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, 14687-14713 [E8-5188]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 73, Number 54 (Wednesday, March 19, 2008)]
[Rules and Regulations]
[Pages 14687-14713]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E8-5188]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 52 and 81

[EPA-R09-OAR-2006-0583, FRL-8542-6]


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: Final rule.

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SUMMARY: EPA is finalizing its proposal to affirm its October 30, 2006, 
determination that the San Joaquin Valley nonattainment area (SJV or 
the Valley) in California has attained the National Ambient Air Quality 
Standard (NAAQS) for particulate matter with an aerodynamic diameter 
less than or equal to a nominal 10 micrometers (PM-10). EPA proposed to 
affirm the determination of attainment in order to take comment on the 
exclusion from a

[[Page 14688]]

determination of attainment of PM-10 exceedances that were caused by 
exceptional events. EPA is concurring with the State's request to flag 
exceedances which occurred in the SJV as being caused by exceptional 
events, i.e., high winds. EPA is also concurring with the Santa Rosa 
Rancheria Tribe's request to flag, as due to an exceptional event, PM-
10 exceedances which occurred on tribal lands located within the 
boundaries of the SJV. EPA is further finding that these exceedances at 
the Santa Rosa Rancheria (SRR) should be excluded from use in 
determining attainment because 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. As a result, EPA is 
affirming its determination that the SJV has attained the PM-10 
standard based on EPA's evaluation of quality-assured data through 
2006.
    In addition, EPA did not receive comments on how the Agency 
addressed the 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, and thus we are denying the petitions.

DATES: Effective Date: This rule is effective on April 18, 2008.

ADDRESSES: EPA has established docket number EPA-R09-OAR-2006-0583 for 
this action. The index to the docket is available electronically at 
www.regulations.gov and in hard copy at EPA Region IX, 75 Hawthorne 
Street, San Francisco, California. While all documents in the docket 
are listed 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 in the FOR FURTHER 
INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: Doris Lo, EPA Region IX, (415) 972-
3959, lo.doris@epa.gov or Bob Pallarino, EPA Region IX, (415) 947-4128, 
pallarino.bob@epa.gov.

SUPPLEMENTARY INFORMATION: Throughout this document, ``we,'' ``us'' and 
``our'' refer to EPA.

Table of Contents

I. Summary of Proposed Action
II. Public Comments and EPA Responses
    A. Earthjustice Comments
    1. Overview Comments
    2. Comments Specific to September 22, 2006--Corcoran, 
Bakersfield and Oildale
    3. Comments Specific to October 25, 2006--Corcoran and 
Bakersfield
    B. Other Comments
    C. List of EPA Figures in the Docket
III. Final Action
IV. Statutory and Executive Order Reviews

I. Summary of Proposed Action

    On August 27, 2007, EPA proposed to affirm its determination that 
the SJV has attained the 24-hour NAAQS for PM-10. 72 FR 49046.\1\ EPA 
issued this proposed rule in order to take comment on the exclusion of 
several PM-10 exceedances that were caused by exceptional events, and, 
in the case of the SRR, improper siting of the monitor for purposes of 
comparison to the NAAQS. These exceedances are summarized in Table 1 in 
the proposed rule. Id. at 49047. For a more detailed discussion of the 
related background for the SJV and of the proposal, please refer to the 
proposed rule.
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    \1\ 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.
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II. Public Comments and EPA Responses

    EPA received three comment letters supporting the proposal to 
affirm the attainment determination. These comments were submitted by 
the California Cotton Ginners and Growers Association, the Tulare 
County Farm Bureau and the Western United Dairymen. In general, these 
commenters support the cases that are made for the exceptional event 
exceedances and discuss the many control measures and efforts that have 
been made to achieve attainment. The commenters also point to the SJV's 
continued efforts to achieve further air quality improvements under the 
PM-2.5 plan development. One commenter provides information to show 
that no cotton harvesting was occurring in September 2006. Finally, the 
commenters question the representativeness of the 2000 comment letters 
received by EPA in response to our July 19, 2006, attainment 
determination proposal (71 FR 40952) since the majority of the 
commenters appear to reside outside the SJV.
    EPA received three adverse comment letters. Two were from private 
citizens from the state of Tennessee and one was from Earthjustice, 
representing Sierra Club, Latino Issues Forum, Medical Advocates for 
Healthy Air, the Steven and Michele Kirsch Foundation, Tri-Valley 
CAREs, Concerned Residents of Lockwood Valley, Fresno Coalition Against 
the Misuse of Pesticides, California Communities Against Toxics, Fresno 
Metro Ministry, Coalition for Clean Air, Center for Biological 
Diversity, and the Association of Irritated Residents.\2\ The majority 
of the comments discussed below are raised by Earthjustice.
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    \2\ The proposal provided a 30 day comment period ending on 
September 26, 2007. EPA received a request for an additional 30 days 
to comment and granted that request extending the comment period 
until October 26, 2007. 72 FR 53743 (September 20, 2007).
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    EPA notes that although it received numerous specific comments on 
the September 22, 2006, October 25, 2006, and the SRR exceedances, no 
adverse comments are directed specifically at EPA's finding that 
exceedances monitored on December 8, 2006, at Corcoran and Bakersfield-
Golden State Highway (Bakersfield) were caused by an exceptional high 
wind event. Thus, EPA does not address any substantive issues regarding 
these exceedances in its responses to comments.
    In subsection A. below we respond to the extensive comments raised 
by Earthjustice. In subsection B. we respond to comments raised by 
other parties.

A. Earthjustice Comments

1. Overview Comments
    Comment 1: Earthjustice explains that its comments analyze EPA's 
proposed affirmation rule under the new Exceptional Events Rule (EER). 
72 FR 13560 (March 22, 2007). In this regard, Earthjustice states that, 
``assuming EPA has the discretion to apply the new rule,'' EPA's 
decision to do so is completely arbitrary given that the San Joaquin 
Valley Air Pollution Control District (District or SJVAPCD) prepared 
its analyses under EPA's prior policies and did not invoke the new 
regulatory requirements.
    Response 1: EPA addressed the issue of the applicability of the new 
EER to the events at issue in this rulemaking in its proposed 
affirmation rule. EPA explained that the statutory provision upon which 
the new rule is based, CAA section 319, as amended by section 6013 of 
the Safe Accountable Flexible Efficient-Transportation Equity Act: A 
Legacy for Users (SAFE-TEA-LU) of 2005, provides that the Agency's pre-
existing guidance documents continue to apply until the effective date 
of the rule. CAA section 319(b)(4). As mandated by section 319, EPA 
finalized and published the final EER in March 2007. This rule became 
effective on May 21, 2007, requiring EPA to follow the rule in making 
exceptional events determinations after that date.

[[Page 14689]]

Therefore, in making and publishing its determination after the 
effective date of the EER, EPA followed its procedures and criteria in 
evaluating the State's exceptional events demonstrations. 72 FR at 
49048.
    Although EPA followed the EER in this particular instance, and 
believes it should be followed in most cases, the Agency recognized 
that there might be certain instances where EPA had not yet made a 
decision on a state's already completed and submitted demonstration of 
an exceptional event and these demonstrations were thus caught 
midstream. In those instances, EPA concluded that a state could choose 
for a limited period to comply with either the provisions of the rule 
or those of the Agency's existing policies and, that if asked, EPA 
would act under the policy on a grandfathering rationale for a short 
time period. EPA continues to believe that this transitional policy was 
reasonable in the absence of an explicit statutory directive addressing 
that situation. Here, the State did not indicate that its submissions 
should be evaluated under the existing policies. Therefore, EPA applied 
the rule, which was already effective, when it made its determinations 
on the exceptional events in the SJV.
    Comment 2: Earthjustice, citing case law, states that EPA must 
provide a rational basis to support its conclusions regarding the 
exclusion of monitoring data showing NAAQS exceedances and that its 
decisions must have a ``substantial basis in facts.'' Earthjustice 
cites 40 CFR 50.14(c)(3)(iii) and CAA section 319(b)(3)(B), 
respectively, for the propositions that for EPA's determination here 
the District must provide actual evidence to support its claims and 
that the occurrence of an exceptional event must be ``demonstrated by 
reliable, accurate data.'' Earthjustice claims that even under a weight 
of evidence standard there must be evidence supporting the specific 
findings and that reliance on a plausible story is not enough.
    Response 2: EPA agrees with Earthjustice's characterization of the 
general demonstration, as stated in our summary of its comment above, 
that must be made in order to exclude data showing NAAQS exceedances. 
EPA believes that it has, both in the proposed affirmation rule and 
this final rule, provided a rational basis supported by reliable, 
accurate data for its conclusions that the September, October and 
December 2006 PM-10 exceedances in the SJV were caused by exceptional 
events. See 72 FR at 59050-49063 and our responses to comments below.
    Comment 3: Regarding its contention concerning the lack of reliable 
and accurate data, Earthjustice cites EPA's statements in the proposed 
affirmation rule at 72 FR at 49053 that activity levels on September 
22, 2006 were ``constant'' and that reasonable controls were in place 
to control particulate matter while providing only general or anecdotal 
evidence in the form of non-specific District inspector observations 
and ``discussions with representatives of agricultural and industrial 
operations.'' Citing CAA section 319(b)(3)(B), Earthjustice claims that 
this does not satisfy the statutory requirement that ``exceptionality'' 
be based on reliable, accurate data.
    Response 3: In the section of the proposed affirmation rule cited 
by Earthjustice we discussed our conclusion that the State's 
documentation demonstrates that the exceedances at Corcoran, 
Bakersfield and Oildale on September 22, 2006 would not have occurred 
but for the wind event on this day. EPA based this conclusion on the 
totality of the evidence presented by the State which included, but was 
not limited to, the information on activity levels and control measures 
singled out by Earthjustice. For the additional factors EPA considered 
in reaching its conclusion, see section V.A.2.d. in our proposed 
affirmation rule (72 FR at 49053) and our responses to comments below.
    Comment 4: Earthjustice claims that EPA offers no evidence to 
support the construction claims regarding the SRR. It asserts that EPA 
cannot say what if anything was occurring on the days in question, 
where it was occurring, or why it could not be reasonably controlled. 
Earthjustice also maintains that EPA cannot show that construction 
activity at the SRR is related to the measured exceedances and, as a 
result, EPA cannot show the required ``clear causal relationship.'' 
Further, EPA cannot say when these events occurred and why these 
allegedly ongoing activities only resulted in exceedances during the 
same period that monitors in other areas of the SJV started monitoring 
exceedances. Earthjustice argues that EPA cannot make the required 
``but for'' showing at the SRR because EPA cannot show that there was 
an event in the first place. Earthjustice further contends that EPA did 
not provide adequate evidence, including written accounts, that the 
construction activity took place on the days the exceedances occurred. 
Earthjustice claims that ``no one was able to produce any written 
account, in the form of contractor records, work orders, schedules, or 
anything else that would confirm that construction activity did, in 
fact, take place on the days in question.'' Finally, Earthjustice 
states that ``mere post hoc speculation and anecdotal accounts of what 
probably happened does not establish a basis for waiving these data.''
    Response 4: First, Earthjustice notes that EPA proposed to exclude 
the SRR violations on two grounds: (1) The monitor was not properly 
sited, and (2) the nearby construction activity was an exceptional 
event. Earthjustice concedes that ``[b]oth of these conclusions seem 
reasonable if the activity can be shown to have occurred on the days 
the monitor recorded violations.'' Earthjustice Comments (EC) at 23.\3\ 
Earthjustice contends, however, that EPA did not provide ``any such 
evidence.''
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    \3\ Earthjustice concedes, moreover, that under the EER the 
requirements for tribal governments appear to be ``much more 
flexible * * * '' and ``[i]t would not take much to make these 
demonstrations.'' EC at 22.
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    Contrary to Earthjustice's assertion, EPA in its proposed 
affirmation rule provided a demonstration that construction activity, 
involving the grading and paving of parking lots, took place in close 
proximity to the SRR monitor during the period the exceedances at the 
SRR monitor occurred, and that this activity caused the exceedances. 
EPA in its proposal set forth information derived from eyewitness 
accounts, meteorological data, contemporaneous tracking reports, and an 
account of an EPA expert's own visit to the site. 72 FR at 49060-49063. 
EPA did include written documentation of the events at issue. This 
written documentation included sample tracking reports that accompanied 
the filters from the monitors and described the conditions at the time 
of the monitoring, and an EPA expert's report of his site visit and 
interviews of witnesses to the events. There is no requirement in the 
EER that documentation of events include specific types of written 
documentation, such as those cited by Earthjustice.\4\ Nor

[[Page 14690]]

is there any requirement for specific types of documentation for EPA to 
demonstrate its alternative ground for excluding the data under 
principles established in 40 CFR part 58, appendix E, that during the 
period of the nearby construction the monitor was not properly sited 
for purposes of collecting data for comparison to the NAAQS. 72 FR at 
49060-49061.
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    \4\ Note that we are not specifying what will be required as a 
minimum level of documentation in all cases because facts and 
circumstances will vary significantly based on, among other things, 
geography, meteorology and the relative complexity of source 
contributions to measured concentrations in any particular location. 
72 FR at 13573. A particular instance may require more or less 
documentation, depending on the particular facts or circumstances. 
The simplest demonstrations could consist of newspaper accounts or 
satellite images to demonstrate that an event occurred together with 
daily and seasonal average ambient concentrations to demonstrate an 
unusually high ambient concentration level, which is clearly 
indicative of an exceptional impact. Such is the case with events 
such as volcanic eruptions and nearby forest fires. Id. More 
documentation would be needed to support situations that are not as 
straightforward.
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    EPA's findings were supported by information from interviews with 
three individuals with firsthand knowledge of the activities that took 
place near the monitor, as well as by contemporaneous documentation 
from filter sample tracking reports. These individuals were the SRR 
environmental technician responsible for overseeing the operation of 
the monitor, the SRR construction superintendent, and a private 
environmental consultant working for the Santa Rosa Rancheria EPA 
(SRREPA). The construction superintendent and the consultant concurred 
with the SRR environmental technician's recollection that grading and 
paving of the parking lots took place in September and October 2006, 
and the environmental technician concluded that these activities caused 
the exceedances on September 14 and 20, 2006 and later in October, when 
the initial paving had to be removed and the parking lot repaved.
    EPA's July 18, 2007, Memorandum, ``On-Site Visit to Santa Rosa 
Rancheria,'' from Bob Pallarino, EPA, to Sean Hogan, EPA (Site Visit 
Memorandum), contains the following account:

    The construction activity entailed grading and leveling the 
ground, application of sub-base material, and paving with asphalt. 
The par[k]ing lot was first paved in September and it is this 
project which [the SRR environmental technician] believed caused the 
exceedances on September 14 and 20. * * * the first paving * * * had 
to be removed and the parking lot repaved.\5\ It is this second part 
of the paving project which [the environmental technician] believed 
caused the October exceedance. * * * [T]he SRR environmental 
consultant stated that he had witnessed these construction 
activities during September and October, 2006. * * * The 
construction supervisor concurred with [the environmental 
technician's] recollection of the construction activity * * *.
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    \5\ The Site Memorandum stated that the first paving project 
``did not pass inspection and the paving had to be removed and the 
parking lot repaved.'' The Facility Manager in his letter of 
December 2007 referred to the first paving of the parking lot as 
``temporary.''

Site Visit Memorandum at 2-3.
    The information about the timing of the construction activity, from 
witnesses with both firsthand and expert knowledge, is confirmed by 
documentation from the California Air Resources Board (CARB) sample 
tracking reports that the SRREPA environmental technician filled out at 
the time the samples were obtained, and forwarded to CARB along with 
the monitored samples. The SRREPA technician observed the ``sampling 
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.'' This was signified by the letter 
``J''. Earthjustice ignores this corroborating documentation, cited by 
EPA in its proposal, and included in the rulemaking docket. 72 FR at 
49062. It is significant that these sample tracking forms were prepared 
before the filters from the monitors were sent to and analyzed by the 
lab. Thus at the time the technician noted that nearby construction was 
occurring during the monitoring, he could not have known whether or not 
an exceedance was recorded that day.
    EPA's proposal also showed that the meteorological data lend 
support to the environmental technician's account of the events of the 
days in question. The winds on the three days that exceeded the NAAQS 
were predominantly from the northwest, north and 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. Site Visit Memorandum at 2.
    Further corroboration of the impact of the construction on the 
monitor came from EPA's assessment of the proximity of the monitoring 
site to the nearby parking lots. EPA's onsite inspection ascertained 
that one of the parking lots was within 25 feet of the monitor, and the 
other was within 100 feet. 72 FR at 49062.
    Reinforcing EPA's conclusion that construction activities near the 
monitor caused the exceedances was the fact, pointed to in the proposed 
rule, that after completion of the paving projects, average PM-10 
concentrations dropped by more than 50 percent. Id.
    Since the proposal, EPA has obtained further documentation that the 
exceedances occurred during the period of construction activity in 
close proximity to the monitor. The Facility Director of the Tribe's 
hotel and casino has provided EPA with a letter stating that asphalt 
work on the parking lots close to the monitoring station was completed 
between August 15 and November 4, 2006. Enclosed with the letter was a 
billing statement from the Tribe's general contractor for the period up 
to August 15, 2006. The statement shows that work on the parking lots 
close to the monitor remained to be completed after August 15. The 
letter from the Facility Director states that at the time of the 
monitored exceedances, there were earthmoving activities nearby and 
paving activities near the site of the monitor ``in a large area for 
parking for Tribal Administrators and for our customers.''
    Thus, in addition to the documentation available at the time of the 
proposal, EPA has provided a letter from the Tribe and a billing 
statement from the general contractor that support the conclusion that 
paving work was occurring at the time of the exceedances.
    Earthjustice argues that because exceedances did not occur on other 
days when construction activities were occurring, this indicates that 
construction did not cause the exceedances in September and October 
2006. But this argument is misleading. Generally, varying degrees, 
types and locations of the construction activity, and changing 
meteorological conditions lead to varying impacts on the monitor. The 
fact that construction activities did not cause exceedances on some 
days does not mean that they were not responsible for the exceedances 
that occurred on other days. In addition, although Earthjustice claims 
that two days of violations at the SRR ``correlate well with violations 
seen in other parts of the Valley,'' no other violations were monitored 
in the Valley on September 14 and 20 and October 26, 2006.
    Earthjustice also claims that EPA ``still needs to make the other 
required showings'' for exceptional events, ``including that these 
sources were reasonably controlled.'' EC at 22. EPA made these showings 
in its proposal, and Earthjustice did not raise any specific grounds to 
challenge them. See 72 FR at 49061-49062. In its proposal EPA, after 
discussing whether the construction activity's impact on the monitor 
was reasonably controllable, concluded that ``under the particular set 
of circumstances presented here, for the purposes of evaluating the 
`reasonably controllable' criterion of the EER, we deem this criterion 
to have been satisfied.'' EPA found that even if control measures had 
been employed, we cannot be certain they would have prevented 
exceedances at the monitor, and that EPA's monitor siting rules provide 
that the monitor should not be operated at such a time and place for 
the purposes for determining attainment. 72 FR at 49062. We note that 
the criteria under the EER do not apply for the

[[Page 14691]]

purposes of our alternative ground, that the monitor was not properly 
sited. See 72 FR at 49060-49061. Thus EPA is finalizing its 
determination that there are two independent bases for determining that 
the exceedances recorded at the SRR in September and October, 2006 
should be excluded from consideration in determining whether the SJV 
has attained the PM-10 standard: (1) The monitor was not properly 
sited, under the principles established in part 58, appendix E, and (2) 
the construction activity constitutes an exceptional event under EPA's 
EER.
    Comment 5: Earthjustice states that EPA cannot point to any 
statutory or regulatory authority that allows it to treat wind-
entrained particulate matter pollution from land that has been 
disturbed by human activities, i.e., agriculture or construction as 
``natural.'' Earthjustice observes that, while EPA cites preamble 
language in the EER regarding high winds, this language was never 
codified even though the final rule does contain provisions relating to 
the treatment of other anthropogenic sources such as fireworks and 
prescribed fire. Earthjustice suggests that even though a natural event 
is defined in 40 CFR 50.1(k) as ``an event in which human activity 
plays little or no direct causal role,'' EPA attempts to define an 
event in which wind-entrained dust from agricultural and industrial 
operations as natural. Earthjustice cites legislative history of the 
1990 Clean Air Act Amendments (CAAA) to support its contention that 
this result defies logic and flies in the face of Congressional intent 
as evidenced by Congress's refusal to excuse dust storms from Mono and 
Owens lakebeds because they were human-caused. Earthjustice claims that 
if the measures in place are not enough to prevent exceedances due to 
wind-entrained dust, then Congress intended that additional controls be 
required.
    Response 5: Section 319, as amended, defines an exceptional event 
as an event that affects air quality, is not reasonably preventable or 
controllable, is a natural event or is an event caused by human 
activity that is unlikely to recur at a particular location. Under this 
definition, for an event to qualify as an exceptional event, both 
natural events and events caused by human activity must be events that 
are not reasonably preventable or controllable. Therefore, 
Earthjustice's conclusion that designating an event ``natural'' would 
``allow air agencies to avoid controls'' is erroneous. An agency 
flagging data as due to an exceptional event, including a high wind 
event, will be required to show that the event was not reasonably 
preventable or controllable. In the preamble to the final rule, EPA 
explained how it would evaluate whether an agency had been able to 
successfully demonstrate that an event met this criteria by taking into 
account the controls in place, the wind speed, and other factors. 72 FR 
at 13565-13566, 13576-13577. As explained elsewhere in our responses to 
comments below, in this particular instance the District's Regulation 
VIII (general fugitive dust rules) and Rule 4550 which limits fugitive 
dust emissions specifically from agricultural operations through 
Conservation Management Practices (CMPs) were in place. In addition, 
the District has adopted and is implementing EPA-approved best 
available control measures (BACM) for all significant sources of PM-10 
in the SJV.
    Earthjustice incorrectly states that if an event is classified as a 
natural event, a state would be able to ``avoid controls.'' In the 
proposed EER, EPA explained that it was proposing to treat high wind 
events that result in exceedances or violations as a natural event 
provided a clear causal relationship between the wind event and the 
measured exceedance was established and contributing anthropogenic 
activities were ``reasonably well-controlled.'' \6\ In the final rule, 
after considering the comments on high wind events including on the 
terminology and the definition, EPA adopted an approach that considers 
high winds a natural event if contributing anthropogenic activities are 
controlled through ``reasonable and appropriate measures.'' 72 FR at 
13566. To qualify as a natural event (a subset of exceptional events 
under the rule) a state must demonstrate, among others, that dust from 
contributing anthropogenic sources was ``reasonably well-controlled at 
the time the event occurred.'' 72 FR at 13576. The EER, therefore, has 
already defined what constitutes a high wind event through appropriate 
notice and comment rulemaking. Thus, the question of whether a high 
wind that causes exceedances or violations due to entrainment of dust 
from anthropogenic sources can be defined as a natural event is not an 
issue that is open for comment in this rulemaking. In this case, the 
Agency has only asked for comments on whether the particular high wind 
event met the criteria and procedures established under the rule, e.g., 
establishing a causal connection, reasonable controls on anthropogenic 
sources, wind speed and direction, etc., and not on whether these 
criteria are appropriate.
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    \6\ EPA made this statement in the context of PM-2.5 because at 
the time, the Agency was considering adopting the PM10-2.5 standard 
and noted that states would be expected to have appropriate controls 
for contributing anthropogenic emissions under the definition of the 
proposed PM10-2.5 indicator. The Agency, eventually, did not 
finalize the PM10-2.5 indicator and instead retained the 24-hour PM-
10 standard.
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    Earthjustice cites to the legislative history of the 1990 CAAA, for 
the discussion on Owens and Mono lakebeds where Congress indicated that 
diversion of water from these lakes created an anthropogenic source of 
dust. From this Earthjustice contrives an overly-broad conclusion that 
any ``dust from lands disturbed by human activity'' must be treated as 
an anthropogenic rather than a natural event. Under this proposition 
gale-force winds, for example of 100 mph, in an urban area could not be 
treated as a natural event because human activity would be a 
contributing factor.
    As a matter of record, the legislative history also demonstrates 
that EPA concurred with Congress that the diversion of water created an 
anthropogenic source of dust in the Owens and Mono lakebeds. Pub. L. 
101-549, CAA Amendments of 1990 House Report No. 101-290(l), May 17, 
1990. EPA, however, does not interpret the statutory language in a 
manner that considers any anthropogenic contribution to a natural event 
as transforming it into an anthropogenic event. In the Mono and Owens 
lakebed situation, EPA believed that the anthropogenic contribution was 
such that dust blown from those areas should be treated as 
anthropogenic rather than natural events. In other high winds 
instances, however, where there were anthropogenic contributions with 
adequate controls in place, EPA treated the high wind events as natural 
events.
    In its Natural Events Policy, EPA stated that it would treat a high 
wind event as a natural event even if the dust originated from 
anthropogenic sources, provided best available control measures were in 
place. Memorandum from Mary D. Nichols, Assistant Administrator for Air 
and Radiation to Regional Air Directors, ``Areas Affected by PM-10 
Natural Events,'' May 30, 1996 (NEP) at 7. Congress was cognizant of 
EPA's existing policies on natural and anthropogenic events and how EPA 
interpreted and implemented these policies. In amending section 319, 
Congress specifically required EPA to continue to apply its NEP during 
the exceptional events rulemaking process, an unlikely action if it 
disagreed with EPA's interpretation of natural events. Section 319 
(b)(4)(B). Under the NEP,

[[Page 14692]]

EPA treated high wind events as natural events and reasonably well-
controlled if contributing anthropogenic sources had BACM in place. NEP 
at 7. During the exceptional events rulemaking, EPA sought comment on a 
number of options for mitigation requirements, including whether to 
continue to require BACM for such events. After considering all 
comments on the proposed options, EPA explained in the preamble to the 
final rule that it would continue to require that anthropogenic sources 
contributing to high wind events be well-controlled through reasonable 
and appropriate measures. 72 FR at 13566. EPA, therefore, believes its 
interpretation of a high wind event as set forth in the preamble to the 
EER conforms to congressional intent and the requirements of section 
319.
    Also, in response to Earthjustice's assertion that EPA cites no 
statutory or regulatory authority that permits us to treat high wind as 
a natural event, as discussed above, Congress was aware of EPA's 
interpretation of natural events as evidenced by the statutory 
reference to the NEP (Section 319(b)(4)(B)) and it is self-evident that 
volcanic, seismic, high wind, and other similar events are natural 
events under section 50.1(k) of the EER. Therefore, EPA did not find it 
necessary to specifically list these events as exceptional events in 
the final rule. When asking for comments in the proposed rule, we noted 
that some of these exceptional events (including volcanic, seismic and 
high wind events) have ``unusual characteristics'' and needed a fuller 
discussion in the preamble regarding how states may meet the 
requirements established in the EER. 71 FR at 12605. EPA believed that 
this explanation in the preamble was sufficient to assist states in 
developing their demonstration requirements and did not make it 
necessary to specifically list these events as exceptional events in 
the final rule.
    Comment 6: Earthjustice claims that even if EPA had codified the 
preamble language allowing dust from lands disturbed by human activity 
to be excused, EPA offers no evidence to show whether the sources that 
allegedly were responsible for the dust were reasonably well controlled 
at the time the event occurred. Earthjustice states that EPA must show 
that the sources were actually controlled, not just that they were 
subject to controls. Earthjustice believes that reasonable controls 
would have prevented dust from being entrained by the stated wind 
speeds and that if the winds at issue picked up the large amounts of 
particulate concentrations claimed, then by definition, these sources 
were not reasonably controlled. With respect to September 22, 2006, 
Earthjustice asserts that the fact that the District claims that the 
dust came from anthropogenic sources being scoured by winds under 25 
mph for a short period of time means that reasonable measures could not 
have been in place. Therefore, Earthjustice claims that either the dust 
was not caused by wind or the sources did not have reasonable controls 
that would have prevented the event. With respect to October 25, 2006, 
Earthjustice asserts that none of the 90 inspections conducted by the 
District was in or around the Lemoore/Corcoran area where the dust 
allegedly originated.
    Response 6: With respect to reasonable controls, in the preamble to 
the EER we explained that ``ambient particulate matter concentrations 
due to dust being raised by unusually high winds will be treated as due 
to uncontrollable natural events where * * * 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.* * * In cases where 
anthropogenic sources are determined to have contributed to exceedances 
or violations due to high wind events at air quality monitoring sites, 
per our decision in this rulemaking concerning the action that States 
must take to mitigate the impact of exceptional events on public health 
* * * States must take reasonable and appropriate measures to mitigate 
the impact associated with the event on public health.'' 72 FR at 
13576-13577.
    As we observed in our proposed affirmation rule, Regulation VIII 
and District Rule 4550 were in place at the time of the events in 
question. Furthermore, we noted that 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). See 72 at 49053 and 49057. Moreover, 
the District conducted numerous inspections of PM-10 sources in the SJV 
on September 22 and October 25, 2006. Thus controls beyond those deemed 
``reasonable'' were being implemented and enforced in the SJV on those 
dates.
    Contrary to Earthjustice's apparent belief, there is nothing in 
either the preamble to the EER or the rule itself that requires EPA to 
show that all sources were ``actually controlled'' at the time of the 
events. Moreover, there are thousands of fugitive dust sources in the 
SJV,\7\ an area of nearly 25,000 square miles which constitutes 
approximately 16 percent of the geographic area of California. 2003 
PM10 Plan for the SJV at 2-1. As a result it would be a practical 
impossibility for the District, a publicly-funded agency, to determine 
whether every source was in compliance with its regulations on any 
given day, the standard Earthjustice evidently espouses. The fact that 
the District conducted 90 inspections on October 25, 2006 and none was 
in Lemoore or Corcoran simply illustrates the magnitude of the task 
Earthjustice suggests should be mandatory for the exclusion of data 
from an exceptional event.
---------------------------------------------------------------------------

    \7\ For example, the District has approved over 6,000 
applications under Rule 4550. ``Conservation Management Practices 
Program Report for 2005,'' January 19, 2006, SJVAPCD at 5.
---------------------------------------------------------------------------

    Finally, Earthjustice presents no support for its contention that 
controls on anthropogenic sources beyond those already in place would 
have prevented dust from being entrained by the stated wind speeds. 
Earthjustice simply asserts (see comment 7) without evidence that there 
are numerous measures available that could have prevented or reduced 
entrainment of particulate matter. As we have shown, reasonable 
controls were in place on the days in question and the exceedances 
occurred notwithstanding those controls. See also our response to 
comment 7 below.
    Comment 7: Earthjustice further asserts that there are numerous 
measures available that could have reduced or prevented the entrainment 
of particulate matter by winds above the entrainment threshold of 18 
mph, many of which are included but not required by the District's 
agricultural CMP rule and Regulation VIII. Earthjustice provides a 
number of examples that it claims are effective in reducing or 
eliminating erosion and transport of soil particles during high wind 
events. Earthjustice concludes that even assuming 100 percent 
compliance with the agricultural CMP rule and Regulation VIII, ``not 
one of these measures is required to be in place by these so-called 
BACM level controls.'' Thus Earthjustice alleges that sources could be 
100 percent in compliance with District rules and still not be doing 
anything to prevent wind-generated entrainment of particulates.
    Response 7: As we stated in the preamble to the EER, where wind 
speed results in particulate matter exceedances, a clear causal 
relationship must be demonstrated between the exceedances measured at 
the air quality monitoring site and the high wind event

[[Page 14693]]

in question in order for data affected by these events to be excluded 
under the weight of evidence approach. 72 FR at 13566, footnote 11. We 
further stated that ``EPA will consider in the weight of evidence 
analysis winds that produce emissions contributed to by anthropogenic 
activities that have been controlled to the extent possible through use 
of all reasonably available reasonable and appropriate measures.'' Id.
    EPA approved Regulation VIII as BACM on February 17, 2006 (71 FR 
8461) and Rule 4550 as BACM on February 14, 2006 (71 FR 7683). The 
control measures in these rules are designed to reduce fugitive dust 
emissions. A number of the measures that sources can choose in 
compliance with the rules are also specifically designed to reduce or 
prevent entrainment of particulate matter during wind events. See, for 
example, in the ``List of Conservation Management Practices,'' May 20, 
2004, for Rule 4550 in the ``Cropland--Other'' category the following 
measures: alternate till, bulk materials control, cover crops, 
permanent crops, surface roughening, wind barrier.
    EPA determines what controls constitute ``all reasonably available 
reasonable and appropriate measures'' on a case by case basis. With 
regard to the SJV, EPA has agreed with the District's finding that ``* 
* * unlike other arid western PM-10 serious nonattainment areas, the 
SJV does not have a regular and repeated windblown dust problem.'' 71 
FR at 7686. In addition, in responding to a comment on its proposed 
approval of the 2003 PM-10 serious area plan for the SJV, EPA observed 
that ``[o]nly five PM-10 exceedance days spanning a 13-year period were 
identified as associated with strong winds.'' 69 FR 30006, 30033 (May 
26, 2004). Under these circumstances, EPA believes that it was not 
necessary for the District's rules to mandate the selection of 
windblown dust measures and that the BACM controls being implemented in 
the SJV constitute ``all reasonably available reasonable and 
appropriate measures.''
    Comment 8: Earthjustice argues that the events at issue cannot be 
claimed as exceptional because the District did not make its 
demonstration according to the procedures outlined in the EER. 
Specifically, Earthjustice states that while EPA relies on 
demonstrations prepared by the District in April and May 2007, the only 
opportunity for public comment provided by the District was on the 
February 2007 version of the analysis. Moreover, Earthjustice states, 
only 15 calendar days were provided for comment on the February version 
and the preamble to EPA's EER provides for a 30-day comment period. 
Earthjustice states that to the extent that EPA believes preamble 
statements to be enforceable, the event cannot be deemed exceptional 
because the District did not meet the procedural requirements in the 
EER. Earthjustice also asserts that since the District's rationale for 
flagging the September 22, 2006 exceedances changed so markedly as to 
make comments on the first draft irrelevant, the documentation should 
have been put out for a second round of public comment. Earthjustice 
further states that insofar as the EER applies to EPA's affirmation 
action, the District also failed to meet its procedural requirements 
that documentation justifying exclusion must be submitted no later than 
12 months before a regulatory decision is made. Here, Earthjustice 
asserts, EPA based its regulatory decision to find the SJV in 
attainment on the exclusion of data before any demonstration supporting 
the exclusion was drafted by the State.
    Response 8: The public did have an adequate opportunity for review 
and comment on the State's documentation of the exceptional events. 
Earthjustice complains that the State did not provide a 30-day comment 
period on the documentation of exceptional events, and further contends 
that there was no opportunity to review and comment after the District 
revised this documentation. EPA's EER provides that a state that has 
flagged data as being due to an exceptional event and that is 
requesting exclusion of the data shall ``after notice and opportunity 
for public comment, submit a demonstration'' to EPA, along with any 
public comments it received. 40 CFR 50.14(c)(3)(i).
    With respect to Earthjustice's first contention regarding the 30-
day comment period, the EER contains no such requirement. The language 
cited by Earthjustice that purports to characterize 30 days as a 
requirement is found in the preamble only, 72 FR 13574, and does not 
reflect the language of the rule. Thus, while indicative of a period 
that EPA would deem reasonable, the preamble language regarding a 30-
day comment period does not serve to make such a period mandatory. Nor 
does it mean that a shorter comment period should be deemed 
unreasonable. Earthjustice concedes that in February 2007 the District 
provided a two week comment period for its initial documentation of the 
September, October and December 2006 exceedances. The District received 
no comments or requests for extension of the comment period.\8\ On 
March 21, 2007, Earthjustice filed with EPA a petition to withdraw 
EPA's October 2006 attainment determination, which cited to and 
discussed the District's initial documentation. This petition, however, 
was directed to EPA and not to the District or the State. Earthjustice, 
having failed to request an extension of the comment period and to 
address comments to the District and the State, cannot now be heard to 
complain about the length of the initial comment period.
---------------------------------------------------------------------------

    \8\ Contrary to Earthjustice's contention (EC at 3, footnote 3), 
EPA in its proposal did nothing to ``hide'' the date that the 
documentation became available. EPA simply stated that the 
documentation became available in February.
---------------------------------------------------------------------------

    Subsequently, the District posted on the ``Public Notices'' section 
of its Web site revised versions of the documentation for exceedances 
on these three days at issue, and thus the revised documentation was 
also available for public review and comment. These revised versions 
modified and clarified the technical analysis of the high wind events. 
For the September 22 event, the District posted on its Web site a 
revised set of documentation, dated April 20, and CARB subsequently 
submitted it to EPA. The District submitted an Addendum to CARB on May 
23, 2007, which it again posted on its Web site, and CARB later 
submitted it to EPA. 72 FR at 49050. For the October 25 event, the 
District posted on its Web site a revised set of documentation, dated 
April 23, and CARB again subsequently submitted it to EPA. 72 FR at 
49054. For the December 8, 2006 event, which Earthjustice does not 
contest is an exceptional event, the District revised its documentation 
and submitted it to CARB on May 23, 2007, and posted it on its Web 
site. At CARB's request the District made further revisions which it 
submitted to CARB on June 6, 2007, and posted on its Web site. 72 FR at 
49057. The State later submitted it to EPA. Id.
    Thus each set of revised documentation was available to the public 
in the ``Public Notices'' section of the District's Web site for months 
prior to EPA's August 15, 2007 issuance of its proposed rule, and EPA 
has found no indication that comments were submitted or inquiries 
received about the revised documentation. EPA therefore believes that 
there was adequate opportunity for the public to comment on the revised 
demonstrations made by the District and CARB. The fact remains that no 
comments were submitted to the District or CARB on the original 
versions of the documentation, nor does it appear that there were any 
requests for an extension of the comment period that closed on March 5,

[[Page 14694]]

2007. Similarly, EPA knows of no comments or requests regarding the 
comment period that were submitted on the subsequent versions of the 
documentation that were posted on the District's Web site.
    Earthjustice further contends that EPA has failed to meet the 
requirement that a demonstration be submitted to EPA no later than 12 
months ``prior to the date'' a regulatory decision ``must'' be made by 
EPA. EER, section 50.14(c)(3)(i). We note initially that this section 
of the EER is designed for EPA's benefit, to furnish adequate time to 
review documentation, and it is thus for EPA to determine whether we 
require the full time allotted by the rule.
    Furthermore, in the preamble we ``recognize that special 
circumstances could dictate more expedited data delivery, flagging, and 
minimal demonstrations * * *.'' 72 FR at 13571. In this case, where EPA 
is acting to affirm a prior attainment determination that recognized 
the need for additional evaluation of preliminary data, EPA finds there 
is value in proceeding expeditiously to obtain and review the State's 
documentation of those data and surrounding exceptional events. 
Moreover, this action to affirm EPA's attainment determination is not a 
regulatory decision that ``must'' be made by a certain date, and 
therefore the 12-month requirement is not applicable. Finally we note 
that the bulk of the revised documentation for the September and 
October 2006 exceedances at issue here was submitted to EPA in April 
and May 2007, well in advance of EPA's final regulatory decision in 
this rulemaking. Thus EPA finds that, for all the reasons set forth 
above, the timing of submission of the documentation here was adequate 
for purposes of section 50.14(c)(3)(i) of the EER.
    Earthjustice also complains that in issuing the October 2006 
determination of attainment, EPA made the determination to finally 
concur in the flagging of exceptional events prior to receiving the 
State's documentation. The procedural validity of the October 2006 
determination, and whether it provided adequate notice and comment, is 
not at issue in today's rulemaking. Thus Earthjustice's contentions 
with regard to notice and comment issues arising from the October 2006 
rulemaking are misplaced here.
    Moreover, Earthjustice's contentions are belied by the facts. EPA's 
October 2006 determination of attainment made clear that the data 
showing exceedances on September 22, 2006 were preliminary. EPA stated 
that once quality-assured data were available, EPA would review those 
data and CARB's request with respect to them, evaluate whether the data 
qualified for exclusion as caused by exceptional events, and determine 
whether the determination should be withdrawn.\9\ See discussion in 
EPA's proposed affirmation rule, 72 FR at 49064. See also 71 FR 63642.
---------------------------------------------------------------------------

    \9\ As EPA noted in its proposed affirmation rule, EPA's 
October, 2006 final determination did not ignore the exceedances 
that occurred in October 2006 since these occurred eight days after 
EPA promulgated its final determination of attainment. 72 FR at 
49064.
---------------------------------------------------------------------------

    In today's rulemaking EPA has fulfilled its promise by providing 
ample opportunity for comment on the State's documentation and EPA's 
evaluation of exceedances under the EER prior to issuing a final 
concurrence. As EPA noted in its proposed affirmation rule, our purpose 
here is not to take comment on the issues raised by the 2006 attainment 
determination, except to the extent that they affect EPA's ability to 
determine that the SJV continued to attain the PM-10 standard through 
2006. 72 FR at 49047. The October 2006 rulemaking, which is not at 
issue in this current action, did not purport to be a final concurrence 
on the State's exceptional events documentation for the September 22, 
exceedances. Today's rulemaking addresses quality-assured data for 
September, October and December 2006, for which the State has provided 
exceptional events documentation.
    Comment 9: Earthjustice states that EPA argues that at the time of 
the attainment finding the Agency merely deferred its determination of 
the impact of the preliminary data until they could be quality assured 
and the State had an opportunity to show that the exceedance was caused 
by an exceptional event. Earthjustice claims that the data at issue had 
in fact been processed by the CARB laboratory and thus already quality 
assured by the State when EPA was notified of the September 22, 2006 
exceedances. In this respect, Earthjustice believes that EPA 
mischaracterized CARB's October 17, 2006 letter to EPA to mean that the 
data from the filter analyses were preliminary. Thus, Earthjustice 
concludes that EPA's decision not to consider the September 22 
exceedances in its October 17, 2006 attainment finding is a violation 
of law and an abuse of discretion. Earthjustice also states that this 
violation of the Administrative Procedure Act (APA) cannot be cured 
with this rulemaking's post-hoc rationalization. Earthjustice 
interprets 40 CFR 51.14(c)(2)(ii) to mean that an exceedance must be 
considered an exceedance unless and until EPA gives final concurrence 
following a thorough, convincing, publicly reviewed demonstration that 
the data can be ignored.
    Response 9: As noted in the response to comment 8 above, the 
adequacy and validity of the October 2006 rulemaking is not at issue in 
this proceeding. Whether the APA was violated in that rulemaking is not 
at issue here. In this current rulemaking, EPA thoroughly reviewed and 
proposed to concur with the documentation submitted by the State, and 
provided full opportunity for public review and comment before 
finalizing its concurrence with the flags, and before excluding the 
data from a final determination of attainment. The purpose of this 
rulemaking is to assess the quality-assured data and documentation of 
exceptional events claims in the context of notice and comment 
rulemaking. Thus, even if, for the sake of argument, we accept 
Earthjustice's contentions that there were procedural deficiencies in 
the October 2006 rulemaking, EPA would have cured any such deficiencies 
with the procedures it has followed in this rulemaking.
    In any event, Earthjustice is incorrect in its assertions that, at 
the time of the October 2006 rulemaking, data for September 22, 2006 
were not preliminary and had been quality assured. The data for the 
September 22 exceedances were plainly preliminary. An EPA staff 
employee e-mailed a CARB branch chief an informal request to ``find out 
if there was any preliminary data available from the ARB lab.'' E-mail 
from Bob Pallarino, EPA, to Karen Magliano, Chief, Air Quality Data 
Branch, Planning and Technical Support Division, CARB, October 12, 
2006. On October 13, 2006 she forwarded to EPA an informal e-mail 
originating from a CARB staffer. The e-mail included data from filter 
analyses of several monitors, which set forth numerical values 
representing monitored data. That e-mail stated clearly: ``Of course, 
all the data is preliminary.'' E-mail from Scott Randall, Inorganic 
Laboratory Section, Northern Laboratory Branch, CARB, to Cliff Popejoy, 
Inorganic Laboratory Section, Northern Laboratory Branch, CARB, October 
13, 2006 (forwarded to Bob Pallarino by Karen Magliano). Thus, CARB 
represented and EPA reasonably believed that the data showing monitored 
exceedances were ``preliminary'' and not quality assured. Indeed, EPA 
believed that the normal data validation and verification processes had 
not been undertaken, and that, in fact, the data had not been

[[Page 14695]]

submitted to EPA's Air Quality System (AQS) database \10\ or certified 
by CARB. The message that the CARB staffer sent was in response to an 
informal request from EPA staff, and in that context EPA did not 
consider it an official CARB submission of data. The informal and 
preliminary nature of the information is further indicated by the fact 
that the numerical values for PM-10 reported in the e-mail were not 
accompanied by scientific units, which would be essential documentation 
in any official submission of quality-assured data, and could only be 
inferred by EPA based on usual practice.
---------------------------------------------------------------------------

    \10\ Data from air monitors operated by state and local agencies 
in compliance with EPA monitoring requirements must be submitted to 
AQS. Heads of monitoring agencies annually certify that these data 
are accurate to the best of their knowledge. See 71 FR at 40953.
---------------------------------------------------------------------------

    EPA did not therefore, as Earthjustice contends, 
``mischaracterize'' the data from the filter analyses, when it 
described the data as ``preliminary.'' EC at 11, footnote 9. CARB 
itself characterized the data as preliminary when it forwarded them to 
EPA.
    In any event, as noted above, what is at issue in this rulemaking 
is EPA's concurrence on the exceptional events documentation for 
quality-assured data subsequent to EPA's October 2006 determination, 
and not the procedural validity of that prior determination. It is 
clear in this rulemaking that EPA is determining to finally concur on 
the State's flagging of the data only after EPA has conducted notice 
and comment rulemaking on documentation that the State has submitted to 
support those flags.
    Comment 10: For the wind events, Earthjustice maintains that the 
data offered by the District and relied upon by EPA does not 
demonstrate a ``clear causal relationship'' because exceedances were 
being measured before the events occurred.
    Response 10: EPA disagrees with Earthjustice's conclusion for the 
reasons discussed below. Initially it is important to understand that 
the 24-hour PM-10 NAAQS, 150 [mu]g/m\3\, is a 24-hour average 
concentration. This means that individual hourly concentrations at any 
given monitoring location may exceed 150 [mu]g/m\3\, but until all 24 
hours of a day are sampled a complete daily reading cannot be 
calculated. Therefore it is incorrect to characterize the data, as 
Earthjustice does, as showing that NAAQS exceedances were measured 
before the wind events.
    To support its contention, Earthjustice states that fugitive dust 
sources in the Lemoore area on September 22 and October 25, 2006 could 
not have caused the Corcoran NAAQS exceedances since the first hourly 
PM-10 concentrations exceeding 150 [mu]g/m\3\ at Corcoran occurred 
either an hour before or at the same time as the Lemoore meteorological 
station recorded wind speeds exceeding the District's threshold wind 
speed. From these facts, Earthjustice concludes that since the monitor 
was already recording an hourly concentration above the NAAQS before 
the dust-laden winds from Lemoore \11\ arrived on September 22 and 
October 25, the monitor could not have been impacted by them.
---------------------------------------------------------------------------

    \11\ Throughout this final rule when we refer to Lemoore, 
Corcoran and Bakersfield, we mean the Lemoore area, the Corcoran 
area, and the Bakersfield area. When analyzing data, the State, 
District and EPA use information collected from specific points 
where the monitors are located, whether meteorological monitors or 
PM-10 monitors. Since it is not possible, due to finite resources, 
to monitor pollutant or meteorological parameters in every location, 
monitoring locations are chosen to be representative of larger 
areas. The size of the area represented by a monitor is dependent on 
a number of factors, including, but not limited to, the parameter 
being measured (e.g., wind speed, PM-10 concentration), the overall 
terrain (e.g., urban, rural, valley, etc.) and any localized 
characteristics that may influence the parameter being measured 
(e.g., obstructions such as buildings or trees).
---------------------------------------------------------------------------

    In evaluating this conclusion it is instructive to look at any 
number of days where the level of an hourly PM-10 concentration at 
Corcoran exceeded the level of the 24-hour NAAQS, yet the 24-hour 
average concentration for the day did not exceed the NAAQS. October 26 
and 27, 2006, March 26 and 27, 2007, April 17, 2007, May 2 and 21, 
2007, and June 5, 2007, all experienced one or more hours exceeding the 
level of the NAAQS yet the NAAQS for the day was not exceeded. See 
Table 1 below. The most extreme example is April 17, 2007, on which 
four continuous hourly concentrations greater than 150 [mu]g/m\3\ were 
recorded from 4:00 p.m. Pacific Standard Time (PST) through 7 p.m. PST 
(181, 466, 460, 236 [mu]g/m\3\, respectively), yet the overall 24-hour 
average concentration for that day was only 91 [mu]g/m\3\.

                 Table 1.--Non-Exceedance Days With One or More Hourly Pm-10 Concentrations Above 150 [mu]g/m\3\ as Measured at Corcoran
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Oct 26     Oct 27     Mar 26     Mar 27     Apr 17     May 2      May 21     Jun 5
                                                                     2006       2006       2007       2007       2007       2007       2007       2007
                              Hour*                                ([mu]g/    ([mu]g/    ([mu]g/    ([mu]g/    ([mu]g/    ([mu]g/    ([mu]g/    ([mu]g/
                                                                    m\3\)      m\3\)      m\3\)      m\3\)      m\3\)      m\3\)      m\3\)      m\3\)
--------------------------------------------------------------------------------------------------------------------------------------------------------
0...............................................................        157         79          8          0         27         18         17         21
1...............................................................        143        135         11          0         26         14         16         15
2...............................................................        146        126          8          1         30         13         15         12
3...............................................................        147         89         11          3         31         11         13         13
4...............................................................        161         69          9          3         29         12         15         24
5...............................................................        175         91         10          3         63         26         16         24
6...............................................................        194        221         22          5         73         23         25         22
7...............................................................        232        184         19          7         34         25         28         19
8...............................................................        115        158         16          0         34         20         35         14
9...............................................................         66        149         12          8         33         13         42         18
10..............................................................         53        107          2          1         22         16         59         23
11..............................................................         92        117          6         18         21         16         66         35
12..............................................................        128         86          8        122         15         20         72         61
13..............................................................        128         70         17        162         26         22         74         87
14..............................................................        133         91          7        152         54         25         85         77
15..........................................