Lyons Quarry Reclamation and South St. Vrain Creek Restoration at Hall 2
Lyons Quarry

Lyons Quarry Reclamation and South St. Vrain Creek Restoration at Hall 2 Open Space

Reclamation of the Lyons Quarry at Hall Ranch 2 Open Space (Hall 2) began in fall 2021, and after some delays, final site stabilization and revegetation are anticipated to be completed by the end of 2024.

Although the property is owned by Boulder County as open space, the quarry and its subsequent reclamation requirements are under the jurisdiction of the State of Colorado’s Division of Reclamation, Mining, and Safety (DRMS) under DRMS Permit M1977-141.

The mining company, Holcim-WCR, Inc., is solely responsible for the reclamation project, including all post-reclamation maintenance and monitoring. DRMS will make the final determination of reclamation success.

Reclamation Plan

Parks & Open Space has coordinated and worked with the mining company since the county purchased Hall 2 for open space in 2011. Since that time, the county, as landowner, has provided comments and recommendations to Holcim-WCR, Inc. (previously Aggregate Industries) and DRMS, but DRMS provides the ultimate oversight and approval of the mining and reclamation permit and work.

The final reclamation plan that was approved by DRMS called for:

  • Regrading the “high wall” (i.e., steep portions of the quarry) to mimic the natural slope of the surrounding landscape through minimal blasting and earth moving.
  • Preserving a section of the exposed dacite1 walls at the base of the mine for geological interpretation purposes.
  • Removing crusher fine material from the floodplain and along South St. Vrain Creek.
  • Constructing rockfall catchment areas at the base of the highwall.
  • Fencing around the reclaimed highwall to ensure public safety.
  • Installing stormwater drainage and erosion control infrastructure.
  • Conditioning soil and seeding native vegetation adapted to the site conditions.

Following regrading and revegetation, Holcim-WCR, Inc. will be required to monitor and maintain the site for several years focusing on weed control, site stability, and native vegetation establishment.

Before Holcim-WCR, Inc. 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)

1 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.

Andesite intrusion between layers of sandstone

Lyons Quarry Plan

South St. Vrain Creek Restoration at Hall 2

In addition to the reclamation of the mine, Parks & Open Space is also planning the restoration of South St. Vrain Creek on Hall 2.

During the 1960s, an approximately half-mile stretch of South St. Vrain Creek adjacent to the Lyons Quarry was moved along the south side of State Highway 7 and channelized. An aerial photograph from 1940 shows a more natural alignment across the floodplain. Because restoring the creek was not part of the DRMS-approved permit and reclamation plan for Lyons Quarry, it was not included in the mine reclamation.

Since 2011 when the county purchased Hall 2, Parks & Open Space has envisioned realigning the creek to its natural alignment across the floodplain. The post-2013 flood assessment, planning, and engineering, which included significant public engagement, supported this vision. A 30% restoration design plan for the site was completed in 2016 as part of the 2013 flood recovery efforts by Matrix Design Group.

The plan shows the creek being realigned and restored into its natural meander using natural channel deign principles and the construction of overflow channels.

As the mine reclamation wraps up, Parks & Open Space has moved forward with finalizing the creek restoration design and is currently working with an engineering firm that specializes in stream restoration. The design will be completed by the end of 2024; however, construction won’t occur until the department secures the necessary implementation funds for the project over the next couple of years.

As established in the 30% design, the goals for the project are to restore and improve the channel and surrounding floodplain to protect life and property and provide a safe, natural, resilient, functioning, and ecologically rich habitat utilizing natural system principles. The project will expedite recovery from past disturbances, including mining and the 2013 floods, and make the area more resilient in future flood events.

Lyons Quarry Map

Aerial photo of the Lyons Quarry area showing the creek had a natural, meandering alignment before it was changed to the current channelized alignment

Future Open Space Planning at Hall 2

Parks & Open Space will not have full management authority of the property until Holcim-WRC, Inc. has successfully reclaimed the Lyons quarry and DRMS releases the mine’s reclamation bond.

At that time, Parks & Open Space plans to conduct a public planning process to determine the future management direction for the Hall 2 open space property, which is part of the larger North Foothills open space complex including Hall Ranch and Heil Valley Ranch.

The site has the potential for many unique opportunities relating to the conservation of significant high value natural resources, environmental and geological education and interpretation, and appropriate recreation and public amenities.

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Parks & Open Space

Ernst Strenge