Subsurface Methane East of Arbor Hills
Modern landfills use a bottom liner to prevent leachate from contaminating the environment. The original Arbor Hills Landfill (Arbor Hills East) is unlined and has historically impacted properties east of Napier Road in Northville Township, Wayne County. EGLE refers to the property directly east of Napier Road as the Arbor Hills Remediation Area due to past remediation performed to remove contaminants from the groundwater. Previous owners of Arbor Hills installed a subsurface slurry wall along the eastern border of Arbor Hills East and a groundwater gradient control system to contain the leakage.
Type II landfill operation; explosive gas control and monitoring (R. 299.4433)
Methane concentrations at the landfill boundary must be monitored at least quarterly, and if limits are exceeded, operators must immediately take all necessary steps to protect human health and notify the Director [EGLE]. Landfill operators are required to ensure that the concentration of methane gas does not exceed the lower explosive limit (LEL)[1] at or beyond the facility property boundary.
If methane escapes the landfill boundaries, it could migrate through the soil and may accumulate in subsurface structures (sewer, conduit, basement, etc.) and pose a fire or asphyxiation risk. Public records indicate that methane detections have persisted beyond these boundaries.
Monitoring data obtained through Freedom of Information Act (FOIA) requests by a local resident revealed that methane continues to be detected beyond the landfill boundaries at concentrations above the lower explosive limit (LEL). These monitoring records, like most records the landfill must submit to EGLE under its permits, are public records but can be difficult to obtain. We applaud this resident's efforts and are helping obtain additional information related to the methane detection.
What does the Data Show
Recent methane detections are concentrated at two monitoring locations. One location (AHTGP18D) is located approximately 950 feet east of Napier Road—nearly half the distance between the landfill and neighboring subdivisions. The other location (AHMP15R2) is located closer to Napier Road and is within approximately 1,000 feet of the DTE Nitro substation and its buried electrical duct. Data from a row of gas probes located closer to the subdivision (TGP19, TGP20, TGP21, TGP22) have remained below the LEL.
Layout of monitoring wells (obtained through FOIA request)
Sample of data reported by GFL to EGLE (obtained through FOIA request)
Arbor Hills Monitor website - contains a detailed summary of publicly available information published by an independent resident who has been investigating this issue
The settlement agreement resolving the Michigan Attorney General's lawsuit in 2022 (Consent Judgment No. 2020-0593-CE, Paragraph 5.12 and Appendix J) required actions intended to correct the methane migration. The consent judgment requires compliance with state regulations (R. 299.4433) and includes stipulated penalties for noncompliance.
Our Concerns
The Conservancy Initiative does not claim subject-matter expertise, but exceeding the Lower Explosive Limit outside the landfill boundary raises obvious concerns for nearby residents.
Given the continuing detections of methane, critical questions should be answered:
What steps have been taken to protect human health?
Have local first responders, nearby property owners, and local businesses been notified of the methane detections?
Does the newly constructed DTE transformer facility heighten any concerns?
Has EGLE issued violations or demanded penalties (up to $1,500 per day) stipulated in Consent Judgment No. 2020-0593-CE?
The Conservancy Initiative is publishing this information to ensure transparency. All data referenced in this report is public information.
[1] LEL is the lowest concentration by volume of a mixture of explosive gases in air that will propagate a flame at 25 degrees Celsius and atmospheric pressure.