esDo.ring line attachment point to the individual piles. Drilling of 

 i&oles for the piiles would be done from a drillship using conventional 

 drillhole re-entry techniques for maneuvering the drill-string into the 

 framework drill guides. "Walking" of the drill bit on the rock surface 

 would be prevented by the drill guides. Required drill bit feed thrust 

 would be reduced to manageable magnitudes by developing a hydraulic- 

 powered, rotary impact tool for drilling of holes up to 0.8 m (30 in.) 

 in diameter. Pneumatic tools are now available for drilling such holes 

 in shallow water depths [7]. Hydraulically powered, rotary impact 

 tools, suitable for drilling holes up to 100 mm (4 in.} diameter in 

 "water depths of 1,000 m (3,000 ft), have been developed [8]. Thus, when 

 needed, the required 0.8-m-(30-in. ) diameter rotary impact drill can be 

 developed. Sufficient thrust for conventional reaming of the upper 

 drillhole to diameters of 2 m (6 ft) can be developed by hanging a drill 

 collar-like assembly from the reamer bit and allowing the reamer bit to 

 support this mass in the tension pile drillhole. 



After each drillhole is completed, a steel tension member and 

 integral shear collar would be grouted into the drillhole and template 

 drill guide using conventional techniques. The drillship would later 

 attach the mooring line to the anchor framework attachment point. 



Procedures for analysis of pile group anchors on hard (rock) sea- 

 floors are satisfactory; however, those procedures for design and instal- 

 lation would definitely require improvement and development before a 

 pile anchor design is selected for an OTEC plant. 



Such improvement and development of the pile anchor system is not 

 warranted at this time because its use by OTEC plants is foreseen to be 

 very limited and because, when used, the pile anchor system will be 

 quite expensive and time-consuming to install. Postponing and possibly 

 cancelling development of the pile anchor system does not mean that OTEC 

 exploitation of the thermal difference resource in the Gulf Stream area 

 should also be postponed or abandoned. Rather, siting of the OTEC 

 plantts will depend on finding a seafloor environment suitable for using 

 free-fall deadweight anchors; i.e., several meters of unconsolidated 

 sedimeiats overlying rock. Available information indicates that most of 



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