Pipeline Construction

A pipeline construction project looks much like a moving assembly line. A large project typically is broken into manageable lengths called “spreads,” and utilizes highly specialized and qualified workgroups. Each spread is composed of various crews, each with its own responsibilities. As one crew completes its work, the next crew moves into position to complete its piece of the construction process.

These tasks include:

1. Pre-construction survey

Before construction begins, Williams surveys environmental features along proposed pipeline segments. Utility lines and agricultural drainages are located and marked to prevent accidental damage during pipeline construction. Next, the pipeline’s centerline and the exterior right of way boundaries are staked.

2. Clearing and grading

The pipeline right of way is cleared of vegetation. Temporary erosion control measures are installed prior to any earth-moving activities.

3. Trenching

Topsoil is removed from the work area and stockpiled separately in agricultural areas. Williams then uses backhoes or trenching machines to excavate a pipeline trench. The soil that is excavated during ditching operations is temporarily stockpiled on the non-working side of the trench.

4. Pipe stringing

Individual joints of pipe are strung along the right of way adjacent to the excavated ditch and arranged so they are accessible to construction personnel. A mechanical pipe-bending machine bends individual joints of pipe to the desired angle at locations where there are significant changes in the natural ground contours or where the pipeline route changes direction.

5. Welding and coating pipe

After the stringing and bending are complete, the pipe sections are aligned, welded together, and placed on temporary supports along the edge of the trench. All welds are then visually and radio graphically inspected. Line pipe, normally mill-coated or yard-coated prior to stringing, requires a coating at the welded joints. Prior to the final inspection, the entire pipeline coating is electronically inspected to locate and repair any coating faults or voids.

6. Lowering pipe in and backfilling

The pipe assembly is lowered into the trench by side-boom tractors. The trench is backfilled using a backfilling or bladed equipment; no foreign materials are permitted in the trench.

7. Testing

After backfilling, the pipeline is hydrostatically tested following federal regulations. Test water is obtained and disposed of in accordance with applicable federal, state and local regulations.

8. Restoration

Williams policy is to clean up and restore the work area as soon as possible. After the pipeline is backfilled and tested, disturbed areas are restored as close as possible to their original contours. Restoration measures are maintained until the area is restored, as closely as possible, to its original condition.

Offshore:

Horizontal Directional Drill

Williams proposes to use a horizontal directional drill for the Rockaway peninsula shore approach. This technology will enable Williams to avoid sensitive environmental areas while burying the pipe at depths greater than could be achieved with traditional trenching. Williams is proposing a drill from an onshore site within the Marine Parkway Interchange to an offshore bore exit site, approximately one mile long Lay Barge A lay barge is a complete seagoing plant that allows the pipeline to be assembled and laid continuously along the selected route either on top of the ocean floor or in trenches on the seafloor. When used in conjunction with supporting tugs and an anchoring system, the lay barge can be self-sufficient for months at a time. A system of wire ropes and anchors holds the lay barge on a precise heading to prevent buckling of the pipe as it is laid. The system also propels the barge as anchor lines are reeled in and out. As the barge progresses to the end of the lines, the system is moved ahead by anchor-handling tugs. The completed pipeline is lowered into the water by way of the inclined ramp and a stinger attached to the ramp to guide the pipeline to the seafloor at the proper angle. The pipe curves downward from the stern through the water until it reaches the “touchdown point,” or its final position on the seabed. The pipeline is coated with a high-density concrete to overcome buoyancy so that it can be sunk into place. The entire pipeline will be buried in a subsea trench. The pipeline will be lowered below the seabed along its entire length such that the top-of-pipe is a minimum of three feet below the pre-disturbed natural bottom. Reference: http://co.williams.com/williams/operations/gas-pipeline/pipeline-construction/ http://co.williams.com/williams/operations/gas-pipeline/expansion-projects/transco-expansion-projects/rockaway-lateral-project/offshore-construction/ .