Harry’s Creek Road sinkhole repairs complete

The sinkhole on Harry’s Creek Road, located five kilometres from the Hume Highway at Euroa, has caused considerable angst for both the Strathbogie Shire and the road’s users due to the road being one lane only for many months.

Specialist Geotech engineers were involved with the initial investigation of the sinkholes and reported back to the Strathbogie Council on their findings.

Now the road has been reconstructed and the sinkholes repaired Director of Sustainable Infrastructure John Harvey has provided an explanation regarding the recent repair work following the 2022 October floods.

“Sinkholes are created by several issues but generally they are caused by the type of soil conditions present, and the impact water has on those conditions,” Mr Harvey said.

“At the Harry’s Creek Road site, the problems stemmed from poorly compacted soils, a legacy issue from the road’s original construction, combined with very dispersive natural soils.

“These dispersive soils, where clay particles separate from one another, were exacerbated by continual water-flow from the gully, which eroded the area and caused the sinkholes.

“If sufficient water flows, particularly with some velocity, these voids (holes) grow larger over time, remaining undetected until the soil can no longer support the bridge over the void, leading to ground collapse.

“The holes found at Harry’s Creek Road during the repairs ranged in depth from 2.5 to 3.0 meters and were about 1 to 2 meters in diameter,” Mr Harvey said.

“To repair them, the surrounding uncompacted dispersive natural materials were removed and replaced with less dispersive materials. This generally involved using mudstone pavement material, which was placed and compacted in 200mm layers.”

Once the base layer was set, crushed rock pavement materials were added and shaped to match the appropriate design for the road section, considering the curve. Further work was also undertaken to divert the gushing water from the table drains beside the road, directing it downstream.

Administrator Peter Stephenson said he was sorry for the inconvenience the works presented but he was pleased to say that the repair has brought about a very positive outcome for residents of Harry’s Creek Road and other road users.

“The investigation and repairs are critical to keeping our roads operational and these sinkholes erode over time, especially in the hilly areas of our Shire,” he said.

Council utilised its own construction team to complete most of the work, only hiring a 20-tonne excavator and a couple of 15-tonne rollers.

The repair work took four weeks to complete, followed by sealing works and line marking.