San Francisco Residence
San Francisco, CA
For a new residence on a very steep site on top of bedrock without infiltration, we were caught between a rock and a hard place, literally! With this difficult situation, we were asked to devleop a novel solution that integrated an on-site water re-use plan. We provided civil engineering and integrated water and building systems engineering, working with the architect and landscape architect to seamlessly combine innovative infrastructure with a strong formal design.
All graywater flows passively into a large biofilter at the low-point of the site, where vegetation surrounds an outdoor deck; pressurized irrigation lines send treated water to a series of 4 living roofs, where secondary treatment occurs through our customized "blue roof" system (up to 5" of graywater are held in aerobic and anaerobic conditions, which simulates a tidal wetland where plants and soil decompose remaining organic compounds). In this way, roof run-off combines treated graywater and rainwater into a storage tank sized to serve as a source for indoor toilet flushing and laundry, while simultaneously providing space to accommodate stormwater retention on our site and offset run-off.