Despite Covid-19 having an adverse effect on the greenfield development of a mine and metallurgical plant, in Sierra Leone, local consulting firm METC Engineering director Dr Steve Cathey says the project is progressing well.

He explains that construction on the Tongo diamond project – located in the eastern province of Sierra Leone, about 314 km from Freetown – started in the last quarter of 2019 and was scheduled to be completed by the end of 2020, but will now be completed only in the fourth quarter of 2021.

METC’s project for Sierra Diamonds, the subsidiary of ASX-listed Newfield Resources, is to deliver and erect an 80 to 100 t/h modular plant for the greenfield project. It is responsible for the engineering, design, procurement and supply of modular plant sections for the fabrication of the processing plants on site.

“The fabrication and installation of modular systems, which will increase speed of construction, will, above all, reduce capital costs and improve plant efficiency,” enthuses Cathey.

Further benefits include reduced drop heights, which assist in decreasing the plants’ environmental footprint by lowering energy consumption.

Mining will be conducted using a decline portal and the first run-of-mine is expected in 12 months’ time, when ample plant feed will be stockpiled to ensure a stable supply to the processing plant.

“The secret is in the simplicity of design,” Cathey comments.

Various mechanical equipment and the sizing of bins and structures have been standardised, allowing for easy maintenance when parts are procured.

He explains that some pumps or electrical drives are oversized, but that interchangeability has been vastly improved by reducing stockholding thus reducing “dead” capital, ensuring that plant operation is streamlined and that downtime is reduced, which, in turn, improves profitability.

The procurement and delivery of equipment to West Africa is challenging and requires integrated planning with clients, suppliers and other project stakeholders. METC recommends the approach where a consulting firm procures “for and on behalf of” clients.

Planning and communication is crucial during the procurement and delivery stage. The METC procurement team – which also includes logistics, expediting and quality-assurance personnel – must ensure that the correct goods are delivered at the right time.

The transit time, from METC’s fabrication plant in Johannesburg to port in Durban and subsequently to Freetown harbour in Sierra Leone, before being sent to site, is about seven to eight weeks, as there are few direct shipping options, meaning most shipments are transhipped.

Cathey stresses that relationships with its clients are important for the company, and that it works closely with shipping agents and suppliers to ensure that each shipment is packed to its full potential, thus consolidating loads to minimise freight costs.

“We also keep a close eye on our suppliers’ progress and quality during manufacturing, with regular inspections, managing the Covid-19 delay impacts as well as METC employees’ observing any testing that is required prior to shipping.”

Cathey concludes that METC was selected for the project because of its proven record of successfully delivering projects in areas such as earthworks, civils, mechanical, electrical, structural, platework and instrumentation, as well as its handover of complex projects in Africa.