Public Transport Authority of Western Australia

PTA Forrestfield Airport Link (FAL) Project, WA (D&C Project 2015-2020)

The Forrestfield Airport Link multidisciplinary project delivered an 8.5km extension of the existing PTA urban rail network in Perth, with twin bored tunnels running beneath the Swan River, Tonkin Highway and Perth Airport.  The project included 3stations (2 underground), 3 emergency egress shafts, 12 cross passages and 2 dive structures.

Tetra Tech Coffey provided extensive geotechnical engineering services (including instrumentation and monitoring, hydrogeological and pavement engineering) for the project, including Mike Hillman as Geotechnical Manager and Peter Lamb as Monitoring Manager, from preliminary design through to completion of the construction phase, working in close collaboration with the constructor – Salini Impregilo (now Webuild Group) NRW (SI-NRW) JV, and PTA (the Owner).

Pre-tender Tetra Tech Coffey was also an instrumentation and monitoring advisor to PTA for preparation of RFP documentation and cost estimation for budgeting purposes.

During the construction phase Tetra Tech Coffey carried out development of scope of works to fill the gaps in the available geotechnical information under strict compliance with Rail Safety Sub-plan (approved by Brookfield Rail/PTA). This included drilling of boreholes, cone penetration testing (CPT), piezometer installation, etc.

On behalf of the SI-NRW JV constructor, Tetra Tech Coffey carried out rigorous analysis and interpretation of field and laboratory test results and provided geotechnical design inputs primarily for the tunnels and surface rail, prepared geotechnical and pavement designs and instrumentation and monitoring plans, from concept (during tender) to Entry into Service (EIS) and IFC stages, through to Practical completion (PC).

Tetra Tech Coffey also prepared and maintained specifications, method statements and reporting, and provided safety in design and quality assurance, for these project components.

Geotechnical Advisory Services (2022 – ongoing)

Tetra Tech Coffey provided geotechnical advisory services to PTA for the following recent key projects:

• Edith Cowan University (ECU) (12-storey) City Campus: Independent review of geotechnical design including bored and CFA piles and effect of the construction on existing bored and cut and cover tunnels around Perth City Station. Monitoring of construction of bored and CFA pile construction.
• Instrumentation and Monitoring of Tunnels: Independent review of design and implementation of instrumentation (prisms, robotic total station, crack meters, strain gauges, vibration meters, cameras, etc.) for monitoring of all bored and cut and cover tunnels in vicinity of ECU City Campus.
• Dorsett Hotel (multi-storey): Independent review of geotechnical design including bored and CFA piles and effect of the construction on existing tunnels and foundations around Perth Arena.

PTA South West Metropolitan Railway: Packages E and F WA (2004)

Geotechnical design studies for the PTA and subsequently Leighton Contractors for the railway link from Perth to Mandurah, involving tunnelling under Perth, two major rail bridges, works on numerous small bridges (strengthening, and in one case relocation), road, drainage and other civil work support.

Tetra Tech Coffey provided:

• Construction support (geotechnical) through the construction phases of both packages E and F.
•  Provided geotechnical design advice on Package A for another client.
• Developed the geotechnical models at both sites and provided geotechnical support for Package F (tunnelling), and all geotechnical design for package E (including Mt Henry and Narrows bridges) including instrumentation and monitoring.

The project was delivered to a high standard within tight timeframe. Tetra Tech Coffey was a joint recipient of the ACEA WA award 2005 as lead geotechnical consultant in the Leighton lead team for package E.

Morley Ellenbrook Line Project

The Morley Ellenbrook Line project comprises a 21 km railway commencing at Bayswater station and ending at Ellenbrook station. The project consists of 2 dive structures and a bridge structure with six additional railway stations to be constructed along the rail alignment. The project is likely to require a number of environmental approvals, together with addressing the requirements of the Contaminated Sites Act 2003.

Tetra Tech Coffey provided environmental advice and investigation services for the project. The scope of works includes the following:

• Development of a baseline environmental dataset and conceptual model, including long-term groundwater level variation, minimum and maximum surface water flows and surface water and groundwater quality. This data set will be used to:
• Calculate the levels of dewatering required at key locations and the effects of this on the surrounding environment;
• Model flood risk potential of certain sections of the rail alignment.
• Assess the risks posed to water quality from the development and generate site specific criteria to protect water quality during construction as well as assessment of the risks posed by contamination to site workers.
• Develop management measures to deal with the above issues.
• Preliminary site investigations to identify potentially contaminating activities along the rail alignment that may pose a risk to the construction project and identify constraints to planning. Following this, design of detailed site investigations, where required, to further assess and manage risk.
• Acid sulfate soil investigations to assess the risks posed by the development in their generation and, in turn, the risks posed to the environment and human health. This information will then be used to design management measures and monitoring programs for dealing with ASS generation during construction.

Tetra Tech Coffey provided a team of specialists to support the project, which includes groundwater and environmental consultants and acid sulfate soil specialists, who are experienced with supporting major construction projects and working with Metronet projects and PTA or similar rail environments.