BART Phase II in Santa Clara County is 6.3 miles long including 4.7 miles of subway being designed and built by the Santa Clara Valley Transportation Authority (VTA). According to the Federal Transit Administration’s estimate of last Fall, the price of Phase II was projected at $9.14 billion, or $1.45 billion per mile. The table below might help to explain why BATWG and other like-minded groups have tried so hard to find ways of bringing down the cost while at the same time improving the convenience and safety of the project.
The table is from a comprehensive ENO study of the urban rail project costs of nine countries throughout the world. For the report see: https://projectdelivery.enotrans.org/international/
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Here again are our concerns, updated by recent events:
BATWG has long had concerns over the large size and great depth of the single bore tunnel. The size of the planned tunnel has recently been increased from 48 feet to 53.4 feet in diameter (the size of a five story building).
The VTA has apparently discarded the earlier twin-bore alternative (featuring two tunnels each 20-feet in diameter) and is no longer willing even to discuss it. The VTA claims that the single bore with a diameter of 53.4 feet would be cheaper. Yet compared to two 20 foot tunnels a tunnel of this size would generate 1,850,000 additional cubic yards (equivalent to 155,000 addition truckloads) of tunnel spoil to be excavated and hauled away. Costs would be further increased because the large tunnel would require significantly thicker concrete tunnel lining and because all the vertical access structures would need to be deeper, longer and more expensive to maintain.
On August 26th, something new was added to the mix. It is now clear that at the Downtown San Jose Station VTA is planning to limit the width of the center-loading platform inside the 53.4 foot tunnel to just 22 feet. Given the significant number of new riders who will be attracted by the newly added southern access passageways and the extensive transit-oriented housing planned for along the route, so narrow a platform could easily lead to severe future capacity and safety problems.
It has never been clear why the BART Phase II subway needs to be so deep. Utilities are usually located relatively close to the surface. In the name of rider convenience and fiscal prudence the subway, whatever the configuration, should be kept as close to street grade as possible.
The huge single bore tunnel is being justified as necessary to avoid building the approximately 900 foot long downtown station by cut-and-cover methods (such as is done everywhere else in the world). In San Jose the cut-and-cover approach is frequently characterized as requiring the “shut down Santa Clara Avenue”. “Shutting down Santa Clara” is a gross exaggeration. Cut and cover excavation is virtually always phased in a manner that keeps at least half the street open at all times. In fact, except at the beginnings and endings of construction periods, the relatively short cut-and-cover sections of street located directly over the stations are entirely supported by temporary timber decking. For this reason streets over stations are typically returned to full use during most of the construction period while the major work goes on below.
On August 26th, the VTA’s Mr. Takus Salpeas stated that cross passages between twin bore tunnels are inherently unsafe. Cross passages are used throughout the BART system with little difficulty. Under the able direction of Chief Engineer George Hammond, BART’s outstanding team of civil, structural, geotechnical and tunnel engineers designed and built the civil parts of the original BART system, which have proven to be very safe for a half a century.
Mr. Salpeas also expressed the opinion that because of space on the mezzanine level there was no need for a large loading platform at the platform level. The fact that pre-COVID, BART’s 35-foot wide platforms in downtown San Francisco were often packed with riders entering and leaving trains demonstrates otherwise.
We’ve heard that the resistance to cut-and-cover station excavation developed because the handful of businesses adjacent to the roughly 900-foot long Downtown station were fearful of being disrupted as the businesses along San Francisco’s Market Street were disrupted during the construction of the original BART subway. It appears that these business people were unaware of the fact that because of an unfortunate S.F. City Hall decision to maintain the existing streetcar service along Market throughout the BART construction period, things were vastly more complicated and expensive than they otherwise would have been. There are no streetcars on Santa Clara Avenue.
The SAP Sports Center is reportedly a proponent of the all-subway approach. Given the proximity of the Julian Street I-87 off-ramp and the configuration of the SAP parking lot, 900 feet or so of cut-and-cover station under Santa Clara Avenue at this location also does not appear to be a show stopper.
As indicated previously if there were ever a project in need of independent professional review and evaluation, BART Phase II is it.