American Council of Engineering Companies of California (ACEC California) recognized Delve Underground and Kleinfelder with an Engineering Excellence Honor Award for the Courthouse Commons Tunnel Project – an $83 million, 23-foot-diameter, 328-foot-long, concrete-lined tunnel and three-story underground transfer facilities shaft for transporting inmates from the Downtown San Diego Central Jail to the new Superior Courthouse.
The firms provided professional engineering and construction services for this challenging project. Delve Underground was the Engineer of Record for the design of the tunnel and transfer facilities shaft, including instrumentation of the surrounding structures, and provided engineering services during construction. Kleinfelder provided comprehensive geotechnical services for design of the tunnel – including serving as the project’s Geotechnical and Earthquake/Seismic Engineer of Record – as well as instrumentation monitoring, geologic mapping, and special inspection and materials testing.
Although the project took place in a highly dense, urban environment, with challenges including utilities coordination, the accommodation of future fault movement, and the requirement of special types of instrumentation because of nearby structures, the public was largely unaware of the work taking place underground. The success of the project resulted in no negative press, nor impact to the public by way of detours and street closures, and only one of three lanes of traffic over a city block was closed during construction.
With the jail and new courthouse being separated by a city block, the tunnel provides a safe connection and eliminates the need for busing between the two locations. This reduces the Sheriff Department’s carbon footprint, the supervision needed during transport of inmates, and the security risks inherent with the transportation of inmates.
Holland Partner Group is developing the Courthouse Commons site for the County of San Diego under a design-build contract. In addition to the tunnel project, the overall redevelopment encompasses three city blocks, including a 37-story mixed-use tower.
Design of the Courthouse Commons Tunnel Project was fast-tracked, and construction was completed in 24 months, on schedule.