Choosing the Right TSF Design: Upstream, Downstream, or Centreline?

In the mining industry, the safe management of tailings is one of the most critical aspects of environmental and operational performance. The design of a Tailings Storage Facility (TSF) determines not only its structural integrity, but also its long-term stability, environmental footprint, and overall risk profile.

Choosing the right TSF design approach Upstream, Downstream, or Centreline requires balancing geotechnical, hydrological, environmental, and operational factors unique to each site.

1. Understanding the Three TSF Design Methods

Upstream Construction

In upstream construction, each new dam lift is built on top of previously deposited tailings. It is the most cost-effective method, using the settled tailings as part of the foundation for future raises.

However, this approach is highly sensitive to tailings strength and saturation. If the deposited materials are not properly consolidated or drained, the structure becomes vulnerable to liquefaction or collapse, especially during heavy rainfall or seismic events.

Pros: Low cost, quicker to build. 

Cons: High risk if tailings are saturated or poorly drained. 

Best suited for: Arid climates and low-seismic zones with dry, stable tailings.

Downstream Construction

In downstream construction, each raise is built outward, away from the stored tailings mass. This approach provides a stronger and more stable structure, as each new stage is founded on previously compacted earth or rockfill, rather than tailings.

While more capital-intensive, downstream designs are considered the safest under variable climatic or seismic conditions.

Pros: Higher stability, suitable for wetter regions and higher-risk environments. 

Cons: Higher construction cost and footprint. 

Best suited for: Regions with high rainfall, soft soils, or seismic risk, such as parts of West Africa.

Centreline Construction

Centreline construction combines features of both upstream and downstream designs. Each raise is built partly on tailings and partly on the previous embankment, maintaining the dam crest along a central axis.

This design offers a balance between cost and stability, providing better control over structural behavior and seepage compared to upstream construction.

Pros: Balanced stability and cost efficiency. 

Cons: Requires detailed monitoring and well-managed drainage. 

Best suited for: Moderate-risk environments with proper geotechnical control.

2. Key Geotechnical Factors in Selecting a TSF Design

The selection process depends on multiple site-specific parameters, including:

• Foundation conditions – bearing capacity, shear strength, and permeability.

• Tailings characteristics – grain size, density, and water content.

• Hydrological conditions – rainfall, drainage, and groundwater flow.

• Seismic potential – regional tectonic activity.

• Environmental and regulatory requirements.

A comprehensive geotechnical investigation, including CPTU, drilling, and laboratory testing, is essential before choosing the dam type.

3. Global Lessons and African Context

While global best practices have evolved following incidents like the Brumadinho disaster in Brazil (2019), the context in Africa demands tailored solutions.Regions like West Africa face challenges such as high rainfall, soft lateritic soils, and limited drainage infrastructure.

In such cases, downstream or centreline designs supported by continuous monitoring and proper water management provide safer and more resilient options.

4. The AES Perspective

At African Engineering Services (AES), our approach to TSF design integrates:

• Rigorous geotechnical characterization.

• Application of risk-based design principles.

• Adherence to international standards, such as the Global Industry Standard on Tailings Management (GISTM).

• A commitment to local context adaptation, ensuring designs are technically sound and environmentally responsible.

Choosing the right TSF design is not only an engineering decision, it is a commitment to safety, sustainability, and long-term operational integrity.