According to the CBC report, fire officials confirmed that three out of five burning tankers had been extinguished with foam; the remaining two more are still on fire and at risk of explosion.

Lac-Mégantic, Québec. Click to enlarge.

According to MM&A, the train was stopped and tied down by the locomotive engineer at 11:25 PM Friday on the mainline at Nantes, a station approximately 6.8 miles (11 km) west of Lac Mégantic (and uphill), for a crew change. Subsequently, the train rolled downhill into the town of Lac-Mégantic, where the derailment occurred.

Nantes (far left), where the train was stopped, and Lac Mégantic (far right). Click to enlarge.

The engineer was not on the train, but had proceeded to his resting point at a hotel in Lac-Mégantic.

MM&A said that railway personnel were able to pull 13 carloads intact from the site at the rear of the train. At the time of its statement, the company did not know how many cars derailed. Further details will be gathered from the event recorder onboard.

The Transportation Safety Board of Canada is sending investigators.

Early speculation on the Internet suggested a BLEVE (Boiling-Liquid Expanding-Vapor Explosion) as potentially responsible for the degree of destruction reported in Lac-Mégantic, and during an onsite press conference broadcast by the CBC, one of the firefighters referenced the danger of BLEVE with two remaining tankers (at 2:37 in the video).

A BLEVE occurs when a container in which a liquid is held above its atmospheric-pressure boiling point ruptures, resulting in the explosive vaporization of a large fraction of the contents. A BLEVE generates three main hazards: blast wave, projections of container fragments and if the liquid is flammable, a fireball.

BLEVEs occur with a certain frequency: the substances that can lead to them (butane, propane, vinyl chloride, chlorine, etc.) are relatively common in the industry, as well as the installations in which they can happen (tanks and tank cars). They can have diverse origins, such as runaway reactions and collisions, but the most frequent one is the action of fire on a container. Table 22.1 (Prugh, 1991) shows a list of the most significant BLEVEs that have occurred between 1926 and 1986. As can be seen, most of these involved fatalities. Another source (Londiche and Guillemet, 1991) mentions 900 fatalities and over 9,000 injured in 77 BLEVEs occurring between 1941 and 1990.

—Casal et al., Modeling And Understanding BLEVEs

Montreal, Maine & Atlantic began operation in January of 2003 and owns more than 510 route miles (821 km) of track, serving Maine, Vermont, Québec and New Brunswick. The pulp and paper, petroleum, forest products and chemicals industries are the major sources of traffic for the railroad.

Resources

• Tasneem Abbasi, S.A. Abbasi (2007) The boiling liquid expanding vapour explosion (BLEVE): Mechanism, consequence assessment, management. Journal of Hazardous Materials, Volume 141, Issue 3 Pages 489-519 doi: 10.1016/j.jhazmat.2006.09.056

• G.A. Pinhasi, A. Ullmann, A. Dayan (2007) 1D plane numerical model for boiling liquid expanding vapor explosion (BLEVE). International Journal of Heat and Mass Transfer, Volume 50, Issues 23–24 Pages 4780-4795 doi: 10.1016/j.ijheatmasstransfer.2007.03.016

• J. Casal, J. Arnaldos, H. Montiel, E. Planas-Cuchi, and J. A. Vílchez, “Modeling And Understanding BLEVEs”, The Handbook of Hazardous Materials Spills Technology, M. Fingas, ed., 2001

• Venart, J. E. S., “Boiling Liquid Expanding Vapor Explosions (BLEVE): Possible failure Mechanisms,” Very Large Scale Fires, ASTM STP 1336, N.R. Keltner, N. J. Alvares, and S. J. Grayson, Eds. American Society for Testing and Materials, 1998