Foster + Partners, and Heller Manus developers Oceanwide Holdings broke ground last week on the Oceanwide Center in San Francisco, a mixed-use project that, when completed, would become the city’s second-tallest tower.

The project, a 2.4-million square foot complex consisting of condominiums, office space, and a hotel, occupies a 1.4-acre site and has been designed to contain public spaces in a pair of adaptively-reused historic structures along the ground floor.

The complex will be composed of two towers: a primary 850-foot, 75-story tall structure containing 1,010,000-square-feet of office space and 111 condominium units and a 605-foot, 54-story tall tower containing a 171-room Waldorf Astoria hotel and 154-condominium units. The taller tower is demarcated by a large-scale, diagonally gridded truss system that climbs the height of the tower, creating a crenelated cap at the apex, while the shorter tower features a gridded facade filled with rectangular, punched openings. The gridded structure of the larger tower meets the floor to create a giant, open-air, landscaped plaza.

The tower complex joins a series of other projects, including the Pelli Clarke Pelli Architects—designed Salesforce tower, the Heller Manus Architects—designed 181 Fremont, and the Handel Architects—designed Millennium Tower, are transforming the Transbay area of San Francisco. The new tower district is rising around the Transbay Terminal, a new multi-modal transit hub also designed by Pelli Clarke Pelli Architects. The first phase of the terminal is due to be completed in late 2017.

Controversy erupted this year when the nearby Millennium Tower began to sink, a result of the fact that the tower is built on a concrete slab supported by 60- to 90-foot deep friction piles and not, as would be more structurally-appropriate for the area’s soil conditions, end-bearing pylons. As a result, the tower’s foundation does not actually reach the bedrock below the city and the tower has not only sunk 16-inches into the ground, but has also tilted between two- and six-inches toward the northwest. To avert a similar problem, Oceanwide Center is designed to be supported by foundation piles that drive down up to 400-feet below ground and connect directly with bedrock.  

Oceanwide Center is due to finish construction in 2021.