Independent peer review: Smith’s Creek odors traced to fugitive landfill gas and sulfate‑rich sludge; mitigation judged effective

An independent peer review presented April 2 concluded that the hydrogen‑sulfide odors detected in the Smith’s Creek landfill area in late 2023 and early 2024 were the result of fugitive landfill gas compounded by a concentrated deposit of sulfate‑rich Domtar paper‑mill sludge in cell eight.

"The odors were produced by an insufficiency in the gas extraction system," Mike Bodwin of Civil and Environmental Consultants (CEC) told the Board. He said the insufficiency was temporary, that mitigation steps were implemented quickly, and that monitoring shows a marked reduction in hydrogen‑sulfide emissions after fixes were applied.

CEC’s findings: The peer review team identified three principal points: (1) fugitive gas escaping the landfill cover produced offsite odors, notably hydrogen sulfide (the "rotten egg" smell reported by residents); (2) a localized accumulation of sulfate‑containing industrial sludge (Domtar paper mill sludge) in cell eight increased hydrogen‑sulfide potential in that area; and (3) remediation — including added vacuum/flaring capacity, perimeter collection trenches and cover improvements — substantially reduced emissions within about a year.

On septage: CEC examined the county’s septage application program in depth and concluded that, while septage increased local liquid volumes, it did not raise moisture or gas production to levels consistent with a widespread bioreactor effect and thus likely was not the primary cause of the odor events. The team noted some small, localized pockets of enhanced activity but not sustained bioreactor conditions across the site.

Recommendations and public access: CEC recommended several operational steps — upgrades to the gas collection system, refined special‑waste approval procedures to screen sulfate or other problematic loads, enhanced labeling and signage, and further monitoring. Commissioners asked about the cost and scope of the peer review; staff said the contract with CEC was $108,000 and that the full report and presentation will be posted on county web pages and made available for public inspection.

Next steps: Commissioners said staff will continue to work with the landfill operator, CTI, and the peer‑review team to prioritize gas‑collection upgrades and to consider whether elements of the recommendations should be folded into the county’s Supplemental Environmental Plan, with a looming court‑ordered deadline in early July for certain SEP filings.