Background
Lagos, with a population of over 20 million, is located on Nigeria’s southwest coast. The city is low-lying and highly flood-prone during heavy rains, worsened by tidal backflow from the Atlantic. Much of the underground drainage system, built in the 1970s–1980s, has deteriorated with blockages and structural failures, leading to frequent flooding and public health concerns.
Challenges
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High groundwater table complicating excavation.
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Traffic management required due to works under busy arterial roads.
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Material shortages, with reliance on imported pipes and liners.
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Narrow construction window during dry season.
Technical Approach
A “Clean – Repair – Expand” method was adopted:
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Pipeline Cleaning & Rehabilitation
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High-pressure jetting and vacuum cleaning.
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Damaged sections rehabilitated using CIPP (Cured-In-Place Pipe) trenchless lining.
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Capacity Expansion
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Installed new reinforced concrete pipes (DN1500–2000) for main collectors.
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HDPE pipes used for secondary branches for corrosion resistance.
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Outfall & Pumping Upgrade
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Backflow gates at discharge points to prevent tidal ingress.
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New pumping stations to boost drainage during heavy storms.
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Construction Highlights
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Sectional works: 200–300 m per phase to minimize disruption.
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Trenchless repair: CIPP with hot steam curing, minimizing open-cut excavation.
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Quality checks: CCTV inspections and pressure/leakage tests on completed sections.
Results
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12 km of pipelines rehabilitated or replaced.
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18-month schedule, aligned with seasonal constraints.
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Flood-prone locations reduced by ~60%, with faster stormwater discharge.
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Improved urban resilience, traffic safety, and sanitation for Lagos residents.