Wells Drilled to Evacuate Methane Gas From School

City work crews Thursday began drilling wells at Francis Polytechnic High School in Sun Valley in an effort to dissipate explosive methane gas that has been seeping for a week into the boys’ gymnasium from the Sheldon-Arleta Landfill across the street.

Officials said late Thursday that three of five gas evacuation wells were completed and in service and that the other two would be drilled today.

William N. Madson, area facilities director for the Los Angeles Unified School District, said the school will be in session Monday but the gym will remain closed if air tests show that methane still is present in the building.

Madson said the gym was closed the afternoon of March 28 after a buildup of the odorless, colorless gas triggered an alarm system in the school at 12431 Roscoe Blvd. The weeklong spring vacation began at the end of classes the next afternoon.

Error With Landfill Valve

Officials with the Los Angeles Bureau of Sanitation, which owns the inactive landfill, said they believe the gas, emitted by decaying trash, leaked out of the dump during a three-week period in March because of an error by an employee who shut off a valve that is part of the dump’s gas capture system.

Officials said that during the past week methane levels in air inside the Poly High School gym have ranged from zero to as much as 27% in isolated areas. Experts say a 5% concentration of methane could burn or explode in the presence of a spark.

But Madson said the highest levels measured, although five times greater than the so-called “lower explosive limit,” have been isolated in areas such as cracks in the floor and vent holes. The concentration falls away quickly when measuring devices are lifted off the floor. As a result, he said, the risk of a large fire or explosion has been minor.

He said the gym has been closed “as a precaution because we have students involved. I have no intention of taking any chances with the students or the employees who work here.”

On March 21 a methane explosion rocked a clothing store in the Fairfax area, injuring 22 people. That gas was emitted, not from a landfill, but from abandoned oil wells.

Gas Capture System

In migrating about 300 yards from the landfill to the gym, the methane eluded an elaborate gas capture system operated by the Bureau of Sanitation.

Robert M. Alpern, principal sanitary engineer with the bureau, said he believes the gas capture system was temporarily overwhelmed after an employee mistakenly turned off a valve on March 1. He said the error was discovered and corrected on March 18 but that a plume of the gas evidently had already migrated beneath Wicks Street to the school.

The 40-acre landfill, which was closed in 1974, has a clay barrier on two sides to block gas migration, 36 gas evacuation wells in its middle and on the other two sides, and six flares to burn off the gas.

Alpern said some of the gas is not burned but piped to the Department of Water and Power’s electric power plant nearby for use as generating fuel. He said DWP officials have admonished the sanitation bureau to keep air out of the gas to reduce the risk of a fire or explosion in DWP pipelines and compressors.

Alpern said that on March 1 a dump employee saw what appeared to be holes in a pipe he believed was connected with the gas supply line. In an effort to keep air out of the gas supply, he shut off a valve he erroneously thought would close off the pipe.

In reality, Alpern said, the valve shut down some of the gas evacuation wells.

On March 18, he said, Bureau of Sanitation workers measured elevated levels of gas at Wicks Street, which runs between the landfill and the boundary of the school. The flow of gas apparently had been too great to be captured by the remaining wells, and some of the gas crossed under Wicks and beneath the campus.

Alpern said no methane buildup had been detected on the Sharp Avenue side of the landfill, which also lacks the clay barrier.

Alpern said that the sanitation bureau checks the high school for gas every Thursday and that on March 21 no methane was detected, even though the gas had already escaped.

He said bureau and school officials did not decide to dig the wells until Tuesday, when gas levels in the gym appeared to be rising.

Warning Lights

He said that on March 29, the day after the methane buildup set off warning lights in the school’s administrative offices, no methane was present in the gym, leading officials to think the gas might already have dissipated.

But on Monday, the first day of school vacation, there was methane in the gym, and the level was still higher on Tuesday.

At that point, officials decided to try venting the gas rather than let it take “its own sweet time,” Alpern said. “We all came to a decision that . . . we had to do something positive.”

Alpern said bureau officials are taking steps to make sure no more such errors occur. He said valves that are part of the gas collection system will be color-coded and employees will be given a written description of what each valve does.

Holes Drilled

As Alpern spoke, workers drilled holes 15 to 20 feet deep through the pavement adjacent to the gym and inserted the first of five plastic tubes. By early afternoon a vacuum device had been attached to the first of the wells, and a measuring device called an “explosimeter” showed that gas was being pulled from the ground.

Alpern said the first gas collection equipment was installed at the landfill in 1971, three years before it closed. That system proved inadequate, and both the boys’ and girls’ gyms at Poly High were closed during part of 1980 because of high concentrations of methane.

The gas capture system was expanded, but another methane buildup occurred at the school in 1983 after the failure of one of the blowers that push the gas into the flares.

Madson said that, during the past week, repeated air measurements have turned up no trace of methane in the girls’ gym or in the auditorium, the other two buildings that have been affected in the past.