State of California
AIR RESOURCES BOARD



### STAFF REPORT



## Analysis of the Imperial County 2009 1997 8-Hour Oz one Modified Air Quality Management Plan and Reasonably Available Control Technology Plan

Date of Release:
Scheduled for Consideration: November 18

, 2010



## California Environmental Protection Agency

Air Resources BoardThis report has been reviewed by the staff of the C alifornia Air Resources Board

and approved for publication. Approval does not si gnify that the contents necessarily reflect the views and policies of the A ir Resources Board, nor does mention of trade names or commercial products const itute endorsement or
recommendation for use.

### Table of Contents

I. Introduction....................................

................................................... .............1

II. Background.....................................

................................................... ............2

III. Moderate Area Requirements....................

................................................... .4

IV. Evaluation of the Imperial County Modified Plan ...........................................6

A. Attainment of the 1997 8-Hour Ozone Standard ....... ...........................................6

B. Moderate Nonattainment Area Requirements........... ...........................................8

V. 2009 RACT SIP ...................................

................................................... .....11

VI. Staff Recommendations ..........................

................................................... .11-1-



## I. Introduction

This staff report reviews plans adopted by the Impe rial County Air Pollution Control District to address federal Clean Air Act ( CAA) nonattainment area plan requirements applicable to moderate ozone nonattain ment areas.

With the promulgation of the 1997 8-hour ozone Nati onal Ambient Air Quality Standard (NAAQS) in April 2004, the United States E nvironmental Protection Agency (U.S. EPA) classified Imperial County as a m arginal nonattainment area. On February 13, 2008, U.S. EPA found that Imperial County had not attained the 1997 8-hour ozone NAAQS by the marginal area deadli ne of June 2007, and reclassified the County as a moderate nonattainment area. U.S. EPA’s action also required the State to submit a moderate area S IP for the Imperial County nonattainment area, by December 31, 2008, that demo nstrates attainment of the 8-hour ozone standard by June 15, 2010.

On February 19, 2009, ARB requested that U.S. EPA m ake a “clean data” finding for Imperial County. The request demonstrated that the area’s 2008 design value for the 8-hour ozone NAAQS, which was based o n monitoring data collected from 2006 through 2008, showed attainment of the standard. U.S. EPA issued its clean data finding on December 3, 2009.

A clean data finding does not constitute a redesign ation to attainment under the national CAA, so Imperial County remains a moderate nonattainment area. The clean data finding suspended some CAA nonattainment area plan requirements. However, the State is still required to submit revi sions to the SIP to address remaining elements required for moderate ozone nona ttainment areas, including rule review and adoption relative to the reasonably available control technology (RACT) requirements, emission inventories, and new source review requirements.

On July 30, 2010, the Imperial County Air Pollution Control District adopted the 2009 1997 8-Hour Ozone Modified Air Quality Managem ent Plan (2009 Ozone Plan) and 2009 Reasonably Available Control Technol ogy State Implementation Plan (2009 RACT SIP) to address the CAA moderate ar ea plan requirements.

ARB staff reviewed the Imperial County 2009 Ozone P lan and RACT SIP and find that both plans meet all applicable CAA requir ements for a moderate
nonattainment area. Staff recommends that the Air Resources Board adopt the Imperial County 2009 Ozone Plan and the 2009 RACT S IP and direct the Executive Officer to submit the plans to U.S. EPA a s proposed revisions to the
California SIP.-2-



## II. Background

Profile of Imperial County

Imperial County is part of the Salton Sea Air Basin . The Imperial County Ozone Nonattainment Area consists of the entire county, a nd is under the jurisdiction of the Imperial County Air Pollution Control District (District).

Imperial County covers 4,482 square miles of mostly arid lands in the
southeastern corner of California. It is bordered by Mexico to the south, Arizona on the east, San Diego County on the west, and Rive rside County on the north. Imperial County’s elevation ranges from more than 2 ,800 feet on the mountain
summits to the east to 230 feet below sea level in the Salton Sea. Winters are mild and dry with daily average temperature ranges between 65 and 75oF, although daily high temperatures of up to 80oF are not uncommon. Summers are extremely hot with daily average temperature ranges between 104 and 115oF and daily high temperatures of up to 120oF. The Co unty has an annual rainfall of approximately 3 inches, occurring mostly from late summer to midwinter.

Imperial County has a population of approximately 1 80,000 people. The County’s major population centers include the citie s of El Centro (25 percent of the county population), Calexico (22 percent), and Brawley (15 percent). Approximately 22 percent of the population resides in unincorporated areas.

Mexicali, Mexico – a city of approximately 900,000 people – spreads southward from the California/Mexico border at Imperial Count y. Mexicali’s residential and industrial centers begin less than 5 miles from Cal exico and 15 and 25 miles, respectively, from El Centro and Brawley. Because the New River is the only geographical feature separating Imperial County fro m Mexicali, air pollution transport between the two areas is possible. ARB’s June, 1993 transport assessment report identified Mexico as the source o f emissions that caused or

contributed to some of the exceedances of the state ozone standard recorded in Imperial County from 1989 to 1991 1

.

Air Quality History

Ozone air quality has improved significantly in Imp erial County in recent years as shown by both the number of days in which ozone val ues exceed the 8-hour ozone NAAQS (exceedance days) and the recorded dail y high ozone concentrations. In 1997, Imperial County exceeded the 1997 8-hour ozone NAAQS of 0.085 parts per million (0.085 ppm), also expressed as 85 parts per billion (85 ppb), on 50 days. In 2009, the number of exceedance days declined to 2. Table 1 shows the progressive decrease in ex ceedance days at each routine monitoring site in Imperial County.

1 Air Resources Board, Assessment and Mitigation of the Impacts of Transported Pollutants on Ozone

Concentrations in California , June 1993-3- Table 1 Imperial County Exceedance Days, 8-Hour Ozone NAAQS

2001 - 2009

Monitoring Site 2001 2002 2003 2004 2005 2006 2007 2008 2009

Calexico East 7 4 0 1 0 0 2 1 0

Calexico Ethel 11 1 0 0 1 1 4 4 0

El Centro 2 9 8 0 5 9 3 0 1

Niland 1 5 0 0 0 0 0 1 0

Westmorland 1 0 0 0 10 5 5 2 1

Figure 1 shows the federal design value trend in Im perial County from 2001 to 2009 and the respective 1997 8-hour ozone standard. The SIP design value is based on the fourth highest value recorded each yea r, averaged over three consecutive years. Imperial County’s 8-hour ozone design value has decreased by ten percent since 2001, and now meets the 1997 f ederal NAAQS.

When compared to other indicators such as peak conc entrations, the design value is a more stable indicator for evaluating yea r to year changes resulting from emission control programs, and is the only ind icator that can be used to determine compliance with the NAAQS. Peak concentr ations measure the severity of ozone exposure but not the frequency, a nd can be influenced by year to year weather variations.

The U.S. EPA is in the process of revising the 8-ho ur ozone NAAQS, and is expected to promulgate its revised standard in late 2010. The range of values the agency is considering for the new NAAQS – from 0.070 ppm to 0.060 ppm (70 ppb to 60 ppb) – is from 29 percent to 17 perce nt more stringent than the current 8-hour ozone NAAQS of 0.085 ppm. Recent mo nitoring data suggests that Imperial County will be designated as nonattai nment for the new standard.-4- Figure 1 Imperial County Design Value

92

87 87

85 84 85 87

82 83

60 80 100

2000 2002 2004 2006 2008 2010

Year8-Hour Ozone Design Values(ppb)

8-Hour Ozone Design Value

8-Hour Ozone Standard



## III. Moderate Area Requirements

On December 3, 2009, U.S. EPA published its finding that Imperial County
attained the 1997 8-hour ozone standard. U.S. EPA’ s “clean data finding” suspends certain SIP elements including the attainm ent demonstration, reasonable further progress demonstration, and cont ingency measures requirements. However, some SIP requirements remai n, and some were added when U.S. EPA reclassified Imperial County from mar ginal to moderate. Table 2 shows SIP elements required for marginal and modera te area plans, and identify the SIP elements suspended by the clean data findin g.-5- Table 2 Marginal and Moderate Ozone Nonattainment Area SIP Requirements and Clean Data Finding Elements

Ozone Part D SIP Requirement marginal

area moderate

area requirement suspended with

clean data finding

Attainment demonstration (182(b)(1)) x x

Subpart 1 Reasonably
Available Control Measures (172(c)(1)) x x x

Reasonable Further Progress (172(c)(2), 182(b)(1)) x x

Contingency measures (172(c)(9)) x x

Vehicle Inspection/Maintenance (182(a)(2)(B), (b)(4)) x x Note: N/A in Imperial County because of population (<200,000)

Stage 2 Gasoline Vapor Recovery (182(b)(3)) Note: Stage 2 GVR no longer required in moderate ozone areas per Onboard Refueling Vapor Recovery rule. CAA 202(a)(6); 59 FR16262 (April 6, 1994).
Emissions Inventory (172(c)(3), 182(a)(1) x x

New Source Review (172(c)(4) and (5); 182(a)(2)(C)) x x

Infrastructure SIP (172(c)(7)) x x
Subpart 2 Reasonably Available Control Technology for VOCs and NOx (182(b)(2), 182(f)) x

Periodic Inventory (182(a)(3)(A)) x x

Emissions Statement Rule (182(a)(3)(B)) x x

Offset Ratio (182(a)(4); 182(b)(5)) 1.1 to 1 1.15 to 1-6-



## IV. Evaluation of the Imperial County Modified Plan

ARB staff has reviewed the Imperial County 2009 Ozone Plan and the Distric t’s supporting technical analysis, and determined that the plan meets CAA SIP requirements for moderate ozone nonattainment areas . The following sections describe the major elements of the plan.



### A. Attainment of the 1997 8-Hour Ozone Standard

On February 19, 2009, ARB requested that U.S. EPA m ake a “clean data” finding for Imperial County. The request demonstrated that the area’s 2008 design value for the 8-hour ozone NAAQS, which was based o n monitoring data collected from 2006 through 2008, show attainment o f the 1997 8-hour ozone NAAQS. On December 3, 2009, U.S. EPA published a c lean data finding for Imperial County. Subsequent monitoring data show t hat the County continues to meet the 1997 8-hour ozone standard. Figure 2 illu strates the Imperial County ozone nonattainment area and monitoring locations.

Figure 2 shows the location of routine ozone monito ring stations in Imperial County. The number of routine ozone monitoring sit es in Imperial County exceeds the monitoring density required in federal regulations for a county of approximately 180,000 residents (40 CFR Part 58, Ap pendix D).-7- Figure 2 Map of Imperial County and Monitoring Stations

Table 3 shows the Imperial County air monitoring st ations design values for 2006 through 2009, representing 2004 through 2009 monito ring data. The design values for all of the monitoring sites are at or be low the mandated 0.085 ppm
threshold. The El Centro 9 th Street and Westmorland started with the highest design values; both show a trend of improving air q uality. The design values for the Niland and Calexico-East sites show slight upwa rd trends, but in both cases

are still well below the 1997 8-hour ozone standard . On the map above, a dot represents an air monitoring station.-8- Table 3 Imperial Monitoring Station County Design Values

(ppm)

Monitoring Sites 2006 2007 2008 2009

El Centro-9th
Street 0.085 0.086 0.082 0.079

Westmorland-W
1st Street 0.085 0.087 0.082 0.079

Niland 0.073 0.074 0.075 0.076

Calexico-Ethel 0.074 0.079 0.080 0.083

Calexico East 0.076 0.079* 0.079* 0.075*

Calexico Grant 0.069 0.072 Closed Closed

* Design values impacted by the deletion of June 20 07 through October 2007 data due to monitoring irregularities.

Pollution transport from Mexico contributed to high readings in some ozone exceedance days in Calexico, and possibly in some o ther Imperial County sites.
The CAA allows the exclusion of concentrations caus ed by transport from another country in the development of attainment de monstration plans. This plan does not utilize international transport exclusion since the clean data finding does not rely on the transport argument.



### B. Moderate Nonattainment Area Requirements

As discussed earlier, U.S. EPA’s clean data finding suspends certain SIP requirements. This section reviews the elements th at the District submitted to fulfill the remaining moderate area nonattainment r equirements.

New Source Review and Offset Ratio

Federal New Source Review (NSR) regulations are app lied to the siting and
modification of sources that are located in areas d esignated as federal nonattainment for NAAQS. The purpose of federal NS R is to ensure that ambient air quality does not deteriorate any furthe r in nonattainment areas. Imperial’s SIP-approved NSR rule, Rule 207, was ado pted by the Imperial County Air Pollution Control Board on November 10, 1980. The CAA requires

moderate nonattainment areas to have offsets ratios of 1.15 to 1. Rule 207 has a 1.15 to 1 offset ratio for ozone precursors. This rule and the offset ratio fulfill the requirements of the CAA.-9-

RACT Analysis

The District completed its RACT analysis in a separ ate document (please refer to Section V). The Imperial County Air Pollution Cont rol Board adopted the 2009 RACT SIP at the July 13, 2010, Board meeting.

Emissions Inventory

The precursors of ozone are oxides of nitrogen (NOx ) and reactive organic gases (ROG). Mobile sources contribute the bulk of Imper ial County’s NOx emissions with heavy duty trucks clearly leading locomotives, and passenger vehicles as the top source (Table 4). Livestock waste, passeng er vehicles, and pesticides constitute the top sources for ROG emissions (Table 5). ROG and NOx emissions decreased significantly in these categori es between 2002 and 2009, as did total emissions, as shown in Tables 4 and 5.

The Emission Statement Rule requires the owner or o perator of each stationary source that emits NOx or ROG to provide a statement for classes or categories of sources showing the actual emissions. The Imper ial County Air Pollution Control Board adopted an Emissions Statement and Ce rtification Rule on February 23, 2010.

Air Quality Planning

In developing this plan, the District held regularl y scheduled SIP working group meetings that included various community representa tives, health, environmental, and industry and military representa tives, local and county governments, and state and federal agencies. The m eetings were initiated in

March 2008 and ended in June 2009. The District al so posted drafts of the 2009 Ozone Plan on their website throughout the process.-10- Table 4 Imperial County NOx Sources

**Imperial County - Top Sources of NOx (tons per day)**
**Rank (2002) Source Category 2002 2009** 

1 HEAVY DUTY DIESEL TRUCKS 13 11

2 LOCOMOTIVES 7 5

3 PASSENGER VEHICLES 6 5
4 FARM EQUIPMENT (COMBINES AND TRACTORS) 3 2

5 OFF-ROAD EQUIPMENT 2 1

6 ELECTRIC UTILITIES 1 1
7 MANUFACTURING AND INDUSTRIAL (BOILERS, IC ENGINES ) 1 1

8 MANAGED BURNING AND DISPOSAL 1 1

9 AIRCRAFT 1 2

10 AGRICULTURAL IRRIGATION PUMPS 1 1

**TOP 10 CATEGORIES TOTAL** 36 31

**TOTAL EMISSIONS** 37 32

**TOP 10 CATEGORIES PERCENT OF TOTAL** 96% 95%

Numbers may not add due to rounding “Top 10” categories are prioritized by 2002 emissio ns

Table 5 Imperial County ROG Sources

**Imperial County - Top Sources of ROG (tons per day)**

**Rank (2002) Source Category 2002 2009** 

1 LIVESTOCK WASTE 9 6

2 PASSENGER VEHICLES 7 5

3 PESTICIDES 5 3

4 OFF-ROAD RECREATIONAL VEHICLES 3 4

5 MANAGED BURNING AND DISPOSAL 2 2
6 ASPHALT PAVING / ROOFING 2 2

7 CONSUMER PRODUCTS 1 1

8 AIRCRAFT 1 2

9 HEAVY DUTY DIESEL TRUCKS 1 1

10 RECREATIONAL BOATS 1 1

**TOP 10 CATEGORIES TOTAL** 33 27

**TOTAL EMISSIONS** 37 32

**TOP 10 CATEGORIES PERCENT OF TOTAL** 87% 86%

Numbers may not add due to rounding “Top 10” categories are prioritized by 2002 emissio ns

The District released the draft 2009 Ozone Plan and the 2009 RACT SIP on June 13, 2010 following several months of coordinated ef forts between District staff and the SIP working group. The District released a notice of public hearing for the adoption of the 2009 Ozone Plan and associated negative declaration 30 days prior to its Board meeting, and held two publi c workshops to discuss both
the 2009 Ozone Plan and 2009 RACT SIP.-11-

Air Pollution Transport

Since Imperial County in effect shares an air basin with the Baja California city of Mexicali, ozone levels in southern part of the coun ty are likely impacted by
emissions from Mexico. The CAA allows states to de monstrate that an area would have attained the NAAQS by the applicable att ainment date but for emissions emanating from outside of the United Stat es (CAA section 179B(b)). Imperial County’s 2009 Ozone Plan does not utilize the international transport provision since it was not needed to demonstrate at tainment of the 1997 8-hour ozone NAAQS. However, ARB has previously assessed the impacts of transported pollutants on violations of the State A mbient Air Quality Standard (SAAQS) for ozone, and determined that transport fr om Mexico can cause or contribute to high ozone levels in Imperial County. ARB, the local District, and U.S. EPA continue to coordinate on efforts to impro ve air quality and reduce transported pollutants throughout the border region

.



## V. 2009 RACT SIP

Ozone non-attainment areas classified as moderate o r above are required by CAA sections 182(b)(2) and 182(f) to implement RAC T for sources subject to Control Techniques Guideline (CTG) documents and fo r all major sources of VOC and NOx that are not subject to a CTG. The 200 9 RACT SIP fulfills CAA requirements for a moderate area, and ARB staff rec ommends that it be submitted as a SIP revision simultaneously with the 2009 Ozone Plan. The District worked closely with U.S. EPA and stakehold ers as it prepared its RACT SIP. The District also released a public notice 30 days prior to its Board hearing, and held two workshops to discuss the draft 2009 RA CT SIP. On July 13, 2010, the Imperial County Air Pollution Control Board ado pted the 2009 RACT SIP.



## VI. Staff Recommendations

ARB staff has reviewed the Imperial County 2009 Ozo ne Plan for the Imperial County ozone nonattainment area, including the 2009 RACT SIP, and consulted with District staff during its review. ARB staff f inds that the Imperial County 2009 Ozone Plan and 2009 RACT SIP meet all applicable CA A requirements for a
moderate nonattainment area. Staff recommends that the Board adopt the Imperial County 2009 1997 8-Hour Ozone Modified Air Quality Management Plan and 2009 Reasonably Available Control Technology St ate Implementation Plan,
and direct the Executive Officer to submit them to U.S. EPA as proposed
revisions to California’s SIP.