Module 17 - Marine Environment
Oil and Fuel Pollution
What you will learn
Prevent routine oil and fuel releases and carry out a stop-contain-report response without using detergent or dilution to disguise pollution.
Oil control starts with a clean, inspected machinery space and a fuel transfer that can be stopped before a drip becomes a spill.
MCA guidance says oil should be retained aboard for disposal to shore reception facilities. A pleasure vessel below 400GT is not required to install approved oily-water separating equipment, so the practical small-yacht default is not to pump oily bilge water overboard. Find and stop the leak, recover free oil with suitable absorbent material or equipment, and follow the marina or waste facility's disposal route.
Prevention includes a clean bilge that makes new contamination visible, an inspected drip tray beneath the engine, sound hoses and joints, an accessible spill kit and a crew member who knows how to stop the transfer. Before refuelling, confirm the correct filler and expected quantity, control ignition sources, keep vulnerable openings protected and attend the nozzle. Slow the delivery before the expected full level; fuel appearing at a vent is evidence of overfill, not a normal stopping method.
If fuel escapes, stop the transfer and close the source if that can be done safely. Raise the alarm, protect drains and water, use the facility's absorbent pads or booms, and contact the fuel berth or harbour authority as required. Detergent, hosing, propeller wash or dilution spreads or hides the pollutant instead of recovering it.
Worked example
During refuelling, diesel appears around the deck filler and starts moving towards a cockpit drain.
- 1Stop the nozzle or delivery pump immediately and close the source if it is safe to do so.
- 2Warn the crew and fuel berth, maintain ignition control and block the route to the drain or water.
- 3Use oil-selective absorbent material or the facility's response equipment; do not add detergent or wash the deck down.
- 4Report the release through the berth or harbour procedure and arrange lawful disposal of contaminated absorbents.
Sense check: The response should leave the fuel stopped and physically recovered or contained—not merely made less visible.
Prepare the transfer before opening the filler
The tank gauge is unreliable and an unfamiliar crew member will hold the nozzle while the skipper monitors the deck.
1. Estimate
Use tank capacity, recent engine use and a conservative fill quantity instead of guessing from the gauge alone.
2. Protect
Position absorbent material, control ignition sources and identify openings or drains that a spill could reach.
3. Communicate
Agree the stop signal and make sure the nozzle operator can stop delivery without waiting for another person.
4. Monitor
Attend the transfer continuously and slow well before the expected full level.
Sense check: If nobody can state who stops the flow or where the spill kit is, the yacht is not ready to refuel.
Common mistake or limitation
- A sheen made invisible by detergent or dilution is still pollution; the task is to stop and recover the contaminant.
- Absorbent pads manage escaped oil but do not replace finding and repairing the leak that contaminated the bilge.
- The unsupported claim that one litre of oil always contaminates one million litres of water is not needed to justify prevention and must not be taught as a universal fact.
Recap
- A small yacht's robust default is to retain oily waste and dispose of it ashore.
- Good preparation makes an overfill less likely and lets one person stop the transfer immediately.
- A spill response stops the source, protects drains and water, contains the fuel and follows the local reporting plan.
Optional quick check
Section 2 of 10
Diesel starts running towards a deck drain during refuelling. What should happen first?
Sources and factual review
Reviewed 20 August 2026 - Compass Revision editorial review.
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