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ISTT Annual Project Award for a remarkable project in South Africa

01. January 2013

Beneath the busy Govan Mbeki Avenue and the newly constructed Bus Rapid Transport lane in the heart of Port Elizabeth’s central business district was the venue for a remarkable trenchless rehabilitation project undertaken by South African contractor Trenchless Technologies c.c. Two parallel sewers, 600 m of a 525 mm and 720 m of a 1050 mm circular pipe, were rehabilitated using the spiral-wound pipe rehabilitation technologies SPR™ EX and SPR™ RO provided by SPR Asia Pacific’s technology provider SEKISUI Rib Loc. The successful project has now achieved international recognition with the ISTT Annual Project Award 2012.

SPR Asia Pacific and its Australian technology company SEKISUI Rib Loc provided the right trenchless technology solution when it came to rehabilitate two circular sewers with diameters of 525 mm and 1050 mm beneath the heavily trafficked Govan Mbeki Avenue and the newly constructed Bus Rapid Transport lane located in the heart of Port Elizabeth’s central business district, South Africa, in 2011. The spiral-wound pipe technology SPR™ EX was utilised to rehabilitate 600 m of the sewer pipe with a diameter of 525 mm in the business district. SPR™ RO relined 720 m of the larger sewer with a diameter of 1050 mm under the Bus Rapid Transport lane. For the Mandela Bay Development Agency this rehabilitation was part of one of a continued pipe rehabilitation and environmental upgrading project. After a CCTV and physical inspection where windows were cut into the concrete sewer pipes, the need for rehabilitation was ascertained. The 525 mm sewer was severely corroded around its whole circumference due to acidic effluent. The measured pH values were as low as 3.3. This old sewer had been cast in 2 sections with horizontal joints running along its full length. The mortar had corroded between the construction joints and the pipe was no longer water tight. The 1050 mm sewer was severely corroded above the water line and the steel reinforcing was exposed and had corroded away in places. The most severe deterioration occurred at the sides and invert of the sewer due to a combination of corrosion and erosion and was particularly severe along those sections of the sewer where the velocity was high. Due to the severity of deterioration and the limited space above-ground, the spiral-wound technology was the only cost-saving process allowing a complete no-dig lining solution through manholes. During the rehabilitation phase unforeseen occurrences, such as a 15 m long 90 degree radius bend in the 525 mm pipe and a 43 m long part where the 1050 mm sewer reduced in diameter to 800 mm, required the introduction of an ambient cure and a UV cured CIPP method. Additionally, pipe bursting of 16 m of a cracked and leaking lateral clay pipe with a diameter of 225 mm became necessary to prevent plugging and overpumping at a critical manhole.

The spiral-wound process
The spiral-wound pipe lining technology is a patented method that includes five different solutions for rehabilitating sewers and stormwater pipes with diameters from 150 mm up to 5000 mm. Circular and non-circular pipes can be rehabilitated using custom shaped profiles for pipe lengths up to several hundred metres. The spiral-wound technologies can structurally rehabilitate brick, concrete, glass reinforced plastic or corrugated metal sewer and stormwater pipelines. The system consists of a single, manageable continuous PVC or HDPE profile strip, steel-reinforced as required, which is spirally wound into the existing sewer or stormwater pipeline via a patented winding machine positioned in the base of an existing manhole or access chamber. The edges of the profile strip either interlock as it is spirally wound into the existing pipeline or are welded to form a liner that is watertight. With the SPR™ EX and SPR™ RO techniques used in Port Elizabeth, the PVC profile formed a new spiral-wound liner that provided a close-fit to the inside of the rehabilitated pipe. In the case of SPR™ EX, the winding machine was
lowered to the base of the access chamber through a standard manhole. The PVC profile was fed from an above ground spool into the winding machine, which then spirally wound the liner into the host pipe. With respect to SPR™ RO however the winding machine rotated and traversed inside the deteriorated pipeline forming a close-fit watertight liner as it progressed.

What has proven successful
This rehabilitation project was executed in 2011 and was the second of two phases. The construction site was located downstream from the first phase which was completed in 2009 and involved the rehabilitation of 570 m of 450 mm sewer using the spiral-wound pipe rehabilitation technology SPR™ EX as well as 560 m of the 840 mm sewer rehabilitated using SPR™ PE. The pipeline rehabilitation took place concurrently with an urban environmental upgrading project involving decorative paving and resurfacing works on the surface above the existing sewer pipes. Mandela Bay Development Agency awarded both relining projects to the rehabilitation company Trenchless Technologies c.c. and used spiral-wound technology to complete the project. CIPP and pipe-bursting had to be utilised for very short sections to deal with unexpected problems where this technology was suitable. Africoast Consulting Engineers (Ltd) provided overall design and management of both Projects.

ISTT Annual Project Award
For many years the International Society for Trenchless Technology (ISTT) has selected an outstanding trenchless pipe rehabilitation project to receive a Project of the Year Award at their annual No-Dig conference. At the 30th International NO-DIG 2012 São Paulo, rehabilitation company Trenchless Technologies c.c. was awarded the ISTT Annual Project Award 2012. SPR Asia Pacific’s technology company SEKISUI Rib Loc was the material and technology provider to the construction team. “The ISTT Award honours an excellent project in which five different trenchless technology options were used to rehabilitate large diameter sewers for use by future generations and solve unexpected site conditions”, says Gordon Combeer, Sales Manager of SPR Asia Pacific and notes further that “with SPR™ EX and SPR™ RO as the main rehabilitation technologies, a growing trend in Africa in the employment of spiral-wound pipe technology is shown.”

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