Table 7 (Continued)
Construction and Rehabilitation History
Date
Cost of the jetty construction was 5,400, and dredging of the
deposition basin was 9,300.
1966
(Cont)
Because of the migration of the navigation channel toward the north
1970
jetty with its potential for scour and undermining, a stone apron
was placed to provide toe protection along the rubble-mound section
of the jetty (Figure 1 )
the first half of the year showed several sections, along the sea-
ward 900 ft of the structure, with centerline elevations up to 5 ft
below the design grade. The centerline elevations over the remain-
der of the rubble-mound section were within 1 ft of the design ele-
vation. The sheet-pile weir section was usually within 0.2 ft of
The survey also showed that
the design elevation of
ft
approximately 50 ft of rubble mound at the seaward end had either
been displaced or had not been placed originally. The toe apron was
placed along the entire channel side of the rubble mound and ex-
tended around the head section, covering an additional 50 ft on the
ocean side. The width of the apron varied from 30 ft at the inner
end to 50 ft at the seaward end of the repair. The apron consisted
of a l-ft-thick stone foundation blanket covered with a 2-ft-thick
to
riprap. In addition, the apron section en-
section of
compassing the head had a third layer, 3 ft thick, of 500 to
riprap. Capstone totaling 510 tons was to be placed to
bring the structure up to grade. On 1-2 November 1969, during the
repairs, a moderate northeasterly storm, with estimated wave heights
close to those of the design wave, displaced an additional
3,400 tons of stone from the structure. Costs of the original re-
pair and subsequent repairs to bring the structure up to grade were
9,400.
Toe protection (Figure 12) was placed along the channel side of the
1,100-ft weir section because of continued movement of the
1974
tion channel and the costs involved should a catastrophic failure
occur (loss of sheet-pile sections resulting from scour and under-
The toe apron was to be 50 ft wide with a l-ft-thick
mining).
to 6-in. stone overlain with a 2.5-ft layer
foundation blanket of
riprap. Total cost of the repair was 8,800.
to
of
Construction of the south jetty, built of quarry stone and concrete
sheet pile to a length of 3,450 ft, began in July 1978 and was
1980
completed in August 1980. A bathymetric survey taken in 1978 showed
the channel to be extremely close to the north jetty with water
depths up to -25 ft
along the rubble-mound section and
along the weir jetty section. Model tests of the south
-12 ft
jetty alignment and geometry, conducted at the US Army Engineer
(Continued)
(Sheet 2 of 4 )
23
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