The Italian flag tanker Laura D’Amato berthed at the Shell Terminal Gore Bay
Sydney, at 1224 on 3 August 1999, with about 90,957 tonnes of Murban Crude Oil.
The loading arms were connected to the ship, the tank ullages measured and the
quantity of oil on board checked. The mate and the Shell shore officer conferred
and signed the ‘Ship/Shore Safety’ checklist. The checklist was also counter
signed by a Sydney Ports inspector.
At 1412, the ship commenced discharging using no. 2 cargo pump. Initially,
the water bottoms were removed at a slow rate of pumping. At 1430, all the cargo
tanks were opened to lower their levels and the discharge rate was increased
to 1000 m/h. At 1650, some cargo tanks were shut, the rate was further increased
to 1500 m/h, and the suction valves for the two slop tanks (six wings port
and starboard) opened.
By about 1815, the mate decided the level of the slop tanks was falling too
slowly. To draw more directly from these two tanks and to increase the rate
of discharge, the mate decided to open no. 3 cargo line to no. 2 pump by opening
two ‘crossover’ valves on the main sea line in the pumproom. At about 1820,
he ordered the cadet to open the two valves.
At 1825, the Shell wharf watchkeeper was returning from a routine check of
the loading arms and moorings, when he suddenly smelled a strong odour of hydrogen
sulphide. He immediately contacted the shore officer reporting the smell and
asking whether the ship was venting its tanks for any reason. It was established
that this was not the case.
The wharf watchkeeper went back to the shore manifold but detected no sign
of a leak. The smell of hydrogen sulphide was still strong and, as he checked
the water between the ship and the shore, he detected a slick of oil, which
he traced to the ship’s port side. He reported to the shore officer, who immediately
ordered the ship to stop pumping.
The ship’s pumps were stopped at 1836. The Shell emergency plan was implemented
immediately.
The mate, who had already ordered the cadet to close the two valves that he
had just opened, then ordered the 3rd mate to stop the cargo pump. He went ashore
to see if he could locate the source of the oil spill. The wharf watchkeeper
showed him the position on the port side, of the vessel, where oil was seen
to be welling to the surface of the water. The mate and the pumpman then went
to the pumproom and checked all the valves. They found the two sea-chest valves
on the sea suction line were fully open.
When the two men attempted to close the sea-chest valves, they found the large,
manual, butterfly valves ‘back-seated’ open. To close the valves, both men had
to use a large wheel key to break the seat. In closing the valves, any security
seals placed between the two adjacent valve handles were broken.
At this point, the flow of Murban crude oil from Laura D’Amato into Gore Bay
ceased.
Conclusions
These conclusions identify the different factors contributing to the incident
and should not be read as apportioning blame or liability to any particular
organisation or individual.
The factors which lead to the escape of crude oil cargo from Laura D’Amato
into Sydney Harbour include but are not limited to:
- The sea-chest valves on the sea suction line adjacent to the port sea chest
in the vessel’s cargo pumproom were open.
- The use of the sea suction line as a cargo pump suction crossover line led
to cargo filling the line and escaping through the open sea-chest valves overboard.
- The ship’s cargo system did not provide for a separate designated cargo
pump suction crossover line or some means of isolating the cargo system from
direct connection to the sea chest.
- The presence, at various times, of seals placed between the sea-chest valves
lead to a false assumption on the part of the ship’s staff that the sea-chest
valves must therefore be shut.
- The false assumption contributed to the fact that the ship’s staff did not
properly check the sea-chest valves, as required by the ISM Code procedure,
the ISGOTT Guide and normal tanker operations, before loading in Jebel Dhanna
and discharging in Sydney.
- There was no remote monitoring, on the cargo control console, of the positioning
of the two sea-chest valves.
- The vessel’s Safety Management System did not adequately detail the pressure
test procedures to be carried out on the sea-chest valves each time they were
to be checked for tightness.
- The independent cargo surveyor in Jebel Dhanna did not recognise that the
sea-chest valves were, in fact, open.
- The Ship/Shore Checklist procedures, in Jebel Dhanna and Sydney, did not
physically check and identify that the sea-chest valves were in a closed position.
- The probability is that the sea-chest valves were opened some time after
leaving Zhanjiang and before arriving at Jebel Dhanna. There was no operational
reason for opening these valves.
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