ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 52

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

Revisions to the California State Implementation Plan, Imperial 

County Air Pollution Control 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 of the 

California State Implementation Plan (SIP) under the Clean Air 

Act as amended in 1990 (CAA or the Act). This action was 

proposed in the Federal Register on February 23, 2010 and 

concerns local rules that regulate coarse particulate matter 

(PM10) emissions from sources of fugitive dust such as 

construction sites, unpaved roads, and disturbed soils in open 

and agricultural areas in Imperial County. 

EFFECTIVE DATE: This rule is effective on [Insert date 30 days 

from the date of publication in the Federal Register].

ADDRESSES: EPA has established docket number EPA-R09-OAR-2010-

0120 for this action. The index to the docket is available 

electronically at www.regulations.gov and in hard copy at EPA 

Region IX, 75 Hawthorne Street, San Francisco, California. While

all documents in the docket are listed in the index, some 
2

information may be publicly available only at the hard copy 

location (e.g., copyrighted material), and some may not be 

publicly available in either location (e.g., CBI). To inspect 

the hard copy materials, please schedule an appointment during 

normal business hours with the contact listed in the FOR FURTHER 

INFORMATION CONTACT section.

FOR FURTHER INFORMATION CONTACT: Andrew Steckel, EPA Region IX, 

(415) 947-4115, Steckel.andrew@epa.gov. 

SUPPLEMENTARY INFORMATION: Throughout this document, “we,” “us” 

and “our” refer to EPA.

Table of Contents 

I. Summary of Proposed Action

II. Public Comments and EPA Responses

III. EPA Action

IV. Statutory and Executive Order Reviews

I. Summary of Proposed Action

On February 23, 2010 (75 FR 8008), EPA proposed a limited 

approval and limited disapproval of the following rules listed in

Table 1, known collectively as Regulation VIII, that were adopted

by ICAPCD and submitted by the California Air Resources Board 

(ARB) for incorporation into the California SIP for the Imperial 

County serious PM10 nonattainment area. 

Table 1 
3

Local 

Agency

Rule # 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

805

Open Areas

Paved & Unpaved Roads

11/08/05

11/08/05

06/16/06

06/16/06

806 Conservation Management 

Practices

11/08/05 06/16/06

We proposed a limited approval because we determined that 

these rules improve the SIP and are largely consistent with the 

relevant CAA requirements. We simultaneously proposed a limited 

disapproval because some provisions of the rules conflict with 

the CAA section 110(a) requirement that SIP rules must be 

enforceable and the requirement in section 189(b)(1)(B) for 

implementation of best available control measures (BACM) in 

serious PM10 nonattainment areas such as Imperial County. We 
4

discuss these statutory requirements and the Regulation VIII 

deficiencies in detail in the proposed rule and in the Technical 

Support Document for that proposal (proposal TSD).1 In the 

proposed rule and proposal TSD we also discuss our determination 

of which fugitive dust source categories addressed by Regulation 

VIII are significant and consequently require BACM pursuant to 

EPA guidance. This determination was based in part on our 2009 

decision2 to not concur with the State‟s request pursuant to 

EPA‟s exceptional events rule3 (EER) to exclude certain 

exceedances of the PM10 National Ambient Air Quality Standard 

(NAAQS) in Imperial County from consideration in regulatory 

actions under the CAA.4

We summarize the Regulation VIII deficiencies addressed in 

our proposed rule below. These deficiencies concern Regulation 

VIII provisions relating to open areas, unpaved roads and 

agricultural lands.

A. BACM-Related Deficiencies for Open Areas 

 

1 Our proposed rule and proposal TSD also describe additional 

improvements that we recommend for future ICAPCD modifications of

the rules. This final action is not based on those 

recommendations. As a result, we do not respond here to all 

comments we received on them.

2 Letter with enclosure from Laura Yoshii (EPA), to James 

Goldstene (ARB), Re: exceptional events requests regarding 

exceedances of the PM10 NAAQS in Imperial County, CA, December 

22, 2009.

3 40 CFR 50.1(j) and 50.14. 

4 Issues related to the Regulation VIII deficiencies, significant 

source categories and our decision not to concur with the State‟s
5

1. Recreational Off-Highway Vehicle Activity

While recreational off-highway vehicle (OHV)5 activity 

causes much of the PM10 emissions from open areas in Imperial 

County, Rule 804 regulates only a small portion of these 

emissions, including those from OHV activity on State lands on 

which the rule is not being implemented. The vast majority of the

OHV emissions in Imperial County are addressed only by 

requirements in Rule 800 section F.5 for dust control plans 

(DCPs) for sources under the control of the Bureau of Land 

Management (BLM). While BLM is required to describe in the DCPs 

the dust control measures that it intends to implement, BLM is 

not required to implement any specific BACM-level controls for 

OHV use. Moreover, ICAPCD has not provided an analysis of BACM 

for OHV activity, including potential OHV activity in open areas 

and on unpaved roads and paths that are exempt from the specific 

requirements and measures in Rules 804 and 805. The proposed rule

and proposal TSD address how ICAPCD can correct these 

deficiencies.6

2. Definition of “Disturbed Surface”

The term “disturbed surface area” is used in several 

 

exceptional events requests are addressed further below in our 

responses to comments we received on the proposed rule.

5 As used here and in the proposal TSD, the term “off-highway 

vehicle” or OHV includes all vehicles subject to the exemption in

Rule 800 section E.6 for recreational use of public lands in 

Imperial County.

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

Regulation VIII rules but is never defined. For example, Rule 

804 applies to a source category for which BACM is required and 

relies on the undefined term to describe rule applicability in 

Rule 804 section B. A definition of this term is necessary in 

order to ensure that these rules are enforceable at a BACM level.

B. BACM-Related Deficiencies for Unpaved Roads

1. Unpaved Non-Farm Roads

While CAA section 189(b)(1)(B) requires ICAPCD to implement 

BACM by 2008 (i.e., four years after reclassification to 

serious),7 Rule 805 section E.7 allows the County until 2015 to 

stabilize heavily-travelled unpaved roads. This schedule is 

inconsistent with the statutory requirement and ICAPCD has not 

provided adequate evidence that this schedule is as expeditious 

as practicable, based upon economic feasibility or any other 

appropriate consideration. In addition, Rule 805 section E.7‟s 

requirement to stabilize all non-exempt unpaved County roads is 

not adequately enforceable as currently structured because it is 

not clear that the County is required to implement (and not just 

submit) a stabilization plan; stabilize different unpaved roads 

each year; and maintain all stabilized roads. The proposed rule 

and proposal TSD address how ICAPCD can correct these 

 

7 On August 11, 2004, EPA reclassified Imperial County as 

serious nonattainment for PM10. 69 FR 48835. Since 2008 has 

passed, BACM is now required to be implemented as expeditiously 

as practicable. Delaney v. EPA, 898 F.2d 687 (9th Cir. 1990).
7

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 

to non-agricultural operation sites. Farm roads and traffic areas

are only required to implement a conservation management practice

(CMP) from the menus for unpaved roads and traffic areas in Rule 

806 in contrast to analogous rules in other geographical areas. 

Rule 806 sections E.3 and E.4 list CMPs intended to control 

emissions from agricultural unpaved roads and traffic areas but 

these measures are broadly defined and there is no other 

mechanism in the rule to ensure specificity. The absence of 

sufficiently defined requirements makes it difficult for 

regulated parties to understand and comply with the requirements,

and makes it difficult for ICAPCD or others to verify compliance 

and to enforce the requirements if necessary. The lack of 

specificity similarly renders it difficult to assess whether the 

measures constitute BACM level controls. The proposed rule and 

proposal TSD address how ICAPCD can correct these deficiencies.9

3. Border Patrol Roads

Rule 800 section F.6.c exempts roads owned or operated by 

the U.S. Border Patrol (BP) from Rule 805 requirements that are 

“inconsistent with BP authority and/or mission.” It is not clear

 

8 75 FR 8008, 8011 and our proposal TSD, section III.B.3.
8

what this exemption is intended to address, or how it would be 

implemented and enforced in order to meet BACM requirements. The 

proposed rule addresses how ICAPCD can correct these 

deficiencies.10

C. BACM-Related Deficiencies for Agricultural Lands

1. Tilling and Harvesting

Rule 806 sections E.1 and E.2 list CMPs intended to control 

emissions from agricultural land preparation and cultivation 

(including tilling), and harvest activities, but these measures 

are broadly defined and there is no other mechanism in the rule 

to ensure specificity. The absence of sufficiently defined 

requirements makes it difficult for regulated parties to 

understand and comply with the requirements, and makes it 

difficult for ICAPCD or others to verify compliance and to 

enforce the requirements if necessary. The lack of specificity 

similarly renders it difficult to assess whether the measures 

constitute BACM level controls. 

In addition, Rule 806 section E requires one CMP from the 

“land preparation and cultivation” category and one CMP from the 

“harvesting” category, while rules in other geographic areas have

more stringent requirements. 

The proposed rule and proposal TSD address how ICAPCD can 

 

9 75 FR 8008, 8011 and our proposal TSD, section III.B.4.

10 75 FR 8008, 8011.
9

correct these deficiencies.11

2. Windblown Dust

Windblown dust from non-pasture agricultural lands is also a 

significant source of PM10 that requires BACM independent of 

agricultural tilling. The CMPs in Rule 806 section E, however, 

mainly control emissions by reducing the number of vehicle passes

across fields, and sources are not required to select BACM level 

practices for controlling windblown dust from active or fallow 

agricultural fields. The proposed rule and proposal TSD address 

how ICAPCD can correct these deficiencies.12

D. Non-BACM Deficiency 

Rule 802 section D.1 allows the Air Pollution Control 

Officer (APCO) to set aside controls that might be used instead 

of water to stabilize surfaces of bulk materials. This discretion

allows ICAPCD to approve alternatives to the applicable SIP 

without following the SIP revision process described in CAA 

section 110. Moreover, ICAPCD has not demonstrated why such 

discretion is needed for measures such as covering, enclosing or 

sheltering material piles. The proposed rule addresses how 

ICAPCD can correct these deficiencies.13

II. Public Comments and EPA Responses

EPA‟s proposed action provided a 30-day public comment 

 

11 75 FR 8008, 8011-8012 and our proposal TSD, section III.B.4.

12 75 FR 8008, 8012 and our proposal TSD, section III.B.4.

13 75 FR 8008, 8012.
10

period. During this period, we received nine unique comment 

letters from public agencies and broad-based organizations. 

Brad Poiriez, Air Pollution Control Officer, Imperial County 

Air Pollution Control District, March 25, 2010 (ICAPCD). 

Daniel Steward, Acting Field Manager, United States 

Department of the Interior, Bureau of Land Management, El 

Centro Resource Area, March 24, 2010 (BLM). 

Kathleen Dolinar, District Superintendent, Ocotillo Wells 

District, California State Parks, Off-Highway Motor Vehicle 

Recreation Division, by email dated March 24, 2010 (OWD).

Gail Sevrens, Acting District Superintendent, Colorado 

Desert District, California State Parks, by email dated 

March 25, 2010 (CDD).

David P. Hubbard, Gatzke Dillon & Balance LLP, on behalf of 

EcoLogic Partners, Inc., March 25, 2010 (EcoLogic).

Lisa T. Belenky, Senior Attorney, Center for Biological 

Diversity, March 25, 2010, representing several listed 

parties (CBD).

Jose Luis Olmedo, Executive Director, Comite Civico Del 

Valle, Inc., March 25, 2010, submitted and joined by other 

parties (Comite). 

Ayron Moiola, Executive Director, Coalition of Labor, 

Agriculture & Business, March 24, 2010 (COLAB).
11

Mark McBroom, President, Imperial County Farm Bureau, March 

24, 2010 (Farm Bureau).

We also received over 100 comment letters from individuals 

and organizations associated with recreational OHV activities. 

We reference these comments below by their identification in the 

federal docket management system (FDMS) found at regulations.gov.

For example, the comment listed in FDMS as document number “EPAR09-OAR-2010-0120-0219” is referenced below as “0219.”

We summarize the comments and provide our responses below. 

In our responses we identify specific commenters in some cases 

but not in others, particularly where many commenters made 

similar points.

A. General 

These overarching comments largely provide general support 

or opposition to our proposal.

General #1: CBD and Comite support EPA‟s proposal to find 

that the Regulation VIII submittal does not fully implement BACM 

level controls for all significant source categories in Imperial 

County, and support EPA‟s nonconcurrence with associated 

exceptional event requests. They ask EPA to finalize the 

proposed limited disapproval of Regulation VIII and to require 

additional PM10 emissions restrictions. Many other commenters 

disagree with EPA‟s proposed limited disapproval, especially with

EPA‟s identification of deficiencies for BACM requirements and 
12

EPA‟s nonconcurrence with exceptional events. ICAPCD, for 

example, believes that EPA‟s proposal is arbitrary and 

capricious, and that California has demonstrated that all 

required BACM are being implemented in Imperial County. 

Response: No response is necessary for the overarching 

statements of support or opposition. Responses are provided 

below to the specific comments that support these general 

statements. 

General #2: Several commenters believe that EPA‟s proposal 

lacks adequate scientific support. One (0144), for example, 

states that passing sweeping air quality regulations in an area 

with unique terrain and climate with only generalities to prove 

the sources of pollution is unethical and appears antidevelopment, anti-OHV and anti-agriculture.

Response: The scientific support for EPA‟s action is 

documented in our proposal and the associated proposal TSD and 

discussed further in response to specific comments below. See, 

for example, response to comment EI #3 below. The serious health 

impacts of exposure to elevated levels of PM10 are well known and 

well documented and need not be reiterated here.

General #3: ICAPCD objects to EPA taking over four years to 

act on its submittals of Regulation VIII for approval and claims 

that EPA is only now raising basic issues that ICAPCD believes 

should have been resolved before rule adoption. For example, 
13

ICAPCD objects to EPA disapproving a definition that it claims is

clear and understood by all affected parties. ICAPCD and others 

(e.g., COLAB) comment that EPA never raised this and other 

concerns despite ICAPCD‟s extensive public process and 

communication with EPA before rule adoption. ICAPCD also cites 

EPA‟s testimony before the District Board in which the Agency 

supported Regulation VIII as BACM. As a result, ICAPCD concludes

that EPA‟s proposal undermines ICAPCD‟s ability to rely on EPA 

comments in the future. 

Response: EPA reviews and comments on many draft State and 

local agency rules during their development prior to submittal to

EPA for formal approval. It is generally more efficient for all 

parties to identify and resolve issues early in the process, 

rather than after rules are adopted and submitted to EPA for 

inclusion into the SIP. EPA‟s formal action on local rules, 

however, can only occur through notice and comment rulemaking 

after rules have been officially submitted to EPA by the State. 

If EPA determines during that process that a submittal does not 

fulfill relevant CAA requirements, we cannot approve the 

submittal. Given time and resource constraints, it is not always

possible for the Agency to identify or analyze fully all issues 

before State or local rule adoption. Moreover, EPA must carefully

consider all public comments submitted on proposed EPA actions on

State and local rules. Such comments often identify issues and 
14

concerns that may not have arisen during the prior evaluation of 

drafts of a rule. We continue to believe, however, that 

communication between EPA and State and local agencies at the 

rule development stage is productive. 

General #4: OWD asks EPA to extend the comment period 

because it was informed of EPA‟s proposal only nine days before 

the close of the comment period. Several commenters also state 

that EPA did not provide adequate notification time (0218.1 and 

0098) or consultation with State Park personnel (0218.1 and OWD).

Response: EPA denied OWD‟s request to extend the comment

period because EPA is under a court order14 to finalize action by 

June 15, 2010, and needs time to analyze all comments submitted 

on the proposal.15 While more time and outreach before EPA 

action is always desirable, nothing in the comments suggests that

EPA failed to follow relevant public notification requirements 

found in the Administrative Procedures Act.16 EPA notes that OWD 

did comment on the proposal and EPA has taken those comments into

consideration in the final action.

B. State Implementation Plan (SIP)

These comments generally address broad SIP issues rather 

than specific Regulation VIII provisions. 

 

14 Comite Civico Del Valle, Inc., v. Jackson, No. 09-cv-04095 PJH 

(N.D. Cal.). 

15 Email from Andrew Steckel, EPA, to Kathleen Dolinar, 

California State Parks, March 29, 2010.

16 See 5 U.S.C. 553.
15

SIP #1: OWD believes the PM10 standard is nearly impossible 

to attain given Imperial‟s climate, natural desert condition, the

cost of inappropriate BACM, and other local conditions. In 

contrast, Comite asks EPA to find that California has failed to 

submit a PM10 plan as required by 72 FR 70222 (December 11, 

2007), and to consider imposing associated CAA section 179 

sanctions and a section 110(c) federal implementation plan (FIP) 

in this area. 

Response: Our proposed action addresses the CAA section 

189(b)(1)(B) requirement for BACM for certain PM10 sources in 

Imperial County. The submittal at issue, Regulation VIII, is but

one portion of the complete SIP that ICAPCD must develop in order

to meet additional CAA requirements. These comments address the 

separate and broader statutory obligations for the State to 

submit a PM10 plan that, among other things, demonstrates 

expeditious attainment of the PM10 NAAQS. Those other obligations 

are not the subject of this action.

SIP #2: ICAPCD does not believe that any additional controls 

such as those that may need to be implemented if EPA partially 

disapproves Regulation VIII will prevent PM10 exceedances during 

high winds or otherwise materially benefit air quality on days 

unaffected by high winds. ICAPCD further believes that such 

additional controls will waste limited resources that should be 

used in other ways to improve local air quality in the area.
16

Response: CAA section 189(b)(1)(B) and EPA guidance17

require that BACM be implemented for all significant source 

categories18 in serious PM10 nonattainment areas such as Imperial 

County. As explained in our proposal,19 we determined that each 

of the subcategories under open areas, unpaved roads and 

agricultural lands below meet or exceed the 5 μg/m3 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:

 

17 “State Implementation Plans for Serious PM-10 Nonattainment 

Areas, and Attainment Date Waivers for PM-10 Nonattainment Areas 

Generally; Addendum to the General Preamble for the 

Implementation of Title I of the Clean Air Act Amendments of 

1990;” 59 FR 41998 (August 16, 1994)(General Preamble Addendum).

18 Under the General Preamble Addendum, a source category “will 

be presumed to contribute significantly to a violation of the 24-

hour NAAQS if its PM10 impact at the location of the expected 

violation would exceed 5 μg/m3.” This is also referred to as the 

de minimis level. Id. at 42011.

19 75 FR 8008, 8010, and proposal TSD, pp. 5-7.
17

- Tilling.

- Windblown Dust, Non-Pasture Agricultural 

Lands.

As EPA stated in the guidance, the structural scheme 

throughout title I of the CAA, including its provisions for the 

PM10 NAAQS, requires the implementation of increasingly stringent 

control measures in areas with more serious pollution problems. 

EPA further stated “that the more serious the air quality 

problem, the more reasonable it is to require States to implement

control measures of greater stringency despite the greater 

burdens such measures are likely to cause.”20 Imperial County 

continues to violate the PM10 standard21 and our proposed action 

identifies several components of the State‟s Regulation VIII 

submittal relating to open areas, agricultural lands and unpaved 

roads that do not fulfill the CAA BACM requirement and the 

enforceability requirements of CAA section 110(a). 

We further address ICAPCD‟s contention that additional 

Regulation VIII controls will not prevent PM10 exceedances during 

high winds in our response to comment EE #1 below. 

SIP #3: Many commenters emphasize the importance of OHV 

areas in Imperial County for recreation, and believe that 

 

20 General Preamble Addendum at 42010. 
18

enjoyment of the desert should not be restricted. Commenters note

that many organizations help keep the desert clean, and one 

commenter (0175.1) believes such efforts would be reduced if OHV 

areas are closed.

Response: Recreation, enjoyment of the desert and clean 

deserts are certainly desirable, whether for OHV use or 

otherwise. However, except as implicit in our response to 

comment OHV #5 below, they are not germane to the evaluation in 

our proposal and in this final rule of Regulation VIII and its 

compliance with the applicable CAA requirements.

SIP #4: Two commenters (OWD and 0218.1) question whether 

EPA‟s proposal is based on statistically significant data since 

there were only three PM10 exceedances within a three year 

period. 

Response: ICAPCD‟s obligation to implement BACM for 

Regulation VIII fugitive dust sources derives from the Imperial 

County‟s designation as nonattainment and classification as 

serious. On November 15, 1990, the date of enactment of the 1990

Clean Air Act Amendments, Imperial County was designated 

nonattainment and classified as moderate.22 On August 11, 2004, 

EPA reclassified the area as serious in compliance with a mandate

 

21 EPA‟s Air Quality System Preliminary Design Value Report (May 

18, 2010) shows 17 exceedances of the 24-hour PM10 NAAQS in 

Imperial County between 2007 and 2009. 

22 56 FR 56694 (November 6, 1991). 
19

of the U.S. Court of Appeals for the Ninth Circuit.23 The 

reclassification, pursuant to CAA section 188(b)(2), was based on

a finding that the area failed to attain the PM10 NAAQS by the 

statutory deadline of December 31, 1994. Once reclassified to 

serious, the area was required to comply with CAA section 

189(b)(1)(B), which required that BACM be implemented for the 

area four years after its reclassification to serious. 

The three exceedances to which OWD refers occurred during 

2006 and 2007. The State requested that these exceedances be 

excluded from use in regulatory actions pursuant to EPA‟s EER.24

Because we did not concur with the State‟s request, BACM is 

required to be implemented for certain windblown dust source 

categories, including open areas, for which such controls would 

not have been required if we had agreed with the State.25 See our 

responses to Exceptional Events comments below. 

We also note that California has chosen to sample PM10 in 

Imperial County only one out of every six days. As a result, by 

regulation, each monitored exceedance is estimated to represent 

approximately six exceedances rather than one.26 For example, in 

2009, ICAPCD reported three monitored exceedances at the Ethel 

Street monitoring site, which are estimated to represent 18.3 

 

23 69 FR 48792; Sierra Club v. United States Environmental 

Protection Agency, et al., 346 F.3d 995 (9th Cir. 2003); cert. 

denied, 542 U.S. 919 (2004). 

24 See section II.D.1 below.

25 75 FR 8008, 8010 and proposal TSD pp. 5-7.
20

exceedances. Exceedances were also monitored at Brawley, El 

Centro, Westmorland and Niland in 2009.27

SIP #5: Comite believes PM10 should be further controlled in 

Imperial County by adoption of local fugitive dust ordinances 

like those in Coachella‟s Cathedral City, and by strengthening 

open burning regulations to be similar to those in the South 

Coast Air Quality Management District (SCAQMD) and the San 

Joaquin Valley Unified Air Pollution Control District (SJVUAPCD).

Response: We assume the commenter refers to title 8, chapter 

8.54 of Cathedral City‟s municipal code which describes 

requirements for construction, unpaved roads and other local dust

sources.28 These requirements are generally similar to the type 

of controls adopted by SCAQMD (e.g., Rule 403), SJVUAPCD (e.g., 

Regulation VIII) and ICAPCD (Regulation VIII). The commenter 

does not identify any specific Cathedral City controls that it 

believes are needed in ICAPCD Regulation VIII to constitute BACM.

Except where identified in our proposal, we believe ICAPCD‟s BACM

analyses include adequate evaluation of analogous fugitive dust 

controls in other areas.29 It is possible that the commenter is 

recommending duplicative city ordinances that overlap County-wide

Regulation VIII. While such redundancy could improve compliance,

 

26 40 CFR part 50, appendix K.

27 EPA‟s Air Quality System Preliminary Design Value Report (May 

18, 2010).

28 Cathedral City Municipal Code, title 8, chapter 8.54, Fugitive 

Dust Control; http://qcode.us/codes/cathedralcity/.
21

it is generally not necessary 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 EI #1. 

SIP #6: Comite cites Vigil v. Leavitt, 381 F.3d 826, 834 

(9th Cir. 2004) and Hall v. EPA, 273 F.3d 1146 (9th Cir. 2001), in 

commenting that measures in other areas can be considered BACM 

for Imperial County and are per se feasible. Comite further 

argues that what constitutes BACM can strengthen over time. In 

contrast, OWD does not believe that Imperial County should apply 

mitigation measures from other geographic areas (e.g., SJVUAPCD 

and Maricopa) that have different geologic and other local 

conditions. Similarly, COLAB believes that different cultural 

practices prevent ICAPCD from blindly implementing controls 

imposed in other areas, although the ICAPCD and SJVUAPCD CMP

rules are very similar. Still another commenter (0119) claims 

that similar restrictions on construction, OHVs, farmers, etc., 

in Las Vegas and elsewhere have not been effective, and there is 

no need for such draconian and ineffective bureaucratic rules. 

Response: EPA believes that it is appropriate, when 

 

29 2009 PM10 SIP table 4.2 and 2005 BACM analysis table 4.2.
22

evaluating what constitutes BACM for a given source category, to 

consider controls that have been adopted and implemented in other

geographical areas. EPA agrees that the facts and circumstances 

in a given area can affect what constitute BACM for that area, 

but that this determination must be based upon appropriate 

consideration of relevant information specific to that area. 

Comite does not explain how the cited cases support its 

position. Nonetheless, we agree that in evaluating BACM for 

Imperial County, ICAPCD should analyze analogous measures in 

other areas and that BACM may strengthen over time.30 Our 

proposal identifies several significant deficiencies in ICAPCD‟s 

analysis to date.31 While BACM is determined on a case-by-case 

basis32 and, as such, the analysis can include evaluation of 

local conditions that might make specific controls economically 

and/or technologically feasible in one area but not another,33

neither the 2009 PM10 SIP34 nor the comment provides sufficient 

detail to adequately address the deficiencies identified in our 

proposal. 

 

30 General Preamble Addendum at 42013-42014.

31 E.g., OHV controls in Arizona Revised Statute §49-457.03 and 

Clark County Air Quality Regulations, section 90 (75 FR 8011, 

February 23, 2010).

32 General Preamble Addendum at 42010 and 42012.

33 In this respect, we do not agree with Comite that measures 

adopted in other areas are automatically transferable to Imperial

County.

34 “2009 Imperial County State Implementation Plan for 

Particulate Matter Less Than 10 Microns in Aerodynamic Diameter, 
23

OWD does not explain how Imperial County differs so markedly

from the San Joaquin Valley and the Maricopa area that it would 

be inappropriate to consider BACM approved in those areas as part

of the evaluation of controls for the same source categories in 

Imperial County. Similarly, COLAB does not elaborate on what 

“cultural practices” in Imperial County would justify 

disregarding approved BACM in the San Joaquin Valley and the 

Maricopa area as part of the evaluation of what controls would be

appropriate for comparable source categories in Imperial County. 

C. Emissions Inventory (EI) 

EI #1: Many commenters oppose further OHV controls because 

they believe OHVs contribute little to Imperial County‟s PM10

pollution problem compared to other sources. Commenters identify

various sources they believe are more significant and/or should 

be further addressed instead, including fallow fields, 

fireplaces, feed lots, agricultural burning, pesticides, dirt 

roads, inefficient street lights, insufficient public 

transportation, insufficient speed limit enforcement, Interstate 

8, the New River, the Salton Sea, Arizona to the east, San Diego 

to the west, Mexican roads, fires and factories to the south, 

rain, wind, erosion, dust storms and other natural occurrences. 

These commenters include OWD, 0096, 0097, 0150, 0139, 0152, 0180,

0192, 0194 and 0219.1.

 

Final,” adopted by ICAPCD Governing Board on August 11, 2009. 
24

Response: Our proposal explains that BACM is required for 

all significant PM10 source categories in Imperial County, that 

windblown dust from open areas is a significant PM10 source 

category, and that OHVs greatly increase emissions from open 

areas in Imperial County.35 Our proposal further explains that 

ICAPCD has not demonstrated implementation of BACM for open areas

with respect to OHVs.36 These conclusions are based on inventory 

information prepared by ICAPCD and ARB and used during 

development of Regulation VIII and the 2009 PM10 SIP.37

The inventory in the 2009 PM10 SIP represents the most 

comprehensive information currently available on OHV emissions in

Imperial County.38 ICAPCD‟s analysis in the 2009 PM10 SIP 

concluded that windblown dust from open areas was not a 

significant source category, but this conclusion was premised 

upon many exceedences of the NAAQS being deemed to be the result 

of exceptional events. However, EPA‟s own conclusion regarding 

those exceedences is that they were not caused by exceptional 

events and, as a result, we consider windblown dust from open 

areas to be a significant source category that is subject to the 

CAA‟s BACM requirement. See response to comment SIP #4 and 

responses to Exceptional Events comments in section II.D below. 

 

(2009 PM10 SIP).

35 Proposal TSD, pp. 5-8.

36 Id. at p. 8.

37 Id. at pp. 5-8.

38 2009 PM10 SIP, Chapter 3; Appendix III.
25

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 also be 

appropriate for the various other sources identified in the 

comments. 

EI #2: One commenter (0188) had driven past many farms in El 

Centro during tilling and observes that the dust was very 

minimal. Another (0201) thinks more attention should be paid to 

agriculture which the commenter believes is exempt from many of 

the environmental regulations. 

Response: See response to comment EI #1. Similar to 

emissions from open areas, EPA has concluded that emissions 

associated with tilling on and windblown dust from agricultural 

lands are significant source categories in Imperial County and, 

as such, ICAPCD needs to meet the BACM requirement for such 

sources.39 

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 

 

39 Proposal TSD, pp. 5-8 and 9-11.
26

category for PM10 in Imperial County, ICAPCD is required to meet 

the CAA‟s BACM requirements for such sources. Any “exemptions” 

for any such sources would need to be justified and explained in 

the context of meeting the BACM requirements. 

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

impact of OHVs on PM10 levels sufficient to require additional 

OHV regulations. OWD notes, for example, that: (1) EPA did not 

analyze extreme terrain, thermal stability and other effects on 

winds in the desert; (2) most emissions from open lands come from

undisturbed shrub/grassland which are not anthropogenic sources; 

and (3) ICAPCD‟s 2009 PM10 SIP, on which EPA relies, uses worstcase assumptions rather than actual soil condition information to

estimate that OHVs represent less than 5% of the County‟s total 

PM10 emissions (13.9 of 282 tpd). OWD states that 99% of these 

total emissions relate to OHVs subject to federal and State 

stewardship. Therefore OWD concludes that actual OHV emissions 

are small compared to worst-case estimates. OWD also questions 

EPA‟s reference for the estimate of 22 tpd of windblown PM10 from 

OHVs. 

EcoLogic believes that EPA needs monitoring in the Ocotillo 

Wells State Vehicle Recreation Area (SVRA) and other areas to 

show how specific OHV activity affects sensitive receptors and 

for EPA to identify OHV activity as a major contributor to the 

County‟s PM10 problem. Another commenter believes EPA lacks data 
27

tying PM to specific OHV activities (0218.1), and several 

commenters believe that any pollution from OHVs is virtually 

immeasurable. Several commenters believe additional inventory 

analysis is particularly important because OHV areas are far from

population centers and monitors with PM10 exceedances. One 

commenter (0131) requests an unbiased third-party study of OHV 

impacts. CDD explains that PM10 emissions from several specific 

parks in Imperial County should be low, partly because OHV 

activity is prohibited. In contrast, CBD supports EPA‟s claim 

that OHVs on BLM land cause considerable PM10 in Imperial County, 

and notes that BLM previously estimated PM10 impacts from OHV 

activities at the Aldodones Dunes alone as high as 11 tpd on 

holiday weekends. 

Response: It is extremely difficult to quantify and speciate 

accurately the myriad sources of PM10 emissions and PM10 precursor 

emissions spatially and temporally for purposes of modeling air 

pollution impacts and developing cost effective control programs.

As a result, emission inventories are constantly being refined 

as more and better science and data become available. However, 

EPA, State and local air pollution agencies must make policy and 

regulatory decisions based on the best information available to 

comply with the CAA. As discussed in response to comment EI #1, 

the inventory and other information underlying our proposal 

regarding the emissions from OHV activity and the impacts of such
28

activity represent the most comprehensive information currently 

available. 

Regarding specific concerns in this comment: 

(1) EPA‟s conclusion that BACM is required for OHV activity 

relies on emissions inventory estimates that ICAPCD developed. 

If appropriate, ICAPCD could choose to refine those estimates to 

take into consideration factors such as terrain, thermal 

stability and other effects on winds in the desert, as well as 

distances between OHV areas and population centers and additional

third party analysis. Such refinements are beyond the level of 

detail normally used in inventories required by CAA section 

172(c)(3).40

(2) ICAPCD in its 2009 PM10 SIP quantifies the impact of 

soil type and land cover (e.g., shrub/grassland) and degree of 

OHV disturbance in OHV emission estimates relied on by our 

proposal.41

(3) ICAPCD used the best available information regarding 

soil types in open areas and determined that the remaining 

uncertainty does not affect the results of the technical 

 

40 See, e.g., AP-42, Fifth Edition, Volume I, Chapter 13: 

Miscellaneous Sources, 13.2.2 – Unpaved Roads, Final Section, 

EPA, November 2006. This document provides EPA guidance on 

estimating emissions on unpaved roads and does not, for example, 

account for road terrain. 

http://www.epa.gov/ttn/chief/ap42/ch13/index.html. 

41 2009 PM10 SIP, appendix III.B.
29

analyses.42

(4) Even OWD‟s 13.9 tpd OHV emission estimate, which we 

believe is too low,43 exceeds the presumptive 5 μg/m3 de minimis 

level for source categories requiring BACM.44

(5) The reference for 22 tpd of windblown OHV emissions is 

accurately explained in our proposal.45

The comment that monitoring is necessary in the Ocotillo 

Wells SVRA and other areas before EPA should require controls for

OHV activities is incorrect. As stated previously, under CAA 

section 189(b) and EPA guidance, BACM is required for all 

significant source categories in the nonattainment area, 

including windblown dust in open areas caused by OHV activity.46

Thus monitoring, which could provide valuable information, is 

nevertheless not necessary to determine which source categories 

require BACM. 

D. Exceptional Events (EE)

1. Background

On March 22, 2007, EPA adopted a final rule to govern the 

review and handling of certain air quality monitoring data for 

 

42 2009 PM10 SIP, p. 3-2.

43 In comparison to ICAPCD‟s 22 tpd estimate. Proposal TSD, 

footnote 32.

44 As discussed on pp. 5-8 of the proposal TSD, depending on the 

specific monitor, 2-3% of Imperial County‟s annual inventory is 

calculated to result in a 5 μg/m3 contribution, which equates to 

about 6-8 tpd emissions.

45 Id.

46 See, e.g., proposal TSD, p. 5.
30

which the normal planning and regulatory processes are not 

appropriate.47 Under the rule, EPA may exclude data from use in 

determinations of NAAQS exceedances and violations if a state 

demonstrates that an “exceptional event” caused the exceedances. 

Before EPA can exclude data from these regulatory determinations,

the state must flag the data in EPA‟s Air Quality System database

and, after notice and opportunity for public comment, submit a 

demonstration to EPA to justify the exclusion. After considering 

the weight of evidence provided in the demonstration, EPA decides

whether or not to concur with each flag.

On May 21, 2009, ARB submitted demonstrations for “high 

wind” events that allegedly caused ten exceedances of the 24-hour

PM10 standard at various monitors in Imperial County in 2006 and 

2007. The demonstrations consisted of the following support 

documents (listed in Table 2) prepared by ARB, ICAPCD, and 

ICAPCD‟s contractor, ENVIRON:

Table 2 

Description Document 

Date

Abbreviated 

Title

Natural Event Documentation: Calexico 

and Westmorland, California - September 

January 

30, 2009

September 

NED48

 

47 “Treatment of Data Influenced by Exceptional Events,” 72 FR 

13560 (March 22, 2007)(EER).

48 We refer to the natural event documentation in these five 

documents, collectively, as the NEDs.
31

2, 2006

Natural Event Documentation: Brawley 

and Westmorland, California - April 12, 

2007 [enclosed with June 13, 2008 

letter to Sean Hogan]

April 15, 

2008

Original 

April NED

Natural Event Documentation: Brawley, 

Calexico, El Centro, Niland, and 

Westmorland, California - June 5, 2007, 

Imperial County Air Pollution Control 

District [enclosed with June 13, 2008 

letter to Sean Hogan]

April 15, 

2008

Original 

June NED

Natural Event Documentation: Brawley 

and Westmorland, California - April 12, 

2007 [addendum to June 13, 2008 

submittal]

March 12, 

2009

April NED

Natural Event Documentation: Imperial 

County, California – June 5, 2007 

[addendum to June 13, 2008 submittal]

March 12, 

2009

June NED

As stated above in section I, on December 22, 2009, EPA 

denied ARB‟s request to exclude all of the exceedances as 

exceptional events. The basis for our decision is specified in 
32

an enclosure which accompanied the December 22, 2009 letter.49 

By letter, including Attachment A and Appendix A1, dated March 3,

2010, ICAPCD asked EPA to reconsider this decision.50

Our proposal on Regulation VIII explained that our 2009 EE 

decision led to an adjustment of ICAPCD‟s significant source 

analysis which in turn led us to modify the list of significant 

sources for which BACM must be implemented in Imperial County 

under CAA section 189(b)(1)(B).51 As a result, our 2009 EE 

decision was the subject of public comments on our proposed 

action. ICAPCD resubmitted its March 3, 2010 letter, including 

Attachment A and Appendix A1, regarding our 2009 EE decision as 

Appendix C to its March 25, 2010 comment letter on our Regulation

VIII proposed action.52 EPA also received comments pertaining to 

our exceptional events decision from Comite and CBD. A summary 

of these comments and our responses follow.

2. Events Not Reasonably Controllable or Preventable

EE #1: ICAPCD (Attachment) disagrees with EPA‟s 

interpretation of the requirement in the EER at 40 CFR 50.1(j) 

that in order for an event to meet the regulatory definition of 

 

49 See footnote 2. We refer to our December 22, 2009 letter and 

the enclosure hereafter as “2009 EE decision.”

50 Letter from Brad Poiriez (ICAPCD) to Jared Blumenfeld (EPA), 

March 3, 2010 with Attachment A and Appendix A1. 

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

52 We refer to ICAPCD‟s March 10, 2010 letter with its Attachment 

A and Appendix A1, collectively, throughout our responses to the 

exceptional events comments in section II.D as “Attachment.”
33

exceptional event, such event must be “not reasonably 

controllable or preventable.” Specifically ICAPCD takes issue 

with EPA‟s statement in our 2009 EE decision that this criterion 

inherently implies “a requirement that the state demonstrate that

anthropogenic sources contributing to the exceedance caused by 

the event were reasonably well controlled.” ICAPCD believes that

under the plain regulatory language it is irrelevant whether 

“reasonable and appropriate” controls are in place on the day of 

an otherwise qualifying event when it can be shown that such 

controls would not reduce emissions and impact at the monitor 

sufficiently to prevent the exceedance. ICAPCD believes that it 

is inconsistent with the intent of the CAA for EPA to refuse to 

concur with an exceptional event claim solely due to EPA‟s 

dissatisfaction with the stringency of certain controls when such

controls could not have prevented the exceedance.

Response: ICAPCD mischaracterizes both the plain language 

and the regulatory intent of 40 CFR 50.1(j) by reading the words 

“reasonably controllable or” out of that section. The regulation

clearly requires a showing that the event is not either 

reasonably controllable or preventable, not as ICAPCD would have 

it, that the event cannot be controlled to the extent that no 

exceedance would have occurred. Furthermore, “control” as 

generally used in the CAA and EPA guidance (e.g., RACT and 
34

BACM53), and as defined in the dictionary means to regulate or to 

reduce the incidence or severity.54 Thus the meaning of the word 

“control” undeniably differs from the words “eliminate” or 

“prevent.” Therefore, to meet the “not reasonably controllable 

or preventable” criterion in 40 CFR 50.1(j), states must 

demonstrate that reasonable controls were implemented to regulate

or reduce emissions regardless of whether the controls would have

prevented exceedances.55 Finally we note that the relevance of 

dust controls is inherent in the District‟s own characterization 

of the “event” as the combination of wind and dust entrainment 

from anthropogenic and nonanthropogenic sources.56 

As discussed in our 2009 EE decision, the State failed to 

demonstrate that reasonable controls were implemented for 

anthropogenic sources contributing to the exceedances, including 

recreational OHVs and fallow agricultural fields.57 Nor does ARB 

or ICAPCD provide convincing evidence in the NEDs or elsewhere to

 

53 “BACM is the maximum degree of emissions reduction of PM10 and 

PM-10 precursors from a source... which is determined on a caseby-case basis, taking into account energy, environmental, and 

economic impacts and other costs, to be achievable for such 

source through application of production processes and available 

methods, systems, and techniques for control of each such 

pollutant.” General Preamble Addendum at 42010.

54 Merriam-Webster‟s Ninth New Collegiate Dictionary.

55 Similarly, EPA explained in the preamble to the EER that 

analysis of exceptional events includes consideration of whether 

anthropogenic activities have been controlled to the extent 

possible through use of all reasonably available reasonable and 

appropriate measures. 72 FR 13560, 13566, footnote 11.

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

57 2009 EE decision, section 4.2.
35

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 of EPA‟s action would be to require control measures 

beyond the area‟s practical abilities – a result the EER is 

specifically designed to avoid. ICAPCD claims that other 

specific provisions are in place to prevent such difficulties, 

and ICAPCD quotes from EPA guidance: “if emissions from 

anthropogenic sources are reduced to the point that it is no 

longer technologically or economically feasible to reduce those 

emissions further, and the area still cannot attain the NAAQS, 

the EPA may consider waiving the serious area attainment date and

appropriate serious area requirements.”58

Response: The provisions to which ICAPCD refers are 

contained in CAA section 188(f) which authorizes EPA to waive 

subpart 4 requirements applicable to serious PM10 nonattainment 

areas, including BACM, where EPA determines that anthropogenic 

sources of PM10 do not contribute significantly to the violation 

of the standard in the area. Under section 188(f), EPA may also 

waive a specific date for attainment of the PM10 standard if the 

Administrator determines that nonanthropogenic sources contribute

significantly to a violation of the standard. 

In guidance, EPA has established the same test for 

 

58 General Preamble Addendum at 42008.
36

determining what constitutes a significant contribution for 

section 188(f) as is used for determining the sources for which 

BACM must be implemented under CAA section 189(b)(1)(B).59 The 

passage in the guidance, quoted in isolation by ICAPCD, is 

preceded by a lengthy discussion regarding the circumstances 

under which a serious area such as Imperial County could qualify 

for section 188(f) waivers. That discussion makes clear that 

before EPA will consider waiving a serious area attainment date 

and requirements for a serious area that failed to attain the

standard by the serious area deadline, the state must demonstrate

that BACMs for significant anthropogenic sources have been 

implemented and that the area cannot attain the NAAQS with the 

implementation of additional control measures to achieve at least

5% annual emission reductions pursuant to CAA section 189(d). As

discussed above and in the proposal,60 ICAPCD has not shown that 

BACM has been implemented as required by CAA section 189(b)(1)(B)

for all significant source categories in Imperial County.61 Thus 

 

59 Id. at 42004. 

60 75 FR 8008, 8010-8012 and proposal TSD, pp. 7-11.

61 The 2009 PM10 SIP for Imperial County that is intended to 

address the 5% requirement in CAA section 189(d) was adopted by 

ICAPCD in August 2009 but has not been submitted to EPA by ARB. 

The plan concludes that the area would have attained the PM10

standard by the end of 2008 but for transported emissions from 

Mexico and with the “exclusion of PM10 measurements affected by 

high-wind exceptional events.” As a result of the claimed 

exceptional events, with which we did not concur in our 2009 EE 

decision, the plan also concludes that “[t]he 5% yearly emission 

reductions requirement does not apply to future years.” 2009 

PM10 SIP, section 5.3. 
37

it would be difficult to show that additional controls are 

“beyond the area‟s practical abilities” or “no longer 

technologically or economically feasible” without a more thorough

BACM analysis. 

EE #3: ICAPCD (Attachment) believes, citing the preamble to

the EER, that the rule only requires reasonable controls for 

anthropogenic sources within the state.

Response: While Imperial County air quality may be affected

by emission sources from areas outside California, such as 

Arizona and Mexico, our 2009 EE decision relies on the lack of 

demonstrated controls for anthropogenic sources within 

California. 

EE #4: ICAPCD (Attachment) believes that EPA has not 

specified criteria for defining de minimis anthropogenic sources 

in the EER context, explained how the EER justifies such 

criteria, or described feasible analyses to implement such 

criteria. 

Response: As noted above, our 2009 EE decision stated that 

inherent in the “not reasonably controllable or preventable” 

criterion of the definition of “exceptional event” in 40 CFR 

50.1(j) “is a requirement that the state demonstrate that 

anthropogenic sources contributing to the exceedance caused by 

the event were reasonably controlled.” We also suggested that 

this requirement be limited to “all non-de minimis anthropogenic 
38

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 of BACM is required

in serious PM10 areas such as Imperial County under section 

189(b) of the CAA, it is appropriate to consider that level of 

control in evaluating whether reasonable controls are in place 

for purposes of the Exceptional Events Rule.” Specifically, 

ICAPCD argues that (1) such a standard would create a new 

standard for exceptional event showings that is inconsistent with

the language and intent of the EER which entails only 

“reasonable” and not “best” control of anthropogenic sources; (2)

the purpose of the EER is to protect states from consequences of 

reclassification as a result of exceptional events; (3) by 

definition, exceptional events fall outside the normal planning 

process and their analysis should not depend on elements of the 

normal planning process including designation status; and (4) the

meaning of “reasonable controls” for the EER should not vary by 

an area‟s nonattainment status and should not be as stringent as 

BACM. 

 

62 2009 EE decision, section 4.2
39

Response: As stated in our 2009 EE decision and in the 

preamble to the EER, EPA addresses the EER criteria, including 

that the event must be “not reasonably controllable or 

preventable,” on a case-by-case basis considering the weight of 

available evidence.64 Thus it is appropriate to consider the 

totality of circumstances in Imperial County in determining what 

constitutes “reasonable” controls. We note again that the County 

has been designated nonattainment and classified as moderate or 

serious since 1990. The area was reclassified to serious in 2004.

In evaluating rules as RACM or BACM, EPA has long considered

it appropriate to consider local conditions since what is 

technologically and economically feasible in one area may not be 

in another.65 Moreover, EPA‟s 2009 EE decision did not define 

reasonable control as BACM in all cases or suggest that the EER 

mandates such an outcome. Rather, we stated that “[b]ecause 

implementation of BACM is required in serious PM10 nonattainment 

areas such as Imperial County under CAA section 189(b), it is 

appropriate to consider that level of control in evaluating 

whether reasonable controls are in place for purposes of the 

Exceptional Events Rule.”66,67 While ICAPCD states that this is 

 

63 See id., section 4.2.1.

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

65 See 57 FR 13498, 13540-13541 (April 16, 1992) and the General 

Preamble Addendum at 42010.

66 2009 EE decision, section 4.2.2; 72 FR 70222.

67 We note that in EPA‟s Natural Events Policy which applied 

prior to the EER, we stated that “BACM must be implemented at 
40

inappropriate reliance on the normal planning process, an area‟s 

nonattainment designation and classification are inherently part 

of the local conditions that are appropriately factored into what

controls are reasonable for purposes of the EER. We also noted 

that ARB had failed to demonstrate any meaningful analysis of 

BACM or any other level of control for either OHVs or fallow 

fields, despite apparent significant emissions and available 

controls imposed elsewhere.68 

EE #6: ICAPCD (Attachment) comments that OHV emissions were

quantified in the 2009 PM10 SIP at EPA‟s request, but EPA ignored 

this information in its analysis of the exceptional event 

requests. 

Response: It is the responsibility of the State to submit 

demonstrations addressing the EER criteria69 to support its 

exceptional event requests and it is generally not appropriate or

feasible for us to correct NED deficiencies by searching for 

additional information. Nonetheless, we did review the 2009 PM10

SIP before preparing the 2009 EE decision and did not ignore 

 

contributing anthropogenic sources of dust in order for PM-10 

NAAQS exceedances to be treated as due to uncontrollable natural 

events under this policy.” This requirement applied to moderate 

areas which otherwise would not have been required to implement 

BACM at all as well as to serious areas. Thus, while the EER does

not include such a mandate, it is entirely appropriate and 

consistent with the Agency‟s past practice to consider a BACM 

level of control in assessing whether reasonable controls are in 

place. Memorandum from Mary D. Nichols, EPA, “Areas Affected by 

PM-10 Natural Events,” May 30, 1996, p. 5. 

68 2009 EE decision, pp. 9-10.
41

ICAPCD‟s efforts to quantify OHV emissions in the 2009 PM10 SIP. 

In fact, the 2009 EE decision references these efforts which 

undermine the assumption in the NEDs70 that windblown dust from 

desert areas is entirely from non-anthropogenic 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 of reasonable controls in documentation supporting

exceptional events requests. It is possible that ICAPCD/ARB may 

be able to demonstrate in support of future exceptional events 

requests that OHV sources are de minimis, that there are no 

reasonable controls for OHVs under certain circumstances (e.g., 

certain illegal uses), and/or that existing regulations 

constitute reasonable controls. The 2009 EE decision, however, 

explains that the NEDs did not provide meaningful analysis of any

level of control for OHVs, and that such analysis should include 

as a starting point evaluation of EPA‟s RACM guidance72 and 

regulations adopted elsewhere under similar conditions.73

EE #8: ICAPCD (Attachment) comments that sand dunes are 

 

69 40 CFR 50.14(c)(3).

70 E.g., June NED, p. 2.

71 E.g., 2009 EE decision, footnotes 12, 15 and 16.

72 57 FR 18070, 18072 (April 28, 1992).

73 2009 EE decision, pp. 8-9.
42

naturally fully disturbed and that the 2009 PM10 SIP 

conservatively projects that OHVs contribute only 0.9 tpd (10%) 

to the total windblown emissions from them. Other commenters 

similarly question EPA‟s assumption that OHVs disturb desert 

crust. OWD, for example, notes that dune laminae are often 

mistaken for a crust but are broken by wildlife, foot traffic and

high winds. 

Response: We agree that effective control of fugitive dust 

is more difficult for the sand dunes than for other parts of 

Imperial County with different soil types. As a result, the 

State may be able to demonstrate in support of future exceptional

events requests, or for other CAA purposes such as section 

189(b)(1)(B) BACM, that dust control for dunes should be 

different from and/or less stringent than controls required for 

other areas with different soil types. However, the September 

NED failed to provide meaningful analysis of reasonable OHV 

controls for the sand dunes or any other areas. This comment has

no bearing on the April and June NEDs because the sand dunes were

not implicated by those events. 

EE #9: ICAPCD (Attachment) comments that OHV activity and 

related direct PM10 entrainment should have been negligible 

because of the high winds during the April 12 and June 5, 2007 

events and thunderstorms on September 2, 2006. OWD notes that 

two of the exceedance events occurred during the OHV off-season 
43

and the third occurred in April, when OHV use is also low. 

Similarly, BLM comments that OHV use is lowest when dust 

potential is highest (June through September).

Response: Our 2009 EE decision appropriately relies on OHV 

emission information from the NEDs and the 2009 PM10 SIP which 

estimate large windblown dust emissions and significantly smaller

directly entrained emissions.74 Thus, even if no OHVs operate 

and entrain dust on any exceedance days, previous75 OHV activity 

still contributes to PM10 emissions by disturbing surfaces that 

subsequently emit windblown dust. As a result, documentation 

supporting future Imperial County exceptional events requests for

events with significant emissions from OHV areas should include 

analysis of reasonable controls for OHVs even if there is no OHV 

activity during the exceedances.

EE #10: ICAPCD (Attachment) comments that Regulation VIII 

agricultural controls are well beyond the reasonableness level 

required in the EER. ICAPCD further states that it and ARB have 

discussed agricultural controls with EPA for many years, worked 

with EPA during development of the 2005 BACM analysis, closely 

modeled Rule 806 on SJVUAPCD Rule 4550 which EPA approved in 

2004, and received EPA testimony in 2005 that Regulation VIII, 

including Rule 806, fulfilled BACM. ICAPCD also points out that 

 

74 E.g., 22 tpd windblown and 1.34 tpd entrained emissions, 2009 

EE decision, p. 9.
44

the emission inventory in the plan shows that agricultural lands 

are significantly less emissive than most of the non-populated 

areas in Imperial County. 

Response: Our 2009 EE decision explains that neither 

Regulation VIII nor any other programs require any level of 

emissions control of certain fallow fields in Imperial County.76

Though ICAPCD comments that emissions from agricultural fields 

are smaller than emissions from other sources in the County, the 

NEDs for the exceptional events requests do not identify any 

anthropogenic sources as being de minimis. Rather, there are 

summary explanations that anthropogenic sources are reasonably 

controlled through Regulation VIII and other local programs.77

The only anthropogenic source discussed in any detail is 

agriculture in the April and June NEDs. These NEDs rely on the 

Imperial Irrigation District‟s (IID) fallowing program as the 

basis for claiming that reasonable measures were in place for 

fallow fields which are not subject to ICAPCD‟s Conservation 

Management Practices (CMP) Rule 806.78 However, there were

approximately 32,000 fallow acres in Imperial County in 2007 that

were not subject to either Rule 806 or IID‟s program which is 

more than the approximately 18,000 acres that were a part of 

 

75 Particularly recent activity where there has not been time or 

conditions to repair surface crusts.

76 2009 EE decision, section 4.2.3.

77 April and June NEDs, pp. 13-14, and September NED, p. 18.

78 April and June NEDs, p. 13.
45

IID‟s program in 2007.79 As explained in our response to comment 

EE #5, we stated in our 2009 EE decision that it is appropriate 

to consider a BACM level of control in evaluating whether 

reasonable controls are in place for purposes of the EER in 

Imperial County. However, EPA found no meaningful analysis of 

BACM or any other level of control for fallow land outside of 

IID‟s program referenced or provided in the NEDs. 

EE #11: ICAPCD (Attachment) comments that EPA‟s 2009 EE 

decision fails to mention Rule 806 in the discussion of controls 

for agricultural lands. ICAPCD notes that fallowed land issues 

were included in the 2005 BACM analysis80 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 

2009 EE decision.81 Although the 2005 BACM analysis includes 

incidental references to fallow lands, neither it nor the NEDs 

attempts to quantify the fallow acreage in Imperial County. Nor 

has the State demonstrated how any existing windblown dust 

controls might constitute BACM for fallow fields outside of IID‟s

program. 

3. High/Unusual Wind Events

EE #12: Comite agrees with EPA‟s disapproval of ARB‟s 

 

79 2009 EE decision, p. 9.

80 “Draft Final Technical memorandum: Regulation VIII BACM 

Analysis,” October 2005 (2005 BACM Analysis).
46

request to exclude the monitored exceedances as exceptional 

events. In support of our disapproval the commenter makes 

several arguments: 1) that there is no statutory or regulatory 

authority which allows windblown dust from land that has been 

disturbed by human activity to be considered “natural;” 2) that 

while the final rule includes specific language regarding the 

treatment of anthropogenic emissions associated with fireworks 

and prescribed burns, it does not include special provisions for 

anthropogenic sources affected by the wind; 3) that the portion 

of the preamble which suggests dust from anthropogenic sources 

may be treated as natural events in certain circumstances was a 

drafting error and is legally null; 4) where the Act does allow 

for consideration of human activity, it is limited to activity 

that is unlikely to recur at a particular location and 

agriculture does not meet that definition; and 5) regardless of 

whether a high wind event is classified as “natural” or “human 

activity,” such an event exists only where the wind is 

objectively a “high wind” and sufficiently high to cause a 

monitored violation even in light of the implementation of 

whatever measures are “necessary” to protect public health under 

CAA section 319(b)(3)(A)(iv). 

Response: Comite‟s support for our decision not to concur 

with the State‟s exceptional events claims is noted. We agree 

 

81 2009 EE decision, p. 9.
47

with Comite that the events in question are not due to human 

activity that is unlikely to recur and that the State failed to 

demonstrate that the events qualify as natural events. However 

our conclusions with respect to natural events are not based on 

all of the legal arguments proffered by the commenter. We also 

are not relying on that portion of the preamble that the 

commenter correctly points out is a legal nullity82 and instead, 

where appropriate, we rely on and cite to other parts of the 

preamble regarding natural events and high winds that remain 

applicable. While EPA‟s views of the statute and the EER differ 

from Comite‟s, we need not address Comite‟s arguments in detail 

because its intent was clearly to support the outcome we have 

reached regarding the exceptional events claims.

EE #13: Comite cites additional support for nonconcurrence 

with the State‟s 2007 exceptional events requests beyond what was

relied upon by EPA, namely that wind speeds were not shown to be 

“exceptional” for the area or "unusual" since the State relied on

flawed comparisons to average wind speeds.

Response: For the 2006 events, the State did not assert that 

the winds were unusually high. For both sets of 2007 events, the

evidence provided by the State did lead EPA to conclude that 

winds were unusually high.83 However, EPA's 2009 EE decision did 

 

82 NRDC v. EPA, 559 F.3d 561, 565 (D.C. Cir. 2009)

83 2009 EE decision, pp. 19-20.
48

not rely on the State‟s conclusions about unusual winds for any 

of the exceedances and we note that this commenter does not 

disagree with EPA's conclusions on the exceptional events, or 

with EPA's proposed limited disapproval of Regulation VIII.

4. Clear Causal Relationship

EE #14: Comite agrees with EPA that the State did not 

demonstrate there was a clear causal relationship between the 

exceedances and the events that are claimed to have occurred, as

required under the EER. With regard to the 2007 exceedances, the

commenter cites the lack of sufficiently detailed source 

attribution data. With regard to the 2006 exceedances, the 

commenter concludes that the proximity and nature of the 

thunderstorms that occurred in northwest Mexico made them 

“unlikely” to be the cause of the winds at Calexico. This 

commenter also believes that the possibility of any winds 

associated with thunderstorm activity north of the County being 

the cause of the Westmorland exceedance is “problematical at 

best.” 

Response: Comite‟s agreement with EPA‟s 2009 EE decision 

regarding the 2006 and 2007 exceedances is noted.

EE #15: ICAPCD (Attachment) objects to EPA‟s analysis of a 

section of the ARB documentation that compares September 2, 2006 

to other days with similar meteorological conditions in order to 

establish a causal relationship between the claimed high wind 
49

event and the Calexico exceedances on September 2, 2006. ICAPCD 

also rejects EPA‟s concerns regarding the effect of emissions 

from OHVs and fallow fields on the September 2, 2006 Calexico 

exceedances. ICAPCD concludes that EPA‟s lack of sound technical 

understanding regarding the meteorological evidence and OHV and 

agricultural emissions led EPA to erroneously reject the State's 

finding of a “clear causal relationship” for the September 2, 

2006 Calexico exceedances. 

Response: In its documentation supporting its exceptional 

events request, the State compared PM10 concentrations on 

September 2, 2006 to those on fifteen other days that had similar

meteorology at Calexico.84 The PM10 concentrations on most of the 

days were low, but on August 18, 2002, August 19, 2003 and 

September 2, 2006 the PM10 concentrations were high. The 

concentrations on these days in 2002 and 2003 are described in 

attachments to the State's Natural Events Documentation85 as 

being due to transport from Mexico under high wind conditions, 

and these conditions are stated to be meteorologically different 

than the other days at locations other than Calexico itself. 

Thus winds at Calexico were similar for all sixteen days, but on 

 

84 September NED, pp. 12-14.

85 September NED, p. 12, and Attachment G, "179B(d) „But For‟ 

Analyses – High-Wind Events from Mexico", excerpt from Technical 

Support Document: Exclusion of PM10 Measurements in Excess of the

24-Hour PM10 NAAQS for Imperial County from 2001 through 2003 Due

to Natural Events and Emissions from Mexico, Volume I of II, 

ENVIRON International Corporation, November 2004.
50

these specific days the wind elsewhere and the Calexico 

concentrations are higher. The State considered this to be 

evidence of an association or causal relationship between high 

wind elsewhere and high Calexico concentrations. 

While we acknowledge that we misinterpreted the above 

portion of the State‟s argument in our initial analysis, our 

ultimate conclusion remains unchanged. As we discussed in our 

2009 EE decision,86 the State‟s argument is flawed because there 

were in fact no high wind measurements on September 2, 2006; 

instead, the State merely assumed that wind speeds increased to 

the east. As a result, the association between the winds and 

concentrations that was seen for the events in 2002 and 2003 may 

not reflect what occurred on September 2, 2006. Thus our 

original conclusion is still valid because the fact remains that 

ARB‟s argument is founded on speculation. As we explained in our

2009 EE decision,87 such speculation is not adequate to establish 

a clear causal relationship. 

Furthermore, as also discussed in our 2009 EE decision,88

significantly lower PM10 measurements in neighboring Mexicali 

contradict ARB‟s assertion that the September 2, 2006 Calexico 

exceedances were caused by windblown dust from a large-scale, 

regional event that originated to the south or southeast of 

 

86 2009 EE decision, pp. 11 and 15.

87 Id. at p. 11.

88 Id. at p. 12.
51

Calexico. Such an event would have affected both Calexico and 

Mexicali. ICAPCD itself concedes that its explanation for the 

Calexico exceedances does not account for the difference in the 

PM10 concentrations 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 that EPA should accept the long range transport argument

because it is the most plausible one.90 To do so would be to 

make a decision based on a predetermined outcome rather than 

reliable scientific data that establish a clear causal 

relationship as required by the EER. 

ICAPCD‟s next objection to our analysis of ARB‟s exceptional

event request with respect to the September 2, 2006 Calexico 

exceedances is that EPA's concern regarding OHV and agricultural 

emissions91 is not relevant because there are no OHV or domestic 

agricultural lands south, southeast or south-southeast of the 

Calexico monitors. EPA disagrees. The September NED states that

the “source of the PM10 that impacted the Calexico stations 

corresponds to lands east and southeast of the Mexicali 

stations...”92 In fact, as shown in the TSD for this final 

 

89 ICAPCD Attachment A, Appendix A-1.

90 Id.

91 2009 EE decision, p. 14.

92 September NED, p. 15.
52

action,93 there is agricultural land immediately east of 

Calexico.94 As also shown in the final TSD,95 the southern end of 

the Imperial Sand Dunes OHV area is also directly east of 

Calexico, though it is admittedly farther away. Thus 

consideration of these sources was not inappropriate.

In summary, we are not persuaded by the above comments and 

we reject the allegation that we did not have a sound technical 

understanding of the claims ARB made as to the cause of the 

exceedances. We therefore reaffirm our conclusion that ARB not 

only failed to demonstrate that a high wind event occurred, but 

also that there was a clear causal relationship between the 

alleged event and the September 2, 2006 exceedances at the 

Calexico monitoring stations.

EE #16: ICAPCD (Attachment) states that EPA mischaracterized

some evidence and inappropriately dismissed other evidence 

provided by the State regarding a causal relationship between the

claimed high wind event and the Westmorland exceedance on 

September 2, 2006, and that this led EPA to erroneously reject 

the State's finding of a clear causal relationship. The comment 

has three parts, relating to alleged EPA mischaracterizations of 

 

93 “Technical Support Document for EPA‟s Notice of Final 

Rulemaking on Revisions to the California State Implementation 

Plan, Imperial County Air Pollution Control District Regulation 

VIII – Fugitive Dust Rules 800-806” EPA Region IX, June 2010 

(final TSD), Figure 1.

94 Similar land use maps were provided in Figure 3 of both the 

April and June NEDs.
53

the timing of high winds, direction of thunderstorm travel, and 

wind trajectories. 

Response: In response to this comment, we have again 

reviewed the wind data provided in the September NED and, as 

explained further below, we believe our original conclusion in 

our 2009 EE decision remains correct, i.e., that the data 

presented by ARB did not demonstrate a clear causal relationship 

between the claimed high wind event and the Westmorland 

exceedance on September 2, 2006.

The first part of ICAPCD‟s comment focuses on a statement 

made by EPA that the increased wind at Oasis toward Westmorland 

was simultaneous with the concentration spike that occurred at 

Westmorland during the 19th hour rather than an hour or two 

before, as would be necessary based on the distance between the 

two locations.96 We agree with the comment that the increased 

wind at Oasis did in fact occur the hour before the concentration

spike. In addition, we stated that this wind was directed toward

Westmorland when in fact it was directed toward the eastnortheast. 

ARB presented the wind speed and direction data in a tabular

format that is difficult to interpret.97 To more clearly 

articulate why we do not believe these data show a clear causal 

 

95 Final TSD, Figure 1.

96 2009 EE decision, p. 16.

97 September NED, Tables 1 and 2, and Figure 19.
54

relationship between the event and the exceedance, we have 

presented the data in the final TSD in a visual form that is more

readily understood.98 The arrows represent the wind directions 

at Indio, Oasis, Salton Sea West, and Westmorland during each of 

the four color-coded hours (e.g., all of the yellow arrows 

represent the wind direction during hour 17, etc.). The numbers 

above each arrow represent the wind speed for that hour, and the 

numbers below the Westmorland arrows represent the PM10

concentration. The data show that the PM10 concentration spike 

occurred during hour 19.

ARB claimed that thunderstorm outflows on September 2, 2006 

led to high wind locally to the northwest and northeast of 

Imperial County, and that dust generated there was carried to 

Westmorland. More specifically, ARB stated the following:

Very high winds were observed at the 17th and 18th hours

north of Imperial County, both to the west (in particular at

the Oasis CIMIS station, see Table 1) and to the east (see 

measurements at the Blythe, Ripley, and Palo Verde stations,

Table 1). These strong winds were of very short duration and

of changing direction..., consistent with the collapse of one 

or several thunderstorm cells north of Imperial County....Very

sharp peaks in PM10 concentrations were also observed at the 

19th hour at the Brawley and Westmorland stations (and to a 

 

98 Final TSD, figure 2.
55

lesser extent at the Niland station), and appear to be longrange effects of the same events (i.e. collapsing 

thunderstorm to the north of Imperial County)....[A]n analysis

of wind direction at select stations between the 18th and 

20th hours indicates that northwest winds (e.g. 6 p.m. at 

the SSW and Indio stations, 7 p.m. at Oasis and Indio, and 8

p.m. at Indio) and east-northeast winds (e.g. 7 p.m. at the 

Niland and SSE stations) likely carried air containing 

elevated PM10 concentrations from areas northwest and 

northeast of Imperial County stations toward the stations. 

(Emphasis added).99

ARB‟s explanation first points to the “very high” winds (of 

23.2 mph) recorded at the Oasis station and the northwest winds 

at Salton Sea West during the 18th hour as factors that 

contributed to the exceedance. As a preliminary matter, we 

note100 that no particular wind speed has been established as 

“high” for Imperial County. Further, winds with an average speed

of 23.2 mph are not what we would consider “very high” in the 

generally accepted meaning of the term. With the exception of 

this value, the data in Figure 2 of our final TSD show that the 

winds in this area were not very elevated.101 We also note that 

 

99 September NED, pp. 10-11. 

100 As we did in our 2009 EE decision, pp. 15 and 19.

101 EPA received comments on its proposed EER which stated that 

we should replace the term “high winds” with the term “wind-
56

the winds at Oasis during the 18th hour had a northerly component 

rather than a southerly one, and while it is true that the winds 

at Salton Sea West were blowing toward Westmorland at this time 

and that these winds could have contained some of the dust that 

may have been generated in the Oasis area, the winds at 

Westmorland were blowing in almost the opposite direction. It is

thus unclear how much, if any, dust generated at Oasis during the

18th hour was actually transported to Westmorland. 

ARB also points to the 7 pm winds at Oasis (hour 19) as a 

contributing factor. While these winds were directed toward 

Westmorland, the winds at Salton Sea West had a distinct westerly

component so it is not clear that the winds at Oasis continued on

this path past Salton Sea West. In addition, as for the previous

hour, the winds at Westmorland were blowing counter to the wind 

at Oasis and it is again not clear that any dust generated north 

of Imperial County was transported to Westmorland during this 

hour as ARB claims. 

The State finally points to the 8 pm winds at Indio as a 

contributing factor. We find it unlikely that these winds made a

significant contribution to the exceedance at Westmorland given 

that they were recorded after the concentration spike occurred 

 

generated dust.” In response to those comments, EPA explained in

the final EER that the Agency chose to retain the original 

language because it accurately connotes the type of natural event

that should be excluded under this rule and it serves as an 
57

and that the winds at Oasis, Salton Sea West, and Westmorland all

had northerly components that ran counter to the winds at Indio. 

As stated in our 2009 EE decision,102 and as ARB stated in 

the paragraph quoted above, the winds northwest of Imperial 

County (particularly around the Oasis and Salton Sea West areas) 

were variable in speed and direction. This variability is 

inconsistent with ARB‟s hypothesis that the winds remained at an 

elevated speed and along a straight line over the 45 mile 

distance between Oasis and Westmorland for an hour or more. Thus

it is anything but clear that dust generated northwest of 

Imperial County caused the exceedance at Westmorland. As a 

result, EPA‟s minor errors regarding the timing and direction of 

the winds at Oasis do not undermine the Agency‟s conclusion that 

the contradictory evidence does not support a finding of a clear 

causal relationship.

The second part of ICAPCD‟s comment on the causal 

relationship regarding the Westmorland exceedance argues that the

speed and direction of the increased winds (27.0 mph) recorded at

the Palo Verde station during hour 17 are consistent with 

transport to Westmorland and that the uncertainty of the precise 

location of the thunderstorms in time is not relevant to a cause 

and effect analysis. The commenter further states that EPA does 

 

indicator concerning the level of wind that caused the 

exceedance. See 72 FR 13560, 13566. 

102 2009 EE decision, p. 16.
58

not appear to argue that the wind speed or direction is 

inconsistent with transport of dust from Palo Verde to 

Westmorland. 

While we agree with the commenter that the winds at Palo 

Verde (which is separated from Westmorland by a north-south 

distance of about 24 miles) were directed toward Westmorland 

during the 17th hour, the winds at Westmorland were consistently 

from the south-southeast, southeast, and east-southeast 

directions beginning at the 6th hour and lasting until the end of 

the day. While it is remotely possible that the winds that 

occurred at Palo Verde during the 17th hour led to the transport 

of dust to Westmorland, the EER requires a demonstration of a 

clear causal relationship and the limited data available do not 

rise to that level. 

We also disagree with the commenter that the location of the

thunderstorms over time is not relevant to a cause and effect 

analysis. The EER explicitly mentions the use of data that show 

the relationship in time between the event, transport of 

emissions, and recorded concentrations in exceptional event 

demonstrations.103 Furthermore, in this case, ARB‟s basic premise 

is that “thunderstorm activity caused strong outflow winds over 

areas in close proximity to Imperial County monitors...[which 

contributed] to the elevated PM10 concentrations that were 

 

103 72 FR 13560, 13573. 
59

recorded in Imperial County on that day.”104 ARB could have 

attempted to provide more support for its case by, for example, 

considering whether historical radar data showed thunderstorms 

were at various locations around the time the high winds 

occurred. 

Given the level of uncertainty as to the cause of the 

concentration spike at Westmorland during the 19th hour and the 

statutory requirement that EPA‟s exceptional events regulations 

be based on the principle that protection of public health is the

highest priority,105 we are again led to the conclusion that the 

data before the Agency does not establish a clear causal 

relationship between the exceedance and the event that is claimed

to have occurred. 

The third part of ICAPCD‟s comment regarding causal 

relationship for the Westmorland exceedance criticizes EPA's use 

of wind trajectories from the HYSPLIT model since it is expected 

to capture the underlying flow pattern but may not be able to 

capture the direction of short-lived high winds that could 

transport dust from the north to Westmorland. 

EPA acknowledges that the HYSPLIT model uses meteorological 

data with relatively coarse resolution, e.g., a 40 km grid, and 

that there may be short-lived or local deviations from the 

overall wind flow. However, it remains true that the HYSPLIT 

 

104 September NED, p. 2. 
60

back-trajectories are inconsistent with transport from northern 

stations since they show winds from the south.106 The HYSPLIT 

data simply add to the list of inconsistencies in the State's 

explanation. In addition, ICAPCD‟s suggestion that the high 

winds were "short-lived" is inconsistent with ARB‟s hypothesis of

straight line transport from the Oasis or Palo Verde stations for

an hour or more over the 45-55 mile distance to Westmorland. 

Thus EPA disagrees with this comment.

EE #17: ICAPCD (Attachment) makes an additional two-part 

comment about the causal relationship claim for the September 2, 

2006 exceedances at both the Calexico and Westmorland monitoring 

stations. In order to buttress its argument that these 

exceedances were not the result of recurring anthropogenic 

sources within Imperial Valley, ICAPCD first states that it is 

extremely unlikely that all monitors in the County would 

simultaneously have had unusually high PM10 concentrations if the 

causes were local to the monitors. The second part of the 

additional comment states that since there were no high winds 

throughout Imperial Valley on September 2, 2006, the cause of the

exceedances could not have been unpaved roads or agricultural or 

OHV land within the Valley. 

Response: With respect to the first part of ICAPCD‟s 

comment, EPA acknowledged the elevation of PM10 at all monitors, 

 

105 See CAA section 319(b)(3)(A)(i).
61

but did not take a position on whether the causes were local or 

regional.107 Rather, we concluded that a clear causal 

relationship had not been demonstrated since the regional sources

alleged by ARB to be the cause were not identified. Related to 

this lack of identification of the contributing sources, EPA 

found that the State did not demonstrate that the event was not 

reasonably controllable or preventable as there was no attempt to

analyze controls on the non-local sources. Thus this comment 

does not affect our decision to not concur with the State‟s 

exceptional event claims.

With respect to the second part of ICAPCD‟s comment, as 

discussed above, the State argued that high winds associated with

thunderstorm activity led to the generation of dust north of the 

County, which was then transported to the Westmorland monitor. 

Even though agricultural land and other anthropogenic sources do 

exist in areas north of the County including Oasis,108 where the 

State claimed winds were high, the State made no attempt to 

analyze controls on contributing sources outside the County in 

order to address the EER requirement that the event must be “not 

reasonably controllable or preventable.” Thus, this requirement 

was not met even if the commenter‟s arguments regarding transport

were correct. With respect to the Calexico exceedances, the 

 

106 2009 EE decision, p. 17.

107 2009 EE decision, p. 14.

108 See Figure 1 in the final TSD.
62

State speculated that high winds occurred east and southeast of 

Calexico based on extrapolation of a west to east trend of 

increasing wind speed. The same argument could have been used to 

conclude that there was high wind east of Calexico within 

Imperial County, including over agricultural and OHV lands. 

Therefore the commenter‟s claim that there were no high winds 

throughout the Imperial County is not completely supported by the

State‟s own arguments that a high wind event occurred.

5. Concentrations in Excess of Normal Historical Fluctuations

EE #18: Comite cites additional support for nonconcurrence 

beyond what was relied upon by EPA. Specifically, the commenter 

states that numerous monitored exceedances comparable to those 

that Imperial County seeks to exclude from the data have been 

measured in the County from 2003-2007. Therefore, the commenter 

claims, the concentrations are not “in excess of normal 

historical fluctuations” as required by the rule and are not 

exceptional events. 

Response: EPA's conclusions about the requirement that the 

events be associated with measured concentrations in excess of 

normal historical fluctuations mainly relied on the 

concentrations‟ rarity relative to past measurements. For 

example, the September NED states that the 167 μg/m3 measurement 

at the Westmorland station was in the 98th percentile of all PM10

recordings at that station in the 2001-2007 time period. As 
63

explained in our 2009 EE decision,109 we found similar evidence 

that the exceedances measured on the other days in question also 

exceeded normal historical fluctuations. However, we do agree 

with the commenter that the monitoring data for Imperial County 

continue to show violations of the 24-hour PM10 standard. We 

believe that improvements to the ICAPCD‟s rules will lead to 

improvements in air quality and we note that this commenter does 

not disagree with EPA's conclusions regarding the State‟s 

exceptional events requests, or with EPA's proposal to disapprove

Regulation VIII.

6. Level of Documentation Required for EER

EE #19: ICAPCD (Attachment) takes issue with EPA‟s 

suggestions that additional data and analysis would have helped 

establish causality for the 2006 Westmorland and the 2007 events.

Specifically, ICAPCD states:

Although EPA suggests that higher levels of documentation 

for source attribution, thunderstorm activity, or 

investigation of other potential causes would be preferred, 

EPA does not suggest reasonable, technically implementable 

analyses to achieve these higher levels of documentation. We

would question what technical analyses EPA suggests should 

be conducted. We would also question whether these analyses 

and the required level of data are achievable or realistic 

 

109 pp. 25-27.
64

now or in the future for similar events in Imperial County 

and in other areas (particularly those surrounded by remote,

non-populated, non-monitored source areas), and whether 

these analyses exceed the requirements for SIP planning 

itself. EPA has not (and, we believe, cannot) propose 

reasonable, technically achievable investigations and 

analyses superior to those produced by the District and ARB 

that would address EPA's stated concerns. Thus, we find that

both EPA's conclusions on causality and EPA's position on 

the level of analysis required to demonstrate causality are 

incorrect and inconsistent with the purpose of the EER....Such

a narrow application of the EER will preclude states from 

excluding from regulatory consideration exceptional PM data 

that are completely inappropriate for inclusion in the 

normal planning process.

ICAPCD also includes a table on page A-8 which cites 

specific passages of EPA‟s 2009 EE decision pertaining to source 

apportionment, satellite imagery, and consideration of other 

causes. 

Response: Regarding the need for better source 

apportionment data, it is important to identify contributing 

sources when evaluating exceptional event claims involving 

windblown dust because it must be demonstrated that anthropogenic

sources contributing to the exceedances at issue were reasonably 
65

controlled.110 Better source identification is especially 

important in situations where we do not have confidence that all 

potential anthropogenic sources are reasonably controlled and 

where there are exceedances just above the NAAQS (such as the 

April 12, 2007 exceedance at Westmorland) which may have been 

preventable with additional controls. In addition, the inability

to identify the source of the PM emissions associated with a wind

event (i.e., the “cause” of the dust that led to the exceedance) 

hinders our ability to make affirmative findings that the “clear 

causal relationship” and “but for” provisions of the EER have 

been satisfied. A County-wide monthly average emission inventory 

such as the one used by ARB that omits some source types (e.g., 

OHVs) is insufficient for these purposes. 

While perhaps not required for all demonstrations, our 

suggestion for a wind field and a more highly resolved inventory 

are not unreasonable given ARB‟s failure in the present case to 

demonstrate that reasonable controls were in place for 

contributing sources. Moreover, a more highly resolved inventory

would provide better support for any future exceptional events 

claims involving Imperial County. Another method ARB could have 

 

110 See, e.g., 2009 EE decision, p. 7 and our responses to 

comments EE #s 1 and 4. See also 72 FR 49046, 49051 (August 27, 

2007) and 72 FR 13560, 13566, footnote 11, explaining that the 

weight of evidence approach to our analysis may consider winds 

that produce emissions contributed to by anthropogenic activities

that have been controlled to the extent possible through use of 

all reasonably available reasonable and appropriate measures.
66

potentially considered for identifying the source of the 

emissions and supporting its claim of a causal relationship is to

collect and examine pollutant species-specific information. As 

discussed in the EER preamble,111 such information may be 

available through routine speciation, monitoring networks, or 

from selective laboratory analysis of archived particulate matter

filters for the day thought to be impacted by an event. In this

case, such an analysis might have helped ascertain how much of 

the PM10 that impacted certain monitors was from agricultural 

sources versus natural desert sources.

Regarding ICAPCD‟s objection to our statement that the 

satellite imagery provided was not frequent enough to compare the

images with the timing of the concentration spike at Westmorland 

during the 19th hour,112 we note that ARB could have provided 

additional information to supplement the satellite imagery. Such

information could include, but may not be limited to radar data 

and weather observations that note the presence of blowing dust 

in areas around the monitors.

Finally, ICAPCD takes exception to our desire for better 

documentation regarding the investigation of other potential 

causes. In this regard, ARB made the following statement:113

(ICAPCD) investigated emission generating activities during 

 

111 72 FR 13560, 13573.

112 2009 EPA decision, pp 17-18.

113 September NED, p. 2.
67

this episode, and found that PM10 emissions for BACM 

controlled sources were approximately constant before, 

during and after the event. The District determined that 

the... concentrations of PM10...were instead primarily the 

result of wind-entrained dust...associated with a mesoscale 

convective system....

Although the preceding passage suggests that ICAPCD 

conducted an active investigation of other emission generating 

activities on the day of the event, this claim is largely 

unsupported except for an interoffice memo included in Attachment

H to the September NED. The memo states that various records 

were inspected in 2008 but that no inspections were conducted on 

the day of the event. We were thus left wondering how a file 

review conducted two years after the fact qualifies as an 

investigation of emission generating activities “during 

[the]episode” and how ICAPCD came to the somewhat substantial 

conclusion that emissions from BACM controlled sources were 

constant before, during, and after the event. 

E. OHV Controls

OHV #1: ICAPCD believes that EPA should have concurred with 

all of the exceptional event requests associated with high winds 

as discussed in the Exceptional Events comments summarized in 

section II.D above. As a result, ICAPCD believes that windblown 

dust from open areas is not a significant source category in 
68

Imperial County, and therefore is not subject to the BACM 

requirement as part of the SIP. 

Response: In our proposed action on Regulation VIII, we 

explained why windblown dust from open areas is treated as a 

significant source category subject to BACM.114 We have not 

received information in the comments or elsewhere that changes 

this conclusion or the related decision to not concur with the 

State‟s exceptional event requests for Imperial County. See also

responses to Exceptional Events comments in section II.D above.

OHV #2: CBD comments that BLM land is the largest PM10

source in Imperial County and should be subject to the same 

controls as adjacent land. CBD believes the Dust Control Plan 

(DCP) requirement for BLM land in Rule 800 section F.5 is 

unenforceable, in conflict with the CAA, while other areas are 

subject to more stringent Regulation VIII requirements. 

In contrast, ICAPCD believes that Rule 800‟s DCP implements 

BACM, and that Rule 800‟s exemption for BLM does not relax other 

Regulation VIII requirements. For example, Rule 800 section 

F.5.c requires BLM‟s DCP to be consistent with Rules 804 and 805 

except where otherwise prohibited, in which case section F.5.e 

requires all feasible control measures during off-road events. 

ICAPCD also notes that where there are such prohibitions, section

F.5.d requires the DCP to discuss and implement “other possible 

 

114 Proposal TSD, pp. 5-7.
69

control measures” and that Rule 800 section D.3 requires the DCP 

to be submitted to ICAPCD, ARB and EPA for review and comment and

to be updated every two years.

ICAPCD believes BLM should be treated separately in 

Regulation VIII because there are many restrictions imposed by a 

variety of laws other than the CAA that apply to actions on 

federal lands and that the District‟s involvement in these issues

would delay implementation of the PM control program on BLM 

lands. ICAPCD also believes that BLM should be treated separately

because some federal land uses preclude traditional dust controls

and because BLM‟s OHV areas are far from Imperial County 

populations. ICAPCD argues that even if Rule 800 section F.5.c 

corresponds to requirements that are less effective than those of

Rules 804 and 805, such lower stringency is both necessary and 

appropriate given the special nature of BLM lands. 

BLM agrees that many traditional BACM are not possible on 

federal land because of the large expanses of desert ecosystems. 

BLM continues evaluating the DCP, however, which has led to 

closing areas and routes to vehicle use, restoring closed 

surfaces to natural conditions, hardening high traffic areas, 

posting and enforcing speed limits, educating desert users, and 

controlling dust from non-OHV activities. 

Response: BACM is required but has not been demonstrated for 
70

OHV activity on BLM land in Imperial County.115 EPA guidance 

explains that this demonstration should include evaluation and 

documentation of the technological and economic feasibility of 

potential control measures, including implementation of measures 

on a limited basis if full implementation is not feasible. As 

stated in our guidance, “the documentation should compare the 

control efficiency of technologically-feasible measures, their 

energy and environmental impacts and the costs of 

implementation.” 116 ICAPCD‟s demonstration should include careful 

consideration of analogous controls implemented on private lands 

in Imperial County and on public lands in Maricopa and Clark 

Counties and elsewhere, as well as controls recommended in EPA‟s 

RACM guidance,117 and suggestions provided in our proposal118 and 

comments on the proposal.119

The evaluation of technological feasibility may 

appropriately consider the alleged “special nature” of BLM lands.

Such an evaluation, if conducted appropriately, may be sufficient

to demonstrate that what constitutes BACM for BLM land in 

Imperial County is different from what constitutes BACM in other 

geographical areas and for private land in Imperial County. The 

 

115 Proposal TSD, pp. 7-8. 

116 General Preamble Addendum at 42012-42014.

117 57 FR 18070, 18072.

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

119 Moreover, as stated in the General Preamble Addendum at 

42013, “any control measures that a commenter indicates during 
71

information provided in the comments and Regulation VIII 

submittal, however, is not sufficient to support such a 

distinction. For example, ICAPCD and other commenters have not 

demonstrated how existing BLM controls implement BACM in the 

Plaster City areas, which are open to OHV activity at all times, 

and, if such controls do constitute BACM, why they cannot be 

incorporated into Regulation VIII and the SIP. 

Furthermore, with regard to CBD‟s comment concerning the 

enforceability of DCPs, state and local requirements that 

implement BACM are subject to the enforceability requirement of 

CAA section 110(a). As we stated in our proposal, BACM has not 

been demonstrated for OHV sources because, among other things, 

none of the OHV restrictions are in regulatory form and submitted

for inclusion in the SIP.120 

OHV #3: OWD notes that California State Parks (CSP) manages 

OHV recreational activity in Imperial County at Heber Dunes State

Vehicular Recreation Area, Ocotillo Wells SVRA, and in an 

interdepartmental joint management agreement at the Freeman 

Properties immediately north of Ocotillo Wells SVRA and east of 

Anza Borrego Desert State Park. OWD also notes that Ocotillo 

Wells SVRA alone represents approximately 85,000 acres of managed

OHV recreational activity within Imperial County. While much of 

 

the public comment period is available for a given area should be

reviewed by the planning agency.”

120 Proposal TSD, p. 14.
72

this land is designated trail riding only and is primarily 

defined by terrain constraints, OWD states that the majority of 

the area is designated open riding, where OHVs are not limited to

defined trails. Rather than implement generalized BACM for OHV 

activity in Ocotillo Wells SVRA and other State Parks, OWD 

explains that it has adopted State mandated soil standards, a 

habitat monitoring system and other policies tailored for the 

case-by-case conditions found in each park unit. OWD believes 

that fencing, and then maintaining, a vast amount of land is 

neither economically nor environmentally feasible. OWD also 

believes that watering, laying gravel, or applying a chemical 

solution to the miles of trails that would be encompassed is 

neither economically nor environmentally feasible. In contrast, 

CBD argues that further implementation of Rule 804 and additional

OHV controls may be needed for State lands including the Ocotillo

Wells SVRA in order to attain air quality standards.

Response: Rule 804 requires all persons, including public 

entities such as CSP, with jurisdiction over open areas in 

Imperial County with over 1000 square feet of disturbed surface 

area to maintain a stabilized surface, limit opacity to 20% and 

comply with at least one of the following: (a) apply and maintain

water or dust suppressant to all unvegetated areas; (b) establish

vegetation on all previously disturbed areas; or (c) pave, gravel
73

or chemically stabilize.121 OWD‟s comment acknowledges that CSP 

has jurisdiction over open areas with over 1000 square feet of 

disturbed surface area within Imperial County. Because these 

areas are not addressed by exemptions in Rule 800 section E or 

Rule 804 section D,122 these areas must comply with the above 

requirements. However, from OWD‟s comment, CSP is clearly not 

currently complying with these requirements. As a result of the 

inclusion of Rule 804 into the SIP, these requirements will 

become federally enforceable upon the effective date of this 

final action, and such noncompliance could result in civil action

under CAA section 113 and/or 304. 

OHV #4: Various commenters argue that controls suggested in 

our proposal as part of the BACM analysis that ICAPCD still needs

to conduct would not reduce PM10 impacts from OHVs in Imperial 

County. 

Many commenters oppose further restrictions during the 

summer, claiming that OHV activity and emissions are very 

low in Imperial County due to high temperatures and existing

red sticker regulations that restrict certain vehicles 

during the summer. BLM concurs that OHV use is already 

lowest in the summer, and ICAPCD also concurs and argues 

 

121 ICAPCD Rule 804, sections B, C.29, E and F.

122 See also “Fugitive Dust Control Plan,” Bureau of Land 

Management El Centro Field Office, June 29, 2006; “Fugitive Dust 

Control Plan,” Bureau of Land Management El Centro Field Office, 
74

that OHV restrictions during the summer would burden public 

resources without reducing emissions. However, one 

commenter (0100) states that OHV use during summer nights is

a great activity which creates minimal dust because travel 

is at low speeds on established trails. Another commenter 

(0204) indicates that many promoters run OHV races at night 

that allow for fun recreational activity in cooler 

temperatures. This commenter believes night races decrease 

risks to spectators which is more important than reducing 

dust emissions. Some commenters also observe that wind 

events can occur in the summer and cause severe dust days. 

By contrast, another commenter (0146) believes that the 

desert is mainly dry and free of wind in the summer. 

ICAPCD believes that restrictions like those in place in 

Arizona, during pollution advisory days, would be 

unproductive because high-PM forecasts in Imperial County 

only occur on high-wind days when OHVs are not used. 

Many commenters (e.g., 0094) observe that OHVs are already 

restricted to certain areas, causing crowding and injuries. 

ICAPCD notes that OHVs are restricted to 11% of local BLM 

land, and additional closure would probably shift OHV 

activity and emissions to other areas nearby. OWD also 

 

January 25, 2010 Draft; email from Andrew Trouette (BLM) to 

Andrew Steckel (EPA), May 24, 2010.
75

believes EPA‟s action could force OHV users to other areas, 

causing environmental effects outside Imperial County. 

ICAPCD comments that EPA cannot demonstrate that OHV 

restrictions would reduce windblown dust emissions because 

there is no basis for EPA‟s contention that surfaces 

impacted by OHVs would form any appreciable crust given 

Imperial‟s low level of rain. OWD similarly comments that 

crust repair would be difficult due to the limited rain in 

Imperial County. Another commenter (0120) believes that 

restricting OHV areas could increase PM10 emissions because 

more vehicles in smaller areas would disturb more soil that 

cannot crust over. See also comment EE #8.

OWD comments that fencing, watering, gravelling or 

chemically stabilizing miles of OHV areas is not feasible. 

For example, water resources are scarce and modification of 

existing OHV trails could alter natural drainage patterns 

and increase erosion.

Response: EPA believes that some of the information provided 

in these comments could be relevant considerations in the 

comprehensive BACM analysis that ICAPCD needs to undertake in 

order to determine what controls constitute BACM for OHV activity

in Imperial County. However, in general, the comments are 

conclusory and not supported by data, detailed information, or 

other evidence that would be required for an adequate BACM 
76

demonstration under our guidance.123 As summarized in the 

guidance:

In summary, the State must document its selection of BACM by

showing what control measures applicable to each source 

category (not shown to be de minimis) were considered. The 

control measures selected should preferably be measures that

will prevent PM-10 emissions rather than temporarily reduce 

them. The documentation should compare the control 

efficiency of technologically-feasible measures, their 

energy and environmental impacts and the costs of 

implementation.124

Furthermore, contradictions in the comments also serve to 

illustrate that there are fundamental factual questions that need

to be addressed about the amount of OHV activity during different

seasons and different times of the day, and the best ways to 

mitigate emissions from such activities. At this juncture, 

ICAPCD has not conducted an adequate analysis. 

OHV #5: Many commenters (e.g., 0108 and OWD) state that 

further OHV restrictions would hurt the already depressed local 

economy, and cite potential effects on local business owners, 

farmers, land owners, OHV users, race car owners, construction 

companies, ranchers, the Imperial Irrigation District and others.

Commenters observe that recreational activities generate 

 

123 General Preamble Addendum at 42010-42014.
77

substantial revenue (0196), and one (0156.1) claims that OHVs 

have contributed several hundred million dollars to the local 

economy. ICAPCD believes that the economic cost of OHV activity 

restrictions is far more than appropriate for BACM. For example,

ICAPCD estimates that closing the Imperial Sand Dunes 

Recreational Area would cost $370,000 to $640,000 per ton of PM10

reductions. ICAPCD provides specific references to support its 

cost/benefit analysis. Another commenter (0219) similarly 

believes that additional OHV restrictions, such as closing land 

in the summer, would provide few benefits given the relatively 

small emissions from OHVs, but would have significant economic 

impacts.

Response: We appreciate the value of OHV tourism to the 

local economy, and agree that ICAPCD must consider economic 

feasibility in BACM analyses evaluating potential controls for 

emissions from OHV activities. However, the relevant inquiry in 

the economic feasibility analysis required in BACM determinations

is “the cost of reducing emissions from a particular source 

category and costs incurred by similar sources that have 

implemented emission reductions.”125 In this case, the cost of 

OHV restrictions on OHV area owners (i.e., the State and federal 

governments) and users would appear to be minimal, and the 

secondary economic impacts on businesses supporting OHV tourism 

 

124 Id. at 42014.
78

are not relevant to the required BACM analysis. In any event, 

ICAPCD needs to evaluate the economic feasibility of potential 

controls, including those adopted in other areas, in determining

what controls constitute BACM in this area. 

OHV #6: EcoLogic asks EPA to clarify whether and where OHV 

restrictions are being contemplated in the Imperial Sand Dunes 

Recreation Area and elsewhere and to what extent OHV activity on 

federal land is subject to the proposed rule or ICAPCD 

jurisdiction. EcoLogic and another commenter (0141) also request

clarification on which of the 250 square miles of OHV areas EPA 

is asking ICAPCD to evaluate for closure and what the basis is 

for claiming that these areas are likely to impact populations. 

Response: State and federal agencies are subject to many 

local requirements including Regulation VIII and other air 

quality related ICAPCD rules.126 Our proposal explains why ICAPCD 

must analyze whether additional controls (potentially including 

closure) are appropriate for public land in Imperial County open 

to OHVs, which ICAPCD estimates at over 250 square miles.127 We 

did not identify any specific geographic areas needing more or 

less analysis or control or having more or less impact on 

populations. Rather, in the analysis ICAPCD should consider all 

potential available OHV controls in all OHV areas in Imperial 

 

125 General Preamble Addendum at 42013.

126 See CAA section 116.

127 See, e.g., proposal TSD, pp. 8 and 13-15.
79

County and, where feasible, should consider whether different 

areas within the County have different impacts on populations or 

areas with exceedances of the NAAQS.

OHV #7: Several commenters believe additional OHV 

restrictions should be analyzed and/or incorporated into 

Regulation VIII. CBD believes that OHV requirements in Rule 804 

are too vague to be enforceable as required by CAA section 

110(a), particularly regarding BLM and State managed land. CBD 

believes Regulation VIII should require specific BACM measures, 

such as restrictions on the number of OHV vehicles operating each

day, to improve emission quantification and control. CBD 

believes such carrying capacity caps or other restrictions should

also address weather conditions when they exacerbate PM10

emissions, such as during windy weather and the summer. Comite 

comments that ICAPCD should analyze whether OHV permit 

requirements, such as those that are required in San Bernardino 

County, should be required in Imperial County. Comite also 

believes that ICAPCD should analyze controls described in the 

California State Parks Off-Highway Motor Vehicle Recreation 

Division‟s 2008 Soil Conservation Standard and Guidelines.128 

Lastly, instead of decreasing the size of OHV areas, one 

commenter (0120) suggested rotating OHV areas to help surface 

crust formation. 

 

128 Submitted as Exhibit D to Comite comment letter.
80

Response: The commenters as a group make constructive 

suggestions that would be appropriate for consideration in a 

comprehensive evaluation of BACM for this source category. We 

believe ICAPCD should analyze all potential available OHV 

controls to meet the CAA‟s BACM requirement, including those 

mentioned in the comments and those adopted in other areas, 

pursuant to EPA guidance.129

F. Definition of Disturbed Surface (DS) 

DS #1: ICAPCD believes the term “disturbed surface” is selfevident and that no questions have been raised about it since 

rule adoption. ICAPCD believes Rule 804 is clear that an area is

deemed disturbed if it shows any sign of man-made disturbance 

(e.g., vehicle traffic) and the owner/operator cannot prove that 

the area meets the characteristics of a stabilized surface. 

ICAPCD is willing to define this term more clearly during the 

next revision to Rule 101, but strongly objects to EPA 

disapproving Regulation VIII on this basis. In contrast, CBD 

supports EPA‟s concerns regarding this definition in Regulation 

VIII, and further believes the definition should be tailored to 

Imperial Valley and explicitly include open areas on BLM land 

that emit significant PM10 including the Algodones Dunes. In 

this regard, CBD suggests specific edits to SJVUAPCD‟s analogous 

rule.

 

129 See, e.g., General Preamble Addendum at 42012-42013.
81

Response: We believe the explanation provided in ICAPCD‟s 

comment is a logical interpretation of the undefined term in its 

regulation. However, we also believe that alternate definitions 

are possible (such as that recommended by CBD in its comment), 

and it is common practice to define all terms used in rules that 

are needed in order to ensure clarity and enforceability. We 

encourage ICAPCD to clarify its regulation by including an 

appropriate definition of this critical term and to consider 

CBD‟s recommendations for the wording of the rule.

G. Unpaved Road (UR) Controls 

UR #1: ICAPCD projects that control of unpaved non-farm 

roads provides 55% of Regulation VIII‟s emission reductions. 

ICAPCD believes this demonstrates a good faith effort to reduce 

PM10 emissions from road stabilization, and asserts that the 

County is trying to increase funding for such projects. ICAPCD 

states that the $2 million/year available to the County 

Department of Public Works (PWD) for road maintenance and 

stabilization reflects great needs and low availability of public

funds in the County. According to ICAPCD, this budget is for 

maintenance of 1,350 miles of paved roads which require 

resurfacing every 10-15 years, or 90 miles of extensive 

maintenance each year. Thus, ICAPCD argues that allocation of 9%

of this budget to stabilize 19 miles of unpaved road represents, 

contrary to EPA‟s assertion, the most expedited schedule possible
82

with the present level of available funding.

Response: Where economic feasibility of control depends on 

public funding, EPA will consider past funding and the future 

availability of funding sources to determine if a good faith 

effort is being made to implement BACM expeditiously.130 The fact 

that unpaved road controls provide 55% of Regulation VIII‟s 

estimated emission reductions is not in itself sufficient to 

demonstrate good faith efforts to control road dust 

expeditiously. Alternatively, for example, this high percentage 

of the total amount of reductions could occur if other sources 

are under-controlled or are less feasible to control. 

Nonetheless, EPA believes that some of the information ICAPCD 

provides in its comment on this point could help to demonstrate a

good faith effort to control road dust expeditiously. Given 

ICAPCD and Imperial County‟s limited resources, we do not believe

this analysis needs to be exhaustive, but it should be more 

thorough and documented than presented in the Regulation VIII 

submittal and this comment. For example, ICAPCD indicates in 

this comment that the County is trying to increase funding for 

road stabilization but provides no documentation to help 

establish this point. Nor has ICAPCD explained how the road 

stabilization budget was derived in light of various federal, 

State, and local (including local Measure D) funding sources for 

 

130 Proposal TSD, p. 16, and General Preamble Addendum at 42013.
83

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 is meeting its commitment to 

implement its submitted plan, which includes stabilizing 

different unpaved roads each year and maintaining all stabilized 

roads as intended by the rule.

Response: CAA section 110(a) requires that control measures 

be enforceable. While Rule 805 section E.7 requires that a 

compliance plan be submitted to ICAPCD, the rule is not clear 

about the specific requirements of the plan (i.e., that the 

County must stabilize different roads each year and must maintain

all stabilized roads) and does not contain a mandate that the 

terms of the plan be carried out. Evidence that Imperial County 

PWD is in fact currently implementing the plan is not sufficient 

to ensure enforceability as required by the CAA.132 ICAPCD should 

revise the rule to clarify this section consistent with 

enforceability requirements of CAA section 110(a). 

UR #3: Comite believes that ICAPCD should incorporate 

additional restrictions into Regulation VIII, including property 

line visible emissions (VE) limits such as those adopted by 

Maricopa County and SCAQMD, dust controls for unpaved roads 

 

131 See proposal TSD, p. 16. 
84

subject to Rule 805 section E.7, and other more stringent 

requirements adopted by SCAQMD, SJVUAPCD, Maricopa County and 

Clark County. 

Response: ICAPCD‟s analysis of BACM did consider controls 

implemented in other areas, including those adopted by SCAQMD, 

SJVUACPD, and Maricopa and Clark Counties. Our proposal TSD 

recommends several specific controls from these areas for further

consideration by ICAPCD, including imposition of a fence-line 

opacity standard.133

However, with the exception of the deficiencies identified 

in our proposal, we believe that ICAPCD sufficiently analyzed 

controls in other areas for potential BACM.134 For example, 

ICAPCD explains that SCAQMD has only a 0% fence-line opacity 

standard, whereas ICAPCD and other agencies with adopted rules 

approved as BACM all have a similar general 20% opacity standard 

applicable everywhere, and not just at the fence-line.135 ICAPCD 

claims that SCAQMD‟s 0% fence-line standard is less stringent 

than a general 20% standard. While it is difficult to compare 

the two standards,136 we do not have evidence that SCAQMD‟s 

 

132 See id., p. 9.

133 Id., p. 11.

134 2005 BACM analysis, chapter 4, and 2009 PM10 SIP, table 4.2.

135 2005 BACM analysis, p. 21.

136 For example, a 40% opacity plume in the middle of a large 

property that disperses to 0% opacity by the property fence-line 

violates ICAPCD‟s rule but not SCAQMD‟s. Conversely, a 10% 

opacity plume that disperses to 5% opacity by the fence-line 

violates SCAQMD‟s rule but not ICAPCD‟s. 
85

standard is more stringent than the general standard used by 

ICAPCD and by other air districts. 

UR #4: One commenter (0154) states that it is not feasible 

or cost effective to eliminate all dust from dirt roads. 

Response: We agree with this comment. Neither Regulation 

VIII nor our proposal or this final action assumes that dust 

emissions can be completely eliminated from farm and non-farm 

dirt roads.

H. Border Patrol (BP) Controls 

BP #1: ICAPCD comments that Rule 800 section F.6.c does not 

explicitly exempt BP from fugitive dust controls, but requires BP

to control dust from roads it owns/operates consistent with Rule 

805 except where inconsistent with BP‟s authority or mission. 

ICAPCD indicates that, while BP does not own any roads, it uses 

public roads to accomplish its mission, and some roads adjacent 

to the border are used exclusively by BP. ICAPCD states that 

most of these roads are below Rule 805‟s applicability threshold,

are located in remote areas that are for the most part restricted

to BP vehicles, and PM10 controls are not feasible and are 

inconsistent with BP‟s mission. ICAPCD explains that although BP

neither owns nor operates these roads, BP is committed to 

implement PM10 controls such as vehicle speed restrictions and 

access controls. ICAPCD indicates that since adoption of 

Regulation VIII, BP has submitted two productive DCPs. 
86

Therefore, ICAPCD disagrees with EPA‟s recommendation to remove 

or narrow the exemption for BP activities, and proposes to 

continue addressing BP through a DCP requirement to insure that 

BP continues controlling fugitive dust.

Response: First, we note that nothing in our proposal 

affects Regulation VIII‟s requirement for BP to develop and 

implement DCPs pursuant to Rule 800 sections F.6.a and F.6.b. 

However, ICAPCD‟s explanation is unclear as to whether or not BP 

operates any roads subject to the rule. If ICAPCD can support 

its assertion that BP neither owns nor operates such roads, the 

exemption in Rule 800 section F.6.c. is simply unnecessary and 

should be removed. If BP does own or operate such roads, we 

continue to believe that the exemption is unnecessarily broad and

should be removed or narrowed and demonstrated to be consistent 

with BACM requirements. 

ICAPCD offers no evidence or explanation to support its 

contention that Rule 805 requirements are potentially 

inconsistent with BP‟s authority and/or mission. We also note 

that BP has not raised concerns with our proposal, although we 

informed BP of it before publication. EPA appreciates BP‟s 

efforts to limit PM10 pollution through DCPs. Our concern, 

however, is with ICAPCD‟s Regulation VIII submittal and the lack 

of clarity in, and analysis to support, the actual provisions in 

Regulation VIII intended to govern these activities. 
87

BP #2: OWD comments that BP frequently goes off-road within 

Ocotillo Wells SVRA, beyond OWD‟s control.

Response: Rule 804 section E imposes requirements on owners 

of open areas such as Ocotillo Wells SVRA regardless of who owns 

vehicles driving on the open areas. Nothing in our proposal 

would affect these existing ICAPCD requirements.

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

Introduction 

The comments summarized in this section and sections II.J 

and K relate to ICAPCD Rule 806, Conservation Management 

Practices. In discussing our proposal regarding Rule 806, a 

number of these comments address various aspects of analogous 

rules adopted by state and local agencies in California and 

Arizona for controlling PM10 from agricultural sources. All of 

these rules are menu-based and as such divide the control 

measures, known as conservation management practices (CMPs) or 

best management practices (BMP), into three or more menus known 

as “categories.” We provide the following information on these 

rules as an introduction to inform our responses to the comments 

in this section and sections II.J and K. 

ICAPCD Rule 806, Conservation Management Practices, is a 

menu-based rule that has four categories: 

land preparation and cultivation 

harvesting 
88

unpaved roads 

unpaved traffic areas 

All persons who own or operate an agricultural operation site of 

forty acres or more are required to implement one CMP from each 

of these categories. Table 3 summarizes the relevant categories 

from Rule 806 and the other menu based rules to which we refer: 

Table 3 

State or Local

Agency Rule Area

Categories 

for

On-field 

Agricultural 

Operations 

Categories 

for Unpaved 

Ag. Roads 

and Traffic 

Areas

Imperial County

APCD (ICAPCD) 806 Imperial County

▪Land 

Preparation 

and 

Cultivation 

(including 

tillage)

▪Harvesting

▪Unpaved 

Roads

▪Unpaved 

Traffic 

Areas

San Joaquin 

Valley Unified 

APCD (SJVUAPCD)

4550

San Joaquin 

Valley 

Planning 

Area137

▪Land 

Preparation 

and 

Cultivation 

(including 

tillage)

▪Harvest

▪Cropland –

Other

▪Unpaved 

Roads

▪Unpaved 

Traffic 

Areas

Arizona 

Department of 

Environmental 

Quality (ADEQ)

Arizona 

Administrative Code 

(A.A.C) R18-

2-610 and 

R18-2-611 

Phoenix 

Planning 

Area138

▪Tillage and 

Harvest 

▪Cropland 

▪Noncropland 

Great Basin 502 Alpine, Inyo, ▪Land ▪Unpaved 

 

137 SJVUAPCD‟s jurisdiction includes the entire counties of San 

Joaquin, Stanislaus, Merced, Madera, Fresno, Tulare, and Kings 

and part of Kern County. SJVUAPCD does not include the parts of 

East Kern that are not in the San Joaquin Valley Air Basin. See 

40 CFR 81.305. 

138 The Phoenix Planning Area includes Maricopa County and a 

portion of Pinal County. See 40 CFR 81.303. 
89

Unified APCD 

(GBUAPCD) 

and Mono 

Counties139

preparation 

▪Harvest 

▪Other 

Cultural 

Practices 

Roads 

▪Unpaved 

Traffic 

Areas

South Coast 

AQMD

Rule 403

And

Agricultural 

Handbook

South Coast 

Air Basin140

▪Active 

Conservation 

Practices 

▪Inactive 

Conservation 

Practices 

▪Unpaved 

Roads 

South Coast 

AQMD

Rule 403 

And

Coachella 

Valley 

Agricultural 

Handbook

Coachella 

Valley 

Planning Area 

▪Active 

Conservation 

Practices 

▪Inactive 

Conservation 

Practices 

▪Unpaved 

Roads 

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 should be 

subject to less stringent requirements than other roads in 

Imperial County (i.e., those subject to Rule 803 regarding trackout/carry-out and Rule 805) and cites San Joaquin Valley where 

such roads must meet CMPs as well as general requirements. In 

contrast, ICAPCD and the Farm Bureau believe Regulation VIII is 

more stringent regarding unpaved farm roads and traffic areas 

 

139 See section 1 and 2 of GBUAPCD Rule 502. Also see 40 CFR 

81.305. 

140 SCAQMD‟s jurisdiction includes the South Coast Air Basin and 

the Coachella Valley Planning Area. For a description of the 

boundaries of the Los Angeles-South Coast Air Basin Area and the 

Coachella Valley Planning Area, see 40 CFR 81.305. The South 

Coast Air Basin includes all of Orange County and the more 

populated portions of Los Angeles, San Bernardino, and Riverside 
90

than analogous rules in other areas even though Imperial County 

farm roads and traffic areas are not subject to opacity limits. 

These latter commenters note that Rule 806 requires CMPs for all 

unpaved roads and traffic areas regardless of vehicle trips per 

day (VTD), unlike SJVUAPCD Rule 4550. COLAB also explains that 

ICAPCD Rule 806 was designed to address all unpaved roads by 

applying to parcels greater than 40 acres (97% of farmland in 

Imperial County) compared to SJVUAPCD‟s Rule 4550 which addresses

roads on parcels larger than 100 acres (91% of farmland in the 

San Joaquin Valley). Lastly, ICAPCD and the Farm Bureau assert 

that most private unpaved farm roads are less used and are 

therefore below Rule 805‟s 50 VTD threshold. Regardless of VTD, 

however, these latter commenters argue that owners of these roads

must implement Rule 806 CMPs.

Response: EPA‟s proposal noted that ICAPCD has not 

demonstrated BACM for unpaved farm roads and traffic areas 

because of the exemption in Rule 805 section D.2 from opacity and

stabilization requirements applicable to non-agricultural 

operation sites. EPA further noted that SJVUAPCD does not 

provide such an exemption, and ICAPCD had not justified such an 

exemption.141

ICAPCD and other commenters do not offer evidence that 

 

Counties. The Coachella Valley Planning Area includes central 

Riverside County in the Salton Sea Basin.

141 Proposal TSD, pp. 8-9.
91

Regulation VIII is as stringent as comparable controls in this 

regard, but instead claim that Regulation VIII is more stringent 

in other respects. For example, no commenter disputes our 

conclusion that an unpaved farm road with 75 VTD would be subject

to opacity standards in SJVUAPCD‟s Rule 8081 but not in ICAPCD‟s 

Regulation VIII. However, ICAPCD and others argue that the 

applicability threshold for unpaved farm roads subject to Rule 

806, for example, is more stringent than SJVUAPCD‟s analogous 

requirements. Because opacity and surface stabilization 

requirements on heavily-used farm roads and traffic areas are 

being implemented in other areas, we believe that, absent an 

adequate explanation, these requirements are at least 

presumptively BACM for this source category in Imperial County. 

Accordingly, these controls should be evaluated as potential BACM

by ICAPCD. However, as stated previously, ICAPCD may consider 

conditions specific to Imperial County in a revised BACM 

evaluation for unpaved roads and traffic areas, as appropriate. 

We also agree with Comite that it is not clear why Rule 803 

section D.1 exempts farm roads and traffic areas from certain 

carry-out and track-out requirements that apply to similar nonfarm roads. We encourage ICAPCD to consider removing this 

exemption, although such a rule modification is not mandated by 

the CAA at this time because carry-out/track-out has not been 

identified as a significant source category subject to the BACM 
92

requirement. 

UFRTA #2: Comite believes that Rule 806‟s CMPs are not 

sufficiently specific regarding agricultural unpaved roads and 

traffic areas. In contrast, ICAPCD comments that Rule 806 

section F.6 requires CMP plans to include other relevant 

information, which gives ICAPCD authority to require adequate 

specificity. COLAB also comments that the CMP forms provided in 

the rule are examples and if the relevant information was 

provided the form could be changed. 

Response: Issues raised regarding specificity of CMPs for 

unpaved roads and traffic areas are similar to issues raised 

regarding the specificity of CMPs for other agricultural 

operations. See response to comment AL #3 below. 

J. Agricultural Land Controls (AL) 

See Introduction in section II.I above.

AL #1: ICAPCD comments that Rule 806‟s CMP requirements are 

similar to requirements adopted by SJVUAPCD, Maricopa County142

and SCAQMD,143 and are directly based on SJVUAPCD requirements 

 

142 Although ICAPCD refers to requirements adopted by Maricopa 

County in its comments, Arizona‟s rules, A.A.C. R18-2-610 and 

R18-2-611, for controlling PM-10 from agricultural sources apply 

to some sources beyond the boundaries of Maricopa County. 

143 As noted in Table 3 above, SCAQMD‟s Rule 403 has requirements 

for agricultural activities that apply to both the South Coast 

Air Basin and Coachella Valley Planning Area. 
93

that EPA approved as BACM in 2004, citing 69 FR 30035.144 ICAPCD 

asserts that the individual CMPs in Rule 806 are similar to those

found in SJVUAPCD Rule 4550 and GBUAPCD Rule 502 and concludes 

that the only differences in the rules are due to differences in 

local agricultural practices. The Farm Bureau also states that 

there is little difference between GBUAPCD and ICAPCD control 

measures. 

Response: We agree that many individual CMPs and 

requirements in the rules outlined in Table 3 are similar. 

However, this overall similarity does not affect the two specific

BACM deficiencies in ICAPCD Rule 806 for tilling and harvesting 

emissions identified in our proposed action.145 One of these 

deficiencies concerns the lack of sufficiently defined 

requirements in contrast to the application submittal and review 

processes in the SJVUAPCD and GBUABCD rules that insure more 

effective implementation and enforcement of the requirements.146

The other deficiency is related to the number of CMPs required by

Rule 806. Rule 806 section E requires one CMP from the "land 

preparation and cultivation" category and one CMP from the 

"harvesting" category, while SJVAPCD Rule 4550 requires an 

additional CMP from the "cropland-other" category. GBUAPCD Rule

 

144 EPA approved SJVUAPCD Rule 4550 in 2006, not in 2004. See 71 

FR 7683. EPA approved a commitment for the San Joaquin Valley CMP

Program in 2004. See 69 FR 30006. 

145 See 75 FR 8008, 8011-8012. 
94

502 also requires that one CMP each be selected from the "land 

preparation and cultivation," "harvest," and the "other cultural 

practices" categories.147 

AL #2: ICAPCD believes that EPA disregards that Imperial 

County crops are irrigated, and that continued irrigation and 

conditioning of soil dramatically reduce its potential for both 

entrained and windblown emissions. ICAPCD believes this fact 

must be considered when comparing Rule 806 to rules in other 

areas. 

Response: As stated previously above, EPA agrees that it is 

appropriate to consider conditions specific to an area when 

evaluating potential BACM.148 However, most of the harvested 

cropland in other areas subject to comparable requirements is 

also irrigated. The following table shows data from the 2007 

Census of Agriculture149 for the total acres of harvested cropland 

 

146 See SJVUAPCD Rule 4550 section 6.3 and 6.4 and GBUAPCD Rule 

502 section 6.3 and 6.4.

147 See SJVUAPCD Rule 4550 section 6.2 and SJVUAPCD “List of 

Conservation Management Practices.” See also GBUAPCD Rule 502 

section 6.2 and, for example, GBUAPCD Supplemental Application 

Form for Alfalfa. See also “Conservation Management Practices for

Farms in Inyo, Mono and Alpine Counties, Program Description and 

Plan Application Forms,” December 19, 2008, Great Basin Unified 

Air Pollution Control District, at 

http://www.gbuapcd.org/farm/CMPprogramdescriptionandforms.pdf. 

148 General Preamble Addendum at 42010 and 42012.

149 2007 Census of Agriculture, California, State and County 

Data, and 2007 Census of Agriculture, Arizona, State and County 

Data, United States Department of Agriculture, National 

Agricultural Statistics Service. See 

http://www.agcensus.usda.gov/Publications/2007/

Full_Report/Volume_1,_Chapter_2_County_Level/California/cav1.pdf 
95

and the acres of irrigated harvested cropland in relevant 

counties in California and Arizona. Imperial County and the 

counties in the SJVUAPCD150 are included. Riverside County in 

California151 and Maricopa County in Arizona are also included. 

Table 4

County, State

Total Harvested 

Cropland (acres) 

Irrigated Harvested 

Cropland (acres)

Imperial, CA 375,904 375,167

Maricopa, AZ 190,182 189,141

Riverside County, CA 163,783 158,437

San Joaquin County, 

CA

444,670 426,670

Stanislaus, CA 307,992 297,053

Merced, CA 466,304 458,017

Madera, CA 264,767 260,596

 

and 

http://www.agcensus.usda.gov/Publications/2007/Full_Report/Volume

_1,_Chapter_2_County_Level/Arizona/azv1.pdf.

150 See footnote 141 above. The census data in Table 4 are for 

all of Kern County. 

151 Of all the counties included in SCAQMD, Riverside County has 

the largest acreage of harvested cropland. According to the 2007 

Census of Agriculture, Orange County has 7,846 acres of harvested

cropland, Los Angeles County has 25,829 acres of harvested 

cropland, San Bernardino County has 27,516 acres of harvested 

cropland, and Riverside County has 163,783 acres of harvested 

cropland. 2007 Census of Agriculture, California, State and 

County Data, United States Department of Agriculture, National 

Agricultural Statistics Service. See 

http://www.agcensus.usda.gov/Publications/2007/

Full_Report/Volume_1,_Chapter_2_County_Level/California/cav1.pdf 
96

Fresno, CA 978,948 960,215

Kings, CA 419,964 419,080

Tulare, CA 560,320 540,887

Kern, CA 764,929 756,645

Thus, the mere fact that crops are grown using irrigation in 

Imperial County does not in and of itself justify different 

standards for BACM. 

AL #3: ICAPCD comments that Rule 806 section F.6 specifies 

that the CMP plan shall include “other relevant information as 

determined by the ICAPCD,” which gives ICAPCD authority to modify

the CMP plans to specify frequency of CMP applicability. 

Therefore ICAPCD believes a mechanism is in place in the rule for

modification of CMPs to provide such details, and therefore this 

should not be a basis for disapproval of Regulation VIII as BACM.

ICAPCD notes its commitment to modify the CMP plans to provide 

such details. 

Response: As noted by ICAPCD, Rule 806 section F.6 provides 

a mechanism that could be used by ICAPCD to provide greater 

specificity. However there is no required process in the rule for

sources to provide such information to ICAPCD or for ICAPCD to 

review the CMPs and/or to require revision of the CMPs that 

sources have chosen to implement. Under section F, sources are 

only required to prepare a plan containing minimal information 
97

and to maintain a copy of the plan. Thus the CMPs would continue 

to be broadly defined unless or until ICAPCD proactively 

determines that greater specificity is needed. Absent such vital 

details, it would be difficult for regulated entities to know 

precisely what is required of them to comply with a BACM level of

control, and it would be difficult for ICAPCD, EPA, or others to 

enforce these requirements.152 In contrast, SJVUAPCD Rule 4550 

section 5 requires sources to prepare and submit a CMP 

application to the District for approval and section 6 requires 

the District to evaluate and either approve or disapprove the 

application in writing. GBUAPCD Rule 502 sections 5 and 6 contain

substantially identical requirements. Such requirements provide a

mandatory process that is far more likely to ensure that the CMPs

 

152 For instance, one of the CMPs that is both in the “land 

preparation and cultivation” category in Rule 806 section E.l and

the “harvesting” category in section E.2 is "equipment 

changes/technological improvements" which is defined in section 

C.15 as "To modify the equipment such as tilling; increase 

equipment size; modify land planning and land leveling; match the

equipment to row spacing; granting to new varieties or other 

technological improvements. It reduces the number of passes 

during an operation, thereby reducing soil disturbance." This 

definition is too broad to ensure enforceability. Moreover, 

because there is no mechanism to narrow the definition for a 

particular agricultural operation, a CMP may be implemented in a 

manner less stringent than a BACM level of control. In a 

similarly broad fashion, Rule 806 section C.34 defines "speed 

limits," a CMP in both the “unpaved roads” category in section 

E.3 and the “unpaved traffic areas” category in section E.4, as 

"enforcement of speeds that reduce visible dust emissions. The 

dust emissions from unpaved roads are a function of speed, 

meaning reducing speed reduces dust." However, an appropriate 

speed limit or range of speed limits is not specified or 

otherwise insured.
98

are implemented and enforceable at a BACM level of control than 

the provision in ICAPCD Rule 806. 

Finally, even if ICAPCD were to routinely exercise its 

discretionary authority in Rule 806 to specify the frequency of 

CMP applicability, the deficiency noted in our proposed action 

related to lack of CMP specificity extends beyond the issue of 

frequency.153

AL #4: ICAPCD claims that BACM should not be required for 

harvest activities because the emissions from these activities 

(0.01 tpd) are negligible. ICAPCD argues that efforts to 

increase regulation of emissions from harvesting would waste 

resources. In addition, ICAPCD claims that the CMPs in Rule 806 

related to harvesting are similar to those in SJVUAPCD Rule 4550.

Response: ICAPCD has identified tilling emissions as a 

significant source.154 As stated in our proposal for this action, 

measures in Rule 806 for harvesting must also meet BACM because 

the activities occur at the same facilities and are integrally 

related to tilling emissions.155 By analogy, where enforceable 

volatile organic compound (VOC) reasonably available control 

technology (RACT) level controls are required for refineries, SIP

rules generally impose leak detection and repair requirements on 

valves, flanges, threaded connections and other related equipment

 

153 See 75 FR 8008, 8011-8012. 

154 Proposal TSD, pp. 5-6.

155 Proposal TSD, p. 10, footnote 25.
99

even if emissions from any one of these taken individually might 

be much smaller than the major source threshold requiring RACT.156

We agree that individual CMPs for emissions from harvesting 

activities in Rule 806 are generally similar to CMPs for such 

emissions in the San Joaquin Valley. However, both SJVUAPCD and 

GBUAPCD require one more CMP for on-field agricultural sources 

than does Rule 806.157 This additional CMP may reduce emissions 

from harvesting activities. ICAPCD must establish that requiring 

fewer controls for on-field agricultural activities is consistent

with BACM requirements. Thus far ICAPCD has not provided a 

convincing justification. 

AL#5: ICAPCD disagrees with our identification of the 

requirements of Rule 806 for tilling as a deficiency in the BACM 

analysis. In support of its position, ICAPCD asserts that San 

Joaquin Valley sources may select two CMPs that reduce emissions 

from tilling from the list of measures, but they are not required

to do so. ICAPCD also claims that because per-acre emissions from

 

156 SJVUAPCD Rule 4451, Valves, Pressure Relief Valves, Flanges, 

Threaded Connections and Process Drains at Petroleum Refineries 

and Chemical Plants, amended April 20, 2005.

157 See SJVUAPCD Rule 4550 section 6.2 and SJVUAPCD “List of 

Conservation Management Practices.” See also GBUAPCD Rule 502 

section 6.2 and, for example, GBUAPCD Supplemental Application 

Form for Alfalfa. See also “Conservation Management Practices for

Farms in Inyo, Mono and Alpine Counties, Program Description and 

Plan Application Forms,” December 19, 2008, Great Basin Unified

Air Pollution Control District, at 

http://www.gbuapcd.org/farm/CMPprogramdescriptionandforms.pdf. 
100

land preparation are about four times as high in the San Joaquin 

Valley as they are in Imperial County, the cost-effectiveness of 

emission reductions from tilling activities through the 

implementation of any CMP should be four times as high in 

Imperial County as in the San Joaquin Valley. For these two 

reasons, ICAPCD believes that Rule 806 requirements for tilling 

are as stringent as analogous SJVUAPCD requirements. In contrast,

Comite comments that Arizona Rules 18-2-610 and 611 require at 

least two CMPs from each category in the rule whereas Rule 806 

requires only one, and that SJVUAPCD requires up to three CMPs. 

Response: Although ICAPCD focuses here on emissions from 

tillage, the deficiency in our proposed rule is related to 

requirements in Rule 806 for sources to implement one fewer CMP 

overall for on-field agricultural sources than is required by 

SJVUAPCD Rule 4550 and GBUAPCD Rule 502. Thus the fact that 

sources subject to SJVUAPCD Rule 4550 are not required to select 

two CMPs for reducing emissions from tillage is irrelevant. 

ICAPCD needs to assess whether additional CMPs for on-field 

agricultural sources are BACM for Imperial County. 

ICAPCD has not established that the agricultural activities 

in Imperial County are significantly different from those in 

other areas. Accordingly, EPA believes that ICAPCD should have 

BACM level controls for both tillage and harvest emissions as do 

other areas with programs for emissions from agricultural 
101

activities, and should consider SJVUAPCD and controls from other 

areas with analogous rules when assessing whether a requirement 

for additional CMPs would be economically and technologically 

feasible to control emissions from these activities. ICAPCD 

claims that implementing tillage CMPs may be more cost-effective 

in the San Joaquin Valley, but does not address whether it would 

be economically feasible to require additional CMPs in Imperial 

County. 

We agree with Comite that sources subject to Arizona Rules 

18-2-610 and 611 are required to implement two practices each 

from the “tillage and harvest” and “cropland” categories. ICAPCD 

needs to consider whether requiring four practices for on-field 

agricultural sources constitute BACM for Imperial County.

AL #6: Comite claims that Maricopa‟s inspection regime for 

agricultural sources is more rigorous than ICAPCD‟s. 

Response: Comite provides no supporting information on 

either the Maricopa County or ICAPCD inspection program on which 

to base a response and we are not otherwise aware of information 

that supports this comment. 

AL #7: The Farm Bureau agrees that SJVUAPCD requires an 

additional CMP from the “cropland-other” category but notes that 

the same requirement is found in ICAPCD‟s “land preparation and 

cultivation” and “harvest activities” categories. As a result, 

the Farm Bureau believes that including an additional category 
102

would be redundant and onerous for participants. 

Response: The deficiency identified in our proposed action 

is related to the requirement in Rule 806 for Imperial County 

sources to implement one fewer practice for on-field agricultural

sources overall without a sufficient justification.158 ICAPCD 

does not necessarily need to add a category to Rule 806 in order 

to address this deficiency. For example, depending on what is 

most appropriate for conditions in Imperial County, ICAPCD may be

able to require that more than one CMP be implemented from the 

categories that currently exist in Rule 806. Moreover, it would 

not be redundant to require Imperial County sources to implement 

an additional CMP for on-field agricultural sources. Rule 806 has

two categories for on-field agricultural sources, “land 

preparation and cultivation” and “harvesting,” and requires 

sources to implement one practice from each category. As noted in

Table 3 above, SJVUAPCD Rule 4550 and GBUAPCD Rule 502 have three

categories for on-field agricultural sources, and require that 

sources implement one practice from each of these categories. 

Moreover, as noted in our response to comment AL #5 above, 

sources subject to Arizona Rules 18-2-610 and 611 are required to

implement four practices for on-field agricultural sources. As 

part of a BACM analysis, ICAPCD should consider the economic and 

technological feasibility of requiring additional CMPs for on-

 

158 75 FR 8008, 8012.
103

field agricultural sources, including consideration of the 

requirements in rules adopted by SJVUAPCD, GBUAPCD and Arizona. 

K. Agricultural Land Windblown Dust Controls (ALWD) 

See Introduction in section II.I above.

ALWD #1: COLAB comments that the deficiencies identified by 

EPA related to windblown dust are particularly troublesome 

because they are so surprising. COLAB believes that Rule 806 

exceeds CAA needs because windblown dust from agriculture is 

insignificant. Comite, on the other hand, notes SCAQMD‟s 

requirements for reducing windblown dust from active and inactive

agricultural fields as BACM measures that ICAPCD should consider 

along with recommendations in U.S. Department of Agriculture‟s 

(USDA) National Agronomy Manual for reducing such dust. 

Response: EPA has determined that windblown dust from 

agriculture is a significant PM10 source category in Imperial 

County for which ICAPCD must demonstrate, but has not yet 

demonstrated, implementation of BACM level controls.159 ICAPCD 

should include in its BACM analysis consideration of whether 

existing SCAQMD controls, among others, and USDA recommendations 

for controlling wind erosion, are economically and 

technologically feasible measures to reduce windblown dust from 

active and fallow agricultural fields. Also see response to 

comment General #3 above. 

 

159 Proposal TSD, pp. 10-11.
104

ALWD #2: ICAPCD believes that EPA should have concurred with 

exceptional event requests associated with high winds as 

discussed in the exceptional event comments above. As a result, 

ICAPCD believes that windblown dust from agricultural lands is 

not a significant source category in SIP development, and 

therefore not subject to BACM. 

Response: In our proposed action on Regulation VIII, we 

explained how we determined that windblown dust from agricultural

lands is a significant source category subject to BACM.160 We 

have not received information in the comments or elsewhere that 

affects this conclusion or the related 2009 EE decision. See also

responses to exceptional event comments above and comment OHV #1.

ALWD #3: ICAPCD disagrees that Rule 806 does not apply to 

fallow agricultural fields. ICAPCD states that there are no 

exemptions in Rule 806 for fallow fields and fallowing is an 

optional CMP to control emissions from “land preparation and 

cultivation” under Rule 806 section E.1. 

Response: Fallowing land is defined in Rule 806 section C.16 

as “Temporary or permanent removal from production. Eliminates 

entire operation/passes or reduces activities.” We note that the 

fallowing CMP is an option under both the “land preparation and 

cultivation” category in section E.1 and the “harvesting” 

category in section E.2. While the fallowing CMP in Rule 806 

 

160 Id., pp. 5-7.
105

section E.1 may reduce emissions from “land preparation and 

cultivation” and from “harvesting,” it does not address any 

windblown dust emissions that may occur once a field is removed 

from production. EPA believes that the evaluation of BACM level 

controls for windblown dust from fallow fields should include 

consideration of USDA-approved conservation systems and 

activities.161 

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 consistent 

with USDA‟s National Agronomy Manual. ICAPCD estimates that longterm irrigation reduces PM10 emissions by 25-45% from the 

predominant cultivated soil types in Imperial County, so local 

fallow and active agricultural land is controlled for windblown 

emissions relative to land not previously used for irrigated 

agriculture. In contrast, ICAPCD believes that SCAQMD‟s farm 

acreage is overwhelmingly devoted to dryland grain farming, and 

EPA has not shown that SCAQMD controls are appropriate for 

ICAPCD‟s irrigated fields. 

Response: Based on data in Table 4, EPA believes that the 

majority of ICAPCD harvested acreage is irrigated. However, EPA 

disagrees that farm acreage subject to SCAQMD controls is 

overwhelmingly devoted to dryland farming. See total harvested 

 

161 Id., pp. 10-11 and 17.
106

cropland acres and irrigated harvested cropland acres for 

Riverside County in Table 4. While historic irrigation may 

provide for some level of control, windblown dust from 

agriculture is a significant source, and ICAPCD is required to 

implement BACM level controls for windblown emissions from active

and fallow agricultural fields. ICAPCD has not provided a 

convincing justification for why controls in the Coachella Valley

Planning Area are not applicable to Imperial sources. ICAPCD‟s 

evaluation for BACM level controls for windblown dust from 

agricultural sources should include requirements in SCAQMD Rule 

403 and the Coachella Valley Agricultural Handbook. 

ALWD #5: ICAPCD notes that winds above 25 mph are extremely 

rare in the agricultural portion of Imperial Valley, and farmers 

usually avoid tilling on windy days to conserve soil. As a 

result, ICAPCD does not believe that SCAQMD‟s restriction for 

soil preparation and maintenance during days with winds above 25 

mph would impact windblown dust emissions from agricultural 

fields in Imperial County. In contrast, Comite points to SCAQMD‟s

requirements as potential BACM that ICAPCD has not properly 

considered. 

Response: ICAPCD must analyze and implement BACM for 

agricultural windblown dust emissions.162 Such analysis may 

consider whether a restriction on tilling activities on days with

 

162 Proposal TSD, pp. 5-7.
107

winds above 25 mph is appropriate in Imperial County pursuant to 

our guidance.163 However, ICAPCD has not provided such analysis 

in the Regulation VIII submittal, its comments or elsewhere. To 

the extent that farmers avoid tilling on windy days to conserve 

soil anyway, this restriction would not seem to be onerous.

ALWD #6: ICAPCD comments that SCAQMD‟s only additional 

requirement for active fields besides the restriction on tilling 

on days with winds above 25 mph is to implement one more CMP from

a list that includes minimum tillage. ICAPCD believes this CMP is

not directly effective at reducing windblown emissions, and hence

ICAPCD believes that by EPA‟s own reasoning, this requirement 

does not require windblown control on active fields in the South 

Coast Basin. 

Response: ICAPCD has not explained why minimum tillage would 

not directly reduce windblown dust from active fields. EPA 

expects that minimum tillage would reduce windblown emissions by 

maintaining more plant residue on the field than conventional 

tillage. Establishing and maintaining land cover is one of the 

five principles noted in the National Agronomy Manual for wind 

erosion control.164

ALWD #7: Comite believes that more specificity and 

information must be provided concerning IID‟s Fallowing Program 

 

163 General Preamble Addendum at 42013.

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

October 2002. 
108

to ensure that emission reductions from it are quantifiable, 

verifiable and enforceable. 

Response: ICAPCD must analyze and implement BACM for 

agricultural windblown dust emissions.165 If, as a result of this 

analysis, ICAPCD concludes that IID‟s Fallowing Program is needed

to implement BACM, then we agree that ICAPCD needs to provide 

more information about IID‟s program and ensure that controls 

that are provided through the program are enforceable. 

ALWD #8: Regarding EPA concerns with agricultural windblown 

dust controls, ICAPCD and the Farm Bureau note that Rule 806 was 

modeled after EPA-approved SJVUAPCD Rule 4550 at EPA‟s 

recommendation. 

Response: EPA‟s guidance provides that BACM is determined on 

a case-by-case basis and can consider the specific conditions of 

the nonattainment area.166 When we approved SJVUAPCD Rule 4550, we 

did not believe that SJVUAPCD had a regular and repeated 

windblown dust problem.167 However, ICAPCD asserts in its 2009 

PM10 Plan that the “overwhelming majority of airborne PM in 

Imperial County is primary PM. The major source of primary PM is 

fugitive windblown dust....”168 Moreover, ICAPCD‟s 2009 PM10 Plan 

discusses how the flat terrain of Imperial Valley and strong 

temperature differentials produce moderate winds and how Imperial

 

165 Proposal TSD, pp. 5-7.

166 See General Preamble Addendum at 42010 and 42012.

167 See, e.g., 73 FR 14687, 14693 (March 19, 2008). 
109

County occasionally experiences high winds with speeds greater 

than 30 mph in April and May. In addition, the 2009 PM10 Plan 

attributes monitored exceedances in September and June to high 

winds.169 As a result, EPA believes that ICAPCD must consider 

windblown dust controls for agricultural sources. Also, see 

responses to comments General #3 and EE #5. 

ALWD #9: The Farm Bureau notes that both Rule 806 and the 

“Agricultural Air Quality Conservation Management Practices for 

Imperial Valley” were developed consistent with rules adopted in 

other areas and EPA recommendations. As a result, the Farm Bureau

believes that this ensured Rule 806 was adequate. 

Response: See response to comment General #3. 

L. Other Controls (OC) 

OC #1: Comite believes Regulation VIII should be further 

strengthened by removing director‟s discretion in Rule 802 

section D.1, and removing the exemption in Rule 802 section D.4. 

ICAPCD objects to EPA‟s concerns regarding Rule 802 section D.1 

because: (1) the APCO‟s discretion is limited to a determination 

of whether any of the controls in sections F.1 through F.3 can be

implemented to satisfy the 20% opacity and stabilized surface 

requirements; (2) where a SIP-approved rule provides APCO 

discretion, the APCO can exercise the discretion without further 

SIP-approval; and (3) EPA has final enforcement authority for 

 

168 2009 PM10 SIP, p. 1-1. 
110

SIP-approved rules.

Response: EPA believes that the director‟s discretion 

provisions in Rule 802 are generally not acceptable under the 

CAA. Regarding ICAPCD‟s first argument, Rule 802 section D.1 

provides the APCO discretion to waive completely the opacity and 

stabilized surface requirements without limiting discretion 

either by a procedure that the APCO must use (e.g., test method 

X) or by boundaries to the discretion (e.g., up to 30% opacity 

instead of 20% opacity). Thus, the discretion is not “limited.” 

Regarding ICAPCD‟s second argument, we note initially that 

EPA has a long history of rejecting such broad APCO discretion in

SIP rules.170 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 SIPapproved rules, as stated, director‟s discretion provisions 

undermine their enforceability because enforcement of the rules 

are constrained by their terms. In this case, EPA or others could

be restricted in enforcing against activity exempted by the APCO 

if this provision were SIP-approved. 

While we share Comite‟s concerns with Rule 802 section D, 

 

169 2009 PM10 SIP, pp. 1-3 and 2-4. 

170 See, e.g., “Guidance Document for Correcting Common VOC and 

Other Rule Deficiencies,” U.S. EPA Region IX, August 21, 2001 

(the Little Bluebook); and “Issues Relating to VOC Regulation 
111

our limited disapproval with respect to Rule 802 section D will 

not trigger sanctions or a FIP obligation because Rule 802 does 

not address a source category identified as significant and thus 

requiring BACM at this time. Therefore our limited disapproval 

will not trigger sanctions under CAA section 179 or a FIP 

obligation under section 110(c) with respect to bulk materials 

regulated by Rule 802. However, should regulation of bulk 

materials be subject to the BACM requirement in the future or to 

meet other SIP planning requirements under CAA title I, part D 

such as reasonable further progress or attainment, the APCO 

discretion in Rule 802 section D.1 or the exemptions in Rule 802 

section D.4 could result in such consequences and/or affect the 

emission reduction credit for the rule.

M. Statutory and Executive Order Reviews (SEO) 

SEO #1: OWD believes that EPA should address Executive Order 

12898, which requires federal agencies to identify and address 

disproportionately adverse health or environmental impacts on 

minority and low-income populations. Specifically, OWD believes 

that EPA‟s action may impact Imperial County‟s Hispanic and lowincome population by reducing tourist income from OHV users. In 

contrast, Comite applauds the commitment of the Regional 

Administrator of EPA Region 9 to environmental justice 

principles, and notes that relatively large portions of the 

 

Cutpoints, Deficiencies, and Deviations,” U.S. EPA, OAQPS, May
112

population in this area are not only Hispanic and poor, but are 

also suffering from poor health and this is exacerbated by air 

pollution problems in this area. 

Response: EPA agrees it is important to consider 

environmental justice in our actions and we briefly addressed 

environmental justice principles in our proposal TSD.171 Executive 

Order 12898, “Federal Actions to Address Environmental Justice in

Minority Populations and Low-Income Populations” (February 16, 

1994) establishes federal executive policy on environmental 

justice. Its main provision directs federal agencies, to the 

greatest extent practicable and permitted by law, to make 

environmental justice part of their mission by identifying and 

addressing, as appropriate, disproportionately high and adverse 

human health or environmental effects of their programs, policies

and activities on minority populations and low-income populations

in the United States. The Executive Order has informed the 

development and implementation of EPA‟s environmental justice 

program and policies. Consistent with the Executive Order and 

the associated Presidential Memorandum, the Agency‟s 

environmental justice policies promote environmental protection 

by focusing attention and Agency efforts on addressing the types 

of environmental harms and risks that are prevalent among 

minority, low-income and Tribal populations.

 

25, 1998 (The Bluebook).
113

This action will not have disproportionately high and 

adverse human health or environmental effects on minority, lowincome or Tribal populations because it increases the level of 

environmental protection for all affected populations without 

having any disproportionately high and adverse human health or 

environmental effects on any population, including any minority 

or low-income population. Specially, EPA‟s limited approval and 

limited disapproval of Regulation VIII would have the affect of 

strengthening environmental requirements throughout ICAPCD, and 

would not relax environmental requirements in any area. Thus it 

promotes environmental justice by increasing the level of human 

health and environmental protection for an area where, as the 

commenters note, relatively large portions of the population are 

low income and/or minority. 

SEO #2: OWD notes that EPA‟s action may be subject to NEPA 

evaluation.

Response: EPA actions under the CAA are exempt from NEPA.172

SEO #3: OWD believes that EPA should address increased 

management costs for Imperial County‟s OHV recreation areas and 

the effects on OHV areas outside Imperial County. As a result, 

OWD does not believe that EPA has a basis to claim (regarding the

Unfunded Mandates Reform Act), that no additional costs result 

from this action.

 

171 Proposal TSD, p. 3.
114

Response: As explained in our proposal, our action would 

approve and disapprove pre-existing requirements under State or 

local law, and impose no new requirements. Accordingly, no 

additional costs to State, local, or tribal governments, or to 

the private sector, result from this action.173 

III. EPA Action

No comments were submitted that change our assessment of 

Regulation VIII as described in our proposed action. Therefore, 

as authorized in sections 110(k)(3) and 301(a) of the Act, EPA is

finalizing a limited approval of the submitted rules. This action

incorporates the submitted rules into the California SIP, 

including those provisions identified as deficient. As 

authorized under section 110(k)(3), EPA is simultaneously 

finalizing a limited disapproval of the rules. As a result, 

sanctions will be imposed in Imperial County unless EPA approves 

subsequent SIP revisions that correct the rule deficiencies 

within 18 months of the effective date of this action. These 

sanctions will be imposed under section 179 of the Act according 

to 40 CFR 52.31. In addition, EPA must promulgate a federal 

implementation plan (FIP) under section 110(c) unless we approve 

subsequent SIP revisions that correct the rule deficiencies 

within 24 months. Note that the submitted rules have been 

adopted by ICAPCD, and EPA‟s final limited disapproval does not 

 

172 See 40 CFR 6.101(b).
115

prevent the local agency from enforcing them.

IV. Statutory and Executive Order Reviews 

A. Executive Order 12866, Regulatory Planning and Review

The Office of Management and Budget (OMB) has exempted this 

regulatory action from Executive Order 12866, entitled 

“Regulatory Planning and Review.”

B. Paperwork Reduction Act

This action does not impose an information collection burden 

under the provisions of the Paperwork Reduction Act, 44 U.S.C. 

3501 et seq. Burden is defined at 5 CFR 1320.3(b). 

C. Regulatory Flexibility Act

The Regulatory Flexibility Act (RFA) generally requires an 

agency to conduct a regulatory flexibility analysis of any rule 

subject to notice and comment rulemaking requirements unless the 

agency certifies that the rule will not have a significant 

economic impact on a substantial number of small entities. Small

entities include small businesses, small not-for-profit 

enterprises, and small governmental jurisdictions. 

This rule will not have a significant impact on a 

substantial number of small entities because SIP limited 

approvals and limited disapprovals under section 110 and 

subchapter I, part D of the Clean Air Act do not create any new 

requirements but simply approve and disapprove requirements that 

 

173 75 FR 8008, 8012-8013.
116

the State is already imposing. Therefore, because this limited 

approval and limited disapproval action does not create any new 

requirements, I certify that this action will not have a 

significant economic impact on a substantial number of small 

entities.

Moreover, due to the nature of the Federal-State

relationship under the Clean Air Act, preparation of flexibility 

analysis would constitute Federal inquiry into the economic 

reasonableness of State action. The Clean Air Act forbids EPA to

base its actions concerning SIPs on such grounds. Union Electric

Co., v. U.S. EPA, 427 U.S. 246, 255-66 (1976); 42 U.S.C. 

7410(a)(2).

D. Unfunded Mandates Reform Act

Under sections 202 of the Unfunded Mandates Reform Act of 

1995 (“Unfunded Mandates Act”), signed into law on March 22, 

1995, EPA must prepare a budgetary impact statement to accompany 

any proposed or final rule that includes a Federal mandate that 

may result in estimated costs to State, local, or tribal 

governments in the aggregate; or to the private sector, of $100 

million or more. Under section 205, EPA must select the most 

cost-effective and least burdensome alternative that achieves the

objectives of the rule and is consistent with statutory 

requirements. Section 203 requires EPA to establish a plan for 
117

informing and advising any small governments that may be 

significantly or uniquely impacted by the rule.

EPA has determined that the limited approval and limited 

disapproval action promulgated does not include a Federal mandate

that may result in estimated costs of $100 million or more to 

either State, local, or tribal governments in the aggregate, or 

to the private sector. This Federal action approves and 

disapproves pre-existing requirements under State or local law, 

and imposes no new requirements. Accordingly, no additional 

costs to State, local, or tribal governments, or to the private 

sector, result from this action.

E. Executive Order 13132, Federalism

Federalism (64 FR 43255, August 10, 1999) revokes and 

replaces Executive Orders 12612 (Federalism) and 12875 (Enhancing

the Intergovernmental Partnership). Executive Order 13132 

requires EPA to develop an accountable process to ensure 

“meaningful and timely input by State and local officials in the 

development of regulatory policies that have federalism 

implications.” “Policies that have federalism implications” is 

defined in the Executive Order to include regulations that have 

“substantial direct effects on the States, on the relationship 

between the national government and the States, or on the 

distribution of power and responsibilities among the various 

levels of government.” Under Executive Order 13132, EPA may not 
118

issue a regulation that has federalism implications, that imposes

substantial direct compliance costs, and that is not required by 

statute, unless the Federal government provides the funds 

necessary to pay the direct compliance costs incurred by State 

and local governments, or EPA consults with State and local 

officials early in the process of developing the proposed 

regulation. EPA also may not issue a regulation that has 

federalism implications and that preempts State law unless the 

Agency consults with State and local officials early in the 

process of developing the proposed regulation.

This rule will not have substantial direct effects on the 

States, on the relationship between the national government and 

the States, or on the distribution of power and responsibilities 

among the various levels of government, as specified in Executive

Order 13132, because it merely approves and disapproves State 

rules implementing a Federal standard, and does not alter the 

relationship or the distribution of power and responsibilities 

established in the Clean Air Act. Thus, the requirements of 

section 6 of the Executive Order do not apply to this rule.

F. Executive Order 13175, Coordination with Indian Tribal 

Governments

Executive Order 13175, entitled “Consultation and 

Coordination with Indian Tribal Governments” (65 FR 67249, 

November 9, 2000), requires EPA to develop an accountable process
119

to ensure “meaningful and timely input by tribal officials in the

development of regulatory policies that have tribal 

implications.” This final rule does not have tribal 

implications, as specified in Executive Order 13175. It will not

have substantial direct effects on tribal governments, on the 

relationship between the Federal government and Indian tribes, or

on the distribution of power and responsibilities between the 

Federal government and Indian tribes. Thus, Executive Order 

13175 does not apply to this rule.

G. Executive Order 13045, Protection of Children from 

Environmental Health Risks and Safety Risks

EPA interprets Executive Order 13045 (62 FR 19885, April 23, 

1997) as applying only to those regulatory actions that concern 

health or safety risks, such that the analysis required under 

section 5-501 of the Executive Order has the potential to 

influence the regulation. This rule is not subject to Executive 

Order 13045, because it approves State rules implementing a 

Federal standard. 

H. Executive Order 13211, Actions that Significantly Affect 

Energy Supply, Distribution, or Use

This rule is not subject to Executive Order 13211, “Actions 

Concerning Regulations That Significantly Affect Energy Supply, 

Distribution, or Use” (66 FR 28355, May 22, 2001) because it is 

not a significant regulatory action under Executive Order 12866.
120

I. National Technology Transfer and Advancement Act

Section 12 of the National Technology Transfer and 

Advancement Act (NTTAA) of 1995 requires Federal agencies to 

evaluate existing technical standards when developing a new 

regulation. To comply with NTTAA, EPA must consider and use 

“voluntary consensus standards” (VCS) if available and applicable

when developing programs and policies unless doing so would be 

inconsistent with applicable law or otherwise impractical.

The EPA believes that VCS are inapplicable to this action. 

Today‟s action does not require the public to perform activities 

conducive to the use of VCS.

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Population

Executive Order 12898, “Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Populations” (February 16, 1994) establishes federal executive 

policy on environmental justice. Its main provision directs 

federal agencies, to the greatest extent practicable and 

permitted by law, to make environmental justice part of their 

mission by identifying and addressing, as appropriate, 

disproportionately high and adverse human health or environmental

effects of their programs, policies and activities on minority 

populations and low-income populations in the United States. The 
121

Executive Order has informed the development and implementation 

of EPA‟s environmental justice program and policies. Consistent 

with the Executive Order and the associated Presidential 

Memorandum, the Agency‟s environmental justice policies promote 

environmental protection by focusing attention and Agency efforts

on addressing the types of environmental harms and risks that are

prevalent among minority, low-income and Tribal populations.

This action will not have disproportionately high and 

adverse human health or environmental effects on minority, lowincome or Tribal populations because it increases the level of 

environmental protection for all affected populations without 

having any disproportionately high and adverse human health or 

environmental effects on any population, including any minority 

or low-income population. Specially, EPA‟s simultaneous limited 

approval and limited disapproval of Regulation VIII would have 

the affect of strengthening environmental requirements throughout

ICAPCD, and would not relax environmental requirements in any 

area.

K. Congressional Review Act

The Congressional Review Act, 5 U.S.C. section 801 et seq., 

as added by the Small Business Regulatory Enforcement Fairness 

Act of 1996, generally provides that before a rule may take 

effect, the agency promulgating the rule must submit a rule 

report, which includes a copy of the rule, to each House of the 
122

Congress and to the Comptroller General of the United States. 

EPA will submit a report containing this rule and other required 

information to the U.S. Senate, the U.S. House of 

Representatives, and the Comptroller General of the United States

prior to publication of the rule in the Federal Register. A 

major rule cannot take effect until 60 days after it is published

in the Federal Register. This action is not a “major rule” as 

defined by 5 U.S.C. section 804(2). This rule will be effective 

on [FEDERAL REGISTER OFFICE: insert date 30 days from date of 

publication of this document in the Federal Register].
L. Petitions for Judicial Review 

Under section 307 (b) (1) of the Clean Air Act, petitions for 

judicial review of this action must be filed in the United States 

Court of Appeals for the appropriate circuit by [FEDERAL REGISTER 

OFFICE: insert date 60 days from date of publication of this 

document in the Federal Register]. Filing a petition for 

reconsideration by the Administrator of this final rule does not 

affect the finality of this rule for the purposes of judicial 

review nor does it extend the time within which a petition for 

judicial review may be filed, and shall not postpone the 

effectiveness of such rule or action. This action may not be 

challenged later in proceedings to enforce its requirements (see 

section 307 (b) (2) ) . 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air pollution control, 

Incorporation by reference, Intergovernmental relations, 

Particulate matter, Reporting and recordkeeping requirement. 
124

Part 52, Chapter I, Title 40 of the Code of Federal 

Regulations is amended as follows:

PART 52 [AMENDED]

1. The authority citation for Part 52 continues to read as 

follows:

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

Subpart F - California

2. Section 52.220 is amended by adding paragraphs (c)(345)(i)(E)

to read as follows:

§52.220 Identification of plan.

* * * * *

(c) * * *

(345)* * * 

(i) * * *

(E) Imperial County Air Pollution Control District

(1) Rule 800,“General Requirements for Control of Fine 

Particulate Matter (PM-10),” adopted on October 10, 1994, 

revised on November 25, 1996 and revised on November 8,

2005.

(2) Rule 801,“Construction & Earthmoving Activities,” Rule 802, 

“Bulk Materials,” Rule 803,“Carry-Out & Track-Out,” Rule 

804,“Open Areas,” Rule 805,“Paved & Unpaved Roads,” Rule 

806,“Conservation Management Practices,” adopted on November

8, 2005.

* * * * *