- Newmont’s engineering, construction and operating standards and technical guidance explicitly cover tailings management and establish requirements to ensure safe and stable facilities throughout their operating and post-mine closure life
- Their approach covers:
- Standards, Guidelines and Governance
- Audits, Inspections and Reporting
- Emergency Response, Planning and Communications
- Annually, Newmont safely manages and disposes more than 100 million tonnes of tailings that are placed within engineered, surface containment facilities; used to backfill former mining pits; or placed as structural backfill paste in underground mines
- Learn about the Investor Mining and Tailings Safety Initiative in this free webinar
- Find out about Decipher’s Tailings Solution
What are tailings?
What are tailings?
Tailings are created as mined ore is processed sand through crushing, grinding and milling. Mined ore is moved to the milling circuit where the rock is reduced into sand and silt sized particles and then mixed with water and moved as slurry through the gold, silver and copper recovery process. The valuable minerals are separated from the rest of the milled rock particles either through physical or chemical recovery processes. After removal of the valuable minerals, the remaining milled rock slurry, now referred to as tailings, is pumped, flows by gravity, or is dewatered and transported by truck or conveyor to a surface engineered facility.
What are the different types of TSF construction methods?
What are the different types of TSF construction methods?
TSFs are designed and constructed to store both tailings and water. The dam construction methods include two main types: (1) water retention dams and (2) progressively raised embankments. Water retention dams are typically constructed to their full height prior to anything being stored upstream and raised embankments are progressively raised in a vertical manner over time to store additional material. Raised embankments are the most commonly used method for TSFs. The raised embankment design methods for TSFs are typically downstream, upstream or centerline. This designates the direction in which the embankment crest moves in relation to the starter dam (dyke). Modified centerline is a construction method combining both upstream and centerline.
UpstreamConstruction of an upstream embankment begins with development of a starter dyke. The tailings are then discharged from the dam crest and form the foundation for future raises. Figure 1 shows an overview of the stages of construction. Figure 1: Upstream construction method
DownstreamDownstream methods commence with a starter dyke, which is often impervious with an internal drainage system, as shown on Figure 2. The tailings are first deposited behind the dyke and the embankment is raised in a downstream manner over time. Figure 2: Downstream construction method
CenterlineWith the centerline method, the embankment is raised vertically, maintaining the dam centerline embankment as shown on Figure 3. This design method often also incorporates internal drainage, and requires construction of a free-draining shell. Modified centerline is a combination of upstream and centerline methods and is done to reduce the volume of construction material that is required to be placed within the embankment. Figure 3: Centerline construction method
Standards, Guidelines and GovernanceNewmont’s Environmental Standard for Tailings and Heap Leach Facility Management sets the minimum requirements for the design and management of TSFs to protect human health, wildlife, flora, groundwater and/or surface water, prevent uncontrolled release to the environment, manage process fluids, and identify requirements for closure and reclamation.
Tailings Management StandardThe standard works in conjunction with other standards and incorporates the International Council on Mining and Metals’ (ICMM’s) position statement on ‘Preventing Catastrophic Failure of Tailings Storage Facilities.’ All Newmont sites identify, assess and comply with laws, regulations, permits, licenses, external standards and other relevant or appropriate requirements.
Planning and Design
- Sites complete a baseline of conditions prior to design of the TSF, including evaluation of land use, hydrology/hydrogeology, geochemistry, biodiversity, cultural resources, geology, seismicity, soil and visual aesthetics.
- Tailings Management plans must be developed to restrict potential releases to the environment.
- Tailings Management plans are expected to include: design and operating criteria, schedules for inspections, monitoring and maintenance, applicable regulatory, legal or other requirements, management methods, risks assessments, overview of instrumentation including KPIs/critical controls, organization structure (roles and responsibilities), training requirements, emergency response plans (inundation mapping and analysis) and concurrent reclamation.
- Fluid management plans describe management of solution levels based on the site-wide water balance. The plan will also identify trigger alert levels and contingency plans during operations, closure and reclamation phases.
- Characterization and specifications for geochemical and physical properties of the construction and tailings materials are performed.
- Engineering requirements for seepage control, liners, and leak collection recovery systems are specified. With excess solutions that may require discharge, compliance with applicable quality and quantity discharge limits based on downstream beneficial use.
- Engineering requirements for geotechnical and erosional stability including such measures as internal filters and drains, buttressing, and systems for storm containment and runoff.
- Requirements for piezometers to monitor solution pore pressures in the embankments, tailings and foundation. Groundwater monitoring wells to establish baseline and monitor potential seepage.
- Risk-based assessments to evaluate whether the design criteria provide adequate levels of protection.
- Quality control and quality assurance protocols are required to document that construction complies with engineering design.
Implementation and Management
- Facilities will have critical controls to mitigate significant risks with risk assessments conducted annually or at major milestones or when significant changes occur.
- Tailings and Fluid Management Plans must be reviewed and updated annually.
- Site-wide water balances are updated over the life of the operations to reflect changes in mine plans, processing and operations, and are regularly calibrated.
- TSFs must be operated within design specifications including piezometric head in embankments and tailings and the management of the pond with design and operational criteria.
- A closure and reclamation plan shall incorporate the requirements of the fluid management plan and support stormwater and erosion management while achieving post-mining land use.
- The TSF is managed to be protective of the environment and adheres to the requirements of the International Cyanide Management Code, permit/license/regulatory requirements, and any other legal obligations or voluntary commitments.
- TSFs shall be inspected regularly for erosional and geotechnical stability, material characterization (geochemical and geotechnical properties), trigger levels and critical controls.
- Annual geotechnical reviews are required by a qualified independent senior geotechnical engineer. Independent Tailings Review Boards (ITRBs) have been implemented at select operations based on technical, social and/or political risks identified by Newmont leadership.
- Routine inspections to verify integrity and to support maintenance and repair programs as defined in the monitoring plans. This includes monitoring instrumentation such as piezometers, inclinometers, and survey monuments as defined in the monitoring plans. Inspection and maintenance activities are also completed following extreme events (rainfall, seismic etc.).
Technical GuidelineNewmont’s Technical Services team has developed Tailings Facility Geotechnical Guidelines that define minimum requirements for TSFs:
- Definitions for tailings embankments
- Responsibilities of engineering and management staff
- Geotechnical input design criteria guidelines for:
- Foundation settlement and consolidation
- Seismic loading
- Hydraulic properties of the foundation, soil liners and drainage layers
- Water management systems
- Tailings rheology and characteristics
- Geotechnical process design for:
- Geotechnical field investigations
- Laboratory testing
- Engineering design
- Geotechnical design requirements for each level of Project Design
- Risk analysis
- Quality assurance/quality control
Inventory and Disclosures
Tailings InventoryThe map below provides an overview of the tailings storage facilities located at our operating mines – the number of dams, the status (active/inactive/closed) and hazard classification. Click here to view the Excel file of our full tailings inventory
Church of England Pensions Board and Swedish Council on Ethics for the AP Public Pension Fund – Tailings Management Approach and Inventory DisclosureNewmont developed a disclosure in response to the Church of England April 10, 2019 request for information concerning tailings dam management. This disclosure provides Newmont’s approach to tailings; communications and risk management; a description of updates to our approach following recent disasters; and an inventory of tailings dam facilities for our operating sites, joint ventures, subsidiaries, and legacy sites as of July 1, 2019.
Decipher empowers you with data and knowledge to effectively monitor your tailings storage facility
- Learn more about The Investor Mining and Tailings Safety Initiative in this FREE webinar
- Speak to our team for a free demo of our Tailings Monitoring solution
- See how our solutions help manage industry stakeholder engagement and operator and regulator compliance requirements here