United States Environmental Protection Agency

General Permit for New or Modified Minor Sources of Air 

Pollution in Indian Country

http://www.epa.gov/air/tribal/tribalnsr.html

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Background Document: General Air Quality Permit for New or Modified Minor 

Source Hot Mix Asphalt Plants in Indian Country

Version 1.0

Last modified: March 23, 2015

1. Hot Mix Asphalt Plants Source Category Definition 

For purposes of this General Permit, a hot mix asphalt (HMA) plant is a facility which manufactures hot mix 

asphalt by heating and drying aggregate and mixing with asphalt cements. An HMA plant is comprised of any 

combination of the following activities: dryers, liquid asphalt storage tanks, fuel oil storage tanks, auxiliary 

heaters (including hot oil heaters), material storage handling and transfer systems, generators, storage 

bins/silos, storage piles, and haul roads. An HMA plant can be constructed as a permanent plant, a skid-mounted 

(easily relocated) plant, or a portable plant. The General Air Quality Permit for New or Modified Minor Source 

Hot Mix Asphalt Plants in Indian Country covers HMA operations that are located at New Source Review (NSR) 

minor sources.

2. Source Category Characterization

HMA paving materials are a mixture of size-graded, high quality aggregate (which can include reclaimed asphalt 

pavement (RAP)), and liquid asphalt cement, which is heated and mixed in measured quantities to produce 

HMA. Aggregate and RAP (if used) constitute over 92 percent by weight of the total mixture. Aside from the 

amount and grade of asphalt cement used, mix characteristics are determined by the relative amounts and 

types of aggregate and RAP used. A certain percentage of fine aggregate (less than 74 micrometers in physical 

diameter) is required for the production of good quality HMA. (AP-42, Chapter 11.1 – Hot Mix Asphalt Plants)

There are four types of HMA plants based on manufacturing process: (1) batch mix plants, (2) continuous mix 

(mix outside dryer drum) plants, (3) parallel flow drum mix plants, and (4) counterflow drum mix plants. About 

85 percent of plants being manufactured today are of the counterflow drum mix design, while batch plants and 

parallel flow drum mix plants account for 10 percent and 5 percent respectively (AP-42, Chapter 11.1 – Hot Mix 

Asphalt Plants).

Emissions from HMA plants consist of: (1) combustion emissions from mixer/dryers, auxiliary heaters, and 

generators; and (2) particulate emissions from the mixing/drying process, material handling process, and fugitive 

emissions from haul roads. Carbon monoxide (CO) emissions from batch mix plants are significantly higher than 

the CO emissions from drum mix plants due to the incomplete combustion process occurring in the batch 

mixer/dryers. 

3. State Minor Source Permit Programs

The U.S. Environmental Protection Agency (EPA) researched state government websites for general permits for 

this source category and examined them for applicability to a permit for Indian Country. The EPA selected 

appropriate elements in developing the documents and regulations in the General Permit for this source 

category. Specifically, we reviewed the following states and local governments with general permits (or similar 

programs) for HMA plants: Alaska, Arkansas, Arizona, Mississippi, New Mexico, Pennsylvania, South Carolina, 

Washington, Wisconsin, and West Virginia. The requirements for the state permitting programs related to HMA 
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plants are summarized in Attachment A. General Permits from these states were chosen for examination 

because of characteristics they possess:

 Readily available; 

 Clear throughput limits; and 

 Organization of the regulations followed the typical form for federal NSR permits:

o Limitations and standards, and 

o Monitoring, testing, recordkeeping, and reporting requirements.

For the ten state general permit programs reviewed, the permit requirements can be categorized into the 

following four categories:

 Emission Limits: Most of the state permit programs reviewed contain emission limits for all criteria 

pollutants. The emission limits typically range from 80 tons per year (tpy) to 100 tpy. The permit 

programs in Arkansas and New Mexico have a lower emission limitation of 50 tpy for sulfur dioxide 

(SO2). 

 Production/Capacity Limits: Most of the state permit programs reviewed include asphalt production 

limits. The limits vary depending on the type of mixer and the attainment status of the location where 

the plant will be located. The permit program for Washington also includes a capacity limit of 150 

MMBtu/hour for the drum mixer/dryer. The permit program for Wisconsin includes a capacity limit of 

700 tons/hour for the asphalt plant. The capacity limits for heaters and engines can be found in the state 

permit programs for New Mexico and South Carolina.

 Fuel Limits: All of the state permit programs reviewed, except for the permit program for Arizona, 

include some kind of fuel restriction, such as on the fuel types allowed, fuel usage limits, and sulfur 

content limits. In general, all the state programs reviewed allow the use of natural gas, propane and 

No.2 fuel oil (diesel). Few state programs allow the use of waste oils. The state program for Mississippi 

also includes a hazardous air pollutant (HAP) content limit for waste oil.

 Other requirements: Most of the state permit programs reviewed include requirements for a fugitive 

dust control plan. The specific requirements in this control plan vary by state. Some of the states include 

operating hour limits for the production unit and/or emergency generator. The state permit program for 

Alaska includes setback requirements for the production unit and generator engine from the nearest 

residence. The state permit program for West Virginia also includes capacity limits for storage tanks.

In addition, all the state general permits reviewed incorporate the requirements of NSPS, Subpart I (Standards of 

Performance for Hot Mix Asphalt Facilities) and NSPS, Subpart Kb (Standards of Performance for Volatile Organic 

Liquid Storage Vessels, (Including Petroleum Liquid Storage Vessels) for Which Construction, Reconstruction, or 

Modification Commenced After July 23, 1984).
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4. Requirements for General Permit

4.1 Documents for General Permit

The EPA developed a standardized set of permit documents in support of the General Permit for HMA plants. 

These consist of the following documents: 

 Questionnaire: Assists the facility owner or operator in determining whether they are eligible for a 

General Air Quality Permit;

 Request for Coverage under the General Air Quality Permit: States the criteria for qualification, gathers 

information on the source, the facility’s actual emissions for those sources undergoing modifications, 

facility location, and source contact, and requests technical information on facility equipment, 

throughput, and attainment status;

 Instructions: Guides the applicant in filling out the Request for Coverage under the General Air Quality 

Permit;

 General Air Quality Permit, Terms and Conditions: Contains the requirements and regulations with 

which the source must comply. The emission limitations, monitoring, recordkeeping and reporting 

requirements are in the permit, including requirements for sources located in nonattainment areas; and

 Potential to Emit (PTE) Calculator Spreadsheet: Allows applicants to calculate their PTE, based on owner 

inputs of the specific equipment present at their source, assuming continuous operation throughout the 

year. The PTE Calculator spreadsheet generates potential emissions, based on these inputs. The 

spreadsheet illustrates the correlation between equipment, raw material throughput, and emissions.

4.2 Exemption and Qualification for General Permits

Facilities applying for the General Permit must meet the emissions limitations established for the General 

Permit.

New facilities with a PTE (or modifications to existing facilities with an increase in potential emissions) lower 

than the minor NSR thresholds specified in the provisions of the Federal Indian Country Minor NSR Rule at 40 

CFR 49.153 are exempt from the minor NSR program. The minor NSR thresholds are listed in Table 1 below. 

Facilities applying for the General Permit may calculate their PTE using the PTE calculator provided to determine 

if they are below these thresholds and, thus, exempt from the minor NSR program.

 Table 1: Minor NSR Thresholds in 40 CFR 49.153

Pollutant Attainment Area Nonattainment Area

CO 10 tpy 5 tpy

Particulate Matter

(PM) 10 tpy 5 tpy

PM10 5 tpy 1 tpy

PM2.5 3 tpy 0.6 tpy

SO2 10 tpy 5 tpy

Nitrogen Oxides (NOX) 10 tpy 5 tpy

Volatile Organic 

Compounds (VOC) 5 tpy 2 tpy

Under current EPA policy, true or synthetic NSR minor sources qualify for the General Permit. Facilities will be 

required to compare their PTE to the NSR major source thresholds to determine if they qualify for the General 
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Permit. The NSR major source threshold for attainment areas is 250 tpy for any criteria pollutant. The NSR major 

source thresholds for nonattainment areas are summarized in Table 2 below:

 Table 2: NSR Major Source Thresholds for Nonattainment Areas

Pollutant Nonattainment Classification NSR Major Source Threshold

Ozone

Marginal 100 tpy of VOC or NOX

Moderate 100 tpy of VOC or NOX

Serious 50 tpy of VOC or NOX

Severe Not eligible for the General Permit

Extreme Not eligible for the General Permit

PM10

Moderate 100 tpy

Serious 70 tpy

CO Moderate 100 tpy

Serious 50 tpy

SO2, NOx, PM2.5 No nonattainment classification 100 tpy

If the facility’s PTE is above the NSR major source threshold of 250 tpy, or above the applicable nonattainment 

area thresholds listed in Table 2 (for any pollutant for which the area in which the source is locating or modifying 

is designated nonattainment), then the facility does not qualify for the General Permit. Sources that will be 

synthetic minor sources and relying on the conditions in the General Permit to qualify as minor sources should 

use the conditions in the permit (such as limits on production and throughput) to determine their PTE and 

eligibility for the General Permit. However, until coverage under the General Permit is obtained, the source is a 

major source. The following documents are available to assist sources in the screening and application process:

 Questionnaire;

 Request for Coverage under the General Air Quality Permit; 

 Instructions for the Request for Coverage under the General Air Quality Permit; and

 PTE calculator.

For facilities not exempt from the minor NSR program and having a PTE below the NSR major source thresholds, 

the facilities will further evaluate if they meet the throughput limits and operating requirements established in 

this General Permit. The specific requirements for the General Permit are discussed in Sections 4.3 and 4.4. The 

emissions associated with the throughput limits are lower than the NSR major source thresholds and were 

derived as described below in Section 5. 

4.3 Specific Permit Requirements for General Permits

The terms and conditions of the General Permit were established according to the required permit content and 

analyses in the Federal Indian Country Minor NSR Rule. The required permit content is listed in 40 CFR 49.155(a) 

– What information must my permit include? Below we describe the basis for the permit conditions.

40 CFR 49.155(a)(1) – General Requirements

The rule establishes general requirements that each permit must identify: the effective date of the permit; the 

date by which the owner/operator must commence construction in order for the permit to remain valid; the 

emission units subject to the permit and their associated emission limitations; and monitoring, recordkeeping, 

and reporting requirements to assure compliance with the emission limitations. 
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The General Permit contains all of this required information, except for the emission units subject to the permit. 

Because of the nature of general permits we believe it is more appropriate to identify the emission units 

covered by the General Permit in the Approval of the Request for Coverage. The General Permit incorporates 

the Approval of the Request for Coverage into the General Permit. Each permit contains a separate section that 

specifically identifies the emission limitations and standards, monitoring and testing, recordkeeping, and 

reporting and notification requirements.

40 CFR 49.155(a)(2) – Emission Limitations

The permit must contain the emission limitations determined by the reviewing authority under 40 CFR 49.154(c) 

for each affected emissions unit. 40 CFR 49.154(c) – How will the reviewing authority determine the emission 

limitations that will be required in my permit? – identifies the case-by-case control technology review that must 

be used by the reviewing authority to determine the appropriate level of control. In carrying out the case-bycase control technology review, the reviewing authority must consider the following factors:

1. Local air quality conditions;

2. Typical control technology or other emission reduction measures used by similar sources in surrounding 

areas;

3. Anticipated economic growth in the area; and

4. Cost-effective emission reduction alternatives.

In addition, the reviewing authority must require a numerical limit on the quantity, rate or concentration of 

emissions for each regulated NSR pollutant emitted by each affected emissions unit, for which such a limit is 

technically feasible. The emission limitation required may also be included as pollution prevention techniques, 

design standards, equipment standards, work practices, operational standards or any combination thereof. 

However, the emission limitations must assure that each affected emission unit will comply with all 

requirements of 40 CFR parts 60, 61, and 63, as well as any federal or tribal implementation plans that apply to 

the unit. Finally, the emission limitations required may not rely on a stack height that exceeds good engineering 

practice or any other dispersion technique, except as allowed by 40 CFR 51.118(b).

To address the requirements for establishing emission limitations, the following considerations were used for 

setting the limits in the General Permit for HMA plants:

1. Local air quality conditions – To address this requirement, the General Permit does not allow sources to 

locate in severe or extreme ozone nonattainment areas and requires sources locating in certain other 

nonattainment areas to meet more stringent requirements. This includes more stringent emission 

limitations, as well as, more stringent fuel use limits. In some cases, we included more stringent 

production limits in addition to limiting fuel use for sources in nonattainment areas to ensure sources 

would still be below the major source thresholds. Fuel use limits also have the effect of limiting a 

source’s production.

2. Typical control technology or other emission reduction measures used by similar sources in surrounding 

areas – For sources locating in attainment areas we looked at the control requirements specified by 40 

CFR parts 60, 61 and 63. These regulations establish minimum technology and emission limitations that 

must be met nationally and also meet the requirements of 40 CFR 49.154(c)(4) to ensure compliance 

with parts 60, 61, and 63. For this General Permit we considered regulations that apply to the 

equipment at HMA facilities:

 40 CFR 60 Subpart I – Standards of Performance for Hot Mix Asphalt Facilities;
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 40 CFR 60 Subpart Kb – Standards of Performance for Volatile Organic Liquid Storage Vessels 

(Including Petroleum Liquid Storage Vessels) for Which Construction, Reconstruction, or 

Modification Commenced after July 23, 1984;

 40 CFR 60 Subpart IIII – Standards of Performance for Stationary Compression Ignition Internal 

Combustion Engines; and

 40 CFR 63 Subpart ZZZZ – National Emission Standards for Hazardous Air Pollutions for Stationary 

Reciprocating Internal Combustion Engines.

These regulations cover emissions from dryers and mixers at HMA facilities:

 The South Coast Air Quality Management District Rule for nitrogen oxides (NOX) Reductions from 

Miscellaneous Sources (CA Rule 1147) for operations located in ozone nonattainment areas;

 The South Coast Air Quality Management District Rule for NOX Reductions from Miscellaneous 

Sources (CA Rule 1155) for operations located in particulate matter less than 2.5 micrometers 

(PM2.5) nonattainment areas; and

 California San Joaquin Valley Rule for Dryers, Dehydrators, and Ovens (San Joaquin Rule 4309) for 

operations located in CO nonattainment areas.

The General Terms and Conditions in the General Permit are a standardized set of boilerplate conditions 

included with general permits. The conditions in the Specific Terms and Conditions section of the 

General Permit are developed from the Federal Indian Country Minor NSR Rule, NSPS, National 

Emissions Standards for Hazardous Air Pollutants (NESHAP), and the state permit examples.

The derivation of the emissions limitations and the production and fuel usage limits in the applicability 

questionnaire, application, and Specific Terms and Conditions section of the General Permit are 

discussed fully in Section 5. The minor NSR thresholds are based on provisions of the Federal Indian 

Country Minor NSR Rule at 40 CFR 49.153 and are also discussed fully in Section 5.

The affected emission units under this General Permit include the following:

 Dryers;

 Systems for screening, handling, storing, and weighing hot aggregate;

 Systems for mixing hot mix asphalt;

 Loading transfer, and storage systems associated with emission control equipment;

 Fuel storage tanks; and

 Stationary engines.

Review of the regulations resulted in permit conditions requiring dryers/mixers to be controlled by a 

baghouse or venturi scrubber, limiting PM emissions from the mixers/dryers to 0.04 gr/scf, limiting 

opacity to 20% from each affected emissions unit, requiring fugitive emissions to be controlled by a 

fugitive dust control plan, requiring new stationary engines to be certified to Tier standards, and 

requiring existing stationary engines to meet maintenance requirements, a 49 ppm CO at 15% O2 limit, 

or a 23 ppm CO at 15% O2 limit based on engine size.

In addition, we also included conditions that fuel used in the dryer/mixer and auxiliary heaters must be 

limited to natural gas, distillate fuel, and biodiesel. The stationary engines are limited to using diesel and 

biodiesel as fuels. All liquid fuels are limited to no more than 0.0015 percent sulfur by weight. These 
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conditions represent the standard fuels used for this equipment and the standard sulfur content these 

fuels must attain. 

For CO and VOC emissions, we looked at San Joaquin Valley Unified Air Pollution Control District Rule 

4309 for Dryers, Dehydrators and Ovens. Based on the limits in this rule, we set a CO emission limitation 

of 600 ppm at 3% O2 for dryers burning liquid fuels and 400 ppm @ 3% O2 for gaseous fuel. This limit will 

ensure good combustion practices for the dryers, which will also limit VOC emissions. 

Although we reviewed the NSPS requirements for tanks, we did not include any limits in the permit as 

the tanks used by HMA facilities will not need to meet the control requirements of the NSPS. The 

questionnaire limits eligibility for the General Permit to tanks less than 151m3that store liquids with a 

true maximum vapor pressure less than 4.0 psi. 

The General Permit includes the following requirements from the applicable NSPS and NESHAP 

requirements:

 40 CFR 60.92(a)(1) – particulate matter standard;

 40 CFR 60.92(a)(2) – opacity standard;

 40 CFR 60.4204 and 60.4201(a) – certification to Tier standards;

 40 CFR 62.6603, 63.6640, and Table 2d to 40 CFR 63 Subpart ZZZZ – Emission limitation and 

operating standards;

 40 CFR 63.6612, 63.6625, 63.6630 and Table 5 to 40 CFR 63 Subpart ZZZZ – Initial compliance 

requirements;

 40 CFR 63.6640 and Table 6 to 40 CFR 63 Subpart ZZZZ – Continuous compliance requirements;

and

 40 CFR 63.6604 – Fuel requirements.

3. Anticipated economic growth in the area – The reviewing authority may consider anticipated economic 

growth when determining whether coverage under the General Permit is justifiable. Considering, 

however, that the General Permit sets emission standards that are consistent with what is required by 

HMA across the country in both attainment and non-attainment areas, we expect that this will rarely be 

a factor. 

4. Cost-effective emission reduction alternatives – The General Permit sets emission standards that are 

consistent with what is required by HMA facilities across the country, based on the particular attainment 

status where the source is locating. As such, the chosen technologies are considered widely available 

and consideration of more cost-effective alternatives is not necessary at this time. We intend to 

periodically review technology costs in the future to determine when more stringent, cost-effective 

technologies become widely available.

5. Co-location with another source – The General Permit allows for a HMA operation to be co-located with 

a stone quarrying, crushing, and screening (SQCS) operation also operating under a general permit. In 

addition, sources may request to take voluntarily lower material throughput limits to keep a co-located 

source below the Title V threshold. The material throughput limits and fuel consumption limits for colocated SQCS and HMA plants are specified in the respective permits.
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40 CFR 49.155(a)(3) – Monitoring Requirements

The General Permit must include monitoring that is sufficient to assure compliance with the emission limitations 

that apply to the source. The General Permit requires monitoring that assures that the baghouse or venturi 

scrubber is operating properly, that opacity is observed on a weekly basis, that fugitive emissions surveys are 

conducted weekly, that a burner tune-up is required each time the source is relocated, and that stationary 

engines with oxidation catalyst monitor the inlet temperature and pressure drop. The venturi scrubber requires 

continuous monitoring, as compared to a baghouse because it is an active control device instead of a passive 

control device. The General Permit also requires initial and continuing compliance testing for the mixer/dryer 

and engine(s). In lieu of an initial compliance test, the permit allows the source to substitute the results of a 

recent performance test, provided that the recent performance test was conducted within the past two years 

and meets the performance test requirements specified in the permit.

40 CFR 49.155(a)(4) – Recordkeeping Requirements

The General Permit must include recordkeeping that is sufficient to assure compliance with the emission 

limitations and monitoring requirements, including certain statements listed in 40 CFR 49.155(a)(4)(i) and (ii). In 

addition to the recordkeeping requirements in 40 CFR 49.155(a)(4)(i), the General Permit also requires records 

of the amount of asphalt produced each month, baghouse inspections, scrubber performance data, visible 

emission surveys, corrective actions taken, results of corrective actions taken, results of source tests, results of 

the dryer/mixer tune-ups, maintenance activities of stationary engines, and oxidation catalyst performance 

data, as applicable, for stationary engines. 

40 CFR 49.155(a)(5) – Reporting Requirements

The General Permit includes the reporting requirements listed in 40 CFR 49.155(a)(5)(i) and (ii) related to annual 

reports and reporting of deviations. 

40 CFR 49.155(a)(6) – Severability Clause

The General Permit includes a severability clause to ensure the continued validity of the other portions of the 

permit in the event of a challenge to a portion of the permit.

40 CFR 49.155(a)(7) – Additional Provisions

The General Permit contains the additional provision required for each permit. These conditions are found in the 

General Provisions of the General Permit.

The questionnaire and the application for the HMA permit contain questions designed to limit the availability of 

this General Permit to sources that have tanks that are not subject to the requirements of the following: 

Standards of Performance for Volatile Organic Liquid Storage Vessels (Including Petroleum Liquid Storage 

Vessels) for Which Construction, Reconstruction, or Modification Commenced After July 23, 1984 (NSPS, Subpart 

Kb). In the permitting documents the EPA basically specifies that facilities with tanks greater than 151 m3in 

capacity (39,890 gallons) and 27.6 kPa (4 psi) vapor pressure are ineligible for the General Permit. 

Other than the production limit and fuel usage limits, the Emission Limitations and Standards section of the 

permit includes the following additional requirements which are necessary to ensure the emissions from the 

entire asphalt plant will be below the emission limitations and production limits:

(1) Limitations for Combustion Units 

The source definition for HMA plants includes all the combustion units on site. The most common combustion 

units include hot oil heaters, engines, and emergency generators. In order to limit the combustions emissions 

from these combustion units, the permit is limited to the following fuels: 
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 Natural gas, propane, distillate fuel, and biodiesel in the dryer/mixer and auxiliary heaters; and

 Diesel and biodiesel in the stationary engines and generators. 

In addition, the total maximum heat input capacity of the auxiliary heaters must be less than 10 MMBtu/hour. 

This ensures the oil heaters at the affected facilities do not trigger the requirements of NSPS, Subpart Dc

(Standards of Performance for Small Industrial-Commercial-Institutional Steam Generating Units). These limits 

are necessary to ensure that the SO2, CO and NOX emissions from all the combustion units (including dyers, 

auxiliary heaters, and engines/generators) will not exceed the emissions limitations. 

(2) Requirements to Limit Particulate Emissions 

Particulate emissions are another concern for asphalt plants. Since asphalt plants may be subject to NSPS, 

Subpart I which was promulgated before January 1, 1980, fugitive emissions from asphalt plants must be 

included in total facility emissions for Title V and PSD major source determination purposes. Therefore, while 

considering the emissions limitations for this General Permit, fugitive emissions from asphalt plants must be

taken into account. In order to limit the particulate emissions from the asphalt plants covered by this General 

Permit, the permit includes the following additional PM control requirements:

 Require the mixer/dryer be controlled by a baghouse or venturi scrubber; and

 Require the facility to operate the production equipment in accordance with the Fugitive Dust Control 

Plan specified in Attachment B of this document and Attachment C of the General Permit. This dust 

control plan is adopted from the General Permit for Hot Mix Asphalt Plants developed by Wisconsin.

The above PM related requirements are necessary because the throughput limits were derived assuming that all 

the particulate emission units at the affected asphalt plants are properly controlled. 

(3) Monitoring Requirements

In order to demonstrate continuous compliance with the PM and opacity limits, the General Permit includes the 

following monitoring requirements:

 Weekly visible emissions surveys.

 Inspections for emissions units controlled by baghouses: 

o Inspect inside the baghouse for “clean” side deposits and evidence of defective bags or leakages 

between the kiln or “dirty” side and stack or “clean” side of each baghouse used at least once 

per week when the associated emission unit is in operation; and

o Inspect and replace filter bags according to the manufacturer’s documentation or more 

frequently as indicated by weekly inspections for “clean” side deposits.

 Continuous monitoring of pressure drop and liquid flow rate for emissions units controlled by a venturi 

scrubber.

The Recordkeeping Requirements section of the permit includes necessary recordkeeping requirements to 

demonstrate compliance with the production and liquid fuel usage limits, fuel type limits, unit capacity limits, 

and records associated with the operation of control devices. The General Permit does not include the following 

limitations which are common in the state permits reviewed. (See Attachment A for a listing of the state permit 

requirements.) The reasons for not including these limits in this General Permit are explained below:

 Plant Capacity Limit: Some state programs include asphalt plant capacity limits (in tons/hour) and dryer 

capacity limits (in MMBtu/hour) in their general permit programs. In general, the plant capacity is 
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limited to less than 700 tons/hour and the dryer capacity is limited to less than 150 MMBtu/hour. Since 

emission factors for asphalt mixer/dryers in AP-42, Chapter 11.1 for Hot Mix Asphalt Plants are in units 

of lb/ton and the emissions are calculated based on the amount of asphalt produced, the capacity of the 

asphalt plant does not determine the actual emissions from the dryer/mixer. Therefore, the permit does 

not include these dryer capacity limits since it is not necessary to show compliance with the emission 

and throughput limits in this General Permit.

 Total Fuel Usage Limit for the Dryer: Since emission factors for asphalt mixer/dryers in AP-42, Chapter 

11.1 for HMA plants are based on the amount of asphalt produced, limiting the annual production of the 

asphalt plant will effectively limit the emissions from the dryer/mixer. Limiting the amount of fuel used 

in the dryer/mixer is not necessary. Note that the definition of HMA plants in this General Permit

includes engines/generators. The CO emissions from engines/generators can be significant. Therefore, a 

total fuel usage limit for the engine/generators is necessary and has been included in the General 

Permit.

4.3.1 Requirements for Sources Located in Nonattainment Areas

For sources located in nonattainment areas we looked at the control requirements required in other 

nonattainment areas in the country, specifically:

 South Coast Air Quality Management District Rule 1147 for Nitrogen Oxides (NOx) Reductions from 

Miscellaneous Sources – this rule is in an ozone nonattainment area; and

 South Coast Air Quality Management District Rule 1155 for Particulate Matter (PM) Control Devices –

this rule is in a PM10 and PM2.5 nonattainment area.

This resulted in applying a PM limit of 0.01 gr/scf (filterable and condensable) for sources located in PM10 or 

PM2.5 nonattainment areas and a NOX limit of 40 ppm at 3% O2 for liquid fuel and 36 ppm at 3% O2 for gaseous 

fuel for sources located in ozone nonattainment areas. The other limits for attainment areas also apply to these 

sources. We did not discover any feasible control technologies or more stringent emission limits that could apply 

in CO nonattainment areas.

There are additional requirements for sources located in nonattainment areas that go beyond those found in the 

NSPS and NESHAP requirements. Since some tribes are located in ozone, PM10, PM2.5, and CO nonattainment 

areas, additional requirements for emissions from HMA plants located in nonattainment areas are necessary. 

Note that this General Permit does not cover facilities located in severe or extreme ozone nonattainment areas. 

This General Permit does cover facilities located in serious CO nonattainment areas. In order to develop 

additional requirements for HMA plants in ozone nonattainment areas, the EPA has reviewed the policy and 

procedures developed by the South Coast Air Quality Management District and added the following additional 

requirements for facilities located in nonattainment areas: for sources located in a serious ozone nonattainment 

area or located in a serious PM10 nonattainment area, NOX emissions from the dryers shall not exceed the limits 

specified in Table 3 below.

 Table 3: NOX Emission Limits for Facilities Located in Ozone, NO2, and PM2.5 Nonattainment Areas

Type of Fuel NOX Emission limitation for Dryers

Gaseous Fuel 36 ppmvd at 3% O2

Liquid Fuel 40 ppmvd at 3% O2
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The NOX emission limitation specified in Table 3 for gaseous fuel was based on the Best Available Control 

Technology (BACT) determination for asphalt batch plants developed by South Coast Air Quality Management 

District (CA BACT Guidelines, Part D). The NOX emission limitation specified in Table 3 for liquid fuel was adopted 

from the South Coast Air Quality Management District (AQMD) Rule for NOX Reductions from Miscellaneous 

Sources (CA Rule 1147). 

If located in a PM2.5 or PM10 nonattainment area, PM emissions (including both filterable and condensable PM) 

from the dryers shall not exceed 0.01 gr/dscf. This PM emission limitation is based on the PM emission limitation 

for HMA production equipment in South Coast AQMD Rule for Particulate Matter (PM) Control Devices (CA Rule 

1155). 

If located in a CO nonattainment area, CO emissions from the dryers shall not exceed the limits specified in 

Table 4 below:

 Table 4: CO Emission Limits for the Facilities Located in CO Nonattainment Areas

Type of Fuel CO Emission Limitation for Dryers

Gaseous Fuel 42 ppmvd at 19% O2

(= 400 ppmvd at 3% O2)

Liquid Fuel 64 ppmvd at 19% O2 or

(= 600 ppmvd at 3% O2)

The CO emission limits in Table 4 above are adopted from the CO emission limits in San Joaquin Valley Unified 

Air Pollution Control District Rule for Dryers, Dehydrators, and Ovens (San Joaquin Rule 4309). 

The EPA will require performance stack testing to demonstrate compliance with the additional NOx, CO, or PM 

emission limits for the facilities located in nonattainment areas. These tests should be repeated every 5 years. 

The affected facilities are required to perform stack testing for NOx, PM and CO according to the test methods 

prescribed in 40 CFR part 60, Appendix A. 

4.4 Information on Completing Screening Processes that Have to Be Satisfied to Request 

Coverage under the General Permit

Prior to obtaining coverage under this General Permit, sources must satisfactorily complete the 

screening processes that the EPA has provided to address: (1) the protection of any and all species that

are federally-listed as threatened or endangered under the Endangered Species Act (ESA) or of habitat

that is federally-designated as “critical habitat” under the ESA; and (2) the potential to cause effectsto

historic properties (pursuant to the National Historic Preservation Act). Attached to the Request for 

Coverage Forms for the general permits, the EPA provides guidance to assist sources in completing 

these processes.
Page 12 of 25

5. Emission Limitations1 and Surrogate Throughput Limits 

5.1 Developing the Surrogate Limits and Limitations

Emission limitations on production and fuel usage limits as surrogate emissions limitations were established 

below the major source thresholds for the NSR and Title V permitting programs. The NSR and Title V major 

source emission thresholds for sources located in attainment areas are 100 tpy for all criteria pollutants. The 

NSR and Title V major source emissions thresholds for facilities located in nonattainment areas vary for each 

pollutant and nonattainment status, as shown in Table 2.

In general, CO and NOx are the pollutants of concern emitted by HMA plants. Because the major source 

thresholds in CO attainment, unclassifiable or attainment/unclassifiable area and moderate nonattainment 

areas are identical (100 tpy), we believe there is no reason to establish separate asphalt production limits as 

surrogates for emissions limitations in these areas. The major source threshold for serious CO nonattainment 

areas is 50 tpy. Although there are currently no CO nonattainment areas in the United States, we have decided 

to allow coverage of the HMA General Permit in serious CO nonattainment areas, but with reduced production 

and fuel usage limits. Should an area become nonattainment for CO in the future, this restriction will prevent an 

HMA plant located in that area from violating the NSR thresholds.

Diesel-fired internal combustion engines that generate mechanical and electrical power at HMA plants can emit 

NOx at levels high enough to make NOx a secondary pollutant of concern. For this reason, we found it necessary 

to establish fuel usage limits as surrogate emissions limitations for the engines that are part of the stationary 

source. Because the major source threshold for NOx is 50 tpy in serious ozone nonattainment areas, we found it 

necessary to establish a lower limit for HMA plants in serious ozone nonattainment areas. The fuel usage limits 

as surrogate emissions limitations do not apply to nonroad engines, such as engines that operate mobile 

equipment (e.g., trucks and loaders) and portable engines that remain at one location for less than 12 months.

The throughput and fuel usage limits are set at levels intended to keep the sources emissions below the NSR

major source thresholds in Table 2, with an adequate margin to account for other pollutants emitted by the 

source. Table 5 shows the emission rates used to determine the throughput and fuel usage limits in the permit

for HMA plants located alone. Table 6 shows the emission rates used to determine the throughput and fuel 

usage limits in the permit for HMA operations co-located with stone quarrying, crushing, and screening 

operations and voluntarily taking lower limits to avoid the Title V program. 

Table 5: Emission Rates used to Determine Throughput

and Fuel Usage Limitations for HMA Plants Located Alone

Pollutant of 

Concern

Attainment, Unclassifiable or 

Attainment/Unclassifiable

Areas

Nonattainment Areas

CO 80 tpy

80 tpy (moderate areas)

40 tpy (serious areas)

PM10* 26 tpy

26 tpy (moderate areas)

26 tpy (serious areas)

 

1 The definition of emission limitation used in this Background Document is the one provided in the Federal Indian Country 

NSR rule (described in Section 4.3) and includes requirements established by the reviewing authority that relate to the 

operation of a source, which allows for the use of production throughput limits.
Page 13 of 25

Pollutant of 

Concern

Attainment, Unclassifiable or 

Attainment/Unclassifiable

Areas

Nonattainment Areas

PM2.5* 14 tpy 14 tpy

SO2 18 tpy 18 tpy

NOX 71 tpy

45 tpy (serious ozone areas)

71 tpy (marginal and moderate ozone areas)

VOC 28 tpy

18 tpy (serious ozone areas)

28 tpy (marginal and moderate ozone areas)

*Note: The emission limitations for these pollutants include fugitive emissions. 

Table 6: Emission Rates used to Determine Throughput and Fuel Usage Limitations for HMA Plants Co-Located 

with a Stone Quarrying, Crushing, and Screening Operation

Pollutant of 

Concern

Attainment, Unclassifiable or 

Attainment/Unclassifiable Areas Nonattainment Areas

CO 78 tpy

78 tpy

(moderate areas)

Not applicable

(serious areas)

PM 86 tpy Not applicable

PM10 63 tpy

63 tpy

(moderate areas)

63 tpy

(serious areas)

PM2.5 30 tpy 30 tpy

SO2 18 tpy 18 tpy

NOX 90 tpy

Not applicable

(serious ozone areas)

90 tpy

(marginal and moderate ozone areas)

VOC 27 tpy

Not applicable

(serious ozone areas)

27 tpy

(marginal and moderate ozone areas)

The General Permit includes the surrogate throughput and fuel usage limits listed in Table 7 for batch mix and 

drum mix HMA plants located in serious ozone nonattainment areas and other areas. The two production limits 

are set at varying levels because potential emissions from this source category are governed by both fuel usage 

and tons of asphalt processed. They are set at levels intended to keep the sources emissions below the 

emissions rates in Table 5 (NOx and CO are the controlling pollutants; the throughput calculations are contained 

in Attachment C).
Page 14 of 25

 Table 7: Surrogate Throughput Limits for HMA Plants

Type of 

HMA 

Plant

Attainment Status Asphalt Production 

Limit (tons/month)

Fuel Usage Limit for 

Engines/Generators 

(gallons/month)

Drum 

Mix

Attainment, Unclassifiable or 

Attainment/Unclassifiable for All 

Pollutants

83,000 12,500

Serious Nonattainment for Ozone 83,000 5,200

Serious Nonattainment for CO 33,000 12,5000

Batch 

Mix

Attainment, Unclassifiable or 

Attainment/Unclassifiable for All 

Pollutants

27,000 12,500

Serious Nonattainment for Ozone 27,000 5,200

Serious Nonattainment for CO 11,000 12,500

Drum 

Mix, CoLocated

All Areas Except, Serious Ozone and 

CO Nonattainment Areas 73,000 18,000

Batch 

Mix, CoLocated

All Areas Except, Serious Ozone and 

Co Nonattainment Areas 25,000 18,000

5.2 Emission Limitations

Two considerations form the basis for the emission limitations for the General Permit:

1. Are there any EPA regulation-based emission limitations?

2. Where do state programs establish eligibility limits? 

5.2.1 EPA Regulation-Based Emissions Limitations 

Facilities in attainment areas with criteria pollutant emissions greater than 100 tpy are subject to Title V 

operating permit programs. This General Permit is not intended to cover Title V major sources. Therefore, the 

emissions limitations included in the permit are based on the Title V major source threshold of 100 tpy for each 

criteria pollutant for HMA plants subject to this General Permit and located in attainment areas. 

For facilities located in nonattainment areas, this General Permit is not intended to cover NSR major sources and 

facilities located in severe and extreme ozone nonattainment areas or serious CO nonattainment areas. The NSR 

major source thresholds vary depending on the classification of the nonattainment areas. For PM10

nonattainment areas, the threshold is 70 tpy for serious areas and 100 tpy for moderate areas. For ozone 

nonattainment areas, the NSR major source thresholds are 50 tpy for VOC or NOX for serious areas and 100 tpy 

for VOC or NOX for marginal and moderate areas. The permit uses the same VOC and NOX thresholds as the 

emission threshold for this General Permit. For CO nonattainment areas, the NSR major source threshold is 100 

tpy for moderate areas. For SO2 and PM2.5 nonattainment areas, the NSR major source thresholds are 100 tpy. 

The emission limitations established in the permit are based on these NSR major thresholds.
Page 15 of 25

5.2.2 State Program Limits

The EPA researched similar types of permits developed by the states of Alaska, Arkansas, Arizona, Mississippi, 

New Mexico, Pennsylvania, South Carolina, Washington, Wisconsin, and West Virginia. The requirements for 

each state program are summarized in Attachment A. Based on the search results, most of the state general 

permits set the emission limitations to be close to 100 tpy for all criteria pollutants and the emission limits range 

from 80 tpy to 100 tpy. As a result, establishing the emissions limitations in the permit using 100 tpy for all 

criteria pollutants for facilities located in attainment areas is within the range of the emission limits in the state 

programs reviewed. 

5.3 Calculating the Throughput Limits

The EPA back-calculated the production limits and fuel usage limits for the engines/generators that resulted in 

emissions rates at the emission thresholds listed in Tables 5 and 6. For these calculations we made the following 

assumptions:

 The dryer is controlled by a baghouse or venturi scrubber;

 All production equipment is properly operated in accordance with the fugitive dust control plan;

 Natural gas, propane, distillate fuel, and biodiesel are used in the dryer;

 Natural gas, propane, distillate fuel, and biodiesel are used as fuels in the auxiliary heaters;

 Diesel and biodiesel are used in the engines/generators;

 The sulfur content of liquid fuel is 0.0015% by weight or less; and

 The total heat input capacity of all the auxiliary heaters at the affected facilities is 10 MMBtu/hour. 

Attachment C contains sample calculation for a hot mix asphalt plant located alone showing how the production 

and fuel usage limits in Table 7 were calculated to correspond to the upper CO emission rates in attainment and 

nonattainment areas as shown in Table 5. Although emissions from asphalt plants include PM and all criteria 

pollutants, CO is the controlling pollutant of concern when developing the production and fuel usage limits. CO 

is emitted from the mixer/dryer, asphalt load-out/silo filling operations, auxiliary heaters, and 

engines/generators. 
Page 16 of 25

References:

2008 National Emission Inventory Data, U.S. Environmental Protection Agency.

http://www.epa.gov/ttn/chief/net/2008inventory.html

40 CFR 49.151 – 40 CFR 49.165, Federal Minor New Source Review (NSR) Program in Indian Country.

http://ecfr.gpoaccess.gov/cgi/t/text/textidx?c=ecfr&sid=ffc06a883374e41e6772cd842b1ac2d4&tpl=/ecfrbrowse/Title40/40cfr49_main_02.tpl

40 CFR Part 60, Subpart Dc - Standards of Performance for Small Industrial-Commercial-Institutional Steam 

Generating Units. 

http://ecfr.gpoaccess.gov/cgi/t/text/textidx?c=ecfr&sid=4502b9bec7883393acc0ba9745803908&rgn=div6&view=text&node=40:6.0.1.1.1.12&idno=40

40 CFR Part 60, Subpart I, Standards of Performance for Hot Mix Asphalt Facilities.

http://ecfr.gpoaccess.gov/cgi/t/text/textidx?c=ecfr&sid=f2c4f71bd50d2a8883adafec36732010&rgn=div6&view=text&node=40:6.0.1.1.1.20&idno=40

40 CFR Part 60, Subpart Kb, Standards of Performance for Volatile Organic Liquid Storage Vessels (Including 

Petroleum Liquid Storage Vessels) for Which Construction, Reconstruction, or Modification Commenced After 

July 23, 1984.

http://ecfr.gpoaccess.gov/cgi/t/text/textidx?c=ecfr&sid=f2c4f71bd50d2a8883adafec36732010&rgn=div6&view=text&node=40:6.0.1.1.1.25&idno=40

40 CFR Part 60, Subpart IIII, Standards of Performance for Stationary Compression Ignition Internal Combustion 

Engines.

http://ecfr.gpoaccess.gov/cgi/t/text/textidx?c=ecfr&sid=f2c4f71bd50d2a8883adafec36732010&rgn=div6&view=text&node=40:6.0.1.1.1.98&idno=40

40 CFR Part 60, Subpart JJJJ, Standards of Performance for Stationary Spark Ignition Internal Combustion 

Engines.

http://ecfr.gpoaccess.gov/cgi/t/text/textidx?c=ecfr&sid=f2c4f71bd50d2a8883adafec36732010&rgn=div6&view=text&node=40:6.0.1.1.1.99&idno=40

40 CFR Part 63, Subpart ZZZZ, National Emission Standards for Hazardous Air Pollutant for Reciprocating Internal 

Combustion Engines (RICE).

http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&rgn=div6&view=text&node=40:13.0.1.1.1.1&idno=40

Alaska Dept. of Environmental Conservation, “Minor General Permit 3 for Asphalt Plants.” 

http://dec.alaska.gov/air/ap/docs/GP3MG3applic%204-8-10.pdf

AP 42, Fifth Edition, Compilation of Air Pollutant Emission Factors, Volume 1: Stationary Point and Area Sources.

http://www.epa.gov/ttn/chief/ap42/index.html

CA BACT Guidelines, Part D - Best Available Control Technology Guidelines for Non-Major Polluting Facilities, 

South Coast Air Quality Management District.

http://www.aqmd.gov/bact/PartD-10-3-2008.pdf 
Page 17 of 25

San Joaquin Valley Rule 4309 - Dryers, Dehydrators, and Ovens, San Joaquin Valley District, California.

http://www.valleyair.org/rules/currntrules/r4309.pdf

South Coast Air Quality Rule 1147- NOX Reductions from Miscellaneous Sources.

http://www.aqmd.gov/rules/reg/reg11/r1147.pdf

South Coast Air Quality Rule 1151- Particulate Matter (PM) Control Devices.

http://www.aqmd.gov/rules/reg/reg11/r1151.pdf

Page 19 of 25

 Attachment A – Summary of the State Permitting Programs for HMA Plants

State

Permit 

Type

Emission 

Limits

Production/Capacity 

Limits Fuel Limits Other Requirements Weblink

AK General 

Permit

PM10 < 100 tpy

NOX < 100 tpy

SO2 < 100 tpy

N/A For SO2 protection 

Area: 

1) Use diesel fuel with a 

sulfur content of ≤ 

0.075% by weight or 

use NG and

2) Diesel electric 

generators or other 

diesel engines may not 

be used. 

Setback from nearest 

residence of 330 feet, 

and 800 feet if more 

than two construction 

seasons.

http://dec.alaska.gov/air/ap/docs/GP

3MG3applic%204-8-10.pdf

AR General 

Permit

PM < 10 tpy

PM10 < 6.5 tpy

NOX < 95 tpy

CO < 95 tpy

VOC < 95 tpy

SO2 < 50 tpy

Production Limit:

< 475,000 tpy for aggregate;

and

< 100,000 tpy for recycled 

shingle.

Fuel Oil Usage Limit:

1) < 2,300,000 

gallons/year for fuel 

oils with sulfur content

< 0.5% and

2) < 1,150,000 and

gallons/year for fuel 

oils with sulfur content

< 1 %.

< 1,500 hrs/year for 

reclaimed asphalt 

pavement processing 

operations; 

dust control 

requirements; and

PM, NOx, CO, VOC and 

opacity stack testing for 

the asphalt plant (every 

5 years). 

http://www.adeq.state.ar.us/air/bra

nch_permits/pdfs/1912-AGP-000.pdf

AZ General 

Permit

< 90 tpy for all 

criteria 

pollutants

Production Limit:

< 5,280 tons/day for PM10

attainment area; and

< 3,150 tons/day for PM10 

nonattainment area.

HAP content limits for 

fuels.

Fugitive Dust Control 

Plan.

http://www.azdeq.gov/environ/air/p

ermits/download/gnhmapapp.pdf

MS

Multimedia 

General 

Permit

< 100 tpy for all 

criteria 

pollutants

Production Limits:

< 360,000 tpy (batch mix);

and

< 500,000 tpy (drum mix).

Fuel Type Limit: NG, 

LPG, fuel oil, liquid bioderived fuel and waste 

oil.

Sulfur content of the 

liquid oil < 1%.

HAP content limits for 

waste oils.

N/A http://www.deq.state.ms.us/MDEQ.

nsf/pdf/epd_AsphaltGeneralPermit/$

File/01General.pdf?OpenElement
Page 20 of 25

State

Permit 

Type

Emission 

Limits

Production/Capacity 

Limits

Fuel Limits Other Requirements Weblink

NM

General 

Constructio

n Permit

PM < 95 tpy

NOX < 95 tpy

CO < 95 tpy

VOC < 95 tpy

SO2 < 50 tpy

Single HAP < 8 

tpy

Total HAPs < 23 

tpy

Production Limit:

< 600 tons/hour

Capacity Limit:

< 180 hp for generators.

Fuel Type Limit:

1) NG, LPG, Gasoline, 

and 

2) No. 2 fuel oil with 

sulfur content < 0.05%.

Operation Hours < 4,380 

hrs/year; and 

Fugitive Dust Control 

Plan.

http://www.nmenv.state.nm.us/aqb/

permit/Permit_Apps/Permit_Apps_4

_GCP-3.html

PA General 

Permit

PM < 0.009 

gr/dscf

PM10 < 0.021 

gr/dscf

NOX < 60 ppmvd

@15%O2 

CO < 200 ppmvd

@15%O2

VOC < 30 ppmvd

@15%O2

N/A Sulfur Content Limits:

1) ≤ 0.3% for No.2 fuel 

oil, biodiesel and 

alternative fuels;

2) ≤ 0.5% for No.4 fuel 

oil and waste-derived 

liquid fuel; and

3) HAP content limits 

for waste-derived liquid 

fuel.

Fugitive dust control 

requirements.

http://www.dep.state.pa.us/dep/dep

utate/airwaste/aq/permits/gp/Final_

General_Permit-13_Conditions.pdf

SC General 

Permit

< 100 tpy for 

criteria 

pollutants

< 10/25 for HAPs

Production Limits:

< 250 tons/hour;

< 493,515 tpy (batch mix);

and

< 1,509,015 tpy (drum mix).

Capacity Limit:

< 10 MMBtu/hour for 

heaters.

Fuel Type Limit:

NG, propane, LPG, and 

approved waste oil.

< 14 hrs/day for units 

using No. 2 fuel oil; and

< 250 hrs/year for 

emergency generators.

http://www.scdhec.gov/environment

/baq/Permitting/GeneralPermits/hot

_mix_asphalt.asp
Page 21 of 25

State

Permit 

Type

Emission 

Limits

Production/Capacity 

Limits

Fuel Limits Other Requirements Weblink

WA

General 

Order for 

Drum Mix 

Asphalt 

Plants

CO < 80 tpy

NOX < 80 tpy

SO2 < 80 tpy

VOC < 5.76 tpy 

(BACT)

Production Limits:

< 500 tons/hour;

< 6,000 tons/day; and

< 300,000 tpy.

Capacity Limit:

< 150 MMBtu/hour for 

drum mixer/dryer.

Fuel Type Limit:

NG, LPG, and Diesel 

with sulfur content < 

0.0015%.

N/A http://www.ecy.wa.gov/programs/ai

r/AOP_Permits/Boiler/GeneralOrders

.htm

WI General 

Permit

SO2 < 80 tpy Production Limits:

< 700 tons/hour and

< 625,000 tons/month.

Total Fuel Usage < 

125,000 gallons/month

Fuel Usage for Engines 

< 14,167 gallons/month

Sulfur content of the 

fuel < 1.3%

Fuel Type Limit:

NG, propane, gasoline, 

diesel, biodiesel, and 

No. 2 through No. 6 

fuel oil. 

Fugitive Dust Control 

Plan; and

Stack Height 

Requirements.

http://dnr.wi.gov/air/pdf/HMAGOPfa

ct.pdf

WV General 

Permit

< 100 tpy for all 

criteria 

pollutants

N/A Sulfur Content Limits:

≤ 0.5% for fuel oils.

HAP content limits for 

used or recycled oils.

Fugitive dust control 

requirements and 

Storage tank capacity 

limit.

http://www.dep.wv.gov/daq/permitt

ing/Documents/GeneralPermits/G20-

B%20Permit-%202009.pdf
Page 22 of 25

Attachment B

Fugitive Dust Control Plan

1. Site Roadways and Plant Yard

a. The dust on the site roadways/plant yard shall be controlled by applications of water, calcium 

chloride or other acceptable and approved fugitive dust control compound. Applications of dust 

suppressants shall be done as often as necessary to meet all applicable emission limits.

b. All paved roadways/plant yards shall be swept as needed between applications.

c. Any material spillage on roads shall be cleaned up immediately.

2. Plant

a. The drop distance at each transfer point shall be reduced to the minimum the equipment can 

achieve. 

b. The transfer point from the re-circulating belt to the feed belt shall be equipped with an 

enclosed chute.

3. Storage Piles

a. Stockpiling of all nonmetallic minerals shall be performed to minimize drop distance and control 

potential dust problems.

b. Stockpiles shall be watered on an as needed basis in order to meet the opacity limits. Also, 

equipment to apply water or dust suppressant shall be available at the site, or on call for use at 

the site, within a given operating day. 

4. Truck Traffic

a. Vehicles shall be loaded to prevent their contents from dropping, leaking, blowing or otherwise 

escaping. This shall be accomplished by loading so that no part of the load shall come in contact 

within six (6) inches of the top of any side board, side panel or tail gate; otherwise, the truck 

shall be tarped.

b. A speed limit sign of 15 miles-per-hour or lower shall be posted on site so that it is visible to 

truck traffic.

5. Corrective Actions

If corrective action needs to be taken, the permittee shall consider and use one or more of the 

following options: adjust the watering and/or sweeping frequencies, reduce drop distances, increase 

cover, and/or take other actions to reduce fugitive dust emissions.
Page 23 of 25

Attachment C: 

Sample Emissions Calculations for 

Production Limits and Engine/Generator Fuel Usage Limits for 

Drum Mix Asphalt Plants Located Alone

Type of Mixer: Drum Mix

Emissions are estimated based on the following assumptions:

 The dryer is controlled by a baghouse or venturi scrubber;

 All production equipment is properly operated in accordance with the fugitive dust control plan;

 Both natural gas and No. 2 fuel oil are used in the dryer;

 Natural gas, propane, and No. 2 fuel oil are used as fuels in the auxiliary heaters;

 Both gasoline and diesel are used in the engines/generators;

 The sulfur content of the No. 2 fuel oil is 0.5% by weight or less; and

 The total heat input capacity of all the auxiliary heaters at the affected facilities is 10 

MMBtu/hour. 

(A) Limits for Facilities Located in Attainment, Unclassifiable or Attainment/Unclassifiable

for All Pollutants Areas and Marginal or Moderate Ozone Nonattainment Areas

Production Limit: 83,000 tons per month of asphalt 

Total Fuel Usage Limit for Engines/Generators: 12,500 gallons per month

The PM and criteria pollutant emissions from all the equipment at this drum mix asphalt plants are 

summarized below (SO2 emissions were not calculated because ultra low sulfur fuel is required):

Process PM10 PM2.5 NOX CO VOC SO2

Dryer/Mixer 11.5 1.44 18.9 64.7 15.9 5.48

Load-out/Silo Filling 0.55 0.55 - 1.22 8.02 -

Conveying 2.74 2.74 - - - -

Screening 0.37 0.02 - - - -

Storage Piles 1.35 0.20 - - - -

Lime Silo Loading 4.82 4.82 - - - -

Auxiliary Heater 1.03 0.80 6.26 3.61 0.48 0.1

Engine/Generator 3.23 3.23 45.5 9.8 3.62 3.01

Total Emissions 25.54 13.81 70.67 79.37 28.06 8.55

Based on the total emissions, CO and NOx are considered the pollutants of concern since they are the 

pollutants with emissions closest to the emission limitation of 100 tpy. By limiting CO and NOx to less 

than 100 tpy, PM, PM10, PM2.5, and VOC emissions are maintained below the major source thresholds for 

both attainment, unclassifiable or attainment/unclassifiable areas and allowed nonattainment areas. 

The CO emissions are from the dryer/mixer, load-out/silo filling operations, auxiliary heaters, and engine 

generators. Emissions were calculated very conservatively assuming full utilization of 10 MMBtu 

auxiliary heaters for 8,760 hours per year and uses AP-42 factors for the dryer/mixer and the engines. 

The CO emissions for each of these processes are detailed below:
Page 24 of 25

1. CO Emission from the drum mix dryer/mixer

= Emission factor x production limit x lbs to tons conversion

= 0.13 lbs/ton x 83,000 tpy x 1 ton/2,000 lbs

= 64.7 tpy

Where the CO emission factor is from AP-42, Table 11.1-7.

2. CO Emission from the asphalt load-out operation

= Emission factor x production limit x lbs to tons conversion

= 0.01349 lbs/ton x 83,000 tpy x 1 ton/2,000 lbs

= 0.67 tpy

Where the CO emission factor is from AP-42, Table 11.1-14.

3. CO Emission from the asphalt silo operation

= Emission factor x production limit x lbs to tons conversion

= 0.001109 lbs/ton x 83,000 tpy x 1 ton/2,000 lbs

= 0.55 tpy

Where the CO emission factor is from AP-42, Table 11.1-16.

4. CO Emission from the auxiliary heaters

= Capacity limit x fuel heat content x emission factor x 8,760 hrs/year x lbs to tons conversion

= 10 MMBtu/hour x 1 MMSCF/1,020 MMBtu x 84 lb/MMSCF x 8,760 hrs/year x 1 ton/2,000 lb

= 3.61 tpy

Where the CO emission factor is for natural gas combustion (worst case scenario among using 

natural gas, propane, and No. 2 fuel) and is from AP-42, Chapter 1.4.

5. CO Emission from the engine/generator

= Fuel usage x 12 months/year x fuel heat content x emission factor x lbs to tons

 conversion

= 17,340 gallons/month x 12 months/year x 1.37 MMBtu/gal x 0.95 lb/MMBtu x 1 ton/2,000 lbs

= 9.8 tpy

Where the CO emission factor is from AP-42, Table 3.3-1.

6. Therefore, the total CO emissions from the entire source are:

= 67.7 tpy + 0.67 tpy + 0.55 tpy + 3.61 tpy + 9.8 tpy 

= 79.37 tpy 
Page 25 of 25

(B) Limits for Facilities Located in Serious Ozone Nonattainment Areas

Production Limit: 

83,000 tons per month of asphalt 

Total Fuel Usage Limit for Engines/Generators: 5,200 gallons per month

The PM and criteria pollutant emissions from all the equipment at this drum mix asphalt plants are 

summarized below:

Process PM10 PM2.5 NOX CO VOC SO2

Dryer/Mixer 11.5 1.44 18.9 64.7 15.9 5.48

Load-out/Silo Filling 0.55 0.55 - 1.22 8.02 -

Conveying 2.74 2.74 - - - -

Screening 0.37 0.02 - - - -

Storage Piles 1.35 0.20 - - - -

Lime Silo Loading 4.82 4.82 - - - -

Auxiliary Heater 1.03 0.80 6.26 3.61 0.48 0.1

Engine/Generator 3.23 3.23 18.9 4.1 1.51 1.25

Total Emissions 25.54 13.81 44.12 73.65 25.94 6.80

Emissions were calculated in the same way as in the attainment area example above. In this case, the 

limiting pollutant is NOx. The potential to emit at full production appears to be very close to the major 

source threshold. However, this value was very conservatively calculated because it assumes full 

utilization of 10 MMBtu/hour auxiliary heaters for 8,760 hours per year, uses AP-42 factors for the dryer 

mixer where the permit requires more stringent emission limits, and uses the AP-42 emission factors for 

small diesel engines rather than the higher factors for engines > 600 hp.