Northern Collector Tunnel


Main Tunnel (km)


Supply Capacity (m3)


Population to Serve

Project Name

Construction of Bulk Water Supply to Nairobi: Northern Collector Tunnel Phase 1 Project

Summary of Findings by IPEs

Baseline Survey

The GOK with the support from the World Bank has been implementing the Water and Sanitation Service Improvement Project (WaSSIP). The Government has now secured further financing from the World Bank under the Water and Sanitation Service Improvement Project Additional Financing (WaSSIP AF) project that was made possible because of the satisfactory implementation of the ‘original’ WaSSIP and its contribution to water services improvement.

AWWDA is using part of the WASSIP AF funds to implement the Northern Collector Tunnel Phase 1. The project is derived from Nairobi Water Master Plan for Developing New Water Sources for Nairobi and 13 Satellite Towns namely Kikuyu, Ruiru-Juja, Kiambu, Karuri, Githunguri, Mavoko Municipality, Ngong Township, Ongata Rongai, Thika, Gatundu, Limuru, Lari and Tala-Kangundo. The Northern Collector Tunnel Phase 1 includes river diversion weir and related intake hydraulic structures at Maragua, Gikigie and Irati Rivers as well as construction of river outlet at Githika River which will convey the additional water to Thika dam. The tunnel is approximately 11.8km long and of 3m finished internal diameter. The objective of this project is to increase water supply in Nairobi County by 121,000m3/day.

In order to effectively monitor the impacts of the tunnel works on the groundwater, AWWDA has prepared a baseline survey of all wells and boreholes along the Northern Collector Tunnel project.

NCT Awareness Survey

AWWDA Service Board commissioned GeoPoll to conduct a perception survey for the Northern Collector Tunnel Project (NCTP) Phase1. AWWDA conducted the survey to meet the following objectives;

  • Measure awareness of NCT amongst Murang’a county residents.
  • Identify source of awareness
  • Understand whether they support/approve of the project
  • Get perception on the cost, quality, texture, taste and reliability of the water in Murang’a County

Independent Panel of Experts

NoName of ConsultantAddressEmailPhone noExpertise Position
1Eng. Japhet K. RutereP.O Box 67744-00200Nairobi, Kenyaruterej@gmail.com0721-609355Principal Dam Specialist Chairman
2Dr. George Dounias9, Yperidou str,105 58 Athensgdounias@edafos.grTel:+30 210 3222050


+30 693 245 0856

Geotechnical and Tunnel Specialist Member
3Angelina Nduta MwendaP.O Box 21343-00505Nairobi, Kenya andutsm@yahoo.com0722-768525Environmental and Ecological Expert Member
4Charity GathuthiN/A charitywgathuthi@yahoo.com0724-526254Community Water Specialist Member
5Dr. Loannis KaravokyrisN/, 6945592383Hydrology and Hydraulic specialist Member

For queries, clarifications and complaints regarding the Northern Collector Tunnel Project, members of the public should write to the Independent Panel of Experts (IPE) on This address is managed by the IPE team.

Muranga Technical Consensus

About NCT 1 Project

Nairobi City is the international, regional, administrative and economic hub for Kenya. The city generates approximately 60% GDP. Nairobi, the capital of Republic of Kenya, is facing chronic water shortage including its surrounding area. This is because the proposed additional water source, the Northern Collector Scheme, was not implemented as proposed in 1998. The scheme was initially planned as part of Third Nairobi Water Supply Project. The target year for implementation of the Northern Collector Phase 1 was year 2010. The expected average production capacity of the now proposed Northern Collector tunnel Phase 1 project is 1.6m3/sec (140,000m3/day) with an 84% reliability. The safe yield at Ndakaini dam will however be 1.24m3/ day with a 90% reliability.

The present water deficit in Nairobi City is 125,000m3/day. In line with the National Development Plan, Vision 2030, the Government of Kenya has prioritized improvement of water services in Nairobi City and the surrounding areas. To achieve this objectives the Northern Collector Tunnel Phase 1 project is a priority project.

ESIA Study

AWWDA Works Development Agency (AWWDA)  commissioned GIBB Africa Ltd to prepare an Environmental and Social Impact Assessment (ESIA) and a Resettlement Action Plan (RAP) for the proposed Bulk Water Supply to Nairobi City – Northern Collector Tunnel, a Raw Water Pipeline, and Treated Water Pipeline to Kabete Reservoir.


For frequently Asked Questions about the Northern Collector Tunnel

Project Scope

The scheme, under Phase 1, is to divert raw water from Maragua, Gikigie and Irati Rivers by means of weir control intakes and convey the intercepted raw water through an 11.7km long tunnel with 3.2m diameter to Thika Dam Reservoir. The total design intercepted flow is 3.0 m³/s. The proposed major elements of the project are:-

  • Construction of 11.712km main tunnel3.
  • Construction of 886m Adits3/day.
  • Construction of 2 No Shafts, each 50m deep
  • Construction of 3 No intake weirs at Maragua, Gikigie and Irati
  • Construction of Githika concrete outfall channel