October 23, 1997

MEMORANDUM

SUBJECT: Interim Implementation of Ne w 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 us e of PM10 as a surrogate for PM2.5 in meeting new source review (NSR) requirement s under the Clean Air Act (Act), including the permit programs for prevention of significan t deterioration of air quality (PSD). The revised national ambient air quality standa rds (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 te chnical difficulties that now exist with respect to PM2.5 monitoring, emissions estimation, and modeling (described below), EPA believes that PM10 may properly be used as a surrogate for PM2.5 in meeting NSR requirements until these difficulties are reso lved. The EPA's views on implementing the ozone and PM10 NAAQS during the interim pe riod following the effective date of the new 8-hour ozone and revise d 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. More over, section 165(a)(3) provides that the emissions from any such source may not cau se 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 Ac t. The EPA's recent promulgation of the primary and secondary standards for PM2.5 mark s 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 PM2.5 in light of significant technical di fficulties which presently exist.

Of specific concern is the lack of necessa ry tools to calculate emissions of PM2.5 and related precursors and project ambient air quality impacts so that sources and permitting authorities can ad equately meet the NSR requirements for PM2.5. Any comprehensive system for regulating PM2.5 must take into account not only the fine particles emitted directly by stationary sour ces but also the various precursors, emitted by certain sources, which result in secondarily -formed fine particles through chemical reactions in the atmosphere. Recent studies s uggest that secondary particulate matter may account for over half of total ambient PM2.5 na tionwide. Emissions factors for the fine particles emitted directly by st ationary 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 emissi ons 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 th e 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 th e information from these sites can be analyzed and evaluated in order to establ ish plans and priorities for implementing the PM2.5 NAAQS, including the promulga tion of section 107 designations.

For the reasons stated above, EPA belie ves that it is administratively impracticable at this time to require sour ces and State permitting authorities to attempt to implement PSD permitting for PM2.5. Th e EPA has projects underway that will

address the current technical and informationa l deficiencies, but it wi ll take 3-5 years to complete these projects. Until these defici encies are corrected, EPA believes that

sources should continue to meet PSD a nd NSR program requirements for controlling PM10 emissions (and, in the case of PM10 nonattainment areas, offsetting emissions) and for analyzing impacts on PM10 air qualit y. 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 PM2.5 NAAQS under Federal, State and local NSR programs. The statements do not bind Stat e 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 es tablish a PM2.5 significant emissions rate, and EPA will also promulgate other appr opriate 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 nonatta inment NSR does not apply until afternonattainment designations are made, im plementation 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 cont act Dan deRoeck at (919) 541-5593.

Addressees: Director, Office of Ecosystem Protection, Region I Director, Division of Environmental Planning and Protection, Region II Director, Air, Radiation, a nd Toxics Division, Region III Director, Air, Pesticides, and Toxics Management Divi sion, Region IV Director, Air and Radiat ion Division, Region V Director, Multimedia Planning a nd 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)