PART 11: SUMMARY OF CORPS BREAKWATER
AND JETTY PROJECTS IN NED
3. NED i presently responsible for 37 jetties and 46 breakwaters which
s
are principal or partial features of 52 projects. All of the projects are
located on or near the Atlantic coastline from northern Maine to western
Connecticut (Figure 1).
There is a total of 154,185
of breakwater
(62.4 percent) and jetty (37.6 percent) structures which are almost entirely
(99.7 percent) of stone construction. With the exception of a few projects
which were originally constructed using regularly shaped stone blocks, the
rubble-mound structures have been built using various sizes of stone. Use of
concrete as a building material has been limited to 2 or 3 projects and has
not been used in the past 35 years. Steel sheet piles were used in construc-
tion of one breakwater (Eastport Harbor).
4 . The cross sections of many structures are constructed with steeper
channel or harbor-side slopes than sea-side slopes. The largest cover stones
are typically placed in a single row on the crown, and the core i usually
s
made up of smaller "quarry
stone. Most of the structures have been built
without blanket or apron stone. Typical crown elevations are from
to
+26 ft mean low water (mlw). The large variation in crown elevations is
mainly due to local tide levels, which vary in the mean from 2 to 1 ft.
8
Relative to mean high water (mhw), crown elevations are typically
to
ft. Crown widths on structures with one stone crown width are typically 4
to 8 ft, while the variation in crown width for all structures is usually from
2 to 20 ft. Side slopes are typically
on the channel or harbor side and
on the sea or ocean side. Side slopes on the newer structures are
on both sides. Repaired side slopes are usually from
typically
to
Cover stone, usually placed to a relative thickness of 1 or
2 layers, varies from a minimum of 0.25 ton in low wave climate environments
tons (Point Judith). The newest projects (Plymouth and
to a maximum of
Provincetown Harbors breakwaters and Andrews River west jetty) were all
completed in the early 1970's.
Sufficient quantitative information on long- or short-term struc-
tural deterioration due to various wave climates was not found. Periodic
*
A table of factors for converting non-SI units of measurement to SI (metric)
units is presented on page 3.
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