MEMORANDUM 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

OCT 1 201 5 

SUBJECT: Implementing the 20 I 5 Ozone National Ambient Air Quality Standards 

FROM: Janet G. McCabe, Acting Assistant Admini st atorc-\~ {._GJ.---

Office of Air and Radiation 

TO: Regional Administrators, Regions 1-1 0 

OFFICE OF 

AIR AND RADIATION 

Following the directives of the Clean Air Act (CAA), on October I, 20 I 5, Administrator McCarthy 

signed a rulemaking action that revises the current national ambient air quality standards (NJ\AQS) for 

ozone to a new, more protective level of0.070 parts per million (70 parts per billion). These revised 

standards will improve the health and well-being of millions of Americans in the coming years. They are 

built on a foundation of sound health and ecosystem science. 

I am '"'riling to you today to let you know about the process going forward for delivering the protections 

afforded by the revised standards. In doing so, I want to emphasize that we will work with our state, 

local, federal and tribal partners to carry out the duties of ozone air quality management in a manner that 

maximizes common sense, nexibil ity and cost-effectiveness while achieving improved public health 

expeditiously and abiding by the legal requirements of the CAA. The goal is achieving cleaner air, while 

recognizing the many other activities underway and the resource constraints that we and our coregulators face. This has proved a successful partnership in the past, and I am confident it will continue 

to be so in the future. In particular, I note that a number of the other clean air programs currently 

underway will work to lower ozone levels nationally, such as Tier 3 vehicle standards, Mercury and Air 

Toxics Standards, measures to address the 20 I 0 sulfur dioxide NAAQS, the Clean Power Plan and 

others. 

The attached document highlights many of the issues related to implementing the revised national ozone 

standards, including policy and techni cal aspects of implementation that we anticipate facing in the 

coming years. It outlines actions that the EPA will take and our expectations of our air agency partners. 

Please share this memo with our state. local and tribal partners within your regions. 

Attachment 

Internet Address (URL) • t111p:flwww.epa.gov 

Recycled/Recyclable • Pnnted with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper 
ATTACHM ENT 

How Air Agencies and the EPA Will Move Forward to Implement the 2015 Ozone Standards 

This document provides an outline of how the EPA wil l work with state, federal and tribal air agencies 

to carry out the duties of air quality management (AQM) for the revised ozone standards in a manner 

that max imizes common sense, fl exibility and cost-effecti veness while abiding by the legal requirements 

of the Clean Air Act (CAA). It highlights many of the key issues and activities related to implementing 

the revised national ozone standards, including policy and technical aspects of implementation that \·Ve 

anti cipate facing together in the coming years. It outlines commitments that the EPA will endeavor to 

meet, and our expectations of our air agency partners with regard to some of these issues. rt is not 

intended to be a comprehensive communication on implementing the revised ozone standards, nor does 

it constitute new guidance. 

A. Plan for Ensuring Air Agencies and Emissions Sources Have Timely Guidance and Clear Rules to 

Follow 

The CAA places important obligations for implementing the ozone National Ambient Air Quality 

Standards (NAAQS) on various parties, but primary responsibility for administering the CAA to assure 

attainment of the NAAQS fa lls to the state and federal governments.' There is now a long history or 

managing ozone air quality under the CAA, underpinned by a wealth of previously-issued EPA rules 

and guidance. While portions of some existing rules and guidance need to be updated when the ozone 

NAAQS arc revised, much of it remains applicable to the revised standards (e.g., the rule that appl ies to 

nonattainment areas for implementing the 2008 NAAQS). The EP/\ is committed to ensuring that air 

agencies have adequate guidance, and nev,, rules where necessary. to carry out CAA directives through 

the state implementation plan (S IP) process. We have identified ex isting rul es and guidance documents, 

and we are developing schedul es for proposing and tinalizing several new guidance documents and 

rul emakings to provide timely support for implementing the revised ozone standards. We will share 

more specific information regarding these actions and documents, including the timing, in the coming 

months. 

To implement the revised ozone NAAQS, all states will need to review their existing air quality 

management (AQM) infrastructure State Implementation Plan (SIP) for ozone tO ensure it is appropriate 

and adequate. The EPA's 20 13 guidance on infrastructure SIPs titled, "Guidance on Infrastructure State 

Implen1entation Plan (S IP) Elements under Clean Air Act Sections I I O(a)( I) and I I O(a)(2)," should be a 

helpful guide for conducting a comprehensive review of the state's AQM infrastructure. States were last 

required to review their AQM infi·astructure SIP for ozone following the 2008 revision to the ozone 

standards. Accordingly, we expect most states will not have to make signifi cant changes to existi ng 

infrastructure SIPs, and will simply need to submit a certification that their ex isting SIP is suffi cient to 

meet applicable CAA AQM requirements Lor the revised ozone standards.2 

1 States also have primary regulatory jurisdiction in non-reservation areas of Indian country (i.e., Indian allotments located 

outside of reservations and dependent Indian communities) within its geographic boundaries unless the EPA or a tribe has 

demonstrated that a tribe has jurisdiction over a particular area of non-reservation Indian country wi thin the state. See 

Oklahoma Department ojEn;,ironmental Quality v. F.PA, 740 F.3d 185 (D.C. Cir. 20 14). For tribal areas of Indian country 

(i.e., •:eservations), tribes are generally not required to submit lribal implementation plans (TIPs), but arc encouraged to 

reference the EPA's current 2008 Ozone NAAQS SIP Requirements Rule (2008 ozone NAA.QS SRR) (80 FR 12264, 

March 6, 20 15) and guidance should they choose to develop a T l P. 1 Certifications are SIP submissions that must meet the requirements of40 CFR part 50 appendix Y and undergo the SIP 

review process required under CA. A. section I I O(k). 
For states with areas that arc designated nonallainmcnl. there are additional planning and control 

obligations that wi ll apply. The final 2008 Ozone AAQS SIP Requirements Rule (2008 ozone AAQS 

RR) contains the EPA ·s latest rul es and guidance for implementing the ozone standards under the 

statutory provisions of'CAA part D, subpart 2. The EPA believes that the overal l framework and policy 

approach reflected in this rule provide an effective and appropriate template lor the general approach 

states would follow in planning lor attainment of the revised ozone standards. llowever, to assist with 

the implementation of the revised ozone standards, the EPA intends to develop and propose an 

additional ozone AAQ implementation rule that will address certain subjects. We also recognize the 

rules and guidance cannot anticipate every possible situation or innovation, and we continue to be 

committed to working one-on-one \.Vith air agencies to explore casc-speci ftc innovative or untested 

approaches that have promise to fullill CAA requirements and achieve clean air raster and more coslciTectivcly. In particular lor areas where states arc still actively working toward attaining the 2008 ozone 

AAQS, we encourage air agencies to look for and take advantage of potential planning and emissions 

control efficiencies that may occur within the horizon for attaining the 2015 standards. Formal 

allai nment plans for the 20 15 standards are not anticipated to be due until 2020 or 202 1, but this 

timcframe would roughly coincide with the next planning cycle for any current Moderate areas that fail 

to attain by the 20 18 deadline for the 2008 ozone NAAQS. 

The EPA has made significant cftorts in recent years to update guidance and rules that relate to A/\.Q 

implementation, so as not to have to update every document each time a AAQS is revised. Below is a 

list or guidance and rules that are current and applicable to the 2015 ozone NAAQS, followed by a list 

or updates to guidance and rules that the EPA expects to complete tor states' usc in 2015 ozone NAAQS 

planning. 

Guidance and Rules That Remain Current and Applicable to the Revised NAAQS 

• Guidance on Infrastructure State Implementation Plan (SIP) Elements under Clean Air Act 

Sections ll O(a)( I) and II O(a)(2) - September 13, 2013 

(hltp:llll'\l''ll.epa.gov/airqualityl urbanair/sipstatuslinji·astruclure.html) 

• Draft Modeling Guidance for Demonstrating Auainment of Air Quality Goals for Ozone, PM2 s. 

and Regional I laze - December 2014 and Guidance on the Usc or Models and Other Analyses 

for Demonstrating Attainment of Air Quality Goals for Ozone. PM2 s. and Regional I laze - April 

2007 (hllp:llwllllli. epa.govhcramOO 1 /guidance _sip. htm) 

• Draft Emissions In ventory Guidance for Implementation or Ozone I Particulate Matter] National 

Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations- April 20 14 

(http:/lwlvlv3.epa.govl ttnlchief/e idocs/ eiRUicl/ index.htm/) 

• Revisions to the General Conformity Regulations (75 FR 17254, April 5, 20 I 0) and guidance (40 

CFR part 93, subpart 8 and 40 CFR part 51, subpart W) 

(hit p :lllll\11\11 3. epa.Kov/airq ual i tylgencoJ?f'ormlreKS. html) 

• Transportation Conformity Rule (77 FR 14979, March 14, 20 12) and Guidance for 

Transportation Conformity Implementation in Multi-Jurisdictional Nonattainment and 

Maintenance Areas - February 20 12 ( 40 CFR part 93, subpart A and 40 CPR part 51, subpart T) 

(http :1/wwwJ. epa. KO vl otaqA t ateresourceslt ranscon.f/i ndex. htm) 

Expected Updates to Implementation-Related Guidance and Rules and other Actions 

• Rulcmaking to establish nonattainmcnt classification thresholds, incorporate SIP due dates into 

the EPA regulations, and update (as necessary) policy interpretations of CAA SIP requirements 

(expected to closely f'o llow the 2008 O?.Onc AAQS SRR) (see section A) 

2 
• Rulemaking to revoke 2008 ozone NAAQS effective l year after initial area designations and 

plan for transitioning from 2008 to 2015 standards (expected to closely fol low the 2008 Ozone 

NAAQS SRR) 

• Analysis of interstate ozone transport contributions for the 2015 NAAQS (expected to include an 

analysis similar to the Notice of Data Availability (NODA) for transport contributions for the 

2008 NAAQS) (see section E) 

• Guidance on meeting transportation conformity requirements for nonattainment areas under the 

revised ozone NAAQS (expected to closely follow the transportation conformity guidance for 

the 2008 ozone NAAQS) (see section H) 

• Exceptional Events Rule revisions and guidance on exceptional events demonstrations for 

wildfire events that may influence ozone concentrations (see section D) 

• Guidance or rulemaking on the use of PSD permit screening tools and offsets in attainment areas 

(see section B) 

• White paper on background ozone and stakeholder workshop (see section D) 

Based on the EPA's recent work with states to identify the types of guidance and rules that would 

facilitate NAAQS implementation and the schedule on which those materials are needed to assist states 

in meeting required submittal dates, the EPA is developing schedules for these materials. The EPA will 

continue to prioritize development of these materials with input from co-regulators and other 

stakeholders. 

B. Plan for Ensuring Major Source Permitting is Effective and Efficient 

Starting on the effective date of the revised ozone NAAQS, the CAA requires permit authorities to 

consider the revised ozone standards when issuing preconstruction permits to new or modified major 

emissions sources. Generally, this means that a proposed source obtaining a prevention of significant 

deterioration (PSD) permit for construction in an ozone attainment area must show that its emissions of 

ozone precursors will not cause or contribute to a violation of the revised standards. However, in the 

ftnal 2015 ozone NAAQS rule the EPA finalized a grand fathering provision that allows some sources 

with PSD permit applications pending to apply the ozone standards that were in effect when certain 

milestones in the application process were reached to satisfy certain PSD requirements. Specifically, this 

provision would apply to applications for which the reviewing authority has either formally determined 

that the application is complete on or before the signature date of the 2015 ozone NAAQS or has 

published a public notice of a draft permit or preliminary determination before the effective date of the 

2015 ozone NAAQS. Although some sources may continue to focus on compliance with the prior ozone 

standards under the grandfathering provision, all existing EPA-issued, permitting-related rules and 

modeling guidelines applicable to ozone remain in effect until they are formally revised. In addition, the 

EPA continues to recommend following its existing permitting guidance pending additional guidance 

specific to ozone and the revised standards. 

We recognize that the owners and operators of emissions sources need clarity and certainty about 

regulatory requirements, especially when there are changes in air quality standards that may affect their 

construction and operations. In an effort to add clarity and certainty for preconstruction permitting 

generally, the EPA is planning some enhancements to existing rules and guidance and providing 

additional guidance to assist with applying PSD requirements to ozone generally, and with 

implementing specific aspects of the 2015 ozone NAAQS. For example, the EPA recently proposed a 

comprehensive update to the PSD permit modeling guidelines in Appendix W of 40 CFR part 51 (80 FR 

45340, July 29, 2015). We intend to finalize the proposed action in 2016. In this proposed action, we 

3 
took comment on incorporating new recommendations for evaluating single-source ozone contributions, 

including the appropriate use of single-source modeling tools. l want to emphasize, however, that until 

final changes are made to Appendix W, the existing guidelines in Appendix W remain applicable to 

ozone. Even if changes are made, we intend to provide a transition period before any new guidelines 

become effective. 

There are a number of existing program tools that can be used to help facilitate the permitting process, 

and the EPA continues to work with stakeholders on others that will improve the permitting process 

while assuring attainment and protection of the ozone standards. These include the use of emission 

offset programs and significant impact levels (SlLs) for ozone for PSD permitting. The existing "PSD 

offsets" tool continues to be available for permit applicants and reviewing authorities to address ozone 

impacts from a proposed source or modification, including in an area that is not designated 

nonattainment but where ambient monitoring data shows ozone concentrations that exceed the revised 

NAAQS. We believe that SILs and related "screening tools"3 are useful in detennining the extent to 

which an ambient impact analysis must be completed to make the required demonstration for the 

applicable pollutant. We intend to provide additional guidance on these screening tools in the near 

future. 

Finally, in areas that are likely to be designated nonattainment for the 2015 ozone NAAQS, state and 

local pennit authorities can help facilitate efficient nonattainment NSR permitting by establishing 

emissions offset banks and registries. 

C. Plan for Ensuring All Areas Are Appropriately Designated 

One of the most important near-term implementation efforts is completing the process for initially 

designating all areas as to whether each area is meeting or not meeting the 2015 ozone NAAQS. 

Because designating areas is typically a 2-year process (and may even, in some cases, be extended 

another year), the final designations will be based in part on future air quality data (i.e., 2014-2016 data). 

CutTent air quality data may not be a reliable indicator of likely nonattainment areas. Nevertheless, 

2012-2014 data indicate that many counties with design values above the 2015 ozone standards have 

previously been designated nonattainment for ozone, which suggests that there is already widespread 

experience with ozone nonattainment planning. 

In early 2016, the EPA will issue new guidance to facilitate the designations process. We expect this 

guidance will be similar in concept and scope to the designations guidance issued for the 2012 PM2.s 

NAAQS (see " Initial Area Designations for the 2012 Revised Primary Annual Fine Particle National 

Ambient Air Quality Standard," April 16, 2013). It will include a discussion ofthe factors that the EPA 

plans to consider in evaluating designation recommendations from states and tribes and in determining 

nonattainment area boundaries. It will also include information on establishing Rural Transport Areas 

under CAA section l82(h) where it is appropriate to do so. Using this guidance approach, the EPA has 

established a good track record of fmalizing designations that are based on sound technical assessment 

and policy judgment, and that have withstood a variety of legal challenges. 

3 For example, in the July 20 15 proposed update to Appendix W, we introduced a new demonstration tool for ozone 

precursors referred to as Model Emissions Rates for Precursors (MERPs). A MERP would represent a level of emissions of 

precursors that is not expected to contribute significantly to concentrations of ozone. 

4 
The statutory deadline for the EPA to linalize area designations is October I, 20 17. State 

recommendations on area designations are clue October I, 20 16. Designations completed by October I. 

2017, would, as noted above. involve ozone uir quality data collected during the most recent 3-year 

period (i .c., 20 14-20 16). Tn some locations, these data may have been impacted by events that could be 

determined to be exceptional events. We recognize the importance of timely review and approval of any 

data exclusions requested under the Exceptional Events Rul e. and will work with states to prioriti7.c 

review or any exceptional events demonstrations that \Vould material ly impact an attainment 

determination or nonattainmcnt area classification. The final ozone AAQS rule establishes October I, 

2016, as the deadline for states to submit exceptional event demonstrations for events that occurred in 

2014 and 2015 , and May 31,20 17, as the deadline lor events that occur in 2016. 

D. Issues Related to Background Ozone 

Background ozone is ozone arising from natural events (e.g., stratospheri c intrusions and wildfires) or 

non-United States (U.S.) anthropogenic sources (e.g .. ozone and ozone precursor emissions from 

Mexico. Canada or other international locations). A number or stakeholders have expressed a concern 

that some locations in the U.S. may violate the ozone standards due to background ozone concentrations. 

We anticipate that there are onl y a few locations in the western U.S. where levels in excess of70 ppb 

could be due to the overwhelming influence or background o7.one. These are generall y high elevation 

sites in. the western U.S. that arc impacted by stratospheric intrusions. sites impacted by large-scale 

wildfires, or locations along the U.S.-Mexican border influenced by ~cxican emissions. 

Under the CAA, states are not responsible lor reducing emissions from background sources. We intend 

to work directly with responsible air managerncnt agencies in these areas to ensure that all CAA 

provisions that would provide regulatory relief associated with background ozone arc recogni zed. 

However, even if elevated levels of ozone arc innuenced by natural events or arc caused by human 

activities outside the U.S., it is critically important that the public is informed about whether the air is 

healthy to breathe. 

The CAA provides for the exclusion of emissions data sho\oving excecdances of the ozone standards 

when such exceedances are caused by certain natural events like stratospheric ozone intrusions and 

wildfires. We acknowledge that the CAA requires that there be demonstrated evidence of these 

exceptiona l events and a public review process in order to use the exclusion; these requirements arc 

provided in the Exceptional Events Rul e (72 FR 12560. March 22. 2007). We fully expect to work with 

states to ensure they are able to exclude such data in locations where they are warranted. Any 

exceedances of the standards that result from stratospheric ozone intrusion events or wi ldiire impacts 

could be evaluated lor exclusion of ambient concentration data under the Exceptional Events Rule. We 

already work closely with states to review exceptional events submissions, and we arc currently 

dev<:.loping revisions to the Exceptional Events Rule to simplify and expedite the process tor states 

developing technical demonstrations and 1or the EPA to approve exclusions for these types of events. 

This proposal, which we expect to issue this 1ll , has been we ll informed by our discussions with states 

and other stakeholders and by our experience with past exceptional events submittals. We arc also 

developing additional guidance for preparing exceptional events demonstrations tor wildfire events that 

may innuence ozone concentrations. It is our intent to finali ze the rulemaking and wildtire event 

guidance before states must submit recommendations on area designations and we stand ready to work 

with states. as needed, in addressing potential exceptional event demonstrations prior to that linal 

rulemak in g. 

5 
For areas impacted by international sources. the CAl\ contains provisions in section 1798 that ensure 

states only need to address man-made sources within their jurisdiction, and onl y need to impose 

emi5sions controls on local sources to the extent they are reasonably available. We intend to ensure that 

states that may be impacted by international sources, such as California, Ari zona, New Mexico and 

Texas, arc able to employ these provisions, where appl icable, and we wi ll offer whatever technical 

assistance we can feasibly provide to these states and impacted communities. 

During this latest review or the ozone AAQS there has been a good deal or discussion about 

background ozone. To further ensure that all interested stakeholders have a common understanding or 

the nature or background ozone and hovv it could be accounted for in implementing the ozone standards, 

we are developing a white paper on background ozone that we will make available soon for stakeholder 

review. We intend to hold a workshop in the next few months to discuss the information in the white 

paper and to further advance our collective understanding of the technical and policy issues that may be 

involved with background ozone. We will evaluate the need for further guidance or regulatory tools to 

address background ozone after receiving stakeholder input and after conducting the workshop. We 

emphasize again that the EPA hcadqum1ers and regional offices will work with states to ensure they can 

successfully invoke all or the CAA provisions that arc legally and technically warranted for ensuring 

background ozone does not result in ineffective air quality management actions. 

In addition, the EPA continues to work with other federal agencies, our counterparts in other countries. 

and the international community to improve our understanding of the sources and impacts of 

background ozone and to enable and motivate control of pollution sources in other countries that affect 

the U.S. Working with the European Commission in the context of the Convention on Long-Range 

Transboundary Air Poll ution, we arc leading an international scientific effort to improve the databases 

and modeling tools that enable us to characterize the intercontinental transport of ozone and assess 

potential control strategics.4 We arc working with Mexico through the Border 2020 Program,

5 with 

Canada under the US-Canada Air Quality Agrcemcnt,6 and with China through agreements on 

cooperation ''vith their environment and science ministrics7 to improve air quality management and 

address key sources in these countries. And we arc working through multil ateral efforts, such as the 

Global Methane lnitiati vcR and the Climate and Clean Air Coalition to Reduce Short Lived Climate 

Pollutants9 to engage both govcmments and the private sector to achieve decreases in methane emissions 

which contribute to background ozone. Ultimately, these efforts will benetit air qua li ty in the United 

tales by decreasing international contributions to background air pollution. 

E Plan.for Addressing Interstate Ozone Transport 

The ··Good leighbm··· provision ofthe CAA, section IIO(a)(2)(D)(i)(T), requires upwind states to 

deve lop SIPs that prohibit emissions of pollutants in amounts that will contribute significantly to 

nonattainment, or interfere with maintenance of, a 1\.AQS in another state. These Good Neighbor ~ IPs 

are due within 3 years of promulgation of a ncv.' or revised NAAQS, meaning that transport SIPs for the 

20 15 ozone NAAQS will be due by October 2018. If" the EPA finds that states have not timely submitted 

SIPs or the EPA disapproves such a SIP, then the EP1\ must promulgate Federal Implementation Plans 

1 http: 11'11"\l'. htap.orgl 

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x https:l/www.gloha/metlume. orgl 

'J hllp:ilwwwccacoalition. org/ 

6 
(F!Ps) that eliminate the emissions that significantly contribute to nonattainmcnt and interfere with 

maintenance of the standards in downwind states. 

We bel ieve that the Good Ne ighbor provision !or the 20 15 NAAQS can be addressed in a timely fash ion 

using the framework of the Cross-State Air Pollution Rule (CSAPR), especiall y given the recent court 

decisions upholding the rule. The CSA PR framework involves a 4-step process to address the · 

requirements of the good neighbor provision: (I) identifying downwind receptors that are expected to 

have problems attaining or maintaining clean air standards (i.e., AAQS); (2) determining which 

upwind states contribute to these problems in amounts surficient to "link·' them to the downwind air 

quality problems; (3) tor states linked to downwind air quality problems, identifying upwind emissions 

that significantly contribute to nonattainmenl or interfere with maintenance by quantifying upwind 

reductions in ozone precursor emissions and apportioning upwind responsibility; and (4) for states that 

arc round to have emissions that significantly contribute to nonattainment or interfere with maintenance 

or the NAAQS downvvind, adopting SIPs or PIPs that eliminate such emissions. 

As a first step in racilitating the implementation or the Good Neighbor provision for the 20 15 NAAQ 

the EPA intends to provide timely information regarding steps I and 2 of the CSA PR framework. We 

expect to conduct modeling necessary to identify projected nonattainment and maintenance receptors 

and identify the upwind states that contri bute significantly to these receptors. We would make such 

inrormation avail able in fall 2016 through a ODA process (similar to the one the EPA recently used in 

deve loping the transport modeling for the 2008 ozone NAAQS) so that air agencies and others can help 

assure that the EPA is using the best available information. 

Finally. in light of our shared responsibili ty to address interstate transport, we intend to continue ongoing discussions with eastern states and to undertake discussions with western states. These discussions 

arc necessary to make sure we have a common understanding of the nature ol' inter-state ozone transport 

in each pan or the country and that we are working together on appropriate solutions. 

F Addressing the Challenges in Cal[j'ornia 

Cali lo rni a has unique challenges among the states in addressing ozone pollution. Air basins surrounded 

by mountains and a generall y warm cl imate combine to make many areas of the stale conducive to 

ozone formation. In parti cular, the South Coast air basin in the Los Angeles area and the San .J oaquin 

Valley in the central part of the state are the onl y two areas in the U.S. classi lied as "Extreme'· 

nonattainment areas for the 1979. 1997 and 2008 ozone standards. Although ozone levels have 

decreased by 30 percent in South Coast and nearly 20 percent in the San .Joaquin Valley since 2000. 

outh Coast still has the highest 20 12-2014 8-hour ozone design value in the nation at I 02 ppb, and an 

Joaquin has the second highest at 95 ppb. Through . eptember 29, 2015, South Coast had exceeded the 

2008 ozone standards on 81 days this year, the San .J oaquin Valley on 73 days. More than 25 million 

people in Califo rni a breathe air that does not meet the 2008 ozone standards. 

1\ir pollution from mobil e sources dominates the ozone precursor emissions in Cali forn ia. With ports 

that bring in forty percent of' the nation's goods and agricultural areas that produce nearl y half or the 

nation·s produce. as well as a population of over 38 mi llion. the state is challenged by high levels or 

'Ox emissions from freight movement and from transportation generall y. Under section 209 or the 

CAA, California has the authority to regulate mobile sources. Beginning in the 1970s, the state has used 

this authority to set stringent emissions standards. In 2008, California began regulating in-use trucks and 

buses to reduce emissions rrom the legacy fleet, the only such mandatory program in the country. More 

7 
recently, it adopted a voluntary low-NOx emissions standards for heavy-duty engines to help engine 

technology move toward even cleaner levels. In addition, the state has funded incentive programs to 

further reduce emissions from the legacy fleet and has pursued numerous advanced mobile source 

techno logies. Since 2008, Cali fornia has spent nea rl y $3 billion in funding the demonstration and 

deployment or innovati ve technologies such as zero-emission trucks and buses, hybrid-electric mediumand heavy-duty vehicles, and zero-emission rreight equipment. The federal government has provided 

more than $200 million, largely through Diesel Emissions Reduction Act grants and the Department of 

Agriculture's Environmental Quality Incentives Program funds. 

Even with these aggressive regul atory and non-regul atory programs to control mobile-source emissions, 

and with the most stringent stationary source emission standards in the U.S., most of central and 

southern Califo rni a is li ke ly to be designated nonattainment for the 20 I 5 ozone standards. The South 

Coast Air Quality Management Distri ct estimates that it will need a reduction of at least 85 percent in 

NOx emissions from 20 12 levels to attain a standard of 70 ppb by 2037.

10 

With the implementation of all the measures currently adopted and planned by 2032 11

, the sources 

contributing the most NOx emissions in Cali forni a's nonattainment areas will be heavy-duty diesel 

trucks, shi ps and commercial boats, off-road equipment, locomotives, aircraft, agricultural engines, and 

passenger cars. For Californi a's ozone nonattainment areas to attain the 2015 ozone standards, the state 

and the EPA have recogni zed that transformational change is I ikely needed. For example, recent 

discussions have focused on a transition to largely zero and near-zero emissions vehi cle technologies as 

well as significant turnover or the legacy neet or vehicles. Additionall y, Californi a is undertaking a 

comprehensive review of its goods movement system with the goal to release a sustainable freight plan 

in .J uly 20 16. The state is also deve loping attainment plans for the 2008 ozone NAAQS, to he submitted 

to the EPA in 20 16. For these and other related efforts, the EPA will work closely with Californi a, local 

air quali ty offi cials, nongovernmenta l organizations, other federal agencies, and interested commercial 

representatives to identify both regulatory and non-regul atory emission control solu tions best designed 

to achieve reductions in the transportation sector. 

Cl. ivfanaKinK Ozone Monitoring Networks 

A sound ambient pollution monitoring program is one of the fo undations of deli vering environmental 

protection. The publi c counts on states and other air agencies to establish and operate air quality 

monitoring networks, and provide reliable, high quality air quality measurement data. We encourage air 

agencies to ensure their ozone networks are eflicient and effecti ve at determining public exposure to 

ozone, and in full compliance with existing air monitoring regul ations. In rul es accompanying the 2015 

revision to the ozone NAAQS, we took three actions related to air monitoring. First, the monito ring 

season period fo r ozone monitors was extended in 32 states and the District of Columbia starting in 

2017. All previously approved ozone monitoring site waivers are now revoked, however we encourage 

air management agencies to work with their respecti ve EPA regional office in cases where they believe 

ncvv waivers should be gi·antcd. We have not changed the process or reasons for granting seasonal 

exemptions fo r collecting monitoring data in cases where access or operations of the monitor are 

af'lected by inclement weather conditions. As a reminder, we expect that the CASTNET monitors will 

10 South Coast Air Quality Management District documents: 

hffp:l/www4. aqmd.gov/enewsletterprol uploadedimages/00000 I /Ce/ia/FactSheet-20 16%20A QM P-v9.pdj; 

htt p :llwww. aqmd. govl dues! deja ult-suurcel Agendas/ aqmp! advisOty4-item 3.pdf? sfvrsn= 2. 11 The year 2032 is the attainment deadline under the 2008 ozone NAAQS for California nonattai nment areas that are 

classi tied Extreme for that standard. 

8 
continue to provide ozone air quality information that is comparable to the ozone NAAQS. The revised 

ozone monitoring seasons become eJfective at state and local air monitoring stations or SLAMS 

(including NCore stations) on .January I. 2017. 

Second. to improve implementation of the CAl\ ·s requirement for "enhanced·· ozone monitoring. we 

modilied the network requirements for Photochemical Assessment Monitoring Stations (PAMS) to 

modernize and streamline the network. These revisions were based on a 20 II evaluation of the network, 

along with consultation with the EPA's independent science advisers (the Clean Air Scientific Advisory 

Committee) and an organization of state air agencies. PAMS will now be required at existing NCorc 

sites in large urban areas with a population of I ,000.000 or more. This change will improve the 

geographi c distribution of PAMS sites, while reducing redundancy in the existing network. In addition, 

monitoring agencies with Moderate (and above) nonattainment areas and states in the Ozone Transport 

Region will now be required to establish Enhanced Monitoring Plans (EMPs). This process gives states 

the Oexibility to detcnnine and coll ect the additional data they need to better understand the ozone 

problems unique to their area. tates will need to comply with the new PAMS monitoring at NCore sites 

by June I, 20 19. States will need to submit EM Ps within 2 years of designations or by October I, 20 19. 

whichever is later. The EPA intends to redistribute available P/\MS funding to support the new 

requirements. 

Third, we established a new procedure f·or determining daily maximum, 8-hour average ozone 

concentrations to avoid "double counting" overlapping daily maximum 8-hour averages. This procedure 

prevents the situation in which we count two exceedances of the A/\QS on 2 consecutive days based 

on overlapping 8-hour periods with up to 7 hours in common. The criteria for determining whether a 

daily maximum 8-hour average is valid for the purpose or calculating a design value has been changed 

accordingly, so that 13 of 17 possible 8-hour averages are now required instead or 18 of24. In addition, 

we have retained the requirement that daily maximum 8-hout· average values greater than the level of" the 

AAQS will be considered valid regardless of data completeness. 

II. Other Implementation Issues 

Community involvement. We believe it is vitally important for state and local air agencies to engage 

with their communities as they plan to address attainment and/or maintenance of the 2015 ozone 

standards. Communities experiencing disproportionate impacts of air pollution may reasonably expect 

more stringent ozone standards to lead to improved air quality that meets the EPA's standards as soon as 

possible. To fully benefit from the opportunities the revised standards present, these communities' 

voices must be heard by the air agencies responsible lor meeting the standards. The EPA recommends 

that state and local air agencies take steps to ensure that minority populations, low-income communities. 

tribes and indigenous populations are involved meaningfully in the development and implementation of 

regulations and programs to meet the 2015 ozone standards. 

The EPA has developed a guidance document titled, .. Guidance on Considering Environmental Justice 

during Development of Regul atory Actions.'· to assist its own staff in considering and addressing 

environmental justice issues as it develops rules. We recommend that state and local air agencies 

consider the approaches described in this document as they undertake their planning activities around 

rhe 2015 ozone standards. For example, the guidance includes spccitie steps to make public involvement 

meaningful and effective, ideas for using web-based tools for communicating with a variety of 

communities. and best practices for engaging environmental justice communities in developing and 

implementing environmental regulations. All communities deserve to breathe air that meets federal 

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standards. We are committed to working with states as they engage their most vulnerable communities 

toward achieving this goal. 

Opportunity for Multi-pollutant Planning. Ozone pollution does not need to be addressed 

independently from other air pollution concerns. Emissions affecting compliance with other criteri a 

pollutant NAAQS and contributing to greenhouse gases may have similar sources. We encourage air 

agencies to consider multi-pollutant planning, as a means to ensure environmental protection and at the 

same time take advantage of potential efficiencies, synergies, and provide more certainty to the 

regulated community. It is possible to work within the statutory requirements to plan and implement in a 

multi-pollutant fashion. Most recently, in the preamble for the final Clean Power Plan, the EPA noted 

·· ... the Clean Power Plan provides an opportunity lor states to consider strategies for meeting future 

CAA planning obligations as they develop their plans under this rulemaking. Multi-pollutant strategies 

that incorporate criteri a pollutant reductions over the planning hori zons specific to particular states, 

jointl y with strategies for reducing C02 emissions from aflected EGUs needed to meet Clean Power 

Plan requirements over the time hori zon of this rul e, may accomplish greater environmental results with 

lower long-term costs.'' We believe that the coincident planning periods for the Clean Power Plan and 

the 1/\AQS for ozone, PM2 s and S0 2, and for the Regional Haze program, should encourage states to 

take a multi-pollutant approach in addressing these regulatory requirements. 

Emissions f rom Wildland Fires. We understand that lire is an unavoidable occurrence on many types of 

wildland, and that changing climate conditions will increase the occurrence or damaging wild tires unl ess 

fuel loads are managed by other means including science-based use or prescribed tirc.

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14 Emissions 

from lires on wild land, particularly large wi ldfires, can impact concentrations of ozone and other 

harmful pollutants, such as PM25, both in the locations with fire and downwind. ln areas where wi ld 

lircs have been prevalent or arc likely, we encourage air agencies to work with state, federal and private 

land managers on promoting prescribed fire and other strategies that may reduce wildfire emissions and 

their effects on ozone exceedances; we appreciate that such strategies may have other public safety, 

ecological, and property protection benefits as we ll. Recogni zing the importance of various fire 

management strategies, in the proposed revisions to the Exceptional Events Rul e we intend to encourage 

air agencies to rely on burn managers· use of basic smoke management practi ces15 by idcnti fying a set 

of generally applicable practices that would be employed during prescribed fires. The EPA and the 

federal land management agencies will support state enorts to educate the public on the ecological role 

or fire, and wildfire and prescribed fire concepts. Where a prescribed fire program has been developed 

and is being implemented in and/or upwind of a nonauainmcnt area, the EPA recommends that air 

agencies account lor the expected prescribed fire emissions in the attainment and maintenance planning 

process. In those areas where prescribed tires are known to be capable of causing occasional ozone 

cxceedances, the EPA wi ll continue to work with air agencies and stakeholders to improve the long-term 

clTectiveness of the existing basic smoke management practices and smoke management programs. 

1

! The Administrator's finding on the adverse effects of greenhouse gases included the observation that wild !ires have 

increased, and that there are potential serious adverse impacts from further wildfire occurrence. (74 FR 66530, December 15, 

2009. 11 Climate n~e in the United Stmes: Benefits of Giuhat A c:tion, U.S. EPA, EPA -4 30-R- 15-00 I , June 20 15. A vai !able at 

It up: www2. epa.guvlc:ira. 

II The ational Strategy: The Final Phase in the Development or the ational Cohesive Wildland Fire Management trategy. 

Report to Congress developed by the U.S. Department of Agriculture and the U.S. Department of the Interior, April 20 14. 

Available at tt ://www..fo sts ndrung land~ rategy estraregy. shrmf. 

~ Bas ic moke M anagement Practices, October 20 II , U .. Forest Service and Natural Resources Conservation Service, 

htlp:llwww. nrcs.usda.gov/lnrerne!IFSE _ DOCUMENTS/sielprdh I O.f63 / l.pdf. 

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Transportation Planning. The CJ\A requires that transportation plans, transportation improvement 

programs (TIPs) and projects must be consistent vlith, or ''conform" to, attainment and maintenance of 

the o7.one NAAQS. The EPA intends to issue an update to existing guidance for purposes of addressing 

issues that arc expected to arise in implementing the 2015 NAAQS in future nonattainment areas. The 

EPA issued a similar guidance update for the 2008 NAAQS. The guidance for the 2015 ozone NAAQS 

will address transportation conformity requirements that apply in ozone nonallainmcnt areas including: 

When wi ll conformity apply for the 20 15 ozone NAAQS; 

Requirements for completing transportation plans and TIP conformity determinations in 

metropolitan areas; and 

Requirements for completing conformity determinations in rura l areas. 

For more details on topics that will be addressed in transportation conformity guidance for the 20 15 

ozone NAAQS please refer to the current guidance lor the 2008 ozone NAAQS, which is available at: 

http:llwww.epa.govl otaql\·tateresourcesltram·coJ?fl2008na(l(ts.htm. With the exception of issues unique 

to the 20 15 ozone NAAQS (such as implementation dates), we expect the new guidance to be very 

similar to the guidance for the 2008 NAAQS. 

The CAA also requires certain areas to implement vehicle inspection and maintenance (l/M) programs. 

These areas are limited to ozone nonatlainment areas that have been classified as Moderate or worse and 

meel CAA-specified pqpulation thresholds (200,000 based upon the 1990 U.S. Census for Moderate 

nonattainment areas, and 200,000 based upon the 1980 U.S. Census for Serious or worse nonattainment 

areas). In addition, any Metropolitan Statistical Area within the Ozone Transport Region with a 1990 

population of 100,000 or more is also required to implement 1/M, regardless of attainment status. 

While it is too soon to knovl, we expect few if any areas not already implementing vehicle IIM programs 

will need to do so as a result ofbeing initially designated and classified nonattainment for the 2015 

ozone standards. For those areas that may eventually be required to implement liM as a result or missing 

their initial attainment deadl ine under the 2015 standards, a great deal of flexibil ity and many 

implementation options exist that were not available during the last period during which new 1/M 

programs were required. This implementation ll exibility is the result of numerous revisions to the 

original TIM rule as well as technological advances such as the use of on board diagnostics on most inuse vehicles. 

Ozone Advance Program. Finall y, we also want to remind states, tribes, and communiti es about the 

EPA's Ozone Advance program, which encourages exped itious emission reductions in ozone attainment 

areas to help these areas continue to meet the ozone NJ\AQS. While the program to date has focused on 

helping attainment areas continue to meet the 2008 NAAQS, we now plan to re-focus the program 

toward continued attainment of the 20 15 NAAQS. Earl y reductions of the pollutants that form ozone can 

be achieved by any area without participating in Ozone Advance, however the program may be of 

interest to areas that would like to work more collaboratively with the EPA when planning and 

implementing measures to reduce ozone. Areas with air quality that currently does not meet the 2015 

NAAQS can participate in Advance until final nonattainment area designations (expected in fall 20 17), 

and for as long as the area is classified as Marginal (and therefore is not subject to planning 

requirements). 

Ozone Advance participants have voluntari ly opted to undertake a variety of emission reducing 

measures, including diesel reductions, congestion mitigation, neet management, alternative fue ls, point 

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and area source reductions, and energy efficiency improvements. They are a lso taking steps to build 

public awareness about the connections between air quality and hea lth and actions individua ls can take 

to improve air quality locally. Further information is available at 

ht 1 p:llwww. epa.govlozoneadvance/part icipants. html. 

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