attracted species of fish-eating birds. One study identified 86 species 

 of birds after impounding as opposed to 55 species in the same areas 

 before impounding [145]. 



Single purpose wildlife and fishery management programs of the past 

 that seek to improve habitats for preferred species are more carefully 

 reviewed today. The feasibility of such a program includes balancing 

 the loss of natural values of the salt marsh or swamp against sustaining 

 or creating management impoundments. As recognized by Delaware's State 

 Planning Office when discussing impoundments: "All marshes should not be 

 converted into impoundments, but on the other hand, the presence of some 

 impoundments may enhance the coastal area and man's enjoyment of it" [145]. 



4.18 OFFSHORE AND PLATFORM STRUCTURES - SUBPROJECT 18 



This subproject addresses the subject of offshore structures, 

 principally platforms used in drilling and oil and gas production. It 

 does not include the transport of oil and gas from the platform to the 

 land (these aspects are discussed in Subprojects 19 and 20). The subject 

 matter includes installation of the structures and their drilling and 

 production operations. 



4.18.1 Summary 



Offshore drilling and production platforms built and used in the 

 United States are large structures made of steel framework welded to 

 tubular steel legs. This framework is called the jacket, and the 

 working surface that rests upon it is the deck. The two are built 

 separately and joined together on location after the jacket itself has 

 been placed on site. The jacket stands on pilings driven through its 

 tubular steel legs into the floor of the sea. 



Drilling derricks are erected upon the platform deck, and up to 

 several dozen production wells may be drilled through the base of a plat- 

 form. When ready, the deck facilities are changed from drilling to pro- 

 duction equipment, and pumping is started. Pipelines are the usual 

 method of transport for oil and gas, but the oil can be shipped by 

 vessel . 



In the Gulf of Mexico the trend has been to construct a master 

 production platform and install crew quarters, separators, compressors, 

 and other components on satellite platforms which are connected by foot- 

 bridges to the production platform. 



4.18.2 Activities 



The location, design, placement, and operation of offshore platforms is 

 a partnership effort between the oil company and its specialized subcontrac- 

 tors and construction is regulated by USGS. However, the major decisions that 



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