Lovat to Supply TBM for Hobson Bay Sewer in AucklandLovat and contractors McConnell Dowell and Fletcher Construction have recently signed a contract for the supply of a new Lovat RME170SE Series 23700 earth pressure balance TBM. The TBM will be used in the construction of the Orakei Main Sewer Hobson Diversion (OMSHD) tunnel project in Auckland, New Zealand. The contract was signed in New Zealand in late March 2007. The 4.33 m-diameter mixed face TBM will bore the 2,953 m-long tunnel uphill and westerly, along a maximum slope of 0.1%. The tunnel will commence at the new PS64 shaft, across the Orakei Domain and under the Orakei Ridge to the east side of Hobson Bay. From there, the tunnel will continue along the southern edge of Hobson Bay alongside the Victoria Avenue peninsula before continuing across the west side of Hobson Bay in a northwest direction to a shaft at Logan Terrace. Visit www.lovat.com and www.macdow.com.auGeological conditions anticipated are characterized by old and recent alluvium and volcanic flows, with the majority of the alignment expected to be in clay-rich weak sandstone and siltstone. The entire tunnel alignment is below the groundwater level, with groundwater heights above the tunnel invert varying between 26 to 55 metres. Despite a low vertical permeability of sandstone and siltstone, vertical joints and crush zones will provide higher permeability pathways from the excavation to the overlying materials and marine environment. Maximum water and EPB pressure is 3 bar. The TBM is scheduled for delivery in early December 2007. Click nz/14. Read E-News Weekly 8/2006 & 8/2002. Visit www.water.co.nz 15/07.