Answer
The EPA divides these 27 incidental discharge streams into four operational categories.
1. Engine Room & Machinery Space Streams
These are the most critical for a Marine Engineer, as they directly impact the machinery under your watch.
1. Bilgewater: Discharges from the oily water separator (OWS). Must be less than 15 ppm and free of any visible sheen.
2. Gas Turbine Washwater: Wastewater generated during the chemical or water washing of gas turbine compressors and turbines.
3. Distillation and Reverse Osmosis (RO) Reject Water: The highly concentrated brine/saltwater byproduct discharged back into the sea from fresh water generators.
4. Exhaust Gas Scrubber (EGCS) Washwater: Wastewater from open or closed-loop exhaust gas cleaning systems containing sulfur oxides, heavy metals, and PAHs.
5. Boiler/Economizer Blowdown: Highly alkaline, hot water discharged from boilers to control chemical concentration and remove sludge.
6. Cathodic Protection: Sacrificial anodes or Impressed Current Cathodic Protection (ICCP) systems that release zinc, aluminum, or electrical currents into the water to prevent hull corrosion.
2. Deck & Cargo Hull Operations
These streams generally fall under deck department management but require engineering support for valves, piping, and pollution prevention systems.
7. Deck Runoff: Rainwater, condensation, or washwater running off the vessel's exposed decks, which may carry grease, dirt, or debris.
8. Ballast Water: Water taken on to manage ship stability and trim. This has the strictest sampling and treatment requirements under VGP and VIDA.
9. Anti-fouling Hull Coatings: Toxin leaching or chemical physical breakdown from the paint applied to the underwater hull to prevent marine growth.
10. Aqueous Film-Forming Foam (AFFF): Runoff or discharges from fire-fighting foam systems during mandatory safety testing or drills.
11. Chain Locker Effluent: Water, mud, and debris accumulated in the chain locker when the anchor chain is hauled in.
12. Controllable Pitch Propeller (CPP) and Thruster Hydraulic Fluids: Any incidental leakage at the oil-to-sea interface from hydraulic steering, thrusters, or propulsion units.
13. Rudder Bearing Lubrication Discharge: Lubricants or greases leaking from the rudder stock housing into the sea.
14. Stern Tube Seals: Oil or lubricants leaking past the stern seals into the water (requires EALs if not a air/void seal system).
15. Underwater Ship Husbandry: Debris, biological growth, or cleaning agents washed off the ship during underwater hull cleaning or propeller polishing.
16. Welldeck Discharges: Water accumulations from specialized commercial transport vessels that flood their lower decks to launch smaller craft.
17. Sonar Dome Fluids: Liquids or discharges from inside the structural housing surrounding a ship's underwater sonar equipment.
3. Hotel & Accommodation Services (Domestic Waste)
These streams are generated by the daily living activities of the crew and passengers onboard.
18. Graywater: Wastewater from cabin showers, sinks, and galley dishwashers. (Note: Blackwater/Sewage is regulated by USCG/MARPOL Annex IV, not the EPA VGP).
19. Graywater Tank Residues: Sludge or concentrated solids left behind when cleaning out graywater holding tanks.
20. Pool and Spa Discharges: Chlorinated or chemically treated water discharged from onboard recreational pools or hot tubs.
21. Refrigeration and Air Conditioning Condensate: Fresh water dripping from galley reefer units or accommodation AC air handlers.
4. Specialized & Vessel-Specific Discharges
These streams apply only to specific industrial ship types, such as oil tankers, fishing vessels, or research ships.
22. Fish Hold Effluent: Wastewater and organic residue drained from cargo spaces used to store fresh or iced fish on commercial fishing boats.
23. Firemain System: Discharges from fire pumps during system testing, cooling, or anchor washdown procedures.
24. Elevator Pit Effluent: Water and oily lubricants collected in the drainage sump at the bottom of a ship's interior cargo or passenger elevator shaft.
25. Motor Vehicle Washwater: Runoff from washing down vehicles transported inside Ro-Ro (Roll-on/Roll-off) car carriers or ferries.
26. Oil-to-Sea Interfaces: A general category covering any other mechanical joint where oil touches seawater (e.g., stabilizer fins, wire ropes).
27. Seawater Cooling Overboard: The thermal discharge of clean seawater used in centralized main engine heat exchangers, condensers, and oil coolers.