Across the length and breadth of Kwa Zulu Natal, Sika has come to the rescue in the refurbishment and sealing of dozens of Eskom Transformer Bunds. Environmentally it is vital that these bunds have a secondary containment lining to prevent contamination of surrounding ground water.

The original tender called for the construction and refurbishment of forty-three transformer bunds throughout the province. There were two types of bunds; transformer bunds measuring 65m2 each and transformer sumps measuring 50m2 each, totaling an area of 4,952m2.

Empangeni was treated as the pilot project to test the tender specification, which called for a lining of HDPE (High Density Polyethylene). Importantly, this lining needed to withstand heavy traffic from cranes and forklifts when a transformer requires installation, maintenance or replacement. However, within approximately two months of application, the HDPE lining on weld joints in the bunds had failed. There were also project delays due to low strength concrete, honeycomb concrete and no strength concrete, as well as non-removal of construction waste and sites left dirty, prior to lining the bund walls.

Engineering company, Preben Naidoo & Associates, contacted Sika requesting technical information on one of their high performance waterproofing products, Sikalastic-841 ST. A meeting between the engineering consultants, Eskom, Sika, and the specialised contractor, Rodcol Contracts, resulted in a decision to replace the HDPE lining. Due to costs, only the transformer bunds were scheduled to be lined with Sikalastic-841 ST. Newcastle was then elected the new pilot project to test the Sikalastic-841 ST system.

Dicks Construction was awarded the contract to construct the Newcastle bunds.

Rodcol Contracts then commenced the pilot project of lining the Newcastle bunds with Sika’s specified coating system; Sikafloor-156 ZA, a two-part epoxy resin was applied as a primer for Sikafloor-261 ZA, a two-part, multi-purpose epoxy resin binder that was bulked with SS1 sand.

These layers were covered with a machine-applied coating of Sikalastic-841 ST (2mm thick).  This fast-curing pure polyurea membrane allows for almost immediate return-to-service time, is 100% solids with zero VOC, and provides excellent crack-bridging properties and corrosion protection. It is suitable for application on many substrates and provides protective coating on bridges, roofs, balconies, industrial facilities, and, after this project has proven its worth, in lining transformer bunds.

When comparing technical performance, there was no contest between the HDPE lining and the Sikalastic-841 ST system, and the Newcastle pilot project was satisfactorily completed with no problems incurred.

Rodcol was also responsible for grit blasting and cleaning the concrete, removing building rubble and site cleaning. For fixing small repairs to the various bunds Rodcol used Sikadur-31 CF Normal, a moisture-tolerant, thixotropic, structural adhesive and repair mortar based on a combination of epoxy resins and special fillers. Easy to use and suitable for dry and damp concrete surfaces, it hardens without shrinkage and is impermeable to liquids and water vapour.

Initially only transformer bunds were to be lined, but a decision was made to line all transformer sumps as well. Having commenced in February 2011, by March 2012, thirty areas in Kwa Zulu Natal had been completed, some having been refurbished, some demolished and rebuilt, while others were newly constructed.

This extensive project was scheduled for completion by the end of 2012 and, thanks to Sika’s superior quality products and systems, Eskom is assured that its transformer bunds are safely and securely lined thus preventing any possible contamination of ground water.