What does NTC 6620 require for ground support plans in underground mining?

NTC 6620 is the Colombian Technical Standard (Norma Técnica Colombiana) that sets the requirements for preparing Ground Support Plans in mining operations and underground civil works: the technical document that defines how to control the rock mass to prevent collapses and rockfalls. It is not a standard on traceability or trade: it is a geomechanical safety standard, and it responds to a very concrete problem: between 2005 and 2022, Colombia recorded 1,904 deaths in mining, and geomechanical failures are the main cause, with 38% of accidents (ANM, 2024).

Why does this standard exist?

Decree 1886 of 2015 (Decreto 1886 de 2015), in its article 76, already required the mining title holder, the mine operator and the mining employer to define and implement a ground support plan for the operation, in line with the geomechanical study of the area and with what was approved in the project’s Programa de Trabajos y Obras (PTO, the approved works and operations programme). The problem, according to the ANM’s (Agencia Nacional de Minería, Colombia’s National Mining Agency) own assessment, is that the industry had not clearly understood what a ground support plan should contain, and the mining authority had no unified reference to evaluate them; there was no unified criterion on the matter.

NTC 6620 fills that gap: it does not create the obligation (that already existed in Decree 1886), but standardises the technical content a ground support plan must have to be considered valid.

What must a ground support plan contain under the standard?

The structure of NTC 6620 is organised into four blocks:

1. Identification and record of geomechanical hazards and risks A document that describes the behaviour of the ground, the predominant failure mechanisms and the associated hazards, supported by regular geomechanical inspections and documented records of any change in the rock mass model.

2. Safe design An iterative process that follows the project from feasibility to closure: geomechanical model, definition of geomechanical domains, the geomechanical design itself and acceptance criteria (typically safety factors, which vary with how long the excavation will stand, from 1.1-1.3 for short-term stability to more than 1.5 for the long term).

3. Implementation of the designs Instrumentation and monitoring of the rock mass and the support elements, data collection and analysis, intervention procedures for unsafe geomechanical conditions, safe work procedures and emergency response plans.

4. Communication, training and supervision Staff training, internal and external audits, and periodic review of the plan.

What does the standard say about instrumentation and monitoring?

This is the most relevant part in operational terms: the standard itself explicitly asks for systematically organised photographic records of walls, roofs and pillars, records of regular inspections and a record of geotechnical instrumentation equipment, all as part of the monitoring used to verify the validity of the models, detect changes in rock mass conditions and identify design limitations as excavations advance.

In other words: NTC 6620 does not just allow instrumented monitoring and systematic visual capture; it requires them as part of the plan’s implementation cycle. Geomechanical mapping supported by isolated manual inspections is exactly the kind of plan that, according to the ANM’s own assessment, has not delivered results. One supported by instrumentation and systematic, georeferenced capture is what the standard describes as the benchmark to follow.

Is NTC 6620 binding on its own?

It is worth being precise here: NTC 6620 is an ICONTEC technical standard, not a decree or a resolution that is mandatory by itself. The legal obligation to have a ground support plan comes from article 76 of Decree 1886 of 2015; NTC 6620 is the technical reference that gives that obligation its content. In practice, this means its binding force depends on how the mining authority incorporates it in each oversight inspection. It is worth confirming with mining legal counsel how it is being applied in your specific case, instead of assuming it is enforceable in the same terms as a resolution.

Frequently asked questions

Does NTC 6620 apply only to underground mining?

Yes, and also to underground civil works associated with the mining operation; it does not apply to open-pit mining.

What happens if a ground support plan is not implemented?

The legal obligation comes from article 76 of Decree 1886 of 2015, independently of NTC 6620. Non-compliance can be subject to oversight and, in the event of an accident, it aggravates the liability of the title holder, mine operator and mining employer.

How common are accidents from geomechanical causes in Colombia?

They are the leading cause of mining accidents in the country, with 38% of the cases recorded between 2005 and 2022, concentrated mainly in coal mining in Boyacá, Cundinamarca and Norte de Santander.

If you want to assess how to instrument geomechanical monitoring in your operation, write to us at hello@bluberri.io.

Source

Agencia Nacional de Minería [ANM]. (2024). Guía técnica para la gestión de los riesgos mineros causados por fallas geomecánicas. Vicepresidencia de Seguimiento, Control y Seguridad Minera; Grupo de Seguridad y Salvamento Minero. anm.gov.co