Despite a decades-long effort to remove heavy metals from the Clark Fork River after a flood more than a century ago washed tons of contaminated mining sludge into the river, a new study suggests the Clark Fork could face a similar disaster if a future flood breaches the berm at the Smurfit-Stone site.
The Smurfit-Stone site, a former pulp mill near Frenchtown, downstream from Missoula, is home to hundreds of acres of unlined ponds storing toxic waste, essentially buried in the Clark Fork floodplain. For years, an earthen berm has existed between the toxic waste and the river, but recent spring runoff eroded the berm and raised concerns about its long-term integrity and the risks it poses to downstream communities.
To better understand the growing risks and urge the Environmental Protection Agency (EPA) to consider the risks of berm failure, the Clark Fork Coalition and American Rivers commissioned a study from River Design Group, a local engineering and restoration firm. The study used site hydraulic models to evaluate various berm failure scenarios under current and future climate conditions.
Smurfit-Stone’s unlined ponds are already leaching dioxins and heavy metals into groundwater and the river. The study found that if the berm breaks, thousands of tons of toxic waste, including heavy metals, PCBs, dioxins and furans, could spill into the Clark Fork River and travel downstream, potentially reaching Lake Pend Oreille in Idaho.
“This study was really intended to put pressure on the EPA to really evaluate the risk of berm failure,” said Andrew Gorder, legal director for the Clark Fork Coalition, a Missoula-based nonprofit dedicated to protecting and restoring Clark Fork River Basin. “The risk of berm failure has been raised by all stakeholders involved in the Superfund process, but EPA has consistently said: ‘We cannot take catastrophic events like berm failure into account when we look at risk assessments. risk'”.
“Berm failure is not a catastrophic event: it is inevitable. It will happen.”
Andrew Gorder, Clark Fork Coalition
EPA is responsible for monitoring and overseeing the cleanup of the Smurfit-Stone site. Smurfit-Stone is not officially designated as a Superfund site, but the previous owners and operators of the mill and property signed an agreement with the EPA to follow the Superfund process and fund the investigation and cleanup. Fourteen years into the process, EPA is still in the remedial investigation phase, collecting data to understand contaminants and their risks to human health and the environment. This phase will continue for a few more years before a feasibility study begins to analyze cleanup options. The real cleanup is likely at least a decade away.
“Berm failure is not a catastrophic event; it is inevitable,” Gorder said. “It will happen.”
During a recent forum to present the study in nearby Alberton, Allie Archer, EPA project manager for the site, said she was impressed by the information in the study and that “we would take it into account when we look at risk assessments and risks.” futures”. “
THE STUDY
The study examined three berm failure scenarios at Smurfit-Stone: pipe, rupture, and overtopping. Sam Carlson, a scientist with the Clark Fork Coalition, said that to understand the risk of flooding in Smurfit, we must look beyond the historical record and consider the possibility of much larger flooding.
The first scenario, “piping,” occurs when water finds a weak spot in the berm, such as a pipe or a hole made by burrowing rodents, that it can pass through. According to the study, at a 1 in 100 chance of flooding under current climate conditions (at approximately 66,000 cubic feet per second (cfs), only slightly higher than flows observed during recent spring floods), the Smurfit site would be vulnerable to pipes. . The pipes could move contaminated sediment and expel contaminants through groundwater.
The second scenario, “breakup,” would occur if flood waters moved fast enough to pick up and transport toxic soil. At a 1 in 100 chance of flooding, with water flowing at approximately 100,000 cfs under projected future climate conditions, approximately one-third of the site would be flooded and the water could carry organic matter and contaminated sediment downstream. Breaks could also occur at smaller flood levels.
“Some of the worst contamination is associated with organic matter as a result of the wood pulp bleaching process,” Carlson said. “That organic matter would definitely be mobilized in a scenario like a breach.”
The third scenario, overtopping, is the least likely but most catastrophic outcome, in which a massive flood would spill over the top of the berm and rush through areas that store toxic waste, spreading pollution downstream. The study estimates a 1 in 500 chance of an overflow (with flows of around 130,000 cfs) occurring under future climate scenarios. The study shows that once the berm begins to fail, it could take as little as two hours for a large breach to occur, making emergency response nearly impossible.
The EPA monitors the condition of the berm and has an emergency response plan, which Archer said includes being on site daily when the river is in flood stage and being on site 24 hours a day if they see water rising to those levels. levels. But Carlson argued that two hours “is not enough time to get the type of heavy equipment and materials that would be needed to reinforce the berm.”
Chris Nelson, an RDG hydraulic engineer who worked on the study, noted that there are many different ways berms can fail.
“They can be associated with different levels of flow and can occur in different locations,” Nelson said. “But the end result is essentially the same. You have a berm failure. “The water enters this contaminated area and then returns to the river.”
POTENTIAL FOR A CATASTROPHE
Any number of combinations of the study scenarios could occur, and the risk of berm failure increases over time due to ongoing climate change.
“Even these rare events are very unlikely in any given year, but in the time periods we’re interested in, those possibilities become quite significant,” Carlson said.
The terms “100-year flood” and “500-year flood” refer to the annual probability of such floods occurring, not their frequency over a century. For example, a “100-year flood” means that there is a 1 in 100 chance of that flood occurring each year, which translates to a 40% chance of it occurring at least once in a 50-year period. .
The Clark Fork River has already experienced flooding that exceeded predictions, such as the flood of 1908. Historical photographs showing water marks on an old mill suggest that a flood of similar size may have occurred in 1887. More recently, the Clark Fork River flood Yellowstone River in 2022, which had less than a 1 in 1,000 chance of occurring, underscored the need to consider how climate change could increase the frequency and severity of extreme weather events. The Yellowstone flood was caused by heavy rain on top of melting snowpack.
In less extreme cases, such as the Clark Fork River flooding in 2018, emergency measures were required to shore up the berm after plumes of pollution, containing heavy metals such as arsenic and manganese, were observed leaching into the river. .
“We have been pressing the EPA since then to take the risks posed by the berm seriously and incorporate them into the final remedy they propose for the site,” Gorder said.
Gorder hopes the EPA will use the study’s data in its risk assessments and scrutinize the berm more closely. He warned that simply reinforcing the berm would be a temporary solution, as it was never intended to protect against flooding.
“This is great information and I would love to discuss it further as we look at protective remedies in the future,” Archer said during the meeting.
The EPA has committed to preparing a climate vulnerability assessment, but Gorder expressed concern that it might not fully analyze potential failure scenarios or include the most recent climate data, based on his review of other EPA climate assessments at the global level. national.
Despite the looming threat of berm failure, Lisa Ronald, associate conservation director for American Rivers in western Montana, said her organization does not want to shortcut completion of the sampling needed to inform the cleanup process.
“We are concerned about the timeliness of the cleanup, but we also want to make sure we have the data we need to do the cleanup that is warranted,” Gorder added.
Ronald also warned against a “waste in place” approach, which involves leaving waste on site with some containment measures.
“What we now think of as our catastrophic floods will become the new norm in the future,” Ronald said. “The consequences of that are simply not worth it at Smurfit. The study presents compelling evidence to suggest that an in-situ waste solution will not work in this case. We cannot consider these berms as a protective structure.”
Ultimately, Gorder said, “we would like to see the most dangerous and toxic material we know exists at the site unearthed and placed in a secure repository that is out of contact with groundwater.”
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