April 26, 2007 11 

1. BACKGROUND 

General SIP Requirements

California’s 2007 State Implementation Plans (SIPs) are a combination of State 

and local air quality planning documents that must show how California will meet 

federal the 8-hour ozone standard statewide. The San Joaquin Valley, South 

Coast Air Basin, Sacramento region, San Diego, Ventura, and a number of air 

districts downwind of urban areas are nonattainment for the ozone standard. 

Ozone SIPs must be submitted to U.S. EPA by June 15, 2007. 

This document is the State’s emission reduction strategy for sources of pollution 

under State and federal authority (State Strategy), and, for every local region not 

meeting federal standards, a demonstration of how attainment of the 8-hour 

ozone standard will be achieved. 

In addition to ozone SIPs, the South Coast and San Joaquin Valley must prepare 

PM2.5 SIPs for submittal to U.S. EPA by April 5, 2008. For the South Coast Air 

Basin, the South Coast Air Quality Management District is developing a PM2.5 

SIP in parallel with the ozone SIP. The San Joaquin Valley PM2.5 SIP in on 

track to be submitted in 2008. 

The 2007/2008 ozone and PM2.5 SIPs are another step in the air quality 

planning process that over the years has helped define new actions to improve 

California’s air quality. ARB has adopted a series of regulations over the past 10 

years to implement measures in the 1994 ozone SIP, as well as additional new 

ARB measures identified in the 2003 SIP update. New mobile source 

regulations, reformulated gasoline, and multiple consumer products regulations 

envisioned in these SIPs have been adopted and are being implemented today. 

And, while California has serious air quality challenges ahead, it is important to 

recognize the progress made as a result of California’s landmark air pollution 

control programs. With that experience and history of success, we need to 

continue to do more. ARB staff recognizes the importance of the new State 

measures and are proposing a full slate of new measures for development and 

consideration by the Board. 
April 26, 2007 12 

National Air Quality Standards

The U.S. EPA adopts standards for ambient (outdoor) air pollutants designed to 

protect public health. Extensive studies on the health effects of air pollution 

worldwide have confirmed the importance of continuing to reduce people’s 

exposure to air pollution. U.S. EPA is required to review its air quality standards 

every five years. 

In July 1997, the federal government announced new national ambient air quality 

standards (NAAQS) for the pollutants ozone and particulate matter (PM). The 

new standards provide more protection from the harmful health effects of these 

pollutants. The ozone standard was revised to protect against longer pollutant 

exposure periods by requiring that ozone concentrations not exceed specified 

levels over an 8-hour period instead of a 1-hour period. A new particulate matter 

standard was added to protect against the smaller inhalable particles, less than 

two and a half microns in diameter (PM2.5). Air quality standards have become 

more stringent over time as new studies have shown adverse health effects at 

lower levels. The standards below are the current benchmark for federal SIP 

requirements. U.S. EPA is currently reviewing the adequacy of the current 

8-hour standard. And in December 2006, U.S. EPA adopted a more stringent 

24-hour PM2.5 standard of 35 micrograms per cubic meter. This will likely mean 

that several new areas will be required to prepare a plan to attain the newer 

standard. Initial State recommendations for nonattainment areas are due in late 

2007, with final nonattainment areas determined by U.S. EPA in early 2010. 

Plans for the revised 24-hour standard will be due in 2013, with attainment dates 

to be determined after U.S. EPA issues transition guidance. 

Ozone Standard PM 2.5 Standards 

How much more stringent is the 8-hour ozone standard than the 1-hour ozone 

standard? The two maps on the following page illustrate a dramatic difference in 

exceedance days (number of days that violated the standard) for the 1-hour 

standard versus the 8-hour standard in the South Coast air basin in 2005. While 

many areas of California continue to be in violation of federal air quality 

standards, real air quality progress has been made, as we will illustrate later. 

The clean air bar simply continues to be raised as we learn more about the 

health effects of air pollution. 

0.08 parts per million for 

8 hours, not to be exceeded, 

based on the fourth highest 

concentration averaged over 

three years. 

65 micrograms per cubic meter for 

24 hours, not to be exceeded, based 

on the 98th percentile concentration 

averaged over three years, and 

15 micrograms per cubic meter 

annual average (arithmetic mean) 

averaged over three years. 
April 26, 2007 13 

Comparison of 1-Hr Ozone Standard and 

More Stringent 8-Hr Ozone Standard 

in the South Coast Air Basin 
April 26, 2007 14 

Health Effects of Ozone and PM2.5 

 Ozone 

 

The formation and health impacts of ozone are very well studied. Ozone is a 

highly reactive gas that forms in the atmosphere through complex reactions 

between chemicals directly emitted from motor vehicles, industrial plants, 

consumer products and many other sources. It forms in greater quantities on 

hot, sunny, calm days making the summer season the key exposure period. 

Considerable research over the past 35 years has investigated how people 

respond to inhaling ozone. These studies have consistently shown that 

inhalation of ozone can lead to inflammation and irritation of the tissues lining the 

human airways. This causes the muscle cells in the airways to spasm and 

contract, thus reducing the amount of air that can be inhaled. Symptoms and 

responses to ozone exposure vary widely, even when the amount inhaled and 

length of exposure is the same. Typical symptoms include cough, chest 

tightness, and increased asthma symptoms. Ozone in sufficient doses can also 

increase the permeability (“leakiness”) of lung cells, making them more 

susceptible to damage from environmental toxins and infection. 

Medical studies of large populations have found that ozone exposure is 

associated with an increase in hospital admissions and emergency room visits, 

particularly for lung problems such as asthma and chronic obstructive pulmonary 

disease. Several studies have also associated ozone exposure with increased 

premature mortality in elderly people with chronic diseases of the lungs and 

circulatory system. 

People who exercise or work outdoors are at greater risk of experiencing adverse 

health effects from ozone exposure because they inhale more ozone. Current 

evidence has linked the onset of asthma to exposure to elevated levels of ozone 

in exercising children. Children and adolescents are at increased risk because 

they are more likely to spend time outdoors engaged in vigorous activities than 

adults and because they inhale more ozone per pound of body weight.

PM2.5 

Particulate matter (PM) air pollution is also well studied. Particulate matter 

pollution is a complex mixture that consists of dry solid fragments, solid cores 

with liquid coatings, and small droplets of liquid. PM can be directly emitted into 

the air in forms such as dust and soot. It can also be formed in the atmosphere 

from the reaction of various gases. Particulate matter is less than 10 microns in 

diameter (a micron is one-millionth of a meter) and is called PM10. Even smaller 

particles, those 2.5 microns or less in diameter, are called “fine particles” or 

PM2.5, and are the target of this SIP. PM2.5 is a component of PM10. 
April 26, 2007 15 

Extensive research has shown that PM can be inhaled into the deep portions of 

the lungs. Some inhaled particles are exhaled again, but others deposit in the 

lungs, which can lead to inflammation in both the lungs and the circulatory 

system. PM2.5 poses an increased health risk because it can penetrate deeper 

into the lungs and may also enter the bloodstream. 

Population-based studies in hundreds of cities around the world have 

demonstrated a strong link between elevated particulate matter levels and 

premature death in people with pre-existing heart or lung disease. The two most 

important of these studies were performed in many cities in the United States, 

and have been ongoing for over 15 years. Both of these studies found a strong 

relationship between long-term PM exposure and premature death. 

Scientists have observed higher rates of hospitalization, emergency room visits 

and doctor’s visits for respiratory illnesses or heart disease during times of high 

PM concentrations. During these periods of high PM levels, scientists also 

observed the worsening of both asthma symptoms and acute and chronic 

bronchitis, and reductions in various measures of lung function. 

The elderly and people with heart and/or lung diseases are particularly at risk of 

experiencing adverse effects from PM exposure. Studies have also shown that 

children may be particularly vulnerable to PM effects. There is evidence from the 

10-year Children’s Health Study funded by the ARB that in communities with high 

levels of PM children's lungs develop more slowly and that at maturity they tend 

to have lower lung capacity than children who grow up in communities with lower 

levels of PM. Just as with ozone, children and infants may also be more at risk 

of experiencing adverse effects from PM because they inhale more air per pound 

of body weight than do adults, they breathe faster, and have smaller body sizes. 

In addition, there is some evidence that children's immature immune systems 

may cause them to be more susceptible to PM than adults. 

Nonattainment Areas and Air Quality Trends 

Geographic areas that exceed a federal air quality standard are called 

nonattainment areas. A comprehensive network of monitoring stations 

throughout California measures air quality and provides the data necessary to 

determine whether an area meets or exceeds federal ozone and PM2.5 air 

quality standards.1

Compliance with the federal ozone and PM2.5 standards is based on pollutant 

concentrations, measured at a comprehensive network of monitoring stations 

throughout California, averaged over three years. These three-year averages 

are called design values. Air quality monitoring in the years 2001 through 2003 

 

1

 More about California’s air quality monitoring network can be found on ARB’s website at: 

http://www.arb.ca.gov/aaqm/aaqm.htm
April 26, 2007 16 

was used by U.S. EPA to designate 15 areas in California as nonattainment for 

the federal 8-hour ozone standard. The San Joaquin Valley and South Coast Air 

Basin are also nonattainment for PM2.5. 

Federal 8-Hour Ozone 

Nonattainment Areas in California

Sacramento Metro Area

San Francisco 

Bay Area

San Joaquin Valley*

Antelope Valley and

Western Mojave Desert

Imperial

San Diego

South Coast Air Basin*

Ventura

Coachella Valley

Eastern Kern

Western Nevada

Central Mountain Counties

Southern Mountain Counties

Sutter Buttes

Butte County

* Also PM2.5 Nonattainment

A specific year’s design value is averaged over three years. For example, the 

design value for the year 2001 reflects the averages for the years 1999, 2000, 

and 2001. Ozone design values are an average of the fourth highest 

concentrations for each of the last three years. Design values for the PM2.5 

annual average reflect annual average (arithmetic mean) concentrations 

averaged over the last three years. The PM2.5 24-hour design values reflect the 

98th percentile concentrations averaged over the last three years. 

For the ozone standard, areas are classified based on the severity of the 

problem. In descending order in terms of magnitude of the problem, the 

classifications are extreme, severe, serious, moderate, and marginal. The Clean 

Air Act provides more time to meet the standard based on the severity of the 

problem. Based on its classification an area is given an attainment deadline. A 

special designation, called basic, refers to nonattainment areas governed under 

a separate set of requirements in the Clean Air Act. For PM2.5, U.S. EPA simply 

designated the South Coast and San Joaquin Valley as nonattainment without 
April 26, 2007 17 

application of the classification scheme used for PM10. This results in an 

attainment deadline of 2015. 

Ozone Nonattainment 

Area 

Nonattainment 

Designation 

(Current / Anticipated) 

Attainment Year 

(Current / 

Anticipated) 

South Coast Air Basin Severe / Extreme 2021 / 2024 

San Joaquin Valley Serious / Extreme 2013 / 2024 

Coachella Valley Serious / Severe 2013 / 2019 

Sacramento Region Serious / Severe 2013 / 2019 

Antelope Valley and 

Western Mojave Desert 

Moderate / Severe 2010 / 2019 or 2021 

Ventura County Moderate / Serious 2010 / 2013 or 2019 

Imperial County Marginal 2007 

San Francisco Bay Area Marginal 2007 

The above table lists the marginal 

through extreme nonattainment areas 

for the federal 8-hour ozone standard, 

while the table to the right lists the 

areas with the special basic ozone 

nonattainment designation. The Clean 

Air Act allows changing of 

nonattainment designations and the 

extension of the attainment deadline if 

the State believes a change is needed 

after analyzing the nature of the ozone problem and challenges to meet the 

standard. So the above table includes the current attainment designations, as 

well as designation changes that may be needed based on regional analyses. 

For this set of SIPs, U.S. EPA has provided guidance on how to interpret the 

attainment deadline as it relates to attainment demonstrations. The question 

arises because the deadlines are mid-year. The ozone attainment deadline is 

June 15 and the PM2.5 deadline is April 5 of the attainment year. To address the 

issue, U.S. EPA guidance calls for the analysis of attainment to be done for the 

year prior to the actual attainment year. So in this document we will be showing 

emission reduction targets and emissions for the year prior to the attainment 

year. For example, if the attainment year is 2024, we will be showing emission 

reduction targets and emissions for the year 2023. 

Ozone Trends 

A snapshot of four ozone nonattainment areas on the next page shows ozone 

levels (design values) relative to the federal standard and number of days over 

the standard since 1990. The ozone levels chart gives a sense of recent 

progress toward meeting the standard as well as how far we still have to go. The 

San Joaquin Valley and the South Coast have the most days exceeding the 

Basic Ozone Nonattainment Areas 

Attainment Year 2009-2014 

Butte County 

Central Mountain Counties 

Eastern Kern County 

San Diego County 

Southern Mountain Counties 

Sutter Buttes 

Western Nevada County 
April 26, 2007 18 

standard and the South Coast has the highest design values. In general, ozone 

trends show the greatest improvement in coastal areas like San Diego and 

Ventura.

Ozone Levels for 4 Nonattainment Areas

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

1990 1992 1994 1996 1998 2000 2002 2004

Ozone Levels (Design Value) 

(parts per million)

8-Hour Standard

VENTURA

SACRAMENTO

SOUTH COAST

SAN JOAQUIN VALLEY 

Days Over Standard: 4 Nonattainment Areas

0

20

40

60

80

100

120

140

160

180

200

1990 1992 1994 1996 1998 2000 2002 2004

Number of Days

VENTURA

SACRAMENTO

SAN JOAQUIN VALLEY 

SOUTH COAST

South Coast’s ozone concentrations have been cut by about a third since 1990, 

but the region’s design value is still 50 percent over the level of the standard and 

progress has slowed in recent years. Fifteen years ago, the highest values were 

widespread throughout the basin. Now, the number of communities within the 

basin experiencing the highest values is substantially smaller. The maps below 

show this progression of air quality progress. 
April 26, 2007 19 

Ozone Air Quality Comparison – South Coast 

1995 to 2005 
April 26, 2007 20 

PM2.5 Trends 

Both the South Coast and San Joaquin Valley are showing good progress toward 

PM2.5 attainment. As of 2005, both regions are meeting the 24-hour standard. 

In addition, annual average PM2.5 design values have declined by 25 percent 

since 2001. In terms of the remaining challenge, the South Coast levels are still 

about 50 percent above the standard, and the San Joaquin Valley levels are 

about 25 percent above the standard. 

24-hr Average PM2.5 Levels

South Coast

40

55

70

85

100

115

Design Values (ug/m3)

2001 2005 2001 2005

Federal 

Standard

San Joaquin Valley

Annual Average PM2.5 Levels

0

5

10

15

20

25

30

35

Design Values (ug/m3)

2001 2005 2001 2005

Federal 

Standard

South Coast San Joaquin Valley

Development of State Strategy

In developing our proposed statewide emission reduction strategy, ARB staff 

worked closely with air districts on attainment demonstrations for ozone for each 

area and on a PM2.5 attainment demonstration for the South Coast. In that 

process, emissions inventories are developed and air quality models are used to 

establish a region’s “carrying capacity” and to calculate the additional emission 

reductions needed for attainment. 

The emission reduction targets serve three purposes. First, they provide an 

indication of how far the existing control program will take each region toward 
April 26, 2007 21 

attainment and if additional reductions from new measures are needed. Second, 

they indicate how much time a region may need to reach the standards and if a 

classification change to a later attainment date is likely needed. And third, they 

provide a benchmark for designing new emission reduction measures. 

The magnitude of the attainment challenges in the South Coast and San Joaquin 

Valley, as shown in the next chapter, are the drivers for ARB staff’s proposed 

statewide strategy. The new SIP measures are also needed for the Sacramento 

region, the Coachella Valley, and the Antelope Valley and Western Mojave 

Desert nonattainment area. California’s other ozone nonattainment areas, 

including San Diego and Ventura, are projected to attain by their assigned 

deadline based on the benefits of previously adopted SIP measures. 

Given the severity of the ozone problems in the South Coast and San Joaquin 

Valley, both regions have indicated in their draft air quality plans that they will be 

requesting a reclassification to extreme with attainment deadlines of 2024. The 

2015 PM2.5 deadline and the South Coast PM2.5 carrying capacity framed 

staff’s analysis of new near-term measures. The other key driver for developing 

new SIP strategies is to reach ozone attainment in both regions as quickly as 

possible. 

Chapter 2 will summarize the process of determining the emission reduction 

targets and show those targets for the South Coast and San Joaquin Valley. The 

process consists of developing an emissions inventory and performing data 

analyses and air quality modeling based on that inventory to establish the 

emissions limits that ensure air quality standards are met. 

Air Pollution Transport

Air pollution transport, by definition is quite simple – air movements carry 

pollutants from one area to another. In reality, air pollution transport is a very 

complex phenomenon. It is three-dimensional and can occur at ground level or 

aloft in upper air levels. With modeling for the State being split into two modeling 

domains – one for Northern and Central California and one for Southern 

California – transport relationships between air districts within these large 

domains are implicitly captured within the models. This is the mechanism ARB 

uses in its oversight role to ensure transport impacts on downwind areas are 

addressed for purposes of both State and federal air quality standards. In terms 

of attainment demonstrations, inputs to the modeling for a downwind area include 

forecasted emission reductions in upwind areas. This way the attainment 

demonstration takes into account the shared responsibility for reducing 

emissions in regions where air pollution transport can at times be significant. 
April 26, 2007 22 

Other Programs 

In addition to SIPs, ARB has multiple plans and programs to reduce air pollution 

throughout California. Emission reduction strategies from many of these 

programs are taken into account in the ozone and PM2.5 SIPs. 

ARB Goods Movement Plan 

The Emission Reduction Plan for Ports and Goods Movement in California, 

approved by ARB in April 2006, is one of the main contributors of new measures 

necessary to meet federal air quality standards. Most goods that move within 

and through California do so by truck. Ships are the largest source of SOx 

emissions in the State. Heavy-duty trucks are the largest statewide source of 

NOx emissions. These air pollution realities make it impossible to tackle the 

PM2.5 challenge without addressing goods movement emissions. Likewise, 

emission reduction targets for ozone will not be met without reducing emissions 

related to goods movement. 

The strategies included in the goods movement emission reduction plan target 

ships and trucks, as well as the other three main sources of goods movement 

emissions: harbor craft, cargo handling equipment, and locomotives. By 2020, 

these strategies will cut statewide goods movement emissions of NOx by 63 

percent, SOx emissions by 78 percent, and will also reduce the statewide health 

risk from goods movement-related diesel particulate matter 85 percent. 

Work on many of the strategies in the goods movement emission reduction plan 

is underway and serves as the starting point for near-term actions to meet the 

emission reduction targets for the SIPs. These strategies will provide essential 

new emission reductions needed for regional attainment, while they reduce the 

air pollution-related health risk for those who live near our ports, railyards, 

distribution centers, and other goods movement facilities. 

ARB Diesel Risk Reduction Plan 

An important source of directly emitted PM2.5 is diesel exhaust. The particulate 

matter from diesel-fueled engines (diesel PM) has been singled out as a 

particularly harmful pollutant and identified as a toxic air contaminant by the Air 

Resources Board in 1998. Nearly 70 percent of the known cancer risk caused by 

air toxics is attributed to diesel PM. In 2000, ARB adopted a plan to reduce 

diesel PM emissions 85 percent by 2020, and has since adopted a number of 

regulatory measures to reduce diesel PM emissions statewide. Additional 

measures are under development. Diesel PM control measures in the plan are 

reducing both direct diesel PM and NOx emissions through a combination of 

engine retrofits and replacements. Upcoming mobile source fleet measures to 

reduce diesel PM and NOx emissions are a critical part of the new SIP strategy 

as well the Diesel Risk Reduction Plan. 
April 26, 2007 23 

Environmental Justice 

The SIPs consist of strategies designed to bring a region’s air quality into 

compliance with federal standards. SIPs must be designed to ensure air quality 

standards throughout the entire region, so achieving air quality standards 

provides public health benefits to every community. This makes SIP 

implementation important to meeting ARB’s community health and environmental 

justice goals. As part of our environmental justice program, ARB has initiated air 

quality studies in several communities and continues to focus resources on 

mobile source enforcement in environmental justice communities. ARB’s Air 

Quality and Land Use Handbook, approved by ARB in May 2005, provides 

guidance to help improve local land use decisions that can negatively impact 

public health at the community level. 

ARB’s SIP strategies have a significant nexus to community health due to the 

emphasis on cleaning up the legacy fleets of diesel engines. Much of the large 

equipment and vehicles that help construct our buildings and highways and move 

our goods are not well controlled and have very long lives. Adopting rules to 

clean up these fleets will have an immediate and significant effect on the 

communities where these sources are concentrated. 

Regional Haze 

The same particulate air pollutants that affect public health also extinguish and 

scatter light, thereby obscuring visibility. The federal Clean Air Act set the farreaching goal of achieving natural visibility conditions by 2064 in the nation’s 

most treasured parks and wilderness areas. Of the 156 designated areas, 29 are 

in California, managed by the National Park Service and the U.S. Forest Service. 

Therefore California is working in concert with fourteen other western states to 

reduce controllable emissions of particulates so that regional haze is reduced in 

the western region of the country. In 1999, the U.S. Environmental Protection 

Agency published rules to guide the preparation of Regional Haze State 

Implementation Plans to reduce regional haze. 

ARB is currently preparing the first regional haze plan for the entire State, for 

transmittal to EPA by the December 17, 2007 deadline. General trends in 

California since the 1990s show that emission controls are improving visibility in 

our parks and wilderness areas. The regional haze plan will show how these 

controls constitute reasonable progress along the path to natural visibility. In 

2012, ARB will conduct a mid-course review of measured visibility changes and 

analyze how emission reductions implemented to achieve the 8-hour ozone and 

the PM2.5 standards will move the State further along the path to natural visibility 

in the future. 
April 26, 2007 24 

Climate Change 

ARB’s implementation of the Global Warming Solutions Act of 2006 (AB 32) is a 

major new effort just underway. These activities, including future rulemaking, will 

occur on a parallel but separate track as we proceed with implementation of our 

SIP strategies. The statutory requirements and timelines are different, so it is not 

appropriate to include potential co-benefits of greenhouse gas strategies in SIP 

documents at this point. However, as greenhouse gas reduction measures are 

developed and adopted, ARB staff will do the necessary technical work to 

determine the impact on ozone and PM2.5 precursor pollutants. 
April 26, 2007 25 

2. TECHNICAL FOUNDATION 

Emissions Inventory Overview

Developing attainment strategies requires an understanding of the sources of 

pollution, the quantities emitted, their geographical distribution, and how air 

pollution controls and growth will impact future emission levels. There are 

multiple types of emission inventories used in air quality programs including 

annual averages, seasonal, and day-specific modeling inventories. SIPs rely on 

region specific inventories that may differ from the statewide picture. In the 

regulatory development process emission inventories are typically refined since 

inventory data is a key input for cost-effectiveness evaluations. This is an 

important inventory improvement mechanism, and ARB staff incorporates these 

updates into the statewide inventory. 

The emissions inventory serves three principal roles in the SIP process: 

• It provides a primary input to the modeling necessary to determine the 

emission reductions needed for attainment; 

• It supplies comprehensive emissions information for the development of 

emission reduction strategies; 

• And after the SIP is approved, it is used to track progress of the emission 

reduction commitments outlined in the plan. 

California is a diverse State with many sources of air pollution. ARB, in 

cooperation with local air districts, maintains a statewide emissions inventory. 

The inventory is constructed based on four major emission categories: 

• Stationary Sources -- generally industrial facilities, which can be 

identified by a name and location. 

• Areawide Sources -- either small individual sources, such as 

residential fireplaces, or widely distributed sources that cannot be tied 

to a single location, such as consumer products and dust from 

unpaved roads. 

• On-Road Mobile Sources -- includes on-road cars, trucks, buses, etc. 

• Off-Road Mobile Sources -- includes off-road vehicles such as boats, 

off-road recreational vehicles, aircraft, trains, ships, industrial and 

construction equipment, farm equipment, and other equipment. 

The statewide emissions inventory developed by ARB and the local air districts 

includes all the main sources of emissions – all of the many on-road and off-road 

mobile sources and all the various stationary and areawide sources. Estimating 

the amount of emissions statewide and in each region is done by summing the 

emissions from each source. The statewide inventory for the 2007 SIP 

development uses ARB’s November 2006 on-road motor vehicle model (EMFAC) 

and ARB’s off-road mobile source model. Stationary source emissions are 
April 26, 2007 26 

provided by local air districts. The regional SIP inventories are discussed in 

Chapter 5, Regional SIP Summaries. 

Precursor Pollutants 

Air pollutants that react to form ozone and PM2.5 in the air are called precursor 

pollutants. For ozone, the main precursor pollutants are nitrogen oxides (NOx) 

and reactive organic gases (ROG). There are four main precursors of PM2.5: 

NOx, ROG, sulfur oxides (SOx) and ammonia (NH3). PM2.5 can also be directly 

emitted into the atmosphere (direct PM2.5) in various forms that include smoke 

from fires, dust from paved and unpaved roads, and particle emissions from the 

burning of fossil fuels. 

PM2.5 pollution is a complex mixture and air quality modeling is used to assess 

the relative effectiveness of reducing each precursor pollutant as well as directly 

emitted PM2.5. Current data analysis and air quality modeling indicates that two 

of the four precursors, NOx and SOx, are significant in reducing PM2.5 

concentrations in the South Coast, and that the PM2.5 emission control strategy 

would be served best by focusing on reducing emissions of these two precursor 

pollutants. There is also a small PM2.5 benefit from ROG emission reductions, 

but benefits from ammonia emission reductions were found to be insignificant. 

Reducing direct PM2.5 is also an effective strategy according to recent modeling. 

NOx. Nitrogen oxide emissions are produced by the combustion of fuels in 

engines, furnaces, or fires. Today mobile sources make up about 85 percent of 

the total statewide NOx emissions. This percentage decreases over time as 

motor vehicle fleets become cleaner. Emissions from less clean sources like 

locomotives, ships, and aircraft continue to grow. Stationary sources of NOx 

include combustion processes in industries such as manufacturing, food 

processing, electric utilities, and petroleum refining. Areawide sources of NOx, 

which include waste burning and residential fuel combustion, contribute a smaller 

portion of total NOx emissions. Air quality science indicates that reductions of 

NOx are more beneficial than reductions of other pollutants to help meet both 

ozone and PM2.5 standards, and therefore NOx is a major focus of the State 

Strategy. 

ROG. Reactive organic gases result primarily from incomplete fuel combustion 

and the evaporation of chemical solvents and fuels. Stationary sources of ROG 

include processes that use solvents such as dry cleaning, degreasing, and 

coating operations. Today mobile sources are the largest ROG emissions 

category. However, other ROG categories become relatively more important 

over time. Areawide ROG sources which grow directly with population begin to 

dominate in the future so that by 2020 consumer products is the largest source 

category. 
April 26, 2007 27 

SOx. Sulfur oxide emissions are dominated by the mobile source category of 

ships and commercial boats. Evaporative losses from petroleum refining (a 

stationary source) are another significant source of SOx. The other sources that 

make up 5 percent or more of the SOx inventory are locomotives and mining and 

cement manufacturing. 

Direct PM2.5. Directly emitted PM2.5 comes mainly in the form of smoke, soot, 

and dust particles. Major sources include managed burning and agricultural 

burning; dust generated by vehicles traveling on paved and unpaved roads, 

residential fireplaces, cooking and fuel combustion; and particle emissions from 

diesel-fueled engines on trucks, ships, and construction equipment. While soot 

from diesel engines is not a major portion of the entire direct PM2.5 emissions 

inventory, it is a major health concern, as it is a toxic air contaminant that can 

cause premature death. 

Forecasting Future Emissions

Estimates of projected future emissions depend on two independent variables: 

growth and control. Different methods are used to estimate the future growth of 

emission sources based on their type. And future emission controls are 

incorporated into the projected emissions for each source category based on 

when the controls are implemented, how much the controls reduce emissions, 

and how many units (vehicles, consumer products, etc.) are affected. 

The charts on the next page show the change in total projected statewide 

emissions for NOx, ROG, and SOx from 2006 to 2023 and the relative emissions 

change in each of these emission source categories. They reflect projected 

growth in each category combined with the benefits of the existing control 

program (those emission controls adopted prior to 2007). For example, SOx 

emissions as a category continue to grow due to ship emission increases. This 

makes ship SOx emissions a high priority for control in the new SIP strategy. 

NOx and ROG emissions are decreasing as a result of existing control programs 

despite substantial growth in population, travel, and the economy. 

ARB uses two computer models to simulate and forecast emissions for on- and 

off-road sources. For cars, sport utility vehicles, minivans, and trucks, ARB used 

EMFAC2007. For off-road vehicles and equipment, ARB used OFFROAD2007. 

Both models were released for public use in November 2006 after a multi-year 

development process. As required by federal guidance, EMFAC2007 uses the 

latest fleet information for vehicles age and population. The data is developed 

from the California Department of Motor Vehicle registration data through 2005. 

For SIP purposes, as required by State law, vehicle activity is based on local 

transportation agency projections, or California Department of Transportation 

data, if local data are not available. 
April 26, 2007 28 

NOx Emission Forecast 2006-2023

0

500

1000

1500

2000

2500

3000

3500

4000

2006 2014 2023

Statewide tons per day

On-Road

Off-Road

Stationary

Areawide

ROG Emission Forecast 2006-2023

0

500

1000

1500

2000

2500

3000

2006 2014 2023

Statewide tons per day

On-Road

Off-Road

Stationary

Areawide

 Note: “Off-Road” includes trains, planes, and ships, as well as all other off-road vehicles 

and equipment. 

SOx Emission Forecast 2006-2023

0

50

100

150

200

250

300

350

400

450

500

2006 2014 2023

Statewide tons per day

Ships

Stationary

All Other

Top Emission Sources

While the top emission categories are mobile sources in all California’s 

nonattainment areas, there is variability in the relative contribution of different 

sources by region. This makes the overall statewide emission reduction strategy 

more challenging and will affect the priorities of local control plans. For example, 

controlling the emissions from ocean-going vessels will have a tremendous 

impact on SOx emissions in the South Coast and therefore is essential to that 

region’s PM2.5 control plan. Reducing SOx from ships has much less 

consequence in the San Joaquin Valley, so increased NOx reductions from 

combustion sources will become even more important for the Valley’s PM2.5 

control strategy. The tables on the next two pages show the top emission 

sources of both NOx and ROG in the South Coast and the San Joaquin Valley. 
April 26, 2007 29 

Here are some things we have learned by analyzing the emissions inventory for 

these two areas: 

• South Coast NOx emissions are significantly impacted by goods movement, 

with the ships, trains, trucks, and off-road equipment that move goods 

contributing about 30 percent of all South Coast NOx emissions. Aircraft NOx 

emissions are also increasing. 

• The impact of goods movement in the San Joaquin Valley is felt mostly by the 

emissions contribution of heavy-duty trucks, which are projected to remain the 

largest NOx emitter through 2023. 

• Emissions of NOx from manufacturing and industrial sources in the San 

Joaquin Valley become increasingly significant as emissions from mobile 

sources decline in the future. 

• The large population in the South Coast is the main reason why consumer 

product emissions are projected to become the number one ROG emissions 

source by 2014. 

• San Joaquin Valley ROG emissions are significantly impacted by agricultural 

sources such as livestock waste. 

• The existing emission control program will cut heavy-duty truck NOx 

emissions about 70 percent in the San Joaquin Valley and South Coast by 

2023, but they need to be cut even more by new strategies to attain ozone 

and PM2.5 standards. 

• Mobile sources under federal and international jurisdiction (like ships, 

locomotives, and aircraft) contribute an increasingly greater proportion of total 

emissions, especially NOx, in future years as emission increases due to 

growth overwhelm the existing control program, while emissions of mobile 

sources under State jurisdiction decrease due to stringent controls. 
April 26, 2007 30 

South Coast Air Basin – Top Sources of NOx 

Summer emissions, tons per day 

Source Category 2006 2014 2023 

HEAVY DUTY DIESEL TRUCKS 259 140 73 

PASSENGER VEHICLES 204 101 53 

OFF-ROAD EQUIPMENT (CONSTRUCTION AND MINING) 120 81 41 

OFF-ROAD EQUIPMENT (COMMERCIAL, INDUSTRIAL) 87 53 35 

SHIPS AND COMMERCIAL BOATS 75 87 116 

GASOLINE-FUELED COMMERCIAL TRUCKS 36 24 17 

LOCOMOTIVES 31 23 28 

RESIDENTIAL FUEL COMBUSTION 18 16 14 

MANUFACTURING & INDUSTRIAL (BOILERS, ENGINES) 17 15 15 

SERVICE AND COMMERCIAL (BOILERS, ENGINES) 16 12 11 

RECREATIONAL BOATS 16 17 18 

AIRCRAFT 16 22 29 

TOTAL OF TOP CATEGORIES 896 589 450 

TOTAL 971 650 505 

TOP CATEGORIES PERCENT OF TOTAL 92% 91% 89% 

San Joaquin Valley – Top Sources of NOx 

Summer emissions, tons per day 

Source Category 2006 2014 2023 

HEAVY DUTY DIESEL TRUCKS 285 155 75 

FARM EQUIPMENT (COMBINES AND TRACTORS) 60 37 17 

PASSENGER VEHICLES 58 31 16 

MANUFACTURING & INDUSTRIAL (BOILERS, ENGINES) 39 44 48 

OFF-ROAD EQUIPMENT (CONSTRUCTION AND MINING) 34 22 12 

OFF-ROAD EQUIPMENT (COMMERCIAL, INDUSTRIAL) 34 23 15 

LOCOMOTIVES 22 21 22 

AGRICULTURAL IRRIGATION PUMPS 16 7 5 

OIL AND GAS PRODUCTION (COMBUSTION) 11 10 10 

COGENERATION (ELECTRICITY GENERATION AND 

HEAT RECOVERY) 9 7 8 

GASOLINE-FUELED COMMERCIAL TRUCKS 9 7 6 

FOOD AND AGRICULTURE (CROP PROCESSING AND 

WINERIES) 9 9 9 

GLASS AND RELATED PRODUCTS 8 9 11 

TOTAL OF TOP CATEGORIES 595 381 253 

TOTAL 650 425 300 

TOP CATEGORIES PERCENT OF TOTAL 92% 90% 84% 

 Note: Emissions do not include impact of State Strategy proposed new measures. 
April 26, 2007 31 

South Coast Air Basin – Top Sources of ROG 

Summer emissions, tons per day 

Source Category 2006 2014 2023 

PASSENGER VEHICLES 207 112 76 

CONSUMER PRODUCTS 101 103 110 

RECREATIONAL BOATS 64 53 51 

OFF-ROAD EQUIPMENT (LAWN AND GARDEN) 52 40 38 

ARCHITECTURAL COATINGS (PAINTS AND THINNERS) 31 29 31 

OFF-ROAD EQUIPMENT (COMMERCIAL, INDUSTRIAL) 28 15 12 

PETROLEUM MARKETING (GASOLINE EVAPORATIVE 

LOSSES) 27 28 31 

COATINGS (PAINTS AND THINNERS - NON 

ARCHITECTURAL) 27 25 28 

GASOLINE-FUELED COMMERCIAL TRUCKS 24 13 8 

GAS CANS 21 10 7 

OFF-ROAD EQUIPMENT (CONSTRUCTION AND MINING) 20 12 8 

TOTAL OF TOP CATEGORIES 600 441 399 

TOTAL 732 567 534 

TOP CATEGORIES PERCENT OF TOTAL 82% 78% 75% 

San Joaquin Valley – Top Sources of ROG 

Summer emissions, tons per day 

Source Category 2006 2014 2023 

PASSENGER VEHICLES 62 37 24 

WASTE DISPOSAL/COMPOSTING 57 72 80 

LIVESTOCK WASTE (DAIRY CATTLE) 40 33 41 

OIL AND GAS PRODUCTION (EVAPORATIVE 

LOSSES/FLARING) 28 26 23 

CONSUMER PRODUCTS 24 26 30 

PESTICIDES 22 20 20 

HEAVY DUTY DIESEL TRUCKS 20 13 8 

RECREATIONAL BOATS 20 17 17 

FOOD AND AGRICULTURE (CROP PROCESSING AND 

WINERIES) 13 12 13 

ARCHITECTURAL COATINGS (PAINTS AND THINNERS) 11 12 13 

OFF-ROAD EQUIPMENT (COMMERCIAL, INDUSTRIAL) 10 6 4 

FARM EQUIPMENT (COMBINES AND TRACTORS) 10 5 3 

TOTAL OF TOP CATEGORIES 317 279 277 

TOTAL 452 410 414 

TOP CATEGORIES PERCENT OF TOTAL 70% 68% 67% 

 Note: Emissions do not include impact of State Strategy proposed new measures.
April 26, 2007 32 

Setting the Emission Reduction Targets

U.S. EPA rules require the use of air quality modeling to set emission reduction 

targets. Modeling is also helpful in guiding the selection of the most effective 

pollutants to control. To set ozone emission reduction targets, air quality 

modeling has been conducted separately for two overarching areas. One area is 

Northern and Central California, encompassing the San Joaquin and Sacramento 

Valleys, the Bay Area and the Sierra Nevada Mountains. ARB staff has been 

doing this modeling. The other area is Southern California, including the South 

Coast Air Basin, Ventura County, Imperial County, and the Mojave Desert area. 

The South Coast air district has been doing this modeling. The South Coast air 

district has also been performing the air quality modeling to set its PM2.5 target. 

 Weight of Evidence Analysis 

A Weight of Evidence analysis provides a set of complementary analyses that 

supplements the SIP-required modeling. These analyses can include 

consideration of measured air quality, emissions, and meteorological data, 

evaluation of other air quality indicators, and additional air quality modeling. A 

Weight of Evidence approach looks at the entirety of the information at hand to 

provide a more informed basis for the attainment strategy. While all analysis 

methods have inherent strengths and weaknesses, examining an air quality 

problem in a variety of ways increases the confidence one has in the results. 

This approach also provides a better understanding of the overall problem and 

the level and mix of emissions controls needed for attainment. 

The discussion in Chapter 4 about South Coast PM2.5 pollution is a weight of 

evidence approach. More detailed weight of evidence analysis will be included in 

ARB staff reports on the local air district plans and in the local plans themselves. 

South Coast Ozone Emission Reduction Targets 

Under State law the South Coast air district is responsible for setting carrying 

capacities for the South Coast Air Basin. While the carrying capacities result in 

large emission reduction targets for both NOx and ROG, the South Coast 

modeling indicates that NOx reductions are more effective at reducing ozone in 

the long run, although ROG reductions are still needed to maximize progress. In 

fact, the air district modified the South Coast Air Basin carrying capacity in its 

February 2007 draft air plan, relying even more heavily on NOx reductions than 

in its earlier estimates. 
April 26, 2007 33 

The emission reduction targets based on the February 2007 carrying capacities 

are presented below. 

Draft South Coast Ozone Emission Reduction Targets 

(tons per day) NOx ROG

2006 Emissions Inventory 972 732 

Carrying Capacity 114 420 

Emission Reduction Target 858 312 

It will be important to revisit the relative carrying capacities in subsequent SIPs to 

factor in inventory improvement, updated modeling, and control measure 

development. 

South Coast PM2.5 Emission Reduction Targets 

As discussed previously, unlike ozone, PM2.5 consists of many different 

components. These components can vary by location and season, with both 

local and regional scale contributions. This complexity and variability presents a 

unique challenge in modeling for attaining the annual standard, and introduces a 

higher level of uncertainty in the results. In addition, while there is a long history 

and body of experience for ozone model application, air quality modeling for 

PM2.5 is relatively more recent, and it has not been applied as extensively. ARB 

will continue to work with air districts on efforts to refine PM2.5 modeling 

techniques. 

Draft South Coast PM2.5 Emission Reduction Targets 

(tons per day) NOx ROG SOx Direct 

PM2.5 

2006 Emissions Inventory 972 732 63 101 

Carrying Capacity 443 469 19 88 

Emission Reduction Target 529 263 44 13 

San Joaquin Valley Emission Reduction Targets 

ARB staff has been using photochemical models for Northern and Central 

California developed as part of the multi-million dollar Central California Air 

Quality Study. This modeling continues to confirm that NOx is the key to long 

term attainment in the San Joaquin Valley. (This is also true for the Sacramento 

Valley and the rural regions downwind.) ROG looks beneficial especially in the 

near term for maximum progress and to supplement NOx reductions long term. 
April 26, 2007 34 

The ozone emission reduction targets for San Joaquin Valley are shown in the 

following table. The ROG carrying capacity is implicit, based on the much larger 

benefit of NOx reductions demonstrated by the modeling. 

San Joaquin Valley Ozone Emission Reduction Targets 

(tons per day) NOx ROG

2006 Emissions Inventory 650 454 

Carrying Capacity 160 342 

Emission Reduction Target 490 112 

San Joaquin Valley PM2.5 modeling is underway and carrying capacities and 

emission reduction targets will be developed later in 2007 for a PM2.5 plan that is 

due to U.S. EPA in April 2008. 
April 26, 2007 35 

3. ARB’s 2007 SIP STATE STRATEGY

The State Strategy maps out how to achieve the emission reductions necessary 

to meet federal air quality standards. The two main emission reduction 

components of the State Strategy are the adopted SIP measures and proposed 

new measures. The adopted SIP measures include those adopted through 

2006. Proposed new measures include those to be adopted after 2006. 

Responsibility for implementing emission reduction measures is shared between 

the agencies with primary responsibility for controlling air pollution in California: 

the Air Resources Board, 35 local air pollution control and air quality 

management districts, and the U.S. Environmental Protection Agency. However, 

given the current status of statewide emissions, ARB has the lion’s share of 

responsibility, followed by U.S. EPA. 

Agency Roles in SIP Measure Development

Local Measures 

Local air districts are primarily responsible for controlling emissions from 

stationary and areawide sources (with the exception of consumer products) 

through rules and permitting programs. Examples include industrial sources like 

factories, refineries, and power plants; commercial sources like gas stations, dry 

cleaners, and paint spray booth operations; residential sources like fireplaces, 

water heaters, and house paints; and miscellaneous non-mobile sources like 

emergency generators. Districts also inspect and test fuel vapor recovery 

systems to check that such systems are operating as certified. 

State Measures 

ARB is responsible for controlling emissions from mobile sources (except where 

federal law preempts ARB’s authority) and consumer products, developing fuel 

specifications, establishing gasoline vapor recovery standards and certifying 

vapor recovery systems, providing technical support to the districts, and 

overseeing local district compliance with State and federal law. The Department 

of Pesticide Regulation is responsible for control of agricultural, commercial and 

structural pesticides, while the Bureau of Automotive Repair runs the State’s 

Smog Check programs to identify and repair polluting cars. 

Federal Measures 

U.S. EPA has the authority to control emissions from mobile sources, including 

sources all or partly under exclusive federal jurisdiction (like interstate trucks, 

some farm and construction equipment, aircraft, marine vessels, and locomotives 

based in this country). U.S. EPA also has oversight authority for state air 

programs as they relate to the federal Clean Air Act. International organizations 

develop standards for aircraft and marine vessels that operate outside the U.S. 
April 26, 2007 36 

Federal agencies have the lead role in representing the U.S. in the process of 

developing international standards. 

Adopted SIP Measures

Many measures already adopted by local, State and federal agencies are 

currently reducing emissions. Many will do so at an accelerated rate in the 

future. Some adopted measures are scheduled to go into effect years hence. 

Adopted SIP measures will have a very significant impact on emissions and air 

quality between now and the target dates (attainment years) in the areas of the 

State that do not meet federal ozone and PM2.5 air quality standards. 

Adopted SIP measures have been developed over the years through the 

combined efforts of air pollution regulators – with a foundation of ARB’s mobile 

source and fuels programs, complementary national actions for pollution sources 

under federal authority, and local air district programs for industrial and 

commercial sources -- as well as transportation plans that integrate transit and 

other alternatives to solo vehicle travel. ARB has adopted 46 emission-reducing 

control measures since the approval of the 1994 1-hour ozone SIP. These 

measures, shown on the table on Page 38 entitled “Air Resources Board SIP 

Control Measures (1994-2006),” comprise the bulk of the benefits of the adopted 

measures. 

 Mobile Sources 

Cleaner Engines and Fuels

California has dramatically tightened emission standards for on-road and off-road 

mobile sources and the fuels that power them. The table below shows how 

significantly the adopted measures have controlled emissions from new engines 

for the major categories of mobile sources. 

California’s emission control program for on-road motor vehicles is the strongest 

in the world. New cars are now 99 percent cleaner than their uncontrolled 

counterparts. Trucks are now 90 percent cleaner, and will be 98 percent cleaner 

by 2010. 

Working in concert with the U.S. EPA, standards for goods movement sources 

have also been tightened dramatically. By requiring low-sulfur fuel, SOx 

emissions from ship auxiliary engines will be cut 96 percent by 2010. New 

locomotive engines are now 50-60 percent cleaner. Harbor craft emission 

standards were cut roughly in half. And new cargo handling equipment will be 95 

percent cleaner by 2011. 
April 26, 2007 37 

Impact of Existing Standards and Emission Limits 

Source Controlled

Since Level of Control* 

ON-ROAD 

Passenger Cars 1961 99% in 2006 (ROG + NOx) 

Trucks and Buses 1988 90% by 2007, 98% by 2010 (NOx) 

98% by 2007 (PM) 

Motorcycles 1975 88% by 2008 (ROG + NOx) 

GOODS MOVEMENT 

Ship Auxiliary Engines (fuel) 2000 96% (SOx), 83% (PM) by 2010 

Locomotives 1973 60% in 2005 (ROG+NOx) 

Harbor Craft 2004 50% in 2004 (NOx) 

Cargo Handling Equipment 2005 95% by 2011-2012 (ROG+NOx, PM) 

OFF-ROAD SOURCES 

Large Off-Road Equipment 1996 98% by 2015 (ROG + NOx) 

Personal Water Craft 1990 88% by 2010 (ROG) 

Recreational Boats 1990 89% by 2010 (ROG) 

Lawn & Garden Equipment 1990 82-90% by 2010 (ROG) 

AREAWIDE SOURCES 

Consumer Products 1989 50 categories controlled 50% (ROG)

* Level of emissions control compared to uncontrolled source. 

California has also drastically lowered standards for off-road sources, from lawn 

and garden equipment, to recreational vehicles and boats, to construction 

equipment and other large off-road sources. From 2010 through 2014, these 

new off-road sources will be manufactured with 80-98 percent fewer emissions 

than their uncontrolled counterparts. 

ARB has worked closely with U.S. EPA to regulate large diesel, gasoline and 

liquid petroleum gas equipment – where authority is split between California and 

the federal government – and by 2014, new large off-road equipment will be 98 

percent cleaner. ARB has also made great strides in reducing emissions from 

the smaller engines under State control, like those used in lawn mowers and jet 

skis, recreational vehicles and boats. From 2010 to 2015, these new off-road 

sources will be manufactured with 82-90 percent fewer emissions than their 

uncontrolled counterparts. 
April 26, 2007 38 

Air Resources Board SIP Control Measures (1994-2006) 

Air Resources Board Action Date Air Resources Board Action Date 

In-Use Diesel Agricultural 

Engine Requirements 

2006 California ZEV Requirement 

Update 

2003 

Consumer Product Lower 

Emission Limits 

2006 Heavy-Duty Gas Truck Emission 

Standards 

2002 

Zero Emission Bus Rule 

Amendments 

2006 Heavy-Duty Diesel Truck 

Emission Standards 

2001 

Off-Highway Recreational 

Vehicle Regulation Amendments

2006 Inboard and Sterndrive Marine 

Engine Emission Standards 

2001 

Forklifts and Other SparkIgnition Equipment Regulation 2006 Architectural Coatings Suggested 

Control Measure 

2000 

Border Truck Inspection 

Program Protocol Improvements 

2006 Urban Transit Bus Fleet Rule 2000 

Ship Auxiliary Engine Cleaner 

Fuel Requirements 

2005 Off-Road Diesel Equipment 

Emission Standards 

2000 

Diesel Cargo Handling 

Equipment Rule 

2005 Reformulated Gas MTBE Phase 

Out 

1999 

Public and Utility Diesel Truck 

Fleet Rule 

2005 Consumer Product Emission 

Limits 

1999 

Heavy-Duty Sleeper Truck Idling 

Limits 

2005 Portable Fuel Can Regulation 1999 

Portable Fuel Container 

Requirements 

2005 Marine Pleasurecraft Emission 

Standards 

1998 

Transit Bus Rule Additions Low-Emission Vehicle Program 

(LEV II) Exhaust Standards 

1998 

Off-Road Diesel Engine Tier 4 

Standards 

2004 Large Off-Road Gas/LPG Engine 

Emission Standards 

1998 

Harbor Craft and Locomotive 

Clean Diesel Fuel Requirement 

2004 Cleaner Burning Gasoline Rule 

Improvements 

1998 

Idling Limits for Trucks 2004 On-Road Heavy-Duty Truck 

Exhaust Emission Standards 

1998 

Consumer Products Rule 2004 Light-Duty Vehicle Off-Cycle 

Emission Controls 

1997 

Chip Reflash to Detect Truck 

Emission Control System Failure

2004 Consumer Product Emission 

Limits 

1997 

Transportation Refrigeration Unit 

Rule 

2004 Locomotive Memorandum of 

Agreement for the South Coast 

1997 

Portable Diesel Engine Emission 

Standards 

2004 Medium- and Heavy-Duty Gas 

Truck Emission Standards 

1995 

Stationary Diesel Engine 

Regulation 

2004 Aerosol Coatings Regulation 1995 

Solid Waste Collection Vehicle 

Regulation 

2003 Large Off-Road Diesel Statement 

of Principles 

1996 

Lawn and Garden Equipment 

Emission Standards 

2003 Medium- and Heavy-Duty 

Gasoline Trucks 

1995 

Low Sulfur Diesel Fuel 

Regulation 

2003 Off-Road Recreational Vehicles 

Regulation 

1994 
April 26, 2007 39 

The charts below clearly illustrate the benefits of adopted SIP measures to reduce 

emissions from mobile sources. The downward emission trends are dramatic given 

California’s projected growth in population, vehicle travel, and goods movement 

activities. But because on-road and off-road mobile sources together account for so 

much of the State's inventory of ozone and PM2.5 forming emissions, further 

reductions in mobile source emissions are essential if air quality standards are to be 

realized. 

 Passenger Vehicles 

Statewide

ROG+NOx (tpd)

0

300

600

900

1200

1500

2006 2014 2023

 Trucks

Statewide

 ROG+NOx (tpd)

0

300

600

900

1200

1500

2006 2014 2023

 Off-Road Equipment

Statewide 

 ROG+NOx (tpd)

0

300

600

900

1200

1500

2006 2014 2023

 Cleaning Up the Legacy Fleet

Adopted SIP measures have made significant strides in reducing emissions from 

those mobile sources already in use – the legacy fleet -- by keeping existing 

vehicles cleaner longer, getting cleaner technology on older vehicles and 

equipment, and replacing older dirtier vehicles and equipment with cleaner ones. 

Whereas new engine emissions have been regulated for a long time, most of the 

in-use control programs have just begun to evolve and have an impact. We still 

have a lot of work to do to clean up the legacy fleet. That is why the majority of 

new measures in the State Strategy are in-use measures. 

Many programs and rules are currently in place to reduce emissions from the 

mobile source legacy fleets. The Smog Check Program ensures that passenger 

vehicles stay clean as they age and on-board diagnostic systems identify smog 

control problems. Heavy-duty truck inspection programs help control smoke 

emissions and detect emission control malmaintenance and tampering. 

ARB has adopted 20 in-use regulations in the last five years. In-use regulations 

have required use of cleaner fuels, greatly reducing emissions from ships and 

harbor craft. Excessive truck and bus idling has been restricted. ARB has 

adopted public and private fleet rules that require local governments and private 

companies to incorporate the cleanest vehicles and equipment into their fleets. 

In-use testing procedures and verification requirements for in-use emission 

control technology have been strengthened. And other operational and emission 

control technology requirements that help reduce emissions from existing vehicle 

and equipment have been put into place. 
April 26, 2007 40 

Incentive programs have worked hand-in-hand with in-use regulations, providing 

added emissions benefits. California is currently investing up to $140 million per 

year to clean up older, higher-emitting sources through the Carl Moyer Program. 

The Smog Check Breathe Easier Campaign pays motorists $1,000 to 

permanently retire their high-polluting vehicles. And local governments use 

special vehicle registration fees to fund projects that further reduce emissions 

from motor vehicles. 

Consumer Products 

ARB has adopted standards to limit 

emissions from nearly 50 consumer product 

categories (such as hair sprays, deodorants, 

and cleaning compounds), as well as over 

35 architectural coatings and aerosol paints 

categories. The Board has adopted and 

implemented voluntary provisions to offer 

greater compliance flexibility to consumer 

product manufacturers while retaining the air quality benefits. Without these 

actions, ROG emissions from these products would be roughly 60 percent 

greater in 2010. But, as you can see from the above chart, the impact of 

population growth begins to counter the benefits of adopted measures – more 

controls are needed. 

Local Rules and Programs 

 Stationary and Area Sources

Local air districts are primarily responsible for controlling emissions from 

stationary and areawide sources, with the exception of consumer products, 

through regulations and permits. Stationary sources include industrial sources 

like factories and power plants, commercial sources like gas stations and dry 

cleaners, and residential sources such as fireplaces and water heaters. 

Areawide sources are diffuse sources of emissions that are spread over a wide 

area, such as paints and pesticides. 

Local air districts help reduce emissions through limits on emissions from new 

sources (the New Source Review program) and technology-based requirements 

for existing sources, called Best Available Retrofit Control Technology and 

Reasonably Available Control Technology requirements. Air districts adopt and 

enforce rules governing these sources of emissions. 

Businesses in California are subject to the most stringent air quality rules in the 

country. Local air districts have adopted a number of innovative rules and 

programs over the years to help reduce emissions. For example, South Coast’s 

innovative program, RECLAIM, provides market incentives for companies to use 

the cleanest possible technologies. And the San Joaquin Valley has adopted a 

Without ARB Program 

With ARB Program 

Consumer Product Emissions

200

250

300

350

400

450

1990 1995 2000 2005 2010

Tons per day ROG

Without ARB Program 

With ARB Program 
April 26, 2007 41 

first-of-its-kind indirect source rule that ensures that new developments bear their 

fair share of the pollution burden. ARB has suggested over 50 control strategies 

for stationary sources that many local air districts have adopted. 

The proposed local air district measures for each nonattainment area are listed, 

described, and quantified in the attainment plans for each area. The local 

measures, coupled with the State Strategy measures, must provide the 

necessary emission reductions to meet the federal standards. 

 Transportation and Land Use Planning

In California, local governments are responsible for transportation and land use 

planning, and transportation plans are an important part of the SIP. Federal law 

requires a metropolitan region’s transportation plan to be complementary to and 

conform with the region’s air quality plan. Transportation and land use strategies 

can help to reduce the rate of growth in vehicle travel and traffic congestion, 

which helps reduce the growth in vehicle emissions. All the major metropolitan 

regions in California have approved plans emphasizing land use strategies that 

complement their transit and transportation systems and bring more people 

closer to more destinations. These strategies will help curb emissions by 

reducing trip distances and increasing use of public transit, carpooling, walking, 

and biking. 

ARB’s Proposed New SIP Measures

If emission reductions from the adopted measures are not enough to attain the 

federal standards, sufficient emission reductions from new strategies must be 

achieved in order to meet the emission reduction target. 

ARB staff is proposing a comprehensive and far reaching set of new measures to 

achieve emission reductions needed to address California’s most challenging 

ozone and PM2.5 problems. These measures are designed to make maximum 

progress toward the federal 8-hour ozone standard in the South Coast and the 

San Joaquin Valley. The measures include aggressive near-term NOx and SOx 

emission reduction goals, reflecting the nature and scope of the PM2.5 problem 

in these regions. To achieve the emission reductions needed for both ozone and 

PM2.5, the State Strategy proposes new near-term actions that can be 

completed by 2010 or soon thereafter. 

 Focus of Proposed New Measures 

Mobile sources are the largest contributor to PM2.5 and ozone-forming 

emissions. Air quality science indicates that reductions of NOx are more 

beneficial than reductions of other pollutant precursors to help reduce levels of 

both ozone and PM2.5. The simple conclusion is that mobile source NOx 

reductions must be a main objective of the State Strategy. And since the State 

and federal government have almost exclusive authority over mobile source 
April 26, 2007 42 

emissions, they also have the bulk of the responsibility for implementing the 

State Strategy. 

Mobile sources currently produce about 90 percent of all NOx emissions in the 

South Coast. About 90 percent of mobile source NOx emissions are produced 

by five major sources – passenger vehicles, heavy-duty diesel trucks, large 

off-road equipment, and two goods movement-related sources -- ships, and 

locomotives. Reducing NOx emissions from these five major sources is 

therefore the key to meeting the objective of the State Strategy. 

More than any other pollution control effort, ARB’s mobile source program has 

moved the State’s nonattainment areas closer to meeting federal air quality 

standards. The majority of emission reductions from adopted SIP measures 

comes from emission standards for new on-road and off-road mobile sources 

and fuels. But as new engines have become cleaner and cleaner, the emissions 

contribution from older vehicles has been growing to the extent that it will soon 

make up the majority of mobile source emissions. For example, all on-road 

vehicles 14 years old or older will produce almost 60 percent of total on-road 

NOx emissions by 2014 but just 20 percent of total miles traveled. That is why 

the majority of proposed new measures in the State Strategy are in-use 

measures – programs to help clean up the legacy fleet of older, dirtier vehicles 

and equipment. We simply cannot wait for the natural turnover of older vehicles 

(1-5 percent annual turnover depending on vehicle or equipment type) being 

replaced with newer ones. 

On-Road Vehicles 

14 Years Old or Older 

In 2014 20% of 

Miles Traveled 

60% of 

NOx Emissions 

Passenger Vehicles 

Heavy-Duty Trucks 

Construction Equip 

Ships 

Locomotives 

90% of 

Mobile Sources 

Mobile Sources 90% of 

All NOx Emissions
April 26, 2007 43 

While action on the proposed in-use measures will be completed by 2010, their 

implementation will extend past 2010 and through 2014 to 2020. Longer-term 

actions will center on the final increment needed to attain the standard in the 

areas with the worst ozone pollution. 

Passenger Vehicles and Heavy-Duty Trucks 

Despite statewide growth in vehicle travel of 35 percent over the last 15 years, 

total car and truck emissions (ROG+NOx) have decreased almost 50 percent. 

California has led the way in adopting stringent regulations for passenger 

vehicles. Compared to uncontrolled vehicles, cars are now 99 percent cleaner. 

A new 1965 car produced about 2,000 pounds of ozone-forming ROG emissions 

during 100,000 miles of driving. California's low-emission standards, coupled 

with reformulated gasoline, have cut that to less than 50 pounds for the average 

new car today. By 2010, California's standards will further reduce ROG 

emissions from the average new 2010 car to approximately 10 pounds. 

ARB’s first diesel engine regulations went into effect in 1988. Significant gains 

began with the introduction of California Clean Diesel fuel in 1993. U.S. EPA and 

ARB worked together to develop and adopt the next phases of on-road diesel 

engine control, with cleaner fuel in 2006 and even cleaner engines in 2007 that 

will reduce per-truck particulate matter emissions by another 90 percent. By 

2010, new trucks will be 98 percent cleaner than new pre-1988 models, providing 

needed NOx reductions. 

NOx

ROG

0

1

2

3

4

5

grams/mile

1970 1975 1980 1990 1995 2000 2005 2010

As new cars and trucks become cleaner, the emissions contribution from older 

vehicles has been growing to the extent that it will soon make up the majority of 

mobile source emissions. Thus, California’s emission control program has also 

had to focus on cleaning up those vehicles already in use – the “legacy” or 

“in-use” fleet. 

California’s Smog Check Program is the cornerstone of the passenger vehicle 

in-use strategy, currently keeping over 400 tons of smog-forming gases from 

entering the air statewide each day. Passenger vehicles are also required to 

NOx

PM (x 10)

0

2

4

6

8

10

12

g/bhp-hr

Pre19881988 1991 1994 1998 2003 2007 2010

Auto Emission Standards Truck Emission Standards 
April 26, 2007 44 

have software incorporated into their on-board computers to detect emission 

control system malfunctions as they occur. ARB’s heavy-duty vehicle inspection 

program and periodic smoke inspection program reduce emissions from the 

legacy truck fleet. Trucks will also be required to have the same emission control 

malfunction detection software as passenger vehicles beginning in 2013. 

Cars and heavy-duty diesel trucks currently produce about 50 percent of the total 

NOx emissions in both the South Coast and San Joaquin Valley. By 2023, that 

percentage will be cut almost in half. But cars and trucks still account for so 

much of the State’s inventory of ozone and PM2.5 emissions, further reductions 

are essential if air quality standards are to be realized. 

Proposed New Passenger Vehicle and Heavy-Duty Truck Measures

 Passenger Vehicles 

Since California’s passenger vehicle emissions standards have done their job to 

cut emissions to near-zero levels, the control focus must shift to keeping vehicles 

clean over their lifetimes. The State Strategy envisions an even stronger Smog 

Check program that would reduce an additional 40 tons per day of emissions 

statewide in 2014. Proposed new Smog Check measures include annual 

inspections for cars with high failure rates, such as vehicles over 15 years old 

and vehicles accumulating high annual miles of travel, and adding inspections of 

motorcycles and smaller diesel vehicles. More attention will be paid to 

evaporative emissions through the addition of a low-pressure evaporative test, 

even as exhaust emission cutpoints are tightened. 

The State Strategy proposes to increase the number of vehicles that are 

voluntarily retired by implementing a scrappage program for vehicles that are off 

cycle from their Smog Check inspections. This strategy will depend upon funding 

and would be targeted primarily in the South Coast and San Joaquin Valley. We 

will also continue to ensure that the fuels used in California are the cleanestburning available, and mitigate the additional evaporative emissions resulting 

from the addition of ethanol to gasoline. 

These proposed passenger vehicle measures would reduce total NOx and ROG 

emissions in the South Coast by about 32 tons per day in 2014 and over 22 tons 

in 2020. Likewise, this measure will reduce total NOx and ROG emissions in the 

San Joaquin Valley by over 10 tons in 2014 and about 7 tons in 2020. 

 Heavy-Duty Diesel Trucks 

Substantially reducing emissions from existing trucks is key to meeting federal air 

quality standards, as well as achieving diesel risk reduction and goods 

movement clean air goals. The State Strategy foresees an expansive in-use 

diesel truck emission reduction program that would reduce NOx emissions by 47 

tons per day in the South Coast and 61 tons per day in the San Joaquin Valley 
April 26, 2007 45 

by 2014. Direct PM2.5 emissions would also be reduced 2-3 tons per day in both 

the South Coast and San Joaquin Valley during the same time period. 

A comprehensive fleet modernization program beginning in 2010 would replace 

older trucks, repower trucks with cleaner engines, and retrofit trucks with devices 

to reduce both NOx and PM. The proposed modernization program would be 

equivalent to replacing approximately 30 percent of the oldest trucks by 2014 

with 2010 model year or newer trucks, and will be accomplished through private 

truck fleet regulations. It is envisioned that the use of public incentive funds will 

be needed as well to facilitate fleet modernization on the scale necessary to 

attain PM2.5 and ozone standards within SIP deadlines. 

The in-use diesel truck program also proposes to reduce emissions from trucks 

registered outside of California and to lessen the effects of emission control 

deterioration. 

Impact of Car and Truck SIP Measures

Adopted SIP measures would reduce passenger vehicle NOx emissions in the 

South Coast by 67 percent between 2006 and 2020. Proposed new SIP 

measures would reduce that by another 15 percent by 2020. 

South Coast Passenger Vehicle Emissions - NOx

0

50

100

150

200

250

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

NOx Tons per Day

With New SIP Measures

With Adopted SIP Measures

Heavy-duty truck NOx emissions would be reduced by adopted SIP measures 

67 percent between 2006 and 2020. Proposed new SIP measures would reduce 

NOx emissions by another 45 percent by 2020. 
April 26, 2007 46 

South Coast Truck Emissions - NOx

0

50

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250

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2010

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NOx Tons per Day

With New SIP Measures

With Adopted SIP Measures

 Good Movement Sources 

The goods movement sector includes the ships, trains, port trucks, and related 

sources that help move materials and goods from the grower or manufacturer to 

the consumer. The air quality impact of the goods movement sector is a major 

issue in areas that host ports, large rail facilities, and major truck routes. Many 

entities have developed or are developing plans to address the impacts of goods 

movement, including the California Environmental Protection Agency and the 

Business, Transportation & Housing Agency, the Air Resources Board, the South 

Coast Air Quality Management District, several California ports, and two major 

railroads. 

Two factors increase the importance of addressing emissions from goods 

movement sources. First, international trade through California’s ports is growing 

rapidly: the volume of goods moving through the Port of Los Angeles and the 

Port of Long Beach – the nation’s busiest port complex – is expected to more 

than double by 2020. Second, the most prominent sources in this sector have 

historically not been regulated as aggressively as stationary sources or other 

mobile sources. Goods movement sources are also powered by diesel engines 

that last longer than their gasoline-powered counterparts, and are often rebuilt 

before being replaced with newer, cleaner equipment. As a result new engine 

standards alone will not provide emission reductions in the timeframe allowed to 

attain the federal PM2.5 and ozone standards. 

New measures in the State Strategy focus on the following goods movement 

sources: ships, locomotives, harbor craft, and port trucks. They closely mirror 

the measures included in Emission Reduction Plan for Ports and Goods 

Movement in California, approved by ARB in April 2006, and summarized briefly 

in Chapter 1. It is estimated that these measures will reduce 20 tons per day of 
April 26, 2007 47 

SOx, 49 tons per day of NOx, and about 4 tons per day of direct PM2.5 in the 

South Coast by 2014. 

 Ships

Emissions from ocean-going vessels, unlike most major pollution sources, are 

not projected to decrease in future years, since ships have little or no emission 

controls and run on high-emitting bunker fuel, and shipments of cargo containers 

are projected to grow significantly over the next two decades. Ships currently 

emit half the statewide SOx emissions, and it is estimated that ships will jump 

from the sixth to the second highest statewide NOx producer by 2023. It is 

essential to reduce ship emissions as they are entering our ports and when they 

are docked through application of demonstrated control technologies, use of 

cleaner fuels, and operational efficiencies. Since ARB does not have authority to 

set ship engine emission standards, we must work with national and international 

authorities, as well as the ports, to implement many of the control measures. 

ARB took a big step in reducing emissions from ships in December 2005 by 

adopting a rule phasing in the use of cleaner low-sulfur fuel in ship auxiliary 

engines that will reduce SOx emissions from auxiliary engines by 96 percent and 

PM2.5 emissions by 83 percent beginning in 2010. 

Proposed New Ship Measures 

In addition to the 2005 auxiliary engine fuel rule, the State Strategy proposes to 

reduce emissions from ship auxiliary engines through cold ironing and other 

clean technology. Cold ironing allows ships to turn off their auxiliary engines and 

instead plug into an electrical system for power when they are docked at a port. 

This measure would phase in the number of ships capable of using cold ironing 

and other at-dock technologies such as the “hood”, which fits onto a ship’s 

exhaust stack and cleans the emissions, and is estimated to reduce NOx 

emissions about 19 tons per day in 2014 and 28 tons per day in 2020. 

The State Strategy proposes to reduce emissions from ship main engines 

through a variety of measures. A main engine fuel rule, patterned after the 

auxiliary engine fuel rule, would help reduce emissions by introducing a cleaner, 

low-sulfur fuel beginning no later than 2010. Increasing the use of cleaner new 

engines or retrofitted engines beginning in 2010 could be implemented via 

regulation, incentives, voluntary agreements, or a combination of these 

approaches. Higher ship speeds cause much higher emissions. So a measure 

is proposed that would strengthen a current voluntary program by requiring ships 

to reduce their speeds to 12 knots within 40 nautical miles of the Ports of Los 

Angeles and Long Beach. The combination of ship main engine measures would 

reduce both NOx and SOx emissions by 20 tons per day and direct PM2.5 

emissions by over 2 tons per day in 2014. These reductions would increase 

substantially through 2023. 
April 26, 2007 48 

 Impact of Ship SIP Measures 

Without new SIP measures, ship NOx emissions are estimated to increase 

almost 90 percent between 2006 and 2020. With proposed new SIP measures, 

NOx emissions from ships would be 67 percent less than the projected 2020 

levels and about 35 percent less than 2006 levels. 

South Coast Ship Emissions - NOx

0

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NOx Tons per Day

With New SIP Measures

Without New Measures

It is estimated that SOx emissions from ships will double without the adopted and 

new SIP measures. The adopted SIP measure (auxiliary engine fuel rule) will 

help reduce SOx more than 50 percent from projected 2014 levels, but emissions 

would then begin increasing due to goods movement growth. With proposed 

new SIP measures, SOx emissions would be reduced to only 2 tons per day in 

the South Coast by 2014 and remain at that low level through 2020. 

South Coast Ship Emissions - SOx

0

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SOx Tons per Day

With New SIP Measures

Without New Measures

With Adopted ARB Measure
April 26, 2007 49 

 Locomotives

Locomotives pose a difficult challenge due to their long life, interstate operations, 

and California’s reliance on U.S. EPA to adopt new engine standards. A rule 

adopted by ARB in 2004 now requires locomotives operating in California to use 

cleaner, low-sulfur fuel that will reduce SOx emissions 90 percent. Several 

strategies are underway to clean up locally-based switcher engines, reduce idling 

emissions at railyards, and concentrate the cleanest available line haul engines 

in the South Coast. These activities are important for community health and NOx 

emission reductions in the short term. But without the introduction of cleaner 

new locomotive engines into California operation, growth is expected to quickly 

catch up to these current actions and begin to steer the NOx emissions curve 

upward. 

In 1998, ARB reached agreement with the rail industry to accelerate introduction 

of Tier 2 locomotives into the South Coast Air Basin to achieve a 67 percent 

reduction. However, as shown below, emissions are projected to begin 

increasing after 2010 due to growth. A similar agreement is needed to 

accelerate introduction of the next generation of cleaner locomotives once EPA 

adopts new standards. 

 Proposed New SIP Measures 

The State Strategy proposes U.S. EPA adoption of more stringent new engine 

standards and a new industry commitment to accelerate introduction of cleaner 

engines in California to meet the attainment needs of the South Coast and the 

San Joaquin Valley. It is anticipated that the new standards will reduce NOx and 

PM emissions by 90 percent. The proposed measure would call for replacement 

of existing locomotive engines with cleaner engines and rebuilds of older engines 

until 100 percent of the statewide locomotive fleet has been upgraded. ARB is 

pushing U.S. EPA to adopt the standards with earliest possible implementation, 

as this measure can only occur once U.S. EPA adopts new locomotive 

standards. 
April 26, 2007 50 

 Impact of Locomotive SIP Measures 

The proposed new SIP measures would reduce NOx emissions from locomotives 

by 13 tons per day in the South Coast and 16 tons per day by from 2006 to 2020. 

South Coast Locomotive Emissions - NOx

0

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NOx Tons per Day

With New SIP Measures

With Existing Controls

 Harbor Craft

Standards adopted by U.S. EPA provide for new harbor craft engines that have 

roughly 50 percent less NOx emissions than uncontrolled engines. The State 

Strategy proposes a new measure requiring harbor craft owners to replace older 

engines with the newer, cleaner engines and/or add control technologies that 

reduce emissions, reducing NOx emissions in the South Coast about 5 tons per 

day by 2014. 

Port trucks

Most port trucks start out as long-haul trucks and then are put into short-haul use 

as they get older and are no longer reliable enough for long-haul service. 

Because port trucks are purchased used, emission standards for new trucks will 

reduce emissions from trucks servicing the ports later than they will impact the 

long-haul fleet. The State Strategy proposes a port truck modernization program 

that would phase in beginning in 2008 and would include replacing older trucks 

with newer, cleaner trucks and retrofitting engines with emission-reducing control 

technology, reducing South Coast NOx emissions 2 tons per day by 2014 and 8 

tons per day by 2020. 
April 26, 2007 51 

 Large Off-Road Equipment 

Emission standards for new off-road diesel engines have become increasingly 

more stringent over the past decade, ensuring that new construction, mining, 

industrial and oil drilling equipment become progressively cleaner. By 2015, new 

large off-road equipment will produce 98 percent less ROG+NOx than their 

uncontrolled counterparts. However, large diesel off-road equipment with more 

than 25 horsepower remain in use for long periods of time, sometimes up to 60 

years. This long life means that new, lower emitting engines are introduced into 

fleets relatively slowly with the result that the emission reductions and associated 

health benefits from these cleaner engines will also be fairly slow to materialize. 

 Proposed New Large Off-Road Equipment Measure

ARB staff is currently in the process of developing a statewide in-use off-road 

equipment regulation which could require initial NOx and PM emissions averages 

to be met, with increasingly lower emissions averages over time. Staff began 

work on the rule in 2004 as part of the Diesel Risk Reduction Program. During 

early SIP development work in 2006, staff identified the necessity for large NOx 

emission reductions from off-road equipment and other diesel sources to meet 

the health-based federal air quality standards. Consequently, staff revised the 

control concept extensively to meet California’s clean air needs relative to diesel 

particulates, ozone, and PM2.5. 

This proposed measure would require owners of equipment larger than 

25 horsepower to meet a stringent average emissions level across all of their 

equipment. The fleet average approach provides equipment owners flexibility in 

how they will comply, including: swapping older, dirtier engines with newer, 

cleaner engines; purchasing newer equipment (with cleaner engines); and, 

adding emission control devices to older engines. Equipment owners could also 

restrict unnecessary equipment idling. 

This measure would reduce 10.5 tons per day of NOx and about 3 tons per day 

of direct PM2.5 in the South Coast and nearly 4 tons per day of NOx and a ton 

per day of direct PM2.5 in the San Joaquin Valley by 2014. It would also cut 

direct PM2.5 emissions by more than half in 2014 and by 70 percent in 2023. 
April 26, 2007 52 

Impact of Large Off-Road Equipment SIP Measures

Adopted SIP measures would reduce large off-road equipment NOx emissions in 

the South Coast by almost 60 percent between 2006 and 2020. Proposed new 

SIP measures would reduce that by another 30 percent by 2020. 

South Coast Construction Equipment 

Emissions - NOx

0

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120

140

160

2006

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2011

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2013

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2015

2016

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2018

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NOx Tons per Day

With New SIP Measures

With Adopted SIP Measures

Agricultural Equipment

The State Strategy will assess an equipment modernization program once 

modeling for the San Joaquin Valley’s PM2.5 SIP shows to what extent 

accelerated fleet modernization may be needed. 

Other Off-Road Sources 

For many gasoline-fueled off-road sources, evaporative emissions are a 

significant portion of total emissions. Leaky hoses, tanks, and other parts of an 

engine’s fuel system and refueling infrastructure release hundreds of tons of 

ROG into the atmosphere a day. Success with low- to no-evaporative emission 

technology in on-road sources supports strategies to reduce evaporative 

emissions to similar low levels in off-road sources. Many newly-regulated 

sources have exhaust standards but do not yet have evaporative standards. The 

State Strategy proposes to set standards where there are none and make 

standards more stringent in sources that are not adequately controlled. 

Off-road sources used mainly for recreational purposes are large emission 

contributors, especially during the summer ozone season. The main focus of the 

State Strategy on this wide array of smaller off-road sources is evaporative 

emissions. Recreational marine boat engines and off-road recreational vehicles 

are the biggest targets, with standards being implemented by 2010 and ROG 

emission reductions growing through 2023 as these newer, cleaner engines 

become a bigger part of the overall recreational fleet. Refueling tanks, portable 
April 26, 2007 53 

fuel tanks, and gas station fueling hoses, where emissions are the result of 

evaporation or permeation of ROG from gasoline, are also targeted. The 

proposed measures covering these off-road sources would reduce a combined 

7 tons per day of ROG in the South Coast and about 4 tons per day in the 

San Joaquin Valley by 2014. 

Areawide Sources 

Consumer Products

Chemically formulated consumer products such as automotive care products, 

household care products, and personal care products have been regulated as a 

source of ROG emissions in five rulemakings since 1989. As a result of these 

measures, statewide emissions from consumer products will be reduced by over 

170 tons per day in 2010, a 40 percent reduction. Despite this progress, 

population growth in the years ahead is expected to reverse the downward trend 

of emissions from consumer products, after the latest standards become 

effective. Therefore, additional controls for this sector will remain important. 

Indeed, consumer products are expected to become the largest source of ROG 

emissions in the South Coast, and the third largest source in the San Joaquin 

Valley by 2020.

The State Strategy will continue ARB’s commitment to reduce ROG emissions 

from consumer products. Rulemakings are expected to be promulgated between 

2007 and 2012, expanding beyond the current category-by-category standards 

and pursuing innovative approaches, reducing ROG emissions about 13 tons in 

the South Coast and almost 4 tons per day in the San Joaquin Valley by 2020.

Pesticides

Pesticide emissions from agricultural and commercial uses fall under the 

Department of Pesticide Regulation’s (DPR) authority. A measure to reduce 

pesticide emissions was included in the SIP adopted in 1994. The State Strategy 

includes an updated version of that measure. It is a strategy to reduce ROG 

emissions from pesticides through regulations that may include limitations on the 

use of products formulated as fumigants, registration standards requiring liquid 

products that contribute less to ozone formation, and incentives promoting pest 

management practices that use less pesticide. 

Local Measures 

The proposed new local air district measures, coupled with the new State 

Strategy measures, must provide the necessary emission reductions to meet the 

federal standards. The new local measures for each nonattainment area are 

listed, described, and quantified in the attainment plans for each area. 
April 26, 2007 54 

Need for Technology Development and Long-term Measures

In developing the proposed State Strategy, ARB staff analyzed whether current 

NOx technologies for mobile sources are clean enough to provide all the 

emission reductions needed for ozone attainment in the South Coast and San 

Joaquin Valley. ARB included in this analysis the phasing in of the cleanest new 

technology standards from 2007-2017 that ARB and U.S. EPA have already 

adopted for diesel engines: 0.2 g/bhp-hr on-road truck standards in 2010, full offroad Tier 4 standards in 2014, and the recent U.S. EPA-proposed low-NOx 

standards for locomotive engines starting in 2017. The table below summarizes 

this analysis. For both areas, the totals of remaining emissions after full clean-up 

of the legacy diesel fleets are still greater than the NOx carrying capacities. 

The clear conclusion is that even cleaner emission standards are needed than 

are in place today. This demonstrates that it necessary for the South Coast and 

San Joaquin Valley SIPs to rely on cleaner – yet to be developed – technologies 

as allowed by federal Clean Air Act section 182(e)(5) for areas with the worst 

pollution. 

All New Fleets Analysis -- Unconstrained by Cost 

Remaining NOx 2020 Emissions 

(tpd) * Source 

South Coast San Joaquin 

Valley 

Passenger vehicles 18 5 

Diesel trucks 37 43 

Construction and other equipment 14 5 

Farm equipment 1 7 

Locomotive 7 5 

Ships and harbor craft 37 1 

Aircraft 27 5 

Stationary/area-wide sources 55 103 

Subtotal of remaining emissions from 

above categories 195 173 

All other NOx sources 52 22 

Total of all remaining emissions 247 195 

Carrying capacity 114 160 

* Numbers may not add exactly due to rounding

For this analysis, ARB staff assumed that in 2020 all passenger cars would be 10 

years old or younger, all diesel trucks would meet the 2010 NOx standards, all 

diesel construction and farm equipment would meet the most stringent tier 4 

standards, all locomotives would meet U.S. EPA’s proposed 2017 NOx 

standards, and the new stationary sources measure in the district SIPs would be 

fully implemented. 
April 26, 2007 55 

The top five rows are italicized to indicate the categories for which we assume 

that all vehicles and equipment meet the cleanest adopted emission standards. 

Included in the category “all other NOx sources” are commercial gas trucks, 

motorcycles, buses, motor homes, off-road recreational vehicles, and gas 

powered off-road equipment. 

ARB staff did the analysis starting with 2020 baseline emissions since that year 

corresponds to the last federal attainment deadline before the 2024 extremeclassification deadline under which the long-term measure provisions of federal 

law apply. The numbers would look nearly identical for an analysis for any year 

between now and 2020 as the starting point. (For example, ARB staff calculated 

the “total of remaining emission” for the San Joaquin Valley using a 2018 starting 

point. The resulting “total of remaining emission” was approximately 195 tons 

per day.) The carrying capacity is independent of the year. Therefore, the 

analysis and conclusion that it is necessary for the South Coast and San Joaquin 

Valley ozone SIPs to rely on cleaner, yet to be developed, technologies is 

general and does not change with year analyzed. 

The results for the San Joaquin Valley demonstrate that the need for cleaner 

technologies includes cleaner technologies for industrial sources, not just 

vehicles. Close to half of the San Joaquin Valley remaining emissions, 103 tons 

per day compared to a carrying capacity of 160 tons per day, are from stationary 

and area-wide sources. Clearly, long-term reductions from new technologies for 

both mobile and stationary sources will be needed. 

Process for Identifying Long-Term Emission Reductions

ARB has a long-standing history of successfully adopting and implementing both 

technology-advancing regulations and innovative emission control techniques. 

By working closely with research scientists and the regulated industry, ARB staff 

have been able to craft regulations that are stringent enough to compel 

technology development, yet flexible enough to encourage industry innovations. 

ARB staff believe a directed process is needed to ensure that future emission 

reduction opportunities are identified that are large enough and arrive in time to 

meet the attainment deadline. 

To accomplish this, ARB staff proposes to take the lead in a coordinated 

government, private, and public effort to establish emission goals for critical 

emission source categories. Each category’s goal will serve as a general target 

for how much cleaner that emission source category will need to be for 

attainment purposes. The setting of the source category emission goals must be 

science-based in two ways. First, the goals must be tied to the State’s overall 

emission reduction needs. Although, estimated emission reduction needs will 

change as modeling and emission inventories are updated, a working estimate of 

how far technology needs to be pushed is critical to a successful outcome. 

Second, the goals must reflect a reasonable assessment of how far technology 

can progress over the time available for attainment. 
April 26, 2007 56 

This process of goal setting will give direction and distance to ARB and air district 

regulatory efforts to set the next generation of emission standards. As ARB and 

air districts identify future feasible emission reduction measures toward the goals, 

those measures will be incorporated into future SIPs. However, to keep nearterm focus on the need to find more emission reductions, ARB staff proposes to 

periodically brief the Board on emerging emission reduction opportunities and 

promising technologies. 

Potential Long-Term Concepts 

Although the identification of long-term emission reductions will begin with the 

emission goal setting for critical emission source categories, specific approaches 

that ARB will evaluate for possible inclusion in the next SIP update include the 

following: 

Passenger vehicles: look for further reductions from reduced deterioration of 

emission reduction components. While new cars are very clean, it may be 

possible to improve the on-board diagnostic capability of passenger vehicles and 

heavy-duty trucks to better target sources of emissions and to improve and 

encourage higher rates of repair. 

Tighten emission standards wherever possible: review all categories of engines 

and vehicles to ensure that the cleanest cost-effective technologies are in place. 

For example: 

• Exhaust and evaporative standards for on-road motorcycles. 

• Second generation catalyst-based emission standards for inboard/stern 

drive marine engines. 

• Tighter exhaust emission limits for small off-road engines. 

Cleaner ground support equipment: push for increased electrification. Captured 

vehicle and equipment fleets used at airports are cleaner today through natural 

turnover and accelerated turnover spurred through cooperative State and local 

government and air company efforts. However, additional opportunities for 

increased electrification remain. 

Air quality priority for federal transportation funding: work with local governments 

to prioritize federal transportation funding uses to better support air quality goals. 

The federal Congestion and Air Quality Improvement (CMAQ) Program annually 

provides to county transportation agencies more than $200 million in the South 

Coast and about $50 million in the San Joaquin Valley through 2009. The 

purpose of the CMAQ Program, according to Federal Highway Administration 

2006 guidance, is to fund transportation projects that will contribute to attainment 

of national ambient air quality standards. 
April 26, 2007 57 

Ideas Requiring Further Exploration 

Air quality control is an ever emerging field. At ARB, new ways to control air 

pollutants and improve public health are continually developed through research 

and other staff work. At any one time, there are always emission reduction ideas 

on the horizon that we have not fully explored or developed. Some of these 

approaches that are in various stages of development could turn out to be 

effective strategies at some point in the future. 

The following approaches show promise as potential emission reduction 

strategies. However, because of technological constraints and uncertain 

authority, they are less defined and will require significant exploration prior to 

becoming concepts. 

Explore opportunities for cleaner fuels. The near-term focus for fuels-related 

efforts in California will be to develop low carbon fuels in response to the 

Governor’s 2007 Executive Order. Separate from that effort, ARB will continue to 

evaluate the opportunities for cost-effective reformulations to reduce criteria 

pollutant emissions. 

Pursue additional emission reductions from consumer products. Despite the 

actions to date and the new measures proposed in this plan, consumer products 

continue to be an ever larger percentage of ROG emissions because of 

population growth. ARB will continue to look for even cleaner consumer product 

technologies and innovative approaches to reduce emissions such as reactivitybased and market-based strategies. This would continue the search for new 

approaches to achieve emission reductions initiated within the near-term 

consumer product measure. 

Explore approaches to further reduce volatile emissions from pesticides. With 

the Department of Pesticide Regulation as the lead, work with interested 

stakeholders to determine how pesticide emissions could be further reduced. 

Continue and enhance current public education and outreach programs. Public 

and private energy conservation and efficiency programs would continue and 

expand. The establishment of a statewide public education campaign to reduce 

air pollution could be considered, and might include ideas to engage the public 

through: (1) public education that more clearly connects voluntary clean air 

actions with public health benefits, and (2) increasing awareness of available 

low-emitting consumer products, paints, vehicles, lawn equipment, and 

recreational vehicles licensed to use clean air “green” labels. 

Advocate for efficient regional land use and transportation strategies. In 

California, local governments have the authority over most transportation funding 

and land use decisions. The most effective way for regions to curb long-term 

growth of vehicle travel and lessen auto emissions is to build on and enhance 

current efforts to implement transportation and land use strategies proven to 

reduce vehicle trips and decrease average trip lengths. 
April 26, 2007 58 

State Implementation Plan Commitments

This section sets forth the State’s SIP commitments for the 2007 State Strategy 

for two of the areas that need the emission benefits from the proposed, new 

State measures to demonstrate attainment – South Coast and San Joaquin 

Valley. Specific commitments for emission reductions as needed for attainment 

in other nonattainment areas, such as the Antelope Valley and Western Mojave 

Desert, Sacramento, and Ventura County, will be developed later and brought for 

Board consideration with SIPs for these regions.

The State’s SIP commitments consist of three components: 

1. Commitment to achieve emission reductions by specific dates; 

2. Commitment to propose defined new SIP measures; and 

3. A long-term strategy commitment. 

The total emission reductions and the obligation to propose specific measures for 

Board consideration would become enforceable upon approval by U.S. EPA of 

the State Strategy and each district’s attainment plan. The commitments for 

emission reductions are calculated using the planning inventory described in 

Appendix A; progress will be tracked in the same inventory currency to assess 

compliance. 

The total emission reductions from the new measures necessary to attain the 

federal standards are an enforceable State commitment in the SIP. While the 

proposed State Strategy includes estimates of the emission reductions from each 

of the individual new measures, it is important to note that the commitment of the 

State Strategy is to achieve the total emission reductions necessary to attain the 

federal standards, which would be the aggregate of all existing and proposed 

new measures combined. Therefore, if a particular measure does not get its 

expected emission reductions, the State still commits to achieving the total 

aggregate emission reductions, whether this is realized through additional 

reductions from the new measures, or from alternative control measures or 

incentive programs. 

For informational purposes, the tables below show the expected emission 

reductions from the proposed new SIP measures in the South Coast and 

San Joaquin Valley in 2014, 2020, and 2023. The first table shows the expected 

NOx and ROG emission reductions for South Coast and San Joaquin Valley for 

2023, the year in which the emission reduction target must be met for the 

expected ozone attainment date of 2024 for these areas. The second table 

shows the expected NOx and ROG emission reductions for the two areas for 

2020 to help illustrate the progress that will be made prior to the proposed 2024 

attainment deadlines for the South Coast and San Joaquin Valley. The third and 

fourth tables show the expected emissions reductions from NOx, ROG, SOx, and 

direct PM2.5 in the South Coast and San Joaquin Valley in 2014, the year in 

which emission reduction targets must be met for the federal PM2.5 standard. 
April 26, 2007 59 

Expected Emission Reductions from Proposed New SIP Measures 

(tons per day) 

 

South Coast and San Joaquin Valley -- 2023 

South Coast San Joaquin 

Valley 

Proposed New SIP Measures NOx ROG NOx ROG

Passenger Vehicles 7.1 10.5 2.1 3.3 

 Smog Check Improvements (BAR) 6.9 7.5 2.1 1.9 

 Expanded Vehicle Retirement 0.2 0.5 0.04 0.1 

 Modifications to Reformulated Gasoline Program -- 2.5 -- 1.3 

Heavy-Duty Trucks 18.3 1.7 21.2 2.3 

 Cleaner In-Use Heavy-Duty Trucks 18.3 1.7 21.2 2.3 

Goods Movement Sources 99.2 1.9 16.4 1.3 

 Ship Auxiliary Engine Cold Ironing & Clean Technology 30.8 -- -- -- 

 Cleaner Main Ship Engines and Fuel 39.9 -- -- -- 

 Port Truck Modernization 7.0 -- -- -- 

 Accelerated Intro. of Cleaner Line-Haul Locomotives 15.6 1.9 16.4 1.3 

 Clean Up Existing Harbor Craft 5.9 NYQ -- NYQ

Off-Road Equipment 13.9 1.9 5.4 0.6 

 Cleaner In-Use Off-Road Equipment (over 25hp) 13.9 1.9 5.4 0.6 

 Cleaner In-Use Agricultural Equipment NYQ NYQ NYQ NYQ

Other Off-Road Sources 2.4 24.0 0.6 11.4 

 New Emission Standards for Recreational Boats 2.4 17.6 0.6 5.3 

 Expanded Off-Road Rec. Vehicle Emission Standards -- 6.4 -- 6.1 

 Additional Evaporative Emission Standards -- NYQ -- NYQ

 Vapor Recovery for Above Ground Storage Tanks -- NYQ -- NYQ

Areawide Sources -- 13.7 -- 6.3 

 Consumer Products Program -- 13.7 -- 3.8 

 Pesticides: DPR Regulation -- NYQ -- 2.5 

Emission Reductions from Proposed New Measures 141 54 46 25 

 

NYQ = Not Yet Quantified. BAR = Bureau of Automotive Repair. DPR = Dept. of Pesticide Regulation. 

Locomotives measure relies on U.S. EPA rulemaking and industry agreement to accelerate fleet turnover. 

Note: Emission reductions reflect the combined impact of regulations and supportive incentive programs. 

Emission reduction estimates for each proposed measure are shown for informational purposes only. Actual 

emission reductions from any particular measure may be greater than or less than the amounts shown. 
April 26, 2007 60 

Expected Emission Reductions from Proposed New SIP Measures 

(tons per day) 

 

South Coast and San Joaquin Valley -- 2020 

South Coast San Joaquin 

Valley 

Proposed New SIP Measures NOx ROG NOx ROG

Passenger Vehicles 9.6 12.9 2.7 4.1 

 Smog Check Improvements (BAR) 8.3 8.7 2.4 2.2 

 Expanded Vehicle Retirement 1.3 1.2 0.3 0.3 

 Modifications to Reformulated Gasoline Program -- 3.0 -- 1.6 

Heavy-Duty Trucks 26.9 2.6 30.2 3.3 

 Cleaner In-Use Heavy-Duty Trucks 26.9 2.6 30.2 3.3 

Goods Movement Sources 87.1 1.8 15.6 1.2 

 Ship Auxiliary Engine Cold Ironing & Clean Technology 28.3 -- -- -- 

 Cleaner Main Ship Engines and Fuel 32.3 -- -- -- 

 Port Truck Modernization 8.0 -- -- -- 

 Accelerated Intro. of Cleaner Line-Haul Locomotives 13.4 1.8 15.6 1.2 

 Clean Up Existing Harbor Craft 5.1 NYQ -- NYQ

Off-Road Equipment 18.7 2.9 7.0 1.0 

 Cleaner In-Use Off-Road Equipment (over 25hp) 18.7 2.9 7.0 1.0 

 Cleaner In-Use Agricultural Equipment NYQ NYQ NYQ NYQ

Other Off-Road Sources 1.6 17.9 0.4 8.7 

 New Emission Standards for Recreational Boats 1.6 12.8 0.4 3.8 

 Expanded Off-Road Rec. Vehicle Emission Standards -- 5.1 -- 4.9 

 Additional Evaporative Emission Standards -- NYQ -- NYQ

 Vapor Recovery for Above Ground Storage Tanks -- NYQ -- NYQ

Areawide Sources -- 13.5 -- 6.1 

 Consumer Products Program -- 13.5 -- 3.6 

 Pesticides: DPR Regulation -- NYQ -- 2.5 

Emission Reductions from Proposed New Measures 144 52 56 24 

 

NYQ = Not Yet Quantified. BAR = Bureau of Automotive Repair. DPR = Dept. of Pesticide Regulation. 

Locomotives measure relies on U.S. EPA rulemaking and industry agreement to accelerate fleet turnover. 

Note: Emission reductions reflect the combined impact of regulations and supportive incentive programs. 

Emission reduction estimates for each proposed measure are shown for informational purposes only. Actual 

emission reductions from any particular measure may be greater than or less than the amounts shown. 
April 26, 2007 61 

Expected Emission Reductions from Proposed New SIP Measures 

(tons per day) 

 

South Coast -- 2014 

 

Direct Proposed New SIP Measures NOx ROG PM2.5 SOx 

Passenger Vehicles 14.4 17.7 0.3 -- 

 Smog Check Improvements (BAR) 12.0 10.5 0.2 -- 

 Expanded Vehicle Retirement 2.4 2.8 0.05 -- 

 Modifications to Reformulated Gasoline Program -- 4.4 -- -- 

Heavy-Duty Trucks 47.3 5.1 3.0 -- 

 Cleaner In-Use Heavy-Duty Trucks 47.3 5.1 3.0 -- 

Goods Movement Sources 49.4 0.7 3.6 20.1 

 Ship Auxiliary Engine Cold Ironing & Clean Technology 18.5 -- 0.3 0.4 

 Cleaner Main Ship Engines and Fuel 20.0 -- 2.4 19.7 

 Port Truck Modernization 2.0 -- 0.5 -- 

 Accelerated Intro. of Cleaner Line-Haul Locomotives 4.3 0.7 0.2 -- 

 Clean Up Existing Harbor Craft 4.6 -- 0.2 -- 

Off-Road Equipment 10.5 2.7 2.6 -- 

 Cleaner In-Use Off-Road Equipment (over 25hp) 10.5 2.7 2.6 -- 

 Cleaner In-Use Agricultural Equipment NYQ NYQ NYQ -- 

Other Off-Road Sources 0.4 6.6 -- -- 

 New Emission Standards for Recreational Boats 0.4 4.2 -- -- 

 Expanded Off-Road Rec. Vehicle Emission Standards -- 2.4 -- -- 

 Additional Evaporative Emission Standards -- NYQ -- NYQ

 Vapor Recovery for Above Ground Storage Tanks -- NYQ -- NYQ

Areawide Sources -- 12.9 -- -- 

 Consumer Products Program -- 12.9 -- -- 

 Pesticides: DPR Regulation -- NYQ -- -- 

Emission Reductions from Proposed New Measures 122 46 9 20 

 

NYQ = Not Yet Quantified. BAR = Bureau of Automotive Repair. DPR = Dept. of Pesticide Regulation. 

Locomotives measure relies on U.S. EPA rulemaking and industry agreement to accelerate fleet turnover. 

Note: Emission reductions reflect the combined impact of regulations and supportive incentive programs. 

Emission reduction estimates for each proposed measure are shown for informational purposes only. 

Actual emission reductions from any particular measure may be greater than or less than the amounts 

shown. 
April 26, 2007 62 

Expected Emission Reductions from Proposed New SIP Measures 

(tons per day) 

 

San Joaquin Valley -- 2014 

 

Direct Proposed New SIP Measures NOx ROG PM2.5 SOx 

Passenger Vehicles 3.8 6.5 0.1 -- 

 Smog Check Improvements (BAR) 3.3 2.9 0.05 -- 

 Expanded Vehicle Retirement 0.5 0.7 0.01 -- 

 Modifications to Reformulated Gasoline Program -- 2.9 -- -- 

Heavy-Duty Trucks 61.4 6.4 3.6 -- 

 Cleaner In-Use Heavy-Duty Trucks 61.4 6.4 3.6 -- 

Goods Movement Sources 7.2 0.5 0.2 -- 

 Ship Auxiliary Engine Cold Ironing & Clean Technology -- -- -- -- 

 Cleaner Main Ship Engines and Fuel -- -- -- -- 

 Port Truck Modernization -- -- -- -- 

 Accelerated Intro. of Cleaner Line-Haul Locomotives 7.2 0.5 0.2 -- 

 Clean Up Existing Harbor Craft -- NYQ -- -- 

Off-Road Equipment 3.7 0.9 0.8 -- 

 Cleaner In-Use Off-Road Equipment (over 25hp) 3.7 0.9 0.8 -- 

 Cleaner In-Use Agricultural Equipment NYQ NYQ NYQ -- 

Other Off-Road Sources 0.1 3.5 -- -- 

 New Emission Standards for Recreational Boats 0.1 1.3 -- -- 

 Expanded Off-Road Rec. Vehicle Emission Standards -- 2.2 -- -- 

 Additional Evaporative Emission Standards -- NYQ -- NYQ

 Vapor Recovery for Above Ground Storage Tanks -- NYQ -- NYQ

Areawide Sources -- 5.7 -- -- 

 Consumer Products Program -- 3.2 -- -- 

 Pesticides: DPR Regulation -- 2.5 -- -- 

Emission Reductions from Proposed New Measures 76 23 5 0 

 

NYQ = Not Yet Quantified. BAR = Bureau of Automotive Repair. DPR = Dept. of Pesticide Regulation. 

Locomotives measure relies on U.S. EPA rulemaking and industry agreement to accelerate fleet turnover. 

Note: Emission reductions reflect the combined impact of regulations and supportive incentive programs. 

Emission reduction estimates for each proposed measure are shown for informational purposes only. 

Actual emission reductions from any particular measure may be greater than or less than the amounts 

shown. 
April 26, 2007 63 

Commitments to Reduce Emissions 

The tables below describe the emission reduction commitment proposal for 

Board approval. ARB staff proposes to commit to achieve the emission 

reductions set forth in these tables, by the dates indicated in the table on Page 

65 entitled, “Schedule for Board Consideration of Proposed ARB Rulemaking.” 

The reductions may be achieved through a combination of actions, including 

regulations, incentives, and other enforceable mechanisms. 

Summary of Emission Reduction Commitments – South Coast 

Year NOx ROG Direct 

PM2.5 SOx 

2014 122 46 9 20 

2020 1 144 52 -- -- 

2023 141 54 -- -- 

2023 CAA 182(e)(5) measures 241 2 40 2 -- -- 

1 The 2020 commitment in the South Coast is necessary to provide for attainment in the downwind 

nonattainment areas. 2 The reductions of NOx and ROG from 182(e)(5) measures will be reassessed as new SIPs are developed 

and revised. 

Summary of Emission Reduction Commitments – San Joaquin Valley 

Year NOx ROG Direct 

PM2.5 SOx 

2014 76 23 5 0 

2020 56 24 -- -- 

2023 46 25 -- -- 

2023 CAA 182(e)(5) measures 81 1 -- 1 -- -- 

1 The reductions of NOx and ROG from 182(e)(5) measures will be reassessed as new SIPs are developed 

and revised. 

Summary of Emission Reduction Commitments – Coachella Valley 

Year NOx ROG 

2018 7 2 
April 26, 2007 64 

Commitment to Propose Defined New SIP Measures

In addition to the commitment to reduce emissions by 2014, 2020 and 2023, ARB 

staff also proposes to commit to submit to the Board and propose for adoption 

the list of proposed new ARB control measures shown in the table below. The 

Board shall take action on or before the dates set forth in the following table. 

Such action by the Board may include any action within its discretion. 

Schedule for Board Consideration of Proposed ARB Rulemaking 

Proposed New SIP Measures Year 

Cleaner In-Use Off-Road Equipment 

Modifications to Reformulated Gasoline Program 

Cleaner Main Ship Fuel 

Clean Up Existing Harbor Craft 

Enhanced Vapor Recovery for Above Ground Storage Tanks 

2007 

Cleaner In-Use Heavy-Duty Trucks 

Port Truck Modernization 

Ship Auxiliary Engines 

Cleaner Line-Haul Locomotives (Enforceable Agreement) 

Consumer Products Program I 

2008 

Cleaner In-Use Agricultural Equipment 

New Emission Standards for Recreational Boats 

Expanded Off-Road Recreational Vehicle Emission Standards 

Additional Evaporative Emission Standards 

2009-2010 

Consumer Products Program II 2010-2012 
April 26, 2007 65 

State Strategy 

Proposed New SIP Measures 

Implementing Agency – Expected Action – Expected Implementation 

Proposed New SIP Measures Implementing

Agency 

Expected 

Action 

Expected 

Implementation 

Passenger Vehicles 

 Smog Check Improvements BAR 2007-2008 By 2010 

 Expanded Vehicle Retirement ARB/BAR 2008-2014 2008-2014 

 Modifications to Reformulated Gasoline 

Program ARB 2007 Phase-in 

starting 2010 

Trucks 

 Cleaner In-Use Heavy-Duty Trucks ARB 2008 2010-2015 

Goods Movement Sources 

 Auxiliary Ship Engine Cold Ironing and 

Other Clean Technology 

EPA/ARB/ 

Local 2007-2008 Phase-in 

starting 2010 

Fuel: 2007 2007-2010 

 Cleaner Main Ship Engines and Fuel EPA/ARB 

Local Engines: 

2009 

Phase-in 

starting 2010 

 Port Truck Modernization ARB/Local 2007-2008 2008-2020 

 Accelerated Introduction of Cleaner 

Line-Haul Locomotives EPA/ARB 2007-2008 Starting in 2012 

 Clean Up Existing Harbor Craft ARB 2007 2009-2018 

Off-Road Equipment 

 Cleaner In-Use Off-Road Equipment ARB 2007 Phase-in 

starting 2008 

 Cleaner In-Use Agricultural Equipment ARB 2009-2010 TBD 

Other Off-Road Sources 

 New Emission Standards for 

Recreational Boats ARB 2009-2010 2012-2013 

 Expanded Off-Road Recreational 

Vehicle Emission Standards ARB By 2010 2012-2015 

 Enhanced Vapor Recovery for Above 

Ground Storage Tanks ARB 2007 Phase-in 

starting 2008 

 Additional Evaporative Emission 

Standards ARB By 2010 2010-2012 

AREAWIDE SOURCES 

2007-2008 By 2010 Consumer Products Program ARB 2010-2012 By 2012-2014 

 DPR Pesticide Regulation DPR 2008 2008 

DPR = Department of Pesticide Regulation. BAR = Bureau of Automotive Repair 

TBD = To Be Determined 
April 26, 2007 66 

Commitment to Reduce Emissions via Long-Term Strategy

Consistent with section 182(e)(5) of the federal Clean Air Act, this SIP includes 

long-term commitments to achieve the last increment of emission reductions 

necessary to meet attainment goals in the South Coast and San Joaquin Valley. 

As the State agency charged with ensuring California’s SIP compliance, ARB is 

ultimately responsible for ensuring the necessary measures are identified no later 

than 2020 (three years prior to the attainment year) and the emission reductions 

achieved by 2023. 

After adoption of the State Strategy, ARB staff proposes to initiate a coordinated 

government, private, and public effort to establish emission goals for critical 

mobile and stationary emission source categories. Following the setting of 

emission goals, ARB will start an ongoing public process to assess technology 

advancement opportunities for the critical categories. ARB staff will periodically 

brief the Board at public meetings on emerging emission reduction opportunities, 

promising technologies, and the progress made in developing long-term emission 

reduction measures. As ARB staff identifies feasible technology-forcing emission 

reduction measures, staff will propose those measures to the Board for inclusion 

into the SIP. 

No later than 2020, ARB and the two air districts will prepare a revision to the 

8-hour Ozone SIP that (1) reflects any modifications to the 2023 emission 

reduction target based on updated science, and (2) identifies any additional 

strategies, including the implementing agencies, needed to achieve the 

necessary emissions reductions by 2023. If the specific measures developed to 

satisfy the long-term obligation affect on-road motor vehicle emissions, we will 

work with the air districts and transportation planning agencies to revise the 

transportation conformity budgets accordingly. 

South Coast: After accounting for the anticipated benefits of both adopted and 

new defined State and local measures, the 2003 SIP demonstrates a need for 

another 281 tpd ROG and NOx reductions from long-term measures. This 

represents 24 percent of the total reductions needed by 2023. We believe that 

this gap can be bridged through a cooperative effort by the local, State and 

federal agencies responsible for specific emission sources. This effort should 

focus on how to most effectively achieve the additional reductions, considering 

the availability and cost of potential controls. 

San Joaquin Valley: After accounting for the anticipated benefits of both 

adopted and new defined State and local measures, the State Strategy 

demonstrates a need for another 81 tpd NOx reductions from long-term 

measures. This represents 13 percent of the total NOx and ROG reductions 

needed by 2023. We believe that this gap can be bridged through a cooperative 

effort by the local, State and federal agencies responsible for specific emission 

sources. This effort should focus on how to most effectively achieve the 

additional reductions, considering the availability and cost of potential controls. 
April 26, 2007 67 

Role of Funding and Incentive Programs

Over the past 40 years, California has steadily improved air quality in the face of 

tremendous economic and population growth. The vast majority of that progress 

has come from effective regulations. Accordingly, ARB staff expects State and 

federal regulations to play the primary role in implementing the State Strategy. In 

the regulatory paradigm, polluting sources pay for the necessary emission 

controls as part of doing business. Regulated industries may pass these costs 

on to consumers in the form of higher prices, although competition and other 

factors may prevent some companies from recouping all of their control costs. 

Low-interest loans with extended payment periods are available to aid smaller 

businesses that need upfront capital to comply. 

In recent years, regulatory programs have been supplemented with financial 

incentives to accelerate voluntary actions, such as replacing older equipment. 

Incentive programs like the Carl Moyer Program are both popular and effective. 

They also help to demonstrate emerging technologies that then can be used to 

set a tougher emissions benchmark for regulatory requirements. Most of the 

existing incentive programs are designed to pay for the incremental cost between 

what is required by regulation and advanced technology that exceeds that level. 

The incentive programs are publicly funded through fees paid by California 

vehicle owners as part of their annual registrations, smog inspections or new tire 

purchases. California is currently investing up to $140 million per year to clean 

up older, higher emission sources. 

The support for clean air incentive funding from Governor Schwarzenegger, the 

Legislature, and California’s voting public is reflected in the passage on 

November 7, 2006, of the Highway Safety, Traffic Reduction, Air Quality, and 

Port Security Bond Act of 2006. The Bond Act includes $1 billion to accelerate 

the cleanup of air pollution caused by goods movement activities in California. 

With appropriation by the Legislature, and subject to such conditions and criteria 

contained in a statute that it will enact, ARB will appropriate this money to fund 

emission reductions from activities related to the movement of freight along 

California’s trade corridors. 

Federal Actions Needed

Measures in the State Strategy to reduce emissions from interstate and 

international sources rely on the federal government to develop more stringent 

emission standards and to ensure these standards go into effect as soon as 

possible. Emission reductions from locomotives, off-road equipment, marine 

auxiliary engines, and harbor craft are a significant part of the State Strategy. 

Proposed State measures would accelerate the introduction of cleaner engines 

and equipment, but the emission reductions rely on the availability of cleaner new 

engines. 

ARB is proposing several measures to reduce ship emissions through a 

combination of regulations, incentives, and actions by ports and the private 
April 26, 2007 68 

sector. However, national and international action to clean up shipping fleets is 

also needed to fully realize our clean air goals. And aircraft emissions, which will 

become one of the South Coast’s top five NOx sources by 2020, are 

unaddressed in the State Strategy due to the lack of effective international 

standards. 

California must rely on U.S. EPA to represent its interests before foreign or 

international regulatory bodies that have the ability to reduce emissions from 

international goods movement sources. In this role, U.S. EPA should advocate 

for the adoption of cleaner ship emission standards and less polluting practices 

by the International Maritime Organization. 

Possible Federal Actions 

Adopt more stringent standards for sources under federal control. U.S. EPA 

should move as fast as possible to lower standards for sources under its control, 

keeping in mind California’s air quality challenge and attainment deadlines. 

There are categories of emission sources that we do not have the authority to 

regulate at the State level. We also do not have the ability to regulate sources in 

markets outside of California that then operate within California. Not only would 

federal action lower emissions for new sources, but it would allow State and local 

actions to lower emissions from existing sources by setting in-use rules that 

speed up the integration of the cleaner engines and technology into California 

fleets. These sources include: ships, locomotives, harbor craft, aircraft, and 

off-road equipment and vehicles. 

Federal incentives for cleaner technology. Federal funding sources for clean air 

projects, as well as federal tax incentives promoting the manufacture, sale, and 

purchase of cleaner vehicles, equipment, and technology, could enhance 

California’s aggressive incentive programs. 
April 26, 2007 69 

Ozone Attainment Demonstrations

The table on the following page illustrates how the State Strategy will meet the 

emission reduction targets for ozone in the South Coast and San Joaquin Valley. 

This document has presented ARB staff’s assessment of the State Strategy for 

the San Joaquin Valley and the South Coast in detail. ARB staff has also 

evaluated the impact of the proposed State Strategy on all 15 ozone 

nonattainment areas. For the remaining areas, modeling results and air quality 

data analyses show that, with the continued reductions in emissions on track to 

occur in each area, all will be able to show attainment by 2021 or earlier with 

identified measures. 

ARB staff expects the districts within the Sacramento nonattainment area will 

request a reclassification from serious to severe and will need additional 

reductions from ARB’s proposed new measures to attain by 2019. San Diego is 

projected to attain by its deadline, while Ventura may consider a reclassification 

to either Serious or Severe. Transport impacted areas, especially downwind of 

the South Coast—the Antelope Valley, the Mojave Desert, and the Coachella 

Valley—will need to rely on new reductions that will occur upwind. We expect 

the local districts to request reclassification to get the needed time. Areas 

downwind of the Central Valley—Western Nevada, Amador, Calaveras, 

Tuolumne, Mariposa, and Kern Counties—are projected to attain by their 2014 

deadline with already adopted measures. Air quality modeling for these areas is 

new and ARB staff is continuing to evaluate the results. Finally, three areas—the 

Bay Area, Butte County, and the Sutter Buttes—now attain the ozone standard. 

Attainment demonstrations for these areas will be included in the individual ARB 

staff reports for each area. 
April 26, 2007 70 

Setting the Ozone Emission Reduction Target (tons per day)

Nonattainment Area 

South Coast 

(2023) 

San Joaquin 

Valley (2023) 

NOx ROG NOx ROG 

2006 Emissions Inventory 972 732 650 454 

Carrying Capacity 114 420 160 342 

Emission Reduction 

Target 858 312 490 112 

(2006 Emissions Inventory) – (Carrying Capacity) = (Emission Reduction Target) 

2006 Emissions Inventory = Amount of ozone-forming emissions. 

Carrying Capacity = Pollutant emissions limit that ensures air quality standards are met. 

Emission Reduction Target = Amount of emissions that must be reduced to meet the standard. 

Meeting the Ozone Emission Reduction Target (tons per day)

Nonattainment Area 

South Coast 

(2023) 

San Joaquin 

Valley (2023) 

NOx ROG NOx ROG 

Emission Reduction 

Target 858 312 490 112 

Emission Reductions from 

Adopted SIP Measures 467 199 355 43 

Emission Reductions from 

New Local Measures 

9 19 8 47 

Emission Reductions from 

New State Measures 

141 54 46 25 

Long-Term Measures 241 40 81 -- 

Total Reductions 858 312 490 115 

Emission Reductions from Adopted SIP Measures = Emissions reduced from measures adopted 

through 2006. 

Emission Reductions from New Measures = Emissions reduced from measures in the State 

Strategy or new local measures adopted after 2006. 

Long-Term Measures = Emissions reduced from measures adopted after 2020 that rely on new or 

evolving technology, as allowed in section 182(e)(5) of the Clean Air Act. 
April 26, 2007 71 

Tracking Progress

The Clean Air Act requires that SIPs show there will be steady progress in reducing 

emissions during the years leading to the attainment date, called reasonable further 

progress, equal to about 3 percent per year. (Each nonattainment area’s 

reasonable further progress is illustrated in the local plans and in Appendix D.) 

Along with tracking progress to meet the SIP requirements, ARB will have a 

stringent tracking process for strategies under its jurisdiction. There will be periodic 

updates to ARB’s governing board on the SIP’s New Strategies. In addition, other 

ARB programs vital to the SIP have their own deadlines and tracking schedules. 

The goal of ARB’s Diesel Risk Reduction Plan is to reduce the health risk from 

diesel emissions 75 percent by 2010 and 85 percent by 2020. The Emission 

Reduction Plan for Ports and Goods Movement in California has specific emission 

reduction milestones in 2010, 2015 and 2020. ARB is committed to achieving all of 

its goals in these plans and the SIP and will be tracking progress on each. 

Contingency Measures Requirement

The federal Clean Air Act requires attainment plans to identify “contingency 

measures” to be implemented if nonattainment areas (except those designated 

“marginal”) fail to meet reasonable further progress requirements or to attain the 

federal air quality standards on time. These contingency measures are to take 

effect without further ARB or air district action, and thus must be measures that 

have already been adopted when the SIP is submitted to U.S. EPA. 

The bulk of emission reductions needed to attain the federal standards are 

achieved through the mobile source measures in the State Strategy’s existing 

program. As we have noted previously, California’s mobile source program has 

been very successful in reducing emissions in California and represents the 

foundation supporting attainment of the federal standards. ARB has a well 

established history of adopting and implementing mobile source control regulations 

on-time or early. As a result, we expect to achieve and even exceed reasonable 

further progress goals without the need for contingency measures. However, the 

Clean Air Act requirements necessitate that we provide contingency measures 

regardless of our expected progress in reducing emissions toward the attainment 

goals. 

For areas designed basic, moderate, and serious, reasonable further progress can 

be demonstrated with already adopted measures and therefore contingency 

measures are not necessary. For areas designated severe and extreme, the 

emission reductions from adopted measures that go beyond the reasonable further 

progress requirements will constitute California’s contingency measure commitment 

implemented in the unlikely event that the State does not meet the reasonable 

further progress goals. 

A more detailed analysis of the contingency measure commitment is included in 

Appendix D.