Monday, 

August 27, 2007 

Part II 

Environmental 

Protection Agency 

40 CFR Parts 52 and 81 

Approval and Promulgation of 

Implementation Plans; Designation of 

Areas for Air Quality Planning Purposes; 

State of California; PM–10; Affirmation of 

Determination of Attainment for the San 

Joaquin Valley Nonattainment Area; 

Proposed Rule 


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49046 Federal Register / Vol. 72, No. 165 / Monday, August 27, 2007 / Proposed Rules 

1EPA’s final determination of attainment 

addressed both the 24-hour and annual PM–10 

standards; however, on October 17, 2006, effective 

on December 18, 2006, EPA revoked the annual 

PM–10 standard. 71 FR 61144. 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Parts 52 and 81 

[EPA–R09–OAR–2006–0583; FRL–8459–2] 

Approval and Promulgation of 

Implementation Plans; Designation of 

Areas for Air Quality Planning 

Purposes; State of California; PM–10; 

Affirmation of Determination of 

Attainment for the San Joaquin Valley 

Nonattainment Area 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: In a final rule published in 

the Federal Register on October 30, 

2006, EPA determined that the San 

Joaquin Valley nonattainment area (SJV 

or the Valley) in California attained the 

National Ambient Air Quality Standards 

(NAAQS) for particulate matter with an 

aerodynamic diameter less than or equal 

to a nominal 10 micrometers (PM–10). 

Since that final determination of 

attainment, the State has flagged several 

exceedances of the PM–10 standard in 

2006 as being caused by exceptional 

events, i.e., high winds, and requested 

that these data be excluded from 

attainment determinations. EPA is 

proposing to concur with the State’s 

request to flag these exceedances and 

thus to exclude that data from use in 

determining PM–10 attainment for the 

SJV. EPA is also proposing to exclude 

from use in determining attainment for 

the SJV exceedances recorded at a 

monitor located at the Santa Rosa 

Rancheria, tribal lands within the 

boundaries of the SJV, on two bases: 

The exceedances occurred while the 

monitor was operating in very close 

proximity to construction activities and, 

as such, the monitor was not properly 

sited during that time for purposes of 

comparison to the NAAQS; and the 

exceedances were caused by an 

exceptional event. EPA is proposing to 

concur with the Santa Rosa Rancheria 

Tribe’s request to flag these exceedances 

as due to an exceptional event. As a 

result, EPA is proposing to affirm its 

determination that the SJV has attained 

the PM–10 standard based on EPA’s 

evaluation of quality-assured data 

through December 2006. In addition to 

providing the public with an 

opportunity to comment on EPA’s 

evaluation and proposed concurrence 

on flagged exceedances that occurred 

through the end of calendar year 2006, 

EPA is in this proposed rule addressing 

issues raised in petitions for 

reconsideration and withdrawal of 

EPA’s 2006 determination of attainment, 

filed by Earthjustice on behalf of the 

Sierra Club, Latino Issues Forum and 

others. 

DATES: Written comments must be 

received on or before September 26, 

2007. 

ADDRESSES: Submit comments, 

identified by docket number EPA–R09– 

OAR–2006–0583, by one of the 

following methods: 

(1) Federal eRulemaking portal: 

http://www.regulations.gov. Follow the 

on-line instructions. 

(2) E-mail: lo.doris@epa.gov. 

(3) Mail or deliver: Doris Lo (AIR–2), 

U.S. Environmental Protection Agency 

Region IX, 75 Hawthorne Street, San 

Francisco, CA 94105–3901. 

Instructions: All comments will be 

included in the public docket without 

change and may be made available 

online at www.regulations.gov, 

including any personal information 

provided, unless the comment includes 

Confidential Business Information (CBI) 

or other information whose disclosure is 

restricted by statute. Information that 

you consider CBI or otherwise protected 

should be clearly identified as such and 

should not be submitted through the 

www.regulations.gov or e-mail. 

www.regulations.gov is an anonymous 

access system, and EPA will not know 

your identity or contact information 

unless you provide it in the body of 

your comment. If you send e-mail 

directly to EPA, your e-mail address 

will be automatically captured and 

included as part of the public comment. 

If EPA cannot read your comment due 

to technical difficulties and cannot 

contact you for clarification, EPA may 

not be able to consider your comment. 

Docket: The index to the docket for 

this action is available electronically at 

www.regulations.gov and in hard copy 

at EPA Region IX, 75 Hawthorne Street, 

San Francisco, California. While all 

documents in the docket are listed in 

the index, some information may be 

publicly available only at the hard copy 

location (e.g., copyrighted material), and 

some may not be publicly available in 

either location (e.g., CBI). To inspect the 

hard copy materials, please schedule an 

appointment during normal business 

hours with the contact listed directly 

below. 

FOR FURTHER INFORMATION CONTACT: 

Doris Lo, EPA Region IX, (415) 972– 

3959, lo.doris@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document, wherever 

‘‘we,’’ ‘‘us,’’ or ‘‘our’’ are used, we mean 

EPA. 

Table of Contents 

I. Background 

II. EPA’s Proposed Actions 

III. Summary of Litigation and 

Administrative Proceedings 

IV. EPA’s Exceptional Events Rule 

V. EPA’s Evaluation of Flagged Exceedances 

A. September 22, 2006 Exceedances at 

Corcoran, Bakersfield and Oildale 

1. Procedural Requirements 

2. Technical Criteria 

3. Mitigation Requirements 

B. October 25, 2006 Exceedances at 

Corcoran and Bakersfield 

1. Procedural Requirements 

2. Technical Criteria 

3. Mitigation Requirements 

C. December 8, 2006 Exceedances at 

Corcoran and Bakersfield 

1. Procedural Requirements 

2. Technical Criteria 

3. Mitigation Requirements 

VI. EPA Evaluation of September 14, 

September 20 and October 26, 2006 

Exceedances Recorded at the Santa Rosa 

Rancheria 

A. Evaluation Under Principles Established 

in 40 CFR Part 58, Appendix E 

B. Evaluation Under the Exceptional 

Events Rule 

1. Procedural Requirements 

2. Technical Criteria 

3. Mitigation Requirements 

VII. Summary of Exceedances from 2004 

through 2006 

VIII. Petitions for Reconsideration and 

Withdrawal 

A. Winds and Wildfires on September 22 

and October 25, 2006 

B. Notice/Comment on September 22 and 

October 25, 2006 Exceedances 

C. Wind Conditions in the Valley 

D. EPA’s Natural Events Policy 

1. BACM Implementation 

2. District’s Natural Events Action Plan 

E. Harvest Activities 

F. Exceedances at Corcoran and Stockton 

in 2004, Bakersfield in 2005 and the 

Santa Rosa Rancheria in 2006 

IX. Statutory and Executive Order Reviews 

I. Background 

On October 17, 2006, EPA finalized 

its determination that the SJV attained 

the NAAQS for PM–10, and on October 

30, 2006, EPA published this 

determination in the Federal Register. 

71 FR 63642. This determination was 

based upon monitored air quality data 

for the PM–10 NAAQS 1 during the 

years 2003–2005 and all available 

quality-assured data through July 31, 

2006. For a more detailed discussion of 

the related background for the SJV, 

please refer to the proposed and final 

rules at 71 FR 40952 (July 19, 2006) and 

71 FR 63642. Shortly before EPA issued 

the determination of attainment, EPA 

learned of preliminary data indicating 

that exceedances had occurred on 


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2Once air quality data have been submitted to 

EPA, it is possible to ‘‘flag’’ specific values for 

various purposes. ‘‘Data flagging’’ refers to the act 

of making a notation in a designated field of an 

electronic data record. The principal purpose of the 

data flagging system in the Air Quality System 

(AQS) data base is to identify those air quality 

measurements for which special attention or 

handling is warranted. These include, but are not 

limited to, those measurements that are influenced 

by exceptional events. See 71 FR 12592, 12598 

(March 10, 2006). 

3A federal reference method (FRM) is an air 

sample collection and analysis method which 

follows the procedures detailed in the appendices 

to 40 CFR part 50. A federal equivalent method 

(FEM) is an air sampling collection and analysis 

method which does not follow the reference 

procedures in 40 CFR part 50, but has been certified 

and designated by the EPA as obtaining 

‘‘equivalent’’ results. 

September 22, 2006, at several monitors, 

and that the State intended to flag 2

them as caused by natural events and to 

request that EPA concur with these 

flags. EPA stated that because the data 

were preliminary and because they may 

qualify as natural events, EPA would 

proceed with its determination of 

attainment at that time. EPA further 

indicated that once quality-assured data 

were available EPA would review those 

data and consider whether the 

determination of attainment should be 

withdrawn. 

Since the October 2006 final 

determination of attainment, EPA has 

obtained information regarding the PM–

10 exceedances summarized in Table 1, 

which were recorded at various 

monitors within the boundaries of the 

SJV: 

TABLE 1.—SUMMARY OF EXCEEDANCES EVALUATED FOR TODAY’S PROPOSED RULE

Date of exceedance Monitor location (type(s)) 

Concentration 

(μg/m3) 

September 22, 2006 ................................... Corcoran (FRM, FEM)* .................................................................................................. 215, 261 

Bakersfield-Golden (FRM, FEM) ................................................................................... 157, 170 

Oildale (FRM) ................................................................................................................. 162 

October 25, 2006 ....................................... Corcoran (FEM) ............................................................................................................. 304 

Bakersfield-Golden State Highway (FEM) ..................................................................... 193 

December 8, 2006 ...................................... Corcoran (FEM) ............................................................................................................. 162 

Bakersfield-Golden State Highway (FEM) ..................................................................... 213 

September 14, 2006 ................................... Santa Rosa Rancheria (FRM) ....................................................................................... 190 

September 20, 2006 ................................... Santa Rosa Rancheria (FRM) ....................................................................................... 158 

October 26, 2006 ....................................... Santa Rosa Rancheria (FRM) ....................................................................................... 157 

* FRM = Federal Reference Method; FEM = Federal Equivalent Method.3

On April 24, 2007, the State 

submitted to EPA documentation 

supporting its claim that the September 

22, 2006 exceedances were caused by 

high winds and wildfires. This 

submittal was supplemented with 

additional documentation on July 10, 

2007. On May 1, 2007, the State 

submitted to EPA documentation 

supporting its claim that the October 25, 

2006 exceedances were caused by high 

winds. On June 12, 2007, the State 

submitted to EPA documentation 

supporting its claim that the December 

8, 2006 exceedances were caused by 

high winds. The State believes that all 

of these exceedances qualify as natural 

events and that the data should thus be 

excluded from consideration in the 

attainment determination. 

On July 9, 2007, EPA met with a 

representative of the Santa Rosa 

Rancheria EPA to discuss exceedances 

recorded on September 14, September 

20 and October 26, 2006. The Tribe has 

flagged these exceedances as being 

caused by an exceptional event related 

to construction activities and EPA has 

compiled documentation to support that 

claim. 

II. EPA’s Proposed Actions 

In this proposed rule, EPA is 

proposing to concur with the State’s 

request to flag exceedances of the PM–

10 standard within the SJV on 

September 22, October 25 and December 

8, 2006 as being caused by exceptional 

events, i.e., high winds, and thus to 

exclude these data from use in 

determining PM–10 attainment for the 

SJV. EPA is also proposing to exclude 

exceedances recorded at the Santa Rosa 

Rancheria, tribal lands within the SJV, 

on September 14, September 20 and 

October 26, 2006 from use in 

determining attainment for the SJV, on 

two bases: (1) The exceedances occurred 

while the monitor was operating in very 

close proximity to construction 

activities and, as such, the monitor was 

not properly sited during that time for 

purposes of comparison to the NAAQS; 

and (2) the exceedances were caused by 

an exceptional event, i.e., construction 

activity in very close proximity to the 

monitor. The Tribe has flagged those 

exceedances, and EPA is proposing to 

concur with those flags. 

As a result, EPA is proposing to affirm 

its October 2006 attainment 

determination based on its evaluation of 

quality-assured data from September 14 

through December 31, 2006. After 

receiving and considering all relevant 

public comments on our proposed rule, 

we will publish our final determination 

as to whether we will concur with the 

State’s and Tribe’s requests to flag the 

exceedances discussed above as affected 

by exceptional events and to exclude 

them from consideration in our 

attainment determination. We will also 

publish our determination as to whether 

we will exclude the exceedances at the 

Santa Rosa Rancheria as a result of the 

monitor siting. EPA is not taking 

comment in these proposed actions on 

any issues that were the subject of the 

2006 attainment determination 

rulemaking except to the extent that 

they affect EPA’s ability to determine 

that the SJV continued to attain the PM–

10 standard through 2006. 

In this proposed rule we are also 

addressing relevant issues raised in the 

petition for reconsideration and petition 

to withdraw the determination of 

attainment filed by the Latino Issues 

Forum and others. 

In our 2006 attainment determination 

we stated that if, after the September 22, 

2006 data were quality-assured, and 

after further evaluating the State’s 

request for exclusion of these data, we 

determine that the data do not qualify 

for exclusion and we believe that if 

included that they would establish that 

the area is in violation of the NAAQS, 

EPA would proceed with appropriate 

rulemaking action to withdraw its 

determination of attainment. 71 FR 

63642. Both EPA’s natural/exceptional 

events policies and its exceptional 

events rule anticipate that the Agency 

will concur or nonconcur on a state’s 

request to exclude data by letter rather 

than rulemaking. 


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4 In the preamble to the final rule, EPA discusses 

specific types of natural events, including high 

wind events (i.e., those that affect ambient 

particulate matter concentrations through the 

raising of dust or through the re-entrainment of 

material that has been deposited). See 72 FR at 

13565–13566 and 13576–13577. EPA’s 

interpretation of the rule with respect to high winds 

is addressed in section V. below. 

Generally we would initiate 

rulemaking following an attainment 

determination for an area only if we had 

preliminarily concluded that a 

withdrawal of that determination would 

be appropriate. That is not the case here. 

However, in this instance both because 

EPA had indicated in its final action 

that it would reassess the attainment 

determination once it had qualityassured data for the September 22, 2006 

exceedances and because of the issues 

raised by the petitions pending before 

the Agency and discussed below, we are 

proposing to concur with the State’s and 

Tribe’s requested flags and affirm our 

2006 attainment determination via 

notice and comment rulemaking. 

Because we generally make 

determinations of attainment on a 

calendar year basis, our proposed rule 

addresses quality assured exceedances 

from September 14 through December 

31, 2006. Moreover the petitions address 

exceedances within this timeframe. 

III. Summary of Litigation and 

Administrative Proceedings 

Earthjustice filed three petitions 

related to EPA’s determination of 

attainment for the SJV. On December 27, 

2006, Earthjustice, on behalf of Latino 

Issues Forum, Medical Advocates for 

Healthy Air and Sierra Club, filed in the 

U.S. Court of Appeals for the 9th Circuit 

a petition for review of EPA’s October 

2006 determination under the Clean Air 

Act that the SJV has attained the PM–

10 standard. Latino Issues Forum v. 

EPA, No. 06–75831 (9th Cir.). On 

December 29, 2006, Earthjustice also 

filed with EPA a petition for 

reconsideration of our attainment 

determination. In the petition, 

Earthjustice alleges, among other things, 

that EPA improperly ignored September 

22, 2006 PM–10 exceedances in the SJV 

that were not subject to public notice 

and comment. Finally, on March 21, 

2007, Earthjustice filed a petition for 

withdrawal of our attainment 

determination. In this petition, 

Earthjustice alleges that the attainment 

determination must be withdrawn 

because, among other things, the 

exceedances that occurred in September 

and October 2006 do not qualify as 

exceptional events. EPA addresses 

issues raised in both of these 

administrative petitions in this 

proposed rule. 

IV. EPA’s Exceptional Events Rule 

On March 22, 2007, EPA issued a 

final rule governing the review and 

handling of air quality data influenced 

by exceptional events. 72 FR 13560. The 

rule became effective on May 21, 2007 

and implements section 319 of the CAA, 

as amended by section 6013 of the Safe 

Accountable Flexible EfficientTransportation Equity Act: A Legacy for 

Users (SAFE–TEA–LU) of 2005. In the 

rule, EPA establishes procedures and 

criteria related to the identification, 

evaluation, interpretation, and use of air 

quality monitoring data related to the 

ozone and particulate matter NAAQS 

where states petition EPA to exclude 

data that are affected by exceptional 

events from certain regulatory actions 

under the CAA. The rule is codified at 

40 CFR 50.1, 50.14, and 51.920. 72 FR 

at 13580–13581. 

In the preamble to the final rule, EPA 

also addresses its applicability to Indian 

Tribes. Where, as here, the Santa Rosa 

Rancheria Tribe operates an air quality 

monitor only in order to gather data for 

informational purposes but does not 

implement other programs such as 

mitigating the effects of exceptional 

events, it is EPA’s responsibility to 

ensure that any exclusion or 

discounting of data in Indian country 

areas comports with the rule’s 

procedures and requirements. EPA 

intends to work with tribes on the 

implementation of the rule. 72 FR at 

13563. 

In 1986 and 1996 EPA issued 

guidance to address the use of data 

influenced by exceptional and natural 

events: ‘‘Guidance on the Identification 

and Use of Air Quality Data Affected by 

Exceptional Events’’ (July 1986) and 

‘‘Areas Affected by PM–10 Natural 

Events,’’ May 30, 1996. CAA Section 

319, as amended by SAFE–TEA–LU, 

states that these guidance documents 

continue to apply until the effective 

date of a final regulation promulgated 

under section 319(b)(2). See CAA 

Section 319(b)(4). SAFE–TEA–LU did 

not however address those situations 

where EPA had not made a 

determination prior to the effective date 

of the rule whether an exceptional event 

had occurred after a state had flagged 

data and submitted a demonstration in 

a timely manner to show that such data 

reflected NAAQS exceedances that were 

caused by an exceptional event. In these 

circumstances, EPA believes that in the 

interests of equity and administrative 

efficiency, a state seeking to exclude 

data affected by exceptional events 

should, for a limited period of time, be 

able to choose to comply with either the 

provisions of the rule or those of the 

guidance documents for a limited 

period of time. This approach would 

have some advantages, such as allowing 

the state to avoid duplicating its 

demonstration process and completing 

the decisionmaking process already 

underway. EPA believes that it is 

reasonable to use this approach until 

December 31, 2007 to complete the 

transition from the policies to the rule. 

However, unless the state in the 

circumstances described above, 

specifically requests that EPA evaluate a 

natural or exceptional event 

demonstration under the guidance 

documents, EPA will presume that the 

rule applies. 

Under 40 CFR 50.14(j), an 

‘‘exceptional event,’’ with specified 

exceptions not relevant here, is defined 

as one ‘‘that affects air quality, is not 

reasonably controllable or preventable, 

is an event caused by human activity 

that is unlikely to recur at a particular 

location or a natural event, and is 

determined by the Administrator in 

accordance with 40 CFR 50.14 

[‘treatment of air quality monitoring 

data influenced by exceptional events’] 

to be an exceptional event.’’ A ‘‘natural 

event’’ is defined as one ‘‘in which 

human activity plays little or no direct 

causal role.’’ 40 CFR 50.14(k).4

The rule establishes a multi-step 

process for identification by states, 

tribes and local agencies of data and 

submission of the requisite 

demonstrations to EPA. 72 FR at 13571. 

In short, a state must notify EPA of its 

intent to exclude measured exceedances 

of a NAAQS as being due to an 

exceptional event by ‘‘flagging’’ the data 

in EPA’s AQS database. 40 CFR 

50.14(c)(2)(i). For PM–10, the state 

should submit the flags, accompanied 

by an initial description of the event, by 

July 1st of the calendar year following 

the year in which the flagged 

measurement occurred. 40 CFR 

50.14(c)(2)(iii). A state that has flagged 

data as being due to an exceptional 

event and is requesting its exclusion 

must, after notice and opportunity for 

public comment, submit a 

demonstration that to EPA’s satisfaction 

shows that the flagged event caused a 

specific concentration in excess of the 

NAAQS at the particular location to 

justify data exclusion. This 

demonstration must be submitted to 

EPA within 3 years of the calendar 

quarter following the event, but no later 

than 12 months prior to an EPA 

regulatory decision. A state must submit 

the public comments it received along 

with its demonstration to EPA. 40 CFR 

50.14(c)(3)(i). 


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5Section 50.1(j) provides the regulatory definition 

of an exceptional event. ‘‘Exceptional event’’ means 

an event that affects air quality, is not reasonably 

controllable or preventable, is an event caused by 

human activity that is unlikely to recur at a 

particular location or a natural event, and is 

determined by the Administrator in accordance 

with 40 CFR 50.14 to be an exceptional event. It 

does not include stagnation of air masses or 

meteorological inversions, a meteorological event 

involving high temperatures or lack of 

precipitation, or air pollution relating to source 

noncompliance. 

6The FEM monitor currently operated at the 

Corcoran site is an automated continuous analyzer 

known as a Tapered Element Oscillating 

Microbalance (TEOM). 

In the preamble to the final rule, EPA 

explained that it will generally review 

the state’s demonstration and provide a 

concurrence or nonconcurrence on the 

flag in the AQS database within 60 days 

of the state’s complete submission. EPA 

expects that, in most cases, this time 

period should be sufficient to review 

and provide a concurrence or 

nonconcurrence regarding a state’s 

request to exclude data affected by an 

exceptional event. However, for more 

complex demonstrations, EPA may 

require additional time to make its 

decision and will notify the state of the 

additional time required. 72 FR at 

13571. Upon its concurrence on a flag, 

EPA will exclude the data from use in 

determinations of NAAQS exceedances 

and violations. 40 CFR 50.14(b). 

The requirements for the 

demonstration to justify data exclusion 

that the state must submit, in this 

instance, to EPA are set forth at 40 CFR 

50.14(a), (b)(1), and (c)(3)(iii). In order to 

be considered for exclusion, the state 

must show that the event satisfies the 

criteria in section 50.1(j), there is a clear 

causal connection between the 

exceedances and the claimed 

exceptional event, the event is 

associated with measured concentration 

in excess of normal historical 

fluctuations including background and 

there would have been no exceedance 

‘‘but for’’ the event. 40 CFR 

50.14(c)(iii)(A)–(D). 

One of the requirements of section 

50.1(j) is that the exceptional event must 

be shown to affect air quality, which is 

met by establishing that the event is 

associated with a measured exceedance 

in excess of normal historical 

fluctuations, including background. 40 

CFR 50.14(c)(iii)(B). In addition, as 

noted above there must be a clear causal 

relationship between the measurement 

under consideration and the event that 

is claimed to have affected the air 

quality in the area. 40 CFR 

50.14(c)(iii)(C). Air quality impact and 

causal connection may be shown 

through a number of methods including 

modeling and speciation analysis. EPA 

will evaluate whether an event affected 

air quality and caused a particular 

concentration using the weight of 

available evidence and considering the 

historical frequency of such measured 

concentrations. States must compare 

contemporary concentrations with 

distribution of historical values and 

these may be presented on a seasonal or 

other temporal basis. 40 CFR 50.14(a)(2) 

and (c)(3)(iii)(A) and (C); 72 FR at 

13569. 

Also, air quality data may not be 

excluded except where states, tribes, or 

local agencies show, through a weight of 

evidence approach, that exceedances or 

violations of applicable standards 

would not have occurred ‘‘but for’’ the 

influence of exceptional events. 40 CFR 

50.14(c)(3)(iii)(D). 72 FR at 13570–

13571. Finally, states must demonstrate 

that they have provided an opportunity 

for public comment and must submit 

any public comments it received to 

EPA. 40 CFR 50.14(c)(3)(i) and (iv). 

States, tribes, or local agencies must 

also demonstrate that the claimed 

exceptional event meets the other 

requirements of § 50.1(j)—that the event 

is not reasonably preventable or 

controllable and that the event is either 

caused by human activity that is 

unlikely to recur at a particular location 

or is a natural event. In this instance, 

the claimed events are high winds, i.e. 

natural events, and construction, i.e., an 

event caused by human activity that is 

unlikely to recur at the particular 

location. 

In order to concur on a state’s request 

to exclude data, EPA must determine 

that the state’s submission is complete 

and demonstrates to EPA’s satisfaction 

that the exceptional event caused the 

exceedances. Although states must meet 

the minimum requirements (e.g. ‘‘but 

for’’ test), EPA did not specify a 

minimum level of documentation in the 

rule because the facts and circumstances 

could vary depending on, among others, 

meteorology, and geography. Instead, 

EPA illustrated through examples the 

kind of information that states could 

consider in meeting the demonstration 

requirements of the rule. In describing 

the documentation process and 

requirement, EPA also stated that 

acceptable documentation would be 

determined through consultation with 

the EPA regional offices. 72 FR at 13573. 

Finally, under 40 CFR 51.930, a state 

requesting to exclude air quality data 

due to exceptional events must take 

appropriate and reasonable actions, 

including public notification, public 

education and implementation of 

measures, to protect public health from 

exceedances or violations of the 

NAAQS. 

V. EPA’s Evaluation of Flagged 

Exceedances 

The State and Tribe have not 

specifically requested that EPA evaluate 

the September 14 through December 31, 

2006 exceedances (which occurred 

before the effective date of the 

Exceptional Events Rule) under EPA’s 

natural events policy or exceptional 

events policy. Therefore we are 

evaluating the State’s submittals and the 

Santa Rosa Rancheria exceedances 

under the Exceptional Events Rule to 

determine whether they meet both the 

procedural requirements and the 

technical criteria for showing that the 

exceedances are exceptional. We will 

discuss whether the State’s submittal 

and the exceedances at Santa Rosa 

Rancheria meet each of these 

requirements and criteria separately. For 

each of the exceedances being discussed 

in today’s proposal, EPA bases its 

evaluation on the procedural 

requirements and technical criteria and 

mitigation requirements of the 

Exceptional Events Rule, as discussed 

above and summarized below: 

Procedural Requirements: 

• Data are flagged in EPA’s AQS 

database. 

• Public had an opportunity to review 

and comment on the state’s 

documentation. 

• The documentation was submitted 

to EPA. 

• EPA concurs with the state’s 

demonstration. 

Technical Criteria: 

• The state must show that the event 

satisfies the criteria in 40 CFR 50.1(j).5

• There is a clear causal connection 

between the exceedance and the 

claimed exceptional event. 

• The event is associated with 

measured concentration in excess of 

normal historical fluctuations including 

background. 

• There would have been no 

exceedances ‘‘but for’’ the event. 

Mitigation Requirements: 

• Provide for prompt public 

notification of exceedance events. 

• Provide for public education on 

how to minimize exposure. 

• Provide for the implementation of 

appropriate measures to protect the 

public. 

A. September 22, 2006 Exceedances at 

Corcoran, Bakersfield, and Oildale 

The 24-hour PM–10 NAAQS was 

exceeded at three monitoring locations 

on September 22, 2006: The Corcoran 

monitoring site recorded concentrations 

of 215 μg/m3 and 261 μg/m3 with a FRM 

sampler and a FEM automated 

continuous analyzer,6 respectively; the 


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49050 Federal Register / Vol. 72, No. 165 / Monday, August 27, 2007 / Proposed Rules 

7 ‘‘Natural Event Documentation, Corcoran, 

Oildale, and Bakersfield, California, September 22, 

2006’’, April 20, 2007 (NED for September 22, 2006) 

at 10. 

8NED for September 22, 2006 at 11, Table 3, 14 

and 37–44. 

9The Bakersfield-Golden State Highway and 

Oildale monitors are approximately 3.5 miles apart. 

For the purposes of this discussion, the analysis for 

the Bakersfield-Golden State Highway and Oildale 

monitors is the same. 

Bakersfield-Golden State Highway 

monitoring site recorded concentrations 

of 157 μg/m3 and 170 μg/m3 with its 

FRM sampler and FEM (TEOM) 

analyzers, respectively; and the Oildale 

monitoring site recorded a 

concentration of 162 μg/m3 with its 

FRM sampler. 

The State concludes that three sources 

of PM–10 contributed to exceedances of 

the 24-hour PM–10 NAAQS on this day: 

Wind-entrained dust from sources in the 

central and southern SJV, which is 

identified as the primary source of PM–

10; wind-entrained dust from regional 

sources from the northern SJV; and 

emissions related to several wildfires 

which are identified as secondary 

sources of PM–10.7 Based on the 

evidence submitted, EPA agrees with 

the State’s demonstration that high 

wind-entrained dust from sources in the 

central and southern SJV caused the 

exceedances at the three monitoring 

locations on September 22, 2006. 

We do not however agree with the 

State that emissions from wildfires or 

regionally transported dust from the 

northern SJV were significant 

contributors. 

After evaluating the State’s 

demonstration under the technical 

criteria established in the Exceptional 

Events Rule, EPA finds that for the 

Corcoran, Bakersfield and Oildale areas, 

the State does not demonstrate that 

emissions from wildfires had a 

significant impact on the PM–10 

concentrations recorded on September 

22, 2006. None of the fires cited in the 

documentation was within the 

boundaries of the SJV. Further, an 

independent review of PM–2.5 

speciation data collected at Bakersfield 

and Fresno on the days preceding and 

after September 22 shows no unusual 

concentrations of carbon. See http:// 

www.epa.gov/cgi-bin/htmSQL/ 

mxplorer/query_spe.hsql. If the fires had 

had a significant effect on PM–10 

concentrations, there would have been 

evidence of increased carbon (one of the 

chemical constituents of wood smoke) 

in the speciation data. The 

documentation submitted by the State 

includes mostly anecdotal evidence of 

the wildfires’ impact and satellite 

photographs showing smoke over parts 

of California. The anecdotal evidence 

consists of newspaper reports of 

reduced visibility due to smoke and the 

odor of wood smoke, as well as 

observations from trained weather 

observers at Lemoore Naval Air 

Station.8 EPA finds that the 

documentation lacks data linking the 

fires to the concentrations given the 

distance of the fires and the lack of 

corroborating speciation data and 

satellite photographs of the smoke, and 

newspaper reports do not rise above 

general or anecdotal evidence to 

establish a clear causal relationship 

between the exceedances on September 

22, 2006 and the emissions from 

wildfires. 

Similarly, EPA believes that the 

State’s documentation that regional 

sources of entrained dust impacted 

monitors in the Corcoran and 

Bakersfield areas does not show a clear 

causal relationship between the 

exceedances and regional transport of 

PM–10 from the northern SJV. EPA 

bases this conclusion on its review of 

the documentation which indicates that 

while there were high hourly averaged 

winds and gusts in the northern central 

valley of California, the State did not 

present any facts, corroborating 

evidence or any convincing argument to 

demonstrate how PM–10 from this area 

could have reached the southern SJV in 

concentrations sufficient to contribute 

to an exceedance of the 24-hour PM–10 

NAAQS. 

Because EPA does not agree with the 

State’s conclusions with respect to 

regional transport of PM–10 from the 

northern SJV and with respect to 

wildfires, in the following discussion 

regarding the September 22, 2006 

exceedances we refer only to the State’s 

conclusion that these exceedances were 

caused by wind-entrained dust from 

sources in the central and southern SJV. 

1. Procedural Requirements 

a. Data Are Flagged in EPA’s AQS 

Database 

All of the September 22, 2006 

exceedances were flagged in EPA’s AQS 

database as of July 2007. 

b. Public Had an Opportunity To 

Review and Comment on the State’s 

Documentation 

In February 2007, the SJV Air 

Pollution Control District (SJVAPCD or 

District) notified the public in local 

newspapers and on its Web site of the 

availability of the document entitled 

‘‘Natural Event Documentation, High 

Winds, Corcoran and Bakersfield, 

California, September 22, 2006,’’ SJV 

Unified Air Pollution Control District, 

February 2007 and requested public 

comments by March 5, 2007. 

The SJVAPCD subsequently revised 

the February 2007 document and 

submitted to the California Air 

Resources Board (CARB) ‘‘Natural Event 

Documentation, Corcoran, Oildale and 

Bakersfield, California, September 22, 

2006,’’ SJV Unified Air Pollution 

Control District, April 20, 2007 (NED for 

September 22, 2006) and posted it on its 

Web site. 

SJVAPCD thereafter provided 

additional information to CARB in 

‘‘Addendum, Natural Event 

Documentation, Corcoran, Oildale and 

Bakersfield, California, September 22, 

2006,’’ SJV Unified Air Pollution 

Control District, May 23, 2007 (NED 

Addendum for September 22, 2006) and 

posted it on its Web site. 

The District indicated that no public 

comments were received during the 

public process. 

c. The Documentation Was Submitted to 

EPA 

The NED for September 22, 2006 and 

the NED Addendum for September 22, 

2006 were subsequently submitted by 

the State to EPA on April 24, 2007 and 

July 10, 2007, respectively, and are the 

documents upon which EPA is basing 

its evaluation below. 

d. EPA Concurs With the State’s 

Demonstration 

In this proposed rule, EPA is 

proposing to concur with the State’s 

demonstration in the NED for 

September 22, 2006 and the NED 

Addendum for September 22, 2006 that 

high wind-entrained dust from the 

central and southern SJV caused the 

exceedances at the three monitoring 

locations on September 22, 2006. 

2. Technical Criteria 

a. Did this event satisfy the criteria in 

section 50.1(j) of the Rule? 

The State needs to show that the 

September 22, 2006 event, windentrained dust from sources in the 

central and southern SJV, affected air 

quality in the Corcoran and Bakersfield 

areas,9 was not reasonably controllable 

or preventable, was a natural event, and 

is determined by EPA through the 

process established in the Rule to be an 

exceptional event. We believe the State 

has supported its claims that winddriven dust from sources of PM–10 in 

the central and southern SJV was the 

cause of the September 22, 2006 

exceedances, as discussed in detail 

below. 


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10NED for September 22, 2006 at 32. 

11 69 FR 30006, 30035 (May 26, 2004); 71 FR 7683 

(February 14, 2006). 

12NED for September 22, 2006 at 32–33. 

13NED for September 22, 2006 at 29; NED 

Addendum for September 22, 2006 at section 4. 

14NED for September 22, 2006 at 29. 

15NED for September 22, 2006 at 13; David Bush, 

T&B Systems Contribution to CRPAQS Initial Data 

Analysis of Field Program Measurements, Final 

Report Contract 2002–06PM Technical & Business 

Systems, Inc., November 9, 2004 (Bush Report). 

16NED Addendum for September 22, 2006 at 11, 

Table 3. 

17 Generally EPA concurs or nonconcurs by letter 

with requests to flag data as caused by exceptional 

events. See our explanation in section II. above 

regarding why we are proceeding by a rulemaking 

here. 

i. Affected Air Quality 

For an event to qualify as an 

exceptional event, the state must show 

that the event affected air quality. This 

criterion can be met by establishing that 

the event is associated with a measured 

exceedance in excess of normal 

historical fluctuations, including 

background, and there is a causal 

connection between the event and the 

exceedance. The demonstration of a 

clear causal relationship is necessary to 

establish that the event affected air 

quality and is also a separate statutory 

requirement as discussed above. 

In the NED for September 22, 2006 

and the NED Addendum for September 

22, 2006, the State provides 

documentation that the measured 

exceedances on September 22, 2006 

were in excess of normal historical 

fluctuations. See subsection c. below. 

The State also establishes a causal 

connection between the high winds 

recorded at Lemoore and the high 

concentrations recorded at the Corcoran, 

Bakersfield, and Oildale monitors. The 

State’s demonstration of the clear causal 

relationship between the event and the 

exceedances on this day is discussed in 

greater detail in subsection b. below. 

ii. Not Reasonably Controllable or 

Preventable 

Section 50.1(j) of the Exceptional 

Events Rule requires that for an event to 

qualify as an exceptional event, whether 

natural or anthropogenic, a state must 

show that the event was not reasonably 

preventable or controllable. Here this 

requirement is met by demonstrating 

that despite reasonable and appropriate 

measures in place, the September 22, 

2006 wind event caused the 

exceedances. During this event there 

were no other unusual dust-producing 

activities occurring in the SJV and 

anthropogenic emissions were 

approximately constant before, during 

and after the event. In addition, the 

State shows that reasonable and 

appropriate measures were in place, 

including Regulation VIII (the District’s 

general fugitive dust rules) and Rule 

4550 which limits fugitive dust 

emissions specifically from agricultural 

operations through Conservation 

Management Practices.10 Moreover, EPA 

has approved the District’s best 

available control measure (BACM) 

demonstration for all significant sources 

of PM–10 in the SJV as meeting CAA 

section 189(b)(1)(B).11

iii. Was a Natural Event 

In the preamble to the Exceptional 

Events Rule EPA states that ambient 

particulate matter concentrations due to 

dust being raised by unusually high 

winds will be treated as due to 

uncontrollable natural events where (1) 

the dust originated from 

nonanthropogenic sources, or (2) the 

dust originated from anthropogenic 

sources within the State, that are 

determined to have been reasonably 

well-controlled at the time that the 

event occurred, or from anthropogenic 

sources outside the State. 72 FR at 

13576. In the preamble EPA also 

explains that ‘‘[s]tates must provide 

appropriate documentation to 

substantiate why the level of wind 

speed associated with the event in 

question should be considered unusual 

for the affected area during the time of 

year that the event occurred.’’ Id. at 

13566. 

On September 22, 2006, the windentrained dust originated from 

anthropogenic sources within 

California, i.e., from usual dustgenerating activities such as agricultural 

and industrial operations.12 We discuss 

the fugitive dust control measures in 

place in the SJV on September 22 above. 

With respect to the wind speed, EPA 

concurs with the State’s demonstration 

that the wind speeds in the central SJV 

were unusually high on September 22, 

2006.13 Meteorological data show that 

the winds at Lemoore reached speeds of 

29 mph with gusts of approximately 40 

mph. According to the State, the 

Department of Water Resources’ extreme 

annual wind statistics indicate that the 

mean annual peak gust for Lemoore is 

42 mph.14 Thus wind gusts observed at 

Lemoore were unusually high because 

they are close to the typical highest 

annual value of 42 mph. The State also 

provides documentation that shows that 

winds of approximately 18 mph will 

entrain and transport dust.15 Winds 

greater than this speed occurred at 

Lemoore and Kettleman Hills, and were 

responsible for transporting this 

entrained dust. Meteorological data 

indicate that the wind direction was 

from the north and northwest and hence 

the entrained dust at that wind speed 

was transported towards Corcoran. 

Winds at Corcoran were not as intense 

during the peak hours at Lemoore. Table 

3 of the State’s submittal indicates the 

winds at Corcoran at 10 a.m. were 9 

mph with gusts to 12 mph.16 These 

wind speeds, though not sufficient to 

erode dust, were sufficient to keep the 

entrained and transported dust from the 

high winds at Lemoore suspended for 

the period during which the 

exceedances occurred. 

iv. Determined by EPA To Be an 

Exceptional Event 

Finally, EPA must determine through 

the process established in the 

Exceptional Events Rule whether an 

exceptional event occurred. We believe 

that the State has met the procedural 

requirements of the rule including 

flagging of the data, submission of 

demonstration, evidence of the public 

opportunity to review and comment on 

the demonstration and mitigation 

requirements as discussed in section 

V.A.1. and 3. of this proposed rule. We 

further believe that the State has also 

met the technical criteria in the 

Exceptional Events Rule as discussed in 

section V.A.2. Therefore, we are 

proposing to concur with the State’s 

determination that an exceptional event, 

i.e., a high wind event, occurred 

resulting in the exceedances on 

September 22, 2006.17

b. Does the State’s documentation show 

a clear causal connection between the 

exceedances and the claimed 

exceptional event? 

Under 40 CFR 50.14(c)(3)(iii)(B), a 

state’s demonstration must establish a 

clear causal relationship between the 

measured exceedance and the claimed 

exceptional event. In addressing this 

requirement for the September 22, 2006 

exceedances, the State identifies a 

source region for the PM–10, an area 

northwest of Corcoran around the area 

of Lemoore. The State provides a 

convincing demonstration showing that 

the winds in the area of the central SJV 

were of sufficient speeds to erode soils 

and entrain dust and that the wind 

direction moved the PM–10 southeast 

towards Corcoran and further to the 

Bakersfield area. 

Meteorological measurements in 

Lemoore show that this area had the 

highest hourly averaged winds in the 

SJV that day, peaking at 10 a.m. with a 

speed of 29 mph from the NNW and 

gusts at the same time reaching 37 


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18NED for September 22, 2006 at 11, Table 3. 

19 Id. 

20 Id. 

21 Id. at 13; Bush Report. 

22NED for September 22, 2006 at 33, Table 15. 

23 Id. at 5 and 32–33. 

24 Id. at 11, Table 3. 

25 Id. at 13; Bush Report. 

26NED Addendum for September 22, 2006 at 7. 

27 Id. at 8, Table A–1. 

28NED Addendum for September 22, 2006 at 8, 

Table A–1. 

29The Oildale monitoring site does not record 

hourly PM–10 concentrations but uses a manual 

PM–10 sampler that provides only 24-hour average 

concentrations. The Bakersfield-Golden State 

Highway monitoring site utilizes both a manual 

sampler for average 24-hour PM–10 concentrations 

and a continuous PM–10 analyzer to provide hourly 

concentrations. Since the Bakersfield-Golden State 

Highway site and the Oildale site are relatively 

close to each other (see footnote 9 above), we 

believe it is appropriate to use the BakersfieldGolden State Highway continuous analyzer to 

characterize the temporal distribution of hourly 

concentrations at both sites. 

30NED Addendum for September 22, 2006 at 10. 

31NED Addendum for September 22, 2006 at 14. 

32From September 1, 2000 to March 22, 2001 the 

Corcoran monitor operated on a once-in-every-sixdays schedule. 

33PM–10 Raw Data Report Corcoran 2000–2006, 

EPA AQS Database, July 30, 2007. 

mph.18 Lemoore is approximately 25 

miles northwest of Corcoran. 

Meteorological measurements were also 

obtained from a site at Kettleman Hills, 

which showed a peak hourly wind at 11 

am of 20 mph from the NNW with gusts 

up to 32 mph.19 Kettleman Hills is 

approximately 28 miles west of 

Corcoran. The wind speed, direction, 

time and distance from monitors 

indicate that the high winds at Lemoore 

entrained the dust carrying it toward 

Corcoran.20 The State cites a 2002 

California Regional PM–10/PM–2.5 Air 

Quality Study (2002 CRPAQS study) 

that established a dust-generating wind 

speed threshold of 17.8 mph to support 

its conclusion that these wind speeds 

were sufficient to erode soils and 

entrain dust into the atmosphere as well 

as to exacerbate the entrainment of dust 

from the anthropogenic activities.21

At about 9:30 a.m. and 10:30 a.m. the 

District received complaints about dust 

emissions in Lemoore.22 This was at the 

time of peak winds in Lemoore. The 

District followed up on the complaints 

but did not issue notices of violation. 

The State indicates that there were PM–

10 generating activities in the area of 

Lemoore on the morning of September 

22, 2006 but that these activities were 

typical for the area and subject to the 

District’s fugitive dust regulations.23

The State shows a clear relationship 

between the wind speeds at Lemoore 

and Kettleman Hills and increased 

concentrations at the Corcoran 

monitoring site. The documentation 

clearly shows that as hourly average 

wind speeds increased at the three 

meteorological sites, hourly 

concentrations at Corcoran also 

increased. The peak hourly 

concentrations at Corcoran were at 10 

a.m. and 11 a.m. (725 μg/m3 and 695 μg/ 

m3, respectively).24 These 

concentrations coincide with the 

highest winds at Lemoore and 

Kettleman Hills. 

The winds at Corcoran showed the 

same pattern of increasing wind speeds 

but at a lower intensity. Hourly average 

winds at Corcoran peaked at 8 a.m. at 

11 mph with a peak average minute gust 

of 15 mph. While these wind speeds 

were not high enough to erode and 

entrain soil, based on the wind speed 

threshold referenced above, they were 

sufficient to keep the coarse particles 

suspended in the atmosphere. The 

winds were also consistently from the 

northwest, which demonstrates that the 

coarse particles which impacted 

Corcoran originated in the areas 

northwest of the monitor, e.g. Lemoore 

where the winds were unusually high. 

Using the threshold wind speed in the 

2002 CRPAQS study, the State shows 

that most of the PM–10 was generated 

upwind of the Corcoran site and then 

transported to the Corcoran area.25

Based on available data, wind speeds at 

Corcoran were not high enough to 

generate dust on their own but were 

high enough to sustain the entrainment 

of PM–10 from upwind areas. 

The wind-driven dust from sources in 

the central and southern SJV, beginning 

in Lemoore, also impacted the 

Bakersfield area on September 22, 2006. 

The State provides the analysis and 

supporting information needed to 

demonstrate that the winds between the 

Corcoran and Bakersfield areas were of 

sufficient intensity to transport the 

plume of PM–10 from Corcoran to the 

Bakersfield and Oildale monitors. The 

Bakersfield area monitors began to 

record hourly concentrations in excess 

of the level of the 24-hour PM–10 

NAAQS two hours after the peak 

Corcoran hourly PM–10 concentration, 

with the Bakersfield hourly PM–10 

concentrations peaking five hours after 

the Corcoran peak hourly PM–10 

concentration. In order to transport a 

plume of dust from Corcoran to the 

Bakersfield area, approximately 55 

miles, wind speeds would have to 

average approximately 11 mph in order 

for the maximum amount of PM–10 to 

impact the Bakersfield area monitors 

five hours later.26 The winds at 

Alpaugh, which is located between 

Corcoran and Bakersfield, averaged 11 

mph.27 As would be expected, the 

concentration of PM–10 in the 

Bakersfield area was lower than in 

Corcoran, but still significant enough to 

exceed the NAAQS. The lower PM–10 

concentrations at Bakersfield are likely 

due to the dispersion of the dust plume 

and possibly deposition of a portion of 

the dust particles along the path from 

the Corcoran area to Bakersfield. 

The State’s demonstration for 

September 22, 2006 includes 

information on wind speed and 

direction 28 that shows the correlation 

between the hourly wind speeds at 

meteorological sites in Alpaugh and 

Bakersfield-Meadows Airfield and the 

hourly PM–10 concentrations recorded 

in the Bakersfield area.29

The State also includes the results of 

a basic meteorological model known as 

Hybrid Single-Particle Lagrangian 

Integrated Trajectory model 

(HYSPLIT).30 It is important to note that 

while this modeling is not meant to 

quantify the particle concentration 

recorded in the Bakersfield area, it does 

offer support of the State’s 

demonstration that the winds on 

September 22, 2006 were of the 

appropriate intensity and direction to 

move a plume of dust from the central 

SJV to the Bakersfield area. 

c. Did the State demonstrate that the 

event is associated with measured 

concentration in excess of normal 

historical fluctuations including 

background? 

For EPA to concur with a state’s claim 

that an exceptional event caused an 

exceedance, one of the requirements 

that the state must meet is to show that 

the event is associated with 

concentrations that are beyond the 

normal historical fluctuations. See 40 

CFR 50.14(c)(3)(iii)(C). 

The NED for September 22, 2006 and 

NED Addendum for September 22, 2006 

include sections that show the 

unusualness of the concentrations 

recorded on that date. Section 4 of the 

Addendum includes Figure A–5 that 

compares the peak 24-hour PM–10 

concentrations recorded at Corcoran, 

Bakersfield and Oildale during the 

month of September for the years 2000 

through 2006.31

The FRM monitor at the Corcoran site 

has mostly operated on a once-in-everythree-days schedule since 2000.32 The 

Corcoran FRM has collected 786 

samples since 2000 and has recorded 

only four exceedances of the 24-hour 

PM–10 NAAQS.33 A further analysis 

shows that, with the exception of a 

flagged natural event in 2004, 24-hour 


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34 138 μg/m3 on September 9, 2004, a 102 μg/m3

on September 24, 2004 and a 112 μg/m3 on 

September 23, 2006; See Id. 

35 ‘‘What are the Sources of Particulate Matter’’, 

Presentation by Karen L. Magliano, California Air 

Resources Board, May 17, 2006 (Magliano 

Presentation). 

36PM–10 Raw Data Report Bakersfield Golden 

2000–2006, EPA AQS Database, July 30, 2007. 

37PM–10 Raw Data Report Oildale 2000–2006, 

EPA AQS Database, July 26, 2007. 

38NED for September 22, 2006 at 32–33. 

39 Id. at 32, Figure 13. 

40 Id. 

41Magliano Presentation. 

42NED for September 22, 2006 at 9. 

43 Id. at 32. 

44 69 FR 30006, 30035 (May 26, 2004); 71 FR 7683 

(February 14, 2006). 

45NED for September 22, 2006 at 45–46. 

PM–10 concentrations exceeded a level 

of 100 μg/m3 only three times during the 

month of September for a seven year 

period, i.e, when we look at the 59 

samples collected during the September 

for the past seven years, a concentration 

greater than 100 μg/m3 occurred only 

five percent of the time.34 Exceedances 

of the NAAQS have occurred twice in 

September, which is less than four 

percent of the days sampled. 

Comparisons for the month of 

September are more relevant than for 

the entire year because September has 

the highest concentration of dust but 

does not typically have the highest PM–

10 concentrations, which occur in the 

winter season. Dust is typically less 

than 50% of the PM–10 during 

September.35 During the winter season 

nitrates are the largest contributor, 

particularly in the southern part of the 

central valley. 

For Bakersfield, which utilizes a FRM 

operating on a once-in-every-six-days 

schedule, 413 samples were collected 

since the year 2000. During this time the 

NAAQS was exceeded three times. 

Again, when we look at data collected 

during the September months from 2000 

to 2006, only one day out of 33 days 

sampled recorded a level greater than 

100 μg/m3 (128 μg/m3 on September 18, 

2003), three percent of the time.36

For Oildale, also operating a FRM on 

a once-every-six-days schedule, 432 

samples were collected from 2000 to 

2006. The PM–10 NAAQS was exceeded 

once during this seven-year period. 

During the September months, only one 

day out of 35 days sampled recorded a 

level greater than 100 μg/m3 (111 μg/m3

on September 14, 2006), less than three 

percent of the time.37

d. Did the State demonstrate that there 

would have been no exceedance ‘‘but 

for’’ the event? 

As discussed above, to qualify as an 

exceptional event the state must also 

demonstrate that there would have been 

no exceedance ‘‘but for’’ the event. 40 

CFR 50.14 (c)(3)(iii)(D). To meet this 

‘‘but for’’ criterion, states must include 

analyses to demonstrate that an 

exceedance or violation would not have 

occurred but for the event. Such 

analyses do not require a precise 

estimate of the estimated air quality 

impact from the event. 72 FR at 13570. 

To meet this ‘‘but for’’ criterion, the 

State first shows that there were no 

unusual activities occurring in the 

affected areas in the Valley on 

September 22, 2006 that could have 

resulted in the exceedances. 

Specifically, based on information from 

District field staff and discussions with 

representatives of agricultural and 

industrial operations in the Valley, 

anthropogenic emissions were 

approximately constant in the Valley 

immediately before, during and after the 

event. The State indicates that there 

were PM–10 generating activities, such 

as agricultural and construction 

operations, in the area of Lemoore on 

the morning of September 22, 2006. 

These types of activities are typical for 

the area.38

The State next indicates that the 

greatest fraction of PM–10 at the 

Corcoran and Bakersfield sites on 

September 22 consisted of particles in 

the size fraction between PM–10 and 

PM–2.5.39 This information indicates 

that geologic dust, as opposed to 

secondary PM or PM from combustion 

sources, was the primary contributor to 

the exceedances. The fraction of coarse 

particles at Corcoran and Bakersfield on 

September 22 was 89% and 79% 

respectively.40 These values must be 

compared to the typical geologic values 

for the Valley during September of 

approximately 30 μg/m3 which are less 

than 50% of the measured PM–10.41

Based on the reported 89% value, the 

estimated geologic material for Corcoran 

was approximately 190 to 230 μg/m3 for 

September 22, 2006. The corresponding 

values for Bakersfield were 123–134 μg/ 

m3. Compared to the typical September 

value of approximately 30 μg/m3, the 

September 22, 2006 values represent an 

excess geologic contribution of 

approximately 160 to 200 μg/m3 for 

Corcoran and approximately 94 to 104 

for Bakersfield. If the typical value of 30 

μg/m3 were used instead of the high 

estimated geologic values derived from 

the PM–10–2.5 size fraction, the 

resulting ‘‘adjusted’’ PM–10 values for 

Corcoran and Bakersfield would be 50–

65 μg/m3. This result favorably 

compares to the typical average 

September concentration of less than 60 

μg/m3. Allowing for a PM–10 geologic 

value of 60 μg/m3, which is twice the 

September norm, would only yield an 

‘‘adjusted’’ concentration of 84 to 96 μg/ 

m3. All of these sets of adjusted values 

for September 22 are consistent with the 

aforementioned historical September 

levels which rarely exceeded 100 μg/m3, 

showing that very few days in 

Bakersfield and Corcoran over the 

period 2000–2006 exceeded the level of 

100 μg/m3. 

In addition, the NED for September 

22, 2006 includes Table 2 that lists the 

PM–10 24-hour average concentrations 

recorded using continuous analyzers for 

the days immediately preceding and 

after September 22, 2006.42 This table 

indicates that 24-hour average PM–10 

concentrations at Corcoran were over 

100% higher on September 22 as 

compared to September 20, 21, 23, and 

24. At Bakersfield, concentrations on 

September 22 were over 100% higher 

than on September 20 and September 24 

and 86% higher than on September 21. 

Compared to September 23 the increase 

was 14%. 

Finally, as discussed above, there 

were reasonable and appropriate 

measures in place to control PM–10 in 

the SJV on September 22, 2006, 

Regulation VIII and Rule 4550.43

Moreover, EPA has approved the 

District’s BACM demonstration for all 

significant sources of PM–10 in the SJV 

as meeting CAA section 189(b)(1)(B).44

Furthermore, District staff performed 46 

inspections in the Valley on September 

22 to ensure that regulated sources were 

complying with the District’s fugitive 

dust rules.45 The District’s Natural 

Events Action Plan, discussed below, 

also addresses the reasonable and 

appropriate measures that the District 

has implemented to address high wind 

events in the SJV. 

Based on the weight of evidence 

presented, EPA concludes that the 

State’s documentation demonstrates that 

the exceedances at Corcoran, and 

Bakersfield and Oildale on September 

22, 2006 would not have occurred but 

for the wind event on this day. 

3. Mitigation Requirements 

Under 40 CFR 51.930, a state 

requesting to exclude air quality data 

due to exceptional events must take 

appropriate and reasonable actions, 

including public notification, public 

education, and implementation of 

measures, to protect public health from 

exceedances or violations of the 

NAAQS. 

The SJVAPCD adopted the ‘‘Natural 

Events Action Plan for High Wind 

Events in the San Joaquin Valley Air 


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46The District operates Tapered Element 

Oscillating Microbalance (TEOM) continuous 

automated analyzers at these two sites in addition 

to the manual high-volume Federal Reference 

Method (FRM) monitors. The FRMs operate at a less 

than everyday schedule, as allowed by EPA 

regulations, but neither of the FRM monitors was 

operating on October 25, 2006. The District operates 

the continuous analyzers so that they may report 

daily PM–10 air quality data to the public. 

Basin’’ (NEAP) on February 16, 2006. 

The NEAP provides the SJVAPCD’s 

approach to forecasting high wind 

events, notifying the public prior to the 

event and educating the public on how 

to minimize exposure during high wind 

events. The document also discusses 

measures that are in place to help 

minimize exposure to elevated PM–10 

levels. EPA believes that the detailed 

processes and measures described in the 

NEAP satisfy the mitigation 

requirements under 40 CFR 51.930. 

a. Provide for Prompt Public 

Notification of Exceedance Events 

Section 6 of the NEAP provides the 

meteorological forecasting criteria that 

the SJVAPCD uses to determine whether 

or not to declare NEAP episodes. When 

the criteria indicate that a NEAP 

episode should be declared, the 

SJVAPCD has a public notification 

program, discussed in Section 7 of the 

NEAP, which involves informing the 

local media, SJVAPCD staff and 

community groups. 

b. Provide for Public Education on How 

To Minimize Exposure 

Section 7 of the NEAP provides a list 

of precautions that can be taken to limit 

exposure during a NEAP episode. The 

list includes keeping windows shut, 

using air conditioners or heaters on the 

recycle/recirculating air mode, limiting 

strenuous activity, and other 

precautions. Section 8 of the NEAP 

discusses the SJVAPCD’s general public 

outreach program on NEAP episodes 

which includes developing and 

providing a brochure and information 

about NEAP episodes by means of 

community events, health fairs, schools 

and civic engagements. 

c. Provide for the Implementation of 

Appropriate Measures To Protect the 

Public 

Section 10 of the NEAP discusses the 

SJVAPCD’s measures that reduce PM–10 

emissions. These measures, including 

those approved by EPA as BACM for the 

SJV, in combination with the 

SJVAPCD’s process for declaring NEAP 

episodes and educating the public on 

how to minimize their exposure during 

a NEAP episode, meet the requirements 

for appropriate measures to protect the 

public during high wind exceptional 

events. 

Conclusion 

EPA believes that the high winds in 

the area of Lemoore on September 22, 

2006 were an exceptional event as 

defined in 40 CFR 50.1(j). EPA also 

believes that the State has provided a 

sufficient weight of evidence 

demonstration to show that these high 

winds generated and transported PM–10 

from the area of Lemoore to Corcoran, 

causing an exceedance of the 24-hour 

PM–10 NAAQS. Winds between 

Corcoran and the Bakersfield area were 

sufficient to transport the dust that 

originated in the Lemoore area such that 

they caused the monitors at BakersfieldGolden State Highway and Oildale to 

also exceed the NAAQS. The 

documentation submitted by the State 

demonstrates that but for the high winds 

in the area of Lemoore, the Corcoran, 

Bakersfield and Oildale monitors would 

not have exceeded the 24-hour PM–10 

NAAQS on September 22, 2006. 

Because EPA believes that the State has 

satisfied the provisions of the 

Exceptional Events Rule, EPA proposes 

to concur with the State’s request to flag 

these exceedances as being due to 

exceptional events and to exclude the 

data from consideration in determining 

whether the area has attained the PM–

10 standard. 

B. October 25, 2006 Exceedances at 

Corcoran and Bakersfield 

On October 25, 2006, the SJV 

recorded exceedances of the 24-hour 

PM–10 NAAQS at two sites, Corcoran 

and Bakersfield-Golden State Highway, 

using continuous PM–10 analyzers 

designated as FEM monitors.46 The 24- 

hour average concentrations recorded 

were 304 μg/m3 at Corcoran and 193 μg/ 

m3 at Bakersfield-Golden State 

Highway. The conditions that 

contributed to these exceedances were 

very similar to those that occurred on 

September 22, 2006. Based on the 

evidence submitted, EPA agrees with 

the State’s demonstration that high 

wind-entrained dust from the central 

and southern SJV caused the 

exceedances at the two monitoring 

locations on October 25, 2006. 

1. Procedural Requirements 

a. Data Are Flagged in EPA’s AQS 

Database 

The October 25, 2006 exceedances 

were flagged in EPA’s AQS database as 

of July 2007. 

b. Public Had an Opportunity To 

Review and Comment on the State’s 

Documentation 

In February 2007, the SJVAPCD 

notified the public in local newspapers 

and on its Web site of the availability of 

the document entitled ‘‘Natural Event 

Documentation, High Winds, Corcoran 

and Bakersfield, California, October 25, 

2006,’’ SJV Unified Air Pollution 

Control District, February 2007 and 

requested public comments by March 5, 

2007. 

The SJVAPCD subsequently revised 

the February 2007 document and 

submitted to CARB the ‘‘Natural Event 

Documentation, Corcoran and 

Bakersfield, California, October 25, 

2006,’’ San Joaquin Valley Unified Air 

Pollution Control District, April 23, 

2007 (NED for October 25, 2006), and 

posted it on its Web site. 

The SJVAPCD indicated that no 

public comments were received during 

its public process. 

c. The Documentation Was Submitted to 

Epa 

The NED for October 25, 2006 was 

submitted by the State to EPA on May 

1, 2007 and is the document upon 

which EPA is basing its evaluation 

below. 

d. EPA Concurs With the State’s 

Demonstration 

In this proposed rule, EPA is 

proposing to concur with the State’s 

demonstration in the NED for October 

25, 2006 that high wind-entrained dust 

caused the exceedances at the two 

monitoring sites. 

2. Technical Criteria 

a. Did this event satisfy the criteria in 

section 50.1(j) of the Rule? 

i. Affected Air Quality 

For an event to qualify as an 

exceptional event, the state must show 

that the event affected air quality. This 

criterion can be met by establishing that 

the event is associated with a measured 

exceedance in excess of normal 

historical fluctuations, including 

background, and there is a causal 

connection between the event and the 

exceedance. The demonstration of a 

clear causal relationship is necessary to 

establish that the event affected air 

quality and is also a separate statutory 

requirement as discussed above. 

In the NED for October 25, 2006, the 

State provides documentation that the 

measured exceedances recorded on 

October 25, 2006 were in excess of 

normal historical fluctuations. See 

subsection c. below. The State also 

establishes a causal connection between 


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47NED for October 25, 2006 at 29. 

48 69 FR at 30035; 71 FR 7683. 

49NED for October 25, 2006 at 29. 

50 Id. at sections 4 and 5. 

51 Id. at 11. 

52 Id. at 22–23. 

53 Id. at 24. 

54NED for October 25, 2006 at 11. 

55 Id. at 12. 

the high winds recorded at Lemoore and 

the high concentrations at the monitors 

recorded at Corcoran and Bakersfield. 

The State’s demonstration of the clear 

causal relationship between the 

exceptional event and the exceedances 

on this day is discussed in greater detail 

in subsection b. below. 

ii. Not Reasonably Controllable or 

Preventable 

Section 50.1(j) requires that for an 

event to qualify as an exceptional event, 

whether natural or anthropogenic, a 

state must show that the event was not 

reasonably preventable or controllable. 

Here this requirement is met by 

demonstrating that despite reasonable 

and appropriate measures in place, the 

October 25, 2006 wind event caused the 

exceedances. During this event, there 

were no other unusual dust-producing 

activities occurring in the SJV and 

anthropogenic emissions were 

approximately constant before, during 

and after the event. In addition, the 

State showed that reasonable and 

appropriate measures were in place, 

including Regulation VIII (the District’s 

general fugitive dust rules) and Rule 

4550 which limits fugitive dust 

emissions specifically from agricultural 

operations through Conservation 

Management Practices.47 Moreover, EPA 

has approved the District’s BACM 

demonstration for all significant sources 

of PM–10 in the SJV as meeting CAA 

section 189(b)(1)(B).48

iii. Was a Natural Event 

In the preamble to the Exceptional 

Events Rule, EPA states that ambient 

particulate matter concentrations due to 

dust being raised by unusually high 

winds will be treated as due to 

uncontrollable natural events where (1) 

the dust originated from 

nonanthropogenic sources, or (2) the 

dust originated from anthropogenic 

sources within the State, that are 

determined to have been reasonably 

well-controlled at the time that the 

event occurred, or from anthropogenic 

sources outside the State. 72 FR at 

13576. In the preamble EPA also 

explains that ‘‘[s]tates must provide 

appropriate documentation to 

substantiate why the level of wind 

speed associated with the event in 

question should be considered unusual 

for the affected area during the time of 

year that the event occurred.’’ Id. at 

13566. 

The wind-entrained dust on October 

25, 2006 originated from anthropogenic 

sources within California, i.e., from 

usual dust-generating activities such as 

agricultural and industrial operations.49

We discuss the fugitive dust control 

measures in place in the SJV on October 

25 above. 

With respect to the wind speed, EPA 

concurs with the State’s demonstration 

that the wind speeds in the central SJV 

were unusually high on October 25, 

2006.50 Table 1 of the NED for October 

25, 2006 lists the wind speeds in the 

Hanford and Lemoore areas. The peak 

hourly averaged winds were in the 

range of 29 to 31 mph at Lemoore, with 

gusts reaching 40 mph. Peak hourly 

winds at Hanford were lower, in the 

range of 17 to 18 mph, but still in line 

with the threshold wind speed of 17.8 

mph. Hanford also recorded peak gusts 

of 22 to 30 mph during the 10 a.m. to 

12 noon period.51 Tables 8, 9, and 11 of 

the NED for October 25, 2006 also 

include information on wind speeds 

throughout the central valley of 

California and the central and southern 

SJV.52 The documentation also states 

that wind speeds of these intensities are 

relatively rare in the southwestern part 

of the SJV and occur less than 5% of the 

time, based on long-term monitoring 

records.53

EPA concurs with the State’s 

demonstration in the NED for October 

25, 2006 that the wind speeds occurring 

in the central SJV were unusually high 

on October 25, 2006. While the winds 

at Corcoran were not as high as those in 

Lemoore and Hanford, as described in 

the State’s documentation, the winds at 

Corcoran during the peak hourly PM–10 

concentrations (8 a.m. to 11 a.m.) ranged 

from 10 to 13 mph, which are unusual 

for this time of year in that area. These 

wind speeds, though not sufficient to 

erode dust, were sufficient to keep the 

entrained and transported dust from the 

high winds at Lemoore suspended for 

the period during which the 

exceedances occurred. 

iv. Determined by EPA To Be an 

Exceptional Event 

Finally, EPA must determine through 

the process established in the 

Exceptional Events Rule whether an 

exceptional event occurred. We believe 

that the State has met the procedural 

requirements of the Rule including 

flagging of the data, submission of 

demonstration, evidence of the public 

opportunity to review and comment on 

the demonstration and mitigation 

requirements as discussed at section 

V.B.1. and 3. of this proposed rule. We 

further believe that the State has also 

met the technical criteria of the Rule as 

discussed at section V.B.2. of this 

proposed rule. Therefore we are 

proposing to concur with the State’s 

determination that an exceptional event, 

i.e., a high wind event, occurred 

resulting in the exceedances on October 

25, 2006. 

b. Does the State’s documentation show 

a clear causal connection between the 

exceedances and the claimed 

exceptional event? 

Under 40 CFR 50.14(c)(3)(iii)(B), a 

state’s demonstration must establish a 

clear causal relationship between the 

measured exceedances and the claimed 

exceptional event. In addressing this 

requirement for the October 25, 2006 

exceedances, the NED for October 25, 

2006 submitted by the State identifies 

the area northwest of Corcoran as the 

source of PM–10 during the October 25, 

2006 event. Winds in the Lemoore area 

were again in excess of the threshold 

wind speed for eroding and entraining 

dust as discussed above. Table 1 of the 

NED for October 25, 2006 shows a clear 

correlation between the wind speeds in 

the Hanford and Lemoore areas and the 

increased hourly concentrations at 

Corcoran.54 In fact the peak wind speeds 

at Lemoore and Hanford, which 

occurred between 10 a.m. and 12 noon 

at Lemoore, coincide with the peak 

hourly concentrations at Corcoran. The 

peak hourly averaged winds were in the 

range of 29 to 31 mph at Lemoore, with 

gusts reaching 40 mph. Peak hourly 

winds at Hanford were lower, in the 

range of 17 to 18 mph, but still in line 

with the threshold wind speed of 17.8 

mph. Hanford also recorded peak gusts 

during the 10 a.m. to 12 noon period of 

22 to 30 mph. Figure 2 of NED for 

October 25, 2006 compares the hourly 

wind speed and PM–10 concentration 

data from Corcoran with the hourly 

wind speed data from Lemoore in a 

graphical format.55 This graphic shows 

the almost perfect correlation between 

increased wind speeds at Corcoran and 

Lemoore with the increased PM–10 

hourly concentrations at Corcoran. 

The dust plume that affected the 

Corcoran monitoring site on October 25, 

2006 continued moving south and 

ultimately impacted the continuous 

PM–10 analyzer operating at the 

Bakersfield-Golden State Highway 

monitoring site. The State provides 

information on wind speed and 

direction from the Alpaugh 

meteorological monitoring station, 


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56 Id. at 22–26. 

57 Id. at 58. 

58 Id. at 24–26. 

59 Id. at 14. 

60 Id. at 27. 

61 ‘‘Continuous PM–10 Data Collected with 

TEOMs, Data Reported to EPA’s AIRNOW 

Website,’’ July 30, 2007, Excel Spreadsheet, Bob 

Pallarino. 

62Corcoran exceeded the 24-hour NAAQS on 

October 29, 2002 with a value of 168 μg/m3; PM–

10 Raw Data Reports, Corcoran 2000–2006 and 

Bakersfield-Golden 2000–2006. 

63NED for October 25, 2006 at 7 and 29. 

64 Id. at 35. 

65 Id. at 28. 

66Magliano Presentation. 

located between Corcoran and 

Bakersfield about 16 miles south 

southeast of the Corcoran monitoring 

site.56 Between the hours of 9 a.m. and 

4 p.m., wind speeds at Alpaugh 

averaged about 12 mph.57 Since the 

meteorological data measured at 

Alpaugh is taken at 2 meters Above 

Ground Level (AGL), the average wind 

speed at 10 meters AGL is about 15 

mph.58 EPA believes this average wind 

speed would have been sufficient to 

keep the dust plume suspended, and 

that it facilitated the transport of the 

dust plume to the Bakersfield area. 

The data in Table 1 of the NED for 

October 25, 2006 show the Bakersfield 

hourly PM–10 concentrations beginning 

to exceed the level of the 24-hour PM–

10 NAAQS at 11 a.m. (177 μg/m3) and 

peaking between the hours of 2 p.m. and 

5 p.m. (415 μg/m3 and 416 μg/m3, 

respectively). Figure 4 provides a graph 

of PM–10 hourly concentrations for 

three continuous PM–10 analyzers 

operated by the District at Corcoran, 

Bakersfield-Golden State Highway, and 

Tracy.59 The graph shows hourly PM–

10 concentrations at Bakersfield-Golden 

State Highway slowly increasing 

through the morning hours of October 

25 until 8 a.m. Hourly concentrations 

increase at a higher rate between 8 a.m. 

and 1 p.m., mirroring the increase at 

Corcoran, but not as dramatic. As the 

Corcoran hourly concentrations are 

dropping between 11 a.m. 4 p.m. we see 

a corresponding sharp increase in 

hourly concentrations at BakersfieldGolden State Highway. This behavior of 

the hourly concentrations supports the 

State’s explanation that the dust plume 

that first affected Corcoran traveled 

south over a period of several hours and 

then impacted the Bakersfield monitor. 

As with the September 22, 2006 

event, the State includes for the October 

25, 2006 event the results of a basic 

meteorological model known as the 

Hybrid Single-Particle Lagrangian 

Integrated Trajectory model 

(HYSPLIT).60 It is important to note that 

while this modeling is not meant to 

quantify the particle concentration 

recorded in the Bakersfield area, it does 

support the State’s demonstration that 

the winds on October 25, 2006 were of 

the appropriate intensity and direction 

to move a plume of dust from the 

central SJV to the Bakersfield area. 

c. Did the State demonstrate that the 

event is associated with measured 

concentrations in excess of normal 

historical fluctuations including 

background? 

For EPA to concur with a state’s claim 

that an exceptional event caused an 

exceedance, one of the requirements 

that the state must meet is to show that 

the event is associated with 

concentrations that are beyond the 

normal historical fluctuations. See 40 

CFR 50.14(c)(3)(iii)(C). 

The State provides data on PM–10 

levels on the days before and after 

October 25, 2006. PM–10 concentrations 

before and after October 25, 2006 were 

significantly lower than the 

concentration recorded on October 25, 

2006. An EPA review of continuous 

PM–10 data from Corcoran and 

Bakersfield-Golden State Highway 

showed that 24-hour average 

concentrations from October 1, when 

the TEOM continuous analyzers began 

reporting data, through October 24 did 

not exceed 100, and while there were a 

number of higher concentrations on the 

days after October 25, not counting the 

exceedances recorded on December 8, 

2006, which are discussed further below 

in subsection d, the PM–10 

concentrations at Corcoran and 

Bakersfield-Golden State Highway fell 

to mostly less than 100 again from 

October 28 through June 30, 2007.61

Historically we can compare data 

from these continuous analyzers only 

with the separate manual FRM samplers 

operated at the sites. When we look at 

typical PM–10 concentrations recorded 

in the month of October from 2000 to 

2006 the maximum value recorded at 

Bakersfield was 116 μg/m3 measured on 

October 16, 2001 and the maximum 

non-exceedance value recorded at 

Corcoran was 150 μg/m3 measured on 

October 31, 2006.62 These 

concentrations indicate that the 

exceedances recorded on October 25, 

2006 were unusual and not 

representative of typical high 

concentrations recorded at these 

monitoring locations. 

d. Did the State demonstrate that there 

would have been no exceedance ‘‘but 

for’’ the event? 

As discussed previously, to qualify as 

an exceptional event the State must also 

demonstrate that there would have been 

no exceedance ‘‘but for’’ the event. 40 

CFR 50.14(c)(3)(iii)(D). To meet this 

‘‘but for’’ requirement, the state must 

include analyses to demonstrate that an 

exceedance or violation would not have 

occurred but for the event. Such 

analyses do not require a precise 

estimate of the estimated air quality 

impact from the event. 72 FR at 13570. 

To meet this ‘‘but for’’ requirement 

the State first shows that there were no 

unusual activities occurring in the 

affected areas in the Valley that could 

have resulted in the exceedances. 

Specifically, based on information from 

District field staff and discussions with 

representatives of agricultural and 

industrial operations in the Valley, 

anthropogenic emissions were 

approximately constant in the Valley 

immediately before, during and after the 

event. The District staff observed no 

unusual emissions other than those 

associated with the wind event. The 

PM–10 generating activities were 

BACM-controlled sources that are usual 

for the area.63 District staff conducted 90 

inspections throughout the SJV on 

October 25 to ensure sources were in 

compliance with District air pollution 

rules.64

The State notes in the NED for 

October 25, 2006 that the PM–2.5 to 

PM–10 ratio on this day was very low, 

which indicates that mostly coarse PM 

was present on the filter, supporting its 

claim that the concentrations recorded 

on this day were affected by a blowing 

dust event.65

When we examine the typical makeup of PM–10 in the SJV during October 

we generally see particle concentrations 

that are mostly in the size fraction of 

PM–2.5, roughly 60–65%, with the 

remaining mass being particles in the 

PM–10–2.5 size fraction.66 Typically, 

fugitive dust is the major constituent of 

the PM–10–2.5 size fraction and makes 

up about 25 to 35% of the total PM–10. 

When we look at a comparison of PM–

2.5 and PM–10 concentrations recorded 

on October 25, 2006, we find that the 

PM–10–2.5 portion of the total PM–10 

represents about 93% of the total PM–

10 at Corcoran and 85 percent of total 

PM–10 at Bakersfield. This high 

percentage of PM–10–2.5, which is 

mostly fugitive dust, is atypical for this 

time of year and supports the State’s 

demonstration that the PM–10 

concentrations on this day consisted of 

mostly coarse geologic material. 

We can also look at the days 

immediately preceding and following 


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

68 Id. at 29. 

69 69 FR at 30035; 71 FR 7683. 

70NED for October 25, 2006 at 35. 

the exceedance day to see if the 

concentrations on October 25 were 

unusual. The PM–10 concentrations 

recorded on October 25 at Corcoran and 

Bakersfield were over three times higher 

than they were on October 24.67 PM–10 

concentrations after the event decreased 

dramatically and by October 28, PM–10 

concentrations at both sites were below 

100. See also the discussion of the 

historical levels at these monitors set 

forth in subsection c. above, which 

further demonstrates that the 

concentrations recorded on October 25 

were unusual. 

Finally, as discussed above, there 

were reasonable and appropriate 

measures in place to control PM–10 in 

the SJV on October 25, 2006, Regulation 

VIII and Rule 4550.68 Moreover, EPA 

has approved the District’s BACM 

demonstration for all significant sources 

of PM–10 in the SJV as meeting CAA 

section 189(b)(1)(B).69 Section 9.2 of the 

NED for October 25, 2006 indicates that 

the District staff performed 90 

inspections on that date to ensure that 

regulated sources were complying with 

District fugitive dust rules.70 The 

District’s Natural Events Action Plan, 

discussed in section V.A.3. above, also 

addresses the reasonable and 

appropriate measures that the District 

has implemented to address high wind 

events in the SJV. 

Based on the weight of evidence 

presented, EPA concludes that the 

State’s documentation demonstrates that 

the exceedances at Corcoran and 

Bakersfield on October 24, 2006 would 

not have occurred but for the wind 

event on this day. 

3. Mitigation Requirements 

See section V.A.3. above. 

Conclusion 

EPA believes that the high winds in 

the area of Lemoore on October 25, 

2006, were an exceptional event as 

defined in 40 CFR 50.1(j). EPA also 

believes that the State has provided a 

sufficient weight of evidence 

demonstration to show that these high 

winds generated and transported PM–10 

from the area of Lemoore to Corcoran, 

causing an exceedance of the 24-hour 

PM–10 NAAQS. Winds between 

Corcoran and the Bakersfield area were 

sufficient to transport the dust that 

originated in the Lemoore area such that 

they caused the monitor at BakersfieldGolden State Highway to also exceed 

the NAAQS. The documentation 

submitted by the State demonstrates 

that but for the high winds in the area 

of Lemoore, the Corcoran and 

Bakersfield monitors would not have 

exceeded the 24-hour PM–10 NAAQS 

on October 25, 2006. Because EPA 

believes the State has satisfied the 

provisions of the Exceptional Events 

Rule, EPA proposes to concur with the 

State’s request to flag these exceedances 

as being due to exceptional events and 

to exclude the data from consideration 

in determining whether the area has 

attained the PM–10 standard. 

C. December 8, 2006 Exceedances at 

Corcoran and Bakersfield 

The SJV recorded exceedances of the 

24-hour PM–10 NAAQS on December 8, 

2006 at two sites, Corcoran and 

Bakersfield-Golden State Highway, 

using continuous PM–10 analyzers 

designated as FEM monitors. The 24- 

hour average PM–10 concentrations 

recorded were 162 μg/m3 at Corcoran 

and 213 μg/m3 at Bakersfield-Golden 

State Highway. 

The State demonstrates that unusually 

high winds in the Bakersfield area 

eroded and entrained dust that 

impacted the continuous PM–10 

analyzer at Bakersfield. Unlike 

September 22 and October 25, 2006, the 

winds in the SJV on this day were 

generally from the southwest, south and 

southeast, transporting dust northward 

and ultimately impacting the 

continuous PM–10 analyzer at Corcoran. 

Based on the evidence submitted, EPA 

agrees with the State’s demonstration 

that high wind-entrained dust caused 

the exceedances at the two monitoring 

locations on December 8, 2006. 

1. Procedural Requirements 

a. Data Are Flagged in EPA’s AQS 

Database 

The December 8, 2006 exceedances 

were flagged in EPA’s AQS database as 

of July 2007. 

b. Public had an opportunity to review 

and comment on the State’s 

documentation 

In February 2007, the SJVAPCD 

notified the public in local newspapers 

and on its Web site of the availability of 

the document entitled ‘‘Natural Event 

Documentation, High Winds, Corcoran 

and Bakersfield, California, December 8, 

2006,’’ SJV Unified Air Pollution 

Control District, February 2007 and 

requested public comments by March 5, 

2007. 

The SJVACPD subsequently revised 

the February 2007 document and 

submitted to the California Air 

Resources Board (CARB) the ‘‘Natural 

Event Documentation, Corcoran and 

Bakersfield, California, December 8, 

2006,’’ SJV Unified Air Pollution 

Control District, May 23, 2007 and 

posted it on its Web site. 

SJVAPCD thereafter made revisions 

per CARB’s request and submitted to 

CARB the ‘‘Natural Event 

Documentation, Corcoran and 

Bakersfield, California, December 8, 

2006,’’ SJV Unified Air Pollution 

Control District, June 6, 2007 (NED for 

December 8, 2006) and posted it on its 

Web site. 

The District indicated that no public 

comments were received during the 

public process. 

c. The Documentation Was Submitted to 

EPA 

The NED for December 8, 2006 was 

subsequently submitted by the State to 

EPA on June 12, 2007 and is the 

document upon which EPA is basing its 

evaluation below. 

d. EPA Concurs With the State’s 

Demonstration 

In this proposed rule, EPA is 

proposing to concur with the State’s 

demonstration in the NED for December 

8, 2006 that high wind-entrained dust 

caused the exceedances at the two 

monitoring locations on December 8, 

2006. 

2. Technical Criteria 

a. Did this event satisfy the criteria in 

section 50.1(j) of the Rule? 

As with the previous events discussed 

in this proposed rule, the State needs to 

show that this event, identified in the 

NED for December 8, 2006 as unusually 

high winds, affected air quality in the 

Corcoran and Bakersfield areas, was not 

reasonably controllable or preventable, 

was a natural event, and is determined 

by EPA to be an exceptional event. 

i. Affected Air Quality 

For an event to qualify as an 

exceptional event, the state must show 

that the event affected air quality. This 

criterion can be met by establishing that 

the event is associated with a measured 

exceedance in excess of normal 

historical fluctuations, including 

background and there is a causal 

connection between the event and the 

exceedance. This demonstration of a 

causal connection is necessary to 

establish that the event affected air 

quality and is also a separate statutory 

requirement as discussed above. 

In the NED for December 8, 2006, the 

State provides documentation that these 

measured exceedances were in excess of 

normal historical fluctuations. See 

subsection c. below. The State also 

establishes a causal connection between 


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71NED for December 8, 2006 at 25. 

72 69 FR at 30035; 71 FR 7683. 

73NED for December 8, 2006 at 25. 

74 Id. at 17. 

75 Id. at 11, Table 3. 

76 Id. at 56. 

77 Id. at 11–12. 

78 Id. at 23. 

the high winds recorded in the 

Bakersfield and Southern SJV area and 

the high concentrations recorded at the 

Corcoran and Bakersfield monitors. The 

State’s demonstration of the clear causal 

relationship between the event and the 

exceedances on this day is discussed in 

greater detail in subsection b. below. 

ii. Not Reasonably Controllable or 

Preventable 

Section 50.1(j) of the Exceptional 

Events Rule requires that for an event to 

qualify as an exceptional event, whether 

natural or anthropogenic, a state must 

show that the event was not reasonably 

preventable or controllable. Here this 

requirement is met by demonstrating 

that despite reasonable and appropriate 

measures in place, the December 8, 2006 

wind event caused the exceedances. 

During this event, there were no other 

unusual dust-producing activities 

occurring in the SJV and anthropogenic 

emissions were approximately constant 

before, during and after the event. In 

addition, the State shows that 

reasonable and appropriate measures 

were in place, including Regulation VIII 

(the District’s general fugitive dust 

rules) and Rule 4550 which limits 

fugitive dust emissions specifically from 

agricultural operations through 

Conservation Management Practices.71

Moreover, EPA has approved the 

District’s BACM demonstration for all 

significant sources of PM–10 in the SJV 

as meeting CAA section 189(b)(1)(B).72

iii. Was a Natural Event 

In the preamble to the Exceptional 

Events Rule, EPA states that ambient 

particulate matter concentrations due to 

dust being raised by unusually high 

winds will be treated as due to 

uncontrollable natural events where (1) 

the dust originated from 

nonanthropogenic sources, or (2) the 

dust originated from anthropogenic 

sources within the State, that are 

determined to have been reasonably 

well-controlled at the time that the 

event occurred, or from anthropogenic 

sources outside the State. 72 FR at 

13576. In the preamble EPA also 

explains that ‘‘[s]tates must provide 

appropriate documentation to 

substantiate why the level of wind 

speed associated with the event in 

question should be considered unusual 

for the affected area during the time of 

year that the event occurred.’’ Id. at 

13566. 

On December 8, 2006, the windentrained dust originated from 

anthropogenic sources within 

California, i.e., from usual dustgenerating activities such as agricultural 

and industrial operations.73 We discuss 

the fugitive dust control measures in 

place in the SJV on December 8, 2006 

above. 

With respect to the wind speed, EPA 

concurs with the State’s demonstration 

that the wind speeds in the southern 

SJV were unusually high on December 

8, 2006. The State includes information 

on the unusual nature of the wind 

speeds in the SJV on December 8, 2006, 

stating that winds of these magnitudes 

are rare, occurring less than 5% of the 

time. The NED for December 8, 2006 

reports that during the blowing dust 

event, Bakersfield reported winds up to 

25 mph with gusts up to 35 mph. 

Farther north in the area of Kettleman 

Hills, located on the west side of the 

San Joaquin Valley, gusts up to 50 mph 

were reported. Kettleman Hills also 

reported a twenty-two hour period with 

gusts of 20 mph or greater (from 6 a.m. 

on December 8, 2006 to 4 a.m. on 

December 9, 2006). Maricopa, located 

on the southwest side of the San Joaquin 

Valley approximately 25 miles 

southwest of Bakersfield, reported a 

one-minute average wind speed of 56 

mph.74

iv. Determined by EPA To Be an 

Exceptional Eevent 

Finally, EPA must determine through 

the process established in the 

Exceptional Events Rule whether an 

exceptional event occurred. We believe 

that the State has met the procedural 

requirements of the Rule including 

flagging of the data, submission of 

demonstration, evidence of the public 

opportunity to review and comment on 

the demonstration and mitigation 

requirements as discussed at section 

V.C.1. and 3. of this proposed rule. We 

further believe that the State has also 

met the technical requirements of the 

Rule as discussed at section V.C.2. 

Therefore, we are proposing to concur 

with the State’s determination that an 

exceptional event, i.e., a wind event, 

occurred resulting in the exceedances 

on December 8, 2006. 

b. Does the State’s documentation show 

a clear causal connection between the 

exceedances and the claimed 

exceptional event? 

Under 40 CFR 50.14(c)(3)(iii)(B), a 

state’s demonstration must establish a 

clear causal relationship between the 

measured exceedances and the claimed 

exceptional event. Unlike September 22 

and October 25, 2006, the winds on 

December 8, 2006 were erratic and 

generally from the east, south, and 

southwest.75 Wind speeds at 

meteorological stations near Bakersfield 

recorded hourly average wind speeds in 

excess of 35 mph and wind gusts in 

excess of 50 mph. Winds at Bakersfield 

on December 8 were from both the 

southwest and southeast during the time 

when peak hourly PM–10 

concentrations were recorded. The 

winds continued to blow from the 

southeast up the Valley, pushing the 

dust plume towards the Corcoran 

monitoring site. The peak hours for 

hourly PM–10 concentrations were from 

1 p.m. to 3 p.m. at both the Corcoran 

and Bakersfield sites, with a second set 

of high hourly concentrations at 

Bakersfield occurring from 5 p.m. to 8 

p.m. Winds measured at Alpaugh, 

located between Bakersfield and 

Corcoran, were highest from 12 p.m. to 

4 p.m. and from the southeast, 

supporting the State’s argument that the 

dust plume moved from the southeast to 

northwest.76

Table 3 and Figure 2 of the NED for 

December 8, 2006 77 show the 

correlation of wind speeds and 

increasing hourly concentrations of PM–

10 recorded by the continuous PM–10 

analyzers at Corcoran and Bakersfield. 

Figure 7 of the NED for December 8, 

2006 includes the results of a basic 

meteorological model known as Hybrid 

Single-Particle Lagrangian Integrated 

Trajectory model (HYSPLIT).78 It is 

important to note that while this 

modeling is not meant to quantify the 

particle concentration recorded in the 

Bakersfield and Corcoran areas, it does 

offer support of the State’s 

demonstration that the winds on 

December 8, 2006 were of the 

appropriate intensity and direction to 

move a plume of dust from the 

southeastern SJV to the Bakersfield area 

and northward to Corcoran. 

c. Did the State demonstrate that the 

event is associated with measured 

concentration in excess of normal 

historical fluctuations including 

background? 

For EPA to concur with a state’s claim 

that an exceptional event caused an 

exceedance, one of the requirements 

that the state must meet is to show that 

the event is associated with 

concentrations that are beyond the 

normal historical fluctuations. See 40 

CFR 50.14(c)(3)(iii)(C). 


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79PM–10 Raw Data Report Corcoran 1997–2006, 

EPA AQS Database, July 30, 2007. 

80PM–10 Raw Data Report Bakersfield Golden 

1997–2006, EPA AQS Database, July 30, 2007. 

81NED for December 8, 2006 at 25. 

82 Id. at 28–29, Figures 8 and 9. 

83Magliano Presentation. 

84NED for December 8, 2006 at Table 1. 

85 Id. at 25. 86 69 FR at 30035; 71 FR 7683. 

As with the discussion above on the 

September 22 and October 25, 2006 

exceedances, we can compare data from 

the continuous analyzers only with the 

separate manual FRM samplers operated 

at the sites, since the continuous 

analyzers have only been in operation 

since late 2006. Figures 8 and 9 of the 

NED for December 8, 2006 demonstrate 

the relative infrequency, over the last 10 

years, of the concentrations recorded at 

Corcoran and Bakersfield on December 

8, 2006. When we look at PM–10 FRM 

concentrations recorded at Corcoran in 

the month of December from 1997 to 

2006, the last non-flagged exceedance of 

the standard was a 174 recorded on 

December 17, 1999.79 Levels exceeding 

100 only occurred 10 times in December 

in the past 10 years, out of 96 FRM days 

sampled. Even when we include the 

continuous daily data collected at 

Corcoran in 2006, there are only the 10 

values over 100 described above. 

For Bakersfield, the last non-flagged 

day exceeding the standard in December 

was 159 recorded on December 30, 

1998. Of the 42 December FRM sample 

days since 1997, 9 days exceed 100. 

Again, even when we include the 

continuous daily data from 2006, the 

result remains 9 days exceeding 100 in 

the last 10 years.80

d. Did the State demonstrate that there 

would have been no exceedance ‘‘but 

for’’ the event? 

As discussed above, to qualify as an 

exceptional event the state must also 

demonstrate that there would have been 

no exceedance ‘‘but for’’ the event. 40 

CFR 50.14(c)(3)(iii)(D). To meet this 

‘‘but for’’ requirement, the state must 

include analyses to demonstrate that an 

exceedance or violation would not have 

occurred but for the event. Such 

analyses do not require a precise 

estimate of the estimated air quality 

impact from the even. 72 FR at 13570. 

To meet this ‘‘but for’’ requirement 

the State first shows that there were no 

unusual activities occurring in the 

affected areas in the Valley that could 

have resulted in the exceedances. 

Specifically, based on information from 

District field staff and discussions with 

representatives of agricultural and 

industrial operations in the Valley, 

activities that generate anthropogenic 

PM–10 were approximately constant in 

the Valley immediately before, during 

and after the event. As on September 22 

and October 25, 2006, activity levels in 

the SJV were typical for the time of year 

and PM–10 emission control programs 

were being implemented, not only for 

fugitive dust-generating activities, but 

also agricultural burning and residential 

wood combustion in parts of the SJV.81

The State provides frequency 

distributions of the maximum PM–10 

24-hour December concentrations for 

the past 10 years. These figures indicate 

that PM–10 concentrations at Corcoran 

and Bakersfield-Golden State Highway 

rarely exceeded the level of the 24-hour 

PM–10 NAAQS.82 This fact is an 

indication that December 8, 2006 was 

unusual in that the normal emission 

activity levels do not cause 

exceedances, based on historical data. 

Examining the make-up of PM–10 on 

this day using PM–2.5 data collected at 

the sites with a continuous PM–2.5 

analyzer, we can see that coarse 

particles, or PM–10–2.5, which are 

associated with windblown dust, 

represented 78% of the total PM–10 

mass collected at Corcoran and 88% of 

the total PM–10 mass at Bakersfield. 

CARB studies indicate that at this time 

of year, fugitive dust generally 

contributes less than 20% of the total 

PM–10 mass.83 The atypical 

contribution of fugitive dust to the 

exceedances recorded on December 8, 

2006 indicates that but for the wind 

event these exceedances would not have 

occurred. 

As discussed above, the State also 

looked at data from the days 

immediately preceding and after 

December 8, 2006.84 Twenty-four hour 

PM–10 concentrations on December 4–

6 were less than 100 μg/m3 at both sites 

and were just over 100 μg/m3 on 

December 7. On December 8, the 

concentration at Corcoran increased by 

more than 50%, exceeding the NAAQS 

with a level of 162 μg/m3, but then fell 

to 32 μg/m3 on December 9 and 

continued dropping for weeks after this 

event. At Bakersfield, on December 8 

there was a greater than 100% increase 

over the December 7 concentration. 

Again, concentrations dropped 

dramatically on December 9 and 

remained low for weeks after. 

Finally, as discussed above, there 

were reasonable and appropriate 

measures in place to control PM–10 in 

the SJV on December 8, 2006, 

Regulation VIII and Rule 4550.85

Moreover, EPA has approved the 

District’s BACM demonstration for all 

significant sources of PM–10 in the SJV 

as meeting CAA section 189(b)(1)(B).86

The District’s Natural Events Action 

Plan, discussed in section V.A.3. above, 

also addresses the reasonable and 

appropriate measures that the District 

has implemented to address high wind 

events in the SJV. 

Based on the weight of evidence 

presented, EPA concludes that the 

State’s documentation demonstrates that 

the exceedances at Corcoran and 

Bakersfield on December 8, 2006 would 

not have occurred but for the wind 

event on this day. 

3. Mitigation Requirements 

See section V.A.3.c above. 

Conclusion 

EPA believes that the high winds in 

the southeastern SJV on December 8, 

2006 were an exceptional event as 

defined in 40 CFR 50.1(j). EPA also 

believes that the State has provided a 

sufficient weight of evidence 

demonstration to show that these high 

winds generated and transported PM–10 

from the area of Bakersfield to Corcoran 

causing exceedances of the 24-hour PM–

10 NAAQS at the Bakersfield and 

Corcoran monitors. The NED for 

December 8, 2006 submitted by the 

State demonstrates that but for the high 

winds in the southern SJV, the Corcoran 

and Bakersfield monitors would not 

have exceeded the 24-hour PM–10 

NAAQS on December 8, 2006. Because 

EPA believes that the State has satisfied 

the provisions of the Exceptional Events 

Rule, EPA proposes to concur with the 

State’s request to flag these exceedances 

as due to exceptional events and to 

exclude the data from consideration in 

determining whether the area has 

attained the PM–10 standard. 

VI. EPA Evaluation of September 14, 

September 20 and October 26, 2006 

Exceedances at the Santa Rosa 

Rancheria 

The 24-hour PM–10 NAAQS was 

exceeded on September 14, 20 and 

October 26, 2006 at a monitor on the 

Santa Rosa Rancheria (SRR), tribal land 

located in Kings County within the SJV. 

The 24-hour average PM–10 

concentrations were 190 μg/m3, 158 μg/ 

m3, and 157 μg/m3, respectively. The 

SRR Tribe flagged the exceedances as 

caused by an exceptional event, i.e., 

construction activities. 

The Santa Rosa Rancheria EPA 

Department (SRREPA) operates a 

monitoring site on the SRR, located on 

the roof of a pumping station at the 

SRR’s water treatment facility. The PM–

10 sampler is a high volume size 


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87 July 18, 2007 Memorandum, ‘‘On-Site Visit to 

Santa Rosa Rancheria,’’ from Bob Pallarino, EPA, to 

Sean Hogan, EPA (Site Visit Memorandum). 

88Site Visit Memorandum. 

89AQS Raw Data Report, Santa Rosa Rancheria 

PM–10 2006 to 2007. 90Site Visit Memorandum. 

selective inlet (SSI) Anderson sampler 

designated as a FRM by EPA. The 

monitoring site also measures ozone and 

meteorological parameters including 

wind speed and wind direction. 

The PM–10 sampler is located near 

the northeast corner on the roof of the 

pumping station. The current land cover 

around the pump station is paved 

parking. There are no obstructions of 

any kind and there is unrestricted 

airflow 360 degrees around the sampler 

inlet.87

To the east of the monitor is a paved 

parking lot, beginning about 25 feet east 

of the monitor location and extending 

approximately 50 feet to the east. 

Beyond the parking area are trailers and 

undeveloped land. To the north of the 

monitor is a larger parking lot, 

beginning about 100 feet north of the 

monitor location and extending north 

approximately 525 feet. Beyond the 

parking lot are a casino hotel, casino, 

and additional parking lots. To the 

immediate south (150 feet) and west 

(300 feet) are the remaining physical 

plant facilities (tanks, pumps, etc.) and 

the area is paved. Further south and 

west are agricultural fields (currently 

alfalfa). Agricultural fields also lie to the 

north beyond the casino and parking lot 

(approximately 0.5 mile). To the east is 

the SRR residential area. 

PM–10 is measured once-in-every-six 

days by the SRREPA according to the 

national sampling schedule. Sampling 

began on August 3, 2006 and continues 

to the present time. 

In 2006 there was a major 

construction project at the SRR, which 

involved construction of a casino hotel 

and associated parking lots. This 

construction activity, located near the 

monitor, was ongoing prior to the time 

the monitor began operation. The 

original intention of the SRREPA was to 

begin operation of the monitor and 

sampling only after completion of the 

parking lots and external portion of the 

hotel. Due to delays, however, the 

construction was not completed until 

November 2006. The monitor began 

operating as scheduled on August 3, 

2006. 

The SRREPA’s environmental 

technician informed EPA that he 

believes that many of the samples 

collected since PM–10 monitoring began 

on August 3, 2006, through midNovember 2006, were unduly 

influenced by the grading and paving of 

parking lots immediately adjacent to the 

monitoring site on the north and east 

sides of the pump station building 

where the PM–10 sampler monitor is 

located.88 In addition to the exceedance 

days, much of the data between August 

3 and November 25, 2006 submitted to 

the AQS database, has been flagged as 

affected by construction activity.89

EPA believes there are two bases for 

excluding the September 14, September 

20 and October 26, 2006 exceedances 

from consideration in determining 

whether the SJV has attained the PM–

10 standard. First, as explained in more 

detail below, EPA believes that, during 

the time period the monitor was 

operating in such close proximity to the 

construction, the monitor should be 

considered to have been improperly 

sited under the principles established in 

40 CFR part 58, appendix E. Second, 

EPA believes that, under its Exceptional 

Events Rule, the construction activity 

that occurred within such close 

proximity to the monitor constitutes an 

exceptional event that caused the 

exceedances. EPA believes that both of 

these rationales, separately or together, 

support EPA’s proposal not to include 

the SRR monitor data recorded during 

the period of parking lot construction in 

our determination of whether the SJV 

has attained the PM–10 NAAQS. 

A. Evaluation Under Principles 

Established in 40 CFR Part 58, 

Appendix E 

40 CFR part 58 establishes criteria and 

requirements for ambient air quality 

monitoring, and appendix E sets forth 

the probe and monitoring path siting 

criteria for ambient air quality 

monitoring. 71 FR 61236 (October 17, 

2006). These include both binding 

requirements and goals. Section 1(b) of 

appendix E, the Introduction, provides 

that ‘‘[t]he probe and monitoring path 

siting criteria discussed in this 

appendix must be followed to the 

maximum extent possible.’’ Section 

58.20 provides that Special Purpose 

Monitors, which may include monitors 

on tribal lands, must meet certain 

requirements of part 58, including 

appendix E, if the data they collect are 

to be used for purposes of comparison 

to the NAAQS. It is not clear whether 

the monitor in Santa Rosa Rancheria is 

intended to be designated a Special 

Purpose Monitor. It is clear, however, 

that EPA does not intend data from a 

monitor to be used for purposes of 

comparison to the NAAQS unless the 

data meet the criteria set forth in section 

58.20, including appendix E. Under the 

principles established in part 58, 

appendix E, EPA believes that it is not 

a reasonable monitoring practice to 

locate a PM–10 monitor, intended for 

purposes of comparison to the NAAQS, 

so close to an obviously temporary dust 

source, as was the case at the SRR. 

Section 3(a) of appendix E, Spacing 

from Minor Sources, addresses the 

siting of monitors, including PM–10 

monitors. It states that close spacing 

between a monitor and a minor source 

may be proper if the purpose of that 

monitoring site is to investigate 

emissions from that source and other 

local sources. However, if, as is the case 

with the SRR monitor here, the site is 

to be used to determine air quality over 

a larger area, such as a neighborhood or 

city, it should not be placed near local, 

minor sources, because the plume from 

the local minor source would 

inappropriately impact the air quality 

data collected at the site. It is plain that 

this occurred in the SRR situation, 

where the monitor, when it began 

operating, was only 25 feet from one 

parking lot construction zone and 100 

feet from another. 

We believe that in general it is 

important to avoid placing a particulate 

monitor inordinately close to a location 

where active but temporary construction 

activity is generating dust emissions. As 

noted above, the SRREPA originally had 

not intended to start operating the 

monitor until after the conclusion of the 

construction activity. As a consequence 

of monitoring while this construction 

was still ongoing, the SRR Tribe was 

compelled to flag data for 12 of the 19 

sampling days that occurred between 

August 3 and November 25, when the 

construction concluded. Thus more 

than 60% of the data collected during 

this time period was considered to be 

unusable for regulatory purposes. 

The dramatic contrast between 

concentrations monitored while 

construction was ongoing and postconstruction concentrations also 

testifies to the impact that the improper 

siting had on the monitored data. After 

construction ceased, average monitored 

PM–10 concentrations declined 50%. 

See discussion below in section 

VI.B.2.d. below. EPA believes that after 

the construction concluded the monitor 

met the appropriate siting criteria.90

EPA has concluded that under the 

very unusual circumstances presented 

in the SRR, it was not appropriate, 

according to the principles established 

in part 58 appendix E, to deploy a new 

PM–10 monitor, for purposes of 

comparison to the NAAQS, so close to 

temporary construction activity, for the 

duration of that activity. EPA believes it 

would be unreasonable for the Agency 


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91 See, for example, SJV Rule 8051 Open Areas 

(Adopted November 15, 2001; Amended August 19, 

2004) and Rule 8071 Unpaved Vehicle/Equipment 

Traffic Areas (Adopted November 15, 2001; 

Amended September 16, 2004). 

92 63 FR 7254, 7265 (February 12, 1998); 72 FR 

at 13563. 

to allow the data from such a monitor 

to determine the attainment status of the 

SJV. 

Conclusion 

EPA is proposing to conclude that the 

exceedances in the SJV at the SRR 

monitor that occurred on September 14, 

2006, September 20, 2006 and October 

26, 2006 should be excluded from 

consideration in determining whether 

the SJV has attained the PM–10 

standard, because during this time 

period EPA deems that the monitor was 

not properly sited, under the principles 

established in part 58, appendix E. 

In proposing to find that, during the 

period of construction, the monitor was 

not properly sited for the purpose of 

comparison to the NAAQS, EPA is 

addressing only the particular facts and 

circumstances presented by the SRR 

monitoring operation. EPA notes that 

the construction activity at the SRR, 

which occurred in extremely close 

proximity to the monitor and on tribal 

land, predated the start of monitoring 

operations, and that monitoring was 

originally intended to begin only after 

the conclusion of construction activity. 

Under these circumstances, EPA 

believes that the September 14, 

September 20 and October 26, 2006 

exceedances should be excluded from 

consideration in determining whether 

the SJV has attained the PM–10 

standard. 

B. Evaluation Under the Exceptional 

Events Rule 

In addition to the rationale regarding 

the siting of the monitor, set forth above, 

EPA proposes to concur with the SRR 

Tribe’s flagging of the exceedances at 

the SRR because EPA believes that the 

construction activity constitutes an 

exceptional event under EPA’s 

Exceptional Events Rule. Our 

application of the requirements of the 

Rule to the SRR exceedances is set forth 

below. 

1. Procedural Requirements 

a. Data Are Flagged in EPA’s AQS 

Database 

The three exceedances were flagged 

by the SRR Tribe by the time the data 

were submitted to the AQS database in 

2006. 

b. Public Had an Opportunity To 

Review and Comment on the Tribe’s 

Documentation 

EPA is assisting the SRR Tribe by 

compiling and evaluating the 

documentation for the exceedances 

which have been flagged as being 

caused by exceptional events. The 

Exceptional Events Rule recognizes that 

tribes may not be in a position to 

address all of the requirements of the 

Rule and thus states that EPA will 

‘‘* * * work with tribes on the 

implementation of this rule, which may 

include appropriate implementation by 

EPA of program elements ensuring that 

any exclusion * * * of data in Indian 

country with air quality affected by 

exceptional events comports with the 

procedures and requirements of this 

rule.’’ 72 FR at 13563. EPA, through this 

proposed rule, is providing the public 

with an opportunity to review and 

comment on the documentation of these 

exceptional events. 

c. The Documentation Was Submitted to 

EPA 

As discussed above, EPA is assisting 

the SRR Tribe by compiling and 

evaluating the documentation of the 

exceedances which they have flagged as 

being caused by exceptional events. 

d. EPA Concurs With the Tribe’s 

Flagging and Demonstration 

EPA is proposing to concur with the 

SRR Tribe’s flagging of these 

exceedances as affected by exceptional 

events. As discussed above, EPA is 

assisting the SRR Tribe by compiling 

and evaluating the documentation of the 

exceedances it has flagged as being 

caused by exceptional events, and by 

ensuring that the public has an 

opportunity, through this rulemaking, to 

review and comment upon it. 

2. Technical Criteria 

a. Did this event satisfy the criteria in 

section 50.1(j) of the Rule? 

i. Affected Air Quality 

For an event to qualify as an 

exceptional event, the state or tribe must 

show that the event affected air quality. 

Here, EPA, on behalf of the SRR Tribe, 

needs to show that the event, identified 

as construction activity, affected air 

quality at the SRREPA PM–10 monitor. 

This criterion can be met by establishing 

that the event is associated with a 

measured exceedance in excess of 

normal historical fluctuations, including 

background, and there is a causal 

connection between the event and the 

exceedance. This demonstration of a 

causal connection is necessary to 

establish that the event affected air 

quality, and it is also a separate 

statutory requirement as discussed 

above. 

Because the SRREPA PM–10 monitor 

has been in operation only since August 

2006, it is not possible to compare the 

data from exceedance days to historical 

levels. In this case, however, we can 

look at data that have been collected 

since the construction and parking lot 

paving was completed to determine 

representative concentrations of PM–10 

in the absence of a large, earthdisturbing project such as the 

construction, grading and paving of 

parking lots. We discuss the range of 

data and its fluctuation in more detail 

in subsection c. below. 

We also need to show the causal 

connection between the exceptional 

event, in this case construction activity, 

and the exceedances recorded. In 

addition to other information provided 

during EPA’s on-site visit, the SRREPA 

has provided EPA with wind speed and 

wind direction data collected at its site 

that show the wind was blowing in the 

appropriate direction and demonstrates 

that the PM–10 monitor was downwind 

of the construction activity on the 

exceedance days. We discuss the causal 

connection between the construction 

activity and the exceedances in more 

detail in subsection b. below. 

ii. Not Reasonably Controllable or 

Preventable 

Section 50.1(j) of the Exceptional 

Events Rule requires that for an event to 

qualify as an exceptional event, whether 

natural or anthropogenic, a state, tribe 

(or, in this case, EPA) must show that 

the event was not reasonably 

preventable or controllable. 

EPA believes that it would not have 

been reasonable to prevent the activity, 

i.e., paving of parking lots that were 

needed for the SRR Tribe’s facilities. 

Paving a parking lot (which involves 

grading the ground, applying a base 

material such as gravel and applying 

asphalt) is a generally accepted form of 

control of PM–10.91 To prevent the 

paving of a parking lot would not only 

be unreasonable, but illogical. 

With respect to whether the event was 

reasonably controllable, we note that the 

SRR Tribe does not have PM–10 control 

measures in place and is not subject to 

the fugitive dust control regulations 

adopted by the SJVAPCD. As discussed 

in the Exceptional Events Rule, ‘‘Tribes 

are not required to develop TIPs or 

otherwise implement relevant programs 

under the CAA. * * *’’ 92 ‘‘EPA 

recognizes Tribal Governments as 

sovereign entities with primary 

authority and responsibility for the 

reservation populace. Accordingly, EPA 

will work directly with Tribal 

Governments as the independent 


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93 59 FR 43956 (August 25, 1994). 

94SJV Rule 8021 Construction, Demolition, 

Excavation, Extraction, and Other Earthmoving 

Activities (Adopted November 15, 2001; Amended 

August 19, 2004). 95Site Visit Memorandum. 

96Santa Rosa Rancheria PM–10 24 hour average 

concentrations, Excel spreadsheet, Bob Pallarino. 

authority for reservation affairs, and not 

as political subdivisions of States or 

other governmental units.’’ 93

While paving itself is a control 

measure, EPA recognizes that other 

control measures may be reasonable 

during a paving process. For example, 

the SJVAPCD regulations require, 

among other things, that regulated 

construction sites apply as appropriate 

water or chemical/organic stabilizers or 

construct and maintain wind barriers.94

In the circumstances of the SRR, 

however, even if these types of 

measures had been actively employed, 

we cannot be certain that they would 

have prevented exceedances at the PM–

10 monitor. This is due in large part to 

the unusual circumstance presented 

here of the very close proximity of the 

construction activity to the monitor. As 

noted above, one of the parking lots was 

within 25 feet of the monitor, and the 

other was within 100 feet. 

EPA’s evaluation of the parking lot 

construction activity’s impact on the 

monitor, and whether it was reasonably 

controllable, during the activity, is 

informed by EPA’s views on what 

constitutes acceptable monitor siting. As 

EPA has set forth in detail above, EPA 

believes that, for the duration of the 

construction activity, the monitor was 

not properly sited for the purposes of 

determining attainment of the SJV, and 

that as a result it was inordinately 

impacted by that activity. 

The provisions of 40 CFR part 58, 

appendix E regarding the siting of PM–

10 monitors, are instructive with respect 

to EPA’s analysis of the exceedances 

under the Exceptional Events Rule. We 

cannot conclude that the activity was 

reasonably controllable given that the 

exceedances were measured at a 

monitor that EPA’s rule provides should 

not be operated at such a time and 

place, for the purposes of determining 

attainment. Thus, under the particular 

set of circumstances presented here, for 

the purposes of evaluating the 

‘‘reasonably controllable’’ criterion of 

the Exceptional Events Rule, we deem 

this criterion to have been satisfied. 

iii. Was an Event Caused by Human 

Activity That is Unlikely to Recur at a 

Particular Location 

In this case, the event was paving of 

parking lots in the vicinity of the PM–

10 monitor, and is a construction 

activity that is not expected to recur at 

that location. 

iv. Determined by EPA To Be an 

Exceptional Event 

Finally, EPA must determine through 

the process established in the 

Exceptional Events Rule whether an 

exceptional event occurred. The 

Exceptional Events Rule has both 

procedural requirements and technical 

criteria that we are assisting the 

SRREPA in meeting. We believe that by 

the initial flagging of the data, and 

through the vehicle of this proposed 

rulemaking we will demonstrate that the 

procedural requirements and technical 

criteria of the rule will have been met. 

b. Is there a clear causal connection 

between the exceedances and the 

claimed exceptional event? 

Under 40 CFR 50.14(c)(3)(iii)(B), a 

clear causal relationship must be 

established between the measured 

exceedance and the claimed exceptional 

event. The information compiled by 

EPA shows a clear causal connection 

between the exceedances and the 

construction activity at the nearby 

parking lots. The SRREPA 

environmental technician observed the 

conditions at the time the monitor was 

operating and noted on the sample 

tracking forms, which are completed 

with each sampling run, that there was 

construction nearby. Copies of these 

tracking forms are included in the 

documentation for this rulemaking. 

The SRREPA measures wind speed 

and wind direction at the SRR 

monitoring site. These meteorological 

data indicate that on the three days that 

exceeded the NAAQS, winds were 

predominantly from the northwest to 

northeast. This would indicate that any 

dust-producing activity north and 

northeast of the monitor would result in 

high concentrations of geologic dust 

being blown towards the monitor. 

The meteorological data lend support 

to the environmental technician’s 

account of the events of that day. EPA 

also discussed these events with the 

SRR construction superintendent, who 

agreed with the environmental 

technician’s account of the construction 

activity. A private consultant working 

for the SRREPA also stated that he had 

witnessed major earth-disturbing 

activities on these days.95

Based on the meteorological data, 

eyewitness accounts, and an on-site 

inspection of the monitoring site 

location and its proximity to the parking 

lots, we believe that there was a clear 

causal connection between the 

construction activity and the recorded 

PM–10 exceedances. 

c. Can it be demonstrated that the event 

is associated with a measured 

concentration in excess of normal 

historical fluctuations including 

background? 

For EPA to concur with the SRREPA’s 

claim that an exceptional event caused 

an exceedance, one of requirements is to 

show that the event is associated with 

concentrations that are beyond the 

normal historical fluctuations. See 40 

CFR 50.14(c)(3)(iii)(C). 

Of the 44 samples collected by the 

SRREPA, nearly 80% of the samples (35 

days) were less than 100 μg/m3. After 

completion of the paving projects in 

mid-November, 2006, average PM–10 

concentrations dropped by more than 

50%, from an average of 97 μg/m3 to an 

average of 45 μg/m3.96 This would 

indicate that the construction activity 

had an obvious effect on the 

concentrations recorded by the SRR 

monitor and that the data collected 

during this construction period, 

including the exceedances recorded in 

September and October, 2006, were not 

representative of typical postconstruction PM–10 concentrations at 

the location of the monitor. 

d. Can it be demonstrated that there 

would have been no exceedance ‘‘but 

for’’ the event? 

To qualify as an exceptional event, 

there must be an analysis which 

demonstrates that there would have 

been no exceedance ‘‘but for’’ the event. 

40 CFR 50.14(c)(3)(iii)(D). Such analyses 

do not require a precise estimate of the 

estimated air quality impact from the 

event. 72 FR at 13570. 

To meet this requirement, EPA 

believes the SRREPA environmental 

technician, consultant and the SRR 

construction superintendent have 

clearly indicated that the exceedances 

occurred on days where nearby 

construction was also occurring. As EPA 

has shown, the proximity of the monitor 

to the construction activity and the 

concomitant infeasibility of control 

measures to prevent the exceedances 

also demonstrate that there would have 

been no exceedances but for the 

construction activity. Given these 

factors and the fact that the average PM–

10 concentrations dropped by more than 

50% after the completion of the paving 

projects, we believe the weight of 

evidence shows that the exceedances 

would not have occurred but for the 

construction activity. 


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3. Mitigation Requirements 

Under 40 CFR 51.930, a state or tribe 

requesting to exclude air quality data 

due to exceptional events must take 

appropriate and reasonable actions, 

including public notification, public 

education and implementation of 

measures, to protect public health from 

exceedances or violations of the 

NAAQS. In the case of the SRR, EPA 

recognizes that tribes may implement 

only portions of air quality programs 

and not be in a position to address each 

of the procedures and requirements 

associated with excluding or 

discounting data. In the preamble to the 

Exceptional Events Rule, EPA cites an 

example of tribes that ‘‘* * * may 

operate a monitoring network for 

purposes of gathering and identifying 

appropriate data, but may not 

implement relevant programs for the 

purpose of mitigating the effects of 

exceptional events. * * *’’ 72 FR at 

13563. That is the case with the SRR. 

Under these circumstances, as indicated 

in the preamble to the Exceptional 

Events Rule, EPA intends to work with 

the SRR on the implementation of the 

Rule. 

Conclusion 

EPA believes that the construction 

activities at the SRR on September 14, 

2006, September 20, 2006 and October 

26, 2006 were exceptional events as 

defined under 40 CFR 50.1(j). EPA 

believes that there is sufficient weight of 

evidence to conclude that the 

construction activities caused the 

exceedances on the exceedance days, 

and that the exceedances would not 

have occurred but for the construction 

activity. The proximity of the 

construction activities to the monitor 

and the wind direction recorded at the 

monitor support this conclusion. 

Because EPA believes that the 

provisions of the Exceptional Events 

Rule have been satisfied, EPA is 

proposing to concur with the SRR 

Tribe’s flags indicating that these 

exceedances were due to exceptional 

events, and to exclude the data from 

consideration in determining whether 

the SJV has attained the PM–10 

standard. 

In proposing to concur with the SRR 

Tribe’s flags that construction activity at 

SRR constituted exceptional events, 

EPA is addressing only the particular 

facts and circumstances presented by 

the SRR monitoring operation. In 

general, fugitive dust control measures 

employed during construction activities 

are helpful in reducing ambient PM–10 

concentrations and avoiding 

exceedances of the NAAQS. However, 

in the specific circumstances of the SRR 

during the days when exceedances were 

recorded, we are not able to conclude 

that the event was reasonably 

controllable due to the very close 

proximity of the monitor to the 

construction activity, and the other 

factors discussed above. Given this 

singular constellation of factors, EPA is 

proposing to concur with the Tribe’s 

flagging of the exceedances on 

September 14, September 20 and 

October 26, 2006 as caused by 

exceptional events. 

VII. Summary of Exceedances From 

2004 Through 2006 

The table below provides a summary 

of exceedances relevant to today’s 

proposed rule that were recorded at 

monitors located within the boundaries 

of the SJV. The table indicates, whether 

in determining attainment, EPA has 

excluded or proposes to exclude the 

exceedance, based on a finding that it 

was due to an exceptional event. The 

24-hour standard is attained when the 

expected number of days per year with 

levels above 150 μg/m3 (averaged over a 

three-year period) is less than or equal 

to one. 40 CFR part 50, appendix K. As 

shown in the table, all of the monitoring 

locations are meeting the PM–10 

standard. 

TABLE SUMMARIZING PM–10 24-HOUR EXCEEDANCES IN THE SJV 

[From 2004 through 2006] 

Monitor Operating schedule 

Recorded (observed) 

exceedances 2004—2006 

Number of estimated exceedances Average number 

of annual 

exceedances 

Date Conc 2004—2006 

Included in 

attn. deter. 

Reason for excluding 

exceedance 

Corcoran Manual FRM ... 1 in 3 day ...................... 9/3/04 217 No ............... Exceptional Event .......... 0 

9/22/06 215 No ................ Exceptional Event .......... ............................

Corcoran TEOM ............. Continuous .................... 9/22/06 261 No ................ Exceptional Event .......... 0 

10/25/06 304 No ................ Exceptional Event .......... ............................

12/8/06 162 No ................ Exceptional Event .......... ............................

Bakersfield Golden Manual FRM.1 in 6 day ...................... 9/22/06 157 No ................ Exceptional Event .......... 0 

Bakersfield Golden BAM Continuous .................... 11/22/05 156 Yes .............. N/A ................................. 0 .67 

11/23/05 180 Yes .............. N/A ................................. ............................

Bakersfield Golden 

TEOM.

Continuous .................... 9/22/06 157 No ................ Exceptional Event .......... 0 

10/25/06 193 No ................ Exceptional Event .......... ............................

12/8/06 213 No ................ Exceptional Event .......... ............................

Tracy BAM ...................... Continuous .................... 9/22/06 161 Yes .............. N/A ................................. 0.33 

Oildale Manual FRM ...... 1 in 6 day ...................... 9/22/06 162 No ................ Exceptional Event .......... 0 

Santa Rosa Rancheria 

Manual FRM.

1 in 6 day ...................... 9/14/06 190 No ................ Exceptional Event .......... 0 

9/20/06 158 No ................ Exceptional Event .......... ............................

10/26/06 157 No ................ Exceptional Event .......... ............................

Sources: 

EPA Air Quality System Database. 

E-mail from Steven Shaw, SJVAPCD to Bob Pallarino, EPA Region 9, April 20, 2006. 

E-mail from Steve Shaw, SJVAPCD to Bob Pallarino, EPA Region 9, October 12, 2006. 


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VIII. Petitions for Reconsideration and 

Withdrawal 

A. Winds and Wildfires on September 

22 and October 25, 2006 

Earthjustice filed its 2006 Petition for 

Reconsideration (PFR) before the State 

provided its exceptional event 

documentation for the September 22, 

2006 exceedances to the public or EPA. 

At that time CARB and the District had 

simply informed EPA that, based on 

preliminary analysis, they believed that 

these exceedances were due to high 

wind and wildfire natural events. 

Similarly, when Earthjustice filed its 

2007 Petition for Withdrawal (PFW) and 

the accompanying Jan Null declaration, 

the State had not yet submitted the 

complete documentation for the 

September and October 2006 

exceedances on which EPA is basing 

this proposed rule. Therefore 

Earthjustice’s conclusion in the 

petitions that the September 22, 2006 

and October 25, 2006 exceedances do 

not qualify as natural events does not 

address the technical analysis of the 

winds and wildfires as ultimately 

submitted by the State and which EPA 

has evaluated in section V. above. To 

the extent that Earthjustice’s 

assessments in the petitions of the 

nature and effect of the winds and 

wildfires are currently relevant, we 

believe our evaluation in section V. 

addresses the significant points raised 

in them. 

In addition, since EPA, as stated in 

section V. above, agrees with the 

petitioners that regional transport from 

north of the SJV and the northern SJV 

and wildfires were not the cause of the 

exceedances on September 22 and 

October 25, it is unnecessary for EPA to 

further address the arguments raised by 

petitioners with respect to these 

theories. 

B. Notice/Comment on September 22 

and October 25, 2006 Exceedances 

The gravamen of the 2006 petition, 

which is reiterated in the Petition for 

Withdrawal, is Earthjustice’s claim that 

EPA did not provide the public with an 

opportunity to comment on the 

September 22, 2006 exceedances and 

thus should not have finalized the 

attainment determination for the SJV. 

PFR at 2–4. Petitioners also complained 

that EPA did not require adequate 

documentation that these exceedances 

were caused by exceptional events. PFR 

at 3–4. 

Contrary to Earthjustice’s assertions, 

EPA did not abuse its discretion in 

addressing the September 22, 2006 

exceedances in its October 2006 

determination of attainment. EPA noted 

at the time that the exceedances were 

based on preliminary data only: 

‘‘Because these data, which were 

collected using manual reference 

method samplers, are preliminary and 

have not been quality assured, and 

because EPA believes that they may 

qualify as caused by natural events, and 

thus be excluded from consideration in 

an attainment determination, EPA is 

proceeding to finalize its determination 

that the area is in attainment.’’ 71 FR 

63642. Thus the data had not been 

quality assured, and in addition EPA 

was on notice that CARB and the 

District intended to flag the data as due 

to exceptional events and to request 

EPA’s concurrence on excluding the 

data from consideration in an 

attainment determination. 

EPA went on to note that ‘‘[i]f, after 

the data is quality assured, and after 

further evaluating CARB’s request with 

respect to these data, EPA determines 

that the data do not qualify for 

exclusion under EPA’s natural events 

policy, and EPA further believes that if 

included that they would establish that 

the area is in violation of the NAAQS, 

EPA will proceed with appropriate 

rulemaking action to withdraw its 

determination of attainment.’’ Id. It was 

thus clear that EPA’s determination was 

subject to revision based on subsequent 

quality assurance and evaluation of the 

data, and EPA outlined its projected 

procedure for dealing with the data once 

they were quality assured and EPA had 

an opportunity to evaluate the 

documentation of the potential 

exceptional events. 

In this proposed rule, EPA is 

following through with this procedure, 

and is now providing for full notice and 

an opportunity for comment, in the 

context of a rulemaking, on whether 

those exceedances qualify as caused by 

exceptional events. EPA is also 

providing notice and opportunity for 

comment on additional claims that 

exceedances were caused by exceptional 

events on October 25, 2006, and 

December 8, 2006, and at the Santa Rosa 

Rancheria on September 14 and 20 and 

October 26, 2006. 

Contrary to Earthjustice’s contention 

in its Petition for Reconsideration and 

Petition for Withdrawal, EPA did not 

reverse the burden of proof required to 

establish an exceptional event, or 

relieve the State from the obligation to 

document its claims. PFR at 4; PFW at 

17. In the final determination, it is clear 

that EPA did not conclusively concur in 

excluding the data without requiring 

appropriate documentation and a 

showing from the State. Rather, EPA 

deferred its determination on the impact 

of the preliminary data until the data 

could be quality assured and the State 

would have an opportunity to meet its 

burden of showing that an exceedance 

qualified as caused by an exceptional 

event. 

Finally EPA notes that Earthjustice 

alleges in its 2007 petition that the 

Agency ignored in its final attainment 

determination the October 25, 2006 

exceedances as well as the September 

22, 2006 exceedances. PFW at 2. This is 

not the case. The exceedances in 

October occurred eight days after EPA 

promulgated its final determination of 

attainment, on October 17, 2006. (The 

notice was published on October 30, but 

the determination had been signed and 

disseminated to the public on October 

17). Thus, EPA had no information on 

these exceedances at the time of its final 

action. 

C. Wind Conditions in the Valley 

With respect to the existence of high 

winds in the Valley generally, 

Earthjustice, in both petitions, 

characterizes statements in the 2003 

PM–10 Plan for the area as concluding 

that wind erosion is not a significant 

contributing factor in dust emissions 

and as suggesting that winds with 

enough velocity to cause erosion 

disperse PM–10 concentrations and/or 

transport PM–10 out of the Valley. PFR 

at 4; PFW at 8. Earthjustice in its 2007 

petition also cites a letter from the 

District to EPA which states that ‘‘there 

is no evidence of any significant linkage 

between high winds and PM–10 federal 

exceedance events [in the Valley].’’ Id. 

at 8–9. 

Earthjustice has taken the statements 

in the 2003 Plan to attain the PM–10 

standard out of context. Chapter 2 of the 

Plan, quoted by Earthjustice, is a 12- 

page general overview of the San 

Joaquin Valley Air Basin, the purpose of 

which is to describe normal or typical 

meteorological conditions. It is not 

intended to nor does it address unusual 

winds such as those under 

consideration here that may occur in the 

Valley. Nevertheless, the District did 

determine that windblown dust is not a 

significant problem in the SJV for the 

purposes of attaining the PM–10 

standard. For example, the Plan states 

that ‘‘[w]ind related PM–10 events are 

rare but possible when conditions are 

right’’ and that ‘‘PM–10 readings in the 

SJVAB are most severe during the fall 

and winter periods when wind speed 

and direction are not conducive to 

interregional transport.’’ 2003 PM–10 

Plan, ES–10, 2–6. The District also states 

that ‘‘winds are effective in dispersing 

PM–10 concentrations and/or 

transporting PM–10 out of the Valley’’

in explaining why the spring and 


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97As noted above, BACM implementation is not 

required under EPA’s exceptional events rule. 

summer months, which are the windier 

months of the year in the SJV, do not 

yield higher PM–10 levels. 

However, the fact that PM–10 

pollution from windblown dust is not 

generally a significant enough problem 

in the SJV that it needs to be controlled 

for the purposes of attaining the PM–10 

standard, does not mean that 

windblown dust cannot cause an 

exceedance of the standard. In addition, 

even if windblown dust were a 

significant problem, there could be 

individual situations where particular 

conditions make it unreasonable to 

expect the District and State to be able 

to control sources in those 

circumstances. For such situations, EPA 

has issued the Exceptional Events Rule, 

and previously its policies, which as 

discussed above allows exceedances 

caused by exceptional events to be 

excluded from regulatory considerations 

as appropriate if certain conditions are 

met. Since there are many variables that 

can cause exceptional event 

exceedances, EPA believes the analyses 

for such events should be reviewed on 

a case by case basis. 72 FR 13560. For 

example, not all high wind days will 

lead to exceedances and not all 

exceedances monitored when high 

winds are recorded are necessarily due 

to those high winds. For the 

exceedances discussed in today’s 

proposal, however, EPA believes the 

State has made an adequate 

demonstration that they were caused by 

exceptional events and have met all of 

the Exceptional Events Rule 

requirements, and thus the data for 

these particular events should be 

excluded from regulatory consideration. 

Earthjustice also cites a letter from the 

District to EPA responding to a letter 

from Charles Swanson to EPA 

commenting on the 2003 PM–10 Plan. 

April 15, 2004 letter from James Sweet, 

SJVAPCD, to Doris Lo, EPA (Sweet 

letter). Mr. Swanson disputes the 

following passage from Table G–15 in 

Appendix G entitled ‘‘BACM 

Comparative Analysis for ‘On-Field 

Activities’’’ concerning the BACM 

justification discussion associated with 

the ‘‘Other’’ category of the District’s 

proposed Agricultural Conservation 

Management Practices: 

The SJV does not have a windblown dust 

problem to anywhere near the extent of the 

other nonattainment areas. The SJV has some 

of the lowest average wind speeds in the 

country. No wind related exceedances have 

been recorded in the basin during the last 

three years. Wind speeds are highest during 

the spring when PM–10 levels are at their 

lowest. The majority of the fugitive dust 

emissions are generated from earth disturbing 

activities. Certain soil types and crops are 

more prone to windblown dust problems. 

The ‘‘Other’’ category will give the farmers 

with the potential to experience wind blown 

dust emissions the flexibility to address this 

issue with a CMP. 

March 18, 2004 letter from Charles 

Swanson to Doris Lo, EPA (Swanson 

letter) at 1. 

In responding to Mr. Swanson, the 

District stated in its April 15, 2004 letter 

that ‘‘[t]he statements in the Plan 

provide a general characterization of the 

San Joaquin Valley (SJV) and, as with all 

generalizations, are not without 

exception.’’ Sweet letter at 1. 

Furthermore, while, as Earthjustice 

points out, the District did also state 

that an analysis of all wind events since 

1990 did not establish a linkage to PM–

10 exceedances, the District also 

enumerated technical limitations that 

bear directly on this conclusion. For 

example, the data used did not report 

wind gusts and the 1 in 6 day sampling 

for PM–10 will not capture all wind 

events. Sweet letter at 7–8. Therefore, 

Earthjustice’s attempts to characterize 

the statements in the Sweet letter 

regarding windblown dust as absolute is 

not warranted. Finally, the District also 

asserts that: 

Evaluation of past events indicates that 

often the area with the highest PM–10 levels 

is not where the wind is highest, but rather 

where the wind begins to slow. To 

understand the dynamics of this pattern we 

need only review the mechanisms for 

entrainment and deposition. When the wind 

slows, it can no longer keep the larger PM–

10 particles aloft and they settle toward the 

surface. The settling of particulates aloft 

* * * results in an increased concentration 

in the deposition area. 

Sweet letter at 2. This scenario is 

precisely what occurred on September 

22 and October 25, 2006 as discussed in 

section V. above. 

D. EPA’s Natural Events Policy 

1. BACM Implementation 

In both petitions Earthjustice asserts 

that EPA’s 1996 Natural Events Policy 

requires that the State demonstrate that 

BACM were in place and that all 

sources were in compliance in order for 

EPA to concur on a high wind natural 

event request. PFR at 5; PFW at 9. 

Earthjustice contends that the State 

cannot demonstrate that agricultural 

sources were in compliance at the time 

of the wind event since it is not clear 

if any compliance inspections had been 

conducted. 

As discussed in sections IV. and V., 

EPA is evaluating the State’s 

exceptional event documentation under 

EPA’s Exceptional Event Rule and not 

under its pre-existing policies. The Rule 

does not require either a showing that 

BACM was in place at the time of the 

event or proof that sources were in 

compliance. Rather, in the preamble to 

the Rule EPA states that the State must 

take reasonable and appropriate 

measures under these circumstances. 72 

FR at 13576–13577. That said, EPA has 

approved the District’s BACM 

demonstration for all significant sources 

of PM–10 in the Valley, including 

agricultural sources, as meeting CAA 

section 189(b)(1)(B). 69 FR at 30035; 71 

FR 7683. Moreover the State’s 

documentation for the September 22 

and October 25, 2006 events includes 

information on compliance inspections 

throughout the SJV. See section V. 

above. 

2. District’s Natural Events Action Plan 

In its 2007 petition Earthjustice 

claims that for the September 22, 2006 

exceedances the District failed to meet 

the requirements of its Natural Events 

Action Plan for ‘‘[a]cceptable 

documentation for establishing an 

extraordinary natural event * * * .’’

Specifically, Earthjustice contends that 

acceptable documentation for 

establishing ‘‘an extraordinary natural 

event’’ includes issuance by the national 

Weather Service of a high wind or 

blowing dust advisory, the occurrence 

of strong winds aloft and surface wind 

maps showing potential for high winds 

to occur at the site. According to 

Earthjustice no adequate documentation 

of these factors was offered. PFW at 11. 

Earthjustice’s statements regarding the 

requirements for documentation under 

the District’s ‘‘Natural Events Action 

Plan for High Wind Events in the San 

Joaquin Valley Air Basin,’’ February 16, 

2006 (NEAP) appear in the portion of its 

2007 petition that addresses the causal 

relationship between high winds and 

the September 22, 2006 exceedances. Id. 

Section 3 of the NEAP concerns the 

documentation of high wind events and 

lists specific sources of documentation 

suggested by EPA: Filter analysis, 

meteorological data, modeling and 

receptor analysis, videos and/or 

photographs, maps, news accounts and 

BACM 97 requirements. Section 6 of the 

NEAP concerns meteorological 

forecasting criteria. This section states 

that if certain enumerated criteria are 

met, the District, in consultation with 

CARB, will declare a NEAP episode. 

The items that Earthjustice contends are 

required to document an exceptional 

event are among these criteria. Thus 

Earthjustice has confused forecasting an 

exceptional event with the 

documentation of it. EPA believes that 


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the State has adequately documented 

the September 22, 2006 exceedances as 

being caused by all exceptional events 

as discussed above in section V.A. 

Finally we note again that EPA is 

proceeding in this rulemaking under its 

Exceptional Events Rule rather than the 

1996 policy it replaces. In the preamble 

to the Rule, EPA explained that 

‘‘following the promulgation of this 

rule, States will no longer be required to 

keep NEAPs in place that were not 

approved as a part of a SIP for an area.’’

72 FR at 13576. 

E. Harvest Activities 

Earthjustice asserts in its 2006 

petition that September is the peak 

harvest season for cotton and almonds 

and that EPA should investigate the 

contribution of these activities to the 

September 22 exceedances. PFR at 6. In 

the 2007 petition Earthjustice states that 

the end of October is generally when 

two of the dustiest crop harvests, cotton 

and almonds, take place and that these 

activities caused the October 25 

exceedances. PRW at 13–14. EPA 

discusses the effect of anthropogenic 

sources on the 2006 exceedances in 

section V. above. 

F. Exceedances at Corcoran and 

Stockton in 2004, Bakersfield in 2005 

and the Santa Rosa Rancheria in 2006 

The 2007 petition raises issues 

regarding several exceedances that have 

already been addressed by the October 

2006 attainment determination. These 

exceedances occurred on September 3, 

2004 at Corcoran and Stockton and on 

November 22–23, 2005 at Bakersfield. 

EPA’s position on these exceedances is 

found in the final rule at 71 FR at 

63658–63661. 

Regarding the September 3, 2004 

exceedance, Earthjustice states that EPA 

must now evaluate whether the Agency 

can concur on the State’s request to flag 

the exceedance as a high wind event 

and cannot continue to rely on the 

argument that it is irrelevant because 

‘‘even if EPA had not concurred with 

the exclusion of this data, the Corcoran 

site would still attain the 24-hour 

NAAQS * * *.’’ Earthjustice takes this 

position because it believes there are 

now other exceedances at Corcoran that 

cannot be excluded and that the 

September 3, 2004 exceedance will thus 

be important in determining the SJV’s 

PM–10 attainment status. PFW at 9. 

EPA disagrees with Earthjustice’s 

contention that there are now other 

exceedances that cannot be excluded. 

As discussed above, EPA believes the 

exceedances on September 22, October 

25 and December 8, 2006 are all due to 

exceptional events and is proposing to 

concur with the State’s request to flag 

these data as caused by high wind 

events. Thus our conclusion that the 

September 3, 2004 exceedance is not 

significant for the attainment 

determination is still valid. 

Regarding the November 2005 

exceedances at Bakersfield, EPA stated 

in its determination of attainment that 

‘‘[e]ven if the Bakersfield-Golden State 

Highway BAM and TEOM data are 

considered together (and even if they 

were quality-assured data not subject to 

natural events), the exceedances 

recorded at these monitors would not 

show that the area is in violation of the 

standard.’’ 71 FR at 63659. As discussed 

above, EPA believes that the 

exceedances at Bakersfield in 2006 were 

due to exceptional events and is 

proposing to concur with the State’s 

request to flag these data. Thus we still 

believe that the 2005 Bakersfield-Golden 

exceedances, when considered for 

purposes of our 2006 attainment 

determination, would not contribute to 

or constitute a violation. 

In the 2007 petition Earthjustice also 

raises questions about exceedances 

recorded at the Santa Rosa Rancheria on 

September 14, 20 and October 26, 2006. 

PFW at 15–16. EPA addresses these 

exceedances in section VI. above. 

IX. Statutory and Executive Order 

Reviews 

Under Executive Order 12866 (58 FR 

51735, October 4, 1993), this proposed 

action is not a ‘‘significant regulatory 

action’’ and therefore is not subject to 

review by the Office of Management and 

Budget. For this reason, this action is 

also not subject to Executive Order 

13211, ‘‘Actions Concerning Regulations 

That Significantly Affect Energy Supply, 

Distribution, or Use’’ (66 FR 28355, May 

22, 2001). This action merely proposes 

a determination based on air quality 

data and does not impose any additional 

requirements. Accordingly, the 

Administrator certifies that this 

proposed rule will not have a significant 

economic impact on a substantial 

number of small entities under the 

Regulatory Flexibility Act (5 U.S.C. 601 

et seq.). Because this proposed rule does 

not impose any additional enforceable 

duty, it does not contain any unfunded 

mandate or significantly or uniquely 

affect small governments, as described 

in the Unfunded Mandates Reform Act 

of 1995 (Pub. L. 104–4). 

Executive Order 13175 (65 FR 67249, 

November 9, 2000) requires EPA to 

develop an accountable process to 

ensure ‘‘meaningful and timely input by 

tribal officials in the development of 

regulatory policies that have tribal 

implications.’’ Several Indian tribes 

have reservations located within the 

boundaries of the SJV. EPA is aware of 

only one tribe in the SJV that operates 

a PM–10 monitor, the Santa Rosa 

Rancheria. EPA has consulted with 

representatives of the Santa Rosa 

Rancheria Tribe on the data recorded by 

their monitor, and the flagging of the 

data, and will continue to work with the 

Tribe, as provided for in Executive 

Order 13175. Accordingly, EPA has 

addressed Executive Order 13175 to the 

extent that it applies to this action. This 

proposed action also does not have 

Federalism implications because it does 

not have substantial direct effects on the 

States, on the relationship between the 

national government and the States, or 

on the distribution of power and 

responsibilities among the various 

levels of government, as specified in 

Executive Order 13132 (64 FR 43255, 

August 10, 1999). This proposed action 

merely makes a determination based on 

air quality data and does not alter the 

relationship or the distribution of power 

and responsibilities established in the 

CAA. Executive Order 12898 establishes 

a Federal policy for incorporating 

environmental justice into Federal 

agency actions by directing agencies to 

identify and address, as appropriate, 

disproportionately high and adverse 

human health or environmental effects 

of their programs, policies, and 

activities on minority and low-income 

populations. Today’s action involves 

proposed determinations based on air 

quality considerations and proposes to 

affirm that the San Joaquin area has 

attained the PM–10 NAAQS. It will not 

have disproportionately high and 

adverse effects on any communities in 

the area, including minority and lowincome communities. 

This proposed rule also is not subject 

to Executive Order 13045 ‘‘Protection of 

Children from Environmental Health 

Risks and Safety Risks’’ (62 FR 19885, 

April 23, 1997), because it is not 

economically significant. The 

requirements of section 12(d) of the 

National Technology Transfer and 

Advancement Act of 1995 (15 U.S.C. 

272 note) do not apply. This proposed 

rule does not impose an information 

collection burden under the provisions 

of the Paperwork Reduction Act of 1995 

(44 U.S.C. 3501 et seq.). 

List of Subjects 

40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Particulate matter, Reporting 

and recordkeeping requirements. 


rmajette on PROD1PC64 with PROPOSALS2
Federal Register / Vol. 72, No. 165 / Monday, August 27, 2007 / Proposed Rules 49067 

40 CFR Part 81 

Environmental protection, Air 

pollution control, National parks, 

Wilderness areas. 

Dated: August 15, 2007. 

Wayne Nastri, 

Regional Administrator, Region 9. 

[FR Doc. E7–16693 Filed 8–24–07; 8:45 am] 

BILLING CODE 6560–50–P 


rmajette on PROD1PC64 with PROPOSALS2