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Wednesday, 21 September 2016

Excavation safety - awareness session

Excavation safety - awareness session




Objective



What we will cover


Excavation Hazards


Surface Encumbrances



Utilities



Utilities



Utilities



Manual Excavation



Access / Egress



Access / Egress



Vehicle Traffic



Exposure to falling loads



Stacking of Material



Mobile Equipment



Hazardous atmospheres



Ventilation



Water accumulation



Water accumulation



Adjacent structures



Loose Rock and soil



Fall protection



Barrication



Cave in



Soil collapse



Soil collapse



Preventing Soil collapse



Soil classification



Soil classification



Protective systems



Angle of Repose



Simple sloping



Simple sloping



Bencing



Shoring



Timber shoring installations


Timber shoring installations



Aluminum shoring installations



Shields (i.e.Trench Boxes)



Protective systems



Protective systems



Soil collapse



Prior to excavation



Excavation inspections



Precautionary measures



Foreman / supervisor



Excavation Rescue



Excavation Rescue



Excavation Rescue



Excavation Rescue



Excavation Rescue



Excavation Rescue



Thank you






WELCOME TO
Excavation Safety SESSION

What We Will Cover
¨Hazards of Excavations
¨Soil Classifications
¨Protective Systems
¡Sloping
¡Benching
¡Shoring
¨Inspections
¨Emergency Response
Excavation Hazards 
¨Soil collapse
¨Surface encumbrances
¨Utilities
¨Access/Egress
¨Vehicle traffic
¨Falling loads
¨Mobile equipment
¨Hazardous atmospheres
¨Water accumulation
¨Adjacent structures
¨Loose rock or soil
¨Falls
¨Cave-in
¡
Surface Encumbrances
¨Need to be removed or supported
¨e.g. Fencing, Piping, Structure, Materials
Utilities
Underground
¡Locate prior to digging
¡Certify deactivation
¡Protect, support, or remove
¨Aboveground
¡De-energize or
¡Isolation from power lines
¨
Manual Excavation

Access/Egress
¨Note:  Poor housekeeping ---  # 1 cause of slips, trips and falls on construction projects
¡Debris kept cleared from work areas
¡Mark hazards  - survey pegs, pillars
¡Barricade
¨Egress provided-
¡ladders
¡ramps
¡stairs
     Ladders - @ every 25mts. length
Gangways ( width not less than 75 cm)
Stairs cut on earth
Stair tower
Vehicle Traffic
Reverse Horn
Banks man
Stop Block
Defined traffic route
Exposure to Falling Loads
¨No work under loads
¨Operators remain in cab
¨Parking away from Excavation
       STACKING OF MATERIAL  
Warning system
Barricades
Hand signals
Mechanical signals
Stop logs
Grade away from excavation
Heavy equipment such as excavating machinery and road traffic shall be kept away from the edge not less than the depth of the trench or at least 6m for trench deeper than 6 m.
Hazardous Atmospheres 
¡Oxygen- not less than 19.5%
¡CO –not more than .01% by vol.
¡C02- –not more than 1% by vol
¡H2S –not more than .002% by vol
¡Flammable gas - –not more than 1.5% by vol
¡Petroleum
¡Other toxics
¡
Ventilation
¨Displace hazardous gases and vapors
¨Considerations
¡Heavier than air or lighter than air contaminant
¡Exhausting or blowing in
¡Volume/time required to lower concentrations to acceptable levels
Water Accumulation
¨Ground water

¨Surface water
¨Protection from hazards associated with water accumulation
¡Protection against cave-in
¡Water removal (pumping)
¡Run-off protection
¡Consider temporary shut-off of water lines
Adjacent Structures
¨Ensure structure stability
¡Shoring
¡Bracing
¡Underpinning
¡Or evaluation by Professional
Engineer.

Loose Rock and Soil
¨Protection of employees from loose rock or soil
¡Scaling
¡Protective barriers
¡Placing material at least 1M from edge
¡No work on slopes above workers
Fall Protection
¨Any surface 6 feet or more above a lower level shall be protected by:
¡walkways with guardrail systems
¡personal fall arrest systems
¨Other options include:
¡warning lines systems
¡safety monitoring systems
BARRICATION
60 kg Lateral Force 
1 M From Excavation Edge 
Cave-in
¨Protection from cave-in requires a systematic approach including:
¡Soil classification
¡Protective systems
¡Inspection
¡Employee training
Soil Collapse
Constitutes 60 % of Excavation accidents.
Severity of Hazard is very high.
Preventing Soil Collapse
SLOPE / SHORING
Above 5 ft. depth.
Soil Classification
¨Soil Classification (Type A,B,or C) determines construction of protective system:
¡Sloping or benching
¡Shoring
úTimber shoring
úAluminum shoring

v Type A- cohesive soils with an unconfined, compressive strength of 1.5 tsf. or greater.  Examples : clay, silty clay, sandy clay, clay loam
v Type B : 0.5 tsf - 1.5 tsf .
 Eg : Granular cohesionless soils including: angular gravel (similar to crushed rock), silt, silt loam, sandy loam

v Type C: > 0.5 tsf
Eg: gravel, sand, loamy sand,Submerged soil or soil from which water is freely seeping; or Submerged rock that is not stable 

Protective Systems
¨Options Include:
¡Sloping and benching
¡Shoring/sheet piling/ shielding (e.g.trench boxes)
¡Designed by P.E. if deeper than 20’
Simple Sloping

Staple Rock          900

¨Type A - 3/4:1  530
Short term upto 12’ -630

¨Type B - 1:1   450

¨Type C - 1½ :1    340
Benching
¨
¨Type A


¨Type B
ú(cohesive soil)

¨Type C           
Shoring
¨Based on Manufacturer data
¨Designed by a Professional Engineer

Timber Shoring Installations
¨Requires soil classification
¨Based on depth and width of trench
¨Consult tables for specs on
¡Cross braces
¡Wales
¡Uprights
Aluminum Shoring Installations
¨Requires soil classification
¨Based on depth and width of trench
¨Consult tables for specs on
¡Hydraulic cylinders
¡Wales
¡Uprights
Shields (i.e. Trench Boxes)
Protective Systems
¨Installation
¡Securely connected
¡Employees clear of area under shields during installation
¡Installed to prevent movement
¡Must protect employees while entering excavation
¨Removal
¡Employees clear of area under shields during removal
¡Shoring removed from the bottom up, SLOWLY!
¡Backfill with removal
Soil Collapse
Prior to Excavation
v Ground condition
v Ground  / Surface Water
vUnder ground utilities
vAdjacent buildings
vDynamic load
Excavation Inspections
¨Daily Inspections of ALL excavations by Competent Person
¡Start of shift, as needed, following rainstorms or other hazard-increasing event
úPossible cave-ins
úProtective system failure
úWater accumulation
úHazardous atmospheres
¡Competent person has authority to remove workers from the excavation
PRECAUTIONARY MEASURES
SURVEY
SOIL TEST REPORT
ASSIGN A FOREMAN / SUPERVISOR
NEED OF WORK PERMIT SYSTEM
PLAN FOR EXCAVATION – slope / shoring, disposal yard, etc.
ACCESS
HAND RAILING & CAUTION BOARDS
LIGHTING
SAFETY ROPE FOR ENTERING TRENCHES
NO LONE WORKERS
Foreman / Supervisor
ØAssign an exp. & competent person as in charge for the activity.
ØResponsible for the strict adherence of safety rules.
ØFull authority to enforce the safety measures.
ØHe has the complete information on under  /above ground utilities.
ØDaily Inspections by the foreman / supervisor.
ØStart of shift, as needed, following rainstorms or other hazard-increasing event.
ØPrepared for emergency requirements- first aid kit.
Excavation Rescue
¨Initial Size-up
¡Type of incident?
úCave-in, flooding, medical, fire, spill
¡Injuries?
úNumber and type
¡Missing personnel?
¡Chemical (or sewage) exposures?
¡Safety of excavation for rescuers?
¨Notify:
¡Field personnel
¡SSC = Emergency Coordinator
¡Fire Department
¡Police Department
¡Emergency Medical Services (EMS)/Hospital
¨Stabilize cave-in
¨Control flooding
¨Hazardous Atmospheres?
¡Ventilate
¡SCBA
¡Safety harness and line
¡Basket stretcher
¨The best rescue is the one you never have to make!
¡Practice proper procedures
úMake sure everything is safe before anybody goes in!



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