Environment Minister Mick Gentleman confirmed the ACT was pursuing the claim after being unable to secure disaster recovery funding from the Commonwealth to help restore the park.

Mr Gentleman said the territory had already provided "substantial' funding for Namadgi and Tidbinbilla restoration works, which were currently under way.

"The ACT is ineligible for funding to restore our national parks under federal disaster recovery arrangements so we are exploring other avenues," Mr Gentleman said.

The ACT government's submission to the Royal Commission into National Natural Disaster Arrangements said the territory had received $10 million in insurance-related payments from the Commonwealth after the fires.

However Mr Gentleman said this figure was wrongly included.

"While a federal payment in the ACT Justice and Community Safety Directorate to the Royal Commission submission was included in error, it does reflect that ACT government officials have made an initial approach to the Australian government for compensation," he said.

The Orroral Valley fire, which burnt out 80 per cent of Namadgi, was sparked by a landing light from a MRH-90 Taipan helicopter.

The Defence helicopter had carried a team of six into a remote part of the park to clear landing sites so craft would easily set down if lightning strikes sparked a blaze in difficult-to-reach terrain.

Instead, they ended up accidentally starting what ACT Chief Minister Andrew Barr called the "most serious" bushfire threat to Canberra since 2003.

Mr Barr told the royal commission that despite efforts to limit the loss of wildlife and sensitive sites in the park, the ecological and environmental damage was extensive.

"Protecting the National Park including the Cotter River catchment, ACT's primary water supply, from further damage and supporting its recovery will be a significant and expensive task that will need to be undertaker jointly with the Australian government," Mr Barr said.

It comes as a two-month program to restore the Lower Cotter catchment and replace rural fencing following the summer bushfires is completed.

The work - worth around $1 million - was fast-tracked as part of the ACT government's efforts to create jobs during the coronavirus pandemic.

"Local contractors and Canberrans who found themselves unemployed due to COVID-19 helped undertake critical catchment restoration works to better protect Canberra's water supply," Mr Gentleman said.

Around 19 kilometres of fencing was repaired or replaced, 14 kilometres of roads cleared, eight kilometres of fencing cleared of overhanging and fallen trees and eight flood gates repaired.

"This work was completed in two months by contractors operating in often remote and difficult terrain," Mr Gentleman said.

In the Lower Cotter catchment, around 300 coir logs and 20,000 sandbags were installed in three eroding gullies. Around 620 hectares of invasive weeds were sprayed and more than 2000 native seedlings planted.

"Sediment and debris in parks and reserves can make its way into our waterways impacting our water quality. It is critical that we continue to monitor and maintain catchment health to safeguard it for generations to come," Mr Gentleman said.