pipeline construction process
Horizontal Directional Drilling (HDD) Construction
Pipeline construction process
Once the design is completed and all approvals granted, the normal pipeline construction process is as follows:
1. LANDHOLDER ENGAGEMENT AND ACCESS APPROVALS: Meetings are held with affected landholders to discuss and agree on access to their properties during pipeline construction and ongoing operation.
2. SURVEY AND FENCING: The pipeline route is surveyed and fencing modified to facilitate access during construction.
3. CLEAR AND GRADE: Graders, bulldozers and excavators are generally used to clear and prepare the easement ready for construction to commence. Topsoil and vegetation are stockpiled separately to assist in restoration works after the pipeline is completed.
4. STRINGING: Pipe is transported into the easement and laid end to end next to where the trench will be dug.
5. BENDING: Where required, specialized machinery is used to bend the pipe to conform with the contours of the land and the pipeline route.
6. WELDING AND NON-DESTRUCTIVE TESTING: Pipe sections are welded together. All welding is tested to ensure quality.
7. JOINT COATING: The areas of weld are cleaned and pipe joints are coated to reduce the possibility of corrosion.
8. TRENCHING: Specialised trenching machines and excavators are used to dig the trench.
9. LOWERING IN AND PADDING: Specialist equipment (side booms) are used to lower the pipe into the trench. The pipe is then covered by fine-grain material (padding) to protect the pipeline coating from stones or other sharp objects.
10. BACKFILLING: The trench is backfilled with the previously excavated subsoil material. Care is taken to maintain separation between topsoil from subsoil during this process. The subsoils are compacted to limit settlement of the trench through the operational life of the pipeline.
11. HYDROSTATIC TESTING: Using water, the pipe is pressure tested (hydrotested) to ensure it is fit for operational service.
12. RESTORATION AND SIGNAGE: Disturbed areas are reinstated to match existing landforms which include re-contouring and installation of permanent erosion control structures. Topsoil conserved during the construction process is respread over areas used for construction. Rehabilitation is undertaken in accordance with approval requirements and landholder considerations. Signs are placed at regular intervals and with line-of-sight of one another to indicate the presence of the buried pipeline.