Oakhampton Road reconstruction planned to fast track opening

The road closed almost one year ago, in March, after a severe storm resulted in the failure of a flood drainage pipe that forms part of the Hunter Valley Flood Mitigation scheme.

The incident also damaged the underlying road formation.

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The Department of Planning Industry and Environment (DPIE) who are responsible for the flood infrastructure, completed repairs to the pipe in December.

It has accepted council's offer to undertake the road reconstruction component of works, with the aim to reduce the time to repair the road and accelerate its reopening for the community.

The aim is to have the road reopened by mid April.

The cost of these works will be covered in full by the DPIE.

Tonight councillors will vote on whether or not to accept DPIE funds for the reconstruction of Oakhampton Road.

In a report, council officers said that during the March 2021 storm event, the area north of Scobies Lane filled with water from the local drainage catchment area.

"This occurs as part of the normal operations of the Hunter Valley Flood Mitigation Scheme where the flood flaps on the banks of the Hunter River close to prevent the ingress of water from the river," the report said.

"As the water receded in the Hunter River the flood gates were opened to allow the area to drain into the river.

"Due to a defect in the 1800mm diameter drainage pipe located 9.0 metres below the surface of the road, the material around the pipe was destabilised resulting in the formation of a sink hole."

DPIE engineers (who are responsible for the pipe and flood mitigation infrastructure) inspected the site and advised council of the pipe failure and the instability of the material surrounding the pipe and the potential safety impact to road users.

Based on this advice, a decision to close the road until investigations could determine the appropriate course of action was enacted.

Discussions with DPIE and council staff have been ongoing during the investigation and repair process, leading to DPIE advising council in December of the completion of repairs to the 1800mm diameter drainage pipe and that the rectification required the pipe to be relined for its full length.

DPIE's Geotechnical Engineer outlined concerns around the instability of the formation material in the vicinity of the road and recommended the reconstruction of Oakhampton Road in vicinity of the drainage pipe.

The proposed reconstruction involves relaying of an existing watermain within the road pavement and reconstruction of the road pavement utilising a geogrid material to strengthen the road and provide support against any future subsidence.

These works would be normally undertaken by DPIE utilising contractors for both design and construction as the damage was associated with works linked to the Hunter Valley Flood Mitigation Scheme.

However, the repair time outlined by DPIE to complete the road reconstruction portion of the rectification was significant.

To accelerate the reopening of the road for community use, council offered to execute the road reconstruction works.

"Council has the inhouse expertise and ability to undertake the works immediately reducing the time frame that the road is closed," the report said.

"That offer was accepted by DPIE. Based on council now being able to expedite the proposed works it is anticipated that reconstruction will be completed by Easter."

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