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: True Minor Source Stone Quarrying, Crushing, and 

Screening Facilities General Permit 

Version 1.0

Last Modified: November 14, 2013

1. Stone Quarrying, Crushing and Screening Source Category Definition

A Stone Quarrying, Crushing, and Screening (SQCS) facility is any 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 stone, sand, gravel, or 

mineral aggregate. 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 True Minor Source SQCS General Permit only covers SQCS operations that are 

located at true 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 

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. 

 

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

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). 

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.

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 

 

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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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.4They 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 

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.

 

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.
Page 4 of 18

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 and Permits by Rule

4.1 Documents for General Permits and Permits by Rule

The EPA developed a standardized set of permit documents in support of a 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, 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 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/Permits by Rule

Facilities applying for the proposed general permit must meet the following criteria:

Must be a true NSR minor source; and

Be below the emission limitations established for the general permit.

New facilities with a PTE or modifications to existing facilities with an emissions increase lower than the minor 

NSR thresholds specified in Table 1 of Tribal NSR Rule (40 CFR 49.153) are exempt from the minor NSR program. 

The exemption thresholds for PM and criteria pollutants are listed in Table 1 below. Facilities applying for the 

proposed general permit may calculate their PTE using the PTE calculator provided to determine if they are 

exempt from the minor NSR program. The EPA is providing a PTE calculator to assist with this task.
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 Table 1: Minor NSR Thresholds in 40 CFR 49.153

Pollutant Attainment Area Nonattainment Area

CO 10 tpy 5 tpy

PM 10 tpy 5 tpy

PM10 5 tpy 1 tpy

PM2.5 3 tpy 0.6 tpy

SO2 10 tpy 5 tpy

NOX 10 tpy 5 tpy

Volatile Organic 

Compounds (VOC) 5 tpy 2 tpy

Under current EPA policy, only true NSR minor sources qualify for the proposed general permit. Therefore, 

facilities will be required to compare their PTE to the NSR major source thresholds to determine if they qualify 

for the proposed general permit. For this source category – stone quarrying, crushing and screening facilities –

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 that is designated nonattainment in the area the source will 

locate), then the facility does not qualify for the proposed general permit. The following documents are 

available to assist sources in the screening and application process: 

Questionnaire; and

Request for Coverage under the General Air Quality Permit.

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 proposed general permit are discussed in 

Sections 4.3, 4.4, 4.5, and 4.6. The emissions associated with the throughput limits are lower than the NSR major 

source thresholds and were derived as described below in Section 5. 
Page 6 of 18

4.3 Specific Permit Requirements for General Permits and Permits by Rule

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

analyses in the Tribal 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 proposed 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 SRGCS facilities:

1. Local air quality conditions – To address this requirement, the general permit requires sources locating 

in ozone nonattainment areas to meet more stringent requirements on fuel use – the main source of 

NOx and VOC emissions at SRGCS facilities. This will also ensure these sources are not major sources in 

those areas. Also, PM emission may be a concern for SRGCS facilities, but the majority of those 
Page 7 of 18

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 required 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 SRGCS facilities:

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

Facilities;

b. 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;

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

Combustion Engines; and

d. 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 SRGCS facilities:

Engines;

Material handling equipment; and

Fuel storage tanks.

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 Review of New Sources and Modifications in Indian 

Country 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.

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 SRGCS 

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. 
Page 8 of 18

3. Anticipated economic growth in the area – The Reviewing Authority may consider anticipated economic 

growth when determining whether coverage under the proposed general permit is justifiable. 

Considering, however, that the proposed general permit sets emission standards that are consistent 

with what is required by SRGCS 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 proposed general permit sets emission standards 

that are consistent with what is required by SRGCS 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.

40 CFR 49.155(a)(3) – Monitoring Requirements

The proposed general permit must include monitoring that is sufficient to assure compliance with the emission 

limitations that apply to the source. The proposed 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 and pressure drop. The proposed general permit also requires initial and continuing testing of 

compliance with the opacity limits.

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

The proposed 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 proposed 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 proposed general permit includes the reporting requirements listed in 40 CFR 49.1559(a)(5)(i) and (ii) 

related to annual reports and reporting of deviations.

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

The proposed 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 proposed general permit contains the additional provision required for each permit. These conditions are 

found in the General Provisions of the proposed general permit.

4.4 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 fuel use. We are not aware of any more stringent State/local control requirements for SRGCS 

facilities in nonattainment areas. The limits on fuel use will ensure that the general permit only applies to true 

minor sources locating in these nonattainment areas.
Page 9 of 18

4.6 Additional Permit Requirements

The EPA added a 150 foot setback requirement from the nearest property boundary and a 1,000 foot setback 

requirement between the rock crusher and the nearest residence to the general permit. These requirements are 

beyond EPA’s NSPS and NESHAP, but are included in the Washington and Alaska permits, respectively. The 

setback requirement in the Washington permit is based on dispersion modeling for a rock crushing facility with a 

high rock throughput rate.

4.7 Requirements of the Endangered Species Act and National Historic Preservation Act

Prior to seeking coverage under this general permit, sources must satisfactorily address the permitting 

requirements related to the Endangered Species Act and National Historic Preservation Act. Attached to the 

request for coverage document for the SQCS general permit, the EPA provides guidance to assist sources in

complying with these two statutes.

5. Emission Limitations7 and Surrogate Throughput Limits 

5.1 Developing the Surrogate Limits and Limitations

The draft 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 

 

7

The definition of emission limitation used in this Background Document is the one provided in the 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 10 of 18

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 

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 

Prevention of Significant Deterioration (PSD), 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 draft permit includes the throughput limits listed in Table 8 for SQCS plants located in attainment and 

nonattainment areas. The two production limits are set at the same levels because the EPA has selected the 

same emissions limitations for attainment and nonattainment areas. They are set at levels intended to keep the 

sources emissions below the Title V major source thresholds in Table 3 (PM is the controlling pollutants the 

throughput calculations are contained in Attachment A).

Table 3: Emission Rates used to Determine Emission Limitations 

for Stone Quarrying, Crushing and Screening Facilities

Pollutant of Concern Attainment Areas Nonattainment Areas

PM 100 tpy 100 tpy

PM10* 100 tpy

100 tpy (moderate areas)

70 tpy (serious areas)
Page 11 of 18

Pollutant of Concern Attainment Areas Nonattainment Areas

PM2.5* 100 tpy 100 tpy

NOX 100 tpy

100 tpy (marginal and moderate ozone areas)

50 tpy (serious ozone areas)

25 tpy (severe ozone areas)

10 tpy (extreme ozone areas)

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

5.2 Emission Limitations

Three considerations form the basis for the upper eligibility emission limitations for general permits and permits 

by rule:

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

2. What do actual emissions data from the 2008 National Emissions Inventory (NEI)8indicate about the size 

profile of the source category? 

3. 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 Analysis of NEI Data

The EPA analyzed 2008 NEI data for existing sand and gravel processing and rock crushing plants across the U.S. 

to evaluate the emission limitations established in the general permit. Although the NEI does not include actual 

emissions information for sources in Indian Country, it reflects the actual emissions from general sand, gravel, 

and rock crushing operations in 50 states. In order to analyze facilities whose emissions are similar to those for 

sources potentially subject to the Indian Country NSR Rule, the EPA selected facilities for analysis with the North 

American Industry Classification System (NAICS) codes listed in Table 4. For sources in these four NAICS codes, 

the EPA selected actual emissions9 within the ranges listed in Table 5. 

 

8

For more information, go to: http://www.epa.gov/ttn/chief/net/2008inventory.html. 

9

Only point source NEI data were used for this analysis. The point source inventory does not include emissions from 

nonroad engines. 
Page 12 of 18

 Table 4: NAICS Codes Selected for Stone Quarrying, Crushing and Screening Facilities

NAICS Code Description

212311 Dimension Stone Mining and Quarrying

212312 Crushed and Broken Limestone Mining and Quarrying

212313 Crushed and Broken Granite Mining and Quarrying

212319 Other Crushed and Broken Stone Mining and Quarrying

212321 Construction Sand and Gravel Mining

Table 5: Emission Ranges Selected for Stone Quarrying, Crushing and Screening Facilities

Criteria Pollutants PM10 PM2.5 NOX

Attainment Area

 Min. Emissions (tpy) 5 3 10

 Max. Emissions (tpy) 250 250 250

Nonattainment Area

 Min. Emissions (tpy) 1 0.6 5

 Max. Emissions (tpy) 250 250 250

The 2008 NEI data does not include emissions information for total PM. The EPA analyzed the emissions rates

listed in Table 3 that were used to establish the surrogate throughput emissions limitations and selected the 

facilities with emission levels similar to the facilities potentially subject to the NSR minor program, i.e., the 

facilities with emissions greater than the minor NSR applicability thresholds in Table 1 of 40 CFR 49.153 (Tribal 

minor NSR Rule) and less than the PSD major source threshold of 250 tpy. For purposes of this analysis, facilities 

located in nonattainment areas are defined as facilities located in counties that are designated nonattainment 

for the pollutant being analyzed. 

With the NAICS codes listed in Table 4 and the emission ranges defined in Table 5, the EPA identified the SQCS

facilities located in attainment and nonattainment areas for NOx, PM10, and PM2.5. The EPA is providing the 

number of facilities (and average emissions) under the proposed emissions limitations and above the minor 

source thresholds. 

Table 6: Number of Facilities and Average Emissions for Hot Mix Asphalt Facilities Selected.

Criteria Pollutants Number of Facilities

Attainment Areas

NOx

Facilities >10 tpy and < 100 tpy 172 (25% of facilities covered)

Average Emissions (tpy) 22

Facilities > 100 tpy and < 250 tpy 2

Average Emissions (tpy) 106

PM2.5

Facilities >3 tpy and < 100 tpy 353 (15% of facilities covered)

Average Emissions (tpy) 11

Facilities > 100 tpy and < 250 tpy 1

Average Emissions (tpy) 126

PM10

Facilities >5 tpy and < 100 tpy 541 (22% of facilities covered)

Average Emissions (tpy) 18
Page 13 of 18

Criteria Pollutants Number of Facilities

Facilities > 100 tpy and < 250 tpy 11

Average Emissions (tpy) 154

Nonattainment Areas

NOx (marginal and moderate)

Facilities >5 tpy and < 100 tpy 25 (36% of facilities covered)

Average Emissions (tpy) 12

Facilities > 100 tpy and < 250 tpy 1

Average Emissions (tpy) 161

NOx (serious)

Facilities >5 tpy and < 50 tpy 1(25% of facilities covered)

Average Emissions (tpy) 6

Facilities > 50 tpy and < 250 tpy 0

Average Emissions (tpy) N/A

NOx (severe)

Facilities >5 tpy and < 25tpy 6 (30% of facilities covered)

Average Emissions (tpy) 11

Facilities > 25 tpy and < 250 tpy 1

Average Emissions (tpy) 60

NOx (extreme)

Facilities >5 tpy and < 10 tpy 2 (9% of facilities covered)

Average Emissions (tpy) 8

Facilities > 10 tpy and < 250 tpy 0

Average Emissions (tpy) N/A

PM2.5

Facilities >5 tpy and < 100 tpy 82 (55% of facilities covered)

Average Emissions (tpy) 3

Facilities > 100 tpy and < 250 tpy 0

Average Emissions (tpy) N/A

PM10 (moderate)

Facilities >5 tpy and < 100 tpy 19 (68% of facilities covered)

Average Emissions (tpy) 12

Facilities > 100 tpy and < 250 tpy 2

Average Emissions (tpy) 165

PM10 (serious)

Facilities >5 tpy and < 70 tpy 35 (90% of facilities covered)

Average Emissions (tpy) 10

Facilities > 70 tpy and < 250 tpy 0

Average Emissions (tpy) N/A

5.2.3 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 
Page 14 of 18

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

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 permit10 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 permit11, 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 permit12 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 permit13 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 7 shows the limits imposed by rock crushing and screening 

permits for the states reviewed.

 Table 7: 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 ft 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 ft Yes Yes

 

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

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

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

13 For more information, go to: http://www.azdeq.gov/environ/air/permits/download/gncspermit.pdf. 
Page 15 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

None

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. 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, and CO in attainment areas. The EPA 

used 100 tpy to establish the limits for PM10, PM2.5, NOX, and CO. 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 8. The calculations indicate that 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 source. 

 Table 8: Surrogate Rock Throughput and Fuel Usage Upper Limits

Attainment Status Upper Rock Throughput 

Limit (tpy)

Upper Fuel Usage 

Limit (gallons per 

year)

Attainment Area 10,500,000 310,000

Nonattainment Area 10,500,000 30,000/ 80,00/ 

153,000a

a

These upper fuel usage limits are for a facility located in extreme, severe, and serious ozone 

nonattainment areas, respectively.
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, Subpar 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, Subpar 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: 

Emissions Calculations for Rock Throughput and Fuel Usage Limits for Attainment Areas

Emissions from Crushing, Screening, and Conveying:

Emission Factors 

(lbs/ton) Emissions (tpy)

Type of Operation PM PM10 PM PM10

Primary Crushing ND ND ND ND

Secondary Crushing ND ND ND ND

Tertiary Crushing 1.20E-03 5.40E-04 6.30 2.84

Fines Crushing 3.00E-03 1.20E-03 15.75 6.30

Screening of Primary Crusher Output 2.20E-03 7.40E-04 11.55 3.89

Screening of Secondary Crusher Output 2.20E-03 7.40E-04 11.55 3.89

Screening (Tertiary Crushing) 2.20E-03 7.40E-04 11.55 3.89

Screening (Fines) 3.6E-03 2.2E-03 18.90 11.55

Conveyor Transfer Point (x12) 1.40E-04 4.60E-05 8.82 2.90

Truck Unloading - Fragmented Stone 1.60E-05 1.60E-05 0.08 0.08

Truck Loading - Conveyor, crushed 

stone 1.00E-04 1.00E-04 0.53 0.53

Total 85.03 35.85

Controlled emission factors from AP 42 Table 11.19.2-2

Sample calculation, Fines Crushing:

PM = 10,500,000 (tons/year) x 3.00E-3 (lb/ton) x 1/2,000 (ton/lb) 

= 93.67 tpy

Emissions from Engines:

Ozone Attainment Areas and Marginal or Moderate Ozone Nonattainment Areas:

NOx = 310,000 (gallons/year) x 7.1 (lb/gallon) x 0.0193(MMBtu/lb) x 4.41 (lb/MMBtu) x 1/2,000 (ton/lb)

= 48.9 tpy

PM10 = 310,000 (gallons/year) x 7.1 (lb/gallon) x 0.0193(MMBtu/lb) x 0.31 (lb/MMBtu) x 1/2,000 (ton/lb)

= 6.58 tpy

Serious Ozone Nonattainment Areas:

NOx = 153,000 (gallons/year) x 7.1 (lb/gallon) x 0.0193(MMBtu/lb) x 4.41 (lb/MMBtu) x 1/2,000 (ton/lb)

= 46.2 tpy

PM10 = 153,000 (gallons/year) x 7.1 (lb/gallon) x 0.0193(MMBtu/lb) x 0.31 (lb/MMBtu) x 1/2,000 (ton/lb)

= 3.25 tpy

Severe Ozone Nonattainment Areas:

NOx = 80,000 (gallons/year) x 7.1 (lb/gallon) x 0.0193(MMBtu/lb) x 4.41 (lb/MMBtu) x 1/2,000 (ton/lb)

= 24.2 tpy

PM10 = 80,000 (gallons/year) x 7.1 (lb/gallon) x 0.0193(MMBtu/lb) x 0.31 (lb/MMBtu) x 1/2,000 (ton/lb)

= 1.70 tpy
Page 19 of 18

Extreme Ozone Nonattainment Areas:

NOx = 30,000 (gallons/year) x 7.1 (lb/gallon) x 0.0193(MMBtu/lb) x 4.41 (lb/MMBtu) x 1/2,000 (ton/lb)

= 9.06 tpy

PM10 = 30,000 (gallons/year) x 7.1 (lb/gallon) x 0.0193(MMBtu/lb) x 0.31 (lb/MMBtu) x 1/2,000 (ton/lb)

= 0.64 tpy