The state electricity agency TransGrid has admitted herbicide was sprayed across a swathe of wilderness in the Kosciuszko National Park, scarring the landscape and killing thousands of alpine plants.
Patches along a 17-kilometre stretch of powerlines, amounting to about 20 hectares, were affected by the herbicide, and the NSW Office of Environment and Heritage is investigating the electricity agency.
Contractors were undertaking ''routine vegetation management'' on behalf of TransGrid along the route of the transmission line in rugged country between Khancoban and the Guthega ski-fields last year, when an ad hoc decision was made to spray the area without approval.
In December, National Parks and Wildlife Service staff spotted what one described as a ''moonscape'' of dead vegetation in some areas. TransGrid had not reported the herbicide use to government agencies.
It is not the first time TransGrid has been caught destroying vegetation in the area's protected wilderness. In 2001, it was found to have mown down trees along cable routes in the Brindabella, Namadgi and Kosciuszko national parks, and was eventually fined $130,000.
This week the electricity agency said it had approval to clear some vegetation from around the powerlines but conceded herbicide should not have been used.
''TransGrid acknowledges … its contractor undertook vegetation management using a method which was not approved under the specifications of the [environmental impact assessment],'' a spokeswoman said.
''TransGrid has investigated the incident and is working closely with the NSW National Parks and Wildlife Service and the NSW Office of Environment and Heritage to implement a specific and targeted rehabilitation plan.''
The agency said about 2 per cent of the area, which forms a corridor about 17 kilometres long and 60 metres wide, was affected.