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ENVIRONMENTAL PROTECTION
AGENCY

40 CFR Part 52 [EPA-R09-OAR-2010-0120; FRL-91169-2]

Revisionsto the California State Implementation Plan, Imperial County Air PollutionControl District
AGENCY: Environmental Protection Agency (EPA). ACTION: Final rule.

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 ofthe 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 (PM 1 o)emissions from sources of fugitive dust such as construction sites, unpaved roads, and disturbed soils in open and agricultural areas in Imperial County.
DATES: EffectiveDate: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 athttp:// www.regulations.govand inhard copy at EPA Region IX, 75 Hawthorne Street, San Francisco, California. While all documents in the docket are listed in the index, some information maybe 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 normalbusiness 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 ofContents

I. Summary ofProposed Action 11.

Public Comments and EPAResponses II.EPA Action IV. Statutory and Executive Order Reviews

I. Summary ofProposed Action

On February 23, 2010 (75 FR 8008), EPA proposed a limited approval and limited disapproval ofthe 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 Requirements for Control of Fine Particulate Matter

....................................... 11/08/05 06/16/06 801 Construction & Earthmoving Activities

........................................................................... 11/08/05 06/16/06 802 Bulk Materials

................................................................................................................ 11/08/05 06/16/06 803 Carry Out &Track Out

................................................................................................... 11/08/05 06/16/06 804 Open Areas

.................................................................................................................... 11/08/05 06/16/06 805 Paved & Unpaved Roads

.............................................................................................. 11/08/05 06/16/06 806 Conservation Management Practices

............................................................................ 11/08/05 06/16/06

We proposed a limited approval because we determined thatthese rules improve the SIP and are largely consistent with the relevant CAA requirements. We simultaneously proposed a limited disapproval because

some provisions oftherules conflict with the CAA section 110(a) requirement that SIP rules must be enforceable andthe requirement in section 189(b)(1)(B) for implementation ofbest available control measures (BACM) in serious PM1ononattainment

areas such as Imperial County. We discuss these statutory requirements and the Regulation VIII deficiencies in detail in the proposed rule andin the Technical Support Document for that proposal (proposal TSD). 1In the proposed rule and proposal TSD we also discuss our determination ofwhich fugitive dust source categories addressed by Regulation VIII are significant and consequently require BACM pursuant to EPA guidance. This

1 Our proposedrule and proposal TSD also describe additional improvements that we recommend for future ICAPCD modifications ofthe rules. This final action is notbased on those recommendations. As a result, we do notrespond here to all comments we received on them. determination was based in part on our 2009 decision 2 tonot concur with the State's request pursuant toEPA's exceptional events rule3(EER) to exclude certain exceedances ofthe PM1o National Ambient Air Quality Standard (NAAQS) in Imperial County from consideration in regulatory actions under the CAA.4

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.

2Letter with enclosure from Laura Yoshii (EPA),

to James Goldstene (ARB), Re: exceptional events requests regarding exceedances ofthe PMlo NAAQS in Imperial County, CA, December 22, 2009.

340 CFR 50.1(j) and 50.14. 4Issues 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. A. BACM-RelatedDeficiencies forOpen Areas

1.Recreational Off-Highway Vehicle Activity

While recreational off-highway vehicle (OHV)5activity causes much of the PMo emissions from open areas in Imperial County, Rule 804 regulates only a small portion ofthese emissions, including those from OHV activity on State lands on which the rule isnot 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 ofthe Bureau ofLand Management (BLM). While BLM is required to describe in the DCPs the dust control measures thatit intends to implement, BLM isnot required to implement any specific BACM-level controls for OHV use. Moreover, ICAPCD has not provided an analysis of BACM for OHV activity, including

5As used here and inthe proposal TSD, the term "off-highway vehicle" orOHV includes all vehicles subject to the exemption in Rule 800 section E.6 for recreational use ofpublic lands in Imperial County. 

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potential OHV activity in open areas and on unpaved roads andpaths 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

2.Definition of"Disturbed Surface"

The term "disturbed surface area" is used in several Regulation VIII rules but is never defined. Forexample, Rule 804 applies to a source category forwhich BACM is required and relies on the undefined term to describe rule applicability in Rule 804 section B. A definition ofthis term is necessary in order to ensure that these rules are enforceable ata BACM level.

B. BACM-RelatedDeficiencies for UnpavedRoads

1.Unpaved Non-Farm Roads

While CAA section 189(b)(1)(B) requires ICAPCD toimplement 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 thatthis 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 isnot clear thatthe County is required to implement (and notjust 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

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 tononagricultural operation sites. Farm roads andtraffic areas are only required to implement a conservation management practice (CMP) from the menusfor

6 75 FR 8008, 8010-8011 and our proposal TSD, section III.B.1.

7 On August 11, 2004, EPA reclassified Imperial County as serious nonattainment for PMlo. 69 FR 48835. Since 2008 has passed, BACM is now required to be implemented as expeditiously as practicable. Delaneyv.EPA, 898 F.2d 687 (9th Cir. 1990).

875 FR 8008, 8011 and our proposal TSD, section
III.B.3. 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 ofsufficiently defined requirements makes itdifficult for regulated parties to understand and comply withthe requirements, and makes itdifficult for ICAPCD or others
to verify compliance and to enforce the requirements ifnecessary. The lack of specificity similarly renders itdifficult
to assess whether the measures constitute BACM level controls. The proposed rule and proposal TSD address how ICAPCD can correct these deficiencies. 9

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 "inconsistentwith BP authority and/or mission." It isnot clear what this exemption is intended to address, or how itwould be implemented and enforced in order to meet BACM requirements. The proposed rule addresses howICAPCD can correct these deficiencies. 10

C.BACM-RelatedDeficiencies for AgriculturalLands

1.Tilling and Harvesting

Rule 806 sections E.1 and E.2 list CMPs intended to control emissions from agricultural land preparation and cultivation (includingtilling), and harvest activities, but these measures

are broadly defined and there is no other mechanism in the rule to ensure specificity. The absence ofsufficiently defined requirements makes itdifficult for regulated parties to understand and comply withthe requirements, and makes itdifficult for ICAPCD or others
to verify compliance and to enforce the requirements ifnecessary. The lack of specificity similarly renders itdifficult
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.

975 FR 8008, 8011 and our proposal TSD, section III.B.4.

10 75 FR 8008, 8011. The proposed rule andproposal TSD address how ICAPCD can correct these deficiencies. 11

2.Windblown Dust

Windblown dust from non-pasture agricultural lands is also a significant

source ofPM10 thatrequires BACM independent of agricultural tilling. The CMPs in Rule 806 section E, however, mainly control emissions by reducing the number ofvehicle 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

D.Non-BACMDeficiency

Rule 802 section D.1 allows the Air Pollution Control Officer (APCO) to set aside controls that might be used instead ofwater to stabilize surfaces of bulkmaterials. This discretion allows ICAPCD to approve alternatives tothe 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
II. Public Comments andEPA 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 ofLand 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, onbehalf ofEcoLogic

1175 FR 8008, 8011-8012 and our proposal TSD, section III.B.4.

1275 FR 8008, 8012 and our proposal TSD,
section III.B.4.

1375 FR 8008, 8012. 

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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 ofLabor, Agriculture & Business, March 24, 2010 (COLAB).

* Mark McBroom, President, Imperial County Farm Bureau, March 24, 2010 (FarmBureau).

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 ourresponses 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 thatthe 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 ofRegulation VIII and to require additional PM1oemissions restrictions. Many other commenters disagree withEPA's proposed limited disapproval, especially with EPA's identification ofdeficiencies 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 tothe 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 thatpassing sweeping air quality regulations in an
area with unique terrain and climate with only generalities to prove the

sources ofpollution 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 El #3 below. The serious health impacts of exposure to elevated levels ofPM10 are well known and well documented and need notbe reiterated here. General#3:ICAPCD objects to EPA taking over four years to act on its submittals ofRegulation VIII for approval and claims thatEPA is only

now raising basic issues thatICAPCD believes should have been resolved before rule adoption.For example, ICAPCD objects to EPA disapproving a definition thatit 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 EPAbefore 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 thatEPA'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. Itis 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 onlyoccur through notice and
comment rulemaking after rules have been officially submitted to EPA by the State. IfEPA determines during that process thata submittal does not fulfill relevant CAA requirements, we cannot approve the submittal. Given time and

resource constraints, itis 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 thatmay not have arisen during the prior evaluation ofdrafts of

a rule. We continue tobelieve, however, that communication between EPA and State and local agencies at the rule development stage isproductive.

General#4:OWD asks EPA to extend the comment period because itwas informed ofEPA's proposal only nine daysbefore the close ofthe comment period. Several commenters also state that EPA did not provide adequate notification time (0218.1 and 0098) or consultation with State Parkpersonnel (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 actionbyJune 15, 2010, and needs time
to analyze all comments submitted on the proposal.'5 While more time and outreach before EPA action is always desirable, nothing in the comments suggests thatEPA failed to follow relevant public notification requirements found in the Administrative Procedures Act.16EPA notes thatOWD did comment on the proposal and EPA has taken those
comments into consideration in the final action.

B. StateImplementationPlan(SIP)

These comments generally address broad SIP issues rather than specific Regulation VIII provisions. SIP#1: OWDbelieves the PM1o standard is nearly impossible to attain given Imperial's climate, natural desert condition, the cost ofinappropriate 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, isbut

one portion ofthe 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 PMo plan that, among other things, demonstrates expeditious attainment ofthe PM1oNAAQS. Those other obligations are not the subject of this action. SIP#2:ICAPCD does notbelieve that
any additional controls such asthose that may need tobe implemented ifEPA partially disapproves Regulation VIII

14ComiteCivico 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.

16See 5 U.S.C. 553. 

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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 shouldbe used in other ways toimprove local air quality in the area.

Response:CAA section 189(b)(1)(B) andEPA guidance 17 require thatBACM 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 ofthe subcategories under open areas, unpaved roads and agricultural lands below meet or exceed the 5pg/m 3 de minimis level in our guidance and are therefore significant source categories in Imperial County:

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 Iof the CAA, including its provisions for the PM1oNAAQS, requires the implementation ofincreasingly stringent control measures in areas with

more serious pollution problems. EPA further stated "thatthe more serious the air quality problem, the more reasonable it is to require States to implement control measures ofgreater stringency despite the greater burdens such

measures are likely to cause." 20 Imperial County continues to violate the PMo standard 21 and ourproposed

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 ofthe Clean Air Act Amendments of 1990;" 59 FR41998 (August 16, 1994) (General Preamble Addendum).

18Under the General Preamble Addendum, a

source category "willbe presumed to contribute significantly to a violation ofthe 24-hour NAAQS if itsPM 10 impact at the location ofthe expected violation would exceed 5pg/M 3." This is also referred to as the de minimis level. Id.at 42011.

1975 FR 8008, 8010, and proposal TSD, pp. 5-7.
20 General Preamble Addendum at 42010. 21EPA's Air Quality System Preliminary Design
Value Report (May 18, 2010) shows 17 exceedances 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 ofCAA section 110(a).

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 ofOHV areas in Imperial County for recreation, and believe that enjoyment ofthe desert should notbe restricted. Commenters note that many organizations help keep the desert clean, and one commenter (0175.1) believes such efforts wouldbe reduced ifOHV 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 ourresponse to comment OHV #5 below, they are not germane to the evaluation in our proposal andin this final rule ofRegulation VIII and its compliance with the applicable CAA requirements. SIP#4:Two commenters (OWD and 0218.1) question whether EPA's proposal isbased on statistically significant data since there were only three PMo 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 ofenactment ofthe 1990 Clean AirAct 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 ofthe U.S. Court ofAppeals for the Ninth Circuit. 23
The reclassification, pursuant to CAA section 188(b)(2), was based on a finding thatthe area failed to attain the PM10 NAAQS bythe statutory deadline ofDecember 31, 1994. Once reclassified
to serious, the area was required to comply with CAA section 189(b)(1)(B), which required that BACMbe implemented for the area four years after its reclassification to serious.

The three exceedances to which OWD refers occurred during 2006 and 2007.

ofthe 24-hour PM1oNAAQS inImperial County between 2007 and 2009.

22 56 FR 56694 (November 6, 1991).

23 69 FR 48792; SierraClubv. UnitedStates EnvironmentalProtection Agency, etal., 346 F.3d 995 (9th Cir. 2003); cert. denied, 542 U.S. 919 (2004). The State requested that these exceedances be excluded from use in regulatory actions pursuant to EPA's EER. 24Because we did not concur with the State's request, BACM isrequired to be implemented for certain windblown dust source categories, including open areas, for which such controls would
not have been required ifwe had agreed with the State.25 See our responses to Exceptional Events comments below.

We also note that California has chosen to sample PM1oin Imperial County only one out ofevery six days. As a result,by regulation, each monitored exceedance isestimated to represent approximately six exceedances rather than one. 26For example, in 2009, ICAPCD reported three monitored exceedances at the Ethel Street monitoring site, which are estimated torepresent 18.3 exceedances. Exceedances were also monitored at Brawley, El Centro, Westmorland and Niland in 2009.27 SIP#5: Comitebelieves PM1oshould be further controlled in Imperial County by adoption oflocal fugitive dust ordinances like those in Coachella's Cathedral City, andby strengthening
openburning regulations to be similar
to those in the South Coast Air Quality Management District (SCAQMD) and the SanJoaquin 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 otherlocal dust

sources.28These requirements are generally similar to the type ofcontrols 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 thatit believes are needed in ICAPCD Regulation VIII to constitute BACM. Except where identified in ourproposal,

we believe ICAPCD's BACM analyses include adequate evaluation of analogous fugitive dust controls in other

areas. 29Itis 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

24See section II.D.1 below. 2575 FR 8008, 8010 and proposal TSD pp. 5-7. 2640 CFR part 50, appendix K. 27

EPA's Air Quality System Preliminary Design
Value Report (May 18, 2010).

28Cathedral City Municipal Code, title 8, chapter 8.54, Fugitive Dust Control; http://qcode.uslcodesl cathedralcity/.

29 2009 PMlo SIPtable 4.2 and 2005 BACM analysis table 4.2. 

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to meet CAA section 110(a) enforceability requirements.

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 El #1.

SIP#6: Comite cites Vigilv. Leavitt, 381 F.3d 826, 834 (9thCir. 2004) and Hallv. EPA, 273 F.3d 1146 (9thCir. 2001), in commenting thatmeasures in other areas canbe 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) thathave 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 isno need for such draconian and ineffective bureaucratic rules.

Response:EPAbelieves thatitis appropriate, when evaluating what constitutes BACM for a given source category, to consider controls thathave 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 thatthis determination
must be based upon appropriate consideration ofrelevant information specific tothat 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 thatBACM may strengthen over time.30 Ourproposal identifies several significant deficiencies in ICAPCD's analysis to date. 31While BACM is determined on a case-by-case basis 32 and, as such, the analysis can include evaluation oflocal conditions thatmight make specific controls economically and/or

30General Preamble Addendum at 42013-42014. 31E.g., OHV controls inArizona Revised Statute §49-457.03 and Clark County AirQuality Regulations, section 90 (75 FR 8011, February 23, 2010).

32

General Preamble Addendum at 42010 and
42012. technologically feasible in one area but
not another,33neither the 2009 PM10 SIP 34 nor the comment provides sufficient detail to adequately address the deficiencies identified in our proposal.

OWD does not explain how Imperial County differs so markedly from the San Joaquin Valley and the Maricopa area that itwould be inappropriate to consider BACM approved inthose areas

as part of the evaluation ofcontrols for the same source categories in Imperial County. Similarly, COLAB does not elaborate onwhat "cultural practices" in Imperial County wouldjustify disregarding approved BACM in the San Joaquin Valley and the Maricopa area as part ofthe evaluation ofwhat controls would be appropriate for comparable

source categories in Imperial County.

C.EmissionsInventory (El)

EI #1: Many commenters oppose further OHV controls because they believe OHVs contribute little to Imperial County's PMio pollution problem compared to other sources. Commenters identify various sources theybelieve 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 limitenforcement, Interstate 8, the New River, the Salton Sea, Arizona to the east, San Diego to the west, Mexican roads, fires and factories tothe 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 ofBACM for open areas with respect to OHVs. 36These conclusions are based on inventory information prepared by ICAPCD and ARB and used during development of

33In this respect, we do notagree with Comite that measures adoptedin other areas are automatically transferable toImperial County.

34 "2009 Imperial County State Implementation Plan forParticulate Matter Less Than 10Microns in Aerodynamic Diameter,Final," adoptedby ICAPCD Governing Board on August 11, 2009. (2009 PM10 SIP).

35Proposal TSD, pp. 5-8. 36 d. at p. 8. Regulation VIII and the 2009 PMo SIP. 37

The inventory in the 2009 PMo SIP represents the mostcomprehensive information currently available on OHV emissions in Imperial County. 38

ICAPCD's analysis in the 2009 PMo SIP concluded that windblown dust from open areas was not a significant source category, but this conclusion was premised upon many exceedences ofthe NAAQS being deemed to be the result ofexceptional events. However, EPA's

own conclusion regarding those exceedences is thatthey were not caused by exceptional events and, as a result, we consider windblown dust from open areas tobe a significant

source category thatis subject to the CAA's BACM requirement. See response to comment SIP #4 and responses to Exceptional Events comments in section II.Dbelow. 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.

EPA's action on the Regulation VIII submittal does not address or depend on whether additional controls may alsobe appropriate for the various other sources identified in the comments.

EI#2:One commenter (0188) had driven pastmany farms in El Centro during tilling and observes thatthe dust

was very minimal. Another (0201) thinks more attention shouldbe paidto agriculture which the commenter believes is exempt from many ofthe environmental regulations.

Response:See response to comment El #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

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 bejustified and explained in the context ofmeeting the BACM requirements.

EI#3: Several commenters claim that EPA has not proved the impact ofOHVs

37

Id. at pp. 5-8.
382009 PM1o SIP, Chapter 3; Appendix II.

39ProposalTSD, pp. 5-8 and 9-11. 

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onPM1olevels sufficient torequire 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 EPArelies, uses worstcase assumptions rather than actual soil condition information to estimate that OHVs represent less than 5% ofthe County's total PM10 emissions (13.9 of 282 tpd). OWD states that 99% ofthese total emissions relate to OHVs subject to Federal and State stewardship. Therefore OWD concludes that actual OHVemissions are small compared to worst-case estimates. OWD also questions EPA's reference forthe estimate of22 tpd ofwindblown 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 PM1o problem. Another commenter believes EPA lacks data tying PM to specific OHV activities (0218.1), and several
commenters believe that any pollution from OHVs isvirtually immeasurable. Several commenters believe additional inventory analysis isparticularly important because OHV areas are far from population centers and monitors with PMo exceedances. One commenter (0131) requests an unbiased third-party study ofOHV impacts. CDD explains that PMo emissions from several specific parks in Imperial County shouldbe low, partlybecause OHV activity isprohibited. In contrast, CBD supports EPA's claim that OHVs on BLM land cause considerable PM10in 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 ofPMo emissions and PM10 precursor emissions spatially and temporally for purposes ofmodeling air pollution impacts and developing cost effective control programs. As aresult, emission inventories are constantly being refined as more andbetter science and data become available. However, EPA, State and local air pollution agencies must make policy and regulatory decisions based on thebest information available to comply with the CAA. As discussed in response to comment El #1, the inventory and other information underlying ourproposal regarding the emissions from OHV activity and the impacts of such activity represent the mostcomprehensive information currently available.

Regardingspecificconcernsin this
comment: (1)EPA's conclusion thatBACM is required for OHV activity relies on emissions inventory estimates that ICAPCD developed. Ifappropriate, ICAPCD could choose torefine 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 ofdetail normally used in inventories required by CAA section 172(c)(3).40

(2)ICAPCD in its 2009 PM10 SIP quantifies the impact of soil type and land cover (e.g., shrub/grassland) and degree ofOHV disturbance in OHV emission estimates relied on by our proposal.41 (3)ICAPCD used the best available information regarding soil types in open

areas and determined thatthe remaining uncertainty does not affect the results of the technical analyses.42 (4) Even OWD's 13.9 tpd OHV emission estimate, which webelieve is
too lOW, 4 3 exceeds the presumptive 5 pg/m 3 de minimis level for source categories requiring BACM. 44 (5)The reference for 22 tpd of windblown OHVemissions is accurately explained in our proposal. 45

The comment thatmonitoring 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 causedby OHV activity.46Thus monitoring, which could provide valuable information, isnevertheless
not necessary to determine which

source categories require BACM.

D.ExceptionalEvents(EE)

1. Background

On March 22, 2007, EPA adopted a final rule to govern the review and handling ofcertain air quality monitoring data for which the normal planning and regulatory processes are not appropriate. 47Under the rule, EPA
may exclude data from use in determinations ofNAAQS exceedances and violations ifa State demonstrates that an "exceptional event" caused the exceedances. Before EPA can exclude datafrom these regulatory determinations, the State must flag the datain EPA's Air Quality System database and, after notice and opportunity for public comment, submit

a demonstration to EPA tojustify the exclusion. After considering the weight ofevidence provided in the demonstration, EPA decides whether or not to concur with each flag.

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

TABLE 

### 2

Description Document date Abbreviated title

Natural Event Documentation: Calexico and Westmorland, California-September 2,

2006. Natural Event Documentation: Brawley and Westmorland, California-April 12, 2007

[enclosed with June 13, 2008 letter to Sean Hogan]. January 30, 2009

................... April 15, 2008

......................... September NED. 48

Original April NED.

40 See, e.g., AP-42, FifthEdition, 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 unpavedroads and does not, for example, account forroad terrain. http://
www.epa.govttn/chief/ap42/ch13index.htmf. 412009 PM10 SIP, appendix III.B. result in a 5 pg/m 3 contribution, which equates to 422009 PM10 SIP, p. 3-2. about 6-8 tpdemissions. 4 3In comparison to ICAPCD's 22 tpd estimate. 45Id. Proposal TSD, footnote 32. 46 See, e.g., proposal TSD, p. 5.

44As discussed on pp. 5-8 ofthe proposalTSD, "Treatment ofData Influenced by Exceptional depending on the specific monitor, 2-3% of Imperial County's annual inventory is calculated to Events," 72 FR 13560 (March 22, 2007) (EER). 

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TABLE 

### 2-Continued

Description Document date Abbreviated title

Natural Event Documentation: Brawley, Calexico, El Centro, Niland, and Westmorland, April 15, 2008

......................... Original June NED.

California-June 5, 2007, Imperial County Air Pollution Control District [enclosed with June 13, 2008 letter to Sean Hogan]. Natural Event Documentation: Brawley and Westmorland, California-April 12, 2007 March 12, 2009

...................... April NED.

[addendum to June 13, 2008 submittal]. Natural Event Documentation: Imperial County, California-June 5, 2007 [addendum to March 12, 2009

...................... June NED.

June 13, 2008 submittal].

As stated above in section I, on December 22, 2009, EPA denied ARB's request to exclude all ofthe exceedances as exceptional events. The basis for our decision is specified in an enclosure which accompanied the December 22, 2009 letter.49By letter, including Attachment A and Appendix Al, dated March 3, 2010, ICAPCD asked EPA to reconsider this decision. 5 °

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

2.Events Not Reasonably Controllable

or Preventable

EE#1: ICAPCD (Attachment) disagrees with EPA's interpretation of the requirement in the EER at40 CFR 50.1(j) thatin order for an event to meet the regulatory definition ofexceptional event, such event mustbe "not reasonably controllable or preventable." Specifically ICAPCD takes issue with EPA's statement in our 2009 EE decision

48 Werefer to the natural event documentation in these five documents, collectively, as the NEDs.

49See footnote 2. Werefer to our December 22, 2009 letterand the enclosure hereafter as "2009 EE decision."

5o

Letterfrom Brad Poiriez (ICAPCD) to Jared Blumenfeld (EPA), March 3, 2010 with Attachment A andAppendix Al.

51

See 75 FR 8010 and the proposal TSD, pp.
5-7.

52

Werefer to ICAPCD's March 10, 2010 letter with its Attachment A and Appendix Al, collectively, throughout our responses to the exceptional events comments in section i.D as "Attachment." 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 thatunder the plain regulatory language itis irrelevant whether "reasonable and appropriate" controls are in place on the day ofan otherwise qualifying event when it can be shown that such controls wouldnot reduce emissions and impact at the monitor sufficiently to prevent the exceedance. ICAPCD believes that itis inconsistent with the intent ofthe CAA for EPA torefuse to concur with an exceptional event claim solely due to EPA's dissatisfaction with the stringency ofcertain controls when such controls could not have prevented the exceedance.

Response:ICAPCD mischaracterizes both the plain language and the regulatory intent of40 CFR 50.1(j) by reading the words "reasonably controllable or" out ofthat section. The regulation clearly requires a showing that the event is not either reasonably controllable or preventable, not as ICAPCD would have it,thatthe event cannot be controlled tothe 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 definedin the dictionary means toregulate orto reduce the incidence or severity. 54Thus the meaning ofthe 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 thatreasonable controls were implemented to regulate

or reduce emissions regardlessof whether the controls would have

53"BACM is the maximum degree ofemissions reduction of PMlo 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 andavailable methods, systems, and techniques for control ofeach such pollutant." General Preamble Addendum at42010.

54Merriam-Webster's Ninth New Collegiate Dictionary. prevented exceedances. 55Finally we note thatthe relevance ofdust controls is inherent in the District's own characterization ofthe "event" asthe combination ofwind and dust entrainment from anthropogenic and nonanthropogenic sources. 56

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.5 7Nor 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.

EE#2:ICAPCD (Attachment)further argues that the consequence ofEPA's action would be to require control

measures beyond the area's practical abilities-a result the EERis specifically designed to avoid. ICAPCD claims that other specific provisions are inplace to prevent such difficulties, and ICAPCD quotes from EPA guidance: "Ifemissions from anthropogenic sources are reduced
to the point thatitis 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

Response:The provisions to which ICAPCD refers are contained in CAA section 188(f) which authorizes EPA to waive subpart 4requirements applicable
to serious PM10 nonattainment areas, including BACM, where EPA determines thatanthropogenic sources ofPM10 do not contribute significantly
to the violation ofthe standard in the

area. Under section 188(f), EPA may

55 Similarly, EPA explained inthe preamble to the EER that analysis ofexceptional events includes consideration ofwhether anthropogenic activities have been controlled to the extentpossible through

use ofall reasonably available reasonable and appropriate measures. 72 FR 13560, 13566, footnote 11.

56 E.g., September NED, p. 9.

57 2009 EE decision, section 4.2. 58 General Preamble Addendum at 42008. 

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also waive a specific date for attainment ofthe PM1ostandard ifthe Administrator determines that nonanthropogenic sources contribute significantly to aviolation ofthe 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 mustbe implemented under CAA section 189(b)(1)(B). 59The 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 thatbefore EPA will consider waiving a serious area attainment date and requirements for a serious area that failed to attain the standard bythe serious area deadline, the State must demonstrate that BACMs for significant anthropogenic sources have been implemented and thatthe

area cannot attain the NAAQS with the implementation ofadditional 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 hasbeen implemented as required by CAA section 189(b)(1)(B) for all significant

source categories in Imperial County.61 Thus itwould be difficult to show that additional controls are "beyond the area's practical abilities" or "nolonger technologically or economically feasible" without a more thorough BACM analysis.

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 maybe affected by emission

sources from areas outside California, such as Arizona and Mexico, our 2009 EE decision relies on the lackof demonstrated controls for

59Id.at 42004.
60 75 FR 8008,8010-8012 and proposal TSD, pp.

7-11.

61 The 2009 PM 1 oSIPfor Imperial County that is
intended to address the 5% requirement in CAA section 189(d) was adopted by ICAPCD in August 2009but has notbeen submitted to EPAby ARB. The plan concludes that the area would have attained the PMo standard by the end of 2008 but for transported emissions from Mexico and withthe "exclusion ofPM10 measurements affected by highwind exceptional events." As a result ofthe claimed exceptional events, with which we did notconcur in our 2009 EE decision, the plan also concludes that "[t]he 5% yearly emission reductions requirement does not apply to future years." 2009 PM1oSIP, section 5.3. 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 thatinherent in the "not reasonably controllable or preventable" criterion ofthe definition of "exceptional event" in 40 CFR 50.1(j) "is arequirement that the State demonstrate that anthropogenic sources contributing to the exceedance caused by the event were reasonably controlled." We also suggested thatthis 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

EE#5: ICAPCD (Attachment)opposes the statement in EPA's 2009 EE decision that "because implementation ofBACM is required in serious PMo areas such

as Imperial County under section 189(b) ofthe CAA, it is appropriate to consider that level ofcontrol 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 ofthe EERwhich entails only "reasonable" and not "best"control of anthropogenic sources; (2)the purpose ofthe EER isto protect states from
consequences ofreclassification as a result ofexceptional events; (3)by definition, exceptional events fall outside the normal planning process and their analysis should not depend on elements ofthe normal planning process including designation status; and (4) the meaning of "reasonable controls" for the EER should notvary by an area's nonattainment status and shouldnot be

as stringent as BACM.

Response:As stated in our 2009 EE decision and in the preamble to the EER, EPA addresses the EERcriteria, including thatthe event mustbe "not reasonably controllable or preventable,"

on a case-by-case basis considering the weight ofavailable evidence.64 Thus it is appropriate to consider the totality of

622009 EE decision, section 4.2. 63 See id., section 4.2.1. 642009 EE decision,pp. 4 and 7; 72 FR 13560,

13569. circumstances in Imperial County in determining what constitutes "reasonable" controls. Wenote again that the County hasbeen designated nonattainment and classified as moderate or serious since 1990. The

area was reclassified to serious in 2004.

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.65Moreover, EPA's 2009 EE decision did not define reasonable control as BACM in all cases

or suggest thatthe EER mandates such

an outcome. Rather, we stated that "[b]ecause implementation ofBACM is required in serious PM10nonattainment

areas such as Imperial County under CAA section 189(b), itis appropriate to consider that level ofcontrol in evaluating whether reasonable controls

are in place for purposes ofthe Exceptional Events Rule." 6667While ICAPCD states that this isinappropriate reliance on the normal planning process, an area's nonattainment designation and classification are inherently part ofthe local conditions that are appropriately factored into what controls are reasonable forpurposes of the EER. We also noted thatARB had failed to demonstrate any meaningful analysis ofBACM or any other level of control for either OHVs or fallow fields, despite apparent significant emissions and available controls imposed elsewhere.68

EE#6: ICAPCD (Attachment)
comments that OHV emissions were quantified in the 2009 PM1o SIP at EPA's request, but EPA ignored this information in its analysis ofthe exceptional event requests.

Response:It isthe responsibility of the State to submit demonstrations addressing the EERcriteria 69 to support its exceptional event requests andit is generally not appropriate or feasible for

65See 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.

67We note that inEPA's NaturalEvents Policy
which applied prior to the EER, we stated that "BACM mustbe implementedat contributing anthropogenic sources ofdust inorder for PM-10 NAAQS exceedances to be treated as dueto uncontrollable natural events underthis 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 theEER does notinclude such a mandate, itis entirely appropriate and consistent with the Agency's past practice to considera BACM level ofcontrol inassessing whether reasonable controls are inplace. Memorandum from MaryD. Nichols, EPA, "Areas Affected by PM-10 Natural Events," May 30, 1996, p. 5.

682009 EE decision, pp. 9-10.

69 40CFR 50.14(c)(3). 

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us to correct NED deficiencies by searching for additional information. Nonetheless, we did review the 2009 PM1oSIP before preparing the 2009EE decision and did not ignore ICAPCD's efforts to quantify OHV emissions in the 2009 PM1oSIP. In fact, the 2009 EE decision references these efforts which undermine the assumption in the NEDs 70that windblown dust from desert areas is entirely from nonanthropogenic sources.71

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 ofreasonable controls in documentation supporting exceptional events requests. It ispossible thatICAPCD/ARB may be able to demonstrate in support offuture exceptional events requests that OHV

sources are de minimis, thatthere 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 ofcontrol for OHVs, and that such analysis should include as a starting point evaluation ofEPA's RACM guidance 72 andregulations adopted elsewhere under similar conditions.73

EE#8: ICAPCD (Attachment)
comments that sand dunes are naturally fully disturbed and thatthe 2009 PM1o SIP conservatively projects that OHVs contribute only 0.9 tpd (10%) to the total windblown emissions fromthem. Other commenters similarly question EPA's assumption that OHVs disturb desert crust. OWD, for example, notes that dune laminae are often mistaken for

a crustbut are broken by wildlife, foot traffic and high winds.

Response:We agree that effective control offugitive dust is more difficult for the sand dunes than for other parts ofImperial County with different soil types. As a result, the State may be able
to demonstrate in support offuture exceptional events requests, orfor other CAA purposes such as section 189(b)(1)(B) BACM, that dust control for dunes shouldbe 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

7 0E.g., JuneNED, p. 2. 71E.g., 2009 EE decision, footnotes 12, 15 and 16.
7257 FR 18070, 18072 (April 28, 1992).

732009 EE decision, pp. 8-9. reasonable OHV controls for the sand dunes or any other areas. This comment has no bearing on the April andJune 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 ofthe high winds during the April 12 andJune 5, 2007 events and thunderstorms on September 2, 2006. OWD notes that two ofthe 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 islowest when dust potential is highest (Junethrough September).

Response: Our 2009 EE decision appropriately relies on OHV emission information from the NEDs andthe 2009 PM10 SIP which estimate large windblown dust emissions and significantly smaller directly entrained emissions. 74Thus, even ifno 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 ofreasonable controls for OHVs even ifthere is no OHV activity during the exceedances.

EE#10: ICAPCD (Attachment)
comments that Regulation VIII agricultural controls are wellbeyond the reasonableness level required in the EER. ICAPCD further states thatit and ARB have discussed agricultural controls with EPA for many years, worked withEPA during development ofthe 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 mostof the non-populated areas in Imperial County.

Response:Our 2009 EE decision explains thatneither Regulation VIII nor any other programs require any level of emissions control ofcertain fallow fields in Imperial County. 76Though ICAPCD comments that emissions from agricultural fields are smaller than

74E.g., 22 tpd windblown and 1.34 tpd entrained emissions, 2009 EE decision, p. 9.

75Particularly recent activity where there has not been time orconditions to repair surface crusts.

76 2009 EE decision, section 4.2.3. emissions from other sources in the County, the NEDs for the exceptional
events requests do not identify any anthropogenic sources asbeing de minimis. Rather, there are summary explanations that anthropogenic sources

are reasonably controlled through Regulation VIII and other local programs. 77The only anthropogenic

source discussed in any detail is agriculture in the April andJune NEDs. These NEDs rely on the Imperial Irrigation District's (lID) fallowing program as thebasis 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 lID's program which is more than the approximately 18,000 acres that were a part ofIID'sprogram in 2007. 79As explained in ourresponse to comment EE #5, we stated in our 2009 EE decision thatit is appropriate to consider aBACM level ofcontrol in evaluating whether reasonable controls

are in place for purposes ofthe EER in Imperial County. However, EPA found

no meaningful analysis ofBACM or any other level ofcontrol for fallow land outside ofIID'sprogram referenced or provided in the NEDs.

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

Response:EPA did consider and reference Rule 806 in our 2009EE decision.81 Although the 2005 BACM analysis includes incidental references
to fallow lands, neither itnorthe 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 oflID'sprogram.
3.High/Unusual Wind Events

EE#12: Comite agrees with EPA's disapproval ofARB's request to exclude the monitored exceedances as

77Apriland June NEDs, pp. 13-14, and SeptemberNED, p. 18.

78Apriland June NEDs, p. 13.
792009 EE decision, p. 9.

80 "DraftFinal Technical memorandum: Regulation VIII BACM Analysis," October 2005 (2005 BACM Analysis).

812009 EE decision, p. 9. 

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exceptional events. In support ofour 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 ofthe preamble which suggests dust from anthropogenic sources maybe treated as natural events in certain circumstances

was a drafting error and is legally null; (4) where the Act does allow for consideration ofhuman activity, it is limited to activity thatis unlikelyto

recur at a particular location and agriculture does not meet that definition; and (5)regardless ofwhether

ahigh wind event is classified as "natural" or "human activity," such an event exists only where the wind is objectively a "highwind" and sufficiently high to cause amonitored violation even in lightofthe implementation ofwhatever measures
are "necessary" toprotect 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 isnoted. We agree with Comite thatthe events in question are not due to human activity that isunlikely to recur andthat the State failed to demonstrate thatthe
events qualify as natural events. However our conclusions with respect to natural events are notbased on all of the legal arguments proffered by the
commenter. We also are notrelying on that portion ofthe preamble that the
commenter correctly points out is a legal nullity 82 and instead, where appropriate, we rely on and cite to other parts ofthe preamble regarding natural
events and high winds that remain applicable. While EPA'sviews ofthe
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.

EE#13: Comite cites additional support for nonconcurrence with the State's 2007 exceptional events requests beyond what was relied upon byEPA, namely that wind speeds were not shown tobe "exceptional" forthe area

or "unusual" since the State relied on flawed comparisons to average wind speeds.

82 NRDCv.EPA, 559 F.3d 561, 565 (DC Cir. 2009). Response:For the 2006 events, the State did not assert thatthe winds were unusually high. Forboth sets of 2007 events, the evidence providedby 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 ofthe 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.

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, asrequired under the EER. With regard tothe 2007 exceedances, the commenter cites the lack ofsufficiently detailed source attribution data. With regard to the 2006 exceedances, the commenter concludes that the proximity and nature ofthe thunderstorms that occurred in northwest Mexico made them "unlikely"
to be the cause ofthe winds atCalexico. This commenter also believes that the possibility of any winds associated with thunderstorm activity north ofthe County being the cause ofthe Westmorland exceedance is "problematical atbest."

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 ofa section ofthe 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 ofsound 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 PMo concentrations on September 2,2006 to those on fifteen other days that had similar meteorology at Calexico.84 The

832009 EE decision,pp. 19-20.

84 September NED, pp. 12-14. PM10 concentrations on most ofthe days

were low,but on August 18, 2002, August 19, 2003 and September 2,2006 the PM1oconcentrations were high. The concentrations on these days in 2002 and 2003 are described in attachments
to the State's Natural Events Documentation 85 asbeing due to transport from Mexico under high wind conditions, and these conditions are statedto 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 tobe evidence ofan association or causal relationship between high wind elsewhere and high Calexico concentrations.

While we acknowledge that we misinterpreted the above portion ofthe 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 validbecause the fact remains thatARB'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.

Furthermore, as also discussed in our 2009 EE decision,88 significantly lower PM1omeasurements in neighboring Mexicali contradict ARB's assertion that the September 2,2006 Calexico exceedances were causedby windblown dust from a large-scale, regional event that originated to the south or southeast ofCalexico. Such an event would have affected both Calexico and Mexicali. ICAPCD itselfconcedes thatits explanation for the Calexico exceedances does not account for the difference in the PM1oconcentrations

85 September NED,p. 12, and Attachment G, "179B(d) 'ButFor' Analyses-High-Wind Events from Mexico", excerpt from Technical Support Document: Exclusion ofPM10 Measurements in Excess ofthe 24-Hour PM10 NAAQS for Imperial County from 2001 through 2003 Due to Natural Events andEmissions from Mexico, Volume I ofII, ENVIRON International Corporation, November 2004.

86 2009 EE decision, pp. 11 and 15.

87Id. at p. 11.
88Id. atp. 12. 

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measured at the Calexico and Mexicali stations.89

ICAPCD further offers what it characterizes as the only three possible explanations for the Calexico exceedances, and suggests thatEPA should accept the longrange transport argument because itisthe 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.

ICAPCD's next objection to our analysis ofARB's exceptional event request with respect to the September 2, 2006 Calexico exceedances isthatEPA's

concern regarding OHV and agricultural emissions 91 is notrelevant because there are no OHV or domestic agricultural lands south, southeast or south-southeast ofthe Calexico monitors. EPA disagrees. The September NED states that the "source ofthe PM1o that impacted the Calexico stations corresponds to lands east and southeast ofthe Mexicali stations * * *" 92 Infact,

as shown in the TSD for this final action,93 there is agricultural land immediately east ofCalexico. 9 4 As also shown in the final TSD, 95the southern end ofthe Imperial Sand Dunes OHV

area is also directly east ofCalexico, though itis admittedly farther away. Thus consideration ofthese sources was not inappropriate.

In summary, we are not persuaded by the above comments and we reject the allegation that we did not have a sound technical understanding ofthe claims ARB made as to the cause ofthe exceedances. We therefore reaffirm our conclusion that ARB not only failed to demonstrate that a high wind event occurred,but also thatthere 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 providedby the State regarding a causal relationship between the claimed high wind event and the Westmorland exceedance on September

89 ICAPCD Attachment A, Appendix A-1.

90 Id.

912009 EE decision, p. 14. 92September NED,p. 15.

93 "Technical Support Document for EPA's Notice ofFinal 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 (finalTSD), Figure 1.

94 Similar land use maps were provided inFigure 3 ofboth the April andJune NEDs.

95 FinalTSD, Figure 1. 2, 2006, andthat 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 ofthe timing ofhigh 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., thatthe 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 ofICAPCD's comment focuses on a statement madeby 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 twobefore, 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 infact

occur the hour before the concentration spike. In addition, we stated thatthis wind was directed toward Westmorland when in fact it was directed toward the east-northeast.

ARB presented the wind speed and direction data in a tabular format thatis difficult to interpret.97To more clearly articulate why we do notbelieve these data show a clear causal relationship between the event and the exceedance,

we have presented the data in the final TSD in avisual form that is more readily understood.98 The arrows represent the wind directions atIndio, Oasis, Salton Sea West, and Westmorland during each ofthe four color-coded hours (e.g., all ofthe yellow

arrows represent the wind direction during hour 17, etc.). The numbers above each arrow represent the wind speed for thathour, and the numbers below theWestmorland arrows represent the PM10 concentration. The data show thatthe PM 10 concentration spike occurred during hour 19.

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

Very high winds wereobservedatthe 17th and18thhoursnorth ofImperialCounty,

962009 EE decision,p. 16.

97 September NED, Tables 1 and 2, and Figure 19. 98Final TSD, figure 2. both to the west (inparticular at the Oasis CIMISstation,see Table 1)and to the east (see measurements at theBlythe, Ripley, and Palo Verde stations, Table 1). These strong winds wereofvery shortdurationandof changingdirection * * *,consistent with the collapse ofone or several thunderstorm cells north ofImperial County * * *. Very sharp peaks in PMlo concentrations were also observed at the 19th hour at the Brawley and Westmorland stations (andto a lesser extent at the Niland station), and appear tobelongrangeeffects ofthe sameevents (i.e. collapsing thunderstorm tothe north of Imperial County) * * *. [A]nanalysis of wind direction at select stations between the 18th and 20th hours indicates that northwest winds (e.g. 6p.m. atthe SSWandIndio stations,7p.m. at OasisandIndio,and8 p.m. atIndio)and east-northeast winds (e.g. 7 p.m. atthe Niland and SSE stations) likely carried air containing elevated PM10 concentrations from areas northwest and northeast ofImperial County stations toward the stations.(Emphasis added). 99

ARB's explanation first points to the "veryhigh" 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 of23.2 mph are not whatwe would consider "veryhigh" in the generally accepted meaning ofthe term. With the exception ofthis value, the data in Figure 2ofour final TSD show that the winds in this area were not very elevated. 101 We alsonote thatthe winds
at Oasis during the 18thhour had a northerly component rather than a southerly one, and while it is true that the winds at Salton SeaWest were blowing toward Westmorland atthis time and that these winds could have contained some ofthe dust thatmay have been generated in the Oasis area, the winds at Westmorland were blowing in almost the opposite direction. It is thus unclear how much, ifany, dust generated at Oasis during the 18th hour

was actually transported to Westmorland.

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

99 September NED,pp. 10-11. 1°°As we did in our 2009 EE decision,pp. 15 and

19.

1 0 1EPA received comments on itsproposed 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 itaccurately connotes the type ofnatural event that should beexcluded under this rule and it serves as an indicator concerning the level ofwind that caused the exceedance. See
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toward Westmorland, the winds at Salton Sea West had a distinct westerly component so itis not clear thatthe winds at Oasis continued on thispath past Salton Sea West. In addition, as for the previous hour, the winds at Westmorland were blowing counter to the wind at Oasis and itis 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 itunlikely thatthese winds made a significant contribution to the exceedance atWestmorland 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 tothe winds at Indio.

As stated in our 2009EE decision, 102 and as ARB stated inthe 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 isinconsistent with ARB's hypothesis thatthe 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 itis anythingbut 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 ofthe winds at Oasis do not undermine the Agency's conclusion that the contradictory evidence does not support a finding ofa clear causal relationship.

The second part ofICAPCD's
comment on the causal relationship regarding theWestmorland 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 thatthe uncertainty oftheprecise location ofthe thunderstorms in time is not relevant to

a cause and effect analysis. The
commenter further states that EPA does
not appear to argue thatthe wind speed

or direction is inconsistent with transport ofdust from Palo Verde to Westmorland.

While we agree with the commenter that the winds at Palo Verde (whichis separated from Westmorland by anorthsouth distance ofabout 24 miles) were directed toward Westmorland during the 17th hour,the winds at Westmorland were consistently from the

1022009 EE decision,p. 16. south-southeast, southeast, and eastsoutheast directions beginning at the 6th hour and lasting until the end ofthe day. While itis remotely possible that the winds that occurred at Palo Verde during the 17th hour led tothe transport ofdust to Westmorland, the EER requires a demonstration ofa clear causal relationship and the limited data available do not rise to that level.

We also disagree with the commenter that the location ofthe thunderstorms

over time is not relevant to a cause and effect analysis. The EER explicitly mentions the use of datathat show the relationship in timebetween the event, transport ofemissions, andrecorded concentrations in exceptional event demonstrations.103 Furthermore, in this
case, ARB'sbasic premise is that "thunderstorm activity caused strong outflow winds over areas in close proximity toImperial County monitors * * * [which contributed] tothe elevated PM10 concentrations that were recorded in Imperial County on that day."' 0 4ARB couldhave attempted to provide more support for its case by, for example, considering whether historical radar data showed thunderstorms were at various locations around the timethe high winds occurred.

Given the level ofuncertainty asto the cause ofthe concentration spike at Westmorland during the 19th hour and the statutory requirement thatEPA's exceptional events regulations be based

on the principle that protection of public health isthe highest priority, 10 5

we are again led to the conclusion that the data before the Agency does not establish a clear causal relationship between the exceedance andthe event that is claimed to have occurred.

The third part ofICAPCD's comment regarding causal relationship for the Westmorland exceedance criticizes EPA's use ofwind trajectories from the HYSPLIT model since itis 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 shortlived 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

103 72 FR 13560, 13573.
104September NED,p. 2. 105 See CAA section 319(b)(3)(A)(i).

106 2009 EE decision, p. 17. simply add to the list ofinconsistencies 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 toWestmorland. Thus EPA disagrees with this comment.

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 ofrecurring 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 PM1oconcentrations ifthe causes were local to the monitors. The second part ofthe additional
comment states that since there were no high winds throughout Imperial Valley

on September 2, 2006, the cause ofthe exceedances could not have been unpaved roads or agricultural or OHV land within the Valley.

Response:With respect to the first part ofICAPCD's comment, EPA acknowledged the elevation of PM10 at allmonitors, but did not take a position

onwhether the causes were local or regional.107 Rather, we concluded that a clear causal relationship had notbeen demonstrated since the regional sources alleged by ARB tobe the cause were not identified. Related to this lackof identification ofthe contributing
sources, EPA found thatthe State did
not demonstrate thatthe 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.

With respect to the second part of ICAPCD's comment, as discussed above, the State argued thathigh winds associated with thunderstorm activity led to the generation ofdust north ofthe County, which was then transported to the Westmorland monitor. Even though agricultural land and other anthropogenic sources do exist in areas north ofthe County including Oasis, 1 0 8
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 EERrequirement that the event must be "not reasonably controllable or preventable." Thus, this requirement

1072009 EE decision, p. 14. 108See Figure 1 in the finalTSD. 

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was not met even ifthe commenter's arguments regarding transport were correct. With respect to the Calexico exceedances, the State speculated that high winds occurred east and southeast ofCalexico based on extrapolation ofa west to east trend ofincreasing wind speed. The same argument could have been used to conclude that there was high wind east ofCalexico within Imperial County, including over agricultural and OHV lands. Therefore the commenter's claim thatthere were

no high winds throughout the Imperial County is not completely supported by the State's own arguments that ahigh wind event occurred.

5.Concentrations in Excess ofNormal 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 fromthe data have been measured in the County from 2003-2007. Therefore, the commenter claims, the concentrations are not "in

excess ofnormal historical fluctuations"

as required by the rule and are not exceptional events.

Response:EPA's conclusions about the requirement thatthe events be associated with measured concentrations in excess ofnormal historical fluctuations mainly relied on the concentrations' rarity relative to past measurements. Forexample, the September NED states thatthe 167 pg/ m3 measurement at the Westmorland station was in the 98th percentile ofall PM10 recordings at that station in the 2001-2007 time period. As explained in

our 2009 EE decision,19 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 thatthe monitoring data for Imperial County continue to show violations ofthe 24-hour PM1ostandard. We believe that improvements tothe ICAPCD's rules will lead to improvements in air quality and we note thatthis commenter does not disagree withEPA's conclusions regarding the State's exceptional events requests, or with EPA's proposal to disapprove Regulation VIII.

6. Level ofDocumentation Required for EER

EE#19: ICAPCD (Attachment)takes issue with EPA's suggestions that additional data and analysis would have

109pp. 25-27. 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, orinvestigation of
other potential causes would be preferred, EPA does not suggestreasonable, technically implementable analyses to achieve these higher levels ofdocumentation. We would question what technical analyses EPA suggests should be conducted. We would also question whetherthese analyses and the required level ofdata are achievable or realistic now or inthe 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 theDistrict and ARB thatwould address EPA's stated concerns. Thus,we find thatboth EPA's conclusions oncausality and EPA's position onthe level ofanalysis required to demonstrate causality are incorrect and inconsistent withthe purpose oftheEER * * *.Such a narrow application oftheEERwill preclude states from excluding fromregulatory consideration exceptional PM data that are completely inappropriate forinclusion 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 ofother causes.

Response:Regarding the need for better source apportionment data, itis important toidentify contributing

sources when evaluating exceptional
event claims involving windblown dust because it mustbe demonstrated that anthropogenic sources contributing to the exceedances at issue were reasonably controlled. 10 Better source identification isespecially important in situations where we do nothave confidence that all potential anthropogenic sources are reasonably controlled and where there are exceedances just above the NAAQS (suchas the April 12, 2007 exceedance
at Westmorland) which may havebeen preventable with additional controls. In addition, the inability to identify the

source ofthe PM emissions associated with a wind event (i.e., the "cause" of the dust that led to the exceedance)

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 ofevidence approach to our analysis may consider winds that produce emissions contributed
to by anthropogenic activities that have been controlled to the extent possible through useof all reasonably available reasonable and appropriate

measures. hinders our ability tomake affirmative findings thatthe "clear causal relationship" and "but for"provisions of the EERhave been satisfied. A Countywide monthly average emission inventory such as the one usedby ARB that omits some source types (e.g., OHVs) is insufficient for these purposes.

While perhaps not required for all demonstrations, our suggestion for a wind field and amore highly resolved inventory are not unreasonable given ARB's failure in thepresent case to demonstrate thatreasonable 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 ofa causal relationship isto collect and examine pollutant species-specific information. As discussed in the EER preamble,III suchinformation maybe available through routine speciation, monitoring networks, or from selective laboratory analysis ofarchived particulate matter filters for the day thought tobe impacted by an event. In this case, such an analysis mighthave helped ascertain howmuch ofthe PM10 that impacted certain monitors was from agricultural sources versus natural desert sources.

Regarding ICAPCD's objection to our statement thatthe 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 notbe limited to radar data and weather observations that note the presence ofblowing dust in areas around the monitors.

Finally, ICAPCD takes exception to

our desire for better documentation regarding the investigation ofother potential causes. In thisregard, ARB made the following statement: 113

(ICAPCD)investigated emission generating activities during this episode, and found that PMlo emissions forBACM controlled sources
were approximately constant before, during and after the event. The District determined that the * * * concentrations of PMo * * *

were instead primarily the result ofwindentrained dust * * * associated with a mesoscale convective system * * *

Although the preceding passage suggests thatICAPCD conducted an

11172 FR 13560, 13573.

1122009 EPA decision, pp 17-18.

113 September NED, p. 2. 

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active investigation ofother emission generating activities on the day ofthe 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 2008but that no inspections were conducted on the day ofthe event. Wewere thus left wondering how a file review conducted
two years after the fact qualifies as an investigation ofemission 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.OHVControls
OHV#1:ICAPCD believes thatEPA should have concurred with all ofthe 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 ofthe 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." 4We have not received information in the comments

orelsewhere that changes this conclusion or the related decision tonot

concur with the State's exceptional
eventrequests for Imperial County. See also responses to Exceptional Events
comments in section II.D above.

OHV#2: CBD comments that BLM land is the largest PM 1osource in Imperial County and should be subject
to the same controls as adjacent land. CBD believes the DustControl 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 thatRule 800's DCP implements BACM, and that Rule 800's exemption for BLM does not relax other Regulation VIII requirements. Forexample, 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 offroad events. ICAPCD also notes that where there are such prohibitions, section F.5.d requires the DCP to discuss and implement "otherpossible

114

Proposal TSD, pp. 5-7. control measures" and thatRule 800 section D.3 requires the DCP to be submitted to ICAPCD, ARB and EPA for review and comment and tobe updated
every two years.

ICAPCD believes BLM should be treated separately in Regulation VIII because there are many restrictions imposed by avariety oflaws otherthan the CAA that apply to actions on Federal lands and thatthe District's involvement in these issues would delay implementation ofthe 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 ifRule 800 section F.5.c corresponds to requirements that are less effective than those ofRules 804 and 805, such lower stringency isboth necessary and appropriate given the special nature of BLM lands.

BLM agrees thatmany traditional BACM are not possible on Federal land because ofthe large expanses ofdesert 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 hightraffic 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. 1 1 5
EPA guidance explains that this demonstration should include evaluation and documentation ofthe technological and economic feasibility ofpotential control measures, including implementation ofmeasures on a limited basis iffull implementation is
not feasible. As stated in our guidance, "the documentation should compare the control efficiency oftechnologicallyfeasible measures, their energy and environmental impacts and the costs of implementation." 116 ICAPCD's demonstration should include careful consideration ofanalogous 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

115Proposal TSD, pp. 7-8.

116 General Preamble Addendum at 42012-42014.

1757 FR 18070, 18072. in our proposal 118 and comments on the proposal. 119

The evaluation oftechnological feasibility may appropriately consider the alleged "special nature" ofBLM lands. Such an evaluation, ifconducted appropriately, may be sufficient to demonstrate that what constitutes BACM for BLM landin Imperial County is different fromwhat 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, ifsuch controls do constitute BACM, why they
cannotbe incorporated into Regulation VIII and the SIP.

Furthermore, with regard to CBD's
comment concerning the enforceability ofDCPs, State and local requirements that implement BACM are subject to the enforceability requirement ofCAA section 110(a). As we statedin our proposal, BACM has notbeen demonstrated for OHV sources because, among other things, none ofthe OHV restrictions are in regulatory form and submitted for inclusion in the SIP.120

OHV#3: OWD notes that California State Parks (CSP) manages OHV recreational activity in Imperial County
atHeber Dunes State Vehicular Recreation Area, Ocotillo Wells SVRA, and in an interdepartmentaljoint management agreement at the Freeman Properties immediately north of Ocotillo Wells SVRA and east ofAnza Borrego Desert State Park. OWD also notes that Ocotillo Wells SVRA alone represents approximately 85,000 acres ofmanaged OHVrecreational activity within Imperial County. While much ofthis land is designated trail riding only and is primarily defined by terrain constraints, OWD states that the majority ofthe 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 ithas 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

118 See proposal TSD, pp. 8 and 14-15. 119

Moreover, as statedin the General Preamble
Addendum at42013, "anycontrol measures that a commenter indicates during the public comment period is available for a given area should be reviewed bythe planning agency."

120Proposal TSD, p. 14. 

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that fencing, and then maintaining, a vast amount ofland is neither economically nor environmentally feasible. OWD alsobelieves that watering, laying gravel, or applying a chemical solution to the miles oftrails that wouldbe encompassed is neither economically nor environmentally feasible. In contrast, CBD argues that further implementation ofRule 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 ofdisturbed surface

area to maintain a stabilized surface, limit opacity to 20% and comply with
atleast one ofthe 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 thatCSP hasjurisdiction

over open areas with over 1,000 square feet ofdisturbed 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

aresult of the inclusion ofRule 804 into the SIP, these requirements willbecome federally enforceable upon the effective date ofthis final action, and such noncompliance could result in civil action under CAA section 113 and/or 304.

OHV#4: Various commenters argue that controls suggested in our proposal

aspart ofthe BACM analysis that ICAPCD still needs to conduct would
not reduce PM1oimpacts 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

1 2 1iCAPCD Rule 804, sections B, C.29, E and F.

122See also "Fugitive Dust Control Plan," Bureau ofLand Management El Centro FieldOffice, 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. reducing emissions. However, one commenter (0100) states that OHVuse during summer nights is agreat 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 forfun 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 thatrestrictions like those in place in Arizona, during pollution advisory days, would be unproductive because high-PM forecasts in Imperial County only occur onhighwind 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% oflocal BLM land, and additional closure would probably shift OHV activity and emissions to other

areas nearby. OWD alsobelieves EPA's action could force OHV users to other
areas, causing environmental effects outside Imperial County. * ICAPCD comments thatEPA cannot demonstrate that OHV restrictions would reduce windblown dust emissions because there is nobasis for EPA's contention that surfaces impacted by OHVs would form any appreciable
crust given Imperial's low level ofrain. OWD similarly comments that crust repair would be difficult due tothe limited rain in Imperial County. Another commenter (0120) believes that restricting OHV areas could increase PMo 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 ofOHV areas is not feasible. Forexample, water resources

are scarce and modification ofexisting 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:

In summary, the State must document its selection ofBACMby showing what control

measures applicable to each source category (not shown to be de minimis) were considered. The control measures selected should preferablybe measures thatwill prevent PM-10 emissions rather than temporarily reduce them. The documentation should compare thecontrol efficiency of technologically-feasible measures, their energy and environmental impacts and the
costs ofimplementation.124

Furthermore, contradictions in the
comments also serve to illustrate that there are fundamental factual questions that needto be addressed about the
amount ofOHV activity during different

seasons and different times ofthe day, and thebest ways to mitigate emissions from such activities. Atthisjuncture, 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 onlocal business
owners, farmers, land owners, OHV
users, race car owners, construction companies, ranchers, the Imperial Irrigation District and others. Commenters observe thatrecreational activities generate substantial revenue (0196), and one (0156.1) claims that OHVs have contributed several hundred million dollars to the local economy. ICAPCD believes thatthe economic cost ofOHV activity restrictions isfar 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 ofPM1oreductions. 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 fewbenefits given the relatively small emissions from OHVs, but would have significant economic impacts.

Response:We appreciate the value of
OHVtourism 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 aparticular

source category and costs incurredby

123General Preamble Addendum at42010-42014.

1 2 4Id.at 42014. 

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similar sources that haveimplemented emission reductions." 125 In this case, the cost ofOHV restrictions on OHV

area owners (i.e.,the State and Federal governments) and users would appear to be minimal, and the secondary economic impacts onbusinesses supporting OHV tourism are not relevant to the required BACM analysis. In any event, ICAPCD needs to evaluate the economic feasibility ofpotential controls, including those adoptedin other areas, in determining what controls constitute BACM in this area.

OHV#6: EcoLogic asks EPA to clarify whether and where OHVrestrictions are being contemplated in the Imperial Sand Dunes Recreation Area and elsewhere andto 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 ofOHV 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. 1 26 Our proposal explains why ICAPCD must analyze whether additional controls (potentially including closure) are appropriate for public land inImperial 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 OHVareas in Imperial County and, where feasible, should consider whether different areas within the County have different impacts on populations or

areas with exceedances ofthe NAAQS.

OHV#7: Several commenters believe additional OHV restrictions should be analyzed and/or incorporated into Regulation VIII. CBDbelieves 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 ofOHV 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

125

General Preamble Addendum at42013.
126See CAA section 116.

127See, e.g., proposal TSD, pp. 8 and 13-15. 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 ofOHV areas, one commenter (0120) suggested rotating OHV areas tohelp surface crust formation.

Response:The commenters as a group make constructive suggestions that would be appropriate for consideration in acomprehensive evaluation ofBACM for this source category. We believe ICAPCD should analyze allpotential 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

F. DefinitionofDisturbedSurface(DS)

DS#1: ICAPCD believes the term "disturbed surface" is self-evident and that no questions havebeen raised about it since rule adoption. ICAPCD believes Rule 804 is clear that an area is deemed disturbed ifit shows any sign ofmanmade 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 nextrevision to Rule 101, but strongly objects to EPA disapproving Regulation VIII on this basis. In contrast, CBD supports EPA's concerns regarding this definition inRegulation 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. Inthis regard, CBD suggests specific edits to SJVUAPCD's analogous rule.

Response:We believe the explanation provided in ICAPCD's comment is a logical interpretation ofthe undefined
term in itsregulation. However, we also believe that alternate definitions are possible (such asthat recommended by CBD in its comment), and itis 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

128 Submitted as Exhibit D to Comite comment letter.

129 See, e.g., General Preamble Addendum at

42012-42013. including an appropriate definition of this critical term and to consider CBD's recommendations for the wording ofthe rule.
G. UnpavedRoad(UR) Controls

UR #1: ICAPCD projects that control ofunpaved non-farm roads provides 55% ofRegulation 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 toincrease fundingfor such projects. ICAPCD states thatthe $2 million/year available to the County Department ofPublic Works (PWD) for road maintenance and stabilization reflects great needs andlow availability ofpublic funds inthe County. According to ICAPCD, this budget is for maintenance of 1,350 miles ofpaved roads which require resurfacing every 10-15years, or 90 miles ofextensive maintenance each year. Thus, ICAPCD argues that allocation of9% ofthis budget to stabilize 19 miles ofunpaved road represents, contrary to EPA's assertion, the mostexpedited schedule possible withthe presentlevel of available funding.

Response:Where economic feasibility ofcontrol depends on public funding, EPA will consider past funding and the future availability offunding sources to determine ifa good faith effort isbeing made to implement BACM expeditiously.130 The fact that unpaved road controls provide 55% ofRegulation VIII's estimated emission reductions is
not in itselfsufficient to demonstrate good faith efforts to control road dust expeditiously. Alternatively, for example, this high percentage ofthe total amount ofreductions could occur ifother sources are under-controlled or

are less feasible to control. Nonetheless, EPA believes that some ofthe 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 notbelieve this analysis needs tobe exhaustive, but it should be more thorough and documented than presented in the Regulation VIII submittal andthis
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 ofvarious Federal,

130Proposal TSD, p. 16, and General Preamble
Addendum at42013. 

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State, and local (includinglocal Measure D) funding sources for public works construction and maintenance, or otherwise provided the demonstration contemplated by the relevant EPA guidance. 131 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 ismeeting its commitment to implement its submitted plan, which includes stabilizing different unpaved roads each year and maintaining all stabilized roads as intended bythe rule.

Response:CAA section 110(a) requires that control measuresbe 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., thatthe County must stabilize different roads each year and
must maintain all stabilized roads) and does not contain a mandate that the
terms ofthe planbe carried out. Evidence thatImperial County PWD is in fact currently implementing the plan is not sufficient to ensure enforceability

asrequired by the CAA.132 ICAPCD should revise the rule to clarify this section consistent with enforceability requirements ofCAA section 110(a). UR #3:Comitebelieves thatICAPCD should incorporate additional restrictions into Regulation VIII, including property line visible emissions (VE) limits such asthose 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 adoptedby SCAQMD, SJVUACPD, and Maricopa and Clark Counties. Our proposal TSDrecommends several specific controls from these areas for further consideration by ICAPCD, including imposition ofa fence-line opacity standard. 13 3 However, with the exception ofthe deficiencies identified in our proposal,

we believe thatICAPCD sufficiently analyzed controls in other areas for potential BACM.1 34 Forexample, ICAPCD explains that SCAQMD has only a 0% fence-line opacity standard, whereas ICAPCD and other agencies with adopted rules approved as BACM

131Seeproposal TSD,p. 16.

132See id.,p. 9.
1 33Id., p. 11.

1342005 BACM analysis, chapter 4, and 2009 PM1 SIP, table 4.2. all have a similar general 20% opacity standard applicable everywhere, and
notjust at the fence-line.1 3 5 ICAPCD claims that SCAQMD's 0% fence-line standard isless stringent than a general 20% standard. While it is difficult to compare the two standards,136 we do
not have evidence thatSCAQMD's standard ismore stringent than the general standard used by ICAPCD and by other air districts. UR #4: One commenter (0154) states that itisnot 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 canbe completely eliminated from farm andnon-farm dirt roads.

H. BorderPatrol(BP)Controls

BP#1: ICAPCD comments thatRule 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 usespublic roads to accomplish its mission, and some roads adjacent to the border are used exclusively by BP. ICAPCD states that
most ofthese 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 PMo controls such as vehicle speed restrictions and

access controls. ICAPCD indicates that since adoption ofRegulation VIII, BP has submitted twoproductive DCPs. Therefore, ICAPCD disagrees with EPA's recommendation to remove or narrow the exemption for BP activities, and proposes to continue addressing BP through aDCP 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 DCPspursuant to Rule 800 sections F.6.a and F.6.b. However, ICAPCD's explanation isunclear as to whether or not BP operates any roads

135 2005 BACM analysis, p. 21.
136 Forexample, a 40% opacityplume inthe
middle ofa 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 butnot ICAPCD's. subject to the rule. IfICAPCD can support its assertion thatBP neither

owns nor operates such roads, the exemption in Rule 800 section F.6.c.is simply unnecessary and shouldbe removed. IfBP does own or operate such roads, we continue to believe that the exemption is unnecessarily broad and should be removed or narrowed and demonstrated tobe 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 ofit before publication. EPA appreciates BP's efforts to limitPM10pollution through DCPs. Our concern, however, is with ICAPCD's Regulation VIII submittal and the lack ofclarity in, and analysis to support, the actual provisions in Regulation VIII intended
to govern these activities.

BP#2:OWD comments thatBP frequently goes off-road within Ocotillo Wells SVRA, beyond OWD's control.

Response:Rule 804 section E imposes requirements on owners ofopen areas such as Ocotillo Wells SVRA regardless ofwho owns vehicles driving onthe open areas. Nothing in ourproposal would affect these existing ICAPCD requirements.

L UnpavedFarmRoadsandTraffic Areas (UFRTA) ControlsIntroduction

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 ofthese comments address various aspects ofanalogous 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) orbest management practices (BMP), into three or more menus known

as "categories." We provide the following information on these rules as

an introduction to inform ourresponses 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 offorty acres

or more are required to implement one 

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

TABLE 3

Catgores or n-feld Categories for unpaved State or local agency Rule Area Categories for on-field Ag. roads and traffic agricultural operations Agrodantafi
areas
Imperial County APCD (ICAPCD) 806

.................................. Imperial County

.............. U Land Preparation and U Unpaved Roads. Cultivation (including tillage). 0 Harvesting

.................. U Unpaved Traffic Areas. San Joaquin Valley Unified 4550

................................ San Joaquin Valley Plan- U Land Preparation and U Unpaved Roads.

APCD (SJVUAPCD). ning Area. 1 37 Cultivation (including tillage). 0 Harvest

....................... U Unpaved Traffic Areas. 0 Cropland-Other. Arizona Department of Environ- Arizona Administrative Phoenix Planning U Tillage and Harvest

.... U Noncropland.

mental Quality (ADEQ). Code (A.A.C) R18-2- Area. 1 38
610 and R18-2-611. 0 Cropland. Great Basin Unified APCD 502

.................................. Alpine, Inyo, and Mono U Land preparation

........ U Unpaved Roads.

(GBUAPCD). Counties. 139

0 Harvest

....................... U Unpaved Traffic Areas. 0 Other Cultural Practices. South Coast AQMD

..................... Rule 403 And Agricul- South Coast Air U Active Conservation U Unpaved Roads. tural Handbook. Basin. 140 Practices. 0 Inactive Conservation

Practices. South Coast AQMD

..................... Rule 403 And Coachella Coachella Valley Plan- U Active Conservation U Unpaved Roads. Valley Agricultural ning Area. Practices. Handbook. 0 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. UFRTA #1: Comite believes that California has not demonstrated why agricultural paved and unpaved roads shouldbe subject to less stringent requirements than other roads in Imperial County (i.e.,those subject to Rule 803 regarding track-out/carry-out andRule 805) and cites SanJoaquin Valley where such roads must meet CMPs as well as general requirements.

137SJVUAPCD's jurisdiction includes the entire counties of SanJoaquin, Stanislaus, Merced, Madera, Fresno, Tulare, and Kings and part ofKern County. SJVUAPCD does notinclude the parts of East Kern that are notin the San Joaquin Valley Air Basin. See 40 CFR 81.305.

13 8 The Phoenix Planning Area includes Maricopa County anda portion of PinalCounty. See 40CFR 81.303.

139 See section 1 and 2 ofGBUAPCD Rule 502. Also see 40 CFR 81.305.

140 SCAQMID's jurisdiction includes the South
Coast AirBasin and the Coachella Valley Planning Area. For a description ofthe boundaries ofthe Los Angeles-South Coast AirBasin Area and the Coachella Valley Planning Area, see 40 CFR81.305. The South Coast Air Basin includes all ofOrange County andthe more populated portions ofLos Angeles, San Bernardino, and Riverside Counties. The Coachella Valley Planning Area includes central Riverside County inthe Salton Sea Basin. 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 thatRule 806 requires CMPs for all unpaved roads and traffic areas regardless ofvehicle trips per day (VTD), unlike SJVUAPCD Rule 4550. COLAB also explains that ICAPCD Rule 806 was designed to address all unpaved roadsby applying

to parcels greater than 40 acres (97% of farmland in Imperial County)compared
to SJVUAPCD's Rule 4550 which addresses roads on parcels largerthan 100 acres (91% offarmland in the San Joaquin Valley). Lastly, ICAPCD and the Farm Bureau assert that mostprivate unpaved farm roads are less used and

are therefore below Rule 805's 50 VTD threshold. Regardless ofVTD, however, these latter commenters argue that

owners ofthese roads must implement Rule 806 CMPs.

Response:EPA's proposal notedthat ICAPCD has not demonstrated BACM for unpaved farm roads and traffic areas because ofthe 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 notjustified such an exemption. 141

ICAPCD and other commenters donot offer evidence that Regulation VIII is as stringent as comparable controls in this regard, but instead claim thatRegulation VIII is more stringent in other respects. For example, no commenter disputes

our conclusion that an unpaved farm road with 75 VTD wouldbe 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 toRule 806, for example, is more stringent than SJVUAPCD's analogous requirements. Because opacity and surface stabilization requirements onheavilyused 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

1 4 1Proposal TSD, pp. 8-9. 

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specific toImperial County in a revised BACM evaluation for unpaved roads andtraffic areas, as appropriate.

We also agree with Comite thatitis
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 nonfarm roads. We encourage ICAPCD to consider removing this exemption, although such a rule modification is not mandated bythe 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 thatRule 806's CMPs are not sufficiently specific regarding agricultural unpaved roads andtraffic 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 ifthe relevant information was provided the form could be changed.

Response:Issues raised regarding specificity ofCMPs for unpaved roads andtraffic areas are similar to issues raised regarding the specificity ofCMPs for other agricultural operations. See
response to comment AL#3 below. 

### J.AgriculturalLandControls(AL)
See Introduction in section 11.1 above. AL #1:ICAPCD comments thatRule 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 thatthe individual CMPs in Rule 806 are similar tothose found in SJVUAPCD Rule 4550 and GBUAPCD Rule 502 and concludes that the only differences in therules are due
to differences in local agricultural practices. The Farm Bureau also states that there is little difference between GBUAPCD andICAPCD control

measures.

Response:We agree that many individual CMPs andrequirements in the rules outlined in Table 3are 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. 1 4 5
One ofthese deficiencies concerns the lack ofsufficiently defined requirements in contrast tothe application submittal and review processes in the SJVUAPCD and GBUABCD rules thatinsure more effective implementation and enforcement oftherequirements.' 46The other deficiency isrelated to the number ofCMPs 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 fromthe "land preparation and cultivation," "harvest," and the "other cultural practices" categories.' 47

AL #2:ICAPCD believes thatEPA disregards that Imperial County crops

are irrigated, and that continued irrigation and conditioning ofsoil dramatically reduce its potential for both entrained and windblown emissions. ICAPCD believes thisfact
must be considered when comparing Rule 806 to rules in other areas.

Response:As stated previously above, EPA agrees thatitis appropriate to consider conditions specific to an area when evaluating potential BACM. 148
However, most ofthe harvested cropland in other areas subject to comparable requirements is also irrigated. The following table shows datafrom the 2007 Census of Agriculture 149 for the total acres of harvested cropland and the acres of irrigated harvested cropland inrelevant counties in California and Arizona. Imperial County and the counties in the SJVUAPCD 15o are included. Riverside County in California 15 and Maricopa County in Arizona are also included.

TABLE 

### 4

Irrigated Total harvested harvested County, State cropland cropland (acres) (acres)

Im

peria l, CA

..................................................................................................................................................... M

aricopa,AZ

................................................................................................................................................... Riv erside County, CA

...................................................................................................................................... SanJ oa

qu

in

Cou n

ty

,CA
................................................................................................................................. Stanislaus, C A

................................................................................................................................................. M

erced,CA

...................................................................................................................................................... M

adera, C A

...................................................................................................................................................... Fresno, C A

....................................................................................................................................................... 375,904 190,182 163,783 444,670 307,992 466,304 264,767 978,948

142Although 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.

143As noted in Table 3 above, SCAQMD's Rule 403 has requirements for agricultural activities that apply toboth the South Coast Air Basinand Coachella Valley Planning Area.

144EPA approved SJVUAPCD Rule 4550 in 2006,
not in2004. See 71 FR 7683. EPA approved a commitment for the San JoaquinValley CMP Program in 2004. See 69 FR 30006.

145 See 75 FR 8008, 8011-8012.

146See 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 ofConservation 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, athttp:// www.gbuapcd.org/farm/ CMPprogramdescriptionan dforms.pdf.

148 General Preamble Addendum at42010 and
42012.

149 2007 Census ofAgriculture, California, State and County Data, and 2007 Census ofAgriculture, Arizona, State and County Data, United States Department ofAgriculture, National Agricultural Statistics Service. See http:// www.agcensus.usda.gov/Publications/2007/ Full Report/Volume 1, Chapter2 County Levell California/cavi .pdf andhttp:// www.agcensus.usda.gov/Publications/2007/ Full Report/Volume 1, Chapter2 CountyLevel/ Arizona/azvl.pdf.

15o

See footnote 141 above. The census data in
Table 4 are forall of Kern County.

151Ofall the counties included in SCAQMD, Riverside County has the largest acreage of harvested cropland. According to the 2007 Census ofAgriculture, Orange County has 7,846 acres of harvested cropland, Los Angeles County has 25,829

acres ofharvested cropland, SanBernardino County has 27,516 acres ofharvested cropland, and Riverside County has 163,783 acres ofharvested cropland. 2007 Census ofAgriculture, California, State and County Data, United States Department of Agriculture, National Agricultural Statistics Service. See http://www.agcensus.usda.govl Publications12007Full Report/ Volume 1, Chapter2 County Level/California/ carl.pdf. 

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TABLE 

### 4-Continued

Total harvested Irrigated harvested County, State cropland cropland (acres) (acres)

K

in

gs, C A

......................................................................................................................................................... 419,964 419,080 Tulare, CA

........................................................................................................................................................ 560,320 540,887 K

ern, C A

.......................................................................................................................................................... 764,929 756,645

Thus, the mere fact that crops are grown using irrigation inImperial County does not in and ofitselfjustify different standards for BACM.

AL #3:ICAPCD comments thatRule 806 section F.6 specifies thatthe CMP plan shall include "otherrelevant information as determined by the ICAPCD," which gives ICAPCD authority tomodify the CMP plans to specify frequency ofCMP applicability. Therefore ICAPCD believes a mechanism is in place in the rule for modification ofCMPs toprovide such details, and therefore this should not be

a basis for disapproval ofRegulation VIII as BACM. ICAPCD notes its commitment to modify the CMP plans
to provide such details.

Response:As notedby ICAPCD, Rule 806 section F.6provides a mechanism that could be usedby ICAPCD to provide greater specificity. However there isno required process in the rule for sources toprovide such information
to ICAPCD or for ICAPCD to review the CMPs and/or to require revision ofthe CMPs that sources have chosen to implement. Under section F, sources are only required to prepare a plan containing minimal information andto maintain a copy ofthe plan.Thus the CMPs would continue to be broadly defined unless or until ICAPCD proactively determines thatgreater specificity is needed. Absent suchvital details, itwould be difficult for regulated entities to knowprecisely what is required of them to comply with

a BACM level ofcontrol, and itwould be difficult for ICAPCD, EPA, or others
to enforce these requirements. 15 2 In

152For instance, one ofthe CMPs that is both in
the "land preparation and cultivation"category in Rule 806 sectionE.1 andthe "harvesting" category in sectionE.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 ofpasses during an operation, thereby reducing soil disturbance." This definition is too broad toensure enforceability. Moreover, because there is no mechanism to narrow the definition for a particular agricultural operation, a CMP maybe implemented in a manner less stringent than a BACM level of control. In a similarlybroad fashion, Rule 806 section C.34 defines "speedlimits," a CMP in both contrast, SJVUAPCD Rule 4550 section 5requires 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 5and 6 contain substantially identical requirements. Such requirements provide a mandatory process that is far

more likely to ensure thatthe CMPs are implemented and enforceable at a BACM level ofcontrol than the provision in ICAPCD Rule 806.

Finally, even ifICAPCD were to routinely exercise its discretionary authority in Rule 806 to specify the frequency ofCMP applicability, the deficiency noted in ourproposed action related to lack of CMP specificity extends beyond the issue of frequency. 153

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 ofemissions fromharvesting 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. 1 54 As statedin ourproposal 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

the "unpaved roads" category in sectionE.3 and the "unpaved traffic areas" category in section E.4, as "enforcement ofspeeds thatreduce visible dust emissions. The dustemissions from unpaved roads

are a function ofspeed, meaningreducing speed reduces dust." However, an appropriate speed limit

or range ofspeed limits is not specified or otherwise insured.

153 See 75 FR 8008, 8011-8012.
154 ProposalTSD, pp. 5-6. 155 ProposalTSD, p. 10, footnote 25. equipment even ifemissions from any
one ofthese taken individually mightbe much smaller than the major source threshold requiring RACT. 15 6

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 isconsistent with BACM requirements. Thus far ICAPCD has not provided a convincing justification.

AL #5: ICAPCD disagrees with our identification ofthe requirements of Rule 806 for tilling as a deficiency in the BACM analysis. In support ofits position, ICAPCD asserts that San Joaquin Valley sources may selecttwo CMPs thatreduce emissions from tilling from the listofmeasures, but they are not required to do so. ICAPCD also claims thatbecause per-acre emissions from land preparation are about four times as high in the SanJoaquin Valley

as they are inImperial County, the costeffectiveness ofemission reductions from tilling activities throughthe implementation ofany CMP should be four times as highin Imperial County as in the SanJoaquin Valley. For these two
reasons, ICAPCD believes thatRule 806 requirements for tilling are as stringent

as analogous SJVUAPCD requirements. In contrast, Comite comments that Arizona Rules 18-2-610 and 611 require atleast twoCMPs from each

156

SJVUAPCD Rule 4451, Valves, Pressure Relief Valves, Flanges, Threaded Connections andProcess Drains at Petroleum Refineries and Chemical Plants, amended April 20, 2005.

157

See SJVUAPCD Rule 4550 section 6.2 and SJVUAPCD "List ofConservation 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, athttp:// www.gbuapcd.org/farm/ CMPprogramdescriptionandforms.pdf. 

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category in the rule whereas Rule 806 requires only one, and that SJVUAPCD requires up tothree 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 onfield 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 forboth 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 wouldbe economically andtechnologically feasible to control emissions from these activities. ICAPCD claims thatimplementing tillage CMPs
may be more cost-effective inthe San Joaquin Valley, but does not address whether itwould 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 thatMaricopa'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 onwhich tobase 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 thatthe 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 isrelated tothe 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 torequire 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 toimplement one practice from each category. As noted in Table 3above, 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 notedin

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 ofa BACM analysis, ICAPCD should consider the economic and technological feasibility ofrequiring additional CMPs for on-field agricultural sources, including consideration oftherequirements in rules adopted by SJVUAPCD, GBUAPCD and Arizona.

K.AgriculturalLandWindblown Dust Controls(ALWD)

See Introduction in section 11.1 above. ALWD #1: COLAB comments that the deficiencies identified by EPArelated 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 ofAgriculture's (USDA) National Agronomy Manual for reducing such dust.

Response:EPA has determined that windblown dust from agriculture is a significant PMo source category in Imperial County for which ICAPCD
must demonstrate, but has notyet demonstrated, implementation ofBACM

15 75 FR 8008, 8012. level controls.159 ICAPCD should include in its BACM analysis consideration ofwhether 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.

ALWD #2:ICAPCD believes thatEPA should have concurred with exceptional
eventrequests associated with high winds as discussed in the exceptional
event comments above. As a result, ICAPCD believes that windblown dust from agricultural lands isnot 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.

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 underboth the "landpreparation 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 thatmay

occur once a field is removed from production. EPAbelieves thatthe evaluation ofBACM level controls for windblown dust from fallow fields should include consideration of USDAapproved conservation systems and activities.' 6'

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

159Proposal TSD, pp. 10-11. 160Id., pp. 5-7.

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consistent with USDA's National Agronomy Manual. ICAPCD estimates that long-term irrigation reduces PM 1o emissions by 25-45% from the predominant cultivated soil types in Imperial County, so local fallow and active agricultural land iscontrolled 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 thatthe 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 ofcontrol, windblown dust from agriculture is a significant
source, andICAPCD isrequired to implement BACM level controls for windblown emissions from active and fallow agricultural fields. ICAPCD has
not provided a convincing justification for why controls inthe 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 inthe agricultural portion ofImperial 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.' 62 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

orelsewhere. To the extent that farmers avoid tilling on windy days to conserve

162Proposal TSD, pp. 5-7. 163General Preamble Addendum at42013. soil anyway, this restriction wouldnot

seem to be onerous.

ALWD #6: ICAPCD comments that SCAQMD's only additional requirement for active fieldsbesides the restriction

on tilling on days with winds above 25 mph isto implement one more CMP from alist thatincludes minimum tillage. ICAPCD believes this CMP is not directly effective at reducing windblown emissions, and hence ICAPCD believes thatby 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 ofthe five principles noted in the National Agronomy Manual for wind erosion control. 164

ALWD #7: Comitebelieves that more specificity and information must be provided concerning lID'sFallowing Program to ensure thatemission reductions from itare quantifiable, verifiable and enforceable.

Response:ICAPCD must analyze and implement BACM for agricultural windblown dust emissions.16 5 If, as a result ofthis analysis, ICAPCD concludes that lID'sFallowing Program is needed to implement BACM, then we agree that ICAPCD needs to provide

more information about lID'sprogram and ensure that controls that are provided through the program are enforceable.

ALWD #8: Regarding EPA concerns with agricultural windblown dust controls, ICAPCD and the Farm Bureau
note thatRule 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-bycase basis and can consider the specific conditions ofthe nonattainment area.' 66
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

164 See p. 502-17 ofthe USDA NRCS National Agronomy Manual, October 2002.

165Proposal TSD, pp. 5-7. 166 See General Preamble Addendum at 42010 and 42012.

167 See, e.g., 73 FR 14687, 14693 (March 19, 2008). primary PM is fugitive windblown dust

* * * 168 Moreover, ICAPCD's 2009
PMo Plan discusses howthe flat terrain ofImperial 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 andJune to high winds.169 As a result,EPAbelieves that ICAPCD must consider windblown dust controls for agricultural sources. Also, see responses to comments General #3 and EE #5.

ALWD #9:The Farm Bureau notes thatboth 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. OtherControls(OC)
OC#1: Comitebelieves 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 toEPA's concerns regarding Rule 802 section D.1 because: (1)The APCO's discretion islimited to

a determination ofwhether any ofthe controls in sections F.A 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:EPAbelieves thatthe director's discretion provisions inRule 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 eitherby a procedure thatthe APCO must use (e.g., testmethod X) or byboundaries to the discretion (e.g., up to 30% opacity instead of20% opacity). Thus, the discretion isnot "limited."

Regarding ICAPCD's second argument, we note initially thatEPA has

along history ofrejecting suchbroad APCO discretion in SIP rules.170

1682009 PM10 SIP, p. 1-1.
169 2009 PM10 SIP, pp. 1-3 and 2-4.
170 See, e.g., "Guidance Document for Correcting
Common VOC and Other RuleDeficiencies," U.S.
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Moreover, we limit such discretion precisely because the APCO can exercise it without further SIP approval where a SIP-approved rule provides APCO discretion.

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 ifthisprovision

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
atthis 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

orthe exemptions in Rule 802 section D.4 could result in such consequences and/or affect the emission reduction credit for the rule.

M. StatutoryandExecutive 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, OWDbelieves that EPA's action mayimpact Imperial County's Hispanic and low-income population by reducing touristincome from OHV users. In contrast, Comite applauds the commitment ofthe Regional Administrator ofEPA Region 9
to environmental justice principles, and
notes thatrelatively large portions ofthe population in this area are not only Hispanic and poor,but are also suffering from poor health and this is exacerbated by airpollution problems in this area.

Response:EPA agrees itis important
to consider environmental justice in our actions and webriefly addressed environmental justice principles in our

EPA Region IX, August 21, 2001 (theLittle Bluebook); and "Issues Relating to VOC Regulation Cutpoints, Deficiencies, and Deviations," U.S. EPA, OAQPS, May 25, 1998 (The Bluebook). proposal TSD. 1 7 1Executive Order 12898, "Federal Actions toAddress 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, tomake environmental justice part oftheir mission by identifying and addressing,

as appropriate, disproportionately high and adverse human health or environmental effects oftheir 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 ofenvironmental 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 ofenvironmental 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 ofstrengthening environmental requirements throughout ICAPCD, and would not relax environmental requirements in any area. Thus itpromotes environmental justice by increasing the level ofhuman health and environmental protection for an

area where, as the commenters note, relatively large portions ofthe population are low income and/or minority.

SEO #2: OWD notes that EPA's action
may be subject toNEPA evaluation.

Response:EPA actions underthe CAA

are exempt from NEPA. 172

SEO #3: OWDbelieves thatEPA 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 thatEPA has a basis to claim (regarding the

171 Proposal TSD, p. 3. 172 See 40 CFR 6.101(b). 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 theprivate sector, result from this action. 173

III. EPAAction

No comments were submitted that change our assessment ofRegulation VIII as described in ourproposed action. Therefore, as authorized in sections 110(k)(3) and 301(a) ofthe Act, EPA is finalizing a limited approval ofthe submitted rules. This action incorporates the submitted rulesinto the California SIP, including those provisions identified as deficient. As authorized under section 110(k)(3), EPA is simultaneously finalizing alimited disapproval ofthe rules. As aresult, sanctions willbe imposed in Imperial County unless EPA approves subsequent SIP revisionsthat correct the rule deficiencies within 18 months of the effective date ofthis action. These sanctions willbe imposed under section 179 ofthe 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 therule deficiencies within 24 months. Note thatthe submitted rules have been adopted by ICAPCD, andEPA's final limited disapproval does not prevent the local agency from enforcing them.

IV. Statutory andExecutive Order Reviews

A. Executive Order12866,Regulatory PlanningandReview

The Office ofManagement and Budget (OMB) has exempted this regulatory action from Executive Order 12866, entitled "Regulatory Planning and Review."

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

C.RegulatoryFlexibility Act
The Regulatory Flexibility Act (RFA) generally requires an agency to conduct

aregulatory flexibility analysis ofany rule subject to notice and comment rulemaking requirements unlessthe

173 75 FR 8008, 8012-8013. 

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agency certifies thatthe rule will not have a significant economic impact on

a substantial number of small entities. Small entities include smallbusinesses, 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 ofthe Clean Air Act do not create any new requirements but simply approve and disapprove requirements thatthe State is already imposing. Therefore, because this limited approval and limited disapproval action does not create any

new requirements, Icertify that this action will not have a significant economic impact on a substantial number ofsmall entities.

Moreover, due tothe nature ofthe Federal-State relationship under the Clean Air Act, preparation offlexibility analysis would constitute Federal inquiry into the economic reasonableness ofState action. The Clean Air Act forbids EPA tobase its actions concerning SIPs on such grounds. UnionElectricCo., v. U.S. EPA, 427U.S. 246, 255-66 (1976); 42 U.S.C. 7410(a)(2).

D. UnfundedMandatesReformAct

Under sections 202 ofthe Unfunded Mandates Reform Act of 1995 ("UnfundedMandates Act"), signed into law on March 22, 1995, EPA must prepare a budgetary impact statement to accompany any proposed or final rule that includes aFederal 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 costeffective and leastburdensome alternative that achieves the objectives ofthe rule and is consistent with statutory requirements. Section 203 requires EPA to establish a plan for informing and advising any small governments thatmay be significantly

oruniquely 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 theprivate sector, result from this action. E.Executive Order13132,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 ofregulatory policies that have federalism implications." "Policiesthat have federalism implications" is defined in the Executive Order to include regulations thathave "substantial direct effects onthe States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels ofgovernment." Under Executive Order 13132, EPA may not issue a regulation that has federalism implications, that imposes substantial direct compliance costs, andthat is not required by statute, unless the Federal government provides the funds necessary to pay the direct compliance
costs incurred by State andlocal governments, orEPA consults with State and local officials early in the process ofdeveloping the proposed regulation. EPA also may not issue a regulation thathas federalism implications and thatpreempts State law unless the Agency consults with State and local officials early in the process ofdeveloping the proposed regulation.

This rule will not have substantial direct effects on the States, onthe relationship between the national government and the States, or onthe distribution ofpower and responsibilities among the various levels ofgovernment, as specified in Executive Order 13132, because it merely approves and disapproves State rules implementing aFederal standard, and does not alter the relationship or the distribution ofpower and responsibilities established in the Clean Air Act. Thus, the requirements of section 6 ofthe Executive Order do not apply to this rule.

F.Executive Order13175, Coordination With IndianTribalGovernments

Executive Order 13175, entitled "Consultation andCoordination with Indian Tribal Governments" (65 FR 67249, November 9, 2000), requires EPA to develop an accountable process to

ensure "meaningful andtimely input by tribal officials in the development of regulatory policies thathave tribal implications." This final rule does not have tribal implications, as specified in Executive Order 13175. Itwill not have substantial direct effects on tribal governments, on the relationship between the Federal government and Indian tribes, or onthe distribution of
power and responsibilities between the Federal government and Indian tribes. Thus, Executive Order 13175 does not apply to this rule.

G.Executive Order13045,Protectionof ChildrenFromEnvironmentalHealth Risks andSafetyRisks

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 thatthe analysis required under section 5-501 ofthe 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 Order13211,Actions That Significantly Affect EnergySupply, 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 itis
not a significant regulatory action under Executive Order 12866.

L NationalTechnologyTransferand AdvancementAct

Section 12 ofthe National Technology Transfer and Advancement Act (NTTAA) of 1995 requires Federal agencies to evaluate existing technical standards when developing anew regulation. To comply with NTTAA, EPA must consider anduse "voluntary

consensus standards" (VCS) ifavailable and applicable when developing programs and policies unless doing so would be inconsistent with applicable law or otherwise impractical.

The EPAbelieves that VCS are inapplicable to this action. Today's action does not require the public to perform activities conducive to the use ofVCS.

J.Executive Order12898:Federal Actions ToAddressEnvironmental Justicein MinorityPopulations and Low-Income Populations

Executive Order 12898, "Federal Actions toAddress 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 oftheir 

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mission by identifying and addressing,

as appropriate, disproportionately high and adverse human health or environmental effects oftheirprograms, 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 andpolicies. 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 ofenvironmental 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

onminority, low-income or Tribal populations because it increases the level ofenvironmental 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 ReviewAct

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

L. Petitions forJudicial Review
Under section 307(b)(1) of the Clean Air Act, petitions forjudicialreview of this action must be filed in the United States Court ofAppeals 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 ofthis rule for the purposes ofjudicial review nor does itextend the time within which a petition forjudicial review maybe filed, and shall not postpone the effectiveness ofsuch rule

or action. This action may notbe challenged later in proceedings to enforce its requirements (see section 307(b)(2)).
List of Subjects in40 CFRPart 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,RegionIX.
* Part52, chapterI, title40 ofthe Code ofFederal Regulations is amended as follows:

PART 52-[AMENDED]

m 1. The authority citation for part52 continues to read as follows:

Authority: 42 U.S.C. 7401 et seq. Subpart F-California

* 2.Section 52.220 is amended by adding paragraph (c)(345)(i)(E) to read

as follows:
§52.220 Identificationof plan.

(c) * * * (345) * * * (i) * * * (E) Imperial County Air Pollution Control District. (1)Rule 800,"General Requirements for Control ofFine 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.

[FRDoe. 2010-16350 Filed 7-7-10; 8:45 am]

BILLING CODE 6560-50-P 

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