[Code of Federal Regulations] [Title 40, Volume 28] [Revised as of July 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 40CFR413.61] [Page 215] TITLE 40--PROTECTION OF ENVIRONMENT CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PART 413_ELECTROPLATING POINT SOURCE CATEGORY--Table of Contents Subpart F_Chemical Etching and Milling Subcategory Sec. 413.61 Specialized definitions. For the purpose of this subpart: (a) The term sq m (``sq. ft.'') shall mean the area exposed to process chemicals expressed in square meters (square feet). (b) The term operation shall mean any step in the chemical milling or etching processes in which metal is chemically or electrochemically removed from the work piece and which is followed by a rinse; this includes related metal cleaning operations which preceded chemical milling or etching, when each operation is followed by a rinse.