After years of resident complaints and speculation, a newly released joint study by the City of Mount Dora and Lake County has identified the likely source of a persistent foul odor affecting parts of the city.

The investigation points to the Mid Florida Materials landfill, located along State Road 46, as the primary contributor of the smell. The landfill, which accepts construction and demolition debris, was found to emit hydrogen sulfide—a gas associated with a strong “rotten egg” odor. The findings mark the most conclusive evidence yet in the long-standing effort to pinpoint the cause of the odor.

The $270,000 study was conducted by Halff Associates with support from V&A Consulting Engineers. While the landfill site was not fully accessible during the review, consultants used perimeter-based assessments, weather data, and odor pattern analysis to narrow in on the source. Weather conditions, particularly periods of calm wind, were found to intensify the problem by trapping the odors in nearby neighborhoods.

In recent years, the city had implemented several costly mitigation measures at its wastewater treatment facility, including a $500,000 carbon biofilter and hydrogen sulfide monitoring equipment. Earlier studies had already indicated the city’s facility was an unlikely cause, but the smell persisted.

The new findings appear to clear the city’s infrastructure of responsibility, placing attention squarely on the privately operated landfill. Investigators identified specific odor hotspots at the landfill, including active dumping areas, retention ponds, and venting systems. While no single component was isolated as the sole source, the cumulative emissions from the facility were consistent with the characteristics of the reported odor.

Secondary odor sources noted in the study included two nearby cannabis facilities, which were found to contribute faint but unrelated smells that did not match those reported by residents. These facilities were ultimately ruled out as significant contributors.

With the source now clearly identified, city and county officials are expected to meet with stakeholders, including representatives from Mid Florida Materials and the Florida Department of Environmental Protection, to discuss next steps. The landfill operator has acknowledged the findings and indicated plans to review the report in coordination with state environmental regulators.

For residents in neighborhoods such as Sullivan Ranch and Stoneybrook, as well as businesses near the intersection of U.S. 441 and SR 46, the conclusion of the study brings long-awaited clarity. The focus now shifts to mitigation, compliance, and enforcement measures that could bring relief after years of odor-related concerns.

Officials say further action will be required to ensure the responsible parties address the issue in a timely and effective manner.