Intervention Design – Pipeline Shore Crossing Stabilisation

Background

An existing pipeline shore crossing corridor, compromising of a number of buried and surface laid pipelines, required intervention for the remedial stabilisation of two surface laid pipelines due to concrete weight coating loss as a result of endured harsh environmental conditions.

Work Performed by Atteris

Atteris was engaged to develop an intervention design concept which would later be detailed for construction. The project remit was to design a stabilisation system which:

  • Did not interfere with the pipeline cathodic protection system
  • Had the ability to deal with changing shoreline elevations
  • Can withstand breaking wave loads
  • Allows future visual pipeline inspections
  • Has minimal interface with the pipelines
  • Considers site access and constructability constraints.

After establishing a regular interface meeting with the client and their installation contractor, Atteris was able to propose an external stabilising structure with adjustable bracing saddles which interface with the pipelines. Crane access to the site was limited and would result in additional site works. Atteris proposed and designed components which would allow for manual handling using aids. Working with the installation contractor, Atteris was able to develop the concept design quickly in preparation for procurement and fabrication. One of the largest and heaviest components was the cross beams. Handling of these was overcome by the installation who floated them in from a small jack up barge located offshore on the high tide.

Benefit

  • Bespoke design which was installed ahead of schedule and under budget
  • Component system eased logistics and handling
  • Minimal construction spreads were needs which resulted in minimal environmental disturbance
  • Pipelines remained accessible for inspection
  • Retention system is fully adjustable to deal with the changing shoreline elevation and burial of the pipelines due to sand transportation