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Good planning and careful attention to the basic precautions of safe loading will prevent most spills or tank overflows from occurring. However, there will occasionally be errors or mechanical failures which cause cargo to escape onto the deck, into the pumproom, or into the sea. The size of the spill will be directly related to the inattention of the cargo watch. If the pumproom is not being carefully monitored, large areas of deck are left unobserved, or the cargo watch officer is absent from the CCR/deck for an extended period, then there is an excellent opportunity for a large spill.

3.31.1 Spill containment installations
Some spill containment preparations begin on the drawing board of the tanker designer, or must be added by conscientious owners if absent from the original design:
- Gutter bars of sufficient height must be provided along the main deck gunwale, separating the main deck from the aft deck and around the aft deck (in event of a spill while fuelling).
- The gutter bar openings and all deck scuppers must be designed so that they can be readily closed oil tight and the closure hardware or devices must be both easy to use and durable. Wooden plug or sliding plate and cement closures are not effective. Expanding rubber plugs are very effective, convenient and durable.

Portable air-powered pumps should be fully rigged before cargo operations begins. Lash the suction hose in position where spilled oil will accumulate. In case of a deck spill, open valve A, then valve B.

- Spill containment tanks can be provided in the original design of the ship, or added as a modification. They should be located at the aft main deck on each side and fitted with a sluice opening so that accumulations of oil can be drained into them by opening a single valve. This valve should be left open at all times while the ship is loading or discharging in fair weather. Transfer fittings and piping must be provided to permit pumping of any accumulations to the slop tank.
- Provide convenient connections for compressed air and deck slop line fittings for air operated pumps to be used to recover spilled oil from the deck.

3.31.2 Management initiatives
Many of the initiatives needed to prevent and control spills are a shipowner's or manager's responsibility. These include:
- Provide a program of training aids to properly prepare the crew to prevent spills or to deal with overflows and spills when they occur.
- Provide spill containment and recovery materials and equipment.
- Ensure that regular training in oil spill counter measures is regularly performed on board and records maintained (per OPA-90 requirements).
- Provide the ship with an effective oil spill contingency plan and ensure that agents, contractors and owner's local representatives regularly call on the ship to discuss their roles in spill response.
- Conduct annual drills of the plan.

3.31.3 Shipboard precautionary measures
On board the tanker, the materials, equipment and plans provided by the owner must be effectively used. Oil spill prevention measures to be taken on board include:
- Regular training exercises in spill counter measures including when/how to apply foam to spills, use of adsorbents and skimmers, rigging of recovery equipment, use of spill containment
tanks, and personnel health and safety considerations when dealing with spills.
- Verification/testing that all cargo deck drains are tightly closed before loading begins.
- Rigging oil recovery pumps at natural spill collection points on deck before loading begins.
- Maintaining spill containment tank sluice valves open while loading in fair weather and closed during periods of heavy rain.
- Instructing deck watch personnel in the proper method of decanting rain water accumulations from the deck.
- Regular inspections of the pumproom(s), all cargo deck areas and all compartments/spaces where oil cargo could possibly leak into during loading.
- Strict adherence to all precautions and procedures while topping off cargo tanks.

All tanker officers should remember that only 10-15% of spilled oil is ever recovered from the water. The best recovery technique is still prevention! The one precaution which will contribute most to prevention is strict adherence by all cargo watch personnel to the simple rule:

When in doubt ... shut down!

3.31.4 First actions in the event of a spill
Should the unhappy event of a spill occur, the cargo watch officer must have a checklist at hand directing his initial response until the master or chief officer arrive to assume command. The following are some essential initiatives. The order of execution is provisional, circumstances and the details of the vessel's contingency plan may dictate a preferred sequence or assign some of these actions to others who have been notified by the ship:
- Stop loading cargo; notify the terminal to shut down and the reason.
- Open an empty tank (if available) on the same system to reduce pressure on the tank/line which is leaking cargo.
- Sound the spill alarm on the ship, or announce it over the PA system. All open lights should be secured when this is heard.
- Instruct the engineering watch to secure accommodation and engine room intake fans as necessary.
- Direct the deck watch to open deck containment tanks (if not already open), or start spill recovery pumps.
- Warn any craft alongside, instructing them to secure all sources of ignition.
- Start or request the engine room to start the fire pump (this may be automatic on sounding of spill alarm).
- Implement the vessel's oil spill contingency plan, including notification of coast guard, owners oil spill response contractor, and others as required.
- If master or chief officer are not on board, initiate the necessary telephone calls to advise them of the situation.
- Advise the vessel's agent or owner's local representative; advising them to notify necessary officials and mobilise the clean up contractor (if required).
- Notify the port vessel traffic service or harbour master by VHF radio.
- Advise the master/chief officer of the grade of cargo spilled and the approximate quantity. The master's responsibilities normally include notification of owners, technical managers, P&I Club representatives.
- Maintain an accurate record of the events and times of response actions, but do not make any log entries until reviewed by the master.
- Ensure that crew members dealing with the spill have equipped themselves with the proper personal protective equipment.
- No dispersants or chemical 'herders' should be used without prior approval of local authorities.

Logbook entries and reports made following a spill incident must be absolutely factual and truthful. An officer who has been conducting his watch properly has little to fear from a spill inquiry and may be confident that the facts will support him. An officer who attempts to conceal some neglect will inevitably have his dishonesty discovered and will be in worse trouble. The more honest the disclosure of events and causes of a spill, the faster the event will be investigated and disappear into the archives and the quicker the participants can resume their normal activities.

3.31.5 Handling dangerous spills on board
Occasionally a cargo spill will be particularly dangerous because of the low flash point and high vapour pressure of the cargo. Such cargoes would include condensates, naphtha and gasolines. These spills are dangerous because of the fire danger created by their uncontrolled release of flammable vapour in confined spaces or on the open deck.
If these cargoes are spilled into the pumproom, a layer of fire fighting foam should be applied to the pumproom bilges before any other measures are taken. The foam will reduce the release of explosive vapour to the atmosphere, cut off oxygen needed or combustion, and permit cargo recovery measures to be taken in more safety.
Foam may also be applied to low flash products spilled on the main deck, but care must be taken to avoid using so much foam or water that the gasoline is washed over the containment.
In some cases where foam cannot be readily applied and the danger of ignition is great, it may be better to wash the spilled cargo overboard before it can ignite. Such a decision should be made only by the master after carefully considering the risk of fire against the certainty of a pollution citation.

3.31.6 Hull leaks
If cargo is seen entering the water through a hull leak, then in addition to the actions in section 3.31.4, the cargo watch officer should immediately take action to transfer cargo from the leaking tank. Cargo can be gravitated or pumped to another ship's tank. If there is no available space in the ship's cargo or slop tanks, then the cargo must be pumped ashore as quickly as possible. These actions must not be delayed by concerns for cargo quality or cargo contamination.

3.31.7 Master's actions
The master must be fully trained and have all necessary information, resources and authority to respond to an oil spill by doing the following:
- Evaluate and properly assess the spill.
- Make the necessary notifications. Use IMO Resolution 680(17) content format for notifications transmitted by telex or radio.
- Direct or cause all necessary actions to minimise, contain, or reduce the escape of oil.
- Activate the vessel and owners 'oil spill contingency plan'.
- Request necessary outside assistance (clean up contractor).
- Maintain detailed action and event logs, having in mind the information which will be required for spill reports.
- Follow up all actions previously ordered to ensure that they are being properly carried out.
- Cause samples to be taken and properly labelled and stored.
- Review media training received and prepare to appropriately respond to their questions.

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