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Cemex’s Cement Plant on June 13, 2022, near Lyons. (Hugh Carey, The Colorado Sun)

Boulder County neighbors who won an unlikely victory shutting down the Cemex cement plant’s mineral mining operation near Lyons are going after the giant cement kiln itself, claiming Cemex must be closed because the way it works now violates rules from four local and state agencies. 

Cemex opponents are also asking the town of Lyons and other Boulder County jurisdictions to sign a letter demanding county officials revoke the cement plant’s land use privileges. Lyons officials will vote on joining the letter Monday. 

Greenhouse gas and local air pollution from Cemex, one of only three cement plants in Colorado and the largest single source of carbon emissions in Boulder County, have long been a target of neighbors and environmental activists.

A loose coalition first succeeded in late 2022, when the Boulder County Commissioners declined to renew the mining permit. For decades, Cemex and predecessors had mined limestone and shale on the north side of Colorado 66 and moved it south to the cement plant on an overhead conveyor. 

Cemex had asked for a long extension of the mining permit, and in exchange offered to transfer hundreds of acres of land for open space that would have connected popular parks and trails. Planning staff had negotiated the trade, but the commissioners ultimately rejected it after hours of emotional public testimony from opponents, countered by pleas from Cemex employees and other supporters. 

Cemex now delivers raw materials from outside Boulder County on 80 or more trucks a day, according to the complaints, a fact the company warned about during contentious public hearings over shutting the mine. Cemex opponents say the trucking and other operational changes violate the company’s county land use restrictions, a state mining agency permit for sourcing of materials, state transportation safety rules, and emissions permits regulated by the state Air Pollution Control Division. 

Closing the rest of Cemex would eliminate 300,000 tons a year of carbon dioxide emissions, the equivalent output of a town of 30,000, the activists say. They have pointed out all along that Boulder County needs to find significant emissions cuts to meet its stated greenhouse gas goals. A closure would also cut diesel traffic and launch the reclamation of operation areas and tailings that periodically produce dust clouds over neighborhoods, the activists say.

For the long term, “we have major concerns with their greenhouse gas emissions,” said Sarah Lorang, speaking for a group of activists and local elected officials who support the Cemex complaints. “But currently, they are breaking rules, and I’d just like to see them accountable.” 

The company took “a calculated risk” in operating the plant after the mine closure in ways that violated various permits, Lorang said, and regulators need to call them out. Lorang’s group, Good Neighbors of Lyons, is working with Save Our St. Vrain Valley and others to ask more Boulder County towns to pressure Cemex. 

Cemex has told local officials it plans to build a new cement-making plant near Laramie, Wyoming, so the production for Colorado projects and the jobs at Lyons could be replaced with a much cleaner plant, Lorang said. 

Cemex’s local and national offices did not respond to requests for an interview. 

Activists looking to shut Cemex completely are filing formal complaints on multiple fronts:

  • Boulder County’s director of land use is asked to investigate and end Cemex’s allowed “nonconforming” uses because of an alleged doubling in truck traffic at the site, and new, larger stockpiles of shale and other materials that are a nuisance to the neighborhood, a complaint says. 
  • The state Division of Reclamation, Mining and Safety is asked to investigate permitted activities at the Lyons Quarry, which is on the cement plant’s side of the highway and separate from the permit for the now-closed Dowe Flats property. Cemex should not be allowed to amend its Lyons Quarry permit to include trucking in materials from off-site, the complaint says. 
  • The trucking and possible emissions from new shale piles could violate Cemex’s permits under the federal Clean Air Act administered by the Colorado Air Pollution Control Division, a complaint alleges. Also, Cemex’s air pollution permit has expired, though the state allows Cemex and companies in the same situation to continue operating under old permit terms while it reviews a renewal application, which can take years. 
  • A complaint with the Colorado Department of Transportation asks the state to review additional road traffic, pavement damage and potential safety of highway use after Cemex’s operational changes. 

Each of the agencies responded they are looking into the citizen requests. 

“Boulder County Community Planning & Permitting received a complaint regarding CEMEX on Jan. 20, 2023. Staff is currently investigating the complaint,” said Richard Hackett, spokesman for the agency. 

State air pollution officials said in a statement, “The division can, and has, taken enforcement action using existing Title V permits awaiting renewal if necessary. CEMEX, like any other regulated facility, is also required to comply with all applicable air regulations. The division responds to and investigates complaints received — this is separate from the permit process.”

Michael Booth is The Sun’s environment writer, and co-author of The Sun’s weekly climate and health newsletter The Temperature. He and John Ingold host the weekly Sun-Up podcast on The Temperature topics every Thursday. He is co-author with...