Hinterland slopes on Lamington National Park Road impacted by Cyclone Debbie landslips were a formidable hurdle successfully overcome by a collaboration between TMR, SMEC, McIlwain Civil and McIlwain’s subcontractor NuGrow.
The rehabilitation project spanned around 20 sites and a total of 6,000m2. With slopes of 45 to nearly 70 degrees, and varied residual soils, ground conditions and rainfall exposure, it demanded a truly tailored solution – site-by-site.
The project also presented the logistics and safety challenges of delivering on a steep, one-track, windy, live road.
Following a series of site visits and tests, the team launched a trial to define the right mix of methods, based on NuGrow’s innovative revegetation solutions.
McIlwain Civils’ Senior Project Engineer, Steve Watson, said all teams took an iterative approach to build on TMR’s specification so the process would work within the unique constraints of such diverse sites.
“Once we got NuGrow involved through site visits with our client and the wider team, we could narrow our options, get everyone on board early, and commit to a clear plan of attack,” Steve said.
SMEC’s Geotechnical Engineer, Chris Melville, said the four-week trial was critical to determining Hydroganics as the preferred option.
“NuGrow’s expertise in developing and managing the revegetation trial, and tailoring options, gave us a confident way forward,” Chris said.
“Getting the right application was essential – and difficult – and that’s where NuGrow’s advice on the process and watering regime worked really well.
“Everyone is happy – the sites quickly grew a thick cover crop and we’ve achieved continual growth since then, with natives already germinating.”
While Hydroganics delivered the winning solution, collaboration drove a productive decision-making process.
“The solution had to cater for a wide range of possibilities, so it was good to work it through together, rather than quickly pick one solution based on one person’s advice,” Chris said.
“The collaboration with all parties is a credit to this project. It’s pretty rare it happens like it did and, as a result, we all had a great outcome,” Steve said.
“Despite the challenging conditions, and time spent on the trial, we met our tight schedule with everyone’s assistance.”
NuGrow’s Manager of Revegetation Services, Ben Brown, said an out-of-the-box solution for sites like these have a high chance of failure, which means costly rework.
“A fully-tailored solution is the only way – taking into consideration a range of possible methods, the logistics of safe delivery, and the technical design of the product mix, application process and watering,” Ben said.
“Hydroganics adapted outstandingly to the conditions. Supported by soil testing, we tailored amelioration and application approaches to multiple site types, providing both effectiveness and efficiency,” he said.
“We also designed a method that used Hydroganics through mesh for about 10% of the project’s areas that faced more concentrated water flow, avoiding delamination.
“The collaboration was among the best I’ve experienced, with everyone openly listening to suggestions and no one cutting corners. Client savings are in a project done once, done right.”
Despite recent weather events on the steep slopes, Hydroganics sustained no loss and altogether solved the problem of rehabilitating a challenging site.