The first phase of the two-phase R474-million Milnerton bulk sewer upgrade to increase the capacity and reliability of the City of Cape Town's bulk sewer system is under way after breaking ground on March 1.

Phase 1, comprising the construction of a new bulk sewer and sand trap and screening facility at the Koeberg Road Pump Station in Montague Gardens, is expected to be completed by February 12, 2025.

The scope of Phase 1 includes the micro-tunnelling of a new 3.78-km-long, 970-mm-diameter bulk sewer around the eastern and northern boundaries of the Montague Gardens industrial area and the micro-tunnelling of a new 300-m-long bulk outfall sewer of 1 350-mm-diameter at the Koeberg Road Pump Station to accommodate the combined flow of the existing Montague Drive bulk sewer and the new Montague Gardens bulk sewer.

The project will further extend and divert the existing 700-mm-diameter Edgemead bulk sewer and 450-mm-diameter Century City bulk sewer into the new infrastructure.

Phase 2 entails future trenchless rehabilitation of the 4-km-long existing 700-mm-diameter to 975-mm-diameter Montague Drive bulk sewer and the diversion of the Century City bulk sewer back into the rehabilitated Montague Drive bulk sewer.

The project was implemented following a 2015 condition assessment of the bulk sewers in the Blaauwberg and Milnerton areas, which had indicated that the structural condition of the Montague Drive bulk sewer had deteriorated significantly owing to sulphuric acid corrosion.

“This meant that the sewer poses a high risk of structural failure. Owing to its location, under the Montague Drive roadway, the collapse on this pipeline could be fatal for motorists and can create substantial interruption to traffic flow in Montague Gardens,” says City of Cape Town Water and Sanitation MMC Councillor Zahid Badroodien.

“As a result, the Montague Drive bulk sewer was earmarked as one of the critical sewers for upgrading and rehabilitation.”

The study concluded that the Montague Drive bulk sewer was operating at full capacity and found it insufficient to accommodate the future upstream requirements of the catchment, with an additional bulk sewer in Montague Gardens recommended to supplement the Montague Drive bulk sewer.

“The installation of a sandtrap and screening facility at the Koeberg Road Pump Station will improve the operation of the bulk sewer system by improving the pump station’s performance and reducing pump breakages caused by foreign objects entering the pump station sump,” says Badroodien, noting that improving the Koeberg Road Pump Station’s operation will also reduce the number of sewer spills into the Diep river and relieve environmental pressure on the City of Cape Town.