46 C.F.R. § 154.453
Failure to meet independent tank type C standards
If the Commandant (CG-ENG) determines during plan review, that a tank designed as an independent tank type C fails to meet the standards under § 154.450, § 154.451, and 154.452 and cannot be redesigned to meet those standards, the tank may be redesigned as an independent tank type A or B.