Local Government, Environmental Affairs and Development Planning

1. The causes of these incidents have been investigated and sewage overflows have been attributed to faults on the delivery pipe line, rising main and at the pump station. These faults include:

• Sewer blockages caused by the disposal of foreign objects into the sewer system (disposable plastic nappies, plastic bags, and sanitary products etc.)
• Possible pump malfunctioning
• Possible rising main malfunctioning

The sewer contents enter the pump station via a gravity flow system and is fed into the pump station (containing three variable speed pumps). From there it enters the high pressure rising main that conveys it to the Melkbosstrand Wastewater Treatment Works, where it is treated. The pump station and rising main are on a telemetry system that monitors and controls the flows through the system (and are regularly maintained).

The volumes of sewage spills vary significantly depending on the length of the malfunction, the time of day (peak or low flows) as well as weather conditions (winter and summer flows). Every effort is made to contain these spills rapidly and effectively once they have occurred. The problem is exacerbated by illegal connections by local residents in which household storm water is discharged into the sewer system that increases the volume significantly.

2. The City of Cape Town has a second generation Wastewater Risk Abatement Plan (W2RAP) that deals with the management of sewage effluent from all its treatment facilities. One of the objectives of this plan is to minimize and reduce the risk of environmental incidents through specific management activities, as well as preventative maintenance of wastewater infrastructure (including pipelines, pump systems and general wastewater treatment machinery).

In terms of this plan these overflows or spillages were responded to as an emergency incident by the City of Cape Town’s Water and Sanitation Branch (Reticulation Department), who immediately addressed the matter and conducted a further investigation into the pump station malfunctions. In addition to the above –mentioned response; a tanker service is on standby to evacuate accumulated sewage at the pump station once problems are experienced. Standby diesel generation capacity is currently also available to deal with possible power outages. In addition to the telemetry system, daily visual inspections of the equipment is done. The condition of the pump station delivery rising main is also being assessed and remedial steps will be taken based on the outcome of this assessment.