The City of Coronado in California wanted to determine the feasibility of constructing a 1.4 mile tunnel beneath the city streets to alleviate daily traffic congestion to and from the North Island Naval Air Station. Kleinfelder conducted preliminary seismic and geotechnical studies for the proposed tunnel.

Planning on Shaky Ground

The active Coronado fault crosses the proposed tunnel alignment, affecting the feasibility of the project. Very little was known about the Coronado fault’s location and its potential to rupture during an earthquake, and whether the fault rupture hazard could be mitigated for the project was uncertain. Six project alternatives were evaluated during the Environmental Impact Statement/Environmental Impact Report phase of the project.

Detailed Fault Study to Determine Feasibility

Kleinfelder’s services included geologic and geotechnical site characterization, development of site-specific ground motions for seismic design, and geotechnical engineering. A detailed study of the fault enabled Kleinfelder to pinpoint its location and to develop ground motions and design fault displacements for the tunnel design. Additional studies included further characterization of engineering geology and geotechnical conditions with respect to tunnel design and construction, as well as characterization of environmental hazardous materials conditions along the project alignment.

Project Results

Kleinfelder’s fault hazard characterization work provided the information needed to prove the tunnel could be designed to safely withstand a fault rupture event, enabling the client to make an informed decision about the project’s feasibility.

Project Details

Location:
Coronado, California

Owner:
City of Coronado, Caltrans