Both directions of Tharwa Drive between the Drakeford Drive roundabout and Mentone View closed at 5am on Monday and the major arterial road isn't expected to reopen until Australia Day while a sewer main pipe for the new South Tuggeranong Fire and Rescue Station is installed.

Drivers criticised the decision to begin the road closures on the day many Canberrans were returning to work after the holiday break and questioned why the work couldn't be undertaken at night with some lanes kept open to ease the congestion.

But Territory and Municipal Services minister Shane Rattenbury defended the move saying it came after consultation with the Tuggeranong Community Council when plans to bore under the road to minimise disruptions had to be abandoned because of poor quality road base.

"They couldn't bore through the area so instead they had to cut a large trench through the area," Mr Rattenbury told the ABC.

"There were two possible ways to do this, one was to do it in stages and close the road at different points that would have taken seven weeks.

"The other option was to do it in one fell swoop, just dig the big trench and get it over and done with which should take 10 or 11 days."

One commuter, James Ludzioweit said it took him 45 minutes to drive from Gordon to Civic on Tuesday morning instead of the usual 25, and on Monday night he was stuck in traffic for an hour.

Others reported delays of more than an hour from Conder on Tuesday morning.

"It's completely ridiculous they had plenty of time over the Christmas break when most people were off work or away to get the work done," Mr Ludzioweit said.

"Given it's not a high density residential area why couldn't they have done it in the evening and commence work at 6pm.

"It just seems really short-sighted to block all but one road in and out of two suburbs Gordon and Banks... anywhere south of Calwell [is affected]."

Mr Rattenbury said contractors were working 18 hours a day to cut the two and half metre wide, three metre deep trench for the major sewer line "as quickly as possible" over a "relatively quiet period" of summer.

"We are aware it's caused massive traffic delays… I'm getting plenty of feedback," he said.

"What it means is the work is done and fully completed before most of Canberra comes back from summer holidays, before school gets underway again… the shorter period was probably better than seven weeks of inconvenience."

Mr Rattenbury said workers were looking at options to improve the congestion including the possible use of the road's shoulder as a slip lane.

"It is going to be a bit tough for coming days, I really urge people to be a bit patient, accept our apologies and try to travel at different times if possible," he said.

"It is necessary work it's going to be a significant new fire and rescue station for the southern part of Canberra."

Mr Ludzioweit said he had complained to Chief Minister Andrew Barr's office and was concerned about the impact of forcing all traffic out along Knoke Avenue and Woodcock Drive if there was an emergency in the area.

"What happens if there was a bushfire? No one can get out then," he said.

"People in four-wheel-drive vehicles are taking to the grass… that raises the next question, what happens if someone speeding along the grass hits a cyclist, pedestrian, child?"

Mr Rattenbury was reluctant to make a promise on the road's exact reopening date as it was weather dependent, but he said the end of next week was the target.

He said he was not involved in the fire station's planning, but believed its location on the busy roundabout had been chosen so crews could respond quickly to the suburbs.