40 CFR 139.11: Bilges.

(a) The requirements in paragraphs (b) through (d) of this section applies to bilgewater, which is the discharge of wastewater from the bilge consisting of water and residue that accumulates in a lower compartment of the vessel's hull below the waterline. This includes, but is not limited to, any water and residue from a cargo area that comes into contact with oily materials or a below-deck parking area or other storage area for motor vehicles or other motorized equipment.

(b) The discharge of bilgewater from any vessel must not contain any flocculants or other additives except when used with an oily water separator or to maintain or clean equipment. The use of any additives to remove the appearance of a visible sheen is prohibited.

(c) For any vessel of 400 GT and above, the discharge of bilgewater must:

(1) Occur when the vessel is underway;

(2) Not have an oil content that exceeds 15 ppm; and

(3) If technologically feasible, occur at least 1 NM from shore.

(d) Additional standards applicable to discharges from bilges when a vessel is operating in federally-protected waters are contained in § 139.40(c).