How to decommission and demolish an asphalt plant safely in Australia

An asphalt plant is a hydrocarbon processing facility that happens to make road base. Treat it like a demolition job and you will get hurt or you will leave a contamination problem in the ground for the next owner. Treat it like a small refinery and it goes fine.

This is the order we work in, what will hurt you, and the mistakes we see when somebody has had a go before calling us.

What you are actually dealing with

Batch plants and drum plants differ, but the same things are on almost every site.

• Hot bitumen storage tanks. Insulated, heated, and holding a product that is stored at temperatures well above the boiling point of water. Even a tank that has been "off" for weeks can hold heat and product in the bottom.
• Fuel and hot oil systems. Diesel, gas or heavy fuel oil for the burner, and a hot oil heater with a circuit of pipework running through the tanks and pipes to keep the bitumen liquid.
• The drum dryer or mixer, burner and baghouse. Fine dust in the baghouse and ductwork, and a burner with its own gas or fuel supply.
• Aggregate cold feed bins, hot bins, screens, elevators and conveyors. Heavy steel, working at height, and bins that can hold hung up material.
• Storage silos for finished mix. Insulated, heated, often more than fifteen metres tall.
• A recycled asphalt pavement system, load out area, weighbridge, control room, workshop and laboratory. The workshop and lab are where the chemicals and solvents live.
• Underground services and, often, underground tanks. Older plants in particular.

Step one: decide what the end state is

Asphalt plants get sold and relocated more often than they get scrapped. Before anybody touches anything, decide whether the plant is being decommissioned and mothballed, dismantled for relocation, or demolished for the land. The three jobs have almost nothing in common after the isolation stage.

If it is being sold, the buyer will want a hazardous material survey before they take it, and so should you before you ship asbestos across a state border in a container.

Step two: investigate before you isolate

Hazardous material survey. Asbestos in gaskets, flange packing, rope seals, burner and flue insulation, older switchboards and control panels, and sheeting on the control room and workshop. Synthetic mineral fibre in tank and pipe insulation. Lead in old paint on the structure.

Contamination assessment. The ground around the bitumen tanks, the fuel tanks, the load out and the hot oil heater is almost always hydrocarbon affected. A preliminary site investigation with soil sampling tells you what you are going to have to classify and where it can go. Doing this after demolition, with the whole site disturbed, costs multiples more.

Underground tank search. Older plants ran underground fuel storage. Find them on paper and with a scan before an excavator finds them.

Services search and isolation plan. Power, gas, water, comms, and the fuel and hot oil circuits. Every one of them gets a positive isolation and a lock, not a switch turned off.

Step three: make the plant safe

This is the part people rush, and it is the part that kills.

Bitumen tanks. Cool down is slow and cannot be hurried. Product is drained as far as it will go, then the tank is cleaned and ventilated. Bitumen tanks can accumulate hydrogen sulphide in the headspace and can carry pyrophoric deposits on the internal steel that ignite when exposed to air. Nobody cuts into a bitumen tank until it has been cleaned, gas tested and declared safe for hot work, and nobody enters one except under a confined space permit with a standby person, gas monitoring and a rescue plan.

Fuel tanks and lines. Drained, purged, gas freed and certified before any cutting. A tank that "only has a bit in the bottom" is the one that goes.

Hot oil circuit. Drained and flushed. The oil is a waste stream in its own right.

Baghouse and ductwork. The dust is fine, dry and gets everywhere once the system is opened. It is vacuumed out under controls before the structure is touched, not knocked down with the dust still in it.

Silos and bins. Emptied and confirmed empty from outside. Nobody goes into a silo to clear hung up material. We have written separately about why nobody should be inside the vessel.

Step four: decontaminate and classify the waste

Everything that comes off an asphalt plant has to be classified before it leaves site. In New South Wales that means the EPA Waste Classification Guidelines, and the other states run equivalent systems. Bitumen residue, hydrocarbon sludge, contaminated insulation, baghouse dust and asbestos each go to a facility licensed to receive them, on a licensed transporter, with the paperwork trail intact.

Asbestos removal is licensed work. The regulator has to be notified before it starts, a licensed supervisor has to be present for friable material, and a clearance certificate is issued before the area is released. Perfect Contracting holds a Class A friable asbestos licence and an EPA waste transport licence, so on our jobs the removal, the transport and the paperwork stay with one contractor.

Step five: take the structure down in the right order

Only now does demolition start, and the order is set by the isolation, not by what looks easiest.

• Top down and outside in. Silos, elevators and the batch tower come down in a controlled sequence, not pushed over. Anything above fifteen metres, anything involving propping, and pre or post tensioned structures are licensed demolition work in New South Wales.
• Tanks last, and remotely where possible. Once cleaned and certified, tanks are cut and lifted in sections. Remote demolition machines keep people out of the firing line on this part.
• Steel is recovered, not dumped. An asphalt plant is mostly structural steel and it has real value as scrap. It is separated at the machine and goes to recovery, not into a mixed load.
• Slabs and footings. Broken, crushed and reused where the material is clean. Where it is hydrocarbon stained it is classified separately.

Step six: the ground

The plant is gone and the site is not finished. Tank pits and hydrocarbon affected soil are excavated, classified and removed, then validated by sampling so the land can be signed off for whatever comes next. Underground tanks are removed, not filled, unless a specialist has assessed and approved leaving one in place. If the site is heading for redevelopment, this is the part the buyer's consultant will check first.

What not to do

• Do not let a scrap merchant "just take the steel." They are not there to find the asbestos or classify the sludge, and the liability for what leaves the site stays with the site owner.
• Do not cut into any tank that has not been cleaned, gas tested and certified. Not the fuel tank, not the bitumen tank, not the hot oil tank. There is no version of this that is worth the time saved.
• Do not send anyone into a silo or bin. Material that looks solid is not.
• Do not assume the plant is cold because it has been off. Insulated tanks hold heat and product for a long time.
• Do not relocate or sell the plant without a hazardous material survey. You will be shipping asbestos to somebody else's site.
• Do not put anything in a mixed general waste load. Once mixed, the whole load is classified by its worst component and it becomes the most expensive load you have ever paid for.
• Do not skip the contamination assessment because "it is only an asphalt plant." That ground has had decades of bitumen and fuel on it.

Approvals and notifications

Demolition needs consent from the local authority in almost every case. Licensed asbestos removal has to be notified to the state regulator before it starts. Demolition work of the licensed kind has its own notification. Contaminated land may bring the EPA into the process, and a site heading for a change of use will need validation. None of this is difficult. All of it is slow if it is started late.

Who should be doing this

A contractor who holds the asbestos licence, the demolition licence and the waste transport licence in their own name, with their own plant, and who has taken industrial process plant apart before. Not a general demolition crew with a subcontractor for each of the hard parts, because the hard parts are the whole job.

Perfect Contracting works on plant decommissioning and industrial demolition in New South Wales and Queensland and travels for the right project. If you have an asphalt plant coming to the end of its life, the earliest conversation is the cheapest one. Call 02 8015 6345 or read more about our plant decommissioning work.