S. A. Healy

Methane gas was detected in a 40 feet deep tunnel that was under construction. The mining machine was automatically shut down, and all the employees were evacuated. Ten minutes later, three employees entered the area to determine if the atmosphere in the tunnel was safe for reentry. An explosive mixture of methane gas had developed in the air. Apparently, the grout pump ignited the gas and caused an explosion. The three employees were badly burned, and they died of asphyxiation due to overexposure to carbon monoxide. The Sewage Commissions had warned all contractors about the possibliity of a methane leak and contractors were told if methane was detected all work must cease for one hour.