2. Plan Shape 



The plan shape, shown in Figure 3, evolved from five basic inter- 

 related considerations: island area and shape, revetments, filter and 

 core, general scheme of construction, and, of course, cost. Area require- 

 ments were established by Richfield to provide space for oil drilling and 

 production facilities consistent with the anticipated drilling and produc- 

 tion program. The final shape was developed from oceanographic, model, 

 design, and economic studies. The west, or seaward, face is designed to 

 withstand heavy seas from winter storms and to protect the rest of the 

 island. The north and south faces, or sides, are designed to be stable 

 against 12-foot waves, since maximum wave height from these directions is 

 limited by the fetch inside the Santa Barbara Channel. The east face, or 

 shore side of the island, is provided with a small wharf protected from 

 ocean waves by the northeast and southeast stub breakwaters, or "wings", 

 as they came to be called. To reduce the cost, the original design did 

 not include a causeway; it was intended that the island would be served 

 by the wharf only. 



The revetment for the west face includes a cellular wall structure 

 adjacent to the double line of conductor pipes that serves as a support 

 platform for the drill rig which straddles the drill cellar. The rig can 

 be skidded in a north-south direction to center over any desired well. 

 The cellular wall structure also serves as a backstop or secondary line of 

 defense for the west face revetment, which is designed to withstand 27-foot 

 waves without damage, but which can sustain significant damage before the 

 wells are exposed to direct wave attack. 



Behavior of the prototype has been as expected, in that the broader 

 west face creates a wave shadow zone providing shelter from westerly waves 

 for the north and south faces. The wings further shelter the east face. 

 No damage to armor rock has occurred on the north, south, and east faces. 

 Assuming that maximum wave heights have been near 27 feet, the high range 

 estimate derived from indirect data, then it appears that the shape is 

 providing the desired attenuation of waves approaching from the west. 



3. Use of Model Tests in Design 



As is typical of many hydraulic design problems, several elements of 

 the design could best be checked by laboratory model tests, which were 

 conducted in two series. The first was a three-dimensional model test to 

 check the configuration of the island and the second involved two-dimen- 

 sional models in a wave channel. Both models were constructed at a linear 

 scale of 1:70,000. To keep costs low and still obtain a maximum amount of 

 information, movies were made of most tests and time-consuming measurements 

 of rimup patterns were kept to a minimum. 



At one stage of the design, Richfield wanted a small concrete slip, 

 about 40 by 150 feet, on the leeward side to be used as a small boat 

 harbor for servicing the island. One purpose of the three-dimensional 

 model tests was to determine if a permeable or partial gate would maintain 



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