[Code of Federal Regulations] [Title 40, Volume 21] [Revised as of July 1, 2004] From the U.S. Government Printing Office via GPO Access [CITE: 40CFR147.303] [Page 742] TITLE 40--PROTECTION OF ENVIRONMENT CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) PART 147_STATE UNDERGROUND INJECTION CONTROL PROGRAMS--Table of Contents Subpart G_Colorado Sec. 147.303 Existing Class I, II (except enhanced recovery and hydrocarbon storage) and III wells authorized by rule. Maximum injection pressure. The owner or operator shall limit injection pressure to the lesser of: (a) A value which will not exceed the operating requirements of Sec. 144.28(f)(3) (i) or (ii) as applicable; or (b) A value for wellhead pressure calculated by using the following formula; Pm=(0.733-0.433 Sg)d where: Pm=injection pressure at the wellhead in pounds per square inch Sg=specific gravity of injected fluid (unitless) d=injection depth in feet.