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Oil-Gobbling Bacteria Clean Soil at Site of Park in Carson

October 11, 1987|GEORGE STEIN | Times Staff Writer

"Pacmen"--mobile little mouths that gobble as they go--is what Carson Mayor Kay Calas calls the billions of bacteria that are helping the city turn an oil-contaminated field into a park.

The bacteria--specially cultured strains of Bacillus-- have been dining on the petrochemicals that are contaminating the soil at the future Veterans Park since June 16. Once the bacteria have finished their meal, all that will remain is harmless carbon dioxide and water.

Tests by Bright & Associates, the Placentia firm seeding the oil-eating bacteria into the soil at the site, show that the process is almost complete. And the city is poised to seek bids for construction of its most elaborate recreation facility, the last project in the city's 20-year master plan.

The park, on a 10-acre site near the intersection of 223rd Street and Moneta Avenue, will have an adult fitness center, five racquetball courts, two baseball diamonds, a gymnasium and children's playground for the use of residents. Construction will cost about $6 million.

Until the city exercised its redevelopment powers and condemned the property in 1981, the site was owned by Moine Salvage Co., which used it for years as a yard for petrochemical tank storage and salvage operations.

"It was horrible," Calas said. "It was an eyesore. We had many complaints from the people in the adjacent mobile home park. We had trouble from the kids cutting through" on the way to Caroldale Elementary School.

Moine's sand-blasting and other cleaning operations left a residue of heavy metals, mainly lead, and petrochemicals that had soaked into the earth. Rather than seal the contaminants under buildings and parking lots, the city decided to get rid of them.

"We wanted to make sure there wouldn't be a contaminant there on account of children playing the park," Calas said. "We may be overly cautious but it is better to be cautious than to be sorry."

Fourteen truckloads of soil laced with lead, which cannot be treated with bacteria, have been taken to a hazardous waste dump at a cost of about $50,000.

But hauling away soil laced with petrochemicals would have cost about $2 million, city officials said. The oily wastes had soaked as deep as five feet and contaminated 10,000 cubic yards of dirt, according to Art Homrighausen, a biologist and environmental specialist with Bright & Associates.

Enter the "Pacmen" bacteria.

The bacteria occur naturally in soil and digest the petrochemicals, turning them into harmless carbon dioxide and water, according to Homrighausen. Certain strains of the bacteria that digest the petrochemicals with particular efficiency have been commercially cultured for use in environmental cleanup. Though many bacteria eat petrochemicals, which particular strain is a trade secret, Homrighausen said.

The process, which Bright & Associates calls "bioaugmentation," takes longer than disposal at a hazardous waste dump--up to a year--but costs much less. Bacterial cleanup costs between $10 and $20 per cubic yard, compared with $200 to $225 a cubic yard for hauling, according to Homrighausen.

The cost of the biological cleanup will be less than the $132,000 budgeted for the job, he said.

The process, commonly used by oil refineries and tank farms that are recycling land, is rarely used for preparing parks, Homrighausen said, adding that his firm had never before used it to prepare a park site.

The process works like this: Bacterial concentrate is mixed with water and sprinkled on the site. To assist the growth of the bacteria, a layer of fertilizer is put on top. To make sure the bacteria can get to the contaminant, the land must be turned with disk plows.

Since the process can only work through 12 inches of soil, it was necessary at the Veterans Park site first to dig up four feet of soil in the spots where the oil had sunk deepest and spread it out in a foot-deep layer.

Once the bacteria are seeded, they need water just like plants. Like a farmer, Homrighausen has been turning on the water in a vast sprinkler system two or three times a week. During last week's high temperatures, the soil needed extra soaking.

And as for the term "Pacmen," Homrighausen said: "We don't ever refer to them as that. . . . We don't like to conjure up images of little critters running around." The bacteria are not harmful to humans, Homrighausen said.

Calas, however, said she couldn't help thinking of Pacmen when Bright & Associates described its plans.

"Those little things eating up those goodies! That's what I thought," she declared.

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