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Gov. J.B. Pritzker recently signed into law a bill that would allow Aurora to dispose of lime sludge used in treating its drinking water.
House Bill 3095 was passed by the state Senate earlier this year, and Pritzker signed it late last week.
Aurora can now dispose of the lime sludge created by treatment of the city’s drinking water in a mine on the edge of town. The process would allow the city to save about $7 million during 10 years of disposal costs under the method the city was going to use.
The bill was sponsored by state Sen. Linda Holmes, D-Aurora, and in the House by state Rep. Barbara Hernandez, D-Aurora.
“Aurora’s Water Treatment Plant has used limestone in its processes since it was built in 1992, but disposing of the residual product was problematic,” said Holmes. “The city of Aurora initiated this legislation, as it cost the city quite a bit of money to dispose of it in landfills or to apply it on farmland. Putting that material back into an underground mine cavity 250 feet below ground will save significant taxpayer dollars.”
The city has been working with LaFarge Aggregates Limestone along Route 25 on the border with North Aurora and Aurora at Route 25 and Interstate 88. The city needed the legislation to allow it to use the worked-out limestone mine for the lime sludge disposal.
The water treatment method leaves behind a limestone residual or sludge that the city disposed of in landfills at great cost, then changed to application on agricultural lands, but also at a great cost.
The city began the land application in 2012, but as far back as 2006 began looking at disposing of the lime residual in the mines. The city received a permit from the Illinois Environmental Protection Agency in 2015 to begin pumping the lime residual into the LaFarge mines.
To do that, the city planned to build a pipeline from the treatment plant to the mines that would have cost an estimated $8 million. But in 2016, the city discovered an alternative method.
In that method, the city would dry the lime at the treatment plant and have the dried residual trucked to the mines where it would be dumped into the mine and then packed by the company.
At that point, the city held off on the pipeline to review the new alternative. City officials estimated that alternative would save the city about $7.7 million during the first 10 years, as much as about $15 million over 19 years.
The city also would save about $8 million it would cost to build the pipeline.
LaFarge’s mine is about 200 to 400 feet underground and is mainly used to produce limestone and dolomite aggregates for construction uses.
The portion of the mine in Aurora is typically referred to as the south mine and has two levels with a third level to be constructed in the future, city officials said. The first two levels of the mine are almost completely excavated and thus are no longer useful for material production.
City officials have said the city would get at least 50 years of disposal in the mines, and the Illinois EPA looked favorably upon the method in part because the lime is being disposed where limestone was mined, so they are like materials.
House Bill 3095 creates a framework to allow limestone residual material to be deposited safely back into unused mines. Under this measure, the Pollution Control Board is tasked with adopting rules to ensure the material is regulated and stored in a manner that best protects the health of the environment.
“For the sake of preserving our natural world, it’s vital that we not immediately dispose of materials so reactively termed ‘waste products,’” said Hernandez. “As we work to build a greener future, it’s time to stop overlooking the potential to reclaim resources that can be valuable to the community.”
The measure will take effect Jan. 1, 2024.