Dams & Hydro

The Berg Water Project augments the water supply of the Western Cape region and specifically that of the City of Cape Town.

The concrete faced rockfill dam (CFRD) is 900m long and 70 m high with an embankment volume of 4 million m³ and a gross storage capacity of 130 million m³.  Due to the variable nature of the foundation, some differential movements are expected across the foundation and the plinth of the CFRD includes articulated slabs with special water-stop features.

The outlet works comprise a dual wet and dry well multi-level intake tower 58 m high with a 5.5 m dia concrete outlet conduit.  One of the features of the outlet works will be their ability to mimic the periodic natural floods that are necessary to mitigate the impact on the ecology and geomorphology in and around the river.  It is possible to cater for a flood up to 200 m³/s, which will be released through the outlet works over a similar period to the natural occurring floods.  The releases will take place through multi-level selector gates, an isolating gate (hydraulically operated bonneted slide gate) and a flow control gate (hydraulically operated radial gate).

The spillway comprises a 40 m long side channel with splitters and an aeration gallery, a discharge chute and deflector bucket and an 18 m deep unlined plunge pool.  The maximum discharge capacity is 740 m³/s.  The plunge pool will also be used as energy dissipater for the flood releases from the outlet works.  Model studies were undertaken of both the spillway and the outlet works.

The Supplement Scheme comprises an abstraction works on the Berg River 9 km downstream of the dam, two pump stations with capacities of 6 and 4m³/s respectively and two steel pipelines of 1 500 mm diameter with a total length of 12.4 km.  The abstraction works include a sand trap that can be hydraulically flushed to remove deposited sand and gravel.

Project details