INTRODUCTION 



Reliable long-term moorings over semiconsolidated-to-hard rock 

 seafloors require specialized anchors. Conventional drag-burial anchors 

 are not capable of penetrating consolidated seafloors; the snagging of 

 flukes on outcrops without full penetration cannot be relied upon to 

 provide a durable mooring. Drilled- in anchor piles are commonly used 

 and have proven reliability. The cost of installing drilled-in piles is 

 reasonable when the mooring is situated near a large center of industry 

 where emplacement equipment is available. This cost becomes excessive 

 for a mooring at a remote location. 



Two remotely located moorings over a soft coral seafloor were 

 required at the U. S. Naval Communication Station, Diego Garcia (a 

 British territory in the Indian Ocean) for petroleum-oil-lubricant (POL) 

 offloading. One was designated the ''temporary'' POL mooring, and the 

 other was designated the ''permanent'' POL mooring. These designations 

 do not necessarily imply the expected use of each mooring because the 

 temporary mooring will probably be used as long as it is functional. 

 The temporary facility, originally completed in 1971, had been scheduled 

 to be replaced eventually by the permanent facility. 



The temporary mooring consisted of conventional drag-burial anchors 

 and concrete clumps connected to mooring buoys. This mooring had been 

 dragged on several occasions during high winds, resulting in breakage of 

 fuel pumping lines on three separate occasions, fortunately without 

 vessel grounding or damage. 



In 1971, the permanent POL mooring was in the design stage; the 

 selected design consisted of large STATO (drag-burial) anchors, weight 

 clumps, and long lengths of 2-1/2-inch (64 mm) A- link chain. Large 

 propellant anchors were suggested to stabilize the temporary mooring. 

 Shortly thereafter, the design of the permanent mooring was re-evaluated 

 because of its potential susceptibility for similar dragging. 



As a result, the CEL* 100K Propellant Anchor System was selected to 

 secure both tanker moorings at Diego Garcia because of the system's 

 adequate capacity, minimal requirements for peripheral hardware, economy 

 of installation at remote sites, compatibility with onsite installation 

 workboats and equipment, and timely availability. This report documents 

 the design of the CEL 100K Propellant Anchor; outlines the mooring 

 requirements; describes the installation procedures, the mooring designs, 

 and the equipment used to install the moorings ; and provides a summary 

 of each anchor installation. 



Civil Engineering Laboratory. 



