Table 5 



Tiger Pass Jetties 



Mississippi River Outlets, Venice, Louisiana 



Date(s) Construction and Rehabilitation History 



1978- Two parallel rubble-mound jetties were built at the entrance to 

 1979 Tiger Pass (Figure 16) in order to reduce the amount of maintenance 

 dredging required for safe navigation. These Jetties were part of 

 navigation improvements which included similar jetties at the en- 

 trance to Baptiste Collette Bayou (Figure 2), also built during this 

 time. These waterways provide a shorter navigational route between 

 east and west gulf waters and are used primarily by smaller vessels. 

 The north and south jetties were 4,700 and 2,700 ft long, 

 respectively, and spaced 540 ft apart with a 17- by 250-ft channel 

 between them. The north jetty extended 2,000 ft past the seaward end 

 of the south jetty. The design cross section (Figure 16) had a crest 

 elevation of +3 ft mlg, a crest width of 26 ft, and 1V:3H side 

 slopes. Shell material was used as core and bedding material (1-ft 

 minimum thickness). A 1-ft-thick layer of graded "c" stone (500-lb 

 maximum) was placed on the core side slopes followed by a 2-ft-thick 

 layer of graded stone (1,200-lb maximum) placed on the side slopes 

 and crown. Plastic filter fabric was placed at four test sections 

 (two per jetty) prior to placing the shell and stone. Two 500-ft 

 sections were at the seaward ends of the jetties and the remaining 

 two (500 and 1,000 ft long on the north and south jetties, 

 respectively) begin 1,000 ft from the landward ends and extend sea- 

 ward. Test sections were subdivided into 250-ft reaches, in which 

 different tensile strength fabric was placed or the design section 

 was modified ("c" stone omitted on two reaches). Settlement plates 

 were placed at 80- to 90-ft intervals within the test sections and 

 500-ft intervals elsewhere. These were placed to monitor settlement 

 and effectiveness of the test sections. The jetties were built on 

 top of mostly soft clays and were expected to settle 2 ft. For this 

 reason, the south jetty, which eventually was to be built up to +6 ft 

 mlg with graded stone (5,000-lb maximum) was to be constructed in two 

 phases, with the portion above +3 ft mlg to be built at a later date. 

 Prior to jetty construction, existing elevations were from +3 to -6 

 ft mlg. The total construction cost was $2,085,000 using 31,500 sq 

 yd of plastic filter fabric, 76,400 cu yd of shell material, and 

 105,200 tons of graded stone. A late 1979 inspection indicated that 

 the jetties had what appeared to be large amounts of differential 

 settlement and already constituted a maintenance problem. 



1984- Repairs were made to both jetties. The south jetty was raised with 

 1985 graded stone (5,000-lb maximum) to an elevation of +6 ft NGVD, a 4-ft 

 crown width, and 1V:2H side slopes. The north jetty was repaired 

 with graded stone (1, 500-lb maximum) to an elevation of +3 ft NGVD, a 

 l4-ft crown width, and 1V:3H side slopes (NGVD datum approximately 

 0.5 ft above mlg datum). Raising the south jetty was the second 



(Continued) 



37 



