Coates helps Brefni deliver award-winning stormwater upgrade ahead of schedule

Faced with steep terrain and sensitive environmental conditions, Brefni turned to Coates for a shoring, dewatering and equipment hire solution

The project

Following repeated extreme weather events, a culvert underneath Cliff Drive in Leura, in NSW’s Blue Mountains region, suffered extensive landslip damage and required urgent replacement. Civil engineering company Brefni was engaged by Blue Mountains City Council to deliver a new culvert.

Designed with significantly larger capacity than the original 1940s structure, the new culvert aimed to manage water flow during heavy rain and make Cliff Drive safe for vehicles. Brefni engaged Coates to support the temporary works for the project.

An aerial view of the excavation and demolition works in progress.  Photo: Courtesy of Brefni 

The challenge

The steep, heavily vegetated site was in a highly constrained area of environmental and cultural significance, requiring careful protection of heritage structures, waterways and local ecology. Construction had to minimise vibration near Chelmsford Bridge – the oldest unreinforced concrete bridge in Australia – limit vegetation disturbance and prevent debris or contaminants from entering the creek. Overhead high-voltage power lines and the nearby Sydney Water sewer main added further complexity.

As a high-profile project for Blue Mountains City Council in a popular recreation area for locals and tourists, maintaining safety and environmental integrity was critical throughout the works.

The site was steep with heavy vegitatation, requiring special attention when designing the solution.  Photo: Courtesy of Brefni 

The solution

Coates Engineering Solutions designed and supplied a Slide Rail steel shoring solution to support the excavation, which was installed by Brefni, as well as a dewatering solution to redirect the creek and keep the worksite dry.

The Slide Rail system measured over 40m long, 5.5m wide and up to 6m deep, creating a safe excavation environment for the construction works. Brefni required precise culvert placement and Slide Rail’s modular design provided the flexibility to meet tight positional constraints, eliminating the need for multiple shoring systems.

“Slide Rail is the most robust and flexible shoring method available for large excavations. It allows customers to take their excavations longer, wider and deeper than with any other product. With an unrivalled pressure rating, it supports excavation depths of up to 9.0m in most conditions and provides the largest under-strut clearance of any product on the market,” says Darren Browne, Sales Manager - Engineering Solutions at Coates.

“Slide Rail systems are renowned for their ability to control ground loss – where soil collapses or shifts into the excavation. This was an essential requirement for Brefni, and where conventional shoring systems would have fallen short.”

The bypass system, designed to operate 24/7 used a combination of submersible pumps, with backup pumps and flow monitoring equipment to safeguard the system in case of a breakdown.

Controlling ground loss was vital – a challenge Slide Rail systems are renowned for overcoming. Photo: Courtesy of Brefni 

The impact

Coates’ modular Slide Rail shoring system and reliable bypass solution were instrumental in enabling efficient excavation and maintaining site safety, contributing to the project’s early completion – six weeks ahead of schedule – with zero safety incidents. Brefni’s outstanding project delivery was recognised at the 2025 Civil Contractors Federation NSW Earth Awards, winning in the $2-5 million project category.

"This was a complex project with strict environmental controls, heritage sensitivities and significant technical demands,” says Cathal McMahon, Project Manager at Brefni. “Coates' engineering expertise and tailored temporary works solutions gave us the confidence to deliver efficiently and safely under pressure. Their Slide Rail system was instrumental in achieving precise placement and maintaining ground stability throughout the excavation, and the collaborative approach from their team made a real difference on the ground."

Inside the completed culvert, delivered six weeks ahead of schedule. Photo: Courtesy of Brefni 

Discover how Coates can support your complex civil project – contact our Engineering Solutions team