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For people who live and work in the area, near the intersection of Interstates 70 and 270, the 52-acre landfill has been at least a nuisance, especially for the past year.

Noxious odors from gases being emitted have prompted hundreds of complaints and stirred concern about potential long-term health effects, especially among young children. Many fear that the subsurface problem could spread to nearby West Lake Landfill, where tons of radioactive waste — the product of nuclear weapons work in the 1940s — are buried.

Unknown to most of the landfill’s neighbors, however, is another, less obvious problem that has persisted for more than a decade.

State and county inspection reports and other public documents from the Missouri Department of Natural Resources show the landfill has been out of compliance with state regulations since the late 1990s for allowing excess levels of methane, a potentially dangerous gas, to seep off-site.

The methane problems — more specifically, efforts to solve them — also raise questions about a possible connection to the mass of overheated waste that continues to smolder deep below the surface of the landfill.

Engineers, including one of the consultants hired to advise the DNR on the situation at Bridgeton, and the U.S. Fire Administration make clear that one of the main causes of underground landfill fires is overdrawing methane gas. When that happens, a vacuum is created that pulls air in from the surface or surrounding soils, providing fuel for combustion.

In a 2002 report titled “,” the U.S. Fire Administration, part of the Federal Emergency Management Administration, states: “Operators must take care to ensure the system is not overdrawn, which can lead to fire ignition.”

Todd Thalhamer, an engineer and firefighter hired last spring to advise the DNR, that Republic was overdrawing the landfill gas system as recently as May.

Republic Services agrees that overdrawing landfill gas systems can cause subsurface fires, but spokesman Richard Callow said the company strongly believes that what’s happening deep underground at the former quarry isn’t a fire — a term that’s been used at least by the DNR, Missouri Attorney General Chris Koster, and the U.S. Environmental Protection Agency.

The company believes the elevated temperatures, which have exceeded 300 degrees in spots, are the result of a chemical reaction, in part because the elevated temperatures are occurring so deep, some 80 to 120 feet below the surface, far below where oxygen would be drawn into the waste.

Still, the company said it isn’t yet ruling anything out and is working with the DNR to determine the origin of what has been called a “smoldering event.”

“Bridgeton Landfill continues to also evaluate factors that may have contributed, or could contribute, to the subsurface smoldering event, but that investigation is ongoing and nothing has been confirmed or eliminated,” the company said in a statement.

State regulators have said little about what they believe caused the smoldering fire.

“While we have several opinions on how the (smoldering event) began, the facts have not revealed a sole source for the event,” DNR Solid Waste Management Program director Chris Nagel told the public at a meeting June 17 at Pattonville High School.

DNR spokeswoman Gena Terlizzi last week said the state, as yet, has not identified the cause for the underground smoldering.

METHANE RISK

While the state regulators and the landfill operator are unable to pinpoint a cause, state records leave no doubt that the landfill has remained out of compliance with methane regulations for 16 years.

Republic, in fact, confirmed last week that monitoring wells along the perimeter of the landfill continue to detect excess methane levels.

Methane is a colorless, odorless gas produced by the decomposition of waste. Besides being a potent greenhouse gas, it’s also potentially dangerous if allowed to seep into confined spaces such as sewers, buildings and basements.

The gas can be explosive at concentrations between 5 to 15 percent by volume, and higher concentrations in confined spaces can displace oxygen and lead to suffocation. Regulations limit methane in the soil at a landfill property boundary to 2.5 percent by volume, or 50 percent of the lower explosive limit.

While explosions or fires related to landfill gases are extremely rare, methane violations aren’t unusual and can be challenging for landfill operators, especially companies that run older landfills that were permitted and put in service before current regulations that require liners that serve as a barrier for gases that move through the soil.

At least 11 Missouri landfills, four of them in ӣ����Ƶ County, have been issued notices of violations by the DNR over the past few years for allowing excess methane levels at the perimeter, according to the department’s website.

While there have been no reported safety incidents related to methane accumulations near the Bridgeton Landfill, DNR records indicate the facility, a former quarry that began accepting waste in 1985, has been out of compliance with methane regulations since 1997.

Republic and the landfill’s previous operator, Allied Waste, were issued three formal violation notices during the past decade, leading to settlement agreements in 2006 and 2011. The department also required the landfill owners to notify property owners within 1,000 feet and offer to provide them methane alarms.

The agreements with the DNR and attorney general’s office established civil penalties of $104,000 against Allied waste in 2006 and $47,000 against Republic in 2011. But in each case, records show the companies didn’t have to pay more than an initial $5,000 fine if they followed plans to bring the facility into compliance by repairing and upgrading the gas collection system.

In the most recent settlement, however, the state granted Republic’s request to suspend its terms in order to address the subsurface fire, said Terlizzi, the DNR spokeswoman, in an email last week. Compliance actions spelled out in that agreement will be addressed as part of the lawsuit filed against the company in March by Attorney General Koster, she said.

“The department continues to monitor the situation as it pertains to methane gas exceedances, although the current focus is geared toward actions related to the subsurface smoldering event,” Terlizzi said.

Still, methane problems persist.

And as recently as a year ago, the company was again cited by state regulators for high methane levels in soils at the landfill perimeter as part of a broader notice of violation concerning the smoldering fire and related odors.

In October, for instance, a gas monitoring probe on the southwest side along Old St. Charles Road near Corporate Exchange Drive measured methane levels as high as 71.3 percent — nearly 30 times greater than the 2.5 percent allowable under state regulations.

Phoenix-based Republic, which acquired the inactive Bridgeton Landfill as part of the company’s $6.1 billion purchase of rival Allied Waste in 2008, said it’s continuing to work with the DNR to address methane migration problems.

From late 2012 to April, the company said it completed the installation of 40 additional gas extraction wells and continues to “fine tune” its collection system to manage landfill gases.

“Bridgeton Landfill has continually worked with MDNR to implement appropriate measures and continue monitoring and assessment to ensure that the site does not pose a risk to site occupants or nearby properties,” the company said.

Editor's note: This updated version clarifies the location of landfill. An earlier version said it was located northeast of the intersection of interstates 270 and 70. The landfill is located at 13570 St. Charles Rock Road, north of 70 and west of 270.