Section 157.39 - Machinery space bilges(a) A tank vessel may discharge an oily mixture from a machinery space bilge that is combined with an oil cargo residue if the vessel discharges in compliance with § 157.37 .(b) A tank vessel may discharge an oily mixture from a machinery space bilge that is not combined with an oil cargo residue if the vessel:(1) Is proceeding en route;(2) Is discharging an effluent with an oil content of less than 15 parts per million; and(3) Has in operation an oil discharge monitoring and control system in compliance with § 157.12 and oil separating equipment in compliance with 33 CFR 155.380 .CGD 74-32, 40 FR 48283, Oct. 14, 1975, as amended by USCG-2000-7641, 66 FR 55573, Nov. 2, 2001; USCG-2004-18939, 74 FR 3382, Jan. 16, 2009