The 8.5' diameter pipeline connects an existing aqueduct feeding San Diego County to the San Vicente reservoir. The system provides additional storage during wet periods and another water source during dry periods or when the main aqueduct suffers a catastrophe such as an earthquake.

The tunnel runs generally east-west across the north end of San Diego County. The west terminus shaft is 100' deep, the east terminus is a portal, and two additional shafts are in between with depths of around 75'. Depth of tunnel varies according to the surface topography but can be as great as 600'. The tunnel encounters varying geology ranging from extremely hard granitic rock near the ends to loosely cemented conglomerate in between. Some of the conglomerate may also be tightly cemented. The water table is below the tunnel for approximately half its length at the "peaked" middle section of the alignment.

Due to the varying geology, multiple tunnel methods were chosen. Two open face shields equipped with excavator arms and replaceable road header type attachments have mined the conglomerates.

These shields were manufactured by Construction Tunneling Service. A refurbished Robbins mainbeam machine mined the rock sections at each end. Conventional excavation methods are used in a section of tunnel which interfaces the rock and conglomerate in an unpredictable fashion. Drill and blast methods, combined with sequential excavation method type techniques are being used.  

At present, the Portal, Slaughterhouse Shaft, Central Shaft, and West Shaft are completed. Reaches 3, 4 West, 5 and 6 excavation is also completed. Excavation continues with both CTS Shields and the Robbins TBM.

Project Gallery:

Construction Method:
Start Date: Notice of Award July 1 2005; Notice to Proceed July 14 2005
Completion Date: In Progress
Owner:San Diego County Water Authority, San Diego, California
Joint Venture: Traylor/J. F. Shea