Richfield' s offshore lease stipulated that the area be drilled from 

 shore, from existing offshore structures, or from a solid island of natu- 

 ral materials. A comparison of the costs of slant drilling from shore with 

 rough estimates of island costs indicated that an offshore island of natu- 

 ral materials would be more economical. Geological criteria dictated the 

 general island location; the basic problem thus became the design of an 

 economical, permanent island of natural materials suitable as a base for 

 oil well drilling and production. Moreover, the installation was not to 

 detract from the natural appearance of the coastal area. 



The size of the island was determined by operational area require- 

 ments plus allowances for armor layer thickness and necessary side slopes. 

 Tliese factors in turn were functions of the optimum number of oil wells 

 on the island, production functions to be done on the island versus those 

 done onshore, ocean wave heights and periods, and many other considerations, 



b. Project Location and General Description - Rincon Island is loca- 

 ted offshore between Santa Barbara and Ventura as shown in Figures 1 and 

 2. The location within the lease area was chosen by Richfield to provide 

 maximum production from the greatest area at the least total cost of 

 installation, drilling, and operation. 



The water depth from the shallowest to the deepest toe of the island 

 ranges from 41 to 48 feet referred to MLLW as datum. Tidal ranges for 

 this area are shown in the following table: 



Table 1. Tidal Ranges at Punta Gorda 



ESL* Data for 



1963-1966 



Extreme High 



7.50 



MHHW 



5.40 



MSL 



2.58 



MLLW 



0.00 



Extreme Low 



-2.5 



* Earth Science Laboratories, National 

 Oceanic and Atmospheric Administra- 

 tion. 



Although Rincon Island is in the Santa Barbara Channel between the 

 mainland and the natural offshore Channel Islands, it is actually in the 

 Pacific Ocean. The Channel Islands provide some protection to the channel 

 and reduce the energy of many ocean storm waves before they reach shallow 

 water, but this protection is by no means complete, nor is it very signi- 

 ficant for a fixed structure. Many ocean storm waves entering the channel 

 proceed easterly with little loss of energy, and their energy can then be 

 further increased by local winds, and by shoaling and refraction. 



The unusual plan-shape of the island, shown in Figure 3, was developed 

 to obtain optimum wave protection. The area of the island on the ocean 

 floor is about 6.3 acres; at MLLW the area is 3.2 acres; gross area at 

 elevation +16 feet is 2.1 acres. Net usable flat area at +16 feet. 



