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
Who will bear the risks, costs and liability?
The Central Subway’s soft costs are over 23% of the project budget. While SFMTA staff use project funds for wages, a parallel consultant has been retained for project management (PM)—further shielding the City from liability. The PM consultant’s contract minimizes its own liability. In a crisis, the City and its PM consultant will shift blame to design professionals and construction contractors.
The City’s construction specifications, general conditions and contracts are crafted by City Attorneys to absolve the City of liability—loading liability on design professionals, general contractors, subcontractors and suppliers. Taxpayers will pay for cost overruns, resulting in decreased Muni operating budgets and transit service.
A Case in Point: The Pagoda Theater TBM Extraction – The SFMTA recently proposed extraction of Tunnel Boring Machines (TBMs) at the Pagoda Theater site. The Pagoda Project’s public process and fragile geotechnical conditions are systemic of the Central Subway’s overall approach. Much of hilly San Francisco has underground water/ streams, subsurface voids, rubble and inconsistent geological conditions—in addition to older buildings, brick foundations, shallow footings, seismic vulnerabilities and hidden conditions. Not all conditions have been studied.
- Merchants and property owners, adjacent to the Pagoda, have not been consulted on engineering plans—in order for their vetting of design adequacy, risks, rights and compensation for damages (operational and structural).
- The SFMTA’s initial design includes an approximately 50’x50’x46’ deep concrete TBM Retrieval Box, with 66’ deep perimeter secant pile walls. The concrete box is within 18’-7” of the adjacent 1907 brick warehouse building.
- An independent geotechnical engineer submitted three letters, questioning the design’s efficacy and warning of likely damage to adjacent buildings due to subsidence.
- In a Fee Proposal, the SFMTA’s own engineering consultant confirmed that potentially adverse effects to adjacent structures, historic buildings and park properties due to ground movement, groundwater inflows, ground loss and settlement had not yet been analyzed— necessitating new geotechnical investigations.
- No nearby building has foundations or basements deeper than 10 feet below grade.
- No part of the 46-foot excavation will likely be in competent bedrock, digging 36 feet below the groundwater table.
- There are inadequate geological/ structural studies of adjacent properties and historical studies of the region.
- Underground springs flow from Russian Hill under the Pagoda Theater and adjacent buildings. Before 1906, on Filbert near Columbus, there once stood the “Palace Baths”, which tapped into underground springs. In the past, neighbors could hear rushing water underground.
- The previous Muriel’s Theater project at the Pagoda encountered underground water, increasing construction costs. Also, removal of gas tanks at the old corner gas station hit underground water.
- On Stockton Street at Washington Square, construction for Moose’s Restaurant encountered underground springs from Telegraph Hill, which flooded neighborhood basements periodically. A workman in the dark basement dropped a tool and heard a splash. His light revealed that he had just missed falling 20 feet into a well.
- The nearby North Beach Pool subsided because of an underground stream, leading to a 2005 structural retrofit.
History of Accidents: Deep Excavation and Tunneling
Relative to other construction techniques, deep excavation and tunneling have extensive failures—especially at sites with older buildings, fragile geological conditions, soil inconsistency, underground water and seismic vulnerabilities. As required by the Federal Transit Administration, all cost overruns are the responsibility of the City & County of San Francisco and its contractors and subcontractors.
LOS ANGELES: Subway sinkhole collapses Hollywood Boulevard. http://articles.latimes.com/1995-06-23/local/me-16226_1_hollywood-boulevardhttp://articles.latimes.com/1995-10-20/news/mn-59073_1_tunnel-collapse
COLOGNE: Historical ArchivesBuilding collapse with two dead:
SEATTLE: Large sinkholes above TBM sewer tunnel.
SAO PAULO: Subway’s deadly collapse with seven dead. http://enr.construction.com/news/transportation/archives/070129a.asp
CAIRO: Downtown TBM Tunnel Collapse:
KOREA: Incheon Subway tunnel collapse with one dead.
GUANGZHOU: Video—Subway construction sinkhole swallows entire building complex.
BUDAPEST: TBM hits unknown water pipe, causing shaft collapse.
BUDAPEST: Highway tunnel collapse and scandal.
TAIWAN: Taipei Expressway tunneling had eleven collapses with twenty-five deaths.
STUTTGART: Tunnel sinkhole and nine dead.
TORONTO: TBM tunnel collapse.
PORTO, PORTUGAL: Three TBM tunnel collapses with one death in house collapse.