Cooling Tower Demolition: Shells, Fill and the Water Nobody Thinks About

Cooling towers look simple and are not. The big hyperbolic concrete shells at power stations are thin, tall and only stable as a complete ring. The timber and fibreglass packed towers at refineries, chemical plants and large commercial sites are full of fill material that may be asbestos cement, are often rotten, and have grown legionella in their basins for years. Both kinds sit on a water system that runs back into the plant.

This is how we approach cooling tower demolition, what will hurt you, and what to have ready before you ask for a price.

What you are actually dealing with

• Hyperbolic reinforced concrete shells: very large, very thin for their size, standing on inclined columns. They are stable as a ring and unstable the moment the ring is broken in the wrong place.
• Mechanical draught towers in timber, concrete or steel frames with fans, drives, drift eliminators and fill. The fill in older towers is commonly asbestos cement sheet or board; newer fill is PVC. Timber towers are treated timber and often rotten at the water line.
• Basins and sumps holding water that has been dosed with biocides, corrosion inhibitors and antiscalants, with sludge at the bottom and legionella in the system.
• Pipework, pumps and valves tying the tower back into the plant's cooling circuit, sometimes still live for the units that keep running.
• Lead paint on steel frames, asbestos in gaskets and insulation, and in power station towers asbestos in the old flue gas desulphurisation connections where they exist.

Step one: disconnect from the plant

The tower is isolated from the cooling circuit with the plant's own permit system, because the other units usually keep running on the same system. Pumps are locked out, pipework is blanked, and the basin is drained with the water treated or disposed of according to what has been dosed into it. Nothing goes to stormwater.

Step two: legionella and the fill

The basin, sump and fill are treated and tested for legionella before anyone works in or around them, because demolition creates exactly the aerosol that spreads it. Fill is sampled for asbestos. Asbestos cement fill is removed under the asbestos licence, wet, in manageable sections, and bagged or wrapped at height before it comes down. PVC fill is bulky and is stripped out and compacted for disposal.

Step three: the method for the shell

A hyperbolic shell comes down one of two ways. Controlled felling or explosive demolition removes a section of the supporting columns on one side so the shell fails and collapses into a prepared zone; it is the standard method where there is room and is a single engineered event with exclusion zones and monitoring. Where there is no room, the shell is reduced top down with remote controlled machines on a climbing platform or a high reach excavator working around the base, which is slower and keeps every piece under control. Mechanical draught towers are simpler: the fans and drives are craned off, the fill and eliminators are stripped, and the frame is cut down with an excavator and shear once it is clean.

Step four: the basin and the ground

Basin sludge is classified and removed before the basin concrete is broken out. Treated timber from a timber tower is regulated waste. The ground under a cooling tower is usually wet and may carry the treatment chemicals, so it is sampled before the slab is lifted and before the void is backfilled.

Step five: the steel and the concrete

Steel frames, fans and drives are recovered and credited. Clean shell concrete is crushed and reused on site where the end use allows, which is a large volume on a power station tower and a real saving on cartage.

What not to do

• Do not break into a hyperbolic shell without an engineer's sequence. It is a ring; cut the ring in the wrong place and it decides when it falls.
• Do not disturb fill or basin water before legionella testing and treatment. The aerosol is the hazard.
• Do not assume the fill is PVC because it is grey. Old fill is asbestos cement far more often than people expect.
• Do not drain the basin to stormwater. It is dosed water and the EPA treats it that way.
• Do not isolate on your own permit. The rest of the plant is on the same cooling circuit.

Approvals and notifications

Licensed demolition notification to the state regulator, licensed asbestos removal notification, explosives permits and blast plan for a felled shell, trade waste or EPA approval for disposal of basin water and sludge, and the plant's own permit to work system for isolation. Councils will want a demolition consent in most cases.

Who should be doing this

A contractor with its own remote controlled and high reach plant, Class A asbestos crews who have worked at height, a structural engineer who has sequenced a shell before, and people who are comfortable isolating inside an operating plant. Perfect Contracting carries out cooling tower, power station and process plant demolition across Australia from its Sydney and Brisbane bases. Read more about our power station decommissioning and plant decommissioning work, or send us the details.