Case Study: Omega Transmission Tower

Standing 432 metres (1,418 ft) high, the Omega Transmission Tower in Darriman, Victoria was the tallest structure in the Southern Hemisphere until its demolition in April 2015.

Contracted by the Department of Defence to carry out the demolition, Liberty Industrial used controlled explosive techniques to bring the redundant Naval communications tower to the ground.

Tight time frames were imposed by the Department of Defence for the delivery of the project with Liberty Industrial contractually bound to complete the demolition of the tower within 6 weeks of the contract award date.

The project team, including experienced explosive demolition experts, structural engineers and a licenced shot firer, promptly began planning and engineering a detailed work methodology for the controlled explosive demolition of the structure.

Three of the tower’s main supports, comprising six cables, two at each support base, would be cut at the plate connection using explosive cutting charges, releasing the tower to fall in the direction of the remaining tower base supports, utilising the weight of the tower cables to assist in toppling the structure in a controlled manner

Leading up to the demolition, Liberty Industrial’s project management team worked closely with state and feral government health and safety agencies, Commcare and Worksafe Victoria, to obtain the required explosives approvals in timeLiberty Industrial’s project management team prepared a comprehensive Blast Management Plan, an Explosives Security Plan, a Demolition Work Plan and other documentation critical for safely managing demolition works involving the controlled use of explosives.

Due to the very limited amount of explosive work completed in Australia each year, the preferred explosive charge, a copper sheathed linear cutting charge, was not available within Australia, and could not be imported to suit the project timeframe

In order to meet the tight project time constraints imposed by the Department of Defence, we worked with a local explosives supplier to utilise the explosives they had available, namely PE and Composition B. We spent two days testing explosives at a firing range. We tested the available explosives on steel plates fabricated to replicate the cable support stay plates we were planning to sever with the cutting charges to determine exactly what depth they could confidently cut through.

After the testing days, we were satisfied that we could at least severe 50mm thick plates with the Comp B explosives charges. However, to ensure that we had some redundancy in the charges, we decided to undertake preparatory oxy cutting on the cable stay support plates to ensure we had a maximum of 40mm thick steel to cut.

With some of the cable stay support plates up to 80mm thick at the outer most support, we utilised GHD Engineering, our preferred Structural Engineering company, to complete a full structural review on the tower and its support stays, to develop a preparatory cutting scheme that ensured we had no steel thicker than 40mm to explosively cut, whilst ensuring the tower remained structurally sound until the cutting charges were initiated.

In the days prior to the implosion, oxy cutting works were carried out to prepare the twelve designated cable support stay plates. Precision and accuracy were paramount to ensure the tower remained structurally sound and to prevent an uncontrolled collapse.

We also carried out the controlled release of one of the 1.5 kilometre aerial cables to prevent collateral damage to existing buildings that were to remain on the site. We utilised a second aerial cable which we had released from the opposite side of the tower and a 36t excavator to secure the tensioned cable, before separating it from its anchor.

We were able to control the release of the cable by tracking it in with the excavator to ensure it was clear of the retained buildings. All other guy and aerial cables were retained to maintain the structure’s stability. The day before the implosion, the explosives were affixed to the twelve designated anchor plates and all necessary checks were carried out in line with the Blast Day Management Plan. Two security guards remained onsite throughout the night to ensure the explosive’s remained secure.

On the day of the implosion we established a 1,000m exclusion zone around the tower, halting traffic on the adjoining highway for a short time while the demolition was undertaken. Representatives from Victoria Police, WorkSafe and the Department of Defence attended the demolition to observe, record and support the project.

Comprehensive planning, calculated engineering and careful preparation delivered a successful outcome for Liberty Industrial’s project team, with the implosion precisely executed and the structure safely grounded in a matter of seconds, reacting as planned and anticipated. The cutting charges successfully severed the plates, releasing the guy cables and causing the lattice truss tower to destabilise and collapse upon itself in four large sections.

Once all explosive charges were accounted for, oxy cutters moved in downsizing sections of the structure unable to be processed mechanically. A 36t Volvo Excavator with shear, grab, and bucket attachments and a 30t Komatsu Excavator with grab and bucket attachments were mobilised to process scrap materials clear the site ofdebris before removing the material from site for recycling. The team recovered more than 700 tonnes ferrous metal and 37 tonnes non-ferrous metal, which accounted for 97% of all waste material

Once the site was clear of debris, a 36t Volvo Excavator with a bucket attachment was used to decontaminate the area that surrounded the felled tower, removing 100mm of topsoil from the area as a precautionary measure, to ensure the site was free of any lead based paint contaminants that may have been released from the structure’s lead paint coating exterior with the impact of the collapse. Soil test results were provided prior to demobilising to certify the area was free of any lead paint contamination.

The 432m Omega Tower is the tallest structure demolished in the Southern Hemisphere to date. This project was awarded the Explosive Demolition Award at the 2015 World Demolition Awards.

Omega Transmissions

Case Study: Hammerhead Crane Deconstruction

The project involved the deconstruction of the historic Hammerhead Crane located at the Garden Island Naval Base for the Department of Defence.

Built to lift up to 250 tonnes, the 61 metre high cantilevered crane was at the time of its construction, the largest crane in the Southern Hemisphere. The decision to remove the monumental crane was due to ongoing maintenance and safety concerns.

Liberty Industrial were able to engineer an efficient alternative design solution for Defence, reducing the proposed number of lifts from the planned 250 lifts to just 70.

Our dismantling strategy reduced the number of lifts required to dismantle the crane, greatly reducing workers’ exposure to heights and significantly minimising the safety risks involved with carrying out the project.

The project team engineered a solution to free stand the FAVCO M120RX, constructing a steel support structure off the wharf and erecting the bottom third of the tower with a 55 tonne mobile crane and completing the assembly with a 300 tonne mobile crane. The base for the Favco M2480D Tower Crane, was provided by Brookfield Johnson Controls, who were managing the project on behalf of Defence. A 230 tonne pin jib truck crane in conjunction with the 300 tonne mobile crane was used to lift the boom into position, self-climbing the last 12 metres.

We carried out spray painting and paint stripping works to prepare the crane for disassembly, encapsulating the crane’s existing paint coating with a high build flexible water-borne acrylic paint to stabilise any flaky paint on the structure, to prevent the release of lead chromate paint. The acrylic was applied by airless spray to avoid disturbing the crane’s hazardous coating.

The predetermined separation locations were carefully marked and the paint removed from these areas to prepare the surface for oxy cutting. This prevent the release of harmful vapours during cutting, and protects the environment and the health of workers and the community.

The structure was progressively dismantled in large sections in an engineered sequence to maintain over structural stability of the crane. Sections of the crane were rigged to the M2480D Tower crane, and separated from the remaining structure by oxy cutting working from a work box rigged to the M120RX Tower Crane. Once separated, the sections were lifted down to the designated materials processing area and downsized. The jib tip was our largest lift at 65 tonne.

We deployed a 33t Volvo EC330LC Hydraulic Excavator with a shear attachment to carry out the heavy duty downsizing and has oxy-cutters assisted to further downscale and process scrap materials, removing paint from the cut locations prior to cutting. The processed components were transported to an offsite recycling facility. An approximate 1700 tonnes of steel was recycled.

In addition to the removal of the structure, the project had a substantial salvage component with the preservation of numerous heritage significant components of the crane. Components including the crane’s main hook assembly, hook platform and trollies, and the driver’s cabin were carefully removed and transported to an offsite facility where they were decontaminated of their coating and refinished. A few machine house plant items and some of the slew motor room equipment did not require refinishing and was stored in its original condition.

Because of their value to the community it was imperative these items were not damaged or structurally altered during the removal and refinishing works so we developed a detailed methodology for the removal, relocation, refinishing and storage of the heritage components to ensure their condition was maintained.

We developed our methodology for the project in accordance with a Heritage Input Technical Specification prepared by Godden Mackay Logan Heritage Consultants on behalf of the Department of Defence and prepared a detailed management plan for the removal, relocation, refinishing and storage of the heritage components to ensure their condition was maintained, even fabricating a specialised frame for the crane’s enormous 25.7 tonne hook assembly, the largest heritage item to be salvaged. At 7m wide and 8m long it was transported under Police Escort to the storage location.

Working alongside 24/7 Naval operations at the Garden Island naval base in Sydney Harbour has presented a few challenges for the project team. We’re faced with the constraints of a live site, a restricted work area and at times, difficult weather conditions. Severely restricted for landing loads and the materials processing workspace. Logistics also presented a challenge at times. It can be difficult getting trucks with oversize loads in and out of the site. These factors had been taken into account at the planning stage of the project, and considerate solutions were adopted to minimise disruption and ensure that the works continued unhampered.

With the preservation of some of Australia’s richest and rarest industrial and maritime heritage, the project showcases Liberty Industrial’s dismantling and salvage capabilities and reinforces our position in the industry as deconstruction specialists

The project was shortlisted as a Finalist for the Contract of the Year over US $1M at the 2015 World Demoliton Awards.


Case Study: Steele Barracks Demolition and Remediation

The Moorebank Intermodal Terminal is major infrastructure project in Western Sydney that will see container freight from the Port of Botany transferred to the site for subsequent loading to trucks in proximity to major transport routes including the M5.

On completion the project will see the removal of approximately 2500 truck per day off roads between Botany and Western Sydney.The facility is being constructed on the former Department of Defence Military School site on Moorebank Avenue. The site is approximately 70Ha and contains over 250 buildings that are required to be demolished prior to construction works commencing. Liberty Industrial has been engaged by Sydney Intermodal Terminal Alliance to carry out the Demolition and Remediation Works package.

The demolition works include the demolition of more than 250 buildings including the identification and removal of hazardous materials and the removal and disposal of all associated in ground infrastructure including existing pavements, hardstands, civil infrastructure and utility services.

The project also involves the remediation of identified sources of contamination including storage tanks, waste pits, waste stockpiles, asbestos impact materials,organochlorine pesticides, polychlorinated biphenyls and hot spots that are located in various locations across the site. This includes the removal and remediation of nine large underground storage tanks located across the site and the remediation of former site tip areas that contains in excess of 80,000m3 of deleterious and contaminated fill.

The remediation strategy includes bioremediation of TPH impacted soil, excavation, sorting segregation, reclassification, disposal and beneficial reuse of impacted fill. Asbestos impacted soils will be remediated through a combination of ‘hen pecking’ for reclassification where practicable, and offsite disposal.

Other works required under the contract include making good and maintaining existing boundary fencing, maintaining site security, maintaining existing vegetation and implementing bush fire protection measures throughout the works.

Liberty Industrial is also undertaking heritage salvage and relocation works including the salvage of European and Aboriginal artefacts. The works include the cataloguing and dismantling of large structures for future reconstruction. Protection of these structures is also required during demolition and remediation of areas adjacent to these buildings.

Due to the high priority placed on the subsequent development and construction Liberty Industrial developed a program of work that included the establishment of six separate demolition, hazardous material removal and remediation crews working concurrently across the site.

In post tender consultation with the client we developed a strategy that broke the site into priority areas so as to enable separate validation and early handover for commencement of construction works