Methane is produced in landfills through the breakdown of waste. The Hunters Point landfill is decades old, which would typically suggest reduced levels of chemical activity. But the dump, although largely unexplored, is known to contain a stew of dangerous pollutants, including oil, solvents, and other chemicals. Environmental regulators fear that methane formed there could concentrate in buildings and explode, or could carry toxic chemicals from the landfill into residential areas.
The federal Agency for Toxic Substances and Disease Registry originally detected methane in the landfill in the early 1990s, according to Richard Mach, base realignment and closure environmental coordinator for the Navy. At that time, federal regulators recommended further testing to determine the extent of the gas. But the tests were not done.
Recently, city officials noted that concentrations of methane gas emerging from the landfill had exceeded acceptable levels in at least two recent surveys. In its response to the Navy's plans for cleaning up the landfill area, a city contractor wrote that "a landfill gas collection and treatment system may already be warranted."
The scenario at Hunters Point is eerily reminiscent of the situation near the former Hamilton Air Force Base in Novato, where construction of new homes was halted earlier this year after methane gas was found to have seeped from an old dump on the base. Army officials have proposed digging a trench around the exterior of the Hamilton dump to stop the gas and other toxic chemicals from traveling outside it.
There is no gas ventilation or collection system in place at the Hunters Point landfill.
A temporary cap was placed over the shipyard landfill in August 2000, to help extinguish a fire that had burned for weeks before the Navy notified nearby residents. Among other government officials, Chein Kao, who oversees Hunters Point cleanup issues for the state Department of Toxic Substances Control, has expressed concern that methane gas that was previously escaping through the soil atop the landfill may, now that it is capped, be moving sideways through the earth and toward residential neighborhoods. Toxic gas concerns were also raised by city and EPA officials after the Navy submitted plans this summer for field tests in the landfill area.
Last month, EPA officials asked the Navy to act immediately on methane gas monitoring, rather than wait until a wider plan for cleanup of the land- fill is hammered out over the course of months. Navy officials say they will begin monitoring for methane immediately.
"We know there are pockets of methane in the landfill," says the Navy's Mach. "I don't think that I've seen anything that is startlingly high.
"We've never found any evidence to show that there's a buildup of methane gas or a buildup of other gases. We will investigate."
The Navy has yet to put forward a formal plan for cleaning up or removing the landfill. Navy officials have said they are considering creating a permanent cap and leaving the landfill in place as an alternative. Any plan would require EPA approval, which is not likely in the immediate future. "The EPA has not taken a position on the landfill," says Michael Work, one of the EPA's project managers for the Hunters Point Shipyard cleanup. "The EPA has been very clear about the fact that we don't see this cap as a final action.
"There's a lot of nervousness inside the community about the landfill. There have been fires, and they [residents] are fearful that something might happen again like happened in August 2000. The community is very nervous about air quality around the landfill."