Another component of the depth of cover maintenance program will be regular in-water surveys of crossings with elevated scour potential.

Transcription

1 CA PDF Page 1 of PIPELINE CONDITION ASSESSMENT To demonstrate that the pipe for conversion from natural gas to oil service will be suitable for the intended service, an EA was completed to assess the condition of the pipeline. The EA was prepared and authenticated by a professional engineer, and is submitted in accordance with CSA Z662-15, Clause (see Appendix 5-1). The EA identifies and addresses hazards the pipelines are potentially subject to, and applies TransCanada s liquid integrity management program (IMP) to the pipeline sections intended for conversion to oil service. This summary includes: an overview of the conversion pipeline and pipe coatings an outline of the phases of the integrity program (including both assessment and remediation) for the sections of pipeline identified for conversion (referred to as the conversion integrity program) a brief overview of the application of consequence assessment in the conversion integrity program a summary of the hazards assessed in the EA a summary, by conversion pipeline segment, of the hazard assessments DEPTH OF COVER Minimum depth of cover requirements for new pipeline installed along the conversion segments will meet or exceed the requirements of CSA Z (see Volume 4,.4.2: Depth of Cover). 2 For the existing gas lines to be converted, the portions of pipeline that might potentially impact a highly sensitive receptor (HSR) as delineated by contributory pipeline segments will be specifically reviewed for depth of cover and potential elevated risk of third-party damage. This will include close interval depth of cover surveys of the top-ranked contributory pipeline segments. Beyond this formalized approach, regular aerial patrols and maintenance activities will monitor for pipe exposures from erosion. Another component of the depth of cover maintenance program will be regular in-water surveys of crossings with elevated scour potential For additional information regarding the management of potentially interacting hazards, see Energy East s response to NEB 5.15 (NEB Filing ID: A4V8G6). For additional information regarding depth of cover issues, see Energy East s response to NEB 5.12 (NEB Filing ID: A4V8G6). May 2016 Page 2-1

2 CA PDF Page 2 of OVERVIEW OF CONVERSION PIPELINE AND COATING TYPE Conversion Pipeline Segments Assessed The pipe to be converted was divided into three segments for assessment based on original installation date, coating type and geographic region: The Prairies Line extends through Saskatchewan and western Manitoba. This line was constructed between 1971 and The pipe coating on this line is primarily asphalt with only 10% of the segment tape-coated. The NOL extends through eastern Manitoba and northern Ontario. The NOL was constructed between 1981 and The pipe coating on this segment is primarily fusion bonded epoxy (FBE) with a few sections of tape. The NBSC extends through eastern Ontario and was constructed between 1991 and The pipe coating is FBE. For a schematic showing the existing TransCanada Mainline gas lines and the segments to be converted to oil service, see Appendix Coating Types and Stress Corrosion Cracking The type of coating applied to the pipe influences the threats and associated assessments required to ensure that the integrity of the pipeline is maintained. Asphalt-and tape-coated pipe, typical for pipelines installed in the 1970s and early 1980s, has been found to be potentially susceptible to the environmentally-induced cracking phenomenon of stress corrosion cracking (SCC). The SCC is observed on the exterior of the pipeline, and three elements are required in order for the cracking to develop: tensile stress (the hoop stress caused by internal pressure) a susceptible material (in this case, carbon steel) a potent environment The FBE-coated pipe is not susceptible to SCC largely because of the strong bond of the coating to the pipe surface. If the coating fails, the cathodic protection will still be effective; thus protecting the steel from the environment that contributes to SCC. 3 3 NEB Proceeding MH-2-95: Public Inquiry Concerning Stress Corrosion Cracking on Canadian Oil and Gas Pipelines. Page 2-2 May 2016

3 CA PDF Page 3 of CONVERSION INTEGRITY PROGRAM The conversion integrity program has four phases: Phase 1 This phase is completed. It involved validating the latest generation electromagnetic acoustic transducer (EMAT) in-line inspection (ILI) tool and evaluating the severity and distribution of the SCC on Line of the Prairies Line. This phase of the program identified features on the pipeline requiring remediation, and by correlating ILI reported features with the findings of field digs, proved the efficacy of the inspection methods and accuracy of the ILI tools used. Phase 2 This phase will be completed before the pipe is removed from gas service and will involve inspecting the pipe through ILI and investigative digs for threats to the pipeline such as internal and external corrosion, dents, SCC in the potentially susceptible pipeline sections, and girth weld cracks associated with the historical recoating program on the Prairies Line. It will also involve ILI runs on a number of FBE-coated sections not previously assessed by ILI. Temporary launchers and receivers will be installed to permit the deployment of the ILI tool. An addendum to the EA will be filed with the Board at the conclusion of this phase detailing the remediation plan arising from these assessments. In detailing its approach to the investigative dig program, Energy East and TransCanada developed preliminary estimates of the number of digs that would occur over a 24-month period. 4 Energy East notes that the Project s schedule has been refreshed such that an updated estimate of digs will be developed and provided to the Board once completed. Energy East remains committed to implementing notification, further engagement, and environmental protection, all as appropriate where digs occur in relatively high numbers and in concentrated timeframes. 5 Phase 3 This phase will involve remediating the features identified in Phase 1 and Phase 2. This will require excavation of the identified features and determining the appropriate method of remediation. In many cases, remediation will likely involve replacing the affected pipe joint with a new pipe joint. This work will be carried out during Project construction activities (see Volume 7, Section 3: Construction Component-Specific Information) on the conversion pipeline. A second addendum to the EA will be provided to the Board at the conclusion of this phase, detailing completion of the remediation plan. 4 For additional information regarding these excavation activities, see Energy East s response to NEB 2.4(a) (NEB Filing ID: A4J6D0), and NEB 4.0 (NEB Filing ID: A4Q4G2). 5 For additional information regarding these commitments, see Energy East s responses to NEB 4.0 (NEB Filing ID: A4Q4G2). May 2016 Page 2-3

4 CA PDF Page 4 of 16 As an additional safety factor in the initial operation of the conversion pipeline, Energy East will restrict the operating pressure to 80% of the original maximum operating pressure (MOP) on those portions of the pipeline that are potentially susceptible to SCC. This restriction would remain in effect until completion of the next phase of the conversion integrity program. Phase 4 This phase will involve a second ILI assessment for SCC using a shear-wave ultrasonic (UT) ILI tool, which can only be run while the pipeline is in oil service and provides finer resolution of features than would be possible for ILI in gas service. This inspection would be performed on the Prairies Line and other sections of the conversion pipeline that have tape or asphalt coating. Features that do not meet the near-term response criteria will be incorporated in the IMP for remediation before the pipeline segment is operated at full pressure. Energy East will file a third addendum to the EA with the Board reporting the results of the Phase 4 inspection activities and associated remediation. On submission of the third EA addendum report, after the pipeline has been put into oil service, Energy East will notify the NEB before operating the conversion pipeline at 100% of the approved MOP. 2.4 CONSEQUENCE ASSESSMENT Energy East has applied the concept of high consequence areas (HCAs) from United States (US) pipeline safety regulations (49 CFR 195) in the absence of specific Canadian guidance or standards. The term HSR was adopted by TransCanada for Canadian jurisdictions in consideration of the distinctions between the Canadian and US contexts, largely arising from the variety of data sources, including federal and provincial agencies (e.g., environmental, fisheries and wildlife, wetlands). The specific sources of HSR data applicable to Energy East are detailed in a report prepared by Stantec Consulting Ltd. entitled Identification of Highly Sensitive Receptors, Energy East Pipeline Project (see Appendix 4-5). 2.5 HAZARDS AND HAZARD ASSESSMENTS Hazards the conversion pipelines might be subject to, and for which the pipelines are being assessed in the EA, include: internal corrosion external corrosion environmentally assisted cracking (stress corrosion cracking) manufacturing defects welding and fabrication defects third-party mechanical damage weather and outside forces (geotechnical) Page 2-4 May 2016

5 CA PDF Page 5 of 16 Where a hazard is determined to potentially exist, it is designated a threat of concern (TOC) for these analyses. Equipment failure and incorrect operations are not relevant to the circumstances of the conversion for the Project and are not substantively addressed in the EA Corrosion Hazard Assessment Corrosion hazard assessment considers both internal and external corrosion External Corrosion The external corrosion hazard is a TOC for all pipeline segments. All conversion pipeline segments are being assessed with ILI tools for external corrosion, as discussed in Section 5: Conversion Design Internal Corrosion In gas service, the internal corrosion hazard was not a TOC on the conversion pipeline given the low dew point (dry nature) of the natural gas transported. When the pipeline in oil service is operated in fully turbulent flow, 7 the potential for water separation or settling out of entrained sediment that could contribute to internal corrosion is reduced. Therefore, internal corrosion is not a TOC where the oil in the pipeline is in turbulent flow. The flow of oil through a pipeline upstream of a batched injection point (the Moosomin tank terminal is the only injection point planned) could be intermittent. Under those operating conditions, internal corrosion could be a TOC because of the potential for both sediment accumulation and water separation. To mitigate this threat, a cleaning tool will be periodically run through these pipe sections to remove accumulated water or sediment. The modifications planned for the conversion pipeline, such as drip leg removal and crossover removal (see Section 3: Isolation of Gas Facilities from the Pipeline) mitigate the potential for internal corrosion by eliminating areas not exposed to turbulent flow Assessment Technologies The primary assessment technique for internal and external corrosion in natural gas service has historically been the ILI runs using magnetic flux leakage (MFL) 6 7 For further reference and information regarding equipment failure and incorrect operations hazards, see Energy East s response to NEB IR 5.21 (NEB Filing ID: A4V8G6). Turbulent flow refers to the motion of a fluid with local velocities and pressures that fluctuate randomly. May 2016 Page 2-5

6 CA PDF Page 6 of 16 technology. Although the ILI runs planned for the conversion pipeline will be focused on investigating the external corrosion hazard, the data will also be reviewed for evidence of internal corrosion, which if identified, will be remediated as required Response Criteria As part of the pipeline IMP, Energy East has developed a set of response criteria for assessing if an identified flaw or defect requires repair, and when that repair should be completed. These criteria are generally expressed in terms of probabilities. Threshold probability values have been established that are used to determine whether a repair response is required Stress Corrosion Cracking Hazard Assessment Stress corrosion cracking is a TOC only for pipeline segments that are either tape or asphalt coated. As previously mentioned, the FBE-coated sections of the conversion line are not susceptible to SCC Assessment Technologies For the conversion, an assessment for SCC is a two-stage process using two ILI technologies. Before the line is removed from gas service, the susceptible sections will be inspected with EMAT technology. The results of these inspections will allow the Project to identify and repair the majority of cracks present, including cracks that would pose a near-term integrity concern, before the lines enter oil service. Once the pipeline enters oil service, the SCC-susceptible sections will be re-inspected with a UT ILI tool. This tool can detect smaller cracks than the EMAT tool, but can only be run in liquid service. Although the EMAT s detection capabilities are more than sufficient to assess the failure potential for cracks in initial oil service, an 80% MOP limit will be instituted on SCC-susceptible sections of pipe until the preliminary shear-wave ultrasonic inspection results validate that no cracking features pose an immediate concern on that section Manufacturing Hazard Assessment Manufacturing Hazard A manufacturing hazard assessment is intended to determine whether there might be issues relating to the original manufacture of the pipeline sections that could affect suitability of the pipeline for oil service. The pipeline for conversion has no documented history of manufacturing-related failures, and the double-submerged arc Page 2-6 May 2016

7 CA PDF Page 7 of 16 weld (DSAW) technique used in the pipeline s manufacture is not associated with manufacturing hazard. The portion of the line upstream of the Moosomin pump station will experience significantly higher pressure cycling in oil operation because of intermittent operation associated with batch injections. The manufacturing hazard will therefore be assumed to be a TOC for that segment Assessment Technologies The technology used to assess SCC (EMAT and UT) can also be used to assess manufacturing flaws (e.g., seam-weld defects) Welding and Fabrication Hazard Assessment A welding and fabrication hazard assessment is intended to consider whether there could have been issues relating to the original installation or subsequent repair of the pipeline sections that could affect suitability of the pipeline for oil service. Although the pipe for conversion does not contain mechanical couplings, non-ductile girth welds (such as oxygen-acetylene girth welds) or wrinkle bends, this hazard will be assumed to be a TOC for the small portion of the line that experienced elevated bending moments from a mid-1990s recoat program. In this program, the pipe was hoisted aboveground in long sections to facilitate inspection and recoating. A leak identified in 2013 was attributed to a flawed girth weld in one of these sections (NEB Filing ID: NEB Incident ) Assessment Technologies Locations with unusual MFL signatures on the girth weld (particularly at bottom dead center) and high strain levels will be flagged for possible investigation. The most significant of these features will be excavated and repaired, if required Third-Party/Mechanical Damage Hazard Assessment The relevant aspect of this hazard to the conversion from gas to oil service is the presence of historical mechanical damage to the pipeline and the impact on the conversion pipeline of cyclic loading, arising from pumping operations in liquid service. 8 For additional information regarding the management of girth welds on conversion pipeline sections, see Energy East s response to NEB 5.13 (NEB Filing ID: A4V8G6). May 2016 Page 2-7

8 CA PDF Page 8 of Assessment Technology The assessment technology to be used is high-resolution caliper and high-resolution MFL ILI. The MFL data will provide additional insight into dents identified by the caliper data. This process has proven successful in identifying dents that could eventually become a problem Weather and Outside Force Hazard Assessment This assessment is intended to determine whether there have been or will be outside forces acting on the conversion pipeline. Phased geologic hazard assessments have been completed along the entire pipeline. These assessments considered potential unstable slopes, seismic hazards, ground subsidence, and collapsible or expansive soils along the alignment. Given the increased consequence of an oil pipeline failure in a watercourse compared with a gas pipeline failure, phased hydrotechnical hazard assessments were completed along the length of the conversion portion of the Project to identify potential scour or erosion hazards that may impact the integrity of the pipeline (see Appendix 5-1). Appropriate measures to mitigate potential geologic and hydrotechnical hazards that may impact the integrity of the pipeline will be implemented, as required, during detailed design. 2.6 SEGMENT-SPECIFIC HAZARD ASSESSMENTS In addition to the general TOC that apply to the conversion pipeline as a whole, there might also be specific hazards associated with the different pipeline segments. These hazards are discussed in the sections that follow Prairies Line This portion of the conversion pipeline is predominantly coated with asphalt enamel, except for two valve sections coated with tape and FBE. Given that incidents of SCC have been found on the coal tar-coated portion of the adjacent Line 100-1, most of the Prairies Line is deemed to have the potential for SCC. All sections of the Prairies Line identified for conversion are currently monitored under a corrosion-defect management program using MFL ILI assessments Historical Operation and Performance To achieve an added margin of safety, the MOP of this line has, on occasion, been reduced in association with defect mitigation or repair activities. This entire segment is currently under an operating pressure restriction, as corrosion features that require Page 2-8 May 2016

9 CA PDF Page 9 of 16 repair have been identified. These features will be remediated as part of Phase 3 of the conversion integrity program. Three historical failures that occurred in this segment are attributed to SCC: hydrostatic test failure on MLV Section 13 in 2008 hydrostatic test failure on MLV Section 31 in 2005 in-service failure at Rapid City, MB in External Corrosion All Prairies Line sections, except the existing Assiniboine River crossing (to be replaced with new 1,067 mm (NPS 42) pipeline as part of the conversion process), were inspected by MFL between 2010 and Internal Corrosion The assessment of internal corrosion during oil operation will be addressed at the same time as inspections for external corrosion, though a number of preventive measures will be implemented as part of the conversion scope. Specifically, the drip leg and crossover assemblies will be removed to minimize the deadlegs 10 these piping configurations represent. In the first year of operation, cleaning tools will be run twice in this section to remove sediment deposited during the fill process and initial operation Environmentally Assisted Cracking Stress Corrosion Cracking As discussed in.3, Phase 1 of the conversion integrity program, the EMAT runs, combined with the associated excavations will mitigate the SCC hazard until the shear-wave ultrasonic ILI runs in early oil operation. The correlation excavations combined with control excavations based on environmental susceptibility, confirmed the EMAT tool s capabilities and provided the opportunity to refine the signal assessment methods for Phase 2. Most of the crack features found in Phase 1 were repaired during excavations to confirm the performance of the EMAT tool. The remaining features will be repaired in Phase 3. 9 For additional information regarding these inspections, see Energy East s response to NEB 5.14 (NEB Filing ID: A4V8G6). 10 As defined by API 2611, Terminal Piping Inspection-Inspection of In-Service Terminal Piping Systems, deadlegs are internal areas of a pipe system having no flow. May 2016 Page 2-9

10 CA PDF Page 10 of Manufacturing Defects Although the EMAT results reported no crack-like features in the seam weld, seven linear features were excavated that would normally be characterized as non-injurious for a DSAW seam. The field excavations confirmed these features to be non-injurious Welding and Fabrication Defects The first production run of the next generation of high-resolution MFL technology will be performed on the MLV 2 to MLV 9 section to provide increased sensitivity to potential circumferential defects in the girth welds. In the absence of significant external loading, girth weld flaws typically remain stable given their orientation relative to the hoop stress in the pipe wall Existing Mechanical Damage No dent features were identified as meeting the near-term remediation criteria as a result of the 2012 caliper inspection of MLV 25 to MLV 34 on Line 100-4, or the 2013 caliper inspection of MLV 36 to MLV 41 on Line Additional caliper inspection runs spanning MLV 2 to MLV 25 were run in 2014 and 2015 to complete assessment of the point-to-point strain on any dents through the Prairies Line. From these caliper inspections covering the Prairies Line, the dent with the highest strain, the deepest dent and the largest dent will be selected for detailed fatigue analysis. Should a dent fail the fatigue criteria, it will be designated for remediation and the next most significant dent of that boundary condition will be assessed, repeating the cycle until the criteria are satisfied. With respect to MLV 17 to MLV 25, inspection data generated in 2010 proved to be of higher quality than that generated in Reanalysis of anomalies identified in the 2010 data is being undertaken through an EA to determine their acceptability. Accordingly, a placeholder sheet for the Prairies Line EA is provided in this as Appendix Weather and Outside Force (Geotechnical) During the phased geologic hazard assessments, some locations along the conversion segment of the pipeline were identified as having moderate or high potential for landslide hazards. These locations are either under instrumented slope monitoring or will undergo additional evaluations during ongoing assessments of the conversion 11 For additional information regarding these inspections, see Energy East s response to NEB 5.16 (NEB Filing ID: A4V8G6). Page 2-10 May 2016

11 CA PDF Page 11 of 16 integrity program. 12 Based on the findings of the monitoring exercise and evaluations, Energy East will implement appropriate remedial measures at locations where potential landslide hazards may impact the integrity of the pipeline. Areas of potential collapsible/expansive soil and subsidence are inspected regularly by aerial surveillance for potential threats to the pipeline. Phased hydrotechnical hazard assessments that were completed along the alignment identified water crossings with high and moderate potential for scour. 13 Further assessments, including depth of cover surveys, will be completed on all water crossings with high potential for scour. The water crossings with moderate potential for hydrotechnical hazards will continue to be managed as part of conversion integrity program Northern Ontario Line Line and Sections of Line The portion of Line identified for conversion is predominantly coated with FBE except for five valve sections, each of which is coated with polyethylene tape. The tape-coated sections are currently under both an SCC hydrotest program and a corrosion-defect management program using MFL-based assessments. However, the FBE-coated sections have not been previously assessed by ILI, other than the commissioning caliper runs after construction to check for mechanical damage. 14 Similarly, the Line sections to be converted are FBE-coated, but have not been assessed by ILI, other than the commissioning caliper runs. Only discrete sections of this line are currently capable of being inspected with ILI tools. Therefore, the majority of the ILI assessments for this line will be completed during Phase 2 of the conversion integrity program using temporary launcher and receiver traps. Additional permanent ILI tool launching and receiving facilities will be installed on this line to ensure complete ILI coverage before the line is put into oil service Historical Operation and Performance Since its original construction, the NOL has been in sweet dry natural gas transmission service at nominally the same pressure as the intended oil service. Occasionally, the MOP has been lowered in association with defect mitigation or repair activities. 12 For additional information regarding slope instability and monitoring, see Energy East s response to NEB 5.17 (NEB Filing ID: A4V8G6). 13 For additional information regarding these assessments, see Energy East s response to NEB 5.20 (NEB Filing ID: A4V8G6). 14 For a discussion of FBE coating performance with respect to external corrosion and SCC, see.2.2. May 2016 Page 2-11

12 CA PDF Page 12 of 16 There have been no hydrostatic test failures or in-service failures on either Line or Line along the NOL External Corrosion The NOL will be inspected with high-resolution MFL during Phase 2 of the conversion integrity program to assess external corrosion Internal Corrosion The assessment of internal corrosion during oil service will be addressed at the same time as the assessment of external corrosion. However, a number of preventive measures will be implemented as part of the conversion. Specifically, drip leg and crossover assemblies will be removed to minimize the deadlegs in those piping configurations. Two cleaning tool runs will be conducted on this segment in the first year of oil service operation to remove sediment deposited during line filling and initial operation Stress Corrosion Cracking The five tape-coated valve sections in this portion of the conversion pipeline are presumed to be susceptible to SCC. However, the remainder of the pipe is FBE-coated and not susceptible to this hazard. The five valve sections will be inspected with the EMAT and its associated circumferential MFL technology to identify and assess any SCC that might be present. The remainder of the pipe will be inspected with the EMAT to identify any other sections of tape-coated pipe in this line. For any tape-coated pipe detected, the EMAT data will be assessed for cracking indications Manufacturing Defects Although this is not a TOC, the cracking detection ILI data will be reviewed for anomalous indications in the seam weld region Welding and Fabrication Defects In the absence of significant external loading, girth weld flaws typically remain stable given their orientation relative to the hoop stress in the pipe wall Third-Party Mechanical Damage Caliper inspection runs are planned for all segments of the NOL (MLV 41 to MLV 116) prior to conversion. The results of these runs will be utilized to complete the assessment of the point-to-point strain on any dents through the NOL. Page 2-12 May 2016

13 CA PDF Page 13 of 16 From these planned caliper inspections of the NOL, the dent with the highest strain, the deepest dent and the largest dent will be selected for detailed fatigue analysis. A dent that fails the fatigue criteria will be designated for remediation and the next most significant dent of that boundary condition will be assessed, repeating the cycle until the criteria are satisfied Weather and Outside Forces (Geotechnical) During phased geologic hazard assessments, some locations along the conversion segment of the pipeline were identified as having moderate or high potential for landslide hazards. These locations are either under instrumented slope monitoring or will undergo additional evaluations during ongoing assessments of the conversion integrity program. Based on the findings of the monitoring exercise and evaluations, Energy East will implement appropriate remedial measures at locations where potential landslide hazards may impact the integrity of the pipeline. 15 Areas of potential collapsible/expansive soil and subsidence are inspected regularly by aerial surveillance for potential threats to the pipeline. Phased hydrotechnical hazard assessments that were completed along the NOL identified water crossings with high and moderate potential for scour and erosion. Further assessments, including depth of cover surveys, will be completed on all water crossings with high potential for scour. The water crossings with moderate potential for hydrotechnical hazards will continue to be managed as part of the conversion integrity program North Bay Shortcut Line The NBSC construction began in the 1990s and continued until the last build in As with other FBE-coated sections, this pipe has not been assessed by ILI other than commissioning caliper runs after construction to check for mechanical damage. 17 The ILI assessments for this line will be performed during Phase 2 of the conversion integrity program Historical Operation and Performance Since its original construction, this line has been in sweet dry natural gas transmission service at nominally the same pressure as the intended oil service. Occasionally, the MOP has been lowered in association with mitigation or repair activities. 15 For additional information regarding slope instability and monitoring, see Energy East s response to NEB 5.17 (NEB Filing ID: A4V8G6). 16 For additional information regarding these assessments, see Energy East s response to NEB 5.20 (NEB Filing ID: A4V8G6). 17 For a discussion of FBE coating performance with respect to external corrosion and SCC, see.2.2. May 2016 Page 2-13

14 CA PDF Page 14 of 16 There have been no hydrostatic test failures or in-service failures on Line External Corrosion The NBSC will be inspected with high-resolution MFL during Phase 2 of the conversion integrity program to assess external corrosion Internal Corrosion The assessment of internal corrosion during oil service will be addressed at the same time as the assessment of external corrosion. A number of preventive measures; however, will be implemented as part of the conversion. Specifically, drip leg and crossover assemblies will be removed to minimize the deadlegs in those piping configurations. Two clearing tool runs will be conducted on this segment in the first year of oil service operation to remove sediment that might be deposited during line filling and initial operation Stress Corrosion Cracking The NBSC will be inspected with EMAT in Phase 2 of the conversion integrity program to identify tape-coated pipe. For any tape-coated pipe detected, the EMAT data will be assessed for cracking indications Manufacturing Defects Although this is not a TOC, the cracking detection ILI data at tape locations will be reviewed for anomalous indications in the seam weld region Welding and Fabrication Defects In the absence of significant external loading, girth weld flaws typically remain stable given their orientation relative to the hoop stress in the pipe wall Third-Party Mechanical Damage Caliper inspection runs are planned for all segments of the NBSC (MLV 1201 to MLV 1401) prior to conversion. The results of these runs will be utilized to complete the assessment of the point-to-point strain on any dents through the NBSC. From these planned caliper inspections of the NBSC, the dent with the highest strain, the deepest dent and the largest dent will be selected for detailed fatigue analysis. A dent that fails the fatigue criteria will be designated for remediation and the next most significant dent of that boundary condition will be assessed, repeating the cycle until the criteria are satisfied. Page 2-14 May 2016

15 CA PDF Page 15 of Weather and Outside Forces (Geotechnical) During the phased geologic hazard assessments, some locations along the conversion segment of the pipeline were identified as having moderate or high potential for landslide hazards. These locations are either under an instrumented slope monitoring or will undergo additional evaluations during ongoing assessments of the conversion integrity program. Based on the findings of the monitoring exercise and evaluations, Energy East will implement appropriate remedial measures at locations where potential landslide hazards may impact the integrity of the pipeline. 18 Areas of potential collapsible/expansive soil and subsidence are inspected regularly by aerial surveillance for potential threats to the pipeline. Phased hydrotechnical hazard assessments that were completed along the alignment identified water crossings with high and moderate potential for scour. No water crossing with high potential for scour was identified on the NBSC. The water crossings with moderate potential for hydrotechnical hazards will continue to be managed as part of conversion integrity program For additional information regarding slope instability and monitoring, see Energy East s response to NEB 5.17 (NEB Filing ID: A4V8G6) 19 For additional information regarding these assessments, see Energy East s response to NEB 5.20 (NEB Filing ID: A4V8G6). May 2016 Page 2-15

16 CA PDF Page 16 of 16 Page 2-16 May 2016