Table 4 (Continued) 



Dabe(s) Construction and Rehabilitation History 



1917- Parallel bulkheads, consisting of wood sheet piles, brush- and rock- 

 1923 filled dikes, and fascine mats for scour protection, were constructed 

 on the channel sides of the Jetties. The bulkheads were spaced 

 2,400 ft apart. The east bulkhead (22,820 ft long) terminated at the 

 seaward end of the east Jetty, and the west bulkhead (16,120 ft long) 

 terminated about 5,400 ft from the seaward end of the west Jetty. 

 Total cost for the bulkheads (construction, scour protection, and 

 maintenance) was $2,584,000. In 1923, the existing spur dikes were 

 extended and new dikes constructed, reducing the effective width of 

 the pass to 1,750 ft. This contraction, combined with dredging, 

 resulted in a 35-ft channel depth. 



I92I- The east Jetty was extended 1,100 ft to 250+00, and the west Jetty 

 1923 was extended 850 ft to 190+50. The extensions and outer ends of the 

 Jetties (approximately 2,900 ft on the east and 4,900 ft on the west) 

 were capped with concrete. Continued settlement and cumulative storm 

 damages had lowered these sections so that at high tide considerable 

 portions were submerged, allowing a significant (10 to 20 percent) 

 amount of overflow. Extensions and capping costs were $664,000 and 

 $614,000, respectively. 



1924- During this period the Jetties were maintained by placing concrete 

 1937 capping and riprap stone (usually as a base for capping). As a re- 

 sult of continued Jetty subsidence, capping was required to maintain 

 flow between the Jetties. During this period, most sections of both 

 Jetties were capped twice with roughly 70,000 lin ft of concrete 

 placed over approximately 32,000 lin ft of active Jetty. (Landward 

 ends were essentially landlocked and required no additional work.) 

 Concrete was placed to an elevation of +4.5 ft mhw (or +5.5 ft mgl) 

 in lifts typically 3 to 4.5 ft high. Widths of the cap varied from 

 about 6 ft at the seaward ends to 3 ft at the landward ends. The 

 total cumulative cost for capping and stone was $1,170,000. In 1937, 

 additional spur dikes were placed along the outer 10,000 ft of the 

 Jetties, reducing the effective channel width to about 1,400 ft. 

 This addition was done in an effort to entirely eliminate maintenance 

 dredging. Figure 13a is an east Jetty cross section of cumulative 

 work done up to 1937 in the general vicinity of 180+00. 



1938- The east Jetty was repaired at the following locations: 163+00 to 

 1939 164+60, 188+30 to 190+90, 197+10 to 198+10, and 206+00 to 210+00. 



Fascine mats (40 ft wide and sunk with 60 lb of stone per sq yd) were 

 placed on each side of the Jetty to prevent scour. The section was 

 composed of 50- to 1,000-lb core stone and 3- to 7- ton cover stone. 

 The design geometry consisted of a +6 ft mgl elevation, 15-ft-wide 

 crown, and IV: 1.25 side slopes. A total of 24,300 tons of stone and 

 7,300 sq yd of mats was used. The seaward end of the east Jetty was 

 capped with concrete. A base of riprap stone was placed to +2 ft 

 mgl, and the cap sections were 10 ft wide, 25 ft long, and placed to 

 +4.7 ft mgl. The total cost of the repairs was $412,000. 



(Continued) 



27 



