Over the decades, Kembla Watertech has completed relining works in many environmentally sensitive areas throughout Australasia, often with difficult access points and restrictive conditions such as tidal areas, heavy bushland, heritage sites and steep vertical drops. Individual solutions to such access restrictions are required to address environmental factors, as well as occupational health and safety requirements, in order for Kembla to safely and successfully complete each project.
During winter 2011, Kembla completed two jobs, one in Sydney, and the other near Geelong, Victoria, that highlighted the problems sometimes encountered in getting Trenchless Technology into difficult locations. In both instances extensive scaffolding erection was deemed to be the best option to provide safe access to the assets in need of repair for personnel and equipment. Scaffolding also resulted in the least environmental impact.
Barwon Heads, VictoriaBarwon City Council contracted Kembla to rehabilitate four 225 mm diameter sewer mains located alongside the Barwon River. While the length of 100 m was rather innocuous by today’s standards, the steep slope of the riverbank was anything but straightforward. The sewer main was located at the bottom of this steep slope making access impossible by any normal means.
The erection of scaffolding was considered the only option and over the course of one day, 15 m (7.5 m high, 2.5 m wide) of scaffolding was constructed around the area. As identified by Kembla and the client, consideration and care of the vegetation surrounding the site was paramount, as well as the bicycle and pedestrian track that weaved through the job site. This pedestrian track is in frequent use and so the job garnered considerable community interest over the two days in which the lining was installed.Article continues below…
Lugarno, NSWFor this job, a site-specific Review of Environmental Factors/Construction Environmental Management Plan (REF/CEMP) was developed by Kembla’s Environmental Engineer in conjunction with consultant firm EMGA Mitchell McLennan. Multiple site visits were required with various parties, including the local council, to determine all the environmental factors and necessary safeguards to ensure the works made as little impact as possible.
Kembla develops site-specific REF/CEMPs for every environmentally sensitive site issued for rehabilitation. This one in particular involved a number of measures ensure to the preservation of the surrounding environment:
- The scaffold and its supports were positioned so they were not in contact with rock outcrops, if possible. Where unavoidable, padding was placed between the structure and the rock outcrop.
- Precautionary measures were in place to identify and avoid impacts to any Powerful Owls and Regent Honeyeaters near the proposed work sites.
- No vegetation was cleared or trimmed other than Lantana. Care was taken to avoid the spread of Lantana into adjoining bushland.
The job involved relining five assets, each being 150 mm in diameter and with an overall length of 94 m. Kembla’s FlexiLiner system was chosen as the lining method because each individual length between access chambers was less than 25 m and the FlexiLiner equipment has a minimal site imprint. The system uses air inversion of a needle-woven felt, soaked with polyester resin, from one maintenance hole either upstream or downstream.
The use of the FlexiLiner system was of a great advantage on this job, for two aspects in particular. The first advantage was the fact that it allowed lining to occur at the dead end at the most upstream section of the line without the need for any excavation to pull the liner through. The second advantage was the fact that the system could be used from the top of a vertical present in the line, downstream around a 90 degree bend to the last access chamber.
In order to gain access to these assets, a complex scaffolding system was built over the area. It took three days to complete and measured over 100m in length. The contractor, Advanced Scaffold, said that whilst this was not the biggest job it has completed, it was certainly one of the most difficult due to the steep slope and heavy vegetation. As can be seen in the photograph, the scaffold was a very impressive structure and as one member of the Kembla crew climbed the demanding 150 steps to reach the work site, he was heard singing his own rendition of the classic Led Zeppelin song ‘Stairway to Heaven’.