The extension's tunnel alignment is more than five miles long and will connect the existing BART Berryessa/North San Jose Station to a new at-grade station in Santa Clara. Three new underground stations are proposed at 28th Street, Downtown San Jose, and the Diridon Transit Facility.  

Shannon & Wilson is providing geotechnical design recommendations for the station support of excavation (SOE), as well as data for the tunnel and connecting audits. To date, we have completed subsurface explorations for the West Portal, Diridon, and Downtown San Jose Stations, including pressuremeter testing and triaxial strength testing to develop strength parameters for the SOE design.  We have installed an array of vibrating wire piezometers (VWPs) to augment previous groundwater readings along the tunnel alignment. 

Using our data, along with existing subsurface information provided by the VTA, Shannon & Wilson has developed geotechnical parameters for the SOE's final design. We have also provided geotechnical design parameters for the West Portal construction staging area, which is underlain by soft clay and requires ground improvements to support the heavy loads of the gantry crane and precast tunnel liner storage area.  

Construction is anticipated to commence in 2023 with operations planned in approximately 10 years.