The Civil Engineering Contractor February 2018 | Page 17

ON SITE the dams. The V-drains vary in width from four to 24m and they also catch some of the subsoil drainage, as some water inevitably ends up below the slab, Keevy informs. “Along the perimeter of the coal stockyard is a fire water supply network, part of an extensive fire suppression system that also has surface fire hydrants. The water in the system is at a constant high pressure to ensure immediate access when required,” he says. Total laid piping (within Esor’s scope of work) snakes an astounding 50km around the site. “This includes concrete drainage piping, HDPE water systems, PVC and UPVC sewage systems, and subsoil drainage from the various buildings on site.” HDPE welding specialists and suppliers on site, Sebetsa Trading, ensured that the high-pressured piping was expertly joined, completing the system to the highest standards. “Diameters varied from 150mm to 640mm,” Keevy says and adds that at the deepest point, the pipes were buried at a depth of 35m. Cable trench special lid preparations. Challenges When a project as intricate as this is undertaken, challenges are inevitable. Within Esor’s scope of work, the initial design on all the pressure piping systems was going to be PVC, Keevy explains. “However, about six months after we had started, that then changed to HDPE, owing to the longer lifespan,” he says. While this change happened before Keevy joined the project, he muses that the change was initiated by the client, Eskom, through the designers. “In the long run, this was the right decision and will reduce maintenance and replacement costs,” Keevy comments. The arduous project management task fell on the shoulders of the Kusile Execution Team (KET): a collaborative effort between Eskom and Black & Veatch, an American consultancy specialising in engineering, procurement and construction (EPC) services for energy, water, and telecommunications. “Prior to handing over the completed piping system, we have to flush and drain it and put a camera through the section. It was then that we discovered sagging pipes in some areas due to unstable surrounds,” he explains and quickly assures: “The areas where we had challenges have been reworked by recompacting and relaying, and in some places, pressure grouting was undertaken to stabilise the ground, around the very deep manholes for example,” he says. “There were some cured in place pipe (CIPP) repairs done by one of our subdivisions, Tuboseal, a piping repair specialist, who realigned and/or relined the relevant pipes.” Storage dams Keevy explains that water is reused on site extensively and stresses that although this aspect was not part of Esor’s scope of work, constructing two dams were: “We were responsible for building two holding, recycling dams. These dams catch the vast amounts of water that is used for heating and cooling the turbines. This water is Earthworks for coal stockyard V-drain. The entire contract comprises the installation of drainage systems and high-pressure fire and water supply piping in a range of diameters from 150mm to 630mm for pressure lines, and up to 2 500mm for bulk stormwater lines. CEC February 2018 - 15