(REF: OZPMRH-2-97)

MEMORANDUM

SUBJECT: Interim Implementation of New Source Review Requirements for PM2.5

FROM: John S. Seitz, Director

Office of Air Quality Planning & Standards (MD-10)

TO: See Addressees

This memorandum addresses the interim use of PM10 as a surrogate for PM2.5 in meeting

new source review (NSR) requirements under the Clean Air Act (Act), including the permit

programs for prevention of significant deterioration of air quality (PSD). The revised national

ambient air quality standards (NAAQS) for particulate matter, which include the revised NAAQS

for PM10 and new NAAQS for PM2.5, became effective on September 16, 1997. In view of the

significant technical difficulties that now exist with respect to PM monitoring, emissions 2.5

estimation, and modeling (described below), EPA believes that PM10 may properly be used as a

surrogate for PM in meeting NSR requirements until these difficulties are resolved. The EPA’s 2.5

views on implementing the ozone and PM10 NAAQS during the interim period following the

effective date of the new 8-hour ozone and revised PM10 NAAQS will be set forth in a separate

EPA memorandum.

Section 165(a)(1) of the Act provides that no new or modified major source may be

constructed without a PSD permit. Moreover, section 165(a)(3) provides that the emissions from

any such source may not cause or contribute to a violation of any NAAQS. Also, section

165(a)(4) requires best available control technology for each pollutant subject to regulation under

the Act. The EPA’s recent promulgation of the primary and secondary standards for PM marks 2.5

the first time that EPA has specifically regulated fine particles--less than 2.5 microns in diameter--

as a discrete indicator for particulate matter. Hence, this memorandum addresses how to

implement PSD for PM in light of significant technical difficulties which presently exist. 2.5

Of specific concern is the lack of necessary tools to calculate emissions of PM2.5 and

related precursors and project ambient air quality impacts so that sources and permitting

authorities can adequately meet the NSR requirements for PM . Any comprehensive system for 2.5

regulating PM2.5 must take into account not only the fine particles emitted directly by stationary

sources but also the various precursors, emitted by certain sources, which result in secondarilyformed fine particles through chemical reactions in the atmosphere. Recent studies suggest that 
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secondary particulate matter may account for over half of total ambient PM nationwide. 2.5 

Emissions factors for the fine particles emitted directly by stationary sources, and for some

important precursors (e.g., ammonia), are largely unavailable at the present time.

The EPA is in the process of developing a comprehensive modeling system which will be

designed to include precursor emissions and account for secondary fine particle formation. The

modeling system will also incorporate a method for nesting small local impacts from individual

point sources within a greater modeling domain. Before this can be completed, it will be 

necessary to collect sufficient monitoring data to verify and validate protocol modeling results.

Ambient monitoring for PSD purposes must be collected from appropriately designed

monitors. Sufficient quantities of such monitors will not be available specifically for PSD

monitoring purposes in the near future. Initially, as these monitors become available, they will be

needed to establish the new monitoring stations for the national network of PM2.5 sites, including

the required core PM2.5 State and local air monitoring stations. A high priority has been placed on

the establishment of the necessary PM2.5 monitoring sites nationwide so that the information from

these sites can be analyzed and evaluated in order to establish plans and priorities for

implementing the PM NAAQS, including the promulgation of section 107 designations. 2.5

For the reasons stated above, EPA believes that it is administratively impracticable at this

time to require sources and State permitting authorities to attempt to implement PSD permitting

for PM2.5 . The EPA has projects underway that will address the current technical and

informational deficiencies, but it will take 3-5 years to complete these projects. Until these

deficiencies are corrected, EPA believes that sources should continue to meet PSD and NSR

program requirements for controlling PM emissions (and, in the case of PM nonattainment 10 10

areas, offsetting emissions) and for analyzing impacts on PM10 air quality. Meeting these

measures in the interim will serve as a surrogate approach for reducing PM2.5 emissions and

protecting air quality. 

This memorandum presents EPA’s views on the issues associated with implementation of

the new PM NAAQS under Federal, State and local NSR programs. The statements do not 2.5

bind State and local governments and the public as a matter of law. When the technical

difficulties are resolved, EPA will amend the PSD regulations under 40 CFR 51.166 and 52.21 to

establish a PM2.5 significant emissions rate, and EPA will also promulgate other appropriate

regulatory measures pertinent to PM2.5 and its precursors. Because the earliest date on which

PM2.5 nonattainment areas will be designated is in 2002, and nonattainment NSR does not apply

until after nonattainment designations are made, implementation of the nonattainment NSR

requirements under part D of title I of the Act need not be addressed at this time.

If you have any questions concerning this memorandum or wish to address any issues

raised herein, please contact Dan deRoeck at (919) 541-5593.
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Addressees:

Director, Office of Ecosystem Protection, Region I

Director, Division of Environmental Planning and Protection, Region II

Director, Air, Radiation, and Toxics Division, Region III

Director, Air, Pesticides, and Toxics Management Division, Region IV

Director, Air and Radiation Division, Region V

Director, Multimedia Planning and Permitting Division, Region VI

Director, Air, RCRA, and Toxics Division, Region VII

Assistant Regional Administrator, Office of Pollution

 Prevention, State and Tribal Assistance, Region VIII

Director, Air and Toxics Division, Region IX

Director, Office of Air Quality, Region X

cc: New Source Review Contacts

Greg Foote (2344)

Mark Kataoka (2344)

Lydia Wegman (MD-10)

 bcc: Karen Blanchard (MD-12)

Tom Curran (MD-12)

Dan deRoeck (MD-12)

Bill Hamilton (MD-15)

Sally Shaver (MD-15)

USEPA:OAQPS:ITPID:IIG:DDEROECK:PJSMITH:CBaines:NCMU:RM700:MD-12:10-21-97

FILENAME: A:\pmmemo.021

revised: 10/21/97