The Mills & Watson Plumbing Conviction — What Happened
- Safety Jon
- Oct 12
- 7 min read
The Mills & Watson Plumbing Pty Ltd case is tied to a broader excavation collapse incident prosecuted under safe work laws in New South Wales. The case is not about plumbing per se, but highlights how even trade contractors can become legally exposed when working adjacent to or within excavation zones without adequate risk controls. The facts are documented in a case summary published in Health & Safety Handbook under the title “Excavation unearths serious safety risk.” Health & Safety Handbook
Here is a consolidated summary:
Parties & Project Context
Bellabrae Homes Pty Ltd was the principal contractor for a residential build in North Kellyville, NSW.
Bellabrae contracted Excon Services Excavation (Excon) to perform the bulk excavations and earthworks.
It also engaged Mills & Watson Plumbing Pty Ltd (M&WP) to carry out internal and external plumbing work, which included excavation adjacent to the main works.
M&WP later subcontracted JG Plumbing & Excavation Pty Ltd (JG) to perform further excavation under the plumbing scope.
The Incident
In May 2022, a site meeting was held between M&WP’s director, Mr Mills and Bellabrae’s director, Mr Jitla, to discuss drainage under the slab. Mr Mills suggested additional excavation adjacent to the existing earthen wall (excavation face) might be needed, but that decision was to be made “on the day.”
On the day of the incident (June 2022), three workers (two from M&WP and one from the subcontractor JG) attended to carry out the additional excavation. None of the workers had previously worked on that site.
Importantly, they had not had a site-specific induction or toolbox talk, and were not informed about the soil conditions or any need for control measures to support the earthen wall.
One worker began digging a narrow trench (300 mm wide) adjacent to the earthen wall. Then another worker entered the trench to remove residual rock in preparation for plumbing pipes. While in the trench, a section of the earthen wall collapsed and buried the worker partly. He was forced to fall sideways, and the soil engulfed him.
The injured worker suffered multiple bone fractures and was unable to return to work for roughly three months.
Court Findings & Penalty
The court found that Bellabrae had not conducted a proper risk assessment, had failed to identify hazards or relevant control measures for the excavation, and had neglected to seek geotechnical or structural advice regarding the stability of the earthen wall.
The court further determined that while Bellabrae commissioned geotechnical and structural advice for other parts of the build, it did not obtain advice about whether the exposed earthen wall, as excavated, was self-supporting or required shoring, battering, or piling.
Crucially, the soil conditions adjacent to the earthen wall (along the eastern boundary) differed from those assumed in the geotechnical report, meaning the fill material’s slope stability was not adequately assessed.
The risk of collapse was deemed "reasonably foreseeable," and it was considered reasonably practicable to provide supports to prevent collapse.
The penalty imposed on Bellabrae was AU$225,000.
While the spotlight was mainly on the principal contractor (Bellabrae), the involvement of M&WP (and its subcontractor) underscores how plumbing or installation trades working in or adjacent to excavations can be legally implicated if they participate in or initiate unprotected excavation activity without due control.
Why This Case Matters — Key Takeaways
This case is instructive for several reasons:
Trade contractors are not immune - Even if your scope is plumbing or installations, when it involves excavation or trenching, you can incur substantial liability if you do not manage the risks appropriately.
Assumed stability is dangerous - Just because an excavation face or earth wall looks stable does not mean it is. Soil conditions change; designs may differ from in situ reality.
Lack of induction and communication is unacceptable - Specifically, the workers in this case had no site induction regarding soil hazards or the need for protective systems. That is a serious gap in safe systems.
Failure to document or consult experts is a weak defence - Bellabrae’s reliance on existing geotechnical reports (except where they excluded the boundary fill) was insufficient. The lack of specific design or validation for the earthen wall compromised its structural integrity.
Reasonably practicable standards are objective and enforced - The court determined that providing supports (shoring, battering, piling) was within the realm of reasonable practicability. Because that control was available and effective, its omission was a breach.
Consequences extend beyond fines - Injury, downtime, reputational damage, legal costs, increased insurance, and regulatory scrutiny all follow such incidents.
What Duty Holders Can Do to Avoid This Outcome
To avoid being in the position M&WP (or Bellabrae) found themselves in, duty holders at all tiers (principal contractors, subcontractors, trade contractors, site managers) must rigorously apply safety management principles. I've included a practical guide for you below.
1. Recognise Scope Overlap & Shared ResponsibilityBattering/benching
Understand that when your trade work requires excavation or trenching, even as part of a sub-contract, you share responsibility for excavation safety.
Don’t assume the principal contractor or earthworks contractor has taken care of all risks — risk gaps often emerge at boundaries or interfaces between trades.
2. Insist on and Participate in Risk Assessment Upfront
Before any excavation adjacent to your work, push for a site-specific risk assessment that includes soil behaviour, slope stability, groundwater, adjacent loads, and boundary conditions.
Request or require geotechnical input specifically for the portions of excavation your trade will affect.
Be part of design and planning discussions, especially where your plumbing, drainage or service excavation will approach an existing cut or exposed face.
3. Demand Adequate Design and Protective Measures
Do not accept an assumption of self-supporting excavation without evidence.
Protective measures may include:
Battering/benching (stepped slopes)
Shoring/bracing/soldier piles/sheet piling
Pile support or underpinning
Temporary retaining systems
Confirm that designs reflect actual soil conditions (including fill zones, lateral loads, and water pressure).
4. Ensure Proper Induction, Training & Toolbox Talks
All personnel entering the site must receive a site-specific induction that addresses soil risks, excavation procedures, exclusion zones, control systems, emergency procedures, and reporting protocols.
Provide toolbox talks before excavation tasks begin, covering how the trench is to be excavated, how far from the bracing/soldieredge materials or workers must stay, and safe ingress/egress.
Train supervisors and workers on soil mechanics basics, collapse risks, protective systems, hazard recognition and what to do if signs of instability appear.
5. Mandate a Competent Person Role & Inspection Regime
Appoint a competent person (knowledgeable in excavation safety) whose duties include inspecting the excavation daily (and more frequently after rain, vibration, or events).
The competent person must have the authority to halt work if signs of instability emerge.
Inspections should examine cracks, bulging, seepage, soil movement, undermining, support integrity, and adjacent conditions.
6. Document Everything & Maintain Records
Keep all design plans, geotechnical reports, correspondence, risk assessments, induction logs, inspection logs, change requests, daily site diaries, and incident/near-miss registers.
If conditions change (e.g. soil softening, groundwater appearance, vibration events), record how these were assessed and what remedial actions were taken.
7. Manage Edge Loads, Materials & Exclusion Zones
Maintain adequate setback distances from trench edges for spoil, materials, equipment, vehicles and even foot traffic.
Never load heavy objects near the face unless the face is designed or supported for that load.
Establish and enforce exclusion zones (areas where workers must not stand under unsupported faces).
8. Provide Safe Access & Egress
Provide ladders, stairways, ramps or other means of ingress/egress consistent with the depth and nature of the trench.
These should be placed at strategic intervals so workers never have to climb unstable slopes or unsafe points.
9. Monitor Conditions & React to Change
After rain, vibration events, rest periods, temperature changes or other external influences, re-inspect thoroughly.
If soil conditions degrade (e.g. moisture increases, cracks form, bulging occurs), suspend work, reassess and implement additional controls before continuation.
Use instrumentation when needed (inclinometers, crack monitors, settlement gauges) in higher-risk or deeper excavations.
10. Prepare Emergency & Rescue Plans
Develop a rescue plan tailored to excavation collapse scenarios. Consider the steps for extricating a buried worker, including removal of spoil, bracing support, utilising lifting equipment, and providing medical response.
Ensure first aid equipment is available, and designated responders know their roles.the steps for extricating a buried worker, including removal of spoil, bracing support, utilising lifting equipment, and providing
Conduct periodic drills or simulations to practice response times.
11. Seek External or Peer Review When Needed
For complex or borderline excavations, consider bringing in external checks (e.g., geotechnical or structural peer review) to ensure the design is robust and safety is verified.
This protects you from undue risk and strengthens the defensibility of your approach.
12. Pause Work On Doubt & Learn from Near Misses
If any team member doubts the stability of a face, or observes changes, stop work immediately, reassess and only resume when safe.
Treat near misses or soil movements as critical learning opportunities — update procedures and share lessons with the team.
How This Safeguards Against Legal & Safety Exposure
If duty holders follow these recommendations, they significantly reduce the chance of being prosecuted or fined in the same way as in the Mills & Watson / Bellabrae case:
Foreseeability is addressed — courts often assess whether a risk was foreseeable and whether control measures were reasonably practicable. By actively planning and designing, you address foreseeability.
Duty of care is demonstrably met — the presence of geotechnical design, inspections, induction, training, and records shows you took your WHS obligations seriously.
Defensible record in prosecution — well kept documentation, correspondence and expert reports help you present a strong defence in the event of a regulatory investigation.
Reduction of actual risk — safer systems, competent oversight, exclusion zones and responsive reviews materially reduce the chance of collapse and injury.
Cultural and reputation protection — showing a proactive safety culture helps in public, client and regulatory perception.
Conclusion
The Mills & Watson Plumbing story is a cautionary tale: even subcontractors working in trenching or plumbing can be drawn into regulatory liability when excavation hazards are not adequately managed. The incident at North Kellyville, tied to Bellabrae’s prosecution, highlights how inadequate risk assessment, poor communication, missing control measures, and weak oversight led to serious injury and a large fine.
For any duty holder — principal, contractor, subcontractor, site manager or tradesperson — the takeaway is clear: never assume safety, always validate and document it. By being proactive, disciplined, and collaborative in excavation safety, you won’t just reduce your legal exposure — you protect lives.
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