Table 30
Lagoon Pond Jetty
Martha's Vineyard, Mass.
Construction and Rehabilitation History
The State of Massachusetts constructed approximately 450 ft of
rubble-mound jetty on the east side of the entrance to Lagoon Pond
(Figure 3 3 ) . It appears that the crown elevation and width were
by 7- by
ft mlw and ft, respectively. The crown consisted of
2-ft granite blocks, and 1- to 5-ton riprap was used on the side
slopes.
part of navigation improvements, to increase harboring areas for
1973
As
the recreational fleet, the jetty was extended 200 ft seaward,
terminating at about the -8
mlw contour. The landward side of the
existing jetty had accreted sediment and created a fillet out to its
seaward end, The plan of improvement called for an 8-ft-deep channel
into Lagoon Pond and an extension of the jetty to reduce future
channel shoaling. The design section called for a 6-ft crown width
at
ft mlw and
side slopes. The seaward end had a
side slope. The jetty was built with a 2-ft-thick bedding layer of
1- to 50-lb stone, a sand tight core of 1- to 300-lb core stone, and
a 4-ft-thick cover layer of 5- to 6-ton armor stone. The design was
based on an 8-ft breaking wave height. The contract cost for placing
an estimated 5,700 tons of stone was ,200.
The jetty and extension were considered to be in excellent condition
during a visual inspection.
1982-
Yearly visual inspections of the jetty revealed that it was in good
1986
condition.
67
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