Asbestos in Soil Guide

How asbestos gets into soil

Asbestos in soil is more common than most people expect, particularly on sites with any history of building activity before 2004.

The most frequent source is past demolition. When older buildings were demolished, asbestos-containing materials were often buried on site or mixed into fill rather than disposed of properly. Imported fill is another common source. Fill brought onto a site for levelling or backfilling may contain fragments of asbestos cement sheeting, pipes or other building products if the source was not verified.

Other sources include fire and storm damage where asbestos materials have broken up and spread across the ground, illegal dumping of building waste, and in some parts of Queensland, naturally occurring asbestos in certain geological formations.

In many cases the contamination is not visible on the surface. Fragments may be buried at depth, mixed through fill layers or broken down into fine pieces that are difficult to distinguish from surrounding soil.

Asbestos fragments buried in soil are often uncovered during excavation, trenching or site preparation for development.

Why it matters

Asbestos in soil poses a risk when the soil is disturbed. Excavation, trenching, grading, landscaping and even gardening can break up buried materials and release fibres into the air.

Beyond the health risk, contaminated soil creates regulatory and commercial obligations. Under the Environmental Protection Act 1994 (Qld), notification duties to the Department of the Environment, Tourism, Science and Innovation (DETSI) can apply when contamination is identified, depending on the statutory triggers and the land status. Contaminated sites may be listed on the Environmental Management Register (EMR) or the Contaminated Land Register (CLR). Both are publicly searchable and are checked during property transactions, development applications and due diligence.

For developers and builders, unidentified soil contamination causes project delays, cost overruns and regulatory complications. Identifying it early through a preliminary site investigation is almost always less expensive than dealing with an unexpected find after earthworks have begun. A preliminary site assessment before ground disturbance can identify the risk before it becomes a problem.

How assessment works

Soil assessment for asbestos follows the National Environment Protection (Assessment of Site Contamination) Measure 2013 (ASC NEPM). This is the national framework for contaminated land assessment. The practical methodology for asbestos specifically is drawn from the WA Guidelines for the Assessment, Remediation and Management of Asbestos-Contaminated Sites (DoH, 2009, revised 2021), which is used nationally including in Queensland.

Assessment follows a staged approach. A preliminary site investigation (desktop review and site walkover) identifies whether contamination is likely based on the site history, previous land use and any visible surface fragments. If contamination is considered likely, a detailed site investigation follows with soil sampling and laboratory analysis.

Sampling grids and methodology

Soil samples are collected on a grid pattern across the site at multiple depth intervals to establish whether asbestos is present and how far it extends. The grid spacing depends on the site size and the level of certainty required.

During sampling, the assessor visually inspects the soil at each location, looking for fragments of building material, fibre bundles, demolition debris and variations in soil type that indicate imported fill. On most sites, sampling is carried out with the assistance of an excavator. The operator opens test pits at each grid location and the assessor inspects the exposed soil profile as material is brought up.

Samples are submitted to a NATA-accredited laboratory. The laboratory separates any asbestos-containing material from the soil, weighs it and reports the result as a percentage of the total sample weight. This is different from building material analysis, where the result is simply “detected” or “not detected.” Soil results are assessed against health-based investigation levels set out in the ASC NEPM, which vary depending on the intended land use.

Soil samples are collected on a grid pattern across the site at multiple depths to establish the presence and extent of contamination.

Defining the zone of contamination

Once sampling confirms asbestos is present, further sampling is carried out to define the zone of contamination (ZOC). This means establishing the boundary of the affected area, both laterally and vertically.

The assessor works outward from the confirmed contamination, collecting additional samples until clean results are returned. The ZOC is the boundary between the last contaminated sample and the first clean sample.

Defining the ZOC accurately is important because it directly determines how much material needs to be excavated and disposed of. If the boundary is too narrow, contaminated material is left behind and the validation will fail. If it is too wide, clean material is being removed as regulated waste unnecessarily, adding cost with no benefit.

Unexpected finds

Asbestos is frequently discovered during excavation or civil works on sites where contamination was not previously identified.

When suspected asbestos is found during ground disturbance, work in the affected area must stop immediately. The area is isolated and access is restricted. A licensed asbestos assessor or environmental consultant attends the site to assess the find and provide a documented response. Work cannot resume in the affected area until the material has been assessed and controls are in place.

Many construction contracts and development approvals now require an unexpected finds protocol before earthworks begin. This protocol sets out who to contact, what to do and how the response will be managed. Having it in place before work starts avoids confusion and delays when a find occurs.

Hazclear can prepare unexpected finds protocols as part of project planning and compliance services.

Asbestos is frequently uncovered during excavation on sites where contamination was not previously identified.

Cross-contamination and plant management

One of the biggest practical risks on a contaminated soil project is spreading contamination to clean areas of the site.

An excavator that has been digging in contaminated soil carries residual material on its bucket, tracks and undercarriage. If that machine moves to a clean area without being decontaminated, it transfers contaminated soil into the clean zone. The same applies to truck tyres, loader buckets and personnel moving between zones on boots and clothing.

Controls include physically separating contaminated and clean zones with signage and barricading, decontaminating all plant and equipment before it leaves the contaminated zone, lining and covering truck trays before transport, capturing washdown water and maintaining designated access routes so vehicles do not track through contaminated ground into clean areas.

On well-managed projects, the movement of each piece of plant between zones is recorded. This creates a documented chain of custody for the equipment and provides evidence that cross-contamination controls were maintained throughout the works.

All plant and equipment must be decontaminated before leaving the contaminated zone to prevent spreading asbestos to clean areas of the site.

Operator training and competency

Everyone working on a site where asbestos-contaminated soil is present must hold appropriate asbestos training under the WHS Regulation 2011 (Qld). This applies to excavator operators, truck drivers, labourers, spotters and anyone else who may come into contact with contaminated material.

At minimum, all personnel require a current asbestos awareness qualification. Workers directly handling contaminated soil or supervising excavation within the contaminated zone typically require completion of the relevant nationally recognised asbestos competency units.

Untrained operators can inadvertently spread contamination, damage containment controls or fail to recognise asbestos fragments in the material they are excavating. Training is verified during site induction before anyone starts work. Training records are retained as part of the project documentation.

Remediation and disposal

The most common remediation approach is to excavate the contaminated soil and dispose of it at a facility licensed to accept asbestos waste. The excavated area is then validated through sampling to confirm that residual contamination is below the relevant investigation level.

Where excavation is not practical (very large volumes or contamination at significant depth), on-site containment may be considered. This involves capping the contaminated material with clean fill and a barrier layer, with a site management plan and ongoing controls to prevent future disturbance. The asbestos remains on site and the land use may be restricted.

Asbestos-contaminated soil is classified as regulated waste under the Environmental Protection Regulation 2019 (Qld) and must be transported by a carrier holding an Environmental Authority. Hazclear holds Environmental Authority No. PEA100505641 for the transport and disposal of regulated waste in Queensland. Waste tracking certificates are required for each consignment.

After remediation, a validation report is prepared confirming the site meets the criteria for its intended use. This report is required for development approvals, site audit submissions and property records.

Contaminated soil is excavated, classified as regulated waste and transported to a licensed facility. The excavation is then validated through sampling.

Legislation and standards

• National Environment Protection (Assessment of Site Contamination) Measure 2013 (ASC NEPM) The national framework for contaminated land assessment, including investigation levels for asbestos in soil.
• Guidelines for the Assessment, Remediation and Management of Asbestos-Contaminated Sites in Western Australia (DoH, 2009, revised 2021) The accepted national technical reference for asbestos in soil assessment.
• Environmental Protection Act 1994 (Qld) Governs contaminated land notification, the EMR and CLR registers and regulated waste obligations.
• Environmental Protection Regulation 2019 (Qld) Classifies asbestos-contaminated soil as regulated waste.
• Work Health and Safety Regulation 2011 (Qld) Requires asbestos to be identified and controlled before workers are exposed.

Frequently asked questions