Fairfax Gas Blast Tied to Decaying Organic Matter
A Los Angeles city task force has determined that decomposing organic matter, not an old oil well, was the probable source of methane gas that exploded in the basement of the Ross Dress for Less store near Farmers Market in March, injuring 21 people.
Its report--submitted Wednesday to the City Council--also outlined a series of safety measures to help prevent any recurrence of the explosion in a 400-block area around the store. Specifically, the panel suggested that homeowners with basements be required to install alarm systems and that owners of larger buildings take other steps that could cost thousands of dollars.
While the neighborhood does lie atop an abandoned oil field, chemical analysis of a gas pocket found below the store indicates that it was formed “from the decomposition of buried plant materials at no deeper than 100 to 200 feet below ground level,” the report said.
Such seepage has been going on for thousands of years, it concluded, but the streets, buildings and parking lots erected over several decades have acted as a huge cap. This extensive construction has kept the gases underground except where they escape through open spaces, such as residential yards and the nearby La Brea Tar Pits.
The problem was exacerbated in the last decade, however, because of unusually high rainfall and a decision by Beverly Hills, adjacent to the area, to buy water elsewhere instead of removing it from wells drilled underneath the Fairfax District, the report said.
These factors combined to raise the underground water level, forcing a methane pocket that had formed 40 feet underground to rise to the surface, where it passed through small openings between the floor slab and foundation walls of the Ross store, leading to the March 24 explosion.
“Once inside, the gas was contained in a room without ventilation and with a source of ignition,” the report said.
It did not identify what that source was, but Fire Department Battalion Chief Donald Bartlett said it may have been a coffee machine or other electrical appliance in an annex housing the store’s employee lounge, which suffered severe damage in the Sunday afternoon blast.
“Being lighter than air, the methane probably built up at the top of the room until there was enough to creep down to whatever the (ignition) source was, and then it let go,” he said.
Oil, Gas Deposits
While no evidence was found to connect oil and gas deposits more than 1,000 feet underground with the explosion and fire, the report said “they still must be considered a potential source for natural gas seepage and a possible migration path for gas to the surface.”
The report concluded that it was impossible to predict the blast, but suggested a series of steps that might give early warning of future gas buildups and lessen the danger of a repetition.
It suggested that an area stretching roughly from Sweetzer Avenue on the west to La Brea Boulevard on the east and from 1st Street on the north to Olympic Boulevard on the south be declared a potential risk zone, of which about 100 blocks would be declared an area of high potential risk.
If these recommendations are adopted by the City Council, owners of one-family dwellings with basements would be required to install commercially available gas detectors, costing between $600 and $2,500. Owners of larger buildings would be asked to put in gas-control vents and developers of new buildings would have to install plastic sheeting underneath foundations to block gas seepage.
Councilman Zev Yaroslavsky, who represents about half of the potential risk zone, said the recommendations will require considerable discussion, since most homeowners are likely to find the expense to be excessive.
“It’s not a foregone conclusion that we will just blanket that area with detection devices at the public’s own expense,” he said. “But safety is also a concern. It may be that in the core area we may have to bite the bullet (and require gas detectors).”
The city, he added, would not be able to foot the bill, though funds from the federal government or low-interest bank loans might be available.
An aide to Councilman John Ferraro, who also represents part of the area, expressed concern that the danger zone designation would cause property values to drop and questioned whether the safety measures were appropriate.
“We don’t want to give anybody a false sense of security,” Bob Hedrick said. “There is in the area a methane problem. That’s been made painfully obvious.”
On the other hand, he said, “It’s just a question of whether the negative impact you’re going to hand on these people’s homes is entirely justified in light of the reality of the situation.”
Homes Less at Risk
In any case, Frank V. Kroeger, general manager of the city’s Department of Building and Safety, said homeowners are less at risk than other property owners because most houses have unpaved yards that generally allow natural ventilation of any gas to reach the surface.
Kroeger’s comments are in an address prepared for a hearing Friday on the aftermath of the gas explosion, to be chaired by Rep. Henry Waxman (D-Los Angeles), chairman of the House subcommittee on health and the environment. The hearing will be held at 9 a.m. at the West Wilshire Recreation Center at 141 S. Gardner St.
Another scheduled witness, Simon Cordova, chief deputy state oil and gas supervisor, said he agreed with the conclusions of the task force, since the old oil wells underneath the Fairfax District have been plugged since early in the century, and the location of many of them is not known.
“So the best thing to do is to prevent the accumulation of gas, to detect where the seepage is going on and vent it, rather than seek wells drilled 80 years ago that may not be causing this,” he said.
The 16-member task force was made up of representatives of numerous agencies, including the Fire Department, county Department of Public Works and the state Division of Oil and Gas.