8.1 Excavation Safety, Shoring, Battering & Underground Services (CR 13)

1. Statutory Framework and Competent Supervision (CR 13(1))

Excavation work is among the most hazardous construction activities: trench collapses, strikes on buried electrical cables and gas mains, undermining of neighbouring structures, and toxic or oxygen-deficient atmospheres all cause deaths. CR 1 defines excavation work as the making of any man-made cavity, trench, pit or depression formed by cutting, digging or scooping. Any excavation work also requires a notification to the provincial director at least 7 days beforehand where no construction work permit applies (CR 4(1)(a)).

Construction Regulation 13(1) requires the contractor to:

• (a) ensure that all excavation work is carried out under the supervision of a competent person appointed in writing for that purpose; and
• (b) evaluate, as far as reasonably practicable, the stability of the ground before excavation work begins.

The Construction Health and Safety Manager should check the appointee's letter, training and experience, because every later duty in CR 13 depends on that person's judgement.

2. Preventing Collapse: Shoring, Bracing or Sloping (CR 13(2)(a)–(c))

A contractor performing excavation work:

• (a) must take reasonable and sufficient steps to prevent any person being buried or trapped by a fall or dislodgement of material;
• (b) may not require or permit anyone to work in an excavation that has not been adequately shored or braced, unless:
  • (i) the sides are sloped to at least the maximum angle of repose measured from the horizontal (CR 1 defines the angle of repose as the steepest angle at which loose or fragmented material will remain stationary in a pile); or
  • (ii) the excavation is in stable material, but only where the appointed competent person has given written permission after evaluating the site conditions, and, where any uncertainty about soil stability remains, the decision of a professional engineer or professional technologist competent in excavations is decisive and must be recorded in writing and signed by both; and
• (c) must ensure that the shoring or bracing is designed and constructed strongly enough to support the sides of the excavation.

There is no depth threshold in CR 13: a 1.2-metre trench in running sand can kill. US OSHA soil-type tables (Type A, B and C soils with set slope ratios) are sometimes quoted on South African sites, but they are not South African law; slopes and support must follow the competent person's evaluation and, where needed, geotechnical or engineering advice.

Typical support systems include hydraulic or screw-strutted trench shields and boxes, timber or steel close-sheeting with walings and struts, slide-rail systems for deeper excavations, soldier piles and lagging, and steel sheet piling where groundwater or running sand is present. Each must be installed before people enter the unsupported section.

3. Loads near the Edge and Adjacent Structures (CR 13(2)(d)–(e))

• (d) No load, material, plant or equipment may be placed or moved near the edge of an excavation where it may cause collapse and endanger anyone, unless precautions such as sufficient and suitable shoring or bracing are taken. The regulation sets no fixed distance; client specifications commonly require spoil to be kept at least 1 m back, and further for deep excavations, soft ground or heavy plant.
• (e) Where the stability of an adjoining building, structure or road is likely to be affected, steps must be taken to ensure its stability and the safety of persons (underpinning, sheet piling, monitoring).

CR 23(1)(g) adds that construction vehicles and mobile plant must be prevented from falling into excavations, for example by edge protection, crash barriers or stop blocks along approach routes.

4. Access and Egress (CR 13(2)(f))

Convenient and safe means of access must be provided to every excavation in which people work, and that access may be no further than 6 metres from the point where any worker in the excavation is working. Along a continuous trench, that means a ladder or ramp at least every 12 metres. Ladders should be secured at the top and bottom and extend about a metre above the edge to give a handhold.

5. Underground Services (CR 13(2)(g))

The contractor must ascertain, as far as reasonably practicable, the location and nature of electricity, water, gas or other services that may be affected, and, before starting excavation work that may affect them, take the steps necessary to make the circumstances safe (CR 24(a) imposes a matching duty for electrical cables). Good practice is a four-stage clearance:

1. Records and wayleaves: obtain service records and wayleave approvals from the municipality, Eskom, telecommunications and pipeline owners, treating drawings as indicative.
2. Detection: scan with a cable avoidance tool and signal generator (power, radio and signal modes), and ground-penetrating radar for non-metallic services.
3. Exposure: expose services by hand digging with suitable tools or by vacuum excavation; keep mechanical excavation outside the distance specified in the wayleave conditions until the service is located.
4. Protection: support exposed services across the trench and isolate live services through the owner's permit-to-work system where work must come close.

6. Inspection and Register (CR 13(2)(h))

Every excavation, including all bracing and shoring, must be inspected by the competent person appointed under CR 13(1):

1. daily, before the start of each shift;
2. after every blasting operation;
3. after an unexpected fall of ground;
4. after damage to supports; and
5. after rain.

The results must be recorded in a register kept on site and made available on request to an inspector, the client, the client's agent, any other contractor or any employee. Tension cracks, bulging, seepage, slumping or strut movement mean immediate withdrawal of workers until the excavation is made safe.

7. Protecting the Public and Warning People (CR 13(2)(i) and (l))

Every excavation that is accessible to the public, adjacent to public roads or thoroughfares, or where people's safety may be endangered must be:

• adequately protected by a barrier or fence at least one metre high, as close to the excavation as practicable; and
• provided with warning illuminants or other clearly visible boundary indicators at night or when visibility is poor,

or other suitable and sufficient precautions must be taken where these are not practicable. Barrier tape is a visual warning, not a barrier. CR 13(2)(l) also requires warning signs next to any excavation where people are working, inspecting or testing.

8. Atmospheric Hazards (CR 13(2)(j))

Excavations can trap gases: hydrogen sulphide and carbon dioxide (heavier than air) near sewers and organic ground, carbon monoxide from engines near the edge, methane from landfill or gas mains, and solvent vapours on contaminated land. CR 13(2)(j) requires the precautions for confined spaces in the General Safety Regulations to be complied with by any person entering any excavation where they apply. Under General Safety Regulation 5, that means the air must be tested and evaluated by a competent person who certifies in writing that the space is safe; where oxygen is or may be below 20% by volume or a hazardous gas may be present, the space must be purged and ventilated (and isolated from pipes and communicating openings), or entrants must use approved breathing apparatus with a harness and lifeline and an attendant trained in resuscitation outside. Flammable gas may not exceed 25% of the lower explosive limit where the work creates no ignition source, or 10% for other work. Engines should never run in or close to an excavation.

9. Explosives (CR 13(2)(k))

Where excavation involves explosives, the contractor must appoint a person competent in the use of explosives for excavation, who must develop a method statement in accordance with the applicable explosives legislation.

10. Summary Matrix