Contractors worked overnight on Wednesday to clear Acton Tunnel on Parkes Way, but the laborious clean-up operation means the tunnel remains closed to westbound peak hour traffic on Thursday morning.
The truck stuck in the tunnel has been freed from the ceiling but the difficulty lies in the removal of the damaged bonded asbestos tiles, which workers have had to pull down by reaching over their heads in the hot and currently unventilated tunnel.
The tiles weigh 85 kilograms when dry and were damaged more extensively than first thought.
Workers have now removed more than 120 panels and structural steel support and have made progress in repairing the sprinkler system, which was also badly damaged.
There are also ongoing concerns of asbestos fibres, and both the truck, excavator and tunnel need to be decontaminated.
On Wednesday, Roads Minister Mick Gentleman said he understood the truck did not have the required permit for its height, and that while only tunnels under 4.6 metres are required to be signposted, the government would review those requirements after the incident.
Earlier on Wednesday, an Emergency Services Agency spokeswoman said the truck was tangled in some of the overhead rigging in the tunnel" and its removal was a delicate operation.
The vehicle was successfully extricated by 2pm.
The discovery of bonded asbestos tiles in the ripped undercarriage of the bridge complicated the operation and initially forced emergency services to put a one-kilometre exclusion zone in place westbound.
While air monitoring confirmed there are no asbestos fibres in the area, WorkSafe ACT was still at the tunnel on Wednesday to supervise the removal of asbestos.
Misting spray was used to stop any fibres from escaping the tunnel and licensed asbestos removalists and assessors were on site, with the ESA saying there was no risk of asbestos exposure outside of the tunnel.
ACT WorkSafe commissioner Mark McCabe said asbestos removalists had worked through Tuesday night to clear the majority of the asbestos, and the material around the truck still needed to be cleared.
"It's quite complicated to remove because the material is caught up in the framework in the ceiling at the top so its not been a simple exercise to get it out," he said on Wednesday afternoon.
"The next step will be to lower the boom and the truck and that might bring some additional material down and with a bit of luck we'll be able to lower the boom properly and take the truck out and have it cleaned and take it away.
"There will still be a fair bit of residual work in the tunnel so the tunnel itself has to be cleaned."
WorkSafe says there are no safety concerns associated with using the eastbound lanes of the tunnel while the remediation work continues.
Once the excavator was freed from the ceiling, both it and the truck had to be decontaminated in a process that continued into Wednesday evening.
On Wednesday, opposition transport spokesman Alistair Coe said lanes in the eastbound tunnel should be used for westbound traffic, including in the afternoon peak.
The plan would require the removal of safety fencing from the median strip. An ACT government spokeswoman said Mr Coe's proposal would not be adopted.
"Roads ACT considered diverting westbound traffic through the eastbound tunnel of Parkes Way but did not adopt this approach as it would divert resources away from preparing the westbound tunnel lanes for re-opening as early and as safely possible and would also significantly impact on traffic in the morning peak," she said.
Roads ACT crews have begun to assess the damage to the tunnel's ceiling.
In the meantime, Parkes Way, one of Canberra's busiest thoroughfares remains closed, more than 24 hours after an excavator on the back of the low loader truck ripped 60 metres off the ceiling of the tunnel on Parkes Way, near the Australian National Botanic Gardens.
No indication has been given as to when the tunnel might be able to be reopened and an engineer will need to determine if there are any structural issues now the truck has been moved.
"The engineer will be able to get in and do a more definitive examination if there are any structural issues," Mr McCabe said.
"He's already done a lot of that but he's been impeded by the truck to see what damage has been done just above the truck so that's another potential hurdle. If the engineer comes back and says theres a structural issue we're not aware of then it could take longer."
Tuesday's incident left traffic on Parkes Way at a standstill and a large section closed in the westbound direction.
Existing road closures were likely to remain in place on Thursday and motorists are being urged to drive carefully on the eastbound section near the Acton tunnel.
Parkes Way eastbound was open but with a 90 kilometre per hour speed limit.
- with Natasha Boddy, Tom McIlroy, Alexandra Back