Civil Engineering · WA · Western Australia
Stormwater infrastructure dispute
Independent civil engineering evidence traced repeated flooding to drainage design and construction deficiencies.
Causation established- Asset
- Industrial estate stormwater network
- Defect
- Undersized pit & pipe network with grade errors
- Forum
- District Court of Western Australia
- Standards
- AS/NZS 3500.3, ARR 2019, local DCP
The dispute
An industrial estate experienced repeated nuisance flooding of access roads and tenancy aprons after rainfall events well below the design ARI. The owner alleged design and construction deficiencies in the stormwater network. Our civil expert was briefed to model the system and identify the failure mode.
Matter: Industrial estate owner vs. civil contractor, WA District Court
Our expert's findings
Hydraulic re-modelling under ARR 2019 confirmed the installed pit and pipe network was undersized for the contributing catchment, with grade reversals in three reaches. The as-built network deviated from the approved design. Modelled and observed flood extents aligned closely, establishing causation.
Outcome
Causation was established against the civil contractor. The matter resolved through mediation with a contribution to rectification and an agreed upgrade scope for the affected reaches.
Frequently asked questions
Was the design also defective?
The approved design was marginal but compliant. The dominant cause was construction deviation — grade reversals and substituted pit sizes.
What modelling was used?
Calibrated 1D hydraulic modelling consistent with ARR 2019 design rainfall and the local drainage authority's parameters.
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