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

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

Source Stone Quarrying, Crushing, and Screening Facilities in Indian Country

Version 1.0

Last Modified: March 23, 2015

1. Stone Quarrying, Crushing and Screening Source Category Definition

A stone quarrying, crushing, and screening (SQCS) facility is any stationary or portable non-metallic mineral 

processing facility which uses rock crushers, grinding mills, screening operations, bucket elevators, belt 

conveyors, bagging operations, storage bins, storage piles, truck loading stations, or railcar loading stations to 

process rock, sand, gravel, or mineral aggregate or that mines rock, stone, sand and gravel for construction. As 

diesel fuel is the most commonly used fuel at SQCS facilities, for the sake of simplicity, the permit is written to 

exclude the use of the General Permit by sources that combust fuels other than diesel fuel/biodiesel. The 

proposed General Air Quality Permit for New or Modified Minor Source Stone Quarrying, Crushing, and 

Screening Facilities in Indian Country only covers SQCS operations that are located at New Source Review (NSR) 

minor sources.

2. Source Category Characterization

The operations and equipment at a typical SQCS facility are described in AP 42, Chapters 11.19.1, Sand and 

Gravel Processing and 11.19.2, Crushed Stone Processing and Pulverized Mineral Processing.1SQCS facilities are 

part of a larger industrial process where stone, sand, gravel, rock, and minerals are removed from the earth and 

prepared for industrial, commercial and residential use. Quarried stone normally is delivered to the processing 

plant by truck, and is dumped into a hoppered feeder, usually a vibrating grizzly type, or onto screens. The

feeder or screens separate large boulders from finer rocks that do not require primary crushing, reducing the 

load to the primary crusher.

2

In sand and gravel processing, deposits of sand and gravel are mined and processed with screens, washing, and 

clarifiers to segregate the material into different particle sizes. Sometimes, crushing equipment is utilized to 

reduce particle sizes. In rock crushing operations, rock is loosened by drilling and blasting and then loaded by 

front-end loader or power shovel into large haul trucks that transport the material to the processing operations. 

Processing operations may include: crushing, screening, size classification, material handling and storage 

operations. Rock is loaded into bins and sent through screens, sorted for size, and conveyed to one or more rock 

crushers until all of the raw material is reduced to the desired size. Each crusher machine has associated 

screening and conveying equipment. After crushing, the rock is sorted according to size in screeners and 

conveyed to storage piles by conveyors. Front end loaders and trucks are used to move finished materials 

 

1 AP-42, Chapters 11.19.1, Sand and Gravel Processing and 11.19.2, Crushed Stone Processing and Pulverized Mineral 

Processing, http://www.epa.gov/ttn/chief/ap42/ch11/index.html.

2 Emission Inventory Improvement Program, Point Source Committee (Joint EPA – STAPPA/ALAPCO Initiative), “Technical 

Assessment Paper: Available Information for Estimating Emissions from Stone Mining and Quarrying 

Operations,” May 1998. 

http://www.dep.wv.gov/daq/planning/inventory/Documents/EIIP%20V02%20Ch13%20Stone%20Mining%20and%20Quarr

ying%20Operations.pdf
Page 2 of 18

offsite. Rock types processed by the crushed stone industry include: limestone, granite, dolomite, traprock, 

sandstone, quartz, quartzite, and lesser amounts of calcareous marl, marble, shell, and slate. 

Electricity for the motors running the crushers, screens, and conveyors is provided either by grid electric power 

or by diesel generators. Criteria pollutant emissions of concern are primarily particulate matter (PM) from 

crushing and screening, and particulate matter and nitrogen oxides (NOx) from diesel generators. For sources 

with available water, water sprays may be used to control particulate emissions. In sand processing, water is 

typically used in clarifiers to sort the sand by size, and the sand is processed wet. Dry particulate control 

methods (baghouses) may also be used to control particulate emissions.3SQCS facilities are distributed almost 

uniformly around the country in proportion to population density, as the need for sand, gravel, and mineral 

aggregates is widespread, the technology is simple, and the barriers to starting a business are low. Information 

gathered from state permits indicates that this source category is not uniform in size or emissions. 

3. State Minor Source Permit Programs

The U.S. Environmental Protection Agency (EPA) researched state air quality permitting websites for examples of 

general permits and permits by rule for sand and gravel facilities and rock crushing facilities. The EPA examined 

these documents for their applicability in developing a general permit for Indian Country. The EPA incorporated 

elements from these permits in developing the documents and regulations in the General Permit for SQCS

facilities. The EPA examined general permit documents for sand and gravel facilities for the States of Florida and 

Indiana. The EPA also examined general permit documents for rock crushing and screening facilities for the 

States of Alaska, Arizona, Florida, Indiana, Washington, and Wisconsin in developing this General Permit. The 

EPA chose general permits from these states 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.

Very few states issue air general permits for sand and gravel facilities. Although Indiana issues both a sand and 

gravel permit and a rock crushing permit, their respective throughput limits are nearly identical. Many states 

issue air general permits for rock crushing facilities, and the EPA found that other states general permits for rock 

crushing and screening facilities are similar in content to the permits from the states listed above. The state 

general permits for SQCS facilities vary from the streamlined (Indiana, at four pages) to the extremely detailed 

and complex (Arizona, at 104 pages). None of the state permits limit throughput based on co-location with 

another source, such as a hot mix asphalt plant.

The state sand and gravel permits typically have throughput limits, but these vary by state. The assumptions and 

methodology for arriving at these throughput limitations are not discussed in the permit application documents, 

and, except for the Washington state rock crushing general permit, the technical support documents used in 

developing the throughput limits are not readily available. The EPA assumes that each state is calculating the 

throughput limits based on different equipment configurations and control scenarios.

 

3 AP-42, Chapters 11.19.1, Sand and Gravel Processing and 11.19.2, Crushed Stone Processing and Pulverized Mineral 

Processing, http://www.epa.gov/ttn/chief/ap42/ch11/index.html.
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Most of the state sand and gravel permit applications mention that the permit cannot be issued to sources 

whose potential to emit (PTE) of particulate matter 10 microns or less (PM10), NOX, or carbon monoxide (CO) is 

greater than 100 tons per year (tpy). The applications do state that rock throughput, fuel throughput, and/or 

engine displacement shall be limited, but the methodology and emissions calculations underlying the 

relationship between the emission threshold(s) and the raw material throughput/fuel usage limit(s) are not 

clearly stated (except for the Washington state rock crushing permit). However, it is clear that these rock 

throughput limits, fuel usage limits, and engine displacement limits are intended to keep emissions below the 

major source thresholds. The Alaska rock crushing permit contains no rock throughput limits, but requires the 

applicant to calculate the PTE of their facility to verify that it is below 100 tpy prior to submitting the application. 

Similarly, the Florida sand and gravel permit does not contain any raw material throughput limits, but merely 

requires that the facility’s PTE be less than 100 tpy for any criteria pollutant. However, these two permits are an 

exception. The state permits typically limit raw materials throughput and fuel usage as a surrogate for limiting 

emissions.

As previously mentioned, many of the state permits regulate emissions from engines, but the type of regulation 

varies. Some state permits that regulate combustion emissions (Alaska and Arizona) delineate between 

stationary engines and nonroad (portable) engines.4 They do not regulate combustion emissions from the 

engines at rock crushing facilities which change location more frequently than once per year because, by 

definition, those engines are nonroad (portable) engines. They also do not regulate the amount of fuel used by 

mobile sources, such as trucks and front end loaders. The Florida and Wisconsin rock crushing permits do 

regulate combustion emissions, but assume that all combustion is from stationary engines. For all of the state 

permits mentioned here, combustion emissions from stationary engines at rock crushing facilities are regulated 

by limiting the amount of fuel that can be combusted per year, or the engine displacement. The fuel usage limits 

vary from state to state, and underlying calculations are not provided, so it is not clear what the intended 

emissions limit is for each state permit. The Indiana and Washington state permits do not regulate combustion 

emissions.

Most state permits (Arizona, Florida, Indiana, Washington, and Wisconsin) require control of particulate 

emissions, but the Alaska permit does not. In Alaska, the water sprays typically used to control particulate may 

freeze on the aggregate and the equipment, creating unsafe and unworkable conditions. All state sand and 

gravel permits require that the operator have a fugitive dust control plan and that fugitive emissions from 

roadways and storage piles be controlled. The Alaska permit qualifies this and requires fugitive emissions control 

if the facility is within 1,000 feet of a residence. The State of Washington conducted dispersion modeling for a 

rock crusher processing 5,300,000 tons of material per year, and determined that a 150 foot setback from the 

rock crusher to the property lines would ensure no violation of the 24-hour National Ambient Air Quality 

Standards for PM10 (150 μg/m3).

5 The state permit for Alaska contains a 400 foot setback provision for the 

crusher and any diesel engine from the nearest residence. All of the state sand and gravel permits include 

opacity limitations, most require an operation and maintenance plan, and all include some variation of the 

monitoring and recordkeeping requirements found in typical minor source permits. The South Coast Air Quality 

Management District of California provides a comprehensive set of regulations6for control of fugitive dust in 

 

4

Stationary engines include all internal-combustion engines that are used either in a fixed application, or in a portable (or 

transportable) application in which the engine will stay at a single site for at least a full year. “Emission Regulations for

Stationary and Mobile Engines” US EPA, EPA420-F-02-034, September 2002.

5 Washington State Dept. of Ecology, “Suitability of Rock Crushing Operations for Air Quality General Order of Approval: 

Evaluation of Control Technology, Ambient Impacts, and Potential Approval Criteria,” June 2006.

6

South Coast Air Quality Management District, Rule 1157 “PM10 Emission Reductions from Aggregate and Related 

Operations,” http://www.aqmd.gov/rules/reg/reg11/r1157.pdf.
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areas of serious or severe nonattainment for PM10 and particulate matter 2.5 microns or less (PM2.5). A fugitive 

dust control plan is included in the permit.

Several of the state general permits incorporate the requirements of New Source Performance Standards (NSPS) 

Subpart OOO (Standards of Performance for Nonmetallic Mineral Processing Plants) into the text of the permit, 

while other states (Florida, Indiana) incorporate the Subpart OOO requirements by reference. Requirements for 

NSPS Subpart IIII (Standards of Performance for Stationary Compression Ignition Internal Combustion Engines) 

and National Emissions Standards for Hazardous Air Pollutants (NESHAP) Subpart ZZZZ (National Emissions 

Standards for Hazardous Air Pollutants for Stationary Reciprocating Internal Combustion Engines) are not 

generally included in state permits for sand and gravel facilities. 

4. Requirements for General Permits

4.1 Documents for General Permits

The EPA developed a standardized set of permit documents in support of the General Permit for SQCS facilities 

located in Indian country. 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

 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 emission 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.
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 Table 1: Minor NSR Thresholds in 40 CFR 49.153

Pollutant Attainment Area Nonattainment Area

CO 10 tons per year (tpy) 5 tpy

PM 10 tpy 5 tpy

PM10 5 tpy 1 tpy

PM2.5 3 tpy 0.6 tpy

Sulfur Dioxide (SO2) 10 tpy 5 tpy

NOX 10 tpy 5 tpy

Volatile Organic 

Compounds (VOC) 5 tpy 2 tpy

Under EPA policy, true and synthetic minor NSR 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 Permit. 

The NSR major source threshold for attainment areas is 250 tpy of 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 25 tpy of VOC or NOX

Extreme 10 tpy of VOC or NOX

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 General 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 could meet the throughput limits and operating requirements 

established in this General Permit. The specific requirements for the General Permit are discussed in Sections 
Page 6 of 18

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. 

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.

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 consideration were used for 

setting the limits in the General Permit for SQCS facilities:
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1. Local air quality conditions – To address this requirement, the General Permit requires sources locating 

in ozone and carbon monoxide nonattainment areas to meet more stringent requirements on fuel use –

the main source of CO, NOx, and VOC emissions at SQCS facilities. This will also ensure these sources are 

not major sources in those areas. Also, PM emission may be a concern for SQCS facilities, but the 

majority of those emissions are fugitive. The permit contains a requirement to take corrective action if 

fugitive dust is visible beyond the property line. This will aid in reducing the local PM air quality impacts.

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 SQCS facilities:

 40 CFR 60 Subpart OOO – Standards of Performance for Nonmetallic Mineral Processing 

Facilities;

 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 the following equipment at SQCS facilities:

 Engines;

 Material handling equipment; and

 Fuel storage tanks.

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, NESHAP, and the 

state permit examples.

The derivation of applicability thresholds and the production and fuel usage limits in the applicability 

questionnaire, application, and conditions in 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. 

Review of the regulations and other existing general permits resulted in permit conditions requiring 

emissions from all crushers, screens, drop points, and other possible release points to be controlled by 

wet suppression, limiting fugitive emissions from crushers to 12% opacity, limiting fugitive emissions 

from all other processes to 7% opacity, 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.
Page 8 of 18

In addition, 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 conditions represent the standard fuels 

used for this equipment and the standard sulfur content these fuels must attain. Although we reviewed 

the NSPS requirements for tanks, we did not include any limits in the permit as the tanks used by SQCS 

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 60.674(b) – requirements for wet suppression systems;

 Table 2 to Subpart OOO of 40 CFR 60 – requirements for fugitive emissions;

 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 

SQCS facilities across the country in both attainment and nonattainment 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 SQCS 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 SQCS facility to be co-located with a 

hot mix asphalt (HMA) plant 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 co-located SQCS and HMA 

plants are specified in the respective permits.

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 wet suppression system 

is operating properly, that a visible emissions survey is conducted on a weekly basis, that fugitive emissions 

surveys are conducted weekly, and that stationary engines with oxidation catalyst monitor the inlet temperature 
Page 9 of 18

and pressure drop. The General Permit also requires initial and continuing testing of compliance with the opacity 

limits.

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 crushed rock, sand, and gravel produced each month, monthly fuel use, visible emission 

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

tests, 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.

4.3.1 Requirements for Sources Located in Nonattainment Areas

We did not include any additional requirements for sources locating in ozone nonattainment areas, other than 

the limits on monthly fuel use. We are not aware of any more stringent state/local control requirements for 

SQCS facilities in nonattainment areas. The limits on monthly fuel use will ensure that the General Permit applies 

to minor sources locating in these nonattainment areas.

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 10 of 18

5. Emission Limitations7 and Surrogate Throughput Limits 

5.1 Developing the Surrogate Limits and Limitations

The General Permit includes a rock, sand, and gravel throughput limit that applies to sources in both attainment 

and nonattainment areas that serves as a surrogate emissions limitation. The General Permit also includes 

surrogate fuel use limits that apply based on the particular ozone attainment or nonattainment classification in 

the area the source will locate. These surrogate limits correspond to a particular tpy emission rate, as discussed 

below.

The tpy emission rates used to determine eligibility for the General Permit for sources located in attainment and 

nonattainment areas corresponds to the source-wide PTE at which a source would become a major source and 

subject to Title V permitting (referred to hereafter as “the Title V major source threshold”). In attainment areas, 

the Title V major source threshold is 100 tpy for any criteria pollutant, 10 tpy for a single hazardous air pollutant 

(HAP), and 25 tpy for any combination of HAPs. The Title V major source threshold in nonattainment areas varies 

by the pollutant and the nonattainment classification.

The rock, sand and/or gravel throughput limit was established based on the Title V major source thresholds and 

assumptions about the equipment configuration at a “typical” rock, sand and/or gravel crushing facility. The 

assumptions about equipment configuration have a significant impact on the level of pollutants emitted. The 

rock, sand and/or gravel crushing permit materials from only two states (Indiana and Washington) contained 

information on the equipment configurations used in determining the PTE and rock throughput limits. The 

Indiana permit had figures for the number of crushing and screening machines for three different permit levels, 

but there was no information on other equipment (conveyors, storage piles, loading and unloading, etc) or how 

the emissions are calculated. The technical support document for the Washington Department of Ecology rock 

crushing permit contains more information on equipment and emissions calculations. The Washington 

Department of Ecology surveyed rock crushing operations and found that a typical rock crusher had three 

crushers, three screens, and six conveying operations. Their calculations include emissions from this equipment, 

as well as transfer operations and haul roads. The “typical facility” calculations supporting this General Permit

use this same equipment configuration, and also include emissions from storage piles and truck unloading and 

loading operations. The EPA developed a limit calculator spreadsheet of PTE calculations showing pollutant 

emissions for the emission units at the “typical” rock, sand and/or gravel crushing and screening facility 

described above using AP 42 emission factors. Since AP 42 emission factors are not available for all types of 

operations at a rock, sand and/or gravel crushing facility, the EPA estimated some emission factors for primary 

and secondary crushing and screening, based on existing emission factors for tertiary crushing and screening and 

the relative surface area of the rock produced in each process. The calculations for these estimated emission 

factors are included in the PTE Calculator and Limit Calculator spreadsheets. The EPA then used the Limit 

Calculator spreadsheet to calculate the materials throughput limits for the SQCS General Permit, based on the 

emission limitations. 

Chapter 11.19.1 (Sand and Gravel Processing) of AP 42 does not contain emission factors for the materials 

handling operations that occur at sand and gravel plants. The discussion in AP 42 on sand processing plants 

indicates that this material is excavated in a wet condition, and is processed with water. Under these conditions, 

particulate emissions would be minimal. In contrast, rock, sand and/or gravel crushing operations process a raw

 

7 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 11 of 18

material that is dry and releases additional fine particulate matter when it is crushed, screened and handled. 

Emission factors for rock crushing operations have been developed, and emission estimates can be quantified, 

based on the amount of material and the steps in the process. The materials throughput limits in this General 

Permit are based on emissions from rock crushing, not sand and gravel processing. As there are no particulate 

emission factors for wet sand and gravel processing, no upper throughput limit for sand processing can be 

calculated. The raw materials limits in the General Permit, which are based on the particulate emissions from a 

specific configuration of rock crushing equipment, have been used for sand and gravel plants.

Although fuel usage limits are included in the permit, it is unknown whether an SQCS facility issued a general 

permit would be restricted by the fuel limit. Stationary rock crushers typically use utility electric power, while 

portable rock crushers use generators, which are nonroad engines. Nonroad engines are not subject to the 

Prevention of Significant Deterioration Program, Title V, or NSPS Subpart IIII, unless the engines remain in one 

place for more than one year, in which case they become stationary engines. For purposes of developing the 

General Permit, no limits have been included precluding the rock crushers from remaining in place for more 

than one year, so emissions from any stationary engines are counted when considering the pollutant thresholds.

The General Permit includes the rock throughput and fuel usage limits listed in Table 6 for SQCS plants located in 

attainment, unclassifiable or attainment/unclassifiable areas and nonattainment areas. The production limits

and fuel usage limits for attainment, unclassifiable or attainment/unclassifiable areas and nonattainment areas 

are set at different levels because the EPA has selected different emissions limitations for attainment, 

unclassifiable or attainment/unclassifiable areas and nonattainment areas. The rock 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 3 shows the emission 

rates used to determine the rock throughput and fuel usage limits in the permit for SQCS facilities located alone.

PM10 is the controlling pollutant. The throughput calculations are contained in Attachment A. Table 4 shows the 

emission rates used to determine the rock throughput and fuel usage limits in the permit for SQCS facilities colocated with HMA plants.

Table 3: Emission Rates Used to Determine Production and Fuel Usage Limitations 

for Stone Quarrying, Crushing and Screening Facilities Located Alone

Pollutant of 

Concern

Attainment, Unclassifiable or 

Attainment/Unclassifiable Areas Nonattainment Areas

CO 19 tpy 19 tpy (moderate and serious areas)

PM10* 63 tpy 63 tpy (moderate and serious areas)

PM2.5* 63 tpy 63 tpy

NOX 88 tpy

88 tpy (marginal and moderate 

ozone areas)

45 tpy (serious ozone areas)

22.5 tpy (severe ozone areas)

9 tpy (extreme ozone areas)

VOC 7 tpy 7 tpy (ozone areas)

*Note: The emission thresholds for these pollutants include fugitive emissions.
Page 12 of 18

Table 4: Emission Rates Used to Determine Production and Fuel Usage Limitations

for Stone Quarrying, Crushing and Screening Facilities Co-Located with Hot Mix Asphalt Facility

Pollutant of 

Concern

Attainment, Unclassifiable or 

Attainment/Unclassifiable

Areas

Nonattainment Areas

CO 78 tpy

78 tpy

(moderate areas)

Not applicable

(serious areas)

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 and above ozone areas)

90 tpy

(marginal and moderate ozone areas)

VOC 27 tpy

Not applicable

(serious and above ozone areas)

27 tpy

(marginal and moderate ozone areas)

5.2 Emission Limitations

Two considerations form the basis for the upper eligibility emission limitations for general permits:

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 

The only EPA regulation-based emissions limitations for rock crushing and screening facilities are the emission 

limitations from the exhaust of affected facilities equipped with capture systems of 0.014 grains per dry 

standard cubic foot of exhaust. Affected facilities are each crusher, grinding mill, screening operation, bucket 

elevator, belt conveyor, bagging operation, storage bin, enclosed truck or railcar loading station. In general, 

facilities in attainment areas with PTE of any criteria pollutant equal or greater than 250 tpy are NSR major 

sources. Facilities with PTE of any criteria pollutant equal to or greater than 100 tpy or HAP emissions greater 

than 10 tpy for a single HAP and 25 tpy for total HAPs are subject to Title V operating permit program. 

5.2.2 State Program Limits

The upper limits in state permits vary in that they either limit pollutant emissions or raw material and fuel 

throughput. Only the Indiana permit limits both emissions and raw material throughput. Indiana limits emissions 

of PM10 from smaller SQCS facilities to less than 25 tpy, and limits emissions of PM10 from large facilities to less 

than 100 tpy. Alaska and Florida limit PM10 emissions to less than 100 tpy. As mentioned previously, the rock 

throughput limits corresponding to the 100 tpy limit on PM10 emissions vary from state to state, and the 
Page 13 of 18

underlying assumptions and calculations are not explicitly stated. Since nearly all states require control of 

emissions from rock crushing equipment, and fugitive emissions as well, this may account for some of the 

variation seen in throughput limits from state to state. The Alaska permit8 does not contain throughput limits, 

but instead requires that applicants calculate their PTE of PM10. This is a source-specific approach, and requires 

skilled permitting staff to verify that the calculations are accurate. The Indiana rock crushing permit9, with its 

100 tpy limit on PM10 emissions, and similar emission control requirements, sets the throughput threshold at 

3,000,000 tpy. The Wisconsin general permit10 is similar to the Indiana general permit in that it has a 100 tpy 

limit on PM10 emissions, emission control requirements, and sets the throughput limit at 250,000 tons per 

month (equivalent to 3,000,000 tpy). A comparison of requirements for attainment and nonattainment areas is 

not possible due to lack of a distinction made in most state programs. The Arizona general permit11 limits 

emissions of PM10 to 13.64 tpy, but this may be due to the fact that nearly half of the counties in Arizona have 

been designated nonattainment for PM10. The Arizona permit is one example of a SQCS permit designed for an 

area designated as nonattainment for PM10. Table 5 shows the limits imposed by rock crushing and screening 

permits for the states reviewed.

 Table 5: State Rock Crushing and Screening Permit Throughput Limits and Emission Limitations

State

Rock 

Throughput 

Limits

Criteria 

Pollutant 

Emission 

Limitations

Engine Fuel 

or Size Limit

Setback 

Required?

Fugitive 

Dust 

Controls 

Required?

Particulate 

Emissions 

Controls 

Required?

Alaska

Min: 5 tons per 

hour

Max: None

All:

100 tpy

Less than 

1,100 bhp 1,000 feet No No

Arizona

Min: 25 tons per 

hour

Max: None

PM10: 13.64 

tpy

NOX, CO: 90 

tpy

None None Yes Yes

Florida Min: None

Max: None

All:

100 tpy

275,000 gal 

diesel/year None Yes Yes

Indiana 

(small)

Min: None

Max: 1,000,000 

tpy

PM10:

25 tpy None None Yes Yes

Indiana 

(large)

Min: None

Max: 3,000,000 

tpy

PM10:

100 tpy None None Yes Yes

Washington

Min: None

Max: 14,500 

tons per day, 

1,500,000 tpy

None None 150 feet Yes Yes

 

8

For more information, go to: http://dec.alaska.gov/air/ap/docs/MG9%20Final%20Permit%204-8-09.pdf.

9

For more information, go to: http://www.in.gov/idem/5157.htm#oaq_permits_ssoa. 

10 For more information, go to: http://dnr.wi.gov/files/PDF/pubs/am/AM381.pdf. 

11 For more information, go to: http://www.azdeq.gov/environ/air/permits/download/gncspermit.pdf. 
Page 14 of 18

State

Rock 

Throughput 

Limits

Criteria 

Pollutant 

Emission 

Limitations

Engine Fuel 

or Size Limit

Setback 

Required?

Fugitive 

Dust 

Controls 

Required?

Particulate 

Emissions 

Controls 

Required?

Wisconsin

Min: None

Max: 250,000 

tons per month

PM10:

100 tpy

20,000 

gal/month 

(6,870 

gal/month in 

ozone nonattainment 

area)

None Yes Yes

5.3 Calculating the Surrogate Throughput Limits

For new or modified SQCS facilities, the Title V major source thresholds are used as the emission rates for 

calculating throughput limits, with an adequate margin to account for other pollutants emitted by the source. 

The EPA evaluated the emission rates at which a new or modified source would become a major source under 

Title V. This is 100 tpy for PM10, PM2.5, NOX, VOC, and CO in attainment areas (the tpy number varies for 

nonattainment areas for these pollutants). The EPA established limits for PM10, PM2.5, NOX, and CO to meet the 

emission rates in Table 3 of this document. The EPA back-calculated the throughput of materials and usage of 

fuels that yielded emissions at these limits by using the equipment profile from the Washington Department of 

Ecology permit support document and emission factors from AP 42, Chapter 11.9.2. These results are shown in 

Table 6 for SQCS facilities located alone. PM10 and NOX are the limiting pollutants. The equivalent materials 

throughput and fuel usage limits are incorporated into the permit documents as the upper limits for materials 

throughput and fuel usage for attainment and nonattainment areas. Using these limits will also ensure that 

major source NSR will not be triggered for any new or modified source. Sample calculations showing the 

methodology used are in Attachment C.

Table 6: Surrogate Rock Throughput and Fuel Usage Upper Limits for a SQCS Facility Located Alone

Attainment Status Upper Rock Throughput Limit 

(tons per month)

Upper Fuel Usage 

Limit (gallons per 

month)

Ozone Attainment, Unclassifiable and 

Attainment/Unclassifiable Areas and 

Marginal/Moderate Areas for Ozone

1,100,000 24,200

Serious Nonattainment Areas for Ozone 1,100,000 12,000

Severe Nonattainment Areas for Ozone 1,100,000 5,500

Extreme Nonattainment Areas for Ozone 1,100,000 1,900

The EPA used the same procedures for calculating the equivalent materials throughput and fuel usage limits for 

a SQCS operation co-located with a HMA operation and voluntarily taking lower limits to avoid the Title V

program. These limits are incorporated into the permit documents as the upper limits for materials throughput 

and fuel usage for co-located SQCS/HMA plants. These results are shown in Table 7.
Page 15 of 18

Table 7: Surrogate Rock Throughput and Fuel Usage Upper Limits

for a SQCS Facility Co-Located with a HMA Plant

Upper Rock Throughput 

Limit (tons per month)

Upper Fuel Usage 

Limit (gallons per 

month)

730,000 18,275
Page 16 of 18

References

40 CFR 49.1 – 40 CFR 49.173, Indian Country Air Quality Planning and Management.

http://www.gpo.gov/fdsys/pkg/CFR-2011-title40-vol1/pdf/CFR-2011-title40-vol1-part49.pdf

40 CFR 52.21, Prevention of Significant Deterioration of Air Quality.

http://www.gpo.gov/fdsys/pkg/CFR-2007-title40-vol3/xml/CFR-2007-title40-vol3-sec52-21.xml

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 OOO, Standards of Performance for Nonmetallic Mineral Processing Plants.

http://www.gpo.gov/fdsys/granule/CFR-2012-title40-vol7/CFR-2012-title40-vol7-part60-subpartOOO/contentdetail.html

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 Department of Environmental Conservation, “Minor General Permit 9 for Rock Crushers.” 

http://www.dec.state.ak.us/air/ap/docs/MG9%20Final%20Permit%204-8-09.pdf

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

U.S. Environmental Protection Agency. http://www.epa.gov/ttn/chief/ap42/

Arizona Department of Environmental Quality, “Crushing and Screening General Permit.”

http://www.azdeq.gov/environ/air/permits/class.html#general

Emission Inventory Improvement Program, Point Source Committee (Joint EPA – STAPPA/ALAPCO Initiative), 

“Technical Assessment Paper: Available Information for Estimating Emissions from Stone Mining and Quarrying 

Operations,” May 1998. 

http://www.dep.wv.gov/daq/planning/inventory/Documents/EIIP%20V02%20Ch13%20Stone%20Mining%20an

d%20Quarrying%20Operations.pdf

Federal Register Vol. 76, No. 127, July 1, 2011, Pages 38748-38808, “Review of New Sources and Modifications 

in Indian Country; Final Rule” (Indian Country NSR Rule).

http://www.gpo.gov/fdsys/pkg/FR-2011-07-01/pdf/2011-14981.pdf

Florida Department of Environmental Protection, “Nonmetallic Mineral Processing Plant (Crusher) Air General 

Permit Registration Form.” http://www.dep.state.fl.us/air/emission/mineral.htm

Indiana Department of Environmental Management, “OA-08 Crushed Stone Processing Plants.” 

http://www.in.gov/idem/5157.htm#oaq_permits_gsd

South Coast Air Quality Management District, Rule 1157 “PM10 Emission Reductions from Aggregate and Related 

Operations.” http://www.aqmd.gov/rules/reg/reg11/r1157.pdf
Page 17 of 18

Washington Department of Ecology, “Suitability of Rock Crushing Operations for Air Quality General Order of 

Approval.” http://www.ecy.wa.gov/programs/air/AOP_Permits/Boiler/TTODd/PDFS/ROCKCRUSHER.PDF

Wisconsin Dept. of Natural Resources, “Air Program Fact Sheet - General Permits for Crushers.” 

http://dnr.wi.gov/files/PDF/pubs/am/AM381.pdf
Page 18 of 18

Attachment A: 

Sample Emissions Calculations for Rock Throughput and Fuel Usage 

Limits for Ozone Attainment and Nonattainment Areas for SQCS Facilities Located Alone

Emissions from Crushing, Screening, and Conveying:

Type of Operation

Emission Factors 

(lbs/ton)

PM10

Truck Unloading – Fragmented Stone 0.000016

Primary Crushing 0.00014

Screening of Primary Crusher Output 0.00019

Conveyor Transfer Point (2 drop points) 0.000046 x 2

Secondary Crushing 0.00027

Screening of Secondary Crusher Output (Controlled) 0.00037

Conveyor Transfer Point (2 drop points) 0.000046 x 2

Tertiary Crushing 0.00054

Screening of Tertiary Crusher Output 0.00074

Conveyor Transfer Point (2 drop points) 0.000046 x 2

Fines Crushing 0.0012

Fines Screening 0.0022

Conveyor Transfer Point (2 drop points) 0.000046 x 2

Dry Sand and Gravel Screening 0.0022

Dry Sand and Gravel Conveying (4 drop points) 0.000046 x 4

Truck Loading – Conveyor, crushed stone 0.0001

Total PM10 Emissions Factor 0.008518

Emission factors from AP 42 Table 11.19.2-2, for controlled sources

PM10 for SQCS operations:

PM10 = Monthly throughput limitation x emissions factor x 12 months/year x lbs to ton conversion

PM10 = 1,100,000 (tons/month) x 0.008518 (lbs/ton) x 12 months/year x 1/2,000 (tons/lb) 

= 56.2 tpy

NOX Emissions from Engines by Ozone Area:

Ozone Attainment Areas and Marginal or Moderate Ozone Nonattainment Areas:

NOX = Monthly throughput limitation x 12 months/year x fuel heat content x emissions factor x lbs to ton

 conversion

NOX = 24,200 (gallons/month) x 12 months/year x 1.37 MMBtu/gal x 4.41 (lb/MMBtu) x

 1/2,000 (tons/lb)

= 88.2 tpy
Page 19 of 18

Serious Ozone Nonattainment Areas:

NOX = Monthly throughput limitation x 12 months/year x fuel heat content x emissions factor x lbs to ton

 conversion

NOX = 12,000 (gallons/month) x 12 months/year x 1.37 MMBtu/gallon x 4.41 (lb/MMBtu) x 1/2,000 (tons/lb)

= 43.7 tpy

Severe Ozone Nonattainment Areas:

NOX = Monthly throughput limitation x 12 months/year x fuel heat content x emissions factor x lbs to ton

 conversion

NOX = 5,500 (gallons/month) x 12 months/year x 1.37 MMBtu/gallon x 4.41 (lb/MMBtu) x 1/2,000 (tons/lb)

= 20.1 tpy

Extreme Ozone Nonattainment Areas:

NOX = Monthly throughput limitation x 12 months/year x fuel heat content x emissions factor x lbs to ton

 conversion

NOX = 1,900 (gallons/month) x 12 months/year x 1.37 MMBtu/gallon x 4.41 (lb/MMBtu) x

 1/2,000 (tons/lb)

= 6.9 tpy