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
apart curving slightly to the southwest, and
terminated in water about 15
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
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 to 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
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-
wide (widest at seaward
tively. The cap blocks were from to 12
high, and placed atop a 1 - to 2-
long, to 5
ends), 20 to 50
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
wide
and 2 to 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
above
flood tide level. Initial settlement of the concrete cap sections
varied from 0.1 to 0.7
with an average of 0.30
for both
east jetty. During September 1882 approximately 3,000 of the east
jetty cap was damaged during a passing hurricane.
Continued
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