From 4th November 1999 the barrage has impounded Cardiff Bay by sealing it off from the sea to create a 500 acre (200 hectare) lake which is no longer influenced by the tide.

The impounded lake produces an eight mile (12.8 Km) waterfront, creating the environment for one of
Europe’s most exciting and ambitious developments. The National Assembly for Wales asked Cardiff
County Council to manage the Barrage and the Bay from April 2000. The Cardiff Harbour Authority was
therefore established by the Council to carry this out.

The barrage  embankment consists of an 800 metre long embankment constructed from sand and rock
and a 300 metre concrete section containing the locks, sluices, fish pass and control building.
The inland face is being landscaped to provide a linear park and the seaward side
is protected with rock stone armour.

Five large sluice gates release the flow of the Taff and Ely rivers out of the Bay.

Cardiff’s vital maritime economy is safeguarded too. The effect of the barrage was tested in a ship
simulator and structural piers have been provided to assist ships entering Cardiff Docks.

The barrage has three locks, one 40 metres long and 10.5 metres wide, and two 40 metres long and
8.0 metres wide. 

The project incorporates a specifically designed fish pass to encourage marine life in the bay and allow
salmon and sea trout to return to the rivers to breed. Salmon counts already are the highest they have
been for seven years.

Above all, the Cardiff Bay barrage project is designed to enhance and improve both the environment and quality of life of the community. It creates an important marina and leisure facility while helping to
attract new investment to the area. The Harbour Authority will facilitate the yacht clubs and their use of
the water and will also encourage and promote water-based local, National and International events.

Some work remains to be completed on the Barrage and once this is achieved this Autumn,
wider public access onto the structure will be permitted. 

Gwent Wetlands Reserve is a new habitat for wading birds and wildfowl, to compensate for the loss of
feeding grounds in Cardiff Bay. The £10.5 million scheme consists of wet reedbeds, wet grasslands
and shallow saline lagoons along the estuary at Uskmouth, Saltmarsh and Goldcliff. It has been
developed in conjunction with the Royal Society for the Protection of Birds (RSPB), the Wetlands and
Wildfowl Trust (WWT) and the Countryside Council for Wales (CCW), who have now resumed
responsibility for the area.

Birds affected by this change of environment at the bay include the Redshank and the Dunlin. However,
the new site aims to attract the Shoveler, Dunlin, Lapwing, Warblers, Wigeon and ultimately Bittern –
of which there are understood to be only 10 breeding pairs in the UK at the moment.

A major part of the project has been to divert short-fall sewage outlets – which previously discharged
into the Bay. Welsh Water (Hyder) is spending £180million on a 25 hectare (62 acre) sewerage
treatment plant on the Eastern edge of the City which will include a visitor and education centre and an
observation tower which will offer views across the Severn Estuary.
 

VITAL STATISTICS

Consulting Engineers - Sir Alexander Gibb & Partners (detail design)
Wallace Evans Ltd (feasibility work)

Construction Project Managers - Bechtel Ltd

Architects - Alsop & Stormer

Landscape Architects - Gillespies

Quantity Surveyors - Bradford Bowen & Partners

Property Surveyors & Valuers - Debenham Tewson 

Artistic Advisor - Gareth Jones

Cost - Projected £220million

Overall length - 1.1 Kilometres 

Basic construction - Rock armoured sandfill 

Barrage embankment - 800 metres

Width at 4.5 above AOD - 75 metres 

Width at crest - 25 metres Height 9.7 metres Comparative inner bay water level, 1.5 metres below
Spring tide Area of impounded water 500 acres (200 hectares)

Water depth - up to 11 metres 

Fish pass - 8 metres wide with a reinforced concrete pool and weir with a capacity of up to 10 cubic
square metres

Sluice gate dimensions - 5 gates each of which are 7.5 metres high and 9 metres wide

Sluice gate capacity - 2300 cubic metres / 0.5 million gallons per second 

Lock dimensions - ONE 40 metres long and 10.5 metres wide, TW0 40 metres long and 8 metres
wide