San Francisco Museum’s Green Redo Keeps Team on Slippery Slopes
 California Academy Of Sciences |
 California Academy Of Sciences |
“We had to tie people off with mountain-climbing gear because the roof was so steep,” says Daniel Payne, construction manager for subcontractor Webcor Concrete, Hayward, Calif.
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| PIANO |
Related Links: With the move-in now in high gear for the Sept. 27 opening of the reincarnated natural history museum, which also contains a planetarium, an aquarium, a rain forest and research facilities, the building team is finally catching its collective breath. Many have toiled since 1999, often on slippery slopes, to build the 410,000-sq-ft symbol of sustainability and survival not only of the 155-year-old academy but of the rooftop inhabitants. The builders also managed to bring the job in on time while meeting the revised $256-million budget.
“It was quite a feat” to substantially complete the three-story big green box, especially considering the roof topography, in just over two years, says Jes Pedersen, senior vice president with general contractor Webcor Builders, San Mateo, Calif. The closest competitor for the guaranteed-maximum-price contract wanted nine months to a year more, he says.
 Webcor |
 Webcor Curved roof steel and eccentric skylight were among trickiest features. |
The original development cost, including the academy’s temporary quarters, was $429 million. The original GMP was $222 million. The increases are largely attributed to rises in materials costs, including steel, concrete and acrylic, and to design changes. “At the end of several design phases, we were significantly over budget,” says Peter Lassetter, project director for engineering services for the local office of Arup. The firm provided structural, mechanical-electrical-plumbing (MEP), lighting, sustainability, facade and fire protection services.
Rather than cut out elements, the academy’s board of trustees decided to raise more money. To date, more than $453 million has been secured, including gifts, $152 million from city bond funds, and state and federal funding.
Infrastructure to support the building’s multiple personalities, live flora and fauna and 20 million specimens was no walk in the park. But it is design architect Renzo Piano’s crowning touch the 4.5-acre roller-coaster roof, with hills as tall as 27 ft and a warped skylight over a piazza that could have pushed the team over the edge.
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| KOCIOLIK |
“We’ve done on-structure rooftop gardens for 40 years, and this is the extreme,” says John Loomis, principal of SWA Group, the job’s Sausalito, Calif., landscape architect.
The tricky terrain rippled through the job. “Renzo was adamant” about having curved roof steel expressed inside, says Larry Chambers, Arup’s structural engineer. “It was a challenge,” especially in a seismic zone, he adds.
Achieving Piano’s vision depended on team collaboration, sources agree. Webcor was on hand for budget reality-checks and constructibility brainstorming three years before the August 2005 groundbreaking. Potential subcontractors were brought in during design. “We didn’t have time to do it twice,” says Pedersen.
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| ROGERS |
In 1999, the academy, facing the need to strengthen its 11-building campus compromised by the 1989 Loma Prieta earthquake and looking to turn around a 20-year decline in attendance, ultimately decided to reinvent itself, says Patrick Kociolik, academy director from 1997-2006 and currently director of the University of Colorado Museum of Natural History, Boulder. The new academy will be filled with light and have changeable, interactive exhibits that showcase biodiversity and ecosystems. The building and the exhibits within are interactive and are meant to educate the public about climate change and sustainability.
 Webcor |
 Arup Curves meet facets. |
Sustainability permeated the project. Webcor recycled or reused more than 90% of the old campus. Arup pulled out all the stops to naturally ventilate the 1.8-million-cu-ft exhibit hall. There is a gray-water collection system. The exhibit hall also has a in-floor hydronic heating and cooling. There are water-saving cooling towers. The green roof, with rainwater collection, insulates as well as reduces stormwater runoff. The exhibits also function sustainably; for instance, aquarium seawater is piped from the nearby Pacific Ocean and natural systems purify nitrate wastes. The list is long. More green data is available at www.calacademy.org.
The green roofscape, itself an exhibit, evokes Teletubbyland, giant anthills and the seven hills of San Francisco. The building’s interior, which resembles a terrarium or ant colony, is made up of a ground-floor podium that supports four concrete shear-wall minibuildings, one in each corner. The minibuildings are separated by a cruciform-in-plan void that consists of the north-south entry corridor with a piazza and the east-west exhibit hall, 430 ft long and 126 ft to 248 ft wide.
 Webcor Roof bears on thin columns. |
The hall contains two 90-ft-dia steel-framed hemispheres that stop 4 ft from the exposed ceiling. The opaque east dome houses the planetarium, which partially cantilevers over the world’s largest captive coral reef; the other is glazed and houses the rain forest. One-and-a-half basement levels contain five concrete aquarium tanks. “It amazes me how much we crammed into one building, on a reasonable budget,” says Kang Kiang, senior associate with local executive architect Stantec Architecture, formerly Chong Partners Architecture.
 Webcor Skylight trusses preassembled on site |
Structurally, each corner building functions as a table leg, with the roof as the top. Lateral loads are taken by concrete shear walls connected to roof and podium diaphragms. A grillage of expressed steel beams, spanning as much as 96 ft over the domes, supports a contoured concrete roof slab. The 504 x 336-ft bilaterally symmetrical roof flattens out at the edges. The hills two of which are 27 ft tall, one 19 ft tall and two 9 ft tall flank the piazza. A roof canopy has 60,000 photovoltaic cells for 5% of the museum’s energy.
 Webcor Erected between Teletubby-like domes |
The roof diaphragm will let the minibuildings behave as one in a quake, which meant it was necessary to prestress the steel cable-net truss system supporting the piazza’s 98 x 72-ft skylight, open to the sky in the center. Upper and lower nets are separated by pipe struts at articulating, cast stainless-steel nodes. The system is supported by a perimeter truss on thin columns that transfers forces to the roof. Skylight panels are made from triangular panes with three-point support. This provides a faceted geometry but costs less than doubly curved glass, says the engineer.
The building is supported on spread footings. Arup left out ground anchors to allow the building to “rock” during a significant quake. The approach, which required nonlinear time history analysis to...