Maximum injection pressure. To meet the operating requirements of Sec. 144.28(f)(3)(i) of this chapter, the owner or operator shall use an injection pressure at the well head no greater than the pressure calculated using the following formula: Pm=(0.733-0.433 Sg)d where: Pm=injection pressure at the well head in pounds per square inchSg=specific gravity of injected fluid (unitless)d=injection depth in feet. [49 FR 45306, Nov. 15, 1984]