Table 24
Cape Cod Canal Jetties
Cape Cod Canal, Mass.
Construction and Rehabilitation History
Two rubble-mound jetties were constructed by non-Federal interests at
eastern entrance (Figure 2 ) The north jetty was
7.
Cape Cod
3,000 ft long, with a
ft mlw crown elevation, a 25-ft crown
width, a
channel side slope, and a composite seaside slope of
and
above and below -12 ft mlw, respectively. Stone
placed above and below -12 ft mlw weighed approximately 3 to 6 tons
to 2 tons, respectively. At the seaward end a concrete
and 1 0
0
cap was placed. The crown width was 30 ft, and the existing bottom
elevation was -32 ft mlw. The south jetty appears to have been
constructed to a length of 600 ft, a
ft rnlw crown elevation, a
side slopes. The south jetty armor
20-ft crown width, and
stone weighed approximately to 5 tons.
The Cape Cod Canal, including the eastern entrance jetties, was
1927
purchased by the Federal government.
The seaward 925 ft of the north jetty was rebuilt to +18 ft mlw.
placed on the structure weighed a minimum of 6 tons,
Stone
except on the 125-ft-long head section, where the minimum size was
12 tons. The head section had a 25-ft crown width and a transition
in the seaward direction. A 20-ft
in side slopes from
to
side slopes were specified on the jetty trunk
crown width and
section. Prior to the repairs, typical crown elevations were from
+14 to +18 ft mlw on the trunk section and from
to +18
rnlw on
the head section. The contract price for placing an estimated
20,000 tons of stone was 0,000.
Inspection reports indicate the north jetty was in good condition,
while the south jetty was in poor condition with numerous voids and
1974
displaced slope stone along its entire length.
The south jetty was rebuilt to +13
mlw. The rebuilt section was
1974
690 ft long and terminated at the jetty's seaward end. Side slopes
A 13-ft crown width and 5- to
were
stone were speci-
fied on the seaward 200 ft. The remaining section required a 10-ft
crown width and 1- to 2.5-ton stone. A
layer of bedding
stone, 0 to 50 lb in size, was placed along the outermost 450 ft of
the jetty's seaside toe. Prior to the repairs, crown elevations were
ft mlw. The contract price for placing an
typically from
to
estimated 15,500 tons of stone was 4,800.
The jetties were visually inspected. The south jetty was found to be
1977
in good condition, while the north jetty needed repairs throughout
its entire length.
1986
Recent yearly visual inspections indicated the jetties were in good
condition.
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