[Federal Register: January 14, 2009 (Volume 74, Number 9)]
[Rules and Regulations]
[Page 1903-1927]
[DOCID:fr14ja09-10]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R06-OAR-2007-0524; FRL-8758-7]

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: Final rule; conditional approval and full approval.

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SUMMARY: The EPA is conditionally approving the Dallas/Fort Worth (DFW)
1997 8-hour ozone State Implementation Plan (SIP) revisions submitted
on May 30, 2007 and November 7, 2008, as supplemented on April 23,
2008. This final conditional approval action is for the attainment
demonstration SIP, which includes the 2009 attainment Motor Vehicle
Emissions Budgets (MVEBs), the Reasonably Available Control Measures
(RACM) demonstration, and the failure-to-attain contingency measures
plan. The approval is conditioned upon Texas adopting and submitting to
EPA prior to March 1, 2009, a complete SIP revision to limit the use of
Discrete Emission Reduction Credits (DERCs), beginning in March 2009.
If the State meets its commitment to submit the DERC SIP revision, EPA
will undertake additional rulemaking action on the approvability of the
DERC SIP revision and, if EPA approves that SIP revision, the
conditional approval of the attainment demonstration will be converted
to a full approval at that time.
    We are fully approving two local control measures relied upon in
the attainment demonstration, the Voluntary Mobile Source Emission
Reduction Plan (VMEP) and Transportation Control Measures (TCMs). We
are also fully approving the DFW area SIP as meeting the Reasonably
Available Control Technology (RACT) requirement for volatile organic
compounds (VOCs) for both the 1-hour and 1997 8-hour ozone standards.
These actions will result in emissions reductions in the DFW 8-hour
ozone nonattainment area and meet section 110 and part D of the Act and
EPA's regulations.

DATES: This final rule is effective on February 13, 2009.

ADDRESSES: EPA has established a docket for this action under Docket
No. EPA-R06-OAR-2007-0524. All documents in the docket are listed on

the www.regulations.gov Web site. 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, is not placed on the Internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available either electronically through
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 or Mr. Bill Deese at<PHONE_NUMBER> 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. Background
II. What Action Is EPA Taking?
    A. What Is EPA Conditionally Approving in This Action?
    B. What Is EPA Fully Approving in This Action?
III. What Happens if the State Fails To Meet the Condition?
IV. What Other Elements Must Be Approved To Allow This Final
Conditional Approval of the Attainment Demonstration SIP?
V. Comments
    A. What Comments Did EPA Receive on the July 14, 2008 Rulemaking
for DFW?
    B. General Comments
    C. Comments on the Texas Emissions Reduction Plan (TERP)
    D. Comments on Photochemical Modeling, Weight of Evidence
Analyses, and Assessment of Demonstration of Attainment
    E. Comments on Discrete Emission Reduction Credits (DERCs)
    F. Comments on Reasonably Available Control Measures (RACM)
    G. Comments on the Failure-to-Attain Contingency Measures Plan
    H. Comments on the Attainment Motor Vehicle Emission Budgets
(MVEBs)
    I. Comments on the Voluntary Mobile Source Emission Reduction
Program (VMEP)
VI. Final Action
VII. Statutory and Executive Order Reviews

I. Background

    On July 14, 2008, 73 FR 40203, EPA proposed conditional approval of
the DFW area's 1997 8-hour ozone attainment demonstration SIP revision,
including the attainment MVEBs, RACM demonstration, and failure-to-
attain contingency measures plan. We proposed to fully approve two
local control measures relied upon in the attainment demonstration--the
VMEP and TCMs. We also proposed to fully approve the DFW area SIP as
meeting the RACT requirement for VOCs for both the 1-hour ozone
standard and the 1997 8-hour ozone standard.
    The proposed approval of the attainment demonstration SIP is
conditioned upon Texas adopting and submitting to EPA 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. If Texas meets the commitment to submit the DERC SIP
revision, EPA will undertake rulemaking to determine whether to approve
the revision and, if approved, EPA would convert the conditional
approval of the attainment demonstration to a full approval.
    We also proposed that final conditional approval of the attainment
demonstration SIP was contingent upon Texas submitting to EPA a
complete and approvable SIP revision for the attainment demonstration
SIP's failure-to-attain contingency measures plan that meets section
172(c)(9) of the Act. EPA specifically identified in the proposal the
elements such submission must contain. The failure-to-attain
contingency measures plan was submitted to EPA on November 7, 2008, and
we have determined that the plan is consistent with the elements
established in our proposed rule (73 FR 40203) and meets section
172(c)(9) of the Act. Because the State submitted a complete failure-
to-attain contingency measures 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, EPA can
proceed with a final conditional approval. (See page 40205, third
column, of the proposed action.)
    Our July 14, 2008, proposal provides a detailed description of the
revisions and the rationale for EPA's proposed actions, together with a
discussion of the opportunity to comment. The public comment period for
these actions closed on August 13, 2008. See the Technical Support
Documents (TSDs) and our proposed rulemaking at 73 FR 40203 for more
information.

II. What Action Is EPA Taking?

A. What Is EPA Conditionally Approving in This Action?

    EPA is conditionally approving the DFW 1997 8-hour ozone attainment
demonstration SIP and, as part of this attainment demonstration SIP,
the 2009 attainment MVEBs, RACM demonstration, and failure-to-attain
contingency measures plan, submitted to EPA on May 30, 2007 and
November 7, 2008, as supplemented on April 23, 2008.
    Our conditional approval is based on our determination that, the
modeling and weight-of-evidence show that the DFW area will attain the
8-hour ozone standard by its attainment date, as a result of the
control strategies relied upon in this plan. In making this
determination, we have considered the comments that we have received on
our proposal. We have also considered the air quality monitoring
information gathered since the proposal, the impact of the Clean Air
Interstate rule (CAIR) vacatur, and the progress in implementing
control measures. As the area approaches the attainment date, recent
monitoring data becomes more important as an indicator of potential
success. The preliminary data from 2008 shows 18 of the 20 monitors had
fourth highs at 84 ppb or below and only two

monitors were slightly above attainment levels at 85 ppb.
    With more emissions reductions to occur before the beginning of the
2009 attainment year ozone season, we believe these data provide strong
support that the area will attain the standard by its attainment date
of June 2010.
    As described in the proposed rule, the condition that must be met
for EPA to fully approve the attainment demonstration is that the TCEQ
must adopt and submit to EPA a complete SIP revision by March 1, 2009,
that includes an enforceable mechanism that provides a 3.2 tpd
restriction on the amount of DERCs available for use in DFW beginning
March 1, 2009. The SIP revision may provide that the amount of DERCs
available for use beginning January 1, 2010, could increase above 3.2
tpd if the revision provides an enforceable mechanism and a
justification that the increase is consistent with attainment and
maintenance of the 1997 8-hour ozone standard. In a letter dated June
13, 2008, TCEQ committed to meeting this condition (the letter is in
the docket for this rulemaking).
    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 EPA and the
public can be assured that attainment will continue to be projected in
future years. The justification and methodology for any increase in
allowable DERC usage must be fully identified in the TCEQ rulemaking
and SIP submittal process.
    The SIP revision submitted by March 1, 2009, must adequately
provide for continued attainment, and include the justification and/or
methodology used by TCEQ to increase the amount of DERCs allowed for
use in DFW starting in calendar year 2010. The justification provided
by TCEQ must satisfy section 110(l) of the Act by demonstrating that
the increase will not interfere with attainment or any other applicable
measure of the Act. The analysis to satisfy section 110(l) will need to
address both quantity and spatial allocation impacts of increased DERC
usage on ozone levels.

B. What Is EPA Fully Approving in This Action?

    EPA is fully approving two local control measures relied upon in
the attainment demonstration: The VMEP and TCMs. We are also fully
approving the DFW area SIP as meeting the RACT requirement for VOCs for
both the 1-hour ozone standard and the 1997 8-hour ozone standard.

III. What Happens if the State Fails To Meet the Condition?

    If Texas fails to adopt and submit to the EPA a complete DERC SIP
revision by March 1, 2009, EPA will issue a letter to the State
converting the conditional approval of the 1997 8-hour ozone DFW
attainment demonstration SIP to 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 FR a notice announcing 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 Regulation (CFR) to reflect the
disapproval of the SIP.
    The State proposed the DERC SIP revision for public review on
August 6, 2008 and the comment period closed September 12, 2008; final
adoption of the revision was on December 10, 2008, in order to meet the
condition to submit a complete DERC SIP revision to EPA by March 1,
2009, and implement the DERC SIP revision by March 1, 2009. As
described in the proposed rule (73 FR 40203), if the State adopts and
submits to EPA by March 1, 2009, a complete DERC SIP revision, and EPA
determines through rulemaking that the submitted DERC SIP revision is
approvable, we will simultaneously convert the conditional approval of
the attainment demonstration SIP to a full approval. If EPA cannot
fully approve the SIP revision concerning the use of DERCs in the DFW
area, EPA will undertake rulemaking to disapprove the submitted DERC
SIP revision and to convert the conditional approval of the attainment
demonstration SIP for the DFW area to a disapproval. In such case, the
18-month clock for sanctions and the 2-year clock for a FIP would start
on the effective date of final disapproval.
    Today's final conditional approval of the attainment demonstration
SIP remains in effect until EPA either determines that the State has
not submitted a complete DERC SIP revision by March 1, 2009 or EPA
completes rulemaking action either approving or disapproving a complete
submitted DERC SIP submission and simultaneous with action on the DERC
SIP submission takes final action to convert the conditional approval
to a full approval or disapproval of the attainment demonstration.

IV. What Other Elements Must Be Approved To Allow This Final
Conditional Approval of the Attainment Demonstration SIP?

    In our proposal, we discussed the elements that must be approved if
we are to finalize the conditional approval of the attainment
demonstration. In order to finalize conditional approval of the DFW
1997 8-hour ozone attainment demonstration SIP, EPA must fully approve
all of the control measures relied upon in the attainment demonstration
and the DFW RFP Plan with the RFP MVEBs and RFP contingency measures.
We approved the DFW RFP Plan with the RFP MVEBs and RFP contingency
measures on October 7, 2008 at 73 FR 58475.
    The State committed to submit a rule restricting DERC usage by
March 1, 2009. In addition, EPA reviewed all DERC Notice of Intent to
Use Forms that the TCEQ Executive Director approved as of November 30
for use in 2009, to ensure that the total amount of DERCs approved for
use beginning on March 1, 2009 does not exceed 3.2 tpd.
    Table 1 below lists the status of EPA action on the control
measures relied upon in the attainment demonstration. The Table
documents that, as of this final action, all control measures and
reductions relied upon to demonstrate attainment have been reviewed and
approved by EPA in this or other Federal Register Actions.

   Table 1--Status of EPA Required Action on Control Strategies Before
   Finalizing Conditional Approval of the Attainment Demonstration SIP
------------------------------------------------------------------------
                Measure                               Status
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The April 9, 2003 Alcoa Federal Consent  Approved August 15, 2008 (73 FR
 Decree.                                  47835).
The DFW Energy Efficiency Measures       Approved August 15, 2008 (73 FR
 Program.                                 47835).
NOX rules for IC engines in DFW........  Approved August 15, 2008 (73 FR
                                          47835).

2002 Base Year Emissions Inventory.....  Approved August 15, 2008 (73 FR
                                          47835).
The VOC rules adopted by Texas on 11/15/ Approved July 17, 2008 (73 FR
 06.                                      40972).
1-hour attainment determination........  Approved October 16, 2008 (73
                                          FR 61357).
East Texas Combustion Sources (i.e.,     Approved December 3, 2008 (73
 the rich burn gas-fired engine rule in   FR 73562).
 the 33 counties east of DFW).
The DFW major source rule..............  Approved December 3, 2008 (73
                                          FR 73562).
The DFW minor source rule..............  Approved December 3, 2008 (73
                                          FR 73562).
The DFW gas-fired engine rule..........  Approved December 3, 2008 (73
                                          FR 73562).
The DFW EGUs rule......................  Approved December 3, 2008 (73
                                          FR 73562).
The DFW non-EGUs rule..................  Approved December 3, 2008 (73
                                          FR 73562).
The Auxiliary steam boilers rule in the  Approved December 3, 2008 (73
 5 counties.                              FR 73562).
The Stationary gas turbines rule in the  Approved December 3, 2008 (73
 5 counties.                              FR 73562).
The Cement kiln rules..................  Approved simultaneously in
                                          today's Federal Register.
The VMEP and its emission reductions...  Approved in this rulemaking.
The TCMs and the associated emission     Approved in this rulemaking.
 reductions.
The TERP emission reductions...........  Approved in this rulemaking as
                                          submitted in the DFW 5% IOP
                                          Plan and the DFW 1997 8-hour
                                          ozone attainment demonstration
                                          SIP.
------------------------------------------------------------------------

V. Comments

A. What Comments Did EPA Receive on the July 14, 2008 Proposed
Rulemaking for DFW?

    We received 26 comment letters on the proposed rulemaking. These
comments are available for review in the docket for this rulemaking.
The comment letters came from the following sources:

    1. August 6, 2008 letter from Linda Koop, City of Dallas
Councilmember, District 11, Chair of the Transportation and
Environment Committee.
    2. August 12, 2008 letter from Ramon Alvarez, PhD, for
Environmental Defense Fund.
    3. August 12, 2008 letter from Bill Cox, citizen.
    4. August 12, 2008 letter from Margaret DeMoss, public health
consultant and citizen.
    5. August 12, 2008 letter from Ed Soph, citizen.
    6. August 12, 2008 letter from Bob Fusinato, citizen.
    7. August 12, 2008 letter from Ramsey Sprague, citizen.
    8. August 13, 2008 letter from Jon Mamula, citizen.
    9. August 13, 2008 letter from Kerrie Kimberling, citizen.
    10. August 13, 2008 letter from Cindy Crutch, citizen.
    11. August 13, 2008 letter from Becky Bornhorst, clean air
advocate.
    12. August 13, 2008 letter from Barbara Downey, citizen.
    13. August 13, 2008 letter from Ricky Pearce, Ryan Whaley
Coldiron Shandy PC, for Holcim LP.
    14. August 13, 2008 letter from Neil Carman, for Sierra Club,
Lone Star Chapter.
    15. August 13, 2008 letter from Gina Hall, citizen.
    16. August 13, 2008 letter from Molly Rooke, citizen.
    17. August 13, 2008 letter from Marc Chytilo, for Downwinders At
Risk and the Lone Star Chapter of the Sierra Club.
    18. August 13, 2008 letter from April Johnson, citizen.
    19. August 13, 2008 letter from Wendi Hammond, for KIDS 4 Clean
Air and Clean Air Institute of Texas.
    20. August 13, 2008 letter from Willem and Paula Noteboom,
citizens.
    21. August 13, 2008 letter from Susan Waskey, citizen.
    22. August 13, 2008 letter from Matthew Kuryla, Baker and Botts
for the BCCA Appeal Group.
    23. August 13, 2008 letter from Matthew Kuryla, Baker and Botts
for the 8-Hour Ozone SIP Coalition.
    24. August 13, 2008 letter from Lon Burnham, State
Representative, District 90, Fort Worth, Texas.
    25. August 14, 2008 letter from Anna Albers, citizen.
    26. August 14, 2008 letter from Sandra Soria, citizen.

B. General Comments

    Comment: Several commenters urge EPA to finalize conditional
approval of the attainment demonstration SIP. One supports EPA's
proposed rule, recognizes the efforts of the local community, and lists
some of the clean air initiatives implemented by the City of Dallas.
    Response: We appreciate the support expressed in these comment
letters. We applaud the actions taken by the local community and
commend the local leaders and implementation staff; their work has and
will continue to assist the area in reducing NOX and VOCs,
the precursors for ambient ozone pollution. EPA encourages local
governments to continue to be involved in these and future local
emissions reductions programs.
    Comment: Two commenters disagree with EPA's position taken in the
proposal that because the DFW area has an attainment deadline of June
15, 2010, air quality monitoring data for the years 2007, 2008, and
2009 would be used to make an attainment determination. Rather, using
the years 2008, 2009, and 2010 would be most consistent with the Act's
requirements for attainment determination. They note that the Act
mandates the attainment determination be made within 6 months after the
attainment date, including any extensions thereof, and be based on the
area's design value as of the attainment date. Although the Phase 1
Rule defines the ``attainment year ozone season'' as the ozone season
immediately preceding the attainment date, they contend that that
regulatory definition can be read as requiring controls timely for
attainment in the attainment year, as required by the statute. They do
not see the definition as relevant to the timing or content of an
attainment determination. EPA's regulations do not specify that the
attainment determination is to be conducted using data from the years
prior to the attainment date, without considering data from the ozone
season that includes the attainment date. They believe such a
determination would be inconsistent with the statutory directive that
the attainment determination be ``based on the area's design value (as
of the attainment date).''
    Response: As an initial matter, EPA set forth its interpretation on
this issue in the preambles to the proposed and final Phase 1 Rule. See
68 FR 32802, at 32817 (June 2, 2003) (In ``determining whether an area
actually attains the NAAQS at the time of the attainment date, EPA
would use the ambient air quality data for the three ozone seasons
prior to the attainment date. As an example, if the effective date of
the

nonattainment designations is May 15, 2004, the maximum attainment date
for an area classified marginal would be May 15, 2007. In this example,
EPA would consider the 8-hour ozone data for the three previous ozone
seasons--2004, 2005 and 2006.''); 69 FR 23951, at 23989 (Apr. 30, 2004)
(noting that the ozone seasons from 2007, 2008 and 2009 would be
considered for an attainment date in May 2010). However, as noted by
the commenter, the statute clearly specifies that a determination of
attainment must be ``based on the area's design value (as of the
attainment date). The attainment date for the DFW area is June 15, 2010
and the design value ``as of the attainment date'' must be determined
using the last three full years of ozone data, i.e., 2007, 2008 and
2009. We see no argument that the design value ``as of the attainment
date'' could be determined based on air quality data that would not
represent a complete ozone season and thus be incomplete as of June 15,
2010.
    Comment: We received many comment letters stating that the plan
does not reflect recommendations made by the North Texas Clean Air
Steering Committee.
    Response: We agree that the plan submitted by the State does not
reflect all of these recommendations. The resolutions were submitted to
the State and addressed by the TCEQ in the SIP package adopted on May
23, 2007, which is in the docket for this rulemaking. The U.S. Supreme
Court has consistently held that under the Act, initial and primary
responsibility for deciding what emissions reductions will be required
from which sources is left to the discretion of the States. Whitman v.
Am. Trucking Ass'ns, 531 U.S. 457 (2001); Train v. NRDC, 421 U.S. 60
(1975). The State has discretion under the Act to determine the
emissions reductions measures to be included in its attainment
demonstration and exercised this authority for this plan. The State's
role is to determine which particular emissions reductions measures are
appropriate for the nonattainment area in order to comply with the
requirements of the Act. As a matter of law, EPA is required to approve
a SIP revision if it meets the Act's requirements, regardless of the
State's choices. It is not EPA's role to rule out the State's choice of
components of its SIP submittal so long as the plan is adequate to meet
the standards mandated by EPA. See Train at 79-80 and Union Electric v.
EPA, 427 U.S. 246 (1976). The EPA's role in reviewing SIP submittals is
to approve state choices, if they meet the criteria of the Act. EPA
disapproves a SIP submittal only if it fails to meet the statutory
requirements. Seabrook v. Costle, 659 F.2d 1349 (5th Cir. 1981).
Federal inquiry into the reasonableness of state action is not allowed
under the Act (see, Union Electric Co. v. EPA, 427 U.S. 246, 255-266
(1976); 42 U.S.C. 7410(a)(2)). As provided in the analyses accompanying
this rulemaking, we have explained why we believe the submitted plan
meets the requirements of the CAA.
    Comment: Many commenters claimed that the SIP sanctions ozone
pollution levels above the 1997 standard yet this standard has been
determined not to be protective of human health by the EPA and is being
replaced.
    Response: The Act contemplates the possibility that scientific
advances would require amending the ozone NAAQS. As such, Section
109(d)(1) of the Act requires EPA to review the ozone standard every
five years based on the current science, and make any revisions that
are appropriate in light of the current science. Today's actions are
being taken in the context of the ozone standard that was promulgated
on July 18, 1997, based on the best available scientific evidence at
the time.
    The 2008 revised 8-hour ozone standard does not replace the
requirements for ozone nonattainment areas to meet the 1997 8-hour
ozone standard by their applicable attainment date. The measures
implemented in this attainment demonstration SIP will assist the DFW
area in progressing toward the 2008 revised 8-hour ozone standard,
ensuring progress continues during the time between the designations
for the 2008 standard and the submission date for the associated SIP
revisions. These measures cannot be removed from the SIP. South Coast
Air Quality Management Dist. v. EPA, 472 F.3d 882 (DC Cir. 2006).
    Comment: A commenter stated that TCEQ approved a permit revision
allowing TXI cement kilns in Ellis County to burn tires as fuel,
questioned whether the change would result in a decrease in
NOX emissions, and expressed concerns about other
pollutants, which result from tire burning. TXI said there would be
NOX reductions but they based this by comparing kilns that
were not similar to the ones TXI would use. TCEQ allows TXI to self-
report, but the checks on the reporting are poor, and TXI also knows
when the inspectors are coming.
    Response: Each cement plant in Ellis County must comply with both
its permits' limits and the State's revised chapter 117 rules for
cement kilns relied upon in the DFW attainment demonstration, whichever
is stricter. In a related rulemaking in today's Federal Register, EPA
is concurrently approving the revised chapter 117 rules for cement
kilns. The revised cement kiln rules establish a NOX source
cap for each of the three cement plants in Ellis County. We disagree
that there will be no decreases in NOX emissions. The
revised NOX rules for cement kilns should result in at least
9.7 tpd of reduction in NOX emissions for the DFW area
regardless of the fuel used including tires. We note also that all of
the cement plants are required to operate continuous emissions monitors
for NOX that must meet rigorous quality assurance and
quality control criteria. Because these stack monitors must operate
continuously, compliance does not rely solely on periodic inspections.
As a consequence, EPA is confident that compliance with the
NOX limits in these rules will be well monitored.
    The commenter's concerns regarding increases of other pollutants
besides NOX, TXI's reliance upon non-similar kilns to claim
NOX reductions, self-reporting, and TCEQ's inspection
program are not pertinent to today's action; the issue in this action
is whether the State has shown that the DFW area will attain the 1997
standard by June 15, 2010.
    Comment: The public is disadvantaged by ``conditional approval''
comment periods. Comments concerning the adequacy of Texas' plan depend
upon how Texas fulfills the requisite conditions, but the public will
not know this information until sometime in the future after the
current comment period has passed. After Texas adopts and submits its
final plans concerning DERCs and the other ``conditions'' to EPA, EPA
should allow additional public comment regarding the adequacy of the
DFW SIP attainment demonstration.
    Response: Congress provided for conditional approval as a type of
SIP processing. The Congress added section 110(k)(4) to the Act in the
1990 amendments to codify the EPA's authority to conditionally approve
SIPs. Section 110(k)(4) provides that EPA may conditionally approve a
plan based on a commitment from the State to adopt specific enforceable
measures by a date certain, but not later than one year after the date
of the final conditional approval action. In this case, if the State
submits by March 1, 2009 (the date certain), a complete DERC SIP
revision submittal (the specific enforceable measures), EPA must
reevaluate the approvability of the DFW attainment demonstration SIP,
as revised by this DERC SIP revision submittal. EPA will perform such
an evaluation through

notice-and-comment rulemaking and the public will have another
opportunity to comment upon the adequacy of the DFW plan as affected by
the DERC changes.
    Comment: A number of commenters are concerned that cities within
the DFW nonattainment area continue to be given more time to attain the
standard instead of requiring them to clean the air now. If the State
had met its responsibilities to submit a timely and approvable 1-hour
attainment demonstration SIP, then this SIP would be incrementally
stronger and have been submitted and implemented sooner. There is a
contention that Texas has not submitted a complete approvable
attainment demonstration SIP for the DFW area for over thirty years.
Moreover, monitoring began in the early 1970's and the DFW area has
never attained the 84 parts per billion (ppb) standard and remains
years from doing so.
    Response: The lack of approvability of past SIP submittals for the
DFW area is not relevant to the requirement for an area to submit a
1997 8-hour ozone attainment demonstration. The State submitted this
SIP revision on May 30, 2007, fifteen days before the June 15, 2007
required submission date. The State was on schedule to submit this SIP
revision even earlier, but received requests from several stakeholders
for an expanded timeline that would allow for a more robust stakeholder
discussion and development of additional technical support.\1\
---------------------------------------------------------------------------

    \1\ See the Settlement Agreement and letters dated March 22,
2006, March 24, 2006 and April 6, 2006 in the docket for this
rulemaking.
---------------------------------------------------------------------------

    This 8-hour ozone attainment demonstration was submitted on time
and deemed complete by operation of law (40 CFR part 51, Appendix V).
Moreover, the attainment date for the 1997 8-hour ozone standard for
the DFW area is June 15, 2010. The State has not requested additional
time for the area to attain this standard, nor has additional time been
granted. EPA is finding today that the control measures relied upon in
this plan, in combination with Federal Measures, and building on
measures already approved in the SIP will ensure that the DFW area
attains the 1997 8-hour ozone standard by the applicable attainment
date of June 15, 2010.
    While past efforts to comply with CAA requirements have not been
without flaws, we note that there have been extensive efforts and
significant progress made over the years in the fast growing DFW area.
These past efforts have built the foundation for the plan being
approved today. They include the 15% Rate of Progress (ROP) plan, the
post-1996 ROP plan, the MVEBs, and the extensive control measures
adopted by the State and approved by EPA into the Texas SIP for the DFW
area to meet the 1-hour ozone standard. The control measures in these
approved plans included among other things: Reformulated gasoline,
enhanced I/M, and controls on power plants locally and in the Central
and East Texas Region.
    Moreover, we note that the area is continuing to look for further
ways to address ozone levels and may submit additional revisions to the
SIP in the future. Three of the largest cities (Arlington, Dallas and
Fort Worth) have passed ordinances addressing the purchase of green
cement, which may yield an additional 1 tpd of NOX
reductions; and local city and county officials have increased their
enforcement of Inspection and Maintenance rules by performing site
inspections, which will yield additional reductions through 2009.
    The measures discussed above have resulted in significant
improvements in air quality. The DFW area now is meeting the 1-hour
standard and has made significant progress toward meeting the 1997 8-
hour ozone standard. As a moderate nonattainment area, the attainment
date for the DFW area is June 15, 2010 and we believe the area will
meet the attainment date.
    Comment: The plan should require more mass transit and industry to
install the latest in air pollution reduction equipment. Airplane
engines and related equipment should be less polluting.
    Response: As explained in an earlier response, the CAA places
responsibility on the State to determine the mix of controls that will
bring an area into attainment with a particular standard and EPA is
delegated to reviewing whether the State's plan will meet the statutory
attainment requirement. Therefore, EPA does not have the authority to
require the State of Texas to submit a plan for the DFW area that
requires more mass transit or imposes the latest in pollution control
equipment on industry.
    We note, however, the expansion of mass transit is ongoing in the
DFW area and can be viewed at http://www.DART.org. Appendix H of the
DFW SIP submittal identifies emission reduction measures for airplanes
and related equipment, which are part of the Voluntary Mobile Source
Emission Reduction Program (VMEP) we are approving today. These
include: Additional electrification of ground support equipment; gate
electrification to eliminate use of aircraft auxiliary power units;
ground tugs for pushback to minimize use of reverse thrust from main
aircraft engines; de-peaking of airline flight schedules; and
implementation of airport surface detection equipment to improve
efficiency during taxi. Furthermore, the local community has
implemented clean air initiatives that include: Outreach for the TERP
and AirCheckTexas programs; reducing environmental impacts by
purchasing hybrids and alternative fueled vehicles when possible;
purchasing 40% of their electric power from renewable resources; green
building policies; development of sustainability policies; developing
purchasing policies for cleaner cement; and passing an ordinance
prohibiting vehicles over 14,000 pounds from idling for more than 5
minutes.
    In addition to the measures in Appendix H, TCEQ submitted a
Supplement with more accurate and updated data for Love Field and the
DFW International Airport, including data on activities and fleet mix.
There were more new aircraft engines and the related equipment was less
polluting than previously recognized. This information is provided in
the docket for this rulemaking.

C. Comments on the Texas Emissions Reduction Plan (TERP)

    Comment: Commenters express significant concerns about whether the
projected emissions reductions from TERP will occur, as predicted. They
believe that the projections are overly optimistic. They provide the
following reasons for their concern about the projections being too
optimistic: 1. Actual TERP reductions have not met previous projected
reductions, and the methodology for calculating the projected TERP
reductions may not take into account that in the future, there will be
fewer emissions reductions per dollar spent (cost-effectiveness
assumption). 2. Although it is clear that TERP emissions reductions
occur, there does not seem to be a satisfactory way to confirm the
projected reductions will actually occur or not. 3. EPA relies upon the
State's assumption that 70% of TERP funds will be used in the DFW area,
but since there is no mechanism for ensuring the specified percentage
of funding will be met, the projections are not enforceable; the
projections should not be relied upon in the attainment demonstration;
the 70% assumption should be reduced; and the SIP should include a
contingency component to address a potential shortfall.

    Response: We agree that for the Increment of Progress SIP revision,
the amount of actual TERP reductions was less than the projections.
Because of this experience, we worked with the State to revise the
methodology for estimating emission reductions in this attainment
demonstration SIP. The revised methodology uses assumptions that are
more conservative. Specifically, the average project life was increased
by 40% and the cost effectiveness was reduced by slightly more than
51%. The formula now relies upon the following assumptions: $6000/ton,
250 days/yr operation and a 7-year project life. Using these revised
assumptions, the TERP emission reduction projections relied upon in the
demonstration modeling and the WOE are greatly reduced. Increasing the
project life has the effect of reducing the emission reductions assumed
in any given year. The cut in the revised cost-effectiveness assumption
is intended to address, among other things, the commenters' concerns
about there being fewer reductions per dollar spent each succeeding
year.
    For comparison, on January 26, 2007, the cost effectiveness of TERP
projects completed in DFW averaged $3730.24/ton; by September 23, 2007,
DFW projects averaged $3743.59/ton; and by April 2, 2008, DFW projects
averaged $3959/ton. California's experience with the Carl Moyer program
\2\ has achieved emissions reductions at an average cost of $3900/ton
through October 2006. We believe the revised cost effectiveness of
$6000/ton provides room for the increase in cost/ton that we are seeing
in the DFW area.
---------------------------------------------------------------------------

    \2\ The Carl Moyer Program 2006 Status Report is in the docket
for this rulemaking and can be viewed at http://www.arb.ca.gov/
msprog/moyer/status/2006status_report.pdf.
---------------------------------------------------------------------------

    In its May 2007 SIP revision, TCEQ indicated as a weight of
evidence (WOE) measure that additional TERP reductions were possible if
additional monies were appropriated by the legislature for the 2008/
2009 legislature. House Bill 1 signed by the Governor on July 15, 2007,
appropriated to TCEQ, TERP funds of $297,144,243 for fiscal years (FYs)
2008/2009. In the April 23, 2008 submittal, relying upon these
additional appropriated monies, TCEQ projected that the TERP could
potentially achieve an additional 14.2 tpd of NOX emissions
reductions. Since these emissions reductions were not available early
enough to include as control measures in the modeling, their impact on
the DFW area's air quality was instead predicted by EPA, using
sensitivity modeling runs, to estimate the ppb change on the monitors
in the modeling-based weight of evidence (WOE) analysis.
    To achieve the projected additional 14.2 tpd of NOX
emissions reductions from TERP, using the revised TERP methodology, the
Texas legislature needed to appropriate to the TCEQ, sufficient FY2008
and FY2009 \3\ TERP funds for the TCEQ to allocate a total of
$149,100,000 \4\ to the DFW area for TERP Emission Reduction Incentive
Grant (ERIG) projects; this amount does not include the funds required
to achieve the IOP shortfall.\5\ TCEQ received a sufficient amount of
TERP monies to have available $188,475,000 to achieve the IOP SIP
shortfall ($39,375,000) and achieve an additional 14.2 tpd
($149,100,000) in 2008 and 2009.
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    \3\ The TCEQ fiscal year runs from September 1 through August
31.
    \4\ Using the revised SIP credit methodology, each ton costs
(6000 x 250 x 7) = $10,500,000. Therefore, 14.2 x 10,500,000 =
$149,100,000.
    \5\ Using the revised SIP credit methodology: 3.75 tpd x
$10,500,000 = $39,375,000 to correct the IOP SIP shortfall.
---------------------------------------------------------------------------

    In the April 2008 submittal, the TCEQ posited that it could achieve
the additional 14.2 tpd of TERP NOX reductions by spending
in the DFW area 50% of the FY2008 TERP funds and 70% of the FY2009 TERP
funds. Whether funds are spent in exactly these percentages each year
however, is not the issue; the essential point is that TCEQ enters into
TERP grant contracts worth at least $149,100,000 in the DFW area for
projects to achieve 14.2 tpd in calendar years 2008 and early 2009.
    TCEQ roughly split in half for each fiscal year, the $297,144,243
appropriated TERP funds--$148,572,121.50. Of this $148,572,121.50
``split,'' TCEQ used approximately $40 million for other TERP programs,
including rebate grants and FY2007 unfunded TERP applications,
including the IOP SIP shortfall. EPA notes that the IOP shortfall has
now been met. Considering the factors meant that TCEQ had approximately
$106,000,000 FY2008 TERP monies for the FY2008 to achieve additional
reductions beyond those considered in the May 2007 SIP submission
through ERIG projects in TERP-eligible counties. Applications submitted
to TCEQ during the FY2008 round of project applications totaled
approximately $94.5 million for the DFW area. Of these applications
however, it appears from the draft September Report that $51,532,511.79
have been selected for funding.\6\
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    \6\ Per the TERP Biennial Report to the Texas Legislature
December 2008 draft, dated September 22, 2008. This draft was
prepared using data from mid-summer. The final report, due in
December 2008, will incorporate all of the contracts awarded or
pending to date. See the docket for this rulemaking.
---------------------------------------------------------------------------

    As a result, to achieve the 14.2 tpd projection, TCEQ needs to
enter into FY2009 TERP grant contracts worth $97,567,488.21
($149,100,000 - 51,532,511.79 = $97,567,488.21). In summary, after
accounting for the tpd of TERP NOX emissions reductions
obtained by the FY2008 grant contracts, to obtain the remaining tpd of
TERP NOX emissions reductions to achieve a total of 14.2 tpd
as projected as part of the WOE, the TCEQ would need to enter into TERP
grant contracts with DFW-area applicants worth $149,100,000 for
projects to be completed as early as possible in calendar 2009. Due to
a number of factors, including Hurricane Ike, the TCEQ will begin its
first round of requests for funding from FY2009 TERP grant monies in
December 2008. For more information concerning the timing of FY2009
TERP projects due to Hurricane Ike, please see the Supplemental TSD
dated December 2008.
    TERP has safeguards to ensure that when funds are provided to
grantees, they must achieve the associated reductions. Grantees are
required to track usage and report to the TCEQ every six months; they
must meet the reporting requirements delineated in their specific grant
contract. TERP is enforceable against the grant recipient. Over the
activity life of each TERP grant-funded activity, the grant recipient
commits the generated emissions reductions to the SIP. The recipient is
responsible for achieving the annual and total NOX emissions
reductions within the eligible areas as defined in the contract.
Recipients will be required to return all or a pro rata share of the
grant funds to the TCEQ if the emissions reductions are not achieved.
    EPA continues to carefully review the biennial reports that TCEQ is
required to submit to the Legislature pursuant to Texas Health and
Safety Code, 386.057 and 386.116(d). The draft September TERP Biennial
Report to the Texas Legislature indicates that 488 projects have been
selected for funding in the DFW area, totaling $51,532,511.79 to reduce
an estimated 3.72 tpd in NOX emissions beyond what was
included in the May 2007 modeling. Based upon the draft September
Report, the average cost/ton for these projects increased to $6710.13,
versus the revised methodology of $6000/ton. At this rate, to achieve
the 14.2 tpd in NOX emissions reductions, the TCEQ must be

able to allocate at least $123 million \7\ to the DFW area for TERP
projects early in calendar 2009. As this report is in draft, these
numbers are subject to change but it now seems likely that
approximately 70% of these TERP emission reductions will occur before
the core ozone season of 2009. We have evaluated the impact of this
change on the attainment demonstration modeling and WOE; this
evaluation is in Subsection D, below.
---------------------------------------------------------------------------

    \7\ (6710.13 x 250 x 7) = $11,742,727.50 x 10.4786 =
$123,047,344.38.
---------------------------------------------------------------------------

    In summary, EPA believes that the TERP program is achieving
significant reductions in NOX. Consistent with its
experience in implementing the program, the State has adjusted its
assumptions used in projecting emission reductions to be more
conservative. EPA believes these revised assumptions begin to address
many of the commenters concerns. Although delays in opening the request
for applications mean the reductions based on FY2009 funds will be
delayed, many reductions can still occur before the peak of the ozone
season. Achieving the 14.2 tpd of reductions from TERP will require
substantial continued efforts. See also Subsection D below, in
particular the last Response, Comment MC-15.

D. Comments on Photochemical Modeling, Weight of Evidence Analyses, and
Assessment of Demonstration of Attainment

    EPA received a number of comments about the photochemical modeling,
the Weight of Evidence Analyses, and our proposed determination that
the area would attain the standard by its attainment date of June 15,
2010. EPA has reviewed all the comments on these topics and provided
responses below.
    The discussion below summarizes our evaluation of the modeling and
evidence, the comments we received, and other factors such as the
State's progress in implementing control strategies, and recent air
quality trends. EPA believes that as the attainment date becomes
closer, measured air quality and planned additional emission reductions
become more important as a predictive tool (compared to modeling) and
the monitoring data should be given additional weight, more so than in
situations where the attainment date is still years away. In 2008, the
preliminary data shows 18 of the 20 monitors have measured attainment
levels with fourth high 8-hour values of 84 ppb or less. The remaining
two monitors were only slightly higher than an attainment level
measuring fourth high values of 85 ppb. EPA believes additional
significant reductions in emissions will occur before the 2009 ozone
season such that the area can attain the standard based on 2007-2009
ambient data or at least qualify for a 1-year extension of the
attainment date by having each monitor's 4th high ozone concentration
in 2009 below 85 ppb.
    We evaluated many factors in our WOE evaluation. These items
included reductions not included in the modeling based projections
(energy efficiencies), unquantifiable measures (AirCheckTexas, Dallas
Sustainable Skyline Initiative, etc.), meteorological analyses of
severity of ozone seasons (both the base period and recent years
including 2007), most recent monitoring in 2007 (a 4th high of 89 ppb
at two monitors and the other 18 monitors had 4th high values of 87 ppb
or less), the court's vacatur of CAIR, progress in implementing the
TERP program, and progress in implementing the early compliance
incentive on natural gas compressor engines outside the DFW area. EPA
has also considered preliminary 2008 ozone monitoring data (4th high
values of 85 ppb at two monitors and at the other 18 monitors the value
was 84 ppb or less) and whether that data supports a trend toward
attainment for the area. We considered that over half of the
NOX estimated emissions reductions between 2007 and 2009
that are estimated to yield a 3-4 ppb drop in ozone levels in the DFW
area, are slated to occur between the 2008 ozone season and the 2009
ozone season. We also expect further ozone reductions in 2009 and
beyond.
    After consideration of all of these analyses, EPA has determined
that the State has demonstrated that the DFW nonattainment area will
attain the 1997 8-hour ozone standard by its attainment date.
    Comment (MC-1): A commenter states that the WOE analysis
underestimates the impact of emission increases from facilities outside
the DFW nonattainment area, upon the DFW area. This underestimate
occurs because the TCEQ issues PSD permits to facilities outside the
DFW area that will affect the ozone concentration level in the DFW area
and says they should address these ozone impacts in the DFW attainment
demonstration SIP. The commenter does not believe that this DFW
attainment demonstration accounts for the impacts from these sources
that have been and will be permitted outside of the DFW area. There
also appears to be no correlation or tracking of these permitted
emission increases in relation to the projected point source emissions
inventories in this DFW attainment demonstration.
    Response (MC-1): The Texas SIP at Section 166.160 (a) (which
incorporates 40 CFR 52.21(k) by reference) requires a new source or
modification subject to PSD to demonstrate that emissions from the
facility will not cause or contribute to a violation of any NAAQS. The
Texas PSD SIP permitting program also provides for an opportunity for
notice and comment, as well as state court judicial review, of each
permitting action.
    EPA disagrees with the commenter that this SIP revision does not
account for the impact of potential emissions increases. In this final
action on the DFW attainment demonstration, we reviewed the analysis to
insure that sources impacting the DFW nonattainment area were included
in the baseline and future case modeling demonstrations. EPA's modeling
guidance (``Guidance on the Use of Models and Other Analyses for
Demonstrating Attainment of Air Quality Goals for Ozone, PM2.5, and
Regional Haze'', EPA-454/B-07-002, April 2007; and earlier modeling
guidance) and emission inventory guidance (``Emissions Inventory
Guidance for Implementation of Ozone and Particulate Matter National
Ambient Air Quality Standards (NAAQS) and Regional Haze Regulations'',
EPA-454/R-05-001, August, 2005, updated November 2005) indicate that a
combination of specific projections and general growth estimates should
be utilized to attempt to obtain a best estimate for the future year
inventory. Future case emissions must be projected to account for
growth and control throughout the modeling domain, which includes
states outside of Texas and the attainment areas of Texas (including
the new proposed sources raised by the commenter). EPA's guidance has
been that new permitted sources, including likely to be permitted
sources based on applications that have been received when the future
year EI is being generated, should be included in the future year
modeling if they are expected to be emitting in the future attainment
year. As a practical matter, the focus has usually been to include
expected new very large sources (such as electric generating units
(EGUs)) and use economic based growth factors to account for growth in
emissions from other industrial source categories. Overall, EPA's
guidance is to provide the best estimate of the future year emission
inventory given the limitations with estimating emissions several years
in the future. Texas' emission projections to the future years are very

detailed and the methods utilized are discussed in the MOAAD TSD and in
TCEQ's DFW SIP submittal, including Appendix B. In nonattainment areas,
major new sources are required to obtain offsets larger than the
proposed source so there is a net decrease in emissions, so no growth
is estimated for these sources in nonattainment areas. Therefore,
within Texas the only areas that point source growth is estimated is in
the areas that are in attainment and our discussion will briefly
explain the methodology for future year estimates of major point
sources in attainment areas of Texas.
    For existing EGUs in Texas, the State used 2005 continuous emission
monitoring data and assumed that there would be no emissions changes.
Texas projected increases in emissions because of new EGUs that were
expected to be emitting in 2009 (these were included in Table 2-8 of
Appendix B of TCEQ's submittal). For all other industrial point source
emissions (non-EGUs) in Texas' attainment areas, TCEQ started with the
1999 reported emission inventory and projected growth in point source
emissions using point source growth projections derived from the
Emissions Growth Analysis System version 4.0 (EGAS 4.0), an EPA-
approved methodology. It is worth noting that the EGAS system for
projecting emissions tends to overstate future emissions since the
system relies principally on economic growth for the projections, and
does not include reductions from regulatory or permit controls.
    In conclusion, we have reviewed the methodologies that TCEQ
utilized to grow EGUs and non-EGUs outside of the DFW area and conclude
that the 2009 level emissions of these sources have been appropriately
estimated using acceptable methods and contrary to the commenter's
concerns the attainment demonstration appropriately accounts for the
potential for new source growth by 2009.
    Comment (MC-2): Commenters state that ozone exceedances continue to
occur in the DFW area and show there still is a serious problem.
Specifically, 14 exceedances have been measured at eight of the
monitors through August 12, 2008 and eight of which are 90 to 99 ppb.
The commenter concluded that this 2008 monitoring data does not seem to
support the WOE.
    Response (MC-2): EPA has reviewed the ozone monitoring data through
November 1, 2008 in response to this comment. While a number of
exceedances of the 1997 8-hour ozone standard occurred during the 2008
ozone season by August 12, 2008, it is very important to note that the
standard is a statistically based standard. The statistical nature of
the standard allows each monitor to have up to 3 days with exceedance
levels at each monitor (with potentially multiple 8-hour exceedances
for each of the three days) and all the monitors in the area could
still have a 4th high value less than 85 ppb (attainment level). The
standard is an average of the daily 4th high value at a monitor for
each year of a consecutive 3-year period. Therefore, it is even
possible to have a 4th high value for one or even two years at a
specific monitor be above the standard, but the 3-year average value to
be below 85 ppb and thus, in attainment.\8\ Furthermore, each monitor
in the area could have up to 3 exceedances at each monitor on differing
days. Given 20 monitors in the DFW area, a total of 60 exceedances
could theoretically occur in the DFW area with all 4th high values at
each monitor still less than 85 ppb. This is a theoretical worse-case
situation but this demonstrates that having several exceedances does
not automatically yield a nonattainment determination.
---------------------------------------------------------------------------

    \8\ For example, if the 4th high value for each of three years
was as follows: 2006--87 ppb; 2007--85 ppb; 2008--81 ppb, the
average over the three year period would be 84 ppb, which is below
the level of the standard.
---------------------------------------------------------------------------

    Since the standard is statistically based, the relevant metric to
examine for determining compliance with the NAAQS is the annual 4th
high values at each monitor. We therefore evaluated the recent 4th high
values for the DFW area 8-Hour Ozone Season (March 1-October 31 for the
85 ppb standard). The 4th high monitoring data from 2008 indicates that
the area is near attainment levels (2008 monitoring data is preliminary
and awaiting QA/QC \9\). The 2008 preliminary data shows the DFW area
had 4th high values of 85 ppb at two monitors and at the other 18
monitors the value was 84 ppb or less. The 2008 preliminary data
indicates the 2006-2008 DV is 91 ppb (down from 95 ppb using 2005-2007
data). For the monitor that has the highest average 2007 and 2008 4th
high values and is likely to be the controlling monitor (or one of the
highest monitors) for determining if the area reaches attainment based
on 2007-2009 data, the monitor's DV for the 2007-2009 period would have
to be less than 85 ppb. For this to occur the monitor (Denton monitor)
would have to have a 4th high value of 82 ppb or less to reach
attainment in 2009. It is important to note that this monitor had a
preliminary 4th high value in 2008 of only 84 ppb.
---------------------------------------------------------------------------

    \9\ 2008 preliminary monitoring data is from EPA's AQS and
AirNow databases and has to undergo final Quality Assurance and
Quality Control.
---------------------------------------------------------------------------

    In comparison with ozone monitoring levels in 2007, the preliminary
2008 monitoring data is lower than the 2007 data. Contrary to the
commenters concerns, EPA believes that the 2008 preliminary data is
consistent with achieving attainment, especially considering that much
of the DFW SIP reductions are still to occur and another year of fleet
turnover will happen. EPA also believes that even if the area does not
attain the standard based on 2007-2009 data, it is very likely to
qualify for a one year extension under sections 172(a)(2)(C) and
181(a)(5) of the Act (see 40 CFR 51.907) by having fourth high at 84
ppb or below at every monitor.
    Comment (MC-3): Commenters believe that we should impose a 2009
mid-course review (MCR) obligation upon the State, triggered by
exceedances at the monitors or a violation of the standard in 2009.
    Response (MC-3): There is no MCR requirement at this time for the
8-hour ozone SIP. In our Phase 2 Implementation Rule, we provided that
we would assess the need for MCR for areas with an attainment date
beyond 6 years after the effective date of the area's designation
(Final Rule To Implement the 8-Hour Ozone National Ambient Air Quality
Standard, Phase 2 (70 FR 71612, 71629). The attainment date for DFW is
June 15, 2010, which is not more than 6 years beyond the effective date
of the area's designation. A mid-course review is for the purpose of
assessing whether an area is on-track for attainment and would
typically be performed several years before the attainment year. This
is because a MCR performed several years before the attainment year
would give the area sufficient time to make corrections to the plan if
it was not performing as anticipated. A review as suggested by the
commenter would not be ``mid-course'' because it would be performed in
the middle of the attainment year ozone season. At that point in time,
there would be no steps that the DFW area could take to move the area
back on track to achieve attainment by the required date.
    Comment (MC-4): Commenters stated that in the DFW area, there are
two monitors critical to the attainment demonstration, one in Frisco
and one in Denton. The commenters, relying upon a February 22, 2006
Memorandum from ENVIRON, state that there is no measurable impact on
these two critical monitors from the TCEQ's chosen controls for the
Ellis County cement plants. The commenters contend that TCEQ has not
performed any analysis showing that the chosen level of

controls on the Ellis County cement plants would assist the DFW area
into coming into compliance with the ozone standard.
    Response (MC-4): As noted in a previous response, the Act gives the
State the primary authority to determine the mix of control measures
necessary to demonstrate attainment. One of the measures that TCEQ
selected in support of its attainment demonstration is controls at
cement plants in Ellis County. EPA evaluated the plan, as a whole, and
agrees that the State has demonstrated that the area will attain the
standard by its attainment date. Thus, EPA does not have authority to
second-guess the mix of controls selected by the State and, in this
case, its decision to further control the cement kilns in Ellis County.
    Although we cannot second-guess the controls selected by the State,
we note that we agree with TCEQ that cement kiln NOX
reductions are an important element of the reductions necessary to
bring the entire DFW area into attainment and the reductions are
expected to reduce high ozone levels and the frequency of ozone
exceedances in the DFW area. The record for this action includes the
information that was evaluated by the State and EPA and that supports
the conclusion that additional NOX controls on cement kilns
are a critical component to reducing ozone exceedance levels in the DFW
area so that the area can timely attain the 1997 8-hour ozone standard.
It is clear from evaluating the SIP, its reports and appendices that
TCEQ has performed numerous analyses concerning the impact of the
cement kilns NOX and VOC emissions on the ozone
concentrations levels of the DFW area. Moreover, contrary to the
commenters' assertion, the chosen strategy has an impact on the Frisco
and Denton monitors, as well as a significant benefit to the western
portion of the nonattainment area, especially in Tarrant County. For
further details, see the TCEQ's Response to Comments document, the
MOAAD TSD, and the Supplemental TSD.
    For the other comments specific to the cement kiln NOX
rule itself, not the attainment demonstration SIP, we provide the
comments and our responses in our final rule for the Control of
Emissions of Nitrogen Oxides from Cement Kilns, concurrently published
in today's Federal Register.
    Comment (MC-5): The commenter asserted that EPA should not accept
TCEQ's revised Relative Response Factor (RRF) calculation.\10\ The
commenter indicated that contrary to the proposal, a 1 ppb difference
between EPA's RRF guidance and TCEQ's revised RRF is significant. The
commenter referred to 73 FR 40211, stating that TCEQ RRF calculation
did not make significant differences in the future design values (FDVs)
with truncation. The commenter wrote that TCEQ's methodology is merely
a paper exercise to obtain additional emission credits, and EPA should
not approve of such tactics.
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    \10\ The RRF is used to calculate the change in model projected
values between the basecase and future case modeling projections and
determine if modeling is projecting attainment in the future. For
further explanations of both the EPA guidance method for calculating
RRFs and TCEQ's RRF calculation method see Section 4.11 of the MOAAD
TSD.
---------------------------------------------------------------------------

    Response (MC-5): We recognize the TCEQ's method of projecting the
future design value differs from the method provided for in EPA's
guidance. EPA's guidance for projecting the future design value is not
a legally binding substantive rule. Therefore, other methods of design
value projections may be evaluated on a case-by-case basis and used to
determine whether an area will meet the standard. Whatever method is
used for a specific demonstration--either that from EPA's Guidance or
another method--is subject to comment during the State and EPA public
participation processes and all substantive concerns about the method
would be addressed in responding to any comments.
    TCEQ shared their RRF method with EPA during their SIP development
process. EPA reviewed the alternate RRF method at the time and
indicated to TCEQ that we would utilize both EPA's method and TCEQ's
method and weigh the results in our review of the modeling projections.
We have continued to follow this approach in our review of this SIP.
For details on how both the TCEQ and EPA RRF methods are calculated and
results from the two methods, please see the MOAAD TSD starting in
Chapter 4.
    In this specific case, TCEQ's method yields projected values that
when compared to values with EPA's method are more conservative at some
monitors and less conservative at other monitors. EPA does not consider
the TCEQ RRF method to be superior to EPA's method, just a different
way to perform the calculation and yield another set of projected
results to consider in our review. We do not believe that either method
is biased towards a particular result. As described below, and
documented in our MOAAD TSD for this action, we have reviewed
projections using both RRF techniques. Both the TCEQ projection and the
EPA projection are consistent with the conclusion that the area will
meet the standard in 2009.
    The results for both RRF (EPA and TCEQ) methods are contained in
tables of the MOAAD TSD that have FDV projections, including Tables in
Chapter 6 (the Summary Chapter). EPA reviewed the FDVs for all modeling
based projections using both RRF techniques and for most monitors, the
TCEQ RRF based FDV calculations make minor differences of only one or
two tenths of a ppb (compared to EPA's RRF method) and generally do not
change the final modeling projected value. Specifically, for the nine
monitors that are assessed, the difference between the two RRF
techniques ranges from minus 0.22 ppb to +0.19 ppb for 8 of the 9
monitors and is +0.59 ppb for the other monitor. See Table 5 of the
proposal notice. As the final step of calculating modeling projections,
EPA guidance recommends truncating the tenths digit and only reporting
integer ppb values to match with the monitored attainment demonstration
procedures that truncate to integer ppb levels. Due to this truncation
procedure, modeling projection changes of a few tenths do not generally
impact the final FDV value. There were a few cases where the different
RRF methods yielded a 1 ppb difference in the final FDV value due to
this truncation process (for the Midlothian monitor's data, the
different RRF methods yield modeling values of 82.83 ppb and 83.05 ppb
and truncation yields final FDVs of 82 ppb and 83 ppb).
    We continue to believe that the difference in the results of these
two techniques is small overall. As discussed in another response
below, we considered the results of both RRF methods (including the few
times that the truncated FDV differed by 1 ppb) and determined that
both the TCEQ projection and the EPA projection are consistent with the
conclusion that the area will meet the standard in 2009.
    Comment (MC-6): The commenter indicated it is unclear whether the
Photochemical Dispersion Modeling Reanalysis 2009 (PDMR 2009)
evaluation uses TCEQ's revised RRF or EPA's guidance. The commenter
indicated that it appears as though it uses only TCEQ's RRF and the
public should be afforded an opportunity to know the PDMR 2009 FDV
under EPA's guidance. The commenter asserted that considering that even
with the more lenient TCEQ revised RRF, the modeling still projects a
worse air quality picture, and thus the EPA guidance projection

will most likely be even worse. The commenter indicated that without
this information, the public is unable to meaningfully review and
comment not only on the overall demonstration, but also on whether
using the TCEQ revised RRF is even proper.
    Response (MC-6): There were five tables that included modeling
projections in the proposal notice. Tables 2, 3, and 5 had projections
for the PDMR 2009 modeling scenario and were marked as TCEQ RRF in the
FDV columns. The proposal notice included calculations of modeling
projections using both the TCEQ's RRF method and the RRF method from
EPA's guidance for the modeling run Combo 10 in Table 1. In referring
to values in Table 1 of the proposal notice, EPA stated on page 40211
``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.'' From that point forward in the proposal
notice, EPA did not include the results from EPA's RRF method in the
Federal Register notice. Tables 2, 3, and 5, including the analyses of
PDMR 2009 only include the TCEQ RRFs as the commenter indicates. This
was done to try to minimize confusion in the notice. EPA did note in
the proposed notice that the results from the EPA RRF method are
contained in the MOAAD TSD. The results for both RRF (EPA and TCEQ)
methods were contained in tables of the MOAAD TSD that had Future
Design Value projections, including Tables in Chapter 6 (the Summary
Chapter). EPA reviewed the FDVs for all modeling based projections
using both RRF techniques. Examination of the modeling results, which
include some WOE adjustments contained in Table 6-3 of the MOAAD TSD,
reveals that the TCEQ RRF based FDV calculation makes only minor
differences of only one or two tenths of a ppb (compared to EPA's RRF
method) for most monitors and did not change the final modeling
projected value except for one monitor.
    Comment (MC-7): A commenter asserted that full credit for the
NOX reductions from gas compressors in 33 East Texas
counties seems overly optimistic. The commenter indicated that their
understanding is that owners or operators of compressor engines
requested a small portion of the $4 million in incentives. The
commenter remains skeptical that the full reductions assumed in Combo
10 will be achieved by 2009. The commenter asserted that the attainment
modeling thus overstates the ozone reductions from the control strategy
and indicated that EPA should consider this effect as part of the
Weight of Evidence analysis, and should give more weight to the PDMR
2009.
    Several commenters indicated that the 2.4 tpd of NOX
reductions from point sources in the DFW area that have 2010 compliance
dates are not likely to be in place by the beginning of the 2009 ozone
season. These commenters also indicated that EPA assumes too much by
relying on the predictions that early compliance will occur for certain
control measures with 2010 implementation dates. They claim that
because of this reliance, the attainment modeling overstates the ozone
reductions from the control strategy. The commenters indicated that EPA
should consider this effect as part of the WOE analysis, and should
give more weight to the PDMR 2009. Furthermore, a commenter wrote that
if any control measure emission reduction will not be enforceable until
after the 2009 compliance date, then those emission reductions cannot
be used to justify EPA's approval.
    Response (MC-7): Combo 10 modeling run was the official attainment
demonstration modeling run submitted by TCEQ to EPA in the SIP revision
submittal. Because of our concerns stemming from the inclusion of
reductions from measures with 2010 compliance dates, it was not the
only modeling run considered by EPA in our evaluation of whether the
DFW area would attain the standard by the deadline. There was another
modeling run available in the TCEQ's public record on its proposed
action for EPA to review; in the proposal and TSDs, we label this
additional modeling scenario the PDMR 2009. We evaluated this PDMR 2009
modeling run as a worst-case projection of the 2009 modeling picture
because it did not project any reductions from the rules with 2010
compliance dates. For example, it did not include the 2.4 tpd of
NOX reductions projected from the major and minor Point
Source rules in the DFW area and any projected reductions from the East
Texas Compressor Engines rules that have 2010 compliance dates. Thus,
PDMR 2009 provides an upper boundary of projected ozone FDVs in the
attainment year.
    The Texas legislature made available to compressor engine owner and
operators $4 million to assist in early compliance. As the commenter
points out, however, the full $4 million was not requested by owners
and operators of compressor engines. Since some requests were made,
some early compliance should occur, but the commenter is correct that
the level of reductions in East Texas by the 2009 ozone season is
probably closer to the PDMR 2009 emission reduction level than the
Combo 10 emission reduction level. As a result of this information, EPA
is putting more weight on the PDMR 2009 results than on Combo 10.
    We have evaluated the modeling outputs based on an approach that
looks at the PDMR 2009 outputs, which predict ozone levels that are
slightly worse than what is likely to occur, as well as the Combo 10
outputs, which predict ozone levels that are more optimistic. This
evaluation of PDMR 2009 sets the upper bound of model predictions for
the FDV in 2009 and the Combo 10 run sets the lower bound. In making
our determination that the State had demonstrated that the DFW area
would attain the 1997 ozone NAAQS by its attainment date, we consider
the TCEQ's official attainment demonstration modeling run (Combo 10),
the results from the PDMR 2009 modeling, and information that some
early compliance would occur by the 2009 ozone season as well as other
weight of evidence analyses. The model projections in Table 6.3 of the
MOAAD TSD give the non-truncated values for the final modeling with
some WOE adjustments for both the modeling runs and both RRF
techniques. The difference between the PDMR 2009 and the Combo 10 run
for each monitor is 0.30 ppb or less when using either the TCEQ or EPA
RRF technique. EPA's modeling guidance recommends the truncation of the
decimal places and reporting of only integer values for the final
modeling based projection values. When the truncation is done to the
MOAAD TSD Table 6.3 values (Modeling-based assessment with some WOE
elements included), the results are identical for both the PDMR 2009
and the Combo 10 modeling runs. Using the EPA RRF procedure, both runs
result with 7 monitors attaining, one monitor at 87 ppb, and one
monitor at 88 ppb. Using the TCEQ RRF procedure, both runs result with
7 monitors attaining, one monitor at 87 ppb, and one monitor at 88 ppb.
    We have considered both the PDMR 2009 and Combo 10 modeling results
and put less weight on the Combo 10 projections because of concerns
over the inclusion of measures with 2010 compliance dates. As discussed
above, however, when EPA's procedures for projecting the future design
value are followed, there is little difference in the results
particularly if one considers that

a small amount of early compliance will occur. Therefore, as further
discussed in response to other comments, the combination of the
Modeling projections and other WOE elements were considered and support
the conclusion that the area will attain by the area's attainment date.
    Comment (MC-8): The commenter indicated that TCEQ intends to reduce
the amount of DERC values included in the modeling because using the
entire balance of the DERC bank is ``overly conservative based on past
usage of DERCs.'' The commenter asserted that DFW's past air quality
violations occurred under scenarios of less DERC usage. The commenter
concluded that this belies a Weight of Evidence (WOE) ``trend'' of
improving air quality because in the future projection nothing is
really changing from the past when violations occurred.
    Response (MC-8): DERCs are banked emission credits generated by
reducing emissions beyond required levels that sources can use to
exceed certain emission limits on a temporary basis. EPA guidance
discusses why emission credits that are being carried in an emissions
bank ought to be included in modeled projections. It can be important
because these banked emissions come back in to the air if the banked
credits are used. As a result, if these banked emissions are not
accounted for in the future projections, the modeling would under-
predict future ozone levels if some or all of the banked credits are
used. EPA guidance advises a conservative approach in which all banked
emissions are included in the modeled future projections. This
conservative approach assumes that the entire bank would be depleted
during the attainment year. The TCEQ Bank held 20.4 tpd of
NOX DERCs when TCEQ reviewed the level of credits in the
bank and included the banked DERCs in their future year modeling. After
finalizing the future year modeling, TCEQ reevaluated the inclusion of
all of the banked DERCs in the future projections. TCEQ believed that
the inclusion of the entire balance of the DERC bank was overly
conservative based on past usage of DERCs. They wished to include 3.2
tpd, rather than 20.4 tpd, of banked DERCs in the future projections.
As discussed previously, Texas committed to adopt a restriction on DERC
usage to ensure that no more than 3.2 tpd of banked DERCs will be used
in 2009 and as a result preventing 17.2 tpd of potential emissions
growth. This approval is conditioned on TCEQ's adoption and submittal
of a complete SIP revision. Consequently, in order for EPA to fully
approve the SIP, the State will need to have an enforceable rule in
place that would not allow 17.2 tpd of the 20.4 tpd banked DERCs
currently modeled in the state's 2009 Combo 10 and PDMR 2009 modeling,
to be used beginning March 1, 2009.
    The modeling submitted May 30, 2007 did include 20.4 tpd of banked
DERCs in the 2009 future projections. Relying upon the State's
commitment to revise the DERC rule to limit the use of banked credits
to 3.2 tpd in 2009, it is appropriate to reduce the 2009 future
modeling projections to 3.2 tpd in 2009. (For the calendar years after
2009, there will be an enforceable mechanism to equate to the limit of
3.2 tpd.) EPA therefore adjusted the modeling projections in Table 3 of
the proposal (also included in the MOAAD TSD) to assess the impacts of
the revised future projections. This was done to provide a modeling
projection that reflected the inclusion of banked DERCs of 3.2 tpd in
2009. This approach is consistent with what would have been projected
if TCEQ had redone the SIP modeling with 3.2 tpd for the banked DERCs
instead of the 20.4 tpd that was included in the Combo 10 and PDMR 2009
modeling. EPA then used the revised 2009 modeling projections in
conjunction with other modeling based analysis and WOE considerations
in our review of the entire attainment demonstration.
    The commenter is correct in the assessment that DERCs have not been
used in the past and past air quality exceedances did not include any
impact from DERC usage (since DERCs have not been used in the DFW
area). Now, with the commitment to adopt a restriction on DERC use, it
is not appropriate to continue with the assumption that all of the
DERCs in the bank will be used in the attainment year in the future
year modeling.
    Because DERC use did not impact past exceedances (again because
DERCs have not been used in the past), EPA did not consider the banked
DERCs 2009 usage restriction, as part of our emissions and ambient
trends analysis that we performed in our WOE evaluation; rather, it is
only in the modeling where it was considered. Consistent with the
commenters concerns, EPA was careful in our WOE evaluations and review
to not consider the revised 2009-banked DERCs usage restriction in our
emission trends analysis and monitoring trends analysis. For example in
Table 5-11 of the MOAAD TSD, estimating the actual emission reductions
between 2007 and 2009, EPA did not include any reductions due to the
restriction on DERC usage. Therefore, EPA believes that we have
appropriately considered the revised banked DERCs tpd usage restriction
in adjusting assumptions about possible future emissions growth in the
modeling but consistent with the commenter's concerns, we have not
considered it in evaluating emissions and monitoring trends (analysis
included in the WOE analysis). For a full discussion of DERCs and
conditional approval, see the DERCs comments section below.
    Comment (MC-9): The commenter indicated that EPA's reliance upon
the low 2007 monitor readings is misplaced since extremely unusual
weather, rain and low temperatures, dominated the 2007 DFW ozone
season. The commenter continued that the first 100+ [deg]F temperature
day was not reached until late August. The commenter concluded that EPA
should not give TCEQ credit for something achieved only by the grace of
God.
    Response (MC-9): We rely on the 2007 monitored air quality levels
as part of our Weight of Evidence analysis. We investigated the 2007
meteorology to determine how it compared with the DFW normal ozone
season meteorology. To help account for all the different variables
that impact the frequency of ozone we utilized a Meteorological
Adjusted Trends analysis that was done by EPA personnel at Office of
Air Quality Planning and Standards (OAQPS) for the DFW area to assess
the ozone conduciveness of the 2007 ozone season. OAQPS's analysis
utilizes temperature and precipitation data in addition to several
other factors. The results of this analysis were included in our
proposal, and indicated that overall 2007 was near the normal
meteorology for DFW's ozone season. See Chapter 5, section 5.15 and
Chapter 6, section 6.3 in the MOAAD TSD.
    The commenter asserts that the 2007 ozone season was biased low due
to the influence of more rain than normal and less 100 [deg]F days than
normal. EPA reviewed monthly meteorological National Climatic Data
Center 2007 data for DFW International Airport (for the DFW ozone
season months of March 1-October 31). We evaluated average monthly
temperature, monthly average maximum temperature, and monthly
precipitation. Looking at this temperature information and
precipitation data, EPA's assessment is that, while for several months
the precipitation was above average, the ozone season and the core
ozone months (June-September) were near normal overall. For more
information, see the Supplemental TSD. Ozone formation is affected by a
number of

meteorological parameters and just looking at these three parameters
does not give a complete evaluation of the ozone conduciveness of the
2007 ozone season.
    The commenter was concerned that the meteorology was unusually
nonconductive for generation of ozone exceedances in 2007. In light of
this, EPA also reviewed ozone exceedance data for 2007, and found that
the first exceedance occurred April 28th, and a number of exceedance
days occurred starting in late July (7/24) and the last exceedance
occurred on October 4th. In all, there were 12 days with exceedances at
one or more monitors in the DFW area in 2007. This is below the long-
term normal trend of approximately 30 exceedance days per year. The
limitation of just evaluating the number of exceedance days to
determine if meteorology was normal or below normal is that exceedance
days are a combination of meteorology and emissions. Emissions
decreases due to fleet turnover among other things could also explain
part or all of a lower than normal number of exceedance days in 2007.
    Finally, we note that one reason we evaluate attainment of a NAAQS
based on three years of data is that use of several years tends to
mitigate any unusual meteorology that occurs during a specific year.
The year 2007 is the first of the three years of data (2007-2009) that
will be used for determining if the DFW area reaches attainment in
2009. The 2007 4th high maximums were all in the 80s ppb range or less
for monitors that are typically near the area's design value. This is
significantly lower than other recent years. Meteorological Trends
analysis indicates that 2007 was closer to normal than 2005 and 2006.
Therefore, the 2007 data is important from both a trends perspective as
well as being the first of three years utilized in determining if the
area reaches attainment in 2009.
    Comment (MC-10): The commenter indicated the DFW emissions
inventory has gaps and that EPA knows that there are hundreds of
industrial sources involved in the gas well drilling and gas pipeline
operations that were not modeled by the TCEQ and which TCEQ assumed to
be insignificant. The commenter asserted that without modeling these
significant sources of NOX emissions, the attainment
demonstration may be in greater jeopardy than EPA or TCEQ admits.
    Response (MC-10): The TCEQ projected the future emissions inventory
for the industrial sources involved in the gas well drilling and gas
pipeline operations with the most recent information available at the
time of the emissions inventory development. Photochemical modeling is
a very complex process and the emissions from natural gas production in
the DFW area were rapidly changing during the last two years of
modeling and SIP development and continue to do so. Improving emission
estimates and projections is one of the elements of photochemical
modeling that always requires an agency to balance the need to
incorporate new information with the time available to complete the
photochemical modeling tool for SIP development, and still meet the
submittal deadline.
    TCEQ's basecase and future year (2009) SIP modeling did include
estimates for emissions from industrial sources involved in gas well
drilling and pipeline operations. During the commissioners meeting when
the TCEQ adopted the DFW attainment demonstration SIP in May 2007,
there were industry comments indicating emission estimates from natural
gas compressor engines should be higher than were in the current
modeling. Although the commissioners moved forward to adopt and timely
submit the DFW 8-Hour Ozone attainment demonstration SIP, they also
directed TCEQ staff to research the accuracy of the emissions
inventories for these sources that were relied on in the attainment
demonstration modeling. TCEQ staff subsequently conducted an additional
survey to re-evaluate the number of stationary, gas-fired engines and
other NOX emission sources that are common at natural gas
production and gathering (P&G) facilities, in the nine-county DFW area.
TCEQ provided that information to EPA as supplemental WOE in a letter
dated April 23, 2008, which EPA has considered in its decision on
whether to approve the attainment demonstration SIP. Details of this
survey, the results, and explanation of how this information was
utilized in EPA's review were included in the proposal package
(Proposal FRN, MOAAD TSD, etc.).
    The survey collected data on existing NOX sources and
expected additional installations by 2009 so that a comparison to
estimated levels in the 2009 SIP modeling could be conducted. The
survey also collected data on when the NOX emitting sources
were installed. The survey indicated that P&G operations grew much more
rapidly than projected in the SIP. Based on the survey results, TCEQ
concluded that the majority of emissions growth would come from the
increase in compressor engines and not from other facets of P&G
operations. TCEQ therefore provided new estimates for the compressor
engines' emissions growth.
    The survey indicated that almost all of the rapid growth that
created the underestimation of additional engines and other related
NOX sources from natural gas P&G emission sources had
occurred after the 1999 base year. Fortunately, TCEQ put in place
regulations that will control rich and lean burn natural gas fired
compressor engines in the DFW area. TCEQ also controlled some engines
involved with drilling operations in the Increment of Progress SIP.
    From the modeling perspective, using the new survey's results, the
underestimation in the growth of emissions is greatly mitigated by
TCEQ's implementation of NOX controls on emission sources in
this industry group in Chapter 117 rules adopted as part of the May 30,
2007 SIP submission. While mitigated to a large extent, the new survey
data indicate that emissions in the demonstration modeling, i.e., the
2009 Combo 10 modeling, from these natural gas P&G sources would add
3.3 tpd based on our analysis of the TCEQ survey data. Using modeling
sensitivity runs, we accounted for this approximate increase of 3.3 tpd
in the projected emissions inventory, and we were able to estimate the
effect on the modeled ozone levels. See Table 4 in the proposal. In
considering the underestimation from a 'real world' standpoint, it is
important to note that due to TCEQ's adopted regulations, a much larger
amount of actual reductions of NOX emissions (estimated as
35.7 tpd) will occur between 2007 and 2009 from the regulations on
compressor engines and these extra reductions will help reduce DFW area
ozone levels.
    While these emissions were not fully accounted for in the initial
photochemical modeling, TCEQ had developed the emission inventory for
this industry group consistent with EPA's guidance. EPA appreciates the
additional survey information that TCEQ provided and, EPA considered
the emissions in reviewing the attainment demonstration and found that
TCEQ's revised emission estimates were acceptable. This information was
clearly presented as part of the proposed rulemaking action and the
commenter has not identified any substantive flaws with that analysis.
    Comment (MC-11): The commenter indicated that the emissions
inventory appears flawed, in part from the observation that the latest
VOC area source emissions inventory was unaffected despite the
substantial revisions to the gas drilling/compressor engine count, as
reflected in revised

NOX area source inventory revisions. The commenter further
indicated that VOC emissions from the engine stacks, and fugitive
emissions from the piping and valves that connect the engines, appear
not to have been incorporated into the emissions inventory, and more
importantly, not to have been considered in the photochemical modeling.
The commenter asserted that the absence of these emissions in the
revised inventory placed additional doubt on to the accuracy of the
photochemical modeling to predict ozone levels in the western part of
the nonattainment area.
    Response (MC-11): The commenter is correct that the VOCs from P&G
facilities in the DFW area may be underestimated, since the number of
P&G facilities and related NOX sources had a large
underestimation. As provided above, there are inherent uncertainties
with emissions inventories. Unlike the NOX emission
discussed previously, however, the VOC emissions from natural gas
production are largely compounds that are not significantly reactive in
the formation of ozone. EPA defines ``Volatile Organic Compounds''
(VOCs) per 40 CFR Part 51.100(s) (as amended through January 18, 2007)
and specifically lists Methane and Ethane as organic compounds that
have been determined to have negligible photochemical reactivity.
Methane and ethane are typically 85-90% or more of the compounds
present in natural gas from gas wells so emissions from natural gas
production would be expected to have a small impact on ozone
production. In addition, modeling sensitivity analyses have shown that
large reductions in all VOC emissions in the DFW area result in only
very small changes in the area's ozone concentration level. Therefore,
an underestimation of P&G VOC emissions would not change the Combo 10
and PDMR 2009 modeling projections significantly. See Section 4.2 of
ENVIRON's ``Ozone Benefits in DFW from Emission Controls in the 2009
and 2012 Future Years,'' September 2006, included as a reference to
Chapter 2 of the TCEQ TSD.
    TCEQ did not collect data on VOC sources in the 2007 survey that
they conducted of natural gas P&G facilities in the DFW area. TCEQ
focused on NOX emission sources in their survey since
numerous photochemical modeling analyses had shown that elevated ozone
levels in the DFW area were much more sensitive to changes in
NOX emissions than VOC emissions. For these same reasons,
EPA does not believe that uncertainty in the natural gas P&G VOC
emissions would result in a significant change in modeling projections
or change our conclusion that the DFW area will attain the 1997 ozone
standard by its attainment date.
    Comment (MC-12): The commenter indicated that the Base Case
Monitoring Data is skewed because it relies on the 1999 episode and,
focusing on the Frisco Monitor, misrepresents the greater and more
current problems associated with monitoring data from monitoring
stations to the northwest and west. The commenter continued that the
use of this 10-year old base case set results in under-emphasis of the
effect of the numerous sources, including the Ellis County cement
kilns, Barnett Shale natural gas and oil drilling, and EGU's to the
south of the metroplex which often have their plume carried in
southeasterly winds into Tarrant County. The commenter asserted that
the 1999 data set is flawed due to the unusual meteorological
conditions as well as its overall lack of representativeness and that
Texas must be directed to develop additional base case data sets for
SIP planning efforts.
    Response (MC-12): EPA does not agree with the commenters'
assertions for several reasons. As discussed in Section 2.3 of EPA's
MOAAD TSD, EPA reviewed this 1999 episode and found it to be acceptable
and representative of the combination of meteorology and emissions that
generate ozone exceedance levels near the DV of the area at the time
episodes were being selected for development of this SIP. The 2009
modeling projections evaluate ozone levels at all the monitors in the
DFW area and, for this episode, both the Denton and Frisco monitors had
the highest FDVs; therefore, the emphasis was not just on the Frisco
monitor as the commenter asserts.
    Photochemical grid modeling takes several years to develop and
thus, at the time of submittal of a SIP, the episodes are typically
several years old. Selection of episodes to model for SIP planning is a
balance of finding historical periods with several days of exceedances
that are representative of the conditions that generate ozone near the
design value for the area and developing acceptable base case modeling
in time to allow for a timely submittal of an attainment demonstration.
At the time that TCEQ proposed the DFW attainment demonstration SIP in
December 2006, the episode was just over 7 years old, not 10 years old
as the commenter indicated.
    Chapter 2 of the MOAAD TSD included sections that detailed EPA's
guidance on episode selection, how the episode was originally chosen
and further discussion and review that occurred in 2005 about the
adequacy of this episode and the potential benefits of other episodes
The DFW area monitors that have been DV monitors or had values near the
area's DV for the period 1999-2005 (the period that was reviewed for
potential episodes was 1998-2004) indicates that all of these monitors
have been either north of the DFW area (Frisco monitor) or in the
northwest sector (Tarrant and Denton Counties monitors). EPA has done a
detailed review of both TCEQ's analyses and EPA's analyses of the
conceptual model for high ozone in DFW and what monitors are the DV
monitors. In years when light winds are more predominantly from the
south, the northern monitors (Denton and Frisco) are the DV monitors.
Other years, the winds and frequency of light winds are predominantly
from the southeast, resulting in the Tarrant and Denton Counties
monitors becoming the DV monitors. The location of the DFW area's DV
monitor depends on the distribution of the frequency of wind directions
during ozone conducive meteorology, but it is consistently on the
downwind side of the DFW area. In fact, assuming the preliminary
monitoring data through October 31, 2008 does not change, the Denton
monitor will be the DV monitor for the 2006-2008 period. Preliminary
data also indicate that the Denton monitor may be the DV monitor for
the period 2007-2009 (based on 2007 and 2008 monitoring data).
Approximately 70% of the local NOX emissions that lead to
high ozone levels are emitted from mobile (On-Road and Nonroad emission
sources) and the highest ozone levels typically occur downwind of the
core DFW emissions area. Figures 3 & 5 of TCEQ's Appendix B of their
SIP submittal illustrate the distribution of NOX emissions
from On-Road and Nonroad emissions. Modeling, monitoring, and aircraft
flights confirm that the highest levels of ozone occur downwind of the
core DFW emissions area. As discussed above, the Frisco and Denton
monitors are often downwind of the core DFW emissions area. Therefore,
EPA does not agree that this episode, the control strategy, and the SIP
overall are biased by the Frisco monitor being one of the highest ozone
monitors in the base year.
    The commenter asserted that using the 1999 episode results in
under-emphasis of the effect of the numerous sources, including the
Ellis County cement kilns, Barnett Shale natural gas and oil drilling,
and EGU's to the south of the DFW metroplex which often have their
plume carried in southeasterly

winds into Tarrant County. As discussed elsewhere in this response and
in EPA's MOAAD TSD, EPA conducted a thorough review of EPA's episode
selection guidance, conceptual model for high ozone events in DFW, and
episodes available for modeling at the time of episode selection and
EPA determined that this episode was appropriate and acceptable. EPA
does not recommend episode selection be based on trying to target
specific industry/emission sources but should weigh a number of factors
in selecting episodes for photochemical grid modeling to be utilized
for SIP development as was done in this situation.
    Afternoon wind from the southeast is one of the more prevalent wind
directions for high ozone in the DFW area. In TCEQ's conceptual model
description for high ozone events in the DFW area, morning winds out of
the south or southwest often occur and then transition to out of the
southeast or east in the afternoon. Therefore, the sources mentioned
can impact the Denton and Frisco monitors for some of the hours of the
day (that contribute to a high 8-hour ozone value). This episode has
two days with winds from the southeast in the afternoon (8/17 and 8/
22). August 17th had winds out of the southwest in the morning that
transitioned to winds out of the southeast in the afternoon. Forward
wind trajectories for the 17th indicate the emissions from the Ellis
County cement kilns were carried over the Frisco and Denton monitors.
On the 17th, it is also likely that emissions from the other sources
mentioned would also be carried over the Denton and potentially Frisco
monitors. Even on days that the winds do not take emissions from these
sources over the Frisco and Denton monitors, the modeling still
utilizes these emissions (and changes in these emissions) in projecting
ozone levels in the modeling domain. Among modeling analyses that can
be impacted by emission reductions at these sources are changes in
ozone exceedance metrics, such as number of grid cell 8-hour ozone
exceedances predicted and other metrics that consider the level of
exceedances predicted for each grid cell.
    In summary, EPA has reviewed the episode and determined that the
episode is representative of the conditions most often associated with
high eight-hour ozone in the DFW area.
    Comment (MC-13): Commenters indicated that the future case
attainment demonstration modeling included NOX reductions
from Phase I Clean Air Interstate Rule (CAIR) controls for EGUs outside
of Texas. Commenters indicated that since these reductions are now
unlikely to occur, at least on the original timeframe, the anticipated
ozone air quality benefits will be reduced. Commenters asserted that
EPA should consider this effect on the modeling and the WOE analysis.
    Response (MC-13): The EPA has considered the impact of a CAIR
vacatur and determined that even an immediate vacatur of CAIR would not
change our conclusion that the modeling and weight of evidence show
that the DFW area will attain the 1997 8-hour ozone standard by the
deadline. The principal reasons for this conclusion are: (1) Chapter
117 rules in the Texas SIP implemented in the entire eastern half of
Texas are equivalent to the Phase I rules of CAIR; (2) evaluation of
controls already installed in the nearest States impacted by CAIR,
Arkansas and Louisiana, show that significant reductions will still be
implemented; (3) many of the more distant states impacted by the CAIR
vacatur are also subject to the NOX SIP call so much of CAIR
Phase I NOX reductions will remain in place; and (4)
available modeling shows that loss of CAIR only has a small impact on
the DFW area.
    Texas implemented NOX controls on EGUs in the entire
eastern half of Texas that are approved into the Texas SIP, are
enforceable, and are equivalent to reductions from CAIR Phase I for
East Texas EGUs. The rules can be found in Texas Administrative Code
Title 30 Part 1 Chapter 117 Subchapter E Division 1 (117.3000-
117.3056). Therefore, the level of NOX reductions from EGUs
within the entire eastern half of Texas for the 2009 period is not
related to the status of the CAIR rules. With regard to EGU emissions
in the western half of Texas, EPA has concluded that emissions from
these sources would rarely be transported to the DFW area during
periods of high ozone in DFW. Thus, any changes in emissions from Texas
EGUs related to a vacatur of CAIR are not expected to impact DFW ozone
exceedance levels prior to the attainment date.
    In fact, the main change in emissions in the DFW photochemical
modeling domain due to a CAIR vacatur is for CAIR states that were not
part of the NOX SIP call and were outside of Texas. Of these
states, Louisiana and Arkansas are the closest upwind states to DFW and
would be expected to have the largest potential impact on ozone level
changes in DFW due to the CAIR vacatur. We have reviewed EPA's Clean
Air Market's Division National Electric Energy Data System database
(July 2008 version) that tracks equipment that has been installed to
meet the CAIR requirements for the EGUs in these two states. Our
evaluation of controls installed at facilities in Arkansas and
Louisiana considered whether installed controls were integral to
operation of the unit (example: Low NOX Burners), or if the
controls could be shut-off (Example: Over-fire Air) or potentially
bypassed (SCR). We have also conferred with Louisiana and Arkansas
Departments of Environmental Quality in an attempt to confirm the
information in the database.
    Our analysis of Louisiana major EGU's indicates that most controls
are based on Over-Fire Air or SCR (based on discussions with LDEQ
(September/October 2008)). However, the Dolette Hills is the closest
large Louisiana coal-fired EGU that is outside Texas and has the
highest potential to impact DFW area ozone levels of any coal-fired EGU
outside of Texas. It is often upwind of the DFW area when the DFW area
has elevated ozone levels. Low NOX burners and Over-Fire air
have been installed at the Dolette Hills unit to reduce NOX
emissions. In the absence of CAIR, it is possible that the utilization
of Over-Fire air could cease, but the Low NOX burners are
integral to the boiler operation and cannot be bypassed. Therefore,
even if the Over-Fire Air were not operated there would still be
permanent large NOX reductions on the order of 2000 to 3000
tpy of NOX (based on Discussions with LDEQ) compared to 4000
to 5000 tpy of NOX with Over-Fire Air and Low NOX
Burners.
    Our analysis of EGUs in Arkansas indicates that for the coal-fired
EGU's, most are being controlled with Over-Fire Air, but one 523 MW
unit is being controlled with Low NOX burners that have been
installed and should remain installed. For the gas-fired EGUs, most are
being controlled with Dry Low NOX burners in combination
with SCR. The Low NOX Burners are integral to the operation.
The SCR, however, conceivably could be turned off. Dry Low
NOX burners can achieve up to a 30% reduction by themselves
so significant reductions will still occur.
    Therefore, even with a vacatur of CAIR, significant reductions will
still occur in Arkansas and Louisiana including at the closest, upwind
plant, Dolette Hills. As for the reductions in other States impacted by
a CAIR vacatur, many of these States were part of the NOX
SIP call. The NOX SIP call reduction requirements remain in
place. States affected by the NOX SIP call include: Alabama,
Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland,
Maine, Michigan, Missouri, New Jersey, New York, North Carolina, Ohio,
Pennsylvania, Rhode

Island, South Carolina, Tennessee, Virginia, West Virginia and the
District of Columbia. While some states' rules implementing the
NOX Budget Trading Program (established by the
NOX SIP call) have a sunset provision in anticipation of
being replaced by the CAIR ozone-season trading program, EPA expects
the majority of controls to remain in place. EPA has asked States with
sunset provisions to move quickly to address this concern.
    We believe that it is reasonable to consider that the reductions
identified above will occur because the previously installed controls
are integral to the operation of the EGUs and are not likely to be
bypassed or circumvented or are required to comply with regulations
implementing the NOX SIP call.
    EPA also considered available modeling evidence in considering the
impact of a CAIR vacatur. First, the photochemical modeling upon which
the CAIR rule itself was based did not result in any other State being
included in the CAIR rules because of its impact on the DFW area. In
other words, no state was included in CAIR because of its impact on the
DFW area.
    No modeling exists that directly evaluates the impact of a CAIR
vacatur on the modeling episodes used in the final DFW SIP modeling so
it is not possible to directly evaluate the impact on Combo 10 or PDMR
2009 control strategy runs. EPA has found two modeling analyses that
help to evaluate the potential impact of the CAIR vacatur on DFW ozone
levels.
    We also have reviewed sensitivity modeling that evaluated potential
CAIR impacts conducted on an earlier version of DFW modeling. This
modeling was included in the HARC 35 Project Phase II Report (``Dallas/
Fort Worth CAMx Modeling: Improved Model Performance and Transport
Assessment Project H35, Phase 2''; ENVIRON; August 2005). The H35 Phase
II report evaluated the impact of the CAIR emission reductions
throughout the Eastern U.S. on DFW ozone levels in 2010. The report
included a bar chart (Figure 10-4), showing episode average
contributions to high 8-hour ozone in the DFW 9-county NAA by source
region and emissions group. Side-by-side bars show the subtle changes
due to the CAIR EGU controls. Controls expected from CAIR reduced
episode average high ozone in the DFW NAA by 0.3 ppb. The episode peak
ozone was also lowered 0.3 ppb over DFW from the CAIR controls. This
early modeling did not include some of the later emission inventory and
meteorological refinements, but a new evaluation with the modeling
submitted with the attainment demonstration would not be expected to
yield significantly differing results.
    We also looked at some earlier modeling that was included in Table
4-1 of the H35 Phase I Report (HARC Project H35, Transport
Contributions From Out-of-State Sources to East Texas Ozone, February
2005). The H35 Phase I report indicated that controlling a 25%
NOX reduction on all EGUs in Arkansas, Louisiana,
Mississippi, Missouri (NOX SIP call state), Oklahoma (non-
CAIR state), Tennessee (NOX SIP call state), and the Gulf of
Mexico (non-CAIR area) yielded a 0.1 ppb reduction in ozone on average
2007 elevated ozone levels (evaluated levels above 75 ppb and 85 ppb)
in DFW area for the DFW's SIP episode. While this analysis is for 2007
and conservatively includes 25% NOX reductions in two
NOX SIP call states, 25% reductions in Oklahoma (non-CAIR
state), and 25% reductions in Gulf of Mexico EGUs; all of which are
additional reductions not related to the CAIR Phase I rule. The 2007
modeling analysis is further evidence that the DFW area is not
influenced by out-of-state EGU emissions at times when elevated ozone
levels occur in DFW.
    Both of these modeling analyses consistently show a picture that
out of state reductions only have a small impact of 0.1 to 0.3 ppb or
less on model projected design values in the DFW area. The two CAIR
assessment analyses (EPA--Fall 2008 and H35 Phase II) are conservative
because they remove all CAIR reductions from the modeling. This does
not take into account that for non-NOX SIP call states, some
CAIR controls will generate reductions because the controls are
integral to the combustion process and will not likely be removed (Low
NOX Burners, etc.). These two CAIR modeling analyses also
rely on 2010 EGU projections, which include an additional year of EGU
growth, compared to the growth that would be included for a 2009
evaluation. These modeling evaluations over predict for NOX
during the 2009 ozone season because many states will still have in
place NOX controls required by the NOX SIP call.
    The worst-case assessment of a 0.1 to 0.3 ppb increase on model
projected FDVs, in itself, is small enough that for most model
projections, no change in the truncated ppb value would occur. Given
that the actual impact of a vacatur on emissions would be smaller than
in these worst case analyses, EPA believes that the status of the CAIR
rules should not impact our decision to approve the DFW attainment
plan.
    We have included further discussions of a vacatur of CAIR on the
modeling and WOE analysis in a separate response to comment that
addresses comments on the adequacy of the WOE analysis and the
conclusion of whether the DFW NAA will reach attainment.
    Comment (MC-14): The commenter indicated that the DFW attainment
demonstration model has considerable challenges as detailed in the
Notice of Proposed Rulemaking. The commenter noted that model
development is a resource intensive process and the state simply needs
to apply additional resources to this process. The commenter stated
that throughout the development of the May 2007 SIP revision, the State
indicated that it had insufficient resources to improve the attainment
demonstration and incorporate alternative and more recent ozone
episodes. The commenter concluded that the State has not allocated
adequate resources to SIP development, including model development, to
develop models robust enough to accurately predict ozone concentrations
in the attainment year and beyond. The commenter then concluded that as
part of any final action, EPA should advise the state that failures to
program sufficient resources to meet CAA requirements in the future
will not be accepted as justification of inadequate or incomplete
demonstrations of attainment.
    Response (MC-14): All states and other entities that conduct
photochemical modeling must address competing priorities and determine
whether additional work will provide significant additional value. They
must consider several factors including the time available for
completion of modeling of episode(s), updating of emissions
inventories, the resources needed to conduct further refinements or
additional episodes, and the overall benefit of delaying the project to
conduct additional modeling work.
    The commenter is correct that modeling is a very resource intensive
process. Photochemical modeling requires creation of very detailed
emission inventories and meteorological modeling to be used in
photochemical modeling in an attempt to replicate a historical event
when ozone exceedances have occurred. Once photochemical modeling has
been created that performs sufficiently well, the basecase modeling can
then be used in conjunction with future case modeling of the same
meteorological conditions to test attainment demonstration strategies.
It often takes many iterations of refinement of emissions and/or
meteorological fields to result in basecase photochemical modeling that
performs sufficiently in

accordance with TCEQ's meteorological performance metrics and EPA model
performance metrics.
    As discussed in the proposal and the MOAAD TSD, TCEQ did consider
and complete exploratory work on other episodes. But initial analyses
indicated that the additional episodes would not give significantly
different results compared to the existing episode. As we explain in
Section 2.3 of the TSD, we believe in this case, the one episode is
acceptable for control strategy development. EPA evaluated the
preliminary analyses of other episodes and concurred that it did not
appear that the additional episodes would alter the model projections
on what was needed to reach attainment.
    EPA believes that the episode selection is appropriate, and that
the modeling was sufficiently robust. The demonstration modeling
combined with the WOE analyses are sufficient to show that the DFW area
will attain by the deadline.
    Comment (MC-15): Commenters indicated that the DFW 8-hr ozone SIP
proposal by TCEQ is significantly flawed and fails to support the
required attainment demonstration by 2010. Commenters continued that
the DFW modeling by TCEQ shows that several ozone monitors in 2010 will
still exceed the rounded-up standard of 84 ppb. A commenter asserts
that the CAA requires that SIPs show clear attainment for all ozone
monitors in a nonattainment area and the reason that the air modeling
shows exceedances in 2010 is because the proposed reductions by TCEQ
are inadequate.
    Commenters also indicated that according to Table 5 of the Federal
Register notice, TCEQ's plan predicts that 2 monitors in the region
would not meet the 8-hour ozone NAAQS after implementation of the
control strategy (PDMR 2009) and consideration of TCEQ's Weight of
Evidence. Commenters continued that they are aware that EPA's ozone
implementation guidance allows a ``Weight of Evidence'' demonstration
to supplement the modeling analysis required by the CAA but assert that
this analysis fails to overcome the inadequacy of the TCEQ's proposed
control strategy to bring the DFW area into attainment.
    Commenters indicated that the proposal establishes repeatedly that
ambient air quality is likely to remain above the artificial rounded-up
standard of 84 ppb (Tables 2, 3 and 5). The commenters went on to
assert that after disclosing that state WOE calculations fall short of
meeting the attainment goal, EPA ultimately relies on their
``simplistic'' analysis concluding that 15% of the NOX
emissions inventory will be reduced by existing measures not present in
2007. The commenters continued that given the degree to which design
values have to fall, from 95 ppb to 84 ppb, and in light of the 2010
attainment date, EPA should consider that the drop in the
NOX and VOC emissions inventories from 2007 to 2009 are
completely insufficient, according to EPA's own studies and guidance,
to bring about the drop in DVs needed to reach attainment. The
commenters further continued that EPA's own analysis of the most recent
TCEQ modeling shows that the State was only able to get all the area's
predicted DVs below 88 ppb with a non-standard and non-approved
calculation of RRF factors and EPA's own analysis with the proper RRF
procedure showed that monitors were still above the 88 ppb threshold.
    A commenter indicated that the WOE approach by the TCEQ is flawed
since it fails to show attainment by 2010 and EPA needs to reject it as
bad science.
    Response (MC-15): We responded to comments on the TCEQ and EPA RRF
methods in a separate response to comments above. Overall, EPA
considered both RRF methods and the results of those methods in our
review. Also, as explained in previous responses, we considered the
results of modeling from both Combo 10 and PDMR 2009 modeling runs.
    EPA disagrees with the commenter that the modeling alone must
demonstrate attainment in order for EPA to approve the attainment
demonstration. EPA discussed both in the DFW MOAAD TSD and the
proposal, EPA's guidance on modeling and WOE usage. As with any
predictive tool, there are inherent uncertainties associated with
photochemical modeling (emission estimates, emission projections,
meteorological modeling, chemical reaction equations and
simplifications, etc.). 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. This was further
updated in 2005 and 2007 for the 1997 8-hour ozone attainment
demonstration procedures to include a WOE analysis as an integral part
of any attainment demonstration due to concerns of modeling
uncertainties. This guidance strongly recommends that all attainment
demonstrations include supplemental analyses beyond the recommended
modeling. These supplemental analyses should provide additional
information such as monitoring data analyses, and emissions and air
quality trends, which help corroborate the overall conclusion from the
photochemical modeling. EPA's modeling guidance specifically recommends
that a WOE analysis be included as part of any attainment demonstration
SIP where the modeling results predict FDVs ranging from 82 to less
than 88 ppb (EPA's 2005 and 2007 A.D. guidance documents). It is
important to note that EPA recommends a WOE analysis even if the
modeling is demonstrating attainment at all the monitors. 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).
    In this case, the commenters are correct that the final modeling
based projections show two monitors above attainment levels. Prior to
conducting the model based projections, the highest modeling values
were 88/89 ppb (TCEQ/EPA RRF method), but after modeling based
adjustments were conducted to account for reduced airport emissions,
DERC usage limitations, and back-up generator reductions, the highest
value using either RRF was 88 ppb. EPA specifically recommends a WOE
analysis be performed when modeling values are within the range
indicated by the DFW analysis.\11\
---------------------------------------------------------------------------

    \11\ The modeling guidance does not specifically preclude the
use of WOE when the modeled values are higher than the recommended
WOE range.
---------------------------------------------------------------------------

    EPA's guidance (2005 A.D. Guidance) does indicate that a local 30%
NOX reduction may only yield a 3-4 ppb change in modeling
values. That assessment was based on coarser resolution photochemical
modeling that is typically less responsive to emission changes than the
finer grid modeling that was used in DFW. Here, EPA is relying on
analyses that were done employing the DFW modeling to determine the
potential change in ozone due to the additional NOX
reductions that are estimated to occur by 2009. Relying on these DFW
analyses, EPA estimates that the 25.4% local DFW area NOX
reductions occurring between 2007 and 2009 would reduce ozone
concentrations by approximately 3-4 ppb. As discussed in detail below,
EPA is considering much more than just the modeling in making our
conclusions on the adequacy of the attainment demonstration and
determining that the 2005-2007 DV of 95 ppb will drop to attainment
levels (84 ppb) in 2009.

    EPA evaluated many factors in the WOE. These items include
reductions not included in the modeling based projections (energy
efficiencies), unquantifiable measures (AirCheckTexas, Dallas
Sustainable Skyline Initiative, etc.), meteorological analyses of
severity of ozone seasons (the base period and recent years, including
2007), most recent monitoring in 2007 (a 4th high of 89 ppb at two
monitors and the other 18 monitors had 4th high values of 87 ppb or
less), the court's vacatur of CAIR, progress in implementing the TERP
program, and progress in implementing the early compliance incentive on
natural gas compressor engines outside the DFW area. The amount of
NOX reductions quantified in the SIP from the 2007 period
that are estimated to occur by 2009 are approximately 15% of the
estimated 2007 EI; these reductions will come from the existing
federal, state, and local measures. When one includes the additional
reductions due to the underestimation of emission reductions from
compressor engines, the backup generators, and the State's progress in
implementing TERP, there would be a 25.4% reduction in NOX
emissions between 2007 and 2009, which could yield approximately a 3-4
ppb drop in ozone based on modeling projections.
    In a response above, we concluded that 2007 had meteorology similar
to normal meteorology. We also examined whether the 2008 data indicates
a trend toward attainment for the area. We examined the 2008
preliminary data, which is awaiting QA/QC. The 2008 preliminary data
show that the DFW area had 4th high values of 85 ppb at two monitors
and at the other 18 monitors, the value was 84 ppb or less. The 2008
preliminary data indicate the 2006-2008 DV is 91 ppb (down from 95 ppb
in using 2005-2007 monitoring data). For the monitor that has the
highest average 4th high values in 2007 and 2008 and is likely to be
the controlling monitor (or one of the highest monitors) for
determining if the area reaches attainment based on 2007-2009 data, the
monitor's DV for the 2007-2009 period would have to be less than 85
ppb. It is important to note that this monitor (Denton) had a
preliminary 4th high value in 2008 of 84 ppb. Considering the 2008
preliminary data with most of the 4th highs of 84 ppb or less, and that
much of the DFW SIP reductions and another year of fleet turnover are
still to occur, the ambient air quality trend strongly supports that
the DFW monitors will reach attainment in 2009. EPA believes that the
closer an area is to its attainment date, the more weight should be
given to the actual ambient data and the expected additional reductions
in considering whether an area will reach attainment.
    We have considered modeling using two emission reduction scenarios
(Combo 10 and PDMR 2009), recognizing that the actual emission control
level would be somewhere in between, and two types of RRF calculations.
We have also considered the impact of additional measures and
reductions documented in the April 23, 2008 letter. With these
adjustments, the modeling is demonstrating 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, after evaluating additional evidence
in a WOE analysis, that the area will attain by its attainment date.
Specifically, we 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 due to
the emission reductions achieved by local and regional rules. We
considered the impact of meteorological adjustments to the design value
projection, which would further indicate the future projections may be
too high. We have recognized emission reduction efforts that have not
been quantified and included in the modeling and model-based WOE
estimates. We also considered and gave significant weight to non-
modeling evidence of recent monitoring and projected NOX
emission changes between 2007 and 2009.
    We have also considered ambient data in 2008 and progress in
implementing control measures in making our final conclusion on the DFW
area's 8-hour Ozone SIP's Attainment Demonstration adequacy. For
example, we weighed a vacatur of the CAIR rules and its potential