In 2010, the National Energy Board (NEB) commissioned a study to identify knowledge gaps related to pipeline abandonment. This review identified several knowledge gaps and recommended several future studies, including work related to corrosion rate modelling and degradation pipelines, structural modelling of pipelines, and soil collapse modelling.
The Pipeline Abandonment Research Steering Committee (PARSC) report Understanding the Mechanisms of Corrosion and their Effects on Abandoned Pipelines examined various corrosion models and structural integrity concerns specific to abandoned pipelines. The results of the study indicated the time to collapse estimated for the range of conditions analyzed was on the order of hundreds to thousands of years. PARSC then sought to determine if other factors could significantly decrease this life expectancy for abandoned pipelines. Alternating Current (AC) interference on pipelines was identified as an issue for further study, due to the commonality of shared utility corridors and the accelerated corrosion rates possible from AC corrosion, to determine its impact on abandoned pipelines.
The objective of this project was to review the technical literature and the state of knowledge concerning the influence of AC power lines on pipelines abandoned in place. Multiple possible threats have been identified related to the impact of AC interference with respect to abandoned pipelines, and can be generally categorized as either corrosion or safety related. The likelihood of these safety and corrosion threats are elaborated within this report.
Throughout the literature review, few documents were discovered specifically addressing AC interference on abandoned pipelines. However, appropriate conclusions could be drawn from the available literature addressing AC interference and pipeline abandonment separately. Based upon the technical literature review performed for this study the following general conclusions can be made regarding the impact of power lines on abandoned pipelines:
- Where AC interference is present, AC corrosion rates on abandoned pipelines would likely increase in the absence of CP, relative to operational pipelines with adequate CP.
- AC accelerated corrosion is not expected to present a significant threat to the expected lifespan of abandoned pipelines, based upon the localized nature of AC corrosion defects and the expected self-limiting progression.
- AC corrosion could accelerate localized through-wall corrosion defects (compared to free corrosion rates in the absence of CP), facilitating faster evolution of water conduits for abandoned pipelines.
- Elevated touch potentials on abandoned pipelines may present shock hazards for public or personnel who may come into contact with exposed sections or appurtenances of the pipeline.
- Abandoned pipelines which had AC mitigation systems installed while in service present a notable threat as the previously mitigated AC interference safety hazard may be reintroduced as the mitigation system degrades post-abandonment.
- This safety hazard is limited to locations where an abandoned pipeline is adjacent to a high-voltage power line and where there remains exposed sections or appurtenances of the abandoned pipeline.