The gravity thickener infrastructure at Exxaro’s Grootegeluk mine in Lephalale, South Africa plays a pivotal role in the recycling of water used for settlement of fines generated through fragmentation (blasting from mining) and degradation (handling processes in pit and plant; loading of trucks, bunkers, silos, chutes, transfer points). When the site operator’s maintenance program deemed it necessary to remediate each of the gravity thickener tanks, Concrete Canvas’s CC HydroTM lining solution was specified.
The work extended the infrastructure’s operational life and ensured efficient, environmentally sound functioning going forward.
GRAVITY THICKENER TANK LINING – AN EXTREME ENVIRONMENT
The mine had only a three-week window in which to carry out maintenance of this nature. Furthermore, it was essential that treated water remained available during any works. Because of this, only one tank was allowed to be remediated at a time.
In fact, the high-level of activity at the mine meant that only one gravity thickener would be scheduled for remediation per year. This meant one could be worked on while three remained available for service during the limited three-week window.
It was initially determined that remediation of the tank floor would be carried out by re-lining with a geomembrane underlay and concrete slab overlay. The major challenge with this solution was installing the system to an area of approximately 4,000m2 in less than three weeks while maintaining quality.
RELATED: Diverting Surface Water from Contaminated Spoils at a Former Mine
Another challenge was the temperatures inside the tank, which often exceeded 40o C (104 o F). It made conventional installation approaches much more difficult.
Ultimately, the project team chose to use an 8mm-thick CC HydroTM (CCH8TM) lining system for the gravity thickener tank floor remediation. The composite material consists of a concrete-impregnated fabric that hardens on hydration and an impermeable, chemically resistant geomembrane.
INSTALLATION
Works were carried out by concrete remediation specialists Ndizani Spec-con, under the supervision of Paterson Cooke engineering consultants.
The limited three-week work window included the draw down and sediment removal time to properly access the gravity thickener tank floor. The existing gravel wearing course also needed to be re-graded and compacted prior to the installation of the new lining system.
In this, the system selection was shown to be strong. The rolls of CCH8TM were able to be installed in just 7 days, which was essentially given that the other works took nearly two weeks.
As the ground preparation was completed, the CC Hydro was delivered to site in bulk rolls. The rolls were lifted into the tank and manipulated on site in accordance with stringent occupational health and safety standards. Then, they were unrolled and positioned, the geomembrane overlaps were thermally welded, and the seams were pressure tested.
With the quality assurance completed on the welding, the lining system was hydrated.
In total, around 4,000m2 of CCH8TM was installed without interruptions in the limited 7-day window.
Avoiding interruption had not been easy. During the installation period, numerous, significant thunder showers passed over the site. Time was not lost, though, as the CC Hydro lining system was able to be installed in wet weather conditions.
The gravity thickener tank was quickly restored to operation.
Learn more about mining, remediation, and other containment applications with Concrete Canvas materials at www.concretecanvas.com.
