Abstract A disastrous gas explosion in a tunnel under Los Angeles in 1971 took the lives of 17 workers. Construction was halted for 2 years while the owner, the contractor and OSHA decided how to proceed safely. Many warning signs preceded the event, but were not fully acknowledged or addressed. A criminal trial for negligence and new State safety orders has resulted in more strict procedures. Tunneling in areas where hydrocarbons are present require special precautions and special procedures.