THE State Planning Commission has given the go-ahead for the construction of a second Nanjing Yangtze River bridge at Baguazhou, eight kilometres downstream from the existing crossing. According to the Nanjing Municipal Government, feasibility studies have already begun on two possible designs: a cable-stayed bridge with a 606-metre span or a suspension bridge with a 1,160-metre span. Either way, it will be one of the biggest bridges of its type in the world and certainly one of the biggest in China, according to Wu Huan Ling, an engineer and vice director with the Office Preparing to Construct the Second Nanjing Yangtze River. Work is not expected to begin on the 4.4 kilometre bridge and approaches until the second half of 1995, with the completion date set for 1999. Based on today's prices, the bridge will cost between two billion and 2.7 billion yuan (between HK$3 billion and $4.05 billion). The existing bridge, built for a maximum capacity of 25,000 vehicles a day, already handles 27,000 vehicles. According to government figures, this is expected to increase to 60,000 by the year 2000 and to reach 288,000 by the year 2020. Incorporating six lanes, the new bridge will also be capable of withstanding earthquakes of up to seven on the Richter Scale. When the first Nanjing Yangtze River bridge was built in 1968 it was described as one of the greatest engineering feats in China. Seven kilometres long, including approaches, it is a double-deck bridge catering for rail and motor vehicles and cost 280 million yuan. When finished, the new bridge will link up with four national highways as well as the Nanjing-Shanghai expressway and the proposed Nanjing ring road. According to the Nanjing Municipal Government, the bridge will be built entirely with foreign capital. The bridge will also be managed and operated by the foreign investor or investors for seven to 11 years after completion, with a rate of return calculated at between 14.9 and 11.5 per cent, depending on the time-frame. The local government says the foreign investor can choose any of three methods of converting yuan into foreign currencies. The proposals are that yuan can be converted into foreign exchange through: The state-regulated foreign exchange market. Free circulation of yuan in Hong Kong and Macau when they come under Chinese jurisdiction. China's admission to the General Agreement on Tariffs and Trade when yuan will ''probably'' become an internationally convertible currency. Mr Wu says the bridge is one of the key infrastructure projects planned for Nanjing.