Transbay Tube Retrofit

The Transbay Tube internal retrofit project involves the installation of a steel liner inside the tube and the installation of a new water pumping system.

The BART Board of Directors awarded a $313 million contract ($267 million base contract with authority to excercise addtional options) on December 1, 2016, to Shimmick Construction and California Engineering Contractors Joint Venture.

The contract's Notice to Proceed date was February 2, 2017.

The project is expected to be completed by early 2023.

BART begins pivotal project to strengthen the Transbay Tube

BART’s role in the region as a lifeline was solidified with the 1989 Loma Prieta earthquake. The system was up and running on a 24-hour emergency schedule to serve the public less than 12 hours after the quake hit.  It was a watershed event, showcasing infrastructure working for the greater good of the region that paid to build it.

Loma Prieta was centered 55 miles south of San Francisco.  Our entire system and the Transbay Tube withstood the shaking. The design and strength of the tube, an engineering marvel sunk into mud in the bottom of the bay, had insulated the train and its passengers from feeling the earth’s movements. 

tube section in bay

More than a decade later in the early 2000’s, BART began to prepare for a major earthquake that could be centered closer to our core system, which runs directly adjacent to the San Andreas and Hayward faults.  On November 2, 2004, voters in Contra Costa, San Francisco and Alameda Counties approved Measure AA, which allowed BART to issue general obligation bonds to fund up to $980 million of the $1.2 billion total cost of earthquake safety improvements.

The Earthquake Safety Program addressed the original system completed in 1972 because system extensions built since the early ‘70s used more stringent seismic criteria than the original system. 

BART's Most Critical Asset

The highest priority for upgrades has been the Transbay Tube, BART's most critical asset which opened for passenger service in 1974.

BART worked with earthquake retrofit specialists using a combination of geotechnical and structural site investigations, computer simulations, and testing of materials and models to develop the retrofit design, which is centered around the installation of an inner steel liner and new water pumping system.

look inside tube

(Inside the Transbay Tube during its construction in the 1960's)

The installation of the inner liner inside of the tube's gallery started in 2017. The next phase began in early 2019. On February 11, 2019, BART shifted from a 4 am to 5 am opening and began single tracking through the tube after 9pm on weekdays to allow more time for the seismic retrofit project. 

The Transbay Tube is structurally sound, but we are preparing for a rare and devasting earthquake- defined as a 1,000-year event- something that happens once every thousand years.  In an event this large, the tube won’t fail but it could crack and leak.

The retrofit will install a curved inner steel lining to key sections of the 3.6-mile-long tube. It will also install an upgraded pumping system to allow larger quantities of water to be removed quickly from the tube.   

A plate handling machine will maneuver sections of the steel plates to form archways inside the tube. Once put in place they will be welded together and bolted into place. Grout will then be used to adhere the plates to the concrete walls via grout ports in the plates.

plate handling machine

(Steel plate handling machine similar to one used for the project)

A different technique using a polymer product covered with concrete will be used under the tracks.

Locomotive Work Train

The retrofit is being done in small sections during a work window of 9:30 pm (Sunday-Thursday) until 5:00 am (Monday-Friday).  

Starting in 2020, crews brought equipment and materials into the tube via a maximum 800-foot long custom-built locomotive work train. 

The work train is a critical component of the project.  It is made up of three new RELCO clean diesel locomotives and 14 flat cars, with each flat car configured for a specific task. The locomotives bookend the consist, with a third locomotive located in the middle. The work train was designed and fabricated at the RELCO facility in Iowa, specifically to operate on BART gauge rail.


(One of three locomotive that make up the Transbay Tube Retrofit Project work train)

There are three 50-foot-long flatcars, seven 40-foot-long flatcars, two 41-foot-long concrete cars, one 55-foot-long steel plate handling device and one 40-foot-long plate handling device flatcar.

The components of the work train were delivered to BART’s Hayward Shops.  It began operations in spring 2020 out of the Oakland Shops. It travels through Lake Merritt and West Oakland stations before heading into the tube. 

Its typical maximum speed is 15 miles per hour, but it runs through switches at five-miles-per-hour or less. It is anticipated the trip into the tube will take approximately an hour.

The work train is clean diesel, Tier IV compliant and meets the latest air quality standards.

The retrofit crew will mobilize and demobilize at certain sections of the Tube each night so passenger service can commence at 5 am.

Safety checks are done before the Transbay Tube work zone is released to passenger service.

One Hour Goes a Long Way

Adding this one hour a will shorten the project timeline by at least 4 months and save a minimum of $15 million.

It also gives crews more time for track inspections, preventative maintenance, and Measure RR bond funded rebuilding projects throughout the system such as power cable replacement through San Francisco and rail replacement. The extra time will speed these other projects up by at least 25%, provide a minimum 12% cost savings and increase the maintenance productivity of our crews by 43-62%. Having the extra hour for our Right of Way maintenance translates to double the amount of rail that can be replaced from 1,600 feet to 3,200 feet per week. It allows us to increase rail grinding work by 20%, going from 20 to 25 miles per week. It increases the number of insulators we can replace each week from 20 to 60, a 150% jump. Rail pad replacement is seeing a 100% improvement, from 20 to 40 pads per night. And the extra hour allows us to more than double our Ultrasonic Rail Detector Testing from an average of 3.1 miles tested each night to 6.4 miles.

In September of 2017, an independent study by Transportation Resource Associates was presented to BART’s board.

Among its findings, continued maintenance reforms are essential for BART’s future success and proper maintenance requires the agency to plan service adjustments.

The decision to start service later, as opposed to ending it sooner each night is largely based on data showing there are far more riders (between 5,000 and 6,000) during the last hour of our service window than the 2,900 riders we carry in the first hour.

Early Bird Express Bus Service

We understand this project will impact our riders.

About 2,900 passengers enter our system in that first hour of service.

Over 2,400 of them begin their trips in the East Bay and 64% of our first hour riders disembark at downtown San Francisco stations.

The Early Bird Express bus service plan was developed to provide an alternative form of transit in the 4 am hour.