Teddy Bear Childcare owner Mark Gillett  bought land about 400 meters away from the contaminated sites but were never told of the pollution the sale of the land never went through.

Teddybears Childcare Centre owner Mark Gillett. Photo: Jay Cronan

The ACT government is selling land around the contaminated Koppers site without telling some potential buyers, including a childcare service, about the nearby pollution.

But authorities say the 34 blocks being released in the multimillion-dollar New West Industrial Park development were tested in 2008 and deemed clear of any contamination from the Koppers site.

The Land Development Agency is in the early stages of releasing 56 hectares of land at the southern end of Hume to try to to significantly grow the industrial hub.

Much of the land lies within 450 metres of the former timber treatment plant Koppers operated from the 1980s to 2005, while six blocks are directly adjacent to the site's north-eastern boundary.

The groundwater beneath the treatment plant was contaminated with up to 2430 times the safe limit of hexavalent chromium, a chemical that can be dangerous if humans or animals are exposed to it for prolonged periods.

The polluted groundwater is thought to be contained, but experts, including former environment protection chief Bob Dunn, have warned it is likely to spread over the long-term.

Tests released last week showed the hexavalent chromium had not moved from the Koppers site, and the Environment Protection Authority has pledged to work with the land's new owner, Canberra Hire, to ensure the pollution is ''actively managed'' into the future.

The pollution poses no risk unless it spreads off site into waterways, or if the groundwater is pumped up for use.

But at least one prospective buyer of land at the New West development is concerned that no warning was given about the nearby contamination.

The sale contract documents for the New West development make no specific mention about the contamination.

Potential buyers are, however, given a standard warning that the government makes ''no warranty or representation as to the environmental condition or state of the soil, groundwater, contamination or the existence or non-existence of any substance on or affecting the land''.

Canberra's Teddybears Childcare Centre was looking to buy a $1 million block of land at New West, roughly 450 metres downhill from the contamination at the former Koppers site.

The organisation was initially told it could build a childcare centre on the land and went through a significant portion of the sale process, including making a deposit and paying for design work.

The sale eventually fell through, but owner Mark Gillett said he was not warned about the contaminated groundwater at any stage.

''If they knew at that time, of course they should have told us,'' he said.

A local formwork company, who paid $1.8 million for a block just across the road from the Koppers site, declined to comment.

Land Development Agency chief executive David Dawes said the blocks for sale were subject to ''extensive studies'' by independent consultant Coffey and found to have no contamination associated with the timber treatment plant.

Those checks took place more than five years ago, in late 2008.

''As part of the due diligence process, contamination studies are undertaken by appropriately qualified professionals who advise the LDA of any potential contamination that may impact the development,'' Mr Dawes said.

But the agency would not comment on whether it warned buyers about the existence of the nearby contamination, saying it could not discuss ''contractual relationships''.

The sale of land for the New West development is in its first stage.

The development is expected to include 34 blocks ranging from 1682 to 32,550 square metres.

It is envisioned 26 large blocks will be sold to industrial businesses, such as freight companies, while eight smaller blocks will be used for services and retail.