Oonah Road - Updates

Oonah Road - Updates

Published on 21 July 2023

21 July 2023

Oonah Road West - OPEN

Civilscape have done remarkably well to have removed so much unsuitable material and place an extraordinary amount of rock in just 5 weeks, especially given the weather conditions.

Oonah Road West will be re opened to the public from 5pm this afternoon (Friday 21 July). Gravel Road and Road Work signage is still in place with maintenance work to continuing next week.

Oonah Road West will re-open at 5pm on Friday 21 July 2023

1600 tones of rock was brought to the site 

Thank you so much to the community for your patience as we rebuilt this road.

14 July 2023

Oonah Road West - Closed

Some small set backs. Oonah Road West will be closed for another week due to delays in laying the final road base. 

Civilscape are currently digging out the last ramp drain, and will be laying the final road base gravel over the current loose rock within the next few days. 

Oonah Road East - Road Remains Closed

Geotechnical investigations are showing that Oonah Road East is still an active landslip. Underground wells and movements are continuingly being monitored. For the publics safety, Oonah Road East will remain closed to all traffic until further notice. Final remediation designs for restoration are ongoing. 

Thank you to the community for your understanding as we continue to work hard for you on repairing these roads

07 July 2023

Oonah Road West - Closed

We're almost there!

Civilscape imported around 1000T of rock yesterday and will have around 600T more by the end of today (Friday 7 July).

Water is freely draining at the bottom of the rock fill per the drainage channels. All going well next week (weather permitting) road gravel will go on and prepped to hopefully open the road next weekend.

Oonah Road East - Road Remains Closed

Geotechnical investigations are ongoing.

25 May 2023

Oonah Road West - Closed

During reconstruction works, unsuitable material has been located at the subgrade level.

The road will be closed between Martin Place and Douglas Road for up to four weeks whilst the unsuitable material is removed and the road reconstructed. Council apologise for the delays. 

Unsuitable material located at the subgrade level 

Oonah Road East - Road Remains Closed

Geotechnical investigations are ongoing.

Thank you to the community for your understanding as we continue to work hard for you on repairing these roads

14 April 2023

Oonah Road West - Road Open to Single Lane Only

Civil scape contracting are currently placing and compacting sub-base material in preparation for top base material.

About 70% of the remediation works have been completed on Oonah Road.

compacting sub-base material

compacting sub-base material

Oonah Road East - Road Remains Closed

Thank you to the community for your understanding as we continue to work hard for you on repairing these roads

3 April 2023

Oonah Road West - Road Open to Single Lane Only

Consolidation work is near complete on the East Bound lane with drainage work commencing on the west bound lane.

Fun fact to date nearly 2,000tons of ballast material (blue metal) has been imported to site, considering this comes in at the rate of 36tons per truck load - that’s a lot of truck loads!

Consolidation work may be finished within two weeks (weather dependant) then work can start rebuilding the road to final level.

Laying the ballast material 

commencing drainage works on the west bound lane

Oonah Road East - Road Remains Closed

Thank you to the community for your understanding as we continue to work hard for you on repairing these roads

10 March 2023

Oonah Road West - Road Open to Single Lane Only

Repair work to Oonah Road West was affected by 45mm of rain through the week. 

Excavations are continuing in order to establish a firm base for rebuilding the road. Site workers have exposed a number of subterranean drains - as remediation work continues.

Thank you to the community for your understanding as we continue to work hard for you on repairing these roads

3 March 2023

Oonah Road West - Road Open to Single Lane Only

Contactors have removed and stockpiled the existing gravel layer and will mix it with road gravel to reinforce it's strength.

The lower culvert embankment excavation works have commenced, with water beening discovered entering from the uphill side and getting under the culvert. It appears to be old water trapped in the embankment. 

Test holes either side of culvert will be cut to determine the extent of embankment water. This section will be monitored to see if any more water appears.

existing top gravel layer is removed

new drainage being installed 

Oonah Road East - Road Remains Closed 

Oonah Road East will remain closed to all traffic until further notice as a final design for restoration is still to be confirmed.

Thank you to the community for your understanding as we continue to work hard for you on repairing these roads

24 February 2023

Oonah Road West - Road Open to Single Lane Only

Contractors have commenced remediation work on Oonah Road West.

Works to rebuild the road include

Clearing of trees on northern side of the road as well as any overhanging trees on the southern side. Upgrading culverts to dewater existing southern side of road Excavating the slip approx. 2.0m to a sound subgrade level Reconstruction of the pavement in layers to ensure stability Seal the road

(above) Remediation work begins at Oonah Road West clearing overhanging trees

Oonah Road East - Road Remains Closed 

We are still some way off identifying the most suitable solution for this part of Oonah Road, and subsequently Oonah Road will be closed in to the near foreseeable future.

30 January 2023

Oonah Road West - Road Open to Single Lane Only

Continue monitoring of this site has shown no further movement. It has been concluded that the road failure is due to improper fill and compaction on the downhill lane.

Repair work to Oonah Road West will commence in the next few weeks and will include:

Rebuilding the downhill lane Creating and upgrading drainage systems to properly direct storm water run off Resealing of the road

Oonah Road East - Road Closed 

Oonah Road East has sustained significant land movement and is still an active slip.

Investigation work in this area is still continuing to identify the best sustainable solution.

Potential options being considered:

Retaining wall to hold the slip Realign road uphill into the less impacted area

Land acquisitions may be required, depending on the solution. 

We are still some way off identifying the most suitable solution for this part of Oonah Road, and subsequently Oonah Road will be closed in to the near foreseeable future.

Thank you to the community for your understanding as we continue to work hard for you on repairing these roads

November 2022

A geotechnical investigation was conducted on the eastern landslide on the 27th of October and the western landslide on the 2nd of November 2022. A public meeting will be scheduled next week for Council Representatives to answer questions regarding the status of the findings to date. Further information will be provide regarding the date and time of the public meeting

Two landslides have occurred along Oonah Road; one within the western portion of Oonah Road (located approximately 500m east of the East Cam River) and the other towards the eastern end of Oonah Road (located approximately 250m east of the Guide Road intersection).

A geotechnical investigation was conducted on the eastern landslide on the 27th of October and the western landslide on the 2nd of November 2022. A public meeting will be scheduled next week for Council Representatives to answer questions regarding the status of the findings to date. Further information will be provide regarding the date and time of the public meeting.

A summary of the engineering investigation are as follows:

Eastern Landslide

The Road has slumped in a section that is approximately 70m long and contain several large cracks. These cracks extend across the entire width of the road and into the natural soils above and below the road. The observations show that the failed section of road has been subject to a previous landslide, and the current failure is a reactivation of the past landslide.

The engineering investigation will continue over the next two weeks to determine the options for this area.  The road will remain closed until further information is obtained, on the basis that this area remains a significant safety risk to the public. 

Western Landslide

The slumped section of road is approximately 125m long and contain several large cracks. This cracking is significant on the downhill side and extends across the entire width of the road. There is evidence of past landslide activity, however no obvious signs of any recent significant landslide activity was observed.

Most recent engineer tests have indicated that there is no significant structural issue with this portion of the road - the council can now look at initial remediation works as follows:

1:    Installing appropriate drainage, which involves cutting in channels which will be done using minimal earthworks. 

2:    Redirection of existing drainage

3:    Sealing of the open cracks to limit any further water damage.  

Once the above has been undertaken, we will consider the reopening of the uphill lane to traffic.  The downhill lane will need to remain closed  until additional remediation works are undertaken.

Any individual or business impacted by the flood event, including those effected by these road closures may be eligible to apply for Tasmanian Recovery Funding through the Tasmanian Government.

https://alert.tas.gov.au/recovery/

Further engineering information can be found below:

Eastern Landslide 

The site is underlain by basalt soils and is within a mapped low landslide hazard band The slumped section of road is approximately 70m long and contains several large tension cracks in a typically semi-circle pattern.  The tension cracks within the road typically have vertical displacement of up to 0.4m and a horizontal displacement of up to 0.2m The cracks within the road extend across the entire width of the road and extend into the natural soils above and below the road Directly above the cracked section of road is amphitheatre shaped hill segment with concave slopes, indicative of a past landslide.  The cracks within the road extend out from this feature; and Based on the site observations we consider that the failed section of road is the reactivation of a past landslide.

Western Landslide 

The slumped section of road is approximately 125m long and contains several large tension cracks in a typically semi-circle pattern.  The tension cracks within the road typically have vertical displacement of up to 0.25m and a horizontal displacement of up to 0.15m.  The cracking is significantly more pronounced on the downhill side of the road  The cracks within the road extend across the entire width of the road and slightly extend into the spoon drain on the upper south eastern side of the road The surrounding natural slopes are typically heavily undulated, consistent with possible past landslide activity, however no obvious signs of any recent significant landslide activity outside the extent of the road and road fill batter slopes was observed Test pits indicate that the failure plane is located at the interface between the fill soils and the natural residual. The failure plane is shallow on the uphill side of the road and increases to 2.0m-2.5m towards the downhill side of the road.  

The intialal remediation works purposed are as follows:

Appropriately drain the depression/gully located above the road.  This will require minimal earthworks, involving cutting a channel from the depression to the upper culvert – approximately 10m long and 1-2m deep;

In the area where the tension cracks intersect the spoon drain on the uphill side of the road, redirect the spoon drain channel around this area (slightly cut the drain into the upper slopes); and Seal up the open cracks to limit any further water ingress.