Further to an invitation for registrations of interest (read E-News Weekly 8/2006), three contractors have been invited last spring by Watercare to participate in a tendering process for tunnel contract 4081 of the Hobson project. Those competing are a Fletcher Construction / McConnell Dowell Constructors joint venture, John Holland and a Multiplex / Zueblin joint venture. Following the shortlisting, a two-stage tender process has started. The first stage was successfully completed at the end of June, and tender documents were issued to potential contractors in early July with tenders scheduled for submission to Watercare in early October. The Hobson project includes a 3 km-long 3.7 m nominal internal diameter sewer tunnel approximately 20 m below sea level from Parnell to the Orakei Domain in Auckland. The tunnel will be excavated using pressurised face TBM in conjunction with a precast reinforced concrete segmental lining. It also includes shafts for access to the tunnel, sewer connections and a new pumping station, among other main associated works. It will connect the Orakei main sewer at Parnell with a new pumping station in the Orakei Domain, and will serve a large part of Auckland City. For more, visit www.water.co.nz 40/06.McConnell Dowell Constructors, in joint venture with Fletcher Construction, have been awarded the Hobson sewer tunnel contract by Watercare Services. The scope of work comprises a 3.7 m nominal internal diameter segment lined tunnel under Hobson Bay, approximately 3 km in length, from a purpose built launch shaft with a 10 m internal diameter and 36 m deep. The works also include a new pumping station, which will be 23 m in diameter and approximately 40 m in depth, complete with dry well, pumps, valves, etc. Included are two other vortex drop shafts, each approximately 30 m deep and 5 to 10 m diameter. The scope also includes demolition of the existing Orakei main sewer and connections into existing works. The project commences in May 2007 and has a duration of 32 months. A Lovat EPB TBM will be used. Click here. Visit www.macdow.com.au and www.water.co.nz 15/07.Lovat and contractor McConnell Dowell have recently signed a contract for the supply of a new RME131SE series 24400 earth pressure balance TBM that will be used in the construction of the Rosedale wastewater treatment plant outfall located in Auckland. This is the second Lovat TBM ordered by McConnell Dowell in 2007. Click here. The 3.3 m-diameter mixed face TBM will bore a total of 2,950 metres, with the final 550 metres being driven offshore. As a result, the TBM has been designed for recovery from a subaqueous shaft in the seabed. The groundwater table is estimated at 1 to 3 m below ground surface, with maximum water height above tunnel invert estimated at 18 metres. Maximum water and EPB pressure is anticipated at up to 4 bar. Geology along the tunnel alignment is characterized by the east coast bay formation, a Miocene marine sedimentary sequence, consisting of moderately weathered to unweathered sandstones, siltstones, and mudstones with probable cemented pockets and lenses of poorly sorted sand to boulder-sized conglomerate. The tunnel is expected to be entirely within the east coast bay formation. The TBM is scheduled for delivery in mid 2008. Visit www.lovat.com and www.mcconnelldowell.com 03/08.
