[Federal Register: August 27, 2007 (Volume 72, Number 165)]
[Proposed Rules]
[Page 49045-49067]
[DOCID:fr27au07-14]

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Part II

Environmental Protection Agency

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40 CFR Parts 52 and 81

 Approval and Promulgation of Implementation Plans; Designation of
Areas for Air Quality Planning Purposes; State of California; PM-10;
Affirmation of Determination of Attainment for the San Joaquin Valley
Nonattainment Area; Proposed Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R09-OAR-2006-0583; FRL-8459-2]

Approval and Promulgation of Implementation Plans; Designation of
Areas for Air Quality Planning Purposes; State of California; PM-10;
Affirmation of Determination of Attainment for the San Joaquin Valley
Nonattainment Area

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: In a final rule published in the Federal Register on October
30, 2006, EPA determined that the San Joaquin Valley nonattainment area
(SJV or the Valley) in California attained the National Ambient Air
Quality Standards (NAAQS) for particulate matter with an aerodynamic
diameter less than or equal to a nominal 10 micrometers (PM-10). Since
that final determination of attainment, the State has flagged several
exceedances of the PM-10 standard in 2006 as being caused by
exceptional events, i.e., high winds, and requested that these data be
excluded from attainment determinations. EPA is proposing to concur
with the State's request to flag these exceedances and thus to exclude
that data from use in determining PM-10 attainment for the SJV. EPA is
also proposing to exclude from use in determining attainment for the
SJV exceedances recorded at a monitor located at the Santa Rosa
Rancheria, tribal lands within the boundaries of the SJV, on two bases:
The exceedances occurred while the monitor was operating in very close
proximity to construction activities and, as such, the monitor was not
properly sited during that time for purposes of comparison to the
NAAQS; and the exceedances were caused by an exceptional event. EPA is
proposing to concur with the Santa Rosa Rancheria Tribe's request to
flag these exceedances as due to an exceptional event. As a result, EPA
is proposing to affirm its determination that the SJV has attained the
PM-10 standard based on EPA's evaluation of quality-assured data
through December 2006. In addition to providing the public with an
opportunity to comment on EPA's evaluation and proposed concurrence on
flagged exceedances that occurred through the end of calendar year
2006, EPA is in this proposed rule addressing issues raised in
petitions for reconsideration and withdrawal of EPA's 2006
determination of attainment, filed by Earthjustice on behalf of the
Sierra Club, Latino Issues Forum and others.

DATES: Written comments must be received on or before September 26,
2007.

ADDRESSES: Submit comments, identified by docket number EPA-R09-OAR-
2006-0583, by one of the following methods:
    (1) Federal eRulemaking portal:  http://www.regulations.gov. Follow

the on-line instructions.
    (2) E-mail<EMAIL_ADDRESS>    (3) Mail or deliver: Doris Lo (AIR-2), U.S. Environmental
Protection Agency Region IX, 75 Hawthorne Street, San Francisco, CA
94105-3901.
    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 the http://www.regulations.gov or e-

mail. 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 e-mail directly to EPA, your e-
mail 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: The index to the docket for this action is available
electronically at http://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 in the index, some information may be publicly
available only at the hard copy location (e.g., copyrighted material),
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 directly below.

FOR FURTHER INFORMATION CONTACT: Doris Lo, EPA Region IX, (415) 972-
3959<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Throughout this document, wherever ``we,''
``us,'' or ``our'' are used, we mean EPA.

Table of Contents

I. Background
II. EPA's Proposed Actions
III. Summary of Litigation and Administrative Proceedings
IV. EPA's Exceptional Events Rule
V. EPA's Evaluation of Flagged Exceedances
    A. September 22, 2006 Exceedances at Corcoran, Bakersfield and
Oildale
    1. Procedural Requirements
    2. Technical Criteria
    3. Mitigation Requirements
    B. October 25, 2006 Exceedances at Corcoran and Bakersfield
    1. Procedural Requirements
    2. Technical Criteria
    3. Mitigation Requirements
    C. December 8, 2006 Exceedances at Corcoran and Bakersfield
    1. Procedural Requirements
    2. Technical Criteria
    3. Mitigation Requirements
VI. EPA Evaluation of September 14, September 20 and October 26,
2006 Exceedances Recorded at the Santa Rosa Rancheria
    A. Evaluation Under Principles Established in 40 CFR Part 58,
Appendix E
    B. Evaluation Under the Exceptional Events Rule
    1. Procedural Requirements
    2. Technical Criteria
    3. Mitigation Requirements
VII. Summary of Exceedances from 2004 through 2006
VIII. Petitions for Reconsideration and Withdrawal
    A. Winds and Wildfires on September 22 and October 25, 2006
    B. Notice/Comment on September 22 and October 25, 2006
Exceedances
    C. Wind Conditions in the Valley
    D. EPA's Natural Events Policy
    1. BACM Implementation
    2. District's Natural Events Action Plan
    E. Harvest Activities
    F. Exceedances at Corcoran and Stockton in 2004, Bakersfield in
2005 and the Santa Rosa Rancheria in 2006
IX. Statutory and Executive Order Reviews

I. Background

    On October 17, 2006, EPA finalized its determination that the SJV
attained the NAAQS for PM-10, and on October 30, 2006, EPA published
this determination in the Federal Register. 71 FR 63642. This
determination was based upon monitored air quality data for the PM-10
NAAQS \1\ during the years 2003-2005 and all available quality-assured
data through July 31, 2006. For a more detailed discussion of the
related background for the SJV, please refer to the proposed and final
rules at 71 FR 40952 (July 19, 2006) and 71 FR 63642. Shortly before
EPA issued the determination of attainment, EPA learned of preliminary
data indicating that exceedances had occurred on

September 22, 2006, at several monitors, and that the State intended to
flag \2\ them as caused by natural events and to request that EPA
concur with these flags. EPA stated that because the data were
preliminary and because they may qualify as natural events, EPA would
proceed with its determination of attainment at that time. EPA further
indicated that once quality-assured data were available EPA would
review those data and consider whether the determination of attainment
should be withdrawn.
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    \1\ EPA's final determination of attainment addressed both the
24-hour and annual PM-10 standards; however, on October 17, 2006,
effective on December 18, 2006, EPA revoked the annual PM-10
standard. 71 FR 61144.
    \2\ Once air quality data have been submitted to EPA, it is
possible to ``flag'' specific values for various purposes. ``Data
flagging'' refers to the act of making a notation in a designated
field of an electronic data record. The principal purpose of the
data flagging system in the Air Quality System (AQS) data base is to
identify those air quality measurements for which special attention
or handling is warranted. These include, but are not limited to,
those measurements that are influenced by exceptional events. See 71
FR 12592, 12598 (March 10, 2006).
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    Since the October 2006 final determination of attainment, EPA has
obtained information regarding the PM-10 exceedances summarized in
Table 1, which were recorded at various monitors within the boundaries
of the SJV:

  Table 1.--Summary of Exceedances Evaluated for Today's Proposed Rule
------------------------------------------------------------------------
                                   Monitor location       Concentration
      Date of exceedance               (type(s))          ([mu]g/m\3\)
------------------------------------------------------------------------
September 22, 2006............  Corcoran (FRM, FEM)*..  215, 261
                                Bakersfield-Golden      157, 170
                                 (FRM, FEM).
                                Oildale (FRM).........  162
October 25, 2006..............  Corcoran (FEM)........  304
                                Bakersfield-Golden      193
                                 State Highway (FEM).
December 8, 2006..............  Corcoran (FEM)........  162
                                Bakersfield-Golden      213
                                 State Highway (FEM).
September 14, 2006............  Santa Rosa Rancheria    190
                                 (FRM).
September 20, 2006............  Santa Rosa Rancheria    158
                                 (FRM).
October 26, 2006..............  Santa Rosa Rancheria    157
                                 (FRM).
------------------------------------------------------------------------
* FRM = Federal Reference Method; FEM = Federal Equivalent Method.\3\

    On April 24, 2007, the State submitted to EPA documentation
supporting its claim that the September 22, 2006 exceedances were
caused by high winds and wildfires. This submittal was supplemented
with additional documentation on July 10, 2007. On May 1, 2007, the
State submitted to EPA documentation supporting its claim that the
October 25, 2006 exceedances were caused by high winds. On June 12,
2007, the State submitted to EPA documentation supporting its claim
that the December 8, 2006 exceedances were caused by high winds. The
State believes that all of these exceedances qualify as natural events
and that the data should thus be excluded from consideration in the
attainment determination.
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    \3\ A federal reference method (FRM) is an air sample collection
and analysis method which follows the procedures detailed in the
appendices to 40 CFR part 50. A federal equivalent method (FEM) is
an air sampling collection and analysis method which does not follow
the reference procedures in 40 CFR part 50, but has been certified
and designated by the EPA as obtaining ``equivalent'' results.
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    On July 9, 2007, EPA met with a representative of the Santa Rosa
Rancheria EPA to discuss exceedances recorded on September 14,
September 20 and October 26, 2006. The Tribe has flagged these
exceedances as being caused by an exceptional event related to
construction activities and EPA has compiled documentation to support
that claim.

II. EPA's Proposed Actions

    In this proposed rule, EPA is proposing to concur with the State's
request to flag exceedances of the PM-10 standard within the SJV on
September 22, October 25 and December 8, 2006 as being caused by
exceptional events, i.e., high winds, and thus to exclude these data
from use in determining PM-10 attainment for the SJV. EPA is also
proposing to exclude exceedances recorded at the Santa Rosa Rancheria,
tribal lands within the SJV, on September 14, September 20 and October
26, 2006 from use in determining attainment for the SJV, on two bases:
(1) The exceedances occurred while the monitor was operating in very
close proximity to construction activities and, as such, the monitor
was not properly sited during that time for purposes of comparison to
the NAAQS; and (2) the exceedances were caused by an exceptional event,
i.e., construction activity in very close proximity to the monitor. The
Tribe has flagged those exceedances, and EPA is proposing to concur
with those flags.
    As a result, EPA is proposing to affirm its October 2006 attainment
determination based on its evaluation of quality-assured data from
September 14 through December 31, 2006. After receiving and considering
all relevant public comments on our proposed rule, we will publish our
final determination as to whether we will concur with the State's and
Tribe's requests to flag the exceedances discussed above as affected by
exceptional events and to exclude them from consideration in our
attainment determination. We will also publish our determination as to
whether we will exclude the exceedances at the Santa Rosa Rancheria as
a result of the monitor siting. EPA is not taking comment in these
proposed actions on any issues that were the subject of the 2006
attainment determination rulemaking except to the extent that they
affect EPA's ability to determine that the SJV continued to attain the
PM-10 standard through 2006.
    In this proposed rule we are also addressing relevant issues raised
in the petition for reconsideration and petition to withdraw the
determination of attainment filed by the Latino Issues Forum and
others.
    In our 2006 attainment determination we stated that if, after the
September 22, 2006 data were quality-assured, and after further
evaluating the State's request for exclusion of these data, we
determine that the data do not qualify for exclusion and we believe
that if included that they would establish that the area is in
violation of the NAAQS, EPA would proceed with appropriate rulemaking
action to withdraw its determination of attainment. 71 FR 63642. Both
EPA's natural/exceptional events policies and its exceptional events
rule anticipate that the Agency will concur or nonconcur on a state's
request to exclude data by letter rather than rulemaking.

    Generally we would initiate rulemaking following an attainment
determination for an area only if we had preliminarily concluded that a
withdrawal of that determination would be appropriate. That is not the
case here. However, in this instance both because EPA had indicated in
its final action that it would reassess the attainment determination
once it had quality-assured data for the September 22, 2006 exceedances
and because of the issues raised by the petitions pending before the
Agency and discussed below, we are proposing to concur with the State's
and Tribe's requested flags and affirm our 2006 attainment
determination via notice and comment rulemaking. Because we generally
make determinations of attainment on a calendar year basis, our
proposed rule addresses quality assured exceedances from September 14
through December 31, 2006. Moreover the petitions address exceedances
within this timeframe.

III. Summary of Litigation and Administrative Proceedings

    Earthjustice filed three petitions related to EPA's determination
of attainment for the SJV. On December 27, 2006, Earthjustice, on
behalf of Latino Issues Forum, Medical Advocates for Healthy Air and
Sierra Club, filed in the U.S. Court of Appeals for the 9th Circuit a
petition for review of EPA's October 2006 determination under the Clean
Air Act that the SJV has attained the PM-10 standard. Latino Issues
Forum v. EPA, No. 06-75831 (9th Cir.). On December 29, 2006,
Earthjustice also filed with EPA a petition for reconsideration of our
attainment determination. In the petition, Earthjustice alleges, among
other things, that EPA improperly ignored September 22, 2006 PM-10
exceedances in the SJV that were not subject to public notice and
comment. Finally, on March 21, 2007, Earthjustice filed a petition for
withdrawal of our attainment determination. In this petition,
Earthjustice alleges that the attainment determination must be
withdrawn because, among other things, the exceedances that occurred in
September and October 2006 do not qualify as exceptional events. EPA
addresses issues raised in both of these administrative petitions in
this proposed rule.

IV. EPA's Exceptional Events Rule

    On March 22, 2007, EPA issued a final rule governing the review and
handling of air quality data influenced by exceptional events. 72 FR
13560. The rule became effective on May 21, 2007 and implements section
319 of the CAA, as amended by section 6013 of the Safe Accountable
Flexible Efficient-Transportation Equity Act: A Legacy for Users (SAFE-
TEA-LU) of 2005. In the rule, EPA establishes procedures and criteria
related to the identification, evaluation, interpretation, and use of
air quality monitoring data related to the ozone and particulate matter
NAAQS where states petition EPA to exclude data that are affected by
exceptional events from certain regulatory actions under the CAA. The
rule is codified at 40 CFR 50.1, 50.14, and 51.920. 72 FR at 13580-
13581.
    In the preamble to the final rule, EPA also addresses its
applicability to Indian Tribes. Where, as here, the Santa Rosa
Rancheria Tribe operates an air quality monitor only in order to gather
data for informational purposes but does not implement other programs
such as mitigating the effects of exceptional events, it is EPA's
responsibility to ensure that any exclusion or discounting of data in
Indian country areas comports with the rule's procedures and
requirements. EPA intends to work with tribes on the implementation of
the rule. 72 FR at 13563.
    In 1986 and 1996 EPA issued guidance to address the use of data
influenced by exceptional and natural events: ``Guidance on the
Identification and Use of Air Quality Data Affected by Exceptional
Events'' (July 1986) and ``Areas Affected by PM-10 Natural Events,''
May 30, 1996. CAA Section 319, as amended by SAFE-TEA-LU, states that
these guidance documents continue to apply until the effective date of
a final regulation promulgated under section 319(b)(2). See CAA Section
319(b)(4). SAFE-TEA-LU did not however address those situations where
EPA had not made a determination prior to the effective date of the
rule whether an exceptional event had occurred after a state had
flagged data and submitted a demonstration in a timely manner to show
that such data reflected NAAQS exceedances that were caused by an
exceptional event. In these circumstances, EPA believes that in the
interests of equity and administrative efficiency, a state seeking to
exclude data affected by exceptional events should, for a limited
period of time, be able to choose to comply with either the provisions
of the rule or those of the guidance documents for a limited period of
time. This approach would have some advantages, such as allowing the
state to avoid duplicating its demonstration process and completing the
decisionmaking process already underway. EPA believes that it is
reasonable to use this approach until December 31, 2007 to complete the
transition from the policies to the rule. However, unless the state in
the circumstances described above, specifically requests that EPA
evaluate a natural or exceptional event demonstration under the
guidance documents, EPA will presume that the rule applies.
    Under 40 CFR 50.14(j), an ``exceptional event,'' with specified
exceptions not relevant here, is defined as one ``that affects air
quality, is not reasonably controllable or preventable, is an event
caused by human activity that is unlikely to recur at a particular
location or a natural event, and is determined by the Administrator in
accordance with 40 CFR 50.14 [`treatment of air quality monitoring data
influenced by exceptional events'] to be an exceptional event.'' A
``natural event'' is defined as one ``in which human activity plays
little or no direct causal role.'' 40 CFR 50.14(k).\4\
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    \4\ In the preamble to the final rule, EPA discusses specific
types of natural events, including high wind events (i.e., those
that affect ambient particulate matter concentrations through the
raising of dust or through the re-entrainment of material that has
been deposited). See 72 FR at 13565-13566 and 13576-13577. EPA's
interpretation of the rule with respect to high winds is addressed
in section V. below.
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    The rule establishes a multi-step process for identification by
states, tribes and local agencies of data and submission of the
requisite demonstrations to EPA. 72 FR at 13571. In short, a state must
notify EPA of its intent to exclude measured exceedances of a NAAQS as
being due to an exceptional event by ``flagging'' the data in EPA's AQS
database. 40 CFR 50.14(c)(2)(i). For PM-10, the state should submit the
flags, accompanied by an initial description of the event, by July 1st
of the calendar year following the year in which the flagged
measurement occurred. 40 CFR 50.14(c)(2)(iii). A state that has flagged
data as being due to an exceptional event and is requesting its
exclusion must, after notice and opportunity for public comment, submit
a demonstration that to EPA's satisfaction shows that the flagged event
caused a specific concentration in excess of the NAAQS at the
particular location to justify data exclusion. This demonstration must
be submitted to EPA within 3 years of the calendar quarter following
the event, but no later than 12 months prior to an EPA regulatory
decision. A state must submit the public comments it received along
with its demonstration to EPA. 40 CFR 50.14(c)(3)(i).

    In the preamble to the final rule, EPA explained that it will
generally review the state's demonstration and provide a concurrence or
nonconcurrence on the flag in the AQS database within 60 days of the
state's complete submission. EPA expects that, in most cases, this time
period should be sufficient to review and provide a concurrence or
nonconcurrence regarding a state's request to exclude data affected by
an exceptional event. However, for more complex demonstrations, EPA may
require additional time to make its decision and will notify the state
of the additional time required. 72 FR at 13571. Upon its concurrence
on a flag, EPA will exclude the data from use in determinations of
NAAQS exceedances and violations. 40 CFR 50.14(b).
    The requirements for the demonstration to justify data exclusion
that the state must submit, in this instance, to EPA are set forth at
40 CFR 50.14(a), (b)(1), and (c)(3)(iii). In order to be considered for
exclusion, the state must show that the event satisfies the criteria in
section 50.1(j), there is a clear causal connection between the
exceedances and the claimed exceptional event, the event is associated
with measured concentration in excess of normal historical fluctuations
including background and there would have been no exceedance ``but
for'' the event. 40 CFR 50.14(c)(iii)(A)-(D).
    One of the requirements of section 50.1(j) is that the exceptional
event must be shown to affect air quality, which is met by establishing
that the event is associated with a measured exceedance in excess of
normal historical fluctuations, including background. 40 CFR
50.14(c)(iii)(B). In addition, as noted above there must be a clear
causal relationship between the measurement under consideration and the
event that is claimed to have affected the air quality in the area. 40
CFR 50.14(c)(iii)(C). Air quality impact and causal connection may be
shown through a number of methods including modeling and speciation
analysis. EPA will evaluate whether an event affected air quality and
caused a particular concentration using the weight of available
evidence and considering the historical frequency of such measured
concentrations. States must compare contemporary concentrations with
distribution of historical values and these may be presented on a
seasonal or other temporal basis. 40 CFR 50.14(a)(2) and (c)(3)(iii)(A)
and (C); 72 FR at 13569.
    Also, air quality data may not be excluded except where states,
tribes, or local agencies show, through a weight of evidence approach,
that exceedances or violations of applicable standards would not have
occurred ``but for'' the influence of exceptional events. 40 CFR
50.14(c)(3)(iii)(D). 72 FR at 13570-13571. Finally, states must
demonstrate that they have provided an opportunity for public comment
and must submit any public comments it received to EPA. 40 CFR
50.14(c)(3)(i) and (iv).
    States, tribes, or local agencies must also demonstrate that the
claimed exceptional event meets the other requirements of Sec.
50.1(j)--that the event is not reasonably preventable or controllable
and that the event is either caused by human activity that is unlikely
to recur at a particular location or is a natural event. In this
instance, the claimed events are high winds, i.e. natural events, and
construction, i.e., an event caused by human activity that is unlikely
to recur at the particular location.
    In order to concur on a state's request to exclude data, EPA must
determine that the state's submission is complete and demonstrates to
EPA's satisfaction that the exceptional event caused the exceedances.
Although states must meet the minimum requirements (e.g. ``but for''
test), EPA did not specify a minimum level of documentation in the rule
because the facts and circumstances could vary depending on, among
others, meteorology, and geography. Instead, EPA illustrated through
examples the kind of information that states could consider in meeting
the demonstration requirements of the rule. In describing the
documentation process and requirement, EPA also stated that acceptable
documentation would be determined through consultation with the EPA
regional offices. 72 FR at 13573.
    Finally, under 40 CFR 51.930, a state requesting to exclude air
quality data due to exceptional events must take appropriate and
reasonable actions, including public notification, public education and
implementation of measures, to protect public health from exceedances
or violations of the NAAQS.

V. EPA's Evaluation of Flagged Exceedances

    The State and Tribe have not specifically requested that EPA
evaluate the September 14 through December 31, 2006 exceedances (which
occurred before the effective date of the Exceptional Events Rule)
under EPA's natural events policy or exceptional events policy.
Therefore we are evaluating the State's submittals and the Santa Rosa
Rancheria exceedances under the Exceptional Events Rule to determine
whether they meet both the procedural requirements and the technical
criteria for showing that the exceedances are exceptional. We will
discuss whether the State's submittal and the exceedances at Santa Rosa
Rancheria meet each of these requirements and criteria separately. For
each of the exceedances being discussed in today's proposal, EPA bases
its evaluation on the procedural requirements and technical criteria
and mitigation requirements of the Exceptional Events Rule, as
discussed above and summarized below:
    Procedural Requirements:
     Data are flagged in EPA's AQS database.
     Public had an opportunity to review and comment on the
state's documentation.
     The documentation was submitted to EPA.
     EPA concurs with the state's demonstration.
    Technical Criteria:
     The state must show that the event satisfies the criteria
in 40 CFR 50.1(j).\5\
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    \5\ Section 50.1(j) provides the regulatory definition of an
exceptional event. ``Exceptional event'' means an event that affects
air quality, is not reasonably controllable or preventable, is an
event caused by human activity that is unlikely to recur at a
particular location or a natural event, and is determined by the
Administrator in accordance with 40 CFR 50.14 to be an exceptional
event. It does not include stagnation of air masses or
meteorological inversions, a meteorological event involving high
temperatures or lack of precipitation, or air pollution relating to
source noncompliance.
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     There is a clear causal connection between the exceedance
and the claimed exceptional event.
     The event is associated with measured concentration in
excess of normal historical fluctuations including background.
     There would have been no exceedances ``but for'' the
event.
    Mitigation Requirements:
     Provide for prompt public notification of exceedance
events.
     Provide for public education on how to minimize exposure.
     Provide for the implementation of appropriate measures to
protect the public.

A. September 22, 2006 Exceedances at Corcoran, Bakersfield, and Oildale

    The 24-hour PM-10 NAAQS was exceeded at three monitoring locations
on September 22, 2006: The Corcoran monitoring site recorded
concentrations of 215 [mu]g/m3 and 261 [mu]g/m3
with a FRM sampler and a FEM automated continuous analyzer,\6\
respectively; the

Bakersfield-Golden State Highway monitoring site recorded
concentrations of 157 [mu]g/m3 and 170 [mu]g/m3
with its FRM sampler and FEM (TEOM) analyzers, respectively; and the
Oildale monitoring site recorded a concentration of 162 [mu]g/
m3 with its FRM sampler.
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    \6\ The FEM monitor currently operated at the Corcoran site is
an automated continuous analyzer known as a Tapered Element
Oscillating Microbalance (TEOM).
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    The State concludes that three sources of PM-10 contributed to
exceedances of the 24-hour PM-10 NAAQS on this day: Wind-entrained dust
from sources in the central and southern SJV, which is identified as
the primary source of PM-10; wind-entrained dust from regional sources
from the northern SJV; and emissions related to several wildfires which
are identified as secondary sources of PM-10.\7\ Based on the evidence
submitted, EPA agrees with the State's demonstration that high wind-
entrained dust from sources in the central and southern SJV caused the
exceedances at the three monitoring locations on September 22, 2006.
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    \7\ ``Natural Event Documentation, Corcoran, Oildale, and
Bakersfield, California, September 22, 2006'', April 20, 2007 (NED
for September 22, 2006) at 10.
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    We do not however agree with the State that emissions from
wildfires or regionally transported dust from the northern SJV were
significant contributors.
    After evaluating the State's demonstration under the technical
criteria established in the Exceptional Events Rule, EPA finds that for
the Corcoran, Bakersfield and Oildale areas, the State does not
demonstrate that emissions from wildfires had a significant impact on
the PM-10 concentrations recorded on September 22, 2006. None of the
fires cited in the documentation was within the boundaries of the SJV.
Further, an independent review of PM-2.5 speciation data collected at
Bakersfield and Fresno on the days preceding and after September 22
shows no unusual concentrations of carbon. See http://www.epa.gov/cgi-bin/htmSQL/mxplorer/query_spe.hsql.
 If the fires had had a significant

effect on PM-10 concentrations, there would have been evidence of
increased carbon (one of the chemical constituents of wood smoke) in
the speciation data. The documentation submitted by the State includes
mostly anecdotal evidence of the wildfires' impact and satellite
photographs showing smoke over parts of California. The anecdotal
evidence consists of newspaper reports of reduced visibility due to
smoke and the odor of wood smoke, as well as observations from trained
weather observers at Lemoore Naval Air Station.\8\ EPA finds that the
documentation lacks data linking the fires to the concentrations given
the distance of the fires and the lack of corroborating speciation data
and satellite photographs of the smoke, and newspaper reports do not
rise above general or anecdotal evidence to establish a clear causal
relationship between the exceedances on September 22, 2006 and the
emissions from wildfires.
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    \8\ NED for September 22, 2006 at 11, Table 3, 14 and 37-44.
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    Similarly, EPA believes that the State's documentation that
regional sources of entrained dust impacted monitors in the Corcoran
and Bakersfield areas does not show a clear causal relationship between
the exceedances and regional transport of PM-10 from the northern SJV.
EPA bases this conclusion on its review of the documentation which
indicates that while there were high hourly averaged winds and gusts in
the northern central valley of California, the State did not present
any facts, corroborating evidence or any convincing argument to
demonstrate how PM-10 from this area could have reached the southern
SJV in concentrations sufficient to contribute to an exceedance of the
24-hour PM-10 NAAQS.
    Because EPA does not agree with the State's conclusions with
respect to regional transport of PM-10 from the northern SJV and with
respect to wildfires, in the following discussion regarding the
September 22, 2006 exceedances we refer only to the State's conclusion
that these exceedances were caused by wind-entrained dust from sources
in the central and southern SJV.
1. Procedural Requirements
a. Data Are Flagged in EPA's AQS Database
    All of the September 22, 2006 exceedances were flagged in EPA's AQS
database as of July 2007.
b. Public Had an Opportunity To Review and Comment on the State's
Documentation
    In February 2007, the SJV Air Pollution Control District (SJVAPCD
or District) notified the public in local newspapers and on its Web
site of the availability of the document entitled ``Natural Event
Documentation, High Winds, Corcoran and Bakersfield, California,
September 22, 2006,'' SJV Unified Air Pollution Control District,
February 2007 and requested public comments by March 5, 2007.
    The SJVAPCD subsequently revised the February 2007 document and
submitted to the California Air Resources Board (CARB) ``Natural Event
Documentation, Corcoran, Oildale and Bakersfield, California, September
22, 2006,'' SJV Unified Air Pollution Control District, April 20, 2007
(NED for September 22, 2006) and posted it on its Web site.
    SJVAPCD thereafter provided additional information to CARB in
``Addendum, Natural Event Documentation, Corcoran, Oildale and
Bakersfield, California, September 22, 2006,'' SJV Unified Air
Pollution Control District, May 23, 2007 (NED Addendum for September
22, 2006) and posted it on its Web site.
    The District indicated that no public comments were received during
the public process.
c. The Documentation Was Submitted to EPA
    The NED for September 22, 2006 and the NED Addendum for September
22, 2006 were subsequently submitted by the State to EPA on April 24,
2007 and July 10, 2007, respectively, and are the documents upon which
EPA is basing its evaluation below.
d. EPA Concurs With the State's Demonstration
    In this proposed rule, EPA is proposing to concur with the State's
demonstration in the NED for September 22, 2006 and the NED Addendum
for September 22, 2006 that high wind-entrained dust from the central
and southern SJV caused the exceedances at the three monitoring
locations on September 22, 2006.
2. Technical Criteria
a. Did this event satisfy the criteria in section 50.1(j) of the Rule?
    The State needs to show that the September 22, 2006 event, wind-
entrained dust from sources in the central and southern SJV, affected
air quality in the Corcoran and Bakersfield areas,\9\ was not
reasonably controllable or preventable, was a natural event, and is
determined by EPA through the process established in the Rule to be an
exceptional event. We believe the State has supported its claims that
wind-driven dust from sources of PM-10 in the central and southern SJV
was the cause of the September 22, 2006 exceedances, as discussed in
detail below.
---------------------------------------------------------------------------

    \9\ The Bakersfield-Golden State Highway and Oildale monitors
are approximately 3.5 miles apart. For the purposes of this
discussion, the analysis for the Bakersfield-Golden State Highway
and Oildale monitors is the same.

---------------------------------------------------------------------------

i. Affected Air Quality
    For an event to qualify as an exceptional event, the state must
show that the event affected air quality. This criterion can be met by
establishing that the event is associated with a measured exceedance in
excess of normal historical fluctuations, including background, and
there is a causal connection between the event and the exceedance. The
demonstration of a clear causal relationship is necessary to establish
that the event affected air quality and is also a separate statutory
requirement as discussed above.
    In the NED for September 22, 2006 and the NED Addendum for
September 22, 2006, the State provides documentation that the measured
exceedances on September 22, 2006 were in excess of normal historical
fluctuations. See subsection c. below. The State also establishes a
causal connection between the high winds recorded at Lemoore and the
high concentrations recorded at the Corcoran, Bakersfield, and Oildale
monitors. The State's demonstration of the clear causal relationship
between the event and the exceedances on this day is discussed in
greater detail in subsection b. below.
ii. Not Reasonably Controllable or Preventable
    Section 50.1(j) of the Exceptional Events Rule requires that for an
event to qualify as an exceptional event, whether natural or
anthropogenic, a state must show that the event was not reasonably
preventable or controllable. Here this requirement is met by
demonstrating that despite reasonable and appropriate measures in
place, the September 22, 2006 wind event caused the exceedances. During
this event there were no other unusual dust-producing activities
occurring in the SJV and anthropogenic emissions were approximately
constant before, during and after the event. In addition, the State
shows that reasonable and appropriate measures were in place, including
Regulation VIII (the District's general fugitive dust rules) and Rule
4550 which limits fugitive dust emissions specifically from
agricultural operations through Conservation Management Practices.\10\
Moreover, EPA has approved the District's best available control
measure (BACM) demonstration for all significant sources of PM-10 in
the SJV as meeting CAA section 189(b)(1)(B).\11\
---------------------------------------------------------------------------

    \10\ NED for September 22, 2006 at 32.
    \11\ 69 FR 30006, 30035 (May 26, 2004); 71 FR 7683 (February 14,
2006).
---------------------------------------------------------------------------

iii. Was a Natural Event
    In the preamble to the Exceptional Events Rule EPA states that
ambient particulate matter concentrations due to dust being raised by
unusually high winds will be treated as due to uncontrollable natural
events where (1) the dust originated from nonanthropogenic sources, or
(2) the dust originated from anthropogenic sources within the State,
that are determined to have been reasonably well-controlled at the time
that the event occurred, or from anthropogenic sources outside the
State. 72 FR at 13576. In the preamble EPA also explains that
``[s]tates must provide appropriate documentation to substantiate why
the level of wind speed associated with the event in question should be
considered unusual for the affected area during the time of year that
the event occurred.'' Id. at 13566.
    On September 22, 2006, the wind-entrained dust originated from
anthropogenic sources within California, i.e., from usual dust-
generating activities such as agricultural and industrial
operations.\12\ We discuss the fugitive dust control measures in place
in the SJV on September 22 above.
---------------------------------------------------------------------------

    \12\ NED for September 22, 2006 at 32-33.
---------------------------------------------------------------------------

    With respect to the wind speed, EPA concurs with the State's
demonstration that the wind speeds in the central SJV were unusually
high on September 22, 2006.\13\ Meteorological data show that the winds
at Lemoore reached speeds of 29 mph with gusts of approximately 40 mph.
According to the State, the Department of Water Resources' extreme
annual wind statistics indicate that the mean annual peak gust for
Lemoore is 42 mph.\14\ Thus wind gusts observed at Lemoore were
unusually high because they are close to the typical highest annual
value of 42 mph. The State also provides documentation that shows that
winds of approximately 18 mph will entrain and transport dust.\15\
Winds greater than this speed occurred at Lemoore and Kettleman Hills,
and were responsible for transporting this entrained dust.
Meteorological data indicate that the wind direction was from the north
and northwest and hence the entrained dust at that wind speed was
transported towards Corcoran. Winds at Corcoran were not as intense
during the peak hours at Lemoore. Table 3 of the State's submittal
indicates the winds at Corcoran at 10 a.m. were 9 mph with gusts to 12
mph.\16\ These wind speeds, though not sufficient to erode dust, were
sufficient to keep the entrained and transported dust from the high
winds at Lemoore suspended for the period during which the exceedances
occurred.
---------------------------------------------------------------------------

    \13\ NED for September 22, 2006 at 29; NED Addendum for
September 22, 2006 at section 4.
    \14\ NED for September 22, 2006 at 29.
    \15\ NED for September 22, 2006 at 13; David Bush, T&B Systems
Contribution to CRPAQS Initial Data Analysis of Field Program
Measurements, Final Report Contract 2002-06PM Technical & Business
Systems, Inc., November 9, 2004 (Bush Report).
    \16\ NED Addendum for September 22, 2006 at 11, Table 3.
---------------------------------------------------------------------------

iv. Determined by EPA To Be an Exceptional Event
    Finally, EPA must determine through the process established in the
Exceptional Events Rule whether an exceptional event occurred. We
believe that the State has met the procedural requirements of the rule
including flagging of the data, submission of demonstration, evidence
of the public opportunity to review and comment on the demonstration
and mitigation requirements as discussed in section V.A.1. and 3. of
this proposed rule. We further believe that the State has also met the
technical criteria in the Exceptional Events Rule as discussed in
section V.A.2. Therefore, we are proposing to concur with the State's
determination that an exceptional event, i.e., a high wind event,
occurred resulting in the exceedances on September 22, 2006.\17\
---------------------------------------------------------------------------

    \17\ Generally EPA concurs or nonconcurs by letter with requests
to flag data as caused by exceptional events. See our explanation in
section II. above regarding why we are proceeding by a rulemaking
here.
---------------------------------------------------------------------------

b. Does the State's documentation show a clear causal connection
between the exceedances and the claimed exceptional event?
    Under 40 CFR 50.14(c)(3)(iii)(B), a state's demonstration must
establish a clear causal relationship between the measured exceedance
and the claimed exceptional event. In addressing this requirement for
the September 22, 2006 exceedances, the State identifies a source
region for the PM-10, an area northwest of Corcoran around the area of
Lemoore. The State provides a convincing demonstration showing that the
winds in the area of the central SJV were of sufficient speeds to erode
soils and entrain dust and that the wind direction moved the PM-10
southeast towards Corcoran and further to the Bakersfield area.
    Meteorological measurements in Lemoore show that this area had the
highest hourly averaged winds in the SJV that day, peaking at 10 a.m.
with a speed of 29 mph from the NNW and gusts at the same time reaching
37

mph.\18\ Lemoore is approximately 25 miles northwest of Corcoran.
Meteorological measurements were also obtained from a site at Kettleman
Hills, which showed a peak hourly wind at 11 am of 20 mph from the NNW
with gusts up to 32 mph.\19\ Kettleman Hills is approximately 28 miles
west of Corcoran. The wind speed, direction, time and distance from
monitors indicate that the high winds at Lemoore entrained the dust
carrying it toward Corcoran.\20\ The State cites a 2002 California
Regional PM-10/PM-2.5 Air Quality Study (2002 CRPAQS study) that
established a dust-generating wind speed threshold of 17.8 mph to
support its conclusion that these wind speeds were sufficient to erode
soils and entrain dust into the atmosphere as well as to exacerbate the
entrainment of dust from the anthropogenic activities.\21\
---------------------------------------------------------------------------

    \18\ NED for September 22, 2006 at 11, Table 3.
    \19\ Id.
    \20\ Id.
    \21\ Id. at 13; Bush Report.
---------------------------------------------------------------------------

    At about 9:30 a.m. and 10:30 a.m. the District received complaints
about dust emissions in Lemoore.\22\ This was at the time of peak winds
in Lemoore. The District followed up on the complaints but did not
issue notices of violation. The State indicates that there were PM-10
generating activities in the area of Lemoore on the morning of
September 22, 2006 but that these activities were typical for the area
and subject to the District's fugitive dust regulations.\23\
---------------------------------------------------------------------------

    \22\ NED for September 22, 2006 at 33, Table 15.
    \23\ Id. at 5 and 32-33.
---------------------------------------------------------------------------

    The State shows a clear relationship between the wind speeds at
Lemoore and Kettleman Hills and increased concentrations at the
Corcoran monitoring site. The documentation clearly shows that as
hourly average wind speeds increased at the three meteorological sites,
hourly concentrations at Corcoran also increased. The peak hourly
concentrations at Corcoran were at 10 a.m. and 11 a.m. (725 [mu]g/
m3 and 695 [mu]g/m3, respectively).\24\ These
concentrations coincide with the highest winds at Lemoore and Kettleman
Hills.
---------------------------------------------------------------------------

    \24\ Id. at 11, Table 3.
---------------------------------------------------------------------------

    The winds at Corcoran showed the same pattern of increasing wind
speeds but at a lower intensity. Hourly average winds at Corcoran
peaked at 8 a.m. at 11 mph with a peak average minute gust of 15 mph.
While these wind speeds were not high enough to erode and entrain soil,
based on the wind speed threshold referenced above, they were
sufficient to keep the coarse particles suspended in the atmosphere.
The winds were also consistently from the northwest, which demonstrates
that the coarse particles which impacted Corcoran originated in the
areas northwest of the monitor, e.g. Lemoore where the winds were
unusually high.
    Using the threshold wind speed in the 2002 CRPAQS study, the State
shows that most of the PM-10 was generated upwind of the Corcoran site
and then transported to the Corcoran area.\25\ Based on available data,
wind speeds at Corcoran were not high enough to generate dust on their
own but were high enough to sustain the entrainment of PM-10 from
upwind areas.
---------------------------------------------------------------------------

    \25\ Id. at 13; Bush Report.
---------------------------------------------------------------------------

    The wind-driven dust from sources in the central and southern SJV,
beginning in Lemoore, also impacted the Bakersfield area on September
22, 2006. The State provides the analysis and supporting information
needed to demonstrate that the winds between the Corcoran and
Bakersfield areas were of sufficient intensity to transport the plume
of PM-10 from Corcoran to the Bakersfield and Oildale monitors. The
Bakersfield area monitors began to record hourly concentrations in
excess of the level of the 24-hour PM-10 NAAQS two hours after the peak
Corcoran hourly PM-10 concentration, with the Bakersfield hourly PM-10
concentrations peaking five hours after the Corcoran peak hourly PM-10
concentration. In order to transport a plume of dust from Corcoran to
the Bakersfield area, approximately 55 miles, wind speeds would have to
average approximately 11 mph in order for the maximum amount of PM-10
to impact the Bakersfield area monitors five hours later.\26\ The winds
at Alpaugh, which is located between Corcoran and Bakersfield, averaged
11 mph.\27\ As would be expected, the concentration of PM-10 in the
Bakersfield area was lower than in Corcoran, but still significant
enough to exceed the NAAQS. The lower PM-10 concentrations at
Bakersfield are likely due to the dispersion of the dust plume and
possibly deposition of a portion of the dust particles along the path
from the Corcoran area to Bakersfield.
---------------------------------------------------------------------------

    \26\ NED Addendum for September 22, 2006 at 7.
    \27\ Id. at 8, Table A-1.
---------------------------------------------------------------------------

    The State's demonstration for September 22, 2006 includes
information on wind speed and direction \28\ that shows the correlation
between the hourly wind speeds at meteorological sites in Alpaugh and
Bakersfield-Meadows Airfield and the hourly PM-10 concentrations
recorded in the Bakersfield area.\29\
---------------------------------------------------------------------------

    \28\ NED Addendum for September 22, 2006 at 8, Table A-1.
    \29\ The Oildale monitoring site does not record hourly PM-10
concentrations but uses a manual PM-10 sampler that provides only
24-hour average concentrations. The Bakersfield-Golden State Highway
monitoring site utilizes both a manual sampler for average 24-hour
PM-10 concentrations and a continuous PM-10 analyzer to provide
hourly concentrations. Since the Bakersfield-Golden State Highway
site and the Oildale site are relatively close to each other (see
footnote 9 above), we believe it is appropriate to use the
Bakersfield-Golden State Highway continuous analyzer to characterize
the temporal distribution of hourly concentrations at both sites.
---------------------------------------------------------------------------

    The State also includes the results of a basic meteorological model
known as Hybrid Single-Particle Lagrangian Integrated Trajectory model
(HYSPLIT).\30\ It is important to note that while this modeling is not
meant to quantify the particle concentration recorded in the
Bakersfield area, it does offer support of the State's demonstration
that the winds on September 22, 2006 were of the appropriate intensity
and direction to move a plume of dust from the central SJV to the
Bakersfield area.
---------------------------------------------------------------------------

    \30\ NED Addendum for September 22, 2006 at 10.
---------------------------------------------------------------------------

c. Did the State demonstrate that the event is associated with measured
concentration in excess of normal historical fluctuations including
background?
    For EPA to concur with a state's claim that an exceptional event
caused an exceedance, one of the requirements that the state must meet
is to show that the event is associated with concentrations that are
beyond the normal historical fluctuations. See 40 CFR
50.14(c)(3)(iii)(C).
    The NED for September 22, 2006 and NED Addendum for September 22,
2006 include sections that show the unusualness of the concentrations
recorded on that date. Section 4 of the Addendum includes Figure A-5
that compares the peak 24-hour PM-10 concentrations recorded at
Corcoran, Bakersfield and Oildale during the month of September for the
years 2000 through 2006.\31\
---------------------------------------------------------------------------

    \31\ NED Addendum for September 22, 2006 at 14.
---------------------------------------------------------------------------

    The FRM monitor at the Corcoran site has mostly operated on a once-
in-every-three-days schedule since 2000.\32\ The Corcoran FRM has
collected 786 samples since 2000 and has recorded only four exceedances
of the 24-hour PM-10 NAAQS.\33\ A further analysis shows that, with the
exception of a flagged natural event in 2004, 24-hour

PM-10 concentrations exceeded a level of 100 [mu]g/m\3\ only three
times during the month of September for a seven year period, i.e, when
we look at the 59 samples collected during the September for the past
seven years, a concentration greater than 100 [mu]g/m\3\ occurred only
five percent of the time.\34\ Exceedances of the NAAQS have occurred
twice in September, which is less than four percent of the days
sampled. Comparisons for the month of September are more relevant than
for the entire year because September has the highest concentration of
dust but does not typically have the highest PM-10 concentrations,
which occur in the winter season. Dust is typically less than 50% of
the PM-10 during September.\35\ During the winter season nitrates are
the largest contributor, particularly in the southern part of the
central valley.
---------------------------------------------------------------------------

    \32\ From September 1, 2000 to March 22, 2001 the Corcoran
monitor operated on a once-in-every-six-days schedule.
    \33\ PM-10 Raw Data Report Corcoran 2000-2006, EPA AQS Database,
July 30, 2007.
    \34\ 138 [mu]g/m\3\ on September 9, 2004, a 102 [mu]g/m\3\ on
September 24, 2004 and a 112 [mu]g/m\3\ on September 23, 2006; See
Id.
    \35\ ``What are the Sources of Particulate Matter'',
Presentation by Karen L. Magliano, California Air Resources Board,
May 17, 2006 (Magliano Presentation).
---------------------------------------------------------------------------

    For Bakersfield, which utilizes a FRM operating on a once-in-every-
six-days schedule, 413 samples were collected since the year 2000.
During this time the NAAQS was exceeded three times. Again, when we
look at data collected during the September months from 2000 to 2006,
only one day out of 33 days sampled recorded a level greater than 100
[mu]g/m\3\ (128 [mu]g/m\3\ on September 18, 2003), three percent of the
time.\36\
---------------------------------------------------------------------------

    \36\ PM-10 Raw Data Report Bakersfield Golden 2000-2006, EPA AQS
Database, July 30, 2007.
---------------------------------------------------------------------------

    For Oildale, also operating a FRM on a once-every-six-days
schedule, 432 samples were collected from 2000 to 2006. The PM-10 NAAQS
was exceeded once during this seven-year period. During the September
months, only one day out of 35 days sampled recorded a level greater
than 100 [mu]g/m\3\ (111 [mu]g/m\3\ on September 14, 2006), less than
three percent of the time.\37\
---------------------------------------------------------------------------

    \37\ PM-10 Raw Data Report Oildale 2000-2006, EPA AQS Database,
July 26, 2007.
---------------------------------------------------------------------------

d. Did the State demonstrate that there would have been no exceedance
``but for'' the event?
    As discussed above, to qualify as an exceptional event the state
must also demonstrate that there would have been no exceedance ``but
for'' the event. 40 CFR 50.14 (c)(3)(iii)(D). To meet this ``but for''
criterion, states must include analyses to demonstrate that an
exceedance or violation would not have occurred but for the event. Such
analyses do not require a precise estimate of the estimated air quality
impact from the event. 72 FR at 13570.
    To meet this ``but for'' criterion, the State first shows that
there were no unusual activities occurring in the affected areas in the
Valley on September 22, 2006 that could have resulted in the
exceedances. Specifically, based on information from District field
staff and discussions with representatives of agricultural and
industrial operations in the Valley, anthropogenic emissions were
approximately constant in the Valley immediately before, during and
after the event. The State indicates that there were PM-10 generating
activities, such as agricultural and construction operations, in the
area of Lemoore on the morning of September 22, 2006. These types of
activities are typical for the area.\38\
---------------------------------------------------------------------------

    \38\ NED for September 22, 2006 at 32-33.
---------------------------------------------------------------------------

    The State next indicates that the greatest fraction of PM-10 at the
Corcoran and Bakersfield sites on September 22 consisted of particles
in the size fraction between PM-10 and PM-2.5.\39\ This information
indicates that geologic dust, as opposed to secondary PM or PM from
combustion sources, was the primary contributor to the exceedances. The
fraction of coarse particles at Corcoran and Bakersfield on September
22 was 89% and 79% respectively.\40\ These values must be compared to
the typical geologic values for the Valley during September of
approximately 30 [mu]g/m\3\ which are less than 50% of the measured PM-
10.\41\ Based on the reported 89% value, the estimated geologic
material for Corcoran was approximately 190 to 230 [mu]g/m\3\ for
September 22, 2006. The corresponding values for Bakersfield were 123-
134 [mu]g/m\3\. Compared to the typical September value of
approximately 30 [mu]g/m\3\, the September 22, 2006 values represent an
excess geologic contribution of approximately 160 to 200 [mu]g/m\3\ for
Corcoran and approximately 94 to 104 for Bakersfield. If the typical
value of 30 [mu]g/m\3\ were used instead of the high estimated geologic
values derived from the PM-10-2.5 size fraction, the resulting
``adjusted'' PM-10 values for Corcoran and Bakersfield would be 50-65
[mu]g/m\3\. This result favorably compares to the typical average
September concentration of less than 60 [mu]g/m\3\. Allowing for a PM-
10 geologic value of 60 [mu]g/m\3\, which is twice the September norm,
would only yield an ``adjusted'' concentration of 84 to 96 [mu]g/m\3\.
All of these sets of adjusted values for September 22 are consistent
with the aforementioned historical September levels which rarely
exceeded 100 [mu]g/m\3\, showing that very few days in Bakersfield and
Corcoran over the period 2000-2006 exceeded the level of 100 [mu]g/
m\3\.
    In addition, the NED for September 22, 2006 includes Table 2 that
lists the PM-10 24-hour average concentrations recorded using
continuous analyzers for the days immediately preceding and after
September 22, 2006.\42\ This table indicates that 24-hour average PM-10
concentrations at Corcoran were over 100% higher on September 22 as
compared to September 20, 21, 23, and 24. At Bakersfield,
concentrations on September 22 were over 100% higher than on September
20 and September 24 and 86% higher than on September 21. Compared to
September 23 the increase was 14%.
---------------------------------------------------------------------------

    \39\ Id. at 32, Figure 13.
    \40\ Id.
    \41\ Magliano Presentation.
    \42\ NED for September 22, 2006 at 9.
---------------------------------------------------------------------------

    Finally, as discussed above, there were reasonable and appropriate
measures in place to control PM-10 in the SJV on September 22, 2006,
Regulation VIII and Rule 4550.\43\ Moreover, EPA has approved the
District's BACM demonstration for all significant sources of PM-10 in
the SJV as meeting CAA section 189(b)(1)(B).\44\ Furthermore, District
staff performed 46 inspections in the Valley on September 22 to ensure
that regulated sources were complying with the District's fugitive dust
rules.\45\ The District's Natural Events Action Plan, discussed below,
also addresses the reasonable and appropriate measures that the
District has implemented to address high wind events in the SJV.
---------------------------------------------------------------------------

    \43\ Id. at 32.
    \44\ 69 FR 30006, 30035 (May 26, 2004); 71 FR 7683 (February 14,
2006).
    \45\ NED for September 22, 2006 at 45-46.
---------------------------------------------------------------------------

    Based on the weight of evidence presented, EPA concludes that the
State's documentation demonstrates that the exceedances at Corcoran,
and Bakersfield and Oildale on September 22, 2006 would not have
occurred but for the wind event on this day.
3. Mitigation Requirements
    Under 40 CFR 51.930, a state requesting to exclude air quality data
due to exceptional events must take appropriate and reasonable actions,
including public notification, public education, and implementation of
measures, to protect public health from exceedances or violations of
the NAAQS.
    The SJVAPCD adopted the ``Natural Events Action Plan for High Wind
Events in the San Joaquin Valley Air

Basin'' (NEAP) on February 16, 2006. The NEAP provides the SJVAPCD's
approach to forecasting high wind events, notifying the public prior to
the event and educating the public on how to minimize exposure during
high wind events. The document also discusses measures that are in
place to help minimize exposure to elevated PM-10 levels. EPA believes
that the detailed processes and measures described in the NEAP satisfy
the mitigation requirements under 40 CFR 51.930.
a. Provide for Prompt Public Notification of Exceedance Events
    Section 6 of the NEAP provides the meteorological forecasting
criteria that the SJVAPCD uses to determine whether or not to declare
NEAP episodes. When the criteria indicate that a NEAP episode should be
declared, the SJVAPCD has a public notification program, discussed in
Section 7 of the NEAP, which involves informing the local media,
SJVAPCD staff and community groups.
b. Provide for Public Education on How To Minimize Exposure
    Section 7 of the NEAP provides a list of precautions that can be
taken to limit exposure during a NEAP episode. The list includes
keeping windows shut, using air conditioners or heaters on the recycle/
recirculating air mode, limiting strenuous activity, and other
precautions. Section 8 of the NEAP discusses the SJVAPCD's general
public outreach program on NEAP episodes which includes developing and
providing a brochure and information about NEAP episodes by means of
community events, health fairs, schools and civic engagements.
c. Provide for the Implementation of Appropriate Measures To Protect
the Public
    Section 10 of the NEAP discusses the SJVAPCD's measures that reduce
PM-10 emissions. These measures, including those approved by EPA as
BACM for the SJV, in combination with the SJVAPCD's process for
declaring NEAP episodes and educating the public on how to minimize
their exposure during a NEAP episode, meet the requirements for
appropriate measures to protect the public during high wind exceptional
events.

Conclusion

    EPA believes that the high winds in the area of Lemoore on
September 22, 2006 were an exceptional event as defined in 40 CFR
50.1(j). EPA also believes that the State has provided a sufficient
weight of evidence demonstration to show that these high winds
generated and transported PM-10 from the area of Lemoore to Corcoran,
causing an exceedance of the 24-hour PM-10 NAAQS. Winds between
Corcoran and the Bakersfield area were sufficient to transport the dust
that originated in the Lemoore area such that they caused the monitors
at Bakersfield-Golden State Highway and Oildale to also exceed the
NAAQS. The documentation submitted by the State demonstrates that but
for the high winds in the area of Lemoore, the Corcoran, Bakersfield
and Oildale monitors would not have exceeded the 24-hour PM-10 NAAQS on
September 22, 2006. Because EPA believes that the State has satisfied
the provisions of the Exceptional Events Rule, EPA proposes to concur
with the State's request to flag these exceedances as being due to
exceptional events and to exclude the data from consideration in
determining whether the area has attained the PM-10 standard.

B. October 25, 2006 Exceedances at Corcoran and Bakersfield

    On October 25, 2006, the SJV recorded exceedances of the 24-hour
PM-10 NAAQS at two sites, Corcoran and Bakersfield-Golden State
Highway, using continuous PM-10 analyzers designated as FEM
monitors.\46\ The 24-hour average concentrations recorded were 304
[mu]g/m\3\ at Corcoran and 193 [mu]g/m\3\ at Bakersfield-Golden State
Highway. The conditions that contributed to these exceedances were very
similar to those that occurred on September 22, 2006. Based on the
evidence submitted, EPA agrees with the State's demonstration that high
wind-entrained dust from the central and southern SJV caused the
exceedances at the two monitoring locations on October 25, 2006.
---------------------------------------------------------------------------

    \46\ The District operates Tapered Element Oscillating
Microbalance (TEOM) continuous automated analyzers at these two
sites in addition to the manual high-volume Federal Reference Method
(FRM) monitors. The FRMs operate at a less than everyday schedule,
as allowed by EPA regulations, but neither of the FRM monitors was
operating on October 25, 2006. The District operates the continuous
analyzers so that they may report daily PM-10 air quality data to
the public.
---------------------------------------------------------------------------

1. Procedural Requirements
a. Data Are Flagged in EPA's AQS Database
    The October 25, 2006 exceedances were flagged in EPA's AQS database
as of July 2007.
b. Public Had an Opportunity To Review and Comment on the State's
Documentation
    In February 2007, the SJVAPCD notified the public in local
newspapers and on its Web site of the availability of the document
entitled ``Natural Event Documentation, High Winds, Corcoran and
Bakersfield, California, October 25, 2006,'' SJV Unified Air Pollution
Control District, February 2007 and requested public comments by March
5, 2007.
    The SJVAPCD subsequently revised the February 2007 document and
submitted to CARB the ``Natural Event Documentation, Corcoran and
Bakersfield, California, October 25, 2006,'' San Joaquin Valley Unified
Air Pollution Control District, April 23, 2007 (NED for October 25,
2006), and posted it on its Web site.
    The SJVAPCD indicated that no public comments were received during
its public process.
c. The Documentation Was Submitted to Epa
    The NED for October 25, 2006 was submitted by the State to EPA on
May 1, 2007 and is the document upon which EPA is basing its evaluation
below.
d. EPA Concurs With the State's Demonstration
    In this proposed rule, EPA is proposing to concur with the State's
demonstration in the NED for October 25, 2006 that high wind-entrained
dust caused the exceedances at the two monitoring sites.
2. Technical Criteria
    a. Did this event satisfy the criteria in section 50.1(j) of the
Rule?
i. Affected Air Quality
    For an event to qualify as an exceptional event, the state must
show that the event affected air quality. This criterion can be met by
establishing that the event is associated with a measured exceedance in
excess of normal historical fluctuations, including background, and
there is a causal connection between the event and the exceedance. The
demonstration of a clear causal relationship is necessary to establish
that the event affected air quality and is also a separate statutory
requirement as discussed above.
    In the NED for October 25, 2006, the State provides documentation
that the measured exceedances recorded on October 25, 2006 were in
excess of normal historical fluctuations. See subsection c. below. The
State also establishes a causal connection between

the high winds recorded at Lemoore and the high concentrations at the
monitors recorded at Corcoran and Bakersfield. The State's
demonstration of the clear causal relationship between the exceptional
event and the exceedances on this day is discussed in greater detail in
subsection b. below.
ii. Not Reasonably Controllable or Preventable
    Section 50.1(j) requires that for an event to qualify as an
exceptional event, whether natural or anthropogenic, a state must show
that the event was not reasonably preventable or controllable. Here
this requirement is met by demonstrating that despite reasonable and
appropriate measures in place, the October 25, 2006 wind event caused
the exceedances. During this event, there were no other unusual dust-
producing activities occurring in the SJV and anthropogenic emissions
were approximately constant before, during and after the event. In
addition, the State showed that reasonable and appropriate measures
were in place, including Regulation VIII (the District's general
fugitive dust rules) and Rule 4550 which limits fugitive dust emissions
specifically from agricultural operations through Conservation
Management Practices.\47\ Moreover, EPA has approved the District's
BACM demonstration for all significant sources of PM-10 in the SJV as
meeting CAA section 189(b)(1)(B).\48\
---------------------------------------------------------------------------

    \47\ NED for October 25, 2006 at 29.
    \48\ 69 FR at 30035; 71 FR 7683.
---------------------------------------------------------------------------

iii. Was a Natural Event
    In the preamble to the Exceptional Events Rule, EPA states that
ambient particulate matter concentrations due to dust being raised by
unusually high winds will be treated as due to uncontrollable natural
events where (1) the dust originated from nonanthropogenic sources, or
(2) the dust originated from anthropogenic sources within the State,
that are determined to have been reasonably well-controlled at the time
that the event occurred, or from anthropogenic sources outside the
State. 72 FR at 13576. In the preamble EPA also explains that
``[s]tates must provide appropriate documentation to substantiate why
the level of wind speed associated with the event in question should be
considered unusual for the affected area during the time of year that
the event occurred.'' Id. at 13566.
    The wind-entrained dust on October 25, 2006 originated from
anthropogenic sources within California, i.e., from usual dust-
generating activities such as agricultural and industrial
operations.\49\ We discuss the fugitive dust control measures in place
in the SJV on October 25 above.
---------------------------------------------------------------------------

    \49\ NED for October 25, 2006 at 29.
---------------------------------------------------------------------------

    With respect to the wind speed, EPA concurs with the State's
demonstration that the wind speeds in the central SJV were unusually
high on October 25, 2006.\50\ Table 1 of the NED for October 25, 2006
lists the wind speeds in the Hanford and Lemoore areas. The peak hourly
averaged winds were in the range of 29 to 31 mph at Lemoore, with gusts
reaching 40 mph. Peak hourly winds at Hanford were lower, in the range
of 17 to 18 mph, but still in line with the threshold wind speed of
17.8 mph. Hanford also recorded peak gusts of 22 to 30 mph during the
10 a.m. to 12 noon period.\51\ Tables 8, 9, and 11 of the NED for
October 25, 2006 also include information on wind speeds throughout the
central valley of California and the central and southern SJV.\52\ The
documentation also states that wind speeds of these intensities are
relatively rare in the southwestern part of the SJV and occur less than
5% of the time, based on long-term monitoring records.\53\
---------------------------------------------------------------------------

    \50\ Id. at sections 4 and 5.
    \51\ Id. at 11.
    \52\ Id. at 22-23.
    \53\ Id. at 24.
---------------------------------------------------------------------------

    EPA concurs with the State's demonstration in the NED for October
25, 2006 that the wind speeds occurring in the central SJV were
unusually high on October 25, 2006. While the winds at Corcoran were
not as high as those in Lemoore and Hanford, as described in the
State's documentation, the winds at Corcoran during the peak hourly PM-
10 concentrations (8 a.m. to 11 a.m.) ranged from 10 to 13 mph, which
are unusual for this time of year in that area. These wind speeds,
though not sufficient to erode dust, were sufficient to keep the
entrained and transported dust from the high winds at Lemoore suspended
for the period during which the exceedances occurred.
iv. Determined by EPA To Be an Exceptional Event
    Finally, EPA must determine through the process established in the
Exceptional Events Rule whether an exceptional event occurred. We
believe that the State has met the procedural requirements of the Rule
including flagging of the data, submission of demonstration, evidence
of the public opportunity to review and comment on the demonstration
and mitigation requirements as discussed at section V.B.1. and 3. of
this proposed rule. We further believe that the State has also met the
technical criteria of the Rule as discussed at section V.B.2. of this
proposed rule. Therefore we are proposing to concur with the State's
determination that an exceptional event, i.e., a high wind event,
occurred resulting in the exceedances on October 25, 2006.
b. Does the State's documentation show a clear causal connection
between the exceedances and the claimed exceptional event?
    Under 40 CFR 50.14(c)(3)(iii)(B), a state's demonstration must
establish a clear causal relationship between the measured exceedances
and the claimed exceptional event. In addressing this requirement for
the October 25, 2006 exceedances, the NED for October 25, 2006
submitted by the State identifies the area northwest of Corcoran as the
source of PM-10 during the October 25, 2006 event. Winds in the Lemoore
area were again in excess of the threshold wind speed for eroding and
entraining dust as discussed above. Table 1 of the NED for October 25,
2006 shows a clear correlation between the wind speeds in the Hanford
and Lemoore areas and the increased hourly concentrations at
Corcoran.\54\ In fact the peak wind speeds at Lemoore and Hanford,
which occurred between 10 a.m. and 12 noon at Lemoore, coincide with
the peak hourly concentrations at Corcoran. The peak hourly averaged
winds were in the range of 29 to 31 mph at Lemoore, with gusts reaching
40 mph. Peak hourly winds at Hanford were lower, in the range of 17 to
18 mph, but still in line with the threshold wind speed of 17.8 mph.
Hanford also recorded peak gusts during the 10 a.m. to 12 noon period
of 22 to 30 mph. Figure 2 of NED for October 25, 2006 compares the
hourly wind speed and PM-10 concentration data from Corcoran with the
hourly wind speed data from Lemoore in a graphical format.\55\ This
graphic shows the almost perfect correlation between increased wind
speeds at Corcoran and Lemoore with the increased PM-10 hourly
concentrations at Corcoran.
---------------------------------------------------------------------------

    \54\ NED for October 25, 2006 at 11.
    \55\ Id. at 12.
---------------------------------------------------------------------------

    The dust plume that affected the Corcoran monitoring site on
October 25, 2006 continued moving south and ultimately impacted the
continuous PM-10 analyzer operating at the Bakersfield-Golden State
Highway monitoring site. The State provides information on wind speed
and direction from the Alpaugh meteorological monitoring station,

located between Corcoran and Bakersfield about 16 miles south southeast
of the Corcoran monitoring site.\56\ Between the hours of 9 a.m. and 4
p.m., wind speeds at Alpaugh averaged about 12 mph.\57\ Since the
meteorological data measured at Alpaugh is taken at 2 meters Above
Ground Level (AGL), the average wind speed at 10 meters AGL is about 15
mph.\58\ EPA believes this average wind speed would have been
sufficient to keep the dust plume suspended, and that it facilitated
the transport of the dust plume to the Bakersfield area.
---------------------------------------------------------------------------

    \56\ Id. at 22-26.
    \57\ Id. at 58.
    \58\ Id. at 24-26.
---------------------------------------------------------------------------

    The data in Table 1 of the NED for October 25, 2006 show the
Bakersfield hourly PM-10 concentrations beginning to exceed the level
of the 24-hour PM-10 NAAQS at 11 a.m. (177 [mu]g/m\3\) and peaking
between the hours of 2 p.m. and 5 p.m. (415 [mu]g/m\3\ and 416 [mu]g/
m\3\, respectively). Figure 4 provides a graph of PM-10 hourly
concentrations for three continuous PM-10 analyzers operated by the
District at Corcoran, Bakersfield-Golden State Highway, and Tracy.\59\
The graph shows hourly PM-10 concentrations at Bakersfield-Golden State
Highway slowly increasing through the morning hours of October 25 until
8 a.m. Hourly concentrations increase at a higher rate between 8 a.m.
and 1 p.m., mirroring the increase at Corcoran, but not as dramatic. As
the Corcoran hourly concentrations are dropping between 11 a.m. 4 p.m.
we see a corresponding sharp increase in hourly concentrations at
Bakersfield-Golden State Highway. This behavior of the hourly
concentrations supports the State's explanation that the dust plume
that first affected Corcoran traveled south over a period of several
hours and then impacted the Bakersfield monitor.
---------------------------------------------------------------------------

    \59\ Id. at 14.
---------------------------------------------------------------------------

    As with the September 22, 2006 event, the State includes for the
October 25, 2006 event the results of a basic meteorological model
known as the Hybrid Single-Particle Lagrangian Integrated Trajectory
model (HYSPLIT).\60\ It is important to note that while this modeling
is not meant to quantify the particle concentration recorded in the
Bakersfield area, it does support the State's demonstration that the
winds on October 25, 2006 were of the appropriate intensity and
direction to move a plume of dust from the central SJV to the
Bakersfield area.
---------------------------------------------------------------------------

    \60\ Id. at 27.
---------------------------------------------------------------------------

c. Did the State demonstrate that the event is associated with measured
concentrations in excess of normal historical fluctuations including
background?
    For EPA to concur with a state's claim that an exceptional event
caused an exceedance, one of the requirements that the state must meet
is to show that the event is associated with concentrations that are
beyond the normal historical fluctuations. See 40 CFR
50.14(c)(3)(iii)(C).
    The State provides data on PM-10 levels on the days before and
after October 25, 2006. PM-10 concentrations before and after October
25, 2006 were significantly lower than the concentration recorded on
October 25, 2006. An EPA review of continuous PM-10 data from Corcoran
and Bakersfield-Golden State Highway showed that 24-hour average
concentrations from October 1, when the TEOM continuous analyzers began
reporting data, through October 24 did not exceed 100, and while there
were a number of higher concentrations on the days after October 25,
not counting the exceedances recorded on December 8, 2006, which are
discussed further below in subsection d, the PM-10 concentrations at
Corcoran and Bakersfield-Golden State Highway fell to mostly less than
100 again from October 28 through June 30, 2007.\61\
---------------------------------------------------------------------------

    \61\ ``Continuous PM-10 Data Collected with TEOMs, Data Reported
to EPA's AIRNOW Website,'' July 30, 2007, Excel Spreadsheet, Bob
Pallarino.
---------------------------------------------------------------------------

    Historically we can compare data from these continuous analyzers
only with the separate manual FRM samplers operated at the sites. When
we look at typical PM-10 concentrations recorded in the month of
October from 2000 to 2006 the maximum value recorded at Bakersfield was
116 [mu]g/m\3\ measured on October 16, 2001 and the maximum non-
exceedance value recorded at Corcoran was 150 [mu]g/m\3\ measured on
October 31, 2006.\62\ These concentrations indicate that the
exceedances recorded on October 25, 2006 were unusual and not
representative of typical high concentrations recorded at these
monitoring locations.
---------------------------------------------------------------------------

    \62\ Corcoran exceeded the 24-hour NAAQS on October 29, 2002
with a value of 168 [mu]g/m\3\; PM-10 Raw Data Reports, Corcoran
2000-2006 and Bakersfield-Golden 2000-2006.
---------------------------------------------------------------------------

d. Did the State demonstrate that there would have been no exceedance
``but for'' the event?
    As discussed previously, to qualify as an exceptional event the
State must also demonstrate that there would have been no exceedance
``but for'' the event. 40 CFR 50.14(c)(3)(iii)(D). To meet this ``but
for'' requirement, the state must include analyses to demonstrate that
an exceedance or violation would not have occurred but for the event.
Such analyses do not require a precise estimate of the estimated air
quality impact from the event. 72 FR at 13570.
    To meet this ``but for'' requirement the State first shows that
there were no unusual activities occurring in the affected areas in the
Valley that could have resulted in the exceedances. Specifically, based
on information from District field staff and discussions with
representatives of agricultural and industrial operations in the
Valley, anthropogenic emissions were approximately constant in the
Valley immediately before, during and after the event. The District
staff observed no unusual emissions other than those associated with
the wind event. The PM-10 generating activities were BACM-controlled
sources that are usual for the area.\63\ District staff conducted 90
inspections throughout the SJV on October 25 to ensure sources were in
compliance with District air pollution rules.\64\
---------------------------------------------------------------------------

    \63\ NED for October 25, 2006 at 7 and 29.
    \64\ Id. at 35.
---------------------------------------------------------------------------

    The State notes in the NED for October 25, 2006 that the PM-2.5 to
PM-10 ratio on this day was very low, which indicates that mostly
coarse PM was present on the filter, supporting its claim that the
concentrations recorded on this day were affected by a blowing dust
event.\65\
---------------------------------------------------------------------------

    \65\ Id. at 28.
---------------------------------------------------------------------------

    When we examine the typical make-up of PM-10 in the SJV during
October we generally see particle concentrations that are mostly in the
size fraction of PM-2.5, roughly 60-65%, with the remaining mass being
particles in the PM-10-2.5 size fraction.\66\ Typically, fugitive dust
is the major constituent of the PM-10-2.5 size fraction and makes up
about 25 to 35% of the total PM-10. When we look at a comparison of PM-
2.5 and PM-10 concentrations recorded on October 25, 2006, we find that
the PM-10-2.5 portion of the total PM-10 represents about 93% of the
total PM-10 at Corcoran and 85 percent of total PM-10 at Bakersfield.
This high percentage of PM-10-2.5, which is mostly fugitive dust, is
atypical for this time of year and supports the State's demonstration
that the PM-10 concentrations on this day consisted of mostly coarse
geologic material.
---------------------------------------------------------------------------

    \66\ Magliano Presentation.
---------------------------------------------------------------------------

    We can also look at the days immediately preceding and following

the exceedance day to see if the concentrations on October 25 were
unusual. The PM-10 concentrations recorded on October 25 at Corcoran
and Bakersfield were over three times higher than they were on October
24.\67\ PM-10 concentrations after the event decreased dramatically and
by October 28, PM-10 concentrations at both sites were below 100. See
also the discussion of the historical levels at these monitors set
forth in subsection c. above, which further demonstrates that the
concentrations recorded on October 25 were unusual.
---------------------------------------------------------------------------

    \67\ NED for October 25, 2006 at 16, Table 3.
---------------------------------------------------------------------------

    Finally, as discussed above, there were reasonable and appropriate
measures in place to control PM-10 in the SJV on October 25, 2006,
Regulation VIII and Rule 4550.\68\ Moreover, EPA has approved the
District's BACM demonstration for all significant sources of PM-10 in
the SJV as meeting CAA section 189(b)(1)(B).\69\ Section 9.2 of the NED
for October 25, 2006 indicates that the District staff performed 90
inspections on that date to ensure that regulated sources were
complying with District fugitive dust rules.\70\ The District's Natural
Events Action Plan, discussed in section V.A.3. above, also addresses
the reasonable and appropriate measures that the District has
implemented to address high wind events in the SJV.
---------------------------------------------------------------------------

    \68\ Id. at 29.
    \69\ 69 FR at 30035; 71 FR 7683.
    \70\ NED for October 25, 2006 at 35.
---------------------------------------------------------------------------

    Based on the weight of evidence presented, EPA concludes that the
State's documentation demonstrates that the exceedances at Corcoran and
Bakersfield on October 24, 2006 would not have occurred but for the
wind event on this day.
3. Mitigation Requirements
    See section V.A.3. above.

Conclusion

    EPA believes that the high winds in the area of Lemoore on October
25, 2006, were an exceptional event as defined in 40 CFR 50.1(j). EPA
also believes that the State has provided a sufficient weight of
evidence demonstration to show that these high winds generated and
transported PM-10 from the area of Lemoore to Corcoran, causing an
exceedance of the 24-hour PM-10 NAAQS. Winds between Corcoran and the
Bakersfield area were sufficient to transport the dust that originated
in the Lemoore area such that they caused the monitor at Bakersfield-
Golden State Highway to also exceed the NAAQS. The documentation
submitted by the State demonstrates that but for the high winds in the
area of Lemoore, the Corcoran and Bakersfield monitors would not have
exceeded the 24-hour PM-10 NAAQS on October 25, 2006. Because EPA
believes the State has satisfied the provisions of the Exceptional
Events Rule, EPA proposes to concur with the State's request to flag
these exceedances as being due to exceptional events and to exclude the
data from consideration in determining whether the area has attained
the PM-10 standard.

C. December 8, 2006 Exceedances at Corcoran and Bakersfield

    The SJV recorded exceedances of the 24-hour PM-10 NAAQS on December
8, 2006 at two sites, Corcoran and Bakersfield-Golden State Highway,
using continuous PM-10 analyzers designated as FEM monitors. The 24-
hour average PM-10 concentrations recorded were 162 [mu]g/m\3\ at
Corcoran and 213 [mu]g/m\3\ at Bakersfield-Golden State Highway.
    The State demonstrates that unusually high winds in the Bakersfield
area eroded and entrained dust that impacted the continuous PM-10
analyzer at Bakersfield. Unlike September 22 and October 25, 2006, the
winds in the SJV on this day were generally from the southwest, south
and southeast, transporting dust northward and ultimately impacting the
continuous PM-10 analyzer at Corcoran. Based on the evidence submitted,
EPA agrees with the State's demonstration that high wind-entrained dust
caused the exceedances at the two monitoring locations on December 8,
2006.
1. Procedural Requirements
a. Data Are Flagged in EPA's AQS Database
    The December 8, 2006 exceedances were flagged in EPA's AQS database
as of July 2007.
b. Public had an opportunity to review and comment on the State's
documentation
    In February 2007, the SJVAPCD notified the public in local
newspapers and on its Web site of the availability of the document
entitled ``Natural Event Documentation, High Winds, Corcoran and
Bakersfield, California, December 8, 2006,'' SJV Unified Air Pollution
Control District, February 2007 and requested public comments by March
5, 2007.
    The SJVACPD subsequently revised the February 2007 document and
submitted to the California Air Resources Board (CARB) the ``Natural
Event Documentation, Corcoran and Bakersfield, California, December 8,
2006,'' SJV Unified Air Pollution Control District, May 23, 2007 and
posted it on its Web site.
    SJVAPCD thereafter made revisions per CARB's request and submitted
to CARB the ``Natural Event Documentation, Corcoran and Bakersfield,
California, December 8, 2006,'' SJV Unified Air Pollution Control
District, June 6, 2007 (NED for December 8, 2006) and posted it on its
Web site.
    The District indicated that no public comments were received during
the public process.
c. The Documentation Was Submitted to EPA
    The NED for December 8, 2006 was subsequently submitted by the
State to EPA on June 12, 2007 and is the document upon which EPA is
basing its evaluation below.
d. EPA Concurs With the State's Demonstration
    In this proposed rule, EPA is proposing to concur with the State's
demonstration in the NED for December 8, 2006 that high wind-entrained
dust caused the exceedances at the two monitoring locations on December
8, 2006.
2. Technical Criteria
a. Did this event satisfy the criteria in section 50.1(j) of the Rule?
    As with the previous events discussed in this proposed rule, the
State needs to show that this event, identified in the NED for December
8, 2006 as unusually high winds, affected air quality in the Corcoran
and Bakersfield areas, was not reasonably controllable or preventable,
was a natural event, and is determined by EPA to be an exceptional
event.
i. Affected Air Quality
    For an event to qualify as an exceptional event, the state must
show that the event affected air quality. This criterion can be met by
establishing that the event is associated with a measured exceedance in
excess of normal historical fluctuations, including background and
there is a causal connection between the event and the exceedance. This
demonstration of a causal connection is necessary to establish that the
event affected air quality and is also a separate statutory requirement
as discussed above.
    In the NED for December 8, 2006, the State provides documentation
that these measured exceedances were in excess of normal historical
fluctuations. See subsection c. below. The State also establishes a
causal connection between

the high winds recorded in the Bakersfield and Southern SJV area and
the high concentrations recorded at the Corcoran and Bakersfield
monitors. The State's demonstration of the clear causal relationship
between the event and the exceedances on this day is discussed in
greater detail in subsection b. below.
ii. Not Reasonably Controllable or Preventable
    Section 50.1(j) of the Exceptional Events Rule requires that for an
event to qualify as an exceptional event, whether natural or
anthropogenic, a state must show that the event was not reasonably
preventable or controllable. Here this requirement is met by
demonstrating that despite reasonable and appropriate measures in
place, the December 8, 2006 wind event caused the exceedances. During
this event, there were no other unusual dust-producing activities
occurring in the SJV and anthropogenic emissions were approximately
constant before, during and after the event. In addition, the State
shows that reasonable and appropriate measures were in place, including
Regulation VIII (the District's general fugitive dust rules) and Rule
4550 which limits fugitive dust emissions specifically from
agricultural operations through Conservation Management Practices.\71\
Moreover, EPA has approved the District's BACM demonstration for all
significant sources of PM-10 in the SJV as meeting CAA section
189(b)(1)(B).\72\
---------------------------------------------------------------------------

    \71\ NED for December 8, 2006 at 25.
    \72\ 69 FR at 30035; 71 FR 7683.
---------------------------------------------------------------------------

iii. Was a Natural Event
    In the preamble to the Exceptional Events Rule, EPA states that
ambient particulate matter concentrations due to dust being raised by
unusually high winds will be treated as due to uncontrollable natural
events where (1) the dust originated from nonanthropogenic sources, or
(2) the dust originated from anthropogenic sources within the State,
that are determined to have been reasonably well-controlled at the time
that the event occurred, or from anthropogenic sources outside the
State. 72 FR at 13576. In the preamble EPA also explains that
``[s]tates must provide appropriate documentation to substantiate why
the level of wind speed associated with the event in question should be
considered unusual for the affected area during the time of year that
the event occurred.'' Id. at 13566.
    On December 8, 2006, the wind-entrained dust originated from
anthropogenic sources within California, i.e., from usual dust-
generating activities such as agricultural and industrial
operations.\73\ We discuss the fugitive dust control measures in place
in the SJV on December 8, 2006 above.
---------------------------------------------------------------------------

    \73\ NED for December 8, 2006 at 25.
---------------------------------------------------------------------------

    With respect to the wind speed, EPA concurs with the State's
demonstration that the wind speeds in the southern SJV were unusually
high on December 8, 2006. The State includes information on the unusual
nature of the wind speeds in the SJV on December 8, 2006, stating that
winds of these magnitudes are rare, occurring less than 5% of the time.
The NED for December 8, 2006 reports that during the blowing dust
event, Bakersfield reported winds up to 25 mph with gusts up to 35 mph.
Farther north in the area of Kettleman Hills, located on the west side
of the San Joaquin Valley, gusts up to 50 mph were reported. Kettleman
Hills also reported a twenty-two hour period with gusts of 20 mph or
greater (from 6 a.m. on December 8, 2006 to 4 a.m. on December 9,
2006). Maricopa, located on the southwest side of the San Joaquin
Valley approximately 25 miles southwest of Bakersfield, reported a one-
minute average wind speed of 56 mph.\74\
---------------------------------------------------------------------------

    \74\ Id. at 17.
---------------------------------------------------------------------------

iv. Determined by EPA To Be an Exceptional Eevent
    Finally, EPA must determine through the process established in the
Exceptional Events Rule whether an exceptional event occurred. We
believe that the State has met the procedural requirements of the Rule
including flagging of the data, submission of demonstration, evidence
of the public opportunity to review and comment on the demonstration
and mitigation requirements as discussed at section V.C.1. and 3. of
this proposed rule. We further believe that the State has also met the
technical requirements of the Rule as discussed at section V.C.2.
Therefore, we are proposing to concur with the State's determination
that an exceptional event, i.e., a wind event, occurred resulting in
the exceedances on December 8, 2006.
b. Does the State's documentation show a clear causal connection
between the exceedances and the claimed exceptional event?
    Under 40 CFR 50.14(c)(3)(iii)(B), a state's demonstration must
establish a clear causal relationship between the measured exceedances
and the claimed exceptional event. Unlike September 22 and October 25,
2006, the winds on December 8, 2006 were erratic and generally from the
east, south, and southwest.\75\ Wind speeds at meteorological stations
near Bakersfield recorded hourly average wind speeds in excess of 35
mph and wind gusts in excess of 50 mph. Winds at Bakersfield on
December 8 were from both the southwest and southeast during the time
when peak hourly PM-10 concentrations were recorded. The winds
continued to blow from the southeast up the Valley, pushing the dust
plume towards the Corcoran monitoring site. The peak hours for hourly
PM-10 concentrations were from 1 p.m. to 3 p.m. at both the Corcoran
and Bakersfield sites, with a second set of high hourly concentrations
at Bakersfield occurring from 5 p.m. to 8 p.m. Winds measured at
Alpaugh, located between Bakersfield and Corcoran, were highest from 12
p.m. to 4 p.m. and from the southeast, supporting the State's argument
that the dust plume moved from the southeast to northwest.\76\
---------------------------------------------------------------------------

    \75\ Id. at 11, Table 3.
    \76\ Id. at 56.
---------------------------------------------------------------------------

    Table 3 and Figure 2 of the NED for December 8, 2006 \77\ show the
correlation of wind speeds and increasing hourly concentrations of PM-
10 recorded by the continuous PM-10 analyzers at Corcoran and
Bakersfield.
---------------------------------------------------------------------------

    \77\ Id. at 11-12.
---------------------------------------------------------------------------

    Figure 7 of the NED for December 8, 2006 includes the results of a
basic meteorological model known as Hybrid Single-Particle Lagrangian
Integrated Trajectory model (HYSPLIT).\78\ It is important to note that
while this modeling is not meant to quantify the particle concentration
recorded in the Bakersfield and Corcoran areas, it does offer support
of the State's demonstration that the winds on December 8, 2006 were of
the appropriate intensity and direction to move a plume of dust from
the southeastern SJV to the Bakersfield area and northward to Corcoran.
---------------------------------------------------------------------------

    \78\ Id. at 23.
---------------------------------------------------------------------------

c. Did the State demonstrate that the event is associated with measured
concentration in excess of normal historical fluctuations including
background?
    For EPA to concur with a state's claim that an exceptional event
caused an exceedance, one of the requirements that the state must meet
is to show that the event is associated with concentrations that are
beyond the normal historical fluctuations. See 40 CFR
50.14(c)(3)(iii)(C).

    As with the discussion above on the September 22 and October 25,
2006 exceedances, we can compare data from the continuous analyzers
only with the separate manual FRM samplers operated at the sites, since
the continuous analyzers have only been in operation since late 2006.
Figures 8 and 9 of the NED for December 8, 2006 demonstrate the
relative infrequency, over the last 10 years, of the concentrations
recorded at Corcoran and Bakersfield on December 8, 2006. When we look
at PM-10 FRM concentrations recorded at Corcoran in the month of
December from 1997 to 2006, the last non-flagged exceedance of the
standard was a 174 recorded on December 17, 1999.\79\ Levels exceeding
100 only occurred 10 times in December in the past 10 years, out of 96
FRM days sampled. Even when we include the continuous daily data
collected at Corcoran in 2006, there are only the 10 values over 100
described above.
---------------------------------------------------------------------------

    \79\ PM-10 Raw Data Report Corcoran 1997-2006, EPA AQS Database,
July 30, 2007.
---------------------------------------------------------------------------

    For Bakersfield, the last non-flagged day exceeding the standard in
December was 159 recorded on December 30, 1998. Of the 42 December FRM
sample days since 1997, 9 days exceed 100. Again, even when we include
the continuous daily data from 2006, the result remains 9 days
exceeding 100 in the last 10 years.\80\
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    \80\ PM-10 Raw Data Report Bakersfield Golden 1997-2006, EPA AQS
Database, July 30, 2007.
---------------------------------------------------------------------------

d. Did the State demonstrate that there would have been no exceedance
``but for'' the event?
    As discussed above, to qualify as an exceptional event the state
must also demonstrate that there would have been no exceedance ``but
for'' the event. 40 CFR 50.14(c)(3)(iii)(D). To meet this ``but for''
requirement, the state must include analyses to demonstrate that an
exceedance or violation would not have occurred but for the event. Such
analyses do not require a precise estimate of the estimated air quality
impact from the even. 72 FR at 13570.
    To meet this ``but for'' requirement the State first shows that
there were no unusual activities occurring in the affected areas in the
Valley that could have resulted in the exceedances. Specifically, based
on information from District field staff and discussions with
representatives of agricultural and industrial operations in the
Valley, activities that generate anthropogenic PM-10 were approximately
constant in the Valley immediately before, during and after the event.
As on September 22 and October 25, 2006, activity levels in the SJV
were typical for the time of year and PM-10 emission control programs
were being implemented, not only for fugitive dust-generating
activities, but also agricultural burning and residential wood
combustion in parts of the SJV.\81\
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    \81\ NED for December 8, 2006 at 25.
---------------------------------------------------------------------------

    The State provides frequency distributions of the maximum PM-10 24-
hour December concentrations for the past 10 years. These figures
indicate that PM-10 concentrations at Corcoran and Bakersfield-Golden
State Highway rarely exceeded the level of the 24-hour PM-10 NAAQS.\82\
This fact is an indication that December 8, 2006 was unusual in that
the normal emission activity levels do not cause exceedances, based on
historical data.
---------------------------------------------------------------------------

    \82\ Id. at 28-29, Figures 8 and 9.
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    Examining the make-up of PM-10 on this day using PM-2.5 data
collected at the sites with a continuous PM-2.5 analyzer, we can see
that coarse particles, or PM-10-2.5, which are associated with
windblown dust, represented 78% of the total PM-10 mass collected at
Corcoran and 88% of the total PM-10 mass at Bakersfield. CARB studies
indicate that at this time of year, fugitive dust generally contributes
less than 20% of the total PM-10 mass.\83\ The atypical contribution of
fugitive dust to the exceedances recorded on December 8, 2006 indicates
that but for the wind event these exceedances would not have occurred.
---------------------------------------------------------------------------

    \83\ Magliano Presentation.
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    As discussed above, the State also looked at data from the days
immediately preceding and after December 8, 2006.\84\ Twenty-four hour
PM-10 concentrations on December 4-6 were less than 100 [mu]g/
m3 at both sites and were just over 100 [mu]g/m\3\ on
December 7. On December 8, the concentration at Corcoran increased by
more than 50%, exceeding the NAAQS with a level of 162 [mu]g/
m3, but then fell to 32 [mu]g/m3 on December 9
and continued dropping for weeks after this event. At Bakersfield, on
December 8 there was a greater than 100% increase over the December 7
concentration. Again, concentrations dropped dramatically on December 9
and remained low for weeks after.
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    \84\ NED for December 8, 2006 at Table 1.
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    Finally, as discussed above, there were reasonable and appropriate
measures in place to control PM-10 in the SJV on December 8, 2006,
Regulation VIII and Rule 4550.\85\ Moreover, EPA has approved the
District's BACM demonstration for all significant sources of PM-10 in
the SJV as meeting CAA section 189(b)(1)(B).\86\ The District's Natural
Events Action Plan, discussed in section V.A.3. above, also addresses
the reasonable and appropriate measures that the District has
implemented to address high wind events in the SJV.
---------------------------------------------------------------------------

    \85\ Id. at 25.
    \86\ 69 FR at 30035; 71 FR 7683.
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    Based on the weight of evidence presented, EPA concludes that the
State's documentation demonstrates that the exceedances at Corcoran and
Bakersfield on December 8, 2006 would not have occurred but for the
wind event on this day.
3. Mitigation Requirements
    See section V.A.3.c above.

Conclusion

    EPA believes that the high winds in the southeastern SJV on
December 8, 2006 were an exceptional event as defined in 40 CFR
50.1(j). EPA also believes that the State has provided a sufficient
weight of evidence demonstration to show that these high winds
generated and transported PM-10 from the area of Bakersfield to
Corcoran causing exceedances of the 24-hour PM-10 NAAQS at the
Bakersfield and Corcoran monitors. The NED for December 8, 2006
submitted by the State demonstrates that but for the high winds in the
southern SJV, the Corcoran and Bakersfield monitors would not have
exceeded the 24-hour PM-10 NAAQS on December 8, 2006. Because EPA
believes that the State has satisfied the provisions of the Exceptional
Events Rule, EPA proposes to concur with the State's request to flag
these exceedances as due to exceptional events and to exclude the data
from consideration in determining whether the area has attained the PM-
10 standard.

VI. EPA Evaluation of September 14, September 20 and October 26, 2006
Exceedances at the Santa Rosa Rancheria

    The 24-hour PM-10 NAAQS was exceeded on September 14, 20 and
October 26, 2006 at a monitor on the Santa Rosa Rancheria (SRR), tribal
land located in Kings County within the SJV. The 24-hour average PM-10
concentrations were 190 [mu]g/m3, 158 [mu]g/m3,
and 157 [mu]g/m3, respectively. The SRR Tribe flagged the
exceedances as caused by an exceptional event, i.e., construction
activities.
    The Santa Rosa Rancheria EPA Department (SRREPA) operates a
monitoring site on the SRR, located on the roof of a pumping station at
the SRR's water treatment facility. The PM-10 sampler is a high volume
size

selective inlet (SSI) Anderson sampler designated as a FRM by EPA. The
monitoring site also measures ozone and meteorological parameters
including wind speed and wind direction.
    The PM-10 sampler is located near the northeast corner on the roof
of the pumping station. The current land cover around the pump station
is paved parking. There are no obstructions of any kind and there is
unrestricted airflow 360 degrees around the sampler inlet.\87\
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    \87\ July 18, 2007 Memorandum, ``On-Site Visit to Santa Rosa
Rancheria,'' from Bob Pallarino, EPA, to Sean Hogan, EPA (Site Visit
Memorandum).
---------------------------------------------------------------------------

    To the east of the monitor is a paved parking lot, beginning about
25 feet east of the monitor location and extending approximately 50
feet to the east. Beyond the parking area are trailers and undeveloped
land. To the north of the monitor is a larger parking lot, beginning
about 100 feet north of the monitor location and extending north
approximately 525 feet. Beyond the parking lot are a casino hotel,
casino, and additional parking lots. To the immediate south (150 feet)
and west (300 feet) are the remaining physical plant facilities (tanks,
pumps, etc.) and the area is paved. Further south and west are
agricultural fields (currently alfalfa). Agricultural fields also lie
to the north beyond the casino and parking lot (approximately 0.5
mile). To the east is the SRR residential area.
    PM-10 is measured once-in-every-six days by the SRREPA according to
the national sampling schedule. Sampling began on August 3, 2006 and
continues to the present time.
    In 2006 there was a major construction project at the SRR, which
involved construction of a casino hotel and associated parking lots.
This construction activity, located near the monitor, was ongoing prior
to the time the monitor began operation. The original intention of the
SRREPA was to begin operation of the monitor and sampling only after
completion of the parking lots and external portion of the hotel. Due
to delays, however, the construction was not completed until November
2006. The monitor began operating as scheduled on August 3, 2006.
    The SRREPA's environmental technician informed EPA that he believes
that many of the samples collected since PM-10 monitoring began on
August 3, 2006, through mid-November 2006, were unduly influenced by
the grading and paving of parking lots immediately adjacent to the
monitoring site on the north and east sides of the pump station
building where the PM-10 sampler monitor is located.\88\ In addition to
the exceedance days, much of the data between August 3 and November 25,
2006 submitted to the AQS database, has been flagged as affected by
construction activity.\89\
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    \88\ Site Visit Memorandum.
    \89\ AQS Raw Data Report, Santa Rosa Rancheria PM-10 2006 to
2007.
---------------------------------------------------------------------------

    EPA believes there are two bases for excluding the September 14,
September 20 and October 26, 2006 exceedances from consideration in
determining whether the SJV has attained the PM-10 standard. First, as
explained in more detail below, EPA believes that, during the time
period the monitor was operating in such close proximity to the
construction, the monitor should be considered to have been improperly
sited under the principles established in 40 CFR part 58, appendix E.
Second, EPA believes that, under its Exceptional Events Rule, the
construction activity that occurred within such close proximity to the
monitor constitutes an exceptional event that caused the exceedances.
EPA believes that both of these rationales, separately or together,
support EPA's proposal not to include the SRR monitor data recorded
during the period of parking lot construction in our determination of
whether the SJV has attained the PM-10 NAAQS.

A. Evaluation Under Principles Established in 40 CFR Part 58, Appendix
E

    40 CFR part 58 establishes criteria and requirements for ambient
air quality monitoring, and appendix E sets forth the probe and
monitoring path siting criteria for ambient air quality monitoring. 71
FR 61236 (October 17, 2006). These include both binding requirements
and goals. Section 1(b) of appendix E, the Introduction, provides that
``[t]he probe and monitoring path siting criteria discussed in this
appendix must be followed to the maximum extent possible.'' Section
58.20 provides that Special Purpose Monitors, which may include
monitors on tribal lands, must meet certain requirements of part 58,
including appendix E, if the data they collect are to be used for
purposes of comparison to the NAAQS. It is not clear whether the
monitor in Santa Rosa Rancheria is intended to be designated a Special
Purpose Monitor. It is clear, however, that EPA does not intend data
from a monitor to be used for purposes of comparison to the NAAQS
unless the data meet the criteria set forth in section 58.20, including
appendix E. Under the principles established in part 58, appendix E,
EPA believes that it is not a reasonable monitoring practice to locate
a PM-10 monitor, intended for purposes of comparison to the NAAQS, so
close to an obviously temporary dust source, as was the case at the
SRR.
    Section 3(a) of appendix E, Spacing from Minor Sources, addresses
the siting of monitors, including PM-10 monitors. It states that close
spacing between a monitor and a minor source may be proper if the
purpose of that monitoring site is to investigate emissions from that
source and other local sources. However, if, as is the case with the
SRR monitor here, the site is to be used to determine air quality over
a larger area, such as a neighborhood or city, it should not be placed
near local, minor sources, because the plume from the local minor
source would inappropriately impact the air quality data collected at
the site. It is plain that this occurred in the SRR situation, where
the monitor, when it began operating, was only 25 feet from one parking
lot construction zone and 100 feet from another.
    We believe that in general it is important to avoid placing a
particulate monitor inordinately close to a location where active but
temporary construction activity is generating dust emissions. As noted
above, the SRREPA originally had not intended to start operating the
monitor until after the conclusion of the construction activity. As a
consequence of monitoring while this construction was still ongoing,
the SRR Tribe was compelled to flag data for 12 of the 19 sampling days
that occurred between August 3 and November 25, when the construction
concluded. Thus more than 60% of the data collected during this time
period was considered to be unusable for regulatory purposes.
    The dramatic contrast between concentrations monitored while
construction was ongoing and post-construction concentrations also
testifies to the impact that the improper siting had on the monitored
data. After construction ceased, average monitored PM-10 concentrations
declined 50%. See discussion below in section VI.B.2.d. below. EPA
believes that after the construction concluded the monitor met the
appropriate siting criteria.\90\
---------------------------------------------------------------------------

    \90\ Site Visit Memorandum.
---------------------------------------------------------------------------

    EPA has concluded that under the very unusual circumstances
presented in the SRR, it was not appropriate, according to the
principles established in part 58 appendix E, to deploy a new PM-10
monitor, for purposes of comparison to the NAAQS, so close to temporary
construction activity, for the duration of that activity. EPA believes
it would be unreasonable for the Agency

to allow the data from such a monitor to determine the attainment
status of the SJV.

Conclusion

    EPA is proposing to conclude that the exceedances in the SJV at the
SRR monitor that occurred on September 14, 2006, September 20, 2006 and
October 26, 2006 should be excluded from consideration in determining
whether the SJV has attained the PM-10 standard, because during this
time period EPA deems that the monitor was not properly sited, under
the principles established in part 58, appendix E.
    In proposing to find that, during the period of construction, the
monitor was not properly sited for the purpose of comparison to the
NAAQS, EPA is addressing only the particular facts and circumstances
presented by the SRR monitoring operation. EPA notes that the
construction activity at the SRR, which occurred in extremely close
proximity to the monitor and on tribal land, predated the start of
monitoring operations, and that monitoring was originally intended to
begin only after the conclusion of construction activity. Under these
circumstances, EPA believes that the September 14, September 20 and
October 26, 2006 exceedances should be excluded from consideration in
determining whether the SJV has attained the PM-10 standard.

B. Evaluation Under the Exceptional Events Rule

    In addition to the rationale regarding the siting of the monitor,
set forth above, EPA proposes to concur with the SRR Tribe's flagging
of the exceedances at the SRR because EPA believes that the
construction activity constitutes an exceptional event under EPA's
Exceptional Events Rule. Our application of the requirements of the
Rule to the SRR exceedances is set forth below.
1. Procedural Requirements
a. Data Are Flagged in EPA's AQS Database
    The three exceedances were flagged by the SRR Tribe by the time the
data were submitted to the AQS database in 2006.
b. Public Had an Opportunity To Review and Comment on the Tribe's
Documentation
    EPA is assisting the SRR Tribe by compiling and evaluating the
documentation for the exceedances which have been flagged as being
caused by exceptional events. The Exceptional Events Rule recognizes
that tribes may not be in a position to address all of the requirements
of the Rule and thus states that EPA will ``* * * work with tribes on
the implementation of this rule, which may include appropriate
implementation by EPA of program elements ensuring that any exclusion *
* * of data in Indian country with air quality affected by exceptional
events comports with the procedures and requirements of this rule.'' 72
FR at 13563. EPA, through this proposed rule, is providing the public
with an opportunity to review and comment on the documentation of these
exceptional events.
c. The Documentation Was Submitted to EPA
    As discussed above, EPA is assisting the SRR Tribe by compiling and
evaluating the documentation of the exceedances which they have flagged
as being caused by exceptional events.
d. EPA Concurs With the Tribe's Flagging and Demonstration
    EPA is proposing to concur with the SRR Tribe's flagging of these
exceedances as affected by exceptional events. As discussed above, EPA
is assisting the SRR Tribe by compiling and evaluating the
documentation of the exceedances it has flagged as being caused by
exceptional events, and by ensuring that the public has an opportunity,
through this rulemaking, to review and comment upon it.
2. Technical Criteria
a. Did this event satisfy the criteria in section 50.1(j) of the Rule?
i. Affected Air Quality
    For an event to qualify as an exceptional event, the state or tribe
must show that the event affected air quality. Here, EPA, on behalf of
the SRR Tribe, needs to show that the event, identified as construction
activity, affected air quality at the SRREPA PM-10 monitor. This
criterion can be met by establishing that the event is associated with
a measured exceedance in excess of normal historical fluctuations,
including background, and there is a causal connection between the
event and the exceedance. This demonstration of a causal connection is
necessary to establish that the event affected air quality, and it is
also a separate statutory requirement as discussed above.
    Because the SRREPA PM-10 monitor has been in operation only since
August 2006, it is not possible to compare the data from exceedance
days to historical levels. In this case, however, we can look at data
that have been collected since the construction and parking lot paving
was completed to determine representative concentrations of PM-10 in
the absence of a large, earth-disturbing project such as the
construction, grading and paving of parking lots. We discuss the range
of data and its fluctuation in more detail in subsection c. below.
    We also need to show the causal connection between the exceptional
event, in this case construction activity, and the exceedances
recorded. In addition to other information provided during EPA's on-
site visit, the SRREPA has provided EPA with wind speed and wind
direction data collected at its site that show the wind was blowing in
the appropriate direction and demonstrates that the PM-10 monitor was
downwind of the construction activity on the exceedance days. We
discuss the causal connection between the construction activity and the
exceedances in more detail in subsection b. below.
ii. Not Reasonably Controllable or Preventable
    Section 50.1(j) of the Exceptional Events Rule requires that for an
event to qualify as an exceptional event, whether natural or
anthropogenic, a state, tribe (or, in this case, EPA) must show that
the event was not reasonably preventable or controllable.
    EPA believes that it would not have been reasonable to prevent the
activity, i.e., paving of parking lots that were needed for the SRR
Tribe's facilities. Paving a parking lot (which involves grading the
ground, applying a base material such as gravel and applying asphalt)
is a generally accepted form of control of PM-10.\91\ To prevent the
paving of a parking lot would not only be unreasonable, but illogical.
    With respect to whether the event was reasonably controllable, we
note that the SRR Tribe does not have PM-10 control measures in place
and is not subject to the fugitive dust control regulations adopted by
the SJVAPCD. As discussed in the Exceptional Events Rule, ``Tribes are
not required to develop TIPs or otherwise implement relevant programs
under the CAA. * * *'' \92\ ``EPA recognizes Tribal Governments as
sovereign entities with primary authority and responsibility for the
reservation populace. Accordingly, EPA will work directly with Tribal
Governments as the independent

authority for reservation affairs, and not as political subdivisions of
States or other governmental units.'' \93\
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    \91\ See, for example, SJV Rule 8051 Open Areas (Adopted
November 15, 2001; Amended August 19, 2004) and Rule 8071 Unpaved
Vehicle/Equipment Traffic Areas (Adopted November 15, 2001; Amended
September 16, 2004).
    \92\ 63 FR 7254, 7265 (February 12, 1998); 72 FR at 13563.
    \93\ 59 FR 43956 (August 25, 1994).
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    While paving itself is a control measure, EPA recognizes that other
control measures may be reasonable during a paving process. For
example, the SJVAPCD regulations require, among other things, that
regulated construction sites apply as appropriate water or chemical/
organic stabilizers or construct and maintain wind barriers.\94\ In the
circumstances of the SRR, however, even if these types of measures had
been actively employed, we cannot be certain that they would have
prevented exceedances at the PM-10 monitor. This is due in large part
to the unusual circumstance presented here of the very close proximity
of the construction activity to the monitor. As noted above, one of the
parking lots was within 25 feet of the monitor, and the other was
within 100 feet.
---------------------------------------------------------------------------

    \94\ SJV Rule 8021 Construction, Demolition, Excavation,
Extraction, and Other Earthmoving Activities (Adopted November 15,
2001; Amended August 19, 2004).
---------------------------------------------------------------------------

    EPA's evaluation of the parking lot construction activity's impact
on the monitor, and whether it was reasonably controllable, during the
activity, is informed by EPA's views on what constitutes acceptable
monitor siting. As EPA has set forth in detail above, EPA believes
that, for the duration of the construction activity, the monitor was
not properly sited for the purposes of determining attainment of the
SJV, and that as a result it was inordinately impacted by that
activity.
    The provisions of 40 CFR part 58, appendix E regarding the siting
of PM-10 monitors, are instructive with respect to EPA's analysis of
the exceedances under the Exceptional Events Rule. We cannot conclude
that the activity was reasonably controllable given that the
exceedances were measured at a monitor that EPA's rule provides should
not be operated at such a time and place, for the purposes of
determining attainment. Thus, under the particular set of circumstances
presented here, for the purposes of evaluating the ``reasonably