Upper Natone - Friday Update - Horseshoe Bend

Published on 25 November 2022

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Friday 25th November 2022 👇

Geotechnical drilling has commenced within the landslide effected area of the road

Initial drainage works have been conducted and survey monitoring readings indicate that only very minor movement has occurred recently, as such it was considered safe to conduct drilling works. 

Several boreholes have been drilled with temporary groundwater monitoring wells installed.  The initial boreholes and further observations indicate/confirm the following:

  • The landslide effected area within the road typically consists of basalt derived landslide deposits, overlying residual granite derived clays
  • The interface between the basalt derived landslide deposits and the residual granite clays is soft and saturated and interpreted as being the slip plane of the landslide feature
  • The slip plane in this area is located at a depth of approximately 1m to 4m below the road
  • The slip plane has a relatively shallow dip angle within the uphill side of the road, before increasing significantly beneath the downhill lane
  • Seepages below the road, on approach to Paton Creek, have almost completely dried up. 

Further drilling work is required to further define the landslide effected area and identify possible remediation options.  This work will begin on Tuesday 29th November 2022.

Based on the survey monitoring results, drainage works and the initial subsurface information, the uphill lane of the road through the landslide effected area can be opened to light vehicles only.

However, before the lane can be reopened some minor roadbase gravel will be required to smooth over the humps and minor steps. Also, the overhanging/leaning trees located to the north along the failed/slumped cut batter slopes, are required to be cut down.

Currently the dam is empty, however if a significant rainfall event is to happen then the drainage works currently in place will most likely not be sufficient.  As such, the dam will fill and then potentially spill over into the landslide headscarp.  If this is to happen then the road will need to be closed again.  A large pump will be on standby to assist in this matter.  This will be required until the drainage remediation works can be undertaken.  


Any individual or business impacted by the flood event, including those effected by these road closures are eligible to apply for Tasmanian Recovery Funding through the Tasmanian Government: Tasmanian Financial Support - Severe Weather Event - October 2022

You can call the Tasmanian Emergency Information Service on 03 6145 5303 for help filling out and completing the grant application forms.

You can also visit the Burnie Public Library @ 30 Alexander Street Burnie. They are happy to assist in completing the applications. A volunteer available at the Library on Mondays, Tuesdays and Wednesdays from 9:30a.m. until 12:00 p.m.

 


 

Friday 18th November 2022 👇

The spring feed dam located above Upper Natone Road - has been drained and no major cracks were found in the dams foundations.

Surveyors have been engaged to develop a grid survey to monitor the sites movement. This will commence today, Friday 18th November.

Geotech engineers have already noted that the slippage area has slowed considerably and seepage has also reduced. Geotech engineers will continue to monitor movement from the active slip.

Some trees will be removed along the banking and once further results are obtained from the Geotech investigations, we will work towards re-opening one lane as soon as possible.

Council has engaged Civil Engineering Specialists to oversee all design and construction works to effect repair of the road and remediate the surrounding slip area.

 

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Natone community, we listened to your other concerns regarding road maintenance in and around your area at the public meeting last week - and we have acted.

Contractors have been engaged to review and remove all low hanging branches from the south Riana/Upper Natone intersection through to Blyth Bridge.

19 Trees are scheduled to be removed from Camena Road to increase visibility and safety for all road users.

Verge maintenance will commence on upper Natone road starting early 2023.

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Any individual or business impacted by the flood event, including those effected by these road closures are eligible to apply for Tasmanian Recovery Funding through the Tasmanian Government: Tasmanian Financial Support - Severe Weather Event - October 2022

You can call the Tasmanian Emergency Information Service on 03 6145 5303 for help filling out and completing the grant application forms.

You can also visit the Burnie Public Library @ 30 Alexander Street Burnie. They are happy to assist in completing the applications. A volunteer available at the Library on Mondays, Tuesdays and Wednesdays from 9:30a.m. until 12:00 p.m.


 

Friday 11th November 2022  👇

Two public meetings were held on Thursday 10th November 2022, at Upper Natone Hall and Natone Hall, to discuss the damage of Horseshoe Bend. There was approximately 60 community members that attended across both sessions. 

Burnie City Council representatives were present, alongside a GeoTon engineer - who are providing geotechnical engineering advice.

The current status of the damage due to the Landslide on Horseshoe Bend was spoken to in detail, relating to the printed site plans to help visualise the scale of the Landslide. 

"It's a Landslide - within a Landslide", as quoted by the GeoTon engineer.

Hillshade Plan - Upper Natone.png

 

The main concern of immediate attention, is draining the the spring fed dam - located above Upper Natone Road. Once this dam can be safely drained into cut-off drains (which will be installed to discharge the water into the gully to the south) further investigations can continue with measuring the grounds movement as the secondary priority. 

The spring fed dam is located on private property - and in order to move ahead with the remediation work, Burnie City Council needs permission from the land owner to work in conjunction with them to drain the dam and commence the emergency remediation work. 

Once the water is disbursed, GeoTon engineers will continue to monitor the movement of the landslide displacement and if the movement has slowed to an acceptable level, the re-opening of one lane of the road can be achieved for light vehicles. Once we survey the area and can demonstrate that the re-emergence of traffic onto this road does not cause any issue, we can then consider opening the road to other forms of vehicles.

The road will continue to remain closed whilst these emergency works are undertaken.

Please remember - this is still an active landslide. It is still moving - and the movement is escalating at this time. Public safety in our number one priority. 

We will continue to monitor the situation, and update the community weekly each Friday. 

 


Any individual or business impacted by the flood event, including those effected by these road closures are eligible to apply for Tasmanian Recovery Funding through the Tasmanian Government: Tasmanian Financial Support - Severe Weather Event - October 2022

You can call the Tasmanian Emergency Information Service on 03 6145 5303 for help filling out and completing the grant application forms.

You can also visit the Burnie Public Library @ 30 Alexander Street Burnie. They are happy to assist in completing the applications. A volunteer available at the Library on Mondays, Tuesdays and Wednesdays from 9:30a.m. until 12:00 p.m. 


Every Friday, we will be updating the community with information regarding the remediation progress of Upper Natone Road. Information can be found:

- burnie.tas.gov.au

- facebook/burniecitycouncil

- Ridgley Post Office - 1006 Ridgley Hwy, Ridgley

- South Riana IGA X-Press - 1705 Pine Road, South Riana

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