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Proposed Minimum Siting Protections

Arbor Hills has recorded wellhead temperatures as high as 177°F. Yet the hottest reading in the assembled record was not classified as a temperature exceedance — and did not trigger the enhanced monitoring applied to wells without an approved higher operating value — because that well held a 180°F HOV.

Before any new landfill or landfill expansion is found consistent with the county's Materials Management Plan, the applicant should have to demonstrate that the new or expanded area will include clear protections to detect elevated temperatures early, determine their cause, prevent their spread, and keep regulators, emergency responders, and the public informed.

Listed below are three protections a neighboring resident is asking the Washtenaw County Materials Management Planning Committee to include in the plan's minimum landfill siting criteria. Every number cited is drawn from the public record, and the principal sources are identified below.

Protections · Local record · Federal gap · Legal basis · Sources

Why the “minimum” set. MCL 324.11585(3)(b) requires a facility to meet the Materials Management Plan's minimum siting criteria. Separately, subsection (3)(c) requires either host-community approval or compliance with the plan's supplemental criteria. Host-community approval can therefore eliminate the need to satisfy supplemental criteria, but it does not replace the minimum criteria. EGLE also independently evaluates the facility's consistency with the plan during its permit or license review under MCL 324.11585(5).

The three protections

For any new landfill or landfill expansion, before waste is placed in the new or expanded area, the applicant would have to demonstrate that the facility's design and proposed EGLE-approved operating and emergency-response plans incorporate these protections for the operating life of that area.

1. Continuous wellhead monitoring, alerting, and public data

2. Corrective action and fire response

The facility's approved operating and emergency-response plans must provide that, for any reading at or above 145°F, regardless of any higher operating value approved for the well:

Resolution must not be based on a single below-threshold reading. The approved plan must require evidence of sustained temperature reduction, stabilization of methane, carbon dioxide, oxygen, and carbon monoxide trends, and no indication that the affected area is spreading.

For any reading at or above 170°F, the approved plans must also provide that waste placement and non-essential activity within 400 feet of the well cease until the resolution criteria are satisfied. Access within that area must be limited to trained personnel acting under an approved Incident Action Plan.

3. Required SET and smolder-prevention plans

The facility must maintain two written, professional-engineer-certified, publicly available plans. The plans must be reviewed at least annually and every four months whenever any well is at or above 160°F.

Salem Township describes its fire department as staffed by paid-on-call members who hold outside jobs. The proposal therefore identifies mutual-aid resources in advance rather than assuming additional response capacity will always be immediately available.

Why these protections — the local record

The operator's own wellhead monitoring, filed with Michigan EGLE under SRN N2688, documents a persistent elevated-temperature condition.

Fifty-seven wells have peaked at or above 131°F — the wellhead-temperature threshold retained in the federal New Source Performance Standards and Emission Guidelines, and identified by EPA research as a common indicator of an elevated-temperature landfill. Approximately 26 wells reached that level in the most recent half-year. During the assembled record, 15 wells reached the NESHAP's 145°F operating threshold, four reached 160°F, and the highest measured temperature was 177°F.

These are wellhead readings, not downhole temperatures. Every temperature shown here is the temperature of landfill gas measured at the surface wellhead. Actual subsurface (downhole) waste temperatures can run higher, because the gas cools as it rises to the wellhead, so these readings tend to understate the reaction itself. That is one reason Protection 3 also requires in-situ, at-depth monitoring within the affected area.

Bar chart of peak wellhead temperature for 57 Arbor Hills wells at or above 131 degrees Fahrenheit, against the 131, 145, 160, and 170 degree action levels; peak 177 degrees.
Peak measured wellhead temperature by well, compared with the applicable temperature levels. The 131°F line represents the federal NSPS/Emission Guidelines operating and corrective-action threshold and an EPA elevated-temperature indicator; the 145°F line represents the default wellhead operating temperature under the landfill NESHAP/MACT provisions applicable at Arbor Hills. The 160°F and 170°F lines are proposed heightened-response levels. Source: operator monitoring filed with Michigan EGLE, July 2021–June 2026. See the well-by-well thermal map.
Line chart of the field-wide maximum wellhead temperature by half-year, 2021 through 2026, peaking at 177 degrees.
Field-wide maximum measured wellhead temperature by half-year. Source: operator monitoring filed with Michigan EGLE.
Bar chart of field-monitoring days per month over the most recent twelve months, about 22 days per month.
The wellfield is currently read by hand, requiring approximately four business weeks each month to complete a monitoring round. The fenceline methane monitors report continuously, but wellhead temperature — the elevated-temperature signal — does not. Source: operator monitoring filed with Michigan EGLE.

Why the existing federal rule is not enough

Federal landfill air regulations do not use a single temperature threshold. Under the federal New Source Performance Standards and Emission Guidelines, 131°F remains a wellhead operating and corrective-action threshold. EPA also identifies temperatures above 131°F as a common indicator of an elevated-temperature landfill.

Under the landfill NESHAP/MACT provisions applicable at Arbor Hills, the default wellhead operating temperature is 145°F. A reading above that applicable operating value ordinarily triggers corrective action and enhanced monitoring. An operator seeking authorization to operate a particular well above 145°F may submit supporting data and request regulatory approval of a higher operating value, or HOV.

This is not hypothetical at Arbor Hills.

On March 14, 2025, well AHW272R4 reached 177°F — the highest measured wellhead temperature in the assembled 2021–2026 record and 32°F above the federal default 145°F operating temperature. EGLE had approved a 180°F HOV for the well on February 19, 2025, just 23 days earlier.

Because 177°F remained below the approved 180°F value, the reading was not counted as a temperature exceedance. The operator's First Semi-Annual 2025 NESHAP compliance report omits AHW272R4 from its temperature-exceedance table, consistent with the report's stated rule:

“The tables in Appendix A don't include wells with approved higher operating values (HOV) if the temperature did not exceed the HOV.”

Dozens of other readings above 145°F occurred at wells that held no such approval. As a result, the 177°F reading at AHW272R4 did not trigger the enhanced-monitoring regime that applied to wells exceeding 145°F without an approved HOV — even where those wells recorded lower temperatures.

This establishes that the HOV changed the reading's compliance classification and enhanced-monitoring treatment. It does not establish that a Violation Notice otherwise would have been issued, and compliance under the HOV does not by itself establish that no subsurface reaction was occurring.

The federal system serves an air-compliance purpose. It does not necessarily answer the different question this proposal addresses: is an abnormal, heat-generating condition developing or spreading beneath the landfill?

Compliance at an individual gas well and detection of an evolving subsurface reaction are not the same thing. EPA's research on elevated-temperature landfills treats rising temperature, falling methane, and increasing carbon dioxide, carbon monoxide, hydrogen, and other changes as indicators of the underlying condition.

When EPA proposed raising the applicable wellhead standard to 145°F, the technical basis it cited — an industry manual of practice — noted that landfill gas above 135°F “indicates a possible subsurface oxidation event” and that temperatures above 140°F “could indicate aerobic conditions.” See EPA's proposed Municipal Solid Waste Landfills NESHAP review, 84 Federal Register 36670, July 29, 2019. Therefore, “145°F is the compliance line” and “nothing concerning is happening below it” are not equivalent statements.

The proposed protections therefore do not treat any single compliance value — whether 131°F, the NESHAP's 145°F default, or a regulator-approved HOV — as the sole measure of whether an abnormal, heat-generating condition is developing or spreading. They use continuous monitoring, gas chemistry, temperature trends, defined response triggers, and evidence-based resolution criteria to evaluate the underlying condition itself.

Michigan law requires the county's Materials Management Plan to establish minimum siting criteria. The statutory framework and EGLE's implementation guidance provide room for criteria that reflect local conditions and differ by facility type.

Read the full Part 115 textual analysis → A detailed brief explains the statutory-construction case, the division between county plan-writing and EGLE enforcement, and the Legislature's facility-specific choices.

This proposal does not ask the County to issue an air permit, replace EGLE as the landfill's operating regulator, or independently administer federal landfill-air rules. It asks that, before a new landfill or expansion is found consistent with the MMP, the applicant demonstrate that its design and proposed EGLE-approved plans incorporate specified elevated-temperature protections.

The committee heard a similar description of its role in its own materials. The county's August 19, 2026 briefing packet said state rules “set the floor,” with “the county layer … on top of these, generally more protective.” It also stated that the 2022 revision of Part 115 prioritized local control of facility siting and regulation of landfill development, reinforcing the role of county MMP criteria where local conditions warrant additional protection.

The persistent elevated-temperature condition documented here — beside homes and two elementary schools — is the type of local condition the committee should consider when establishing its minimum siting criteria.

A model advancing into law

California's AB 28 (2026), which addresses landfill subsurface temperatures, passed both houses of the California Legislature and was enrolled on September 4, 2026. As of September 7, 2026, it was awaiting action by the Governor.

The enrolled bill would define a landfill “subsurface elevated temperature event” as an event in which subsurface gas or waste temperatures persistently exceed 131°F over a substantial area and meet additional performance criteria established by the responsible state agency. It would authorize monitoring, notification, corrective-action, multiagency-response, public-health, and enforcement measures.

Independent academic researchers and scientists at the U.S. Environmental Protection Agency have also published extensively on elevated-temperature landfills. The committee can obtain independent technical assistance from those researchers when evaluating these proposed protections.

In closing

The question before the committee is narrow and forward-looking: what should a new landfill or expansion have to prove before it is found consistent with the county's Materials Management Plan? The elevated-temperature record documented here, next to occupied homes and two elementary schools, is why the answer should include the ability to detect an abnormal subsurface condition early, to act on it on a defined schedule, and to keep emergency responders and the public informed throughout. Writing these three protections into the minimum siting criteria would not slow responsible development or displace EGLE as the landfill's regulator. It would set a clear, enforceable baseline so that the next facility is designed and operated to catch a subsurface reaction while it is still small, rather than after it has spread beneath the community.

Principal sources