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Cardiff Bay

Locks, sluices and the fish pass are all operated from an electronics packed control building, an award winning steel-clad structure designed by architect Alsop & Stormer. Closed circuit TV systems enable the operations staff to see key areas. This includes views into the three deep locks and across the sluices and fish pass, which can all be operated remotely, as can the bascule bridges for the road across the lock entrances. Direct visual contact is also possible with the nearest lock.

The sluice gates can be operated in either 'manual' or 'automatic' mode. The bay water level will be regulated by the five sluice gates working in 'overshot' in a predetermined sequence to discharge river flows to the estuary.

Eventually the system will give the barrage completely automated control although there were some difficulties getting it running. Gates were found to be 'hunting' in the first few days after the impoundment of the barrage.

Explains Paul Neal: 'There are level detectors for the water on the tidal side and the barrage lake side and these take readings at short intervals'. If there is a rise in level of more than 10mm from the norm a step sequence opening of the gates is made and water flow increases. Another step is made at 20mm, and so on following through a programmed sequence. But the gates are specified to take two and a half minutes to move the step fully, by which time the level signal from the detectors had changed, sending a new instruction.The gates were oscillating as a result.

'It's a matter of tuning the software,' adds Eric Westwood of Bechtel, 'rather than a big problem'. Readings for the detectors are averaged over a ten minute period to eliminate the effects of wave variation and the way this is done will be altered.

Water height detectors, electronically monitored floats like those used in the petrochemical industry, also suffered silt intrusion on the seaward side. This clogged the delicate float mechanism in the measuring tubes. They are being changed for radar detectors.

The barrage sluice gates have back up systems. There are duplicated 11kv electrical supplies from the National Grid. However, in the event of Grid failure a generator will automatically take over supplying power to essential services. Three portable electrically driven power packs can also be deployed to operate each gate.

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