Last updated 30 November 2022
Road closure and road works, business support and viability and health and well-being issues were among key concerns discussed at a round table meeting between Tyalgum business and community representatives and NSW Government agencies and Council at Tyalgum on 16 November.
Held at the Tyalgum Hotel, which is currently being refurbished in preparation of a mid December opening, the meeting agenda covered a wide range of issues identified as by the Tyalgum community as having major impacts.
Council Director Engineering David Oxenham provided and update on the engagement of contractors and consultants looking at not only restoring the major land slip but also slips on Limpinwood Road.
Mr Oxenham said Council, in consultation with Transport for NSW, was looking at what would be the best approach to the Flood Recovery work, reassuring the meeting that Tyalgum road access was among Council’s top priorities.
Council is also addressing directional signage to Tyalgum and following up on request to assess speed zones on Limpiinwood and Zara Roads.
The major landslip on Tyalgum Road is about 950 metres east of Van Den Broek Road. There is another slip about 1 km west of this major landslip.
The damage site is more than 100 metres in width, some 60 metres in length and appears to comprise of some 6-10 metres depth of material which has slipped.
Geotechnical engineers have advised Council that results from test drilling show that it is not safe for a temporary track to be created as the continued movement poses an unacceptable public safety risk for a public road.
Ongoing geotechnical monitoring at the site will provide additional data to assess if this continues to be the case.
In the meantime, short-listed construction contractors are commencing the Concept design stage with the aim of having designs and tender pricing to Council by mid-December.
The contractors are using the geotechnical reports Council received in September and are supplementing this information with further geotechnical drilling being carried out at the site this and next week.
Once designs are complete, Council will select the most suitable contractor to carry out the work, with works expected to start on site in mid-2023.
Transport for NSW has confirmed in principle funding approval to cover the cost of repairs.
The geotechnical investigation found the roadway too dangerous for temporary repairs at the site of the main slip, about 950 metres east of Van Den Broek Road. This section of Tyalgum Road will remain closed until permanent repairs can be undertaken.
This is a major landslip which extends from land above the slip, across the road and down to the Oxley River. Restoration will be very challenging.
One-way traffic arrangements at the secondary landslip site, about 1 km west of the main slip, will remain in place.
The process of rebuilding
The list below summarises the high level processes we need to follow to fix the landslips at Tyalgum Road. Given our current knowledge of the sites, it’s difficult to provide accurate dates for each part of the process. There may be opportunities to run some of those in parallel however, we won’t know until we start to confirm the preferred solution. The outline below will give you an idea of why the works will take at least 12 months.
- Geotechnical procurement (underway)
Fixing landslips is a complex engineering task. It is crucial that the foundation of the slip is properly stabilised to prevent a similar failure occurring in the future. Specialist geotechnical engineers are used by Council to investigate the best option suited to Tyalgum Road’s specific site conditions. Only then can the missing piece of road be constructed over this new foundation.
The geotechnical assessment is broken up into 2 stages:
- Stage 1 is a preliminary assessment to make recommendations about the short term safety of the site.
- Stage 2 involves boring holes to investigate the soil in and around the slip including scientific testing, this information is used to determine options to fix the slip.
- Design and construction tender
We draft a design and construction document in preparation for the tender process. We then advertise the tender, evaluate all submissions then select the preferred tenderer based on the NSW legislation and our Procurement Policy which define specific processes and minimum timeframes. The tenderer then develops the design for approval by Council and Transport for NSW.
All work Council undertakes, including the repairs required on Tyalgum Road, requires approval under the Environmental Planning and Assessment Act – in much the same way as residents need a Development Approval to carry out renovations on their homes. This is to ensure there is minimal environmental impact during the construction of the work and that the final construction won’t cause any additional impacts to residents or the environment.
- Consultation with the community
We will consult with residents and businesses who will be directly impacted by the works to ensure they are not adversely affected by our activities. If they are, we will put in place measures to minimise these impacts.
There are several properties through which we are likely to require access to carry out the work.
At high level, a typical construction process to fix significant damage such as those sustained along Tyalgum Road would involve site establishment, excavation of slip areas, foundation works, wall construction or stabilisation structural works as well as earthworks, drainage, road subbase, pavement, line marking and safety barrier works.
At this stage, it is difficult to estimate the time required by the contractor to complete the works as it is dependent on the geotechnical solution as well as the expertise and resources of the contractor.