33 CFR § 157.140 - Tank vessel inspections.
(a) Before issuing a letter under § 157.142, the Coast Guard makes an initial inspection of each U.S. tank vessel having a COW system under § 157.10(e), § 157.10(a)(2), or § 157.10c(b)(2) and each foreign tank vessel whose owner or operator submitted the plans under § 157.102 to determine whether or not, when entering a port, the cargo tanks that carry crude oil meet the following:
(1) After each tank is crude oil washed but not water rinsed, except the bottom of the tank may be flushed with water and stripped, each tank is essentially free of oil residues to a degree acceptable to the Coast Guard inspector.
(2) After the tanks that are to be used as ballast tanks when leaving the port are crude oil washed and stripped but not water rinsed or bottom flushed, they are filled with water and the total volume of crude oil floating on top of the water in these tanks is 0.085 percent or less of the total volume of these tanks.
(b) Except on a tank vessel under § 157.10(e), if the initial inspection under paragraph (a) of this section has been passed and the vessel arrives at the first cargo loading port after completing a ballast voyage, the Coast Guard monitors the discharge of effluent from those tanks that have been crude oil washed, water rinsed, stripped, and filled with ballast water to determine whether or not the oil content of the effluent is 15 ppm or less.