A person using mechanized equipment to dig on the Nyack College campus inadvertently caused Tuesday's gas-fueled explosion after hitting a gas line and dislodging it from its coupling, Orange & Rockland Utilities said Thursday.
Authorities aren't sure who was doing the digging, and while they say Nyack College is fully cooperating with the police and utility investigations, the college hasn't been able to tell them whether an employee or contractor was responsible. What they do know: The person operating the backhoe or other piece of equipment didn't consult the utility or call 811 as is required by law to mark out the locations of underground lines before beginning to dig.
Investigators from the Rockland County Sheriff's Office and the utility company realized what happened after running pressure tests on gas mains. After diagnostic tests showed the mains were not the problem, O&R spokesman Mike Donovan said investigators realized pressure dropped off on a gas line that runs through the campus toward an old gymnasium and the Sky Island Lodge, the two-story academic building that exploded Tuesday, injuring eight people.
OFFICIALS: BACKHOE LED TO PROBLEM
The person doing the digging didn't actually puncture the two-inch, vinyl-coated steel gas pipe, Donovan said, but the impact of the strike dislodged the pipe from its coupling about 100 feet away in a wooded area.
"Our working theory is a backhoe was working back there and somehow snagged the line...and ended up pulling the gas service line out of the main up above," Donovan said. "These guys probably didn't know they hit anything."
Investigators knew they'd found the spot where the gas pipe disconnected because it "rose up almost like a big ant hill, a big bulge" from the gas buildup underneath the dirt, Donovan said.
On the other end, gas levels were rising inside the Sky Island Lodge. Most people think of a cigarette lighter or stove burner sparking a gas buildup, but Donovan said buildings and homes are filled with devices that could ignite built-up gas.
"A doorbell could set it off. A telephone could set it off," he said.
Officials aren't sure how much time passed between the underground gas pipe being dislodged from its coupling and the explosion, but Donovan said muddy tracks and fresh vegetation cuts at the scene of the construction indicate the two events happened in relatively quick succession.
PREVIOUS GAS LINE INCIDENTS
Contractors are required to consult with utility companies or call 811, operated industry group Common Ground Alliance, so they're aware of underground lines before they start digging. Gas-related explosions can be devastating and fatal, and such accidents have been attributed to amateurs as well as professionals.
Most recently, a Garnerville man hit a gas line while digging in his backyard to bury his dead dog in August 2012. That case was unusual because the man was using hand tools instead of power tools. The man quickly reported the incident and no one was injured.
Four people, including two firefighters, were injured in January 2012 when a subcontractor installing a Verizon FiOS cable struck a gas line. In that case, the contractor didn't consult 811 or the local utility, and later pleaded guilty to felony first-degree reckless endangerment, while the owner of the company pleaded guilty to felony first-degree assault.