Eastern Beach Outfall Sewer

Commissioned by the Buffalo City Metropolitan Municipality, this project is a major upgrade to the main outfall sewer to East London’s primary waste water treatment works, including minor upgrades to the treatment works itself.

The works included

• The rehabilitation of the two bioreactors
• Replacement of internal baffle walls, mechanical and electrical upgrades and upgrades to monitoring probes and equipment
• The construction of a new chlorination dosing station, including all instrumentation and automation facilities
• Construction of new inlet and outlet structures to the lei dam for improvement of the final clarification process of the final effluent.

A baffle wall was also constructed in the middle of the dam to direct the effluent flow path and ensure the correct chlorine contact time was achieved. Construction of twin 1.1 km ø1200 gravity outfall sewer along the Eastern Beach to the Bats Cave pump station, capable of each delivering 1400lps to the Bats Cave Pump station.

The works to the outfall sewer also included the construction of a new overflow chamber to the pump station and a new pipe bridge over the Blind River. In total 2 235m³ of concrete and 150 tonnes of reinforcing was used across the project.

The works along Eastern Beach and Blind River were undertaken in challenging environment:

• Access along the beach was limited and works could only be undertaken at low tide.
• Strict environmental control measures that influenced construction techniques had to be adhered to.
• Shifting dunes also made excavations difficult and deep.
• Existing sewer line and treatment works had to be kept live at all times and tie ins and connections had to be done in periods of low flow, often in the early hours of the morning.
• Concrete mix designs were specifically formulated to protect reinforcement from corrosion in the harsh natural in sewer environment.

The project improved the treatment process, improving the quality of the treated effluent. The construction of the outfall sewer improved the capacity of the main East London outfall sewer and helped replaced ageing infrastructure that experienced frequent spillages onto a public beach. Both outcomes not only improve service delivery of BCMM but also contribute to their stated aim of achieving Blue Flag status across various beaches in the metropolitan area.