Construction Activities Update: November 2013
The Fourth Bore’s state-of-the-art tunnel systems have been tested to ensure that incidents inside the tunnel, such as a car accident or fire, are detected and suppressed rapidly. Fire drills, including emergency responder preparedness exercises, were successfully completed the week of November 11th. Learn more about the tunnel’s life safety systems in the recent Fact Sheet(PDF).
In late September, Caltrans started testing the Variable Message Signs (VMS) in Bores #3 and #4. The signs will illuminate with pre-programmed messages in the event of an incident in the tunnel, from a stalled car or a lane closure to a more serious incident. The messages can also be tailored to the circumstances. The purpose of the signs is to provide important life-safety instructions to motorists in the two bores. The signs will only be illuminated if there is an issue in the tunnel.
The testing of the VMS is just one of many elements of the Fourth Bore’s Fire & Life Safety systems that are being thoroughly tested prior to the tunnel opening to traffic.
Shown: TOS (Traffic Operations System) interface in the Caldecott Tunnels' new Operations and Maintenance Control (OMC) facility near the western portals.
In progress: the installation of state-of-the-art fire and safety systems in the Fourth Bore. These systems include state-of-the-art fire detection and suppression systems. When the Fourth Bore opens to traffic in late 2013, TOS and SCADA (Supervisory Control And Data Acquisition) systems will provide specially-trained operators with real-time information and management capabilities for the four tunnels’ traffic, fire detection, power supply, ventilation and lighting systems.
The installation of the Fourth Bore’s state-of-the-art Fire and Life Safety Systems is underway. The tragic fire of 1982 in the Third Bore resulted in extensive revision to national tunnel fire safety standards, and the Fourth Bore is designed to meet these stringent requirements. Nineteen jet fans, which were installed earlier this summer, will remove smoke from the tunnel in the event of a fire. The jet fans will be triggered by fire alarms, carbon monoxide detectors, and nitrous oxide detectors located throughout the tunnel. All of the Fire and Life Safety systems will undergo extensive testing before the tunnel opens to traffic in late 2013. Learn more about these systems in the Spring 2013 Fact Sheet.
Clockwise from top left: Workers install one of 19 jet fans in the crown of Fourth Bore. Workers mount stainless steel panels along the length of the tunnel; designed primarily for aesthetic purposes, the panels will also will help create a “tunneling effect” to focus motorists’ attention on the road ahead. Workers dismantled an enormous temporary soundwall on the western side of the tunnel in Oakland; the wall has been replaced by a permanent berm and soundwall. All photos by Karl Nielsen, MTC.
A Project Update Fact Sheet is available for download. Click here to view - May 2013 (PDF, 541 KB)
Work on the final retaining walls continued, along with facade work at both portals, and preparation for roadway paving.
Clockwise from top left: Roadway paving, Crosspassage ventilation system, Final retaining wall, near east portal. All photos by Karl Nielsen, MTC.
Finishing work, clockwise from top left: Support rods for the electrical system are custom fitted inside the tunnel. Crews put final touches on one of seven cross passages between bores #3 and #4. A worker completes a trench as part of the drainage system currently being installed. All photos by Karl Nielsen, MTC.
A Project Update Document is available for download. Click here to view - September 2012 (PDF, 636 KB)
On August 8th, just two weeks shy of the second anniversary of the start of tunneling, primary excavation of the Fourth Bore tunnel was completed. Work continues on excavating the "invert," which is a trench, filled with concrete and rebar, to compensate for groundswell on the East side of the Hills. The tunnel’s waterproof membrane, rebar cage, and final lining continue to be installed from West to East, and the final lining is approximately one-third complete.
This gantry system is a frame that slides on a track to facilitate installation of the tunnel waterproofing and final lining.
As work progresses on the bench, or bottom portion of the tunnel, tunneling crews are beginning work on the waterproof membrane and final lining near the western portal.
The first step is to apply 7 mm of waterproofing membrane that is made of a polymer-based material over the top of the smoothed shotcrete that has already been applied throughout the length of the tunnel. For the final lining, the contractor will cast a wall of reinforced concrete by assembling a rebar cage, constructing formwork to contain the concrete and pouring the concrete through holes in the form and then plugging the holes when the wall space is filled.
The formwork will glide forward as work on the lining progresses.
Excavation of the top portion, or topheading, of the Fourth Bore was completed on November 29th, 2011. Crews are currently excavating the bottom portion, or bench, of the tunnel from the west side using the project’s excavator and from the east side with the roadheader. Click here for details on this progress.
As excavation on the west side proceeds crews will begin working on the waterproofing and concrete lining that must be in place before the final concrete is poured for the arch and roadway surface.
Work on the safety cross passages between bores four and three is ongoing. To date, crews have completed excavation of two of the seven cross passages.
Click here to view the construction photo gallery.
Click here to view the current activity archive.