Rehabilitation of National Route 7 (TR11/1)

First project in South Africa to reprocess an existing bitumen stabilized material (BSM)

Use of recycled materials while generating sustainable design solutions

Restoration of old Diep River Bridge to safety, while protecting its heritage value

350 jobs created, 60,000 working days for locals

Challenges

The Western Cape Government’s (WCG) Department of Transport and Public Works recognized the need to rehabilitate the existing N7 (TR11/1) in Cape Town from the Bosmansdam Interchange to the Melkbosstrand Interchange as part of their broader goal to upgrade the N7 to freeway status.
This section of the N7 arterial route links numerous residential, farming, industrial, and manufacturing areas between the Western Cape towns of Melkbosstrand and Cape Town. It witnesses a daily vehicle count of 55,000.
We provided a full scope of services in line with Engineering Council of South Africa (ECSA) guidelines for the periodic maintenance of the N7. These services encompassed inception, concept and viability studies, detail design, and construction monitoring.
There was a pressing need for a cost-effective, sustainable solution that would minimize disruptions to the local community.
Aimed to set a benchmark for effective maintenance of the Western Cape Government (WCG) road network, recognizing the current economic climate's limitations in material resources.
Explored the utilization of recycled materials and collaborated with the client, utilizing effective knowledge transfer and risk management to generate optimal design solutions.
Pioneered the use of a novel and specialized road repair practice in South Africa: reprocessing bitumen stabilized material (BSM), marking a first in South Africa.

Solutions

The N7 rehabilitation and upgrade is a sole-sourced project bringing together design engineers, environmental services, construction administration, and supervision from Hatch.
The innovative approach involves reprocessing the existing BSM and using it in the new road's base layer, effectively providing the material with its third life cycle. Asphalt surfacing is placed on bitumen stabilized material, utilizing 100 percent reclaimed material in the base layer and 20 percent reclaimed material in the surfacing layers.
The cost-saving approach includes reducing the cost of virgin materials and disposing of these valuable materials.
For construction purposes, the periodic maintenance of the N7 is split into 2 sections. The Bosmansdam Interchange to Potsdam Interchange portion involves milling, resurfacing, and raising to allow the construction of two new road over road (underpass) structures. The portion from Potsdam Interchange to Melkbosstrand involves strengthening on the slow lanes, resurfacing, repairing, and rehabilitating several portions of the N7.

Highlights

This is the first project in South Africa to reprocess existing BSM, effectively giving this road material its third life cycle. It is also the second project in the Western Cape to utilize 100 percent recycled materials in the base layer of a road.
We recycled 36,000 cubic meters of existing road material and used it as a new base layer that will remain intact for decades.
The project had a positive impact on the local community, creating 350 jobs and 60,000 working days for locals. The positive relationship with the local community was fostered as the public understood and welcomed the economic benefits of the project, with minimal complaints related to the day-to-day impacts for travelers on the N7.
To achieve a fast-track delivery of the detailed design on the first portion of the N7, tender documentation, and project execution, the team implemented proper testing and quality assurance measures, as well as a robust plan for knowledge transfer between the team and subcontractors.
The project included the restoration of the old Diep River Bridge for safety and the construction of two new bridges, which provide safe passage for vehicles and allow pedestrians to safely cross beneath the N7. Hatch restored the old Diep River Bridge while preserving its heritage value.

“Hatch has successfully set the benchmark for effective maintenance of the WCG road network.”

Azni November | Chief Engineer of Asset Management, Department of Transport and Public Works at the WCG