The Alameda Siphons extend approximately 1 km across the Sunol Valley in California. They cross the Calaveras Fault and are vulnerable to a major earthquake on that fault. A new buried 66-inch-diameter welded steel pipeline called Alameda Siphon No. 4 was built to remain in continuous operation when subjected to approximately 1 m of fault displacement during seismic activities.
The design of the new pipeline considered uncertainty in fault location, rupture displacement, subsurface conditions, and the installation of strain sensors to confirm pipeline design and assess the need for strengthening in the fault zone. More than 1000 m of distributed Fiber Optic sensing cable SMARTProfile were affixed onto the epoxy-coated steel pipe to measure strain and deformation all long the pipe. Excessive strain is detected and analyzed by a DiTeSt Brillouin interrogator for Distributed Fiber Optic Sensor, providing strain and temperature information every meter along the SMARTProfile sensor. With the location of any abnormal strain along the pipe, corrective measures can be undertaken at minimal time and expense so as to ensure the water system performs properly and water can be delivered to users after an earthquake.