Kenya’s Thiba Dam is currently under construction in Kirinyaga County about 130km northeast of Nairobi. The dam is being built on the Thiba River and will be 40m high and 1km wide creating a reservoir capable of holding 15 million m3 of water helping to secure year-round water supply for the country’s agricultural sector. The civil works are being carried out by Strabag International for the National Irrigation Board.

The contract value amounts to approximately € 72 million and also includes the connection to the existing road network as well as facilities for water draw-off and safe floodwater drainage. The construction of the project started in March 2018 and is expected to be completed by November 2021 under the current construction period of 45 months.

With challenging site conditions and risk of flooding, a carefully designed drainage system was required to expel both surface and subsurface water. The system needed to effectively separate drainage media from intermixing with fine soil particles with minimal use of natural resources.

GEA was able to provide a nonwoven geotextile with excellent drainage and filtration capabilities to provide an effective and affordable long-term solution to a problem that required a quick and durable response.

The specified geotextile used in the blanket drains and around the perforated subsoil drainage pipes is GeoMatt TB15, manufactured from 100% virgin polypropylene and UV stabilised. It’s excellent mechanical and hydraulic properties made it suitable for required functions in separation, filtration and drainage. Apart from being installed under all the drains it was also used beneath riprap on the upstream slopes of the dam for wave protection.