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NEBOSH Construction Certificate > Element 11 - Excavation Work & Confined Spaces > Flashcards

Element 11 - Excavation Work & Confined Spaces Flashcards

1
Q

What are the hazards associated with excavation work?

A
  • Buried Services
  • People Falling In
  • Objects and Materials Falling In
  • Collapse of Sides
  • Collapse of Adjacent Structures
  • Water Ingress
  • Use of Cofferdams and Caissons
  • Contaminated Ground
  • Toxic and Asphyxiating Atmospheres
  • Mechanical Hazards
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2
Q

What are the factors to consider when conducting a Risk Assessment for Excavations?

A
  • Depth of Excavation
  • Soil Type (Non-cohesive, Cohesive, Rock)
  • Type of Work (side of a road, in a housing development, laying pipes/cables, trenches, pits)
  • Use of mechanical equipment (types being used)
  • Proximity of the excavation to roadways, watercourses. structures, schools, hospitals
  • Presence of the public/children
  • Weather
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3
Q

In relation to Buried Services, what action should be taken before work is carried out?

A
  • Check any available plans
  • Contact local services providers and owners (electric, gas, water, TV)
  • Survey the site and surrounding area to identify indicators of the existence of cables (streetlights, junction boxes)
  • Use cable locators/detectors with trained operators
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4
Q

Identify some safe digging methods/procedures?

A
  • Using locators to determine position and route of cables/pipes
  • Look for evidence of pipes/cables….plastic pipes will not be detected by locator
  • If contact is made with pipes/cables, STOP work until it is safe to proceed
  • Regard all buried cables as LIVE until disconnection is proven. Pot-ended cables cannot be assumed as dead/disused
  • Excavators and power tools tools should not be used within 0.5m of the indicated line of a cable or pipe
  • Hand digging should be employed when nearing a cable/pipe
  • Spades/shovels should have curved edges and used rather than forks/picks
  • Report damage to appropriate services…keep personnel clear until it is repaired
  • Have an emergency plan to deal with damaged pipes/cables
  • Exposed cables/pipes should be supported/protected against damage by back-filling. Don’t use as foot/hand holds
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5
Q

List the types of excavation support?

A
  • Battering
  • Shoring
  • Trench Boxes
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6
Q

What factors determine which excavation support is used?

A
  • Type of ground being excavated
  • Length of time excavation will be open and in use
  • Type of work being carried out
  • Groundwater conditions and potential for flooding
  • Depth of excavation
  • Number of people in excavation
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7
Q

List some General precautions associated with Excavations?

A
  • Identify buried services
  • Support sides
  • Provide suitable access/egress
  • Provide crossing points
  • Barriers, lights and signs used to demarcate danger areas
  • Remove spoil and store at safe distance
  • De-watering and freezing methods used to remove water
  • Vehicles and material kept away from sides
  • Provide workers with suitable/appropriate PPE
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8
Q

What are the particular requirements for excavating Contaminated Ground?

A
  • Soil testing
  • Additional/specific welfare facilities
  • Health Surveillance
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9
Q

When are inspections required for excavations?

A
  • At the start of each shift
  • After any event likely to have affected the strength or stability of the excavation (e.g. flooding)
  • After any material unintentionally falls or is dislodged
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10
Q

Explain the criteria associated with an Inspection Report of an excavation?

A
  • The report must be completed before the end of the shift in which the excavation was inspected
  • A copy of the report must be given to the person in charge of the worksite within 24 hours of the inspection
  • Reports must be retained at the site until the excavation work is completed and thereafter for 3 months
  • Only 1 written report is needed every 7 days, unless the strength or stability of the excavation is affected.
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11
Q

What must an excavation report contain?

A
  • Date, time, location and a description of workplace inspected
  • Name and position of person inspecting/making the report
  • Name of the person on whose behalf the inspection was carried out (i.e. person in charge of worksite)
  • Details of anything identified as a HSE risk, and actions taken to control them
  • Details of any further actions considered necessary
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12
Q

What is the definition of a Confined Space?

A

It is any enclosed space where there is a reasonably foreseeable specified risk of injury associated with it

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13
Q

Give examples of Confined spaces?

A

Trenches, Sewers, Manholes, Chambers, Pits, Tanks, Vats, Silos, Reaction Vessels, Flues, Ductwork

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14
Q

What are the “Specified Risks” associated with Confined Spaces?

A
  • Serious Injury arising from Fire or Explosion
  • Loss of consciousness arising from an increase in body temperature
  • Loss of consciousness arising from asphyxiation due to gas, fume, vapour or lack of oxygen
  • Drowning arising from a free-flowing solid (e.g. flour, grain, sand)
  • The inability to reach a respirable environment due to entrapment by a free-flowing solid
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15
Q

What are the key duties associated with the Confined Spaces Regulations 1997?

A
  • Avoid entry where possible (e.g. do the work from the outside)
  • If entering then follow a safe system of work and put in place adequate emergency arrangements before work starts
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16
Q

What Hazards are associated with Confined Spaces?

A
  • Toxic Atmospheres
  • Explosive or Flammable Atmospheres
  • Oxygen-Deficient or Enriched Atmospheres
  • Heat
  • Water
  • Free-Flowing Solids
  • Restricted Space
17
Q

How does Oxygen Depletion occur?

A
  • Through displacement (the addition of a gas or vapour to the space displaces the oxygen. e.g. Purge Gas, Pipe Freezing, Gas leaking from elsewhere
  • Through consumption (oxygen depleted by a chemical reaction. e.g.Oxidation, Rusting, Bacterial Growth
  • Through welding operations
  • By people working
  • By any process of combustion
  • Where there is a reaction between some soils and the oxygen in the atmosphere
  • Following the action of groundwater on chalk and limestone (can produce carbon dioxide and displace normal air)
18
Q

How does Oxygen Enrichment occur?

A
  • When oxygen is artificially introduced into a space
  • Where the chemical contents of a space release oxygen as they degrade
  • As a result of leaking equipment
19
Q

List some additional precautions when working in Confined Spaces with Water?

A
  • Take note of the weather forecast
  • Establish local on-site procedures to deal with large volumes of water
  • Safety harnesses and chain barriers to prevent workers being washed away
  • Workers awareness of personal hygiene and inoculations
20
Q

What are the precautions for Safe Entry into a Confined Space?

A
  • Avoidance where possible
  • Risk Assessment must be carried out
  • Planning must take place
  • Establish a Permit to Work system
  • Atmospheric Testing must take place
  • Safe means of access/egress must be provided
21
Q

How can you reduce the need to enter/work in a Confined Space?

A
  • Modify the space so entry is not necessary
  • Do the work from outside (blockages cleared by remotely operated air purgers etc)
  • Inspection, sampling and cleaning can often be done from the outside, using appropriate equipment/tools
  • Remote cameras can be used for internal inspection of vessels
22
Q

Identify what a Confined Space Risk Assessment must consider?

A
  • Whether entry can be avoided
  • What work needs to be done
  • Methods of working (tools/equipment)
  • Entry with or without breathing apparatus
  • Hazard identification in the Plant
  • Hazards from neighbouring Plant/vessels
  • Suitability of those carrying out the work
  • Steps necessary to make the job safe (safe system of work)
  • Arrangements for emergencies and rescue facilities
23
Q

List the essential features of a permit-to-work system?

A
  • Clear identification of who may authorise particular jobs
  • Who is responsible for specifying the necessary precaution (i.e. isolation, gas testing, emergency arrangements)
  • The inclusion of contractors engaged to carry out work
    Training and instruction in the issue and use of permits
  • Monitoring and auditing to ensure that the system works as intended
24
Q

List the requirements laid out in the safe system of work?

A
  • Hazard identification
  • Hazard control
  • Isolation and/or locking off
  • Permit system
  • Information/signs for employees
  • Prevention of unauthorised entry
  • Employee training
  • Equipment
  • Rescue
  • Protection from external hazards
  • Duty to other employers
25
Q

What should atmospheric testing look for?

A
  • A flammable gas, vapour or mist in excess of 10% of its LEL (Lower Explosive Limit)
  • An atmospheric oxygen concentration below 19.5% or above 22%
  • An atmospheric concentration of any substance for which a WEL (Workplace Exposure Limit) is published in EH40 by the HSE and which could result in employee exposure in excess of permissible limits.
  • An airborne combustible dust at a concentration that obscures vision at a distance of 5 feet (1.52m) or less
  • Any atmospheric condition recognised as immediately dangerous to life or health
26
Q

When may monitoring be required?

A
  • Before first entry
  • At the start of each shift
  • At each entry
  • After each break
  • At a specified time limit, as set out in the permit
  • Continuously
27
Q

Identify what rescue equipment should consist of?

A
  • Breathing apparatus sets
  • Rescue and resuscitation equipment, harnesses, lifting tripods and winch, stretchers, first aid equipment
  • Fire-fighting equipment
  • Means of communication and summoning help (tug-rope, radio, etc)
  • Lifelines
  • Oxygen

NEBOSH Construction Certificate (13 decks)

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