Client Information
Project Summary:
The UHSC engaged Daracon to undertake rehabilitation works of Coulsons Creek Road in 2023, through a project governance framework, involving public works, TfNSW, Daracon and UHSC.
Earlier upgrades were completed in 2019, to improve road user experience and accommodate B-Double vehicles however defects began to show early through pavement cracking and slope instability. By January 2021, the situation had deteriorated so severely that geotechnical inspections found cracking extending beyond the centre line, forcing the complete closure of the road. A major natural landslip soon followed, causing extensive ground movement that undermined the pavement, damaged drainage structures, and destabilised the surrounding escarpment. The route remained closed for almost five years.
Following the collapse, UHSC engaged TfNSW and Public Works Advisory to find a different solution. The new design incorporated soil nailing, anchored slopes, shotcrete, rock mesh and gabion retaining walls to stabilise the steep terrain and protect the road from future landslips. The reconstruction became a $48.26 million project, jointly funded by the Australian Government and NSW Government.
Project Scope:
The scope of work for the project included the following:
- Clearing works associated with batter widening works.
- Establishment of soil and erosion controls.
- Cut to Stockpile of 128,000m³ of cut material generated from removed of the existing colluvial soils within landslips.
- Removal, redesign and replacement of all drainage structures and causeway redesign and rebuild.
- Installation of shotcrete lined drains atop the batters, down to the roadway and along the cut batter toe, to direct water to newly constructed drainage structures.
- Widening and reconstruction of the pavement.
- Processing of cut material to produce gabion rock, alternate gabion wall backfill and reno mattress backfill.
- Geotechnical protection works including gabion basket retaining walls, rock fencing and rock bolting.
- Existing Guardrail removal and replacement.
- Signage and line marking.
- The works were delivered to TfNSW specifications via a GC21 ‘Construct Only’ contract.
- Gabion wall stormwater outlet drop structures, earthlok and reno mattress lining of outlets.
- Day and Night Road Safety Audits.
Key Challenges:
- Delivering a significant project in a remote location to TfNSW specifications. The project required modifications of shotcrete mix designs using steel fibres instead of poly fibres due to known ejection and pollution risks. Utilising small regional concrete plants to allow for delivery times.
- Managing the ongoing mobilisation of a large number of plant and labour resources including subcontractors all ‘living away from home’ to deliver the works to program.
- Steep location required extensive focus on erosion and sediment control, including diverting clean water though the works to minimise the impact of rain events.
- Required detailed programming of the works around the construction of the large number of gabion walls which drove the critical path. This required extensive management of subcontractor to meet program, along with Daracon processing cut material to produce gabion basket rock in sufficient quantities in the required timeframe.
Key Success Factors:
- The project won the $30 - $75 million project category at the 2026 Civil Contractors Federation NSW (CCF NSW) Earth Awards.
- A value‑engineered road realignment removed an entire downstream gabion wall, reduced fill volumes and clearing (saved a number of habitat trees from removal), improved sight lines and lowered geotechnical risk - saving approximately $300,000 and one month in program and providing better environmental outcomes.
- Adapted concrete mix design and material use in a regional context, collaborating with the local batcher to achieve TfNSW compliance despite long haul times, steep and long pump lines.
- Management of onsite materials for reuse in the work.
