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AN ASSESSMENT OF TECHNIQUES FOR REMOVING OFFSHORE STRUCTURES AN ASSESSMENT OF TECHNIQUES FOR REMOVING OFFSHORE STRUCTURES Committee on Techniques for Removing Fixed Offshore Structures Marine Board Commission on Engineering and Technical Systems National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1996
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AN ASSESSMENT OF TECHNIQUES FOR REMOVING OFFSHORE STRUCTURES NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the panel responsible for the report were chosen for their special competencies and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce M. Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Harold Liebowitz is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. Harold Liebowitz are chairman and vice-chairman, respectively, of the National Research Council. The program described in this report is supported by cooperative agreement No. 14-35-0001-30475 between the Minerals Management Service of the U.S. Department of the Interior and the National Academy of Sciences and by interagency Cooperative Agreement No. DTMA91-94-G-00003 between the Maritime Administration of the U.S. Department of Transportation and the National Academy of Sciences. Limited copies are available from: Marine Board Commission on Engineering and Technical Systems National Research Council 2101 Constitution Avenue, N.W. Washington, D.C. 20418 Copyright 1996 by the National Academy of Sciences. All rights reserved. Printed in the United States of America
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AN ASSESSMENT OF TECHNIQUES FOR REMOVING OFFSHORE STRUCTURES COMMITTEE ON TECHNIQUES FOR REMOVING FIXED OFFSHORE STRUCTURES F. PAT DUNN, Chair, Columbus, Texas KAREN A. BJORNDAL, Archie Carr Center for Sea Turtle Research, University of Florida, Gainesville JAMES M. COLEMAN, NAE, Louisiana State University, Baton Rouge WILLIAM E. EVANS, Texas Institute of Oceanography, Texas A&M University, Galveston RICHARD A. KASPRZAK, Louisiana Department of Wildlife and Fisheries, Baton Rouge JAMES E. KIESLER, Global Movible Offshore, Amelia, Louisiana PATRICK E.G. O'CONNOR, Amoco Production Co., Houston, Texas ALAN POWELL, Department of Mechanical Engineering, University of Houston, Texas ALLAN G. PULSIPHER, Center for Energy Studies, Louisiana State University, Baton Rouge DANIEL J. SULLIVAN, McDermott, Inc., Morgan City, Louisiana J. PACE VanDEVENDER, Sandia National Laboratories, Albuquerque, New Mexico PETER K. VÉLEZ, Shell Offshore, Inc., New Orleans, Louisiana Liaisons GREGG GITSCHLAG, National Marine Fisheries Service, Galveston, Texas CHARLES SMITH, Minerals Management Service, Herndon, Virginia MARY ANN TURNER, Minerals Management Service, Herndon, Virginia Staff SUSAN GARBINI, Project Officer AURORE BLECK, Administrative Assistant
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AN ASSESSMENT OF TECHNIQUES FOR REMOVING OFFSHORE STRUCTURES MARINE BOARD RICHARD J. SEYMOUR, Chair, Texas A&M University, College Station, and Scripps Institution of Oceanography, La Jolla, California BERNARD J. ABRAHAMSSON, University of Wisconsin, Superior JERRY A. ASPLAND, Arco Marine, Inc. (retired), Long Beach, California ANNE D. AYLWARD, Volpe National Transportation Systems Center, Cambridge, Massachusetts MARK Y. BERMAN, Amoco Corporation, Houston, Texas BROCK B. BERNSTEIN, EcoAnalysis, Ojai, California JOHN W. BOYLSTON, Argent Marine Operations, Inc., Solomons, Maryland SARAH CHASIS, Natural Resources Defense Council, Inc., New York, New York CHRYSSOSTOMOS CHRYSSOSTOMIDIS, Massachusetts Institute of Technology, Cambridge BILIANA CICIN-SAIN, University of Delaware, Newark JAMES M. COLEMAN, NAE, Louisiana State University, Baton Rouge BILLY L. EDGE, Texas A&M University, College Station MARTHA GRABOWSKI, LeMoyne College and Rensselaer Polytechnic Institute, Cazenovia, New York M. ELISABETH PATÉ-CORNELL, Stanford University, Stanford, California DONALD W. PRITCHARD, NAE, State University of New York at Stony Brook STEPHANIE R. THORNTON, El Cerrito, California KARL K. TUREKIAN, NAS, Yale University, New Haven, Connecticut ROD VULOVIC, Sea-Land Service, Inc., Elizabeth, New Jersey E.G. “SKIP” WARD, Shell Offshore, Inc., Houston, Texas ALAN G. YOUNG, Fugro-McClelland BV, Houston, Texas Staff CHARLES A. BOOKMAN, Director DONALD W. PERKINS, Associate Director DORIS C. HOLMES, Staff Associate
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AN ASSESSMENT OF TECHNIQUES FOR REMOVING OFFSHORE STRUCTURES Preface BACKGROUND Nearly 3,800 platforms populate the U.S. federal outer continental shelf. Most of these are off the coast of Louisiana and Texas (MMS, 1995). The Minerals Management Service (MMS) of the U.S. Department of the Interior requires removal of platforms within one year after termination of the lease. Lease operators may remove platforms when the costs of operating and maintaining structures exceed revenues or when structures are obsolete or damaged. The options for disposing of offshore structures include complete removal with disposal ashore, placement in an approved ocean disposal site, conversion to a fishing reef, or removal for refurbishing and replacement elsewhere. In approved cases, maintenance in place is an alternative to removal. Removal must be to a depth that safeguards ocean shipping, that does not obstruct shrimp-trawling operations, or that allows for submarine passage and minimizes the threat of seabed obstructions. The pace of platform removals continues to accelerate as aging platforms built in the boom years of the late 1960s and 1970s are taken out of service. More than 100 platforms have been removed from service in each of the last several years (181 were removed in 1993). The most common procedure for removing fixed offshore structures is by cutting them into sections and removing them by lifting. The necessary submarine cutting is most often accomplished by submarine explosives, which can harm fish, turtles, and marine mammals. Damage from explosives can be mitigated by careful timing and operational procedures, but the extent of damage and the potential for mitigation have not been well documented. An alternative to explosives is cutting with jetting tools and torches or with mechanical cutting devices. Many operators prefer using explosives because they cost less and are less risky. Experience has shown that, in most situations, severing and retrieving structures can be accomplished in one operation using explosives. Uncertainty is increased substantially if nonexplosive techniques prove to be inadequate or are unsuccessful during the removal process. Such failures may require active intervention, such as diver cutting. Diver interaction with a structure that has been damaged to an undetermined extent is inherently dangerous, time consuming, and expensive. The prevailing judgment of platform owners and operators is that explosive cutting is cheaper, safer, more flexible, and more reliable than available or reasonably prospective nonexplosive technologies for most platform removals. Most of the problems with the explosive method are associated with the environmental impact, especially mortality of marine life in the region affected by the detonation. Although the presence of turtles and marine mammals around platforms is not well documented, the National Marine Fisheries Service of the U.S. Department of Commerce has identified explosive removals of offshore structures as a possible contributor to turtle and marine mammal mortality. Fish kills associated with explosive removals are also of concern; however, only fragmentary data pertinent to fish kills are available. The range at which fish can be killed by explosives depends on several factors: the intensity of the explosive shock wave as determined by the type, configuration, and amount of explosive used; reflection and refraction of the shock wave, which varies with bottom material and water conditions (temperature, salinity, etc.); and the susceptibility of specific fish species to various shock waves. The U.S. General Accounting Office (GAO) recently reviewed offshore structure removal operations and concluded that nonexplosive technologies merit further consideration and development because of concerns about the impact of explosive removal techniques on biological communities (GAO, 1994). The agency also concluded that the MMS has not adequately studied the costs and benefits of using nonexplosive technology that would reduce the risk of environmental damage from the removal of offshore structures. Moreover, the GAO concluded that certain actions by MMS may actually discourage the use of nonexplosive platform removal measures (e.g., an MMS proposal to relax limits on the use of explosives). The MMS requested that the National Research Council (NRC) address the issues raised in the GAO report. A committee was convened to undertake a study of the technical issues and recommend alternatives for future MMS action. Specifically, the committee was asked to: review platform removal technology, including the costs of alternative techniques examine and appraise innovative technologies and techniques under development
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AN ASSESSMENT OF TECHNIQUES FOR REMOVING OFFSHORE STRUCTURES assess the occupational and environmental hazards of explosive and alternative removal techniques identify ways to mitigate the identified hazards In the course of the study, the committee also learned about the requirements and concerns of other users of the marine environment (including shrimpers, fishers, recreational boaters, and people concerned about environmental damage), which should be taken into account in developing federal procedures for full or partial platform removal and for site clearance. The committee also assessed the adequacy of existing MMS regulations governing the removal of fixed offshore structures. Based on its work, the committee prepared this report, which provides a comparative assessment of offshore structure removal technologies and existing and potential mitigation strategies for decreasing the damage to living marine resources. This report is intended to provide guidance to the MMS on the technical basis for development of offshore structure removal techniques and for updating pertinent federal rules and procedures. The report identifies alternatives for minimizing damage to the marine ecosystem from offshore structure removals. COMMITTEE COMPOSITION AND SCOPE OF THE STUDY A committee of 12 people was convened by the NRC Marine Board. Biographies of committee members appear in appendix A. Members of the committee include experts on offshore civil engineering, geotechnical engineering, marine construction, underwater blast effects and mitigation, technical assessment, biology, ecology, and management of living marine resources. Composition of the committee provided the scientific, technical, economic, policy, and practical expertise to assess current conditions and make recommendations for the future. The points of view of the offshore oil and gas industry and associated service industries were represented on the committee, as were the views of scientists involved in research on the specific living marine resources (sea turtles, marine mammals, and fish) that may be affected by explosives used to remove offshore structures. The committee was assisted by liaison representatives from the MMS, which sponsored the study, and the National Marine Fisheries Service (NMFS), which is charged with ensuring compliance with regulations protecting living marine resources. The principle guiding the committee, consistent with NRC policy, was not to exclude any information because of possible bias, if the information was vital to the study, but to treat all points of view fairly. The committee focused on the assessment of offshore structure removal technologies and associated hazards and the development of strategies to mitigate environmental damage. Disposal of platforms after removal, either on site, in deep water, or onshore, was outside the scope of this study. Although issues concerning the requalification of offshore structures for extended service and their reuse through statesponsored “rigs-to-reefs programs” were originally excluded from the scope of the study, the committee found it necessary, for a full understanding of the complexity of the issues, to include a limited examination of the latter program and to present findings concerning the role of these programs in the Gulf of Mexico ecosystem. Although the assessment may provide valuable insights concerning removal of offshore structures from state as well as federal waters, an assessment of state rules was beyond the scope of the study. This report addresses technical and regulatory issues relating to the safe removal of offshore structures and minimizing harm to living marine resources. HOW THE STUDY WAS CONDUCTED The committee initiated the study with briefings from MMS and NMFS representatives involved in overseeing offshore removal activities. Experts from government, industry, and the research and environmental communities were invited to present information and insights on present and alternative methods of removal; the costs, reliability, safety, and measures for mitigating damage to the environment; and on regulatory issues, including possible changes in existing regulations. The committee reviewed available scientific literature on the effects of removals on living marine resources and invited representatives of other users of the marine environment, including the fishing, shrimping, boating, and recreation communities, to present their concerns about the effects of explosive removals on their activities and on the Gulf of Mexico ecosystem. The committee also heard presentations and obtained information from private companies about new technologies for nonexplosive removals and devices to mitigate the damage from explosions to marine animals. A notice was issued in the Federal Register offering interested parties the opportunity to contribute information on all the major issues in the study. A copy of the notice and a list of those who responded can be found in Appendix B. This information was used by the committee in its analysis. The report is not intended as a sourcebook on removal technology but as an assessment of the current status of explosive, nonexplosive, and mitigation techniques. The objective of this assessment is to formulate a strategy to ensure that as little harm is inflicted on the environment and on living marine resources as is compatible with safe, cost-effective operations. ORGANIZATION OF THE REPORT The report represents a synthesis of information gathered by the committee through briefings, review of the literature,
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AN ASSESSMENT OF TECHNIQUES FOR REMOVING OFFSHORE STRUCTURES technical presentations, analysis, and review of additional information gathered from interviews and articles. The Executive Summary is a synopsis of the report. Chapter 1 is an overview of the status of platforms at the present time and the regulations governing removals. Chapter 2 is an assessment of alternative cutting techniques. Chapter 3 is a discussion of technical considerations relevant to the selection of particular removal methods. Chapter 4 presents the environmental effects of current removal technologies. Chapter 5 is a comparative summary of the costs and benefits of alternative approaches to removals. Chapter 6 presents the major conclusions and recommendations that follow from the findings of the investigation. Appendices provide the reader with additional background information, a list of individuals who made presentations to the committee, the respondents to the Federal Register notice, and biographies of committee members. This report is intended as a guide to the Minerals Management Service for making decisions about regulations governing the removal of offshore structures and about strategies for encouraging the use of techniques that will decrease damage to the environment and to living marine resources. ACKNOWLEDGMENTS The committee wishes to thank the federal liaisons, Charles Smith and Mary Ann Turner of the Minerals Management Service and Gregg Gitschlag of the National Marine Fisheries Service, for invaluable information on agency activities and perspectives on the issues under examination in this study. Other staff members of both agencies also made timely and enthusiastic contributions of time and information to the committee. Special thanks are also extended to individuals who spoke to the committee on behalf of professional and public interest groups (see appendix C). These presentations enabled the committee to gasp the broader context in which the technical issues are embedded. REFERENCES GAO (U.S. General Accounting Office). Offshore Oil and Gas Resources: Interior Can Improve Its Management of Lease Abandonment. Washington, D.C.: U.S. Government Printing Office. MMS (Minerals Management Service). 1995. Offshore Statistics. First Quarter, 1995. Washington, D.C.: U.S. Department of the Interior.
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