When located at sufficient depths, single point moorings eliminate 

 the need for deepening existing harbors, channels or turning basins, 

 future maintenance dredging or the extension of existing piers. The SPM 

 is anchored to the seabed and the tanker moves freely around the mooring 

 to a position of least resistance to wind, waves and currents. This 

 enables a tanker to remain moored in relatively severe weather conditions. 



SPM systems may be a practical, and environmentally acceptable, 

 alternative to traditional port facilities for transferring cargoes 

 between the shore and Very Large Crude Carriers (VLCC) and Supertankers. 

 While more than 150 SPM's are operating in oil producing and consuming 

 areas around the world, none have yet been installed in the United 

 States. 



Several SPM Systems are planned for the United States. We rely on 

 overseas supplies of crude oil for over 40 percent of our needs. With 

 approximately 65 percent of the world's known producible oil reserves 

 located in the Middle Eastern and African nations, VLCC's, which range 

 in size from 160,000 DWT (dead weight tons) to 500,000 DWT, represent 

 the most economical means of transporting large volumes of crude oil 

 over large distances. The majority of U.S. harbors, however, are currently 

 unable to receive VLCC's. The controlling depth of U.S. harbors, except 

 for Puget Sound and the Virgin Islands, is 52 feet or less which precludes 

 all VLCC's larger than 160,000 DWT [29]. Figure 23 illustrates channel 

 depths for major oil terminal ports in the United States. 



SPM's are planned for two offshore "ports" on the Gulf Coast, LOOP 

 (Louisiana Offshore Oil Port) located 18 miles south of Grand Isle, 

 Louisiana, and "Seadock," 26 miles south of Freeport, Texas. Another 

 SPM is contemplated as part of the development of the Santa Ynez field 

 near Santa Barbara, California. 



Description 



SPM: these are floating mooring systems located offshore in water 

 depths of 50 to 150 feet. A tanker is moored to the SPM by lines, or a 

 rigid yoke, connecting its bow to a buoy or tower structure floating on 

 the surface. Oil can be transferred to and from onshore and offshore 

 storage tanks by submarine pipelines connected to the SPM and the VLCC. 

 Vessels usually can be moored at SPM's without the aid of tugs. Oil can 

 be pumped by onshore pumping stations, offshore pumping platforms or by 

 the VLCC itself. Offshore pumping platforms are constructed either when 

 SPM's are located a considerable distance offshore or when high pumping 

 rates are required (Figure 24). 



There are two types of SPM systems in widespread use: the Catenary 

 Anchor Leg Mooring (CALM) and the Single Anchor Leg Mooring (SALM). 



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