Table 32 



Perdido Pass Jetties 



Perdido Pass, Alabama, SAM 



Date(s) Construction and Rehabilitation History 



1968- Twin converging jetties (Figure 56), spaced 600 ft apart at their 

 1969 seaward ends, were constructed as part of a weir-jetty system to 



help stabilize the natural inlet at Perdido Pass. The west jetty, 

 1,800 ft long, was of rubble-mound construction and extended from 

 the south end of a vertical seawall constructed by the Alabama High- 

 way Department. The east jetty, also 1,800 ft long, consisted of 

 1,290 ft of steel-reinforced concrete sheet pile and 560 ft of rub- 

 ble mound (50 ft of overlap between the two sections) . The west 

 jetty trunk section (Figure 57) was built to a crown width of 10 ft 

 at +6 ft mlw with 1V:1.5H side slopes. One layer of 2- to 3-ton 

 cover stone and 400- to 1,000-lb core stone were placed on a 1.5-ft- 

 thick bed of 5- to 100-lb blanket material. (A 2.5-ft-thick bed was 

 used on all other rubble-mound sections.) The west jetty head sec- 

 tion (Figure 57) was built to a crown width of 15 ft at +9 ft mlw 

 with IV: 2H side slopes. Two layers of 12- to 16-ton cover stone, 1 

 layer of 1- to 1.5-ton underlayer stone, and 400- to 1,000-lb core 

 stone were placed. The east jetty head section was similar except 

 for a +6 ft mlw crown elevation and 1V:2.5H side slopes. The 

 transition section on the west jetty consisted of 1 to 2 layers of 

 3- to 12-ton cover stone and 1,000- to 2,000-lb core stone. The 

 east jetty trunk section was similar to the west jetty section 

 except for the use of 3- to 5-ton cover stone placed in one or two 

 layers. The east jetty transition section consisted of two layers 

 of 5- to 12-ton cover stone and 1,000- to 2,000-lb core stone. The 

 east jetty sheet-pile weir section was 1,000 ft long with a top ele- 

 vation of -0.5 ft mlw. The shoreward 100 ft of the sheet pile was 

 set to +6 ft mlw followed by a 140-ft transition section to the weir 

 section. The concrete sheet-pile sections were 13 ft long (18 ft 

 long at the landward end), 2.5 ft wide, and 8 in. thick and were 

 reinforced with prestressed steel cable. The sheet pile was secured 

 via tongue-and-groove joints and mechanically fastened through their 

 support ends with 12- by 12-in. timber wales (on both sides of the 

 sheet pile) and steel connectors. The sheet pile was secured to the 

 existing dune line at its landward end with dredged material built 

 up to a crest elevation of +10 ft mlw. The water depths at the sea- 

 ward ends were 13 and 11 ft for the east and west jetties, respec- 

 tively. The jetty design used Hudson's equation with design wave 

 heights of 15 and 14 ft for the east and west jetties, respectively. 

 The wave heights were determined assuming depth-limiting conditions 

 and a 10-year frequency tide elevation of +6 ft mlw. Design of the 

 jetties was based partly on the recently completed project at 

 Masonboro Inlet, North Carolina, and discussion with personnel from 

 CERC. Placement of the weir on the east jetty was based on the 



(Continued) 



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