The U.S Environmental Protection Agency will visit the former Smurfit-Stone mill site west of Missoula this week to inspect the berms, and it will likely be there when the Clark Fork River crests on Thursday.

Allie Archer, project manager with the EPA, said the berms have been identified as essential infrastructure, standing as a barrier between the shifting river and the former industrial plant's pollutants.

The berms are inspected for signs of erosion monthly from April through July, and regardless of river flows. But plans call for more frequent inspections at certain river heights. And with rain the forecast, the integrity of the berms is once again a concern.

“Weekly inspections will begin if the Clark Fork River below Missoula accedes 10.5 feet for any part of the week, and daily inspections if it accedes 11 feet,” Archer told Missoula County officials on Tuesday. “There are response actions identified in our contingency plans.”

The EPA assured Missoula County in 2017 that more than 8 miles of earthen berms at the former pulp mill will be inspected during peak runoff to ensure they are not breached, sending toxins into the Clark Fork River.

Built between 1958 and 1970, the berms were intended to quarantine polluted water and papermaking chemicals in ponds to keep them out of the Clark Fork, which runs alongside the shuttered mill.

Keith Large with the Montana Department of Environmental Quality said the river has come up fast in recent days – a combination of rainfall and snowmelt.

“The Clark Fork River below Missoula, at the gauge station we follow, should peak Thursday at 10.3 feet, which is right below the action stage of 10.5,” he said. “I looked at the USGS gauge this morning (Tuesday) and it had a foot of gauge height overnight, so the river is coming up quick. We'll keep our eye on this every five or six hours.”

While the EPA considered the berms' stability in 2017, it learned a bit from the 2018 floods, which neared record highs along parts of the Clark Fork River corridor in Missoula.

An estimated 4.7 miles of berms run directly adjacent to the river. Another 3.7 miles of berms are in the interior of the mill site, where they outline the sludge ponds.

“The real concern is channel migration and a massive cut-through of the sludge pond and the interior berm,” said Travis Ross, supervisor of the county's water quality district. “We're still working on that channel migration zone study that will include this section of the Clark Fork River. We look to have that report out in the next couple months.”