The Cemex-owned cement plant near Lyons must pay US$1.5m in penalties and beefed-up environmental monitoring as part of a settlement with Colorado regulators over air pollution violations spanning three years.

The agreement, among the largest air pollution penalties ever issued by state environmental regulators, stems from allegations that the plant, owned by Mexico-based Cemex violated limits on dust emissions and operating temperatures at various times between 2004 and 2006.

The plant has been the target of a vigorous campaign by activists who have long complained about excessive dust and a tyres-to-fuel burning operation and their effects on air quality and respiratory health. Concerns that plant emissions are raising pollution in Rocky Mountain National Park just to the west were also cited.

Under the settlement with the state health department’s Air Pollution Control Division, Cemex must pay a US$350,000 fine to the state’s general fund, spend US$200,000 on air monitoring at the plant site, spend US$500,000 toward so-called "supplemental environmental projects" that aid the local community, and pay US$450,000 to the StEPP Foundation, a nonprofit organization that supports a variety of environmental work.

In addition, the company agreed to a moratorium on burning tyres for fuel for 12 months.