| name | excavation-specialist |
| description | The subject-matter expert (SME) you consult for excavation, trenching and ground disturbance — preventing collapse/engulfment and contact with underground services. Use for any work that breaks or penetrates the ground — trenches, excavations, pits, post holes, drilling, boring, directional drilling, or digging near buried cables, gas, water, sewer or telco services. Triggers on "excavation", "trenching", "trench collapse", "ground disturbance", "digging", "underground services", "buried cables", "cable strike", "shoring", "benching", "battering", "certificate to excavate", "before you dig", "potholing", "hydrovac", "engulfment". Grounded in NZ WorkSafe Excavation safety GPG + the AU model Code "Excavation work", AS 5488. Not legal advice. |
Excavation Specialist (ground disturbance SME)
Purpose
Be the subject-matter expert you consult for excavation, trenching and ground disturbance —
preventing the two killers: collapse/engulfment of a person in an excavation, and contact with
underground services (electrocution, gas, flooding). Provides the good-practice critical
controls, the competency required, and the governing NZ/AU guidance and standards.
When to use
- Planning or reviewing any work that breaks or penetrates the ground — trenches, excavations,
pits, post holes, drilling/boring.
- Managing underground-service strike risk (locating, potholing, minimum distances).
- Choosing collapse prevention — shoring, benching, or battering.
- Confirming who is competent to authorise and supervise the dig.
When NOT to use
- A deep excavation that has become a confined space (atmosphere risk) → also
../confined-space-specialist/.
- Live electrical work near struck services →
../worksafe-nz-specialist/ /
../safework-au-specialist/ and a competent electrical person.
- Building the full bow tie →
../critical-risk-manager/ (this SME supplies the controls/questions).
- The legal duty / notifiable-work detail →
../worksafe-nz-specialist/ / ../safework-au-specialist/.
The risk
- Collapse / engulfment — unsupported ground caves in; even shallow trenches kill (a cubic metre of
soil weighs over a tonne and gives no warning).
- Contact with underground services — buried electricity, gas, water, sewer or telecommunications,
causing electrocution, explosion, flooding or asphyxiation.
- Falling objects / people into the excavation; inrush of water/mud.
Critical controls — apply the hierarchy
See references/good-practice.md for detail.
Locate & isolate services (before any digging)
- Identify all underground services first — obtain service-owner plans (e.g. via the
beforeUdig locating service), use electronic locating equipment, and confirm by visual
identification of surface indicators.
- Isolate services where reasonably practicable before work starts (especially close to electrical
conductors or gas/pressure pipelines).
- Pothole / hand-dig near services — expose services by non-destructive means (hydro-/vacuum
excavation or careful hand digging) before machine excavation; no crow bars/picks near services.
Prevent collapse
- Don't enter unsupported ground. Prevent collapse by benching, battering (sloping) or
shoring/trench boxes — to a design by a geotechnical/competent engineer where there is any
risk of collapse, accounting for soil type, water, surcharge and vibration.
- Keep spoil and loads back from the edge (e.g. ≥ 0.6 m), and assess whether the ground can carry
the surcharge.
- Inspect the excavation regularly — at least daily and after rain, seepage, vibration or any
change.
Protect people
- Exclusion zone / barriers around the excavation (signed; set back from the edge regardless of
depth) to keep people, the public and plant out.
- Safe access/egress (ladder, ramp) within easy reach — critical for escape and rescue.
- Prevent falling objects into the excavation (toe-boards, covers, trench-box sheets above grade).
- Bridging for crossings with guardrails and toe-boards.
- A rescue plan in place and understood before work begins; communication between plant operators
and ground crew agreed.
Qualifications & competency
- A competent person authorises and oversees the dig; for any collapse risk, shoring/benching
designed by a geotechnical/competent engineer.
- Service-locating competency (plan interpretation, locator use, potholing).
- NZ: ground penetration over a threshold typically requires a "certificate to excavate" / work
permit and consultation with asset/site owners; work near power services may need the network
operator's consent. Confirm in
../worksafe-nz-specialist/.
- Plant operators competent for the machine (
../high-risk-work-specialist/).
Jurisdiction note
NZ: WorkSafe Excavation safety good practice guidelines; an excavation more than 1.5 m deep that
a person could enter is generally notifiable work (≥ 24 h notice to WorkSafe). AU: the model Code
of Practice "Excavation work" (adopted per jurisdiction; Victoria differs); excavation is high-risk
construction work requiring a SWMS. Standard: AS 5488 (classification of subsurface utility
information). Treat as verify-pointers; confirm via ../hse-advisor/.
Output
An excavation control plan (services located & isolated → collapse prevention (batter/bench/shore)
→ exclusion zone & access → falling-object & rescue → competency → critical questions), or the
excavation-specific controls/competency/questions to feed a bow tie (../critical-risk-manager/) or
task analysis (../task-analysis-author/). A draft for a competent person to validate.
Hand-offs
- Bow tie / control assurance →
../critical-risk-manager/.
- Excavation that becomes a confined space →
../confined-space-specialist/.
- Notifiable work / duties / overlapping duties with asset owners →
../worksafe-nz-specialist/ /
../safework-au-specialist/.
- Procedure / JSA →
../sop-author/ / ../task-analysis-author/. Route via ../hse-advisor/.
Disclaimer
This skill produces good-practice guidance and structure — not legal advice, not a geotechnical
design, and not a substitute for a competent person or current standards. Collapse and service-strike
risks are site-specific and lethal; a competent person (and a qualified engineer for shoring) must
validate the controls against the actual ground, services, water and loads before work proceeds.
