, the plant would have operated at a higher temperature to

provide the extra heat to evaporate the water associated with RAP since the RAP is stored

in the open and not dried. When the change occurs to a formulation without RAP, the plant

loadout will emit a higher level of organics because of overheating. This is a frequent

problem at batch plants though this type of problem is not restricted to only batch plants.

(Examples of this type of excursion exist in the data collected at Plant C, a drum mix plant

where emissions increased by a factor of two to three over a 40 minute period8

.) This again

means that the episodes of high emissions caused by variations such as high temperatures are

missed by the total reliance on averages of data collected under ideal conditions, even though

the high emissions on the day of the test did affect the average.

The citizens, based on personal observations, believe that such periods of high emissions are

frequent, especially at batch plants. Further, the public health impacts of these emissions are

more significant since batch plants are more numerous than drum plants, located closer to

homes and service the small independents who are more likely to demand hotter asphalt. The

Table below, Table 1, is based on equations published by EPA relating volatiles content and

production temperature to various emissions. (Please refer to the Emissions Assessment

Report9, Table 1 on page 6 and Table 11.1-14 on page 11.1-31 in appendix A.) Table 1 on

page 9 of this report shows the differences between EPA’s numbers and ours on the basis of

assuming 1% volatile content and an operating/loadout temperature of 375o F.

It can be seen that the emissions calculated by using EPA-derived equations, particularly

emissions of noxious organic compounds, increase by more than 600% under conditions of

higher operating temperature and volatility content. Both the EPA and the Citizen numbers

would be increased by another 20 to 40% to compensate for the low bias introduced by the

“background correction” and “Method 204", discussed later in this report. Finally, it should

be noted that although the numbers in Table 1 are shown on an annual basis to help compare

them to Table 1 in the Executive Summary of the Emission Assessment Report, the citizens

are aware that actual annual emissions will be lower since a plant will not always operate with

an asphalt with a high volatiles content at high temperatures. On the other hand, the table

clearly shows the type of variation in emissions that is likely to occur under such conditions

with its effects on nearby residents.

2. Issues relating to how the data was collected and analyzed

This process of planning, data collection and analysis has involved many discussions,

agreements and disagreements. 
9

10. Ravi Nadkarni & Lloyd Fillion, Comments on EPA reports relating to AP-42 Section

11.1, August 31, 2000

The citizens are concerned that with time, EPA’s responses have become more rigid,

inconsistent and not based on data (or the lack thereof) in the reports. Only a few of the key

issues are mentioned below. Others are found in the previous comments by the citizens to

various draft reports by EPA8, 10 .

Table 1: Effect of Different Volatile Contents and Operating Temperatures on emissions

<Batch plant data> <Drum plant data>

EPAa Citizensb EPAc Citizensd

Loadout emissionse

 - Total Particulate Matter 52 257 104 515

 - Organic Particulate Matter 34 239 68 478

 - Total Organic Compounds (Method 25A) 416 2,918 832 5,836

 - Carbon Monoxide 135 947 270 1,893

Silo filling emissionsf

 - Total Particulate Matter 59 211 117 423

 - Organic Particulate Matter 25 178 51 356

 - Total Organic Compounds (Method 25A) 1,219 8,550 2,437 17,100

 - Carbon Monoxide 118 828 236 1,656

a. EPA estimates for batch plant in lb/100,000 tons of HMA. Volatility of 0.5%, 325o F.

b. Citizen estimates for batch plant in lb/100,000 tons of HMA. Volatility of 1.0%, 375o

 F.

c. EPA estimates for drum plant in lb/200,000 tons of HMA. Volatility of 0.5%, 325o

 F.

d. Citizen estimates for drum plant in lb/200,000 tons of HMA. Volatility of 1.0%, 375o

 F.

e. Loadout emissions for both batch and drum plants - See Table 11.1-14. AP-42.

f. Loadout emissions for plants with silo storage- mainly, but not exclusively, drum plants. See Table 11.1-14.

AP-42.

a. The issue of the “Background” correction

Many of the methodological problems which occurred throughout this program are

crystallized under EPA’s topic of the “background correction”. Background correction at

Plant C refers to EPA’s attempts to separately measure loadout emissions mixed with truck

exhaust and just truck exhaust in order to subtract the truck exhaust values from the former

to obtain a “pure” value for loadout emissions. But, the equipment for collecting the

emissions in the tunnel at Plant C was not 100% efficient. Under such conditions of

inefficient collection, the standard engineering practice is to use a tracer gas to measure the

collection efficiency and then correct the raw emission data for this inefficiency of capture

to arrive at a more appropriate estimate of the actual emissions. ( Whether a single average
10

collection efficiency factor should be used for adjusting all three runs or whether more timespecific collection efficiency factors should be used has been discussed extensively in previous

comments8

 by the citizens. Also, the math works out such that if the truck exhaust value is

high, the net value for the “pure” loadout emissions will be low.) 

EPA conducted such a “background” run to measure just truck emissions. However, the

data collected during the run had so many problems that EPA abandoned standard data

reduction procedures to obtain an answer that they liked. There are three problems: First, the

raw data shows a doubling in the background emissions from the first half to the second half

of the run. What caused this doubling? Second, even if one uses the background data from

the low first half of the run, the numbers are still too high. What is the cause of this result?

Third, why did EPA abandon the standard engineering procedure for correcting measured

emissions for capture efficiency? These various problems with this background run are

discussed below:

i. Inconsistent raw data: The raw data, i.e., data as recorded, and not corrected

for capture efficiency, shows two very distinct regimes in the run, with a break

in between. The first regime is flat with little fluctuation and shows an

average reading of 0.8 ppm of total hydrocarbons (THC). The second regime,

which is also relatively flat, shows a value about twice this level. The first

issue is what caused this doubling of measured emissions. EPA was unable

to provide a credible explanation. The citizens believed that this increase was

achieved by parking a second truck at the entrance to the tunnel so that the

second regime was based on measuring emissions from two trucks. In the

final RESPONSE TO COMMENTS report5

, EPA used only the first portion

of the background run, hoping to avoid this inference that the background

numbers were inflated. However, the second truck was at the entrance even

in the first portion of the run, though for shorter time periods. Thus, as shown

below, it is not clear that the lower values measured in the first regime

represent exhaust from just one truck.

ii. Is the background reading from the first half of the run low enough?: By

selecting only the data from the first half of the run and by not averaging the

two regimes, it would appear that EPA has avoided problems with data

reduction. Unfortunately, this is not the case. 

iii. Problems with data corrected for capture efficiency: Standard protocol

requires that when collection is not 100% efficient, the raw data has to be

corrected for capture efficiency. Capture efficiency is measured with a tracer

gas. Unfortunately, when correction is applied to the background data from

the first half of the background run and subtracted from the combined loadout

plus truck emissions to get “pure” loadout emissions, one gets negative values

for several hazardous air pollutants. Since this is an impossible result, EPA

decided to use the raw uncorrected background number rather than the

capture-efficiency-corrected background number. Even after adopting this

unusual procedure, some “pure” loadout emissions were still negative and

they were assumed to be zero. There is a major problem with this procedure.
11

There is no technical/ scientific justification for ignoring capture efficiency.

The only justification is that it produces numbers acceptable to EPA. The

citizens suggested that the background “correction” be eliminated and the

loadout emissions data reported as “truck plus loadout emissions”. This

suggestion was summarily rejected. We reproduce the first paragraph of

EPA’s summary rejection (3.2.2):

“The background adjustment was appropriate. There was no improper

manipulation of the data from the background test at Plant C and EPA did

not manipulate the placement of the trucks to obtain higher uncorrected

emissions for the background run. Further, we do not agree that the

background run demonstrates that data was manipulated to produce biased

results and do not believe that concurrently measured truck exhaust and

road dust emissions should be included in the emission factor for load-out

emissions.”

EPA states further that:

“The only additional instruction provided to the truck drivers during the

background test was to reduce the time of their travel from the exit of the

tunnel to the arrival at the tunnel entrance.......At about the time trucks began

driving faster to reduce gaps between trucks, the wind speed increased. This

may have caused an increase in the diesel exhaust that entered the tunnel

entrance or increased the capture of the diesel exhaust of the truck that was

inside the tunnel.” (Emphasis added.)

The problem with these explanations is that the raw data clearly shows that the reading

doubled in the second half of the run. This doubling needs to be explained. Above, EPA is

admitting that there may have been an increase in diesel exhaust entering the tunnel entrance,

i.e., exhaust from two trucks was being counted, but this possible explanation is two

paragraphs after the original denial. Also, note the statement, “Dr. Nadkarni [the citizen

observer at the Plant C tests] observed the operation of the trucks during the background

run. The issue of manipulating the placement of the trucks was not raised by him during the

test to either of the EPA personnel present.” This statement is incorrect. On the day of the

run, he left early to catch a plane and was not present when the second half of the data was

collected. Further, problems of this type are visible only after the data has been collected and

viewed. Such insights are impossible in the field. Dr. Nadkarni had objected originally to the

background “correction” because it seemed to be an unnecessary manipulation of data and

the results. In retrospect, his concerns were well founded. 

The explanations of why the background reading was not corrected for capture efficiency, in

3.3.4, are mutually contradictory. The tracers used to measure capture efficiency showed that

capture efficiency was high early in the morning and decreased as the day wore on during all

the runs at Plant C. The most reasonable explanation was that as the land around the plant

heated up, there was an on-shore breeze which blew through the tunnel and decreased the
12

capture efficiency. The capture efficiency data for the background run is consistent with this

general statement. This also means that truck emissions captured in the second half of the

background run, when corrected for capture efficiency, were three times those in the first half.

This further confuses the issue. To the citizens, these problems raise serious questions about

both the first and second half of the run. The general scientific procedure when data can’t be

explained is to reject it.

Finally, it should also be noted that the auditors from RTI were apparently not involved in a

detailed analysis of this procedure of collecting “background” data.

This background correction introduces a low-bias in the published results for load out

emissions. EPA’s estimate of this bias introduced by not correcting for capture is about 20%.

Both EPA and citizens’ numbers in Table 1 would have to be increased by this amount to

compensate for this unexplainable “background” factor. The citizens believe that the entire

procedure is faulty and should be rejected.

b. Problems with enclosures

At Plant C, because the loadout enclosure did not meet the requirements of Method 204, an

EPA protocol for constructing total enclosures for measuring pollutant emissions, a tracer gas

was used to measure the capture efficiency. At Plant D, because the specially constructed

loadout enclosure met the requirements of Method 204, it was assumed that all the emissions

would be “captured”. Method 204 gives precise design requirements which put limits on the

size of Natural Draft Openings compared to the surface area of the walls, floor and ceiling of

the enclosure with the desired ratio being less than 5%, the velocity at Natural Draft Openings

to be at least 200 ft per minute and other limitations on the distance between the opening and

the emission source. In essence, under Method 204, an induced draft fan collects the fumes

from inside the enclosure and delivers them to the instrumentation at the sampling point. By

controlling the openings (Natural Draft Openings) to a specific size, the intent is to force

outside air into the enclosure, avoiding any loss of the material being sampled. As the data

shows8, 10, complying with these requirements still does not result in proper sampling of fumes

inside this enclosure. This point is illustrated by the following situation. 

i. The loadout enclosure is empty. The instrumentation measuring hydrocarbons

is showing zero hydrocarbons since the fan is pulling in just air from the empty

enclosure. (See paragraph vi below.)

ii. A truck stops under the loadout point. Hot mix asphalt is dumped into the

truck from a silo (a single dump) or from a batch mixer (several dumps with

a waiting period in between). During this period, the air and asphalt fume in

the enclosure are pulled past the hydrocarbon measuring instrumentation by

a fan. 

iii. The truck loadout is complete, but the instrumentation continues to indicate

and record hydrocarbon emissions from the hot mix sitting in the truck

iv. The truck leaves the enclosure. One should expect the fan to evacuate all of

the fume from inside the enclosure and for the hydrocarbon reading to go to
13

zero quickly. But this does not happen. As a matter of fact, the readings

persist at a non-zero value for a long period of time showing that Method 204

does not do a good job of delivering hydrocarbons from inside the enclosure

to the measuring point. In other words, since the emissions lingering in the

enclosure are not delivered to the instrumentation for measurement, they are

not “captured”. 

v. The truck will continue to emit hydrocarbons in the yard of the manufacturing

plant. These are not captured by the sampling system attached to the

enclosure. In the report, these have been estimated as the so-called “yard

emissions”.

vi. The next truck enters the enclosure. If the enclosure was doing the proper

job, it would have shown an initial reading of zero, as mentioned above under

i. However, this is rarely the case since these emissions linger in the

enclosure.

 

Criticism of Method 204 was provided to the EPA before the Plant D tests but was ignored.

One of the problems with Method 204 was illustrated during the first day of testing at Plant

D. Method 204 requires that the inward velocity at any opening be maintained over 200 feet

per minute (fpm) so that air is flowing into the enclosure and not out of the enclosure. Note

that 200 fpm is less than 2.3 miles per hour, which is not much of a breeze. At Plant D, the

citizens observed that some of the fumes were escaping from the top or the bottom openings

in the downwind door of the tunnel because of an ambient breeze. The contractors corrected

this by decreasing the size of the openings by about half at the end of the first day of testing.

Once this was done, this upset condition did not occur again. EPA’s recollection of this event

is quite different. (3.1.2). 

In spite of these deficiencies, EPA position was: 

“As the analysis is an extrapolation of only two data runs and the enclosure was designed

to Method 204 criteria, EPA believed that the actual uncaptured emissions are most likely

smaller than estimated by our analysis. Therefore, no further adjustments were made to the

loadout emissions from Plant D.” (3.1.2)

This is a confusing argument. The citizens position is that EPA again biased the results by

this action. EPA’s estimate of this bias is of the order of 10% and this adjustment would have

to be used to adjust the EPA and citizen numbers in Table 1, but this adjustment could easily

be double this value, i.e. 20%, in our opinion.

c. EPA’s flat denial of errors in the report

In the Introductory Section of our last response10, reproduced in the current report as 1.1.1,

we commented that we were dissatisfied with the report review process because EPA released

draft reports that were not sufficiently finalized. We specifically referred to the following

problems; incorrect references, missing and incorrectly referenced appendices and numerical

and logical errors in the analysis. We were referring to the entire review process, not just the
14

11. R. Nadkarni, written communication to Chief, Emission Factor and Methodologies

Section, USEPA-RTP, November 7, 1994; R. Nadkarni, written communication to Mr. Ron

current cycle. Also, our point was that EPA should produce draft reports that are free from

error and the review process should not become a search for a needle in a haystack if a large

document is referred to without providing a page number. Further, once the responsibility for

finding each mistake is entirely passed to the reviewers who are volunteering their time for

the review, such mistakes will persist in the final report as such volunteer reviewers miss

them. In their current response to comments5

, EPA responded on page 1: 

“The comment with respect to numerical and calculational errors is unsubstantiated

in that no instances of any numerical or calculational errors were provided by the

commentors.” 

This comment is not accurate. In the previous round of comments8, such numerical and

calculational errors were shown. These included averaging data over a period when there

were no emissions because trucks were absent, and showing a wrong number as a maximum

value. These mistakes were not caught by EPA’S auditor Research Triangle Institute (RTI).

Although chances are that RTI’s contract focused on data collection procedures and did not

include an auditing of data reduction and data analysis, their role is being exaggerated in the

final report. At industry’s urging, EPA is including the following statement in the Final

Report. “For example, two scientific auditors from the Research Triangle Institute were

employed to independently audit the test and reporting process.” (1.4.38). If RTI is to be

given credit for the audit process, they should also be assigned blame for its failures. 

EPA did admit to problems with references and appendices but stated that the missing

appendices were provided on October 6 (1.1.2) or October 3 (1.4.54). They fail to mention

that this was over a month after the end of the comment period. 

At Plant D, two citizen observers noted what appeared to be errors in protocol for sampling.

Specifically, when the sampling train was rinsed to recover condensed organic matter, the

observers saw that the entire tube was not being rinsed. When this issue was mentioned,

EPA’s denial was immediate and strong, even before the citizens had explained their

observations.

Numerous logical errors and examples of bias were pointed in comment letters8, 10, To this,

EPA’s response is, “The information presented in the reports as drafted are (sic) unbiased.”

(1.2.6). An example of an “unbiased” statement, we suppose, is the following from 2.4.6:

“The lack of data to substantiate the statement is not a reason to eliminate the statement”.

d. Unfounded Leaps of Faith

In 3.7.2, while criticizing the use of model compounds by others at a time when no data on

the composition of asphalt fume was available11, EPA defends its own use of model
15

Ryan of EPA of October 26, 1995 and November 16, 1995; and R. Nadkarni, written

communication to Mr. David Mobley of July 5, 1996.

compounds when such data on composition of asphalt fume is available. Furthermore, this

data clearly shows that the two substances selected by EPA as model compounds, docosane

and tricosane, are not the major measured constituents of asphalt fume. Standard scientific

practice would be to use the best information available for this purpose. When data is

available on the major constituents of asphalt fume, EPA chose these two compounds purely

for expediency when data shows otherwise. EPA states, “The Antoine’s coefficients for

aliphatic hydrocarbons that come the closest to producing a working loss emission estimate

of 32 pounds per million gallons of asphalt throughput for this approximate molecular

weight are docosane and tricosane.” In other words, these compounds are chosen because

they give the desired result.

A similar contradiction exists in 3.7.6. Here EPA admitted that reference 360 in Appendix

B, a report of certain tests by Division of Air Quality, North Carolina Department of

Environment and Natural Resources, 1998, was not evaluated critically but then EPA ignored

the comments offered by the citizens. These comments had pointed out that the authors of

the reference had selectively ignored high readings of ambient benzene concentrations and

used only the low readings. Further, they had used questionable methodology to convert an

ambient concentration to an emission rate. Nevertheless, EPA decided to retain this defective

information in the final report stating: “The reference was not read critically................ the

results that were developed for truck load-out (in this reference) do provide limited support

for the load-out emission estimates for benzene.” In other words, EPA will continue to use

this faulty information because it, purely by accident, appears to provide limited support to

an EPA-derived number.

e. Problems with witnessing tests

The citizens were permitted to witness the actual tests at Plant C and Plant D. One individual,

Dr. Nadkarni, was allowed to be present at Plant C and up to 3 individuals, were allowed at

Plant D. While there can be justifiable concerns about visitor safety and owner liability when

visitors are allowed to wander unfettered around an operating industrial plant, the usefulness

and limitations of allowing a single witness need to be discussed.

The first issue is what a single witness can see when data is being gathered using complex

instruments or complex sampling trains in various places simultaneously. Second, when

access is also prevented under the claim of confidentiality, much information is shielded from

citizen observers and discrepancies are seen by the citizen observers only after the data has

been published in a draft report. (See references 8 and 10 for details on the questions raised

about the data.) In an industry where the manufacturing equipment is available from several

competing firms who will provide all the necessary details in order to sell this equipment, and

the product is produced to published customer specifications, our view is that there IS little

proprietary content. If plant operating procedures are proprietary, they would be of interest
16

only to another HMA manufacturer and access to these details would be obtained, as in other

industries, by hiring away a plant operator. Yet, access to information was blocked on many

occasions under the cloak of confidentiality. Following are specific incidents where there were

differences between the observations by the citizen observer and the EPA.

i. Emissions from the downwind end of the tunnel: In the discussions leading up

to the actual testing at Plant C, EPA asserted several times that they had not

observed any fugitive emissions exiting the tunnel at Plant C. However, they

agreed to use tracers to measure capture efficiency. When Dr. Nadkarni

arrived at Plant C on the day before the first test, he was surprised to see

visible emissions exiting from the tunnel. (Such emissions were seen during

each day of the test, typically later in the day when the ambient breeze became

stronger.) Several times when this phenomenon was pointed out to EPA

staff, they ascribed these emissions to a plant malfunction. Since citizens

could not take photographs but EPA could, he requested that this fume be

photographed and several times his request to document this photographically

was turned down because the fumes might not be visible in a photo. When

the draft report was published, the capture efficiency numbers corroborated

this observation that fume was escaping from the downwind side of the

tunnel, contrary to EPA assertions during planning, but there is little

photographic evidence. Yet, at Plant C, the EPA Project Director spent

almost an entire day with a videographer hired by the industry association

consulting him on what to videotape.

In case of Plant D, no tracers were employed because the specially

constructed enclosure was presumed to meet Method 204 requirements. The

shortcomings of method 204 were obvious to the citizen observers on the first

day of testing. Two citizen observers noted that the streamers at the Natural

Draft Openings on the downwind side (above and below the door) were

pointing towards the outside showing that a breeze was counteracting the

draft induced by the fan. Again, there is no photographic evidence. While

this problem was corrected for days 2 and 3 by installing plywood to reduce

the size of the openings by half, EPA claims that this observation was not

communicated to them until much later. (See 3.1.2) Similarly, the citizens

observed that the fume lingered for a long time inside the enclosure at Plant

D and was not transferred to the measurement point, as was discussed earlier

in Section 1.b. Again, the citizens could not document this because of the

restriction against photography.

ii. Lack of information sharing and access to instrumentation: At Plant C, the

control room was cleared of all observers several times. Therefore it was not

possible to take actual readings to double check the readings taken by EPA

contractors. (This is not to cast any aspersions on the contractors who took

these readings. Our point is that it was not possible to double check these

readings). EPA had information on the volatile content of asphalt prior to and
17

during testing at both plants. This information was not shared until much

later. 

iii. Prejudging of final outcome: On the day before the start of testing at Plant C,

the industry hosted a dinner attended by the senior EPA staff member and the

citizen observer. The citizen observer was quite surprised when the industry

was told by the EPA staff member that EPA had no intention of regulating

fugitive emissions from their industry. 

Conclusion

Citizens, industry and EPA-RTP have undergone a lengthy process during the last six years to

examine fugitive emissions from asphalt plants. This process suggests that there are lessons to be

learned regarding a number of aspects of this exercise. 

1. An epidemiological study should be undertaken by the government to better understand the

quantity and intensity of health problems caused by exposure to asphalt fume. In our very

limited casual interaction with individuals across the country, we have had too many

anecdotal histories come to our attention to ignore this public health problem. These histories

include the deaths of otherwise healthy farm animals barned within several hundred yards of

an asphalt plant in the northeast section of the country, rashes and difficulty breathing by

humans all across the country, each living in close proximity to one of these facilities, and

cancer clusters in proximity to asphalt storage tanks at terminals. It is hard to believe that

each of these instances is due solely to uncaring plant operators lacking concern for the

impact of their business on the surrounding neighborhood. Even if the cause is determined to

be hypersensitivity by individuals to certain chemicals, this is an issue that should not be faced

by each individual citizen as his or her "problem" but rather is a responsibility for society as

a whole, as well as for the industry. 

2. A number of the EPA's regional offices have extensive experience in working through

environmental concerns in concert with citizens rather than in opposition to the public. Some

of the citizens who are working with this problem of asphalt fume have heretofore had

productive relations with their regional offices of EPA on other industrial concerns. It may

be that EPA-RTP has not had reason to develop protocols for interaction with the public,

possibly because more of its business is conducted with industrial representatives.

Nevertheless, it may be appropriate that EPA-RTP review its approach to citizens to find

ways of encouraging that dialogue with an emphasis on cooperation and mutual respect. It

is important that the public understands that it IS no less a partner with government at every

level than is industry. 

3. Industry and state environmental departments place great reliance on AP-42 emissions factors

during the process of local permitting. However, AP-42 contains averaged data collected

under the best of circumstances and is a poor source to determine “worst case” environmental

impact scenarios. Many of the factors representing these worst cases are not as clearly

represented in that document as it could be. To avoid misuse, simple changes in the layout
18

could be accomplished such that where appropriate, the limitations of factors are made more

evident, without recourse to the introductory language of this lengthy government

publication. Even a standard "warning" or notice attached to each table could begin to

highlight this complexity. 

4. Industrial proprietary information varies from industry to industry. While some industries’

competition may involve truly cutting edge technology, methodology and technique, other

industries’ competition is based on non-technical non-proprietary factors such as location and

market power. Restrictions on oversight by the public during EPA financed tests as were

conducted may be appropriate in one instance, and in other instances may more reflect an

attempt by industry to hinder open and frank discourse. We believe that Government should

aggressively challenge, where appropriate, unsubstantiated demands for secrecy by industry

which ultimately reflect negatively on both that industry and on the government.

5. Henry Nowick, Nowick Environmental Associates, Springfield MA
Gary Fore, Vice President

Environment and Safety

National Asphalt Pavement Association

Lanham, MD
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NAPA

NATIONAL ASPHALT PAVEMENT ASSOCIATION

NAPA Building l 5100 Forbes Boulevard . Lanham, Maryland, USA 20706-4413

Toll Free: l-888-468-6499 9 Tel: 301-731-4748 . Fax: 301-731-4621

Mike Acott, President

February 1,200 1

Mr. Bob McConnell

EPA Region’1

1 Congress Street/CAQ 1

Suite 1000

Boston, MA 02114

Reference: Draft Hot Mix Asphalt Plants - Emission Assessment Report; AP-42

Section 11.1; Emission Factor Documentation for AP-42 Section 11.1

Dear Mr. McConnell;

In 1996, the National Asphalt Pavement Association began working with government and

citizen groups to determine the amount of emissions that are emitted during silo and truck

load-out operations. In order to develop emission factors for the HMA industry, more

than 390 emission test reports and other types of documentation were compiled and

reviewed. The question of truck load-out and silo emissions has been answered. As a

result, the Hot Mix Asphalt industry is now one of the most thoroughly studied industries

in the United States. During testing, quality assurance scientists from Research Triangle

Park, North Carolina were deployed on-site to independently audit the testing program

and procedures. We have every reason to believe that the test data are representative of

average emissions from HMA facilities.

This test data has proven conclusively that emissions from asphalt plants are low, well

controlled and not “major sources” of emissions. The evidence is quite extensive, the

industry and states need the data, and it is now time to bring finality to the process of

testing.

We appreciate the diligence put forth in successfully completing a project of this

magnitude.

Sincerely,

R. Gar

Vice P:

Environment, Heann &

,’

email: napa@ hotmix.org www.hotmix.org
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Chapter 4

Hot Mix Asphalt Plants

Response to Comment on

Draft Emissions Assessment Report,

AP-42 Section and AP-42 Background Report

Released December 2000
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RESPONSE TO COMMENT ON DRAFT EMISSIONS ASSESSMENT

REPORT, AP-42 SECTION AND AP-42 BACKGROUND REPORT

(Released December 20, 2000 and to be published in the Stakeholder Opinions Report)

This response to comments was prepared by:

Source Monitoring and Technology Group

Emissions Monitoring and Analysis Division

Office of Air Quality Planning and Standards

United States Environmental Protection Agency

Research Triangle Park, NC

December 2000
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i

Contents

1.0 Process, Report Organization, Presentation and Bias ............................... 1

1.1 Process ............................................................... 1

1.2 Organization .......................................................... 3

1.3 Perspective ............................................................ 6

1.4 Presentation ........................................................... 7

1.5 Reference Citations .................................................... 25

2.0 Industry Characterization and Structure ........................................ 28

2.1 Capacity and Production Levels .......................................... 28

2.2 Type of Fuels Used by Typical Production Facility ........................... 36

2.3 Process Descriptions ................................................... 39

2.4 Plant Characteristics ................................................... 40

3.0 Development and Evaluation of Available and Derived Information ................. 43

3.1 Deficiencies in EPA Method 204 ......................................... 43

3.2 Compensation for Asphalt Temperature and Volatility ........................ 54

3.3 Adjustment for Background Truck Operation Emissions ....................... 63

3.4 Assignment of Quality Ratings ........................................... 71

3.5 Emission Factor Development Methods .................................... 76

3.6 Characterization of Emissions ........................................... 103

3.7 Evaluation of Unused Information ....................................... 114
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1

1.0 Process, Report Organization, Presentation and Bias

1.1 Process

1.1.1 CAAP Process Comment Number 1 (Ravi Nadkarni & Lloyd Fillion) - 

Commentors Introduction, Section A

Before discussing the results of our review, we want to comment on the review process

and our general dissatisfaction with it. When complex, technical documents are sent to a

wide audience for review, one assumes that both the EPA and their contractors did their

best to produce as final a draft as possible. One would not only expect that most of the

typos and numerical errors have been found and eliminated but that the authors wrote the

report in a way that makes it easy for the reviewer to go back to the primary references

and original sources (assuming that they are available) to check a particular point. On

both these counts, the reports, just like the previous set of reports reviewed last year, fail

resoundingly. Many key comments are not referenced at all; in some cases, the references

are incorrect; in other cases, the reference is made to a large document without giving a

page number, making it difficult and time-consuming to check. Appendix B refers to its

Appendix B and Appendix C on page 4-137. But these appendices, which presumably

contain the statistical results and the data sets, are not provided, making it impossible to

even spot check the analysis. This, combined with the severe time constraints, makes it

impossible to review the reports in any but a cursory fashion, using random spot checks,

to make sure that the numbers are correct. Unfortunately, the reports also fail on that

count since numerical or logical errors in the analysis have been found.

1.1.2 Response to CAAP Process Comment Number 1 - The commentors have identified a

few areas where the report could benefit by more specificity in the wording of the

statements. However, EPA believes that these reports present this large amount of highly

technical information in a clear and organized fashion. Most respondents did not

comment on the reports structure which appears to indicate most reviewers could

understand the reports as drafted. The comment with respect to numerical or

calculational errors is unsubstantiated in that no instances of any numerical or

calculational errors were provided by the commentors. The primary references for this

report are the almost 350 emission test reports used to develop the emission factors for

the source category. All of the key comments in the report refer to the information

contained within these test reports or were derived from compiled information contained

in these test reports. While some ancillary information contained in the report was not

referenced in the draft report, additional reference citations supporting this information

were added to the final report. While we do not believe it is necessary to cite individual

references in the main report, each of the test reports are cited in Appendix A and B. To

assist the reader, in the main report we have included the location in Appendix A, B or C

where more detailed reference citations are available. These test reports (which were

summarized in Chapter 4 of Appendix B) are generally over 50 pages in length and some

may be over one thousand pages (like the Plant C test report). EPA obtained most

non-EPA test reports from State or local air pollution control agency files. Typically,

copies of these reports are not routinely provided to reviewers. However, specific source
2

test reports can be provided upon request. While the detailed results of the statistical

analysis were inadvertently excluded from the report, the data were presented in the tables

in chapter 4 and the methodology and conclusion was presented in that chapter as well. 

The detailed results of the statistical analysis were provided to all of the commentors on

October 6, 2000 and are included in the final report.

1.1.3 CAAP Process Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Commentors Introduction, Section A

 We also need to air another complaint regarding the process. For about 6 weeks before

the report was finally issued, we received phone calls informing us that the release of the

reports was imminent. While we appreciate receiving this advance warning, it also turns

out that the actual release of the reports was much later than announced. One of us (Ravi

Nadkarni) had cancelled attendance at the Annual Meeting of IPMI in mid-June in

response to these calls. Because of weddings in the family, Ravi was going to be

unavailable after July 17 and wanted to start the review process as soon as possible, hence

the cancellation. Unfortunately, the reports were received only on June 28. This means

that he missed an important Annual Meeting where he is on the Board of Directors. We

appreciate getting the extra time until the end of August to complete this review. 

Appendix C was prepared in 1996. Why was this 69-page document not provided earlier

so that it could have been reviewed before this “crunch” period? Also, are comments on

such a document, which has undergone a “final” review, relevant at this stage? Finally,

why was this document not released to us when the citizen groups and the EPA were

discussing sampling issues, when that document might have provided an additional

viewpoint? For all these reasons, this third document has not been reviewed.

1.1.4 Response to CAAP Process Comment Number 2 - EPA reasonably accommodated

reviewers by providing additional time and flexibility for the review of the Emissions

Assessment Report. While the report was release later than originally anticipated, EPA

provided notice of this delay and extended the review period for the report to provide

flexibility to the reviewers schedules. Additionally, most of the information in the draft

report had been available for over two years on the Emissions Factors and Inventory web

site and both of the commentors had previously commented on at least two items in this

earlier draft report. EPA postponed completing this 1998 draft AP-42 Section and

background report pending completion of the load-out emissions testing. Almost all of

the stack test data and analyses in the current draft were also contained in the previous

draft. The information added since 1998 concerned the development of factors for the

silo filling, load-out and yard emissions based largely on tests conducted at the request of

the commentors and other stakeholders with similar interests. The data and EPA analyses

for this information were clearly available to all of the stakeholders and were identified in

the EPA report Response to Comments on Testing for Asphalt Plants C and D. There

was a limited amount of information that was not available to the stakeholders until we

circulated the draft. This information included the approximately thirty emission test

reports submitted by the State of Wisconsin in response to the circulation of the first draft

of the AP-42 Section and background report for Hot Mix Asphalt Plants. In addition, the
3

36 page main body of the Emissions Assessment Report was also new to reviewers. The

review time provided was more than adequate to review information not previously made

available for review.

With regard to Appendix C, the purpose of this appendix was to provide background

information to reviewers on how the revised emission factors could be used with

available techniques for preparing an emission inventory for hot mix asphalt plants. This

type of information is not presented in AP-42 sections nor in the background reports for

the AP-42 sections. As stated in the introduction to the EIIP document (Appendix C),

“The purposes of the preferred methods guidelines are to describe emission estimation

techniques for stationary point sources in a clear and unambiguous manner and to provide

concise example calculations to aid in the preparation of emission inventories. While

emissions estimates are not provided, this information may be used to select an emission

estimation technique best suited to a particular application.” It should be noted that the

primary audience for the EIIP reports are engineers and environmental scientists that are

assembling local or regional emissions inventories. Information on the availability of the

draft of this EIIP document was provided in a letter from Ronald B. Ryan of EPA to Dr.

Ravinda Nadkarni (with copy to Lloyd Fillion) dated September 5, 1995. The letter

clearly states that the purpose of the EIIP document is to explain how to inventory

emissions from hot mix plants. The letter further stated that additional information on

fugitive emissions from truck loading was not included in the document. The draft

document was available for comments on the EPA web from October 1995 to about

March of 1996. The commentors did not request a paper copy of the draft EIIP document

and did not provide any comment on this document at that time. As with most emission

factor and inventory documents, the documents are revised from time to time. All of the

commentors were advised that Appendix C was a final report in EPA’s June 2000 cover

letter transmitting the Emissions Assessment Report. Additionally, this cover letter stated

“Comments on Appendix C of the EA Report will be forwarded to the EIIP Point Source

Committee for their consideration in future revisions.”

1.2 Organization

1.2.1 CAAP Organizational Comment Number 1 (Ravi Nadkarni & Lloyd Fillion) -

Commentors General Comments, Section B

AP-42 is essentially a “cookbook” for engineers/contractors who need to produce

emissions estimates for local regulatory authorities to obtain permits to construct and

operate plants. In view of this, the overall organization of the three reports does not make

sense. In the long run, Appendix A will be used most often for estimating emissions. 

When necessary, the background information in Appendix B will be reviewed. The

“main” report will remain either as a political document used by lobbyists or fade away. 

As it now stands, the “main” volume repeats in a vague and biased way, the information

in first two appendices. The same information is presented in a marginally better format

and with slightly less “spin” in Appendix A. If the main document is supposed to be an

Executive Summary to Appendix B, it is a poor summary and reads more like a political

tract. This is particularly true since only emissions data on plants using natural gas is
4

given in the main report; i.e. there is a deliberate attempt to show only the lowest

emissions. Most of the caveats associated with the summary information in the main

report are well concealed in Appendix B. If EPA is serious about making the main

document useful, it should use the main document to calculate the total emissions to the

environment from a batch and a drum asphalt plant. This type of rewrite, where other

emissions (for example from materials handling and storage piles, storage tanks, from

traffic and truck exhaust, and so on) are also calculated and shown for typical plants, will

result in a guidebook for industry contractors and help them by demonstrating how such

calculations should be made. (In Massachusetts, specific plants will employ a wide range

of pollution control technology and then argue that it is “state of the art” and is BACT

(Best Available Control Technology)). Other emissions are currently only listed and

cross-referenced in Section 2.3 on page 16. These include emissions from storage tanks

(AP-42 Chapter 7), materials handling and storage piles (AP-42 Sections11.19.2

and13.2.4), vehicular traffic (AP-42 Sections 13.2.1 and13.2.2) and emissions from

trucks bringing in the raw materials and taking away the hot mix asphalt (AP-42 Volume

II).

1.2.2 Response to CAAP Organizational Comment Number 1 - The organization of the

three reports was designed to meet the needs of a diverse audience. The “main” report

presents a summary of the detailed technical information presented in Appendices and

provides emission estimates for a typical facility. Because of limiting the volume of

technical information, information representing HMA plants using fuel oil (an estimated

10 to 30% of the fuel used by the industry) were omitted from the “main” report. The

presentation of technically factual information representing the two different production

methods of average size, using fuel used by between 70 and 90% of the industry, is most

representative of nationwide emissions from hot mix asphalt plants. While it is

recognized that the use of fuel oil results in higher emissions of some pollutants, fuel oil

is seldom used when natural gas is available and is primarily used as a backup fuel. 

However, it is recognized that the “main” report should include information that fuel oil

is used to produce approximately 10 to 30% of the HMA, that the use of fuel oil creates

higher emissions. The main body of the report will include a revised summary of

emissions for both oil fired and gas fired facilities.

As stated above, the purpose of the “main” report is to provide a summary of more

technical information. It is agreed that the “main” report may benefit by the addition of

fugitive emissions calculated from emission factors contained in other AP-42 sections. 

These emissions include diesel exhaust, dust from truck traffic and dust from raw

aggregate handling. The main body of the report is not a stand alone guidebook for

contractors. Industry contractors and State agency permit and inventory specialists will

use AP-42, the EIIP document (included as Appendix C) and other supplementary

information to make the required calculations.
5

1.2.3 CAAP Organizational Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Commentors General Comments, Section B

Finally, it is unclear whether this “main” report has a number or whether

EPA-454/R-00-0XX is the final designation. The reason for asking this is because

reference 1 of Appendix A has the same name and a designation of EPA-454/R-00-019,

but this reference is dated May 2000. What is going on?

Commentors Summary Comments, Section C

Confusing Report Designations: The designation of the reports is confused. The main

report is called EPA-454/R-00-0XX. But Reference 1 of Appendix A has the same name

and a designation of EPA-454/R-00-019, and this reference is dated May 2000 while the

main report is dated June 2000.

1.2.4 Response to CAAP Organizational Comment Number 2 - The EPA report number

was requested for this report in advance so that all of the reports associated with the Hot

Mix Asphalt projects would be numbered consecutively. The EPA report number on the

title page of the report was changed to XX to avoid the draft report being considered a

published EPA report. The actual date of publication of the report was used for the final

report. The use of this report as the citation for the first reference in Appendix A is

circuitous. Appendix A and Appendix B are being made available as separate

independent reports through the various mechanisms used to distribute the AP-42

sections and their associated background reports. As a result, a more proper citation

reflecting the Appendix B material was used.

1.2.5 CAAP Organizational Comment Number 3 (Ravi Nadkarni & Lloyd Fillion) -

Commentors Summary Comments, Section C

Sloppy Report Preparation: The reports are full of minor errors, are poorly organized,

repeat the same paragraphs in different documents, and have incorrect references. Many

key comments are not referenced at all; in some cases, the references are incorrect; in

other cases, the reference is made to a large document without giving a page number,

making it difficult and time-consuming to check. The data sets used for statistical

analysis are not provided, making it impossible to even spot check the analysis. All

indications are that there was no complete internal review of the report within EPA before

releasing it.

Commentors Summary Comments, Section C

Poor Organization: The overall organization of the three reports does not make sense. In

the long run, Appendix A will be used most often for estimating emissions. When

necessary, the background information in Appendix B will be reviewed. The “main”

report will remain either as a political document used by lobbyists or fade away. The

main report shows the industry’s emissions in the best possible light with most of the

caveats associated with information being well concealed in Appendix B. If EPA is

serious about making the main document useful, it should use the main document to

calculate the total emissions to the environment from a batch and a drum asphalt plant,

rather than show the information from AP-42 with the decimal point moved to the right.
6

1.2.6 Response to CAAP Organizational Comment Number 3 - These reports present the

large amount of highly technical information in a clear and organized fashion, and

therefore it is reasonable to encounter some minor editorial errors in the final report

review. While the document benefitted by some editorial corrections, the reports

contained few errors and these errors were not substantive.

The organization of the three reports was designed to meet the needs of a diverse

audience. In order to meet these needs, some information was repeated in all four parts of

the report. As explained elsewhere, all three Appendices are available separately. 

Therefore, some background information is repeated so users do not have to obtain all

three Appendices to understand any one Appendix. While future uses of the “main”

report will be modest compared to Appendix A and B, it is unlikely to be used to support

any air emissions permit for any new or existing facility. The information presented in

the reports as drafted are unbiased. 

1.2.7 CAAP Organizational Comment Number 4 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

1. Page 1-1, final paragraph: The organization of the entire report is confusing. The last

line refers to Section 5, which is the same as Appendix A. Which is the main report

and which are the subsidiary appendices?

1.2.8 Response to CAAP Organizational Comment Number 4 - As stated previously, the

report is organized such that each part of the report can stand by itself. The main body of

the report provides summary information from the three Appendices. Appendix A is the

AP-42 section for Hot Mix asphalt which is generally written for use by air pollution

professionals. Appendix B is the background information for the AP-42 section and is

typically used by researchers and the few air pollution professionals looking for more

detailed information than is presented in the AP-42 section. Appendix C is an existing

document describing emission inventory methodologies applicable to Hot Mix Asphalt

Plants and was published for air pollution professionals specializing in emission

inventories and air quality management.

As each of the Appendices is intended to be stand alone reports, the last line was revised

to “The final AP-42 Section 11.1, Hot Mix Asphalt Production is presented elsewhere.”

1.3 Perspective

1.3.1 CAAP Comment on Report Perspective (Ravi Nadkarni & Lloyd Fillion) -

Commentors General Comments, Section B

The main report is a political document for the following reasons. The EPA’s

pro-industry bias shows on almost each page. Every attempt is made to minimize

emissions, for example, by calculating emissions for plants burning natural gas only in

the “main” report. The report also provides qualitative comments to indicate that

emissions could be even lower in many cases; for example, “counterflow drum mix plants
7

will likely have lower organic compound emissions than parallel flow drum plants”, page

11.1-9. Such comments are not substantiated in the detailed information provided in

Appendix B. Yet, caveats regarding conditions under which the emissions might be

higher are few and far between. This tilting is not surprising given the proindustry bias

expressed many times by the Project Officer during the course of testing.

Commentors Summary Comments, Section C

Pro-industry Bias: The EPA’s pro-industry bias shows on almost each page. Every

attempt is made to minimize emissions shown. The report also provides qualitative

comments to indicate that emissions could be even lower in many cases. We don’t see

why EPA makes such statements in the absence of data. Yet, caveats regarding conditions

under which the emissions might be higher are few and far between.

1.3.2 Response to CAAP Comment on Report Perspective - The EPA has conducted a fair

and balanced process to consider stakeholder’s opinions during the development of

emissions information for hot mix asphalt industry. Consistently, EPA has

accommodated CAAP concerns at additional cost and delay in completing EPA’s

evaluation of hot mix asphalt plant emissions. In response to these latest comments, EPA

has made additional changes to the Emissions Assessment Report. As stated elsewhere,

the report was revised to suggest that the natural gas is used to manufacture HMA at

approximately 70 and 90% of the HMA facilities in the US. Where appropriate, the

report includes separate emission factors for oil-fired and gas-fired HMA plants. 

The commentor quotes a statement in a part of the report that describes general process

information. There are no statements in the “main” report or Appendix A which would

provide support for using a lower emission factor in the report. It is not clear how the

reporting of technically accurate information based on known engineering principles to

generally characterize “typical” facilities of each, major production process, fired with the

most commonly used fuel to fire most of the HMA plants in the U.S., shows a bias.

1.4 Presentation

1.4.1 Industry Presentation Comment Number 1 (Steve Zemba, Cambridge

Environmental) -

General: A list of acronyms at the front of the document might e helpful to readers.

1.4.2 Response to Industry Presentation Comment Number 1 - A list of acronyms was

added to the front of the document.

1.4.3 Industry Presentation Comment Number 2 -(Steve Zemba, Cambridge

Environmental) -

Hot Mix Asphalt Plants Emissions Assessment Report

The last sentence third pgh. of pg 1 contains a typo: the 100,000 tons of production

corresponds to a batch plant, not a drum plant.
8

1.4.4 Response to Industry Presentation Comment Number 2 - The word drum was

changed to batch in this sentence.

1.4.5 Industry Presentation Comment Number 3 - (Steve Zemba, Cambridge

Environmental) -

Hot Mix Asphalt Plants Emissions Assessment Report

1

st pgh. of p. 10: Does the emission assessment report provide stack emission rates for a

typical counterflow or parallel flow drum plant? If the estimates are for a parallel flow

plant, it might make sense to mention in the text the approximate difference expected for

emissions from a counterflow plant (e.g.. this could be mentioned in a footnote to

Table 2).

1.4.6 Response to Industry Presentation Comment Number 3 - The emissions estimates

provided in Table 2 are appropriate for both parallel flow and counter flow drum plants. 

While the statements in the AP-42 section and background reports concerning potential

differences in organic emissions between these two dryer designs are based on valid

engineering criteria, sufficient information is not available to quantify these differences. 

As a result, data from both types of facilities were combined to determine the volatile

organic and organic particulate emission factors.

1.4.7 Industry Presentation Comment Number 4 - (Steve Zemba, Cambridge

Environmental) -

Hot Mix Asphalt Plants Emissions Assessment Report

p. 3: EPA might want to provide the regulatory definition or a better explanation of

criteria pollutants and HAPs.

1.4.8 Response to Industry Presentation Comment Number 4 - A brief regulatory

definition of criteria pollutants and HAPs was included in the Glossary which be added to

the document.

1.4.9. Industry Presentation Comment Number 5 - (Steve Zemba, Cambridge

Environmental) -

Hot Mix Asphalt Plants Emissions Assessment Report

p. 2, 3rd pgh: Might want to mention the number of tests (> 300) that survived the

screening process (i.e., were usable for the development of emission factors).

1.4.10 Response to Industry Presentation Comment Number 5 - We agree that more

detailed information on the number of tests that were used to develop the resulting

emissions factors is needed in this paragraph. In addition to stating that over 300 tests

cleared the initial screening process, general information on the number of tests that

support broad classes of pollutants was provided. Also, the reader was referred to

Appendix A and B for more specific information on the number of supporting tests and

quality ratings of individual pollutants. The paragraph was revised as follows: “To

develop emission factors for the HMA industry, data from about 370 emission test reports

and other documents on the industry were compiled and reviewed. Through a careful
9

screening process, about fifty of the reports were determined to be unusable for emission

factor development and were excluded from further evaluation. About 310 reports

remained and were compiled by plant type, emission source, pollutant, and emission

control. For each emission test, emission factors were calculated by dividing the

measured emission rates by the HMA production rate measured at the time of the

emission test. These emission factors were then grouped by source, pollutant, and control

device, and an average emission factor was calculated for each group. While particulate,

CO2, CO and TOC emission factors are based upon over one hundred tests, most of the

remaining criteria pollutant emission factors are based on between five and ten tests. A

few HAP emission factors are based upon more than five tests, although the majority are

based upon between two and five tests. Information on the supporting data for specific

emission factors and the quality rating assigned to the emission factor is included in the

emission factor tables in Appendix A and B. Generally, the number of supporting data

are typical of many AP-42 sections. However, the number of data supporting particulate,

CO2, CO and TOC emission factors is greater than most AP-42 sections.”

1.4.11 Industry Presentation Comment Number 6 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 4: A. Add in (source classification code in parentheses) under Figure 1 Typical

Page 5: A. Add in (source classification code in parentheses) under Figure 2 

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-3: A. Add in (source classification code in parentheses) under Figure 11.1-1

General ...

Page 11.1-4: A. Add to Figure 11.1-2. General process flow diagram for parallel-flow

drum mix asphalt plants. 

B. Add in (source classification code in parentheses) under Figure 11.1-2 General ...

Page 11.1-6: A. Add in (source classification code in parentheses) under Figure 11.1-3

General ...

1.4.12 Response to Industry Presentation Comment Number 6 - The titles of the figures

were revised to include that the source classification codes are in parentheses within the

figures and that Figure 11.1-2 is a parallel-flow drum mix plant..

1.4.13 Industry Presentation Comment 7 - (Gary Fore, Vice President National Asphalt

Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 2: A. Paragraph 1, second line -please add the following: ...and PM-2.5 and very

small amounts of hazardous air pollutant. .. 
10

C. Second sentence - please add the following: ...VOC and very small amounts of

volatile HAP organic compounds.

Page 10: B. 4th paragraph - Please correct as follows: ... CO; and very small amounts of

organic compounds ...

Page 11: A. 1st paragraph - Please add the following: ... organic aerosol may contain

very small amounts ...

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-7: A. In the fourth line, second paragraph under 11.1.2.1 - Batch Mix plants,

please add the word very before the word small. The sentence will then read “and very

small amounts of organic compounds”

Page 11.1-8: B. In the second line from the top of page - please add the word very before

the word small. The sentence will then read “may contain very small amounts of HAP”

Page 11.1-9: A. I n the first paragraph under section 11.1.2.3 - please add the word very

before the word small. The sentence will then read “and very small amounts of organic

compounds of various species” 

1.4.14 Response to Industry Presentation Comment Number 7 - The additional modifier

“very” would not add any substantial information to the sentences and may be

misinterpreted to be a relative indication that the emissions of these compounds or the

relative proportion of these compounds from HMA plants are less than other similar type

sources.

1.4.15 Industry Presentation Comment Number 8 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-10: A. 2nd paragraph -Suggest a more typical loss-on-heating of 0.25 not 0.41 

a. To estimate total PM emissions from drum mix plant load-out operations using an

asphalt loss-on-heating of 0.25 percent and temperature of 290°F, HMA mix, the

following calculation is made: 

EF = 0.000181 + 0.00067 (-v)e((0.0251) (290 + 460) -20.43)

0.000181 + 0.00067 (-(0.25))e((0.0251)(290 + 460) -20.43)

0.000181 + 0.00067(0.25)e(-1.605)

0.000181 + 0.00067(0.25)(0.2009)

0.000181 + 0.0000485

0.000215 Ib/ton of asphalt loaded 
11

NOTE: The correlation factor in the equation should be 0.00067 and not 0.00059. 

This loss-on-heating value is a value that is seen on a daily basis within the Industry.

1.4.16 Response to Industry Presentation Comment Number 8 - As indicated in the

sentence preceding the equations, this is an example to show the user how to calculate the

emissions with the various equations presented in Table 11.1-14. A temperature and a

loss-on-heating value was selected for this equation that would not be confused with the

recommended default values in the footnote to Table 11.1-14. We agree that the

constant for the MCEM portion of the equation should have been 0.00067. However,

based upon other comments, the batch and drum mix equations were combined into one

equation. As a result, the revised constant value of 0.00141 was used in the example

equation.

1.4.17 Industry Presentation Comment Number 9 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-17 : A. In the title for Table 11.1-6, please delete the word formaldehyde from

title 

1.4.18 Response to Industry Presentation Comment Number 9 - The word formaldehyde

was deleted since it is not included in the table.

1.4.19 Industry Presentation Comment Number 10 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

General comment - Tables tend to be confusing. For example, Place HAPs contiguously

with HAPS and follow with Non-HAPs together. Also, suggest adding a set of batch table

and drum tables with contiguous HAPs listing, non- HAPs listing and metals HAPs vs.

non-metal HAPs listing.

General comment - Suggest following the same table order as found in the Emissions

Assessment Report. Much less confusing.

Page 11.1-20 : 

A. Sub title: Hazardous air pollutants under Pollutant Heading - For easier reader

understanding, please change subtitle from Hazardous air pollutants to non PAH/HAPs 

B. Please add a line totaling the non-PAHs hazardous air pollutants section. Currently

very confusing. 

C. Sub title PAHs - Please change from PAHs to PAH/HAPs 

D. Please add row and sum the NO.6 fuel "organic HAPs" 
12

E. Please change non-HAP subtitle to Non Organic HAPs 

F. Sub title: Hazardous air pollutants -Please change to PAH/HAPs

G. Left side column under Dryer with fabric filter - Please add natural gas, propane,

fuel oil, or waste oil fired. Confusing as is and fails to distinguish between these fuels

and No.6 fuel oil.

G. Footnote b -Please change as follows: Natural gas, propane, fuel oil, or waste oil fired

dryer. For pollutants that are marked with a “*”, separate emission factors are presented

for No. 6 fuel oil fired dryers. Substitute these factors for above factors when burning

No.6 oil. 

Page 11.1-21,22,23: A. Use the same format and comments as suggested for above Table

11.1-9 

Page 11.1-22 and 23: A. Please add Dioxins and Furans to above referenced Organics

and HAPs 

Page 11.1-24:B. Footnote b - Please change as follows: Natural gas, propane, fuel oil, or

waste oil fired dryer. For pollutants that are marked with a “*”, separate emission factors

are presented for No. 6 fuel oil fired dryers. Substitute these factors for above factors

when burning No.6 oil.

Page 11.1-27: 

A. Overall comment - Should create subtitles for Metal HAPs category and a Metal NonHAPs categories. Also suggest moving to 11.1-9. 

B. Adjust footnotes accordingly. 

Page 11.1-28: 

B. Use the same format and comments as suggested for above Table 11.1-9. Should be

the same for both drum and batch. 

C. Please delete Footnote b. unnecessary.

D. To make the table easier to read, suggest switch last two sections of the table. The

section pertaining to lead and mercury should come last. 

Page 11.1-30: 

A. Place PAH/Organic PM (%) up above PAHs line in the left column. It should be a

title, not a part of the data. 

B. Change Subtitle from PAHs to PAH/HAPs 
13

C. Total PAHs, subtitle -Change to total PAH/HAPs

Page 11.1-31: 

A. Move subtitle -Compound TOC (%) up to be included in the titles for the columns. 

B. Create Sub title - non-VOC/non-HAP’s

C. Please a Percent sign (%) to every EF as in table 11.1-15. It is currently very confusing

because the other tables in this document do not contain percents.

D. Total- add line total volatile organic HAPs 

E. Please add to the example on page 11.1-10. It would be helpful to illustrate the use of

Table 11.1-16. 

1.4.20 Response to Industry Presentation Comment Number 10 - The reorganization of

the emission factors tables for organic and metal HAPs address most of the issues

identified by the commentor. Although the revised presentation causes repetition of most

of the compound or element specific emission factors, this presentation makes this

information less confusing. Within source category types, the compounds were

segregated into broad classifications (non-HAP organic compounds, PAH HAP,

non-PAH HAP, Dioxin and Furan) and the sums of these classifications were provided. 

These three changes should make it easier for the reader to use this information. The

following suggested revisions of specific details in the tables were also accommodated. 

Specific comment for page 11.1-27 (A & B) - Rather than creating HAP and non-HAP

categories of metals in this table, a separate footnote was created. To more clearly alert

the reader of the HAP classification of the element, the footnote letter now follows the

metal name in the pollutant column. Specific comment for page 11.1-30 (A, B & C) - 

The title was moved to the top of the column as a single heading for the load-out and yard

column and the silo filling column. Also, the subtitles in the Pollutant column for PAH

and Total PAH’s were changed to PAH HAPs and Total PAH HAPs. Specific comment

for page 11.1-31 (A) - The subtitle was moved to the top of the column as a single

heading for the load-out and yard column and the silo filling column. Specific comment

for page 11.1-31 (B) - The speciation profile for VOC was moved to the top of the

column and a subtitle non-VOC/non-HAP was added between VOC and the other

compounds. Specific comment for page 11.1-31 © - Percent signs were added to the

values for each speciation profile percentage. Specific comment for page 11.1-31 (D) - A

row was added to the bottom of the table to present Total Volatile Organic HAPs. 

Specific comment for page 11.1-31 (E) - An example to illustrate the use of speciation

information in Tables 11.1.15 and 11.1.16 was added to page 11.1-10 between the

paragraph describing the speciation profiles and the paragraph describing methods to

estimate emissions from asphalt storage tanks.
14

1.4.21 Industry Presentation Comment Number 11 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-29: A. Question[ing] why [the table] include[s] total PM when it includes

organic PM? This is very confusing. 

1.4.22 Response to Industry Presentation Comment Number 11 - Total PM does include

organic PM. Organic PM is included as one of the known components of fine particulate

matter as this information may be needed in air quality management analysis for PM fine. 

The speciation of the total PM (also PM-2.5) into the organic and inorganic components

provides some information that will be needed to help prepare regional control strategies. 

EPA has established a network of air samplers that determine the constituents of fine

particulate matter. The important major constituents include sulfates, nitrates,

ammonium, organic carbon (a.k.a. organic PM), elemental carbon and a number of

elements. Similar information is presented for the stack emissions although the

nomenclature is slightly different. This difference in nomenclature recognizes that the

organic constituents in stack gas are vapors and will condense after cooling to ambient

temperatures. The users of AP-42 and FIRE should be aware that, for stack sources, total

PM is the summation of Filterable PM, condensible inorganic PM and condensible

organic PM.

1.4.23 Industry Presentation Comment Number 12 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-29: B. Footnote a. -Please change the word asphalt to HMA mix to prevent

confusion as to mix temperature or liquid temperature.

1.4.24 Response to Industry Presentation Comment Number 12 - The text in footnote a

which defines the term T in the equation was changed to “T = HMA mix temperature

in EF”.

1.4.25 Industry Presentation Comment Number 13 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-32: A. Please correct Reference No.2. Katherine is spelled Kathryn 

1.4.26 Response to Industry Presentation Comment Number 13 - The correct spelling

was used.

1.4.27 Industry Presentation Comment Number 14- (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 2: B. Second sentence - delete the "e" off of the end of with 
15

1.4.28 Response to Industry Presentation Comment Number 14 - The spelling of with

was corrected.

1.4.29 Industry Presentation Comment Number 15 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

D. paragraph 2 - please add the following: ...emissions for specific facilities where

source specific emissions is not available or where source testing is cost prohibitive. 

1.4.30 Response to Industry Presentation Comment Number 15 - The phrase “where

source specific emissions are not available or where source testing is cost prohibitive”

was added to the end of the last sentence in the second paragraph.

1.4.31 Industry Presentation Comment Number 16 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 10: A. 2nd paragraph - Please add the following: ... counterflow drum mix plants

will likely have organic stack emissions ... 

1.4.32 Response to Industry Presentation Comment Number 16 - The clarifying word

“stack” was added to the sentence.

1.4.33 Industry Presentation Comment Number 17 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 11: B. Last paragraph - Please add the following: An initial screening the of these

documents...

1.4.34 Response to Industry Presentation Comment Number 17 - The sentence was

corrected to say “An initial screening of these documents....”

1.4.35 Industry Presentation Comment Number 18 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 12: A. 1st paragraph - Please add the following: ... truck prior to these departure for

the job site”)”. Missing end parentheses.

1.4.36 Response to Industry Presentation Comment 18 - The closing parenthesis was

added to the end of the phrase.

1.4.37 Industry Presentation Comment Number 19 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page13: B. 4th paragraph - Prior to the last sentence please add the following sentence. ...

developed from the data. For example, two scientific auditors from the Research
16

Triangle Institute were employed to independently audit the test and reporting

process. These additional steps ...

1.4.38 Response to Industry Presentation Comment Number 19 - The additional sentence

was added to the paragraph prior to the last sentence.

1.4.39 Industry Presentation Comment Number 20 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 20: A. Sub title PAH - Please change as follows: PAH (semi volatile HAPs). 

1.4.40 Response to Industry Presentation Comment Number 20 - The parenthetical

phrase was added to the sub title.

1.4.41 Industry Presentation Comment Number 21 - (Gary Fore, Vice President National

Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 20: B. Please delete line between methylene chloride and MTBE

1.4.42 Response Industry Presentation Comment Number 21 - The line was deleted.

1.4.43 CAAP Presentation Comment Number 1 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

12. Page 4-2 to page 4-117: On these pages, each reference is reviewed and commented

upon. There are several problems with this section. Initially, section 4.2.1.1

discusses reference 1, section 4.2.1.2 discusses reference 2 and so on. By the time

one reaches the end of this chapter, the numbering is no longer synchronized. Section

4.2.1.327 refers to reference 354. In between, some references are not discussed (42,

43, 115, 116, 120, 127, 131 and so on). In other cases, missing references are

discussed, for example reference 258. In addition, the same reference numbers refer

to different documents. For example, on page 4-6, during the discussion of reference

23, references 26 and 27 are discussed. One has to read the citations carefully to

realize that these are references from the document called reference 23. But the

exact citations for 26 and 27 are not given. A careful reading also shows many

inconsistencies. In some cases, the data is downrated because some information is

missing; in other cases, it is not. See for example reference 181 where the data is

still rated A although information about RAP processing was not provided. On page

4-106, it appears that the cross references are incorrect.

1.4.44 Response to CAAP Presentation Comment Number 1 - Historical consistency of

reference numbers with previous versions of this section was considered a more

important criterion than synchronizing the paragraph numbering with the reference

numbering. This consistency facilitates the understanding of some of the differences in

national, regional and site specific emission inventories over time. In addition, this
17

consistency assists individuals reviewing or revising existing permits that include

emission estimates made with emission factors from previous versions of AP-42.

The lack of synchronization beginning at paragraph 4.2.1.42 is the result of

approximately 40 source tests excluded from emission factor derivation due to critical

deficiencies. Rather than discussing the nature of the critical deficiencies for each test in

the text, Table 4-1 provides the reasons the references cited are not considered further. 

Some of the critical deficiencies include “Flow rates provided; cannot calculate emission

rates,” “No production data provided,” “Insufficient process description and production

data,” and “Test methods not comparable to EPA reference methods.”

Reference 258 (described in paragraph 4.2-233) was not missing and was summarized on

page 4-84 and listed in the references on page 4-365 of the draft Appendix B report. 

Reference 284 (described in paragraph 4.2.1.258) was also not missing and was

summarized on page 4-91 and 4-92 of the draft Appendix B report and listed in the

references on page 4-336. 

Reference 23 is a document that provides information concerning the particulate size

distribution of kiln stack emissions. As indicated in the discussion, the information is

considered a secondary reference since the report provides limited detail on the contents

of unavailable test reports. Also the discussion states that primary reference material is

available for some information cited in the report. The discussion explains that because

of a lack of the primary reference information, some emission factors were developed

based on the secondary reference when no primary reference information was available.

It is recognized that a reader may misinterpret the reference numbering within the

discussion of Reference 23 and that citations for references 26 and 27 of Reference 23

need to be provided. We have revised the way this information is presented and cited so

that the reader can better discern that these citations are internal to reference 23.

Data are down rated because of the lack of critical information for quantifying the mass

emissions or for quantifying the production rate in units of the emission factor developed. 

Data were not down rated due to the lack of information on normal operating parameters

although this information might result in a slightly better understanding of the effects of

these operating parameters on emissions. While it would have been helpful in evaluating

the relationship between RAP usage and emissions, the lack of information on RAP usage

does not affect the ability to assessing the quality of the measured emissions.

1.4.45 CAAP Presentation Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

12. Page 4-2 to page 4-117: The section ends with the review of reference 354 on page

4-117. This review resumes on page 4-167. This is poor formatting for a report.
18

1.4.46 Response CAAP Presentation Comment Number 2 - To facilitate the issuance of

this report, including the addition of approximately 30 references, we have adopted the

format summarizing all of the references in one section. As with the draft background

report, we considered keeping the information related to the separate processes together

to improve the users comprehension of the emission factor development for each

emission point within a facility. However, this would have required renumbering the

more recent references for load-out and silo filling to present unrelated processes

separately. We believe that maintaining the numerical order of the references in the final

report with the numbering in the draft is more important.

1.4.47 CAAP Presentation Comment Number 3 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

13. Pages 4-118 through 4-147: There are two sections in this report: 4.2.4 Results of

Data Analysis and 4.3 Statistical Approach which more or less cover the same

ground. They should be combined so that the exposition is complete and consistent. 

In many cases, common sense should tell us that the emissions to the atmosphere are

either a result of the performance of a control device or the result of the presence of

a pollutant in the feedstock. A good example of the former is the PM emission

factor from dryers controlled with a fabric filter. Here, the emission factor for PM is

not dependent on fuel type. An example of the latter, is the sulfur dioxide emission

factor for dryers. Here, the emissions are dependent on fuel type since the control

devices do not remove any substantial amount of this pollutant. Yet, these issues are

never discussed.

1.4.48 Response to CAAP Presentation Comment Number 3 - We did not integrate the

two analyses because we believed it would make it more difficult for users familiar with

other AP-42 background reports to understand the basis upon which the emission factors

for HMA were developed. Essentially all of the statistical analyses performed could not

discern effects that many knowledgeable individuals, with good engineering judgement,

would support. The inability of the statistical analyses to discern statistically significant

effects are discussed elsewhere (see response 3.5.2 and 3.5.16). The HMA source

category is one of few AP-42 sections that had sufficient data for us to consider a

statistical analysis. 

Generally, decisions on combining or separating data from different production methods

or different control types are justified with good engineering judgement (e.g. common

sense). Integrating the inconclusive statistical analyses, which provide no useable

information, and the practical information typical users need, will obfuscate their

understanding of the decisions we made to develop the emission factors. Additionally,

we believe that some users would misinterpret the statements in the statistical analyses

and perceive the quality of the factor is lower than the data indicate.
19

We have identified similar commentor misinterpretations concerning the criteria used for

establishing the emission factor quality ratings. Specifically, in the comments presented

in section 3.4.1, 3.4.3, 3.4.5 and 3.4.9, the commentor considered variation between

sources (either range of data or standard deviation) as a primary criterion for assigning a

low quality rating. Variations between sources is normally used as one of several

secondary criteria to make minor adjustments to a rating. We believe that integrating the

statistical analyses would further exacerbate misinterpretations of the established

emission factor rating criteria. This is especially true when most statistical analyses were

inconclusive even when there were hundreds of supporting data. Presenting the

traditional emission factor derivation methods separate from the voluminous inconclusive

statistical analyses will enable customary users of the background reports to better

understand the derivations.

1.4.49 CAAP Presentation Comment Number 4 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

19. Page 4-137, paragraph 1: The description of the box plots is extremely short and

incomplete. Obviously, the authors do not intend to make it easy for readers to

understand these plots. Technically, what is shown is a “Box-and-Whisker” Plot,

which is used to show characteristics of univariate data. The data is ordered and

ranked and then divided into four equal parts. For example, a data set of 20 points

would be divided into four portions, each containing five data points. The box

encloses the middle 50% of the data. The text states that the whiskers “represent

adjacent values”. Our understanding is that the whiskers either enclose the entire

data range, i.e. the upper whisker shows the range of values for the higher 25% of the

data and the lower whisker encloses the range of values for the lower 25% of the

data. Alternately, in modified Box plots, the upper whisker is drawn to the highest

point within 1.5 times the interquartile range and the lower whisker is drawn to the

lowest point within 1.5 times the interquartile range. The interquartile range is the

difference between the 75th and 25th percentile values. Values outside the range

bounded by the whiskers are plotted individually. None of this has been bought out

in the terse description.

1.4.50 Response to CAAP Presentation Comment Number 4 - There are a number of

common variants of box-plots or box-and-whisker plots. Although short, the description

on page 4-137 is sufficient to explain the information presented in the plots. We agree

that the statement “The horizontal lines above and below each box represent adjacent

values,” could easily be misunderstood by many readers and requires clarification. We

have added the following definition “The upper adjacent value is defined as the largest

data point less than or equal to the 75th percentile plus 1.5 times the interquartile range;

the lower adjacent value is defined as the smallest data point greater than or equal to the

25th percentile minus 1.5 times the interquartile range.”
20

1.4.51 CAAP Presentation Comment Number 5 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

20. Page 4-137, paragraph 3: The paragraph lists the statistical analyses performed. 

However, the box plots shown are for only a few of the analyses listed. Where are

the remaining plots?

1.4.52 Response to CAAP Presentation Comment Number 5 - Box plots and scatter

diagrams were not developed for small data sets because these statistical visualization

tools provide little assistance in understanding the potential relationships that may exist

between and among the individual data points. All of the box plots and scatter diagrams

that were developed to facilitate understanding the distribution and relationships of the

data are presented. 

1.4.53 CAAP Presentation Comment Number 6 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

21. Page 4-137, paragraph 5: This paragraph refers to Appendices B & C. Where are

they?

1.4.54 Response to CAAP Presentation Comment Number 6 - There were only two

Appendices (A and B) that were developed for the 1997 draft of this background report. 

These Appendices were inadvertently left out of the revised draft provided to the

commentors. The indication that there are three Appendices is a typographical error. 

Appendix A is the statistical analysis of batch mix driers and Appendix B is the statistical

analysis of the drum mix driers. A copy of these two appendices were e-mailed to all of

the commentors on October 3 and was included in the final report. 

1.4.55 CAAP Presentation Comment Number 7 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

22. Page 4-138, paragraph 2: This paragraph refers to Appendix A. Where is it?

1.4.56 Response to CAAP Presentation Comment Number 7 - As stated above Appendix

A was inadvertently left out of the revised draft.

1.4.57 CAAP Presentation Comment Number 8 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

23. Page 4-139, paragraph 1: This paragraph refers to Figure 4.2. Note that Figure 4.7

has an identical caption. The two figures should be labeled properly. One has to

read the text very carefully to realize that Figure 4.2 refers to batch plants and 4.7

refers to drum plants.
21

1.4.58 Response to CAAP Presentation Comment Number 8 - The captions for Figures

4-1 through 4-6 were revised to include the term “batch plants” and the captions for

Figures 4-7 through 4-11 were revised to include the term “drum mix plants.” This

should clarify which processes are presented in each set of figures.

1.4.59 CAAP Presentation Comment Number 9 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

26. Page 4-144, paragraph 2: The first sentence is incomplete.

1.4.60 Response to CAAP Presentation Comment Number 8 - We revised the first

sentence to read , “The linear model analysis indicated that neither of the continuous

variables modeled (RAP content, production rate) had a significant effect on filterable

PM emissions. Furthermore, analysis of the scrubber data indicated that the effect of

scrubber pressure drop on filterable PM emissions also was negligible.”

1.4.61 CAAP Presentation Comment Number 10 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

29. Page 4-147, paragraph 4: This is the beginning of the review of the more recent data

on load-out emissions. As noted earlier, there is a change in format of the report at

this point in that the discussion of data sets is split into three separate parts.

1.4.62 Response to CAAP Presentation Comment Number 10 - Separate discussions of

stack and fugitive emission sources were intended to keep the reference numbers the

same as previous AP-42 sections and present unrelated emissions processes separately. 

However, approximately thirty additional emission test reports on HMA plants in

Wisconsin were submitted for evaluation. These reports include tests supporting industry

comments on the emission factors for SO2 and benzene for stack emissions from drum

mix plants. As a result, the summaries and evaluations of test reports for the stack

emissions and fugitive production emissions were aggregated and presented in the

approximate order that the references were reviewed and summarized for emission factor

development.

1.4.63 CAAP Presentation Comment Number 11 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

34. Page 4-151, paragraph 4: The last line is ambiguous. Silo emissions were measured

only at Plant C. They can’t be “combined” with any other measurements.

1.4.64 Response to CAAP Presentation Comment Number 11 - The last sentence was

revised to read “The following sections will describe the basis for performing these

adjustments to arrive at load-out and silo filling emissions at a standardized temperature

and asphalt volatility. This will allow the two load-out data sets to be compared and,

where appropriate, combined.”
22

EF [(C ) (C )]

EF

C

prod back

prod

prod

cor = − ×

[( ) ( )]

"

EFcor C C

EF

C

prod back

prod

prod

= − ×

1.4.65 Industry Presentation Comment Number 22 - (Norman Ostroff) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

On page 4-153 you present the following equation:

EFcor = ((Cprod) - (Cback))*(EFprod/Cprod)

If this equation were written in “algebra” rather than “computerese,” it might look like:

This small change would make the equation more “readable” to me and perhaps others. I

understand the physics of the equation, but recommend that the definition of the

parameter Cprod be repeated here; it is not specifically stated. I assume that this equation

is dimensionally correct, but recommend you include the units for the respective terms. 

In the numerical example that follows (in the text), I recommend that you indicate to the

reader the exact source of the input data. I could not find the reference to Run 1 MCEM,

but could have missed it while reading the report. Also, demonstrating the calculation of

Cprod from raw data would have been helpful to me.

1.4.66 Response to Industry Presentation Comment Number 22 - The equation was

placed in an equation format to make it more readable. In addition, the text that follows

was revised to include units for the various terms and the table containing the source of

the input data will included. The text will read as follows:

Where:

EFcor = Background corrected emission factor (lb/ton).

Cprod = Capture efficiency corrected production concentration (gr/dscf).

Cback = Measured background concentration (gr/dscf).

EFprod = Capture efficiency corrected emission factor (lb/ton).

The following values were obtained from Table 4-22. REPORTED

PARTICULATE-BASED LOAD-OUT EMISSIONS – PLANT C.

Cprod = 1.68x10 -3 gr/dscf (from MCEM row, second column).

Cback = 3.78x10 -4 gr/dscf (from MCEM row, eighth column).

EFprod = 3.12x10 -4 lb/ton (from MCEM row, third column).

EFcor = ((1.68x10 -3 ) - (3.78x10 -4 )) * (3.12x10 -4 / 1.68x10 -3 )

= 1.30x10 -3 * 1.86x10 -1

= 2.42x10 -4 ”
23

1.4.67 Industry Presentation Comment Number 23 - (Norman Ostroff) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

On the bottom of page 4-154 and the top of page 4-155, you present a short discussion of

vapor pressure. I agree that the Clausius-Clapyron (CC) equation generates a linear

relationship between (the logarithm of the) vapor pressure and (the reciprocal of the

absolute) temperature. The Antoine equation is a refinement of the CC equation in which

a third constant has been added. The CC equation is a special case of the Antoine

equation in which the third constant is 273.16. Please double check your references, the

(CRC) Handbook of Chemistry and Physics provides tabulated numerical vapor pressure

(verses temperature) data for a large number of compounds and Lange’s handbook

provides Antoine equation constants.

1.4.68 Response to Industry Presentation Comment Number 23 - The commentor is

correct that the Clausius-Clapyron equation uses two constant terms to predict vapor

pressure and that Antoine’s equation adds a third constant for improved accuracy under

some conditions. The TANKS program can accept vapor pressure information in three

ways. Two of the ways use vapor pressure curve equations. One of these ways uses the

three terms as described by the commentor, this is described as “Constants for Antoine’s

equation (using C)”. The other way uses two terms and is described as “Constants for

Antoine’s equation (using K)”. In the TANKS documentation, Antoine's Equation (using 

K) has the form

Log P = (-0.05223 A) / T) + B

where:

log (P) is the logarithm (base 10) of the vapor pressure (P).

P = vapor pressure in mmHg.

T = temperature for vapor pressure determination in EK.

The TANKS documentation describes the two parameters A and B as the constants in

Antoine's equation. The constants A and B for the aliphatic hydrocarbons used to

empirically develop the “Antoine’s (using K) constants” were obtained from the

Handbook of Chemistry and Physics; 45th Edition; CRC Press; June 1973 from the table

titled Vapor Pressures, Critical Temperatures and Critical Pressures of Organic

Compounds. The two term form of Antoine’s equation as stated in the TANKS software

program was used in the draft report since interpolation between constants for two

compounds is simpler than when using the three constants version of Antoine’s equation. 

Based on the commentors statements we considered deriving the more proper Antoine’s

constants using three terms. However, the highest molecular weight aliphatic

hydrocarbon in Lange‘s handbook is eicosane. Since eicosane is more volatile than the

compounds best representing asphalt, the more proper Antoine’s constants are not

available to predict vapor pressure. In addition, the improved accuracy is not required. 

While the proper terminology would refer to the Clausius-Clapyron equation, the
24

( ) EF EF 0.5

V

e Std Corr

0.0231 325 T

=

 −











−

. . . . . . . . . . . . . . . . . . . . . . . (4.13)

terminology used in the text is consistent with the terminology in the TANKS program. 

Therefore, to avoid confusing some readers, the terminology will not be revised.

1.4.69 Industry Presentation Comment Number 24 - (Norman Ostroff) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

In the second line of the next paragraph, I recommend that you remove the words “The

industry indicates that higher temperatures are avoided...”

1.4.70 Response to Industry Presentation Comment Number 24 - The text was removed.

1.4.71 Industry Presentation Comment Number 25 - (Norman Ostroff) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

On the bottom of page 4-155, you cite equation numbers 4-11 and 4-12. Where are

equations 4-1 through 4-10? Again, these equations, as presented, are somewhat difficult

to follow. The equations can be simplified and perhaps the following sentence added:

“Equation 4-11 can be rearrange to give:

My Equation (4.13) is mathematically identical to your Equation (4.11). In addition, I

have found (in my own writing) that the use of the dotted line, connecting the equation

and the equation number, simplifies reading. Am I correct in my understanding that EFStd

is the emission factor to be used for prediction of future emissions? If so, then I believe

this should be clearly stated.

1.4.72 Response to Industry Presentation Comment Number 25 - Equation 4-1 is on page

4-139 and Equation 4-10 is on page 4-145. It is recognized that the equations are

somewhat difficult to follow since the standard condition values remain in the equation. 

These equations were not simplified to demonstrate the methodology EPA used to adjust

the measured data to the standard condition. In order to use the report, the user is not

required to use either of these equations. The equations that are to be used to predict

future emissions are developed later in the background report and are presented on pages

4-160 through 4-162. The equations to be used for prediction of future emissions are

reduced to the simple form suggested by the commentor.

1.4.73 Industry Presentation Comment Number 26 - (Norman Ostroff) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

Fifteen figures are referred to at various points. In their current location, reader must stop

reading the document and look for the figures then return to the text. This is distracting,

interrupts the smooth flow of information, and can be avoided if the figures were placed

directly into the text (perhaps reduced in size).
25

1.4.74 Response to Industry Presentation Comment Number 26 - We agree that moving

the figures so that they are closer to the text where they are referenced will help the reader

locate them easier. However, we also believe that a significant size reduction will make

some of details too difficult to see. Most of the figures are associated with the statistical

analysis that was performed. We explored moving the figures for batch mix dryers to

follow Section 4.3.1 and the figures for drum mix dryers to follow Section 4.3.2. This

arrangement would also be distracting to some and interupt the smooth flow of

information in the text. As a result, the location of the figures was not changed.

1.4.75 CAAP Presentation Comment Number 12 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

54. Table 4-15: When will this table be completed? 

1.4.76 Response to CAAP Presentation Comment Number 12 - There is no table to be

inserted at this location. The final document will have no blank tables and the table

numbering was revised so that all tables are numbered consecutively.

1.4.77 CAAP Presentation Comment Number 13 - (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

55. Table 4-19: Footnote a is incorrect. R2 is the correlation coefficient, not the “squared

correlation coefficient.” We believe the terminology calls R the coefficient of

determination, so that R2 could be called the “squared coefficient of determination”. 

The more common usage is to stick with “correlation coefficient” or R2.

1.4.78 Response to CAAP Presentation Comment Number 13 - The footnote is correct. 

The term R is the correlation coefficient. R2 is called the coefficient of determination or

the correlation index.

1.5 Reference Citations

1.5.1 CAAP Reference Citations Comment Number 1 (Ravi Nadkarni & Lloyd Fillion) -

Hot Mix Asphalt Plants Emissions Assessment Report

3. Page 2, paragraph 3: This paragraph needs a cross reference, even if it is to the

relevant sections in Appendix B. In general, we need page number references to

information in Appendix B which is over 400 pages long.

1.5.2 Response to CAAP Reference Citations Comment Number 1 - To help locate the

primary references for the key information presented in the main report, the reader is

referred to specific tables or page numbers in the Appendices. However, to produce a

report that is uncluttered with voluminous citations that would hinder the readability of

the report, all of the primary references will not be used in the main body of the

Emissions Assessment Report. Instead, a sentence was added to inform the reader that a

comprehensive listing of references is contained in the Appendices. In addition, a table
26

has been added to the main body of the Emissions Assessment Report that provides a

cross reference directing the reader to the specific section or table in the appendices

where the more important information is located.

1.5.3 CAAP Reference Citations Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Hot Mix Asphalt Plants Emissions Assessment Report

16. Page 15, paragraph 3: The first line refers to “emission tests described in previous

paragraphs”. Since the previous paragraphs refer to more than one plant test, it is

preferable to have a proper reference; for example, the text can refer to the test at

Plant C or Plant D.

1.5.4 Response to CAAP Reference Citations Comment Number 2 - Since there are a

limited number of emission tests which were used to establish emission factors for hot oil

heaters, load out, silo filling, asphalt storage tanks and yard emissions, the specific

reference numbers used in Appendix B were cited to describe the test(s) used to establish

these emission factors.

1.5.5 CAAP Reference Citations Comment Number 3 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

16. Page 11, paragraph 2: What exactly is reference 1? Is it the main report with a

different date and number? Also, the derivation of the factor is properly described,

not in Reference 1 but in Appendix B.

1.5.6 Response to CAAP Reference Citations Comment Number 3 - Reference 1 for this

part of the report should be Appendix B or the Emission Factor Documentation for AP42 Section 11.1, Hot Mix Asphalt Production. This reference citation was revised.

1.5.7 CAAP Reference Citations Comment Number 4 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

17. Table 1: There are many problems here. Footnotes k through p refer to Reference 1. 

That is incorrect. If you want to refer to Appendix B, provide specific page number

and citation.

18. Table 3: Same problems as Table 1; i.e. use of Reference1 which does not really

contain the primary data and uncontrolled emissions equal controlled emissions.

19. Table 5: Same problems as Table 1; i.e. use of Reference1 which does not really

contain the primary data.

23. Table 14: Same problems as Table 1; i.e. use of Reference1 which does not really

contain the primary data.

1.5.8 Response to CAAP Reference Citations Comment Number 4 - Reference 1 for this

part of the report should be Appendix B or the Emission Factor Documentation for

AP-42 Section 11.1, Hot Mix Asphalt Production. This reference citation was revised. 
27

We decided that citing each of the over 150 references used to derive these emission

factors would add text that would confuse the typical user. Additionally, citing over 150

references would potentially hide information that adds value. As a result, we decided

that we would reference only the background report. We agree that presenting a specific

location in the footnote will assist a user find the information needed to better understand

the basis for the emission factor. To provide this assistance, the table number in the

background report was specified.

1.5.9 CAAP Reference Citations Comment Number 5 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

20. Table 6: Unlike previous tables, descriptive statistics about the data sets are not

presented.

22. Table 8: Unlike previous tables, descriptive statistics about the data sets are not

presented.

1.5.10 Response to CAAP Reference Citations Comment Number 5 - Generally, we

present descriptive statistics only when more than 20 supporting data are available.

1.5.11 CAAP Reference Citations Comment Number 6 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

23. Table 14: This and many other tables, especially in appendix B, have footnote “a”

obscured because it is superimposed over the last letter of the table heading

1.5.12 Response to CAAP Reference Citations Comment Number 6 - The print over of

footnote “a” is not evident in the electronic file or page printed from the file. It is

possible that the Adobe Acrobat software used by the commentor is not the version

provided on the CD-ROM that the commentor is using. There also may be a problem

with the printer or printer driver used by the commentor. However, all of the footnotes in

the tables were evaluated for the situation the commentor describes.

1.5.13 CAAP Reference Citations Comment Number 7 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

2. Page 2-1, Section title: Reference 1 is to an earlier version of AP-42. Why is an

obsolete version of the same document being used as the reference? Reference 3 is a

personal communication from the head of an industry lobbying group. Is this

information in the public domain? Can we get a copy?

1.5.14 Response to CAAP Reference Citations Comment Number 7 - Reference 1 was

revised to indicate the original source of the information characterizing the industry. All

of the information cited in this report is in the public domain. A copy of Reference 3 was

provided to the commentor. 
28

2.0 Industry Characterization and Structure

2.1 Capacity and Production Levels

2.1.1 CAAP Production Level Comment Number 1 - (Ravi Nadkarni & Lloyd Fillion) -

Commentors’ General Comments, Section B

The report and its appendices contain little or no information about industry structure. 

For example, Appendix B asserts that drum plants are 90% larger than batch plants in

terms of annual throughput. This really falls out of an assumption made by the authors. 

There is little or no backup for this conclusion. Similarly, there is no information on what

proportion of plants use natural gas and what proportion use other fuels.

Commentors’ Summary Section C

Undocumented Information on Industry Structure: The report and its appendices contain

little or no documented information about industry structure. Yet such information is used

to derive average plant sizes and share of annual production between batch and drum

plants.

Commentors’ Summary Section C

Industry Comments on Capacity Are Given More Weight than Data Collected by EPA or

State Agencies: The report states that the hourly capacity data was averaged from the

capacities of precisely 98 batch plants and 162 drum plants. Since most of the data was

gathered during performance tests at full capacity and witnessed by State Agencies, it is

unlikely that hourly production rate data is incorrect. It is interesting that “conversations

with industry” are all that is needed to supercede this data. In the report, it is clear that

the authors believe that batch plants generally operate fewer hours per year than drum

plants. Reasons for this (not necessarily explained in the report) include the lack of silos

for HMA storage, small customers using smaller trucks, and so on. The report keeps

talking about hourly production rates when the discussion should focus on annual

production, i.e. hourly rate times hours operated per year.

Comments on Hot Mix Asphalt Plants Emissions Assessment Report

1. Page 1, paragraph 3: In this paragraph, 1996 production statistics are presented along

with an estimate of the number of plants in the country. There are no references to

the source of these data. In Appendix B, page 2-1, the same paragraph is repeated. 

On page 2-2 and 2-3 of Appendix B, calculations are presented which derive average

annual production rates for batch and drum plants. We will comment on the

problems with these calculations in our page-by-page discussion of Appendix B. 

However, the entire discussion is aimed at showing that drum plants produce more

HMA compared to batch plants without actual data.

5. Page 8, paragraph 4: More industry statistics are presented without a source or a

measure of precision or accuracy.
29

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

1. Page 1, paragraph 3: This paragraph is repeated in the main volume, and in the first

two appendices. It would be more useful to discuss the source of this data and

comment on its reliability, rather than repeat it in three places.

Comments on Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot

Mix Asphalt Production, June 2000 Draft

3. Page 2-1, paragraph 3: The key information in this paragraph about the number of

plants in the country and the type of plants being built is not referenced so the reader

can’t judge the reliability of the information. 

4. Page 2-2, paragraph 1: The key information in this paragraph about 1996 production

is not referenced so the reader can’t judge the reliability of the information. Further,

since road building tends to be a cyclical activity (at least locally), production or

output over several years might be a more reliable way to establish these levels than

the output in a single year. Dept of Commerce or USGS/Mineral Industry Surveys

probably collect and publish this information.

5. Page 2-2, paragraph 2 and 3: If the hourly capacity data was averaged from the

capacities of precisely 98 batch plants and 162 drum plants, the numbers are

probably correct, unless these plants consistently misrepresented the capacity. Such

misrepresentation is not likely to go unnoticed since most of the data was gathered

during performance tests at full capacity in the presence of State agencies to make

sure that emissions limits were being met. It is interesting that “conversations with

industry” are all that is needed to supercede this data. Why are we not surprised!

Overall, this paragraph is attempting to relate hourly capacity to annual production. 

That goal is not achieved. The discussion in paragraph 3 is totally confused and

needs to be rewritten. Hourly production rates are easy to measure. If the data set

referred to in the previous paragraph is for obtaining operating permits from the

relevant State Air Pollution Control Agencies, as is the case in Massachusetts, the

plant is supposed to be running at or close to the design hourly capacity when the

emissions are sampled. Therefore, We believe that the hourly capacity

measurements are correct because these numbers are measured during State

compliance testing and should not be superceded by “industry comments”. 

The discussion should be talking about the fact that batch plants, especially batch

plants without silos for HMA storage, don’t operate for as many hours a year as

drum plants because they service customers using small trucks/small volume

customers and because of the difficulties in matching hot mix production with truck

arrivals. (Note that because batch plants store dried, hot stone, there is storage

available, but the stored quantity is generally much smaller than that available with

HMA storage silos.) In contrast, because of their large production contracts, drum

plants operate for more hours each year and the ability to store HMA in silos also

facilitates long production runs. The entire paragraph keeps talking about hourly
1 Available by internet at URL http://minerals.usgs.gov/minerals/pubs/commodity/myb/

30

production rates when the discussion is really trying to focus on annual production,

i.e. hourly rate times hours operated per year. 

Also note that the key assumption is that drum plants produce 90% more HMA than

batch plants ON AN ANNUAL BASIS. This assumption is not backed up with

anything; no footnotes or anything. If this is EPA’s assumption, say so. 

Interestingly, in the main report, this assumption transforms into a finding that drum

plants produce 100% more than batch plants on an annual basis. 

If one assumes that the empirical 80/20 rule applies, the average annual output from

batch plants would be 108,000 tons per year and that from drum plants would be

194,000 tons per year. This means that the purported annual industry output of 500

million tons is shared almost equally between batch and drum plants. 

It should also be noted that there is no information provided on distribution between

small jobs and large jobs, which would also provide information on how the total

production is split between batch and drum plants. Is it possible that this is because

industry information was provided by a lobbying group supported mainly by the

large producers? This means that the production information has a bias favoring

large producers and making them appear more important.

2.1.2 Response to CAAP Production Level Comment Number 1 - Information presented

in the Emissions Assessment Report (and the AP-42 Section and Background Report)

includes references to the original source of information when it is relevant to the purpose

of the document. The primary purpose of the document is not intended to provide a

detailed information on the industry structure. The information considered most relevant

to the purpose of the Emissions Assessment Report is the development of methodologies

to estimate air emissions from available production and air pollution control device

information. National production statistics, the number and type of production facilities

and the average annual production at the different types of facilities are provided for the

user to have a basic understanding of the source category when conducting an inventory

of air emissions on a regional or national scale. Significant differences in the production

level, the total number of plants and the number of plants by production method may

exist between States and even within regions of States. Local emission inventories or

individual facility permits should use locally developed information on the number, type,

capacity and demonstrated or expected actual production levels to derive improved

estimates of emissions.

Although it is believed that the national trade association for the HMA industry has a

good assessment of the national production levels, EPA performed an independent

assessment of HMA production. As suggested by the commentor, reviewed information

in the USGS Mineral Yearbook1 for production of aggregate by identified end uses. It
31

was determined that 1996 has the greatest reported use of bituminous aggregate. 

Information useful for estimating HMA production is divided between reports on

Crushed Stone and Construction Sand and Gravel. Within these two categories the

information is further divided.

For Crushed Stone, the following information is presented in Table 13:

In addition, Table 20 presents a Total of 1,350,000 Mt of Recycled asphalt for 1996.

For Construction Sand and Gravel, the following information is presented in Table 6:

In addition, Table 14 presents a Total of 3,740,000 Mt of Recycled asphalt for 1996.

Both chapters in the Minerals Yearbook recommend that the unspecified uses’ categories

be distributed as the specified uses categories. Adjusting the Total Crushed Stone

production of 1,330,000,000 Mt to the ratio of reported total specified use totals for HMA

usage verses the total specified uses of Crushed Stone yields 236,904,000 Mt

(1,330,000,000 X (138,580,000 ÷ 778,000,000). Adjusting the Total Sand and Gravel

Coarse aggregate, graded:

Bituminous aggregate, coarse 88,900,000 Mt

Bituminous surface-treatment aggregate 22,900,000 Mt

Fine aggregate (-3/8 inch):

Stone sand, bituminous mix or seal 25,500,000 Mt

Special:

Asphalt fillers or extenders 1,280,000 Mt

Unspecified: 4/

Actual 370,000,000 Mt

Estimated 182,000,000 Mt

Total 1,330,000,000 Mt

4/ Includes production reported without a breakdown by end use and estimates for

nonrespondents.

Figure 1. Excerpt from Table 13 of the 1996 USGS Minerals Yearbook.

Asphaltic concrete aggregates and

 other bituminous mixtures 70,800,000 Mt

Unspecified: 2/

Actual 174,000,000 Mt

Estimated 203,000,000 Mt

Total 914,000,000 Mt

2/ Includes production reported without a breakdown by end use and estimates for

nonrespondents.

Figure 2. Excerpt from Table 6 of the USGS Minerals Yearbook.
32

production of 914,000,000 Mt to the ratio of reported total specified use total for HMA

usage verses the total specified uses for Sand and Gravel yields 120,505,000 Mt

(914,000,000 X (70,800,000 ÷ 537,000,000). Asphalt is added to this newly quarried

aggregate total of 357,409,000 Mt to produce HMA that is 6% asphalt (or 94% aggregate)

to yield 380,222,000 Mt of HMA. In addition to newly quarried aggregate, the USGS

reported that a total of 5,090,000 MT of recycled asphalt was used in HMA. Based on

these reported values from USGS, the production of HMA for 1996 is estimated to be

385,312,000 Mt or 424,614,000 tons. However, given the emphasis on recycling in State

paving contracts, a recycled asphalt to new HMA ratio of only 1.0% appears very low and

is probably significantly under estimated by USGS.

In a 1993 joint Federal Highway Administration and EPA report (A Study of the Use of

Recycled Paving Material - Report to Congress; FWHA-RD-93-147; EPA 600/R-93-095;

June 1993), it was estimated that 73 million metric tons (80.4 million tons) of RAP were

recycled annually. This report documents several methods of reprocessing RAP for reuse

as pavement or other materials. However, the report does not provide estimates of

reprocessing by each method. Based on this report, EPA concluded that the majority of

RAP reprocessing is in HMA plants. Assuming all of the RAP is reprocessed in HMA

plants, an early 1990's upper bound estimate of 16.1% recycled asphalt produced can be

calculated [73,000,000 ÷ (380,222,000 Mt + 73,000,000 Mt) ×100% = 16.1%]. 

Recongizing this estimate includes reprocessing not in HMA plants, EPA examined an

alternative method of estimating national RAP usage in HMA plants.

At Plants C and D between 80 and 90% of the asphalt produced included RAP. When

RAP was used, Plants C and D included 30 percent and 10 percent RAP in their

respective final asphalt mixes during EPA emission testing. Extrapolating this

production information to an annual estimate, Plants C and D use between 8 and 27%

RAP with a midpoint of 17.5 percent. While this number is larger than the FHA derived

upper bound estimate of 16.1%, it may be more representative of RAP usage rates in the

late 1990's. Using the midpoint (17.5%) of this range yields a revised RAP usage of

80,653,000 Mg (88,905,000 tons). Using the revised RAP usage yields a total estimated

HMA production for 1996 of 469,102,000 Mg or 516,096,000 tons.

Since the industry has an economic interest in understanding the annual production of

their industry, it is reasonable that this independently developed value is close to the

value provided by the industry and used in the draft report. EPA’s review of the USGS,

FHA and EPA studies indicates the national RAP usage rate is likely between 15-20%. 

Accordingly, EPA used the above information and the mid-point of the estimated RAP

usage range (17.5%) to estimate annual HMA production of 516,096,000 tons for the

United States.

The commentor is correct that the paragraph including the explanation and comparison of

estimated average drum mix plant annual production and average batch mix plant is

confusing and is revised. However, based on statements in the fifth comment on

Appendix B, it appears that the commentor understands the derivation and rationale in the
33

comparison of drum mix and batch mix asphalt plants; the development of annual

production levels for typical batch mix and drum mix plants. In addition to presenting the

development of the estimated annual production of HMA, we have revised Section 2.1 of

the background report to read as follows:

“Information provided by the HMA industry indicates that HMA is produced by

approximately 2,300 batch plants and 1,300 drum-mix plants. Using a national asphalt

production estimate of 517 million tons of HMA, an estimate of the national annual

production capacity at drum and batch mix plants was determined as follows:

Based on available production capacity data from emission compliance tests of 98 batch

mix plants and 162 drum-mix plants, the average maximum production rates are:

Batch – 214 tons/hr

Drum – 272 tons/hr

Extrapolating these averages to the entire HMA industry yields an estimated, theoretical 

national production capacity of 7,409 million tons of HMA if all plants could operate

8760 hours in a year. The 2,300 batch mix plants would produce 4,311.7 million tons

and the 1,300 drum mix plants would produce 3,097.5 million tons.

Based upon the above estimates of HMA production and available plant capacity, the

estimated utilization rate of the industry is only about 7 percent (517 million ÷ 7,409

million). This significant under utilization is caused by limitations on when pavements

can be laid that are created by weather conditions, contract specifications on times of the

day when pavement construction can be performed, the local demands for paving

construction and repair, the distance that HMA can be trucked to a paving site, the desire

to be able to meet short term peak production demands and a variety of other factors. A

number of differences between drum and batch mix asphalt plants suggest the estimated 7

percent utilization ratio is not likely to be equal distributed among batch mix and drum

mix plants. These differences include:

1) production methods,

2) capability to make and store product ahead of the time, 

3) ability for loading to occur significantly quicker at facilities with storage silos, 

4) the general lack of storage capability at batch mix plants, and

5) the economic desire to shift higher production demands to the higher capacity and

more cost efficient drum mix plants. 

All drum mix plant require HMA storage silos to store product ahead of demand. It is

estimated that for a maximum production day, a typical drum mix plants will begin

production three hours prior to the first truck load-out in order to stay ahead of demand. 

For days with less than maximum production, a typical drum mix plants will maintain

this relative production advantage, although it is not necessary to begin production three

hours ahead of the first truck load-out. Since a typical batch mix plant does not have

storage for a significant amount of aggregate, it cannot produce significantly ahead of

demand. For an eight-hour load-out schedule and equal production capacity, the drum
34

mix plant would be able to produce 38% more product (11 ÷ 8 = 1.38). It is also

estimated that for about 30 minutes over the eight hour day, a typical batch mix plant will

need to stop production because there are no transport trucks to load. As a result, the

batch mix plant will only be able to produce 94 percent of its hourly target production

(7.5 ÷ 8 = 0.938). As a result the eight-hour load-out capability for drum mix plants

would be 147% of the eight-hour production capacity for batch mix plants (1.38 ÷ 0.938

= 1.47). Since the average production capacity of drum mix plants is 27% greater than

batch mix plants (272 ÷ 214 = 1.27), the overall eight-hour load-out advantage of the

average drum mix plant (as compared to the average batch mix plant) would be 187

percent of the eight-hour production capacity (1.47 x 1.27 = 1.87). Using this estimate, if

517 million tons of HMA are produced per year by the 2,300 batch and 1,300 drum-mix

plants then:

517 x 10 6 = 2,300 x B + 1,300 x D

and

D = 1.87 B

where:

B = average production of a batch mix plant (tons/yr)

and

D = average production of a drum-mix plant (tons/yr)

Solving the equations for B:

517 x 10 6 = 2,300 x B + 1,300 (1.87 x B)

517 x 10 6 = 4,731 x B

B = 109,000 tons/yr

D = 204,000 tons/yr

Using these average production rates, the total 1996 HMA production from batch and

drum-mix plants is estimated at about 251 million tons and 265 million tons,

respectively.”

At the estimated annual production levels, the average batch plant would have a 5.5%

utilization rate compared to an 8.1% utilization rate for drum mix plants. It is believed

that using these estimates of annual production provides a reasonable differentiation in

the utilization rates of batch mix plants and drum mix plants. Given the conditions stated

above that would tend to influence the use of newer, higher production and more efficient

plants, a 50% difference in utilization appears reasonable. In addition, the information

that was obtained on the capacity and annual production of Plant C and Plant D

(References 355 and 356 in the AP-42 section and background reports) supports these

utilization rates. In the test report for Plant D, the hourly capacity is listed at 255 tons per

hour and the typical annual production is about 100,000 tons per year. In addition to

being very close to the average capacity and estimated annual production cited above, the
35

utilization rate is 4.5%. While this is slightly less than the estimated national average

utilization rate, it is very close to the value estimated. In the test report for Plant C, the

hourly capacity is listed as 650 tons per hour and the annual production is about

1,000,000 tons per year. While this facility has a much higher capacity than the estimate

for the average plant, it is one of the newest plants in the nation and is likely one of the

highest capacity plants in the nation. Based upon plant C production and capacity

information, the utilization rate of this plant is 17.5%. This is significantly higher than

the average utilization estimated above. However, the plant is located in southern

California where the temperature is suitable for paving all year and where there are on

average only 30 rain days a year to limit the laying of pavement. In addition, the facility

was built to provide HMA for the construction of California Highway 241, which is a

new 30 mile toll road west of Irvine, CA. It is unlikely that there are many other

locations where the combination of weather and demand for major road construction

would support the high utilization rate of Plant C. Weather conditions in the majority of

the United States restricts paving operations to about nine months due to low

temperatures. Further, for the eastern half of the United States, the average 100 days of

precipitation further limits the number of paving days. Considering these situations, it is

not unreasonable for plant C to have twice the utilization of the average HMA facility in

the United States.

As indicated in the more detailed response provided later, information on the derivation

of an estimated proportion of gas and fuel oil usage by the industry was presented in the

revised industry description contained in Appendix B. In addition, statements were added

to the “main” report and Appendix A that between 70% and 90% of the energy estimated

to be used at HMA plants in 1998 was from natural gas. Further detail on the

characteristics of the HMA industry such as the distribution between small jobs and large

jobs are outside the scope of this report. This type of information would be highly

specific to the location and type of the facility. It is not known whether this type of

information is available outside the individual companies that own the 3600 plants and

obtaining this information would require significant effort and time. 

2.1.3 CAAP Production Level Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot

Mix Asphalt Production, June 2000 Draft

10. Page 3-2, paragraph 1: The sentence states that emission data must be from a primary

reference. In chapter 2, however, secondary references and anecdotal comments are

used to supercede primary reference data on hourly capacity.

2.1.4 Response to CAAP Production Level Comment Number 2 - The information

presented in chapter 2 which is derived from secondary references is not emission data

and does not supercede primary reference data. As indicated in previous response, the

discussion on the derivation of annual production from reported hourly capacity data was

revised to more clearly indicate the basis for the derivation. 
36

2.2 Type of Fuels Used by Typical Production Facility

2.2.1 State Fuel Usage Comment Number 1 (Massachusetts State Senator Stephen F.

Lynch) -

In reading this report and its appendices, along with comments sent to my office by Ravi

Nadkarni, it is my understanding that this report only shows emissions results from

asphalt plants burning natural gas as a source of fuel.

The report also fails to provide information about what percentage of asphalt plants cited

in the report used natural gas and what percentage of those plants used alternative fuels. 

Although I am not an environmental engineer, it is obvious to see that emissions result

from asphalt plants burning only natural gas, as opposed to other fuels, will show

considerably lower emissions result. This would clearly indicate to me that the results in

this report are skewed. I would like to see more thorough testing of various data included

in the final report, especially if this report is to be considered an emissions standard for all

asphalt plants.

2.2.2 CAAP Fuel Usage Comment Number 1 (Ravi Nadkarni & Lloyd Fillion) -

Hot Mix Asphalt Plants Emissions Assessment Report

18. Page 16, paragraph 3: The second line refers to Tables 4 through 11 which present

more detailed information about “typical” plants. Unfortunately, this is the emission

factor data of Appendix A multiplied by 100,000 for batch plants and by 200,000 for

drum plants. The implication is that the reader can’t move the decimal point to the

right or multiply by 2. Further, in keeping with their bias for showing only low

numbers, these tables are for natural gas only and not for oil-fired heaters. Why? 

Finally, what is the basis for assuming (third bullet on page 17) that PM emissions

from load-out and silo filling are entirely PM-10? We would have thought that a

better assumption was that these were PM-2.5.

2.2.3 Response to State and CAAP Fuel Usage Comments Number 1 - Presentation of 

emissions representative of an average gas fired HMA facility data in the draft Emissions

Assessment report was reasonable. Over 95% of the fuels (by energy content) used in

industrial sources is gas and fuel usage by HMA plants is likely similar. However, in

response to commenters concerns we conducted a limited survey to obtain additional

information on fuel useage and added emission factor tables for fuel oil fired HMA

plants.

A very limited survey of available, but limited, fuel usage information from five State

agencies suggests that approximate 70 - 90% of HMA plants are gas fired. Limitations

on the available data from these five State agencies could not precisely discern fuel usage

at HMA plants. However, we have revised the Emissions Assessment Report by adding

text on page 3 characterizing this range of fuel usage in the industry.

We also recognize that there are local situations where a HMA plant may primarily use

fuel oil and, as a result, may generate more emissions than the typical gas fired HMA
2 Available by internet at URL 

http://www.eia.doe.gov/pub/oil_gas/petroleum/data_publications/fuel_oil_and_kerosene_sales/current/pdf/table1.pdf

3 Available by internet at URL 

http://www.eia.doe.gov/pub/oil_gas/natural_gas/data_publications/natural_gas_annual/current/pdf/table_014.pdf

4 Available by internet at URL http://www.eia.doe.gov/emeu/mecs/mecs94/consumption/mecs4a.html

37

facility. We have revised the Emissions Assessment Report to indicate that many HMA

plants have the capability to use fuel oil as an alternative to gas. The report was also

revised to note that fuel oil fired HMA plants would have higher emissions of SO2, NOx

and HAP compounds. In addition, Emissions Assessment Report Tables 1 and 2 were

revised to include a column for fuel oil. The footnotes to these tables were revised to

indicate that natural gas is used to produce between 70 and 90% of the HMA and fuel oil

to produce between 10 and 30% of the HMA. Also, Tables 4 and 7 include columns

presenting emissions for fuel oil. The footnotes to Tables 4 and 7 now indicate that

between 70 and 90% of the HMA produced is with natural gas fuels and between 10 and

30% of the HMA is produced with fuel oil.

We have also documented the basis of the statements added to the main report in

Appendix B. The following paragraph was added to Section 2.1 following the derivation

of the estimates for the average annual production of batch and drum mix plants.

“The Department of Energy indicates that annual distillate fuel sales to industrial

customers in the US for 1998 was 2,462,355,000 gallons2 compared to natural gas sales

of 8,686,147,000,000 cubic feet3. At a typical energy content of 140,000 Btu/gal for

distillate oil and 1050 btu/ft3 for natural gas, 96.3% of the energy used by industries was

natural gas. We expect that many of the factors that promote the preferential use of gas

fuels are common within many industries. Therefore, we expect fuel usage at Hot Mix

Asphalt plants is very similar to other industrial sources. Some of these factors are fuel

cost, delivery system requirements, and equipment maintenance requirements. The

Energy Information Agency reported in the Manufacturing Consumption of Energy 1994

(Combined Consumption and Fuel Switching) report4 that the national average cost

industry paid for a million Btu of energy was $2.15 for natural gas, $4.84 for distillate oil

and $4.71 for LPG. This report also separates these energy costs by four regions of the

United States. Of the four regions, the differences in the costs of the various fuels are

smallest in the northeast region. In this region, the average fuel costs were $3.39 for

natural gas, $4.89 for distillate oil and $5.69 for LPG. In addition, the delivery of fuel oil

and LPG must be scheduled and stored near the production unit. The storage tanks and

supporting mechanical equipment require monitoring and maintenance that is not

required when the plant is fueled with natural gas. Also, burners for firing fuel oil require

a higher level of maintenance than natural gas burners. Lastly, it is recognized that the

combustion of fuel oil produces more air emissions than natural gas combustion. 

Therefore, it is believed that, where it is available, natural gas is and will remain the

predominant fuel used at HMA plants. However, many plants will maintain the
38

capability to use fuel oil as an alternate or supplementary fuel. A few plants will use only

fuel oil due to the unavailability or high local cost of natural gas. As a spot check of the

DOE information on industrial fuel usasge, an informal telephone survey of five States

was conducted. The survey confirmed that HMA plants use natural gas when it is

available. The fuel usage information in the States’ emission inventories shows a range

of about 50 percent to 99 percent gas usage. However, the fuel usage information

reported by industry was incomplete. Also, for some States, energy usage per ton of

product was over 50 percent higher than emission tests where fuel usage and production

information was available. As a result, it is estimated that between 70 and 90 percent of

HMA is produced with gas fuels.”

While the main body of the Emissions Assessment report only presented estimated

emissions for gas fired HMA plants, the appendices present emission factors for not only

natural gas fired facilities but also coal, butane, propane, fuel oil and waste oil fired

facilities. Most industrial facilities can fire both natural gas and fuel oil. Additionally,

emissions performance tests with few exceptions are conducted under worst case

conditions. This includes conducting emission tests while firing fuel oil in plants that

almost always use natural gas. As a result, the use of test data presented in this report to

estimate the percentage of facilities firing different fuels would provide a skewed

estimate of the actual fuel usage by the industry.

The Emissions Assessment Report does not establish a national emission standard. The

introduction to AP-42, EPA advises users that emission factors are not recommended as

source-specific permit limits because emission factors are averages. Since emission

standards are a “not to exceed” value, using the average emission factor without any

engineering analysis would likely cause half the facilities to violate their permit limit. 

The background report compiles a significant amount of data that may not otherwise be

available in one document. While not establishing emission standards or rules, this data

can be part of the information used in rule or State Implementation Plan development.

EPA’s primary purpose for AP-42 is for air quality planning purposes. This includes

providing State and local agencies with reliable information to assist them to develop

comprehensive emission inventories. The information presented in the report is based

upon emission tests of many facilities. Although all facilities were not tested for all

possible pollutants, the information available to characterize emissions from HMA plants

is more than adequate to characterize emissions from these facilities for air quality

planning purposes.

As the commentor states, the information presented in the tables is the emission factor

data of Appendix A multiplied by 100,000 or 200,000. This information is presented in a

simpler and more concise format to help non-technical readers understand the results. 

More technical information is included Appendicies A and B. The multipliers used in the

main body of the Emissions Assessment Report are the approximate, average production

levels for the typical batch mix plant and drum mix plant respectively. We have
39

explained how we determined the average production levels in Section 2.1.2. Response

to CAAP Production Level Comment Number 1.

While it is reasonable to assume that organic emissions from load-out and silo filling are

predominantly PM-2.5, the inorganic emissions are likely to be rock dust. The organic

particulate emissions result from a condensation phenomenon which is expected to

predominantly form particulate that is less than one micrometer in diameter. Therefore,

all emissions from load-out and silo filling are PM-10 as well as PM-2.5. Footnote b in

Table 11.1-14 in Appendix A of the draft report states “Total PM is assumed to be

predominantly PM-2.5 since emissions consist of condensed vapors.” While PM-2.5 has

recently been designated by EPA as an additional particulate pollutant of concern for

ambient air quality, the use of PM-10 was selected because it is the particulate pollutant

with which most people are familiar.

2.3 Process Descriptions

2.3.1 CAAP Process Description Comment Number 1 (Ravi Nadkarni & Lloyd Fillion) -

Hot Mix Asphalt Plants Emissions Assessment Report

2. Page 1, paragraph 4: The statement in line 1 is incorrect. The primary emission

source is the dryer, not the mixer, as stated. This is the case because combustion of

fuel for generating heat for drying generates large quantities of criteria pollutants. 

This error of confusing dryers and mixers is repeated several times, (for example in

Table 1), and we have not bothered to find all instances of such misuse. The best

way to clarify this issue is to substitute “dryer/mixer” for drum plants where the two

units are connected. In the case of batch plants, the dryer and the mixer (pug mill)

are typically uncoupled through hot storage bins. Emissions from both however are

often captured by the same piece of air pollution control equipment.

2.3.2 Response to CAAP Process Description Comment Number 1 - Whether the dryer or

the mixer is the primary emission source for batch plants depends on the pollutant that is

being considered. As stated by the commentor, emissions from both sources are often

captured by the same air pollution control device. Compared to other combustion

sources, the majority of emissions of particulate, VOC and possibly CO are not due to

fuel combustion. However, it is likely that most of the particulate emissions are

generated in the dryer drum at batch mix plants. At batch mix plants, substantial

particulate emissions may also be generated by the hot screens and the pug mill when the

hot aggregate is transferred to these processes. However, to clarify the issue, the text was

revised to clarify that the source of the batch mix emissions is the dryer, hot bins and

mixer.

2.3.3 CAAP Process Description Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Hot Mix Asphalt Plants Emissions Assessment Report

10. Page 9, paragraph 1: The sentence on line 6 is confusing. Do you mean RAP is

added to the “hot” bins or is it added to the pug mill?
40

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

3. Page 2, paragraph 3: This paragraph repeats the ambiguity in the main report on page

9 paragraph 2. Is RAP added to the weigh hopper or to the hot bins?

Comments on Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot

Mix Asphalt Production, June 2000 Draft

6. Page 2-3, last paragraph: The writing should make clear whether the RAP is added

to the hot storage bins or directly to the mixer/muller.

2.3.4 Response to CAAP Process Description Comment Number 2 - Although a few

batch mix plants may mix RAP with the hot aggregate prior to the combined aggregate

storage in the “hot” bins, it is more typical for the cold RAP to be combined with the hot

aggregate in the pug mill. Some newer batch mix plants have a RAP silo with the “hot”

bins to dry and partially heat the RAP before combining the RAP and the hot aggregate in

the pug mill. The wording in the EA-Report, AP-42 Section and Background Report was

revised to more clearly describe the more prevalent process.

2.3.5 Industry Process Description Comment Number 1 (Gary Fore, Vice President

National Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 8: A. 3rd paragraph - ...(2) continuous mix (mix outside dryer drum) plants, ...

Please add the word dryer when using the "mix outside dryer drum" phrase. This will

allow for both past and present types of plants.

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-1: A. Hot mix asphalt paving materials can be manufactured by: ... (2)

continuous mix (mix outside dryer drum) plants, ... Please add the word dryer when

using the "mix outside dryer drum" phrase. This will allow for both past and present

types of plants.

2.3.6 Response to Industry Process Description Comment Number 1 - The word dryer

was added to the sentence to allow for both past and present types of plants.

2.4 Plant Characteristics

2.4.1 CAAP Plant Characteristics Comment Number 1 (Ravi Nadkarni & Lloyd Fillion) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

2. Page 2, paragraph 1: The statement that raw aggregate is stockpiled “near” the plant

is ambiguous. Such aggregate is normally stockpiled within the plant site and is

moved to the cold feed bins with a front-end loader.

2.4.2 Response to CAAP Plant Characteristics Comment Number 1 - The term plant in

this statement is intended to designate the kiln, hot screens and pug mill and not the

property site in general. The statement was revised to state that the raw aggregate is

stockpiled near the production unit. 
41

2.4.3 CAAP Plant Characteristics Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

4. Page 5, paragraph 2: In counterflow plants, the baghouse is preceded by a cyclone

to reduce the load on the baghouse. This is a trade off issue where it is cheaper to

use a cyclone than to increase bag house size and bag cleaning frequency to achieve

the same result. Since the industry prefers counterflow plants to parallel flow

plants(page 1 paragraph 3), the use of an additional particulate separation device in

the former is obviously not a disadvantage, on an economic or a technical basis.

2.4.4 Response to CAAP Plant Characteristics Comment Number 2 - The decision on

using a cyclone before the baghouse is more of a consideration of the baghouse

manufacturer than the manufacturer of the HMA plant. The size of the baghouse depends

on the gas flow, the bag cleaning method, and the type of fabric used for the bags and not

a function of the inlet dust concentration. The statement only identifies one air pollution

control advantage of a parallel flow plant. Other production tradeoffs may be considered

by the plant manufacturer and operator in the selection of the final design of the plant. 

The statement as drafted provides information that is useful to individuals and the report

will not be changed. 

2.4.5 CAAP Plant Characteristics Comment Number 3 (Ravi Nadkarni & Lloyd Fillion) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

4. Page 5, paragraph 2: If you have data to support the statement that organic emissions

may be greater from this process, present it; otherwise eliminate the statement.

2.4.6 Response to CAAP Plant Characteristics Comment Number 3 - The lack of data to

substantiate the statement is not a reason to eliminate the statement. As with many other

emissions that were statistically evaluated, there is insufficient information about the

relevant process variables, an insufficient number of data and relatively high variation in

the emissions to properly evaluate the potential effect. However, the statement was

revised to indicate that the available data is insufficient to discern any differences in

emissions because the process.

2.4.7 CAAP Plant Characteristics Comment Number 4 (Ravi Nadkarni & Lloyd Fillion) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

5. Page 5, paragraph 5: We believe the real issue is that with counterflow plants, the

air from the mixing drum acts as secondary and tertiary air for the combustion

process which eliminates many of the organic compounds through combustion. This

point needs to be brought out. Further, is there data to support the statement that a

counterflow plant can process RAP at ratios up to 50% with little or no observed

effect on emissions? If not, the statement belongs in industry sales literature and not

in an EPA document.

2.4.8 Response to CAAP Plant Characteristics Comment Number 4 - It is unlikely that a

significant portion of the air from the mixing drum is used as combustion air for the
42

burners. Typically, the exit CO2 concentration from HMA stacks is around 4% indicating

that the combustion gases are only about 30% of the stack gas. The mixing of a

significant portion of the air from the mixing drum in the combustion zone of the burner

would quench the combustion and result in increased emissions of CO and uncombusted

hydrocarbons (THC). As a result it is also unlikely that a significant reduction in the

organic emissions results from the combustion process. With respect to the processing of

high percentages of RAP, several emissions tests of facilities processing RAP at ratios of

50% are used in the development of the emission factors. The statistical analysis

performed to evaluate the effect RAP percentage on emissions indicated that only the

condensible organic particulate was affected by the RAP percentage. However, the

squared correlation coefficient was only 0.11 (with a correlation of 1.0 being perfect)

indicating that the RAP percentage explained very little of the variability in the data.

2.4.9 CAAP Plant Characteristics Comment Number 5 (Ravi Nadkarni & Lloyd Fillion) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

5. Page 5, paragraph 5: Similarly, the comment about “improved thermal efficiencies”

begs the question of what is being compared to what and what is the degree of

improvement. The statement belongs in industry sales literature and not in an EPA

document.

2.4.10 Response to CAAP Plant Characteristics Comment Number 5 - While it is clear

that the report text on thermal efficiency compares currently designed plants to those of

earlier designs, it does not add information needed to characterize the industry with

respect to air emissions and was removed.

2.4.11 CAAP Plant Characteristics Comment Number 6 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

6. Page 7, paragraph 1: The statement that RAP with new aggregate and fresh asphalt

is used to “produce a high quality grade of HMA” is another salesmanlike statement. 

The point is that the HMA industry produces products to meet a specification. If the

specification requires the use of RAP, it is used; if not, RAP is not used. The point

you want to make is that the use of RAP does not impair the ability to meet the

specifications for certain grades of HMA since the specs might actually require that

RAP is used. Or is EPA implying that the industry used RAP when specifications

call for the use of only virgin materials?

2.4.12 Response to CAAP Plant Characteristics Comment Number 6 - The statement

was revised to state “new asphalt cement is added to produce HMA that meets the

required quality specifications”.
43

3.0 Development and Evaluation of Available and Derived Information

3.1 Deficiencies in EPA Method 204

3.1.1 CAAP Capture Efficiency Comment Number 1 - (Ravi Nadkarni & Lloyd Fillion) -

Commentors Summary Section C

Deficiencies in Method 204: Tracers were not used at Plant D because it met the

requirements of Method 204. Unfortunately, Method 204 is inadequate to achieve the

results it tries to achieve. Further, the contention that the estimate of unmeasured

emissions is an “upper bound” is incorrect. At Plant D, a mild ambient breeze was

sufficient to cause some of the fumes to escape from the top or the bottom openings in the

downwind door of the tunnel. Therefore, the size of the openings was decreased further

at the end of the first day of testing. This means that the Method 204 criterion of

maintaining over 200 fpm at a natural draft opening is not adequate. Note that 200 fpm is

less than 2.3 miles per hour, which is not much of a breeze. Therefore it is not surprising

that these criteria are inadequate to assure total containment within a TTE as

contemplated by method 204. 

Further, Method 204 has a more serious and fundamental problem. Although the size of

natural draft openings is specified, the method does not contain any criteria to ensure that

the emissions are pulled/sucked past the sampling point in a reasonable period of time. As

is well-known, residence time calculations, based on enclosure volume and fan capacity,

generally provide incorrect information by underestimating the time to evacuate the

enclosure because of channeling. At Plant D, the tunnel was not evacuated in the

approximately 15 second time gap between the final HMA drop and the opening of the

doors. This can be clearly seen in the fact that THC readings did not drop to zero before

the doors were opened. This fact was also observed visually inside the TTE enclosure

since SVOCs are visible. Thus, the report contains compelling evidence that the

collected sample had a low bias, not only because some emissions escaped through the

natural draft openings but also because these emissions did not travel to the sampling

point but were lost when the doors were opened.

Comments on Hot Mix Asphalt Plants Emissions Assessment Report

11. Page 13, paragraph 4: This paragraph is wrong in several ways. The capture

efficiency was measured and calculated using tracers; it was not “estimated” as

stated. To me, the word “estimation” denotes a weaker approach to quantification

than calculations based on actual measurements. Equally, important, the EPA

requirements for total enclosure were shown to be totally inadequate during the

testing at Plant D in Massachusetts. A mild breeze was sufficient to cause visible

emissions from the total enclosure even when a hand-held velometer showed that

Method 204 criteria were being met. Why is this factor, which suggests that Method

204 criteria were inadequate and that the measured emissions have a low bias, not

discussed in this paragraph?
44

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

45. Page 4-163, paragraph 3 - 5: We further find that the contention that the estimate of

unmeasured emissions being an “upper bound” to be unpersuasive and incorrect. 

Our reasons for saying so result from the inadequacies of Method 204. These were

outlined in Ravi Nadkarni’s letter of September 15, 1999. They are:

a. At Plant C, two precautions were taken to ensure that we could measure or

estimate the amount of organic fugitive emissions that did not reach the primary

sampling ports. The first was the use of sulfur hexafluoride tracer gas, and the

second was the use of impingement/deposition plates in the ducts which collected

organic particulates which would be deposited upstream of the sample port.

Although all the emissions did not reach the sampling ports (some was deposited

inside the tunnel and some was pumped out of the tunnel by ambient breeze or by

truck movement), the tracer gas enabled an estimation the VOC portion of this

loss. (As was pointed out during the planning, the tracer gas was a good proxy

only for non-condensible emissions but not for condensible emissions.)

At Plant D, a tracer gas was not used although requested by the citizens because

the TTE was constructed to meet Method 204 criteria, yet visual observations and

THC readings showed the following: 

b. An ambient breeze was sufficient to cause some of the fume to escape from the

top or the bottom openings in the downwind door of the tunnel. Therefore the

size of the openings was decreased further. This means that the Method 204

criterion of maintaining over 200 fpm at a natural draft opening is not adequate. 

Note that 200 fpm is less than 2.3 miles per hour, which is not much of a breeze. 

Therefore it is not surprising that these criteria are inadequate to assure total

containment within the TTE. We observed visible emissions of fume from the

entrance, further emphasizing that the Method 204 criteria are inadequate. 

c. Further, Method 204 has a more serious and fundamental problem. Although the

size of natural draft openings is specified, the method does not contain any criteria

to ensure that the emissions are pulled/sucked past the sampling point in a

reasonable period of time. As is well-known, residence time calculations, based

on enclosure volume and fan capacity, generally provide incorrect information by

underestimating the time to evacuate the enclosure because of channeling. Note

that Method 204 does not require a specific location for the natural draft openings,

a problem that was pointed out during the planning sessions. At Plant D, even

after the size of the opening was decreased, and the little pieces of colored tape at

the Natural Draft Openings were indicating airflow towards the inside of the TTE,

the tunnel was not evacuated in the approximately 15 second time gap between

the final drop and the opening of the doors. This can be clearly seen in the fact

that THC readings did not drop to zero even when the sample averaging time is

less than 1 minute. This fact was also observed visually inside the TTE enclosure
45

since SVOCs are visible. Thus, in the absence of a tracer gas, we have

compelling evidence that the collected sample had a low bias. For example, the

extended period test results in MRI-D-Table 4-4, show that final concentration did

not drop to zero but stayed between 1 ppm and 2.1 ppm . Yet, this low bias is not

mentioned anywhere in the report nor in Appendix B of the MRI Report which

contains the original data. These emissions did not reach the instrumentation but

were emitted to the environment causing a low bias.

3.1.2 Response to CAAP Capture Efficiency Comment Number 1 - There was no

indication during the testing at Plant D that EPA Method 204 was inadequate for

determining the ability of the enclosure to completely capture the emissions. The

individuals that opened and closed the doors of the enclosure also periodically observed

the tail tale streamers attached above the openings above and below the doors. At all

times when both doors were closed they noticed that the tail tales showed that air was

being drawn into the enclosure. Additionally, while it is stated that the citizen observers

present at the test observed visible emissions leaving the natural draft openings to the

enclosure, EPA was not advised of this until a meeting to discuss EPA’s draft responses

to comments on the test reports. Three EPA representatives were present at the test to

address and resolve these type of issues. If EPA were advised of the presumed

observations by the citizens, the cause could be investigated during the emission test. If it

were determined that the complete capture of emissions was being compromised,

corrective action would have been instituted.

The adequacy of EPA Method 204 criteria to assess whether the enclosure attained

essentially complete capture was addressed in the draft of the “Response to Comments on

Testing Program for Asphalt Plants C and D Report” submitted to commentors

previously. Response number 15 “THC Emissions During Extended Period Tests” in the

draft document was divided into two areas. The first area addressed the issue of the

capture efficiency at Plant D. The second area addressed the issue of additional

emissions following the load-out operation. In a meeting held in Boston on January 20,

2000, one point of discussion was EPA’s interpretation of Ravi Nadkarni’s comments. 

Based upon this discussion, EPA understood that the intention of Ravi Nadkarni’s

comments was not to question the capture effectiveness of the enclosure at Plant D since

it met EPA Method 204 criteria. As a result, EPA proposed to delete the first area of the

response. In the capture efficiency portion of the draft response, several evaluations were

presented that provided various estimates of the capture efficiency obtained by the

enclosure at Plant D. The text on the following six pages is reproduced from page 21

through 26 of the draft “Response to Comments on Testing Program for Asphalt Plants C

and D Report” submitted to commentors.
46

* * *

Capture Efficiency and Post Loadout Emissions

15. THC Emissions During Extended Period Tests

COMMENT: Several commentors (Nadkarni, Fillion, Toxics Action Center, Yatzyshyn,

Lynch) expressed concern over the determination of static emission rates (e.g., trucks sitting in the

yard) based on the Plant D extended period tests. As a related issue, the same commentors were

also concerned that holding the trucks for 15 sec following the final drop was not long enough,

and that some fraction of the emission was missed. Additional clarification on both of these issues

was requested.

RESPONSE: The commentors raise a valid concern that some portion of the emissions

may have been missed due to opening and closing of the TTE doors. This represents a situation

different from that in California, where tracer gases were used to determine capture. As discussed

earlier in Response 11, MRI insured that the TTE design did meet all necessary criteria to assume

100% capture. However, the commentors are correct in that the TTE was intended to allow trucks

to remain stationary until emission levels returned to baseline, which required 3 to 7 min as shown

by the extended period tests. Since this is clearly longer than the 15 sec allowed most of the

trucks, some accounting for the less than 100% capture efficiency was considered. Emissions due

to trucks sitting in the yard are also related to these calculations and are discussed below.

Capture Efficiency

Commentor Nadkarni performs a mathematical analysis of the data set to arrive at a factor

of 1.74, meaning that the measured emissions should be multiplied by 1.74 to arrive at the total

(Total = sum of measured + unmeasured). The basic approach presented by the commentor is one

of several of methods that seem reasonable. However, since the commentors calculations are

21

Figure 3. Excerpt from page 21 of the Draft “Response to Comments on Testing Program for

Asphalt Plants C and D Report.”
47

not clearly presented, calculations based upon the commentors approach have been performed as part

of this response, and a different value is presented.

Figures 2 and 3 show load-out data for two truck loadings during the Plant D testing. One of

the loadings was during Test 2 and logged 10-sec data points prior to the extended period test from

1333 to 1338. The second loading was during Run 3 and logged 1-sec data points for an entire

load-out cycle. These two data sets provide the only detailed data clearly showing both the load-out

cycle and the extended tail-off to the baseline. Thus, these two data sets can be used to estimate the

capture efficiency.

Measured emissions are represented by the area under the curve (integrated value) from the

beginning of load-out until the doors are opened (i.e., 15 sec after the final drop). Figures 2 and 3 are

marked with vertical lines at these times to provide clarity. It is believed that the commentor

determined what he called “unmeasured” emissions by integrating from the 15-sec mark until the

emissions return to baseline. The Extended Period column in Table 1 shows the results of this

integration.

Table 1. Estimate of Capture Efficiency Adjustment

Extended Period

(>5 min)

Typical Period

(30 sec)

Test 2 Data Set

Measured 

Unmeasured

Total

Capture Efficiency Adjustment Factor

18.14 ppm-min

7.66 ppm-min

25.8 ppm-min

1.42

18.14 ppm-min

1.80 ppm-min

19.94 ppm-min

1.10

Test 3 Data Set

Measured

Unmeasured

Total

Capture Efficiency Adjustment Factor

29.35 ppm-min

9.75 ppm-min

39.10 ppm-min

1.33

29.35 ppm-min

1.67 ppm-min

31.02 ppm-min

1.06

Thus, using the Extended Period (as used by the commentor), the above calculations show that

the estimated Capture Efficiency Adjustment Factor might be 1.33 to 1.42 (or a capture efficiency of

between 70% and 75%), rather than the 1.74 (capture efficiency of 57%) calculated by the commentor. 

Furthermore, these calculations are overly conservative (i.e., high) for three reasons:

a. Integration of a greater than 5-min tail-off period is not representative of actual plant

operations during the test. Under normal operating conditions, a truck left the load-out area

no more than 30 sec after the final drop. In fact, as the commentors noted, a high volume of

truck traffic forced MRI to shorten the waiting time to 15 sec during the actual

22

Figure 4. Page 22 from Draft “Response to Comments on Testing Program for Asphalt Plants C

and D Report.”
48

Figure 2. “Unmeasured Emissions” Integration

(Test 2, period 13: 33 - 13: 38)

23

Figure 5. Page 23 from Draft “Response to Comments on Testing Program for Asphalt Plants C

and D Report.”
49

Figure 3. “Unmeasured Emissions” Integration

(Test 3, 1 sec logging)

24

Figure 6. Page 24 from Draft “Response to Comments on Testing Program for Asphalt Plants C

and D Report.”
50

tests. Thus, the greater than 5 min period integrated above clearly over estimates load out

emissions. The greatest portion of what the commentors refer to as “unmeasured” emissions

would be better termed “yard emissions,” which are dealt with later in this section.

b. Almost all of the time periods between truck loadings were 2 min or less, and most were less

than 1 min. Thus, not all of the emission went unmeasured when the doors were opened and

closed around a new truck. In other words, not all of the lingering fumes were dissipated

when a new truck entered the TTE in quick succession. Some of the “unmeasured”

emission calculated above was actually measured as part of the next truck load-out and

therefore was double counted.

c. As discussed in Response 11, both Plant C and Plant D enclosures were very similar except

for the operating doors. The minimum measured capture efficiency for Plant C was 52%

during the background run when only two trucks were available and 61% during production

operations. One would expect that the addition of operable doors that significantly

improved capture during about 80% of the time would improve capture efficiency to 90 to

95% rather than the 70 to 75% as estimated by the commentor.

Evidence of better capture than estimated by the commentor can be seen in the presentations

of 1-min THC readings in Appendix B of the test report. Many times the drop in THC concentrations

between loadings is less than 1 ppm from a value of about 3 to 5 ppm. Sometimes there is no

perceptible drop in the THC concentrations between successive loading operations. The subsequent

loadings begin from one to two minutes after the end of the previous loading. Based upon this

information, one would expect the capture efficiency to be better than 90% {((6min*3ppm) +

(2min*2ppm))/(8min*3ppm) = 0.92}. For loading times longer than 6 min, higher loading

concentrations than 3 ppm, and shorter times between loadings than 2 min, the capture efficiency may

be as high as 98% {((8min*5ppm) + (1min*4ppm))/(9min*5ppm) = 0.98}.

Additional evidence of better capture efficiency can be made based upon the assumption that

the emissions from one complete drop out of seven is missed. This provides an estimated capture

efficiency of 85%.

Note also that the two integrated data sets were from load-outs of 6 drops (Run 2) and 8 drops

(Run 3). The lower factor (1.33) is from the 8-drop load-out. This makes sense since the measured

emission is greater for 8 drops. Truck-loading operations for Plant D used both drop rates frequently,

so an actual factor would fall somewhere between the two factors calculated.

A better method of estimating capture efficiency would be to select an interval more

representative of actual plant operations than the greater than 5-min period used above. Under normal

operations, a truck would not sit for more than 15 to 20 sec after the final drop before leaving the

load-out area. Additionally, the doors were open an equally short period to allow an empty truck to

replace the truck that was just loaded. Thus, an interval of 30 sec after the final drop can be used as a

representative time period and will give a biased low estimate of the capture efficiency. Data

presented in the table show that this method results in a biased high estimate for unmeasured emission

of 6% to 10%, and that the scaling factor would be from 1.06

25

Figure 7. Page 25 from Draft “Response to Comments on Testing Program for Asphalt Plants C

and D Report.”
51

 to 1.10 (capture efficiency between 91% and 94%). As discussed in items b and c above,

these estimates are also biased low due to multiple counting of emissions and comparison to

the capture efficiency testing at Plant C.

Although biased low, Capture Efficiency Adjustment Factors in the range of 1.06 to

1.10 appear to be the more representative of actual plant operations and test conditions

encountered than the commentors calculations. However, the analysis that follows for Yard

emissions indicates that other factors appear to overestimate emissions, therefore we did not

apply this adjustment to the data. Inclusion of the long tail-off period (emissions returning to

baseline) is not appropriate since these emissions are more realistically included as yard

emissions and will be described below.

* * *

26

Figure 8. Excerpt from Page 25 from Draft “Response to Comments on Testing Program for

Asphalt Plants C and D Report.”
52

This earlier, draft response indicates that, if commenters assertions are correct that

opening doors 15 seconds after loadout did release some load out emissions from the

enclosure before capture and measurement, the uncaptured and unmeasured release were

small (less than 10%). As the analysis is an extrapolation of only two data runs and the

enclosure was designed to Method 204 criteria, EPA believed that the actual uncaptured

emissions are most likely smaller than estimated by our analysis. Therefore, no further

adjustments were made to the loadout emissions from Plant D.

Although the capture efficiency for Plat C was based upon measurements and calculations

using a tracer, these measurements still provide an estimate of the capture efficiency of

the ventilation system during the emission testing. First, EPA Method 204 recommends

that sources to use lower 90% confidence level of the measured data as a safety factor for

demonstrating compliance with regulatory requirements. While the calculated lower 90%

confidence level capture efficiency for Plant C averaged 61.3%, the actual measured

capture efficiency averaged 67.9%. Second, as explained in item 60 on page 74 of the

Response to Comments on Testing Program for Asphalt Plants C and D Report, many

factors could contribute to variations in the correlation between what is measured from

the release of process emissions and the tracer gas emissions. Quoting from this report,

the first four items state:

“1. The tracer gas was released outside the edge of the tallest truck bed, whereas

actual emissions occurred generally from the entire bed area but primarily from the

center. Therefore, the tracer gas was not thoroughly mixed with the gas containing

the emissions.

2. The hot asphalt generated a buoyant stream that quickly rose to the ventilation

system. This buoyant stream contained a concentrated mass of the emissions,

whereas the tracer gas was injected toward the edge of this buoyant stream. 

Therefore, the gas containing the emissions would be captured better than the air

containing the tracer gas.

3. The asphalt was loaded intermittently with emissions (both visible and measured)

that peaked during the loading, decreased rapidly while the truck waited to be

released, and then tailed off slowly after the truck left. This is significantly different

than the constant continuous release of the tracer gas. Most of the visible emissions

were released during a very short period when the truck was stopped in the tunnel. 

The truck being loaded (and the next truck waiting to enter the tunnel) blocked the

movement of air through the tunnel, allowing for more effective capture of emissions

and tracer gas. If a truck were not in the tunnel, wind effects would lower capture

efficiency below the capture efficiency during actual load out. The tracer gas was

also being injected during the time that trucks were moving in the tunnel and when

there was no buoyant effect to help transport the tracer gas to the hood. The piston

effect of truck movement would create air movement across the whole cross-section

of the tunnel to draw the tracer gas away from the capture hood, thereby lowering the

measured capture efficiency. Higher load-out rates (trucks per period) would
53

exacerbate this situation and increase the differences in the capture of the emissions

and tracer gas.

4. Not only were the nozzles that injected the tracer gas at the edge of the gas stream

of the emissions, but they were splayed to inject the tracer gas from 45E below

horizontal to 45E above horizontal. For the majority of trucks, about 33% of the

tracer gas was injected down from a point even with, and about two feet from, the

upper edge of the truck bed. As a result, the capture of the tracer gas would be

diminished.”

While the design of the system to inject the tracer could not replicate exactly the release

conditions of the emissions, it was as close as could be achieved given the dynamic

nature of the load out process. The inability to replicate the release conditions results in

situations that predominantly underestimate the actual capture efficiency. The magnitude

of this underestimation cannot be determined and thus capture efficiency is considered an

estimate. To avoid confusion created by using the non-qualified term “estimated,” the

term “quantitatively estimated ” was used in the Emissions Assessment Report.

3.1.3 CAAP Capture Efficiency Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot

Mix Asphalt Production, June 2000 Draft

32. Page 4-150, paragraph 3: There are several fundamental issues here that need to be

explained. First, EPA argued for a long time that the tunnel at Plant C was adequate

to capture all the emissions, based on visual observations by EPA - which were

contradicted later by observations by the citizens. EPA reluctantly agreed to use

tracers only because the tunnel did not meet Method 204 criteria. (In discussion of

Plant D, We will discuss why Method 204 criteria are inadequate). Next, EPA

averaged the efficiency over several runs and used a single capture efficiency

correction. It was only after the citizens showed that capture efficiency varied during

the day, typically declining as the on-shore wind picked up as the land around the

plant heated up, that EPA agreed to correct data for the individual capture

efficiencies. Finally, the so-called correction for truck emissions, discussed later,

continues to be a sham. But that sham is not really discussed here when the quality

of data is being considered. See our comments with reference to page 4-152 below. 

Also, note that there is a typographical error in EMD GD-035 “ Guidelines for

Determining Capture Efficiency”. On page 9, in the formula for p in equation 7, xavg

value should be 100.8 not 110.8. The calculated value of p is correct, however. 

3.1.4 Response to CAAP Capture Efficiency Comment Number 2 - It is not clear what

information contained in the paragraph is incorrect and the commentor wants EPA to

revise. The commentors statements concerning EPA’s decision to use a tracer to

characterize capture efficiency are inaccurate. We had previously concluded that, with

doors open, Plant C enclosure did not meet EPA Method 204 criteria. We estimated that

the capture efficiency was between 70% and 90%. EPA’s decision to revise the

calculation of capture efficiency was based on our established criteria in the guidance
54

document “Capture Efficiency Testing Guidance” (EMC GD-035). This guideline

specifies that the lower 90% confidence level capture efficiency is to be used rather than

the average measured capture efficiency. The variations in the capture efficiency were

not germane in our decision to revise the calculation of the capture efficiency. The

addition of this information to the current information describing capture efficiency

adjustment is not needed. We agree that the intermediate value presented in equation 7 of

the example calculation on page 10 of the guideline document is a typographical error. 

As the commentor notices, the value for p that results from the calculation is correct. In

addition, the text preceding the equation presents the correct calculated value for term

used in the equation.

3.2 Compensation for Asphalt Temperature and Volatility

3.2.1 CAAP Temperature and Volatility Comment Number 1 (Ravi Nadkarni & Lloyd

Fillion) -

Commentors Summary Section C

Incorrect Approach in Compensating for Volatiles Content of Asphalt: The methods used

in these reports to correct for volatiles content of asphalt are contrary to the agreement

that was reached between the EPA and various citizen groups. The citizens had argued

that the asphalt specifications allow the use of asphalt with a much higher weight loss

compared to the asphalt used in Plant C and Plant D tests. The older AC specifications

allow for a 0.5% loss on heating, which can be waived by an engineer on site who can

then allow the use of an asphalt with up to 1% weight loss. The new Superpave

specifications allow for a 1% loss on heating and therefore represent a relaxation of the

previous AC grade standards. In view of this and the industry’s use of various additives

and diluents (which would increase the vapor pressure), the citizens argued and the EPA

agreed that maximum number of 0.5% should be used. Note that this was a compromise

since the newer specification allows the use of asphalt with twice that amount of

volatiles. This issue is particularly important since the measurements by State agencies

quoted here appear to be for asphalt prior to blending with additives, in spite of

suggestions to the contrary, in some cases. The EPA, by providing an equation where a

hypothetical RTFOT value can be plugged in, is encouraging misrepresentation by a

proponent of any new asphalt plant, who, once the permit is received, can then switch to

an asphalt with a different RTFOT value with impunity. 

As long as the specifications allow for up to 1% volatiles in asphalt (even before

additives are used), it is misleading for EPA to state that their approach in Appendix B -

Table 4-27 “encourages the use of site specific data”. The primary use of AP-42 is to

prepare calculations to get permits to build and operate hot mix plants. Therefore, there

is no site specific data that can be used other than fictional data. Unfortunately, the

industry has a long history of providing low-ball estimates, designed to fool the public

and get permits from agencies that are not particularly anxious to ask difficult questions.

Incorrect Substitution of Delivery Temperature for Loadout Temperature: The statement

that “325o F, which is the maximum load-out temperature recommended by industry” is
55

imprecise. Most specifications require this to be the maximum temperature at a job site

where HMA is to be spread and compacted. (The minimum temperature is 275o F.) The

maximum load out temperature is much more variable and can be higher if the plant is

producing asphalt for a distant job or for a small job, where there can be considerable

cooling of the HMA mass between loadout and delivery. 

Hot Mix Asphalt Plants Emissions Assessment Report

13. Page 14, paragraph 2: The statement that “325o F, which is the maximum load-out

temperature recommended by industry” is imprecise. Most specifications require

this to be the maximum temperature at a job site where HMA is to be spread and

compacted with rollers. (The minimum temperature is 275o F.) The maximum load

out temperature is much more variable and can be higher if the plant is producing

asphalt for a distant job or for a small job, where there can be considerable cooling of

the HMA mass between loadout and delivery. This same error is repeated in the last

sentence of the next paragraph and in many portions of Appendix B.

This paragraph also states that -0.5% was selected as a default value for weight loss

in a rolling thin film oven test. The methods used to apply the correction for

volatility are contrary to the agreement that was reached between the EPA and

various citizen groups. The citizens had argued that the asphalt specifications allow

the use of asphalt with a much higher weight loss. The older AC specifications

allow for a 0.5% loss on heating, which can be waived by an engineer on site who

can then allow the use of an asphalt with up to 1% weight loss. The new Superpave

specifications allow for a 1% loss on heating and therefore represent a relaxation of

the previous AC grade standards. In view of this and the industry’s use of various

additives and diluents (which would increase the vapor pressure) which are often

added after the asphalt has been sampled for the measurement of the weight loss, the

citizens argued and the EPA agreed that maximum number of 0.5% should be used

at all times. Note that this was a compromise since the newer specification allows

the use of asphalt with twice that amount of volatiles. This issue is particularly

important since the measurements by State agencies quoted here appear to be for

asphalt prior to blending with additives. The EPA, by providing an equation where a

hypothetical RTFOT value can be plugged in, is encouraging misrepresentation by a

proponent of any new asphalt plant, who, once the permit is received, can then

switch to an asphalt with a different RTFOT value with impunity.

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

14. Page 10, paragraph 2, 3: The comments here are a major problem. The methods

used to apply the correction for volatility are contrary to the agreement that was

reached between the EPA and various citizen groups. The citizens had argued that

the asphalt specifications allow the use of asphalt with a much higher weight loss

than that suggested by limited sampling. The older AC specifications allow for a

0.5% loss on heating, which can be waived by an engineer on site who can then

allow the use of an asphalt with up to 1% weight loss. The new Superpave

specifications allow for a 1% loss on heating. In view of this and the industry’s use
56

of various additives and diluents which would increase the vapor pressure after

sampling for the measurement of the weight loss, the citizens argued and the EPA

agreed that maximum number of 0.5% should be used at all times. Note that this

was a compromise since the newer specification allows the use of asphalt with twice

that amount of volatiles. This issue is particularly important since the measurements

by State agencies quoted here appear to be for asphalt prior to blending with

additives. The EPA, by providing an equation where a hypothetical RTFOT value

can be plugged in, in encouraging misrepresentation by a proponent of any new

asphalt plant, who, once the permit is received on the basis of a low RTFOT value,

can then switch to an asphalt with a different RTFOT value. This entire paragraph

has to be rewritten with -0.5% weight loss and 325o F or higher temperature.

Comments on Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot

Mix Asphalt Production, June 2000 Draft

39. Page 4-155, paragraph 2: The statement is that “The industry has stated that good

paving practices dictate that load-out temperatures in excess of 325o F should be

avoided.” Who has stated this and in what context? The specification for highways

is that hot mix temperature before the pavement is laid down should be between 325

and 275o F. Hot mix outside this temperature range can be rejected. The

temperature at load out depends on the distance between the plant and the location

where the new pavement is being laid and the size of the truck since smaller loads

will cool faster than larger loads.

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

43. Page 4-159 - 162: As discussed earlier, the entire loss on heating discussion should

be rewritten so that a RTFOT value of -0.5% is used in all cases. This way, the EPA

will not be providing yet another opportunity for builders of new plants to

misrepresent what might happen once the plant starts operating. The same applies

for the formulae which promote the use of variable temperatures.

3.2.2 Response to CAAP Temperature and Volatility Comment Number 1 - EPA does

not agree that we should present a single emission factor based upon the maximum

allowable asphalt volatility and maximum load-out temperature. Both the volatility (as

determined by the Rolling Thin Film Oven Test) and the HMA load-out temperature vary

with a number of parameters. EPA has obtained data showing a regional variation in the

volatility of asphalts used in road construction. EPA also has obtained information

showing that the storage and mixing temperatures for different asphalt binder grades are

different. Additionally, EPA recognizes that there are minimum delivery temperature

requirements for paving operations. Therefore, manufacturers will vary the load-out

temperature to accommodate transport times and ambient temperatures. EPA’s equations

provide a reasonable estimate of emissions when used with asphalt volatility and

temperature information determined by valid measurements. 
57

We recognize that the various citizens’ groups requested EPA to require the tested

facilities to use an asphalt with 1% loss on heating. Also, as we explained in the many

meetings preceding the tests, it should be recognized that EPA could not require HMA

plants to use 1% loss on heating asphalt during the emission tests. We also recognize that

the various citizens’ groups requested EPA to adjust the data to a 1% loss on heating as

an alternative to using an asphalt with 1% loss on heating. EPA’s analysis before the

emissions tests revealed that the adjustment to a 1% loss on heating is clearly not

supported by data collected by the Strategic Highway Research Program (SHRP)/National

Academy of Sciences (NAS). Additional data collected by EPA from selected State

Highway Departments, also does not support adjustment to a 1% loss on heating value. 

The limited data obtained from the State Highway Departments also supported a much

lower loss on heating value. The State Highway Department data also indicates that the

use of a single loss on heating value for all States or regions is not supported.

EPA’s commitment is clearly stated in item 4 on page 3 and in the third paragraph on

page 63 of the Response to Comments on Testing Program for Asphalt Plants C and D

Report. This commitment is that while emissions presented in the EA-Report would be

adjusted to 0.5% loss on heating for consistency, additional adjustments would be

recommended to accommodate local and State specific conditions. In March 2000, EPA

provided to all of the stakeholders 1) copies of all changed pages of the Plant C and D test

reports and 2) copies of all changed pages of the Response to Comments on Testing

Program for Asphalt Plants C and D report. EPA committed to change these pages as a

result of written and verbal comments from stakeholders. Specifically, page 3 of the

Response to Comments on Testing Program for Asphalt Plants C and D was included. 

EPA provided the stakeholders 30 days to review the changed pages to verify that EPA’s

commitments were properly reflected in the changed pages. There was no response from

any stakeholder.

As stated in Item 52 on page 62 through 65 of the Response to Comments on Testing

Program for Asphalt Plants C and D Report, less than 3% of the asphalts analyzed by the

SHRP/NAS nationally have a loss on heating greater than 1%. As shown in the test

reports for plants C and D, the earlier analysis method (used by SHRP/NAS) results in

loss on heating values about half the presently recommended RTFOT analysis method for

the same asphalt. The revised maximum loss on heating specifications is a recognition of

the differences between the previous analysis method and the presently recommended

RTFOT analysis method. The revised specification is not a relaxation of the standards for

asphalt.

RTFOT data provided by State Departments of Transportation and presented in Table 10

on page 64 of the Response to Comments on Testing Program for Asphalt Plants C and D

Report also show that adjustment to a 1% loss on heating using the presently

recommended test method is not supported. For four of the five States less than 0.0004%

of the asphalts analyzed would exceed the 1% loss on heating value. Only about 3% of

the asphalts obtained and analyzed by one state (Minnesota) would exceed the 1% loss on

heating value. As stated on page 63 of the Response to Comments on Testing Program
58

for Asphalt Plants C and D Report the value of 0.5% reflects the 99.99% upper

confidence level for the average loss on heating value obtained from the State of

Minnesota.

While EPA agreed to present data adjusted to 0.5% loss on heating for consistency, this

would not be appropriate for the remainder of the States shown in Table 10. For the State

of Massachusetts, only 1.5% of the 44 individual asphalts tested had a loss on heating

greater than 0.5%. For most pollutants and most situations, the average loss on heating

value is the most appropriate value to be used. However, some State Agencies may wish

to use an alternate value for estimating emissions to address specific conditions of interest

to them. This alternate approach could be based upon a statistical analysis of loss on

heating data representative of the specific locality rather than a maximum value allowed

by a product specification.

The commentors have made statements previously that diluents and additive are added at

the distribution terminal after the State Transportation Department has obtained samples

for analysis. However, as presented on page 64 of the Response to Comments on Testing

Program for Asphalt Plants C and D Report each of the State Department of

Transportation employees that provided the data on loss on heating indicated that the

samples obtained were to be used without further blending. We recognize that asphalt

distributors blend asphalts and include other additives so that the asphalt supplied to the

HMA plant meets the required specifications. However, there is no evidence that

indicates diluents are added following the collection of samples by the State Department

of Transportation. Furthermore, the loss on heating analyses of samples collected during

the pre-test survey and during the emission test of plant D compare very favorably with

the loss on heating analyses performed by the State of Massachusetts Department of

Transportation.

The equation presented in the report is not to be used with a hypothetical loss on heating

value as implied by the commentor. The report specifically states that without regional or

site-specific data for asphalt volatility, a default loss on heating value of -0.5% should be

used. In addition, if State permitting authorities are concerned that a source may switch

to asphalts that are significantly more volatile than what was stated in their application for

the permit, the State could include enforceable limitations in the permit to preclude this

switch. This enforceable limitation could be based upon a statistical analysis of loss on

heating data representative of the specific locality rather than a maximum value allowed

by a product specification.

We do not know of any specifications for maximum delivery temperature. However, as

shown on Figures 1 and 2, the Asphalt Pavement Environmental Council’s published

“Best Practices” brochure published on 4/00 provides guidance for controlling fumes,

emissions and odors from HMA plants and paving operations. The second side of the

brochure (Figure 2) includes recommendations for the range and midpoint temperatures

for both the storage of asphalt and the mixing of the HMA product. These temperatures

vary by the asphalt binder grades. The numbers in the binder grade are indications of the 
59

Figure 9. Asphalt Pavement Environmental Council, Best Practices Brochure, Side 1.

Reprinted with the permission of the National Asphalt Pavement Association.
60

Figure 10. Asphalt Pavement Environmental Council, Best Practices Brochure, Side 2.

Reprinted with the permission of the National Asphalt Pavement Association.
61

project-specific temperature extremes (in degrees centigrade) for which the asphalt

mixture is being designed. As such, a PG82-22 grade asphalt is intended for use when

average 7-day maximum pavement design temperature is 82E C (179E F) and the

minimum pavement design temperature is 22E C (-8E F). The midpoint HMA Plant

Mixing temperatures range from 264E F to 315E F. As shown on in Figure 2, the highest

HMA mixing temperature is associated with a binder used for the most severe

temperature conditions.

In addition, in a letter dated September 14, 1999 commenting on the Hot Mix Asphalt

Emissions Tests and Report for “Plants C & D” sent to Robert McConnell of EPA

Region I by Massachusetts State Senator Stephen F. Lynch, a copy of the Massachusetts

Highway Department 1995 Standard Specifications for Bituminous Materials was

attached. The standard includes three separate maximum temperatures measured at the

production facility. The maximum temperature standard for drum mix plants is 163E C

(325E F) measured at the point where HMA is loaded onto the hot mix conveyor (see

page III.25 Paragraph I). For batch mix plants there are two maximum temperature

standards, one for HMA containing RAP and one for HMA without RAP. The maximum

temperature for HMA containing RAP is 150E C (302E F). HMA that does not include

RAP is allowed to have a maximum temperature of 190E C (374E F).

The 1995 standard specifications provide no explanation for why there are three different

maximum production temperatures. However, process differences in batch mix and drum

mix plants do provide a reasonable rationale for why there would be differences in

achievable temperatures based upon the target temperature and RAP content of the

predominant product. Drum mix plants make and store multiple loads ahead of their

customers need for a given product. With relatively long production runs, they can

change the new aggregate temperature to accommodate the temperature and percentage of

RAP for that product. As a result, the production temperature can be the same despite the

type of product or the ratio of RAP required. On the other hand, batch plants store

sufficient preheated and screened aggregate for two to four truck loads of HMA. 

Therefore, any changes in aggregate temperature must be anticipated at least two

transport trucks in advance and there is little capability to change aggregate temperatures

for every product specification. As a result, it would be difficult for a batch plant to

concurrently produce HMA with and without RAP and meet the same temperature

requirements. It is believed that most batch mix facilities would heat the new aggregate

to the temperature requirements of the predominant product but within a range that is also

acceptable for production of the other products. As a result, for the more typical case

where the predominant product includes RAP, products which do not contain RAP will

be at a higher temperature. For example, a batch mix plant with a predominant product

which contains 10% RAP at the maximum load-out temperature of 150E C (302E F)

would heat the new aggregate to approximately 165E C (330E F). As a result, when a

customer requests HMA without RAP, the load-out temperature will be 165E C (330E F). 

The statements with respect to the maximum recommended load out temperature are

sufficiently accurate. Therefore, the use of a default temperature of 325E F is a

reasonably high default value to accommodate all but the most extreme conditions.
62

3.2.3 CAAP Temperature and Volatility Comment Number 2 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

23. Table 14: This table has to be redone so that an actual emission factor is given; not a

formula for calculating low emissions based on fictitious values of asphalt volatility.

3.2.4 Response to CAAP Temperature and Volatility Comment Number 2 - Many other

Sections of AP-42 employ equations to improve the precision of emission factors when

there are documented characteristics which are readily available for use to develop a

regionally or locally specific emission factor. Some examples are paved and unpaved

roads, surface coal mines, wind erosion, and several emission factors for fuel combustion. 

The table presents formulas that allow emissions to be calculated based upon measured

(not fictitious) parameters representative of the regional or site specific conditions. In the

December 17, 1999 draft and the May 2000 final version of the Response to Comments

on Testing Program for Asphalt Plants C and D Report, the adjustments for the volatility

and load out temperature were specified. The basis of these adjustments is clearly

documented in the text and tables in response numbers 52 and 53. While the equations

are different in appearance from that presented in response numbers 52 and 53, the

equations implement the tabular values for the adjustments presented.

3.2.5 CAAP Temperature and Volatility Comment Number 3 (Ravi Nadkarni & Lloyd

Fillion) -

Hot Mix Asphalt Plants Emissions Assessment Report

14. Page 14, paragraph 3: EPA again makes the same recommendation which is to

assume that the load out temperature can never exceed 325o F. This is incorrect. For

example, Mr. Webster, the industry expert who has attended many of the

EPA/citizen group/industry meetings has looked at the photographs that Ravi

Nadkarni submitted to the EPA in 1994 and are in the EPA files. His comment was

that the photos were typical of a plant loading out material at a high temperature

when supplying small contractors. If this practice is common enough to be readily

identified at a glance, EPA’s comments about 325o F being the maximum

temperature under all conditions are wrong and need to be corrected.

3.2.6 Response to CAAP Temperature and Volatility Comment Number 3 - The

statement is correct. At the time the citizens, EPA and industry agreed to request the

facilities tested by EPA to target a load-out temperature of 325E F, the industry stated that

this temperature was their best practices’ recommendation. While a facility may target a

specific load-out temperature, variations in storage time and some characteristics of the

aggregate and RAP may cause small variations in the actual load out temperature. It is

expected that temperature variations at batch mix plants would be greater than at drum

mix plants. This is because batch mix plants generally do not store HMA product. 

However, they store aggregate heated to the desired temperature for their projected

principal product. Using the previous example, if the principal product was HMA

containing 10% RAP with a desired load-out temperature of 302E F, the new aggregate

would be stored at about 330E F. If a single load of HMA with no RAP was required, the
63

load-out temperature for that load would be about 330E F. Based upon these two

temperatures, for load-outs of equal amounts of these two materials, the HMA with no

RAP would have emissions that are about twice the emissions of the HMA with RAP. 

Because of the difference in these emissions, the visual appearance of these two load-outs

would be markedly different. It is believed that this is the type of situation described to

Ravi Nadkarni by Mr. Webster. This type of situation occurred during emissions testing

at Plant D about 10% of the time. It is expected that the situation described by the

commentor would occur at about the same percentage of time. However, batch mix

facilities that routinely produce significantly more than about 10% of their product

without RAP should accommodate the emissions differences by adjusting the average

load-out temperature used in the emission estimation equation.

3.3 Adjustment for Background Truck Operation Emissions

3.3.1 CAAP Background Emissions Comment Number 1 (Ravi Nadkarni & Lloyd

Fillion) -

Commentors Summary Section C

Improper Manipulation of Data from the “Background” Test, Run 4, at Plant C: The

report states correctly: “The most reliable method to adjust for emissions measured

during background operations would be to separately adjust each run for the measured

capture efficiency and then subtract these adjusted background emissions from the

adjusted emissions measured during production operations.” However, because this

“procedure produces negative values for both the PM and MCEM and many other HAP

compounds”, a new unsound procedure is adopted because it gives results that please

EPA and industry by showing low but positive emissions. This new procedure is to use

background emissions uncorrected for capture efficiency. If the actual emissions have to

be corrected for capture efficiency because the enclosure does not capture all the

emissions, there is no justification for ignoring the capture efficiency for the background

run. Having used this incorrect analysis, the authors then have the temerity to advise us

that this result might even have a “high bias” relative to the correct method mentioned

above. 

The report justifies this faulty procedure because this situation “cannot be accommodated

retroactively.” This statement is not correct. The best way to eliminate improper data

manipulation is to discard the phony background adjustment and report the data as that

from loadout plus truck exhaust. Since silos always dump hot mix into a truck, these

combined emissions are present at each silo loadout point. Further, in the unlikely event

that a local permitting authority requires inclusion of truck exhaust emissions (unlikely

because we have not seen such calculations associated with any local permitting

requirements), note that the truck spends about 1⁄2 minute under the silo but many more

minutes, typically 3 to 8, on site. As a result, the truck emissions that are included under

loadout correspond to the 1⁄2 minute portion. Therefore, the double counting of truck

exhaust emissions would be minimal and can be adjusted for by subtracting the 1⁄2 minute

from residence time of the truck on site.
64

Overall, the background run demonstrates how data collection was manipulated to

produce biased results. The EPA Project Officer was interested in recording a high

background and the original data showed that he was able to manipulate truck placement

near the entrance of the tunnel in such a way that uncorrected emissions in the second half

of the run were about twice the emissions in the first half. If these emissions are

corrected for the lower capture efficiency in the second half of the run, the corrected

emissions from the second half are almost three times the corrected emissions from the

first half. In spite of using the emissions from the first portion of the background run, it

appears that they were still too high when corrected for capture efficiency and resulted in

negative or zero emissions to the environment.

Commentors Summary Section C

Unexplained Differences Between MCEM and TOC: The comparison of Plant C and

Plant D results shows a wide variation between emission rates for MCEMs and TOC. 

MCEM PMs and TOC are generated the same way and from the same source. Therefore,

if MCEM generation is a function of loadout time, TOC generation should also be a

function of loadout time and TOC emissions should be higher for a batch plant in the

same ratio. The report does not explain this discrepancy. Of course, the comparison is

further complicated and made meaningless by the bogus “background” correction for

drum plants discussed earlier. To eliminate the confusion, separate emission factors

should be prepared for batch and drum plants in all cases.

Comments on Hot Mix Asphalt Plants Emissions Assessment Report

12. Page 13, paragraph 5: This paragraph discusses the subtraction of “background

emissions”, which reduced the calculated loadout emissions significantly. Our

detailed comments are in our page-by-page discussion of Appendix B, which show

that the method used is totally without foundation or theoretical support, and the only

excuse for using it is that it gives non-negative results in several cases.

3.3.2 Response to CAAP Background Emissions Comment Number 1 - The background

adjustment was appropriate. There was no improper manipulation of the data from the

background test at Plant C and EPA did not manipulate the placement of the trucks to

obtain higher uncorrected emissions for the background run. Further, we do not agree

that the background run demonstrates that data was manipulated to produce biased results

and do not believe that concurrently measured truck exhaust and road dust emissions

should be included in the emission factor for load-out emissions.

As stated in Appendix B (AP-42 Background Report) and in item 51 on page 56 through

61 of the Response to Comments on Testing Program for Asphalt Plants C and D Report,

the background adjustment was performed to accommodate the emissions from the

operation of the trucks within and near the enclosure. The information presented on

pages 56 through 61 of the Response to Comments on Testing Program for Asphalt Plants

C and D Report shows that the emissions measured during the background run agree

reasonably well with published data for diesel engine emissions. This is also explained in

Section 3.3.6 of this response. As explained in Section 3.3.6, the truck drivers were
65

instructed to operate their trucks (including the placement prior to entering the tunnel and

placement to simulate loading) as they did during normal operation. The only additional

instruction provided to the truck drivers during the background test was to reduce the

time of their travel from the exit of the tunnel to the arrival at the tunnel entrance. 

During the emission test at Plant C, Dr. Nadkarni observed the operation of the trucks

during the background run. The issue of manipulating the placement of the trucks was

not raised by him during the test to either of the EPA personnel present.

The differences in THC concentrations recorded for the first and second half of the

background run do not indicate that either truck placement or data were manipulated. At

about the time trucks began driving faster to reduce gaps between trucks, the wind speed

increased. This may have caused an increase in the diesel exhaust that entered the tunnel

entrance or increased the capture of the diesel exhaust of the truck that was inside the

tunnel. Given that the THC concentrations during the background run were low, the

differences in concentrations appear more significant.

Commentors raised concerns with the calculated average background THC concentrations

at a stakeholders meeting to discuss EPA’s draft document “Response to Comments on

Testing Program for Asphalt Plants C and D.” At the meeting, commentors raised

concerns with the differences between the first and second half of the background test run

suggesting the second half run measured emissions from two trucks; one in the tunnel and

one waiting at the tunnel entrance. While EPA disagreed with the commentors

assertions, we agreed to use only the first half run data (0.83 ppm) in lieu of the average

of the entire run (1.2 ppm) to determine the background concentration to be used in

adjusting for background concentrations that were attributed to truck engine emissions. 

This change of background concentration lowered the THC background adjustment from

9.7% to 6.7% of the capture efficiency adjusted THC emissions. If the background

concentration of 0.83 ppm were adjusted for the 45% capture efficiency for Run 4, the

background adjustment to the THC emission factor calculation would be 1.84 ppm. 

Adjusting for capture efficiency would have resulted in a 14.5% reduction of THC

emissions compared to the 6.7% reduction used by EPA.

Publishing load-out emission factors, which includes diesel exhaust and road dust

emissions as the commentor suggests does not address diesel exhaust or road dust

emissions. These emissions were excluded since more comprehensive methods to

calculate these emissions are available in other parts of AP-42. Specifically, mobile

source factors are available for different engine type by milage and year of production and

fugitive dust emission factors are available that accommodate the type and dustiness of

the road surface. Excluding emissions not related to load-out operations isolates the

emissions of concern, precludes future double counting emissions and precludes other

improper manipulation of emissions data.
66

3.3.3 CAAP Background Emissions Comment Number 2 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot

Mix Asphalt Production, June 2000 Draft

35. Page 4-152, paragraph 3: This paragraph presents a major problem in this report. 

The second line states correctly: “The most reliable method to adjust for emissions

measured during background operations would be to separately adjust each run for

the measured capture efficiency and then subtract these adjusted background

emissions from the adjusted emissions measured during production operations.” 

However, because this “procedure produces negative values for both the PM and

MCEM and many other HAP compounds”, a new unsound procedure is adopted

because it gives results that please EPA and industry by by showing low but positive

emissions. This new procedure is to use background emissions uncorrected for

capture efficiency. If the actual emissions have to be corrected for capture efficiency

because the enclosure does not capture all the emissions, there is no justification for

ignoring the capture efficiency for background.

Having used this incorrect analysis, the authors then have the temerity to advise us

that this result might even have a “high bias” relative to the most correct method

mentioned above. In a very narrow sense, this comment might be correct, but in the

current context, given the consistent efforts of the Project Officer to bias the results

to favor industry, this comment is totally off base. 

Line 5 states that this situation “cannot be accommodated retroactively.” This

statement is not correct. The best way to eliminate improper data manipulation is to

discard the phony background adjustment and report the data as that from loadout

plus truck exhaust. Since silos always dump hot mix into a truck, these combined

emissions are present at each silo loadout point. Further, if a local permit application

requires the inclusion of an estimate for truck emissions on site (and we have yet to

see a local permit that requires this), note that the truck spends about 1⁄2 minute under

the silo but many more minutes, typically 3 to 8, on site. As a result, the truck

emissions that are included under loadout correspond to the 1⁄2 minute portion. 

Therefore, the double counting of truck exhaust emissions would be minimal and can

be adjusted for by subtracting the 1⁄2 minute from residence time of the truck on site.

We strongly recommend that Tables 4-25 and 4-26 be revised to reflect this

approach.

3.3.4 Response to CAAP Background Emissions Comment Number 2 - The goal of the

test program and the document being commented on was to develop emission factors for

publication in AP-42 for the various criteria and hazardous air pollutants resulting from

truck loading and silo filling. Emission factors for specific process operations reduce the

possibility of inappropriate and inconsistent manipulation of emissions to satisfy the

differing State and local requirements for permit and inventories. Different methods are

used by some states to evaluate and control fugitive, mobile source and point source

emissions which occur within a facility.
67

Since emission factors for diesel truck tailpipe emissions and for paved and unpaved road

emissions are available elsewhere, emissions sources may satisfy some States request to

segregate these emissions. A known example of this occurs with unpaved and paved road

emission factors. Both emission factors include the vehicle tailpipe emissions since they

were not accommodated in the emission tests that provide the supporting data for the

emission factors. EPA, and many State and local agencies subtract the estimated tailpipe

emissions as calculated with the emission factors for the type of vehicle generating the

fugitive emissions. This is reasonable for situations where the driving conditions of the

vehicles are similar to the Federal Test Procedure for motor vehicles. However, in some

situations (such as low load and mild acceleration conditions) this adjustment would over

correct the emissions estimate. This latter situation is a distinct possibility for the

combined load-out, diesel exhaust and fugitive dust emissions described in this comment.

Emissions for many pollutants measured during the background run agreed reasonably

well with information published by EPA’s Office of Transportation and Air Quality and

in two journal articles for diesel emissions. It should be noted that additional information

is being developed by EPA and others to better characterize diesel engine emissions for a

wider variety of engines. Many AP-42 emission factors are revised from time to time to

reflect improved information and changes that may occur due to improvements in

emissions control. For diesel engine emissions, this is highly probable. Many diesel

engine manufacturers are developing revised engine designs and exhaust controls. These

revisions could potentially result in a significant reduction of diesel engine emissions.

The availability of separate emission factors for individual, distinctly different processes

allow State and local agencies to more effectively meet the individual requirements of

their programs. Additionally, separate emission factors eliminate the possibility for

inconsistent and erroneous adjustments to the composite emission factor for truck

load-out.

There are several justifications for not adjusting the background emissions for the

measured capture efficiency as part of the process for isolating the load-out emissions

from the composite emissions measured. First, it is evident that most of the visible

particulate emissions were from the load-out operations and relatively little came from

road dust and truck exhaust. Correcting the background emissions for the measured

capture efficiency resulted in background particulate that exceeded the capture efficiency

corrected emissions measured during the production tests. In addition, the capture

efficiency corrected background organic particulate emissions (MCEM) were 99.5% of

the capture efficiency corrected emissions measured during the production tests. This is

clearly contrary to the observed situation. Since only two trucks were available during

the background run, the entrance to the tunnel was obstructed less than half the time by a

truck waiting to enter the tunnel. During the production tests, the tunnel entrance was

obstructed over 90% of the time. The lack of obstruction allowed the prevailing winds to

scavenge the tracer gas away from the capture hood and result in poorer capture of the

tracer than would occur otherwise. Without the thermal lift created by the hot asphalt, the

tracer was not drawn into the capture hood like during the production runs. And lastly,
68

excluding the capture efficiency adjustment would tend to understate the significance of

the road dust and truck exhaust and provide a moderate and acceptable safety factor to the

truck load-out emissions.

The adjustments to the data were reasonable. As stated above, the modification of the

method used to adjust the composite emissions measured during the production periods

provide at most a moderate safety factor to the truck load-out emissions while resulting in

adjusted emissions that agree to the situations observed during the emissions tests. 

Further, published emission factors for diesel exhaust use the number of vehicle miles

traveled and not on the time of operation. Adjusting road dust and diesel exhaust

emissions for the time period or distance trucks’ travel introduces additional complexities

into calculating emissions for a facility and for an area. The availability of separate

emission factors representing only truck load-out emissions will allow State and local

agencies to meet multiple individual requirements with a minimum of inconsistent and

potentially erroneous adjustments to the composite emission factor for truck load-out.

3.3.5 CAAP Background Emissions Comment Number 3 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot

Mix Asphalt Production, June 2000 Draft

36. Page 4-152, paragraph 4: This paragraph further demonstrates the problems with

EPA’s background run. The EPA project officer was interested in recording a high

background and the original data showed that he was able to manipulate truck

placement in such a way that uncorrected emissions in the second half of the run

were about twice the emissions in the first half. If these emissions are corrected for

the lower capture efficiency in the second half of the run, the corrected emissions

from the second half are almost three times the corrected emissions from the first

half. This further points out the problems with EPA’s manipulation of and

placement of trucks to maximize exhaust emissions inside the tunnel. 

We have to apologize for not taking this particular analysis far enough a year ago

during a review of the Plant C draft. When the data for Run 4, the background run,

was reviewed, it was clear that there was data manipulation going on since the raw

data showed that emissions in the second half of the run were double those in the

first half. When these emissions were adjusted for capture efficiency, the emissions

from the second half almost tripled. We felt that the data from the first half of the

run was more appropriate than that from the second half. We did not realize that this

data, after correcting for capture efficiency, still overwhelmed and negated the load

out emissions and was therefore also tainted. 

3.3.6 Response to CAAP Background Emissions Comment Number 3 - Differences

between the THC measured during the first and second half of the background run cannot

be fully explained without some conjecture. However, there was neither manipulation of

the truck placement nor manipulation of the data. As explained in response number 41 of

the “Response to Comments on Testing Programs for Asphalt Plants C and D” document,
69

we instructed the two truck drivers used during the background run to replicate normal

operations as much as possible. This included, the location where they stopped before

entering the tunnel and the time and location within the enclosure to simulate loading. 

During normal production, there was almost always a truck parked about two to four feet

from the tunnel entrance waiting for a signal to enter the tunnel for loading. Since only

two trucks were available for the background run, the tunnel entrance was blocked

between 20 and 70 percent of the time. The remainder of the time was required for a

truck to exit the tunnel, circle the plant and return to the tunnel entrance. At about the

midpoint of the background run, the truck drivers were asked to drive a little faster to

return to the tunnel entrance quicker. As a result, the last half of the background run

approximated normal operations more closely than the first half. In addition to increasing

the time the tunnel entrance was blocked by a truck, the wind appeared to increase in

velocity during the second half of the background run. During the tests during

production, generally the emission testing was complete by the time the wind velocity

increased.

While the commentors compare the differences in THC emissions between the first and

second half of the background run, they fail to notice that the first and second half

background emissions are only 10 and 20 percent of the emissions during production. In

addition, by adjusting only the production runs for capture efficiency, the correction for

background emissions for all pollutants is minimized. Contrary to the statement by the

commentors, few background corrections overwhelmed or negated the emissions

measured during the production runs. The above corrections of 10 to 20 percent for THC

are comparable to the background corrections for most other pollutants. There are

explanations for the few instances where there was a significant background correction

for a pollutant. For example, the non-MCEM particulate matter is probably fugitive dust

generated from the roadways approaching and within the tunnel. Additionally, emissions

of chlorinated hydrocarbons (Methylene Chloride, Tetrachloroethene, 1,1,1 -

Trichloroethane, Trichloroehtene etc.) would not be expected from asphalt.

In addition, the commentors ignore the comparison of mass emissions measured during

the background run with the published emission rates from diesel trucks made in response

number 51 of the “Response to Comments on Testing Programs for Asphalt Plants C and

D” document and specifically in Tables 7 and 8 in this document. The last paragraph on

page 57 and the first full paragraph on page 59 of this document summarizes the

comparisons. The last sentences of the paragraph on page 57 states, “The uncorrected

emissions measured during the background run was 0.66 g/min for THC, 1.2 g/min for

CO, and 0.54 g/min for PM. Except for PM, these agree very well with the estimated

emissions from AP-42. It should be noted that the fugitive PM emissions are not

accounted for in the above comparison.” And the last sentences of the paragraph on page

59 states, “For all but four compounds, the emission rate during the background run was

lower than presented in the articles. For these four compounds, the emission rate was

within a factor of two of the rates presented in the articles. More background run

compounds do not compare more favorably to the emission rates presented in the articles
70

because the Federal Test Procedure begins with a cold start and the acceleration

requirements are greater than the truck accelerations used during the test.”

3.3.7 CAAP Background Emissions Comment Number 4 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

56. Table 4-23, 4-25: In view of the comments earlier about the background run, these

tables need to be revised.

3.3.8 Response to CAAP Background Emissions Comment Number 4 - Based on EPA’s

response to comments in Section 3.3.6, the tables were not changed.

3.3.9 CAAP Background Emissions Comment Number 5 (Ravi Nadkarni & Lloyd

Fillion) -

Hot Mix Asphalt Plants Emissions Assessment Report

17. Page 16, paragraph 1: How do the truck exhaust emission factors published by EPA

compare with the background measurement from Run 4 at Plant C? Why is such a

comparison missing from the entire report?

3.3.10 Response to CAAP Background Emissions Comment Number 5 - A comparison

of the background measurement from Run 4 at Plant C was compared to the truck exhaust

emission factors published by EPA and others were presented on pages 57 to 59 and in

Table 8 in item 51 of the Response to Comments on Testing Program for Asphalt Plants

C and D Report. While the acceleration conditions for the trucks during Run 4 are less

severe than during conditions use to develop EPA published truck exhaust emission

factors, the emissions agreed reasonably well. A comparison is not made in this report

since the validity of the test results is independent of other measures of diesel truck

emissions by others.

3.3.11 CAAP Background Emissions Comment Number 6 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot

Mix Asphalt Production, June 2000 Draft

33. Page 4-151, paragraph 2: Note that Cambridge Environmental has calculated the

cooling of a mass of HMA. Their results are not supported by any measurements. 

3.3.12 Response to CAAP Background Emissions Comment Number 6 - It is not clear

how the calculations made by Cambridge Environmental relate to this paragraph. In

addition, the emission factor developed for the period following load-out account for only

the first eight minutes following load-out and do not account for any cooling of the hot

mix asphalt in the transport truck.
71

3.4 Assignment of Quality Ratings

3.4.1 CAAP Quality Ratings Comment Number 1 - (Ravi Nadkarni & Lloyd Fillion) -

Commentors Summary Section C

Inconsistent Assignment of Ratings: In one portion of the report, the emission factor for

sulfur dioxide was assigned an E rating because the data ranged over an order of

magnitude. This might have been simply the result of the variation in sulfur content of

the fuel. In the case of filterable PM, the range is over two orders of magnitude but the

emission factor got an A rating

Comments on Hot Mix Asphalt Plants Emissions Assessment Report

7. Page 12, paragraph 2: Is the rating system applied consistently? The discussion in

Appendix B indicates that it was not.

3.4.2 Response to CAAP Quality Ratings Comment Number 1 - The emission factor

rating system was applied consistently. The discussion in Appendix B Section 3 includes

a synopsis of the emission factor rating system. More detail is included in the reference

cited at the end of Section 3. The commentor may be confusing the between source

variations of the supporting data as the basis for the emission factor rating. While

characteristics such as the variability of the supporting data may be used to adjust the

emission factor rating, the primary criteria for assigning the emission factor rating are the

quality of the supporting emission test data, the representativeness of the facilities tested

to the source category and the number of facilities tested.

3.4.3 CAAP Quality Ratings Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Hot Mix Asphalt Plants Emissions Assessment Report

9. Page 13, paragraph 1: The quality rating needs to be quantified so that one can get a

numerical feel for the differences in ratings. If, as stated, the quality ratings are a

“function primarily of the number of data points”, these various quality ratings can

be related to the standard error of estimate and using t-values, a range can be shown

about the mean.

3.4.4 Response to CAAP Quality Ratings Comment Number 2 - As stated, the emission

factor quality ratings are related to the number of data points used to develop the emission

factor. As such, the rating is primarily an indicator of the robustness of the emission

factor. For example, an emission factor that is likely to change significantly with the

addition or deletion of data would be rated low. Whereas, an emission factor that is not

likely to change significantly with the addition or deletion of data would be rated high. 

Information on the variability of the data supporting the emission factors are presented in

an appropriate location when sufficient supporting data are available to provide a

reasonable estimate of the variability.
72

3.4.5 CAAP Quality Ratings Comment Number 3 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

11. Page 3-3, final paragraph: The comments here refer to variations or fluctuations in

measured results which could not be explained readily. While we agree that such

results might be given a lower rating, in many cases, variations are a normal part of

the production process. For example, if a batch plant is producing a mix with a high

RAP content, the crushed stone is heated to a high temperature to provide the heat

for evaporation of the moisture associated with RAP stored in the open. If another

customer comes in for a RAP-free mix at this stage, the hot mix will be loaded out at

a much higher temperature and will emit more than the usual amount of fugitive

organics. This is a normal transient.

3.4.6 Response to CAAP Quality Ratings Comment Number 3 - The point of the

comment is not clear. The paragraph on page 3-3 is addressing the criteria used to

evaluate source test reports for sound methodology and adequate detail. As stated in the

paragraph if the test results have a high variation without process information that may

explain the high variation, the source test is downrated. While one could assume that

undocumented process variations were the cause of the variation in emissions, facilities

generally monitor their process closely during emissions tests. While the information

monitored may not be documented in the source test report, a source test run is not begun

until the process is operating within the normal variation and source test runs are stopped

when the process begins operating out on normal. It is recognized that variations are a

normal part of the production process. It is also recognized that there will be a normal

variation in the emissions of a facility. However, when the emission variation for one

source test is significant compared to data from multiple facilities, it is likely that the

variations are an indicator of the quality of the source test contractor. The example the

commentor gives would result in short term variations in emissions. However, the

emission tests cited in the background report for the batch mix facility were conducted

over six or more hours. Although most of the HMA produced during the test included

10% RAP, approximately 15% of the HMA produced had no RAP. It is recognized that

the short term variations that may occur with this situation are normal for this process and

the source test was not downgraded because of the variations.

3.4.7 CAAP Quality Ratings Comment Number 4 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

11. Page 3-3, final paragraph: There are many factors which contribute to the emissions

which were not measured. For example, SO2 emissions from combustion are

dependent on sulfur in the fuel. The emission factors for different fuel types are a

result of the maximum sulfur content allowed under the fuel specifications. No such

analysis is presented. The same comments hold true for organic fugitive emissions

being dependent on volatile content of the asphalt.
73

3.4.8 Response to CAAP Quality Ratings Comment Number 4 - It is agreed that there

may be many factors which might contribute to differences in emissions which were not

measured. However, if the information is not presented in the test report, an analysis

cannot be performed. The vast majority of the emission tests used to develop the

emission factors were obtained from the source test files of State and local air pollution

control agencies. As a minimum, these source tests contain the information the State

agency requires for determining compliance with applicable emission standards for the

facility. As indicated in the summaries of the over 350 test reports reviewed for this

section, additional information that would be helpful to evaluate a number of process

variables were not available in most of the source test reports. Specifically for SO2, there

were very few source test reports for oil fired HMA plants. In addition, the fuel usage

and fuel analysis for the fuel was not available for all of the oil fired tests. Therefore, a

detailed analysis was not possible. However, the industry has supplied 14 source test

reports for SO2 which include fuel usage and sulfur analysis. These tests were evaluated

to determine whether there was any relationship between the sulfur in the fuel and SO2

emissions. Because of a variable reduction of the SO2 emissions, no relationship between

SO2 emissions and the more typical parameters (fuel sulfur content, fuel usage, control

device temperature) that affect SO2 emissions could be found. With respect to the

availability of the volatile content of the asphalt used during emissions testing, if this

information were included in any of the over 350 kiln stack test reports it was not noticed

during the review of the source test reports and generally State Agencies do not require

this information to be collected during compliance tests.

3.4.9 CAAP Quality Ratings Comment Number 5 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

15. Page 4-122, paragraph 4: This paragraph states that the emission factor for sulfur

dioxide was assigned an E rating because the data ranged over an order of

magnitude. This might have been simply the result of the variation in sulfur content

of the fuel. In the case of filterable PM (page 4-118), the range is over two orders of

magnitude but the emission factor got an A rating. A little consistency would help.

3.4.10 Response to CAAP Quality Ratings Comment Number 5 - The assignment of the

emission factor ratings is consistent. The paragraph does not state that the sole reason for

assigning an E rating to the emission factor for sulfur dioxide for #2 fuel oil fired drum

mix dryers was the variability of the data. It should be noted that all of the sulfur dioxide

emission factors for drum mix dryers are rated D or E. The primary reason for the low

rating was the availability of only three to six source tests. An additional adjustment

from a D rating to an E rating was made because of the low number of tests and the

higher variability of the data. The rating of A was assigned to the emission factor for

filterable PM for fabric filter-controlled drum-mix dryers because there were 145 tests.

This is well in excess of the number of tests that would justify an A rating. While the

data ranged over two orders of magnitude, the large number of data contributed to the

magnitude or the range of the data. In addition, the relative standard deviation of this

data is near one and is typical of many emission factors for PM.
74

3.4.11 CAAP Quality Ratings Comment Number 6 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

16. Page 4-125, paragraph 4: This paragraph states that the emission factor for trace

metals was assigned an E rating because the data ranged over two orders of

magnitude. This might have been simply the result of the variation in trace metal

content of the feed materials and fuel.

3.4.12 Response to CAAP Quality Ratings Comment Number 6 - The paragraph states

“An emission factor rating of E was assigned to data sets with only one or two data

points. An emission factor rating of D generally was assigned to data sets with three or

more data points, and an emission factor rating of C generally was assigned to data sets

with seven or more data points.” The paragraph further states that a rating of E was

assigned for silver because there were only three data points and the data ranged over two

orders of magnitude. While it is likely that the variation of all of the metals emission

factor are the result of variations in trace metal content of the feed materials, the metals

content of the fuel and the effectiveness of the control device, the factor rating system

would not accommodate these variations unless there was data to correlate the emissions

with the process information.

3.4.13 CAAP Quality Ratings Comment Number 7 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

30. Page 4-148, paragraph 1: Reference 6 (fourth line) is incorrect. What is the proper

reference? We are also amused that this report has been given an A rating for data

because of the “few problems in the Technical systems Audit Report” etc. 

Unfortunately, this audit report missed all of the errors found by the citizens. 

Further, the citizens caught the errors through spot checking and there are no

guarantees that they caught everything. If such errors can exist in a report that was

guaranteed a high degree of scrutiny, how sure is the EPA that the other data is error

free? We am particularly concerned about this point because the data, which is

supposedly in appendices A, B and C, is not attached to the material sent to us for

review. Also, it raises the question of whether EPA staff do any of their own

reviews and spot checks before accepting a report from a contractor. It does not

appear to be the case.

3.4.14 Response to CAAP Quality Ratings Comment Number 7 - We agree that citing

Reference 6 is a typographical error. In addition, the “Response to Comments on Testing

Programs for Asphalt Plants C and D” document cited is not included in the references at

the end of the Chapter. This document was added to the list of references at the end of

the chapter and the proper citation replaced the citation in this paragraph. The audit

report was an independent evaluation of the sampling and analyses performed for the

testing at Plant C. The citizens did not identify any additional errors that were not

identified in the audit report. The citizens did comment on one statement in the audit

report which was not accurate and is identified in response number 43 on page 50 and 51
75

of the Response to Comments on Testing Program for Asphalt Plants C and D. While the

draft audit report stated that the “VOST and Modified Method 5 methods have not been

validated for all chemical compounds of interest in asphalt plant emissions,” response

number 43 corrected this statement by providing information on why the test methods

used provided a reasonable assessment of the emissions. Page 2 of the Response to

Comments on Testing Programs for Asphalt Plants C and D reports provides summaries

of changes made to the test reports. There were two changes that might be considered

significant errors in the original test reports. The other seven identified changes in the

test reports either result in a very minor difference in the emissions presented in the draft,

added emissions of some pollutants that an instrument was capable of measuring but was

not presented in the draft, make the presentation of some information more prominent, or

provide some editorial changes in the text. The final reports are free of significant errors

and have been reviewed multiple times by EPA staff and EPA contractors to produce a

document which can withstand the most critical unbiased evaluation of the quality of the

data presented. Because of the thorough documentation of the high quality emission

testing activities, and the adherence to an established and approved quality assurance test

plan, the source test exceeds the criteria for receiving an A rating.

3.4.15 Local Health Agency Quality Ratings Comment Number 1 (Elaine T. Krueger,

Environmental Toxicology Program (BEHA) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

As we have previously noted, it is important to understand the limitations of the emission

testing at the Barre and Irvine plants, some of which were discussed in EPA: response to

comments (i.e., “Emission Tests of Hot Mix Asphalt Plants, Response to Comments for

Asphalt Plants C and D”). EPA noted that resources were not available to perform

emission testing at different times of year or at different locations to determine whether

there is a relationship between emissions and asphalt cooling or variability of emissions

of specific chemical compounds. This information could be important in determining

emissions of specific chemical compounds. This information could be important in

determining emission from plants in different areas of the country. While we appreciate

that limited resources may have prevented more comprehensive testing, unfortunately a

number of uncertainties remain regarding opportunities for exposure and health concerns. 

In addition to those noted above, uncertainties also exist due to the variations in modes of

operation, materials, and plant designs. Therefore emission data from previous asphalt

studies may not be applicable to the Barre plant. We would recommend that these

important limitations be outlined in the final document, rather than just in the response to

comments.

3.4.15 Response to Local Health Agency Quality Ratings Comment Number 1 - It would

not be reasonable to assess the limitations of the emissions information without knowing

the intended final use and without comparing this information to other source categories. 

The most significant uncertainties and limitations of the emission factors for HMA plants

is very similar to the uncertainties and limitations of emission factors for most source

categories. The quality and quantity of chemical specific emissions information available

for HMA plants is at least comparable to many source categories in AP-42 where this
76

information is available. In fact, many people familiar with chemically specific emissions

information would consider the information for HMA plants to be superior to the

information for most other source categories. First, chemically specific emissions

information is not available for many source categories that may potentially create the

greatest exposure to the individuals. Second, compound specific stack emission factors

based on more than three to five emission tests is atypical of most source categories in

AP-42. Third, the use of additional laboratory analyses was very successful and as a

result allows site specific conditions with respect to asphalt volatility and load-out

temperature to be used as parameters to more reliably estimate the load-out and silo

filling emissions. Many of the uncertainties and limitations of emission factors are

presented in the Introduction to AP-42, pages 3 through 5

(http://www.epa.gov/ttn/chief/ap42/c00s00.pdf). It is highly recommended that AP-42

emission factors users read this introduction to understand the development, use and

limitations of these emission factors. When developing AP-42 emission factors, EPA

assembles the best and most complete information available. As a result, the information

that is presented in the AP-42 section and background report for HMA plants is the best

data available and additional comments with respect to general uncertainties and

limitations was not included in the final report.

3.5 Emission Factor Development Methods

3.5.1 CAAP Factor Development Comment Number 1 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Hot Mix Asphalt Plants Emissions Assessment Report

8. Page 12, paragraph 4: This paragraph presumably refers to the statistical analysis

presented in Appendix B, but there is no direct link or reference. Our detailed

comments regarding the statistical analysis are in our page-by-page discussion of

Appendix B. However, the entire paragraph is wrong or inconsistent with

information in other parts of the report. It states that the statistical analysis showed

“no strong correlation” between parameters such as fuel type and emissions factors. 

When such correlation is absent, the approach has been to use the same emission

factor in both cases. Yet, Table 11.1-5 in Appendix A shows different emission

factors for NOx and SO2 for different fuel types. For NOx , the emission factor is

different for natural gas and oil fired dryers. For SO2, there are three different

emissions factors, one for gas, one for No. 2 oil and one for No. 6 oil. The backup

analysis is not shown in Appendix B. But obviously, the analysis showed that fuel

type did affect emissions, otherwise a single factor would have been used. Overall,

the two sets of comments need to be made more explicit and explained more

carefully and the inconsistencies removed.

3.5.2 Response to CAAP Factor Development Comment Number 1 - There is no error in

what was stated and there is no inconsistency between what is stated in this paragraph and

the remainder of the report. The information presented in this paragraph is based upon

the detailed statistical analysis which attempted to discern a relationship between several

operating characteristics and emissions. As stated in Appendix B, where the quantity of

data should be sufficient to discern a relationship, no relationship could be documented. 
77

As a result, the data were combined to arrive at a single emission factor for the differing

characteristics. However, for some pollutants such as NOx and SO2, there were few

supporting data and the reports lacked the necessary information that would help to

discern the relationship. For example the NOx and SO2 emission factors for batch plants

were based on less than six test reports. While there were less than 12 test reports

supporting the NOx and SO2 factors for drum plants, this was still not sufficient to discern

a statistical difference. In addition, few test reports include information on fuel usage and

detailed fuel analysis that would provide the additional information needed to establish a

correlation. Although there was insufficient data to establish a statistically based

correlation, separate emission factors were developed for gas and oil fired HMA plants. 

An additional 30 Wisconsin test reports that were submitted which contain fuel usage and

fuel analyses. However, a statistical evaluation of these data was unable to discern any

strong statistical correlations between the available operating characteristics (fuel usage,

fuel sulfur content, process type and control device temperature) and SO2 emissions.

3.5.3 CAAP Factor Development Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Comments on Hot Mix Asphalt Plants Emissions Assessment Report

10. Page 13, paragraph 2: This paragraph is confusing. It is stated that only a single test

report was available for an oil-fired hot oil heater. Does this mean that only one hot

oil heater was sampled out of 364 plants and test reports? Finally, why does EPA go

out of their way Further, if most of such heaters are fired with natural gas, why was

an oil-fired heater sampled? to here to point out that “emission factors developed

from this data would not be representative of gas-fired heaters”. While this comment

is correct, since oil fired burners emit more pollutants than gas-fired burners, there is

a consistent bias in such comments. The reports point out the possibility of a

high-bias each time such possibility exists, inviting the user of AP-42 to discount the

published number. But, when the reported emission factors have a low bias, there is

no such comment. For example, see the issue of the phony correction for

background emissions to truck loadout discussed later on the same page.

3.5.4 Response to CAAP Factor Development Comment Number 2 - As stated in the

paragraph, only one emission test of a hot oil heater was available. As indicated on page

4-17 of Appendix B (Emission Factor Documentation for AP-42 Section 11.1 Hot Mix

Asphalt Production), the hot oil heater test was conducted as part of a more

comprehensive test program to quantify trace metals and trace organic pollutants from the

combustion sources as required by California Air Resources Board (CARB) rules. The

title of the test report (see reference 35 on page 4-350 of Appendix B) indicates that the

CARB rule that the test was conducted to satisfy was the Air Toxics "Hot Spots"

Information and Assessment Act of 1987 (AB 2588). The test report did not provide

specific information on the rationale for testing the hot oil heater nor on the use of oil as

the fuel for the unit when propane was the fuel for the dryer. However, two goals of the

“Hot Spots” program were to collect emissions data and to identify facilities with

localized impacts (see http://www.arb.ca.gov/ab2588/ab2588.htm). As this test was

conducted for the California “Hot Spots” program, it likely that the oil fired tests were

performed to obtain a reasonable “worst case” scenario for possible “hot spot” evaluation.
78

The comment with respect to the applicability of this emissions information to gas fired

facilities was made to place the information into the proper perspective. The primary

reason that there are no indications of low bias is that when information is not available

to make a reasonable unbiased evaluation, an assumption is made that provides a bias that

is protective of the public health. The objective is not to invite the user to discount the

published number but to use the information as a screening tool and to collect additional

data if the biased information results in concerns with respect to the potential

environmental impacts.

The correction for the measured background conditions created by the emissions from

diesel engines during the emissions test at plant C does not provide a positive bias to the

resulting data. As explained in item 51 beginning on page 56 of the Response to

Comments on Testing Program for Asphalt Plants C and D Report, the emissions

measured during the background run are consistent with other measurements of diesel

exhaust and a methodology was used that could be considered to provide a high bias for

load-out emissions.

3.5.5 CAAP Factor Development Comment Number 3 (Ravi Nadkarni & Lloyd Fillion) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

15. Page 11, paragraph 1: The industry’s own MSDS sheets provide a molecular weight

of asphalt as “over 2000" ( a number we personally don’t believe). It is refreshing to

see EPA use a lower number of 345.69

3.5.6 Response to CAAP Factor Development Comment Number 3 - The molecular

weight provided is not the molecular weight of the asphalt as specified in the MSDS’s. 

Data presented in the document SHRP Materials Reference Library: Asphalt Cements: A

Concise Data Compilation (SHRP-A-645; Strategic Highway Research Program;

National Research Council; Washington, DC; May1993) indicates that the molecular

weight of asphalts from single crude oil sources ranges from 700 to 1300. As indicated in

Appendix C, the molecular weight of 345.69 is the average molecular weight of

tetracosane and pentacosane. These two compounds were single compound surrogates

that resulted in approximately the same vapor concentration at saturation as the complex

mixture emitted from the storage silos. The molecular weight of 345.69 is also not the

estimated average molecular weight of the emissions. The FTIR analysis of the silo vent

indicated that most of the hydrocarbons emitted were similar in spectra (and therefore

molecular structure) to hexane. Since the aliphatic hydrocarbons from about pentane to

nonane have similar spectra, the molecular weight of the vaporous emissions are probably

between 86 and 128. Therefore, to prevent additional misconceptions by users that the

specified molecular weight is either the average molecular weight of the liquid asphalt or

the head space vapors, the information presented on page 11 was revised to show the

estimated molecular weights of the liquid and vapor. This required the TANKS program

to be run to determine the appropriate surrogate compound to use to estimate the

appropriate Antoine’s coefficients. The Antoine’s coefficients for aliphatic hydrocarbons

that come the closest to producing a working loss emission estimate of 32 pounds per

million gallons of asphalt throughput for this range of molecular weights were docosane
79

and tricosane. As a result, the background report was changed to describe this revised

methodology. The revised Antoine’s coefficients are “A = 75350.06" and “B = 9.00346"

with a vapor molecular weight of 105 g/g-mole and are included in the background report

and AP-42 section.

3.5.7 CAAP Factor Development Comment Number 4 (Ravi Nadkarni & Lloyd Fillion) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

21. Table 7: Same problems as Table 1; i.e. use of Reference1 which does not really

contain the primary data. Furthermore, there is no discussion why a batch plant dryer

using the same range of fuels e.g. natural gas, No. 2 fuel oil and other fuel oil and a

drum dryer using the same fuel oil should have different emission factors for NOx

and SO2.

3.5.8 Response to CAAP Factor Development Comment Number 4 - Reference 1 for this

part of the report should be Appendix B or the Emission Factor Documentation for

AP-42 Section 11.1, Hot Mix Asphalt Production. This reference citation was revised. 

However, it was decided that since citing each of the over 150 references used to derive

these emission factors would add text that would confuse the typical user and potentially

hide information that adds value, only the background report would be referenced. We

agree that presenting a specific location in the footnote will assist a user find the

information needed to better understand the basis for the emission factor. To provide this

assistance, the table number in the background report was specified. A discussion on the

reasons why two different technologies would have different emission factors is not

germane for the development of emission factors. However, one of the primary reasons

for industries migration from batch plants to parallel flow drum mix plants to counterflow

drum mix plants is improved energy efficiency of the basic process. In addition, the

higher production rates for drum mix plants makes fuel efficiency more critical. As a

result of energy efficiency concerns, it seems reasonable that the CO2, and SO2 emission

factors for batch mix plants are slightly higher than for drum mix plants. It is also

realistic that the NOx emissions may be slightly higher from attempts to improve

combustion efficiency.

3.5.9 CAAP Factor Development Comment Number 5 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

14. Page 4-119, paragraph 1: Was there any attempt to correlate capture efficiency in

venturi scrubbers with the pressure drop?

3.5.10 Response to CAAP Factor Development Comment Number 5 - Information on the

scrubber pressure drop was not available for many of the facilities where venturi

scrubbers were used to control the particulate emissions. As a result, a statistical analysis

was performed only for drum mix facilities. This analysis attempted to correlate the

emission factor with the scrubber pressure drop. As stated on page 4-143 of Appendix B,

only the type of control device significantly affected filterable PM emissions. On this
80

page it is explained that the lack of statistical power associated with small data sets and

the large variability in the data is one reason for not finding a statistical association.

3.5.11 CAAP Factor Development Comment Number 6 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

17. Page 4-126, paragraph 2:. This paragraph points out the inconsistencies in the

approach taken in several places in the report. Because there was no analysis of the

feed materials or of the fuel used, it is not clear whether the measured trace metals

are present on the site or are a result of sample contamination in the lab or elsewhere

or whether the detection of trace metals at the exhaust and non-detection at the

entrance to the control device represents random error in the measurements. The

approach of discarding inconvenient data is not acceptable.

3.5.12 Response to CAAP Factor Development Comment Number 6 - It is not clear how

this paragraph points out any inconsistencies in sampling or analysis. The cited reference

should be 340 rather than 356. Data were not discarded because they were inconvenient,

the data were discarded because they provided no useful information. Sufficient

information is provided to explain the reasons for discarding the data. Where the metal

was not detected, other more useful data are available. In the one situation where the

silver was higher at the outlet than was measured at the inlet of the control device, the

outlet data was judged to be superior since the volume of flue gas sampled was greater. 

One would expect the control effectiveness to be greater than 90% as with other metals

measured at both the inlet and outlet, and the potential for matrix effects is less for the

inlet samples. An analysis of the feed material and the fuel used would not have altered

this result or provided information to explain the inability to measure some metals. 

However, the differences in sample volumes and sample mass collected do provide an

explanation of the differences in the mass of metal that were detectable. Because of the

high particulate, loading at the inlet of the control device only about 50 cubic foot of flue

gas was sampled. At the outlet of the control device where the particulate loading was

significantly lower, approximately 200 cubic foot of flue gas was sampled. This

difference in sample volumes is reasonable to detect metals at both the inlet and outlet. It

is unlikely that the measured trace metals are the result of sample contamination. As

provided in Chapter 6 (Quality Assurance/Quality Control Procedures and Results) in the

test report (which was provided to the commentors), of the sixteen metals analyzed, the

only metal that showed possible contamination was nickel.

3.5.13 CAAP Factor Development Comment Number 7 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

18. Page 4-135, last line: We are told that the statistical analysis is restricted to

references up to number 338. Why? Several of the subsequent references, up to
81

reference 355, contain the same type of data as that being analyzed and should have

been incorporated. 

3.5.14 Response to CAAP Factor Development Comment Number 7 - The statistical

analysis presented was performed in 1997 when the previous draft of the AP-42 section

and background report were circulated for review. Only fifteen additional emissions tests

of HMA kiln stacks were submitted in response to the draft section. Considering the over

300 source tests used in the statistical analysis, the lack of correlation that existed within

these data, the resources required to reanalyze the data and the high probability that the

results would be the same as for the earlier analysis, it was decided that the statistical

analysis would not be repeated.

3.5.15 CAAP Factor Development Comment Number 8 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

24. Page 4-139, paragraph 2: There is a discussion of attempts to correlate wet scrubber

performance with other parameters. Any engineering handbook will tell you that

scrubber performance will correlate with pressure drop, yet this measurement was

either not made or not used. As it now stands, this paragraph finds that although the

emission factor for venturi scrubbers is less than half that for other, unspecified

scrubbers, this result is not statistically significant. 

3.5.16 Response to CAAP Factor Development Comment Number 8 - As stated

elsewhere, the vast majority of emission tests were obtained from the files of State and

local air pollution control agencies. It is recognized that with other parameters being

equal, scrubber performance will correlate with pressure drop. However, there are many

other design and operating parameters that can also affect the performance of wet

scrubbers. Some more important parameters are scrubber geometry, scrubber water flow,

mixing of scrubber water and flue gas, scrubber water solids content, flue gas cooling,

mist eliminator performance, inlet particulate concentration and inlet particle size

distribution. As explained in the paragraph, “the lack of statistical power associated with

the small data sets is the likely explanation for this result.” The lack of statistical power

is caused primarily by the large variations in the data that may be attributable to

parameters other than differences in the pressure drops. The inability to statistically

differentiate the performance of these control devices can be seen on the box plots

(figures 4-2 and 4-7) where the middle 50% of the data overlap. For emission factor

development, statistical analyses provide additional support for engineering evaluations. 

Although no statistical support was found for segregating scrubber and fabric filter

controls, the magnitude of the differences in the emission factors provides sufficient

support to provide separate emission factors for these two control types.
82

3.5.17 CAAP Factor Development Comment Number 9 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

25. Page 4-141, paragraph 1: This entire paragraph is confusing. Figure 4.3 shows that

there is a relationship between RAP content and condensible inorganic PM. The

relationship appears to be non linear. Alternately, looking at just the 0% RAP data

points, it is clear that there is great variability in the condensible inorganic PM

emissions even without RAP. Without any analysis of feedstocks and fuels, the

source of these condensible inorganic PM.s can’t be isolated. To add further

confusion, the last sentence jumps to a discussion of carbon dioxide emissions. The

reference to Figure 4.3 in context of CO2 emissions is incorrect.

3.5.18 Response to CAAP Factor Development Comment Number 9 - Although initially

one may observe a relationship between RAP content and condensible inorganic PM, as

the commentor points out that there is great variability in the condensible inorganic PM

emissions without RAP. A similar variability would be expected if more than a single

emission test were available for the higher RAP contents. As a result, when the data are

evaluated with this additional information, it is evident that any correlation developed

from this data would be highly speculative. In addition, when one considers that the

primary components of condensible inorganic particulate would be formed from sulfur (in

the fuel or in the asphalt) and nitrogen (from the fuel, air or asphalt), the possible

relationship may be related more to fuel usage than RAP content. While there may be a

correlation between RAP usage and fuel usage, other factors (such as moisture content of

the new aggregate, final mixing temperature and fuel efficiency) may have a more

dominant role in the fuel usage. The reference made to CO2 is a typographical error and

was changed from CO2 to RAP.

3.5.19 CAAP Factor Development Comment Number 10 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

27. Page 4-145, paragraph 1: The invocation of engineering principles in the fifth line

is interesting because they have been ignored in many instances up to this point; e.g.

discussion of scrubber efficiencies without consideration of the pressure drops. 

VOCs, by definition, don’t condense even when cooled to ambient temperatures. 

Therefore, if a control device has an effect on VOC emissions, this attenuation must

be a result of a mechanism other than condensation, such as adsorption on solids. 

The data quoted show lower emission factors (by a factor of 4) for fabric filters

compared to wet scrubbers, but the authors find this result surprising. Although they

don’t tell us which engineering principle they are referring to, one has to assume that

they are referring to the ability of water to capture gases through dissolution. 

Unfortunately, the components of VOCs are only sparingly soluble in water and the

pressure drops/retention times in such scrubbers are quite modest. Therefore, this is

a bad place to invoke such engineering principles when they contradict the data. 
5

 Available by internet at URL http://www.epa.gov/ttn/catc/products.html#aptecfacts

6

 Available by internet at URL http://www.epa.gov/ttn/catc/dir1/fimpinge.pdf

7

 Available by internet at URL http://www.epa.gov/ttn/catc/dir1/fpack.pdf

8

 Available by internet at URL http://www.epa.gov/ttn/catc/dir1/fsprytwr.pdf

9

 Available by internet at URL http://www.epa.gov/ttn/catc/dir1/fventuri.pdf

83

3.5.20 Response to CAAP Factor Development Comment Number 10 - As stated

elsewhere, in the development of emission factors are generally supported by a known

engineering principle. Statistical analyses are used to characterize the significance of an

observed effect. Although the engineering principles are not specifically cited in all of

the summaries of the individual statistical analyses performed, they were the basis for

many evaluations. While water-based scrubbers are not generally installed at HMA

facilities to control VOC’s, they may provide some incidental control. Air Pollution

Technology Fact Sheets and Technical Bulletins5 are available on the Clean Air

Technology Center (CATC) web site that provides information on the ability of various

scrubbers to control VOC’s. Information on the ability of water-based scrubbers to

control VOC’s are specifically mentioned in the fact sheets for Impingement-Plate/

Tray-Tower Scrubbers6, Packed-Bed/ Packed-Tower Wet Scrubbers7, Spray-Chamber/

Spray-Tower Wet Scrubbers8 and Venturi Scrubbers9. As indicated in the paragraph, one

would generally expect that the fabric filter to provide little or no control of VOC. It is

also stated in the paragraph that the data sets were small which would make any

difference suspect. Therefore, the paragraph states that data were not segregated to

develop the emission factors.

3.5.21 CAAP Factor Development Comment Number 11 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

28. Page 4-147, paragraph 2: The comment in the last line is that emissions are a

function of RAP content and production rate. Yet, earlier on page 4-139, these same

conclusions were rejected because of low correlation coefficients. Which conclusion

is correct?

3.5.22 Response to CAAP Factor Development Comment Number 11 - Both of the

statements cited by the commentor are correct. Statements on both pages indicate that

filterable PM emissions show an association with production rate and RAP content. 

However, in the discussion on batch mix dryers on page 139, there is an additional

qualifying statement. The qualifying statement is, “However, the squared correlation

coefficient (R 2) value for the model is 0.22, which indicates that the model explains only

a small percentage of the variability in the data.”
84

3.5.23 CAAP Factor Development Comment Number 12 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

31. Page 4-148, paragraph 2: The discussion should point out that Plant C is atypical of

drum plants in the industry. Figure 4.6 shows CO2 emissions factors for drum plants

as a function of production. Although there is considerable scatter, it is interesting to

note that all high emission points are associated with lower production and none are

associated with high production. Does this behavior extend to the emission of other

pollutants?

3.5.24 Response to CAAP Factor Development Comment Number 12 - As explained in

many meetings during the planning phase for testing of Plant C, and in the “Response to

Comments on Testing Programs for Asphalt Plants C and D” document, Plant C is typical

of drum mix plants with respect to all characteristics affecting emissions generation from

silo filling and truck loading operations. The method of loading hot mix asphalt into the

storage silos is identical to other hot mix asphalt plants. Additionally, the method of

loading hot mix asphalt into the transport trucks is identical to other hot mix plants. 

While there are characteristics that differentiate this plant from drum mix plants in other

parts of the US, these characteristics relate more to the collection of emissions generated

during silo filling and truck loading, the maximum production capacity of the plant and

the ability of the plant to operate for a much larger percentage of the time than other

facilities. It should be noted that to test the batch mix plant (Plant D) EPA constructed an

enclosure and emissions collection system almost identical to Plant C.

With respect to the association between CO2 emission factor and production rate noted by

the commentors, the higher emission factors appear to be centered on about 180 tons per

hour rather than the lower production rates. However, this observation may be

misleading due to visual aspects of the data. The one or two high data points at 100 tons

per hour production and the four high data points at about 200 tons per hour may be

visually misleading since the remaining data do not show a strong relationship. The

summary of the statistical analysis (page 4-142) states “The linear model analysis

indicated that CO2 emissions can be estimated as a function of RAP content (p = 0.052),

production rate (p = 0.0002), and the RAP content-production rate cross-product (p =

0.043). However, the squared correlation coefficient ® 2 ) value for the model is 0.23,

which indicates that the model explains only a small percentage of the variability in the

data.” For most combustion sources, CO2 emissions are primarily a function of the fuel

usage and the carbon content of the fuel used. Differences in fuel efficiency, moisture

content of the aggregate and mixing temperature would also affect the CO2 emissions. 

Other than the weak associations identified in the statistical analysis, no association

between production rate and emission factor was evident.
85

3.5.25 Industry Factor Development Comment Number 1 (Gary Fore, Vice President

National Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-18 : B. Footnote D - There is a question that the range to 96 lb/ton is too high. 

Where is source for this number?

3.5.26 Response to Industry Factor Development Comment Number 1 - The results of

individual source test analyses that were used to develop the CO2 emission factor are

presented in Table 4-7 of the background report (Appendix B of the Emissions

Assessment Report). In this table near the bottom of page 4-272 is summary information

from Reference 347 which is a drain oil fueled facility that had measured CO2 emissions

of 96 lb/ton.

3.5.27 Industry Factor Development Comment Number 2 (Gary Fore, Vice President

National Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-16: A. Footnote C -Suggest striking SO2 or add 50% attenuation of SO2.

Please review attached stoechiometry and SO2 attenuation data. 

Page 11.1-18 : A. Footnote c -Suggest striking SO2 or add 50% attenuation of SO2. 

Please review attached stoechiometry and SO2 attenuation data. 

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

The Hot Mix Asphalt Industry is providing additional data specifically relevant to SO2

attenuation and benzene to EPA for possible inclusion into the Emissions Factors

Document (AP-42). Attached are three binders containing stack test reports. All of the

tests were consist of three 1-hour runs and were conducted for compliance purposes. 

NOTE: NAPA is sending one copy of this material and one copy of the comments to Ron

Myers. Only the comments document is being sent to EPA Region I. 

SO2

The Draft Emissions Assessment (EA) offers an EF for SO2 of 0.078 lbs/ton hot mix

from drum mix plants firing waste oil (Draft EA,, Table 11.1-7). The Draft EA also

suggests via footnote (c.) of Table 11.1-7 that AP-42, Chapter 1 also be used to estimate

SO2. Chapter 1 Emission Factors (EF) incorporate fuel sulfur content to determine SO2

emissions. 

It is believed that a more accurate approach should be used to determine SO2 emissions

from plants firing oil, especially waste oil.

Several stack tests for SO2 were conducted. Samples of each plant's burner fuel supply

during each test were taken and analyzed for sulfur content. The amount of SO2
86

produced during combustion of the burner fuel was calculated. There was an assumption

that all of the sulfur in the fuel would be converted to SO2. Then, using a mass balance

approach, the actual stack emissions of SO2 was compared with the calculated SO2 as a

product of combustion, and determined a control (i.e., emission reduction) factor for SO2,

from a hot mix asphalt plant, firing oil.

The proposed means of control would be the adsorption of SO2 by dust particles

suspended in the ductwork and captured on the bags in the baghouse. For a plant

producing 250 tons/hour hot mix and firing 500 gallons/hour waste oil having a sulfur

content of 0.046% by weight and a specific gravity of 0.89, the amount of SO2 generated

by combustion would be 500 gal/hr x 8.34 lbs/gal x 0.89 x 0.46/100 x 2 (lb SO2/ lb S) =

34.14 lb SO2/hr. At the same time, the uncontrolled particulate emissions from the plant

would be 28 lbs PM/ton (Draft Table 11.1-3) x 250 tons/hour = 7000 lbs PM/hour. The

available reaction surface area of the dust particulate provides significant acid gas capture

opportunity by any alkaline solid material suspended in the exhaust stream or

accumulated on the bag house bags.

The results from the 15 tests demonstrate SO2 control ranging from 47% to 97%, with an

average control of 62%. Test result averages show little variation in control among

different plant types, aggregate types or recycle asphalt pavement (RAP) content in the

mix. Please refer to the attached table: “Asphalt Plant SO2 Emissions Summary”

The Wisconsin Department of Natural Resources (WDNR) has reviewed these stack tests

and will adopt a conservative control factor of 50% for future permitting and emission

inventory purposes. Please refer to the attached letter from Lloyd Eagan, Director of

Bureau of Air Management from the State of Wisconsin - Department of Natural

Resource.

3.5.28 Response to Industry Factor Development Comment Number 2 - The emission

tests that were submitted were evaluated and added to the test information in the draft

background report (Appendix B). The measured emissions were used to develop a

revised SO2 emission factor of 0.058 lb/ton for drain oil/waste oil/No. 6 fuel oil-fired

dryers. The additional emission test data also included fuel usage and fuel sulfur content. 

This data was analyzed to discern a relationship between measured emissions, the results

of sulfur mass balances (as SO2) and several available operating parameters. Like the

commentors, EPA could not find a correlation with the stated operating parameters. 

While EPA found no reasonable correlation, we did verify that control levels for SO2

ranged from 47% to 92% and averaged 62%. Additionally, the available data indicate

that a maximum of 0.1 lb/ton of SO2 is retained in the product (which includes recycled

baghouse dust). This analysis was described in more detail in the final background

report. Based upon this analysis, we have added the following sentence to footnote c of

Table 11.1-7: “50 percent of the fuel-bound sulfur, up to a maximum (as SO2) of 0.05

kg/Mg (0.1 lb/ton) of product, is expected to be retained in the product, with the

remainder emitted as SO2.”
87

3.5.29 Industry Factor Development Comment Number 3 (Gary Fore, Vice President

National Asphalt Pavement Association) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

The Hot Mix Asphalt Industry is providing additional data specifically relevant to SO2

attenuation and benzene to EPA for possible inclusion into the Emissions Factors

Document (AP-42). Attached are three binders containing stack test reports. All of the

tests were consist of three 1-hour runs and were conducted for compliance purposes. 

NOTE: NAPA is sending one copy of this material and one copy of the comments to Ron

Myers. Only the comments document is being sent to EPA Region I. 

Benzene

Stack tests were also conducted for benzene from drum mix plants, firing either waste oil

or natural gas. The reports from 17 tests are enclosed. These reports indicate average

benzene emissions of approximately 0.0003 lbs benzene/ton hot mix asphalt, with no

significant variation for fuel type. The draft EA lists a benzene EF of 0.00051 lbs/ton

(Table 11.1-10).

3.5.30 Response to Industry Factor Development Comment Number 3 - The emission

tests that were submitted were evaluated and added to the background report (Appendix

B). As with the benzene data in the draft report, the fuel type did not appear to affect

emissions. Therefore all 19 sets of data were averaged to produce a single emission

factor for all fuel types. The background document section and table describing the

development of benzene emission factors for drum mix plants were revised. The

resulting benzene emission factor of 0.00040 lb/ton replaced the draft benzene emission

factor in Table 11.1-10.

3.5.31 CAAP Factor Development Comment Number 13 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

37. Page 4-153, last paragraph: In the 10th line, there is an unnecessary caveat about the

relationship being uncertain. The simplest assumption is one of proportionality. 

Unless lab scale data are collected that indicate otherwise, this is the best way to deal

with the issue. Are you forgetting Occam’s Razor?

3.5.32 Response to CAAP Factor Development Comment Number 13 - The simplest

assumption that emissions are proportional to the results obtained from the RTFOT is

being made. However, future laboratory and field data may reveal that the loss in mass

obtained by the RTFOT analysis may not explain all the emissions from the asphalt. 

Specifically, there are some asphalts which lose very little weight or gain weight during

this analysis. It is unlikely that these asphalts do not have any emissions or remove

pollutants from the air. While the commentors may believe that this caveat is
88

unnecessary, it is provided because there have been only two emission tests of fairly

similar asphalt (with respect to the RTFOT analysis) to verify the relationship.

3.5.33 CAAP Factor Development Comment Number 14 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

38. Page 4-154, paragraphs 1 - 2: These paragraphs repeat industry propaganda (along

with that from State highway department laboratories who share the same

road-building mind set). The specifications allow for measurements of unblended

asphalt and the information represents the results of tests on unblended asphalt. In

the Boston area, the terminal in Chelsea has a tank holding such additives for

blending with the asphalt. After a meeting at EPA-Region 1, where the industry

representatives had denied that any blending took place, Mr. Frank Singleton, the

Board of Health Agent for Chelsea showed me this tank which is clearly labeled as

containing an asphalt additive. The citizens submitted a list of many such additives

from Roads and Bridges magazine to the EPA/citizen group which was ignored by

the EPA Project Manager, who instead chooses to believe the asphalt industry’s

lobbyists who insist that such additives are not used. Also, we have examined the

application from one of the terminals in Chelsea which said that they proposed to

add these additives directly to the tanker truck whereby they would mix in the truck

while being transported to the user. This would mean that a sample taken at the

terminal would be a sample of unmixed asphalt.

The third paragraph needs to be deleted. As long as the specifications allow for up to

1% volatiles in asphalt (even before additives are used), it is misleading for EPA to

state that their approach in Table 4-27 “encourages the use of site specific data”. The

primary use of AP-42 is to prepare calculations to get permits to build and to operate

hot mix plants. Therefore, there is no site specific data that can be used other than

fictional data. Unfortunately, the industry has a long history of providing low-ball

estimates, designed to fool the public and get permits from agencies that are not

particularly anxious to ask difficult questions. 

3.5.34 Response to CAAP Factor Development Comment Number 14 - The information

in these paragraphs is not from industry but are results of preliminary laboratory analyses

performed as part of a broader quality control program for State and Federal road

construction. The State Departments of Transportation laboratories perform a quality

control function to verify that the pavement being purchased (directly or indirectly

through a contractor) meets the specifications for the road being constructed. The

RTFOT analysis is only a preparatory step for the rheological analyses that determine the

predicted performance of the asphalt. It is recognized that there are a variety of additives

which are designed to be added to blended asphalt to improve the physical characteristics. 

It is also recognized that to meet some physical characteristics of some more recent

performance graded asphalts, the use of additives is necessary. However, the contacts at

the State Department of Transportation laboratories stated that they analyze samples of
89

asphalts that are to be used without further blending. If an asphalt distributor or a hot mix

asphalt production plant adds a diluent or other additive that changes the physical

characteristics, it is possible that they could be considered to be violating the State

contract specifications.

In addition, no test information has been provided which would support the contention

that asphalt distributors modify the asphalt provided to hot mix asphalt plants following

the collection of samples for the State Department of Transportation analysis. In fact, the

samples obtained during the pre-test survey and the emission test at Plant D in

Massachusetts were within 2% of the average volatility for asphalts analyzed by the

Massachusetts Department of Transportation laboratory. Also as stated previously, State

and local departments of environment have the option of including enforceable

requirements in the operating permits which limit the volatility of the asphalts used by the

hot mix asphalt plants. If there are concerns that asphalt distribution terminals or hot mix

asphalt plants are altering the asphalt, the collection and analysis of the final product by

any authorized State or local transportation, environmental or health inspector seems in

order.

The paragraph discussing the use of site specific information does not need to be deleted. 

There is ample information that the volatility of asphalts can vary both between and

within States. The available information does not support the use of 1% as the only

volatility value to use. There is also ample information that independent information on

the volatility of asphalts used within States are readily available. It is not misleading to

allow State and local agencies to use this readily available and independently collected

data as a locally specific parameter for calculating emissions. The primary use of AP-42

is not to prepare calculations to get permits to build and operate plants. The primary use

of AP-42 is to calculate unbiased actual emissions estimates for use in understanding and

managing the combined emissions from all sources in a geographic area of interest. 

While AP-42 is used by industries and State agency reviewers to calculate emissions for

various permits, these emissions are generally maximum limitations that are not to be

exceeded by the facility. Although some facilities may provide low ball estimates in their

permits for a variety of reasons, these values in permits are not estimates but are

enforceable limitations. When the permit is issued, the facility must operate within this

limitation and the company official signing the permit is held accountable.

3.5.35 CAAP Factor Development Comment Number 15 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

39. Page 4-155, paragraph 2: On the 13th line, the statement is that “this hypothesis has

not been validated by emissions testing but provides an adjustment that is

directionally correct.” This comment is totally unnecessary and needs to be deleted. 

Is EPA saying that the Clausius-Clapeyron equation should be thrown out? 

Alternately, is EPA saying that the degree of precision and accuracy associated with

emissions testing methodology is good enough to provide this type of data?
90

3.5.36 Response to CAAP Factor Development Comment Number 15 - The EPA is

neither saying that the Clausius-Clapeyron equation nor that the precision and accuracy

associated with emissions testing are in question. However, the relationship between

temperature and emissions has been derived from a standard laboratory test that measures

the loss of weight of the asphalt during heating and not on a measurement of emissions

during this test. It is expected that there will be some differences in the mass emissions

and loss of weight due to the uptake of oxygen or nitrogen by the asphalt and result in

some small weight gain. It is believed that this phenomenon is at least one explanation

for the few asphalts which have demonstrated a weight gain during the test. EPA

obtained the temperature relationship for asphalts by performing three laboratory tests. 

While one of these tests was the standard laboratory test, the other two were at

temperatures 25E F above and below the standard temperature. Asphalts that do not lose

weight or that gain weight during the standard laboratory test, would have weight losses

that are incompatible for developing the proper constants for the Clausius-Clapeyron

equation.

3.5.37 CAAP Factor Development Comment Number 16 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

40. Page 4-157, paragraph 2: In this paragraph, the groundwork is being laid to explain

why inorganic PMs were much higher at Plant D than Plant C. This is further

elaborated on page 158. We strongly disagree with the conclusion that the additional

dust was a result of truck movements. While Plant D was unpaved, water sprays

were used to keep the dust down as noted in the report and as observed. At Plant C,

because of the practice of cleaning the silos at the end of the day with crushed stone,

there was considerable dust present in the tunnel. Furthermore, one ofthe silos had

dumped hot mix on the floor and cleaning it up generated a lot of dust. Our

recollection is that if anything, the tunnel at Plant C was dustier than the one at Plant

D. We believe the explanation for the higher PM load at Plant D is the relatively

short residence time in the mixer at any batch plant. Because of this, during mixing,

there are small pockets of stone dust that are not coated with asphalt and these are

the source of the high PM readings. In contrast, the vapors inside a silo have time to

permeate through the mass of hot mix in the silo and coat any uncoated dust

particles. Once coated, the fine dust coagulates and is no longer airborne particulate

matter. This hypothesis is supported by the visual observation that dumps from the

mixer at Plant D were dustier than those at Plant C when observed from inside the

tunnel.

3.5.38 Response to CAAP Factor Development Comment Number 16 - The justification

presented in paragraph 2 and supported by the presentation on page 158 are valid and the

conclusion is reasonable. It is recognized that the unpaved road at Plant D was watered to

minimize the dust created by truck movement. In first full paragraph on page 4-158 of

the draft background report, an assumed surface moisture content of 15 percent was used

to calculate the road dust emissions. This moisture content was used because it is
91

representative of a highly watered unpaved gravel road. At Plant C, emission testing was

completed by the end of the day and the tests did not include the dust created by the silo

cleaning with crushed stone. Additionally, emission testing was stopped temporarily

during the clean up of the hot mix accidently dropped on the floor of the enclosure.

Although the suspended particulate within the Plant C enclosure appeared greater than

within the Plant D enclosure, this increased suspended particulate was not due to

suspended road dust as purported by the commentors. At Plant C, the load-out emission

rate was much greater than at Plant D making the collection and removal by the

ventilation system more difficult. First, at Plant C, the production rate averaged four

times the production rate of Plant D with some periods of high production being six to

seven times greater. Second, the volatility of the asphalt used at Plant C was about 40%

greater than at Plant D. Third, the ventilation system at Plant C captured an estimated 60

to 70 percent of the emissions compared to essentially 100 percent capture at Plant D. In

addition, the suspended particulate at Plant C was more visible since the enclosure was

open on both ends thereby presenting a background more conducive to seeing the

suspended particulate.

The hypothesis which the commentors contended explain the high inorganic PM

measured at Plant D is remote. While there may be a small probability that small pockets

of uncoated stone dust may periodically occur during batch mix operations, the one

minute of vigorous agitation in the pug mill makes this highly unlikely. Additionally, the

coating process for both batch and drum mix plants depends on the significance of this

agitation and mixing not on additional coating in the silo due to the availability of vapors. 

Since the aggregate is also heated to approximately the same temperature as the asphalt,

vapors inside the silo would not condense on any uncoated dust particles. Moreover, dust

emissions even from highly watered unpaved roads have been measured and can account

for a significant portion of the inorganic PM measured at Plant D.

3.5.39 CAAP Factor Development Comment Number 17 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

41. Page 4-158, paragraph 2, 3: See the comments above. The adjustment is indeed

“speculative” and should be eliminated. Separate emissions factors should be used

for inorganic PM emissions from batch and drum plants.

3.5.40 Response to CAAP Factor Development Comment Number 17 - The equation

used to adjust for background dust emissions from the unpaved road is not speculative

but is based upon emissions measured at other sources. Since the basis of the unpaved

roads emission factor equation is over 180 emissions tests we believe that it is a

reasonably reliable indicator of unpaved road emissions.
92

3.5.41 CAAP Factor Development Comment Number 18 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

42. Page 4-159, paragraph 2, 3: There is a fundamental problem with the two paragraphs

which has not been explained. MCEM PMs and TOC are generated the same way

and from the same source. Therefore, if MCEM generation is a function of loadout

time, TOC generation should also be a function of loadout time. Of course, the

comparison is further complicated and made meaningless by the bogus “background”

correction discussed earlier. To eliminate the confusion, separate emission factors

should be prepared for batch and drum plants in all cases.

3.5.42 Response to CAAP Factor Development Comment Number 18 - The commentor

is correct in that both MCEM PM and TOC emissions are generated as a result of organic

material vaporizing from the asphalt binder. While the more volatile organic material

remains a vapor and is measured as TOC, the less volatile material condenses to become

a particulate and is measured as MCEM PM. The sum of the TOC and MCEM PM is the

total organic emissions from the load-out operation and should be compared to determine

whether drum mix and batch plants should have separate emission factors. Table 4-32

presents the emissions adjusted to a consistent asphalt volatility and temperature. The

sum of the MCEM PM and the TOC load-out emissions presented in this table are

0.00421 (4.21 e-3) lb/ton for Plant C and 0.00477 (4.77 e-3) lb/ton for Plant D. The Plant

D emissions are only 13% greater than Plant C. First, this agreement is better than most

of the data supporting the kiln stack emission factors. Second, this level of agreement is

remarkable given that the data have been adjusted to account for differences in measured

load-out temperature and asphalt volatility. Given that the load-out times at Plant D were

from six to eight times longer than at Plant C one would expect that differences in the

total organic emissions would be close to this ratio. However, the emissions are very

nearly the same and well within the uncertainties of the adjustments performed and the

precision of the measurement methods. Therefore, there is insufficient data to conclude

that emissions are a function of the load-out time. By presenting a single set of load-out

equations for batch plants and drum mix plants, there should be no confusion on the

applicability of the equation. As a result, the two paragraphs were revised as follows:

“The next most significant difference in emissions between Plant C and D is the MCEM

PM. The MCEM PM from Plant D is slightly over four times the emissions from Plant

C. This difference could be explained by the longer time required to complete the

load-out operations at batch plants compared to drum-mix plants and other test-specific

factors. However, the asphalt dependent mechanism that generates emissions of MCEM

PM and TOC is the same for both pollutants. This volatilization should cause similar

MCEM PM and TOC load-out emissions after adjustments for asphalt volatility and

temperature. Both emissions are the result of vaporization of organic material from the

asphalt binder. The more volatile organic material remains a vapor and is measured by

Method 25A and is generally referred to as TOC. The less volatile organic material

condenses into an aerosol and is measured by Method 315 and is referred to as MCEM
93

PM. When summed, the TOC and MCEM PM emissions from Plant D are only 13

percent higher than the TOC and MCEM PM emissions from Plant C. Given the

variations in the run-by-run data, the low number of runs and the uncertainty in adjusting

emissions to a consistent temperature and volatility, the difference is not significant.

Therefore, for the purposes of developing emission factors for load-out operations, both

the MCEM PM and TOC data from Plant C and Plant D were averaged and an equation

that represents the averaged data was developed.”

3.5.43 CAAP Factor Development Comment Number 19 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Hot Mix Asphalt Plants Emissions Assessment Report

15. Page 15, paragraph 2: It is ironic that EPA, after rejecting our repeated pleas for

collecting some fundamental data on asphalts such as its vapor pressure, states

“Although vapor pressure information on paving asphalt is not available......”. A

more appropriate way to state what has happened would be to state that vapor

pressure measurements are not available because of EPA’s refusal to measure the

vapor pressure. 

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

44. Page 4-163, paragraph 1: The first line states that “vapor pressure information .... is

not available”. The report fails to state that this was only because of EPA’s refusal

to collect this information.

3.5.44 Response to CAAP Factor Development Comment Number 19 - Vapor pressure

information is not available for paving asphalt because there is no established

methodology to measure vapor pressures for this type of material. First, the collection of

vapor pressure information would have required the development of a suitable test

method to measure the vapor pressure of this material. While within the last year, the

Lawrence Berkeley Laboratory has submitted a procedure for determining vapor pressures

of heavy crude oils, this method was not available at the time the HMA project was

started. To develop and validate their method required over a year of effort. This method

requires quantification of almost all of the individual organic species in the vapor space. 

This method has not been attempted for hydrocarbons that are more volatile than the

heavy California crude oils their method addresses. Although no acceptable standard

methodology to measure the vapor pressure of asphalt is available, determining the

maximum head space concentration of organic compounds above an organic substance is

suitable for use in the TANKS equations. The use of this concentration provides an

alternative to developing a laboratory method to determine vapor pressure for the

complex mixtures of the compounds and mixtures requiring elevated storage

temperatures.
94

3.5.45 CAAP Factor Development Comment Number 20 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

45. Page 4-163, paragraph 3 - 5: Please explain what you mean by “pegged TOC

readings”? As it stands we can’t understand this at all. Furthermore, Figures 4-9

through 4-13 are missing from our copy. Finally, it is not clear whether you are

referring to Plant C or Plant D in this discussion, though the context suggests

Plant C.

3.5.46 Response to CAAP Factor Development Comment Number 20 - The phrase

“pegged” TOC readings means that the emissions being measured exceeded the

maximum concentration of 1,000 ppm that the instrument was capable of measuring. The

paragraphs explain how an estimate of the maximum TOC concentration was

extrapolated from the measured data converging on 1,000 ppm. The paragraph and the

figure cited describe how the lines of increasing and decreasing concentration on both

sides of the plateau of 1,000 ppm were extended to determine the concentration where

these lines crossed. In addition, the paragraphs explain by comparison to other similar

situations which were within the instruments measurement capability why the actual

maximum TOC concentration is likely to be less than was estimated by this extrapolation. 

The paragraph was edited to make the discussion more clear and to reinforce the source

of the emission information.

All of the figures the commentors state were missing from their copy are included in the

version available from the hot mix asphalt web page (www.epa.gov/ttn/emc/asphalt.html)

and on the master use to produce the approximately 50 CD-ROMs that were mailed to

individuals that requested the reports in this format (including the CD-ROM mailed to

Ravi Nadkarni on July 24, 2000). If the commentors would have informed EPA of

missing pages from the few paper versions mailed to stakeholders, we could have

supplied the missing pages or informed the commentors on how to print them from the

CD-ROM version.

3.5.47 CAAP Factor Development Comment Number 21 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

45. Page 4-163, paragraph 3 - 5: We further find that the contention that the estimate of

unmeasured emissions being an “upper bound” to be unpersuasive and incorrect. 

Our reasons for saying so result from the inadequacies of Method 204. These were

outlined in Ravi Nadkarni’s letter of September 15, 1999. They are:

a. At Plant C, two precautions were taken to ensure that we could measure or

estimate the amount of organic fugitive emissions that did not reach the primary

sampling ports. The first was the use of sulfur hexafluoride tracer gas, and the

second was the use of impingement/deposition plates in the ducts which collected
95

organic particulates which would be deposited upstream of the sample port.

Although all the emissions did not reach the sampling ports (some was deposited

inside the tunnel and some was pumped out of the tunnel by ambient breeze or by

truck movement), the tracer gas enabled an estimation the VOC portion of this

loss. (As was pointed out during the planning, the tracer gas was a good proxy

only for non-condensible emissions but not for condensible emissions.)

At Plant D, a tracer gas was not used although requested by the citizens because

the TTE was constructed to meet Method 204 criteria, yet visual observations and

THC readings showed the following: 

b. An ambient breeze was sufficient to cause some of the fume to escape from the

top or the bottom openings in the downwind door of the tunnel. Therefore the

size of the openings was decreased further. This means that the Method 204

criterion of maintaining over 200 fpm at a natural draft opening is not adequate. 

Note that 200 fpm is less than 2.3 miles per hour, which is not much of a breeze. 

Therefore it is not surprising that these criteria are inadequate to assure total

containment within the TTE. We observed visible emissions of fume from the

entrance, further emphasizing that the Method 204 criteria are inadequate. 

c. Further, Method 204 has a more serious and fundamental problem. Although the

size of natural draft openings is specified, the method does not contain any criteria

to ensure that the emissions are pulled/sucked past the sampling point in a

reasonable period of time. As is well-known, residence time calculations, based

on enclosure volume and fan capacity, generally provide incorrect information by

underestimating the time to evacuate the enclosure because of channeling. Note

that Method 204 does not require a specific location for the natural draft openings,

a problem that was pointed out during the planning sessions. At Plant D, even

after the size of the opening was decreased, and the little pieces of colored tape at

the Natural Draft Openings were indicating airflow towards the inside of the TTE,

the tunnel was not evacuated in the approximately 15 second time gap between

the final drop and the opening of the doors. This can be clearly seen in the fact

that THC readings did not drop to zero even when the sample averaging time is

less than 1 minute. This fact was also observed visually inside the TTE enclosure

since SVOCs are visible. Thus, in the absence of a tracer gas, we have

compelling evidence that the collected sample had a low bias. For example, the

extended period test results in MRI-D-Table 4-4, show that final concentration did

not drop to zero but stayed between 1 ppm and 2.1 ppm . Yet, this low bias is not

mentioned anywhere in the report nor in Appendix B of the MRI Report which

contains the original data. These emissions did not reach the instrumentation but

were emitted to the environment causing a low bias.

3.5.48 Response to CAAP Factor Development Comment Number 21 - The paragraph

three to five on page 4-163 pertains only to the methodology used to estimate a maximum

TOC concentration from data collected during silo filling operations at Plant C and the
96

rationale why this methodology would lead to an “upper bound estimate of this

concentration. It does not discuss any measurements at Plant D. However, since the

commentor makes specific statements related to the ability of the enclosure constructed at

Plant D to capture essentially all of the emissions, a response to the remainder of these

statements is provided in Section 3.1.2.

3.5.49 CAAP Factor Development Comment Number 22 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

46. Page 4-164, paragraph 2: There is reason to believe that the numbers derived are low. 

We base this on several facts: Material Safety Data Sheets contain the following

warning: “Studies have shown that low flash point substances, such as hydrogen

sulfide and low-boiling hydrocarbons, may accumulate in the vapor space of hot

asphalt tanks and bulk transport compartments. Such vapors may exhibit

flammability characteristics of a significantly lower flash product than would be

indicated by the open cup test.” A review of light hydrocarbon compound properties

in the Handbook of Chemistry and Physics indicates that the lower explosive limit is

reached at vapor concentrations around 1%. Therefore, this warning makes sense

only if the TOC concentration is around 10,000 ppm, not the 2000 ppm level used. 

Second, storage tank temperatures are generally higher than 325o F and closer to 350o

 F. Finally, the assumed vapor pressure is low in comparison to data from Nelson’s

Petroleum Refinery Engineering, which would indicate a vapor pressure over 10 mm

Hg. 

3.5.50 Response to CAAP Factor Development Comment Number 22 - It is assumed that

the commentor is directing the statements to not only the paragraph stated but to all of

section “4.4.2.5 Storage Tank Emissions.” The warning cited by the commentor from an

asphalt suppliers Material Safety Data Sheet (MSDS) could not be found in other

MSDS’s from other asphalt suppliers. However, neither this warning nor the

concentration correlating with the lower explosive limit support using a vapor

concentration of around 10,000 ppm. First, the open cup test method yields flash points

that are from 10 to 25% higher than the closed cup test methods. For asphalts, this flash

point difference could be more than 100 EF. While the flash point supplied in the MSDS

should use the results obtained from the Pensky-Martens Closed Tester, the statement

provides additional insurance that a user would not rely on other flash point information. 

For a closed liquid storage tank, the head space vapor would be at the lower explosive

limit when the tank temperature is at the closed cup flash point. Measured flash points

are available in a report that was previously provided to the commentors. The range of

flash points for 86 asphalts analyzed by the Asphalt Institute (Properties of Asphalt

Cements, V. P. Puzinauskas, Asphalt Institute Research Report No. 80-2, Asphalt

Institute, November 1980) was from 450 EF to 685 EF.

The derivation of the information presented in this paragraph was explained on page

4-162 through 4-163 of the draft report. As explained on these pages the emissions for
97

storage tanks are derived from estimates of the maximum THC concentrations measured

during the silo filling operations at Plant C. The validity of the derivation of these

emissions depends mostly on the assumption that when operated at the same temperature,

the estimated maximum THC concentration observed from the silo filling is the

maximum THC concentration in the head space of asphalt storage tanks. At the meeting

held in Boston on January 20, 2000, Dr. Nadkarni and others appeared to agree that it was

reasonable to assume that the vapors in the exhaust from the silo were saturated. As

stated by the commentor, we estimated that this maximum concentration was 2,000 ppm. 

At this concentration, emissions from an asphalt storage tank maintained at an average

temperature of 325 EF would be 32 lb per million gallons of asphalt throughput.

If the average storage tank temperature was raised to 450 EF, the emissions would be

increased to 570 lb per million gallons of asphalt throughput. Since these emissions are

the result of the venting of the vapors due to the periodic displacement by liquid asphalt

(working losses), the head space vapor concentration for the higher temperature tank can

be calculated. The head space vapor concentration of the storage tank maintained at 450

EF would be 35,600 ppm. Given that the FTIR analysis of the silo exhaust indicated that

most of the vapors were likely to be aliphatic hydrocarbons between pentane and nonane,

the lower explosive limit concentration of 1% estimated appears reasonable. For the head

space vapor concentration to be 10,000 ppm, the average temperature of the asphalt

storage tank would need to be only 390 EF. As a result, the statement in the MSDS may

also be a warning about the relative flammability of the head space vapors compared to

the flash point. Therefore, the information derived in this section supports the statements

in the MSDS.

Many safety and health related requirements are instituted at a percentage of the lower

explosive limit rather than at the lower explosive limit. For example EPA safety

requirements preclude entry into an environment that is above 10% of the lower explosive

limit. As a result, the commentors inference that the vapor concentration in the asphalt

storage tank is at or above the lower explosive limit is inappropriate. Therefore, the

information presented in the paragraph does not contradict the information in the Material

Safety Data Sheets cited by the commentors.

The information presented in the paragraph also does not contradict the information in

Nelson’s Petroleum Refinery Engineering. The commentors statement concerning the

vapor pressure of 10 mm Hg neither specifies the boiling point for the hydrocarbon nor

the temperature corresponding to the vapor pressure. To have a vapor pressure of 10mm

Hg at a temperature of 325 EF, the boiling point of the hydrocarbon would have to be

about 600 EF (See Point “A” on Figure R-1 which is adapted from Petroleum Refinery

Engineering, Fourth Edition, Wilbur L. Nelson, McGraw-Hill, 1958). In a review of the

physical properties of asphalts {CONCAWE: Bitumens and Bitumen Derivatives

(92/104), CONCAWE, Brussels (December 1992)}, the range of boiling points for

asphalts is from greater than 400 EC (752 EF) to greater than 550 EC (1,022 EF). Based

upon the boiling point data presented in the CONCAWE review and the vapor pressure

relationships presented in Petroleum Refinery Engineering, the vapor pressure for an
98

asphalt at 325 EF with a boiling point of 900 EF (about the midpoint of the range) would

be less than 0.01 mm Hg. The range of vapor pressures at 325 EF corresponding to the

extremes of the boiling points would be from about 0.0002 mm Hg to about 0.2 mm Hg. 

These vapor pressure extremes are shown as Points “B” and “C” on Figure R-1. The

Asphalt Institute (http://www.asphaltinstitute.org/faq/acbfaqs.htm) states “It is estimated

that at a typical inventory temperature of 325EC, the vapor pressure of petroleum asphalt

is less than 0.01 psia (1.5e-3 kPa).” A vapor pressure of 0.01 psia is equal to 0.52 mm

Hg. In addition, EPA confirmed with the Asphalt Institute that the stated temperature is a

typographical error and should be 325EF. EPA does not know what type of asphalt the

Asphalt Institutes estimate of vapor pressure is based upon nor what methodology was

used to estimate the vapor pressure. However, the vapor pressure of 0.95 mm Hg

estimated by the silo filling data is reasonably consistent with these other estimates of

vapor pressure for asphalt.

The purpose of the commentors statement that the storage tank temperatures are generally

greater than 325 EF and closer to 350 EF is unclear. There is nothing in the paragraph

that indicates the typical storage tank temperature. The storage tank temperature used in

the paragraph was the recorded temperature for the material being loaded into the silo on

July 27, 1998 at 7:36 when the peak concentration was observed. The same temperature

is used to provide consistency in the concentration of the vapors emitted for both

emission sources to estimate the most appropriate Antoine’s constants representing the

asphalt. The use of a storage tank temperature of 350 EF at this point would generate

Antoine’s constants that represent a significantly less volatile substance than is indicated

by the data. In addition, the commentors statement is in contrast to the industry

recommendations for asphalt storage temperature (Asphalt Pavement Environmental Best

Practices, Asphalt Pavement Environmental Council, April 2000) as previously shown in

Figure 2. The industry guidance provide different recommended storage temperatures for

different performance graded asphalts. The highest midpoint storage temperature

recommended is 325 EF for PG82-22 asphalt. The numbers in the grade are indications

of the project-specific temperature extremes (in degrees centigrade) for which the asphalt

mixture is being designed. As such, a PG82-22 grade asphalt is intended for use when

average 7-day maximum pavement design temperature is 82 EC (179 EF) and the

minimum pavement design temperature is 22 EC (-8 EF). Of the asphalts included in the

recommendations, this asphalt grade is for use in a severe application where the

maximum design temperature is the highest.
99

Figure 11. Vapor Pressure of Hydrocarbons. Adapted from

Petroleum Refinery Engineering, W. L. Nelson, 1958.
100

3.5.51 CAAP Factor Development Comment Number 23 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

47. Page 4-166, paragraph 4: This needs to be rewritten. It is obvious that this paragraph

is recycled from some other writeup. There is no relevant “response 53" in the

present writeup. Further, emissions are not only dependent on temperature, they are

also dependent on convective effects, i.e. evaporation rate increases in the presence

of strong convection.

3.5.52 Response to CAAP Factor Development Comment Number 23 - We agree that

there is no relevant “response 53". In addition, the document to which “Response 53"

refers is missing from the reference list at the end of the chapter. The statement refers to

Response number 53 in the EPA report “Response to Comments on Testing Program for

Asphalt Plants C and D.” The reference number of this report was added to the text. It is

not clear that convective effects would have a significant impact on the emissions from

asphalt in the bed of transport trucks. First, emissions of low molecular weight

hydrocarbons are more likely a function of the rate at which volatile compounds can

reach the asphalt surface, the rate that the high molecular weight asphalt molecules crack

thereby creating the more volatile compounds within the asphalt and the rate at which

these volatile compound can migrate from air spaces inside the asphalt pile to the surface

of the pile. Second, near the surface of the asphalt pile in the transport truck without

ambient air movement, the concentration of these volatile compounds was measured at

about 10 ppm. This is much lower than the saturation concentration of these compounds. 

In order for convection effects to significantly influence the evaporation rate, the surface

concentrations would need to approach saturation without air movement. Third, in many

States, the asphalt in the transport truck bed is required to be covered. This cover limits

the convective effects the asphalt is exposed to during transport.

3.5.53 CAAP Factor Development Comment Number 25 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

48. Page 4-166, final paragraph: This paragraph presents a single emissions factor for

yard emissions. This is exactly what needs to be done with the RTFOT equations. 

They should be eliminated and only a single factor, based on RTFOT of 0.5%

presented in AP-42.

3.5.54 Response to CAAP Factor Development Comment Number 25 - EPA believes that

a single RTFOT value would overestimate emissions in the majority of locations in the

US and also would underestimate the emissions in a few locations. The adjustment of

measured emission to accommodate differences in emissions due to the effects of

temperature and asphalt volatility was encouraged by the commentors. EPA believes that

this adjustment has accommodated two parameters that would have otherwise been

viewed as imprecision in the measurement of these emissions. Additionally, the use of
101

these two parameters improves the reliability of the final emissions estimates and the

ability to adapt for different regional, regulatory and health impact situations and goals.

3.5.55 CAAP Factor Development Comment Number 26 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

53. Tables 4-4 to 4-14: There are numerous deletions of data shown in these tables

where emission factors for each plant are presented. The reasons for the deletion are

not explained in the text.

3.5.56 Response to CAAP Factor Development Comment Number 26 - There were 89

pieces of data presented in Tables 4-4 to 4-14 that were not used in developing emission

factors. For 56 pieces of data the quality rating of the data is D. In Chapter Three of this

appendix, the criteria for assigning the emission factor ratings are explained. As

indicated, generally only lowest quality rated emission factors include D rated data and D

rated data are generally not used when data of a higher quality rating are available. For

12 pieces of data, an explanation is provided in the text summarizing the specific

reference or in the text describing the development of the emission factor. For the

remaining 21 pieces of data, explanations were added to either the text summarizing the

specific reference or the text describing the development of the emission factor. The

following table provides information on the data that were not used and the 21 instances

where explanations for the reason why the data was not used were added.

Emission Test Data Referenced and Not Used to Develop an Emission Factor

Table No. Page No. Reference No Comment

4-6 4-263 22 D rated data.

4-6 4-266 56 Explanation in Table.

4-6 4-266 11 Report rating was revised from C to D.

4-7 4-267 209 D rated data.

4-7 4-274 350 Explanation was added.

4-7 4-275 236, 22 D rated data.

4-8 4-276 142 D rated data (three instances).

4-8 4-277 142 D rated data (two instances).

4-8 4-278 142 D rated data.

4-8 4-278 340 D rated data.

4-8 4-279 340 D rated data & explanation in text.
Emission Test Data Referenced and Not Used to Develop an Emission Factor

Table No. Page No. Reference No Comment

102

4-9 4-281 40 Explained in text.

4-9 4-281 50 Explanation was added.

4-9 4-281 48 Explanation was added.

4-9 4-282 141 D rated data.

4-9 4-282 40 D rated data (six instances).

4-9 4-283 40 D rated data (eight instances).

4-9 4-283 146 D rated data.

4-9 4-284 48 Explanation was added.

4-9 4-285 50 Explained in text.

4-9 4-285 48 Explanation was added.

4-9 4-285 340 D rated data (eight instances).

4-9 4-286 340 D rated data (eight instances).

4-9 4-287 340 D rated data.

4-11 4-293 240, 46 Explanation was added.

4-11 4-293 331 Data was used for factor development.

4-11 4-296 1 Explained in text (three instances).

4-11 4-298 1 Explained in text (two instances).

4-11 4-298 76 Explanation was added.

4-11 4-298 15, 40 Explanations were added (five instances).

4-11 4-299 40 Explanations were added (two instances).

4-12 4-300 296 D rated data.

4-12 4-305 90 D rated data.

4-12 4-305 161 Explained in text.

4-13 4-306 317, 318, 319 Explanation was added.

4-14 4-308 47, 49 Explained in text.
Emission Test Data Referenced and Not Used to Develop an Emission Factor

Table No. Page No. Reference No Comment

103

4-14 4-310 40 D rated data (nine instances).

4-14 4-310 143 D rated data.

4-14 4-311 49 Explained in text.

3.6 Characterization of Emissions

3.6.1 State Emissions Characterization Comment Number 1 - (Massachusetts State

Senator Stephen F. Lynch) -

Additionally, as I mentioned in my last letter dated September 14, 199, it is my

understanding that this report, again, neglects to specify the composition (ratio of

bituminous cement to aggregate) of the asphalt used in the study. Due to various

engineering standards/requirements associated with asphalt, it is very important that this

information be provided so that test results can be adjusted accordingly.

3.6.2 Response to State Emissions Characterization Comment Number 1 - Information

on the ratio of bituminous cement to aggregate was included in the draft and final reports

of both load-out emission tests. As indicated in Section 2.1 Process Description of the

EPA test report Hot Mix Asphalt Plants, Truck Loading and Silo Filling Instrumental

Methods Testing, Asphalt Plant C, Los Angeles, California, Final Report

(EPA/R-00-024, May 2000), “The percent by weight of liquid asphalt in the mix varies

from 4.8% to 6.0% depending on the size of the aggregate (the smaller the aggregate, the

higher the liquid asphalt content).” Additionally, as shown on the last four pages of

Appendix B of the EPA test report Final Report, Hot Mix Asphalt Plants, Truck Loading

Manual Methods Testing, Asphalt Plant D, Bare, MA, (EPA/R-00-028, May 2000), the

percent weight of asphalt in the mix ranged from 4.4% to 7.2%. During the emissions

test for plant C, the average asphalt used was 5.0% and for the five days of the test ranged

from 4.9% to 5.2%. During the emission test for plant D, the average asphalt used was

5.2% and for the three days of the test ranged from 4.5% to 5.7%. Although the above

information was added to the text reviewing the specific data sets in the AP-42

Background Report (Emissions Assessment Report Appendix B) EPA does not support

adjusting the data further to accommodate the variations of the asphalt content of the

HMA produced. While the range of asphalt content in any specific HMA formulation

may vary significantly, as indicated by the two EPA tests, the range of asphalt content

averaged over a days operation of a typical plant would be significantly less. 

Furthermore, the range asphalt content averaged over longer periods (months or entire

year) would show very little variation. It is believed that the average asphalt content of

5.1% for the HMA produced during the EPA emissions tests are very close to the typical

average asphalt content of most HMA plants. Additionally, differences between this

value and measurement made at other plants are within the precision and accuracy of the
104

weigh scales used by the plants for measuring the materials. As a result, it would be

unclear whether differences in the adjusted emissions are due to actual differences in the

asphalt content in the HMA or differences due to measurement errors of the weigh scales.

3.6.3 Local Health Agency Emissions Characterization Comment Number 1 (Elaine T.

Krueger, Environmental Toxicology Program (BEHA) -

Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

A final comment regards EPA reporting averages of data collected without presenting the

range of numbers. This concern has also been raised by others. The use of average 

values may be appropriate for evaluating risks of long-term health effects e.g., cancer

risk, but may underestimate the potential for health effects associated with other issues,

e.g., short-term odors, that have been reported to be associated with these types of

facilities. Clearly, some of the chemicals, e.g., naphthalene, contained in the asphalt have

very low odor thresholds. For that reason, we recommend that EPA present the full range

of predicted emissions data including upper-bound or maximum estimates of emissions as

they relate to the potential for shorter term effects, such as odors. This is particularly

important given that odors have been important issues at other facilities like this

elsewhere in the U.S. (E.g., Michigan).

3.6.4 Response to Local Health Agency Emissions Characterization Comment

Number 1 - There are a variety of reasons why AP-42 does not include additional

emissions factors that would predict upper-bound or maximum values. First, AP-42 is

primarily used for making source-specific emission estimates for area wide inventories. 

These inventories have many purposes including ambient dispersion modeling and

analysis, control strategy development, and in screening sources for compliance

investigations. Generally, long averaging times reduce the concern over short term

variabilities and the over and under estimations (due to disparities between estimated

emissions and actual emissions) tend to cancel each other. Second, not all emission

factors are based upon the same amount of data nor the same quality of data. Emission

factors based upon large data sets (like the HMA section) will have a greater difference

between the average value and the maximum value. Conversely, emission factors based

upon few data are likely to have a relatively small difference between the average value

and the maximum value. Third, emission factors for source categories where emissions

can be highly controlled, also have some supporting data from a few facilities with

relatively high emissions. Their high emissions may be due to their location in a State

without stringent emission limits or because they are an older facility that is grand

fathered. Fourth, this type of information is rarely required and presenting this type of

information in the AP-42 section would further complicate information that is already

technically complex. Fifth, the range of possible time frames different individuals would

want is great. For example, where one individual might want a 15 minute value while

another would want a one hour value. And lastly, local situations may necessitate the use

of either a value based on unique conditions or may require the collection of additional

locally specific information that cannot be reflected in a “one size fits all” value. 

Additionally, different compounds may have health and nuisance thresholds that may

have differing averaging times.
105

The HMA section has a background report which contains a significant amount of

information which individuals can use to accommodate individual concerns related to a

variety of uncertainties including estimating upper bound and short-term emissions. If

required, copies of a few test reports could be obtained if more detailed information is

required. In using this information, the user should develop an understanding for the

conditions under which the data were collected. For example most tests are three run

averages where each run was collected over one to six hour time frames. Estimating

shorter term values from this data may involve significant uncertainties. In addition, the

user should assess the probabilities (even if they can only be assumed) of simultaneous

unlikely scenarios occurring since using multiple worst case type assumptions generally

infers a highly improbable or almost impossible result.

3.6.5 Industry Emissions Characterization Comment Number 1 (Steve Zemba,

Cambridge Environmental) -

Hot Mix Asphalt Plants Emissions Assessment Report

General: Tables 1 and 2 claim to present emissions for a “typical” plant. This is probably

true for mixer emissions, but is not the case for the fugitive sources, as indicated by

statements on p. 14. Specifically, the fugitive emission estimates assume a high-end

volatility of asphalt cement, and also a maximum recommended load-out temperature. I

would thus characterize the fugitive emission estimates as “high-end” for a

typically-sized plant. EPA might want to clarify this matter somewhat, since the actual

ratio of fugitive-to-stack emissions for a typical plant running at typical conditions will be

lower than that implied in Tables 1 and 2.

3.6.6 Response to Industry Emissions Characterization Comment Number 1 - It is

recognized that the loss on heating of 0.5% is likely an upper bound estimate of volatility

of asphalt for a number of States based upon information that has been collected. It is

also recognized that an average load-out temperature of 325E F is near the maximum

target value for HMA plants. As a result of both of these conditions, it is estimated that

the resulting emission estimate may be higher but as much as a factor of three over the

operating conditions at the typical HMA plant. However, as currently drafted, the HAP

emissions for load-out, storage, the eight minutes following load-out and HMA storage

silo (for drum mix plants) are only 1.5% of the total of the HAP emissions for batch

plants and only 5% of the total for drum mix plants. Since this is a relatively small

percentage, it is not necessary to add text regarding the relative significance of these

emission as this is readily apparent from the estimates derived.

3.6.7 Industry Emissions Characterization Comment Number 2 (Steve Zemba,

Cambridge Environmental) -

Hot Mix Asphalt Plants Emissions Assessment Report

p. 13: Are emissions from hot oil heaters included in any of the categories in Tables 1 & 2

(e.g., the “mixer” category)? If not, does it make sense to mention the likely magnitude

of these emissions relative to other sources (qualified, of course, by the large degree of

uncertainty resulting from the dearth of test data)? Might it also be possible to use
106

emission factors from similar burners (used in other industries) to evaluate hot oil heater

emissions?

3.6.8 Response to Industry Emissions Characterization Comment Number 2 - As stated

elsewhere, emissions from other sources at HMA plants were added to Tables 1 and 2. In

addition to adding an emissions estimate for hot oil heaters, road dust emissions, material

handling emissions, and emissions from diesel truck exhaust were added.

3.6.9 CAAP Emissions Characterization Comment Number 1 (Ravi Nadkarni & Lloyd

Fillion) -

Hot Mix Asphalt Plants Emissions Assessment Report

4. Page 2, paragraph 4: In this and in other paragraphs and tables to follow, emissions

and/or emission factors are given as averages. If this data was derived by averaging

emissions from many plants, as indicated in Appendix B, measures of variability

such as standard deviation should also be given. At present, this information is

buried in the tables in the two appendices.

3.6.10 Response to CAAP Emissions Characterization Comment Number 1 - The

presentation of information on the variability of the supporting data in the body of the

Emissions Assessment Report would only complicate the already complex set of values

presented. The two appendices provide increasingly technical discussions which support

the information presented in the body of the report. As the commentor has stated in other

comments, the appendices do include the standard deviation for some emission factors. 

Most emission factors do not include information on the variability of the supporting

data. However, appendix B includes the individual data supporting all of the emissions

factors that are provided. With the individual data, the user is not limited to one measure

of variability and can develop statistical information that is tailored to the specific

situation that they may be assessing.

3.6.11 CAAP Emissions Characterization Comment Number 2 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

7. Page 7, paragraph 5: The fourth line from bottom uses the word “gas” when “ vapor

of organic compounds” would be more correct.

3.6.12 Response to CAAP Emissions Characterization Comment Number 2 - The report

has been revise to use the more proper term vapor in place of gas.

3.6.13 CAAP Emissions Characterization Comment Number 3 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

8. Page 8, paragraph 1: The second line states that both the low and high molecular

weight compounds “may” contain small amounts of HAP. We were under the

impression that such asphalt-derived compounds always contain some HAPs. Is
107

EPA suggesting that certain asphalts don’t contain any HAPs? Is there any data to

support this statement?

3.6.14 Response to CAAP Emissions Characterization Comment Number 3 - The word

“may” was deleted from the report.

3.6.15 CAAP Emissions Characterization Comment Number 4 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

9. Page 8, paragraph 3: In the fourth line, a particle size analysis of cold feed is

presented. We don’t see the relevance of this sentence since the previous sentence

and the subsequent sentence both talk about fugitive dust and cold feed is not a

major contributor to fugitive dust.

3.6.16 Response to CAAP Emissions Characterization Comment Number 4 - The

percentage of silt (less than 74 Fm or minus 200 mesh) is used as a variable in calculating

some fugitive particulate emissions. Although a silt content that is specific for the facility

improves the predictive accuracy of the emission estimate, the presentation of a average

estimate is useful when a facility specific value is unavailable.

3.6.17 CAAP Emissions Characterization Comment Number 5 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

10. Page 8, paragraph 4: If as you say in the last sentence that data are not available to

support the hypothesis, EPA should not be repeating the hypothesis. Again, such a

statement belongs in industry sales literature and not in an EPA document.

3.6.18 Response to CAAP Emissions Characterization Comment Number 5 - While the

available data to support the hypothesis are very weak and other process parameters are

probably responsible for the majority of the variations, the hypothesis is worthy of

mention. The statement that data are not available to support the hypothesis was revised

to “temperature during processing, data supporting this hypothesis is very weak. 

Specifically, although the data show a relationship only between RAP content and

condensible organic particulate emissions, 89% of the variations in the data were the

result of other unknown process variables.”

3.6.19 CAAP Emissions Characterization Comment Number 6 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

11. Page 9, paragraph 1: Most of this paragraph is again a replay of industry assertions. 

The only relevant issue is whether or not these process modifications work to reduce

“blue smoke”. We notice that the industry favorite, the wet electrostatic precipitator

or smog hog is conspicuous by its absence from this list.
108

3.6.20 Response to CAAP Emissions Characterization Comment Number 6 - The

technologies mentioned have been demonstrated and are mentioned to provide

individuals that encounter facilities with these problems to understand that solutions are

available. It is unknown whether any wet electrostatic precipitator has been used to

control PM and/or blue haze from the kiln exhaust. As a result, this control technology

was not mentioned.

3.6.21 CAAP Emissions Characterization Comment Number 7 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

12. Page 9, paragraph 2: A repeat of the comment on page 5 about how such plants “will

likely have lower ..... emissions”. If you have the data, show it; if not, let the

industry do its own PR.

3.6.22 Response to CAAP Emissions Characterization Comment Number 7 - The

statements concerning the organic compound emissions address the location that organic

material (from either RAP or asphalt cement) is added to the new aggregate and whether

those emissions would be ducted to the kiln exhaust stack. Information, of this type is

useful to State and local agencies that review permits. However, to clarify the statement,

it was revised to “not in contact with the hot exhaust gas stream, counterflow drum mix

plants will likely have lower organic compound emissions from the kiln stack than

parallel flow drum mix plants. However, variations in the emissions due to other

unknown process variables are more significant. As a result, emission factors for parallel

flow and counter flow drum mix plants are the same.”

3.6.23 Industry Emissions Characterization Comment Number 3 (Gary Fore, Vice

President National Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 15: A. Last paragraph - Please add the following sentence to the end of the

paragraph. ...equation developed from the emission data. It should be noted that truck

emissions would decrease rapidly with time as a result of surface cooling and crusting and

industry practice of covering loads with tarps.

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-8: A. In the first partial sentence on the page, please add prior to tarping after

truck. The sentence will then read: Organic vapor ... bed of the truck prior to tarping,

...”

3.6.24 Response to Industry Emissions Characterization Comment Number 3 -

Although the surface material of tarped or un-tarped HMA may cool rapidly during

transport, it is believed that only the organic particulate emissions may be reduced due to

condensation on the cooler surface material. The emission factor discussed in the

paragraph is for the compounds that remain vapors after cooling to ambient conditions. It

is believed that the emissions of these more volatile compounds would not be reduced as

rapidly as the particulate or visible emissions. It is believed that the more volatile
109

emissions are reduced more slowly over time as a result of the more general cooling of

the hot mix asphalt as a whole. This cooling is much slower than the cooling of the

surface material. The addition of the phrase “prior to tarping” infers that the tarping of

the HMA somehow inhibits the emissions of organic vapor from the bed of the truck. 

While tarping may limit to some extent the visible emissions from the truck bed, it is not

believed that tarping inhibits the emissions of the volatile organic compounds that were

measured during load-out. Even if there were information that supported a reduction in

organic vapor emissions due to tarping, it is likely that these emissions would only be

delayed until the tarp was removed. In addition, the presence of some covers may inhibit

the loss of heat from the asphalt in the bed of the truck. The higher temperature retained

by the HMA may in turn result in slightly higher emissions for a given load-out

temperature. As a result the changes suggested by the commentor were not made.

3.6.25 Industry Emissions Characterization Comment Number 4 (Gary Fore, Vice

President National Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-17 :B. Note there is an error under VOC for natural gas-fired dryer and the

No.2 fuel oil-fired dryer. They should be 0.0076 for both not 0.0082

3.6.26 Response to Industry Emissions Characterization Comment Number 4 - While

there appears to be a mathematical error in the table, the differences in the VOC emission

factor are due to the rounding of the formaldehyde, methane and THC emission factors. 

The arithmetic was reviewed. The emission factor is correct. A clarifying footnote was

added to indicate that the values presented are different due to rounding.

3.6.27 Industry Emissions Characterization Comment Number 5 (Gary Fore, Vice

President National Asphalt Pavement Association) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

Page 11.1-22 and 23: B. Delete uncontrolled from this table because to be consistent

with other HAPs, we should use data collected after filtration in the stack. Please make a

footnote reference that the uncontrolled numbers are in the Emission Factor

documentation for AP-42 Section 11.1 Hot Mix Asphalt Production.

Page 11.1-24: A. Delete uncontrolled from this table because to be consistent with other

HAPs, we should use data collected after filtration in the stack. Please make a footnote

reference that the uncontrolled numbers are in the Emission Factor documentation for

AP-42 Section 11.1 Hot Mix Asphalt Production. 

Page 11.1-28: A. Delete uncontrolled from this table because to be consistent with other

HAPs, we should use data collected after filtration in the stack. Please make a footnote

reference that the uncontrolled numbers are in the Emission Factor documentation for

AP-42 Section 11.1 Hot Mix Asphalt Production.

3.6.28 Response to Industry Emissions Characterization Comment Number 5 - When

available, emission factors prior to air pollution control devices are provided in AP-42. 
110

Information on uncontrolled emissions is used by some individuals to assess the

regulatory status of some facilities, assess the potential impact due to air pollution control

device by-pass during start up or shut down or to assess the potential impact of a

temporary malfunction of the air pollution control device.

3.6.29 Industry Emissions Characterization Comment Number 6 (Gary Fore, Vice

President National Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page 3: A. At the end of the last paragraph -Please add an editors note: "HAPs

emissions are typical of emissions that result from fossil fuel combustion."

3.6.30 Response to Industry Emissions Characterization Comment Number 6 - A

limited comparison of the AP-42 emission factors for a drum mix HMA plant with a fuel

oil fired boiler firing the same quantity of fuel oil (1.6 gal per ton of HMA) indicates that

HMA plants generally have higher emissions than an industrial or commercial boiler. 

Therefore, the statement will not be added.

3.6.31 Industry Emissions Characterization Comment Number 7 (Gary Fore, Vice

President National Asphalt Pavement Association) -

Hot Mix Asphalt Plants Emissions Assessment Report

Page13: A. 2"d paragraph -Please add to the end of the paragraph. ...”representative of

gas-fired heaters. As a practical matter theses units represent a very small

combustion source when compared to the dryer.

3.6.32 Response to Industry Emissions Characterization Comment Number 7 - At this

location in the report, this statement is not believed to be appropriate. However,

estimated emissions from the hot oil heater were added to Tables 1, 2, 6 and 10. In

addition, the basis for the emissions estimates are included in Section 2.5. The following

information was included in this basis. The typical HMA plant has two asphalt storage

tanks that are 50 ft long by 8 ft diameter. It is estimated that these storage tanks require a

total heating capacity of about 200,000 Btu/hr based on a heat loss of 60 Btu/ft2 of tank

surface area. The asphalt storage tanks are kept hot continuously for the five months the

HMA plant operates. As a result 720 million Btu’s are used to maintain the temperature

of the asphalt in the storage tank. For a gas fired hot oil heater, 720,000 cubic feet of gas

would be combusted. For an oil fired hot oil heater, 5,100 gallons of fuel oil would be

combusted. It is estimated that this fuel usage is about 3% of the fuel used in a typical

batch mix plant (100,000 tons HMA/year) and 1.6% of the fuel used in a typical drum

mix plant (200,000 tons HMA/year).

3.6.33 CAAP Emissions Characterization Comment Number 8 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

7. Page 2-4, last paragraph: This is a repeat comment in the last line. If you don’t have

the data about organic emissions, don’t speculate about “potential”.
111

3.6.34 Response to CAAP Emissions Characterization Comment Number 8 - The

statements concerning the organic compound emissions address the location that organic

material (from either RAP or asphalt cement) is added to the new aggregate and whether

those emissions would be ducted to the kiln exhaust stack. Information, of this type is

useful to State and local agencies that review permits. However, to clarify the statement

it was revised to “asphalt cement occurs in the hot combustion product flow, there is a

potential for kiln stack organic emissions (gaseous and liquid aerosols) to be greater than

in counterflow plants and some batch plants. However, this increased emissions is not

evident in the data due to variations in the emissions due to other unknown process

variables are more significant.”

3.6.35 CAAP Emissions Characterization Comment Number 9 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

8. Page 2-7, paragraph 3: Same comment as above under item ? regarding dataless

conclusions. The last sentence belongs in an industry sales brochure, not in an EPA

document.

3.6.36 Response to CAAP Emissions Characterization Comment Number 9 - The lack of

data to substantiate the statement is not a reason to eliminate the statement. As with

many other emissions that were statistically evaluated, there is insufficient information

about the relevant process variables, an insufficient number of data and relatively high

variation in the emissions to properly evaluate the potential effect. However, the

statement was revised to indicate that the available data is insufficient to discern any

differences in emissions because of the differences in the process. With respect to the

processing of high percentages of RAP, a number of emissions tests of facilities

processing RAP at ratios of 50% are used in the development of the emission factors. 

The statistical analysis performed to evaluate the effect RAP percentage on emissions

indicated that only the condensible organic particulate was affected by the RAP

percentage. However, the squared correlation coefficient was only 0.11 (with a

correlation of 1.0 being perfect) indicating that the RAP percentage explained very little

of the variability in the data.

3.6.37 CAAP Emissions Characterization Comment Number 10 (Ravi Nadkarni & Lloyd

Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

9. Page 2-10, paragraph 4: The last sentence belongs in an industry sales brochure, not

in an EPA document.

3.6.38 Response to CAAP Emissions Characterization Comment Number 10 - The

technologies mentioned have been demonstrated and are mentioned to provide

individuals that encounter facilities with these problems to understand that solutions are

available.
112

3.6.33 CAAP Emissions Characterization Comment Number 11 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

13. Page 9, paragraph 4: The last three lines appear to be a plug for one particular firm

“Compliance Monitoring Service”. Is it EPA’s role to do this?

3.6.34 Response to CAAP Emissions Characterization Comment Number 11 - The only

source test information available indicating the potential benefits of combustion

monitoring was this report supplied by the State of New Jersey. While the report was

produced by Compliance Monitoring Service, it is no more an endorsement of their

services than any other test contractor referenced as performing any of the tests of Hot

Mix Asphalt Plants. In addition, we would not think that this statement would provide a

strong recommendation for this company since there was insufficient information in this

report for EPA to quantify the emissions benefits of this monitoring and the contractor

used a variety of assumptions rather than collecting the needed process information to

allow the use of this test data.

3.6.35 Industry Emissions Characterization Comment Number 8 (Steve Zemba,

Cambridge Environmental) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

General: Many HMA plants are now installing condensers on their asphalt storage tank

vents and silo vents; some are enclosing or partially enclosing their loadout areas. The

fugitive emissions discussed in this document are for uncontrolled sources. In fact, the

estimates in Tables 1 and 2 implicitly assume controls on the mixer (dryer) stack but no

controls for fugitive emissions. This assumption should be made explicit (perhaps in a

footnote to the tables). EPA might also want to offer some opinion/conjecture on the

efficacy of engineering controls for the various fugitive sources.

3.6.36 Response to Industry Emissions Characterization Comment Number 8 - The

potential for controlling the emissions from asphalt storage tanks and HMA storage silos

can be evaluated based upon the composition of these emissions. The composition of the

organic emissions can be determined from the measured emissions from the silo vent

during the emissions test at Plant C. The emissions measured were about 95% volatile

organic compounds and about 5% particulate organic compounds. In addition, the FTIR

analysis inferred that the majority of the volatile organic compounds were aliphatic

hydrocarbons between about pentane and nonane. While it is likely that atmospheric

condenser would provide some control of these organic compounds, the control efficiency

would only be a conjecture. Normally, the control effectiveness of condensers is

dependent on the temperature of the condenser and the concentration of the components

in the vent stream. While atmospheric condensers should be highly effective at reducing

the particulate components of the emissions and therefore the visible emissions, these are

a small portion of the overall emissions from these sources. Atmospheric condensers

would be significantly less effective in controlling relatively low concentrations (2,000

ppm) of low molecular weight compounds. The effectiveness of enclosing the load-out

areas provides no control of emissions unless combined with an emissions control device. 
113

In addition to having about the same situation as the asphalt storage tank and HMA

storage tank emissions, these emissions would be more dilute because of the high air flow

rates required to capture these emissions from load-out operations. Although the wet ESP

at Plant C may not have been operating properly during the industry sponsored emissions

test by AIRx Testing, this test showed essentially no control of either the particulate or

vapor phase emissions. While there may be a cost effective control strategy that would be

effective on these sources, it is premature to include such a statement in the AP-42

section since there is no basis at this time.

3.6.35 CAAP Emissions Characterization Comment Number 12 (Ravi Nadkarni & Lloyd

Fillion) -

Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

17. Table 1: We are totally confused by the data on condensible inorganic and organic

PM. These are defined in footnote b as being method-driven. It would have been

helpful if additional details had been presented. In particular, we are curious about

the chemical components of the condensible inorganic PM fraction. The table shows

that uncontrolled emissions are numerically the same as controlled emissions. 

Footnote j states that “uncontrolled “values are assumed to be equal to the maximum

controlled value measured”. Since the controlled values of 0.013 and 0.0042 are

averages (arithmetic means), and are the same as the uncontrolled values, is the table

saying that the average is the same as the maximum value in the data set? Please

explain. We recall that this problem has been in table 1 in previous versions of

AP-42.

3.6.36 Response to CAAP Emissions Characterization Comment Number 12 - The

commentor is correct that the components of particulate matter are method defined. The

addition of details to explain the test method is beyond the scope of AP-42 and the

background report for this section. The presentation of PM emission factors in this

manner is common throughout AP-42 where information on the condensible fractions of

particulate matter are available. More detail on pollutant terminology and conventions

are contained in the Introduction to AP-42. Beyond the Introduction to AP-42, the

introductions to the various EPA reference test methods may include additional detail on

the constituents that are measured by the test methods. This information is presented for

future assistance in reconciling ambient speciation information on fine particulate with

the speciated information from the emission sources. While EPA Method 202 does not

include determining the components in the inorganic or organic fractions, the inorganic

fractions are generally sulfates and nitrates with lesser amounts of other inorganic

substances. These inorganic substances are vapors at the filtration temperature used to

avoid water condensation on the filter of EPA Method 5, EPA Method 201a or EPA

Method 17. The values for the controlled and uncontrolled condensible (inorganic and

organic portions) particulate are the same because fabric filter control devices (the most

prevalent in use by HMA plants) are not expected to control vapors and there is no

uncontrolled data for these components of particulate. While wet scrubbers may be

expected to control these components of particulate, no test data was available to indicate
114

a suitable controlled emission factor with this type of control. The values are not

maximums but are averages, the word maximum was removed from the footnote.

3.7 Evaluation of Unused Information

3.7.1 CAAP Unused Information Comment Number 1 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

49. Page 4-167, paragraph 2 - 4: This is a critique of Ravi Nadkarni’s original

submission in 1994. There are several problems here. If you are going to critique

this work, you should refer to all of submissions to the EPA, not just the first one

from 6 years ago. The complete list would include his response to Mr. Ryan of EPA

of October 26, 1995 and November 16, 1995 and to Mr. Mobley of July 5, 1996. We

find it particularly interesting that the estimate of vapor pressure of asphalt from

1994, based on several model compounds has been represented as one based on a

single model compound. Second, “people who live in glass houses should not throw

stones”. In using the TANKS program, (see page 4-165) the authors used another set

of model compounds whose presence at the required concentrations is also not

supported by the same data that is used to attack this work. For example, if

naphthalene and 2-methyl naphthalene are predominant species of PAH in emissions

from asphalt DRYERS, why were tetracosane and pentacosane used as model

compounds for TANKS? Can you please recalculate the TANK emissions using 

naphthalene and 2-methyl naphthalene? 

Next, why is the Cambridge Environmental letter not listed in the references? It

should have been reference 358. Cambridge Environmental used another set of

model compounds to come up with a different figure. That does not make their

calculation any more valid since both estimates were done years ago in the absence

of data on components of asphalt vapor. (This also begs the question of why

DRYER emissions are used here when better data is now available from silo

emissions.) Given Cambridge Environmental’s track record as an extreme advocate

for their industrial clients in the public health area, we would not characterize their

work as “independent”. (In one case, they compared emissions from a single plant

versus emissions from all industrial plants of all types in a county and the state. 

Even the most polluting plant can appear to be a winner under that criterion.) There

is more to the Cambridge Environmental story. In a public meeting in Uxbridge, Dr.

Zemba, the principal author of the letter, reversed his position and stated that he now

believed that the calculations are in the correct range, or only modestly overestimate

the actual emissions. Specifically, he said, “When I originally looked at the

calculations, I thought that these were grossly overestimated. I can see your point

though and they might not be overestimated by as much as I originally thought.” He

also admitted that he had not studied Ravi Nadkarni’s two 1995 letters to the EPA. A

specific critique of the Cambridge Environmental work is in the 1996 letter to David

Mobley. 
115

We agree that calculations done in the absence of actual measurements should be

discarded when actual measurements are available. But any critique should fairly

represent the work and its shortcomings. 

3.7.2 Response to CAAP Unused Information Comment Number 1 - We believe that the

summary and the shortcomings identified are an accurate representation of the reference. 

The original submission is cited since it was submitted to EPA for use as the basis for

emission factor for this source and has received wide distribution by the author. The

reference cited is intended to include not only the submission by Dr. Nadkarni but also

the various follow up submissions by Dr. Nadkarni and others. Data collected during the

EPA emissions tests of Plant C and Plant D and analyzed by agreed upon procedures

support the shortcomings that were identified in the analysis. The purpose of the

discussion is to provide a brief summary of the information and describe its usefulness in

developing the final emission factor. It is not intended to provide detailed critiques of all

aspects of the methodology described nor the critiques by others.

With respect to EPA’s selection of compounds to represent asphalt in the TANKS

equations, this selection was based upon measured emissions and not assumptions about

the minor constituents of the mixture and the physical processes that are occurring. It

would not be appropriate to use molecular weight information from other compounds

unless the Antoine’s coefficients are changed to produce emission concentrations at

325 EF that are the same as the saturated vapor concentration measured at the HMA

storage silos at Plant C. The TANKS software uses both the vapor pressure calculated

with the Antoine’s coefficients and the molecular weight to calculate mass emissions. 

While the molecular weights of naphthalene and 2-methyl naphthalene could be

substituted, the Antoine’s coefficients for these compounds would not be appropriate. 

Instead, a revised set of Antoine’s coefficients would have to be selected so that the mass

emissions are 32 pounds per million gallons of asphalt throughput. In addition, these two

compounds comprise only 0.004% and 0.01% of the organic emissions (PM plus TOC)

from silo filling and all PAH’s are only 0.024% of the organic emissions. At these

percentages, these compounds are not a significant portion of the vapor pressure of head

space organic compounds. The test data strongly support the conclusions that the

emissions are mostly aliphatic hydrocarbon vapors, a small component of aromatic

hydrocarbon vapors, a small component of organic particulate and trace amounts of

specific identified organic HAP compounds. The FTIR data also support the assumption

that the molecular weight of the vapor is between pentane (72 g/g-mole) and nonane (128

g/g-mole). Since the presentation of the liquid and vapor molecular weight as well as the

Antoine’s coefficients for a model compound between tetracosane and pentacosane has

been misinterpreted by the commentors and may be misinterpreted by others, the median

molecular weight of 105 g/g-mole was used for tanks emissions. The Antoine’s

coefficients for aliphatic hydrocarbons that come the closest to producing a working loss

emission estimate of 32 pounds per million gallons of asphalt throughput for this

approximate molecular weight are docosane and tricosane. As a result, the background

report was changed to describe this revised methodology. The revised Antoine’s
116

coefficients “A = 75,350.06" and “B = 9.00346", vapor molecular weight of 105 g/g-mole

and liquid molecular weight of 1,000 g/g-mole were included in the AP-42 section.

3.7.3 CAAP Unused Information Comment Number 2 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

50. Page 4-168, paragraph 2 - 4: The evaluation of reference 359 indicates that the

reference was not read critically. Tables 4-42 and 4-43 are presented without any

critical evaluation of the contents. The table shows about the same concentrations at

an upwind site and a downwind site. How is this possible, unless the measurements

represent background readings? There is no comment as to why higher

concentrations were detected at a residential site and how the residential site

compared to the upwind and downwind sites. If you are not going to evaluate the

information, don’t present the tables.

3.7.4 Response to CAAP Unused Information Comment Number 2 - The reference was

not read critically since it was impossible to derive an emission factor from the test. A

more critical review would have been attempted should the samples from the railcar hatch

and storage tank vent been within the calibration range of the GC/MS. However, it does

offer limited support for the estimated concentration of THC for asphalt storage tank

emissions that was used to develop Antoine’s constants for use with the TANKS

equations. Assuming that the residential site was near the source, an insignificant

difference between upwind and downwind concentrations provides information that

indicates that emissions are low relative to the background concentrations. Finding

significant increases in downwind concentrations requires at least four conditions to

occur. The source strength (mass per unit of time) be significant relative to the other

conditions. The downwind measurement must be close enough to the source so that the

pollutant is not significantly diluted due to dispersion in the air. The test method should

be capable of detecting the difference in concentrations. Last, the variations in the

upwind and downwind concentrations should be insignificant when compared to the

differences in upwind and downwind concentrations.

3.7.5 CAAP Unused Information Comment Number 3 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

51. Page 4-169, paragraph 2 - 6: Again, the comments indicate that reference 360 was

not read critically. For example, the high outliers were rejected. Having read the

original report, we know that the authors don’t plead that the instrument

malfunctioned. Therefore, the high measurements must be explained. Or are they

supposed to be background? It is likely that the wide variation in measured

concentrations was a function of measuring technique? Low readings were obtained

upwind of the emission source and high readings were obtained near the source and

downwind from it. Under these conditions, when the instantaneous wind direction

and sampling location with respect to the source were not recorded, there is no

justification for rejecting the high data points. Note that the determination of the
117

high data points as outliers was based on a purely statistical argument (the “outliers”

were many standard deviations away from the rest of the data; therefore they don’t

belong with the rest of the dataset); not one based on measurement errors or other

relevant factors.

The final paragraph again uncritically quotes the process used by the authors to

convert the measurement into a mass rate in g/sec. The concentration of benzene

was measured in concentration units i.e. g/l which can be converted to g/m3. This

was then converted to an “emission factor” (actually a mass rate) by multiplying the

concentration by wind velocity in m/sec and the vehicle area in m2. This is data

manipulation of the worst sort. If one is trying to measure the flux of benzene

escaping from the truck, the flux would be expressed in units of mass flow per

second per unit area or g/sec-m2. The relevant area is that perpendicular to the

direction of flow of the flux that you are trying to characterize. In this reference,

concentration, wind velocity and truck area are combined in a way that might be

dimensionally correct but make no physical sense. In particular, it is difficult to see

how a measured wind velocity relates to the area of the truck. EPA does disservice

to the reader when material of this type is presented in detail over 4 tables without

critical evaluation.

3.7.6 Response to CAAP Unused Information Comment Number 3 - The reference was

not read critically since the derivation of an emission factor from the test would require a

number of additional unsubstantiated assumptions. For example, the amount of asphalt

loaded during the one minute period, the temperature of the asphalt and the volatility of

the asphalt. In addition, based upon the description of the sample collection, the air

velocities and concentrations are probably biased high since the funnel was located within

the bed of the truck near the falling HMA. While the authors excluded the high values

due to statistical criteria, for emission factor development outlier evaluations are

typically used to identify data requiring further evaluation. However, the test does

provide a reasonable semi-quantitative estimate of emissions for use in a dispersion

model used to determine the need for more sophisticated emissions testing. Within this

context, the results that were developed for truck load-out do provide limited support for

the load-out emission estimates for benzene.

3.7.7 CAAP Unused Information Comment Number 4 (Ravi Nadkarni & Lloyd Fillion) -

Appendix B: Emission Factor Documentation for AP-42, Section 11.1, Hot Mix Asphalt

Production, June 2000 Draft

52. Page 4-172, reference 364: This reference is the AIRx report of measurements at

Plant C. We want to see exactly what procedure was used to estimate capture

efficiency at 70 to 90%. Otherwise, this comment should be eliminated. 

3.7.8 Response to CAAP Unused Information Comment Number 4 - The statement

concerning the estimate of the capture efficiency of the enclosure should have indicated

that the assessment was made during the evaluation of the test report done prior to

capture efficiency testing. While the capture efficiency testing at Plant C supports the
118

estimates of capture efficiency that were made, this test report is not being used for

developing the final emission factor. Therefore, no additional evaluations are necessary. 

The paragraph was revised to:

“Capture efficiency of the control system was not measured during the test. However, in

an evaluation of the test report by an EPA contractor, an assessment of the capture

efficiency was made. The assessment was made based upon the available information on

the load-out area in this test report. The assessment indicates that an average face

velocity of building air of about 42 feet per minute was estimated from data in the report. 

It was recognized that this velocity is outside the recommended range of 50 and 100 feet

per minute specified in the Industrial Ventilation Manual. It also was recognized that the

enclosure did not meet all of the criteria for a permanent total enclosure (PTE) specified

in the EPA document The Measurement Solution: Using a Temporary Total Enclosure for

Capture Efficiency Testing. Finally the assessment provides an estimated range of

capture efficiency of the system at between 70 and 90 percent. While this capture

efficiency assessment could be re evaluated using the measured capture efficiency and

emissions documented in reference 355, this is unnecessary since this test was not used in

developing the final emission factor.”
Chapter 5

Stakeholder Comments on 

Draft Emissions Assessment Report,

AP-42 Section and AP-42 Background Report
This Page is intentionally left blank.
Stephen F. Lynch

Massachusetts State Senator

First Suffolk District
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August 31, 2000 

Mr. Robert McConnell 

Environmental Engineer 

Air Quality Planning Unit 

U.S. Environmental Protection Agency

John F. Kennedy Federal Building

Boston, MA 02203-0001 

RE: EPA-454/R-00-0XX Hot Mix Asphalt Plants Emission Assessment

Report.

Dear Mr. McConnell:

This letter is in regard to the EPA-454/R-00-0XX Hot Mix Asphalt Plants

Emission Assessment Report. As you may know, there have been various

proposals to locate an asphalt plant in my district in the South Bay area of 

Boston. As the State Senator for the Dorchester, South Boston, South End 

and Roxbury neighborhoods which would be most impacted by this 

proposed plant, I appreciate the opportunity to comment on this report. 

In reading this report and its appendices, along with comments sent to my 

office by Ravi Nadkarni, it is my understanding that this report only shows

emissions results from asphalt plants burning natural gas as a source of fuel. 

The report also fails to provide information about what percentage of asphalt

plants cited in the report used natural gas and what percentage of those

plants, used alternative fuels. Although I am not an environmental engineer, 

it is obvious to see that emission results from asphalt plants burning only
PAGE TWO 

August 31, 2000 

Mr. Robert F. McConnell, Environmental Engineer 

natural gas, as opposed to other fuels, will show a considerably lower

emissions result. This would clearly indicate to me that the results in this

report are skewed. I wol1ld like to see more thorough testing of various data

included in the final report, especially if this report is to be considered an

emissions standard for all asphalt plants. 

Additionally, as I mentioned in my last letter dated September 14, 1999, it is 

my understanding that this report, again, neglects to specify the composition 

(ratio of bituminous cement to aggregate) of the asphalt used in the study. 

Due to the various engineering standards/requirements associated with 

asphalt, it is very important that this information be provided so that the test

results can be adjusted accordingly. 

As the elected Senator for this district, I would appreciate a response to these

issues. 

Thank you for the opportunity to comment on this important matter. I look

forward to your response. If I can be of any further assistance, please do not

hesitate to contact my office.

Sincerely,

STEPHEN F. LYNCH

State Senator
Lloyd Fillion - Boston, MA

Ravi Nadkarni - Wrentham, MA

Coalition Against the Asphalt Plant
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

Comments on EPA reports relating to AP-42 Section 11.1

August 31, 2000

Table of Contents

A. Introduction ............................................................. 1

B. General Comments about the Package .......................................... 2

C. Summary of Major Deficiencies ............................................... 3

D. Page-by page Comments on Hot Mix Asphalt Plants Emissions Assessment Report - EPA-454/R00-0XX, June 2000 .................................................... 7

E. Page-by page Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft . 11

F. Page-by page Comments on Appendix B: Emission Factor Documentation for AP-42, Section

11.1, Hot Mix Asphalt Production, June 2000 Draft ........................... 14

A. Introduction

This letter is a review of the Draft of “Hot Mix Asphalt Plants Emissions Assessment Report” dated

June 2000. The report is designated EPA-454/R-00-0XX. It comes with three appendices: 

• Appendix A is Section 11.1 of AP-42 of June 2000

• Appendix B is “Emissions Factor Documentation” for the above

• Appendix C is on Preferred and Alternative Methods for Estimating Air Emissions from Hot

Mix Asphalt Plants dated July 1996.

The overall package is 3" thick and contains over 500 pages. 

Before discussing the results of our review, we want to comment on the review process and our

general dissatisfaction with it. When complex, technical documents are sent to a wide audience for

review, one assumes that both the EPA and their contractors did their best to produce as final a draft

as possible. One would not only expect that most of the typos and numerical errors have been found

and eliminated but that the authors wrote the report in a way that makes it easy for the reviewer to

go back to the primary references and original sources (assuming that they are available) to check a

particular point. On both these counts, the reports, just like the previous set of reports reviewed last

year, fail resoundingly. Many key comments are not referenced at all; in some cases, the references

are incorrect; in other cases, the reference is made to a large document without giving a page number,

making it difficult and time-consuming to check. Appendix B refers to its Appendix B and Appendix
2

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

C on page 4-137. But these appendices, which presumably contain the statistical results and the data

sets, are not provided, making it impossible to even spot check the analysis. This, combined with the

severe time constraints, makes it impossible to review the reports in any but a cursory fashion, using

random spot checks, to make sure that the numbers are correct. Unfortunately, the reports also fail

on that count since numerical or logical errors in the analysis have been found.

We also need to air another complaint regarding the process. For about 6 weeks before the report

was finally issued, we received phone calls informing us that the release of the reports was imminent.

While we appreciate receiving this advance warning, it also turns out that the actual release of the

reports was much later than announced. One of us (Ravi Nadkarni) had cancelled attendance at the

Annual Meeting of IPMI in mid-June in response to these calls. Because of weddings in the family,

Ravi was going to be unavailable after July 17 and wanted to start the review process as soon as

possible, hence the cancellation. Unfortunately, the reports were received only on June 28. This

means that he missed an important Annual Meeting where he is on the Board of Directors. We

appreciate getting the extra time until the end of August to complete this review. 

Appendix C was prepared in 1996. Why was this 69-page document not provided earlier so that it

could have been reviewed before this “crunch” period? Also, are comments on such a document,

which has undergone a “final” review, relevant at this stage? Finally, why was this document not

released to us when the citizen groups and the EPA were discussing sampling issues, when that

document might have provided an additional viewpoint? For all these reasons, this third document

has not been reviewed.

In our review, we present general comments about the package and then a summary of major

deficiencies. Finally, a page-by-page sets of comments are presented. The “major deficiencies” will

repeat discussions in the page-by-page comments and readers might argue with our selection of

certain areas to highlight as major deficiencies. However, because of the numerous problems with

the reports, the page-by-page comments became very voluminous. Hence the decision was made to

highlight some of the deficiencies in a separate section, even at the cost of some repetition, which

mirrors the repetitions in various segments of the reports.

B. General Comments about the Package

AP-42 is essentially a “cookbook” for engineers/contractors who need to produce emissions estimates

for local regulatory authorities to obtain permits to construct and operate plants. In view of this, the

overall organization of the three reports does not make sense. In the long run, Appendix A will be

used most often for estimating emissions. When necessary, the background information in Appendix

B will be reviewed. The “main” report will remain either as a political document used by lobbyists

or fade away. As it now stands, the “main” volume repeats in a vague and biased way, the

information in first two appendices. The same information is presented in a marginally better format

and with slightly less “spin” in Appendix A. If the main document is supposed to be an Executive

Summary to Appendix B, it is a poor summary and reads more like a political tract. This is
3

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

particularly true since only emissions data on plants using natural gas is given in the main report; i.e.

there is a deliberate attempt to show only the lowest emissions. Most of the caveats associated with

the summary information in the main report are well concealed in Appendix B. If EPA is serious

about making the main document useful, it should use the main document to calculate the total

emissions to the environment from a batch and a drum asphalt plant. This type of rewrite, where

other emissions (for example from materials handling and storage piles, storage tanks, from traffic

and truck exhaust, and so on) are also calculated and shown for typical plants, will result in a

guidebook for industry contractors and help them by demonstrating how such calculations should be

made. (In Massachusetts, specific plants will employ a wide range of pollution control technology

and then argue that it is “state of the art” and is BACT (Best Available Control Technology)). Other

emissions are currently only listed and cross-referenced in Section 2.3 on page 16. These include

emissions from storage tanks (AP-42 Chapter 7), materials handling and storage piles (AP-42

Sections11.19.2 and13.2.4), vehicular traffic (AP-42 Sections 13.2.1 and13.2.2) and emissions from

trucks bringing in the raw materials and taking away the hot mix asphalt (AP-42 Volume II).

The main report is a political document for the following reasons. The EPA’s pro-industry bias

shows on almost each page. Every attempt is made to minimize emissions, for example, by

calculating emissions for plants burning natural gas only in the “main” report. The report also

provides qualitative comments to indicate that emissions could be even lower in many cases; for

example, “counterflow drum mix plants will likely have lower organic compound emissions than

parallel flow drum plants”, page 11.1-9. Such comments are not substantiated in the detailed

information provided in Appendix B. Yet, caveats regarding conditions under which the emissions

might be higher are few and far between. This tilting is not surprising given the proindustry bias

expressed many times by the Project Officer during the course of testing.

The report and its appendices contain little or no information about industry structure. For example,

Appendix B asserts that drum plants are 90% larger than batch plants in terms of annual throughput.

This really falls out of an assumption made by the authors. There is little or no backup for this

conclusion. Similarly, there is no information on what proportion of plants use natural gas and what

proportion use other fuels. 

Finally, it is unclear whether this “main” report has a number or whether EPA-454/R-00-0XX is the

final designation. The reason for asking this is because reference 1 of Appendix A has the same name

and a designation of EPA-454/R-00-019, but this reference is dated May 2000. What is going on?

C. Summary of Major Deficiencies

This section will highlight our major concerns some of which have already been covered in the

introduction or will be discussed in the page-by-page review in greater detail.

• Sloppy Report Preparation: The reports are full of minor errors, are poorly organized, repeat

the same paragraphs in different documents, and have incorrect references. Many key
4

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

comments are not referenced at all; in some cases, the references are incorrect; in other cases,

the reference is made to a large document without giving a page number, making it difficult

and time-consuming to check. The data sets used for statistical analysis are not provided,

making it impossible to even spot check the analysis. All indications are that there was no

complete internal review of the report within EPA before releasing it.

• Poor Organization: The overall organization of the three reports does not make sense. In

the long run, Appendix A will be used most often for estimating emissions. When necessary,

the background information in Appendix B will be reviewed. The “main” report will remain

either as a political document used by lobbyists or fade away. The main report shows the

industry’s emissions in the best possible light with most of the caveats associated with

information being well concealed in Appendix B. If EPA is serious about making the main

document useful, it should use the main document to calculate the total emissions to the

environment from a batch and a drum asphalt plant, rather than show the information from

AP-42 with the decimal point moved to the right. 

• Pro-industry Bias: The EPA’s pro-industry bias shows on almost each page. Every attempt

is made to minimize emissions shown. The report also provides qualitative comments to

indicate that emissions could be even lower in many cases. We don’t see why EPA makes

such statements in the absence of data. Yet, caveats regarding conditions under which the

emissions might be higher are few and far between. 

• Undocumented Information on Industry Structure: The report and its appendices contain

little or no documented information about industry structure. Yet such information is used to

derive average plant sizes and share of annual production between batch and drum plants.

• Confusing Report Designations: The designation of the reports is confused. The main report

is called EPA-454/R-00-0XX. But Reference 1 of Appendix A has the same name and a

designation of EPA-454/R-00-019, and this reference is dated May 2000 while the main

report is dated June 2000.

• Deficiencies in Method 204: Tracers were not used at Plant D because it met the requirements

of Method 204. Unfortunately, Method 204 is inadequate to achieve the results it tries to

achieve. Further, the contention that the estimate of unmeasured emissions is an “upper

bound” is incorrect. At Plant D, a mild ambient breeze was sufficient to cause some of the

fumes to escape from the top or the bottom openings in the downwind door of the tunnel.

Therefore, the size of the openings was decreased further at the end of the first day of testing.

This means that the Method 204 criterion of maintaining over 200 fpm at a natural draft

opening is not adequate. Note that 200 fpm is less than 2.3 miles per hour, which is not much

of a breeze. Therefore it is not surprising that these criteria are inadequate to assure total

containment within a TTE as contemplated by method 204. 
5

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

Further, Method 204 has a more serious and fundamental problem. Although the size of

natural draft openings is specified, the method does not contain any criteria to ensure that the

emissions are pulled/sucked past the sampling point in a reasonable period of time. As is wellknown, residence time calculations, based on enclosure volume and fan capacity, generally

provide incorrect information by underestimating the time to evacuate the enclosure because

of channeling. At Plant D, the tunnel was not evacuated in the approximately 15 second time

gap between the final HMA drop and the opening of the doors. This can be clearly seen in

the fact that THC readings did not drop to zero before the doors were opened. This fact was

also observed visually inside the TTE enclosure since SVOCs are visible. Thus, the report

contains compelling evidence that the collected sample had a low bias, not only because some

emissions escaped through the natural draft openings but also because these emissions did not

travel to the sampling point but were lost when the doors were opened.

• Incorrect Approach in Compensating for Volatiles Content of Asphalt: The methods used

in these reports to correct for volatiles content of asphalt are contrary to the agreement that

was reached between the EPA and various citizen groups. The citizens had argued that the

asphalt specifications allow the use of asphalt with a much higher weight loss compared to

the asphalt used in Plant C and Plant D tests. The older AC specifications allow for a 0.5%

loss on heating, which can be waived by an engineer on site who can then allow the use of an

asphalt with up to 1% weight loss. The new Superpave specifications allow for a 1% loss on

heating and therefore represent a relaxation of the previous AC grade standards. In view of

this and the industry’s use of various additives and diluents (which would increase the vapor

pressure), the citizens argued and the EPA agreed that maximum number of 0.5% should be

used. Note that this was a compromise since the newer specification allows the use of asphalt

with twice that amount of volatiles. This issue is particularly important since the

measurements by State agencies quoted here appear to be for asphalt prior to blending with

additives, in spite of suggestions to the contrary, in some cases. The EPA, by providing an

equation where a hypothetical RTFOT value can be plugged in, is encouraging

misrepresentation by a proponent of any new asphalt plant, who, once the permit is received,

can then switch to an asphalt with a different RTFOT value with impunity. 

As long as the specifications allow for up to 1% volatiles in asphalt (even before additives are

used), it is misleading for EPA to state that their approach in Appendix B - Table 4-27

“encourages the use of site specific data”. The primary use of AP-42 is to prepare

calculations to get permits to build and operate hot mix plants. Therefore, there is no site

specific data that can be used other than fictional data. Unfortunately, the industry has a long

history of providing low-ball estimates, designed to fool the public and get permits from

agencies that are not particularly anxious to ask difficult questions. 

• Incorrect Substitution of Delivery Temperature for Loadout Temperature: The statement that

“325oF, which is the maximum load-out temperature recommended by industry” is imprecise.

Most specifications require this to be the maximum temperature at a job site where HMA
6

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

is to be spread and compacted. (The minimum temperature is 275oF.) The maximum load out

temperature is much more variable and can be higher if the plant is producing asphalt for a

distant job or for a small job, where there can be considerable cooling of the HMA mass

between loadout and delivery. 

• Improper Manipulation of Data from the “Background” Test, Run 4, at Plant C: The report

states correctly: “The most reliable method to adjust for emissions measured during

background operations would be to separately adjust each run for the measured capture

efficiency and then subtract these adjusted background emissions from the adjusted emissions

measured during production operations.” However, because this “procedure produces

negative values for both the PM and MCEM and many other HAP compounds”, a new

unsound procedure is adopted because it gives results that please EPA and industry by

showing low but positive emissions. This new procedure is to use background emissions

uncorrected for capture efficiency. If the actual emissions have to be corrected for capture

efficiency because the enclosure does not capture all the emissions, there is no justification

for ignoring the capture efficiency for the background run. Having used this incorrect analysis,

the authors then have the temerity to advise us that this result might even have a “high bias”

relative to the correct method mentioned above. 

The report justifies this faulty procedure because this situation “cannot be accommodated

retroactively.” This statement is not correct. The best way to eliminate improper data

manipulation is to discard the phony background adjustment and report the data as that from

loadout plus truck exhaust. Since silos always dump hot mix into a truck, these combined

emissions are present at each silo loadout point. Further, in the unlikely event that a local

permitting authority requires inclusion of truck exhaust emissions (unlikely because we have

not seen such calculations associated with any local permitting requirements), note that the

truck spends about 1⁄2 minute under the silo but many more minutes, typically 3 to 8, on site.

As a result, the truck emissions that are included under loadout correspond to the 1⁄2 minute

portion. Therefore, the double counting of truck exhaust emissions would be minimal and can

be adjusted for by subtracting the 1⁄2 minute from residence time of the truck on site.

Overall, the background run demonstrates how data collection was manipulated to produce

biased results. The EPA Project Officer was interested in recording a high background and

the original data showed that he was able to manipulate truck placement near the entrance of

the tunnel in such a way that uncorrected emissions in the second half of the run were about

twice the emissions in the first half. If these emissions are corrected for the lower capture

efficiency in the second half of the run, the corrected emissions from the second half are

almost three times the corrected emissions from the first half. In spite of using the emissions

from the first portion of the background run, it appears that they were still too high when

corrected for capture efficiency and resulted in negative or zero emissions to the environment.
7

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

• Industry Comments on Capacity Are Given More Weight than Data Collected by EPA or

State Agencies: The report states that the hourly capacity data was averaged from the

capacities of precisely 98 batch plants and 162 drum plants. Since most of the data was

gathered during performance tests at full capacity and witnessed by State Agencies, it is

unlikely that hourly production rate data is incorrect. It is interesting that “conversations

with industry” are all that is needed to supercede this data. In the report, it is clear that the

authors believe that batch plants generally operate fewer hours per year than drum plants.

Reasons for this (not necessarily explained in the report) include the lack of silos for HMA

storage, small customers using smaller trucks, and so on. The report keeps talking about

hourly production rates when the discussion should focus on annual production, i.e. hourly

rate times hours operated per year. 

• Unexplained Differences Between MCEM and TOC: The comparison of Plant C and Plant

D results shows a wide variation between emission rates for MCEMs and TOC. MCEM

PMs and TOC are generated the same way and from the same source. Therefore, if MCEM

generation is a function of loadout time, TOC generation should also be a function of loadout

time and TOC emissions should be higher for a batch plant in the same ratio. The report does

not explain this discrepancy. Of course, the comparison is further complicated and made

meaningless by the bogus “background” correction for drum plants discussed earlier. To

eliminate the confusion, separate emission factors should be prepared for batch and drum

plants in all cases.

• Inconsistent Assignment of Ratings: In one portion of the report, the emission factor for

sulfur dioxide was assigned an E rating because the data ranged over an order of magnitude.

This might have been simply the result of the variation in sulfur content of the fuel. In the

case of filterable PM, the range is over two orders of magnitude but the emission factor got

an A rating.

D. Page-by page Comments on Hot Mix Asphalt Plants Emissions Assessment Report - EPA454/R-00-0XX, June 2000

1. Page 1, paragraph 3: In this paragraph, 1996 production statistics are presented along with

an estimate of the number of plants in the country. There are no references to the source of

these data. In Appendix B, page 2-1, the same paragraph is repeated. On page 2-2 and 2-3

of Appendix B, calculations are presented which derive average annual production rates for

batch and drum plants. We will comment on the problems with these calculations in our

page-by-page discussion of Appendix B. However, the entire discussion is aimed at showing

that drum plants produce more HMA compared to batch plants without actual data.

2. Page 1, paragraph 4: The statement in line 1 is incorrect. The primary emission source is the

dryer, not the mixer, as stated. This is the case because combustion of fuel for generating

heat for drying generates large quantities of criteria pollutants. This error of confusing dryers
8

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

and mixers is repeated several times, (for example in Table 1), and we have not bothered to

find all instances of such misuse. The best way to clarify this issue is to substitute

“dryer/mixer” for drum plants where the two units are connected. In the case of batch plants,

the dryer and the mixer (pug mill) are typically uncoupled through hot storage bins. Emissions

from both however are often captured by the same piece of air pollution control equipment.

3. Page 2, paragraph 3: This paragraph needs a cross reference, even if it is to the relevant

sections in Appendix B. In general, we need page number references to information in

Appendix B which is over 400 pages long.

4. Page 2, paragraph 4: In this and in other paragraphs and tables to follow, emissions and/or

emission factors are given as averages. If this data was derived by averaging emissions from

many plants, as indicated in Appendix B, measures of variability such as standard deviation

should also be given. At present, this information is buried in the tables in the two

appendices.

5. Page 8, paragraph 4: More industry statistics are presented without a source or a measure of

precision or accuracy. 

6. Page 9, paragraph 1: The sentence on line 6 is confusing. Do you mean RAP is added to the

“hot” bins or is it added to the pug mill?

7. Page 12, paragraph 2: Is the rating system applied consistently? The discussion in Appendix

B indicates that it was not.

8. Page 12, paragraph 4: This paragraph presumably refers to the statistical analysis presented

in Appendix B, but there is no direct link or reference. Our detailed comments regarding the

statistical analysis are in our page-by-page discussion of Appendix B. However, the entire

paragraph is wrong or inconsistent with information in other parts of the report. It states that

the statistical analysis showed “no strong correlation” between parameters such as fuel type

and emissions factors. When such correlation is absent, the approach has been to use the

same emission factor in both cases. Yet, Table 11.1-5 in Appendix A shows different

emission factors for NOx and SO2 for different fuel types. For NOx , the emission factor is

different for natural gas and oil fired dryers. For SO2, there are three different emissions

factors, one for gas, one for No. 2 oil and one for No. 6 oil. The backup analysis is not shown

in Appendix B. But obviously, the analysis showed that fuel type did affect emissions,

otherwise a single factor would have been used. Overall, the two sets of comments need to

be made more explicit and explained more carefully and the inconsistencies removed.

9. Page 13, paragraph 1: The quality rating needs to be quantified so that one can get a

numerical feel for the differences in ratings. If, as stated, the quality ratings are a “function
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

primarily of the number of data points”, these various quality ratings can be related to the

standard error of estimate and using t-values, a range can be shown about the mean.

10. Page 13, paragraph 2: This paragraph is confusing. It is stated that only a single test report

was available for an oil-fired hot oil heater. Does this mean that only one hot oil heater was

sampled out of 364 plants and test reports? Further, if most of such heaters are fired with

natural gas, why was an oil-fired heater sampled? Finally, why does EPA go out of their way

to here to point out that “emission factors developed from this data would not be

representative of gas-fired heaters”. While this comment is correct, since oil fired burners

emit more pollutants than gas-fired burners, there is a consistent bias in such comments. The

reports point out the possibility of a high-bias each time such possibility exists, inviting the

user of AP-42 to discount the published number. But, when the reported emission factors

have a low bias, there is no such comment. For example, see the issue of the phony

correction for background emissions to truck loadout discussed later on the same page. 

11. Page 13, paragraph 4: This paragraph is wrong in several ways. The capture efficiency was

measured and calculated using tracers; it was not “estimated” as stated. To me, the word

“estimation” denotes a weaker approach to quantification than calculations based on actual

measurements. Equally, important, the EPA requirements for total enclosure were shown

to be totally inadequate during the testing at Plant D in Massachusetts. A mild breeze was

sufficient to cause visible emissions from the total enclosure even when a hand-held velometer

showed that Method 204 criteria were being met. Why is this factor, which suggests that

Method 204 criteria were inadequate and that the measured emissions have a low bias, not

discussed in this paragraph?

12. Page 13, paragraph 5: This paragraph discusses the subtraction of “background emissions”,

which reduced the calculated loadout emissions significantly. Our detailed comments are in

our page-by-page discussion of Appendix B, which show that the method used is totally

without foundation or theoretical support, and the only excuse for using it is that it gives nonnegative results in several cases.

13. Page 14, paragraph 2: The statement that “325o F, which is the maximum load-out

temperature recommended by industry” is imprecise. Most specifications require this to be

the maximum temperature at a job site where HMA is to be spread and compacted with

rollers. (The minimum temperature is 275o F.) The maximum load out temperature is much

more variable and can be higher if the plant is producing asphalt for a distant job or for a small

job, where there can be considerable cooling of the HMA mass between loadout and delivery.

This same error is repeated in the last sentence of the next paragraph and in many portions

of Appendix B.

This paragraph also states that -0.5% was selected as a default value for weight loss in a

rolling thin film oven test. The methods used to apply the correction for volatility are
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

contrary to the agreement that was reached between the EPA and various citizen groups. The

citizens had argued that the asphalt specifications allow the use of asphalt with a much higher

weight loss. The older AC specifications allow for a 0.5% loss on heating, which can be

waived by an engineer on site who can then allow the use of an asphalt with up to 1% weight

loss. The new Superpave specifications allow for a 1% loss on heating and therefore

represent a relaxation of the previous AC grade standards. In view of this and the industry’s

use of various additives and diluents (which would increase the vapor pressure) which are

often added after the asphalt has been sampled for the measurement of the weight loss, the

citizens argued and the EPA agreed that maximum number of 0.5% should be used at all

times. Note that this was a compromise since the newer specification allows the use of

asphalt with twice that amount of volatiles. This issue is particularly important since the

measurements by State agencies quoted here appear to be for asphalt prior to blending with

additives. The EPA, by providing an equation where a hypothetical RTFOT value can be

plugged in, is encouraging misrepresentation by a proponent of any new asphalt plant, who,

once the permit is received, can then switch to an asphalt with a different RTFOT value with

impunity. 

14. Page 14, paragraph 3: EPA again makes the same recommendation which is to assume that

the load out temperature can never exceed 325o F. This is incorrect. For example, Mr.

Webster, the industry expert who has attended many of the EPA/citizen group/industry

meetings has looked at the photographs that Ravi Nadkarni submitted to the EPA in 1994 and

are in the EPA files. His comment was that the photos were typical of a plant loading out

material at a high temperature when supplying small contractors. If this practice is common

enough to be readily identified at a glance, EPA’s comments about 325o F being the maximum

temperature under all conditions are wrong and need to be corrected.

15. Page 15, paragraph 2: It is ironic that EPA, after rejecting our repeated pleas for collecting

some fundamental data on asphalts such as its vapor pressure, states “Although vapor

pressure information on paving asphalt is not available......”. A more appropriate way to state

what has happened would be to state that vapor pressure measurements are not available

because of EPA’s refusal to measure the vapor pressure. 

16. Page 15, paragraph 3: The first line refers to “emission tests described in previous

paragraphs”. Since the previous paragraphs refer to more than one plant test, it is preferable

to have a proper reference; for example, the text can refer to the test at Plant C or Plant D.

17. Page 16, paragraph 1: How do the truck exhaust emission factors published by EPA compare

with the background measurement from Run 4 at Plant C? Why is such a comparison missing

from the entire report?

18. Page 16, paragraph 3: The second line refers to Tables 4 through 11 which present more

detailed information about “typical” plants. Unfortunately, this is the emission factor data of
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

Appendix A multiplied by 100,000 for batch plants and by 200,000 for drum plants. The

implication is that the reader can’t move the decimal point to the right or multiply by 2.

Further, in keeping with their bias for showing only low numbers, these tables are for natural

gas only and not for oil-fired heaters. Why? Finally, what is the basis for assuming (third

bullet on page 17) that PM emissions from load-out and silo filling are entirely PM-10? We

would have thought that a better assumption was that these were PM-2.5.

E. Page-by page Comments on Appendix A: AP-42 Hot Mix Asphalt Plants June 2000 Draft

1. Page 1, paragraph 3: This paragraph is repeated in the main volume, and in the first two

appendices. It would be more useful to discuss the source of this data and comment on its

reliability, rather than repeat it in three places.

2. Page 2, paragraph 1: The statement that raw aggregate is stockpiled “near” the plant is

ambiguous. Such aggregate is normally stockpiled within the plant site and is moved to the

cold feed bins with a front-end loader.

3. Page 2, paragraph 3: This paragraph repeats the ambiguity in the main report on page 9

paragraph 2. Is RAP added to the weigh hopper or to the hot bins? 

4. Page 5, paragraph 2: In counterflow plants, the baghouse is preceded by a cyclone to reduce

the load on the baghouse. This is a trade off issue where it is cheaper to use a cyclone than

to increase bag house size and bag cleaning frequency to achieve the same result. Since the

industry prefers counterflow plants to parallel flow plants(page 1 paragraph 3), the use of an

additional particulate separation device in the former is obviously not a disadvantage, on an

economic or a technical basis.

If you have data to support the statement that organic emissions may be greater from this

process, present it; otherwise eliminate the statement.

5. Page 5, paragraph 5: We believe the real issue is that with counterflow plants, the air from

the mixing drum acts as secondary and tertiary air for the combustion process which

eliminates many of the organic compounds through combustion. This point needs to be

brought out. Further, is there data to support the statement that a counterflow plant can

process RAP at ratios up to 50% with little or no observed effect on emissions? If not, the

statement belongs in industry sales literature and not in an EPA document.

Similarly, the comment about “improved thermal efficiencies” begs the question of what is

being compared to what and what is the degree of improvement. The statement belongs in

industry sales literature and not in an EPA document.
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

6. Page 7, paragraph 1: The statement that RAP with new aggregate and fresh asphalt is used

to “produce a high quality grade of HMA” is another salesmanlike statement. The point is

that the HMA industry produces products to meet a specification. If the specification requires

the use of RAP, it is used; if not, RAP is not used. The point you want to make is that the

use of RAP does not impair the ability to meet the specifications for certain grades of HMA

since the specs might actually require that RAP is used. Or is EPA implying that the industry

used RAP when specifications call for the use of only virgin materials?

7. Page 7, paragraph 5: The fourth line from bottom uses the word “gas” when “ vapor of

organic compounds” would be more correct.

8. Page 8, paragraph 1: The second line states that both the low and high molecular weight

compounds “may” contain small amounts of HAP. We were under the impression that such

asphalt-derived compounds always contain some HAPs. Is EPA suggesting that certain

asphalts don’t contain any HAPs? Is there any data to support this statement?

9. Page 8, paragraph 3: In the fourth line, a particle size analysis of cold feed is presented. We

don’t see the relevance of this sentence since the previous sentence and the subsequent

sentence both talk about fugitive dust and cold feed is not a major contributor to fugitive dust.

10. Page 8, paragraph 4: If as you say in the last sentence that data are not available to support

the hypothesis, EPA should not be repeating the hypothesis. Again, such a statement belongs

in industry sales literature and not in an EPA document.

11. Page 9, paragraph 1: Most of this paragraph is again a replay of industry assertions. The only

relevant issue is whether or not these process modifications work to reduce “blue smoke”.

We notice that the industry favorite, the wet electrostatic precipitator or smog hog is

conspicuous by its absence from this list.

12. Page 9, paragraph 2: A repeat of the comment on page 5 about how such plants “will likely

have lower ..... emissions”. If you have the data, show it; if not, let the industry do its own

PR.

13. Page 9, paragraph 4: The last three lines appear to be a plug for one particular firm

“Compliance Monitoring Service”. Is it EPA’s role to do this?

14. Page 10, paragraph 2, 3: The comments here are a major problem. The methods used to

apply the correction for volatility are contrary to the agreement that was reached between the

EPA and various citizen groups. The citizens had argued that the asphalt specifications allow

the use of asphalt with a much higher weight loss than that suggested by limited sampling.

The older AC specifications allow for a 0.5% loss on heating, which can be waived by an

engineer on site who can then allow the use of an asphalt with up to 1% weight loss. The
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

new Superpave specifications allow for a 1% loss on heating. In view of this and the

industry’s use of various additives and diluents which would increase the vapor pressure after

sampling for the measurement of the weight loss, the citizens argued and the EPA agreed that

maximum number of 0.5% should be used at all times. Note that this was a compromise since

the newer specification allows the use of asphalt with twice that amount of volatiles. This

issue is particularly important since the measurements by State agencies quoted here appear

to be for asphalt prior to blending with additives. The EPA, by providing an equation where

a hypothetical RTFOT value can be plugged in, in encouraging misrepresentation by a

proponent of any new asphalt plant, who, once the permit is received on the basis of a low

RTFOT value, can then switch to an asphalt with a different RTFOT value. This entire

paragraph has to be rewritten with -0.5% weight loss and 325o F or higher temperature.

15. Page 11, paragraph 1: The industry’s own MSDS sheets provide a molecular weight of

asphalt as “over 2000" ( a number we personally don’t believe). It is refreshing to see EPA

use a lower number of 345.69

16. Page 11, paragraph 2: What exactly is reference 1? Is it the main report with a different date

and number? Also, the derivation of the factor is properly described, not in Reference 1 but

in Appendix B.

17. Table 1: There are many problems here. Footnotes k through p refer to Reference 1. That

is incorrect. If you want to refer to Appendix B, provide specific page number and citation.

We are totally confused by the data on condensable inorganic and organic PM. These are

defined in footnote b as being method-driven. It would have been helpful if additional details

had been presented. In particular, we are curious about the chemical components of the

condensable inorganic PM fraction. The table shows that uncontrolled emissions are

numerically the same as controlled emissions. Footnote j states that “uncontrolled “values are

assumed to be equal to the maximum controlled value measured”. Since the controlled values

of 0.013 and 0.0042 are averages (arithmetic means), and are the same as the uncontrolled

values, is the table saying that the average is the same as the maximum value in the data set?

Please explain. We recall that this problem has been in table 1 in previous versions of AP-42.

18. Table 3: Same problems as Table 1; i.e. use of Reference1 which does not really contain the

primary data and uncontrolled emissions equal controlled emissions. 

19. Table 5: Same problems as Table 1; i.e. use of Reference1 which does not really contain the

primary data.

20. Table 6: Unlike previous tables, descriptive statistics about the data sets are not presented.
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

21. Table 7: Same problems as Table 1; i.e. use of Reference1 which does not really contain the

primary data. Furthermore, there is no discussion why a batch plant dryer using the same

range of fuels e.g. natural gas, No. 2 fuel oil and other fuel oil and a drum dryer using the

same fuel oil should have different emission factors for NOx and SO2. 

22. Table 8: Unlike previous tables, descriptive statistics about the data sets are not presented.

23. Table 14: This and many other tables, especially in appendix B, have footnote “a” obscured

because it is superimposed over the last letter of the table heading. This table has to be

redone so that an actual emission factor is given; not a formula for calculating low emissions

based on fictitious values of asphalt volatility. 

Same problems as Table 1; i.e. use of Reference1 which does not really contain the primary

data.

F. Page-by page Comments on Appendix B: Emission Factor Documentation for AP-42,

Section 11.1, Hot Mix Asphalt Production, June 2000 Draft

1. Page 1-1, final paragraph: The organization of the entire report is confusing. The last line

refers to Section 5, which is the same as Appendix A. Which is the main report and which

are the subsidiary appendices?

2. Page 2-1, Section title: Reference 1 is to an earlier version of AP-42. Why is an obsolete

version of the same document being used as the reference? Reference 3 is a personal

communication from the head of an industry lobbying group. Is this information in the public

domain? Can we get a copy?

3. Page 2-1, paragraph 3: The key information in this paragraph about the number of plants in

the country and the type of plants being built is not referenced so the reader can’t judge the

reliability of the information. 

4. Page 2-2, paragraph 1: The key information in this paragraph about 1996 production is not

referenced so the reader can’t judge the reliability of the information. Further, since road

building tends to be a cyclical activity (at least locally), production or output over several

years might be a more reliable way to establish these levels than the output in a single year.

Dept of Commerce or USGS/Mineral Industry Surveys probably collect and publish this

information.

5. Page 2-2, paragraph 2 and 3: If the hourly capacity data was averaged from the capacities of

precisely 98 batch plants and 162 drum plants, the numbers are probably correct, unless these

plants consistently misrepresented the capacity. Such misrepresentation is not likely to go

unnoticed since most of the data was gathered during performance tests at full capacity in the
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

presence of State agencies to make sure that emissions limits were being met. It is interesting

that “conversations with industry” are all that is needed to supercede this data. Why are we

not surprised!

Overall, this paragraph is attempting to relate hourly capacity to annual production. That goal

is not achieved. The discussion in paragraph 3 is totally confused and needs to be rewritten.

Hourly production rates are easy to measure. If the data set referred to in the previous

paragraph is for obtaining operating permits from the relevant State Air Pollution Control

Agencies, as is the case in Massachusetts, the plant is supposed to be running at or close to

the design hourly capacity when the emissions are sampled. Therefore, We believe that the

hourly capacity measurements are correct because these numbers are measured during State

compliance testing and should not be superceded by “industry comments”. 

The discussion should be talking about the fact that batch plants, especially batch plants

without silos for HMA storage, don’t operate for as many hours a year as drum plants

because they service customers using small trucks/small volume customers and because of the

difficulties in matching hot mix production with truck arrivals. (Note that because batch plants

store dried, hot stone, there is storage available, but the stored quantity is generally much

smaller than that available with HMA storage silos.) In contrast, because of their large

production contracts, drum plants operate for more hours each year and the ability to store

HMA in silos also facilitates long production runs. The entire paragraph keeps talking about

hourly production rates when the discussion is really trying to focus on annual production,

i.e. hourly rate times hours operated per year. 

Also note that the key assumption is that drum plants produce 90% more HMA than batch

plants ON AN ANNUAL BASIS. This assumption is not backed up with anything; no

footnotes or anything. If this is EPA’s assumption, say so. Interestingly, in the main report,

this assumption transforms into a finding that drum plants produce 100% more than batch

plants on an annual basis. 

If one assumes that the empirical 80/20 rule applies, the average annual output from batch

plants would be 108,000 tons per year and that from drum plants would be 194,000 tons per

year. This means that the purported annual industry output of 500 million tons is shared

almost equally between batch and drum plants. 

It should also be noted that there is no information provided on distribution between small

jobs and large jobs, which would also provide information on how the total production is split

between batch and drum plants. Is it possible that this is because industry information was

provided by a lobbying group supported mainly by the large producers? This means that the

production information has a bias favoring large producers and making them appear more

important.
16

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

6. Page 2-3, last paragraph: The writing should make clear whether the RAP is added to the hot

storage bins or directly to the mixer/muller. 

7. Page 2-4, last paragraph: This is a repeat comment in the last line. If you don’t have the data

about organic emissions, don’t speculate about “potential”.

8. Page 2-7, paragraph 3: Same comment as above under item 7regarding dataless conclusions.

The last sentence belongs in an industry sales brochure, not in an EPA document.

9. Page 2-10, paragraph 4: The last sentence belongs in an industry sales brochure, not in an

EPA document.

10. Page 3-2, paragraph 1: The sentence states that emission data must be from a primary

reference. In chapter 2, however, secondary references and anecdotal comments are used to

supercede primary reference data on hourly capacity.

11. Page 3-3, final paragraph: The comments here refer to variations or fluctuations in measured

results which could not be explained readily. While we agree that such results might be given

a lower rating, in many cases, variations are a normal part of the production process. For

example, if a batch plant is producing a mix with a high RAP content, the crushed stone is

heated to a high temperature to provide the heat for evaporation of the moisture associated

with RAP stored in the open. If another customer comes in for a RAP-free mix at this stage,

the hot mix will be loaded out at a much higher temperature and will emit more than the usual

amount of fugitive organics. This is a normal transient.

There are many factors which contribute to the emissions which were not measured. For

example, SO2 emissions from combustion are dependent on sulfur in the fuel. The emission

factors for different fuel types are a result of the maximum sulfur content allowed under the

fuel specifications. No such analysis is presented. The same comments hold true for organic

fugitive emissions being dependent on volatile content of the asphalt. 

12. Page 4-2 to page 4-117: On these pages, each reference is reviewed and commented upon.

There are several problems with this section. Initially, section 4.2.1.1 discusses reference 1,

section 4.2.1.2 discusses reference 2 and so on. By the time one reaches the end of this

chapter, the numbering is no longer synchronized. Section 4.2.1.327 refers to reference 354.

In between, some references are not discussed (42, 43, 115, 116, 120, 127, 131 and so on).

In other cases, missing references are discussed, for example reference 258. In addition, the

same reference numbers refer to different documents. For example, on page 4-6, during the

discussion of reference 23, references 26 and 27 are discussed. One has to read the citations

carefully to realize that these are references from the document called reference 23. But the

exact citations for 26 and 27 are not given. A careful reading also shows many

inconsistencies. In some cases, the data is downrated because some information is missing;
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Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

in other cases, it is not. See for example reference 181 where the data is still rated A although

information about RAP processing was not provided. On page 4-106, it appears that the

cross references are incorrect. 

The section ends with the review of reference 354 on page 4-117. This review resumes on

page 4-167. This is poor formatting for a report. 

13. Pages 4-118 through 4-147: There are two sections in this report: 4.2.4 Results of Data

Analysis and 4.3 Statistical Approach which more or less cover the same ground. They

should be combined so that the exposition is complete and consistent. 

In many cases, common sense should tell us that the emissions to the atmosphere are either

a result of the performance of a control device or the result of the presence of a pollutant in

the feedstock. A good example of the former is the PM emission factor from dryers

controlled with a fabric filter. Here, the emission factor for PM is not dependent on fuel type.

An example of the latter, is the sulfur dioxide emission factor for dryers. Here, the emissions

are dependent on fuel type since the control devices do not remove any substantial amount

of this pollutant. Yet, these issues are never discussed.

14. Page 4-119, paragraph 1: Was there any attempt to correlate capture efficiency in venturi

scrubbers with the pressure drop?

15. Page 4-122, paragraph 4: This paragraph states that the emission factor for sulfur dioxide was

assigned an E rating because the data ranged over an order of magnitude. This might have

been simply the result of the variation in sulfur content of the fuel. In the case of filterable

PM (page 4-118), the range is over two orders of magnitude but the emission factor got an

A rating. A little consistency would help.

16. Page 4-125, paragraph 4: This paragraph states that the emission factor for trace metals was

assigned an E rating because the data ranged over two orders of magnitude. This might have

been simply the result of the variation in trace metal content of the feed materials and fuel.

17. Page 4-126, paragraph 2:. This paragraph points out the inconsistencies in the approach

taken in several places in the report. Because there was no analysis of the feed materials or

of the fuel used, it is not clear whether the measured trace metals are present on the site or

are a result of sample contamination in the lab or elsewhere or whether the detection of trace

metals at the exhaust and non-detection at the entrance to the control device represents

random error in the measurements. The approach of discarding inconvenient data is not

acceptable. 
18

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

18. Page 4-135, last line: We are told that the statistical analysis is restricted to references up

to number 338. Why? Several of the subsequent references, up to reference 355, contain the

same type of data as that being analyzed and should have been incorporated. 

19. Page 4-137, paragraph 1: The description of the box plots is extremely short and incomplete.

Obviously, the authors do not intend to make it easy for readers to understand these plots.

Technically, what is shown is a “Box-and-Whisker” Plot, which is used to show

characteristics of univariate data. The data is ordered and ranked and then divided into four

equal parts. For example, a data set of 20 points would be divided into four portions, each

containing five data points. The box encloses the middle 50% of the data. The text states

that the whiskers “represent adjacent values”. Our understanding is that the whiskers either

enclose the entire data range, i.e. the upper whisker shows the range of values for the higher

25% of the data and the lower whisker encloses the range of values for the lower 25% of the

data. Alternately, in modified Box plots, the upper whisker is drawn to the highest point

within 1.5 times the interquartile range and the lower whisker is drawn to the lowest point

within 1.5 times the interquartile range. The interquartile range is the difference between the

75th and 25th percentile values. Values outside the range bounded by the whiskers are plotted

individually. None of this has been bought out in the terse description. 

20. Page 4-137, paragraph 3: The paragraph lists the statistical analyses performed. However,

the box plots shown are for only a few of the analyses listed. Where are the remaining plots?

21. Page 4-137, paragraph 5: This paragraph refers to Appendices B & C. Where are they?

22. Page 4-138, paragraph 2: This paragraph refers to Appendix A. Where is it?

23. Page 4-139, paragraph 1: This paragraph refers to Figure 4.2. Note that Figure 4.7 has an

identical caption. The two figures should be labeled properly. One has to read the text very

carefully to realize that Figure 4.2 refers to batch plants and 4.7 refers to drum plants.

24. Page 4-139, paragraph 2: There is a discussion of attempts to correlate wet scrubber

performance with other parameters. Any engineering handbook will tell you that scrubber

performance will correlate with pressure drop, yet this measurement was either not made or

not used. As it now stands, this paragraph finds that although the emission factor for venturi

scrubbers is less than half that for other, unspecified scrubbers, this result is not statistically

significant. 

25. Page 4-141, paragraph 1: This entire paragraph is confusing. Figure 4.3 shows that there

is a relationship between RAP content and condensable inorganic PM. The relationship

appears to be non linear. Alternately, looking at just the 0% RAP data points, it is clear that

there is great variability in the condensable inorganic PM emissions even without RAP.

Without any analysis of feedstocks and fuels, the source of these condensable inorganic PM.s
19

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

can’t be isolated. To add further confusion, the last sentence jumps to a discussion of carbon

dioxide emissions. The reference to Figure 4.3 in context of CO2 emissions is incorrect.

26. Page 4-144, paragraph 2: The first sentence is incomplete.

27. Page 4-145, paragraph 1: The invocation of engineering principles in the fifth line is

interesting because they have been ignored in many instances up to this point; e.g. discussion

of scrubber efficiencies without consideration of the pressure drops. VOCs, by definition,

don’t condense even when cooled to ambient temperatures. Therefore, if a control device has

an effect on VOC emissions, this attenuation must be a result of a mechanism other than

condensation, such as adsorption on solids. The data quoted show lower emission factors (by

a factor of 4) for fabric filters compared to wet scrubbers, but the authors find this result

surprising. Although they don’t tell us which engineering principle they are referring to, one

has to assume that they are referring to the ability of water to capture gases through

dissolution. Unfortunately, the components of VOCs are only sparingly soluble in water and

the pressure drops/retention times in such scrubbers are quite modest. Therefore, this is a bad

place to invoke such engineering principles when they contradict the data. 

28. Page 4-147, paragraph 2: The comment in the last line is that emissions are a function of

RAP content and production rate. Yet, earlier on page 4-139, these same conclusions were

rejected because of low correlation coefficients. Which conclusion is correct?

29. Page 4-147, paragraph 4: This is the beginning of the review of the more recent data on

load-out emissions. As noted earlier, there is a change in format of the report at this point

in that the discussion of data sets is split into three separate parts.

30. Page 4-148, paragraph 1: Reference 6 (fourth line) is incorrect. What is the proper

reference? We are also amused that this report has been given an A rating for data because

of the “few problems in the Technical systems Audit Report” etc. Unfortunately, this audit

report missed all of the errors found by the citizens. Further, the citizens caught the errors

through spot checking and there are no guarantees that they caught everything. If such errors

can exist in a report that was guaranteed a high degree of scrutiny, how sure is the EPA that

the other data is error free? We am particularly concerned about this point because the data,

which is supposedly in appendices A, B and C, is not attached to the material sent to us for

review. Also, it raises the question of whether EPA staff do any of their own reviews and

spot checks before accepting a report from a contractor. It does not appear to be the case.

31. Page 4-148, paragraph 2: The discussion should point out that Plant C is atypical of drum

plants in the industry. Figure 4.6 shows CO2 emissions factors for drum plants as a function

of production. Although there is considerable scatter, it is interesting to note that all high

emission points are associated with lower production and none are associated with high

production. Does this behavior extend to the emission of other pollutants?
20

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

32. Page 4-150, paragraph 3: There are several fundamental issues here that need to be explained.

First, EPA argued for a long time that the tunnel at Plant C was adequate to capture all the

emissions, based on visual observations by EPA - which were contradicted later by

observations by the citizens. EPA reluctantly agreed to use tracers only because the tunnel

did not meet Method 204 criteria. (In discussion of Plant D, We will discuss why Method

204 criteria are inadequate). Next, EPA averaged the efficiency over several runs and used

a single capture efficiency correction. It was only after the citizens showed that capture

efficiency varied during the day, typically declining as the on-shore wind picked up as the land

around the plant heated up, that EPA agreed to correct data for the individual capture

efficiencies. Finally, the so-called correction for truck emissions, discussed later, continues

to be a sham. But that sham is not really discussed here when the quality of data is being

considered. See our comments with reference to page 4-152 below. Also, note that there

is a typographical error in EMD GD-035 “ Guidelines for Determining Capture Efficiency”.

On page 9, in the formula for p in equation 7, xavg value should be 100.8 not 110.8. The

calculated value of p is correct, however. 

33. Page 4-151, paragraph 2: Note that Cambridge Environmental has calculated the cooling

of a mass of HMA. Their results are not supported by any measurements. 

34. Page 4-151, paragraph 4: The last line is ambiguous. Silo emissions were measured only at

Plant C. They can’t be “combined” with any other measurements.

35. Page 4-152, paragraph 3: This paragraph presents a major problem in this report. The

second line states correctly: “The most reliable method to adjust for emissions measured

during background operations would be to separately adjust each run for the measured

capture efficiency and then subtract these adjusted background emissions from the adjusted

emissions measured during production operations.” However, because this “procedure

produces negative values for both the PM and MCEM and many other HAP compounds”, a

new unsound procedure is adopted because it gives results that please EPA and industry by

by showing low but positive emissions. This new procedure is to use background emissions

uncorrected for capture efficiency. If the actual emissions have to be corrected for capture

efficiency because the enclosure does not capture all the emissions, there is no justification

for ignoring the capture efficiency for background.

Having used this incorrect analysis, the authors then have the temerity to advise us that this

result might even have a “high bias” relative to the most correct method mentioned above.

In a very narrow sense, this comment might be correct, but in the current context, given the

consistent efforts of the Project Officer to bias the results to favor industry, this comment is

totally off base. 
21

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

Line 5 states that this situation “cannot be accommodated retroactively.” This statement is

not correct. The best way to eliminate improper data manipulation is to discard the phony

background adjustment and report the data as that from loadout plus truck exhaust. Since

silos always dump hot mix into a truck, these combined emissions are present at each silo

loadout point. Further, if a local permit application requires the inclusion of an estimate for

truck emissions on site (and we have yet to see a local permit that requires this), note that the

truck spends about 1⁄2 minute under the silo but many more minutes, typically 3 to 8, on site.

As a result, the truck emissions that are included under loadout correspond to the 1⁄2 minute

portion. Therefore, the double counting of truck exhaust emissions would be minimal and can

be adjusted for by subtracting the 1⁄2 minute from residence time of the truck on site. We

strongly recommend that Tables 4-25 and 4-26 be revised to reflect this approach.

36. Page 4-152, paragraph 4: This paragraph further demonstrates the problems with EPA’s

background run. The EPA project officer was interested in recording a high background and

the original data showed that he was able to manipulate truck placement in such a way that

uncorrected emissions in the second half of the run were about twice the emissions in the first

half. If these emissions are corrected for the lower capture efficiency in the second half of the

run, the corrected emissions from the second half are almost three times the corrected

emissions from the first half. This further points out the problems with EPA’s manipulation

of and placement of trucks to maximize exhaust emissions inside the tunnel. 

We have to apologize for not taking this particular analysis far enough a year ago during a

review of the Plant C draft. When the data for Run 4, the background run, was reviewed, it

was clear that there was data manipulation going on since the raw data showed that emissions

in the second half of the run were double those in the first half. When these emissions were

adjusted for capture efficiency, the emissions from the second half almost tripled. We felt that

the data from the first half of the run was more appropriate than that from the second half.

We did not realize that this data, after correcting for capture efficiency, still overwhelmed and

negated the load out emissions and was therefore also tainted. 

37. Page 4-153, last paragraph: In the 10th line, there is an unnecessary caveat about the

relationship being uncertain. The simplest assumption is one of proportionality. Unless lab

scale data are collected that indicate otherwise, this is the best way to deal with the issue. Are

you forgetting Occam’s Razor?

38. Page 4-154, paragraphs 1 - 2: These paragraphs repeat industry propaganda (along with that

from State highway department laboratories who share the same road-building mind set). The

specifications allow for measurements of unblended asphalt and the information represents

the results of tests on unblended asphalt. In the Boston area, the terminal in Chelsea has a

tank holding such additives for blending with the asphalt. After a meeting at EPA-Region 1,

where the industry representatives had denied that any blending took place, Mr. Frank

Singleton, the Board of Health Agent for Chelsea showed me this tank which is clearly labeled
22

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

as containing an asphalt additive. The citizens submitted a list of many such additives from

Roads and Bridges magazine to the EPA/citizen group which was ignored by the EPA Project

Manager, who instead chooses to believe the asphalt industry’s lobbyists who insist that such

additives are not used. Also, we have examined the application from one of the terminals in

Chelsea which said that they proposed to add these additives directly to the tanker truck

whereby they would mix in the truck while being transported to the user. This would mean

that a sample taken at the terminal would be a sample of unmixed asphalt.

The third paragraph needs to be deleted. As long as the specifications allow for up to 1%

volatiles in asphalt (even before additives are used), it is misleading for EPA to state that their

approach in Table 4-27 “encourages the use of site specific data”. The primary use of AP-42

is to prepare calculations to get permits to build and to operate hot mix plants. Therefore,

there is no site specific data that can be used other than fictional data. Unfortunately, the

industry has a long history of providing low-ball estimates, designed to fool the public and get

permits from agencies that are not particularly anxious to ask difficult questions. 

39. Page 4-155, paragraph 2: The statement is that “The industry has stated that good paving

practices dictate that load-out temperatures in excess of 325o F should be avoided.” Who has

stated this and in what context? The specification for highways is that hot mix temperature

before the pavement is laid down should be between 325 and 275o F. Hot mix outside this

temperature range can be rejected. The temperature at load out depends on the distance

between the plant and the location where the new pavement is being laid and the size of the

truck since smaller loads will cool faster than larger loads. 

On the 13th line, the statement is that “this hypothesis has not been validated by emissions

testing but provides an adjustment that is directionally correct.” This comment is totally

unnecessary and needs to be deleted. Is EPA saying that the Clausius-Clayperon equation

should be thrown out? Alternately, is EPA saying that the degree of precision and accuracy

associated with emissions testing methodology is good enough to provide this type of data?

40. Page 4-157, paragraph 2: In this paragraph, the groundwork is being laid to explain why

inorganic PMs were much higher at Plant D than Plant C. This is further elaborated on page

158. We strongly disagree with the conclusion that the additional dust was a result of truck

movements. While Plant D was unpaved, water sprays were used to keep the dust down as

noted in the report and as observed. At Plant C, because of the practice of cleaning the silos

at the end of the day with crushed stone, there was considerable dust present in the tunnel.

Furthermore, one ofthe silos had dumped hot mix on the floor and cleaning it up generated

a lot of dust. Our recollection is that if anything, the tunnel at Plant C was dustier than the

one at Plant D. We believe the explanation for the higher PM load at Plant D is the relatively

short residence time in the mixer at any batch plant. Because of this, during mixing, there are

small pockets of stone dust that are not coated with asphalt and these are the source of the

high PM readings. In contrast, the vapors inside a silo have time to permeate through the
23

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

mass of hot mix in the silo and coat any uncoated dust particles. Once coated, the fine dust

coagulates and is no longer airborne particulate matter. This hypothesis is supported by the

visual observation that dumps from the mixer at Plant D were dustier than those at Plant C

when observed from inside the tunnel.

41. Page 4-158, paragraph 2, 3: See the comments above. The adjustment is indeed “speculative”

and should be eliminated. Separate emissions factors should be used for inorganic PM

emissions from batch and drum plants.

42. Page 4-159, paragraph 2, 3: There is a fundamental problem with the two paragraphs which

has not been explained. MCEM PMs and TOC are generated the same way and from the

same source. Therefore, if MCEM generation is a function of loadout time, TOC generation

should also be a function of loadout time. Of course, the comparison is further complicated

and made meaningless by the bogus “background” correction discussed earlier. To eliminate

the confusion, separate emission factors should be prepared for batch and drum plants in all

cases.

43. Page 4-159 - 162: As discussed earlier, the entire loss on heating discussion should be

rewritten so that a RTFOT value of -0.5% is used in all cases. This way, the EPA will not

be providing yet another opportunity for builders of new plants to misrepresent what might

happen once the plant starts operating. The same applies for the formulae which promote the

use of variable temperatures.

44. Page 4-163, paragraph 1: The first line states that “vapor pressure information .... is not

available”. The report fails to state that this was only because of EPA’s refusal to collect this

information.

45. Page 4-163, paragraph 3 - 5: Please explain what you mean by “pegged TOC readings”?

As it stands we can’t understand this at all. Furthermore, Figures 4-9 through 4-13 are

missing from our copy. Finally, it is not clear whether you are referring to Plant C or Plant

D in this discussion, though the context suggests Plant C.

We further find that the contention that the estimate of unmeasured emissions being an “upper

bound” to be unpersuasive and incorrect. Our reasons for saying so result from the

inadequacies of Method 204. These were outlined in Ravi Nadkarni’s letter of September 15,

1999. They are:

a. At Plant C, two precautions were taken to ensure that we could measure or estimate

the amount of organic fugitive emissions that did not reach the primary sampling

ports. The first was the use of sulfur hexafluoride tracer gas, and the second was the

use of impingement/deposition plates in the ducts which collected organic particulates

which would be deposited upstream of the sample port. Although all the emissions did
24

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

not reach the sampling ports (some was deposited inside the tunnel and some was

pumped out of the tunnel by ambient breeze or by truck movement), the tracer gas

enabled an estimation the VOC portion of this loss. (As was pointed out during the

planning, the tracer gas was a good proxy only for non-condensible emissions but not

for condensible emissions.)

At Plant D, a tracer gas was not used although requested by the citizens because the

TTE was constructed to meet Method 204 criteria, yet visual observations and THC

readings showed the following: 

b. An ambient breeze was sufficient to cause some of the fume to escape from the top

or the bottom openings in the downwind door of the tunnel. Therefore the size of the

openings was decreased further. This means that the Method 204 criterion of

maintaining over 200 fpm at a natural draft opening is not adequate. Note that 200

fpm is less than 2.3 miles per hour, which is not much of a breeze. Therefore it is not

surprising that these criteria are inadequate to assure total containment within the

TTE. We observed visible emissions of fume from the entrance, further emphasizing

that the Method 204 criteria are inadequate. 

c. Further, Method 204 has a more serious and fundamental problem. Although the size

of natural draft openings is specified, the method does not contain any criteria to

ensure that the emissions are pulled/sucked past the sampling point in a reasonable

period of time. As is well-known, residence time calculations, based on enclosure

volume and fan capacity, generally provide incorrect information by underestimating

the time to evacuate the enclosure because of channeling. Note that Method 204 does

not require a specific location for the natural draft openings, a problem that was

pointed out during the planning sessions. At Plant D, even after the size of the

opening was decreased, and the little pieces of colored tape at the Natural Draft

Openings were indicating airflow towards the inside of the TTE, the tunnel was not

evacuated in the approximately 15 second time gap between the final drop and the

opening of the doors. This can be clearly seen in the fact that THC readings did not

drop to zero even when the sample averaging time is less than 1 minute. This fact

was also observed visually inside the TTE enclosure since SVOCs are visible. Thus,

in the absence of a tracer gas, we have compelling evidence that the collected sample

had a low bias. For example, the extended period test results in MRI-D-Table 4-4,

show that final concentration did not drop to zero but stayed between 1 ppm and 2.1

ppm . Yet, this low bias is not mentioned anywhere in the report nor in Appendix B

of the MRI Report which contains the original data. These emissions did not reach the

instrumentation but were emitted to the environment causing a low bias.

46. Page 4-164, paragraph 2: There is reason to believe that the numbers derived are low. We

base this on several facts: Material Safety Data Sheets contain the following warning:
25

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

“Studies have shown that low flash point substances, such as hydrogen sulfide and low-boiling

hydrocarbons, may accumulate in the vapor space of hot asphalt tanks and bulk transport

compartments. Such vapors may exhibit flammability characteristics of a significantly lower

flash product than would be indicated by the open cup test.” A review of light hydrocarbon

compound properties in the Handbook of Chemistry and Physics indicates that the lower

explosive limit is reached at vapor concentrations around 1%. Therefore, this warning makes

sense only if the TOC concentration is around 10,000 ppm, not the 2000 ppm level used.

Second, storage tank temperatures are generally higher than 325o F and closer to 350o F.

Finally, the assumed vapor pressure is low in comparison to data from Nelson’s Petroleum

Refinery Engineering, which would indicate a vapor pressure over 10 mm Hg. 

47. Page 4-166, paragraph 4: This needs to be rewritten. It is obvious that this paragraph is

recycled from some other writeup. There is no relevant “response 53" in the present writeup.

Further, emissions are not only dependent on temperature, they are also dependent on

convective effects, i.e. evaporation rate increases in the presence of strong convection.

48. Page 4-166, final paragraph: This paragraph presents a single emissions factor for yard

emissions. This is exactly what needs to be done with the RTFOT equations. They should

be eliminated and only a single factor, based on RTFOT of 0.5% presented in AP-42.

49. Page 4-167, paragraph 2 - 4: This is a critique of Ravi Nadkarni’s original submission in 1994.

There are several problems here. If you are going to critique this work, you should refer to

all of submissions to the EPA, not just the first one from 6 years ago. The complete list

would include his response to Mr. Ryan of EPA of October 26, 1995 and November 16,

1995 and to Mr. Mobley of July 5, 1996. We find it particularly interesting that the estimate

of vapor pressure of asphalt from 1994, based on several model compounds has been

represented as one based on a single model compound. Second, “people who live in glass

houses should not throw stones”. In using the TANKS program, (see page 4-165) the

authors used another set of model compounds whose presence at the required concentrations

is also not supported by the same data that is used to attack this work. For example, if

naphthalene and 2-methylnaphthalene are predominant species of PAH in emissions from

asphalt DRYERS, why were tetracosane and pentacosane used as model compounds for

TANKS? Can you please recalculate the TANK emissions using naphthalene and 2-

methylnaphthalene? 

Next, why is the Cambridge Environmental letter not listed in the references? It should have

been reference 358. Cambridge Environmental used another set of model compounds to

come up with a different figure. That does not make their calculation any more valid since

both estimates were done years ago in the absence of data on components of asphalt vapor.

(This also begs the question of why DRYER emissions are used here when better data is now

available from silo emissions.) Given Cambridge Environmental’s track record as an extreme

advocate for their industrial clients in the public health area, we would not characterize their
26

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

work as “independent”. (In one case, they compared emissions from a single plant versus

emissions from all industrial plants of all types in a county and the state. Even the most

polluting plant can appear to be a winner under that criterion.) There is more to the

Cambridge Environmental story. In a public meeting in Uxbridge, Dr. Zemba, the principal

author of the letter, reversed his position and stated that he now believed that the calculations

are in the correct range, or only modestly overestimate the actual emissions. Specifically, he

said, “When I originally looked at the calculations, I thought that these were grossly

overestimated. I can see your point though and they might not be overestimated by as much

as I originally thought.” He also admitted that he had not studied Ravi Nadkarni’s two 1995

letters to the EPA. A specific critique of the Cambridge Environmental work is in the 1996

letter to David Mobley. 

We agree that calculations done in the absence of actual measurements should be discarded

when actual measurements are available. But any critique should fairly represent the work

and its shortcomings. 

50. Page 4-168, paragraph 2 - 4: The evaluation of reference 359 indicates that the reference was

not read critically. Tables 4-42 and 4-43 are presented without any critical evaluation of the

contents. The table shows about the same concentrations at an upwind site and a downwind

site. How is this possible, unless the measurements represent background readings? There

is no comment as to why higher concentrations were detected at a residential site and how

the residential site compared to the upwind and downwind sites. If you are not going to

evaluate the information, don’t present the tables.

51. Page 4-169, paragraph 2 - 6: Again, the comments indicate that reference 360 was not read

critically. For example, the high outliers were rejected. Having read the original report, we

know that the authors don’t plead that the instrument malfunctioned. Therefore, the high

measurements must be explained. Or are they supposed to be background? It is likely that

the wide variation in measured concentrations was a function of measuring technique? Low

readings were obtained upwind of the emission source and high readings were obtained near

the source and downwind from it. Under these conditions, when the instantaneous wind

direction and sampling location with respect to the source were not recorded, there is no

justification for rejecting the high data points. Note that the determination of the high data

points as outliers was based on a purely statistical argument (the “outliers” were many

standard deviations away from the rest of the data; therefore they don’t belong with the rest

of the dataset); not one based on measurement errors or other relevant factors.

The final paragraph again uncritically quotes the process used by the authors to convert the

measurement into a mass rate in g/sec. The concentration of benzene was measured in

concentration units i.e. g/l which can be converted to g/m3. This was then converted to an

“emission factor” (actually a mass rate) by multiplying the concentration by wind velocity in

m/sec and the vehicle area in m2. This is data manipulation of the worst sort. If one is trying
27

Comments by Ravi Nadkarni & Lloyd Fillion August 31, 2000

to measure the flux of benzene escaping from the truck, the flux would be expressed in units

of mass flow per second per unit area or g/sec-m2. The relevant area is that perpendicular to

the direction of flow of the flux that you are trying to characterize. In this reference,

concentration, wind velocity and truck area are combined in a way that might be

dimensionally correct but make no physical sense. In particular, it is difficult to see how a

measured wind velocity relates to the area of the truck. EPA does disservice to the reader

when material of this type is presented in detail over 4 tables without critical evaluation.

52. Page 4-172, reference 364: This reference is the AIRx report of measurements at Plant C.

We want to see exactly what procedure was used to estimate capture efficiency at 70 to 90%.

Otherwise, this comment should be eliminated. 

53. Tables 4-4 to 4-14: There are numerous deletions of data shown in these tables where

emission factors for each plant are presented. The reasons for the deletion are not explained

in the text.

54. Table 4-15: When will this table be completed? 

55. Table 4-19: Footnote a is incorrect. R2 is the correlation coefficient, not the “squared

correlation coefficient.” We believe the terminology calls R the coefficient of determination,

so that R2 could be called the “squared coefficient of determination”. The more common

usage is to stick with “correlation coefficient” or R2. 

56. Table 4-23, 4-25: In view of the comments earlier about the background run, these tables

need to be revised.
This Page is intentionally left blank.
Elane Kruger, Chief

Environmental Toxicology Unit

Bureau of Environmental Health Assessment

Massachusetts Department of Health

Boston, MA
This Page is intentionally left blank.
September 7, 2000 

Robert F. McConnell

Environmental Engineer

Air Quality Planning Group

United States Environmental Protection Agency

Region I

John F. Kennedy Building

Boston, MA 02203-0001 

Dear Mr. McConnell: 

Thank you for extending the deadline for submitting our comments. The Massachusetts Department of

Public Health (MDPH) Bureau of Environmental Health Assessment (BEHA) is "Writing this letter in

response to the U.S. Environmental Protection Agency's (EPA) request for comments on the draft

emissions assessment report and draft AP-42 section regarding emissions from hot-mix asphalt plants

(i.e., “Hot Mix Asphalt Plants Emission Assessment Report” and "Hot Mix Asphalt Plants AP-42

Section 11.1”). These documents are the culmination of work done by EPA to characterize uncontrolled

emissions during loading operations at hot mix asphalt plants. As well as reviewing asphalt plant test

reports and related documents, EPA performed its own emission testing at asphalt plants in Irvine,

California, and Barre, Massachusetts. Using these data, EP A produced emission factors which can be

used to estimate area-wide emissions from many facilities as welt as emissions from specific facilities.

Previously, MDPH had submitted comments concerning the two-part protocol for emission testing at the

hot mix asphalt plant in Barre, Massachusetts, and the 8-volume draft report on results for emission

testing at the Barre and Irvine plants. MDPH comments focused primarily on whether speciated

emissions data, which were gathered solely from the Cal1fornia facility, were applicable to the Barre

facility due to differences in modes of operation and material between the two plants and whether dust

particles collected at the elbow junctions of the Barre plant exhaust system were included in the study. 

In response, EPA explained that limited resources precluded conducting analyses at the Barre plant to

better speciate emission data. However, EPA also stated that applicable specific emissions data for

asphalt could be gathered from previous asphalt studies. In addition, EPA stated that those dust particles

that were deposited at the elbow junctions were recovered and analyzed.
As we have previously noted, it is important to understand the limitations of the emission testing at the

Barre and Irvine plants, some of which were discussed in EPA: response to comments (i.e., "Emission

Tests of Hot Mix Asphalt Plants, Response to Comments for Asphalt Plants C and D"). EPA noted that

resources were not available to perform emission testing at different times of year or at different 

locations to determine whether there is a relationship between emissions and asphalt cooling or 

variability of emissions of specific chemical compounds. This information could be important in

determining emissions from plants in different areas of the country. While we appreciate that limited

resources may have prevented more comprehensive testing, unfortunately a number of uncertainties

remain regarding opportunities for exposure and health concerns. In addition to those noted above,

uncertainties also exist due to the variations in modes of operation, materials, and plant designs. 

Therefore emission data from previous asphalt studies may not be applicable to the Barre plant. We

would recommend that these important limitations; be outlined in the final document, rather than just in

the response to comments.

A final comment regards EPA reporting averages of data collected without presenting the range of

numbers. This concern has also been raised by others. The use of average values may be appropriate 

for evaluating risks of long-term health effects e.g., cancer risk, but may underestimate the potential for

health effects associated with other issues, e.g., short-term odors, that have been reported to be 

associated with these types of facilities. Clearly, some of the chemicals, e.g., naphthalene, contained in

the asphalt have very low odor thresholds. For that reason, we recommend that EPA present the full

range of predicted emissions data including upper-bound or maximum estimates of emissions as they

relate to the potential for shorter term effects, such as odors. This is particularly important given that

odors have been important issues at other facilities like this elsewhere in the U.S. (e.g.) Michigan). 

We appreciate the substantial amount of technical work that was undertaken by EPA and others in 

regard to this project and applaud EPA's efforts to freely discuss the results of this with a variety of

concerned individuals and organizations. Thank you for your attention and consideration. If you have 

any questions, please do not hesitate to call me or Michael Celona at 617-624-5757.

Sincerely,

Elaine T. Krueger, Chief 

Environmental Toxicology Program (BEHA) 

cc: Suzanne K. Condon, Assistant Commissioner

Martha J Steele, Deputy Director, BEHA 

Michael Celona, Environmental Analyst, BEHA
Gary Fore, Vice President

Environment and Safety

National Asphalt Pavement Association

Lanham, MD
This Page is intentionally left blank.
email: napa@hotmix.org www.hotmix.org

NATIONAL ASPHALT PAVEMENT ASSOCIATION

NAPA Building P 5100 Forbes Boulevard P Lanham, Maryland 20706-4413

Toll Free: 1-888-468-6499 P Tel: 301-731-4748 P Fax: 301-731-4621

Mike Acott, President

August 17, 2000

Bob McConnell

EPA Region I 

Q Congress Street/CAQ

Suite 1000

Boston, MA 02114 

Reference: Draft Hot Mix Asphalt Plants -Emission Assessment Report;

Draft AP-42 Chapter 11.1; Background Report 

Dear Mr. McConnell:

We have reviewed the above referenced draft reports and offer comments and

suggestions for your consideration.

This letter will be broken into two sections. Section I will discuss the suggested

corrections and comments per above referenced document. Section II will

discuss additional stack test report data. This data offers significant additional

information relative to Benzene and Sulfur Dioxide (SO2). 

Section I

Chapter 11.1 Hot Mix Asphalt Plants (Draft 2000)

General comment - Tables tend to be confusing. For example, Place HAPs

contiguously with HAPS and follow with Non-HAPs together. Also, suggest

adding a set of batch table and drum tables with contiguous HAPs listing, nonHAPs listing and metals HAPs vs. non-metal HAPs listing.

General comment - Suggest following the same table order as found in the

Emissions Assessment Report. Much less confusing.

% Page 11.1-1 

A. Hot mix asphalt paving materials can be manufactured by: ... (2) continuous

mix (mix outside dryer drum) plants, ...

Please add the word dryer when using the "mix outside dryer drum" phrase. 

This will allow for both past and present types of plants. 
August 17, 2000

EPA -OAR

Page 2

% Page 11.1-3

A. Add in (source classification code in parentheses) under Figure 11.1-1 

General ...

% Page 11.1-4

A. Add to Figure 11.1-2. General process 11ow diagram for parallel-flow drum

mix asphalt plants. 

B. Add in (source classification code in parentheses) under Figure 11.1-2

General ...

% Page 11.1-6

A. Add in (source classification code in parentheses) under Figure 11.1-3

General ...

% Page 11.1-7

A. In the fourth line, second paragraph under 11.1.2.1 - Batch Mix plants,

please add the word very before the word small. The sentence will then read

“and very small amounts of organic compounds”

% Page 11.1-8

A. In the first partial sentence on the page, please add prior to tarping after

truck. The sentence will then read: Organic vapor ... bed of the truck prior to

tarping, ...”

B. In the second line from the top of page - please add the word very before

the word small. The sentence will then read “may contain very small

amounts of HAP”

% Page 11.1- 9

A. In the first paragraph under section 11.1.2.3 - please add the word very

before the word small. The sentence will then read “and very small amounts

of organic compounds of various species” 
August 17, 2000

EPA -OAR

Page 3

% Page 11.1-10

A. 2nd paragraph -Suggest a more typical loss-on-heating of 0.25 not 0.41 

a. To estimate total PM emissions from drum mix plant load-out operations

using an asphalt loss-on-heating of 0.25 percent and temperature of

290/F, HMA mix, the following calculation is made: 

EF = 0.000181 + 0.00067 (-v)e ((0.0251) (290 + 460) -20.43)

= 0.000181 + 0.00067 (-(0.25))e ((0.0251)(290 + 460) -20.43)

= 0.000181 + 0.00067(0.25)e (-1.605)

= 0.000181 + 0.00067(0.25)(0.2009)

= 0.000181 + 0.0000485

= 0.000215 Ib/ton of asphalt loaded 

NOTE: The correlation factor in the equation should be 0.00067 and not

0.00059. 

This loss-on-heating value is a value that is seen on a daily basis within

the Industry.

% Page 11.1-16

A. Footnote C -Suggest striking SO2 or add 50% attenuation of SO2. Please

review attached stoechiometry and SO2 attenuation data. 

% Page 11.1-17 

A. In the title for Table 11.1-6, please delete the word formaldehyde from title 

B. Note there is an error under VOC for natural gas-fired dryer and the No.2

fuel oil-fired dryer. They should be 0.0076 for both not 0.0082

% Page 11.1-18 

A. Footnote C – Suggest striking SO2 or add 50% attenuation of SO2. Please

review attached stoechiometry and SO2 attenuation data. 

B. Footnote D – There is a question that the range to 96 lb/ton is too high. 

Where is source for this number?
August 17, 2000

EPA -OAR

Page 4

% Page 11.1-20 

A. Sub title: Hazardous air pollutants under Pollutant Heading – For easier

reader understanding, please change subtitle from Hazardous air pollutants to

non PAH/HAPs 

B. Please add a line totaling the non-PAHs hazardous air pollutants section.

Currently very confusing. 

C. Sub title PAHs – Please change from PAHs to PAH/HAPs 

D. Please add row and sum the NO. 6 fuel "organic HAPs" 

E. Please change non-HAP subtitle to Non Organic HAPs 

F. Sub title: Hazardous air pollutants – Please change to PAH/HAPs

G. Left side column under Dryer with fabric filter – Please add natural gas,

propane, fuel oil, or waste oil fired. Confusing as is and fails to distinguish

between these fuels and No.6 fuel oil.

G. Footnote b – Please change as follows: Natural gas, propane, fuel oil, or

waste oil fired dryer. For pollutants that are marked with a “*”, separate

emission factors are presented for No. 6 fuel oil fired dryers. Substitute these

factors for above factors when burning No.6 oil. 

% Page 11.1-21,22,23 

A. Use the same format and comments as suggested for above Table 11.1-9 

% Page 11.1-22 and 23 

A. Please add Dioxins and Furans to above referenced Organics and HAPs 

B. Delete uncontrolled from this table because to be consistent with other

HAPs, we should use data collected after filtration in the stack. Please make

a footnote reference that the uncontrolled numbers are in the Emission Factor

documentation for AP-42 Section 11.1 Hot Mix Asphalt Production.
August 17, 2000

EPA -OAR

Page 5

% Page 11.1-24 

A. Delete uncontrolled from this table because to be consistent with other

HAPs, we should use data collected after filtration in the stack. Please make

a footnote reference that the uncontrolled numbers are in the Emission Factor

documentation for AP-42 Section 11.1 Hot Mix Asphalt Production. 

B. Footnote b – Please change as follows: Natural gas, propane, fuel oil, or

waste oil fired dryer. For pollutants that are marked with a “*”, separate

emission factors are presented for No. 6 fuel oil fired dryers. Substitute these

factors for above factors when burning No.6 oil.

% Page 11.1-27 

A. Overall comment – Should create subtitles for Metal HAPs category and a

Metal Non-HAPs categories. Also suggest moving to 11.1-9. 

B. Adjust footnotes accordingly. 

% Page 11.1-28 

A. Delete uncontrolled from this table because to be consistent with other

HAPs, we should use data collected after filtration in the stack. Please make

a footnote reference that the uncontrolled numbers are in the Emission Factor

documentation for AP-42 Section 11.1 Hot Mix Asphalt Production.

B. Use the same format and comments as suggested for above Table 11.1-9.

Should be the same for both drum and batch. 

C. Please delete Footnote b. unnecessary. 

D. To make the table easier to read, suggest switch last two sections of the

table. The section pertaining to lead and mercury should come last. 

% Page 11.1-29 

A. Question why include total PM when it includes organic PM? This is very

confusing. 

B. Footnote a. – Please change the word asphalt to HMA mix to prevent

confusion as to mix temperature or liquid temperature.
August 17, 2000

EPA -OAR

Page 6

% Page 11.1-30 

A. Place PAH/Organic PM (%) up above PAHs line in the left column. It

should be a title, not a part of the data. 

B. Change Subtitle from PAHs to PAH/HAPs 

C. Total PAHs, subtitle – Change to total PAH/HAPs

% Page 11.1-31 

A. Move subtitle – Compound/TOC(%) up to be included in the titles for the

columns. 

B. Create Sub title – non-VOC/non-HAPs

C. Please a Percent sign (%) to every EF as in table 11.1-15. It is currently

very confusing because the other tables in this document do not contain

percents. 

D. Total – add line total volatile organic HAPs 

E. Please add to the example on page 11.1-10. It would be helpful to

illustrate the use of Table 11.1-16. 

% Page 11.1-32 

A. Please correct Reference No.2. Katherine is spelled Kathryn.

Emission Assessrnent Report (Draft 2000) 

% Page 2

A. Paragraph 1, second line -please add the following: ...and PM-2.5 and

very small amounts of hazardous air pollutant...

B. Second sentence – delete the "e" off of the end of with.

C. Second sentence – please add the following: ...VOC and very small

amounts of volatile HAP organic compounds.
August 17, 2000

EPA -OAR

Page 7

D. paragraph 2 - please add the following: ...emissions for specific facilities

where source specific emissions is not available or where source

testing is cost prohibitive. 

% Page 3

A. At the end of the last paragraph -Please add an editors note: "HAPs

emissions are typical of emissions that result from fossil fuel

combustion."

% Page 4

A. Add in (source classification code in parentheses) under Figure 1 Typical

% Page 5

A. Add in (source classification code in parentheses) under Figure 2 

% Page 8

A. 3rd paragraph – ...(2) continuous mix (mix outside dryer drum) plants, ...

Please add the word dryer when using the "mix outside dryer drum" phrase. 

This will allow for both past and present types of plants.

% Page 10 

A. 2nd paragraph – Please add the following: ... counterflow drum mix plants

will likely have organic stack emissions ... 

B. 4th paragraph – Please correct as follows: ... CO; and very small amounts

of organic compounds ...

% Page 11

A. 1st paragraph – Please add the following: ... organic aerosol may contain

very small amounts ...

B. Last paragraph – Please add the following: An initial screening the of these

documents...

% . Page 12

A. 1st paragraph – Please add the following: ... truck prior to these departure

for the job site”)”. Missing end parentheses.
August 17, 2000

EPA -OAR

Page 8

% Page13

A. 2nd paragraph – Please add to the end of the paragraph. ...”representative

of gas-fired heatlers. As a practical matter theses units represent a very

small combustion source when compared to the dryer.

B. 4th paragraph – Prior to the last sentence please add the following

sentence. ... developed from the data. For example, two scientific

auditors from the Research Triangle Institute were employed to

independently audit the test and reporting process. These additional

steps ...

% Page 15

A. Last paragraph – Please add the following sentence to the end of the

paragraph. ...equation developed from the emission data. It should be

noted that truck emissions would decrease rapidly with time as a result

of surface cooling and crusting and industry practice of covering loads

with tarps.

% Page 20

A. Sub title PAH – Please change as follows: PAH (semi volatile HAPs). 

B. Please delete line between methylene chloride and MTBE

Section II

The Hot Mix Asphalt Industry is providing additional data specifically relevant to

S02 attenuation and benzene to EPA for possible inclusion into the Emissions

Factors Document (AP-42). Attached are three binders containing stack test

reports. All of the tests were consist of three 1-hour runs and were conducted for

compliance purposes. 

NOTE: NAPA is sending one copy of this material and one copy of the

comments to Ron Myers. Only the comments document is being sent to EPA

Region I. 
August 17, 2000

EPA -OAR

Page 9

S02

The Draft Emissions Assessment (EA) offers an EF for SO2 of 0.078 lbs/ton hot

mix from drum mix plants firing waste oil (Draft EA,, Table 11.1-7). The Draft EA

also suggests via footnote (c.) of Table 11.1-7 that AP-42, Chapter 1 also be

used to estimate SO2. Chapter 1 Emission Factors (EF) incorporate fuel sulfur

content to determine SO2 emissions. 

It is believed that a more accurate approach should be used to determine SO2

emissions from plants firing oil, especially waste oil.

Several stack tests for SO2 were conducted. Samples of each plant's burner fuel

supply during each test were taken and analyzed for sulfur content. The amount

of SO2 produced during combustion of the burner fuel was calculated. There

was an assumption that all of the sulfur in the fuel would be converted to SO2. 

Then, using a mass balance approach, the actual stack emissions of SO2 was

compared with the calculated SO2 as a product of combustion, and determined a

control (i.e., emission reduction) factor for SO2. from a hot mix asphalt plant,

firing oil.

The proposed means of control would be the adsorption of SO2 by dust particles

suspended in the ductwork and captured on the bags in the baghouse. For a

plant producing 250 tons/hour hot mix and firing 500 gallons/hour waste oil

having a sulfur content of 0.046% by weight and a specific gravity of 0.89, the

amount of SO2 generated by combustion would be 500 gal/hr x 8.34 lbs/gal x

0.89 x 0.46/100 x 2 (lb S02/ lb S) = 34.14 lb SO2/hr. At the same time, the

uncontrolled particulate emissions from the plant would be 28 lbs PM/ton (Draft

Table 11.1-3) x 250 tons/hour = 7000 lbs PM/hour. The available reaction

surface area of the dust particulate provides significant acid gas capture

opportunity by any alkaline solid material suspended in the exhaust stream or

accumulated on the bag house bags.

The results from the 15 tests demonstrate SO2 control ranging from 47% to 97%,

with an average control of 62%. Test result averages show little variation in

control among different plant types, aggregate types or recycle asphalt pavement

(RAP) content in the mix. Please refer to the attached table: “Asphalt Plant SO2

Emissions Summary”
August 17, 2000

EPA -OAR

Page 10

The Wisconsin Department of Natural Resources (WDNR) has reviewed these

stack tests and wil adopt a conservative control factor of 50% for future

permitting and emission inventory purposes. Please refer to the attached letter

from Lloyd Eagan, Director of Bureau of Air Management from the State of

Wisconsin – Department of Natural Resource.

Benzene

Stack tests were also conducted for benzene from drum mix plants, firing either

waste oil or natural gas. The reports from 17 tests are enclosed. These reports

indicate average benzene emissions of approximately 0.0003 lbs benzene/ton

hot mix asphalt, with no significant variation for fuel type. The draft EA lists a

benzene EF of 0.00051 Ibs/ton (Table 11.1-10).

Thank you for your attention to these matters. If you have any questions or

comments, please feel free to call either Una Connolly or myself at 301-731-

4748. 

Sincerely,

Gary Fore

Vice President - 

Environment & Safety 

attachments



This Page is intentionally left blank.
Norman Ostroff, PhD, PE

Stamford, CT
This Page is intentionally left blank.
N ORMAN O STROFF, PhD, P.E.

87 FISHING TRAIL

STAMFORD, CONNECTICUT 06903

(203) 322-5559

2000.190

August 25, 2000

Mr. Robert McConnell

Environmental Engineer

Air Quality Planning Group

USEPA - Region 1

1 Congress Street - Suite 1100

Boston. MA 02114-2023

Dear Bob:

I am writing to discuss several points in the recently issued draft report titled “Hot Mix

Asphalt Plants, Emission Assessment Report” EPA-454/R-OO-OXX. Please extend my

congratulations to all those who worked on its preparation for a job very well done. Please

also accept the comments I make in this letter as purely constructive.

In general, I my comments will concern the readability of equations, rather than their

derivation, which I took to be correct. My primary area of concern at this time involves VOC

emissions during truck load-out operations; my comments will be mainly concerned with this

section of the draft and will cite examples based upon Appendix B, pages 4-147 et seq.

I recommend you consider adding equation numbers wherever needed. When reviewing the

document (especially Appendix B) I found it somewhat difficult to follow because of the lack

of equation numbers.

On page 4.153 (Appendix B) you present the following equation:

EFcor = ((C,,,,)-(C,,,,))*(EF,,,IC,,,)

If this equation were written in “algebra” rather than “computerese,” it might look like:

EF,,, = [(Carti)-(C,&p

prod

This small change would make the equation more “readable” to me and perhaps to others. I

understand the physics of the equation, but recommend that the definition of the parameter

C,,, be repeated here; it is not specifically stated. I assume that this equation is dimensionally

correct, but recommend you include the units for the respective terms. In the numerical
Mr. Robert McConnell

August 25, 2000

2000.190 Page 2

example that follows (in the text), I recommend that you indicate to the reader the exact source

of the input data. I could not find the reference to Run 1 MCEM, but could have missed it

while reading the report. Also, demonstrating the calculation of C,,, from raw data would

have been helpful to me.

On the bottom of page 4-154 and the top of page 4-155, you present a short discussion of

vapor pressure. I agree that the Clausius-Clapyron (CC) equation generates a linear

relationship between (the logarithm of the) vapor pressure and (the reciprocal of the absolute)

temperature. The Antoine equation is a refinement of the CC equation in which a third

constant has been added. The CC equation is a special case of the Antoine equation in which

the third constant is 273.16. Please double check your references, the (CRC) Handbook of

Chemistry and Physics provides tabulated numerical vapor pressure (versus temperature) data

for a large number of compounds and Lange’s handbook provides Antoine equation constants.

I suggest that the form of the two equations at the top on page 4-155 are somewhat difficult to

read. For example:

would be easier to read if it were in the form:

Loss = -EXP[O.O231(t+460) - 19.281

I don’t think the minus sign is necessary in these equations, but I understand it being placed

there to re-enforce the fact that the asphalt is losing mass during heating.

Return to the CC equation for a moment. The linearized form of the equation is:

ln(VP) = A + +

0

Where A and B are compound-specific constants. If one would make the same transformation

on the empirical equations (ignoring the minus sign) the form of the equations would be:

ln(Loss) = AT + B

Please note the difference in form between the two equations.

In the second line of the next paragraph, I recommend that you remove the words “The

industry indicates that higher temperatures are avoided .”

On the bottom of page 4-155, you cite equation numbers 4-I 1 and 4-12. Where are equations

4-1 through 4-lo? Again, these equations, as presented, are somewhat difficult to follow,

The equations can be simplified and perhaps the following sentence added:
Mr. Robert McConnell

August 25, 2000

1 2000.190 Page 3

“Equation 4-l 1 can be rearranged to give:

-0.5

EFs,,, = EFc,,, c_

! e

fm3l(325- T)

. .._.____..,.,......___.,.,

V

(4.13)”

My Equation (4.13) is mathematically identical to your Equation (4.11). In addition, I have

found (in my own writing) that the use of the dotted line, connecting the equation and the

equation number, simplifies reading. Am I correct in my understanding that EF,,, is the

emission factor to be used for prediction of future emissions? If so, then I believe this should

be clearly stated.

Fifteen figures are referred to at various points. In their current location, reader must stop

reading the document and look for the figures then return to the text. This is distracting,

interrupts the smooth flow of information, and can be avoided if the figures were placed

directly into the text (perhaps reduced in size).

Finally, I have been interested in the emissions from this phase of hot mix asphalt manufacture

for some time and have developed a purely theoretical model to describe VOC emissions from

freshly prepared asphalt starting the instant that it is discharged from a storage hopper or a pug

mill. My model predicted temperature changes during discharge and during transfer to the

paving site, and the VOC emissions accompanying the the transfer. My (theoretical) analysis

of the period in the truck is extremely close to your measurements. Your measured emission

factor was of 0.0011 pounds of VOC per ton of asphalt in 8 minutes, my value was 0.00046

pounds of VOC per ton of asphalt in 3.3 minutes. I am enclosing a copy of my report, you

may find it interesting.

Please accept my congratulations for a job very well done. Thank you for the printed reviewcopy you provided, and for the opportunity to comment on it.

Very truly yours,

Norman Ostroff, PhD, P.E.

Consulting Engineer

enclosure

cc: Mr. Ron Myers, US EPA, RTPNC
This Page is intentionally left blank.
I

.

DEVELOPMENT OF EMISSION FACTORS

FOR

FUGITIVE EMISSIONS

FROM

HOT MIX ASPHALT PLANTS

A THEORETICAL EVALUATION

Norman Ostroff, Ph.D, P.E.

87 Fishing Trail

Stamford, CT 06903

(203) 322 5559

April 1998

(Revised January 2000)
This Page is intentionally left blank.
DEVELOPMENT OF

EMISSION FACTORS FOR FUGITIVE EMISSIONS

FROM HOT MIX ASPHALT PLANTS

A THEORETICAL EVALUATION

Norman Ostroff, PhD, P.E.

Consulting Engineer

1. INTRODUCTION AND THEORY

1.1 Introduction

There are no published emission factors to quantify the fugitive emissions at hot mix asphalt

plants. The fugitive emissions in this study will be limited to VOCs. Fugitive particulate

emissions from blended product are expected to be negligible because of the binding action of

the asphalt.

The emission factors will be studied by following the temperature history of the product and

relating it to the rate of evaporation of volatile compounds.

There are two points in the process during which fugitive emissions can occur. These are:

1. The period during which the blended material is being dropped from the pug

mill into the transport truck, and

2. The period when the material is in the truck and is being transported to the

paving site.

In the case of blended hot mix asphalt, there are three mechanisms by which heat can be lost

from the mass. These are:

1. Radiation of heat from the hot particles to the atmosphere,

2. Convection from the surface of the mix to the atmosphere, and

3. Evaporative cooling accompanying evaporation of volatile components from the

mass.
1.2 Radiation

. _ The equation for heat transfers by radiation between a solid wall and a gas [l] is:

; = 0.173,[ (g4 - (&J4] (l-l)

where E is the emissivity of the gas which will be assumed to be 0.1 based on published data

for water vapor and CO, [2]. Take 325°F (785”R) as the surface temperature of the asphalt

mix and 60°F (520”R) as the air temperature. Substitute these quantities in Equation (1) to

get:

; = 0.173x0.1 ~[7.85~ - 5.204] = 50.3=

hrft’

. . . . . .., (l-2)

1.3 Convection

The equation for heat loss from the mass to the atmosphere by convection is given by:

-_;-h(T,-T,) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (1-3)

Where T, is the surface temperature and T, is the air temperature. The heat transfer coefficient for heat loss from a flat plate to still air [3a] is:

h = 0.38(T, - T,)‘=

Substitute in Equation (l-4) to get:

h = 0.38x(325 - 60)‘a5 = 1.53 ,;;rUE

and in Equation (l-3) to get:

-

Q

A

 = 1.53 x (325 - 60) = 406.3 =

ft2 hr

..............

..............

(l-6)

......... (l-4)

......... (l-5)

The heat loss per unit area (assuming an average convective heat transfer coefficient approximately of 1.5 BTU/hr ft’ OF) is approximately 400 BTU/hr ft*.

-2-
1.4 Evaporative Cooling

The heat loss accompanying evaporative cooling of asphalt compounds from the surface of the

mass is approximately 100 BTU/lb of asnhalt evaoorated. Since asphalt only comprises

approximately 5 percent of the mass, and only a small amount of the asphalt will be evaporated, this quantity of heat will not be included in the heat balances that follow.

1.5 Particle Heat Loss Summary

Convective heat transfer (406 BTU/h&) from the surface of the mixed mass is the primary

mechanism for heat loss from the surface and radiative heat transfer (53 BTU/hrft*) accounts

for approximately ten percent of the convective loss. To simplify the calculations that follow,

a combined convective-radiative heat transfer coefficient whose value is (1.1x1 S) 1.65

BTU/hr ft* “F will be used in this study.

1.6 Conduction

The mechanism of heat transfer within the mass is conduction. The equation describing the

temperature profiles in a solid is the Laplace Equation [5a] of conduction which, in this case

is:

s = a(V’T) (l-7)

In this case, the asphalt mass will be modeled as a semi infinite solid, Equation (l-7) becomes:

a2T aT

a-=- ,,,,,,

ax2 at

. . . . . . . ..__._........_.._... (l-8)

In Equation (l-8), T is temperature, t is time, and CI is a parameter called “thermal diffusivity”

defined by:

k

a=-

PC,

. . . . . . . . . . . . (l-9)

in which k is the thermal conductivity, p is the density of the solid, and C, is its heat capacity.

Equation (l-8) is made dimensionless by introducing the following parameter:

@= T, - T

T, _T, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._......... (l-10)

-3.
Substitute Equation (l-10) in Equation (l-8) to get:

a20 ao

n--=-

ax2 at . . . . . .

. .

(l-11)

The initial and boundary conditions used to solve Equation (l-11) are:

o=o when t = 0 all X (l-12a)

O=l when t ) 0 X = 0 (I-12b)

o=o when t ) 0 x + m (l-12c)

The solution to Equation (l-l 1) is [5d] :

T, -T

T, - T,

“. “‘. _. _, (l-13)

In which erf(Z) is defined by:

erf (Z) = $aem’ du . . . . . . . . . . . . . . . . .._......._......._ (1-14)

erf(0) = 0 ............................................(1-15)

erf (m) = 1 ............................................(I-16)

The heat flux is given by:

Differentiate Equation (1-13) with respect to X to get:

&[~~~s]=&[l-erf[&J] . . . . . . . . . . . . . . . . . . . . . . . (l-18)

Evaluate Equation (l-18) using the identity:

&[ erf(Z)] = -[$emP]g (l-19)
with:

z =* (l-20)

and:

g=* (l-21)

Substitute Equations (1-19) and (l-20) in Equation (l-18), and rearrange slightly to get

The temperature gradient at the solid surface (X = 0) is:

aT

C-J

Ts - To

a x

x=0= J?[at . . . . . . . . . . . . . . . . . . . . . . . ..__._.....

and the conductive heat flux is:

. . . . . . . ., ..,

(l-22)

(l-23)

(l-24)

Heat transfer by convection (corrected for radiation) is the primary mechanism for removing

heat from the surface of the mass of the asphalt; it will be assumed that it is the only mechanism, and the conductive heat flow in the mass will be equated with the convective heat flux.

It will be necessary to adjust the surface temperature (T,) as time progresses.

-5-
2. PHYSICAL PROPERTIES

Asphalt is not a single compound, but a mixture of hundreds of individual compounds that are

found in the residuum of petroleum refining. Asphalt is the material that remains after the

more volatile components have been distilled away, often at high vacuum. The hydrocarbon

components in asphalt are generally C,, and higher. Since it was impossible to find all

required physical properties of asphalt in available literature, the compound hexacosane

(C,,H,,) was used as a physical property model. Physical properties that were not available

were estimated using standard methods. The following data were available [4]:

Molecular Weight 366.72 API gravity 50.3”

Specific Gravity 0.7783 UOP K factor 13.7

Boiling Point 262°C at 15 mmHg

Vapor Pressure:

mmHg

T”C

T”F

1 10 40 100 760

204.0 257.4 295.2 323.2 399.8

399.2 495.3 563.4 614.1 751.6

The vapor pressure data were correlated by:

P” (mm Hg) = 9.695~ lo9 [erp (-iyrO)] (2-l)

The following properties were estimated using accepted methods:

Propertv Method m

Critical Temperature Nokay [6a] 543.2”C

Critical Pressure Lyderson [6a] 9.412 atm

Critical Volume Lyderson [6a] 1470 cm’/mol

Heat of Vaporization Othmer [3b] 103.7 BTU/lb at 325°F

Liquid Viscosity Orick and Erbar [6b]:

u(cp) = l.l6xlO-3 [exp(g)] (2-2)

Liquid Heat Capacity Luria and Benson [6c] :

C,(molar) = - 16.724 + 1.69(T) - 5.063~ 10e3 (T*) + 5.79~ 10m6(T3) (2-3)

Thermal Conductivity Robbins and Kingrea [6d]:

k = 3.314~ 1O-4 Note: C, in molar units in this equation (2-4)

-6-
.

3. TEMPERATURE PROFILES

3.1 Introduction

The system will be modeled in two stages. The first is the period during which a batch of

asphalt product is dropped from the pug mill mixer into the truck. The second is the period

when the batch is in the truck. The second period will be assumed to begin at the conclusion

of the first.

3.2 First Period

During this period, the asphalt will be assumed to be in the form of 114 inch (2.08x10-’ ft)

spheres at a uniform temperature of 325°F. Since the spheres are moving (they are falling into

the truck), it is assumed that the heat transfer coefficient, between the spheres and the air, is

(10x1.5) 15 BTU/ft*hr”F.

The Biot number [7] in the sphere is:

Bi =E = 2.08 x lo-* x 0.132 = ,,* x,o-4

h IS

., ., (3-l)

Since the Biot number is very low, one can safely assume that the convective heat transfer

(from the surface) is controlling and the internal temperature is relatively constant. Assume

that the heat transfer coefficient will be approximately ten times as high as the value calculated

using Equation 1-5, the rate of heat loss from the sphere is:

2 BTU

A = h(T,- T_,)= 15x(325- 60)= 3980~ hrft’

In which T, is the temperature of the air and T, is the surface temperature of the particle. The

area of the sphere is:

A = nD* = n(2.0810-2)2 =136x 10-s ft* (3-3)

Assume that the particle must fall 10 feet from the mill outlet to the truck. The elapsed time

is:

t = ~=0.788 set . . . . (3-4)

Which is equivalent to (0.78813600) 2.19~10.~ hours. The amount of heat lost from the

particle is:

-7.
QWde = 398Oxl.36xlO-~~2.l9xlO-~ = l.lS~lO-~ BTU (3-5)

The mass of the particle is:

7CD’ Mass = __6 P=

n x 2.08 x IO-‘) x (0.7885 x 62.4) (

6

= 2.32 x 1O-4 lbs (3-6)

The temperature change in the particle (using the heat capacity of asphalt) is:

AT = 1.18x10-s

2.32 x 10m4 x 0.656

= 78°F (3-7)

This estimate can be refined with several additional iterations, but for the purpose of this

study, it is sufficiently accurate to take the temperature change as 7°F and the initial temperature of the asphalt in the truck to be (325 - 7) 318°F.

3.3 Temperature Changes in the Truck

This period will be evaluated using the equations developed in Sections 1.3 and 1.5. It will be

assumed that the mass in the truck is homogeneous, and its physical properties are equal to

those of asphalt (or hexacosane). In this case, the Biot number is very large and the internal

temperature profiles must be considered. The development of the temperature profiles will be

developed first using numerical methods; the emission rate from the mass will be computed

using the results of the temperature calculation.

The conductive heat flux through the asphalt has been given by Equation (l-24):

$= -k(~jxzo = krTs) (l-24)

and the convective heat flux from the surface has been given by Equation (l-3):

$=h(T,-T,) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (l-3)

Since the heat flux is the same in the solid and gas phases, equate Equations (l-23) and (l-5)

to get:

=h(T,-T,) . . . . . . . . . . . . . . . . . . . . . . (3-8)

Now solve Equation (3-8) for the surface temperature T, to get:

-8.
T = hT,fi+kT,

s

hfi<+k

. . . . . ., (3-9)

Equation (3-9) is a relationship between the surface temperature of the mass, and the elapsed

time since it was deposited in the truck.

The thermal boundary layer is that portion of the mass in which all of the temperature changes

occur. Outside of this boundary layer, the temperature is constant at the temperature of the

initial deposit (318°F). In order to evaluate the boundary layer thickness, a trial and error

approach was used. The temperature profile, given in Equation (l-12) was solved for T:

T(x,t) = T, - (To - T,) . . . . . (3-10)

The time was assumed and values of X were found so that the temperature was within

tolerance of the initial temperature. The boundary layer thickness was found to be approximately 1 inch at 3.3 minutes.

-9-
4. EMISSION RATES

The emission rates were determined based upon published AP-42 emission factors. These are:

TABLE 4-l

AP-42 Emission Factors for VOC

From Hot Mix Asphalt Plants

Entries in lb/ton

Natural Gas

Fuel Oil

Batch Mode Drum Mode

0.017 0.051

0.046 0.069

Of these, the factor for VOC emission using fuel oil in the drum mode was chosen for this

study because it provided the most conservative (high) estimate.

The data in Table 4-l represents the amount of VOC that will be emitted during the production

of a ton of hot mix asphalt. The amount of fuel required to produce a ton of hot mix asphalt

has been reported to be 0.5 gallons of Number 2 fuel oil. This is equivalent to (05x140,000)

70,000 BTU or (70,000/1000) 70 standard cubic feet of natural gas.

The AP-42 factor for VOC emission during Number 2 fuel oil combustion is 0.20 lb/mgal; the

AP-42 factor for VOC emission during natural gas combustion is 2.78 lb/mmSCF. The VOC

emission associated with fuel combustion during hot mix asphalt production are (0.5~10~~~0.2)

1.0~10-~ lb/ton for fuel oil and (7O~lO-~x2.78)

1.95~10-~ lb/ton. These quantities are small and will not be considered here.

For the purposes of this investigation, the emission factors given in Table 4-l were interpreted

as lb/ton per hour. That is, if one ton of hot mix asphalt could be maintained under manufacturing process conditions, it would emit the AP-42 factor.

When dealing with fugitive emissions, the process conditions are not maintained. If fact the

mass cools quickly, and a thermal boundary layer is created. The emissions of VOC are

dependent upon three parameters:

1.

2.

3.

The rate at which liquid can flow to the surface,

The ease with which the liquid can be vaporized (volatility), and

The rate with which the volatilized asphalt components can be removed from

the vicinity of the cooling mass (diffusion).

In order to develop a liquid flow factor, it will be assumed that the liquid flow to the surface

of the mass occurs by capillary flow, which is a form of laminar flow. The equation for

pressure drop in a fluid system is:

-lO-
. . . . . . . .._._........._.......,. (4.1)

The (D’Arcy-Moody) friction factor in laminar flow is:

f= _=p @ 64~ . . . . . . . . .._.............................

N, Dvp (4-2)

substitute Equation (4.2) in Equation (4.1) and solve for v to get:

v = H,D* Pg 32~t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (4-3)

If it is assumed that the capillary pressure is constant, and the diameter of the passages arc

constant, Equation (4-3) demonstrates that the liquid flow rate is inversely proportional to the

viscosity of the liquid.

The volatility is simply expressed as the vapor pressure (of hexacosane) at the surface

temperature of the mass.

The diffusion coefficient is more difficult to estimate. There are no published data describing

diffusion of compounds of this type in air. The diffusion coefficient for asphalt vapor in air

(at 25°C) was estimated by noting the a strong correlation between diffusion coefficient and

geometric mean molecular weight shown in Figure 4-l. The data were correlated using the

method of least squares; the resulting empirical equation is:

D As = 20.78(MW)-‘392 (4-4)

The index of correlation (r’) is 0.91, indicating a good fit to the data. Equation (4-4) was

evaluated at the geometric mean molecular weight of air and hexacosane [(29 +366)0.5] 103 to

obtain an estimate of 0.0327 cm2/sec at 25°C. Admittedly, this is a small extrapolation but

represents the best available information.

The Chapman-Enskog [5b] kinetic theory was used to relate the diffusion coefficient to

temperature. The Chapman-Enskog equation is rather complex, but for this discussion has

been simplified as:

in which 5 is a constant related to the system and 0, is a function of temperature that is

usually presented in tabular form [5c]. For use in this investigation, Q, was plotted against

the temperature function (which is the product of two system-specific constants and the

absolute temperature). The graph is presented Figure 4-2.

- ll-
FIGURE 4.1

Diffusion Coefficients of Various

Compounds in Air at 25°C [8]

-

-

i

-

-

1.

’

L

, . 7

8 .

.C_...~

-

_

-1

1

L 4-z

9

0

- 12 -
FIGURE 4-2

The Cl, Function [5c]

(uo!sng!G) e6au1~

- 13-
A power law equation (similar to Equation 4-3) was fit to the published data again using the

method of least squares; the resulting empirical equation is:

R, = 1.583(KT / c)mo34 (4-6)

The index of correlation (r*) is 0.93, indicating another good fit. Equation (4-5) is a simple

and relatively accurate relationship which is satisfactory for use here. Since both K and E are

compound-specific constants, Equation (4-6) indicates that the 8, function is proportional to

the (absolute) temperature raised to the (-0.34) power. When this is substituted in Equation

(4-5) it becomes:

Equation (4-7) will be used to estimate the variation of diffusion coefficient with temperature,

In order to predict emission rates as the mass cools, it was assumed that the full value of the

AP-42 factor was applicable when the mass was being prepared and was maintained at the

mixer temperature of 325°F.

The AP-42 factor is adjusted using three “parameter correction factors” defined:

F,

,

= ‘iPi(3250F) CT& (4.8)

in which P is the parameter (vapor pressure, viscosity, diffusivity) and Fi is the respective

correction factor defined as the ratio between the value of the parameter at the instantaneous

surface temperature of the asphalt, divided by the value of the same parameter at 325°F. The

overall correction factor is:

F, =

F, FLX,

FM,

. . . . . . . . . ., (4-9)

The emission rate is computed as the product of the overall correction factor and the AP-42

factor. Recall that the oil/drum factor will be used here because it provides the most conservative (high) estimate:

= F, x(AP42EmissionFactor) (4-10)

- 14-
5. CALCULATIONS

*. The calculations were in the following order:

5.1 A time was assumed.

5.2 The surface temperature was calculated using Equation (3-9).

5.3 The physical and transport properties of the mass were evaluated at the surface using

the surface temperature computed in Step 5.2.

5.4 The thickness of the thermal boundary layer was computed using Equation (3-10) and a

trial and error solution. The assumed thickness (X) was varied until the computed

temperature [T(X,t)] was equal to the initial temperature (T,).

5.5

5.6

The vapor pressure, liquid viscosity, and diffusion coefficient, at the surface temperature were computed using Equations (2-l), (2.2), and (4.6), respectively.

The parameter correction factors for vapor pressure, liquid viscosity, and diffusion

coefficient were computed using Equation (4-7), and the overall correction factor was

computed using Equation (4-8).

5.7

5.8

5.9

5.10

The emission rate was computed using Equation (4-9). Recall that this rate is only

valid for the period defined in Step 5.1.

The amount of VOC emitted during the period is equal to the product of the emission

rate calculated in Step 5.7 and the duration of the time period. The emission is

expressed in the units of lb/ton.

The total emission is calculated by adding the amount emitted (Step 5.7) to that

computed in previous iterations.

Assume a new temperature and repeat Steps 5.2 through 5.9.

These calculations were performed by computer, the output is appended.

- 15 -
6. RESULTS

The results of this study are summarized in Figures 6-1, 6-2, and 6-3 which relate surface

temperature, thermal boundary layer thickness, total emissions, and instantaneous emission

rate; respectively; to elapsed time. The study was conducted over a time period of 3.3

minutes from the time that the pug mill is empties into a truck. The emission rate has decayed

considerably and only adds a small increment to the total.

The “3.3 minute emission factor” is 4.21~10~~ pounds per ton, which will be increased by 10

percent to (1.1~4.21~10~~) 4.63~10.~ pounds per ton to account for any emissions that might

occur after the 3.3 minute period has elapsed.

This number is approximately two orders of magnitude smaller than the AP-42 factors (Table

4-1) because the asphalt is cooling and thereby severely restricting its ability to emit,

The stack emissions from a batch mix hot mix asphalt facility, operating in the batch mix

mode, using natural gas fuel, and producing 300 tph of product are:

VOC emissions = 0.017 x 300 = 5.10 lbihr (6-l)

The fugitive emission from the truck would be:

Fugitives = (4.63~10.~) x 300 = 0.14 lb/hr (6-2)

Which is about 2.7 percent of the stack emissions.

The emission rate, defined as the rate at which VOC evaporates from the surface of the

asphalt, is initially equal to the evaporation rate from the asphalt during the mixing, falls to

approximately ten percent of the initial rate after approximately 3 minutes. This is shown in

Figure 6.4.

- 16 -
FIGURE 6.1

Surface Temperature of Cooling Asphalt Mass

(d 6ap) aJn)eJadUJal a3QInS

- 17- c:\lcwi11*\asplemp,pm
,

.

i

.

FIGURE 6.2

Development of the Thermal Boundary Layer

in Cooling Asphalt Mass

-

\-

-

-

‘.

._.!L

I

ik

0

-

-

,

1

-

-

-

i.

-

.; 4

-

\

-tm

d

(sayxt!) ssauy3!yl Mei depunog

d
‘. FIGURE 6.3

.

Fugitive VOC Emissions from Cooling Asphalt Mass

Development of the Emission Factor

- 19 c:\lcwinZ\asp-emm.prn
-.

I

t

FIGURE 6.4

Fugitive Emission Rate from

Cooling Asphalt

- 20
.

Appendix 1: Computer Output Sheets

.

-2l-
Appendix 2 Literature Cited

1 VI 1989 Ashrae Handbook, Fundamentals, Page 3.11

[21 RH Perry, D Green “Perry’s Chemical Engineers’ Handbook, 6/ed” McGraw

Hill (1984) pp 10.62, 10.63

t31

WI

JH Perry, ed. “Chemical Engineers’ Handbook, 3ied” McGraw Hill (1950) p

414

Ibid, Page 300

141 RC Weast, ed. “Handbook of Chemistry and Physics, 49ied” (1968) assorted

pages

PaI

[5bl

r5c1

WI

RB Bird, WE Stewart, EN Lightfoot “Transport Phenomena” Wiley (1960),

Chapter 10

Ibid, Page 510

Ibid, Page 746

Ibid, Section Il. 1

[6al RC Reid, JM Prausnitz, TH Sherwood “The Properties of Gases and Liquids,

3/ed” McGraw Hill (1977), Page 12

WI Ibid, Page 439, 440

[6cl Ibid, Page 155, 156

[6dl Ibid, Page 519

171

[81

DQ Kern “Process Heat Transfer” McGraw Hill (1950) Page 37

CO Bennett, JE Myers “Momentum, Heat, and Mass Transfer, 2ied” McGraw

Hill (1974) Page 787

- 22
Steven Zemba

Cambridge Environmental Inc.

Cambridge, MA
This Page is intentionally left blank.
zemba@cambridgeenviro

nmental.com

09/22/00 10:34 AM

To: Ron Myers/RTP/USEPA/US

cc:

Subject: Belated Comments on the Hot Mix Asphalt Emissions Assessment Report

Hi Ron:

I apologize for not geeting these comments to you within the official

comment period, but since I did review the emission assessment report at

a cursory level, I thought I would pass along my notes belatedly in the

hope that they still might be useful to you. My notes/comments are

contained in the attached file. Feel free to call/write with any

questions on them. I hope that this represents the end of the process

for you!

Take care,

Steve

--

Stephen Zemba (mailto:Zemba@CambridgeEnvironmental.com)

Cambridge Environmental Inc.

58 Charles St.

Cambridge, MA 02141

617-225-0810 (Voice)

617-225-0813 (FAX)

http://www.CambridgeEnvironmental.com

 - asphalt_comments.PDF
Comments and notes on “Hot Mix Asphalt Plants, Emission Assessment Report”

General: A list of acronyms at the front of the document might e helpful to readers.

General: Tables 1 and 2 claim to present emissions for a “typical” plant. This is probably true for mixer

emissions, but is not the case for the fugitive sources, as indicated by statements on p. 14. Specifically,

the fugitive emission estimates assume a high-end volatility of asphalt cement, and also a maximum

recommended load-out temperature. I would thus characterize the fugitive emission estimates as “highend” for a typically-sized plant. EPA might want to clarify this matter somewhat, since the actual ratio

of fugitive-to-stack emissions for a typical plant running at typical conditions will be lower than that

implied in Tables 1 and 2.

General: Many HMA plants are now installing condensers on their asphalt storage tank vents and silo

vents; some are enclosing or partially enclosing their loadout areas. The fugitive emissions discussed in

this document are for uncontrolled sources. In fact, the estimates in Tables 1 and 2 implicitly assume

controls on the mixer (dryer) stack but no controls for fugitive emissions. This assumption should be

made explicit (perhaps in a footnote to the tables). EPA might also want to offer some

opinion/conjecture on the efficacy of engineering controls for the various fugitive sources.

Specific comments

The last sentence third pgh. of pg 1 contains a typo: the 100,000 tons of production corresponds to a

batch plant, not a drum plant.

1

st pgh. of p. 10: Does the emission assessment report provide stack emission rates for a typical

counterflow or parallel flow drum plant? If the estimates are for a parallel flow plant, it might make

sense to mention in the text the approximate difference expected for emissions from a counterflow plant

(e.g.. this could be mentioned in a footnote to Table 2).

p. 3: EPA might want to provide the regulatory definition or a better explanation of criteria pollutants

and HAPs.

p. 2, 3rd pgh: Might want to mention the number of tests (> 300) that survived the screening process

(i.e., were usable for the development of emission factors).

p. 13: Are emissions from hot oil heaters included in any of the categories in Tables 1 & 2 (e.g., the

“mixer” category)? If not, does it make sense to mention the likely magnitude of these emissions

relative to other sources (qualified, of course, by the large degree of uncertainty resulting from the

dearth of test data)? Might it also be possible to use emission factors from similar burners (used in

other industries) to evaluate hot oil heater emissions?
TECHNICAL REPORT DATA

(Please read Instructions on reverse before completing)

1. REPORT NO.

 EPA-454/R-00-030

2. 3. RECIPIENT'S ACCESSION NO.

4. TITLE AND SUBTITLE

Hot Mix Asphalt Plants

Stakeholders Opinions Report

5. REPORT DATE

April 2001 

6. PERFORMING ORGANIZATION CODE

7. AUTHOR(S)

 Ron Myers (EPA)

8. PERFORMING ORGANIZATION REPORT NO.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

 U.S. Environmental Protection Agency

 Office of Air Quality Planning and Standards

 Research Triangle Park, NC 27711

10. PROGRAM ELEMENT NO.

11. CONTRACT/GRANT NO.

12. SPONSORING AGENCY NAME AND ADDRESS

 Office of Air Quality Planning and Standards

 Office of Air and Radiation

 U.S. Environmental Protection Agency

 Research Triangle Park, NC 27711

13. TYPE OF REPORT AND PERIOD COVERED

14. SPONSORING AGENCY CODE

EPA/200/04

15. SUPPLEMENTARY NOTES

16. ABSTRACT

The United States Environmental Protection Agency (EPA) Source Measurement Technology Group (SMTG) and

Emission Factors and Inventory Group (EFIG) are investigating the Hot Mix Asphalt industry to identify and quantify

criteria and hazardous air pollutants (HAP’s) emitted from kiln stacks, transport truck loading and silo filling at hot mix

asphalt plants. The EPA report titled “Hot Mix Asphalt Plants - Emissions Assessment Report” (EPA 454/R-00-019,

December 2000) presented the findings from these investigations. As part of the investigation, EFIG obtained over 300

emission tests from kiln stacks that characterize emissions of criteria pollutants and hazardous air pollutants’ emissions. 

Additionally, SMTG sponsored two kiln stack emission tests and two emission tests of the transport truck and silo filling

operations. The primary objective of the testing program was to characterize uncontrolled emissions of the criteria

pollutants particulate matter (PM) and total hydrocarbons (THC) and emissions of volatile and semi-volatile organic

HAP’s. The results of the four test reports and responses to comments on these test reports are covered in separate EPA

reports (EPA 454/R-00-020, EPA 454/R-00-021, EPA 454/R-00-022, EPA 454/R-00-023, EPA 454/R-00-024,

EPA 454/R-00-025 (a through h), EPA 454/R-00-026, EPA 454/R-00-027, EPA 454/R-00-028 and

EPA 454/R-00-029). This document includes stakeholder comments on the draft version of the Emissions Assessment

Report, EPA’s response to these comments, stakeholder opinions on the final version of the Emissions Assessment

Report and EPA responses on new issues raised by stakeholders.

17. KEY WORDS AND DOCUMENT ANALYSIS

a. DESCRIPTORS b. IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group

Hot Mix Asphalt

Silo Filling

Truck Loading

Particulate Matter

Volatile Organic Compounds

Total Hydrocarbons

Hazardous Air Pollutants

Air Pollution control

18. DISTRIBUTION STATEMENT

 Release Unlimited

19. SECURITY CLASS (Report)

 Unclassified

21. NO. OF PAGES

288

20. SECURITY CLASS (Page)

 Unclassified

22. PRICE

EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION IS OBSOLETE
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