Bertha has arrived! 04 Apr 2017

Scale of the 17.48m cutterhead as workers emerge through the spokes

Bertha has arrived! The giant 17.48m diameter machine manufactured by Hitachi Zosen of Japan completed excavation of the double-deck highway tunnel along the waterfront and under the city centre of Seattle, USA, and made its historic final breakthrough at 11.15am local time on Tuesday 4 April 2017.

After a marathon journey that began some 1,344 days ago, on July 30, 2013 at the south portal launch structure and under the shadows of the Alaskan Way Viaduct that the tunnel will eventually replace, Bertha broke through the headwall of the north portal reception struction having completed its 2,848.5m (9,265ft) drive.

Officials representing the project owner, WSDOT, were on site with its design-build contractor, Dragados/Tutor Perini to celebrate the breakthrough.

TunnelTalk was among the media gathered at the breakthrough reception site to report the historic occasion, and recorded events as the occasion unfolded.