2011 Maui Pipeline Failure Technical Investigation Report

Transcription

1 2011 Maui Pipeline Failure Technical Investigation Report Prepared for Maui Development Limited by Vector Gas Limited, Technical Operator for the Maui Pipeline April 2012

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3 CONTENTS Executive Summary... 4 A. Introduction and Scope... 7 B. Key Findings... 7 C. Investigation Description... 8 D. Findings of Investigation Streams... 9 E. Cause of Pipeline Failure F. Applicable Legislation G. Technical Operator Pipeline Management H. Historical Information I. Implications for Other Pipeline Sections J. Ongoing Threat At Pukearuhe K. Options for Additional Integrity Assessment L. Recommendations Appendix 1 Photos... 19

4 EXECUTIVE SUMMARY 1. On the evening of Monday 24 October 2011, a gas escape was confirmed adjacent to the Maui pipeline in the Pukearuhe area, north Taranaki. This set in train a course of events that over the next five days saw an emergency response team mobilized to determine the source of the leak, the pipeline closed, gas supply to large parts of the North Island curtailed, the pipeline excavated, a damaged section of the pipe removed and replaced, and the gas supply restored. 2. Vector Gas Limited, as Technical Operator for the pipeline for Maui Development Limited (MDL), has undertaken a technical investigation of the cause of the failure. 3. Vector Limited acquired NGC New Zealand Limited (now Vector Gas Limited) in 2006 which under the terms of a contract signed in 1974, provides operation and maintenance services as Technical Operator of the Maui pipeline to MDL. Key Findings 4. In 1977, while the Maui pipeline was being built, the Kapuni pipeline, then owned by the government through The Natural Gas Corporation of New Zealand, failed in the Pukearuhe area, close to the 2011 failure site. On investigation, it was discovered that the Kapuni pipeline was situated in a slow-moving landslide. Construction of the Maui pipeline at Pukearuhe was suspended and the route was re-designed by the Ministry of Works, which was undertaking the project, to take the pipeline clear of the landslide. The current investigations established that 25 m of the Maui pipeline is presently within the edge of the landslide. It is unclear whether the landslide has grown in width to now encompass the pipeline or whether the exact extent of the landslide was not fully understood in 1977 when the Maui pipeline was laid. The surface area towards the middle of the landslide has moved approximately 1.75 m over the previous 33 years. It is unclear what movement has occurred at the edge of the landslide where the pipeline is located but it may be considerably less than 1.75 m. 5. The Technical Operator s geotechnical advisors, Institute of Geological and Nuclear Sciences Limited (GNS), undertook an assessment of geophysical risks to the Urenui to Otorohanga section of the pipeline in This determined the threat risk at Pukearuhe to be intermediate (now low). The Technical Operator and MDL followed GNS consequent recommendation to continue monthly line flights to monitor the pipeline in this area and these identified no issues. 6. In October 2011 the pipeline failed suddenly due to overload. The failure was not contributed to by any material property, material defect, or flaw in the pipe. 7. The pipeline overload was caused by the landslide movement Maui Pipeline Failure Technical Investigation Report Page 4 of 19

5 8. The repaired section of pipeline remains within the landslide, but with mitigation measures implemented to prevent failure in the short to medium term, until a long term solution is developed and implemented. 9. The longer section of the pipeline with difficult terrain conditions (Urenui to Otorohanga) has been reviewed since the failure in October 2011 in light of the further expert advice obtained and no new threats identified. Some existing threats require more detailed assessment in the light of the Pukearuhe failure. 10. Compliance with relevant statutory industry standards and health and safety obligations for the operation and maintenance of the Maui pipeline is externally certified by Lloyds Register. Recommendations 11. The Technical Operator recommends that MDL considers the following: (a) Following a section of the pipeline being found to be within the edge of a landslide, mitigation measures have been taken at the site of the pipeline failure to ensure pipeline integrity until a long term solution is developed and implemented. These mitigation measures include: relieving the pipeline from built up stresses; embedding the pipeline in a loose granular material to facilitate any ongoing movement; improved and additional drainage of the landslide and surrounding areas; and ongoing monitoring. A long-term solution for resolving the impact of the landslide on the pipeline at Pukearuhe is now required, and development of the solution is recommended to commence in (b) The pipeline is managed in accordance with required regulatory controls, industry standards, and key processes including: High Pressure Pipeline Safety and Operating Plan; Pipeline Integrity Management Plan (PIMP); Safety Management Studies; MDL Annual Maintenance Plan; and Maui Technical Operator Budget Governance Framework. Routine inspections are also carried out including: monthly line flights; geotechnical assessments; and intelligent pigging Maui Pipeline Failure Technical Investigation Report Page 5 of 19

6 To provide additional integrity assessment knowledge of the Urenui to Otorohanga section of the pipeline, two key areas of focus are recommended: a one-off enhanced intelligent pigging to assess pipeline geometry and precise geospatial location, in addition to standard corrosion detection; and further geotechnical assessment into the pipeline s sensitivity at Pukearuhe and other potentially similar areas to the effects of landslides and consideration of the findings as appropriate into the Safety Management Study processes Maui Pipeline Failure Technical Investigation Report Page 6 of 19

7 A. INTRODUCTION AND SCOPE 12. The Maui pipeline is owned and operated by MDL on behalf of the Maui mining companies. It runs for 291km from Oaonui in western Taranaki, where gas and condensate from the off-shore Maui platform come ashore and are processed, to Huntly in the Waikato (see photos in Appendix 1). A long section of the pipeline (Urenui to Otorohanga) is located in difficult terrain conditions. 13. Vector Limited acquired NGC New Zealand Limited (now Vector Gas Limited) in Vector Gas Limited under the terms of a contract signed in 1974, provides operation and maintenance services as Technical Operator of the Maui pipeline, including the gas control function, to MDL. 14. On the evening of Monday 24 October 2011, a gas escape was confirmed adjacent to the Maui pipeline in the Pukearuhe area, north Taranaki. This set in train a course of events that over the next five days saw an emergency response team mobilized to determine the source of the leak, the pipeline closed, gas supply to large parts of the North Island curtailed, the pipeline excavated, a damaged section of the pipe removed and replaced, and the gas supply restored. 15. As the owner of the pipeline, MDL has requested Vector, as the Technical Operator, to report into the cause of the pipeline failure. B. KEY FINDINGS 16. In 1977, while the Maui pipeline was being built, Kapuni pipeline, then owned by the government through The Natural Gas Corporation of New Zealand), failed in the Pukearuhe area, close to the 2011 failure site. On investigation, it was discovered that the Kapuni pipeline was situated in a slowmoving landslide. Construction of the Maui pipeline at Pukearuhe was suspended and the route was re-designed by the Ministry of Works, which was undertaking the project, to take the pipeline clear of the landslide (See section H Historical Information). The current investigations established that 25 m of the Maui pipeline is presently within the edge of the landslide. It is unclear whether the landslide has grown in width to now encompass the pipeline or whether the exact extent of the landslide was not fully understood in 1977 when the Maui pipeline was laid. The surface area towards the middle of the landslide has moved approximately 1.75 m over the previous 33 years. It is unclear what movement has occurred at the edge of the landslide where the pipeline is located but it may be considerably less than 1.75 m. (See section D Findings of Investigation Streams). 17. GNS undertook an assessment of geophysical risks to the Urenui to Otorohanga section of the pipeline in This determined the threat risk at Pukearuhe to be intermediate (now low) (See section G Vector Pipeline 2011 Maui Pipeline Failure Technical Investigation Report Page 7 of 19

8 Management). The Technical Operator and MDL followed GNS consequent recommendation to continue monthly line flights to monitor the pipeline in this area and these identified no issues. 18. The pipeline failed suddenly due to overload. The failure was not contributed to by any material property, material defect, or flaw in the pipe (See section D). 19. The pipeline overload was most likely caused by the landslide movement (See section E). 20. The repaired section of pipeline remains within the landslide, but with mitigation measures implemented to prevent failure in the short to medium term, until a long term solution is implemented (See section J). 21. The longer section of the pipeline with difficult terrain conditions (Urenui to Otorohanga) has been reviewed and no new threats identified. Some existing threats require more detailed assessment in the light of the Pukearuhe failure (See section K). C. INVESTIGATION DESCRIPTION 22. As is usual in cases like this, the damaged piece of pipe that was removed from Pukearuhe was retained to allow for testing to assist in determining the immediate cause of the failure. 23. Immediately following the failure, the Technical Operator s geotechnical advisors GNS were called to undertake various geotechnical investigations. This allowed them to undertake thorough real-time analysis of the land in which the pipeline is buried. For safety reasons, the excavation surrounding the pipe was filled in once the repairs where finished. 24. To facilitate a thorough investigation the Technical Operator established two specific workstreams which focused on identifying the cause of the failure. These were metallurgical investigations (carried out by Quest Integrity) and geotechnical investigations (carried out by GNS). 25. The Technical Operator identified two additional workstreams as a supplement to the metallurgical and geotechnical workstreams to provide further information should the metallurgical and geotechnical investigations prove inconclusive. These were a review of the 2005 intelligent pigging data to determine if there were any indications in the failure zone, and the preparation of a piping model for stress evaluation. These additional workstreams were subsequently not required as the metallurgical and geotechnical investigations are conclusive Maui Pipeline Failure Technical Investigation Report Page 8 of 19

9 26. This report also contains in sections F & G a review of Technical Operator key pipeline management processes. D. FINDINGS OF INVESTIGATION STREAMS Metallurgical 27. The metallurgical investigations were carried out by Quest Integrity, in accordance with instruction from the Technical Operator as documented on an Inspection and Test Plan. 28. Quest Integrity carried out the following metallurgical investigations: Laser scan of buckled sample to produce a 3D model; Magnetic Particle Inspection of seam weld; Chemical analysis; Fractography; Metallography; Hardness; Ultrasonic examination; and Testing to API 5 LX requirements tensile, impact etc. 29. The metallurgical investigations are now complete. Quest Integrity has reported: The initial findings, from the assessment to date [since confirmed by Quest Integrity in its final investigation report], indicate that the failure occurred as a result of overload and that condition of the pipeline prior to the failure had not been compromised by any of the following; Internal corrosion External corrosion Mechanical damage In addition, from the assessment to date [also confirmed by Quest Integrity in its final investigation report], it is considered highly unlikely that the failure was associated with any pre-existing defect in the pipe such as poor quality pipe material, poor quality welding or in-service cracking from fatigue or stress corrosion cracking. The crack formed in the pipe is very small for the amount of deformation observed. This indicates that the pipe material is highly likely to be very fine grained and tough, i.e. good quality. Overload failure will occur when the applied load exceeds the local tensile strength of the material. The local tensile stress was probably induced by the bending in the pipe and the resulting deformation. As the contours either side of the fracture are even it indicates that the cracking occurred after or during the buckling and not prior to the buckling Maui Pipeline Failure Technical Investigation Report Page 9 of 19

10 30. The Quest Integrity Mechanical Testing report concludes The results of the testing indicates that the pipe as supplied, conformed to the requirements of API 5LX (20th Edition and also confirm to the current requirements of API 5LX (44th Edition). The results of the longitudinal test did not meet the requirements of the code. This was probably a result of the pipe being deformed during the failure. For definitive longitudinal test results the test will be re-run with pipeline material which is undamaged, however these results are not relevant to the pipeline failure. Geotechnical 31. The geotechnical investigations were carried out by GNS, in accordance with instruction from the Technical Operator. 32. The report Geotechnical assessment of the site of the October 2011 Maui gas pipeline failure near Pukearuhe, northern Taranaki covers the site of the pipeline failure. The report focuses on the observations made in the exploratory trench excavations at the failure site, observations of surface geomorphological features within metres of the failure, the acquisition and analysis of relevant survey data and the immediate steps taken to mitigate further ground movement that may impact on the Maui pipeline. 33. GNS observes that the Maui pipeline failure is in the same vicinity as the 1977 Kapuni pipeline failure and is thought to be within about 50 metres of that failure. Landslide movement was considered to be the cause of the Kapuni pipeline failure. 34. The GNS report concludes that the Maui pipeline was subject to landslide movement of a large, slow-moving landslide, which had been moving for the duration of the 33 years that the Maui pipeline had been in existence. GNS reports that information from two specific survey pegs (located more to the middle of the landslide and close to each other) indicates a total movement over 33 years of m and m, and that the rate of landslide movement has increased over the years. GNS advises that it cannot determine if the movement is continuous, episodic or a combination of the two. 35. GNS also reports that a 25m section of the Maui pipeline is presently within the edge of the landslide, and that the landslide will continue to move. The report states that The lateral margin of a large landslide is clearly identifiable in the walls of the 2011 Maui pipeline repair excavation. GNS also concludes that The Maui pipeline is presently situated across the lateral margin of a large, slow-moving (mm/year) landslide. 36. GNS has identified that the adjacent Kapuni pipeline does not have any part within the landslide Maui Pipeline Failure Technical Investigation Report Page 10 of 19

11 E. CAUSE OF PIPELINE FAILURE 37. From the metallurgical and geotechnical investigations it is reasonable to conclude that: the pipeline was in sound metallurgical condition with no defects, corrosion, material properties etc which would compromise its integrity; the pipeline was embedded in the edge of a slow-moving landslide; the landslide movement has caused overloading of the pipeline; and the pipeline failed from the overload. F. APPLICABLE LEGISLATION 38. The following is a description of the applicable legislative regime for the technical aspects of Maui pipeline operation. This section is provided as an overview of the legislative provisions and operating requirements for high pressure gas transmission pipelines. 39. The Maui pipeline has legislative controls derived from both the Gas Act 1992 and the Health and Safety in Employment Act The Gas Act primarily addresses market conditions and is therefore not further discussed in this report. 41. The Health and Safety in Employment (Pipelines) Regulations 1999 require that, amongst other requirements, for a pipeline such as the Maui pipeline: there must be a pipeline manager appointed to manage the pipeline operation and supervise the health and safety aspects of the pipeline operation (Regulation 5). The Technical Operator appoints the pipeline manager for the Maui Pipeline; all practicable steps must be taken to prevent the release of hazardous vapours and gases, detect accumulations and protect pipeline workers (Regulation 6); the location of the pipeline must be clearly identifiable on land (Regulation 7); the pipeline operation must be operated and maintained in accordance with specified standards (Regulation 8) (The regulation refers to AS/NZS :1997); the pipeline and all equipment necessary for the safe operation of the pipeline must not be operated unless it has a current certificate of fitness (Regulation 11); land occupiers must be informed of contact details for matters relating to the pipeline, and for any hazards likely to be involved in respect of work in the vicinity of the pipeline (Regulation 15); 2011 Maui Pipeline Failure Technical Investigation Report Page 11 of 19

12 practicable steps must be taken to ensure that any work on, in, or around a pipeline is undertaken in such a manner as to minimise any significant hazards. The manager must be notified of any specified work that is likely to adversely affect the structural integrity or operation of the pipeline and create a significant hazard (Regulation 16); and emergency procedures must be prepared (Regulation 17). 42. As required by regulation 8 a Safety Management Study (SMS) must be prepared in accordance with NZS/AS :1997. AS :1997 has been superseded by AS :2007 and this Standard is now used by the Technical Operator for SMSs. A SMS is undertaken every 5 years and when triggered by other conditions specified in the Standard, including an event such as the pipeline failure. G. TECHNICAL OPERATOR PIPELINE MANAGEMENT 43. Compliance with relevant statutory industry standards (AS2885.1) and obligations under the Health and Safety in Employment (Pipelines) Regulations 1999 is externally certified by Lloyds Register. This certification is renewed 5 yearly (most recently on 9 June 2011) and is reviewed annually. 44. The Technical Operator manages the Maui pipeline for MDL as a Reasonable and Prudent Operator consistent with Vector s management of it s own pipelines and pipelines it manages for other parties. All annual operating and maintenance plans, procedures and budgets are approved by MDL as part of an annual planning process. 45. Key processes used by the Technical Operator to manage the Maui pipeline are set out in the following documents: High Pressure Pipeline Safety and Operating Plan; Pipeline Integrity Management Plan (PIMP); SMS; MDL Annual Maintenance Plan; and Maui Technical Operator Budget Governance Framework The PIMP sets out the pipeline monitoring and maintenance activities to be undertaken in a specified financial year. The activities support the safe and reliable operation of the pipeline systems operated and maintained by the Technical Operator, including the Maui pipeline. The PIMP is reviewed annually in accordance with the PIMP Review Process and considers monitoring data and pipeline activities from the previous year and identifies any change in risks associated with a range of threats including: third party interference; corrosion; and nature (including flooding, earthquakes and landslips) Maui Pipeline Failure Technical Investigation Report Page 12 of 19

13 Pipeline Condition Assessment 47. Pipeline material condition is primarily determined by periodic intelligent pigging, performed 10 yearly for the section which includes Pukearuhe. The most recent pigging of the failed pipeline section was in 2005 (which covered Frankley Road to Mokau Compressor Station). 48. The 2005 pigging survey reported 86 metal loss features, of which 11 were identified as significant. However, no defect required immediate remedial action, and none of these defects were in close proximity to the area of the failure. 49. As observed during excavations for corrosion repairs, the coal tar epoxy coating on this section of the Maui pipeline is considered to be in very good condition. Safety Management Studies 50. SMSs are described in AS and as such are required under regulation 8 of the Health and Safety in Employment (Pipelines) Regulations When the Pipelines Regulations were introduced in 1999 the requirement for a pipeline certificate of inspection (CofI) was introduced. To obtain a CofI a SMS in accordance with NZS/AS :1997 had to be completed by May This was done for the Maui pipeline and a CofI was obtained. A SMS is undertaken for the Maui pipeline every 5 years and most recently in late 2010 and early 2011 in accordance with AS : The SMS is an extensive study of pipeline threats and their possible impact on the pipeline, and is a systematic review undertaken by a skilled team. The pipeline is reviewed metre by metre to identify the impact of threats and to evaluate the impact of a pipeline failure on adjacent properties. 53. The outcome of the SMS is an identified list of actions made up of routine monitoring and surveillance, specified studies to provide better knowledge in areas of uncertainty and, where necessary, enhancements and repairs to improve pipeline integrity. Geotechnical Assessments 54. Landslides and coastal erosion are clearly identified threats to pipeline integrity where they are in the vicinity of the pipeline. Such threats are identified and monitored, and, where necessary, controls are established to provide adequate drainage, stability etc. 55. A specific assessment of the Urenui to Otorohanga section of the Maui pipeline was carried out in 2009 (GNS Science Consultancy Report Assessment of 2011 Maui Pipeline Failure Technical Investigation Report Page 13 of 19

14 landslide and other erosion hazards along the Kapuni and Maui pipeline alignments: Urenui to Otorohanga 2009/157). This report identified 59 landslide and other erosion hazards on both the Maui and Kapuni pipelines. Of the 59 hazards, 11 were classified as high risk, 32 as intermediate and 16 as low. The landslides occur north of the Pukearuhe area as the report states that it is apparent that the main areas of landslide related problems are those underlain by mudstone on the Maui pipeline between the Mokau and Awakino Rivers, and for both pipelines between Mahoenui and Te Kuiti. The 11 high risk threats all apply to the Maui pipeline, and 10 of them are for landslide threats. None of these high risk threats relate to Pukearuhe which was identified as intermediate (now low). The report notes that there was good consistency between sites considered as high risk at the time of construction and those considered high risk in The report further noted that many of the high risks had not yet impacted the pipeline, but they remained a potential risk to the pipelines. 56. The recommendations relating to the threats at Pukearuhe identified in the GNS 2009/157 report were already reflected in the SMS and the Technical Operator will incorporate other identified threats in the SMS review process supported by appropriate further geotechnical expert advice. 57. Immediately after the pipeline failure, the 2009 route was flown again to review the previously identified threats and identify any new ones. (GNS report Urenui Otorohanga Line-flight, 31 October 2011.) This report states that the inspection revealed no obvious signs of any increased threat to pipeline integrity since In addition the report states that no new threat locations were seen, and none of the threat levels stated in our 2009 had changed to a higher level. The report identifies a small number of existing threats (none of these relate to Pukearuhe) which should have increased monitoring or assessment and hence will be included in the review process. Line flights 58. The pipeline routes are flown by pipeline technicians each month with the objective of observing changes in ground layout or structure, recent land movements, and land activities etc that may be a threat to the pipeline. Specific ground features which are previously identified as threats are monitored on each flight. Where appropriate, flight observations are followed up with on ground assessment. 59. The GNS 2009/157 report advises that line flights are considered to be adequate for assessing changes in those threats classified as intermediate or low, as well as for identifying new threats along the pipeline. 60. The Technical Operator pipeline technicians who carry out the line flights have been trained in what to look for and how to record it. They also extensively photograph the terrain they pass over Maui Pipeline Failure Technical Investigation Report Page 14 of 19

15 H. HISTORICAL INFORMATION Pukearuhe Landslide 61. As a result of the Kapuni pipeline failure in 1977, the route of the Maui pipeline, then still in the construction stages, was re-designed by the Ministry of Works and the Kapuni pipeline subsequently re-laid along the same route. 62. From a review of the reports prepared at the time (1977/78) and subsequent GNS reports it is apparent that the geotechnical experts believed that the Maui and Kapuni pipelines had been re-routed to be outside the landslide itself (but close to it). Relevant early reports are: Engineering Geological Assessment of Gas Pipeline Routes at Site of Failure of Kapuni Pipeline, North Taranaki B. W. Riddolls NZGS Aug 1977; Maui Pipeline Project: Evaluation of As-Built Slope Stability B. W. Riddolls NZGS Jan 1978; Failure of the Kapuni Auckland high-pressure gas pipeline T. P. Thompson, NZ Engineering Journal 15 July 1978; and Maui Pipeline Project Paper to Gas Association Conference 1979 by T. G. Shadwell. 63. Later reports also support the belief that both pipelines were outside the landslide, apparently relying on information from the time of construction and no indication of landslide outside the previously indicated boundary. Later reports include: GNS Science Consultancy report 2009/157 July 2009; and Geotechnical assessment of the site of the October 2011 Maui gas pipeline failure near Pukearuhe, northern Taranaki G. D. Dellow, G. Archibald, F. Aubertin, Report 2012/75 March GNS advises that landslides may grow in size, and it cannot be excluded that this has occurred at Pukearuhe. Other Threats 65. Substantial information on threats identified at the time of construction of the Maui pipeline is contained in Ministry of Works and Development (MWD) and GNS files. Subsequent reviews and reports by GNS have referred to this information and list the observed threats on the pipeline. Such threats that are still considered current are actively reviewed in the SMS process, and are routinely monitored. 66. Whilst not contributing to the failure at Pukearuhe, it was observed during the establishment of the additional drainage on the landslide that there were 2011 Maui Pipeline Failure Technical Investigation Report Page 15 of 19

16 drainage features from the time of construction associated with the landslide that were not fully operational. The Technical Operator has noted this and will review other relevant sites to ensure that such secondary controls are identified and functioning effectively if required. I. IMPLICATIONS FOR OTHER PIPELINE SECTIONS 67. The pipeline section between Urenui and Otorohanga is the section of the pipeline with the most difficult terrain. As such it is this section which attracts the most attention from a geotechnical perspective. 68. The geotechnical review carried out by GNS in 2009 identified a series of threats, many of which were already recorded. The line flight of the same pipeline section in late October 2011 confirmed that there were no new or deteriorated threats. 69. GNS has advised that some threat locations (none relate to Pukearuhe) should now have increased monitoring and assessment post the pipeline failure. The necessary actions will be addressed in the pending review of the SMS required as a result of the failure. J. ONGOING THREAT AT PUKEARUHE 70. The repaired pipeline at Pukearuhe still sits within the landslide to the same extent as it did prior to the failure. A range of mitigation measures were taken during and after the repair, including: improved and additional drainage of the landslide and surrounding areas; embedding the pipeline in a loose granular material to facilitate movement; built up stresses in the pipeline have been relieved; and ongoing monitoring. 71. GNS states that the landslide will continue to move in the future, but it cannot predict the rate of movement. The mitigation measures are considered effective to provide a short to medium term solution, until a long-term solution is developed and implemented. GNS provides recommendations in its report for further work to improve the knowledge of the impact of the landslide on the pipeline and this work will be used to support the development of proposals for long-term solutions for MDL. K. OPTIONS FOR ADDITIONAL INTEGRITY ASSESSMENT 72. In accordance with MDL s request the Technical Operator is preparing proposals for additional integrity assessment. These proposals will focus on two key areas, being one-off enhanced intelligent pigging and additional geotechnical 2011 Maui Pipeline Failure Technical Investigation Report Page 16 of 19

17 review, and will be incorporated into the Maui pipeline planning process for consideration by MDL in accordance with normal procedure. Intelligent Pigging 73. A set of options has been prepared for MDL for an intelligent pigging of the Maui pipeline in The options include running a combination tool, comprising Caliper (Geometry), Magnetic Flux Leakage (MFL) and Geospatial Mapping (IMU) units. The Geometry tool provides detailed information about the location and size of geometrical features such as welds, valves, bends, fittings, obstructions, ovality, wrinkles and dents. The MFL tool measures metal loss in the pipe wall and the data can be interpreted to provide information on pipeline anomalies. The Geospatial mapping tool determines three-dimensional geographical co-ordinates of the pipeline, and provides information on the pipe s location in three dimensions. Geotechnical 74. Reports from GNS recommend additional geotechnical evaluation, both of the Pukearuhe landslide and other geotechnical threats. 75. As a result of the pipeline failure GNS is recommending further investigation at each landslide to resolve issues such as pipeline sensitivity to landslide creep, pipelines crossing landslide margins, and landslide movement resulting in compression of the pipeline (particularly where there is a pipeline bend nearby). L. RECOMMENDATIONS 76. The Technical Operator recommends that MDL considers the following: (a) Following a section of the pipeline being found to be within the edge of a landslide, mitigation measures have been taken at the site of the pipeline failure to ensure pipeline integrity until a long term solution is developed and implemented. These mitigation measures include: relieving the pipeline from built up stresses; embedding the pipeline in a loose granular material to facilitate any ongoing movement; improved and additional drainage of the landslide and surrounding areas; and ongoing monitoring Maui Pipeline Failure Technical Investigation Report Page 17 of 19

18 A long-term solution for resolving the impact of the landslide on the pipeline at Pukearuhe is now required, and development of the solution is recommended to commence in (b) The pipeline is managed in accordance with required regulatory controls, industry standards, and key processes including: High Pressure Pipeline Safety and Operating Plan; Pipeline Integrity Management Plan (PIMP); Safety Management Studies; MDL Annual Maintenance Plan; and Maui Technical Operator Budget Governance Framework. Routine inspections are also carried out including: monthly line flights; geotechnical assessments; and intelligent pigging. To provide additional integrity assessment knowledge of the Urenui to Otorohanga section of the pipeline, two key areas of focus are recommended: a one-off enhanced intelligent pigging to assess pipeline geometry and precise geospatial location, in addition to standard corrosion detection; and further geotechnical assessment into the pipeline s sensitivity at Pukearuhe and other potentially similar areas to the effects of landslides and consideration of the findings as appropriate into the Safety Management Study processes Maui Pipeline Failure Technical Investigation Report Page 18 of 19

19 APPENDIX 1 PHOTOS Above: Pukearuhe area Above: Waikoroa area north of Pukearuhe 2011 Maui Pipeline Failure Technical Investigation Report Page 19 of 19