If you were building a road up the escarpment today, you wouldn't build something like Bulli Pass.
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Transport for NSW's Richard Heffernan is the senior project manager for the slope stabilisation work on Bulli Pass and elsewhere in the Illawarra.
That repair work is being done on a road that wouldn't pass muster under today's standards.
"The difficulty we have with all these mountain passes - I think Bulli Pass is from the 1860s or something - they didn't have the investigation and geotech and design standards we have today," Mr Heffernan said.
"So we're repairing what would have started out as a track for a horse and cart. With design standards today you wouldn't be able to build a road that steep or that narrow. It just doesn't meet any of our modern-day design standards."
During the slope stabilisation work on Thursday night an issue with the road surface occurred at the worst of the four landslip sites - where the edge of the road has nothing underneath providing support.
"We've got contractors up there dressing three of the sites and at one of the sites with the heavy equipment we've got there we've noticed more movement than we're happy with there," he said.
"That's made the road surface uneven so we've put a speed limit on it and a load limit in it.
"We're just organising some temporary repair works so that we can remove that load limit and speed limits quickly as we can."
Cold mix asphalt has been placed on the section of road while plans are made to properly resurface the road.
Mr Heffernan said it should be a "matter of days not weeks" before the road is repaired, in part because those repairs needed to be completed before the heavy vehicles carrying out the slope stabilisation can be used on that section.
The slope stabilisation work has exacerbated the problem with the road surface; there is a 35-tonne machine drilling holes in the mountainside that has to park on the road at that location.
"There was a failure there; we could see it had affected the road surface," he said.
"But with the heavy equipment there sitting in one spot it's just made it worse. It's not unexpected and that's why we monitor it closely."
The speed limit between the top of the pass and the hairpin bend has been dropped to 40km/h for southbound vehicles.
Also, vehicles heavier than 4.5 tonnes are banned from travelling south on the pass until the section has been repaired.
The stabilisation work on the pass includes inserting soil nails into the mountain side and spraying sections with shotcrete - the same process that was used to address problems with the slope at Stanwell Park.
"The works we did up there were at nine separate locations and in that large rainfall event in March 2022 we didn't have any issue with those slopes on Bald Hill," Mr Heffernan said.
"So it gives us confidence that the stabilisation methods we're using work. Hopefully we can get these ones on Bulli Pass fixed from that event and Bulli Pass should be much, much more reliable in the future for further events."