Almost all public asbestos material is about houses and school buildings. This job was neither. It sits in the quadrant of the Code’s contents matrix that hardly anyone writes about — friable asbestos on plant and equipment — and it shows regs 475 and 477 doing exactly what they were designed to do.
About this case study
The site is a decommissioned alumina refinery in the Northern Territory, undergoing a multi-year closure and demolition programme. The parties are described by role: the demolition contractor designed and built the enclosures; the hygiene consultant held the occupational hygiene scope; Environics was engaged in support of the hygiene consultant, supplying licensed asbestos assessor, air monitoring and clearance capability. Client and contractor names are withheld.
The problem
Friable asbestos on the exterior surfaces of vertical process tanks. Not a wall, not a ceiling: a cylinder several storeys high, standing in the open, in a live demolition area, with the material to be removed on the outside of it and work proceeding at height all the way round.
The regulatory position is not in doubt. Friable material of any quantity is Class A work. Reg 477 requires the removal area to be enclosed, negative pressure to be used with a leak-tested enclosure, and the wet method to be used. Reg 475 requires an independent licensed asbestos assessor to conduct air monitoring, and reg 477 requires that monitoring to be running before removal starts.
The engineering problem is how you enclose a tank.
The enclosure specification
The controlling document was a written specification for a Class A enclosure around upright tanks, issued to the demolition contractor and the client, with the hygiene consultant copied. Its opening statement is a fair summary of the whole exercise:
An A Class Enclosure is designed for high-risk asbestos removal operations, ensuring the safe and effective containment of airborne asbestos fibres during removal processes.
1. Enclosure construction
- Fabricated from heavy-duty plastic sheeting
- Sheeting air-tight and impermeable to asbestos fibres
- All seams and joints sealed with appropriate tape or adhesive to ensure air-tightness
- The enclosure completely surrounds the tank, with sufficient clearance for workers and equipment
- Large enough for workers to move safely and for proper decontamination units to be installed
2. Access and egress
- An air-lock system to prevent the release of asbestos fibres into surrounding areas
3. Negative pressure ventilation
- A pressure differential of at least −12 Pa
- HEPA-filtered exhaust units filtering air before it leaves the enclosure
- Regular monitoring and maintenance of the system
4. Decontamination
- A minimum three-stage decontamination unit for workers — dirty area, shower area, clean area
- A separate decontamination area for equipment and waste (bag room)
- Each area to provide the necessary amenities
Read that against the Appendix B matrix and the correspondence is close to line-for-line: enclosure size, shape and structure; smoke testing; location of negative pressure exhaust units; temporary buildings including decontamination units with water, lighting and power; detailed decontamination procedures for the workplace, tools, people and non-disposable PPE and RPE. This is what the “Yes” column for friable plant and equipment looks like when someone actually builds it.
The enclosure arrangement
Redrawn as a clean schematic from the labelled elements of the project drawing. It is indicative of the arrangement, not a reproduction of the contractor’s design, and it is not to scale.
Two things about that arrangement are worth pointing out because they are easy to get wrong.
The intake and the exhausts are on opposite sides. Negative pressure is not just a number on a manometer — it is a directed sweep of air across the work face and out through filtration. Put the intake next to the extraction and the enclosure can hold −12 Pa while air short-circuits and half the volume never moves.
People and waste leave by different routes. The three-stage decontamination unit is for workers. The bag rooms — two of them — are for equipment and waste. Sharing one route is how contamination gets carried out of an enclosure that was otherwise well run.
What was actually done, day to day
- Smoke testing of each enclosure, certified per tank. Reg 477 conditions the negative pressure requirement on the enclosure having been tested for leaks. On this job that produced a document per asset, not a verbal assurance.
- Negative pressure verified above the 12 Pa requirement and recorded, with a dedicated air pressure test point built into the enclosure so it could be checked without breaching the envelope.
- Daily air monitoring routinely below 0.01 fibres/mL — below the method detection limit. That is the clearance criterion, being met continuously during removal rather than only at handover.
- Boundary monitoring alongside the in-enclosure positions, so the question “did anything escape” had a measured answer and not an inference.
- Synthetic mineral fibre sampling run in parallel, because insulation on plant of this vintage is rarely only one thing.
- Respirable crystalline silica personal monitoring run concurrently — typically four personal samples a day. A demolition site does not stop presenting other hazards because the asbestos scope is under control.
- A separate visual clearance on enclosure dismantling, reported in its own right. Pulling the enclosure down is itself a disturbance, and clearing the removal does not clear the teardown.
- Localised clean-up of hot spots, each with its own visual clearance.
- Clearance certificates issued per asset, in a controlled series, so that each tank could be traced to its own certificate.
The failures that were recorded, because they are the interesting part
Sampling pumps failed and voided samples, which meant re-running them rather than reporting a short-duration result as though it were valid. A monitor position in an elevating work platform basket was judged inappropriate and relocated — a basket moves, and a sampler that moves is not measuring the position it is supposed to be measuring.
Neither of those is a scandal. They are what a monitoring regime looks like when it is actually being run by someone whose job is to be sceptical about the results. A record with no voided samples and no relocated monitors over a multi-year programme would be a reason to look harder, not a sign of a clean job.
Where independence sat in the contracting chain
This is worth setting out precisely, because contracting chains on large industrial sites are where the independence test most often gets muddled.
| Party | Role on the job |
|---|---|
| Asset owner | Principal; commissioned the closure and demolition programme |
| Demolition contractor | Designed and built the enclosures; carried out the removal |
| Hygiene consultant | Held the occupational hygiene scope, including air monitoring and clearance |
| Environics | Supplied licensed asbestos assessor and air monitoring capability to the hygiene consultant |
Environics supplied assessor and hygiene capability to the hygiene consultant, not to the removal contractor. Neither limb of the independence test is engaged: we were not involved in the removal for that job, and we were not part of a business that was. The chain runs owner → hygiene consultant → assessor, with the removal contractor on a separate branch entirely.
The independence test in full →
What made it work
- The enclosure was specified in writing before it was built, in a document issued to the contractor and the client. Air-tightness, clearance around the tank, the air-lock, −12 Pa, HEPA filtration, three-stage decontamination and a separate bag room were requirements to be met, not aspirations to be negotiated once scaffolding was up.
- The enclosure was proved, not assumed. Smoke test per tank, pressure verified through a purpose-built test point, both recorded.
- Monitoring started before removal did, as reg 477 requires, and ran continuously — inside, at the boundary, and on people.
- Clearance was granular. Per asset, plus a separate clearance on enclosure dismantling, plus clearances on localised clean-ups. Not one certificate at the end of a campaign.
- The independence was structural, arising from the contracting arrangement rather than from an assurance given at a site meeting.
None of that is exotic. It is the Code of Practice, executed at industrial scale with the documents actually produced. The reason it is worth publishing is that it demonstrates what “Yes” in the friable plant-and-equipment column of Appendix B costs to deliver — and that it can be delivered.
Photography to follow. Enclosure construction, decontamination units in position and the monitoring set-up will be added here, subject to permission and de-identification.