sentences:  As the Earth Pressure Balance tunnel boring machine (TBM) would be able to bore much closer to the surface than techniques assumed during the design phase, the cut and cover tunneling technique was not required below Great North Road.That meant that a duct below Great North Rd to a stack on the east side could not be constructed at the same time as the tunnels.The northern location for the stack had been studied earlier but dismissed because of greater cost, and the location had also created concerns among locals due to greater visual effects than that finally chosen by the Board of Inquiry.