Quantify underground risk before tender close — not after ground breaks. A staged AS5488 investigation from QL-D records through to QL-A physical exposure at clash points, delivering an attributed CAD and GIS dataset across Victoria.
Before You Dig Australia (BYDA) is the starting point for any investigation — not the endpoint. BYDA plans are drawn from utility authority records, and those records default to AS5488 Quality Level D: existing documentation only, no field detection, no depth, no confirmation that the service is still in place.
BYDA itself states that plans are "indicative only" and do not show private or domestic services. When a tender is priced against QL-D data, depth assumptions are guesses, clash allowances are guesses, and service-protection measures are based on guesses. That is where latent-condition claims begin.
A pre-tender utility investigation replaces those guesses with AS5488-attributed survey data — so that risk is priced in, not discovered mid-excavation. For more on services that fall outside the BYDA network entirely, see our page on underground services not on plans.
Underground utility risk sits at the intersection of contract law, safety legislation, and professional duty. Understanding the exposure before tender close is not optional — it is due diligence.
The standard Australian construction contract deems a latent condition — a physical condition that could not reasonably have been anticipated — to be a variation. A contractor must give written notice within 28 days of becoming aware of the condition. Bidding on unverified QL-D data without investigation weakens any latent-condition claim and can leave the contractor absorbing cost that should have been quantified at tender.
Under NEC4, a compensation event arises where physical conditions encountered are such that an experienced contractor would have judged them to have a sufficiently small chance of occurring that it would have been unreasonable to have allowed for them. Courts and adjudicators look closely at the investigation scope at tender stage when assessing whether the condition was "judged" or should have been anticipated.
Australian courts have affirmed that contractors owe a duty of care in conducting pre-excavation investigations and cannot rely on BYDA plans as a complete defence — see D&V Services v SA Power Networks [2018] SASCFC 92 and Abigroup v Sydney Catchment Authority [2006] NSWCA 282. The quality and extent of the pre-tender investigation is examined directly when disputes arise.
Victoria's Occupational Health and Safety Regulations 2017 require that before any excavation work begins, the controller of the work must ensure the location of underground essential services in the vicinity of the excavation has been determined. This is a duty that cannot be delegated by contract. A pre-tender investigation that reaches QL-B across the corridor and QL-A at critical locations provides the documented evidence base required to satisfy this obligation and to brief subcontractors and plant operators on verified service locations.
Four stages aligned with AS5488 — from records to an attributed deliverable your estimating and design teams can use directly.
We obtain all available BYDA records, utility authority plans, council drainage data, and historical site information — establishing a QL-D baseline and identifying data gaps before any field work is commissioned.
A site walk correlates surface infrastructure (pits, valve covers, marker posts, conduit risers) with existing records. Our NULCA-certified technicians then run EML and GPR along the full works corridor, elevating data from QL-D to QL-B.
At identified clash points and areas of uncertainty, non-destructive digging physically exposes services. Exposed utilities are surveyed to ±50 mm — giving precise depth, material, and condition data for pricing and design.
All field data is compiled into a georeferenced CAD plan and GIS deliverable with full AS5488 quality-level attribution, supported by a site investigation report and QL-A exposure sheets.
All deliverables are produced to AS5488 attribution requirements and referenced to MGA Zone 55 and AHD. See the full utility data deliverables catalogue for format specifications.
| Deliverable | Who Uses It |
|---|---|
| Georeferenced CAD plan (DWG/DXF) | Design engineers, estimators |
| GIS file with AS5488 quality-level attribution | Project managers, infrastructure authorities |
| Site investigation report (methods, limitations, confidence) | Principals, superintendents |
| QL-A exposure sheets with coordinates, depth, material, photographs | Estimators, subcontractors |
| Clash matrix — proposed works vs. existing services | Design engineers, project managers |
| Aerial base map with combined surface/subsurface overlay | Developers, DA submissions |
Data is also available as subsurface utility mapping outputs including IFC/BIM models for Revit integration. Targeted QL-A exposure is delivered by non-destructive digging.
Price underground risk before locking in a fixed-price or lump-sum tender. Know the depth, material, and clash profile before you price protection measures and service-diversion allowances.
Commission due diligence before lodging a DA or finalising a feasibility. Identify utility constraints, required diversions, and authority connection points before design is advanced.
Enter the enabling-works phase — particularly the FY-start capital window — with a verified utility dataset that can be briefed to all subcontractors and integrated into the site construction plan.
Discharge the pre-excavation duty under the OHS Regulations 2017, document reasonable investigation for latent-condition risk management, and provide contractors with verified information at tender.
Pre-tender utility due diligence is a staged AS5488 investigation — QL-D records review through to QL-A physical exposure at identified clash points — completed before a contractor prices a job or a developer submits a development application. It converts unknown underground risk into a quantified, documented cost that can be priced, contingency-budgeted, or designed around before tender close.
Under AS 4000-1997 Clause 25, a contractor may claim a latent condition — that is, a physical condition which could not reasonably have been anticipated — as a deemed variation. However, the contractor must give written notice within 28 days of becoming aware of the condition. If a competent pre-tender investigation would have identified the service, the latent-condition claim may be difficult to sustain. Courts have also found that contractors owe a duty of care when undertaking investigations — making the quality of the pre-tender investigation a central issue in any dispute.
At minimum, a pre-tender investigation should reach QL-B across the works corridor — geophysical detection using electromagnetic induction (EML) and ground penetrating radar (GPR), with utility positions verified to AS5488 tolerances of ±300 mm horizontal and ±500 mm vertical. At identified clash points — where proposed works cross or run alongside existing services — targeted QL-A exposure by non-destructive digging gives precise depth and material data for tender pricing. The appropriate scope depends on project complexity, corridor length, and the asset classes present.
For a typical urban corridor of 500–1,000 m, a combined QL-B geophysical survey and targeted QL-A proving programme can be delivered in 5–10 business days from site mobilisation, including deliverable production. Larger or more complex sites — particularly those with dense service environments or multiple utility authorities — take longer. Early engagement is recommended: investigations commissioned 4–6 weeks before tender close allow time for redesign if clashes are identified.
Deliverables are produced to AS5488 attribution requirements and include: a georeferenced CAD plan (DWG/DXF) and GIS file showing all detected and proved services with quality-level attribution; a site investigation report covering methods, equipment, limitations, and confidence levels; QL-A exposure sheets for each pothole with survey-grade coordinates, depth, material, and photographs; and a clash matrix identifying locations where proposed works are within tolerance of existing services. Data is referenced to MGA Zone 55 and AHD.
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