In 2010 Dawnus commenced a series of projects as part of the infrastructure works at Tonkolili Iron Ore Mine in central Sierra Leone, for client Africa Minerals (AML). Since starting on site we have been engaged on numerous projects and support tasks.
These works included construction of mine haul roads, foundations and related infrastructure for major processing facilities and crushing plant, process waste storage weir and a tailings dam. These works have included 1,100,000m3 of earthworks.
Aggregates for concrete, filter media, mass rock fill and rail ballast required at Tonkolili were quarried and processed by the on-site Wendugu Quarry. An onsite laboratory for testing was constructed and set-up to provide for analysis of all construction materials, products supplied, produced and incorporated into the works.
As part of these works, Dawnus delivered a raw water dam weir at the Tonkolili site. The weir was built within an existing rock ravine and its construction required extensive temporary works including an earth cofferdam and control pipework to deal with existing flows. The structure, which is comprised of 3800 cubic metres of concrete and 570 tonnes of reinforcement is 89m long and 17m in height, and was constructed in 20 weeks using a team of 60 nationals mentored and supervised by our expat foreman. The weir has a 2m square cast iron penstock to control outflow in dry seasons.
The formwork, which is owned by Dawnus was all in the form of Peri Trio, which aids faster shuttering times and standardises joints. The site team amended the temporary works design to make the construction simpler, which included amending the cofferdam to facilitate the working platform for the crawler crane, thus saving cost and time.
On all our projects in West Africa we have employed local people and provided training and development in a range of construction disciplines, to European standards.