More than three months after a freakish series of explosions rocked the Near Northwest Side, killing four people, federal investigators still have not determined what caused the natural-gas surge that touched off the blasts.
A top official of the National Transportation Safety Board, which investigates pipeline disasters, said Monday that agency investigators will return to Chicago next month to conduct further tests of Peoples Gas Light and Coke Co. equipment near where the Jan. 17 blasts occurred.
Investigators also plan to take statements a week later from Peoples Gas officials ”regarding their policies and practices as it may relate to this incident,” said Charles Batten, chief of the safety board`s pipeline division.
The separate trips will mark the third and fourth times that safety-board officials have traveled to Chicago to investigate the accident.
From the start, investigators have focused on the activities of a three- man Peoples Gas crew that was performing routine maintenance on underground regulators at West Erie and North Green Streets shortly before the explosions and fires began.
As federal officials have tried to determine whether the crew failed to monitor or wrongly manipulated equipment, the three workers have been placed in what People Gas calls ”non-safety-sensitive” jobs.
But Batten refused Monday to blame the workers. And the safety board`s intention to re-examine the underground regulators indicates that officials still don`t know whether mechanical failure, human error or a combination of the two caused the explosions.
Even though the federal investigators have not ruled out equipment problems, Peoples Gas officials say the safety of residents in the West Town neighborhood is not in jeopardy.
The company has spent about $2 million in the last three months installing a new, safer gas-distribution system throughout the area where the blasts occurred.
In the new system, each home or business has its own pressure regulator, which reduces the flow of gas so it can be burned by appliances.
In the neighborhood`s old distribution system, which remains in place throughout 80 percent of Chicago, a common underground regulator reduces gas pressure for hundreds of homes and businesses.
When a regulator fails in the old system, high-pressure gas can surge into many buildings. In the new system, a regulator failure puts only one building at risk of explosion and fire.
Peoples Gas spokesman Ed Joyce said the utility understands that safety board officials will return to town May 5-7 ”to observe some testing by us at the Erie and Green regulator site.”
Batten said his agency has been busy investigating other disasters and that it is not unusual for a report to take even longer than three months to complete.
Batten said the safety board may never know for sure what caused the explosions. But he added that the agency usually writes a report offering at least a probable cause.
