Root Investigations NSW — In-House Air Spade, Mobilised in Days Not Weeks

An Air Spade is a pneumatic excavation tool that uses high-pressure compressed air to remove soil from around tree roots without damaging the root tissue. Unlike a shovel, mattock or even a hydro-vac, the Air Spade can expose fine roots intact, allowing visual inspection, measurement and photographic documentation of root distribution, root condition, and structural root architecture. It’s the AS 4970-2025-aligned method for non-destructive root investigation in arboriculture.

The Air Spade tool is useless without a compressor producing the right air pressure and volume to drive it. Our compressor is a 250 CFM trailer-mounted unit — it travels with us, on the same trailer, every job. Most arborists who own an Air Spade hire the compressor per job, which adds $300–500/day to the engagement cost (passed through to you), creates scheduling dependency on the hire firm (often a 1–2 week wait), and means if the scope expands on the day, you can’t extend the visit because the hire return slot is already booked. We own the compressor outright. Investigations get done on the day they need to get done, with no compressor-hire pass-throughs in your invoice.

A single-tree investigation typically takes 2–4 hours on site depending on the depth, the soil type, and the extent of root mapping required. A multi-tree investigation on a constrained site can take a full day. We’ll quote the on-site time at scoping — you’ll know what to expect before we arrive.

Usually yes — Air Spade investigation generates noise (the compressor) and dust (the excavated soil), but it doesn’t shut down the rest of the site. We coordinate with your site supervisor on access, fencing-off the investigation area, and clean-up afterwards. For investigations triggered by an excavation-within-TPZ consent condition, the rest of the build continues while we work.

Yes — where the investigation supports a pre-approved scope of works (e.g. preparing a TPZ-adjacent footing trench under an existing consent condition) and the investigation findings support proceeding, selective root pruning to AS 4373 standards can be performed during the same visit by the AQF5 on site. This is a meaningful efficiency: one mobilisation, one fee, investigation + selective pruning + sign-off all closed out together.

Most root investigations are quoted on an hourly rate rather than a fixed fee — the work is groundwork, and soil conditions, root density, depth and unforeseen obstructions all affect how long the excavation actually takes. Charging an hourly rate is the honest way to price it. Where the scope is genuinely predictable (e.g. a single-tree DA-stage assessment with a defined deliverable), we’ll quote a fixed fee instead. Either way the pricing model and indicative cost are agreed at scoping, so you know what to expect before we mobilise.

Yes. Our reports are written to AS 4970-2025, photo-stamped, GPS-referenced where relevant, signed by an AQF Level 5 Consulting Arborist, and structured to address the specific consent condition or design question that triggered the investigation. We’ve delivered investigations supporting DAs across NSW Government, ASX-listed contractors, major civil construction firms and Hunter region councils — the report format is one council assessors are familiar with.

Hydro-vac (vacuum excavation using high-pressure water) is used heavily in services-locating work, where the question is “where is the pipe” and incidental root damage is irrelevant. For arboricultural root investigation it’s a different story:

• Hydro-vac cuts through most fine roots. The high-pressure water doesn’t distinguish between soil and small woody material. The result is that calculating root density outside the large structural roots is almost impossible afterwards — the fine root network has been destroyed in the process, and the data your tree-protection decisions depend on is gone.
• Hydro-vac removes the periderm — the protective corky outer layer on woody roots that manages water loss and resists pathogen entry. Periderm loss is permanent: it doesn’t grow back. The exposed roots are then vulnerable to desiccation and infection. Air Spade pneumatic excavation leaves the periderm intact.
• Operator background. Hydro-vac operators are typically utilities-trained, not arboricultural specialists — the soil moves correctly but no one on site is reading what the exposed roots are telling you about the tree.

That said, hydro-vac has a legitimate place: it’s the right tool when Air Spade isn’t appropriate or practical — heavy clay that pneumatic excavation can’t penetrate efficiently, deep narrow trenches the Air Spade can’t reach, or contaminated soil where wet slurry handling is safer than airborne dust. For those specific cases we’ll recommend hydro-vac over Air Spade and coordinate the right specialist. For everything else, Air Spade run with AQF5 oversight is the AS 4970-2025-aligned standard.