Pipe installation company Trenchless Technologies has recently completed and continues to work on a number of new pipe installation and rehabilitation projects to improve South Africa’s ageing sewer pipe infrastructure.
One of its most recent projects was an R11-million sewer pipe rehabilitation contract for the Nelson Mandela Bay municipality, which Trenchless Technologies managing member Sam Efrat says was a milestone project for the company. The project was runner-up for the South African Society for Trenchless Technology Award of Excellence in 2011.
The project, which was started in May and completed in December 2011, entailed the rehabilitation of two existing parallel concrete sewer pipelines beneath Govan Mbeki drive from the City Hall towards Russell road up to Manchester road – the main road in the Port Elizabeth central business district.
The existing infrastructure comprised two parallel running sewers, one 600-m-long pipe with a diameter of 525 mm and one 720-m-long pipe of 1 050 mm in diameter.
Trenchless Technologies used its RibLoc Expanda technology to line the 525-mm-diameter pipeline, while a RibLoc Rotoloc liner was wound inside the 1 050-mm-diameter existing pipeline.
This nonintrusive method of sewer renovation required no excavation and was chosen to limit the potential disruption that may have occurred if a traditional trenching method was used.
Another project undertaken by the company in Port Elizabeth entailed the rehabilitation of pipelines in the Helenvale area.
Directional drilling technology was used on three 150-mm-diameter sewer pipes to back ream the existing pipe to a larger diameter. Thereafter, a 400-mm-diameter high-density polyethylene (HDPE) pipe was pulled through in its place to complete the installation.
According to Efrat, this project proved to be the most challenging to date, as the operation was carried out on an elevated embankment.
Two out of the three pipe installations were completed on the first attempt; however, the installation of the last sewer pipe crossing was difficult.
There was a large amount of boulder backfill in the embankment. During back reaming, the boulders kept collapsing into the borehole through which the company was working, compromising the borehole. After several attempts, it proved impossible to pull the 400 mm HDPE pipe through.
This resulted in various other trenchless methods being tried before the installation was successful.
By using a TR 360 Terra Hammer with 840 t of impact force, a 508 mm steel sleeve was pipe-rammed through a distance of 48 m of the embankment, completing the installation.
Meanwhile, Trenchless Technologies expects to complete a R31-million pipe replacement project in Tshwane in June.
The contract was awarded in June 2009 and entails the use of the pipe-cracking method to replace existing 160 mm mid-block sewer piping in the Ga-Rankuwa and Shoshanguve areas.
The technique, which is also known as pipe bursting, fractures the existing pipeline from the inside and pushes the broken pipe remains into the surrounding ground, while simultaneously laying a new pipe, of the same or a larger diameter, in place behind the cracking device.
Efrat notes that limited investment is being made to maintain existing buried infrastructure, as there is more of an emphasis on investing in new housing and new water and sanitation infrastructure.
According to Trenchless Technologies’ projections, about R1.9-billion a year should be spent on trenchless sewer rehabilitation methods, where only R500-million a year is currently being invested on this, Efrat maintains.
He notes that, while the construction of new infrastructure is important, the government’s methodology of focusing only on creating new infrastructure should change to also protecting investment and improving existing infrastructure.
“Damaging roadways and existing buried infrastructure in urban areas by using opencut methods is unnecessary when trenchless alternatives are available. Costs are cut when existing infrastructure is not damaged, needing rebuilding,” he says.
He explains that the advantages of using trenchless methods are that fewer accidents occur, as no dangerous trenches are dug in roadways; dust and noise pollution, as well as carbon emissions, are reduced, as less earth is moved; and a smaller workforce is required.
Health and safety issues are also mitigated where deep trenches would be required using opencut techniques. Also, there is a smaller work footprint creating less impact on the environment.
Meanwhile he points out that, in terms of trenchless work, Trenchless Technologies has a 7% market share of rehabilitation projects and a 5% market share in new pipe installations, with a yearly growth in turnover of more than 20% a year, achieved between 1993 and the present.
“The company’s directional drilling method of pipe installation generates between 20% and 30% of its turnover. In five years’ time, we hope to increase it to 50%,” says Efrat.
The company is currently involved as a subcontractor in a directional drilling project involving the installation of 110-mm-diameter HDPE sleeves for fibre-optic cable installation projects between Johannesburg and Kimberley.
“The conditions have proved challenging at times, owing to the underground terrain comprising of hard rock and boulder,” says Efrat.
Further, he points out that, in the past three years, the emphasis has changed from sewage to water projects, owing to the looming water crisis that has placed pressure on cities to sustain water resources.
As a result, water projects are on the increase and more money is likely to be spent on water, despite there being a backlog in both water and sewage systems.
“We hope that more upgrade and installation projects are commissioned sooner rather than later, as skills are continually being lost within the industry, creating a race against time to rehabilitate the buried infrastructure in our country,” cautions Efrat.