Background:
The Pipeline Abandonment Research Steering Committee of the Petroleum Technology Alliance of Canada commissioned CH2M HILL Energy Canada, Ltd. (CH2M) to undertake a review of a previous pipeline abandonment program, which involves a surface assessment of three 20-inch-diameter (508-millimetre outside diameter) pipeline segments of the TransCanada Peace River Mainline (PRML)
Pipeline (the Project), abandoned between 1972 and 1979. Based on historical information, CH2M assumes that these segments were abandoned due to integrity concerns, given that each segment was looped with new pipeline. A total of approximately 12 kilometres (km) of previously abandoned pipeline right-of-way (ROW) were included in the surface assessment. Figure A-1 in Appendix A shows the nominal pipe size (NPS) 20 PRML Retirement Program previously abandoned sections identified as 1379404, 1379405, and 1379406.
The Project objective is to review the condition of a medium diameter pipeline that was abandoned more than 10 years ago, and includes the following.
- Review the abandonment methodologies implemented at the time of pipeline abandonment
- Conduct a field surface assessment, to determine if there was evidence of environmental effects or potential environmental effects of pipeline abandonment in-place as currently understood by industry
- Identify if any environmental effects of pipeline abandonment were in evidence, which were outside of the current industry understanding of the risks of abandonment
- Identify areas along the abandoned segments, where subsurface testing could be conducted to further confirm the presence or absence of those potential effects
Upon investigation, it was determined that formal abandonment plans or details of the abandonment methodologies for the abandoned segments of the PRML proposed for assessment were not available and, as such, this scope of work was removed from the Project. The following objectives were removed from the Project:
- Evaluate the outcomes achieved by the abandonment program
- Develop suggestions for additional testing of the abandoned pipeline to further assess the abandonment program
The suggested potential effects of abandonment in-place include:
- Ground subsidence and frost heave
- Soil and groundwater contamination
- Subsidence at road, railway, and utility crossings
- Watercourse and wetland crossings
- Erosion
- Creation of water conduits
The abandoned pipeline segments were assessed both from the air, using a helicopter, and by ground-truthing, to determine if there was surficial evidence of the potential environmental effects of pipeline abandonment in-place and to suggest locations where further assessment (that is, subsurface investigation) is recommended to visualize the pipe and surrounding soil for the potential environmental effects described in this report.
Summary:
The objectives of the Project were to undertake a surface-level assessment for the potential environmental effects of pipelines abandoned in-place along three previously abandoned segments of the NGTL PRML Pipeline, and to identify areas where further subsurface assessment could be performed to provide additional information pertaining to a pipeline abandoned in-place. The surface level assessment did not reveal any evidence of the potential environmental effects of abandoning a pipeline in-place. Areas where additional assessment may be considered were determined using the most recent pipeline abandonment research and applying it to the locations identified during the literature review and field assessment.