```

[Federal Register Volume 79, Number 139 (Monday, July 21, 2014)]
[Proposed Rules]
[Pages 42258-42275]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2014-16575]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R09-OAR-2013-0735; FRL-9913-61-OAR]

Approval of Implementation Plans and Designation of Areas for Air 
Quality Planning Purposes; Las Vegas Valley, Nevada; Redesignation to 
Attainment for PM10

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing to 
approve a revision to the Nevada state implementation plan that 
provides for the maintenance of the national ambient air quality 
standard for particulate matter with an aerodynamic diameter less than 
or equal to a nominal ten micrometers (PM10) in Las Vegas 
Valley for the next ten years and to approve the related motor vehicle 
emissions budgets. Based in part on the proposed approval of the 
PM10 maintenance plan, EPA is also proposing to approve the 
State of Nevada's request for redesignation of Las Vegas Valley to 
attainment for the PM10 standard. Consistent with the 
assumptions of the maintenance plan, EPA is proposing to approve 
revisions to certain local fugitive dust rules to ensure their 
continued applicability after redesignation of the area to attainment. 
Lastly, EPA is proposing to delete the area designation for Las Vegas 
Valley for the revoked national standard for total suspended 
particulate because the designation is no longer necessary.

DATES: Comments must be received on or before August 20, 2014.

ADDRESSES: Submit your comments, identified by Docket ID Number EPA-
R09-OAR-2013-0735, by one of the following methods:
    1. http://www.regulations.gov: Follow the on-line instructions for 
submitting comments.
    2. E-Mail: oconnor.karina@epa.gov.
    3. Mail or Deliver: Karina OConnor (AIR-2), U.S. Environmental 
Protection Agency, Region IX, 75 Hawthorne Street, San Francisco, CA 
94105-3901. Deliveries are only accepted during the Regional Office's 
normal hours of operation.
    Instructions: All comments will be included in the public docket 
without change and may be made available online at http://www.regulations.gov, including any personal information provided, 
unless the comment includes Confidential Business Information (CBI) or 
other information whose disclosure is restricted by statute. 
Information that you consider CBI or otherwise protected should be 
clearly identified as such and should not be submitted through http://www.regulations.gov or email. http://www.regulations.gov is an 
anonymous access system, and EPA will not know your identity or contact 
information unless you provide it in the body of your comment. If you 
send email directly to EPA, your email address will be automatically 
captured and included as part of the public comment. If EPA cannot read 
your comment due to technical difficulties and cannot contact you for 
clarification, EPA may not be able to consider your comment.
    Docket: Documents in the docket for this action are generally 
available electronically at www.regulations.gov and in hard copy at EPA 
Region IX, 75 Hawthorne Street, San Francisco, California. While all 
documents in the docket are listed at www.regulations.gov, some 
information may be publicly available only at the hard copy location 
(e.g., copyrighted material, large maps), and some may not be publicly 
available in either location (e.g., CBI). To inspect the hard copy 
materials, please schedule an appointment during normal business hours 
with the contact listed in the FOR FURTHER INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: Karina O'Connor, Air Planning Office 
(AIR-2), U.S. Environmental Protection Agency, Region IX, (775) 434-
8176, oconnor.karina@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document, whenever ``we,'' 
``us,'' or ``our'' is used, we mean the EPA. This SUPPLEMENTARY 
INFORMATION section is arranged as follows:

Table of Contents

I. Summary of Today's Proposed Action
II. Background
III. Procedural Requirements for Adoption and Submittal of SIP 
Revisions
IV. Substantive Requirements for Redesignation
V. Evaluation of the State's Redesignation Request for the Las Vegas 
Valley PM10 Nonattainment Area
    A. Determination That the Area Has Attained the PM10 
NAAQS.
    B. The Area Must Have a Fully-Approved SIP Meeting Requirements 
Applicable for Purposes of Redesignation Under Section 110 and Part 
D.
    1. Basic SIP Requirements Under CAA Section 110
    2. SIP Requirements Under Part D
    3. Conclusion With Respect to Sections 107(d)(3)(E)(ii) and (v)
    C. The Area Must Show the Improvement in Air Quality Is Due to 
Permanent and Enforceable Emissions Reductions.
    D. The Area Must Have a Fully-Approved Maintenance Plan Under 
CAA Section 175A.
    1. Attainment Inventory
    2. Maintenance Demonstration
    3. Monitoring Network
    4. Verification of Continued Attainment
    5. Contingency Provisions
    6. Subsequent Maintenance Plan Revisions
    7. Motor Vehicle Emissions Budgets
VI. Evaluation of Revisions to Clark County Fugitive Dust Rules
VII. Proposed Deletion of TSP Designation for Las Vegas Valley
VIII. Proposed Action and Request for Public Comment
IX. Statutory and Executive Order Reviews

I. Summary of Today's Proposed Action

    Under Clean Air Act (CAA or ``Act'') section 110(k)(3), EPA is 
proposing to approve a submittal from the Nevada Division of 
Environmental Protection (NDEP) dated September 7, 2012 of the 
Redesignation Request and Maintenance Plan for Particulate Matter 
(PM10), Clark County, Nevada (August 2012) (``Las Vegas Valley 
PM10 Maintenance Plan'') as a revision to the Nevada state 
implementation plan (SIP).
    EPA finds that the Las Vegas Valley PM10 Maintenance 
Plan adequately demonstrates that the area will maintain the 
PM10 national ambient air quality standard (NAAQS or 
``standard'') for 10 years beyond redesignation and includes sufficient 
contingency provisions to promptly correct any violation of the 
PM10 standard which occurs after redesignation and thereby 
meets the requirements for maintenance plans under CAA section 175A. 
EPA is also proposing to approve the motor vehicle emissions budgets 
(MVEBs) in the Las Vegas Valley PM10 Maintenance Plan 
because we find they meet the

[[Page 42259]]

applicable transportation conformity requirements under 40 CFR 
93.118(e).
    Under CAA section 107(d)(3)(D), EPA is also proposing to approve 
NDEP's request to redesignate the Las Vegas Valley PM10 
nonattainment area from ``nonattainment'' to ``attainment'' for the 
PM10 standard. We are doing so based on our conclusion that 
the Las Vegas Valley has attained the PM10 standard; that 
the relevant portions of the Nevada SIP are fully approved; that the 
improvement in air quality is due to permanent and enforceable 
emissions reductions; that the State of Nevada has met all of the 
requirements applicable to the Las Vegas Valley PM10 
nonattainment area with respect to section 110 and part D of the CAA; 
and, based on our proposed approval as described above, that the Las 
Vegas Valley PM10 Maintenance Plan meets the requirements 
for maintenance plans under section 175A of the CAA; and that, 
therefore, the State of Nevada has met the criteria for redesignation 
under CAA section 107(d)(3)(E) for the Las Vegas Valley PM10 
nonattainment area.
    Third, we are proposing to approve certain fugitive dust rules that 
Clark County has amended to ensure their continued applicability after 
the area is redesignated to attainment. NDEP submitted the amended 
rules on May 27, 2014 as a revision to the Nevada SIP.
    Lastly, EPA is proposing to delete the area designation for Las 
Vegas Valley for the revoked NAAQS for total suspended particulate.

II. Background

    On April 30, 1971 (36 FR 8186), pursuant to section 109 of the CAA, 
as amended in 1970, EPA promulgated the original NAAQS for the 
``criteria'' pollutants, which included carbon monoxide, hydrocarbons, 
nitrogen dioxide, photochemical oxidant, sulfur dioxide, and 
particulate matter. The NAAQS are set at concentrations intended to 
protect public health and welfare. The original NAAQS for particulate 
matter was defined in terms of a reference method that called for 
measuring particulate matter up to a nominal size of 25 to 45 
micrometers or microns. This fraction of total ambient particulate 
matter is referred to as ``total suspended particulate'' or TSP. Within 
nine months thereafter, each State was required under section 110 of 
the 1970 amended Act to adopt and submit to EPA a plan, referred to as 
a State Implementation Plan (SIP), which provides for the 
implementation, maintenance, and enforcement of each of the NAAQS 
within each State. The State of Nevada submitted its SIP on January 28, 
1972, and EPA approved it later that year. See 37 FR 10842 (May 31, 
1972).
    Generally, SIPs were to provide for attainment of the NAAQS within 
three years after EPA approval of the plan. However, many areas of the 
country did not attain the NAAQS within the statutory period. In 
response, Congress amended the Act in 1977 to establish a new approach, 
based on area designations, for attaining the NAAQS. Under section 
107(d) of the 1977 amended Act, States were to make recommendations for 
all areas within their borders as attainment, nonattainment, or 
unclassifiable for each of the NAAQS, including TSP, and EPA was to 
designate areas based on those recommendations, as modified if 
appropriate. For the State of Nevada, the State recommended, and EPA 
approved, the use of hydrographic areas as the geographic basis for 
designating air quality planning areas. See 67 FR 12474 (March 19, 
2002). For the TSP NAAQS, EPA designated a number of areas in Nevada as 
``nonattainment,'' including Las Vegas Valley \1\ (hydrographic area 
(HA) 212). See 43 FR 8962, at 9012 (March 3, 1978). The area 
designations for air quality planning purposes within the State of 
Nevada are codified at 40 CFR 81.329.
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    \1\ The Las Vegas Valley encompasses roughly 1,500 square miles 
within Clark County and includes the cities of Las Vegas, North Las 
Vegas, and Henderson. Roughly two million people reside in Clark 
County, mostly within Las Vegas Valley. NDEP is the state agency 
under state law that is responsible for SIP matters for the State of 
Nevada. Within Clark County, the Clark County Board of County 
Commissioners, acting through the Clark County Department of Air 
Quality (Clark County DAQ), is empowered under state law to develop 
air quality plans and to regulate stationary sources within the 
county with the exception of certain types of power plants, which 
lie exclusively within the jurisdiction of NDEP.
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    As amended in 1977, the CAA required States to revise their SIPs by 
January 1979 for all designated nonattainment areas. The various local 
entities and the State of Nevada responded by developing and submitting 
attainment plans for the TSP nonattainment areas, including Las Vegas 
Valley, and in 1981, EPA approved these plans on condition that the 
State submit, within a prescribed period of time, revisions to correct 
certain deficiencies. See 46 FR 21758 (April 14, 1981). In 1982, we 
found that the State had submitted the required revisions correcting 
the identified deficiencies, and we revoked the conditions placed on 
our approval of the TSP plans. See 47 FR 15790 (April 13, 1982).
    In 1987, EPA revised the NAAQS for particulate matter, eliminating 
TSP as the indicator for the NAAQS and replacing it with the 
``PM10'' indicator. See 52 FR 24634 (July 1, 1987). 
PM10 refers to particles with an aerodynamic diameter less 
than or equal to a nominal 10 microns. At that time, EPA established 
two PM10 standards: A 24-hour standard of 150 micrograms per 
cubic meter ([micro]g/m\3\) and an annual standard of 50 [micro]g/
m\3\.\2\ We indicated in the preamble to our regulations implementing 
the then-new PM10 NAAQS that we would consider deletion of 
TSP area designations once EPA had reviewed and approved revised SIPs 
that include control strategies for the PM10 NAAQS and once 
EPA had promulgated PM10 increments for the prevention of 
significant deterioration (PSD) program. See 52 FR 24672, at 24682 
(July 1, 1987).
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    \2\ In 2006, EPA retained the 24-hour PM10 standard 
but revoked the annual PM10 standard. See 71 FR 61144 
(October 17, 2006). More recently, as part of the Agency's periodic 
review of the NAAQS, EPA reaffirmed the 24-hour PM10 
NAAQS. See 78 FR 3086 (January 15, 2013). See 40 CFR 50.6 
(``National primary and secondary ambient air quality standards for 
PM10'').
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    Under our regulations for implementing the revised particulate 
matter NAAQS (i.e., the PM10 NAAQS), EPA did not designate 
areas as nonattainment, attainment, or unclassifiable but categorized 
areas into three groups, referred to as Group I, Group II, or Group 
III. Group I areas were those that had a probability of not attaining 
the PM10 NAAQS (based on existing TSP data) of at least 90%. 
Group I areas were required to submit SIP revisions that contain full 
PM10 control strategies including a demonstration of 
attainment. See 52 FR 24672, at 24681 (July 1, 1987). We identified the 
Las Vegas (HA 212) and Reno (HA 87, known as 
``Truckee Meadows'') planning areas as Group I areas. See 52 FR 29383 
(August 7, 1987) and 55 FR 45799 (October 31, 1990).
    The CAA was significantly amended in 1990. Under the 1990 amended 
Act, Congress replaced the PM10 regulatory approach 
established by EPA in 1987 with the area designation concept and 
designated former ``Group I'' areas and certain other areas as 
nonattainment areas for PM10 by operation of law. See 
section 107(d)(4)(B) of the Act. As former ``Group I'' areas, the Las 
Vegas planning area was designated as nonattainment areas for 
PM10 by operation of law. See 56 FR 11101 (March 15, 1991).
    Las Vegas Valley was initially classified as a ``moderate'' 
PM10 nonattainment area but was later re-classified as a 
``serious'' PM10 nonattainment area. See 58 FR 3334 (January 
8, 1993). States with ``serious''

[[Page 42260]]

PM10 nonattainment areas were required under the CAA, as 
amended in 1990, to submit revisions to their SIPs to, among other 
things, demonstrate attainment of the PM10 standard as 
expeditiously as practicable, but no later than 2001. See CAA section 
188(c). However, EPA is authorized to extend the attainment date for 
such an area by up to 5 years if the State qualifies for an extension 
under the terms specified in the statute. See CAA section 188(e). To 
qualify, among other requirements, a State must demonstrate that the 
plan includes the most stringent measures (MSM) that are included in 
the SIP of any State or are achieved in practice in any State, and can 
feasibly be implemented in the area.
    In 2001, NDEP submitted the PM-10 State Implementation Plan for 
Clark County (June 2001) (``Las Vegas Valley PM10 Attainment 
Plan'') to EPA as a revision to the Nevada SIP to meet the requirements 
for ``serious'' PM10 nonattainment areas. In 2002, NDEP 
submitted certain amendments to the Las Vegas Valley PM10 
Attainment Plan and a set of local fugitive dust rules relied upon by 
the plan. In 2004, EPA approved the Las Vegas Valley PM10 
Attainment Plan, as amended, and the set of fugitive dust rules. See 69 
FR 32273 (June 9, 2004).
    Specifically, as part of our 2004 final action, EPA approved the 
following SIP elements:
     The baseline and projected emissions inventories as 
required under CAA section 172(c)(3);
     The demonstration that attainment of the 24-hour standard 
by December 31, 2001 is impracticable as required under CAA section 
189(b)(1)(A);
     The demonstration that attainment of the 24-hour standard 
will occur by the most expeditious alternative date practicable, in 
this case, December 31, 2006, as required under CAA sections 
189(b)(1)(A) and 188(e);
     The demonstration that the plan includes MSM as required 
under CAA section 188(e);
     The demonstration that the plan provides for 
implementation of best available control measures (BACM) as required 
under CAA section 189(b)(1)(B);
     The demonstration that major sources of PM10 
precursors such as nitrogen oxides and sulfur dioxide do not 
significantly contribute to violations of the PM10 standards 
as authorized under CAA section 189(e);
     The demonstration that the plan provides for reasonable 
further progress and quantitative milestones as required under CAA 
sections 189(c) and 172(c)(2);
     The contingency measures as required under CAA section 
172(c)(9);
     Transportation conformity motor vehicle emissions budgets, 
including a budget of 141.41 tons per day beginning in year 2006; and
     Clark County fugitive dust rules: Section 90 (``Fugitive 
Dust from Open Areas and Vacant Lots''), section 91 (``Fugitive Dust 
from Unpaved Roads, Unpaved Alleys and Unpaved Easement Roads''), 
section 92 (``Fugitive Dust from Unpaved Parking Lots, Material 
Handling & Storage Yards, & Vehicle & Equipment Storage Yards''), 
section 93 (``Fugitive Dust from Paved Roads & Street Sweeping 
Equipment''), and section 94 (``Permitting & Dust Control for 
Construction Activities'').
    As noted above, EPA approved the demonstration in the Las Vegas 
Valley PM10 Attainment Plan of December 31, 2006 as the most 
expeditious practicable alternative attainment date, and in 2010, based 
on a review of the ambient monitoring data for years 2004-2006, EPA 
determined that the Las Vegas Valley PM10 nonattainment area 
had attained the 24-hour PM10 NAAQS by the approved 
alternative attainment date, i.e., December 31, 2006. See 75 FR 45485 
(August 3, 2010).
    On September 7, 2012, NDEP submitted the Las Vegas Valley 
PM10 Maintenance Plan and requested that EPA redesignate the 
Las Vegas Valley PM10 nonattainment area to attainment for 
the 24-hour PM10 NAAQS, and on May 27, 2014, NDEP submitted 
revised versions of Clark County's fugitive dust rules that were 
amended by Clark County to ensure their continued applicability once 
the area is redesignated to attainment. In today's proposed rule, we 
are proposing action on NDEP's September 7, 2012 submittal of the Las 
Vegas Valley PM10 Maintenance Plan and request for 
redesignation to attainment, as well as the amended Clark County 
fugitive dust rules.
    The 1990 Act Amendments also provided for the continued transition 
from TSP to PM10. Specifically, section 107(d)(4)(B) states 
in relevant part: ``Any designation for particulate matter (measured in 
terms of total suspended particulates) that the Administrator 
promulgated pursuant to this subsection (as in effect immediately 
before November 15, 1990) shall remain in effect for purposes of 
implementing the maximum allowable increases in concentrations of 
particulate matter (measured in terms of total suspended particulates) 
pursuant to section 163(b) of this title, until the Administrator 
determines that such designation is no longer necessary for that 
purpose.''
    Section 166(f) of the 1990 amended Act authorizes EPA to replace 
the TSP increments with PM10 increments, and in 1993, EPA 
promulgated the PM10 increments and revised the PSD 
regulations accordingly. See 58 FR 31622 (June 3, 1993). In our June 
1993 final rule, we indicated that the replacement of the TSP 
increments with PM10 increments negates the need for the TSP 
attainment or unclassifiable area designations to be retained. We also 
indicated that we would delete such TSP designations in 40 CFR part 81 
upon the occurrence of, among other circumstances, EPA's approval of a 
State's or local agency's revised PSD program containing the 
PM10 increments. See 58 FR 31622, at 31635 (June 3, 1993).
    In November 2002, we deleted the TSP attainment or unclassifiable 
area designations throughout the State of Nevada, except for those in 
Clark County. See 67 FR 68769 (November 13, 2002). In April 2013, we 
deleted the TSP attainment or unclassifiable area designations within 
Clark County and deleted the TSP nonattainment area designations for 
all of the Nevada TSP nonattainment areas, except for the Las Vegas 
planning area (i.e., HA 212, Las Vegas Valley) and the Reno 
planning area (i.e., HA 87, Truckee Meadows).\3\ See 78 FR 
22425 (April 16, 2013). In today's proposed rule, we are proposing to 
delete the TSP nonattainment area designation for Las Vegas Valley.
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    \3\ In June 1992, the State of Nevada requested that we 
reclassify the eight existing TSP nonattainment areas in Nevada to 
``unclassifiable'' status. See letter from L.H. Dodgion, 
Administrator, NDEP, to Daniel W. McGovern, Regional Administrator, 
EPA Region IX, dated June 15, 1992. We believe that deletion of the 
TSP nonattainment designations is administratively more efficient 
than redesignation of the area to unclassifiable. As noted above, we 
have already deleted six of the TSP nonattainment area designations 
and are proposing to delete the one for Las Vegas Valley herein. We 
will consider deletion of the one other remaining TSP area 
designation, i.e., the TSP designation for Reno (HA 87, 
Truckee Meadows), in a future rulemaking.
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III. Procedural Requirements for Adoption and Submittal of SIP 
Revisions

    Sections 110(a)(1) and 110(l) of the Act require States to provide 
reasonable notice and public hearing prior to adoption of SIP 
revisions. In this action, we are proposing action on NDEP's September 
7, 2012 submittal of the Las Vegas Valley PM10 Maintenance 
Plan (August 2012) as a revision to the Nevada SIP.\4\ We are also 
proposing action on NDEP's May 27, 2014

[[Page 42261]]

submittal of Clark County's amended fugitive dust rules as a revision 
to the Nevada SIP. These two submittals contain documentation of the 
public review process followed by Clark County and NDEP in adopting the 
SIP revisions prior to submittal to EPA. As discussed below, the 
documentation provides sufficient evidence that reasonable notice of 
public hearings was provided to the public and that public hearings 
were conducted prior to adoption.
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    \4\ NDEP's September 7, 2012 submittal of the Las Vegas Valley 
PM10 Maintenance Plan became complete by operation of law 
on March 7, 2013.
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    NDEP's submittal of the Las Vegas Valley PM10 
Maintenance Plan includes a letter dated August 27, 2012 from Lewis 
Wallenmeyer, Director, Clark County Department of Air Quality (Clark 
County DAQ), to Colleen Cripps, Administrator, NDEP, submitting the Las 
Vegas Valley PM10 Maintenance Plan and redesignation request 
to NDEP. NDEP's letter dated September 7, 2012 transmitting the plan to 
EPA and requesting that EPA approve the plan and redesignation request 
constitutes NDEP's adoption of the plan as a revision to the Nevada 
SIP.
    Appendix B (``Documentation of the Public Review Process'') of the 
Las Vegas Valley PM10 Maintenance Plan includes a copy of 
the notice to the public published in a newspaper of general 
circulation on January 15, 2012 announcing a 30-day comment period on 
the proposed Las Vegas Valley PM10 Maintenance Plan and a 
public hearing after the close of the comment period; a copy of 
comments received and Clark County DAQ's responses; various web notices 
issued by Clark County DAQ in connection with review of the proposed 
plan; and documentation of the public hearing on the proposed plan and 
subsequent adoption of the plan by the Clark County Board of County 
Commissioners on August 21, 2012. These materials adequately document 
the public review process followed by Clark County in adopting the plan 
prior to transmittal to NDEP and provide sufficient evidence that 
reasonable notice of a public hearing was provided to the public and 
that a public hearing was conducted prior to adoption.
    NDEP's May 27, 2014 submittal of Clark County's amended fugitive 
dust rules includes documentation of the public process used by Clark 
County to adopt the changes, including publication of notice of a 30-
day public review and comment period (February 22, 2014-March 25, 2014) 
and related public hearing in a newspaper of general circulation. As 
documented in the submittal, Clark County Board of County Commissioners 
adopted the amendments on April 15, 2014, effective April 29, 2014.
    Based on the documentation included in NDEP's submittals, discussed 
above, we find that the submittals of the Las Vegas Valley 
PM10 Maintenance Plan and the amended fugitive dust rules as 
SIP revisions satisfy the procedural requirements of sections 110(a) 
and 110(l) of the Act for revising SIPs.

IV. Substantive Requirements for Redesignation

    The CAA establishes the requirements for redesignation of a 
nonattainment area to attainment. Specifically, section 107(d)(3)(E) 
allows for redesignation provided that the following criteria are met: 
(1) EPA determines that the area has attained the applicable NAAQS; (2) 
EPA has fully approved the applicable implementation plan for the area 
under section 110(k); (3) EPA determines that the improvement in air 
quality is due to permanent and enforceable reductions in emissions 
resulting from implementation of the applicable SIP, applicable federal 
air pollution control regulations, and other permanent and enforceable 
reductions; (4) EPA has fully approved a maintenance plan for the area 
as meeting the requirements of CAA section 175A; and (5) the State 
containing such area has met all requirements applicable to the area 
under section 110 and part D of the CAA.
    EPA provided guidance on redesignations in a document titled, 
``State Implementation Plans; General Preamble for the Implementation 
of Title I of the Clean Air Act Amendments of 1990,'' published in the 
Federal Register on April 16, 1992 (57 FR 13498), and supplemented on 
April 28, 1992 (57 FR 18070). Other relevant EPA guidance documents 
include: ``Procedures for Processing Requests to Redesignate Areas to 
Attainment,'' Memorandum from John Calcagni, Director, Air Quality 
Management Division, EPA Office of Air Quality Planning and Standards, 
September 4, 1992 (referred to herein as the ``Calcagni memo''); ``Part 
D New Source Review (part D NSR) Requirements for Areas Requesting 
Redesignation to Attainment,'' Memorandum from Mary D. Nichols, 
Assistant Administrator for Air and Radiation, October 14, 1994; and 
``State Implementation Plans for Serious PM10 Nonattainment 
Areas, and Attainment Date Waivers for PM10 Nonattainment 
Areas Generally; Addendum to the General Preamble for the 
Implementation of title I of the Clean Air Act Amendments of 1990,'' 59 
FR 41998 (August 16, 1994).
    For the reasons set forth below in section V of this document, we 
propose to approve NDEP's request for redesignation of the Las Vegas 
Valley PM10 nonattainment area to attainment for the 24-hour 
PM10 NAAQS based on our conclusion that all of the criteria 
under CAA section 107(d)(3)(E) have been satisfied.

V. Evaluation of the State's Redesignation Request for the Las Vegas 
Valley PM10 Nonattainment Area

A. Determination That the Area Has Attained the PM10 NAAQS

    CAA section 107(d)(3)(E)(i) states that, for an area to be 
redesignated to attainment, EPA must determine that the area has 
attained the relevant NAAQS. In this case, the relevant NAAQS is the 
PM10 NAAQS. As noted above, in 2010, EPA determined that the 
Las Vegas Valley nonattainment area attained the PM10 
standard by the area's applicable attainment date of December 31, 2006 
based on data for years 2004-2006. Today's action updates this 
determination based on the most recent available PM10 
monitoring data.
    Generally, EPA determines whether an area's air quality is meeting 
the 24-hour PM10 NAAQS based upon complete,\5\ quality-
assured, and certified data gathered at established state and local air 
monitoring stations (SLAMS) in the nonattainment area and entered into 
the EPA Air Quality System (AQS) database. EPA will consider air 
quality data from air monitoring stations other than SLAMS in the 
nonattainment area provided those stations meet the federal monitoring 
requirements for SLAMS, including the quality assurance and quality 
control criteria in 40 CFR part 58, appendix A. See 40 CFR 58.20; 71 FR 
61236, 61242; (October 17, 2006).
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    \5\ For PM10, a complete set of data includes a 
minimum of 75 percent of the scheduled PM10 samples per 
quarter. See 40 CFR part 50, Appendix K, section 2.3(a).
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    Data from air monitors operated by state, local, or tribal agencies 
in compliance with EPA monitoring requirements must be submitted to 
AQS. These monitoring agencies certify annually that these data are 
accurate to the best of their knowledge. Accordingly, EPA relies 
primarily on data in AQS when determining the attainment status of an 
area. See 40 CFR 50.6; 40 CFR part 50, appendices J and K; 40 CFR part 
53; and, 40 CFR part 58, appendices A, C, D, and E. All valid data are 
reviewed to determine the area's air quality status in accordance with 
40 CFR part 50, appendix K.
    Attainment of the 24-hour PM10 standard is determined by 
calculating the expected number of exceedances of the standard in a 
year. The 24-hour PM10 standard is attained when the

[[Page 42262]]

expected number of exceedances averaged over a three-year period is 
less than or equal to one at each monitoring site within the 
nonattainment area. Three consecutive years of air quality data are 
required to show attainment of the 24-hour PM10 standard. 
See 40 CFR part 50 and appendix K. More than three years may be 
considered if all additional representative years of data meeting the 
75 percent criterion are utilized. Data not meeting these criteria may 
also suffice to show attainment; however, such exceptions must be 
approved by the appropriate Regional Administrator in accordance with 
EPA guidance. See 40 CFR part 50, appendix K, section 2.3.
    Clark County DAQ is responsible for monitoring ambient air quality 
within Clark County. Clark County submits annual monitoring network 
plans to EPA. These network plans describe the monitoring network 
operated by Clark County DAQ within Clark County. These plans discuss 
the status of the air monitoring network, as required under 40 CFR 
58.10.
    EPA regularly reviews these annual plans for compliance with the 
applicable reporting requirements in 40 CFR part 58. With respect to 
PM10, EPA has found that the area's network plans meet the 
applicable reporting requirements under 40 CFR part 58.\6\ EPA also 
concluded from its 2012 Technical System Audit that Clark County DAQ's 
monitoring network currently meets or exceeds the requirements for the 
minimum number of SLAMS for PM10 in the Las Vegas Valley 
nonattainment area.\7\ Clark County DAQ annually certifies that the 
data it submits to AQS are complete and quality-assured.\8\
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    \6\ See, e.g., letter from Meredith Kurpius, Manager, Air 
Quality Analysis Office, EPA Region IX, to Phil Wiker, Engineering 
Manager, Clark County DAQ, dated December 11, 2013, approving the 
relevant portions of Clark County DAQ's 2013 Annual Network Plan.
    \7\ See EPA Region IX, Technical System Audit Report, Clark 
County Department of Air Quality Ambient Air Monitoring Program, 
July 26-July 27, 2012, Final report, July 2013, page 8. Enclosed 
with letter from Deborah Jordan, Director, Air Division, U.S. EPA 
Region IX, to Lewis Wallenmeyer, Clark County DAQ (August 1, 2013).
    \8\ See, e.g., letter from Lewis Wallenmeyer, Clark County DAQ, 
to Fletcher Clover, Air Quality Analysis Office, EPA Region IX, 
certifying 2013 ambient air quality data and quality assurance data 
(April 22, 2014).
---------------------------------------------------------------------------

    During the 2004-2006 period, Clark County DAQ operated 13 
PM10 SLAMS monitoring sites within Las Vegas Valley. See 75 
FR 45485, at 45488 (August 3, 2010). Between 2006 and 2009, four of the 
sites were closed or stopped monitoring PM10. In 2010, Clark 
County DAQ discontinued PM10 monitoring at three more sites: 
Lone Mountain (northwest Las Vegas), Orr School (central-southeast Las 
Vegas), and Craig Road (North Las Vegas).\9\ Notwithstanding the 
decrease in the number of PM10 monitoring sites, Clark 
County DAQ continues to meet EPA requirements for the minimum number of 
PM10 monitoring sites in Clark County.
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    \9\ EPA has approved Clark County DAQ's discontinuation of 
PM10 monitoring at these sites. See letter from Matthew 
Lakin, U.S. EPA Region IX, to Mike Sword, Clark County DAQ (June 5, 
2013) (Lone Mountain and Orr sites), and letter from Meredith 
Kurpius, U.S. EPA Region IX, to Mike Sword, Clark County DAQ 
(October 30, 2013) (Craig Road site).
---------------------------------------------------------------------------

    In 2012, Clark County DAQ established a new PM10 
monitoring site,\10\ and thus, at the present time, Clark County DAQ 
operates seven PM10 SLAMS monitoring sites within Las Vegas 
Valley: Green Valley (Henderson), J.D. Smith School (North Las Vegas), 
Joe Neal (northwest Las Vegas), Paul Meyer Park (southwest Las Vegas), 
Palo Verde School (west Las Vegas), Sunrise Acres School (central Las 
Vegas), and Jerome Mack (east Las Vegas).\11\ All seven sites monitor 
PM10 concentrations on a continuous, year-round basis using 
beta attenuation methods. See Clark County DAQ's Annual Monitoring 
Network Plan Report (June 2013). Each of these methods has been granted 
the Federal Equivalent Method (FEM) designation by EPA. The 
PM10 monitoring sites have been established to monitor for 
population exposure in the middle or neighborhood scale.\12\
---------------------------------------------------------------------------

    \10\ The new site is the Jerome Mack site, AQS ID: 32-003-0540. 
In addition, in 2013, the Las Vegas Paiute tribe began monitoring 
for PM10 at an eighth site within the Las Vegas Valley 
PM10 nonattainment area. This eighth site has not been 
approved by EPA for NAAQS compliant monitoring.
    \11\ Figure 2-1 of the Las Vegas Valley PM10 
Maintenance Plan illustrates the locations of Clark County DAQ 
PM10 monitoring sites (other than Jerome Mack).
    \12\ In this context, ``middle scale'' refers to conditions 
characteristic of areas from 100 meters to half a kilometer, and 
``neighborhood scale'' refers to conditions throughout some 
reasonably homogeneous urban sub-region with dimensions of a few 
kilometers. See 40 CFR part 58, appendix D, section 4.6.
---------------------------------------------------------------------------

    Consistent with the requirements contained in 40 CFR part 50, EPA 
has reviewed the quality-assured and certified PM10 ambient 
air monitoring data as recorded in AQS for the applicable monitoring 
period collected at the monitoring sites in the Las Vegas Valley 
nonattainment area and determined that the data are of sufficient 
completeness for the purposes of making comparisons with the 
PM10 standards.
    EPA's review of monitoring data for the PM10 standard 
for Las Vegas Valley includes exceedances of the standard recorded 
during the 2011-2013 time period. However, EPA is excluding the 
exceedances of the standard in 2011 from the attainment determination 
presented herein because they were the result of an exceptional event. 
On April 16, 2014 Clark County DAQ submitted a demonstration for a high 
wind PM10 exceptional event covering the two exceedances 
recorded on July 3, 2011 at the J.D. Smith and Sunrise Acres monitoring 
sites. EPA reviewed the documentation that Clark County DAQ provided to 
demonstrate that the exceedances on these days meet the criteria for an 
exceptional event under EPA's Exceptional Events Rule (EER).\13\ EPA 
concurred with Clark County DAQ's request for exceptional event 
determination that, based on the weight of evidence, the two 
exceedances were caused by a high wind exceptional event.\14\ 
Accordingly, EPA has determined that the monitored exceedances 
associated with this exceptional event should be excluded from use in 
determinations of exceedances and violations, including the evaluation 
of whether Las Vegas Valley has attained the standard for the purposes 
of redesignation under CAA section 107(d)(3)(E)(i).
---------------------------------------------------------------------------

    \13\ 40 CFR 50.1(j), (k), (l); 50.14; 51.930.
    \14\ See letter from Jared Blumenfeld, EPA Region IX, to Lewis 
Wallenmeyer, Clark County DAQ, dated June 25, 2014.
---------------------------------------------------------------------------

    Table 1 below shows the maximum 24-hour PM10 
concentrations monitored at the seven PM10 sites over the 
most recent three-year period (2011-2013) and lists the calculated 
expected exceedances per year at each of the sites over that same 
period. As shown in table 1 below, exceedances were monitored at four 
of the sites in 2012, and at all of the sites in 2013. All of the 
exceedances in 2012 were recorded on May 10, 2012, and all of the 
exceedances in 2013 were recorded on two days, April 15 and October 28, 
2013. Clark County DAQ has flagged these exceedances as exceptional 
events. As noted above in connection with the 2011 exceedances, if EPA 
concurs on exceedances as exceptional events, they are excluded from 
the determination of whether the area is attaining the NAAQS, but EPA 
has not taken action to concur on any of the exceedances in 2012 or 
2013, and thus, the 2012 and 2013 exceedances are not being excluded 
from today's evaluation.

[[Page 42263]]

                                          Table 1--Summary of Las Vegas Valley PM10 Monitoring Data, 2011-2013
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                            Highest 24-hour PM10 concentration ([mu]g/    2nd Highest 24-hour PM10 concentration ([mu]g/     Expected
                                                               m\3\)                                           m\3\)                        exceedances
    Monitoring site  (AQS Monitor ID)    ------------------------------------------------------------------------------------------------    per year
                                                                                                                                         ---------------
                                               2011            2012            2013            2011            2012            2013          2011-2013
--------------------------------------------------------------------------------------------------------------------------------------------------------
Green Valley (32-003-0298)..............             143             145         \b\ 196              82             125              88             0.3
J.D. Smith (32-003-2002)................              71         \b\ 203         \b\ 237              66              82         \b\ 169             1.0
Jerome Mack (32-003-0540)...............              NA         \b\ 228         \b\ 243              NA             138             121         \a\ 0.7
Joe Neal (32-003-0075)..................             130         \b\ 182         \b\ 226             100              88             131             0.7
Palo Verde (32-003-0073)................              89             138         \b\ 212              43              94             119             0.3
Paul Meyer (32-003-0043)................             103             147         \b\ 164              62             139              74             0.3
Sunrise Acres (32-003-0561).............              85         \b\ 211         \b\ 267              66              81             136             0.7
--------------------------------------------------------------------------------------------------------------------------------------------------------
NA = Not applicable. The Jerome Mack site opened in 2012.
\a\ The listed design value is not valid because it does not meet completeness requirements.
\b\ Values represent exceedances of the 150 [mu]g/m\3\ NAAQS. Violations occur when the ``expected exceedances per year'' averaged over a three-year
  period exceed 1.0.
Source: Letter and attachments from Lewis Wallenmeyer, Clark County DAQ, to Fletcher Clover, Air Quality Analysis Office, EPA Region IX, certifying 2013
  ambient air quality data and quality assurance data (April 22, 2014).

    Based on a review of air quality data during the most recent 
complete three-year period (2011-2013) (summarized above in table 1) 
and without excluding the 2012 or 2013 exceedances, we find that the 
expected number of exceedances per year for Las Vegas Valley is 1.0 
days per year (based on the J.D. Smith monitoring site). The 24-hour 
PM10 standard is attained when the expected number of 
exceedances averaged over a three-year period is less than or equal to 
one at each monitoring site within the nonattainment area. Therefore, 
we find that, based on complete, quality-assured, and certified data 
for three most recent years (2011-2013) that the Las Vegas Valley 
PM10 nonattainment area has attained the 24-hour 
PM10 standard. SLAMS data for 2014 are not yet available 
from these monitoring sites but will be reviewed prior to final action 
to ensure that they are consistent with continued attainment.

B. The Area Must Have a Fully Approved SIP Meeting Requirements 
Applicable for Purposes of Redesignation Under Section 110 and Part D

    Section 107(d)(3)(E)(ii) and (v) require EPA to determine that the 
area has a fully-approved applicable SIP under section 110(k) that 
meets all applicable requirements under section 110 and part D for the 
purposes of redesignation.
1. Basic SIP Requirements Under CAA Section 110
    Section 110(a)(2) sets forth the general elements that a SIP must 
contain in order to be fully approved. Although section 110(a)(2) was 
amended in 1990, a number of the requirements did not change in 
substance, and therefore, EPA believes that the pre-amendment EPA-
approved SIP met these requirements in Clark County with respect to 
PM10. As to those requirements that were amended, (see 57 FR 
27936 and 27939, June 23, 1992), many are duplicative of other 
requirements of the Act.
    On numerous occasions over the past 38 years, NDEP has submitted, 
and we have approved, provisions addressing the basic CAA section 110 
provisions. The Clark County portion of the approved Nevada SIP 
contains enforceable emission limitations; requires monitoring, 
compiling and analyzing of ambient air quality data; requires 
preconstruction review of new or modified stationary sources; provides 
for adequate funding, staff, and associated resources necessary to 
implement its requirements; and provides the necessary assurances that 
the State maintains responsibility for ensuring that the CAA 
requirements are satisfied in the event that Clark County is unable to 
meet its CAA obligations.\15\
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    \15\ The applicable SIP for NDEP and Clark County may be found 
at http://yosemite.epa.gov/r9/r9sips.nsf/allsips?readform&state=Nevada. We note that SIPs must be fully 
approved only with respect to applicable requirements for purposes 
of redesignation in accordance with section 107(d)(3)(E)(ii). Thus, 
for example, CAA section 110(a)(2)(D) requires that SIPs contain 
certain measures to prevent sources in a state from significantly 
contributing to air quality problems in another state. However, the 
section 110(a)(2)(D) requirements for a state are not linked with a 
particular nonattainment area's designation and classification in 
that state. EPA believes that the requirements linked with a 
particular nonattainment area's designation and classification are 
the relevant measures to evaluate in reviewing a redesignation 
request. The transport SIP submittal requirements, where applicable, 
continue to apply to a state regardless of the designation of any 
one particular area in the state.
    Thus, we do not believe that these requirements should be 
construed to be applicable requirements for purposes of 
redesignation. In addition, EPA believes that the other section 110 
elements not connected with nonattainment plan submissions and not 
linked with an area's attainment status are not applicable 
requirements for purposes of redesignation. The State will still be 
subject to these requirements after Las Vegas Valley is 
redesignated. The section 110 and part D requirements, which are 
linked with a particular area's designation and classification, are 
the relevant measures to evaluate in reviewing a redesignation 
request. This policy is consistent with EPA's existing policy on 
applicability of conformity (i.e., for redesignations) and 
oxygenated fuels requirement. See Reading, Pennsylvania, proposed 
and final rulemakings 61 FR 53174-53176 (October 10, 1996), 62 FR 
24826 (May 7, 1997); Cleveland-Akron-Lorain, Ohio, final rulemaking 
61 FR 20458 (May 7, 1996); and Tampa, Florida, final rulemaking 60 
FR 62748 (December 7, 1995). See also the discussion of this issue 
in the Cincinnati redesignation at 65 FR 37890 (June 19, 2000), in 
the Pittsburgh redesignation at 66 FR 53099 (October 19, 2001), and 
in the Los Angeles redesignation at 72 FR 6986 (February 14, 2007) 
and 72 FR 26718 (May 11, 2007). EPA believes that section 110 
elements not linked to the area's nonattainment status are not 
applicable for purposes of redesignation.
---------------------------------------------------------------------------

    There are no outstanding or disapproved applicable SIP submittals 
with respect to the Clark County portion of the SIP that prevent 
redesignation of the Las Vegas Valley PM10 nonattainment 
area for the 24-hour PM10 standard.\16\ Therefore, we find 
that

[[Page 42264]]

NDEP and Clark County have met all SIP requirements for Clark County 
applicable for purposes of redesignation under section 110 of the CAA 
(General SIP Requirements).
---------------------------------------------------------------------------

    \16\ In 2012, EPA took final limited approval and limited 
disapproval action on updated new source review (NSR) rules adopted 
by Clark County and submitted as a revision to the Nevada SIP (77 FR 
64039, October 18, 2012) and issued a partial approval and partial 
disapproval of Nevada's ``infrastructure'' SIP for the 1997 8-hour 
ozone NAAQS and the 1997 and 2006 PM2.5 NAAQS (77 FR 
64737, October 23, 2012). While these two final rules are not full 
approvals, they do not represent an obstacle to redesignation of the 
Las Vegas Valley PM10 nonattainment area because the 
``infrastructure'' SIP elements that EPA disapproved are not related 
to the nonattainment SIP requirements for the Las Vegas Valley 
PM10 nonattainment area and thus are not relevant for the 
purposes of redesignation and because, notwithstanding the limited 
approval and limited disapproval of the amended NSR rules, the Clark 
County DAQ NSR rules continue to meet the fundamental SIP 
requirements for NSR in ``serious'' PM10 nonattainment 
areas.
---------------------------------------------------------------------------

2. SIP Requirements Under Part D
Part D Requirements Other Than NSR or Conformity
    Subparts 1 and 4 of part D, title I of the CAA contain air quality 
planning requirements for PM10 nonattainment areas. Subpart 
1 contains general requirements for all nonattainment areas of any 
pollutant, including PM10, governed by a NAAQS. The subpart 
1 requirements include, in relevant part, provisions for emissions 
inventories, reasonable further progress (RFP), a program for 
preconstruction review and permitting of new or modified major 
stationary sources (``New Source Review,'' or NSR), contingency 
measures, and conformity.
    Subpart 4 contains specific SIP requirements for PM10 
nonattainment areas. The requirements set forth in CAA sections 189(a), 
(c), and (e) apply specifically to ``moderate'' PM10 
nonattainment areas and include, in relevant part: (1) Provisions for 
implementation of reasonably available control measures (RACM); (2) 
quantitative milestones demonstrating RFP toward attainment by the 
applicable attainment date; and (3) provisions to ensure that the 
control requirements applicable to major stationary sources of 
PM10 also apply to major stationary sources of 
PM10 precursors except where EPA has determined that such 
sources do not contribute significantly to PM10 levels that 
exceed the NAAQS in the area. Under CAA section 189(b), ``serious'' 
PM10 nonattainment areas, such as Las Vegas Valley, must 
meet the ``moderate'' area requirements discussed above and, in 
addition, must develop and submit an attainment demonstration as well 
as provisions to assure the implementation of best available control 
measures (BACM) for the control of PM10.
    As noted previously, in 2004, EPA approved the PM-10 State 
Implementation Plan for Clark County (June 2001) (``Las Vegas Valley 
PM10 Attainment Plan'') as a revision to the Nevada SIP. See 
69 FR 32273 (June 9, 2004). The Las Vegas Valley PM10 
Attainment Plan was developed to meet the SIP requirements for 
``serious'' PM10 nonattainment areas under subparts 1 and 4 
of part D, except those related to NSR or conformity. More 
specifically, as part of our 2004 final action, EPA approved the Las 
Vegas Valley PM10 Attainment Plan as meeting the following 
requirements: Baseline and projected emissions inventories as required 
under CAA section 172(c)(3); the demonstration that the plan provides 
for RFP and quantitative milestones as required under CAA sections 
172(c)(2) and 189(c); the contingency measures as required under CAA 
section 172(c)(9); the demonstration that major sources of 
PM10 precursors such as nitrogen oxides and sulfur dioxide 
do not significantly contribute to violations of the PM10 
standards as provided in CAA section 189(e); the attainment 
demonstration under CAA sections 189(b)(1)(A); and the demonstration 
that the plan provides for implementation of BACM as required under CAA 
section 189(b)(1)(B). Because the demonstration of BACM subsumes the 
demonstration of RACM, a separate analysis to determine if the measures 
represent a RACM level of control was not necessary. EPA's approval of 
the BACM demonstration in the Las Vegas Valley PM10 
Attainment Plan, therefore, also represented a finding that the plan 
provides for the implementation of RACM as required under CAA section 
189(a)(1)(C). See 69 FR 32273 (June 9, 2004).
    Thus, for the reasons given above, and excluding NSR and 
conformity, which we address separately below, we find that Clark 
County has a fully-approved PM10 SIP with respect to the 
part D requirements for RACM, BACM, and other serious PM10 
area SIP requirements.
Permits for New and Modified Major Stationary Sources
    To meet the requirements of CAA sections 172(c)(5) and 
189(a)(1)(A), states must submit SIP revisions that meet the 
requirements under 40 CFR 51.165 (``Permit requirements''). Under 40 
CFR 51.165, states are required to submit SIP revisions that establish 
certain requirements for new or modified stationary sources in 
nonattainment areas, including provisions to ensure that major new 
sources or major modifications of existing sources of nonattainment 
pollutants incorporate the highest level of control, referred to as the 
Lowest Achievable Emission Rate (LAER), and that increases in emissions 
from such stationary sources are offset so as to provide for reasonable 
further progress towards attainment in the nonattainment area. See CAA 
section 173(a)(1)(A) and 40 CFR 51.165(a)(9)(ii)(A).
    The process for reviewing permit applications and issuing permits 
for new or modified stationary sources of air pollution is referred to 
as ``New Source Review'' (NSR). With respect to nonattainment 
pollutants in nonattainment areas, this process is referred to as 
``nonattainment NSR.'' With respect to pollutants for which an area is 
designated as attainment or unclassifiable, states are required to 
submit SIP revisions that ensure that major new stationary sources and 
major modifications of existing stationary sources meet the Federal 
requirements for Prevention of Significant Deterioration (PSD), 
including application of ``best available control technology,'' for 
each applicable pollutant emitted in significant amounts, among other 
requirements.
    Within the Las Vegas PM10 nonattainment area, two 
agencies are responsible for meeting the requirements for nonattainment 
NSR and PSD: NDEP and Clark County DAQ. Under Nevada law, exclusive 
NDEP jurisdiction extends to specific electric steam-generating 
emission units (i.e., power plants) throughout the State of Nevada, and 
thus, state regulations govern air pollution permits issued to those 
types of units within Clark County. Clark County DAQ is responsible for 
all other stationary source emissions units within Clark County, and 
Clark County regulations govern air pollutant permits issued to them.
    With respect to those sources that are under State jurisdiction, we 
have approved a State rule (Nevada Administrative Code (NAC) section 
445B.22083) that prohibits new power plants or major modifications to 
existing power plants under State jurisdiction within the Las Vegas 
Valley nonattainment area. See 69 FR 31056, 31059 (June 2, 2004) and 69 
FR 54006, at 54017 (September 7, 2004). In 2008, we approved an amended 
version of NAC section 445B.22083 that clarifies the application of NSR 
requirements to any relocation of power generating units. See 73 FR 
20536 (April 16, 2008).

[[Page 42265]]

The submittal and approval of the State's prohibition on new major 
power plants or major modifications to existing power plants in Las 
Vegas Valley adequately substitutes for submittal and approval of a SIP 
revision meeting nonattainment NSR requirements in Las Vegas Valley 
with respect to sources under NDEP jurisdiction.
    With respect to sources under Clark County DAQ jurisdiction, we 
approved Clark County's NSR rules as meeting the requirements of 
section 172(c)(5) and, for PM10, section 189(a)(1)(A). See 
69 FR 54006 (September 7, 2004); also, see our proposed rule at 69 FR 
31056, at 31059 (June 2, 2004) for details on how Clark County's NSR 
rules complied with CAA requirements for PM10 nonattainment 
areas. In recent years, Clark County DAQ has adopted comprehensive 
changes to its NSR program and, in 2012, EPA issued a limited approval 
and limited disapproval for the revised program. See 77 FR 64039 
(October 18, 2012). With respect to nonattainment NSR, EPA found a 
number of deficiencies; however, the Clark County NSR rules continue to 
meet the basic requirements for a serious PM10 nonattainment 
NSR area, including a definition of ``major stationary source'' as a 
stationary source which emits, or has the potential to emit, seventy 
(70) tons per year or more of PM10, emissions limitations 
that constitute LAER, and emissions reductions to offset emissions 
increases that would otherwise occur.\17\ See Clark County section 
12.3.2 (``Definitions,'' subsection (y) ``Major Stationary Source''); 
12.3.5.2 (``Permit Requirements to Achieve LAER''); and 12.3.6 
(``Emissions Offset'').
---------------------------------------------------------------------------

    \17\ The deficiencies that have any bearing on PM10 
are limited to a few definitions: ``allowable emissions,'' 
``baseline actual emissions,'' ``net emissions increase,'' and 
``major modification.'' See 77 FR 64039, at 64047 (October 18, 
2012).
---------------------------------------------------------------------------

    Moreover, Clark County's SIP-approved NSR rules have served as a 
federally-enforceable constraint on the growth of stationary source 
emissions, and thus have supported the region's efforts to lower 
ambient PM10 concentrations in Las Vegas Valley. Therefore, 
given the prohibition on new sources or major modifications of existing 
sources under NDEP jurisdiction and given that the fundamental 
nonattainment NSR requirements are approved into the SIP for sources 
under Clark County DAQ jurisdiction, we conclude that the State has met 
the applicable NSR requirements for the Las Vegas PM10 
nonattainment area for the purposes of redesignation of the area to 
attainment for the PM10 standard.
General and Transportation Conformity Requirements
    Under section 176(c) of the Clean Air Act Amendments of 1990, 
States are required to establish criteria and procedures to ensure that 
Federally supported or funded projects conform to the air quality 
planning goals in the applicable SIP. Section 176(c) further provided 
that State conformity provisions must be consistent with Federal 
conformity regulations that the CAA required EPA to promulgate. EPA's 
conformity regulations are codified at 40 CFR part 93, subparts A 
(referred to herein as ``transportation conformity'') and B (referred 
to herein as ``general conformity''). Transportation conformity applies 
to transportation plans, programs, and projects developed, funded, and 
approved under title 23 U.S.C. or the Federal Transit Act, and general 
conformity applies to all other Federally-supported or funded projects. 
SIP revisions intended to address the conformity requirements are 
referred to herein as ``conformity SIPs.''
    In November 2008, EPA approved Clark County's transportation 
conformity criteria and procedures as meeting the related SIP 
requirements under part 51, subpart T (``Conformity to State or Federal 
Implementation Plans of Transportation Plans, Programs, and Projects 
Developed, Funded or Approved Under Title 23 U.S.C. or the Federal 
Transit Laws''). See 73 FR 66182 (November 7, 2008).
    In August 2005, Congress passed the Safe, Accountable, Flexible, 
Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU), 
which eliminated the requirement for States to adopt and submit 
conformity SIPs addressing general conformity requirements. See 75 FR 
17254 (April 5, 2010) for conforming changes to EPA's general 
conformity regulations. Based on our approval of Clark County's 
transportation conformity SIP and SAFETEA-LU's elimination of the 
general conformity SIP requirement, we find that Clark County and the 
State have met the requirements for conformity SIPs in the Las Vegas 
Valley PM10 nonattainment area under CAA section 176(c). In 
any event, EPA believes it is reasonable to interpret the conformity 
requirements as not applicable for purposes of evaluating a 
redesignation request under section 107(d)(3)(E). See Wall v. EPA, 265 
F.3d 426, 439 (6th Cir. 2001) upholding this interpretation.
3. Conclusion With Respect to Sections 107(d)(3)(E)(ii) and (v)
    Thus, EPA finds, based on our review of EPA's previous rulemakings 
on the relevant portions of the Nevada SIP and for the reasons provided 
above, that the Las Vegas Valley has a fully approved applicable SIP 
under section 110(k) that meets all applicable requirements under 
section 110 and part D for the purposes of redesignation, and thereby 
meets the criteria for redesignation under CAA sections 
107(d)(3)(E)(ii) and (v).

C. The Area Must Show the Improvement in Air Quality Is Due to 
Permanent and Enforceable Emissions Reductions

    Section 107(d)(3)(E)(iii) precludes redesignation of a 
nonattainment area to attainment unless EPA determines that the 
improvement in air quality is due to permanent and enforceable 
emissions reductions resulting from implementation of the applicable 
SIP and applicable Federal air pollution control regulations and other 
permanent and enforceable regulations. Under this criterion, the state 
must be able to reasonably attribute the improvement in air quality to 
emissions reductions which are permanent and enforceable. Attainment 
resulting from temporary reductions in emissions rates (e.g., reduced 
production or shutdown due to temporary adverse economic conditions) or 
unusually favorable meteorology would not qualify as an air quality 
improvement due to permanent and enforceable emission reductions. See 
the Calcagni memo, page 4.
    The Las Vegas Valley PM10 Maintenance Plan credits a 
number of local and Federal control measures for having reduced 
PM10 emissions and concentrations within Las Vegas Valley 
sufficiently to attain the NAAQS, and relies on their continued 
implementation to provide for maintenance of the NAAQS now that the 
NAAQS has been attained. The local control measures cited in the 
maintenance plan include certain Clark County Air Quality Regulations 
(AQR), such as the NSR rule (AQR section 12), the acid rain permit rule 
(AQR section 21), and the fugitive dust rules (AQR sections 90 through 
94); best available retrofit technology to meet the requirements of 
EPA's regional haze rule; the transportation conformity process; and 
the Clark County Natural Events Action Plan. Federal control measures 
cited in the maintenance plan include the National Emissions Standards 
for Hazardous Air Pollutants (NESHAPs) and Standards of

[[Page 42266]]

Performance for New Stationary Sources (NSPS).
    While we agree that all of the measures cited above contributed to 
attainment and will contribute to maintenance of the PM10 
NAAQS in Las Vegas Valley, the backbone of the control strategy that 
provided for attainment of the PM10 NAAQS was Clark County's 
section 90 series regulations governing fugitive dust sources. Clark 
County's section 12 NSR rule and local ordinances (Clark County, and 
the cities of Las Vegas, North Las Vegas, and Henderson) regulating new 
fireplaces also contributed to attainment of the standard and will 
contribute to maintenance of the standard.
    In our approval of the BACM demonstration in the Las Vegas Valley 
PM10 Attainment Plan, we described the BACM analysis in 
terms of a series of steps intended to identify all of the sources or 
source categories that significantly contribute to exceedances of the 
NAAQS and to provide for implementation of BACM for all of those 
sources or source categories. Clark County's approved BACM 
demonstration identified certain fugitive dust sources, including 
disturbed vacant land/unpaved parking lots, construction (including 
highway construction), paved roads, unpaved roads, and race tracks as 
the source categories that significantly contribute to exceedances of 
the PM10 NAAQS in Las Vegas Valley. See 68 FR 2954, at 2959 
(January 22, 2003). In the approved Las Vegas Valley PM10 
Attainment Plan, Clark County further demonstrated how Clark County AQR 
sections 90 through 94 implemented BACM for the relevant source 
categories.\18\ EPA approved these regulations as part of the SIP at 
the same time that EPA approved the Las Vegas Valley PM10 
Attainment Plan, 69 FR 32273 (June 9, 2004), and since then, the Clark 
County fugitive dust regulations have been federally enforceable. Clark 
County's section 12 NSR rule has been approved as part of the SIP, most 
recently at 77 FR 64039 (October 18, 2012), as have the local fireplace 
ordinances cited above, 68 FR 52838 (September 8, 2003).
---------------------------------------------------------------------------

    \18\ The 90 series rules include Clark County AQR section 90 
(``Fugitive Dust from Open Areas and Vacant Lots''), section 91 
(``Fugitive Dust from Unpaved Roads, Unpaved Alleys and Unpaved 
Easement Roads''), section 92 (``Fugitive Dust from Unpaved Parking 
Lots, Material Handling & Storage Yards, & Vehicle & Equipment 
Storage Yards''), section 93 (``Fugitive Dust from Paved Roads & 
Street Sweeping Equipment''), and section 94 (``Permitting & Dust 
Control for Construction Activities'').
---------------------------------------------------------------------------

    We also note that Clark County's 90 series regulations were 
implemented in the early 2000s, and a rough indication of their impact 
on ambient PM10 concentrations can be seen in figure 2-2 in 
the Las Vegas Valley PM10 Maintenance Plan that shows a 
steep decline in design values \19\ for Las Vegas Valley from the late 
1990s beginning in 2002 to a level below the NAAQS beginning in 2005. 
This improvement occurred despite a 30 percent increase in population 
in Las Vegas Valley during the same period.\20\ Thus, the improvement 
in air quality since 2000 may reasonably be attributed to 
implementation of Clark County's 90 series (i.e., fugitive dust) rules. 
Moreover, while we recognize that annual rainfall during the 2003-2005 
period in Las Vegas Valley was higher than normal, we note that the 
downward trend in concentrations began prior to that time and that 
maintenance of the NAAQS has continued since the mid-2000s despite 
lower-than-normal rainfall from 2006-2009.\21\
---------------------------------------------------------------------------

    \19\ In this context, the design value at each monitoring site 
refers to the first-, second-, third-, or fourth-highest measured 
concentration (depending on the frequency of monitoring) over a 
three-year period. The highest design valley among the monitoring 
sites determines the design value for the nonattainment area. A 
design value for a given year reflects the data for that year and 
the previous two years. For example, a design value for 2002 
reflects 2000-2002 data.
    \20\ See population figures in table 4-1 of the Las Vegas Valley 
PM10 Maintenance Plan.
    \21\ See section 4.3 of the Las Vegas Valley PM10 
Maintenance Plan for wind and rainfall data in Las Vegas Valley.
---------------------------------------------------------------------------

    Thus, we find that the improvement in air quality in the Las Vegas 
Valley PM10 nonattainment area is the result of permanent 
and enforceable emissions reductions from a combination of permanent 
and enforceable measures, including, but not limited to fugitive dust 
rules, the NSR rule, and fireplace ordinances, and is not the result of 
adverse economic conditions or unusual meteorological conditions. As 
such, we find that the criterion for redesignation set forth at CAA 
section 107(d)(3)(E)(iii) is satisfied.

D. The Area Must Have a Fully-Approved Maintenance Plan Under CAA 
Section 175A

    Section 175A of the CAA sets forth the elements of a maintenance 
plan for areas seeking redesignation from nonattainment to attainment. 
Under CAA section 175A, a maintenance plan must demonstrate continued 
attainment of the applicable NAAQS for at least ten years after EPA 
approves a redesignation to attainment. Eight years after 
redesignation, the State must submit a revised maintenance plan that 
demonstrates continued attainment for the subsequent ten-year period 
following the initial ten-year maintenance period. To address the 
possibility of future NAAQS violations, the maintenance plan must 
contain such contingency provisions as EPA deems necessary to promptly 
correct any violation of the NAAQS that occurs after redesignation of 
the area.
    To meet these requirements, maintenance plans should include the 
following core elements: Attainment inventory, maintenance 
demonstration, continuation of an adequate monitoring network, 
verification of continued attainment, and contingency plan. See 
Calcagni memo, pages 8 through 13. Based on our review and evaluation 
of the plan, as detailed below, we are proposing to approve the Las 
Vegas Valley PM10 Maintenance Plan because we have found 
that it meets the requirements of CAA section 175A.
1. Attainment Inventory
    A maintenance plan for the 24-hour PM10 standard must 
include an inventory of emissions of PM10 in the area to 
identify a level of emissions sufficient to attain the 24-hour 
PM10 NAAQS.\22\ This inventory must be consistent with EPA's 
most recent guidance on emissions inventories for nonattainment areas 
available at the time and should represent emissions during the time 
period associated with the monitoring data showing attainment. The 
inventory must also be comprehensive, including emissions from 
stationary point sources, area sources, nonroad mobile sources, and on-
road mobile sources, and must be based on actual emissions during the 
appropriate season or episode, if applicable. In the following 
paragraphs, we summarize our findings with respect to the emissions 
inventories prepared for the Las Vegas Valley PM10 
Maintenance Plan.
---------------------------------------------------------------------------

    \22\ PM10 precursor emissions may also be required 
depending upon the contribution of secondarily-formed particulate 
matter to ambient PM10 concentrations. As discussed in 
our proposed approval of the Las Vegas Valley PM10 
Attainment Plan, 68 FR 2958 (January 22, 2003), Clark County 
determined, based on analyses of inventories (see chapter 4, section 
4.2.1 of the Attainment Plan) and Chemical Mass Balance modeling, 
that secondary particulate contributes less than significant amounts 
to ambient PM10 concentrations. Therefore, 
PM10 precursors, including oxides of nitrogen, sulfur 
dioxide and volatile organic compounds, are not included in the Las 
Vegas Valley PM10 Maintenance Plan, and we find their 
absence acceptable.
---------------------------------------------------------------------------

    First, emissions inventories for attainment or maintenance plans 
are generally developed for the entire nonattainment area. For the Las 
Vegas Valley PM10 Maintenance Plan, Clark County DAQ 
developed emissions

[[Page 42267]]

inventories for a subset of the nonattainment area referred as to the 
BLM disposal area.\23\ See figure 1-1 in the Las Vegas Valley 
PM10 Maintenance Plan for a map showing the BLM disposal 
area in relation to the Las Vegas Valley PM10 nonattainment 
area. EPA accepted the BLM disposal area as the geographic basis for 
the emissions inventories in the Las Vegas Valley PM10 
Attainment Plan (see 68 FR 2954, at 2958 (January 22, 2003), and we do 
so again for the Las Vegas Valley PM10 Maintenance Plan. The 
BLM disposal area remains an appropriate geographic basis for air 
quality planning purposes because more than 99 percent of the 
population within the nonattainment area lives within BLM disposal 
area, more than 98 percent of the vehicle miles traveled within the 
nonattainment area occurs within the BLM disposal area, and nearly all 
of the anthropogenic sources within the nonattainment area are located 
within the BLM disposal area.
---------------------------------------------------------------------------

    \23\ The Las Vegas Valley PM10 Maintenance Plan 
explains that most of the land in Nevada is under federal 
jurisdiction, and most of the federal land is managed by the Bureau 
of Land Management (BLM). In 1998, Congress passed the Southern 
Nevada Public Land Management Act, which allowed BLM to sell, trade, 
or lease public land within a specific area around Las Vegas. There 
was an amendment to the boundary for this area in 2003, and minor 
adjustments thereafter. The area currently comprises approximately 
327,000 acres and is known as the BLM disposal area.
---------------------------------------------------------------------------

    Furthermore, most of the area within the nonattainment area but 
outside the BLM disposal area lies under the jurisdiction of the 
federal government, and all lands controlled by the federal government 
outside the BLM disposal area are to remain in their native or managed 
state. The disposal area boundary can only be changed by an act of 
Congress. Continued reliance on the BLM disposal area for air quality 
planning purposes was confirmed in 2007 by a PM10 monitoring 
study conducted by Clark County DAQ under which samplers were deployed 
outside the BLM disposal area. No violations were recorded. We note 
that, while the inventory corresponds to the BLM disposal area, the 
regulations adopted by Clark County DAQ to address PM10 
sources apply to the entire PM10 nonattainment area.
    Second, as to the year selected for attainment inventory purposes, 
Clark County DAQ selected year 2008 as the year for the attainment 
inventory in the Las Vegas Valley PM10 Maintenance Plan. 
Emissions during year 2008 are reflected in three three-year periods 
that could be used to evaluate whether the area is attaining the 
standard: 2006-2008, 2007-2009, and 2008-2010. In the latter two 
periods, the expected number of exceedances averaged over the relevant 
three-year period was less than 1.0, which reflects attainment 
conditions. The period 2006-2008 has an expected number of exceedances 
of 1.1, which represents a violation of the standard; however, the 
value of 1.1 reflects two exceedances for which Clark County DAQ has 
flagged as exceptional events. Under these circumstances, we do not 
believe that the violation calculated for the 2006-2008 period should 
preclude the selection of 2008 for the inventory and find its selection 
by Clark County DAQ to be acceptable.
    Third, the emissions inventories developed by Clark County DAQ for 
the Las Vegas Valley PM10 Maintenance Plan reflect ``design 
day'' conditions. The specific day selected for emissions inventory 
purposes was April 15, 2008. Clark County DAQ selected that day based 
on a review of data from all of the PM10 monitoring sites 
that operated from 2008 through 2010 that showed April 15, 2008 to be 
the day during which the highest PM10 concentration not 
unduly affected by high-wind events was measured. We find the use of a 
design day inventory, and selection of April 15, 2008 as the specific 
day for the inventory, to be acceptable.
    Fourth, as to comprehensiveness, we find that the emissions 
inventories in the maintenance plan to be comprehensive in that they 
include estimates of PM10 from all of the relevant source 
categories, which the plan divides among point sources,\24\ nonpoint 
sources,\25\ on-road mobile sources, nonroad mobile sources, and 
emission reduction credits. See table 6-2 of the Las Vegas Valley 
PM10 Maintenance Plan for a summary of the attainment 
inventory (2008), as well as future year emissions projections for 
years 2015 and 2023. Appendix A to the PM10 Maintenance Plan 
contains source-category-specific descriptions of emission calculation 
procedures and sources of input data.
---------------------------------------------------------------------------

    \24\ ``Point sources'' refer to those stationary source 
facilities that are required to report their emissions to Clark 
County DAQ or NDEP.
    \25\ ``Nonpoint sources'' refer to those stationary and area 
sources that fall below point source reporting levels and that are 
too numerous or small to identify individually.
---------------------------------------------------------------------------

    Table 2 below summarizes the attainment inventory (for 2008) in the 
Las Vegas Valley PM10 Maintenance Plan, and also summarizes 
the plan's projected emissions inventories for an interim year (2015) 
and the maintenance plan's horizon year (2023). Based on the estimates 
in table 2, the nonpoint category of emissions accounted for nearly 99% 
of the PM10, with wind erosion from vacant lands making up 
62%, wind erosion from construction making up 26%, and paved road dust 
and construction emissions each making up 4% of the total 
PM10 inventory for 2008.

             Table 2--Total Daily Las Vegas Valley PM[ihel1][ihel0] Emissions, 2008, 2015, and 2023
----------------------------------------------------------------------------------------------------------------
                                                                                 PM[ihel1][ihel0] (tons per day)
                                                                                               \a\
                   Category                               Subcategory           --------------------------------
                                                                                    2008       2015       2023
----------------------------------------------------------------------------------------------------------------
Point........................................  ................................       2.19       2.60       2.88
Nonpoint.....................................  Wind Erosion (Vacant Lands).....     439.05     288.16     122.77
                                               Wind Erosion (construction).....     183.97     217.70     249.21
                                               Construction....................      30.93      37.69      41.22
                                               Paved Road......................      30.85      38.04      48.78
                                               Unpaved Road....................       5.84       6.51       7.49
                                               Other...........................       6.59       7.24       7.89
On-Road Motor Vehicles.......................  ................................       3.08       2.52       2.75
Nonroad Mobile Sources.......................  ................................       3.74       2.95       1.94
Emission Reductions Credits..................  ................................       0.31       0.31       0.31
                                                                                --------------------------------
    Totals...................................  ................................     706.55     603.72     485.24
----------------------------------------------------------------------------------------------------------------
\a\ Emissions correspond to the BLM disposal Area portion of the Las Vegas Valley nonattainment area and reflect
  design day conditions.
Source: Derived from estimates in table 6-2 of the Las Vegas Valley PM10 Maintenance Plan.

[[Page 42268]]

    Lastly, we reviewed the methods, factors, and assumptions used by 
Clark County DAQ to develop the emissions inventories in the Las Vegas 
Valley PM10 Maintenance Plan to ensure that the inventories 
are consistent with EPA's most recent guidance for such inventories. As 
noted above, Clark County DAQ's inventory is divided into five broad 
categories (point sources, nonpoint sources, on-road mobile sources, 
nonroad mobile sources, and emission reduction credits). Multiple 
subcategories of emissions are calculated within each of these broad 
categories.
    For point sources, Clark County DAQ based the inventory estimates 
on source-reported actual 2008 emissions data. For nonpoint or area 
wide sources, Clark County calculated emissions based on county-wide 
reported data for fuel usage, product sales, population, employment 
data, land area, and other parameters covering a wide range of 
activities. The largest emission sources for the PM10 
inventory, wind erosion from construction and wind erosion from vacant 
lands, are included in nonpoint emissions. These two source categories 
contribute over 80% of the total PM10 emissions in 2008. 
Emission factors for windblown fugitives were developed based on a 
series of wind-tunnel studies conducted by University of Nevada, Las 
Vegas (UNLV). These emission factors were combined with estimates of 
vacant land and developed land from the Clark County Department of 
Comprehensive Planning (DCP)'s Geographic Integrated Land Use 
Information System (GILIS).
    The nonroad mobile source category includes aircraft, boats, and 
off-road vehicles and equipment used for construction, farming, 
commercial, industrial, and recreational activities. With respect to 
such sources, Clark County DAQ used EPA's nonroad emissions model 
NONROAD2008a, the current version of the model at the time the plan was 
created. The model includes both emissions factors and default county 
level population and activity data. The model estimates both emissions 
factors and emissions. This includes more than 80 basic and 260 
specific types of non-road equipment, and further stratifies equipment 
by horsepower rating and fuel type. The model has default estimates, 
variables and factors used in the calculations. No local data sets were 
available for Clark County, therefore only model defaults were used.
    The on-road mobile source category consists of trucks, automobiles, 
buses, and motorcycles. The on-road emissions inventory estimates in 
the Las Vegas Valley PM10 Maintenance Plan were prepared by 
Clark County DAQ using EPA's Motor Vehicle Emissions Simulator 
(MOVES2010a) model and AP-42. The vehicle miles traveled were developed 
from vehicle activity data from the Regional Transportation Commission 
of Southern Nevada (RTC) using the transportation demand model, 
TransCAD.
    The on-road emissions estimates for the Las Vegas Valley 
PM10 Maintenance Plan assumed the implementation of the 
federal heavy-duty diesel rule, limits to Reid Vapor Pressure (RVP) of 
9 pounds per square inch (PSI) with a 1.0 psi waiver for ethanol-
blended fuels, the phase-in of federal tier 2 motor vehicle emission 
standards, and the continuation of the SIP-approved enhanced vehicle 
inspection and maintenance (I/M) program in the urban areas of Clark 
County.\26\
---------------------------------------------------------------------------

    \26\ The EPA's most recent action on Nevada's I/M program 
updated the corresponding State statutes and rules. 73 FR 38124 
(July 3, 2008).
---------------------------------------------------------------------------

    Based on our review of the emissions inventories (and related 
documentation) from the Las Vegas Valley PM10 Maintenance 
Plan, we find that the inventory for 2008 is comprehensive, that the 
methods and assumptions used by Clark County to develop the emission 
inventory are reasonable, and that, therefore, the 2008 inventory 
reasonably estimates actual PM10 emissions in an attaining 
year. Moreover, we find that the emissions inventory in the 
PM10 Maintenance Plan reflects the latest planning 
assumptions and emissions models available at the time the plan was 
developed, and provides a comprehensive and reasonably accurate basis 
upon which to forecast PM10 emissions for years 2015 and 
2023.
2. Maintenance Demonstration
    Section 175A(a) of the CAA requires a demonstration of maintenance 
of the NAAQS for 10 years after redesignation. A state may generally 
demonstrate maintenance of the NAAQS by either showing that future 
emissions of a pollutant or its precursors will not exceed the level of 
the attainment inventory, or by modeling to show that the future 
anticipated mix of sources and emission rates will not cause a 
violation of the NAAQS. See Calcagni memo, pages 9 through 11.
    The Las Vegas Valley PM10 Maintenance Plan includes 
emissions inventory projections for 2015 and 2023 and corresponding 
estimates of future-year design values to demonstrate maintenance 
through 2023. In doing so, Clark County DAQ relies on ``rollback,'' the 
scaling of measured concentrations proportional to emissions, with 
conservative assumptions for the rollback concentration target and for 
the background concentration. In this case, Clark County DAQ predicted 
future year design values by adjusting a 2008 design value by the 
proportional change in overall PM10 emissions from the 
attainment inventory (2008) relative to the inventories for the future 
years (2015 and 2023), taking into account a background level (on the 
design value day) of approximately 40 [micro]g/m\3\. We find Clark 
County DAQ's use of a ``rollback'' type of analysis appropriate in this 
case given that ambient PM10 concentrations in Las Vegas 
Valley are driven primarily by ground-level direct PM10 
emissions (in particular fugitive dust) with generally consistent 
dispersion characteristics.
    The foundation for the maintenance demonstration is the emissions 
projections for year 2015 and 2023 because, using the rollback method, 
the predicted future year design values will remain below the 
attainment-year design value (and thus below the NAAQS) if the 
emissions projections for the future years are less than the 
attainment-year inventory. In this case, Clark County DAQ identified 98 
[mu]g/m\3\ as the design value for 2008 (40 [mu]g/m\3\ of which 
represents the background as noted above). The design value of 98 
[mu]g/m\3\ excludes two exceedances measured in Las Vegas Valley in 
2008 that were flagged and documented by Clark County DAQ as 
exceptional events. EPA has not taken action to concur, or not to 
concur, on the flagged exceedances, and if the two exceedances were 
taken into account (in determining the design value rather than being 
excluded), the design value for 2008 would be 123 [mu]g/m\3\, rather 
than 98 [mu]g/m\3\. Regardless of whether the 2008 design value is to 
be 123 [mu]g/m\3\ or 98 [mu]g/m\3\, the general principle still applies 
because both design values are well below the 24-hour PM10 
NAAQS of 150 [mu]g/m\3\. Namely, if the future-year emissions 
projections remain below the emissions estimated for the attainment 
year, then future-year concentrations should remain below the design 
value for the attainment year and thus well below the NAAQS.
    Given the importance of the future-year emissions projections, EPA

[[Page 42269]]

reviewed the methods and assumptions used by Clark County DAQ to adjust 
the attainment-year (2008) emissions inventory to develop emissions 
projections for 2015 and 2013, with particular attention paid to those 
source categories that contribute most to the overall inventory. The 
documentation for Clark County DAQ's emissions projections are found in 
appendix A (``Technical Support Document'') to the Las Vegas Valley 
PM10 Maintenance Plan.
    One of the principle assumptions on which the maintenance plan is 
based is the continued implementation of Clark County's fugitive dust 
rules, particularly the 90 series rules (i.e., sections 90 through 94). 
As approved into the SIP, these rules, other than section 94, apply 
within the ``PM10 nonattainment area.'' Redesignation to 
attainment would presumably have undercut continued implementation of 
the rules. However, Clark County has recently amended the rules to 
apply within a PM10 nonattainment area or an area subject to 
a PM10 maintenance plan, to ensure continued applicability 
after the area is redesignated attainment, and thus to be consistent 
with the assumptions of the maintenance demonstration in the Las Vegas 
Valley PM10 Maintenance Plan. Because EPA cannot redesignate 
a nonattainment area to attainment without approval of a maintenance 
plan, see CAA section 107(d)(3)(E)(4), Clark County's extension of 
applicability of the fugitive dust rules to areas subject to a 
maintenance plan ensures continued implementations of the rules after 
redesignation. In section VI of this document, we are proposing to 
approve the amended fugitive dust rules as a part of this action.
    As described in appendix A to the maintenance plan, Clark County 
DAQ relied primarily on growth factors generated by EPA's Economic 
Growth Analysis System, Version 5 (EGAS); however, population forecasts 
were also used to estimate future-year emissions or activity throughput 
where applicable. With respect to population forecasts, Clark County 
DAQ relied on the most recent forecasts developed by the Center for 
Business and Economic Research (CBER) at the University of Nevada, Las 
Vegas (UNLV) using 2010 U.S. Census data. CBER forecasts a population 
increase from 2008 to 2015 of 8.6% and a population increase from 2008 
to 2023 of 25%.\27\ Examples of source categories for which population 
forecasts were used to develop the emissions projections include 
construction, wind erosion, and unpaved road sectors. We find this 
approach to be acceptable.
---------------------------------------------------------------------------

    \27\ See page 2-1 of appendix A (``Technical Support Document'') 
to the Las Vegas Valley PM10 Maintenance Plan.
---------------------------------------------------------------------------

    While EGAS growth factors were used for many source categories, 
other than those driven by population, Clark County DAQ declined to use 
EGAS factors for certain sources or source categories if more accurate 
local data were available. These source and source categories and 
related data sources include Nellis Air Force Base; fuel consumption 
projections from the U.S. Energy Information Agency; Union Pacific 
railroad operations; and vehicle miles traveled (VMT) projections from 
the Regional Transportation Commission of Southern Nevada (RTC) for use 
in estimating entrainment of PM10 from vehicle travel over 
paved roads.\28\ Clark County DAQ also included banked emissions 
reduction credits (ERCs) for 2015 and 2023 in the event that the ERCs 
are used for the purposes of issuing permits for new or modified 
stationary sources in the air quality planning area.\29\ We find these 
data sources to be appropriate for use in developing emissions 
projections for the maintenance plan.
---------------------------------------------------------------------------

    \28\ See page 4-13 of appendix A (``Technical Support 
Document'') to the Las Vegas Valley PM10 Maintenance 
Plan.
    \29\ See Las Vegas Valley PM10 Maintenance Plan, 
section 6.4.4.
---------------------------------------------------------------------------

    Representing approximately 62% of the overall inventory, wind 
erosion over vacant lands represents the single largest source category 
in terms of its contribution to the overall PM10 inventory 
for year 2008 for the BLM disposal area. Clark County DAQ estimated 
that emissions from this category would decline from approximately 440 
tons per day in 2008 to 290 tons per day by 2015 and then to 123 tons 
per day by 2023. Given this significant predicted decrease in emissions 
relative to existing conditions, EPA reviewed in detail the assumptions 
and basis for these forecasts.
    As described in section 5.2 of appendix A to the Las Vegas Valley 
PM10 Maintenance Plan, the emissions projections for wind 
erosion from vacant lands were made using emissions factors that were 
developed based on a series of wind-tunnel studies conducted by UNLV, 
combined with soil inventory data based on satellite imagery and 
estimates of vacant land and developed land from the Clark County 
Department of Comprehensive Planning (DCP's) Geographic Integrated Land 
Use Information System (GILIS), adjusted over time based on a vacant 
land consumption rate of approximately 3,400 acres per year and 
projected population growth rates. The rate for vacant land consumption 
from 2011 to 2023 is projected to be approximately 23% less than the 
30-year average vacant land consumption rate (approximately 4,400 acres 
per year). The decrease in emissions projected for the wind erosion 
over vacant lands reflects the reduction in total disturbed unstable 
lands within the BLM disposal area from approximately 10,100 acres in 
2008 to 8,200 acres in 2015 and then to 6,100 acres in 2023. We believe 
Clark County DAQ's approach to projecting emissions from this source 
category to be reasonable and find that projected decrease in emissions 
from this source category is logical given the extent to which the 
lands within the BLM disposal area are already developed or remain as 
native desert.
    Based on our review described above, we find that the methods, 
growth factors, and assumptions used by Clark County DAQ to project 
emissions in 2015 and 2023 based on the attainment inventory for 2008 
are reasonable. Given that the projections (summarized in Table 2 
above) show future emissions in 2015 (603.72 tons per day) and 2023 
(485.24 tons per day) to be well below those in 2008 (706.55 tons per 
day), we find that the projections provide an adequate basis to 
demonstrate maintenance of the PM10 NAAQS within the Las 
Vegas Valley area through 2023. Also, as described further in section 
V.D.7 of this document, Clark County DAQ has chosen to include ``safety 
margins'' in the motor vehicle emissions budgets for 2015 (90.63 tons 
per day) and 2023 (78.29 tons per day), but we find that the overall 
emissions projections, including the safety margins for the budgets, 
for 2015 (694.35 tons per day) and 2023 (563.53 tons per day) remain 
below those in 2008 (706.55 tons per day), and thus, the safety margins 
are consistent with maintenance of the NAAQS through 2023.
    Lastly, we note that, under CAA section 175A(a), a maintenance plan 
must provide for maintenance of the NAAQS in the area ``for at least 10 
years after the redesignation.'' Although final EPA action on this 
proposed redesignation will not occur until year 2014, we find that the 
Las Vegas Valley PM10 Maintenance Plan satisfies the 
requirement to provide for maintenance of the NAAQS for at least 10 
years after redesignation, which in this case, means through 2024, 
because (1) significant emissions controls (e.g. Clark County's 
fugitive dust regulations) remain in place and will continue to provide 
reductions that keep the area in

[[Page 42270]]

attainment; (2) the 2023 projected emission inventory is well below the 
2008 attainment year level and is expected to decline or remain stable 
during the 2023 to 2024 period due to continued developed of lands 
within the BLM disposal area and corresponding reduction in wind 
erosion over vacant disturbed land; and (3) air quality concentrations 
are well below the 24-hour PM10 NAAQS, and, when coupled 
with the emission inventory projections through 2023, clearly show it 
would be very unlikely for a PM10 violation to occur in 
2024.
    For the above reasons, EPA believes that the area will continue to 
maintain the 24-hour PM10 NAAQS at least through 2024 and 
that the Las Vegas Valley PM10 Maintenance Plan provides for 
maintenance for a period of ten years following redesignation. Thus, if 
EPA finalizes its proposed approval of the Las Vegas Valley 
PM10 Maintenance Plan in 2014, it is based on a showing, in 
accordance with section 175A, that the Las Vegas Valley PM10 
Maintenance Plan provides for maintenance for at least ten years after 
redesignation.
3. Monitoring Network
    Continued ambient monitoring of an area is generally required over 
the maintenance period. As discussed in section V.A. of this document, 
PM10 is currently monitored by Clark County DAQ within the 
Las Vegas Valley PM10 nonattainment area. In the Las Vegas 
Valley PM10 Maintenance Plan (see section 6-8 of the plan), 
Clark County commits to continue operation of an air quality monitoring 
network that meets or exceeds the minimum monitoring requirements and 
will be relying on ambient PM10 monitoring to verify 
continued attainment of the 24-hour PM10 NAAQS. The Las 
Vegas Valley PM10 Maintenance Plan also notes that a review 
of the entire monitoring network will be undertaken annually as 
required by federal regulations.\30\ We find Clark County's commitment 
for continued ambient PM10 monitoring as set forth in the 
Las Vegas Valley PM10 Maintenance Plan to be acceptable.
---------------------------------------------------------------------------

    \30\ EPA's requirements for annual review of monitoring networks 
are found at 40 CFR 58.10.
---------------------------------------------------------------------------

4. Verification of Continued Attainment
    Clark County has the legal authority to implement and enforce the 
requirements in the Las Vegas Valley PM10 Maintenance Plan. 
This includes the authority to adopt, implement and enforce any 
emission control contingency measures determined to be necessary to 
correct 24-hour PM10 NAAQS violations. To verify continued 
attainment, Clark County commits in the PM10 Maintenance 
Plan to the continued operation of a PM10 monitoring network 
that meets EPA ambient air quality surveillance requirements.
    Second, the transportation conformity process, which would require 
a comparison of on-road motor vehicle emissions that would occur under 
new or amended regional transportation plans and programs with the 
MVEBs in the Las Vegas Valley PM10 Maintenance Plan, 
represents another means by which to verify continued attainment of the 
24-hour PM10 NAAQS in the Las Vegas Valley. Lastly, while 
not cited in the plan, Clark County must inventory emissions sources 
and report to EPA on a periodic basis under 40 CFR part 51, subpart A 
(``Air Emissions Reporting Requirements''). These emissions inventory 
updates will provide a third way to evaluate emissions trends in the 
area and thereby verify continued attainment of the NAAQS. These 
methods are sufficient for the purpose of verifying continued 
attainment.
5. Contingency Provisions
    CAA section 175A(d) requires that maintenance plans include 
contingency provisions, as EPA deems necessary, to promptly correct any 
violations of the NAAQS that occur after redesignation of the area. 
Such provisions must include a requirement that the State will 
implement all measures with respect to the control of the air pollutant 
concerned that were contained in the SIP for the area before 
redesignation of the area as an attainment area. In this instance, the 
Las Vegas Valley PM10 Maintenance Plan does not provide for 
the repeal or relaxation of any of the measures that contributed to 
attainment of the PM10 standard in Las Vegas Valley, and 
thus, the plan need not provide for any such measures to be 
reinstituted as a contingency in the event of an exceedance of the 
NAAQS.
    Contingency provisions for maintenance plan purposes are 
distinguished from those generally required for nonattainment areas 
under section 172(c)(9) in that they are not required to be fully-
adopted measures that will take effect without further action by the 
state in order for the maintenance plan to be approved. However, the 
contingency plan is considered to be an enforceable part of the SIP and 
should ensure that the contingency measures are adopted expeditiously 
once they are triggered by a specified event. The maintenance plan 
should clearly identify the measures to be adopted, a schedule and 
procedure for adoption and implementation, and a specific timeline for 
action by the State. As a necessary part of the plan, the State should 
also identify specific indicators or triggers, which will be used to 
determine when the contingency measures need to be implemented.
    As required by section 175A of the CAA, Clark County has adopted a 
contingency plan to address possible future PM10 air quality 
problems. See section 6.9 of the Las Vegas Valley PM10 
Maintenance Plan. As described in section 6.9 of the maintenance plan, 
Clark County DAQ intends to rely on its continuous ambient 
PM10 monitoring network to track PM10 
concentrations and has selected a confirmed violation of the 
PM10 NAAQS, defined as more than one expected exceedance per 
year averaged over a three-year period, as the primary triggering 
mechanism. Clark County DAQ refers to the date sixty days from such a 
violation as the trigger date after which the contingency plan would go 
into effect.
    Under the contingency plan, within 45 days of the trigger date, 
Clark County DAQ would notify EPA that an internal review process has 
begun to evaluate potential contingency measures. The list of potential 
contingency measures, not intended to be inclusive, includes:
    (1) Implementing a new dust control permit requirement for short-
term activities that disturb or have the potential to disturb soils 
that emit PM10, such as mechanized weed abatement, fair, 
carnivals, Christmas tree and Halloween pumpkin lots, art sales;
    (2) Conducting a comprehensive review and update of Clark County's 
Construction Activities Dust Control Handbook to increase the 
effectiveness of existing Best Management Practices (BMPs) and to 
identify new BMPs. Examples include: new management practices for soil-
disturbing activities and practices for roadway and detention basin 
maintenance activities;
    (3) Reviewing dust mitigation plan requirements in Clark County 
Rule 90 and 92, focusing on reducing acreage-trigger thresholds, 
incorporating additional mitigation plan criteria and lowering 
applicability thresholds for unpaved parking lots;
    (4) Reassigning staff to provide additional field enforcement of 
the air quality regulations that control sources of fugitive dust 
emissions;
    (5) Mapping construction activities during inspections to collect 
PM10 data to provide greater accuracy for calculating 
emissions from these activities;
    (6) Developing a new dust control database to strengthen oversight 
of dust control permits and improve compliance; and

[[Page 42271]]

    (7) Amending fugitive dust regulations to incorporate new 
technologies and measure for controlling emissions and prevent them 
from crossing property lines or causing a nuisance.
    Within 90 days of the notification to EPA, Clark County DAQ has 
committed to send EPA an informational report outlining recommended 
actions. Clark County DAQ will then solicit public involvement and 
Clark County Board of Commissioners and/or the State Environmental 
Commission will hold public hearings, as necessary, to consider 
recommended contingency measures. Under the contingency plan, the 
selected contingency measures must be adopted and implemented within 18 
months of the submittal of the informational report to EPA.
    Based on our understanding of the contingency plan, as summarized 
above, we find that the contingency provisions of the Las Vegas Valley 
PM10 Maintenance Plan clearly identify specific contingency 
measures, contain tracking and triggering mechanisms to determine when 
contingency measures are needed, contain a description of the process 
of recommending and implementing contingency measures, and contain 
specific timelines for action. Thus, we conclude that the contingency 
provisions of the Las Vegas Valley PM10 Maintenance Plan are 
adequate to ensure prompt correction of a violation and therefore 
comply with section 175A(d) of the Act.
6. Subsequent Maintenance Plan Revisions
    CAA section 175A(b) provides that States shall submit a SIP 
revision 8 years after redesignation providing for maintaining the 
NAAQS for an additional 10 years. The Las Vegas Valley PM10 
Maintenance Plan includes a commitment to prepare and submit a revised 
maintenance plan eight years after redesignation to attainment. See 
section 6.10 of the Las Vegas Valley PM10 Maintenance Plan.
7. Motor Vehicle Emissions Budgets
    Transportation conformity is required by section 176(c) of the CAA. 
Our transportation conformity rule (codified in 40 CFR part 93, subpart 
A) requires that transportation plans, programs, and projects conform 
to SIPs and establishes the criteria and procedures for determining 
whether or not they do so. Conformity to the SIP means that 
transportation activities will not produce new air quality violations, 
worsen existing violations, or delay timely attainment of the national 
ambient air quality standards.
    PM10 maintenance plan submittals must specify the 
maximum emissions of transportation-related PM10 emissions 
\31\ allowed in the last year of the maintenance period, i.e., the 
motor vehicle emissions budgets (MVEBs). (MVEBs may also be specified 
for additional years during the maintenance period.) The MVEBs serve as 
a ceiling on emissions that would result from an area's planned 
transportation system. The MVEB concept is further explained in the 
preamble to the November 24, 1993, transportation conformity rule (58 
FR 62188). The preamble describes how to establish MVEBs in the SIP and 
how to revise the MVEBs if needed.
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    \31\ Transportation-related emissions of volatile organic 
compounds (VOC) and/or oxides of nitrogen (NOX) emissions 
must also be specified in PM10 areas if EPA or the state 
finds that transportation-related emissions of one or both of these 
precursors within the nonattainment area are a significant 
contributor to the PM10 nonattainment problem and has so 
notified the metropolitan planning organization (MPO) and the U.S. 
Department of Transportation (DOT), or if the applicable SIP 
revision or SIP revision submittal establishes an approved or 
adequate budget for such emissions as part of the RFP, attainment or 
maintenance strategy. 40 CFR 93.102(2)(iii). Neither of these 
conditions apply to the Las Vegas Valley PM10 
nonattainment area, and thus, the Las Vegas Valley PM10 
Maintenance Plan establishes MVEBs only for PM10, not for 
PM10 precursors.
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    The maintenance plan submittal must demonstrate that these 
emissions levels, when considered with emissions from all other 
sources, are consistent with maintenance of the NAAQS. In order for us 
to find these emissions levels or ``budgets'' adequate and approvable, 
the submittal must meet the conformity adequacy provisions of 40 CFR 
93.118(e)(4) and (5). For more information on the transportation 
conformity requirement and applicable policies on MVEBs, please visit 
our transportation conformity Web site at: http://www.epa.gov/otaq/stateresources/transconf/index.htm.
    EPA's process for determining adequacy of a MVEB consists of three 
basic steps: (1) Notifying the public of a SIP submission; (2) 
providing the public the opportunity to comment on the MVEB during a 
public comment period; and, (3) making a finding of adequacy or 
inadequacy. The process for determining the adequacy of a submitted 
MVEB is codified at 40 CFR 93.118(f).
    On November 7, 2012, EPA announced the availability of the Las 
Vegas Valley PM10 Maintenance Plan with MVEBs and a 30-day 
public comment period on EPA's Adequacy Web site at: http://www.epa.gov/otaq/stateresources/transconf/currsips.htm. The comment 
period for this notification ended on December 7, 2012, and EPA 
received no comments from the public. Note, however, that a second 
mechanism is also provided for EPA review and public comment on MVEBs, 
as described in 40 CFR 93.118(f)(2). This mechanism provides for EPA's 
review of the adequacy of an implementation plan MVEB simultaneously 
with its review and approval and/or disapproval of the applicable SIP 
revision itself. In this action, EPA used the web notification 
discussed above to solicit public comments on the adequacy of Clark 
County's MVEBs, but is taking comment on the approvability of the 
submitted MVEBs through this proposed rule.
    The Las Vegas Valley PM10 Maintenance Plan contains 
design-day PM10 MVEBs for the BLM disposal area portion of 
the Las Vegas Valley PM10 nonattainment area for the last 
year of the maintenance period (2023), as well as the 2008 base year 
(attainment inventory) and an interim year (2015). Table 3 presents the 
MVEBs from the Las Vegas Valley PM10 Maintenance Plan and 
shows how they are derived. Specifically, the MVEBs represent the sum 
of certain source categories or subcategories from the emissions 
inventories prepare for the Las Vegas Valley PM10 
Maintenance Plan plus a safety margin. The applicable source categories 
or subcategories included in the MVEBs include vehicle emissions 
(including exhaust, brake wear, and tire wear), paved road dust, 
unpaved road dust, and three construction-related source subcategories 
(road construction dust, construction track-out, and wind erosion 
associated with road construction). The safety margins represent the 
difference between the sum of the emissions from the source categories 
or subcategories described above and the PM10 MVEB currently 
in effect in Las Vegas Valley under the approved Las Vegas Valley 
PM10 Attainment Plan (i.e., 141.41 tons per day).

[[Page 42272]]

  Table 3--Motor Vehicle Emissions Budgets in the Las Vegas Valley PM10
                            Maintenance Plan
------------------------------------------------------------------------
                                   Design-day emissions  (PM10, tons per
                                                  day) \a\
             Category             --------------------------------------
                                       2008         2015         2023
------------------------------------------------------------------------
Vehicle (exhaust, brake wear, and         3.08         2.52         2.75
 tire wear)......................
Paved Road Dust..................        30.85        38.04        48.78
Unpaved Road Dust (public).......         0.28         0.32         0.36
Road Construction Dust...........         1.54         1.87         2.05
Construction Track-Out...........         0.25         0.30         0.33
Wind Erosion (road construction).         6.53         7.73         8.85
                                  --------------------------------------
    Subtotals....................        42.53        50.78        63.12
Safety Margin....................        98.88        90.63        78.29
                                  ======================================
        Totals...................       141.41       141.41       141.41
------------------------------------------------------------------------
\a\ Corresponds to the BLM disposal area portion of Las Vegas Valley.
Source: Derived from tables 7-1, 7-2, and 7-3 in section 7.0 in the Las
  Vegas Valley PM10 Maintenance Plan.

    The MVEBs in the Las Vegas Valley PM10 Maintenance Plan 
reflect: (1) On-road motor vehicle emission factors from EPA's current 
motor vehicle emissions factor model (MOVES); (2) fugitive paved and 
unpaved road and road construction emission factors from Compilation of 
Air Pollutant Emission Factors (AP-42); \32\ and (3) updated vehicle 
activity data from the Regional Transportation Commission of Southern 
Nevada's (RTC's) Clark County Activity-Based Travel Demand Simulation 
Model (TransCAD) transportation modeling system.
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    \32\ AP-42, Compilation of Air Pollutant Emission Factors, is 
the primary compilation of EPA's emission factor information. It 
contains emission factors and process information for more than 200 
air pollution source categories, including paved roads. EPA released 
an update to AP-42 in January of 2011, which revised the equation 
for estimating paved road dust emissions based on an updated 
regression that included new emission tests results. Clark County 
DAQ used the updated AP-42 equation with local data on vehicle 
weight and silt loading data collected in 2003-2006 with Vehicle 
Miles Traveled (VMT) data from RTC's TransCAD model to estimate 
paved road emissions.
---------------------------------------------------------------------------

    As described above, the Las Vegas Valley PM10 
Maintenance plan uses a 2008 attainment-year emissions inventory to 
project emissions to 2015 and 2023 and show continually decreasing 
emissions, thereby demonstrating maintenance of the NAAQS through 2023. 
As shown in table 2 of this document, the Las Vegas Valley 
PM10 Maintenance Plan estimates that design-day emissions in 
the BLM disposal area portion of the Las Vegas PM10 
nonattainment area will decrease from approximately 710 tons per day in 
2008 to approximately 600 tons per day in 2015 and will then further 
decrease to approximately 490 tons per day in 2023.
    A state may choose to apply a safety margin under our 
transportation conformity rule so long as such margins are explicitly 
quantified in the applicable plan and are shown to be consistent with 
attainment or maintenance of the NAAQS (whichever is relevant to the 
particular plan). See 40 CFR 93.124(a). For the Las Vegas Valley 
PM10 Maintenance Plan, Clark County DAQ increased the motor 
vehicle related emissions estimates (i.e., vehicle, paved and unpaved 
road dust, construction track-out, and road construction (including 
related wind erosion) to equal 141.41 tons per day, which is the 2006 
attainment-year MVEB approved in connection with the Las Vegas Valley 
PM10 Attainment Plan. The Las Vegas Valley PM10 
Maintenance Plan demonstrates continued maintenance with the additional 
safety margins by showing that, with the safety margins added to the 
estimates for 2015 and 2023, the overall emissions in 2015 (694.35 tons 
per day) and 2023 (563.53 tons per day) would still be less than the 
emissions inventory for the attainment year 2008 (706.55 tons per day). 
See table 7-3 of the Las Vegas Valley PM10 Maintenance Plan.
    EPA is proposing to approve the MVEBs for 2008, 2015 and 2023, 
shown in table 3 above, as part of our approval of Las Vegas Valley 
PM10 Maintenance Plan. EPA has determined that the MVEB 
emission targets are consistent with emission control measures in the 
SIP and are consistent with maintenance of the 24-hour PM10 
standard in Las Vegas Valley through 2023. The details of EPA's 
evaluation of the MVEBs for compliance with the budget adequacy 
criteria of 40 CFR 93.118(e) are provided in a separate memorandum \33\ 
included in the docket of this rulemaking. Because the budgets EPA 
approved in 2004 are the same level as the budgets EPA is proposing to 
approve in this action, if EPA approves the MVEBs in the final 
rulemaking action, it would not change the budgets currently in use for 
transportation conformity determinations for Clark County. Any and all 
comments on the approvability of the MVEBs should be submitted during 
the comment period stated in the DATES section of this document.
---------------------------------------------------------------------------

    \33\ See EPA memorandum dated October 28, 2013 titled, 
``Adequacy Documentation for Plan Motor Vehicle Emission Budgets in 
August 2012 Clark County PM10 Maintenance State 
Implementation Plan.''
---------------------------------------------------------------------------

VI. Evaluation of Revisions to Clark County Fugitive Dust Rules

    As noted above, the Las Vegas Valley PM10 Maintenance 
Plan relies on the continued application of the county's fugitive dust 
rules, particularly sections 90 through 94; however, these rules, with 
the exception of section 94, as approved into the SIP, apply within the 
``PM10 nonattainment area (hydrographic basin 212).'' 
Section 94 applies county-wide, not just in the PM10 
nonattainment area. Redesignation of the Las Vegas Valley 
PM10 nonattainment area to attainment, as proposed herein, 
could undermine continued applicability and enforceability of the 
rules. To address this issue, the Clark County Board of County 
Commissioners recently adopted revisions to the rules to clarify their 
continued applicability within both a ``PM10 nonattainment 
area'' and an ``area subject to a PM10 maintenance plan.''
    Clark County section 90 specifies requirements and measures to be 
implemented within the nonattainment area (and Apex Valley) for control 
of fugitive dust emissions from open areas and vacant lots. Section 91 
specifies requirements and measures to be implemented within the 
nonattainment area (and Apex Valley) for control of

[[Page 42273]]

fugitive dust from unpaved roads, unpaved alleys, and unpaved easement 
roads. Section 92 specifies requirements and measures to be implemented 
within the nonattainment area (and Apex Valley) for control of fugitive 
dust from unpaved parking lots, material handling and storage yards, 
and vehicle and equipment storage yards, not otherwise regulated under 
Clark County section 94 (``Permitting & Dust Control for Construction 
Activities''). Section 93 specifies requirements and measures to be 
implemented within the nonattainment area (and Apex Valley) for control 
of fugitive dust from paved roads and street sweeping equipment.
    EPA most recently approved section 90 at 71 FR 63250 (October 30, 
2006); section 91 at 69 FR 32272 (June 9, 2004), section 92 at 71 FR 
63250 (October 30, 2006); and section 93 at 71 FR 63250 (October 30, 
2006). Relative to the existing SIP versions, as discussed above, the 
rules have been amended to ensure that the rules continue to apply once 
the area is redesignated to attainment for PM10. The rules 
have also been amended to reflect changes in the name of the county's 
air pollution control district and to use the term ``hydrographic 
area'' instead of ``hydrographic basin.'' Lastly, Clark County has 
amended section 92 to add an exemption from the paving requirement for 
new equestrian staging areas so long as the applicable performance 
standards in the rule are met. We find that these changes generally 
improve the SIP as well as providing the necessary support for the Las 
Vegas PM10 Maintenance Plan. Moreover, we find that the 
limited and qualified exemption from the paving requirement under Clark 
County section 92 for new equestrian staging areas would have no effect 
on continued maintenance of the PM10 standard in Las Vegas 
Valley and is acceptable.
    NDEP's May 27, 2014 SIP revision submittal of amended Clark County 
fugitive dust rules also includes an amended version of section 41 
(``Fugitive dust''). The most recent approval by EPA of Clark County 
section 41 was at 46 FR 43141 (August 27, 1981). This older fugitive 
dust rule establishes general fugitive dust requirements and measures 
applicable throughout Clark County but that are largely superseded with 
respect to construction activities by section 94 and, within the 
PM10 nonattainment area (and Apex Valley), by the specific 
measures and other requirements in sections 90 through 93. Section 41 
also contains certain provisions related to off-road vehicle and 
motocross racing that apply only within the nonattainment area. The 
recent amendments adopted by the Clark County Board of County 
Commissioners ensure the continued applicability of the off-road 
vehicle and motocross-related provisions once the area is redesignated 
to attainment. Other changes relative to the SIP version include the 
deletion of provisions addressing vacant lots from which topsoil was 
removed prior to 1973 and the addition of provisions intended to 
clarify the conditions that the rule seeks to avoid through application 
of ``reasonable precautions.'' Within Las Vegas Valley and Apex Valley, 
vacant lots are now addressed by the specific measures and other 
requirements in Clark County section 90. The other changes in section 
41 generally improve the SIP as well as provide support for the Las 
Vegas Valley PM10 Maintenance Plan.\34\
---------------------------------------------------------------------------

    \34\ As amended on April 15, 2014, section 41 (see subsection 
41.2.3) continues to include outdated references to Clark County 
section 15, which was replaced by section 12 a number of years ago. 
We recommend that Clark County update section 41 with the correct 
references to the appropriate subsections of section 12.
---------------------------------------------------------------------------

    Therefore, for the reasons discussed above, we find that Clark 
County fugitive dust rules sections 90 through 93, and 41, as amended 
by the Clark County Board of County Commissioners on April 15, 2014 
(effective April 29, 2014) and submitted by NDEP on May 27, 2014, would 
not interfere with attainment or maintenance of any of the NAAQS and 
would provide necessary support for the Las Vegas Valley 
PM10 Maintenance Plan, and thus are approvable under CAA 
section 110(l).\35\ As such, we propose to approve the amended Clark 
County fugitive dust rules as a revision to the Nevada SIP.
---------------------------------------------------------------------------

    \35\ CAA section 110(l) provides, in relevant part, that EPA 
shall not approve a SIP revision if the SIP revision would interfere 
with any applicable requirement concerning attainment and reasonable 
further progress, or any other applicable requirement of the CAA.
---------------------------------------------------------------------------

VII. Proposed Deletion of TSP Designation for Las Vegas Valley

A. General Considerations

    Consistent with section 107(d)(4)(B), we have considered the 
continued necessity for retaining the remaining TSP area designations 
in Nevada, and as discussed below, we have decided that the TSP 
nonattainment designation for Las Vegas Valley (HA 212) is no 
longer necessary. As a result, we are proposing to delete it from the 
TSP table in 40 CFR 81.329.
    To evaluate whether the TSP area designation should be retained or 
can be deleted, we have relied upon the final rule implementing the 
PM10 NAAQS (see 52 FR 24634, July 1, 1987), a policy 
memorandum on TSP redesignations (see memo dated May 20, 1992 from 
Joseph W. Paisie, Acting Chief, SO2/Particulate Matter 
Programs Branch, EPA Office of Air Quality Planning and Standards, to 
Chief, Air Branch, Regions I-X, entitled ``TSP Redesignation 
Request''), and our proposed and final rules establishing maximum 
allowable increases in concentrations (also known as ``increments'') 
for PM10 (see the proposed rule at 54 FR 41218, October 5, 
1989, and the final rule at 58 FR 31622, June 3, 1993).
    Based on the above references, we believe that the relevant 
considerations for evaluating whether the necessity of retaining the 
TSP area designations depend upon the status of a given area with 
respect to TSP and PM10. For areas that are nonattainment 
for TSP but attainment for PM10, we generally find that the 
TSP designations are no longer necessary and can be deleted when EPA 
(1) approves a State's revised PSD program containing the 
PM10 increments, (2) promulgates the PM10 
increments into a State's SIP where the State chooses not to adopt the 
increments on their own, or (3) approves a State's request for 
delegation of PSD responsibility under 40 CFR 52.21(u). See 58 FR 
31622, at 31635 (June 3, 1993).
    For areas that are nonattainment for TSP and nonattainment for 
PM10, an additional consideration is whether deletion of the 
TSP designations would automatically relax any emissions limitations, 
control measures or programs approved into the SIP. If such a 
relaxation would occur automatically with deletion of the TSP area 
designations, then we will not delete the designations until we are 
satisfied that the resulting SIP relaxation would not interfere with 
any applicable requirement concerning attainment, reasonable further 
progress (RFP), or maintenance of the NAAQS or any other requirement of 
the Clean Air Act in the affected areas. See section 110(l) of the Act.
    In the case of Las Vegas Valley, we believe that the considerations 
for both types of areas described above are relevant because although 
Las Vegas Valley is nonattainment for PM10, we are proposing 
to redesignate the area to attainment for PM10 in today's 
action. Thus, we must take into account both the potential for 
relaxation that would be inconsistent with continued maintenance of the 
PM10 NAAQS as well as protection of the PM10 
increments (as applies in areas designated attainment or 
unclassifiable).

[[Page 42274]]

B. Deletion of TSP Nonattainment Area Designation for Las Vegas Valley

    With respect to protection of the PM10 increments, the 
TSP nonattainment designations are no longer necessary in Las Vegas 
Valley because we have approved Clark County's NSR regulations as 
satisfying the related PSD requirements. See 69 FR 54006 September 7, 
2004.\36\ We recognize that NDEP retains jurisdiction over certain 
types of sources in Clark County but note that EPA's PSD pre-
construction permit program promulgated at 40 CFR 52.21 apply to those 
sources under a delegation agreement between NDEP and EPA. See 40 CFR 
52.1485(b).
---------------------------------------------------------------------------

    \36\ More recently, EPA has taken limited approval and limited 
disapproval of amendments to Clark County's NSR regulations. 77 FR 
64039 (October 18, 2012). In our 2012 final rule, we identified a 
number of deficiencies in the Clark County's NSR regulations, but 
none of these deficiencies relate directly to protection of the 
PM10 increments.
---------------------------------------------------------------------------

    To ensure that deletion of the TSP nonattainment designation for 
Las Vegas Valley would not result in any automatic relaxations in SIP 
emissions limitations, control measures or programs that would 
interfere with attainment, RFP or maintenance of the NAAQS (including 
PM10) or any other requirement of the Act, we reviewed the 
following portions of the Nevada SIP:
     The TSP portions of the Las Vegas Valley Air Quality 
Implementation Plan (AQIP) adopted in response to the CAA, as amended 
in 1977;
     State stationary source rules including NAC 445B.22017 
(``Visible emissions: Maximum opacity; determination and monitoring of 
opacity'') and NAC 445B.2203 (``Emissions of particulate matter: Fuel-
burning equipment'');
     Clark County stationary source rules, including section 26 
(``Emission of visible air contaminants''), section 27 (``Particulate 
matter from process weight rate''), section 28 (``Fuel burning 
equipment''), section 30 (``Incinerators''), and section 42 (``Open 
burning''); and
     Clark County fugitive dust rules, including section 41 and 
sections 90 through 94, as proposed for approval herein (see section VI 
of this document).
    Based on our review of the TSP provisions in the Las Vegas Valley 
AQIP and the various rules cited above, we find that none are 
contingent upon continuation of the TSP nonattainment designations, and 
thus deletion of the TSP designations would not automatically relax any 
standard. More specifically:
     The Las Vegas Valley AQIP relies primarily on fugitive 
dust controls, which are now codified in section 41 and sections 90 
through 94, and for which applicability does not depend on TSP 
designations;
     State stationary source rules that apply to coal-fired 
power plants (i.e., the sources that fall under State jurisdiction in 
Clark County) contain percent opacity limits and PM10 limits 
for which the TSP designation is irrelevant;
     Clark County stationary source rules sections 26, 27, 28, 
30, and 42 do not contain requirements for which the TSP area 
designation is relevant; and
     The applicability of the relevant portion of the Clark 
County rule section 41 (``Fugitive dust'') and the other county 
fugitive dust rules sections 90 through 94 are expressed in terms of 
the designated boundaries of the PM10 nonattainment area (or 
area subject to a PM10 maintenance plan), and not in terms 
of the boundaries of the TSP area.
    In summary, because the PSD PM10 increments apply in Las 
Vegas Valley and because the deletion of the TSP nonattainment 
designation for Las Vegas Valley would not automatically relax any 
emissions limitation or control measure in the Nevada SIP, we find that 
the TSP nonattainment designation is no longer necessary and can be 
deleted. Based on the above discussion and evaluation, therefore, we 
are proposing to delete the TSP nonattainment area designation for Las 
Vegas Valley (HA 212) from the ``Nevada-TSP'' table in 40 CFR 
81.329.

VIII. Proposed Action and Request for Public Comment

    Under CAA section 110(k)(3), and for the reasons set forth above, 
the EPA is proposing to approve NDEP's submittal dated September 7, 
2012 of the Redesignation Request and Maintenance Plan for Particulate 
Matter (PM10), Clark County, Nevada (August 2012) (``Las Vegas Valley 
PM10 Maintenance Plan'') as a revision to the Nevada SIP. 
The EPA finds that the maintenance demonstration showing how the area 
will continue to attain the 24-hour PM10 NAAQS for 10 years 
beyond redesignation, and the contingency provisions describing the 
actions that Clark County will take in the event of a future monitored 
violation, meet all applicable requirements for maintenance plans and 
related contingency provisions in CAA section 175A. The EPA is also 
proposing to approve the motor vehicle emissions budgets in the Las 
Vegas Valley PM10 Maintenance Plan (i.e., 141.14 tons per 
day in 2008, 2015, and 2023) because we find they meet the applicable 
transportation conformity requirements under 40 CFR 93.118(e).
    Second, under CAA section 107(d)(3)(D), we are proposing to approve 
NDEP's request, which accompanied the submittal of the maintenance 
plan, to redesignate the Las Vegas Valley PM10 nonattainment 
area to attainment for the 24-hour PM10 NAAQS. We are doing 
so based on our conclusion that the area has met the five criteria for 
redesignation under CAA section 107(d)(3)(E). Our conclusion in this 
regard is in turn based on our proposed determination that the area has 
attained the 24-hour PM10 NAAQS, that relevant portions of 
the Nevada SIP are fully approved, that the improvement in air quality 
is due to permanent and enforceable reductions in emissions, that 
Nevada has met all requirements applicable to the Las Vegas Valley 
PM10 nonattainment area with respect to section 110 and part 
D of the CAA, and based on our proposed approval as part of this action 
of the Las Vegas Valley PM10 Maintenance Plan. Our proposed 
determination that the area has attained the 24-hour PM10 
NAAQS is based in part on our concurrence with Clark County DAQ that 
the exceedances monitored in Las Vegas Valley on July 3, 2011 were 
caused by a high wind exceptional event and our related exclusion of 
the exceedances from the attainment determination.
    Third, EPA is proposing to approve revisions to Clark County 
fugitive dust rules sections 41, and 90 through 93 that were submitted 
on May 27, 2014 as a revision to the Nevada SIP because we find that 
they ensure continued implementation of the rules after redesignation 
of Las Vegas Valley to attainment and because they meet all other 
applicable requirements. Proposing to do so is consistent with the 
assumptions upon which the maintenance plan is based.
    Lastly, EPA is proposing to delete the area designation for Las 
Vegas Valley for the revoked national standard for total suspended 
particulate because the designation is no longer necessary.
    EPA is soliciting public comments on the issues discussed in this 
document or on other relevant matters. We will accept comments from the 
public on this proposal for the next 30 days. We will consider these 
comments before taking final action.

IX. Statutory and Executive Order Reviews

    Under the CAA, redesignation of an area to attainment and the 
accompanying approval of a maintenance plan under section 107(d)(3)(E) 
are actions that affect the status of a geographical area and do not

[[Page 42275]]

impose any additional regulatory requirements on sources beyond those 
imposed by State law. Redesignation to attainment does not in and of 
itself create any new requirements, but rather results in the 
applicability of requirements contained in the CAA for areas that have 
been redesignated to attainment. Moreover, the Administrator is 
required to approve a SIP submission that complies with the provisions 
of the Act and applicable Federal regulations. 42 U.S.C. 7410(k); 40 
CFR 52.02(a). Thus, in reviewing SIP submissions, EPA's role is to 
approve State choices, provided that they meet the criteria of the 
Clean Air Act. Accordingly, these actions merely propose to approve a 
State plan and redesignation request as meeting Federal requirements 
and do not impose additional requirements beyond those by State law. 
For these reasons, these proposed actions:
     Are not a ``significant regulatory action'' subject to 
review by the Office of Management and Budget under Executive Order 
12866 (58 FR 51735, October 4, 1993) and Executive Order 13563 (76 FR 
3821, January 21, 2011);
     Do not impose an information collection burden under the 
provisions of the Paperwork Reduction Act (44 U.S.C. 3501 et seq.);
     Are certified as not having a significant economic impact 
on a substantial number of small entities under the Regulatory 
Flexibility Act (5 U.S.C. 601 et seq.);
     Do not contain any unfunded mandate or significantly or 
uniquely affect small governments, as described in the Unfunded 
Mandates Reform Act of 1995 (Pub. L. 104-4);
     Do not have Federalism implications as specified in 
Executive Order 13132 (64 FR 43255, August 10, 1999);
     Are not an economically significant regulatory action 
based on health or safety risks subject to Executive Order 13045 (62 FR 
19885, April 23, 1997);
     Are not a significant regulatory action subject to 
Executive Order 13211 (66 FR 28355, May 22, 2001);
     Are not subject to requirements of Section 12(d) of the 
National Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 
note) because application of those requirements would be inconsistent 
with the CAA; and
     Do not provide EPA with the discretionary authority to 
address disproportionate human health or environmental effects with 
practical, appropriate, and legally permissible methods under Executive 
Order 12898 (59 FR 7629, February 16, 1994).
    In addition, this proposed rule does not have Tribal implications 
as specified by Executive Order 13175 (65 FR 67249, November 9, 2000), 
because the SIP is not approved to apply in Indian country located in 
the State, and EPA notes that it will not impose substantial direct 
costs on Tribal governments or preempt Tribal law. Nonetheless, EPA has 
discussed the proposed action with the one Tribe, the Las Vegas Paiute 
Tribe, located within the Las Vegas Valley PM10 
nonattainment area.

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Intergovernmental 
relations, Nitrogen dioxide, Particulate matter, Reporting and 
recordkeeping requirements, Sulfur dioxide.

40 CFR Part 81

    Environmental protection, Air pollution control, National parks, 
Wilderness areas.

    Dated: June 27, 2014.
Alexis Strauss,
Acting Regional Administrator, Region IX.
[FR Doc. 2014-16575 Filed 7-18-14; 8:45 am]
BILLING CODE 6560-50-P
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