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October 28, 1988 Review of De Minimis Emissions - Sanctions 4.39 4.42
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4.39 ---------- | SEE ALSO | | 4.42 | ---------- October 28,1988 MEMORANDUM SUBJECT: Review of De Minimis Emissions - Sanctions
FROM: Ronald Shafer, Chief
TO: Ron Van Mersbergen The purpose of this memorandum is to comment on your draft reply to the State of Illinois explaining SSCD's January 5, 1983 applicability determination. The 1983 memorandum addressed the question of whether nonsignificant (de minimis) net emission increases that accumulate over time will trigger PSD reviews when the total net emissions exceed significance levels. The 1983 memorandum stated that even though the preamble to the PSD regulations addressed the question of accumulation of emissions, the PSD regulations themselves did not. SSCD decided that those changes which occur over time (within a contemporaneous time frame, that is, five years) and whose emissions when reviewed as distinct entities are not signifi- cant, should not be combined and would not trigger PSD review (PSD permit issuance and imposition of BACT controls) when significance levels are reached. This was a policy decision based on concerns about the reasonableness of requiring permit- ting and imposition of controls for the most recent small increase in emissions. These policy considerations apply only to the permitting requirements for PSD and NSR and do not apply to the rules governing sanctions (40 CFR 52.24).
It is very important to note that the 1983 memorandum affirmed that even though individual de minimis increases do not accumulate to trigger a PSD review, they do consume PSD increment and ambient air quality must be protected. Likewise, in nonattainment areas, de minimis net emission increases must be aggregated and considered in evaluating air quality impacts so the NAAQS will be attained. Under the nonattainment rules, aggregated de minimis emissions will trigger sanctions when significance levels are reached. Emissions are aggregated as follows: any emissions increase as a result of a physical change or change in the method of operation must be evaluated to see if the cumulative net emissions increase over the past five years is significant. We are now reconsidering the January 5, 1983 applicability determination and intend to write to you later about this. If you have any comments or further questions, please call me or Myra Cypser on my staff (382-2872).
cc: Judy Katz, OECM |