San Francisco Chronicle - 
Saturday, March 10, 2001 
Army Ordered To Test In Marin Methane Leak At Subdivision
         (Front page of North Bay section)
 Jim Doyle, Chronicle Staff Writer      (c)2001 San Francisco Chronicle
       
        State regulators have ordered the Army to look into the possibility that leaking methane gas from an old dump may combine with other hazardous chemicals and pose a health risk to residents of a new Marin subdivision.

        The volatile gas, experts say, could act as a conduit for toxic chemicals to escape from the capped landfill, poison the groundwater and create hazardous fumes in nearby homes at the old Hamilton Air Force Base in Novato.

        Explosion remains the primary risk from methane gas that is seeping up within 100 feet of home sites in the partially completed Hamilton Meadows.

        The California Regional Water Quality Control Board has told the Army to come up with a plan to reduce the landfill's high levels of methane gas, but also to study the potential threat of other hazardous gases in and around the former military dump. Home buyers have already been warned of underground contamination of the gasoline additive MTBE, which leaked from underground storage tanks at a gas
station.

        In a Feb. 7 letter to the U.S. Army Corps of Engineers, the water board voiced its concern that, based on data collected at other landfills, volatile organic chemicals "may also be present" in the leaking methane gas.

        The 15-acre former dump at Hamilton Field, known as Landfill 26, contains 10 such chemicals, including benzene, which can cause cancer and birth  defects.

        Water board officials ordered the Army to submit a detailed response by March 30, and warned that an inadequate reply may result in civil fines of as much as $1,000 a day.

        Jim McAlister, a project manager for the Army Corps of Engineers, said yesterday that the Army has tested previously for volatile organic  compounds at the water agency's request.

        "We did detect (the chemicals) out there but in very low concentrations," said McAlister. The low levels did not pose a health risk, he said. "We continue to monitor for it and watch for it."

        Construction at Hamilton Meadows was halted last month because tests showed that the methane gas had migrated into a 150- to 200-foot buffer zone between the landfill and new homes.

        Almost one-third of 235 planned homes at Hamilton Meadows have been built, and more than a dozen have been occupied. Construction of dozens more have been put on hold while air and water tests are conducted.

        "Methane is an excellent transport or channel for volatile organic compounds, such as MTBE and benzene," said Elena Belsky, the Marin investigator for WaterKeepers Northern California, a watchdog group. "It has the ability to mix with the groundwater and the other toxics in the landfill. You have the potential for a lot of movement of these toxics."

        Stephen Lester, a toxicologist for the Center for Health, Environment and Justice in Falls Church, Va., said methane and the hazardous chemicals "follow the path of least resistance."

        "It's a little like the (chemicals) are hitchhiking with the methane, going along for a free ride they wouldn't ordinarily get. Without the methane, they wouldn't be able to get there as quickly."

        The Air Force stopped using the dump in 1974 and vacated the base a year later, turning it over to the Army, Navy and Coast Guard. In the 1980s, the Army and state inspectors determined that Landfill 26 contained high levels of toxic chemicals including lead and other heavy metals, pesticides such as DDT, fuel residues and other cancer-causing agents including polychlorinated biphenyls.

        The Air Force capped the dump with high-strength plastic in 1995, but it hasn't kept the methane from creeping toward the subdivision.

        Hamilton Meadows also sits atop a plume of MTBE, or methyl tertiary butyl ether, that leaked from a Navy gas station. State water quality officials concluded that the MTBE would not endanger residents -- as long as they did not plant fruit trees, dig wells or expose themselves to polluted groundwater.

        Methane, an odorless and colorless gas, is commonly generated by decomposing dumps. The gas can cause an explosion if ignited in confined spaces.

        The developer, Shea Homes, has hired a consultant to determine whether methane gas has entered any homes. The home builder has also pressed the Army to prevent the methane gas from migrating across the buffer zone.

        E-mail Jim Doyle at jdoyle@sfgate.com.

        (c)2001 San Francisco Chronicle