Massive Slope Collapse at Limestone Quarry; Enforcement Actions Ensue

Around 3 p.m. on Jan. 18, 2023, a massive slope collapse struck the Rocky Mountain Industrials (RMI) limestone quarry. The collapse caused a rockslide about 300 feet wide. It brought boulders and huge slabs of limestone tumbling down onto the mined slope below.

A person in the vicinity described the noise as “multiple jet planes grumbling, getting closer and closer and getting louder and louder, for about 15 to 20 seconds.”

The debris spread across a large area of the quarry’s production bench and engulfed a front-end loader.

Luckily, quarry employees were all working elsewhere on the site that afternoon, and no injuries were reported.

Inspectors from the federal Mine Safety and Health Administration and the Colorado Division of Reclamation, Mining and Safety visited the quarry and studied the slope collapse in the ensuing days.

Bobby Wagner, RMI vice president of engineering, told state inspectors that the slide first broke loose on the west side of the quarry, where the limestone deposit tilts downward at a 45-degree angle.

A highwall on the east side of the quarry, where the limestone tilts downward at a less-steep, 30-degree angle, did not break loose. RMI blasted in this area most recently on Dec. 13, 2022.

The area that broke loose had not been mined since before RMI purchased the quarry operation in 2016, but RMI was actively mining limestone below the slide area.

Both agencies issued notices of enforcement actions for suspected permit violations.

The slope collapse at the Rocky Mountain Industrials limestone quarry occurred around 3:00 p.m. on Jan. 18, 2023. This image was captured shortly after the collapse occurred, as dusk moved across the landscape.

An overhanging cliff face remains at the top of the collapsed slope at the Rocky Mountain Industrials limestone quarry.

Permit Enforcement Actions by Federal and State Agencies

U.S. Mine Safety and Health Administration (MSHA)
Control 103(k) Order No. 9154256

Issued Jan. 19, 2023, at 5:00 p.m. by Matthew Lemons, District Manager for Colorado, MSHA

Description of incident:
“A non-injury accident occurred at this mine on 1/18/2023 when the highwall of the limestone quarry collapsed at about 1500 hours. The huge landslide from the top of the highwall covered the benches below and overwhelmed the catch basin on the mine floor and partially covered an unoccupied Cat 966 front-end loader.”

103(k) Order:
“No miner will be permitted in the quarry except by MSHA authorization while this order is in place. This order, which includes all of the quarry and the crusher plant located on the quarry floor, is issued to assure the safety of all persons in the mine and will remain in place until it is safe to resume normal mining operations in the quarry.”

The order applies to:
“All of the quarry including the face, the highwall, the quarry floor where the crusher plant is located, and the road leading into the quarry floor.”

Requirements for Rocky Mountain Industrials:
“The operator will provide MSHA a written plan to recover the Cat 966 loader and a written plan to recover the benches and face stability in the quarry.”

Download the MSHA 103(k) of Jan. 19, 2023 (obtained from MSHA by GSCA via a Freedom of Information Act request)

MSHA modified the closure order at some point during the winter months of 2023 to allow RMI to continue to work in parts of the quarry and to retrieve the front-end loader that had been engulfed by rockslide debris.

RMI continues to operate under the partial closure order.

Colorado Division of Reclamation, Mining and Safety (DRMS)
Reason to Believe a Violation Exists

Issued Jan. 25, 2023, by Virginia Brannon, DRMS Director

Colorado DRMS mine inspectors Amy Yeldell and Dustin Czapla visited the quarry on Jan. 23, 2023. Bobby Wagner, RMI vice president of engineering, and Brian Fallin, RMI CEO, accompanied the state inspectors.

Yeldell produced a detailed report describing the slide, including photos of the debris in relation to quarry facilities and highwalls. (Document links below.)

On Jan. 25, 2023, DRMS Director Virginia Brannon issued a letter to RMI citing a possible violation of the company’s state mining permit and calling RMI to appear before the Colorado Mined Land Reclamation Board for a formal public hearing. With deep snow cover and wintry weather limiting access, the hearing was delayed until April 19, 2023.

Prior to the April 19 hearing, DRMS staff and RMI reached a Stipulated Agreement. Conditions are:

  • RMI acknowledges “awareness” of its failure to protect areas outside its permit boundary from slides or damage.
  • RMI must seek a technical revision to its permit to establish a long-term geologic monitoring and stability plan. The application must include a geotechnical stability plan prepared by an accredited engineering firm.
  • A cease-and-desist order is imposed limiting allowed work areas until the technical revision is approved by DRMS.
  • RMI must coordinate its efforts with MSHA and BLM to ensure that monitoring and stability analysis and plans meet their requirements.
  • Any disturbance to lands outside RMI’s state mining permit boundary will require a permit amendment.
  • Failure to comply may lead to an enforcement hearing before the MLRB.

Watch the hearing on the DRMS YouTube channel. (Fast-forward to 0:40:00 to view the RMI agenda item.)

The Technical Revision process began in October 2023, after RMI submitted its Rock Failure Analysis and Stability Report. (Learn about the report here.)

A Technical Revision (TR) is handled directly between DRMS staff and the mine operator. Public comment is not a part of this process, and Colorado Mined Land Reclamation Board (MLRB) action is not needed to finalize the TR.

On April 1, 2024, DRMS approved RMI’s Technical Revision. The approval letter states, “This Technical Revision does not authorize the operator to initiate the methods discussed in the report. Nor does it allow the operator to circumvent any other agency’s requirements.”

RMI would face a higher-level Permit Amendment if it seeks an expansion of acreage beyond current permit boundaries. The amendment process includes public comment and requires MLRB action to finalize.

DRMS holds a reclamation bond for the RMI quarry of $336,000. The agency expects to increase the bond to account for inflation in the coming months. Additional bond money could be required if the agency conducts an amendment process.

Archive of DRMS documents

DRMS 01-25-2023 Notice of Possible Violation, Inspection Report with photos (11 pages, 14.4 MB)

DRMS 01-25-2023 Notice of Possible Violation cover letter (2 pages, 2 MB)

DRMS 01-25-2023 Inspection Report without photos (3 pages, 5.4 MB)

DRMS 01-25-2023 Inspection Report with photos (9 pages, 12.3 MB)

DRMS 04-19-2023 Stipulated Agreement (4 pages, 338 KB)

DRMS 04-01-2024 Approval of Technical Revision  (2 pages, 1.2 MB)