On December 10, 2005, it was finished. It stretches 32.5 kilometers (20.2 miles) from mainland Shanghai's Pudong New Area to the offshore Yangshan Deep-Water Port in Zhejiang's Shengsi County. The majority of the bridge consists of a low-level viaduct. There are nine large bridges and several small ones along its route. The world's longest continuous truss bridge, it has 12 spans each weighing about 45 million pounds (20 million kg). The total length of the main part of the bridge is 3.6 miles (5.8 km). It provides an alternative route for vehicles traveling between Shanghai and Hangzhou, the capital of Zhejiang Province. The old southern section of the Jinggang Road, which runs through downtown Guangzhou, is also a continuous truss bridge but only two miles (3 km) long. It is expected that the life expectancy of this bridge will be more than 50 years. The first phase of the project was completed in 1998 and the second phase in 2005. It took ten years to build the bridge and its construction involved more than 100,000 m² (1,120,000 ft²) of concrete. The main challenge in building this bridge was its location near the coast. Waves can be very powerful and can damage even a strong bridge. So the designers built the road underneath the sea level so that the bridge would not be exposed to floods.