Excavations & Confined Spaces

Under CDM 2015, what is an 'excavation'?

• ATrenches dug for drainage or service runs, once they become deeper than the height of the person working inside them at the time
• BA hole or depression in the ground made by removing material, including trenches, pits, shafts, and underground chambers✓
• CA permanent structure built below ground level, such as a basement
• DHoles deeper than 1.2 metres, which are the ones requiring support

Answer: CDM 2015 reg 2 defines an excavation as including any earthwork, trench, well, shaft, tunnel or underground working, with no minimum depth. Reg 22 requires all practicable steps, such as support or battering, to prevent collapse, falling material and people or plant falling in, and a competent person must inspect supported or battered excavations at the start of each shift. HSE warns that no ground can be relied on to stand unsupported.

What are the main hazards associated with excavations?

• ACollapse of sides, falls of persons/objects, water ingress, and atmospheric hazards✓
• BTool theft
• CDust and noise from the excavator, which become the main hazards once the sides have been battered back
• DExcavations are inherently safe

Answer: Excavation hazards include: collapse of excavation sides, falls of people or objects into excavations, water ingress, gases (atmospheric hazards), and struck-by hazards.

What is 'trench support' and when is it required?

• AWaived for shallow trenches
• BTemporary structures (shoring, sheet piling, supports) preventing collapse; required based on soil type and depth✓
• CNeeded for trenches deeper than three metres, since shallower ground will stand unsupported for the length of a shift
• DFitted if workers complain

Answer: Trench support is required to prevent collapse of trench sides. The type and depth of support depends on soil type, depth, and weather. Competent persons must design support.

What is 'benching' in excavation work?

• AA rest area cut into the side of an excavation where operatives can shelter from the weather during their rest breaks
• BA method of compacting the base of an excavation before concrete is poured, unrelated to the stability of the sides
• CA technique used only in deep mining, not permitted on construction sites
• DA stepped or sloped formation of excavation sides to prevent collapse (used as alternative to full support)✓

Answer: Benching involves creating steps or slopes in excavation sides instead of vertical walls. This reduces collapse risk and can be an alternative to support systems if designed correctly.

What must be done regarding 'water management' in excavations?

• APlacing sandbags around the top of the excavation, which is enough to keep surface water out of the trench during rain
• BAssess water risk, implement controls (pumping, dewatering, drains), prevent flooding of adjacent properties✓
• CPumping water out only once it reaches waist height on the operative, discharging it to the nearest surface drain
• DAllow water to drain naturally, since pumping can destabilise the sides

Answer: Water management in excavations includes: risk assessment, pumping systems, dewatering arrangements, checking for water damage to adjacent structures, and preventing flooding.

What is a 'confined space' under health and safety law?

• AA substantially enclosed space where a specified risk, such as lack of oxygen, is reasonably foreseeable✓
• BRooms which have been sealed off from the outside air by airtight doors and hatches
• CA space located below ground level, such as a basement or a cellar
• DAn enclosed area, such as a store room, plant room or site cabin

Answer: Under the Confined Spaces Regulations 1997, a confined space has two defining features: it is substantially (though not always entirely) enclosed, and one or more specified risks is present or reasonably foreseeable. The specified risks are serious injury from fire or explosion; loss of consciousness from raised body temperature; loss of consciousness or asphyxiation from gas, fume, vapour or lack of oxygen; drowning; and asphyxiation or entrapment by a free-flowing solid. Difficult access is not part of the UK test, and open-topped chambers and poorly ventilated rooms can qualify (HSE L101 and INDG258).

What are the main hazards in confined spaces?

• ADarkness, restricted movement and poor mobile phone signal
• BHazardous atmospheres (gases, oxygen deficiency), flooding, physical hazards, isolation, loss of consciousness✓
• CExtremes of temperature, which is the principal risk in such spaces
• DNoise on its own, which is controlled through the use of hearing protection

Answer: Confined space hazards include: hazardous atmospheres (toxic gases, oxygen deficiency, flammable gases), flooding, drowning, engulfment, heat stress, physical hazards, and isolation.

What is a 'confined space permit' and what should it contain?

• ASet aside where entrants have been trained in confined space working and hold a current certificate for the type of space involved
• BA single document issued once for the whole project, listing the confined spaces on site and the operatives who are trained to enter them
• CFormal authorisation system specifying hazards, controls, gas test results, rescue procedures, and competent persons involved✓
• DA permit needed only where a space has previously been found to contain gas, as recorded in the site's confined space register

Answer: A confined space permit formalises authorisation for entry, specifying: identified hazards, test results (atmospheric monitoring), control measures, rescue arrangements, and authorised personnel.

What is 'atmospheric monitoring' in confined spaces?

• ATesting the air before and during entry for oxygen level, toxic gases, and flammable atmosphere✓
• BUnnecessary provided that the space is left open and ventilated for an hour before anyone enters it
• CA visual inspection of the space carried out before entry is permitted
• DTesting required only in spaces below ground level, since spaces at or above ground level ventilate naturally

Answer: HSE's confined spaces ACOP (L101) says the air is tested before entry (oxygen first, then flammable gas, then toxic gases such as H₂S and CO) and monitored during the work where conditions could change. Normal air holds 20.9% oxygen and any departure is investigated; HSE sets no fixed band, but many UK detectors alarm at 19.5% (falling) and 23.5% (rising).

What is the 'entry supervisor' role in confined space work?

• AA competent person managing the confined space entry, coordinating rescue, monitoring conditions, and ensuring procedures are followed✓
• BAn administrative role, issuing the permit and filing it once work is complete
• CA role that is only ever required for excavation work being carried out on a site of any size
• DA duty carried out by the person entering the space themselves

Answer: An entry supervisor remains outside the confined space, monitors conditions, maintains communication with entrants, manages rescue readiness, and can order evacuation if needed.

What is a 'rescue team' and what must they be trained in?

• APointless, because the site's emergency plan already names the fire and rescue service as the responders for any confined space incident on the project
• BCompetent personnel trained in rescue techniques, equipment use, first aid, and emergency procedures for safely extracting people from confined spaces✓
• CThe site's appointed first aiders, who may enter the space to retrieve a casualty as soon as the alarm is raised, provided that they are wearing a dust mask
• DSite security staff, who are on site already and can call the emergency services

Answer: A rescue team must be trained and equipped to safely rescue a person from the confined space using proper equipment and techniques without risking the rescuers.

What is 'engulfment' in confined spaces?

• ABeing surrounded or buried by material (e.g., grain, sand, liquid) causing asphyxiation or injury✓
• BFlooding of a space by rainwater entering through the access hatch during a period of heavy weather
• CBeing locked inside a space when the access hatch is closed by another worker who is unaware of the entry
• DLoss of lighting inside the space, leaving the entrant unable to see the route back to the access point

Answer: Engulfment is being surrounded or buried by solids or liquids in a confined space, often causing rapid asphyxiation. Examples include grain silos and tanks.

What emergency response measures are needed for confined spaces?

• AA telephone kept in the site office so that the emergency services can be called if the entrant fails to reappear within the expected time
• BA mobile phone is sufficient; entrants are expected to make their own way out and call for help if the conditions change inside
• CA first aid kit, a mobile phone and the number for the emergency services
• DEmergency procedures, rescue equipment, communication systems, trained rescue team, and prompt access to emergency services✓

Answer: Confined space work requires: emergency response plan, rescue equipment, communication systems (radio, rope systems), trained rescue team on standby, and access to emergency services.

What is 'ventilation' in confined space management?

• AA measure used once gas detectors have raised an alarm inside
• BPumping out water
• CAdding pure oxygen
• DSupplying fresh air to remove hazardous atmospheres or maintain safe conditions during work✓

Answer: Ventilation involves supplying fresh air via fans or blowers to displace hazardous gases and maintain safe atmospheric conditions. Both natural and mechanical ventilation may be used, but pure oxygen must never be used to freshen the air because it greatly increases the fire risk.

What is a 'competent person' for excavation and confined space work?

• AA chartered civil engineer registered with the ICE, who personally supervises each entry and excavation on the site each day
• BAnyone with a hammer
• CPerson with knowledge, experience, and training to manage excavations/confined spaces, assess safety, and supervise work✓
• DHSE inspectors

Answer: Competent persons for excavations and confined spaces need: understanding of soil types and support systems, ability to assess hazards, knowledge of regulations, and practical experience.

What must be done to control 'dust' in excavation work?

• AMeasures needed only in windy conditions, when dust is carried beyond the boundary hoarding into neighbouring property
• BIssuing disposable masks to the gang, which removes the need to control the dust at the point where it is created
• CIgnored in the open air, because dust generated outdoors disperses before it can reach a harmful concentration
• DUse water spraying, local extraction, respiratory protection, and work planning to minimise dust inhalation✓

Answer: Dust control measures include: water spraying, extraction systems, personal respiratory protection (as last resort), and work methods that minimise dust generation.

What is a 'competent support system' for an excavation?

• AStacked concrete blocks
• BA propping arrangement the gang considers adequate, provided the operatives have several years of experience in excavation work
• CEngineering-designed support system (shoring, sheet piling, or braces) appropriate for soil conditions, depth, and workload✓
• DLoose timber props

Answer: Competent support systems are engineered specifically for the excavation considering: soil type and stability, depth, water table, ambient temperature, and work activities.

What must be done regarding 'utility strike prevention' in excavations?

• AOf little concern
• BIdentify underground utilities, mark locations, use safe digging practices, contact utility companies before excavation✓
• CObtain the utility drawings, then dig with a mechanical excavator under supervision
• DOnly relevant for large projects

Answer: Utility strike prevention requires: locating utilities (electrical, gas, water, telecommunications), marking their position, using safe digging techniques, and contacting utility companies.

What is 'sloping' versus 'shoring' in excavation design?

• AShoring is required by law, because sloping the sides of an excavation is prohibited in the UK where it uses more ground than necessary
• BThe same thing
• CSloping angles the sides; shoring supports vertical sides using engineered systems. Choice depends on soil type and space available✓
• DSloping needs props

Answer: Sloping (battering) cuts the sides back to a safe angle chosen by a competent person for the ground conditions. No ground can be relied upon to stand unsupported in all circumstances. Shoring uses support systems for vertical or near-vertical sides when sloping is not feasible.

What is a 'rescue plan' for confined space entry?

• AA plan prepared by the entrants themselves once they are inside the space, based on the conditions they find after the atmosphere has been tested
• BA short written note kept with the permit which states that the emergency services will be called if one of the entrants gets into difficulty inside the space
• CAn optional document, produced where the entrants named on the permit have not previously worked in a confined space of that type on this site before
• DA detailed plan specifying rescue equipment, trained rescue team, communication methods, and procedure for safely removing a person in distress✓

Answer: A rescue plan must specify: available rescue equipment, trained rescue team contact/location, communication systems, extraction procedures, medical support, and testing protocols.