China Communications Construction Company Limited (CCCC), contractors of the Nairobi – Naivasha SGR Phase 2A, have successfully drilled the longest railway tunnel in East Africa, at Embulbul in Kajiado County, Kenya. The 4.5 km Ngong tunnel has been designed as a single-track railway tunnel with a clearance height of 9 meters and a width of 7
CCCC engineers used the New Austrian Tunneling Method (NATM) of drilling and blasting to build the tunnel. This is the first time that such a method has been used on such a large scale in Kenya. The tunneling method is economical, efficient and has strong adaptability
for different geological and groundwater conditions. The NATM method controls surface collapse effectively and enhances the working environment during construction. A 533-meter wide emergency rescue channel has also been built within the tunnel to allow for vehicle access in case of emergencies.
About 600 workers and engineers worked tirelessly overcoming all odds for twenty four months to accomplish the engineering marvel. The Embulbul tunnel is the first of the three sections of the 7.14km SGR tunnel. The other two sections of the tunnel located in Nachu – Kikuyu Constituency cover 1km and 1.64km respectively. The tunnel is on the 120-kilometer Nairobi-Naivasha route of the Standard Gauge Railway (SGR). The 120km line is the first of the three segments that make up the second phase of the SGR construction that is expected to terminate at Malaba. Phase 2A to Naivasha will pass through the five counties of Nairobi, Kajiado, Kiambu, Nakuru and Narok.
The development of the line is expected to be completed within 2019.