Bespoke frames support construction of cyclone-proof water tank

Coates designs a complex temporary works solution using proprietary propping components

The project

In November 2020, global construction group SRG was awarded the contract to replace an existing steel plate water tank in Karratha, damaged during Tropical Cyclone Damien, with a new 20-million-litre cyclone-proof concrete tank. The new tank is one of three tanks to be constructed by SRG across WA, as part of a major water infrastructure investment program to improve water security in the region.

In July 2021, Coates was engaged to design and supply temporary works to support construction of the $15 million tank, as well as specialist equipment and expertise.

The problem

Sam Pearce, SRG Global Construction Manager, explains: “The construction involved the installation of 32 large concrete panels weighing over 55 tonnes each, with the challenge for the site team to find a robust solution to temporarily support these during installation. 

“In developing the solution, we also had to consider how to safely construct the works, as the site was on the top of a hill with limited access, as well as the severe weather of the Pilbara.”

Measuring 16m above ground, Karratha’s new tank is the tallest of three tanks recently constructed by SRG in the Wheatbelt, Eastern Goldfields and Pilbara regions of WA. To accommodate a small construction site, Karratha’s tank features the narrowest design in relation to its height, making design and construction even more difficult.

The solution

Coates devised a temporary works solution to support construction and to help SRG work through ongoing design and site challenges.

“A total of 25 frames were fabricated and moved around site to support the installation of 28 regular concrete panels each weighing 55 tonnes, and 4 buttress panels each weighing 55 tonnes,” says Doug Norton, Coates Temporary Works Engineer.”

Robust but complex temporary works design
According to Doug, a frame of this size would traditionally be constructed from 5-10 steel members in two different sizes, with a connection at each end. The bespoke frames designed by Coates and installed by SRG feature approximately 14,000 bolted connections over 25 frames.

“Given the small size of the site and various access issues the client was facing, it would’ve been extremely difficult to unload and rig up an entirely prefabricated frame for this project,” says Doug. “So Coates combined a range of proprietary Universal SYS 15, 30, 60 and 100 propping components piece-by-piece to form an entirely new solution that could easily be transported and assembled on site.”

As the frames weren’t fixed to the tank floor, each frame also required a 16-tonne concrete cyclone counterweight to restrain movement of the panels and to ensure the integrity of the temporary works solution. Coates supplied these concrete counterweights locally to minimise transportation costs and environmental impact.
 

Total equipment solution
Much of the equipment was sourced from local Coates branches, with some specialist equipment brought in from branches in Sydney and Melbourne, despite ongoing lockdowns in Victoria and New South Wales. 

Coates also supplied a range of access and materials handling equipment and a dedicated account manager to ensure the smooth coordination of all Coates products and services on site. 

By using Coates’ existing Universal SYS props (rather than fabricating structural steel frames), SRG was able to assemble the frames on site in pieces and meet their tight installation schedule. 

The impact

“Coates’ ability to offer an end-to-end solution for the temporary works was what appealed to us,” says Sam. “Coates had the experience and the equipment to support all of our temporary works’ requirements which streamlined the process of developing a solution and being able to procure all the necessary items to hire.”  

Installation began in August 2021 and the frames were successfully removed in November once all concrete tank panels were in place. The first phase of commissioning commenced in late 2021 and the tank is expected to be fully operational early next year.