Boulder County is buying the second of two parcels of Cemex’s Dowe Flats property, about 24 years after signing an agreement that gave the county the option to acquire it as open space.

The Boulder County commissioners on Tuesday signed off on exercising the option to buy the larger, 613-acre parcel for $1.5 million.

The Dowe Flats property, which totals 766 acres and includes the plant’s closed quarry, is north of Colorado 66 and adjacent to the county’s Ron Stewart Preserve at Rabbit Mountain open space. The cement plant, which is still operating, is a separate property on the other side of Colorado 66.

The county is using its open space fund to pay for the Dowe Flats purchase, with a goal of returning the site to a native grassland. Boulder County’s option to purchase the property was established by a 2002 agreement.

The smaller, 153 acre-parcel includes the rights to develop 11 lots. In exchange for the county purchasing the $5.1 million in development rights, Cemex is transferring the 153 acres to the county for open space. The county commissioners signed off on that purchase in October 2024, then the county and Cemex agreed in January 2025 to delay closing until the initial reclamation of the land was complete. The 153-acre parcel will be conveyed to the county at the same time as the larger parcel, according to county officials.

The larger parcel includes Cemex’s quarry, which is substantially reclaimed, according to county officials. The deadline for the county to agree to purchase the property was Nov. 5. The expected closing date is in February.

The Dowe Flats quarry closure came after Boulder County commissioners in 2022 denied Cemex’s application to continue mining at the quarry for 15 more years. The county had authorized Cemex in 1994 to mine the quarry for a maximum 25-year period.

After the quarry’s closure, Cemex agreed to complete reclamation.

Boulder County spokesperson Summer Alameel said Cemex has removed all of the infrastructure associated with mining, including the transport conveyor pipe that went over Colorado 66, with the exception of a few structures Boulder County asked the company to retain. Cemex also filled in the mine pit, completed all earthwork and grading, and seeded and mulched the area.

With the earthwork complete, she said, Colorado’s Division of Reclamation, Mining and Safety reduced the amount of money Cemex must post as a bond from about $12.6 million to about $1.2 million. The remaining amount is to ensure Cemex addresses future reclamation needs, such re-seeding, she said. Fulfilling the reclamation requirements is expected to take two to five years.

While the quarry is closed, the plant continues to operate. Boulder County in 2024 ordered the plant to shut down, citing increased heavy truck traffic. After Cemex appealed, the county reversed its decision in May.

Good Neighbors of Lyons and Save Our St. Vrain Valley have appealed the county’s reversal. A hearing on their appeal, which was scheduled for Nov. 4, recently was rescheduled to Feb. 3.

Good Neighbors of Lyons and Save Our St. Vrain Valley requested the delay after Cemex issued a federally required notice that it intended to lay off at least 70 employees, starting Nov. 21. Worker Adjustment and Retraining Notification Act, or WARN, notices generally are required when a company with more than 100 employees is planning a mass layoff or to close.

“Cemex will be rebalancing staffing levels at its Lyons cement plant beginning in the fall 2026, resulting in the elimination of some positions. Although positions will be eliminated, cement sales and distribution at the Lyons plant will continue,” according to a statement from the company.