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San Francisco’s New Central Subway Construction Enters Phase II

Builders of San Francisco’s new Central Subway light rail project describe it as the Bay Area’s most significant capital investment in generations.

Mon November 02, 2015 - West Edition
Chuck Harvey

Builders of San Francisco’s new Central Subway light rail project describe it as the Bay Area’s most significant capital investment in generations. Considering the billion dollar-plus price tag and the scope of the project, it’s hard to argue with that assessment.

The Central Subway project has already achieved some major milestones including attainment of environmental clearance from the Federal Transit Administration and relocation of numerous utility lines in preparation for station construction and tunneling. Construction began in 2013 and will continue through 2017. Then the system will be tested.

The Central Subway is slated to open for business in the first quarter of 2019.

Tunnel boring has been completed and now crews are installing concrete and light-rail tracks. They also are installing four new light-rail train stations. The new line will run from the Mission Bay area just south of AT&T ballpark north through Union Square and on to Chinatown. The project will speed riders along while reducing vehicle traffic in an area heavily used by commuters and tourists.

Spearheaded by the San Francisco Municipal Transportation Agency, the 6.8-mi. (10.9 km) project has rolled into phase II, the final phase of work. Phase I included restoration of rail service along San Francisco’s 3rd Street corridor, a busy area that had been without rail service for 50 years.

Phase II will extend the T-Third Line rail service in the densely-developed Bayview and Mission Bay areas to downtown and Chinatown. The T-Third Line is part of San Francisco’s Muni-Metro line.

The 1.7-mi. (2.73 km) light rail line extension will serve Union Square, Moscone Convention Center, Yerba Buena and AT&T Park. It also will directly connect to Bay Area Rapid Transit (BART) and Caltrain, the Bay Area’s two largest regional commuter rail services. Ultimately, it will connect to the planned California High Speed Rail line.

The project is funded by local, state and federal sources. Total funding for phase II is $1.57 billion. Phase I and II combined comes to $2.22 billion. Phase II is moving along on schedule with no major glitches.

“The project is 55 percent complete,” said Randal Curtis, community outreach manager of the Central Subway project.

She added the tunnel boring was completed in October of this year, less than one year after twin tunnel-boring machines began work underground. Currently, roof decks for the subway system are being installed.

Roof decks hold the utilities including electricity to run the subway trains.

About 100 workers are on the job each day, primarily working the day shift. Some night work also is being done, Curtis said.

Major Contractors

The San Francisco Municipal Transportation Agency awarded an $840 million contract to Sylmar, Calif.-based Tutor Perini Corp. to construct the Central Subway’s stations, train tracks and operating systems. The $840 million figure was the low bid for the work.

Barnard Impregilo Healy Joint Venture of Bozeman, Mont., had the successful low bid of $233.5 million for the tunneling work.

Program and construction management is being handled by Central Subway Partners: AECOM of Los Angeles, and EPC Consultants Inc. JV, of San Francisco. The two firms had the winning bid of $147.3 million for management service.

Michael Willis Architects Inc. of San Francisco, Oakland and Portland, Ore., and Kwan Henmi Architecture of San Francisco designed the stations under a $35 million contract.

The project has five subcontractors, Curtis said. All contracts were awarded to low bidders, she added.


The Central Subway will provide direct connections to retail, sporting and cultural venues while transporting riders to jobs and schools in the area. The light-rail trains also will provide transportation to a burgeoning technology and digital-media hub.

The four new light-rail stations to be built are 4th and Brannan, YerbaBuena/Moscone, Union Square/Market Street and Chinatown. The 4th and Brannan Station will be built at street level. The other three will be underground subway stations.

In late September, excavation was being conducted at the 4th and Brannan station. Work included cutting of pavement. Curtis said some streets would have to be replaced. However, once the project is completed, people in cars will be able to use the same routes as before. Some lanes are closed during the work, but a lane is left open for cars to use during construction.

“We inform the community about lane closures, Curtis said.

Still, as with major construction projects commuters have faced delays, especially at peak hours. Curtis said once the project is finished, car traffic above ground should be reduced. That’s because ridership on the Central Subway is expected to be high, Curtis said.

“It’s the first north-south route,” she said.

San Francisco has an east-west subway route in use. The new rail line operation is forecast to cost $15.21 million annually. Ridership is expected to start at 24,900 on average for weekdays and reach a 35,100-weekday average by 2030.

Siemens in Sacramento is building new light rail vehicles for the Central Subway.

Tunnel Boring

To build the subway system, a construction approach called deep tunneling is used. Deep tunneling allows most of the work to be done below ground, reducing disruption on the surface.

Twin boring machines, each 350 ft. (106.68 m) long and weighing 750 tons (680.4 t) have been boring under the streets of San Francisco. The boring machines even have names: “Mom Chung” and “Big Alma”.

The only visible tunneling activity is at the portal location on 4th Street between Bryant and Harrison streets and at the excavation site at Columbus Avenue and Union Street. The tunnels are approximately 8,300 ft. (2,530 m) long and range in depth from 40 ft. (12.19 m) to 120 ft. (36.57 m).

Construction crews will install two types of track for the Central Subway project. Direct fixation track will be installed in the tunnels and embedded track will be built on surface.

Direct fixation track consists of rails held in place with special rail fasteners that are anchored into concrete placed on the bottom of tunnels. Embedded track is attached to concrete slabs located below the street pavement. Northbound and southbound tracks will run down the middle of 4th Street.

In addition to helping residents travel locally, the rail system will help carry large crowds attending events at convention and professional sports venues in the South of Market area. The South of Market area is expected to experience strong growth over the next two decades.

For now, construction crews are focusing on building above-ground track and the rail stations with the least amount of disruption of daily life in the area. Night work from midnight to 5 a.m. began in early September.

The San Francisco Municipal Transportation Authority reports that as the Central Subway Project continues, construction schedules, bus routes and roadway stops are subject to change based on unforeseen conditions. Signs are posted at affected stops to advise of service changes.

Central Subway Benefits

Once the Central Subway project is completed, the T Third Line will accommodate current and projected high ridership in the corridor, reducing trip times and providing direct connections to regional transit systems, Curtis said.

Jobs and population in the area are projected to grow significantly over the next two decades and planners consider the Central Subway essential to ensuring mobility and accommodating increased passenger demand.

The new line is expected to create thousands of employment and job training opportunities as more businesses come to the area.

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