Ann Arbor officials say they’re still not sure what caused a fire at the city’s recycling plant last month, but they’ve identified some possible causes, including spontaneous combustion of accumulated materials inside the facility.

Another possible cause is friction due to the baler feed conveyor and waste material in and around the conveyor.

City Administrator Howard Lazarus highlighted those concerns in a Sept. 12 memo to the City Council, noting steps the city is taking to address the fire hazards at the Platt Road plant.

More than a year after the city fired the previous operator of the city’s recycling plant because of safety concerns, including multiple fires, the city — now working with local nonprofit Recycle Ann Arbor — is still working to address lingering safety issues.

In his memo, Lazarus also noted a steel push wall inside the recycling plant — next to the tip floor where recyclable material from collection trucks is unloaded — is dislodged from its structural supports and damaged in multiple locations, presenting a safety concern.

“A structural inspection of the push wall has been performed by a structural engineer indicating the repairs that need to be made to the wall,” he wrote. “The condition of the wall and the need to not operate adjacent to it has allowed for the accumulation of additional material to occur in proximity to the wall.”

Since the Aug. 8 fire, Lazarus said, the city has been providing a city staff member to serve as a “fire monitor” during operations until all accumulated material can be removed from the facility.

“In addition, staff has solicited quotes from contractors to provide services to remove the waste material and dust that has accumulated in the facility to mitigate this identified fire hazard, as well as quotes to repair the damaged steel push wall,” he wrote.

In order to remove the hazards and address the wall as soon as possible, Lazarus said he approved emergency contracts to address those conditions. As loading operations at the city’s recycling plant need to be suspended during the upcoming work, the City Council voted this week to approve a short-term agreement with the Western Washtenaw Recycling Authority for up to $36,000 worth of recyclable processing services.

The city expects the waste removal and steel push wall work will be done between Friday, Sept. 22, and Sunday, Oct. 1, affecting one work week. The short-term deal with the Western Washtenaw Recycling Authority is for up to two weeks.

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