Table 32 (Continued) 



Date(s) Construction and Rehabilitation History 



1968- predominantly westward littoral drift. The deposition basin located 

 1969 on the channel side of the weir was to have a AOOjOOO-cu yd capacity 

 (Cont) and provide for at least a 2-year volume of littoral drift. Esti- 

 mated stone quantities, sheet pile, and costs (including dredging) 

 were 49,400 tons, 7,190 lin ft, and $1,180,000. 



1969 Portions of the timber wale system on the weir section were lost 

 shortly after project completion. Subsequent inspections revealed 

 that the wales were slowly, but progressively, being lost. This 

 problem was also encountered on the Masonboro Inlet weir jetty. 



1970 An annual surveillance survey completed in March revealed a scour 

 trough on the channel side immediately adjacent to, and extending 

 almost the entire length of the weir. The scour appeared to be the 

 result of the extreme turbulences created by waves breaking over the 

 weir section. Immediate action was required to prevent possible 

 failure of the concrete sheet-pile weir; therefore, the scour trough 

 was filled with sand pumped by hydraulic dredge. During the summer 

 the channel side of the 1,000-ft weir was rehabilitated with armor 

 stone. The section (Figure 58) was to be placed at -6.5 ft mlw with 

 a 2-ft layer of 5- to 100-lb blanket stone and a 3-ft layer of 



100- to 500-lb cover stone. The crown width was 10 ft, the crown 

 elevation was -1.5 ft mlw, and the side slopes were 1V:1.5H. The 

 estimated amount of stone required was 4,850 tons. Cost of the 

 repair work was $84,000. 



1972 A SAM report on the weir jetty (prepared for CERC) indicated that 

 the deposition basin had filled to capacity during the first 

 2 years. The pattern of filling indicated that in addition to the 

 westerly littoral drift material sand movement on the ebb tide was 

 interrupted and collected in the basin. Subsequent encroachment of 

 additional material into the navigation channel indicated the need 

 for prompt dredging of the deposition basin on a regular basis. 



1974 The rubble-mound sections of both jetties were rehabilitated to 



bring them up to design cross sections. A field survey taken prior 

 to the rehabilitation showed substantial losses of material on both 

 jetties. Crest elevations on the east jetty were (a) inner 75 ft at 

 +0.5 ft mlw, (b) the next 200 ft from +3 to +5 ft mlw, and (c) the 

 remainder (including the head section) within ±1 ft of the design 

 elevation of +6 ft mlw. The entire west jetty appeared to have 

 undergone a substantial loss of bedding layer (it was 5 to 10 ft 

 wide) and cover stone on the channel side when compared to the de- 

 sign cross sections (no previous survey data found) . The crest 

 elevations on the trunk section varied from ft mlw to +5 ft mlw, 

 and the head section crest elevations were at or above the design 

 elevations. 



(Continued) (Sheet 2 of 3) 



102 



