Wolwedans Dam

34°0′49″S 22°13′0″E / 34.01361°S 22.21667°E / -34.01361; 22.21667PurposeWater supplyOpening date1990Owner(s)Department of Water AffairsDam and spillwaysType of damArch-gravityImpoundsGreat Brak RiverHeight70 metres (230 ft)Length268 metres (879 ft)ReservoirCreatesWolwedans Dam ReservoirTotal capacity25,530,000 cubic metres (902,000,000 cu ft)Catchment area123 km²Surface area117 hectares (290 acres)

Wolwedans Dam is a concrete dam in South Africa located on the Great Brak River near Mossel Bay, Western Cape, South Africa. The dam is the main source of water for the municipality of Mossel Bay^[1] as well as the gas-to-liquids refinery PetroSA. The dam serves mainly for municipal and industrial water supply purposes.

Design

Completed in early 1990, it was the first in the world single center arch-gravity dam made of roller-compacted concrete fully relying on three-dimensional arch action for stability. The 70-m high dam has a vertical upstream face and a stepped downstream face at a slope of 0.5:1 (H:V). It has a constant extrados radius of 135 m and a crest length of 268 m. The non-overflow crest is 5 m wide. The dam was built of 0.25 m thick roller-compacted concrete layers with induced joints at 10 m spacing and de-bounding every 4th layer. The RCC of approximately 200,000 m³ (260,000 cu yd) was placed in October and November 1988 and between May and November 1989. The induced joints were grouted in winter, between July and November 1993. The reservoir was filled to capacity in 1992.

Composition of the high-paste RCC

Portland Cement	Fly Ash	Water	Coarse Aggregate	Fine Aggregate
kg/m3	kg/m3	kg/m3	kg/m3	kg/m3
58	136	100	1510	625

The RCC mix properties were:

• RCC density: 2,400 kg/m³
• Average 1-year RCC compressive strength: 35 MPa (5,076 psi)

See also

• List of reservoirs and dams in South Africa
• List of rivers of South Africa

Notes

References

• Roller-Compacted Concrete Dams, ICOLD, Bulletin 126
• List of South African Dams from the Department of Water Affairs