the decline by creating the Upper Clyde Shipbuilders consortium, but the consortium became mired in controversy and collapsed in 1971. After that, James Callaghan's Labour government implemented the Aircraft and Shipbuilding Industries Act, which nationalised most of the Clyde's shipyards and grouped them with other major British shipyards, such as the firm British Shipbuilders. Today, two major shipyards on the Upper Clyde remain in operation. They are both owned by a naval defence contractor, BAE Systems Surface Ships, which specialises in the design and construction of technologically advanced warships for the Royal Navy and other navies around the world. The two yards are the former Yarrow yard at Scotstoun, and Fairfields at Govan. In addition, the King George V Dock is operated by the Clyde Port Authority. Ferguson Shipbuilders, at Port Glasgow on the Lower Clyde, is now owned by the Scottish government. It is the last survivor of the many shipyards that once dominated Port Glasgow and Greenock. Its core business is now the construction of car ferries. Regeneration , the Clyde Waterfront Regeneration project was expected to attract investment of up to £5.6bn in the area from Glasgow Green to Dumbarton. Market gardens and garden centres have sprung up on the fertile plains of the Clyde Valley. Tourism has also brought many people back to the riverside, especially in Glasgow, where former docklands have given way to housing and amenities on the banks in the city. Examples include the Glasgow Harbour project, the Glasgow Science Centre, and the Scottish Exhibition and Conference Centre. The commercial Port of Glasgow has been moved downriver to take advantage of the deeper waters of the Firth of Clyde. And the river, which used to be plagued by pollution and sewage, has been extensively cleaned up to make it suitable for recreational use. The Clyde Walkway, completed in 2005, is a foot- and mountain-bike path that follows the course of the Clyde between Glasgow and New Lanark. Scottish Natural Heritage has designated it one of Scotland's Great Trails. Pollution The British Geological Survey has identified and evaluated organic chemical pollutants in the sediment of the Clyde estuary. Surface sediments from the Glasgow reaches of the Clyde and Cuningar to Milton, were previously found to contain polyaromatic hydrocarbons (PAH) from 630 µg/kg to 23,711 µg/kg and polychlorinated biphenyl (PCB) in the range of 5 to 130.5 µg/kg, which puts these sediments in the range