excluding the wharf, is 1.1 acres, although additional usable space is 

 obtained by the effective use of vertical wall surfaces inside the rock 

 armor . 



Rincon Island was constructed of rock revetments containing sand 

 fill. It was constructed in stages and contains many types and gradations 

 of rock. The most exposed, western face is protected with 1,130 concrete 

 tetrapods , each weighing 31 tons. (Covered by U.S. Patent No. 2,766,592 

 issued 16 October 1956 to Establissements Neyrpic which has given Sotramer 

 (Societe d' Exploitation de Brevets pour Travaux a la Mer) an exclusive 

 license to promote and exploit the use of tetrapods throughout the United 

 States. The U.S. patent and the agreement expired 16 October 1973.) The 

 top elevation of the seaward breakwater wall is at +41 feet, the sides at 

 +24 feet, and the wharf and working area at +16 feet. Including the 

 35,000 tons of tetrapods, there are approximately 618,000 tons of material 

 in the island. The exterior sides of rock rubble slope at 1.5 on 1 except 

 on the east wings which are at 1.25 on 1. The tetrapod armor slopes at 

 1.5 on 1. Figure 4 shows vertical sections through the island. Locations 

 for these sections appear in Figure 3. 



A small wharf of prestressed concrete piles, concrete cap, and timber 

 deck was constructed on the lee side of the island within a semiprotected 

 harbor created by two "wings", or rock breakwater stubs. A single- lane 

 causeway, of steel pipe piles and timber decking on steel stringers, 

 extends from this wharf to the abutment on shore some 2,730 feet away. 

 Most bents are at 40-foot centers, and are of alternating single-pile and 

 double-battered-pile construction. The deck level climbs sharply from +16 

 feet at the island and is level for most of its course at 35 feet above 

 MLLW. 



c. Site Investigation - Bottom contours from National Ocean Survey 

 (formerly U.S. Coast and Geodetic Survey) charts were supplemented by 

 lead- line soundings and fathometer runs from one of Richfield 's exploratory 

 drilling ships, the La Cienoia. By several methods, soil borings of the 

 ocean bottom were made from the La Cienoia with two primary purposes . Tlie 

 first was to examine the suitability of the ocean floor as a foundation 

 for the island; the second was to see if a satisfactory source of dredge- 

 fill material for the island core was available within economical pumping 

 distance. The simplest sampling device for obtaining samples of the sur- 

 face material on the ocean floor is a snapper, or small spring-loaded 

 clamshell. The dart sampler is a heavily weighted stabbing device which, 

 when dropped to the ocean floor, recovers a cylindrical sample up to 3 feet 

 long. A jet-chum rig was used to recover cylindrical samples from various 

 depths by jet-churning to the desired depth and then stabbing samples from 

 the bottom of the hole. This last rig was later replaced by a rotary rig 

 which could also obtain cylindrical samples by the same method. The first 

 two methods of sampling were used in the search for dredge-fill material, 

 and the latter two for obtaining deeper information near the island site. 



Bottom conditions vary uniformly throughout the lease area. Over- 

 burden material on the ocean floor is a silty sand ranging into sandy silt. 



