Background

The WSX project will extend BART approximately 5.4 miles south of the existing BART Fremont Station, through the Irvington and Warm Springs districts of Fremont. The project includes the proposed Warm Springs Station and an optional station at Irvington. An approximately 1.2-mile-long subway (tunnel) section extends beneath Fremont Central Park and the northeastern tip of Lake Elizabeth. The alignment crosses active strands of the Hayward Fault at three locations.

Fugro's Role

Fugro’s scope of services included both geotechnical site characterization and analyses. The site characterization scope of work included:

• Conducting site reconnaissance
• Researching previous studies in the immediate alignment vicinity,
  
• Obtaining permits/permissions from govt agencies and private owners for field exploration access.
  
• Exploring subsurface conditions with subsurface borings (41) and Cone Penetration Test (24) soundings
  
• Borings required a variety of drilling techniques to accommodate varying surface and subsurface conditions
  
• Installing and monitoring piezometric wells
  
• Laboratory testing,
  
• Developing interpretative subsurface cross sections
  
• Preparing geotechnical data and site characterization reports.
  
• Geotechnical analyses for the project included:
  
• Conventional and GIS-based analyses of soil liquefaction,
  
• Site-specific seismic hazard analyses including near-source and directivity considerations,
  
• Development of spectrum compatible acceleration time histories using a time-domain spectral matching procedure.
  
• Equivalent linear and non linear Soil Structure Interaction (SSI) analyses to develop racking curves for the subway section
  
• Embankment static and seismic stability and settlement evaluations,
  
• Retaining wall design,
  
• Construction considerations for tunnel section, embankments, and retaining walls,and
  
• Evaluation of the magnitude of fault offset during the design (moment magnitude 7.0) event and fault creep
  

Schedule

Fugro has met all schedule milestones and budget targets for this project. This achievement was facilitated by: 1) Detailed advance planning of all field operations; 2) Capable field engineers who were able to adjust rapidly to changed conditions with minimum schedule/budget impact; and 3) close interaction with BART's review team and the client's engineers to develop an early consensus relative to design criteria and analytical methods.

Significant Features/Accomplishments:

• Program management of a complex site investigation in a highly urban environment.

• Obtaining permits from a variety of agencies including Alameda County Water District, BART, City of Fremont, and Alameda County Flood Control & Water Conservation Districts, as well as permission from a number of private owners.

• On-time, on-budget preparation of the project GDR which integrates existing geotechnical data with large volumes of new subsurface data

• Close coordination with Ed Matsuda, head of BART's Seismic Safety Group to develop the new generation of seismic design criteria for BART facilities;