Processing the flammable waste sitting in a tank at the old phosphorus plant 10 miles west of Butte will create a new, inert byproduct, a spokeswoman for the Environmental Protection Agency told Butte-Silver Bow County commissioners Wednesday.
That new, non-hazardous byproduct will be returned to the same tank and stored permanently, said EPA site manager Christina Cosentini.
Belgium-based Solvay owns the tank full of hazardous sludge and the 150-acre moonscape it sits on. The black slag dunes that surround the tank are visible south of Interstate 90 at the Ramsay exit.
Solvay delivered a proposal last year to EPA. To process the dangerous sludge on site is "the only viable option," Solvay project manager Dan Bersanti told the commissioners. That proposal, greenlighted by EPA, is up for public comment until October 26.
If the sludge comes into contact with the air, it ignites. It is capped by 2 to 3 feet of water and black “bird balls” to discourage migratory fowl from landing. The material stored in the tank is 500,000 gallons of byproduct from decades of processing phosphorous. Phosphorous is used in a variety of products, including food and fertilizer.
The expected cost to build the plant is an estimated $25 million. Solvay anticipates to recoup $2.5 million from mining the residual phosphorus out of the sludge, according to the company’s proposed plan.
EPA gave Solvay more than a decade to decide what it wanted to do with the dangerous byproduct stored within the tank.
Commissioner Cindy Purdue-Dolan asked Bersanti why a potential solution took so long.
Bersanti said Solvay conducted “several studies” and called it “a fairly lengthy process.”
Commissioner Cindi Shaw asked about the proposed plant becoming the recipient of hazardous waste from other sites. Solvay has proposed that the plant could be become a permanent commercial site.
Bersanti said that wouldn't happen until the hazardous waste on site has been dealt with. It could take 10 years for the sludge to be completely processed, given the experimental nature of the project, EPA said previously at a public meeting in Ramsay last month.
Cosentini added that if Solvay goes in the direction of commercial processing, it will need a permit from the state Department of Environmental Quality to operate.
Cosentini said the tank will be “the final repository for these (waste) materials.” Once the work is complete, the tank will be capped, receive vegetation, and be fenced off.