Seament Shoreline Systems, Inc.
8229 Lighthouse Lane
King George, VA 22485
540-850-4744 mobile
540-775-4895 office
540-775-1481 fax
You need Java to see this applet.
Groins are placed perpendicular to the shoreline to slow the water
current and allow sand to settle and accumulate. Groins should be
placed with a gap between them equal to 150 to 200% of their
length. This will allow for a fairly even beach to form without large
gaps in the beach along the shoreline.

Sand will still shift up and down the groin field with wind and tide
changes. The groins will act to hold the existing sand on the beach
that was once washed downstream only to be replaced by sand
from the eroding bank. With a bulkhead installed to stop bank
erosion, the existing beach would probably wash away without a
groin field or other structures to hold it in place as the local sand
supply has been removed.
T wall Groin/ retaining wall:
Seament Shoreline Systems Inc. uses an upside down "T" design
of concrete sections that are bolted together to form the groins.
Each piece is ten feet long, two feet nine inches high and two feet
six inches wide. The concrete is minimum 6000 psi Department of
Transportation bridge grade mix strengthened with fibers and rebar
placed horizontally and vertically. They weigh approximately one
ton each. A tongue and groove joint is used between each section  
as well as steel plates to hold them together.
An angled cut-out on the land ward end of the Type A unit allows it
to fit up against the L wall bulkhead splash plate. The Type B unit
is a regular rectangular piece. The Type C unit has a taper slanting
to the seaward end to present a "low profile" groin. The ten foot
long sections are placed in a line and bolted together to form a
groin as long as needed.
A similar rock groin would cover more than ten feet of the beach
and be very difficult and dangerous to cross over. Wooden or vinyl
walls have a  similar footprint on the beach but do not last long
under the forces  of the waves hitting them because of their
weaker construction materials, as well as using poisons to slow
the attack of wood boring worms.
Copyright 2009 Seament Shoreline Systems, Inc. All rights Reserved.