Songdo IDB – South Korea builds out and up

South Korea isn’t a small country, but most of its land area is mountainous and inhospitable. Despite that they still have to accommodate industrial growth and a rising population without putting too much pressure on agricultural land, so innovative solutions are needed. A private consortium has used one increasingly popular method – land reclamation – to create a new “smart city” development on the waterfront of Incheon. It’s called the Songdo International Business District and it’s likely to inspire many imitators over the next few decades.
The Songdo IBD is a truly international project in more ways than one. It’s not a South Korean government initiative; the private consortium that designed and built it is 70% US-owned, with 30% held by Korean steelmaker Posco. The city was designed to take advantage of the Incheon Free Economic Zone’s favourable tax rules without using scarce and expensive existing land. Reclamation was the most economical way to do this, but it presented some unique engineering challenges.
The location for the new land was on an area of tidal flats. These provided a stable foundation that was already above water at low tide, but 600 hectares (1,500 acres) had to be raised to a height safely above maximum high tide levels with a safety margin for storm surges and other events. This was done by dredging around 500 million tons of sand from the seabed offshore and dumping it on the project area, surrounded by erosion barriers. However the sand has an extremely high salt content and is highly corrosive, so water-permeable geotextiles were used to isolate structures from the salt while allowing rainwater to drain into the soil. Over time rain will leach the salt deeper into the soil, removing the risk.
Land reclamation and construction in the Songdo IBD spanned a ten-year period, completed earlier this year. As a planned city it was possible to design in sustainability and liveability enhancements right from the start, and the success of this is immediately obvious. Streets are much wider than in most Korean cities, reducing congestion and accident black spots. There’s a high density of cycle lanes and walkways. Public transportation is also plentiful. Direct buses run to the capital Seoul, 40 miles away, and there are also subway links. It’s easy to get to Incheon International Airport and the city has eight stations on the Incheon Metro system.
Construction in Songdo includes 80,000 apartments, 5,000,000 square metres of office space and 900,000 square metres of retail premises. Korea’s tallest building, the 305-metre Northeast Asia Trade Tower, stands at the centre of the business district. There are four universities in the city including foreign campuses of the State University of New York, George Mason University and the University of Utah. All major buildings meet Leadership in Energy and Environmental Design standards for environmental efficiency, only the second city in the world to achieve this.
While there has been plenty of construction the planners’ environmental aims are also obvious. Around 40% of the city’s area is reserved for green spaces, including a replica of New York’s Central Park. There are numerous charging points for electric vehicles and an advanced waste collection system that operates without rubbish trucks. Green roofs are a common feature and storm water is collected for use.
While Songdo IDB itself is now completed there will be many future developments nearby, as the corridor between the city and Seoul is developed; Songdo is likely to be a powerful magnet for overseas forms looking for a competitively priced location near the capital, and that will draw investment into the surrounding area. With land for development in short supply we can also expect similar projects to become more common in the future.
Songdo IDB Facts and Figures

  • Total budget around $35 billion
  • 600 hectares of new land, including 240 hectares of green spaces
  • 65,000 permanent residents
  • 500 million tons of fill used