ActewAGL proposes a 15km-long route through old trees with habitat hollows to establish a second bulk power source, critical for energy-hungry enterprises such as data centres.

The Commonwealth's Department of Environment, Heritage and Arts says the work will have a significant impact on threatened species.

The department wants more details on the project and a plan to rehabilitate 38ha of similar woodland south of Canberra to offset the loss of habitat.

On a separate development front, the ACT Conservation Council says a Government report on a new 73.4ha industrial suburb Hume West understates the national significance of white box, yellow box and Blakely's red gum grassy woodland.

The council's executive director, John Hibberd, said he understood the need for a broader economic base and was not opposed to a new industrial estate. Nevertheless, an environmental impact statement was needed because more than half a hectare of native vegetation, the amount specified in legislation, was to be cleared.

Mr Hibberd said Hume West included 12ha of white box, yellow box and red gum grassy woodland which was part of a highly fragmented community.

Environmental consultant David Hogg, whose firm prepared the report on Hume West for the Land Development Agency, said its ecological value was subjective.

He said the assessment was prepared under Environment Protection and Biodiversity Conservation Act guidelines and expressed no opinion on whether the land should developed.

''We stand by the assessment that it is a woodland community but in poor condition,'' Mr Hogg said.

Heavily dependent on land sales revenue and the Commonwealth for jobs, the Stanhope Government is under pressure to broaden Canberra's economic base.

The ACT Government proposes accelerating industrial land because:

Fyshwick and Mitchell are accommodating more offices and retailers, forcing out industries.

Projects like the gas-fired power station and data centre, which was approved last week, will take up more land in Hume.

Fuel prices are driving demand for centralised warehousing in industrial suburbs.

The ACT's industrial land needs to be price competitive in a national market context.

ActewAGL's new 132kV transmission line from Williamsdale to Theodore will cross nine rural leases and the Rob Roy Nature Reserve.

One hundred 25m-high suspension poles and 15 sets of twin poles are proposed, requiring a 45m-wide easement.

Environmental consultancy Geoff Butler and Associates lists four threatened bird species, the brown treecreeper, hooded robin, white winged triller and varied sittella in nearby woodlands.

Planning Minister Andrew Barr has waived the need for an environmental impact statement for the $18.7million subtransmission project.