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Caldecott Tunnel Work to Wrap Up Fall 2014

Construction crews are still on site as work is continuing on the roadway approaches as well as testing of the fire safety systems and punch list items.

Thu June 12, 2014 - West Edition
Irwin Rapoport

While the Caldecott Tunnel was officially opened to traffic on Nov. 16, 2013, construction crews are still on site as work is continuing on the roadway approaches (realigning the approaches), as well as testing of the fire safety systems and punch list items.

The remaining roadwork will be completed by the fall of 2014. The landscape project will be advertised later this year under a separate contract.

“The Caldecott Fourth Bore has been very well received by motorists, who are excited about the wide lanes and the 10-foot shoulder, as well as the jet fans and other state-of-the-art technology,” said Ivy Morrison, public information officer, Caldecott Fourth Bore Project. “Perhaps the motorists who are most excited are those who travel in the off-peak direction. Before the fourth bore opened to traffic late last year, these motorists had to merge from four freeway lanes into two tunnel lanes. This would cause considerable delays. Since the fourth bore opened to traffic, Caltrans has been able to dedicate two tunnel lanes permanently in each direction. This has also added a lot more predictability to the daily commute.”

Prior to the tunnel opening, Caltrans and project partners had worked closely with the California State Fire Marshal and emergency service and response agencies to develop an Emergency Response Plan outlining emergency scenarios in the fourth bore — ranging from a stalled vehicle to a 100 mW fire (of the same magnitude as the tragic 1982 fire in third bore of the Caldecott Tunnel.)

The tunnel’s fire and life safety systems, as well as tunnel operators and emergency response crews, were put to the test in acting out the emergency scenarios through a series of fire drills prior to the tunnel opening. With the successful completion of the fire drills, the State Fire Marshal commissioned the Caldecott Fourth Bore on Nov. 15, and it was opened to traffic at about 4:25 a.m. on Nov. 16.

The remaining work currently underway in the median and approaches on the western side of the tunnel is keeping construction crews busy. This work is currently focused on realigning and regrading the eastbound approach to bore #2, which had been designed for both east and westbound traffic before the fourth bore opened.

“To minimize impacts to traffic on state Route 24, and with public and worker safety considerations as our highest priority, much of this work must be performed at night,” said Morrison.

The median work entails the removal of the k-rail; installation of about 3,000 ft. (900 m) of permanent concrete barrier rail in the median — between bores three and two; and the paving of the shoulders on both sides of the new barrier.

Work also has commenced on the east side of the tunnel. The realignment of the eastbound approach to bore #2 and nighttime bore 2 closures are expected to be done over the summer.

“We’ll be improving the existing approach to bore #2 by re-grading and straightening it,” said Morrison, “but to complete the eastbound realignment work for bores 1 and 2, it is anticipated that Caltrans will close bore #2 during night-time hours for several months.”

It is all a question of managing traffic and to accommodate the realignment work for bore #2, the lanes approaching bore #1 will be temporarily shifted to the south where there is a wide shoulder.

“The temporary lane realignment approaching bore #1 is clearly delineated,” said Morrison. “Work entails the demolition of the existing barrier rail between bores 1 and 2, followed by the construction of permanent concrete barriers and the repaving of the approach. The public has appreciated our efforts to construct the fourth bore and has been very helpful and patient in ensuring that we can do the work efficiently and rapidly and safely.”

A variety of standard excavators, backhoes, compactors, and pavers are being used to complete the remaining work.

The completion of the tunnel was in many ways a Herculean task that brought together many elements and technologies and required many innovative solutions.

Crews began work on Jan. 13, 2010 for the $417 million project to construct a fourth bore (tunnel) for the Caldecott Tunnel. The completed project should be delivered in fall 2014 after four years of hard and intense efforts to cut through some very solid and tough rock.

The 3,389-ft. (1,033 m) tunnel cuts through the Berkeley Hills in the East Bay to provide an additional link between Oakland and Orinda (Alameda and Contra Costa counties). The project, put forward by the California Department of Transportation (Caltrans), the Contra Costa Transportation Authority and the Alameda County Transportation Commission, is funded by the federal government’s American Recovery and Reinvestment Act (45 percent) and Contra Costa Measure J funds (30 percent).

The goal of the project is to relieve westward traffic congestion during off-peak hours for motorists traveling on SR 24. The horseshoe-shaped tunnel, 50 ft. (15 m) in diameter, was mined by the sequential excavation method (SEM) or better known as the New Austrian Tunneling Method (NATM). When complete it will provide two 12 ft. (3.7 m) lanes, a 10 ft. (3 m) shoulder on the north side and a 2 ft (.6 m) shoulder with a 3 ft. (.9 m) walkway on the south side.

Tunneling operations on the east side began in August 2010, while it began in February 2011 for the west side. Crews working on the top heading met when the initial breakthrough took place on Nov. 29, 2011.

The project is being undertaken by Tutor Saliba Corporation, a subsidiary of Tutor Perini Corporation, which is employing 40 subcontractors, including Drill Tech Drilling & Shoring Inc., FoxFire Constructors Inc., Gordon N. Ball Inc., Harris Salinas Rebar Inc., Johnson Western Gunite Co., Roadway Engineering Works Inc., and Wisko America Inc. At peak, with crews working day and night, there were approximately 200 workers on site.

“The initial support for the tunnel consisted of fiber reinforced shotcrete, spiles, rockbolts and lattice girders,” said Patrick Jennings, project manager of Tutor Saliba. “After the initial support, a smoothing shotcrete layer and waterproofing was installed. The final fifteen inches reinforced concrete liner was then placed. Sidewalks, electrical, drainage, metal panels on the sidewalls, ventilation systems and a two lane concrete roadway follow the final lining.”

The fourth bore parallels three existing tunnels and interconnects with the third tunnel via seven cross passages. The project also includes construction of a new 6,000 sq. ft. (1,829 sq m) Operations and Maintenance Center (OMC) building — the existing maintenance building had to be demolished first), new retaining walls and roadway approaches on the east and west sides of the tunnel (54,000 sq. ft. [5,017 sq m]), and a berm and permanent sound wall on the west side.

The tunnel, primarily mined with a 130 ton (118 t) Wirth heavy duty roadheader (Type T3.20) at the east heading, was completed on Sept. 21, 2012. The tunnel’s waterproof membrane, rebar cage, and final lining were installed from west to east.

Mining the tunnel led to approximately 350,000 tons (317,515 t) of earth, rock and other materials (spoils) being removed from the site. This was shipped to Treasure Island and much will be recycled for use in future projects.

“Working under a gassy tunnel environment was a challenge,” said Bill Monahan, Tutor Saliba’s tunnel superintendent. “This required significant expenditures in adapting equipment for this condition. The top heading of the tunnel was mined completely through using roadheaders, followed by simultaneous bench excavation from both the west and east ends. Another challenge was the incorporation of microfibers in the concrete final liner mix, which reduced the ability to pump this concrete over long distances. The concrete final liner was placed in 50-foot segments using an EFCO tunnel form with a traveler on rails.

“The NATM is a process of sequential excavation in which the length of the excavated section is based on the surrounding geology,” he continued. “The rock is assessed on a scale of one through four, with one being the hardest rock. The harder the rock, the farther the workers can tunnel before installing supports.”

Crews have made solid progress and the tunnel is scheduled to open to motorists on the weekend of Nov. 16 according to Caltrans. This means that motorists taking Highway 24 via the East Bay Hills will have the choice of using two tunnels (four lanes in each direction).

Once the roadway and tunnel walls are completed, the closing phase will have TPC crews finish the road-striping, link the new tunnel to the highway, and remove the vast array of equipment used for the project.

TPC owns much of the equipment that is and was used for the project and it had to be MSHA approved equipment for use in gassy tunnels. This includes: several Wirth heavy duty roadheaders and Sandvik LS175 LHD loaders/muckers, a Fletcher DR-13EL-F roof bolter, a RDH Drillmaster 200 DH 2 boom drill jumbo (185 hp with basket boom), a RDH Liftmaster 600R scissor lift (116 hp 4 wheel drive), RDH 800-26 haul trucks, a John Deere 50C mini-excavator (converted to electric power), a Gardner-Denver ATD 3800T, an Air Trac shotcrete robotic nozzle, an Allentown AST 25 robotic nozzle manipulator, reed C50HPS shotcrete pump, and a CemenTech SCD2-50 volumetric mixer.

SHA approved equipment for use in potentially gassy tunnels includes Caterpillar — 966G rubber tired loaders, a 446B 4x4 backhoe loader, a D6M dozer, and a D8 dozer; Putzmeister BSA 14000 GHP-D trailer pumps and a 40 m concrete boom pump; a Chemgrout CG-600 colloidal grout pump; JLG 600S telescopic boom lifts; and Skytrack Model 8042 forklifts.

Miscellaneous equipment used includes a Grove 90-ton (82 t) R/T crane, a Caterpillar 330 excavator and 200 kW generator, a Ford 4000 gal. (15,142 L) water truck, a Tymco 600 BAH sweeper, Miller 400D welders, an Ingersoll-Rand 915 cfm air compressor, and an Atlas Copco 1000 cfm compressor.

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