Niagara team may face re-alignment

摘要

In a bid to mitigate the schedule impact of slow advances on the 6.5-mile (10.4km) long Niagara Tunnel Project, in Canada, Strabag has proposed changes to the alignment of the 47ft (14.4m) diameter bore. As main contractor for the tunnel work, Strabag has advised Ontario Power Generation (OPG) that difficulties with fractured rack mean TBM advance has been slower than anticipated. The problems are highlighted in OPG's 2007 annual report, which notes that excavation work began in September 2006 and the TBM had advanced 5,279ft (1,609m) by December 2007. The first 7,546ft (2,300m) of tunnel was always expected to be problematic, due to the learning curve and variable geology.