The tunnel “breakthrough” – when the east and west sides of the tunnel met – occurred November 29th, 2011 at 2:37 p.m. Breakthrough marks the completion of excavation of the top portion, or topheading, of the Fourth Bore and is a major project milestone.
Breakthrough Interview
Breakthrough Facts
Excavation Began:
Eastern side (Orinda) – August 2010
Western side (Oakland) – March 2011
Equipment:
A 130-ton roadheader excavating from the east side completed excavation of the Fourth Bore’s topheading
Location:
The breakthrough occurred approximately 200 meters in from the western portal.
Excavated Length:
990 meters (3,248 feet)
Watch a video of the breakthrough
Breakthrough Factsheet
Additional images and videos are available to view and download on the Media Resources page.
