Durban’s new artery

2010-02-01 00:00

DRIVE along the N3 these days and you can’t miss the pipe-laying activity going on adjacent to the freeway between Inchanga and Umlaas Road. The excavation, installation and rehabilitation in progress all adds up to the Western Aqueduct, a huge joint-venture project commissioned by eThekwini Municipality’s Water and Sanitation Department costing in excess of R800 million.

“These pipes are the arteries of a nation, without them it doesn’t operate,” says Pedro Rodrigues of Knight Pi é sold Consulting and lead engineer on the project, who was speaking on behalf of eThekwini Water and Sanitation. “Just like with the arteries of our bodies, we only worry when they can no longer cope.”

Those worries began in the mid-nineties when the increased demand for water in Durban, particularly in the western areas where new suburbs were springing up such as in Hillcrest, Assagay and Waterfall, saw the Western Aqueduct project first initiated. “The water pipes taking water­ into Durban laid in the sixties were simply not big enough to cope with the increasing water demand,” says Rodrigues.

But Durban kept growing and so did the size of the project. “Durban experienced growth westwards with the migration of residents and business from the traditional residential and commercial areas of Durban,” says Rodrigues. “The northern areas of Durban were experiencing similar expansion such as Sunningdale, Newlands, Mount Edgecombe, as well as the densification of townships such as Ntuzuma and Inanda and surrounding rural areas.”

The consequent pressure on the water- supply infrastructure, compounded by its age, resulted in pipe failures leading to water outages and increased water loss. The demand continued to increase as the government pushed on with plans to extend water services to peri-urban rural communities who had previously been without. “The existing water supply infrastructure just couldn’t cope,” says Rodrigues. “Originally the proposed new pipeline was planned to terminate in Pinetown but with pressing needs to also supply the vast areas­ of Ntuzuma, Inanda New Town and Mzinyati, the scope of the Western Aqueduct was extended to supply these areas north of the Umgeni River.”

The year 2000 was the intended start date of the project but financing was not available until 2005, by which time water demands in the region had increased further. “A year ago the project was augmented for the third time because of additional bulk water supply demands of other areas adjacent to this project,” says Rodrigues. “But we are now sitting with the ultimate capacity that this project can carry which is dictated not only by the sizes of the pipelines that have already been laid but also by the amount of water that is actually available at the source of supply,” says ­Rodrigues. “We are now at the limits of how much the Western Aqueduct project can expand.”

•••••••••

The route of the Western Aqueduct parallels­ the N3 from Umlaas Road to Inchanga railway station where it moves away from the N3 traversing Drummond, Assegai and Hillcrest. Thereafter it parallels the M13 freeway through Everton and Kloof, heading towards Ntuzuma via Wyebank, branching through New Germany to Mount Moriah and with a feed through Haygarth Road in Kloof heading to Tshelimnyama. At different sites along its route, branch pipelines will supply water to more than 10 Strategic Bulk Water Distribution Reservoir sites serving the Western Areas.

Construction of the Western Aqueduct project has been divided into two phases: phase one, currently in progress, is being constructed by WK Construction and stretches from Umlaas Road Reservoir — where water is sourced from Midmar Dam — to Inchanga, a distance of about 20 kilometres. The 55-kilometre phase two is planned to get under way towards the middle of this year and should be completed by 2013.

The project is being undertaken by the Western Aqueduct Consultants Joint Venture comprising three companies Knight Piésold Consulting, Naidu Consulting and Stewart Scott International (SSI), all acting as eThekwini Water and Sanitation’s agents on this project.

Construction of phase one of the project, which began last January, is 50% complete. “Phase one runs through farmland, small plots, chicken farms and open country,” says Rodrigues. “This is an easy route, where there is generally free access to the construction corridor and work is able to progress unrestricted with little impact to business, residents and commuters.”

Construction of phase two will be a different story as the pipeline literally goes up hill and down dale before arriving in heavily built-up urban areas. “Here the impact of construction activities will be felt more strongly,” says Rodrigues. “There are physical restrictions to working in built-up areas and the impact will inevitably be high; people living on the route will be inconvenienced and there will be an impact on traffic and commuters.”

In a bid to lessen this impact and keep affected residents informed, an ongoing public relations programme has been put in place. As well as keeping residents up to speed on what to expect and when, it is hoped it will also get buy-in to eThekwini­’s vision to provide all residents in its area of supply with safe potable water­, a vision which the Western Aqueduct will help realise.

THE 75-kilometre-long Western Aqueduct is made up of steel pipe sections 18 metres in length and in a range of diameters ranging from 1,6 metres down to 0,4 metres.

Eight pipe-storage yards have already been established in strategic locations to serve this project in New Germany, Pinetown, Mount Moriah, Cato Ridge Camperdown, Hammersdale and Ntuzuma.

Laying the larger diameter pipes involves excavating a trench at least three metres wide and between three and four metres deep, within a pipe construction corridor which is fenced off and only accessible at certain controlled points. “Construction staff are expressly forbidden to cross the fence of the construction corridor into private property and noise and dust from construction activities are to be contained as much as practically possible, especially when traversing built-up areas,” says Pedro Rodrigues of Knight Piésold Consulting and lead engineer on the project. “These are some of several measures to minimise the impact of construction on the surrounds.”

A rehabilitation programme sees the land disturbed by the pipeline excavation and pipe installation restored to its former state or even better. Steering this work is a Plant Rescue and Rehabilitation Plan, and Knight Piésold’s lead environmental scientist Claire Blanche says: “It is hoped that sensitive sites will eventually offer a plant variety and habitat equal or better than that before construction.”

Environmental concerns have also helped dictate the pipeline route. For example, the construction corridor in phase one was rerouted at the cost of R280 000 to avoid the habitat of two endangered frogs, one of which is classified as a Red Data species. Prior to investigation of the pipeline route the frogs were not known to live along the route of the pipeline. Other discoveries along the pipeline route include remnants of the Voortrekker route to Durban and an Iron Age settlement in the uMngeni Valley, all of which will receive special attention to ensure that they are protected from any damage during the construction of this project.

Once the trench is excavated the steel pipes need to be bedded in river sand. “This has become a major logistic problem for the contractor in this project,” says Rodrigues, “because throughout the Durban and Pietermaritzburg region there is a big shortfall of river sand arising from the many years of extensive harvesting of river sands for construction from all major river courses of the region.”

To sustain the required rate of pro-gress with the construction of phase one, the project needs about 600 cubic metres of bedding material a day which is not able to be delivered from local commercial supplies and is having to be supplemented with alternative crushed materials at greater cost. The requirements for river sand for the construction of phase two of the Western Aqueduct remain a major logistics challenge in this project. About 210 000 m³ of river sand need to be hauled into this project, which equates to roughly 21 000 truckloads of material.

In addition, about 270 000 m³ of excess material from the pipeline excavations also needs to be disposed of in environmentally approved dumping sites. The haulage of this material equates to about 27 000 truckloads of material.

Another challenge facing this project is the standard of skills available, particularly when it comes to welding. “In phase one, more than 100 welders were interviewed and tested for the contractor to eventually take 18, [as] the rest of the welders were below standard,” says Rodrigues. “The availability of skills in the country for work of this nature is extremely low or non-existent. The project will need about 80 pipe welders for phase two. The successful contractor will have to recruit API coded welders from Malaysia or the Mediterranean countries where those artisans are experienced in working on gas and oil pipelines.”

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