Pipeline construction is costly and complex. Forty foot sections of 

 steel pipe are coated ashore and transported to the OCS site. The 

 coated sections (generally greater than 12-inch diameter) are welded 

 together on a "lay barge" and allowed to sink under their own weight to 

 the sea floor. In water depths less than 200 feet, the pipeline is 

 buried by water jet excavation as required by US6S. As the pipeline 

 comes ashore, it is buried deeply enough to avoid being exposed to storms. 

 Due to these difficult construction stages, costs for a long, deep pipe- 

 line may exceed $1 million per mile [7]. Oil production of about 

 1,000 B/D per mile of pipeline is needed to justify such a large 

 capital investment. 



The decision to build oil or gas pipelines is made when a hydrocarbon 

 reservoir is developed. If there is sufficient gas, a pipeline will be 

 built because gas cannot be shipped by barge. If there is not enough gas 

 it is reinjected or capped for possible later pipelines. Large volumes of 

 oil are also generally piped if the water is not too deep. The oil and 

 gas can be piped together for short distances, but there are technical 

 difficulties involved in pumping an incompressible fluid and a compressible 

 gas in the same pipeline [7]. Thus, oil and gas are usually separated 

 on the offshore platform before delivery to the pipelines. Partial 

 processing at the platform to remove formation water has two additional 

 savings. There is a smaller volume of fluids to pump ashore and there 

 is less corrosion inside the pipeline. 



Submerged bottoms or coastal wetlands and their associated 

 organisms, may be seriously affected by pipeline installation. In 

 addition, dredging produces spoil, which must be disposed of (^ee 

 Section 4.1 for problems of spoil disposal). Disposal of spoil can 

 destroy habitat that may extend beyond the area of primary concern. 



The U.S. Geological Survey regulates submerged pipelines from oil and 

 gas fields. Information that the operator is required to provide the 

 Survey includes: proposed route, water depths, capacity, operating 

 pressures, size and grade of pipe, burial depth, corrosion protection, 

 protective coating, connecting and metering facilities, and pressure 

 control fa,cilities. The methods of welding and laying, installation, 

 and connecting facilities are monitored and a hydrostatic test is made 

 upon completion of installation [2]. 



4.20.2 Location 



The general location of a pipeline landfall site is primarily 

 determined by the shortest possible route between the production platform 

 and land. Once the general location for landing a pipeline has been 

 selected, the choice of landfall site will depend upon the physical 

 characteristics of the shore and the company's production plans [7]. 



Major potential disturbances to fish and wildlife stem from 

 construction of the pipeline in vital areas, and from oil leaks and 



201 



