Following a tragedy at the San Francisco Zoo on Christmas Day 2007, when a tiger escaped and attacked three men, killing one, Yerba Buena was chosen to do an emergency renovation of the big cats exhibit. Yerba Buena’s crew of about 30 people worked 16- to 18-hour days, putting in nearly 6,000 worker hours to finish the emergency portion of the project so the animals could be returned and the exhibit could safely reopen on Feb. 21, 2008.

The 500-foot-long, semicircular exhibit consisted of four separate grottos, bounded by a concrete dry moat. Our workers removed the exhibit walls, barriers, railings, and irrigation system, and the asphalt outside the enclosure. After clearing and grubbing, they formed, reinforced, poured, and finished the new concrete wall.

The height was raised from 12.5 feet to 16.4 feet to meet Association of Zoos and Aquariums guidelines. Then, in the viewing areas, they added a barrier of specially ordered, 1-inch-thick, reinforced-glass on top of the wall, bringing the total height to 19 feet. Steel supports held the glass in place. On the sides, they topped the wall with stainless steel flexible cable mesh fencing. They also installed electric hotwire below the glass on the inside of the concrete wall.

Outside the enclosure, the workers put in new storm drainage and irrigation systems designed by Yerba Buena. They regraded, making sure the slopes of the new viewing platforms were ADA compliant. After compacting the base rock, they installed over 20,000 square feet of reconfigured, ADA-compliant paths and platforms.

They also installed new concrete curbs to form planters and planted them. About 15 to 20 days of heavy winter rains complicated but did not stop the construction. The weather

  • Project Name: San Francisco Zoo Tiger Exhibit Renovation
  • Category: Emergency Response, Parks, Other
  • Client/Owner: San Francisco Recreation and Park Department
  • Location: San Francisco, CA
  • Dollar Amount: $1,545,650

Project Features:

  • Emergency response
  • Extreme time pressure
  • High-visibility project
  • Design-build (landscaping, irrigation, storm drain system design)
  • Multidiscipline construction
  • Harsh weather conditions
  • Reinforced concrete wall
  • High-strength, reinforced glass with special steel supports
  • Electric hotwire
  • Earthwork
  • Structural reinforcement
  • Underground utilities
  • ADA-compliant paths and platforms