Technical Support Document 

for the

Bay Area Winter Emission Inventory 

for 

Primary PM2.5 & PM Precursors: Year 2010

Adopted by the Bay Area Air Quality Management District on November 7, 2012

Submitted to EPA on January 14, 2013 by the California Air Resources Board

December 20, 2013
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I. Introduction

The purpose of this document is to supplement the technical information provided in the direct 

final federal register notice approving the 2010 PM2.5 Emissions Inventory for the San Francisco Bay 

Area (Bay Area emissions inventory),1 adopted by the Bay Area Air Quality Management District 

(District or BAAQMD) on November 7, 2012, and submitted by the California Air Resources Board 

(CARB) on behalf of the District to EPA on January 14, 2013. Any questions pertaining to this technical 

support document (TSD) should be directed to Nancy Levin at 415-972-3848 or levin.nancy@epa.gov.

II. Procedural Requirements for Adoption and Submittal of SIP Revisions

Sections 110(a)(1) and 110(l) of the Act require states to provide reasonable notice and public 

hearing prior to adoption of SIP revisions. Section 110(k)(1)(B) requires EPA to determine whether a 

SIP submittal is complete within 60 days of receipt. Any plan that we have not affirmatively determined 

to be complete or incomplete will become complete six months after the day of submittal by operation 

of law. A finding of completeness does not approve the submittal as part of the SIP nor does it indicate 

that the submittal is approvable. It does start a 12-month clock for EPA to act on the SIP submittal. See 

CAA section 110(k)(2).

a. Reasonable notice and public hearing

CARB’s submittal to EPA documents the public review process followed by San Francisco Bay 

Area Air Quality Management District (BAAQMD) and CARB in adopting the Bay Area emissions 

inventory prior to submittal to EPA as a revision to the SIP. 

The documentation provides evidence that reasonable notice of a public hearing was provided to 

the public and that a public hearing was conducted prior to adoption.2 CARB’s submittal includes a 

copy of the notice to the public published on September 26, 2012, announcing a public hearing to be

held on November 7, 2012. The notice for the public hearing was published in the San Francisco 

Chronicle and the San Jose Mercury News, newspapers of general circulation, on September 26, 2012. 

The Bay Area Emissions Inventory was also made available for viewing on the District's website and at 

the District office on and after September 26, 2012. CARB’s submittal includes a memorandum dated 

October 25, 2012 from Jack P. Broadbent, Executive Director/Air Pollution Control Officer to the 

Chairperson and members of the Board of Directors recommending that at the upcoming public hearing 

the Board adopt the 2010 PM2.5 emissions inventory for transmittal to CARB. These materials document 

the public review process followed by BAAQMD in adopting the Bay Area Emissions Inventory prior to 

transmittal to CARB and provide evidence that reasonable notice of a public hearing was provided to the 

public and that a public hearing was conducted prior to adoption. 

 

1 CARB adopted the 2010 PM2.5 Emission Inventory for the Bay Area in 2012 and refers to the submittal as the “2012 PM2.5 Emission 

Inventory to the State Implementation Plan for the San Francisco Bay Area.” However, the actual inventory in the 2012 CARB submittal 

(Appendix D) is the “Bay Area Winter Emissions Inventory for Primary PM2.5 & PM Precursors: Year 2010.” For purposes of this action, 

any reference to the 2012 PM2.5 Emissions Inventory is equivalent to the Bay Area 2010 winter-time PM2.5 emission inventory. 2 BAAQMD Board of Directors Regular Meeting Approved Minutes, November 7, 2012 

http://www.baaqmd.gov/~/media/Files/Board%20of%20Directors/2012/brd_min_110712.ashx?la=en
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CARB’s submittal documents the adoption of the Bay Area Emissions Inventory by the 

BAAQMD Board of Directors. On November 7, 2012, the BAAQMD Board of Directors approved the 

Bay Area Emissions Inventory and directed BAAQMD staff to forward the inventory to CARB, the 

Governor of California’s designee for SIP matters.3

 CARB’s submittal documents the adoption of the 

Bay Area Emissions Inventory by the BAAQMD Board of Directors. 

The submittal also includes CARB’s public hearing notice,

4 transcript,5 and December 6, 2012 

Board resolution approving the Bay Area emissions inventory.6 On January 14, 2013, CARB submitted 

the Bay Area emissions inventory to EPA for approval as a revision to the California SIP.

Based on the documentation included in CARB’s submittal, we find that the submittal of the Bay 

Area emissions inventory, as a SIP revision, satisfies the procedural requirements of sections 110(l) of 

the Act for revising SIPs. 

b. Completeness review

A completeness review allows us to determine if the submittal includes all the necessary items and 

information we need to act on it. We make completeness determinations using criteria we have 

established in 40 CFR part 51, Appendix V. These criteria fall into two categories: administrative 

information and technical support information. The administrative information provides documentation 

that the State has followed basic administrative procedures during the SIP-adoption process and thus we 

have a legally-adopted SIP revision in front of us. The technical support information provides us the 

information we need to determine the impact of the proposed revision on attainment and maintenance of 

the air quality standards. We notify a state of our completeness determination by letter unless the 

submittal becomes complete by operation of law. The Bay Area Emissions Inventory became complete 

by operation of law on July 14, 2013.

III. Summary of SIP Revisions

The emission inventory for the San Francisco Bay Area nonattainment area submitted by CARB on 

January 14, 2013 provides a 2010 inventory in tons per day (tpd) winter-time emission estimates for 

PM2.5 and PM2.5 precursors (i.e., nitrogen oxides (NOx), volatile organic compounds (VOCs),7

ammonia (NH3) and sulfur dioxide (SO2)). The Bay Area Winter Emissions Inventory for Primary 

PM2.5 and PM Precursors: Year 2010 is attached. The federal register notice approving this inventory 

provides a summary of the inventory and the procedural and technical basis for approval. In addition to 

the information provided in the federal register notice, we provide information in the following sections 

IV and V.

 

3 BAAQMD Resolution No. 2012-11, November 7, 2012. 4 CARB Notice of Public Meeting to Consider Approval of the 2012 PM2.5 Emission Inventory Submittal to the State Implementation Plan 

fo the San Francisco Bay Area, November 13, 2012.

5 Meeting, State of California, Air Resource Board, South Coast Air Quality Management District Auditorium, Diamond Bar, California, 

December 6, 2012.

6 CARB Resolution 12-37, December 6, 2012. 7 BAAQMD uses the term Reactive Organic Gas (ROG) rather than VOC. EPA formerly defined the regulated organic compounds in 

outdoor air as ROG. However, EPA later changed that terminology to “VOC.” 
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IV. Clarification Regarding Calculation of PM2.5 Emissions from Paved Roads 

The 2010 emissions inventory for the San Francisco Bay Area nonattainment area submitted by 

CARB estimates PM2.5 emissions from paved roads to be approximately 3.5 tons per day. CARB 

estimated annual PM10 emissions using the January 2011 AP-42 paved road dust emission factor 

equation with California-specific silt loadings. Historical days of rain were used for the rainfall 

adjustment factor. CARB used California speciation profile #471 to calculate PM2.5 from PM10 (PM2.5 = 

0.15 * PM10). http://www.arb.ca.gov/ei/speciate/dnldoptvv10001.php#specprof. This differs from the 

25% particle size fraction for PM2.5/ PM10 given in the AP-42. Emissions estimates used 2008 

annualized VMT per average weekday from EMFAC-2011SG, apportioned to road category using 2008 

Caltrans HPMS travel fractions. 2008 base year emissions for the San Francisco Bay Area were 

projected to 2010 using centerline miles.8

EPA has reviewed CARB’s methodology for estimating PM2.5 emissions from paved roads and 

determined that the methodology used for calculating the 2008 base year is acceptable; however, use of 

centerline miles to project the 2010 inventory has not been approved by EPA. Because the paved road 

emissions estimate is not being used to create a motor vehicle emissions budget (MVEB) for the San 

Francisco Bay Area PM2.5 nonattainment area and because the difference in emissions between 2008 

and 2010 is expected to not be significant, EPA is not requiring at this time that CARB revise the PM2.5

emissions estimate for paved roads. If in the future a MVEB and a maintenance plan for the area are 

submitted to EPA, the paved road PM2.5 emissions estimate would need to be derived by a method 

approved by EPA.

V. Attachment

Bay Area Winter Emissions Inventory for Primary PM2.5 and PM Precursors: Year 2010, Attachment 1.

 

8 December 11 and 12, 2013 emails from Janet Spencer, CARB, to John Ungvarsky, EPA Region 9.
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