New Fire Surpression Systems to Make Tunnels Safe for Flamable Trucks

One of the issues concerning proponents for replacing the Alaskan Way Viaduct with another elevated structure is the ability to move flammable cargos to Ballard. Some fear that tunnel options will cut off Ballard from critical fuel supplies and pose public safety threats if fuel trucks are forced to use surface streets through downtown. Many assume that new tunnel options would restrict flammable cargo from being transited through them.

There is no doubt that tunnel fires can be very hazardous. One of the worst tunnel accidents occurred in France in 1999 as reported by an article published by The Independent where 35 people lost their lives in a 40 vehicle pile-up. The vintage 1960’s era single bore tunnel was lacking modern fire suppression, escape routes and adequate ventilation according to investigators. Much has been learned since then says experts.

A number of recent patents filed for tunnel fire suppression systems is evidence that tunnel builders have made extensive progress in making tunnels safe for trucks, busses and cars. One such technology uses a breathable gas to dowse flames, allowing fires to be quickly extinguished in enclosed tunnel environments. Extensive work has been done to retrofit tunnels in Japan and Europe with automatic water spray and mists systems which reportedly cool the air quickly around a fire to minimize the effect of hot gasses.

It is not clear yet what fire suppression technologies will be used in a bored tunnel option under downtown, but it is apparent that engineers have a wide range of options to consider. Citizens for Seattle Tube is pressing engineers to come up with a way to allow safe passage of freight through the 2.2 mile long twin bore tunnel it proposes under 6th avenue connecting South Lake Union with the Sodo District.

A few interesting resources:

Challenges for use of fixed fire suppression systems in road tunnel fire protection

Comparison of Fixed Fire Fighting System Effectiveness in Road Tunnels-
High-Pressure Mist vs. Standard Sprinkler

Numerical Simulation of Water Mist Suppression of Tunnel Fire Scenarios

Latest Tunnel Design Concepts For Complete Fire Safety [Download PPT File]

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