CENTRAL SUBWAY: Liability and High Construction Risks
The Shifting of Unforeseen Costs To Contractors and Taxpayers, and why the public needs to be involved in all large development decisions before any contracts get signed and why protecting CEQA is important.
If the Central Subway Project is completed in 2019, most of today’s politicians will be out of office—“immune” from any fiscal crisis left behind. The Board and staff of the San Francisco Municipal Transportation Agency (SFMTA) will avert personal liability. Legally-crafted construction specifications will shift blame to general contractors, subcontractors and suppliers—and cost overruns will fall to taxpayers. However, in matters of life-safety, political immunity from construction failures should not be so easily granted, particularly when basic engineering and physics have known consequences.
Are high risks known?
Yes. In the Federal Transit Administration (FTA) letter of 1-10-10 to the SFMTA:
“The Central Subway Project is a high risk project located in a densely populated urban center. It is the largest, most complex project ever undertaken by SFMTA.”
The FTA has knowledge of past construction accidents (See “History of Accidents” below) and risky excavation in older areas of Downtown, Chinatown and NorthBeach. Unlike Hollywood Boulevard’s sinkhole or Cologne’s building collapse, the Central Subway is digging in narrower streets and in closer proximity to old buildings and shallow foundations—exacerbated by hilly terrain, underground water and saturated/ inconsistent soils.
What is the likelihood of construction cost overruns?
In the SF Weekly, 2-27-13, “Central Subway: Muni’s Drilling Plan Strains Credulity”
“An audit by the firm CGR Management Consultants pegged the likelihood of the Central Subway coming in on budget at 30 percent.”
Even highly-developed countries with the best engineers have been stunned by construction accidents involving deep excavations and tunneling (See “History of Accidents” below). If the Central Subway goes over budget, the additional dollars will be taken from local Muni sources.
Have construction risks and liability been mitigated?
Not to the highest degree. Like the proposed Pagoda Theater excavation (See “A Case in Point” below), rudimentary assumptions have been made regarding geotechnical and building conditions. Nearby buildings have not had full structural analysis—only condition assessments. More pre-testing would reveal hidden aboveground and underground conditions. Standard construction procedures are insufficient, given the inconsistent soil conditions.
- For excavations underneath 100-year old buildings, into inconsistent soils with high water tables, basic physics can predict the immense forces that can stress structures, streets and utilities.
- The excavations’ lateral proximity to existing structures increases the odds of soil subsidence and cavity formations, especially with sloping hills, intervening alluvial-filled valleys and fractured rock.
- Excavating to depths from 40-120 feet, the structural loading of saturated soils, combined with the dead loads of buildings and their contents, is large—prone to increased hydrostatic pressures, collapse of voids and soil subsidence.
- The 1906 Earthquake and Fire affected the narrow streets along the route of the Central Subway, leaving remnants of rushed demolitions, underground rubble, artificial fill and voids.
- Hilly terrain and alluvial valleys propel rainfall and underground water, saturating sandy soils, creating instability, vertical displacements…..
- Inconsistent soils are difficult to stabilize by compensation grouting alone, likely requiring expensive shoring, underpinning. slurry piles, tremie concrete construction…..
- Even in recent American tunneling projects, property owners have complained of noise, sewage floods, cracked foundations and other problems—much less catastrophic collapses.
Are there fiscally prudent alternatives?
Taxpayers, designers and builders need to assure due diligence to protect their own interests. Existing and hidden conditions require thorough analysis. Project contingencies must cover cost overruns. The City’s underlying politics is to construct 2,000 foot tunnels for the northerly subway extension—-without environmental reviews. Business associations and real estate interests want to escalate land values and large development prospects. But fiscally prudent alternatives exist to conserve funds. The SFMTA plans to spend $9.15 million from its operating funds for the Pagoda Theater Project, in order to retrieve two TBMs valued at $4.4 million. Moreover, the twin 2,000 foot tunnels from Chinatown to NorthBeach will cost up to $70 million. If the TBMs are extracted or buried at the Chinatown Station, SFMTA can save $79 million—better spent on construction contingency and Muni service enhancements.
Regards, Howard Wong, AIA