ARCHIVED - Pipeline Abandonment Physical Issues Committee - Key Abandonment Issues Summary
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- Ground Subsidence
- Prevention of Pipeline Collapse Under Railways and Roads
- Additional Abandonment Issues
- Post-Abandonment Issues
Potential Abandonment Knowledge Gaps
1. Ground Subsidence
There is a valid assumption that if a pipeline is left in the ground with no cathodic protection that it will deteriorate over time and potentially cause a surface disturbance in the form of ground subsidence. The gaps in knowledge on this topic include:
- How does a pipe collapse mechanism occur?
- What are contributing factors to pipe collapse (corrosion rates, size of pipes etc.)?
- What are the regional effects of soil conditions on structural failure of buried pipe (moisture, consolidation, porosity, climate etc.)?
- Does subsidence occur over a very long time and if so will it be noticeable on the ground surface?
- Is there a relationship between farm machinery and pipe collapse in fields?
- What is the potential for subsurface animal habitat being established and causing settlement?
- In what situations should the removal of pipeline or abandonment-in-place be given priority?
- What would be the best means of removing various sizes of pipe and what would be the estimated reclamation needs?
- Is there any low cost means of filling pipelines?
2. Prevention of Pipeline Collapse Under Railways and Roads
The options available for abandoning a pipeline under a road or railway include removing the pipe, filling it and leaving it as is. Gaps in knowledge include:
- The degree of subsidence of replacement material that occurs if a pipe is removed versus settlement from corrosion of a pipeline remaining in place.
- What are the tolerance for settlement under a transportation corridor and the recommended approach for different magnitudes of roads and railways?
- What design considerations should be incorporated in new designs to accommodate abandonment under transportation corridors?
- If filling is to occur what is the recommended procedure?
- The types of fill material that could be used and their effectiveness.
- If filling a pipeline is to occur should it be throughout the right of way?
- There is a lack of knowledge on the effects of pipe deterioration under a corridor depending on:
- vehicle loading by type and frequency,
- use of pipe sleeves,
- the type of surface on the road, and
- the size of pipe.
- The amount of increased corrosion due to factors such as vibration and drainage.
3. Additional Abandonment Issues
The period for abandonment is normally from the end of a pipe's useful life to the point where the owner has completed all required work to make the pipeline meet abandonment requirements. Typically all above ground facilities are removed and water crossings are to be dealt with in a fashion that prevents pipes from floating or becoming avenues for contamination (plugging is recommended). However, the following gaps in knowledge for this phase include:
a. Pipe Cleanliness
- What is an acceptable level of pipe cleanliness?
- Need research to identify all potential contaminants and quantify acceptable levels.
- Run pigs and then measure residue.
- Measure residue on abandoned pipe.
- Accelerate internal coating decomposition.
- Is conventional cleaning procedure acceptable?
b. Right of Way Contamination
Some contamination is expected at pump stations, compressor stations, tank farms and documented spills. The NEB will determine the acceptable risk through the public hearing process and then clean up will be to standards of the day for that jurisdiction. Gaps in knowledge are:
- Given that the degree of clean up is dependent on land use;
- Can a cross-Canada standard be arrived at to apply to all pipelines for remediation under each land use?
- What if land use changes?
- What assurance is there that crops will not be affected?
- What assurance is there that agricultural workers would not be affected?
- Is a change in standards retroactive?
- Is it possible to have the clean up exceed minimum requirements?
- What is the risk to groundwater and soil from undetected leaks?
- What would be the anticipated natural degradation of contaminants?
- How to document that contamination was cleaned up?
- facilitates environmental assessments and land transfers.
- What are the effects of external pipe coating degradation?
4. Post-Abandonment Issues
Following physical pipeline abandonment work the pipeline enters a post-abandonment phase that lasts until either the pipeline is removed or there are no further issues. Issues of ground subsidence and transportation corridor protection have already been identified. There have been concerns expressed relating to liability, financial responsibility and jurisdiction. These are generally beyond the scope of the committee. However, some relate to being able to address physical issues. Other physical issues and potential gaps in knowledge include the following:
- The location and maintenance of records regarding the residual pipeline equipment.
- The means of ensuring signage, pipe locates and ongoing monitoring occurs.
- The mechanism to ensure land title retains the ROW when necessary. (preferred regulatory jurisdiction)
- Means of dealing with unforeseen contaminants found after abandonment (this is related to the NEB initiative to address financial issues through companies setting aside funds).
- Potential for frost heave of pipes when not in use under different soil conditions.
- What criteria should be in place for creation of a road over an abandoned pipeline?
- What approach is recommended where a land use change means a development or house is to be put over a pipeline?
- How to determine the optimum location for pipeline plugs to prevent pipelines from becoming water conduits (potentially carrying contaminated water and causing erosion).
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