Civil Engineering June 2022 | Vol 30 No 5

PROJECT OVERVIEW Amatola Water is the implementing agent for the rollout of the Mthatha Bulk Regional Water Supply Scheme. This KSD Presidential Intervention (PI) mega project was initiated in 2013 and is due for comple- tion in 2025. The first (primary bulks) phase is expected to cost R3.5 billion, with the subsequent phase (to link the primary bulks to existing and new reticulation) expected to cost R1.5 billion. Expenditure on the primary bulks to date is R2.5 billion. The Thornhill Water Treatment Works (WTW) is currently Mthatha’s sole source of potable water. The KSD PI Bulk Water Scheme Masterplan required the capacity of this system to be doubled to supply all areas and development corri- dors to the south of the Mthatha River. In addition, it called for the construction of a new 50 Mℓ/day water treatment works to the immediate east of the Mthatha Dam (the Highbury WTW) to supply all areas and development corridors north of the Mthatha River. The primary bulk system includes 200 km of steel and GRP pipelines (1 200 mm to 250 mm), 24 reservoirs (20 Mℓ down to 6 Mℓ) and 10 pumpsta- tions (5.5 MW at Thornhill WTW down to 40 kW in outer areas). The secondary bulk system includes an additional 350 km of smaller pipelines, 65 small reservoirs and seven pumpstations. The primary bulks construction work was broken up into 75 contracts, 68 of which are completed or nearing comple- tion). The secondary bulks contracts are of a similar number, but only around 20% are complete. The lead engineering con- sultant, GIBB, is a South African company with 67% black ownership. 35% of the work is shared with various SMME en- gineering firms and other local technical service providers, thereby building up the local technical skills base. Figure 1 outlines the layout of the primary bulk infrastructure, showing the current status of completion. THORNHILL RAW WATER SUPPLY, WTW AND CLEAR WATER PUMPSTATION UPGRADE The early stages of the KSD PI Bulk Water Scheme saw the replacement of the original 600 mm fibre-cement and 800 mm steel raw water pipelines from a booster pumpstation at Mthatha Dam to Thornhill WTW with a new single 1 200 mm / dual 800 mm steel pipeline that can deliver the required ultimate 120 Mℓ/day. This in- volved the construction of three new pipe bridges where the pipeline route crosses the meandering Mthatha River. Maintaining the supply of water to Mthatha while upgrading the Thornhill Clear Water Pumpstation and associated electrical power and control equipment presented many construction challenges, including: Figure 2 1 200 mm steel raw water boosted gravity main – avoiding high points Civil Engineering  June 2022 15 Figure 3 One of three 1 200 mm steel pipe bridges over the Mthatha River