Numerical Simulation of the Howard Street Tunnel Fire , Baltimore , Maryland , July 2001

This report documents a study undertaken to estimate the thermal environment of theHoward Street Tunnel in Baltimore, Maryland, following the derailment in July 2001 of afreight train and the burning of spilled tripropylene and the contents of surrounding rail cars. Anumerical fire model developed by the National Institute of Standards and Technology (NIST)has been used to simulate the fire’s growth and spread in the tunnel. The fire model has beenvalidated for this application using temperature data collected during a series of fire experi-ments conducted at a decommissioned highway tunnel in West Virginia. The cross-sectionalarea of the tunnel and the fire sizes used in the West Virginia experiments are similar to theHoward Street Tunnel.For the Howard Street Tunnel fire, the peak calculated temperatures within the tunnel wereapproximately 1,000 ◦C (1,800 ◦F) within the flaming regions, and on average approximately500 ◦C (900 ◦F) when averaged over a length of the tunnel equal to three to four rail carlengths. Because of the insulation provided by the thick brick walls of the tunnel, the calculatedtemperatures within a few car lengths of the fire were relatively uniform, consistent with whatone would expect to find in an oven or furnace. The peak wall surface temperature reachedabout 800 ◦C (1,500 ◦F) where the flames were directly impinging, and on average 400 ◦C(750 ◦F) over the length of three to four rail cars. The steel temperature of the rail cars wouldbe expected to be similar to the surrounding gas temperature because of the long exposure timeand the high thermal conductivity of steel.