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the United States alone is estimated to average 10 plants per year (15), 
worth a total of more than $2 billion, for the next several decades. 
Another benefit, perhaps the most important, is that the construc- 
tion of a powerplant. at a shipyard has the potential for significant 
savings in construction time. A shipyard maintains the permanent 
base of shops, equipment, and skilled labor that is lacking in the 
traditional methods: of powerplant construction. This provides for 
(1) increased stability of the skilled labor force, (2) increases in the 
efficiency of the skilled labor force by allowing a learning curve to 
develop as additional stations are built, and (3) elimination of dupli- 
cative areas of management, management support, engineering, 
construction support, and quality control presently necessitated by 
separate construction locations. Shipyards are also frequently hubs 
of transportation networks that can use the most efficient combina- 
tions of land, sea, and air facilities to reduce transportation costs 
over onsite construction of land-based plants. The possibility of 
shortened construction times to help the power industry stay ahead 
of rapidly increasing consumer demands, together with a potentially 
large savings in capital outlays by utility companies for new plants, 
are most encouraging prospects in these times when substantial 
delays in construction are both costly and commonplace. . 
Several designs for offshore power stations have been proposed in 
the literature. (See app. A for a ‘‘Selected Bibliography of Reports on 
the Offshore Concept.’’) These designs usually fall mto two broad 
categories: the basic choice is between floating platforms or enclosures 
(indirectly coupled to the ocean floor by a mooring system) and fixed 
structures that are solidly attached to the bottom. 
Fized structures 
Fixed structures can be of several forms: (1) Man-made islands; 
(2) fixed-pile platforms; (3) jackup platforms; (4) grounded barge. 
(1) Manmade islands—The technology of this scheme does not 
differ in any appreciable way from that of land-based plants, except in 
the added complexities (and cost) of site preparation and transporta- 
tion of men and equipment across a water gap. Studies investigating 
the feasibility of this concept have been undertaken on both the Hast 
(16) and West (17) coasts. 
(2) Fized-pile structures—In this scheme, piles are floated or 
barged to a given location and erected permanently. A platform is then 
erected on these piles, similar to a Texas-tower configuration. Japanese 
engineers (18) have proposed construction of an offshore power station 
based on this design. Like the manmade island concept, this design 
entails conventional land-based construction techniques, again with 
the added complexities of offshore onsite construction. 
(3) Jackup platform.—The power station is constructed in a shipyard 
atop a platform equipped with extendable legs, floated to the chosen 
site, then jacked up on the legs (grounded to the seabed), out of the 
water, and into a position similar to that of the fixed-pile structure. 
The jackup system is generally thought to be useful in depths up to 
250 feet, while 300 feet is accepted as the practical limit. 
(4) Grounded barge—This scheme involves the permanent ground- 
ing of a floating bargelike platform to the ocean floor (in shallow water) 
or on a prepared site. The barge and power station are again con- 
structed in a shipyard, towed into position, and then ballasted until 
the grounding is complete. : 
