Document ID: EPA-R09-OAR-2006-0583-0071
Agency: epa
Document Type: Proposed Rule
Title: 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
Posted Date: 2007-08-27T04:00Z

[Federal Register: August 27, 2007 (Volume 72, Number 165)]
[Proposed Rules]               
[Page 49045-49067]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr27au07-14]                         

[[Page 49045]]

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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

[[Page 49046]]

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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: lo.doris@epa.gov.
    (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, lo.doris@epa.gov.

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

[[Page 49047]]

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.

[[Page 49048]]

    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).

[[Page 49049]]

    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

[[Page 49050]]

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.
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    \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.

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[[Page 49051]]

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\
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    \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.
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    \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

[[Page 49052]]

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

[[Page 49053]]

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

[[Page 49054]]

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

[[Page 49055]]

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,

[[Page 49056]]

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

[[Page 49057]]

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

[[Page 49058]]

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).

[[Page 49059]]

    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\
---------------------------------------------------------------------------

    \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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \84\ NED for December 8, 2006 at Table 1.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    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

[[Page 49060]]

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\
---------------------------------------------------------------------------

    \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\
---------------------------------------------------------------------------

    \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

[[Page 49061]]

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

[[Page 49062]]

authority for reservation affairs, and not as political subdivisions of 
States or other governmental units.'' \93\
---------------------------------------------------------------------------

    \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).
---------------------------------------------------------------------------

    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 
controllable'' criterion of the Exceptional Events Rule, we deem this 
criterion to have been satisfied.
iii. Was an Event Caused by Human Activity That is Unlikely to Recur at 
a Particular Location
    In this case, the event was paving of parking lots in the vicinity 
of the PM-10 monitor, and is a construction activity that is not 
expected to recur at that location.
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. The 
Exceptional Events Rule has both procedural requirements and technical 
criteria that we are assisting the SRREPA in meeting. We believe that 
by the initial flagging of the data, and through the vehicle of this 
proposed rulemaking we will demonstrate that the procedural 
requirements and technical criteria of the rule will have been met.
b. Is there a clear causal connection between the exceedances and the 
claimed exceptional event?
    Under 40 CFR 50.14(c)(3)(iii)(B), a clear causal relationship must 
be established between the measured exceedance and the claimed 
exceptional event. The information compiled by EPA shows a clear causal 
connection between the exceedances and the construction activity at the 
nearby parking lots. The SRREPA environmental technician observed the 
conditions at the time the monitor was operating and noted on the 
sample tracking forms, which are completed with each sampling run, that 
there was construction nearby. Copies of these tracking forms are 
included in the documentation for this rulemaking.
    The SRREPA measures wind speed and wind direction at the SRR 
monitoring site. These meteorological data indicate that on the three 
days that exceeded the NAAQS, winds were predominantly from the 
northwest to northeast. This would indicate that any dust-producing 
activity north and northeast of the monitor would result in high 
concentrations of geologic dust being blown towards the monitor.
    The meteorological data lend support to the environmental 
technician's account of the events of that day. EPA also discussed 
these events with the SRR construction superintendent, who agreed with 
the environmental technician's account of the construction activity. A 
private consultant working for the SRREPA also stated that he had 
witnessed major earth-disturbing activities on these days.\95\
---------------------------------------------------------------------------

    \95\ Site Visit Memorandum.
---------------------------------------------------------------------------

    Based on the meteorological data, eyewitness accounts, and an on-
site inspection of the monitoring site location and its proximity to 
the parking lots, we believe that there was a clear causal connection 
between the construction activity and the recorded PM-10 exceedances.
c. Can it be demonstrated that the event is associated with a measured 
concentration in excess of normal historical fluctuations including 
background?
    For EPA to concur with the SRREPA's claim that an exceptional event 
caused an exceedance, one of requirements 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).
    Of the 44 samples collected by the SRREPA, nearly 80% of the 
samples (35 days) were less than 100 [mu]g/m3. After 
completion of the paving projects in mid-November, 2006, average PM-10 
concentrations dropped by more than 50%, from an average of 97 [mu]g/
m\3\ to an average of 45 [mu]g/m3.\96\ This would indicate 
that the construction activity had an obvious effect on the 
concentrations recorded by the SRR monitor and that the data collected 
during this construction period, including the exceedances recorded in 
September and October, 2006, were not representative of typical post-
construction PM-10 concentrations at the location of the monitor.
---------------------------------------------------------------------------

    \96\ Santa Rosa Rancheria PM-10 24 hour average concentrations, 
Excel spreadsheet, Bob Pallarino.
---------------------------------------------------------------------------

d. Can it be demonstrated that there would have been no exceedance 
``but for'' the event?
    To qualify as an exceptional event, there must be an analysis which 
demonstrates that there would have been no exceedance ``but for'' the 
event. 40 CFR 50.14(c)(3)(iii)(D). Such analyses do not require a 
precise estimate of the estimated air quality impact from the event. 72 
FR at 13570.
    To meet this requirement, EPA believes the SRREPA environmental 
technician, consultant and the SRR construction superintendent have 
clearly indicated that the exceedances occurred on days where nearby 
construction was also occurring. As EPA has shown, the proximity of the 
monitor to the construction activity and the concomitant infeasibility 
of control measures to prevent the exceedances also demonstrate that 
there would have been no exceedances but for the construction activity. 
Given these factors and the fact that the average PM-10 concentrations 
dropped by more than 50% after the completion of the paving projects, 
we believe the weight of evidence shows that the exceedances would not 
have occurred but for the construction activity.

[[Page 49063]]

3. Mitigation Requirements
    Under 40 CFR 51.930, a state or tribe 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. In the case of the SRR, EPA recognizes that 
tribes may implement only portions of air quality programs and not be 
in a position to address each of the procedures and requirements 
associated with excluding or discounting data. In the preamble to the 
Exceptional Events Rule, EPA cites an example of tribes that ``* * * 
may operate a monitoring network for purposes of gathering and 
identifying appropriate data, but may not implement relevant programs 
for the purpose of mitigating the effects of exceptional events. * * 
*'' 72 FR at 13563. That is the case with the SRR. Under these 
circumstances, as indicated in the preamble to the Exceptional Events 
Rule, EPA intends to work with the SRR on the implementation of the 
Rule.

Conclusion

    EPA believes that the construction activities at the SRR on 
September 14, 2006, September 20, 2006 and October 26, 2006 were 
exceptional events as defined under 40 CFR 50.1(j). EPA believes that 
there is sufficient weight of evidence to conclude that the 
construction activities caused the exceedances on the exceedance days, 
and that the exceedances would not have occurred but for the 
construction activity. The proximity of the construction activities to 
the monitor and the wind direction recorded at the monitor support this 
conclusion. Because EPA believes that the provisions of the Exceptional 
Events Rule have been satisfied, EPA is proposing to concur with the 
SRR Tribe's flags indicating that these exceedances were due to 
exceptional events, and to exclude the data from consideration in 
determining whether the SJV has attained the PM-10 standard.
    In proposing to concur with the SRR Tribe's flags that construction 
activity at SRR constituted exceptional events, EPA is addressing only 
the particular facts and circumstances presented by the SRR monitoring 
operation. In general, fugitive dust control measures employed during 
construction activities are helpful in reducing ambient PM-10 
concentrations and avoiding exceedances of the NAAQS. However, in the 
specific circumstances of the SRR during the days when exceedances were 
recorded, we are not able to conclude that the event was reasonably 
controllable due to the very close proximity of the monitor to the 
construction activity, and the other factors discussed above. Given 
this singular constellation of factors, EPA is proposing to concur with 
the Tribe's flagging of the exceedances on September 14, September 20 
and October 26, 2006 as caused by exceptional events.

VII. Summary of Exceedances From 2004 Through 2006

    The table below provides a summary of exceedances relevant to 
today's proposed rule that were recorded at monitors located within the 
boundaries of the SJV. The table indicates, whether in determining 
attainment, EPA has excluded or proposes to exclude the exceedance, 
based on a finding that it was due to an exceptional event. The 24-hour 
standard is attained when the expected number of days per year with 
levels above 150 [mu]g/m\3\ (averaged over a three-year period) is less 
than or equal to one. 40 CFR part 50, appendix K. As shown in the 
table, all of the monitoring locations are meeting the PM-10 standard.

                                                 Table Summarizing PM-10 24-Hour Exceedances in the SJV
                                                                [From 2004 through 2006]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                Recorded (observed)            Number of estimated exceedances           Average number
                                                              exceedances 2004--2006  -------------------------------------------------     of annual
              Monitor                  Operating schedule   --------------------------    Included in attn.      Reason for excluding      exceedances
                                                                 Date         Conc              deter.                exceedance           2004--2006
--------------------------------------------------------------------------------------------------------------------------------------------------------
Corcoran Manual FRM................  1 in 3 day............       9/3/04          217  No.....................  Exceptional Event.....              0
                                                                 9/22/06          215  No.....................  Exceptional Event.....  ................
Corcoran TEOM......................  Continuous............      9/22/06          261  No.....................  Exceptional Event.....              0
                                                                10/25/06          304  No.....................  Exceptional Event.....  ................
                                                                 12/8/06          162  No.....................  Exceptional Event.....  ................
Bakersfield Golden Manual FRM......  1 in 6 day............      9/22/06          157  No.....................  Exceptional Event.....              0
Bakersfield Golden BAM.............  Continuous............     11/22/05          156  Yes....................  N/A...................              0.67
                                                                11/23/05          180  Yes....................  N/A...................  ................
Bakersfield Golden TEOM............  Continuous............      9/22/06          157  No.....................  Exceptional Event.....              0
                                                                10/25/06          193  No.....................  Exceptional Event.....  ................
                                                                 12/8/06          213  No.....................  Exceptional Event.....  ................
Tracy BAM..........................  Continuous............      9/22/06          161  Yes....................  N/A...................              0.33
Oildale Manual FRM.................  1 in 6 day............      9/22/06          162  No.....................  Exceptional Event.....              0
Santa Rosa Rancheria Manual FRM....  1 in 6 day............      9/14/06          190  No.....................  Exceptional Event.....              0
                                                                 9/20/06          158  No.....................  Exceptional Event.....  ................
                                                                10/26/06          157  No.....................  Exceptional Event.....  ................
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sources:
EPA Air Quality System Database.
E-mail from Steven Shaw, SJVAPCD to Bob Pallarino, EPA Region 9, April 20, 2006.
E-mail from Steve Shaw, SJVAPCD to Bob Pallarino, EPA Region 9, October 12, 2006.

[[Page 49064]]

VIII. Petitions for Reconsideration and Withdrawal

A. Winds and Wildfires on September 22 and October 25, 2006

    Earthjustice filed its 2006 Petition for Reconsideration (PFR) 
before the State provided its exceptional event documentation for the 
September 22, 2006 exceedances to the public or EPA. At that time CARB 
and the District had simply informed EPA that, based on preliminary 
analysis, they believed that these exceedances were due to high wind 
and wildfire natural events. Similarly, when Earthjustice filed its 
2007 Petition for Withdrawal (PFW) and the accompanying Jan Null 
declaration, the State had not yet submitted the complete documentation 
for the September and October 2006 exceedances on which EPA is basing 
this proposed rule. Therefore Earthjustice's conclusion in the 
petitions that the September 22, 2006 and October 25, 2006 exceedances 
do not qualify as natural events does not address the technical 
analysis of the winds and wildfires as ultimately submitted by the 
State and which EPA has evaluated in section V. above. To the extent 
that Earthjustice's assessments in the petitions of the nature and 
effect of the winds and wildfires are currently relevant, we believe 
our evaluation in section V. addresses the significant points raised in 
them.
    In addition, since EPA, as stated in section V. above, agrees with 
the petitioners that regional transport from north of the SJV and the 
northern SJV and wildfires were not the cause of the exceedances on 
September 22 and October 25, it is unnecessary for EPA to further 
address the arguments raised by petitioners with respect to these 
theories.

B. Notice/Comment on September 22 and October 25, 2006 Exceedances

    The gravamen of the 2006 petition, which is reiterated in the 
Petition for Withdrawal, is Earthjustice's claim that EPA did not 
provide the public with an opportunity to comment on the September 22, 
2006 exceedances and thus should not have finalized the attainment 
determination for the SJV. PFR at 2-4. Petitioners also complained that 
EPA did not require adequate documentation that these exceedances were 
caused by exceptional events. PFR at 3-4.
    Contrary to Earthjustice's assertions, EPA did not abuse its 
discretion in addressing the September 22, 2006 exceedances in its 
October 2006 determination of attainment. EPA noted at the time that 
the exceedances were based on preliminary data only: ``Because these 
data, which were collected using manual reference method samplers, are 
preliminary and have not been quality assured, and because EPA believes 
that they may qualify as caused by natural events, and thus be excluded 
from consideration in an attainment determination, EPA is proceeding to 
finalize its determination that the area is in attainment.'' 71 FR 
63642. Thus the data had not been quality assured, and in addition EPA 
was on notice that CARB and the District intended to flag the data as 
due to exceptional events and to request EPA's concurrence on excluding 
the data from consideration in an attainment determination.
    EPA went on to note that ``[i]f, after the data is quality assured, 
and after further evaluating CARB's request with respect to these data, 
EPA determines that the data do not qualify for exclusion under EPA's 
natural events policy, and EPA further believes that if included that 
they would establish that the area is in violation of the NAAQS, EPA 
will proceed with appropriate rulemaking action to withdraw its 
determination of attainment.'' Id. It was thus clear that EPA's 
determination was subject to revision based on subsequent quality 
assurance and evaluation of the data, and EPA outlined its projected 
procedure for dealing with the data once they were quality assured and 
EPA had an opportunity to evaluate the documentation of the potential 
exceptional events.
    In this proposed rule, EPA is following through with this 
procedure, and is now providing for full notice and an opportunity for 
comment, in the context of a rulemaking, on whether those exceedances 
qualify as caused by exceptional events. EPA is also providing notice 
and opportunity for comment on additional claims that exceedances were 
caused by exceptional events on October 25, 2006, and December 8, 2006, 
and at the Santa Rosa Rancheria on September 14 and 20 and October 26, 
2006.
    Contrary to Earthjustice's contention in its Petition for 
Reconsideration and Petition for Withdrawal, EPA did not reverse the 
burden of proof required to establish an exceptional event, or relieve 
the State from the obligation to document its claims. PFR at 4; PFW at 
17. In the final determination, it is clear that EPA did not 
conclusively concur in excluding the data without requiring appropriate 
documentation and a showing from the State. Rather, EPA deferred its 
determination on the impact of the preliminary data until the data 
could be quality assured and the State would have an opportunity to 
meet its burden of showing that an exceedance qualified as caused by an 
exceptional event.
    Finally EPA notes that Earthjustice alleges in its 2007 petition 
that the Agency ignored in its final attainment determination the 
October 25, 2006 exceedances as well as the September 22, 2006 
exceedances. PFW at 2. This is not the case. The exceedances in October 
occurred eight days after EPA promulgated its final determination of 
attainment, on October 17, 2006. (The notice was published on October 
30, but the determination had been signed and disseminated to the 
public on October 17). Thus, EPA had no information on these 
exceedances at the time of its final action.

C. Wind Conditions in the Valley

    With respect to the existence of high winds in the Valley 
generally, Earthjustice, in both petitions, characterizes statements in 
the 2003 PM-10 Plan for the area as concluding that wind erosion is not 
a significant contributing factor in dust emissions and as suggesting 
that winds with enough velocity to cause erosion disperse PM-10 
concentrations and/or transport PM-10 out of the Valley. PFR at 4; PFW 
at 8. Earthjustice in its 2007 petition also cites a letter from the 
District to EPA which states that ``there is no evidence of any 
significant linkage between high winds and PM-10 federal exceedance 
events [in the Valley].'' Id. at 8-9.
    Earthjustice has taken the statements in the 2003 Plan to attain 
the PM-10 standard out of context. Chapter 2 of the Plan, quoted by 
Earthjustice, is a 12-page general overview of the San Joaquin Valley 
Air Basin, the purpose of which is to describe normal or typical 
meteorological conditions. It is not intended to nor does it address 
unusual winds such as those under consideration here that may occur in 
the Valley. Nevertheless, the District did determine that windblown 
dust is not a significant problem in the SJV for the purposes of 
attaining the PM-10 standard. For example, the Plan states that 
``[w]ind related PM-10 events are rare but possible when conditions are 
right'' and that ``PM-10 readings in the SJVAB are most severe during 
the fall and winter periods when wind speed and direction are not 
conducive to interregional transport.'' 2003 PM-10 Plan, ES-10, 2-6. 
The District also states that ``winds are effective in dispersing PM-10 
concentrations and/or transporting PM-10 out of the Valley'' in 
explaining why the spring and

[[Page 49065]]

summer months, which are the windier months of the year in the SJV, do 
not yield higher PM-10 levels.
    However, the fact that PM-10 pollution from windblown dust is not 
generally a significant enough problem in the SJV that it needs to be 
controlled for the purposes of attaining the PM-10 standard, does not 
mean that windblown dust cannot cause an exceedance of the standard. In 
addition, even if windblown dust were a significant problem, there 
could be individual situations where particular conditions make it 
unreasonable to expect the District and State to be able to control 
sources in those circumstances. For such situations, EPA has issued the 
Exceptional Events Rule, and previously its policies, which as 
discussed above allows exceedances caused by exceptional events to be 
excluded from regulatory considerations as appropriate if certain 
conditions are met. Since there are many variables that can cause 
exceptional event exceedances, EPA believes the analyses for such 
events should be reviewed on a case by case basis. 72 FR 13560. For 
example, not all high wind days will lead to exceedances and not all 
exceedances monitored when high winds are recorded are necessarily due 
to those high winds. For the exceedances discussed in today's proposal, 
however, EPA believes the State has made an adequate demonstration that 
they were caused by exceptional events and have met all of the 
Exceptional Events Rule requirements, and thus the data for these 
particular events should be excluded from regulatory consideration.
    Earthjustice also cites a letter from the District to EPA 
responding to a letter from Charles Swanson to EPA commenting on the 
2003 PM-10 Plan. April 15, 2004 letter from James Sweet, SJVAPCD, to 
Doris Lo, EPA (Sweet letter). Mr. Swanson disputes the following 
passage from Table G-15 in Appendix G entitled ``BACM Comparative 
Analysis for `On-Field Activities''' concerning the BACM justification 
discussion associated with the ``Other'' category of the District's 
proposed Agricultural Conservation Management Practices:

    The SJV does not have a windblown dust problem to anywhere near 
the extent of the other nonattainment areas. The SJV has some of the 
lowest average wind speeds in the country. No wind related 
exceedances have been recorded in the basin during the last three 
years. Wind speeds are highest during the spring when PM-10 levels 
are at their lowest. The majority of the fugitive dust emissions are 
generated from earth disturbing activities. Certain soil types and 
crops are more prone to windblown dust problems. The ``Other'' 
category will give the farmers with the potential to experience wind 
blown dust emissions the flexibility to address this issue with a 
CMP.

    March 18, 2004 letter from Charles Swanson to Doris Lo, EPA 
(Swanson letter) at 1.
    In responding to Mr. Swanson, the District stated in its April 15, 
2004 letter that ``[t]he statements in the Plan provide a general 
characterization of the San Joaquin Valley (SJV) and, as with all 
generalizations, are not without exception.'' Sweet letter at 1. 
Furthermore, while, as Earthjustice points out, the District did also 
state that an analysis of all wind events since 1990 did not establish 
a linkage to PM-10 exceedances, the District also enumerated technical 
limitations that bear directly on this conclusion. For example, the 
data used did not report wind gusts and the 1 in 6 day sampling for PM-
10 will not capture all wind events. Sweet letter at 7-8. Therefore, 
Earthjustice's attempts to characterize the statements in the Sweet 
letter regarding windblown dust as absolute is not warranted. Finally, 
the District also asserts that:

    Evaluation of past events indicates that often the area with the 
highest PM-10 levels is not where the wind is highest, but rather 
where the wind begins to slow. To understand the dynamics of this 
pattern we need only review the mechanisms for entrainment and 
deposition. When the wind slows, it can no longer keep the larger 
PM-10 particles aloft and they settle toward the surface. The 
settling of particulates aloft * * * results in an increased 
concentration in the deposition area.

    Sweet letter at 2. This scenario is precisely what occurred on 
September 22 and October 25, 2006 as discussed in section V. above.

D. EPA's Natural Events Policy

1. BACM Implementation
    In both petitions Earthjustice asserts that EPA's 1996 Natural 
Events Policy requires that the State demonstrate that BACM were in 
place and that all sources were in compliance in order for EPA to 
concur on a high wind natural event request. PFR at 5; PFW at 9. 
Earthjustice contends that the State cannot demonstrate that 
agricultural sources were in compliance at the time of the wind event 
since it is not clear if any compliance inspections had been conducted.
    As discussed in sections IV. and V., EPA is evaluating the State's 
exceptional event documentation under EPA's Exceptional Event Rule and 
not under its pre-existing policies. The Rule does not require either a 
showing that BACM was in place at the time of the event or proof that 
sources were in compliance. Rather, in the preamble to the Rule EPA 
states that the State must take reasonable and appropriate measures 
under these circumstances. 72 FR at 13576-13577. That said, EPA has 
approved the District's BACM demonstration for all significant sources 
of PM-10 in the Valley, including agricultural sources, as meeting CAA 
section 189(b)(1)(B). 69 FR at 30035; 71 FR 7683. Moreover the State's 
documentation for the September 22 and October 25, 2006 events includes 
information on compliance inspections throughout the SJV. See section 
V. above.
2. District's Natural Events Action Plan
    In its 2007 petition Earthjustice claims that for the September 22, 
2006 exceedances the District failed to meet the requirements of its 
Natural Events Action Plan for ``[a]cceptable documentation for 
establishing an extraordinary natural event * * * .'' Specifically, 
Earthjustice contends that acceptable documentation for establishing 
``an extraordinary natural event'' includes issuance by the national 
Weather Service of a high wind or blowing dust advisory, the occurrence 
of strong winds aloft and surface wind maps showing potential for high 
winds to occur at the site. According to Earthjustice no adequate 
documentation of these factors was offered. PFW at 11.
    Earthjustice's statements regarding the requirements for 
documentation under the District's ``Natural Events Action Plan for 
High Wind Events in the San Joaquin Valley Air Basin,'' February 16, 
2006 (NEAP) appear in the portion of its 2007 petition that addresses 
the causal relationship between high winds and the September 22, 2006 
exceedances. Id. Section 3 of the NEAP concerns the documentation of 
high wind events and lists specific sources of documentation suggested 
by EPA: Filter analysis, meteorological data, modeling and receptor 
analysis, videos and/or photographs, maps, news accounts and BACM \97\ 
requirements. Section 6 of the NEAP concerns meteorological forecasting 
criteria. This section states that if certain enumerated criteria are 
met, the District, in consultation with CARB, will declare a NEAP 
episode. The items that Earthjustice contends are required to document 
an exceptional event are among these criteria. Thus Earthjustice has 
confused forecasting an exceptional event with the documentation of it. 
EPA believes that

[[Page 49066]]

the State has adequately documented the September 22, 2006 exceedances 
as being caused by all exceptional events as discussed above in section 
V.A.
---------------------------------------------------------------------------

    \97\ As noted above, BACM implementation is not required under 
EPA's exceptional events rule.
---------------------------------------------------------------------------

    Finally we note again that EPA is proceeding in this rulemaking 
under its Exceptional Events Rule rather than the 1996 policy it 
replaces. In the preamble to the Rule, EPA explained that ``following 
the promulgation of this rule, States will no longer be required to 
keep NEAPs in place that were not approved as a part of a SIP for an 
area.'' 72 FR at 13576.

E. Harvest Activities

    Earthjustice asserts in its 2006 petition that September is the 
peak harvest season for cotton and almonds and that EPA should 
investigate the contribution of these activities to the September 22 
exceedances. PFR at 6. In the 2007 petition Earthjustice states that 
the end of October is generally when two of the dustiest crop harvests, 
cotton and almonds, take place and that these activities caused the 
October 25 exceedances. PRW at 13-14. EPA discusses the effect of 
anthropogenic sources on the 2006 exceedances in section V. above.

F. Exceedances at Corcoran and Stockton in 2004, Bakersfield in 2005 
and the Santa Rosa Rancheria in 2006

    The 2007 petition raises issues regarding several exceedances that 
have already been addressed by the October 2006 attainment 
determination. These exceedances occurred on September 3, 2004 at 
Corcoran and Stockton and on November 22-23, 2005 at Bakersfield. EPA's 
position on these exceedances is found in the final rule at 71 FR at 
63658-63661.
    Regarding the September 3, 2004 exceedance, Earthjustice states 
that EPA must now evaluate whether the Agency can concur on the State's 
request to flag the exceedance as a high wind event and cannot continue 
to rely on the argument that it is irrelevant because ``even if EPA had 
not concurred with the exclusion of this data, the Corcoran site would 
still attain the 24-hour NAAQS * * *.'' Earthjustice takes this 
position because it believes there are now other exceedances at 
Corcoran that cannot be excluded and that the September 3, 2004 
exceedance will thus be important in determining the SJV's PM-10 
attainment status. PFW at 9.
    EPA disagrees with Earthjustice's contention that there are now 
other exceedances that cannot be excluded. As discussed above, EPA 
believes the exceedances on September 22, October 25 and December 8, 
2006 are all due to exceptional events and is proposing to concur with 
the State's request to flag these data as caused by high wind events. 
Thus our conclusion that the September 3, 2004 exceedance is not 
significant for the attainment determination is still valid.
    Regarding the November 2005 exceedances at Bakersfield, EPA stated 
in its determination of attainment that ``[e]ven if the Bakersfield-
Golden State Highway BAM and TEOM data are considered together (and 
even if they were quality-assured data not subject to natural events), 
the exceedances recorded at these monitors would not show that the area 
is in violation of the standard.'' 71 FR at 63659. As discussed above, 
EPA believes that the exceedances at Bakersfield in 2006 were due to 
exceptional events and is proposing to concur with the State's request 
to flag these data. Thus we still believe that the 2005 Bakersfield-
Golden exceedances, when considered for purposes of our 2006 attainment 
determination, would not contribute to or constitute a violation.
    In the 2007 petition Earthjustice also raises questions about 
exceedances recorded at the Santa Rosa Rancheria on September 14, 20 
and October 26, 2006. PFW at 15-16. EPA addresses these exceedances in 
section VI. above.

IX. Statutory and Executive Order Reviews

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), this 
proposed action is not a ``significant regulatory action'' and 
therefore is not subject to review by the Office of Management and 
Budget. For this reason, this action is also not subject to Executive 
Order 13211, ``Actions Concerning Regulations That Significantly Affect 
Energy Supply, Distribution, or Use'' (66 FR 28355, May 22, 2001). This 
action merely proposes a determination based on air quality data and 
does not impose any additional requirements. Accordingly, the 
Administrator certifies that this proposed rule will not have a 
significant economic impact on a substantial number of small entities 
under the Regulatory Flexibility Act (5 U.S.C. 601 et seq.). Because 
this proposed rule does not impose any additional enforceable duty, it 
does not contain any unfunded mandate or significantly or uniquely 
affect small governments, as described in the Unfunded Mandates Reform 
Act of 1995 (Pub. L. 104-4).
    Executive Order 13175 (65 FR 67249, November 9, 2000) requires EPA 
to develop an accountable process to ensure ``meaningful and timely 
input by tribal officials in the development of regulatory policies 
that have tribal implications.'' Several Indian tribes have 
reservations located within the boundaries of the SJV. EPA is aware of 
only one tribe in the SJV that operates a PM-10 monitor, the Santa Rosa 
Rancheria. EPA has consulted with representatives of the Santa Rosa 
Rancheria Tribe on the data recorded by their monitor, and the flagging 
of the data, and will continue to work with the Tribe, as provided for 
in Executive Order 13175. Accordingly, EPA has addressed Executive 
Order 13175 to the extent that it applies to this action. This proposed 
action also does not have Federalism implications because it does not 
have substantial direct effects on the States, on the relationship 
between the national government and the States, or on the distribution 
of power and responsibilities among the various levels of government, 
as specified in Executive Order 13132 (64 FR 43255, August 10, 1999). 
This proposed action merely makes a determination based on air quality 
data and does not alter the relationship or the distribution of power 
and responsibilities established in the CAA. Executive Order 12898 
establishes a Federal policy for incorporating environmental justice 
into Federal agency actions by directing agencies to identify and 
address, as appropriate, disproportionately high and adverse human 
health or environmental effects of their programs, policies, and 
activities on minority and low-income populations. Today's action 
involves proposed determinations based on air quality considerations 
and proposes to affirm that the San Joaquin area has attained the PM-10 
NAAQS. It will not have disproportionately high and adverse effects on 
any communities in the area, including minority and low-income 
communities.
    This proposed rule also is not subject to Executive Order 13045 
``Protection of Children from Environmental Health Risks and Safety 
Risks'' (62 FR 19885, April 23, 1997), because it is not economically 
significant. The requirements of section 12(d) of the National 
Technology Transfer and Advancement Act of 1995 (15 U.S.C. 272 note) do 
not apply. This proposed rule does not impose an information collection 
burden under the provisions of the Paperwork Reduction Act of 1995 (44 
U.S.C. 3501 et seq.).

List of Subjects

40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Particulate matter, Reporting and recordkeeping 
requirements.

[[Page 49067]]

40 CFR Part 81

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

    Dated: August 15, 2007.
Wayne Nastri,
Regional Administrator, Region 9.
[FR Doc. E7-16693 Filed 8-24-07; 8:45 am]

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