Civil Engineering June 2021 | Vol 29 No 5

34 June 2021 Civil Engineering to little recharge of the aquifers, with resulting decline in the water table over the past years. In 2017 and 2018 almost no winter rains occurred, with the Karee Dam never impounding more than 40%. The Karee Dam’s yield lasted for only three months before going completely dry. This led to increased dependency on the boreholes which, as a result of the low rainfall over several years, had received no significant recharge. These circumstances placed the town of Calvinia and the Hantam Municipality in dire straits, as the boreholes were not able to provide sufficient water. Severe water restrictions were implemented and work commenced to address this problem. BVi Consulting Engineers con- ducted a feasibility study to determine the most cost-effective medium- to long-term solution for the water supply of Calvinia. Three options were considered, namely: Q Q Surface water from the Orange River located 278 km from Calvinia Q Q Surface water from the Doring River located 101 km from Calvinia Q Q Extension of the groundwater sources from several new wellfields. During 2018, the Namakwa district was declared a disaster area and the Department of Water and Sanitation provided funds for drought relief. These funds were used by Hantam to embark on an exploration drilling project for new groundwater sources in a radius of 40 km around Calvinia. Some 44 boreholes were drilled and, after extensive testing for quantity and water quality, 13 boreholes were identified as future production wells for Calvinia. Three new wellfields were envisaged, one towards the south along the Ceres-Karoo Road, one towards the northwest along the Calvinia- Loeriesfontein Road, and one towards the northeast along the Klipwerf road. The feasibility study showed that both surface water options where technically feasible, but not economic. The Orange River option was disqualified due to the distance involved, while the Doring River option was disqualified due to the significant difference in elevation. The Doring River is located some 900 m below Calvinia, and the cost of lifting this water with pumps was in excess of R10 million per annum, pushing the unit cost of the water to beyond R18/kℓ. Subsequently, the extension of the groundwater sources proved to be the most cost-effective medium- to long-term solution. This project comprises the fol- lowing components: Q Q Equipping of 11 new boreholes at Calvinia at the following wellfields: Q Q Four boreholes at Kreitzberg deliv- ering 35.3 ℓ/s Q Q Two boreholes at Northwest deliv- ering 17 ℓ/s Q Q Five boreholes at the North Wellfield delivering 12.6 ℓ/s Q Q Refurbishment of six existing boreholes at Calvinia to ensure full potential is reached Q Q Construction of 7.8 km of 110 mm diameter rising mains to connect the North Wellfield to the Calvinia Water Treatment Plant Q Q Construction of a new 200 mm diameter uPVC gravity main pipeline from Kreitzberg to the Calvinia Water Treatment Plant over a distance of 31 km Q Q Construction of a new 160 mm diameter uPVC rising main from the Northwest boreholes to the Calvinia Water Treatment Plant over a distance of 33 km Q Q Construction of a new 1.5 Mℓ reinforced concrete storage reservoir to provide a total storage of at least 48 hours Q Q Upgrade of the Calvinia Water Treatment Plant to a capacity of 4 Mℓ/‌day Q Q Construction of a 30 ℓ/s activated alu- mina fluoride removal and filtration facility at Calvinia to render the water quality safe for long-term future use Q Q Construction of four 1 000 m 2 evapo- ration ponds to discharge the waste from the fluoride treatment plant Q Q Construction of an 11 kV mains power supply line to each of the wellfields with a length of 60 km Q Q Installation of a telemetry system to control the borehole pumps and reser- voir levels from the Calvinia municipal offices. The project was estimated to cost in the order of R184 million. Unfortunately, the Figure 8 Completed Calvinia Water Treatment Plant