CETN III-47
(3/92)
the 1959 sealing material has disappeared, and longshore
sediments -appear to be again passing through the jetties into the
navigation channel.
Buhne Point, California, Groin Sealinq:
Situated in Humboldt Bay, California, two rock groins were
constructed as part of the Buhne Point Shoreline Erosion
Demonstration Project.
One was shore-connected and the other was
an extension of a groin built in an earlier phase of
construction.
Each groin was permeable to sand transport.
In 1985 the groins were sealed by the injection of concrete
through holes drilled through the jetty crests.
The sealant mix
entailed fine and coarse aggregate, cement, clay, calcium
chloride, water, and air.
It was injected through a 3-in
d i a m e t e r hose through sealant holes drilled about 2 1/2 ft apart
along the groin centerline.
After completion of the work, inspection revealed 25 to 30 small
areas in the total 1,200 ft cumulative length of the sealed
groins where possible sand transport could occur.
No leaks are
known to exist below the +5 ft mlw elevation, or to cause a
problem of sand transport in significant quantities.
The groins
are performing their design function to this point.
Other California Harbor Jetty Sealinq Experiences:
Jetty sealing, using cementitious materials and injection
techniques similar to those used at Mission Bay and Buhne Point,
has been accomplished over the years in California at Oceanside
Harbor north and south jetties, San Luis Rey River jetties,
groins in the vicinity of Newport Beach, Marina Del Rey jetties,
and the Santa Cruz west breakwater.
Of all these sealed
structures,
only the Santa Cruz project resulted in slightly less
than expected effectiveness.
Insufficient sealant spread is
expected to be the reason for incomplete filling of the voids in
the Santa Cruz breakwater which allows minimal passage of
sediments through the structure.
Palm Beach Harbor. Florida, South Jetty Sealinq:
Between 1978 and 1985, a shoal occurred every year at Palm Beach
Harbor on the channel side of the south jetty.
The shoal, caused
by the passage of sand through the jetty, was very restrictive to
deep-draft vessels using the harbor.
In 1985 the jetty was sealed by the injection of sealant through
l-in diameter pipe inserted in holes drilled on 5-ft centers
along the crest.
Landward portions of the jetty where the voids
were filled with sand were sealed with chemical grout consisting
of a mixture of sodium silicate, reactants, and accelerators.
Cement-sand mixtures were initially attempted to seal voids in
the remaining portions of the jetty, but it appeared that only
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