Casa Loma Siphon Barrel No. 1 Seismic Retrofit Project

The Metropolitan Water District of Southern California (Metropolitan) retained Carollo Engineers Inc. to provide preliminary design, final design, and engineering services during construction to replace the 148-inch Casa Loma Siphon Barrel No. 1 at the Casa Loma Fault crossing.

The Casa Loma Siphon Barrel No. 1 is a part of the Colorado River Aqueduct (CRA), which delivers water supply from the Colorado River to Southern California. The Casa Loma Siphon Barrel No. 1 is vulnerable to failure due to seismic displacement and ground subsidence at the fault crossing.

The project, which will be completed in 2023, seeks to retrofit the Casa Loma Siphon Barrel No. 1 for the anticipated fault displacement and long-term settlement, improve the operational capability during and after an earthquake, and design the pipeline to allow Metropolitan to return the pipeline to service within a reasonable amount of time if damage occurs.

The project team performed geologic field investigations to determine the Casa Loma Fault location, angle of the fault, and the estimated fault displacement resulting from a 2,475-year earthquake event. The project team performed sophisticated finite element modeling to estimate pipeline performance during an earthquake event. The model utilized joint springs to simulate the behavior of earthquake resistant ductile iron pipe and soil springs to simulate the pipe to soil interactions.

The project replaces approximately 1,200 feet of the 148-inch diameter Colorado River Aqueduct with dual 104-inch earthquake resistant ductile iron pipelines and welded steel pipe at the fault crossing. The dual 104-inch pipelines are designed for 12.8 feet of fault displacement at the fault crossing. The pipeline backfill design utilizes expanded polystyrene geofoam to soften the system’s response and help absorb the large horizontal fault displacement. Carollo designed the connections to the existing pipe to allow the Contractor to install the connections during a four-week shutdown of the CRA.