As shown in Figure 11, postconstruction settlements have been much 

 slower than settlements during construction. The west revetment has 

 settled about 1.5 feet, the south wall about 0.5 feet, and the north wall 

 about 0.3 feet. The sumps have settled 0.2 to 0.3 feet, the cellular wall 

 up to 0.5 feet, and the east wings about 0.4 to 0.5 feet. No check points 

 on the interior of the island could be retained, and the pile-supported 

 wharf has shown little settlement. 



c. Evaluation of Settlement - Settlement of parts of the island rela- 

 tive to the island bench mark is primarily attributed to deterioration of 

 the Class F and G quarry-run material. This conclusion is deduced from the 

 following: 



(1) Magnitude of settlement tends to conform to the degree of 

 wave exposure, but armor materials show no relative displacement typical 

 of wave damage. 



(2) Weathering loss observed on exposed rock indicates that a 

 significant deterioration of the Class F and G material is occurring. 

 The average quality of the smaller quarry-run F and G material was known 

 to be poorer and thus probably more subject to deterioration. 



(3) The east face, which shows little or no settlement, contains 

 a Ventura River gravel Class G material, chosen so that piles could be 

 driven through it. This gravel is of sounder quality and is less erodible 

 than the quarry-run Class G material used elsewhere. 



(4) The settlement rate has not changed radically since construc- 

 tion. This tends to eliminate development by wave action of a graded filter 

 in the Class F and G materials as a source of settlement since a decreasing 

 rate of settlement is characteristic of that mechanism. 



(5) Loss of core material by wave action would produce a similar 

 result, (i.e., larger settlement where wave action was strongest) but such 

 settlement would be more irregularly developed. The uniformity of settle- 

 ment in any particular area therefore suggests that loss of core material 

 is not occurring. Also, there has been no noticeable discoloration of 

 adjacent water during periods of severe wave attack, as would be expected 

 with loss of core material. The island's filter zones were designed to 

 preclude such loss of core material, and observation of effects elsewhere 

 in this area suggests that they are effective. 



6. Littoral Transport 



Rincon Island is situated in a coastal region which is characterized 

 by substantial littoral transport with a pronounced longshore movement of 

 sand. The prevailing direction of the longshore transport is downcoast 

 toward Ventura. 



Studies of longshore transport at Santa Barbara Harbor, as summarized 

 by Wiegel (1964) , provide a better than average estimate of average annual 



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