64774 Federal Register / Vol. 83, No. 242 / Tuesday, December 18, 2018 / Proposed Rules 

1For a given air pollutant, ‘‘primary’’ national 

ambient air quality standards are those determined 

by the EPA as requisite to protect the public health. 

‘‘Secondary’’ standards are those determined by the 

EPA as requisite to protect the public welfare from 

any known or anticipated adverse effects associated 

with the presence of such air pollutant in the 

ambient air. CAA section 109(b). 

2 78 FR 3086, 3088 (January 15, 2013). 

3EPA, Air Quality Criteria for Particulate Matter, 

No. EPA/600/P–99/002aF and EPA/600/P–99/ 

002bF, October 2004. 

4 62 FR 38652. 

(2) With the exception of demolition 

crews, entry into or remaining in this 

safety zone is prohibited. 

(3) All vessels within this safety zone 

when this section becomes effective 

must depart the zone immediately. 

(4) The Captain of the Port, North 

Carolina can be reached through the 

Coast Guard Sector North Carolina 

Command Duty Officer, Wilmington, 

North Carolina at telephone number 

910–343–3882. 

(5) The Coast Guard and designated 

security vessels enforcing the safety 

zone can be contacted on VHF–FM 

marine band radio channel 13 (165.65 

MHz) and channel 16 (156.8 MHz). 

(d) Enforcement. The U.S. Coast 

Guard may be assisted in the patrol and 

enforcement of the safety zone by 

Federal, State, and local agencies. 

(e) Enforcement Period. This 

regulation will be enforced from 

February 1, 2019 through February 29, 

2020 

(f) Public Notification. The Coast 

Guard will notify the public of the 

active enforcement times at least 48 

hours in advance by transmitting 

Broadcast Notice to Mariners via VHF– 

FM marine channel 16. 

Dated: December 7, 2018. 

Bion B. Stewart, 

Captain, U.S. Coast Guard Captain of the 

Port North Carolina. 

[FR Doc. 2018–27385 Filed 12–17–18; 8:45 am] 

BILLING CODE 9110–04–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2017–0728; FRL–9988–01– 

Region 9] 

Approval and Promulgation of Air 

Quality State Implementation Plans; 

California; Plumas County; Moderate 

Area Plan for the 2012 PM2.5 NAAQS 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve 

most elements of the state 

implementation plan (SIP) revisions 

submitted by California to address Clean 

Air Act (CAA or ‘‘Act’’) requirements for 

the 2012 annual fine particulate matter 

(PM2.5) national ambient air quality 

standards (NAAQS or ‘‘standards’’) in 

the Plumas County Moderate PM2.5

nonattainment area (‘‘Portola 

nonattainment area’’). The SIP revisions 

are the ‘‘Portola Fine Particulate Matter 

(PM2.5) Attainment Plan’’ submitted on 

February 28, 2017, and the 2019 and 

2022 transportation conformity motor 

vehicle emission budgets (‘‘budgets’’) 

submitted on December 20, 2017. We 

refer to these submittals collectively as 

the ‘‘Portola PM2.5 Plan’’ or ‘‘Plan.’’ The 

EPA is proposing to approve the 

following elements of the Portola PM2.5

Plan: The 2013 base year emissions 

inventories, the reasonably available 

control measure/reasonably available 

control technology (RACM/RACT) 

demonstration, the attainment 

demonstration, the reasonable further 

progress (RFP) demonstration, the 

quantitative milestones, and the budgets 

for 2019 and 2021. The EPA is not 

proposing any action at this time on the 

contingency measures in the Portola 

PM2.5 Plan. 

DATES: Any comments must arrive by 

January 17, 2019. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–R09– 

OAR–2017–0728 at https://

www.regulations.gov, or via email to 

John Ungvarsky, at Ungvarsky.john@

epa.gov. For comments submitted at 

Regulations.gov, follow the online 

instructions for submitting comments. 

Once submitted, comments cannot be 

removed or edited from Regulations.gov. 

For either manner of submission, the 

EPA may publish any comment received 

to its public docket. Do not submit 

electronically any information you 

consider to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Multimedia submissions (audio, video, 

etc.) must be accompanied by a written 

comment. The written comment is 

considered the official comment and 

should include discussion of all points 

you wish to make. The EPA will 

generally not consider comments or 

comment contents located outside of the 

primary submission (i.e., on the web, 

cloud, or other file sharing system). For 

additional submission methods, please 

contact the person identified in the FOR

FURTHER INFORMATION CONTACT section. 

For the full EPA public comment policy, 

information about CBI or multimedia 

submissions, and general guidance on 

making effective comments, please visit 

http://www2.epa.gov/dockets/ 

commenting-epa-dockets. 

FOR FURTHER INFORMATION CONTACT: John 

Ungvarsky, EPA Region IX, (415) 972– 

3963, ungvarsky.john@epa.gov. 

SUPPLEMENTARY INFORMATION: 

Throughout this document, ‘‘we,’’ ‘‘us’’ 

and ‘‘our’’ refer to the EPA. 

Table of Contents 

I. Background for Proposed Action 

II. Clean Air Act Requirements for Moderate 

PM2.5 Nonattainment Area Plans 

III. Completeness Review of the Portola PM2.5

Attainment Plan 

IV. Review of the Portola PM2.5 Plan 

V. Summary of Proposed Actions and 

Request for Public Comment 

VI. Statutory and Executive Order Reviews 

I. Background for Proposed Action 

Under section 109 of the CAA, the 

EPA has established NAAQS for certain 

pervasive air pollutants (referred to as 

‘‘criteria pollutants’’) and conducts 

periodic reviews of the NAAQS to 

determine whether they should be 

revised or whether new NAAQS should 

be established. The EPA sets the 

NAAQS for criteria pollutants at levels 

required to protect public health and 

welfare.1 Particulate matter is one of the 

criteria pollutants for which the EPA 

has established health-based standards. 

The CAA requires states to submit 

regulations that control particulate 

matter emissions. 

Particulate matter includes particles 

with diameters that are generally 2.5 

microns or smaller (PM2.5) and particles 

with diameters that are generally 10 

microns or smaller (PM10). It contributes 

to effects that are harmful to human 

health and the environment, including 

premature mortality, aggravation of 

respiratory and cardiovascular disease, 

decreased lung function, visibility 

impairment, and damage to vegetation 

and ecosystems. Individuals particularly 

sensitive to PM2.5 exposure include 

older adults, people with heart and lung 

disease, and children.2 PM2.5 can be 

emitted by sources directly into the 

atmosphere as a solid or liquid particle 

(‘‘primary PM2.5’’ or ‘‘direct PM2.5’’) or 

can be formed in the atmosphere 

(‘‘secondary PM2.5’’) as a result of 

various chemical reactions among 

precursor pollutants from sources such 

as nitrogen oxides (NOX), sulfur dioxide 

(SO2), volatile organic compounds 

(VOC), and ammonia.3

On July 18, 1997, the EPA revised the 

NAAQS for particulate matter to add 

new standards for PM2.5.4 The EPA 

established primary and secondary 

annual and 24-hour standards for PM2.5. 

The annual standard was set at 15.0 

micrograms per cubic meter (mg/m3) 


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5The primary and secondary standards were set 

at the same level for both the 24-hour and the 

annual PM2.5 standards. 

6Under EPA regulations at 40 CFR part 50, the 

primary and secondary 2006 24-hour PM2.5 NAAQS 

are attained when the annual arithmetic mean 

concentration, as determined in accordance with 40 

CFR part 50, Appendix N, is less than or equal to 

35 mg/m3 at all relevant monitoring sites in the 

subject area, averaged over a 3-year period. 

7 71 FR 61144. 

8 78 FR 3086. 

9 80 FR 2206 (January 15, 2015). 

10From 2000 through early 2013, the Portola 

PM2.5 monitoring site was located at 161 Nevada 

Street. In 2013, the site was relocated to 420 Gulling 

Street. 

11 General Preamble, 57 FR 13498 (April 16, 

1992). 

12 57 FR 13538. 

13 81 FR 58010, August 24, 2016. 

14 40 CFR 51.1006 and 51.1009. 

based on a 3-year average of annual 

mean PM2.5 concentrations, and the 24- 

hour (daily) standard was set at 65 mg/ 

m3 based on the 3-year average of the 

annual 98th percentile values of 24-hour 

PM2.5 concentrations at each 

population-oriented monitor within an 

area.5

On October 17, 2006, the EPA 

retained the annual average NAAQS at 

15 mg/m3 but revised the level of the 24- 

hour PM2.5 NAAQS to 35 mg/m3 based 

on a 3-year average of the annual 98th 

percentile values of 24-hour 

concentrations.6 7

On January 15, 2013, the EPA 

finalized the 2012 PM2.5 NAAQS, 

including a revision of the annual 

standard to 12.0 mg/m3 based on a 3-year 

average of annual mean PM2.5

concentrations, and retaining the 

current 24-hour standard of 35 mg/m3

based on a 3-year average of the 98th 

percentile of 24-hour concentrations.8

Following promulgation of a new or 

revised NAAQS, the EPA is required by 

CAA section 107(d) to designate areas 

throughout the nation as attaining or not 

attaining the NAAQS. The EPA 

designated and classified the Portola 

area as ‘‘Moderate’’ nonattainment for 

the 2012 annual PM2.5 standards based 

on ambient monitoring data that showed 

the area was above 12.0 mg/m3 for the 

2011–2013 monitoring period.9 For the 

2011–2013 period, the annual PM2.5

design value for the Portola area was 

12.8 mg/m3 based on monitored readings 

at the 161 Nevada Street and 420 

Gulling Street monitors.10

The Portola PM2.5 nonattainment area 

includes the City of Portola (‘‘Portola’’), 

which has a population of 

approximately 2,100 and is located at an 

elevation of 4,890 feet in an 

intermountain basin isolated by rugged 

mountains. Portola averages 20 inches 

of precipitation annually. From October 

through March the nonattainment area 

has very cold temperatures with the 

average daily low temperature of 

approximately 22 degrees Fahrenheit. 

The combination of mountains, cold 

temperatures, and elevation can cause 

inversions and impair PM2.5 dispersion, 

especially during the winter. For a 

precise description of the geographic 

boundaries of the Portola PM2.5

nonattainment area, see 40 CFR 81.305. 

The local air district with primary 

responsibility for developing a plan to 

attain the 2012 annual PM2.5 NAAQS in 

this area is the Northern Sierra Air 

Quality Management District (NSAQMD 

or ‘‘District’’). The District worked 

cooperatively with the California Air 

Resources Board (CARB) in preparing 

the Portola PM2.5 Plan. Under state law, 

authority for regulating sources under 

state jurisdiction in the Portola 

nonattainment area is split between the 

District, which has responsibility for 

regulating stationary and most area 

sources, and CARB, which has 

responsibility for regulating most 

mobile sources. 

II. Clean Air Act Requirements for 

Moderate PM2.5 Nonattainment Area 

Plans 

With respect to the statutory 

requirements for attainment plans for 

the 2012 annual PM2.5 NAAQS, the 

general CAA part D nonattainment area 

planning requirements are found in 

subpart 1, and the Moderate area 

planning requirements specifically for 

particulate matter are found in subpart 

4. 

The EPA has a longstanding general 

guidance document that interprets the 

1990 amendments to the CAA, 

commonly referred to as the General 

Preamble for the Implementation of 

Title I of the Clean Air Act Amendments 

of 1990 (‘‘General Preamble’’).11 The 

General Preamble addresses the 

relationship between the subpart 1 and 

the subpart 4 requirements and provides 

recommendations to states for meeting 

certain statutory requirements for 

particulate matter attainment plans. As 

explained in the General Preamble, 

specific requirements applicable to 

Moderate area attainment plan SIP 

submissions for the particulate matter 

NAAQS are set forth in subpart 4 of part 

D, title I of the Act, but such SIP 

submissions must also meet the general 

attainment planning provisions in 

subpart 1 of part D, title I of the Act, to 

the extent these provisions ‘‘are not 

otherwise subsumed by, or integrally 

related to,’’ the more specific subpart 4 

requirements.12

To implement the PM2.5 NAAQS, the 

EPA has also promulgated the ‘‘Fine 

Particle Matter National Ambient Air 

Quality Standard: State Implementation 

Plan Requirements; Final Rule’’ 

(hereinafter, the ‘‘PM2.5 SIP 

Requirements Rule’’).13 The PM2.5 SIP 

Requirements Rule provides additional 

regulatory requirements and guidance 

applicable to attainment plan 

submissions for the PM2.5 NAAQS, 

including the 2012 annual PM2.5

NAAQS at issue in this action. 

The subpart 1 statutory requirements 

for attainment plans include: (i) The 

section 172(c)(1) requirements for 

RACM/RACT and attainment 

demonstrations; (ii) the section 172(c)(2) 

requirement to demonstrate RFP; (iii) 

the section 172(c)(3) requirement for 

emissions inventories; (iv) the section 

172(c)(5) requirements for a 

nonattainment new source review 

(NNSR) permitting program; and (v) the 

section 172(c)(9) requirement for 

contingency measures. 

The more specific subpart 4 statutory 

requirements for Moderate PM2.5

nonattainment areas include: (i) The 

section 189(a)(1)(A) and 189(e) NNSR 

permit program requirements; (ii) the 

section 189(a)(1)(B) requirements for 

attainment demonstrations; (iii) the 

section 189(a)(1)(C) requirements for 

RACM; and (iv) the section 189(c) 

requirements for RFP and quantitative 

milestones. Under subpart 4, states with 

Moderate PM2.5 nonattainment areas 

must provide for attainment in the area 

as expeditiously as practicable but no 

later than December 31, 2021, for the 

2012 PM2.5 annual NAAQS. In addition, 

under subpart 4, direct PM2.5 and all 

precursors to the formation of PM2.5 are 

subject to control unless the EPA 

approves a demonstration from the State 

establishing that a given precursor does 

not contribute significantly to PM2.5

levels that exceed the PM2.5 NAAQS in 

the area.14

III. Completeness Review of the Portola 

PM2.5 Attainment Plan 

CAA sections 110(a)(1) and (2) and 

110(l) require each state to provide 

reasonable public notice and 

opportunity for public hearing prior to 

the adoption and submission of a SIP or 

SIP revision to the EPA. To meet this 

requirement, every SIP submission 

should include evidence that adequate 

public notice was given and an 

opportunity for a public hearing was 

provided consistent with the EPA’s 

implementing regulations in 40 CFR 

51.102. 

Both the District and CARB satisfied 

applicable statutory and regulatory 

requirements for reasonable public 


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15The District public notice posted on its website 

for January 23, 2017 public hearing (undated); 

February 14, 2017 proof of publication from Plumas 

County News of public notice for January 23, 2017 

public hearing; December 14, 2016 proof of 

publication from Feather Publishing Co., Inc. of 

public notice that public notice for January 23, 2017 

public hearing published in the Feather River 

Bulletin, Indian Valley Record, and Portola 

Reporter during the week beginning December 14, 

2016; and NSAQMD Governing Board Resolution 

2017–01, ‘‘In the Matter of Adopting the Portola 

Fine Particulate Matter (PM2.5) Attainment Plan 

(Portola Plan) as required by the Federal Clean Air 

Act,’’ January 13, 2017. 

16CARB, Notice of evidence of listserve 

publication, ‘‘arbcombo—Notice of Public Meeting 

for February 16, 2017,’’ and ‘‘Notice of Public 

Meeting to Consider the Approval of the Portola 

PM2.5 State Implementation Plan,’’ both dated 

January 13, 2017; CARB Board Resolution 17–2, 

‘‘Portola PM2.5 State Implementation Plan,’’ 

February 16, 2017. 

17CARB Board Resolution 17–28, ‘‘Supplemental 

Transportation Conformity Emissions Budgets for 

the Portola Fine Particulate Matter (PM2.5) 

Attainment Plan,’’ October 26, 2017. 

18The EPA released an update to AP–42 in 

January 2011 that revised the equation for 

estimating paved road dust emissions based on an 

updated data regression that included new emission 

tests results. 

19 76 FR 6328 (February 4, 2011). 

20The EMFAC model (short for EMission FACtor) 

is a computer model developed by CARB. The EPA 

approved EMFAC2014 for use in SIP revisions and 

transportation conformity at 80 FR 77337 

(December 14, 2015). 

21 40 CFR 51.1007(a), 51.1008(b), and 51.1009(f); 

see also U.S. EPA, ‘‘Emissions Inventory Guidance 

for Implementation of Ozone [and Particulate 

Matter] National Ambient Air Quality Standards 

(NAAQS) and Regional Haze Regulations,’’ 

available at http://www.epa.gov/sites/production/ 

files/2014-10/documents/2014revisedeiguidance_

0.pdf. 

22The Portola PM2.5 Plan generally uses ‘‘sulfur 

oxides’’ or ‘‘SOX’’ in reference to SO2 as a precursor 

to the formation of PM2.5. We use SOX and SO2

interchangeably throughout this notice. 

23CARB’s facility search engine website shows 

for 2016 in the Portola PM2.5 nonattainment area 

there are no major stationary sources and only three 

non-major stationary sources. Two of the non-major 

sources reported zero particulate matter (PM) 

emissions in 2016, and the third non-major source 

(i.e., White Cap Ready Mix #1) reported 1.9 tons per 

year of PM emissions. For more information see 

https://www.arb.ca.gov/app/emsinv/facinfo/ 

facinfo.php. 

24The EPA regulations refer to ‘‘nonroad’’ 

vehicles and engines whereas California Air 

Resources Board (CARB) regulations refer to ‘‘offroad’’ vehicles and engines. These terms refer to the 

same types of vehicles and engines, and for the 

purposes of this action, we will be using CARB’s 

chosen term, ‘‘off-road,’’ to refer to such vehicles 

and engines. 

25Portola PM2.5 Plan, Appendix B. 

notice and hearing prior to adoption and 

submission of the Portola PM2.5 Plan. 

The District provided a 30-day public 

comment period prior to its January 23, 

2017 public hearing to adopt the main 

SIP submission.15 CARB provided the 

required public notice and opportunity 

for public comment prior to its February 

16, 2017 public hearing and adoption of 

the main SIP submission.16 CARB then 

adopted its supplemental SIP 

submission pertaining to 2019 and 2022 

transportation conformity motor vehicle 

emission budgets at its October 26, 2017 

Board meeting after reasonable public 

notice.17 Each submission includes 

proof of publication of notices for the 

respective public hearings. We find, 

therefore, that the Portola PM2.5 Plan 

meets the requirements for reasonable 

notice and public hearings in CAA 

sections 110(a) and 110(l). 

CAA section 110(k)(1)(B) requires the 

EPA to determine whether a SIP 

submission is complete within 60 days 

of receipt. This section also provides 

that any plan that the EPA has not 

affirmatively determined to be complete 

or incomplete will become complete by 

operation of law six months after the 

date of submission. The EPA’s SIP 

completeness criteria are found in 40 

CFR part 51, appendix V. The February 

28, 2017 and December 20, 2017 SIP 

submissions became complete by 

operation of law on August 28, 2017 and 

June 20, 2018, respectively. 

IV. Review of the Portola PM2.5 Plan 

A. Emissions Inventory 

1. Requirements for Emissions 

Inventories 

CAA section 172(c)(3) requires that 

each SIP include a ‘‘comprehensive, 

accurate, current inventory of actual 

emissions from all sources of the 

relevant pollutant or pollutants in [the] 

area . . . .’’ By requiring an accounting 

of actual emissions from all sources of 

the relevant pollutants in the area, this 

section provides for the base year 

inventory to include all emissions that 

contribute to the formation of a 

particular NAAQS pollutant. For the 

2012 PM2.5 NAAQS, this includes 

emissions of direct PM2.5 as well as the 

main chemical precursors to the 

formation of secondary PM2.5: NOX, 

SO2, VOC, and ammonia. Primary PM2.5

includes condensable and filterable 

particulate matter. 

A state must include in its SIP 

submission documentation explaining 

how the emissions data were calculated. 

In estimating mobile source emissions, 

a state should use the latest emissions 

models and planning assumptions 

available at the time it develops the SIP 

submission. States are also required to 

use the EPA’s ‘‘Compilation of Air 

Pollutant Emission Factors’’ (AP–42) 18

road dust method for calculating reentrained road dust emissions from 

paved roads.19 The latest EPA-approved 

version of California’s mobile source 

emission factor model is EMFAC2014.20

In addition to the base year inventory 

submitted to meet the requirements of 

CAA section 172(c)(3), the State must 

also submit future ‘‘baseline 

inventories’’ for the projected 

attainment year and each RFP milestone 

year, and any other year of significance 

for meeting applicable CAA 

requirements.21 By ‘‘baseline 

inventories’’ (also referred to as 

‘‘projected baseline inventories’’), we 

mean projected emissions inventories 

for future years that account for, among 

other things, the ongoing effects of 

economic growth and adopted 

emissions control requirements. The SIP 

submission should include 

documentation to explain how the state 

calculated the emissions projections. 

2. Emissions Inventory in the Portola 

PM2.5 Plan 

The Portola PM2.5 nonattainment area 

emissions inventory is typical of a 

small, high elevation mountain 

community. There are no major 

stationary sources or large industrial 

sources (existing or anticipated) and 

residential wood burning is a significant 

source of direct PM2.5. A summary of the 

planning emissions inventories for 

direct PM2.5 and all PM2.5 precursors 

(NOX, SOX, VOC, and ammonia) 22 for 

the Portola PM2.5 nonattainment area is 

found in section III. Detailed inventories 

for the Portola PM2.5 nonattainment area 

together with documentation for the 

inventories are found in Appendix B of 

the Plan. CARB and District staff 

worked jointly to develop the emissions 

inventory for the Portola PM2.5

nonattainment area. The District worked 

with operators of the three stationary 

facilities in the nonattainment area to 

develop the stationary source emissions 

estimates.23 CARB staff developed the 

emissions inventory for mobile sources, 

both on-road and off-road.24 The District 

and CARB shared responsibility for 

developing estimates for the area 

sources such as residential wood 

burning and paved road dust. 

The Plan includes annual average 

emissions inventories for the 2013 base 

year and estimated emissions for the 

2019, 2021, and 2022 future baseline 

years. Future baseline inventories are a 

projection of the base year inventory 

taking into account expected growth 

trends for each source category and 

emission reductions from control 

measures adopted prior to January 1, 

2013. CARB develops emissions 

projections by applying growth and 

control profiles to the base year 

inventory.25

Each inventory includes emissions 

from stationary, area, on-road, and nonVerDate Sep<11>2014 17:26 Dec 17, 2018 Jkt 247001 PO 00000 Frm 00027 Fmt 4702 Sfmt 4702 E:\FR\FM\18DEP1.SGM 18DEP1

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26Portola PM2.5 Plan, Appendix B. 

27 Id. 

28 40 CFR 51.1006(a)(1). 

29 Id. 

30EPA Office of Air Quality Planning and 

Standards, ‘‘PM2.5 Precursor Demonstration 

Guidance,’’ EPA–454/P–16–001, November 17, 

2016 draft, available at https://www.epa.gov/pmpollution/draft-pm25-precursor-demonstrationguidance. 

road sources. The inventories use 

EMFAC2014 for estimating on-road 

motor vehicle emissions.26 Re-entrained 

paved road dust emissions were 

calculated using the EPA’s AP–42 road 

dust methodology.27

Table 1 provides a summary of the 

annual average inventories in tons per 

day (tpd) of direct PM2.5 and PM2.5

precursors for the base year of 2013. 

These inventories provide the basis for 

the control measure analysis and the 

RFP and attainment demonstrations in 

the Portola PM2.5 Plan. For a detailed 

breakdown of the inventories, see 

Appendix B, Tables 6–10 in the Portola 

PM2.5 Plan. 

TABLE 1—PORTOLA ANNUAL AVERAGE EMISSIONS INVENTORY FOR DIRECT PM2.5 AND PM2.5 PRECURSORS FOR THE

2013 BASE YEAR (tpd) 

Category Direct PM2.5 NOX SOX VOC Ammonia 

Stationary Sources ............................................................... 0.007 0.002 0.000 0.016 0.018 

Area Sources ....................................................................... 0.468 0.048 0.015 0.661 0.142 

On-Road Mobile Sources .................................................... 0.005 0.181 0.0003 0.101 0.005 

Off-Road Mobile Sources .................................................... 0.011 0.273 0.0001 0.162 0.0001 

Totals ............................................................................ 0.490 0.504 0.016 0.940 0.149 

Source: Portola PM2.5 Plan, Section III, Table 3 (p. 24) and Appendix B, Tables 6–10. 

3. The EPA’s Evaluation and Proposed 

Action 

The inventories in the Portola PM2.5

Plan are based on the most current and 

accurate information available to the 

State and District at the time the Plan 

and its inventories were being 

developed in 2015 and 2016, including 

the latest version of California’s mobile 

source emissions model, EMFAC2014. 

The inventories comprehensively 

address all source categories in the 

Portola PM2.5 nonattainment area and 

were developed consistent with the 

EPA’s inventory guidance. For these 

reasons, we are proposing to approve 

the 2013 base year emissions inventory 

in the Portola PM2.5 Plan as meeting the 

requirements of CAA section 172(c)(3). 

We are also proposing to find that the 

projected baseline inventories in the 

Plan provide an adequate basis for the 

RACM, RFP, and attainment 

demonstrations in the Portola PM2.5

Plan. 

B. PM2.5 Precursors 

1. Precursor Requirements 

The provisions of subpart 4 of part D, 

title I of the CAA do not define the term 

‘‘precursor’’ for purposes of PM2.5, nor 

do they explicitly require the control of 

any specifically identified PM 

precursor. The statutory definition of 

‘‘air pollutant’’ in CAA section 302(g), 

however, provides that the term 

‘‘includes any precursors to the 

formation of any air pollutant, to the 

extent the Administrator has identified 

such precursor or precursors for the 

particular purpose for which the term 

‘air pollutant’ is used.’’ The EPA has 

identified SO2, NOX, VOC, and 

ammonia as precursors to the formation 

of PM2.5. Accordingly, the attainment 

plan requirements of subpart 4 apply to 

emissions of all four precursor 

pollutants and direct PM2.5 from all 

types of stationary, area, and mobile 

sources, except as otherwise provided in 

the Act (e.g., in CAA section 189(e)). 

Section 189(e) of the Act requires that 

the control requirements for major 

stationary sources of direct PM10 (which 

includes PM2.5) also apply to major 

stationary sources of PM10 precursors, 

except where the Administrator 

determines that such sources do not 

contribute significantly to PM10 levels 

that exceed the standard in the area. 

Section 189(e) contains the only 

expressed exception to the control 

requirements under subpart 4 for 

sources of PM2.5 precursor emissions. 

Although section 189(e) explicitly 

addresses only major stationary sources, 

the EPA interprets the Act as 

authorizing it also to determine, under 

appropriate circumstances, that 

regulation of specific PM2.5 precursors 

from other sources in a given 

nonattainment area is not necessary. 

Under the PM2.5 SIP Requirements 

Rule, a state may elect to submit to the 

EPA a ‘‘comprehensive precursor 

demonstration’’ for a specific 

nonattainment area to show that 

emissions of a particular precursor from 

all existing sources located in the 

nonattainment area do not contribute 

significantly to PM2.5 levels that exceed 

the standard in the area.28 Such a 

comprehensive precursor demonstration 

must include a concentration-based 

contribution analysis (i.e., evaluation of 

the contribution of a particular 

precursor to PM2.5 levels in the area) 

and may also include a sensitivity-based 

contribution analysis (i.e., evaluation of 

the sensitivity of PM2.5 levels in the area 

to a decrease in emissions of the 

precursor). If the EPA determines that 

the contribution of the precursor to 

PM2.5 levels in the area is not significant 

and approves the demonstration, the 

state is not required to control emissions 

of the relevant precursor from existing 

sources in the current attainment plan.29

The EPA issued the draft PM2.5

Precursor Demonstration Guidance 

(‘‘Draft Guidance’’) to provide 

recommendations to states for 

appropriate precursor demonstrations in 

nonattainment plan SIP submissions.30

For the annual PM2.5 NAAQS, section 

2.2 of the Draft Guidance recommends 

use of 0.2 mg/m3 as a threshold below 

which ambient air quality impacts could 

be considered ‘‘insignificant,’’ i.e., 

impacts that do not ‘‘contribute’’ to 

PM2.5 concentrations that exceed the 

NAAQS. When considering whether a 

precursor contributes significantly to 

PM2.5 levels which exceed the NAAQS 

in the area, a state may also consider 

additional factors based on the facts and 

circumstances of the area. As to air 

quality impacts that exceed the 0.2 mg/ 

m3 contribution threshold, states may 

provide additional support for a 

conclusion that a particular precursor 

does not contribute significantly to 

ambient PM2.5 levels that exceed the 

NAAQS. States may consider 

information such as the amount by 

which the impacts exceed the 

recommended contribution threshold, 

the severity of nonattainment at relevant 

monitors and/or grid cell locations in 

the area, anticipated growth or loss of 

sources, analyses of speciation data and 


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31 Id. at 17. 

32Portola PM2.5 Plan, 51. 

33 IMPROVE is a monitoring program managed by 

the EPA and other federal and state agencies to 

assess visibility and aerosol conditions including 

PM2.5 species in Class I areas such as national parks. 

For more information, go to http://

vista.cira.colostate.edu/Improve/reconstructed-finemass/. 

34PMF is a multivariate source apportionment 

method that attributes PM2.5 observed 

concentrations to sources through statistical and 

meteorological interpretation of data. PMF is one of 

several EPA recommended receptor modeling 

methods for understanding of source impacts on 

ambient PM2.5 levels. 

35Portola PM2.5 Plan, 53. 

36 Id. at 47. 

37Email with attachment (i.e., Species 

Trends.xlsx) dated February 13, 2018, from Kasia 

Turkiewicz, CARB, to Scott Bohning and John 

Ungvarsky, EPA. 

precursor emission inventories, and air 

quality trends.31

2. Precursor Demonstration in the Plan 

Section V.C. of the Plan contains the 

State’s demonstration that emissions of 

SOX, NOX, ammonia, and VOC from all 

existing sources in the nonattainment 

area do not contribute significantly to 

PM2.5 levels that exceed the NAAQS. 

The demonstration includes a 

concentration-based portion, a 

sensitivity-based portion, and additional 

relevant information. The 

concentration-based portion is 

summarized in Table 8 of the Plan, 

based on 2013–2014 species 

composition data, and used to represent 

the base year design value used as the 

starting point in the rollback attainment 

demonstration as described in section 

IV.E.32 All four precursors together 

account for 6.3% of the 2013 PM2.5

design value. Organic matter and 

elemental carbon, mainly from wood 

burning, are the dominant contributors 

and account for 89% of the 2013 design 

value. 

For VOC emissions, the 

corresponding ambient PM2.5

component is anthropogenic Secondary 

Organic Aerosol (SOA). Based on 

comparison to ambient SOA 

concentrations per ton of total VOC 

emissions at other California locations, 

the State estimated Portola SOA 

concentrations of 0.02–0.05 mg/m3. The 

State also noted that seasonal organic 

carbon (OC) measurements at Portola 

are indistinguishable from background 

levels during the summer. Because SOA 

is a subset of OC, and summer is when 

SOA is highest due to the warmer 

temperatures, the State found that 

Portola’s SOA is comparable to the 0.06 

mg/m3 observed at nearby background 

interagency monitoring of protected 

visual environments (IMPROVE) sites 33

and well below the 0.2 mg/m3

contribution threshold. 

The ambient species concentrations 

corresponding to SOX, NOX, and 

ammonia were 0.41, 0.46, and 0.48 mg/ 

m3, respectively. Because these are all 

above the recommended contribution 

threshold of 0.2 mg/m3, the State 

conducted a follow-up sensitivity-based 

analysis. The sensitivity-based portion 

of the precursor demonstration used a 

variant of the rollback attainment 

demonstration based on Positive Matrix 

Factorization (PMF) as described in 

section IV.B.2 of this notice.34 The 

rollback model scales PM2.5 component 

concentrations (excluding background) 

according to changes in emissions. 

Ammonium nitrate was scaled 

proportional to NOX emissions; 

ammonium sulfate was scaled 

proportional to SOX emissions; and 

ammonium was scaled proportional to 

ammonia emissions. These were all on 

a conservative one-to-one basis; that is, 

a 1% emission change leads to a 1% 

concentration change. The sensitivity 

emission reductions modeled were 

10%, 25%, 30%, 50%, and 70%. 

As in the attainment demonstration, 

the precursor demonstration used the 

estimated 2021 design value. The PM2.5

effect of both the sensitivity reductions 

and the yearly reductions were 

combined to estimate the effect on the 

design value. Table 9 of the Plan lists 

the PM2.5 design values resulting from a 

10 to 70% reduction in emissions of 

each pollutant.35 For SOX and ammonia, 

the reductions have a negligible impact 

on the attainment year design value. 

The design values listed for the 70% 

emission reduction show PM2.5

responses of 0.09 and 0.11 mg/m3 for 

SOX and ammonia respectively, both 

well below the recommended 

contribution threshold. 

For NOX sensitivity, the Plan includes 

a discussion of the ambient response to 

a 30% reduction, 0.16 mg/m3, which is 

below the 0.2 mg/m3 contribution 

threshold. However, the given design 

values for 50% and 70% reductions 

show responses of 0.26 mg/m3 and 0.39 

mg/m3 respectively, which are above the 

recommended contribution threshold. 

Beyond the concentration-based and 

sensitivity-based analyses, the Plan 

provides several pieces of additional 

information to help assess the 

significance of NOX as a PM2.5

precursor. Table 7 of the Plan shows 

that NOX emissions in the Portola 

nonattainment area, estimated at 0.5 

tpd, are far smaller than the NOX

emissions in several other California 

counties, which range from 46.5 to 

104.0 tpd.36 The Plan also shows that 

90% of the NOX emissions in Portola are 

from mobile sources, which already are 

stringently controlled; PM2.5

concentrations would be not be 

sensitive to realistic additional control 

on these sources. 

Supporting supplemental data from 

CARB shows trends in emissions and 

species concentrations during 2002– 

2016.37 The data are for the Mountain 

Counties Air Basin, which comprises 

Plumas County and eight other similar 

counties that are also largely rural, 

wooded areas spanning the foothills to 

the crest of the Sierra Nevada 

mountains. Ammonia emissions during 

this period were essentially constant, 

but NOX and SOX emissions decreased 

by 46% and 67%, respectively. During 

the same time span, nitrate and sulfate 

concentrations decreased by 23% and 

16%, respectively. Since nitrate and 

sulfate were responding to NOX and 

SOX emissions reductions, this suggests 

that ammonium nitrate formation is 

NOX-limited and ammonium sulfate is 

SOX-limited, rather than either being 

ammonia-limited. These observations 

support a finding that ammonia is an 

insignificant PM2.5 precursor, for which 

controls would be of little benefit. 

Based on its evaluations, the State 

concluded that additional controls on 

PM2.5 precursors would have an 

insignificant effect on PM2.5

concentrations, and that precursors 

need not be included in the controls 

analysis. 

3. The EPA’s Evaluation and Proposed 

Action 

The comprehensive precursor 

demonstration provided in the Plan 

meets the requirements of 40 CFR 

51.1006(a)(1) and is consistent with the 

EPA’s recommendations in the Draft 

Guidance. The demonstration contains a 

concentration-based contribution 

analysis for VOC and sensitivity-based 

contribution analyses for NOX, SOX, and 

ammonia, together with additional 

information about the Portola area, as 

recommended in the Draft Guidance 

(e.g., emission inventory and ambient 

PM2.5 composition data). 

For the SO2 concentration-based 

analysis, the Plan states that background 

sulfate concentrations are 97% of the 

0.41 mg/m3 measured at Portola. The 

remaining 3% of the sulfate, or 0.012 

mg/m3, is attributable to Portola sources. 

This 3% contribution from Portola 

sources to PM2.5 levels above the 

NAAQS is well below the EPA’s 0.2 mg/ 

m3 contribution threshold. 

For the VOC concentration analysis, 

the Plan provides several estimates of 

SOA at Portola. The estimates, which 


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38Plan, Figure 9, 20, and Table 8, 51. 

39 Draft Guidance, 23. 40 81 FR 58010, 58020 (August 24, 2016). 

41This interpretation is consistent with guidance 

provided in the General Preamble at 13540. 

can be considered ‘‘data analysis 

techniques’’ as described in the Draft 

Guidance, are appropriate for refining 

SOA estimates from available 

measurements and provide a convincing 

case that VOCs do not contribute 

significantly to PM2.5 levels that exceed 

the NAAQS in the area. 

For NOX, the Plan’s estimate for the 

nitrate contribution and the 

corresponding sensitivity to NOX

reductions may be unrealistically high. 

The PMF modeling results estimated the 

secondary nitrate contribution to be 

5.1% of the total PM2.5, whereas the raw 

chemical composition data estimated 

only 3.3%.38 In addition, the 

concentration-based analysis may have 

overestimated nitrate concentrations 

because it does not apply the sulfate, 

adjusted nitrate, derived water, inferred 

carbonaceous balance approach 

(SANDWICH) 39 for reconciling the mass 

from speciation measurements with that 

from the Federal Reference Method 

(FRM) used for design values. Because 

the SANDWICH adjustment generally 

reduces nitrate, due to nitrate losses 

from FRM monitors, the precursor 

demonstration in the Plan may be 

overestimating the amount of nitrate 

and the nitrate response to NOX

emission reductions. Thus, the 

approach used in the Plan results in a 

more conservative precursor 

demonstration. 

The sensitivity-based precursor 

analysis relies on the same methodology 

as the attainment demonstration, 

including the very conservative 

assumption that the ambient response to 

NOX reductions is in a 1:1 ratio to the 

emission change (on a percent basis). 

The responses to SO2 and ammonia 

reductions were below the 

recommended 0.2 mg/m3 contribution 

threshold, but the response to NOX was 

above the threshold at 50% and 70% 

reductions. 

The Plan includes additional 

information supporting a conclusion 

that NOX emissions do not contribute 

significantly to PM2.5 levels that exceed 

the NAAQS in the area. The information 

includes the small size of the NOX

emission inventory relative to other 

areas and recognition that mobile 

sources are already highly controlled. 

These are indications that ambient PM2.5

levels would not be sensitive to 

additional NOX controls. 

The EPA also considered two other 

implications of the data provided with 

the Plan or as a supplement. The 

supplemental 2002–2016 emissions and 

speciation trends can be used to derive 

a response factor, the percent change in 

nitrate concentration for each percent 

change in NOX emissions. Because 

ammonia emissions are constant, they 

provide a reasonable factor to use as the 

response to reductions of NOX in the 

sensitivity analysis. Using 2002–2016 

data results in a NOX response factor of 

0.378. Using this in a variant of the 

Plan’s NOX sensitivity analysis in place 

of the 1:1 assumption, the EPA found 

that the ambient PM2.5 response to a 

50% NOX reduction is 0.105 mg/m3, and 

the response to a 70% reduction is 0.147 

mg/m3. Both of these are below the 

EPA’s recommended contribution 

threshold of 0.2 mg/m3. (The original 

responses were 0.277 and 0.388 mg/m3.) 

Since the years 2013–2016 were 

somewhat anomalous, with some nitrate 

increases, the EPA carried out the same 

exercise using just 2002–2011 data, 

which resulted in a NOX response factor 

of 0.625. In turn, this results in a 50% 

response of 0.173 mg/m3 and a 70% 

response of 0.243 mg/m3. The 70% 

response is above but considerably 

closer to the recommended 0.2 mg/m3

contribution threshold. When 

considered in light of the additional 

information discussed above, the 70% 

response supports a conclusion that 

NOX emissions do not contribute 

significantly to PM2.5 levels that exceed 

the NAAQS in the area. 

A second implication of the data from 

the Plan concerns the effect of a 70% 

NOX reduction on the year that the 

Portola area can attain the NAAQS. 

Under the PM2.5 SIP Requirements Rule 

at 40 CFR 51.1009(a)(4)(i), if a Moderate 

PM2.5 nonattainment area, such as the 

Portola area, can show that reducing 

emission of a precursor is not necessary 

for expeditious attainment of the 

NAAQS and cannot advance attainment 

by a year,40 then that precursor need not 

be controlled for attainment purposes. 

Even assuming a NOX reduction of 70%, 

which is very large in comparison with 

the historical reductions of about 6% 

per year, and assuming an 

unrealistically conservative 1:1 nitrate 

response ratio, the resulting response is 

0.388 mg/m3, which is less than the 

average 0.41 mg/m3 per year PM2.5

decrease seen during 2019–2021 in the 

attainment demonstration. This 

observation supports a conclusion that 

controlling NOX is not necessary for 

expeditious attainment of the NAAQS 

because it would not advance the 

attainment date by a year in the Portola 

nonattainment area. 

The EPA is proposing to approve the 

State’s demonstration that emissions of 

PM2.5 precursors (i.e., SOX, NOX, 

ammonia, and VOC) from all existing 

sources located in the nonattainment 

area do not contribute significantly to 

PM2.5 levels that exceed the standards in 

the area. If the EPA finalizes this 

proposal, the State and District would 

not be required to control emissions of 

these precursors from existing sources 

in the Portola PM2.5 Plan for purposes of 

the 2012 annual PM2.5 NAAQS. The 

State, District, and the EPA will 

reexamine this issue if the Portola area 

fails to attain the NAAQS and EPA 

reclassifies the area to Serious for the 

2012 annual PM2.5 NAAQS. 

C. Reasonably Available Control 

Measures/Reasonably Available Control 

Technology 

1. Requirements for RACM/RACT 

The general subpart 1 attainment plan 

requirement for RACM and RACT is 

described in CAA section 172(c)(1), 

which requires that attainment plan 

submissions ‘‘provide for the 

implementation of all reasonably 

available control measures as 

expeditiously as practicable (including 

such reductions in emissions from 

existing sources in the area as may be 

obtained through the adoption, at a 

minimum, of reasonably available 

control technology)’’ and provide for 

attainment of the NAAQS. 

The attainment planning 

requirements specific to PM2.5 under 

subpart 4 likewise impose upon states 

with nonattainment areas classified as 

Moderate an obligation to develop 

attainment plans that require RACM/ 

RACT on sources of direct PM2.5 and all 

PM2.5 plan precursors. CAA section 

189(a)(1)(C) requires that Moderate area 

PM2.5 SIPs contain provisions to assure 

that RACM/RACT are implemented no 

later than 4 years after designation of 

the area. The EPA reads CAA sections 

172(c)(1) and 189(a)(1)(C) together to 

require that attainment plans for 

Moderate nonattainment areas provide 

for the implementation of RACM and 

RACT for existing sources of PM2.5 and 

those PM2.5 precursors subject to control 

in the nonattainment area as 

expeditiously as practicable but no later 

than 4 years after designation.41

The PM2.5 SIP Requirements Rule 

defines RACM as ‘‘any technologically 

and economically feasible measure that 

can be implemented in whole or in part 

within 4 years after the effective date of 

designation of a PM2.5 nonattainment 

area and that achieves permanent and 

enforceable reductions in direct PM2.5

emissions and/or PM2.5 plan precursor 


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42 40 CFR 51.1000. ‘‘PM2.5 plan precursors’’ are 

defined as ‘‘those PM2.5 precursors required to be 

regulated in the applicable attainment plan and/or 

NNSR program’’ and ‘‘PM2.5 precursors’’ are SO2, 

NOX, VOC, and ammonia. 

43 General Preamble at 13541 and 57 FR 18070, 

18073–74 (April 28, 1992). 

44 40 CFR 51.1000, 51.1009(a)(i)(B), and 

51.1009(a)(ii)(B). 

45 40 CFR 51.1009(a)(3). 

46 40 CFR 51.1009(a)(3); see also 57 FR 18070, 

18073–74. 

47 Id. 

48 57 FR 18070, 18074. 

49See, e.g., CAA sections 110(a)(2)(A), 172(c)(6), 

and 183(e)(4). 

50A ‘‘discretionary economic incentive program’’ 

is ‘‘any EIP submitted to the EPA as an 

implementation plan revision for purposes other 

than to comply with the statutory requirements of 

sections 182(g)(3), 182(g)(5), 187(d)(3), or 187(g) of 

the Act.’’ 40 CFR 51.491; see also 59 FR 16690 

(April 7, 1994) (codified at 40 CFR part 51, subpart 

U) and ‘‘Improving Air Quality with Economic 

Incentive Programs,’’ EPA, January 2001 (‘‘2001 EIP 

Guidance’’). 

51 2001 EIP Guidance, section 4.1. 

emissions from sources in the area.42

RACM includes reasonably available 

control technology (RACT).’’ The EPA 

has historically defined RACT as the 

lowest emission limitation that a 

particular stationary source is capable of 

meeting by the application of control 

technology (e.g., devices, systems, 

process modifications, or other 

apparatus or techniques that reduce air 

pollution) that is reasonably available 

considering technological and economic 

feasibility.43

Under the PM2.5 SIP Requirements 

Rule, those control measures that 

otherwise meet the definition of RACM 

but ‘‘can only be implemented in whole 

or in part during the period beginning 

4 years after the effective date of 

designation of a nonattainment area and 

no later than the end of the sixth 

calendar year following the effective 

date of designation of the area’’ must be 

adopted and implemented by the state 

as ‘‘additional reasonable measures.’’ 44

States must provide written 

justification in a SIP submission for 

eliminating potential control options 

from further review on the basis of 

technological or economic 

infeasibility.45 An evaluation of 

technological feasibility may include 

consideration of factors such as a 

source’s process and operating 

conditions, raw materials, physical 

plant layout, and non-air quality and 

energy impacts (e.g., increased water 

pollution, waste disposal, and energy 

requirements).46 An evaluation of 

economic feasibility may include 

consideration of factors such as cost per 

ton of pollution reduced (costeffectiveness), capital costs, and 

operating and maintenance costs.47

Absent other indications, the EPA 

presumes that it is reasonable for similar 

sources to bear similar costs of 

emissions reductions. Economic 

feasibility of RACM and RACT is thus 

largely informed by evidence that other 

sources in a source category have in fact 

applied the control technology, process 

change, or measure in question in 

similar circumstances.48

Consistent with these requirements, 

NSAQMD must implement RACM, 

including RACT, for direct PM2.5

emission sources no later than April 15, 

2019, and must implement additional 

reasonable measures for these sources 

no later than December 31, 2021. 

The CAA explicitly provides for the 

use of economic incentive programs 

(EIPs), such as the Portola voluntary 

wood stove change-out program, as one 

tool for states to use to achieve 

attainment of the NAAQS.49 EIPs use 

market-based strategies to encourage the 

reduction of emissions from stationary, 

area, and mobile sources in an efficient 

manner. The EPA has promulgated 

regulations for statutory EIPs required 

under section 182(g) of the Act and has 

issued guidance for discretionary 

EIPs.50 Where a state relies on a 

discretionary EIP in a SIP submission, 

the EPA evaluates the programmatic 

elements of the EIP to determine 

whether the resulting emission 

reductions are quantifiable, surplus, 

enforceable and permanent.51 These 

four fundamental ‘‘integrity elements,’’ 

which apply to all EIPs and other 

incentive/voluntary measures relied on 

for SIP purposes, are designed to ensure 

that such programs and measures satisfy 

the applicable requirements of the Act. 

2. RACM/RACT Analysis in the Portola 

PM2.5 Plan 

The State’s RACM and RACT analysis 

is in section VI.D of the Portola PM2.5

Plan. The emissions inventory analysis, 

conducted as part of the RACT analysis, 

confirmed that no major stationary 

sources of direct PM2.5 or any PM2.5

precursor are located in the Portola 

PM2.5 nonattainment area. As discussed 

above in section IV.C, the State 

provided a demonstration that PM2.5

precursor emissions do not contribute 

significantly to ambient PM2.5 levels that 

exceed the standards in the area. 

Therefore, the Portola PM2.5 Plan 

contains a RACM demonstration 

addressing only sources of direct PM2.5. 

3. Primary Sources of PM2.5 in the 

Nonattainment Area 

PM2.5 concentrations in the Portola 

PM2.5 nonattainment area are dominated 

by direct PM2.5 emissions from 

residential wood burning. Chapter II of 

the Plan documents the State and 

District’s bases for concluding that 

wood burning is the dominant source of 

PM2.5 throughout the nonattainment 

area. The documentation includes 

seasonal and diurnal patterns in PM2.5

concentrations, chemical composition 

data, PMF modeling, and statistical 

correlations between PM2.5 mass and 

levoglucosan (a wood burning tracer). 

The PMF model estimated that 76% of 

ambient PM2.5 on an annual basis is 

from wood burning. Burning of garbage 

in stoves, fireplaces, and in open burn 

piles contributes another 2.5% of 

annual PM2.5 levels. 

4. RACM Measures 

Table 2 lists the RACM measures in 

the Portola PM2.5 Plan. We discuss each 

of these measures in detail further 

below. 

TABLE 2—SUMMARY OF RACM IN PORTOLA PM2.5 NONATTAINMENT AREA

Measure 

Direct PM2.5

emission 

reductions 

(tpd) 

Scheduled action Implementation 

year 

Voluntary Wood Stove Change-out Program with Enforceable Commitment ..... 0.062 a ................... 2016 ...................... 2016–2020. 

City of Portola Wood Stove and Fireplace Ordinance Mandatory Wood Burning 

Curtailment.

Not estimated b ...... 2016 ...................... 2021. 

Other Provisions in City of Portola Wood Stove and Fireplace Ordinance c ....... Not estimated d ...... 2016 ...................... 2016. 

Open Burning Requirements (NSAQMD Rules 300–317) ................................... Not estimated e ...... 2019 ...................... 2019. 

CARB Mobile Source Programs ........................................................................... 0.006 ..................... Ongoing ................. Ongoing. 

Opacity Rule (NSAQMD Rule 202) ...................................................................... Not estimated ........ Ongoing ................. Ongoing. 


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52Throughout this notice, we use the term 

‘‘uncertified wood stove’’ to refer to a wood heater 

that is not certified under the applicable Phase II 

requirements of the EPA’s new source performance 

standards (NSPS) promulgated in 1988 for new 

residential wood heaters at 40 CFR part 60, subpart 

AAA, as effective February 26, 1988 (53 FR 5860). 

In 2015, the EPA revised subpart AAA, Standards 

of Performance for New Residential Wood Heaters 

(‘‘2015 NSPS’’) with an effective date of May 15, 

2015, and a sell-through date of December 31, 2015. 

See 53 FR 5860 (March 15, 2015). Because the 

Voluntary Wood Stove Change-out Program began 

after December 31, 2015, all new certified wood 

heaters sold in the Portola PM2.5 nonattainment area 

must meet the applicable requirements in the 2015 

NSPS. 

53The Targeted Air Shed grant program is 

intended to improve air quality in areas of the US 

with the highest levels of pollution. For more 

information, see https://www.epa.gov/grants/airgrants-and-funding. 

54 In the Matter of H&S Performance, LLC, 

Consent Agreement and Final Order (docket no. 

CAA–HQ–2015–8248), entered December 17, 2015. 

Under this agreement, H&S Performance, LLC 

agreed to provide $400,000 to the NSAQMD to 

replace, retrofit, or upgrade at least 400 inefficient 

wood-burning appliances. 

55Portola Monthly Air Quality Update from 

NSAQMD, September 2018. 

TABLE 2—SUMMARY OF RACM IN PORTOLA PM2.5 NONATTAINMENT AREA—Continued 

Measure 

Direct PM2.5

emission 

reductions 

(tpd) 

Scheduled action Implementation 

year 

Educational Campaign ......................................................................................... Not estimated f ...... Ongoing ................. Ongoing. 

Voluntary Wood Burning Curtailment Program (‘‘Clear the Air; Check Before 

You Light’’).

Not estimated f ...... 2016 ...................... 2017. 

aThe reductions from the wood stove change-out program are based on the average of the cumulative annual emission reductions from 2019– 

2021 (i.e., 0.045 tpd in 2019, 0.065 tpd in 2020, and 0.077 tpd in 2021). bAdditional reductions not calculated because a variety of factors affect the amount of any potential reductions still available after implementation of change-out program (e.g., number of remaining uncertified wood stoves within City of Portola; whether the 30 μg/m3 air quality threshold 

is triggered to implement the curtailment; and enforcement of the curtailment). cAdditional reductions from the other provisions in the Ordinance and the distribution of 20 moisture meters per year are uncertain (e.g., reductions from prohibition on burning unseasoned wood) and/or overlap with reductions from the change-out program. To avoid double counting 

of reductions from the Ordinance and the change-out programs, no additional reductions from the Ordinance are relied on for attainment. dOther provisions that apply in the Ordinance include, for example, prohibiting: Installation of an uncertified wood burning device, unqualified 

fireplace, or uncertified fireplace in new construction or remodel; more than one certified wood burning heater per dwelling unit in new construction; a wood burning device as the sole source of heat in new construction; installation of an outdoor wood-burning boiler or hydronic heater; 

uncertified wood burning heater remaining in any property upon change of ownership; burning of garbage or unpermitted fuels, including unseasoned wood (less than 20% moisture content) in a wood burning devices. eAdditional reductions from strengthening requirements applicable to non-agricultural open burning (e.g., backyard and barrel burning) to be 

determined at time of anticipated rulemaking in 2019, but because the non-agricultural open burning inventory is small, the additional reductions 

will not advance attainment. fFor RACM, attainment, and RFP, the District is not relying on any reductions from the educational programs or the voluntary wood burning 

curtailment program. 

Source: Portola PM2.5 Plan, 37 (Table 4). 

a. Voluntary Wood Stove Change-Out 

Program 

Because ambient PM2.5 in the Portola 

area is primarily caused by residential 

wood burning, CARB and the NSAQMD 

have chosen to implement a voluntary 

wood stove change-out program as the 

primary RACM control strategy for the 

entire Portola PM2.5 nonattainment area. 

Appendix L of the Plan details the 

voluntary wood stove change-out 

program. Its implementation began in 

2016 and will continue through 2020. 

See Table 3 below for the phased 

schedule of changeouts. 

TABLE 3—WOOD STOVE CHANGE-OUT

SCHEDULE

Year 

Stove changeouts 

Per year Cumulative 

2016 .......... 100 100 

2017 .......... 100 200 

2018 .......... 150 350 

2019 .......... 150 500 

2020 .......... 100 600 

2021 .......... 0 600 

2022 .......... 0 600 

The woodstove change-out program is 

primarily funded by the EPA and the 

District. The District has approximately 

$3 million to fund the replacement of 

600 of the estimated 664 uncertified 

wood stoves 52 in use in the 

nonattainment area. The District is 

utilizing $2.48 million through the 

EPA’s 2015 Targeted Air Shed Grant 

program 53 and $400,000 from H&S 

Performance (H&S) pursuant to a 

December 17, 2015 Consent Agreement 

and Final Order between H&S and the 

EPA.54 Additionally, the District is 

contributing up to $60,000 from the 

Plumas County portion of the District’s 

Assembly Bill 2766 Motor Vehicle 

Registration fee surcharge. 

The change-out program includes 

specific requirements designed to 

achieve quantifiable, surplus, 

enforceable, and permanent PM2.5

emission reductions in the entire 

Portola PM2.5 nonattainment area. The 

program requirements ensure, among 

other things, that older, dirtier wood 

stoves currently in operation in the 

Portola PM2.5 nonattainment area will be 

replaced with EPA-certified wood 

stoves or other less-polluting devices. 

Residents of the City of Portola and lowincome residents living outside the city 

but within the nonattainment area 

qualify for up to $3,500 to replace an 

uncertified wood burning device with 

an EPA-certified wood burning device. 

The $3,500 covers all or most of the 

change-out costs. In an effort to replace 

the uncertified devices with the cleanest 

technology available, the District offers 

an additional $1,000 to city residents or 

low-income residents within the 

nonattainment area for every uncertified 

wood stove replaced with a pellet, 

propane, or kerosene device. For all 

other residents living outside the City of 

Portola but within the nonattainment 

area, the District offers $1,500 to replace 

an uncertified wood burning device 

with an EPA-certified wood burning 

device and $3,000 to replace an 

uncertified wood burning device with a 

pellet, propane or kerosene heating 

device. An incentive is available within 

the entire nonattainment area, but the 

two-tier funding approach increases the 

likelihood of the greatest number of 

changeouts occurring in the city, the 

area with the greatest concentration of 

people and low-income residents in the 

nonattainment area. As of September 30, 

2018, approximately 260 changeouts 

were completed, and an additional 49 

applications were approved for possible 

future changeouts.55

The change-out program also includes 

requirements for participating 


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56The District also developed a memorandum of 

understanding with the City of Portola to destroy 

the replaced stoves. The City matches the stove 

with the program tracking number, cuts the stove 

in half with a plasma torch, and stores the stove in 

a locked yard. The City fills out and signs a 

verification of destruction form and submits it to 

the District. The form contains the tracking number 

and photo of the destroyed stove. See Portola PM2.5

Plan, 32. 

57See section 15.10.060 of the City Ordinance. In 

section 15.10.020 of the City Ordinance, ‘‘wood 

burning heater’’ is defined as an enclosed woodburning device capable of and intended for space 

heating such as a wood stove, pellet-fueled wood 

heater, or wood-burning fireplace insert, and ‘‘EPAcertified’’ is defined as any wood burning heater 

with a Phase II certification or a more stringent 

certification as currently enforced in the NSPS. 

58EPA, ‘‘Strategies for Reducing Residential 

Wood Smoke,’’ Publication No. EPA–456/B–13– 

001, revised March 2013. 

59See e.g., South Coast Air Quality Management 

District Rule 445 (amended May 3, 2013), paragraph 

(f)(7)(A), and Sacramento Metropolitan Air Quality 

Management District Rule 421 (amended September 

24, 2009), paragraph 112. 

contractors/retailers to sign a contract 

with NSAQMD. Contractors/retailers 

must meet licensing, permitting, and 

certification requirements. The contract 

includes specific requirements for the 

collection and retention of documents, 

such as: 

D Program tracking form, 

D Copy of change-out cost estimate 

with District approval signature, 

D Photo of uncertified woodstove 

installed and operational in home (prior 

to replacement by certified device),56

D Photo of certified device installed, 

D Copy of building permit, 

D Acknowledgement of training form 

(homeowner/renter), and 

D Final invoice. 

The retailer/contractor must also meet 

the following requirements for retention 

of records and providing training to 

homeowners: 

D Accounting records relating to the 

change-out program must be retained for 

five years and made available for 

possible review by federal, State and 

District agencies, 

D Encourage homeowners to consider 

replacing wood appliances with 

alternative fuel devices, such as 

propane, pellet or kerosene, and 

D Train homeowners on proper 

appliance operation and acceptable 

fuels to maximize the emission 

reductions, including a form signed by 

homeowners stating that they were 

trained to properly operate their new 

heating device. 

To provide assurance that the 

voluntary change-out program will 

achieve the intended emissions 

reductions, the District adopted an 

enforceable commitment to replace 600 

uncertified stoves with cleaner burning 

devices by December 31, 2020. The EPA 

approved this enforceable commitment 

into the SIP at 83 FR 13871 (April 2, 

2018). The enforceable commitment 

obligates the NSAQMD to achieve 

specific amounts of PM2.5 emission 

reductions through implementation of 

the woodstove change-out program by 

specific years, to submit annual reports 

to the EPA detailing its implementation 

of the program and the projected 

emission reductions, and to adopt and 

submit substitute measures by specific 

dates if the EPA determines that the 

woodstove change-out program will not 

achieve the necessary emission 

reductions. The EPA’s Technical 

Support Document for its April 2, 2018 

final action has more information about 

the enforceable commitment. 

b. City of Portola Wood Stove and 

Fireplace Ordinance 

On June 22, 2016, the City of Portola 

adopted Ordinance No. 344, ‘‘An 

Ordinance of the City of Portola, County 

of Plumas Amending Chapter 15.10 of 

the City of Portola Municipal Code 

Providing for Regulation of Wood 

Stoves and Fireplaces’’ (‘‘City 

Ordinance’’). The City Ordinance is in 

Appendix M of the Plan. The EPA 

approved the City Ordinance into the 

SIP at 83 FR 9213 (March 5, 2018). 

The City Ordinance includes a 

mandatory burning curtailment 

provision effective January 1, 2021. The 

mandatory curtailment will restrict 

wood burning under specific 

conditions. If the District determines 

that adverse meteorological conditions 

are expected to persist and PM2.5 may 

exceed 30 mg/m3 on a given day in 

January, February, November, or 

December, the District will call a ‘‘No 

Burn Day.’’ When a No Burn Day is 

called, no person may operate a wood 

burning heater, wood burning fireplace, 

wood-fired fire pit or wood-fired 

cookstove within the city limits unless 

it is an approved and currently 

registered EPA-certified wood burning 

heater.57 The curtailment provision 

encourages owners of uncertified stoves 

to upgrade to certified stoves or risk not 

being able to use their uncertified wood 

burning device on No Burn Days called 

after January 1, 2021. The curtailment 

provision does not take effect until 

January 1, 2021, giving homeowners and 

renters time to change their stoves to 

EPA-certified devices during the fiveyear implementation of the voluntary 

change-out program. 

The City Ordinance and the District’s 

wood stove change-out program 

collectively establish most of the 

recommended program elements 

outlined in the EPA’s guidance 

document entitled ‘‘Strategies for 

Reducing Residential Wood Smoke,’’ 58

including: 

D A wood burning curtailment 

program (section 15.10.060), 

D Requirements to remove uncertified 

wood burning stoves upon home resale 

(section 15.10.040.A), 

D Restrictions on wood burning 

devices in new construction (section 

15.10.030.B), 

D Restrictions on the installation of 

wood burning fireplaces (sections 

15.10.030.A and 15.10.040.B), 

D A requirement that all wood 

burning stoves sold or transferred 

within the District meet the EPA’s 

current new source performance 

standard certification (section 

15.10.030.A), 

D A prohibition on the installation of 

wood fired boilers or hydronic heaters 

(sections 15.10.030.15, 15.10.030.A and 

15.10.070), 

D Requirements regarding wood 

moisture content (section 15.10.050.A), 

D Restrictions on types of materials 

that may be burned (seasoned wood, 

uncolored paper, pellets, and 

manufactured logs) (section 15.10.050), 

D A wood burning stove change-out 

program (described above), and 

D Education and outreach programs, 

including a requirement for wood stove 

retailers to distribute educational 

materials provided by the District 

(section 15.10.080). 

Although natural gas is not available 

in the area, the City Ordinance does not 

include any exemption for a residence 

where an uncertified wood stove is the 

sole source of heat. The City Ordinance 

is thus more stringent than curtailment 

provisions implemented by other air 

districts, most of which exempt 

households using wood stoves as a sole 

source of heat from curtailment 

requirements.59

The District considered expanding the 

requirements of the City Ordinance to 

the entire nonattainment area but 

determined that this was not feasible 

because the District did not have 

sufficient funding to offer incentives to 

cover the full cost of changeouts outside 

of the City of Portola. Some residents 

living outside of the city limits may not 

have sufficient resources to changeout 

their stoves. For these residents, the 

wood burning prohibition in the City 

Ordinance could cause unintended 

health risks if their sole source of heat 

is an uncertified wood stove, and they 

were prohibited from using it. In the 

future, expanding application of the 

City Ordinance beyond city limits will 

be contingent upon availability of more 

generous incentive funds for people 

residing outside the city limits. The 


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60Portola PM2.5 Plan, Table 4, 84–85. 

61 Id. at 22. 

62 Id. at 36. 

63CARB has unique authority under CAA section 

209 (subject to a waiver or authorization by the 

EPA) to adopt and implement new emissions 

standards for many categories of vehicles and 

engines. CARB has adopted standards and other 

requirements related to the control of emissions 

from numerous types of new and in-use on-road 

and off-road vehicles and engines, such as trucks, 

buses, motorcycles, passenger cars, off-road engines 

(gasoline and diesel-powered), off-road diesel 

fueled fleets, portable equipment, and marine 

engines. Generally, these regulations have been 

submitted and approved as revisions to the 

California SIP. See, e.g., 77 FR 20308 (April 4, 

2012), 81 FR 39424 (June 16, 2016), 82 FR 14446 

(March 21, 2017), and 83 FR 23232 (May 18, 2018). 

64NSAQMD Rule 202, ‘‘Visible Emissions’’ 

(adopted September 11, 1991). 

65Portola PM2.5 Plan, 34–35. 

66NSAQMD Press Release dated October 25, 

2017, Greater Portola Area Wintertime Advisory 

Program in Effect. 

67EPA, ‘‘Strategies for Reducing Residential 

Wood Smoke,’’ Publication No. EPA–456/B–13– 

001, revised March 2013, and EPA, ‘‘Residential 

Wood Combustion Summary of Measures— 

DRAFT,’’ January 2016. 

68 83 FR 9213 (November 3, 2017) and EPA, 

Region IX Air Division, ‘‘Technical Support 

Document for the EPA’s Rulemaking for the 

Continued 

Plan states that if additional funding 

becomes available in the future, the 

District will offer more generous 

incentives to residents living outside 

city limits and consider expanding 

mandatory burning curtailment to the 

entire nonattainment area.60

c. Open Burning (NSAQMD Rules 300– 

317) 

The District enforces open burning 

requirements in NSAQMD Rules 300— 

317 that apply to a variety of area 

sources such as agricultural burning, 

forest burning, range improvement, and 

residences. The District’s smoke 

management program ensures that open 

burning occurs on days with good 

dispersion to minimize the impact from 

PM2.5 concentrations. The EPA 

approved these rules into the SIP at 62 

FR 48480 (September 16, 1997) and 64 

FR 45170 (August 19, 1999). 

Within the Portola nonattainment 

area, wood smoke can originate from 

open burning or from home heating 

devices. Residents of this area 

occasionally burn yard debris in open 

piles. Land managers (e.g., U.S. Forest 

Service) perform prescribed burns of 

timber harvest waste to promote fire 

safety and maintain forest health. Both 

residents and land managers must 

request a burn permit prior to starting a 

fire. The District, in coordination with 

CARB, makes a declaration of either a 

permissive Burn Day or a No Burn Day 

in the context of open burning only. It 

does not apply to wood burning devices 

and is distinct from the more stringent 

No Burn Day program previously 

described in the City Ordinance. The 

District and CARB consider a number of 

factors in making no-burn declarations 

to ensure that smoke from open burning 

will not unduly contribute to the 

ambient PM2.5 mass.61

To further reduce PM2.5 emissions 

during winter, the Portola PM2.5 Plan 

contains a commitment by the District 

to strengthen its open burning rule in 

2019. The District is assessing the 

feasibility of green waste collection in 

the nonattainment area and will 

consider whether to adopt open burning 

requirements similar to District Rule 

318 (‘‘American Valley Burning 

Restrictions’’), which prohibits the open 

burning of yard waste and debris or 

other rubbish from November 15 to 

March 15 in a portion of the American 

Valley containing Quincy and East 

Quincy.62

d. Mobile Source Measures 

Mobile sources account for 

approximately 3% of the overall direct 

PM2.5 emissions inventory in the Portola 

PM2.5 nonattainment area. The Plan 

projects that CARB’s continued 

implementation of adopted mobile 

source control measures 63 will decrease 

direct PM2.5 emissions by 2021 and 

provide 7% of the total reductions 

needed to attain the 2012 PM2.5 NAAQS. 

As part of the State’s RACM analysis for 

the mobile source control program, 

described on pages 86–90 of the Portola 

PM2.5 Plan, CARB concludes that in 

light of the comprehensiveness and 

stringency of its mobile source program, 

all RACM under CARB’s jurisdiction are 

already being implemented. 

e. Visible Emissions (NSAQMD Rule 

202) 

Rule 202 limits visible emissions (e.g., 

particulates) and is enforced by 

NSAQMD. The EPA approved this rule 

into the SIP at 62 FR 48480 (September 

16, 1997). Enforcement of Rule 202 will 

help identify households with highly 

visible emissions that may still be using 

uncertified wood stoves and possibly 

eligible for the change-out program. 

Rule 202 prohibits any person from 

discharging into the atmosphere any air 

contaminant for more than 3 minutes in 

any hour that is as dark as, or darker in 

shade than, that designated as No. 1 on 

the Ringelmann Chart or ‘‘of such 

opacity as to obscure an observer’s view 

to a degree equal to or greater than does 

smoke.’’ 64

f. Educational Campaign 

The District is developing other 

voluntary measures to reduce the 

impact of wood smoke on PM2.5. The 

District is conducting an aggressive 

outreach and educational campaign to 

help residents understand the benefits 

of changing from an old wood stove to 

a cleaner home heating device and the 

importance of clean burning. The 

District worked closely with the City of 

Portola and enlisted outreach partners 

such as the local hardware and grocery 

store, post office, library, senior 

community center, and schools to assist 

in the distribution of educational 

materials and advertise the change-out 

program. In addition, the Ordinance 

includes a requirement that retailers and 

contractors provide educational 

materials with the sale of a woodburning device.65

g. Voluntary Wood Burning Curtailment 

Program 

On November 1, 2017, the District 

began implementing ‘‘Clear the Air; 

Check Before You Light,’’ a voluntary 

wood burning curtailment program that 

runs during the peak wood-burning 

period (i.e., November 1 through 

February 28) in the Portola 

nonattainment area. When conditions 

exist for potentially poor air quality, the 

District will issue an air quality 

advisory to notify the public. When an 

advisory is triggered the District will 

recommend avoiding the use of any 

wood burning device (including wood 

stoves, fireplaces, fire pits and cook 

stoves) to help reduce potential health 

impacts and possibly prevent an 

exceedance of federal/state air pollution 

standards. Use of alternative sources of 

heat such as electricity, propane or 

kerosene, are encouraged when an 

advisory is announced.66

5. The EPA’s Evaluation and Proposed 

Action 

As part of the EPA’s March 5, 2018, 

final action approving the City 

Ordinance into the SIP, the EPA 

considered whether the City Ordinance 

includes all technologically and 

economically feasible measures for 

wood burning devices. We compared 

the provisions in the City Ordinance 

with other wood burning rules and with 

the recommendations in the EPA’s 

guidance document entitled ‘‘Strategies 

for Reducing Residential Wood 

Smoke.’’ 67 Based on this evaluation, we 

concluded that the City Ordinance and 

the District’s wood stove change-out 

program collectively implement RACM 

and additional reasonable measures for 

residential wood burning devices in the 

Portola nonattainment area.68


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California State Implementation Plan, Northern 

Sierra Air Quality Management District, City of 

Portola Ordinance 344, Wood Stove and Fireplace 

Ordinance,’’ July 2017. 

69Committee for a Better Arvin v. EPA, 786 F.3d 

1169 (9th Cir. 2015) (‘‘Arvin’’). In Arvin, the Ninth 

Circuit concluded that CAA section 110(a)(2)(A) 

requires that all state and local control measures on 

which SIPs rely to attain the NAAQS, including 

California waiver measures, be included in the SIP 

and thereby subject to enforcement by the EPA and 

the general public. This decision struck down the 

EPA’s longstanding practice of approving California 

plans that rely on emissions reductions from waiver 

measures notwithstanding their lack of approval as 

part of the SIP. 

70See, e.g., 81 FR 39424 (June 16, 2016), 82 FR 

14447 (March 21, 2017), and 83 FR 23232 (May 18, 

2018). 

71See, e.g., the EPA’s approval of standards and 

other requirements to control emissions from in-use 

heavy-duty diesel-powered trucks, at 77 FR 20308 

(April 4, 2012), revisions to the California on-road 

reformulated gasoline and diesel fuel regulations at 

75 FR 26653 (May 12, 2010), and revisions to the 

California motor vehicle I/M program at 75 FR 

38023 (July 1, 2010). 

72 General Preamble, 13539 and 13541–42. There 

are no major stationary sources (existing or 

anticipated) of direct PM2.5 or PM2.5 precursors in 

the Portola PM2.5 nonattainment area. 

73 81 FR 58528 at 58010 (August 24, 2016). 

74 40 CFR part 51 Appendix W, ‘‘Guideline on Air 

Quality Models,’’ 82 FR 5182, January 17, 2017; 

available at https://www.epa.gov/scram/clean-airact-permit-modeling-guidance. 

We note that the curtailment 

provisions of the City Ordinance do not 

take effect until 2021. Given that 

uncertified wood stoves are currently 

the primary source of heat for many 

residents in Portola, we do not believe 

it is reasonable to require 

implementation of a mandatory 

curtailment program prior to 

implementation of the District’s fiveyear wood stove change-out program, 

which provides funding for the 

replacement of 600 uncertified wood 

stoves between 2016 and 2020. After 

these incentive funds are disbursed, 

however, implementation of a 

mandatory curtailment program in the 

Portola nonattainment area is feasible. 

We propose to find that the District’s 

enforceable commitments concerning 

implementation of the wood stove 

change-out program and related 

monitoring and reporting commitments 

implement RACM for the control of 

PM2.5 emissions from residential wood 

burning in the Portola area. Because the 

curtailment provision in the City 

Ordinance otherwise meets the 

definition of RACM but is implemented 

during the period beginning 4 years 

after the area’s designation as 

nonattainment and before the 

attainment date, we consider it an 

additional reasonable measure for 

purposes of attaining the 2012 PM2.5

NAAQS. 

Under the CAA, the EPA is charged 

with establishing national emissions 

limits for mobile sources. States are 

generally preempted from establishing 

such limits except for California, which 

can establish these limits subject to EPA 

waiver or authorization under CAA 

section 209 (referred to herein as 

‘‘waiver measures’’). Over the years, the 

EPA has issued waivers (for on-road 

vehicles and engines measures) or 

authorizations (for non-road vehicle and 

engine measures) for many mobile 

source regulations adopted by CARB. 

In the past, the EPA allowed 

California to take into account 

emissions reductions from waiver 

measures, notwithstanding the fact that 

these regulations had not been approved 

as part of the California SIP. However, 

in response to the decision by the 

United States Court of Appeals for the 

Ninth Circuit in Committee for a Better 

Arvin v. EPA,69 the EPA approved 

waiver measures as revisions to the 

California SIP.70 CARB’s mobile source 

program extends beyond regulations 

that are subject to the waiver or 

authorization process set forth in CAA 

section 209 to include standards and 

other requirements to control emissions 

from in-use heavy duty trucks and 

buses, gasoline and diesel fuel 

specifications, and many other types of 

mobile sources. Generally, these 

regulations have been submitted and 

approved as revisions to the California 

SIP.71 The Portola PM2.5 Plan relies to 

a very small extent on emissions 

reductions from implementation of the 

waiver measures through the use of 

emissions models such as EMFAC2014. 

The EPA is proposing to find that the 

District’s enforceable commitment to 

implement the voluntary wood stove 

change-out program, the City 

Ordinance, CARB’s mobile source 

program, the District’s commitment to 

strengthen its open burning measure, 

and other controls on sources in the 

nonattainment area together implement 

all RACM and RACT for the control of 

direct PM2.5 in the Portola 

nonattainment area. This collective set 

of PM2.5 control requirements, 

particularly with respect to homes 

where wood-burning is the sole source 

of heat, is at least as stringent as 

analogous measures implemented in 

other Moderate PM2.5 nonattainment 

areas with similar geography and 

demographics. Accordingly, the EPA is 

proposing to approve the PM2.5 RACM 

demonstration in the Portola PM2.5 Plan 

as meeting the requirements of CAA 

sections 172(c)(1) and 189(a)(1)(C) and 

40 CFR 51.1009. 

D. Major Stationary Source Control 

Requirements Under CAA Section 

189(e) 

Section 189(e) of the Act specifically 

requires that the control requirements 

applicable to major stationary sources of 

direct PM2.5 also apply to major 

stationary sources of PM2.5 precursors, 

except where the Administrator 

determines that such sources do not 

contribute significantly to PM2.5 levels 

that exceed the standards in the area.72

The control requirements applicable to 

major stationary sources of direct PM2.5

in a Moderate PM2.5 nonattainment area 

include, at minimum, the requirements 

of a NNSR permit program meeting the 

requirements of CAA sections 172(c)(5) 

and 189(a)(1)(A). In the PM2.5 SIP 

Requirements Rule, we established a 

deadline for states to submit NNSR plan 

revisions to implement the PM2.5

NAAQS 18 months after an area is 

initially designated and classified as a 

Moderate nonattainment area.73 On 

September 6, 2016, California submitted 

the required NNSR SIP revisions. We 

are not proposing any action on the 

NNSR submittal at this time and will 

address these requirements in a separate 

rulemaking. 

E. Air Quality Modeling 

1. Requirements for Air Quality 

Modeling 

Section 189(a)(1)(B) of the CAA 

requires that a plan for a Moderate PM2.5

nonattainment area include a 

demonstration (including air quality 

modeling) that the plan will provide for 

attainment by the applicable attainment 

date, or a demonstration that attainment 

by such date is impracticable. An 

attainment demonstration must show 

that the control measures in the plan are 

sufficient for attainment of the NAAQS 

by the attainment date. The attainment 

demonstration predicts future ambient 

concentrations for comparison to the 

NAAQS, making use of available 

information on ambient concentrations, 

meteorology, and current and projected 

emissions inventories, including the 

effect of control measures in the plan. 

This information is typically used in 

conjunction with a computer model of 

the atmosphere. 

The EPA has provided additional 

modeling requirements and guidance for 

modeling analyses in the ‘‘Guideline on 

Air Quality Models’’ (‘‘Guideline’’).74

For areas where emissions are 

dominated by primary PM10 or PM2.5

emitted by many small dispersed 

sources, such as fugitive dust or 

residential wood burning, states have 

historically used a ‘‘rollback model’’ to 

evaluate the impacts of emissions on 

ambient air quality. EPA recently 


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75 81 FR 36176 (June 6, 2016), docket EPA–R10– 

OAR–2013–0005 for Klamath Falls; and 83 FR 5537 

(February 8, 2018), docket EPA–R10–OAR–2017– 

0051 for Oakridge-Westfir. 

76Levoglucosan is an organic compound formed 

from the pyrolysis of carbohydrates, such as starch 

and cellulose, the key component of wood. As a 

result, levoglucosan is often used as a chemical 

tracer for biomass burning in atmospheric 

chemistry studies, particularly with respect to 

airborne particulate matter. Jordan, T., Seen, A., 

Jacobsen, G., 2006, ‘‘Levoglucosan as an 

atmospheric tracer for woodsmoke,’’ Atmospheric 

Environment, 40 (27): 5316–5321. 

77Portola PM2.5 Plan Appendix E, Figure 1 and 

Table 2. The Burn Wise Emission Calculator is 

available at https://www.epa.gov/burnwise/burnwise-additional-resources. 

approved rollback-based attainment 

demonstrations in the wood smokedominated Klamath Falls and OakridgeWestfir PM2.5 nonattainment areas in 

Oregon.75 In a simple rollback model, 

the monitored ambient concentration 

(excluding any unchanging background 

concentration) is assumed to be 

proportional to emissions; when 

emissions are reduced by a given 

percentage, the concentration is 

assumed to scale or ‘‘roll back’’ by the 

same percentage. A variant is 

‘‘proportional rollback,’’ in which 

rollback is applied to each emission 

source category individually, then 

summed in proportion to their ambient 

contributions. The proportions, or 

source apportionment, can be estimated 

using chemically speciated PM2.5

measurements. This can be done with a 

receptor model such as the Chemical 

Mass Balance model or the PMF model, 

which compute the source category 

contributions that are the best statistical 

fit to the measured chemical species 

concentrations, given measured or 

estimated source species profiles. 

2. Modeling in the Portola PM2.5 Plan 

The attainment demonstration, 

described in section V of the Plan, is 

based on proportional rollback, with 

source category proportions (source 

apportionment) determined using the 

PMF receptor model. Section V of the 

Plan describe the concentration starting 

point for the rollback, background 

concentrations, the mapping of ambient 

PM2.5 components to PM2.5 emission 

categories, and the rollback calculation 

procedure. In addition to a ‘‘Traditional 

Rollback,’’ the Plan also provides an 

‘‘Alternative Rollback,’’ which is based 

on a more precise accounting of the 

impacts of various wood stove types. 

The concentration starting point for 

rollback is typically a base year design 

value concentration that corresponds to 

the base year emissions. Instead of using 

the 2013 design value for the base year, 

the Plan used 13.9 mg/m3, the average of 

the design values from 2013, 2014, and 

2015. Because a single design value is 

a three-year average, the Plan’s 

procedure gives a five-year weighted 

average centered on 2013, using 

concentrations from 2011–2015. This 

was done to reduce the effect of year-toyear variability, and to avoid basing the 

attainment demonstration solely on the 

unusually warm, dry years of 2011– 

2013. 

In rollback, the area’s emissions are 

used to scale only the portion of the 

concentration due to sources in the 

nonattainment area, excluding 

background concentrations. CARB chose 

speciated PM2.5 concentrations from 

Bliss State Park next to Lake Tahoe in 

the Plan as background concentrations 

that would occur in the airshed in the 

absence of local anthropogenic 

emissions. 

The State determined the 

contributions of emission source 

categories to ambient PM2.5 using the 

PMF receptor model, described in Plan 

Appendix A. PMF was applied to 2011– 

2014 speciated PM2.5 data for 15 

chemical species. PMF determines 

source species profiles and source 

contribution levels that best fit the full 

set of data. The result was a source 

apportionment with estimates for the 

ambient contributions of six source 

categories: Wood burning, refuse 

burning, mobile, airborne soil, 

secondary nitrate, secondary sulfate. 

The contributions of these source 

categories to the rollback base year 

PM2.5 concentration are shown in the 

Figure 9 pie chart in the Plan, ‘‘2011– 

2015 Annual Average PM2.5 Source 

Contribution.’’ Wood burning 

contributed by far the largest amount, 

76.1%; mobile sources contributed 

7.6%; airborne soil 3.9%; and refuse 

burning 2.5%. Secondary PM2.5 in the 

form of ammonium nitrate and 

ammonium sulfate contributed 5.1% 

and 4.8%, respectively, of ambient 

PM2.5 concentrations. Figure 11 in the 

Plan shows the strong correlation 

between concentrations of PM2.5 and of 

levoglucosan, a marker for wood 

combustion.76 This correlation 

corroborates the significant contribution 

of wood burning to Portola’s ambient 

PM2.5 levels. 

Table 12 in the Portola PM2.5 Plan 

shows the State’s rollback calculation, 

in which the percent changes in the 

2013 emissions of the inventory source 

categories are applied to their respective 

2013 base year ambient contributions 

(excluding background). The main 

emissions change between base year and 

future emissions is for wood burning, 

reflecting the effect of the wood stove 

change-out program. For this source 

category, the State calculated emission 

reductions due to the wood stove 

change-out program during that period 

for each of the years from 2017 to 2021 

using the EPA’s Burn Wise Emission 

Calculator.77 CARB applied reductions 

in tpd to the baseline emission 

inventory projections for annual average 

direct PM2.5 emissions from residential 

wood burning in Table 8 of Appendix 

B in the Plan. 

The Plan includes future year 

contributions from 2017 to 2021 for 

each source category and a total 

concentration for each year. Only the 

wood burning emissions differed for 

each of these years; emissions from 

other categories reflected their 2021 

values. CARB then averaged the 

predicted concentrations for the 2019– 

2021 period to arrive at a 2021 predicted 

design value. The State’s procedure of 

averaging projected concentrations for 

the three individual years 2019, 2020, 

and 2021 is similar to the procedure 

used for computing the 2021 monitored 

design value. The result of the rollback 

was a predicted 2021 PM2.5 annual 

design value of 12.03 mg/m3; with the 

rounding to one digit prescribed by 40 

CFR 50 App. N, section 4.3, this meets 

the 12.0 mg/m3 NAAQS. 

Section V.F. of the Plan provided an 

‘‘Alternative Rollback’’ model that more 

precisely quantified the effect of the 

stove change-out program on wood 

burning emissions. For this rollback 

model, all other source category 

emissions and their ambient 

contributions were assumed to remain 

at their base year 2013 levels. CARB 

calculated wood stove emissions and 

contributions separately for new 

certified stoves and uncertified stoves. 

This approach used the individual 

heating efficiency and emissions factors 

for these sources from the EPA’s Burn 

Wise Emission Calculator and 

accounted for the number of each type 

of stove and the number of stove 

changeouts expected to occur in 2019, 

2020, and 2021. CARB applied the 

fractional changes in emissions for these 

years to the wood burning portion of the 

5-year weighted 13.9 mg/m3 design 

value, and the three years’ results 

averaged to arrive at a 2021 design value 

of 11.1 mg/m3, which meets the 12.0 mg/ 

m3 NAAQS. 

3. The EPA’s Evaluation and Proposed 

Action 

The EPA evaluated the State’s choice 

of model for the attainment 

demonstration, as well as how the State 

applied the model, in terms of 


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78Portola PM2.5 Plan, 20 (Figure 9, 2011–2015 

Annual Average PM2.5 Source Contribution). 

79The attainment demonstration need only show 

that emissions in the attainment year and the 

resulting projected concentration are consistent 

with attainment of the NAAQS; it does not need to 

show that the projected three-year design value 

meets the NAAQS. Future emissions need only be 

projected to the attainment year itself. See EPA, 

Office of Air Quality Planning and Standards, 

‘‘Modeling Guidance for Demonstrating Attainment 

of Air Quality Goals for Ozone, PM2.5, and Regional 

Haze,’’ December 2014 Draft, 17 (section 2.3.2, 

Future Year Selection); available at https://

www.epa.gov/scram/state-implementation-plan-sipattainment-demonstration-guidance. 80 40 CFR 51.1011(a). 

concentration starting point, 

background concentrations, mapping of 

emissions to concentrations, and the 

calculations used. The choice of an 

appropriate model for the District’s 

attainment demonstration was informed 

by particular circumstances in the 

Portola PM2.5 nonattainment area, most 

notably the dominance of primary PM2.5

in ambient concentrations, the 

dispersed nature of the many small area 

sources responsible for it, and the 

relatively small fraction that is 

composed of secondary particulate 

matter. As discussed in the Plan, wood 

burning emissions of organic carbon and 

elemental carbon contribute 76% and 

8%, respectively, of annual PM2.5

concentrations in the Portola area.78

Based on examination of meteorology, 

PM2.5 emissions data and ambient PM2.5

data, the Plan provides a well-supported 

demonstration that residential wood 

burning is the dominant contributor to 

the PM2.5 air quality problem in the 

Portola area. The key assumption in a 

rollback analysis, i.e., that ambient 

concentrations are proportional to 

emissions, is true for these primary 

PM2.5 emissions. The EPA modeling 

guidance cited above does not mention 

rollback for attainment demonstrations 

but also does not fully address 

situations like that in the Portola area, 

where the dominant contributor to 

ambient PM2.5 is primary PM2.5 from 

many small area sources. Given that the 

key contributor to the air quality 

problem in the Portola area is already 

understood, neither photochemical grid 

models nor dispersion models would 

provide much information that is not 

already available from the rollback 

model. The EPA agrees that the use of 

rollback analysis under these facts and 

circumstances is consistent with EPA 

guidance and is appropriate for the 

Portola attainment demonstration and 

meets the Clean Air Act requirement for 

air quality modeling. 

In addition, the EPA agrees that the 

Plan identifies an appropriate starting 

point concentration for the rollback 

model. The use of a five-year weighted 

average for the design value is not 

standard for rollback, but is consistent 

with the EPA’s recommendation for the 

starting point of photochemical 

modeling attainment demonstrations. 

The Plan contains a reasonable 

justification for using a longer period to 

determine the starting point for the 

design value, based on the variable 

meteorology of the 2011–2015 period; 

the chosen procedure thus yields a more 

representative concentration that is 

appropriate for the rollback attainment 

demonstration. It makes for a more 

robust attainment demonstration that is 

not overly dependent on meteorological 

conditions in any one particular year. 

The Plan contains convincing 

arguments for the State’s selection of 

Bliss State Park as the source of 

background concentrations. The EPA 

agrees that the Plan’s estimates for 

background concentrations are 

appropriate. The source attribution 

using PMF carried out for the Plan 

provides a good basis for the rollback 

model. The States also used several 

conservative assumptions, such as 

keeping certain ambient components 

constant instead of declining with 

emissions, so that the final 

concentration result is likely higher 

than would be expected with a more 

precise accounting. 

As noted above, the Plan used the 

average of projections for the individual 

years 2019, 2020, and 2021 for the 

future year projection. In comparison 

with projecting just the single 

attainment year emissions and 

concentration, the approach used by the 

State is conservatively high, because the 

2019 and 2020 projections do not 

account for all of the emission 

reductions from stove changeouts that 

will occur by the 2021 attainment 

year.79

The Plan also provides a second 

rollback model, termed ‘‘Alternative 

Rollback.’’ A key difference between the 

two rollback approaches is that the 

‘‘Alternative’’ rollback relies more 

completely on the emission 

methodology for the residential wood 

burning category in the Burn Wise 

Emission Calculator. For both rollback 

approaches, the wood stove change-out 

program was by far the greatest source 

of emission and concentration 

reductions. The approaches relied on 

PMF source apportionment for the 

ambient effect of reductions, and they 

accounted for both the PM2.5 reductions 

per amount of wood burned in certified 

stoves and for the lower amount of 

wood burned from their increased burn 

efficiency. The ‘‘Alternative’’ rollback 

corroborated the results of the 

‘‘Traditional’’ rollback model and 

provides additional confidence in the 

attainment demonstration. 

The EPA finds that the State correctly 

implemented the rollback model in a 

reasonable way, used an appropriate 

mapping of ambient PM2.5 components 

to emission inventory categories, and 

incorporated an appropriate degree of 

conservatism. For these reasons, the 

EPA finds that the rollback modeling in 

the Plan is adequate for purposes of 

supporting the Portola attainment 

demonstration for the 2012 annual PM2.5

NAAQS. 

F. Attainment Demonstration 

1. Requirements for Attainment 

Demonstrations 

CAA section 189(a)(1)(B) requires that 

each state in which all or part of a 

Moderate PM2.5 nonattainment area is 

located submit an attainment plan that 

includes, among other things, either a 

demonstration (including air quality 

modeling) that the plan will provide for 

attainment by the applicable attainment 

date or a demonstration that attainment 

by such date is impracticable. In 

addition, CAA section 172(c)(1) 

generally requires, for each 

nonattainment area, a plan that provides 

for the implementation of all RACM and 

RACT as expeditiously as practicable 

and provides for attainment of the 

NAAQS. The EPA interprets these two 

provisions together to require that an 

attainment demonstration for a 

Moderate PM2.5 nonattainment area 

meet the following criteria: 

(1) The attainment demonstration 

must show the projected attainment 

date for the Moderate nonattainment 

area that is as expeditious as 

practicable; 

(2) The attainment demonstration 

must meet the requirements of 40 CFR 

part 51, appendix W and must include 

inventory data, modeling results, and 

emission reduction analyses on which 

the state has based its projected 

attainment date; 

(3) The base year for the emissions 

inventory required for the attainment 

demonstration must be one of the 3 

years used for designations or another 

technically appropriate inventory year if 

justified by the state in the plan 

submission; and 

(4) The control strategies modeled as 

part of the attainment demonstration 

must be consistent with the control 

strategy requirements under 40 CFR 

51.1009(a), including the requirements 

for RACM/RACT and additional 

reasonable measures.80


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81 Id. 82See, e.g., EPA, Office of Air Quality Planning 

and Standards, ‘‘Incorporating Emerging and 

Voluntary Measure in a State Implementation Plan 

(SIP),’’ October 4, 2004 (‘‘2004 Emerging and 

Voluntary Measures Guidance’’), 9; EPA, Office of 

Air Quality Planning and Standards and Office of 

Transportation and Air Quality, ‘‘Guidance on 

Incorporating Bundled Measures in a State 

Implementation Plan,’’ August 16, 2005 (‘‘2005 

Bundled Measures Guidance’’), 8; and EPA, Office 

of Air Quality Planning and Standards, ‘‘Guidance 

for Quantifying and Using Emission Reductions 

from Voluntary Woodstove Changeout Programs in 

State Implementation Plans,’’ EPA–456/B–06–001, 

January 2006 (‘‘2006 Woodstove Guidance’’), 4. 

83See, e.g., 2004 Emerging and Voluntary 

Measures Guidance, 9; 2005 Bundled Measures 

Guidance, 8, n. 6, and 2006 Woodstove Guidance, 

4. 

In addition, the attainment 

demonstration must provide for the 

implementation of all control measures 

needed for attainment as expeditiously 

as practicable and no later than the 

beginning of the year containing the 

applicable attainment date.81

Under longstanding guidance, the 

EPA has recommended presumptive 

limits on the amounts of emission 

reductions from voluntary and other 

nontraditional measures that may be 

credited in an attainment plan. 

Specifically, for voluntary stationary 

and area source measures, the EPA has 

identified a presumptive limit of 6% of 

the total amount of emission reductions 

required for RFP, attainment, or 

maintenance demonstration purposes.82

The EPA may, however, approve 

measures for SIP credit in amounts 

exceeding the presumptive limits 

‘‘where a clear and convincing 

justification is made by the State as to 

why a higher limit should apply in [its] 

case.’’ 83

We discuss each of these 

requirements and recommendations for 

attainment demonstrations below. 

2. Attainment Demonstration in the 

Portola PM2.5 Plan 

Table 4 shows the relationship 

between the 2013 base year inventory 

and the 2021 attainment year inventory 

before and after the wood stove changeout program. The changes to the 

inventory reflect a 17% reduction in the 

direct PM2.5 emissions inventory is 

needed to demonstrate attainment by 

December 31, 2021. 

TABLE 4—SUMMARY OF ATTAINMENT DEMONSTRATION

Category Direct PM2.5

(tpd) 

a. 2013 Baseline Emissions ................................................................................................................................................................ 0.490 

b. Projected 2021 Emissions without Change-out Program a ............................................................................................................. 0.486 

c. Reductions from Wood Stove Change-out Program b .................................................................................................................... 0.062 

d. Attainment Year Emission Inventory = Projected 2021 Emissions (b) minus Reductions from Wood Stove Change-out Program (c) ............................................................................................................................................................................................ 0.424 

a Mobile source reductions of 0.006 tpd from previously adopted measures credited in projected 2021 emission inventory. See Table 8 in Appendix B of Portola PM2.5 Plan. b The average reduction for the 2019–2021 time frame is 0.062 tpd. Source: Portola PM2.5 Plan, Table 4, 37. 

Traditional rollback analysis as 

described in section IV.B. of this 

proposed rule indicates that direct PM2.5

reductions from the woodstove changeout program (i.e., 0.062 tpd average for 

2019–2021 as used in the rollback) and 

CARB’s mobile source program (i.e., 

0.006 tpd) result in a predicted 2021 

design value of 12.03 mg/m3 and is 

adequate for the State to demonstrate 

that the Portola area will attain the 2012 

annual PM2.5 standards by the outermost 

statutory attainment date as a Moderate 

nonattainment area of December 31, 

2021.84 Table 5 below shows the 

projected cumulative impact of the 

change-out program on emission 

reductions and design values. The 

cumulative reductions and design value 

calculations are offset by one year to 

allow for full deployment of stove 

changeouts in a prior year. Because the 

bulk of the changeouts presumably 

occur during the late spring, summer, 

and early fall, the October-December 

period of a given year would likely see 

the greatest air quality benefits from that 

year’s changeouts, but the JanuaryMarch period would not. The State’s 

calculations result in a conservative 

estimate of the benefits of the wood 

stove change-out program because the 

State is only taking credit for 

changeouts that have been in effect for 

a full year. Thus, the projected benefit 

of changing out 600 stoves will not be 

fully reflected in the design value until 

the 2023 design value, which will 

include 2021, 2022, and 2023, the first 

period of three consecutive years with 

the 600 new certified devices in 

operation. The Portola PM2.5 Plan also 

includes an alternative rollback 

modeling demonstration that results in 

a 2021 DV of 11.1 mg/m3. The alternative 

rollback is described in section IV.B. of 

this proposed rule and in section V.F. of 

the Plan. 

TABLE 5—RELATIONSHIP BETWEEN CUMULATIVE STOVE CHANGEOUTS, REDUCTIONS, AND DESIGN VALUES FROM

ROLLBACK ANALYSIS

Year Stove 

change-outs 

Cumulative 

stove 

changeouts 

credited 

towards 

attainment 

Cumulative 

direct PM2.5

reductions in 

rollback 

analysis 

credited 

towards 

attainment 

(tpd) 

Annual 

average DV 

(μg/m3) 

2016 ............................................................................................... 100 0 0 Not calculated. 

2017 ............................................................................................... 100 100 .013 13.22. 

2018 ............................................................................................... 150 200 .026 12.91. 

2019 ............................................................................................... 150 350 .045 12.45. 


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85EPA, Region IX Air Division, ‘‘Technical 

Support Document for EPA’s Notice of Proposed 

Rulemaking for the California State Implementation 

Plan, Evaluation of incentive-based emission 

reductions relied upon in the Portola Fine 

Particulate Matter (PM2.5) Attainment Plan,’’ 

December 2017. 

86Portola PM2.5 Plan, 20. 

87 Id. at 8–9. 

88Email dated November 29, 2017, from 

Katarzyna Turkiewicz, CARB, to Rynda Kay, EPA, 

RE: questions about the number of wood stoves in 

the Portola nonattainment area. 

89U.S. Census, 2011–2015 American Community 

Survey 5-year estimate for City of Portola, CA and 

State of California. 

90Additional information on unemployment rates 

in Portola is available at http://

www.homefacts.com/unemployment/California/ 

Plumas-County/Portola/96122.html. 

91Portola PM2.5 Plan, 20. 

92 Id. at 29. 

93The average residential electricity rate in the 

City of Portola is 17.87¢/kWh, which is 

approximately 50% greater than the national 

average rate. See Electricity Local at http://

www.electricitylocal.com/states/california/portola/. 

94Portola PM2.5 Plan, 21. 

95See Portola PM2.5 Plan, 81–82, and our 

discussion of RACM/RACT and additional 

reasonable measures in section IV.D of this 

proposed rule. 

TABLE 5—RELATIONSHIP BETWEEN CUMULATIVE STOVE CHANGEOUTS, REDUCTIONS, AND DESIGN VALUES FROM

ROLLBACK ANALYSIS—Continued 

Year Stove 

change-outs 

Cumulative 

stove 

changeouts 

credited 

towards 

attainment 

Cumulative 

direct PM2.5

reductions in 

rollback 

analysis 

credited 

towards 

attainment 

(tpd) 

Annual 

average DV 

(μg/m3) 

2020 ............................................................................................... 100 500 .065 11.97. 

2021 ............................................................................................... 0 600 .077 11.68. 

Projected 2021 DV (average of 2019–2021) ................................ ........................ .............................. .............................. 12.03. 

Source: Portola PM2.5 Plan, 56–57 (tables 10 and 11). 

The Portola PM2.5 Plan relies on the 

wood stove change-out program to 

achieve 0.077 tpd of PM2.5 emission 

reductions in 2021, approximately 93% 

of the PM2.5 reductions relied upon in 

the Plan to demonstrate attainment by 

the December 31, 2021 attainment date. 

The remaining 7% of necessary 

emission reductions will be achieved 

through ongoing implementation of 

federal emission reduction programs 

and CARB’s mobile source control 

program. To justify this extensive 

reliance on the voluntary wood stove 

change-out program for attainment 

purposes, the Plan: (1) Provides a 

detailed description of the clear need for 

PM2.5 emission reductions from wood 

stove changeouts in the Portola area, (2) 

describes features of the wood stove 

program that provide a greater level of 

certainty in the quantification of 

emission reductions than that normally 

associated with voluntary programs, and 

(3) includes a detailed, enforceable 

commitment by the District to monitor 

and report on program implementation 

and to submit substitute measures by 

specific dates if necessary to remedy 

any shortfall in required emission 

reductions.85

The PM2.5 problem in the Portola 

nonattainment area is overwhelmingly 

caused by residential wood smoke. The 

District estimates that between 2011 and 

2015, residential wood smoke emissions 

contributed 76% of annual average 

PM2.5 concentrations and 86% of daily 

PM2.5 concentrations on days exceeding 

35 mg/m3 at the PM2.5 monitor located in 

the City of Portola. Other sources 

contributing to annual average PM2.5

concentrations include refuse burning 

(2.5%), mobile sources (7.6%), 

secondary sulfates (4.8%), secondary 

nitrates (5.1%), and airborne soil 

(3.9%).86

The average daily low temperature 

from October to March in the Portola 

nonattainment area is 21.8 degrees 

Fahrenheit with an average of 218 frost 

days per year, necessitating ample home 

heating.87 CARB estimates that of 2,458 

households in the nonattainment area, 

1,401 use wood burning devices as a 

primary or secondary heating source. Of 

those wood burning devices, 664 are 

uncertified woodstoves.88 The 2011– 

2015 median household income in the 

Portola area was 54% that of the state 

median and home values were 40% of 

the state median.89 The unemployment 

rate for the City of Portola averaged 

10.6% during the 2014–2016 time 

frame.90 According to the District, most 

residents cannot afford to replace their 

uncertified wood burning devices 

without significant financial 

assistance.91 Natural gas is not an option 

for residential heating because it is not 

available in the Portola nonattainment 

area.92 While propane and electric 

options are available, the abundance of 

wood in the area (at no or low cost) and 

high cost of these alternative forms of 

residential heat limit their feasibility as 

primary heat sources.93

The bowl-shaped topography, cold 

stagnant winters, and extensive use of 

residential wood stoves in the Portola 

nonattainment area have caused evening 

and morning PM2.5 concentrations to 

peak during the winter. According to 

the District, the diurnal and seasonal 

pattern of PM2.5 concentrations peaking 

in the winter evening and overnight 

hours further suggests that residential 

wood burning is the primary cause of 

elevated PM2.5 concentrations in the 

Portola area rather than open burning of 

agricultural wastes, forest management, 

and other burning activities.94 Although 

the District has implemented many 

other control measures for other sources 

of direct PM2.5 emissions in the area,95

these measures alone are not sufficient 

to provide for attainment in the Portola 

area given the small percentage of the 

PM2.5 emissions inventory attributed to 

these emission sources. 

The Plan describes a number of 

features of the wood stove program that 

provide a greater level of certainty in the 

quantification of emission reductions 

than that normally associated with 

voluntary programs. First, full funding 

is already secured to entirely fund the 

replacement of 600 wood stoves, which 

the State projects to be sufficient to 

provide for attainment of the 2012 

annual PM2.5 NAAQS by the applicable 

attainment date. Second, the emission 

reduction projections are conservative 

and relatively well understood 

compared to other voluntary programs. 

This is because wood stove technologies 

are generally well understood; wood 

stoves usually remain in the residence 

in which they are installed and have a 

long useful life; usage is generally 

predictable due to the fixed size of the 

home and heating needs; emission 

control technology is unlikely to be 


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96CARB, ‘‘Portola Wood Stove Change-Out, 2017 

Progress Report, Covering Change-outs Completed 

Through 12/31/2017’’ (‘‘2017 Annual Report’’), 3. 

97 Id. at 6 and 13–18. 

98 83 FR 13871 (April 2, 2018). 99 80 FR 2206 (January 15, 2015). 

100Addendum to the General Preamble, 59 FR 

41998 (August 16, 1994), 42015. 

101 Id. 

tampered with; education campaigns 

and training requirements help ensure 

proper operation and fuel selection; and 

conservative emission factors are used 

in emission projections. Third, the 

program infrastructure is wellestablished. The State and District’s 

2017 annual report on the wood stove 

program shows that as of December 31, 

2017, the program had successfully 

funded the replacement of 196 stoves.96

The State and District estimated that 

replacement of these 196 uncertified 

stoves achieved 0.031 tpd of PM2.5

emission reductions, 19% higher than 

the projected emissions reductions 

accounted for in the attainment 

demonstration, due to the fact that new 

stoves were cleaner than assumed in the 

attainment demonstration.97

Finally, the Plan includes detailed, 

enforceable commitments by the District 

to monitor and report on program 

implementation in advance of the 

attainment date and to submit substitute 

measures, if necessary, to remedy any 

shortfall in required emission 

reductions. Specifically, the District has 

committed to: Implement the necessary 

number of woodstove changeouts in 

accordance with specific program 

criteria provided in the SIP submission; 

to achieve, by identified dates, specific 

amounts of PM2.5 emission reductions 

from projected baseline levels identified 

in the Portola PM2.5 Plan; to submit 

annual reports to the EPA that identify 

the calculator used to quantify emission 

reductions and describe, among other 

things, the projects implemented, 

actions taken by the State to confirm 

project compliance, and any changes to 

program implementation forms; and to 

adopt and submit to the EPA, by 

specific dates, any substitute measures 

necessary to address a shortfall in 

required emission reductions. These 

commitments became federally 

enforceable under the CAA upon the 

EPA’s approval of the commitments into 

the SIP.98

3. The EPA’s Evaluation and Proposed 

Action 

The EPA has reviewed the emissions 

inventories, RACM/RACT 

demonstration, air quality modeling, 

and control strategy fully described in 

the Portola PM2.5 Plan. 

In summary and as described in 

section IV.B of this action, the State 

used two modeling techniques to 

demonstrate attainment of the 2012 

annual PM2.5 NAAQS in the Portola 

nonattainment area. First, the State used 

a traditional rollback model to 

demonstrate attainment of the 2012 

annual PM2.5 NAAQS. Second, the State 

corroborated the results of the 

traditional rollback model by using an 

alternative rollback model to also 

demonstrate attainment. The results 

using the alternative rollback model 

provide additional confidence in the 

attainment demonstration. The EPA 

accepts these modeling approaches for 

the attainment demonstration in the 

Portola PM2.5 Plan. 

Consistent with the requirements of 

40 CFR 51.1011(a), the attainment 

demonstration shows the projected 

attainment date that is as expeditious as 

practicable in the Portola area, meets the 

requirements of 40 CFR part 51, 

appendix W, and includes inventory 

data, modeling results, and emission 

reduction analyses on which the State 

has based its projected attainment date. 

In addition, the base year for the 

emissions inventory used in the 

attainment demonstration, 2013, is one 

of the three years used for designation 

of the Portola area as a nonattainment 

area 99 and the control strategies 

modeled as part of the attainment 

demonstration are consistent with the 

control strategy requirements under 40 

CFR 51.1009(a), including the 

requirements for RACM/RACT and 

additional reasonable measures. 

With respect to the wood stove 

change-out program, the EPA believes 

that the Portola PM2.5 Plan provides a 

clear and convincing justification for 

more extensive reliance on a voluntary 

incentive program to achieve emission 

reductions necessary for attainment 

than the EPA normally recommends. 

First, the District has shown a clear 

need for additional reductions from the 

wood stove program, as additional 

regulatory measures for other PM2.5

emission sources in the area are not 

sufficient to provide for attainment, and 

a mandatory curtailment on use of wood 

stoves on high-PM2.5 winter days is not 

economically feasible for 

implementation at this time in the 

Portola area. Second, the State and 

District have identified a number of 

program features that provide adequate 

assurance that the wood stove 

changeout program will achieve, at 

minimum, the emission reductions 

attributed to it in the attainment 

demonstration. Third, the District’s SIPapproved enforceable commitment 

ensures that the EPA and citizens can 

hold the District responsible for 

achieving the emission reductions 

attributed to the wood stove change-out 

program in the attainment 

demonstration. 

Finally, the City Ordinance includes a 

mandatory curtailment of uncertified 

stoves on days when the 24-hour 

average PM2.5 concentration is 

forecasted to exceed 30 mg/m3 that 

begins January 1, 2021. This clear 

prohibition on the operation of 

uncertified wood stoves on days with 

higher PM2.5 levels after January 1, 2021, 

provides additional assurance that 

projected emission reductions will 

occur in time to provide for attainment 

of the 2012 PM2.5 NAAQS by the 

December 31, 2021 attainment date. 

For all of these reasons, we propose 

to approve the attainment 

demonstration in the Portola PM2.5 Plan 

as satisfying the requirements of 

sections 189(a)(1)(B) and 172(c)(1) of the 

CAA and 40 CFR 51.1011(a). 

G. Reasonable Further Progress and 

Quantitative Milestones 

1. Requirements for Reasonable Further 

Progress and Quantitative Milestones 

CAA section 172(c)(2) states that all 

nonattainment area plans shall require 

reasonable further progress (RFP). In 

addition, CAA section 189(c) requires 

that all PM2.5 nonattainment area SIPs 

include quantitative milestones to be 

achieved every three years until the area 

is redesignated to attainment and which 

demonstrate RFP, as defined in CAA 

section 171(1). Section 171(1) defines 

RFP as ‘‘such annual incremental 

reductions in emissions of the relevant 

air pollutant as are required by [Part D] 

or may reasonably be required by the 

Administrator for the purpose of 

ensuring attainment of the applicable 

[NAAQS] by the applicable date.’’ 

Neither subpart 1 nor subpart 4 of part 

D, title I of the Act requires that a set 

percentage of emissions reductions be 

achieved in any given year for purposes 

of satisfying the RFP requirement. 

For purposes of the PM2.5 NAAQS, 

EPA has interpreted the RFP 

requirement to require that 

nonattainment area plans show annual 

incremental emission reductions 

sufficient to maintain generally linear 

progress toward attainment by the 

applicable deadline.100 As discussed in 

EPA guidance in the Addendum to the 

General Preamble (‘‘Addendum’’),101

requiring linear progress in reductions 

of direct PM2.5 and any individual 

precursor in a PM2.5 plan may be 

appropriate in situations where: 


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102 Id. 103 Id. at 42015. 104 Id. at 42016. 105 Id. 

106 40 CFR 51.1012(a). 

107 81 FR 58010, 58056 (August 24, 2016). 

108 Id. at 42016, 42017. 

109 General Preamble, 13539 and Addendum, 

42016. 

110 40 CFR 51.1013(a)(1). 

111 80 FR 2206 (January 15, 2015). 

• The pollutant is emitted by a large 

number and range of sources, 

• The relationship between any 

individual source or source category 

and overall air quality is not well 

known, 

• A chemical transformation is 

involved (e.g., secondary particulate 

significantly contributes to PM2.5 levels 

over the standard), and/or 

• The emission reductions necessary 

to attain the PM2.5 standard are 

inventory-wide.102

The Addendum indicates that 

requiring linear progress may be less 

appropriate in other situations, such as: 

• Where there are a limited number of 

sources of direct PM2.5 or a precursor, 

• Where the relationships between 

individual sources and air quality are 

relatively well defined, and/or 

• Where the emission control systems 

utilized (e.g., at major point sources) 

will result in swift and dramatic 

emission reductions. 

In nonattainment areas characterized 

by any of these latter conditions, RFP 

may be better represented as step-wise 

progress as controls are implemented 

and achieve significant reductions soon 

thereafter. For example, if an area’s 

nonattainment problem can be 

attributed to a few major sources, EPA 

guidance indicates that ‘‘RFP should be 

met by ‘adherence to an ambitious 

compliance schedule’ which is likely to 

periodically yield significant emission 

reductions of direct PM2.5 or a PM2.5

precursor.’’ 103

Attainment plans for PM2.5

nonattainment areas should include 

detailed schedules for compliance with 

emission regulations in the area and 

provide corresponding annual emission 

reductions to be realized from each 

milestone in the schedule.104 In 

reviewing an attainment plan under 

subpart 4, the EPA considers whether 

the annual incremental emission 

reductions to be achieved are reasonable 

in light of the statutory objective of 

timely attainment. Although early 

implementation of the most costeffective control measures is often 

appropriate, states should consider both 

cost-effectiveness and pollution 

reduction effectiveness when 

developing implementation schedules 

for its control measures and may 

implement measures that are more 

effective at reducing PM2.5 earlier to 

provide greater public health 

benefits.105

The PM2.5 SIP Requirements Rule 

establishes specific regulatory 

requirements for purposes of satisfying 

the Act’s RFP requirements and 

provides related guidance in the 

preamble to the rule. Specifically, under 

the PM2.5 SIP Requirements Rule, each 

PM2.5 attainment plan must contain an 

RFP analysis that includes, at minimum, 

the following four components: (1) An 

implementation schedule for control 

measures; (2) RFP projected emissions 

for direct PM2.5 and all PM2.5 plan 

precursors for each applicable milestone 

year, based on the anticipated control 

measure implementation schedule; (3) a 

demonstration that the control strategy 

and implementation schedule will 

achieve reasonable progress toward 

attainment between the base year and 

the attainment year; and (4) a 

demonstration that by the end of the 

calendar year for each milestone date for 

the area, pollutant emissions will be at 

levels that reflect either generally linear 

progress or stepwise progress in 

reducing emissions on an annual basis 

between the base year and the 

attainment year.106 States should 

estimate the RFP projected emissions for 

each quantitative milestone year by 

sector on a pollutant-by-pollutant 

basis.107

Section 189(c) requires that 

attainment plans include quantitative 

milestones that demonstrate RFP. The 

purpose of the quantitative milestones is 

to allow for periodic evaluation of the 

area’s progress towards attainment of 

the NAAQS consistent with RFP 

requirements. Because RFP is an annual 

emission reduction requirement and the 

quantitative milestones are to be 

achieved every three years, when a state 

demonstrates compliance with the 

quantitative milestone requirement, it 

will demonstrate that RFP has been 

achieved during each of the relevant 

three years. Quantitative milestones 

should provide an objective means to 

evaluate progress toward attainment 

meaningfully, e.g., through imposition 

of emission controls in the attainment 

plan and the requirement to quantify 

those required emission reductions. The 

CAA also requires states to submit 

milestone reports (due 90 days after 

each milestone), and these reports 

should include calculations and any 

assumptions made by the state 

concerning how RFP has been met, e.g., 

through quantification of emission 

reductions to date.108

The CAA does not specify the starting 

point for counting the three-year periods 

for quantitative milestones under CAA 

section 189(c). In the General Preamble 

and Addendum, the EPA interpreted the 

CAA to require that the starting point 

for the first three-year period be the due 

date for the Moderate area plan 

submission.109 Consistent with this 

longstanding interpretation of the Act, 

the PM2.5 SIP Requirements Rule 

requires that each plan for a Moderate 

PM2.5 nonattainment area contain 

quantitative milestones to be achieved 

no later than milestone dates 4.5 years 

and 7.5 years from the date of 

designation of the area.110 Because the 

EPA designated the Portola area 

nonattainment for the 2012 annual 

PM2.5 NAAQS effective April 15, 

2015,111 the applicable quantitative 

milestone dates for purposes of the 

Portola PM2.5 Plan are October 15, 2019 

and October 15, 2022. 

2. RFP Demonstration and Quantitative 

Milestones in the Portola PM2.5 Plan 

The RFP demonstration and 

quantitative milestones are in section 

VI.A of the Portola PM2.5 Plan. The Plan 

estimates that emissions of direct PM2.5

will decline steadily from 2016 to 2021 

and that emissions of direct PM2.5 will 

generally remain below the levels 

needed to show step-wise progress 

toward attainment. According to the 

State and District, step-wise progress 

toward attainment is justified here 

because before the Portola area was 

designated as a PM2.5 nonattainment 

area in 2015, the area was designated 

attainment for all NAAQS and was not 

required to implement any air quality 

control program. The development of 

the wood stove change-out program 

involved an intensive effort to secure 

funding, establish requirements for 

contractors/retailers, identify and 

educate potential applicants, review and 

process completed applications, 

coordinate the installation of new stoves 

along with the removal and destruction 

of the old stoves, and track the progress 

of the program at every step. Given the 

time necessary to develop this program, 

direct PM2.5 emissions remained flat 

between 2013, the base year of the Plan, 

and 2016, the year that the District 

began to implement the wood stove 

change-out program. By 2016, however, 

the District had secured the necessary 

funding and developed the program 

infrastructure, enabling it to begin full 

implementation of its five-year 

voluntary wood stove change-out 

program to provide for attainment by 

December 2021, the earliest practicable 

attainment date for the 2012 annual 


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112Portola PM2.5 Plan, 66–72. 

113 Id. at Appendix B. 

114 Id. at 66–70. 

115 Id. at 71–72. 

116 Id. at Appendix E, 10. The EPA approved this 

commitment into the SIP at 83 FR 13871 (April 2, 

2018). 

117 Id. at 71. 

PM2.5 NAAQS in this area. The District 

estimates that the change-out program 

will achieve PM2.5 emission reductions 

representing generally linear progress 

toward attainment between 2016 and 

2022. Because the majority of the 

changeouts will be completed during 

the summer months when homeowners 

are not heating their homes, the District 

expects that direct PM2.5 concentrations 

during the second half of the year will 

be lower than during the first half of the 

year. For RFP purposes, only the 

changeouts accomplished during the 

prior year are accounted for in the 

projected emission reductions (i.e., only 

reductions from changeouts in effect for 

a full year are credited toward RFP).112

The Plan’s emissions inventory shows 

that direct PM2.5 is emitted 

predominantly by residential wood 

combustion.113 The Plan specifically 

describes the District’s procedures for 

calculating the 2019 and 2022 RFP 

targets for direct PM2.5 and documents 

the District’s conclusion that projected 

PM2.5 emission levels, based on the 

adopted control strategy for the area, 

would meet the RFP targets in both 

milestone years, as shown in Table 6 

below.114

TABLE 6—RFP DEMONSTRATION FOR DIRECT PM2.5 (TPD) 

Description 2013 2019 2022 

Baseline inventory a ..................................................................................................................... 0.490 0.487 0.487 

Reductions from RACM control strategy a ................................................................................... 0.000 0.045 0.077 

Inventory after RACM control strategy implemented b ................................................................ 0.49 0.44 0.41 

RFP target b ................................................................................................................................. 0.44 0.41 

RFP target achieved? .................................................................................................................. Yes Yes 

a Reductions from CARB’s mobile source measures are already included in the projected 2019 and 2022 baseline inventories. 

b Rounding to two decimal places (hundredths of a ton). 

With respect to quantitative 

milestones, the Portola PM2.5 Plan 

identifies RFP emissions levels for 

direct PM2.5 in 2019 and 2022 that 

show, beginning in 2016, stepwise 

progress towards attaining the annual 

PM2.5 NAAQS in 2021. The quantitative 

milestones are the differences in 

emissions between the future baseline 

inventories and the future controlled 

inventories for 2019 and 2022, i.e., the 

projected emission reductions in each of 

these years, as shown in Table 7.115

TABLE 7—RFP PROJECTED EMISSION REDUCTIONS FOR QUANTITATIVE MILESTONE YEARS (TPD) 

Sector 2019 2022 

Wood Stove Changeouts ......................................................................................................................................... 0.045 0.077 

Total .................................................................................................................................................................. 0.045 0.077 

Source: Portola PM2.5 Plan, 71–72. 

The Portola PM2.5 Plan also contains 

an enforceable commitment by the 

District to implement specific numbers 

of wood stove change-out projects and 

to achieve specific amounts of PM2.5

emission reductions through 

implementation of these projects by the 

2019 RFP year and the 2021 attainment 

year.116

Finally, the Portola PM2.5 Plan states 

the District’s commitment to track, 

quantify, and report to the EPA on its 

implementation of the adopted control 

strategy and on the area’s progress 

toward attainment. The Plan also states 

that the District will submit to the EPA 

a quantitative milestone report no later 

than 90 days after a given milestone 

date (i.e., by January 15, 2020 and 

January 15, 2023, respectively), each of 

which will include the following 

information: 

D Certification that the SIP strategy is 

being implemented consistent with RFP; 

D Technical support, including 

calculations to document completion 

statistics for each quantitative 

milestone; and 

D Discussion of whether the PM2.5

NAAQS will be attained by the 

projected attainment date.117

3. The EPA’s Evaluation and Proposed 

Action 

a. Reasonable Further Progress 

Demonstration 

As discussed in section IV.C. of this 

proposed rule, we are proposing to 

determine that PM2.5 precursors do not 

contribute significantly to ambient 

PM2.5 levels that exceed the 2012 annual 

PM2.5 NAAQS in the Portola PM2.5

nonattainment area and, accordingly, 

that no RFP demonstrations for PM2.5

precursors are necessary for purposes of 

the 2012 annual PM2.5 NAAQS in this 

area. 

With respect to direct PM2.5, we agree 

that step-wise progress is an appropriate 

measure of RFP for the 2012 PM2.5

NAAQS in the Portola area. It is 

justified because direct PM2.5 is emitted 

primarily from hundreds of individual 

residential wood combustion sources, 

and the District needed adequate time to 

secure funding and develop the 

infrastructure necessary to implement a 

wood stove change-out program. 

Accordingly, the emission reductions 

that result from this program did not 

begin until 2016, but will continue 

throughout the duration of the Plan. 

The Portola PM2.5 Plan documents the 

State’s conclusion that it is 

implementing all RACM and RACT and 

additional reasonable measures for 

direct PM2.5 as expeditiously as 

practicable and identifies projected 

levels of direct PM2.5 emissions in 2019 

and 2022 that reflect full 

implementation of the State’s and 


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118Portola PM2.5 Plan, Chapter VI, section D.3. 

119Portola PM2.5 Plan, Chapter VI, section A. 

120 Id. at Appendix E, 10. 

121Addendum, 42017. 

122See 40 CFR 51.1014(a). 

123See 81 FR 58010, 58066; see also Addendum, 

42015. 

124See 81 FR 58010, 58066; see also General 

Preamble, 13512, 13543–44 and Addendum, 42014– 

42015. 

125Bahr v. EPA, 836 F.3d 1218, 1235–1237 (9th 

Cir. 2016). 

District’s attainment control strategy for 

direct PM2.5.118 The wood stove changeout program provides incremental 

reductions of direct PM2.5 emission from 

2016 to 2021. CARB’s mobile source 

measures also provide incremental 

reductions of direct PM2.5 emissions 

from 2013 to 2022, and the City 

Ordinance is projected to achieve 

emission reductions beginning in 2021, 

to the extent those reductions have not 

already occurred through 

implementation of the wood stove 

change-out program. All of these 

measures achieve PM2.5 reductions each 

year and the State and District will be 

reporting on RFP in the 2019 and 2022 

RFP milestone years and through the 

2021 attainment year.119

Thus, the Portola PM2.5 Plan 

demonstrates that emissions of direct 

PM2.5 will be reduced at rates 

representing stepwise progress toward 

attainment. The Plan also demonstrates 

that all RACM, RACT, and additional 

reasonable measures that provide the 

bases for the direct PM2.5 emissions 

projections in the RFP analysis in the 

Plan are being implemented as 

expeditiously as practicable. 

Accordingly, we propose to determine 

that the Plan requires the annual 

incremental reductions in emissions of 

direct PM2.5 that are necessary for the 

purpose of ensuring reasonable further 

progress towards attainment of the 2012 

annual PM2.5 NAAQS by 2021, in 

accordance with the requirements of 

CAA sections 171(1) and 172(c)(2). 

b. Quantitative Milestones 

The Plan adequately documents the 

District’s methodology for identifying 

and calculating appropriate RFP targets 

for the 2019 and 2022 milestone years 

and contains, as part of the RACM 

control strategy for the area, an 

enforceable commitment by the District 

to implement specific numbers of wood 

stove change-out projects and thereby 

achieve specific amounts of PM2.5

emission reductions by the 2019 RFP 

year and the 2021 attainment year.120

These quantitative milestones provide 

an objective means for evaluating the 

area’s progress toward attainment of the 

PM2.5 NAAQS. We propose to approve 

these quantitative milestones in the 

Portola PM2.5 Plan as meeting the 

requirements of CAA section 189(c) and 

40 CFR 51.1013(a)(1). We note that, 

consistent with the requirements of 

CAA section 189(c)(2) as interpreted in 

longstanding EPA policy, each of the 

upcoming milestone reports should 

include technical support sufficient to 

document completion statistics for 

appropriate milestones, e.g., 

calculations and any assumptions made 

concerning emission reductions to 

date.121

H. Contingency Measures 

1. Requirements for Contingency 

Measures 

Under CAA section 172(c)(9), each 

SIP for a nonattainment area must 

include contingency measures to be 

implemented if an area fails to meet RFP 

(‘‘RFP contingency measures’’) or fails 

to attain the NAAQS by the applicable 

attainment date (‘‘attainment 

contingency measures’’). Under the 

PM2.5 SIP Requirements Rule, PM2.5

attainment plans must include 

contingency measures to be 

implemented following a determination 

by the EPA that the state has failed: (1) 

To meet any RFP requirement in the 

approved SIP; (2) to meet any 

quantitative milestone in the approved 

SIP; (3) to submit a required quantitative 

milestone report; or (4) to attain the 

applicable PM2.5 NAAQS by the 

applicable attainment date.122

Contingency measures must be fully 

adopted rules or control measures that 

are ready to be implemented quickly 

upon failure to meet RFP or failure of 

the area to meet the relevant NAAQS by 

the applicable attainment date.123

The purpose of contingency measures 

is to continue progress in reducing 

emissions while a state revises its SIP to 

meet the missed RFP requirement or to 

correct ongoing nonattainment. Neither 

the CAA nor the EPA’s implementing 

regulations establish a specific level of 

emissions reductions that 

implementation of contingency 

measures must achieve, but the EPA 

recommends that contingency measures 

should provide for emissions reductions 

equivalent to approximately one year of 

reductions needed for RFP, calculated 

as the overall level of reductions needed 

to demonstrate attainment divided by 

the number of years from the base year 

to the attainment year. In general, we 

expect all actions needed to effect full 

implementation of the measures to 

occur within 60 days after the EPA 

notifies the State of a failure to meet 

RFP or to attain.124

To satisfy the requirements of 40 CFR 

51.1014, the contingency measures 

adopted as part of a PM2.5 attainment 

plan must consist of control measures 

for the area that are not otherwise 

required to meet other nonattainment 

plan requirements or that achieve 

emissions reductions not otherwise 

relied upon in the control strategy for 

the area (e.g., to meet RACM/RACT 

requirements) and must specify the 

timeframe within which their 

requirements become effective following 

any of the EPA determinations specified 

in 40 CFR 51.1014(a). 

The Ninth Circuit Court of Appeals 

recently rejected the EPA’s 

interpretation of CAA section 172(c)(9) 

to allow approval of already 

implemented control measures as 

contingency measures, in a decision 

called Bahr v. EPA (‘‘Bahr’’).125 In Bahr, 

the Ninth Circuit concluded that 

contingency measures must be measures 

that are triggered only after the EPA 

determines that an area fails to meet 

RFP requirements or to attain by the 

applicable attainment date, not before. 

Thus, within the geographic jurisdiction 

of the Ninth Circuit, states cannot rely 

on already implemented measures to 

comply with the contingency measure 

requirements under CAA section 

172(c)(9). 

2. Contingency Measures in the 2016 

PM2.5 Plan 

The District’s contingency measures 

are described in section VI.B of the 

Portola PM2.5 Plan. 

3. The EPA’s Evaluation and Proposed 

Action 

We are not proposing any action at 

this time on the contingency measures 

in the Portola PM2.5 Plan. We intend to 

work with the State and District to assist 

them with the development and 

submission of contingency measures 

consistent with the Bahr decision and to 

act on the revised contingency 

measures, as appropriate, through a 

subsequent rulemaking. 

I. Motor Vehicle Emission Budgets 

1. Requirements for Motor Vehicle 

Emissions Budgets 

Section 176(c) of the CAA requires 

federal actions in nonattainment and 

maintenance areas to conform to the 

SIP’s goals of eliminating or reducing 

the severity and number of violations of 

the NAAQS and achieving expeditious 

attainment of the standards. Conformity 

to the SIP’s goals means that such 

actions will not: (1) Cause or contribute 

to violations of a NAAQS, (2) worsen 

the severity of an existing violation, or 


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126The Portola nonattainment area does not lie 

within, or share a border with any MPO, nor does 

any MPO model any projects within the Portola 

nonattainment area. Therefore, the Portola 

nonattainment area meets the definition in the 

transportation conformity rule for an isolated rural 

nonattainment area. The California Department of 

Transportation performs many of the functions in 

isolated rural nonattainment areas that the 

conformity rule requires of MPOs. Isolated rural 

nonattainment areas have no federally required 

metropolitan transportation plan or program. A 

regional emissions analysis is required only when 

a non-exempt regionally significant project is 

proposed in the isolated rural area. For further 

details on isolated rural nonattainment areas and 

the transportation conformity requirements in those 

areas, see 40 CFR 93.101 and 93.109(g). 

127 40 CFR 93.118(e)(4)(v). 

128 40 CFR 93.102(b)(3), 93.102(b)(2)(v), and 

93.122(f); see also conformity rule preamble at 69 

FR 40004, 40031–40036 (July 1, 2004). 

129 40 CFR 93.102(b)(2)(iv). 

130 40 CFR 51.1013(a)(1). 

131Because the Portola area was designated 

nonattainment effective April 15, 2015, the first 

milestone date is October 15, 2019 and the second 

milestone date is October 15, 2022. 80 FR 2206 

(January 15, 2015). 

132 81 FR 58010, 58058 and 58063–64 (August 24, 

2016). 

133Portola PM2.5 Plan, section VI.C (for 2021 

budgets) and ‘‘Transportation Conformity Budgets 

for the Portola PM2.5 SIP Plan Supplement’’ (for 

2019 and 2022 budgets) dated December 20, 2017, 

and adopted by CARB Board on October 26, 2017. 

134Plan at Chapter VI, section C.4, 77. 

135See footnote 20. 

(3) delay timely attainment of any 

NAAQS or any interim milestone. 

Actions involving Federal Highway 

Administration (FHWA) or Federal 

Transit Administration (FTA) funding 

or approval are subject to the EPA’s 

transportation conformity rule, codified 

at 40 CFR part 93, subpart A. Under this 

rule, metropolitan planning 

organizations (MPOs) in nonattainment 

and maintenance areas coordinate with 

state and local air quality and 

transportation agencies, EPA, FHWA, 

and FTA to demonstrate that an area’s 

regional transportation plans and 

transportation improvement programs 

conform to the applicable SIP.126 This 

demonstration is typically done by 

showing that estimated emissions from 

existing and planned highway and 

transit systems are less than or equal to 

the motor vehicle emissions budgets 

(‘‘budgets’’) contained in all control 

strategy SIPs. An attainment, 

maintenance, or RFP SIP should include 

budgets for the attainment year, each 

required RFP milestone year, and the 

last year of the maintenance plan, as 

appropriate. Budgets are generally 

established for specific years and 

specific pollutants or precursors and 

must reflect all of the motor vehicle 

control measures contained in the 

attainment and RFP demonstrations or 

maintenance plan, as applicable.127

All direct PM2.5 SIP budgets should 

include direct PM2.5 motor vehicle 

emissions from tailpipes, brake wear, 

and tire wear. With respect to PM2.5

from re-entrained road dust and 

emissions of VOC, SO2.and/or ammonia, 

the transportation conformity provisions 

of 40 CFR part 93, subpart A, apply only 

if the EPA Regional Administrator or the 

director of the state air agency has made 

a finding that emissions of these 

pollutants within the area are a 

significant contributor to the PM2.5

nonattainment problem and has so 

notified the MPO and Department of 

Transportation (DOT), or if the 

applicable implementation plan (or 

implementation plan submission) 

includes any of these pollutants in the 

approved (or adequate) budget as part of 

the RFP, attainment or maintenance 

strategy.128

By contrast, transportation conformity 

requirements apply with respect to 

emissions of NOX unless both the EPA 

Regional Administrator and the director 

of the state air agency have made a 

finding that transportation-related 

emissions of NOX within the 

nonattainment area are not a significant 

contributor to the PM2.5 nonattainment 

problem and have so notified the MPO 

and DOT, or the applicable 

implementation plan (or 

implementation plan submission) does 

not establish an approved (or adequate) 

budget for such emissions as part of the 

reasonable further progress, attainment 

or maintenance strategy.129 The criteria 

for insignificance determinations can be 

found in 40 CFR 93.109(f). In order for 

a pollutant or precursor to be 

considered an insignificant contributor, 

the control strategy SIP must 

demonstrate that it would be 

unreasonable to expect that such an area 

would experience enough motor vehicle 

emissions growth in that pollutant/ 

precursor for a NAAQS violation to 

occur. Insignificance determinations are 

based on factors such as air quality, SIP 

motor vehicle control measures, trends 

and projections of motor vehicle 

emissions, and the percentage of the 

total SIP inventory that is comprised of 

motor vehicle emissions. The EPA’s 

rationale for the providing for 

insignificance determinations is 

described in the July 1, 2004 revision to 

the Transportation Conformity Rule at 

69 FR 40004. 

For motor vehicle emissions budgets 

to be approvable, they must meet, at a 

minimum, the EPA’s adequacy criteria 

(40 CFR 93.118(e)(4)). 

Under the PM2.5 SIP Requirements 

Rule, each attainment plan submittal for 

a Moderate PM2.5 nonattainment area 

must contain quantitative milestones to 

be achieved no later than 4.5 years and 

7.5 years after the date the area was 

designated nonattainment.130 The 

second of these milestone dates, October 

15, 2022,131 falls after the attainment 

date for the Portola area, which is 

December 31, 2021. As the EPA 

explained in the preamble to the PM2.5

SIP Requirements Rule, it is important 

to include a post-attainment year 

quantitative milestone to ensure that, if 

the area fails to attain by the attainment 

date, the EPA can continue to monitor 

the area’s progress toward attainment 

while the state develops a new 

attainment plan.132 Although the postattainment year quantitative milestone 

is a required element of a Moderate area 

plan, it is not necessary to demonstrate 

transportation conformity for 2022 or to 

use the 2022 budgets in transportation 

conformity determinations until such 

time as the area fails to attain the 2012 

PM2.5 NAAQS. 

2. Motor Vehicle Emissions Budgets 

in the Portola PM2.5 Plan 

The Portola PM2.5 Plan includes 

budgets for direct PM2.5 for 2019 and 

2022 (RFP milestone years) and 2021 

(projected attainment year for the 2012 

annual NAAQS).133 The direct PM2.5

budgets include tailpipe, brake wear, 

and tire wear emissions.134

The PM2.5 budgets were calculated 

using EMFAC2014, CARB’s latest 

approved version of the EMFAC model 

for estimating emissions from on-road 

vehicles operating in California,135 and 

reflect annual daily average emissions 

consistent with the 2019 and 2022 RFP 

milestone years and the 2021 attainment 

demonstration for the annual PM2.5

NAAQS. The 2019 and 2021 conformity 

budgets for direct PM2.5, expressed in 

annual average tons per day, are 

provided in Table 8. As explained 

further below, we are not acting on the 

2022 budgets at this time. 

TABLE 8—ANNUAL AVERAGE CONFORMITY BUDGETS FOR PM2.5 (TPD) 

Category 2019 2021 

Direct exhaust, tire, 

and brake wear from 

on road vehicles a .... 0.0026 0.0026 

Total ......................... 0.0026 0.0026 

Conformity Budget b .... 0.003 0.003 

a Calculated from default EMFAC2014 v.1.07 output for Plumas County adjusted to reflect only the 

emissions from the Portola nonattainment area. bBudgets are rounded up to the nearest 0.001 ton. 

Appendix P of the Portola PM2.5 Plan 

contains the State’s evaluation of PM2.5

precursors and the bases for its 

conclusion that emissions of VOC, SO2, 


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136Portola PM2.5 Plan, Appendix P. 

137Portola PM2.5 Plan, Appendix B, Table 7. 

138Under the Transportation Conformity 

regulations, the EPA may review the adequacy of 

submitted motor vehicle emission budgets 

simultaneously with the EPA’s approval or 

disapproval of the submitted implementation plan. 

40 CFR 93.118(f)(2). 

139 40 CFR 93.118(e)(1). 

140Letter dated December 20, 2017, from Richard 

W. Corey, Executive Officer, California Air 

Resources Board, to Alexis Strauss, Acting Regional 

Administrator, EPA Region 9. 

NOX, and ammonia from on-road motor 

vehicles are not significant contributors 

to the PM2.5 nonattainment problem in 

the Portola area. The State focused its 

analysis on the contribution of on-road 

emissions of each precursor to the PM2.5

design value in the Portola area, the 

changes in emission levels from 2013 to 

2021, and motor vehicle emission 

control measures included in the Plan. 

Table 1 in Appendix P of the Portola 

PM2.5 Plan shows that the on-road 

emission totals for direct PM2.5 and all 

precursors decrease from 2013 to the 

2021 attainment year. According to the 

State, on-road emissions of direct PM2.5

and all precursors contribute less than 

10% and on-road NOX emissions 

contribute less than 2% to the PM2.5

design value in the Portola area, 

compared to wood burning, which 

accounts for over 76% of the PM2.5

design value.136 On-road NOX emissions 

account for approximately 36% of the 

total 2013 base year inventory but 

decline to 29% and 26% of the 2019 

and 2021 inventories, respectively. The 

on-road NOX emissions decrease from 

the 2013 base year is 0.07 tpd (or 37%) 

in 2019 and 0.09 tpd (or 47%) in 

2021.137 The State also evaluated onroad construction dust and paved and 

unpaved road dust and concluded that 

emissions of these pollutants are not 

significant contributors to the PM2.5

nonattainment problem in the Portola 

area. Therefore, the Plan does not 

include budgets for VOC, SO2, NOX, 

ammonia, or PM2.5 from re-entrained 

road dust or dust from road 

construction. 

3. The EPA’s Evaluation and Proposed 

Actions 

With respect to PM2.5 from reentrained road dust, VOC, SO2, and 

ammonia, neither the EPA nor the State 

has made a finding that on-road 

emissions of any of these pollutants or 

precursors are a significant contributor 

to the PM2.5 nonattainment problem in 

the Portola area, and neither the 

approved California SIP for Portola nor 

the submitted Portola PM2.5 Plan 

establish adequate budgets for such 

emissions as part of an RFP, attainment 

or maintenance strategy for the PM2.5

NAAQS. Accordingly, the 

transportation conformity provisions of 

40 CFR part 93, subpart A, do not apply 

with respect to PM2.5 from re-entrained 

road dust or to emissions of VOC, SO2

or ammonia for purposes of the 2012 

PM2.5 NAAQS in the Portola area. 

With respect to NOX emissions, we 

find that the State’s evaluation of 

emission trends, projections of motor 

vehicle emissions, and the percentage of 

the total SIP inventory that is comprised 

of motor vehicle emissions is sufficient 

to demonstrate, consistent with 40 CFR 

93.109(f), that it would be unreasonable 

to expect that this area would 

experience such growth in NOX

emissions from motor vehicles as to 

result in a violation of the PM2.5

NAAQS. Accordingly, the EPA is 

proposing to determine that 

transportation-related emissions of NOX

are insignificant contributors to the 

PM2.5 nonattainment problem in the 

Portola area. 

We have evaluated the submitted 

direct PM2.5 budgets for 2019 and 2021 

in the Plan against our adequacy criteria 

in 40 CFR 93.118(e)(4) and (5) as part of 

our review of the budgets’ approvability 

and will complete the adequacy review 

concurrent with our final action on the 

Portola PM2.5 Plan.138 On January 5, 

2018, the EPA announced the 

availability of the budgets in the Portola 

PM2.5 Plan and provided a 30-day public 

comment period. This announcement 

was posted on the EPA’s Adequacy 

website at: https://www.epa.gov/stateand-local-transportation/stateimplementation-plans-sip-submissionscurrently-under-epa#portola2018. The 

comment period for this notification 

ended on February 5, 2018, and we did 

not receive any comments. 

The EPA has not yet reviewed and is 

not taking any action at this time on the 

submitted budget for 2022 for the 

Portola PM2.5 nonattainment area. 

Therefore, the submitted budget for 

2022 for the Portola nonattainment area 

will not be used in transportation 

conformity determinations at this time. 

The EPA will begin reviewing the 2022 

budget for adequacy and approval only 

if the area fails to attain the PM2.5

NAAQS by December 31, 2021, the 

applicable Moderate area attainment 

date. 

If the EPA were to either find 

adequate or approve the post-attainment 

milestone year motor vehicle emissions 

budgets now, those budgets would have 

to be used in transportation conformity 

determinations that are made after the 

effective date of the adequacy finding or 

approval even if the Portola PM2.5

nonattainment area ultimately attains 

the PM2.5 NAAQS by the Moderate area 

attainment deadline. As a result, the 

California Department of 

Transportation, which performs many of 

the MPO functions in the Portola PM2.5

nonattainment area, would be required 

to demonstrate conformity for the postattainment date milestone year and all 

later years addressed in the conformity 

determination to the post-attainment 

date RFP motor vehicle emissions 

budgets rather than the budgets 

associated with the attainment year for 

the area (i.e., the motor vehicle 

emissions budgets for 2021). The EPA 

does not believe that it is necessary to 

demonstrate conformity using these 

post-attainment year budgets in areas 

that either the EPA anticipates will 

attain by the attainment date or in areas 

that, in fact, attain by the attainment 

date. 

If the EPA determines that the Portola 

area has failed to attain the PM NAAQS 

by the applicable attainment date, the 

EPA will begin the budget adequacy and 

approval processes for the postattainment year (2022) budget. If the 

EPA finds the 2022 budget adequate or 

approves it, that budget will have to be 

used in subsequent transportation 

conformity determinations. The EPA 

believes that initiating these processes 

following a determination that the area 

has failed to attain by the attainment 

date ensures that transportation 

activities will not cause or contribute to 

new violations, increase the frequency 

or severity of any existing violations, or 

delay timely attainment or any required 

interim emission reductions or 

milestones in the Portola area, 

consistent with the requirements of 

CAA section 176(c)(1)(B). 

For the reasons discussed in sections 

V.E.v and V.F of this proposed rule, we 

are proposing to approve the RFP and 

attainment demonstrations in the 

Portola PM2.5 Plan. The budgets, as 

given in Table 9 of this proposed rule, 

are consistent with these 

demonstrations, are clearly identified 

and precisely quantified, and meet all 

other applicable statutory and 

regulatory requirements including the 

adequacy criteria in 40 CFR 93.118(e)(4) 

and (5). For these reasons, the EPA 

proposes to approve the budgets listed 

in Table 8 above. 

The transportation conformity rule 

allows us to limit the approval of 

budgets,139 and CARB requested that we 

limit the duration of our approval of the 

budgets in the Plan to the period before 

the effective date of the EPA’s adequacy 

finding for any subsequently submitted 

budgets.140 However, we will consider 


amozie on DSK3GDR082PROD with PROPOSALS1
Federal Register / Vol. 83, No. 242 / Tuesday, December 18, 2018 / Proposed Rules 64795 

141 67 FR 69141 (November 15, 2002), limiting 

our prior approval of budgets in certain California 

SIPs. 

the State’s request to limit an approval 

of its budgets only if the request 

includes the following elements: 141

• An acknowledgement and 

explanation as to why the budgets under 

consideration have become outdated or 

deficient; 

• A commitment to update the 

budgets as part of a comprehensive SIP 

update; and 

• A request that the EPA limit the 

duration of its approval to the time 

when new budgets have been found to 

be adequate for transportation 

conformity purposes. 

Because CARB’s request does not 

include all of these elements, we cannot 

at this time propose to limit the 

duration of our approval of the 

submitted budgets. In order to limit the 

approval, we would need the 

information described above in order to 

determine whether such limitation is 

reasonable and appropriate in this case. 

Once CARB has provided the necessary 

information, we intend to review it and 

take appropriate action. If we propose to 

limit the duration of our approval of the 

budgets in the Portola PM2.5 Plan, we 

will provide the public an opportunity 

to comment. The duration of the 

approval of the budgets, however, 

would not be limited until we complete 

such a rulemaking. 

V. Summary of Proposed Actions and 

Request for Public Comment 

Under CAA sections 110(k)(3), the 

EPA is proposing to approve SIP 

revisions submitted by California to 

address the Act’s Moderate area 

planning requirements for the 2012 

PM2.5 NAAQS in the Portola 

nonattainment area. Specifically, the 

EPA is proposing to approve the 

following elements of the Portola PM2.5

Plan: 

1. The 2013 base year emissions 

inventories as meeting the requirements 

of CAA section 172(c)(3); 

2. The reasonably available control 

measure/reasonably available control 

technology demonstration as meeting 

the requirements of CAA sections 

172(c)(1) and 189(a)(1)(C); 

3. The attainment demonstration as 

meeting the requirements of CAA 

sections 172(c)(1) and 189(a)(1)(B); 

4. The reasonable further progress 

demonstration as meeting the 

requirements of CAA section 172(c)(2); 

5. The quantitative milestones as 

meeting the requirements of CAA 

section 189(c); and 

6. The motor vehicle emissions 

budgets for 2019 and 2021, because they 

are derived from approvable attainment 

and RFP demonstrations and meet the 

requirements of CAA section 176(c) and 

40 CFR part 93, subpart A. 

The EPA is not proposing any action 

at this time on the contingency 

measures or the post-attainment year 

(2022) budget in the Portola PM2.5 Plan. 

We will accept comments from the 

public on these proposals for the next 

30 days. The deadline and instructions 

for submission of comments are 

provided in the DATES and ADDRESSES

sections at the beginning of this 

preamble. 

VI. Statutory and Executive Order 

Reviews 

Under the Clean Air Act, the 

Administrator is required to approve a 

SIP submission that complies with the 

provisions of the Act and applicable 

federal regulations. 42 U.S.C. 7410(k); 

40 CFR 52.02(a). Thus, in reviewing SIP 

submissions, the EPA’s role is to 

approve state choices, provided that 

they meet the criteria of the Clean Air 

Act. Accordingly, this proposed action 

merely proposes to approve state law as 

meeting federal requirements and does 

not impose additional requirements 

beyond those imposed by state law. For 

that reason, this proposed action: 

• Is not a ‘‘significant regulatory 

action’’ subject to review by the Office 

of Management and Budget under 

Executive Orders 12866 (58 FR 51735, 

October 4, 1993) and 13563 (76 FR 3821, 

January 21, 2011); 

• Is not an Executive Order 13771 (82 

FR 9339, February 2, 2017) regulatory 

action because SIP approvals are 

exempted under Executive Order 12866; 

• Does not impose an information 

collection burden under the provisions 

of the Paperwork Reduction Act (44 

U.S.C. 3501 et seq.); 

• Is certified as not having a 

significant economic impact on a 

substantial number of small entities 

under the Regulatory Flexibility Act (5 

U.S.C. 601 et seq.); 

• Does not contain any unfunded 

mandate or significantly or uniquely 

affect small governments, as described 

in the Unfunded Mandates Reform Act 

of 1995 (Pub. L. 104–4); 

• Does not have Federalism 

implications as specified in Executive 

Order 13132 (64 FR 43255, August 10, 

1999); 

• Is not an economically significant 

regulatory action based on health or 

safety risks subject to Executive Order 

13045 (62 FR 19885, April 23, 1997); 

• Is not a significant regulatory action 

subject to Executive Order 13211 (66 FR 

28355, May 22, 2001); 

• Is not subject to requirements of 

section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (15 U.S.C. 272 note) because 

application of those requirements would 

be inconsistent with the Clean Air Act; 

and 

• Does not provide the EPA with the 

discretionary authority to address 

disproportionate human health or 

environmental effects with practical, 

appropriate, and legally permissible 

methods under Executive Order 12898 

(59 FR 7629, February 16, 1994). 

In addition, the SIP is not approved 

to apply on any Indian reservation land 

or in any other area where the EPA or 

an Indian tribe has demonstrated that a 

tribe has jurisdiction. In those areas of 

Indian country, the rule does not have 

tribal implications and will not impose 

substantial direct costs on tribal 

governments or preempt tribal law as 

specified by Executive Order 13175 (65 

FR 67249, November 9, 2000). 

List of Subjects in 40 CFR Part 52 

Environmental protection, Air 

pollution control, Incorporation by 

reference, Intergovernmental relations, 

Particulate matter, Reporting and 

recordkeeping requirements. 

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

Dated: December 4, 2018. 

Deborah Jordan, 

Acting Regional Administrator, Region IX. 

[FR Doc. 2018–27257 Filed 12–17–18; 8:45 am] 

BILLING CODE 6560–50–P 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 52 

[EPA–R09–OAR–2018–0787; FRL–9988–18– 

Region 9] 

Air Plan Approval; California; Antelope 

Valley Air Quality Management District; 

Optional General SIP Category 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing to approve a 

revision to the Antelope Valley Air 

Quality Management District 

(AVAQMD) portion of the California 

State Implementation Plan (SIP). This 

revision concerns emissions of volatile 

organic compounds (VOCs) from 

organic liquid loading. We are 

proposing to approve revisions to a local 

rule to regulate these emission sources 

under the Clean Air Act (CAA or the 

Act). We are taking comments on this 


amozie on DSK3GDR082PROD with PROPOSALS1