Civil Engineering June 2022 | Vol 30 No 5

Civil Engineering June 2022 29 doubling-up of the existing Quarry Reservoir capacity (the latter being part of the existing Umgeni Water South Coast Pipeline System). 3. Ngwadini System: Raw water abstrac- tion, pumping and conveyance to a 10 Mm 3 , 52 m high concrete-faced rockfill off-channel storage dam on the Ngwadini River (a small tributary of the Umkhomazi River some 16 km upstream of the Goodenough abstrac- tion). This system allows for aug- menting very low Umkhomazi River flows in times of drought so as not to compromise the LUBWSS’s required high level of assurance of supply as a primary source of potable water to the South Coast area. GIBB was appointed for the detailed design development and contract administration of the two raw water systems and Ingerop/ V3/NSC JV was appointed for the detailed design development and contract admin- istration of the Clear Water System. This article covers the two raw water systems. GOODENOUGH SYSTEM The Goodenough System comprises a weir and abstraction structure with a low lift ‘dry well’ pumping system (three duty and one standby 500 kW pumpsets) to deliver raw water to two balancing tanks via a cluster of nine hydrocyclones, a high- lift pumpstation, a 1.1 km long 1 200 mm diameter rising main, two 12.5 Mℓ open- topped storage reservoirs and a 6 km long 1 200 mm gravity main to the water treatment works at Craigieburn. The raw water delivery capacity is 135 Mℓ/day. The abstraction works was designed to allow periodic effective flushing of the accumulated sediment from within the abstraction structure and to exclude as much of the suspended sediment from the pump intakes as possible. The upper works are set above the 1:100-year flood level; some 20 m above the riverbed level. A fish ladder and ‘creepy crawly’ ramp have been incorporated into the design to Figure 3 Goodenough abstraction and pumping system site layout North bank South bank Abstraction works Goodenough crump weir RCC retaining wall Abstraction works platform Umkhomazi River Low-lift pumpstation Generator building Site access road Transformer rooms VSD rooms High-lift pumpstation Balancing tank Hydrocyclones Figure 2 LUBWSS overall locality plan Ngwadini abstraction and pumping Ngwadini Dam Goodenough abstraction, desilting and pumping Goodenough reservoirs LUBWSS Water Treatment Works Quarry reservoir Craigieburn Dududu Umkhomazi River Ngwadini Site Goodenough Site