By the start of this week, about 8500 tonnes of illegally dumped material had been dug out of two areas, either from beneath the carriageway or on the road edge.
The cleanup of vulnerable coastal dump sites is expected to cost the Waitaki District Council $12 million-$15m.
About 2.5km of Beach Rd has been closed since August 19 and will be until at least December while historic fly-tipping is cleaned up from the scenic coastal stretch.
The council has previously said it was "the aim" to reinstate the road by December, although the long-term future of the road remains an open question.
With coastal erosion rates advancing in the district, both of the Beach Rd sites and the former Hampden dump just north of Moeraki Boulders were previously identified as a ticking environmental time bomb.
Already the council has removed 43,000tonnes of material from the vulnerable beachside Hampden site as that environmental cleanup draws to a close.
Waitaki District Council solid waste manager Steve Clarke said this week about 8500tonnes of historic dump material had so far been carted from the Beach Rd site to the Palmerston landfill.
At this point they believed the quantity of material from the two identified Beach Rd sites would be about 12,000 tonnes.
"However, this does depend on what’s found as we excavate," Mr Clarke said.
To date, no nasty surprises like asbestos or historic coal tar material had been found at Beach Rd.
"Most of the waste has decomposed and is of an earthy clay texture.
"There are plastics, ceramics, scrap and the like of what would be typical of an uncontrolled dump site."
Mr Clarke said the council had done a fair amount of investigation to determine the extent of the fly-tipping issue at Beach Rd.
This had included drilling for core samples below the known dump areas.
"Detailed site investigations were completed prior to excavation," he said.
"However, there was some uncertainty about the consistency of depth across sites ... some areas had deeper pockets of waste than others."
Mr Clarke said the five-month timeframe for the road closure was fluid in line with the unknown amount of material and the subsequent work to rebuild the road.
The width and breadth of the historic fly tipping excavation would "inform the remediation requirements for the road".
"This will become clearer as the excavation progresses."
Meanwhile, the Hampden clean up was "nearing the end".
"There’s still some waste to be extracted from under the rock revetment at the toe of the site, and the removal of those rocks for redeployment elsewhere on the coast.
"We also need to shape the site as we complete works there."
Under the project, the Palmerston landfill, which is due to close by 2027, was given a life extension with a $5.5m new purpose-built cell to take the material from both sites.
