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ENVIRONMENTAL PROTECTION AGENCY

Environmental Protection Agency

CFR Citation: 40 CFR Parts 52 and 81

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

NOTICE: RULES

ACTION: Approval and Promulgation of Implementation Plans; Designation of Areas for Air Quality Planning Purposes:

DOCUMENT ACTION: Final rule.

SUBJECT CATEGORY: 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

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

DOCUMENT 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 (PM10). EPA proposed to affirm the determination of attainment in order to take comment on the exclusion from a
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determination of attainment of PM10 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 PM10 standard based on EPA's evaluation of qualityassured 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.

SUMMARY: California,

SUPPLEMENTAL 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, 2006Corcoran, Bakersfield and Oildale

3. Comments Specific to October 25, 2006Corcoran 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 24hour NAAQS for PM10. 72 FR 49046.\1\ EPA issued this proposed rule in order to take comment on the exclusion of several PM10 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.
\1\ On October 17, 2006, EPA finalized its determination that the SJV attained the NAAQS for PM10 and on October 30, 2006, EPA published this determination in the Federal Register. 71 FR 63642. 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 PM2.5 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, TriValley 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. \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).

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 EfficientTransportation Equity Act: A Legacy for Users (SAFETEALU) 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.
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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 PM10 exceedances in the SJV were caused by exceptional events. See 72 FR at 5905049063 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 nonspecific 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.''
\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.

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 4906049063. 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
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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 4906049061.
\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.

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, ``OnSite 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 subbase 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 * * *. \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 23.

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 dustproducing 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 PM10 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 4906149062. 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
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purposes of our alternative ground, that the monitor was not properly sited. See 72 FR at 4906049061. 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 PM10 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 windentrained 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 humancaused. Earthjustice claims that if the measures in place are not enough to prevent exceedances due to windentrained 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 1356513566, 1357613577. 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 EPAapproved best available control measures (BACM) for all significant sources of PM10 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 wellcontrolled.'' \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 wellcontrolled 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.
\6\ EPA made this statement in the context of PM2.5 because at the time, the Agency was considering adopting the PM102.5 standard and noted that states would be expected to have appropriate controls for contributing anthropogenic emissions under the definition of the proposed PM102.5 indicator. The Agency, eventually, did not finalize the PM102.5 indicator and instead retained the 24hour PM 10 standard.

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 overlybroad conclusion that any ``dust from lands disturbed by human activity'' must be treated as an anthropogenic rather than a natural event. Under this proposition galeforce 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. 101549, CAA Amendments of 1990 House Report No. 101290(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 PM10 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,
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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 wellcontrolled 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 selfevident 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 wellcontrolled 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 1357613577.

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 PM10 in the SJV as meeting CAA section 189(b)(1)(B). See 72 at 49053 and 49057. Moreover, the District conducted numerous inspections of PM10 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 21. As a result it would be a practical impossibility for the District, a publiclyfunded 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 socalled 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 windgenerated 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
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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 ``CroplandOther'' 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 PM10 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 PM10 serious area plan for the SJV, EPA observed that ``[o]nly five PM10 exceedance days spanning a 13year 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 30day 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 30day 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 12month 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 qualityassured 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 PM10 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 qualityassured 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 posthoc 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 qualityassured 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 emailed a CARB branch chief an informal request to ``find out if there was any preliminary data available from the ARB lab.'' Email 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 email originating from a CARB staffer. The email included data from filter analyses of several monitors, which set forth numerical values representing monitored data. That email stated clearly: ``Of course, all the data is preliminary.'' Email 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 PM10 reported in the email were not accompanied by scientific units, which would be essential documentation in any official submission of qualityassured 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 qualityassured 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 24hour PM10 NAAQS, 150 [mu]g/m\3\, is a 24hour 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 PM10 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 dustladen 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 PM10 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, PM10 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 PM10 concentration at Corcoran exceeded the level of the 24hour NAAQS, yet the 24hour 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 24hour average concentration for that day was only 91 [mu]g/m\3\.
Table 1.NonExceedance Days With One or More Hourly Pm10 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.............................................................. 115 69 7 190 138 28 84 254 16.............................................................. 126 87 18 54 181 151 94 169 17.............................................................. 152 116 19 86 466 239 195 145 18.............................................................. 151 140 128 47 460 61 180 173 19.............................................................. 145 116 407 8 236 27 127 235 20.............................................................. 161 126 48 17 136 13 108 65 [[Page 14696]]
21.............................................................. 147 118 16 15 34 14 66 34 22.............................................................. 124 141 4 9 14 29 61 27 23.............................................................. 130 105 0 10 7 16 66 49 Daily Average................................................... 137 116 34 38 91 36 65 67 Source: EPA Air Quality System Database.
* Hours are in PST. All State and local ambient air pollutant monitoring equipment in California operates on PST all year and is never adjusted for Daylight Savings Time. For example, hour 12 in the table is 1 p.m. Pacific Daylight Time (PDT).

Thus, as can be seen from Table 1 and the discussion above, Earthjustice is incorrect when it concludes that dustladen winds from Lemoore could not have affected the Corcoran monitor on September 22 and October 25, 2006 because concentrations above the level of the NAAQS were recorded at the monitor before the winds arrived. By failing to account for all 24 hours of the day, Earthjustice has misinterpreted how EPA determines compliance with the 24hour PM10 NAAQS.

Earthjustice further 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 PM10 concentrations exceeding the level of the NAAQS at Corcoran occurred either an hour before or at the same time as the Lemoore meteorological station recorded wind speeds exceeding the 18 mph threshold speed.\12\ Earthjustice notes that on September 22 the 6:00 a.m. hourly PM10 concentration at Corcoran exceeded the level of the NAAQS and wind speeds recorded in Lemoore did not exceed the threshold wind speed until 7 a.m. On October 25 the Corcoran hourly PM10 concentration first exceeded the level of the NAAQS at 6 a.m., the same time the Lemoore meteorological station recorded winds in excess of the threshold speed.\13\ However, as set forth below, the data show that on September 22 the winds at Lemoore began exceeding the threshold speed at 6 a.m. PST, and likely began affecting the concentrations at the Corcoran monitor by the time concentrations were recorded at 7 a.m. PST.\14\ On October 25, the winds recorded at Lemoore exceeded the threshold speed at 5 a.m. PST and likely affected the concentrations recorded at the Corcoran monitor beginning at 6 a.m. PST. Thus on both days there was at most a period of one or two hours where the concentrations at the monitor that exceeded the standard might not have been attributable to the winds from Lemoore.
\12\ The State cites a 2002 California Regional PM10/PM2.5 Air Quality Study (2002 CRPAQS Study) that established a dustgenerating 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. See our proposal at 72 FR at 49052.
\13\ As will be discussed further below, EPA uncovered an error in the reporting of the meteorological data from Lemoore. The data for Lemoore winds were reported in the State's documentation in PDT as opposed to the other meteorological and PM10 concentration data which were reported in PST. This means that the wind speeds increased an hour earlier than had previously been reported in the State's documentation. Therefore when Earthjustice refers to wind data from Lemoore at 6 a.m. and 7 a.m., the actual times were 5 a.m. and 6 a.m. PST.
\14\ Hourly concentrations recorded by PM10 continuous monitors are reported in the beginning hour. That is, an hourly average concentration calculated from readings taken between the hours of 7 a.m. and 8 a.m. would be reported as the average hourly

concentration for 7 a.m.

Nevertheless, based upon meteorological data, EPA believes that the high concentrations measured beginning at 7 a.m. PST on September 22 and 6 a.m. on October 25 and continuing throughout the day were due to transport of dust by high winds in the Lemoore area, and thus resulted in the exceedance of the 24hour NAAQS. In reaching this conclusion, EPA evaluated the available hourly concentration data from the Corcoran monitoring site \15\ from October 1, 2006 through June 30, 2007 to determine how often the Corcoran site recorded high hourly concentrations in the morning. While high morning concentrations were relatively rare in the data we evaluated, when they do occur they do not always result in a 2

FOR FURTHER INFORMATION CONTACT Doris Lo, EPA Region IX, (415) 972- 3959, lo.doris@epa.gov or Bob Pallarino, EPA Region IX, (415) 9474128, pallarino.bob@epa.gov.