BART-to-San Jose Extension….More of the Same?

Bay Area transportation infrastructure projects tend to cost much more than expected (and in some cases more than necessary) and invariably take much longer than expected to complete. It appears that the Phase II BART subway proposed for San Jose may be no exception.

Map.pngThe following critique responds to the presentation made to the BART & VTA Partnership “Special Committee meeting at BART’s Oakland Headquarters on May 31, 2019. Santa Clara Valley Transportation Authority’s (VTA) is proceeding with its 16 mile long, two-phased extension of BART from the current Warms Springs terminal all the way through San Jose to a future terminal station in Santa Clara. Phase I, covering the first 10 miles of the project will be constructed mostly on viaduct and include the Milpitas and Berryessa Stations. Phase II will proceed from Berryessa for six miles in mostly subway and include the Alum Rock, Downtown San Jose, Diridon and Santa Clara stations. Phase II is where things really get expensive. According to the EIR, the total cost of Phase II is projected to be $4.7 billion. It is anticipated that five of the six miles of this phase will be tunneled 65 feet below street grade (equivalent to the height of a six story building) and that diameter of the hole needed for the entire 5 miles is 55 feet 10 inches. This raises several questions:

TunnelTrain1. Why is the tunnel diameter between stations as large as it is inside the station? In stations, to accommodate the width of two BART trains, one on each side of the proposed 24-foot center loading platform plus safety walkways plus the platform, the stations are placed in a tube whose outside diameter is a humongous 54 feet 2 inches. But the four stations account for only 10% of the length of the subway. So why should their width determine the size of the tunnels in the rest of the 5 miles? Sizing the sections between the stations based upon need rather than on what happens inside the stations would reduce the required subway excavation by at least 60%. There appear to be at least two ways of avoiding so large a subway diameter between stations. The first would be to replace the center loading platforms with two side loading platforms, thereby allowing the tunnel diameter to be reduced from 55 feet 10 inches to about 35 feet. The second would be to separately excavate two 25 foot diameter tunnels instead of the proposed 55 foot 10 inch diameter tunnel.

2. Why is the subway so deep? San Franscisco’s Market Street subway contains three levels: the mezzanine level, the Muni level and the BART level. Yet the BART track level lies only 70 feet below street level. Why should the bottom of the San Jose subway…with only one train level…be 121 feet down (65 feet to the top of the subway plus the subway diameter of 56 feet)?

3. With respect to the stations themselves, why so narrow a center-loading platform? Since the Region is projected to continue to grow significantly in both jobs and population, and since subways usually tend to hang around for hundreds of years, it seems likely that a 24-foot wide platform would become overcrowded long before the end of the economic life of the subway.

Tunnels are frequently trumpeted as virtually eliminating disruption at street level . And that’s true…between stations. But stations, whether tunneled or not, need significant vertical access and other street disrupting elements including escalators, emergency stairways, elevators and utility relocation. As anyone who has witnessed the 5-year construction mess that San Francisco’s  “you-won’t-even-know-we’re-there“ Central Subway has made of Chinatown knows full well.

Needless to add, if the need to conserve on construction funds ever arises, a tighter construction budget could be accommodated. Optimal savings could be achieved by placing the subway as close to street grade as possible and by significantly reducing the size of the tunnels between stations.

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