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Tunnel Safety |
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“Because of the confined environment, accidents in tunnels, and particularly fires, can have dramatic consequences. The fires in the Mont Blanc and Tauern tunnels in 1999 and in the Gotthard tunnel in 2001 have put the risks in tunnels in the spotlight again and call for decisions at the political level.”1
“Accidents are normally caused by a combination of several factors. In the case of accidents in tunnels the factors could be related to characteristics of the tunnel – the length of the tunnel, the illumination, the portal height, the curviness, the longitudinal gradient…”
Accidents in tunnels and other underground structures often lead to serious consequences, more serious in general than would have been the case in the open air. In addition to the serious direct consequences in the tunnel, large societal consequences are associated with the closure of such life lines.”
It is important to keep in mind the following special distinctions about tunnel engineering and operation:
· Vehicles burn, not tunnels. · People do not behave as engineers would like them to behave. · Fires can " jump" from one vehicle to another and involve more vehicles (and therefore more fuel) than expected. · Although the severity of fires is normally discussed in terms of fire size (heat release rate measured in megawatts), the rate of fire growth is equally or even more important and must be evaluated. · The height of the tunnel ceiling affects the rate of fire growth. Low ceilings increase heat [the ceilings in the Alaskan Way deep bored tunnel are only going to be 16.5’ high] · Ventilation promotes the spread of fire, and longitudinal ventilation can promote the spread of fire longitudinally in the tunnel. · Fire departments need clear response plans supplemented by training and drills.
For these reasons careful consideration of risk and safety in tunnels is necessary.”2 However in the case of the Alaskan Way Deep Bored Tunnel project, the careful consideration that the public has a right to expect and should be able to depend upon for their safety is nowhere in sight. Rather than building a world class tunnel (as was promised), instead the Federal Highway Administration (FHWA), Washington Department of Transportation (WSDOT), and the Seattle Department of Transportation (SDOT) are compromising the public’s safety. Their goal is to get the tunnel built as quickly as possible before the public can reject the compromises that are going into this project. Rather than designing a tunnel that abides by the high engineering standards and criteria set out in the assorted design and engineering manuals used by WSDOT and its engineers, including the WSDOT Design Manual, American Association of State Highway Transportation Officials (AASHTO), A Policy on Geometric Design of Highways and Streets, National Fire Protection Association Publication 502, Standard for Road Tunnels, Bridges, and Other Limited Access Highways, and the AASHTO publication, A Policy on Design Standards Interstate System, WSDOT with the complicity of FHWA is designing a tunnel that deviates substantially from those guidelines, which means that the end result will be a tunnel that is technically built to code, but realistically is substandard in terms of safety and engineering.
Before the ink was barely dry on the Governor’s agreement to build the tunnel WSDOT was already thinking of ways to cut corners in order to bring about this impossibly under-estimated, under-funded tunnel project. First to go in the project in order to save money and time is the public’s safety. Early this year WSDOT filed three design deviations with the FHWA, requesting federal approval to deviate from the engineering standards that are meant to ensure the highest level of safety and engineering for a tunnel-based highway. Those design deviations are for narrower shoulders in the tunnel, non-regular ramps, and for grade modifications which negatively affect the tunnel’s safety and environmental footprint: · Design Deviation Request 1 - Shoulders · Design Deviation Request 2 - Ramps · Design Deviation Request 3 - Grade
_________________ 1 “Identification of Indicators to assess the Implementation of the White Paper on European Transport Policy.” European Commission Directorate General Energy and Transport, Institute of Studies for the Integration of Systems. 2 Kohler, Jochen, Matthias Schubert, and Michael Faber. "Analysis of Tunnel Accidents Using Bayesian Networks." 5th International Probabilistic Workshop. Institute of Structural Engineering IBK, ETH Zurich. (2007): Print. |
