BOARD MEETING DATE: October 6, 2006
AGENDA NO. 36

Adopt the Staff Recommended Methodology for Calculating PM2.5 and PM2.5 Regional and Localized Significance Thresholds to Determine PM2.5 Significance in CEQA and NEPA Documents

SYNOPSIS: 

In response to adoption of PM2.5 ambient air quality standards by U.S. EPA and CARB, AQMD staff has developed a methodology for calculating PM2.5 emissions when preparing air quality analyses for CEQA or NEPA documents.  Further, to determine if PM2.5 air quality impacts are significant, staff has also developed recommended regional and localized significance thresholds.  During the development of the PM2.5 thresholds, AQMD staff met with a stakeholder working group and held a public workshop to solicit public input.

COMMITTEE:

Mobile Source, July 28, 2006

RECOMMENDED ACTION:

Adopt the attached resolution adopting the Methodology to Calculate Particulate Matter (PM) 2.5 and PM2.5 Significance Thresholds, which includes directly emitted PM2.5 Fraction Tables and Localized Significance Threshold Look-up Tables, and to incorporate these as part of the revised CEQA Air Quality Handbook.

Barry R. Wallerstein, D.Env.
Executive Officer

Background

In the last few years, both California and the federal government have established ambient air quality standards for fine particulate matter (PM) less than or equal to 2.5 microns in diameter (PM2.5).  As a result, AQMD staff has developed a methodology for calculating directly emitted PM2.5 and proposed localized and regional PM2.5 significance thresholds for the purpose of analyzing local and regional PM2.5 air quality impacts in California Environmental Quality Act (CEQA) and National Environmental Policy Act (NEPA) air quality analyses.

Proposal

          Calculation Method

Because there are currently few or no PM2.5 emission factors for mechanical or combustion processes, staff is recommending an indirect approach to calculating PM2.5 emissions until such time as PM2.5 factors are developed.  Total suspended PM (TSP) emissions typically contain specific fractions of PM10 and PM2.5 that can be measured.  Since PM2.5 is a subset of PM10, the current methodology for calculating PM10 from fugitive dust sources (grading, demolition, unpaved roads, open storage piles, etc.) and combustion sources (stationary combustion sources, vehicle exhaust, etc.) will continue to be used and would then be multiplied by the applicable PM2.5 fraction, derived by emissions source category fraction, using PM profiles developed by the California Air Resources Board (CARB).  The CARB PM fraction profiles are used to develop emission inventories for a variety of sources and operations in the Air Quality Management Plan (AQMP).  The California Emission Inventory Data and Reporting System (CEIDARS) PM profiles have been streamlined to be used for most types of processes that would be encountered in a CEQA or NEPA analysis.  The streamlined CARB PM fraction profiles can be found in Appendix A of Attachment D. 

Significance Thresholds

         Localized Significance Thresholds

In addition to the PM2.5 calculation methodology, staff is also proposing localized and regional significance thresholds for both construction and operation of proposed projects.  Localized significance thresholds (LSTs) were developed in response to the SCAQMD Governing Board’s environmental justice (EJ) initiatives (EJ initiative I-4) in recognition of the fact that criteria pollutants, carbon monoxide (CO), oxides of nitrogen (NOx), and PM10 in particular, can have local air quality impacts as well as regional impacts to receptors. 

To establish operational PM2.5 LSTs, staff reviewed the AQMP combustion inventories, which indicates that PM2.5 comprises 99 percent of the combustion PM10 emissions.  Since combustion PM10 and PM2.5 fractions are essentially equivalent, staff is recommending that the operational localized significance threshold for PM2.5 be the same as the current operational localized significance threshold for PM10, i.e., 2.5 micrograms per cubic meter (μ g/m³).

Similarly, to develop a PM2.5 construction significance threshold for localized impacts, staff considered the PM2.5 contribution from fugitive sources and the PM2.5 contribution from combustion sources (construction equipment).  Modeling conducted as part of this effort showed that the contribution of off-road combustion PM2.5 emissions can be three to four times higher than the contribution of PM2.5 from fugitive sources.  Based on the modeling results, staff is recommending a PM2.5 construction LST of 10.4 μ g/m3, the same as the construction LST for PM10.  As part of the current staff proposal staff has created PM2.5 look-up tables for both operation and construction (see Appendix B of Attachment D). 

           Regional Significance Thresholds

PM emissions also affect air quality on a regional basis.  When fugitive dust enters the atmosphere, the larger particles of dust typically fall quickly to the ground, but smaller particles less than 10 microns in diameter may remain suspended for longer periods, giving the particles time to travel across a regional area and affecting receptors at some distance from the original emissions source.  Fine PM2.5 particles have even longer atmospheric residency times.  Staff is recommending a PM2.5 regional significance threshold based on the following EPA proposal.

On September 8, 2005, EPA published in the Federal Register “Proposed Rule to Implement the Fine Particle National Ambient Air Quality Standards,” which proposed a significant emission rate for PM2.5 of 10 tons per year.  Staff is proposing to use EPA’s significant emission rate for PM2.5 to develop the daily mass emission regional significance threshold for PM2.5.  Converting the annual rate, 10 tons, into a daily rate produces a daily emission rate, or in this case a regional significance threshold, of approximately 55 pounds per day.  A similar approach was used to derive the operational regional significance thresholds for NO2 and VOC.  Similar to the regional significance threshold for PM10 of 150 pounds per day, the proposed PM2.5 regional significance threshold of 55 pounds per day would apply to both construction and operation.

Summary of Proposed PM2.5 Significance Thresholds

            Implementation

Once the Governing Board approves the staff PM2.5 proposals, staff would implement the proposals according to the following timetable:

• Conduct further public outreach after Board adoption;
• Implement the proposals for AQMD lead agency projects for any new projects received after board adoption;
• As part of AQMD intergovernmental review (IGR) commenting responsibilities, begin submitting comments relative to the PM2.5 proposal on CEQA documents beginning January 2007.
• Revise Air Quality Handbook to incorporate the new methodology and significance thresholds.

Public Outreach

Staff conducted a Public Workshop on the staff proposals August 9, 2006, to solicit public comment on the staff proposals.  In addition to the Public Workshop, AQMD staff held three stakeholder working group meetings to seek guidance from stakeholders on the staff proposals.

Legal Authority

CEQA Guidelines §15022(a) states that a public agency shall adopt objectives, criteria, and specific procedures consistent with CEQA and these [State] Guidelines for administering its responsibilities under CEQA.  CEQA Guidelines 15022(d) states further, “In adopting procedures to implement CEQA, a public agency may adopt the State CEQA Guidelines through incorporation by reference.  The agency may then adopt only those specific procedures or provisions, described in subsection [15022] (a), which are necessary to tailor the general provisions of the guidelines to the specific operations of the agency.”  At the December 11, 1998 Public Hearing the AQMD Board formally incorporated by reference the State CEQA Guidelines as the implementing guidelines for the AQMD’s CEQA program.  Adopting PM2.5 significance thresholds would be consistent with CEQA Guidelines §15022 provision to tailor a public agency’s implementing guidelines by adopting criteria relative to the specific operations of the AQMD.

Specifically with regard to thresholds of significance, CEQA Guidelines §15064.7(a) states, " Each public agency is encouraged to develop and publish thresholds of significance that the agency uses in the determination of the significance of environmental effects.”  Subsection (b) of the same section states further, “Thresholds of significance to be adopted for general use as part of the lead agency’s environmental review process must be adopted by ordinance, resolution, rule or regulation, and developed through a public review process and be supported by substantial evidence.”  The methodology for developing LSTs and the resulting LSTs developed by the AQMD staff have undergone an extensive public review process as part of stakeholder working group meetings that were open to the public.  One public workshop meeting was also held.  The attached methodology document provides the substantial evidence relative to the methodology for calculating PM2.5 emissions and developing the PM2.5 significance thresholds.  The LST proposal is also being heard by the AQMD Board at a public meeting, where it will be considered for adoption by resolution, consistent with CEQA Guidelines §15064.7(b).  Upon Board adoption, AQMD staff will implement the PM2.5 calculation methodology and significance thresholds as discussed below

Key Issues

The following summarizes the key comments received during the development of the staff proposal.

•   Availability of PM2.5 Mitigation Measures

Stakeholders requested that AQMD staff compile a list of mitigation measures for reducing PM2.5 emissions and associated cost information.  At the second stakeholder working group meeting on July 11, 2006, AQMD staff provided handouts listing fugitive dust and off-road construction mitigation measures.  The lists showed applicable control efficiencies for the relevant pollutants.  At that time, staff indicated that the same control efficiencies applied to PM10 emissions should be applied to PM2.5 emissions unless otherwise listed.  Such information can currently be found in Chapter 11 of the AQMD’s CEQA Air Quality Handbook and staff will clarify in the revised Handbook that PM10 mitigation measures are applicable to PM2.5 as well.  In connection with an AQMD Governing Board directive, staff is currently compiling lists of goods management-related mitigation measures and for other  applications where emission control efficiencies are known, including: fugitive dust, on-road heavy-duty vehicles, off-road vehicles, etc.  Staff began uploading these lists of mitigation measures onto the AQMD’s CEQA webpages in September and will continue uploading lists as they are completed.  All mitigation measure lists will be updated periodically as new information becomes available.

•   Effects of the PM2.5 significance thresholds on preparation of CEQA documents

Stakeholders were concerned that with the introduction of PM2.5 significance thresholds, more CEQA documents would show significant impacts than would otherwise be the case.  In response, staff revisited the construction scenarios developed as part of the original LST proposal and, using the same construction characteristics, calculated PM2.5 emissions.  Staff demonstrated that all construction scenarios would not exceed the PM2.5 construction LST, except that the five-acre scenario required modifying equipment hours of operation from eight hours to seven hours.  Operators at most construction sites do not typically operate their equipment continuously more than seven hours per day anyway.  If they do, PM10 emissions may be of greater concern.  With regard to the PM2.5 regional significance threshold during construction, the construction scenarios show that PM2.5 emissions did not exceed the PM2.5 LST and were, in fact, substantially less than the regional significance threshold of 55 pounds per day.

With regard to operational emission impacts, for most projects, emissions are primarily generated by mobile sources.  PM2.5 emissions from mobile sources are generally relatively small compared to other pollutants such as NOx and CO.  As a result, it is not expected that the proposed PM2.5 significance thresholds will trigger significance to a greater extent than is currently the case. 

• Regional significance threshold for construction should be higher than operational  phase

After completion of the 2007 AQMP, which will include PM2.5 control strategies and monitoring the implementation of the proposed significance thresholds, staff may reevaluate the proposed significance thresholds and revise as necessary.

Resource Impacts

If approved by the Governing Board implementation of staff’s PM2.5 proposals will be phased in according to the timetable listed in the preceding section.  Existing AQMD resources will be used to implement this policy.

Attachments (EXE 136kb)

A.        LST Development Process
B.        Resolution
C.        Stakeholder Working Group Members
D.        Draft - Localized Significance Threshold Methodology Document

ATTACHMENT A

DEVELOPMENT OF PM2.5 CALCULATION METHODOLOGY AND PROPOSED PM2.5 LOCALIZED AND REGIONAL SIGNIFICANCE THRESHOLDS

ATTACHMENT B

RESOLUTION NO. 06-_____

                        A Resolution of the Governing Board of the South Coast Air Quality Management District (AQMD) approving the Staff Recommended Methodology for Calculating PM2.5 and PM2.5 Regional and Localized Significance Thresholds to Determine PM2.5 Significance in CEQA and NEPA Documents prepared by the AQMD and recommended for use by other public agencies.

                          WHEREAS, the U.S. EPA adopted National Ambient Air Quality Standards for PM2.5 in 1997 and CARB adopted California Ambient Air Quality Standards for PM2.5 in 2002; and

                          WHEREAS, since adoption of ambient air quality standards for PM2.5 by U.S. EPA and CARB, there has been a need to develop a methodology for calculating PM2.5 when preparing air quality analyses for National Environmental Policy Act (NEPA) or CEQA documents; and

                          WHEREAS, there is also a need for establishing PM2.5 significance thresholds to determine whether or not PM2.5 emissions from projects analyzed in NEPA or CEQA documents may contribute to significant adverse air quality impacts; and

                          WHEREAS, the PM2.5 calculation methodology and proposed localized and regional significance thresholds were originally developed in connection with a stakeholders’ working group; and

                        WHEREAS, the AQMD established and held three stakeholder working groups meetings in 2006 comprised of local government planners; representatives of local councils of government; environmental groups; the building and construction industries; and other interested individuals to solicit input on the localized significance thresholds; and

                        WHEREAS, pursuant to CEQA Guidelines §15064.7(b), the AQMD staff conducted a public workshop on August 9, 2006, to solicit additional public testimony on the PM2.5 calculation methodology and staff proposal for PM2.5 localized and regional significance thresholds; and

                        WHEREAS, the Methodology to Calculate Particulate Matter (PM) 2.5 and PM 2.5 Significance Thresholds document, which includes the PM2.5 calculation methodology, staff proposal for PM2.5 localized and regional significance thresholds, PM2.5 fractions of PM10, and PM2.5 localized significance threshold look-up tables for construction and operation, was released for public review in May 2006, and updated in September and October 2006 to incorporate stakeholder working group comments and revise the PM2.5 fraction inventories; and

                        WHEREAS, it is intended that the PM2.5 calculation methodology and staff proposal for PM2.5 localized and regional significance thresholds be use in connection with air quality analysis tools such as the URBEMIS2002 land use model; and

                        WHEREAS, AQMD staff has developed construction scenarios for small projects that include assumptions, equations, types of equipment, etc.; to further assist local public agencies with evaluating construction impacts; and

                        WHEREAS, AQMD staff has modified the construction scenarios for small projects to include PM2.5 emissions.

                        WHEREAS, it is the policy of the AQMD to reduce emissions from all possible sources that hinder the region’s ability to achieve the federal and state ambient air quality standards.  Use of the localized significance thresholds may serve to reduce emissions from future projects to the extent that additional mitigation measures are required and implemented.  This policy encourages local governments and other public agencies to consider localized air quality impacts in a CEQA or NEPA analysis.

                          NOW, THEREFORE BEIT RESOLVED that the AQMD Governing Board does hereby adopt the PM2.5 calculation methodology and staff proposals for PM2.5 localized significance thresholds of 10.4 micrograms per cubic meter (ug/m3) for construction and 2.5 ug/m3 for operation and regional significance threshold of 55 pounds per day for both construction and operation (Attachment D) pursuant to CEQA Guidelines §15064.7 (b).

                        BE IT FURTHER RESOLVED that the PM2.5 calculation methodology and staff proposal for PM2.5 localized and regional significance thresholds will be incorporated into the AQMD’s Handbook in December 2006.

                          BE IT FURTHER RESOLVED that the Governing Board hereby directs the Executive Officer to annually update the PM2.5 localized significance thresholds based upon the most current air quality monitoring data.

                        BE IT FURTHER RESOLVED that the AQMD staff will provide outreach on the use of the PM2.5 calculation methodology and staff proposal for PM2.5 localized and regional significance thresholds to other public agencies and stakeholders and provide a report, including implementation issues identified, to the Governing Board’s Mobile Source Committee one year after adoption.

DATE:  _________________      

___________________________________________________________________

                                                                        CLERK OF THE BOARDS

ATTACHMENT C

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