33 C.F.R. § 157.43 – Discharges of clean and segregated ballast: Seagoing tank vessels of 150 gross tons or more.

(a) Clean ballast may not be discharged overboard unless the discharge is verified as clean ballast through use of an approved oil discharge monitoring and control system or, if discharged before the required oil discharge monitoring and control system installation date, by visual examination of the ballast contents immediately before discharge. This paragraph applies to discharges of clean ballast:
1. (1) From dedicated clean ballast tanks; and
2. (2) Into the navigable waters of the United States from any other tank.
(b) Segregated ballast may not be discharged overboard unless a visual examination, or a test of the ballast contents with an oil/water interface detector, immediately before the discharge shows that there is no oily mixture in the ballast. Use of an oil discharge monitoring and control system is not required. This paragraph applies to discharges of segregated ballast:
1. (1) Into the navigable waters of the United States; and
2. (2) Below the waterline at sea from an existing vessel that does not have an above the waterline discharge point for segregated ballast.
(c) All discharges of clean ballast and segregated ballast must be through an above waterline discharge point described in § 157.11(b)(2), except that:
1. (1) A vessel may discharge clean ballast and segregated ballast below the waterline when in port or at an offshore terminal.
2. (2) A vessel may discharge clean ballast and segregated ballast at sea by gravity below the waterline.
3. (3) An existing vessel that does not have above waterline discharge points for dedicated clean ballast tanks may discharge clean ballast from those tanks below the waterline at sea.
4. (4) An existing vessel that does not have above waterline discharge points for segregated ballast tanks may discharge segregated ballast below the waterline at sea.
(d) This section applies only to seagoing tank vessels of 150 gross tons or more.

[CGD 76-088b, 48 FR 45721, Oct. 6, 1983; 48 FR 46985, Oct. 17, 1983; USCG-2000-7641, 66 FR 55573, Nov. 2, 2001; USCG-2004-18939, 74 FR 3382, Jan. 16, 2009]