brown trout, many of which were killed in 2006 when three tonnes of aluminium sulphate spilled into the river from the Pontsticill Water Treatment Works, which United Utilities operate on behalf of Dwr Cymru Welsh Water. The pollution turned the water white for at least downstream of the works and killed approximately 23,000 fish, including wild brown trout, bullheads, stickleback and pike, and a large number of invertebrates. Environment Agency Wales estimated that the river would take six to twelve years to recover. The trout population had resumed breeding by 2009. Below the confluence Just below the confluence of the Taf Fawr and Taf Fechan, the river is crossed by the Pont-y-Cafnau tramroad bridge. This was probably the first iron railway bridge to be built, and was unusual in that it had three levels. The main deck carried the -gauge Gurnos Tramway, beneath which there was an iron trough to carry water from the Taf Fechan leat, while a second water supply was carried in a wooden launder above the tramway tracks. The cast iron structure was manufactured at the Cyfarthfa Ironworks. On the west bank of the river are the remains of the ironworks, which began operating in 1765. The artifacts include seven blast furnaces, which formed part of the largest ironworks in the world in its heyday. The river runs through the western edges of Merthyr Tydfil, where it is crossed by modern bridges carrying the A4054 and A4102 roads, and by Jackson's Bridge, an early 19th century single span structure that carried the Dowlais tramway and a road. Two modern bridges in central Merthyr Tydfil carry the northbound carriageway of the A4054 across the river to its west bank and back again, with a weir between them. Nant Rhyd-y-car joins on the west bank at Cae-draw, just before the A4102 crosses. As it approaches Abercanaid Industrial Estate, the railway from Merthyr Tydfil railway station joins the east bank of the river and runs parallel to it for much of its length. It curves around the eastern edge of Abercanaid, below which it is crossed by the A4060 road bridge. At Troed-y-rhiw the B4285 Bridge Street crosses, and the Afon Tâf High School if located on the east bank. A little further south, Ynysowen Community Primary School is on the west bank and the river curves around the eastern edge of Aberfan, part of the Merthyr Vale community.