Ground water at the two Scholl Canyon landfills in Glendale and seven other locations from Oxnard to Pomona is threatened by the liquid waste produced when methane is extracted from decomposing garbage, state water officials say.
Samples of the liquid, called gas condensate, taken from the nine landfills all contained unacceptable levels of hazardous chemicals, according to a study conducted by the state-run Los Angeles Regional Water Quality Control Board. The study, begun after contamination of ground water was found at several landfills in 1984, was released last week at a regular meeting of the regional board.
At the meeting, the board considered ordering all the landfills to stop the condensate disposal within 90 days. But several of the landfill operators argued that the state had overestimated the condensate problem and that more tests and more time were needed to solve the problem.
The board delayed any action until April. In the meantime, the landfill operators, including the county and city sanitation departments, have been told to devise plans to eliminate discharge of the liquid.
The northerly part of the two Scholl Canyon landfills was closed 10 years ago and converted into a municipal golf course and recreation area. However, methane is still being extracted there. Most of it is burned to fuel a small electrical generating plant.
Even before the state proposal was made, the city was planning to build a treatment facility and sewer line disposal system for the 20 to 50 gallons of the liquid that is now collected daily above ground at the generating plant and returned to the landfill, according to Ron Stassi, Glendale's power management director. Stassi said the city would simply store the materials in a holding tank if such a facility is not completed in time to comply with any possible state order.
However, the city also collects about 85 gallons a day of the liquid in underground traps beneath the old landfill and allows it to leach back into the soil, according to state records.
Stassi said it would be much more difficult to change that underground system.
"The city would like more proof that it is polluting the water table before taking any action on that," he said.
The other landfill in Scholl Canyon is still open and is run by the county. Methane gas collected there is burned on the site, but about 122 gallons a day of the byproduct condensate drains back into the landfill, according to state records.
State officials say that there is no potable water directly beneath Scholl Canyon. However, they are concerned that the chemicals could travel in plumes and pollute well fields elsewhere in the area. Analysis of the condensate at both landfills shows high concentration of such hazardous materials as toluene and benzene, according to the state.
For years, many landfills in the region, including some that are closed, have had systems in place to extract methane, which is produced when bacteria and other microorganisms consume buried garbage.
As the waste decomposes, methane, carbon dioxide and other gases are released. If the methane is not collected, it can migrate through the ground, creating an odor and posing a risk of explosion if it collects in enclosed spaces.
Gas-extraction systems are typically a network of perforated pipes sunk into the layers of aging waste, said Steve Maguin, head of Los Angeles County's Solid Waste Management Department, which runs the still-operating part of the Scholl Canyon landfill and three others on the state's list. A vacuum pump pulls any gas accumulating in the waste into the pipes. It is then burned in flares or used to power electrical generators.
The condensate is unintentionally created as the methane, water vapor and other gases, all warmed by chemical reactions that occur when the microbes devour the waste, cool as they are drawn into the pipes. Condensation forms in the pipes in a process similar to the misting of a window as hot breath hits cool glass.
In most gas-extraction systems, the condensate trickles down the pipes to traps at low points in the pipe network. Until now, in most cases, it has been allowed to drain from the traps directly into the underlying soil.
Officials first realized that gas condensate could carry toxic chemicals into ground water in 1984, after extensive testing at landfills in West Covina, Azusa and Monterey Park disclosed that such pollution had taken place, said Raymond Delacourt, senior waste resource control engineer for the regional board.
The board ordered those landfills to stop discharging gas condensate and instead have it hauled to licensed toxic-waste dumps. That is also when the board started the broad study of all landfills within its jurisdiction--encompassing most of Los Angeles and Ventura counties--that extracted gas and might have a condensate-disposal problem, Delacourt said.
The 30 or so landfills in the area that have gas-extraction systems were assessed, he said.