Sydney Gateway Stages 1 and 3

Tetra Tech Coffey is providing detailed geotechnical site investigation and temporary works design, together with groundwater, contamination, and occupational hygiene services for Sydney Gateway Stages 1 and 3.

Transport for NSW (TfNSW) are undertaking this transformative project to reduce travel times in Sydney by up to 40 minutes for motorists travelling from Parramatta to Sydney Airport; provide capacity for 100,000 vehicles per day; and to create a shared cycling and pedestrian path linking Tempe Reserve with the airport terminals.

John Holland-Seymour White (JHSW) JV are delivering two sections which cover 5.1 kilometres of arterial road. This consists of 2.7-kilometre active transport link and 21 bridges and viaducts to be delivered by December 2024.

Geotechnical site investigation works – to inform the detailed design cuttings, fill embankments, pavements, ground treatments over areas affected by soft soils, culvert and other structure foundations, including:

  • Cone Penetrometer Testing (CPTs) for fill embankments and cutting design and ground treatments over soft ground
  • CPTs for bridge approach embankment design
  • Boreholes for bridge, culvert and retaining structure foundations
  • Boreholes with vibrating wire piezometers (VWP) and inclinometers for monitoring
  • Test pits; pavement cores and pavement boreholes for pavement design & subgrade assessment
  • Geophysical seismic survey (shear-wave & compressional wave) through Tempe landfill.

Temporary Works Design – geotechnical and structural designs for temporary working platforms and sheetpile cofferdams, include:

  • Temporary working platforms designed to support 350T to 750T cranes for bridge girder lifting and 80T – 120T piling rigs over difficult ground conditions such as landfill or loose/soft alluvium with shallow groundwater table and adjacent to the Alexandra Canal banks
  • Geotechnical design, structural design, and drafting services were provided for the sheetpile cofferdam design for construction of drainage outlets and temporary piling platforms along the Alexandra Canal banks. Full packages of geotechnical and structural designs were provided
  • 3D and 2D numerical analyses were used in designing the temporary working platforms and sheetpile cofferdams. 3D nature of surcharge from cranes and piling rigs was considered for optimum solution of the temporary platform and sheetpile wall designs.

Hydrogeological and Groundwater – Assessment of Tempe Lands (State land), Northern Lands & Northern Lands carpark (Sydney Airport Land), Sydney Airport Land extending south of Alexandra Canal along Airport Drive to the Northern Pond, and Qantas Drive (Sydney Airport Land).

  • The interpretative report provided identification of hydrogeological or groundwater related hazards across the project and supported the assessment of project-related groundwater impacts, development of groundwater mitigation design and groundwater monitoring, and management frameworks to be adopted.

Contamination – assessment with respect to the Tempe Lands (former landfill site) and the Northern Lands Carpark in Stage 1.

  • Gas assessment, risk monitoring and management
  • Landfill capping/cover and gas mitigation design for landscaped mounds, noise mounds & spoil retention underneath Motorway paved carriageways
  • Modification of schematic gas venting system design for the Northern Lands Carpark
  • Long term Environmental Management Plan advice for capping & landfill gas management
  • High-level technical review of the D&C contractor’s Tempe Lands Leachate Treatment Design, with respect to flow/volume, ammonia concentrations, suitability of the treatment technology
  • Compliance monitoring during construction phase to help client manage leachate and LFG risks.

Occupational Hygiene Services

  • Provision of occupational health and hygiene management program
  • Health risk assessments
  • Occupational exposure monitoring, control monitoring, exposure control plans and critical control auditing
  • Stakeholder engagement, training and raising awareness of occupational health and hygiene.

Client name: John Holland-Seymour White (JHSW) JV
Location: Mascot, NSW
Duration: 2021 – 2025
Services provided: Specialist geotechnical site investigation and temporary works design together with groundwater, contamination and occupational hygiene services

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