The hills of San Francisco are notorious, so you can imagine the challenges of building on them. KPFF San Francisco Structural Engineers are accustomed to significant grade changes across a site but building a fruit orchard over a garage on such a site was a unique challenge!
Alchemy by Alta includes four multi-family residential buildings with a total of 330 units, 308 car stalls and 125 bike racks. An existing historic 34,000-sf, reinforced concrete, classroom building was converted into housing units and community space. The project provides much needed housing, plus stunning views of the City accessible to pedestrians. Also, for you wellness fans, the stairs have become a favorite public work out spot!
There is almost a 50’ grade change from one side of site to the other. Stairs traverse across the development as a public walkway named “Waller Park”. The new buildings constructed also act as retaining walls. Several complicated landscaping features are integral to the project, including bioswales over the podia, a terraced orchard supported by the structured parking, and a twenty-foot tall retaining wall braced by tiebacks.
The BIM model shown below gives an idea of the amount of structure below that can’t be seen but is supporting the development and the orchard on top of the garage. Tree wells are 4’ deep on the podium to hold soil and to promote good tree health and allow the roots to grow. The orchard ended up weighing more than the buildings adjacent to it! The structure is designed to resist both permanent loads imposed by the hillside and temporary loads due to wind and earthquakes.
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