CHAPTER 6

CLEAN AIR ACT REQUIREMENTS

Introduction

Federal Clean Air Act Requirements

Carbon Monoxide Attainment Demonstration

1997 Nitrogen Dioxide Maintenance Plan

California Clean Air Act Requirements
Chapter 6 Federal and State Clean Air Act Requirements

6 - 1

INTRODUCTION

The 1997 AQMP is designed to satisfy: 1) the State Implementation Plan (SIP) 

requirements under Title I of the Clean Air Act (CAA) and 2) Plan requirements of the 

California Clean Air Act (CCAA). The emphasis of this Plan is to meet federal CAA 

requirements for PM10 that are due by February 8, 1997 and to meet CCAA requirements 

to prepare a comprehensive plan update by December 31, 1997. In addition, based on 

new technical information, previous SIP submittals such as the 1994 California Ozone 

SIP and the Carbon Monoxide SIP are updated as part of this Plan.

The District has authority over the South Coast Air Basin (Basin) and this Plan satisfies 

the PM10 attainment demonstration requirements of the federal CAA, which is classified 

as a serious nonattainment area for PM10. In addition, the District has jurisdiction over 

the Coachella Valley located in the Salton Sea Air Basin and the Los Angeles County 

portion of the Mojave Desert Air Basin. The Coachella Valley is also designated as a 

serious nonattainment area for PM10. A separate Coachella Valley Maintenance Plan 

will be submitted to meet federal CAA requirements for this area (see Chapter 8). The 

Los Angeles County portion of the Mojave Desert Air Basin, known as the Antelope 

Valley, is currently unclassified for PM10 and there are no state or federal PM10 planning 

requirements.

The 1994 AQMP satisfied the ozone attainment and VOC rate-of-progress demonstration 

requirements of the CAA for the South Coast Air Basin, Antelope Valley, and Coachella 

Valley. The 1994 AQMP addressed the separate ozone attainment and VOC rate-ofprogress demonstrations for each of these areas. Based on the control strategy provided 

in Chapter 4, ozone attainment and rate-of-progress demonstrations are presented in this 

chapter for the South Coast Air Basin and in Chapter 8 for the Antelope Valley and 

Coachella Valley.

FEDERAL CLEAN AIR ACT REQUIREMENTS

PM10 Planning Requirements

Results of ambient air quality monitoring data indicate that the Basin exceeds federal and 

state standards for PM10. These microscopically fine particles can originate from several 

industrial processes, including direct emission and atmospheric chemical reactions which 

convert gases into particles (referred to as “secondary” particulates), and from a variety 

of fugitive dust sources, both natural and man-made. In the western portions of the 

Basin, secondary particulates account for about 45 percent of the annual average PM10, 

while soil dust (referred to as “fugitive dust”) accounts for about 30 percent. In the 
FINAL 1997 AQMP

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eastern portion of the Basin, the contributions from secondary particulates and fugitive 

dust are approximately 40 percent each. Mobile sources also contribute directly to 

ambient PM10 levels through tailpipe emissions and, indirectly, through resuspension of 

paved road dust.

Under the 1990 Clean Air Act Amendments the South Coast Air Basin was originally 

classified as a “moderate” PM10 nonattainment area. In response to State Implementation

Plan (SIP) submittal requirements of the CAA for “moderate” areas, the District 

submitted applicable portions of the 1991 AQMP to the U.S. EPA prior to the November 

15, 1991 statutory deadline. In accordance with the CAA requirements for moderate 

PM10 nonattainment areas, the moderate area PM10 SIP submittal proposed the 

implementation of “reasonably available control measures” (RACM) for fugitive dust 

sources, and relied upon the AQMP for reductions in precursor gaseous emissions as part 

of the ozone attainment plan. Modeling contained in the moderate area PM10 SIP 

demonstrated that the Basin would not attain the PM10 standards by December 1994 and 

would subsequently be reclassified as a “serious” nonattainment area. In February 1993, 

EPA reclassified the Basin from a “moderate” to a “serious” nonattainment area for 

PM10. The moderate area SIP further showed that the complexity of the problem was of 

sufficient magnitude that the PM10 standards could not be attained by 2001 -- the 

deadline for serious nonattainment areas. The CAA provides a maximum five year 

extension to the attainment date for those areas that cannot meet the 2001 date after all 

best available control measures (BACM) have been implemented by 1997; thus making 

2006 the latest attainment year possible. The District has shown in the 1994 AQMP that 

it will need until 2006 to meet the federal PM10 standards. 

CAA Section 189(b)(2) requires areas reclassified as serious to submit a SIP revision 

within 18 months of a reclassification. For the Basin, the PM10 BACM SIP, submitted as 

part of the 1994 AQMP, met this requirement.

Current PM10 Requirements

For areas such as the Basin that are classified as serious nonattainment for PM10, Section 

189(b)(3) defines major PM10 sources that would be subject to CAA major source 

requirements. Sections 189(e) and 189(b)(1)(B) of the CAA require the implementation 

of “best available control technology” (BACT) for point sources of PM10 and precursor 

emissions (i.e., precursors of secondary particulates) and BACM for area sources of 

fugitive dust by February 8, 1997. U.S. EPA guidance1also states that, in instances 

where mobile sources contribute significantly to the area’s exceedance of federal PM10

standards, transportation control measures (TCMs) are also to be included as part of the 

 

1U.S. EPA, State Implementation Plans for Serious PM-10 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, Federal Register, pp. 41998-42017, August 16, 1994.
Chapter 6 Federal and State Clean Air Act Requirements

6 - 3

PM10 SIP submittal. An attainment demonstration for PM10 is required by the CAA as 

part of the SIP submittal due February 8, 1997. Section 189(c) requires the 

establishment of emission reduction milestones. Lastly, contingency measures for PM10, 

in the event of failure to meet emission reduction milestones or achieve attainment, are 

also required as part of the SIP submittal.

Major PM10 Source Requirements

Section 189(b)(3) of the CAA defines a major source of PM10 as any stationary source 

that emits or has a potential to emit at least 70 tons per year of PM10. These major 

sources then would be subject to major source requirements contained in the CAA. 

District Rule 1302(p) defines major PM10 sources in accordance with the CAA, making 

them subject to the major source requirements under New Source Review (NSR).

BACT for Point Sources

As mentioned in the 1994 AQMP, BACT for point sources of PM10 and PM10 precursors 

is presently addressed through the District’s NSR and RECLAIM programs (District 

Rules 1303 and 2005).

BACM for Fugitive Dust Sources

For fugitive dust sources, the selection of BACM to be implemented must be based on a 

combination of technical feasibility, cost-effectiveness, and energy/environmental 

considerations; the selected BACM controls must be implemented by February 8, 1997. 

These candidate BACM are generally similar to the RACM (Reasonably Available 

Control Measure) strategy adopted in District Rule 403, except that they are elevated to a 

higher level of stringency. This is consistent with U.S. EPA policy, which states that “... 

more stringent control measures are needed in cases when the current control 

requirements will be insufficient to bring a particular area into attainment.”2 The District 

developed a list of candidate BACM as part of the 1994 PM10 BACM SIP submittal. 

These measures have been refined and updated for the 1997 AQMP. The following is a 

list of candidate BACM that are being considered as part of the 1997 PM10 SIP revision 

(a complete description of the candidate BACM can be found in Appendix IV, Section 

1):

CM #97BCM-01: Paved Roads

1a Minimal Track-Out

1b Routine Street Cleaning

1c Post Event Street Cleaning

1d/1e Curbs and Gutters / Chemical Stabilization of 

Unpaved Road Shoulders

 

2 U.S. EPA,. State Implementation Plans for Serious PM-10 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, Federal Register, pp. 41998-42017, August 16, 1994.
FINAL 1997 AQMP

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CM #97BCM-02: Construction/Demolition Activities

Wider Application of Dust Control Plans

CM #97BCM-03: Unpaved Roads

Paving/Chemical Treatment/Speed Reductions

CM #97BCM-04: Agricultural Activities

Soil Conservation Plans

CM #97BCM-05: Miscellaneous Sources

Controls on Weed Abatement

CM #97BCM-06: Further Emission Reductions from Fugitive Dust Sources 

to meet Best Available Control Measures 

Requirements (RACM to BACM Upgrade)

In the 1994 PM10 BACM SIP, the District committed to adopt all identified candidate 

BACM via rulemaking action by December 31, 1996 and implement these BACM by 

February 8, 1997. However, any candidate measure may not be adopted if it is 

determined prior to September 1996 that such candidate BACM does not meet the 

technological and cost feasibility criteria for BACM acceptability. Such criteria are 

defined in Chapter 4.

To complete the technological and cost feasibility analyses, the District has undertaken 

the following actions:

(1) Participated in a fast-track emissions inventory update, as indicated in the 

Emissions Inventory Update Workplan, coordinated through the BACM SIP 

Working Group. This effort provided data on missing and incomplete fugitive 

dust source categories and processes. In addition, the District supplemented 

this effort through the PM10 Technical Enhancement Program (PTEP) emission 

inventory projects.

(2) The District compiled a revised baseline inventory for the fugitive dust 

emission sources and completed the revised inventory process, discussed in 

Chapter 3.

(3) Based on the revised emissions inventory and other available information, each 

of the candidate BACM are being evaluated for cost-effectiveness and control 

efficiency. The District has completed the BACM technological and cost 

feasibility analysis prior to July 1996. As discussed in Chapter 4, BCM01(a/b/c), BCM-03, BCM-04, and BCM-06 meet both the technological and 

cost feasibility criteria.

(4) The District has identified those candidate BACM not meeting either the 

technological or cost feasibility criteria. Those candidate BACM, described in 

Chapter 9, are included as PM10 contingency measures. These measures are 
Chapter 6 Federal and State Clean Air Act Requirements

6 - 5

CTY-12 (formerly BCM-01d/e), CTY-13 (formerly BCM-02), and CTY-14 

(formerly BCM-05).

The results of the initial feasibility and cost-effectiveness analysis are also discussed in 

Chapter 4. The federal CAA requires that the BACM and related contingency measures 

be adopted and implemented by February 8, 1997. The 1994 AQMP provided for the 

adoption of these measures by December 31, 1996. The BACM and contingency 

measures are under rule development as Proposed Amendments to Rule 403 (PAR 403) 

and Proposed Rule 1186 (PR 1186) and are scheduled to be considered for adoption in 

early 1997.

Transportation Control Measures

Transportation control measures meeting the CAA requirements have been submitted in 

previous SIPs, including the 1994 California Ozone SIP. Updated transportation control 

measures necessary of attainment of the federal PM10 and ozone standards are described 

in Appendix IV, Section 3.

PM10 Attainment Demonstration

Section 189(b)(1)(a) of the CAA requires a PM10 attainment demonstration. The results 

of the attainment demonstration are summarized in Chapter 5. The air quality modeling 

used for the PM10 attainment demonstration is described in Appendix V.

Establishing PM10 Milestone Targets

Section 189(c) of the CAA requires the establishment of PM10 milestone targets. The 

future milestone years for PM10 are 2000, 2003, and 2006. The milestone targets are set 

based on expected emission reductions in the target years. The PM10 milestone targets 

are shown in Table 6-1 and Appendix V.

TABLE 6-1

PM10 Milestone Targets

(Average Annual Day - Tons per Day)

1997 2000 2003 2006

PM 309 307 303 301

NOx 998 864 748 635

SOx 71 66 64 67

VOC 993 866 746 623

TOTAL 2,371 2,103 1,861 1,626
FINAL 1997 AQMP

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Contingency Measures for PM10

The federal CAA requires PM10 contingency measures to be implemented in the event of 

failure to meet milestone emission reduction targets and/or failure to attain the standard 

by the attainment date in 2006. The PM10 contingency measures are those BACM 

measures that have failed either the technical feasibility or cost-effectiveness criteria or 

both. For the 1997 AQMP, those measures that have failed the criteria based on initial 

estimates of feasibility and cost-effectiveness are listed in Chapter 9. In addition to the 

fugitive dust contingency measures, other contingency measures for ozone serve as 

contingency for PM10 to reduce VOCs and oxides of nitrogen which are precursors to 

particulate organics and nitrates. The full descriptions of each of the PM10 contingency 

measures are contained in Appendix IV, Section 6.

Other Federal Clean Air Act Requirements

This section describes how the 1997 AQMP meets the major ozone planning 

requirements of the federal Clean Air Act (CAA) for the South Coast Air Basin. The 

requirements specifically addressed here are:

 the post-1996 VOC rate-of-progress requirements,

 the ozone attainment demonstration,

 the contingency measure requirements, and

 the average vehicle occupancy requirement.

Post-1996 VOC Rate-of-Progress

The reasonable further progress requirements in the CAA are intended to ensure that 

each ozone nonattainment area provide for sufficient precursor emission reductions to 

attain the ozone national ambient air quality standard. More specifically, Section 

182(c)(2) requires that each serious and above ozone nonattainment area achieve actual 

VOC emission reductions of at least three percent per year averaged over each 

consecutive 3-year period beginning 6 years after enactment of the Act until the area’s 

attainment date (i.e., November 15, 2010 for the South Coast Air Basin). This is called 

the “post-1996 rate-of-progress” requirement of the CAA.

According to Section 182(c)(2)(C), actual oxides of nitrogen (NOx) emission reductions 

which occur after 1990 can be used to meet post-1996 VOC emission reduction 

requirements provided the NOx reductions satisfy the following criteria. First, the 

control strategy used to demonstrate attainment must consist of both VOC and NOx

control measures. More specifically, the mix of VOC and NOx emission reductions used 

to satisfy the post-1996 rate-of-progress requirements of the CAA must be consistent 
Chapter 6 Federal and State Clean Air Act Requirements

6 - 7

with the controlled VOC and NOx emission levels used in the modeling demonstration. 

And lastly, the combined annual VOC and NOx reductions must average 3 percent per 

year.

The post-1996 rate-of-progress demonstration is presented in Appendix V; Figure 6-1 

and Table 6-2 summarize the results. Shown in the figure are the VOC (Figure 6-1a) and 

NOx (Figure 6-1b) emission target levels and the projected uncontrolled baseline. 

Controlled emission levels are not shown since the VOC and NOx emission reductions 

from existing District and ARB rules are sufficient to meet the CAA rate-of-progress 

requirements.

For the milestone years 1999 and 2002, the baseline VOC emission levels are below the 

target levels. Beginning in 2005, the VOC reductions in the baseline are insufficient and 

NOx substitution is necessary and allowed according to Section 182(c)(2)(C) of the CAA. 

The proposed reduction rates for milestone years are shown in Table 6-2. These rates are 

determined by applying all the creditable VOC reductions at each milestone and 

providing sufficient NOx reductions to satisfy VOC reduction requirements of Section 

182(c)(2). Note that NOx substitution is used to satisfy most of the post-1996 rate-ofprogress requirements after the year 2002.

TABLE 6-2

Percent of VOC and NOx Emission Reductions to Meet the

Post-1996 Rate-of-Progress Requirements

Year VOC NOx CAA*

1999 24.0 0.0 24.0

2002 9.0 0.0 9.0

2005 6.0 3.0 9.0

2008 0.5 8.5 9.0

2010 0.5 5.5 6.0

* The percent VOC and NOx reductions must equal the CAA percent 

reduction requirements listed here.
FINAL 1997 AQMP

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a) VOC

0

500

1000

1500

1999 2002 2005 2008 2010

Milestone Year

Emissions (tpd)

Target Level Projected Baseline

b) NOx

0

500

1000

1500

1999 2002 2005 2008 2010

Milestone Year

Emissions (tpd)

Target Level Projected Baseline

FIGURE 6-1

Post-1996 Rate-of-Progress Requirements
Chapter 6 Federal and State Clean Air Act Requirements

6 - 9

Ozone Attainment Demonstration

Under the Clean Air Act, air quality modeling is an integral part of the planning process 

to achieve clean air. Specifically, Section 182(b)(1)(A) requires that moderate and above 

ozone nonattainment areas must reduce VOC and NOx emissions sufficiently to attain the 

national ambient air quality standard for ozone. It is not sufficient for extreme ozone 

nonattainment areas to meet the post-1996 rate-of-progress requirements of the CAA; 

extreme ozone nonattainment areas, such as the Basin, must also demonstrate attainment 

by November 15, 2010. This may result in emission reductions in addition to those 

required by the reasonable further progress components of the CAA [i.e., Sections 

182(b)(1) and 182(c)(2)]. In this Plan, the modeling requirements are met by applying 

the U.S. EPA-recommended photochemical grid model called the Urban Airshed Model 

(UAM)3using U.S. EPA-approved modeling techniques4.

A summary of the ozone attainment demonstration is provided in Table 5-2 of Chapter 5. 

The ozone attainment demonstration is fully described in Appendix V.

Contingency Measures

Section 172(c)(9) of the 1990 CAA requires that the plan shall provide for 

implementation of specific measures in the event an area fails to make reasonable further 

progress or to attain the applicable standards by the specified dates. Such measures shall 

be included in the Plan revision as contingency measures to take effect without further 

action by the State or the Administrator. Measures which cannot be fully adopted by the 

time EPA acts on the Plan will be adopted within one year of EPA approval to satisfy 

conditional approval requirement of Section 110(k)(4). Section 182(c)(9) refers to 

contingency measures if the area does not achieve the applicable milestone; these 

measures are required to be submitted along with the November 15, 1994 ozone 

attainment demonstration. The District has already adopted a CO contingency measure, 

Rule 1504, parking cash-out, which implements existing state law.

Section 187(a)(3) of the 1990 CAA requires that adopted and enforceable contingency 

measures be included in the carbon monoxide attainment demonstration plan submittal 

(see Appendix IV). Contingency measures are required for carbon monoxide attainment 

planning, to be implemented if the area fails to attain the federal standard by the 

designated attainment date or fails to achieve the specific annual emission reductions 

necessary for attainment. A deviation from the forecasted VMT of more than a given 

percentage triggers implementation of contingency measures to offset either excess VMT 

or carbon monoxide emissions due to the additional VMT or equivalent emissions. 

 

3 User’s Guide for the Urban Airshed Model; prepared for the South Coast Air Quality Management District by 

Systems Applications International; June 18, 1990.

4 Guidance on Urban Airshed Model (UAM) Reporting Requirements for Attainment Demonstration; U.S. 

Environmental Protection Agency; OAQPS, Research Triangle Park, NC, December 1993; EPA-454/R-93-056.
FINAL 1997 AQMP

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According to the EPA General Preamble [Section 532(c)(1)], this percentage is three 

percent for 1997 and subsequent years or other appropriate values. The cumulative VMT 

growth cannot be greater than or equal to five percent above the VMT forecast used as 

the basis of the attainment demonstration.

A list of the contingency measures developed for these CAA requirements is provided in 

Chapter 9.

Average Vehicle Occupancy Requirements (AVO)

Section 182 (d)(1)(A) of the CAA requires the District to include in the Plan 

transportation control measures that offset any growth in emissions from growth in 

vehicle trips and vehicle miles traveled and attain reduction of mobile source emissions. 

Such control measures must be developed in accordance with the guidelines listed in 

Section 108(f) of the CAA. The programs listed in Section 108(f) of the CAA include, 

but are not limited to, transit improvement projects, traffic flow improvement projects, 

the construction of high occupancy vehicle (HOV) facilities and other mobile source 

emission reduction programs. Transportation Control Measure - 01, Transportation 

Improvements included in Appendix IV of the 1997 AQMP, has been developed to meet 

the requirements of Section 182(d)(1)(A) and 108(f) of the CAA and includes the 

capital-based and non-capital-based facilities, projects and programs contained in the 

Regional Mobility Element and programmed through the RTIP process. As an additional 

measure of reducing mobile source emissions, Section 182(d)(1)(B) of the CAA allows 

the implementation of employer-based trip reduction programs that are aimed at 

improving the average vehicle occupancy (AVO) rates. As an alternative to trip 

reduction programs, Section 182(d)(1)(B) also allows the substitution of these programs 

with alternative programs that achieve equivalent emission reductions. Rule 2202 - OnRoad Motor Vehicle Mitigation Options, adopted in December 1995, was developed to 

comply with the CAA requirements and was submitted to EPA for approval.

CARBON MONOXIDE ATTAINMENT DEMONSTRATION

The South Coast Air Basin is designated as a serious nonattainment area for carbon 

monoxide (CO) under the federal Clean Air Act and is required to implement emissions 

reduction measures as “expeditiously as practicable” in order to attain federal carbon 

monoxide standards by December 31, 2000. A Federal Attainment Plan for Carbon 

Monoxide was approved by the District Governing Board on November 12, 1992 and 

submitted to the U.S. EPA. The Plan was revised for the 1994 AQMP as discussed in 

Appendix I-F of the 1994 Plan. It should be noted that the state 1-hour CO standard was 

met for the first time in the Basin in 1995, so CO air quality continues to improve. It is 

necessary to revise the CO Plan in the 1997 AQMP due to new VMT and emissions data 
Chapter 6 Federal and State Clean Air Act Requirements

6 - 11

and adjustments to the control strategy. As discussed in Chapter 5, the modeling results 

indicate that the state and federal 8-hour CO standards are projected to be met in 2000 

through existing District and ARB rules. The proposed control strategy will get some 

additional CO air quality improvement. The revised CO attainment demonstration is 

contained in Appendix V.

As part of the federal Clean Air Act requirements under Section 187(d)(1), a carbon 

monoxide milestone demonstration was submitted to U.S. EPA in March 1996. 

However, the submittal was based on emissions estimates from the 1994 Plan. A 

commitment was made to submit carbon monoxide emissions as of December 31, 1995 

for all sources with the adoption of the 1997 AQMP. The carbon monoxide emissions 

inventory for 1995 is provided in Appendix V.

1997 NITROGEN DIOXIDE MAINTENANCE PLAN

Under the CAA, an area can be redesignated as attainment if, among other requirements, 

the U.S. EPA determines that the NAAQS have been attained. Section 175A of the CAA 

states that any district that submits a request under Section 107(d) for redesignation of a 

nonattainment area to attainment must submit a revision of the applicable SIP that 

demonstrates attainment for at least 10 years after the redesignation. U.S. EPA guidance 

states that a determination of compliance with the NAAQS must be based on three 

complete, consecutive calendar years of quality-assured air quality monitoring data.

Over the past three years (1993 through 1995), ambient nitrogen dioxide measurements 

in the South Coast Air Basin have shown that annual nitrogen dioxide concentrations are 

below the federal air quality standard of 0.053 ppm. As such, based on the ambient 

nitrogen dioxide measurements and the demonstration shown in Chapter 5 that the Basin 

will maintain the federal nitrogen dioxide air quality standard with the projected baseline 

future-year emissions, this Plan serves as the Nitrogen Dioxide Maintenance Plan for the 

South Coast Air Basin.

CALIFORNIA CLEAN AIR ACT REQUIREMENTS

The California Clean Air Act established a number of legal mandates to facilitate 

achieving health-based state air quality standards at the earliest practicable date. The 

following CCAA requirements are addressed in the remainder of this chapter:

(1) Demonstrate the overall effectiveness of the air quality program;

(2) Reduce nonattainment pollutants at a rate of five percent per year, or include 

all feasible measures and an expeditious adoption schedule;
FINAL 1997 AQMP

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(3) Ensure no net increase in emissions from new or modified stationary sources;

(4) Reduce population exposure to severe nonattainment pollutants according to 

a prescribed schedule;

(5) Include any other feasible controls that can be implemented, or for which 

implementation can begin, within 10 years of adoption; and

(6) Rank control measures by cost-effectiveness.

Plan Effectiveness

The CCAA requires, beginning on December 31, 1994 and every three years thereafter, 

that the District demonstrate the overall effectiveness of its air quality program [H&SC 

40924(b)]. Trends in the following air quality indicators are used to demonstrate the 

recent (i.e., for the three preceding years) effectiveness of the District’s program:

(1) VOC, NOx, and carbon monoxide (CO) emissions;

(2) NO2, CO and ozone exceedance days; and

(3) NO2, CO, and ozone population exposure.

Trends in Basin-wide VOC, NOx, and CO emissions since 1993 are shown in Chapter 3. 

Since 1993 VOC, NOx, and CO emissions have decreased by 3 percent, 3 percent, and 5 

percent, respectively, due to current efforts. These decreases have occurred in spite of 

strong population growth over the period.

The percent of days exceeding state standards in 1990 through 1995 for ozone, CO, and 

PM10 air quality are illustrated in Figure 6-2. Even over this relatively short time period, 

it is evident that air quality has improved in the Basin. 

Trends in nitrogen dioxide (NO2) air quality are not shown in Figure 6-2; however, 

improvement in that pollutant is also evident in the last six years. The federal annual 

NO2 standard was met for the first time in 1992 and the standard has been met every year 

since. Since 1993, the South Coast Air Basin has not experienced any exceedances of 

the state NO2 air quality standard and the region has been redesignated to attainment for 

the state NO2 air quality standard. The reader is referred to Appendix II for a more 

comprehensive discussion of local air quality trends.
Chapter 6 Federal and State Clean Air Act Requirements

6 - 13

0

50

100

150

200

1990 1991 1992 1993 1994 1995

Percent of Days

O3 C O PM10

FIGURE 6-2

Percent of Days Exceeding State Standard

Trends in population exposure are shown in Table 6-3. Population exposure is a 

particularly good indicator of air quality trends since it takes into account spatial and 

temporal changes in air quality. For example, per-capita population exposure reflects the 

length of time the Basin population is exposed to unhealthful air quality. Table 6-3 

shows the per-capita exposure to ozone, CO, and NO2 for the historical period 1986-88 

and for two recent years, 1993 and 1995. The per-capita levels shown in the table 

represent average exposure above the state 1-hour standard levels for each pollutant.
FINAL 1997 AQMP

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TABLE 6-3

Trends in Annual Average Per-Capita Exposure to Ozone, 

Carbon Monoxide (CO), and Nitrogen Dioxide (NO2)

Based on 1-Hour Averages

Annual Average Per-Capita Exposure

Period 

or Year

Ozone

(pphm-hrs)

CO

(ppm-hrs)

NO2

(pphm-hrs)

1986-88 198.5 8.4 2.8

1993 71.8 0.1 < 0.1

1995 46.6 0.0* 0.0

*Exposures to 8-hr CO conditions are not calculated, but are estimated to be close to zero.

The table clearly shows that the per-capita exposure to ozone, carbon monoxide, and 

nitrogen dioxide has decreased dramatically since the 1986-88 period. The Basin is 

below the state 1-hour NO2 standard, therefore the per-capita exposure to NO2 is zero. 

The per-capita exposure to the state 8-hour CO standard is also near zero, since the Basin 

is, for the most part, in attainment of the standard. In 1995, the 8-hour CO standard was 

exceeded in the south-central Los Angeles area and the San Fernando Valley.

In summary, the trends of all the indicators show improved air quality in the South Coast 

Air Basin over the last five to eight years; the population is being exposed to unhealthful 

air quality less and less each year. These air quality improvements are the direct result of 

AQMP implementation.

Emission Reductions

The ARB has developed “planning inventories” to characterize emissions during periods 

when air quality standards are exceeded and to serve as the basis for emissions reduction 

accounting (see Chapter 3). As shown in Chapter 3, the planning inventories are 2 to 5 

percent higher than the comparable annual average emission inventories. This difference 

is primarily due to seasonal temperature changes and the corresponding effects on 

pollutant emissions rates (e.g., higher solvent and gasoline evaporative emissions on hot 

summer days; more fuel combustion on cold days).

Table 6-4 presents baseline emissions and estimated emission reductions for the 

reporting years 1997 and 2000. These estimates are based on the adoption and 

implementation schedules contained in Chapter 7. As seen in the table, the proposed 

control strategy falls short of the CCAA emission reduction goals (i.e., five percent per 

year for all nonattainment pollutants) for all pollutants for all years even with the 
Chapter 6 Federal and State Clean Air Act Requirements

6 - 15

implementation of maximum feasible controls and an expeditious adoption schedule. 

Nonetheless, the strategy represents the all feasible control measures and an expeditious 

adoption schedule as permitted under H&S Code 40914.

TABLE 6-4

Summary of 1997 AQMP Controlled Emissions Based on 

Planning Inventory Emissions (tons/day)*

Summer

O3 Inventory

Winter

NO2 Inventory

Winter

CO Inventory

Year VOC NOx NOx CO

1990 Baseline 1,733 1,472 1,537 9,277

Emission Reductions

1997 702 (41%) 438 (30%) 456 (30%) 3,538 (38%)

CCAA Requirement (35%) (35%) (35%) (35%)

2000 825 (48%) 573 (39%) 595 (39%) 4,309 (46%)

CCAA Requirement (50%) (50%) (50%) (50%)

*Emission reductions are estimated as the 1990 equivalent. Percent reduction from 1990 Baseline are shown in parenthesis.

Population Exposure

The CCAA also requires a reduction in overall population exposure to criteria pollutants. 

Specifically, exposure to severe nonattainment pollutants above standards must be 

reduced by at least:

(1) 25 percent by December 31, 1994;

(2) 40 percent by December 31, 1997; and

(3) 50 percent by December 31, 2000.

Reductions are to be calculated based on per-capita exposure and the severity of 

exceedances. This provision is applicable to ozone, CO and NO2 in the Basin [H&SC 

40920(c)]. The definition of exposure is the number of persons exposed to a specific 

pollutant concentration level above the state standard times the number of hours exposed. 

The per-capita exposure is the population exposure (units of pphm-persons-hours) 

divided by the total population.
FINAL 1997 AQMP

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Methodology

For the 1997 AQMP, the Regional Human Exposure (REHEX) model is used to estimate 

per-capita exposure reduction. It considers population mobility; time spent indoors, 

outdoors and in transit; exposure by age classification; and activity pattern by season and 

weekday/weekend. In addition, REHEX utilizes future-year predicted ozone 

concentrations from the Urban Airshed Model (UAM) to project population exposure. 

The methodology and the model are discussed in more detail in Appendix V of the 1997 

AQMP and in Technical Report V-H of the 1991 AQMP.

Ozone

An analysis using the REHEX model indicates that the CCAA exposure reduction targets 

will be achieved for ozone with a margin of safety. Thus, public health will be 

significantly improved with the implementation of the 1997 AQMP. Figure 6-3 

summarizes the results and compares estimated exposure reductions to the targets. The 

exposure reductions shown in 1997 are the actual population exposures in 1995. Actual 

exposures in 1995 serve as better indicators of the 1997 exposure than model-predicted 

estimates.

1994 1997* 2000

Year

Percent Reduction

CAA Requirements REHEX

100

80

40

20

0

60

* 1997 exposure based on actual 1995 data.

FIGURE 6-3

Percent Reductions in Annual Average Per-Capita Exposure to Ozone
Chapter 6 Federal and State Clean Air Act Requirements

6 - 17

The REHEX model also allows more detailed exposure reduction estimates 

disaggregated by age group and county. These results are summarized in Figures 6-and 

6-5, respectively. As shown, the greatest exposure reduction for an individual age class 

is for children, who have longer exposure to outdoor concentrations; the geographic 

location with the most improvement for all age groups is that comprised of the two 

inland counties.

Carbon Monoxide

The REHEX modeling results for CO are shown in Figure 6-6. As shown, the proposed 

control strategy will greatly exceed the CCAA reduction requirements for CO exposure. 

As discussed in Chapter 5 and in Appendix V, the 1-hour and 8-hour CO standards are 

projected to be met by the year 2000. Therefore, the Basin population will not be 

exposed to unhealthful CO levels and thus per capita exposure is reduced 100 percent 

from the 1986-88 base levels. The exposure reductions shown in 1997 are the actual 

population exposures in 1995 and as discussed earlier the 1-hour CO standard was met 

for the first time in 1995.

0

20

40

60

80

100

120

All Ages Children Adolescents Adults

Hours

1987 2000 Control

FIGURE 6-4

Per-Capita Ozone Exposure Above the State Standard by Age Group
FINAL 1997 AQMP

6 - 18

0

20

40

60

80

100

120

140

Basin Los

Angeles

Orange Riverside San

Bernardino

Hours

1987 2000 Control

FIGURE 6-5

Per-Capita Ozone Exposure Above the State Standard by County

1994 1997 2000

Percent Reduction

CAA Requirements REHEX

0

20

40

60

80

100

*1997 Exposure based on actual 1995 data (which met the standard).

FIGURE 6-6

Percent Reductions in Annual Average Per-Capita Exposure to Carbon Monoxide
Chapter 6 Federal and State Clean Air Act Requirements

6 - 19

Nitrogen Dioxide

As discussed earlier, the 1-hour NO2 standard was met in 1994 and 1995. In addition, 

the NOx reductions from existing District and ARB rules assure that the NO2 standards 

will continue to be met (see Chapter 5). Therefore, since 1994 and projected into the 

future the Basin’s population will not be exposed to unhealthful levels of NO2. The 

CCAA exposure goals have been satisfied through the District’s AQMP.

Cost Effectiveness Ranking

The CCAA requires the District Governing Board to determine that the AQMP is a costeffective strategy that will achieve attainment of the state standards by the earliest 

practicable date [H&SC 40913(b)]. In addition, the Plan must include an assessment of 

the cost-effectiveness of available and proposed measures and a list of the measures 

ranked from the least cost-effective to the most cost-effective [H&SC 40922].

Table 6-5 and Table 6-6 provide a listing of the short- and intermediate-term measures 

that have available cost information for stationary and mobile source measures, 

respectively. The cost-effectiveness for stationary source measures ranges from under 

$100 to as high as $12,300 per ton of pollutant reduced. Two methods are used to 

calculate the cost-effectiveness of the mobile source measures. The ARB transmitted the 

cost-effectiveness values for the mobile source measures based on incremental cost 

analyses, published reports and other internal methods. However, the District uses the 

Discount Cash Flow method in its calculations. The District has been using the Discount 

Cash Flow method since the 1987 AQMP. The Discount Cash Flow method is more 

versatile in analyzing complex financial cash flows and is the most widely used cost 

methodology by major businesses. In order to be consistent with the stationary source 

method, the District recalculated the mobile source cost-effectiveness values. Both sets 

of cost-effectiveness estimates are provided for consistency with ARB reported values. 

The proposed implementation schedule for these measures is provided in Chapter 7 and 

is based on this information and other relevant factors.
FINAL 1997 AQMP

6 - 20

TABLE 6-5

Cost-Effectiveness Ranking of Stationary Source Control Measures1

Measure 

Number

Description Dollars/Ton

(1996 dollars)

Ranking by

Cost Effectiveness*

Stationary Source Measures

CTS-02N Further Emission Reductions from Solvent 

Degreaser (R1122) (Formerly Part of 

ADV-CT1)

< $100 1

BCM-01 Emissions Reductions from Paved Roads 

(R403)

< $100 2

BCM-04 Emission Reductions from Agriculture 

Activities (R403)

$170 3

BCM-06 Further Emission Reductions from Fugitive 

Dust Sources to meet BACM Requirements 

(R403)

$240 4

BCM-03 Further Emission Reductions from 

Unpaved Roads

$630 5

CMB-06 Emission Reductions from Commercial and 

Residential Water Heaters (NOx)

$660 6

CTS-02O Further Emission Reductions from Usage 

of Solvents (R442) (Formerly Part of ADVC T1)

$2,470 7

PRC-03 Emission Reductions from Restaurant 

Operations

$3,700 8

CTS-02H Further Emission Reductions on Metal 

Parts and Products (R1107)

$4,560 9

CMB-02B Control of Emissions from Small Boiler 

and Process Heater

$4,650 10

CTS-02M Further Emissions Reductions from Plastic, 

Rubber, and Glass Coatings (R1145) 

(Formerly Part of ADV-CT1)

$4,850 11

CTS-02E Further Emission Reductions from 

Adhesives (R1168)

$6,850 12

PRC-01 Emission Reductions from Woodworking 

Operations (PM10)

$8,160 13

CTS-07 Further Emission Reductions from 

Architectural Coatings (R1113)

$12,270 14

* The cost-effectiveness values of these measures are based on the discounted cashflow methodology and 4 

percent real interest rate.

1 CP-02: Consumer products has a cost-effective value of $2100/ton calculated by ARB. However, a different 

methodology is used by ARB; therefore, it can not be ranked with other control measures.
Chapter 6 Federal and State Clean Air Act Requirements

6 - 21

TABLE 6-6

Cost-effectiveness Ranking of Mobile Source Control Measures

Measure Description District* ARB**

Number $/Ton Ranking $/Ton Ranking

Mobile Source Measures

M-16 Pleasure Craft; Nationwide Emission 

Standards

$120 1 $120 1

M-11 Industrial Equipment, Gas & LPG -

CA; Three-Way Catalyst Technology 

(ARB)

$410 2 $410 2

M-12 Industial Equipment, Gas & LPG -

CA; Three-Way Catalyst Technology 

(U.S. EPA)

$430 3 $440 3

M-15 Aircraft; Nationwide Emission 

Standards

*** $2,080 4

ADV-M-9 Off-Road 2.5g/bhp NOx Standard $2,430 6 $2,370 5

M-10 Off-Road Diesel Equipment; 

2.5g/bhp-hr NOx Standard - National

$1,190 5 $2,370 6

M-13 Marine Vessels; Nationwide 

Standards, New and Rebuilt

*** $2,570 7

ADV-M-2 Enhanced LEV $640 4 $2,600 8

M-14 Locomotives; Nationwide Standards, 

New and Rebuilt

*** $3,120 9

M-05 Heavy-Duty Diesel Vehicle; 

additional NOx Reductions in CA

$3,120 7 $3,330 10

M-06 Heavy-Duty Diesel Vehicle; 2g/bhphr NOx Standard - National$3,120 8 $3,330 11

M-07 Accelerated Retirement of HDVs $4,840 9 $6,550 12

M-04 Heavy-Duty Diesel Vehicle; 2g/bhphr NOx Engines$8,990 11 $8,990 13

M-01 Accelerated Retirement of LDVs $5,500 10 $12,480 14

* District methodology for calculating cost-effectiveness is based on discounted cashflow methodology and 4 

percent real interest rate.

** Cost-effectiveness calculated by ARB.

*** Insufficient data to calculate based on discounted cashflow methodology.