Elevated pipes are sometimes used to cross wide rivers if the bottom is 

 particularly difficult to excavate or if the pipe can be easily elevated high 

 enough above navigable water. 



Most river or channel crossings are submerged, and the methods for cross- 

 ing often depend on the circumstance. When navigable waters are crossed, the 

 pipe-laying company cannot obstruct traffic for long. Therefore, a trench is 

 excavated across the bottom by dragline. The pipe is prepared immediately 

 adjacent to the area. Usually a long enough string of sections is made so 

 that the pipe span necessary to cross the river may be laid at one time. The 

 pipe is floated into position, and the floats are removed. The pipe is guided 

 into the ditch across the entire river in one operation. Then coarse filler, 

 gravel, and rocks, are used to backfill the trench. A variation of this is to 

 lay the entire span across the river, on the bottom. Then a jet barge is used 

 to bury the pipe. 



For streams that are not navigable, a diversion dam may be built so that 

 the pipeline may be assembled section by section and placed across the river. 

 As the laying progresses, the dam is moved at the front of the pathway and 

 taken up at the rear. 



Regardless of which method is used, reinforcement is always required 

 where the pipeline crosses the river bank; concrete bulkheading may be placed 

 where cuts were made in the bank. 



Pump station construction. Intermediate stations along pipelines are 

 required for pumps, compressors, and traps for scrapers, pigs, and balls. 

 These stations may be 64 to 80 km (40 to 50 mi) apart, depending on the terrain 

 and materials transported. Usually these pump stations contain scraper traps 

 and launchers for cleaning and scraping the insides of the pipeline. 



A permanent road is built to the site of the pump station. Since the 

 station is built at the time of pipeline construction on the pipeline route, 

 the road will probably carry some of the supplies for the pipeline construction 

 as well. Methods for road construction are the same as those for roads to 

 well sites. 



Usually the areas have parts of the pipes and most of the equipment 

 exposed above a foundation. Often a large foundation area is dug that will 

 contain the entire pump station. The area is comparable to the wellsite 

 location size. Valves, traps, launchers, some treatment equipment, pumps or 

 compressors, and monitoring devices are usually mounted on poured concrete 

 foundations. After all equipment is placed, the shallow foundation is filled 

 with shell or gravel . 



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