Dunedin City Council acting infrastructure services general manager Tom Dyer said council staff were back at the site early yesterday morning to devise a plan, after the boulder broke off a larger rock formation on Tuesday.
A consultant engineer, a geotechnical expert and contractors also attended to advise the best course of action.
Advice suggested that work to make the boulder safe would include bolting it to the larger rock formation to anchor it, and then building an earth bund below the boulder to secure it.
The boulder was 5m wide by 3.5m and its exact weight was unknown but could be 100 tonne, Mr Dyer said.
A traffic diversion would remain in place, as shipping containers would continue to be placed on the road as a precaution, to protect houses below the site, although the risk to properties was still considered low, he said.
Council staff had visited properties directly below the affected site to offer homeowners information and reassurance, and more information would be distributed today.
Independent advice indicated there was "no reason for residents to be alarmed", but the council was still "taking every step to ensure motorists and homeowners remain safe".
Rhonda Robinson, who lives near the northern end of the closed road, appreciated the safety issues, but said the closure was "very inconvenient".
To reach Port Chalmers, she and some others in the area had to undertake a detour of more than 10km.
