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
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
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
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
5
Q
List the types of excavation support?
A
- Battering
- Shoring
- Trench Boxes
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
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
8
Q
What are the particular requirements for excavating Contaminated Ground?
A
- Soil testing
- Additional/specific welfare facilities
- Health Surveillance
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
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.
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
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
13
Q
Give examples of Confined spaces?
A
Trenches, Sewers, Manholes, Chambers, Pits, Tanks, Vats, Silos, Reaction Vessels, Flues, Ductwork
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
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
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
