A $2.26 billion, one million ft2 transit center that opened in August in the heart of San Francisco was closed to the public after a fissure in a steel beam was discovered.

The Transbay Joint Powers Authority (TJPA) closed the facility Sept. 25 after conferring with builder Webcor/Obayashi and structural engineers Thornton Tomasetti to investigate and inspect all similarly designed locations throughout the center.

September 25 image of the fissure located on flange on the bottom portion of the beam that spans over Fremont Street. Credit: TJPA.orgSeptember 25 image of the fissure located on flange on the bottom portion of the beam that spans over Fremont Street. Credit: TJPA.orgThe initial fissure was found in the ceiling of the third level bus deck near Fremont Street. Inspections showed an additional fissure on an adjacent beam. TJPA says that current analysis suggests that the problem is contained to this area of the terminal.

In a statement, the TJPA says it will conduct additional ultrasonic testing to determine the extent of the damage. Inspections on First Street, where a similar design exists, showed no similar issues. The TJPA says that it will continue to monitor and test the First Street location.

The agency says that its engineers and contractors are developing a shoring plan for the Fremont Street location to relieve loading on the beams to prevent further damage. The TJPA will then design a permanent repair and schedule construction to make repairs.

(Click to enlarge.) Artist's view of the Transbay Transit Center with San Francisco Bay in the background. Credit: TJPA.org(Click to enlarge.) Artist's view of the Transbay Transit Center with San Francisco Bay in the background. Credit: TJPA.orgMetro Transit Hub

The Transit Center replaces the seismically deficient Transbay Terminal with a transportation hub that is intended to connect transit systems throughout the Bay Area. The new center also includes retail, a public art program, shopping and dining; and a 5.4-acre rooftop public park. The Transit Center stretches four blocks, with four stories above ground and two stories below ground to accommodate future regional and high-speed trains.

The Transit Center was built by a Webcor/Obayashi joint venture and designed by Pelli Clarke Pelli Architects. It includes a bridge crossing several streets to provide direct bus access from the Bay Bridge to the Transit Center, potentially reducing congestion and improving travel times for commuters. The building is designed to withstand an 8.0-magnitude earthquake on the San Andreas Fault.

Sinking Neighbor

Just days before the transit center was forced to close, a San Francisco Superior Court Judge limited the amount of legal costs that would have to be covered by TJPA in lawsuits brought against Mission Street Development (MSD), the developer of the sinking and tilting Millennium Tower, which is next to the transit center.

The Millennium Tower, which opened in 2009, has sunk down about 17 in, and tilted 14 in to the west and 6 in to the north at the roof line.

The building sits on a 10 ft thick mat foundation, held in place by 950 reinforced concrete piles sunk 60 to 90 ft deep into clay and mud. They do not, however, reach bedrock.

To retrofit the tower, engineers in April proposed boring 275 to 300 steel and concrete micropiles — each 13.625 in in diameter — down to bedrock.

In the Sept. 20 court ruling, the judge rejected MSD’s request that TJPA be required to defend MSD in six lawsuits. Those lawsuits were brought against MSD for the excessive settlement and tilt of the tower. The ruling stopped short of determining what caused the excessive settlement and tilt of the Millennium Tower. That issue will be determined in a trial set for June 2019.

MSD argued that the TJPA was required under a 2008 easement agreement to defend MSD against all claims. The court rejected that argument and held that the TJPA only must defend MSD against two claims in one case filed by the homeowners association for the tower.

In its court arguments, the TJPA alleged that the excessive settlement and tilt of the tower was caused “solely by MSD’s fatally flawed foundation design.”