Table 1
Mississippi River Gulf Outlet Jetties
Mississippi River Gulf Outlet, Louisiana
Date s
Construction and Rehabilitation History
1960
The River and Harbor Act of 29 March 1956 authorized construction of
a 35-ft-deep by 500-ft-wide channel from New Orleans to the Gulf of
Mexico as an alternative and necessary route in the event of emer-
gency, war, or blockage of the Mississippi River. A part of the
s
navigation improvements, jetties at the channel entrance also were
)
between
and
was completed at this time. The design
section (Figure
called for shell and riprap to be placed between
retaining dikes composed of dredged fill. The dikes were placed from
25 to 35
on either side of the planned jetty center line and built
up to elevations of
or
ft mean low water
on existing
ground above or below -2
mlw, respectively. The shell material
was placed to a center-line elevation of
ft mlw and
side
slopes. The 150- to 500-lb riprap was placed to an elevation of
ft mlw, a top width of 20 ft, and
side slopes. Due to soil
conditions, which consisted of predominantly fat clay with low shear
strength, additional capping stone was to be added at a later date,
thus allowing the existing soil mass to consolidate. A will be
s
seen, this method was used throughout construction of the jetties. A
tons of riprap and 78,300 cu yd of shell was placed
total
at a cost of
||content||
,211,500.
1961
Capping stone was placed on the existing north jetty, and south jetty
construction was completed between
and
On the north
capping stone was placed to an el-
and
jetty, between
side slopes
evation of
ft mlg, a crest width of 12 ft, and
Stone size varied from 200 lb to tons with 80 percent
(Figure
ranging from 2 to tons. The larger pieces were placed on exposed
surfaces. Existing jetty elevations, prior to capping, varied from
ft mlg. A total of 59,860 tons of stone was placed at a cost of
to
8,700. South jetty construction was identical to 1960 Phase I
construction of the north jetty. The jetties are parallel and spaced
1,400 ft apart (Figure 3. A total of 115,190 tons of riprap and
)
90,360 cu yd of shell was placed at a cost of 6,300.
1962
The south jetty was capped between
and
with
to
in a
6-ton stone. In addition, 500-lb to 2-ton stone was placed
2-ft-thick by 15-ft-wide layer on the channel side slope of the jetty
adjacent to the capped section (Figure
The cap design geometry
with a
ft mlg crown
was identical to the north jetty cap of
side slopes. Prior to
elevation, 12-ft crown width, and
capping, typical elevations on the Jetty (February 1962 survey) were
ft mlg. A total of 107,500 tons of stone was placed
from
to
at a cost of 7,100.
(Continued)
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