Table 6
Bayou Fontanelle Jetties
Empire, Louisiana
Construction and Rehabilitation History
1950
out) in conjunction with a 9- by 80-ft navigable channel (between
Empire, Louisiana, and the Gulf of Mexico). The jetties were
constructed out to the -6 ft mlg contour (original lengths unknown)
and spaced 425 ft apart. The jetties were of rubble-mound construc-
tion placed on fascine mattresses. The design geometry (Figure 17)
had a
mlg crown elevation, 10-ft crown width, and
side
slopes.
1970
The seaward ends of the jetties were repaired, the landward end of
the west jetty was repaired and extended 420 ft, a 475-ft-long groin
was constructed 300 ft west of the west jetty, and a 325-ft-long tie
dike was built, connecting the groin to the west jetty (Figure 17,
repair history prior to 1970 not known). Prior to repairs, the east
and west jetties were 1,800 and 1,850
long, respectively, and typ-
ical center-line elevations (1970 surveys) varied from
to
ft
mlg on the east jetty, and from
to
ft mlg on the west jetty.
The landward end of the west jetty had been flanked and was about
300 ft from the existing shoreline with intervening water depths to
-7.5 ft mlg. The jetty sections were to be built to an elevation of
ft mlg, a 10-ft crown width, and
side slopes. Sections of
the seaward ends of the east and west jetties, 960 and
ft long,
respectively, and the landward end of the west jetty, 400 ft long,
were repaired with 1- to 6-ton stone. The groin, dike, and west
jetty extension were constructed with 300-lb to 2-ton stone and a
shell blanket, to be placed to -2.5
mlg or a minimum thickness of
1 ft. A shell core placed to -1 ft mlg, a top width of 20 ft, and
side slopes was used on the west jetty extension where the
existing grade was less than -3.5 ft mlg. The
stone side
slopes of this section were approximately
The shallower side
slopes provided a cover layer of stone along the exposed toes of the
shell core. Prior to this modification, scour and undermining were
removing the shell material. The groin and dike design elevations
were
and
ft mlg, respectively, with 6-ft crown width and
side slopes. The cost for placing an estimated 16,900 tons
of stone and 7,400 cu yd of shell was 6,000.
The west jetty was repaired along 75- and
sections at the
1978
landward and seaward ends, respectively; its landward end was ex-
tended 325 ft; and the tie dike and groin were repaired. A graded
stone, with a maximum stone size of 5,000 lb, was placed on the
design geometries. (The jetty extension
structures using the
shell bedding layer.) The preexisting center-line
had a
and
elevations (April survey) on the west jetty averaged
(Continued)
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