The sweet, sharp smell of natural gas hung in the air Monday morning, expelled from a punctured underground gas line between Cooke Hall and the Civil Engineering Building, forcing the evacuation of four University buildings.
A construction worker digging a hole with a 24-inch auger — a vehicle with a large drilling bit — pierced a marked gas line on Pillsbury Drive, causing a plume of dirt and natural gas to shoot up in the air.
Cooke Hall, the Civil Engineering Building, and the Aquatic and Recreation centers were evacuated by University Police and fire department officials, as two crews from Minnegasco worked to cap and repair the damaged pipe.
It is unclear if the site had been marked incorrectly or if the operator of the auger was at fault. If it was mismarked, Minnegasco is liable for repair costs; otherwise, the contractors will shoulder the expenses.
The owner of Total Construction, the company hired by the University to dig post holes on campus, said the University was responsible for having the digging locations checked and any gas lines marked.
However, contractors are typically responsible for getting sites marked before digging, said Tim Busse, of Facilities Management.
Also, digging within two feet of a marked gas line can only be done by hand, said Michael Austin, who was on-site monitoring gas levels for the University’s Environmental Health and Safety department.
There were no injuries, explosions or fires as a result of the gas leak. According to gas and University officials, the rupture was not major, but emergency crews responded conservatively to the incident.
“Anytime you have a gas leak, it’s serious,” said Dennis Homolka, a Minnegasco supervisor on the scene. There was no major danger to people in the area, just “probably to the operator of the machinery,” he said.
University officials and emergency crews were concerned about natural gas being trapped underground in air pockets or being vented along other underground pipes into neighboring buildings.
Natural gas is lighter than air, and although combustible, it is not toxic, Austin said. A sulphur compound is added to natural gas in order to make small quantities smell stronger for easier detection. The odorant is toxic.
University police and 16 firefighters arrived on the scene at 9:50 a.m., blocking off all traffic from Church and Union streets and Pillsbury Drive. Minnegasco and University officials arrived soon afterwards.
The site was under control by 11:30 a.m., said Frank Kurth, Station 19 fire captain.
“Our biggest problem was getting pedestrians to obey the yellow (emergency) strips,” said Judson Freed, assistant director of the University’s Emergency Management department. “I even had people going under the yellow tape.”
Gas workers dug a hole about 20 to 30 feet from the leak to reach the plastic gas line and squeezed it with a vice-like device to shut off the flow of gas to the leak. They then applied a temporary seal to the leak, as other monitors checked out the buildings for any gas pockets that might have collected. Each building was given a clean bill of safety.
Gas detectors measure the percentage of natural gas in the air by volume. If gas levels of 1 percent — the lowest explosive concentration level is 5 percent — are found, the detectors go off, and gas crews work to ventilate the area.
“What happens a lot, even if there is no gas, is people smell it because they think there should be some left,” Austin said.