In February 2014, Sydney Rapid Transport (SRT) awarded Hagstrom Drilling the tender to complete the next phase of one of Sydney’s major infrastructure projects. SRT has the task of delivering Transport for New South Wales’ (TfNSW) new Rapid Transit Rail Network, inline with Stage 5 of the NSW Government’s Sydney Rail Future plan.
The main feature of the project was to investigate the site for twin underground tunnels under Sydney’s famous harbor. Hagstrom was the perfect match for an extensive marine investigation as it is one of Australia’s leading geotechnical drilling companies with over 25 years of history. In partnership with Australian Barge Hire (ABH), their sister company, they have rapidly become a single source, low risk leader in overwater investigations.
The investigation for the proposed site of twin underground 12.5 km tunnels required the following services to be used:
The actual scope of work completed was significantly higher than first anticipated due to early findings of the investigation which revealed much deeper sediments in the Harbour than anticipated.
Once the project was awarded the mobilisation plans kicked into gear. Hagstrom again stood out from the crowd with its dedicated HSE and operation teams constantly liaising with Golder/Douglas and TfNSW to meet the challenging needs of a project in the middle of Australia’s largest city.
The barges were assembled and made sea fast at Waterways Construction in nearby Rozelle Bay. The drill rigs were mobilised onto the barges and then transported to their respective work sites
Once on location, the barges were raised up several meters above the water surface to provide a stable work platform unaffected by water conditions and local ferry traffic.
The casing was set firmly into the seafloor and the drilling program commenced using a combination of HQ diamond and rotary mud drilling techniques. Core samples were taken from depths of up to 60 meters below the harbour.
In addition to the drilling scope, Hagstrom was engaged to conduct Cone Penetration Tests. CPT parameters included tip resistance, sleeve resistance; pore pressure and dissipations measurements were recorded.
Hagstroms’ unique position of being both a drilling and CPT contractor enables them to test to depths which are not possible as a sole operator of CPT equipment.
Hagstrom completed a total of 51 CPTs overwater including 42 dissipation tests.
The Geotechnical work completed has provided the client with accurate information of underlying rock and groundwater conditions. This will ensure appropriate measures are taken when tunnelling commences.