By Eng. Cyrus Njonde & Imelda Nasubo
Introduction
This article is a reflection on how tailings and mine waste can be safely stored and how such areas can eventually form part of a mine’s broader rehabilitation plan. This reflection is the collaborative work of Imelda Nasubo and Eng. Cyrus Njonde. Leveraging Nasubo’s first-hand operational insights from Base Titanium, and Eng. Njonde’s perspective on the mirrored realities in small-scale mining, combined with our shared writing experience, we were inspired to co-author this piece.
What is a TSF?
A view of a water laden Tailing storage facility integrated with siphon dewatering systems
A Tailings Storage Facility (TSF) is a man-made engineered structure, often resembling a dam, created to store fine-grained waste materials known as tailings. These tailings are generated after valuable minerals are extracted from ore during mineral processing.
Tailings from mineral processing that use chemicals like cyanide or sulfuric acid can harm the environment if they are returned to mine pits without treatment. Slimes (fine, sticky particles under 0.063 mm) are especially tricky. They settle slowly, hold water, and lack the strength needed for safe backfilling. While Base Titanium successfully mixed slimes with sand to backfill deep pits (Mixing improves particle size and stability, but it must be done carefully) this approach isn’t always possible in other types of mining. In most cases, a specially designed facility is needed to store these tailings safely during mining and after closure.
TSFs serve a critical role in any mining operation that involves ore separation from host rock or soil. Tailings typically contain a mixture of water and residual material, and sometimes chemicals. And without proper management, these materials pose a serious risk to the environment. A TSF provides a long-term containment solution that allows the water to gradually drain and the solids to dry, enabling future rehabilitation. Over time, if well managed, such a facility can be converted into a safe and restored landscape.
Deep Dive on Base Titanium’s TSF
Base Titanium’s TSF covers at least 250 hectares. Construction began with two starter embankments placed in areas where ground conditions were weaker and prone to failure. These walls stabilized the structure and reduced future geotechnical risks. Beneath the TSF, a network of underdrain pipes was installed. Perforated on the upper side, these pipes drain water from the tailings while keeping solids in place.
Tailings at Base Titanium are water-laden due to the mining and separation process, which relies heavily on water. This is where TSF engineering becomes crucial, ensuring solid waste is safely retained while excess water is efficiently drained. In addition to underdrains, Base Titanium installed artificial drainage systems called penstocks. A penstock includes decant towers, vertical columns that extend from the base to the top of settled tailings, and a pipeline that runs to the settlement pond. It collects surface water and pumps it out, maintaining required water levels.
Penstocks, though effective in draining water, face structural challenges due to their vertical design. As tailings settle and shift, the towers can be damaged, disrupting water management and causing unwanted water buildup or release in the TSF. To address this, a siphon system was added to support the penstocks. This system pumps about 9,000 cubic meters of water daily to settlement ponds, speeding up the drying of tailings.
In these ponds, suspended solids naturally settle, leaving clearer water at the top. This treated water is then recycled back into the hydraulic mining process, reducing the need for fresh water from rivers or underground sources. The system forms a closed-loop, conserving water and cutting operational costs, especially important since hydraulic mining consumes around 2,400 m³ of water per hour when both units are running.
TSF Monitoring and Water Control
It’s important to emphasize that such water drainage systems must be located at the lowest levels of the dam so that gravity naturally pulls water toward them, allowing easier separation from the solids. Based on current conditions, it is estimated that the entire dam could take at least 15–20 years to fully dry and reach a state considered safe for final closure and rehabilitation.
Base Titanium has also ensured continued monitoring of the TSF’s safety and structural integrity through the use of piezometers that measure pore water pressure within the tailings dam and surrounding ground. The piezometers provide real-time data that serves as part of an early warning system for TSF instability. Sudden increases in pore water pressure may indicate potential failure, prompting the company to take immediate action.
While at the surface, another key management measure in Tailings Storage Facilities is the use of impermeable, bitumen dam liners. It prevents water from saturating the retaining walls, reducing pore pressure and minimizing the risk of structural failure thereby ensuring greater stability and safety of the facility.
Rehabilitating a TSF
The rehabilitation process of a TSF starts with water management and proceeds to measures that prevent further water infiltration. The primary goal is to stabilize the solid materials and restore the land for post-mining use. Once the tailings are sufficiently dewatered, efforts focus on minimizing environmental risks through surface stabilization and revegetation.
The main goal of this process is to stabilize the tailings and prepare the land for safe use after mining. Once the tailings are dry enough, focus shifts to reducing environmental risks through surface stabilization and planting.
Base Titanium has planted over 250,000 eucalyptus trees on the TSF. This tree species is ideal because it absorbs a lot of water, helping the area dry faster and stay stable. Since the ground is still damp, holes are drilled using augers and filled with fertile soil and manure to support healthy tree growth.
This green approach works alongside engineering efforts to restore the land into a safe, sustainable landscape. Long-term monitoring is required to ensure stability and prevent any contamination of nearby water sources. Some maintenance may continue even years after the mine closes.
Lessons for Small-Scale Mining on Tailings Management Best Practice
Tailings management should not be exclusive to large-scale operations. In small-scale mining, the challenges are well known: lack of technology, limited capacity for waste management,and frequent reprocessing of tailings piles. This practice can be hazardous if not done correctly. In many cases, tailings are simply stockpiled or abandoned, leading to environmental degradation and public health risks.
Small-scale operations can adopt a simplified version of a TSF. Even if reprocessing is expected in the future, storing tailings properly now is crucial. A well-planned TSF, even a basic one, can protect the environment, ensure operational safety, and create a path for future resource recovery.
Reprocessing tailings when better technology becomes available could become economically viable. But without controlled storage, such future efforts can be environmentally damaging and financially wasteful. Therefore, we encourage small-scale miners to develop structured tailings facilities now. Wet tailings, especially those that appear dry on the surface but have water just beneath, can be dangerous and misleading. Dried surfaces can crack, yet remain unstable and unsafe for people or livestock. Such areas must be properly fenced, marked, and treated as no-go zones.
Whether in large- or small-scale mining, water is the biggest threat to TSF integrity. Excess water can weaken dam walls and increase the risk of failure in nearby streams. Simple dewatering methods and, where applicable, water treatment before release or catchment are necessary. Such practices do not require heavy investment but do require careful planning and commitment to safety.
Closing Remarks From The Authors
Eng. Cyrus Njonde : As Kenya transitions toward more structured and formalized small-scale mining, it is time to adopt best practices in tailings management. TSFs are not just waste containment structures; they are essential to responsible mining, safe closure, and environmental protection.
Imelda Nasubo: The experience at Base Titanium reinforced my belief that sustainable mining is achievable through the combination of environmental foresight and smart engineering in the designing, managing, and rehabilitation of TSFs.
This article has been jointly published on Eng Cyrus Njonde’s Newsletter and Nasubo’s blog, jewelinthemines, to reach wider audiences in our mining community.