San Jose extension adopts single-hole tunnel design, BART worries about making emergency evacuation more difficult_1
The San Jose extension of the BART (Bay Area Rapid Transit) system is set to break ground in the summer of 2024. However, the Santa Clara Valley Transportation Authority (VTA) continues to advocate for a single-bore tunnel design, raising serious concerns about emergency evacuations. This project, which has an estimated cost of $12.7 billion, has seen ongoing contention between BART and the VTA.
Documents obtained by NBC Bay Area indicate that BART expressed concerns as early as 2017 regarding the feasibility of evacuating passengers to safety within six minutes with a single-bore design in downtown San Jose. Despite this, the VTA remains steadfast, claiming that they have alternative safety measures in place to ensure passenger safety.
The VTA’s preference for a single-bore tunnel stems from lower costs and the theoretical reduction of impacts on surface traffic. However, the extension will reach depths of up to 100 feet, double that of BART’s existing deep stations. A fire incident earlier this year at the downtown Oakland station necessitated a full evacuation, highlighting similar potential risks for the San Jose area.
BART’s 2017 assessment emphasized that the five-mile extension, with a diameter of 54 feet and a single-bore design, poses significant challenges for disaster evacuation, with numerous critical impediments noted by retired BART fire safety engineer Barney Smits.
In a recent interview, Smits reiterated the lack of intention from the VTA to reconsider its stance. He pointed out that passengers would need to rely on three escalators to reach the platform level, but these escalators would automatically shut off during emergencies, requiring those at the bottom to climb eight flights of stairs to reach safety.
“Assuming there are 2,000 passengers on the platform, plus firefighters rushing down, it’s simply impossible to evacuate within six minutes,” he said, referencing standards set by the National Fire Protection Association.
BART board member and civil engineer Liz Ames questioned whether VTA’s insistence on this design has inadvertently compromised safety. Along with fellow board member Debora Allen, she has called for BART to officially endorse the safety measures since the concerns regarding the single-bore tunnel remain unresolved, a sentiment echoed by Smits.
The primary difference between single-bore and twin-bore tunnels lies in the evacuation options available in emergencies. In a twin-bore system, passengers can use one tunnel to escape if the other faces an issue. In contrast, a single-bore design leaves no escape path in the event of a fire, as the passage becomes blocked.
However, the VTA maintains that additional refuge areas are available on either side of each platform, providing safe spaces for passengers unable to reach the surface. They assert that this design fully complies with regulations and is currently undergoing reviews by federal and state authorities, along with local safety evaluations.
Additional concerns extend beyond the station areas, including evacuation procedures if a train catches fire within the tunnel and issues related to heat and smoke management. The VTA has indicated that the extension will feature a “single-point extraction system” that automatically activates smoke and heat vents near the incident site, claiming to be more effective than BART’s existing systems.
