A gateway to the underground

National Precast Member PERMAcast manufactured and supplied critical precast concrete manhole covers to one of Australia’s largest natural gas projects – the Gorgon Project in Western Australia.The benefits of precast concrete products are being realised by many facets of the construction industry through major infrastructure projects opting to cast off site.

That’s certainly been the case for one of WA’s major resource and infrastructure projects – the Gorgon Project, which has utilised the benefits of precast concrete manholes over their in-situ product counterparts.

Developed by Chevron, Gorgon is one of the world’s largest natural gas projects and sits among the largest single resource developments in Australia’s history. The project is located on Barrow Island, a Class A nature reserve 60 kilometres off the coast in northwest WA. It includes a liquefied natural gas facility and a domestic gas plant capable of supplying 300 terajoules of gas per day to the WA population.

But it is under the ground where precast has played a vital role. Approximately 610 precast concrete manholes have been installed to provide access to underground pipes.

Capabilities essential in awarding contract 

Given the number and size of the manholes, Leighton Contractors needed to award the project’s precast package to a precast manufacturer that had the required expertise and an extensive manufacturing capability. The requirement was for a precaster with a strong track record supplying major infrastructure, oil and gas projects – one with a highly skilled and technically competent engineering team as well as a large-scale precast facility that not only had manufacturing capacity but a large storage facility too.

Perth-based precast concrete specialist and National Precast member PERMAcast was awarded the contract to manufacture and supply the manholes, together with conversion slabs and access shafts for the project.

With its highly skilled and experienced team of in-house engineers and a stringent quality management system, the company was able to ensure that all products were designed and manufactured to specification.

“Even though no two manholes were the same, we were able to meet supply requirements,” explains PERMAcast Managing Director Alberto Ferraro

“The sheer volume of products might have been difficult in terms of storage for other precasters, but we have 250,000 square metres of storage area, so for us it was no problem.”

Precision to meet quarantine requirements

The 610 manholes each weighed between 15 and 20 tonnes, manufactured to a +/- 5-millimetre tolerance and measuring on average 1500 by 1500 millimetres internally.

Being a Class A nature reserve, the quality and finish of the manholes was critical for the project. To prevent the introduction of non-indigenous animals and plants into the area, a best practice quarantine management system set an unprecedented level of quarantine benchmarks. A high quality finish was necessary to minimise the risk of introducing non-indigenous insects. Each manhole was manufactured with a single pour to ensure no joints and therefore, no potential for leaks.

“Neither the quantity nor the quality was an issue for us at all,” says Mr. Ferraro. “Our team is always up for a challenge.”

Adding value

“We also managed logistics between our company, Leighton and their sub-contractor. Those skills added value to the project in terms of construction efficiency,” says Mr. Ferraro.

The company also supplied and installed the ladders for the manholes. “We always add value where we can,” he adds.

Project: Gorgon Project

Location: Northwest WA

Precaster: PERMAcast

Builder: Leighton Contracting

Client: Chevron

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