San Francisco Airport Flood Wall
BackgroundSan Francisco International Airport is one of the busiest airports in the world. It is land locked, mostly by the San Francisco Bay, so land and space is at a premium. To make matters worse, some of the land adjacent to the bay was flooding regularly. This flooding caused much of the areas to be considered wetlands and therefore unavailable for development and/or expansion of their runway and taxi system. Several extremely costly and critical runway expansions were needed in order to service the latest generation of jumbo jets.
Project ScopeThe San Francisco Bay is a very environmentally sensitive area. Permitting and regulations regarding construction in or around the bay area make projects very challenging. Steel and concrete were considered for the flood wall, but were eliminated in part due to installation disadvantages. On the other hand, PVC sheet piling would reduce the chance of negative effects from the construction process by requiring far less equipment and people to install. In addition to environmental concerns, limited work space made PVC sheets easier to use. The ShoreGuard sheets were also specified due to the fact they are produced using more than 90% recycled materials and considered a “green” material. The flood wall would be completed in 3 different phases, and was funded by the city, FEMA, and the FAA.
PerformanceShoreGuard PVC sheet piling had several performance advantages when compared to steel and concrete. A steel wall would need continuous upkeep to prevent excessive corrosion. ShoreGuard walls typically require no maintenance. Steel also requires heavy machinery for unloading and staging. ShoreGuard is comparatively light and easy to handle. Concrete was a poor material choice due to its heavy weight combined with the unstable bay mud. Two patented features also figured heavily in the material selection process. The CMI patented I-Beam Lock provides the most efficient sheet pile lock connection system. The performance advantages of the I-Beam Lock have long been recognized and documented by industry experts such as the USACE. Most of the project also utilized the patented ShoreGuard box profile which allows for faster installation and better performance.
ConstructionJMB Construction and William P Young Construction installed the materials. A combination of vibratory hammers and hydraulically driven vibratory plates were used. The ease of handling CMI sheets, compared to steel or concrete, allowed for efficient staging with minimal pieces of equipment and manpower required. Such efficient operations produced up to 200 linear feet of wall in place per day. A ShoreGuard AW 1075 Marine Grade Aluminum Cap was used to cap the wall. In some areas near radar equipment, a TimberGuard cap system was used.
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