```

[Federal Register: July 8, 2010 (Volume 75, Number 130)]
[Rules and Regulations]               
[Page 39365-39390]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr08jy10-20]                         

[[Page 39365]]

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Part III

Environmental Protection Agency

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40 CFR Part 52

Revisions to the California State Implementation Plan, Imperial County 
Air Pollution Control District; Final Rule

[[Page 39366]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

[EPA-R09-OAR-2010-0120; FRL-9169-2]

 
Revisions to the California State Implementation Plan, Imperial 
County Air Pollution Control District

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: EPA is finalizing a limited approval and limited disapproval 
of revisions to the Imperial County Air Pollution Control District 
(ICAPCD or the District) portion of the California State Implementation 
Plan (SIP) under the Clean Air Act as amended in 1990 (CAA or the Act). 
This action was proposed in the Federal Register on February 23, 2010 
and concerns local rules that regulate coarse particulate matter 
(PM10) emissions from sources of fugitive dust such as 
construction sites, unpaved roads, and disturbed soils in open and 
agricultural areas in Imperial County.

DATES: Effective Date: This rule is effective on August 9, 2010.

ADDRESSES: EPA has established docket number EPA-R09-OAR-2010-0120 for 
this action. The index to the docket is available electronically at 
http://www.regulations.gov and in hard copy at EPA Region IX, 75 
Hawthorne Street, San Francisco, California. While all documents in the 
docket are listed in the index, some information may be publicly 
available only at the hard copy location (e.g., copyrighted material), 
and some may not be publicly available in either location (e.g., CBI). 
To inspect the hard copy materials, please schedule an appointment 
during normal business hours with the contact listed in the FOR FURTHER 
INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: Andrew Steckel, EPA Region IX, (415) 
947-4115, Steckel.andrew@epa.gov.

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

Table of Contents

I. Summary of Proposed Action
II. Public Comments and EPA Responses
III. EPA Action
IV. Statutory and Executive Order Reviews

I. Summary of Proposed Action

    On February 23, 2010 (75 FR 8008), EPA proposed a limited approval 
and limited disapproval of the following rules listed in Table 1, known 
collectively as Regulation VIII, that were adopted by ICAPCD and 
submitted by the California Air Resources Board (ARB) for incorporation 
into the California SIP for the Imperial County serious PM10 
nonattainment area.

                                 Table 1
------------------------------------------------------------------------
  Local agency      Rule No.      Rule title      Adopted     Submitted
------------------------------------------------------------------------
ICAPCD..........          800  General             11/08/05     06/16/06
                                Requirements
                                for Control of
                                Fine
                                Particulate
                                Matter.
                          801  Construction &      11/08/05     06/16/06
                                Earthmoving
                                Activities.
                          802  Bulk Materials.     11/08/05     06/16/06
                          803  Carry Out &         11/08/05     06/16/06
                                Track Out.
                          804  Open Areas.....     11/08/05     06/16/06
                          805  Paved & Unpaved     11/08/05     06/16/06
                                Roads.
                          806  Conservation        11/08/05     06/16/06
                                Management
                                Practices.
------------------------------------------------------------------------

    We proposed a limited approval because we determined that these 
rules improve the SIP and are largely consistent with the relevant CAA 
requirements. We simultaneously proposed a limited disapproval because 
some provisions of the rules conflict with the CAA section 110(a) 
requirement that SIP rules must be enforceable and the requirement in 
section 189(b)(1)(B) for implementation of best available control 
measures (BACM) in serious PM10 nonattainment areas such as 
Imperial County. We discuss these statutory requirements and the 
Regulation VIII deficiencies in detail in the proposed rule and in the 
Technical Support Document for that proposal (proposal TSD).\1\ In the 
proposed rule and proposal TSD we also discuss our determination of 
which fugitive dust source categories addressed by Regulation VIII are 
significant and consequently require BACM pursuant to EPA guidance. 
This determination was based in part on our 2009 decision \2\ to not 
concur with the State's request pursuant to EPA's exceptional events 
rule \3\ (EER) to exclude certain exceedances of the PM10 
National Ambient Air Quality Standard (NAAQS) in Imperial County from 
consideration in regulatory actions under the CAA.\4\
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    \1\ Our proposed rule and proposal TSD also describe additional 
improvements that we recommend for future ICAPCD modifications of 
the rules. This final action is not based on those recommendations. 
As a result, we do not respond here to all comments we received on 
them.
    \2\ Letter with enclosure from Laura Yoshii (EPA), to James 
Goldstene (ARB), Re: exceptional events requests regarding 
exceedances of the PM10 NAAQS in Imperial County, CA, 
December 22, 2009.
    \3\ 40 CFR 50.1(j) and 50.14.
    \4\ Issues related to the Regulation VIII deficiencies, 
significant source categories and our decision not to concur with 
the State's exceptional events requests are addressed further below 
in our responses to comments we received on the proposed rule.
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    We summarize the Regulation VIII deficiencies addressed in our 
proposed rule below. These deficiencies concern Regulation VIII 
provisions relating to open areas, unpaved roads and agricultural 
lands.

A. BACM-Related Deficiencies for Open Areas

1. Recreational Off-Highway Vehicle Activity
    While recreational off-highway vehicle (OHV) \5\ activity causes 
much of the PM10 emissions from open areas in Imperial 
County, Rule 804 regulates only a small portion of these emissions, 
including those from OHV activity on State lands on which the rule is 
not being implemented. The vast majority of the OHV emissions in 
Imperial County are addressed only by requirements in Rule 800 section 
F.5 for dust control plans (DCPs) for sources under the control of the 
Bureau of Land Management (BLM). While BLM is required to describe in 
the DCPs the dust control measures that it intends to implement, BLM is 
not required to implement any specific BACM-level controls for OHV use. 
Moreover, ICAPCD has not provided an analysis of BACM for OHV activity, 
including

[[Page 39367]]

potential OHV activity in open areas and on unpaved roads and paths 
that are exempt from the specific requirements and measures in Rules 
804 and 805. The proposed rule and proposal TSD address how ICAPCD can 
correct these deficiencies.\6\
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    \5\ As used here and in the proposal TSD, the term ``off-highway 
vehicle'' or OHV includes all vehicles subject to the exemption in 
Rule 800 section E.6 for recreational use of public lands in 
Imperial County.
    \6\ 75 FR 8008, 8010-8011 and our proposal TSD, section III.B.1.
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2. Definition of ``Disturbed Surface''
    The term ``disturbed surface area'' is used in several Regulation 
VIII rules but is never defined. For example, Rule 804 applies to a 
source category for which BACM is required and relies on the undefined 
term to describe rule applicability in Rule 804 section B. A definition 
of this term is necessary in order to ensure that these rules are 
enforceable at a BACM level.

B. BACM-Related Deficiencies for Unpaved Roads

1. Unpaved Non-Farm Roads
    While CAA section 189(b)(1)(B) requires ICAPCD to implement BACM by 
2008 (i.e., four years after reclassification to serious),\7\ Rule 805 
section E.7 allows the County until 2015 to stabilize heavily-travelled 
unpaved roads. This schedule is inconsistent with the statutory 
requirement and ICAPCD has not provided adequate evidence that this 
schedule is as expeditious as practicable, based upon economic 
feasibility or any other appropriate consideration. In addition, Rule 
805 section E.7's requirement to stabilize all non-exempt unpaved 
County roads is not adequately enforceable as currently structured 
because it is not clear that the County is required to implement (and 
not just submit) a stabilization plan; stabilize different unpaved 
roads each year; and maintain all stabilized roads. The proposed rule 
and proposal TSD address how ICAPCD can correct these deficiencies.\8\
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    \7\ On August 11, 2004, EPA reclassified Imperial County as 
serious nonattainment for PM10. 69 FR 48835. Since 2008 
has passed, BACM is now required to be implemented as expeditiously 
as practicable. Delaney v. EPA, 898 F.2d 687 (9th Cir. 1990).
    \8\ 75 FR 8008, 8011 and our proposal TSD, section III.B.3.
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2. Unpaved Farm Roads and Traffic Areas
    Rule 805 section D.2 exempts agricultural roads and traffic areas 
from the opacity and stabilization requirements applicable to non-
agricultural operation sites. Farm roads and traffic areas are only 
required to implement a conservation management practice (CMP) from the 
menus for unpaved roads and traffic areas in Rule 806 in contrast to 
analogous rules in other geographical areas.
    Rule 806 sections E.3 and E.4 list CMPs intended to control 
emissions from agricultural unpaved roads and traffic areas but these 
measures are broadly defined and there is no other mechanism in the 
rule to ensure specificity. The absence of sufficiently defined 
requirements makes it difficult for regulated parties to understand and 
comply with the requirements, and makes it difficult for ICAPCD or 
others to verify compliance and to enforce the requirements if 
necessary. The lack of specificity similarly renders it difficult to 
assess whether the measures constitute BACM level controls. The 
proposed rule and proposal TSD address how ICAPCD can correct these 
deficiencies.\9\
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    \9\ 75 FR 8008, 8011 and our proposal TSD, section III.B.4.
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3. Border Patrol Roads
    Rule 800 section F.6.c exempts roads owned or operated by the U.S. 
Border Patrol (BP) from Rule 805 requirements that are ``inconsistent 
with BP authority and/or mission.'' It is not clear what this exemption 
is intended to address, or how it would be implemented and enforced in 
order to meet BACM requirements. The proposed rule addresses how ICAPCD 
can correct these deficiencies.\10\
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    \10\ 75 FR 8008, 8011.
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C. BACM-Related Deficiencies for Agricultural Lands

1. Tilling and Harvesting
    Rule 806 sections E.1 and E.2 list CMPs intended to control 
emissions from agricultural land preparation and cultivation (including 
tilling), and harvest activities, but these measures are broadly 
defined and there is no other mechanism in the rule to ensure 
specificity. The absence of sufficiently defined requirements makes it 
difficult for regulated parties to understand and comply with the 
requirements, and makes it difficult for ICAPCD or others to verify 
compliance and to enforce the requirements if necessary. The lack of 
specificity similarly renders it difficult to assess whether the 
measures constitute BACM level controls.
    In addition, Rule 806 section E requires one CMP from the ``land 
preparation and cultivation'' category and one CMP from the 
``harvesting'' category, while rules in other geographic areas have 
more stringent requirements.
    The proposed rule and proposal TSD address how ICAPCD can correct 
these deficiencies.\11\
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    \11\ 75 FR 8008, 8011-8012 and our proposal TSD, section 
III.B.4.
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2. Windblown Dust
    Windblown dust from non-pasture agricultural lands is also a 
significant source of PM10 that requires BACM independent of 
agricultural tilling. The CMPs in Rule 806 section E, however, mainly 
control emissions by reducing the number of vehicle passes across 
fields, and sources are not required to select BACM level practices for 
controlling windblown dust from active or fallow agricultural fields. 
The proposed rule and proposal TSD address how ICAPCD can correct these 
deficiencies.\12\
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    \12\ 75 FR 8008, 8012 and our proposal TSD, section III.B.4.
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D. Non-BACM Deficiency

    Rule 802 section D.1 allows the Air Pollution Control Officer 
(APCO) to set aside controls that might be used instead of water to 
stabilize surfaces of bulk materials. This discretion allows ICAPCD to 
approve alternatives to the applicable SIP without following the SIP 
revision process described in CAA section 110. Moreover, ICAPCD has not 
demonstrated why such discretion is needed for measures such as 
covering, enclosing or sheltering material piles. The proposed rule 
addresses how ICAPCD can correct these deficiencies.\13\
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    \13\ 75 FR 8008, 8012.
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II. Public Comments and EPA Responses

    EPA's proposed action provided a 30-day public comment period. 
During this period, we received nine unique comment letters from public 
agencies and broad-based organizations.
     Brad Poiriez, Air Pollution Control Officer, Imperial 
County Air Pollution Control District, March 25, 2010 (ICAPCD).
     Daniel Steward, Acting Field Manager, United States 
Department of the Interior, Bureau of Land Management, El Centro 
Resource Area, March 24, 2010 (BLM).
     Kathleen Dolinar, District Superintendent, Ocotillo Wells 
District, California State Parks, Off-Highway Motor Vehicle Recreation 
Division, by e-mail dated March 24, 2010 (OWD).
     Gail Sevrens, Acting District Superintendent, Colorado 
Desert District, California State Parks, by e-mail dated March 25, 2010 
(CDD).
     David P. Hubbard, Gatzke Dillon & Balance LLP, on behalf 
of EcoLogic

[[Page 39368]]

Partners, Inc., March 25, 2010 (EcoLogic).
     Lisa T. Belenky, Senior Attorney, Center for Biological 
Diversity, March 25, 2010, representing several listed parties (CBD).
     Jose Luis Olmedo, Executive Director, Comite Civico Del 
Valle, Inc., March 25, 2010, submitted and joined by other parties 
(Comite).
     Ayron Moiola, Executive Director, Coalition of Labor, 
Agriculture & Business, March 24, 2010 (COLAB).
     Mark McBroom, President, Imperial County Farm Bureau, 
March 24, 2010 (Farm Bureau).
    We also received over 100 comment letters from individuals and 
organizations associated with recreational OHV activities. We reference 
these comments below by their identification in the Federal docket 
management system (FDMS) found at regulations.gov. For example, the 
comment listed in FDMS as document number ``EPA-R09-OAR-2010-0120-
0219'' is referenced below as ``0219.''
    We summarize the comments and provide our responses below. In our 
responses we identify specific commenters in some cases but not in 
others, particularly where many commenters made similar points.

A. General

    These overarching comments largely provide general support or 
opposition to our proposal.
    General #1: CBD and Comite support EPA's proposal to find that the 
Regulation VIII submittal does not fully implement BACM level controls 
for all significant source categories in Imperial County, and support 
EPA's nonconcurrence with associated exceptional event requests. They 
ask EPA to finalize the proposed limited disapproval of Regulation VIII 
and to require additional PM10 emissions restrictions. Many 
other commenters disagree with EPA's proposed limited disapproval, 
especially with EPA's identification of deficiencies for BACM 
requirements and EPA's nonconcurrence with exceptional events. ICAPCD, 
for example, believes that EPA's proposal is arbitrary and capricious, 
and that California has demonstrated that all required BACM are being 
implemented in Imperial County.
    Response: No response is necessary for the overarching statements 
of support or opposition. Responses are provided below to the specific 
comments that support these general statements.
    General #2: Several commenters believe that EPA's proposal lacks 
adequate scientific support. One (0144), for example, states that 
passing sweeping air quality regulations in an area with unique terrain 
and climate with only generalities to prove the sources of pollution is 
unethical and appears anti-development, anti-OHV and anti-agriculture.
    Response: The scientific support for EPA's action is documented in 
our proposal and the associated proposal TSD and discussed further in 
response to specific comments below. See, for example, response to 
comment EI 3 below. The serious health impacts of exposure to 
elevated levels of PM10 are well known and well documented 
and need not be reiterated here.
    General #3: ICAPCD objects to EPA taking over four years to act on 
its submittals of Regulation VIII for approval and claims that EPA is 
only now raising basic issues that ICAPCD believes should have been 
resolved before rule adoption. For example, ICAPCD objects to EPA 
disapproving a definition that it claims is clear and understood by all 
affected parties. ICAPCD and others (e.g., COLAB) comment that EPA 
never raised this and other concerns despite ICAPCD's extensive public 
process and communication with EPA before rule adoption. ICAPCD also 
cites EPA's testimony before the District Board in which the Agency 
supported Regulation VIII as BACM. As a result, ICAPCD concludes that 
EPA's proposal undermines ICAPCD's ability to rely on EPA comments in 
the future.
    Response: EPA reviews and comments on many draft State and local 
agency rules during their development prior to submittal to EPA for 
formal approval. It is generally more efficient for all parties to 
identify and resolve issues early in the process, rather than after 
rules are adopted and submitted to EPA for inclusion into the SIP. 
EPA's formal action on local rules, however, can only occur through 
notice and comment rulemaking after rules have been officially 
submitted to EPA by the State. If EPA determines during that process 
that a submittal does not fulfill relevant CAA requirements, we cannot 
approve the submittal. Given time and resource constraints, it is not 
always possible for the Agency to identify or analyze fully all issues 
before State or local rule adoption. Moreover, EPA must carefully 
consider all public comments submitted on proposed EPA actions on State 
and local rules. Such comments often identify issues and concerns that 
may not have arisen during the prior evaluation of drafts of a rule. We 
continue to believe, however, that communication between EPA and State 
and local agencies at the rule development stage is productive.
    General #4: OWD asks EPA to extend the comment period because it 
was informed of EPA's proposal only nine days before the close of the 
comment period. Several commenters also state that EPA did not provide 
adequate notification time (0218.1 and 0098) or consultation with State 
Park personnel (0218.1 and OWD).
    Response: EPA denied OWD's request to extend the comment period 
because EPA is under a court order \14\ to finalize action by June 15, 
2010, and needs time to analyze all comments submitted on the 
proposal.\15\ While more time and outreach before EPA action is always 
desirable, nothing in the comments suggests that EPA failed to follow 
relevant public notification requirements found in the Administrative 
Procedures Act.\16\ EPA notes that OWD did comment on the proposal and 
EPA has taken those comments into consideration in the final action.
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    \14\ Comite Civico Del Valle, Inc., v. Jackson, No. 09-cv-04095 
PJH (N.D. Cal.).
    \15\ E-mail from Andrew Steckel, EPA, to Kathleen Dolinar, 
California State Parks, March 29, 2010.
    \16\ See 5 U.S.C. 553.
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B. State Implementation Plan (SIP)

    These comments generally address broad SIP issues rather than 
specific Regulation VIII provisions.
    SIP #1: OWD believes the PM10 standard is nearly 
impossible to attain given Imperial's climate, natural desert 
condition, the cost of inappropriate BACM, and other local conditions. 
In contrast, Comite asks EPA to find that California has failed to 
submit a PM10 plan as required by 72 FR 70222 (December 11, 
2007), and to consider imposing associated CAA section 179 sanctions 
and a section 110(c) Federal implementation plan (FIP) in this area.
    Response: Our proposed action addresses the CAA section 
189(b)(1)(B) requirement for BACM for certain PM10 sources 
in Imperial County. The submittal at issue, Regulation VIII, is but one 
portion of the complete SIP that ICAPCD must develop in order to meet 
additional CAA requirements. These comments address the separate and 
broader statutory obligations for the State to submit a PM10 
plan that, among other things, demonstrates expeditious attainment of 
the PM10 NAAQS. Those other obligations are not the subject 
of this action.
    SIP #2: ICAPCD does not believe that any additional controls such 
as those that may need to be implemented if EPA partially disapproves 
Regulation VIII

[[Page 39369]]

will prevent PM10 exceedances during high winds or otherwise 
materially benefit air quality on days unaffected by high winds. ICAPCD 
further believes that such additional controls will waste limited 
resources that should be used in other ways to improve local air 
quality in the area.
    Response: CAA section 189(b)(1)(B) and EPA guidance \17\ require 
that BACM be implemented for all significant source categories \18\ in 
serious PM10 nonattainment areas such as Imperial County. As 
explained in our proposal,\19\ we determined that each of the 
subcategories under open areas, unpaved roads and agricultural lands 
below meet or exceed the 5 [micro]g/m\3\ de minimis level in our 
guidance and are therefore significant source categories in Imperial 
County:
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    \17\ ``State Implementation Plans for Serious PM-10 
Nonattainment Areas, and Attainment Date Waivers for PM-10 
Nonattainment Areas Generally; Addendum to the General Preamble for 
the Implementation of Title I of the Clean Air Act Amendments of 
1990;'' 59 FR 41998 (August 16, 1994) (General Preamble Addendum).
    \18\ Under the General Preamble Addendum, a source category 
``will be presumed to contribute significantly to a violation of the 
24-hour NAAQS if its PM10 impact at the location of the 
expected violation would exceed 5 [micro]g/m\3\.'' This is also 
referred to as the de minimis level. Id. at 42011.
    \19\ 75 FR 8008, 8010, and proposal TSD, pp. 5-7.
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    Open areas:

--Windblown Dust, Other Open Area.

    Unpaved roads:

--Entrained Unpaved Road Dust, City/County.
--Entrained Unpaved Road Dust, Canal.
--Windblown Dust, Unpaved City/County Road.
--Windblown Dust, Unpaved Canal Road.
--Windblown Dust, Unpaved Farm Road.

    Agricultural lands:
--Tilling.
--Windblown Dust, Non-Pasture Agricultural Lands.

    As EPA stated in the guidance, the structural scheme throughout 
title I of the CAA, including its provisions for the PM10 
NAAQS, requires the implementation of increasingly stringent control 
measures in areas with more serious pollution problems. EPA further 
stated ``that the more serious the air quality problem, the more 
reasonable it is to require States to implement control measures of 
greater stringency despite the greater burdens such measures are likely 
to cause.'' \20\ Imperial County continues to violate the 
PM10 standard \21\ and our proposed action identifies 
several components of the State's Regulation VIII submittal relating to 
open areas, agricultural lands and unpaved roads that do not fulfill 
the CAA BACM requirement and the enforceability requirements of CAA 
section 110(a).
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    \20\ General Preamble Addendum at 42010.
    \21\ EPA's Air Quality System Preliminary Design Value Report 
(May 18, 2010) shows 17 exceedances of the 24-hour PM10 
NAAQS in Imperial County between 2007 and 2009.
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    We further address ICAPCD's contention that additional Regulation 
VIII controls will not prevent PM10 exceedances during high 
winds in our response to comment EE 1 below.
    SIP #3: Many commenters emphasize the importance of OHV areas in 
Imperial County for recreation, and believe that enjoyment of the 
desert should not be restricted. Commenters note that many 
organizations help keep the desert clean, and one commenter (0175.1) 
believes such efforts would be reduced if OHV areas are closed.
    Response: Recreation, enjoyment of the desert and clean deserts are 
certainly desirable, whether for OHV use or otherwise. However, except 
as implicit in our response to comment OHV 5 below, they are 
not germane to the evaluation in our proposal and in this final rule of 
Regulation VIII and its compliance with the applicable CAA 
requirements.
    SIP #4: Two commenters (OWD and 0218.1) question whether EPA's 
proposal is based on statistically significant data since there were 
only three PM10 exceedances within a three year period.
    Response: ICAPCD's obligation to implement BACM for Regulation VIII 
fugitive dust sources derives from the Imperial County's designation as 
nonattainment and classification as serious. On November 15, 1990, the 
date of enactment of the 1990 Clean Air Act Amendments, Imperial County 
was designated nonattainment and classified as moderate.\22\ On August 
11, 2004, EPA reclassified the area as serious in compliance with a 
mandate of the U.S. Court of Appeals for the Ninth Circuit.\23\ The 
reclassification, pursuant to CAA section 188(b)(2), was based on a 
finding that the area failed to attain the PM10 NAAQS by the 
statutory deadline of December 31, 1994. Once reclassified to serious, 
the area was required to comply with CAA section 189(b)(1)(B), which 
required that BACM be implemented for the area four years after its 
reclassification to serious.
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    \22\ 56 FR 56694 (November 6, 1991).
    \23\ 69 FR 48792; Sierra Club v. United States Environmental 
Protection Agency, et al., 346 F.3d 995 (9th Cir. 2003); cert. 
denied, 542 U.S. 919 (2004).
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    The three exceedances to which OWD refers occurred during 2006 and 
2007. The State requested that these exceedances be excluded from use 
in regulatory actions pursuant to EPA's EER.\24\ Because we did not 
concur with the State's request, BACM is required to be implemented for 
certain windblown dust source categories, including open areas, for 
which such controls would not have been required if we had agreed with 
the State.\25\ See our responses to Exceptional Events comments below.
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    \24\ See section II.D.1 below.
    \25\ 75 FR 8008, 8010 and proposal TSD pp. 5-7.
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    We also note that California has chosen to sample PM10 
in Imperial County only one out of every six days. As a result, by 
regulation, each monitored exceedance is estimated to represent 
approximately six exceedances rather than one.\26\ For example, in 
2009, ICAPCD reported three monitored exceedances at the Ethel Street 
monitoring site, which are estimated to represent 18.3 exceedances. 
Exceedances were also monitored at Brawley, El Centro, Westmorland and 
Niland in 2009.\27\
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    \26\ 40 CFR part 50, appendix K.
    \27\ EPA's Air Quality System Preliminary Design Value Report 
(May 18, 2010).
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    SIP #5: Comite believes PM10 should be further 
controlled in Imperial County by adoption of local fugitive dust 
ordinances like those in Coachella's Cathedral City, and by 
strengthening open burning regulations to be similar to those in the 
South Coast Air Quality Management District (SCAQMD) and the San 
Joaquin Valley Unified Air Pollution Control District (SJVUAPCD).
    Response: We assume the commenter refers to title 8, chapter 8.54 
of Cathedral City's municipal code which describes requirements for 
construction, unpaved roads and other local dust sources.\28\ These 
requirements are generally similar to the type of controls adopted by 
SCAQMD (e.g., Rule 403), SJVUAPCD (e.g., Regulation VIII) and ICAPCD 
(Regulation VIII). The commenter does not identify any specific 
Cathedral City controls that it believes are needed in ICAPCD 
Regulation VIII to constitute BACM. Except where identified in our 
proposal, we believe ICAPCD's BACM analyses include adequate evaluation 
of analogous fugitive dust controls in other areas.\29\ It is possible 
that the commenter is recommending duplicative city ordinances that 
overlap County-wide Regulation VIII. While such redundancy could 
improve compliance, it is generally not necessary

[[Page 39370]]

to meet CAA section 110(a) enforceability requirements.
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    \28\ Cathedral City Municipal Code, title 8, chapter 8.54, 
Fugitive Dust Control; http://qcode.us/codes/cathedralcity/.
    \29\ 2009 PM10 SIP table 4.2 and 2005 BACM analysis 
table 4.2.
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    Finally, our proposed action only addresses the ICAPCD controls for 
certain PM10 source categories encompassed by Regulation 
VIII, and therefore does not address control of open burning or many 
other air pollution sources in Imperial County. See also responses to 
comments SIP 1 and EI 1.
    SIP #6: Comite cites Vigil v. Leavitt, 381 F.3d 826, 834 (9th Cir. 
2004) and Hall v. EPA, 273 F.3d 1146 (9th Cir. 2001), in commenting 
that measures in other areas can be considered BACM for Imperial County 
and are per se feasible. Comite further argues that what constitutes 
BACM can strengthen over time. In contrast, OWD does not believe that 
Imperial County should apply mitigation measures from other geographic 
areas (e.g., SJVUAPCD and Maricopa) that have different geologic and 
other local conditions. Similarly, COLAB believes that different 
cultural practices prevent ICAPCD from blindly implementing controls 
imposed in other areas, although the ICAPCD and SJVUAPCD CMP rules are 
very similar. Still another commenter (0119) claims that similar 
restrictions on construction, OHVs, farmers, etc., in Las Vegas and 
elsewhere have not been effective, and there is no need for such 
draconian and ineffective bureaucratic rules.
    Response: EPA believes that it is appropriate, when evaluating what 
constitutes BACM for a given source category, to consider controls that 
have been adopted and implemented in other geographical areas. EPA 
agrees that the facts and circumstances in a given area can affect what 
constitute BACM for that area, but that this determination must be 
based upon appropriate consideration of relevant information specific 
to that area.
    Comite does not explain how the cited cases support its position. 
Nonetheless, we agree that in evaluating BACM for Imperial County, 
ICAPCD should analyze analogous measures in other areas and that BACM 
may strengthen over time.\30\ Our proposal identifies several 
significant deficiencies in ICAPCD's analysis to date.\31\ While BACM 
is determined on a case-by-case basis \32\ and, as such, the analysis 
can include evaluation of local conditions that might make specific 
controls economically and/or technologically feasible in one area but 
not another,\33\ neither the 2009 PM10 SIP \34\ nor the 
comment provides sufficient detail to adequately address the 
deficiencies identified in our proposal.
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    \30\ General Preamble Addendum at 42013-42014.
    \31\ E.g., OHV controls in Arizona Revised Statute Sec.  49-
457.03 and Clark County Air Quality Regulations, section 90 (75 FR 
8011, February 23, 2010).
    \32\ General Preamble Addendum at 42010 and 42012.
    \33\ In this respect, we do not agree with Comite that measures 
adopted in other areas are automatically transferable to Imperial 
County.
    \34\ ``2009 Imperial County State Implementation Plan for 
Particulate Matter Less Than 10 Microns in Aerodynamic Diameter, 
Final,'' adopted by ICAPCD Governing Board on August 11, 2009. (2009 
PM10 SIP).
---------------------------------------------------------------------------

    OWD does not explain how Imperial County differs so markedly from 
the San Joaquin Valley and the Maricopa area that it would be 
inappropriate to consider BACM approved in those areas as part of the 
evaluation of controls for the same source categories in Imperial 
County. Similarly, COLAB does not elaborate on what ``cultural 
practices'' in Imperial County would justify disregarding approved BACM 
in the San Joaquin Valley and the Maricopa area as part of the 
evaluation of what controls would be appropriate for comparable source 
categories in Imperial County.

C. Emissions Inventory (EI)

    EI #1: Many commenters oppose further OHV controls because they 
believe OHVs contribute little to Imperial County's PM10 
pollution problem compared to other sources. Commenters identify 
various sources they believe are more significant and/or should be 
further addressed instead, including fallow fields, fireplaces, feed 
lots, agricultural burning, pesticides, dirt roads, inefficient street 
lights, insufficient public transportation, insufficient speed limit 
enforcement, Interstate 8, the New River, the Salton Sea, Arizona to 
the east, San Diego to the west, Mexican roads, fires and factories to 
the south, rain, wind, erosion, dust storms and other natural 
occurrences. These commenters include OWD, 0096, 0097, 0150, 0139, 
0152, 0180, 0192, 0194 and 0219.1.
    Response: Our proposal explains that BACM is required for all 
significant PM10 source categories in Imperial County, that 
windblown dust from open areas is a significant PM10 source 
category, and that OHVs greatly increase emissions from open areas in 
Imperial County.\35\ Our proposal further explains that ICAPCD has not 
demonstrated implementation of BACM for open areas with respect to 
OHVs.\36\ These conclusions are based on inventory information prepared 
by ICAPCD and ARB and used during development of Regulation VIII and 
the 2009 PM10 SIP.\37\
---------------------------------------------------------------------------

    \35\ Proposal TSD, pp. 5-8.
    \36\ Id. at p. 8.
    \37\ Id. at pp. 5-8.
---------------------------------------------------------------------------

    The inventory in the 2009 PM10 SIP represents the most 
comprehensive information currently available on OHV emissions in 
Imperial County.\38\ ICAPCD's analysis in the 2009 PM10 SIP 
concluded that windblown dust from open areas was not a significant 
source category, but this conclusion was premised upon many exceedences 
of the NAAQS being deemed to be the result of exceptional events. 
However, EPA's own conclusion regarding those exceedences is that they 
were not caused by exceptional events and, as a result, we consider 
windblown dust from open areas to be a significant source category that 
is subject to the CAA's BACM requirement. See response to comment SIP 
4 and responses to Exceptional Events comments in section II.D 
below. Therefore ICAPCD has failed to meet the BACM requirement for 
windblown dust from open areas, in part because ICAPCD has not 
evaluated what controls might be appropriate for OHV activities in such 
areas.
---------------------------------------------------------------------------

    \38\ 2009 PM10 SIP, Chapter 3; Appendix III.
---------------------------------------------------------------------------

    EPA's action on the Regulation VIII submittal does not address or 
depend on whether additional controls may also be appropriate for the 
various other sources identified in the comments.
    EI #2: One commenter (0188) had driven past many farms in El Centro 
during tilling and observes that the dust was very minimal. Another 
(0201) thinks more attention should be paid to agriculture which the 
commenter believes is exempt from many of the environmental 
regulations.
    Response: See response to comment EI 1. Similar to 
emissions from open areas, EPA has concluded that emissions associated 
with tilling on and windblown dust from agricultural lands are 
significant source categories in Imperial County and, as such, ICAPCD 
needs to meet the BACM requirement for such sources.\39\
---------------------------------------------------------------------------

    \39\ Proposal TSD, pp. 5-8 and 9-11.
---------------------------------------------------------------------------

    The commenter (0201) concerned about exemptions for agriculture did 
not specify which regulations exempt agriculture. As explained in our 
proposal, however, because certain agricultural-related activities 
constitute a significant source category for PM10 in 
Imperial County, ICAPCD is required to meet the CAA's BACM requirements 
for such sources. Any ``exemptions'' for any such sources would need to 
be justified and explained in the context of meeting the BACM 
requirements.
    EI #3: Several commenters claim that EPA has not proved the impact 
of OHVs

[[Page 39371]]

on PM10 levels sufficient to require additional OHV 
regulations. OWD notes, for example, that: (1) EPA did not analyze 
extreme terrain, thermal stability and other effects on winds in the 
desert; (2) most emissions from open lands come from undisturbed shrub/
grassland which are not anthropogenic sources; and (3) ICAPCD's 2009 
PM10 SIP, on which EPA relies, uses worst-case assumptions 
rather than actual soil condition information to estimate that OHVs 
represent less than 5% of the County's total PM10 emissions 
(13.9 of 282 tpd). OWD states that 99% of these total emissions relate 
to OHVs subject to Federal and State stewardship. Therefore OWD 
concludes that actual OHV emissions are small compared to worst-case 
estimates. OWD also questions EPA's reference for the estimate of 22 
tpd of windblown PM10 from OHVs.
    EcoLogic believes that EPA needs monitoring in the Ocotillo Wells 
State Vehicle Recreation Area (SVRA) and other areas to show how 
specific OHV activity affects sensitive receptors and for EPA to 
identify OHV activity as a major contributor to the County's 
PM10 problem. Another commenter believes EPA lacks data 
tying PM to specific OHV activities (0218.1), and several commenters 
believe that any pollution from OHVs is virtually immeasurable. Several 
commenters believe additional inventory analysis is particularly 
important because OHV areas are far from population centers and 
monitors with PM10 exceedances. One commenter (0131) 
requests an unbiased third-party study of OHV impacts. CDD explains 
that PM10 emissions from several specific parks in Imperial 
County should be low, partly because OHV activity is prohibited. In 
contrast, CBD supports EPA's claim that OHVs on BLM land cause 
considerable PM10 in Imperial County, and notes that BLM 
previously estimated PM10 impacts from OHV activities at the 
Aldodones Dunes alone as high as 11 tpd on holiday weekends.
    Response: It is extremely difficult to quantify and speciate 
accurately the myriad sources of PM10 emissions and 
PM10 precursor emissions spatially and temporally for 
purposes of modeling air pollution impacts and developing cost 
effective control programs. As a result, emission inventories are 
constantly being refined as more and better science and data become 
available. However, EPA, State and local air pollution agencies must 
make policy and regulatory decisions based on the best information 
available to comply with the CAA. As discussed in response to comment 
EI 1, the inventory and other information underlying our 
proposal regarding the emissions from OHV activity and the impacts of 
such activity represent the most comprehensive information currently 
available.
    Regarding specific concerns in this comment:
    (1) EPA's conclusion that BACM is required for OHV activity relies 
on emissions inventory estimates that ICAPCD developed. If appropriate, 
ICAPCD could choose to refine those estimates to take into 
consideration factors such as terrain, thermal stability and other 
effects on winds in the desert, as well as distances between OHV areas 
and population centers and additional third party analysis. Such 
refinements are beyond the level of detail normally used in inventories 
required by CAA section 172(c)(3).\40\
---------------------------------------------------------------------------

    \40\ See, e.g., AP-42, Fifth Edition, Volume I, Chapter 13: 
Miscellaneous Sources, 13.2.2--Unpaved Roads, Final Section, EPA, 
November 2006. This document provides EPA guidance on estimating 
emissions on unpaved roads and does not, for example, account for 
road terrain. http://www.epa.gov/ttn/chief/ap42/ch13/index.html.
---------------------------------------------------------------------------

    (2) ICAPCD in its 2009 PM10 SIP quantifies the impact of 
soil type and land cover (e.g., shrub/grassland) and degree of OHV 
disturbance in OHV emission estimates relied on by our proposal.\41\
---------------------------------------------------------------------------

    \41\ 2009 PM10 SIP, appendix III.B.
---------------------------------------------------------------------------

    (3) ICAPCD used the best available information regarding soil types 
in open areas and determined that the remaining uncertainty does not 
affect the results of the technical analyses.\42\
---------------------------------------------------------------------------

    \42\ 2009 PM10 SIP, p. 3-2.
---------------------------------------------------------------------------

    (4) Even OWD's 13.9 tpd OHV emission estimate, which we believe is 
too low,\43\ exceeds the presumptive 5 [micro]g/m\3\ de minimis level 
for source categories requiring BACM.\44\
---------------------------------------------------------------------------

    \43\ In comparison to ICAPCD's 22 tpd estimate. Proposal TSD, 
footnote 32.
    \44\ As discussed on pp. 5-8 of the proposal TSD, depending on 
the specific monitor, 2-3% of Imperial County's annual inventory is 
calculated to result in a 5 [micro]g/m\3\ contribution, which 
equates to about 6-8 tpd emissions.
---------------------------------------------------------------------------

    (5) The reference for 22 tpd of windblown OHV emissions is 
accurately explained in our proposal.\45\
---------------------------------------------------------------------------

    \45\ Id.
---------------------------------------------------------------------------

    The comment that monitoring is necessary in the Ocotillo Wells SVRA 
and other areas before EPA should require controls for OHV activities 
is incorrect. As stated previously, under CAA section 189(b) and EPA 
guidance, BACM is required for all significant source categories in the 
nonattainment area, including windblown dust in open areas caused by 
OHV activity.\46\ Thus monitoring, which could provide valuable 
information, is nevertheless not necessary to determine which source 
categories require BACM.
---------------------------------------------------------------------------

    \46\ See, e.g., proposal TSD, p. 5.
---------------------------------------------------------------------------

D. Exceptional Events (EE)

1. Background
    On March 22, 2007, EPA adopted a final rule to govern the review 
and handling of certain air quality monitoring data for which the 
normal planning and regulatory processes are not appropriate.\47\ Under 
the rule, EPA may exclude data from use in determinations of NAAQS 
exceedances and violations if a State demonstrates that an 
``exceptional event'' caused the exceedances. Before EPA can exclude 
data from these regulatory determinations, the State must flag the data 
in EPA's Air Quality System database and, after notice and opportunity 
for public comment, submit a demonstration to EPA to justify the 
exclusion. After considering the weight of evidence provided in the 
demonstration, EPA decides whether or not to concur with each flag.
---------------------------------------------------------------------------

    \47\ ``Treatment of Data Influenced by Exceptional Events,'' 72 
FR 13560 (March 22, 2007) (EER).
---------------------------------------------------------------------------

    On May 21, 2009, ARB submitted demonstrations for ``high wind'' 
events that allegedly caused ten exceedances of the 24-hour 
PM10 standard at various monitors in Imperial County in 2006 
and 2007. The demonstrations consisted of the following support 
documents (listed in Table 2) prepared by ARB, ICAPCD, and ICAPCD's 
contractor, ENVIRON:

                                                     Table 2
----------------------------------------------------------------------------------------------------------------
                   Description                           Document date                Abbreviated title
----------------------------------------------------------------------------------------------------------------
Natural Event Documentation: Calexico and          January 30, 2009........  September NED.\48\
 Westmorland, California--September 2, 2006.
Natural Event Documentation: Brawley and           April 15, 2008..........  Original April NED.
 Westmorland, California--April 12, 2007
 [enclosed with June 13, 2008 letter to Sean
 Hogan].

[[Page 39372]]

Natural Event Documentation: Brawley, Calexico,    April 15, 2008..........  Original June NED.
 El Centro, Niland, and Westmorland, California--
 June 5, 2007, Imperial County Air Pollution
 Control District [enclosed with June 13, 2008
 letter to Sean Hogan].
Natural Event Documentation: Brawley and           March 12, 2009..........  April NED.
 Westmorland, California--April 12, 2007
 [addendum to June 13, 2008 submittal].
Natural Event Documentation: Imperial County,      March 12, 2009..........  June NED.
 California--June 5, 2007 [addendum to June 13,
 2008 submittal].
----------------------------------------------------------------------------------------------------------------

    As stated above in section I, on December 22, 2009, EPA denied 
ARB's request to exclude all of the exceedances as exceptional events. 
The basis for our decision is specified in an enclosure which 
accompanied the December 22, 2009 letter.\49\ By letter, including 
Attachment A and Appendix A1, dated March 3, 2010, ICAPCD asked EPA to 
reconsider this decision.\50\
---------------------------------------------------------------------------

    \48\ We refer to the natural event documentation in these five 
documents, collectively, as the NEDs.
    \49\ See footnote 2. We refer to our December 22, 2009 letter 
and the enclosure hereafter as ``2009 EE decision.''
    \50\ Letter from Brad Poiriez (ICAPCD) to Jared Blumenfeld 
(EPA), March 3, 2010 with Attachment A and Appendix A1.
---------------------------------------------------------------------------

    Our proposal on Regulation VIII explained that our 2009 EE decision 
led to an adjustment of ICAPCD's significant source analysis which in 
turn led us to modify the list of significant sources for which BACM 
must be implemented in Imperial County under CAA section 
189(b)(1)(B).\51\ As a result, our 2009 EE decision was the subject of 
public comments on our proposed action. ICAPCD resubmitted its March 3, 
2010 letter, including Attachment A and Appendix A1, regarding our 2009 
EE decision as Appendix C to its March 25, 2010 comment letter on our 
Regulation VIII proposed action.\52\ EPA also received comments 
pertaining to our exceptional events decision from Comite and CBD. A 
summary of these comments and our responses follow.
---------------------------------------------------------------------------

    \51\ See 75 FR 8010 and the proposal TSD, pp. 5-7.
    \52\ We refer to ICAPCD's March 10, 2010 letter with its 
Attachment A and Appendix A1, collectively, throughout our responses 
to the exceptional events comments in section II.D as 
``Attachment.''
---------------------------------------------------------------------------

2. Events Not Reasonably Controllable or Preventable
    EE #1: ICAPCD (Attachment) disagrees with EPA's interpretation of 
the requirement in the EER at 40 CFR 50.1(j) that in order for an event 
to meet the regulatory definition of exceptional event, such event must 
be ``not reasonably controllable or preventable.'' Specifically ICAPCD 
takes issue with EPA's statement in our 2009 EE decision that this 
criterion inherently implies ``a requirement that the State demonstrate 
that anthropogenic sources contributing to the exceedance caused by the 
event were reasonably well controlled.'' ICAPCD believes that under the 
plain regulatory language it is irrelevant whether ``reasonable and 
appropriate'' controls are in place on the day of an otherwise 
qualifying event when it can be shown that such controls would not 
reduce emissions and impact at the monitor sufficiently to prevent the 
exceedance. ICAPCD believes that it is inconsistent with the intent of 
the CAA for EPA to refuse to concur with an exceptional event claim 
solely due to EPA's dissatisfaction with the stringency of certain 
controls when such controls could not have prevented the exceedance.
    Response: ICAPCD mischaracterizes both the plain language and the 
regulatory intent of 40 CFR 50.1(j) by reading the words ``reasonably 
controllable or'' out of that section. The regulation clearly requires 
a showing that the event is not either reasonably controllable or 
preventable, not as ICAPCD would have it, that the event cannot be 
controlled to the extent that no exceedance would have occurred. 
Furthermore, ``control'' as generally used in the CAA and EPA guidance 
(e.g., RACT and BACM \53\), and as defined in the dictionary means to 
regulate or to reduce the incidence or severity.\54\ Thus the meaning 
of the word ``control'' undeniably differs from the words ``eliminate'' 
or ``prevent.'' Therefore, to meet the ``not reasonably controllable or 
preventable'' criterion in 40 CFR 50.1(j), states must demonstrate that 
reasonable controls were implemented to regulate or reduce emissions 
regardless of whether the controls would have prevented 
exceedances.\55\ Finally we note that the relevance of dust controls is 
inherent in the District's own characterization of the ``event'' as the 
combination of wind and dust entrainment from anthropogenic and 
nonanthropogenic sources.\56\
---------------------------------------------------------------------------

    \53\ ``BACM is the maximum degree of emissions reduction of 
PM10 and PM-10 precursors from a source * * * which is 
determined on a case-by-case basis, taking into account energy, 
environmental, and economic impacts and other costs, to be 
achievable for such source through application of production 
processes and available methods, systems, and techniques for control 
of each such pollutant.'' General Preamble Addendum at 42010.
    \54\ Merriam-Webster's Ninth New Collegiate Dictionary.
    \55\ Similarly, EPA explained in the preamble to the EER that 
analysis of exceptional events includes consideration of whether 
anthropogenic activities have been controlled to the extent possible 
through use of all reasonably available reasonable and appropriate 
measures. 72 FR 13560, 13566, footnote 11.
    \56\ E.g., September NED, p. 9.
---------------------------------------------------------------------------

    As discussed in our 2009 EE decision, the State failed to 
demonstrate that reasonable controls were implemented for anthropogenic 
sources contributing to the exceedances, including recreational OHVs 
and fallow agricultural fields.\57\ Nor does ARB or ICAPCD provide 
convincing evidence in the NEDs or elsewhere to support the claim that 
controls on these sources could not have either prevented the 
exceedances or reduced emissions.
---------------------------------------------------------------------------

    \57\ 2009 EE decision, section 4.2.
---------------------------------------------------------------------------

    EE #2: ICAPCD (Attachment) further argues that the consequence of 
EPA's action would be to require control measures beyond the area's 
practical abilities--a result the EER is specifically designed to 
avoid. ICAPCD claims that other specific provisions are in place to 
prevent such difficulties, and ICAPCD quotes from EPA guidance: ``If 
emissions from anthropogenic sources are reduced to the point that it 
is no longer technologically or economically feasible to reduce those 
emissions further, and the area still cannot attain the NAAQS, the EPA 
may consider waiving the serious area attainment date and appropriate 
serious area requirements.'' \58\
---------------------------------------------------------------------------

    \58\ General Preamble Addendum at 42008.
---------------------------------------------------------------------------

    Response: The provisions to which ICAPCD refers are contained in 
CAA section 188(f) which authorizes EPA to waive subpart 4 requirements 
applicable to serious PM10 nonattainment areas, including 
BACM, where EPA determines that anthropogenic sources of 
PM10 do not contribute significantly to the violation of the 
standard in the area. Under section 188(f), EPA may

[[Page 39373]]

also waive a specific date for attainment of the PM10 
standard if the Administrator determines that nonanthropogenic sources 
contribute significantly to a violation of the standard.
    In guidance, EPA has established the same test for determining what 
constitutes a significant contribution for section 188(f) as is used 
for determining the sources for which BACM must be implemented under 
CAA section 189(b)(1)(B).\59\ The passage in the guidance, quoted in 
isolation by ICAPCD, is preceded by a lengthy discussion regarding the 
circumstances under which a serious area such as Imperial County could 
qualify for section 188(f) waivers. That discussion makes clear that 
before EPA will consider waiving a serious area attainment date and 
requirements for a serious area that failed to attain the standard by 
the serious area deadline, the State must demonstrate that BACMs for 
significant anthropogenic sources have been implemented and that the 
area cannot attain the NAAQS with the implementation of additional 
control measures to achieve at least 5% annual emission reductions 
pursuant to CAA section 189(d). As discussed above and in the 
proposal,\60\ ICAPCD has not shown that BACM has been implemented as 
required by CAA section 189(b)(1)(B) for all significant source 
categories in Imperial County.\61\ Thus it would be difficult to show 
that additional controls are ``beyond the area's practical abilities'' 
or ``no longer technologically or economically feasible'' without a 
more thorough BACM analysis.
---------------------------------------------------------------------------

    \59\ Id. at 42004.
    \60\ 75 FR 8008, 8010-8012 and proposal TSD, pp. 7-11.
    \61\ The 2009 PM10 SIP for Imperial County that is 
intended to address the 5% requirement in CAA section 189(d) was 
adopted by ICAPCD in August 2009 but has not been submitted to EPA 
by ARB. The plan concludes that the area would have attained the 
PM10 standard by the end of 2008 but for transported 
emissions from Mexico and with the ``exclusion of PM10 
measurements affected by high-wind exceptional events.'' As a result 
of the claimed exceptional events, with which we did not concur in 
our 2009 EE decision, the plan also concludes that ``[t]he 5% yearly 
emission reductions requirement does not apply to future years.'' 
2009 PM10 SIP, section 5.3.
---------------------------------------------------------------------------

    EE #3: ICAPCD (Attachment) believes, citing the preamble to the 
EER, that the rule only requires reasonable controls for anthropogenic 
sources within the State.
    Response: While Imperial County air quality may be affected by 
emission sources from areas outside California, such as Arizona and 
Mexico, our 2009 EE decision relies on the lack of demonstrated 
controls for anthropogenic sources within California.
    EE #4: ICAPCD (Attachment) believes that EPA has not specified 
criteria for defining de minimis anthropogenic sources in the EER 
context, explained how the EER justifies such criteria, or described 
feasible analyses to implement such criteria.
    Response: As noted above, our 2009 EE decision stated that inherent 
in the ``not reasonably controllable or preventable'' criterion of the 
definition of ``exceptional event'' in 40 CFR 50.1(j) ``is a 
requirement that the State demonstrate that anthropogenic sources 
contributing to the exceedance caused by the event were reasonably 
controlled.'' We also suggested that this requirement be limited to 
``all non-de minimis anthropogenic sources.'' \62\ In this case, 
however, rather than further interpreting the EER, we relied on 
statements in the NEDs acknowledging anthropogenic contributions in 
order to determine which anthropogenic sources were contributing to the 
2006 and 2007 exceedances.\63\
---------------------------------------------------------------------------

    \62\ 2009 EE decision, section 4.2.
    \63\ See id., section 4.2.1.
---------------------------------------------------------------------------

    EE #5: ICAPCD (Attachment) opposes the statement in EPA's 2009 EE 
decision that ``because implementation of BACM is required in serious 
PM10 areas such as Imperial County under section 189(b) of 
the CAA, it is appropriate to consider that level of control in 
evaluating whether reasonable controls are in place for purposes of the 
Exceptional Events Rule.'' Specifically, ICAPCD argues that (1) such a 
standard would create a new standard for exceptional event showings 
that is inconsistent with the language and intent of the EER which 
entails only ``reasonable'' and not ``best'' control of anthropogenic 
sources; (2) the purpose of the EER is to protect states from 
consequences of reclassification as a result of exceptional events; (3) 
by definition, exceptional events fall outside the normal planning 
process and their analysis should not depend on elements of the normal 
planning process including designation status; and (4) the meaning of 
``reasonable controls'' for the EER should not vary by an area's 
nonattainment status and should not be as stringent as BACM.
    Response: As stated in our 2009 EE decision and in the preamble to 
the EER, EPA addresses the EER criteria, including that the event must 
be ``not reasonably controllable or preventable,'' on a case-by-case 
basis considering the weight of available evidence.\64\ Thus it is 
appropriate to consider the totality of circumstances in Imperial 
County in determining what constitutes ``reasonable'' controls. We note 
again that the County has been designated nonattainment and classified 
as moderate or serious since 1990. The area was reclassified to serious 
in 2004.
---------------------------------------------------------------------------

    \64\ 2009 EE decision, pp. 4 and 7; 72 FR 13560, 13569.
---------------------------------------------------------------------------

    In evaluating rules as RACM or BACM, EPA has long considered it 
appropriate to consider local conditions since what is technologically 
and economically feasible in one area may not be in another.\65\ 
Moreover, EPA's 2009 EE decision did not define reasonable control as 
BACM in all cases or suggest that the EER mandates such an outcome. 
Rather, we stated that ``[b]ecause implementation of BACM is required 
in serious PM10 nonattainment areas such as Imperial County 
under CAA section 189(b), it is appropriate to consider that level of 
control in evaluating whether reasonable controls are in place for 
purposes of the Exceptional Events Rule.'' 66 67 While 
ICAPCD states that this is inappropriate reliance on the normal 
planning process, an area's nonattainment designation and 
classification are inherently part of the local conditions that are 
appropriately factored into what controls are reasonable for purposes 
of the EER. We also noted that ARB had failed to demonstrate any 
meaningful analysis of BACM or any other level of control for either 
OHVs or fallow fields, despite apparent significant emissions and 
available controls imposed elsewhere.\68\
---------------------------------------------------------------------------

    \65\ See 57 FR 13498, 13540-13541 (April 16, 1992) and the 
General Preamble Addendum at 42010.
    \66\ 2009 EE decision, section 4.2.2; 72 FR 70222.
    \67\ We note that in EPA's Natural Events Policy which applied 
prior to the EER, we stated that ``BACM must be implemented at 
contributing anthropogenic sources of dust in order for PM-10 NAAQS 
exceedances to be treated as due to uncontrollable natural events 
under this policy.'' This requirement applied to moderate areas 
which otherwise would not have been required to implement BACM at 
all as well as to serious areas. Thus, while the EER does not 
include such a mandate, it is entirely appropriate and consistent 
with the Agency's past practice to consider a BACM level of control 
in assessing whether reasonable controls are in place. Memorandum 
from Mary D. Nichols, EPA, ``Areas Affected by PM-10 Natural 
Events,'' May 30, 1996, p. 5.
    \68\ 2009 EE decision, pp. 9-10.
---------------------------------------------------------------------------

    EE #6: ICAPCD (Attachment) comments that OHV emissions were 
quantified in the 2009 PM10 SIP at EPA's request, but EPA 
ignored this information in its analysis of the exceptional event 
requests.
    Response: It is the responsibility of the State to submit 
demonstrations addressing the EER criteria \69\ to support its 
exceptional event requests and it is generally not appropriate or 
feasible for

[[Page 39374]]

us to correct NED deficiencies by searching for additional information. 
Nonetheless, we did review the 2009 PM10 SIP before 
preparing the 2009 EE decision and did not ignore ICAPCD's efforts to 
quantify OHV emissions in the 2009 PM10 SIP. In fact, the 
2009 EE decision references these efforts which undermine the 
assumption in the NEDs \70\ that windblown dust from desert areas is 
entirely from non-anthropogenic sources.\71\
---------------------------------------------------------------------------

    \69\ 40 CFR 50.14(c)(3).
    \70\ E.g., June NED, p. 2.
    \71\ E.g., 2009 EE decision, footnotes 12, 15 and 16.
---------------------------------------------------------------------------

    EE #7: ICAPCD (Attachment) believes it is not clear whether OHV 
sources should be considered de minimis, what controls EPA expects for 
illegal OHV use, and why current regulations do not constitute 
reasonable controls.
    Response: As stated previously, the State must demonstrate 
implementation of reasonable controls in documentation supporting 
exceptional events requests. It is possible that ICAPCD/ARB may be able 
to demonstrate in support of future exceptional events requests that 
OHV sources are de minimis, that there are no reasonable controls for 
OHVs under certain circumstances (e.g., certain illegal uses), and/or 
that existing regulations constitute reasonable controls. The 2009 EE 
decision, however, explains that the NEDs did not provide meaningful 
analysis of any level of control for OHVs, and that such analysis 
should include as a starting point evaluation of EPA's RACM guidance 
\72\ and regulations adopted elsewhere under similar conditions.\73\
---------------------------------------------------------------------------

    \72\ 57 FR 18070, 18072 (April 28, 1992).
    \73\ 2009 EE decision, pp. 8-9.
---------------------------------------------------------------------------

    EE #8: ICAPCD (Attachment) comments that sand dunes are naturally 
fully disturbed and that the 2009 PM10 SIP conservatively 
projects that OHVs contribute only 0.9 tpd (10%) to the total windblown 
emissions from them. Other commenters similarly question EPA's 
assumption that OHVs disturb desert crust. OWD, for example, notes that 
dune laminae are often mistaken for a crust but are broken by wildlife, 
foot traffic and high winds.
    Response: We agree that effective control of fugitive dust is more 
difficult for the sand dunes than for other parts of Imperial County 
with different soil types. As a result, the State may be able to 
demonstrate in support of future exceptional events requests, or for 
other CAA purposes such as section 189(b)(1)(B) BACM, that dust control 
for dunes should be different from and/or less stringent than controls 
required for other areas with different soil types. However, the 
September NED failed to provide meaningful analysis of reasonable OHV 
controls for the sand dunes or any other areas. This comment has no 
bearing on the April and June NEDs because the sand dunes were not 
implicated by those events.
    EE #9: ICAPCD (Attachment) comments that OHV activity and related 
direct PM10 entrainment should have been negligible because 
of the high winds during the April 12 and June 5, 2007 events and 
thunderstorms on September 2, 2006. OWD notes that two of the 
exceedance events occurred during the OHV off-season and the third 
occurred in April, when OHV use is also low. Similarly, BLM comments 
that OHV use is lowest when dust potential is highest (June through 
September).
    Response: Our 2009 EE decision appropriately relies on OHV emission 
information from the NEDs and the 2009 PM10 SIP which 
estimate large windblown dust emissions and significantly smaller 
directly entrained emissions.\74\ Thus, even if no OHVs operate and 
entrain dust on any exceedance days, previous \75\ OHV activity still 
contributes to PM10 emissions by disturbing surfaces that 
subsequently emit windblown dust. As a result, documentation supporting 
future Imperial County exceptional events requests for events with 
significant emissions from OHV areas should include analysis of 
reasonable controls for OHVs even if there is no OHV activity during 
the exceedances.
---------------------------------------------------------------------------

    \74\ E.g., 22 tpd windblown and 1.34 tpd entrained emissions, 
2009 EE decision, p. 9.
    \75\ Particularly recent activity where there has not been time 
or conditions to repair surface crusts.
---------------------------------------------------------------------------

    EE #10: ICAPCD (Attachment) comments that Regulation VIII 
agricultural controls are well beyond the reasonableness level required 
in the EER. ICAPCD further states that it and ARB have discussed 
agricultural controls with EPA for many years, worked with EPA during 
development of the 2005 BACM analysis, closely modeled Rule 806 on 
SJVUAPCD Rule 4550 which EPA approved in 2004, and received EPA 
testimony in 2005 that Regulation VIII, including Rule 806, fulfilled 
BACM. ICAPCD also points out that the emission inventory in the plan 
shows that agricultural lands are significantly less emissive than most 
of the non-populated areas in Imperial County.
    Response: Our 2009 EE decision explains that neither Regulation 
VIII nor any other programs require any level of emissions control of 
certain fallow fields in Imperial County.\76\ Though ICAPCD comments 
that emissions from agricultural fields are smaller than emissions from 
other sources in the County, the NEDs for the exceptional events 
requests do not identify any anthropogenic sources as being de minimis. 
Rather, there are summary explanations that anthropogenic sources are 
reasonably controlled through Regulation VIII and other local 
programs.\77\ The only anthropogenic source discussed in any detail is 
agriculture in the April and June NEDs. These NEDs rely on the Imperial 
Irrigation District's (IID) fallowing program as the basis for claiming 
that reasonable measures were in place for fallow fields which are not 
subject to ICAPCD's Conservation Management Practices (CMP) Rule 
806.\78\ However, there were approximately 32,000 fallow acres in 
Imperial County in 2007 that were not subject to either Rule 806 or 
IID's program which is more than the approximately 18,000 acres that 
were a part of IID's program in 2007.\79\ As explained in our response 
to comment EE 5, we stated in our 2009 EE decision that it is 
appropriate to consider a BACM level of control in evaluating whether 
reasonable controls are in place for purposes of the EER in Imperial 
County. However, EPA found no meaningful analysis of BACM or any other 
level of control for fallow land outside of IID's program referenced or 
provided in the NEDs.
---------------------------------------------------------------------------

    \76\ 2009 EE decision, section 4.2.3.
    \77\ April and June NEDs, pp. 13-14, and September NED, p. 18.
    \78\ April and June NEDs, p. 13.
    \79\ 2009 EE decision, p. 9.
---------------------------------------------------------------------------

    EE #11: ICAPCD (Attachment) comments that EPA's 2009 EE decision 
fails to mention Rule 806 in the discussion of controls for 
agricultural lands. ICAPCD notes that fallowed land issues were 
included in the 2005 BACM analysis \80\ and concludes that failure to 
address Rule 806 makes EPA's conclusions regarding agricultural areas 
suspect.
---------------------------------------------------------------------------

    \80\ ``Draft Final Technical memorandum: Regulation VIII BACM 
Analysis,'' October 2005 (2005 BACM Analysis).
---------------------------------------------------------------------------

    Response: EPA did consider and reference Rule 806 in our 2009 EE 
decision.\81\ Although the 2005 BACM analysis includes incidental 
references to fallow lands, neither it nor the NEDs attempts to 
quantify the fallow acreage in Imperial County. Nor has the State 
demonstrated how any existing windblown dust controls might constitute 
BACM for fallow fields outside of IID's program.
---------------------------------------------------------------------------

    \81\ 2009 EE decision, p. 9.
---------------------------------------------------------------------------

3. High/Unusual Wind Events
    EE #12: Comite agrees with EPA's disapproval of ARB's request to 
exclude the monitored exceedances as

[[Page 39375]]

exceptional events. In support of our disapproval the commenter makes 
several arguments: (1) That there is no statutory or regulatory 
authority which allows windblown dust from land that has been disturbed 
by human activity to be considered ``natural;'' (2) that while the 
final rule includes specific language regarding the treatment of 
anthropogenic emissions associated with fireworks and prescribed burns, 
it does not include special provisions for anthropogenic sources 
affected by the wind; (3) that the portion of the preamble which 
suggests dust from anthropogenic sources may be treated as natural 
events in certain circumstances was a drafting error and is legally 
null; (4) where the Act does allow for consideration of human activity, 
it is limited to activity that is unlikely to recur at a particular 
location and agriculture does not meet that definition; and (5) 
regardless of whether a high wind event is classified as ``natural'' or 
``human activity,'' such an event exists only where the wind is 
objectively a ``high wind'' and sufficiently high to cause a monitored 
violation even in light of the implementation of whatever measures are 
``necessary'' to protect public health under CAA section 
319(b)(3)(A)(iv).
    Response: Comite's support for our decision not to concur with the 
State's exceptional events claims is noted. We agree with Comite that 
the events in question are not due to human activity that is unlikely 
to recur and that the State failed to demonstrate that the events 
qualify as natural events. However our conclusions with respect to 
natural events are not based on all of the legal arguments proffered by 
the commenter. We also are not relying on that portion of the preamble 
that the commenter correctly points out is a legal nullity \82\ and 
instead, where appropriate, we rely on and cite to other parts of the 
preamble regarding natural events and high winds that remain 
applicable. While EPA's views of the statute and the EER differ from 
Comite's, we need not address Comite's arguments in detail because its 
intent was clearly to support the outcome we have reached regarding the 
exceptional events claims.
---------------------------------------------------------------------------

    \82\ NRDC v. EPA, 559 F.3d 561, 565 (DC Cir. 2009).
---------------------------------------------------------------------------

    EE #13: Comite cites additional support for nonconcurrence with the 
State's 2007 exceptional events requests beyond what was relied upon by 
EPA, namely that wind speeds were not shown to be ``exceptional'' for 
the area or ``unusual'' since the State relied on flawed comparisons to 
average wind speeds.
    Response: For the 2006 events, the State did not assert that the 
winds were unusually high. For both sets of 2007 events, the evidence 
provided by the State did lead EPA to conclude that winds were 
unusually high.\83\ However, EPA's 2009 EE decision did not rely on the 
State's conclusions about unusual winds for any of the exceedances and 
we note that this commenter does not disagree with EPA's conclusions on 
the exceptional events, or with EPA's proposed limited disapproval of 
Regulation VIII.
---------------------------------------------------------------------------

    \83\ 2009 EE decision, pp. 19-20.
---------------------------------------------------------------------------

4. Clear Causal Relationship
    EE #14: Comite agrees with EPA that the State did not demonstrate 
there was a clear causal relationship between the exceedances and the 
events that are claimed to have occurred, as required under the EER. 
With regard to the 2007 exceedances, the commenter cites the lack of 
sufficiently detailed source attribution data. With regard to the 2006 
exceedances, the commenter concludes that the proximity and nature of 
the thunderstorms that occurred in northwest Mexico made them 
``unlikely'' to be the cause of the winds at Calexico. This commenter 
also believes that the possibility of any winds associated with 
thunderstorm activity north of the County being the cause of the 
Westmorland exceedance is ``problematical at best.''
    Response: Comite's agreement with EPA's 2009 EE decision regarding 
the 2006 and 2007 exceedances is noted.
    EE #15: ICAPCD (Attachment) objects to EPA's analysis of a section 
of the ARB documentation that compares September 2, 2006 to other days 
with similar meteorological conditions in order to establish a causal 
relationship between the claimed high wind event and the Calexico 
exceedances on September 2, 2006. ICAPCD also rejects EPA's concerns 
regarding the effect of emissions from OHVs and fallow fields on the 
September 2, 2006 Calexico exceedances. ICAPCD concludes that EPA's 
lack of sound technical understanding regarding the meteorological 
evidence and OHV and agricultural emissions led EPA to erroneously 
reject the State's finding of a ``clear causal relationship'' for the 
September 2, 2006 Calexico exceedances.
    Response: In its documentation supporting its exceptional events 
request, the State compared PM10 concentrations on September 
2, 2006 to those on fifteen other days that had similar meteorology at 
Calexico.\84\ The PM10 concentrations on most of the days 
were low, but on August 18, 2002, August 19, 2003 and September 2, 2006 
the PM10 concentrations were high. The concentrations on 
these days in 2002 and 2003 are described in attachments to the State's 
Natural Events Documentation \85\ as being due to transport from Mexico 
under high wind conditions, and these conditions are stated to be 
meteorologically different than the other days at locations other than 
Calexico itself. Thus winds at Calexico were similar for all sixteen 
days, but on these specific days the wind elsewhere and the Calexico 
concentrations are higher. The State considered this to be evidence of 
an association or causal relationship between high wind elsewhere and 
high Calexico concentrations.
---------------------------------------------------------------------------

    \84\ September NED, pp. 12-14.
    \85\ September NED, p. 12, and Attachment G, ``179B(d) `But For' 
Analyses--High-Wind Events from Mexico'', excerpt from Technical 
Support Document: Exclusion of PM10 Measurements in Excess of the 
24-Hour PM10 NAAQS for Imperial County from 2001 through 2003 Due to 
Natural Events and Emissions from Mexico, Volume I of II, ENVIRON 
International Corporation, November 2004.
---------------------------------------------------------------------------

    While we acknowledge that we misinterpreted the above portion of 
the State's argument in our initial analysis, our ultimate conclusion 
remains unchanged. As we discussed in our 2009 EE decision,\86\ the 
State's argument is flawed because there were in fact no high wind 
measurements on September 2, 2006; instead, the State merely assumed 
that wind speeds increased to the east. As a result, the association 
between the winds and concentrations that was seen for the events in 
2002 and 2003 may not reflect what occurred on September 2, 2006. Thus 
our original conclusion is still valid because the fact remains that 
ARB's argument is founded on speculation. As we explained in our 2009 
EE decision,\87\ such speculation is not adequate to establish a clear 
causal relationship.
---------------------------------------------------------------------------

    \86\ 2009 EE decision, pp. 11 and 15.
    \87\ Id. at p. 11.
---------------------------------------------------------------------------

    Furthermore, as also discussed in our 2009 EE decision,\88\ 
significantly lower PM10 measurements in neighboring 
Mexicali contradict ARB's assertion that the September 2, 2006 Calexico 
exceedances were caused by windblown dust from a large-scale, regional 
event that originated to the south or southeast of Calexico. Such an 
event would have affected both Calexico and Mexicali. ICAPCD itself 
concedes that its explanation for the Calexico exceedances does not 
account for the difference in the PM10 concentrations

[[Page 39376]]

measured at the Calexico and Mexicali stations.\89\
---------------------------------------------------------------------------

    \88\ Id. at p. 12.
    \89\ ICAPCD Attachment A, Appendix A-1.
---------------------------------------------------------------------------

    ICAPCD further offers what it characterizes as the only three 
possible explanations for the Calexico exceedances, and suggests that 
EPA should accept the long range transport argument because it is the 
most plausible one.\90\ To do so would be to make a decision based on a 
predetermined outcome rather than reliable scientific data that 
establish a clear causal relationship as required by the EER.
---------------------------------------------------------------------------

    \90\ Id.
---------------------------------------------------------------------------

    ICAPCD's next objection to our analysis of ARB's exceptional event 
request with respect to the September 2, 2006 Calexico exceedances is 
that EPA's concern regarding OHV and agricultural emissions \91\ is not 
relevant because there are no OHV or domestic agricultural lands south, 
southeast or south-southeast of the Calexico monitors. EPA disagrees. 
The September NED states that the ``source of the PM10 that 
impacted the Calexico stations corresponds to lands east and southeast 
of the Mexicali stations * * *'' \92\ In fact, as shown in the TSD for 
this final action,\93\ there is agricultural land immediately east of 
Calexico.\94\ As also shown in the final TSD,\95\ the southern end of 
the Imperial Sand Dunes OHV area is also directly east of Calexico, 
though it is admittedly farther away. Thus consideration of these 
sources was not inappropriate.
---------------------------------------------------------------------------

    \91\ 2009 EE decision, p. 14.
    \92\ September NED, p. 15.
    \93\ ``Technical Support Document for EPA's Notice of Final 
Rulemaking on Revisions to the California State Implementation Plan, 
Imperial County Air Pollution Control District Regulation VIII--
Fugitive Dust Rules 800-806'' EPA Region IX, June 2010 (final TSD), 
Figure 1.
    \94\ Similar land use maps were provided in Figure 3 of both the 
April and June NEDs.
    \95\ Final TSD, Figure 1.
---------------------------------------------------------------------------

    In summary, we are not persuaded by the above comments and we 
reject the allegation that we did not have a sound technical 
understanding of the claims ARB made as to the cause of the 
exceedances. We therefore reaffirm our conclusion that ARB not only 
failed to demonstrate that a high wind event occurred, but also that 
there was a clear causal relationship between the alleged event and the 
September 2, 2006 exceedances at the Calexico monitoring stations.
    EE #16: ICAPCD (Attachment) states that EPA mischaracterized some 
evidence and inappropriately dismissed other evidence provided by the 
State regarding a causal relationship between the claimed high wind 
event and the Westmorland exceedance on September 2, 2006, and that 
this led EPA to erroneously reject the State's finding of a clear 
causal relationship. The comment has three parts, relating to alleged 
EPA mischaracterizations of the timing of high winds, direction of 
thunderstorm travel, and wind trajectories.
    Response: In response to this comment, we have again reviewed the 
wind data provided in the September NED and, as explained further 
below, we believe our original conclusion in our 2009 EE decision 
remains correct, i.e., that the data presented by ARB did not 
demonstrate a clear causal relationship between the claimed high wind 
event and the Westmorland exceedance on September 2, 2006.
    The first part of ICAPCD's comment focuses on a statement made by 
EPA that the increased wind at Oasis toward Westmorland was 
simultaneous with the concentration spike that occurred at Westmorland 
during the 19th hour rather than an hour or two before, as would be 
necessary based on the distance between the two locations.\96\ We agree 
with the comment that the increased wind at Oasis did in fact occur the 
hour before the concentration spike. In addition, we stated that this 
wind was directed toward Westmorland when in fact it was directed 
toward the east-northeast.
---------------------------------------------------------------------------

    \96\ 2009 EE decision, p. 16.
---------------------------------------------------------------------------

    ARB presented the wind speed and direction data in a tabular format 
that is difficult to interpret.\97\ To more clearly articulate why we 
do not believe these data show a clear causal relationship between the 
event and the exceedance, we have presented the data in the final TSD 
in a visual form that is more readily understood.\98\ The arrows 
represent the wind directions at Indio, Oasis, Salton Sea West, and 
Westmorland during each of the four color-coded hours (e.g., all of the 
yellow arrows represent the wind direction during hour 17, etc.). The 
numbers above each arrow represent the wind speed for that hour, and 
the numbers below the Westmorland arrows represent the PM10 
concentration. The data show that the PM10 concentration 
spike occurred during hour 19.
---------------------------------------------------------------------------

    \97\ September NED, Tables 1 and 2, and Figure 19.
    \98\ Final TSD, figure 2.
---------------------------------------------------------------------------

    ARB claimed that thunderstorm outflows on September 2, 2006 led to 
high wind locally to the northwest and northeast of Imperial County, 
and that dust generated there was carried to Westmorland. More 
specifically, ARB stated the following:

    Very high winds were observed at the 17th and 18th hours north 
of Imperial County, both to the west (in particular at the Oasis 
CIMIS station, see Table 1) and to the east (see measurements at the 
Blythe, Ripley, and Palo Verde stations, Table 1). These strong 
winds were of very short duration and of changing direction * * *, 
consistent with the collapse of one or several thunderstorm cells 
north of Imperial County * * *. Very sharp peaks in PM10 
concentrations were also observed at the 19th hour at the Brawley 
and Westmorland stations (and to a lesser extent at the Niland 
station), and appear to be long-range effects of the same events 
(i.e. collapsing thunderstorm to the north of Imperial County) * * 
*. [A]n analysis of wind direction at select stations between the 
18th and 20th hours indicates that northwest winds (e.g. 6 p.m. at 
the SSW and Indio stations, 7 p.m. at Oasis and Indio, and 8 p.m. at 
Indio) and east-northeast winds (e.g. 7 p.m. at the Niland and SSE 
stations) likely carried air containing elevated PM10 
concentrations from areas northwest and northeast of Imperial County 
stations toward the stations.(Emphasis added).\99\
---------------------------------------------------------------------------

    \99\ September NED, pp. 10-11.

    ARB's explanation first points to the ``very high'' winds (of 23.2 
mph) recorded at the Oasis station and the northwest winds at Salton 
Sea West during the 18th hour as factors that contributed to the 
exceedance. As a preliminary matter, we note \100\ that no particular 
wind speed has been established as ``high'' for Imperial County. 
Further, winds with an average speed of 23.2 mph are not what we would 
consider ``very high'' in the generally accepted meaning of the term. 
With the exception of this value, the data in Figure 2 of our final TSD 
show that the winds in this area were not very elevated.\101\ We also 
note that the winds at Oasis during the 18th hour had a northerly 
component rather than a southerly one, and while it is true that the 
winds at Salton Sea West were blowing toward Westmorland at this time 
and that these winds could have contained some of the dust that may 
have been generated in the Oasis area, the winds at Westmorland were 
blowing in almost the opposite direction. It is thus unclear how much, 
if any, dust generated at Oasis during the 18th hour was actually 
transported to Westmorland.
---------------------------------------------------------------------------

    \100\ As we did in our 2009 EE decision, pp. 15 and 19.
    \101\ EPA received comments on its proposed EER which stated 
that we should replace the term ``high winds'' with the term ``wind-
generated dust.'' In response to those comments, EPA explained in 
the final EER that the Agency chose to retain the original language 
because it accurately connotes the type of natural event that should 
be excluded under this rule and it serves as an indicator concerning 
the level of wind that caused the exceedance. See 72 FR 13560, 
13566.
---------------------------------------------------------------------------

    ARB also points to the 7 p.m. winds at Oasis (hour 19) as a 
contributing factor. While these winds were directed

[[Page 39377]]

toward Westmorland, the winds at Salton Sea West had a distinct 
westerly component so it is not clear that the winds at Oasis continued 
on this path past Salton Sea West. In addition, as for the previous 
hour, the winds at Westmorland were blowing counter to the wind at 
Oasis and it is again not clear that any dust generated north of 
Imperial County was transported to Westmorland during this hour as ARB 
claims.
    The State finally points to the 8 p.m. winds at Indio as a 
contributing factor. We find it unlikely that these winds made a 
significant contribution to the exceedance at Westmorland given that 
they were recorded after the concentration spike occurred and that the 
winds at Oasis, Salton Sea West, and Westmorland all had northerly 
components that ran counter to the winds at Indio.
    As stated in our 2009 EE decision,\102\ and as ARB stated in the 
paragraph quoted above, the winds northwest of Imperial County 
(particularly around the Oasis and Salton Sea West areas) were variable 
in speed and direction. This variability is inconsistent with ARB's 
hypothesis that the winds remained at an elevated speed and along a 
straight line over the 45 mile distance between Oasis and Westmorland 
for an hour or more. Thus it is anything but clear that dust generated 
northwest of Imperial County caused the exceedance at Westmorland. As a 
result, EPA's minor errors regarding the timing and direction of the 
winds at Oasis do not undermine the Agency's conclusion that the 
contradictory evidence does not support a finding of a clear causal 
relationship.
---------------------------------------------------------------------------

    \102\ 2009 EE decision, p. 16.
---------------------------------------------------------------------------

    The second part of ICAPCD's comment on the causal relationship 
regarding the Westmorland exceedance argues that the speed and 
direction of the increased winds (27.0 mph) recorded at the Palo Verde 
station during hour 17 are consistent with transport to Westmorland and 
that the uncertainty of the precise location of the thunderstorms in 
time is not relevant to a cause and effect analysis. The commenter 
further states that EPA does not appear to argue that the wind speed or 
direction is inconsistent with transport of dust from Palo Verde to 
Westmorland.
    While we agree with the commenter that the winds at Palo Verde 
(which is separated from Westmorland by a north-south distance of about 
24 miles) were directed toward Westmorland during the 17th hour, the 
winds at Westmorland were consistently from the south-southeast, 
southeast, and east-southeast directions beginning at the 6th hour and 
lasting until the end of the day. While it is remotely possible that 
the winds that occurred at Palo Verde during the 17th hour led to the 
transport of dust to Westmorland, the EER requires a demonstration of a 
clear causal relationship and the limited data available do not rise to 
that level.
    We also disagree with the commenter that the location of the 
thunderstorms over time is not relevant to a cause and effect analysis. 
The EER explicitly mentions the use of data that show the relationship 
in time between the event, transport of emissions, and recorded 
concentrations in exceptional event demonstrations.\103\ Furthermore, 
in this case, ARB's basic premise is that ``thunderstorm activity 
caused strong outflow winds over areas in close proximity to Imperial 
County monitors * * * [which contributed] to the elevated 
PM10 concentrations that were recorded in Imperial County on 
that day.'' \104\ ARB could have attempted to provide more support for 
its case by, for example, considering whether historical radar data 
showed thunderstorms were at various locations around the time the high 
winds occurred.
---------------------------------------------------------------------------

    \103\ 72 FR 13560, 13573.
    \104\ September NED, p. 2.
---------------------------------------------------------------------------

    Given the level of uncertainty as to the cause of the concentration 
spike at Westmorland during the 19th hour and the statutory requirement 
that EPA's exceptional events regulations be based on the principle 
that protection of public health is the highest priority,\105\ we are 
again led to the conclusion that the data before the Agency does not 
establish a clear causal relationship between the exceedance and the 
event that is claimed to have occurred.
---------------------------------------------------------------------------

    \105\ See CAA section 319(b)(3)(A)(i).
---------------------------------------------------------------------------

    The third part of ICAPCD's comment regarding causal relationship 
for the Westmorland exceedance criticizes EPA's use of wind 
trajectories from the HYSPLIT model since it is expected to capture the 
underlying flow pattern but may not be able to capture the direction of 
short-lived high winds that could transport dust from the north to 
Westmorland.
    EPA acknowledges that the HYSPLIT model uses meteorological data 
with relatively coarse resolution, e.g., a 40 km grid, and that there 
may be short-lived or local deviations from the overall wind flow. 
However, it remains true that the HYSPLIT back-trajectories are 
inconsistent with transport from northern stations since they show 
winds from the south.\106\ The HYSPLIT data simply add to the list of 
inconsistencies in the State's explanation. In addition, ICAPCD's 
suggestion that the high winds were ``short-lived'' is inconsistent 
with ARB's hypothesis of straight line transport from the Oasis or Palo 
Verde stations for an hour or more over the 45-55 mile distance to 
Westmorland. Thus EPA disagrees with this comment.
---------------------------------------------------------------------------

    \106\ 2009 EE decision, p. 17.
---------------------------------------------------------------------------

    EE #17: ICAPCD (Attachment) makes an additional two-part comment 
about the causal relationship claim for the September 2, 2006 
exceedances at both the Calexico and Westmorland monitoring stations. 
In order to buttress its argument that these exceedances were not the 
result of recurring anthropogenic sources within Imperial Valley, 
ICAPCD first states that it is extremely unlikely that all monitors in 
the County would simultaneously have had unusually high PM10 
concentrations if the causes were local to the monitors. The second 
part of the additional comment states that since there were no high 
winds throughout Imperial Valley on September 2, 2006, the cause of the 
exceedances could not have been unpaved roads or agricultural or OHV 
land within the Valley.
    Response: With respect to the first part of ICAPCD's comment, EPA 
acknowledged the elevation of PM10 at all monitors, but did 
not take a position on whether the causes were local or regional.\107\ 
Rather, we concluded that a clear causal relationship had not been 
demonstrated since the regional sources alleged by ARB to be the cause 
were not identified. Related to this lack of identification of the 
contributing sources, EPA found that the State did not demonstrate that 
the event was not reasonably controllable or preventable as there was 
no attempt to analyze controls on the non-local sources. Thus this 
comment does not affect our decision to not concur with the State's 
exceptional event claims.
---------------------------------------------------------------------------

    \107\ 2009 EE decision, p. 14.
---------------------------------------------------------------------------

    With respect to the second part of ICAPCD's comment, as discussed 
above, the State argued that high winds associated with thunderstorm 
activity led to the generation of dust north of the County, which was 
then transported to the Westmorland monitor. Even though agricultural 
land and other anthropogenic sources do exist in areas north of the 
County including Oasis,\108\ where the State claimed winds were high, 
the State made no attempt to analyze controls on contributing sources 
outside the County in order to address the EER requirement that the 
event must be ``not reasonably controllable or preventable.'' Thus, 
this requirement

[[Page 39378]]

was not met even if the commenter's arguments regarding transport were 
correct. With respect to the Calexico exceedances, the State speculated 
that high winds occurred east and southeast of Calexico based on 
extrapolation of a west to east trend of increasing wind speed. The 
same argument could have been used to conclude that there was high wind 
east of Calexico within Imperial County, including over agricultural 
and OHV lands. Therefore the commenter's claim that there were no high 
winds throughout the Imperial County is not completely supported by the 
State's own arguments that a high wind event occurred.
---------------------------------------------------------------------------

    \108\ See Figure 1 in the final TSD.
---------------------------------------------------------------------------

5. Concentrations in Excess of Normal Historical Fluctuations
    EE #18: Comite cites additional support for nonconcurrence beyond 
what was relied upon by EPA. Specifically, the commenter states that 
numerous monitored exceedances comparable to those that Imperial County 
seeks to exclude from the data have been measured in the County from 
2003-2007. Therefore, the commenter claims, the concentrations are not 
``in excess of normal historical fluctuations'' as required by the rule 
and are not exceptional events.
    Response: EPA's conclusions about the requirement that the events 
be associated with measured concentrations in excess of normal 
historical fluctuations mainly relied on the concentrations' rarity 
relative to past measurements. For example, the September NED states 
that the 167 [mu]g/m3 measurement at the Westmorland station was in the 
98th percentile of all PM10 recordings at that station in 
the 2001-2007 time period. As explained in our 2009 EE decision,\109\ 
we found similar evidence that the exceedances measured on the other 
days in question also exceeded normal historical fluctuations. However, 
we do agree with the commenter that the monitoring data for Imperial 
County continue to show violations of the 24-hour PM10 
standard. We believe that improvements to the ICAPCD's rules will lead 
to improvements in air quality and we note that this commenter does not 
disagree with EPA's conclusions regarding the State's exceptional 
events requests, or with EPA's proposal to disapprove Regulation VIII.
---------------------------------------------------------------------------

    \109\ pp. 25-27.
---------------------------------------------------------------------------

6. Level of Documentation Required for EER
    EE #19: ICAPCD (Attachment) takes issue with EPA's suggestions that 
additional data and analysis would have helped establish causality for 
the 2006 Westmorland and the 2007 events. Specifically, ICAPCD states:

    Although EPA suggests that higher levels of documentation for 
source attribution, thunderstorm activity, or investigation of other 
potential causes would be preferred, EPA does not suggest 
reasonable, technically implementable analyses to achieve these 
higher levels of documentation. We would question what technical 
analyses EPA suggests should be conducted. We would also question 
whether these analyses and the required level of data are achievable 
or realistic now or in the future for similar events in Imperial 
County and in other areas (particularly those surrounded by remote, 
non-populated, non-monitored source areas), and whether these 
analyses exceed the requirements for SIP planning itself. EPA has 
not (and, we believe, cannot) propose reasonable, technically 
achievable investigations and analyses superior to those produced by 
the District and ARB that would address EPA's stated concerns. Thus, 
we find that both EPA's conclusions on causality and EPA's position 
on the level of analysis required to demonstrate causality are 
incorrect and inconsistent with the purpose of the EER * * *. Such a 
narrow application of the EER will preclude states from excluding 
from regulatory consideration exceptional PM data that are 
completely inappropriate for inclusion in the normal planning 
process.

    ICAPCD also includes a table on page A-8 which cites specific 
passages of EPA's 2009 EE decision pertaining to source apportionment, 
satellite imagery, and consideration of other causes.
    Response: Regarding the need for better source apportionment data, 
it is important to identify contributing sources when evaluating 
exceptional event claims involving windblown dust because it must be 
demonstrated that anthropogenic sources contributing to the exceedances 
at issue were reasonably controlled.\110\ Better source identification 
is especially important in situations where we do not have confidence 
that all potential anthropogenic sources are reasonably controlled and 
where there are exceedances just above the NAAQS (such as the April 12, 
2007 exceedance at Westmorland) which may have been preventable with 
additional controls. In addition, the inability to identify the source 
of the PM emissions associated with a wind event (i.e., the ``cause'' 
of the dust that led to the exceedance) hinders our ability to make 
affirmative findings that the ``clear causal relationship'' and ``but 
for'' provisions of the EER have been satisfied. A County-wide monthly 
average emission inventory such as the one used by ARB that omits some 
source types (e.g., OHVs) is insufficient for these purposes.
---------------------------------------------------------------------------

    \110\ See, e.g., 2009 EE decision, p. 7 and our responses to 
comments EE s 1 and 4. See also 72 FR 49046, 49051 (August 
27, 2007) and 72 FR 13560, 13566, footnote 11, explaining that the 
weight of evidence approach to our analysis may consider winds that 
produce emissions contributed to by anthropogenic activities that 
have been controlled to the extent possible through use of all 
reasonably available reasonable and appropriate measures.
---------------------------------------------------------------------------

    While perhaps not required for all demonstrations, our suggestion 
for a wind field and a more highly resolved inventory are not 
unreasonable given ARB's failure in the present case to demonstrate 
that reasonable controls were in place for contributing sources. 
Moreover, a more highly resolved inventory would provide better support 
for any future exceptional events claims involving Imperial County. 
Another method ARB could have potentially considered for identifying 
the source of the emissions and supporting its claim of a causal 
relationship is to collect and examine pollutant species-specific 
information. As discussed in the EER preamble,\111\ such information 
may be available through routine speciation, monitoring networks, or 
from selective laboratory analysis of archived particulate matter 
filters for the day thought to be impacted by an event. In this case, 
such an analysis might have helped ascertain how much of the 
PM10 that impacted certain monitors was from agricultural 
sources versus natural desert sources.
---------------------------------------------------------------------------

    \111\ 72 FR 13560, 13573.
---------------------------------------------------------------------------

    Regarding ICAPCD's objection to our statement that the satellite 
imagery provided was not frequent enough to compare the images with the 
timing of the concentration spike at Westmorland during the 19th 
hour,\112\ we note that ARB could have provided additional information 
to supplement the satellite imagery. Such information could include, 
but may not be limited to radar data and weather observations that note 
the presence of blowing dust in areas around the monitors.
---------------------------------------------------------------------------

    \112\ 2009 EPA decision, pp 17-18.
---------------------------------------------------------------------------

    Finally, ICAPCD takes exception to our desire for better 
documentation regarding the investigation of other potential causes. In 
this regard, ARB made the following statement: \113\
---------------------------------------------------------------------------

    \113\ September NED, p. 2.

    (ICAPCD) investigated emission generating activities during this 
episode, and found that PM10 emissions for BACM 
controlled sources were approximately constant before, during and 
after the event. The District determined that the * * * 
concentrations of PM10 * * * were instead primarily the 
result of wind-entrained dust * * * associated with a mesoscale 
---------------------------------------------------------------------------
convective system * * *.

    Although the preceding passage suggests that ICAPCD conducted an

[[Page 39379]]

active investigation of other emission generating activities on the day 
of the event, this claim is largely unsupported except for an 
interoffice memo included in Attachment H to the September NED. The 
memo states that various records were inspected in 2008 but that no 
inspections were conducted on the day of the event. We were thus left 
wondering how a file review conducted two years after the fact 
qualifies as an investigation of emission generating activities 
``during [the] episode'' and how ICAPCD came to the somewhat 
substantial conclusion that emissions from BACM controlled sources were 
constant before, during, and after the event.

E. OHV Controls

    OHV #1: ICAPCD believes that EPA should have concurred with all of 
the exceptional event requests associated with high winds as discussed 
in the Exceptional Events comments summarized in section II.D above. As 
a result, ICAPCD believes that windblown dust from open areas is not a 
significant source category in Imperial County, and therefore is not 
subject to the BACM requirement as part of the SIP.
    Response: In our proposed action on Regulation VIII, we explained 
why windblown dust from open areas is treated as a significant source 
category subject to BACM.\114\ We have not received information in the 
comments or elsewhere that changes this conclusion or the related 
decision to not concur with the State's exceptional event requests for 
Imperial County. See also responses to Exceptional Events comments in 
section II.D above.
---------------------------------------------------------------------------

    \114\ Proposal TSD, pp. 5-7.
---------------------------------------------------------------------------

    OHV #2: CBD comments that BLM land is the largest PM10 
source in Imperial County and should be subject to the same controls as 
adjacent land. CBD believes the Dust Control Plan (DCP) requirement for 
BLM land in Rule 800 section F.5 is unenforceable, in conflict with the 
CAA, while other areas are subject to more stringent Regulation VIII 
requirements.
    In contrast, ICAPCD believes that Rule 800's DCP implements BACM, 
and that Rule 800's exemption for BLM does not relax other Regulation 
VIII requirements. For example, Rule 800 section F.5.c requires BLM's 
DCP to be consistent with Rules 804 and 805 except where otherwise 
prohibited, in which case section F.5.e requires all feasible control 
measures during off-road events. ICAPCD also notes that where there are 
such prohibitions, section F.5.d requires the DCP to discuss and 
implement ``other possible control measures'' and that Rule 800 section 
D.3 requires the DCP to be submitted to ICAPCD, ARB and EPA for review 
and comment and to be updated every two years.
    ICAPCD believes BLM should be treated separately in Regulation VIII 
because there are many restrictions imposed by a variety of laws other 
than the CAA that apply to actions on Federal lands and that the 
District's involvement in these issues would delay implementation of 
the PM control program on BLM lands. ICAPCD also believes that BLM 
should be treated separately because some Federal land uses preclude 
traditional dust controls and because BLM's OHV areas are far from 
Imperial County populations. ICAPCD argues that even if Rule 800 
section F.5.c corresponds to requirements that are less effective than 
those of Rules 804 and 805, such lower stringency is both necessary and 
appropriate given the special nature of BLM lands.
    BLM agrees that many traditional BACM are not possible on Federal 
land because of the large expanses of desert ecosystems. BLM continues 
evaluating the DCP, however, which has led to closing areas and routes 
to vehicle use, restoring closed surfaces to natural conditions, 
hardening high traffic areas, posting and enforcing speed limits, 
educating desert users, and controlling dust from non-OHV activities.
    Response: BACM is required but has not been demonstrated for OHV 
activity on BLM land in Imperial County.\115\ EPA guidance explains 
that this demonstration should include evaluation and documentation of 
the technological and economic feasibility of potential control 
measures, including implementation of measures on a limited basis if 
full implementation is not feasible. As stated in our guidance, ``the 
documentation should compare the control efficiency of technologically-
feasible measures, their energy and environmental impacts and the costs 
of implementation.'' \116\ ICAPCD's demonstration should include 
careful consideration of analogous controls implemented on private 
lands in Imperial County and on public lands in Maricopa and Clark 
Counties and elsewhere, as well as controls recommended in EPA's RACM 
guidance,\117\ and suggestions provided in our proposal \118\ and 
comments on the proposal.\119\
---------------------------------------------------------------------------

    \115\ Proposal TSD, pp. 7-8.
    \116\ General Preamble Addendum at 42012-42014.
    \117\ 57 FR 18070, 18072.
    \118\ See proposal TSD, pp. 8 and 14-15.
    \119\ Moreover, as stated in the General Preamble Addendum at 
42013, ``any control measures that a commenter indicates during the 
public comment period is available for a given area should be 
reviewed by the planning agency.''
---------------------------------------------------------------------------

    The evaluation of technological feasibility may appropriately 
consider the alleged ``special nature'' of BLM lands. Such an 
evaluation, if conducted appropriately, may be sufficient to 
demonstrate that what constitutes BACM for BLM land in Imperial County 
is different from what constitutes BACM in other geographical areas and 
for private land in Imperial County. The information provided in the 
comments and Regulation VIII submittal, however, is not sufficient to 
support such a distinction. For example, ICAPCD and other commenters 
have not demonstrated how existing BLM controls implement BACM in the 
Plaster City areas, which are open to OHV activity at all times, and, 
if such controls do constitute BACM, why they cannot be incorporated 
into Regulation VIII and the SIP.
    Furthermore, with regard to CBD's comment concerning the 
enforceability of DCPs, State and local requirements that implement 
BACM are subject to the enforceability requirement of CAA section 
110(a). As we stated in our proposal, BACM has not been demonstrated 
for OHV sources because, among other things, none of the OHV 
restrictions are in regulatory form and submitted for inclusion in the 
SIP.\120\
---------------------------------------------------------------------------

    \120\ Proposal TSD, p. 14.
---------------------------------------------------------------------------

    OHV #3: OWD notes that California State Parks (CSP) manages OHV 
recreational activity in Imperial County at Heber Dunes State Vehicular 
Recreation Area, Ocotillo Wells SVRA, and in an interdepartmental joint 
management agreement at the Freeman Properties immediately north of 
Ocotillo Wells SVRA and east of Anza Borrego Desert State Park. OWD 
also notes that Ocotillo Wells SVRA alone represents approximately 
85,000 acres of managed OHV recreational activity within Imperial 
County. While much of this land is designated trail riding only and is 
primarily defined by terrain constraints, OWD states that the majority 
of the area is designated open riding, where OHVs are not limited to 
defined trails. Rather than implement generalized BACM for OHV activity 
in Ocotillo Wells SVRA and other State Parks, OWD explains that it has 
adopted State mandated soil standards, a habitat monitoring system and 
other policies tailored for the case-by-case conditions found in each 
park unit. OWD believes

[[Page 39380]]

that fencing, and then maintaining, a vast amount of land is neither 
economically nor environmentally feasible. OWD also believes that 
watering, laying gravel, or applying a chemical solution to the miles 
of trails that would be encompassed is neither economically nor 
environmentally feasible. In contrast, CBD argues that further 
implementation of Rule 804 and additional OHV controls may be needed 
for State lands including the Ocotillo Wells SVRA in order to attain 
air quality standards.
    Response: Rule 804 requires all persons, including public entities 
such as CSP, with jurisdiction over open areas in Imperial County with 
over 1,000 square feet of disturbed surface area to maintain a 
stabilized surface, limit opacity to 20% and comply with at least one 
of the following: (a) Apply and maintain water or dust suppressant to 
all unvegetated areas; (b) establish vegetation on all previously 
disturbed areas; or (c) pave, gravel or chemically stabilize.\121\ 
OWD's comment acknowledges that CSP has jurisdiction over open areas 
with over 1,000 square feet of disturbed surface area within Imperial 
County. Because these areas are not addressed by exemptions in Rule 800 
section E or Rule 804 section D,\122\ these areas must comply with the 
above requirements. However, from OWD's comment, CSP is clearly not 
currently complying with these requirements. As a result of the 
inclusion of Rule 804 into the SIP, these requirements will become 
federally enforceable upon the effective date of this final action, and 
such noncompliance could result in civil action under CAA section 113 
and/or 304.
---------------------------------------------------------------------------

    \121\ ICAPCD Rule 804, sections B, C.29, E and F.
    \122\ See also ``Fugitive Dust Control Plan,'' Bureau of Land 
Management El Centro Field Office, June 29, 2006; ``Fugitive Dust 
Control Plan,'' Bureau of Land Management El Centro Field Office, 
January 25, 2010 Draft; e-mail from Andrew Trouette (BLM) to Andrew 
Steckel (EPA), May 24, 2010.
---------------------------------------------------------------------------

    OHV #4: Various commenters argue that controls suggested in our 
proposal as part of the BACM analysis that ICAPCD still needs to 
conduct would not reduce PM10 impacts from OHVs in Imperial 
County.
     Many commenters oppose further restrictions during the 
summer, claiming that OHV activity and emissions are very low in 
Imperial County due to high temperatures and existing red sticker 
regulations that restrict certain vehicles during the summer. BLM 
concurs that OHV use is already lowest in the summer, and ICAPCD also 
concurs and argues that OHV restrictions during the summer would burden 
public resources without reducing emissions. However, one commenter 
(0100) states that OHV use during summer nights is a great activity 
which creates minimal dust because travel is at low speeds on 
established trails. Another commenter (0204) indicates that many 
promoters run OHV races at night that allow for fun recreational 
activity in cooler temperatures. This commenter believes night races 
decrease risks to spectators which is more important than reducing dust 
emissions. Some commenters also observe that wind events can occur in 
the summer and cause severe dust days. By contrast, another commenter 
(0146) believes that the desert is mainly dry and free of wind in the 
summer.
     ICAPCD believes that restrictions like those in place in 
Arizona, during pollution advisory days, would be unproductive because 
high-PM forecasts in Imperial County only occur on high-wind days when 
OHVs are not used.
     Many commenters (e.g., 0094) observe that OHVs are already 
restricted to certain areas, causing crowding and injuries. ICAPCD 
notes that OHVs are restricted to 11% of local BLM land, and additional 
closure would probably shift OHV activity and emissions to other areas 
nearby. OWD also believes EPA's action could force OHV users to other 
areas, causing environmental effects outside Imperial County.
     ICAPCD comments that EPA cannot demonstrate that OHV 
restrictions would reduce windblown dust emissions because there is no 
basis for EPA's contention that surfaces impacted by OHVs would form 
any appreciable crust given Imperial's low level of rain. OWD similarly 
comments that crust repair would be difficult due to the limited rain 
in Imperial County. Another commenter (0120) believes that restricting 
OHV areas could increase PM10 emissions because more 
vehicles in smaller areas would disturb more soil that cannot crust 
over. See also comment EE 8.
     OWD comments that fencing, watering, gravelling or 
chemically stabilizing miles of OHV areas is not feasible. For example, 
water resources are scarce and modification of existing OHV trails 
could alter natural drainage patterns and increase erosion.
    Response: EPA believes that some of the information provided in 
these comments could be relevant considerations in the comprehensive 
BACM analysis that ICAPCD needs to undertake in order to determine what 
controls constitute BACM for OHV activity in Imperial County. However, 
in general, the comments are conclusory and not supported by data, 
detailed information, or other evidence that would be required for an 
adequate BACM demonstration under our guidance.\123\ As summarized in 
the guidance:
---------------------------------------------------------------------------

    \123\ General Preamble Addendum at 42010-42014.

    In summary, the State must document its selection of BACM by 
showing what control measures applicable to each source category 
(not shown to be de minimis) were considered. The control measures 
selected should preferably be measures that will prevent PM-10 
emissions rather than temporarily reduce them. The documentation 
should compare the control efficiency of technologically-feasible 
measures, their energy and environmental impacts and the costs of 
implementation.\124\
---------------------------------------------------------------------------

    \124\ Id. at 42014.

    Furthermore, contradictions in the comments also serve to 
illustrate that there are fundamental factual questions that need to be 
addressed about the amount of OHV activity during different seasons and 
different times of the day, and the best ways to mitigate emissions 
from such activities. At this juncture, ICAPCD has not conducted an 
adequate analysis.
    OHV #5: Many commenters (e.g., 0108 and OWD) state that further OHV 
restrictions would hurt the already depressed local economy, and cite 
potential effects on local business owners, farmers, land owners, OHV 
users, race car owners, construction companies, ranchers, the Imperial 
Irrigation District and others. Commenters observe that recreational 
activities generate substantial revenue (0196), and one (0156.1) claims 
that OHVs have contributed several hundred million dollars to the local 
economy. ICAPCD believes that the economic cost of OHV activity 
restrictions is far more than appropriate for BACM. For example, ICAPCD 
estimates that closing the Imperial Sand Dunes Recreational Area would 
cost $370,000 to $640,000 per ton of PM10 reductions. ICAPCD 
provides specific references to support its cost/benefit analysis. 
Another commenter (0219) similarly believes that additional OHV 
restrictions, such as closing land in the summer, would provide few 
benefits given the relatively small emissions from OHVs, but would have 
significant economic impacts.
    Response: We appreciate the value of OHV tourism to the local 
economy, and agree that ICAPCD must consider economic feasibility in 
BACM analyses evaluating potential controls for emissions from OHV 
activities. However, the relevant inquiry in the economic feasibility 
analysis required in BACM determinations is ``the cost of reducing 
emissions from a particular source category and costs incurred by

[[Page 39381]]

similar sources that have implemented emission reductions.'' \125\ In 
this case, the cost of OHV restrictions on OHV area owners (i.e., the 
State and Federal governments) and users would appear to be minimal, 
and the secondary economic impacts on businesses supporting OHV tourism 
are not relevant to the required BACM analysis. In any event, ICAPCD 
needs to evaluate the economic feasibility of potential controls, 
including those adopted in other areas, in determining what controls 
constitute BACM in this area.
---------------------------------------------------------------------------

    \125\ General Preamble Addendum at 42013.
---------------------------------------------------------------------------

    OHV #6: EcoLogic asks EPA to clarify whether and where OHV 
restrictions are being contemplated in the Imperial Sand Dunes 
Recreation Area and elsewhere and to what extent OHV activity on 
Federal land is subject to the proposed rule or ICAPCD jurisdiction. 
EcoLogic and another commenter (0141) also request clarification on 
which of the 250 square miles of OHV areas EPA is asking ICAPCD to 
evaluate for closure and what the basis is for claiming that these 
areas are likely to impact populations.
    Response: State and Federal agencies are subject to many local 
requirements including Regulation VIII and other air quality related 
ICAPCD rules.\126\ Our proposal explains why ICAPCD must analyze 
whether additional controls (potentially including closure) are 
appropriate for public land in Imperial County open to OHVs, which 
ICAPCD estimates at over 250 square miles.\127\ We did not identify any 
specific geographic areas needing more or less analysis or control or 
having more or less impact on populations. Rather, in the analysis 
ICAPCD should consider all potential available OHV controls in all OHV 
areas in Imperial County and, where feasible, should consider whether 
different areas within the County have different impacts on populations 
or areas with exceedances of the NAAQS.
---------------------------------------------------------------------------

    \126\ See CAA section 116.
    \127\ See, e.g., proposal TSD, pp. 8 and 13-15.
---------------------------------------------------------------------------

    OHV #7: Several commenters believe additional OHV restrictions 
should be analyzed and/or incorporated into Regulation VIII. CBD 
believes that OHV requirements in Rule 804 are too vague to be 
enforceable as required by CAA section 110(a), particularly regarding 
BLM and State managed land. CBD believes Regulation VIII should require 
specific BACM measures, such as restrictions on the number of OHV 
vehicles operating each day, to improve emission quantification and 
control. CBD believes such carrying capacity caps or other restrictions 
should also address weather conditions when they exacerbate 
PM10 emissions, such as during windy weather and the summer. 
Comite comments that ICAPCD should analyze whether OHV permit 
requirements, such as those that are required in San Bernardino County, 
should be required in Imperial County. Comite also believes that ICAPCD 
should analyze controls described in the California State Parks Off-
Highway Motor Vehicle Recreation Division's 2008 Soil Conservation 
Standard and Guidelines.\128\ Lastly, instead of decreasing the size of 
OHV areas, one commenter (0120) suggested rotating OHV areas to help 
surface crust formation.
---------------------------------------------------------------------------

    \128\ Submitted as Exhibit D to Comite comment letter.
---------------------------------------------------------------------------

    Response: The commenters as a group make constructive suggestions 
that would be appropriate for consideration in a comprehensive 
evaluation of BACM for this source category. We believe ICAPCD should 
analyze all potential available OHV controls to meet the CAA's BACM 
requirement, including those mentioned in the comments and those 
adopted in other areas, pursuant to EPA guidance.\129\
---------------------------------------------------------------------------

    \129\ See, e.g., General Preamble Addendum at 42012-42013.
---------------------------------------------------------------------------

F. Definition of Disturbed Surface (DS)

    DS #1: ICAPCD believes the term ``disturbed surface'' is self-
evident and that no questions have been raised about it since rule 
adoption. ICAPCD believes Rule 804 is clear that an area is deemed 
disturbed if it shows any sign of man-made disturbance (e.g., vehicle 
traffic) and the owner/operator cannot prove that the area meets the 
characteristics of a stabilized surface. ICAPCD is willing to define 
this term more clearly during the next revision to Rule 101, but 
strongly objects to EPA disapproving Regulation VIII on this basis. In 
contrast, CBD supports EPA's concerns regarding this definition in 
Regulation VIII, and further believes the definition should be tailored 
to Imperial Valley and explicitly include open areas on BLM land that 
emit significant PM10 including the Algodones Dunes. In this 
regard, CBD suggests specific edits to SJVUAPCD's analogous rule.
    Response: We believe the explanation provided in ICAPCD's comment 
is a logical interpretation of the undefined term in its regulation. 
However, we also believe that alternate definitions are possible (such 
as that recommended by CBD in its comment), and it is common practice 
to define all terms used in rules that are needed in order to ensure 
clarity and enforceability. We encourage ICAPCD to clarify its 
regulation by including an appropriate definition of this critical term 
and to consider CBD's recommendations for the wording of the rule.

G. Unpaved Road (UR) Controls

    UR #1: ICAPCD projects that control of unpaved non-farm roads 
provides 55% of Regulation VIII's emission reductions. ICAPCD believes 
this demonstrates a good faith effort to reduce PM10 
emissions from road stabilization, and asserts that the County is 
trying to increase funding for such projects. ICAPCD states that the $2 
million/year available to the County Department of Public Works (PWD) 
for road maintenance and stabilization reflects great needs and low 
availability of public funds in the County. According to ICAPCD, this 
budget is for maintenance of 1,350 miles of paved roads which require 
resurfacing every 10-15 years, or 90 miles of extensive maintenance 
each year. Thus, ICAPCD argues that allocation of 9% of this budget to 
stabilize 19 miles of unpaved road represents, contrary to EPA's 
assertion, the most expedited schedule possible with the present level 
of available funding.
    Response: Where economic feasibility of control depends on public 
funding, EPA will consider past funding and the future availability of 
funding sources to determine if a good faith effort is being made to 
implement BACM expeditiously.\130\ The fact that unpaved road controls 
provide 55% of Regulation VIII's estimated emission reductions is not 
in itself sufficient to demonstrate good faith efforts to control road 
dust expeditiously. Alternatively, for example, this high percentage of 
the total amount of reductions could occur if other sources are under-
controlled or are less feasible to control. Nonetheless, EPA believes 
that some of the information ICAPCD provides in its comment on this 
point could help to demonstrate a good faith effort to control road 
dust expeditiously. Given ICAPCD and Imperial County's limited 
resources, we do not believe this analysis needs to be exhaustive, but 
it should be more thorough and documented than presented in the 
Regulation VIII submittal and this comment. For example, ICAPCD 
indicates in this comment that the County is trying to increase funding 
for road stabilization but provides no documentation to help establish 
this point. Nor has ICAPCD explained how the road stabilization budget 
was derived in light of various Federal,

[[Page 39382]]

State, and local (including local Measure D) funding sources for public 
works construction and maintenance, or otherwise provided the 
demonstration contemplated by the relevant EPA guidance.\131\
---------------------------------------------------------------------------

    \130\ Proposal TSD, p. 16, and General Preamble Addendum at 
42013.
    \131\ See proposal TSD, p. 16.
---------------------------------------------------------------------------

    UR #2: ICAPCD disagrees with EPA that there could be problems 
enforcing Rule 805 section E.7. As evidence, ICAPCD explains that 
Imperial County PWD is meeting its commitment to implement its 
submitted plan, which includes stabilizing different unpaved roads each 
year and maintaining all stabilized roads as intended by the rule.
    Response: CAA section 110(a) requires that control measures be 
enforceable. While Rule 805 section E.7 requires that a compliance plan 
be submitted to ICAPCD, the rule is not clear about the specific 
requirements of the plan (i.e., that the County must stabilize 
different roads each year and must maintain all stabilized roads) and 
does not contain a mandate that the terms of the plan be carried out. 
Evidence that Imperial County PWD is in fact currently implementing the 
plan is not sufficient to ensure enforceability as required by the 
CAA.\132\ ICAPCD should revise the rule to clarify this section 
consistent with enforceability requirements of CAA section 110(a).
---------------------------------------------------------------------------

    \132\ See id., p. 9.
---------------------------------------------------------------------------

    UR #3: Comite believes that ICAPCD should incorporate additional 
restrictions into Regulation VIII, including property line visible 
emissions (VE) limits such as those adopted by Maricopa County and 
SCAQMD, dust controls for unpaved roads subject to Rule 805 section 
E.7, and other more stringent requirements adopted by SCAQMD, SJVUAPCD, 
Maricopa County and Clark County.
    Response: ICAPCD's analysis of BACM did consider controls 
implemented in other areas, including those adopted by SCAQMD, 
SJVUACPD, and Maricopa and Clark Counties. Our proposal TSD recommends 
several specific controls from these areas for further consideration by 
ICAPCD, including imposition of a fence-line opacity standard.\133\
---------------------------------------------------------------------------

    \133\ Id., p. 11.
---------------------------------------------------------------------------

    However, with the exception of the deficiencies identified in our 
proposal, we believe that ICAPCD sufficiently analyzed controls in 
other areas for potential BACM.\134\ For example, ICAPCD explains that 
SCAQMD has only a 0% fence-line opacity standard, whereas ICAPCD and 
other agencies with adopted rules approved as BACM all have a similar 
general 20% opacity standard applicable everywhere, and not just at the 
fence-line.\135\ ICAPCD claims that SCAQMD's 0% fence-line standard is 
less stringent than a general 20% standard. While it is difficult to 
compare the two standards,\136\ we do not have evidence that SCAQMD's 
standard is more stringent than the general standard used by ICAPCD and 
by other air districts.
---------------------------------------------------------------------------

    \134\ 2005 BACM analysis, chapter 4, and 2009 PM10 
SIP, table 4.2.
    \135\ 2005 BACM analysis, p. 21.
    \136\ For example, a 40% opacity plume in the middle of a large 
property that disperses to 0% opacity by the property fence-line 
violates ICAPCD's rule but not SCAQMD's. Conversely, a 10% opacity 
plume that disperses to 5% opacity by the fence-line violates 
SCAQMD's rule but not ICAPCD's.
---------------------------------------------------------------------------

    UR #4: One commenter (0154) states that it is not feasible or cost 
effective to eliminate all dust from dirt roads.
    Response: We agree with this comment. Neither Regulation VIII nor 
our proposal or this final action assumes that dust emissions can be 
completely eliminated from farm and non-farm dirt roads.

H. Border Patrol (BP) Controls

    BP #1: ICAPCD comments that Rule 800 section F.6.c does not 
explicitly exempt BP from fugitive dust controls, but requires BP to 
control dust from roads it owns/operates consistent with Rule 805 
except where inconsistent with BP's authority or mission. ICAPCD 
indicates that, while BP does not own any roads, it uses public roads 
to accomplish its mission, and some roads adjacent to the border are 
used exclusively by BP. ICAPCD states that most of these roads are 
below Rule 805's applicability threshold, are located in remote areas 
that are for the most part restricted to BP vehicles, and 
PM10 controls are not feasible and are inconsistent with 
BP's mission. ICAPCD explains that although BP neither owns nor 
operates these roads, BP is committed to implement PM10 
controls such as vehicle speed restrictions and access controls. ICAPCD 
indicates that since adoption of Regulation VIII, BP has submitted two 
productive DCPs. Therefore, ICAPCD disagrees with EPA's recommendation 
to remove or narrow the exemption for BP activities, and proposes to 
continue addressing BP through a DCP requirement to insure that BP 
continues controlling fugitive dust.
    Response: First, we note that nothing in our proposal affects 
Regulation VIII's requirement for BP to develop and implement DCPs 
pursuant to Rule 800 sections F.6.a and F.6.b. However, ICAPCD's 
explanation is unclear as to whether or not BP operates any roads 
subject to the rule. If ICAPCD can support its assertion that BP 
neither owns nor operates such roads, the exemption in Rule 800 section 
F.6.c. is simply unnecessary and should be removed. If BP does own or 
operate such roads, we continue to believe that the exemption is 
unnecessarily broad and should be removed or narrowed and demonstrated 
to be consistent with BACM requirements.
    ICAPCD offers no evidence or explanation to support its contention 
that Rule 805 requirements are potentially inconsistent with BP's 
authority and/or mission. We also note that BP has not raised concerns 
with our proposal, although we informed BP of it before publication. 
EPA appreciates BP's efforts to limit PM10 pollution through 
DCPs. Our concern, however, is with ICAPCD's Regulation VIII submittal 
and the lack of clarity in, and analysis to support, the actual 
provisions in Regulation VIII intended to govern these activities.
    BP #2: OWD comments that BP frequently goes off-road within 
Ocotillo Wells SVRA, beyond OWD's control.
    Response: Rule 804 section E imposes requirements on owners of open 
areas such as Ocotillo Wells SVRA regardless of who owns vehicles 
driving on the open areas. Nothing in our proposal would affect these 
existing ICAPCD requirements.

I. Unpaved Farm Roads and Traffic Areas (UFRTA) Controls Introduction

    The comments summarized in this section and sections II.J and K 
relate to ICAPCD Rule 806, Conservation Management Practices. In 
discussing our proposal regarding Rule 806, a number of these comments 
address various aspects of analogous rules adopted by State and local 
agencies in California and Arizona for controlling PM10 from 
agricultural sources. All of these rules are menu-based and as such 
divide the control measures, known as conservation management practices 
(CMPs) or best management practices (BMP), into three or more menus 
known as ``categories.'' We provide the following information on these 
rules as an introduction to inform our responses to the comments in 
this section and sections II.J and K.
    ICAPCD Rule 806, Conservation Management Practices, is a menu-based 
rule that has four categories:
     Land preparation and cultivation.
     Harvesting.
     Unpaved roads.
     Unpaved traffic areas.
    All persons who own or operate an agricultural operation site of 
forty acres or more are required to implement one

[[Page 39383]]

CMP from each of these categories. Table 3 summarizes the relevant 
categories from Rule 806 and the other menu based rules to which we 
refer:

                                                     Table 3
----------------------------------------------------------------------------------------------------------------
                                                                          Categories for on-    Categories for
     State or local agency               Rule                Area         field agricultural   unpaved Ag. roads
                                                                              operations       and traffic areas
----------------------------------------------------------------------------------------------------------------
Imperial County APCD (ICAPCD)..  806................  Imperial County...  [dec221] Land       [dec221] Unpaved
                                                                           Preparation and     Roads.
                                                                           Cultivation
                                                                           (including
                                                                           tillage).
                                                                          [dec221]            [dec221] Unpaved
                                                                           Harvesting.         Traffic Areas.
San Joaquin Valley Unified APCD  4550...............  San Joaquin Valley  [dec221] Land       [dec221] Unpaved
 (SJVUAPCD).                                           Planning            Preparation and     Roads.
                                                       Area.\137\          Cultivation
                                                                           (including
                                                                           tillage).
                                                                          [dec221] Harvest..  [dec221] Unpaved
                                                                                               Traffic Areas.
                                                                          [dec221] Cropland--
                                                                           Other.
Arizona Department of            Arizona              Phoenix Planning    [dec221] Tillage    [dec221]
 Environmental Quality (ADEQ).    Administrative       Area.\138\          and Harvest.        Noncropland.
                                  Code (A.A.C) R18-2-
                                  610 and R18-2-611.
                                                                          [dec221] Cropland.
Great Basin Unified APCD         502................  Alpine, Inyo, and   [dec221] Land       [dec221] Unpaved
 (GBUAPCD).                                            Mono                preparation.        Roads.
                                                       Counties.\139\
                                                                          [dec221] Harvest..  [dec221] Unpaved
                                                                                               Traffic Areas.
                                                                          [dec221] Other
                                                                           Cultural
                                                                           Practices.
South Coast AQMD...............  Rule 403 And         South Coast Air     [dec221] Active     [dec221] Unpaved
                                  Agricultural         Basin.\140\         Conservation        Roads.
                                  Handbook.                                Practices.
                                                                          [dec221] Inactive
                                                                           Conservation
                                                                           Practices.
South Coast AQMD...............  Rule 403 And         Coachella Valley    [dec221] Active     [dec221] Unpaved
                                  Coachella Valley     Planning Area.      Conservation        Roads.
                                  Agricultural                             Practices.
                                  Handbook.
                                                                          [dec221] Inactive
                                                                           Conservation
                                                                           Practices.
----------------------------------------------------------------------------------------------------------------

    We also refer below to SJVUAPCD's Rule 8081, Agricultural Sources, 
which has opacity and stabilization requirements for high traffic 
agricultural unpaved roads and traffic areas.
---------------------------------------------------------------------------

    \137\ SJVUAPCD's jurisdiction includes the entire counties of 
San Joaquin, Stanislaus, Merced, Madera, Fresno, Tulare, and Kings 
and part of Kern County. SJVUAPCD does not include the parts of East 
Kern that are not in the San Joaquin Valley Air Basin. See 40 CFR 
81.305.
    \138\ The Phoenix Planning Area includes Maricopa County and a 
portion of Pinal County. See 40 CFR 81.303.
    \139\ See section 1 and 2 of GBUAPCD Rule 502. Also see 40 CFR 
81.305.
    \140\ SCAQMD's jurisdiction includes the South Coast Air Basin 
and the Coachella Valley Planning Area. For a description of the 
boundaries of the Los Angeles-South Coast Air Basin Area and the 
Coachella Valley Planning Area, see 40 CFR 81.305. The South Coast 
Air Basin includes all of Orange County and the more populated 
portions of Los Angeles, San Bernardino, and Riverside Counties. The 
Coachella Valley Planning Area includes central Riverside County in 
the Salton Sea Basin.
---------------------------------------------------------------------------

    UFRTA #1: Comite believes that California has not demonstrated why 
agricultural paved and unpaved roads should be subject to less 
stringent requirements than other roads in Imperial County (i.e., those 
subject to Rule 803 regarding track-out/carry-out and Rule 805) and 
cites San Joaquin Valley where such roads must meet CMPs as well as 
general requirements. In contrast, ICAPCD and the Farm Bureau believe 
Regulation VIII is more stringent regarding unpaved farm roads and 
traffic areas than analogous rules in other areas even though Imperial 
County farm roads and traffic areas are not subject to opacity limits. 
These latter commenters note that Rule 806 requires CMPs for all 
unpaved roads and traffic areas regardless of vehicle trips per day 
(VTD), unlike SJVUAPCD Rule 4550. COLAB also explains that ICAPCD Rule 
806 was designed to address all unpaved roads by applying to parcels 
greater than 40 acres (97% of farmland in Imperial County) compared to 
SJVUAPCD's Rule 4550 which addresses roads on parcels larger than 100 
acres (91% of farmland in the San Joaquin Valley). Lastly, ICAPCD and 
the Farm Bureau assert that most private unpaved farm roads are less 
used and are therefore below Rule 805's 50 VTD threshold. Regardless of 
VTD, however, these latter commenters argue that owners of these roads 
must implement Rule 806 CMPs.
    Response: EPA's proposal noted that ICAPCD has not demonstrated 
BACM for unpaved farm roads and traffic areas because of the exemption 
in Rule 805 section D.2 from opacity and stabilization requirements 
applicable to non-agricultural operation sites. EPA further noted that 
SJVUAPCD does not provide such an exemption, and ICAPCD had not 
justified such an exemption.\141\
---------------------------------------------------------------------------

    \141\ Proposal TSD, pp. 8-9.
---------------------------------------------------------------------------

    ICAPCD and other commenters do not offer evidence that Regulation 
VIII is as stringent as comparable controls in this regard, but instead 
claim that Regulation VIII is more stringent in other respects. For 
example, no commenter disputes our conclusion that an unpaved farm road 
with 75 VTD would be subject to opacity standards in SJVUAPCD's Rule 
8081 but not in ICAPCD's Regulation VIII. However, ICAPCD and others 
argue that the applicability threshold for unpaved farm roads subject 
to Rule 806, for example, is more stringent than SJVUAPCD's analogous 
requirements. Because opacity and surface stabilization requirements on 
heavily-used farm roads and traffic areas are being implemented in 
other areas, we believe that, absent an adequate explanation, these 
requirements are at least presumptively BACM for this source category 
in Imperial County. Accordingly, these controls should be evaluated as 
potential BACM by ICAPCD. However, as stated previously, ICAPCD may 
consider conditions

[[Page 39384]]

specific to Imperial County in a revised BACM evaluation for unpaved 
roads and traffic areas, as appropriate.
    We also agree with Comite that it is not clear why Rule 803 section 
D.1 exempts farm roads and traffic areas from certain carry-out and 
track-out requirements that apply to similar non-farm roads. We 
encourage ICAPCD to consider removing this exemption, although such a 
rule modification is not mandated by the CAA at this time because 
carry-out/track-out has not been identified as a significant source 
category subject to the BACM requirement.
    UFRTA #2: Comite believes that Rule 806's CMPs are not sufficiently 
specific regarding agricultural unpaved roads and traffic areas. In 
contrast, ICAPCD comments that Rule 806 section F.6 requires CMP plans 
to include other relevant information, which gives ICAPCD authority to 
require adequate specificity. COLAB also comments that the CMP forms 
provided in the rule are examples and if the relevant information was 
provided the form could be changed.
    Response: Issues raised regarding specificity of CMPs for unpaved 
roads and traffic areas are similar to issues raised regarding the 
specificity of CMPs for other agricultural operations. See response to 
comment AL 3 below.

J. Agricultural Land Controls (AL)

    See Introduction in section II.I above.
    AL #1: ICAPCD comments that Rule 806's CMP requirements are similar 
to requirements adopted by SJVUAPCD, Maricopa County \142\ and 
SCAQMD,\143\ and are directly based on SJVUAPCD requirements that EPA 
approved as BACM in 2004, citing 69 FR 30035.\144\ ICAPCD asserts that 
the individual CMPs in Rule 806 are similar to those found in SJVUAPCD 
Rule 4550 and GBUAPCD Rule 502 and concludes that the only differences 
in the rules are due to differences in local agricultural practices. 
The Farm Bureau also states that there is little difference between 
GBUAPCD and ICAPCD control measures.
---------------------------------------------------------------------------

    \142\ Although ICAPCD refers to requirements adopted by Maricopa 
County in its comments, Arizona's rules, A.A.C. R18-2-610 and R18-2-
611, for controlling PM-10 from agricultural sources apply to some 
sources beyond the boundaries of Maricopa County.
    \143\ As noted in Table 3 above, SCAQMD's Rule 403 has 
requirements for agricultural activities that apply to both the 
South Coast Air Basin and Coachella Valley Planning Area.
    \144\ EPA approved SJVUAPCD Rule 4550 in 2006, not in 2004. See 
71 FR 7683. EPA approved a commitment for the San Joaquin Valley CMP 
Program in 2004. See 69 FR 30006.
---------------------------------------------------------------------------

    Response: We agree that many individual CMPs and requirements in 
the rules outlined in Table 3 are similar. However, this overall 
similarity does not affect the two specific BACM deficiencies in ICAPCD 
Rule 806 for tilling and harvesting emissions identified in our 
proposed action.\145\ One of these deficiencies concerns the lack of 
sufficiently defined requirements in contrast to the application 
submittal and review processes in the SJVUAPCD and GBUABCD rules that 
insure more effective implementation and enforcement of the 
requirements.\146\ The other deficiency is related to the number of 
CMPs required by Rule 806. Rule 806 section E requires one CMP from the 
``land preparation and cultivation'' category and one CMP from the 
``harvesting'' category, while SJVAPCD Rule 4550 requires an additional 
CMP from the ``cropland-other'' category. GBUAPCD Rule 502 also 
requires that one CMP each be selected from the ``land preparation and 
cultivation,'' ``harvest,'' and the ``other cultural practices'' 
categories.\147\
---------------------------------------------------------------------------

    \145\ See 75 FR 8008, 8011-8012.
    \146\ See SJVUAPCD Rule 4550 section 6.3 and 6.4 and GBUAPCD 
Rule 502 section 6.3 and 6.4.
    \147\ See SJVUAPCD Rule 4550 section 6.2 and SJVUAPCD ``List of 
Conservation Management Practices.'' See also GBUAPCD Rule 502 
section 6.2 and, for example, GBUAPCD Supplemental Application Form 
for Alfalfa. See also ``Conservation Management Practices for Farms 
in Inyo, Mono and Alpine Counties, Program Description and Plan 
Application Forms,'' December 19, 2008, Great Basin Unified Air 
Pollution Control District, at http://www.gbuapcd.org/farm/CMPprogramdescriptionandforms.pdf.
---------------------------------------------------------------------------

    AL #2: ICAPCD believes that EPA disregards that Imperial County 
crops are irrigated, and that continued irrigation and conditioning of 
soil dramatically reduce its potential for both entrained and windblown 
emissions. ICAPCD believes this fact must be considered when comparing 
Rule 806 to rules in other areas.
    Response: As stated previously above, EPA agrees that it is 
appropriate to consider conditions specific to an area when evaluating 
potential BACM.\148\ However, most of the harvested cropland in other 
areas subject to comparable requirements is also irrigated. The 
following table shows data from the 2007 Census of Agriculture \149\ 
for the total acres of harvested cropland and the acres of irrigated 
harvested cropland in relevant counties in California and Arizona. 
Imperial County and the counties in the SJVUAPCD \150\ are included. 
Riverside County in California \151\ and Maricopa County in Arizona are 
also included.
---------------------------------------------------------------------------

    \148\ General Preamble Addendum at 42010 and 42012.
    \149\ 2007 Census of Agriculture, California, State and County 
Data, and 2007 Census of Agriculture, Arizona, State and County 
Data, United States Department of Agriculture, National Agricultural 
Statistics Service. See http://www.agcensus.usda.gov/Publications/2007/Full_Report/Volume_1,_Chapter_2_County_Level/California/
cav1.pdf and http://www.agcensus.usda.gov/Publications/2007/Full_Report/Volume_1,_Chapter_2_County_Level/Arizona/azv1.pdf.
    \150\ See footnote 141 above. The census data in Table 4 are for 
all of Kern County.
    \151\ Of all the counties included in SCAQMD, Riverside County 
has the largest acreage of harvested cropland. According to the 2007 
Census of Agriculture, Orange County has 7,846 acres of harvested 
cropland, Los Angeles County has 25,829 acres of harvested cropland, 
San Bernardino County has 27,516 acres of harvested cropland, and 
Riverside County has 163,783 acres of harvested cropland. 2007 
Census of Agriculture, California, State and County Data, United 
States Department of Agriculture, National Agricultural Statistics 
Service. See http://www.agcensus.usda.gov/Publications/2007/Full_Report/Volume_1,_Chapter_2_County_Level/California/cav1.pdf.

                                 Table 4
------------------------------------------------------------------------
                                                            Irrigated
                                       Total harvested      harvested
            County, State                 cropland          cropland
                                           (acres)           (acres)
------------------------------------------------------------------------
Imperial, CA........................           375,904           375,167
Maricopa, AZ........................           190,182           189,141
Riverside County, CA................           163,783           158,437
San Joaquin County, CA..............           444,670           426,670
Stanislaus, CA......................           307,992           297,053
Merced, CA..........................           466,304           458,017
Madera, CA..........................           264,767           260,596
Fresno, CA..........................           978,948           960,215

[[Page 39385]]

Kings, CA...........................           419,964           419,080
Tulare, CA..........................           560,320           540,887
Kern, CA............................           764,929           756,645
------------------------------------------------------------------------

    Thus, the mere fact that crops are grown using irrigation in 
Imperial County does not in and of itself justify different standards 
for BACM.
    AL #3: ICAPCD comments that Rule 806 section F.6 specifies that the 
CMP plan shall include ``other relevant information as determined by 
the ICAPCD,'' which gives ICAPCD authority to modify the CMP plans to 
specify frequency of CMP applicability. Therefore ICAPCD believes a 
mechanism is in place in the rule for modification of CMPs to provide 
such details, and therefore this should not be a basis for disapproval 
of Regulation VIII as BACM. ICAPCD notes its commitment to modify the 
CMP plans to provide such details.
    Response: As noted by ICAPCD, Rule 806 section F.6 provides a 
mechanism that could be used by ICAPCD to provide greater specificity. 
However there is no required process in the rule for sources to provide 
such information to ICAPCD or for ICAPCD to review the CMPs and/or to 
require revision of the CMPs that sources have chosen to implement. 
Under section F, sources are only required to prepare a plan containing 
minimal information and to maintain a copy of the plan. Thus the CMPs 
would continue to be broadly defined unless or until ICAPCD proactively 
determines that greater specificity is needed. Absent such vital 
details, it would be difficult for regulated entities to know precisely 
what is required of them to comply with a BACM level of control, and it 
would be difficult for ICAPCD, EPA, or others to enforce these 
requirements.\152\ In contrast, SJVUAPCD Rule 4550 section 5 requires 
sources to prepare and submit a CMP application to the District for 
approval and section 6 requires the District to evaluate and either 
approve or disapprove the application in writing. GBUAPCD Rule 502 
sections 5 and 6 contain substantially identical requirements. Such 
requirements provide a mandatory process that is far more likely to 
ensure that the CMPs are implemented and enforceable at a BACM level of 
control than the provision in ICAPCD Rule 806.
---------------------------------------------------------------------------

    \152\ For instance, one of the CMPs that is both in the ``land 
preparation and cultivation'' category in Rule 806 section E.1 and 
the ``harvesting'' category in section E.2 is ``equipment changes/
technological improvements'' which is defined in section C.15 as 
``To modify the equipment such as tilling; increase equipment size; 
modify land planning and land leveling; match the equipment to row 
spacing; granting to new varieties or other technological 
improvements. It reduces the number of passes during an operation, 
thereby reducing soil disturbance.'' This definition is too broad to 
ensure enforceability. Moreover, because there is no mechanism to 
narrow the definition for a particular agricultural operation, a CMP 
may be implemented in a manner less stringent than a BACM level of 
control. In a similarly broad fashion, Rule 806 section C.34 defines 
``speed limits,'' a CMP in both the ``unpaved roads'' category in 
section E.3 and the ``unpaved traffic areas'' category in section 
E.4, as ``enforcement of speeds that reduce visible dust emissions. 
The dust emissions from unpaved roads are a function of speed, 
meaning reducing speed reduces dust.'' However, an appropriate speed 
limit or range of speed limits is not specified or otherwise 
insured.
---------------------------------------------------------------------------

    Finally, even if ICAPCD were to routinely exercise its 
discretionary authority in Rule 806 to specify the frequency of CMP 
applicability, the deficiency noted in our proposed action related to 
lack of CMP specificity extends beyond the issue of frequency.\153\
---------------------------------------------------------------------------

    \153\ See 75 FR 8008, 8011-8012.
---------------------------------------------------------------------------

    AL #4: ICAPCD claims that BACM should not be required for harvest 
activities because the emissions from these activities (0.01 tpd) are 
negligible. ICAPCD argues that efforts to increase regulation of 
emissions from harvesting would waste resources. In addition, ICAPCD 
claims that the CMPs in Rule 806 related to harvesting are similar to 
those in SJVUAPCD Rule 4550.
    Response: ICAPCD has identified tilling emissions as a significant 
source.\154\ As stated in our proposal for this action, measures in 
Rule 806 for harvesting must also meet BACM because the activities 
occur at the same facilities and are integrally related to tilling 
emissions.\155\ By analogy, where enforceable volatile organic compound 
(VOC) reasonably available control technology (RACT) level controls are 
required for refineries, SIP rules generally impose leak detection and 
repair requirements on valves, flanges, threaded connections and other 
related equipment even if emissions from any one of these taken 
individually might be much smaller than the major source threshold 
requiring RACT.\156\
---------------------------------------------------------------------------

    \154\ Proposal TSD, pp. 5-6.
    \155\ Proposal TSD, p. 10, footnote 25.
    \156\ SJVUAPCD Rule 4451, Valves, Pressure Relief Valves, 
Flanges, Threaded Connections and Process Drains at Petroleum 
Refineries and Chemical Plants, amended April 20, 2005.
---------------------------------------------------------------------------

    We agree that individual CMPs for emissions from harvesting 
activities in Rule 806 are generally similar to CMPs for such emissions 
in the San Joaquin Valley. However, both SJVUAPCD and GBUAPCD require 
one more CMP for on-field agricultural sources than does Rule 806.\157\ 
This additional CMP may reduce emissions from harvesting activities. 
ICAPCD must establish that requiring fewer controls for on-field 
agricultural activities is consistent with BACM requirements. Thus far 
ICAPCD has not provided a convincing justification.
---------------------------------------------------------------------------

    \157\ See SJVUAPCD Rule 4550 section 6.2 and SJVUAPCD ``List of 
Conservation Management Practices.'' See also GBUAPCD Rule 502 
section 6.2 and, for example, GBUAPCD Supplemental Application Form 
for Alfalfa. See also ``Conservation Management Practices for Farms 
in Inyo, Mono and Alpine Counties, Program Description and Plan 
Application Forms,'' December 19, 2008, Great Basin Unified Air 
Pollution Control District, at http://www.gbuapcd.org/farm/CMPprogramdescriptionandforms.pdf.
---------------------------------------------------------------------------

    AL #5: ICAPCD disagrees with our identification of the requirements 
of Rule 806 for tilling as a deficiency in the BACM analysis. In 
support of its position, ICAPCD asserts that San Joaquin Valley sources 
may select two CMPs that reduce emissions from tilling from the list of 
measures, but they are not required to do so. ICAPCD also claims that 
because per-acre emissions from land preparation are about four times 
as high in the San Joaquin Valley as they are in Imperial County, the 
cost-effectiveness of emission reductions from tilling activities 
through the implementation of any CMP should be four times as high in 
Imperial County as in the San Joaquin Valley. For these two reasons, 
ICAPCD believes that Rule 806 requirements for tilling are as stringent 
as analogous SJVUAPCD requirements. In contrast, Comite comments that 
Arizona Rules 18-2-610 and 611 require at least two CMPs from each

[[Page 39386]]

category in the rule whereas Rule 806 requires only one, and that 
SJVUAPCD requires up to three CMPs.
    Response: Although ICAPCD focuses here on emissions from tillage, 
the deficiency in our proposed rule is related to requirements in Rule 
806 for sources to implement one fewer CMP overall for on-field 
agricultural sources than is required by SJVUAPCD Rule 4550 and GBUAPCD 
Rule 502. Thus the fact that sources subject to SJVUAPCD Rule 4550 are 
not required to select two CMPs for reducing emissions from tillage is 
irrelevant. ICAPCD needs to assess whether additional CMPs for on-field 
agricultural sources are BACM for Imperial County.
    ICAPCD has not established that the agricultural activities in 
Imperial County are significantly different from those in other areas. 
Accordingly, EPA believes that ICAPCD should have BACM level controls 
for both tillage and harvest emissions as do other areas with programs 
for emissions from agricultural activities, and should consider 
SJVUAPCD and controls from other areas with analogous rules when 
assessing whether a requirement for additional CMPs would be 
economically and technologically feasible to control emissions from 
these activities. ICAPCD claims that implementing tillage CMPs may be 
more cost-effective in the San Joaquin Valley, but does not address 
whether it would be economically feasible to require additional CMPs in 
Imperial County.
    We agree with Comite that sources subject to Arizona Rules 18-2-610 
and 611 are required to implement two practices each from the ``tillage 
and harvest'' and ``cropland'' categories. ICAPCD needs to consider 
whether requiring four practices for on-field agricultural sources 
constitute BACM for Imperial County.
    AL #6: Comite claims that Maricopa's inspection regime for 
agricultural sources is more rigorous than ICAPCD's.
    Response: Comite provides no supporting information on either the 
Maricopa County or ICAPCD inspection program on which to base a 
response and we are not otherwise aware of information that supports 
this comment.
    AL #7: The Farm Bureau agrees that SJVUAPCD requires an additional 
CMP from the ``cropland-other'' category but notes that the same 
requirement is found in ICAPCD's ``land preparation and cultivation'' 
and ``harvest activities'' categories. As a result, the Farm Bureau 
believes that including an additional category would be redundant and 
onerous for participants.
    Response: The deficiency identified in our proposed action is 
related to the requirement in Rule 806 for Imperial County sources to 
implement one fewer practice for on-field agricultural sources overall 
without a sufficient justification.\158\ ICAPCD does not necessarily 
need to add a category to Rule 806 in order to address this deficiency. 
For example, depending on what is most appropriate for conditions in 
Imperial County, ICAPCD may be able to require that more than one CMP 
be implemented from the categories that currently exist in Rule 806. 
Moreover, it would not be redundant to require Imperial County sources 
to implement an additional CMP for on-field agricultural sources. Rule 
806 has two categories for on-field agricultural sources, ``land 
preparation and cultivation'' and ``harvesting,'' and requires sources 
to implement one practice from each category. As noted in Table 3 
above, SJVUAPCD Rule 4550 and GBUAPCD Rule 502 have three categories 
for on-field agricultural sources, and require that sources implement 
one practice from each of these categories. Moreover, as noted in our 
response to comment AL 5 above, sources subject to Arizona 
Rules 18-2-610 and 611 are required to implement four practices for on-
field agricultural sources. As part of a BACM analysis, ICAPCD should 
consider the economic and technological feasibility of requiring 
additional CMPs for on-field agricultural sources, including 
consideration of the requirements in rules adopted by SJVUAPCD, GBUAPCD 
and Arizona.
---------------------------------------------------------------------------

    \158\ 75 FR 8008, 8012.
---------------------------------------------------------------------------

K. Agricultural Land Windblown Dust Controls (ALWD)

    See Introduction in section II.I above.
    ALWD #1: COLAB comments that the deficiencies identified by EPA 
related to windblown dust are particularly troublesome because they are 
so surprising. COLAB believes that Rule 806 exceeds CAA needs because 
windblown dust from agriculture is insignificant. Comite, on the other 
hand, notes SCAQMD's requirements for reducing windblown dust from 
active and inactive agricultural fields as BACM measures that ICAPCD 
should consider along with recommendations in U.S. Department of 
Agriculture's (USDA) National Agronomy Manual for reducing such dust.
    Response: EPA has determined that windblown dust from agriculture 
is a significant PM10 source category in Imperial County for 
which ICAPCD must demonstrate, but has not yet demonstrated, 
implementation of BACM level controls.\159\ ICAPCD should include in 
its BACM analysis consideration of whether existing SCAQMD controls, 
among others, and USDA recommendations for controlling wind erosion, 
are economically and technologically feasible measures to reduce 
windblown dust from active and fallow agricultural fields. Also see 
response to comment General 3 above.
---------------------------------------------------------------------------

    \159\ Proposal TSD, pp. 10-11.
---------------------------------------------------------------------------

    ALWD #2: ICAPCD believes that EPA should have concurred with 
exceptional event requests associated with high winds as discussed in 
the exceptional event comments above. As a result, ICAPCD believes that 
windblown dust from agricultural lands is not a significant source 
category in SIP development, and therefore not subject to BACM.
    Response: In our proposed action on Regulation VIII, we explained 
how we determined that windblown dust from agricultural lands is a 
significant source category subject to BACM.\160\ We have not received 
information in the comments or elsewhere that affects this conclusion 
or the related 2009 EE decision. See also responses to exceptional 
event comments above and comment OHV 1.
---------------------------------------------------------------------------

    \160\ Id., pp. 5-7.
---------------------------------------------------------------------------

    ALWD #3: ICAPCD disagrees that Rule 806 does not apply to fallow 
agricultural fields. ICAPCD states that there are no exemptions in Rule 
806 for fallow fields and fallowing is an optional CMP to control 
emissions from ``land preparation and cultivation'' under Rule 806 
section E.1.
    Response: Fallowing land is defined in Rule 806 section C.16 as 
``Temporary or permanent removal from production. Eliminates entire 
operation/passes or reduces activities.'' We note that the fallowing 
CMP is an option under both the ``land preparation and cultivation'' 
category in section E.1 and the ``harvesting'' category in section E.2. 
While the fallowing CMP in Rule 806 section E.1 may reduce emissions 
from ``land preparation and cultivation'' and from ``harvesting,'' it 
does not address any windblown dust emissions that may occur once a 
field is removed from production. EPA believes that the evaluation of 
BACM level controls for windblown dust from fallow fields should 
include consideration of USDA-approved conservation systems and 
activities.\161\
---------------------------------------------------------------------------

    \161\ Id., pp. 10-11 and 17.
---------------------------------------------------------------------------

    ALWD #4: ICAPCD comments that ICAPCD farms are all irrigated and 
historically well watered, which leads to stable clods and/or 
aggregates that lower susceptibility to wind erosion

[[Page 39387]]

consistent with USDA's National Agronomy Manual. ICAPCD estimates that 
long-term irrigation reduces PM10 emissions by 25-45% from 
the predominant cultivated soil types in Imperial County, so local 
fallow and active agricultural land is controlled for windblown 
emissions relative to land not previously used for irrigated 
agriculture. In contrast, ICAPCD believes that SCAQMD's farm acreage is 
overwhelmingly devoted to dryland grain farming, and EPA has not shown 
that SCAQMD controls are appropriate for ICAPCD's irrigated fields.
    Response: Based on data in Table 4, EPA believes that the majority 
of ICAPCD harvested acreage is irrigated. However, EPA disagrees that 
farm acreage subject to SCAQMD controls is overwhelmingly devoted to 
dryland farming. See total harvested cropland acres and irrigated 
harvested cropland acres for Riverside County in Table 4. While 
historic irrigation may provide for some level of control, windblown 
dust from agriculture is a significant source, and ICAPCD is required 
to implement BACM level controls for windblown emissions from active 
and fallow agricultural fields. ICAPCD has not provided a convincing 
justification for why controls in the Coachella Valley Planning Area 
are not applicable to Imperial sources. ICAPCD's evaluation for BACM 
level controls for windblown dust from agricultural sources should 
include requirements in SCAQMD Rule 403 and the Coachella Valley 
Agricultural Handbook.
    ALWD #5: ICAPCD notes that winds above 25 mph are extremely rare in 
the agricultural portion of Imperial Valley, and farmers usually avoid 
tilling on windy days to conserve soil. As a result, ICAPCD does not 
believe that SCAQMD's restriction for soil preparation and maintenance 
during days with winds above 25 mph would impact windblown dust 
emissions from agricultural fields in Imperial County. In contrast, 
Comite points to SCAQMD's requirements as potential BACM that ICAPCD 
has not properly considered.
    Response: ICAPCD must analyze and implement BACM for agricultural 
windblown dust emissions.\162\ Such analysis may consider whether a 
restriction on tilling activities on days with winds above 25 mph is 
appropriate in Imperial County pursuant to our guidance.\163\ However, 
ICAPCD has not provided such analysis in the Regulation VIII submittal, 
its comments or elsewhere. To the extent that farmers avoid tilling on 
windy days to conserve soil anyway, this restriction would not seem to 
be onerous.
---------------------------------------------------------------------------

    \162\ Proposal TSD, pp. 5-7.
    \163\ General Preamble Addendum at 42013.
---------------------------------------------------------------------------

    ALWD #6: ICAPCD comments that SCAQMD's only additional requirement 
for active fields besides the restriction on tilling on days with winds 
above 25 mph is to implement one more CMP from a list that includes 
minimum tillage. ICAPCD believes this CMP is not directly effective at 
reducing windblown emissions, and hence ICAPCD believes that by EPA's 
own reasoning, this requirement does not require windblown control on 
active fields in the South Coast Basin.
    Response: ICAPCD has not explained why minimum tillage would not 
directly reduce windblown dust from active fields. EPA expects that 
minimum tillage would reduce windblown emissions by maintaining more 
plant residue on the field than conventional tillage. Establishing and 
maintaining land cover is one of the five principles noted in the 
National Agronomy Manual for wind erosion control.\164\
---------------------------------------------------------------------------

    \164\ See p. 502-17 of the USDA NRCS National Agronomy Manual, 
October 2002.
---------------------------------------------------------------------------

    ALWD #7: Comite believes that more specificity and information must 
be provided concerning IID's Fallowing Program to ensure that emission 
reductions from it are quantifiable, verifiable and enforceable.
    Response: ICAPCD must analyze and implement BACM for agricultural 
windblown dust emissions.\165\ If, as a result of this analysis, ICAPCD 
concludes that IID's Fallowing Program is needed to implement BACM, 
then we agree that ICAPCD needs to provide more information about IID's 
program and ensure that controls that are provided through the program 
are enforceable.
---------------------------------------------------------------------------

    \165\ Proposal TSD, pp. 5-7.
---------------------------------------------------------------------------

    ALWD #8: Regarding EPA concerns with agricultural windblown dust 
controls, ICAPCD and the Farm Bureau note that Rule 806 was modeled 
after EPA-approved SJVUAPCD Rule 4550 at EPA's recommendation.
    Response: EPA's guidance provides that BACM is determined on a 
case-by-case basis and can consider the specific conditions of the 
nonattainment area.\166\ When we approved SJVUAPCD Rule 4550, we did 
not believe that SJVUAPCD had a regular and repeated windblown dust 
problem.\167\ However, ICAPCD asserts in its 2009 PM10 Plan 
that the ``overwhelming majority of airborne PM in Imperial County is 
primary PM. The major source of primary PM is fugitive windblown dust * 
* *.'' \168\ Moreover, ICAPCD's 2009 PM10 Plan discusses how 
the flat terrain of Imperial Valley and strong temperature 
differentials produce moderate winds and how Imperial County 
occasionally experiences high winds with speeds greater than 30 mph in 
April and May. In addition, the 2009 PM10 Plan attributes 
monitored exceedances in September and June to high winds.\169\ As a 
result, EPA believes that ICAPCD must consider windblown dust controls 
for agricultural sources. Also, see responses to comments General 
3 and EE 5.
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    \166\ See General Preamble Addendum at 42010 and 42012.
    \167\ See, e.g., 73 FR 14687, 14693 (March 19, 2008).
    \168\ 2009 PM10 SIP, p. 1-1.
    \169\ 2009 PM10 SIP, pp. 1-3 and 2-4.
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    ALWD #9: The Farm Bureau notes that both Rule 806 and the 
``Agricultural Air Quality Conservation Management Practices for 
Imperial Valley'' were developed consistent with rules adopted in other 
areas and EPA recommendations. As a result, the Farm Bureau believes 
that this ensured Rule 806 was adequate.
    Response: See response to comment General 3.

L. Other Controls (OC)

    OC #1: Comite believes Regulation VIII should be further 
strengthened by removing director's discretion in Rule 802 section D.1, 
and removing the exemption in Rule 802 section D.4. ICAPCD objects to 
EPA's concerns regarding Rule 802 section D.1 because: (1) The APCO's 
discretion is limited to a determination of whether any of the controls 
in sections F.1 through F.3 can be implemented to satisfy the 20% 
opacity and stabilized surface requirements; (2) where a SIP-approved 
rule provides APCO discretion, the APCO can exercise the discretion 
without further SIP-approval; and (3) EPA has final enforcement 
authority for SIP-approved rules.
    Response: EPA believes that the director's discretion provisions in 
Rule 802 are generally not acceptable under the CAA. Regarding ICAPCD's 
first argument, Rule 802 section D.1 provides the APCO discretion to 
waive completely the opacity and stabilized surface requirements 
without limiting discretion either by a procedure that the APCO must 
use (e.g., test method X) or by boundaries to the discretion (e.g., up 
to 30% opacity instead of 20% opacity). Thus, the discretion is not 
``limited.''
    Regarding ICAPCD's second argument, we note initially that EPA has 
a long history of rejecting such broad APCO discretion in SIP 
rules.\170\

[[Page 39388]]

Moreover, we limit such discretion precisely because the APCO can 
exercise it without further SIP approval where a SIP-approved rule 
provides APCO discretion.
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    \170\ See, e.g., ``Guidance Document for Correcting Common VOC 
and Other Rule Deficiencies,'' U.S. EPA Region IX, August 21, 2001 
(the Little Bluebook); and ``Issues Relating to VOC Regulation 
Cutpoints, Deficiencies, and Deviations,'' U.S. EPA, OAQPS, May 25, 
1998 (The Bluebook).
---------------------------------------------------------------------------

    Regarding ICAPCD's third argument, while we can enforce SIP-
approved rules, as stated, director's discretion provisions undermine 
their enforceability because enforcement of the rules are constrained 
by their terms. In this case, EPA or others could be restricted in 
enforcing against activity exempted by the APCO if this provision were 
SIP-approved.
    While we share Comite's concerns with Rule 802 section D, our 
limited disapproval with respect to Rule 802 section D will not trigger 
sanctions or a FIP obligation because Rule 802 does not address a 
source category identified as significant and thus requiring BACM at 
this time. Therefore our limited disapproval will not trigger sanctions 
under CAA section 179 or a FIP obligation under section 110(c) with 
respect to bulk materials regulated by Rule 802. However, should 
regulation of bulk materials be subject to the BACM requirement in the 
future or to meet other SIP planning requirements under CAA title I, 
part D such as reasonable further progress or attainment, the APCO 
discretion in Rule 802 section D.1 or the exemptions in Rule 802 
section D.4 could result in such consequences and/or affect the 
emission reduction credit for the rule.

M. Statutory and Executive Order Reviews (SEO)

    SEO #1: OWD believes that EPA should address Executive Order 12898, 
which requires Federal agencies to identify and address 
disproportionately adverse health or environmental impacts on minority 
and low-income populations. Specifically, OWD believes that EPA's 
action may impact Imperial County's Hispanic and low-income population 
by reducing tourist income from OHV users. In contrast, Comite applauds 
the commitment of the Regional Administrator of EPA Region 9 to 
environmental justice principles, and notes that relatively large 
portions of the population in this area are not only Hispanic and poor, 
but are also suffering from poor health and this is exacerbated by air 
pollution problems in this area.
    Response: EPA agrees it is important to consider environmental 
justice in our actions and we briefly addressed environmental justice 
principles in our proposal TSD.\171\ Executive Order 12898, ``Federal 
Actions to Address Environmental Justice in Minority Populations and 
Low-Income Populations'' (February 16, 1994) establishes Federal 
executive policy on environmental justice. Its main provision directs 
Federal agencies, to the greatest extent practicable and permitted by 
law, to make environmental justice part of their mission by identifying 
and addressing, as appropriate, disproportionately high and adverse 
human health or environmental effects of their programs, policies and 
activities on minority populations and low-income populations in the 
United States. The Executive Order has informed the development and 
implementation of EPA's environmental justice program and policies. 
Consistent with the Executive Order and the associated Presidential 
Memorandum, the Agency's environmental justice policies promote 
environmental protection by focusing attention and Agency efforts on 
addressing the types of environmental harms and risks that are 
prevalent among minority, low-income and Tribal populations.
---------------------------------------------------------------------------

    \171\ Proposal TSD, p. 3.
---------------------------------------------------------------------------

    This action will not have disproportionately high and adverse human 
health or environmental effects on minority, low-income or Tribal 
populations because it increases the level of environmental protection 
for all affected populations without having any disproportionately high 
and adverse human health or environmental effects on any population, 
including any minority or low-income population. Specially, EPA's 
limited approval and limited disapproval of Regulation VIII would have 
the affect of strengthening environmental requirements throughout 
ICAPCD, and would not relax environmental requirements in any area. 
Thus it promotes environmental justice by increasing the level of human 
health and environmental protection for an area where, as the 
commenters note, relatively large portions of the population are low 
income and/or minority.
    SEO #2: OWD notes that EPA's action may be subject to NEPA 
evaluation.
    Response: EPA actions under the CAA are exempt from NEPA.\172\
---------------------------------------------------------------------------

    \172\ See 40 CFR 6.101(b).
---------------------------------------------------------------------------

    SEO #3: OWD believes that EPA should address increased management 
costs for Imperial County's OHV recreation areas and the effects on OHV 
areas outside Imperial County. As a result, OWD does not believe that 
EPA has a basis to claim (regarding the Unfunded Mandates Reform Act), 
that no additional costs result from this action.
    Response: As explained in our proposal, our action would approve 
and disapprove pre-existing requirements under State or local law, and 
impose no new requirements. Accordingly, no additional costs to State, 
local, or tribal governments, or to the private sector, result from 
this action.\173\
---------------------------------------------------------------------------

    \173\ 75 FR 8008, 8012-8013.
---------------------------------------------------------------------------

III. EPA Action

    No comments were submitted that change our assessment of Regulation 
VIII as described in our proposed action. Therefore, as authorized in 
sections 110(k)(3) and 301(a) of the Act, EPA is finalizing a limited 
approval of the submitted rules. This action incorporates the submitted 
rules into the California SIP, including those provisions identified as 
deficient. As authorized under section 110(k)(3), EPA is simultaneously 
finalizing a limited disapproval of the rules. As a result, sanctions 
will be imposed in Imperial County unless EPA approves subsequent SIP 
revisions that correct the rule deficiencies within 18 months of the 
effective date of this action. These sanctions will be imposed under 
section 179 of the Act according to 40 CFR 52.31. In addition, EPA must 
promulgate a Federal implementation plan (FIP) under section 110(c) 
unless we approve subsequent SIP revisions that correct the rule 
deficiencies within 24 months. Note that the submitted rules have been 
adopted by ICAPCD, and EPA's final limited disapproval does not prevent 
the local agency from enforcing them.

IV. Statutory and Executive Order Reviews

A. Executive Order 12866, Regulatory Planning and Review

    The Office of Management and Budget (OMB) has exempted this 
regulatory action from Executive Order 12866, entitled ``Regulatory 
Planning and Review.''

B. Paperwork Reduction Act

    This action does not impose an information collection burden under 
the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. 
Burden is defined at 5 CFR 1320.3(b).

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to conduct a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements unless the

[[Page 39389]]

agency certifies that the rule will not have a significant economic 
impact on a substantial number of small entities. Small entities 
include small businesses, small not-for-profit enterprises, and small 
governmental jurisdictions.
    This rule will not have a significant impact on a substantial 
number of small entities because SIP limited approvals and limited 
disapprovals under section 110 and subchapter I, part D of the Clean 
Air Act do not create any new requirements but simply approve and 
disapprove requirements that the State is already imposing. Therefore, 
because this limited approval and limited disapproval action does not 
create any new requirements, I certify that this action will not have a 
significant economic impact on a substantial number of small entities.
    Moreover, due to the nature of the Federal-State relationship under 
the Clean Air Act, preparation of flexibility analysis would constitute 
Federal inquiry into the economic reasonableness of State action. The 
Clean Air Act forbids EPA to base its actions concerning SIPs on such 
grounds. Union Electric Co., v. U.S. EPA, 427 U.S. 246, 255-66 (1976); 
42 U.S.C. 7410(a)(2).

D. Unfunded Mandates Reform Act

    Under sections 202 of the Unfunded Mandates Reform Act of 1995 
(``Unfunded Mandates Act''), signed into law on March 22, 1995, EPA 
must prepare a budgetary impact statement to accompany any proposed or 
final rule that includes a Federal mandate that may result in estimated 
costs to State, local, or tribal governments in the aggregate; or to 
the private sector, of $100 million or more. Under section 205, EPA 
must select the most cost-effective and least burdensome alternative 
that achieves the objectives of the rule and is consistent with 
statutory requirements. Section 203 requires EPA to establish a plan 
for informing and advising any small governments that may be 
significantly or uniquely impacted by the rule.
    EPA has determined that the limited approval and limited 
disapproval action promulgated does not include a Federal mandate that 
may result in estimated costs of $100 million or more to either State, 
local, or tribal governments in the aggregate, or to the private 
sector. This Federal action approves and disapproves pre-existing 
requirements under State or local law, and imposes no new requirements. 
Accordingly, no additional costs to State, local, or tribal 
governments, or to the private sector, result from this action.

E. Executive Order 13132, Federalism

    Federalism (64 FR 43255, August 10, 1999) revokes and replaces 
Executive Orders 12612 (Federalism) and 12875 (Enhancing the 
Intergovernmental Partnership). Executive Order 13132 requires EPA to 
develop an accountable process to ensure ``meaningful and timely input 
by State and local officials in the development of regulatory policies 
that have federalism implications.'' ``Policies that have federalism 
implications'' is defined in the Executive Order to include regulations 
that 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.'' Under Executive Order 13132, EPA may not issue a 
regulation that has federalism implications, that imposes substantial 
direct compliance costs, and that is not required by statute, unless 
the Federal government provides the funds necessary to pay the direct 
compliance costs incurred by State and local governments, or EPA 
consults with State and local officials early in the process of 
developing the proposed regulation. EPA also may not issue a regulation 
that has federalism implications and that preempts State law unless the 
Agency consults with State and local officials early in the process of 
developing the proposed regulation.
    This rule will 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, because it 
merely approves and disapproves State rules implementing a Federal 
standard, and does not alter the relationship or the distribution of 
power and responsibilities established in the Clean Air Act. Thus, the 
requirements of section 6 of the Executive Order do not apply to this 
rule.

F. Executive Order 13175, Coordination With Indian Tribal Governments

    Executive Order 13175, entitled ``Consultation and Coordination 
with Indian Tribal Governments'' (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.'' This final rule does not have 
tribal implications, as specified in Executive Order 13175. It will not 
have substantial direct effects on tribal governments, on the 
relationship between the Federal government and Indian tribes, or on 
the distribution of power and responsibilities between the Federal 
government and Indian tribes. Thus, Executive Order 13175 does not 
apply to this rule.

G. Executive Order 13045, Protection of Children From Environmental 
Health Risks and Safety Risks

    EPA interprets Executive Order 13045 (62 FR 19885, April 23, 1997) 
as applying only to those regulatory actions that concern health or 
safety risks, such that the analysis required under section 5-501 of 
the Executive Order has the potential to influence the regulation. This 
rule is not subject to Executive Order 13045, because it approves State 
rules implementing a Federal standard.

H. Executive Order 13211, Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    This rule is not subject to Executive Order 13211, ``Actions 
Concerning Regulations That Significantly Affect Energy Supply, 
Distribution, or Use'' (66 FR 28355, May 22, 2001) because it is not a 
significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act

    Section 12 of the National Technology Transfer and Advancement Act 
(NTTAA) of 1995 requires Federal agencies to evaluate existing 
technical standards when developing a new regulation. To comply with 
NTTAA, EPA must consider and use ``voluntary consensus standards'' 
(VCS) if available and applicable when developing programs and policies 
unless doing so would be inconsistent with applicable law or otherwise 
impractical.
    The EPA believes that VCS are inapplicable to this action. Today's 
action does not require the public to perform activities conducive to 
the use of VCS.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898, ``Federal Actions to Address Environmental 
Justice in Minority Populations and Low-Income Populations'' (February 
16, 1994) establishes Federal executive policy on environmental 
justice. Its main provision directs Federal agencies, to the greatest 
extent practicable and permitted by law, to make environmental justice 
part of their

[[Page 39390]]

mission by identifying and addressing, as appropriate, 
disproportionately high and adverse human health or environmental 
effects of their programs, policies and activities on minority 
populations and low-income populations in the United States. The 
Executive Order has informed the development and implementation of 
EPA's environmental justice program and policies. Consistent with the 
Executive Order and the associated Presidential Memorandum, the 
Agency's environmental justice policies promote environmental 
protection by focusing attention and Agency efforts on addressing the 
types of environmental harms and risks that are prevalent among 
minority, low-income and Tribal populations.
    This action will not have disproportionately high and adverse human 
health or environmental effects on minority, low-income or Tribal 
populations because it increases the level of environmental protection 
for all affected populations without having any disproportionately high 
and adverse human health or environmental effects on any population, 
including any minority or low-income population. Specially, EPA's 
simultaneous limited approval and limited disapproval of Regulation 
VIII would have the effect of strengthening environmental requirements 
throughout ICAPCD, and would not relax environmental requirements in 
any area.

K. Congressional Review Act

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. EPA will submit a report containing this rule and other 
required information to the U.S. Senate, the U.S. House of 
Representatives, and the Comptroller General of the United States prior 
to publication of the rule in the Federal Register. A major rule cannot 
take effect until 60 days after it is published in the Federal 
Register. This action is not a ``major rule'' as defined by 5 U.S.C. 
section 804(2). This rule will be effective on August 9, 2010.

L. Petitions for Judicial Review

    Under section 307(b)(1) of the Clean Air Act, petitions for 
judicial review of this action must be filed in the United States Court 
of Appeals for the appropriate circuit by September 7, 2010. Filing a 
petition for reconsideration by the Administrator of this final rule 
does not affect the finality of this rule for the purposes of judicial 
review nor does it extend the time within which a petition for judicial 
review may be filed, and shall not postpone the effectiveness of such 
rule or action. This action may not be challenged later in proceedings 
to enforce its requirements (see section 307(b)(2)).

List of Subjects in 40 CFR Part 52

    Environmental protection, Air pollution control, Incorporation by 
reference, Intergovernmental relations, Particulate matter, Reporting 
and recordkeeping requirement.

    Dated: June 15, 2010.
Jared Blumenfeld,
Regional Administrator, Region IX.

0
Part 52, chapter I, title 40 of the Code of Federal Regulations is 
amended as follows:

PART 52--[AMENDED]

0
1. The authority citation for part 52 continues to read as follows:

    Authority:  42 U.S.C. 7401 et seq.

Subpart F--California

0
2. Section 52.220 is amended by adding paragraph (c)(345)(i)(E) to read 
as follows:

Sec.  52.220  Identification of plan.

* * * * *
    (c) * * *
    (345) * * *
    (i) * * *
    (E) Imperial County Air Pollution Control District.
    (1) Rule 800,``General Requirements for Control of Fine Particulate 
Matter (PM-10),'' adopted on October 10, 1994, revised on November 25, 
1996 and revised on November 8, 2005.
    (2) Rule 801,``Construction & Earthmoving Activities,'' Rule 802, 
``Bulk Materials,'' Rule 803,``Carry-Out & Track-Out,'' Rule 804,``Open 
Areas,'' Rule 805,''Paved & Unpaved Roads,`` Rule 806,''Conservation 
Management Practices,'' adopted on November 8, 2005.
* * * * *
[FR Doc. 2010-16350 Filed 7-7-10; 8:45 am]
BILLING CODE 6560-50-P
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