Trunk Sewers Update: Will Nairobi River Regeneration Project Succeed?

The government continues to advance major trunk sewer construction along the Nairobi River as the cornerstone of the wider Nairobi River Regeneration Programme. Workers are installing large diameter pipes on both banks of the river and its tributaries to intercept raw wastewater before it pollutes the waterway.

Nairobi Rivers Commissioner Mumo Musuva has repeatedly highlighted that the existing sewer network was built in the 1970s for a city of about one million people. With Nairobi's population now exceeding five million, the old system is badly overstretched, resulting in constant raw sewage spills into the river.

The current phase involves construction of around 56 to 60 kilometres of new trunk sewer lines. Once finished, the expanded network is expected to collect and convey up to 310 million litres of wastewater daily to treatment plants instead of letting it flow into the river.

Trunk Sewers Up Close/Nairobi County

President William Ruto formally launched the Nairobi River Regeneration and Engineering Works Programme in March 2025 at a total projected cost of KSh50 billion. The multi component initiative covers trunk sewers, river dredging, bridge repairs, riparian restoration, and development of green public spaces along the corridor. It is also designed to generate thousands of jobs during construction.

A critical boost came from the cooperation agreement between the national government and Nairobi County Governor Johnson Sakaja. Under the pact, the national government committed substantial funding, part of a broader KSh80 billion support package for the county, specifically for sanitation and trunk sewer works. This includes dedicated resources for two parallel trunk sewer lines running nearly 27 kilometres each along the river. The agreement has improved coordination between the Nairobi Rivers Commission, national ministries and the county government.

Physical works on the trunk sewers gained momentum after the March 2025 launch. Construction is now visible on both the eastern and western sections of the river, with integration ongoing to connect new lines to existing transverse sewers and feed into facilities such as the expanded Kariobangi Wastewater Treatment Plant.

The project is scheduled for substantial completion around 2027, though full regeneration benefits, including improved water quality and public spaces, will unfold over a longer period.

Success will hinge on several factors. Timely delivery without major cost overruns remains essential, alongside strict enforcement against illegal connections and industrial effluent. Sustained community engagement to prevent dumping and vandalism of the new infrastructure will also be decisive.

If delivered as planned, the trunk sewers should dramatically cut pollution loads, reduce waterborne disease risks in informal settlements, and finally provide the missing foundation that earlier river cleanup attempts lacked. The visible heavy machinery and pipe laying activity along the riverbanks offer tangible signs of progress after decades of inaction.

Whether the KSh50 billion investment ultimately transforms the Nairobi River into a cleaner, more usable urban asset will depend on continued funding discipline, strong inter governmental coordination, and effective long term maintenance once the assets are handed over. For now, the project represents one of the most serious attempts yet to tackle pollution at its source.