Brent Spar

Shell UK chose an innovative re-use proposal from the British/Norwegian consortium Wood-GMC as its preferred solution for the Brent Spar storage and loading buoy. The Spar's hull was used to build a quay extension at Mekjarvik near Stavanger in Norway. Shell submitted the proposal to the UK Government for approval.

In 1995, Shell U.K. Exploration and Production (Shell Expro) launched a programme called "Our Way Forward". It aimed to establish the optimum solution for the disposal of the Brent Spar and stressed public consultation. Many proposals were received and assessed. The investigation led Shell UK to conclude that Wood-GMC's re-use proposal was the Best Practicable Environmental Option (BPEO) for the decommissioning of the Brent Spar. The decision was based on detailed analyses of the Short List proposals both by Shell and the independent Norwegian foundation Det Norske Veritas (DNV), and took into account the views and values gathered during two years of Brent Spar Dialogue.

The Stavanger Port Authority was planning a quay extension at Mekjarvik with or without Brent Spar, to provide new Roll-On/Roll-Off ferry facilities from the summer of 1999. It was hoped that using slices of the Spar's hull would save both money and energy that would otherwise have been spent in new steel construction.

Wood-GMC planned to raise the Spar vertically in the water by building a lifting cradle, place it underneath the Spar and connect it by cables to jacks on board heavy barges. Jacking the cables upwards would raise the Spar so that its hull could be cut into 'rings' and slid onto a barge.

After careful cleaning, the rings would be placed in the sea beside the existing quay at Mekjarvik and filled with ballast. The construction of the quay extension was to be completed by placing a concrete slab across the rings. The Spar's topsides, its living and operations module, were to be removed and scrapped onshore at a Norwegian yard.

Shell worked with the BPEO definition established by the UK's Royal Commission on Environmental Pollution (see Notes below), and guidance notes published by the Environment Agency of England and Wales. The process involves first establishing the technically acceptable options, then from these selecting the best from an environmental point of view. The safety aspects are assessed next, then costs. The Shell evaluation was informed throughout by feedback from the Dialogue.

Technical: From the Short List, the top options on technical feasibility were the proposals from Wood-GMC, Brown and Root, and AMEC; and deep sea disposal.

Environment: The environmental analyses covered energy balance, emissions to air, resource consumption and waste disposal, containment, ecological effects, aesthetic impacts, local societal effects and contractors' environmental management systems.

In the Dialogue, there was widespread agreement that there would be no significant environmental impact from any of the proposals, including deep sea disposal. However, in comparing the small environmental differences, Dialogue participants suggested that two of the more important aspects were a positive energy balance, in which the solution saves more energy than it consumes; and the waste hierarchy, in which re use is preferred to recycling, and recycling preferred to disposal, with the aim of minimising waste.

All the options had a positive energy balance except deep sea disposal. Of the best four technical options, Wood-GMC's had the best energy balance and is highest in the waste hierarchy, with re-use at more than 80%. Its other environmental `positives' include the best all-round balance of emissions to air amongst the top four technical options. The Wood-GMC proposal was judged the all-round best on the environmental criteria. However, ultimately, figures show that the object of generating a positive energy balance from re-using the Spar ring-sections and recycling the topsides and transition column was not achieved.

Safety: Of the best four technical options, the work involved in AMEC's had higher safety risks. All the others had acceptable safety risks, comparable to those in normal offshore construction operations. Wood GMC and deep sea disposal had the lowest potential for loss of life and risks of major accidents.

Costs: The costs to be considered must represent the full cost to Shell Expro. These therefore not only included the contractor's bid price (previously published) but also charges such as insurance, inspection and monitoring of the work, costs of the Shell management team and a normal project contingency allowance.

Wood-GMC's published bid price (£21.5 million) rises to a £23-£26 million total cost. Brown and Root's bid price (£48 million) is by far the highest, and rises to a £49-£52 million total cost. The cost of deep sea disposal remains the lowest, but its total cost rises to significantly more than the basic £4.7 million price for towing from Norway and sinking. (Some £5 million of engineering, testing and cleaning was done in 1995.) The total project cost of deep sea disposal was a projected £17-20 million. (In the end the total cost of dismantling Brent Spar via the Wood-GMC plan amounted to far more than had been expected: £41 million.)

The innovative Wood-GMC re-use option emerged from the BPEO evaluation as technically sound, with the best all-round environmental benefits, a good safety profile, and an estimated cost of £23-£26 million. The `benchmark' option, deep sea disposal, emerged as technically sound, with fewer environmental benefits but no significant environmental impacts, a good safety profile and an estimated cost of £17-£20 million.

Shell concluded there was a high degree of equivalence between the Wood-GMC re-use option and the `benchmark', deep sea disposal. Both were sound on technical feasibility and safety, and have small differences on environmental benefits and costs. In balancing these two aspects, Shell took note of Dialogue concerns about whether the value of the environmental gains with the re-use option were worth the additional cost of obtaining them.

However in line with the position of the Royal Commission on Environmental Pollution, namely that in determining the BPEO, "financial considerations should not be overriding", Shell concluded that the BPEO for Brent Spar was the Wood-GMC proposal for the re-use of Spar in a quay development project, subject to approval from the uk Government's Department of Trade and Industry.

The BPEO is defined by the Royal Commission on Environmental Pollution as "the option that provides the most benefit or least damage to the environment as a whole, at acceptable cost, in the long term as well as the short term". It requires comparative assessment of technical feasibility, environmental impacts to atmosphere, land and water, risks to health and safety of the workforce, economics and public acceptability.