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Management guide for marine
protected areas of the
Mediterranean sea
Permanent
ecological
moorings
This work should be referenced as:
Francour P., Magréau J.F., Mannoni P.A., Cottalorda J.M., Gratiot J. 2006. Management guide for Marine
Protected Areas of the Mediterranean sea, Permanent Ecological Moorings. Université de Nice-Sophia
Antipolis & Parc National de Port-Cros, Nice : 68 pp.
Photos: © All rights reserved
Jean-Michel Cottalorda, Mathieu Foulquié-Adena, Jean-François Magréau, Patrice Francour, Philippe
Robert.
Design and layout:
Pierre-Alain Mannoni
Translation:
Briane Loram
«Permanent Ecological Moorings» was designed as a
guide for managers of coastal or marine areas and for all
the administrative and associative structures who face
the recurrent problems of moorings. This guide sum-
marizes key issues and shows the various choices
available as well as being a technical guide. It wants
to answer the main questions that one faces while ma-
naging the diverse activities involved in mooring and
anchorage.
Anchorage or mooring? The authors of this guide have
voluntarily considered that the two terms are synony-
mous . Two categories of anchorage (or mooring) can be
defi ned : temporary mooring and permanent moo-
ring. A permanent mooring cannot be moved quickly or
easily. A temporary mooring is (usually) an anchor stored
onboard a boat (or a fl oating structure that needs to be
clamped down) and is re-hauled onboard when the boat
starts to move again.
The act of mooring with an anchor means, dropping
an anchor overboard to enable the immobilization of a
boat because the anchor falls and is wedged onto the
bottom. When removed , this anchor will be pulled up
forcibly in order to be freed from the seabed. Depending
on the fragility of the seabed or of the sea life (animals
or plants) that are developing there, the impact can
be signifi cant. The areas most adapted to moorings
are dependent on hydrological factors (currents, wave
exposure) and meteorological factors (wind exposure).
Along a stretch of coast these areas are not especially
numerous and the pressure of moorings on the seabed
can be frequent and signifi cant.
Every manager or organization in charge of managing a
coastal marine area will be facing this choice: preserve
as good as possible the seabed or allow unregulated
moorings with all the potential negative results that
can ensue. In addition to general boat use, the mana-
gers themselves may need to moor: their own boats,
permanent fl oating structures ( pontoon, barge, buoy)
or immersed structures (canalization , sign for diving
trail). How does one choose in cases like these an ecolo-
gical solution that has minimal negative impact for the
environment?
This guide will help in the choice of the most adapted
ecological solution depending on the environment in
question. It is divided into two main parts: the descrip-
tion of the major environments and the technical
description of various permanent ecological moo-
rings recommended.
Five main categories of environments have been selec-
ted: Sand and mud, Pebbles and cobbles, Boulders
and bedrock, Coralligenous formations, and Posido-
nia meadows. Each environment is briefl y described
and its ecological importance is detailed. The sensitivity
and vulnerability of each of these environments are
then evaluated depending on their particular characte-
ristics: speed of regeneration, structural complexity (its
architecture), ecological role, etc. These elements should
enable us to understand why one environment is more
or less fragile and why it is necessary to look for alterna-
tive solutions to moor with an anchor.
The technical solutions include a description of the im-
mersed parts (the ones laid on or pushed into the sea
bed) and the parts at the surface without forgetting
the connecting elements between the surface and the
bottom. Advice on the installation is also given. When
many solutions are possible for a given environment
they are presented in a comparative table in a syntheti-
cal manor that will help the manager to choose the opti-
mum solution taking into account the usage, the quality
of the substrate, and the estimated effort involved.
Please note: if this guide shows the various choices
between the different technical solutions, in no way
does it pretend to be nor replace a technical manual
necessary to calibrate the mooring. Further more it
does not address the juridical issues attached to pro-
blems of authorization or management of moorings.
If the place for a mooring does not need to be at a
precise location, a manager might then have the choice
between different substrates. In order to help this choice
a table summarizes the vulnerability of each environ-
ment, from the least to the most sensitive and vulnera-
ble.
At the end of this guide three appendixes give additio-
nal information: a list of bibliographic references , a
glossary and a list of contact addresses. The glossary
defi nes the terminology used in both the descriptive
environment and the technical part. This terminology
is written in blue in the text. The contact appendix
contains a non exhaustive list of addresses or Internet
sites in the assessment, installation, sale or calibration of
ecological solutions for permanent moorings.
Introduction
Contents
Part 1. Ecological moorings adapted to the habitats
SAND AND MUD
• The environment
• Adapted mooring techniques
• Solutions and estimated cost
PEBBLES AND COBBLES
• The environment
• Adapted mooring techniques
• Solutions and estimated cost
BOULDERS AND ROCKS
• The environment
• Adapted mooring techniques
• Solutions and estimated cost
CORALLIGENOUS FORMATIONS
• The environment
• Adapted mooring techniques
• Solutions and estimated cost
POSIDONIA MEADOWS
• The environment
• Adapted mooring techniques
• Solutions and estimated cost
Part 2. Sensitivity and vulnerability of the habitats : summary
Part 3. Intermediary elements and surface elements
Part 4. Product suppliers, contacts
Part 5. Glossary
Part 6. Bibliography
7
Ecological moorings
SAND
and MUD
Sand and mud
8
The environment
I - Description
Using simple terms such as mud, fi ne
sandy mud, coarse sand etc. indicates
clearly that the nature of this particular
environment, is one of soft substrates.
Fundamentally the nature of sediments
is determined by the geological structure
of the watershed and the shore. The
presence of fi ne particles (under 63
micrometers) is in relation to the muddy
fraction. Above one millimeter, particles
are considered as gravels or small
blocks of rock ( see Part 1, “Pebbles and
cobbles”) .
These soft substrates (sand and mud), can
be seen from the shore ( supralittoral
zone) down to the great depths (abyssal
zone). Moorings, whatever their type will
happen only in areas stretching from a
few meters to a maximum of 20 to 30
meters. The only zones affected are
therefore the infralittoral and lower
sublittoral zone .
The infralittoral zone starts just below
the low waters of the spring tides. The
shallowest zones can be covered by fi ne
sands usually quite heterogeneous, most
of the time mixed
with a small fraction
of dead shells and
small gravel or
debris from dead
Posidonia leaves.
Going fur ther down,
up to 20 meters
deep, sands are
fi ne, well calibrated
and usually without
coarse elements because these elements
are thrown ashore by the hydrodynamic
energy of the sea. Going even deeper,
the sea fl oor can be made up of various
substrates (Posidonia meadows, rocks)
or it can remain loose with almost
no vegetal cover, but there is then
a signifi cant fraction which is either
muddy or coarse.
The presence of sediments more or less
muddy indicates the beginning of the
lower sublittoral zone .
Depending on the hydrodynamism, the
depth and the topography of the coast,
the respective parts of sand, mud, and
organogenic debris ( shells, tests, etc.)
are highly variable and characterize
several biocenoses reaching depths of
up to 90 meters.
II - Ecological benefi ts
The presence of soft sediments allows
animals to bury easily as opposed to
more compact environments (Posidonia
meadows, pebbles, rocks or coralligenous
bottoms).
This physical characteristic explains
why, at fi rst sight a sandy bottom looks
deserted . A few fl at fi sh can swim
over it or rest on it ; some tubeworms
(Mediterranean fanworm, feather-duster
worm, Lanice) can stick out but the
diversity seems generally low compared
to other environments.
However, deeper in the sediment or
at night, the situation is very different.
These environments shelter a certain
type of fauna generally small in size and
with the capacity to bury itself. Within the
large size species there are numerous
bivalve shells (Tellina, Venus, Donax, etc.),
annelid worms (Nepthys, Owenia, etc.),
crustaceans (Upogenia, Callianassa, etc.),
echinoderms (Echinocardium, etc.), fi sh
(Gobius, Callionymus, Solea, etc.). A large
number of small size species making
up the meiobenthos and interstitial
fauna also live in this sand and mud
environment. They live most of the time
buried and occupy the interstitial space
left vacant between the grains of sand .
The ecological importance of a sand
and mud environment is considerable
because the animals living there are
for the most part preferential prey for
numerous species living in Posidona
meadows, rocky environments (Coris,
Symphodus, Serranus, etc.) or even in
the same soft bottom environments
(Mullus, Solea, etc.). It is also an area
of recruitment for numerous fi sh of
economical interest, small scale fi shing
(Mullus , Solea, etc.) or protected species
of invertebrates (Pinna nobilis ) .
Finally on these soft environments
vegetal formations can develop. They
are made of phanerogams: Zostera
meadows (Zostera noltii) or Cymodocea
meadows ( Cymodocea nodosa). These
two marine phanerogams are protected
Sand and mud
9
Physically these environments are
characterized by their low mechanical
holding power . They are for this reason
often avoided as sites for long term
moorings, except if proper precautions
are taken (e.g. length of chain). These
environments can also be characterized
by their lack of three-dimensional
structure, at least at the scale of the
mooring device. At the surface these
environments look fl at with no asperity
or bio-construction.
The presence of a large proportion of
mud or fi ne particles in the sediment will
create a strong suction effect “pull out
resistance” on a fl at surface. This physical
characteristic can sometimes be used
to reinforce the strength of a mooring.
Whatever the mooring type is, only the
surface of the sediment will be concerned
and because of its architecture no (or
very few) three-dimensional structures
risk being destroyed. In the case of a
temporary mooring or the installation
of a permanent structure, the abilities
for animals to bury themselves or move
quickly will probably protect them from
being highly affected. However, to date,
no scientifi c study has been carried
out to quantify such impacts on soft
bottoms.
On the contrary some large size species
with a limited ability to move can be
highly vulnerable: pen shell (Pinna
nobilis), heart urchin (Echinocardium), etc.
The same will happen if some vegetal
species (Zostera, Cymodocea, Caulerpa,
Penicillus) are present. The impacts can
therefore be signifi cant (ripping out,
destruction, covering up)
Fragments of Caulerpa taxifolia or
Caulerpa racemosa developing in this
environment are sometimes being lifted
by anchors or chains after a mooring. If
these fragments are not carefully put
ashore they could colonize a new site,
once the anchor is removed.
Permanent moorings have the
ecological benefi t of limiting the risks of
dissemination with Caulerpas invading
other areas through anchors and boat
chains .
III - Sensitivity and vulnerability
species: C. nodosa (Statutory order 19
July 1988, J.O. 9 August 1988) ; Z. noltii
(Statutory order 9 May 1994 J.O. 26 July
1994) .
Some algae of high
natural
heritage interest can also be
found in these coastal soft
bottom environments: for
example Penicillus capitatus
and Caulerpa prolifera .
As opposed to Posidonia
meadows that can also be
found on sandy bottoms (see
Part 1, “Posidonia meadows”),
these different formations do
not build three-dimensional
structures and therefore stay
only on a horizontal level.
The sandy or muddy areas not subjected
to a strong hydrodynamism (protected
bay, etc.) can also be colonized by two
species of introduced Caulerpas : Caulerpa
taxifolia and Caulerpa racemosa.
This vegetation might little by little
cover a large area of this “open” substrate
and not encounter many obstacles to its
growth or be ripped out during strong
swells.
Sand and mud
10
Adapted mooring techniques
A sand screw is a device made of a shaft
with one or several discs in a shape of an
helix or spire of an Archimedes screw.
It is well adapted to all sorts of
sedimentary bottoms and has a wide
range of usage : from the fastening of
small marking buoys to large ships.
One advantage of this system is that
it is removable, the sand screw can be
unscrewed and reused on another site.
I - Defi nition
A - Sand screw
II - Model description
Built of galvanized
steel, the sand screw
exists in light or heavy
models.
For the light models the
shaft, which is the body
of the screw, is made of
a steel bar of 18 to 30
mm in diameter. The
disc diameter can vary
from 150 to 250 mm.
The head of the shaft
is bent to form a closed
loop welded to itself.
For the heavier models,
the central shaft is
made of a pipe with
an external diameter
of at least 60 mm. The
diameter of the screw
part itself (coned or
straight) can vary
between 250 to 400
mm.
These anchoring
devices can be installed
individually or in a line
of 2 or 3 with a coupling
bar.
The pullout resistance
of the buried anchor in
sand is directly linked to
the volume and nature
of the materials of the
inversed cone, situated
above the inferior turn
of the screw.
A suction effect also
exists on the inferior
side of the disc .
This resistance
varies according to
3 parameters which
are: the depth of the
screw in the sediment
, the diameter and
thickness of the disc
or the helix, and the
mechanical resistance
of the sediment.
III - Holding principle
Sand and mud
11
IV -Ecological benefi ts
The impact of the sand screw on the sand
and mud environment is extremely low.
The size of the sand screw is reduced with
only the head uncovered sticking out a
few centimeters from the substrate.
This advantage is particularly valuable in
areas subjected to currents. In this case
the whole volume of sediment moved
creates a hydraulic turbulence which
in turn provokes a
scouring effect. This
specifi c effect does not happen with the
use of a sand screw because the volume
of the head is insignifi cant. The
biotope
is not modifi ed during the installation of
the anchor because there is no movement
of material or mixing of the sediment. This
enables us to consider that the biocenose
is not particularly disturbed.
The implementation of the sand screw
is straight forward and doesn’t involve
heavy equipment or techniques which
could cause secondary damage. The
accurate positioning of the device allows
the installation to take place at a very
precise site (e.g. a small patch of sand in a
middle of a posidonia meadow) .
V - Installation technique
The installation of the sand screw does
not require important nautical equipment.
The required space and the weight of
the installation equipment is not that
signifi cant and the size of the working
boat involved can equally be small.
Manual screwing
This technique can be considered only
with the small models of sand screws
(short length) and in a substrate where
the mechanical resistance is not too high.
With the use of a lever bar placed in the
head loop, two underwater workers
facing each other turn the anchor into
the ground until completion. The limits
of this technique are the physical force
that can be developed by the arms of the
underwater workers as well as the length
of the lever used. The absence of a real
fulcrum in a sand and mud environment
considerably reduces the development of
a signifi cant force.
Machine assisted screwing
This technique allows the development
of very high screwing torques and if
necessary to work at different depths
while controlling the power applied to
the system. It also avoids the underwater
workers using too much physical efforts.
The equipment needed is composed of
a hydraulic power unit , 2 hydraulic hoses
of suffi cient length and a screw gun with
a hydraulic engine and a head adapted
to the anchor head. This screwing tool
possesses two arms so that it can be
handled by the workers. These workers
standing on the seafl oor provide an
anchor point (as much as they can). Above
an anchor length of 1,5 meters, some fi xed
anchor points will be required because
the arms of the screwing system become
unreachable and not easy to use.
The screwing with a hydraulic machine is
by far the best installation technique.
Recommendation
The best combination of substrate and
anchor device must always be found.
The conditions of use must be properly
identifi ed as well as the wind, the wave
height and the volume and nature of the
object (boat, pontoon, and buoy) that it
will hold. The maximum wind speed and
wave height will allow an estimation of
the maximum force that the projected
moorings will be able to resist.
The mooring needs to be completely
anchored in the sediment. To release
any doubt in the case of an incomplete
screwing, the sand screw should be
unscrewed and moved to another place
to be properly set up. It is not advisable
to try to help the screwing with the use
of the hydro-jetting technique (high
pressure water gun).
Sand and mud
12
According to its use
It is the desired resistance of
the mooring that determines
the choice of a model. A general
rule is that the resistance is
proportional to the diameter
of the disc and the total length
of the anchor. Whether the
direction of the effort on the
anchor is consistent or not,
is also an important criteria
in the choice of the device. If
the direction is known and
consistent (e.g. mooring of a
fi xed pontoon or a marking
buoy in a strain type mooring)
it is necessary to screw the
anchor in the same axis so that
the effort applied is applied
only in an axial direction on the
shaft of the screw. In all these
cases model 1 can be used, it
is just necessary to adapt the
diameter of the disc and the
total length of the shaft.
If the direction of the load
applied to the anchor changes
in direction and angle ( e.g.
swinging mooring of a boat
with variations due to the wind
and the swell), it is necessary
to screw the anchor vertically
into the sea fl oor. In this type of
situation the shaft of the anchor
will be affected by lateral/
horizontal stress created by the
boat’s mooring lines.
In all these situations, the second
and third model are suitable.
The shaft made of a tube will
be able to resist much more to
being defl ected laterally than
a thinner steel bar of 20 to 30
mm in diameter. The length of
the shaft and the diameter of
the discs must be adapted to
the estimated load.
V - Choice of models
According to the quality of
the substrate
The mechanical resistance of
the sea fl oor is the major issue
in the choice of the anchor size.
It is not necessary to accurately
calculate this resistance, as done
by soil mechanic specialists
with tools such a penetrome-
ter or vane tester, but rather to
evaluate and estimate it.
It is necessary to check the
available thickness of the sedi-
ment in relation to the mini-
mum length of the anchor to
be installed. With an identical
load on different substrates,
the more fl uent , soft and mud-
dy, and of low compaction the
sediment is, the more the an-
chor will need to be long and
with a large disc diameter or
even better with discs on two
levels.
The shaft also will need to be
very rigid if a horizontal stress is
applied (model 3) or with a so-
lid shaft (model 1) if the stress
is only axial.
The more the soil is compact,
dense, with fi ne particles, and
not sensitive to scouring by
hydraulic effects, the more the
anchor will need to be of «nor-
mal proportions». This means
a medium length and disc dia-
meter but with a very rigid shaft
resistant to the torque applied
at the installation.
According to the estimated load
Standard sizes of sand screws varies
between 0.80 m to 3 m. Above this
size the technique used for installa-
tion is heavier and requires larger
boats.
The whole implementation can have
a signifi cant impact on the environ-
ment (moving of large boats, repea-
ted anchoring, repositioning). It is
therefore more advantageous to
increase the number of screws in or-
der to divide the load, than to put in
place one large anchor.
Triple sand screw on a sand and
mud environment.
An anchoring device can be made
up of one or several screws (2 or 3)
attached together with a coupling
bar (model 4).
It is equally possible to hookup
together for example two sets of
triple sand screws. In this case the
traction load is shared out between
six anchors.
Model 1
Model 2
Model 3
Model 4
Sand and mud
13
The deadweight mooring is an
object with a high density sunk
onto the sea fl oor to provide
a permanent anchor. It is well
adapted to sandy bottoms and
compact sediments and also has
a wide range of usage: from the
mooring of small marking buoys
to the mooring of large vessels.
I - Defi nition
B - Deadweight mooring
II - Model description
In general a classic deadweight
mooring has a square shape; its
height is equal to 1/5 or ¼ of its
length. The material often used
for practical reasons is concrete,
with sea-worthy qualities if pos-
sible.
Internal metal work is highly re-
commended as it provides a bet-
ter mechanical resistance and
increases the density of the struc-
ture.
The central anchor-ring is made
up of a steel bar with a large dia-
meter, for example in the shape of
an omega and attached inside to
the metal work. Certain deadwei-
ght moorings have on their un-
derside a cavity that increases its
suction effect. Others can have a
polyedric shape (a base of a squa-
re pyramid) which improves its
stability and limits the possibility
of overturning .
The pull-out resistance of
a dead weight mooring
is linked to two principle
factors: its apparent wei-
ght (dry weight minus the
Archimedes force) and the
size of the surface in con-
tact with the seabed.
III - Holding principle
Sand and mud
14
IV -Ecological benefi ts
The deadweight can be consi-
dered as a technical solution
acceptable on sandy substrate
on condition that, the volume
of the material used in this en-
vironment does not have any
secondary impact other than its
own presence.
Nevertheless some disadvanta-
ges of this type of mooring are:
the permanent occupation of
the seabed surface and the risk
of sliding and ripping because
of a too heavy load or a bad es-
timation of the mooring line.
For areas affected by currents,
the volume of the dead-weight
mooring above the surface of
the sea fl oor generates hydrau-
lic turbulences and causes a
scouring effect.
V - Installation technique
The installation process is done in seve-
ral phases:
•Land transportation of the deadweight
mooring.
•Handling in order to load it onto a barge
or a working boat, or placing it in the wa-
ter to be towed when the deadweight
mooring has a fl oatability chamber.
•Maritime transportation.
•Immersion of the mooring and placing
it safely on the sea bed in the allotted
place.
The resources used should be proportio-
nal to the weight of the mooring to be
put in place.
Small deadweight moorings
For small deadweight moorings, all han-
dling can be manual or assisted by a
handling boom, a small winch or a hoist.
The descent to the bottom can be sim-
ply controlled with its own mooring line
or any other line properly secured and
controlled by a cleat or a bollard.
Medium and large moorings
For medium and large moorings, all the
handling is more tricky and requires
professional intervention (land based
lifting crane, hydraulic crane on a boat,
management of the moving weight on
the boat).
The descent to the bottom is generally
done with the help of a winch at the
end of the arm-crane on the boat. Pro-
perly adapted boats and equipment are
always a safety precautions. There exists
other ways such as, fl oating chambers
catamaran style with a handling boom
and a winch and small barge with a cen-
tral hole and winch.
The use of a lift bag (large soft bag fi lled
with air) is possible but reserved to hi-
ghly trained and experienced personal.
The uncontrolled variations in the air
in the lift bag and potential leaks can
be very dangerous. It is not considered
to be a good idea to directly release
the deadweight mooring from the sur-
face with its complete mooring line. In
these conditions the deadweight does
not descend vertically, the speed of the
descent on its underside creates a lift
and therefore its trajectory is skew and
random. The landing on the seabed is
uncontrolled and very imprecise and the
deadweight mooring can completely
overturn trapping its mooring line. For a
large size deadweight mooring, installed
in deep places, it is indispensable to use
a specialized boat.
Recommendations
The dead weight should include a se-
cond anchor ring that will be used when
the fi rst is worn out (the replacing of an
anchor ring on a deadweight mooring
already in place is an expensive and diffi -
cult operation).
The section of the anchor ring must be
oversized as it is the only wearable part.
The use of a mobile anchor ring (e.g. a
few chain links attached to the concrete)
must be avoided, as the movement of
the links means that permanent wearing
will take place.
The conditions of use must be properly
identifi ed as well as the wind, the wave
height and the volume and nature of the
object (boat, pontoon, and buoy) that it
will hold. The maximum wind speed and
wave height will allow an estimation of
the maximum force that the projected
moorings will be able to resist.
The shape and weight must therefore be
adapted to the load expected. Finally the
cost of handling and transportation must
be taken into account when looking at
the option of a deadweight mooring.
Sand and mud
15
According to use
This choice is relatively simple aside from
the calculation of the sliding coeffi cient
done by soil specialists. It is the apparent
weight and the shape which will infl uen-
ce the choice. As with all types of ancho-
rage, the deadweight will be subjected
to an important stress.
When in a situation where the stress is
mainly vertical and the fl oating objects
on the surface may be submerged (mar-
king buoys anchored with a tight or
short mooring line to limit the swinging
space); a fl at shape is not essential, but
the apparent weight of the deadweight
should be superior to the Archimedes
force provoked by the total immersion
of the object attached on the surface.
The shape of the concrete block will be
very important due to the fact that, in the
majority of cases the stress is horizontal
and is applied by a structure through a
long line. The largest surface possible is
then preferable. Its apparent weight will
be proportional to the force created by
the attached fl oating object.
V - Choice of models
According to the quality of the
substrate
Fine sediment, dense and slightly
muddy will clearly improve the suc-
tion effect of the deadweight and
increase its hold. The same block
submitted to the same force with a
coarse shell or madrepore sand will
slide more easily.
On a softer muddy-sand the hold
will be of poor quality, the deadwei-
ght will be moved easily in a lateral
way and will bury itself until it fi nds
a substrate suffi ciently dense to hold
it properly.
According to the estimated load
As opposed to other techniques of moo-
ring, the deadweight mooring is the only
one that is placed on the sea fl oor. If its
dimensions are incorrect, it will move in
the direction of the dynamic force.
This often happens when some signifi -
cant swell makes the working angle of
the mooring line vary greatly.
The traditional deadweight mooring
is made of a block of a certain weight
and a simple mooring line. This simple
mooring line is made of a few meters of
ground mooring chain of large diameter,
plus a longer mooring chain of a smal-
ler diameter then linked to a rope made
of technical textile. This classic method
gives an overall good resistance. The
various elements of the system enable
the absorption of the load. In the case
of a small force, only the mooring chain
is under tension. However if the force is
greater, the mooring chain as well as the
length of the ground-mooring chain, is
under stress. With a very important force,
the two chains absorb a large part of the
force while the weight of the deadwei-
ght absorbs the residual effort.
This traditional conception of a mooring
line is today banned because of its des-
tructive impact on the environment due
to the incessant sweeping of the chain
on the sea fl oor. In Part 3, intermediary
and surface elements, we will detail tech-
niques for having mooring lines that are
more environmentally respectful.
If we take away the absorbing effect of
the chains, the weight of the deadwei-
ght must be increased and the correct
working angle of the mooring line must
be respected.
The trenching of the deadweight (to
bury the deadweight in a hole of iden-
tical depth to the height of the concre-
te block) increases the resistance and
avoids the effect of scouring and keeps
the draught identical (height of water
above the sea bottom).
The installation is longer and more
costly, the equipment required (hydro-
lift, hydro-jetting, etc.) is heavier, and the
moving of the substrate material and
the resuspension of the fi ne sediment
has a negative impact on the living en-
vironment.
Sand and mud
16
- L= length in mm
- TØ = shaft diametrer in mm
- DØ = disc diameter in mm
- PR = Dry weight in tons
- FSS = sub-surface fl oat, diameter in mm
- BRCC = rigid buoy with central chimney
- Estimated cost of supplies in euros (without tax and delivery cost)
- All dimensions in mm
- Floating line: rope linking marking buoys together and fastened to these
- Floating structure : a swimming platform of 4 x 4 m on a swinging mooring
Sand screw
LIGHTWEIGHT BOATS < 7 METERS
Screw: L 1500, TØ 20/30, DØ 250
Polyamide line Ø 18, buoy FSS 11 litres + BRCC
Cost anchor only: 60
MEDIUM WEIGHT BOATS 7 TO 11 METERS
Screw: L 1500/1800, TØ 60, DØ 300
Polyamide line Ø 20 , buoy FSS 11 litres + BRCC
Cost anchor only: 400
HEAVYWEIGHT BOATS 12 TO 18 METERS
Screw: L 2000, TØ 60, DØ 350
Single screw, double or triple depending on size and wea-
ther conditions
Polyamide line Ø 24/30, buoy FSS 11/25 litres ,BRCC 650
Cost anchor only: Simple 500 , double 1200 , triple 1500
MARKING BUOYS
Buoy 400/600 : Screw: L 800/1000/1500, TØ 16/18/20, DØ
200/250
Buoy 800 : Screw: L 1500, TØ20, DØ 200/250
Polyamide line Ø 14/16, chain 12-16
Buoy FSS 6/8 litres
Cost anchor only: 30 to 60
FLOATING LINE
Screw: L 1500, TØ20, DØ 250
Polyamide line Ø 14/16 , chain Ø 12 / 16
Buoy FSS 6/8 litres
Estimated cost anchor only: 60
FLOATING STRUCTURE
Screw: L 1500/2000, TØ 60, DØ 350
Polyamide line Ø 24, FSS 11 litres, swivel Ø 20
chain in mid-water Ø 20
Estimated cost anchor only: 500
IMMERSED STRUCTURES
Depending on the nature of the object and its fl oatability, a
specifi c study is needed
Dead weight
LIGHTWEIGHT BOATS < 7 METERS
PR= 0,8 to 1,5 t
Polyamide line Ø 18 , buoy FSS 11 litres + BRCC
Cost anchor only: 100 to 250
MEDIUM WEIGHT BOATS 7 TO 11 METERS
PR= 2 to 3,5 t
Polyamide line Ø 20 , buoy FSS 11 litres + BRCC
Cost anchor only: 450
HEAVYWEIGHT BOATS 12 TO 18 METERS
PR= 4 to 6 t
Polyamide line Ø 24/30, buoy FSS 11/50 litres ,BRCC 650
Cost anchor only: 550 to 800
MARKING BUOYS
Buoy 400/600 : PR= 0,12 t to 0,25 t
Buoy 800 : PR= 0,40 t
Polyamide line Ø 14/16, chain 12-16
Buoy FSS 6-8 litres
Cost anchor only: 60 to 100
FLOATING LINE
PR = 0.4 t
Polyamide line Ø 14/16, chain 12 / 16
Estimated cost anchor only: 100
FLOATING STRUCTURE
PR = 2.5 t
Polyamide line Ø 24,
Buoy FSS 11 litres , swivel Ø 20, chain in mid-water Ø 20
Estimated cost anchor only: 400
IMMERSED STRUCTURES
Depending on the nature of the object and its fl oatability, a
specifi c study is needed
Solutions and estimated cost
Sand and mud
17
Ecological moorings
on PEBBLES and
COBBLES
Pebbles and cobbles
18
I - Description
Intermediary between the soft and
hard substrate, the areas of pebbles
and cobbles are characterized by
the presence of mobile elements of
a variable size (several centimeters
to several decimeters in diameter)
resting in layers of different
thickness.
In the coves of rocky coasts more
or less exposed to waves, areas of
pebbles are often seen. The average
diameter of these pebbles doesn’t
exceed tens of centimeters in
diameter. Above this size we talk of
small blocks of rock, crushed rock or
cobbles.
In calmer areas, with a lower
hydrodynamism, the continuous
sedimentation of fi ner particles
helps to turn the environment into a
sandier zone.
These areas of pebbles are strongly
linked to the hydrodynamism of
the site. Because the hydrodynamic
energy quickly reduces at higher
depths, such areas are rarely seen
below a depth of a few meters. It is
possible to see cobbles at only a few
meters from the surface and up to 50
meters or more.
The elements composing these
zones are more or less mobile in
accordance to their size. When their
size becomes too signifi cant ( a
meter or more in diameter), the term
cobbles becomes inappropriate
and it is better to talk of boulders or
blocks.
If pebbles can be seen only on fl at
bottoms, the cobble zones can
affect areas with quiet steep slopes.
The instability of these bottoms will
be greater when the slope is more
signifi cant.
Depending on the regularity of the
size of the elements making up a
fl oor of pebbles or cobbles, the space
between these elements will be very
different. The space will be greatly
reduced
The environment
Pebbles and cobbles
19
These environments are characterized by
their considerable mechanical instability.
As a result they are often avoided for
long term moorings unless proper
precautions are taken (e.g. signifi cant
length of chain, etc.).
Whatever the average size of the
elements that make up the bottom, they
are a problem when mooring.
On pebble fl oors, the instability is so high
that it is a risky operation to moor using
an anchor, in particular for boats when
they are unable to wedge the anchor
into the substrate. For this reason these
substrates are often avoided by leisure
boats.
It is actually very diffi cult to estimate the
vulnerability of such environments. In
comparison with other environments,
the specifi c diversity is limited and the
ecological interest is certainly less.
The act of mooring will create a
movement of elements by displacing or
overturning the elements.
As the majority of living species in this
environment are adapted to the mobility
or instability of the substrate, the impact
can be very slight.
If the rubble bottom is made up of
elements of a signifi cant size, some of
the species can live attached to the
underside of the small elements.
The presence of living organisms on
the underside illustrates the sciaphil
characteristic of the organisms. Any
turning-over of these elements thus
causes the deaths of the organisms.
II - Ecological importance
III - Sensitivity and vulnerability
These environments as previously
described, are characteristically unstable.
This instability strongly limits or totally
prevents the installation of sessile
organisms at the surface of the pebbles
or small rocks.
Sessile fauna or fl ora will only be seen
in the presence of elements of large size,
stable or not very mobile.
In the case where neither sand nor
fi ne gravel can clog up the interstices
between the pebbles, the ecosystem
is very simple: organic debris brought
by the sea and stuck in the interstices
feed two detritivorous amphipod
crustaceans (Melita hergensis and
Allochestes aquilinus). These can be prey
for a Gobiescidae (Gouania wildenowii).
While the size of the cobbles increases,
the instability decreases and the density
of the fl ora and fauna increases.
However large fi xed species present
on the rocks (see part 1, “Boulders and
bedrock”) are absent. Most of the specifi c
diversity is represented by small mobile
species living in the interstices or fi xed
under the elements. Nevertheless the
diversity is far from reaching the one
present in fi elds of large blocks.
Taking into account what has been
mentioned, the ecological importance
of these environments is certainly
more limited than others (coralligenous
formations, phanerogam meadows,
etc.).
However certain species are strictly
confi ned to these environments and
for this reason, they are considered very
rare. The small Gouania wildenowii is a
typical example
Pebbles and cobbles
20
adapted mooring techniques
The sand screw adapted to pebbles
and cobbles correspond to models 2,
3 and 4 (see also sand screw in Part 1,
Sand and mud)
I - Defi nition
A - Sand screw (see also sand screw in Part 1, Sand and mud)
II - Model description
The adapted models are only the hea-
vy duty ones with a central shaft made
up of a tube with an external diameter
of 60 mm or more.
The diameter of the spires can vary
from 250 to 400 mm. The total length
varies between 1 to 2 meters. The he-
lix is cone-shaped (see model 2). The
small size of the cutting edge allows
the screw to move between the peb-
bles more easily.
The pitch of the screw (distance
between two sides of the spire during
a complete turn) will always be supe-
rior to the maximum diameter of the
biggest pebbles present at the site.
This mooring can be installed indi-
vidually or attached in lines of 2 or 3
with a coupling bar.
As the ecological interest of the
environment is less than that of
the other environments, the eco-
logical value of the sand screw is
fairly limited.
Model 2
Model 3
Model 4 : Sand screws with a
coupling bar
V - Installation techniques
IV -Ecological benefi ts
The use of a hydraulic power unit is re-
quired. The installation will also be hel-
ped by the use of a stabilizing frame gi-
ving an anchor point to the screw gun .
This frame will absorb blows when the
screw is being dug into the pebbles.
The size of the pebbles and small cob-
bles will have to be estimated as well as
the presence of sand or small gravel. If
the pebbles have a diameter over 10 cm
and if the cobbles are large and mixed
together with absence of sand and gra-
vel, the device will not screw into the
substrate. Another technique will have
to be used (see other techniques in Part
1, Pebbles and cobbles”).
If the ground is made of pebbles,
sparse cobbles and sand then the
best combination of sand screw mo-
del and the substrate will need to be
looked for.
The conditions of use for the perma-
nent mooring need to be defi ned
and limits chosen (in connection to
wave height and wind speed) in the
size and weight of the objects moored
to the permanent mooring. Wind speed
and wave height allows the calculation
of the maximum load that will have to
be faced by the system (including inter-
mediary elements). The shaft must be
entirely screwed into the substrate and
if the screwing is incomplete the equip-
ment needs to be removed to satisfacto-
rily install it at another location. It is dif-
fi cult with this type of substrate to easily
evaluate the thickness available and the
consistency of its composition.
The pull-out resistance will be satisfac-
tory to very good if the following con-
ditions are met: stability of the pebble
area and the presence of sand and
fi ne gravel giving a good cohesion for
the layer of substrate affected.
III - Holding principle
Pebbles and cobbles
21
The deadweight mooring is a technique
adapted to pebbles and cobbles.
The mechanical characteristics of this
ground, compared to a sandy or muddy
ground, change the pull out resistance
of a dead weight.
In the presence of pebbles and cobbles,
the suction effect no longer exists; the
underside of the concrete block lays only
on a reduced number of contact points.
The contact area is proportionally low
and the soil is relatively unstable and the
round shape of the pebbles promotes
the sliding effect.
I - Characteristics
B - Dead weight mooring: see also Dead weight in Part 1, Sand and mud
II - Description
With the same conditions of use,
the models for pebbles and cob-
bles have to be heavier than those
for softer substrates to compen-
sate for the sliding effect.
A positive advantage can be obtai-
ned if there is a cavity on the un-
derside of the deadweight.
The deadweight will settle better
on the seafl oor, coping with irre-
gularities of the surface and of the
protruding cobbles.
As the ecological interest of the
environment is less than for
most of the other environments,
the ecological value of the dead-
weight is fairly limited.
V - Installation techniques
III - Ecological benefi ts
In case of an irregular fl oor of cobbles,
the precise location of the deadweight
will need to be chosen. This needs to be
where the concrete block lays the best
and would itself be blocked by bigger
and sticking out cobbles. If necessary
prepare the place by moving certain
cobbles.
In the presence of pebbles, it is better to
prepare the zone to get a uniform sup-
port and a good trim for the deadwei-
ght. Partial trenching of the deadweight
into the substrate will improve the pul-
lout resistance.
Recommendations
The dead weight should include a se-
cond anchor ring that will be used when
the fi rst is worn out (the replacing of an
anchor ring on a deadweight mooring
already in place is an expensive and diffi -
cult operation).
The section of the anchor ring must be
oversized as it is the only wearable part.
The use of a mobile anchor ring (e.g. a
few chain links attached to the concrete)
must be avoided as movements of the
links create a permanent wearing effect.
The conditions of use must be properly
identifi ed as well as the wind, the wave
height and the volume and nature of the
object (boat, pontoon and buoy) that it
will hold. The maximum wind speed and
wave height will allow an estimation of
the maximum force that the projected
moorings will be able to resist. The shape
and weight must therefore be adapted
to the load expected.
Finally the cost of handling and trans-
portation must be taken into account
when looking at the option of a dead-
weight mooring
IV - Technical principle
The pullout resistance is
closely linked to the appa-
rent weight.
Pebbles and cobbles
22
Solutions and estimated cost
- L= length in mm
- TØ = shaft diametrer in mm
- DØ = disc diameter in mm
- PR = Dry weight in tons
- FSS = sub-surface fl oat, diameter in mm
- BRCC = rigid buoy with central chimney
- Estimated cost of supplies in euros (without tax and delivery cost)
- All dimensions in mm
- Floating line: rope linking marking buoys together and fastened to these
- Floating structure : a swimming platform of 4 x 4 m on a swinging mooring
Sand screw
LIGHTWEIGHT BOATS < 7 METERS
Screw: L 1500, TØ 60, DØ 250/300
Polyamide line Ø 18, buoy FSS 11 litres + BRCC
Cost anchor only: 400
MEDIUM WEIGHT BOATS 7 TO 11 METERS
Screw: L 1500/2000, TØ 60, DØ 300
Single screw or double
Polyamide line Ø 20 , buoy FSS 11 litres + BRCC
Cost anchor only: simple 500 , double 1200
HEAVYWEIGHT BOATS 12 TO 18 METERS
Screw: L 2000, TØ 60, DØ 350
Screw double or triple depending on size and weather con-
ditions
Polyamide line Ø 24/30, buoy FSS 11/25 litres ,BRCC 650
Cost anchor only: double 1200 , triple 1500
MARKING BUOYS
Buoy 400/600 , Screw: L 800/1000/1500,
TØ 16/18/20, DØ 200/250
Buoy 800, Screw: L 1500, TØ20, DØ 200/250
Polyamide line Ø 14/16, chain 12-16
Buoy FSS 6/8 litres
Cost anchor only: 30 to 60
FLOATING LINE
Screw: L 1500, TØ20, DØ 250
Polyamide line Ø 14/16 , chain Ø 12 / 16
Buoy FSS 6/8 litres
Estimated cost anchor only: 60
FLOATING STRUCTURE
Screw: L 1500/2000, TØ 60, DØ 350
Polyamide line Ø 24, buoy FSS 11 litres, swivel 20
chain in mid-water 20
Estimated cost anchor only: 500
IMMERSED STRUCTURES
Depending on the nature of the object and its fl oatability, a
specifi c study is needed
Dead weight
LIGHTWEIGHT BOATS < 7 METERS
PR= 0,8 to 1,5 t
Polyamide line Ø 18 , buoy FSS 11 litres + BRCC
Cost anchor only: 100 to 250
MEDIUM WEIGHT BOATS 7 TO 11 METERS
PR= 2 to 3,5 t
Polyamide line Ø 20 , buoy FSS 11 litres + BRCC
Cost anchor only: 450
HEAVYWEIGHT BOATS 12 TO 18 METERS
PR= 4 to 6 t
Polyamide line Ø 24/30, buoy FSS 11/50 litres ,BRCC 650
Cost anchor only: 550 to 800
MARKING BUOYS
Buoy 400/600 : PR= 0,12 t to 0,25 t
Buoy 800 : PR= 0,4 t
Polyamide line Ø 14/16, chain 12-16
Buoy FSS 6-8 litres
Cost anchor only: 60 to 100
FLOATING LINE
PR = 0.4 t
Polyamide line Ø 14/16 , chain Ø 12 / 16
Estimated cost anchor only: 100
FLOATING STRUCTURE
PR = 2.5 t
Polyamide line Ø 24,
Buoy FSS 11 litres , swivel 20, chain in mid-water 20
Estimated cost anchor only: 400
IMMERSED STRUCTURES
Depending on the nature of the object and its fl oatability, a
specifi c study is needed
Pebbles and cobbles
23
Ecological moorings
on BOULDERS
and BEDROCK
BOULDERS and BEDROCK
24
I - Description
Areas of boulders and bedrock are
defi nitely part of the hard substrate
category. Made of blocks of large size
(from a few decimeters to several meters
in diameter) or continuous bedrock,
these seafl oors are characterized by
the immobility of the elements they are
made up of.
These areas of boulders and bedrock can
be seen from the surface along rocky
coasts down to high depths.
If the biocenoses of supralittoral or
mediolittoral are not much affected
by anchorages due to their closeness
to the surface, this is not the case in
deeper areas for the biocenoses of
photophil algae that make up most of
this environment. The description of this
environment will thus focus mainly on
this biocenose.
The stability of the elements that
make up this environment allows the
development of a dense fi xed fl ora and
fauna at the surface of the boulders or of
the bedrock.
The presence of boulders will mean
the presence of numerous spaces in
between them. In contrast to a bedrock
substrate, the number of cavities will
be very reduced or inexistent. These
microhabitats (cavities or spaces
between the boulders) can be colonized
by a vagile or sessile fauna, usually
sciaphilic.
The absence of cavities therefore
reduces specifi c richness. Other
physical factors such as the quantity of
light and hydrodynamism will equally
have an impact on the richness of this
environment. A strong hydrodynamism
will reduce the abundance of large
size sessile animal species while the
vegetation (Cystoseira algae) will still be
present.
Excepted for rocky environments
made of large fl at rocks, the boulders
and bedrock environments are fairly
heterogeneous and often home to
a mosaic of habitats. The habitats
are usually organized in layers from
sciaphilic (cavities) to photophilic
(upper side of boulders and bedrock)
zones.
Hard substrates populations are
dominated qualitatively and
quantitatively by the vegetation in the
infralittoral (and to a smaller degree
lower sublittoral) zones.
Bio-constructions can develop on
rocks (boulders or bedrock), like the
calcareous horizontal structures built by
the Lithophyllum or the coralligenous
but they will not be described here.
The Lithophyllum “pavements” or
“sidewalks” are too high to be concerned
the environment
BOULDERS and BEDROCK
25
These environments are part of the hard
substrate category. The major obstacle
to moorings would be the hardness of
the substrate. The heterogeneity of the
substrate (cavities for bedrock areas or
spaces between the boulders) reinforce
the problems presented by anchoring in
these environments (high risk of having
the anchor stuck).
On the contrary the size of the blocks
is such that it makes the environment
stable in comparison to pebbles and
cobbles. The ability for the anchor to
hook onto something will therefore be
very likely.
As opposed to boulders and bedrock
cavities, a large area of fl at rock can
cause diffi culties when anchoring
because of the absence of infractuosity
for an anchor to hook onto. It is certain
taking into account the great ecological
importance of this environment that
the impact of unadapted moorings
can be very signifi cant. In fact, the
development of algal communities of
large size species (several decimeters for
Cystoseira forests) represents a major
factor of vulnerability.
If an anchor does not modify the three-
dimensional structure because of the
stability the elements, it still can erode
the algae forest. These environments
shelter a fauna of high diversity which
is a source for food for others species
living in the interstices or the cavities.
Any reduction in the surface of algae,
especially macro algae brings with
it considerable reduction of specifi c
richness similar to a pollution
accident. The signifi cant reduction
of the production can then have
indirect repercussion on the adjacent
environments supplied with organic
matter from these areas.
II - Ecological importance
III - Sensitivity and vulnerability
The biocenose of the photophilic algae
occupy mainly areas of boulders and
bedrock. This biocenose of high richness
regroups several algal communities.
At depths animal species (gorgons,
Eunicella) can also occur in these
environments.
The specifi c richness of this biocenose
is reinforced by the level of heterogeneity
and the number of layers present. Very
often, several hundreds of species can be
seen in this environment with always the
main groups being algae, polychaetes,
mollusks, and crustaceans.
The production is high and the food
webs are complex but open to other
hard and soft substrate biotopes
through exportation of organic material
(preys, waste,etc). Aside from Posidonia
meadows (see “Posidonia meadows”)
these environments have the highest
production rate of the Mediterranean.
This great ecological importance is
reinforced by the role of being nurseries
to several species of fi sh of high
economical interest or natural heritage
value: seabream (Diplodus), comber
(Serranus), dusky grouper (Epinephelus
marginatus) and brown meager (Sciaena
umbra).
Depending on the species, the juveniles
will seek refuge in Cystoseira forests
(combers and wrasses) or in the cavities
between the boulders (brown meager,
dusky grouper). Several other species of
fi sh frequent this environment when in
the juvenile stage (Symphodus roissali)
or at the adult stage (several gobies
some of which are very rare or inexistent
outside this habitat).
BOULDERS and BEDROCK
26
adapted mooring techniques
A grouted anchor is a system made of a
plate or a single anchor ring with one or
many threaded rods, or ringbolts resin-
bonded into the rock with an underwa-
ter injected grout.
It is well adapted to homogeneous rocky
substrates and has a wide range of use:
from the anchoring of small marking
buoys to large fl oating or immersed
structures.
This anchoring system is not reversible
and the parts used are not reusable.
I - Defi nition
Grouted anchor
II - Model description
The plate and bolts are made of heated
galvanized steel or in A4 quality stain-
less steel. Depending on the use and
the eligible load, light or heavy duty
models can be designed.
For example, for light loads, a rod or a
ringbolt of adapted length and diame-
ter with an anchor ring can clearly be a
suffi cient anchor point.
Heavier and stronger models can be
made of a reinforced plate with a multi
directional structural resistance and
fastened to the rock with several bolts
of appropriate size.
The illustrations shown are just there
for examples.
The impact of a grouted anchor on a
boulder or the bedrock can be consi-
dered negligible. The holes in the rock
for fastening one or many bolts do not
create particular disturbances.
The injected grout used in very small
quantities and very locally can not have
a signifi cant negative impact.
The required space is very small; the
surface area for a standard plate is only
0.15 m².
The installation is simple and does not
require heavy equipments or techni-
ques that might create indirect nega-
tive effects. The positioning is very pre-
cise and allows the choice of the most
adapted location.
IV - Ecological benefi ts
As for any grouted anchor the re-
sistance of the anchor point takes
into account the internal resistance
of each of its components:
- anchor parts (quality of the mate-
rial and the welds),
- grouting material , substrate (me-
chanical resistance of the rock)
III -Holding principle
The installation of anchors grou-
ted in the rock requires the use
of equipment of a limited size.
The space required and the wei-
ght of the parts is negligible.
The space required and weight
of the installation equipment is
minimal. The size of the boat can
therefore stay small.
The installation has several pha-
ses:
1) Final choice of the most ap-
propriate location and basic
preparation of the surface if ne-
cessary of the chosen rock.
2) Drilling of the rock to the re-
quired diameter and length
with an underwater drilling gun
either pneumatic or hydraulic.
A pneumatic system requires an
air compressor with a high rate
of fl ow and can only work at
shallow depths because of loss
of pressure at depths: 1 bar per
10 meters of waters.
The hydraulic gun is prefera-
ble, it allows consistent work at
any depth and the space requi-
red for a hydraulic power unit
V - Installation technique
BOULDERS and BEDROCK
27
VI - Choice of models
A/ According to its use
Being well adapted to its use is essen-
tial. If the anchor receives, for example,
a mooring line, anchor ring will have an
interior diameter adapted to the size of
the chosen shackle.
If the anchor is designed to frequently
receive a line passed quickly through by
a diver, the anchor ring will have a very
different shape. Not necessarily circular,
but with a large diameter to facilitate the
quick release, of the line.
If the direction of the applied load is
known and constant, the drilling direc-
tion will have to be adjusted so that the
bonded parts work more by shearing
than in axial pulling. If the direction of
the load is variable in both direction and
angle, an anchor able to uniformly resist
multi directional forces must be used .
B/ According to the quality of the
substrates
The substrate is the most important ele-
ment and it is the most diffi culty to accu-
rately assess.
The rock at the chosen location must
be homogeneous and with no sign of
cracks or faults. The vibrations of the
drilling gun can actually weaken a part
of rock which is already weak. The speed
at which the drilling progresses is an in-
dication of the hardness and the quality
of the rock.
The smoothness and uniformity of the
sides of the hole is also a good sign of
the resistance of the rock. In a rock of
lower resistance the drilling depth will
be signifi cantly deeper.
In the case of grouting an anchor on
an isolated boulder, the boulder will be
transformed into a natural deadweight
mooring. It is necessary to be sure of the
boulder’s stability, its supporting points
and its apparent weight.
C/ According to the estimated load
The dimensions and design of the an-
chor part must take into account the va-
lue of the estimated load.
The dynamic forces that are short and
often violent (e.g. the backwash effect)
must also be taken into account.
The diameters and thickness of the parts
will need to increase proportionally with
the increase of the load. The more the
load increases the longer and more spa-
ced the screws will have to be.
is much smaller than with a
pneumatic system. In addition
the hydraulic gun reduces the
physical effort needed (the
weight of the gun improves
the drilling) and the absence
of pneumatic air exhaust pre-
serves the eardrums of the
diver.
Aside from the drill gun, the
rest of the required equip-
ment is a hydraulic power
unit and 2 hydraulic hoses of
appropriate length.
3) Bonding the anchor.
After cleaning the hole with
pressured air, injection of the
underwater grout (supplied
in cartridges)
4) Immediately afterward ca-
refully insert one or many
rods into the holes fi lled with
resin. Remove the extra resin
if necessary. Wait the advised
time as written on the instruc-
tions manual, without moving
the parts during the harde-
ning time.
5) The grouted anchor is
ready to use. The rest of the
elements can then be instal-
led (e.g. install and tighten a
plate)
Recommendations
Always look for the best adap-
ted anchor for the substrate.
The conditions of use of a
permanent mooring will have
to be defi ned and limits will
be chosen in relation to the
wave height, wind speed and
size and weight of the objects
moored
Measuring the . wind and
wave allows the calculation
of the maximum load that will
to be placed onto the system
(including intermediary ele-
ments).
Time has to be taken to assess
the nature and the quality of
the rocky substrate chosen. It
is not always easy to identify
the presence of cracks and
faults. They are often hidden
by alga or coralligenous.
In order to avoid the pro-
blems created by electrolysis
reactions it is recommended
to make the equipment out of
materials of the same quality.
The proximity of different ma-
terials such as standard steel,
stainless steel, aluminum, cop-
per, bronze and other alloys
must at all costs be avoided.
This rule must also be applied
to the metallic parts that can
be present in the mooring
line, or attached to the anchor
(shackles, eyes etc.).
Concerning the choice of
the parts to be grouted, it is
a good security measure to
obtain elements well adapted
to this use from a supplier of
lifting equipments. The parts
supplied will carry informa-
tion of maximum load use in
kilo grams, tons or daN . The
security coeffi cient when lif-
ting is 5.
BOULDERS and BEDROCK
28
Solutions and estimated cost
- L= length in mm
- TØ =rod diametre in mm
- FSS = sub-surface fl oat, diameter in mm
- BRCC = rigid buoy with central chimney
- Estimated cost of supplies in euros (without tax and delivery cost).
- All dimensions in mm
- Floating line: rope linking marking buoys together and fastened to these
- Floating structure : a swimming platform of 4 x 4 m on a swinging mooring
Grouted anchor
LIGHTWEIGHT BOATS < 7 METERS
Ringbolt L 250, TØ 20,
Polyamide line Ø 18 , buoy FSS 11 litres + BRCC
Cost anchor only: 50
MEDIUM WEIGHT BOATS 7 TO 11 METERS
Either Ringbolt L 250, TØ 20, either small plate with 2 bolts 250 X 20
Polyamide line Ø 20 , buoy FSS 11 litres + BRCC
Cost anchor only: ringbolt 50 , plate 550
HEAVYWEIGHT BOATS 12 TO 18 METERS
Plate with 2 or 4 bolts L 250/300, TØ 20/24, depending on the rock type
Polyamide line Ø 24/30, buoy FSS 11/25 litres , BRCC 650
Cost anchor only: 550 to 650
MARKING BUOYS
Buoy 400/600/800
Ringbolt L 200 TØ 16/20
Polyamide line Ø 14/16, Chain 12-16,
Buoy FSS 6/8 litres
Cost anchor only: 35 to 50
FLOATING LINE
Ringbolt L 250, TØ 20
Polyamide line Ø 14/16 , chain Ø 12 / 16
mooring buoy FSS 6/8 litres
Estimated cost anchor only: 50
FLOATING STRUCTURE
Either ringbolt : L 250, TØ 20, either small plate with 2 bolts 250 X 20
Polyamide line Ø 24, buoy FSS 11 litres, swivel 20
Chain in mid-water 20
Estimated cost anchor only: 50 to 550
IMMERSED STRUCTURES
Depending on the nature of the object and its fl oatability, a specifi c study
is needed
BOULDERS and BEDROCK
29
Ecological moorings
on
coralligenous
formations
coralligenous
30
I - Description
Rocky bottoms of the Mediterranean
sea have a biological natural heritage
of great value, creating renowned
underwater landscapes. This resource is
coralligenous formations and is being
more and more exploited for commercial
use such as diving tourism.
The rocky bottoms of the lower
sublittoral zone have several levels, one
of them is the so called ‘coralligenous
formations’ or ‘coraligenous assemblages’
in the broader meaning of the word,
with coralligenous walls, coralligenous
concretions, semi shaded cavities,
hangovers and totally shaded cavities or
caves.
Because of their location, the cavities are
not generally affected by anchors.
Coralligenous concretions can reach a
thickness of several meters. While the
construction takes place on a rocky base,
the aggregation of smaller concretions
can also develop on a soft substrate.
The main constructing agents are the
calcareous red algae Corallinacea or
Peyssonneliacea. These algal concretions
cans be reinforced by secondary
building agents; sciaphilic invertebrates
with calcareous tests or skeletons
(Foraminifera, Madrepora, Bryozoans,
Mollusks, red tube worms)
The spatial distribution of coralligenous
populations is the result of a combination
of factors: light, hydrology, sedimentation,
and biological interactions.
Coralligenous communities on vertical
walls, refered to as coralligenous walls,
are vertical rocks where the calcareous
algae which make up the coralligenous,
are limited in their horizontal growth
mainly due to the slope of the bedrock.
In areas of more gentle slopes, the
thickness of the concretions can become
signifi cant, and real reefs are built.
At low depths, coralligenous formations
in its general meaning can be preceded
by pre-coralligenous transitory
populations’ assemblages with the more
photophilic infralittoral populations
The species present on coralligenous
walls are mainly large sessile
invertebrates with a protruding shape:
gorgons (Paramuricia, Eunicella) , all
the cnidarians colonies (Geradia)
large Bryozoans (Adeonella, Myrapora,
Pentapora ) or sponges (Axinella )
This Structure that builds progressively
can be attacked by diggers of calcareous
substrates (microphyts, sponges,
cliones, some mollusks or grasers like
Lithophaga). The balance between
construction and foraging builds a
three-dimensional structure highly
anfractuous with a high variety of
adjacent micro-habitats
the environnement
coralligenous
31
In coralligenous concretions, the
construction of the structure happens
very slowly, hardly a millimeter per year,
and by successive layers.
The large upright species of invertebrates
which are characteristic of these
coralligenous concretions also have a
very slow growth rate: for example many
tens of years for a gorgon.
Several thousands of years are therefore
needed for large coralligenous
concretions to be created. Furthermore
the most superfi cial layers, which
are the more recent, are not yet well
consolidated and are easily destroyed
by mechanical shocks.
Likewise hard substrate coralligenous
formations which develop in thin layers
can easily be eroded too.
The large upright elements (gorgons,
sponges) are relatively fl exible and even
if they are damaged, they rarely break as
a direct result of a mechanical shock.
In contrast to this the substrate to which
they are attached, red calcareous algae is
much more fragile. Therefore these large
upright elements will often be ripped
out rather than broken.
The great vulnerability of these
coralligenous environments is due to:
1- their very slow growth rate (which is
also their rate of recovery)
2 their relative absence of mechanical
resistance, at least for the superfi cial
layers.
A mechanical shock or repeated rubbing
will therefore quickly result in a total
erosion of the top layers.
The large upright elements which give
this particular physiognomy to the
coralligenous landscape will also be
the fi rst victims of these impacts , due
to either their size (large bryozoans ) or
the weakness of the anchor point on the
substrate (gorgons, sponges).
This effortless erosion of the fi rst layers
of the coralligenous will undoubtedly
have important impacts on all the other
micro-habitats.
These coralligenous concretions are
entirely made up of micro-habitats. In
addition to the visible impacts there
is also all the indirect and invisible
impacts.
II - Ecological importance
III - Sensitivity and vulnerability
This spatial heterogeneity results in a
very high specifi c richness (more than
600 species for a single area).
These coralligenous areas are a real eco-
ethological crossroads for scientists.
Along the coasts of the north western
Mediterranean sea, they shelter more
than 1700 species, which includes 300
species of algae, 1200 invertebrates, and
a 100 species of fi sh.
In addition to its ecological importance,
is a major economical one: coralligenous
areas along with ship wrecks and caves
are the places the most sort after by
divers. Emblematic species like the dusky
grouper, magnifi cent landscapes of
submarine walls covered with gorgons
constitutes attractions for underwater
tourism.
coralligenous
32
adapted mooring techniques
Hard substrate coralligenous forma-
tions are an environment in which
the original substrate is rocky.
The technique of grouting into rock
is accordingly adapted, but the great
vulnerability of this environment and
its relatively weak mechanical resis-
tance, necessitates particular pre-
cautions when using this anchoring
technique.
I - Defi nition
Grouted anchor : see also grouted anchor in Part 1, Boulders and bedrock
II - Model description
Basically the models adapted to hard
substrate coralligenous formations
have the same general shape and prin-
ciples as the ones for the boulders and
bedrock environment.
However parts must be optimized in
order to fi nd the best balance between
the required pull out resistance and mi-
nimal surface area of contact with the
substrate. Knowing this, it is preferable,
where possible to grout an individual
rod of a larger diameter and embedded
deeper into the rock.
Concerning the plates themselves, any
surface that is not indispensable must
be removed, in order to protect the en-
vironment.
The great vulnerability of this envi-
ronment totally justifi es the use of
this technique for which the impact is
negligible.
The installation is straightforward and
does not require heavy equipment or
techniques that could create secon-
dary degradations.
The precise positioning of the holes
allows the most appropriate location
to be chosen.
V - Installation technique
III - Ecological benefi ts
The pull out resistance of the grouted
anchor is excellent if the quality of the
rock provides a good mechanical resis-
tance.
IV - Holding principle
A lot of care must be taken when
looking for the intended position
of the anchor.
A rocky substrate of good quality
must be chosen while minimi-
zing the impact on the corallige-
nous formations.
The rod must be grouted into
the rock underneath the coralli-
genous layer.
During the installation the fol-
lowing precautions must be ta-
ken: avoid secondary impacts,
stabilize the working boat wi-
thout anchoring in the area,
use hangers under the boat to
attach the equipment needed,
instruct the underwater workers
on how to act in this fragile envi-
ronment.
In addition, avoid contact
between the equipment and the
bottom and the rock face; relieve
the hydraulic hoses of their wei-
ght with rigid fl oating devices in
order to obtain at depth a slight-
ly positive or neutral fl oatability.
Recommendations:
Time has to be taken to assess
the nature and the quality of the
rocky substrate chosen. It is s not
always easy to identify the pre-
sence of cracks and faults. They
are often hidden by corallige-
nous algae.
In order to avoid problems crea-
ted by electrolysis reactions, it
is recommended to make the
equipment out of materials of
the same quality. The proximity
of different materials such as
standard steel, stainless steel,
aluminum, copper, bronze and
other alloys must at all costs be
avoided. This rule must also be
applied to the metallic parts that
can be present in the mooring
line, or attached to the anchor
(shackles, eyes, etc.).
coralligenous
33
Solutions and estimated cost
- L= length in mm
- TØ = shaft diametrer in mm
- FSS = sub-surface fl oat, diameter in mm
- BRCC = rigid buoy with central chimney
- Estimated cost of supplies in euros (without tax and delivery cost)
- All dimensions in mm
- Floating line: rope linking marking buoys together and fastened to these
- Floating structure : a swimming platform of 4 x 4 m on a swinging mooring
Grouted anchor
LIGHTWEIGHT BOATS < 7 METERS
Ringbolt L 250, TØ 20,
Polyamide line Ø 18 , buoy FSS 11 litres + BRCC
Cost anchor only: 50
MEDIUM WEIGHT BOATS 7 TO 11 METERS
Either Ringbolt L 250, TØ 20. either small plate with 2 bolts 250 X 20
Polyamide line Ø 20 , buoy FSS 11 litres + BRCC
Cost anchor only: ringbolt 50, plate 550
HEAVYWEIGHT BOATS 12 TO 18 METERS
Plate with 2 or 4 bolts L 250/300, TØ 20/24, depending on the rock
type.
Polyamide line Ø 24/30, buoy FSS 11/25 litres , BRCC 650
Cost anchor only: 550 to 650
MARKING BUOYS
Buoy 400/600/800
Ringbolt L 200/300 TØ 16/20
Polyamide line Ø 14/16, chain 12-16
Buoy FSS 6/8 litres
Cost anchor only: 35 to 50
FLOATING LINE
Ringbolt L 250/300, TØ 20
Polyamide line Ø 14/16 , chain Ø 12 / 16
mooring buoy FSS 6/8 litres
Cost anchor only: 50
FLOATING STRUCTURE
Either ringbolt : L 250, TØ 20, either small plate with 2 bolts 250 X 20.
Polyamide line Ø 24, buoy FSS 11 litres, swivel 20
Chain in mid-water 20
Cost anchor only: 50 to 550
IMMERSED STRUCTURES
Depending on the nature of the object and its fl oatability, a specifi c study
is needed
coralligenous
34
coralligenous
35
Ecological moorings
on Posidonia
meadows
Posidonia meadows
36
I - Description
Posidonia oceanica (Linnaeus) Delile is
a marine phanerogam endemic to the
Mediterranean sea and which makes up
massive underwater prairies, meadows
, also called seagrass beds from the
surface down to 30 to 40 meters in clear
waters.
Posidonia meadows are most often
installed on soft substrates (fi ne to
coarse sand) or in some cases on rocky
substrates. The bathymetric limits
of the distribution of the seagrass is
characteristic of the infralittoral zone
Posidonia as a phanerogam has leaves,
roots, a stem and can reproduce by
using its fl owers. A Posidonia shoot is
a part of the rhizome carrying 7 to 10
leaves of different lengths .The youngest
and shortest being situated in the center
of the shoot. The rhizome can grow
horizontally (it is called plagiotropic ) or
vertically (it is called orthotropic).
Whatever the direction of the rhizome
the distance between the rhizome and
the substrate is called the baring. Even
when uncovered by the sediment, the
rhizome is attached to the substrate by
its roots
Upright in open water, leaves can reach a
length of 1 meter. It acts as a screen that
effi ciently reduces the movement of the
seawater.
Transported by the current, the fi nest
particles are trapped and settle in
the seagrass meadows between the
rhizomes. The fi nest particles will
inevitably cause the rhizomes to
be buried. The vertical growth of the
rhizomes is a way to counter act this
situation.
This results in the development of a
structure where rhizomes, roots, and
sediments are interwoven. It is the mat
of the seagrass bed.
The reproduction of Posidonia oceanica
is mainly vegetative and rarely sexual .
The fl owering of Posidonia oceanica
is indeed hardly ever observed, at
least in the case of the north western
Mediterranean sea.
The vegetative reproduction (duplication
of the rhizome) produces a vertical or
horizontal growth of the seagrass bed. In
addition to the vertical development of
the mat (already described), this growth
allows the seagrass bed to colonize
extensive horizontal surface areas
(however at a very slow rate: less than 10
cm per year).
The vast stretches of seagrass must
therefore be considered as monumental
constructions slowly assembling
throughout the centuries. Any signifi cant
destruction is therefore on a human scale,
quasi non reversible. These vast areas
can be continuous or discontinuous,
depending on the level of cover (0 % - no
seagrass to 100 % - continuous seagrass
bed).
Hydrological events can also cause
the appearance of structures without
vegetation, that is to say
without shoots of posidonia;
these are intermats and
intermat channels . The erosion
and the topography, at a local
level, result in the appearance
of mat cliffs, of a few decimeters
to a few meters high .
Erosion , whatever its cause , can
also result in the appearance
of a surface area covered by
dead mat, areas where dead
rhizomes with no leaves are
exposed .
In the majority of cases the
growth of a seagrass bed
happens on soft substrates.
A theoretical ecological
succession of phases has been
described with the installation
fi rst of meadows of Cymodocea
(see Part 1, Sand and mud)
on soft sediments (fi ne sand)
then as time goes with the
appearance of Posidonia
meadows. If the succession
stays theoretical, it is certain that the
vertical growth of the seagrass bed of
Posidonia is bound to happen.
When the leaves reach the surface the
structure that is formed takes the name
of “barrier reef”. This terminology is
adopted because this event is observed
in most cases at the bottom of bays
where the exposed leaves form an arc
parallel to the shore in a very similar way
as fringing coral reefs.
The space created between the
barrier reef and the shore works as a
lagoon : Cymodocea nodosa, another
marine phanerogam is found in these
conditions optimal for development.
When these ecological conditions and
the health of the meadow is good,
Posidonia can grow on rocks to give a
unique construction: bedrock meadows.
The mat is therefore relatively thin, the
baring is limited and the shoot density
is high.
the environment
Posidonia meadows
37
Posidonia meadows or the areas of
dead mat are characterized by a highly
variable mechanical resistance.
The mat can present a level of
compaction highly variable according
to the nature of the sediment, found :
fi ne particles in the sediment will give
a lower level of compaction; fi ne and
coarse sand with a few fi ne particles
considerably increases the level of
compaction of the mat.
The mechanical resistance of the
seagrass bed to an external impact will
therefore be very different.
Furthermore an important baring of
the rhizomes accentuates the sensitivity
of the meadows to mooring pressure: a
bare rhizome distant from the sediment
will be more easily ripped out by an
anchor slid underneath the rhizome
layer next to the substrate.
Moreover, the ecological importance of
seagrass is linked in a great part to its
three-dimensional structure. Repeated
actions of ripping-out shoots by anchors
can provoke a deep modifi cation of this
bio-construction and as a consequence
a probable reduction of its ecological
role.
As an interface between the terrestrial
and the offshore zone, seagrass beds
are probably to date the environment
that has suffered the most from
anthropogenic impacts. The reasons for
these regressions are numerous. They are
for a great majority created by nuisances
of an anthropogenic origin like domestic
pollution, constructions on the coastline,
pollution from industries, use of trawl
nets.
For several years numerous authors have
alerted scientists and governing bodies
to the problem of the damaging impact
of temporary moorings on the Posidonia
seagrass.
By their extent and their reputation of
being a good anchoring ground, the
seagrass is often the victim of leisure
boat activities.
The investigations carried out clearly
show that the large majority of leisure
boats prefer to anchor on seagrass beds
rather than on other bottoms (sand,
rock) in order to have a secure temporary
mooring.
Recently several studies have clearly
indicated and quantifi ed the impact of
boat anchors on the seagrass. Studies
recommend without reservation, when
it’s possible the use of other methods
than boat anchors.
II - Ecological importance
III - Senstivity and vulnerability
Posidonia meadows are today
considered as one of the most important
ecosystem if not the key ecosystem of all
Mediterranean coastal spaces.
Similar to a forest on land, the
Posidonia meadow is the fi nal event of
a succession of populations. Its presence
is the essential factor for the ecological
balance of many Mediterranean coastal
ecosystems.
The seagrass bed has an impact on the
quality of coastal waters (production
of oxygen, trapping of sediments). It
represents a peak of biodiversity (20 to
25% of vegetal and animal species are
found there) and are at the base of a
number of food chains.
The meadow is a home, a spawning area
and a nursery for a number of animal
species who fi nd their food, refuge and
protection. It also plays a fundamental
role in the protection against erosion
of the coast and the beaches, without
which the actual coastline would be
greatly altered.
The vegetal biomass produced in a
meadow is considerable. In a surprising
way, very few herbivorous benefi t: in
the western Mediterranean sea only the
herbivorous fi sh, Salema (Sarpa salpa)
and a few invertebrates (sea urchins)
feed preferentially on it. The major part
of this primary production is hence
exported to other environments, mainly
in the guise of dead leaves.
If the invertebrates are not feeding only
from Posidonia, they do contribute to
breaking up this vegetal biomass. It
then becomes more available for the
other trophic levels.
The hydrodynamic forces from the
waves and the current that sweep the
seagrass bed signifi cantly contribute
to the dispersion of these fragments of
leaves.
A number of ecosystems, coastal or
deeper benefi t from this exportation of
organic matter to insure their existence.
This undeniable ecological importance
has promoted concrete actions to
protect the meadows: French Statutory
Order for the Protection of Posidonia (19
July 1998), decree law (20 September
1989) of the “Loi Littoral” (3 January
1988) and European Directive for the
conservation of natural habitats (21
may 1992). Marine seagrass beds are
also taken into consideration by Unesco
since the Rio Conference in 1992.
Finally, the global economic importance
of the seagrass is undeniable and
along with estuaries they are major
environments: their economical value
is estimated as three times that of the
coral reefs environment.
Posidonia meadows
38
adapted mooring techniques
The steel coil anchor Harmony type P.
is a device made of a steel coil (in the
shape of a corkscrew) where the wire,
the exterior diameter, the length and
the pitch enables the penetration into
the substrate, particularly the seagrass
mat, to give a strong anchoring point.
Perfectly adapted to all types of sea-
grass mat, living or dead, the range
of use is very wide :mooring of small
boats to large vessels.
In certain conditions the meadow de-
velops on rocks, the thickness of the
mat is hence really low. In this situa-
tion, the technical solutions described
in part 1, “Boulders and bedrock” can
be used with special care to avoid da-
maging the seagrass.
In the case of a very sparse Posidonia
meadow with isolated shoots where
the substrate isn’t really a
mat but is
sandier, the sand screw technique must
be used. The steel coil anchor Harmony
type P. permanent mooring is reversi-
ble and can be removed and reused on
other locations.
I - Defi nition
The steel coil anchor Harmony type P.
II - model description
The steel coil anchor Harmo-
ny type P is made of special
heated galvanized steel.
Depending on the projected
use and the maximum load
expected there are models
which vary in length.
As general rule, the average
values characterizing the
steel coil anchor are:
-diameter of the wire : 30mm
- exterior diameter : 350 mm
- length: 800 to 1600 mm,
- weight:25 to 42 kg.
The anchoring points are
made of clamps with loop-
holes attached to the top
turn. It is easily removable to
be placed elsewhere. These
coils can be installed indivi-
dually or attached together
in a line of 2 or 3 with a cou-
pling bar.
These models are under an
extended European patent.
The steel coil permanent anchor pene-
trates the seagrass mat with its whole
length by screwing.
This mat is made up of a dense
network of entangled rhizomes and
plant roots.
The very rigid wire of this giant corks-
crew creates its own path through this
network without cutting, crushing or
destroying the elements which cons-
titute the seagrass mat.
It is the absence of degradation of the
mat which will gives an excellent pull-
out resistance to the mooring.
Under traction, the coil harnesses an
enormous volume of soil around it-
self because the efforts are distribu-
ted throughout the whole rhizomes
network.
III - Holding principle
Posidonia meadows
39
IV - Ecological benefi ts
The installation of a steel coil
permanent anchor in a healthy
seagrass bed does not have a ne-
gative impact. This is the conclu-
sion of a scientifi c study.
The shape of the anchor does not
affect neither the leaves nor the
plant rhizomes. No surface area
of the seagrass bed is covered.
There is no scouring created if
the system is screwed well enou-
gh into the substrate. There is no
alteration of the mat during the
installation. The implementation
of the steel coil anchor does not
require heavy equipmentthat
may create secondary degrada-
tions.
V - Installation technique
Manual screwing
This technique can be conside-
red only with small models (short
length). With the use of a lever going
through the 2 loopholes mounted
on the top turn, 2 underwater wor-
kers facing each other turn the an-
chor until it is completely screwed
into the mat.
The limitation of this technique is
linked to the physical force develo-
ped by the workers arms and by the
length of the lever used.
This method of installation is techni-
cally possible but is not recommen-
ded due to the stamping on the sea-
grass during the manual screwing.
Hydraulic machine assisted
screwing
This technique enables:
- important screwing torques if
needed
- the ability to work at any depth
while controlling the power, avoi-
ding physical efforts of the unde-
rwater workers
- fi nally avoiding stamping on the
seagrass bed.
The required equipment includes:
- a hydraulic power unit
- 2 hydraulic hoses of suffi cient
length
- a hydraulic screwing gun with a
special head for holding the steel
coil. This tool has two arms to be
used by the divers.
The divers are standing on the
ground and are working as anchor
points doing no excessive efforts.
The screwing-in using a hydraulic
machine is by far the best installa-
tion technique.
Recommendations:
The best choice of substrate and an-
chor device must always be found.
The conditions of use must be pro-
perly identifi ed as well as the wind,
wave height, volume and nature of
the object (boat, pontoon, buoy)
that it will be supporting.
A calculation of the maximum wind
speed and wave height will allow an
estimation of the maximum effort
that will be supported by the projec-
ted moorings.
Always use non aggressive techni-
ques for moving the anchor parts
and the installation equipment (tow
the equipment with a fl oat, careful
choice of place to the temporay an-
choring of the working boat, etc.).
The mooring needs to be comple-
tely screwed into the sediment. In
the case of an incomplete screwing,
the steel coil should be unscrewed
and moved to another place to be
properly set up.
Posidonia meadows
40
A/ According to its use
It is the required pull-out resis-
tance of the anchor that will de-
termine the choice of model. As a
general rule, the resistance is pro-
portional to the total length of the
anchor.
B/ According to the quality of
the substrate.
The mechanical resistance of the
Posidonia
mat varies greatly due
to its variable compaction level.
This compaction level is linked to
the density of the Posidonia sea-
grass bed (number of shoots per
square meter) and to the nature
and grain size distribution of the
sediment trapped.
This guide does not set out to cal-
culate accurately this resistance
which can be done by soil stability
specialists with the use of tools
like penetrometer, vane tester
and core sampling apparatus.
It is however necessary to check
the available thickness and com-
paction of the seagrass mat and
to put it in relation to the mini-
mum length of the anchor to be
installed.
With an identical load on mats
with different compaction levels,
the lower the level of compaction,
the more the anchor will need to
be long to have a better resistance
to lateral forces, and the more the
numbers of coils for a single moo-
ring will be needed.
The more the mat is compact, the
more the anchor will need to be
of «normal proportions» and the
coupling of 2 or 3 coils together
is needed only for very heavy ob-
jects
According to the estimated effort.
The steel coil permanent anchor
has standard sizes of 0,80 m to
1,60 m.
Above this size, installation tech-
niques become more compli-
cated. The equipment has to be
bigger and the whole installation
can have a signifi cant impact on
the environment (repeated mo-
vements of boats and temporary
moorings, repositioning).
It is therefore more important to
increase the number of anchor
points to divide the load than to
make one single large steel coil
anchor.
With a similar level of compaction
of the seagrass mat, the higher
the pull-out force is, the more the
anchor points will need to be cou-
pled together (multiple anchor
points can even be coupled to
each other).
Dramatic confusion
A sand-screw must not be pla-
ced in the seagrass bed for many
reasons.
The cutting edge of the sand-
screw disc during its rotation will
cut or pull-out the shoots at the
surface of the soil and along the
whole path of the screw.
The rhizomes will be broken, rip-
ped-out or crushed.
This destructive impact brings
with it another consequence: the
mechanical resistance of the mat
is decidedly weakened by the
breaking up of the three-dimen-
sional structure of its elements
which means that the pull-out re-
sistance is very low.
VI - Choice of model
Posidonia meadows
41
Solutions and estimated cost
- L= length in mm
- ExtØ =external diameter of the coil in mm
- FØ =wire diameter in mm
- FSS = sub-surface fl oat, diameter in mm
- BRCC = rigid buoy with central chimney
- Estimated cost of supplies in euros (without tax and delivery cost)
- All dimensions in mm
- Floating line: rope linking marking buoys together and fastened to these
- Floating structure : a swimming platform of 4 x 4 m on a swinging mooring
steel coil anchor Harmony type P.
LIGHTWEIGHT BOATS < 7 METERS
Coil : L 1000/1200, ExtØ 350, FØ 30
Polyamide line Ø 18 , buoy FSS 11 litres + BRCC
Cost anchor only: 300
MEDIUM WEIGHT BOATS 7 TO 11 METERS
Coil : L 1500, ExtØ 350, FØ 30
Polyamide line Ø 20 , buoy FSS 11 litres + BRCC
Cost anchor only: 400
HEAVYWEIGHT BOATS 12 TO 18 METERS
Coil : L 1500/1600, ExtØ 350, FØ 30
Polyamide line Ø 24/30, buoy FSS 11/25 litres , BRCC 650
Cost anchor only: simple 450 , double 1200 , triple 1500
MARKING BUOYS
Buoy 400/600
Coil : L 800/1000, ExtØ 300, FØ 22
Buoy 800
Coil : L 1000/1200, ExtØ 350, FØ 30
Polyamide line Ø 14/16, chain 12/16, buoy FSS 6/8 litres
Cost anchor only: 250 to 300
FLOATING LINE
Coil : L 1500, ExtØ 350, FØ 30
Polyamide line Ø 14/16 , chain Ø 12 / 16
Buoy FSS 6/8 litres
Cost anchor only: 400
FLOATING STRUCTURE
Coil : L 1500, ExtØ 350, FØ 30 single or double
Polyamide line Ø 24, buoy FSS 11 litres, swivel 20
Chain in mid-water 20
Cost anchor only: 450 to 1200
IMMERSED STRUCTURES
Depending on the nature of the object and its fl oatability, a specifi c study
is needed
Posidonia meadows
42
Posidonia meadows
43
Part 2.
Sensitivity and vulnerability of the habitats.
Summary
Habitats summary
44
The sensitivity and vulnerability of
an habitats can be appreciated in
relation to its different characteristics:
mechanical resistance (holding power
of an anchor), resistance to a shock,
stability, three-dimensional structure,
presence of bio-constructions and
ecological importance.
A permanent mooring does not need
to be in a specifi c location and a
manager can always have the choice
between different substrates.
Even if different ecological anchoring
techniques have been described,
it necessary to choose, when
possible, the environment which is
the least sensitive and vulnerable.
Theoretically any habitat, whatever
it is, will suffer a negative impact.
However the consequences at the
level of its ecological organization
or its organic integrity will not be
the same. Ecological quality and
integrity will not be damaged in the
habitats the least sensitive and the
least vulnerable .
Sand and mud Pebbles and cobbles
Pull-out resistance (holding
power)
low medium
Resistance to a shock
good good
Stability of the substrate
good stability of the substrate very low stability of the
substrate
Three-dimensional struc-
ture
none, variable slope none, variable slope
Bio-construction
absent absent
Other characteristics
Suction effect can be important
(mud). Quick dispersal of C. taxifolia
and C. racemosa
Ecological importance
high limited
Sensitivity and
vulnerability
medium to high (if Cymodo-
cea or Zostera)
limited
Sensitivity and vulnerability
Habitats summary
45
Boulders and bedrock Coralligenous formations Posidonia meadows
good good variable
good low variable
variable stability of the substrate good stability of the substrate good stability of the substrate
From variable slope to very signi-
fi cant relief
high (concretions) high (mat)
absent yes (concretions) yes (mat)
potentially high heterogeneity of
the substrate
vulnerability depends on the
baring of the rhizomes and the
compaction level of the mat
high very high very high
medium to high (for upri-
ght species)
very high high to very high
On the contrary in environments which are the most sensitive
and the most vulnerable, the integrity of the habitats can be
damaged with the destruction of its spatial architecture and
simplifi cation of its complexity.
The specifi c biodiversity of a biocenose is closely linked
to the diversity of its habitats and its spatial complexity.
The destruction of its spatial architecture can have major
consequences on the way it works (disappearance of species,
reduction in the production).
of the habitats - Summary
Habitats summary
46
Habitats summary
47
Part 3.
Intermediary and surface elements
intermediary elements
48
intermediary elements
Intermediary elements are
all the elements situated
between a fi xed mooring
point (anchor) and an object
or a structure.
This system is designed to en-
sure the fastening between
these two elements in order
to make them connected.
In this guide, the whole link is
called the mooring line.
I - Defi nition
The mooring line ensures that the move-
ment of the object which is attached is
either limited or immobilized.
All the forces applied (wave, wind, cur-
rent) on a moored object generate an
effort, mainly horizontal, that is entirely
transferred by the mooring line to the
anchor point on the seafl oor.
The intermediary elements or mooring
line are therefore under variable and im-
portant stress.
The tension in the mooring line changes
according to 2 parameters: the value of
the horizontal effort and the value of the
angle between the mooring line and the
horizontal.
The working angle will therefore be one
of the parameters to be taken into ac-
count when designing a mooring line.
As an example,
Horizontal load Angle Tension
1 ton 0° 1 ton
1 ton 30° 1.2 ton
1 ton 60° 2 ton
1 ton 80° 5.8 ton
1 ton 85° 11.4 ton
II - Principle
The mooring line must be perfectly
adapted to the use as well as the wor-
king conditions.
The parameters to be taken into account
in the design of the mooring line are: the
resistance, the length, the absorbing ef-
fect, the life span, the maintenance and
the reduction or the absence of negative
impacts on the environment.
There are several options for the moo-
ring of an object.
Mooring on a single mooring line:
On a swinging mooring where the ob-
ject can freely move 360 degrees around
its anchor point will always face the wind
or the sea.
This system of free swinging gives fl exi-
bility and smoothness in movement and
reduces to a minimum the potential load
applied to the mooring object.
On the surface the swinging cir-
cle can be a problem in the ma-
nagement of the mooring area.
Swinging moorings are recom-
mended on sites exposed to
wind of variable strengths and
direction.
Mooring on two opposite
mooring lines:
Mooring head and stern. The ob-
ject can move only on a fore-and-aft axis
with a limited lateral movement.
This system which greatly reduces the
movements provokes jerks and there-
fore increases the power of the dynamic
efforts.
When the wind and the sea come from
the side of the object moored (head and
stern mooring), the surface areas ex-
posed to these forces are much higher
than the surface areas exposed in the
case of a facing wind.
Care must be taken to allow free verti-
cal movements of the objects moored.
The head and stern mooring reduces
the required surface area on the water ,
but puts more stresses on the mooring
points , the mooring lines and the an-
III - Design
intermediary elements
49
The required resistance will be calcula-
ted with regards to the maximum theo-
retical load transferred by the mooring
line according to the given conditions
of use.
The tension will be estimated with the
angle which creates the biggest pull out
force. The value obtained must be multi-
plied by a safety coeffi cient to take into
account the extreme values of the dyna-
mic forces and the possible wearing of
some elements (shackles, etc.).
The mooring line must have over its
whole length an homogeneous resis-
tance.
The individual resistance of each of the
components (shackle, chain, cable, rope,
swivel, etc.) must be checked.
The fastening techniques (knots, splices,
whippings) used must not create weak
links.
The resistances given by the manufac-
turers are provided in terms of breaking
values or maximum working load wi-
thout a safety coeffi cient or in terms of
maximum working load with a safety
coeffi cient.
IV - Resistance
This length will be calculated
with the parameters of water
height (spring high water added
to the possible wave height) and
the desired working angle under
those conditions.
The total length of the mooring
line will therefore be equal to
the hypotenuse of a right angled
triangle for which the height is
equal to the maximum water hei-
ght and the angle adjacent to the
base is the working angle of the
mooring line.
To maintain appropriate tension
it is recommended that the maxi-
mum angle be 45 degrees.
For this value the tension in the
mooring line will be equal to the
horizontal load multiplied by
1.414.
Furthermore the working angle
of 45 degrees is a good compro-
mise between tension and swin-
ging space.
If the working angle decreases,
the tension decreases but the
swinging space increases.
V - Length (except for tightly drawn mooring)
chor points .
The head and stern mooring is recom-
mended on sites which are relatively
sheltered with a wind of constant direc-
tion which will infl uence the orientation
of the equipment to be installed.
Multi point mooring
This technique allows the almost total
immobilization of an object in the hori-
zontal plane.
This is the case for the mooring of a fl oa-
ting pontoon perpendicular to a dock
for example or for an isolated platform.
In these cases the mooring lines will be
designed to allow vertical movement of
the structure held.
Tightly drawn mooring
The length of the mooring line will not
allow any vertical movement of the moo-
red object. The position of the object is
stable but the resistance of the mooring
line must be much higher than the value
of the Archimedes force provoked by the
total immersion of the object moored
intermediary elements
50
VI - Absorbing effect
The absorbing effect is desirable in order to
reduce the jerking provoked by the swell
and the backwash on all the mooring ele-
ments.
The opposite force required to absorb the
movements has generally been a ground
mooring chain attached to the anchor point
on the bottom (see “deadweight mooring”
in Part 1 “Sand and Mud”).
This effi cient technique is not used any-
more because of its negative impact on the
environment (constant swing and banging
of the chain over the substrate) .
Another technique uses the Archimedes
principle with an immersed fl oat attached
at mid depth on the mooring line.
This fl oat of suffi cient volume maintains
with its pull the lower part of the mooring
line tightened vertically.
This permanent vertical pull acts as an op-
posite force to the horizontal load applied
on the object moored.
The absorbing effect will be proportional
to the volume of the sub-surface fl oat ins-
talled.
This effect is also increased by the drag
created by the movements of the immersed
element (relation between the speed, the
surface area and the density of the fl uid).
This solution has two major advantages: the
absorbing effect of the movements and the
absence of negative impact on the environ-
ment. In fact the pull of the fl oat stops any
contact of the mooring line with the subs-
trate.
A mixed solution uses advantages of both
techniques. A sub-surface fl oat is installed
at mid depth and maintains the tension in
the fi rst part of the mooring line, which is
made of rope. The second part between the
mid depth fl oat and the surface is made of a
chain of large diameter.
The pull of the fl oat acts as a fi rst shock ab-
sorber while the length and the weight of
the hanging chain absorb the larger jerks.
The volume of the fl oat is calculated to ob-
tain a signifi cant pull irrespective of the wei-
ght of the hanging chain.
The position of the fl oat and the length of
the chain are chosen so that no contact of
the mooring line with the substrate is pos-
sible.
The material used for a mooring line can
in itself have an absorbing effect because
of its mechanical characteristics. This is the
case for example with a polyamide line with
3 strands: at 75% of the breaking load the
lengthening is 45%.
There also exists specifi c elements designed
to be shock absorbers (spring, elastomer,
etc.).
intermediary elements
51
The mooring line equipped with
an intermediary fl oat which re-
mains, whatever the conditions,
in mid-water without direct
contact with the substrate, pre-
sents and undeniable ecological
advantage of the highest order.
All of the substrates on which
this type of non disturbing
mooring line will be installed
will benefi t .
VIII - Ecological benefi ts
The life span of a mooring line is
linked to its design (good adap-
tation to its use) and to the qua-
lity of its components.
Simple and effi cient assembles
are always recommended. To
increase the life span, wearing
must be avoided.
Any movement creating a fric-
tion causes wearing (e.g. a shac-
kle in the eye ring of a buoy, or a
shackle in a swivel, or a shackle
in a thimble).
It is therefore important to look
for assembles where the inces-
sant movements of the parts are
avoided.
It is recommended to use inter-
mediary rings between shackles
and eye rings, as well as repla-
cing intermediary links such as
shackles and thimbles with clo-
sely tight knots.
In the case where the chain
works as a weight (e.g. under a
mooring buoy) it is preferable
to use a shorter chain of a large
diameter rather than a chain
of small diameter and longer
length.
This type of chain wears much
quicker because of the electro-
lysis and the friction of the links
against each other.
A monobloc weight such as a
piece of cast iron can be used
to replace a chain. It must be
fastened to a textile rope and if
it is at a good distance from the
fl oating buoy, it will not be espe-
cially worn out.
VII - Life span and maintenance
intermediary elements
52
Materials of good quality must be used
especially for shackles where the thread
of the shackle pin becomes often quic-
kly oxidized.
The shackles must always be block wired
(the shackle pin is held by a tie to avoid
being unscrewed). It is preferable to use
a nylon tie rather than a metallic wire.
The slack between the various fastened
elements (shackle, thimble, eye ring,
chain, swivel) must be minimal.
The chains are permanently being worn
out because of the movement of the
links with each other. In order to reduce
this wearing, for an identical weight it is
preferable to have a short chain and of
large diameter , than a longer chain of
smaller diameter.
A mixed rope for all or part of the moo-
ring line is a good replacement of a
chain.
The installation below a buoy of a poly-
amide line with a tubular weight of steel
or cast iron placed a few meters below
the buoy is an excellent long term solu-
tion. It is then only necessary to protect
the upper section in polyamide from
propellers with the use for example of a
PEHD tube.
The potential electrolysis between the
different parts must be checked. The
mechanical abrasions must be avoided
on all the textile parts. If necessary the
parts have to be protected with braided
sleeves, sections of polyethylene tubes
or protections in PEHD.
A few benchmarks
A shackle mounted to a chain must be of
a diameter just above that of the chain
(e.g. chain 14 mm, shackle 16 mm).
Average lengthening at 75 % of the
breaking load
Steel cable 2.5%
Coaxial polyester 17%
Coaxial polyamide 22%
8 strands polypropylene 25%
3 strands polypropylene 27%
8 strands polyester 28%
3 strands polyester 32%
8 strands polyamide 35%
3 strands polyamide 45%
©Cousin-Trestec
Ømm Chain polyamide
8 2300 1330
10 4300 2040
12 5000 2940
14 7000 4020
16 9000 5200
18 11500 6570
20 14000 8140
22 9800
24 11800
30 17400
Compared resistances in tons between chain
and 3 strands polyamide rope.
Boat
length
Displacement Ø mm
8 m 2 - 4 t 12 -14
10 m 5 - 6.5 t 14 - 16
12 m 8 - 11 t 16- 20
16 m 12 t 20
20 m 20 t 24
©Cousin-Trestec
Moorings : recommanded diameter for a 3
strands polyamide and a 3 strands polyester
rope
X - Recommandations.
As a general rule, the material used for
mooring lines is metallic, textile, polymer,
or a combination of the last two.
All the metallic materials are resistant
but will always be corroded due to oxi-
dation or electrolysis.
All types of chain wear out quickly due
to shocks and friction provoked by re-
peated movements.
All the fl exible materials of a textile type
(polyester, polyamid, polypropylen, po-
lyethylen, etc. ) stranded or braided are
very strong and resistant to most of the
chemical or organic agents. However
they have a very low resistance to me-
chanical wearing due to repeated fric-
tion against any object.
The ratio resistance/life-span will be in
favor of textile elements as long as these
are properly protected from friction and
chafi ng.
All ropes with an external braided sleeve
in polyester are well resistant to friction
and abrasive wear.
Braided ropes of 8 strands (4 x 2) in poly-
amid are well resistant to unstranding.
Polyamid ropes with 3 strands have
a good lengthening ratio and absorb
shocks well.
Textile cables with a core braided in ara-
mid (Kevlar) and with an outer sleeve
braided in polyester have a ratio resis-
tance/life-span exceptionally high (e.g.
diameter 17.5 mm, resistance 20 tons,
weight per meter 242 grams).
Some ropes are a combination of textile
and metal, it is the mixed ropes, e.g. poly-
propylen rope with multi strands where
the core of each strand is made of a steel
cable.
This rope resists fairly well to chafi ng
and maintains a reasonable fl exibility.
IX - Choice of materials.
intermediary elements
53
Defi nition :
A mooring buoy is a fl oating buoy that
locates the presence of a mooring sys-
tem and that holds a line available for
the user.
The mooring buoy in certain situations is
reduced to a simple marker buoy equip-
ped with a small line allowing the collec-
tion of a mooring line laying on the fl oor.
But as a general rule for security reasons,
ease and comfort, the buoy combines
functions.
Visual Signal: in the shape of a sphere
or a cone, and often white, its size should
permit it to be easily seen and to place
information on it (N°, size of boat, limits
of use, pictogram).
This buoy must be resistant, withstand
accidental shocks against the hull and
withstand UV rays and chemicals.
Mooring support:
The buoy is not a mooring element, it
simply allows access to the mooring line
to tie-up the boat correctly.
A mooring buoy is not designed to offer
the mechanical resistance of an interme-
diary part between the bow line of the
boat and the mooring line.
Numerous buoys are equipped with a
rod going through their center and with
an eye ring at the top and a swivel at the
bottom.
These buoys are often badly used. In rea-
lity numerous boats moor directly to the
top eye ring of the rod, however this eye-
ring should be used only to catch the
buoy, it is not a strong element of the
mooring.
Choice of mooring buoy:
Numerous choices of buoys exist with
varying designs and prices.
Infl atable spherical buoy with a cen-
tral through rod.
This solution is cheap but is not long-
term reliable and the material is often
sensitive to UV rays. In the case of a
puncture the buoy is not unsinkable. It is
diffi cult to mark information on the fl oat
and the through rod creates incorrect
usage.
The shape of the fl oat requires ballasts
to hold itself vertical and fi nally it is not
easy to tie the bow-line of the boat to
the mooring line hanging from below
the buoy
Bi-conic shaped buoy with a central
through rod
An unbreakable material must be cho-
sen (e.g. PEHD is preferred to PVC) as well
as a model where the interior volume is
fi lled with foam to ensure a perfect fl oa-
tability whatever happens.
The through rod can create an incorrect
usage. The shape of the fl oat requires
ballasts to hold itself vertical and fi nally
it is not easy to tie the bow-line of the
boat to the mooring line hanging from
below the buoy
Conic shaped buoy with a central chi-
mney
The body of the buoy is made of PEHD
and the inside volume is foam fi lled. It
has a very good life span and if neces-
sary can be easily marked.
There is no through rod and therefore
no corrosion. Mooring on it is easy as
the mooring line goes through the chi-
mney and the loop can even be lifted up
to 2.5m above the surface with the use
of a protection tube slipping inside the
chimney of the buoy.
This buoy is designed to be used with a
textile mooring line and does not requi-
re a weight to be kept vertical.
I - Mooring buoy for boats
Surface elements
surface elements
54
Marking buoys in general, and in par-
ticular the ones used for beaches, are
standardized for each country.
They are in general yellow in color and
of spherical shape for the delineation of
areas.
According to the nature of the activity
in the zone, the restrictions and prohi-
bitions, the diameters used are between
400, 600 and 800 mm and the spacing is
proportional to their diameter.
For France, the system of buoyage and
the marking-out of the coastal stretch is
noted in the Statutory Order of 27 march
1991 (J.O. 28 avril 1991).
Channel buoys are coned shaped if star-
board (black or green) or cylindrical if
portside (red); however channel buoys
can also be yellow ( access channels to
beaches).
Buoys indicating a specifi c site as shown
on marine charts can have various sha-
pes.
It is advised to check the regulations in
each country with the governing bodies
concerned.
The equipment
A lot of manufacturers propose standard
buoys and the choice will only be on the
nature of the material, its robustness and
unsinkability.
The buoys the most resistant are made of
High Density Polyethylen (PEHD) roto-
molded with an injection of polyuretha-
ne foam to ensure the unsinkability.
The eye ring of the buoy is protected
and reinforced by a metal eye set tight
into the hole. A buoy with these charac-
teristics will be one of the most expen-
sive models.
The installation
The installation of seasonal or perma-
nent buoy in a traditional way creates a
non negligible repeated impact on the
environment. In practice the mooring
lines are almost always made up of a
ground mooring.
The length is always superior to the hei-
ght of the water to take into account the
tidal range and the swell.
Under each marking buoy, several me-
ters of chain incessantly sweep and bash
onto the substrate (it is that part of the
chain which is worn-out extremely rapi-
dly).
All that is needed is to replace or modify
the mooring line to eliminate the ne-
gative impact. The technique described
above has 2 advantages:
- absence of degradation: the ballast
chain, shorter (but equivalent in weight)
does not stay on the sea bottom.
- reduced wearing-out of the equipment:
the vertical position of the chain in the
water insures a much better life span.
II - Marking buoys
surface elements
55
Whatever the type of structure, the an-
chor points receiving the mooring lines
must satisfy the following criteria:
- the shape of the parts making up the
anchor points must allow the forces to
work in axial way in order to create a
pull out stress and not a shear stress.
- the parts under stress must be suffi -
ciently reinforced to transfer the load
with no risk of breaking.
In the case of a fl oating structure an-
chored in a swinging mooring, two an-
chor points located up wind (end of the
structure facing the wind) and both sha-
ring the load enables the distribution of
efforts and stabilization of movements.
The same structure could also be moo-
red from a single centre anchor point.
With immersed structures, the anchor
points must be carefully placed in order
to withstand consistently the Archime-
des force affecting the structure.
IV - Floating or immersed structure
This equipement complements the mar-
king buoys. Its goal is to reinforce the
marking of an impenetrable barrier. It is
often used to ensure a better protection
for swimmers or visitors of underwater
trails or to implement the ban of access
to a totally protected area or a mooring
prohibited area.
Depending on the country and site whe-
re this device is set up, it is necessary to
check the potential consequences that it
might cause. In France for example the
establishing of buoys linked together by
a fl oating line along the coast is often a
creation of a zone reserved exclusively
to swimmers. If it the case, this zone must
be under the surveillance of lifeguards.
The equipment
The equipment is made of a polypropy-
lene rope orange or “safety yellow” on
which are threaded and fastened cylin-
drical fl oats approximately every 2 me-
ters and have at the ends large spliced
loops.
There are not many different materials in
this type of equipment. Complete fl oa-
ting lines can be found of 10, 20, 25, 30,
50 and 100 meters.
The installation
The best setting must be found during
the installation for the tension of the
fl oating line.
It must not be extremely tight between
2 buoys. It is also important to protect
from friction the contact points between
the fl oating lines and the anchor points
on the buoys. This connection must be
fi xed solid and protected by a sleeve of
PEHD.
The mooring lines of the buoys used as
anchor points to attach the fl oating line
must withstand, without wearing, the
movements of these fl oating lines.
III - Floating line
surface elements
56
surface elements
57
Part 4.
Product suppliers - Contacts
suppliers and contacts
58
suppliers and contacts
I - Mooring devices.
- Sand screw.
-Small and medium size models
Local or regional suppliers selling galvaniized or
black chain and other maritime and harbor equi-
pments.
-Medium and large size models
Neptune Environnement.
Ancrages Harmony
446 Rte des catalanes
83230 Bormes-les-Mimosas
France
+33 (0) 494 152 638
neptune.env@wanadoo.fr
- Dead weights
Companies doing harbour and maritime work.
Companies selling prefabricated concrete pro-
ducts. Information can be obtain by contacting
concrete plants
- Steel coil anchors for Posidonia
Neptune Environnement.
Ancrages Harmony
446 Rte des catalanes
83230 Bormes-les-Mimosas
France
+33 (0) 494 152 638
neptune.env@wanadoo.fr
- Grouted anchor
Threaded rods and anchor rings : from all stainless
steel (A4) suppliers.
From supliers for the maritime and lifting industry
(high resistance steel, stainless steel products A4)
- Anchor plates and special parts
At blacksmith and ironworkers working with stain-
less steel (doing laser assisted cutting or not)
- Underwater anchor grout
From suppliers of grout for the building industry.
Company HILTY for example (require underwater
use)
These pages present a non exhaustive list of
manufacturers, suppliers and service providers.
It is in no way the result. of a selection or a re-
commandation of the authors.
It is rather a business directory of companies
which products are regularly used for the sup-
ply and installation of various ecological moo-
rings in the north western Mediterranean.
This directory will expand with the experience
and knowledge of all the managers of marine
protected areas of the Mediterrean.
59
suppliers and contacts
III - Floating structures
- Modular collapsible pontoons
CUBISYSTEM France
+33 (0) 233 045 000
contact@cubisystem.com
JETFLOAT International
+43 (0) 624 674 294
offi ce@jetfl oat-international.com
- Rigid aluminium pontoons
Poralu Marine
ZI rue des Bouleaux
01460 Port - France
+33 (0) 474 767 811
Dealer of SEAFLEX.
contact-marine@poralu.com
II - Mooring lines
- Textile ropes
COUSIN Trestec SA
8 rue Abbé Bonpain BP 39
59117 Wervicq Sud.
France
+33 (0) 320 144 000
contact@cousin-trestec.com
- All type of fl oats
MOBILIS SA
370 rue Jean de Guiramand
13290 Les Milles - France
+33 (0) 442 371 500
mobilis@mobilis-sa.com
- Accessories : thimble, shackle, swivel
From local or regional dealers seling black and gal-
vanized chain.
From maritime and harbour equipment dealers
From supliers for the maritime and lifting industry
(high resistance steel, stainless steel products A4)
Sté LEVAC to Lyon, Toulon, Alger
info@levac.fr
http://www.levac.fr
- Mixed rope, fl oating line
SIMA
88 rue Delbos BP 36
33028 Bordeaux Cedex
sima.france@wanadoo.fr
- Surface buoys
Mooring buoy, buoy with central chimney, marking
buoy, etc.
MOBILIS SA
370 rue Jean de Guiramand
13290 Les Milles - France
+33 (0) 442 371 500
mobilis@mobilis-sa.com
60
suppliers and contacts
61
Part 5.
Glossary
GLOSSARY
62
Abyssal
Relating to the region of the ocean bottom between the
bathyal and hadal zones, from depths of approximately 3,000
to 6,000 meters (10,000 to 20,000 feet).
Anchor ring
Heavy duty ring, eye loop or bail made out of metal.
Baring
Distance betwenn a rhizome (equivalent of the stem for the
Posidonia) and the substrate. The increase of the baring is
generally due to a shortage of sediments. Even when strongly
bared, a rhizome is still alive (with shoot and leaves) if it stays
fi xed to a substrate by its roots.
Biocenose
A group of interacting organisms that live in a particular
habitat and form an ecological community more or less stable
within a defi ned territory.
Bio-construction
Three-dimensional structure erected by marine organisms
either vegetal or animal.
Biomass
The total mass of living matter within a defi ned space. The
value is generally expressed as units of biomass per surface
unit (e.g. grams by squared meter).
Biotope
A biological area containing the defi ned ecological factors
necessary for the normal existence of a community of
organisms either animal or vegetal.
Chafi ng
Deterioration due to the rubbing of an element against
another.
Compaction
The state of being pressed close, concentrated, fi rmly united.
It describes the resistance of a soil to being penetrated
by an object. In a soil with a low compaction level, the
object will penetrate more easily than in compact soil. The
level of compaction can be measured with the help of a
penetrometer.
Detritivorous
Feeding diet made up of organic detritus vegetal or animal.
Endemic
Species confi ned to a certain region or site.
Food-web
Vegetal and animal organisms related to each other through
trophic relationships (predator/prey) make up a food chain.
Several food chains can be interconnected, they therefore
make up a food web or trophic network.
Infralittoral
Zone between the low water of the spring tides and the lower
limit of the phanerogam meadows which is also the limit for
pluricellular photophilic algae (it is 15-20 m in the ocean
and 30 to 40 m in the Mediterranean sea). It is colonized by
organisms which require permanent immersion.
Interstitial
Relating to or situated in the small, narrow spaces between
objects more or less spherical piled one on top of the other
(grains of sand, gravel, stones, rocks).
Lower sublittoral (= circalittoral)
Defi ne the underwater zone where the only vegetation
that can develop is made of algae. It is situated between the
Infralittoral zone (where phanerogam meadows develop) as
the upper limit and the end of the euphotic zone as the lower
limit. The depth of the lower limit depends on the turbidity of
the water (usually 100 m, where only sciaphilic algae develop).
Mat
Monumental construction resulting from the horizontal
and vertical growth of Posidonia rhizomes with entangled
rhizomes, roots and particles of sediments trapped in.
Mediolittoral
Zone of the coastal space situated between the highest high
tides and the lowest low tides.
Meiobenthos
Group of Metazoa that can pass through a mesh of 500
micrometers but will be retained by a mesh of between 100
to 40 micrometers.
GLOSSARY
63
Natural heritage
The natural heritage can be considered as the biodiversity upon
which man has an impact by transforming it, exploiting it, ( in
the sense of using up a ressource), conserving it, restoring it
and giving thereafter an economical, ecological, socio-cultural,
and even ethical value.
Nursery
Area where juvelines or young invidiuals fi nd the micro-habitat
required for their development into the sub-adult stage.
Organogenic debris
Debris of organic origin, that is to say biological structures built
by animals (tests, urchin needles, mollusks shells, fragments of
skeletons of bryosoans or cnidarians)or vegetals (calcareous
thallus).
Phanerogam
A plant that has roots, branches and leaves and has a sexual
reproduction by fl ower and seeds. In the coastal Mediterranean
area there are some marine phanerogams living in the shallows
(needing light for photosynthesis) Zostera, Cymodocea,
Posidonia.
Photophilic
Characterize the organisms which require or are able to
withstand strong light.
Antonym : sciaphilic
Penetrometer
Tool used to measure by penetration the level of consistency
or resistance of a sediment sample.
Production
In ecology, it means the quantity of living matter (organic
matter) created by a link of the food chain per unit of time, of
surface or of volume. There is a distinction between the primary
production (vegetal) and secondary production (animal)
Recruitment
Process htrough which the youngest fraction of the population
integrates for the fi rst time the groups of adult and sub-adult
fi shes. This recruitment usually results in a change of habitats
(from open water toward the seafl oor). For fi shing specialists it
is the fraction of the youngest fi shes which becomes accessible
for exploitation.
Sciaphilic
Characterize the organisms which are not able to withstand
strong light.
Antonym : photophylic
Scouring effect
Digging of the sediment, erosion by hydraulique action (the
force of moving water: currents, whirlpools, swirling).
Sessile
Living organism fi xed to a solid substrate.
Antonym : vagile
Specifi c diversity
Value related to the number of species present in an
environment or a given site. Several parameters have been
developped to measure this diversity but the most straight
forward remains the number of species.
Specifi c richness
See specifi c diversity.
Screw torque
Two forces, parallel, equal and of opposite direction. The forces
acting in opposite directions at the extremities of a lever.
Spawning area
Place where several individuals of the same species come
together to reproduce by emmission of their gamets in open
water. Generally, the gathering together for spawning hapens
after animals have come to the site from places near or far.
Supralittoral
Coastal zone just above high water of spring tides. The
Supralittoral zone (splash zone, sometimes also referred to as
the white zone) outlines the stretch above the high water level.
The width of this zone changes with the slope of the shore,
variations in light and shade, exposure to waves and spray,
tidal range.
Tidal range
The periodic variation in the surface level of the oceans and
of bays, gulfs, inlets, and estuaries, caused by gravitational
attraction of the moon and sun.
GLOSSAIRE
64
Trenching
Act of burying into the seafl oor after digging a trench. It is
used for a boat or an object (cable, etc.) sank to the bottom and
situated in a depression (natural or artifi cial) in the sediment. It
is also used for solid blocks resting on the seafl oor.
Vagile
Living organism capable of movement on the seafl oor (walk,
crawl, jump, etc.) or of swimming.
Antonym : sessile
Vane tester
Tool used to determine the resistance to shearing of fi ne soils.
GLOSSARY
65
Part 6.
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