Thursday, March 30, 2023

Cleanup of Kaiser Mead plant lends clues into CFAC future

Hungry Horse News | March 18, 2023 12:00 AM

The cleanup at the former Kaiser Mead aluminum smelter near Spokane, Washington could provide insight as to how the Columbia Falls Aluminum Co. plant is ultimately cleaned up as well.

Like the Columbia Falls site, former smelter is also a Superfund site, though with one difference — it's managed by the state of Washington.

But the two defunct plants have many things in common, most notably buried spent potliner from the aluminum smelters and high levels of cyanide and fluoride in the groundwater.

A quick lesson on cyanide:

The cyanide of greatest concern is free cyanide, which can be highly toxic. For example, apple seeds contain amygdalin, a cyanogenic glycoside composed of cyanide and sugar. When metabolized in the digestive system, this chemical degrades into highly poisonous hydrogen cyanide. A lethal dose of it can kill within minutes, notes an entry in the Encyclopedia Britannica.

But in the case of an apple, a person would not only have to eat the seeds, they'd have to eat a lot of them (at least 150 to several thousand) and chew the seeds as well. The poison isn’t released just by swallowing the whole seed, the seed must be crushed.

Cyanide can also combine with organic and inorganic materials, noted Garin Schrieve, the Kaiser Mead project manager for the Washington Department of Ecology.

At Kaiser Mead, they treat the groundwater by pumping it to the surface and then through three different cells. Imagine a pond, but the pond is so full of rocks that there is no actual surface water.

Bacteria grows on the rocks. As the water runs through it, the bacteria metabolize it, Schrieve explained, converting it into a nitrogen compound and carbon dioxide.

By the time the water flows through the three cells and goes through the biological process, the cyanide is removed to safe levels (there’s also a process to remove nitrates as well.)

But the water treatment isn’t done. It takes another process called electrocoagulation to remove the fluoride, Schrieve explained.

The water flows over aluminum and iron plates with an electric current running through it. In the end, the fluoride is removed and precipitates out the water.

The treated water is then pumped back into the aquifer.

The system does not pay for itself. Kaiser Mead went bankrupt in 2004 and as part of that bankruptcy settlement a trust was created. It’s the trust that provides the funding to run the 24/7 operation and pay the staff, which is done under contract with a private company.

As for the spent potliner at the plant, it was consolidated and put in a lined and capped landfill.

The contamination continues at the site largely because of the years of dumping wastes into the ground. The Columbia Falls Aluminum Co. site has the same issues — there’s high concentrations of contaminants not only from spent potliner, but also from wastewater that was pumped out of the plant for years.

The EPA is expected to release a proposed action for the site this spring.

A feasibility study/remedial investigation feasibility study completed by the company last June looked at several alternatives and scored a slurry containment wall combined with bolstering existing landfills as the best alternative for dealing with contamination at the site.

It also calls for treating the water to remove cyanide and fluoride.

A slurry wall would be a wall 3 to 6 feet thick and 100 feet deep designed to contain groundwater from leaching from the site.

Local critics, however, claim a slurry wall could crack if there’s an earthquake. Many residents have lobbied to see the potliner and contaminated soil removed entirely and hauled away to a dump in Oregon.

But based on cleanups either in the works or completed at other defunct aluminum plants, that doesn’t seem likely.

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