Executive Summary

More than 20,000 miles of marine pipelines lace the coastal waters of the United States, nearly all in the Gulf of Mexico, with a few hundred miles off the coasts of Southern California and Alaska. Since its first ventures into the shallows in the early 1950s, the pipeline industry has steadily improved its designs, materials, and techniques for construction, operation, and maintenance. Today pipelines are operated with confidence in waters as deep as 1,700 feet, with near-term plans for 3,000 feet. Marine pipelines carry about one-fourth of the nation's gas production and one-ninth of its crude oil.

Yet several dramatic accidents in the late 1980s raised new public concerns about the safety and integrity of marine pipelines. These events, and in particular two separate fatal incidents in which the fishing vessels Sea Chief and Northumberland, in shallow waters, struck pipelines that were no longer properly buried, drew attention to the fact that pipelines must share the waters with some of the nation's busiest ports and most productive fisheries, and must retain their integrity for decades in the face of frequent storms, coastal erosion, and, in California, seismic activity. These and other factors have led owners and regulators to ask whether the practices and standards that evolved over the past 40 years are adequate today. Hurricane Andrew, by closing down much of the marine pipeline network in the Gulf of Mexico for weeks in late 1992, brought home the economic impact of interrupted service, and the vital importance of the integrity of the marine pipeline system for the long term.

To gain fresh perspective on these risks, the Minerals Management Service (MMS) of the U.S. Department of the Interior and the Office of Pipeline Safety (OPS) of the U.S. Department of Transportation requested that the Marine Board conduct an interdisciplinary review and assessment of the many technical, regulatory, and jurisdictional issues that affect the safety of the marine pipelines in U.S. offshore waters. The Committee on the Safety of Marine Pipelines, under Marine Board auspices, accordingly reviewed the causes of past pipeline failures (except for seismic activity); the potential for future failures; and means of preventing or mitigating them, including operational measures, inspection techniques, data collection efforts, and improvements in the regulatory framework. For the committee, the term “safety” encompasses all of the potential consequences of pipeline failure: human injury or death, environmental pollution, and property damage.



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IMPROVING THE SAFETY OF MARINE PIPELINES Executive Summary More than 20,000 miles of marine pipelines lace the coastal waters of the United States, nearly all in the Gulf of Mexico, with a few hundred miles off the coasts of Southern California and Alaska. Since its first ventures into the shallows in the early 1950s, the pipeline industry has steadily improved its designs, materials, and techniques for construction, operation, and maintenance. Today pipelines are operated with confidence in waters as deep as 1,700 feet, with near-term plans for 3,000 feet. Marine pipelines carry about one-fourth of the nation's gas production and one-ninth of its crude oil. Yet several dramatic accidents in the late 1980s raised new public concerns about the safety and integrity of marine pipelines. These events, and in particular two separate fatal incidents in which the fishing vessels Sea Chief and Northumberland, in shallow waters, struck pipelines that were no longer properly buried, drew attention to the fact that pipelines must share the waters with some of the nation's busiest ports and most productive fisheries, and must retain their integrity for decades in the face of frequent storms, coastal erosion, and, in California, seismic activity. These and other factors have led owners and regulators to ask whether the practices and standards that evolved over the past 40 years are adequate today. Hurricane Andrew, by closing down much of the marine pipeline network in the Gulf of Mexico for weeks in late 1992, brought home the economic impact of interrupted service, and the vital importance of the integrity of the marine pipeline system for the long term. To gain fresh perspective on these risks, the Minerals Management Service (MMS) of the U.S. Department of the Interior and the Office of Pipeline Safety (OPS) of the U.S. Department of Transportation requested that the Marine Board conduct an interdisciplinary review and assessment of the many technical, regulatory, and jurisdictional issues that affect the safety of the marine pipelines in U.S. offshore waters. The Committee on the Safety of Marine Pipelines, under Marine Board auspices, accordingly reviewed the causes of past pipeline failures (except for seismic activity); the potential for future failures; and means of preventing or mitigating them, including operational measures, inspection techniques, data collection efforts, and improvements in the regulatory framework. For the committee, the term “safety” encompasses all of the potential consequences of pipeline failure: human injury or death, environmental pollution, and property damage.

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IMPROVING THE SAFETY OF MARINE PIPELINES The committee found that the marine pipeline network does not present an extraordinary threat to human life. Pipeline accidents involving deaths or injuries are disastrous, but rare. The most widespread risks are due to oil pollution, mainly from pipelines damaged by vessels and their gear. These risks are not precisely quantifiable with the data available; however, they generally can be managed with available technology, and without major new regulations, if enforcement of some current regulations is improved. Better coordination among operators and regulators in gathering safety data, assessing risks, and planning and implementing risk management programs is the most fundamental requirement. SHARED REGULATORY JURISDICTION Safety regulation of marine pipelines is shared by federal and state agencies. In the federal waters of the outer continental shelf (OCS), the OPS regulates nearly 13,000 miles of so-called transmission pipelines (generally larger, longer pipelines that carry oil and gas ashore), and the Minerals Management Service about 4,000 miles of production pipelines (associated with production and initial processing). In state waters, OPS has jurisdiction over transmission pipelines, and the states over production pipelines. OPS certifies state agencies to enforce its regulations for intrastate transmission pipelines. MMS has extraordinarily broad regulatory authority. Under the Outer Continental Shelf Lands Act of 1978 (43 U.S.C. 1334), it issues permits and rights-of-way for all OCS activities, including pipelines, to ensure “maximum environmental protection.” In pursuit of this goal, the agency sometimes also applies its regulatory requirements to OPS-regulated pipelines that begin on the OCS and extend to state waters. Implementation of the Oil Pollution Act of 1990 (P.L. 101-380) will expand MMS's authority further, making the agency responsible for ensuring oil spill prevention and response capability for all pipelines off the nation's shores. Other federal, state, and local agencies are involved. The U.S. Army Corps of Engineers issues permits for pipeline crossings of waterways, shorelines, and navigation fairways. The U.S. Coast Guard may declare pipelines hazards to navigation; it also conducts annual safety inspections of ports, including pipelines, and may close facilities that fail to meet its standards. State and local agencies issue permits for coastal activities, under their coastal zone management plans. SAFETY EXPERIENCE Analysis of past pipeline failures is difficult, because data collection by federal and state agencies has been inconsistent and incomplete. MMS, OPS, and the Coast Guard all receive reports on pipeline failures for their particular purposes, but have never assembled a coordinated data base.1 Most state regulatory agencies have only rudimentary records, with the exception of California. Only for the Gulf of Mexico OCS did the committee find an organized and reasonably complete data base on pipeline failures, their causes, and their consequences. Even that information is insufficient to establish such important statistical connections as those between rates of corrosion leaks and pipeline 1   This committee uses the term “failure” to refer generally to any pipeline damage required to be reported to safety regulators. Such damage ranges from small pinhole leaks caused by corrosion to major failures resulting in fires, explosions, or large oil spills.

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IMPROVING THE SAFETY OF MARINE PIPELINES age or product carried; and this information cannot be used to find patterns in the locations of corrosion failures or anchor damage that would help in setting risk management priorities. Several important patterns do appear, however: Corrosion, although it was the reported cause of nearly half of the 1,047 OCS pipeline failures recorded between 1967 and 1990, produced only about 2 percent of the pollution from pipelines. Damage from vessels (and especially from anchors and groundings) is dramatically more significant than corrosion as a source of pollution and other consequences, including deaths and injuries. Anchor damage alone accounted for 90 percent of the pipeline-related pollution on the Gulf OCS. A very few incidents have produced most of the pollution. The largest 11 pipeline spills, all caused by vessels, accounted for 98 percent of the pollution from pipelines. Deaths and injuries are rare. Six incidents, over 24 years, resulted in all of the deaths (24) and serious injuries (17) associated with pipeline failures. (The committee considered only deaths and injuries associated with pipeline failures; casualties in routine operations and maintenance or in production activities were outside its charge.) It must be emphasized that these patterns emerge from incomplete data. Most importantly, except for the data on deaths and injuries, they do not reflect experience in state waters. MAINTAINING THE INTEGRITY OF MARINE PIPELINES Although it is not a major source of oil pollution or other safety consequences, corrosion remains a troublesome inspection problem. Much of the pipeline system has remained in service for more than 30 years, thanks to improvements in corrosion control and leak detection; small pinhole leaks, however, are a continuing concern. Repairs and inspection are costly for underwater pipelines, and the industry accordingly emphasizes prevention of damage and deterioration. To limit external corrosion, pipelines are coated and have cathodic protection systems, which apply a small electrical current to counteract the electrochemical interaction of pipeline steel and seawater at any coating defects that may develop. The systems are designed to provide uniform protection for at least 25 years, and are renewed as necessary. The uniform electrochemical characteristics of seawater make external corrosion protection simpler than it is on shore or on pipeline areas that are intermittently immersed, such as risers on platforms. Verifying the adequacy of protection, on the other hand, is more difficult offshore than on shore because access points are more limited. Internal corrosion is more difficult to locate and quantify. Marine pipelines, to varying degrees, carry corrosive mixtures of brine, microorganisms, and other materials along with the hydrocarbons. Operators monitor the corrosivity of pipeline fluids, injecting corrosion inhibitors as needed and scheduling runs with internal cleaning devices called “pigs.” Furthermore, operators can usually predict the circumstances in which internal corrosion will occur, so that specific inspection and remediation techniques can be used in situations where they will be most effective. In-line internal inspection devices, or “smart pigs,” have been in use, with steady improvement, for more than 20 years. These instrumented devices transit pipes and measure and record changes in magnetic flux or ultrasonic signals to indicate cracks, dents,

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IMPROVING THE SAFETY OF MARINE PIPELINES corrosion pits, or other problems. They have seen increasing use in pipelines onshore, and in a few marine pipelines. However, they are limited in several ways by the nature of offshore operations. Physical access to suspected faults is more difficult and costly offshore than onshore, particularly because false indications of faults are common. In addition, most marine pipelines physically cannot accommodate these large (8 to 12 feet long) devices, because of their tight bends and multiple subsea pipeline connections. Finally, existing offshore platforms often have little or no room for the bulky launching and receiving fittings required by smart pigs. (California is a special case; because most marine pipelines there run directly to shore, with relatively few lateral tie-ins to other pipelines, regulators require the use of smart pigs there as a matter of course.) The smaller and more accurate devices of the future are likely to see increasingly wide use offshore. Leak detection options for operating pipelines are varied, depending on operational and environmental conditions: Visual detection of gas bubbles or oil sheens, during periodic overflights, can detect small or large leaks, but may take several days, depending on the frequency of overflights. Manual line-balance calculations, comparing volumes delivered into a pipeline system with volumes delivered out, are nearly as sensitive as visual detection, and are quicker to indicate problems. These techniques are not applicable to gas pipelines, owing to the pressure and temperature variations of natural gas. Line-balance calculations made automatically by supervisory control and data acquisition (SCADA) systems, which remotely monitor and/or control key operating parameters, can detect even small leaks in liquid lines, provided they have simple geometries and minimal variations in pressure. (Detection of smaller leaks takes longer.) They require meters at inputs and outputs to the pipeline system. A growing number of marine pipelines—and nearly all transmission pipelines—have SCADA systems. “Setpoint-limit” control systems, which use changes in pressure or flow rates to signal leaks, can detect large leaks promptly, but require fairly steady flow conditions, and are not appropriate for pipelines with multiple inputs and wide variations in flow. Leak detection thus involves a number of coordinated and complementary techniques. No one system or combination is sufficient for every pipeline. Timely notification is as important as timely detection. The discoverer of a leak may find it difficult to identify and establish the precise location of the leaking pipeline, and notify the operator or operators likely to be affected. (It is commonly necessary to shut down in an orderly way the pipelines and platforms injecting into the leaking pipeline.) A more effective process of notification is needed. AVOIDING OUTSIDE INTERFERENCE WITH PIPELINES The most significant pipeline failures, as noted earlier, are those that result from damage by vessels and their gear. Impacts of anchors, nets, trawl boards, and hulls of cargo, fishing, and offshore service vessels and mobile drilling rigs can lead to major pollution incidents, costly repairs and replacements, and even injuries and deaths. No available sensor technology allows moving vessels to detect pipelines at a distance in time to avoid them. While satellite-based location technology is improving rapidly, and is now accurate enough to be used to reduce the risk of vessel and pipeline

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IMPROVING THE SAFETY OF MARINE PIPELINES interaction, the benefits of this technology can seldom be realized since older pipelines are often inaccurately charted. It is therefore incumbent on the operators of pipelines to anticipate interactions with vessels. In some cases, such as the anchoring of supply boats near platforms, fixed mooring systems for service vessels and improved communications between platforms and vessels can provide protection. In most areas, sufficient pipeline burial (pipes are placed in a trench but not covered over) is the only practical way to reduce the chance of interactions with vessels. For this reason, regulatory standards and engineering practice require pipelines to be buried below the bottom (generally by at least 3 feet) in waters less than 200 feet deep, with coatings of adequate weight to keep them in place. But occasionally, and in rare cases tragically, they become exposed. A recent survey ordered of OPS-regulated pipelines found that 1.7 percent of the pipeline mileage in less than 15 feet of water (enough to accommodate the drafts of large fishing and service vessels) had less than one foot of cover. (The survey, ordered by Congress in the wake of the Sea Chief and Northumberland accidents, was an attempt to shed light on the potential for additional accidents of that kind.) Burial in the Gulf of Mexico is complicated by the area's coastal dynamics, which feature large movements of sediments and a general pattern of shoreline erosion and retreat, modulated by severe storms. Pipelines in shallow water and those near the shore must be inspected regularly to ensure that they remain adequately covered. PLACING RESPONSIBILITY FOR SAFETY By law, the responsibility for safety lies with the operator, not the regulator. Regulatory standards are minimum requirements and must be supplemented by sound engineering and operating practice. Mere compliance is not enough. Every pipeline operator must appreciate the unique circumstances affecting each pipeline, and take the necessary steps to control risk. The industry as a whole must recognize that the entire offshore oil and gas industry could be severely weakened by major pollution incidents or fatal accidents resulting from pipeline failures. This observation does not minimize the importance of a strong and consistent regulatory framework. Regulatory agencies are responsible for setting appropriate policies for risk management on the basis of objective risk assessments. To do so, they need detailed and comprehensive information about pipeline failures, and they need the engineering knowledge to translate their priorities into standards that provide cost-effective solutions. In the case of marine pipelines, where several agencies are involved, they need a consensus about their priorities. MAJOR CONCLUSIONS AND RECOMMENDATIONS The safety record of marine pipelines is a good one, but it can be improved. During the late 1980s, the Gulf of Mexico OCS experienced about one reportable pipeline failure every five days. Most of these failures were small leaks of gas or small oil spills caused by corrosion. Still, transmission and production pipelines account for about 98 percent of all the oil spilled by OCS oil and gas operations (nearly 11,000 barrels annually from the late 1960s to the late 1980s).2 Although it is estimated that petroleum hydrocarbons (including crude oil and its refined products) enter the Gulf of Mexico from river and 2   This average obscures great variation from year to year.

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IMPROVING THE SAFETY OF MARINE PIPELINES stream runoff and from natural seeps in significant volumes (greater than the spillage from offshore operations and accidents), offshore oil and gas operations and tank vessel accidents are two areas where preventive action can possibly be effective in reducing pollution. The volume of oil that enters the Gulf from the oil and water mixture produced from offshore wells (known as “produced waters”) is estimated to be the largest source of oil into the Gulf from offshore oil and gas operations (which do not include ship transportation). This report addresses the second largest source of spillage from offshore oil and gas operations, that from pipeline accidents and line failures. Accidental pipeline spills have released more volume than offshore drilling accidents during the past ten years. Tank vessel and tank barge accidents are another source of spills which, like pipeline accidents, result in widely varying annual volumes of oil spilled into the Gulf. The great uncertainties in rates from source to source, owing to large annual variations (as in the case of tanker spills) and lack of data (in the case of runoff) make quantitative comparisons about oil pollution in the Gulf of Mexico meaningless. Improvement depends on better information, to put safety planning on a sound basis. Pipeline failures and spills are reported to several different agencies, which have different reporting formats and information requirements. No agency coordinates the collection of information. The available data on failures of offshore pipelines are correspondingly incomplete. The responsible agencies must improve the process of information gathering, archiving, analysis, and reporting. The committee, therefore, recommends that the regulatory agencies involved develop a common safety data base, covering both state and federal waters, andperiodically review their data requirements. The focus should be on collecting,archiving, analyzing, and reporting safety data with the intent of improving design and operating regulations. The extended data base should include the information needed for risk and cost-benefit analysis. MMS, which has the greatesttest experience and resources in data gathering, should coordinate this effort. Even in the absence of better safety data, safety planning can be improved. Modern risk analysis methods, using incomplete data supported by inferences and expert opinion about the nature and distribution of risks, can clarify priorities for risk management. For example, the risks to human safety and to the environment due to failures of marine pipelines are not uniform across the Gulf of Mexico. Resources being limited, a risk analysis approach that compares risks in different geographic areas (or “zones”) would allow cost-effective risk management decisions. In this way, regulations can be developed to address safety everywhere and provide the basis for strengthening regulations in high-risk areas. The goal is a consistent risk management strategy that involves both regulatory agencies and the pipeline operators in the process of reducing human and environmental risks. The committee recommends that safety regulations be based on sound risk analyses and cost-benefit analyses. Specifically, regulatory agencies should agree on a consistent risk management strategy for setting priorities about human safety criteria, and about the use of cost-benefit analysis for the reduction of property and environmental damage. A zone-based risk analysis model, based on the zonation approach outlined in Chapter 3 of this report, should be developed on the basis of currently available information and then be regularly updated, to

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IMPROVING THE SAFETY OF MARINE PIPELINES help determine whether regulations should be revised, strengthened, or relaxed and to assist in establishing priorities for the operational use of resources by both government and industry for enhancing pipeline safety (such as inspection coverage and frequency, use of internal inspection devices, and establishment of burial depths for areas having high erosion rates). Enforcement of safety regulations also reflects a lack of coordination among agencies. This situation is largely related to the great differences in the scope and approach of the enforcement programs of OPS and MMS. OPS is responsible for over 1.7 million miles of interstate and intrastate pipelines on land and under the waters of the United States. The marine portion of the OPS jurisdiction is small, consisting of nearly 13,000 miles of pipelines (in the OCS), or less 1 one percent of the total OPS mileage, and presents little risk to public safety and the environment compared with land lines that traverse densely populated and industrial urban areas and are exposed to frequent threats to their system integrity. In contrast, the 4,000 miles of pipeline under MMS jurisdiction are all in the marine environment. The marine inspection resources assigned by each of the two agencies and the approaches taken to inspection reflect the differences in the scope of their individual regulatory responsibilities. MMS assigns 70 inspectors to the Gulf of Mexico region to make regular on-site inspections of pipeline maintenance and safety systems and spot inspections of construction and repair activities. By comparison, OPS assigns only 2 of the 30 inspectors on their staff to this region. Although OPS also has the services of approximately 250 state inspectors who are assigned (by agreement with the OPS) to both interstate and intrastate pipeline inspection, these personnel are not available for OCS inspection assignments. OPS inspection efforts are conducted primarily through periodic audits of company records. Although, these differences in resources and approaches focused on marine pipeline inspection reflect differences in the physical location of facilities and the safety issues faced by the two agencies, it appears likely that OPS enforcement personnel are too few to cover adequately the 13,000 miles of marine pipelines and more than 160 operating companies in the Gulf of Mexico region of the OCS that are under OPS jurisdiction. To make better use of inspection resources and help integrate enforcement of MMS and OPS marine pipeline safety regulations, the committee recommends that enforcement of OPS regulations offshore be performed by the MMS, through an interagency agreement or redefinition of the memorandum of understanding that defines the jurisdictional division between OPS and MMS. Such a system would continue OPS's role in regulating offshore pipelines, while strengthening the application and enforcement of such regulations by bringing to bear MMS's greater resources. Another regulatory discrepancy is apparent in the MMS and OPS requirements for internal inspection of pipelines. MMS, under its law requiring the use of the “best available and safest technology,” has established a general requirement for the use of in-line inspection devices (generally known as smart pigs) where practicable. OPS is studying the matter, under congressional mandate. The committee finds that the technology of smart pigs is progressing, and that these devices are seeing increasing use onshore. However, the vast majority of today's marine pipelines cannot physically accommodate smart

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IMPROVING THE SAFETY OF MARINE PIPELINES pigs, and modification of pipelines generally would be impractical and uneconomic. In addition, the current devices are relatively inaccurate in locating flaws. Because the costs of verifying suspected flaws are much greater offshore than onshore, this inaccuracy is a greater handicap. The use of smart pigs offshore will not be widely practical until further technical improvements are made, especially in the reliability and accuracy of three-dimensional anomaly measurement and in the compactness and maneuverability of smart pigs themselves. The committee recommends that marine pipelines already constructed be exempted from federal or state requirements for the use of currently available smart pigs for external or internal corrosion detection. New medium- to large-diameter pipelines running from platform to platform or platform to shore should be designed to accommodate smart pigs whenever reasonably practical. Pipeline operators and regulators should continue to assess developments in smart pigging technology and seek cost-effective opportunities for its use. Detecting and limiting leaks quickly is as important as preventing them in the first place. A variety of techniques is available. Periodic aerial surveillance can detect leaks of all sizes, but sometimes with a delay of days to weeks. Setpoint-limit control systems (which monitor changes in pressure or flow rates) can detect large leaks, but are not effective for pipeline systems with routinely varying pressures and flow rates. For liquid pipelines, manual or automated line-balance calculations (comparing volumes in with volumes out) can detect small to large leaks, with speed and accuracy that depend on the complexity of the pipeline system and its operation. Manual calculations are generally made only once per day, while automated calculations may be made more frequently (with substantial additional costs for the necessary monitoring and communications equipment). Many leaks are first detected through visual sightings by parties other than the pipeline operators. The detector of a leak generally cannot identify the operator of the pipeline. Often there is no agency or entity that can establish the responsible party in a timely fashion. The responsible operator in turn, once made aware of a leak, can have difficulty contacting in a timely manner all connecting pipeline and platform operators who must take action. Pipeline operators should use a combination of leak detection methods to ensure timely detection of a broad range of leaks. Setpoint-limit control systems, where practical, should be used to provide quick detection of relatively, large leaks. Line-balance calculations— either manual or SCADA-based—should be conducted at least daily, where practical, to monitor pipeline systems for small- to medium-sized leaks (which can be detected in this way with a time delay of 1 to 24 hours).Periodic visual surveillance (with a time delay of 1 hour to 2 weeks) should be used to detect very small leaks and those that have gone undetected by other means. The method chosen will depend partly on the product transported, the throughput of the pipeline system, the potential consequences of leaks in particular locations, and the nature of the pipeline system's operations (such as its relative stability of operating conditions and its location and accessibility by personnel). MMS should coordinate an effort by appropriate federal and state regulatory

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IMPROVING THE SAFETY OF MARINE PIPELINES agencies and industry to establish a system through which leaks detected by thirdparties can be reported to a single agency or notification center with continuouscoverage around the clock. This one central location should have a comprehensive data base permitting easy identification of the operator of any marine transmission or production line based on the reported sighting location. All maritimeentities should be encouraged to use this single reporting center. Pipeline operators, in turn, should have 24-hour telephone numbers or a means of immediatelycontacting all other pipeline and platform operators who must take action. No sensor technology is available to permit moving vessels to detect nearby pipelines at a distance, and thereby avoid them. Location-determining technologies are too inaccurate. However, there are operational measures by which vessels can lessen the risks of inadvertently interfering with pipelines. An obvious but difficult problem is the control of the mooring of supply and service vessels in areas adjacent to offshore platform installations. A specific risk is that these vessels may drop anchors on nearby pipelines or flowlines, or interfere with pipeline risers. Clear communications between vessels and offshore platform operators would help avoid these risks. In areas where supply and service vessels operate adjacent to fixed platforminstallations associated with high densities of pipelines or flowlines, permanentmooring systems should be considered. In other circumstances, platform operators should be required to provide detailed and timely information to vessel operators on the configurations of local pipelines or flowlines, so that the vesselscan anchor in designated areas. To lessen the risks of damage further in thesecongested areas, new pipelines should be installed whenever possible in well-defined “corridors.” In shallow waters (generally less than 200 feet deep), the best protection against the interference of vessels and pipelines, generally, is burial of the pipelines, with enough weight coating to keep it in place. In the shifting, often unconsolidated coastal sediments and eroding shorelines of the Gulf of Mexico, however, achieving and maintaining adequate burial requires care and vigilance. Pipeline installation must take into account detailed knowledge of soils, currents, and shoreline processes, so the pipeline can be buried and weighted to keep it in place, even if its surrounding soils are fluidized by currents and wave action. The committee has no information leading it to believe that the initial burial depths required by regulatory agencies are either adequate or inadequate. Anecdotal evidence suggests that initial cover may be adequate, but loss of cover over time, through erosion or fluidization of surrounding soils, exposes pipelines to interference by vessels. Pending further study, the current regulatory standard for depth of initial burial must be considered adequate, if it is maintained through the life of the pipeline. Much of the Gulf shoreline is eroding rapidly. This erosion may expose pipelines buried at installation and can be accelerated by the trenching used to install pipelines across the shoreline. The directional bore method of installing pipelines under beaches without breaking the surface minimizes this problem and is also attractive from the standpoint of construction and maintenance costs.

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IMPROVING THE SAFETY OF MARINE PIPELINES The need for periodic inspections of pipelines, to ensure that they do not lose cover or become exposed, is not addressed in standard industry practice or in regulations. Geotechnical studies of soil conditions, with sampling at intervals determined bylocal site conditions, should be required as a condition of marine pipeline construction permits. Soil core samples should be analyzed and interpreted for design parameters relative to weight, specific gravity, grain size, shear strength,and potential for liquefaction and fluidization. Permitting and regulatory agencies should work with industry to develop criteria for specific gravities of marinepipelines in varying soil environments. To provide baseline data for subsequent depth of cover and bottom status surveys,newly installed pipelines should be surveyed at once and their depths of coverrecorded, with reference to Global Positioning System locations. Maintenance ofthis baseline data should be required by the agencies issuing the constructionpermits. All agencies involved in the permitting of pipelines crossing shorelines shouldrequire the use of the directional bore installation method wherever feasible. In waters less than 15 feet deep (where interactions between vessels and pipelinesmay, albeit rarely, expose vessels and crews to fire and explosion), periodicdepth-of-cover surveys in the Gulf of Mexico should be scheduled according tothe specific local shoreline and seabed dynamics, and the passage of severestorms, according to the criteria outlined in Chapter 5 (“Periodic Depth of CoverInspections). In brief, a baseline depth of cover measurement should be established for each pipeline, and subsequent inspections should be made —at intervals determined by local shoreline and seabed dynamics and storms—to determine the direction and rate of change of the depth of cover. Later inspection intervals canbe lengthened or shortened according to this rate; this approach might be called“self-adjusting.” Pipeline operators and regulatory and permitting agencies should conduct studies to determine the appropriate standards for initial depth of burial under various shoreline and seabed conditions, using the results of the recommended periodic depth-of-cover surveys. Abandonment of marine pipelines will continue to increase as producing fields reach maturity and are shut-in. Most of these abandoned lines are in shallower state waters. A properly abandoned pipeline poses no risk to public safety or to the environment. Abandoned pipelines have not been reported to cause any loss of life or significant property or environmental damage. The current practice of remediating abandoned pipelines once they come to the attention of the operators is adequate, so long as operators are vigilant and responsive. A more aggressive periodic inspection program is not warranted until, and unless, public safety or the environment is shown to be adversely affected. The committee recommends that pipeline abandonment standards include a requirement for a one-time inspection at the time of abandonment to verify that

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IMPROVING THE SAFETY OF MARINE PIPELINES abandonment requirements were met. Removal, continuing surveillance, or periodic inspection of abandoned pipelines should be required only where uniquepublic safety or environmental conditions exist, such as rapid coastal erosion inareas of high vessel traffic. Pipeline operators should take timely corrective action when they are made aware of problems caused by their abandoned pipelines.Remediation should be the responsibility of the owner or successors until orunless the abandoned pipeline is removed.