Legendary engineer Charles Yelverton 'CY' O'Connor once dreamed of a scheme to supply fresh water from Western Australia's coast to the dry interior.

Key points: The remaining 300kms of an iconic above-ground pipeline completed 117 years ago is set to be removed

The remaining 300kms of an iconic above-ground pipeline completed 117 years ago is set to be removed About 100,000 people and the mining and agriculture sector rely on the fresh water the pipeline delivers

About 100,000 people and the mining and agriculture sector rely on the fresh water the pipeline delivers Water takes up to 11 days to travel from Perth's Mundaring Weir

But 117 years after its celebrated completion, the Goldfields or Golden Pipeline could be replaced.

In a public notice released this week, Water Corporation WA has proposed removing the original above-ground parts and installing new pipes below ground over the next 50 years.

While some sections of the Perth-to-Kalgoorlie scheme have already been upgraded, more than 300 kilometres of the original pipeline is still in service today.

The Water Corporation WA document said the surviving pipeline was "not fit for purpose" and experienced "a number of leaks and bursts".

One of these bursts was captured on camera by a motorist this month.

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The video showed the water shooting into the sky and over the Great Eastern Highway, which runs parallel to the pipeline.

CY O'Connor's great-grandson Mike Lefroy said he was surprised and saddened to hear of the plan to replace an "incredible piece of engineering".

"It's such a prominent reminder of his work, but when I thought about it, it had to be replaced at some time," he said.

Construction of the Goldfields Water Supply Scheme took place in 1902. ( Supplied: State Library of Western Australia )

The pipeline was relocated above ground in the 1930s in a move which also raised public awareness among future generations — a visual reminder of the project's significance.

"So many people in the 70s, 80s [and] little kids would have run across it, would have ducked under it, worked in the various pumping stations," Mr Lefroy said.

Mr Lefroy says his great-grandfather's legacy is an "incredible piece of engineering". ( ABC Perth: Benjamin Gubana )

"Thousands and thousands of people have connections to it."

He was hoping the replaced pipeline parts would be kept and put on public display — a request supported by the water supplier.

"The Water Corporation values the historical significance of the pipeline and will be preserving some sections of the original pipeline, as per the heritage approval," a Water Corporation WA spokesperson said.

'A scheme of madness'

At the time of its completion, the pipeline was the longest freshwater pipeline in the world at 566 kilometres long.

If it were to be built today, it is estimated the project would cost about $1.5 billion.

WA's chief engineer Charles Yelverton O'Connor was behind the Goldfields water supply scheme. ( Supplied: State Library of Western Australia )

Kalgoorlie-Boulder historian Tim Moore said the pipeline enabled a boom for the WA Goldfields and put an end to deaths from the waterborne diseases found in the unsafe groundwater supply.

"Once we got fresh water along this pipeline, the health and the growth of this region took off, it just exploded, so it was an incredibly important scheme for the Goldfields people," he said.

Today, about 100,000 people and the mining/agriculture sector rely on fresh water delivered by the pipeline, which takes up to 11 days to travel from Perth's Mundaring Weir.

Without it, the City of Kalgoorlie-Boulder and surrounding towns would not exist today, according to Mayor John Bowler.

He believes the original pipeline should be maintained, not replaced, because "you always get a couple of leaks" and this plan would be "a waste of money".

"When CY O'Connor built this, he would never have envisaged that they'd just replace it because it might be running out of its lifespan," he said.

"It's still a very good pipeline, it's still very cost efficient [and] it's iconic."

The pipeline is a familiar sight for motorists on the Great Eastern Highway, which connects Perth to Kalgoorlie. ( ABC Goldfields: Rhiannon Stevens )

Water Corporation WA said it did not have an estimated cost of the works because the plan was seeking "50-year approval for an ongoing program of work".

Previously, it required individual approvals each time a section needed to be upgraded.

"An example of a current planned project is the replacement of about three kilometres of the pipeline near Merredin, about 200km east of Perth, for an estimated cost of $8 million," a spokesperson said.