Cardiff in making iron and later steel, brought to the sea by packhorse from Merthyr Tydfil. This was first achieved by the construction of a long canal from Merthyr (510 feet above sea-level) to the Taff Estuary at Cardiff. Eventually the Taff Vale Railway replaced the canal barges and massive marshalling yards sprang up as new docks were developed in Cardiff – all prompted by the soaring worldwide demand for coal from the South Wales valleys. At its peak, Cardiff's port area, known as Tiger Bay, became the busiest port in the world and – for some time – the world's
Cardiff Bay Barrage 1987, prior to approval of the construction of the barrage, the Cardiff Bay Development Corporation was established to proceed with redeveloping the docklands, a sixth of the entire area of the city of Cardiff. In November 1999, the barrage was completed, with the sluice gates closed at high water, to retain the seawater from the Bristol Channel within the 500 acre (200 hectare) bay. At first major water quality problems ensued which required the bay to be drained dry overnight and refilled each day. Eventually, oxygenation systems (based on those used at the Swansea Barrage) were installed which improved water