Tabcorp Building Demolition and Excavation

The Tabcorp Building project at 495 Harris Street in Ultimo involved the comprehensive demolition of a multi-storey structure and subsequent civil works, including excavation and site remediation. Located on the fringe of Sydney’s Central Business District, the site was bounded by commercial buildings and residential dwellings, necessitating careful planning and execution to minimise disruption and ensure safety. DECC was engaged as the Principal Contractor, responsible for managing the entire process, including hazardous material removal, structural demolition, excavation of class 1 sandstone, and complex civil works to prepare the site for redevelopment.

Internal Strip-Out and Hazardous Materials Removal: DECC conducted an internal strip-out of the building, which included the removal of all hazardous materials such as asbestos. This phase was completed in strict compliance with environmental and safety regulations, ensuring that the site was safe for subsequent demolition activities.

Structural Demolition: The demolition of the structure was complex due to the building's composite nature, which included a combination of concrete-framed, steel-framed, and timber-framed sections. The building had been augmented over a 50-year period, adding to the complexity. DECC employed a combination of conventional demolition techniques, including the “cut and lift” method and induced collapse, in accordance with AS2601. The demolition was carefully staged, beginning with the removal of the upper floors using small excavators, and progressing to the lower sections with larger excavators fitted with hydraulic attachments such as pulverisers and shears.

Excavation of Class 1 Sandstone: Following the demolition, DECC undertook the excavation of approximately 35,000m³ of Class 1 sandstone. The minimal horizontal seams in the rock made it difficult to rip using a dozer, so large excavators up to 70 tonnes were used to hammer the rock. Perimeter and internal saw cutting with a 21-tonne excavator assisted in achieving the desired finish and facilitated the hammering process.

Civil Works and Site Retention: DECC performed civil works that included underpinning the existing retaining wall along Bulwarra Road and heritage buildings along the north elevation. This involved anchoring, the construction of soldier pile walls along the north, west, and south elevations, and the installation of a blast wall delineating the site substation. The site retention works were crucial for ensuring the stability of the excavation and protecting adjacent structures during the construction process.

Removal of Underground Storage Tanks: The project included the removal of underground storage tanks (USTs) and associated localised remediation works to address hydrocarbon contamination. This was a critical step in ensuring that the site met environmental standards for redevelopment.

Noise and Vibration Monitoring: Throughout the civil works stage, the site was subject to constant noise and vibration monitoring, with two noise and two vibration monitors installed. Inclinometers were also used to measure any shoring wall deflection along Harris Street, which is a major road managed by RMS (Roads and Maritime Services).