Fourth Bore of Caldecott Tunnel and Building

Project Details


Tutor Perini Civil
Prime Contractor
Contract Amount: $269 Million

Desert Mechanical Inc.
Mechanical Subcontractor
Contract Amount: $4.1 Million

State of California, Department of Transportation

Contra Costa and Alameda Counties, CA

1.2 Miles


Project Description

The tunnel has two 12-foot lanes, a 10-foot north shoulder, a two-foot south shoulder, and emergency walkways. The tunnel is approximately 41 feet wide and 3,389 feet in length. Other elements of the tunnel include seven emergency cross passages, a two-story O&M building, retaining walls and a noise barrier, pavement overlay at the SR 24/Caldecott Lane interchange, improvements to eastbound SR 24, and improvements to the Fish Ranch Road on-ramps.

Construction was based on using the Sequential Excavation Method (SEM), and the use of shotcrete, rock dowels, lattice girders, and grouted steel piles in various combinations to provide initial support. The excavation sequence utilizes a full-width top heading and a full- or split-bench excavation behind the heading excavation. Some sections of the tunnel required a shotcrete invert arch in both the top heading and at the base of the bench excavation. The final lining system for the tunnel consists of reinforced cast-in-place concrete backed by a waterproof membrane and a drainage fleece.


Project of the Year 2013 - California Transportation Foundation

Top Road Project of 2013 - Roads & Bridges Magazine 

2015 Excellence in Transportation Award - Caltrans