"Existing Part 70 hazardous air pollutant (HAP) source" means a Part 70 HAP source, for which construction or reconstruction is commenced before the proposal of a HAP emission limitation by EPA, or if no proposal was published by EPA for a Part 70 HAP source, then on or before the date 18 months after the scheduled date for promulgation by EPA.
06- 096 C.M.R. ch. 100, § 51