Approval and Promulgation of Air Quality Implementation Plans; State of Nevada; Regional Haze State Implementation Plan, 36450-36468 [2011-15238]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 76, Number 120 (Wednesday, June 22, 2011)]
[Proposed Rules]
[Pages 36450-36468]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-15238]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 51

[EPA-R09-OAR-2011-0130, FRL-9320-5]


Approval and Promulgation of Air Quality Implementation Plans; 
State of Nevada; Regional Haze State Implementation Plan

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: EPA is proposing to approve a revision to the Nevada State 
Implementation Plan (SIP) to implement the regional haze program for 
the first planning period through July 31, 2018. The Clean Air Act 
(CAA) requires states to prevent any future and remedy any existing 
man-made impairment of visibility in 156 national parks and wilderness 
areas designated as Class I areas. Regional haze is caused by emissions 
of air pollutants from numerous sources located over a broad geographic 
area. States must submit SIPs that assure reasonable progress toward 
the national goal of achieving natural visibility conditions in Class I 
areas.

DATES: Written comments must be received at the address below on or 
before July 22, 2011.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-R09-
OAR-2011-0130 by one of the following methods:
    1. Federal Rulemaking portal: https://www.regulations.gov. Follow 
the on-line instructions for submitting comments.
    2. E-mail: Webb.Thomas@epa.gov.
    3. Fax: 415-947-3579 (Attention: Thomas Webb).
    4. Mail: Thomas Webb, EPA Region 9, Planning Office, Air Division, 
75 Hawthorne Street, San Francisco, California 94105.
    5. Hand Delivery or Courier: Such deliveries are only accepted 
Monday through Friday, 8:30 a.m.-4:30 p.m., excluding Federal holidays. 
Special arrangements should be made for deliveries of boxed 
information.
    Instructions: Direct your comments to Docket ID No. EPA-R09-OAR-
2011-

[[Page 36451]]

0130. Our policy is that EPA will include all comments received in the 
public docket without change. EPA may make comments available online at 
https://www.regulations.gov, including any personal information 
provided, unless the comment includes information claimed to be 
Confidential Business Information (CBI) or other information whose 
disclosure is restricted by statute. Do not submit information that you 
consider to be CBI or otherwise protected through https://www.regulations.gov or e-mail. The https://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA, without 
going through https://www.regulations.gov, EPA will include your e-mail 
address as part of the comment that is placed in the public docket and 
made available on the Internet. If you submit an electronic comment, 
EPA recommends that you include your name and other contact information 
in the body of your comment and with any disk or CD-ROM you submit. If 
EPA cannot read your comment due to technical difficulties and cannot 
contact you for clarification, EPA may not be able to consider your 
comment. Electronic files should avoid the use of special characters, 
any form of encryption, and be free of any defects or viruses. For 
additional information about EPA's public docket visit the EPA Docket 
Center homepage at https://www.epa.gov/epahome/dockets.htm.
    Docket: All documents in the docket are listed in the https://www.regulations.gov index. Although listed in the index, some 
information is not publicly available (e.g., CBI or other information 
whose disclosure is restricted by statute). Certain other material, 
such as copyrighted material, will be publicly available only in hard 
copy form. Publicly available docket materials are available either 
electronically at https://www.regulations.gov or in hard copy at the 
Planning Office of the Air Division, Air-2, EPA Region 9, 75 Hawthorne 
Street, San Francisco, CA 94105. EPA requests you contact the 
individual listed in the FOR FURTHER INFORMATION CONTACT section to 
view the hard copy of the docket. You may view the hard copy of the 
docket Monday through Friday, 9-5:30 PST, excluding Federal holidays.

FOR FURTHER INFORMATION CONTACT: Thomas Webb, U.S. EPA, Region 9, 
Planning Office, Air Division, Air-2, 75 Hawthorne Street, San 
Francisco, CA 94105. Thomas Webb can be reached at telephone number 
(415) 947-4139 and via electronic mail at webb.thomas@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document wherever ``we,'' 
``us,'' or ``our,'' is used, we mean the United States Environmental 
Protection Agency (EPA).

Table of Contents

I. State Submittals
II. Background
    A. Description of Regional Haze
    B. History of Regional Haze Regulations
    C. Roles of Agencies in addressing Regional Haze
III. Requirements for Regional Haze SIPs
    A. Regional Haze Rule
    B. Determination of Baseline, Natural and Current Visibility 
Conditions
    C. Determination of Reasonable Progress Goals (RPGs)
    D. Best Available Retrofit Technology (BART)
    E. Long-Term Strategy (LTS)
    F. Coordination of the Regional Haze SIP and Reasonably 
Attributable Visibility Impairment
    G. Monitoring Strategy
    H. SIP Revisions and Progress Reports
    I. Coordination with Federal Land Managers (FLMs)
IV. EPA's Analysis of Nevada's RH SIP
    A. Affected Class I Areas
    B. Visibility Conditions and Uniform Rate of Progress (URP)
    1. Baseline and Natural Visibility Conditions
    2. Uniform Rate of Progress Estimate
    C. Nevada Emissions Inventories
    1. Emissions Inventories for 2002 and 2018
    2. Analysis of Statewide Emissions by Pollutant
    3. Analysis of Natural versus Anthropogenic Emissions
    D. Sources of Visibility Impairment
    1. Sources of Visibility Impairment at Jarbidge
    2. Nevada's Contributions to Visibility Impairment in Class I 
Areas Outside of the State
    E. Determination of Best Available Retrofit Technology
    1. Sources eligible for BART
    2. Sources subject to BART
    3. BART Determinations
    a. Tracy Generating Station
    b. Fort Churchill Generating Station
    c. Reid Gardner Generating Station
    d. Mohave Generating Station
    4. EPA's Assessment
    F. Determination of Reasonable Progress Goal
    1. Visibility Projections for 2018
    2. Establishing the Reasonable Progress Goal
    3. Interstate Consultation
    G. Long-Term Strategy
    1. BART Controls
    2. Ongoing Air Pollution Control Programs
    3. Construction Activities
    4. Source Retirement and Replacement Schedules
    5. Smoke Management Programs
    6. Other Measures supporting the LTS
    7. Interstate Transport Requirements for Visibility
    H. Monitoring Strategy
    1. Coordination of RAVI with RHR
    2. Additional Monitoring Sites
    3. Using and Reporting Monitoring Data
    4. Statewide Emissions Inventory
    I. State and Federal Land Manager Coordination
    J. Periodic SIP Revisions and 5-year Progress Reports
V. EPA's Proposed Action
VI. Statutory and Executive Order Reviews

I. State Submittals

    The Nevada Division of Environmental Protection (NDEP) adopted and 
transmitted its ``Nevada Regional Haze State Implementation Plan'' 
(Nevada RH SIP) to EPA Region 9 in a letter dated November 18, 2009. 
EPA determined the plan complete by operation of law on May 18, 2010. 
The SIP was properly noticed by the State and available for public 
comment for 30 days prior to a public hearing held in Carson City, 
Nevada, on May 20, 2009. There was a separate public notice and hearing 
on the proposed Best Available Retrofit Technology (BART) controls for 
four stationary sources, which the State adopted on April 23, 2009. The 
State submitted to EPA additional documentation of public process and 
adoption of a more stringent emission limit for one of the BART sources 
on February 18, 2010. Nevada included in its SIP responses to written 
comments from EPA Region 9, the National Park Service, and a consortium 
of conservation organizations. As a result of the State's participation 
with 13 other states, Tribal nations and Federal agencies in the 
Western Regional Air Partnership (WRAP), Nevada's RH SIP reflects a 
consistent approach toward addressing regional visibility impairment at 
116 Class I areas in the West.

II. Background

A. Description of Regional Haze

    Regional haze is the impairment of visibility across a broad 
geographic area produced by numerous sources and activities that emit 
fine particles and their precursors, primarily sulfur dioxide 
(SO2) and nitrogen oxide (NOX), and in some 
cases, ammonia (NH3) and volatile organic compounds (VOC). 
Fine particle precursors react in the atmosphere to form fine 
particulate matter (PM2.5), primarily sulfates, nitrates, 
organic carbon, elemental carbon, and soil dust, which impair 
visibility by scattering and absorbing light. Visibility impairment 
reduces the clarity, color, and visible distance that one can see. 
PM2.5 can also cause

[[Page 36452]]

serious health effects and mortality in humans and contributes to 
environmental effects such as acid deposition and eutrophication.
    Data from existing visibility monitors, the ``Interagency 
Monitoring of Protected Visual Environments'' (IMPROVE) network, 
indicate that visibility impairment caused by air pollution occurs 
virtually all the time at most Federally protected national parks and 
wilderness areas, known as Class I areas. The average visual range in 
many Class I areas in the western United States is 100 to 150 
kilometers, or about one-half to two-thirds of the visual range that 
would exist without man-made air pollution.\1\ In most of the eastern 
Class I areas of the United States, the average visual range is less 
than 30 kilometers, or about one-fifth of the visual range that would 
exist under estimated natural conditions. 64 FR 35715 (July 1, 1999).
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    \1\ Visual range is the greatest distance, in kilometers or 
miles, at which one can view a dark object against the sky.
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B. History of Regional Haze Regulations

    In section 169(A)(1) of the 1977 Amendments to the CAA, Congress 
established as a national goal the ``prevention of any future, and the 
remedying of any existing, impairment of visibility in mandatory class 
I Federal areas which impairment results from man-made air pollution.'' 
Visibility was determined to be an important value in 156 mandatory 
Class I Federal areas \2\ as listed in 40 CFR 81.400-437. In the first 
phase of visibility protection, EPA promulgated regulations on December 
2, 1980, to address visibility impairment in Class I areas that is 
``reasonably attributable'' to a single source or small group of 
sources, i.e., ``reasonably attributable visibility impairment'' or 
RAVI. 45 FR 80084. EPA deferred action on regional haze that emanates 
from a variety of sources until monitoring, modeling and scientific 
knowledge about the relationship between pollutants and visibility 
impairment were improved.
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    \2\ Areas designated as mandatory Class I Federal areas consist 
of national parks exceeding 6000 acres, wilderness areas and 
national memorial parks exceeding 5000 acres, and all international 
parks that were in existence on August 7, 1977. 42 U.S.C. 7472(a). 
In accordance with section 169A of the CAA, EPA, in consultation 
with the Department of Interior, promulgated a list of 156 areas 
where visibility is identified as an important value. 44 FR 69122 
(November 30, 1979). Although states and Tribes may designate as 
Class I additional areas which they consider to have visibility as 
an important value, the requirements of the visibility program set 
forth in section 169A of the CAA apply only to ``mandatory Class I 
Federal areas.'' Each mandatory Class I Federal area is the 
responsibility of a ``Federal Land Manager.'' 42 U.S.C. 7602(i). 
When we use the term ``Class I area'' in this action, we mean a 
``mandatory Class I Federal area.''
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    Congress added section 169B to the CAA in 1990 to conduct 
scientific research on regional haze. This legislation established the 
Grand Canyon Visibility Transport Commission (GCVTC), which issued its 
report, ``Recommendations for Improving Western Vistas,'' on June 10, 
1996. These recommendations informed the regulatory development of a 
regional haze program, and provided an option for certain western 
states to address visibility at 16 Class I areas on the Colorado 
Plateau under 40 CFR 51.309.
    EPA promulgated a rule to address regional haze on July 1, 1999 
known as the Regional Haze Rule (RHR) (64 FR 35713). The RHR revised 
the existing visibility regulations to include provisions addressing 
regional haze impairment and established a comprehensive visibility 
protection program for Class I areas. The requirements for regional 
haze, found at 40 CFR 51.308 and 51.309, are included in EPA's 
visibility protection regulations at 40 CFR 51.300-309. Some of the 
major elements of the RHR requirements are summarized in section III of 
this notice. The requirement to submit a regional haze plan revision 
applies to all 50 states, the District of Columbia, and the Virgin 
Islands. States were required to submit the first implementation plan 
addressing regional haze visibility impairment no later than December 
17, 2007. 40 CFR 51.308(b). Since most states, including Nevada, did 
not submit SIPs prior to the deadline, EPA made a Finding of Failure to 
Submit that extended the deadline to January 15, 2011, for EPA to 
approve a SIP or publish a Federal Implementation Plan (FIP). 74 FR 
2392 (January 15, 2009). EPA is publishing this proposal to meet this 
obligation.

C. Roles of Agencies in Addressing Regional Haze

    Successful implementation of the regional haze program will require 
long-term coordination among states, Tribal governments and various 
Federal agencies. As noted above, pollution affecting the air quality 
in Class I areas can result from the transport of pollutants over long 
distances, even hundreds of kilometers. Therefore, states and Tribal 
nations need to develop coordinated strategies to take into account the 
effect of emissions from one jurisdiction on the air quality in 
another. To support a regional approach to the planning process, EPA 
founded five regional planning organizations (RPOs) to assist states 
and Tribes in addressing regional haze and related issues. The RPOs 
first evaluated technical information to better understand how 
emissions impact Class I areas across the country, and then pursued the 
development of regional strategies to reduce pollutants contributing to 
regional haze.
    The Western Regional Air Partnership (WRAP), one of five RPOs 
nationally, is a voluntary partnership of State, Tribal, Federal, and 
local air agencies focusing on improving visibility at 116 Class I 
areas in the West. WRAP member states include: Alaska, Arizona, 
California, Colorado, Idaho, Montana, New Mexico, North Dakota, Oregon, 
South Dakota, Utah, Washington and Wyoming. WRAP Tribal members include 
Campo Band of Kumeyaay Indians, Confederated Salish and Kootenai 
Tribes, Cortina Indian Rancheria, Hopi Tribe, Hualapai Nation of the 
Grand Canyon, Native Village of Shungnak, Nez Perce Tribe, Northern 
Cheyenne Tribe, Pueblo of Acoma, Pueblo of San Felipe, and Shoshone-
Bannock Tribes of Fort Hall. While Nevada is not a formal member of the 
WRAP, State representatives participated fully in the WRAP and relied 
on its technical services and products as the basis for its plan.
    While EPA regulates visibility at Class I areas, Federal Land 
Managers (FLMs) from the National Park Service, Fish and Wildlife 
Service, and Forest Service have a special role in the program because 
they have primary jurisdiction over Class I areas. FLMs may submit 
comments and make recommendations on a state's plan, and states are 
required to coordinate and consult with FLMs on most major planning and 
implementation requirements.

III. Requirements for Regional Haze SIPs

 A. Regional Haze Rule

    Regional haze SIPs must establish a long-term strategy that ensures 
reasonable progress toward achieving natural visibility conditions in 
each Class I area affected by the state's emissions. For each Class I 
area within its boundaries, the state must establish a reasonable 
progress goal (RPG) for the first planning period that ends on July 31, 
2018. The long-term strategy must include enforceable emission limits 
and other measures as necessary to achieve the RPG. State 
implementation plans must also give specific attention to certain 
stationary sources that were in existence on August 7, 1977, but were 
not in operation before August 7, 1962. These sources, where 
appropriate, are required to install Best Available Retrofit Technology 
(BART) controls to eliminate or reduce visibility

[[Page 36453]]

impairment. The specific regional haze SIP requirements are summarized 
below.

 B. Determination of Baseline, Natural and Current Visibility 
Conditions

    The RHR establishes the deciview (dv) as the principal metric for 
measuring visibility. This visibility metric expresses uniform changes 
in haziness in terms of common increments across the entire range of 
visibility conditions, from pristine to extremely hazy conditions. 
Visibility expressed in deciviews is determined by using air quality 
measurements to estimate light extinction and then transforming the 
value of light extinction to deciviews using a logarithmic function. 
The deciview is a more useful measure for tracking progress in 
improving visibility than light extinction because each deciview change 
is an equal incremental change in visibility as perceived by the human 
eye. Most people can detect a change in visibility at one deciview.\3\
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    \3\ The preamble to the RHR provides additional details about 
the deciview. 64 FR 35714, 35725 (July 1, 1999).
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    The deciview is used to express reasonable progress goals; define 
visibility conditions; and track changes in visibility. To track 
changes in visibility at each of the 156 Class I areas covered by the 
visibility program (40 CFR 81.401-437), and as part of the process for 
determining reasonable progress, states must calculate the degree of 
existing visibility impairment at each Class I area and periodically 
review progress midway through each ten-year implementation period. To 
do this, the RHR requires states to determine the degree of impairment 
(in deciviews) for the average of the 20 percent least impaired 
(``best'') and 20 percent most impaired (``worst'') visibility days 
over a specified time period at each of their Class I areas. In 
addition, states must develop an estimate of natural visibility 
conditions for the purpose of comparing progress toward the national 
goal. Natural visibility is determined by estimating the natural 
concentrations of pollutants that cause visibility impairment and then 
calculating total light extinction based on those estimates. EPA has 
provided guidance to states regarding how to calculate baseline, 
natural and current visibility conditions in documents titled, EPA's 
Guidance for Estimating Natural Visibility Conditions Under the 
Regional Haze Rule, September 2003, (EPA-454/B-03-005 located at https://www.epa.gov/ttncaaa1/t1/memoranda/rh_envcurhr_gd.pdf), (hereinafter 
referred to as ``EPA's 2003 Natural Visibility Guidance''), and 
Guidance for Tracking Progress Under the Regional Haze Rule (EPA-454/B-
03-004 September 2003 located at https://www.epa.gov/ttncaaa1/t1/memoranda/rh_tpurhr_gd.pdf), hereinafter referred to as ``EPA's 2003 
Tracking Progress Guidance'').
    For the first regional haze SIPS that were due by December 17, 
2007, ``baseline visibility conditions'' were the starting points for 
assessing ``current'' visibility impairment. Baseline visibility 
conditions represent the degree of visibility impairment for the 20 
percent least impaired days and 20 percent most impaired days for each 
calendar year from 2000 to 2004. Using monitoring data for 2000 through 
2004, states are required to calculate the average degree of visibility 
impairment for each Class I area, based on the average of annual values 
over the five-year period. The comparison of initial baseline 
visibility conditions to natural visibility conditions indicates the 
amount of improvement necessary to attain natural visibility, while the 
future comparison of baseline conditions to the then current conditions 
will indicate the amount of progress. In general, the 2000-2004 
baseline period is considered the time from which improvement in 
visibility is measured.

C. Determination of Reasonable Progress Goals

    The vehicle for ensuring continuing progress towards achieving the 
natural visibility goal is the submission of a series of regional haze 
SIPs that establish two RPGs (i.e., two distinct goals, one for the 
``best'' and one for the ``worst'' days) for every Class I area for 
each (approximately) ten-year implementation period. The RHR does not 
mandate specific milestones or rates of progress, but instead calls for 
states to establish goals that provide for ``reasonable progress'' 
toward achieving natural (i.e., ``background'') visibility conditions. 
In setting reasonable progress goals (RPGs), states must provide for an 
improvement in visibility for the most impaired days over the 
(approximately) ten-year period of the SIP, and ensure no degradation 
in visibility for the least impaired days over the same period.
    States have significant discretion in establishing RPGs, but are 
required to consider the following factors established in section 169A 
of the CAA and in EPA's RHR at 40 CFR 51.308(d)(1)(i)(A): (1) The costs 
of compliance; (2) the time necessary for compliance; (3) the energy 
and non-air quality environmental impacts of compliance; and (4) the 
remaining useful life of any potentially affected sources. States must 
demonstrate in their SIPs how these factors are considered when 
selecting the RPGs for the best and worst days for each applicable 
Class I area. States have considerable flexibility in how they take 
these factors into consideration, as noted in EPA's Guidance for 
Setting Reasonable Progress Goals under the Regional Haze Program, July 
1, 2007, memorandum from William L. Wehrum, Acting Assistant 
Administrator for Air and Radiation, to EPA Regional Administrators, 
EPA Regions 1-10 (pp. 4-2, 5-1) (``EPA's Reasonable Progress 
Guidance''). In setting the RPGs, states must also consider the rate of 
progress needed to reach natural visibility conditions by 2064 
(referred to as the ``uniform rate of progress'' (URP) or the ``glide 
path'') and the emission reduction measures needed to achieve that rate 
of progress over the ten-year period of the SIP. Uniform progress 
towards achievement of natural conditions by the year 2064 represents a 
rate of progress that states are to use for analytical comparison to 
the amount of progress they expect to achieve. In setting RPGs, each 
state with one or more Class I areas (``Class I state'') must also 
consult with potentially ``contributing states,'' i.e., other nearby 
states with emission sources that may be affecting visibility 
impairment at the Class I state's areas. 40 CFR 51.308(d)(1)(iv).

D. Best Available Retrofit Technology

    Section 169A of the CAA directs states to evaluate the use of 
retrofit controls at certain larger, often uncontrolled, older 
stationary sources in order to address visibility impacts from these 
sources. Specifically, section 169A(b)(2)(A) of the CAA requires states 
to revise their SIPs to contain such measures as may be necessary to 
make reasonable progress towards the natural visibility goal, including 
a requirement that certain categories of existing major stationary 
sources \4\ built between 1962 and 1977 procure, install, and operate 
the ``Best Available Retrofit Technology'' as determined by the state. 
Under the RHR, states are directed to conduct BART determinations for 
such ``BART-eligible'' sources that may be anticipated to cause or 
contribute to any visibility impairment in a Class I area. Rather than 
requiring source-specific BART controls, states also have the 
flexibility to adopt an emissions trading program or other alternative 
program as

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long as the alternative provides greater reasonable progress towards 
improving visibility than BART.
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    \4\ The set of ``major stationary sources'' potentially subject 
to BART is listed in CAA section 169A(g)(7).
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    EPA published on July 6, 2005, the Guidelines for BART 
Determinations under the Regional Haze Rule at Appendix Y to 40 CFR 
part 51 (hereinafter referred to as the ``BART Guidelines'') to assist 
states in determining which of their sources should be subject to the 
BART requirements and in determining appropriate emission limits for 
each applicable source. In making a BART determination for a fossil 
fuel-fired electric generating plant with a total generating capacity 
in excess of 750 megawatts, a state must use the approach set forth in 
the BART Guidelines. A state is encouraged, but not required, to follow 
the BART Guidelines in making BART determinations for other types of 
sources.
    States must address all visibility-impairing pollutants emitted by 
a source in the BART determination process. The most significant 
visibility impairing pollutants are SO2, NOX and 
PM. EPA has indicated that states should use their best judgment in 
determining whether VOC or NH3 compounds impair visibility 
in Class I areas.
    Under the BART Guidelines, states may select an exemption threshold 
value for their BART modeling, below which a BART-eligible source would 
not be expected to cause or contribute to visibility impairment in any 
Class I area. The state must document this exemption threshold value in 
the SIP and must state the basis for its selection of that value. Any 
source with emissions that model above the threshold value would be 
subject to a BART determination review. The BART Guidelines acknowledge 
varying circumstances affecting different Class I areas. States should 
consider the number of emission sources affecting the Class I areas at 
issue and the magnitude of the individual sources' impacts. An 
exemption threshold set by the state should not be higher than 0.5 
deciview.
    In their SIPs, states must identify potential BART sources, 
described in the RHR as ``BART-eligible sources,'' and document their 
BART control determination analyses. In making BART determinations, 
section 169A(g)(2) of the CAA requires that states consider the 
following factors: (1) The costs of compliance; (2) the energy and non-
air quality environmental impacts of compliance; (3) any existing 
pollution control technology in use at the source; (4) the remaining 
useful life of the source; and, (5) the degree of improvement in 
visibility which may reasonably be anticipated to result from the use 
of such technology. States are free to determine the weight and 
significance assigned to each factor.
    A regional haze SIP must include source-specific BART emission 
limits and compliance schedules for each source subject to BART. Once a 
state has made its BART determination, the BART controls must be 
installed and in operation as expeditiously as practicable, but no 
later than five years after the date EPA approves the regional haze 
SIP. CAA section 169(g)(4). 40 CFR 51.308(e)(1)(iv). In addition to 
what is required by the RHR, general SIP requirements mandate that the 
SIP must also include all regulatory requirements related to 
monitoring, recordkeeping and reporting for the BART controls on the 
source. States have the flexibility to choose the type of control 
measures they will use to meet the requirements of BART.

E. Long-Term Strategy

    Consistent with the requirement in section 169A(b) of the CAA that 
states include in their regional haze SIP a ten- to fifteen-year 
strategy for making reasonable progress, section 51.308(d)(3) of the 
RHR requires that states include a long-term strategy (LTS) in their 
regional haze SIPs. The LTS is the compilation of all control measures 
a state will use during the implementation period of the specific SIP 
submittal to meet applicable RPGs. The LTS must include ``enforceable 
emissions limitations, compliance schedules, and other measures needed 
to achieve the reasonable progress goals'' for all Class I areas within 
and affected by emissions from the state. 40 CFR 51.308(d)(3).
    When a state's emissions are reasonably anticipated to cause or 
contribute to visibility impairment in a Class I area located in 
another state, the RHR requires the impacted state to coordinate with 
contributing states to develop coordinated emissions management 
strategies. 40 CFR 51.308(d)(3)(i). In such cases, the contributing 
state must demonstrate that it has included in its SIP, all measures 
necessary to obtain its share of the emission reductions needed to meet 
the RPGs for the Class I area. The RPOs have provided forums for 
significant interstate consultation, but additional consultation 
between states may be required to sufficiently address interstate 
visibility issues (e.g., where two states belong to different RPOs).
    States should consider all types of anthropogenic sources of 
visibility impairment in developing their LTS, including stationary, 
minor, mobile, and area sources. At a minimum, states must describe how 
each of the following seven factors listed below are taken into account 
in developing their LTS: (1) Emission reductions due to ongoing air 
pollution control programs, including measures to address RAVI; (2) 
measures to mitigate the impacts of construction activities; (3) 
emissions limitations and schedules for compliance to achieve the RPG; 
(4) source retirement and replacement schedules; (5) smoke management 
techniques for agricultural and forestry management purposes including 
plans as currently exist within the state for these purposes; (6) 
enforceability of emissions limitations and control measures; and, (7) 
the anticipated net effect on visibility due to projected changes in 
point, area, and mobile source emissions over the period addressed by 
the LTS. 40 CFR 51.308(d)(3)(v).

F. Coordination of the Regional Haze SIP and Reasonably Attributable 
Visibility Impairment

    As part of the RHR, EPA revised 40 CFR 51.306(c) regarding the 
long-term strategy for RAVI to require that the RAVI plan must provide 
for a periodic review and SIP revision not less frequently than every 
three years until the date of submission of the state's first plan 
addressing regional haze visibility impairment, which was due December 
17, 2007, in accordance with 40 CFR 51.308(b) and (c). On or before 
this date, the state must revise its plan to provide for review and 
revision of a coordinated LTS for addressing RAVI and regional haze, 
and the state must submit the first such coordinated LTS with its first 
regional haze SIP. Future coordinated LTSs, and periodic progress 
reports evaluating progress towards RPGs, must be submitted consistent 
with the schedule for SIP submission and periodic progress reports set 
forth in 40 CFR 51.308(f) and 51.308(g), respectively. The periodic 
review of a state's LTS must report on both regional haze and RAVI 
impairment and must be submitted to EPA as a SIP revision.

G. Monitoring Strategy

    Section 51.308(d)(4) of the RHR requires a monitoring strategy for 
measuring, characterizing, and reporting on regional haze visibility 
impairment that is representative of all mandatory Class I areas within 
the state. The strategy must be coordinated with the monitoring 
strategy required in 40 CFR 51.305 for RAVI. Compliance with this 
requirement may be met through ``participation'' in the Interagency 
Monitoring of Protected Visual

[[Page 36455]]

Environments (IMPROVE) network, i.e., review and use of monitoring data 
from the network. The monitoring strategy is due with the first 
regional haze SIP, and it must be reviewed every five years. The 
monitoring strategy must also provide for additional monitoring sites 
if the IMPROVE network is not sufficient to determine whether RPGs will 
be met. The SIP must also provide for the following:
     Procedures for using monitoring data and other information 
in a state with mandatory Class I areas to determine the contribution 
of emissions from within the state to regional haze visibility 
impairment at Class I areas both within and outside the state;
     Procedures for using monitoring data and other information 
in a state with no mandatory Class I areas to determine the 
contribution of emissions from within the state to regional haze 
visibility impairment at Class I areas in other states;
     Reporting of all visibility monitoring data to the 
Administrator at least annually for each Class I area in the state, and 
where possible, in electronic format;
     Developing a statewide inventory of emissions of 
pollutants that are reasonably anticipated to cause or contribute to 
visibility impairment in any Class I area. The inventory must include 
emissions for a baseline year, emissions for the most recent year for 
which data are available, and estimates of future projected emissions. 
A state must also make a commitment to update the inventory 
periodically; and,
     Other elements, including reporting, recordkeeping, and 
other measures necessary to assess and report on visibility.

H. SIP Revisions and Progress Reports

    The RHR requires control strategies to cover an initial 
implementation period through 2018, with a comprehensive reassessment 
and revision of those strategies, as appropriate, every ten years 
thereafter. Periodic SIP revisions must meet the core requirements of 
section 51.308(d) with the exception of BART. The requirement to 
evaluate sources for BART applies only to the first regional haze SIP. 
Facilities subject to BART must continue to comply with the BART 
provisions of section 51.308(e), as noted above. Periodic SIP revisions 
will assure that the statutory requirement of reasonable progress will 
continue to be met.
    Each state also is required to submit a report to EPA every five 
years that evaluates progress toward achieving the RPG for each Class I 
area within the state and outside the state if affected by emissions 
from within the state. 40 CFR 51.308(g). The first progress report is 
due five years from submittal of the initial regional haze SIP 
revision. At the same time a 5-year progress report is submitted, a 
state must determine the adequacy of its existing SIP to achieve the 
established goals for visibility improvement. 40 CFR 51.308(h). The RHR 
contains more detailed requirements associated with these parts of the 
Rule.

I. Coordination With Federal Land Managers

    The RHR requires that states consult with Federal Land Managers 
(FLMs) before adopting and submitting their SIPs. 40 CFR 51.308(i). 
States must provide FLMs an opportunity for consultation, in person and 
at least sixty days prior to holding any public hearing on the SIP. 
This consultation must include the opportunity for the FLMs to discuss 
their assessment of impairment of visibility in any Class I area and to 
offer recommendations on the development of the RPGs and on the 
development and implementation of strategies to address visibility 
impairment. Furthermore, a state must include in its SIP a description 
of how it addressed any comments provided by the FLMs. Finally, a SIP 
must provide procedures for continuing consultation between the state 
and FLMs regarding the state's visibility protection program, including 
development and review of SIP revisions, five-year progress reports, 
and the implementation of other programs having the potential to 
contribute to impairment of visibility in Class I areas.

IV. EPA's Analysis of Nevada's RH SIP

A. Affected Class I Areas

    Nevada has one Class I area, the Jarbidge Wilderness Area 
(hereinafter referred to as Jarbidge), located within the Humboldt 
National Forest in the northeastern corner of the State. NDEP 
identified 24 other Class I areas \5\ located outside the State that 
may be affected by its emissions. These other Class I areas are in 
Arizona (5), California (11), Idaho (2), Oregon (3) and Utah (3). In 
Arizona, the Class I areas are Grand Canyon National Park (NP), 
Sycamore Canyon Wilderness Area (WA), Pine Mountain WA, Mazatal WA, and 
Sierra Ancha WA. In California, they are Desolation WA, Dome Land WA, 
Hoover WA, Joshua Tree NP, Kaiser WA, Lassen Volcanic NP, Lava Beds WA, 
San Gabriel WA, San Gorgonio WA, Sequoia NP, and Yosemite NP. In Idaho, 
the areas are Craters of the Moon WA and Sawtooth WA. In Oregon, the 
areas are Crater Lake NP, Hells Canyon WA and Eagle Cap WA. In Utah, 
the areas are Bryce Canyon NP, Capitol Reef NP and Zion NP. EPA is 
proposing to find that NDEP has identified all affected Class I areas 
within and outside the State that are potentially affected by its 
emissions.
---------------------------------------------------------------------------

    \5\ These Class I areas were identified using Particle Source 
Apportionment Tracking (PSAT) modeling results for sulfate and 
nitrate extinction. Tables 4-3 and 4-4 in the Nevada Regional Haze 
SIP identify the rank and percentage of the total modeled 
concentration due to SO2 emissions and NOX 
emissions from sources in Nevada to the IMPROVE monitors 
representing Class I areas in the five adjacent states. Where a 
monitoring site is not located within a specific national park or 
wilderness area, the closest Class I area is listed.
---------------------------------------------------------------------------

B. Visibility Conditions and Uniform Rate of Progress

    NDEP developed the visibility estimates in its RH SIP using air 
quality models and analytical tools provided by the WRAP. Based on 
EPA's review of the WRAP's technical analyses and products, we found 
that the models were used appropriately, and were consistent with EPA 
guidance in effect at the time of their use. The models used by the 
WRAP were state-of-the-science at the time the modeling was conducted, 
and model performance was adequate for the purposes that they were 
used.\6\
---------------------------------------------------------------------------

    \6\ For our detailed review and discussion, please see 
``Technical Support Document for Technical Products Prepared by the 
Western Regional Air Partnership in support of Western Regional Haze 
Plans'', Final, February 2011 (WRAP TSD).
---------------------------------------------------------------------------

1. Baseline and Natural Visibility Conditions
    Baseline visibility conditions represent the degree of visibility 
impairment for the 20 percent least impaired days and 20 percent most 
impaired days for each calendar year from 2000 to 2004. Using 
monitoring data for 2000 through 2004, states are required to calculate 
the average degree of visibility impairment for each Class I area, 
based on the average of annual values over the five-year period.
    NDEP calculated that on the 20 percent worst days at Jarbidge, the 
baseline visibility condition is 12.07 dv and the natural visibility 
condition is 7.87 dv. The natural visibility condition represents the 
long-term national goal of no man-made impairment. Since a state must 
ensure visibility improvement on the worst days, a baseline of 12.07 dv 
and an endpoint of 7.87 dv are used to measure progress. On the 20 
percent best days, the baseline visibility condition is 2.56 dv and the 
natural visibility condition is 1.14 dv. The baseline visibility 
condition on best

[[Page 36456]]

days is a value that must be maintained in future years.
2. Uniform Rate of Progress Estimate
    NDEP calculated the uniform rate of progress (URP) estimate for 
Jarbidge using the deciviews for the 2000-2004 baseline and natural 
background conditions on the 20 percent worst days. The URP is 
represented as a straight line between a Class I area's baseline value 
and natural conditions in 2064. 40 CFR Section 51.308(d)(1)(i)(B). This 
line is linear and assumes the same increment of progress every year 
for 60 years.
    NDEP calculated the URP for Jarbidge in 2018 as 11.09 dv. (See 
Table 1). Given baseline conditions of 12.07 dv and an estimate of 
natural conditions of 7.87 dv, the overall visibility improvement 
necessary to reach the national goal is 4.20 dv. As the regional haze 
rule requires the URP to be calculated over a 60-year period from 
baseline to natural conditions (2004 to 2064), the URP is an average 
annual improvement of 0.07 dv (4.20 dv divided by 60 years). A uniform 
rate of progress in the first planning period (2004 to 2018) would 
result in an improvement of 0.98 dv (14 years times .07 dv). Therefore, 
the URP in 2018 for Jarbidge is 11.09 dv (12.07 dv minus 0.98 dv).
    NDEP produced the following visibility estimates in deciviews for 
its one Class I area: baseline visibility conditions, uniform rate of 
progress estimate for 2018, and natural conditions estimate for 2064. 
We propose to find that these estimates are consistent with the 
requirements of the RHR, particularly the requirements at 40 CFR 
51.308(d)(2)(i) and (iii).

                                  TABLE 1--Visibility Calculations for Jarbidge
                                                 [In deciviews]
----------------------------------------------------------------------------------------------------------------
                                                              2018
                                             2000-20004      Uniform        2018          2064        2000-2004
                                              Baseline       rate of      Reduction      Natural      Baseline
               Class I area                   Condition     progress    needed  (20%    condition     condition
                                             (20% worst    (20% worst    worst days)   (20% worst     (20% best
                                                days)         days)                       days)         days)
----------------------------------------------------------------------------------------------------------------
Jarbidge Wilderness Area..................        12.07         11.09          0.98          7.87         2.56
----------------------------------------------------------------------------------------------------------------
Source: Table 2-1, page 2-7, Nevada RH SIP.

C. Nevada's Emissions Inventories

1. Emissions Inventories for 2002 and 2018
    The RHR requires a statewide emissions inventory of pollutants that 
are reasonably anticipated to cause or contribute to visibility 
impairment in any mandatory Class I area. 40 CFR 51.308(d)(4)(v). NDEP 
provides a statewide emissions inventory for 2002, representing the 
mid-point of the 2000-2004 baseline period, and a projected emissions 
inventory for 2018, the end of the first 10-year planning period. The 
2018 inventory is based on visibility modeling conducted by the WRAP's 
Regional Modeling Center using the Community Multi-Scale Air Quality 
(CMAQ) model. The emissions inventories for 2002 and 2018 provide 
estimates of annual emissions for haze producing pollutants by source 
category as summarized by EPA in Tables 2 and 3 based on information in 
Chapter 3 of Nevada's RH SIP. The inventoried pollutants include sulfur 
oxides (SOx), nitrogen oxides (NOX), volatile 
organic compounds (VOCs), fine particulate matter under 2.5 microns 
(PM2.5), coarse particulate matter under 10 microns 
(PM10), ammonia (NH3), primary organic aerosol 
(POA),\7\ and elemental carbon (EC). The emissions are divided into six 
source categories: point, area, mobile on-road, mobile off-road, 
natural and other. Natural sources include natural fire, biogenic and 
windblown dust. Other includes oil and gas, road dust, fugitive dust 
and anthropogenic fire. EPA is proposing to find that the emission 
inventories in Nevada's RH SIP were calculated using approved EPA 
methods.
---------------------------------------------------------------------------

    \7\ Instead of using the category of Organic Carbon, Nevada used 
the POA primary organic aerosol that includes organic molecules or 
compounds that are directly emitted from the combustion of organic 
material. These organic compounds include organic carbon, hydrogen, 
oxygen as well as other organic atoms.

                                           TABLE 2--Summary of 2000-2004 Average Baseline Emissions for Nevada
                                                                     [tons per year]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              SOX         NOX         VOC        PM2.5       PM10         NH3         POA         EC
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point...................................................      50,947      59,873       2,215       2,158       4,093         339         256          13
Area....................................................      13,037       5,728      28,592         830         897       8,009         687          96
Mobile On-Road..........................................         510      41,089      36,257           0         245       2,030         314         235
Mobile Off-Road.........................................       1,672      32,565      18,094           0           0          22         572       1,354
Natural.................................................       2,784      23,103     811,745      11,844      99,122       1,684      22,501       4,674
Other...................................................          28         117         199       6,138      56,786           8         405          37
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................      68,978     162,475     897,102      20,970     161,143      12,092      24,734       6,409
Percent.................................................         (5)        (12)        (66)       (1.5)        (12)         (1)         (2)       (0.5)
--------------------------------------------------------------------------------------------------------------------------------------------------------


[[Page 36457]]


                                                      TABLE 3--Summary of 2018 Emissions for Nevada
                                                                     [Tons per year]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              SOX         NOX         VOC        PM2.5       PM10         NH3         POA         EC
--------------------------------------------------------------------------------------------------------------------------------------------------------
Point...................................................      28,320      67,632       3,866       2,211       4,717         864         168          13
Area....................................................      14,280       7,418      53,014       1,150       1,012       8,535         776         115
Mobile On-Road..........................................         336      15,049      17,085           0         360       3,385         422         121
Mobile Off-Road.........................................         473      22,182      11,784           0           0          30         393         668
Natural.................................................       2,784      23,103     811,745      11,844      99,122       1,684      22,501       4,674
Other...................................................          30         114         213       8,928      83,076           5         561          47
                                                         -----------------------------------------------------------------------------------------------
    Total...............................................      46,223     135,498     897,707      24,133     188,287      14,503      24,822       5,638
Percent.................................................       (3.5)        (10)        (67)         (2)        (14)         (1)         (2)       (0.5)
--------------------------------------------------------------------------------------------------------------------------------------------------------

2. Analysis of Statewide Emissions by Pollutant
    NDEP's analysis of each pollutant in its emissions inventory, as 
summarized below, informs the relationship between the State's 
emissions and visibility impairment at Jarbidge as well as Class I 
areas outside the State.
     Sulfur Dioxide: SO2 emissions are mostly from 
coal combustion at electrical generation facilities, but smaller 
amounts are from natural gas combustion, mobile sources and wood 
combustion. In Nevada, SOX emissions are predominantly from 
point sources (61 percent) and area sources (31 percent). Statewide 
emissions of SO2 are projected to decrease 33 percent by 
2018 as compared to the baseline due to planned BART controls on power 
plants and to reductions in mobile source emissions due to Federal 
diesel fuel standards. Comparing 2018 projections to the baseline, 
SOX emissions from point sources decrease 44 percent; area 
sources increase 10 percent; off-road mobile decrease 72 percent; and 
on-road mobile decrease 34 percent.
     Nitrogen Oxide: NOX is generated during any 
combustion process where nitrogen and oxygen from the atmosphere 
combine to form nitric oxide and to a lesser extent nitrogen dioxide. 
NOX emissions are predominantly from point sources (50 
percent) and mobile sources (27 percent). Statewide emissions of 
NOX are expected to decrease by 17 percent by 2018, 
primarily due to an estimated 36,423 ton reduction in emissions from 
mobile sources due to new Federal vehicle emission standards. While 
NOX from point sources is projected to increase by 13 
percent, the 2018 emissions inventory data does not include 
NOX reductions from the installation of BART controls in 
Nevada. The projected increase of 29 percent in area sources by 2018 is 
largely due to forecasted increases in activity from population growth.
     Volatile Organic Compounds: VOCs are gases emitted by a 
wide array of man-made products and sources, but in Nevada are mostly 
from living organisms (90 percent), a natural source categorized as a 
biogenic. VOCs impact visibility as emissions condense in the 
atmosphere to form an organic aerosol. Projected emissions of VOCs are 
not expected to change by 2018.
     PM2.5: PM fine emissions are composed of fine 
particulates that can remain suspended in the atmosphere for long 
periods of time and travel long distances. In Nevada, these emissions 
are generated mostly by natural fires (49 percent) and area sources (37 
percent) such as woodstoves. Statewide emissions of PM2.5 
are expected to increase by 15 percent by 2018. Most of the increase is 
associated with fugitive dust related to increases in population. 
Overall, PM2.5 is a relatively small part of the visibility 
problem compared to other pollutants.
     PM10: PM coarse emissions are larger particles 
that travel shorter distances, but still contribute to regional 
visibility impairment. In Nevada, PM coarse emissions are predominately 
due to windblown dust (50 percent) and fugitive dust (36 percent). 
PM10 emissions are expected to increase about 17 percent by 
2018 due mostly to projected increases in road dust and fugitive dust 
linked to increases in population. Windblown dust is not projected to 
change by 2018, and remains the primary source category for these 
emissions.
     Ammonia: NH3 emissions are from a variety of 
sources including wastewater treatment facilities, livestock 
operations, fertilizer applications and mobile sources. NH3 
emissions are predominantly from area sources (59 percent) and on-road 
mobile sources (23 percent). The 2018 projections indicate a net 
increase of 20 percent, mostly from on-road mobile sources due to 
projected increases in population, and by extension, vehicular traffic. 
While emission estimates for NH3 are hard to quantify, these 
pollutants are important because they react with SO2 and 
NOX to form ammonium sulfate (SO4) and ammonium 
nitrate (NO3) particles that are very effective in impairing 
visibility.
     Primary Organic Aerosol: POA includes organic molecules or 
compounds directly emitted from the combustion of organic material. 
Natural fire emissions (91 percent) dominate this category of statewide 
emissions.
     Elemental Carbon: EC particulates are emitted as a primary 
aerosol from fossil fuel combustion (vehicles, boilers, and other 
industrial processes), wild fires and other types of burning. In 
Nevada, the primary source of EC emissions is natural fire (83 percent) 
followed by off-road mobile (12 percent). Total EC emissions are 
projected to decrease 12 percent by 2018, mostly from mobile source 
emissions reductions resulting from Federal regulations.
3. Analysis of Natural Versus Anthropogenic Emissions
    NDEP distinguishes between natural and anthropogenic sources of 
statewide emissions to indicate the type and level of emissions within 
the State that are amenable to controls. Table 4 provides a summary of 
anthropogenic and natural emissions based on the 2018 emissions 
inventory. The last column provides the percentage change in total 
emissions from the average emissions baseline.

[[Page 36458]]



                       Table 4--Natural v. Anthropogenic Sources Emissions Summary in 2018
                                                 [Tons per year]
----------------------------------------------------------------------------------------------------------------
                                             Anthropogenic              Natural                         Change
                                       ------------------------------------------------   Total in       from
                                                                                            2018       baseline
                                        Tons/ year  % of total  Tons/ year  % of total                    (%)
----------------------------------------------------------------------------------------------------------------
SOX...................................      43,440          94       2,784           6        46,224       -33.0
NOX...................................     112,394          83      23,102          17       135,496       -16.6
EC....................................         964          17       4,674          83         5,638       -12.0
PM2.5.................................      12,289          51      11,845          49        24,134        15.1
PM10..................................      89,165          47      99,122          53       188,287        16.8
NH3...................................      12,819          88       1,684          12        14,503        19.9
POA...................................       2,321           9      22,501          91        24,822         0.4
VOC...................................      85,962          10     811,745          90       897,707         0.1
                                       -------------------------------------------------------------------------
    Total.............................     359,354          27     977,458          73     1,336,811        -1.3
----------------------------------------------------------------------------------------------------------------
Source: Table 3-6, page 3-14, Nevada RH SIP.

    NDEP estimates that about 73 percent of its statewide emissions in 
2018 are projected to come from natural sources (i.e., natural fires, 
windblown dust and biogenics). Natural sources contribute most of the 
emissions of EC, POA and VOC, and about half the emissions of 
PM2.5 and PM10. While anthropogenic sources 
comprise only 27 percent of the projected inventory in 2018, these 
sources are important contributors of SOX, NOX 
and NH3 as well as half of PM2.5 and 
PM10.

D. Sources of Visibility Impairment

    NDEP used baseline monitoring data presented in Table 5 to analyze 
the contribution of pollutants to light extinction (i.e., visibility 
impairment) on the worst days at Jarbidge. The pollutants causing the 
highest levels of light extinction are associated with the sources 
causing the most visibility impairment. The primary contributors to 
light extinction at Jarbidge are organic matter carbon (40 percent), 
coarse matter (22.3 percent), and sulfates (16.7 percent). Elevated 
levels of organic carbon and its seasonal pattern suggest these 
particles are from wildfires and biogenic sources. Two components of 
organic carbon, POA and VOCs, are each 90 percent from natural sources 
as listed above in the 2018 emissions inventory. While anthropogenic 
emissions contributing to organic carbon may include fossil fuels 
combustion and wood burning, these are not likely sources at Jarbidge, 
which is an isolated national park. Similarly, coarse matter, also 
known as PM10, is due mostly to naturally occurring events 
of windblown dust and fugitive dust based on the 2018 emissions 
inventory. Ammonia sulfate (SO4) is the third highest 
contributor to light extinction on the worst days (16.7 percent), and 
the one most closely associated with anthropogenic sources. Soil 
(PM2.5) and elemental carbon (EC) are mostly from natural 
fire, and ammonia nitrates (NO3) have only a minimal 
contribution to light extinction at Jarbidge. This analysis indicates 
that most of the light extinction at Jarbidge is due to natural 
sources.
---------------------------------------------------------------------------

    \8\ While the baseline period is from 2000 to 2004, the 
monitoring data for 2000 at Jarbidge was invalid because it failed 
to meet EPA's data completeness criteria.

                               Table 5--Percentage of Light Extinction at Jarbidge
                                              [Baseline Period \8\]
----------------------------------------------------------------------------------------------------------------
            Year                  SO4         NO3         OMC         EC         Soil         CM       Sea salt
----------------------------------------------------------------------------------------------------------------
                                              20 Percent Worst Days
----------------------------------------------------------------------------------------------------------------
2001........................        14.6         3.5        38.6         8.4        10.4        24.2         0.3
2002........................        11.5         5.6        48.4         6.5        10.9        17.1         0.0
2003........................        17.3         3.1        40.8         6.3         7.7        24.8         0.0
2004........................        23.6         5.7        32.4         5.0         9.7        23.0         0.7
                             -----------------------------------------------------------------------------------
    Average.................        16.7         4.5        40.0         6.5         9.7        22.3         0.3
----------------------------------------------------------------------------------------------------------------
Source: Table 2-2, page 2-19, Nevada RH SIP.

 1. Sources of Visibility Impairment at Jarbidge
    NDEP relied on source apportionment modeling \9\ conducted by the 
WRAP to determine the sources of sulfate and nitrate particles at 
Jarbidge since these pollutants are commonly associated with 
anthropogenic sources. The source apportionment modeling results for 
the WRAP region on the worst days at Jarbidge in 2018 indicate that the 
relative contribution of particulate sulfate concentrations is 
primarily from point sources and natural fires in Idaho, Oregon, 
Washington, Nevada and California (in descending order). If one expands 
the modeling domain to include all areas outside the WRAP region, the 
areas of greatest sulfate contribution are Outside Domain \10\

[[Page 36459]]

(43.8 percent), Idaho (10.3 percent), Oregon (7.2 percent), and Pacific 
Offshore (6.9 percent). Based on this analysis, Nevada contributes a 
relatively small amount (less than 5 percent) of sulfate at Jarbidge, 
which primarily comes from outside the United States.
---------------------------------------------------------------------------

    \9\ The WRAP's Regional Modeling Center used the Particulate 
Matter Source Apportionment Technology (PSAT) algorithm in the 
Comprehensive Air Quality Model with Extensions (CAMx) to attribute 
particle species, particularly sulfate and nitrate, from specific 
source areas and source categories within the WRAP region. The PSAT 
algorithm applies nitrate-sulfate-ammonia chemistry to a system of 
tracers to track chemical transformation, transport and dissipation 
of emissions based on a 36 kilometer grid cell within a specified 
source area.
    \10\ Outside Domain represents the background concentrations of 
pollutants that enter the modeling domain from sources outside the 
United States as well as portions of Canada and Mexico that are 
included in the modeling domain.
---------------------------------------------------------------------------

    Source apportionment modeling indicates that the areas of greatest 
nitrate contribution in the WRAP region on the worst days at Jarbidge 
in 2018 is primarily from area and mobile sources in Idaho, and mobile 
sources in Utah and Nevada. Point sources in all three states are also 
significant contributors. Including all areas outside the WRAP region, 
Idaho is the largest source of nitrates on the worst days (30.3 
percent), followed by Outside Domain (27.5 percent), Nevada (13.1 
percent), and Utah (10.6 percent). This analysis indicates that Nevada 
contributes a small amount of nitrates at Jarbidge.
    In summary, the analysis of light extinction indicates that organic 
carbon and coarse matter from natural sources account for most of the 
visibility impairment at Jarbidge. While sulfates are an important 
contributor to light extinction, the vast majority of sulfate particles 
are from outside of Nevada.
2. Nevada's Contributions to Visibility Impairment in Class I Areas 
Outside of the State
    NDEP identified the rank and percentage of sulfate extinction and 
nitrate ext