Too Hot to Ignore

A Hot Well is a Symptom, not a Diagnosis 

Subsurface elevated temperature (SET) events develop underground, out of sight, so they must be diagnosed the same way physicians diagnose a patient: by looking at multiple indicators together and, critically, how those indicators change over time. Well-head temperature is only one piece of the picture. Landfill operators and regulators should evaluate solids temperatures from borings inside the landfill, gas trends including methane, carbon dioxide, oxygen, carbon monoxide, hydrogen, volatile organic compounds (VOCs), gas well pressures and vacuum but also physical and operational conditions that can help explain why temperatures are changing. These include odors, smoke, settlement, cracking, changes in leachate levels, the integrity of the landfill cover, evidence of air intrusion, changes to gas collection operations, whether leachate recirculation is occurring, whether reactive materials such as incinerator ash or slag have been disposed of in the affected area, and what types of waste and cover materials are present A single measurement rarely provides the answer, but changes across several indicators can reveal whether a landfill is operating normally or beginning to transition toward abnormal and potentially dangerous conditions.

Just as important as the values themselves are the trends. For example, a well that slowly reaches 140°F over several years presents a different situation than one that jumps from 100°F to 140°F in a few weeks.  Knowing what is inside the landfill is also important. What is the temperature of the solids inside of the landfills? Are there reactive wastes like slag? The goal should not be to document that a hot well has remained stable enough to justify a higher operating temperature. The goal should be to identify the root cause of the abnormal conditions and return the landfill to stable operation before temperatures continue to rise and the risk of more severe subsurface reactions increases.

The High Cost of Failure

Underground landfill fires are among the most costly failures a landfill can experience. Once a subsurface reaction becomes established, there is no quick fix. Landfill operators may spend decades trying to contain heat, control odors, rebuild damaged gas collection systems and manage contaminated leachate.

The costs extend far beyond the landfill itself. Communities are left living with the health and economic consequences of a disaster they did not create. Nearby residents can lose the use and value of their homes, businesses can suffer economic losses, and local governments often devote substantial resources to emergency response, public health investigations, and ongoing oversight. One stark example is Virginia's Shoosmith Landfill, where years of mismanagement left the landfill bankrupt, a catastrophic environmental disaster in its wake, and the community holding the $173 million bill. 

Preventing subsurface elevated temperature events is far less expensive than responding to them. Finding the root cause of rising temperatures, correcting air intrusion, installing additional wells, removing liquid, fixing gas collection and using modern monitoring technologies cost a fraction of the long-term engineering projects required once a subsurface fire becomes established.

Finding 1: A system that too often substitutes paperwork for actual investigation

Higher operating temperature approvals are supposed to serve a specific function: they allow a landfill to continue operating gas wells above the standard regulatory threshold only when an operator can demonstrate that the elevated temperatures do not indicate harmful conditions. The logic of the HOV process depends on that demonstration happening before the approval is granted. Regulators should understand why temperatures are elevated at a landfill and what the operator is doing about it before they decide that a higher temperature is acceptable.

In practice, across multiple states and at dozens and dozens of landfills, that logic is frequently inverted. Regulators approve the higher operating temperatures without requiring the operator to first identify and verify the actual cause of the heat. Root cause analyses, when they are conducted at all, are often retained at the site rather than submitted to regulators, meaning that the technical basis for an approval is never subjected to independent scrutiny.  

Instead, landfill operators generally provided a short description of observations that no smoke, burning odors, or unusual settlement have been seen, along  with wellhead monitoring data — usually temperature, methane, carbon dioxide, oxygen and carbon monoxide, balance gas (rarely hydrogen) — along with narrative explanations for the elevated temperature. Requests sometimes included descriptions of operational measures such as gas extraction, dewatering, or leachate management. What they generally did not provide are direct investigations of conditions inside the waste mass, such as downwell temperature measurements, subsurface borings, or other evidence that independently verifies what is actually causing the elevated temperatures. As a result, regulator approvals are frequently based on inferences rather than direct confirmation of conditions within the landfill.

This matters because elevated temperatures in a landfill gas system can have multiple causes, and those causes have very different implications. Heavy rainfall is one possible explanation, but so are chemical reactions within the waste mass, air intrusion triggering oxidation, or developing subsurface elevated-temperature conditions that, if not addressed, can spread and intensify. Without a credible root cause analysis, there is no way to distinguish a benign explanation from a dangerous one. 

Oregon Let Landfills Approve Their Own Hot Wells Under Standing Procedures

The Oregon records reveal a concerning regulatory approach. DEQ approved a standing operating procedure at Waste Management’s Riverbend Landfill in 2005, and later approved a similar procedure for Columbia Ridge Landfill. Under that approval, Waste Management, not the state regulator, applied the procedure to determine whether individual wells at Riverbend Landfill could continue operating above the regulatory temperature limit. This protocol did not include a root cause analysis or downwell borings to show the temperature within the waste mass. A 2012 DEQ email later acknowledged that Riverbend had not originally submitted information about specific wells and stated that DEQ did not need to approve updated well lists each time because there was already "general approval" under the permit. By 2012 and again in 2014, Riverbend was periodically submitting lists of dozens of wells operating under the approved procedure, with allowable temperatures up to 166°F. Columbia Ridge adopted a similar approach. In 2010, Oregon DEQ approved a procedure allowing Columbia Ridge to add future wells to its Higher Operating Value (HOV) program when they exceeded the regulatory temperature threshold and met the established criteria. In 2025, the landfill notified DEQ that additional wells had been added under the standing procedure rather than submitting a new technical demonstration for each well.

Separate corrective-action records illustrate the limits of that approach at the Riverbend Landfill. Under the federal rules, landfill operators must perform a root cause analysis and identify corrective actions when wellhead temperature exceedances are not corrected within the required timeframe.

One well remained above the regulatory temperature limit for approximately 232 days and reached 181.1°F, —more than 36°F above the federal operating limit of 145°F and above the temperature at which methanogenic microorganisms are expected to become significantly inhibited. As methanogens are lost, the landfill's gas chemistry can fundamentally change, making it increasingly difficult to distinguish a stable landfill from one experiencing an abnormal subsurface reaction. Yet the 2025 root cause analysis listed the initial assessment simply as "Temperature change – cause unknown," with no further explanation. Rather than requiring the operator to determine why temperatures had reached such an extreme level before allowing continued operation, the records reviewed suggest that the regulatory process shifted from independently scrutinizing individual hot wells to trusting landfill operators to manage them under an approved HOV procedure.

U.S. EPA Approved Hotter Landfills in Illinois, Despite Troubling Gas Composition 

Unlike some of the state records we reviewed, U.S. EPA Region 5 generally considered a broader set of information before approving higher operating temperatures at Illinois landfills. The records include approvals at several landfills — Cottonwood Hills, Milam Recycling and Disposal Facility, Quad Cities Phase IV, and multiple requests at Indian Creek Landfill — covering dozens of individual gas wells with approved temperatures ranging from approximately 136°F to 165°F.

Across these approvals, a consistent pattern emerged: the U.S. EPA did not require a documented root cause investigation before approving the higher temperatures. The U.S. EPA typically reviewed gas composition (methane, oxygen, carbon monoxide, and sometimes hydrogen), field observations, and monitoring data to determine whether the landfill showed signs of active combustion or whether elevated temperatures appeared to be inhibiting methane production. In some cases, EPA also reviewed corrective actions the landfill had already taken, such as increased gas extraction, dewatering, or ending leachate recirculation.

At GFL Environmental’s Indian Creek Landfill in Tazewell County, Illinois, the monitoring data provided in the HOV request consistently show abnormal landfill conditions. The wells exhibited sustained elevated temperatures, declining methane concentrations and increasing carbon dioxide concentrations. In fact, the request letter literally says, “A review of landfill gas quality data collected during the October 2023 - March 2024 timeframe indicates that CH4 has often decreased while CO2 has increased. This is indicative of elevated temperature landfill (ETLF) conditions within this small area of the site.” The landfill attributed the elevated temperatures to leachate recirculation and described corrective actions it took, but the request presents that explanation as a suspected cause rather than documenting a formal root cause investigation. This approval demonstrates that U.S. EPA Region 5 conducted a more substantive review than many HOV approvals examined in this report. However, the approval still relies on the landfill's proposed explanation for the elevated temperatures rather than documenting an independent determination of their root cause. The approval explains why EPA concluded the wells could continue operating safely under enhanced monitoring, but it does not establish why conditions developed in the first place or demonstrate that the suspected cause had been verified.

At the Quad Cities Phase IV Landfill, which is owned by Waste Connections and operated by subsidiary Millennium Waste, EPA approved a higher operating value of 165°F without requiring the landfill operator to determine why the well had reached such an unusually high temperature.

“Your letter states that Millennium has struggled to maintain well EW23 below 131 °F since it was installed in December 2013, and that it has become progressively more difficult in recent months. Your letter goes on to say that temperature measurements at the well have been consistently above 131 °F in 2016 and as high as 155 °F. You have provided data showing strong anaerobic decomposition and low levels of carbon monoxide. You request an HOV of 165 T. We are somewhat concerned about this request because 165 °F is higher than most, if not all, HOV requests that come into this office. We will grant the requested HOV of 165 T at this time. However, we request that you maximize vacuum at the well and continue to closely watch carbon monoxide levels to ensure they are below 500 ppm.”

- Excerpt from U.S. EPA approval of HOV request at Quad Cities Phase IV Landfill, August 16, 2016.

A landfill doesn't suddenly reach 165°F for no reason. Without understanding the root cause, regulators cannot know whether they are looking at a stable condition or the early stages of a much more serious problem. Rising temperatures can be caused by operational problems, oxygen intrusion, reactive wastes, or developing underground heat events. Those causes require different corrective actions. Without identifying the root cause, regulators cannot know whether the landfill is experiencing a manageable operational issue or the early stages of a much more serious reaction. Instead, the approvals focused primarily on whether methane production continued, carbon monoxide remained below specified thresholds, and conditions did not appear to indicate an active fire. Those are important observations, but they answer a different question.

The U.S. EPA seems to have asked: "Does this look like a fire today?" They should have asked: "Why is this landfill getting hotter, and what needs to change to stop it?" The regulator's response should have focused on verification rather than acceptance. In many approvals the focus remained on demonstrating that the elevated temperatures did not appear to indicate an active fire, rather than establishing why the landfill had become unusually hot in the first place.

A General Explanation Is Not a Root Cause Analysis

At Republic Services' Sauk Trail Hills Landfill in Michigan, the landfill operator requested approval to continue operating at elevated temperatures, and, along with data points, provided a general explanation that landfills naturally contain different types of methane-producing bacteria and that temperatures between 140°F and 160°F are not uncommon because of thermophilic decomposition. What Republic did not provide was a root cause analysis: Why temperatures at these specific wells had increased and what had changed inside the landfill.

A root cause analysis should answer questions such as:

• Why did temperatures increase?

• What evidence supports that conclusion?

• Could oxygen intrusion, poor cover, reactive wastes, or another operational issue be contributing?

• What corrective actions are needed to prevent conditions from worsening?

Modern research and EPA guidance recognize that elevated temperatures alone do not establish that a landfill is simply experiencing normal thermophilic decomposition. Rather, elevated temperatures are recognized as an indicator that warrants a broader investigation into landfill conditions, including changes in landfill gas chemistry, carbon monoxide, hydrogen, methane production, pressure, settlement, and temperatures within the waste mass.

Every elevated-temperature event results from underlying landfill conditions. Regulators cannot determine whether the reason for the elevated temperature is benign or developing a dangerous underground reaction without requiring landfill operators to identify and document that cause.

Republic Services’ Broadhurst Landfill in Georgia’s records reveal concerns about gas composition. In the January 2017 HOV request, monitoring data for three wells showed methane had collapsed from the normal ~50 percent to as low as 0.4 percent, replaced almost entirely by "balance gas," the catch-all for gases that aren't methane, carbon dioxide, or oxygen. At 50 percent to 62 percent, that balance gas is at very concerning levels. A fourth well showed methane drop over just ten weeks from 42 percent to 11 percent while balance gas climbed toward 50 percent. The regulator denied the HOV requests for the three worst wells, and required an expansion of the gas collection system per the permit conditions. But what it did not do, and was not required to do under the regulatory framework, was require any investigation. No root cause analysis explaining why methane had effectively disappeared from those portions of the landfill. No assessment of whether the abnormal gas zone was spreading. Instead, on the same day the three worst wells were denied, five others with CO readings up to 600 ppm were approved at 180°F — a temperature where normal methogenic activity has ceased — and the process moved on.