Geotechnical Challenges on the BART Fremont Central Park Subway Project

The Bay Area Rapid Transit (BART) District will be extending BART service south along an 8.7-km (5.4-mile) -long corridor in the city of Fremont, California as part of the Warm Springs Extension (WSX). The WSX project will link the existing BART system to the proposed BART to San Jose extension. A segment of WSX is located in Fremont Central Park (referred to as the Fremont Central Park Subway Project). This segment is considered the most geologically and geomorphologically complicated portion of the project. The project consists of (1) an underground subway box being constructed not only in the middle of the largest park in Fremont and crossing under a lake, but also subject to high hydrostatic water pressure from the underlying aquifer and (2) a fill embankment over the Hayward Fault. This paper presents the geotechnical challenges that have to be addressed both in the design stage and during construction.