Civil Engineering April 2022 | Vol 30 No 3

Civil Engineering April 2022 43 T he state-of-the-art water treatment facility treats contaminated un- derground mine water to drinking water quality. The bulk of this water is supplied directly to municipal reservoirs and the balance is used by the mine for its own purposes. It serves as a stellar example of private sector involvement in service delivery, supplementing stressed municipal water supplies. Over the years of treating corrosive mine water, the concrete of the water purification plant had fallen into a poor condition and required extensive repairs. Greene Consulting Engineers designed and supervised the remedial work. This was an extensive undertaking that entailed repairing the two concrete tanks and the interconnecting pipe, as well as the water purification plant’s clarifier and thickener. Citi-Con was appointed as the specialist contractor to undertake the repairs to the water purification plant. The company offers permanent concrete protective coatings that penetrate the concrete surface so that it can resist extreme hydrostatic pressure from either positive or negative surfaces. These liquid resistant qualities become an integral part of the concrete substrate. They are highly impervious to aggressive chemical attack, while also sealing hairline shrinkage cracks and enabling the concrete to breathe. CONCRETE REPAIRS Work commenced with the repair of the bases of the two concrete tanks, with workers lowered down the 6 m-high struc- tures using rope-suspended platforms. “We first drilled a hole into the damaged areas of the bases of the two water-retaining structures. An acrylic reinforced cementitious, flexible water- proof coating was then used to plug these areas. Forming a hard wearing, seamless, waterproof membrane, the liquid was poured directly into the damaged areas via a conduit that was inserted into the various holes that we drilled in the dam- aged areas of the base of the reservoir,” explains Andre Vermeulen, Director of Citi-Con. One of the challenges on this project was repairing the 1 m diameter pipeline between the two tanks, with the team having to work in an extremely confined space to seal areas that were leaking. The damaged areas of the clarifiers were repaired using epoxy-injected grouting methods and Hypalon bandage, which was also deployed to repair con- crete defects on the thickeners. Rope access systems were used by the specialist contractor to gain access to various damaged areas. All of the company’s rope access practitioners have completed their Rope Access Level 2 training and have therefore undertaken many thousands of hours working in the field. Notably, it also provides a safer method of working at heights. Working for a mine, the company had to ensure that it complied with very strict mine health and safety protocols, and there were no major incidences during the entire duration of the project.  State-of-the-art concrete repairs for water purification plant A water purification plant in the Mpumalanga coal fields, operated by a leading coal miner, recently required major concrete repairs due to corrosion. The damaged concrete was repaired with a protective coating in a project that required strict safety protocols for working at heights. Work commenced with the repair of the bases of the two concrete tanks