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

Neighbors of the Cemex quarry and cement kiln near Lyons say a deal to extend mining and cement production for 15 years in exchange for valuable open space breaks Boulder County commitments to end the heavy industrial operation and cut the largest local sources of greenhouse gas emissions. 

They also say Cemex may be leaving the door open for another large, polluting operation on the site after 2037, when the proposed agreement with Boulder County Parks and Open Space ends. 

“Any promises Cemex makes to Boulder County are proven to be unreliable,” said Amanda Dumenigo, executive director of the nonprofit Save Our St. Vrain Valley. 

Cemex has long operated a rock mine surrounded by Rabbit Mountain Open Space north of Colorado 66 near Lyons, sending stone in a conveyor tube over the highway to its massive cement kiln on the south. The state-permitted cement kiln can operate indefinitely, creating cement for concrete for projects across the state but also putting more than 350,000 tons of carbon dioxide into the air each year from its blast furnace. 

The Cemex mine needs a new permit this year from Boulder County. The Mexico-based cement company has offered to close the kiln and mine together in 2037 as a permit condition, while also giving Boulder County more than $10 million in open space and higher land lease payments. The open space donations and discounted prices would add 1,800 open space acres and stitch together a broad natural area. 

Boulder County Parks and Open Space officials, who signed off on the deal, announced the proposal in May, and the next stop is the Boulder Planning Commission in July. A full county commissioners’ vote would come later in the year. 

County residents who have fought for years to cut pollution at the Lyons site say the proposal could let other companies use the cement kiln, or start another heavy industrial use. They claim another company has a permit to open an asphalt plant in the St. Vrain Valley, and fear it could launch at the Cemex site. 

Cemex officials did not respond to requests for comment about the residents’ concerns. 

Opponents of an extension for Cemex point to documents where county officials demand the mine end all operations and begin reclamation in October 2022. 

Boulder County negotiated local property rights from landowners in a 2002 agreement that “establishes a commitment by Boulder County to prevent, to the extent possible, use of the property for mining after December 31, 2021,” according to a letter to Cemex from county planning director Dale Case in 2019. 

In the same letter, archived by Save Our St. Vrain Valley, Case mentions the mine’s current permit conditions, and adds “the county cannot agree to extend mining any further, so September 30, 2022, is the date when mining must cease.”

this is the correct version updated by BoCo June 2022
A proposed agreement between Boulder County and Cemex would allow the mining and cement company to continue operations through 2037, in exchange for Cemex giving Boulder valuable open space. (Boulder County Parks and Open Space handout)

What’s different now from that 2019 letter, Case said Wednesday, is that Cemex officials “have applied to extend the mining period,” which they had the right to do. “If it is approved they can extend the period to the new date approved. If it is not approved, the previous review requirements will apply and mining is to end in 2022.”

Opponents say extension of the past closure deadlines, and details of the current Cemex extension proposal, show far too much willingness on Boulder County officials’ part to accept 15 more years of unchecked operations by the county’s biggest greenhouse gas polluter.

“How does the county reconcile putting open space acquisition ahead of the county’s climate goals? There is nothing in the negotiation that reduces the enormous carbon emissions from this plant over the next 15 years,” said Sarah Lorang, who owns property in the area and helped start an online information group called Good Neighbors of Lyons.

County open space officials, who negotiated the current proposal with Cemex, said the offer to stop using the kiln in 2037 is significant, and means what it says.

“The requirement that all plant operations cease was a primary focus for Boulder County to achieve,” said Janis Whisman, real estate division manager for Boulder County Parks and Open Space. “The exact phrasing in Cemex’s application, though less specific, means conclusion of all plant operations. That requirement will be well-documented in a new option agreement if Cemex’s application to extend mining is approved.”

A decision on the proper balance between open space needs and cutting greenhouse gas emissions is now up to other county officials and residents, Whisman said. 

“Parks and Open Space has not made such a conclusion and the question is not one for Parks and Open Space to decide,” she said. “This question will be considered during the (planning) application process. The Board of County Commissioners will conclude what constitutes the best outcome for the community at the public hearing when they will consider the application.”

Clean air advocates in the county have asked Cemex to put the cement kiln and its emissions under a county permitting process, in the same way the mine is permitted, to create more local control. 

The open space division asked Cemex to agree to that during the current negotiations, Whisman said, but the company declined. 

Cemex has mining operations for various materials throughout the world, and has reached agreements in the past to reclaim and donate open space in states such as California

The Boulder County cement kiln, meanwhile, has long been the site of tussles with neighbors and environmental advocates, who say cement operations are some of the dirtiest industries around and have brought suit to force changes. Cemex agreed to a $1 million EPA fine for violations of the Clean Air Act at the Lyons kiln that released too much toxic nitrogen oxide and particulates, though the company said the violations occurred before it acquired the plant. 

Opponents of the Cemex extension will continue to organize against it and demand more details from county officials at public hearings, they said. 

“We will pack the house, as we’ve done in the past,” Dumenigo said. 

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...