Highfield subdivision may have TC3 land
Houses at the proposed Highfield subdivision in north Christchurch will cost the same and the development timetable will be unchanged, the developer says, despite the site needing more stringent geotechnical work than first thought.
The 2200-lot residential subdivision is planned for a 180-hectare site between Redwood, Belfast and Mairehau and Marshland. The site includes two shopping precincts, parks and roads.
To go ahead, the subdivision needs to win a rezoning from rural to residential through a plan change application to the Christchurch City Council that will be heard next week. The council's report to the two independent hearing commissioners is in favour of approval.
The developers' preliminary geotechnical assessment was done between August 2010 and September 2011 and complied with the regulations at the time.
Since then more stringent regulations have been put in place, but reviewing engineer URS New Zealand, enlisted by the council, said the information was adequate to evaluate the land's characteristics and the likelihood of liquefaction.
In her review, URS principal geotechnical engineer Karen Hartel said further ground investigations would be needed to determine the technical class (TC) of land within the subdivision if the plan change were approved.
Testing at the site had shown 11 locations within subdivision would be classified TC3, another 14 areas would be TC2 and one location TC1.
However, more testing under the new regulations might mean more sites would be considered TC3, she said.
A shallow-treatment non-liquefiable layer of between 3 and 5 metres across the site proposed by the developers would not be enough as a blanket strategy for the subdivision, she said.
Instead, most of the land would probably need deep treatments such as deep soil mixing, stone columns, low mobility grouting (a type of compaction) or deep foundations.
Highfield is owned by Maxim Projects and an investment company owned by Brian Thompson, who was involved with the Northwood development north of Christchurch.
Maxim managing director Roy Hamilton said nothing in the council's geotech report changed the overall picture of the project and the subdivision would continue with the same pricing for its house and land packages, as well as its development timeframe.
Homes would range from apartments to million-dollar houses.
Prices start at $275,000, with most homes between $300,000 and $400,000.
Hamilton, who has an engineering background, said it had been "understood from day one" that work would need to be done on the site before building and the developers were prepared for it.
The techniques were used routinely overseas and the equipment and expertise was now in New Zealand, he said.
Land improvement will be standard for most building sites in Christchurch, which will give building owners more peace of mind knowing it has been specifically engineered to prevent liquefaction and subsidence, he said.
"It's something that seems unusual; it seems that way because it hasn't been done much in New Zealand."
There was a lot of misunderstanding about the technical land categories, he said.
"TC2 and TC3 don't imply bad land, it just implies that if you shake it hard enough it can move a bit so we're just trying to compress the ground and make it tighter so there's not so much room for it to move as much."
If the plan change were approved, he hoped to start civil works by next summer and complete the first homes in the first half of 2014. Stage one would produce about 400 homes.
Two independent commissioners will hear the application to the Christchurch City Council, running all next week at the Chateau on the Park.
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