Ageing municipal water and sanitation infrastructure is a major concern for Johannesburg Water (JW). In August 2007 JW conducted a study for the replacement of ageing water infrastructure across the city. Following the successful rehabilitation and upgrading of the Klipspruit Sewer Drainage Basin, consultants Vela VKE Consulting Engineers (Pty) Ltd and contractor Trenchless Technologies cc were chosen to complete the Kibler Park water mains replacement. Kibler Park is a suburb of South Africa, Johannesburg. The Klipspruit Sewer Drainage Basin stretches from Braamfontein in the north to Devland in the south of Johannesburg in the Gauteng province of South Africa.

Kibler Park – mains replacement

JW will invest $US9.34 million to replace old systems in eight suburbs. For the Kibler Park mains replacement Trenchless Technology is a key aspect of the programmed works.

JW Managing Director Gerald Dumas said “All these projects are aimed at improving and extending our infrastructure and replacing old and outdated infrastructure so as to deliver a better service to our customers.” JW also have a program in place that allows site managers to visit different areas every month to keep track of water infrastructure.

The Kibler Park major water secondary mains replacement encompasses two sub-projects of approximately equal pipe length. Cedric Bessit of Vela VKE Consulting Engineers explains that one will be executed conventionally, while the other will employ pipe bursting. This approach will allow the water utility to compare certain characteristics of the sub-projects, such as cost, implementation time, customer and public inconvenience, health and safety, environmental impacts, quality and sustainability.

The project will involve the replacement of approximately 10 kilometres of existing asbestos water mains, ranging in diameter from 75 – 200 mm. The pipes have either neared the end of their life cycle or have been damaged by other adjacent construction activities over the years. At present, the maintenance cost of keeping these pipes operational and the frequent inconvenience to customers far exceeds the budget to rehabilitate.

Rewarding Trenchless Technology

The total sewer length of the Klipspruit Sewer Drainage Basin is 560 kilometres. The replacement and rehabilitation works were commissioned by Johannesburg Water, with consultants Vela VKE Consulting Engineers. The contractor was Trenchless Technologies cc.

The project works consisted of the rehabilitation and upgrading of 2.3 kilometres of sewers, with diameters greater than 150 mm. Mr Bessit said that Trenchless Technology was utilised due to the location of the pipes.

In 2006, the preliminary scope of work was based on previous CCTV surveys, but the need for a pre-implementation CCTV survey was identified and included as part of the contractor’s scope of work. Thus, on appointment the contractor was allowed to continue with all upgrading and localised point-repair work. For example where existing pipes had to be enlarged by pipe bursting and localised point repairs by conventional trenching.

An existing clay sewer next to the Oriental Plaza, a local shopping centre, required pipe bursting, CIPP lining and HDD to overcome water infiltration and to increase the size of the pipes. The pipe bursting works involved the up-sizing of 394 metres of 250 mm diameter clay pipe to 355 mm diameter HDPE PN10 PE100 pipe. CIPP was utilised to overcome the water infiltration and root ingress; the contractor installed 170 metre Berolina lightspeed liner in an existing 250 mm diameter clay pipe. HDD was used to install 175 metre of new 250 mm diameter HDPE PN10 PE100 pipe.

In Rosettenville, a suburb of Johannesburg, pipe bursting was required to overcome pipe corrosion and various localised structural collapse. The rehabilitated sewer was located in a major arterial road and crossed underneath a railway line. Limited disruption was therefore a priority. This involved the up-sizing of 1.52 kilometre of 160 – 200 mm diameter clay and concrete pipe to 225 mm pipe. The water infiltration in this area also required CIPP lining of 86 metres of Berolina lightspeed liner in an existing concrete encased 200 mm diameter clay pipe.

The Southern African Society for Trenchless Technology (SASTT) recognised this project with the 2008 Award for Excellence. The Association said the project demonstrated why Trenchless Technology is the technology of the country’s urban future; it largely eliminated both disruption of traffic and damage to the environment, and resulted in significant savings for the client.

Developing the industry in South Africa

Mr Bessit, a passionate supporter of the trenchless industry, spoke to Trenchless International about the challenges encountered in South Africa in regards to building the industry.

The shortage of adequate trenchless support equipment and materials remains a concern. There is a limited number of competent contractors that can perform trenchless projects or who own trenchless equipment to perform pipe bursting, CIPP, swagelining and sliplining. Currently, in South Africa, pipe bursting and HDD are mainly supported with HDPE pipe. Due to past experiences certain local clients are reluctant to use HDPE pipes as a replacement of water lines in excess of 250 mm diameter and/or where excessive pressures are existent in the system. Therefore there is a need for alternative trenchless supporting materials.

Although Mr Bessit recognises the industry is slowly changing, with other foreign-based manufacturers of trenchless equipment and materials now entering the South African market, he believes further improvement is necessary. “I urge local manufacturers or distributors of equipment and material to increase their array of equipment and materials to support this rapid growing local need,” says Mr Bessit.

Mr Bessit also advocates the institution of national standards to complement a program of client and consultant education. Currently each consultant has developed a rudimentary set of trenchless specifications and where local municipal clients have paid the consultant to write specifications, these are copyright protected. Therefore, the specifications are seldom shared between municipalities. Mr Bessit explains that irrespective of the quality of the specifications the lack of a national standard can lead to conflict during the project execution.

Vela VKE Consulting Engineers are currently in the process of rasing funds to conduct research in the South African trenchless industry. The outcome of this research could involve a guide on the various Trenchless Technologies available both locally and internationally; a guide for the ‘appropriate application of Trenchless Technologies’, with a primary focus on sustainability and cost effectiveness; and finally, the availability of tertiary education locally or internationally on the design of trenchless rehabilitation of pipes.

The SASTT has been actively campaigning for government funding to facilitate the development of national industry standards. The Association is also designing a code of conduct and developing standards for the Trenchless Technology industry.