# Approval and Promulgation of Air Quality Implementation Plans; Pennsylvania; 1990 NOINFX/INF Base Year Emission Inventory for the Philadelphia Ozone Nonattainment Area
> **Rule** · Direct final rule. · Published 1999-06-17 · Effective 1999-08-16 · 64 FR 32422
## Document
- **Document number:** 99-15267
- **Category:** air-emissions
- **Federal Register citation:** 64 FR 32422
- **CFR reference:** 40 CFR 52
- **Publication date:** 1999-06-17
- **Effective date:** 1999-08-16
- **State:** PA
- **EPA docket:** PA121-4088a
## Abstract

EPA is approving a State Implementation Plan (SIP) revision request that the Commonwealth of Pennsylvania submitted on July 31, 1998 for the Philadelphia severe ozone nonattainment area. The Commonwealth submitted this SIP revision in response to the Clean Air Act, which requires all ozone nonattainment areas to submit a comprehensive inventory of oxides of nitrogen (NO<INF>X</INF>) emissions, from all sources, for the calendar year 1990. This emission inventory is known as the 1990 base year inventory. This SIP revision applies to the Pennsylvania portion of the Philadelphia ozone nonattainment area, which consists of Bucks, Chester, Delaware, Montgomery, and Philadelphia Counties. EPA is approving the 1990 NO<INF>X</INF> base year inventory as a revision to Pennsylvania's SIP in accordance with the requirements of the Clean Air Act.

## Source
- [Federal Register document](https://www.federalregister.gov/documents/1999/06/17/99-15267/approval-and-promulgation-of-air-quality-implementation-plans-pennsylvania-1990-noinfxinf-base-year)
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