Civil Engineering June 2022 | Vol 30 No 5

M thatha was founded in 1883 in the Eastern Cape along the banks of the Mthatha River. Nearly a century later, in 1977, the Mthatha Dam was constructed on the Mthatha River about 6 km upstream of the town. The Mthatha Dam is an earthfill dam, currently managed by the National Department of Water and Sanitation (DWS), that provides the surrounding areas with water for domestic and indus- trial purposes. The outlet works of the Mthatha Dam feeds water through two pipes located underneath the dam spillway return channel via a pump station to the Thornhill Water Treatment Works (WTW) in Mthatha. These pipes provide the main supply of raw water to the city of Mthatha. There has been a significant reduction of water supply to the WTW, and inves- tigations were undertaken by the internal engineers within the DWS who discov- ered that one of the pipes from the outlet works had burst underneath the spillway return channel, resulting in excessive leakage and a high drop in pressure. The pressure drop had resulted in a significant reduction of supply to the Thornhill WTW, which is insufficient to meet the current requirements of the town. There are hospitals, universities, shopping malls, etc. in Mthatha, and if this problem is not resolved it could lead to a catastrophic water shortage for the town. The leaking water is also resulting in excessive erosion in the area surrounding the leak, accelerating the deterioration of the infrastructure. PROJECT DESCRIPTION The work to address the problem entails construction and installation of a 320 m bypass siphon pipeline over the Mthatha Dam embankment on the side of the non- overspill crest, as well as a pipeline from the siphon to the connection point at the existing pump station to the Thornhill WTW. The siphon pipeline will have suf- ficient capacity to supply the WTW with 85 Mℓ/day over a 24-hour period under gravity flow conditions. Construction of a temporary bypass siphon at Mthatha Dam Ayanda Anderson Shumane Construction Project Manager Department of Water and Sanitation shumanea@dws.gov.za When the Department of Water and Sanitation discovered that a pipe from the outlet works underneath the Mthatha Dam’s spillway return channel had burst, urgent intervention was required to ensure continued water supply to the city of Mthatha. 20 June 2022  Civil Engineering Concrete pouring