4 Cofferdams (Temporary Works) Risk Assessment Templates Planned Cofferdam excavation in areas where live services may be present including: • Electrical; • Water; • Sewerage; • Gas; • Telecoms; PRIOR TO WORKS Cofferdam Design under Temporary Works Cofferdam excavation Cofferdam sheet piling Lifting operations Confined space working – cofferdam Installation of wales, bracing etc. Maintenance of cofferdam

1. HEALTH SAFETY AND ENVIRONMENT Author: Approved:
RISK ASSESSMENT: ACT/HSE/RA 001 COFFERDAMS (TEMPORARY WORKS)
Issued: Rev. Date:
Revision: 0
Page 1 of 2 HSEQ -Rev-01(Aug-2018))
No
Specific Task Step
(In sequence of
works)
Hazard Details Consequence/Risk
Initial Risk
Rating Control Measures Residual Risks
Additional Control
Measures
RR
P S RR
1
Planned Cofferdam
excavation in areas
where live services
may be present
including:
 Electrical;
 Water;
 Sewerage;
 Gas;
 Telecoms;
PRIOR TO
WORKS
 Presence oflive
underground services;
 Services not in area
specified on drawings;
 Heavy plant or
vehicles accessing
work area;
 Presence of
unmarked services;
 Incorrect cofferdam design;
 Risk of explosion due to gas line
rupture;
 Risk of flooding of excavation and
adjacentareas 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;
 Risk of vehicles / Plant entering
open excavation;
4 5
20
HIGH
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 competentpersons;
iv. Service clearly marked on ground, using posts,tags etc.;
v. Any unidentified services marked on ground and drawing by TemporaryWorks
Coordinator or TemporaryWorks Supervisor;
vi. All services clearlycommunicated 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 PlantOperators instructed to stay within designated area and access
route;
ix. All excavation barriers to be planned and to RTA Traffic ManagementManual if adjacent
to live roads;
Workers not
complying with
controls
All supervision to
monitor operation;
Regular topic in
TBT’s
Low
2
Cofferdam Design
under Temporary
Works
 Excavating cofferdam;
 Collapse ofcofferdam due to
incorrectdesign;
 Collapse during construction due
to inadequate Method Statement;
 Unable to rescue workers in the
event of an unplanned incident;
 Flooding;
4 4
16
HIGH
i. The loads imposed on the cofferdam structure by construction equipmentand operations
mustbe considered,both during installation ofthe cofferdam and during installation of
any equipmentor 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 ofsufficientstrength 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 ofadequate
access,lightand ventilation, shall be controlled by the TemporaryWorks Coordinator;
iv. Installation ofbracing,waling etc. shall be considered to ensure the cofferdam design
can be proven. Welders are competentand 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 mustinclude the provision ofsafe access/egress/safe area and
emergencyrescue ofworkers in the event of ill health, cofferdam flooding etc. such as a
platform for rescue tripod,man basketetc.;
vi. Sheets mustbe of suitable length and driven to adequate depth to ensure no exposed
soil at base ofcofferdam,posing a risk of water ingress and undercutting ofsoil;
No competentTW
designer in-house
Third Party approved
TW designer to be
used
Low
RISK SCORE CALCULATOR
Use the Risk Score Calculator to Determine the Level of Risk of each Hazard
What would be the
CONSEQUENCE
of an occurrence be?
What is the LIKELIHOOD of an occurrence? Hierarchy of Controls
Frequent/Almost certain (5)
Continuous or will happen
frequently
Often (4)
6 to 12 times a year
Likely (3)
1 to 5 times a year
Possible (2)
Once every 5 years
Rarely (1)
Less than once every 5
years
Can the hazard be Eliminated or removed
from the w ork place?
Catastrophic (5)
Multiple Fatalities
High 25 High 20 High 15 Medium 10 Medium 5
Can the product or process be substitutedfor
a less hazardous alternative?
Serious (4)
Class 1 single fatality
High 20 High 16 High 12 Medium 8 Low 4
Can the hazard be engineered aw ay w ith
guards or barriers?
Moderate (3)
Class2 (AWI or LTI) or Class 1
Permanently disabling effects
High 15 High 12 Medium 9 Medium 6 Low 3
Can Administration Controls be adopted
I.e. procedures, job rotation etc.
Minor (2)
Medical attention needed, no work
restrictions. MTI
Medium10 Medium 8 Medium 6 Low 4 Low 2 Can Personal Protective Equipment &
Clothing be w orn to safe guard against
hazards?Insignificant (1)
FAI
Medium10 Medium 4 Low 3 Low 2 Low 1
Project Name: xxx
RA Ref No.: xxx
RA compilation
Date:
Review date:
Date:
Compiled by:
Reviewed by:
Approved by:
Overall Task Details
Formation of deep cofferdam.Classed as TemporaryWorks
Use in conjunction with RA10 - Excavations
Relevant Applicable MAS:
 00246 – Excavations;
 01413 – Underground services;
Additional Training required:
TemporaryWorks Coordinator to be designated
NOC’s Required for task:
Dubai Municipality

2. HEALTH SAFETY AND ENVIRONMENT Author: Approved:
RISK ASSESSMENT: ACT/HSE/RA 001 COFFERDAMS (TEMPORARY WORKS)
Issued: Rev. Date:
Revision: 0
Page 2 of 2 HSEQ -Rev-01(Aug-2018))
No
Specific Task Step
(In sequence of
works)
Hazard Details Consequence/Risk
Initial Risk
Rating Control Measures Residual Risks
Additional Control
Measures
RR
P S RR
3 Cofferdam excavation
See Risk
AssessmentNo.10
4 Cofferdam sheetpiling
See Risk
AssessmentNo.16
5 Lifting operations
See Risk
AssessmentNo.12
6
Confined space
working – cofferdam
 Workers required to
work in confined
space;
 Excess or lack of oxygen;
 Presence ofToxic gases;
 Ingress ofwater or other
substances;
 Explosion due to build-up of
gases;
 Sudden water ingress into
cofferdam;
 Restricted emergency
evacuation;
 Access/egress;
4 4
16
HIGH
i. Permitto be issued & gas monitoring undertaken ifrequired before works commence;
ii. Adequate air circulation & lighting to be maintained in work areas;
iii. Equipmentwhich mayrelease excess oxygen or carbon monoxide gases shall notbe
used in confined space areas withoutadequate extraction;
iv. Local weather forecastshould be noted to watch for heavy rains which maycause
flooding;
v. Dewatering pumps to be implemented,the number required dictated by the water table
depth, size of cofferdam etc.;
vi. Special consideration to be given to any hot works inside a cofferdam;
vii. Means of rescue from the cofferdam mustbe implemented,rescue platform,man
basketstationed in area etc.;
viii. Scaffold stairs should be installed,ladders are unsuitable for access into deep
cofferdams;
ix. Top man to be appointed atthe entry of the confined space area as required;
x. Workers should be physicallyfit and competent to enter and undertake the work in
confined spaces;
Workers not
adhering to
requirements;
Gas detector not
calibrated
resulting in
incorrectreading
Supervision to
constantlymonitor
workers;
Regular TBT’s &
Trainings to be given
on working Confined
space;
Gas detector to be
calibrated to
standards and
manufacturers
recommendations.
Low
6
Installation ofwales,
bracing etc.
 Lifting operations;
 Welding operations;
 Falling materials;
 Electrical shock; 4 4
16
HIGH
i. Wales and bracing to be implemented as per approved TW design;
ii. Wales or bracing mustbe of the correct length,no gaps,to ensure welding is of
sufficientstrength and integrity to ensure cofferdam is to design;
iii. Where possible jacks or bolted sections should be used where integritycan be proven;
iv. Welders should be suitablyexperienced and competentin multi-positional welding;
v. Welding sets should be placed outside ofcofferdam,checked by competentelectrician
and suitablyearthed;
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;
Low
5
Maintenance of
cofferdam
 Adverse weather;
 Cofferdam open for
long periods;
 Unapproved
amendments to
design;
 Collapse ofexcavation due to
alterations;
 Damage to excavations due to
incidentor adverse weather;
 Incidentdue to removal of
barriers
3 3
9
Med
i. Cofferdam checked after heavy rains,severe winds etc., stand by pumps to be
available as required;
ii. Weekly recorded inspections undertaken;
iii. Implemented warning signage maintained;
iv. Housekeeping inside cofferdam to be maintained,all rubbish and waste material to be
removed daily;
Low