In Construction: Anchoring Innovation in Santa Clara

Before walls could rise on a new global tech headquarters in Santa Clara, California, LPA’s team had to solve a complicated problem: anchoring the five-story, 350,000-square-foot office/lab/data center building within its one-story underground parking garage while resisting the buoyance of nearly 15 feet of marshland-saturated soil.

A standard deep pile foundation system wasn’t ideal due to the soft ground conditions and high water table. Structural engineers, architects, soil engineers, materials specialists, the construction teams and a host of collaborators worked the issues. “At every step we evaluated the effects on the building macrostructure and waterproofing systems, as well as the carbon impact of each option,” structural Project Manager Daniel Stone says.

Ultimately, they settled on a solid 3-foot-thick mat slab spanning the entire 100,000-square-foot subterranean garage footprint. Engineered from a specially developed low-carbon concrete mix, which significantly reduced the project’s embodied carbon, the slab supports the structure above and counters buoyant forces below in the high-water-table conditions.

Pouring the slab was an event. This mat slab “bathtub” covered an area the size of eight Olympic swimming pools and required more than 12,000 cubic yards of concrete. Weeks of preparation were required before the pour. “All the waterproofing layers, rebar, electrical conduit, drainpipes and sump pumps had to be carefully installed and inspected before being completely and simultaneously encased within this mammoth slab,” says Project Architect Erik Holliday. When the time came, the concrete was delivered by more than 1,000 trucks arriving in carefully controlled intervals over three days, a tightly choreographed dance to lay the foundation for the innovative new facility.