The land – on the block surrounded by Tuam, Madras, Lichfield and Barbadoes streets – is being bought from Turners and Growers. The deal will be settled on 1 July.

Christchurch City Mayor Garry Moore says getting to the point where work starts is likely to take at least a year. In the meantime the vendor, Turners and Growers, will lease the site for at least 15 months.

“This is a fantastic opportunity for the city to create a modern public space that can give us new housing and park in an area of the city which is crying out for it,” Mr Moore says.

In investigations of the site leading to the purchase, a small area was found to contain a thin layer of material believed to be coke deposits from boilers used in an old city fire station. Coke is one of many materials that test positive as being a PAH (polycyclic aromatic hydrocarbon). PAHs are formed from the incomplete burning of material such as coal, oil and gas, rubbish and other organic substances and, if exposed, in some cases can be a health risk.

The coke layer showed up in two of 21 bore samples on the site. Council staff say the layer is safely sandwiched between silt and gravel and does not pose any immediate problems. Staff are looking at how best to deal with it as the development proceeds.

The Central City Strategy aims to enhance and promote the Central City – the area within the four avenues – and ensure the heart of Christchurch remains lively and a good place to do business. Its goals are to make the Central City a great place to live, work, play, shop, socialize, invest, visit and learn.

Among its core principles is a desire to concentrate effort on the east side of Colombo Street, to promote developments that bring together ratepayer and private investment, and to look for development opportunities that combine housing and commerce. The strategy identified that the east side needed improved public spaces.