TYPE OF PROJECT: Culvert Rehabilitation
WHEN: June, 2020
Pipe Management Australia was contracted to undertake drainage works on Sir Bertram Stevens Drive to restore hydraulic capacity to four under road culverts in Royal National Park. The project was undertaken by VBA on behalf of Transport for New South Wales as a component of the Sydney South Stewardship Maintenance Contract (SMC).
Royal National Park
Sir Bertram Stevens Drive runs through Royal National Park, 45 minutes South-West of Sydney’s CBD. The park is maintained by the NSW National Parks and Wildlife Service, however road maintenance is controlled by TfNSW. This project was located within the Sutherland Shire Local Government Area and the La Perouse Aboriginal Land Council area. Sir Bertram Stevens Drive is a connecting road between the communities of Waterfall in the West, to Bundeena in the North East.
Four culverts were identified as medium to high risk due to the number of defects identified during routine investigation. These defects posed a risk to the health and safety of road users, and the environmental condition of the surrounding areas, especially downstream. The purpose of this project was the rehabilitation of the identified culverts to ensure structural stability.
The project was located on a moderately straight section of road approximately 1km in length. The culverts are positioned equidistantly along the length of the road segment, with approximately 300m between each culvert. The original culverts were constructed from local, heritage sandstone, likely installed between 1910 and 1914.
This project was undertaken within the Royal National Park amongst some strict work restrictions around plant movements, and the presence of endangered species. The Red-Crowned Toadlet is endemic to the Sydney Basin and is found in small colonies. This means any disturbance could have a significant impact on a local population. The area was also home to various species of native microbats, whose local populations could also be impacted by any major disruption. As these bats typically dwell in areas synonymous with culverts, PMA would need to ensure precautions were taken during the project.
The location of the project was specifically challenging as there was no phone reception across the site. This meant that all works and resources had to be strategically planned and rehearsed prior to establishing each night to ensure that all resources were onsite to complete the tasks at hand.
Due to the location VBA had no option but to detour all traffic from this road to allow the works to be completed safely. This involved a 15km detour, one of the larger detours that VBA had to put in place during their Stewardship Maintenance Contract.
To ensure the structural longevity of the culverts, and minimize risk to the public or the environment, the following work was carried out:
|475105||Excavate and replace 2.4m of existing 750mm pipework at the outlet and install a new concrete headwall. Installation of four in situ patch liners.|
|475108||Excavate and replace 11m of 600mm box culvert / 750mm round culvert and replace with 750mm concrete pipe.|
|475109||Installation of four in situ patch liners.|
|475142||Excavate and replace 8.6m of existing 600mm x 300mm box culvert with 600mm concrete pipe.|
Managing environmental issues
PMA and VBA collectively managed the environmental issues by investing considerable time before the project in the creation of the site-specific Construction Environmental Management Plan (CEMP) and project documentation.
Through collaboration between PMA, VBA and Eco Logical Australia there were no encounters with endangered species throughout the project. This was due to the presence of Eco Logical Australia being on site and the control in place. All culverts were inspected by hand by an ecologist for the Red-Crowned Toadlet prior to any works and microbat exclusion controls were put in place weeks prior to the project to deter bats from nesting within the culverts.
Additionally, all debris was removed by hand. Erosion and sediment controls were also implemented on each culvert. Through management of all the project variables (like rainfall) and frequent environmental, Work Health & Safety inspections there were no reported incidents or issues throughout the duration of the project.
Contingencies for a remote project
The remote location was managed effectively by PMA. All work shifts were planned and discussed to ensure the correct resources were onsite when needed. This included having a contingency for unforeseen issues such as providing excess backfill and road plates. VBA also had a satellite phone onsite at all times in case of emergency and all relevant stakeholders were given the phone number.
Systems for traffic management
VBA and one of their traffic control providers (Altus) were able to manage the detour of traffic effectively by giving the surrounding community advance notice of the works. For the duration, Altus had Variable Message Sign (VMS) boards strategically placed in the local government area advising of the road closure. In case a vehicle breached the initial roadblocks, additional protection was provided to the crews onsite by utilising remote controlled boom gates.
PMA provided value to VBA over and above the brief through the quality of our project documentation (site specific CEMP) as well as the professionalism and quality of our workmanship on site. Our project manager was on site for each shift to directly manage any issues or change events directly with the VBA site supervisor which allowed for efficient decisions for construction and financial purposes.
Considering the large impact on the community due to the closure arrangement it was imperative the project to be completed on time. Although the project was forecasted to take 15 shifts, PMA were able to dramatically overachieve and completed this project in less than 10 shifts. This allowed the asset to be handed back to the community ahead of schedule.
All environmental benchmarks of the project were achieved with additional efficiencies made on site in the form of reusing materials.
Reusing materials for sustainability
The culverts replaced were constructed out of sandstone blocks. Instead of dumping these, PMA reused the sandstone blocks at the culvert outlet to create a make shift headwall and additional scour protection. This was beyond the scope of work. Any remaining sandstone was then delivered to the Royal National Park depot for reuse throughout the park. PMA reused over 81% of all materials onsite. The only disposal was of asphalt and concrete pipe from the project. All rehabilitated assets hit the brief requirements and achieved an Assessed Risk Level rating of four or above.
As a result of the work carried out, strength was given back to the road to allow for the local community and visitors an unimpeded journey through the National Park, while keeping local wildlife safe.