Los Angeles, CA

Terminal Hill Tunnel and Shaft

Los Angeles Department of Water and Power


The San Fernando Earthquake in 1971 and Northridge Earthquake in 1994 caused significant damage to the Second Los Angeles Aqueduct (SLAA) where it crosses Terminal Hill at the northern end of San Fernando Valley. During both earthquakes, the pipeline section on the upper north slope and crest of Terminal Hill was damaged by severe ground shaking.

The Terminal Hill Tunnel and Shaft project consisted of relocating the portion of the SLAA situated on Terminal Hill’s north facing slope. The relocated section connects to the existing pipeline in Magazine Canyon and continues through a new tunnel containing approximately 580 feet (177 m) of 84-inch (2,135 mm) steel pipe. The replacement steel pipe connects to the existing pipeline on the top of Terminal hill via an approximately 290-foot (88 m) vertical shaft.

Fast Facts
  • 290-foot (88 m) vertical shaft
  • 580 feet (177 m) of 84-inch (2,135 mm) steel pipe

Scope of Work

Delve Underground provided technical services during design and construction, including assisting the Geotechnical Engineering Group at LADWP with structural design of the final tunnel lining and preparation of the Geotechnical Baseline Report; reviewing contractor submittals; and conducting construction observations.

Challenges & Innovations

The project used microtunneling to minimize aboveground disturbances.