Sustainable drainage for mine's rail yard

Paul Boughton

Solving surface drainage problems at an iron ore mine's integrated rail marshalling yard

Tonkolili mine represents one of the largest iron ore resources in the world contributing substantial economic benefits to Sierra Leone.

To support the iron ore project, African Minerals has developed a significant port and rail infrastructure that is fully integrated into the mining operations. Part of the railway, which provides the link between the mine and the port facility at Pepel, 200km away, was originally built in the 1930s; this 74km section has been completely replaced, and extended by a further 125km of new rail to complete the link.

For the surface drainage of the rail marshalling yard at the Tonkolili iron ore mine in Sierra Leone, the mine operator, African Minerals Ltd, chose the Ridgidrain system from UK manufacturer Polypipe. The company supplied to the project over 4,000m of 300mm Ridgidrain perforated twinwall pipe, a product that combines both technology and sustainability.

Specifying HDPE (high-density polyethylene) as a sustainable solution for the surface drainage at the new marshalling yard, African Minerals selected Polypipe through a competitive tender process.The company cited a number of factors that determined its choice, including excellent and effective communications, and the ability to work closely with both African Minerals and their shipping agent to ensure that all of the materials involved were manufactured to a precise specification and that tight shipping deadlines were met.

Provision of full documentation was also a key factor, as African Minerals Project Manager Gary Nel explains: “This project is extremely important to Sierra Leone and as the mine operator, African Minerals is committed to applying the highest standards to everything that we do. We are working to internationally recognised performance standards and so we place high demands on the materials we acquire for the mine infrastructure. The Polypipe product is backed up by full certification, so meets our specification in terms of documentation and traceability.”

The Polypipe Ridgidrain system is designed to satisfy both the strict demands of UK planning regulations and UK and European legislation.

The structured wall design of Ridgidrain gives high ring stiffness and strength and has a lower weight compared to clay or concrete products, which means reduced transport and installation costs and improved health and safety benefits for installers. HDPE provides excellent resistance to abrasion and chemical attack and withstands ground movement and differential settlement. The longer pipe lengths available reduce the number of joints required, significantly reducing the risk of leakage, while its extremely smooth bore resists blockage and makes the pipework system more easy to maintain. The product supplied for the Tonkolili project was fully perforated to allow effective sub-soil drainage.

Polypipe Export Sales Manager Philip Wood says: “HDPE is the material of choice in many mining infrastructure applications. In this case, African Minerals have specified HDPE  for the rail marshalling yard in the knowledge that it is capable of delivering many years of reliable service in a very demanding environment.” 

Video 1: Sierra Leone hopes to become Africa's biggest exporter of iron ore with the opening of a new mine in the central Tonkolili district

Video 2: Africa Minerals is one of the main companies investing in Sierra Leone


Sierra Leone Hopes to Become Africa's Biggest Exporter of Iron Ore

African Mineral Sierra Leone

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