[Federal Register: July 14, 2008 (Volume 73, Number 135)]
[Proposed Rules]
[Page 40203-40228]
[DOCID:fr14jy08-15]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R06-OAR-2007-0524; FRL-8690-7]

Approval and Promulgation of Air Quality Implementation Plans;
Texas; Attainment Demonstration for the Dallas/Fort Worth 1997 8-Hour
Ozone Nonattainment Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is proposing to conditionally approve the 1997 8-hour
ozone attainment demonstration State Implementation Plan (SIP) revision
for the Dallas/Fort Worth moderate 8-hour ozone nonattainment area (DFW
area) submitted by the State of Texas on May 30, 2007 and supplemented
on April 23, 2008. We are also proposing to approve the associated
attainment Motor Vehicle

Emissions Budgets (MVEBs), the Reasonably Available Control Measures
(RACM) demonstration, and two local control measures relied upon in the
attainment demonstration. The proposed approval of the attainment
demonstration is conditioned on Texas adopting and submitting to EPA
prior to March 2009, a complete SIP revision to limit the use of
Discrete Emission Reduction Credits (DERCs), beginning in March 2009.
Final conditional approval of the DFW 1997 8-hour ozone attainment
demonstration SIP is contingent upon Texas adopting and submitting to
EPA an approvable SIP revision for the attainment demonstration SIP's
failure-to-attain contingency measures plan that meets section
172(c)(9) of the Clean Air Act (the Act).
    We also are proposing to fully approve the DFW area SIP as meeting
the Reasonably Available Control Technology (RACT) requirement for
volatile organic compounds (VOCs). EPA is proposing these actions in
accordance with section 110 and part D of the Act and EPA's
regulations.

DATES: Comments must be received on or before August 13, 2008.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R06-
OAR-2007-0524, by one of the following methods:
     Federal Rulemaking Portal: http://www.regulations.gov.
Follow the on-line instructions for submitting comments.
     U.S. EPA Region 6 ``Contact Us'' Web site: http://epa.gov/
region6/r6coment.htm. Please click on ``6PD'' (Multimedia) and select
``Air'' before submitting comments.
     E-mail: Mr. Guy Donaldson at<EMAIL_ADDRESS>Please
also send a copy by email to the person listed in the FOR FURTHER
INFORMATION CONTACT section below.
     Fax: Mr. Guy Donaldson, Chief, Air Planning Section (6PD-
L), at fax number<PHONE_NUMBER>.
     Mail: Mr. Guy Donaldson, Chief, Air Planning Section (6PD-
L), Environmental Protection Agency, 1445 Ross Avenue, Suite 1200,
Dallas, Texas 75202-2733.
     Hand or Courier Delivery: Mr. Guy Donaldson, Chief, Air
Planning Section (6PD-L), Environmental Protection Agency, 1445 Ross
Avenue, Suite 1200, Dallas, Texas 75202-2733. Such deliveries are
accepted only between the hours of 8 a.m. and 4 p.m. weekdays except
for legal holidays. Special arrangements should be made for deliveries
of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-R06-OAR-
2007-0524. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Do not submit through http://
www.regulations.gov or e-mail, information that you consider to be CBI
or otherwise protected. The http://www.regulations.gov Web site is an
``anonymous access'' system, which means EPA will not know your
identity or contact information unless you provide it in the body of
your comment. If you send an e-mail comment directly to EPA without
going through http://www.regulations.gov, your e-mail address will be
automatically captured and included as part of the comment that is
placed in the public docket and made available on the Internet. If you
submit an electronic comment, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses. For additional information about EPA's public
docket visit the EPA Docket Center homepage at http://www.epa.gov/
epahome/dockets.htm.
    Docket: All documents in the docket are listed in the http://
www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the Air Planning
Section (6PD-L), Environmental Protection Agency, 1445 Ross Avenue,
Suite 700, Dallas, Texas 75202-2733. The file will be made available by
appointment for public inspection in the Region 6 FOIA Review Room
between the hours of 8:30 a.m. and 4:30 p.m. weekdays except for legal
holidays. Contact the person listed in the FOR FURTHER INFORMATION
CONTACT paragraph below to make an appointment. If possible, please
make the appointment at least two working days in advance of your
visit. There will be a fee of 15 cents per page for making photocopies
of documents. On the day of the visit, please check in at the EPA
Region 6 reception area at 1445 Ross Avenue, Suite 700, Dallas, Texas.
    The State submittal, which is part of the EPA record, is also
available for public inspection at the State Air Agency listed below
during official business hours by appointment: Texas Commission on
Environmental Quality, Office of Air Quality, 12124 Park 35 Circle,
Austin, Texas 78753.

FOR FURTHER INFORMATION CONTACT: Ms. Carrie Paige, Air Planning Section
(6PD-L), Environmental Protection Agency, Region 6, 1445 Ross Avenue,
Suite 700, Dallas, Texas 75202-2733, telephone<PHONE_NUMBER>; fax
number<PHONE_NUMBER>; e-mail address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us,''
and ``our'' means EPA.

Table of Contents

I. What Has the State Submitted?
II. What Action Is EPA Proposing?
    A. What Must Happen Before We Can Finalize Conditional Approval?
III. Why Is This Proposed Approval Conditional and What Are the
Implications of a Conditional Approval?
IV. Background.
    A. What Are the National Ambient Air Quality Standards?
    B. What Is a SIP?
    C. What Is Ozone and Why Do We Regulate It?
    D. Background of the Texas SIP for the DFW Area.
    E. Background of This SIP Revision To Address the 1997 Ozone
NAAQS.
    F. What Is an Attainment Demonstration?
V. Evaluation of the DFW 1997 8-Hour Ozone Attainment Demonstration
SIP.
    A. Legal Requirements for Approval
    B. Eight-Hour Attainment Demonstration Modeling and Weight of
Evidence.
    a. What Were the Results of the Photochemical Modeling
Attainment Demonstration?
    i. What Is a Photochemical Grid Model?
    ii. What Episode Did Texas Choose to Model?
    iii. How Well Did the Model Perform?
    iv. Once the Base Case Is Determined To Be Acceptable, How Do
You Use the Modeling for the Attainment Demonstration?
    v. What Modeling Approaches Were Used for This Attainment
Demonstration?
    vi. What Did the Results of TCEQ's Combo 10 Modeling Show?
    vii. Evaluation of Other Modeling Projections Without Benefit of
Measures With a 2010 Compliance Date
    viii. Refinements and Adjustments to Future Year (2009) Emission
Inventory and Modeling-Based Projected Changes to the SIP Modeling
FDVs
    ix. What are EPA's Conclusions of the Modeling Demonstration?

    b. What Weight of Evidence Has Been Evaluated?
    i. What Additional Modeling-Based Evidence Did Texas Provide?
    1. Texas Emission Reduction Plan
    2. Compressor Engines
    ii. Other Non-Modeling WOE From TCEQ
    iii. EPA WOE Analysis
    1. EPA Meteorological Adjusted Trends Analysis
    iv. Other WOE Items From Texas Not Currently Quantified:
Additional Programs/Reductions
    1. AirCheckTexas
    2. Local Quantified and Unquantified Measures
    c. Is the 8-Hour Attainment Demonstration Approvable?
    C. Control Measures Relied Upon by the State in the Attainment
Demonstration SIP
    D. Local Measures Relied Upon in the Control Strategy Modeling
    a. Voluntary Mobile Source Emission Reduction Programs
    b. Transportation Control Measures (TCMs)
    c. Measures Discussed in the April 23, 2008 Letter From TCEQ
    i. Texas Emission Reduction Plan (TERP)
    ii. Discrete Emission Credits (DECs)
    E. Reasonably Available Control Measures (RACM)
    F. Failure-To-Attain Contingency Measures
    G. Attainment Motor Vehicle Emission Budgets
    H. Section 110(l) Analysis
VI. Reasonably Available Control Technology (RACT)
VII. Proposed Action
VIII. Statutory and Executive Order Reviews

I. What Has the State Submitted?

    On May 30, 2007, Texas submitted a plan designed to attain the 8-
hour National Ambient Air Quality Standard (NAAQS) for ozone adopted in
1997 (the 1997 8-hour ozone standard). Texas supplemented this
submission with additional information in a letter dated April 23,
2008. The attainment demonstration relies on a variety of controls on
minor and major stationary sources and controls on mobile source
emissions. The emissions reductions are achieved through a combination
of Federal, State and Local measures. These measures are projected to
reduce emissions of NOX, a precursor to ozone formation, in
the DFW area by over 50% from 1999 levels. Some of the measures that
have been relied on in this demonstration are being reviewed in this
Federal Register (FR). Many are being reviewed or have been reviewed in
other FR notices. All of the measures that are relied on in the plan
must be approved before we can finalize our approval. The Texas
Commission on Environmental Quality (TCEQ) used photochemical modeling
and other corroborative evidence to predict the improvement in ozone
levels that will occur due to these controls while taking into account
the growth in the DFW area.
    The State's submission does not directly address the new ozone
standard issued March 12, 2008. The new ozone standard is more
protective and will require further reductions to attain, but the Texas
plan will provide progress toward this new standard.

II. What Action Is EPA Proposing?

    The EPA is proposing to conditionally approve the 1997 8-hour ozone
attainment demonstration SIP revision for the DFW area (8-hour DFW SIP)
submitted on May 30, 2007 and supplemented on April 23, 2008. This
submittal provides photochemical modeling, corroborative analyses,
additional control measures not explicitly accounted for in the
photochemical modeling, and a combination of adopted Federal, State,
and local measures to demonstrate that the DFW area will attain the
1997 8-hour ozone standard by June 15, 2010. It also includes, as part
of the attainment demonstration SIP, an attainment MVEB, a RACM
analysis, and control measures. In today's action, we are proposing to
approve two local measures relied upon in the attainment
demonstration--the Voluntary Mobile Source Emission Reduction Program
(VMEP) and Transportation Control Measures (TCMs); we are proposing to
adopt the attainment MVEBs into the DFW SIP; and we are proposing to
approve the demonstration that all RACM have been adopted for the DFW
area. Finally, in today's action, EPA also is proposing to fully
approve the VOC RACT submissions for both the 1-hour and the 1997 8-
hour ozone standards.

A. What Must Happen Before We Can Finalize Conditional Approval?

    Before finalizing conditional approval of the attainment
demonstration SIP, we must fully approve all of the control measures
relied on in the attainment demonstration and the Reasonable Further
Progress (RFP) Plan. In the 8-hour DFW SIP, the State included new
NOX emissions reductions measures and rules (found in Title
30 of the Texas Administrative Code, Chapter 117--denoted 30 TAC 117 or
Chapter 117), a VMEP, and TCMs. The revisions to Chapter 117 include
NOX reductions from the following sources: Industrial,
Commercial, and Institutional (ICI) Sources, Minor Sources, Electric
Generating Facilities (EGFs), Cement Kilns and East Texas Combustion
Sources. The measures in the 8-hour DFW SIP also include rules that
were adopted under the 1-hour ozone standard, which have been extended
to the larger 8-hour ozone nonattainment area (NAA). These previously
adopted rules were approved in earlier actions and are listed in
section V-C of today's rulemaking. In separate rulemakings, we are
proposing to approve the 2007 RFP SIP and the remaining control
measures including NOX controls submitted on May 30, 2007,
for point and area sources, which include ICI Sources, EGFs, Minor
Sources, Cement Kilns and East Texas Combustion Sources. We will also
take action on other emissions reduction measures submitted on May 13,
2005, which include the April 9, 2003 Alcoa Federal consent decree, an
Energy Efficiencies Program and NOX rules.
    A description of all the measures that must be approved by EPA
before any final approval of the attainment demonstration SIP is in
section V of today's action.
    In addition, we cannot finalize the proposed conditional approval
until Texas submits an approvable SIP revision to satisfy the section
172(c)(9) requirement for contingency measures that would be triggered
if the area fails to attain the 8-hour ozone standard by its attainment
date. This SIP revision (the contingency for final conditional
approval) must be a complete approvable failure-to-attain contingency
measures plan. Texas has committed to adopt and submit a plan that
relies upon three VOC SIP rules for Offset Lithographic Printing;
Degassing or Cleaning of Stationary, Marine and Transport Vessels; and
Petroleum Dry Cleaning, as well as fleet turnover from mobile sources
after 2009 as contingency measures. These measures are more fully
described in a commitment letter submitted by the State, dated June 13,
2008 (this letter is in the docket for this action). If the State
submits a complete failure-to-attain contingency measures plan that
relies upon the four above-noted control measures, EPA could proceed
with a final conditional approval of the attainment demonstration SIP.
Any comments concerning whether these four measures are sufficient to
meet the failure-to-attain contingency measure requirement should be
raised at this time. EPA does not plan to provide an additional
opportunity for comment unless the State modifies these measures or
submits a failure-to-attain contingency measures plan relying on other
measures.

III. Why Is This Proposed Approval Conditional and What Are the
Implications of a Conditional Approval?

    Our proposed approval of the attainment demonstration SIP is
conditional because the attainment demonstration submitted in May 2007
relies upon unlimited usage of DERCs, whereas the April 2008
supplemented attainment demonstration relies upon a limited usage of
DERCs; as yet there is no State rule implementing this change. The
condition is based on a commitment by the State of Texas to adopt and
submit by March 1, 2009, a complete SIP revision that includes an
enforceable mechanism that would allow no more than 3.2 tons per day
(tpd) of DERCs to be used in 2009 in the DFW area. If Texas intends to
allow for more than 3.2 tpd of DERCs to be used beginning January 1,
2010, then the SIP revision must also provide appropriate limits on the
use of DERCs and a detailed justification explaining how the future
adjustments to the allowed DERC usage will be consistent with continued
attainment of the 8-hour ozone standard. The justification must provide
sufficient detail such that the public can be assured that attainment
will continue to be projected in future years. For further explanation
of the limitation on DERCs, see section V-D.
    Under section 110(k) of the Act, EPA may conditionally approve a
plan based on a commitment from the State to adopt specific enforceable
measures within one year from the date of approval. The TCEQ submitted
a commitment letter to EPA committing to adopt and submit to EPA by
March 1, 2009, a SIP revision addressing the DERC restrictions for 2009
and addressing the use of DERCs in subsequent years. This letter, dated
June 13, 2008, is in the docket for this action.
    If EPA issues a final conditional approval of the SIP before March
1, 2009 and Texas subsequently fails to adopt and submit the DERC SIP
revision as committed to in its letter, EPA will issue a letter to the
State converting the conditional approval of the 1997 8-hour ozone DFW
attainment demonstration SIP to a disapproval. Such disapproval will
start the 18-month clock for sanctions in accordance with section
179(b) and 40 CFR 52.31 and the 2-year clock for a Federal
Implementation Plan (FIP) under section 110(c). EPA would publish in
the Federal Register a notice regarding the disapproval of the SIP and
the start of sanctions and FIP clocks for the DFW area, and would
revise the provisions in the Code of Federal Regulations (CFR) to
reflect the disapproval of the SIP.
    The State anticipates the DERC and contingency measure SIP
revisions to be proposed for public review and comment in Summer 2008,
and final adoption of the revisions is expected early in 2009 in order
to meet the commitment to submit the revisions to EPA by March 1, 2009.
If EPA finds that the submitted DERC SIP rule is approvable, we will
propose approval of the rule and could proceed with final full approval
of the attainment demonstration. Final conditional approval of the
attainment demonstration SIP would remain in effect until EPA takes
final action to convert the conditional approval to a full approval or
disapproval of the attainment demonstration. If EPA cannot fully
approve the revision concerning the use of DERCs in the DFW area, EPA
will propose disapproval of the submitted SIP rule and the attainment
demonstration SIP for the DFW area. The 18-month clock for sanctions
and the 2-year clock for a FIP start on the date of final disapproval.

IV. Background

A. What Are the National Ambient Air Quality Standards?

    Section 109 of the Act requires EPA to establish National Ambient
Air Quality Standards (NAAQS or standards) for pollutants that ``may
reasonably be anticipated to endanger public health and welfare,'' and
to develop a primary and secondary standard for each NAAQS. The primary
standard is designed to protect human health with an adequate margin of
safety, and the secondary standard is designed to protect public
welfare and the environment. EPA has set NAAQS for six common air
pollutants, referred to as criteria pollutants: carbon monoxide, lead,
nitrogen dioxide, ozone, particulate matter, and sulfur dioxide. These
standards present State and local governments with the minimum air
quality levels they must meet to comply with the Act. Also, these
standards provide information to residents of the United States about
the air quality in their communities.

B. What Is a SIP?

    The SIP is a set of air pollution regulations, control strategies,
other means or techniques, and technical analyses developed by the
State, to ensure that the State meets the NAAQS. The SIP is required by
section 110 and other provisions of the Act. These SIPs can be
extensive, containing State regulations or other enforceable documents
and supporting information such as emissions inventories, monitoring
networks, and modeling demonstrations. Each State must submit these
regulations and control strategies to EPA for approval and
incorporation into the federally-enforceable SIP. Each Federally-
approved SIP protects air quality primarily by addressing air pollution
at its point of origin.

C. What Is Ozone and Why Do We Regulate It?

    Ozone is a gas composed of three oxygen atoms. Ground-level ozone
is generally not emitted directly from a vehicle's exhaust or an
industrial smokestack, but is created by a chemical reaction between
NOX and VOCs in the presence of sunlight and high ambient
temperatures. Thus, ozone is known primarily as a summertime air
pollutant. NOX and VOCs are precursors of ozone. Motor
vehicle exhaust and industrial emissions, gasoline vapors, chemical
solvents and natural sources emit NOX and VOCs. Urban areas
tend to have high concentrations of ground-level ozone, but areas
without significant industrial activity and with relatively low
vehicular traffic are also subject to increased ozone levels because
wind carries ozone and its precursors hundreds of miles from their
sources.
    Repeated exposure to ozone pollution may cause lung damage. Even at
very low concentrations, ground-level ozone triggers a variety of
health problems including aggravated asthma, reduced lung capacity, and
increased susceptibility to respiratory illnesses like pneumonia and
bronchitis. It can also have detrimental effects on plants and
ecosystems.

D. Background of the Texas SIP for the DFW Area

    The original Texas SIP was submitted to EPA by the Texas Air
Control Board (renamed twice and known today as the TCEQ), on January
31, 1972. On May 31, 1972, EPA conditionally approved the SIPs for all
States in Volume 37 of the Federal Register beginning on page 10842
(denoted 37 FR 10842). The Texas SIP was conditionally approved (37 FR
10842, 10895) and the status of the Texas SIP was codified in Title 40,
Part 52 of the U.S. Code of Federal Regulations (denoted 40 CFR 52),
Subpart SS, sections 52.2270 to 52.2280. Since 1972, many revisions for
the DFW area have been submitted by the State and approved by EPA.
These include numerous control measures implemented under the 1-hour
ozone standard to reduce NOX and VOC emissions from area,
point and mobile

sources; the Post-1996 Rate-of-Progress (ROP) Plan; and the 15% ROP
Plan. As a result of the implementation of these measures, the area's
1-hour ozone values have declined significantly in the past several
years; the 2004-2006 1-hour design value for the DFW area is 124 parts
per billion (ppb) and the preliminary \1\ 1-hour design value for 2005-
2007 is also 124 ppb, which meets the 1-hour standard, although this
standard was revoked in 2005.
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    \1\ The value is considered preliminary because TCEQ has not
certified that it has completed the quality assurance and quality
control checks. We expect the data certification by by July 1, 2008.
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E. Background of This SIP Revision To Address the 1997 Ozone NAAQS

    On July 18, 1997, EPA promulgated a revised 8-hour ozone standard
of 0.08 parts per million (ppm), which is more protective than the
previous 1-hour ozone standard (62 FR 38855).\2\ Under EPA regulations
at 40 CFR part 50, Appendix I, the 1997 8-hour ozone standard is
attained when the 3-year average of the annual fourth highest daily
maximum 8-hour average ambient ozone concentrations is less than or
equal to 0.08 ppm (i.e., 0.084 ppm when rounding is considered). For
ease of communication, many reports of ozone concentrations are given
in parts per billion (ppb); ppb = ppm x 1,000. Thus, 0.084 ppm becomes
84 ppb.
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    \2\ EPA issued a revised 8-hour ozone standard on March 27, 2008
(73 FR 16436). The designation and implementation process for that
standard is just starting and does not affect EPA's action here.
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    The EPA published the 1997 8-hour ozone designations and
classifications on April 30, 2004 (69 FR 23858). The DFW area was
designated nonattainment, classified as moderate, and includes nine
counties: Collin, Dallas, Denton, and Tarrant counties (these
constitute the former 1-hour ozone NAA, hereafter referred to as the
core counties), and Ellis, Johnson, Kaufman, Parker and Rockwall
counties. The effective date of designation for the 1997 8-hour ozone
NAAQS was June 15, 2004. The attainment demonstration for the DFW area
was due by June 15, 2007 and was submitted on time. The attainment date
for the DFW area is June 15, 2010.
    EPA also published the first rule governing implementation of the
8-hour ozone standard (Phase 1 Rule) on April 30, 2004 (69 FR 23951).
The Phase 1 Rule addresses classifications for the 8-hour NAAQS;
revocation for the 1-hour NAAQS; how anti-backsliding principles will
ensure continued progress toward attainment of the 8-hour NAAQS;
attainment dates; and the timing of emissions reductions needed for
attainment.
    On December 22, 2006, the U.S. Court of Appeals for the District of
Columbia Circuit vacated EPA's Phase 1 Rule in South Coast Air Quality
Management Dist. v. EPA, 472 F.3d 882 (D.C. Cir. 2006). On June 8,
2007, in response to several petitions for rehearing, the court
modified the scope of vacatur of the Phase 1 Rule. See 489 F.3d 1245
(D.C. Cir. 2007), cert. denied, 128 S.Ct. 1065 (2008). The court
vacated those portions of the Phase 1 Rule that provide for regulation
of the 1997 8-hour ozone NAAQS in some nonattainment areas under
Subpart 1 in lieu of Subpart 2 and that allowed areas to revise their
SIPs to no longer require certain programs as they applied for purposes
of the 1-hour NAAQS; new source review, section 185 penalties, and
contingency plans for failure to meet RFP and attainment milestones.
The decision does not affect the requirements for areas classified
under subpart 2, such as the DFW area, to submit an attainment
demonstration plan for 1997 8-hour ozone NAAQS and to attain the NAAQS
no later than the outside date for attainment required for the area's
classification.
    EPA published a second rule governing implementation of the 8-hour
ozone standard (Phase 2 Rule) on November 29, 2005 (70 FR 71612), as
revised on June 8, 2007 (72 FR 31727). The Phase 2 Rule addresses,
among other things, the following control and planning obligations as
they apply to areas designated nonattainment for the 1997 8-hour ozone
NAAQS: RACT, RACM, photochemical modeling, and attainment
demonstrations. EPA issued the Phase 2 Rule so States and Tribes would
know how these statutory control and planning obligations apply and
when SIP revisions are due for these obligations so that the States
could develop timely submissions consistent with the statutory
obligations and attain the NAAQS as expeditiously as practicable, but
no later than the attainment dates specified for each area's
classification. Litigation on the Phase 2 Rule is pending before the
D.C. Circuit Court of Appeals.
    On May 23, 2007, the TCEQ approved revisions to the SIP for the DFW
8-hour ozone nonattainment area. The SIP revisions were submitted to
EPA on May 30, 2007 and supplemented on April 23, 2008. Today we are
addressing the 1997 8-hour ozone attainment demonstration SIP for the
DFW area and a RACT finding for both the 1-hour and 1997 8-hour ozone
standards.

F. What Is an Attainment Demonstration?

    In general, an ozone attainment demonstration includes a
photochemical modeling analysis and other evidence (referred to as
``weight of evidence'') showing how an area will achieve the standard
as expeditiously as practicable, but no later than the attainment date
specified for its classification. For purposes of the 8-hour ozone
standard, a determination of attainment (or failure to attain) is based
on the most recent three complete years of data prior to the area's
attainment date. Thus, since the DFW moderate area has a maximum
attainment date of June 15, 2010, the most recent three years of data
for determining attainment in the DFW area will be from the three
preceding calendar years, i.e., the air quality monitoring data from
2007, 2008 and 2009. Alternatively, an area may qualify for up to two
one-year extensions. The first extension can be granted if the area's
4th highest daily 8-hour average is 0.084 ppm or less. The second can
be granted if the 4th highest value averaged over the attainment year
and the extension year is 0.084 ppm or less (40 CFR 51.907).
    To demonstrate attainment, an area must predict that emissions
during the ozone season preceding the attainment date will meet the
standard. EPA requires areas to implement all the measures necessary to
demonstrate attainment as expeditiously as practicable, but no later
than the start of the final complete ozone season preceding the area's
attainment date (40 CFR 51.908). The DFW area's ozone season runs from
March 1st through October 31st (62 FR 30270, June 3, 1997 and 40 CFR
part 58, Appendix D); therefore, all of the control strategies relied
upon in the attainment demonstration must be implemented by March 1,
2009.
    In addition to the approvable modeling and weight of evidence
components of an attainment demonstration SIP, for the attainment
demonstration SIP to be approvable, it must contain the following
elements which must also be approved: attainment MVEBs for
transportation conformity purposes; the measures relied on as necessary
to demonstrate attainment; RACM; an RFP plan and the RFP/failure-to-
attain contingency measures requirements for the area. (See Sierra Club
v. EPA, 294 F.3d 155, 163 (D.C. Cir. 2002).

V. Evaluation of the DFW 1997 8-Hour Ozone Attainment Demonstration SIP

    Below, we discuss the statutory and regulatory requirements that
prescribe our review of the State's attainment demonstration, the
elements in the State's submittal, and our evaluation of those elements
comprising the attainment demonstration SIP. Separate from our review
of the State's attainment demonstration SIP is our review of the
State's VOC RACT demonstration, and we discuss the VOC RACT statutory
and regulatory requirements in section VI.

A. Legal Requirements for Approval

    The Act requires SIPs for nonattainment areas to demonstrate that
the area will attain the 8-hour ozone standard as expeditiously as
practicable, but no later than outside dates established by the Act.
The Phase 2 Rule provides timing and guidance for this requirement for
the 1997 8-hour ozone standard and identifies the modeling guidance
available to make the demonstration. Moderate 1997 8-hour ozone
nonattainment areas must attain the standard no later than June 15,
2010. An attainment demonstration SIP must include technical analyses
to locate and identify sources of emissions that are causing violations
of the NAAQS within nonattainment areas; adopted measures with
schedules for implementation and other means and techniques necessary
and appropriate for attainment; and contingency measures required under
section 172(c)(9) of the Act that can be implemented without further
action by the State or the Administrator to cover failures to meet RFP
milestones and/or attainment. The attainment demonstration SIP must
include a demonstration that the area is meeting RACM. An attainment
demonstration SIP must also identify MVEBs for transportation
conformity purposes. EPA's regulations at 40 CFR 51.908(c) specifically
require that areas classified as moderate and above submit a modeled
attainment demonstration based on a photochemical grid modeling
evaluation or any other analytical method determined by the
Administrator to be at least as effective as photochemical modeling.
Section 51.908(c) also requires each attainment demonstration to be
consistent with the provisions of section 51.112, including Appendix W
to 40 CFR part 51 (i.e., ``EPA's Guideline on Air Quality Models,'' 68
FR 18440, April 15, 2003). See also EPA's ``Guidance on the Use of
Models and Other Analyses in Attainment Demonstrations for the 8-hour
Ozone NAAQS,'' October 2005 and ``Guidance on the Use of Models and
Other Analyses for Air Quality Goals in Attainment Demonstrations for
Ozone, PM2.5, and Regional Haze,'' April 2007 (hereafter referred to as
``EPA's 2005 and 2007 A.D. guidance documents''), which describe
criteria that an air quality model and its application should meet to
qualify for use in an 8-hour ozone attainment demonstration. For the
detailed review of modeling and the Weight of Evidence (WOE) analyses
and EPA's conclusions on the DFW 8-hour Ozone Attainment Demonstration
see the ``Modeling and Other Analyses Attainment Demonstration''
(MOAAD) Technical Support Document (TSD). The MOAAD TSD also includes a
complete list of applicable modeling guidance documents. These guidance
documents provide the overall framework for the components of the
attainment demonstration, how the modeling and other analyses should be
conducted, and overall guidance on the technical analyses for
attainment demonstrations.
    As with any predictive tool, there are inherent uncertainties
associated with photochemical modeling. EPA's guidance recognizes these
limitations and provides approaches for considering other analytical
evidence to help assess whether attainment of the NAAQS is likely. This
process is called a WOE determination. EPA's modeling guidance (updated
in 1996, 1999, and 2002) discusses various WOE approaches. EPA's
modeling guidance has been further updated in 2005 and 2007 for the
1997 8-hour attainment demonstration procedures to include a WOE
analysis as an integral part of any attainment demonstration. This
guidance strongly recommends that all attainment demonstrations include
supplemental analyses beyond the recommended modeling. These
supplemental analyses would provide additional information such as data
analyses, and emissions and air quality trends, which would help
strengthen the overall conclusion from the photochemical modeling. A
WOE analysis is specifically recommended to be included as part of any
attainment demonstration SIP where the modeling results predict Future
Design Values (FDVs) ranging from 82 to less than 88 ppb (EPA's 2005
and 2007 A.D. guidance documents). EPA's interpretation of the Act to
allow a WOE analysis has been upheld. See 1000 Friends of Maryland v.
Browner, 265 F.3d 216 (4th Cir. 2001) and BCCA Appeal Group v. EPA, 355
F.3d 817 (5th Cir. 2003).
    Since much of TCEQ's initial work was conducted prior to the 2005
guidance document, the earlier draft 1999 modeling guidance document
(EPA-454/R-99-004, May 1999; ``DRAFT Guidance on the Use of Models and
Other Analyses in Attainment Demonstrations for the 8-Hour Ozone
NAAQS'') was also used by TCEQ and EPA prior to the October 2005
guidance issuance. There are two main changes compared to EPA's
modeling attainment demonstration guidance issued in 1991. First, EPA
recommends a modeled attainment test in which model predictions are
used in a relative rather than absolute sense. Second, the role of the
WOE determination, when used, has been expanded. That is, where the use
of WOE was previously considered optional, it is now strongly
recommended as an integral part of an attainment demonstration in
addition to the modeled attainment test.
    TCEQ submitted the DFW attainment demonstration SIP with
photochemical modeling and WOE analyses. The results of the
photochemical modeling and WOE analyses are discussed below in
Subsection B. The projected growth rates and emissions reductions (or
increases) for the control measures and other means relied upon in the
modeling are discussed in Subsection C.

B. Eight-Hour Attainment Demonstration Modeling and Weight of Evidence

a. What Were the Results of the Photochemical Modeling Attainment
Demonstration?
i. What Is a Photochemical Grid Model?
    Photochemical grid models are the state-of-the-art method for
predicting the effectiveness of control strategies in reducing ozone
levels. The models use a three-dimensional grid to represent conditions
in the area of interest. TCEQ chose to use the Comprehensive Air Model
with Extensions (CAMx), Version 4.31 photochemical model for this
attainment demonstration SIP. The model is based on well-established
treatments of advection, diffusion, deposition, and chemistry. Another
important feature is that NOX emissions from large point
sources can be treated with the plume-in-grid sub-model that helps
avoid the artificial diffusion that occurs when point source emissions
are inserted into a grid volume. The use of the newer version improves
the plume dispersion algorithms and adds full NOX and VOC
chemistry in the plumes. TCEQ has used the CAMx model in other SIPs and
EPA has approved many SIPs using CAMx based modeling analyses. Part 51
Appendix W indicates that photochemical grid models should be used for
ozone SIPs and lists a

number of factors to be considered in selecting a photochemical grid
model to utilize. EPA has reviewed TCEQ reasons for selecting CAMx and
EPA agrees with the choice by TCEQ to utilize CAMx for this SIP.
    In this case, TCEQ has developed a grid system that consists of
three nested grids. The outer grid stretches from west of Austin to
Maine and parts of the Atlantic Ocean to the east, and from parts of
southern Canada in the north to the southern tip of Texas and the Gulf
of Mexico on the southern edge. The model uses nested grid cells of 36
km on the outer portions, 12 km in east Texas and portions of nearby
States and a 4-km grid cell covering the DFW Nonattainment Area. For
more information on the modeling domain, see the MOAAD TSD. The model
simulates the movement of air and emissions into and out of the three-
dimensional grid cells (advection and dispersion); mixes pollutants
upward and downward among layers; injects new emissions from sources
such as point, area, mobile (both on-road and nonroad), and biogenic
into each cell; and uses chemical reaction equations to calculate ozone
concentrations based on the concentration of ozone precursors and
incoming solar radiation within each cell. Air quality planners choose
historical time period(s) (episode(s)) of high ozone levels to apply
the model. Running the model requires large amounts of data inputs
regarding the emissions and meteorological conditions during an
episode.
    Modeling to duplicate conditions during an historical time period
is referred to as the base case modeling and is used to verify that the
model system can predict historical ozone levels with an acceptable
degree of accuracy. It requires the development of a base case
inventory, which represents the emissions during the time period for
the meteorology that is being modeled. These emissions are used for
model performance evaluations. Texas modeled a 1999 episode, so the
base case emissions and meteorology are for 1999. If the model can
adequately replicate the ozone levels in the base case and responds
adequately to diagnostic tests, it can then be used to project the
response of future ozone levels to proposed emission control
strategies.
ii. What Episode Did Texas Choose To Model?
    Texas chose an historical episode, August 13-22, 1999, that had
been previously used in modeling for the Early Action Compact modeling
of the Northeast Texas Area. The episode encompasses ten days with 8-
hour ozone exceedances every day, except for the first day which is one
of the two spin-up days. The first two days are considered spin-up days
that are usually not used in the modeling analysis because it
ordinarily takes 1-2 days to work out the initial condition biases. Of
the eight days (ten days minus the two spin-up days) that have
exceedances, all but one day have multiple monitors with exceedances
(2-7 of the nine monitors). On average, the eight exceedance days have
four monitors exceeding the standard each day. This episode contains a
variety of meteorological conditions which resulted in high
concentrations of ozone in the area as measured on both a 1-hour and 8-
hour basis, and many of the days had conditions similar to the
predominant types of meteorological conditions that yield high ozone in
the DFW NAA.
    We evaluated Texas' episode selection for consistency with our
modeling guidance (1991, Draft 1999, 2005, and 2007 versions). Among
items that we considered were the ozone levels during the selected
period compared to the Design Value \3\ (DV) at the time; how did the
meteorological conditions during the proposed episode match with the
conceptual model of ozone exceedances that drive the area's DV; were
enough days modeled; and was the time period selected robust enough to
represent the area's problem for evaluating future control strategies.
EPA's guidance indicates that all of these items should be considered
when evaluating available episodes and selecting episodes to be
modeled. EPA believes that the episode from August 13-22, 1999, is an
acceptable episode for development of the 8-hour ozone attainment plan.
It has a number of meteorological conditions that match the conditions
that yield high ozone in the conceptual model for the DFW NAA, and was
among the episode periods evaluated with the highest number of ozone
exceedances. In selecting episodes, it is advantageous to select
episodes with several exceedance days and with multiple monitors
exceeding the standard each day when possible. This episode was among
the best episodes for the periods evaluated when the selection was
being conducted initially, and also had the benefit that significant
work was being conducted for this period for the Early Action Compact
for the Tyler/Longview/Marshall area of Northeast Texas. See the MOAAD
TSD for further discussion and analysis.
---------------------------------------------------------------------------

    \3\ The design value is the 3-year average of the annual fourth
highest daily maximum 8-hour average ozone concentration (40 CFR 50,
Appendix D.
---------------------------------------------------------------------------

iii. How Well Did the Model Perform?
    Model performance is a term used to describe how well the model
predicts the meteorological and ozone levels in an historical episode.
EPA has developed various diagnostic, statistical and graphical
analyses that TCEQ has performed to evaluate the model's performance to
determine if the model is working adequately to test control
strategies. TCEQ has done many analyses of both interim model runs and
the final base case model run and deemed the model's performance
adequate for control strategy development. As described below, we agree
with their assessment.
    From 2003 to 2005, several iterations of the modeling were
preformed incorporating various improvements to the meteorological
modeling, the 1999 base case emissions inventory, and other model
parameters. These iterations totaled over 40 combinations as TCEQ
worked to refine the modeling. EPA reviewed these interim modeling
steps and provided comments and suggestions. When TCEQ felt the model
performance was acceptable, EPA (Region 6 and the Office of Air Quality
Planning and Standards) and TCEQ had a detailed meeting on February 1,
2005 to cover all aspects of the episode selected and model performance
(meteorological, emissions, and photochemical). TCEQ shared a compact
disc with detailed statistical and graphical analysis of the different
modeling (meteorology and photochemical). This data included analysis
of meteorological outputs compared to benchmark statistical parameters
that TCEQ previously developed as target values that are being used in
many areas of the country. TCEQ also shared graphical analyses of the
meteorology. TCEQ also shared extensive analyses of the photochemical
modeling for several base case modeling runs that included: diagnostic
tests with reductions/increases of precursor emissions, time series of
1-hour and 8-hour ozone, EPA 1-hour statistics, EPA 8-hour statistics,
ozone spatial plots, quantile-quantile plots, ozone pre-cursor data,
and ozone animations.
    After extensive review, EPA was satisfied that the meteorological
modeling was meeting most of the statistical benchmarks, and was
transporting air masses in the appropriate locations for most of the
days of the episode. EPA also conducted a thorough review of the
model's performance in predicting ozone and ozone pre-cursors and found
that

performance was within the recommended 1-hour ozone statistics for
almost all days and all statistics. We also evaluated the 8-hour
statistics, results of diagnostic and sensitivity tests, and multiple
graphical analyses and determined that overall the ozone performance
was acceptable for Texas to move forward with future year modeling and
development of an attainment demonstration. EPA's acceptance of the
modeling is documented in a June 6, 2005 letter.
    Subsequently, TCEQ made further minor refinements to the modeling
which are discussed in the MOAAD TSD. EPA agrees that after these minor
refinements, the overall model performance remains acceptable. The
final base case modeling evaluation, Run 46 using CAMx 4.31, further
reduced negative bias and reduced the total errors in the modeling
system. EPA agrees that the overall model performance (Run 46) is
adequate, but notes that even with the refinements, the modeling still
tends to have some bias on the higher ozone days. This bias may make
future year assessments conservative, i.e., the amount of ozone
reduction predicted is likely less than will actually occur, if the
modeling is not fully replicating local ozone generation. See the MOAAD
TSD for further analysis.
iv. Once the Base Case Is Determined To Be Acceptable, How Do You Use
the Modeling for the Attainment Demonstration?
    Once the base case modeling is determined to be consistent with
EPA's guidance and acceptable for replicating the ozone levels observed
in the 1999 episode period, the modeling can be used as the basis for
developing the future year modeling. TCEQ then evaluated the base case
emission inventory, and made some minor adjustments to the inventory to
account for things that would not be expected to occur again or that
were not normal (example: inclusion of EGUs that were not operating due
to temporary shutdown during the base case period but were expected to
be operating in 2009). This emission inventory is called the 1999
baseline emission inventory. The photochemical model is then executed
again to obtain a 1999 baseline model projection.
    EPA's guidance recommends using 2002 as the baseline inventory
year, but there are several possible methodologies available to
calculate baseline design values. For example, if a state models
episodes from other years it can project (or back-cast) to 2002 to
provide a starting point for future year projections. Alternatively, a
state may use a baseline year earlier than 2002 for the following
reasons: (1) Availability of air quality and meteorological data from
an intensive field study, (2) the desire to use meteorological data
that may be ``more representative'' of typical ozone conditions
compared to the baseline design value period, and (3) availability of a
past modeling analysis in which the model performed well. Texas chose
1999 as the baseline year. There was extensive air quality and
meteorological modeling available for the 1999 episode from Early
Action Compact Modeling in Northeast Texas; 1999's meteorology
represented typical ozone conditions. Therefore, EPA and TCEQ weighed
the pros and cons and concurred, based upon the above-noted reasons,
that it was not necessary to attempt to project to a 2002 baseline
emission inventory in this specific case.
    The baseline emission inventory is also used as the basis, along
with other data, to project and estimate the future case emission
inventory along with consideration of any state and Federal regulations
that result in emission changes from the 1999 period. Since DFW is
classified as a moderate NAA, the attainment deadline is as
expeditiously as practicable but no later than June 15, 2010. Any
emissions reductions must be implemented no later than the beginning of
the previous ozone season; in this case, March 1, 2009, which is the
beginning of the final full ozone season preceding the attainment date,
if the reductions are to support attainment. The meteorological
modeling that has been reviewed and determined to be acceptable for the
base case is also used for the meteorological conditions in the future
year modeling (no changes are made). The future case modeling uses the
base case meteorology and estimated 2009 emissions to assess the impact
of economic growth in the region and State and Federal control measures
that will become effective during the modeling period from 1999 to
March 1, 2009. After the State develops a 2009 future baseline emission
inventory, photochemical modeling is conducted to get the 2009 baseline
ozone levels. The State then begins conducting modeling sensitivities
and modeling assessments of potential additional emission reductions to
aid in the planning of a control strategy that will demonstrate
attainment.
    The 8-hour ozone modeling guidance changed the attainment test to
use the modeling analysis in a relative sense instead of an absolute
sense as was done in 1-hour ozone demonstrations. To predict ozone
levels in the future, we estimate a value that we refer to as the FDV.
First, we need to calculate a Base Design Value (BDV). The BDV is
calculated for each monitor that was operating in the base period by
averaging the three DVs that include the base year (1999); that would
be the DV for 1997-1999, 1998-2000, and 1999-2001 to result in a
center-weighted BDV.
    To estimate the FDV, a value is also calculated for each monitor
that is called the Relative Response Factor (RRF) using the baseline
and future modeling. The RRF value is calculated by taking the ratio of
the sum of the daily highest 8-hour ozone value predicted around a
monitor in 2009 and dividing by the sum of the daily highest 8-hour
ozone value predicted around the same monitor in the 1999 baseline
analysis. ``Around the monitor'' for DFW modeling (4km grid) is defined
as the 7x7 array of grid cells surrounding the monitor (with the
monitor in the middle). EPA's guidance indicates that only days that
had a baseline value above a threshold concentration (TCEQ used 70 ppb,
which is the minimum value indicated by EPA guidance) should be used in
the RRF calculations. For each monitor, EPA recommends adding up all
the daily maximum 8-hour ozone values (for days that the maximum 8-hour
ozone value in the baseline were above the threshold in the area around
the monitor) and dividing that sum by the sum of the daily maximum 8-
hour ozone values predicted in 2009 around the monitor. This
calculation yields the RRF for that monitor. The RRF is then multiplied
by the Base Design Value (BDV) for that monitor to yield the FDV for
that monitor. This step is conducted for each monitor. The modeled
values for each monitor may be calculated to the hundredths of a ppb
which is rounded to get to tenths of a ppb, which is then truncated to
an integer (in ppb) at the end of the process (as recommended by EPA's
guidance). The truncated values are included in the tables in this
notice (Example: Modeled value of 84.94 is rounded to 84.9 and then
truncated to 84; Example 2: Modeled value of 84.95 is rounded to 85.0
and then truncated to 85).
v. What Modeling Approaches Were Used for This Attainment
Demonstration?
    TCEQ submitted photochemical modeling labeled Combo 10 in its
attainment demonstration SIP. Combo 10 contains the control measures
outlined in Section D, including additional control measures with
compliance deadlines of March 1, 2010. The 2010 compliance dates apply
to

certain rich-burn natural gas fired engines for oil and gas compressors
in 33 Texas counties, all of which are outside the DFW NNA. Despite the
fact that the controls noted above are not required to be implemented
until 2010, Combo 10 assumes that all control measures will be in
effect by the beginning of the 2009 ozone season. TCEQ assumed that
early compliance would occur as a result of incentive grants for early
compliance provided by the State Legislature. Texas SB2000 provides an
appropriation of $4 million to compensate operators of the regulated
oil and gas compressors who comply with new emission reduction
standards early. There is also a large population of emission units in
this category and it is also likely that a percentage of these will be
controlled before the 2009 ozone season, or before the beginning of the
core part of the ozone season. Due to the large number of emission
units in this category and the incentive for early compliance, TCEQ
believes these units will provide significant reductions by 2009.
    A small portion of the point source NOX Controls in the
DFW NAA, that yield about 2.4 tpd of NOX reductions, also
have 2010 compliance dates. TCEQ did not attempt to assess the
potential impact of not having these additional point source reductions
in place by the beginning of the 2009 ozone season. The 2.4 tpd of
NOX reductions from these sources is less than 10% of the
NOX emission reductions adopted for the DFW NAA. EPA also
notes that some of these 2.4 tpd NOX reductions are in the
western part of the DFW NAA and would not directly affect the modeled
impact at the monitors with the highest modeled FDVs (Frisco and Denton
monitors) for this episode, but would be expected to help reduce ozone
impacts at other monitors in Parker and Tarrant counties that have been
added to the DFW area monitoring network since 1999.
    For a more complete description of the modeling procedures
conclusions and EPA's evaluation of these procedures and conclusions,
see the MOAAD TSD in the Docket for this action (EPA-RO6-OAR-2007-
0524).
vi. What Did the Results of TCEQ's Combo 10 Modeling Show?
    The results of modeling the final control strategy runs are shown
in Table 1. As previously discussed, the State submitted modeling
(Combo 10) that took into account all the reductions from adopted
regulations, including those with 2010 compliance dates. TCEQ has
proposed an alternative RRF calculation method that calculated a daily
RRF for each monitor and then averaged the values to yield the RRF that
was multiplied by the BDV to yield the FDV. In the following Table 1,
we evaluate the model FDV calculations using both EPA's guidance method
for RRF calculation and the alternate RRF calculation approach that
TCEQ had developed. Details on the two methods are included in the TSD.
For most monitors, the alternate FDV calculations make only minor
differences. We have calculated the FDVs in the following tables using
the final truncated numbers in accordance with EPA guidance. Since the
TCEQ RRF calculation method did not make significant differences in the
FDVs and with the truncation to whole numbers, we have used the TCEQ
RRFs for the final assessment with consideration of the FDVs using
EPA's RRF method. The results of EPA's RRF method are contained in the
MOAAD TSD. Table 1 includes the modeling projections prior to
evaluating any other modeling runs, any additional model based
projections, and any WOE considerations for the Combo 10 modeling run.
Table 1 also includes the results from the two methodologies to
calculate the FDVs.

                   Table 1.--June 15, 2007 SIP Control Strategy Modeling Projections for 2009
----------------------------------------------------------------------------------------------------------------
                                                                                FDV 1999 Combo 10
                            Monitor                                  BDV 1999    -------------------------------
                                                                                EPA            TCEQ
----------------------------------------------------------------------------------------------------------------
Frisco.........................................................            100.3              89              88
Dallas Hinton C60..............................................             92                85              85
Dallas North C63...............................................             93                84              84
Dallas Exec C402...............................................             88                78              78
Denton.........................................................            101.5              88              88
Midlothian.....................................................             92.5              83              83
Arlington......................................................             90.5              80              80
Ft Worth C13...................................................             98.3              85              85
Ft Worth C17...................................................             96                84              84
----------------------------------------------------------------------------------------------------------------

    The first column is the Base DV for the 1999 period that is used
with the modeling RRFs for calculating the FDVs. For Combo 10, the
analysis shows that 5 of the 9 monitors are projected to be in
attainment (at or below 84 ppb); two monitors (Ft. Worth C13 and Dallas
Hinton C60) are projected to be very near attainment with 85 ppb; and
projections for the other two monitors are 88 ppb for Denton and 88/89
ppb for the Frisco monitor. As shown in Table 1, the FDVs are on the
order of 8-12 ppb less than the Base DVs, which is a large reduction in
ozone levels due to existing State and Federal measures and the newly
adopted measures.
    For a more complete description of the modeling procedures
conclusions and EPA's evaluation of these procedures and conclusions,
see the MOAAD TSD in the Docket for this action (EPA-RO6-OAR-2007-
0524).
    In addition to the modeling results, TCEQ has presented other
evidence to demonstrate that attainment will be reached. These
additional WOE analyses are evaluated in Section 2 below. Since TCEQ's
May 30, 2007 submittal, TCEQ has also provided additional information
dated April 23, 2008 that supplements the modeling analysis (discussed
in part h below) and also the WOE (also discussed in section 2 below).
vii. Evaluation of Other Modeling Projections Without Benefit of
Measures With a 2010 Compliance Date
    Due to our concerns that not all control measures relied on in the
Combo 10 analysis are required to be implemented prior to the 2009
ozone season, we also reviewed an alternative photochemical modeling
analysis. The additional modeling, which we refer to as Photochemical
Dispersion Modeling Reanalysis 2009 (PDMR 2009), evaluates the ozone
levels in 2009 based on the TCEQ control measures with

compliance dates of March 1, 2009 or earlier and does not consider the
impact from the adopted rules that have compliance dates after March 1,
2009. The adopted SIP included 2.4 tpd of NOX emission
reductions in the DFW NAA with a 2010 compliance date, while the
adopted reductions within the DFW NAA with a 2009 compliance date of
March 1, 2009 or earlier yield 23.48 tpd of NOX reductions.
The adopted SIP also included 22.4 tpd of NOX reductions
outside the DFW NAA due to the control of rich-burn compressor engines
with a compliance date after March 1, 2009. Since these emission
reductions occur outside the DFW NAA, they would not be expected to
yield the same amount of ozone benefit as similar reductions in the DFW
NAA would yield. The PDMR 2009 modeling helps to assess the potential
impacts of these 2010 compliance rules.
    This evaluation of PDMR 2009 sets the lower bound of model
predictions for the FDV in 2009 and the Combo 10 run sets the upper
bound. This approach is consistent with attempting to consider the
bounds of potential benefit from the adopted measures included in the
SIP.
    Table 2 includes the modeling projections for both the Combo 10 and
PDMR 2009 modeling runs.

                   Table 2.--June 15, 2007 SIP Control Strategy Modeling Projections for 2009
----------------------------------------------------------------------------------------------------------------
                                                                                FDV Combo 10    FDV PDMR 2009
                            Monitor                                  BDV 1999    -------------------------------
                                                                                TCEQ RRF        TCEQ RRF
----------------------------------------------------------------------------------------------------------------
Frisco.........................................................            100.3              88              88
Dallas Hinton C60..............................................             92                85              85
Dallas North C63...............................................             93                84              85
Dallas Exec C402...............................................             88                78              79
Denton.........................................................            101.5              88              88
Midlothian.....................................................             92.5              83              84
Arlington......................................................             90.5              80              81
Ft Worth C13...................................................             98.3              85              85
Ft Worth C17...................................................             96                84              85
----------------------------------------------------------------------------------------------------------------

    For PDMR 2009, the analysis shows that 3 of the 9 monitors are
projected to be in attainment (at or below 84 ppb); four monitors (Ft.
Worth C13, Ft. Worth C17, Dallas North C63, and Dallas Hinton C60) are
projected to be very near attainment with 85 ppb; and projections for
the other two monitors are 88 ppb for the Denton and Frisco monitors.
This analysis indicates a slightly worse air quality picture than the
results from the Combo 10 analysis. The FDVs for several monitors were
higher, but the actual difference is only a few tenths of a ppb at most
monitors of concern. The largest difference between the PDMR 2009
modeling and the Combo 10 modeling was an increase of 0.3 ppb at the
Frisco monitor.
    As previously discussed, reductions from rules with a March 2010
compliance date are included in the Combo 10 run. Due to the incentives
for early compliance and consideration that some sources will likely be
controlled early, we conclude some of the reductions from rules with a
March 2010 compliance date will likely be completed early. Therefore,
we have evaluated the modeling outputs based on an approach that looks
at both the PDMR 2009 outputs, which predicts ozone levels that are
slightly worse than what actually will occur and Combo 10 outputs which
may be somewhat optimistic. For most monitors, the difference between
the PDMR 2009 and Combo 10 outputs is only a few tenths of a ppb of
ozone. For more details see the MOAAD TSD for this notice.
viii. Refinements and Adjustments to Future Year (2009) Emission
Inventory and Modeling-Based Projected Changes to the SIP Modeling FDVs
    Texas provided supplemental information to EPA on April 23, 2008
that expands and confirms information in the May 30, 2007 SIP
submittal. See TCEQ's April 23, 2008 letter in the docket. The letter
addresses the issues discussed below related to the airport emission
inventory, DERCs and back-up generators, demonstrating that the
projected emissions in these categories will be lower in 2009 than the
projections in the May 30, 2007 SIP submittal. To support the
adjustment to the DERC projections, Texas also provided a commitment
letter on June 13, 2008 to adopt a SIP revision to limit the use of
DERCs that is evaluated below and in section V-D of this notice. This
commitment was made by TCEQ in order to strengthen the attainment
demonstration.
    Regarding airport emissions, TCEQ provided a report performed by
Eastern Research Group for Love Field, a Dallas inner city airport,
which indicated that emission projections based on more recent data are
much lower in 2009 than emission projections relied on in the Combo 10
and PDMR 2009 modeling. The emissions are lower primarily due to
changes in market demand post-- 9/11/2001 and the accelerated
replacement of engines which occurred in order to reduce fuel usage
because of the drastic increase in fuel costs over the last few years.
Projections at Love Field were also impacted by changes in the Wright
Amendment Restrictions, a Federal law restricting flights in and out of
the airport that imposed restrictions on the number of gates that could
be operated (Pub. L. 109-352). TCEQ and North Central Texas Council of
Governments (NCTCOG) have provided EPA with updated information which
became available since the May 30, 2007 submittal which refines the
2009 future year emission projections for Love Field and also the DFW
International Airport (DFWIA). Both airports agree with their revised
projections. With the reduced projections at DFWIA and Love Field,
total airport emissions for all airports in the DFW NAA are reduced
from 24.05 tpd (the amount that was included in the attainment
demonstration modeling submitted May 30, 2007) to a lower emission
totals of 14.66 tpd (aircraft and ground support equipment). In other
words, the new estimates result in a 9.39 tpd airport emission
inventory reduction from the May 30, 2007 SIP modeling estimates for
the two airports. We have reviewed the updated information and agree
that 14.66 tpd NOX (a decrease of 9.39 tpd from the May 30,
2007 submittal values) represents a more accurate estimate of the
projected emissions from the DFW NAA airports.

    Consistent with EPA's guidance, sections 12 and 16 of ``Improving
Air Quality with Economic Incentive Programs'' (EPA-452/R-01-001,
January 2001), TCEQ included in the 2009 modeled projections, all of
the Emission Reduction Credits (ERCs) and Discrete Emission Reduction
Credits (DERCs) in the bank. EPA guidance calls for emission credits
that are being carried in the emissions bank to be included in modeled
projections because these emissions will come back in the air when the
credits are used. The TCEQ Bank currently holds 20.4 tpd of DERCs. Upon
review of the DERC values included in the modeling, TCEQ felt that the
inclusion of the entire balance of the DERC bank was overly
conservative based on past usage of DERCs. After discussions with EPA,
TCEQ committed to adopt and submit as a SIP revision, additional
regulations prior to the 2009 ozone season that will limit the usage of
DERCs by facilities in the DFW NAA. TCEQ plans to propose a DERC usage
limitation such that 17.2 tpd of the 20.4 tpd currently in the 2009
modeling, will not be allowed to be used in 2009. The TCEQ submitted a
commitment to EPA to adopt and submit to EPA as a SIP revision, an
enforceable mechanism by March 1, 2009 that would limit DERC usage to a
maximum daily usage of 3.2 tpd of NOX DERCs effective March
1, 2009. Texas also committed to adopt and submit as a SIP revision, an
enforceable mechanism that would provide a review procedure to ensure
that future allowable use of DERCs after January 1, 2010, would not
interfere with continued attainment of the 8-hour NAAQS. We have
concluded that an enforceable mechanism, as described in more detail
elsewhere in this notice, can provide the basis for revising the
quantity of DERCs that were modeled in the May 30, 2007 SIP submittal.
    In the May 30, 2007 SIP submittal, TCEQ also included requirements
on the operation of back-up generators with a March 1, 2009 compliance
date that had been estimated as potentially generating 0.9 tpd of
NOX reductions in the DFW NAA. TCEQ quantified and discussed
these rules in the WOE section of the SIP rather than including the
estimated emission reductions in their modeling. The April 23, 2008
letter, includes an estimate of the reduction of ozone that would occur
based on the 0.9 tpd of NOX reduction.
    In its letter, TCEQ provided estimates of the predicted impact on
modeled ozone that would occur due to the changes in emission
projections for airports, DERCs and back-up generators. TCEQ based
these estimates on sensitivity runs of the model, which showed the
model's response to various levels of ``across-the-board'' reductions
for various emissions categories. These runs differ from more refined
modeling because emissions reductions are not assigned to the
particular grid cell where they are expected to occur.
    EPA considers the use of modeling sensitivity runs, based on the
adjustments to the Combo 10 modeling and similar sensitivity runs, to
estimate the revised modeling FDV projections to be acceptable in these
limited circumstances. In this case, the EPA's modeling sensitivity
runs using the future control strategies modeling run, indicate the
modeling is reacting very linearly over this limited range. Therefore,
estimating changes to ozone levels due to limited emission changes to
the 2009 emissions inventory will yield results similar to what would
be predicted if there were a new refined future control strategies
modeling run using a 2009 emissions inventory reflecting the revised
emissions for the airport, DERCs, and back-up generators. Additionally,
our analysis is that these modeling sensitivity runs are similar in
spatial allocation to how these emission changes for the airports,
DERCs, and back-up generators would be analyzed in a new future control
strategies model run using a revised 2009 emissions inventory. EPA
therefore finds the use of modeling sensitivities runs, based on the
adjustments to the Combo 10 modeling and similar sensitivity runs, is
acceptable in this fact-specific instance, to estimate the revised
modeling FDV projections. Therefore, EPA considers these adjustments to
modeled ozone levels to be refinements to the previous modeling
(submitted in the May 30, 2007, SIP) that would have been included in
TCEQ's original submittal if additional time would have been available
to incorporate the changes. EPA has reviewed these three revisions to
the emissions inventories and TCEQ's projection of their impact on the
future ozone concentration levels and finds that TCEQ provided a
reasonable assessment of projected ozone levels. In fact we believe,
particularly in the case of the airport emissions adjustment, that if
these reductions had been modeled specifically rather than spread
across the off road mobile emissions category, there would have been
greater ozone reduction benefit because of the location of these
emissions when compared to the location of the highest monitors. A more
detailed discussion of our analysis is contained in the MOAAD TSD.
Relying on these modeling-based estimates presumes that Texas will
adopt an enforceable measure that will limit the use of DERCs to 3.2
tpd.
    Table 3 lists the estimated level of ozone when the adjustments to
airport, DERC and back-up generator emissions are considered.

                                                        Table 3.--Adjusted Modeling Projections.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                DERC       Airport       Backup
                                                                             emissions    emissions    generators                   FDV          FDV
                     Monitor                       FDV combo     FDV PDMR  ---------------------------------------    Total       adjusted     adjusted
                                                       10          2009      (17.2 tpd    (9.39 tpd     (0.9 tpd    reduction     combo 10    PDMR 2009
                                                                              reduced)     reduced)     reduced)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                     TCEQ RRF     TCEQ RRF     DERC ppb  Airport ppb     B.G. ppb          ppb     TCEQ RRF     TCEQ RRF
--------------------------------------------------------------------------------------------------------------------------------------------------------
Frisco..........................................         88.7         89.0        -0.39        -0.32        -0.03        -0.74           87           88
Dallas Hinton...................................         85.6         85.8        -0.36        -0.26        -0.02        -0.64           84           85
Dallas North....................................         84.8         85.1        -0.36        -0.28        -0.03        -0.66           84           84
Dallas Exec.....................................         78.8         79.0        -0.47        -0.19        -0.02        -0.68           78           78
Denton..........................................         88.6         88.8        -0.32        -0.43        -0.04        -0.79           87           88
Midlothian......................................         83.9         84.1        -0.66        -0.09        -0.01        -0.75           83           83
Arlington.......................................         80.9         81.0        -0.67        -0.24        -0.02        -0.94           79           80
Ft Worth C13....................................         85.6         85.7        -0.57        -0.34        -0.03        -0.95           84           84
Ft Worth C17....................................         84.8         85.0        -0.37        -0.43        -0.04        -0.85           84           84
--------------------------------------------------------------------------------------------------------------------------------------------------------

    With the addition of these new reductions included in the April 23,
2008, letter, Combo 10 projects using TCEQ's RRF that 7 of 9 are in
attainment (at or below 84 ppb); and projections for the other two
monitors are 87 ppb for the Denton and Frisco monitors. EPA believes it
is reasonable to consider the above values as a sufficient
representation of outputs of refined future year control strategy runs.
Thus EPA considers the modeling values estimated in Table 3 to
represent the final attainment demonstration modeling analysis.
ix. What Are EPA's Conclusions of the Modeling Demonstration?
    Using the TCEQ's RRF method and Combo 10 run with the three
refinements, both the Frisco and Denton monitors are at 87 ppb and the
rest of the monitors are projected to be attaining the standard. EPA
also considered EPA's RRF method and determined that while the EPA
method gives slightly higher results in some cases, it does not make a
significant difference. In addition, EPA concludes that the modeling
provided results that are in the range (82 ppb to <88 ppb) where it is
recommended other WOE be considered to determine if attainment will be
reached.
    Although the modeled attainment test is not met at all of the DFW
monitors, EPA recognizes that models are approximations of complex
phenomena. The modeling analyses used to demonstrate that various
emission reduction measures will help to bring the DFW area into
attainment of the 1997 8-hour ozone standard, contain many elements
that are uncertain (e.g., emission projections, meteorological inputs,
model response, simplified chemistry, simplified temporal and spatial
allocation of emissions, etc.). These uncertain aspects of the DFW
analyses can prevent definitive assessments of future attainment
status. The confidence in the accuracy of the quantitative results from
a modeled attainment test should be a function of the degree to which
the uncertainties in the analysis were minimized. However, while
Eulerian air quality models represent the best tools for integrating
emissions and meteorological information with atmospheric chemistry and
no single additional analysis can replace that, EPA believes that all
attainment demonstrations are strengthened by additional analyses that
help confirm whether the planned emissions reductions will result in
attainment of the standard.
    EPA's modeling guidance indicates that when the maximum attainment
demonstration modeling projections are within the 82 to less than 88
ppb range, further WOE analyses should be included in the attainment
demonstration and evaluated in addition to the modeling projections.
EPA's guidance also allows for WOE to be used when the modeled levels
are 88 ppb or greater, but notes the further the projected levels are
from attainment levels, the more substantial the WOE must be to
conclude that the area would reach attainment by the attainment date.
EPA's 2005 and 2007 A.D. guidance documents indicate that even though
the photochemical modeling demonstration projections do not predict
attainment of the standard (the modeled attainment test), assessment of
a WOE analysis could yield a determination that the area will attain
the standard by its attainment date. The next section will discuss the
WOE that has been evaluated for this demonstration and EPA's review of
the WOE.
b. What Weight of Evidence Has Been Evaluated?
    Both EPA's 2005 and 2007 A.D. guidance documents recommend that in
addition to a modeling demonstration, the states include additional
analyses, called weight-of-evidence (WOE) when the modeling results in
FDVs are greater than 82 ppb. EPA's 2005 and 2007 A.D. guidance
documents both discuss additional relevant information that may be
considered as WOE. A WOE analysis may provide additional scientific
analyses as to whether the proposed control strategy, although not
modeling attainment, will likely achieve attainment by the attainment
date. The intent of EPA's guidance is to utilize the WOE analysis to
consider potential uncertainty in the modeling system and future year
projections. Thus, in the DFW case, even though the specific control
strategy modeling predicts some monitors to be above the NAAQS,
additional information (WOE) may provide a basis to conclude monitored
attainment may be achieved. Since the attainment year is just a year
away, EPA places greater significance on the WOE, especially
consideration of current measured ozone levels and reductions still
expected. As models have to make numerous simplifying assumptions and
when the system being modeled is very complex, model predictions are
not perfect. As a result of some of these inherent uncertainties, EPA's
guidance is to consider other evidence (WOE) to help assess whether
attainment of the NAAQS is likely. EPA's guidance indicates that
several items should be included in a WOE analyses, including the
following: Additional modeling, additional reductions not modeled,
recent emissions and monitoring trends, known uncertainties in the
modeling and/or emission projections, and other pertinent scientific
evaluations. Pursuant to EPA's guidance, TCEQ supplemented the control
strategy modeling with WOE analyses.
    Today we are discussing the more significant components of the WOE
that impacted EPA's evaluation of the attainment demonstration. Many
other elements are discussed in the MOAAD TSD that had some impact on
EPA's evaluation. We are briefly covering the more significant elements
in this notice. For EPA's complete evaluation of the WOE considered for
this notice, see the MOAAD TSD.
i. What Additional Modeling-Based Evidence Did Texas Provide?
    Texas submitted a significant body of information as WOE in the May
30, 2007, submittal. Texas also provided supplemental information and
clarifications in a letter to EPA dated April 23, 2008.
1. Texas Emission Reduction Plan (TERP)
    TERP reductions for previous years was included in a previous SIP
revision, the Increment of Progress (IOP) SIP and included in the
modeled projections. Texas provided information in its May 30, 2007,
submission and the April 23, 2008, letter documenting that additional
reductions from the TERP Program (in 2008 and 2009) which were not
included in the modeling are projected to occur. The impact of these
reductions can be estimated in the WOE analysis.
    The additional TERP funding is expected to produce air quality
benefits above-and-beyond those modeled for the SIP. The modeling
includes reductions expected for TERP through 2007. Not all of the
reductions were accounted for and this shortfall must be achieved
before additional WOE reductions can be achieved. As additional WOE,
TCEQ estimated that 14.2 tpd reductions in NOX emissions in
the DFW area could be achieved, if 50 percent of available 2008 funding
and 70 percent of the 2009 funding were used for projects in the DFW
area. This calculation is based upon funding for the DFW area at $53
million in FY2008 and $94 million in FY2009, an average seven-year
project life with 250 days/year utilization, an estimated $6,000 cost
per ton for TERP program emissions reductions, and using 2008 funds
remaining after the short-fall is met ($6000/ton x 250 days/year x 7
years life cycle = $10.5 million for 1 tpd

of NOX reductions). As of April 2008, requests in 2008 for
TERP projects in the DFW area totaled $94.5 million. Therefore, once an
estimated $39 million of project requests is utilized to fill the
previous shortfall, there is an additional $55.5 million of project
requests in the DFW area for further NOX reductions. These
project requests will be reviewed by TCEQ to determine whether the
projects are cost effective and TCEQ will make determinations about
funding of the projects that pass review. Pending TCEQ's review and
granting decisions, the surplus DFW area FY2008 new project requests
(estimated surplus of $55.5 million in requests that are estimated to
yield 5.25 tpd in NOX reductions) seem to be in line with
the calculated project requests needed to achieve a 14.2 tpd reduction
in NOX emissions if another $94 million (estimated to yield
8.95 tpd in NOX reductions) in requests are received by TCEQ
in FY2009.
    It should be noted that the $94 million in requests that was
received in FY2008 is much larger than any previous annual request in
the DFW area.
2. Compressor Engines
    In the April 23, 2008, letter, TCEQ provided supplemental
information regarding emissions from stationary, gas-fired engines.
During the May 23, 2007, adoption agenda before the TCEQ commissioners
for the 30 TAC Chapter 117 rules and DFW 1997 8-hour ozone attainment
demonstration SIP, stakeholders commented that the number of
stationary, gas-fired engines in the DFW area was likely underestimated
in the modeling projections because of the growing exploration and
production of natural gas from the Barnett Shale. The commissioners
directed the TCEQ's staff to research the issue. TCEQ staff
subsequently conducted a survey to re-evaluate the number of
stationary, gas-fired engines in the nine-county DFW area. The 2007
TCEQ survey results show there is a much larger fleet of stationary,
gas-fired internal combustion engines than estimated in the SIP
submittal. Almost all of these engines came into service after the 1999
base year so represent emissions growth. This growth in emissions will
be greatly mitigated by the implementation of controls in response to
the Chapter 117 rules adopted as part of the May 30, 2007, SIP
submission. While mitigated to a large extent, emissions in the model
from these sources would be expected to be 3.3 tpd higher than the
model projected. Using previously discussed modeling sensitivity runs,
we account for this increase in projected emissions and estimate its
effect on modeled ozone levels in Table 4.
    Table 4 includes the estimates for the amount of ozone reductions
for these additional TERP and Compressor Engines WOE emission changes.
Table 5 is included below and includes the estimated FDVs with
consideration of the two adjustments.

            Table 4.--Assessment of Additional WOE Emission Reductions and Potential Ozone Reductions
----------------------------------------------------------------------------------------------------------------
                                                                    TERP using     NG compressor   Total change
                                                                      nonroad      engines using ---------------
                                                                    sensitivity       nonroad
                     Monitor                        EPA nonroad  ----------------   sensitivity
                                                    sensitivity                  ---------------- Net tpd  -10.9
                                                                   tpd reduction   tpd increase
                                                                       -14.2            3.3
----------------------------------------------------------------------------------------------------------------
                                                         ppb/ton      ppb change      ppb change  Net ppb change
----------------------------------------------------------------------------------------------------------------
Frisco..........................................        -0.03387         -0.4810           0.112           -0.37
Dallas Hinton C60...............................        -0.03060         -0.4345           0.101           -0.33
Dallas North C63................................        -0.02866         -0.4070           0.095           -0.31
Dallas Exec C402................................        -0.02455         -0.3487           0.081           -0.27
Denton..........................................        -0.05343         -0.7587           0.176           -0.58
Midlothian......................................        -0.01332         -0.1891           0.044           -0.15
Arlington.......................................        -0.02868         -0.4072           0.095           -0.31
Ft Worth C13....................................        -0.03347         -0.4753           0.110           -0.36
Ft Worth C17....................................        -0.04906         -0.6967           0.162           -0.53
----------------------------------------------------------------------------------------------------------------

    As shown in Table 5, using the TCEQ RRF method for both the Combo
10 and PDMR2009 runs with the three modeling refinements and also these
modeling-based WOE adjustments, the Frisco and Denton monitors are 87
ppb and the rest of the monitors are projected to be attaining the
standard. Other WOE factors, discussed below, indicate further progress
that we believe will lead to attainment of the standard.

                       Table 5.--Modeling-Based Assessment With Some WOE Elements Included
----------------------------------------------------------------------------------------------------------------
                                                                  Total modeling-      FDV with WOE emission
                                                                     based WOE      estimates w/ modeling-based
                                                                     reduction     ozone adjustments applied to
                                                                 ----------------  previously adjusted modeling
             Monitor               FDV adjusted    FDV adjusted                               values
                                     combo 10        PDMR2009                    -------------------------------
                                                                        ppb                          Adjusted
                                                                                Adjusted combo   PDMR2009  w/
                                                                                10  w/WOE          WOE
----------------------------------------------------------------------------------------------------------------
                                        TCEQ RRF        TCEQ RRF        TCEQ RRF        TCEQ RRF        TCEQ RRF
----------------------------------------------------------------------------------------------------------------
Frisco..........................            87.9            88.2           -0.37              87              87
Dallas Hinton...................            84.9            85.2           -0.33              84              84

Dallas North....................            84.1            84.4           -0.31              83              84
Dallas Exec.....................            78.1            78.3           -0.27              77              78
Denton..........................            87.8            88.0           -0.58              87              87
Midlothian......................            83.2            83.4           -0.15              83              83
Arlington.......................            79.9            80.1           -0.31              79              79
Ft Worth C13....................            84.6            84.8           -0.36              84              84
Ft Worth C17....................            84.0            84.2           -0.53              83              83
----------------------------------------------------------------------------------------------------------------

ii. Other Non-Modeling WOE From TCEQ
    EPA believes that, with only one year left until attainment, it is
important to look at the current air quality and the amount of
reductions that are yet to occur to evaluate whether it is realistic
that the area can attain by 2009.
    The preliminary highest value for the 4th high 8-hour exceedance
value monitored at any monitor in the DFW NAA in 2007 was 89 ppb. (The
value is considered preliminary because TCEQ has not certified that it
has completed the Quality Assurance and Quality Control Checks, a
process that will be completed shortly). This is the lowest level that
has ever been achieved for the fourth high in this area.
    In the May 30, 2007 submittal, TCEQ also provided additional WOE of
ozone trends that show the area had monitored attainment for the 1-hour
ozone standard (now revoked). The data indicates emission trends and 8-
hour ozone levels have decreased despite large population increases. As
included in references in TCEQ's TSD for this SIP revision, TCEQ and
others have also provided ozone source apportionment assessments
showing that DFW emissions can contribute up to approximately 40% of
the ozone exceedance values projected by the model at monitors downwind
of DFW on high ozone days, while the episode average of all monitors
was 24%. Ozone source apportionment techniques are tools used to
estimate the contribution of various sources or source categories to
modeled ozone levels. In this case, source apportionment is showing
that ozone levels on some days during the episode are much more heavily
influenced by emissions within the nonattainment area which are the
primary target of the control strategy. The attainment test relies on a
relative response factor which is an average value that is based on
most of the days of the episode. The response of the RRF to local
controls would be expected to be consistent with 24% of the ozone level
being driven by local emissions since both the RRF and 24% source
apportionment are averaged across the episode. However, on specific
days when a monitor is more directly impacted by DFW area emissions
(downwind of the core DFW area) the ozone value reflected at the
monitor may be 40% due to local DFW NAA emissions. Therefore, the
attainment test with the averaging of days with different wind
directions is likely under-estimating the benefit of local reductions
in the DFW NAA.
    TCEQ also submitted WOE components that are further discussed in
the TSD including the following: Ozone design value trends, ozone
variability analysis and trends, model projected RRFs at area monitors
that have been installed since the base case period and were not
utilized in the modeling, NOX and VOC monitoring trends,
emission trends, NOX and VOC chemistry limitation analysis,
local contribution analyses, and mobile emission sensitivity runs.
Details of these WOE components are included in Chapter 3 of the May
30, 2007 SIP submittal. TCEQ also provided updated data for some of
these elements in their April 23, 2008 letter.
    Additional quantified WOE emissions reductions (without ozone
reductions calculated) include a number of energy efficiency measures
(Residential and Commercial Building Codes, municipality purchase of
renewable energies, political subdivision projects, electric utility
sponsored programs, Federal facilities EE/RE Projects, etc.) that TCEQ
has estimated will yield 2.12 tpd NOX reductions.
III. EPA WOE Analysis
    Since the May 30, 2007 submittal, EPA has worked with TCEQ to
quantify emission reductions that will occur between the latest ozone
monitoring season (2007) and the attainment year 2009. EPA has
generated an estimate of how much reduction in emissions is expected to
occur between 2007 and 2009. Our estimate is that an additional 70 tpd
of NOX reductions will occur due to the existing rules. With
the inclusion of all of the potential WOE reduction elements (including
14.2 tpd of NOX reductions from TERP and additional
estimated reductions of 35.7 tpd from control of the underestimated
compressor engines) the total potential reductions are estimated as 120
tpd of NOX. Based on an estimated 2007 NOX
emission inventory, these SIP rules (and other State and Federal
requirements) are estimated to reduce NOX emissions 15% from
2007 levels. With inclusion of all the potential WOE elements
identified, the amount of reduction of daily NOX from 2007
levels increases to 26%. These are large expected changes to the DFW
NAA NOX inventory.
    Utilizing multiple sensitivity runs conducted by EPA and TCEQ, we
have estimated that the additional 15% reductions which occur after the
2007 ozone season could result in a 2.3 ppb decrease in ozone levels at
the controlling monitors (Frisco and Denton). EPA's assessment,
including both the SIP and WOE emission reductions estimated to occur
after the 2007 ozone season, indicates a 3-4 ppb drop in ozone levels
is possible. The 3-4 ppb drop is a rough estimate that could be larger
(greater than 4 ppb) and that value would yield a value of 84 ppb or
lower to indicate attainment.

    The monitored attainment test is monitor specific and in the future
the highest monitor that is used to determine attainment (using 2007-
2009 data) may not be the one that recorded a high value of 89 ppb in
2007. Only 2 of the 20 monitors in the DFW area monitored 4th high 8-
hour values of 89 ppb. The 4th high 8-hour ozone levels monitored at
the other 18 monitors were: 88 ppb at one monitor, 87 ppb at one
monitor and the rest were 84 ppb or below. If the monitor used for the
2009 attainment test is one of the monitors that recorded a value less
than 89 ppb (18 of the 20 monitors), then a 3-4 ppb drop from the 4th
high value recorded in 2007 would indicate attainment with a value of
84 ppb or lower. With the emission reductions to occur after 2007, we
could expect a 4th high value for the DFW area of approximately 84-85
ppb or lower. Based on this analysis, it is not unreasonable to
conclude that attainment in 2009 is possible considering the recent
downward monitoring trend (2006-2007) and the preliminary 2007
monitoring values of 89 ppb value.
    This simplistic analysis alone does not conclusively prove that the
area will attain the standard by 2009, but EPA believes that the most
recent preliminary monitoring values from 2007, coupled with the
estimated impact of the additional reductions, estimated ozone
decreases (estimated as 3-4 ppb), are consistent with reaching
attainment by 2009.
1. EPA Meteorological Adjusted Trends Analysis
    EPA performed a draft meteorological adjusted trends analysis in
October 2007 for many areas in the eastern half of the United States.
Meteorological adjusted trends analyses attempt to remove the
variability in ozone levels due to differing meteorology and adjust the
ozone values to the average meteorology level. These analyses are
called met adjusted design values and can be used to indicate whether
nonattainment areas are closer to (or farther from) attainment than
their actual most recent design values would otherwise indicate. The
technique and estimated values should not be used in an absolute sense,
but rather as a directional assessment tool.
    EPA performed a meteorological adjusted analysis for select DFW
monitors with higher DVs for the last 10 years of data (where
available). The most recent DFW NAA DV (based on preliminary monitoring
data for 2007) is 95 ppb (2005-2007). EPA's meteorological adjusted
trends analysis yields a value of 91.7 ppb for the 2005-2007 period.
Thus, the analysis indicates that the 2005-2007 period was worse than
normal meteorology. So if average meteorology occurs in the future, the
DV may potentially drop on the order of 3 ppb without consideration of
additional emission reductions. The met adjusted trends analysis also
included an assessment of the years around the 1999 base period of the
modeling. The assessment of the base period indicated that the
meteorology was worse than normal, and when this is taken into account,
the highest Base DVs would be about 0.8 ppb lower. If the
meteorological adjusted Base DV is used for the modeling projection,
the 2009 modeling values would be approximately 0.8 ppb less, thus the
2009 modeling would be closer to attainment. If this 0.8 ppb level
decrease is used for the Frisco and Denton monitors, the future
modeling and WOE projection would also drop. The resultant estimates
would be that Combo 10 would yield 86 ppb at the Denton and Frisco
monitors, and for the PDMR2009 modeling the values would be 87 ppb at
Frisco and 86 ppb at Denton monitor.
iv. Other WOE Items From Texas Not Currently Quantified: Additional
Programs/Reductions
    These are additional items in TCEQ's WOE analysis that are not
easily quantifiable and are difficult to estimate expected ozone
decreases. These elements can still add to the overall WOE analysis but
may not warrant as much emphasis as more refined technical analyses.
1. AirCheckTexas
    The AirCheckTexas (ACT) program provides funds to individuals as an
incentive to retire older, more polluting vehicles or aid in the repair
of vehicles' emission control systems. TCEQ included discussion of the
ACT program in the WOE section in their May 30, 2007 submittal, but did
not include a benefit due to the ACT program in the modeling.
    The May 30, 2007 submittal also states that the Texas Legislature
was considering additional funding for the ACT--Drive a Clean Machine
program. During the 80th Legislative Session, Senate Bill 12 was passed
and subsequently signed by the Governor on June 15, 2007. The ACT
program for the DFW area was funded at $21,348,583 each for fiscal
years 2008 and 2009. Currently the program funding has been increased
to approximately $20 million/year for two years in DFW NAA. The
Legislature significantly increased the amount paid for replacement of
vehicles older than 10 years old (or vehicles that have failed emission
testing and can't be reasonably fixed) to $3,000 for a new/recent model
year vehicle and $3500 for a hybrid vehicle. Promotion of this program
has been unprecedented and recently the State and local agencies have
received and processed applications for the $20 million allotted to DFW
area this year, well in advance of the State fiscal year end date of
August 31st.
    The North Central Texas Council of Governments (NCTCOG) is the
local entity implementing the program and processing applications.
Since the SB 12 enhanced program started on December 12, 2007, there
has been high interest and 15,092 applications submitted. Again,
outreach by TCEQ, NCTCOG, local business leaders, and local governments
has been unprecedented, and recently the NCTCOG indicated that there
were 6,986 vouchers issued by April 4, 2008. With the level of voucher
issuance and usage, it is likely the program will result in emission
reductions greater than considered in the WOE portion of the May 30,
2007 SIP submittal.
    Other unquantified WOE emissions reductions include Luminant's
(formerly TXU) announcement that they are going to spend $1 billion to
yield emission reductions at some of their plants in East and North
Central Texas. Luminant has initially indicated that their plans
include installing SCR at the Martin Lake plant, SNCR at Monticello and
Big Brown plants and improving their Low NOX burners at one
of the Monticello units. We sent a letter to Luminant asking for
clarification on what NOX controls may be in place by the
2009 DFW ozone season, and are currently waiting for a response from
Luminant. If we receive a response from Luminant, we will include it in
the docket for review. These facilities are to the East and Southeast
of the DFW area, and are often upwind of DFW during ozone events.
Reductions at these plants will help lower background ozone and pre-
cursor entering DFW area on many ozone conducive days and would be
expected to yield reductions in ozone levels at the DFW area monitors
on many ozone conducive days.
2. Local Quantified and Unquantified Measures
    Other unquantified measures include Dallas Sustainable Skylines
Initiative, Smartway, Intelligent Transportation System, Truck Lane
Restriction, LED Traffic Signal replacement, Blue Skyways
Collaborative, Parking Cash-out Program, Roadway Peak Period Pricing,
Clean School Bus Program, $4

million incentive for early NG engine control, etc. These programs are
not included in the VMEP program and therefore are not being double-
counted.
    Through the actions of citizens and local governments, an approach
to purchase cement that is produced with less NOX emissions
is being considered by local cities. Currently three of the largest
cities (Dallas, Ft. Worth, and Arlington) have passed city ordinances
addressing the purchase of green cement. These ordinances may yield an
additional 1 tpd of NOX reductions, but this estimate is not
certain at this time. We expect additional reductions will be achieved
and that the location of the reductions would be beneficial to reducing
the area's ozone levels.
    Local city and county officials have increased their enforcement of
Inspection and Maintenance (I&M) rules by performing site inspections.
In certain cases, officials discovered fraudulent transactions,
including inspection sticker counterfeiting. The enforcement
initiatives by local governments will result in additional emission
reductions from mobile sources in the DFW area. Some of these benefits
are already considered in the modeling, but these efforts will yield
additional actual reductions between 2007 and 2009.
c. Is the 8-Hour Attainment Demonstration Approvable?
    EPA is proposing that, taken in balance, the available modeling,
evidence, analyses, adopted control strategies (including rules with
2010 compliance dates), the DERCs condition, monitoring data, and
additional information support that the DFW area will reach attainment
of the 1997 8-hour ozone standard by its attainment date. In making
this determination, we have considered supplemental information not
available at the time the attainment modeling was performed by TCEQ,
including evidence that NOX emissions reductions will occur
that are in addition to the measures adopted and quantified in the May
30, 2007 SIP submittal.
    We have considered modeling using two emission reduction scenarios
(Combo 10 and PDMR2009), recognizing that the actual emission control
level would be somewhere in between. We have also considered the impact
of additional measures and reductions documented in the April 23, 2008
letter. With these adjustments, the modeling is showing significant
reductions of 7-13 ppb in ozone from the base period, but is still
slightly short of attainment. The modeling predicts values greater than
84 ppb at two of the nine monitors, but we believe the WOE assists in
bridging the gap to attainment.
    We also considered that the model's under prediction of high ozone
levels may be biasing the model predictions, and therefore potentially
underestimating the ozone reduction that could occur by the emission
reductions achieved by local and regional rules and additional WOE
elements. We also have considered the impact of meteorological
adjustments to the design value projection which would further indicate
the future projections may be too high. Finally, we have recognized
emission reduction efforts that have not been quantified and included
in the modeling or model based WOE estimates.
    EPA is also considering non-modeling evidence. One factor that EPA
believes is of particular importance is the total NOX
reductions expected in the DFW NAA from 2007 to 2009, which are
expected to decrease ozone levels from the 89 ppb fourth high maximum
monitored in 2007 to levels consistent with attainment. We have
confidence that ozone levels will improve because NOX
emissions are projected to decrease by 26% in the time period 2007-
2009. Finally, EPA has considered the most recent ambient data which
indicates that the area is on a track that is consistent with achieving
attainment of the 8-hour standard by 2009.
    Taking these factors together, we believe the modeling, including
all the WOE measures, is consistent with attainment.

C. Control Measures Relied Upon by the State in the Control Strategy
Modeling

    Section 172 of the Act provides the general requirements for
nonattainment plans. Section 172(c)(6) and section 110 require SIPs to
include enforceable emissions limitations, and such other control
measures, means or techniques as well as schedules and timetables for
compliance, as may be necessary to provide for attainment by the
applicable attainment date. The DFW attainment demonstration SIP is
mainly directed at reductions of NOX since the modeling
shows that NOX reductions will be most effective in bringing
the area into attainment of the standard, but the SIP includes VOC
emissions reductions as well. The modeling includes Federal, State and
local measures. The attainment demonstration modeling also relies on
regional measures applied in east and central Texas and measures
applied in the Houston (HG) and Beaumont (BPA) ozone nonattainment
areas. The State adopted controls to reduce NOX emissions
from mobile sources, ICI Sources, EGFs, Minor Sources, Cement Kilns,
and East Texas Combustion Sources. Today's action proposes approval of
emissions reductions from two mobile source strategies not previously
adopted into the SIP. These strategies are the new VMEP and the new
TCMs included in the May 30, 2007 SIP submittal. In separate actions,
we are finalizing approval of the April 9, 2003 Alcoa Federal Consent
Decree, the Energy Efficiencies Program, and the May 13, 2005,
NOX rules, and we are proposing to approve the
NOX rules for ICI Sources,EGFs, Minor Sources, Cement Kilns,
and East Texas Combustion Sources. These actions will assist the area
in meeting the 8-hour ozone standard and are relied upon in the control
strategy modeling.
    The following is the identification of the control measures
reflected in the 2009 inventory for the May 30, 2007 revision Future
Control Strategy Case modeling run. In addition, we identify which of
the State and local controls are addressed in this proposed action and
which will be addressed in separate rulemaking actions.

     Table 6.--Federal Measures Reflected in the DFW 2009 Inventory
------------------------------------------------------------------------

-------------------------------------------------------------------------
Federal Tier 1 Federal Motor Vehicle Control Program (FMVCP)
Federal Tier 2 FMVCP
Federal 2007 Heavy Duty Diesel FMVCP standards
Federal National Low Emission Vehicle Program (NLEV)
Federal Tier I and Tier II Locomotive NOX standards
Federal New Non-road Spark Ignition Engines rule
Federal Heavy Duty Non-road Diesel Engines rule
Federal Tier 1, 2, and 3 Non-road Diesel Engines rule
Federal Small Non-road Spark Ignition Engines rule
Federal Large Non-road Spark Ignition Engines and Recreational Marine
 rule
Non-road RFG--Federal/state opt in--the 4 core counties
------------------------------------------------------------------------

    We believe that the State correctly projected the growth rates and
emissions reductions for sources subject to these Federal measures.

      Table 7.--State Measures Reflected in the DFW 2009 Inventory
------------------------------------------------------------------------
                Measures                              Status
------------------------------------------------------------------------
DFW gas-fired engine rule..............  EPA is taking action in a
                                          separate rule.
DFW non-EGUs--banked ERCs and DERCs for  Approved September 6, 2006 (71
 VOC and NOX emissions.                   FR 52703).
DFW EGUs...............................  EPA is taking action in a
                                          separate rule.
DFW non-EGUs...........................  EPA is taking action in a
                                          separate rule.
Auxiliary steam boilers in the 5         EPA is taking action in a
 counties.                                separate rule.
Stationary gas turbines in the 5         EPA is taking action in a
 counties.                                separate rule.
DFW Major Source Rule..................  EPA is taking action in a
                                          separate rule.
DFW Minor Source Rule..................  EPA is taking action in a
                                          separate rule.
Stage I Program, expanded from the 4     Approved January 19, 2006 (71
 core to all 9 counties.                  FR 3009).
Surface Coating Rules, expanded from     Approved January 19, 2006 (71
 the 4 core to all 9 counties.            FR 3009).
Inspection/Maintenance (I/M) Program,    Approved November 14, 2001 (66
 expanded from the 4 core to all 9        FR 57261).
 counties.
Anti-tampering Rule....................  Approved July 1, 1998 (63 FR
                                          35839).
RFG in the 4 core counties.............  Approved October 8, 1992 (57 FR
                                          46316).
VOC Rules, expanded from the 4 core to   EPA is taking action in a
 all 9 counties, adopted by TCEQ on 11/   separate rule.
 15/06.
Portable Fuel Container Rule...........  Approved February 10, 2005 (70
                                          FR 7041).
Reid Vapor Pressure Rule...............  Approved April 26, 2001 (66 FR
                                          20927).
------------------------------------------------------------------------

    We believe that the State correctly projected the growth rates and
emissions reductions for sources subject to these State measures.

      Table 8.--Local Measures Reflected in the DFW 2009 Inventory
------------------------------------------------------------------------
                Measures                              Status
------------------------------------------------------------------------
VMEP...................................  Proposed for approval in this
                                          action.
TERP...................................  Program already approved; SIP
                                          credits proposed for approval
                                          in this action.
TCMs...................................  Proposed for approval in this
                                          action.
Energy Efficiencies Program (EEP)......  EPA is taking action in a
                                          separate rule.
Speed Limits...........................  Approved October 11, 2005 (70
                                          FR 58978).
------------------------------------------------------------------------

    We believe that the State correctly projected the growth rates and
emissions reductions for sources subject to these local measures.

  Table 9.--Texas Regional Measures Reflected in the DFW 2009 Inventory
------------------------------------------------------------------------
                Measures                              Status
------------------------------------------------------------------------
Agreed Orders for Alcoa and Texas        Approved October 26, 2000 (65
 Eastman.                                 FR 64148).
East Texas Chapter 117 NOX requirements  Approved March 16, 2001 (66 FR
                                          15195).
East Texas Combustion Rule.............  EPA is taking action in a
                                          separate rule.
April 9, 2003 Alcoa Federal Consent      EPA is taking action in a
 Decree.                                  separate rule.
TxLED (includes locomotives)...........  Approved November 14, 2001 (66
                                          FR 57196).
Portable Fuel Container Rule (34         Approved February 10, 2005 (70
 counties).                               FR 7041).
Stage I................................  Approved December 20, 2000 (65
                                          FR 79745).
Lower RVP..............................  Approved April 26, 2001 (66 FR
                                          20927).
Cement kiln rules......................  EPA taking action in a separate
                                          rule.
------------------------------------------------------------------------

    We believe that the State correctly projected the growth rates and
emissions reductions for sources subject to these Regional measures.

   Table 10.--Houston (HG) and Beaumont (BPA) Ozone Nonattainment Area
              Measures Reflected in the DFW 2009 Inventory
------------------------------------------------------------------------
                Measures                              Status
------------------------------------------------------------------------
Chapter 117 NOX requirements for HG....  Approved November 14, 2001 (66
                                          FR 57230).
Chapter 117 NOX requirements for BPA...  Approved 26, 2000 (65 FR
                                          64158); September 9, 2000 (65
                                          FR 53172); and March 3, 2000
                                          (65 FR 11468).
HG MECT rule for HG EGUs...............  Approved September 6, 2006 (71
                                          FR 52664).
HG non-EGUs--banked ERCs and DERCs for   Approved September 6, 2006 (71
 VOC and NOX emissions and the MECT NOX   FR 52664).
 cap.
HG highly-reactive VOC cap (HRVOC) rule  Approved September 6, 2006 (71
                                          FR 52659).

BPA non-EGUs--banked ERCs and DERCs for  Approved March 16, 2001 (66 FR
 VOC and NOX emissions.                   15195).
Agreed Orders for Premcor, Exxon         Approved April 12, 2005 (70 FR
 Chemical, and Motiva in the BPA Ozone    18995).
 SIP.
------------------------------------------------------------------------

    We believe that the State correctly projected the growth rates and
emissions reductions for sources subject to these measures in the HG
and BPA ozone nonattainment areas.

D. Local Measures Relied Upon in the Control Strategy Modeling

    Today's action proposes approval of two new emission reductions
from local strategies not previously adopted into the SIP. These
strategies are the VMEP and TCMs. These controls should assist the area
in meeting the 8-hour ozone standard. Approval of the relied-upon
control measures must be finalized before EPA takes final action
approving the attainment demonstration SIP.
 a. Voluntary Mobile Source Emission Reduction Programs
    A voluntary mobile source emissions reductions program (VMEP) is an
overall control strategy that attempts to complement existing
regulatory programs through voluntary, non-regulatory changes in local
transportation activities or changes in in-use vehicle and engine
composition. Authority for our approval of the VMEP is primarily
grounded in section 110(a)(2) of the Act, as well as sections
182(g)(4)(A) and 108. Section 110(a)(2) establishes that a SIP must
include ``enforceable emissions limits and other control measures,
means or techniques * * * as well as schedules and timetables for
compliance, as may be necessary or appropriate to meet the applicable
requirements of this chapter.''
    In interpreting 110(a)(2) of the Act, EPA issued a guidance
document entitled, ``Guidance on Incorporating Voluntary Mobile Source
Emission Reduction Programs in State Implementation Plans (SIPs),''
Memorandum from Richard D. Wilson, Acting Assistant Administrator for
Air and Radiation, dated October 24, 1997, which allows for SIP credit
for voluntary measures. The Fifth Circuit Court of Appeals upheld, as a
reasonable interpretation of the Act, EPA's VMEP policy and allowed the
State to consider estimated emissions reductions from a VMEP in the
Houston area 1-hour ozone attainment demonstration. See BCCA Appeal
Group v. EPA, 355 F.3d 817, 825 (5th Cir. 2003).
    The EPA's VMEP Guidance provides a detailed framework for states to
obtain SIP emissions reduction credit for such voluntary emissions
reductions. EPA guidance allows VMEP to provide a maximum of 3% of the
total future year emissions reductions required to attain the
appropriate NAAQS. In addition, states must identify and describe the
voluntary measures in a VMEP and include supportable projections of
emissions reductions associated with the measures. The state must also
make an enforceable commitment to monitor, assess, and report on the
implementation and emissions effects of the VMEPs, as well as to remedy
timely any shortfall in emissions reductions that do not meet the
projected levels.
    The EPA guidance sets forth specific minimum criteria for approval
of VMEPs into the SIP. The criteria specify that VMEP emissions
reductions be quantifiable, surplus, enforceable, permanent, and
adequately supported. The state must promptly assess and backfill any
shortfall pursuant to enforceable commitments in the SIP in the event
that the projected emission reductions are not achieved. In addition,
VMEPs must be consistent with attainment of the standard and with the
RFP requirements and must not interfere with other requirements of the
Act.
    The NCTCOG, as the regional metropolitan transportation planning
agency for the DFW area, has committed to implement the projects and/or
programs outlined in the DFW VMEP submittal. The estimated benefits
listed are calculated for the year 2009. The NCTCOG will be responsible
for monitoring and reporting the emissions reductions to the TCEQ. The
NCTCOG, through TCEQ, will cover any VMEP shortfall (of the total 2.63
tpd of NOX committed) by supplementing additional
Transportation Emission Reduction Measures (TERMs). The program areas
that may be used to remedy a shortfall are traffic signal improvements;
intelligent transportation systems (ITS); and/or freeway and/or
arterial bottleneck removal. Texas submitted adequate program
descriptions that project emissions reductions attributable to each
specific voluntary program and included the basis for the quantified
emissions reductions. The DFW VMEP will be implemented in each of the
nine counties within the DFW area.
    NCTCOG identified seven voluntary programs that will aid in the
improvement of the DFW area's air quality, as described below. Table 11
lists the programs and projected credits:

   Table 11.--Voluntary Mobile Emission Reduction Programs and Credits
                                 Claimed
------------------------------------------------------------------------
          Program type             2009 NOX benefits   2009 VOC benefits
------------------------------------------------------------------------
Clean Vehicle Program...........                0.24                0.05
Employee Trip Reduction.........                0.43                0.28
Locally Enforced Idling                         0.62                0.02
 Restriction....................
Diesel Freight Idling Reduction                 0.33                0.01
 Program........................
SmartWay Transport Demonstration                0.00                0.00
 Project........................
Public Agency Policy for                        0.06                0.01
 Construction Equipment.........
Aviation Efficiencies...........                0.95                0.24
                                 ---------------------------------------
    Total Benefits..............                2.63                0.61
------------------------------------------------------------------------

    As stated above, the State commits to evaluating each program to
validate estimated credits, to evaluating and reporting on the program
implementation and results, and to promptly remedy any credit
shortfall. The State also commits to additional TERMs that can be
substituted for any shortfall in credit from the estimated credits for
VMEP. These include traffic signal improvements, ITS; and/or freeway
and/or arterial bottleneck removal.
    EPA's analysis of all the VMEP measures shows that each creditable
measure is quantifiable. All VMEP measures must be in place by March 1,
2009, in order to be relied on for purposes of attainment by June 15,
2010. The emissions benefits for the measures are calculated for 2009
and are permanent as the NCTCOG is responsible to monitor, assess,
report on future emissions reductions from the measures and remedy any
shortfall. The reductions are surplus by not being substitutes for
mandatory, required emissions reductions and are not being counted in
any other control strategy. The SIP with voluntary measures is
enforceable because the State has committed to fill any shortfall in
credit, thus any enforcement will be against the State. Each measure is
adequately supported by personnel and program resources for
implementation. The State's goal is 2.63 tpd of NOX benefit
from the VMEP. Our detailed evaluation of the State's VMEP is in the
TSD.
    The DFW VMEP meets the criteria for credit in the SIP. The State
has shown that the credits are quantifiable, surplus, enforceable,
permanent, adequately supported, and consistent with the SIP and the
Act. We propose to approve the VMEP into the DFW SIP and agree with the
projected NOX emissions reductions of 2.63 tpd and the
projected VOC emissions reductions of 0.61 tpd from the VMEP.
 b. Transportation Control Measures (TCMs)
    TCMs are transportation related projects or activities designed to
reduce on-road mobile source emissions. Section 108 of the Act outlines
allowable types of TCMs. Federal regulations at 40 CFR 93.101 define a
TCM as any measure that is specifically identified and committed to in
the applicable implementation plan that is either one of the types
listed in section 108 of the Act, or any other measure for the purposes
of reducing emissions or concentrations of air pollutants from
transportation sources by reducing vehicle use or changing traffic flow
or congestion conditions.
    Nonattainment areas may submit TCMs as air quality control measures
into the SIP. TCMs used as an emissions reductions control strategy
must be specific and enforceable as required by the Act and EPA
guidance. TCMs in the SIP must include an identification of each
project, location, length of each project (if applicable), a brief
project description, implementation date, and emissions reductions for
NOX and VOC. (See ``Transportation Control Measures: State
Implementation Plan Guidance,'' September 1990 (EPA 450/2-89-020)).
    The process for TCM selection and inclusion in the SIP is based on
consideration of all potential measures specified in section 108 of the
Act and other emerging transportation control measures that may be
reasonably available for implementation and used for emissions
reductions. The TCMs identified through this process and included in
the SIP are contained and funded in the region's metropolitan
transportation plan and Transportation Improvement Program. This
ensures that the TCMs were properly adopted, funded and received
appropriate approval. Inclusion of TCMs in the SIP also shows evidence
of a specific schedule to plan, implement and enforce the measures. EPA
approved the Texas TCM rule as a revision to the SIP on December 5,
2002 (67 FR 72379).
    The NCTCOG identified in Appendix F of the SIP submittal TCMs for
use as a control strategy for attainment of the ozone NAAQS. Appendix F
of the submittal lists seven categories of TCMs: bicycle-pedestrian
projects; grade separation projects; high-occupancy vehicle/managed
lane projects; intersection improvement projects; park and ride
projects; rail transit projects; and vanpool projects. The TCMs have
been, or will be, implemented in the nine-county DFW area. By the start
of the 2009 ozone season, the TCMs should reduce NOX
emissions in the DFW area by 1.53 tpd and VOC emissions by 1.61 tpd.
    The State has shown that the DFW TCMs meet the requirements of the
Act and applicable EPA guidance. The list of TCMs provided in Appendix
F of the State's submittal provides identification of each project,