Caldecott Breakthrough

The east top heading of the Caldecott Fourth Bore Tunnel broke through to the west top heading at approximately 2:39 p.m. on Nov. 29, 2011, about 655 feet (200 m) from the West Portal. Pre-support, face support and careful operation of the Wirth T3.2 roadheader resulted in a controlled excavation of the less than 3-ft wide (1 m) rock pillar separating the two headings. The headings were aligned within 0.5 in. (13 mm) of each other. Benching has already progressed 440 ft (134 m) from the West Portal, and a second benching operation toward the East Portal started on Dec. 9, 2011. Excavation and support of the bench are anticipated to be completed in April 2012. Jacobs Associates performed final design as a subconsultant to Parsons and is providing design support services during construction. The contractor is Tutor-Saliba. The owner is CalTrans.