Home Sales Resume Despite Gas Levels

State officials have permitted home sales at the Manhattan Village development to resume despite recent findings that show underground methane gas readings of more than eight times the explosive level.

State Department of Health Services spokesman Ric Notini said no immediate health hazard is posed by the high levels, which exceed 400,000 parts per million in some areas. Methane gas becomes explosive at 53,000 ppm.

Sales were suspended in March by the state Department of Real Estate when tests at the site showed methane soil readings of up to 51,000 ppm throughout the development, which includes more than 160 residential units and the Manhattan Village Mall.

Department of Real Estate spokesman Robert Gilmore said the agency lifted the ban Saturday in exchange for a commitment from the owner, Chevron Land Co., to install a vapor venting system and to monitor soil and ground water.

City officials say the latest monitoring shows methane readings of more than 400,000 parts per million near homes in the project, and 200,000 ppm directly underneath some homes. No vapors have been found in the homes themselves.

Carl Abel, Manhattan Beach public services director, said methane levels of more than 300,000 parts per million have been found under the Hughes Aircraft Employees Federal Credit Union building on Rosecrans Avenue near the mall. Consultants are still testing under the nearby TRW building on Rosecrans, he said.

Abel and state health officials said the high readings pose no immediate danger because the vapors are underground, are not under pressure and are not close to any ignition source that could trigger an explosion.

Notini said the gas is the result of decomposing oily dirt found throughout the 187-acre site. Until the late 1960s, the land was used by Chevron USA Inc. as a tank farm to store crude oil and other heavy fuel compounds.

Chevron Land Co. spokesman Mo Tidemanis said the tank farm was dismantled in the late 1960s when the company decided to develop the property. Scheduled for completion in 1986, the development will include the mall, 550 units of residential housing, an office park, a medical building, a hotel and recreational facilities.

During the dismantling process, he said, large amounts of oil apparently were spilled. In addition, he said, there probably was leakage during the 40 years the tank farm was there.

Notini said that “large pockets” of oily dirt throughout the site will continue to generate methane gas, but that the possibility of explosion is “remote.”

“We’ve concluded that no immediate danger exists,” he said. “Our efforts now will be focused on possible long-term hazards.”

Notini said studies also have shown “extremely low levels” of benzene, a potent carcinogen. “We do not believe there is a short-term risk from exposure to benzene,” he said, “but we will continue monitoring.”

Because the source of the methane cannot be removed, Notini said, Chevron officials will install an extensive underground piping system that will suck up methane and vent it through a charcoal filter into the atmosphere. South Coast Air Quality Management District officials said they will monitor emissions to ensure that they do not exceed allowable levels.

Tidemanis of Chevron Land said that as a condition of resuming sales, the company also has agreed to:

- Continue vapor readings in all homes to ensure that fumes do not migrate into the structures and rise to explosive levels.

- Develop guidelines for homeowners who encounter oily dirt in their yards or wish to install hot tubs or other items that require digging.

- Continue monitoring sewers, storm drains and ground water. Some contamination of shallow ground water has been found already, and the Regional Water Quality Control Board has requested additional studies. While the contaminated water is not used for drinking, deeper aquifers under the project are.

- Disclose to all homeowners and potential buyers that methane gas exists on the property. The company must make available the results of all investigations and studies.

Cost to the company for testing, monitoring and installation of the venting system is expected to surpass $1.2 million, Tidemanis said.

Testing at Manhattan Village began in February, shortly after large amounts of gasoline-based hydrocarbons were found to be seeping from Chevron’s El Segundo refinery into surrounding areas of El Segundo and the El Porto area of Manhattan Beach.

In an effort to assuage the fears of city officials and residents that the hydrocarbons had migrated as far south as Manhattan Village, Chevron began extensive testing at the site. No evidence of the hydrocarbons was found, but high levels of methane were discovered almost immediately.