HEALTH SAFETY AND ENVIRONMENT
RISK ASSESSMENT: ACT/HSE/RA 001
COFFERDAMS (TEMPORARY WORKS)
RISK SCORE CALCULATOR
Use the Risk Score Calculator to Determine the Level of Risk of each Hazard
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Hierarchy of Controls
What w ould be the
CONSEQUENCE
of an occurrence be?
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frequently
Often (4)
Likely (3)
Possible (2)
6 to 12 times a year
1 to 5 times a year
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years
Catastrophic (5)
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Multiple Fatalities
Serious (4)
Class 1 single fatality
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Class2 (AWI or LTI) or Class 1
Permanently disabling effects
Rarely (1)
Can the hazard be Elim inated or removed
from the w ork place?
Can the product or process be substituted for
a less hazardous alternative?
Can the hazard be engineered aw ay w ith
guards or barriers?
Can Adm inistration Controls be adopted
I.e. procedures, job rotation etc.
Author:
Approved:
Issued:
Rev. Date:
Revision: 0
Project Name:
xxx
RA Ref No.:
xxx
RA compilation
Date:
Review date:
Date:
Compiled by:
Reviewed by:
Minor (2)
Medical attention needed, no work
restrictions. MTI
Insignificant (1)
FAI
Overall Task Details
Formation of deep cofferdam . Classed as Temporary Works
Use in conjunction with RA10 - Excavations
No
1
Specific Task Step
(In sequence of
works)
Planned Cofferdam
excavation in areas
where live services
may be present
including:

Electrical;

Water;

Sewerage;

Gas;

Telecoms;
Hazard Details
 Presence of live
underground services;
 Services not in area
specified on drawings;
 Heavy plant or
vehicles accessing
work area;
 Presence of
unmarked services;
PRIOR TO
WORKS
Relevant Applicable MAS:
 00246 – Excavations;
 01413 – Underground services;
Consequence/Risk
Initial Risk
Rating
P
S
RR
 Incorrect cofferdam design;
 Risk of explosion due to gas line
rupture;
 Risk of flooding of excavation and
adjacent areas due to water main
damage;
 Risk of electrocution or fire due to
cable strike;
 Risk of hazardous waste entering
excavation or water systems due
to live sewerage damage;
 Risk of damage to low depth
underground services from heavy
vehicles;
4
5
 Risk of vehicles / Plant entering
open excavation;
2
 Excavating cofferdam;
 Collapse during construction due
to inadequate Method Statement;
 Unable to rescue workers in the
event of an unplanned incident;
 Flooding;
4
4
Additional Training required:
NOC’s Required for task:
Temporary Works Coordinator to be designated
Dubai Municipality
Control Measures
16
HIGH
i. The loads imposed on the cofferdam structure by construction equipment and operations
must be considered, both during installation of the cofferdam and during installation of
any equipment or construction of a structure within the cofferdam ;
ii. The cofferdam, and every part thereof, shall be of suitable design and construction, of
suitable and sound material and of sufficient strength and capacity for the purpose for
which it is used;
iii. Correct construction, verification that the structure is being constructed as design,
monitoring the behaviour of the cofferdam and surrounding area, provision of adequate
access, light and ventilation, shall be controlled by the Temporary Works Coordinator;
iv. Installation of bracing, waling etc. shall be considered to ensure the cofferdam design
can be proven. Welders are competent and where practicable structures can be bolted
so integrity can be as per design; Removal of bracing etc. shall be considered during
design;
v. The cofferdam design must include the provision of safe access/egress/safe area and
emergency rescue of workers in the event of ill health, cofferdam flooding etc. such as a
platform for rescue tripod, man basket etc.;
vi.
Page 1 of 2
Approved by:
i. All existing utility service drawings reviewed for known service details and position;
ii. NOC and Utility provider and HLG Excavation permits to be completed, unique number
added and recorded in log;
iii. Work Area, including access route for plant, to be CAT scanned to locate exact position
of service by competent persons;
iv. Service clearly marked on ground, using posts, tags etc.;
v. Any unidentified services marked on ground and drawing by Temporary Works
20
Coordinator or Temporary Works Supervisor;
HIGH
vi. All services clearly communicated to all workers at briefings and TBT’s, signed off and
recorded;
vii. Permit/NOC/JSEA/Approved design copies to be with supervisor in work area for review;
viii. Supervision and Plant Operators instructed to stay within designated area and access
route;
ix. All excavation barriers to be planned and to RTA Traffic Managem ent Manual if adjacent
to live roads;
 Collapse of cofferdam due to
incorrect design;
Cofferdam Design
under Temporary
Works
Can Personal Protective Equipm ent &
Clothing be w orn to safe guard against
hazards?
Residual Risks
Additional Control
Measures
RR
Workers not
complying with
controls
All supervision to
monitor operation;
Regular topic in
TBT’s
Low
No competent TW
designer in-house
Third Party approved
TW designer to be
used
Low
Sheets must be of suitable length and driven to adequate depth to ensure no exposed
soil at base of cofferdam, posing a risk of water ingress and undercutting of soil;
HSEQ -Rev-01(Aug-2018))
HEALTH SAFETY AND ENVIRONMENT
RISK ASSESSMENT: ACT/HSE/RA 001
No
Specific Task Step
(In sequence of
works)
Hazard Details
3
Cofferdam excavation
See Risk
Assessment No. 10
4
Cofferdam sheet piling
See Risk
Assessment No. 16
5
Lifting operations
See Risk
Assessment No. 12
6
 Workers required to
work in confined
space;
Confined space
working – cofferdam
Consequence/Risk

Excess or lack of oxygen;


Presence of Toxic gases;
Ingress of water or other
substances;

Explosion due to build-up of
gases;

COFFERDAMS (TEMPORARY WORKS)
Initial Risk
Rating
P
S
RR
iv.
v.
4
Sudden water ingress into
cofferdam;

Restricted emergency
evacuation;

Access/egress;
16
HIGH
vi.
vii.
viii.
ix.
x.
i.
ii.
6
Installation of wales,
bracing etc.

Lifting operations;

Welding operations;
 Adverse weather;
5
Maintenance of
cofferdam
 Cofferdam open for
long periods;
 Unapproved
amendments to
design;
Page 2 of 2

Falling materials;

Electrical shock;

Collapse of excavation due to
alterations;

Damage to excavations due to
incident or adverse weather;

Incident due to removal of
barriers
4
4
16
HIGH
3
3
Rev. Date:
Permit to be issued & gas monitoring undertaken if required before works commence;
Adequate air circulation & lighting to be maintained in work areas;
Equipment which may release excess oxygen or carbon monoxide gases shall not be
used in confined space areas without adequate extraction;
Local weather forecast should be noted to watch for heavy rains which may cause
flooding;
Dewatering pumps to be implemented, the number required dictated by the water table
depth, size of cofferdam etc.;
Special consideration to be given to any hot works inside a cofferdam;
Means of rescue from the cofferdam must be implemented, rescue platform, man
basket stationed in area etc.;
Scaffold stairs should be installed, ladders are unsuitable for access into deep
cofferdams;
Top man to be appointed at the entry of the confined space area as required;
Workers should be physically fit and competent to enter and undertake the work in
confined spaces;
ii.
iii.
iv.
Revision: 0
Residual Risks
Workers not
adhering to
requirements;
Gas detector not
calibrated
resulting in
incorrect reading
Additional Control
Measures
RR
Supervision to
constantly monitor
workers;
Regular TBT’s &
Trainings to be given
on working Confined
space;
Low
Gas detector to be
calibrated to
standards and
manufacturers
recommendations.
Wales and bracing to be implemented as per approved TW design;
Wales or bracing must be of the correct length, no gaps, to ensure welding is of
sufficient strength and integrity to ensure cofferdam is to design;
iii. Where possible jacks or bolted sections should be used where integrity can be proven;
iv. Welders should be suitably experienced and competent in multi-positional welding;
v. Welding sets should be placed outside of cofferdam, checked by competent electrician
and suitably earthed;
vi. Welded joins in bracing should be avoided, to ensure integrity;
vii. Consideration should be given to the removal of wales and bracing after completion of
the works, lifting points etc.;
viii. Completed bracing shall be reviewed by Temporary Works Coordinator prior to use;
i.
9
Med
Approved:
Issued:
Control Measures
i.
ii.
iii.
4
Author:
Cofferdam checked after heavy rains, severe winds etc., stand by pumps to be
available as required;
Weekly recorded inspections undertaken;
Implemented warning signage maintained;
Housekeeping inside cofferdam to be maintained, all rubbish and waste material to be
removed daily;
Low
Low
HSEQ -Rev-01(Aug-2018))