Driftsands sewer project to unlock further development

HDPE lined pipes were installed to protect the infrastructure from attack against biogenic corrosion

Commencing in the western suburbs and terminating at the Driftsands Wastewater Treatment Works (WWTW), the Driftsands Collector Sewer Project is a critical component of the city’s expansion plan to serve the growing western suburbs, and the economic nodes developing alongside the N2, Fairview and Walmer.

According to Melanie Geyer, project manager: Planning and Research Division, Nelson Mandela Bay Municipality (NMBM), the existing Driftsands sewer line – which is 12.5 km long – was constructed in 1983 and commissioned in 1986. “Numerous new developments have been built since 1986. The pipeline has reached its design limitations and must therefore be augmented to allow all wastewater to drain to the Driftsands WWTW. There are two other collector sewer lines in the western suburbs – Lorraine/Fairview and Walmer Heights – that discharge wastewater into the Driftsands Collector Sewer at different points. Therefore, any upgrades or augmentation to those two collector sewer lines, prior to increasing the capacity of the Driftsands Collector Sewer, would be pointless.”

The project has a significant economic impact on the municipal environment because any future developments in the area (such as the Baywest Development on the N2) may not be approved by the municipality’s Wastewater Conveyance Division until the Driftsands sewer line has sufficient additional capacity. Furthermore, a portion of the existing sewer line passes through premises belonging to Airports Company of South Africa (ACSA). As ACSA is anticipating the expansion of Chief Dawid Stuurman Airport, a portion of the Driftsands sewer line must be diverted to accommodate a future runway.

The Drift Sands Collector Sewer is primarily a gravity line and is made up of different pipe materials like fibre cement, concrete and high-density polyethylene (HDPE). With the upgrade, NMBM chose to install concrete HDPE lined pipes, with chambers and manholes lined with Fondag C and HDPE liner to protect the infrastructure from attack against biogenic corrosion.

The majority of the Driftsands Collector Sewer Project’s funding has come from National Treasury through the Urban Settlements Development Grant. A portion

Melanie Geyer, project manager: Planning and Research Division, Nelson Mandela Bay Municipality

The excavation level for Phase 2 varies between 8 m and 12 m deep

of loan funding has also been provided for both Phase 1 and Phase 2.

Loan funding was specifically approved for this project through the NMBM Council process, as the funding will unlock various new developments in the medium-class range, which will result in income generation for the NMBM through the monthly Rates & Taxes accounts process.

Phase 2

The project team is focused on preserving the environment as far as possible. A ‘search and rescue’ operation was conducted prior to site clearance to find small animals like snakes, birds, frogs and tortoises. There was also a concerted effort to conserve all indigenous trees.

Greyer maintains that Phase 2 is a complex project. “We experience fluctuating soil conditions, from soft sand to solid rock, random rock pockets and groundwater. Compared to Phase 1 – where the pipeline was above ground in some sections and the landscape required a build-up, or was at very shallow depths below the ground – the excavation level for Phase 2 varies between 8 m and 12 m deep. Furthermore, as part of Phase 2 is constructed on ACSA property, special clearances as well as permits for the installation of the pipes must be obtained from ACSA, and work at night was forbidden. Phase 2 is in close proximity to a densely populated township, so sufficient safety requirements must be in place, such as barricades and fences, in an attempt to prevent children and animals from falling into trenches.”

Community involvement and emerging micro enterprises (EMEs)

While the Driftsands Collector Sewer Project is not labour intensive, an effort has been made to employ any available skilled and unskilled people from the local community.

NMBM abides by the Preferential Procurement Policy Framework Act (No. 5 of 2000) and 30% of the contract is executed by EME contractors. A total of 21 EME contractors were employed in Phase 1 and 27 EME contractors will be employed in Phase 2. These EMEs also receive training in terms of health and safety, interpreting project documentation, and preparing a work plan.

Further phases

“Phase 1 to Phase 4 involves the augmentation of the pipeline capacity to allow for developments in the city to take place. Phase 3 will be more complicated than Phase 1 and Phase 2 because half of the pipeline construction will run through the dense Gqeberha (Walmer township) area. This will necessitate community engagement, social facilitation and negotiations in terms of relocations or compensation. Phase 3 will not commence until the necessary social aspects have been dealt with,” adds Geyer. “Phase 5 and Phase 6 will encompass the rehabilitation of the existing pipeline. In Phase 5, we will get rid of a maintenance headache by replacing a siphon with a gravity sewer line.

“While the current focus is on the upgrade of the bulk sewer pipelines, NMBM has prioritised the upgrade of its WWTWs to ensure sufficient capacity to treat the received wastewater,” concludes Geyer.

THE DRIFTSANDS COLLECTOR SEWER PROJECT WILL BE IMPLEMENTED IN A PHASED APPROACH, THROUGH SIX PHASES:

• Phase 1: Construction of parallel 1.8 km 1 500 mm diameter concrete HDPE lined pipe - Commenced: March 2017 - Completed: August 2019 - Contract value: R52 800 000 (including 14% VAT) - Contractor: WK Construction - Consulting engineer: Bosch Projects • Phase 2: Construction of parallel 925 m 1 500 mm diameter concrete

HDPE lined pipe - Commenced: June 2019 - Anticipated completion date: July 2022 - Contract value: R75 878 147 (including 15% VAT) - Contractor: HT Pelatona Projects - Consulting engineer: Bosch Projects • Phase 3: Construction of parallel 1.8 km 1 500 mm diameter concrete

HDPE lined pipe • Phase 4: Construction of parallel 380 m 1 500 mm diameter concrete

HDPE lined pipe • Phase 5: Replacing existing siphon with 1 500 mm diameter concrete

HDPE lined pipe • Phase 6: Relining of existing sewer pipelines