Q&A: What are the unique engineering challenges for the Sutter Health CPMC project on Cathedral Hill?

CPMC Van Ness and Geary, located in the bottom left of the image, is on Cathedral Hill in San Francisco, CA

CPMC Van Ness and Geary (bottom left of the image) is on Cathedral Hill in San Francisco, CA.

The Sutter Health CPMC Van Ness and Geary Campus is highly visible: it is located in the heart of city, considered to be a future flagship medical center, and involves demolitions, deep excavations, and constructing an underground tunnel. This year, our geotechnical and environmental engineers focused heavily on the hospital excavation and the tunnel construction underneath one of San Francisco’s most congested and centrally located roadways, U.S. Highway 101/ Van Ness Avenue.

Closing down the road for the initial stage of the tunnel construction was the foremost challenge, but it was a necessary component. Earlier this year, the development team obtained the City and County of San Francisco’s approval and coordinated extensively with Caltrans to close down Van Ness between Geary and Post for three 72-hour periods, from Friday at 12:01 a.m. to Sunday at 11:59 p.m. The first two closures were completed last spring and the final closure will occur later this year.

During the first two closure periods, our field staff worked around-the-clock in rotating eight-hour shifts to help ensure that every necessary task was completed within the allotted time frame. Soldier beams were installed on either side of the tunnel to provide temporary excavation support and also to support temporary, traffic-rated decking atop them. During the first two closure periods, the construction team installed all soldier piles and completed an excavation of about 5 feet below Van Ness Avenue. As the excavation progressed, timber lagging boards were installed between the soldier piles. The tunnel excavation work then moved to the hospital side, where hand-digging equipment is being used to complete the tunnel, which will bottom approximately 25 feet below Van Ness Avenue.

Construction on the CPMC Van Ness and Geary site in San Francisco, CA

Construction on the CPMC Van Ness and Geary site in San Francisco, CA

The entire project team, including architects, engineers, contractors, and subcontractors, has also been dedicated to sustainability. For example, an estimated 51,000 tons of concrete and 5,000 tons of steel were recycled from the hotel demolition. The team is aiming for LEED Silver certification for this project, which will make Sutter Health CPMC Van Ness and Geary one of the largest LEED-certified hospital campuses in the world and only the fourth LEED-certified hospital in California.

Bringing this extraordinary project to fruition has required close coordination, efficient project integration, and creative problem solving. Our focus has been highly responsive and we have completed tasks on, or ahead of, schedule. We are eager to see this project come to life and serve the community.

Answer provided by Cary E. Ronan, PE, GE
Cary has over 18 years of experience performing and managing geotechnical investigations and construction observation services for numerous projects throughout the San Francisco Bay Area. She provides project management and supervision services during investigations for commercial, retail, and residential developments, including high-rise developments as well as healthcare, school, university, and museum facilities.

Cary directs subsurface investigations, designs and evaluates foundations systems, performs engineering analyses, and directs field and office personnel. She has performed engineering analyses to determine settlement behavior of soil under loading, bearing capacity for shallow foundations, lateral and vertical capacity for deep foundations, and evaluated slope stability and seismic hazards including liquefaction potential.

Photography: ©2015 Brian Haux – SkyHawk Photography