A number of unexpected conditions have added to the cost of removing a pile of waste material at the former Bonner mill site, prompting Missoula County to increase its reimbursement for cleanup.

Commissioners last week sided with the Missoula Development Authority and its recommendation that the county increase its “do-not-exceed” amount from the original $3 million to $3.9 million. The county also extended the required completion date to June 2022.

The three-acre site, now owned by Bonner Property Development LLC, contains soil and debris contaminated with petroleum compounds and polychlorinated biphenyls, or PCBs, once used at the former Stimson lumber mill.

“The repository removal at Bonner was not what we thought it was going to be,” said Emily Brock, the county's director of Economic and Land Development. “We didn't have access to the site until we started the cleanup. It was controlled by DEQ. There was more tonnage and cleanup is more tedious than previously thought.”

The original bid, set by the county last year, covered the cost of removing 60,000 tons of waste and included around 10,000 added tons as a contingency. Within a month after the work began, 70,000 tons of waste had been hauled to the landfill.

It became clear, Brock said, that the $3 million contract was not enough to cover full removal. By August, more than 85,000 tons had been hauled away for a total cost of $3.4 million. It will cost an additional $555,000 to complete the work, she said.

“There's still about $555,000 of work remaining to clean up the site and get it building ready per the development agreement,” Brock said. “Fully cleaning the site is the priority for the county. The property owners didn't create the waste, they just got left with it.”

Missoula County last year approved the agreement between Territorial Landworks and Bonner Property Development. The county agreed to contribute $3 million in tax increment funds to finance the work.

The Montana Department of Environmental Quality has said the repository stems from cleanup work that occurred at the mill in 2011. The initial cleanup netted more waste material than initially expected, and the added waste was capped on site.

The remaining contaminants rest in the location of the old kilns, where wood was dried as it left the sawmill and before it went to the planer, where it was cut into various products. Once the site is cleaned, the property owners plan to develop the site, bringing more revenue into the taxing district.

“The (Missoula Development Authority) board landed on paying for the full cleanup,” said Brock. “The property owners have acted in good faith. The reason it's costing more is because of conditions outside their control. They are planning to build on that site, so we will see tax increment once its cleaned up.”

The county will finance the added costs over a 10-year period with hopes of sunsetting the taxing district sooner than initially planned.

More From Missoula Current