State of California

Staff Report

Yuba City-Marysville PM2.5 Maintenance 

Plan and 

Redesignation Request 

Release Date: 

Scheduled for Consideration: April 25, 2013

 

California Environmental Protection Agency

AIR RESOURCES BOARD
This document has been reviewed by the staff of the California Air Resources Board 

and approved for publication. Approval does not signify that the contents necessarily 

reflect the views and policies of the Air Resources Board, nor does the mention of trade 

names or commercial products constitute endorsement or recommendation for use.
TABLE OF CONTENTS

I. BACKGROUND...................................................................................................... 1

II. REDESIGNATION REQUIREMENTS .................................................................... 2

III. EVALUATION OF THE REDESIGNATION REQUEST/MAINTENANCE PLAN ... 2

A. Monitoring Shows Compliance with PM2.5 Standard........................................ 3

B. Applicable Act Requirements are Satisfied ....................................................... 4

C. Attainment Results from Permanent and Enforceable Emission Reductions .... 4

D. Maintenance Plan Provides for Continuing Attainment ..................................... 4

1. Attainment Year Emission Inventory............................................................ 4

2. Maintenance Demonstration........................................................................ 6

3. Motor Vehicle Emission Budgets ................................................................. 8

4. PM2.5 Monitoring Network .......................................................................... 8

5. Verification of Continued Attainment ........................................................... 8

6. Contingency Plan ........................................................................................ 8

IV. STAFF RECOMMENDATION ................................................................................ 9
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I. BACKGROUND

The Yuba City-Marysville area in the Feather River Air Quality Management District 

(District) was designated as nonattainment for the 2006 24-hour fine particulate (PM2.5) 

National Ambient Air Quality Standard (standard) on December 14, 2009. The 

nonattainment area includes Sutter County and a portion of Yuba County and was 

designated nonattainment based on 2005 to 2007 Federal Reference Monitor (FRM) 

data. Figure 1 outlines the nonattainment area and shows the location of the monitoring 

site. The Yuba City-Marysville nonattainment area has a single PM2.5 FRM monitor, 

which in 2007 had a design value of 40 ug/m3. Beginning in 2008, the 24-hour design 

value has been below the standard.

Figure 1. Map of the Yuba City-Marysville PM2.5 Nonattainment Area
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II. REDESIGNATION REQUIREMENTS 

On June 8, 2010, ARB submitted a request to the U.S. Environmental Protection 

Agency (U.S. EPA) to find the Yuba City-Marysville nonattainment area in attainment of 

the 35 ug/m3 24-hour PM2.5 standard. The U.S. EPA took final action on 

January 10, 2013 determining that the area attained the standard. This clean data 

finding, under the U.S. EPA Clean Data Policy for the Fine Particulate National Ambient 

Air Quality Standards (Clean Data Policy), suspends the majority of the planning 

elements under the Clean Air Act (Act). 

Air Resources Board (ARB) staff reviewed the District’s Yuba City-Marysville PM2.5 

Nonattainment Area Redesignation Request and Maintenance Plan (Redesignation 

Request/Maintenance Plan) within the context of the Act, which identifies the following 

requirements an area must meet to be redesignated to attainment:

A. The area has attained the standard;

B. The applicable implementation plan is fully approved under Act section 110 (k),

and the area has met all applicable requirements of Act section 110 and part D;

C. The PM2.5 air quality improvements are due to permanent and enforceable 

emission reductions; and

D. The area has a fully approved maintenance plan satisfying section 175A of the 

Act.

The Act also sets the general framework for maintenance plans1. Each PM2.5

maintenance plan must provide for continued maintenance of the PM2.5 standard for 

ten years after redesignation and include the following components:

1. Attainment emission inventory; 

2. Maintenance demonstration;

3. Commitment to continue the monitoring network operation;

4. Commitment for verification of continued attainment; and

5. Contingency plan to promptly correct any violation of the PM2.5 standard that 

occurs after the area has been redesignated.

III. EVALUATION OF THE REDESIGNATION REQUEST/MAINTENANCE PLAN

Based on review of the District Redesignation Request/Maintenance Plan and 

supporting technical analysis, ARB staff concurs that the Redesignation 

Request/Maintenance Plan meets the Act’s requirements. The following sections 

describe the major elements of the Redesignation Request/Maintenance Plan.

 

1 Calcagni, John, Memorandum, Procedures for Processing Requests to Redesignate Areas to 

Attainment, Office of Air Quality Planning and Standards, Research Triangle Park, North Carolina, 

September 4, 1992. http://www.epa.gov/ttn/oarpg/t5/memoranda/redesignmem090492.pdf
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A. Monitoring Shows Compliance with PM2.5 Standard

As shown in Figure 2, PM2.5 air quality has improved significantly over the last few 

years in the Yuba City-Marysville nonattainment area. PM2.5 is measured at a single 

monitoring station, Yuba City-Almond Street (Figure 1), where an FRM sampler collects 

24-hour average samples daily. The area first reached compliance with the 24-hour 

standard in 2008, with a design value of 33 ug/m3. The design value represents the 

3-year average of the 98th percentile of 24-hour PM2.5 concentrations. 

Although wildfires that occurred in the summer of 2008 resulted in a number of 

exceedances of the 24-hour standard, U.S. EPA’s exceptional events rule allows for 

exclusion of exceedances due to natural events. Since then, the area has continued to 

measure compliance with the 24-hour standard. Figure 2 shows the design values at 

the Yuba City site between 2001 and 2012, demonstrating attainment. 

Between 2001 and 2012, annual average and 24-hour PM2.5 design values in the Yuba 

City-Marysville nonattainment area decreased by nearly 50 percent due to ongoing 

emission reductions. The downward trend was not a result of “unusually favorable 

meteorology”. Between 2008 and 2012, the area experienced a variety of 

meteorological conditions, including 2011 which was extremely conducive to high 

PM2.5 pollution including stagnation that persisted over 20 days. Despite this, 2011 

and 2012 design values are significantly below the 24-hour standard. 

Figure 2. 24-hour Design Values at Yuba City*

* 2008 wildfire impacts excluded from the design value calculation
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B. Applicable Act Requirements are Satisfied

ARB and the District have met all of the Act requirements applicable for a PM2.5

nonattainment area to be considered for redesignation. On June 8, 2010, ARB 

requested a “clean data” finding for the 24-hour PM2.5 standard for this area. On 

January 10, 2013, U.S. EPA signed a final rule determining that the Yuba 

City-Marysville nonattainment area has attained the 24-hour PM2.5 standard based on 

2009-2011 data. This clean data finding suspended the obligation to submit State 

Implementation Plan (SIP) elements that provide for attainment of the standard, 

implementation of all reasonably available control measures, reasonable further 

progress (RFP), and implementation of contingency measures for failure to meet 

deadlines for RFP and attainment. The only SIP element remaining is an emission 

inventory. To address the remaining SIP requirement, the District Redesignation 

Request/Maintenance Plan includes a 2011 winter emission inventory. 

C. Attainment Results from Permanent and Enforceable Emission Reductions

Numerous District and State emission control programs have been adopted and 

implemented over the last several years, providing permanent and enforceable 

reductions in direct PM2.5 and PM2.5 precursor emissions. Many of these programs 

will provide additional emission reductions during the maintenance period, ensuring 

continued compliance with the standard. The Redesignation Request/Maintenance 

Plan lists post-2006 control measures that are responsible for the significant 

improvements in PM2.5 air quality, including restrictions on open burning and residential 

fuel combustion, and on-road and off-road motor vehicle and equipment control 

programs. 

D. Maintenance Plan Provides for Continuing Attainment

Section 175A of the Act establishes the required elements of a maintenance plan for 

areas seeking redesignation from nonattainment to attainment. Using an attainment

year inventory and future inventory projections, plans must demonstrate continued 

attainment through the first 10-year maintenance period. Comprehensive inventories 

were developed for the representative attainment year (2011), an interim year (2017), 

and the end of the maintenance period (2024) for directly emitted PM2.5 and PM2.5 

precursors. 

1. Attainment Year Emission Inventory

An emission inventory is a critical tool used to support evaluation, control, and mitigation 

of air pollution which is comprised of a systematic listing of the sources of air pollutants 

along with the amount of pollutants emitted from each source or category over a given 

period of time. Emission inventories are estimates of the air pollutant emissions 

released into the environment – they are not direct ambient concentration 
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measurements. As part of the maintenance plan, the District submitted an attainment 

year inventory characterizing emissions in the maintenance area. 

U.S. EPA recommends that the attainment year inventory be from one of the three 

years used to demonstrate attainment. In case of the Yuba City-Marysville 

nonattainment area, 2011 was selected as an attainment year inventory coinciding with 

the last year in the U.S. EPA clean data finding. The attainment year inventory includes 

emissions of PM2.5, volatile organic compounds (VOCs), oxides of nitrogen (NOx), 

oxides of sulfur (SOx), and ammonia (NH3). 

An emission inventory should be consistent with the nature of the air quality problem. 

Since the 2006 24-hour PM2.5 standard was designated to protect against peak 

exposures, the inventory should reflect the season when most exceedances occur. As 

demonstrated in the Redesignation Request/Maintenance Plan and also shown in 

Figure 3, all of the highest PM2.5 concentrations in the Yuba City-Marysville 

nonattainment area over the course of the year occur during the winter. Therefore, the 

winter inventory developed for the attainment year and future years is the most 

appropriate for SIP planning purposes. Table 1 lists 2011 winter emission inventories

split by source category.

Figure 3. Total Count of Exceedance Days per Month Based on 11 Years of Data

* Excluding data affected by exceptional events.

Table 1. Attainment Year Winter Emission Inventory (tons/day)

Category VOC NOX SOX PM2.5 NH3

STATIONARY 4.0 4.4 0.1 0.9 0.4

AREAWIDE 5.5 1.1 0.1 3.8 4.5

ON-ROAD MOTOR VEHICLES 2.8 8.4 0.0 0.3 0.2

OTHER MOBILE SOURCES 2.3 5.4 0.1 0.3 0.0

TOTAL 14.6 19.3 0.4 5.3 5.0
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2. Maintenance Demonstration

In order to demonstrate maintenance of the PM2.5 24-hour standard through the year 

2024, the District compiled an emission inventory for an attainment year (2011) and 

formulated projections for the intermediate year (2017) and for the final year of the 

maintenance period (2024). The attainment year and projected inventories represent 

winter emissions which reflect the nature of the PM2.5 problem in the area. If each of 

the projected emission levels is less than the emissions for the attainment year, 

maintenance of the standard is demonstrated. This approach assumes that ambient 

concentrations will remain below the standard as long as future emissions are kept 

below the attainment year emissions. The interim and future year inventories include 

banked Emission Reduction Credits (ERCs) to demonstrate that the addition of ERC’s 

will not compromise attainment. 

The maintenance demonstration includes emissions of direct PM2.5, SOx, and NOx. 

The U.S. EPA PM2.5 implementation rule specifies that a precursor is considered 

“significant” for control strategy development purposes when a significant reduction in 

the emission of that precursor pollutant leads to a significant decrease in PM2.5 

concentration. Such pollutants are known as “PM2.5 attainment plan precursors” 

(72 FR 20586). The PM2.5 implementation rule also established a presumption that 

PM2.5, NOx, and SOx are attainment plan precursors, while VOCs and ammonia are 

not unless they are needed for attainment demonstration or are significant for 

maintaining the NAAQS. 

Although speciation data is not routinely collected, limited data provided by the 

U.S. EPA as part of the designation process indicates that carbonaceous aerosols and 

nitrate are main contributors to high PM2.5 values. Carbonaceous aerosols are the 

largest component, contributing about 54 percent of the mass, followed by nitrate, which 

is responsible for about 38 percent of the mass. Although these data are based on 

2004-2006 samples, the data collected at other northern and central California sites

indicate that while the number of high days has decreased, the high day composition 

remains similar from year to year due to the nature of the PM2.5 problem. 

High PM2.5 values occur exclusively under stagnant winter conditions leading to 

accumulation of primary pollutants and formation of secondary components. While 

carbonaceous aerosols are primarily directly emitted into the air, nitrates are secondary 

pollutants formed in the atmosphere from gaseous NOx emissions and ammonia. 

ARB’s programs aimed at reducing NOx emissions have played an important role in 

reducing the nitrate fraction of PM2.5. Long term nitrate and NOx data collected 

throughout the State demonstrate that reductions in ambient NOx concentrations have 

resulted in commensurate reductions in PM2.5 nitrate concentrations. Past modeling 

and monitoring studies in northern and central California highlight that reductions in 

VOCs are not important for reducing either carbonaceous aerosols or nitrate; therefore,

they would not provide any benefit in reducing PM2.5 concentrations. Based on the 

nature of the PM2.5 problem and an understanding of precursor effectiveness, as well 
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as the fact that the area has already attained the standard, VOCs and ammonia are 

therefore not significant PM2.5 precursors. 

The consolidated emission projections for the Yuba City-Marysville nonattainment area

are presented in Table 2. Between 2011 and 2024, emissions of NOx are projected to 

decline 37 percent while emissions of SOx and direct PM2.5 are projected to increase 

by a small amount. The plan demonstrates maintenance of the 24-hour PM2.5 

standard because the potential increase in directly emitted PM2.5 and SOx emissions 

will be fully offset by a greater decrease in nitrate concentrations, as illustrated in 

Figure 5. Additionally, the level of 2011 emissions corresponds to a design value of 

27 ug/m3, which is 24 percent below the standard. This provides additional assurance 

that 2017 and 2024 design values will remain below the standard.

Table 2. Projected Changes in Emissions between 2011 and 2024 (tons/day)

Year 2011 2017 2024 2024-2011

PM2.5 5.3 5.5 5.4 0.2

NOx 19.3 15.3 11.6 -7.7

SOx 0.4 0.6 0.6 0.2

ERC's included in the Above Future Year Inventories

PM2.5 1.3 1.3

NOx 0.9 0.9

SOx 0.2 0.2

Figure 5. Comparison of Measured 2011 and Projected 2024 Design Value
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3. Motor Vehicle Emission Budgets

The Redesignation Request/Maintenance Plan establishes PM2.5 and NOx 

transportation conformity budgets for 2017 and 2024 to ensure that future emissions 

from on-road mobile sources provide for continuing attainment of the PM2.5 24-hour

standard (Table 3). The District determined that mobile source emissions of VOCs, 

ammonia, SOx, re-entrained road dust, and highway and transit construction dust are 

not significant for maintaining the standard and do not need motor vehicle emission 

budgets.

Table 3. Motor Vehicle Emission Budgets (tons/day)

Year NOx PM2.5

Adjusted 

Budgets

Safety 

Margin

Total 

Budgets

Total 

Budgets

2017 4.6 0.7 5.3 0.2

2024 2.6 0.5 3.1 0.2

4. PM2.5 Monitoring Network

The existing PM2.5 monitoring network in the Yuba City-Marysville nonattainment area

includes a PM2.5 FRM monitor located at 773 Almond Street in Yuba City operating on 

a daily schedule, and a non-Federal Equivalence Method (non-FEM) Beta Attenuation 

Monitor (BAM) running in parallel to the FRM. Together, these two monitors provide the 

necessary data to demonstrate continuous compliance with the standard as well as 

support Air Quality Index reporting, forecasting air quality episodes, and making burn 

decisions in the agricultural burning program. 

5. Verification of Continued Attainment

The ARB is responsible for monitoring PM2.5 air quality within the Yuba City-Marysville 

nonattainment area. The ARB also oversees the quality assurance of PM2.5 data and 

submits annual monitoring network plans to U.S. EPA on behalf of the District. The 

ARB commits to maintaining an appropriate PM2.5 monitoring network through the 

maintenance period, with any potential changes to be developed in collaboration with 

U.S. EPA and subject to stakeholder review. To verify continued attainment of the 

PM2.5 standard, the ARB will continue to conduct PM2.5 monitoring and expeditiously 

review data as it becomes available to evaluate any risk of impending violations. This 

will be used as potential trigger for early action in the contingency plan.

6. Contingency Plan

The Act requires the maintenance plan to include contingency provisions for prompt 

correction of any PM2.5 standard violation that might occur after the area has been 

redesignated to attainment. The maintenance plan is not required to contain fully 

adopted contingency measures that will go into effect without further state action as is 
9

required in attainment SIPs. Instead, for maintenance plans, the area must have a plan 

to ensure that contingency measures are adopted once they are triggered. 

The District will use the 24-hour design value as the contingency plan trigger. In the 

event that the 24-hour design value exceeds the standard, within 60 days the District 

will commence analysis, including meteorological evaluation of high PM2.5 days and 

emission inventory assessment. The District will also analyze the PM2.5 and 

meteorological data to rule out exceptional events or instrument malfunction. If a design 

value triggers the contingency plan, the District will complete sufficient analyses, by 

November 1 of the following year, to begin adoption of necessary rules for ensuring 

attainment and maintenance of the 24-hour standard. If new rules are necessary, they 

would be adopted by August 31 of the year following the completed analysis. ARB staff 

believes the contingency requirements in the Redesignation Request/Maintenance Plan

are adequate to protect air quality in the area. 

IV. STAFF RECOMMENDATION

ARB staff has reviewed the Redesignation Request/Maintenance Plan for the Yuba 

City-Marysville nonattainment area and consulted with District staff during this review. 

ARB staff finds that the Redesignation Request/Maintenance Plan meets all applicable 

Act requirements. The monitoring data shows that the area has attained the 24-hour

PM2.5 standard, and the maintenance demonstration shows that the standard will be 

maintained for ten years. 

Therefore, staff recommends that the Board adopt the Yuba City-Marysville PM2.5 

Nonattainment Area Redesignation Request and Maintenance Plan as a revision to the 

California SIP for submittal to U.S. EPA. In addition, ARB staff recommends that the 

Board approve the District’s request that the Yuba City-Marysville nonattainment area

be redesignated from nonattainment to attainment for the federal 24-hour PM2.5

standard.