Civil Engineering June 2022 | Vol 30 No 5

and electrical equipment will commence shortly. Although currently being con- structed with a capacity of 50 Mℓ/‌day, it has been designed with provision for doubling the capacity when needed in the future. PIPELINES AND RESERVOIRS A decision by Amatola Water was taken early on in the project to use GRP pipes for all the primary gravity mains (all rising mains are continuously welded steel). The GRP pipe manufacturer sup- plied on-site technical support to the local contractors and the experience has been that the completed pipelines passed the required pressure tests without difficulty. With the steep topography and wide range of elevations of reservoirs in the Mthatha area, there was a need for robust, heavy-duty, low-maintenance inlet control valves that can safely handle high pres- sures and limit the rate of inflows where multiple reservoirs draw from a common gravity supply pipeline. There has therefore been extensive use of locally designed and fabricated stainless steel bodied rubber diaphragm control valves combined with stainless steel fixed ratio (maintenance free) pres- sure reducing valves (only where inlet heads exceed 80 m) and imported ‘Maric’ maintenance free (but non-adjustable) 18 June 2022  Civil Engineering Figure 11 Through-the-floor locally made inlet control valve (20 Mℓ reservoir) Figure 9 50 Mℓ/day Highbury WTW taking shape (Mthatha Dam in the background) Figure 10 Imported maintenance-free robust flow-limiting ‘Maric’ valve Low pressure High pressure Full open Throttling Control ring