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_____________________________________________________________________________________

Final Technical Support Document

_____________________________________________________________________________________

Final Rulemaking Action on the South Coast PM10

Redesignation Request and Maintenance Plan

June 2013
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For questions about this document, please contact Wienke Tax, EPA Region 9, 415-947-4192, or 

LaWeeda Ward, 213-244-1812.

Table of Contents

I. Background

A. PM10 NAAQS

B. PM10 NAAQS Designations

C. PM10 Planning Requirements

II. Review of SIP Submittal

A. Maintenance Plan Requirements

1. Attainment Emissions Inventory

2. Maintenance Demonstration

3. Monitoring Network

4. Commitment to Subsequent Maintenance Plan Revision

B. Transportation Conformity

III. Response to Comments

List of Tables

Table B.1. South Coast Air Basin PM10 Expected Exceedances (EE) and Completeness, 2007-

2012

Table C-1. Annual Average Day Attainment Baseline Emissions Inventory (tons per day)

Table C-2. Annual Average Day Attainment Emissions Inventory for PM10 Sources (tons per day)

Table D-1. PM10 Peak Concentrations

Table D-2. County Level Estimate of Fine and Coarse PM10 Peak Concentration

Table D-3. County Level Estimate of Relative Reduction Factors for Fine PM10 Peak 

Concentrations

Table D-4. Projected 24-hour PM10 (μg/m3) for 2023 and 2030

Table E-1. 2009 South Coast PM10 Redesignation Request and Maintenance Plan Motor Vehicle 

Emissions Budgets as submitted in the

Final South Coast PM10 Redesignation Request and Maintenance Plan

Table E-2. Transportation Conformity Budgets Detail for PM 10

Table E.3. Evaluation of the Motor Vehicle Emissions Budget for the Request for PM10

Redesignation and Maintenance Plan for South Coast Air Basin

List of Figures

Figure B-1 Ambient PM10 Monitoring Locations in the South Coast Air Basin
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I. Background

A. PM10NAAQS

The Clean Air Act (CAA or Act), which was last amended in 1990, requires the United 

States Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards 

(NAAQS or standards) for wide-spread pollutants from numerous and diverse sources 

considered harmful to public health and the environment. The CAA also requires EPA to 

periodically review the standards to ensure that they provide adequate health and 

environmental protection, and to update those standards as necessary. Thus EPA set NAAQS 

for particulate matter and five other pollutants considered harmful to public health and the 

environment (the other pollutants are ozone, nitrogen oxides, carbon monoxide, sulfur dioxide 

and lead). These six pollutants are known as “criteria pollutants”.

"Particulate matter," also known as particle pollution or PM, is a complex mixture of 

extremely small particles and liquid droplets. Particle pollution is made up of a number of 

components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil 

or dust particles. The size of particles is directly linked to their potential for causing health 

problems. EPA is concerned about particles that are 10 micrometers in diameter or smaller 

because those are the particles that generally pass through the throat and nose and enter the 

lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health 

effects. EPA groups particle pollution into two categories:

 "Inhalable coarse particles," such as those found near roadways and dusty industries, 

and possess aerodynamic diameters larger than 2.5 micrometers and smaller than 10 

micrometers (PM10). 

 "Fine particles," such as those found in smoke and haze, possess aerodynamic 

diameters 2.5 micrometers in diameter and smaller (PM2.5). These particles can be 

directly emitted from sources such as forest fires, or they can form when gases 

emitted from power plants, industries and automobiles react in the air. 

Within the South Coast Air Basin, PM10 particles are either directly emitted into the 

atmosphere (e.g., primary particles), or are formed through atmospheric chemical reactions 

from precursor gases (e.g., secondary particles). Primary PM10 includes road dust, diesel soot, 

combustion products, and other sources of fine particles. Direct PM10emissions in the South 

Coast are dominated by re-entrained road dust from paved and unpaved roads, construction 
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and demolition, and on-and off-road mobile sources. Secondary products, such as sulfates, 

nitrates, and complex carbon compounds are formed from reactions with oxides of sulfur, 

oxides of nitrogen, volatile organic compounds (VOCs) and ammonia. 

While NAAQS are set for PM2.5, the subject of this rulemaking is PM10. EPA first set a 

NAAQS for total suspended particulates (TSP) in 1971. At that time, the reference method for 

collecting particulate samples for comparison to the standard was the "high-volume" sampler. 

This type of sampler collected particulate matter up to a size of 45 micrometers (μm) in 

diameter. The 24-hour primary and secondary TSP NAAQS were set at 260 and 150 micrograms 

per cubic meter (μg/m3), respectively, while the annual TSP NAAQS was set at 75 μg/m3. EPA

revised the NAAQS for particulate matter on July 1, 1987 (52 FR 24672), replacing standards for 

TSP with new standards applying only to PM10. At that time, EPA established both an annual 

PM10 standard and a 24-hour standard.

 The annual PM10 standard of 50 micrograms per cubic meter (μg/m3) is attained 

when the expected annual arithmetic mean of the 24-hour samples averaged over a 

3-year period does not exceed 50 μg/m3.

 The 24-hour standard of 150 μg/m3is attained if samples taken for 24-hour periods 

have no more than one expected exceedance per year, averaged over three years.

1

 

On July 18, 1997, EPA established a new NAAQS for PM2.5 (62 FR 38652). In this same 

action EPA also revised the standards for PM10 but these revised PM10 standards were later 

vacated by the court, and the 1987 PM10 standards remained in effect. On October 17, 2006, 

EPA retained the 24-hour PM10 standards but revoked the annual standards, effective 

December 18, 2006. (71 FR 61144) On January 13, 2013, EPA announced that it was again 

retaining the 24-hour PM10 NAAQS as a 24-hour standard of 150 micrograms per cubic meter 

(μg/m3).2

B. PM10 NAAQS Designations

On the date of enactment of the 1990 CAA Amendments, PM10 areas, including the 

 

1

See 40 CFR 50.6 and 40 CFR part 50, appendix K.

2

See 78 FR 3086.
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South Coast Air Basin,

3 meeting the qualifications of section 107(d)(4)(B) of the amended Act, 

and in accordance with CAA section 188(a) were initially designated “moderate” nonattainment 

by operation of law4 with an applicable attainment deadline of December 31, 2001. Section 

188(b)(1) of the Act further provides that moderate areas can subsequently be reclassified as 

“serious” before the applicable moderate area attainment date if at any time EPA determines 

that the area cannot “practicably” attain the PM10NAAQS by this attainment date.

EPA determined on January 8, 1993, that the South Coast could not practicably attain 

the PM10NAAQS by the applicable attainment deadline for moderate areas (December 31, 

1994, pursuant to section 188(c)(1) of the Act), and reclassified the area as serious (58 FR 

3334).

C. PM10 Planning Requirements

The 1990 CAA Amendments established new planning requirements that states must 

use to demonstrate attainment of the NAAQS. The most fundamental of these nonattainment 

area provisions applicable to the South Coast Air Basin is the requirement that the State submit 

a State Implementation Plan (“SIP” or “Plan”) demonstrating attainment of the PM10NAAQS. 

This demonstration must be based upon enforceable measures to achieve emission reductions 

leading to emissions at or below the level predicted to result in attainment of the NAAQS 

throughout the nonattainment area. The measures must meet the standard for Reasonably 

Available Control Measures (RACM), and the measures must be implemented expeditiously and 

ensure attainment no later than the applicable CAA deadline.

5

After the South Coast Air Basin was reclassified as serious nonattainment for PM10, in

accordance with section 189(b)(2) of the CAA, the State was required to make the following SIP 

submittals:

1. The State had to submit by August 8, 1994, a SIP to ensure the implementation of Best 

Available Control Measures (BACM) no later than four years after reclassification, as 

required by CAA section 189(b)(1)(B).

 

3

The South Coast air basin includes Orange County, the southwestern two-thirds of Los Angeles County, 

southwestern San Bernardino County, and western Riverside County (see 40 CFR 81.305).

4

See 56 FR 11101 (March 15, 1991) and 40 CFR 81.305.

5

See CAA Section 189(b)
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2. The State had to submit a SIP by February 8, 1997, providing for progress and 

expeditious attainment, as required by CAA section 189(b)(1)(A).

3. The State requested an extension of the attainment date for the South Coast beyond 

the applicable deadline of December 31, 2001, therefore, under CAA section 188(e) the 

State also had to demonstrate that the plan contained the most stringent measures 

(MSM) that are included in any implementation plan or are achieved in practice, and can 

feasibly be implemented in the area.

D. PM10 Nonattainment Plans for the South Coast Area

Commencing in the 1970s and continuing to the present, the South Coast Air Quality 

Management District (SCAQMD) and the California Air Resources Board (CARB) have adopted

numerous rules and SIPs to address planning requirements for the South Coast PM10

nonattainment area under the CAA. In 2003, EPA fully approved a PM10 attainment plan for the 

South Coast as meeting all CAA requirements for serious PM10 areas, and as part of that action 

we also granted attainment date extensions for the area for both the 24-hour and annual PM10

NAAQS, from December 31, 2001 to December 31, 2006, pursuant to CAA section 188(e).

6 On 

August 1, 2003, the SCAQMD adopted the 2003 South Coast Air Quality Management Plan 

(2003 South Coast AQMP or 2003 South Coast SIP) including the motor vehicle emissions

budgets (budgets) for the area. CARB adopted the plans on October 23, 2003, and submitted 

the plans to EPA on January 9, 2004. EPA proposed to approve the portions of the 2003 South 

Coast AQMP relating to attainment of the PM10 standards on July 28, 20057and finalized our 

approval on November 14, 2005.

8

CARB also submits local rules adopted by SCAQMD as well as its own rules to EPA as 

revisions to the SIP. Examples of rules adopted by SCAQMD and approved by EPA as revisions 

to the California SIP PM10 control strategy include:

 Rule 403 - Fugitive Dust;

 Rule 1186 – PM10 Emissions from Paved and Unpaved Roads, and Livestock Operations; 

 

6

For more information on the 2003 approval of the South Coast PM10 plan, please see our proposed and final 

rulemaking notices. The proposal was issued on December 17, 2002 (67 FR 77212) and the final approval was 

issued on April 18, 2003 (68 FR 19316). 

7

see 70 FR 43663

8

see 70 FR 69081
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 Rule 1156 – PM10 Emissions Reductions from Cement Manufacturing Facilities;

 Rule 1157 - PM10 Emissions Reductions from Aggregate and Related Operations. 

Examples of rules adopted by CARB and approved by EPA as revisions to the California SIP PM10

control strategy include:

 CCR, Title 13, Section 2025 (“Regulation to Reduce Emissions of Diesel Particulate 

Matter, Oxides of Nitrogen and other Criteria Pollutants, from In-Use Heavy-Duty DieselFueled Vehicles”); 

 Section 2027 (“In-Use On-Road Diesel-Fueled Heavy-Duty Drayage trucks”); and

 Section 2262 (“California Reformulated Gasoline Phase 2 and Phase 3 Standards”). 

1. SCAQMD’s Request for Redesignation and Maintenance Plan 

SCAQMD has submitted both a maintenance plan and a request for redesignation to 

attainment of the PM10 standard. According to CAA Section 175A(a), a maintenance SIP should 

provide for maintenance of the PM10 standard for at least 10 years after the redesignation.

Additionally, as required in CAA Section 175A(b), 8 years after redesignation, South Coast is 

required to submit a revision of the SIP that demonstrates maintenance of the standard for 10 

years after the expiration of the original 10-year maintenance period. We expect to act on this 

redesignation request in 2013, therefore the submitted SIP and budgets must show 

maintenance of the PM10 standard through at least the year 2023 (10-years after the date of 

redesignation).

The SCAQMD adopted the Final PM10 Redesignation Request and Maintenance Plan 

for the South Coast Air Basin (December 2009) (2009 South Coast PM10 Redesignation Request 

and Maintenance Plan) on January 8, 2010 and forwarded it to CARB on January 15, 2010. CARB 

held a Board Hearing on March 25, 2010 to adopt the 2009 South Coast PM10 Redesignation 

Request and Maintenance Plan. The plan was submitted to EPA on April 28, 2010.

9

CARB's SIP 

submittal includes the following documents:

 April 28, 2010 letter to Jared Blumenfeld, Regional Administrator, U.S. EPA Region 9, 

from James N. Goldstene, Executive Officer, CARB transmitting the redesignation 

request and maintenance plan; 

 

9

See letter, James N. Goldstene, Executive Officer, to Jared Blumenfeld, Regional Administrator, EPA Region 9, 

dated April 28, 2010.
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 January 15, 2010 transmittal letter to James N. Goldstene, Executive Officer, CARB, 

from Elaine Chang, DrPH, Deputy Executive Officer, SCAQMD;

 October 17, 2009 Proof of Publication of Public Notice for Public Hearing on “Final 

PM10 Redesignation Request and Maintenance Plan for the South Coast Air Basin 

(December 2009)” and the January 8, 2010 SCAQMD Board Hearing;

 Transcripts of public hearings;

 SCAQMD Board Resolution of Adoption 10-1 approving and adopting the 2009 

South Coast PM10 Maintenance Plan;

 CARB’s February 17, 2010 Notice of Public Hearing for consideration of the adoption 

and approval of the 2009 South Coast PM10 Redesignation Request and 

Maintenance Plan and associated motor vehicle emissions budgets on March 25, 

2010;

 Final PM10 Redesignation Request and Maintenance Plan for the South Coast Air 

Basin (December 2009);

 CARB Board Resolution 10-21 adopting the 2009 South Coast PM10 Redesignation 

Request and Maintenance Plan and transportation conformity budgets.

2. Requirements for Redesignation

CAA Section 107(d)(3)(E) describes the following criteria for redesignating an area from 

nonattainment to attainment:

 EPA must determine that the area has attained the applicable NAAQS;

 EPA has fully approved the applicable implementation plan for the area under 

section 110(k) of the CAA;

 EPA must determine that the improvement in air quality is due to permanent and 

enforceable reductions in emissions resulting from implementation of the 

applicable SIP, applicable Federal air pollution control regulations, and other 

permanent and enforceable reductions;

 EPA must fully approve a maintenance plan for the area as meeting the 

requirements of section 175A of the CAA; and

 The State has met all applicable requirements for the area under section 110 and 

Part D10 of the CAA. 

 

10 The Clean Air Act, as amended in 1990, contains six subchapters. Subchapter I, “Programs and Activities” is 

divided in six parts (Parts A through D). Part A, “Air Quality and Emission Limitations” contains section 110, which 
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3. EPA Regulations and Guidance

EPA has issued the “State Implementation Plans; General Preamble for the 

Implementation of Title I of the Clean Air Act Amendments of 1990,” (“General Preamble”) that 

describes the Agency's preliminary views on how EPA intends to act on SIPs submitted under 

Title I of the Act.

11 Additional guidance is provided in the following:

 “Procedures for Processing Request to Redesignate Areas to Attainment,” John 

Calcagni, Director, Air Quality Management Division, EPA Office of Air Quality 

Planning and Standards, September 4, 1992 EPA guidance document, (referred 

to as the “Calcagni memo”)

 “Part D New Source Review (part D NSR) Requirements for Areas Requesting 

Redesignation to Attainment,” Mary D. Nichols, Assistant Administrator for Air 

and Radiation, October 14, 1994 (Nichols Memo);

 “State Implementation Plans for Serious PM10 Nonattainment Areas, and 

Attainment Date Waivers for PM10 Nonattainment Areas Generally; Addendum 

to the General Preamble for the Implementation of title I of the Clean Air Act 

Amendments of 1990,” 59 FR 41998 (August 16, 1994) (PM10 Addendum).

 

provide for basic SIP requirements. Section 110 identifies a comprehensive list of elements that SIPs must include, 

and part D establishes the SIP requirements for nonattainment areas. Additional SIP requirements for nonattainment areas are contained in Part D, “Plan Requirements for Nonattainment Areas”. Part D is further divided 

into six subparts. Generally applicable nonattainment SIP requirements are found in part D, subpart 1, and the 

particulate-specific nonattainment SIP requirements are found in part D, subpart 4.

11 See 57 FR 13498 (April 16, 1992), 57 FR 18070 (April 28, 1992)
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II. Review of the South Coast Submittal

A. Selected Redesignation Request and Maintenance Plan Requirements

The criteria for redesignating an area from nonattainment to attainment were discussed 

in Section I of this document. Following is a review of the criteria described above as it pertains 

to attainment of the standard, the emissions inventories, modeling, and motor vehicle 

emissions budgets.

B. Monitored Attainment

CAA section 107(d)(3)(E)(i) requires that we determine that the area has attained the 

applicable NAAQS. Generally, EPA determines whether an area’s air quality is meeting the 24-

hour PM10 NAAQS based upon complete,12, 13 quality-assured, and certified data gathered at 

established state and local air monitoring stations (SLAMS) in the nonattainment area, and 

entered into the EPA Air Quality System (AQS) database. Data from air monitors operated by 

State, local, or Tribal agencies in compliance with EPA monitoring requirements must be 

submitted to AQS. These monitoring agencies certify annually that these data are accurate to 

the best of their knowledge. Accordingly, EPA relies primarily on data in AQS when determining 

the attainment status of an area.

14

 EPA will also consider air quality data from other air 

monitoring stations in the nonattainment area provided those stations meet the Federal 

monitoring requirements for SLAMS, including the quality assurance and quality control criteria 

in 40 CFR part 58, appendix A.

15

The 24-hour PM10 standard is attained when the expected number of days per calendar 

year with a 24-hour average concentration above 150 μg/m3 , as determined in accordance

with 40 CFR appendix K , and averaged over a three-year period,

16 is equal to or less than one. 

 

12 For PM10, a “complete” set of data includes a minimum of 75 percent of the scheduled PM10 samples per 

quarter. See 40 CFR part 50, appendix K, section 2.3(a).

13Because the annual PM10 standard was revoked effective December 18, 2006, this document discusses only 

attainment of the 24-hour PM10 standard. See 71 FR 61144; (October 17, 2006).

14 See 40 CFR 50.6; 40 CFR part 50, appendices J and K; 40 CFR part 53; and, 40 CFR part 58, appendices A, C, D, and 

E.

15 See 40 CFR 58.14 (2006) and 58.20 (2007)15; 71 FR 61236, 61242; (October 17, 2006). All valid data are 

reviewed to determine the area’s air quality status in accordance with 40 CFR part 50, appendix K.

16 See 40 CFR part 50, appendix K, section 2.1(a)
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For the purpose of determining attainment of the primary and secondary standards, particulate 

matter shall be measured in the ambient air as PM10 (particles with an aerodynamic diameter 

less than or equal to a nominal 10 micrometers) by a reference method based on 40 CFR 

appendix J and designated in accordance with 40 CFR part 53 of this chapter, or an equivalent 

method designated in accordance with 40 CFR part 53.

17

According to 40 CFR Part 50 Appendix K, section 2.3 (b), to demonstrate attainment of 

the 24-hour standards at a monitoring site, the monitor must provide sufficient data (at least 75 

percent complete) to perform the required calculations in 40 CFR part 50, appendix K 18 for 

expected exceedances.19 The amount of data required varies with the sampling frequency, data 

capture rate, and the number of years of record. In all cases, three years of representative 

monitoring data that meet the 75 percent criterion discussed earlier should be utilized, if 

available. More than three years may be considered, if all additional representative years of 

data meeting the 75 percent criterion are utilized. Data not meeting these criteria may also 

suffice to show attainment; however, such exceptions must be approved by the appropriate 

Regional Administrator in accordance with EPA guidance.

20

In the South Coast PM10 nonattainment area, the SCAQMD is the agency responsible for 

assuring that the area meets air quality monitoring requirements including its submittal of

annual monitoring network plans to EPA. The SCAQMD network plans describe the monitoring 

network operated by SCAQMD in the South Coast nonattainment area. These plans discuss the 

status of the air monitoring network, as required under 40 CFR 58.10. As shown in Figure B-1, 

SCAQMD operates 23 air quality monitoring stations for PM10 in the South Coast Air Basin. As 

required by 40 CFR part 58, the SCAQMD conducts annual reviews of the air quality monitoring 

network and forwards these reviews to CARB and EPA for evaluation. Since 2007, EPA regularly 

reviews these annual plans for compliance with the applicable reporting requirements in 40 

 

17 See 40 CFR 50.6.

18 See 40 CFR part 50, appendix K, section 2.3(b).

19 See 40 CFR part 50, appendix K, section 3.0(a).

20 See 40 CFR part 50, appendix K, section 2.3.
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Figure B-1. Ambient PM10 Monitoring Locations in the South Coast Air Basin21

 

21 Source: http://aqmd.gov/tao/AQ-Reports/AQMonitoringNetworkPlan/AppendixA.pdf
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CFR part 58. Concerning PM10, EPA has found that the areas’ network plans submitted by 

SCAQMD meet the applicable requirements under 40 CFR part 58.

22

EPA also concluded from its Technical System Audit of the CARB Primary Quality 

Assurance Organization (PQAO), conducted during the spring of 2010, that the combined 

ambient air monitoring network operated by SCAQMD currently meets or exceeds the 

requirements for the minimum number of SLAMS for PM10 in the South Coast nonattainment 

area. 23 SCAQMD annually certifies that the data it submits to AQS are complete and qualityassured.24

Since comprehensive monitoring began for PM10 in the South Coast in the 1960s, the 

area has seen a significant decline in ambient levels. Table B-1 displays the certified PM10 data 

for the South Coast area for the years 2007-2012. All data have been certified by SCAQMD. As 

shown in Table B-1, there were a total of five missing quarters out of a possible total of 92 for 

the 2009-2011 period. In total, there were 87 complete quarters for this time period. To meet 

the 75 percent minimum completeness requirements, the South Coast Monitoring network 

would require 18 sites to have 100 percent data completeness, with a total of 72 quarters

complete. The South Coast Monitoring network exceeds this number of complete quarters. It 

should also be noted that the two sites (Perris and Fontana) with highest number of expected 

exceedances in 2007 period both had 100 percent data completeness for all four quarters 

during the 2009-2011 period.25

In accordance with 40 CFR part 50, appendix K, 2.1 (a), the expected number of 

exceedances for a 3-year period is estimated by averaging the individual annual estimates for 

the past 3 years. The 3-year average expected number of exceedances for these sites that 

 

22 See Letter from Sean Hogan, Manager, Air Quality Analysis Office, U.S. EPA Region IX, to Dr. Chung Liu, Deputy 

Executive Officer, SCAQMD, dated May 30, 2008; Letter from Joe Lapka, Acting Manager, Air Quality Analysis 

Office, U.S. EPA Region IX, to Dr. Chung Liu, Deputy Executive Officer, SCAQMD, dated November 12, 2009; 

Letter from Matthew Lakin, Manager, Air Quality Analysis Office, U.S. EPA Region IX, to Dr. Chung Liu, Deputy 

Executive Officer, SCAQMD, dated November 1, 2010; and Letter from Matthew Lakin, Manager, Air Quality 

Analysis Office, U.S. EPA Region IX, to Dr. Chung Liu, Deputy Executive Officer, SCAQMD, dated November 1, 2011.

23

 Technical System Audit Report, South Coast Air Quality Management District , April 13 – April 16, 2010, 

Conducted by Air Quality Analysis Office and Quality Assurance Office, US EPA Region 9, 75 Hawthorne Street, San 

Francisco, California 94105, March 2011.

24 See, e.g., Letter, Chung Liu, Ph.D., Deputy Executive Officer Science and Technology Advancement, South Coast 

Air Quality Management District, to Jared Blumenfeld, Regional Administrator, U.S. EPA Region IX, certifying 

calendar year 2011 ambient air quality data and quality assurance data, May 1, 2012.

25 See EPA, Air Quality System Design Value Reports dated December 18, 2012 – January 2, 2013 in the docket for 

today’s action.
Page 14 of 37

Table B.1. South Coast Air Basin PM10 Expected Exceedances (EE) and Completeness, 2007-2012

Site AQS ID 2007 2008 2009

Ann 

EE

3-

year

EE

Comp

quart

Ann 

EE

3-

year

EE

Comp

quart

Ann 

EE

3-

year

EE

Comp

quart

Azusa 060370002 6.1 2 4 0 2 3 0 2 3

Burbank 060371002 0 0 1 0 0 4 0 0 4

Glendora 060370016 0 0 4 0 0 2

LAX Hastings 060375005 0 0 4 0 0 4 0 0 4

Los Angeles –

Main St.

060371103 0 0 4 0 0 4 0 0 4

North Long 

Beach

060374002 6.1 2 4 0 2 4 0 2 4

Santa Clarita 060376012 6.1 2 4 0 2 4 0 2 4

South Long 

Beach

060374004 0 0 1 0 0 4 0 0 4

Anaheim 060590007 6.1 2 4 0 2 4 0 2 4

Mission Viejo 060592022 0 0 4 0 0 4 0 0 4

Banning 

Airport

060650012 0 0 3 0 0 4 0 0 4

Lake Elsinore 060659001 0 0 4 0 0 4

Mira Loma 

(Van Buren)

060658005 0 0 4 0 0 4 0 0 4

Norco 060650003 6.1 2 4 0 2 4 0 2 4

Perris 060656001 29.1 9.7 3 0 9.7 3 0 9.7 4

Site AQS ID 2007 2008 2009

Ann EE 3-year

EE

Comp

quart

Ann EE 3-year

EE

Comp

quart

Ann EE 3-year

EE

Comp

quart

Azusa 060370002 6.1 2 4 0 2 3 0 2 3

Burbank 060371002 0 0 1 0 0 4 0 0 4

Glendora 060370016 0 0 4 0 0 2

LAX Hastings 060375005 0 0 4 0 0 4 0 0 4

Los Angeles – Main St. 060371103 0 0 4 0 0 4 0 0 4

North Long Beach 060374002 6.1 2 4 0 2 4 0 2 4

Santa Clarita 060376012 6.1 2 4 0 2 4 0 2 4

South Long Beach 060374004 0 0 1 0 0 4 0 0 4

Anaheim 060590007 6.1 2 4 0 2 4 0 2 4

Mission Viejo 060592022 0 0 4 0 0 4 0 0 4

Banning Airport 060650012 0 0 3 0 0 4 0 0 4

Lake Elsinore 060659001 0 0 4 0 0 4

Mira Loma (Van Buren) 060658005 0 0 4 0 0 4 0 0 4

Norco 060650003 6.1 2 4 0 2 4 0 2 4

Perris 060656001 29.1 9.7 3 0 9.7 3 0 9.7 4

Riverside (Magnolia) 060651003

Rubidoux 060658001 3.1 1 4 0 0 4 0 1 4

Crestline 060710005 0 0 3 0 0 1 0 0 3

Fontana 060712002 13.2 4.4 4 0 4.4 4 0 4.4 4

Ontario Fire Station 060710025 6.1 2 4 0 2 4 0 2 4

Redlands 060714003 0 0 4 0 0 4 0 0 4

San Bernardino 060719004 6.1 2 4 0 2 4 0 2 4

Upland 060711004 0 0 4 0 0 4
Page 15 of 37

Table B.1. South Coast Air Basin PM10 Expected Exceedances (EE) and Completeness, 2007-2012

(continued)

 

26 2012 air quality monitoring data and completeness data have not been certified. 

Site AQS ID 2010 2011 201226

Ann EE 3-year

EE

Comp

quart

Ann EE 3-year

EE

Comp

quart

Ann EE 3-year

EE

Comp

quart

Azusa 060370002 0 0 4 0 0 4 0 0 NA

Burbank 060371002 0 0 4 0 0 4 0 0 NA

Glendora 060370016 0 0 3 0 0 4 0 0 NA

LAX Hastings 060375005 0 0 4 0 0 4 0 0 NA

Los Angeles – Main St. 060371103 0 0 4 0 0 4 0 0 NA

North Long Beach 060374002 0 0 4 0 0 4 0 0 NA

Santa Clarita 060376012 0 0 4 0 0 4 0 0 NA

South Long Beach 060374004 0 0 4 0 0 4 0 0 NA

Anaheim 060590007 0 0 4 0 0 4 0 0 NA

Mission Viejo 060592022 0 0 4 0 0 4 0 0 NA

Banning Airport 060650012 0 0 4 0 0 4 0 0 NA

Lake Elsinore 060659001 0 0 4 0 0 4 0 0 NA

Mira Loma (Van Buren) 060658005 0 0 4 0 0 4 0 0 NA

Norco 060650003 0 0 4 0 0 4 0 0 NA

Perris 060656001 0 0 4 0 0 4 0 0 NA

Riverside (Magnolia) 060651003 0 0 4 0 0 NA

Rubidoux 060658001 0 0 4 0 0 4 0 0 NA

Crestline 060710005 0 0 4 0 0 4 0 0 NA

Fontana 060712002 0 0 4 0 0 4 0 0 NA

Ontario Fire Station 060710025 0 0 4 0 0 4 0 0 NA

Redlands 060714003 0 0 4 0 0 4 0 0 NA

San Bernardino 060719004 0 0 4 0 0 4 0 0 NA

Upland 060711004 0 0 4 0 0 4 0 0 NA
Page 16 of 37

include the year 2007 (e.g. 2007-2009), all have at least two expected exceedances. South 

Coast began attaining the PM10 standard in the year 2008. The first year where the 3-year 

average expected number of exceedances is attaining is 2010 (i.e. for the 3-year period 2008-

2010). Therefore, annual PM10 levels in South Coast are below the standard with no or zero

expected exceedances for the 2008-2011 period at all sites in the South Coast nonattainment

area for the most recent 3-year period of certified, quality-assured data.27 

We received a comment related to monitoring data from the South Coast Air Quality 

Management District, which is addressed in Section III. Response to Comments.

C. Attainment Inventory

Section 172(c)(3) of the CAA requires plan submittals to include a comprehensive, 

accurate, and current inventory for the base year from all sources in the nonattainment area. In 

demonstrating maintenance in accordance with CAA section 175A and the Calcagni memo,28

the State should provide an attainment emissions inventory to identify the level of emissions in 

the area sufficient to attain the NAAQS. Where the State has made an adequate demonstration 

that air quality has improved as a result of the SIP, the attainment inventory should generally 

contain actual emissions at the time the area attained the standard. The inventory should also 

include direct and secondary PM10 emissions, and all stationary, area and mobile sources of 

emissions.

In evaluating the State’s inventory, EPA reviewed the following documents:

 South Coast Air Quality Management District, Final PM10 Redesignation Request 

and Maintenance Plan For the South Coast Air Basin, December, 2009, 

Attachment C.

 Chapter 3, Base Year and Future Emissions, Introduction, Emission Inventories, 

Base Year Emissions, Future Emissions, Top Ten Source Categories (2002, 2014,

2023)

 

27 See EPA, Air Quality System Design Value Reports dated December 18, 2012 – January 2, 2013 in the docket for 

today’s action. A design value is an ambient concentration calculated using a specific methodology from monitored 

air quality data and is used to compare an area’s air quality to a NAAQS. The methodologies for calculating design 

values for the 24-hour PM10 NAAQS are found in 40 CFR 50, Appendix N, Section 1(c)(2).

28 “Procedures for Processing Request to Redesignate Areas to Attainment,” John Calcagni, Director, Air Quality 

Management Division, EPA Office of Air Quality Planning and Standards, September 4, 1992.
Page 17 of 37

 South Coast Air Quality Management District, Final 2007 AQMP, Appendix III, 

Base and Future Year Emission Inventories,

June 2007.

 California Environmental Protection Agency, Air Resources Board, Staff Report, 

Analysis of the South Coast Air Basin PM10 Redesignation Request, Maintenance 

Plan, and Conformity Budgets. February 22, 2010.

Table C-1 depicts the annual average day baseline emissions inventories for PM10, PM2.5, NOx, 

VOC and SOX as presented in the 2009 South Coast PM10 Redesignation Request and 

Maintenance Plan for the years 2002 through 2030. The District estimates that 56% of the total 

mass of average peak concentrations of PM10 is attributable to PM2.5 and 44% to coarse PM 

(fugitive dust).

29 Table C-2 provides a detailed breakout of the baseline attainment inventory 

for the PM10 emission subcategories. In the South Coast, the majority of daily PM10 emissions 

are estimated to come from re-entrained road dust from paved and unpaved roads at 133.7 

tons per day (47.6% of total emissions) in 2010. The District is using the year 2010 as the 

maintenance plan base year. EPA finds 2010 to be an appropriate base year because it is one of 

the years in the most recent three-year periods (2008-2010, 2009-2011, and 2010-2012) in 

which attainment of the PM10 NAAQS was monitored.

As depicted in Table C-2, future PM10 emissions are projected to nominally increase 

from 2002 to 2030 (primarily due to growth in the construction/demolition source categories),

from an estimated 274.7 tons per day in 2002 to an estimated 329.6 tons per day in 2030.

30

Overall, the PM10 baseline emissions inventory will increase approximately seven (7) percent 

from 2010 to 2020 and ten (10) percent from 2020 to 2030.

31

Based on our review of the 2009 South Coast PM10 Redesignation Request and 

Maintenance Plan, we find that the emissions inventories in the plan are comprehensive,

32 in 

that they include estimates of PM10 and its precursors from all of the relevant source 

categories.

 

29 See 2009 South Coast PM10 Plan, p. 5.

30 See 2009 South Coast PM10 Plan, p. 22.

31 See 2009 South Coast PM10 Plan, p. 20.

32 EPA's primary guidance in evaluating these inventories is the document entitled, “PM10 Emissions Inventory Requirements,” 

EPA, OAQPS, EPA-454/R-94-033 (September 1994) which can be found at: http://www.epa.gov/ttn/chief/eidocs/pm10eir.pdf.
Page 18 of 37

While 2010 is the appropriate attainment plan base year, CAA Section 175A states that 

a request for redesignation of a nonattainment area shall provide for the maintenance of the 

NAAQS for at least 10 years after the redesignation. EPA expects to act on the South Coast 
Page 19 of 37

Table C-1. Annual Average Day Attainment Baseline Emissions Inventory (tons per day)

Pollutant 2002 2006 2008 2010 2011 2012 2014 2020 2023 2030

PM10 274.7 282.8 277.5 280.9 283.0 284.8 288.7 300.3 307.8 329.6

PM2.5 99.1 104.2 101.5 101.4 101.5 101.6 101.6 103.2 105.2 113.6

NOx 1093.2 970.7 853.7 774.7 742.9 711.6 653.6 525.2 506.4 511.8

VOC 844.2 695.9 608.0 572.4 559.4 547.9 527.7 498.5 496.0 508.4

SOx 53.3 54.8 40.9 39.2 40.1 40.7 42.8 51.4 55.1 71.7
Page 20 of 37

Table C-2. Annual Average Day Attainment Emissions Inventory for PM10 Sources (tons per day)

Category 2002 2006 2008 2010 2011 2012 2014 2020 2023 2030

Stationary – Point 

sources

21.1 20.1 17.1 17.3 17.4 17.6 17.9 18.9 19.5 20.9

Construction and

Demolition

39.9 46.9 49.8 52.9 54.3 55.8 58.7 66.0 69.7 78.9

Entrained Road 

Dust/Paved

125.4 123.5 122.3 123.4 124.0 124.5 125.8 129.3 131.1 135.2

Entrained Road 

Dust/Unpaved

13.6 11.5 10.3 10.3 10.3 10.3 10.3 10.2 10.2 10.2

Farming Operations 0.8 0.7 0.6 0.6 0.6 0.6 0.5 0.4 0.4 0.3

Fugitive Windblown 

Dust

2.8 2.4 2.3 2.2 2.2 2.1 2.0 1.8 1.7 1.6

Other Area Sources 23.3 28.8 29.4 30.0 30.3 30.6 31.2 32.6 33.3 35.0

On-road Mobile 

Sources

24.8 26.5 24.9 24.3 24.3 24.2 24.0 23.6 23.6 24.7

Off-road Mobile 

Sources

23.1 22.5 20.7 19.9 19.6 19.2 18.4 17.4 18.1 22.7

Total PM10 274.7 282.8 277.5 280.9 283.0 284.8 288.7 300.3 307.7 329.6
Page 21 of 37

AQMD request for redesignation in 2013, therefore the maintenance period is anticipated to 

last through at least the year 2023. The district has provided inventories through the year 

2030. In conclusion, EPA finds that the selection of 2010 as the attainment year inventory and 

2030 for the maintenance year inventory is appropriate since 2010 is one of the years the area 

was determined to have attained, and the plan demonstrates maintenance of the standard 

through 2030. We have reviewed the plan’s estimated attainment year emission inventory and 

determined that it is current, accurate and comprehensive, and meets EPA guidance and the 

CAA. Therefore we are approving the 2010 inventory, which also serves as the maintenance 

plan’s attainment year inventory, under section 172(c) of the CAA.

We did not receive any comments on our proposed approval of the emissions inventory.

D. Modeling Demonstration of Maintenance of the NAAQS for 10 Years After Redesignation

Section 175A of the CAA requires a demonstration of maintenance of the NAAQS for 10 

years after redesignation. A state generally may demonstrate maintenance of the NAAQS by 

either showing that future emissions of a pollutant or its precursors will not exceed the level of 

the attainment inventory, or by modeling to show that the future anticipated mix of sources 

and emission rates will not cause a violation of the NAAQS. For this plan, the state chose the 

second option and demonstrated maintenance of the 24-hour PM10NAAQS by modeling to 

show that the future anticipated mix of sources and emission rates will not cause a violation of 

the NAAQS in the South Coast Air Basin. 

In evaluating the State’s attainment demonstration modeling, EPA reviewed the 

following documents:

 South Coast Air Quality Management District, Final PM10 Redesignation Request 

and Maintenance Plan For the South Coast Air Basin, December, 2009, 

Attachment C.

 South Coast Air Quality Management District, Final 2007 AQMP, Appendix V, 

Modeling and Attainment Demonstrations, June 2007.

 U.S. Environmental Protection Agency, Region 9, Final Technical Support 

Document and Response to Comments, Final Rulemaking Action on the South 

Coast 2007 AQMP for PM2.5 and the South Coast Portions of the Revised 2007 

State Strategy.
Page 22 of 37

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

Standards, PM10 SIP Development Guideline, EPA-450/2-86-001, June 1987.

 U.S. Environmental Protection Agency, Guideline on Air Quality Models , 40 CFR 

Part 51 Appendix W.

EPA guidance recommends use of use of receptor and dispersion models in 

combination.33 In regulatory applications, dispersion models have been used in conjunction with 

receptor models to attribute source (or source category) contributions.34 For this plan, the 

state demonstrated maintenance of the 24-hour PM10 NAAQS by a combination of techniques, 

including dispersion modeling, and primary and precursor contribution based on filter analysis. 

The state’s analysis projected the maximum future year PM10 concentration for each of 

the four counties in the South Coast Air Basin. The highest maximum concentration observed 

during each of the years 2005, 2006, and 2007 at any ambient air quality monitoring site in the 

county was selected to represent the potential peak concentration for the county. These 

values, and the site where the value was measured, are shown in Table D-1 below.

Table D-1. PM10 Peak Concentrations

County Highest Site Peak Year Peak PM10

2005-2007

μg/m3

Los Angeles South Coastal LA County -2 2005 131

Orange Central Orange County 2006 104

Riverside Mira Loma 2007 142

San Bernardino Central San Bernadino-1 2006 142

The future PM10 levels were modeled in a two-part analysis, using separate methods for 

projecting the future values of the fine fraction (PM2.5) and the coarse fraction (PM2.5 to PM10) 

fraction of PM10. First, the fine and coarse fractions for each of the site-specific PM10 peak 

concentrations were determined by a county averaged ratio of the PM2.5 and PM10 maximum 

concentrations. These values are listed in TableD-2, below. 

 

33 Chapter 4.0, Air Quality Modeling for PM10, PM10 SIP Development Guideline, EPA-450/2-86-001, June 1987.

34 40 CFR Part 51 Appendix W, 5.2.2.2, PM–10.
Page 23 of 37

Table D-2. County Level Estimate of Fine and Coarse PM10 Peak Concentration

County Peak PM10

2005-2007

μg/m3

County specific 

PM2.5/ PM10 ratio

Fine Mass

μg/m3

Coarse Mass

μg/m3

Los Angeles 131 0.603 79 52

Orange 104 0.595 62 42

Riverside 142 0.573 81 61

San Bernardino 142 0.486 69 73

For the PM2.5 fraction of PM10, the modeling demonstration was based on applying sitespecific relative reduction factors (RRFs) for each of the future years to the fine mass fraction. 

The relative reduction factors which were generated from the regional modeling analysis for 

2007 PM2.5 Plan, which accounted for the chemical formation of secondary particulate matter.35 

EPA’s evaluation of the 2007 PM2.5modeling is provided in the Final Technical Support 

Document and Response to Comments, Final Rulemaking Action on the South Coast 2007 AQMP 

for PM2.5 and the South Coast Portions of the Revised 2007 State Strategy.

36

 The Air Quality 

Model Selection, Episode Selection, Domain Size and Spatial Resolution, Initial and Boundary 

Conditions, Meteorological Model, and Air Quality Model Performance for the regional PM2.5

modeling are discussed in detail in that document.

The PM2.5 RRFs were calculated from the regional modeling, based on the sites listed in 

Table D-3 below, for each of the years 2010, 2011, 2012, 2014, 2020, 2023, and 2030. The

county specific relative reduction factor for each year was multiplied by the county-specific fine 

mass peak concentration. The projected fine mass for each county for the years 2023 and 

2030 are shown in Table D-4 Projected 24 hour PM10 (μg/m3) for 2023 and 2030.

 

35 Final 2007 AQMP, Appendix V, Modeling and Attainment Demonstrations, June 2007, South Coast Air Quality 

Management District.

36Final Technical Support Document and Response to Comments, Final Rulemaking Action on the South Coast 2007 

AQMP for PM2.5 and the South Coast Portions of the Revised 2007 State Strategy, Section II. Evaluation of the 

South Coast 2007 AQMP for PM2.5, B. Air Quality Modeling.
Page 24 of 37

Table D-3. County Level Estimate of Relative Reduction factors for Fine PM10 Peak 

Concentrations.

County Sites used for development of Relative Reduction Factors

Los Angeles Los Angeles, Long Beach, Burbank, Compton, Wilmington

Orange Anaheim

Riverside Rubidoux

San Bernardino Fontana

Table D-4. Projected 24-hour PM10 (μg/m3) for 2023 and 2030

County 2023 2030

Fine Coarse Total 

Mass

Fine Coarse Total 

Mass

Los Angeles 47 56 103 49 60 109

Orange 36 45 81 37 48 86

Riverside 53 66 118 54 70 125

San Bernardino 50 79 128 52 84 136

The future levels of the “coarse” fraction (PM2.5-PM10) of the PM10 mass were projected 

by emissions-based rollback. Estimation of the future-year PM10 coarse particulate 

concentration was conducted by multiplying the coarse mass peak concentration by the 

projected changes in the emission level. Baseline PM10 emissions for 2020, 2023 and 2030 show 

increases of 5, 8, and 15 percent respectively over 2005 levels. The projected coarse mass for 

each county for the years 2023 and 2030 are shown in Table D-4 below.

The projected total PM10 mass was estimated for each of the future years by adding the 

fine mass fraction to the coarse mass fraction. The county-specific projected PM10 levels for 

2023 and 2030 are also shown in the Table D-4.37

The reduction in particulate matter precursor emissions results in a reduction in the 

levels of PM10, demonstrating maintenance of the PM10 NAAQS for the South Coast Air Basin for 

ten years after redesignation, and beyond.

38 The modeled PM10 levels are below the 24-hour 

 

37 Final 2007 AQMP, Appendix V, Modeling and Attainment Demonstrations, June 2007, South Coast Air Quality 

Management District.

38 24 hour average PM10 values were projected for the years 2010, 2011, 2012, 2014, 2020, 2023, and 2030. Plan 

p. 69.
Page 25 of 37

PM10 NAAQS level of 150 μg/m3 for each of the future modeled years for each of the counties 

in the South Coast Air Basin including the year 2023, and beyond (2030). 

EPA finds that the methodology used in the plan to project the levels of PM10 for 10 years and 

beyond is reasonable and meets EPA’s guidance. EPA finds the forecasted decreases in 24-hour 

PM10 levels, based on the decrease in particulate matter precursor (NOx and VOC) emissions, 

are consistent with the control measures that are scheduled for implementation. Based on our 

review of the information presented in the 2009 South Coast PM10 Redesignation Request and 

Maintenance Plan, we find that the State has shown that attainment of the PM10NAAQS will be 

maintained in the South Coast Air Basin for at least ten years after redesignation.

We did not receive any comments on our proposed approval of the maintenance 

demonstration and modeling.

E. Transportation Conformity

1. Requirements for Transportation Conformity and Motor Vehicle Emissions Budgets

CAA section 176(c) requires Federal actions in nonattainment and maintenance areas to 

conform to the SIP’s goals of eliminating or reducing the severity and number of violations of 

the NAAQS and achieve expeditious attainment of the standards. Conformity to the SIP’s goals 

means that such actions will not: (1) cause or contribute to violations of a NAAQS, (2) worsen 

the severity of an existing violation, or (3) delay timely attainment of any NAAQS or any interim 

milestone.

Actions involving Federal Highway Administration (FHWA) or Federal Transit 

Administration (FTA) funding or approval are subject to the EPA’s transportation conformity 

rule, codified at 40 CFR part 93, subpart A. Under this rule, metropolitan planning organizations 

(MPOs) in nonattainment and maintenance areas coordinate with state and local air quality and 

transportation agencies, EPA, FHWA, and FTA to demonstrate that an area’s regional 

transportation plans (RTP) and transportation improvement programs (TIP) conform to the 

applicable SIP. This demonstration is typically done by showing that estimated emissions from 

existing and planned highway and transit systems are less than or equal to the motor vehicle 

emissions budgets (budgets) contained in all control strategy SIPs. An attainment, 

maintenance, or reasonable further progress (RFP) SIP should include budgets for the 

attainment year, each required RFP year or last year of the maintenance plan, as appropriate. 

Budgets are generally established for specific years and specific pollutants or precursors.
Page 26 of 37

PM10 maintenance plans should identify budgets for direct PM10 and PM10 precursors. 

All direct PM10 SIP budgets should include direct PM10 motor vehicle emissions from tailpipe, 

brake wear, tire wear, and re-entrained paved and unpaved road dust. A state must also 

consider whether construction-related dust is a significant contributor and should be included 

in the direct PM10 budget.

39

MPOs may use budgets in a submitted but not yet approved SIP, only if EPA has first 

determined that the budgets are adequate. Budgets are deemed adequate and may eventually 

be approved if the submittal meets the conformity adequacy requirements of

40 CFR § 93.118(e)(4) and is approvable under all pertinent SIP requirements. In addition, the 

budgets must reflect all of the motor vehicle control measures contained in the attainment and 

RFP demonstrations.40

2. Motor Vehicle Emissions Budgets in the 2009 South Coast PM10 Redesignation Request and 

Maintenance Plan

The motor vehicle emissions budgets for the South Coast are summarized in Table E-1. 2009 

South Coast PM10 Redesignation Request and Maintenance Plan, submitted on April 28, 2010,

includes a set of PM10 budgets for the years 2010, 2020 and 2030 for directly emitted PM10, 

VOC (in California, also known as ROG) ,

41 and NOx.42, 43, 44

 CARB revised the budgets in the 

 

39 See 40 CFR § 93.122.

40 See 40 CFR § 93.118(e)(4)(v).

41 The California Air Resources Board (CARB) uses the term reactive organic gases (ROG) for planning and 

inventory purposes and uses it synonymously with its own definition of “volatile organic compound” for regulatory 

purposes. The value of ROG for inventory purposes is derived by multiplying the reported Total Organic Gases 

(TOG) by the Fraction of Reactive Organic Gases (FROG). Each source category is keyed to one of several hundred 

available chemical speciation profiles. For each category, the FROG value is calculated as the weight fraction of 

those species designated by the ARB as reactive in the speciation profile applicable to the category. CARB’s organic 

gas speciation profiles are available for download at http://www.arb.ca.gov/ei/speciate/speciate.htm. EPA defines 

and uses the term volatile organic compounds (VOC), which relies upon a list of exempted compounds having 

negligible photochemical reactivity, that is periodically updated. EPA codifies its definition of VOC at 40 CFR part 

51 section 51.100, Definitions. Although some differences existed in the past between California’s use of the term 

“ROG” and EPA’s definition of “VOC”, the two terms are now nearly identical in that CARB’s current definitions for 

ROG and VOC include a list of low-reactive organic compounds which have been exempted by EPA. Source: 

Definitions of ROG and TOG (As of January 2009) ( See http://www.arb.ca.gov/ei/speciate/voc_rog_dfn_1_09.pdf)

42 See CARB Resolution 10-21 and the 2010 CARB Staff Report, “Analysis of the South Coast Air Basin PM10 

Redesignation Request, Maintenance Plan,” and supplementary information, which is an update to the Final PM10 

Redesignation Request and Maintenance Plan for the South Coast Air Basin (South Coast PM10 Plan).

43 See letter, James N. Goldstene, Executive Officer, to Jared Blumenfeld, Regional Administrator, EPA Region 9, 

dated April 28, 2010, transmitting the 2009 South Coast PM10 Redesignation Request and Maintenance Plan, CARB 
Page 27 of 37

2009 South Coast PM10 Redesignation Request and Maintenance Plan in response to EPA 

comments. Additional information associated with the motor vehicle emission budget 

calculations is provided in a technical analysis accompanying a March 19, 2013 letter from 

SCAQMD to EPA.

45

Table E-1. 2009 South Coast PM10 Redesignation Request and Maintenance Plan Motor 

Vehicle Emissions Budgets as submitted in the Final South Coast PM10 Redesignation Request 

and Maintenance Plan

(Annual Average tons per day)

Emissions Budget 2010 2020 2030

PM10 159 164 175

NOx 372 180 116

ROG 182 110 81

The details for each component of the budgets for the South Coast are shown in Table E-2

and are comprised of direct on-road mobile source emissions, road construction emissions, 

fugitive emissions from paved and unpaved roads, and safety margins. The budgets include a 

 

Board Resolution 10-21 adopting the 2009 South Coast PM10 Maintenance Plan and Transportation conformity 

budgets at the CARB Board hearing.

44 The South Coast Air Quality Management District (SCAQMD) adopted its Final PM10 Redesignation Request and 

Maintenance Plan for South Coast Air Basin (2009 South Coast PM10 Plan) on January 8, 2010. Shortly before plan 

adoption, SCAQMD developed revised budgets for the plan based on U.S. EPA (EPA) comments that the budgets 

only include emission reductions from adopted control measures. Thus SCAQMD removed the budgets prior to 

Board consideration. SCAQMD and the California Air Resources Board (CARB) revised the budgets prior to CARB’s 

adoption of the South Coast PM10 Plan. Concurrent with its 45-day notice for 2009 South Coast PM10 Plan

consideration on February 22, 2010, CARB posted the revised budgets for a 30-day public review on February 22, 

2010. CARB approved both the budgets and the South Coast PM10 Plan as a revision to the California State 

Implementation Plan (SIP) at a public hearing on March 25, 2010.

45

 See Letter from Elaine Chang, Deputy Executive Officer, SCAQMD to Deborah Jordan, Director Air Division, EPA, 

Region 9, and accompanying technical analysis (“South Coast Air Basin Paved Road Dust Calculation PM10 Based 

on 2011 AP-42 Default Silt Loading and EMFAC2011 VMT”), dated March 19, 2013.
Page 28 of 37

safety margin, and even with this safety margin, the total emissions in the maintenance plan 

are less than the emissions carrying capacity calculated for the attainment year. A state may 
Page 29 of 37

Table E-2. Transportation Conformity Budgets Detail for PM 10

(Annual Average tons per day)

2010 2020 2030

ROG NOx PM10 ROG NOx PM10 ROG NOx PM10

On-Road Emissions from

EMFAC 2007 174.3 386.4 23.1 107.1 191.1 22.0 79.4 127.7 22.6

Paved Road Dust __ __ 70.6 __ __ 73.4 __ __ 78.8

Un-paved Road Dust __

__ 10.3 __ __ 10.2 __ __ 10.2

Road Construction Dust __ __ 2.4 __ __ 2.4 __ __ 2.5

Adjustments to Baseline* -0.3 -14.7 -0.2 -1.1 -11.8 -0.3 -2.1 -11.7 -0.6

Safety Margin 7.0 __ 52.8 4.0 __ 56.9 3.0 __ 61.4

Net Inventory 181.1 371.1 159.0 110.0 179.3 163.6 80.3 116.0 174.9

Conformity Budget** 182 372 169 110 180 164 81 116 175

* Reductions from adopted rules not reflected in EMFAC

** Budget is obtained by rounding up to the nearest ton.

Notes: Paved and unpaved road dust is calculated by the South Coast AQMD and is reported in Table 3-2 in the adopted plan, and revised in March 19, 2013 letter

Road construction dust is a component of the Construction/Demolition category in Table 3-2 in the adopted plan.

Vehicle activity data used in EMFAC was received from SCAG in April 2009, and reflects SCAG's 2008 RTP, Amendment 1.

The safety margin is to account for additional directly emitted PM 10 from anticipated growth in VMT. The adopted maintenance plan analyzes the impact of an additional 20 

tons per day of PM 10 beyond the 2007 AQMP/SIP baseline and concludes that the Basin will continue to maintain the PM 10 standard.

An additional 5 tons of PM10 is added to account for this anticipated VMT growth while setting an emissions budget that ensures continued maintenance of the standard.

An additional 7, 4 and 3 tons of ROG is added in 2010, 2020 and 2030, respectively to account for increased ROG emissions from anticipated growth in VMT.

Analysis by the South Coast District concluded that these budgets are consistent with continued maintenance of the standard and allowed for additional safety margin 

emissions. See the Supplementary Information for a discussion of the South Coast District analysis.

Columns may not add due to rounding.
Page 30 of 37

choose to apply a safety margin under our transportation conformity rule so long as such 

margins are explicitly quantified in the applicable plan and are shown to be consistent with 

attainment or maintenance of the NAAQS (whichever is relevant to the particular plan).46 In this 

instance, the safety margin has been explicitly quantified and shown to be consistent with 

continued maintenance of the PM10 NAAQS in South Coast PM10 nonattainment area through 

the applicable maintenance period, through 2030.

47

The budgets were developed using emission factors generated by CARB’s EMFAC2007 48

model for direct emissions, and EPA’s AP-42 was used to develop emissions for the fugitive and 

construction emissions.49 The paved road emissions were originally calculated using the 2006 

version of AP-42 as a component of the 2007 South Coast Air Quality Management Plan 

(AQMP) emissions inventory projected to 2010, 2020 and 2030. The calculation relied on a 

California profile of silt loading, weather, roadway centerline miles and Vehicle Miles Traveled 

(VMT) growth.50 

EPA released an update to AP-42 in January 2011 which revised the equation for estimating 

paved road dust emissions based on an updated regression that included new emission tests

results. The SCAQMD staff conducted a technical analysis that accompanied the March 19, 

2013 letter from SCAQMD to EPA51 of their paved road dust emission projections using the 

updated equation and the latest planning assumptions to ensure that the budgets are 

consistent with the currently approved modeling tools and data. In the analysis, SCAQMD 

applied the default values of silt loading for freeways, arterial, collectors and local roads of 

0.03, 0.06, 0.06 and 0.2 grams per meter squared (g/m2), respectively and a default PM10

particle size multiplier of 0.0022 pounds per VMT (lbs/VMT). VMT estimates were extracted 

 

46 See 40 CFR 93.124(a).

47 See the 2009 South Coast PM10 Plan, page 25, Table 3-5 and Appendix-4.

48 EMFAC (EMission FACtor) is California’s model for estimating emissions from on-road vehicles operating in 

California. It is built on decades of vehicle testing and analysis, and is informed by DMV registration data, the Smog 

Check program, and many other data sources. EPA approved EMFAC2007 on January 18, 2008 (73 FR 3464). 

CARB’s latest release is EMFAC 2011 which EPA approved on March 6, 2013 (78 FR 14533).

49 AP-42, Compilation of Air Pollutant Emission Factors, is a document published by EPA as the primary collection of 

EPA approved emission factor information. The emission factors have been developed and compiled from source 

test data, material balance studies, and engineering estimates. EPA has published supplements and updates to the 

each of the chapters available in Volume I, Stationary Point and Area Sources at the following web site:

http://www.epa.gov/ttnchie1/ap42/. 

50 In the South Coast PM10 Plan, as adopted by the SCAQMD on January 8, 2010.

51

 See Letter from Elaine Chang, Deputy Executive Officer, SCAQMD to Deborah Jordan, Director Air Division, EPA, 

Region 9, and accompanying technical analysis (“South Coast Air Basin Paved Road Dust Calculation PM10 Based 

on 2011 AP-42 Default Silt Loading and EMFAC2011 VMT”), dated March 19, 2013.
Page 31 of 37

from the CARB’s EMFAC2011 for 2010, 2020 and 2030. The technical analysis showed that the 

updated paved road dust emissions were less than the attainment inventory emissions of paved 

road dust for all years for which motor vehicle emission budgets were estimated in the original 

submittal. For example, in the technical analysis, emissions of paved road dust in 2030 (done 

with the latest AP-42 version and the updated silt loading factors and particle size multiplier)

were estimated to be 78.8 tpd. The 2009 South Coast PM10 Redesignation Request and 

Maintenance Plan demonstrates that the PM10 NAAQS can be maintained with re-entrained 

road dust emissions from paved roads at 135.2 tpd (see technical analysis in March 19, 2013 

letter). Therefore, the revised future year emissions estimates resulting from the technical 

analysis are much lower (e.g. 56.4 tpd) than the levels that were shown as needed to attain and 

maintain the PM10 in the original analysis submitted by the SCAQMD. 

3. Final Action on the Budgets 

We did not receive any comments on our proposed approval of the budgets in the PM10

maintenance plan. In today’s action, EPA is approving the budgets in the 2009 South Coast PM10

Redesignation Request and Maintenance Plan and therefore is reviewing the budgets against 

our adequacy criteria in 40 CFR § 93.318(a)(4) as part of our review of the approvability of the 

submitted budgets. The results of this review are shown in the Table E-3. EPA is not required 

under its Transportation Conformity rule to find budgets adequate prior to proposing approval 

of them. As described in the Federal Register notice of proposed rulemaking, EPA notified the 

public that we reviewed the adequacy of the budgets and the public had 30 days to comment, 

after which we would make a finding on the adequacy of the budgets.

We are approving the maintenance demonstration in the 2009 South Coast PM10

Redesignation Request and Maintenance Plan. As discussed above in Section C, Attainment 

Inventory, the motor vehicle emissions portions of these budgets (i.e., the evaporative and 

tailpipe emissions) were developed using the EMFAC2007 motor vehicle emissions factors, 

along with activity levels reflecting current information provided by SCAG. The fugitive emission 

estimates in the budgets are consistent with EPA’s AP-42 model and contain a safety margin 

consistent with maintenance of the standard for the maintenance period. We are approving the 

motor vehicle emission budgets consistent with CAA section 176(c)(2)(A) and the adequacy 

criteria of 40 CFR 93.118(e)(4), including consistency with the 2009 South Coast PM10

Redesignation Request and Maintenance Plan emissions inventories, the motor vehicle control 

measure emission reductions used in the maintenance demonstration, and the reductions

needed for continued maintenance of the standard.
Page 32 of 37

On the effective date of our final action, SCAG and the U.S. Department of 

Transportation will be required to use the revised budgets in transportation conformity 

determinations. Due to the formatting of the budgets (including adjustments to the baseline 

emissions to account for additional reductions from control measures) CARB will need to 

provide SCAG with emission reductions associated with the control measures incorporated into 

the budgets for the appropriate analysis years in future conformity determinations so that they 

can include these reductions pursuant to 40 CFR § 93.122. In addition, for these conformity 

determinations, the motor vehicle emissions from implementation of the transportation plan 

should be projected and compared to the budgets at the same level of accuracy as the budgets 

in this maintenance plan, for example emissions should be rounded to the whole number (e.g. 

11 tpd). 
Table E.3. Evaluation of the Motor Vehicle Emissions Budget for the Request for the 

Final PM10 Redesignation and Maintenance Plan for the South Coast Air Basin

Adequacy Review Criteria

(40 CFR Part 93)

Is Criterion

Satisfied?

Y/N

Reference in SIP Document/Comments

Sec. 93.118(e)(4)(i) The plan was endorsed by the 

Governor (or designee) and 

was subject to a public 

hearing.

Y Both the South Coast Air Quality Management District (SCAQMD) and the California Air Resources 

Board (CARB) satisfied applicable statutory and regulatory requirements for reasonable public 

notice and hearing prior to adoption and submittal of the Final PM10 Redesignation Request and 

Maintenance Plan for the South Coast Air Basin (2009 South Coast PM10 Redesignation Request 

and Maintenance Plan ) and Motor Vehicle Emissions Budgets (budgets). SCAQMD approved the

2009 South Coast PM10 Redesignation Request and Maintenance Plan at a public hearing on 

January 8, 2010 and transmitted Board Resolution 10-1 with the plan and other supporting 

documentation to CARB on January 15, 2010. Shortly before plan adoption, SCAQMD developed 

revised budgets for the plan based on U.S. EPA (EPA) comments that the budgets only include 

emission reductions from adopted control measures. Thus SCAQMD removed the budgets prior to 

Board consideration. SCAQMD issued “A Notice of Public Hearing”, made the draft plan available 

on the District's website, and published the notice in five local publications on October 21, 2009.

After the SCAQMD Board approved the plan on January 8, 2010, CARB distributed a 45-day notice 

for the 2009 South Coast PM10 Redesignation Request and Maintenance Plan consideration on 

February 22, 2010. Additionally, CARB posted the revised budgets for a 30-day public review on

February 22, 2010. CARB approved both the budgets and the 2009 South Coast PM10

Redesignation Request and Maintenance Plan as a revision to the California State Implementation 

Plan (SIP) at a public hearing on March 25, 2010. See CARB Resolution 10-21. CARB received no 

comments on the plan.

The April 28, 2010 transmittal letter submitting the 2009 South Coast PM10 Redesignation Request 

and Maintenance Plan was sent to EPA by the CARB’s Executive Officer, James Goldstene, the 

Governor’s designee. Both the January 15 2010 and April 28 2010 submittals contain proof of 

publication and evidence that the SCAQMD and CARB public hearings were properly noticed.
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Sec. 93.118(e)(4)(ii) The plan was developed 

through consultation with 

federal, state and local 

agencies; full implementation 

plan documentation was 

provided and EPA’s stated 

concerns, if any, were 

addressed.

Y Consultation with federal, state and local agencies was undertaken; this consultation took place 

with the Southern California Association of Governments (SCAG) and an interagency consultation 

working group. Members of the consultation group include: EPA, FHWA, FTA, CARB, Caltrans, 

SCAQMD, SCAG (the area’s Metropolitan Planning Organization [MPO]), and county transportation 

agencies. EPA received a copy of the draft South Coast PM10 Redesignation Request and 

Maintenance Plan on July 21, 2009, and provided written comments on August 18, 2009. The 

South Coast AQMD addressed the comments by incorporating revisions into the final 2009 South 

Coast PM10 Redesignation Request and Maintenance Plan, dated December 2009. Revisions 

include: 1) an addition of emissions for 2008; 2) a revision of daily vehicle miles traveled (VMT) 

provided by CARB’s EMFAC2007 model; and 3) explanation of the relevancy of the 2002 base year.

The district also addressed EPA comments submitted previously by revising the original budgets to 

only include emissions reduction resulting from control measures that were already adopted.

Sec. 93.118(e)(4)(iii) The motor vehicle emission 

budget(s) is clearly identified

and precisely quantified.

Y CARB’s Staff Report, Analysis of the South Coast Air Basin PM10 Redesignation Request, 

Maintenance Plan, and Conformity Budgets, released to the public on February 22, 2010, contains 

Table 4, Transportation Conformity Emissions Budgets for PM10 in the South Coast Air Basin, which 

clearly identifies and precisely quantifies the budgets and the methodology for the years 2010, 

2020 and 2030.

Sec. 93.118(e)(4)(iv) The motor vehicle emissions 

budget(s), when considered 

together with all other 

emission sources, is 

consistent with applicable 

requirements for reasonable 

further progress, attainment, 

or maintenance (whichever is 

relevant to the given plan).

Y EPA has determined that the budgets, when considered together with all other emission sources, 

are consistent with applicable requirements for maintenance of the PM10 National Ambient Air 

Quality Standard of 150 μg/m3(24-hour). 

Prior to the District’s Board hearing, the District revised the transportation conformity budgets in 

the 2009 South Coast PM10 Redesignation Request and Maintenance Plan to reflect U.S. EPA‘s 

comment that the budgets only include emission reductions from already adopted control 

measures. In Chapter 3 of the 2009 South Coast PM10 Redesignation Request and Maintenance 

Plan, a PM10 modeling sensitivity analysis was conducted for the years 2010 through 2030 to 

evaluate the impact of adding 20 tons per day (tpd) of directly emitted PM10 to the Basin baseline 

inventory. After consultation with the District and the metropolitan planning organization (MPO) 

for the region, the Southern California Association of Governments (SCAG), 5 tpd of directlyemitted PM10 were added to the conformity budget for 2030 and 7 tpd, 4 tpd, and 3 tpd of ROG to 

the budgets for 2010, 2020, and 2030, respectively. Based on established modeling ratios, the 

additional ROG emissions translate to adding 1 tpd of PM10 emissions of ROG equivalency 
ii.

(rounding to whole tpd) for 2010, 2020, and 2030, respectively. Therefore, total additions for the 

2030 budget are the equivalent of 6 tpd of PM10. The additional 6 tpd of PM10 represents only 30 

percent of the 20 tpd PM10 safety margin identified in the 2009 South Coast PM10 Redesignation 

Request and Maintenance Plan. The 6 tpd of PM10 facilitates anticipated growth while setting an 

emissions budget that ensures continued maintenance of the standard.

EPA released an update to AP-42 in January of 2011 which revised the equation for estimating 

paved road emissions based on an updated regression of emission tests. The SCAQMD staff 

conducted additional technical analysis of their paved road emission projections using the 

updatedAP-42 equation and the latest planning assumptions, to ensure that the motor vehicle 

emission budgets were still consistent with the currently approved modeling tools and data and 

the maintenance demonstration. The technical analysis showed that the updated paved road 

emissions provided a significant safety margin as compared to the attainment inventory emissions

of paved road dust for all years for which motor vehicle emission budgets were estimated, 

therefore the total motor vehicle emissions budgets are consistent with maintenance of the 

standard.

Sec. 93.118(e)(4)(v) The plan shows a clear 

relationship among the 

emissions budget(s), control 

measures and the total 

emissions inventory.

Y Emissions inventory estimates and modeling analyses are documented in Section 3 of the 2009 

South Coast PM10 Redesignation Request and Maintenance Plan. The attainment baseline emission 

inventories for all point, area and mobile sources are listed for PM10, PM2.5, NOx, VOC and SOX for 

the years 2002 (Inventory Base Year), 2006, 2008 2010, 2011, 2012, 2020, 2023 and 2030. Section 

3 also includes a detailed breakout of the updated baseline attainment inventory for the PM10

emission subcategories, which includes emissions estimates from paved and unpaved entrained 

road dust. Budget estimates contained in the 2009 South Coast PM10 Redesignation Request and 

Maintenance Plan were not adopted on January 8, 2010 with the rest of the plan. However, the 

district developed and CARB posted to its website, revised budget estimates on February 22, 2010. 

These budget estimates, when considered together with adjustments made to the baseline 

inventories are consistent with and show a clear relationship to the emissions inventory contained 

in Section 3 of the 2009 South Coast PM10 Redesignation Request and Maintenance Plan. South 

Coast provided an explanation of budget adjustments made to reflect both a safety margin and the 

relative contribution from Reactive Organic Gases in a February 19, 2010 letter from Deputy 

Executive Officer, Elaine Chang to Lynn Terry, Deputy Executive Officer, California Air Resources 

Board. All other adjustments to baseline inventories and 2020 and 2030 budget estimates for 

PM10 were minor and conform to the emissions inventory submitted in Section 3 of the 2009 South 
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Coast PM10 Redesignation Request and Maintenance Plan.

Sec. 93.118(e)(4)(vi) Revisions to previously 

submitted control strategy or 

maintenance plans explain 

and document any changes to 

any previous submitted 

budgets and control 

measures; impacts on point 

and area source emissions; 

any changes to established 

safety margins (see §93.101 

for definition), and reasons 

for the changes (including the 

basis for any changes to 

emission factors or estimates 

of VMT.

Y CARB submitted to EPA the draft South Coast PM10 Redesignation Request and Maintenance Plan

on July 21, 2009, and EPA provided written comments on August 18, 2009. South Coast finalized 

this plan in December 2009. South Coast made a number of editorial revisions to the plan, 

however, the most significant revisions were made to the budgets. Budgets contained in the both 

the draft and final versions of the 2009 South Coast PM10 Redesignation Request and Maintenance 

Plan were revised. Prior to the District’s Board hearing on January 8, 2010, the District revised the 

transportation conformity budgets to reflect U.S. EPA‘s comment that the budgets only include 

emission reductions from already adopted control measures. The submitted budgets are contained 

in Table E-1 of this report. In addition to the consideration of the EPA’s comments, the 2030 

budgets also include an additional 6 tpd safety margin to facilitate growth. The additional 

technical analysis performed by the SCAQMD, using the 2011 version of AP-42 showed that 

additional emissions are available for inclusion in the safety margins for the motor vehicle emission 

budgets.

Sec. 93.118(e)(5) EPA has reviewed the State’s 

compilation of public 

comments and response to 

comments that are required 

to be submitted with any 

implementation plan.

Y Neither CARB nor SCAQMD received public comments on the 2009 South Coast PM10

Redesignation Request and Maintenance Plan and Transportation Conformity Budgets.
III. Response to Comments

EPA provided for a 30-day public comment period on our proposed action. The 

comment period ended on May 8, 2013. We received one comment letter from the South Coast 

Air Quality Management District (SCAQMD or District) on May 8, 2013.52We respond to that 

comment here.

Comment: SCAQMD strongly supports EPA’s proposed action. The District also commented that 

it submitted, through CARB, exceptional events packages requesting exclusion of monitoring 

data from multiple sites in the SCAQMD network from October 21, 2007 and July 5, 2007 under 

EPA’s Exceptional Events Rule (72 FR 28612, May 22, 2007). The exceptional events requests 

were submitted to EPA by CARB on October 23, 2009 and December 22, 2009, respectively. The 

letter also requested EPA to acknowledge the requests if EPA did not evaluate these requests 

before taking final action on this proposal. 

Response: EPA is not taking any action on the exceptional events requests cited in the District’s 

comment letter. It is not necessary for EPA to process those requests because this final action is 

based on monitored data occurring after the time of those requests. Therefore, whether we 

granted or denied the exceptional events requests concerning data from 2007 would not have 

any bearing on our action today. 

 

52 See letter, Elaine Chang, DrPH, Deputy Executive Officer, South Coast Air Quality Management District, to 

Wienke Tax, US Environmental Protection Agency, Region IX, dated May 8, 2013, in the docket for today’s action.