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Lyons Quarry Reclamation
Lyons Quarry

Lyons Quarry Reclamation at Hall 2 Open Space

This project is separate from the Colorado Highway 7 project with road closures. Learn more about that project at

Aggregate Industries has begun reclamation of the Lyons Quarry at Hall 2 Open Space under a mining and reclamation permit issued by the State of Colorado’s Division of Reclamation, Mining, and Safety (DRMS). Although the property is owned by Boulder County as open space, the quarry and its subsequent reclamation requirements are under the jurisdiction of DRMS, and Aggregate Industries is solely responsible for the reclamation project and operations.

Blasting Activities

As part of the re-grading activities for the Lyons Quarry reclamation, Aggregate Industries plans to perform blasting within the quarry. Blasting is expected to begin around May 24 and will likely occur every other week until the operations are complete. Liquid blasting material will be loaded into holes that are drilled 35 feet into the ground. Material is not expected to be blasted into the air as the process is meant to loosed up the substrate. The entire blast will occur within a matter of minutes and is not expected to cause any disruption. At this time, the project does not plan for any traffic impacts to Colorado Highway 7.

Reclamation Plan

Aggregate Industries has coordinated and worked with Parks & Open Space since the county purchased the property in 2011. Although the property is owned by Boulder County for open space purposes, the quarry and its subsequent reclamation requirements are under the jurisdiction of the state’s DRMS. The county, as landowner, has provided comments and recommendations to Aggregate Industries and DRMS, but DRMS provides the ultimate oversight and approval of the mining and reclamation permit and work.

The final reclamation plan calls for:

  • Regrading the “high wall” (i.e., steep portions of the quarry) to match the natural slope of the surrounding landscape. This will be achieved through minimal blasting and earth moving.
  • Preserving a section of the exposed dacite walls at the base of the mine for geological interpretation purposes. Dacite is a type of granite. This hard rock has intruded, or pushed through, softer rock throughout the Rockies, creating our magnificent mountains. At this site in particular, the granite has intruded into the sandstone. You can see this in the exposed rock where sandstone is found both above and below the dacite. Local geologists believe this is the terminus of the “mineral belt” of hard rock where gold, silver and other ore are mined from SW Colorado to Lyons.
  • Removing crusher fine material and berms from the floodplain and along South St. Vrain Creek.
  • Constructing rockfall catchment areas at the base of the highwall.
  • Scaling and stabilizing the remaining highwall slopes.
  • Installing stormwater drainage and erosion control infrastructure.
  • Conditioning soil and planting native vegetation adapted to the site conditions.
Andesite intrusion between layers of sandstoneAndesite intrusion between layers of sandstone

Lyons Quarry Plan


Features of the reclaimed site will include:

  • Exposed rock/dacite wall providing a geological feature for education.
  • Native vegetation.
  • Public access as defined by/approved by future management planning process.

Site Impacts & Timing

  • All reclamation work will occur within the current footprint of the existing mine to avoid impacts to adjacent undisturbed habitat.
  • Reclamation work on the highwall is expected to begin in September 2021, while work in the floodplain is expected to begin after high flows in 2022. The deadline for completion of all grading and revegetation throughout the quarry has not been finalized with DRMS but is expected to be complete by the end of 2022.
  • Following regrading and revegetation, Aggregate Industries will be required to monitor and maintain the site for several years including weed control, monitoring site stability, and establishing native vegetation, to ensure the site is stable and the revegetation efforts are successful.
  • Before Aggregate Industries can be released from their reclamation bond, the site must meet the following DRMS requirements:
    Rule 3.1.10(1) In those areas where revegetation is part of the Reclamation Plan, land shall be revegetated in such a way as to establish a diverse, effective, and long-lasting vegetative cover that is capable of self-regeneration without continued dependence on irrigation, soil amendments or fertilizer, and is at least equal in extent of cover to the natural vegetation of the surrounding area.
    (from Minerals Rules and Regulations of the Colorado Mined Land Reclamation Board for Hard Rock, Metal, and Designated Mining Operations (2019)

Lyons Quarry Map

Future Open Space Planning at Hall 2

Parks & Open Space will not have full management authority of the property until Aggregate Industries has successfully reclaimed the Lyons quarry and DRMS releases the mine’s reclamation bond. To help determine the best uses of the property, the department wants staff and the public to have a good view of what the post-reclamation landscape will look like before starting a planning process.

At that time, Parks & Open Space staff will conduct a public planning process to determine the future management direction for the Hall 2 open space property. This property is part of the larger North Foothills open space complex which includes Hall Ranch and Heil Valley Ranch. The site has the potential for many unique opportunities for recreation, appropriate public amenities, education and interpretation, and the conservation of significant natural resources.


The site has been mined by various operators since the 1950s with most of the active mining occurring between 1977 and 2008 under DRMS permit M-1977-141. Although the site was under a five-year “temporary cessation” between 2011 and 2016, whereby Aggregate Industries was allowed by DRMS to postpone all mining and reclamation activities, the company continued to revise their reclamation plan and met with Parks & Open Space staff several times to hear about the department’s interests and long-term plans for the site.

The 2013 flood did a lot of damage in the mine’s floodplain and washed out the county bridge across South St. Vrain Creek, which had previously provided access to the quarry.

Starting in 2017, after the bridge was repaired by Boulder County and the temporary cessation had ended, Aggregate Industries began to finalize their reclamation plan and has continued to work with Parks & Open Space as they further revised their reclamation plan.

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