Table 1 (Continued)
2
Date(
Construction and Rehabilitation History
north jetty were rehabilitated (Figure
Of
1972
ft mlt and 1 ft,
6
The design elevation and top width were
respectively. The design side slopes were
on the inner
190
and
on the head semicircle, with a
slope transi-
tion section between. The
to
cubical granite cover stone
was placed in a double layer on the head semicircle and a single
layer elsewhere. The remainder of the cross section employed
to
core stone. A 5-ft-thick blanket of 0.5-in. to
stone
was placed beneath the toe of those sections where the new stone
intersected the existing ground. The blanket extended from 1 to
0
20 ft beyond the toe of the cover layer. The design was based on
Hudson's slope stability formula and a maximum wave height of 31 ft.
The design surge level was + 1 1 ft mlt. The computed slope stability
coefficient varied from 11.9 to 14.3 (above the no-damage criteria).
The design was chosen for economic reasons and the expected temporary
nature of the repairs. A
jetty extension was in the
planning stages. Total cost of the repair was 6,024 using
42,350 tons of stone. Hurricane Edith's passage in September 1971
temporarily halted completion of the repairs until the following
year. (Storm waves damaged sections which exposed core stone.)
By the end of 1977, sections of the north jetty concrete cap had
collapsed, other sections were cracking, and its seaward end needed
repair. All of the noted areas of cap damage were located along the
channel side. The damaged areas were similar to those seen pre-
viously on the south jetty cap where undermining and settlement of
the underlying stone had created cavities beneath the cap. It was
thought that Hurricane Anita in August
was the force which
triggered most of the cover stone breakage and collapse, because the
jetty was considered to be in good condition during a June 1977 in-
spection. The north jetty channel shoreline was continuing to erode.
Since 1962, the shoreline had receded about 200 ft, a rate of 13 ft
per year. The channel end of the 1 7 shoreline protection was now
91
shore protection stone was virtually non-
offshore. (The
existent.) During 1978-1979, repairs were made
1,700 ft of the
and adjacent shore protection. The seaward 35
jetty trunk were brought up to grade using
to
cover stone,
to
core stone
maximum on landward 1,000 of
blanket stone. The trunk section
trunk), and 0.5-in. to
starting 500 ft from the seaward end
a
crown width, a
side slopes. The concrete cap
stone projecting above
the shore protection (Figure
cover stone then were placed
geometry. A
bedding
(Continued)
51
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