Small Explosion at School : Classrooms Emptied Because of Gas Leak

An underground pocket of natural gas at Northridge Junior High School forced school officials to empty seven classrooms this week, administrators said.

The pocket was discovered Feb. 3 when gas seeped inside a classroom wall and a spark from a light switch ignited the gas, causing a small explosion, Principal Jean Williams said.

No one was injured and damage was minor, she said. A subsequent inspection found a ruptured underground gas line.

“We don’t feel there is a threat,” Williams said. “We have sectioned off the area and and are monitoring it.”

The line apparently was ruptured last spring when the school grounds were repaved, said Bill Piazza, a safety officer for the Los Angeles Unified School District. The line was replaced after last month’s explosion but the ground contains substantial amounts of natural gas, Piazza said.

“It looks like it had been leaking for about a year,” he said. Recent rains forced more of the gas to the surface and the area was sectioned off because the seepage was potentially explosive, he said.

Natural gas is not toxic but is potentially explosive when it reaches a concentration of 4% to 14% in air and a source of ignition is present, said Richard Puz, a spokesman for Southern California Gas Co.

Tests by the gas company Feb. 26 showed natural gas levels of 5% outside and less than 1% in some classrooms, Puz said.

After the explosion, about 40 holes approximately 1-by-3 feet were drilled in the asphalt to allow the gas to escape and dissipate, Piazza said. Compressed air is being pumped into the holes to speed the process, and gas levels have begun to drop.

Extent Unknown

“We have no way of knowing how much is really there,” Piazza said. “It might be a little deeper than we thought.”

The pocket’s exact location is unknown, he said.

Since Monday, the affected students have been sent to other classrooms. They will not return to their regular classrooms until the end of next week, Williams said.

District officials will continue to monitor gas levels daily.

For the past three weeks, school administrators have limited electrical use in the classrooms and have shut off wall heaters. This week, gas and electricity was shut off to the affected portion of the campus.