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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

REGION 6 

MULTIMEDIA PLANNING AND PERMITTING DIVISION 

1445 ROSS AVENUE, SUITE 1200 

DALLAS, TX 75202-2733 

DATE: October 21, 2009 

SUBJECT: Technical Review of the Redesignation Request / Revisions to the Arkansas SIP for 

Crittenden County 

FROM: Jeffrey Riley 

 Air Planning Section, 6 PD-L 

TO: Files 

THROUGH: Guy Donaldson, Chief 

 Air Planning Section, 6 PD-L 

Background

EPA is proposing to approve the State of Arkansas’ February 24, 2009 request to redesignate the 

Arkansas portion of the bi-state Memphis Tennessee-Arkansas (Memphis TN-AR) 1997 8-hour 

ozone nonattainment area to attainment for the 8-hour ozone National Ambient Air Quality 

Standard (NAAQS), as well as the accompanying State Implementation Plan (SIP) revision 

containing an 8-hour ozone maintenance plan for the Arkansas portion of the bi-state Memphis 

TN-AR Area. This proposed approval of Arkansas’ redesignation request and supporting 8-hour 

ozone maintenance plan is based on EPA’s determination that Arkansas has demonstrated that 

Crittenden County has met the criteria for redesignation to attainment specified in the Clean Air 

Act (CAA), including the determination that the entire Memphis TN-AR ozone nonattainment 

area has attained the 1997 8-hour ozone standard. 

This document is intended to provide further demonstration of air quality improvements in Crittenden 

County than what is presented in the proposed approval. 

Analysis of the State’s Submittal

 Monitored Data

Attainment of the 8-hour ozone NAAQS is based on the design valuea

 for a given area. Design 

values for each site for each three-year period ending in 2002 through 2008 are listed in and 

graphically displayed in Figure 1. Monitoring data for 2008 for both ADEQ and the 

 

a

 The 8-hour ozone design value for a given site is the three-year average of the annual fourth highest 8-hour 

ozone concentration at that site. The design value for a given area is the maximum over all sites in the area. 
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Memphis/Shelby County Health Department has undergone quality assurance, been certified and 

submitted to the EPA AQS database. ADEQ included certified ozone monitoring data reports 

for the Marion monitor, as well as copies of associated certification letters in the submittal. Of 

the four monitors represented in Table 1 and Figure 1, the Marion monitor is the only one located 

in Crittenden County. The Hernando monitor, located in DeSoto County, Mississippi, was 

included in several data figures provided by ADEQ, because of its inclusion in the Memphis 

Metropolitan Statistical Area. However, DeSoto County is not part of the Memphis 8-hour 

ozone nonattainment area, and EPA’s approval of the redesignation request does not consider 

DeSoto County data – it was included by ADEQ to further demonstrate improvements in air 

quality. 

Table 1. 8-Hour Ozone Design Values (ppb) for 2000 through 2008 forOzone Monitoring Sites 

in the Memphis Area. 

Design Value Period Site 

2000-2002 2001-2003 2002-2004 2003-2005 2004-2006 2005-2007 2006-2008 

Frayser 87 84 80 79 79 82 82 

Orgill 90 89 84 81 80 81 80 

Marion 94 92 87 86 87 89 82 

Hernando 86 81 83 80 83 85 81 

Figure 1. 8-Hour Ozone Design Values (ppb) for 2000 through 2008 for Ozone Monitoring Sites 

in the Memphis Area 

8-Hour Ozone Design Values

55

65

75

85

95

105

2000-2002 2001-2003 2002-2004 2003-2005 2004-2006 2005-2007 2006-2008

ppb

Frayser Orgill Marion Hernando

Between 2000 and 2007, the Marion monitor measured some of the highest 1- and 8-hour average 

ozone concentrations in the Memphis MSA and this is reflected in the design values. However, for 

the most recent three-year design value period, the design values for all four sites are similar and 

the highest value (82 ppb) represents both the Frayser and Marion sites. 
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The 8-hour design values for all four monitors are characterized by a downward trend between 

2002 and 2005, followed by both increases and decreases between 2005 and 2008. The Crittenden 

County maintenance plan addresses the prior 8-hour ozone NAAQS which requires a design value 

of less than 85 ppb. Thus for the 2006-2008 period, all sites, and thus the Memphis area, are in 

attainment of the prior 8-hour ozone NAAQS. 

This tendency toward lower ozone is also reflected in the number of exceedance days. Figure 2 

shows the number of exceedances of the 85 ppb 8-hour NAAQS for each year from 2000 to 2008, 

based on the maximum 8-hour ozone concentration over all monitoring sites in the area. 

Figure 2 demonstrates that from 2006 through 2008, a consistent downward trend in the number 

of 8-hour ozone exceedance days has occurred. 

Figure 2. Number of 8-Hour Ozone Exceedance Days per Year for 2000 through 2008 for the Memphis Area 

No. of 8-Hour Ozone Exceedance Days

0

5

10

15

20

25

2000 2001 2002 2003 2004 2005 2006 2007 2008

No. of Day

s

As demonstrated in the preceding examples, monitoring data for the area has shown a continued 

downward trend in design values and 8-hour ozone exceedance days from 2006-2008. 

Preliminary data for the 2009 8-hour ozone season indicates a highest value of 76 ppb for the 

Marion monitor, and a highest value for the area (for both the Hernando and Frayser monitors) at 

78 ppb, indicating a continued downward trend. 

 Modeled Data

The Crittenden County maintenance plan establishes a period of maintenance for the relevant 

NAAQS (8-hour ozone) for at least 10 years after the area is redesignated, as per the 

requirements of Section 175A of the Clean Air Act. The base year for this maintenance period 

was established as 2006, and emissions values for the four source types (point, non-point, nonroad, on-road) were developed utilizing the EPA-approved methods briefly described below: 

 Point Source 

Facility-level emission estimates were based on the 2005 point source data submitted to EPA 

for the NEI 2005 by State of Arkansas. 

 

 Non-Point Source 
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County-level emission estimates for non-point source were based on the EPA NEI Version 2 

data. The non-point data include two parts: actual 2005 wildfire emissions and emissions for 

other categories. According to EPA, the emissions included in the second part are the 2002 

emissions in the NEI Version 4 (these were not updated). 

 Non-Road Source 

County-level emission estimates for the majority of non-road source categories were developed 

using EPA’s NONROAD2005 model (EPA, 2005) with June maximum, minimum and average 

temperatures (calculated from the 1970-2000 30-year historical averages) for State of Arkansas. 

Aircraft, commercial marine vessel, and locomotive sources are not included in the NONROAD 

model, and the emissions for the categories were taken from the EPA 2005 NEI Version 2 data. 

 

 On-road Source 

The county-level emission estimates for the on-road mobile source emissions were developed 

using MOBILE6.2.03 with 2006 county-level daily vehicle miles traveled (VMT), speed and 

registration information provided by the Arkansas Department of Transportation (ADOT), 

and 30-year historical average temperatures and humidity data for the month of June. 

ADEQ established the end of the maintenance period as 2021, and in the submittal, ADEQ 

provided discussion and documentation of the methodology for projecting the 2006 base year 

emissions inventory for Crittenden County to the future years (2009, 2012, 2015, 2017, 2018 and 

2021), as required by EPA. Projections for 2009, 2017 and 2021 were conducted as described 

below. The projections for years 2012, 2015 and 2018 were derived from simple interpolation 

between these years. 

Methodology 

 Point and Non-Point Sources 

The development of future year emissions estimates for point and non-point sources includes 

the application of growth and control factors to the base-year emissions. The growth factors 

used in this assessment are the Regional Economic Models, Inc. (REMI) 6.0 factors contained 

in EPA’s Economic Growth and Analysis System (EGAS), Version 5.0 (EGAS 5.0) (Abt, 

2006). These growth factors were applied to the various industrial sectors and source 

categories to reflect expected future growth (or decline) in industrial activity and resulting 

emissions. The emission estimates for wildfires were kept at the base-year (2006) level. 

For fuel combustion sources, energy adjustment factors, which were developed from the U.S. 

Department of Energy (DOE) publication Annual Entergy Outlook 1999 (DOE, 1998), were 

applied to the base year emissions to account for expected increases in fuel combustion and 

process efficiency for the future years. Additional controls were applied for residential wood 

combustion and Stage II VOC for gasoline service stations. 

 Non-Road Sources 

The future-year emission estimates for the majority of source categories from non-road 

sources are based on EPA’s NONROAD2005 model, which includes estimates for growth 

based on expected future economic conditions and other factors, as well as any national 
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controls that apply to these sources in the future years. In applying the NONROAD2005 

model, June maximum, minimum, and average temperatures were used. 

To estimate the future-year emissions for aircraft, commercial marine vessels and 

locomotives, the EGAS 5.0 REMI 6.0 growth factors were applied to the base-year emissions. 

In March 2008, EPA finalized more stringent emissions standard for locomotives and marine 

compression-ignition engines (EPA, 2008). Based on the information provided in the EPA 

regulatory announcement for the final rule, the NOx emissions reductions were estimated as 

5.6%, 22% and 36% for 2009, 2017 and 2021 from 2005 emissions levels, respectively. These 

reductions were incorporated into the future-year emission estimates for commercial marine 

vessels and locomotive engines for Crittenden County. 

 On-road Sources 

The Arkansas Highway and Transportation Department provided different VMT yearly 

growth factors for two ten-year periods (2007-2017 and 2017-2027) by road type based on 

2007 levels. The projection factors for each of the future years were calculated by applying 

the growth factors to 2007 VMT to obtain the VMT estimates for 2009, 2017 and 2021. 

The county-level emission estimates for the on-road mobile source emissions were developed using 

MOBILE6.2.03 with future year county-level daily VMT, state provided speed and registration 

information, and 30-year historical average temperatures and humidity data. 

As shown in Figure 3 below, substantial and consistent reductions in nitrogen oxide (NOx) 

emissions are projected to occur between the years 2006 and 2021. Small increases in point 

source emissions are offset by much larger projected reductions in non-road and on-road 

emissions. These reductions are anticipated in large part due to fleet turnover (Federal Motor 

Vehicle Control Program [40 CFR Part 86], Heavy Duty Diesel Rule/2007 Highway Rule [66 FR 

5001, Amended 71 FR 51481]), and Tier 2 fuel and vehicle emission standards (65 FR 6697). A 

similar trend is reflected in volatile organic compound (VOC) emissions through these years, 

although not to the scale seen in NOx emissions. 
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Figure 3. Emissions Totals for NOx, and VOC for the Base Year (2006) 

and Future Years (2009, 2017, and 2021) for Crittenden County 

Crittenden County NOx Emissions for 2006, 2009, 2012, 

2015, 2017, 2018 and 2021

0

5

10

15

20

Point Area Non-road On-road Total

(tons/day)

2006 2009 2012 2015 2017 2018 2021

Crittenden County VOC Emissions for 2006, 2009, 2012, 

2015, 2017, 2018 and 2021

0

5

10

15

20

25

30

35

Point Area Non-road On-road Total

(tons/day)

2006 2009 2012 2015 2017 2018 2021

Plan to Maintain Air Quality 

Section 175A of the Clean Air Act defines the general framework of a maintenance plan. The 

maintenance plan must provide for maintenance of the relevant NAAQS for at least 10 years after 
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the area is redesignated. Because section 107(d)(3)(D) grants the Administrator up to 18 months 

from receipt of a complete submittal to process a redesignation request, ADEQ has developed this 

maintenance plan for the time from March 1, 2009 through November 30, 2021, a period of twelve 

years and nine months. The plan to maintain air quality contains a commitment to continue 

applicable existing programs, and in the event unforeseen developments overwhelm the 

effectiveness of the mandated effort to maintain the 1997 8-hour ozone NAAQS, to implement the 

programs and measures necessary to promptly correct any violation of the NAAQS that occur after 

redesignation of the area. 

Supporting Analyses 

The maintenance plan is designed to prevent deterioration of ozone air quality in Crittenden 

County through 2021. The following analyses provide corroborative evidence that the observed 

8-hour ozone concentrations are representative of typical meteorological conditions and that 

future maintenance of the 85 ppb 8-hour ozone NAAQS is expected. 

Considering the form of the design value metric, 8-hour ozone design values can be influenced 

by meteorology. Year-to-year variations in meteorology and especially unusually persistent 

meteorological conditions during one or more of the years comprising a design-value cycle can 

lead to variations in the design values that are not necessarily reflective of emissions or air quality 

changes. Thus it is important to account for the effects of meteorology in examining design value 

trends. Figure shows actual and meteorologically adjusted design values for the Marion 

monitoring site. The meteorologically adjusted design values were obtained using a series of data 

analyses beginning with Classification and Regression Tree (CART) analysis. CART was applied 

for the period 2000-2008. Each day was placed into a classification bin that corresponds to a 

certain range of 8-hour ozone concentration and a specific set of meteorological conditions. The 

category of a bin reflects the concentration or severity associated with the bin’s meteorological 

conditions, and the number of days in a bin represents the frequency with which those conditions 

occur. Using this information, each individual year was normalized such that the different sets 

of meteorological conditions are represented no more or less than they are on average over all 

years in the period. The meteorologically adjusted design values were then calculated using the 

“data” for each normalized year. 
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Figure 4. Actual and Meteorologically Adjusted 8-Hour Ozone Design Values (ppb) 

for 2000 through 2008 for the Marion, AR Monitoring Site 

 8-hr Ozone DV: Marion

65

75

85

95

105

2000-2002 2001-2003 2002-2004 2003-2005 2004-2006 2005-2007 2006-2008

ppb

Actual Adjusted

As expected, the adjusted design values exhibit less variation among years than the observationbased values. For most periods, the meteorologically adjusted design values are lower than the 

observation-based values. Both the actual and meteorologically adjusted design values show a 

downward trend. Although slightly higher than observed, the meteorologically adjusted design 

value for 2006-2008 also indicates attainment. 

This same method was used to estimate the meteorologically adjusted number of exceedance days 

for the Memphis area, as shown in Figure 5: 

Figure 5. Number of Actual and Meteorologically Adjusted 8-Hour Ozone 

Exceedance Days for 2000 through 2008 for the Memphis Area 

 No. of Exceedance Days (85 ppb): All Sites

0

10

20

30

40

2000 2001 2002 2003 2004 2005 2006 2007 2008

No. of Day

s

Actual Adjusted

In 2006, the State of Arkansas established Crittenden County as a Zone Targeted for Economic 

Development (EDZ) and petitioned the EPA to approve emissions growth allowances and 

permitting regulations that would apply to the EDZ. Arkansas was required to demonstrate that the 

level of growth in ozone precursor emissions that was established for the EDZ would not; cause or 
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contribute to violations, or interfere with maintenance, of the 1997 8-hour ozone standard. These 

regulations are codified in Arkansas Pollution Control and Ecology Commission Regulation No. 31 

- Nonattainment New Source Review Requirements as Regulation 31.305 - Zones Targeted for 

Economic Development. These regulations describe specific provisions for permitting new 

emissions sources in such zones. In order to assure continued maintenance of the 1997 8-hour 

ozone standard, ADEQ will continue to administer these provisions. Regulation 31.305 describes 

available quantities of VOC and NOx emissions that may be allocated to new facilities within the 

EDZ without interfering with attainment, or maintenance, of the eight-hour ozone standard. 

Figure 6 displays the results from two different modeling studies (the ATMOS and EDZ 

modeling analyses. In both cases, the baseline (or current) year is 2002. ATMOS examined four 

projection years (2007, 2009, 2012, and 2017) and the EDZ modeling examined two projection 

years (2007 and 2009). The emissions for the EDZ modeling are slightly more up to date than 

those used for ATMOS. In the figure, the 2002 value is the average design value for the three 

three-year periods ending in 2002, 2003 and 2004. This is the EPA recommended basis for the 

modeled attainment test (EPA, 2005). The remaining estimated design values (EDVs) were 

calculated using the modeling results and the EPA modeled attainment test. The results 

presented in Figure 6 show that the modeling results are consistent with the reduction in design 

value observed between 2002 and 2008. The results indicate attainment of the 85 ppb 8-hour 

ozone NAAQS by 2007/2009 and continued maintenance of the standard through 2017 for the 

Marion site and the entire Memphis area. 

Figure 6. Observation-Based (Weighted-Average) and Model-Based Estimated Design Values (EDVs) for the 

Memphis Area Ozone Monitoring Sites for the ATMOS and EDZ Simulations 

Frayser

83.7

77 77 75

78

83.7

78 79

60

65

70

75

80

85

90

95

2002 2007 2009 2012 2017

ppb

ATMOS EDZ

Orgill

87.7

77 78

74

80

87.7

77

79

60

65

70

75

80

85

90

95

2002 2007 2009 2012 2017

ppb

ATMOS EDZ

Marion

91

83 83 81

84

91

83 84

60

65

70

75

80

85

90

95

2002 2007 2009 2012 2017

ppb

ATMOS EDZ

Hernando

83.3

77

73

76 75 77 76

83.3

60

65

70

75

80

85

90

95

2002 2007 2009 2012 2017

ppb

ATMOS EDZ
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Emissions Reduction Programs

Permanent and Enforceable Emission Reductions (2000-2008) 

Ozone precursor emissions reductions of oxides of nitrogen (NOx), volatile organic compounds 

(VOC), and carbon monoxide (CO) have occurred in Crittenden County during the period 2000 – 

2008. The majority of these reductions have been realized from Federal and State measures, 

primarily related to mobile sources. Table 2 below provides a summary of these measures, with 

estimated benefits, as well as several voluntary emission reductions enacted for Crittenden 

County. 

Point Source Reductions 

Emission reductions from point sources in Crittenden County have occurred during, or since, the 

2006 base-year. These permanent reductions in point source emissions were the result of two 

changes in permitted facility operations. 

Proform Company, LLC, a source previously permitted to emit 0.1 tons per day VOC, closed in 

2006 and the air permit has been voided. 

On December 15, 2008 CIBA Corporation was reclassified from a major source to a minor 

source when it modified operations in order to comply with an applicable MACT standard. This 

modification resulted in reductions of 1.6 tpy NOx, 448 tpy VOC and 0.2 tpy CO. 

Area Source Reductions 

In 2004, ADEQ adopted a regulation requiring Stage I Vapor Recovery systems to be installed 

and operated at gas stations in Crittenden County. This requirement applies to approximately 70 

facilities in the County. 

Additional area source VOC emissions reductions were likely realized during this period due to 

federal controls on architectural coatings, roadway paints, auto body refinishing, manufacturing, 

and other commercial and consumer solvent products. These reductions should be considered 

excess, since they were not quantified by ADEQ in the development of the Crittenden County 

maintenance plan. 

Non-Road Source Reductions 

During 2000-2008, a number of federal measures and emissions standards were promulgated to 

address fuel usage and engine specifications for a number of non-road categories. The Tier 1 

and Tier 2 diesel engine standards were phased in during this period. In 2004, EPA’s Clean Air 

Nonroad Diesel Rule specified limits on sulfur in diesel fuel used in marine vessel engines. This 

will primarily affect particulate matter (PM) emissions. In addition, EPA has also implemented a 

program that requires engine manufacturers to integrate engine and fuel controls to reduce NOx 

and PM emissions. These requirements came into effect in 2007 for various non-road engines 

used in construction and farming. These controls would affect NOx, VOC and CO emissions. A 

number of recent rules promulgated by EPA will also affect future emissions of smaller 

commercial marine vessel engines, gasoline boat engines, personal watercraft, forklifts, 

generators, compressors, lawn and garden equipment, diesel locomotives, dirt bikes, and all-
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terrain vehicles (ATV’s). As equipment is replaced over time and these controls are fully phased 

in from 2009 through 2011, more emissions reductions are expected from these sources in the 

future. 

Mobile Source Reductions 

The largest reductions in ozone precursor emissions in Crittenden County during this period 

were from the on-road mobile sector. This is primarily the result of engine improvements 

mandated by the Federal Motor Vehicle Control Program (FMVCP), which has stipulated 

extended warranties on emission control devices and improvements in fuel efficiency. Also, 

beginning in 2004, EPA’s Tier 2 motor vehicle emissions and fuel standards program was 

initiated and applied to passenger cars and light trucks. These measures also require a reduction 

of sulfur in gasoline which will result in more efficient and longer lasting onboard emission 

control systems. In addition, the replacement of older vehicles with newer, cleaner vehicles 

(fleet-turnover) was likely responsible for a good portion of the realized reductions during this 

period. A newer on-road mobile fleet provides reductions in NOx, VOC and CO emissions. 

Also, EPA’s Heavy Duty Diesel Rule (also referred to as the “2007 Highway Rule”), which was 

originally promulgated in 2001 and was expected to take effect in 2006, would likely have 

resulted in some precursor emissions reductions from the high volume of diesel trucks transiting 

the county through the I-40 and I-55 corridors. 

Table 2. Crittenden County Emission Reductions Programs 

Mobile Sources Basis

o Tier 2 Fuel and Vehicle Emission Standards 65 FR 6697 

o Federal Motor Vehicle Control Program 40 CFR Part 86 

o Heavy Duty Diesel Rule (2007 Highway Rule) 66 FR 5001, Amended 71 

FR 51481 

State and Local Measures 

o Stage I Vapor Recovery 72 FR 18394 

o Proform Company, LLC closure, air permit voided Voids permit - allowed 

249.32 tpy of VOC 

o CIBA Corporation reclassified to minor source, MACT 

standard modifications 

Reduction of 1.6 tpy NOx, 

448 tpy VOC 

Additional Voluntary Reductions

o Diesel Emissions Reduction Act – ADEQ received State 

Clean Diesel Grant in October 2008 

Title VII(G) of Public Law 

109-58 

o Retrofit of city and county (21 on-road, 12 non-road 

trucks w/diesel oxidation catalyst – 2007 

3.27 tpy reduction of 

hydrocarbons over life of 

vehicles 

o Retrofit of 50 Marion and West Memphis School District 

buses w/diesel oxidation catalyst – 2006 

59 tpy reduction of 

hydrocarbons over life of 

vehicles 

o Retrofit of 12 City of West Memphis refuse trucks 

w/diesel oxidation catalyst – 2006 

15 tpy reduction of 

hydrocarbons over life of 

vehicles 

o 196 California Air Resources Board certified gas cans 

exchanged in Crittenden County, May-August 2008 

1,136 lbs/yr estimated 

reduction of VOCs 

o Truck stop electrification (equipped 65 parking spaces in EPA SmartWay funds 
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Crittenden County) – 2004 awarded to state 

EPA Conclusion and Recommendation

I recommend approval of the State of Arkansas’ February 24, 2009 request to redesignate the Arkansas 

portion of the Memphis Tennessee-Arkansas 1997 8-hour ozone nonattainment area to 

attainment for the 8-hour ozone National Ambient Air Quality Standard (NAAQS), as well as the 

accompanying State Implementation Plan (SIP) revision containing an 8-hour ozone 

maintenance plan for the Arkansas portion of the bi-state Memphis TN-AR Area. EPA’s review 

of the submittal indicates that it is consistent with EPA’s guidance, and that the redesignation 

request and monitoring data demonstrate that the Crittenden County portion of the Memphis TNAR area has attained, and will continue to maintain the 1997 8-hour ozone standard. 
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Guidance/Websites: 

1. 40 CFR Part 51, Appendix V - Criteria for Determining the Completeness of Plan 

Submissions 

2. "Procedures for Processing Requests to Redesignate Areas to Attainment," - Memorandum 

from John Calcagni, Director, Air Quality Management Division, September 4, 1992: 

http://www.epa.gov/ozonedesignations/1997standards/redesig/documents/Redesignation-Guidance-9-04-92.pdf 

3. State Implementation Plans; "Ozone and Carbon Monoxide Design Value Calculations", 

Memorandum from Bill Laxton, June 18, 1990: 

4. "Maintenance Plans for Redesignation of Ozone and Carbon Monoxide Nonattainment 

Areas," - Memorandum from G. T. Helms, Chief, Ozone/Carbon Monoxide Programs Branch, 

April 30, 1992: 

http://www.epa.gov/ozonedesignations/1997standards/redesig/documents/MainPlans_043092.pdf 

5. "State Implementation Plan (SIP) Requirements for Areas Submitting Requests for 

Redesignation to Attainment of the Ozone and Carbon Monoxide (CO) National Ambient Air 

Quality Standards (NAAQS) On or After November 15, 1992," - Memorandum from Michael H. 

Shapiro, Acting Assistant Administrator for Air and Radiation, September 17, 1993: 

http://www.epa.gov/ozonedesignations/1997standards/redesig/documents/9-17-93Shapiro.pdf