Byproduct of Methane at 9 Landfills May Imperil Water

Ground water at landfills in Calabasas, Sun Valley 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 a variety 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 the discharge of the liquid.

System in Place for Years

For years, many landfills in the region--including some that no longer accept waste--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 operates the 416-acre Calabasas 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.

Risk Discovered in ’84

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.

The landfills that were tentatively identified as having unacceptable condensate-disposal systems are: Sheldon-Arleta Landfill in Sun Valley, Watson Landfill in Wilmington, Calabasas Landfill in Agoura, Mission Canyon Landfill in Los Angeles, Puente Hills Landfill in La Puente, Santa Clara Landfill in Oxnard, Spadra Landfill in Pomona and two landfills in Scholl Canyon, one operated by the county, the other by the city of Glendale.

The level of risk posed by the disposal of gas condensate at the landfills was determined by weighing several factors, including the amount of liquid discharged, the concentration of pollutants in the liquid and the proximity of each landfill to ground water used for drinking.

One of the most serious potential problems exists at the Sheldon-Arleta Landfill, which lies near an important source of Los Angeles drinking water, Delacourt said.

The landfill is next to Los Angeles Department of Water and Power “spreading grounds,” where water brought to Los Angeles in aqueducts is released and enters the soil, replenishing San Fernando Valley ground water, according to the state report.

Evidence of Leak

There is evidence of a leak between the DWP facility and the landfill, according to the report, which pointed out: “Therefore, disposal of any liquid at this site may have a detrimental effect on the usable water.”

Another factor that put Sheldon-Arleta on the list is the porous, gravelly composition of the soil beneath the landfill, which would allow any pollutants to migrate away from the site. The landfill was built on what was formerly a gravel pit, the report said.

Tests of condensate from the city-run landfill turned up relatively low concentrations of hazardous substances, including the solvent toluene, but the dump made the list because the estimated amount of condensate produced and dumped there is high--227 gallons a day, according to the regional board’s report.

Robert Alpern, principal sanitary engineer for the city Bureau of Sanitation, said the bureau recognizes the problem. A new sample of gas condensate was drawn Tuesday and is being tested by city laboratories for the presence of hazardous chemicals, he said. He said a plan will be worked out for eliminating any pollution that is found.

A sample of gas condensate from the Calabasas Landfill, which accepted toxic waste until 1980, showed high levels of a number of chemicals. According to Maguin, who provided the test results used by the regional board in its assessment, the sample contained 70 parts per billion of benzene. That is 100 times the state-set maximum of 0.7 ppb for that suspected carcinogen.

The sample also contained 200 ppb--five times the state limit of 40 ppb--of methylene chloride, a common industrial solvent that is suspected of causing cancer.

Toluene, another common solvent, was detected in the sample at a concentration of 660 ppb. The state limit is 100 ppb.

Maguin said the state may have overestimated the hazard posed by these chemicals. He said the actual amount of condensate produced at the Calabasas Landfill is about 30 gallons a day, not the 125 gallons a day listed in the state report.

Widely Distributed

Moreover, the liquid drains into the ground from 24 traps in the gas-collecting system, he said, adding, “It’s distributed over a wide area” and thus is diluted and its movement slowed.

Delacourt agreed that pollutants would become diluted as they migrate into the soil, but, referring to the documented contamination of ground water in 1984, he said the state does not want to risk having a similar situation develop at other landfills.

Alpern said any solution to the gas-condensate problem is going to be costly. “We’d have to seal the condensate traps with concrete, then we’d have to have a licensed Class 1 hauling firm take this material away,” he said, referring to expensive commercial firms that dispose of toxic waste.

But, he added, the city plans to cooperate with the state water board when it decides how to proceed in April.