TL: Brent Spar Abandonment. A Review of the Technical Case to Support Deep Water Dumping. SO: Greenpeace International DT: 1995 Table of Contents 1. Executive Summary 2. Introduction 3. Brent Spar Description 3.1 Description of the Brent Spar 3.2 History of the Brent Spar 3.3 Spar material inventory 4. Engineering to support the selection of the Best Practicable Environmental Option 4.1 General `Standard' Project Development Methodology 4.2 Brent Spar Disposal Option Selection Methodology 5. A review of the Brent Spar Deep Water Dump Abandonment Plan Supporting Documentation 5.1 AURIS Report. 5.1.1 Areas of Concern. 5.1.2 Risk Analysis Validity 5.2 The BPEO Assessment 6. Alternatives to Deep Water Dumping 6.1 Horizontal Dismantling 6.2 Vertical Dismantling 6.3 In field Disposal 6.4 Refurbish & Reuse 6.5 Continued Maintenance 6.6 Similar Abandonment Experiences/Planned Abandonments 7. Conclusions 8. References 9. Biography 1. Executive Summary The Brent Spar is a floating oil storage and offloading facility, located in the Brent Field in UK Block 211/29 in 140 metres of water. The Spar was decommissioned in 1991 and is due to be removed from the field during the second and third quarter of 1995. An abandonment plan has been submitted to the UK Government in accordance with the Petroleum Act 1982, supported by a Best Practical Environmental Option Assessment and an Impact Hypothesis. The Spar will be the first offshore facility to apply for a license to dump in deep water, on removal, and as such, may well set a precedent for subsequent submissions. A high level screening review reduced 13 potential abandonment options to two plausible options that, it was felt, warranted further consideration. Aberdeen University Research and Industrial Services conducted a comparison of these options, whilst still at their preliminary state of definition, reviewing the technical complexities, environmental impacts, and risks to health and safety. The conclusion reached in the AURIS Report of Jan. 1994 -`The Removal and Disposal of the Brent Spar - A Safety and Environmental Assessment of the Options' was that the BPEO was to Deep Water Dump the Brent Spar. A detailed review of the AURIS report, and the BPEO Assessment prepared by Rudall Blanchard Associates Ltd for Shell Expro, indicates that the level of definition of the 2 Options, was not sufficient to justifiably reach the conclusions drawn with any degree of certainty, and that the comparative assessment suffered from a lack of basic specific data. The following comments from within the AURIS report support this statement:- Page 42 Onshore Disposal Risk Analysis - `The likelihood's of occurrence shown beneath each deviation are merely indications of the orders of magnitude, and were obtained by consideration of the engineering task involved, Page 18 Condition of the Spar for Onshore Disposal - `The Brent Spar has been damaged, and at present it is not known without a detailed survey and structural analysis whether it would be able to withstand...' Page 19 Inventories - `The amount of hydrocarbons in the sludge is not accurately known because the two samples analysed gave widely different values for the concentration of hydrocarbons' The structural conditions, and the inventories of the Spar are not known with any certainty. Without this basic data neither Option, but especially the Onshore Disposal Option, can be engineered to such a level that the proposed activities are of minimum risk, thus impacting Best Practicable Environmental Option selection. The technical case for selecting the Deep Water Dumping as BPEO is further weakened by the BPEO Assessment acceptance that Onshore Disposal is feasible (6.1.1.) and Onshore Disposal is as environmentally attractive as Deep Water Dumping (8.4.3) whilst ignoring the potential to reduce the risks associated with either option, but the Onshore Disposal Option in particular, by the use of Best Available Techniques. In summary - Further engineering works to more fully gauge the structural ability of the Spar to withstand any of the proposed abandonment operations, and to more fully appreciate the risks/hazards involved are warranted, prior to the selection of the BPEO. - More detailed analyses of the hazardous wastes is required to verify that the estimates given are truly reflective of the Spar inventory, and to allow more definitive hazardous waste removal methodologies to be developed. - The full use of Best Available Techniques should be considered, as part of Risk Mitigation works that are needed for both Options. - The technical case for the Deep Water Dumping of the Brent Spar, based upon the limited technical information available is unproven. 2. Introduction To date, a limited number of facilities have been removed from the UK sector of the North Sea, these being either floating production facilities or smaller fixed platforms from the Southern Sector of the North Sea. In each case the facilities have been totally removed and recovered to shore. The Brent Spar is a floating oil storage and offloading facility, located in the Brent Field in UK Block 211/29 in 140 metres water depth. The Spar was installed in 1976, decommissioned in 1991 and is due to be removed from the field during the second and third quarter of 1995. The Brent Spar is also the first facility for which a license to deep water dump has been submitted, and its approval may well set a precedent for those larger UK Northern North Sea Platforms due to be decommissioned within the next five year. An Abandonment Plan has been submitted to the UK Government in accordance with the Petroleum Act 1987, supported by a Best Practical Environment Option Assessment, an Impact Hypothesis, the combined AURIS Environmental Impact and Risk Analysis Report, and other supporting documentation. The selected abandonment option for the Brent Spar is to dump the facility in deep water, the decision being based upon a number of studies that have considered various abandonment options from the viewpoint of their risks to Health & Safety, technical feasibility, costs and environmental impacts. The purpose of this report is to independently review the BPEO Assessment, the Environmental Impact Hypothesis and AURIS Report in order to verify that the case for Deep Water Dumping Application is based upon sound engineering methods and judgment. 3. Brent Spar Description Brent is the UK's largest field in terms of oil and gas reserves. The Brent complex consists of four fixed platform facilities. Initially oil was exported by offshore loading to tankers through the Brent Spar facility, but since 1979 oil has been exported by pipeline with the Spar retained as a back up facility (figure1). The Brent field is located in the UK block 211/29, in 140 metres water depth. The Spar was installed in 1976 (figure 2). Figure 1 Brent Field Layout (Ref. 1) In 1993 the UK Minister for Energy approved the œ1.3 billion Brent Redevelopment project designed to unlock substantial new reserves of oil and gas. Key objectives of the plan included:- Replacing and upgrading facilities to extend the field life. Simplifying technical complexity to enhance operational safety, Improving operational reliability, Improving equipment maintainability, and Reducing long term operating costs. As part of the redevelopment plan, it was proposed to decommission and remove the redundant Brent Spar Facility. Figure 2 Location of the Brent Field (Ref. 1) 3.1 Description of the Spar The Brent Spar is a floating oil storage and offloading facility, located in latitude 61 03' 15''N, longitude 01 40' 04''E, 2.9 km from Brent A and 2.4 km from Brent B. The Spar is a large cylindrical buoy floating vertically at an operating draft of 109 m. The diameter of the Spar hull is 29.1m, and is divided internally to provide six oil storage tanks, of 300,000 bbl total capacity, and twelve buoyancy tanks. Stability is provided by some 6,800 tonnes of fixed ballast in the lower part of the unit. The diameter reduces to 17m where the buoy protrudes through the water surface, and connects the main body with the superstructure. The superstructure consists of deck levels A through to H containing the control rooms, accommodation, utilities, turntable. offloading booms and heli-deck (figure 3). The hull structure anti-corrosion system consists of 1000+ aluminum/zinc sacrificial anodes, and is held on location by a six leg catenary mooring system. Each anchor leg has a 285m chain length at the buoy and an 800 m wire length to a 1000 tonne concrete anchor block. Figure 3 Main Components of the Brent Spar (Ref.1) 3.2 History of the Spar In order to allow the transportation to shore of Crude Oil recovered by the Brent A platform, a Spar buoy was installed in June 1976 to operate as a 300,000 bbl oil storage and tanker loading system. The operating methodology was that Crude Oil was pumped via a pipeline, to a manifold beneath the Spar, and then through flexible risers into the Spar storage tanks. As oil was offloaded to a tanker, seawater was pumped back into the storage tanks to maintain draught; incoming oil similarly displaced the seawater which was pumped overboard. The Spar hull was fabricated, by Wilton-Fijenood BV at Rotterdam, using typical shipbuilding techniques, utilizing a thin outer skin of sheet steel, stiffened by ribs and internal bulkheads. The hull body was fabricated in a dry dock. The top column section was fabricated in the vertical, rotated through ninety degrees and transported by barge to mate with the hull body in a partially flooded dry dock (figure 4). The superstructure was fabricated by IHC Gusto BV at Schiedam. After installation of the fixed ballast the Spar main body was towed to Norway, to a sheltered deepwater site for upending and mating with the superstructure (figure 5). The upending procedure was based on the controlled ballasting of the storage tanks with seawater whilst monitoring the pressure difference through the outside wall of the storage tanks. The two components were mated at an inshore completion by Netherland Offshore Co. (NOC) at Erfjord, in Norway (figure 6). Installation of the complete buoy on station was undertaken by Heerema in June 1976. Figure 4 Construction Sequence of the Brent Spar (Ref. 4) In January 1977 two of the main storage tanks were ruptured during ballasting operations. It is understood that this was due to pressure differentials between the seawater (at depth) and the internal tank exceeding the material strengths. The damaged tanks were patched to preserve structural integrity of the hull structure, although the tanks were not subsequently used for oil storage, and remained filled with seawater. In 1978 the Brent export pipeline was commissioned as the prime means of export for Brent Crude. The Spar was decommissioned in 1991. Oil was removed from the storage tanks and replaced with seawater, process pipework was flushed through with seawater and the remaining storage tank emulsion pumped into the export tankers. The Spar is currently classified as a not normally manned installation with a limited certificate of fitness which expires in 1995. To renew the certificate a detailed integrity assessment and refurbishment program, estimated to cost some œ90 Million, would be required. (Ref. 3) As a consequence the decision was taken to remove the facility from the field. Figure 5 Tow of the Brent Spar Body to deepwater upend site Figure 6 Mating of superstructure with Spar body 3.3 Brent Spar Material Inventory The Brent Spar currently contains most of the equipment, piping systems and fittings with which it was originally commissioned and operated. As a consequence it is anticipated that tanks, pipework and valve bodies will still be contaminated with hydrocarbon residues, these being materials on the black list. The Brent Spar BPEO Assessment (Ref. 3) estimates the inventory of material to be as follows:- The bulk of the structure is composed of 6,700 tonne of structural steel and 6,800 tonnes of hematite ballast, and 1,000 tonnes of equipment. The hull structure corrosion protection consists of 1,000+ sacrificial anodes containing the following material; Aluminum 28.7 tonnes Zinc 10.2 tonnes Cadmium 8 kg Lead 0.6 kg Mercury 0.1 kg Equipment on board includes; - Lifting gear, electrics and batteries - Firepumps - Motors, generators - Workshops, water supply facilities - Communication equipment - Transformers, air compressors and fuel pumps - Pipework and valves - Anchor fittings, laboratory equipment - Air driven hydraulic pumps - Hydraulic rams and pumps - Electric pumps - Accommodation fixtures and fittings. Such items will consist largely of steel, with quantities of stainless steel, copper, plastics, rubber and wood. Reference 8 quotes associated quantities of regulated materials to include 13.5 tonnes of copper in cables, 3.5 tonnes of zinc in paint products, trace quantities of lead and nickel in batteries and traces of PCB's in the transformers. The oil storage tank estimated material inventories include; Component Material Quantities Sea water - 48000 cubic m .. hydrocarbons 40 ppm .. zinc 12 ppm .. aluminum 19 ppm Oily Sludge 100 tonnes .. oil 9.2 tonnes .. cadmium 5.8 kg .. chromium 2.1 kg .. copper 42.9 kg .. nickel 3.9 kg .. lead 8.9 kg .. zinc 87.4 kg .. arsenic 0.3 kg .. mercury 0.2 kg .. sand Tank walls oil/wax 41.3 tonnes 4.0 Engineering to Support the Selection of the Best Practicable Environmental Option. The exact route of defining and reviewing the various options that can be considered for the abandonment of any UKCS Offshore Oil & Gas Facility, such that an Abandonment Plan can be presented, is not yet fully defined. A draft Guideline Document on the expectations of the Regulatory Bodies is understood to be in circulation from the DTI and is due to be issued in the near future. As such the Operators who are currently considering abandoning structures are having to play matters to a certain extent `by ear', and adjust their routes to producing abandonment plans as a result of discussions with the various Authorities and other Operators experiences. From a general overview there is not expected to be too much difference between the project definition route that occurs for new facilities (such as to support an Annex B application), and that for abandonment project definition. 4.1 General `Standard' Project Development Methodology The following paragraphs are a general description of the basic steps that are normally considered for any new project. Comparisons with Abandonment Projects are made subsequently. Stage 1 Project Necessity Decision. This stage is primarily the birth of any project, where a basic decision is made, that subject to further more detailed information's and reviews, a project is to occur. The prime drivers for these decisions are usually financial, but may also be mandatory, such as environmental protection measures to comply with new or modified laws. Stage 2 Conceptual Studies/Feasibility Studies This stage reflects the first attempts to produce documentation that supports the continuation of a project to more defined stages. The overall project requirements are reviewed, and methods of achieving them developed. As the titles suggest these are usually high level studies that propose concepts that could be utilized, and verify their technical feasiblity, without giving definitive details as to exactly how the project would proceed under that concept. There may be more than one group of studies during this stage; the first being to act as a high level option screening of concepts, the subsequent ones to review the remaining concepts in more detail, and confirm their suitability for further consideration; or the initial study may be an extended one, in scope, cost and duration terms. These multiple or extended studies are generally required to improve the levels of confidence needed to make concept choices at such a relatively early stage of a project. Typical considerations at these high levels are Order of Magnitude Estimates, general technical feasibility, initial safety reviews (Level 1 HAZOPS), and environmental impacts. Although any latter or extended studies may improve the accuracy of cost estimates, and produce more detailed understandings of the concepts being considered, they would not usually be any more accurate than +/- 25%, and would still require identified areas of detailed analysis/engineering to be carried out to verify concept acceptability. Stage 3 Front End Engineering and Design (FEED) Front End Engineering and Design is the natural progression from Feasibility/Conceptual Study towards Detailed Design and project field execution. Here the option, or indeed options, under consideration undergo a detailed and thorough reviewing and development process to identify all the potential areas of concern (risk identification - HAZOPS Levels 2 and possibly 3) and then engineer them such as to reduce or remove these elements (risk mitigation). This stage requires all pertinent details that apply to the project to be available in as detailed a form as is possible. Should these not be available at the outset, or poorly defined, then the first activities of this stage are to obtain these information's, in order to allow a definitive Basis of Design and a set of Basic Engineering Data to be established. Based upon this Basis and Data, all necessary analyses will be performed, all general project methodologies (e.g. Construction Procedure Principles etc.) will be defined, and fixed, costings for equipment items will be obtained, and depending upon the particular project a +/- 15% estimate prepared for project sanction purposes. If the Project Schedule demands it some FEED stages place orders for long lead items. On occasion this estimate can be firmed up to `Lump Sum' price level. This latter route is more usually associated with Onshore plant. If multiple options for any project are being considered in the same FEED stage, then it is usual to develop them to the same level, such that an equal and fair assessment between the options can be made. It should be noted that these options may not cost the same to develop to the same level, as the costs of the FEED stage are usually related to the `Risk Levels' associated with the option, and the complexities that have to be overcome. Stage 4 Detailed Design The successful completion of Stage 3 will lead to the final project route being selected for implementation. In the case of multiple options the comparison made in Stage 3 between the `equally developed' options will allow a final project route to be selected. The detailed engineering and design stage is the finalizing of the exact method of project field execution. This is usually undertaken by the Field Execution Contractor, who will be responsible for the safe, on schedule, and to cost, completion of the project. Final estimates for Project Cost Control will be developed, as will any Field Erection Instructions (e.g. Construction and Commissioning Procedures), and Safety Instructions. Orders for materials of construction will be placed, and depending on project schedule, field offices may be established, groundwork's etc. started. Stage 5 Field Execution This is really a number of smaller stages, such as fabrication, erection, commissioning and handover, but is basically the final stages of the project, where all the engineering, procurement, and design works are combined to, hopefully, a successful conclusion. Recent studies show that; the greater the detailing of Stages 1,2, 3 & 4, the greater the chances of minimizing problems in the field (which is where any problems that arise usually cause greater cost and schedule damage to any project), and also that any extra development works undertaken at these early stages can produce overall project savings well in excess of the additional costs incurred. The above general methodology can now be reviewed against an expected course of action for the preparation of an Abandonment Plan, and the selection of a Best Practicable Environmental Option. Stage 1 is clearly made at the end of the facilities economic life, be it the cessation of production of hydrocarbons from the field due to reservoir depletion, when the operation/maintenance costs (OPEX) exceed the value of the recoverable reserves, or when there is some technical reason for shutting the facility down early, (e.g. the arrival of the Brent Pipeline, making the Spar effectively redundant). Stage 2 Conceptual/Feasibility Studies, are definitely initially covered by Initial Option Screening Studies, where a number of possible abandonment options are subjected to a high level comparison, such that a number of options can be screened out for reasons of technical non-feasibility, politically unacceptable etc. Although costs can be used at this stage as a coarse screening mechanism, the relatively low level of accuracy of the estimates (Order of Magnitude) does not readily recommend them as a prime comparative assessment criteria. Owing to the relatively high numbers of options that may pass this initial screening, it could reasonably be expected that further feasibility studies will take place to allow a more considered screening to occur, with the intention to reduce the number of options to two, which is the minimum number generally used for further consideration. (see next paragraph.) Stage 3 FEED - in this stage there is an increased likelihood of there being more than one option under consideration when preparing abandonment plans. This is because there is always the possibility of `dumping' the structure in the sea, subject to meeting the various regulations, in addition to recovering some or all of the facility. Generally for all Offshore Oil & Gas facilities partial, or total, recovery is considered feasible, and realistically only FEED activities will produce the necessary sufficient high levels of confidence in the technical feasibility, and detailing of activities to allow well detailed and informed risk, environmental and safety assessments between options to be made. Detailed Design (Stage 4) will clearly be needed for Abandonment activities, owing to the mandatory requirement to present a detailed Safety Case to the HSE, amongst other documentation. Most contractors will undertake these activities as a matter of course, as they will be needed for risk identification, and management, as well as project control. Stage 5, the field execution is again similar to that for `standard' engineering projects, although it should be noted that in the case of Abandonment Projects, Stages 3, 4, & 5 may be split into two activities e.g. decommissioning of the facility, being conducted after Cessation of Production, but possibly some period ahead of final facility abandonment. 4.2 The Brent Spar Disposal Option Selection Methodology It is not exactly known how the current proposed Brent Spar Abandonment Plan evolved, but it is believed that it will have followed the above general route in some similar manner, and owing to Shell's internal Auditing regime, Shell will no doubt be able to produce an auditable trail of exactly how the decisions came about, should the need arise. For the purposes of this report it is assumed that above `expectations' for abandonment project development can be applied to the Brent Spar documentation being reviewed, namely the Brent Spar Abandonment Best Practicable Environmental Option of Dec. 1994 document prepared by Rudall Blanchard Associates Limited for Shell Expro, and the AURIS combined `Environmental Impacts of Two Possible Disposal Options for the Brent Spar', and `A Risk Analysis of Two Possible Disposal Options for the Brent Spar Buoy' report, with a view to establishing the level of engineering definition that existed to support the `Deep Water Dumping' application, and commenting thereon. 5.0 A Review of the Brent Spar Deep Water Dump Abandonment Plan Supporting Documentation From an initial reading it is clear that the BPEO Assessment is an overview of the supporting documentation. This document does however highlight some areas of concern that warrant further detailed review. Primarily the document draws upon the AURIS combined `Environmental Impacts of Two Possible Disposal Options', and `A Risk Analysis of Two Possible Disposal Options' report of Jan 1994., to support the Deep Water Disposal Application. Reviewing the two AURIS reports there is little doubt that the Authors have reached the only conclusion that would be possible, given the level of engineering conducted at the time of the studies, and other available documentation. It must however be pointed out that there is evidence of the Authors expecting considerable additional works for both the options considered being conducted, in particular for the Onshore Disposal Option. 5.1. The AURIS Report 5.1.1 Areas of Concern (i) Lack of Equitable Engineering Definitions between the Two Options. Pages 66/67 of the report give listings of `Main Credible Unplanned Potential Impacts' and `Critical Unknown Factors', which show a high number of Onshore Disposal Option `Unknowns/Uncertainties', with very few for the Deep Water Disposal Option. This is somewhat disconcerting as to be able to conduct a balanced assessment of the options one would expect there to be similar numbers of unknowns and uncertainties for each option. Too many unknowns for one Option will increase the perceived levels of risk; without a more complete definition of the Option concerned the comparison will become biased towards the better defined Option. Furthermore, the reports show no allowances being made during the assessment for the potential reductions in risk, and the reduced likelihood of `unplanned' events that could be gained by more thorough examination of the highlighted areas of concern for the Onshore Disposal Option. It should be pointed out that very few if any of the `Critical Unknown Factors' and `Main Credible Unplanned Potential Impacts' for the Onshore Disposal Option cannot be resolved by the use of current Best Available Techniques, originating from marine construction and onshore demolition experience. (ii) Unknown Structural Condition of the Spar. The report indicates that the Spar was subjected to overstressing during initial upending operations, and that local yielding occurred in the submerged part of the structure. The extent of any damage sustained is not however indicated in any of the reports. Furthermore the structure sustained damaged during operation, with two of the storage tanks being ruptured. The reports states `The Brent Spar has been damaged, and at present it not known, without a detailed survey and structural analysis, whether it would be able to withstand.... the pressures to which it might be subjected during a reverse upending procedure'. (Author's Italics)(Page 18). Detailed surveys will allow the extent of the damage to tanks to be accurately assessed, and a detailed structural analysis would define the expected level of existing structural integrity. (Note a detail analysis of the structure may well confirm that the structure is incapable of withstanding reverse upending, or even that towing & sinking operations are not as simple as assumed). It is therefore surprising that a detailed analysis has not been conducted for the Spar, as it is an essential part of determining the basis of design for either option. It should be noted that Shell performed a structural analysis for the Fulmer SALM abandonment project, so internally Shell have set a precedence for conducting detailed structural analyses. The AURIS report indicates that an assumption was made that the Deep Water Disposal of the Spar will result in the intact sinking of the Spar, but that it may break up on impact with the sea bed. (page 61) There is however no real guarantee of this, not only because the exact structural condition of the Spar is unknown, but also because it is damaged, and will be further so when the explosive sinking charges are detonated. The full scale of structural damage caused by overpressure loads and structural response cannot be fully calculated, without knowing the present condition of the Spar. The response of the damaged sinking Spar to water drag loadings, and the possible sea anchor effect of the topsides would need evaluation to ensure that the integrity of the Spar remains as assumed. It should also be noted that there has been some 18 years of structural engineering analysis development since the installation of the Spar. Modern surveying and analytical methods are significantly more advanced than when the Spar was designed, so a detailed survey and analysis, with a high confidence level in any `present condition' analysis of the Spar Buoy is achievable. (iii) Ill defined Inventories The whole basis for the Environmental Impact Hypothesis (Rudall Blanchard), and the AURIS Environmental Impact Assessment is the inventories. There is however a considerable degree of uncertainty about those inventories aboard the Spar Buoy. The AURIS report indicates an extremely large variation in the results of the limited samples taken and analyzed, (by an order of magnitude in the case of the 2 hydrocarbons in sludge samples). Incomplete analysis of the samples taken (2 tanks out of 6 for hydrocarbons), or even estimates based on findings from other near by facilities (LSA scale activity levels from Brent A & B platforms) as no Spar specific data exists, further reveal the incomplete levels of basic data. Further examples of lack of definition are given below:- * The tonnages of anodes appears to be underestimated. The usual estimates used are some 5 % of the structural steel weights. Thus for a steel structure weighing some 6,700 tonnes (the Spar hull) the anode weights would be estimated at some 335 tonnes, against the approx. 39 tonnes stated in the AURIS report. * The estimated tonnages of oil in sludge are also questionable. The AURIS report states that `the amount of hydrocarbons in the sludge is not accurately known because the two samples analyzed gave widely different values for the concentration of total hydrocarbons (approximately 32,000 ppm, and 344,000 ppm respectively). (Author's Italics)(Page 19). Presumably the hydrocarbon concentrations in the other sampled, but apparently unanalyzed tanks, (66% of the number of tanks) will fall between these values, but it is not certain. If one assumes that the 100 tonnes of sludge are evenly distributed between tanks (i.e. 16.66 tonnes each) then 2 of the remaining tank sludge contents could contain up to 5.73 tonnes of hydrocarbons each, the levels in the other two (the damaged tanks) could be less, due to their limited exposure to oil storage duties. If this is the case then the 9.2 tonnes of hydrocarbons in sludge estimated could be low. * The Radium 226 and Actinium 228 activity levels for the sludge are clearly known for 5 of the tanks (AURIS page 21). The sludge activity levels range from 0.8 Bq/gm (Actinium 228) to 8.0 Bq/gm (Radium 226) (Environmental Impact Hypothesis Dec. 1994 Page 33). If the five tanks samples are known then it is not clear why accurate activity levels have not been reported for the sludges in each tank, as the information apparently exists, and averages have been presented instead. The 30 tonnes of LSA scale estimated to be located in the pipework is of greater concern, as there is no hard Brent Spar specific data on which to base any assumptions. The estimate is that 10 mm of scale has formed on the inside of the pipework, and it's activity levels are an average of the scales found on Brent A and B platforms. The Environmental Impact Hypothesis (Ref. 6) shows the ranges found on these two nearby facilities go from 1.7 - 46.6 Bq/gm for Radium 226, and 1.3 - 50.8 Bq/gm for Actinium 228. Whilst it is outwith the scope of this report to go into the legality of the deep water dumping of the Brent Spar, the following points should be noted when considering the LSA Scales in particular. The Radioactive Substances Acts 1960 and 1993 clearly define the activity levels that classify a material to be radioactive or radioactive waste. Schedules (1) and (2) respectively define radioactive materials and wastes. The base limits for Radium and Actinium are 0.37 Bequerels/gram [ Bq/gm] in solid form, and 3.7x10-4 Bq/gm in liquid form, below which the material is not defined as radioactive. Under these definitions both the LSA scale and the LSA within the sludge are radioactive materials, and can only be disposed of in an approved fashion with the prior authorization of the Chief Inspector or appropriate Minister. The Ionising Radiation Regulations 1985, similarly stipulate that materials with radioactivity levels above certain activity limits require protective measures to be taken to ensure the safety of any workers who may be exposed to those materials. Under these regulations, the limits are generally 100 Bq/gm, but allowances have been made to protect workers dealing with materials with activity levels of only 0.3 Bq/gm. This latter limit covers Naturally Occurring Radioactive Materials found in Low Specific Activity scales. Examples of such materials are Uranium 238 and Thorium 232, and their daughters, which includes the Radium 226 and Actinium 228 found in the Brent Spar sludge, and scales. The levels of radioactivity found in the Brent Spar at a stated average 4.5 Bq/gm Radium 226, 3.0 Bq/gm Actinium 228 for the sludge, and estimated average (based on Brent `A' scales) 17.5 Bq/gm Radium 226, 15.1 Bq/gm Actinium 228 for the scale clearly mean that these materials are defined as radioactive under both the Radioactive Substances Act 1993/1960 and the Ionizing Radiation Regulations 1985. The Radioactive Substances (Phosphatic Substances, Rare Earth etc.) Exemption (Scotland) Order 1962 applies to naturally occurring radioactive substances, and raises the activity levels at which certain materials become classified as radioactive. In the case of the particular elements Radium, and Actinium (i.e. the ones found on the Spar) the level rises to 14.8 Bq/gm for each element. This now introduces a large inconsistency, as the LSA bearing sludge is now re- defined as non radioactive material under this exemption order, and as such can be disposed of without any authorization. However, the moment personnel begin to work with it, it becomes radioactive material (IRR 1985). As such the exact status of the LSA bearing sludge becomes ambiguous. It should be noted that the upper limits of Brent `A' and `B' scales are 3.14 and 3.43 times above the activity limit specified in the 1962 Radioactive Substances (Phosphatic Substances, Rare Earths etc.) Exemption (Scotland) Order, for Naturally Occurring Radioactive Materials (NORMs) below which materials are not classified as radioactive. Even the average figures for the scale applied to the Brent Spar are above this limit at 17.6 Bq/gm and 15.2 Bq/gm for Radium 226 and Actinium 228 respectively. i.e. the materials would be deemed radioactive by the legal definitions given in the 1993 Radioactive Substances Act, 1985 IRR and 1962 Radioactive Substances (Phosphatic Substances, Rare Earths etc.) Exemption (Scotland) Order. It is likely that Shell have been given permission to include the mass of the contaminated materials in the calculations of scale activity levels by the Authorities. This would mean the total reported activity levels of the scale can be reduced by dividing the total activity calculated by the contaminated pipework tonnages in the Spar. This would indeed reduce the levels to such low levels that the Spar would be classified as non radioactive. This is however a practise that is not entertained by organisations, such as BNFL, UKAEA etc., that handles/deals with radioactive materials. The LSA scales in the pipe are removable (a routine operation for Offshore equipments) and as such are the materials that would be classified as `waste' as a result of cleaning, whilst the base contaminated item once de-scaled would be re classified as non radioactive materials. The activity levels of these scales then becomes the factor that has to be considered when disposal at sea is being considered. Further to the ratification of the London Dumping Convention 1972, in November 1993, the UK Government and other contracting parties placed a total ban on the dumping of all radioactive materials at sea. The AURIS report however indicates (page 24) that there is doubt as to whether or not any NORMs on the Brent Spar fall under the provisions of the London Dumping Convention 1972, and as to whether or not the NORMs are classified as `Radioactive Materials or wastes' or not. The BPEO gives this matter no serious consideration, nor does it explain on what basis the dumping of the NORMs is justified on. One further concern about the dumping of these NORMs is that their activity levels are above a substantial amount of the LLWs stored on the mainland, and banned from being dumped in the sea, by BNFL/UKAEA etc. thus a precedent for the resumption of dumping LLWs could be set if the Spar NORMs are classified as `radioactive wastes' and the Spar is dumped. Further sampling of the sludges, more detailed radiological surveying of the pipework etc. would therefore appear essential in order to clarify the question of inventory accuracy, and raise the confidence levels that the Environmental Impact Assessments reflect the actual situation. (iv) Risk Mitigation With a more defined methodology for executing either abandonment option, the expected financial, safety and environmental risks for each option can be more accurately assessed, thus allowing a balanced comparison as to the Best Practicable Environmental Option to be made. As can be seen from above significant amounts of accurate base data is not currently available, and detailed appraisals of all basic activities for each option have not been fully developed, nor can they, realistically, be until such data is made available. One of the primary purposes of modern project engineering methodologies is to minimize risk, hence the use of financial risk analyses, environmental impact assessments, and the HAZOP procedures. There is an indication that the Brent Spar Deep Water Disposal Application has been made based on comparisons made between a poorly defined/detailed option (Onshore Disposal Option) and one that by its nature is less risky, and easier to define, with correspondingly higher levels of confidence (Deep Water Disposal). No attempt has been made to develop risk mitigation methods for the Onshore Disposal Option, so developing the option to a similar level of engineering, and then evaluate the financial, safety and environmental costs of each option. Detailed work procedures and controls would remove or substantially reduce the potential for `Credible Unplanned Potential Impacts' (For example, creating and working with Radioactive Dusts is considered routine for the Nuclear Industry - adoption of their procedures would resolve some 75% minimum, of the potential for an unplanned `Creation of LSA/LSA Sludge dust' event). Again a detailed structural analysis would have to be performed to allow many of these detailing activities to be conducted from a sound base. The AURIS report does however indicate that these additional works will be warranted. Page 4 of the Summery states `detailed engineering studies would berequired prior to all operations' when discussing the Onshore Option, and page 8 states `Many of the risks associated with both options can be minimized by careful engineering, the adoption of the appropriate procedures, close supervision of the execution of the work, and the preparation and planning of suitable contingency measures. Indeed the very process of identifying and planning for risks and accidents will highlight the risk potential and reduce the likelihood of accidents happening.' These statements clearly show that the Authors felt that both the Options needed further detailed studies, that at the time had not taken place, and are currently understood to still be outstanding. 5.1.2 Risk Analysis Validity The previous section (Section 4) shows that there are a considerable number of elements that would normally be expected to be resolved prior to any major decisions being made as to the most preferable option. Clearly the Onshore Disposal Option is a more technically complex exercise than the Deep Water Disposal Option, and at an initial level appears to be more risky. The Risk Analysis conducted by AURIS however assesses the risks at this initial high level, rather than between two equally developed and more defined options. At this initial early stage the analysis can easily be expected to confirm that Onshore Disposal is the more risky operation, especially if no allowances have been made for risk mitigation methods. However the AURIS report page 39 statement that `there is no reason to suppose that, with necessary supervision, care and attention to good engineering practice, the onshore dismantling operation would be any more hazardous than normal offshore construction and diving works.' serves to indicate that the Onshore Disposal Option is not unacceptably risky. Details within the Risk Analysis The comparison between the two options for the risk analysis contains some discrepancies, which are described in the following paragraphs:- The analysis for both the Onshore Disposal and Offshore Disposal Options contain allowances for expected `unplanned' events, this misses the point that if an event, be it planned or not, is expected, then risk mitigation methods will automatically be put into place by the contractor, prior to project execution, thus reducing the risk. The size of the expected workforce (averaging 200 for 1 year) for the Onshore Disposal Option quoted on page 42, and the number of expected `manhours' (360,000) to complete the operation appears to be very high. Given the apparently poor level of detailing of the Onshore Disposal Option, it is unclear how this figure was derived. These numbers appear to include the total workforce, including marine vessel crews (e.g. page 40 - a Dive Support Vessel crew of 58 being considered), and possibly engineering teams. In reality the operational crews conducting the actual abandonment works are likely to be substantially smaller, and the exposure levels accordingly reduced. Supporting crews, engineers in the office etc, would need to be considered at their corresponding risk levels. i.e. a ship's cook would be exposed to the risks associated with being a ship's cook, not the same levels of risk as an offshore construction worker, or diver. A tentative estimate for operational abandonment crew sizes would be as follows:- Diving Activities 3 - 4 divers/4-5 support crew Decommissioning/Cutting Offshore 12 -15 operatives Upending Crews 15 operatives/7 diving crew Onshore Demolition Crews 12 -16 operatives Thus the validity of including personnel (e.g. engineers, and marine vessel crew) who are not directly involved in actual abandonment activities at the higher risk levels used in the risk analysis for abandonment operations is questionable. Similar arguments apply to the Deepwater Disposal Option, but not to such high a degree, as the estimated manhours, duration etc. are lower, so any `magnification' of errors will be smaller The high use of mechanisation (Best Available Technologies - BAT) e.g. potentially using ROVs for surveys, and certainly using hydraulic shears for steel cutting and remotely operated abrasive water jet cutting equipment or possibly shaped explosive charges for onshore demolition activities, will further reduce the project duration, and reduce personnel exposure to hazardous operations. The risk analysis does not seem to address the use of BAT. The Deep Water Disposal Option contains a proposal to `remove hazardous materials, where possible, to minimize the potential environmental impact of deepwater disposal,' yet the risk analysis appears to make no allowances for these activities. It is unclear if Asbestos is on the structure, it may be located within the walls of the topsides, as it was a common construction material in the 1970s, but even if not present presumably some stripping out of hazardous materials will be involved. These additional offshore activities are likely to be more hazardous than similar activities that would occur in the controlled environment onshore in the other considered option. Given that the definition of `materials that would be removed' is loose, the location of the materials to be removed is not specified, nor the volumes of materials, it is not easy to see how an accurate risk assessment for these activities can be made. The Safety figures used are based upon statistical averages, which is standard practice. However, it should be noted that using an average over a say ten year spread can actually distort the statistics against the latest figures. For example a figure of say 0.3 fatal diving events per year may be obtained from statistical information's, but recent figures for 1992/3 from McDermott Underwater Services show NO reportable incidents. Safety matters figure significantly in all contractor operations, and they continuously strive to reduce their accident rates towards zero, Offshore abandonment matters would therefore be treated with exactly the same degree of caution as any other Offshore activites. As with the Engineering comparison, the Risk Analysis comparison is conducted at a high level. This is reflected in the AURIS page 42 statement concerning the Onshore Disposal Option `unplanned' events, ` The likelihood's of occurrence shown beneath each deviation are merely indications of the orders of magnitude, and were obtained by consideration of the engineering task involved, and the events that would be necessary for the deviation to occur.' Thus the basis for the risk analysis is tending towards an Order of Magnitude Risk Analysis, not a definitive Analysis, which would be more appropriate to allowing a fully informed choice of option to be made. 5.2 The BPEO Assessment As stated before the BPEO Assessment is based heavily upon the AURIS reports, and as it can be seen there is cause for concern about the basis of the AURIS findings from a technical viewpoint in a number of instances, that cast doubt upon the validity of the justification for selecting the Deepwater Disposal Option as the BPEO. Based upon the previous discussions there are BPEO Assessment statements that can now be defined as questionable as to their validity. These are as follows:- Section 3.3 Inventory of Materials As previously discussed there is considerable uncertainty as to the exact inventory of materials on the Brent Spar, not least with regards to Anode tonnages (3.3.2) , Oil in Sludge tonnages (3.3.3) and Low Specific Activity Radioactive Scales. (3.3.4.) Section 3.4 Regulatory Framework It is surprising that a matter that is clearly within a complex UK and International framework receives only a one page diagrammatic review, and the statement that `the abandonment of the Brent Spar will comply with all UK legislation.' No mention is made to the fact that the Radioactive Scales at their claimed activity levels appear to fall under the 1962 Radioactive Substances (Phosphatic Substances, Rare Earths etc.) exemption (Scotland) Order, in addition to the 1985 IRR and 1993 Radioactive Substances Act. Nor is there any explanation as to why it is felt that these, amongst other waste substances can be legally dumped in the sea. A more detailed explanation of the interpretations used, and statements showing how compliance with International Conventions, Laws and EEC/UK Laws exists, is required to justify the selection. Section 4.0 Option Screening The summarization of the various options considered fails to make it clear that these options have been developed at a high level only. The inference that the remaining 2 short listed options had the Engineering Complexity, Risk to Health and Safety of Workforce, Environmental Impact, Cost, and Consultation Process aspects `looked at in detail' fails to address the fact that the basic level of development of both Options, but especially the Onshore Disposal Option, is not sufficiently detailed enough for conclusively proving, with any degree of confidence, that the Onshore Disposal Option is not feasible, too hazardous, or costly when compared to the Deep Water Disposal Option. More detailed engineering and analyses is warranted before being able to reach these conclusions. As stated before even AURIS expected further development works to be carried out for both options.(AURIS Report pages 4 and 8) The basic summaries of each of the options initially considered use `emotive' language such as `extremely complex operations', `significant exposure of the workforce to hazardous operations', `high potential for unplanned events' and `high comparative cost' (4.2.2 Option 1 - Horizontal Dismantling). Yet these statements are not supported by the AURIS report (page 39 - `there is no reason to suppose that, with necessary supervision, care and attention to good engineering practice, the onshore dismantling operation would be any more hazardous than normal offshore construction and diving works.') `High comparative costs' are derived from high level Order of Magnitude estimates, not definitive estimates. A similar case exists for `High Potential for unplanned events', which fails to take into account any risk identification and mitigation procedures that could be applied to both the Deep Water Disposal and especially the Onshore Disposal Option. The definition of `high' is also not defined, is it a one in ten or one in a thousand chance? It should be remembered that contractors will strike a balance between level of risk, economics and safety considerations, when following risk mitigation procedures, and will make considered judgments based upon these factors and experience of conducting similar operations. Section 5.0 Description of Short Listed Options This sections of the BPEO Assessment give a general overview of the short listed options. However the statement in 5.1.7 that `it would not be possible to remove any water that subsequently leaks into the tanks' infers that this would be a major problem. As previously discussed risk mitigation methods would be employed - in the example given, tank level monitoring systems would be installed to gauge water levels, and procedures prepared to deal with any excessive ingress of water - such as heave to and reconnect pumps/repair leaks. These activities, and any other mitigation techniques are not particularly innovative or complex in nature, and would not generally be considered outside Marine Engineering experiences. This latter point is confirmed in Section 6.2.2 of the BPEO `The operations, whilst they have been used in the Offshore Oil & Gas Industry, involve technically demanding marine engineering techniques.' The use of the term `technically demanding' depends on the perspective from which the activity is being seen. Experienced Marine Salvage experts might view these activities as `technically demanding', but of normal operation. Section 5.2.3 when discussing the Deep Water Disposal Option states `as much of the potentially hazardous materials as possible will be removed', yet the level of definition of which materials will be removed, and where they are located is not specified in any report. These clean out activities could have a noticeable impact on the overall safety aspects of this option, but clearly have not been fully appraised. Section 6.0 Engineering Complexity 6.1.1 states that `both options are significantly different in terms of their engineering complexity, and uncertainties inherent in their engineering execution, but both are considered technically feasible.' Thus there is no argument presented to the effect that Deep Water Disposal is the only feasible option. 6.2.3 indicates the low level of definition of the engineering of the Onshore Disposal Option when it discusses the possible effects of the upending operation - `it is believed that a similar condition would occur during reverse upending..'. The case for concern would be considerably strengthened if it could be stated with a high level of certainty that this was the case. i.e a detailed upending marine/structural analysis would be required. Section 7.0 Safety and Risk Implications As previously discussed there is a question over the assumed man-hours used for the risk analysis, and the assumption that the works will be `labour intensive'. The use of `Best Available Technologies' can realistically be expected to reduce both the numbers of personnel involved, and the risks that they are exposed to. Safe working procedures would similarly reduce risks. The 7.2.1 statement about the onshore disposal being highly labour intensive and thus producing `consequently high' exposures to risk is therefore debatable. The assumption that the onshore demolition activities introduce `high exposures to the hazards of onshore breaking operations' fails to reflect the fact that onshore demolition contractors favour mechanisation, and remote demolition wherever possible. The use of linear cutting explosives also allows remote operations, whilst the recent clampdown by the Health and Safety Executive for all onshore and offshore demolition works will ensure strict compliance to procedures, and that detailed definition of demolition methodologies have been engineered, further reducing the risk levels. The estimated man hours for onshore breaking appear excessive and fail to reflect the use of BAT, thus the whole basis of 7.2.2 appears to be unsound. 7.2.3. again believes that a `significant potential for occupational health risks' exists for the onshore disposal option. It should be noted that the Deep Water Disposal topsides clean out operation, alluded to in Section 6.3.2, would introduce similar levels of potential for exposure, but in a more difficult environment (i.e. Offshore, rather than Onshore.). The materials listed, however, as potential sources of risk are however commonly found in industry, and would not be expected to cause any of the Hazardous Material Handling specialists any untoward problems, or require any activities that have not been dealt with before. Section 8.0 Environmental Considerations The overall conclusion of this section states `The environmental impacts of each option are therefore evenly balanced' (8.4.3). This conclusion appears to be based upon the fact that there is a greater `potential for an unplanned event...' and if this occurred the environmental impact would be `significant', with the Onshore Disposal Option (8.4.3). This assumed fact appears to cancel out the overall benefits that would be gained by a successful Onshore Disposal, which is a debatable stance to adopt, given the low level of Onshore Disposal Option development. This section also fails to address the fact that the Onshore Disposal Option is to a large extent `reversible', as the operations can largely be stopped and the Spar reinstated, if problems are encountered. The Deep Water Disposal Option is however irreversible. Once the sinking charges have been detonated there is now going back. Recovery of the wreck from the deep Atlantic would not only be extremely difficult to execute, but would be extremely expensive. As stated before by this report and by the AURIS report page 8 `Many of the risks associated with both options can be minimized by careful engineering, the adoption of the appropriate procedures, close supervision of the execution of the work, and the preparation and planning of suitable contingency measures. Indeed the very process of identifying and planning for risks and accidents will highlight the risk potential and reduce the likelihood of accidents happening.' As such the use of `potential' to cause unplanned events, environmental damage, etc. without having completed detailed project definition activities, as justification for the selection of one option over another appears to be an extremely weak argument. Section 9.0 Cost Considerations Again the lack of option detail definition gives cause for concern that the use of costings for decisions on preferred options is somewhat premature. Final detailed planning may cause either of the two options to significantly alter in cost. The estimate for the Onshore Disposal Option is believed to be in the +/- 40% range as a minimum, due to the number of uncertainties that are currently unresolved. The requirement to strip out significant quantities of hazardous materials from the Spar topsides prior to Deep water disposal, could also introduce significant additional costs. The BPEO fails to address the levels of accuracy of the estimates for each option. The use of the Best Available Techniques Not Entailing Excessive Costs principle for the abandonment option selection also raises the question of the level at which an option becomes `excessive.' It should be noted that the œ46 Million estimated for the Onshore Disposal Option, represents only 3.5% of the Brent Field Redevelopment Project expenditure. Section 10.0 Consultations It is assumed that the information contained within the BPEO, Environmental Impact Hypothesis, and AURIS reports were made available to `interested parties' for review. If this was the case then it is unlikely that any of the reviewing bodies has sufficient specific engineering methodology to be able to constructively comment on the proposals, given the level of engineering definition of the onshore disposal option in particular, and the lack of detailed information as to the exact current condition and inventories of the Spar. It therefore not unexpected that Shell received no objections to their proposal. 6.0 Alternatives To Deepwater Dumping Initially in the project development a high level screening review of 6 plausible abandonment options out of 13 was undertaken, the conclusion to which was that the Onshore Disposal Option and Deep Water Disposal option were the 2 most viable routes to pursue. If these options are now re-considered (at a high level) then the potential for avoiding Deep Water Dumping can be appraised:- 6.1 Horizontal Dismantling was considered the most feasible alternative disposal method to Deep Water Disposal. As can be seen in the above paragraphs the level of development of this option is still low. Should a structural survey and analysis conclude that the Spar is weakened to such a extent that reverse upending is not feasible, there may be a possibility of attaching a support frame to strengthen the structure. This frame could then be attached to Heavy Lift Vessels, this reducing the possibility of the structure sinking during upending operations. Examples of lifting frames being used in difficult circumstances are the recovery of the Mary Rose Man of War (approx. 400 years old rotting wooden wreck), and the recovery of the Piper Alpha Accommodation block - damaged, upside down, and filled with an unknown amount of silt, that was expected to shift (altering the center of gravity) during lifting operations. Both were recovered successfully. It should further be noted that the `Peace Dividend' is allowing hitherto unknown technologies developed by the Military to become available. Techniques for recovering submarines may be available from UK, US or FSU navies, that could be applied to the Brent Spar. It should be noted that the Fulmar SALM was recently towed into Stavanger (section 6.11), and so there is the possibility that the Spar could be upended in a fjord, for later return to the UK for onshore demolition, subject to Norwegian Authority approvals. The further development of this option relies entirely on the execution of a detailed structural survey and analysis. 6.2 Vertical Dismantling although technically feasibility and less complex than option 1. This option was rejected as no suitable deep water sites were identified. Whilst this is true of the UK, the deepwater sites in Norway, of which the original inshore mating was undertaken (section 3.2), seems to have been ignored. It could however be considered if horizontal disposal is not deemed feasible, as it would subject the Spar body to less stress loading.(no upending required). The mitigation of possible releases of unconfined hazardous wastes during dismantling would need to be subjected to detailed planning and reviewing if this option was to be re considered seriously. 6.3 In-Field Disposal was originally rejected on the grounds that it would not be acceptable given the available alternatives, and effectively it is the same as the Deep Water Disposal option. These reasons for rejection still apply. 6.4 Refurbish and Re-use was rejected as no third party purchasers were identified. Refurbishment costs are also understood to be in the region of œ90 Million, and would merely delay then abandonment of the Spar by say some 30+ years. The structure will require removal at some time, and similar problems to those being encountered today could reasonably anticipated. 6.5 Continued Maintenance was rejected on the basis that Shell Expro did not wish to incur continued maintenance costs whilst they did not foresee any future use for the structure. As above this option only delays abandonment. 6.6 Similar Abandonment Experiences/Planned Abandonment's Within the BPEO Assessment several comments are made referring to the technical complexities associated with the horizontal dismantling option. Within this section, two examples are given, of many available, to demonstrate the marine industries capacity to undertake such activities. The recent return of Brent Bravo modules to shore is also discussed. 6.6.1 The M.T. Betelgeuse (Ref 4) On 6th January, 1979 the 122,000 ton dead weight tanker `Betelgeuse' was moored alongside the Gulf Oil Terminal at Bantry Bay, Ireland. The vessel caught fire and exploded with significant loss of life, causing the vessel to break into three parts and to sink in 100 feet of water. The paper (Ref. 4) describes the work associated with plugging and patching the damaged vessel bulkheads by divers prior to recovery of the separated mid, aft and forward sections. 6.6.2 Fulmar SALM The Shell Fulmar Single Anchor Leg Mooring (SALM) in the UK North Sea was successfully removed and towed to Stavenger in Norway in July 1994 (ref. 6).The Fulmar SALM consisted of a rigid buoy structure connected to a seabed base with a universal joint. The buoy had a net upward buoyancy of 2000 tons when connected to the base. The SALM consists of a 96 metre long hull structure, 15.9 metre diameter of its maximum. The structure is conventional stiffened plate divided into 18 compartments. At the top of the SALM a yoke connects to the permanently moored floating storage unit (FSU) converted from the VLCC SS Medora. The SALM was installed in 1981. In December 1988 the SALM broke away from its base during storms, and drifted away, still attached to the FSU until recovered by tugs. After repair and modifications carried out by Verolme Botlek in Holland, the SALM was reinstalled in October 1989. The method of removal of the SALM buoy was to cut through the hubs which formed part of the universal joint. During preparation for the operation, detail finite element analysis was carried out to verify the structure integrity during the cutting sequence. Critical aspects of the operation were subject to project reviews and HAZOP analysis as part of the overall safety and contingency planning. The offshore marine spread was mobilized on July 11th, 1994. The SALM successfully broke away on July 19th, after which it was towed by two tugs to a location near Stavenger, where it was handed over to a mooring contractor. 6.6.3 Brent Modules In 1994 the first of three groups of redundant topside modules from the Brent Field Redevelopment Project, was delivered to the UK mainland for resale/scrapping/recycling as deemed appropriate. These modules were removed from the Brent Bravo to make way for replacement modules. The Shell team dealing with these modules decided that for whatever reasons (possibly a combination of recovering the remaining assets values of the modules, and the protection of the environment) that deep water disposal was not acceptable, so they were/are to be returned to shore. It should be noted that the lifting off of the modules, and onshore demolition activities will expose/has exposed the workforce to more risk than the proposed lifting off of the considerably smaller Brent Spar topsides (20,000 tonnes against 1,570), by the very fact that there are more lifting operations, and onshore dismantling operations involved. Yet this is Shell's selected route. This would appear to weaken the case for dumping the Spar with topsides on. Further weakening of the case for dumping the Spar topsides is due to the fact that the material inventories of these modules are very similar in nature to those on the Spar topsides. It does not appear to be a logical argument for the same project team to on one hand recover these materials for disposal onshore, whilst another part of that team argues that deep water dumping of the Spar topsides is the most practicable option. It is further noted that the recovery of the topsides for onshore disposal is not considered in depth by the BPEO Assessment for the Brent Spar. 6.6.4 Planned Abandonment's There are a number of Abandonment Plans being prepared currently, some of which contain similar end points as the deep water dumping of the Brent Spar, such as:- Esso Odin - currently understood to be proposing to topple the jacket only to form an artificial reef. This proposal is understood to be the subject of significant objections from a number of sources (Reference 8). Elf N.E. Frigg Control Tower - this abandonment is under review, but the current operators favored proposal is understood to dumping of the steel tower and concrete base.(Dumping at Sea). Counter proposals are being made for recycling the tower, and possible dumping of the concrete gravity base. These options are the subject of much discussion in Norway. (Ref. 7) As can be seen most of these projects will be larger in nature and duration than the disposal of the Spar, even in the case of Onshore Disposal due to the size of the platforms involved, yet the recovery to shore of materials is being actively considered 7.0 Conclusions This report raises a number of concerns about the validity of key considerations that have been made to date to support the application for a Deep Water Dumping license. These concerns show that, given the defined information levels and low level of engineering detailing of one of the two considered options in particular, the ability to select a BPEO in a balanced, and meaningful manner, with any degree of confidence, becomes questionable. These doubts are supported by the unsubstantiated technical arguments presented as the justification for the selection of the Deep Water Dumping Option as BPEO. The paragraphs below highlight the weaknesses The BPEO concludes in favour of the Deep Sea Disposal of the Brent Spar on the basis that: * Alternative methods are technically complex. This may be so, but equally there are alternatives that are acknowledged in the BPEO as feasible, and there is experience in dealing with marine operations that are technically equal or more complex. The feasible alternatives are not developed sufficiently enough to discount them on technical grounds, further works are required. The AURIS supporting report to the BPEO Assessment acknowledges this on page 8 of its summary. * It greatly reduces the risk to personnel engaged in the abandonment. By the application of risk reduction strategies it may be feasible to reduce the level of alternative option risks. Scant regard is paid in the BPEO Assessment to the use of Best Available Techniques in the risk analysis for these alternatives, and there are doubts as to justification of using the large workforce estimated for the onshore disposal route, due to the poor level of definition of this option. It should also be noted that additional decontamination work is alluded to for the Deep Water Dumping Option, but this does not appear to have been defined, or allowed for in the risk assessment. Should these activities be required then the associated risks will increase. Allowances have been made in the `risk analysis' for expected `unplanned' events, which ignores that fact that expected events will be planned for, and risk mitigation methods adopted, thus reducing the risk levels. An option should only be rejected on this basis if it shown to result in a level of unacceptable potential risk, with little probability of successfully being able to apply risk reduction measures. The current level of development of the options is insufficient to reach this sort of conclusion. * It offers negligible environmental disadvantage and reduces the risk to other assets and resources at sea and on the coast. Within the BPEO it is concluded that the environmental impacts of each option are evenly balanced, yet this seems to be because the alternative option to Deep Water Dumping has a higher potential for `unplanned events' occurring. As stated above the BPEO Assessment has failed to address the fact that risk mitigation methods would significantly reduce this potential. A fully developed Onshore Disposal Option, with consequent reduced `potential' for `unplanned' events, successfully executed has a better overall environmental impact than the chosen option, and would therefore appear to be the best environmental option. The alternative also offers the potential for reversing disposal operations, and will result in a controlled disposal of wastes. The selected option once dumped is extremely difficult to reverse, even if the structure remained intact (unproved), and offers no control over the waste materials within. * It is the lowest cost option. Under the polluter pays principle, cost should not be a deciding selection criteria. However even if it is, the costings used in the BPEO are not sufficiently fixed to allow a sound judgment to be made. As stated above there is a considerable scope for changes in the works in either of the options considered, which could have dramatic cost implications. * It is acceptable to the authorities and their consultees. Based upon the information reviewed in this report it is not unexpected that the BPEO Assessment is acceptable. It is felt however that the level of information presently used to justify the BPEO choice is not of sufficiently high enough definition, especially in the case of the Onshore Disposal Option, to allow the consultees and authorities to be able to take a balanced, well informed look at the options available. All of the above concerns lead to the conclusion that there are insufficient definitive technical grounds for justifying the selection of the Deep Water Disposal Option at this particular stage of the Abandonment Project development. It is clear that there is a substantial quantity of engineering data gathering and analysis, and firming up of proposed methodologies, needed to allow a high confidence level decision to be made as to which option is the BPEO. 8. References 1. The North Sea Field Development Guide 4th Edition published by OPL. 2. Paper `On the Typical Qualities of Spar type structures for Initial or Permanent Field Development'. J.A. Von Sonten and K. deWerk, Gusto BV Offshore Technology Conference paper OTC 2716. 3. Brent Spar Abandonment BPEO - Dec. 1994 prepared for Shell UK E & P by Rudall Blanchard Associates Ltd. 4. The Wreck Removal Operation of the MT `Betelgeuse', Captain P. Birkenhead. Proceedings First International Conference on Decommissioning Offshore, Onshore and Nuclear Works - 1988 published by UMIST - UK. 5. Article `Contractor's cold cut frees Fulmar buoy from its Base'- Offshore Magazine Nov 1994 p.166 6. Brent Spar Abandonment - Impact Hypothesis - Dec 1994 prepared for Shell UK E & P by Rudall Blanchard Associates Ltd. 7. Page 5 European Offshore Petroleum Newsletter 29/3/95 8. Euroil Magazine Vol 6. Issue 4. April 1995 (p8) 9. Biography Mike Corcoran Mike Corcoran has had over 25 years of heavy construction experience, of which the last sixteen years has been spent in the Oil and Gas Industry. He has lectured on, and published over 20 papers on offshore design and decommissioning. Between 1991 and 1995, he was a manager of a Decomissioning and Salvage Operations Group at McDermott International. Since that date he has acted as a consultant to various clients advising on all maters relating to the decommissioning and salvage of offshore/onshore oil and gas facilities. 1