33 CFR 151.43: Control of NLS residue discharge and notification

Last reviewed: October 14, 2026

This section covers how NLS residue must be handled by oceangoing ships and what notice a ship must give a U.S. port or terminal. A ship that cannot discharge NLS residue into the sea under the cited 46 CFR sections must retain it or discharge it to a reception facility. It also sets notification content and a rule for U.S. ships in a special area.

Applies toMasters or persons in charge of oceangoing ships, and of U.S. ships in a special area; fixed or floating drilling rigs or other platforms operating under an NPDES permit are excepted from paragraph (a).

What it says

  1. The master or person in charge of an oceangoing ship that cannot discharge NLS residue into the sea under 46 CFR 153.1126 or 153.1128 must ensure the residue is retained on board or discharged to a reception facility, unless the ship is a drilling rig or other platform operating under an NPDES permit.

    33 CFR 151.43(a)“the master or person in charge of an oceangoing ship that cannot discharge NLS residue into the sea in accordance with 46 CFR 153.1126 or 153.1128 shall ensure that the NLS residue is—”

  2. If Category A, B, or C NLS cargo or NLS residue is to be transfered at a U.S. port or terminal, the master or person in charge of each oceangoing ship carrying it must notify the port or terminal at least 24 hours before entering.

    33 CFR 151.43(b)“the master or person in charge of each oceangoing ship carrying NLS cargo or NLS residue shall notify the port or terminal at least 24 hours before entering the port or terminal of—”

  3. The notice must give the name, category and volume of the NLS cargo to be unloaded.

    33 CFR 151.43(b)(2)“(2) The name, category and volume of NLS cargo to be unloaded;”

  4. For certain Category B or C high viscosity or solidifying NLS cargo listed in Table 1 of 46 CFR part 153 with the stated references, the notice must give the time of day the ship is estimated to be ready to discharge NLS residue to a reception facility.

    33 CFR 151.43(b)(3)“the time of day the ship is estimated to be ready to discharge NLS residue to a reception facility;”

  5. For any other Category B or C NLS cargo, the notice must say whether or not the ship meets the stripping requirements under 46 CFR 153.480, 153.481, or 153.482.

    33 CFR 151.43(b)(4)“whether or not the ship meets the stripping requirements under 46 CFR 153.480, 153.481, or 153.482;”

  6. The notice must give the name and amount of any cleaning agents to be used during the prewash required by 46 CFR 153.1120.

    33 CFR 151.43(b)(7)“The name and amount of any cleaning agents to be used during the prewash required by 46 CFR 153.1120.”

  7. The master or person in charge of a U.S. ship in a special area must operate the ship in accordance with 46 CFR 153.903.

    33 CFR 151.43(c)“The master or person in charge of a U.S. ship in a special area shall operate the ship in accordance with 46 CFR 153.903.”

Common questions

What must a ship do with NLS residue it cannot discharge into the sea?

The master or person in charge must ensure the residue is retained on board or discharged to a reception facility. This does not apply to drilling rigs or other platforms operating under an NPDES permit.

“(1) Retained on board; or”

How much advance notice must a ship give a port before transferring NLS cargo?

The master or person in charge must notify the port or terminal at least 24 hours before entering it.

“shall notify the port or terminal at least 24 hours before entering the port or terminal of—”

When must the COTP be notified about a Category A NLS prewash?

The note says 46 CFR 153.1101 requires notifying the COTP at least 24 hours before a prewash surveyor is needed.

“is required under 46 CFR 153.1101 to notify the COTP at least 24 hours before a prewash surveyor is needed.”

The text of 33 CFR 151.43

Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR

Control of discharge of NLS residues

(a) Unless the ship is a fixed or floating drilling rig or other platform operating under an National Pollution Discharge Elimination System (NPDES) permit, the master or person in charge of an oceangoing ship that cannot discharge NLS residue into the sea in accordance with 46 CFR 153.1126 or 153.1128 shall ensure that the NLS residue is—

(1) Retained on board; or

(2) Discharged to a reception facility.

(b) If Category A, B, or C NLS cargo or NLS residue is to be transfered at a port or terminal in the United States, the master or person in charge of each oceangoing ship carrying NLS cargo or NLS residue shall notify the port or terminal at least 24 hours before entering the port or terminal of—

(1) The name of the ship;

(2) The name, category and volume of NLS cargo to be unloaded;

(3) If the cargo is a Category B or C high viscosity NLS cargo or solidifying NLS cargo listed in Table 1 of 46 CFR part 153 with a reference to “§ 153.908(a)” or “§ 153.908(b)” in the “Special Requirements” column of that table, the time of day the ship is estimated to be ready to discharge NLS residue to a reception facility;

(4) If the cargo is any Category B or C NLS cargo not under paragraph (b)(3) of this section, whether or not the ship meets the stripping requirements under 46 CFR 153.480, 153.481, or 153.482;

(5) The name and the estimated volume of NLS in the NLS residue to be discharged;

(6) The total volume of NLS residue to be discharged; and

(7) The name and amount of any cleaning agents to be used during the prewash required by 46 CFR 153.1120.

(c) The master or person in charge of a U.S. ship in a special area shall operate the ship in accordance with 46 CFR 153.903.

Note: The master or person in charge of a ship carrying Category A NLS that is required to prewash tanks under the procedures in 46 CFR part 153.1120 is required under 46 CFR 153.1101 to notify the COTP at least 24 hours before a prewash surveyor is needed.

Sections it refers to

The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.