UNITEDSTATES ENVIRONMENTAL PROTECTIONAGENCY WASHINGTON, D.C. 20460



# DEC

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# 4 

# 2008

MEMORANDUM OFFICE OF AIR AND RADlAnON



### SUBJECT: Area Designations for the 2008 Revised Ozone National Ambient Air Quality Standards 

# -

FROM:

TO: Regional Administrators, Regions I-X

This memorandum provides information on the timeline for designating areas for the purpose ofimplementing the 2008 revised primary and secondary ozoneNational Ambient Air Quality Standards (NAAQS). In addition, this memorandum identifies important factors states and tribes should consider in making recommendationsfor area designations. Please share this information with the state and tribal agencies in your Region.

TheU.S. Environmental Protection Agency (EPA)revised the ozoneNAAQS onMarch 12,2008(73 

### FR 16436; March 27,2008). The new primary ozone standard was lowered from 0.08 parts per million (ppm) to a level of 0.075ppm based on numerous epidemiological studies conducted during the past decade in which many ofthe health effects associated with ozone exposure were identified. These studies showed health effectsat and below the level ofthe 0.08 ppm standard, which was promulgated in 1997. Prolonged (i.e., 8-hour) exposureto ozone is associated with increased mortality and a range of serious morbidity health effects, including aggravation of a variety ofrespiratory symptoms and lung impairment, asthma attacks, respiratory hospital admissions and emergency department visits, and cardiovascular problems. In March 2008, EPA also strengthened the secondary ozone standard to provide increased protection against adverse public welfare effects including impacts on vegetation and forested ecosystems. EPA made the secondary standard identical in all respects to the revised primary standard.

Section 107(d)ofthe Clean Air Act (CAA) governs the process forarea designations following the establishment ofnew orrevised NAAQS. Under section 107(d), states are required to submit recommendations on designationsfor their areasto EPA not later than one year after the promulgation ofa new or revised standard. 

### If, after careful consideration of the recommendations, EPA intends to promulgate a designation that deviates from a state recommendation, EPA must notify the state at least 120daysprior to promulgating the final designation, and EPA must provide the statean opportunity to demonstrate why the potential

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### modification is inappropriate. The CAA requires EPA to complete the designation process within two years of promulgation of a new or revised NAAQS unless the Administrator has insufficient information to make these decisions. In such a case, EPA may take up to an additional year tomake the designations. While the language of section 107specifically addresses states, EPA intends to followthe sameprocess for tribes to the extent practicable, pursuant to section 301(d) ofthe CAA and the Tribal Authority Rule, or TAR (see 63 FR 7254).

Accordingly, state designation recommendations forthe 2008revised ozone standards should be submitted to the Administrator no later than March 12,2009. Areas should be identified as attainment, nonattainment, or unclassifiable on the basis of available information. We will notify states by letter no later than November 12,2009if we plan to modify a state's recommendation. In order to consider public input in the designationprocess, we plan to provide

a 30-day public comment period immediately following issuance ofEPA's response letters to the states and tribes; we anticipate the commentperiod would conclude in mid-December 2009. If a state ortribe has additional information that they want EPA to consider with respect to a designationrecommendation EPA plans to modify, we would request such information be submitted by January 12,201 0. This will ensure that EPA 

### can fully consider any such information as we move forward to issue designationsby March 12,2010. Because the 2008 revised primary and secondary ozone NAAQS are identical, EPA expectsthat each area will have the same designation and boundary forboth standards.

We recommend that states and tribes identify violating areas using the most recent three consecutive years ofquality-assured, certified airquality data. In most cases, we expect these to be data from 2005-2007 or 2006-2008 (if these 2006-2008 data have been certified more quickly than is required) that are stored in the EPA Air Quality System (AQS).1 

### In general, violations are identified using data from Federal reference method (FRM) and Federal equivalent method (FEM) monitors that are sited and operated in accordance with 

### 40 CFR Part 58. Special Purpose Monitors (SPM)using an FRM or FEM which have operated for more than 24 months are eligible for comparisonto the relevant NAAQS, subject to the requirements given in the October 17,2006 Revision to Ambient Air Monitoring Regulations (71 FR 61236). Procedures for using the air quality data to determine whether a violation has occurred are given in 40 CFR Part 50 Appendix P, as revised on March 27,2008 (73 FR 1651 1). We expect to base the final designations in March 2010onthe most recent quality-assured data which would be from 2006- 2008 or 2007-2009.
Air quality monitoring data affected by exceptional events may be excluded from use in identifying a violation if they meet the criteria for exclusion, as specified in the Final Rule on the Treatment ofData Influenced by Exceptional Events (72 FR 13560;March 22,2007). We recently issued a directfinal rule to provide schedules for flagging exceptional event data and submitting documentation specificallyfor ozone data collected from 2005 through 2009that are used in the designations process for the 2008 ozone NAAQS. (See 73 FR 58042; October 6, 

### 2008). These schedulesreflect our interest in assuring that the exceptional events claims can be fully considered by EPA in the final designations.



# ' This information is available on EPA's website at www.epa.gov/ttn/airs/airsaqs/.Section 107(d)(l)ofthe CAA defines an area asnonattainrnent if it is violating the NAAQS or if it is contributing to a violation in a nearby area. Ground-level ozone and ozone precursor emissions are pervasive and readily transported. Therefore, EPA believes it is important to examine ozone-contributing emissions across a relatively broad geographic area. Accordingly, we recommend that the Core Based Statistical Area (CBSA) or Combined StatisticalArea (which includes 2 or more adjacent CBSA's) associated with the violating monitor(s) serve asthe starting point or "presumptive" boundary for evaluating the geographic boundaries of an ozone nonattainment area. CBSA is a collective term that refers to both 'metropolitan and micropolitan statistical areas, which are distinguished based onpopulation size.2 Each CBSA consists of a county or countiescontaining at least oneurban core plus adjacent counties that have a high degree of social and economic integration with the urban core
as measured by commuting ties. EPA recommends starting with this presumption because the factors used to establish the CBSAsand CSAs are similar to the factors EPA plans to consider in determining whether a nearby area is contributing tothe violation(s) of the standard. EPA used this same conceptual approach in the designations process for the 1997ozone NAAQS.~.'Where

a violating monitor is not located in a CBSA or CSA, we recommend that the boundary of the county containing the monitor serve asthe starting point for considering the extent ofthe nonattainment area.

EPA believes that each potential nonattainment area should be evaluated on a case-bycase basis and recognizes that these area-specific analyses conducted by states, tribes, and/or EPA may support nonattainment areaboundaries that are larger or smaller than the presumptive area starting point. As a framework for area-specific analyses, we recommend that statesand tribes base their boundary recommendations on an evaluation of the 9 factors listed in,attachment 2. These factors are consistent with those used in the designations process for the 1997 ozone standard and are factors EPA plans to consider in evaluating and making decisions on the nonattainment area boundaries for the 2008 ozone standards. Additionally, statesand tribes may

The Office of Management and Budget (OMB)delineates CBSAs (metropolitan and micropolitan statistical areas) and CSAs. OMBadopted new standards for defining metropolitan and micropolitan statistical areas on December 27, 2000 (65 FR 82229). A micropolitan statistical area has a population of at least 10,000 but less than 50,000. A metropolitan statistical area has a population of at least 50,000.

For lists ofthe CBSAsand CSAs and their geographic components see 

### www.census.~ov/populatiod~~~/metroareas/metrodef.html. EPA recommends using the most recent available updated lists ofthe statistical areas. The lists are updated annually to reflect the
most recent Census Bureau population estimates. Memorandum from John S. Seitz, Director of Office ofAir Quality Planning and Standards to Air Directors, Regions 

### I-X, "Boundary Guidance on Air Quality Designations for the 8-Hour OzoneNational Ambient Air Quality Standards," March 23, 2000.

In addition, CAA section 107(d)(4) established the consolidated metropolitan statistical area or metropolitan statistical area asthe presumptive boundary for the most polluted areasthat were designated nonattainment by operation of law in 199

### 1 for the 1-hour ozone NAAQS.identify and evaluate other relevant factors or circumstances specific to a particular area,

In addition to nearby areas with sources contributing to nonattainment, ozone concentrations in a local area may be affected by long-range transport of ozone and its precursors (notably nitrogen oxides). In certain parts ofthe country, such asthe eastern United States, ozone is a widespread problem. Where this Is the case, the CAA doesnot require that all contributing areasbe designated nonattainment, only the nearby areas. Regional strategies, such

asthose employed in the Ozone Transport Region and EPA's NOxSIPCall are needed to address the long-range transport component of ozone nonattainment, while the local component must be addressed through local planning in and around the designated nonattainment area.

Thismemorandum provides EPA's current views on how boundaries should be determined for ozone designations. The guidance is not binding on states, tribes, the public, or EPA. Issues concerning nonattainment area boundaries will be addressed in EPA's action to designate areas under the 2008 ozone standard. When EPA promulgates designations, those determinations will be binding on states,tribes, the public, and EPA as a matter of law. Ozone nonattainment areas will be classified at the time ofdesignation. The approach EPA will use to classify nonattainment areasunder the 2008 revised ozoneNAAQS will be established through 

### a separate notice-and-comment rulemaking. Informationrelated to the designationsfor the 2008 revised ozone NAAQS will be provided on EPA's website at www.epa.gov/ozonedesignations.

Attachment 1isa timeline ofimportant dates in the designation process for the revised 2008 ozoneNAAQS designation process. Attachment 

### 2 provides the list ofnine factors that EPA plans to consider in evaluating and making decisions on nonattainment area boundaries.

Staffin EPA's Office of Air Quality Planning and Standards are available for assistance and consultation throughout the designation process. Questions on this guidancemay be directed
to Carla Oldham at 919-541-3347.

Attachments (2)

cc: Air Division Directors, RegionsI-X Greg Green, OAQPS Bill Harnett, OAQPS Brian McLean, OAP Margo Oge, OTAQ Stephen 

### D. Page, OAQPS Peter Tsirigotis, OAQPS Richard Wayland, OAQPS Lydia Wegman, OAQPS

### ATTACHMENT 1



### TIMELINE FOR REVISED 2008 OZONE NAAQS DESIGNATION PROCESS*

Milestone 

# I EPA promulgated revised ozoneNAAQS 

# I State and tribal recommendations due for ozone 

# I designations

EPA notifies statesand tribes concerning any modifications to their recommendations (I20-day letters).
EPA publishes public notice of state recommendations and EPA's proposed modifications and initiates 30-day public comment period.

End of 30-day public comment period.

- -- 

### States and Tribes submit additional informationto demonstrate why an EPA modification is inappropriate.
EPA promulgates final ozonedesignations. 

### Date
March,12,2008

-- 

### No later than March 12,2009

No later than November 12,2009 (120 daysprior 

### to final designations)

Mid-November 2009

Mid-December 2009

No later than 

### January 12'20 10

No later than March 12,2010



### * This schedule assumes EPA has sufficient information to promulgate designationswithin 2 years. In the event EPA determines that insufficient information is available to do so, the designation process could be extended up to oneyear, but no later than March 12,20 1 1.

### ATTACHMENT 2

Factors EPA Plans to Consider in Determining Nonattainment Area Boundaries in Designations for the2008 Ozone NAAQS

EPA recommends that the Core Based Statistical Area (CBSA) or Combined Statistical Area (CSA) (which includes 

### 2 or more adjacent CBSA's) serve asthe startingpoint or "presumptive" boundary for considering what should be the geographic boundaries of an ozone nonattainrnent area.6 Where a violating monitor is not located in a CBSA or CSA, we recommend that the boundary ofthe county containing the monitor serve as the presumptive boundary for the nonattainment area. As a framework for area-specific analyses to support nonattainment area boundary recommendations and final boundary determinations, we recommend an evaluation ofthe 

### 9 factors listed below:

Air quality data Emissions data (location of sources and contribution to ozone concentrations) Population density and degree ofurbanization (including commercial development) Traffic and commuting patterns Growth rates and patterns Meteorology (weatherltransport patterns) Geographyltopography (mountain ranges or other air basin boundaries) Jurisdictional boundaries (e.g., counties, air districts, existing nonattainment areas, Reservations, metropolitan planning organizations (MPOs)) Level of control ofemission sources

Analysis ofthese factors may support nonattainment boundaries that are either larger or smaller than the presumptive boundary. EPA plans to consider these factors, along with any other relevant information, in determining whether to make modifications to the boundary recommendations from states and tribes. The factors listed above, while generally comprehensive, are not intended to be exhaustive. States and tribes may submit additional information they believe is relevant for EPA to consider. In general, a state's or tribe's demonstration supporting their boundary recommendation for an area should showthat: 

### 1) violations are not occurring in nearby portions that are excluded from the recommended area, and 2) the excluded nearby portions donot contain emission sources that contribute meaningfully to the observed violations. While states are not bound to use the approach outlined here, EPA plans to evaluate a state recommendation and determine whether tomodify such recommendation based onthe above factors and any other information the Agency determines is relevant.

For lists ofthe CBSAs and CSAsand their geographic components see 

### www.census.~ov/population/www/metroareas/metrodef.html.