Table 3 



South Pass Jetties 



South Pass, Louisiana 



Date Construction and Rehabilitation History 



1875- East and west Jetties, 11,170 and 7,550 ft long, respectively, were 

 1882 constructed to provide protection and minimize maintenance dredging 

 for a 26- by 200-ft channel from the Gulf of Mexico to the 

 Mississippi River via South Pass (Figure 7). The jetties were built 

 parallel, 1,000 ft apart curving slightly to the southwest, and 

 terminated in water about 15 ft deep. The east Jetty extended about 

 200 ft past the west Jetty seaward end. The Jetties were built on a 

 base of fascine mattresses buttressed against rows of creosoted 

 timber piles. The mats were sunk in place by accumulating sediment 

 and addition of riprap stone. Multiple layers were placed in this 

 fashion with narrower mats placed in successive layers up to about 

 flood tide level. The mats were constructed of brush and timber of 

 various sizes, bound together, from 30 to 60 ft wide, 75 to 100 ft 

 long, and 2 to 2.5 ft thick. Timber cribs were placed at 100- to 

 200-ft intervals along the seaward several hundred feet of each 

 Jetty, providing additional protection and strength. The cribs con- 

 sisted of timber piles laid in alternate horizontal courses, crossing 

 each other at right angles. The piles in the floor courses were 

 placed in contact with each other, and those of the upper courses 

 were from 5 to 7 ft apart, thus forming compartments from 4 to 6 ft 

 square. The cribwork was held together with metal connectors and 

 sunk by filling the compartments with stone. The cribs were from 25 

 to 70 ft long, 15 to 20 ft wide, and 5 to 15 ft in height. 

 (Depending on water depth, the tops were at about flood tide level.) 

 Most of the cribs were placed on either side of the Jetty mats (i.e. 

 river or sea side). During 1881-1882 additional crib work was placed 

 mostly on the east jetty landward of the existing cribs. Concrete 

 cap blocks (cast in place) were placed along 5,430- and 2,750-ft-long 

 sections at the seaward ends of the east and west Jetties, respec- 

 tively. The cap blocks were from 4 to 12 ft wide (widest at seaward 

 ends), 20 to 50 ft long, 3 to 5 ft high, and placed atop a 1- to 2- 

 ft-thick layer of riprap stone. In addition, the east Jetty had a 

 parapet wall, built partly of mortared stone and partly of concrete, 

 placed on top of the cap blocks. The wall was from 3 to 4 ft wide 

 and 2 to 4 ft high with original top elevations varying from 4.5 to 

 6.8 ft above flood tide level. The original top elevations of the 

 remaining capped jetty sections were typically from 2 to 3 ft above 

 flood tide level. Initial settlement of the concrete cap sections 

 varied from 0.1 to 0.7 ft/yr with an average of 0.30 ft/yr for both 

 jetties. Figure 8 is an 1880 cross section of the seaward end of the 

 east Jetty. During September 1882 approximately 3,000 ft of the east 

 Jetty cap was damaged during a passing hurricane. 



(Continued) 



