Scandpower study (2004) for MMS:
Overall Conclusion
Currently, there are no regulations that require removal of subsea pipelines if they are not an obstruction to navigation. Based on the high costs for removing the pipelines, the personnel risk involved in the removal operations, the negative effect on overall emissions to air and the very limited reduction in discharges to sea, the overall conclusion is that it is better to leave the pipelines in place. If possible, re-use of the pipelines is the optimal solution.
Environmental Impacts
The impacts on the environment and the marine environment from pipelines and cables left in place were found to be very minor. Conversely recovery operations will have a negative impact on the environment. The number of vessels required for removal operations and long operating hours will result in considerably more releases and emissions than leaving the pipelines in place. In addition the energy savings benefit from recycling the pipeline materials will be exceeded by the energy required to remove the pipelines and separate the materials.
Pipeline Decommissioning: Environmental Impact Metric (per Scandpower)
| Remove/ recycle | Remove/ landfill | Reuse or preserve | Bury | Abandon in place | |
| Energy | High | High | Low | Moderate | None |
| Emissions | High | High | Low | Low | Low |
| Discharges | Low | Low | Moderate | Low | Low |
| Habitat | Low | Low | Moderate | Low | Low |
| Aesthetics | Low | Moderate | None | None | None |
| Resource Utilization | High | None | High | None | None |
| Littering | Low | Low | Low | Low | Moderate |
The “Habitat” impacts row seems questionable. Pipeline removal certainly has a greater impact on habitat than abandonment in place, particularly for buried pipelines.
Bud's Offshore Energy (BOE) 