Pipeline construction is a sequential operation involving several distinct 

 activities occurring in a particular order. Because the sequence of opera- 

 tions occurs at all points along the pipeline in a particular order, the 

 equipment and activities are stretched out over several km, and the sequence 

 (called a "spread") moves along the entire pipeline from beginning to end. It 

 is not unusual for a spread to move 3.2 km (2 mi) per day and on a large pipe- 

 line, 250 to 500 workers may be involved (Petroleum Extension Service, 1972). 



After the area is cleared, a road may be graded adjacent to the route. 

 Ditchers and backhoes dig the pipeline ditch, and trucks bring in the pipe. 

 It is bent if necessary, and sections are welded end to end. A machine cleans, 

 coats, and wraps the pipe surface and then the pipe is placed into the earth. 

 The excavated material is backfilled into the ditch, the earth is tamped and 

 leveled, and revegetation and restoration proceed. 



In marsh or open waters, many complications arise because of the lack of 

 firm substrate for vehicle movement. In open-water areas, all pipe construc- 

 tion and protection activities take place in sequence on a lay barge, with the 

 pipe being lowered to the bottom after the barge passes by. In marshes, 

 sometimes wide sections of marsh are dredged to allow passage of a pipeline 

 barge. A method known as the "push-method" uses a stationary pipeline barge 

 with the free end of the pipe pushed through a narrow canal dug by equipment 

 mounted on marsh buggies. 



Pipeline construction - uplands. A survey crew enters and stakes the 

 pipeline location and the units of the pipeline right-of-way. Some vegetation 

 may be cleared. The crew may survey a continuous line or series of segments. 

 Equipment such as dozers, draglines, backhoes, and augers enter the area, and 

 a clearing crew begins to cut a pathway along the route. Since pipeline 

 construction is an activity traversing a considerable distance, many routes of 

 access are required for moving men and equipment to the construction site. 

 While pipeline contractors use existing routes as much as possible, it is 

 often necessary to create new access roads or trails to reach some parts of 

 the operation. 



The crew cuts or clears all standing vegetation across the width of the 

 route. The brush is stacked, and the usual method of disposal is burning. 

 The right-of-way is then leveled, graded, or filled until it is suitable as a 

 roadway for heavy digging and pipe-laying apparatus. In spots where the 

 surface is soft, fill, shell, or gravel may be brought in by truck and compacted 

 on the surface. There may be temporary board crossings in some spots. The 

 object of the clearing and pathway preparation is to allow easy passage of the 

 equipment. Therefore, drainage paths may be partially blocked for a short 

 time. After the spread has passed the area, the surface is restored to its 

 original contour and often is seeded. 



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