CARBON MONOXIDE REDESIGNATION REQUEST

AND MAINTENANCE PLAN FOR 

THE MARICOPA COUNTY NONATTAINMENT AREA

MAY 2003
CARBON MONOXIDE REDESIGNATION REQUEST

AND MAINTENANCE PLAN FOR 

THE MARICOPA COUNTY NONATTAINMENT AREA

Prepared by:

May 2003

Technical Assistance Provided By:

Arizona Department of Environmental Quality

Arizona Department of Transportation

Maricopa County Environmental Services Department

U.S. Environmental Protection Agency
i

CARBON MONOXIDE REDESIGNATION REQUEST AND MAINTENANCE PLAN

FOR THE MARICOPA COUNTY NONATTAINMENT AREA

TABLE OF CONTENTS

CHAPTER PAGE

EXECUTIVE SUMMARY ....................................... ES-1

ONE INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

NATIONAL AMBIENT AIR QUALITY STANDARDS FOR 

CARBON MONOXIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

CHARACTERISTICS AND HEALTH EFFECTS OF

CARBON MONOXIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

NONATTAINMENT AREA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

REQUIRED COMPONENTS OF A REDESIGNATION

REQUEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

TWO REDESIGNATION REQUEST . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

REQUIRED COMPONENTS OF A REDESIGNATION

REQUEST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

ATTAINMENT OF THE CARBON MONOXIDE STANDARDS . . 2-1

APPROVAL OF THE CARBON MONOXIDE

NONATTAINMENT SIP ELEMENT FOR THE MARICOPA

COUNTY AREA .................................... 2-10

IMPROVEMENT IN AIR QUALITY DUE TO PERMANENT

AND ENFORCEABLE EMISSION REDUCTIONS .......... 2-10

ATTAINMENT AND MAINTENANCE CONTROL

MEASURES ....................................... 2-11

CLEAN AIR ACT SECTION 110 AND PART D 

REQUIREMENTS ................................... 2-17
ii

CHAPTER PAGE

THREE MAINTENANCE PLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

MAINTENANCE PLAN CONTROL MEASURES . . . . . . . . . . . . 3-1

EMISSION INVENTORIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

MAINTENANCE DEMONSTRATION . . . . . . . . . . . . . . . . . . . . . 3-9

MOBILE SOURCE CARBON MONOXIDE EMISSIONS

BUDGETS ........................................ 3-12

MONITORING NETWORK / VERIFICATION OF

CONTINUED ATTAINMENT .......................... 3-15

CONTINGENCY PROVISIONS ........................ 3-15

SUBSEQUENT MAINTENANCE PLAN REVISIONS ........ 3-16
iii

CARBON MONOXIDE REDESIGNATION REQUEST AND MAINTENANCE PLAN

FOR THE MARICOPA COUNTY NONATTAINMENT AREA

LIST OF TABLES

TABLE PAGE

ES-1 1994 Base Case and 2015 Committed Maintenance Measures ........ ES-4

ES-2 1994 Base Case and 2015 Committed Maintenance Measure

Emissions ................................................. ES-5

2-1 1998 Carbon Monoxide Monitoring Data Summary for the Maricopa

County Nonattainment Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

2-2 1999 Carbon Monoxide Monitoring Data Summary for the Maricopa

County Nonattainment Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

2-3 2000 Carbon Monoxide Monitoring Data Summary for the Maricopa

County Nonattainment Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

2-4 2001 Carbon Monoxide Monitoring Data Summary for the Maricopa

County Nonattainment Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

3-1 Committed Measures Used for Numeric Credit in the 

Carbon Monoxide Maintenance Plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

3-2 Summary of 2015 Emission Reductions from Committed Maintenance

Measures Used for Numeric Credit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

3-3 1994 Base Case and 2006 and 2015 Committed Maintenance

 Measure Emissions. .......................................... 3-10

3-4(a) Emission Totals for a Friday in December. ......................... 3-11

3-4(b) Emission Totals for a Saturday in December. ....................... 3-11

3-5 The 1994, 2006 and 2015 Maximum Simulated Eight-Hour Carbon

Monoxide Concentrations for the December 16-17 Episode. ........... 3-11

3-6 Combined UAM/CAL3QHC 2006 and 2015 Maximum Eight-Hour Carbon

Monoxide Concentrations (ppm) for the December 16-17 Episode ...... 3-13
iv

CARBON MONOXIDE REDESIGNATION REQUEST AND MAINTENANCE PLAN

FOR THE MARICOPA COUNTY NONATTAINMENT AREA

LIST OF FIGURES

FIGURE PAGE

ES-1. Carbon Monoxide Trends (1994-2001) ........................... ES-3

ES-2. 2015 Carbon Monoxide Emission Reductions from Individual

Maintenance Measures ....................................... ES-7

ES-3 Carbon Monoxide Emission Reductions from Individual Contingency

Measures in 2000 ........................................... ES-8

2-1. Carbon Monoxide Monitoring Sites in the Maricopa County

Nonattainment Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8

2-2. Carbon Monoxide Trends (1994-2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

3-1. 2015 Carbon Monoxide Emission Reductions from Individual

Maintenance Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

3-2. Carbon Monoxide Emission Reductions from Individual Contingency

Measures in 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
v

CARBON MONOXIDE REDESIGNATION REQUEST AND MAINTENANCE PLAN

FOR THE MARICOPA COUNTY NONATTAINMENT AREA

APPENDICES

APPENDIX A

Exhibit I: 1999 Periodic Carbon Monoxide Emission Inventory for the Maricopa

County, Arizona Nonattainment Area. Maricopa County Environmental

Services Department. November 2001, Revised August 2002.

Exhibit 2: Technical Support Document for Carbon Monoxide Modeling in Support

of the Carbon Monoxide Redesignation Request and Maintenance Plan

for the Maricopa County Nonattainment Area. April 2003.

APPENDIX B

Exhibit 1: Public Hearing Process Documentation

Exhibit 2: Certification of Adoption
CARBON MONOXIDE REDESIGNATION REQUEST

AND MAINTENANCE PLAN FOR 

THE MARICOPA COUNTY NONATTAINMENT AREA

EXECUTIVE SUMMARY
ES-1

CARBON MONOXIDE REDESIGNATION REQUEST AND MAINTENANCE PLAN

FOR THE MARICOPA COUNTY NONATTAINMENT AREA

EXECUTIVE SUMMARY

The Maricopa Association of Governments (MAG) is requesting that the U.S.

Environmental Protection Agency (EPA) redesignate the Maricopa County nonattainment

area to attainment for the National Ambient Air Quality Standards for carbon monoxide.

The area was designated a nonattainment area for carbon monoxide in April 1977, but no

violations of the standards have occurred since 1996. With the submittal of this

redesignation request and maintenance plan, the MaricopaCountynonattainment area has

satisfied all of the requirements for redesignation to attainment for carbon monoxide.

Under the 1990 Clean Air Act Amendments, the nonattainment area was classified as a

Moderate Area for carbon monoxide. The MAG 1993 Carbon Monoxide Plan, addressing

the Moderate Area requirements, was submitted to the Environmental Protection Agency

(EPA) in November 1993. An Addendum to this Moderate Area plan was submitted to

EPA in March 1994. In July 1996, the nonattainment area was reclassified to Serious due

to a failure to attain the eight-hour carbon monoxide standard by December 31, 1995. The

MAG 1999 Serious Area Carbon Monoxide Plan for the Maricopa County Nonattainment

Area was submitted to EPA in July 1999.

In 2000, the Arizona Legislature passed House Bill 2104, which repealed the Random

Onroad Testing Requirements from the Vehicle Emissions Inspection program. MAG

conducted new air quality modeling and documented the impact of the repeal of this

program in the Revised MAG 1999 Serious Area Carbon Monoxide Plan for the Maricopa

County Nonattainment Area. The Revised MAG Serious Area Carbon Monoxide Plan was

submitted to EPA in April 2001. 

The Environmental Protection Agency has indicated that approval of the Revised MAG

1999 Serious Area Carbon Monoxide Plan will occur in 2003. If the Plan is not approved

before this redesignation request is submitted to EPA, the Serious Area Carbon Monoxide

Plan and redesignation request can be approved simultaneously.

The Clean Air Act defines the following criteria that must be met before a nonattainment

area can be redesignated to attainment:

EPA must fully approve the Revised MAG 1999 Serious Area Carbon Monoxide Plan

and any related State Implementation Plan (SIP) components.

EPA must determine that the area has attained the carbon monoxide standards.

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

enforceable reductions in emissions.

The State must meet all applicable requirements for State Implementation Plans

(SIPs) and Nonattainment Areas as defined in the Clean Air Act.

EPA must approve a maintenance plan for the area. The plan must demonstrate

maintenance of the carbon monoxide standard for a period of at least ten years

following the redesignation to attainment by EPA. 
ES-2

As indicated above, it is anticipated that the Revised MAG 1999 Serious Area Carbon

Monoxide Plan will be approved by EPA in 2003. Chapter Two of this document provides

monitoring data to support the finding that the carbon monoxide standards have been met

in the nonattainment area since 1996. Figure ES-1 shows the continuous downward trend

in the second-highest carbon monoxide concentration occurring in the nonattainment area.

Chapter Two demonstrates that these improvements in air quality are attributable to

permanent, enforceable reductions in carbon monoxide emissions. The second chapter

also documents that other Clean Air Act requirements for SIPs and nonattainment areas

have been met.

Generally, the overall approach taken in preparing the Maintenance Plan is to demonstrate

maintenance of the carbon monoxide standard in 2015 with the committed measures in the

Revised MAG 1999 Serious Area Carbon Monoxide Plan. Therefore, the Maintenance

Plan relies heavily upon the Revised MAG 1999 Serious Area Carbon Monoxide Plan and

its supporting documents, including the commitments to implement control measures.

Chapter Three contains the Carbon Monoxide Maintenance Plan for the nonattainment

area. The Maintenance Plan shows that the area will continue to maintain the eight-hour

standard through 2015, a period of at least ten years following redesignation to attainment

by EPA. Maintenance of the standard through 2015 will be achieved, despite growth in

regional population, employment, and vehicle travel, due to more stringent federal controls

on vehicles and fuels, and state and local committed measures in the Maintenance Plan.

Table ES-1 identifies the base case control measures for which numeric credit was taken

in validating the air quality models for 1994. The nine committed maintenance measures

for which numeric credit is taken in the Maintenance Plan are also identified in Table ES-2.

All nine of these were also committed measures in the Revised MAG 1999 Serious Area

Carbon Monoxide Plan. In the Serious Area Plan, six were attainment measures, two were

contingency measures, and Off-road Vehicle and Engine Standards was not quantified,

because the standards had not been adopted at the time the plan was submitted.

Table ES-2 compares total carbon monoxide emissions in the 1994 base case to

emissions in 2015 with the committed maintenance measures. The maximum eight-hour

carbon monoxide concentration modeled in 1994 was 10.71 parts per million (ppm). The

maximum eight-hour concentration in 2015 is projected to be 8.06 ppm, or ten percent

below the standard of 9 ppm.
ES-3
ES-4

TABLE ES-1

1994 BASE CASE AND 2015 COMMITTED MAINTENANCE MEASURES

Base Case Measures Assumed in the

1994 Model Validation for the Carbon

Monoxide Maintenance Plan

Committed Maintenance

Measures Used for Credit in the

Carbon Monoxide Maintenance

Plan

1. Inspection/Maintenance (I/M) idle test

was required for all gasoline vehicles

1. CARB Phase 2 with 3.5%

Oxygenate in Winter

2. I/M waiver rates of 10% assumed for

pre-1981 model year vehicles and 4%,

for 1981 and newer vehicles

2. Phased-In Emission Test Cutpoints

3. Oxygenate content and Reid Vapor

Pressure (RVP) were based on actual

fuel properties from surveys

3. One-Time Waiver from Vehicle

Emissions Test

4. Vehicles participating in I/M test - 88%;

not-participating - 12%

4. Defer Emissions Associated with

Government Activities

5. Coordinate Traffic Signal Systems

6. Develop Intelligent Transportation

Systems

7. Tougher Enforcement of Vehicle

Registration and Emission Test

Compliance

8. Clean Burning Fireplace

Ordinances

9. Off-Road Vehicle and Engine

Standards
ES-5

December 1994

December 2015

TABLE ES-2

1994 BASE CASE AND 2015 COMMITTED MAINTENANCE MEASURE EMISSIONS

Friday, December 1994

Source Category Metric Tons

per Day

Percent

Point 2.5 0.2

Area 21.0 2.0

Nonroad Mobile 155.1 14.8

Onroad Mobile 869.6 83.0

Total 1048.2* 100.0*

Friday, December 2015

Source Category Metric Tons

per Day

Percent

Point 32.2 3.6

Area 36.2 4.0

Nonroad Mobile 169.9 18.9

Onroad Mobile 662.9 73.6

Total 901.2* 100.0*

* Note that the sum of the source categories may

not equal 100.0 percent due to rounding.

Point Sources - Industrial, Manufacturing,

and Electrical Power

Generation Facilities

Area Sources - Residential Wood and Industrial Fuel Combustion, On-site Incineration, and

Open Burning

Nonroad Mobile - Utility, Lawn & Garden, Construction, Farm, and Recreational Equipment,

Aircraft and Locomotives
ES-6

Figure ES-2 illustrates the emissions reduction attributable to each of the maintenance

measures in 2015. With the committed measures, the Maintenance Plan projects that

onroad mobile sources will contribute about 73.6 percent of the total carbon monoxide

emissions in 2015 or 662.9 metric tons per day. This figure, 662.9 metric tons per day,

represents the motor vehicle emissions conformity budget for carbon monoxide in 2015.

In addition, the Maintenance Plan establishes an interim conformity budget for carbon

monoxide of 699.7 metric tons per day in 2006.

The Clean Air Act also requires that a maintenance plan contain contingency provisions.

The maintenance plan is not required to contain fully adopted contingency measures.

ChapterThree identifiesthree contingencymeasures that were also contingency measures

in the Revised MAG 1999 Serious Area Carbon Monoxide Plan. These measures have

already been adopted and implemented in the nonattainment area. Early implementation

of contingency measures is allowed by EPA. The contingency measures in this

Maintenance Plan are: Expansion of Area A Boundaries, Gross Polluter Option for I/M

Program Waivers, and Increase Waiver Repair Limit Options. Figure ES-3 illustrates the

emission reductions attributable to each of these contingency measures in 2000. Chapter

Three also describes the process and schedule to be followed if monitoring data indicate

additional measures are needed in the future.
0.1%

0.1%

0.2%

0.2%

0.2%

0.3%

1.9%

21.5%

Defer Emissions Associated

Develop Intelligent

One Time Waiver from

Tougher Enforcement of

Phased-in Emission

Coordinate Traffic

Clean Burning

Off-Road Vehicle

CARB Phase 2 with 3.5%

0.0% 0.5% 1.0% 1.5% 2.0% 22.0%

Percent Reduction

with Government Activities2

Transportation Systems

Vehicle Emissions Test

Vehicle Registrations

Test Cutpoints

Signal Systems

Fireplace Ordinances

and Engine Standards

Oxygenate in Winter1

2

This measure influences when emissions occur rather than their magnitude; 6 percent

of emissions from two-stroke gasoline-powered engines used by public agencies were

shifted from post-2 p.m. period to the pre-2 p.m. period on the modeled week day.

NOTE: Individual impact of measures are not additive.

ES-7

FIGURE ES-2

2015 CARBON MONOXIDE EMISSION REDUCTIONS

FROM INDIVIDUAL MAINTENANCE MEASURES

( ) Percent Reduction in Total Emissions

1

Of the 21.5 percent reduction in emissions, the majority (21.1 percent) is due to

the low sulfur content of the fuel.
ES-8
1-1

CHAPTER ONE

INTRODUCTION

The Maricopa Association of Governments (MAG) is requesting that the U.S.

Environmental Protection Agency (EPA) redesignate the Maricopa County nonattainment

area to attainment for the National Ambient Air Quality Standards for carbon monoxide.

The area was designated a nonattainment area for carbon monoxide in April 1977, but has

not violated the standard since 1996. Therefore, the area is now eligible for redesignation.

Chapter Two contains the formal redesignation request and supporting documentation.

Chapter Three provides the Maintenance Plan which demonstrates continued attainment

of the carbon monoxide standard through the year 2015. 

In 1978, the Governor of Arizona designated the Maricopa Association of Governments as

the lead air quality planning agency for Maricopa County. Together with the State, MAG

is responsible for determining which elements of the State Implementation Plan will be

planned, implemented and enforced by State and local governments in Arizona. In 1992,

the Arizona Legislature recertified MAG as the regional air quality planning agency. MAG

coordinates with the Arizona Department of Environmental Quality, Arizona Department

of Transportation and the Maricopa County Environmental Services Department in

developing the plans necessary to attain and maintain the national standards.

This redesignation request and Maintenance Plan have been reviewed and approved by

the MAG Air Quality Technical Advisory Committee, the MAG Management Committee,

and the MAG Regional Council. The MAG Air Quality Technical Advisory Committee was

established in 1995 with representatives from State, county and local governments, private

industry, environmental groups, and the public-at-large. TheAir Quality Technical Advisory

Committee makes recommendations to the MAG Management Committee on air quality

plans, projects, funding and other pertinent issues.

The MAG Management Committee is comprised of managers from each of the MAG

member agencies that include twenty-five cities and towns, the Salt River Pima-Maricopa

and Gila River Indian Communities, Maricopa County, and the Arizona Department of

Transportation. The MAG Management Committee makes recommendations to the MAG

Regional Council. The Regional Council is the MAG decision-making body and is

composed of elected officials from the MAG member agencies.

MAG has also conducted a public hearing on this redesignation request and maintenance

plan in accordance with federal requirements. All public comments and responses are

provided in the Appendix.
1-2

NATIONAL AMBIENT AIR QUALITY STANDARDS FOR CARBON MONOXIDE

There are two federal standards for carbon monoxide (CO): an eight-hour standard of 9

parts per million (ppm) and a one-hour standard of 35 ppm. A violation occurs when two

or more exceedances of the standard are recorded at the same monitoring site during a

calendar year. An exceedance is considered as a monitored value of 9.5 ppm (or 35.5

ppm) or greater.

The last exceedance of the one-hour carbon monoxide standard in the nonattainment area

was recorded in 1984. There has been only one exceedance of the eight-hour CO

standard since 1996; this occurred at the Phoenix Grand Avenue monitor in 1999. Since

only one exceedance occurred at that site in 1999, the standard was not violated. There

were no exceedances of the eight-hour carbon monoxide standard at any of the fifteen

carbon monoxide monitors located in the nonattainment area in 1997, 1998, 2000 and

2001. There have been no violations of the eight-hour carbon monoxide standard since

1996.

CHARACTERISTICS AND HEALTH EFFECTS OF CARBON MONOXIDE

Carbon monoxide is produced by the incomplete combustion of carbon contained in fossil

fuels. Most carbon monoxide is emitted from tailpipes of on-road and non-road motor

vehicles. Some is a by-product of commercial and residential heating. Peak

concentrations typically occur along roadways and near intersections with high levels of

traffic congestion. Calm winds during the late fall and winter, coupled with night and early

morning ground-based temperature inversions, can cause a build-up of CO concentrations

in urban areas.

Carbon monoxide is a colorless, odorless and tasteless gas. When inhaled, CO enters the

lungs and is absorbed by the hemoglobin in the body’s red blood cells. By displacing

oxygen in the hemoglobin, carbon monoxide reduces the flow of oxygen to human organs,

tissues and the central nervous system. Prolonged exposure at high concentrations poses

the greatest risk to young people, pregnant women, and those with cardiovascular or

pulmonary disease. Common symptoms of carbon monoxide poisoning are dizziness,

headaches, fatigue, visual impairment and disorientation. Healthy individuals can also

experience detrimental effects from carbon monoxide, such as a reduced ability to

concentrate.

NONATTAINMENT AREA

The Maricopa County carbon monoxide nonattainment area encompasses approximately

2,000 square miles in central Arizona. The northern boundary of the nonattainment area

is located approximately six miles north of Carefree Highway and the southern boundary,

generally along Hunt Highway. To the east, the area is bounded by the Pinal County Line

and the Tonto National Forest; on the west, by Jackrabbit Trail and Beardsley Canal. The

area contains portions of twenty-two cities and towns, the Fort McDowell, Gila River and
1-3

Salt River Pima-Maricopa Indian Communities, and some unincorporated areas of

Maricopa County. According to the U.S. Census, the population of Maricopa County in

2000 was 3.1 million. Most of these residents live and work within the nonattainment area

boundaries.

The nonattainment area is located in the Salt River Valley at 1,100 feet above mean sea

level and is almost completely surrounded by mountains. The climate in the nonattainment

area is arid continental, with temperatures ranging from a mean of 52 degrees Fahrenheit

in January to 91 degrees, in July. The sun shines 86 percent of the time and the annual

rainfall is about 7.44 inches. In general, the prevailing wind direction is from E/SE to

W/SW, although the winds can shift in the afternoon to a more westerly direction.

HISTORY

In accordance with the Clean Air Act, an urbanized portion of Maricopa County was

formally designated as a nonattainment area for carbon monoxide in April 1977. Under the

1990 Clean Air Act Amendments, the nonattainment area was classified as Moderate for

carbon monoxide. In order to meet the Moderate area requirements, the MAG 1993

Carbon Monoxide Plan was submitted to the Environmental Protection Agency by

November 15, 1993. An Addendum to this Plan was submitted in March 1994. On July

29, 1996, the nonattainment area was reclassified to Serious due to failure to attain the

carbon monoxide standard by December 31, 1995. The Serious Area reclassification was

effective on August 28, 1996.

On July 8, 1999, the Arizona Department of Environmental Quality submitted the MAG

1999 Serious Area Carbon Monoxide Plan for the Maricopa County Nonattainment Area

to EPA. A completeness finding was issued by EPA on September 9, 1999.

Following the submission of this Plan, the Arizona Legislature passed House Bill 2104

during the 2000 regular session, which repealed the Random Onroad Testing

Requirements (Remote Sensing Program) from theVehicle EmissionsInspection Program.

EPA then indicated that the Serious Area Carbon Monoxide Plan that had been submitted,

including the attainment demonstration for December 2000, would need to be revised to

reflect the repeal of the Remote Sensing Program. In response, MAG conducted new air

quality modeling and documented the impact of the repeal of the Remote Sensing Program

in the Revised MAG 1999 Serious Area Carbon Monoxide Plan for the Maricopa County

Nonattainment Area, dated March 2001.

On April 18, 2001, the Arizona Department of Environmental Quality submitted the Revised

MAG Serious Area Carbon Monoxide Plan to EPA. A completeness finding was issued by

EPA on October 9, 2001. While this latest SIP has not been approved under section

110(k), it is anticipated that EPA approval will occur before this request for redesignation

is submitted. If not, approval action on SIP elements of the Revised Serious Area Carbon

Monoxide Plan and the redesignation request may occur simultaneously.
1-4

REQUIRED COMPONENTS OF A REDESIGNATION REQUEST

Sections 107(d)(3)(D) and (E) of the Clean Air Act define the criteria that must be met

before an area can be redesignated to attainment. With the submittal of this redesignation

request and maintenance plan, the Maricopa County nonattainment area meets the five

required criteria, summarized below:

1. Attainment of the Standard

Chapter Two shows that the area has attained the national standards for carbon monoxide.

2. State Implementation Plan Approval

EPA issued a completeness finding on the Revised MAG 1999 Serious Area Carbon

Monoxide Plan for the Maricopa County Nonattainment Area in October 2001. Approval

of this plan is expected in 2003.

3. Improvement in Air Quality Due to Permanent and Enforceable Emission

Reductions

Chapter Two discusses the evidence that the improvement in air quality leading to

attainment and maintenance of the standards has been due to permanent and enforceable

emissions reductions.

4. Clean Air Act Section 110 and Part D Requirements

Chapter Two discusses how requirements of Clean Air Act Section 110 (for SIPs) and Part

D (for nonattainment areas) are satisfied by the Revised MAG 1999 Serious Area Carbon

Monoxide Plan for the Maricopa County Nonattainment Area and the Maintenance Plan

provided in Chapter Three of this document. 

5. Maintenance Plan

Chapter Three contains the Maintenance Plan for the Maricopa County carbon monoxide

nonattainment area. The Maintenance Plan demonstrates that the area will continue to

maintain the eight-hour carbon monoxide standard through 2015, a period of at least ten

years following redesignation to attainment by EPA. The Maintenance Plan also contains

contingency measures that have been implemented and describes the process and

schedule that will be used to consider additional measures, if eight-hour carbon monoxide

concentrations of 9.0 ppm or more are recorded at two or more monitoring sites in a future

calendar year.
2-1

CHAPTER TWO

REDESIGNATION REQUEST

The Maricopa Association of Governments (MAG) requests that the U.S. Environmental

Protection Agency (EPA) redesignate the Maricopa County nonattainment area to

attainment for the National Ambient Air Quality Standards for carbon monoxide. The area

was designated a carbon monoxide nonattainment area in April 1977, but has not violated

the standard since 1996. Therefore, the area is eligible for redesignation.

REQUIRED COMPONENTS OF A REDESIGNATION REQUEST

The EPA Administrator may not redesignate an area to attainment, unless the following

requirements of Section 107(d)(3)(E) of the Clean Air Act (CAA) are met. These four

requirements for redesignation are discussed in this chapter.

1. The Administrator determines that the area has attained the national ambient air

quality standards.

2. The Administrator has fully approved the applicable implementation plan under

Section 110(k).

3. The Administrator determines that the improvement in air quality is due to

permanent and enforceable reductions in emissions.

4. The State has met all applicable requirements under Section 110 and Part D.

A fifth requirement for redesignation to attainment is that:

5. The EPA Administrator approve a maintenance plan for the area that meets the

provisions of Section 175A.

Chapter Three contains the maintenance plan that is being submitted to EPA to fulfill this

fifth and final requirement.

ATTAINMENT OF THE CARBON MONOXIDE STANDARDS

Attainment of the National Ambient Air Quality Standards for carbon monoxide is

demonstrated when two consecutive years of monitoring data for each site show no more

than one exceedance per year of the 8-hour (9 ppm) and 1-hour (35 ppm) standards. The

following information demonstrates, as required by Section 107(d)(3)(E) of the Clean Air

Act, that the Maricopa County nonattainment area has attained the national standards for

carbon monoxide. This is based on quality assured monitoring data representing all

monitoring locations in the nonattainment area, including two microscale monitors that

record the highest carbon monoxide concentrations in the region.
2-2

Historical Perspective

Data from the regional monitoring network and two microscale monitoring sites indicate

that the Maricopa County nonattainment area has not violated the eight-hour standard for

carbon monoxide (CO) since 1996. The last exceedance of the one-hour standard was

recorded in 1984. In addition, both the frequency of exceedance days and the magnitude

of observed CO concentrations have declined dramatically since air quality monitoring

began in the late 1960's.

In contrast to the lack of eight-hour violations since 1996, eighty-six exceedance days were

recorded in 1984. There was a noticeable decline in the number of exceedance days from

1984 through 1990. In 1994 through 1996 period, there were a total of eight exceedance

days, three each in 1994 and 1995, and two in 1996. There were two violation sites in

1994 (West Indian School and West Phoenix sites), and one each in 1995 and 1996 (both

at the Phoenix Grand Avenue site). There were no exceedances of the standard at any

site in 1997,1998, 2000, 2001 or 2002. There was a single exceedance of the eight-hour

standard in 1999 at the Phoenix Grand Avenue site, but this one exceedance did not

constitute a violation of the standard.

The carbon monoxide concentrations measured by the regional monitoring network

indicate that steady progress toward attainment has been achieved over the past 30 years.

Since 1990, the two microscale monitors (Phoenix Grand Avenue and West Indian School)

have recorded the highest carbon monoxide concentrations and the majority of the

exceedances in the nonattainment area. The West Indian School monitor commenced

operation in 1981 near the intersection of 35th Avenue, Grand Avenue, and Indian School

Road. This station recorded 69 exceedance days in its first year of operation. The number

of exceedance days at the site has decreased steadily since then, to the point where only

three were recorded in 1994, one in 1995, and none since 1996. The annual eight-hour

maximum concentration at the West Indian School site has declined by two-thirds, from

20.3 ppm in 1981 to 6.8 ppm in 2001.

It is important to examine monitoring data for spatial and temporal trends, in order to gain

a better understanding of the conditions most likely to result in an exceedance. All of the

exceedances during the 1994 to 1996 period were recorded at four monitoring sites,

located in the west-central portion of the nonattainment area. Three of the four sites are

within 1.5 miles of one another. The majority of the exceedance days occurred in

December, with occasional exceedances in November and January, and half of the

exceedance days occurred on Saturday. All recorded eight-hour exceedance periods

ended between 0100 and 0400 hours. The highest hourly concentrations were monitored

between 2100 and 2400 hours on the days prior to the recorded exceedances.

These data suggest that the highest carbon monoxide readings in the region continue to

occur during winter inversion conditions. These inversions cause a layer of warmer air aloft

to trap the cold air near the ground surface and effectively eliminate convective circulation.

As a result of the inversion conditions, the pollutants normally dispersed by mixing
2-3

accumulate beneath the lid of warm air. After sunrise, the ground surface is reheated and

the inversion rapidly breaks down. The temperature of the lower atmosphere increases

as the warm air rises and the pollutants are then dispersed through natural vertical mixing.

Most of the carbon monoxide trapped by the inversion layer is emitted by vehicular traffic

during the afternoon and evening before the high concentration is observed. The fact that

the highest CO readings are now well below the standard indicates that motor vehicle

emissions have declined dramatically over the past 30 years, due to the Federal Motor

Vehicle Emission Standards and other control measures included in the Revised 1999

MAG Serious Area Carbon Monoxide Plan for the Maricopa County Nonattainment Area,

March 2001 (Revised Serious Area Carbon Monoxide Plan).

Carbon Monoxide Monitoring Network

The ambient air monitoring network for carbon monoxide in the Maricopa County

nonattainment area consists of three National Air Monitoring Stations (NAMS), nine State

and Local Air Monitoring Stations (SLAMS), and three Special Purpose Monitors (SPM)

operated by the Maricopa County Environmental Services Department and the Arizona

Department of Environmental Quality. The CO monitoring sites are identified, along with

summary data from 1998 through 2001, in Tables 2-1 through 2-4. Figure 2-1 shows the

geographical distribution of the regional monitoring network.

Monitoring Results and Attainment Demonstration

The monitoring data presented in Tables 2-1 through 2-4 verify that the Maricopa County

nonattainment area has been in attainment of the national standards for carbon monoxide

since 1997, as well as for the most recent two-year period (2000-2001), in accordance with

the federal requirements of 40 CFR 50.8. Data recovery rates for the monitors exceed the

75 percent completeness requirements for all years and all state and federal quality

assurance procedures have been followed. Figure 2-2 illustrates the continuous downward

trend in the second-highest carbon monoxide concentrations at all monitors in the

nonattainment area.

Quality Assurance Program

Carbon monoxide data for the Maricopa County area has been collected and qualityassured in accordance with 40 CFR, Part 58, Appendix A, EPA’s “Quality Assurance

Handbook for Air Pollution Measurement Systems, Volume II; Ambient Air Specific

Methods”, the Maricopa County Ambient Air Monitoring Program QA/QC Procedures, and

the ADEQ Quality Assurance Project Plan. The data are recorded in the EPA Aerometric

Information Retrieval System (AIRS) and are also available for public review in air quality

monitoring reports produced annually by the Maricopa County Environmental Services

Department and the Arizona Department of Environmental Quality.
2-4

TABLE 2-1

1998 CARBON MONOXIDE MONITORING DATA SUMMARY FOR

THE MARICOPA COUNTY NONATTAINMENT AREA

STANDARDS: 1-HOUR: 35 PPM; 8-HOUR: 9 PPM*

Site Name

1-Hour 8-Hour

Max

ppm

2nd Max

ppm

Max

ppm

2nd Max

ppm

West Chandler, 163 S. Price Rd.** 4.1 4 2.9 2.9

Gilbert, 535 N. Lindsay Rd. 3.5 3.3 2.7 2.7

Glendale, 6000 W. Olive 5 4.9 3.4 3.3

Mesa, 370 S. Brooks 6.5 6.1 4.4 4.3

South Phoenix, 4732 S. Central 8.2 7.9 5.4 5.4

Central Phoenix, 1845 E. Roosevelt 9.1 8.9 7.1 7.1

North Phoenix, 601 E. Butler 8 7.3 6.1 5.9

West Indian School, 3315 W. Indian

School

9.7 9.4 8.1 8.1

West Phoenix, 3847 W. Earll 10.7 9.6 7.7 7.7

Phoenix Post Office, 3905 N. 7th Ave. 9.4 9.3 8.2 6.9

Phoenix Grand Ave., 27th

Ave/Grand/ThomasS

10.7 9.6 7.3 6.8

JLG Supersite, 4530 N. 17th Ave. S 9.6 8.9 7.2 6.6

Greenwood, I-10 and 27th Ave. 9.4 8.9 7.5 7.3

Maryvale, 6180 W. Encanto 7.5 7.5 6.1 6.1

South Scottsdale, 2857 N. Miller 5.5 5.2 3.7 3.6

* Due to mathematical rounding, values > 35.5 and 9.5 ppm are necessary to exceed the

standard.

**The West Chandler monitor was moved to Frye Rd. and Ellis in 1999.

S Seasonal monitor operating from January to March and October to December.
2-5

TABLE 2-2

1999 CARBON MONOXIDE MONITORING DATA SUMMARY FOR 

THE MARICOPA COUNTY NONATTAINMENT AREA

STANDARDS: 1-HOUR: 35 PPM; 8-HOUR: 9 PPM*

Site Name

1-Hour 8-Hour

Max

ppm

2nd Max

ppm

Max

ppm

2nd Max

ppm

West Chandler, Frye Rd. & Ellis ** S 4.3 4 2.9 2.8

Gilbert, 535 N. Lindsay Rd. S 3.8 3.7 2.4 2.4

Glendale, 6000 W. Olive S 5.7 5.3 3.8 3.4

Mesa, 370 S. Brooks S 7.2 5.8 4.4 4

South Phoenix, 4732 S. Central,

(Closed Aug-Nov)

7.8 7.7 4.6 4.4

Central Phoenix, 1845 E. Roosevelt 11.3 9.3 7.2 5.9

North Phoenix, 601 E. Butler S 7.8 6.3 3.5 3.5

West Indian School, 3315 W. Indian

School

11.8 11.7 7.6 7.5

West Phoenix, 3847 W. Earll 12.3 11.9 7.7 7.4

Phoenix Post Office, 3905 N. 7th Ave. 

(Closed 4/1)

8.5 7.4 5.8 5.7

Phoenix Grand Ave., 27th

Ave/Grand/ThomasS

18.4 13.4 10.5 8

JLG Supersite, 4530 N. 17th Ave. 8.5 8.2 7 6.6

Greenwood, I-10 and 27th Ave. 10.8 9.5 6.7 6.6

Maryvale, 6180 W. Encanto S 9.7 9 7.2 6.6

South Scottsdale, 2857 N. Miller S 6 5.8 4.3 4.1

* Due to mathematical rounding, values > 35.5 and 9.5 ppm are necessary to exceed the

standard.

** The West Chandler monitor was operated at 163 S. Price Rd. from January through

March 1999 and at its present location from October through December 1999.

S Seasonal monitor operating from January to March and October to December.
2-6

TABLE 2-3

2000 CARBON MONOXIDE MONITORING DATA SUMMARY FOR 

THE MARICOPA COUNTY NONATTAINMENT AREA

STANDARDS: 1-HOUR: 35 PPM; 8-HOUR: 9 PPM*

Site Name

1-Hour 8-Hour

Max

ppm

2nd Max

ppm

Max

ppm

2nd Max

ppm

West Chandler, Frye Rd. & Ellis S 5.7 3.8 2.5 2.3

Gilbert, 535 N. Lindsay Rd. S # 3.7 3.3 2 2

Glendale, 6000 W. Olive S 4.6 4.6 3.5 3.2

Mesa, 370 S. Brooks S 6 5.1 4.3 3.4

South Phoenix, 4732 S. Central S 10 8.4 5.9 4.7

Central Phoenix, 1845 E. Roosevelt 8.1 8 5.3 5

North Phoenix, 601 E. Butler S 6 5.9 3.1 3.1

West Indian School, 3315 W. Indian

School

11.9 8.9 6.8 6.7

West Phoenix, 3847 W. Earll 10.6 10.4 7.4 7.2

Phoenix Grand Ave., 27th

Ave/Grand/ThomasS

10.5 10.5 6 6

JLG Supersite, 4530 N. 17th Ave. 9.1 7.9 6.9 6.4

Greenwood, I-10 and 27th Ave. 8.1 8.1 5.6 5.6

Maryvale, 6180 W. Encanto S 9.3 9.1 7 7

South Scottsdale, 2857 N. Miller S 5 4.9 3.3 3.1

Tempe, College Av., N. of Daily Park # 5 4.6 3.7 3.5

* Due to mathematical rounding, values > 35.5 and 9.5 ppm are necessary to exceed the

standard.

# Less than 75 percent data recovery available in one or more calendar quarters. S Seasonal monitor operating from January to March and October to December.
2-7

TABLE 2-4

2001 CARBON MONOXIDE MONITORING DATA SUMMARY FOR

THE MARICOPA COUNTY NONATTAINMENT AREA

STANDARDS: 1-HOUR: 35 PPM; 8-HOUR: 9 PPM*

Site Name

1-Hour 8-Hour

Max

ppm

2nd Max

ppm

Max

ppm

2nd Max

ppm

West Chandler, Frye Rd. & Ellis S 3.3 3.1 2.2 2.1

Surprise, 18600 N. Reems Rd. S 2.6 2.5 1.2 1

Glendale, 6000 W. Olive S 4.7 4.7 3.1 2.8

Mesa, 370 S. Brooks S 4.6 3.8 2.9 2.6

South Phoenix, 4732 S. Central S 6.8 6.3 4.5 3.4

Central Phoenix, 1845 E. Roosevelt 6 5.8 4.8 4.2

North Phoenix, 601 E. Butler S 5.2 4.7 2.5 2.5

West Indian School, 3315 W. Indian

School

8 7.7 6.8 6.5

West Phoenix, 3847 W. Earll 8.4 8.2 7.5 6.5

Phoenix Grand Ave., 27th

Ave/Grand/ThomasS

10.3 9.6 6.6 6.1

JLG Supersite, 4530 N. 17th Ave. 7 6.5 5.7 5.2

Greenwood, I-10 and 27th Ave. 7 6.9 5.2 4.6

Maryvale, 6180 W. Encanto S 9 7.5 7.6 5.2

South Scottsdale, 2857 N. Miller S 4.5 4.4 3.2 3.1

Tempe, College Av., N. of Daily Park 4.3 4.2 3.2 3

* Due to mathematical rounding, values > 35.5 and 9.5 ppm are necessary to exceed the

standard.

S Seasonal monitor operating from January to March and October to December.
2-8

FIGURE 2-1

CARBON MONOXIDE MONITORING SITES IN 

THE MARICOPA COUNTY NONATTAINMENT AREA

WC = West Chandler, Frye Rd & Ellis S

GI = Gilbert, 535 N. Lindsay Rd. S

GL = Glendale, 6000 W. Olive S

ME = Mesa, 370 S. Brooks S

SP = South Phoenix, 4732 S. Central S

CP = Central Phoenix, 1845 E. Roosevelt

NP = North Phoenix, 601 E. Butler S

WI = West Indian School, 3315 W. Indian

School

WP = West Phoenix, 3847 W. Earll

GA = Phoenix Grand Ave., 27th Ave/

Grand/Thomas S

JS = JLG Supersite, 4530 N. 17th Ave.

GR = Greenwood, I-10 and 27th Ave.

MA = Maryvale, 6180 W. Encanto S

SS = South Scottsdale, 2857 N. Miller S

TE = Tempe, College Ave., N. of Daily

Park

S

 = Seasonal Monitor
2-9
2-10

APPROVAL OF THE CARBON MONOXIDE NONATTAINMENT SIP ELEMENT FOR THE

MARICOPA COUNTY AREA

In accordance with the 1990 Clean Air Act Amendments, the Maricopa County

nonattainment area was initially classified as Moderate for carbon monoxide. In order to

meet the Moderate area requirements, the MAG 1993 Carbon Monoxide Plan was

submitted to the Environmental Protection Agency by November 15, 1993. An Addendum

to this Plan was submitted in March 1994. On July 29, 1996, the nonattainment area was

reclassified to Serious due to failure to attain the carbon monoxide standard by December

31, 1995. The Serious Area reclassification was effective on August 28, 1996.

On July 8, 1999, the Arizona Department of Environmental Quality submitted the MAG

1999 Serious Area Carbon Monoxide Plan for the Maricopa County Nonattainment Area

to EPA. A completeness finding was issued by EPA on September 9, 1999.

Following the submission of this Plan, the Arizona Legislature passed House Bill 2104

during the 2000 regular session, which repealed the Random Onroad Testing

Requirements (Remote Sensing Program) from the Vehicle EmissionsInspectionProgram.

EPA then indicated that the Serious Area CO Plan that had been submitted, including the

attainment demonstration for December 2000, would need to be revised to reflect the

repeal of the Remote Sensing Program. In response, MAG conducted new air quality

modeling and documented the impact of the repeal of the Remote Sensing Program in the

Revised MAG 1999 Serious Area Carbon Monoxide Plan for the Maricopa County

Nonattainment Area, dated March 2001.

On April 18, 2001, the Arizona Department of Environmental Quality submitted the Revised

MAG Serious Area Carbon Monoxide Plan to EPA. A completeness finding was issued by

EPA on October 9, 2001. While this latest SIP has not been approved under Section

110(k), it is anticipated that EPA will approve the Revised CO Plan before this request for

redesignation is submitted. If not, approval action on SIP elements of the Revised Serious

Area Carbon Monoxide Plan and the redesignation request can occur simultaneously.

IMPROVEMENT IN AIR QUALITY DUE TO PERMANENT AND ENFORCEABLE

EMISSION REDUCTIONS

This section is intended to demonstrate that the improved air quality in the Maricopa

County nonattainment area has occurred as a result of permanent and enforceable

emissions reductions. The monitoring data clearly indicate that carbon monoxide

concentrations have declined steadily since 1994. This continuous decline in emissions

and concentrations has occurred during a period when the area has experienced more

than a 25 percent increase in population, employment, and vehicle miles of travel.

According to the EPA memorandum, Procedures for Processing Requests to Redesignate

Areas to Attainment, September 4, 1992, “The state must be able to reasonably attribute
2-11

the improvement in air quality to emission reductions which are permanent and

enforceable.” As Figure 2-2 illustrates, there has been a continuous downward trend in CO

concentrations at all monitors in the nonattainment area. The second-highest CO levels

decreased by 33 percent between 1994 and 2000, at the same time population,

employment and vehicle travel in the nonattainment area increased by about 30 percent.

Modeling in the Revised Serious Area Carbon Monoxide Plan TSD (p. III-75) indicated that

a 10.9 percent reduction in CO concentrations would be needed to meet the eight-hour

standard in 2000. The modeling also showed that control measures in the Revised Serious

Area Plan would reduce emissions by 10.4 percent in 2000 (p. 9-8) which would be

sufficient to attain the standard of 9 ppm. These results indicate that there is a high

correlation between reductions in CO emissions and concentrations. Since the target

reductions in concentrations were actually achieved by 2000, it is reasonable to assume

that the permanent and enforceable control measures in the Revised Serious Area Carbon

Monoxide Plan were responsible for the reductions in emissions necessary to meet the

eight-hour standard.

The Maintenance Plan described in the next chapter models the year 2015. Table VII-2

in the Carbon Monoxide Maintenance Plan Technical Support Document summarizes the

emission reductions attributable to control measures in 2015. The next section describes

the control measures for which numeric emission reduction credit was assumed in order

to maintain the CO standards through 2015.

ATTAINMENT AND MAINTENANCE CONTROL MEASURES

Generally, the overall approach taken in preparing the Maintenance Plan is to demonstrate

maintenance of the carbon monoxide standard in 2015 with the committed measures in the

Revised MAG 1999 Serious Area Carbon Monoxide Plan. Therefore, the Maintenance

Plan relies heavily upon the Revised MAG 1999 Serious Area Carbon Monoxide Plan and

its supporting documents, including the commitments to implement control measures.

Detailed descriptions of the fifty-five control measures contained in the Revised Serious

Area Carbon Monoxide Plan are contained in Chapter Eight of that Plan. The committed

measures used for numeric emissionreduction credit in the Carbon Monoxide Maintenance

Plan for 2015 are described below. These measures, which are permanent and

enforceable, are anticipated to be in place through the maintenance year of 2015.

Continued implementation of these measures, as well as others in the Revised Serious

Area Carbon Monoxide Plan, will ensure continuing reductions in emissions through 2015

and beyond. 

1. Phased-In Emission Test Cutpoints

The Arizona Vehicle Inspection Maintenance Program was established in 1976 to promote

the clean operation of motor vehicles by controlling vehicle exhaust emissions. The

program is operated by the Arizona Department of Environmental Quality and contains the
2-12

provisions listed in Section 182(c)(3) of the Clean Air Act for an Enhanced Vehicle

Inspection and Maintenance Program.

The Vehicle Emissions Inspection Maintenance Program was significantly enhanced and

strengthened by the Arizona Legislature in 1993 (H.B. 2001). The Legislature established

a biennial, transient loaded (I/M 240) emissions test for gasoline powered vehicles model

year 1981 or newer with a gross vehicle weight of up to 8,500 pounds, beginning

January 1, 1995.

In 1993, the Arizona Legislature passed H.B. 2001 which increased the repair threshold

limits for gasoline powered vehicles in order to be eligible for a waiver through the Vehicle

Emissions Inspection Maintenance Program. The repair limits were increased in the

following manner: 1967-1974 from $50 to $100; 1975-1980 from $200 to $300; and 1981

and newer from $300 to $450. The bill also increased the repair threshold limits from $300

to $500 for diesel powered vehicles with tandem axles or a gross vehicle weight in excess

of 26,000 pounds.

The Arizona Legislature passed H.B. 2237 in 1997 which contained an appropriation of

$120,000 from the State General Fund to the Arizona Department of Environmental Quality

to develop and implement an alternative test protocol to reduce the false failure rates

associated with the more stringent pass-fail standards for the Vehicle Emissions Testing

Program (Section 19 of H.B. 2237).

In addition, the Arizona Department of Environmental Quality was to implement Interim

Test Cutpoints for the Vehicle Emissions Inspection Program until issues were resolved

with the final test cutpoints for the I/M 240 Program. The Interim Cutpoints were selected

to achieve the following failure rates in three vehicle class categories (Light Duty Gasoline

Vehicles, Light Duty Gasoline Trucks 1, and Light Duty Gasoline Trucks 2: 50 percent for

Model Years 1981-85; 25 percent for 1986 to 1989 model years, and 10 percent for Model

Years 1990-93). This measure is a committed attainment measure in the Revised Serious

Area Carbon Monoxide Plan and a committed maintenance measure in the Maintenance

Plan. This measure is estimated to provide a 2.7 percent reduction in emissions in the

year 2000 and a 0.2 percent reduction, in 2015. Additional information on this measure

can be found in the Revised Serious Area Carbon Monoxide Plan on page 8-5 and the

Carbon Monoxide Maintenance Plan TSD on page VII-10.

2. One-Time Waiver from Vehicle Emissions Test

The Arizona Legislature passed S.B. 1002 in 1996 which limits the issuance of a waiver

for failure to comply with the emission testing requirements to one-time only beginning

January 1, 1997 (A.R.S. 49-542 D). This measure is a committed attainment measure in

the Revised Serious Area Carbon Monoxide Plan and a committed maintenance measure

in the Maintenance Plan. This measure is estimated to provide a 0.3 percent reduction in

emissions in the year 2000, and a 0.1 percent reduction, in 2015. Additional information
2-13

on this measure can be found in the Revised Serious Area Carbon Monoxide Plan on page

8-10 and the CO Maintenance Plan Technical Support Document on page VII-11.

3. Winter Fuel Reformulation: California Phase 2 Reformulated Gasoline with 3.5

Percent Oxygen Content November 1 through March 31

The Arizona Legislature passed H.B. 2347 in 1998 which contains requirements for all

gasoline produced and shipped to Maricopa County and sold or offered for sale for use in

motor vehicles in Area A from and after November 1, 2000 through March 31, 2001 and

from the period beginning November 1 through March 31 of each subsequent year. The

fuel must comply with the standards for California Phase 2 Reformulated Gasoline,

including alternative reformulations allowed by the predictive model, as adopted by the

California Air Resources Board, and must meet the maximum vapor pressure requirements

of 9 pounds per square inch in A.R.S. 41-2083, Subsections D and F. The fuel must also

contain a minimum oxygen content by weight of 3.5 percent as required in A.R.S. 41-2123,

Subsection A, Paragraph 2. 

This measure is a committed attainment measure in the Revised Serious Area Carbon

Monoxide Plan and a committed maintenance measure in the Maintenance Plan. This

measure accounts for a 6.8 percent reduction in emissions in the year 2000, and a 21.5

percent reduction, in 2015. Additional information on this measure can be found in the

Revised Serious Area Carbon Monoxide Plan on page 8-17 and the Carbon Monoxide

Maintenance Plan Technical Support Document on page VII-8.

4. Coordinate Traffic Signal Systems

The Arizona Legislature passed H.B. 2001 in 1993 which required that Maricopa County

and the cities and towns in the vehicle emissions control area (Maricopa County

nonattainment area) synchronize traffic control signals on all roadways, within and across

jurisdictional boundaries, which have a traffic flow exceeding 15,000 motor vehicles per

day.

The synchronization of existing signals, as well as the enhancement of coordination among

signal systems that are already synchronized, has been identified by many jurisdictions

through a number of programs. Enhancement efforts range from large scale programs

covering broad geographic areas to incremental additions of a few synchronized signals

to the network. This includes both individual city projects and regional programs, such as

AZTech, also mentioned below.

This measure is a committed attainment measure in the Revised Serious Area Carbon

Monoxide Plan and a committed maintenance measure in the Maintenance Plan. This

measure is estimated to provide a 0.6 percent reduction in emissions in the year 2000 and

a 0.2 percent reduction, in 2015. Additional information on this measure can be found in

the Revised Serious Area CO Plan on page 8-88 and the CO Maintenance Plan TSD on

page VII-13.
2-14

5. Develop Intelligent Transportation Systems

Many local jurisdictions have begun planning and implementing advanced technology

based solutions to address complex traffic management issues on the regional

transportation network. These technologies involve the application of electronics,

telecommunications and sensor technologies and are collectively referred to as Intelligent

Transportation Systems (ITS).

A key component of the regional Intelligent Transportation Infrastructure is the Freeway

Management System (FMS) operated by the Arizona Department of Transportation

(ADOT). The FMS currently covers 42 miles of the freeway system and provides services

such as traveler advisories and incident management. The other major regional ITS

initiative is the AZTech project. This project was selected and funded by USDOT to serve

as one of four ITS Model Deployment Initiatives in the nation. Key elements of the AZTech

project are the interconnection of 13 local traffic management centers and the

instrumentation of eight “smart” corridors that cover nearly 150 miles of arterial streets.

This measure is a committed attainment measure in the Revised Serious Area Carbon

Monoxide Plan and a committed maintenance measure in the Maintenance Plan. This

measure accounts for a 0.4 percent reduction in emissions in the year 2000 and a 0.1

percent reduction, in 2015. Additional information on this measure can be found in the

Revised Serious Area Carbon Monoxide Plan on page 8-31 and the Carbon Monoxide

Maintenance Plan TSD on page VII-14.

6. Defer Emissions Associated with Government Activities

A number of jurisdictions have identified their intent to pursue methods for deferring

emissions out of critical air pollution periods. These activities include restructuring use of

two-cycle gasoline-powered lawn and garden maintenance equipment after 2:00 p.m.,

placing requirements on maintenance contractors, and encouraging employees to limit

vehicle idling and other activities which may contribute to air pollution during critical

periods.

This measure is a committed attainment measure in the Revised Serious Area Carbon

Monoxide Plan and a committed maintenance measure in the Maintenance Plan. This

measure does not result in a reduction in daily emissions of CO in 2000 and 2015, but

rather, shifts the emissions-producing activity to earlier in the day (6 a.m. to 2 p.m.). This

reduces the contribution of emissionsto eight-hour carbon monoxide concentrations during

winter inversion conditions. Additional information on this measure can be found in the

Revised Serious Area CO Plan on page 8-47 and the Carbon Monoxide Maintenance Plan

Technical Support Document on page VII-12.
2-15

7. Tougher Enforcement of Vehicle Registration and Emissions Test Compliance

The Motor Vehicle Division (MVD) of the Arizona Department of Transportation (ADOT)

has instituted a comprehensive vehicle registration enforcement program. Three key

elements of the new program are a Registration Enforcement Team, a Registration

Enforcement Tracking System, and a New Resident Tracking Program. Through public

participation, consistent policy and procedure application, and new tracking methods, MVD

will enforce the Arizona registration laws to ensure vehicles in question are registered

properly. This will be an ongoing effort.

Another phase of the Program is an initiative to coordinate ADOT efforts with other law

enforcement agencies to assist MVD personnel in enforcing registration compliance. Other

initiatives include a system user agreement between MVD and the City Courts to utilize

information in conjunction with registration compliance and discussions with U.S. West

(now known as Qwest) for obtaining information relating to new connect customers.

The Arizona Legislature passed S.B. 1427 in 1998 which requires school districts and

special districts in Area A to prohibit parking in employee parking lots by employees who

have not complied with emissions testing requirements. Cities, towns, and counties in

Area A and Area B are currently subject to this provision (A.R.S. 49-552).

In 1999, the Arizona Legislature passed H.B. 2254 which requires each vehicle that is

owned by the United States government and that is domiciled in this state for more than

ninety consecutive days and each vehicle that is owned by a state or political subdivision

of this state to comply with A.R.S. 49-542.

Collectively, the provisions in H.B. 2254 that apply to Tougher Enforcement of Vehicle

Registration and Emissions Test Compliance include A.R.S. 49-557 and 49-541.01 D.

and E.

This measure is a committed contingency measure in the Revised Serious Area Carbon

Monoxide Plan and is estimated to reduce emissions by 0.4 percent in the year 2000. This

measure is a committed maintenance measure in the Maintenance Plan and accounts for

a 0.2 percent reduction in 2015. Additional information on this measure can be found in

the Revised Serious Area Carbon Monoxide Plan on page 8-13 and the Carbon Monoxide

Maintenance Plan Technical Support Document on page VII-15.

8. Clean Burning Fireplace Ordinances

The Arizona Legislature passed S.B. 1427 in 1998 which requires cities, towns, and

counties in Area A to adopt, implement and enforce an ordinance that complies with the

clean burning fireplace standards adopted by the Metropolitan Planning Organization that

is responsible for air quality planning in Area A by December 31, 1998. The ordinance

must prohibit the installation or construction of a fireplace or wood stove unless it is one

of the following:
2-16

1. A fireplace that has a permanently installed gas or electric log insert.

2. A fireplace, a wood stove or any other solid fuel burning appliance that is any

of the following:

(a) Certified by the U.S. Environmental Protection Agency as in

compliance with 40 Code of Federal Regulations Part 60, Subpart

AAA in effect on July 1, 1990.

(b) A wood stove tested and listed by a nationally recognized testing

agency to meet performance standards equivalent to those in 40

Code of Federal Regulations Part 60, Subpart AAA in effect on

July 1, 1990.

(c) Determined by the County Air Quality Control Officer to meet

performance standards equivalent to those in 40 Code of Federal

Regulations Part 60, Subpart AAA in effect on July 1, 1990.

3. A fireplace that has a permanently installed wood stove insert that complies

with paragraph 2, subdivision (a), (b) or (c) of this section.

The ordinance is required to prohibit the subsequent conversionor alteration of a permitted

fireplace or wood stove to a nonpermitted use. The ordinance may provide for exemptions

from regulation for heating or industrial equipment, cooking devices and outdoor fireplaces.

The state income tax subtraction of $500 dollars for the purchase and installation of a

qualified wood stove, wood fireplace or gas fired fireplace and non-optional equipment is

removed. The subtraction of $500 dollars for the conversion of an existing wood fireplace

to a qualified fireplace is retained.

A county that contains any portion of Area A that has a population of less than 1,200,000

according to the most recent U.S. decennial census shall adopt, implement, and enforce

the ordinance only in those portions of the county which are located in Area A (A.R.S. 9-

500.16 and 11-875).

This measure is a committed contingency measure in the Revised Serious Area Carbon

Monoxide Plan and is estimated to reduce emissions by 0.1 percent in the year 2000. This

measure is a committed maintenance measure in the Maintenance Plan and accounts for

a 0.3 percent reduction in 2015. Additional information on this measure can be found in

the Revised Serious Area Carbon Monoxide Plan on page 8-53 and the Carbon Monoxide

Maintenance Plan Technical Support Document on page VII-17.

9. Off-Road Vehicle and Engine Standards

The Arizona Legislature passed H.B. 2237 in 1997 which requires the Arizona Department

of Environmental Quality to adopt rules for air pollution emission standards for off-road
2-17

vehicles and engines marketed in the State beginning with the 1999 model year. The

standards may include the following categories:

a. Heavy duty Diesel vehicles rated at 175-750 horsepower.

b. Small utility and lawn and garden equipment engines rated at less

than 25 horsepower.

c. Recreational vehicles rated at less than 25 horsepower.

d. Specialty engines and go-carts rated at greater than 25 horsepower.

e. Off-road motorcycles and all terrain vehicles.

The Arizona Department of Environmental Quality is also required to adopt air pollution

emission standards for golf cart engines in Maricopa County (A.R.S. 49-542.04).

Since the adoption of H.B. 2237, federal standards for the same class and types of off-road

engines and equipment became effective that are either equivalent to or more stringent

than California’s standards. Consequently, the Arizona Department of Environmental

Quality submitted a letter to EPA on September 7, 2001 to inform EPA of ADEQ’s intent

to withdraw from adopting California’s standards for off-road vehicles and engines

marketed in the state, beginning with the 1999 model year. Therefore, the federal off-road

standards are being implemented in this state.

This measure is a committed attainment measure in the Revised Serious Area Carbon

Monoxide Plan and is estimated to reduce emissions by 0.4 percent in the year 2000.

However, no numeric credit was assumed for this measure in the Revised Serious Area

Carbon Monoxide Plan, because the standards had not been adopted at the time the Plan

was submitted. This measure is a committed measure in the maintenance plan and

accounts for a 1.9 percent reduction in 2015. Additional information on this measure can

be found in the Revised Serious Area Carbon Monoxide Plan on page 8-42 and the

Carbon Monoxide Maintenance Plan Technical Support Document on page VII-19.

CLEAN AIR ACT SECTION 110 AND PART D REQUIREMENTS

Before an area can be redesignated to attainment, it must meet the requirements of

Section 110 and Part D of the Clean Air Act. The provisions of Section 110(a)(2) and Part

D are required as part of the State Implementation Plan to bring the Maricopa County

nonattainment area into attainment, and have been addressed in plan submissions

currently under review by EPA. EPA has indicated that they expect to approve the Revised

MAG 1999 Serious Area Carbon Monoxide Plan for the Maricopa County Nonattainment

Area in 2003. Upon approval of this Plan, EPA will have determined that all applicable

provisions of Section 110 and Part D have been met. The following section lists the

applicable requirements of Section 110 and Part D and provides references from the

Revised Serious Area Carbon Monoxide Plan that address those requirements.

Section 110(a)(2) addresses general requirements for State Implementation Plans. A

discussion of how each of these requirements is addressed in the Revised Serious Area
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Carbon Monoxide Plan follows. The numbers in parentheses indicate the subsection of

the following narrative in which each of the Section 110(a)(2) requirements is addressed

below.

(A) Include enforceable measures and schedules necessary to show compliance. (1)

(B) Monitor and compile data on ambient air quality. (2)

(C) Provide a program to enforce measures in (A) and regulate stationary sources.

(1),(4)

(D) Prohibit sources from emitting pollutants that would contribute significantly to

nonattainment, interfere with maintenance of the standard, or interfere with

Prevention of Significant Deterioration (PSD) or visibility in other states. (3)

(E) Provide assurances that there are adequate resources to implement the plan,

nothing in the SIP is otherwise prohibited by law, and the State has responsibility

for ensuring adequate implementation. (1)

(F) Stationary source emissions monitoring and reporting. (4)

(G) Provide for emergency powers authority. (5)

(H) Provide for the revisions to the plan. (6)

(I) Meet the applicable requirements of Part D for nonattainment areas. (10)

(J) Meet the requirements of Section 121 (consultation). (9);Section 127 (public

notification);(7) and part C (PSD and visibility). (3),(4)

(K) Perform air quality modeling. (8)

(L) Permitting fees for major stationary sources. (4)

(M) Consultation and participation by local political subdivisions affected by the SIP. (9)

(1) Enforcement, Adequate Resources, and Responsibility for Adequate

Implementation

Sections 110(a)(2)(A), (C) and (E) concerning plan enforcement and implementation

requirements are addressed in Chapter Eight (page 8-146) and Chapter Eleven (page 11-

1) of the Revised Serious Area Carbon Monoxide Plan. In order to comply with these

sections, a State law was passed in 1992 which provides an approach for assurances that

State and local committed measures will be adequately implemented (A.R.S. Section 49-

406 I. and J).

Regarding committed measures, A.R.S. Section 49-406 G. (passed by the Legislature in

1992) requires that each agency which commits to implement any control measure

contained in the State Implementation Plan must describe the commitment in a resolution.

The resolution must be adopted by the appropriate governing body of the agency. State

law also requires the entity to specify the following information in the resolutions: (1) its

authority for implementing the limitation or measure as provided in statute, ordinance, or

rule; (2) a program for the enforcement of the limitation or measure; and (3) the level of

personnel and funding allocated to the implementation of the measure.

Chapter Eleven of the Revised Serious Area Carbon Monoxide Plan includes resolutions

from the MAG member agencies and other implementing entities. The resolutions indicate
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specific commitments to implement various control strategies. Generally, the authorities

of cities and towns to implement the types of measures that they have committed to in their

respective resolutions are provided under A.R.S. § 9-240 Powers of Common Council.

The general authorities of the County to implement the measures in the commitments are

provided under A.R.S. § 11-251 and A.R.S. § 49-478. Copies of these local and county

government authorities are included in Chapter Eleven of the Revised Serious Area

Carbon Monoxide Plan.

If any person (includes State, County, local governments, regional agencies, and other

entities) fails to implement a committed measure, the County would file an action in

Superior Court to have the Court order that the measure be implemented. Likewise, the

Director of the Arizona Department of Environmental Quality will backstop the County if it

fails to implement a committed measure or if the County fails to backstop the local

governments and regional agencies (see Appendix C, Exhibit 2, Revised Serious Area

Carbon Monoxide Plan).

(2) Monitoring and Compiling of Data on Ambient Air Quality

Section 110(a)(2)(B) establishes the requirement to monitor, compile, and analyze ambient

air quality data. Appendix A, Exhibit 2 of the Revised 1999 Plan contains the 1992

Memorandum of Agreement for Air Quality Planning. This agreement identifies Maricopa

County and the Arizona Department of Environmental Quality as having the primary roles

for air quality monitoring, including special purpose air quality and meteorological

monitoring for plan development.

Chapter Four of the Revised Serious Area Carbon Monoxide Plan (page 4-5) provides

additional evidence that the monitoring requirements for the region are being met through

the efforts of the Maricopa County Environmental Services Department and the Arizona

Department of Environmental Quality. Arizona Statutes 49-406. Nonattainment area plan

and 49-424. Duties of Department provide the regulatory basis for air quality monitoring in

the State and any nonattainment areas. Additional information on the current ambient air

quality monitoring network operated in the Maricopa nonattainment area is detailed earlier

in this chapter.

(3) Provisions to Prohibit Sources from Impacting Air Quality in Other States

Section 110(a)(2)(D) requires that a SIP contain adequate provisions prohibiting any

source or other type of emissions activity within the State from emitting any air pollutant in

amounts which will contribute significantly to nonattainment in, or interfere with

maintenance by, any other State with respect to any such national primary or secondary

ambient air quality standard; or interfere with measures required to be included in the

applicable implementation plan for any other State under Part C to prevent significant

deterioration of air quality or to protect visibility.
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Visibility, as defined in Part C of the Clean Air Act, is currently addressed through a Federal

Implementation Plan for the State of Arizona. The transient nature of carbon monoxide

emissions and the lack of proximity to another state make it unlikely that carbon monoxide

emissions are transported from the nonattainment area to another state.

(4) Preconstruction Review for All New and Modified Stationary Sources; Stationary

Source Emissions Monitoring; and Permitting Fees for Major Stationary Sources

The requirements of Sections 110(a)(2)(C), (F), and (L) concerning preconstruction review,

emissions monitoring, and permitting fees for stationary sources are addressed by the

State in Title 49. Article 2. State Air Pollution Control, and Article 3. County Air Pollution

Control, of the Arizona Revised Statutes. Compliance with this requirement is the

responsibility of the Arizona Department of Environmental Quality or applicable county

agency. Appendix A, Exhibit 2 of the Revised Plan contains the 1992 Memorandum of

Agreement for Air Quality Planning. This agreement identifies Maricopa County as having

the lead role for stationary source emissions control.

Following adoption by the State, Maricopa County adopted new source review regulations

designed to prevent significant deterioration of air quality, patterned after the State

regulations. The Maricopa County Regulations contain requirements for obtaining

installation permits for new major sources located in nonattainment, attainment, or

unclassifiable areas. Both the State and Maricopa County new source review regulations

are currently in effect.

The Maricopa County Air Pollution Control Regulations contain the regulations that

constitute the legal basis for control of air pollution sources in Maricopa County, Arizona.

They are adopted to implement the policy set forth in Title 49 of the Arizona Revised

Statutes and to fulfill the State’s responsibilities under the Federal Clean Air Act and its

amendments to provide a legally enforceable State Implementation Plan for the attainment

and maintenance of the National Ambient Air Quality Standards.

Applicable Maricopa County Air Pollution Control Regulations include; Rule 240 - Permits

for New Major Sources and Major Modifications to Existing Major Sources, Rule 241 -

Permits for New Sources and Modifications to Existing Major Sources, and Rule 245 -

Continuous Source Emission Monitoring.

(5) Provide for Authority Comparable to that in Section 303 for Emergency Powers

Section 110(a)(2)(G) addresses the authority for emergency powers. Under Section 303

of the Clean Air Act, upon receipt of evidence that a pollution source or combination of

sources (including moving sources) is presenting an imminent and substantial

endangerment to public health or welfare, or the environment, the EPA Administrator may

bring suit on behalf of the United States in the appropriate United States district court to

immediately restrain any person causing or contributing to the alleged pollution to stop the

emission of air pollutants causing or contributing to such pollution or to take such other
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action as may be necessary. If it is not practicable to assure prompt protection of public

health or welfare or the environment by commencement of such a civil action, the

Administrator may issue such orders as may be necessary to protect public health or

welfare or the environment.

Emergency powers for the State of Arizona are addressed under A.R.S. 49-465. Imminent

and substantial endangerment, 49-462.07 Violation; injunctive relief, and 49-465 Air

Pollution Emergency.

(6) Provide for Plan Revisions to Account for Changes to the NAAQS or When a Plan

is Found Substantially Inadequate to Attain a Standard

Section 110(a)(2)(H) requires a plan revision to take account of revisions of such national

primary or secondary ambient air quality standard, or the availability of improved or more

expeditious methods of attaining such standard, and whenever the Administrator finds that

the plan is substantially inadequate to attain the national ambient air quality standard.

A.R.S. 49-404 State Implementation Plan and 49-406 Nonattainment Area Plan provisions

provide for State, county, and local agencies to revise the SIP to account for changes to

air quality standards or if a plan is found to be inadequate. The applicable documentation

for making plan revisions can be found in Appendix A, Exhibit 2, 1992 Memorandum of

Agreement for Air Quality Planning.

(7) Meet the Applicable Requirements of Section 127 (Relating to Public Notification)

Section 110(a)(2)(J) requires a plan revision to meet the applicable requirements of

Section 127 relating to Public Notification. Public notification procedures followed for the

Revised Serious Area Carbon Monoxide Plan are documented in the section, Public

Participation in the Preparation of the MAG 1999 Serious Area Carbon Monoxide Plan and

MAG 1999 Serious Area PM-10 Plan, in Chapter Ten (page 10-3).

(8) Air Quality Modeling

Section 110(a)(2)(K) provides for the performance of such air quality modeling as the

Administrator may prescribe for the purpose of predicting the effect on ambient air quality

of any emissions of any air pollutant for which the Administrator has established a national

ambient air quality standard, and the submission, upon request, of data related to such air

quality modeling to the Administrator.

Chapter Nine, Demonstration of Attainment Status (page 9-1) and Appendix B, Exhibit 4 -

Revised Technical Support Document for Carbon Monoxide Modeling in Support of the

Revised 1999 Serious Area Carbon Monoxide Plan for Maricopa County, Arizona,

document the air quality modeling conducted in support of the local air quality plans.

Chapter Nine includes several of the key elements of the carbon monoxide modeling
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process, including an assessment of future air quality conditions, a summary of committed

control measure impacts, and projected attainment status.

(9) Consultation and Participation by Local Political Subdivisions Affected by the SIP

Evidence for consultation and participation by local political subdivisions affected by the

SIP can be found in Chapter Ten, Public Participation (page 10-1). The decision-making

structure of the Maricopa Association of Governments includes twenty-five cities and

towns, the Salt River Pima-Maricopa and Gila River Indian Communities, Maricopa County

and the Arizona Department of Transportation.

Appendix A, Exhibit 2 -1992 Memorandum of Agreement for Air Quality Planning from the

Revised MAG 1999 Serious Area Carbon Monoxide Plan, and Chapter One of this

document detail the consultation and participation process for development of the local air

quality plans.

(10) Meet the Applicable Requirements of Part D

The requirement for Nonattainment Plan Provisions are established in Part D, Subpart 1,

Section 172(c), and in Subpart 3, Section 187. Section 172 lists general nonattainment

plan provisions, and Section 187 lists additional provisions for carbon monoxide

nonattainment areas. In those instances where an area is subject to both the general

nonattainment provisions in subpart 1 as well as one of the pollutant-specific subparts, the

general provisions may be subsumed within, or superseded by, the more specific

requirements of Subpart 3.

Subpart 1, Section 172(c), Nonattainment Plan Provisions

1. Implement all reasonably available controlmeasures as expeditiously as practicable

The fifty-five control measures in Chapter Eight of the Revised Serious Area Carbon

Monoxide Plan (page 8-5) have been implemented. Many of these measures go well

beyond reasonably available control measures. The effective implementation of the

measures in the adopted plan was an important element in achieving attainment before the

required date of December 31, 2000. Effective and expeditious implementation of the

control measures resulted in meeting the standard before the attainment date and will also

assist in the continued maintenance of that standard.

In addition, the Maricopa County Environmental Services Department reviews the

implementation status of the various measures contained in the air quality plans on an

annual basis. In order to accurately monitor or track plan implementation, the Maricopa

County Environmental Services Department requests that the implementing agencies and

jurisdictions complete an annual progress report form. The Environmental Services

Department reviews and summarizes this information, preparing an implementation status

report, and then presents the report to the MAG Air Quality Technical Advisory Committee.
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The most recent progress report at the time of the Revised 1999 Serious Area Carbon

Monoxide Plan was the MAG Air Quality Plan 1996 Annual Progress Report (July 1998)

that was provided in Appendix B, Exhibit 2 (see also Chapter 8 Tracking Plan

Implementation, page 8-146).

2. Plans shall require reasonable further progress

In Part D of the Clean Air Act, Section 171 indicates that the term “Reasonable Further

Progress” means such “annual incremental reductions in emissions of the relevant air

pollutant as are required by this part or may reasonable be required by the Administrator

for the purpose of ensuring attainment of the applicable national ambient air quality

standard by the applicable date.” The modeling results presented in Chapter Nine of the

Revised Serious Area Carbon Monoxide Plan supported the conclusion that the Maricopa

County Nonattainment Area would achieve reasonable further progress in meeting the CO

standard by the applicable attainment date, December 31, 2000 (Chapter Nine,

Reasonable Further Progress, page 9-15). Since the attainment date of 2000 has passed

and attainment and reasonable progress targets have been met, annual incremental

reductions are not longer required.

However, in order to track the progress of the maintenance plan, periodic emission

inventories will be prepared every three years in accordance with Section 187(a)(5) of the

Clean Air Act. Maricopa County will coordinate and compile the inventory with input and

assistance from the Arizona Department of Environmental Quality, Arizona Department of

Transportation, and Maricopa Association of Governments, as described in the 1992 Air

Quality Memorandum of Agreement. Changes in the inventory will be reviewed and

evaluated through the regional air quality planning process to determine if additional

measures should be considered. 

3. Plans shall include a comprehensive, accurate, current inventory of actual

emissions from all sources of the relevant pollutant or pollutants in the area and

periodic revisions

The Clean Air Act requires a comprehensive, accurate, and current inventory of actual

emissions from all sources. In 1996, the Maricopa County Environmental Services

Department compiled a 1993 base year emission inventory to determine the sources of

carbon monoxide (CO) for the nonattainment area. During October - November, 1998,

Maricopa County completed a draft 1996 carbon monoxide emissions inventory. Both the

1993 and 1996 inventories are summarized in Chapter Four - Sources of Carbon Monoxide

Emissions, and Figures 4-1 and 4-2, respectively, of the Revised Serious Area Carbon

Monoxide Plan.

The sources of emissions are grouped into four major categories: onroad mobile, nonroad

mobile, stationary area, and stationary point. Collectively, these four sources contributed

a total of 871.5 tons and 1030 tons of CO per day to the nonattainment area during the

1993 and 1996 winter seasons, respectively. Figures 4-1 and 4-2 of the Revised Serious
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Area Carbon Monoxide Plan show the relative contribution of each category for 1993 and

1996. A complete description of these sources and the corresponding methodology used

to calculate Carbon Monoxide emissions for the 1993 base year are included in the

Maricopa County 1993 Periodic Carbon Monoxide Emission Inventory, September 5, 1996

(Appendix A, Exhibit 4 of the Revised Serious Area CO Plan). The Maricopa County 1996

Base Year Carbon Monoxide Emission Inventory, December 16, 1998 is contained in

Appendix A, Exhibit 5 of the Revised Serious Area CO Plan.

In addition to the 1993 and 1996 periodic emissions inventories, the Revised Serious Area

Carbon Monoxide Plan contains emissions used for modeling the episode days of

December 16-17 of 1994 and the attainment year of 2000. The 1994 and 2000 base case

emissions are summarized in Table II-4 of the Revised Serious Area Carbon Monoxide

Plan TSD and the 2000 committed measure package emissions are shown in Table VI-1

of that same document. After the Revised Serious Area Carbon Monoxide Plan was

submitted to EPA, a 1999 periodic CO emissions inventory was prepared by the Maricopa

County Environmental Services Department with input from the Arizona Department of

Environmental Quality, Arizona Department of Transportation, and Maricopa Association

of Governments. The 1999 periodic CO emissions inventory was submitted to EPA in

August 2002.

4. The plan provisions shall identify and quantify the emissions of any pollutant

allowed from the construction and operation of major new or modified stationary

sources in the area

Chapter Four of the Revised Serious Area Carbon Monoxide Plan gives details on

stationary sources emissions, including major new or modified sources. Chapter Nine

documents the impacts from major stationary sources. The 1992 Memorandum of

Agreement for Air Quality Planning found in APPENDIX A, Exhibit 2, provides the

distribution of responsibilities for local air quality planning. The Maricopa County

Environmental Services Department regulates stationary sources in Maricopa County

through the Maricopa County Air Pollution Control Regulations, including Regulation II -

Permit and Fees, and Rule 240 - Permit Requirements for New Major Sources and Major

Modifications to Existing Major Sources.

Section 172(c)(4) requires an area, in developing its plan for attainment, to identify

expected emissions increases that will result from new or modified major sources in a

"zone to which economic development should be targeted" according to

Section 173(a)(1)(B). These provisions effectively allow the State to provide a "growth

allowance" for sources in such an area in lieu of the offset requirements under

Section 173(a)(1)(A). Since this is an optional alternative to requiring the acquisition of

offsets under Section 173(a)(1)(A), it is not a prerequisite to redesignation. Moreover, once

the area is redesignated attainment, these provisions will not apply since the Prevention

of Significant Deterioration (PSD) requirements of Part C will become effective.
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5. The plan provisions shall require permits for the construction and operation of new

or modified major stationary sources anywhere in the nonattainment area

Generally, the requirements of the Part D New Source Review (NSR) permitting

nonattainment program will be replaced by the Prevention of Significant Deterioration

(PSD) program once an area is redesignated to attainment. However, to ensure that the

PSD program can become fully effective immediately upon redesignation, EPA will require

an area to make any needed NSR corrections to their Part C NSR programs prior to

redesignation.

Maricopa County received SIP approval of its major and minor source NSR program in

1988 (See 53 FR 30220, 53 FR30224, and 53 FR 30238, August 10, 1988). Effective

November 22, 1993, EPA delegatedPreventionof Significant Deterioration (PSD) authority

to Maricopa County via a PSD Delegation Agreement. On August 15, 1994, ADEQ

submitted a SIP revision containing portions of the State permitting program that are

applicable to major sources, major source modifications, and minor sources. Part of the

SIP revision, under a separate cover, included applicable Maricopa County rules, pertinent

to the NSR/PSD program. The amendments to Maricopa County Rules 100, 200, 210,

220, 240, and Appendix B were submitted as a revision to the NSR/PSD program. The

submittal also requested approval of synthetic minor provisions under Section 112 (l) of the

CAA. On September 1, 1994, EPA deemed both the ADEQ and Maricopa County SIP

revision complete and each is currently awaiting full approval. To assure adequate SIP

revisions required by Section 110(a)(2)(E) of the CAA, the Director of ADEQ is authorized

under ARS §§ 49-402B to assert jurisdiction over major NSR/PSD and minor NSR sources,

excluding those located on Indian Reservations. ADEQ received SIP approval of its

NSR/PSD program effective May 3, 1983 and delegation of PSD authority for PM-10

effective March 12, 1999.

The EPA guidance memorandum, Part D New Source Review (Part D NSR) Requirements

for Areas Requesting Redesignation to Attainment, October 14, 1994, states that

“nonattainment areas may be redesignated to attainment notwithstanding the lack of a

fully-approved part D NSR program, provided the program is not relied upon for

maintenance.” In addition, the EPA guidance indicates that part D NSR rules do not need

to be placed in the contingency portion of the maintenance plan. It is important to note that

the Carbon Monoxide Maintenance Plan for the Maricopa County nonattainment area does

not rely on credit for the NSR program to demonstrate maintenance.

6. Include enforceable emission limitations and other control measures, means, or

techniques, as well as schedules and timetable for compliance to provide for

attainment of such standard

Since attainment has been achieved, no additional measures are needed to provide for

attainment. The need for additional measures to ensure that maintenance continues is

addressed under the requirements for maintenance plans. Areas should consider the need
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for offsets under the Part C program to ensure that new sources do not "cause or

contribute" to an increase in pollutant levels that would take the area out of compliance.

7. Plans shall meet the applicable requirements of Section 110(a)(2)

In the requests for SIP redesignation, States must show that their plans satisfy the

requirements under Section 110. These requirements specify that the plans must contain

enforceable emission limits, monitoring requirements, procedures to prevent interstate

pollution problems, adequate resources to carry out the control programs, and other

provisions related to the development and administration of effective air pollution control

programs.

The Arizona Revised Statutes Title 49-401 through 470 contain the requirements for the

State Air Pollution Control Program administered by the Arizona Department of

Environmental Quality. Also, the Arizona Revised Statutes Title 49-471 through 516

contain the requirements for the County Air Pollution Control Program. The Maricopa

County Environmental Services Department is the local air pollution control department for

Maricopa County. In addition, the State and local government commitments to implement

specific air quality measures address the actual implementation and resources necessary

for a wide variety of measures. The Commitments documents which accompany the

Revised MAG 1999 Serious Area Carbon Monoxide Plan include the State legislation and

local government commitments for measure implementation.

The Arizona SIP already includes the provisions required by Section 110(a)(2) and Part D

of the Clean Air Act. In approving the Revised MAG 1999 Serious Area Carbon Monoxide

Plan, EPA will be determining that the State has met the requirements of Section 110(a)(2)

and Part D of the Clean Air Act.

8. States may use equivalent techniques for modeling, emission inventories, planning

procedures unless they are less effective than the methods specified by the

Administrator

The provisions of Section 172(c)(8) allow the State to use equivalent techniques for

modeling, inventorying, or other planning activities unless EPA determines that the

techniques are less effective. This allowance will continue to apply with respect to the

requirements of the maintenance plan.

9. Provide for specific contingency measures to be undertaken if the area fails to make

reasonable further progress, or to attain the NAAQS by the applicable attainment

date

The Clean Air Act requires contingency measures to be implemented in three cases: (1)

if the area fails to make reasonable further progress or to attain the National Ambient Air

Quality Standard by the applicable attainment date, (2) if the area fails to meet an

applicable milestone, or (3) if any estimate of vehicle miles traveled (VMT) or updated
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projections of future VMT submitted in an annual report exceeds the VMT predicted in the

most recent prior forecast, taking into account reasonable margins of predictive error (see

Chapter Three of the Revised Serious Area CO Plan). Based on EPA guidance,

committed, implemented measures may be considered contingency measures if they are

not needed to show attainment and do not hasten attainment. 

EPA guidance does not mandate a specific reduction level to be attained by contingency

measures. However, EPA considers measures that offset one year of VMT growth to be

an appropriate guideline for the impact of contingency measures. For the Maricopa County

Carbon Monoxide nonattainment area, annualized VMT growth from 2000 to 2005 is 2.6

percent. Based on the 2000 base case emissions inventory, onroad mobile emissions

account for 67 percent of the carbon monoxide emissions in the nonattainment area.

Therefore, contingency measures that provide approximately a 1.7 percent reduction in

total carbon monoxide emissions should be adopted to meet the EPA guidelines regarding

contingency measure impacts.

The impact of each contingency measure has been estimated individually (see Section V

of the Revised TSD). The results of these analyses are shown in Figure 9-3 of the Revised

Serious Area Carbon Monoxide Plan. The sum of the impacts attributed to the contingency

measures is approximately 1.7 percent. However, due to possible interactions between

contingency measures, the combined effect of simultaneously implementing all of the

contingency measures may not equal the sum of the individual effects. The diverse nature

of the contingency measures helps ensure that each of the larger source categories (i.e.,

area, nonroad mobile, and onroad mobile) are addressed (Chapter 9 CONTINGENCY

MEASURES, Revised Serious Area Carbon Monoxide Plan).

The Section 172(c)(9) requirements for contingency measures are directed at ensuring

reasonable further progress and attainment by the applicable date. These requirements

no longer apply when an area has attained the standard and is eligible for redesignation.

Furthermore, Section 175(A) for maintenance plans (discussed above) provides specific

requirements for contingency measures that effectively supersede the requirements of

Section 172(c)(9) for these areas.

Subpart 3, Section 187(b), Plan Submissions and Requirements, Serious Area

Requirements

1. Meet requirements for Moderate areas with a design value of 12.7 or greater

a. Emissions Inventory

The State is required to submit a comprehensive, current, and current emission inventory

of all sources as described in Section 172(c)(3). This requirement was addressed earlier

in paragraph 3 of the requirements for Subpart 1, Section 172(c), Nonattainment Plan

Provisions.
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b. Vehicle Miles Traveled

Section 187(a) of the Clean Air Act Amendments of 1990 requires that states containing

a carbon monoxide nonattainment area with a design value greater than 12.7 ppm at the

time of classification must forecast vehicle miles traveled (VMT) in the nonattainment area

for each year before the attainment year. EPA has prepared guidance, dated January

1992, regarding compliance with this requirement. For Moderate areas reclassified as

Serious, such as the Maricopa County area, EPA is to issue new SIP guidance pertaining

to implementation of the Section 187 forecasting and tracking provisions at the time of

reclassification.

Upon reclassification of the Maricopa County nonattainment area to Serious, MAG

consulted with EPA and was advised to apply the January 1992 guidance in preparing the

Serious Area CO Plan. Accordingly, the VMT estimation procedures used in the Plan are

consistent with Section 187 guidance for Serious Carbon Monoxide nonattainment areas.

Details of the forecasts and procedures are presented in Chapter Three, Vehicle Miles of

Travel Forecasting and Tracking, in the Revised Serious Area Carbon Monoxide Plan.

According to EPA Section 187 guidance, VMT tracking reports must be submitted to EPA

beginning in the year the Serious Area Carbon Monoxide Plan is submitted (i.e., 1999),

continuing through the year after attainment (i.e., 2001). MAG made a commitment in the

Revised Serious Area Carbon Monoxide Plan to submit annual VMT tracking reports to

EPA after providing for consultation among all affected agencies.

MAG submitted VMT tracking reports to EPA in 1999, 2000 and 2001. The contents of

these annual reports complied with all requirements of Section 187 guidance. The final

report required under this provision, the MAG, 2001 Vehicle Miles of Travel Forecasting

and Tracking Report ,was submitted to EPA in November 2001.

c. Vehicle Inspection & Maintenance Program

The State Vehicle Inspection Maintenance Program established in 1976 is designed to

promote the clean operation of motor vehicles by controlling vehicle exhaust emissions.

The program is operated by the Arizona Department of Environmental Quality and contains

the provisions listed in Section 182(a)(2)(B) of the Clean Air Act for a Vehicle Inspection

and Maintenance (I/M) Program.

The Vehicle Emissions Inspection Maintenance Program was significantly enhanced and

strengthened by the Arizona Legislature in 1993 (H.B. 2001). The Legislature established

a biennial, transient loaded (I/M 240) emissions test for gasoline powered vehicles model

year 1981 or newer with a gross vehicle weight of up to 8,500 pounds, beginning

January 1, 1995.
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H.B. 2001 also increased the repair threshold limits for gasoline powered vehicles in order

to be eligible for a waiver through the Vehicle Emissions Inspection Maintenance Program.

The repair limits were increased in the following manner: 1967-1974 from $50 to $100;

1975-1980 from $200 to $300; and 1981 and newer from $300 to $450. The bill also

increased the repair threshold limits from $300 to $500 for diesel powered vehicles with

tandem axles or a gross vehicle weight in excess of 26,000 pounds.

The Arizona Legislature passed S.B. 1002 in 1996 which limits the issuance of a waiver

for failure to comply with the emission testing requirements to one-time only beginning

January 1, 1997 (A.R.S. 49-542 D.). This measure is documented in the Revised Serious

Area CO Plan as “One-Time Waiver from Vehicle Emissions Test,” on page 8-10; and in

the Technical Support Document, beginning on page V-14.

The Arizona Legislature passed H.B. 2237 in 1997 which contains an appropriation of

$120,000 from the State General Fund to the Arizona Department of Environmental Quality

to develop and implement an alternative test protocol to reduce the false failure rates

associated with the more stringent pass-fail standards for the Vehicle Emissions Testing

Program (Section 19 of H.B. 2237). This measure is documented in the Revised Serious

Area Carbon Monoxide Plan as “Phased-In Emission Test Cutpoints,” beginning on page

8-5; and in the Technical Support Document, beginning on page V-8.

d. Periodic inventories, no later than every three years until attainment of the

standard

This requirement was addressed earlier in this section under requirements for Section 172,

Nonattainment Plan Provisions. Appendix A, Exhibits 4 and 5, of the Revised 1999

Serious Area Carbon Monoxide Plan contain the 1993 and 1996 periodic emission

inventories for the Maricopa County Nonattainment Area. In addition, the Maricopa County

Environmental Services Department has completed a carbon monoxideperiodic emissions

inventory for 1999, the latest version of which was submitted to EPA in August, 2002.

e. Enhanced vehicle inspection and maintenance program

An enhanced vehicle emissions inspection and maintenance program is operated in Area

A of Maricopa and Pinal Counties by the Arizona Department of Environmental Quality.

The program contains the provisions in Section 182(c)(3) of the Clean Air Act for an

Enhanced Vehicle Inspection and Maintenance Program. The State’s complete inspection

and maintenance program is documented in the Final Arizona State Implementation Plan

Revision, Basic and Enhanced Vehicle Emissions Inspection/Maintenance Programs,

Volumes 1 and 2, Air Quality Division, Arizona Department of Environmental Quality, June

2001. EPA proposed approval of the Arizona I/M program in August 2002 and signed the

final approval notice on October 31, 2002. The final approval notice was published in the

Federal Register on January 22, 2003.
2-30

f. Attainment demonstration and specific annual emission reductions to

demonstrate attainment of the standard

Attainment of the standard was addressed earlier in this chapter based on two consecutive

years of clean air quality monitoring data. The Revised Serious Area Carbon Monoxide

Plan addresses this requirement in Chapter Nine, Demonstration of Attainment Status.

2. Transportation control measures as required to attain the standard

Section 108(f) of the Clean Air Act contains a list of sixteen transportation control

measures which may be considered for reducing air pollution. The Arizona Revised

Statutes 49-402 requires that the regional air quality planning agency consider a list of

twenty-four measures. Both sets of measures were incorporated into the Draft

Comprehensive List (see Table 7-1 in the Revised Serious Area Carbon Monoxide Plan).

A comparison of the Suggested List of Measures for Particulate Matter and Carbon

Monoxide with the Section 108(f) Clean Air Act Measures and the measures in State law

is presented in Tables 7-2 and 7-3 of the Revised Serious Area CO Plan. From the

comparison, it is evident that both sets of measures were considered by the regional air

quality planning agency and included in the Suggested List of Measures.

Existing transportation control measures are addressed in the Revised Serious Area

Carbon Monoxide Plan in Chapter Five, Overview of Existing Control Measures. New

transportation control measures and existing measures which are being strengthened are

described in Chapter Eight, The Adopted Plan and Implementation Schedule for the

Revised MAG 1999 Serious Area Carbon Monoxide Plan.

3. Oxygenated gasoline during the portion of the year in which the area is prone to

high ambient concentrations of carbon monoxide, as is necessary to attain the

standard

The Arizona Legislature established a mandatory oxygenated fuels program for the

Maricopa County area in 1988. The program was then enhanced with legislation passed

in 1991 and 1992. Consequently, all gasoline sold from October 1 through March 30 of

each year was required to contain a minimum oxygen content of 2.7 percent by weight.

This requirement was met through the sale of ethanol and MTBE gasoline blends (see

MAG1993 Carbon Monoxide Plan for the Maricopa County Area, “Mandatory Oxygenated

Fuels Program,” on page 4-27).

The Arizona Legislature passed H.B. 2001 in 1993 which required that the oxygen content

of all winter gasoline ethanol blends sold in Maricopa County be increased from 7.3 to 10

percent ethanol by volume. Unleaded gasoline-ethanol blends will not contain more than

the maximum percentage of oxygen allowed by EPA fuel waiver provisions. The increased

oxygen content provisions begin October 1, 1994 through March 31, 1994. This

requirement is in effect from October 1 through March 31 of each year thereafter (see the
2-31

Revised Serious Area Carbon Monoxide Plan, “Increased Oxygen Content of Ethanol

Blends,” page 5-1).

House Bill 2001 also reduced the maximum winter vapor pressure of gasoline fuel sold in

Maricopa County from 10 to 9 pounds per square inch beginning October 1, 1994 through

March 31, 1994. The requirement is also in effect from October 1 through March 31 of

each year thereafter (see the Revised Serious Area Carbon Monoxide Plan, “Reduced

Gasoline Volatility,” page 5-1).

The Arizona Legislature passed H.B. 2347 in 1998 which contains requirements for all

gasoline produced and shipped to Maricopa County and sold or offered for sale for use in

motor vehicles in Area A from and after November 1, 2000 through March 31, 2001 and

from the period beginning November 1 through March 31 of each subsequent year. The

fuel must comply with the standards for California Phase 2 Reformulated Gasoline,

including alternative reformulations allowed by the predictive model, as adopted by the

California Air Resources Board, and must meet the maximum vapor pressure requirements

of 9 pounds per square inch in A.R.S. 41-2083, Subsections D and F. The fuel must also

contain a minimum oxygen content by weight of 3.5 percent as required in A.R.S. 41-2123,

Subsection A, Paragraph 2 (see the Revised Serious Area Carbon Monoxide Plan, “Winter

Fuel Reformulation: California Phase 2 Reformulated Gasoline with 3.5 Percent Oxygen

Content November 1 through March 31,” beginning on page 8-17; and in the Technical

Support Document, beginning on page V-5).

Conformity Requirements

In addition to the above requirements, the State Implementation Plan must demonstrate

that its provisions are consistent with Section 176(c)(4) conformity requirements. These

provisions ensure that federally funded or approved projects and actions and other

regionally significant projects conform to the State Implementation Plan prior to the projects

or actions being implemented.

State rules for transportation conformity were adopted on April 12, 1995, by the Arizona

Department of Environmental Quality, in response to requirements in Section 176(c)(4)(C)

of the Clean Air Act as amended in 1990. These rules became effective upon their

certification by the Arizona Attorney General on June 15, 1995 and, as required by the

federal conformity rule, were submitted to EPA as a revision to the State transportation

conformity SIP.

To date, a State transportation conformity SIP has not received approval by EPA. Section

51.390(b) of the federal conformity rule states: “Following EPA approval of the State

conformity provisions (or a portion thereof) in a revision to the applicable implementation

plan, conformity determinations would be governed by the approved (or approved portion

of the) State criteria and procedures.” The federal transportation conformity rule therefore

still governs, as a transportation conformity SIP has not yet been approved for this area.
2-32

The State rule specifies that Metropolitan Planning Organizations (i.e., MAG, for this

region) must develop specific conformity guidance and consultation procedures and

processes. MAG has developed and adopted two conformity guidance documents to meet

State requirements. MAG developed the “Transportation Conformity Guidance and

Procedures” document, which was adopted initially on September 27, 1995 by the MAG

Regional Council. The document was revised by the MAG Regional Council on

March 27, 1996. This guidance document addresses both the determination of “regional

significance” status for individual transportation projects, and the process by which

regionally significant projects may be approved.

MAG also developed the “Conformity Consultation Processes” document, which was

adopted on February 28, 1996 by the MAG Regional Council. This guidance document

details the public and interagency consultation processes to be used in the development

of regional transportation plans, programs, and projects within the Maricopa County

nonattainment area. Adherence to the above rules, guidance, procedures, and processes

ensure that the SIP provisions are consistent with conformity requirements.
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CHAPTER THREE

MAINTENANCE PLAN

Section 107(d)(3)(E) of the Clean Air Act stipulates that for a nonattainment area to be

redesignated to attainment, Environmental Protection Agency (EPA) must fully approve a

maintenance plan which meets the requirements of the Clean Air Act Section 175A. The

maintenance plan is a State Implementation Plan (SIP) revision and must provide for

maintenance of the relevant National Ambient Air Quality Standards (NAAQS) in the area

for at least ten years after redesignation by EPA.

In determining the amount of lead time to allow, EPA indicated that 18 months, as granted

in section 107(d)(3)(D) of the Clean Air Act, should be assumed for EPA to approve a

redesignation request. Due to uncertainties regarding the time that the area will be

redesignated to attainment, the year 2015 was modeled to assure that the 8-hour carbon

monoxide NAAQS is maintained at least ten years past an official notice of redesignation

to attainment by EPA.

The EPA has established the core elements listed below as necessary for approval of

maintenance plans.

1. Description of the control measures for the maintenance period

 Emission inventories for base and future years

 Maintenance demonstration

 Mobile source emissions budget

 Approved monitoring network

 Verification of continued attainment

 Contingency plan

 Subsequent maintenance plan revisions

MAINTENANCE PLAN CONTROL MEASURES

Generally, the overall approach taken in preparing the Maintenance Plan is to demonstrate

maintenance of the carbon monoxide standard in 2015 with the committed measures in the

Revised MAG 1999 Serious Area Carbon Monoxide Plan. Therefore, the Maintenance

Plan relies heavily upon the Revised MAG 1999 Serious Area Carbon Monoxide Plan and

its supporting documents, including the commitments to implement control measures.

The primary purpose of conducting areawide modeling is to demonstrate control strategy

effectiveness in maintaining the 8-hour Carbon Monoxide National Ambient Air Quality

Standards (NAAQS) for at least ten years after the Maricopa County Nonattainment area

has been redesignated to attainment status. The committed control measures included

in this plan are the same measures included in the Revised MAG 1999 Serious Area

Carbon Monoxide Plan for the Maricopa County Nonattainment Area (March 2001).

However, two committed contingency measures in the Revised Carbon Monoxide Plan

have become committed maintenance measures in the maintenance plan. In addition,
3-2

although not quantified in the Revised Serious Area Carbon Monoxide Plan, Off Road

Vehicle and Engine Standards is a maintenance measure for which emission reduction

credit has been taken in the Maintenance Plan.

It should be noted that two contingency measures in the Revised Carbon Monoxide Plan,

the Voluntary Lawn Mower Emission Reduction Program and the Catalytic Converter

Replacement Program, are not included in the Maintenance Plan. The Arizona Legislature

did not provide additional funding for the Voluntary Lawn Mower Emission Reduction

Program in 2001. In addition, on January 12, 2003, the Arizona Republic reported that the

State’s Clean Air Fund could be used to help reduce the State’s FY 2003 budget deficit.

Since the Clean Air Fund provides support for the Catalytic Converter Replacement

Program, there is a possibility that this program could be eliminated for one or more years.

Since funding of the Program is uncertain, MAG modeled the interim year of 2006 and the

2015 maintenance demonstration without assuming emission reduction credit for this

measure.

In addition, the LEV program included in the Revised Serious Area Carbon Monoxide Plan

as a contingency measure is no longer a control measure in the maintenance plan. This

is because the maintenance plan modeling effort incorporates vehicle emission factors

from the EPA MOBILE6 model, which includes the effects of the National LEV program by

default. In the case of the Revised Serious Area Carbon Monoxide Plan, the MOBILE5a

model was utilized. Since MOBILE5a did not include the National LEV program by default,

the benefits of the program were included as a contingency measure in that plan.

Descriptions of the committed control measures in the Maintenance Plan are organized in

three groups below. The first group of measures includes those for which numeric credit

is assumed in the maintenance demonstration. The combined emission reduction impact

of this group of measures, described as maintenance measures, is reflected in the 2006

and 2015 modeling inventories described in Section VII-3 of the Technical Support

Document. Two contingency measures and one measure not quantified in the Revised

Serious Area Carbon Monoxide Plan are included in this first group of maintenance

measures. The modeling methodologies for the measures in this group are summarized

in Section VII-2 of the Technical Support Document, with more detailed descriptions

provided in Appendix VII of the Technical Support Document. 

The second group of measures includes the committed measures that are part of the

contingency plan described in Section VII-5 of the Technical Support Document. For these

measures, a benefit is quantifiable, but no credit was taken in the maintenance

demonstration. The impact of these measures is not reflected in the 2006 or 2015

modeling inventories.

The third group of measures includes additional measures for which commitments were

received in the Revised Serious Area Carbon Monoxide Plan, but numeric emission

reduction credit was not taken. The impacts of these measures are not readily

quantifiable. However, these measures represent additional legally-enforceable

commitments to reduce emissions and improve air quality in the region.
3-3

A summary of the committed maintenance and contingency measures taken for numeric

credit is provided in Table 3-1. For comparison purposes, Table 3-1 also indicates the

status of these measures in the Revised Serious Area Carbon Monoxide Plan (i.e., whether

they were attainment, contingency, or not-quantified measures).

The general approaches used to model the emission reductions from the individual

measures are similar to those used in the Revised Serious Area Carbon Monoxide Plan.

Figure 3-1 illustrates the emission reduction impact of the individual maintenance

measures in 2015. Table 3-2 quantifies the emission reductions from the committed

maintenance measures in metric tons per day. Figure 3-2 illustrates the emission

reduction impact of the individual contingency measures in 2000. The emission reductions

are shown for the year 2000, because contingency measures can be triggered in

accordance with the provisions of the Contingency Plan anytime after 2000.

Measures Used for Numeric Credit

The nine committed measures assumed in modeling maintenance of the eight-hour carbon

monoxide standard through 2015 are described in Chapter Two. Figure 3-1 identifies the

emission reduction credit for each of the individual maintenance measures. Although not

quantified in the Revised Carbon Monoxide Plan, Off Road Vehicle and Engine Standards,

is a maintenance measure for which emission reduction credit has been taken in the

maintenance plan. Two of the maintenance measures were formerly contingency

measures in the Revised Serious Area Carbon Monoxide Plan. These include Tougher

Enforcement of Vehicle Registration and Emission Test Compliance and Clean Burning

Fireplace Ordinances. Table 3-1 summarizes the maintenance measures and identifies

their comparable status in the Revised Serious Area Carbon Monoxide Plan. These

measures are described in detail in Section VII-2-1 of the Technical Support Document.

Measures Included in the Contingency Plan

Expansion of Area A Boundaries, Gross Polluter Option for I/M Program Waivers, and

Increase Waiver Repair Limit Options are contingency measures in both the Revised

Serious Area Carbon Monoxide Plan and the Carbon Monoxide Maintenance Plan. These

measures are described in Chapter VII of the CO Maintenance Plan TSD. Figure 3-2

identifies the emission reduction credit for each of the individual contingency measures in

2000. The emission reductions are shown for the year 2000, because contingency

measures can be triggered in accordance with the provisions of the Contingency Plan

anytime after 2000. These three contingency measures have already been implemented

in the nonattainment area. Early implementation of contingency measures is allowed by

EPA and helps to ensure that the standard will be maintained through 2015. The

Contingency Provisions in this Chapter identify procedures that will be followed to consider

and implement additional contingency measures, as needed.
3-4

TABLE 3-1

COMMITTED MEASURES USED FOR NUMERIC CREDIT

IN THE CARBON MONOXIDE MAINTENANCE PLAN

Measures Used for Numeric

Credit in the Carbon Monoxide

Maintenance Plan

Status in the

Carbon Monoxide

Maintenance Plan

Status in the

Revised Serious

Area CO Plan

 CARB Phase 2 with 3.5%

Oxygenate in Winter

Maintenance Measure Attainment Measure

 Phased-In Emission Test

Cutpoints

Maintenance Measure Attainment Measure

 One-time Waiver from Vehicle

Emissions Test

Maintenance Measure Attainment Measure

 Defer Emissions Associated with

Government Activities

Maintenance Measure

(affects timing rather than

magnitude of emissions)

Attainment Measure

 Coordinate Traffic Signal

Systems

Maintenance Measure Attainment Measure

 Develop Intelligent Transportation

Systems

Maintenance Measure Attainment Measure

 Tougher Enforcement of Vehicle

Registration and Emission Test

Compliance

Maintenance Measure Contingency Measure

 Catalytic Converter Replacement

Program

Removed Due to

Uncertain Funding

Contingency Measure

 Clean Burning Fireplace

Ordinances

Maintenance Measure Contingency Measure

 Off-Road Vehicle and Engine

Standards

Maintenance Measure Not-Quantified

Measure

 National Low Emission Vehicle

Program

Assumed in MOBILE6 by

Default

Contingency Measure

 Expansion of Area A Boundaries Contingency Measure Contingency Measure

 Gross Polluter Option for I/M

Program Waivers

Contingency Measure Contingency Measure

 Increase Waiver Repair Limit

Options

Contingency Measure Contingency Measure

 Lawn Mower Reduction Program Removed Due to

Uncertain Funding

Contingency Measure
0.1%

0.1%

0.2%

0.2%

0.2%

0.3%

1.9%

21.5%

Defer Emissions Associated

Develop Intelligent

One Time Waiver from

Tougher Enforcement of

Phased-in Emission

Coordinate Traffic

Clean Burning

Off-Road Vehicle

CARB Phase 2 with 3.5%

0.0% 0.5% 1.0% 1.5% 2.0% 22.0%

Percent Reduction

with Government Activities2

Transportation Systems

Vehicle Emissions Test

Vehicle Registrations

Test Cutpoints

Signal Systems

Fireplace Ordinances

and Engine Standards

Oxygenate in Winter1

2

This measure influences when emissions occur rather than their magnitude

NOTE: Individual impact of measures are not additive.

; 6 percent

of emissions from two-stroke gasoline-powered engines used by public agencies were

shifted from post-2 p.m. period to the pre-2 p.m. period on the modeled week day.

3-5

FIGURE 3-1

2015 CARBON MONOXIDE EMISSION REDUCTIONS

FROM INDIVIDUAL MAINTENANCE MEASURES

( ) Percent Reduction in Total Emissions

1

Of the 21.5 percent reduction in emissions, the majority (21.1 percent) is due to

the low sulfur content of the fuel.
3-6

TABLE 3-2

SUMMARY OF 2015 CARBON MONOXIDE EMISSION REDUCTIONS FROM

COMMITTED MAINTENANCE MEASURES USED FOR NUMERIC CREDIT

2015 Emissions Without Maintenance Measures

(metric tons/day)

1253.5

Maintenance Measure

Emission

Reductions

(metric

tons/day)

Percent

Reduction in

Emissions

CARB Phase 2 with 3.5% Oxygenate in Winter1 269.7 21.5%

Off-Road Vehicle and Engine Standards 24.18 1.9%

Clean Burning Fireplace Ordinances 3.82 0.3%

Coordinate Traffic Signal Systems 2.98 0.2%

Phased-in Emission Test Cutpoints 2.92 0.2%

Tougher Enforcement of Vehicle Registrations 2.25 0.2%

One-time Waiver from Vehicle Emissions Test 1.51 0.1%

Develop Intelligent Transportation Systems 0.89 0.1%

Defer Emissions Associated with Government

Activities2

0.0 0.0%

1

Of the 21.5 percent reduction in emissions, the majority (21.1 percent) is due to the low

sulfur content of the fuel.

2

Affects timing rather than magnitude of emissions.
3-7
3-8

The contingency measures are described in detail in Section VII-2-2 of the Technical

Support Document. It is also important to note that two contingency measures in the

Revised Serious Area Carbon Monoxide Plan, Tougher Enforcement of Vehicle

Registration and Emission Test Compliance and Clean Burning Fireplace Ordinances, are

maintenance measures in the Maintenance Plan. 

Two other contingency measures in the Revised Serious Area Carbon Monoxide Plan,

Voluntary Lawn Mower EmissionReductionProgramand Catalytic Converter Replacement

Program, are not included in the Maintenance Plan, because funding for these programs

after 2000 is uncertain. Table 3-1 summarizes the maintenance and contingency

measures in the Maintenance Plan and identifies their comparable status in the Revised

Serious Area Carbon Monoxide Plan. 

Measures Which Improve Air Quality, But Were Not Used for Numeric Credit

The third group represents measures that were not quantified for emission reduction credit,

but are committed measures in both the attainment and maintenance plans. These nonquantified measures are described in detail in Section VII-2-3 of the Technical Support

Document.

EMISSION INVENTORIES

This section summarizes the base year 1994, the interim year 2006, and the maintenance

year 2015 carbon monoxide (CO) emission inventories for use in the Urban Airshed Model

(UAM) simulations. The emissions inventories include onroad mobile, point, area, aviation,

and nonroad mobile sources. The onroad mobile emissions are the major source of CO

emissions in the Maricopa County Nonattainment Area.

The 1994 inventory was developed for December 16-17 and reflected control measures

in place at that time. The future year emission inventories include projected emission

reductions resulting from committed control measures that were implemented after 1994.

Sections III-1 and VII-3 of the Technical Support Document documents the technical

details of the CO emission inventories for 1994, 2006 and 2015.

Demographic and Transportation Data

Growth factors for the future years were based on the latest population projections

approved by the MAG Regional Council in June 1997 and developed from the 1995

Special Census. The 2006 and 2015 employment growth factors by Standard Industrial

Classification (SIC) were based on projections prepared by the Arizona Department of

Economic Security (DES) in August 1997.

The 2006 and 2015 emissions from all sources, except peaking power plants and aircraft,

were increased by six and fifteen percent, respectively. These increases were applied
3-9

regardless of hour of the day or location in the modeling domain, because of an expected

increase in population and employment projections for the State. The DES is in the

process of developing new population projections for the State and counties based on the

2000 Census. These projections will not be available from DES until sometime in mid2003. However, preliminary data indicate that the new population projections will be about

six and fifteen percent higher, respectively, than previous 2006 and 2015 projections for

Maricopa County.

Summary of the Emission Inventories

The 1994 base case, 2006 interim year, and 2015 maintenance year emission inventories

for carbon monoxide are summarized in Table 3-3. In all three inventories, onroad mobile

source emissions represent the largest source of CO emissions in the modeling domain:

83 percent of total emissions in 1994, 77 percent, in 2006 and 74 percent, in 2015.

With the implementation of the committed maintenance measures and stricter Federal

controls on vehicles and fuels, onroad mobile emissions decrease by 19.5 percent between

1994 and 2006, and another 5.3 percent between 2006 and 2015. (See Table 3-4 (a)).

Area source emissions increase 41.4 percent between 1994 and 2006, and another 21.9

percent between 2006 and 2015, due to anticipated growth in regional population. Between

1994 and 2015, point source emissions increase almost twelve-fold, as a result of

expected increases in power plant emissions. Nonroad mobile source emissions increase

about ten percent between 1994 and 2015, because control measures do not fully offset

growth in the number of nonroad engines. With implementation of the committed

maintenance measures, total emissions decrease by thirteen percent between 1994 and

2006, and another one percent between 2006 and 2015.

MAINTENANCE DEMONSTRATION

To demonstrate maintenance of the 8-hour carbon monoxide NAAQS, the results from the

urban airshed modeling analyses should not show predicted 8-hour maximum carbon

monoxide concentrations greater than 9.0 ppm anywhere in the modeling domain for the

episode modeled. The maintenance demonstration follows the deterministic procedure

prescribed in the EPA Guideline.

UAM Analysis

The purpose of future year simulations is to illustrate the effects of projected emission

changes on simulated air quality for a given episode. Comparison of the base and future

year emission totals indicates that total carbon monoxide emissions for 2015 are 14.0

percent lower than the 1994 emissions estimates for the first simulation day and 12.6

percent lower for the second simulation day (see Tables 3-4(a) and 3-4(b)). The 1994,

2006, and 2015 maximum simulated carbon monoxide eight-hour concentrations are

provided in Table 3-5 for comparison.
3-10

December 2006

December 1994

December 2015

TABLE 3-3

1994 BASE CASE AND 2006 AND 2015 COMMITTED MAINTENANCE MEASURE

EMISSIONS

Friday, December 1994

Source Category Metric Tons

per Day

Percent

Point 2.5 0.2

Area 21.0 2.0

Nonroad Mobile 155.1 14.8

Onroad Mobile 869.6 83.0

Total 1048.2* 100.0*

Friday, December 2006

Source Category Metric Tons

per Day

Percent

Point 21.9 2.4

Area 29.7 3.3

Nonroad Mobile 161.0 17.6

Onroad Mobile 699.7 76.7

Total 912.3* 100.0*

Friday, December 2015

Source Category Metric Tons

per Day

Percent

Point 32.2 3.6

Area 36.2 4.0

Nonroad Mobile 169.9 18.9

Onroad Mobile 662.9 73.6

Total 901.2* 100.0*

*Note that the sum of the source categories may not

equal 100.0 percent due to rounding.
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TABLE 3-4(a)

EMISSION TOTALS FOR A FRIDAY IN DECEMBER

(METRIC TONS/DAY)

Source 1994 2006 2015 1994-2006

Change (%)

1994-2015

Change (%)

Point 2.5 21.9 32.2 776.0 1188.0

Area 21.0 29.7 36.2 41.4 72.4

Nonroad Mobile 155.1 161.0 169.9 3.8 9.5

Onroad Mobile 869.6 699.7 662.9 -19.5 -23.8

Total 1048.2 912.3 901.2 -13.0 -14.0

TABLE 3-4(b)

EMISSION TOTALS FOR A SATURDAY IN DECEMBER

(METRIC TONS/DAY)

Source 1994 2006 2015 1994-2006

Change (%)

1994-2015

Change (%)

Point 2.5 21.3 31.5 752.0 1160.0

Area 21.3 27.7 35.3 30.1 65.7

Nonroad Mobile 207.7 203.1 208.1 -2.2 0.2

Onroad Mobile 538.1 494.7 398.0 -8.1 -26.0

Total 769.6 746.8 672.9 -3.0 -12.6

TABLE 3-5

THE 1994, 2006 AND 2015 MAXIMUM SIMULATED EIGHT-HOUR CARBON MONOXIDE 

CONCENTRATIONS FOR THE DECEMBER 16-17 EPISODE

Year

Regional Maximum Simulated

Eight-hour Concentration (ppm) Location

1994 10.71 (15,13)

2006 8.92 (14,13)

2015 8.06 (14,13)
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The 2006 and 2015 maximum simulated carbon monoxide concentrations are lower than

in 1994 for the episode (8.92 and 8.06 ppm, respectively, compared to 10.71 ppm for

1994). The Quality Assurance and Diagnostic Analyses and Performance Evaluation for

the UAM runs are documented in Chapters III and VI, respectively, of the Carbon Monoxide

Maintenance Plan Technical Support Document.

Microscale Analysis

The microscale analyses performed for the 2006 interim year and 2015 committed

maintenance measure package were performed using the same general methodology as

for the 1994 base case analysis. The microscale analyses are documented in Chapter V

of the Carbon Monoxide Maintenance Plan Technical Support Document. 

For the 2006 and 2015 microscale analyses, the traffic volumes were updated to reflect the

2015 time frame and emission factors from the EPA mobile model were updated to reflect

the appropriate future year and effects of the committed measures. In addition, the overall

configuration of the Thomas Road/Grand Avenue/27th Avenue intersection was updated

to reflect a “fly-over” expected to be completed by the end of 2003. 

Combined UAM/CAL3HQC Results

The modeling results showed maintenance of the NAAQS for carbon monoxide in 2006

and 2015 for the Maricopa County nonattainment area, since the simulated CO

concentrations are all below 9 ppm. The maximum carbon monoxide modeled

concentrations at the grid cells where the receptors for the hot spots were located in 1994

are summarized in Table 3-6. The simulated maximum carbon monoxide concentration

is 8.92 ppm in 2006 and 8.06 ppm in 2015.

MOBILE SOURCE CARBON MONOXIDE EMISSIONS BUDGETS

In accordance with the 1990 Clean Air Act Amendments, conformity requirements are

intended to ensure that transportation activities do not result in air quality degradation.

Section 176 of the Clean Air Act requires that transportation plans, programs, and projects

conform to applicable air quality plans before the transportation action is approved by a

Metropolitan Planning Organization (MPO). The designated MPO for the Maricopa County

area is MAG.

Section 176(c) of Clean Air Act provides the framework for ensuring that Federal actions

conform to air quality plans under section 110. Conformity to an implementation plan

means that proposed activities must not (1) cause or contribute to any new violation of any

standard in any area, (2) increase the frequency or severity of any existing violation of any

standard in any area, or (3) delay timely attainment of any standard or any required interim

emission reductions or other milestones in any area.
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TABLE 3-6

COMBINED UAM/CAL3QHC 2006 AND 2015 MAXIMUM EIGHT-HOUR CARBON

MONOXIDE CONCENTRATIONS (PPM) FOR THE DECEMBER 16-17 EPISODE

In 2006

Location

UAM

Grid Cell

UAM

Concentration

CAL3QHC

Concentration Total

Ending

Hour

WISR Monitor (11,15) 7.22 0.06 7.28 0300

WISR Receptor # 9 (11,15) 7.17 1.08 8.25 0200

WISR Receptor # 8 (11,15) 7.17 0.91 8.08 0200

WISR Receptor # 20 (11,15) 7.17 0.68 7.85 0300

PHGA Monitor * N/A N/A N/A 0.00 N/A

PHGA Receptor # 30 (12,15) 7.74 0.50 8.24 0300

PHGA Receptor # 29 (12,15) 7.89 0.19 8.08 0300

PHGA Receptor # 46 (12,14) 7.74 0.29 8.03 0300

UAM Maximum (14,13) 8.92 - 8.92 0400

In 2015

Location

UAM

Grid Cell

UAM

Concentration

CAL3QHC

Concentration Total

Ending

Hour

WISR Monitor (11,15) 6.56 0.03 6.59 0300

WISR Receptor # 9 (11,15) 6.23 1.81 8.04 0200

WISR Receptor # 8 (11,15) 6.23 1.61 7.84 0200

WISR Receptor # 20 (11,15) 6.56 0.88 7.44 0300

PHGA Monitor * N/A N/A N/A 0.00 N/A

PHGA Receptor # 30 (12,15) 7.16 0.65 7.81 0300

PHGA Receptor # 29 (12,15) 7.16 0.29 7.45 0300

PHGA Receptor # 46 (12,14) 7.19 0.20 7.39 0300

UAM Maximum (14,13) 8.06 - 8.06 0400

WISR = West Indian School Road monitor

PHGA=Phoenix Grand Avenue monitor

* Due to the reconfiguration of the PHGA intersection, the location of the actual monitor at that

intersection in future years is unknown.
3-14

EPA transportation conformity regulations (August 1997) establish criteria involving

comparison of projected transportation plan emissions with the motor vehicle emissions

assumed in applicable air quality plans. The regulations define the term “motor vehicle

emissions budget” as meaning “the portion of the total allowable emissions defined in a

revision of the applicable implementation plan (or in an implementation plan revision which

was endorsed by the Governor or his or her designee) for a certain date for the purpose

of meeting reasonable further progress milestones or attainment or maintenance

demonstrations, for any criteria pollutant or its precursors, allocated by the applicable

implementation plan to highway and transit vehicles.”

The transportation conformity budget for carbon monoxide was established in ChapterNine

of the Revised Serious Area Carbon Monoxide Plan in the section, Motor Vehicle

Emissions Budget for Conformity. The budget was established at 412.2 metric tons per

day for 2000 for the modeled area. EPA issued a notice of adequacy in the Federal

Register on October 17, 2001, finding that this budget was adequate for transportation

conformity purposes. This budget will be used in MAG transportation conformity analyses

until the maintenance plan is approved or the maintenance budgets are found to be

adequate. At that time, new transportation conformity budgets for carbon monoxide will

be established for 2006 and 2015 for use in subsequent conformity analyses.

The projections in this Maintenance Plan indicate that the daily carbon monoxide emissions

in 2006 and 2015 would be 912.3 and 901.2 metric tons per day, respectively, with the

committed maintenance measures, which includes an onroad mobile source contribution

of 699.7 metric tons per day in 2006 and 662.9 metric tons per day in 2015 (from Table 3-

3). The total onroad mobile source emissions of 662.9 metric tons per day represents the

motor vehicle emissions conformity budget for carbon monoxide in 2015. Since 2006 was

also modeled, the Maintenance Plan establishes an interim motor vehicle emissions

conformity budget for carbon monoxide of 699.7 metric tons per day in 2006. The 2006

and 2015 emission inventories used to establish the mobile source emissions budgets are

documented in Appendix VII of the CO Maintenance Plan TSD. 

After EPA finds the maintenance budgets to be adequate or approves the maintenance

plan, MAG will apply the provisions of the EPA transportation conformity regulations

(August 15, 1997), 40 CFR Part 93 Section 93.118(b). This Maintenance Plan establishes

motor vehicle emissions budgets for the maintenance year of 2015 and the interim year

of 2006. In accordance with 40 CFR Part 93 Section 93.118(b), MAG will use the new

interim mobile source carbon monoxide emissions budget for the conformity horizon years

of 2006 through 2014 and the new 2015 mobile source carbon monoxide emissions budget

for conformity horizon years after 2014. 

Onroad mobile source emissions for 2006 and 2015 were developed by MAG using the

EPA-approved MOBILE6 model and Highway Performance Monitoring System (HPMS)

reconciliation methodology. Documentation of the HPMS reconciliation methodology and

an EPA approval letter are contained in Appendix III-iv of the Technical Support Document.
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After the new 2006 and 2015 motor vehicle emissions budgets are found to be adequate

or are approved by EPA for conformity purposes, MAG will apply MOBILE6 and the HPMS

reconciliation procedure to estimate onroad mobile source emissions for the conformity

horizon years of 2006 and beyond.

MONITORING NETWORK / VERIFICATION OF CONTINUED ATTAINMENT

Air quality monitoring data in Maricopa County confirm that the attainment date of

December 31, 2000 was met, since no violation of the CO standard has occurred at any

monitor since 1996. As a result of the “clean” data at the monitors, the State of Arizona

requested a carbon monoxide attainment determination from EPA on July 23, 1999.

Once the Maricopa County Nonattainment Area has been redesignated to attainment

status by EPA, the Arizona Department of Environmental Quality (ADEQ) and the Maricopa

County Environmental Services Department (MCESD) will continue to operate an

appropriate air quality monitoring network of National Air Monitoring Stations (NAMS) and

State and Local Air Monitoring Stations (SLAMS) monitors in accordance with 40 CFR Part

58 to verify the continued attainment of the carbon monoxide standard. If measured

mobile source parameters (e.g., vehicle miles traveled, congestion, fleet mix, etc.) change

significantly over time, ADEQ and MCESD will perform the appropriate studies to

determine whether additional and/or re-sited monitors are necessary. Annual reviewof the

NAMS/SLAMS air quality surveillance system will be conducted in accordance with 40 CFR

58.20(d) to determine whether the system continues to meet the monitoring objectives

presented in Appendix D of 40 CFR Part 58.

In order to track the progress of the maintenance plan, periodic emission inventories will

also be prepared every three years in accordance with Section 187(a)(5) of the Clean Air

Act. Maricopa County will coordinate and compile the inventory with input and assistance

from the Arizona Department of Environmental Quality, Arizona Department of

Transportation, and Maricopa Association of Governments, as described in the 1992 Air

Quality Memorandum of Agreement. Changes in the inventory will be reviewed and

evaluated through the regional air quality planning process to determine if additional

measures should be considered. 

CONTINGENCY PROVISIONS

Section 175A(d) of the Clean Air Act requires that maintenance plans contain contingency

provisions. EPA guidance on the required content of the contingency plan is provided in

the September 4, 1992 EPA memorandum. This memo indicates that the contingency plan

is not required to contain fully adopted contingency measures. However, the plan should

contain clearly identified contingency measures to be adopted, a schedule and procedure

for adoption and implementation, and a specific time limit for action by the State. In

addition, specific indicators should be identified which will be used to determine when the

contingency measures need to be implemented. The Maintenance Plan addresses each

of these requirements for an approvable contingency plan.
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Consistent with the August 13, 1993 EPA guidance memorandum titled, “Early

Implementation of Contingency Measures for Ozone and Carbon Monoxide (CO)

Nonattainment Areas”, the contingency plan described in the maintenance plan is

comprised of committed control measures that are expected to be implemented early.

Early implementation of contingency measures in a maintenance plan has been approved

by EPA in the redesignation of the Salt Lake City Carbon Monoxide Nonattainment Area

to attainment (see page 3216 of the January 21, 1999 Federal Register). In that action,

EPA noted that both contingency measures in the Salt Lake City contingency plan had

already been partially implemented.

The three contingency measures in the Maintenance Plan are Area A Expansion, Gross

Polluter Option for I/M Program Waivers, and Increased Waiver Repair Limit Options.

Emissions reduction credit for these contingency measures was not taken in the

maintenance demonstration.

A description of these individual measures is provided in Section VII-2-2 of the Technical

Support Document. Figure 3-2 provides the emission reductions in 2000 for the individual

contingency measures. Early implementation of these contingency measures provides

additional confidence that the carbon monoxide standard will be maintained through 2015.

The success of an air quality program is measured by the concentrations recorded at the

monitors. In order to ensure that violations of the CO standard do not occur in the future,

ambient air quality monitoring data will be examined to determine if additional contingency

measures are needed. Two verified readings exceeding 9.0 ppm at two or more SLAMS

or NAMS monitors during a single carbon monoxide season (i.e. October 1 through March

31) will trigger consideration of additional measures, which may include the strengthening

of contingency measures shown in Figure 3-2. Since a violation of the NAAQS for eighthour carbon monoxide occurs when the second highest reading at the same monitor over

two consecutive years is greater than or equal to 9.5 ppm, this trigger is more stringent

than the standard and will serve to prevent the occurrence of future violations. When the

trigger is activated, additional measures would be considered on the following schedule:

(A) verification of the monitoring data to be completed three months after activation of the

trigger; (B) applicable measure to be considered for adoption six months after date

established in A above; and (C) resultant committed measure to be implemented within six

to twelve months, depending upon the time needed to put the measure in place. 

SUBSEQUENT MAINTENANCE PLAN REVISIONS

It is required that a maintenance plan revision be submitted to the EPA eight years after

the original redesignation request/maintenance plan is approved. The purpose of this

revision is to provide for maintenance of the carbon monoxide NAAQS for an additional ten

years following the first ten-year period. As the designated Regional Air Quality Planning

Agency for the Maricopa County area, the Maricopa Association of Governments intends

to prepare a revised maintenance plan eight years after redesignation to attainment, as

required by the Clean Air Act and the Environmental Protection Agency.