 such as control rooms, workshops, warehouses and admin blocks are remotely located, or protected by the natural topography of the side, or man made earthwork, or other means to divert pressure waves. Fire breaks should contain the fire to the module or area affected. Onshore plants handling hazardous substances can often be scattered over an area measurable in square miles. So given that the probability of loss of containment cannot be reduced to negligible levels, onshore plant design and layout restricts the potential consequences of such an event should it occur?
Shell accepts that the Prelude LNG facility would normally occupy an area 4 times greater than it does if on land. But taking the example of a modern day plant complying with UK standards and Codes of Practice, and the results of Social Impact studies etc, the facility at Mossmorran covers a substantial area (this Esso/Shell plant is of course more than a LNG plant but it is an excellent example of where space and topography is used not only to reduce risks at the plant, but to facilities and people outside the plant boundaries). The Shell section of the plant is 5 miles from its Braefoot Terminal jetty with the storage tanks containing chilled liquids circa ½ mile from the jetty. The reality is that an LNG plant on land could cover a considerable land area much greater than an area 4 times the size of the Prelude deck space.
These factors conspire together to increase the potential loss of life on Prelude especially when the total population required to operate, service and maintain this facility live, work and sleep within the plant boundaries, and, the plant is 300 miles from the nearest town
The LNG industry itself accepts this argument. Studies carried out have determined that the highest risk category for an LNG or LPG FPSO is the collective risk to onboard workers. Various media outlets suggest Prelude will have manning levels around 200. On land, an LNG plant has a dayshift and nightshift; staff go home at the end of their shift which reduces the population within the plant gates at any one time. Authorized access to process areas is needed for operators and maintenance crew. Non-operational personnel are located in occupied building which by location and design should not be at risk. Civil assets, police, ambulance and Fire Brigades are available to assist in a major crisis and carry out combined emergency exercises for that purpose.
Although Prelude will be the largest floating structure in the world, its dimensions at 488 by 75 by 105 m are minimal when compared to the many acres afforded to an onshore plant. The total population needed to run the show offshore remains constant. And at least initially Prelude will need to tackle the emergency on its own. If a major accident occurs, with serious injuries, burns etc, ambulances cannot arrive within 12 minutes or so at the gates of the Prelude plant. Given that search and rescue will commence from Broome, this town is 300 miles from Prelude. On a good day, outward and return journey time could be 5 hours with an additional ½ hour loading injured persons on board – plus refueling the aircraft prior to its return. If onward transition of seriously injured persons is necessary, on the assumption that Broome will have limited facilities, getting casualties to a hospital that can handle serious burns, and provide intensive care otherwise, involves another 2 and ½ hour flight to Perth.
How does the total number of persons offshore have such an influence on the quantification of risk?
This is simply because, as with all offshore installations, the total number of persons required to run the LNG plant, day and night, are present within the plant boundaries so the potential loss of life (PLL), should something go seriously wrong, takes that fact into account. There is no getting away from this; it’s just the way the arithmetic of risk works. PLL for Prelude will be quantified as the average risk to an individual on the facility multiplied by the total numbers on board.
Can due diligence by the Board of Royal 