40 CFR 1700.31: Seawater cooling overboard discharge.

(a) For discharges from vessels that are less than 79 feet in length:

(1) To the greatest extent practicable, minimize non-contact engine cooling water, hydraulic system cooling water, refrigeration cooling water and other seawater cooling overboard discharges when the vessel is in port.

(2) To reduce the production and discharge of seawater cooling overboard discharge, the vessel should use shore based power when in port if:

(i) Shore power is readily available for the vessel from utilities or port authorities; and

(ii) Shore based power supply systems are capable of providing all needed electricity required for vessel operations; and

(iii) The vessel is equipped to connect to shore-based power and such systems are compatible with the available shore power.

(3) Fouling organisms must be removed from seawater piping on a regular basis. The discharge of fouling organisms removed during cleanings is prohibited.

(b) For discharges from vessels that are greater than or equal to 79 feet in length:

(1) To the greatest extent practicable, minimize non-contact engine cooling water, hydraulic system cooling water, refrigeration cooling water and other seawater cooling overboard discharges when the vessel is in port.

(2) To reduce the production and discharge of seawater cooling overboard discharge, the vessel should use shore based power when in port if:

(i) Shore power is readily available for the vessel from utilities or port authorities; and

(ii) Shore based power supply systems are capable of providing all needed electricity required for vessel operations; and

(iii) The vessel is equipped to connect to shore-based power and such systems are compatible with the available shore power.

(3) Maintenance of all piping and seawater cooling systems must meet the requirements of § 1700.32 (Seawater Piping Biofouling Prevention). For all vessels, except submarines, fouling organisms removed during maintenance must not be discharged.