Innovative work sees firm scoop award

Innovative work sees firm scoop award
The GeoSpray system was used in the successful restoration of the South Karori stormwater culvert.

The successful completion of the difficult and challenging restoration of the South Karori stormwater culvert has won its main contractor, Concrete Treatments NZ, a 2019 Civil Contractors New Zealand Hirepool Construction Excellence Award in the projects up to $5 million category.
“This was a major award win for us, as we’ve been selected from a large group of contractors working on some great projects across New Zealand,” says Concrete Treatments director Leigh Bishop.
“It was an unexpected win but we believed we had done something pretty special with this job.
“We were innovative, managed the site well, worked collaboratively with the client and their consultant, and selected good subcontractors, suppliers and products. All of those things combined to make a successful project.”
The 50-year-old, 220m long, severely eroded and corroded South Karori stormwater culvert had been on Wellington Water’s project list for a while, and without a suitable and safe repair method, it was becoming a problem.
Concrete Treatments’ proposed solution was to prep the culvert and install a structural mortar product, GeoSpray- a corrosion-resistant geopolymer system with a lower carbon footprint than standard cement products.
“Essentially we would create a new pipe inside the failing culvert, extending the life of the asset.” Leigh says old pipes, brick sewers, culverts, or structures showing signs of breakdown and corrosion can often be more economical to repair and restore than replace.
“The GeoSpray system is one of the most innovative and environmentally friendly systems available in the New Zealand market today. Designed and engineered to be sprayed over existing structures, this product creates a slip resistant and durable surface with excellent abrasion and chemical resistance.
“GeoSpray adds structural strength to the substrate it is applied to and at engineered thicknesses, forms a structure in its own right.”
Concrete Treatments had to work on a site in a densely populated residential area, with steep embankments and difficult access to the culvert through a section of native forest that limited use of mechanical equipment and completely eliminated vehicle access.
Initial preparation works were required to relocate fish species, remove protruding connections, manage ground water inflows, prepare the corroded base, and provide a weir with bypass to over pump a live stream and stormwater from upstream of the job.
The specific condition and alignment of the pipe was at first largely unknown, but soon discovered to be curvy with tight bends and a fully deteriorated corrugated culvert invert.
The team worked 11m underground to pump concrete and centrifugally cast GeoSpray mortar with pump distances in excess of 100m.
At 220m in length, the South Karori stormwater culvert renewal project was the longest lineal meterage of GeoSpray installed in New Zealand to date.
Leigh says the success of this project would not have been possible without the amazing efforts of the team working on the site and the great working relationships between Concrete Treatments, its client, subcontractors, and suppliers.
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